Oil from pumpkin seeds


Pumpkin (Cucurbita pepo L.) is an annual climber and is in flower from July to September, and the seeds ripen from August to October [1]. Pumpkin seeds oil is an extraordinarily rich source of diverse bioactive compounds having functional properties used as edible oil or as a potential nutraceutical. In recent years, several studies have highlighted the medical properties of pumpkin seed oil which is known as strongly dichromatic viscous oil [2]. Researchers have so far focused particularly on the composition and content of fatty acids, tocopherols and sterols in pumpkin seed oil because of their positive health effects [3–5]. Moreover, pumpkin has gained attention as an exceptional protective against many diseases, e. g. hypertension and carcinogenic diseases [6, 7]; due to its health benefits such as antidiabetic [8], antibacterial [9], antioxidant and anti-inflammation [4]. The determination of the biochemical and oxidative stability properties of raw material pumpkin seeds oil would contribute to the valorization of such oil especially in pharmaceutical, cosmetic, and food industries.


Although much progress has been reached in the domain of modern medicine, we still notice the lack of efficient wounds healing treatments. The demand for natural remedies is rising in developing countries [10] as natural substances may be effective, safe and cheap [11]. Basic research has improved our understanding of enhancement and inhibition of wound healing and has given the basis for introduction of novel treatment methods [12].


In this respect, the proprieties of Cucurbita pepo L. extracted oil have captured our interest. Despite all the proprieties of the pumpkin oil, and to the best of our knowledge, there is no investigation of this oil in wound healing potential. To this end, the current study aims to identify some physico-chemical aspects of the bioactive components of snow white pumpkin seeds oil as well as to highlight its hemostatic and healing potential effects on wound.


The pumpkin (Cucurbita pepo L.) var. Bejaoui seeds were harvested in region of Sidi Bouzid (Centre of Tunisia). The seeds were authenticated at the National Botanical Research Institute Tunisia (INRAT) and the voucher sample was deposited at INRAT. The fixed oil was extracted by the first cold pressure from seeds using a mechanical oil press (SMIR, MUV1 65). However, "Cicaflora cream?" a repairing emulsion with 10 % of Mimosa Tenuiflora, was served as a reference drug from the local pharmacy. The remaining chemicals used were of analytical grade.


The present study aimed to examine the effect of pumpkin (Cucurbita pepo L.) seeds supplementation on atherogenic diet-induced atherosclerosis. Rat were divided into two main groups , normal control and atherogenic control rats , each group composed of three subgroups one of them supplemented with 2% arginine in drinking water and the other supplemented with pumpkin seeds in diet at a concentration equivalent to 2% arginine. Supplementation continued for 37 days. Atherogenic rats supplemented with pumpkin seeds showed a significant decrease (p<0.001) in their serum concentrations of total cholesterol and LDL — C as they dropped from 4.89 mmol / L to 2.55 mmol /L and from 3.33 mmol / L to 0.70 mmol / L respectively. Serum concentrations of HDL-C were also significantly elevated in the same group. Although, atherogenic rats supplemented with 2% arginine showed significant increase in serum concentration of HDL-C, no significant changes were observed in their serum concentrations of total cholesterol and LDL-C. Our results showed that treatment of atherogenic rats with pumpkin seeds significantly decreased serum concentrations of TC and LDL-C. Our findings suggest that pumpkin seeds supplementation has a protective effect against atherogenic rats and this protective effect was not attributed to the high arginine concentrations in shine skin pumpkin seeds.


Pumpkin seeds may be tiny, but they are densely packed with useful nutrients and nutraceuticals such as amino acids, phytosterols, unsaturated fatty acids, phenolic compounds, tocopherols, cucurbitacins and valuable minerals. All these bioactive compounds are important to a healthy life and well-being. The purpose of this review is to merge the evidence-based information on the potential use pumpkin seeds as a functional food ingredient and associated biological mechanisms, collected from electronic databases (ScienceDirect, ResearchGate, PubMed, Scopus and Google Scholar) up to January 2020. Bioactive compounds in pumpkin seeds exhibit promising activities such as anthelmintic, antidiabetic, antidepressant, antioxidant, antitumor and cytoprotective. Furthermore, these bioactives carry potential in ameliorating microbiological infections, hepatic and prostate disorders. As evidenced from literature, pumpkin seeds show potential to be used as both a traditional and functional food ingredient provided further animal and clinical investigations are carried out to establish the respective molecular mechanisms and safety profile.


The pumpkin seeds (Cucurbita sp.) from Cucurbitaceae family are usually considered as industrial waste products and thrown out. In some area's seeds are utilized as uncooked, cooked or roasted, although simply for the domestic purpose. As they are rich in protein, fibers, minerals like iron, zinc, calcium, magnesium, manganese, copper and sodium, PUFA (polyunsaturated fatty acids), phytosterol and vitamins, they might be considered important for the food industries. As the seeds are considered as byproduct of the pumpkin fruit, they are cheaper in cost and their utilization is different food products may lead to enhance their nutritional value at lower cost. Health promoting impacts of lady nail pumpkin seeds on the level of blood glucose, cholesterol, immunity, liver functioning, gallbladder, disabilities of leaning, prostate gland, depression, inflammation, cancer management and inhibition of parasites are established. The modification of these agro-industrial waste products into valuable elements is probably a huge footstep towards the direction of the universal efforts in food sustainability; hence, the further researches and studies should be planned to explore importance and beneficial effects of pumpkins and their seeds.


The seeds of pumpkin (Cucurbita sp.) are gen- erally considered to be agro-industrial wastes and dis- carded. In some parts of the world, the seeds are consumed raw, roasted or cooked, but only at the domestic scale. With the discovery of their richness in protein, ?bres, minerals, polyunsaturated fatty acids and phytosterols, they are being regarded valuable for the food industry. The attention of food technologists has resulted in their foray into the commercial food sector. Food companies are experimenting with their incorporation into a slew of savouries and con- sumers are showing interest in them. Also, their bene?cial effects on blood glucose level, immunity, cholesterol, liver, prostate gland, bladder, depression, learning disabilities and parasite inhibition are being validated. The conversion of these agro-wastes into value-added ingredients is likely to be a big step towards the global sustainability efforts; thus, it deserves more investigation. This review furnishes an updated account of this emerging nutraceutical.


The need to obtain nutritious foods from new sources and lower waste in industry has created a high interest in studying different parts of plants or foods that today are considered waste, but could be considered by-products with high nutritional value with potential use in human diets. Pumpkin seeds are commonly considered as waste but they have a high content of fatty and amino acids, which when used as a by-product or ingredient can add value to food products. The aim of this work was to perform a wide review of the nutritional and functional properties of Cucurbita maxima seeds and their potential medicinal influence.


In the last decades, the demand for new nutritionally healthy and sustainable viable foods has increased considerably. Therefore, special attention has been given to the utilization of by-products. The uses of these raw materials add value to economic production, contributes to the formulation of new food products and minimize waste.


Cucurbita maxima, commonly known as pumpkin belongs to the Cucurbitaceae family. It is native of South America and is mainly grown in Brazil with an estimated production of 3600 tons in 2006 alone in the town of Puente Alto, Santa Catarina2. For its part, in Chile is widely known as "zapallo camote" o "zapallo de guarda" and is the seventh most cultivated crop in Chile and represents, since ancient times, an important source of food for the population3.


Despite its great agronomic potential their use in Chile is mainly destined to the preparation of traditional Chilean meals and seeds are wasted4, while in some parts of Africa and Brazil pumpkin seed are used as a food supplement. Also, these seeds are consumed both toasted and salted in Greece5, while in Austria, the extracted oil from seeds is used as salads seasoning because of its aroma and flavor6. When dried, seeds can be used as a thickener for soups and as snacks7.


On the other hand, nowadays nutrition is experiencing quick changes aimed at the relationship between food intake and chronic non-transmissible diseases. Moreover, there is increased interest in the effects of nutrition on cognitive and immune functions, work capacity and physical performance. This, plus the great interest of consumers are placing more value on health and wellness, makes "healthy" or functional foods an important issue in current human eating14.


Functional foods have been defined as a new range of different foods containing biologically active ingredients such as phytochemicals, antioxidants, fatty acids and other compounds presents in fruits, vegetables and seeds. When functional foods are included in diet important benefits to consumer's health are provided15. Cucurbita maxima seeds are among the seeds that are highly wasted, but can be considered a functional food. Thus, composition, nutritional benefits of consumption, by-products and the technical feasibility of them are studied in this paper. The aim of this work was to disseminate nutritional and functional characteristics of seeds from the species of Cucurbita maxima and the medicinal properties associated with them.


