TRANSFER EFFICIENCIES OF PESTICIDES FROM HOUSEHOLD FLOORING SURFACES TO FOODS

Science.gov (United States)

The transfer of pesticides from household surfaces to foods was measured to determine if excess dietary exposure potentially occurs when children's foods contact contaminated surfaces prior to being. Three common household surfaces (ceramic tile, hardwood flooring, and carpet) w...

Food contact surfaces coated with nitrogen-doped titanium dioxide: effect on Listeria monocytogenes survival under different light sources

Energy Technology Data Exchange (ETDEWEB)

Rodrigues, D.; Teixeira, P. [Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Tavares, C.J. [Center of Physics, University of Minho, Campus de Azurém, 4800-058 Guimarães (Portugal); Azeredo, J., E-mail: jazeredo@deb.uminho.pt [Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal)

2013-04-01

Improvement of food safety is a very important issue, and is on the basis of production and application of new/modified food contact surfaces. Titanium dioxide (TiO{sub 2}) and, more recently, nitrogen-doped titanium dioxide (N-TiO{sub 2}) coatings are among the possible forms to enhance food contact surfaces performance in terms of higher hygiene and easier sanitation. In this context, the present work aimed at evaluating the bactericidal activity of an N-TiO{sub 2} coating on glass and stainless steel under two different sources of visible light – fluorescent and incandescent – and ultraviolet (UV) irradiation. Listeria monocytogenes was chosen as representative of major foodborne pathogens and its survival was tested on N-TiO{sub 2} coated coupons. In terms of survival percentage, good results were obtained after exposure of coated surfaces to all light types since, apart from the value obtained after exposing glass to fluorescent light (56.3%), survival rates were always below 50%. However, no effective disinfection was obtained, given that for a disinfectant or sanitizing agent to be claimed as effective it needs to be able to promote at least a 3-log reduction of the microbial load, which was not observed for any of the experimental conditions assessed. Even so, UV irradiation was the most successful on eliminating cells on coated surfaces, since the amount of bacteria was reduced to 1.49 × 10{sup 6} CFU/ml on glass and 2.37 × 10{sup 7} on stainless steel. In contrast, both visible light sources had only slightly decreased the amount of viable cells, which remained in the range of 8 log CFU/ml. Hence, although some bactericidal effect was accomplished under visible light, UV was the most effective light source on promoting photocatalytic reactions on N-TiO{sub 2} coated coupons and none of the experimental conditions have reached a satisfactory disinfection level. Thus, this surface coating needs further research and improvement in order to become truly

Stainless steel in contact with food and bevarage

Directory of Open Access Journals (Sweden)

Sveto Cvetkovski

2012-12-01

Full Text Available Stainless steels are probably the most important materials in the food and beverage industries. The main reason for such broad implementation of stainless steel in contact with food are excellent properties which they possess such as corrosion resistance, resistance to high and low temperatures, very good mechanical and physical properties, aesthetic appeal, inertness of surface, durability, easy cleaning and recycling. Low thermal conductivity of these steels produces steeper temperature coefficient provoking an increased distortion, shrinkage and stresses compared with carbon steel.

The estimation of dynamic contact angle of ultra-hydrophobic surfaces using inclined surface and impinging droplet methods

Science.gov (United States)

Jasikova, Darina; Kotek, Michal

2014-03-01

The development of industrial technology also brings with optimized surface quality, particularly where there is contact with food. Application ultra-hydrophobic surface significantly reduces the growth of bacteria and facilitates cleaning processes. Testing and evaluation of surface quality are used two methods: impinging droplet and inclined surface method optimized with high speed shadowgraphy, which give information about dynamic contact angle. This article presents the results of research into new methods of measuring ultra-hydrophobic patented technology.

Contact and non-contact ultrasonic measurement in the food industry: a review

International Nuclear Information System (INIS)

Mohd Khairi, Mohd Taufiq; Ibrahim, Sallehuddin; Md Yunus, Mohd Amri; Faramarzi, Mahdi

2016-01-01

The monitoring of the food manufacturing process is vital since it determines the safety and quality level of foods which directly affect the consumers’ health. Companies which produce high quality products will gain trust from consumers. This factor helps the companies to make profits. The use of efficient and appropriate sensors for the monitoring process can also reduce cost. The food assessing process based on an ultrasonic sensor has attracted the attention of the food industry due to its excellent capabilities in several applications. The utilization of low or high frequencies for the ultrasonic transducer has provided an enormous benefit for analysing, modifying and guaranteeing the quality of food. The contact and non-contact ultrasonic modes for measurement also contributed significantly to the food processing. This paper presents a review of the application of the contact and non-contact mode of ultrasonic measurement focusing on safety and quality control areas. The results from previous researches are shown and elaborated. (topical review)

Contact and non-contact ultrasonic measurement in the food industry: a review

Science.gov (United States)

Taufiq Mohd Khairi, Mohd; Ibrahim, Sallehuddin; Yunus, Mohd Amri Md; Faramarzi, Mahdi

2016-01-01

The monitoring of the food manufacturing process is vital since it determines the safety and quality level of foods which directly affect the consumers’ health. Companies which produce high quality products will gain trust from consumers. This factor helps the companies to make profits. The use of efficient and appropriate sensors for the monitoring process can also reduce cost. The food assessing process based on an ultrasonic sensor has attracted the attention of the food industry due to its excellent capabilities in several applications. The utilization of low or high frequencies for the ultrasonic transducer has provided an enormous benefit for analysing, modifying and guaranteeing the quality of food. The contact and non-contact ultrasonic modes for measurement also contributed significantly to the food processing. This paper presents a review of the application of the contact and non-contact mode of ultrasonic measurement focusing on safety and quality control areas. The results from previous researches are shown and elaborated.

Rough Surface Contact

Directory of Open Access Journals (Sweden)

T Nguyen

2017-06-01

Full Text Available This paper studies the contact of general rough curved surfaces having nearly identical geometries, assuming the contact at each differential area obeys the model proposed by Greenwood and Williamson. In order to account for the most general gross geometry, principles of differential geometry of surface are applied. This method while requires more rigorous mathematical manipulations, the fact that it preserves the original surface geometries thus makes the modeling procedure much more intuitive. For subsequent use, differential geometry of axis-symmetric surface is considered instead of general surface (although this “general case” can be done as well in Chapter 3.1. The final formulas for contact area, load, and frictional torque are derived in Chapter 3.2.

Scientific Challenges in the Risk Assessment of Food Contact Materials

DEFF Research Database (Denmark)

Muncke, Jane; Backhaus, Thomas; Geueke, Birgit

2017-01-01

formed in the production processes. Several factors hamper effective RA for many FCMs, including a lack of information on chemical identity, inadequate assessment of hazardous properties, and missing exposure data. Companies make decisions about the safety of some food contact chemicals (FCCs) without......Food contact articles (FCAs) are manufactured from food contact materials (FCMs) that include plastics, paper, metal, glass, and printing inks. Chemicals can migrate from FCAs into food during storage, processing, and transportation. Food contact materials' safety is evaluated using chemical risk...... to enhance the safety of food contact articles. Based on our evaluation of the evidence, we conclude that current regulations are insufficient for addressing chemical exposures from FCAs. RA currently focuses on monomers and additives used in the manufacture of products, but it does not cover all substances...

Changes in contact angle providing evidence for surface alteration in multi-component solid foods

International Nuclear Information System (INIS)

Reinke, Svenja K; Hauf, Katharina; Heinrich, Stefan; Vieira, Josélio; Palzer, Stefan

2015-01-01

Chocolate blooming, one of the major problems in the confectionery industry, is the formation of visible white spots or a greyish haze on the surface of chocolate products due to large sugar or fat crystals on the surface. This leads to aesthetic changes and deterioration of taste and thus large sales losses for the confectionery industry due to consumer complaints. Chocolate blooming is often related to migration of lipids or sugar molecules to the chocolate surface, where they recrystallize with an associated polymorphic change of crystal structure on the surface. The wetting behaviour from contact angle measurements gives further insight into surface properties and is needed to determine surface energies and to evaluate possible migration mechanisms and preferred pathways. Therefore, an equilibrium contact angle is needed which is not directly accessible and is influenced by surface texture and interaction between solid and test liquid. In this study, the surface of cocoa butter and conventional chocolates was characterized by measuring the contact angle with the sessile drop protocol. The influence of roughness, test liquid and pre-crystallization of the samples as well as the storage temperature were investigated. In case of no pre-crystallization, a change in surface properties due to storage at 20 °C was detected, whereas samples stored at 30 °C showed the same wetting behaviour as fresh samples. This is associated with polymorphic transformation from thermodynamically less stable crystals to more stable configurations. (paper)

Changes in contact angle providing evidence for surface alteration in multi-component solid foods

Science.gov (United States)

Reinke, Svenja K.; Hauf, Katharina; Vieira, Josélio; Heinrich, Stefan; Palzer, Stefan

2015-11-01

Chocolate blooming, one of the major problems in the confectionery industry, is the formation of visible white spots or a greyish haze on the surface of chocolate products due to large sugar or fat crystals on the surface. This leads to aesthetic changes and deterioration of taste and thus large sales losses for the confectionery industry due to consumer complaints. Chocolate blooming is often related to migration of lipids or sugar molecules to the chocolate surface, where they recrystallize with an associated polymorphic change of crystal structure on the surface. The wetting behaviour from contact angle measurements gives further insight into surface properties and is needed to determine surface energies and to evaluate possible migration mechanisms and preferred pathways. Therefore, an equilibrium contact angle is needed which is not directly accessible and is influenced by surface texture and interaction between solid and test liquid. In this study, the surface of cocoa butter and conventional chocolates was characterized by measuring the contact angle with the sessile drop protocol. The influence of roughness, test liquid and pre-crystallization of the samples as well as the storage temperature were investigated. In case of no pre-crystallization, a change in surface properties due to storage at 20 °C was detected, whereas samples stored at 30 °C showed the same wetting behaviour as fresh samples. This is associated with polymorphic transformation from thermodynamically less stable crystals to more stable configurations.

Siloxanes in silicone products intended for food contact

DEFF Research Database (Denmark)

Cederberg, Tommy Licht; Jensen, Lisbeth Krüger

oligomers which might migrate to the food when the product is being used. DTU has proposed two action limits for low molecular weight siloxanes in food contact materials. For the sum of cyclic siloxanes D3 to D8 the limits are 12 mg/kg food for adults and 2 mg/kg food for children. For the sum of cyclic...... siloxanes D3 to D13 and linear siloxanes L3-L13 the limit is 60 mg/kg food. In 49 samples of silicone products intended for food contact from the Norwegian markets content of siloxanes has been measured. Coated paper for baking constituted 8 of the samples and in none of those samples siloxanes were found......Silicone is used in food contact materials due to its excellent physical and chemical properties. It is thermostable and flexible and is used in bakeware and kitchen utensils. Silicone is also used to coat paper to make it water and fat resistant. There is no specific regulation in EU which covers...

Apparent contact angle and contact angle hysteresis on liquid infused surfaces.

Science.gov (United States)

Semprebon, Ciro; McHale, Glen; Kusumaatmaja, Halim

2016-12-21

We theoretically investigate the apparent contact angle and contact angle hysteresis of a droplet placed on a liquid infused surface. We show that the apparent contact angle is not uniquely defined by material parameters, but also has a dependence on the relative size between the droplet and its surrounding wetting ridge formed by the infusing liquid. We derive a closed form expression for the contact angle in the limit of vanishing wetting ridge, and compute the correction for small but finite ridge, which corresponds to an effective line tension term. We also predict contact angle hysteresis on liquid infused surfaces generated by the pinning of the contact lines by the surface corrugations. Our analytical expressions for both the apparent contact angle and contact angle hysteresis can be interpreted as 'weighted sums' between the contact angles of the infusing liquid relative to the droplet and surrounding gas phases, where the weighting coefficients are given by ratios of the fluid surface tensions.