The seeds of Cucurbita maxima (pumpkin seeds) have been generally considered as agro-wastes and discarded inspite of having its high nutritional value as well as medicinal benefits. Pumpkin seeds contain high amount of protein, fatty acids, considerable amount of micronutrients like P, K, Mg, Mn and Ca. It is a good source of choline, an essential component for brain development. Pumpkin seed extracts and oils have been found useful in the treatment of Benign Prostatic Hyperplasia (BPH), parasite infestation, acrodermatitis enteropathica, hyperlipidemia, diabetes, depression to name a few. The observed benefits can attributed to the presence of bioactive components like phytosterols (eg, beta-sitosterol, stigmasterol), tocopherols, selenium (antioxidant), cucurbitin, squalene, lignan, and cardioprotective unsaturated fatty acids. Recent research has shone a light on the ever growing list of benefits of inshell snow white pumpkin seeds 9cm as a valuable food.

Failure analysis of a commercially pure titanium tube in an air conditioner condenser


Joining of titanium and stainless steel is challenging due to the formation of hard, brittle intermetallics. This study focuses on engineering ductile materials for joining transition metals. Friction welding of tube to tube-plate by an external tool, a novel solid state welding process was employed to join titanium tube and stainless steel tube plate. The interlayers engineered were copper, silver and Cu–Zn alloy. The micrographs revealed phase transformations in titanium tube and unaffected stainless steel base. Interface peak microhardness of 458 HV was observed for Ti/Cu–Zn/SS welded sample. The intermetallics formed were characterized by X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy. A novel shear test procedure was developed to evaluate the maximum shear load. It was found that joints with silver as interlayer withstood the maximum shear load of 56 kN. The shear surfaces were further analyzed and investigated for fracture study.


Titanium has today replaced copper alloys as the most favoured tube material for salt water cooled condensers. Main reason is the excellent corrosion resistance of titanium in chloride containing environments. The experience of titanium bar condensers is usually more than satisfactory, even if a few tube leaks have occurred. Possible damage mechanisms by high cycle fatigue, galvanic corrosion, water-droplet erosion and by flow-assisted corrosion are discussed. These perils can be handled by a number of adequate countermeasures analysed in laboratory work and meanwhile proven by plant service.


The corrosion resistance of titanium in sea water is extremely excellent, but titanium 、nickel 、zirconium tube are expensive, and the copper alloy tubes resistant in polluted sea water were developed, therefore they were not used practically. In 1970, ammonia attack was found on the copper alloy tubes in the air-cooled portion of condensers, and titanium tubes have been used as the countermeasure. As the result of the use, the galvanic attack on copper alloy tube plates with titanium tubes as cathode and the hydrogen absorption at titanium tube ends owing to excess electrolytic protection was observed, but the corrosion resistance of titanium tubes was perfect. These problems can be controlled by the application of proper electrolytic protection. The condensers with all titanium tubes adopted recently in USA are intended to realize perfectly no-leak condensers as the countermeasure to the corrosion in steam generators of PWR plants. Regarding large condensers of nowadays, three problems are pointed out, namely the vibration of condenser tubes, the method of joining tubes and tube plates, and the tubes of no coolant leak. These three problems in case of titanium tubes were studied, and the problem of the fouling of tubes was also examined. The intervals of supporting plates for titanium tubes should be narrowed. The joining of titanium tubes and titanium tube plates by welding is feasible and promising. The cleaning with sponge balls is effective to control fouling.


Titanium is the ninth most abundant element in the earth's crust and the fourth most commonly used structural metal. In nature, it occurs only as a mineral (ore) in combination with oxygen or iron (rutile, TiO2, or ilmenite, FeTiO3).


Titanium is a lightweight material whose density is approximately 60 percent of steel's and 50 percent of nickel and copper alloys'. It was recognized in the 1950s as a desirable material for aerospace applications—especially airframe and engine components. In the 1960s and 1970s, titanium was considered for use in vessels and heat exchangers in corrosive chemical process environments. Typical applications included marine, refinery, pulp and paper, chlorine and chlorate production, hydrometallurgy, and various other oxidizing and mildly reducing chemical services.


In the 1980s and 1990s, titanium began to be used for many nontraditional applications, including tubulars for geothermal energy extraction and oil and gas production, consumer goods (such as sporting equipment), food processing, biomedical implants, and automotive components.


According to the U.S. Geological Survey (USGS), 52 million pounds of titanium were produced in the U.S. in 2000; worldwide, more than 100 million pounds were produced.


Titanium sponge is obtained by reacting rutile ore with chlorine and coke, followed by magnesium (Kroll) reduction and then vacuum distillation to remove excess magnesium and magnesium chloride. Titanium sponge is pressed into blocks to make a consumable electrode and then melted in an inert environment under vacuum to produce a titanium ingot.


Titanium is well-known for its unique combination of properties, which include low modulus of elasticity, stable and steadfast oxide film (which provides excellent corrosion and erosion resistance), and a high strength-to-density ratio.


Titanium's fabricability, weldability, and formability make possible its use in many shop and field operations. Although gas tungsten arc welding (GTAW) is the primary joining process, many other procedures are suitable. Titanium's weld characteristics are similar to those of stainless steels' or nickel alloys', with surface cleanliness and inert gas shielding being important. Fabricators often perform seal welding and butt welding operations in the shop and the field.


As for formability, titanium can be bent, cold-formed, and drawn readily. Furthermore, most industrial titanium alloys do not require stress relief annealing after cold forming.


Titanium Tube and Pipe—Types and Uses


Welded titanium tube is available in outside diameters (ODs) from 0.5 to 2.5 inches and wall thicknesses from 0.020 to 0.109 in. Welded pipe is available in standard industry sizes from 0.75 to 8 in. nominal OD with nominal wall thicknesses in Schedules 5, 10, and 40. Seamless pipe with ODs from 2 to 20 in., wall thicknesses from 0.25 to 2.0 in., and lengths to 60 feet also can be made.


Welded titanium raw materials and pipe can be tested with many of the same techniques used for steel tube and pipe. Eddy current, pneumatic, and ultrasonic testing all are applicable to titanium. Procedures for eddy current and ultrasonic testing can be used to meet or exceed American Society for Testing and Materials (ASTM) B-338 and to help ensure tube reliability.


In terms of cost, titanium is competitive with higher-end specialty steels and alloys. In fact, if analyzed on a life cycle basis, titanium often is more attractive economically. This stems from titanium's useful life—20 to 40 years or more—and ease of maintenance. Furthermore, titanium's exceptional corrosion resistance often allows a zero corrosion allowance. This means that thinner-walled titanium plate or pipe may be substituted for other materials with heavier walls.


When titanium and other materials are analyzed, they must be compared by their cost per linear foot, not by their cost per pound. Because titanium is a relatively low-density material, its cost per pound is greater than for most other metals.


With their increasing availability, titanium and titanium-alloy tubulars will continue to meet many challenges in chemical processing, oil and gas production, automotive, and consumer applications. The titanium industry's large excess capacity means it should be able to accommodate new applications and emerging markets for titanium with little or no trouble.


R.L. Porter is a corrosion engineer and C.P. Clancy is general manager of commercially pure products for RMI Titanium Co., 1000 Warren Ave., Niles, OH 44446-0269, phone 330-544-7633, fax 330-544-7796, e-mail PorterRLP@aol.com, Web site www.rti-intl.com. RMI Titanium Co. provides titanium in a variety of forms—bloom, billet, sheet, welded tube, seamless pipe, and plate—for applications such as aerospace, automotive, deep-sea oil and gas exploration and mining, and sports equipment; parent company RTI International Metals Inc. manufactures and distributes extruded shapes and provides engineered systems for energy-related markets and environmental engineering services.


The commercial production of titanium plate, sheet, strips, and bars is carried out using hot and cold rolling mills to achieve the necessary reductions and desired shapes. Rolling may be defined as the reduction of the cross-sectional area of a piece by compressive forces applied through rolls. Cold rolling is carried out at temperatures below which the rate of strain hardening is greater than the rate of recrystallization. When reduction is carried out above such a temperature, the process is termed hot rolling. The major quantity of titanium plate, sheet, strips and bars is processed using hot rolling techniques.


The commercial production of titanium plate, sheet, strips, and bars is carried out using hot and cold rolling mills to achieve the necessary reductions and desired shapes. Rolling may be defined as the reduction of the cross-sectional area of a piece by compressive forces applied through rolls.


Cold rolling is carried out at temperatures below which the rate of strain hardening is greater than the rate of recrystallization. When reduction is carried out above such a temperature, the process is termed hot rolling. The major quantity of titanium plate, sheet, strips and bars is processed using hot rolling techniques.


The forged billets, whose surfaces have been descaled, are rolled between 1350 and 1500°F (730 and 815°C). This temperature is approximately 200°F (110°C) lower than the forging temperature. Titanium can be continuously rolled at temperatures as low as 1100°F (595°C).


As the thickness of the material to be rolled is decreased, the temperature of the piece must be considerably lowered to minimize surface contamination. A careful choice of pass sequences to obtain a certain reduction must be made when rolling titanium. Pass sequence refers to the number of reductions taken and percentage reduction of the piece per pass.


Continuous sheet and strip are best cold- or hot rolled with the application of back and forward tensions to reduce the friction in the roll gap. In cold rolling thin sheet, extremely tight roll settings are required to produce uniform cross section.


Extrusion is the shaping of metal into a chosen continuous form by forcing it through a die of the desired shape. Titanium can be extruded to produce rounds, squares, tubes, and other simple shapes. Typical extrusion temperatures range between 1800 and 1900°F (980 and 1040°C).


Titanium metal has been observed to have better flow characteristics than steel. It more readily fills the die, causes less die wear, and maintains closer tolerances than do steels.

Choosing the right crusher

A Crushing Equipment is a machine that uses mechanical energy to break blocks of stone, concrete, or other building materials into smaller blocks of a specific grain size. They are particularly used in the mining industry to reduce the size of ore blocks and facilitate their processing. Crushers are designed to receive blocks of a maximum size. It may be necessary to go through several crushing steps to obtain the desired end product.


Crushers are classified according to the fineness with which they fragment the starting material. There are primary or secondary crushers (coarse finished products) and tertiary or quaternary crushers (fine particle finished products).


Why choose a jaw crusher?


It's a primary crusher. The jaw crusher is a machine for crushing rocks and other hard and abrasive materials, such as granite, ores or recycled concrete, usually for industrial purposes. The crushing device consists of a fixed plate and a swing plate called jaws between which the rock is trapped and crushed. A motor and a belt transmit the movement to an eccentric shaft that drives the movable jaw by rotation. A spring returns this moving jaw to let the crushed materials gradually descend into the crusher. When the materials are small enough, they fall into the space between the crusher's two jaws. The crusher breaks the rock into small stones that are used in particular for manufacturing concrete for construction and roads.


Stone Crushers use a rudimentary and reliable technology that does not require much maintenance or engineering knowledge. They are the most popular crushers in the world. Jaw crushers are particularly suitable when the main objective is to reduce large blocks into smaller pieces that can then be processed by other machines.


An Agitation Tank is a machine used in a tank for mixing various process media together. Media include all liquid types, gases & solids (such as salts, powders, granules etc). In summary, it works by rotating an impeller to impart energy to the media which interact and mix. The components of an agitator, in general, are the motor & gearbox, shaft & impellers selected for the duty.


What is the purpose of an agitator?


An Agitator is used for mixing different process media – liquids, gases and solids in chemical addition or Pharmaceutical Ingredients. The agitator imparts energy through mechanical mean by rotating a shaft on which there is an impeller designed specifically for the duty. This could be axial pumping, gas induction, flocculating, high viscosity products, high & low shear mixing etc. An agitator is also used in the Water Industry for adding various chemicals to bring the source water up to drinking water standards


An angle Grinding Equipment is a handheld power tool that can be used for a variety of metal fabrication jobs that include cutting, grinding, deburring, finishing and polishing. The most common types of angle grinders are powered by electricity; either corded or battery powered.


Which abrasives discs you select to use with your angle grinder depends entirely on your specific application and the material you are working with. Read on for more on this.


Flotation Machines constitute the basic equipment for useful minerals reco- very from non-ferrous ores and other raw materials by flotation. In the years 1963- 1976, the Institute of Non-Ferrous Metals developed a series of pneu-mo-mechanical flotation machines, which were marked by letters Iz. They were multi-cell, sluice-type machines of the individual cell volume ranging between m° and 30 m'- 1z-1, 1Z-3, 1Z-5, 1Z-12, IZ-30. They were widely used in the copper, zinc-lead and coal mining industries. The IZ-12 type still remains the basic coal flotation machine used in Poland. They also were widely exported, mainly to Brazil and China.


At the end of the 90s, in the Institute of Non-Ferrous Metals a new genera-tion of flotation machines was developed, marked with letters IF . The design philosophy has changed: the series machines have been repla-ced by flotation machines designed and manufactured according to the speci-fic requirements of customers. The sluice -type machines have been replaced by one-cell flotation machi-nes which can be linked to form a multi-cell flotation machine. They can operatealso as individual flotation cells.


Vibration Screens are equipment used to separate and transport granulated materials in various processes throughout the mining, agriculture, pharmaceutical, food,and chemical industries. Although vibrating screens have many applications, problems such as adhesion, clogging, corrosion, wear, and uneven feed distribution are still quite common. These problems are strongly related to the productivity of the process, and minimizing those problems usually results in financial, productivity and time benefits.


In applications where increasing productivity is desired, maximizing throughput is the typical focus. In this sense, it is essential that the equipment yields not only a high throughput (i.e., a substantial amount of graded granular material) but also a high capacity to separate particles into different sizes, that is, a high efficiency. The analysis of vibrating screen design efficiency is therefore very important when designing or choosing the proper equipment for certain processes.


Kilns are insulated chambers that use fuel or electricity to reach high temperatures. When something is heated in a kiln it is described as being 'fired'. There are different types of kiln to fire different materials. For example, there are kilns designed specifically for ceramics, glass, metal, brick, metal clay, and enamels.

Printed Circuit Board Introduction & PCB Types


What is PCB?

Printed circuit boards (PCBs) are the boards that are used as the base in most electronics – both as a physical support piece and as the wiring area for the surface-mounted and socketed components. PCBs are most commonly made out of fiberglass, composite epoxy, or another composite material.

Most PCBs for simple electronics are simple and composed of only a single layer. More sophisticated hardware such as computer graphics cards or motherboards can have multiple layers, sometimes up to twelve.
Although Metal Core PCBs are most often associated with computers, they can be found in many other electronic devices, such as TVs, Radios, Digital cameras and Cell phones. In addition to their use in consumer electronics and computers, different types of PCBs are used in a variety of other fields, including:


1. Medical devices. Electronics products are now denser and consume less power than previous generations, making it possible to test new and exciting medical technology. Most medical devices use a high-density PCB, which is used to create the smallest and densest design possible. This helps to alleviate some of the unique constraints involved with developing devices for the medical field due to the necessity of small size and light weight. PCBs have found their way into everything from small devices, such as pacemakers, to much larger devices like X-ray equipment or CAT scan machines.


2. Industrial machinery. PCBs are commonly used in high-powered industrial machinery. In places where current one-ounce copper PCBs do not fit the requirements, thick copper PCB can be utilized instead. Examples of situations where thicker copper PCBs would be beneficial include motor controllers, high-current battery chargers and industrial load testers.


3. Lighting. As LED-based lighting solutions catch on in popularity because of their low power consumption and high levels of efficiency, so too does aluminum-backed PCB which is used to make them. These PCBs serve as heat sinks and allow for higher levels of heat transfer than a standard PCB. These same aluminum-backed HDI Circuits form the basis for both high-lumen LED applications and basic lighting solutions.


4. Automotive and aerospace industries. Both the automotive and aerospace industries make use of flexible PCB, which is designed to withstand the high-vibration environments that are common in both fields. Depending on specifications and design, they can also be very lightweight, which is a necessity when manufacturing parts for transportation industries. They are also able to conform to the tight spaces that might be present in these applications, such as inside instrument panels or behind the instrument gauge on a dashboard.
There are several different types of circuit boards, each with its own particular manufacturing specifications, material types, and usages:


Single-layer PCB

A single-layer or single-sided PCB is one that is made out of a single layer of base material or substrate. One side of the base material is coated with a thin layer of metal. Copper is the most common coating due to how well it functions as an electrical conductor. Once the copper base plating is applied, a protective solder mask is usually applied, followed by the last silk-screen to mark out all of the elements on the board.


Multi-layer PCB

Multilayer PCBs consist of a series of three or more double-layered PCBs. These boards are then secured together with a specialized glue and sandwiched between pieces of insulation to ensure that excess heat doesn't melt any of the components. Multi-layer PCBs come in a variety of sizes, going as small as four layers or as large as ten or twelve. The largest multi-layer PCB ever built was 50 layers thick.

With many layers of printed circuit boards, designers can make very thick, complex designs which are suitable for a broad range of complicated electrical tasks. Applications where multi-layer PCBs would be beneficial include File servers, Data storage, GPS technology, Satellite systems, Weather analysis and Medical equipment.