Contact lens surface by electron beam

International Nuclear Information System (INIS)

Shin, Jung Hyuck; Lee, Suk Ju; Hwang, Kwang Ha; Jeon Jin

2011-01-01

Contact lens materials needs good biocompatibility, high refractive index, high optical transparency, high water content etc. Surface treat method by using plasma and radiation can modify the physical and/or chemical properties of the contact lens surface. Radiation technology such as electron beam irradiation can apply to polymerization reaction and enhance the functionality of the polymer.The purpose of this study is to modify of contact lens surface by using Eb irradiation technology. Electron beam was irradiated to the contact lens surface which was synthesized thermal polymerization method and commercial contact lens to modify physical and chemical properties. Ft-IR, XP, UV-vis spectrophotometer, water content, oxygen trans-metastability were used to characterize the surface state, physicochemical, and optical property of the contact lens treated with Eb. The water content and oxygen transmissibility of the contact lens treated with Eb were increased due to increase in the hydrophilic group such as O-C=O and OH group on the contact lens surface which could be produced by possible reaction between carbon and oxygen during the Eb irradiation. All of the lenses showed the high optical transmittance above 90%. In this case of B/Es, TES, Ti contact lens, the optical transmittance decreased about 5% with increasing Eb dose in the wavelength of UV-B region. The contact lens modified by Eb irradiation could improve the physical properties of the contact lens such as water content and oxygen transmissibility

Ocular surface displacement with and without contact lenses during non-contact tonometry.

Science.gov (United States)

Rimayanti, Ulfah; Kiuchi, Yoshiaki; Uemura, Shohei; Takenaka, Joji; Mochizuki, Hideki; Kaneko, Makoto

2014-01-01

To evaluate the displacement of the central ocular surface during non-contact tonometry with and without soft contact lenses and determine the factors associated with the displacement of the central ocular surface and intraocular pressure (IOP) reading changes caused by wearing soft contact lenses (CLs). One eye each in 21 subjects was studied. The cornea was photographed using a high-speed camera at 5,000 frames/sec during non-contact tonometry without contact lenses (NCL), with -5.0 diopters (D), -0.5 D and +5.0 D CL. The displacement of the ocular surface and the factors affecting displacement at the IOP reading and maximum displacement time were investigated. The IOP readings while wearing +5 D CL were significantly higher than those obtained while wearing -5 D CL. The ocular surface displacement between +5 D CL and other groups were significantly different. A significant positive correlation was found between the ocular surface displacement of subjects at the IOP reading time and the IOP obtained with the non-contact tonometer. A significant negative correlation was found between the ocular surface curvature and the IOP obtained using the non-contact tonometer. The radius of curvature of the ocular surface affected the displacement during the IOP reading and maximum displacement time. Our results indicate that soft contact lens use changes the ocular surface behavior and IOP readings during non-contact tonometry. The radius of curvature of the eye affects the ocular surface displacement and IOP readings in this situation.

Antimicrobial activity of nisin adsorbed to surfaces commonly used in the food industry.

Science.gov (United States)

Guerra, Nelson P; Araujo, Ana Belén; Barrera, Ana M; Agrasar, Ana Torrado; Macías, Cristina López; Carballo, Julia; Pastrana, Lorenzo

2005-05-01

The adsorption isotherms of nisin to three food contact surfaces, stainless steel, polyethyleneterephthalate (PET), and rubber at 8, 25, 40, and 60 degrees C, were calculated. For all surfaces, the increase in temperature led to a decrease in the affinity between nisin and the surface. The rubber adsorbed a higher amount of nisin (0.697 microg/cm2) in comparison with PET (0.665 microg/cm2) and stainless steel (0.396 microg/cm2). Adsorption of nisin to the stainless steel surface described L-2 type curves for all temperatures assayed. However, for PET and rubber surfaces, the isotherms were L-2 type (at 40 and 60 degrees C) and L-4 type curves (at 8 and 25 degrees C). Nisin retained its antibacterial activity once adsorbed to the food contact surfaces and was able to inhibit the growth of Enterococcus hirae CECT 279 on Rothe agar medium. The attachment of three Listeria monocytogenes strains to the three surfaces was found to be dependent on the surface, the strain, and the initial bacterial suspension in contact with the surface. The adsorption of Nisaplin on surfaces reduced the attachment of all L. monocytogenes strains tested. The effect of PET-based bioactive packaging in food was very encouraging. When applied to a food system, nisin-adsorbed PET bottles reduced significantly (P < 0.05) the levels of the total aerobic plate counts in skim milk by approximately 1.4 log units after 24 days of refrigerated storage (4 degrees C), thus extending its shelf life.

Ocular surface displacement with and without contact lenses during non-contact tonometry.

Directory of Open Access Journals (Sweden)

Ulfah Rimayanti

Full Text Available PURPOSE: To evaluate the displacement of the central ocular surface during non-contact tonometry with and without soft contact lenses and determine the factors associated with the displacement of the central ocular surface and intraocular pressure (IOP reading changes caused by wearing soft contact lenses (CLs. METHODS: One eye each in 21 subjects was studied. The cornea was photographed using a high-speed camera at 5,000 frames/sec during non-contact tonometry without contact lenses (NCL, with -5.0 diopters (D, -0.5 D and +5.0 D CL. The displacement of the ocular surface and the factors affecting displacement at the IOP reading and maximum displacement time were investigated. RESULTS: The IOP readings while wearing +5 D CL were significantly higher than those obtained while wearing -5 D CL. The ocular surface displacement between +5 D CL and other groups were significantly different. A significant positive correlation was found between the ocular surface displacement of subjects at the IOP reading time and the IOP obtained with the non-contact tonometer. A significant negative correlation was found between the ocular surface curvature and the IOP obtained using the non-contact tonometer. The radius of curvature of the ocular surface affected the displacement during the IOP reading and maximum displacement time. CONCLUSIONS: Our results indicate that soft contact lens use changes the ocular surface behavior and IOP readings during non-contact tonometry. The radius of curvature of the eye affects the ocular surface displacement and IOP readings in this situation.

The contact sport of rough surfaces

Science.gov (United States)

Carpick, Robert W.

2018-01-01

Describing the way two surfaces touch and make contact may seem simple, but it is not. Fully describing the elastic deformation of ideally smooth contacting bodies, under even low applied pressure, involves second-order partial differential equations and fourth-rank elastic constant tensors. For more realistic rough surfaces, the problem becomes a multiscale exercise in surface-height statistics, even before including complex phenomena such as adhesion, plasticity, and fracture. A recent research competition, the “Contact Mechanics Challenge” (1), was designed to test various approximate methods for solving this problem. A hypothetical rough surface was generated, and the community was invited to model contact with this surface with competing theories for the calculation of properties, including contact area and pressure. A supercomputer-generated numerical solution was kept secret until competition entries were received. The comparison of results (2) provides insights into the relative merits of competing models and even experimental approaches to the problem.

Chemical identification of contaminants in paper and board food contact materials

DEFF Research Database (Denmark)

Bengtström, Linda

Paper and board are used for a variety of food contact materials, such as baking paper, microwave popcorn bags and packaging for cereals as well as fast foods. Despite this extensive use, there are currently large data gaps about the chemical composition of different paper and board food contact...

Surface contact fatigue failures in gears

CSIR Research Space (South Africa)

Fernandes, PJL

1997-06-01

Full Text Available Surface contact fatigue is the most common cause of gear failure. It results in damage to contacting surfaces which can significantly reduce the load-carrying capacity of components, and may ultimately lead to complete failure of a gear. Three types...

Evaluating use stage exposure to food contact materials in a LCA framework

DEFF Research Database (Denmark)

Ernstoff, Alexi; Jolliet, Olivier; Fantke, Peter

2015-01-01

We present novel methods to incorporate exposure to chemicals within food contact materials (FCM) (e.g. packaging) into life cycle impact assessment (LCIA). Chemical migration into food is modeled as a function of contact temperature, time, and various chemical, FCM, and food properties. In order...... in a way compatible with intake fraction, iF, a metric traditionally used in LCIA. The model predicts PiF increases with temperature and for compounds with lower octanol-water partition coefficients within more permeable materials which are in contact with foods with high ethanol equivalencies (fatty foods)....

Surface Energy and Setting Process of Contacting Surfaces

Directory of Open Access Journals (Sweden)

M. V. Musokhranov

2014-01-01

Full Text Available The paper deals with a challenge in terms of ensuring an accuracy of the relative position of the conjugated surfaces that is to determine a coefficient of friction. To solve it, there is a proposal to use the surface energy, as a tool that influences the contacting parts nature. Presently, energy of the surface layers at best is only stated, but not used in practice.Analysis of the conditions of interaction between two contacting surfaces, such as seizing and setting cannot be explained only from the position of the roughness parameters. It is found that these phenomena are explained by the appearing gripe (setting bridges, which result from the energy of interaction between two or more adjacent surfaces. The emerging phenomenon such as micro welding, i.e. occurring bonds, is caused by the overflow of energy, according to the theory of physics, from the surface with a high level of energy to the surface with the smaller one to balance the system as a whole.The paper shows that through the use of process, controlling the depth of the surface layer and creating a certain structure, the energy level of the material as a whole can be specified. And this will allow us to provide the necessary performance and mechanical properties. It means to create as many gripe bridges as possible to ensure continuous positioning i.e. a fixed connection of the contacting surfaces.It was determined that to increase a value of the friction coefficient, the physical and mechanical properties of the surface layer of the parts material must be taken into account, namely, in the part body accumulate the energy to be consumed for forming the surface.The paper gives recommendations for including the parts of the surface energy in the qualitative indicators of characteristics. This will make a technologist, when routing a process, to choose such operations and modes to provide the designer-specified parameters not only of the accuracy and surface finish, but also of the

The loaded surface profile: a new technique for the investigation of contact surfaces

OpenAIRE

McBride, J.W.

2006-01-01

Contact between rough surfaces produces a complex contact profile. The contact area is usually estimated according to roughness statistics in conjunction withsurface models or by examining the surfaces before and after contact. Most of the existing literature on loaded surface profiles is theoretical or numerical in nature. This paper presents a methodology for a new system to measure the loaded surface profile, based on a non-contact 3D laser profiler. The system allows the measurement of...

Effect of inoculum size, bacterial species, type of surfaces and contact time to the transfer of foodborne pathogens from inoculated to non-inoculated beef fillets via food processing surfaces.

Science.gov (United States)

Gkana, E; Chorianopoulos, N; Grounta, A; Koutsoumanis, K; Nychas, G-J E

2017-04-01

The objective of the present study was to determine the factors affecting the transfer of foodborne pathogens from inoculated beef fillets to non-inoculated ones, through food processing surfaces. Three different levels of inoculation of beef fillets surface were prepared: a high one of approximately 10 7  CFU/cm 2 , a medium one of 10 5  CFU/cm 2 and a low one of 10 3  CFU/cm 2 , using mixed-strains of Listeria monocytogenes, or Salmonella enterica Typhimurium, or Escherichia coli O157:H7. The inoculated fillets were then placed on 3 different types of surfaces (stainless steel-SS, polyethylene-PE and wood-WD), for 1 or 15 min. Subsequently, these fillets were removed from the cutting boards and six sequential non-inoculated fillets were placed on the same surfaces for the same period of time. All non-inoculated fillets were contaminated with a progressive reduction trend of each pathogen's population level from the inoculated fillets to the sixth non-inoculated ones that got in contact with the surfaces, and regardless the initial inoculum, a reduction of approximately 2 log CFU/g between inoculated and 1st non-inoculated fillet was observed. S. Typhimurium was transferred at lower mean population (2.39 log CFU/g) to contaminated fillets than E. coli O157:H7 (2.93 log CFU/g), followed by L. monocytogenes (3.12 log CFU/g; P < 0.05). Wooden surfaces (2.77 log CFU/g) enhanced the transfer of bacteria to subsequent fillets compared to other materials (2.66 log CFU/g for SS and PE; P < 0.05). Cross-contamination between meat and surfaces is a multifactorial process strongly depended on the species, initial contamination level, kind of surface, contact time and the number of subsequent fillet, according to analysis of variance. Thus, quantifying the cross-contamination risk associated with various steps of meat processing and food establishments or households can provide a scientific basis for risk management of such products. Copyright © 2016 Elsevier Ltd

Surface coating for blood-contacting devices

Science.gov (United States)

Nair, Ajit Kumar Balakrishnan

The major problems always encountered with the blood-contacting surfaces are their compatibility, contact blood damage, and thrombogenicity. Titanium nitride (TiN) is a hard, inert, ceramic material that is widely used in the engineering industry. TiN has been proven to be a good biomaterial in its crystalline form, in orthopedic, and in tissue implant applications. This dissertation describes a method to coat amorphous TiN on the blood-contacting surfaces of certain medical devices using the room-temperature sputtering process and to characterize, to test, and to evaluate the coating for a reliable, durable, and compatible blood-contacting surface The blood-compatibility aspects were evaluated with standard, established protocols and procedures to prove the feasibility. An amorphous TiN coating is developed, characterized, tested, and blood compatibility evaluated by applying to the blood-contacting surfaces of stainless steel, catheters, and blood filters. The flexibility characteristics were proven by applying it to the diaphragms of the pulsatile pneumatic ventricular assist device. The results show that amorphous titanium nitride is flexible and adherent to polymeric substrates like polyurethane and polyester. Blood compatibility evaluation showed comparable results with catheters and superior behavior with stainless steel and polyester filters. It is concluded that amorphous titanium nitride can be considered to be applied to the surfaces of some of the medical devices in order to improve blood compatibility.