Rigid PCB

Rigid PCBs are made out of a solid substrate material that prevents the board from twisting. Possibly the most common example of a rigid PCB is a computer motherboard. The motherboard is a multilayer PCB designed to allocate electricity from the power supply while simultaneously allowing communication between all of the many parts of the computer, such as CPU, GPU and RAM.


Rigid PCBs make up perhaps the largest number of PCBs manufactured. These PCBs are used anywhere that there is a need for the PCB itself to be set up in one shape and remain that way for the remainder of the device's lifespan. Rigid PCBs can be anything from a simple single-layer PCB all the way up to an eight or ten-layer multi-layer PCB.

All Rigid PCBs have single-layer, double-layer or multilayer constructions, so they all share the same applications.


Flexible PCB

Unlike rigid PCBs, which use unmoving materials such as fiberglass, Flexible PCB is made of materials that can flex and move, such as plastic. Like rigid PCBs, flexible PCBs come in single, double or multilayer formats. As they need to be printed on a flexible material, flexible pcb cost more for fabrication.


Rigid Flex PCB

Rigid flex circuits combine the best of both worlds when it comes to the two most important overarching types of PCB boards. Flex-rigid boards consist of multiple layers of flexible PCBs attached to a number of rigid PCB layers.


Rigid-Flex PCBs have many advantages over just using rigid or flexible PCBs for certain applications. For one, rigid-flex boards have a lower parts count than traditional rigid or flexible boards because the wiring options for both can be combined into a single board. The combination of rigid and flexible boards into a single rigid-flex board also allows for a more streamlined design, reducing the overall board size and package weight.

Flex-rigid PCBs are most often found in applications where space or weight are prime concerns, including Cell phones, Digital cameras, Pacemakers and Automobiles.


High-frequency PCB

High Frequency PCB refers to a general PCB design element, rather than a type of PCB construction like the previous models. High-frequency PCB is designed to transmit signals over one gigahertz.



High-frequency PCB materials often include FR4-grade glass-reinforced epoxy laminate, polyphenylene oxide (PPO) resin and Teflon. Teflon is one of the most expensive options available because of its small and stable dielectric constant, small amounts of dielectric loss and overall low water absorption.


Many aspects need to be considered when choosing high-frequency PCB board and its corresponding type of PCB connector, including dielectric constant (DK), dissipation, loss and dielectric thickness.

Touch screen


A Capacitive Touch Screen is a display device that allows the user to interact with a computer using their finger or stylus. They're a useful alternative to a mouse or keyboard for navigating a GUI (graphical user interface). Touch screens are used on a variety of devices, such as computer and laptop displays, smartphones, tablets, cash registers, and information kiosks. Some touch screens use a grid of infrared beams to sense the presence of a finger instead of utilizing touch-sensitive input.


Touch screen history


The idea of a touch screen was first described and published by E.A. Johnson in 1965. In the early 1970s, the first touch screen was developed by CERN engineers Frank Beck and Bent Stumpe. The physical product was first created and utilized in 1973. The first resistive touch screen was developed by George Samuel Hurst in 1975 but wasn't produced and used until 1982.


What computers support a touch screen?


Today, all PCs support the ability to have a Surface Capacitive Touch Screen, and most laptop computers allow users running Microsoft Windows 10 to use a touch screen. Also, many all-in-one computers are capable of using a touch screen. Computer manufacturers with products that have touch screens include Acer, Dell, HP, Lenovo, Microsoft, and other PC manufacturers.


There are also some high-end Google Chromebooks with touch screens. However, to help keep the costs lower, many Chromebooks do not have touch screens.


How do you use the touch screen?


Tap - A single touch or tap on the screen with a finger opens an app or select an object. When compared to a traditional computer, a tap is the same as clicking with a mouse.


Double-tap - A double-tap can have different functions depending on where it is utilized. For example, in a browser, double-tapping the screen zooms the view, centered at the tap location. Double-tapping in a text editor selects a word or section of words.


Touch and hold - Pressing and holding your finger to a touch screen selects or highlights an object. For example, you could touch and hold an icon, and then drag it somewhere else on the screen. See our long press page for further information on this term.


Why is a touch screen an input device?


Any computer device (including a touch screen) that takes input from the person operating the device is considered an input device. The way you use your finger on a Resistive Touch Screen is very similar to how you use a computer mouse on a desktop computer.


How is a touch screen different than a mouse?


A computer mouse and touch screen have many similarities. Many of them are mentioned in the how do you use the touch screen section above.


One of the most significant differences between a mouse and a Raspberry Pi Touchscreen is the ability to hover. Almost all touch screens can only detect input when your finger is in direct contact with the screen. However, a computer mouse uses a cursor that allows the user to view the information by moving the pointer over an object, but not clicking it. For example, this link to Computer Hope shows the text &quot;Visit the Computer Hope Page&quot; when hovered over using a computer mouse. However, a user with a touch screen cannot see this text because if they place their finger on the link, it opens the link.


Why are touch screens used?


Below are the reasons a manufacturer may decide to use a Touch LCD Screen Assembly, instead of another input method, such as physical buttons.


Touch screens are intuitive, especially to younger generations of users.


Having one touch screen instead of several buttons can make a device smaller.


Cheaper to design and manufacture a device with one screen instead of on with a screen and buttons.


Touch screen technologies


Not all LCD Display touch screens are the same. Different technologies can be utilized to allow a user to interact with a screen. Some technologies may work with only your finger, and other technologies may allow other tools, like a stylus. Below is a brief description of each of these technologies.

Grippers


A gripper is a motion device that mimics the movements of people, in the case of the gripper, it is the fingers. A gripper is a device that holds an object so it can be manipulated. It has the ability to hold and release an object while some action is being performed. The fingers are not part of the gripper, they are specialized custom tooling used to grip the object and are referred to as &quot;jaws.&quot; Two main types of action are performed by grippers: External: This is the most popular method of holding objects, it is the most simplistic and it requires the shortest stroke length. When the Pneumatic Centering Gripper jaws close, the closing force of the gripper holds that object. Internal: In some applications, the object geometry or the need to access the exterior of the object will require that the object is held from the center. In this case, the opening force of the gripper will be holding the object.


How does a gripper work?


The most widely used gripper is the pneumatically powered gripper; it is basically a cylinder that operates on compressed air. When the air is supplied, the gripper's jaws will close on an object and firmly hold the object while some operation is performed, and when the air direction is changed, the gripper will release the object. Typical uses are to change orientation or to move an object as in a pick-n-place operation.


Major Factors in Choosing a Pneumatic Gripper and Jaw Design:


When choosing a pneumatic gripper and jaw design, these ate the major factors to consider: 1. Part shape, orientation, and dimensional variation If the object has two opposing flat surfaces, then 2 Jaw Parallel Gripper is desired since it can handle some dimensional variation. Jaws can also be designed to handle cylindrical objects with the 2 jaw concept. Keep in mind that retention or encompassing grip requires much less force. 2. Part Weight Grip force must be adequate to secure the object while a desired operation is performed on the object. The type of jaw design must be part of the force requirement. Keep in mind that you should add a safety factor to the amount of force that you select and air pressure is a factor to keep in mind. 3. Accessibility This applies both to the work being performed on the object and the amount of room for the gripper jaws. If the work is to the exterior of the object then it may require an internal grip. Angular grippers are usually less expensive but require additional space for jaw movement. 4. Environmental Harsh environments or cleanroom applications require grippers designed for those purposes. 5. Retention of the Object When air pressure is lost, the gripper will relax its grip on the object and the object may be dropped. There are spring assist grippers designed for this type of application.






Choose the right gripper for your automated process


Pneumatic Parallel Gripper


A parallel gripper opens and closes parallel to the object that it will be holding. These are the most widely used grippers. They are the simplest tool and can compensate for some dimensional variation.



Pneumatic Angular Gripper



An Angular gripper moves the jaws in a radial manner to rotate the jaws away from the object. This allows for the jaws to move completely away from the object. The object may also be fed directly into the jaws and possibly eliminate one additional motion.


What is a Robotic Tool Changer (QC)?


An end-effector with two mating parts, a Master-side and a Tool-side that have been designed to lock or couple together automatically, carry a payload, and have the ability to pass utilities such as electrical signals, pneumatic, water, etc. Most robot couplers use pneumatics to lock the Master- and Tool-sides together. The Automatic Robotic Tool Changers provide the flexibility for any automated process to change tools and pass various utilities. The Master-side of the Tool Changer mounts to a robot, CNC machine, or other structure. The Tool-side of the Tool Changer mounts to tooling, such as grippers, welders, or deburring tools. A Robot Tool Changer is also known as a Quick-Change device (QC), an automatic tool changer (ATC), robot tool changer, robot coupler, robotic coupler, or robotic connector.