Effect of surfaces similarity on contact resistance of fractal rough surfaces under cyclic loading

Science.gov (United States)

Gao, Yuanwen; Liu, Limei; Ta, Wurui; Song, Jihua

2018-03-01

Although numerous studies have shown that contact resistance depends significantly on roughness and fractal dimension, it remains elusive how they affect contact resistance between rough surfaces. The interface similarity index is first proposed to describe the similarity of the contact surfaces, which gives a good indication of the actual contact area between surfaces. We reveal that the surfaces' similarity be an origin of contact resistance variation. The cyclic loading can increase the contact stiffness, and the contact stiffness increases with the increase of the interface similarity index. These findings explain the mechanism of surface roughness and fractal dimension on contact resistance, and also provide reference for the reliability design of the electrical connection.

Contact area measurements on structured surfaces

DEFF Research Database (Denmark)

Kücükyildiz, Ömer Can; Jensen, Sebastian Hoppe Nesgaard; De Chiffre, Leonardo

In connection with the use of brass specimens featuring structured surfaces in a tribology test, an algorithm was developed for automatic measurement of the contact area by optical means.......In connection with the use of brass specimens featuring structured surfaces in a tribology test, an algorithm was developed for automatic measurement of the contact area by optical means....

Selection Criteria and Methods for Testing Different Surface Materials for Contact Frying Processes

DEFF Research Database (Denmark)

Ashokkumar, Saranya

Inner surfaces of industrial process equipment for food are often coated to give the surfaces particular properties with respect to adhesion and cleanability. Existing coating materials (PTFE (Teflon®) or silicone based polymers) suffer from drawbacks when used in contact frying, because these co...... surface materials for contact frying processes. The surfaces selected for this purpose cover a wide spectrum of materials that range from hydrophobic to hydrophilic materials. The different surface materials investigated include stainless steel (reference), aluminium (Al Mg 5754), PTFE......, an experimental rig has been constructed which enabled a controlled fouling of different coatings on steel and aluminium substrates under realistic frying conditions. A subjective rating procedure was employed for screening different surfaces according to their non-stick properties when used for frying of a model...... defects and surface roughness play a significant role. The wear resistance of the coatings was tested by performing abrasive wear experiments. The ceramic coatings: TiAlN and ZrN were found to show the best wear resistance properties. The experiments also revealed the poor wear resistance of stainless...

[Type IV contact allergies in the food processing industry: an update].

Science.gov (United States)

Bauer, A; Schubert, S; Geier, J; Mahler, V

2018-05-02

The food sector is one of the high-risk areas for occupational irritative and allergic contact eczema. The present work provides an overview of the main allergens as well as sensitization frequencies and risk in various food industry occupations. The literature on type IV sensitization in the food sector is summarized. The relative risk of developing a work-related eczema in food processing is increased by more than 3 times. The comparison group was calculated on the basis of the proportion of documented cases in the IVDK (Informationsverbund Dermatologischer Kliniken) network per 100,000 working persons in relation to the average of the years 2005 and 2010. For this purpose, the average risk of all patients was set as reference to 1. Bakers, pastry chefs, cooks and meat and fish processors are mainly affected. In addition to irritant contact eczema, allergic contact eczema and protein contact dermatitis often occur. Leading haptens (main allergens) are rubber ingredients, but also disinfectants and compositae. Only a few contact allergens are responsible for the majority of job-relevant sensitizations in the food industry.

Wettability and Contact Time on a Biomimetic Superhydrophobic Surface

Science.gov (United States)

Liang, Yunhong; Peng, Jian; Li, Xiujuan; Huang, Jubin; Qiu, Rongxian; Zhang, Zhihui; Ren, Luquan

2017-01-01

Inspired by the array microstructure of natural superhydrophobic surfaces (lotus leaf and cicada wing), an array microstructure was successfully constructed by high speed wire electrical discharge machining (HS-WEDM) on the surfaces of a 7075 aluminum alloy without any chemical treatment. The artificial surfaces had a high apparent contact angle of 153° ± 1° with a contact angle hysteresis less than 5° and showed a good superhydrophobic property. Wettability, contact time, and the corresponding superhydrophobic mechanism of artificial superhydrophobic surface were investigated. The results indicated that the micro-scale array microstructure was an important factor for the superhydrophobic surface, while different array microstructures exhibited different effects on the wettability and contact time of the artificial superhydrophobic surface. The length (L), interval (S), and height (H) of the array microstructure are the main influential factors on the wettability and contact time. The order of importance of these factors is H > S > L for increasing the apparent contact angle and reducing the contact time. The method, using HS-WEDM to fabricate superhydrophobic surface, is simple, low-cost, and environmentally friendly and can easily control the wettability and contact time on the artificial surfaces by changing the array microstructure. PMID:28772613

Growth and biofilm formation by Listeria monocytogenes in catfish mucus extract on four food-contact surfaces at 22°C and 10°C and their reduction by commercial disinfectants

Science.gov (United States)

The objective of this study was to determine the effect of strain and temperature on growth and biofilm formation by Listeria monocytogenes (Lm) in high and low concentrations of catfish mucus extract on different food-contact surfaces at 10°C and 22°C. The second objective of this study was to eval...

Fabrication of zero contact angle ultra-super hydrophilic surfaces.

Science.gov (United States)

Jothi Prakash, C G; Clement Raj, C; Prasanth, R

2017-06-15

Zero contact angle surfaces have been created with the combined effect of nanostructure and UV illumination. The contact angle of titanium surface has been optimized to 3.25°±1°. with nanotubular structures through electrochemical surface modification. The porosity and surface energy of tubular TiO 2 layer play critical role over the surface wettability and the hydrophilicity of the surface. The surface free energy has been enhanced from 23.72mJ/m 2 (bare titanium surface) to 87.11mJ/m 2 (nanotubular surface). Similar surface with TiO 2 nanoparticles coating shows superhydrophilicity with contact angle up to 5.63°±0.95°. This implies liquid imbibition and surface curvature play a crucial role in surface hydrophilicity. The contact angle has been further reduced to 0°±0.86° by illuminating the surface with UV radiation. Results shows that by tuning the nanotube morphology, highly porous surfaces can be fabricated to reduce contact angle and enhance wettability. This study provides an insight into the inter-relationship between surface structural factors and ultra-superhydrophilic surfaces which can help to optimize thermal hydraulic and self cleaning surfaces. Copyright © 2017. Published by Elsevier Inc.

Apparent Contact Angle and Contact Angle Hysteresis on Liquid Infused Surfaces

OpenAIRE

Semprebon, Ciro; McHale, Glen; Kusumaatmaja, Halim

2016-01-01

We theoretically investigate the apparent contact angle and contact angle hysteresis of a droplet placed on a liquid infused surface. We show that the apparent contact angle is not uniquely defined by material parameters, but also has a strong dependence on the relative size between the droplet and its surrounding wetting ridge formed by the infusing liquid. We derive a closed form expression for the contact angle in the limit of vanishing wetting ridge, and compute the correction for small b...

Efficacy of low-pressure foam cleaning compared to conventional cleaning methods in the removal of bacteria from surfaces associated with convenience food.

Science.gov (United States)

Lambrechts, A A; Human, I S; Doughari, J H; Lues, J F R

2014-09-01

Food borne illnesses and food poisoning are cause for concern globally. The diseases are often caused by food contamination with pathogenic bacteria due largely to poor sanitary habits or storage conditions. Prevalence of some bacteria on cleaned and sanitised food contact surfaces from eight convenience food plants in Gauteng (South Africa) was investigated with the view to evaluate the efficacy of the cleaning methods used with such food contact surfaces. The microbial load of eight convenience food manufacturing plants was determined by sampling stainless steel food contact surfaces after they had been cleaned and sanitised at the end of a day's shift. Samples were analysed for Total Plate Count (TPC), Escherichia coli, Salmonella species, Staphylococcus aureus and Listeria species. Results showed that 59 % of the total areas sampled for TPC failed to comply with the legal requirements for surfaces, according to the Foodstuffs, Cosmetics and Disinfectants Act ( 0.05) in terms of Listeria species isolates obtained from both cleaning methods. The LPF method proved to be the superior cleaning option for lowering TPC counts. Regardless of cleaning method used, pathogens continued to flourish on various surfaces, including dry stainless steel, posing a contamination hazard for a considerable period depending on the contamination level and type of pathogen. Intensive training for proper chemical usage and strict procedural compliance among workers for efficient cleaning procedures is recommended.

Consequences of occupational food-related hand dermatoses with a focus on protein contact dermatitis

DEFF Research Database (Denmark)

Vester, Lotte; Thyssen, Jacob P; Menné, Torkil

2012-01-01

Background. Protein contact dermatitis is a frequent disorder among hand eczema patients who have occupational food contact. Knowledge about the consequences of having protein contact dermatitis is lacking. Objectives. To investigate the consequences of having occupational skin disease on the hands...... resulting from food handling, with a focus on protein contact dermatitis. Material and methods. One hundred and seventy-eight patients who were identified as having skin disease related to occupational food exposure and who answered a questionnaire concerning the consequences of their skin disease were......%, respectively, of the patients with other occupational food-related hand dermatoses (p = 0.02). Sixty-two per cent and 43%, respectively, had to change job because of skin problems (p = 0.02). Atopic dermatitis was equally common in the two groups. Conclusion. We found that the patients with protein contact...

Characterisation and potential migration of silver nanoparticles from commercially available polymeric food contact materials.

Science.gov (United States)

Addo Ntim, Susana; Thomas, Treye A; Begley, Timothy H; Noonan, Gregory O

2015-01-01

The potential for consumer exposure to nano-components in food contact materials (FCMs) is dependent on the migration of nanomaterials into food. Therefore, characterising the physico-chemical properties and potential for migration of constituents is an important step in assessing the safety of FCMs. A number of commercially available food storage products, purchased domestically within the United States and internationally, that claim to contain nanosilver were evaluated. The products were made of polyethylene, polypropylene and polyphenylene ether sulfone and all contained silver (0.001-36 mg kg(-1) of polymer). Silver migration was measured under various conditions, including using 3% acetic acid and water as food simulants. Low concentrations (sub-ppb levels) of silver were detected in the migration studies generally following a trend characterised by a surface desorption phenomenon, where the majority of the silver migration occurred in the first of three consecutive exposures. Silver nanoparticles were not detected in food simulants, suggesting that the silver migration may be due solely to ionic silver released into solution from oxidation of the silver nanoparticle surface. The absence of detectable silver nanoparticles was consistent with expectations from a physico-chemical view point. For the products tested, current USFDA guidance for evaluating migration from FCMs was applicable.

Asperity interaction in adhesive contact of metallic rough surfaces

International Nuclear Information System (INIS)

Sahoo, Prasanta; Banerjee, Atanu

2005-01-01

The analysis of adhesive contact of metallic rough surfaces considering the effect of asperity interaction is the subject of this investigation. The micro-contact model of asperity interactions developed by Zhao and Chang (2001 Trans. ASME: J. Tribol. 123 857-64) is combined with the elastic plastic adhesive contact model developed by Chang et al (1988 Trans. ASME: J. Tribol. 110 50-6) to consider the asperity interaction and elastic-plastic deformation in the presence of surface forces simultaneously. The well-established elastic adhesion index and plasticity index are used to consider the different contact conditions. Results show that asperity interaction influences the load-separation behaviour in elastic-plastic adhesive contact of metallic rough surfaces significantly and, in general, adhesion is reduced due to asperity interactions

Linear and non-linear simulation of joints contact surface using ...

African Journals Online (AJOL)

The joint modelling including non-linear effects needs accurate and precise study of their behaviors. When joints are under the dynamic loading, micro, macro- slip happens in contact surface which is non-linear reason of the joint contact surface. The non-linear effects of joint contact surface on total behavior of structure are ...