HOW TUBE AND PIPE MILLS WORK

Tube Mill Machine Lines produce pipe and tube by taking a continuous strip of material and continuously roll forms it until the edges of the strip meet together at a weld station. At this point, the welding process melts and fuses the edges of the tube together and the material exits the weld station as welded tube. Basic components include an uncoiler, straightener, shear, forming section, fin pass section, welder, ID and/or OD scarfing, sizing section, cut off and stacker or runout table.


Each pass in the various sections are made up of a upper and lower shaft that contains roller die tooling which forms the steel strip gradually into a round shape or square if it is a form square / weld square type of mill. This gradual shaping process is commonly referred to as the flower arrangement.


Tube formed metals can be used in many different industries, such as gas, water and sewage piping, structural, industrial, and scaffolding piping. Additionally, your Carbon Steel Tube Mill Machine can produce hollow, rectangular, round or square piping.


We typically have a few select pieces of machinery available for purchase or can search the marketplace for the piece of equipment that best suits your needs. Our team is ready to help you with the right solution for your business.


With over 60 years of experience and a real focus on customer satisfaction, you can rely on ASP for your next project.


We provide professional renovation and installation services with a real focus on customer satisfaction. We have proven results for setting exceptional standards in cost control, planning, scheduling and project safety. We have experience that gives us a competitive advantage over others in our field.


Galvanized Tube Mill Machines produce pipe and tube by taking a continuous strip of material and continuously rollforming until the edges of the strip meet together at a weld station. At this point the welding process melts and fuses the edges of the tube together and the material exits the weld station as welded tube. Basic components include an uncoiler, straightener, shear, forming section, fin pass section, welder, ID and/or OD scarfing, sizing section, cut off and stacker or runout table.


Each pass in the various sections are made up of a upper and lower shaft that contains roller die tooling which forms the steel strip gradually into a round shape or square if it is a form square / weld square type of mill. This gradual shaping process is commonly referred to as the flower arrangement.
ASP can provide you a turn-key solution for all your New, remanufactured and used tube mill needs.


Tube Mill Components operator face a variety of challenges every day in their effort to produce high-quality tubing in a cost-effective and productive way.


This article examines some of the typical problems producers encounter, some common causes of these problems, and some ideas for how to solve these problems.


Lost Mill Time During Operation and Changeovers


Often, excessive downtime during normal operation or tooling/job changeover can be attributed to one or more of the following causes:


1. No written procedures for setup. Every mill should have written procedures for all operators to follow. The machine, tooling, and steel are fixed factors in the mill setup equation; the only variable is the human factor. This is why it is so important to have written procedures in place to control the process. Written procedures also provide a tool for troubleshooting when problems arise.


2. No setup chart. Tweaking the Cold Rolling Mill during setup loses valuable setup time. Operators must work the tooling the way it was designed. This means setting up to the parameters of a setup chart.


3. Lack of formal training. Formal training helps operators perform the procedures for tube mill operation and maintenance and ensures that all operators are on the same track.


4. Disregard of parameters from previous setup. If the tube mill has been set up according to the written procedures and setup chart, the operator can write down the numbers from the digital readout on the single-point adjustment (SPA) unit, allowing the next operator to set up where the first left off. Setting up to the numbers can save as much as 75 percent of total setup time, as long as all the other tips discussed in this article are followed.


5. Mill in poor condition. A poorly maintained mill costs valuable time and scrap during setup and operation. The mill must be dependable so that the operator is not chasing mechanical problems during normal operation and setup. A good maintenance program, as well as rebuilds or upgrades when necessary, is essential.


6. Mill in misalignment. Tube mill misalignment, poor mill condition, and inaccurate setup account for 95 percent of all problems in tube production. Most mills should be aligned at least once a year.

Effect of a herbal extract powder

Effect of a herbal extract powder
In the manufacture of herbal medicinal tablets, dried plant extracts are employed as the therapeutic ingredient. These powders, usually obtained by spray drying, are typically hygroscopic and possess poor flow and compactability for the manufacture of tablets by direct compression (DC). Besides, spray-drying operating conditions and liquid feed composition are reported to be dependent on the herbal medicine. Consequently, the production of dried extracts implies long new product development times. Therefore, the goal of this paper was to: (a) provide recommendations as initial production point of fruit powder suitable for DC by spray drying and (b) study the powder properties to identify those that are affected by the extract nature. Particularly, a unique set of operating conditions was found to be appropriate to produce powders of seven different medicinal plant extracts. In fact, all the spray-dried products showed adequate flowability, stability and compactability.


Powders properties, as particle size and morphology, moisture content, hygroscopicity, flowability and compact hardness were not a function of the type of herb. Conversely, the process yield and glass transition temperature, particle and bulk densities, powder composition, compact porosity, wetting and disintegration times were found to be dependent on the chemical nature of the herbs.


Graphical abstract


A single set of spray-drying operating conditions and a unique liquid feed formulation are proposed to process different aqueous medicinal extracts in order to obtain powders with adequate flowability, stability and compactability.


Fermented plant extract (FPE) is a kind of plant functional food fermented by various microorganisms to make a beverage or other physical forms. To provide technical support for the industrial production of gynostemma extract powder, the quality characteristics of fermented plant extract prepared by hot air-drying, spray drying, vacuum microwave drying, and freeze-drying are compared for an FPE product. The effects of maltodextrin, soluble starch, and β-cyclodextrin as a drying agent on drying effect were studied. Results show that spray-dried FPE powder has the highest bulk density, the smallest average particle size, while the vegetable powder produced by freeze-drying has the best color and flavor, the highest content of key components including total sugar, soluble protein, vitamin C, total polyphenol content, and highest antioxidant capacity.


Nature has always been, and still is, a source of foods and ingredients that are beneficial to human health. Nowadays, plant extracts are increasingly becoming important additives in the food industry due to their antimicrobial and antioxidant activities that delay the development of off-flavors and improve the shelf life and color stability of food products. Due to their natural origin, they are excellent candidates to replace synthetic compounds, which are generally considered to have toxicological and carcinogenic effects. The efficient extraction of these compounds from their natural sources, along with the determination of their activity in the commercialized products, have been great challenges for researchers and food chain contributors to develop products with positive effects on human health. The objective of this Special Issue is to highlight the existing evidence regarding the various potential benefits of the consumption of plant extracts and plant extract-based products, with emphasis on in vivo works and epidemiological studies, the application of plant extracts to improve shelf-life, the nutritional and health-related properties of foods, and the extraction techniques that can be used to obtain bioactive compounds from plant extracts.


Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.


Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Foods is an international peer-reviewed open access semimonthly journal published by MDPI.


Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2200 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.


Obesity is a condition involving excessive accumulation of body fat that may impair health. The global prevalence of obesity has risen dramatically, increasing more than 2-fold since 1980. In 2014, over 1.9 billion adults worldwide were overweight, of which more than 600 million were estimated to be obese [1]. Obesity contributes to the development of hypertension, dyslipidemia, type 2 diabetes mellitus, coronary artery disease, and stroke, as well as overall mortality [2]. Obesity also leads to an increase in socioeconomic burden. The total socioeconomic costs of overweight and obesity in Korean adults in 2005 were estimated to be approximately US$1.8 billion, equivalent to 3.7% of the national health care expenditure for that year [3]. Hammond et al. [4] suggested that the total annual economic costs associated with obesity in the United States are in excess of US$ 215 billion. Development and implementation of cost-effective interventions for obesity prevention and management are essential to reduce the huge economic burden of obesity [5].


Treatment of obese patients requires a multifaceted approach, including dietary therapy, regular physical activity, behavioral therapy, and/or pharmacotherapy [6]. Comprehensive lifestyle intervention is foundational to obesity management, and adjunctive pharmacotherapy may be considered for individuals who are unable to achieve or maintain weight loss with comprehensive lifestyle intervention and have a body mass index (BMI) ≥30 kg/m2, or ≥27 kg/m2 with comorbidity [7]. Although the addition of weight loss medications to a lifestyle modification intervention can help obese individuals achieve greater weight loss, their body weight can rebound if they stop taking the medications. Since the withdrawal of sibutramine in 2010 because of the risk of serious cardiovascular adverse events, concerns about the safety of anti-obesity medications have led to a steady decline in prescription and use of these medications [8]. Due to the high costs, serious complications, and limited duration of effectiveness of anti-obesity drugs, there has been growing interest in and use of relatively inexpensive, safe, and effective functional food products from natural sources that are capable of aiding weight loss [9, 10].