Bacterial biofilm formation in different surfaces of food industries

Directory of Open Access Journals (Sweden)

Karine Angélica Dalla Costa

2017-06-01

Full Text Available The term biofilm describes the sessile microbial life form, characterized by microorganism adhesion to any surface and with the production of extracellular polymeric substances. In food industries, the formation of biofilms results in serious problems, since it can be a contamination source of the food product, compromising the final product quality and consumer health. The aim of this study was to verify the adhesion of biofilms (sessile cells of pathogenic and/or deteriorating bacteria against surfaces of the food industry. The bacterial species tested were Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 29213, Listeria monocytogenes ATCC 19117 and Salmonella Typhimurium ATCC 14028. It was used stainless steel and polypropylene coupons as contact surfaces. The results demonstrated that P. aeruginosa and S. Typhimurium showed higher biofilm formation capacity. Statistically, there was no difference in count of P. aeruginosa and S. Typhimurium (p > 0.05 cells. The same occurred between L. monocytogenes and S. aureus. However, the counts of P. aeruginosa and S. Typhimurium cells were statistically higher than S. aureus and L. monocytogenes (p < 0.05. By means of scanning electron microscopy it was also found increased adhesion of P. aeruginosa. The results revealed that P. aeruginosa was the bacterial species with higher biofilm formation capacity among the others.

Liquid-bridge stability and breakup on surfaces with contact-angle hysteresis.

Science.gov (United States)

Akbari, Amir; Hill, Reghan J

2016-08-10

We study the stability and breakup of liquid bridges with a free contact line on surfaces with contact-angle hysteresis (CAH) under zero-gravity conditions. Non-ideal surfaces exhibit CAH because of surface imperfections, by which the constraints on three-phase contact lines are influenced. Given that interfacial instabilities are constraint-sensitive, understanding how CAH affects the stability and breakup of liquid bridges is crucial for predicting the drop size in contact-drop dispensing. Unlike ideal surfaces on which contact lines are always free irrespective of surface wettability, contact lines may undergo transitions from pinned to free and vice versa during drop deposition on non-ideal surfaces. Here, we experimentally and theoretically examine how stability and breakup are affected by CAH, highlighting cases where stability is lost during a transition from a pinned-pinned (more constrained) to pinned-free (less constrained) interface-rather than a critical state. This provides a practical means of expediting or delaying stability loss. We also demonstrate how the dynamic contact angle can control the contact-line radius following stability loss.

[Street food: analysis of hygienic and sanitary conditions of food handlers].

Science.gov (United States)

de Souza, Giovanna Carbonera; dos Santos, Celso Tadeu Barbosa; Andrade, Anderson Assunção; Alves, Luciene

2015-08-01

The consumption of street food is an economical and practical alternative for the population. However, concerns regarding the safety of these foods are increasing. Thus, this study aimed to analyze the hygienic and sanitary conditions of the street food trade in Uberaba in the State of Minas Gerais. For this purpose, 30 street vending sites were evaluated using a structured questionnaire and microbiological analysis of food handlers' hands and food contact recipients and surfaces. The findings showed low adequacy of street food regarding hand hygiene and food contact surfaces. With respect to surfaces, the results for mesophilic aerobic microorganisms revealed that only 23.3% had satisfactory sanitary conditions. The level of contamination of hands by fecal thermotolerant coliforms and/or Coagulase positive Staphylococci was unsatisfactory in approximately 47% of food handlers. The conclusion drawn is that the hygienic and sanitary conditions of food handlers in Uberaba are poor. It is therefore necessary to adopt effective and permanent training programs on food safety for food handlers urgently.

VASCo: computation and visualization of annotated protein surface contacts

Directory of Open Access Journals (Sweden)

Thallinger Gerhard G

2009-01-01

Full Text Available Abstract Background Structural data from crystallographic analyses contain a vast amount of information on protein-protein contacts. Knowledge on protein-protein interactions is essential for understanding many processes in living cells. The methods to investigate these interactions range from genetics to biophysics, crystallography, bioinformatics and computer modeling. Also crystal contact information can be useful to understand biologically relevant protein oligomerisation as they rely in principle on the same physico-chemical interaction forces. Visualization of crystal and biological contact data including different surface properties can help to analyse protein-protein interactions. Results VASCo is a program package for the calculation of protein surface properties and the visualization of annotated surfaces. Special emphasis is laid on protein-protein interactions, which are calculated based on surface point distances. The same approach is used to compare surfaces of two aligned molecules. Molecular properties such as electrostatic potential or hydrophobicity are mapped onto these surface points. Molecular surfaces and the corresponding properties are calculated using well established programs integrated into the package, as well as using custom developed programs. The modular package can easily be extended to include new properties for annotation. The output of the program is most conveniently displayed in PyMOL using a custom-made plug-in. Conclusion VASCo supplements other available protein contact visualisation tools and provides additional information on biological interactions as well as on crystal contacts. The tool provides a unique feature to compare surfaces of two aligned molecules based on point distances and thereby facilitates the visualization and analysis of surface differences.

Evaluation of Tire/Surfacing/Base Contact Stresses and Texture Depth

Directory of Open Access Journals (Sweden)

W.J.vdM. Steyn

2015-03-01

Full Text Available Tire rolling resistance has a major impact on vehicle fuel consumption. Rolling resistance is the loss of energy due to the interaction between the tire and the pavement surface. This interaction is a complicated combination of stresses and strains which depend on both tire and pavement related factors. These include vehicle speed, vehicle weight, tire material and type, road camber, tire inflation pressure, pavement surfacing texture etc. In this paper the relationship between pavement surface texture depth and tire/surfacing contact stress and area is investigated. Texture depth and tire/surfacing contact stress were measured for a range of tire inflation pressures on five different pavement surfaces. In the analysis the relationship between texture and the generated contact stresses as well as the contact stress between the surfacing and base layer are presented and discussed, and the anticipated effect of these relationships on the rolling resistance of vehicles on the surfacings, and subsequent vehicle fuel economy discussed.

Contact Angle Hysteresis on Graphene Surfaces and Hysteresis-free Behavior on Oil-infused Graphite Surfaces

Energy Technology Data Exchange (ETDEWEB)

Wu, Cyuan-Jhang; Li, Yueh-Feng [Department of Chemical and Materials Engineering, National Central University, Jhongli 320, Taiwan (China); Woon, Wei-Yen [Department of Physics, National Central University, Jhongli 320, Taiwan (China); Sheng, Yu-Jane, E-mail: yjsheng@ntu.edu.tw [Department of Chemical Engineering, National Taiwan University, Taipei 106, Taiwan (China); Tsao, Heng-Kwong, E-mail: hktsao@cc.ncu.edu.tw [Department of Chemical and Materials Engineering, National Central University, Jhongli 320, Taiwan (China); Department of Physics, National Central University, Jhongli 320, Taiwan (China)

2016-11-01

Highlights: • Contact angle hysteresis(CAH) on four graphitic surfacesisinvestigated. • The hysteresis loopof water drops on the polished graphite sheetshowsparticularly small receding contact angle. • The significant CAH observed on CVD graphene and highly oriented pyrolytic graphite is attributed mainly to adhesion hysteresis. • An oil-infused surface of a graphite sheet is produced by imbibition of hexadecane into its porous structure. • The hysteresis-free property for water drops on such a surface is examined and quantitatively explained. - Abstract: Contact angle hysteresis (CAH) on graphitic surfaces, including chemical vapor deposition (CVD) graphene, reduced electrophoretic deposition (EPD) graphene, highly oriented pyrolytic graphite (HOPG), and polished graphite sheet, has been investigated. The hysteresis loops of water drops on the first three samples are similar but the receding contact angle is particularly small for the polished graphite sheet.The significant CAH observed on CVD graphene and HOPG associated with atom-scale roughness has to be attributed mainly to adhesion hysteresis (surface relaxation), instead of roughness or defects.The difference of the wetting behavior among those four graphitic samples has been further demonstrated by hexadecane drops. On the surface of HOPG or CVD graphene,the contact line expands continuously with time, indicating total wetting for which the contact angle does not exist and contact line pinning disappears. In contrast, on the surface of reduced EPD graphene, spontaneous spreading is halted by spikes on it and partial wetting with small contact angle (θ≈4°) is obtained. On the surface of polished graphite sheet, the superlipophilicity and porous structure are demonstrated by imbibition and capillary rise of hexadecane. Consequently, an oil-infused graphite surface can be fabricated and the ultralow CAH of water (∆θ≈2°) is achieved.

Dynamic contact angle cycling homogenizes heterogeneous surfaces.

Science.gov (United States)

Belibel, R; Barbaud, C; Mora, L

2016-12-01

In order to reduce restenosis, the necessity to develop the appropriate coating material of metallic stent is a challenge for biomedicine and scientific research over the past decade. Therefore, biodegradable copolymers of poly((R,S)-3,3 dimethylmalic acid) (PDMMLA) were prepared in order to develop a new coating exhibiting different custom groups in its side chain and being able to carry a drug. This material will be in direct contact with cells and blood. It consists of carboxylic acid and hexylic groups used for hydrophilic and hydrophobic character, respectively. The study of this material wettability and dynamic surface properties is of importance due to the influence of the chemistry and the potential motility of these chemical groups on cell adhesion and polymer kinetic hydrolysis. Cassie theory was used for the theoretical correction of contact angles of these chemical heterogeneous surfaces coatings. Dynamic Surface Analysis was used as practical homogenizer of chemical heterogeneous surfaces by cycling during many cycles in water. In this work, we confirmed that, unlike receding contact angle, advancing contact angle is influenced by the difference of only 10% of acidic groups (%A) in side-chain of polymers. It linearly decreases with increasing acidity percentage. Hysteresis (H) is also a sensitive parameter which is discussed in this paper. Finally, we conclude that cycling provides real information, thus avoiding theoretical Cassie correction. H(10)is the most sensible parameter to %A. Copyright © 2016 Elsevier B.V. All rights reserved.

Elastic–plastic adhesive contact of non-Gaussian rough surfaces

Indian Academy of Sciences (India)

Adhesion; asymmetric roughness; elastic–plastic contact; non-Gaussian rough surfaces. ... model of contact deformation that is based on accurate Finite Element Analysis (FEA) of an elastic–plastic single asperity contact. ... Sadhana | News.

Contact angle hysteresis on doubly periodic smooth rough surfaces in Wenzel's regime: The role of the contact line depinning mechanism.

Science.gov (United States)

Iliev, Stanimir; Pesheva, Nina; Iliev, Pavel

2018-04-01

We report here on the contact angle hysteresis, appearing when a liquid meniscus is in contact with doubly sinusoidal wavelike patterned surfaces in Wenzel's wetting regime. Using the full capillary model we obtain numerically the contact angle hysteresis as a function of the surface roughness factor and the equilibrium contact angle for a block case and a kink case contact line depinning mechanism. We find that the dependencies of the contact angle hysteresis on the surface roughness factor are different for the different contact line depinning mechanisms. These dependencies are different also for the two types of rough surfaces we studied. The relations between advancing, receding, and equilibrium contact angles are investigated. A comparison with the existing asymptotical, numerical, and experimental results is carried out.

Drop shape visualization and contact angle measurement on curved surfaces.

Science.gov (United States)

Guilizzoni, Manfredo

2011-12-01

The shape and contact angles of drops on curved surfaces is experimentally investigated. Image processing, spline fitting and numerical integration are used to extract the drop contour in a number of cross-sections. The three-dimensional surfaces which describe the surface-air and drop-air interfaces can be visualized and a simple procedure to determine the equilibrium contact angle starting from measurements on curved surfaces is proposed. Contact angles on flat surfaces serve as a reference term and a procedure to measure them is proposed. Such procedure is not as accurate as the axisymmetric drop shape analysis algorithms, but it has the advantage of requiring only a side view of the drop-surface couple and no further information. It can therefore be used also for fluids with unknown surface tension and there is no need to measure the drop volume. Examples of application of the proposed techniques for distilled water drops on gemstones confirm that they can be useful for drop shape analysis and contact angle measurement on three-dimensional sculptured surfaces. Copyright © 2011 Elsevier Inc. All rights reserved.

Drops and bubbles in contact with solid surfaces

CERN Document Server

Ferrari, Michele

2012-01-01

The third volume in a series dedicated to colloids and interfaces, Drops and Bubbles in Contact with Solid Surfaces presents an up-to-date overview of the fundamentals and applications of drops and bubbles and their interaction with solid surfaces. The chapters cover the theoretical and experimental aspects of wetting and wettability, liquid-solid interfacial properties, and spreading dynamics on different surfaces, including a special section on polymers. The book examines issues related to interpretation of contact angle from nano to macro systems. Expert contributors discuss interesting pec

Development of Titanium Dioxide (TiO2 ) Nanocoatings on Food Contact Surfaces and Method to Evaluate Their Durability and Photocatalytic Bactericidal Property.

Science.gov (United States)

Yemmireddy, Veerachandra K; Farrell, Glenn D; Hung, Yen-Con

2015-08-01

Titanium dioxide (TiO2 ) is a well-known photocatalyst for its excellent bactericidal property under UVA light. The purpose of this study was to develop physically stable TiO2 coatings on food contact surfaces using different binding agents and develop methods to evaluate their durability and microbicidal property. Several types of organic and inorganic binders such as polyvinyl alcohol, polyethylene glycol, polyurethane, polycrylic, sodium and potassium silicates, shellac resin, and other commercial binders were used at 1:1 to 1:16 nanoparticle to binder weight ratios to develop a formulation for TiO2 coating on stainless steel surfaces. Among the tested binders, polyurethane, polycrylic, and shellac resin were found to be physically more stable when used in TiO2 coating at 1:4 to 1:16 weight ratio. The physical stability of TiO2 coatings was determined using adhesion strength and scratch hardness tests by following standard ASTM procedures. Further, wear resistance of the coatings was evaluated based on a simulated cleaning procedure used in food processing environments. TiO2 coating with polyurethane at a 1:8 nanoparticle to binder weight ratio showed the highest scratch hardness (1.08 GPa) followed by coating with polycrylic (0.68 GPa) and shellac (0.14 GPa) binders. Three different techniques, namely direct spreading, glass cover-slip, and indented coupon were compared to determine the photocatalytic bactericidal property of TiO2 coatings against Escherichia coli 0157:H7 at 2 mW/cm(2) UVA light intensity. Under the tested conditions, the indented coupon technique was found to be the most appropriate method to determine the bactericidal property of TiO2 coatings and showed a reduction of 3.5 log CFU/cm(2) in 2 h. © 2015 Institute of Food Technologists®

Ion-Induced Surface Modification of Magnetically Operated Contacts

Directory of Open Access Journals (Sweden)

Karen Arushanov

2012-02-01

Full Text Available A study has been made of permalloy (iron-nickel contacts of reed switches before and after ion-induced surface modification using atomic force and optical microscopy, Auger electron and X-ray photoelectron spectroscopy. It has been found that the formation of surface nitride layers enhances corrosion and erosion resistance of contacts. We proposed to produce such layers directly into sealed reed switches by means of pulsing glow-discharge nitrogen plasma.

Migration of compounds from food contact materials and articles

DEFF Research Database (Denmark)

Petersen, Jens Højslev

2003-01-01

This chapter presents the different types of food contact/packaging materials (plastics, paper and cardboard, metals, glass, rubbers, lacquers and coatings) and discusses the EU legislation concerning the safety of using these materials. Case studies on the migration of lead, bisphenol A, bisphen...

Electrostatic application of antimicrobial sprays to sanitize food handling and processing surfaces for enhanced food safety

International Nuclear Information System (INIS)

Lyons, Shawn M; Harrison, Mark A; Law, S Edward

2011-01-01

Human illnesses and deaths caused by foodborne pathogens (e.g., Salmonella enterica, Listeria monocytogenes, Escherichia coli O157:H7, etc.) are of increasing concern globally in maintaining safe food supplies. At various stages of the food production, processing and supply chain antimicrobial agents are required to sanitize contact surfaces. Additionally, during outbreaks of contagious pathogenic microorganisms (e.g., H1N1 influenza), public health requires timely decontamination of extensive surfaces within public schools, mass transit systems, etc. Prior publications verify effectiveness of air-assisted, induction-charged (AAIC) electrostatic spraying of various chemical and biological agents to protect on-farm production of food crops...typically doubling droplet deposition efficiency with concomitant increases in biological control efficacy. Within a biosafety facility this present work evaluated the AAIC electrostatic-spraying process for application of antimicrobial liquids onto various pathogen-inoculated food processing and handling surfaces as a food safety intervention strategy. Fluoroanalysis of AAIC electrostatic sprays (-7.2 mC/kg charge-to-mass ratio) showed significantly greater (p<0.05) mass of tracer active ingredient (A.I.) deposited onto target surfaces at various orientations as compared both to a similar uncharged spray nozzle (0 mC/kg) and to a conventional hydraulic-atomizing nozzle. Per unit mass of A.I. dispensed toward targets, for example, A.I. mass deposited by AAIC electrostatic sprays onto difficult to coat backsides was 6.1-times greater than for similar uncharged sprays and 29.0-times greater than for conventional hydraulic-nozzle sprays. Even at the 56% reduction in peracetic acid sanitizer A.I. dispensed by AAIC electrostatic spray applications, they achieved equal or greater CFU population reductions of Salmonella on most target orientations and materials as compared to uncharged sprays and conventional full-rate hydraulic

Electrostatic application of antimicrobial sprays to sanitize food handling and processing surfaces for enhanced food safety

Energy Technology Data Exchange (ETDEWEB)

Lyons, Shawn M; Harrison, Mark A [Food Science and Technology Department, University of Georgia, Athens, GA, 30602-2610 (United States); Law, S Edward, E-mail: edlaw@engr.uga.edu [Biological and Agricultural Engineering Department, Applied Electrostatics Laboratory www.ael.engr.uga.edu, University of Georgia, Athens, GA, 30602-4435 (United States)

2011-06-23

Human illnesses and deaths caused by foodborne pathogens (e.g., Salmonella enterica, Listeria monocytogenes, Escherichia coli O157:H7, etc.) are of increasing concern globally in maintaining safe food supplies. At various stages of the food production, processing and supply chain antimicrobial agents are required to sanitize contact surfaces. Additionally, during outbreaks of contagious pathogenic microorganisms (e.g., H1N1 influenza), public health requires timely decontamination of extensive surfaces within public schools, mass transit systems, etc. Prior publications verify effectiveness of air-assisted, induction-charged (AAIC) electrostatic spraying of various chemical and biological agents to protect on-farm production of food crops...typically doubling droplet deposition efficiency with concomitant increases in biological control efficacy. Within a biosafety facility this present work evaluated the AAIC electrostatic-spraying process for application of antimicrobial liquids onto various pathogen-inoculated food processing and handling surfaces as a food safety intervention strategy. Fluoroanalysis of AAIC electrostatic sprays (-7.2 mC/kg charge-to-mass ratio) showed significantly greater (p<0.05) mass of tracer active ingredient (A.I.) deposited onto target surfaces at various orientations as compared both to a similar uncharged spray nozzle (0 mC/kg) and to a conventional hydraulic-atomizing nozzle. Per unit mass of A.I. dispensed toward targets, for example, A.I. mass deposited by AAIC electrostatic sprays onto difficult to coat backsides was 6.1-times greater than for similar uncharged sprays and 29.0-times greater than for conventional hydraulic-nozzle sprays. Even at the 56% reduction in peracetic acid sanitizer A.I. dispensed by AAIC electrostatic spray applications, they achieved equal or greater CFU population reductions of Salmonella on most target orientations and materials as compared to uncharged sprays and conventional full-rate hydraulic

Contact angle of a nanodrop on a nanorough solid surface.

Science.gov (United States)

Berim, Gersh O; Ruckenstein, Eli

2015-02-21

The contact angle of a cylindrical nanodrop on a nanorough solid surface is calculated, for both hydrophobic and hydrophilic surfaces, using the density functional theory. The emphasis of the paper is on the dependence of the contact angle on roughness. The roughness is modeled by rectangular pillars of infinite length located on the smooth surface of a substrate, with fluid-pillar interactions different in strength from the fluid-substrate ones. It is shown that for hydrophobic substrates the trend of the contact angle to increase with increasing roughness, which was noted in all previous studies, is not universally valid, but depends on the fluid-pillar interactions, pillar height, interpillar distance, as well as on the size of the drop. For hydrophilic substrate, an unusual kink-like dependence of the contact angle on the nanodrop size is found which is caused by the change in the location of the leading edges of the nanodrop on the surface. It is also shown that the Wenzel and Cassie-Baxter equations can not explain all the peculiarities of the contact angle of a nanodrop on a nanorough surface.

Multipoint contact modeling of nanoparticle manipulation on rough surface

Energy Technology Data Exchange (ETDEWEB)

Zakeri, M., E-mail: m.zakeri@tabrizu.ac.ir; Faraji, J.; Kharazmi, M. [University of Tabriz, School of Engineering Emerging Technologies (Iran, Islamic Republic of)

2016-12-15

In this paper, the atomic force microscopy (AFM)-based 2-D pushing of nano/microparticles investigated on rough substrate by assuming a multipoint contact model. First, a new contact model was extracted and presented based on the geometrical profiles of Rumpf, Rabinovich and George models and the contact mechanics theories of JKR and Schwartz, to model the adhesion forces and the deformations in the multipoint contact of rough surfaces. The geometry of a rough surface was defined by two main parameters of asperity height (size of roughness) and asperity wavelength (compactness of asperities distribution). Then, the dynamic behaviors of nano/microparticles with radiuses in range of 50–500 nm studied during their pushing on rough substrate with a hexagonal or square arrangement of asperities. Dynamic behavior of particles were simulated and compared by assuming multipoint and single-point contact schemes. The simulation results show that the assumption of multipoint contact has a considerable influence on determining the critical manipulation force. Additionally, the assumption of smooth surfaces or single-point contact leads to large error in the obtained results. According to the results of previous research, it anticipated that a particles with the radius less than about 550 nm start to slide on smooth substrate; but by using multipoint contact model, the predicted behavior changed, and particles with radii of smaller than 400 nm begin to slide on rough substrate for different height of asperities, at first.

Mathematical modelling of contact of ruled surfaces: theory and practical application

Science.gov (United States)

Panchuk, K. L.; Niteyskiy, A. S.

2016-04-01

In the theory of ruled surfaces there are well known researches of contact of ruled surfaces along their common generator line (Klein image is often used [1]). In this paper we propose a study of contact of non developable ruled surfaces via the dual vector calculus. The advantages of this method have been demonstrated by E. Study, W. Blaschke and D. N. Zeiliger in differential geometry studies of ruled surfaces in space R3 over the algebra of dual numbers. A practical use of contact is demonstrated by the example modeling of the working surface of the progressive tool for tillage.

A novel method for the determination of migration of contaminants from food contact materials

International Nuclear Information System (INIS)

Thompson, D.; Parry, S.J.; Benzing, R.

1996-01-01

A neutron activation method has been developed for the analysis of high density polyethylene, low density polyethylene, polypropylene, polyethylene terephthalate and polystyrene food contact plastics. The method provides determination of over 50 elements at concentrations below 1 mg kg -1 . This technique has now been extended to study migration from food contact materials into standard food simulants (olive oil, acetic acid, ethanol and water). Samples of plastic are irradiated in a thermal neutron flux to procedure radionuclides of the elements present in the plastic. (author). 5 refs., 7 tabs

Contact angle measurements at the colemanite and realgar surfaces

Science.gov (United States)

Koca, Sabiha; Savas, Mehmet

2004-03-01

Colemanite is one of the most important boron minerals and covers an important part of Turkey's boron mineral deposits. The friable nature of the colemanite tends to produce a large amount of fines. Flotation appears to be a promising technique to recover colemanite from such fines. During flotation process, selectivity problem arises between colemanite and associated gangue minerals such as realgar. There is a close relationship between floatability of minerals and contact angle. Therefore, surface hydrophobicity of colemanite and realgar minerals were investigated by receding contact angle measurements in the absence and presence of flotation reagents. The water contact angle values at the colemanite surface remained almost unchanged at 32-35° in the solutions of potassium amyl xanthate (KAX), potassium ethyl xanthate (KEX) and petroleum sulphanate (R825) while another petroleum sulphanate (R840), sodium oleate and tallow amine (Armac-T) affected hydrophobicity of colemanite, and the contact angle values increased up to 47°. The contact angle values of 62, 63, 45, 46, 39, and 43° at the realgar surface were obtained in the solutions of KAX, KEX, sodium oleate, R825, R840 and Armac-T, respectively.

Capillary surfaces in a wedge: Differing contact angles

Science.gov (United States)

Concus, Paul; Finn, Robert

1994-01-01

The possible zero-gravity equilibrium configurations of capillary surfaces u(x, y) in cylindrical containers whose sections are (wedge) domains with corners are investigated mathematically, for the case in which the contact angles on the two sides of the wedge may differ. In such a situation the behavior can depart in significant qualitative ways from that for which the contact angles on the two sides are the same. Conditions are described under which such qualitative changes must occur. Numerically computed surfaces are depicted to indicate the behavior.

Effect of surface texturing on superoleophobicity, contact angle hysteresis, and "robustness".