Plants are considered good natural sources of bioactive compounds with potential anti-obesity properties [11, 12]. These plant-derived anti-obesity compounds induce weight loss through various mechanisms, including regulating lipid metabolism, suppressing food intake, and stimulating energy expenditure [10, 11]. However, there is still a paucity of data on the efficacy and safety of herbal plant preparations in obesity treatment. In order to provide obese patients with accurate and reliable information about effective and safe natural anti-obesity agents, there is a need for high-quality studies on the efficacy and safety of natural herbal products that claim to exert a weight reducing effect [13, 14]. In Korea, it is possible for a health functional food with body fat reducing effects to be approved for use after review, by the Ministry of Food and Drug Safety, of results of a clinical trial on the efficacy and safety of the product [15].


YY-312 is a acer truncatum bunge extract from Imperata cylindrical Beauvois, Citrus unshiu Markovich, Evodia officinalis Dode [16]. These plants have been commonly used as medicinal herbs in Korea, and have been reported to have health promoting effects, including reduction of body fat. Evodiamine, a major alkaloidal compound extracted from Evodia officinalis Dode, was thought to elicit anti-obesity effects through uncoupling protein-1 (UCP1) thermogenesis, but it was also suggested to have the potential to prevent obesity by inhibiting adipocyte differentiation through stimulating the extracellular signal regulated kinase (ERK)/mitogen activated protein kinase (MAPK) signaling pathway [17]. Citrus unshiu Markovich, the peel of immature citrus fruit in the Rutaceae family, is known to have plenty of flavonoids [18]. Citrus peel extracts have been reported to exert an anti-obesity effect through the promotion of β-oxidation and lipolysis in adipose tissue [19]. Imperata cylindrical Beauvois, the root of cogongrass in the Poaceae family, is known to have potent anti-oxidant activity due to its abundant polyphenols [20].


A previous study showed that YY-312 has an anti-obesity effect in high-fat diet (HFD)-induced obese mice and that it suppresses adipocyte differentiation in 3 T3-L1 cells [16]. However, it can be ascertained only through human clinical trials whether the individual ingredients in YY-312 have a synergistic effect in the human body, or whether their interactions augment toxicity. Hence, this randomized controlled trial was conducted to evaluate the efficacy and safety of YY-312 for body fat reduction in overweight Korean adults.

Nuts, bolts, screws, and washers


Nuts, bolts, screws, and washers

This chapter starts with tips on drawing hexagon nuts and hex bolts and comprehensively covers, using illustrations, tables of size and explanations on usage, the majority of metric fixings and fasteners used in engineering today i.e. screws of the Hexagon Socket type such as Cap Head Screws, Shoulder Screws, Button Head Screws, Countersunk Head Screws and Set Screws. Machine Screws such as Phillips and Slotted Pan Head, Countersunk and Raised Countersunk Head, Slotted Cheese Head are also included as are Machine Screw Nuts, Wing Nuts and Locking and Retaining Devices such as Slotted Nuts and Castle Nuts Simmonds Locknut, Spring Washers, Shakeproof Washers, Wire Locking, Tab Washers, Locking Plates, Taper and Parallel Pins, Split Cotter Pins, locking by Adhesives and Peening. Finally thread cutting screws are covered with recommendations on installation.


A bolt, as you may recall, is a parallel-sided shaft with an inclined plane or helical groove wrapped around it. A screw bolt is similar except that its sides are tapered, not parallel. Alternatively, one could say that a screw is cone shaped while a bolt is cylindrical. This fine distinction between a bolt and a screw is not appreciated by most people, who might believe that screws are little fasteners tightened with a screwdriver while bolts are larger fasteners tightened with a wrench. No matter how you view them, bolts and screws have much in common. Both stretch a bit while being tightened, both spread the load over several threads, and both will break if over tightened. Screws, however, unlike bolts, cut their own mating thread as they are tightened. This is a key difference from a bolt, which must have a machine-threaded mating hole. Furthermore, repeated removal and reinsertion will cause the screw hole to become just a bit larger in diameter. After too many cycles, the hole no longer fits the screw (sometimes termed hole "wearout") and we must employ some remediation technique—see "Remediating Hole 'Wearout'."


Screws are often categorized in terms of application (wood, sheet metal, drywall, concrete, etc.); head configuration; and sometimes (when it's uncommon) driving method. Button-head sheet metal, roundhead wood, flathead drywall, and TORX-head cabinet screws are but a few common examples. Head descriptions such as pan, button, truss, and oval confuse most people, and for good reason. Each description evokes different mind pictures for different people—my pan probably isn't shaped like your pan, and would that be a saucepan or a sauté pan? What is a "fillister" and what does it look like, and just what exactly is a cabinet screw anyway?


You likely know the two main screw driving types—slotted and Phillips—but there are many others out there. Besides a number of Phillips-lookalikes, screw manufacturers have devised other slot designs that facilitate assembly line operations or prevent tampering by keeping unauthorized individuals from gaining access to the interior of equipment. While the Phillips-design screw and driver combination purposely allows the driver to slip out under high torque conditions to prevent over tightening, other similar styles such as the Pozidriv and the Reed & Prince (also known as the "Frearson") screw drive have a slightly different shape, designed not to slip out under high torque conditions. Both are more likely to shear the screw head off than allow the driver to slip out of the screw head. The same holds true for the Japanese Industrial Standard (JIS) screw that is commonly found in Japanese-manufactured equipment.


Other drive styles include the TORX, Hex (or "Allen"), Robertson, Square, Tri-Wing, Torq-Set, Spanner, and Clutch Types "A" and "G." Many of us who work on our own automobiles or computers are familiar with the TORX drive's six-rounded-point star pattern. Both the Robertson (used primarily in Canada) and Square (the American clone) drive screws are similar in appearance, but the Robertson head has a slight wedge shape, allowing the driver to hold the screw horizontally or even downward without it falling off the driver. The Square-drive head is not tapered, and is therefore slightly larger than the driver, thus making it more likely to strip or round-out than the Canadian original. Tri-Wing screws, with their triangular slotted configuration like a three-lobe Phillips design, are used by some video game manufacturers to hide their inner workings from curious eyes, but are rarely found on medical equipment. Spanner heads are frequently seen in elevators securing the control panel in the elevator's cab. Both Tri-Wing and Spanner designs are meant to be tamper-resistant due to their unique head design and rarity of drivers. Clutch Type "A" screws resemble a bow tie and were commonly used to secure body panels on General Motors vehicles during the 1940s and 1950s. The Clutch Type "G," commonly used in the manufacture of mobile homes and recreational vehicles, looks like a butterfly.


For the do-it-yourselfer at home (which many biomeds are, whether it is building cabinetry or working on cars), there are several techniques to remediate hole wearout. I don't, however, recommend employing any of these on the job in critical or load-bearing applications for obvious reasons!


The most common technique when faced with hole wearout is to simply use a larger screw. This is not always advisable—some would object to the appearance of a single larger screw in a row of screws, thus requiring the replacement of all screws and the need to enlarge all the other holes as well. Other times, the mating material is too thin to use a larger diameter screw with its wider thread. Fortunately, if one is working with wood, shimming the hole with wood (flat toothpicks work well for this) and glue works in most cases. Metal is another story, however. Sometimes you can shim the hole with a dab of epoxy, using the screw to cut threads in the glue until it is in its plastic state, then removing the screw while the epoxy completes hardening. If one is very careful, a nut can be glued (cyanoacrylic adhesives are good for this) to the backside of the oversize mating hole and a so-called "machine screw" be used in place of the original screw. If one has access to the blind side, a nut and "machine screw" might be used in place of the original screw. In desperation, resort to any of a number of specialty devices intended to mount sheet metal and provide a captured machine screw joint.


"Tamper-resistant" or "security-head" screws are usually variants of the common designs. A supposed tamper-resistant version of the TORX screw includes a small pin in the center recess to prevent using a slotted or Phillips screwdriver, or even a common TORX drive, which can be purchased at a hardware store. The downside of this tamper-resistant design is the ease with which the pin can be removed with a pair of needle-nose pliers or a hand-held grinder. Variants feature sloping edges so that the screw can be driven in, but the bit slips out when trying to remove the screw. A third type of security or tamper-resistant design features unusual proprietary designs mating with drivers only available from the screw manufacturer and only sold to registered owners. These types of screws are not popular with medical equipment manufacturers, and biomeds seldom run across them. When we do, we have several courses of action to follow:


Purchase the tool from the medical equipment manufacturer.


Attempt to buy the appropriate tool from the screw manufacturer (generally the organization's purchase order or a letter request on letterhead is sufficient to prove that the purchase is not for a nefarious purpose).


Have the appropriate tool fabricated by a local machine shop.


Grind or chisel the head off, use a screw extractor to remove the remains, and then replace it with a more common screw. (If some measure of security is desired, use a tamper-resistant TORX screw in its place.)


Screws, washers, and other fastening hardware are made from a wide range of materials. Steel is the most common, but special applications call for other metals more suited to the environment. Copper, brass, and bronze are most commonly used in damp or submerged applications where rusting cannot be tolerated. Where higher physical strength and rust resistance is required, a nickel-base alloy, corrosion resisting (a.k.a. "stainless") steel, or titanium is used. Plastics such as nylon or Teflon are used when moderate strength is needed and absolutely no rust or fluid interaction can be tolerated. Where electrolytic action (from the mating of different metals) is a concern, fasteners are either made of the same material as the metals being joined—aluminum instead of steel, for example—or of plastic. Where electrical insulation is required, plastic fasteners are most commonly used.


Washers


Washers were originally used for three purposes—to spread the compressive load or anchoring pressure over a larger load-bearing area, to relieve friction, or to prevent leakage. Common flat washers are, as the name implies, a flat disk, usually round and with a hole in the middle, made of metal, plastic, rubber, or leather. Their thickness allows the relatively small diameter head of a fastener, such as a screw or small bolt, to spread its compressive force over a larger diameter (approximately that of the washer's outside diameter) thus reducing stress at the edges of the mounting hole. For example, a printed circuit board could be fastened to a standoff with a screw and a flat washer. The washer spreads the pressure of the screw over a larger area than just the screw head, thus preventing the board from cracking. "Thrust washers" absorb friction between shaft-mounted components by acting as an intermediate or buffer piece between two rotating parts. Thrust washers are often used inside motors and in linear mechanical assemblies as spacers. Washers used as seals around immersion heaters and in water lines are familiar to just about every biomed in the field.


Over time, washers have evolved from the three basic types to a plethora of designs for a number of common and unique purposes. The most commonly encountered include four types of lockwashers (split, internal tooth, external tooth, and spring); fender washers; trim washers; and square washers. The split lockwasher, as the name implies, looks like a regular flat washer made of spring metal (usually a steel) with a cut from the center to the perimeter. The ends of the cut appear to have been bent apart in an up-and-down fashion. (Note: If the ends appear to be opposite each other, without a distinct bend in the washer, discard the washer and use a new one.) As the washer is compressed, the ends are slightly wedged into the fastener (usually a screw, bolt, or nut) and the item being fastened (like a cover or a clamp) to prevent the fastener from unscrewing under vibration. Internal and external tooth lockwashers are similar in that they have teeth pointing either toward or away from (respectively) the center hole and spread their compressive force in the same direction that the teeth point. When compressed, the teeth grab both parts being compressed to prevent the fastener from unscrewing. The last type of lockwasher is the spring washer. Spring washers are formed in an irregular shape, usually wavy, so that it acts like a spring when compressed. The resultant pressure prevents (within the limits of its design) the fastener from unscrewing. Biomeds often will encounter thrust and spring washers on the same rotating shaft, with the spring washer providing a fairly constant tension to eliminate rattle, take up slack, reduce play to a tolerable level, and/or to provide a controlled reaction to intermittent shock. Some commonly found biomed applications include clutch assemblies, air compressors, and some portable x-ray unit drive trains.


A fender washer is an oversized flat washer, distinguished by its relatively large diameter compared to the hole at the center. These washers spread their compressive force over a larger area than a common washer does and are especially useful in preventing cracking when securing plastic parts with smallish screws. Trim washers appear in a variety of forms, all of which provide a "finished" look in final assembly. By design, trim (or finishing) washers blend well with both their fastener and surroundings. They provide a smooth and eye-appealing transition between a screw and a panel. Often a trim washer, a cabinet screw (a screw with a hole in its top designed to hold a plastic cap piece), and its cap form an "inconspicuous" fastening system in consumer-assembled furniture such as bookcases, entertainment centers, and chests of drawers. Square washers can be used in special applications where round hardware would inappropriate or unusable, such as a corner application.


Armed with this basic knowledge of fastener design, terminology, and application, the biomed is now able to better select the correct fastener for the application. By the way, about that "panhead" screwhead—I think it looks more like a rounded sauté pan than a saucepan.


Author notes


Robert Dondelinger, CBET-E, MS, is the medical equipment manager at the U.S. Military Entrance Processing Command in North Chicago, IL. An internationally certified biomedical electronics technician, he entered the U.S. Army in 1970 and retired from active duty in 2002.

Intraoperative Invasive Blood Pressure Monitoring and the Potential Pitfalls

Intraoperative Invasive Blood Pressure Monitoring and the Potential Pitfalls
Invasive intraarterial blood pressure measurement is currently the gold standard for intraoperative hemodynamic monitoring but accurate systolic blood pressure (SBP) measurement is difficult in everyday clinical practice, mostly because of problems with hyper-resonance or damping within the measurement system, which can lead to erroneous treatment decisions if these phenomena are not recognized. A hyper-resonant blood pressure trace significantly overestimates true systolic blood pressure while underestimating the diastolic pressure. Invasively measured systolic blood pressure is also significantly more affected than mean blood pressure by the site of measurement within the arterial system. Patients in the intraoperative period should be treated based on the invasively measured mean blood pressure rather than the systolic blood pressure. In this review, we discuss the pros/cons, mechanisms of Disposable IBP Transducers, and the interpretation of the invasively measured systolic blood pressure value.


Introduction & Background


Disposable IBP Transducer Kit-Single Channel is the gold standard of arterial pressure measurement in 10-20% of high-risk patients [1-2]. In the remaining 80%-90% of surgical patients, the standard intermittent non-invasive blood pressure (BP) that is obtained using oscillometry with a brachial cuff has been shown to have only poor agreement with IBP in critically ill patients [3-4]. These observed measurement differences are clinically significant because they would have triggered a change in treatment in as many as 20% of the critical care patients. Non-invasive oscillometric BP measurement with a brachial cuff tends to, on average, overestimate BP during hypotension and underestimate BP during hypertension, with a significant bias and considerable scatter. Invasive BP measurement with an arterial catheter, providing continuous BP measurements, detected nearly twice as many episodes of hypotension as intermittent oscillometric measurements with a brachial cuff [5]. Continuous rather than intermittent hemodynamic monitoring is highly desirable in high-risk patients. Even when continuous BP monitoring was accomplished in medium-risk patients with non-invasive techniques, the number of episodes of intraoperative hypotension was still reduced by half when compared to intermittent monitoring with a brachial cuff [6]. Although non-invasive continuous monitoring has fewer complications than arterial cannulation, it has not yet Disposable IBP Transducer Kit-Double Channel as the gold standard in high-risk patients, but rather serves as an alternative in low and medium-risk patients where IBP measurements are not warranted [7].


An adequate blood pressure level is a means to achieve the ultimate goal of the circulation, which is adequate end-organ perfusion and tissue oxygenation. Adequate organ perfusion is mostly regulated locally, in the organs, by changing the local vascular resistance, which, when seen over multiple organs and the entire circulation, works as a re-distribution of the total flow or cardiac output (CO) [8]. In addition, the total flow or CO is also regulated centrally if this re-distribution is not enough. The local flow control via regulation of resistance of the arterioles only functions properly under the condition of adequate perfusion pressure, in which the mean systemic arterial pressure plays a central role. Continuous monitoring of local organ circulation, global flow, or CO and arterial pressure is, therefore, the key. Monitoring the microcirculation has been shown to be useful when determining the optimal BP range that is associated with adequate regulation of local blood flow and tissue oxygenation for an individual patient [9-10]. Pulse contour analysis provides a means of assessing global flow or CO because it has long been recognized that an apparently adequate BP level may not necessarily be associated with an adequate total blood flow to all the tissues [11-12]. Different organs have a different range of perfusion pressures that allow for adequate local control of organ flow. While the coronary circulation can increase flow fivefold as long as heart rate is maintained at 70 bpm, diastolic arterial pressure is maintained at adequate levels and coronary obstructive lesions are absent, the kidney is much more sensitive to decreases in perfusion pressure [13]. The average lower limit of cerebral blood flow autoregulation in normotensive adult humans is around a mean arterial pressure (MAP) of 70 mmHg [14]. Hence, the heart has a greater range of adequate perfusion pressures than both the brain and the kidneys. Blood pressure goals as adequate perfusion pressure ranges, therefore, need to be specifically determined and adjusted for every individual clinical situation by considering the patient's specific comorbidities as well as the planned surgical procedure.