Science.gov (United States)

Zhao, Hong; Park, Kyoo-Chul; Law, Kock-Yee

2012-10-23

Previously, we reported the creation of a fluorosilane (FOTS) modified pillar array silicon surface comprising ~3-μm-diameter pillars (6 μm pitch with ~7 μm height) that is both superhydrophobic and superoleophobic, with water and hexadecane contact angles exceeding 150° and sliding angles at ~10° owing to the surface fluorination and the re-entrant structure in the side wall of the pillar. In this work, the effects of surface texturing (pillar size, spacing, and height) on wettability, contact angle hysteresis, and "robustness" are investigated. We study the static, advancing, and receding contact angles, as well as the sliding angles as a function of the solid area fraction. The results reveal that pillar size and pillar spacing have very little effect on the static and advancing contact angles, as they are found to be insensitive to the solid area fraction from 0.04 to ~0.4 as the pillar diameter varies from 1 to 5 μm and the center-to-center spacing varies from 4.5 to 12 μm. On the other hand, sliding angle, receding contact angle, and contact angle hysteresis are found to be dependent on the solid area fraction. Specifically, receding contact angle decreases and sliding angle and hysteresis increase as the solid area fraction increases. This effect can be attributable to the increase in pinning as the solid area fraction increases. Surface Evolver modeling shows that water wets and pins the pillar surface whereas hexadecane wets the pillar surface and then penetrates into the side wall of the pillar with the contact line pinning underneath the re-entrant structure. Due to the penetration of the hexadecane drop into the pillar structure, the effect on the receding contact angle and hysteresis is larger relative to that of water. This interpretation is supported by studying a series of FOTS pillar array surfaces with varying overhang thickness. With the water drop, the contact line is pinned on the pillar surface and very little overhang thickness effect

77 FR 14022 - Guidance for Industry: Testing for Salmonella Species in Human Foods and Direct-Human-Contact...

Science.gov (United States)

2012-03-08

...-contact animal foods, and the interpretation of test results, when the presence of Salmonella spp. in the... eggs) and direct-human-contact animal foods, and the interpretation of test results, when the presence... DEPARTMENT OF HEALTH AND HUMAN SERVICES Food and Drug Administration [Docket No. FDA-2011-D-0091...

Preservation of atomically clean silicon surfaces in air by contact bonding

DEFF Research Database (Denmark)

Grey, Francois; Ljungberg, Karin

1997-01-01

When two hydrogen-passivated silicon surfaces are placed in contact under cleanroom conditions, a weak bond is formed. Cleaving this bond under ultrahigh vacuum (UHV) conditions, and observing the surfaces with low energy electron diffraction and scanning tunneling microscopy, we find that the or...... reconstruction from oxidation in air, Contact bonding opens the way to novel applications of reconstructed semiconductor surfaces, by preserving their atomic structure intact outside of a UHV chamber. (C) 1997 American Institute of Physics.......When two hydrogen-passivated silicon surfaces are placed in contact under cleanroom conditions, a weak bond is formed. Cleaving this bond under ultrahigh vacuum (UHV) conditions, and observing the surfaces with low energy electron diffraction and scanning tunneling microscopy, we find...... that the ordered atomic structure of the surfaces is protected from oxidation, even after the bonded samples have been in air for weeks. Further, we show that silicon surfaces that have been cleaned and hydrogen-passivated in UHV can be contacted in UHV in a similarly hermetic fashion, protecting the surface...

Nano-enhanced food contact materials and the in vitro toxicity to human intestinal cells of nano-ZnO at low dose

International Nuclear Information System (INIS)

Claonadh, Niall O; Casey, Alan; Mukherjee, Sanchali Gupta; Chambers, Gordon; Lyons, Sean; Higginbotham, Clement

2011-01-01

Nano Zinc Oxide (nZnO) has been shown to display antimicrobial effects which have lead to its application in a number of areas such as antimicrobial surface coatings, anti bacterial wound dressings and more recently in polymer composite systems for use in food contact materials. Concerns have been raised due to the incorporation of nanoparticles in food packaging stemming from the possibility of repeated low dose direct exposure, through ingestion, primarily due to degradation and nanoparticle leaching from the polymer composite. To address these concerns, composites consisting of nZnO and polyethylene were formed using twin screw extrusion to mimic commercial methods of food contact material production. A leaching study was performed using Atomic Absorption Spectroscopy in order to determine the concentration of nZnO leached from the composite. Composite stability studies were performed and a leached nZnO concentration was evaluated. This concentration range was then utilised in a series of tests aimed at determining the toxicity response associated with nZnO when exposed to an intestinal model. In this study two human colorectal carcinoma cell lines, HT29 (ATCC No: HTB-38) and SW480 (ATTC No: CCL-228), were employed as a model to represent areas exposed by ingestion. These lines were exposed to a concentration range of nZnO which incorporated the concentration leached from the composites. The cytotoxic effects of nZnO were evaluated using four cytotoxic endpoints namely the Neutral Red, Alamar Blue, Coomassie Blue and MTT assays. The results of these studies are presented and their implications for the use on nano ZnO in direct food contact surfaces will be discussed.

Nano-enhanced food contact materials and the in vitro toxicity to human intestinal cells of nano-ZnO at low dose

Energy Technology Data Exchange (ETDEWEB)

Claonadh, Niall O; Casey, Alan; Mukherjee, Sanchali Gupta; Chambers, Gordon [Nanolab Research Centre, Focas Institute, Dublin Institute of Technology, Dublin (Ireland); Lyons, Sean; Higginbotham, Clement, E-mail: Niall.OClaonadh@DIT.ie, E-mail: Alan.Casey@DIT.ie [Materials Research Institute, Athlone Institute of Technology, Westmeath (Ireland)

2011-07-06

Nano Zinc Oxide (nZnO) has been shown to display antimicrobial effects which have lead to its application in a number of areas such as antimicrobial surface coatings, anti bacterial wound dressings and more recently in polymer composite systems for use in food contact materials. Concerns have been raised due to the incorporation of nanoparticles in food packaging stemming from the possibility of repeated low dose direct exposure, through ingestion, primarily due to degradation and nanoparticle leaching from the polymer composite. To address these concerns, composites consisting of nZnO and polyethylene were formed using twin screw extrusion to mimic commercial methods of food contact material production. A leaching study was performed using Atomic Absorption Spectroscopy in order to determine the concentration of nZnO leached from the composite. Composite stability studies were performed and a leached nZnO concentration was evaluated. This concentration range was then utilised in a series of tests aimed at determining the toxicity response associated with nZnO when exposed to an intestinal model. In this study two human colorectal carcinoma cell lines, HT29 (ATCC No: HTB-38) and SW480 (ATTC No: CCL-228), were employed as a model to represent areas exposed by ingestion. These lines were exposed to a concentration range of nZnO which incorporated the concentration leached from the composites. The cytotoxic effects of nZnO were evaluated using four cytotoxic endpoints namely the Neutral Red, Alamar Blue, Coomassie Blue and MTT assays. The results of these studies are presented and their implications for the use on nano ZnO in direct food contact surfaces will be discussed.

Adhesive friction for elastic-plastic contacting rough surfaces considering asperity interaction

International Nuclear Information System (INIS)

Sahoo, Prasanta

2006-01-01

The paper describes a theoretical study of adhesive friction at the contact between rough surfaces taking asperity interaction into consideration and using an elastic-plastic model of contact deformation that is based on an accurate finite element analysis of an elastic-plastic single asperity contact. The micro-contact model of asperity interactions, developed by Zhao and Chang, is integrated into the improved elastic-plastic rough surface adhesive contact analysis to consider the adhesive friction behaviour of rough surfaces. The model considers a large range of interference values from fully elastic through elastic-plastic to fully plastic regimes of contacting asperities. Two well-established adhesion indices are used to consider different conditions that arise as a result of varying load, surface and material parameters. Results are obtained for the coefficient of friction against applied load for various combinations of these parameters. The results show that the coefficient of friction depends strongly on the applied load for the no-interaction case while it becomes insensitive to the load for interaction consideration. Moreover, the inclusion of elastic-plastic asperities further reduces the friction coefficient

The biofilm-positive Staphylococcus epidermidis isolates in raw materials, foodstuffs and on contact surfaces in processing plants.

Science.gov (United States)

Schlegelová, J; Babák, V; Holasová, M; Dendis, M

2008-01-01

Isolates from the "farm to fork" samples (182 isolates from 2779 samples) were examined genotypically (icaAB genes) and phenotypically (in vitro biofilm formation, typical growth on Congo red agar; CRA) with the aim to assess the risk of penetration of virulent strains of Staphylococcus epidermidis into the food chain. The contamination of meat and milk products was significantly higher in comparison with raw materials. Contamination of contact surfaces in the meat-processing plants was significantly lower than that of contact surfaces in the dairy plants. The ica genes (which precondition the biofilm formation) were concurrently detected in 20 isolates that also showed a typical growth on CRA. Two ica operon-negative isolates produced biofilm in vitro but perhaps by an ica-independent mechanism. The surfaces in the dairy plants and the milk products were more frequently contaminated with ica operon-positive strains (2.3 and 1.2 % samples) than the other sample types (0-0.6 % samples).

On ruled surface in 3-dimensional almost contact metric manifold

Science.gov (United States)

Karacan, Murat Kemal; Yuksel, Nural; Ikiz, Hasibe

In this paper, we study ruled surface in 3-dimensional almost contact metric manifolds by using surface theory defined by Gök [Surfaces theory in contact geometry, PhD thesis (2010)]. We also studied the theory of curves using cross product defined by Camcı. In this study, we obtain the distribution parameters of the ruled surface and then some results and theorems are presented with special cases. Moreover, some relationships among asymptotic curve and striction line of the base curve of the ruled surface have been found.

Surface charging, discharging and chemical modification at a sliding contact

DEFF Research Database (Denmark)

Singh, Shailendra Vikram; Kusano, Yukihiro; Morgen, Per

2012-01-01

Electrostatic charging, discharging, and consequent surface modification induced by sliding dissimilar surfaces have been studied. The surface-charge related phenomena were monitored by using a home-built capacitive, non-contact electrical probe, and the surface chemistry was studied by X...... are also able to comment on the behavior and the charge decay time in the ambient air-like condition, once the sliding contact is discontinued. XPS analysis showed a marginal deoxidation effect on the polyester disks due to the charging and discharging of the surfaces. Moreover, these XPS results clearly...

Survey of the occurrence of 1,6-hexanediol diglycidyl ether in food contact materials

DEFF Research Database (Denmark)

producers and importers. The substance is not allowed for use in plastic materials for food contact. One Danish company reported a possible use of HDDGE in coating of drinking tanks and pipelines. This is the only use of HDDGE confirmed in relation to food contact materials in Denmark. The project...... is following up on a previous survey under the Danish EPA’s LOUS-review (Environmental Project no. 1472)....

Identification and risk assessment of unknown contaminants migrating from Food Contact Materials

DEFF Research Database (Denmark)

Pieke, Eelco Nicolaas

The exposure of humans to possibly thousands of chemical compounds through food poses a health risk that is questioning our ability to ensure high standards for food safety. Food contact materials (FCM) are a major source of extraneous chemical compounds in food, yet not much knowledge is available...... interpretations. Risk prioritization is successful in classifying estimated risk based on predicted exposure and predicted hazard, and is valuable for to preliminary RA studies. The overarching strategy in this study shows that explorative techniques are valuable tools to help ensure food safety in the future...

Methods for Recovering Microorganisms from Solid Surfaces Used in the Food Industry: A Review of the Literature

Directory of Open Access Journals (Sweden)

Perrine Gay-Perret

2013-11-01

Full Text Available Various types of surfaces are used today in the food industry, such as plastic, stainless steel, glass, and wood. These surfaces are subject to contamination by microorganisms responsible for the cross-contamination of food by contact with working surfaces. The HACCP-based processes are now widely used for the control of microbial hazards to prevent food safety issues. This preventive approach has resulted in the use of microbiological analyses of surfaces as one of the tools to control the hygiene of products. A method of recovering microorganisms from different solid surfaces is necessary as a means of health prevention. No regulation exists for surface microbial contamination, but food companies tend to establish technical specifications to add value to their products and limit contamination risks. The aim of this review is to present the most frequently used methods: swabbing, friction or scrubbing, printing, rinsing or immersion, sonication and scraping or grinding and describe their advantages and drawbacks. The choice of the recovery method has to be suitable for the type and size of the surface tested for microbiological analysis. Today, quick and cheap methods have to be standardized and especially easy to perform in the field.

Plasma surface modification of rigid contact lenses decreases bacterial adhesion.