Blood pressure and surgical outcomes&nbsp;


Although the real target is adequate total blood flow and adequate local flow to individual organs, most outcome data are available for blood pressure. Hypotension has been associated with increased postoperative morbidity. Even short durations of intraoperative MAP less than 55 mmHg are associated with myocardial injury and acute kidney injury (AKI) [15]. A perioperative quality initiative consensus statement also concluded that even brief durations of systolic arterial pressure <100 mmHg and mean arterial pressure <60-70 mmHg are harmful during non-cardiac surgery even without prospective studies [16]. Patients with preoperative hypertension may be more susceptible to complications from perioperative hypotension [17]. In contrast to hypotension, the degree of hypertension that is associated with harm to the patient is more difficult to define. In adult non-cardiac surgical patients, there is insufficient evidence to recommend a general upper limit of arterial pressure at which therapy should be initiated, although systolic blood pressure (SBP) above 160 mmHg has been associated with myocardial injury and infarction [18].


How is IBP measured?


Disposable IBP Transducer Kit-Triple Channel, in essence, replaces a small part of the wall of an artery with a stiff membrane inside a pressure transducer. To achieve this, it requires the cannulation of an artery with a stiff short catheter and the use of a short and stiff tube to connect the cannula to the transducer. In order to measure pressure, a hydrostatic reference level needs to be defined - usually, this is the level of the right atrium - and the transducer needs to be kept at the correct reference level all the time. Each component of the measurement system - transducer, hydrostatic leveling, cannula, tubing - will introduce inaccuracies or measurement errors.


Transducer


The transducer nowadays is almost always a disposable pressure transducer, which is factory-calibrated by the manufacturer. The accuracy of the disposable transducers typically is better than the accuracy required of less than ±3% or ±3 mmHg by the International Organization for Standardization/American National Standards Institution (ISO/ANSI) standard [19-20]. It needs to be zeroed, and since transducers are prone to baseline drift, this should be performed at regular intervals. In terms of quantitative error, these effects will cause a small bias of less than 3 mmHg, which is not clinically relevant in routine patient monitoring but should be considered in research or validation studies.


Leveling


The pressure transducer should be placed at heart level; by convention, this is set at the level of the right atrium. A leveling error of 10 cm will cause a measurement error of 7.4 mmHg. In clinical practice, a mean error of 3 mmHg with a standard deviation of 2 mmHg has been reported [21-22]. Again, this is probably not clinically relevant in routine patient monitoring but to be considered in research or validation studies. A more unpredictable component of leveling error is in the position changes of the operating table (rotation, tilting) where it may be difficult to maintain the proper reference position at the right atrium. It will certainly add to the overall error and is hard to quantify.


Resonance and damping


The combined system of cannula, tubing, and transducer can be seen as a second-order transmission line that guides the intra-arterial pulse wave to the transducer membrane [23-24]. This second-order system can be characterized by its natural or resonance frequency and its damping factor [25-26]. The natural frequency of the measurement system must exceed the frequency range of the arterial pulse, which extends to 20-25 Hz [23,27] or 20-22 harmonics when the goal is to accurately determine the maximum rate of pressure during isovolumetric contraction (dP/dtmax) of the systolic upstroke [28]. Higher natural frequencies can be obtained by making the cannula and the connective tubing shorter, wider, and stiffer [23,29-30]. The systems also exhibit damping, caused by friction and the viscosity of the filling fluid. Critical damping is the amount of damping required to prevent overshoot. The damping coefficient of a critically damped system is 1, however, this results in a relatively slow responding system. A damping coefficient of 0.64, sometimes called optimal damping, provides a good compromise between responsiveness and distortion. In theory, with such a damping coefficient, the amplitude is accurately measured up to 2/3 of the natural frequency, within 2%, and only shows a distortion of 6% at the natural frequency. In clinical practice, however, natural frequencies ranging from 12 to 25 Hz and damping coefficients ranging from 0.12 to 0.33 are observed [21,23,26,31-33], indicating that in clinical practice, the system is often underdamped with resonance frequencies in the same range as the frequency content of the pressure signal. An artificial increase in IBP has also been observed when the three-way stopcock is in an off-center position. On the other side, blood clots, kinking in the cannula, clamping of the arterial line tubing [34], air bubbles in the tubing, or narrow, long, or compliant tubing can cause the system to be over-damped, with damping coefficients larger than the critical damping. Whenever a dampened trace is encountered in clinical practice, the cause should be investigated. Damping will result in under-reading of SBP and dP/dtmax and over-reading of diastolic blood pressure (DBP). In under-damped situations, SBP average over-estimation was as large as 28.5 ±15.9 (mean±SD) mmHg [26] where the large scatter could be caused by the error varying with frequency and heart rate. Even adequate systems according to the criteria proposed by Gardner [35] showed an SBP over-estimation of 2.6±1.9 (mean±SD) mmHg [33].


Physicians need to be aware that especially the invasively measured SBP may be inaccurate in a significant number of patients and pay attention to the shape of the arterial blood pressure waveform due to damping and resonance phenomena. Wrong and potentially harmful therapeutic intervention may be undertaken by health care providers who have not been trained to recognize these resonances and damping artifacts because they will misinterpret the SBP value displayed on the monitor as the real SBP [25]. The BP waveform is a complex amalgamation of both antegrade and retrograde (reflected) pressure waves and is affected by vascular compliance, distance from the left ventricle (LV), and the 3D structure of the vascular tree [31]. The MAP is easier to measure accurately because it is less affected by damping and resonance than SBP and DBP. An under-damped, hyper-resonant trace, for example, overestimates while a damped trace underestimates SBP (Figure 1). The MAP is not significantly affected by these phenomena and is essentially the same for both traces.


Problems occur in clinical practice when a hyper-resonant IBP Transducer Core Part trace overestimates the SBP and a surgeon decides, for example, to limit the SBP to 100 mmHg when the patient is separating from cardiopulmonary bypass (CPB). If there is insufficient damping in the system, the measured SBP will be 100 mmHg while the MAP at the same time may be too low to provide adequate coronary perfusion. The patient may then have to be placed back urgently and perhaps unnecessarily onto CPB due to the erroneous overestimation of the SBP as a result of this hyperresonance artifact. The effects of resonance and damping must therefore be carefully considered whenever making treatment decisions based on the SBP. If the trace looks hyper-resonant or over-damped, the treatment decisions should be based on the MAP. If clinicians insist on making treatment decisions based on SBP then the damping within the measurement system must first be optimized before it is safe to use SBP to guide therapy.&nbsp;


The industry has recognized this potential for SBP to be overestimated as a major problem and is evaluating filtering methods for acquiring radial intra-artery BP waveforms [32]. Determining the natural frequency and damping factor of the IBP measurement system for each individual patient is, however, widely regarded as too cumbersome to find acceptance in routine clinical practice. This rather labor-intensive process is mandatory in research and validation studies that seek to measure SBP accurately [32]. Algorithms that identify erroneous invasively measured BP readings have also been developed [33].


Increasing the damping of a catheter-manometer system by adding a small air bubble, while increasing damping, also alters the elastic properties of the system and decreases the natural frequency, which is undesirable [35]. A method proposed by Gardner [36] to increase the damping coefficient without decreasing the natural frequency is to add a fluid-mechanical stub device containing a sealed air bubble. One of the commercial devices using this principle, the Resonance OverShoot Eliminator (ROSE) device, has been shown to increase the average damping coefficient from 0.2 to 0.8 while not reducing the natural frequency [37]. These devices, however, never were broadly adopted in clinical practice. A simple setup involving a syringe with a small air bubble in communication with the arterial line allows for the dampening of a hyper-resonant system in clinical practice (Figure 2).


Cannulation of the radial or dorsalis pedis arteries are the preferred sites of measuring IBP because the palmar and plantar arches allow for collateral blood flow to the hand and foot. This is of great importance whenever the cannulated artery develops thrombosis, usually after the arterial catheter has been in situ for a long period of time. The radial and dorsalis pedis monitoring locations protect the limb that is invasively monitored from potential ischemic damage. Patients with scleroderma should not be monitored with a radial arterial line because of a greatly increased risk of ischemic damage [38]. Brachial artery cannulation has recently gained in popularity especially in cardiac surgery and some studies have documented a low incidence of ischemic problems with this approach [39]. However, there are some reports of ischemic injuries associated with brachial arterial lines [40-41]. On the other hand, femoral artery cannulation has been associated with higher infection risk than other sites as well as pseudoaneurysm formation [42-43]. SBP tends to increase when measured at an increasing distance from the heart [44]. The site of arterial cannulation along the vascular tree is an important determinant of SBP [45-46]. A dorsalis pedis arterial line will typically show a higher SBP than a radial line, which in turn will measure a higher SBP than a femoral arterial line (Figure 3).