Science.gov (United States)

Wang, Yingming; Qian, Xuefeng; Zhang, Xiaofeng; Xia, Wei; Zhong, Lei; Sun, Zhengtai; Xia, Jing

2013-11-01

Contact lens safety is an important topic in clinical studies. Corneal infections usually occur because of the use of bacteria-carrying contact lenses. The current study investigated the impact of plasma surface modification on bacterial adherence to rigid contact lenses made of fluorosilicone acrylate materials. Boston XO and XO2 contact lenses were modified using plasma technology (XO-P and XO2-P groups). Untreated lenses were used as controls. Plasma-treated and control lenses were incubated in solutions containing Staphylococcus aureus or Pseudomonas aeruginosa. MTT colorimetry, colony-forming unit counting method, and scanning electron microscopy were used to measure bacterial adhesion. MTT colorimetry measurements showed that the optical density (OD) values of XO-P and XO2-P were significantly lower than those of XO and XO2, respectively, after incubation with S. aureus (P lenses and to the XO2-P versus XO2 lenses incubated with S. aureus (P lenses incubated with P. aeruginosa (P lenses. Plasma surface modification can significantly decrease bacterial adhesion to fluorosilicone acrylate contact lenses. This study provides important evidence of a unique benefit of plasma technology in contact lens surface modification.

Contact mechanics for layered materials with randomly rough surfaces.

Science.gov (United States)

Persson, B N J

2012-03-07

The contact mechanics model of Persson is applied to layered materials. We calculate the M function, which relates the surface stress to the surface displacement, for a layered material, where the top layer (thickness d) has different elastic properties than the semi-infinite solid below. Numerical results for the contact area as a function of the magnification are presented for several cases. As an application, we calculate the fluid leak rate for laminated rubber seals.

Experimental Investigations on Microshock Waves and Contact Surfaces

Science.gov (United States)

Kai, Yun; Garen, Walter; Teubner, Ulrich

2018-02-01

The present work reports on progress in the research of a microshock wave. Because of the lack of a good understanding of the propagation mechanism of the microshock flow system (shock wave, contact surface, and boundary layer), the current work concentrates on measuring microshock flows with special attention paid to the contact surface. A novel setup involving a glass capillary (with a 200 or 300 μ m hydraulic diameter D ) and a high-speed magnetic valve is applied to generate a shock wave with a maximum initial Mach number of 1.3. The current work applies a laser differential interferometer to perform noncontact measurements of the microshock flow's trajectory, velocity, and density. The current work presents microscale measurements of the shock-contact distance L that solves the problem of calculating the scaling factor Sc =Re ×D /(4 L ) (introduced by Brouillette), which is a parameter characterizing the scaling effects of shock waves. The results show that in contrast to macroscopic shock waves, shock waves at the microscale have a different propagation or attenuation mechanism (key issue of this Letter) which cannot be described by the conventional "leaky piston" model. The main attenuation mechanism of microshock flow may be the ever slower moving contact surface, which drives the shock wave. Different from other measurements using pressure transducers, the current setup for density measurements resolves the whole microshock flow system.

Comparison of surface roughness and bacterial adhesion between cosmetic contact lenses and conventional contact lenses.

Science.gov (United States)

Ji, Yong Woo; Cho, Young Joo; Lee, Chul Hee; Hong, Soon Ho; Chung, Dong Yong; Kim, Eung Kweon; Lee, Hyung Keun

2015-01-01

To compare physical characteristics of cosmetic contact lenses (Cos-CLs) and conventional contact lenses (Con-CLs) that might affect susceptibility to bacterial adhesion on the contact lens (CL) surface. Surface characteristics of Cos-CLs and Con-CLs made from the same material by the same manufacturer were measured by atomic force microscopy (AFM) and scanning electron microscopy. To determine the extent and rate of bacterial adhesion, Cos-CL and Con-CL were immersed in serum-free Roswell Park Memorial Institute media containing Staphylococcus aureus or Pseudomonas aeruginosa. Additionally, the rate of removal of adherent bacteria was evaluated using hand rubbing or immersion in multipurpose disinfecting solutions (MPDS). The mean surface roughness (root mean square and peak-to-valley value) measured by AFM was significantly higher for Cos-CL than for Con-CL. At each time point, significantly more S. aureus and P. aeruginosa adhered to Cos-CL than to Con-CL, which correlated with the surface roughness of CL. In Cos-CL, bacteria were mainly found on the tinted surface rather than on the noncolored or convex areas. Pseudomonas aeruginosa attached earlier than S. aureus to all types of CL. However, P. aeruginosa was more easily removed from the surface of CL than S. aureus by hand rubbing or MPDS soaking. Increased surface roughness is an important physical factor for bacterial adhesion in Cos-CL, which may explain why rates of bacterial keratitis rates are higher in Cos-CL users in CL physical characteristics.

Improving the contact resistance at low force using gold coated carbon nanotube surfaces

Science.gov (United States)

McBride, J. W.; Yunus, E. M.; Spearing, S. M.

2010-04-01

Investigations to determine the electrical contact performance under repeated cycles at low force conditions for carbon-nanotube (CNT) coated surfaces were performed. The surfaces under investigation consisted of multi-walled CNT synthesized on a silicon substrate and coated with a gold film. These planar surfaces were mounted on the tip of a PZT actuator and contacted with a plated Au hemispherical probe. The dynamic applied force used was 1 mN. The contact resistance (Rc) of these surfaces was investigated with the applied force and with repeated loading cycles performed for stability testing. The surfaces were compared with a reference Au-Au contact under the same experimental conditions. This initial study shows the potential for the application of gold coated CNT surfaces as an interface in low force electrical contact applications.

Liquid-solid contact measurements using a surface thermocouple temperature probe in atmospheric pool boiling water

International Nuclear Information System (INIS)

Lee, L.Y.W.; Chen, J.C.; Nelson, R.A.

1984-01-01

Objective was to apply the technique of using a microthermocouple flush-mounted at the boiling surface for the measurement of the local-surface-temperature history in film and transition boiling on high temperature surfaces. From this measurement direct liquid-solid contact in film and transition boiling regimes was observed. In pool boiling of saturated, distilled, deionized water on an aluminum-coated copper surface, the time-averaged, local-liquid-contact fraction increased with decreasing surface superheat. Average contact duration increased monotonically with decreasing surface superheat, while frequency of liquid contact reached a maximum of approx. 50 contacts/s at a surface superheat of approx. 100 K and decreased gradually to 30 contacts/s near the critical heat flux. The liquid-solid contact duration distribution was dominated by short contacts 4 ms at low surface superheats, passing through a relatively flat contact duration distribution at about 80 0 K. Results of this paper indicate that liquid-solid contacts may be the dominant mechanism for energy transfer in the transition boiling process

Effect of the cut off frequency on rough point and flat surface contacts

International Nuclear Information System (INIS)

Meng, Fan Ming

2012-01-01

In the past years, contact between two bodies has been studied from various ways that do not consider the cut off frequency effect on the contact mechanism. This paper reports the correlation between rough point contact and flat surface contact at different cut off frequencies of filter. The similarity and difference between the two types of contact mechanisms are presented for materials with linear or elastic perfectly plastic deformation. The conjugate gradient method (CGM) is used for analysing the rough point contact, while the rough flat surface contact is studied with an improved CGM in which the influence coefficient for the elastic deformation of the rough flat surface is obtained with finite element method. Numerical results show that for the above two types of contacts, their von Mises stress and maximum shear stress are greatly affected by the cut-off frequency of a high pass filter. Moreover, a decrease in the cut-off frequency leads to an increase in the contact area and a decrease in the approach for the rough flat surface contact, while the opposite variations is for the point contact between rough bodies with the small radii

The influence of rail surface irregularities on contact forces and local stresses

Science.gov (United States)

Andersson, Robin; Torstensson, Peter T.; Kabo, Elena; Larsson, Fredrik

2015-01-01

The effect of initial rail surface irregularities on promoting further surface degradation is investigated. The study concerns rolling contact fatigue formation, in particular in the form of the so-called squats. The impact of surface irregularities in the form of dimples is quantified by peak magnitudes of dynamic contact stresses and contact forces. To this end simulations of two-dimensional (later extended to three-dimensional) vertical dynamic vehicle-track interaction are employed. The most influencing parameters are identified. It is shown that even very shallow dimples might have a large impact on local contact stresses. Peak magnitudes of contact forces and stresses due to the influence of rail dimples are shown to exceed those due to rail corrugation.

Contact Angles and Surface Tension of Germanium-Silicon Melts

Science.gov (United States)

Croell, A.; Kaiser, N.; Cobb, S.; Szofran, F. R.; Volz, M.; Rose, M. Franklin (Technical Monitor)

2001-01-01

Precise knowledge of material parameters is more and more important for improving crystal growth processes. Two important parameters are the contact (wetting) angle and the surface tension, determining meniscus shapes and surface-tension driven flows in a variety of methods (Czochralski, EFG, floating-zone, detached Bridgman growth). The sessile drop technique allows the measurement of both parameters simultaneously and has been used to measure the contact angles and the surface tension of Ge(1-x)Si(x) (0 less than or equal to x less than or equal to 1.3) alloys on various substrate materials. Fused quartz, Sapphire, glassy carbon, graphite, SiC, carbon-based aerogel, pyrolytic boron nitride (pBN), AIN, Si3N4, and polycrystalline CVD diamond were used as substrate materials. In addition, the effect of different cleaning procedures and surface treatments on the wetting behavior were investigated. Measurements were performed both under dynamic vacuum and gas atmospheres (argon or forming gas), with temperatures up to 1100 C. In some experiments, the sample was processed for longer times, up to a week, to investigate any changes of the contact angle and/or surface tension due to slow reactions with the substrate. For pure Ge, stable contact angles were found for carbon-based substrates and for pBN, for Ge(1-x)Si(x) only for pBN. The highest wetting angles were found for pBN substrates with angles around 170deg. For the surface tension of Ge, the most reliable values resulted in gamma(T) = (591- 0.077 (T-T(sub m)) 10(exp -3)N/m. The temperature dependence of the surface tension showed similar values for Ge(1-x)Si(x), around -0.08 x 10(exp -3)N/m K, and a compositional dependence of 2.2 x 10(exp -3)N/m at%Si.

Analysis of Wetting and Contact Angle Hysteresis on Chemically Patterned Surfaces

KAUST Repository

Xu, Xianmin; Wang, Xiaoping

2011-01-01

Wetting and contact angle hysteresis on chemically patterned surfaces in two dimensionsare analyzed from a stationary phase-field model for immiscible two phase fluids. We first study the sharp-interface limit of the model by the method of matched asymptotic expansions. We then justify the results rigorously by the γ-convergence theory for the related variational problem and study the properties of the limiting minimizers. The results also provide a clear geometric picture of the equilibrium configuration of the interface. This enables us to explicitly calculate the total surface energy for the two phase systems on chemically patterned surfaces with simple geometries, namely the two phase flow in a channel and the drop spreading. By considering the quasi-staticmotion of the interface described by the change of volume (or volume fraction), we can follow the change-of-energy landscape which also reveals the mechanism for the stick-slip motion of the interface and contact angle hysteresis on the chemically patterned surfaces. As the interface passes throughpatterned surfaces, we observe not only stick-slip of the interface and switching of the contact angles but also the hysteresis of contact point and contact angle. Furthermore, as the size of the patternde creases to zero, the stick-slip becomes weaker but the hysteresis becomes stronger in the sense that one observes either the advancing contact angle or the receding contact angle (when the interface ismoving in the opposite direction) without the switching in between. © 2011 Society for Industrial and Applied Mathematics.

A Modified Approach in Modeling and Calculation of Contact Characteristics of Rough Surfaces

Directory of Open Access Journals (Sweden)

J.A. Abdo

2005-12-01

Full Text Available A mathematical formulation for the contact of rough surfaces is presented. The derivation of the contact model is facilitated through the definition of plastic asperities that are assumed to be embedded at a critical depth within the actual surface asperities. The surface asperities are assumed to deform elastically whereas the plastic asperities experience only plastic deformation. The deformation of plastic asperities is made to obey the law of conservation of volume. It is believed that the proposed model is advantageous since (a it provides a more accurate account of elasticplastic behavior of surfaces in contact and (b it is applicable to model formulations that involve asperity shoulder-to shoulder contact. Comparison of numerical results for estimating true contact area and contact force using the proposed model and the earlier methods suggest that the proposed approach provides a more realistic prediction of elastic-plastic contact behavior.

[Determination of photoinitiators in printing inks used in food contact materials].

Science.gov (United States)

Han, Wei; Yu, Yanjun; Li, Ningtao; Wang, Libing

2011-05-01

A new analytical method based on gas chromatography-mass spectrometry (GC-MS) techniques was developed for the determination of five photoinitiators (PIs), benzophenone (BP), 4-methylbenzophenone (MBP), ethyl-4-dimethylaminobenzoate (EDAB), 2-ethylhexyl-4-dimethylaminobenzoate (EHDAB) and 1-hydroxycyclohexyl phenyl ketone (Irgacure 184), in the printing inks used in food contact materials. The test solutions were extracted from selected food contact materials using Soxhlet extractor with ethyl acetate as the extraction solvent. By adding 50 and 200 microg/L of a standard mixture of photoinitiators into the extracts of the blank packaging materials, the recoveries obtained were in the range of 66.7%-89.4%. The repeatability of the method was assessed by determining the contents of the photoinitiators in five types of food contact materials, and the results were lower than 10%. The instrumental detection limits (IDLs) and method quantification limits (MQLs) were in the range of 2.9-6.0 microg/L and 0.0017-0.0036 mg/dm2, respectively. The method was applied in the analysis of about twenty real samples (yogurt carton, milk carton, fruit juice carton and plastic bags samples). The most significant pollutants were BP and MBP. The concentrations of Irgacure 184, EDAB and EHDAB found in three individual samples were 0.84 mg/dm2, 0.2 mg/dm2 and 1.2 mg/dm2, respectively. The work proposed a new method to analyze the migration level of initiators from the inks.

Sub-discretized surface model with application to contact mechanics in multi-body simulation

Energy Technology Data Exchange (ETDEWEB)

Johnson, S; Williams, J

2008-02-28

The mechanics of contact between rough and imperfectly spherical adhesive powder grains are often complicated by a variety of factors, including several which vary over sub-grain length scales. These include several traction factors that vary spatially over the surface of the individual grains, including high energy electron and acceptor sites (electrostatic), hydrophobic and hydrophilic sites (electrostatic and capillary), surface energy (general adhesion), geometry (van der Waals and mechanical), and elasto-plastic deformation (mechanical). For mechanical deformation and reaction, coupled motions, such as twisting with bending and sliding, as well as surface roughness add an asymmetry to the contact force which invalidates assumptions for popular models of contact, such as the Hertzian and its derivatives, for the non-adhesive case, and the JKR and DMT models for adhesive contacts. Though several contact laws have been offered to ameliorate these drawbacks, they are often constrained to particular loading paths (most often normal loading) and are relatively complicated for computational implementation. This paper offers a simple and general computational method for augmenting contact law predictions in multi-body simulations through characterization of the contact surfaces using a hierarchically-defined surface sub-discretization. For the case of adhesive contact between powder grains in low stress regimes, this technique can allow a variety of existing contact laws to be resolved across scales, allowing for moments and torques about the contact area as well as normal and tangential tractions to be resolved. This is especially useful for multi-body simulation applications where the modeler desires statistical distributions and calibration for parameters in contact laws commonly used for resolving near-surface contact mechanics. The approach is verified against analytical results for the case of rough, elastic spheres.

Drop evaporation on superhydrophobic PTFE surfaces driven by contact line dynamics.

Science.gov (United States)

Ramos, S M M; Dias, J F; Canut, B

2015-02-15

In the present study, we experimentally study the evaporation modes and kinetics of sessile drops of water on highly hydrophobic surfaces (contact angle ∼160°), heated to temperatures ranging between 40° and 70 °C. These surfaces were initially constructed by means of controlled tailoring of polytetrafluoroethylene (PTFE) substrates. The evaporation of droplets was observed to occur in three distinct phases, which were the same for the different substrate temperatures. The drops started to evaporate in the constant contact radius (CCR) mode, then switched to a more complex mode characterized by a set of stick-slip events accompanied by a decrease in contact angle, and finally shifted to a mixed mode in which the contact radius and contact angle decreased simultaneously until the drops had completely evaporated. It is shown that in the case of superhydrophobic surfaces, the energy barriers (per unit length) associated with the stick-slip motion of a drop ranges in the nJ m(-1) scale. Furthermore, analysis of the evaporation rates, determined from experimental data show that, even in the CCR mode, a linear relationship between V(2/3) and the evaporation time is verified. The values of the evaporation rate constants are found to be higher in the pinned contact line regime (the CCR mode) than in the moving contact line regime. This behavior is attributed to the drop's higher surface to volume ratio in the CCR mode. Copyright © 2014 Elsevier Inc. All rights reserved.

Wear-less floating contact imaging of polymer surfaces

International Nuclear Information System (INIS)

Knoll, A; Rothuizen, H; Gotsmann, B; Duerig, U

2010-01-01

An atomic force microscopy (AFM) technique is described combining two operating modes that previously were mutually exclusive: gentle imaging of delicate surfaces requiring slow dynamic AFM techniques, and passive feedback contact mode AFM enabling ultra-fast imaging. A high-frequency force modulation is used to excite resonant modes in the MHz range of a highly compliant cantilever force sensor with a spring constant of 0.1 N m -1 . The high-order mode acts as a stiff system for modulating the tip-sample distance and a vibration amplitude of 1 nm is sufficient to overcome the adhesion interaction. The soft cantilever provides a force-controlled support for the vibrating tip, enabling high-speed intermittent contact force microscopy without feedback control of the cantilever bending. Using this technique, we were able to image delicate polymer surfaces and to completely suppress the formation of the ripple wear patterns that are commonly observed in contact AFM.

77 FR 19670 - Agency Information Collection Activities; Proposed Collection; Comment Request; Food Contact...

Science.gov (United States)

2012-04-02

... Nutrition, Food and Drug Administration, 5100 Paint Branch Pkwy (HFS-275), College Park, MD 20740, 240-402... Nutrition using Form FDA 3480 whether it is submitted in electronic or paper format. FDA recently made minor... food contact articles. These notifications require the submission of Form FDA 3479 (``Notification for...

Surface modification of fluorosilicone acrylate RGP contact lens via low-temperature argon plasma

International Nuclear Information System (INIS)

Yin Shiheng; Wang Yingjun; Ren Li; Zhao Lianna; Kuang Tongchun; Chen Hao; Qu Jia

2008-01-01

A fluorosilicone acrylate rigid gas permeable (RGP) contact lens was modified via argon plasma to improve surface hydrophilicity and resistance to protein deposition. The influence of plasma treatment on surface chemical structure, hydrophilicity and morphology of RGP lens was investigated by X-ray photoelectron spectrometer (XPS), contact angle measurements and scanning electron microscope (SEM), respectively. The contact angle results showed that the hydrophilicity of the contact lens was improved after plasma treatment. XPS results indicated that the incorporation of oxygen-containing groups on surface and the transformation of silicone into hydrophilic silicate after plasma treatment are the main reasons for the surface hydrophilicity improvement. SEM results showed that argon plasma with higher power could lead to surface etching

In vitro biofilm forming capacity on abiotic contact surfaces by outbreak-associated Vibrio harveyi strains

Directory of Open Access Journals (Sweden)

Pallaval Veera Bramha Chari

2014-02-01

Full Text Available Objective: To evaluate the in vitro biofilm forming capacity on abiotic food contact surfaces by Vibrio harveyi (V. harveyi strains. Methods: Thirty six Gram-negative V. harveyi strains were isolated from various street vended seafood outlets in a food processing line and evaluated for their ability to produce mucoid biofilms on food contact surfaces using a microplate assay. Phenotypic characterization of mucoid biofilm producing V. harveyi strains were screened on Congo red agar, thiosulfate-citrate-bile salts-sucrose agar and tryptic soy agar, respectively. Results: Only five V. harveyi strains (14% were mucoid biofilm producers characterized by formation of black colonies, whereas the remaining 31 strains (86% were not capable of producing biofilm characterized by formation of red colonies or pinkish-red colonies with darkening at the centre. The morphological, physiological and biochemical characteristics of these isolates were studied using standard protocols. Strain identification was confirmed by polymerase chain reaction targeted to species-specific polymerase chain reaction primers VH-1 and VH-2 corresponding to variable regions of V. harveyi 16S rRNA sequence. All the biofilm-forming strains showed resistance to at least three antimicrobial compounds tested. V. harveyi strains isolated from various seafood were able to form biofilms of different capacity, and the strains VB267, VB238 and VB166 isolated from cat fish, shrimp and eel fish exhibited significantly greater biofilm forming ability compared to other isolates. Conclusions: It can be concluded from the present study that the strain VB166 was able to better attach and form subsequent biofilms on glass and stainless steel compared to high density polyethylene. These properties allow these bacteria to survive, proliferate and persist in street vended seafood outlets.

3D geophysical inversion for contact surfaces

Science.gov (United States)

Lelièvre, Peter; Farquharson, Colin

2014-05-01

Geologists' interpretations about the Earth typically involve distinct rock units with contacts (interfaces) between them. In contrast, standard minimum-structure volumetric inversions (performed on meshes of space-filling cells) recover smooth models inconsistent with such interpretations. There are several approaches through which geophysical inversion can help recover models with the desired characteristics. Some authors have developed iterative strategies in which several volumetric inversions are performed with regularization parameters changing to achieve sharper interfaces at automatically determined locations. Another approach is to redesign the regularization to be consistent with the desired model characteristics, e.g. L1-like norms or compactness measures. A few researchers have taken approaches that limit the recovered values to lie within particular ranges, resulting in sharp discontinuities; these include binary inversion, level set methods and clustering strategies. In most of the approaches mentioned above, the model parameterization considers the physical properties in each of the many space-filling cells within the volume of interest. The exception are level set methods, in which a higher dimensional function is parameterized and the contact surface is determined from the zero-level of that function. However, even level-set methods rely on an underlying volumetric mesh. We are researching a fundamentally different type of inversion that parameterizes the Earth in terms of the contact surfaces between rock units. 3D geological Earth models typically comprise wireframe surfaces of tessellated triangles or other polygonal planar facets. This wireframe representation allows for flexible and efficient generation of complicated geological structures. Therefore, a natural approach for representing a geophysical model in an inversion is to parameterize the wireframe contact surfaces as the coordinates of the nodes (facet vertices). The geological and

Food-safe modification of stainless steel food processing surfaces to reduce bacterial biofilms.

Science.gov (United States)

Awad, Tarek Samir; Asker, Dalal; Hatton, Benjamin D

2018-06-11

Biofilm formation on stainless steel (SS) surfaces of food processing plants, leading to foodborne illness outbreaks, is enabled by the attachment and confinement within microscale cavities of surface roughness (grooves, scratches). We report Foodsafe Oil-based Slippery Coatings (FOSCs) for food processing surfaces that suppress bacterial adherence and biofilm formation by trapping residual oil lubricant within these surface cavities to block microbial growth. SS surfaces were chemically functionalized with alkylphosphonic acid to preferentially wet a layer of food grade oil. FOSCs reduced the effective surface roughness, the adhesion of organic food residue, and bacteria. FOSCs significantly reduced Pseudomonas aeruginosa biofilm formation on standard roughness SS-316 by 5 log CFU cm-2, and by 3 log CFU cm-2 for mirror-finished SS. FOSCs also enhanced surface cleanability, which we measured by bacterial counts after conventional detergent cleaning. Importantly, both SS grades maintained their anti-biofilm activity after erosion of the oil layer by surface wear with glass beads, which suggests there is a residual volume of oil that remains to block surface cavity defects. These results indicate the potential of such low-cost, scalable approaches to enhance the cleanability of SS food processing surfaces and improve food safety by reducing biofilm growth.

A Congruence Theorem for Minimal Surfaces in $S^{5}$ with Constant Contact Angle

OpenAIRE

Montes, Rodrigo Ristow; Verderesi, Jose A.

2006-01-01

We provide a congruence theorem for minimal surfaces in $S^5$ with constant contact angle using Gauss-Codazzi-Ricci equations. More precisely, we prove that Gauss-Codazzi-Ricci equations for minimal surfaces in $S^5$ with constant contact angle satisfy an equation for the Laplacian of the holomorphic angle. Also, we will give a characterization of flat minimal surfaces in $S^5$ with constant contact angle.

Tyre-road contact using a particle-envelope surface model

Science.gov (United States)

Pinnington, Roger J.

2013-12-01

Determination of the contact forces is the central problem in all aspects of road-tyre interaction: i.e. noise, energy loss and friction. A procedure to find the contact forces under a rolling tyre is presented in four stages. First, the contact stiffness of a uniform peak array from indentations in the rubber tread, and also tyre carcass deflection, is described by some new simplified expressions. Second, a routine divides a single surface profile into equal search intervals, in which the highest peaks are identified. These are used to obtain the parameters for the interval, i.e. the mean envelope and the mean interval. The process is repeated at geometrically decreasing search intervals until the level of the data resolution, thereby describing the profile by a set of envelopes. The ‘strip profile’ ultimately used to describe the surface, is obtained by selecting the highest points across the profiles of one stone's width. The third stage is to combine the strip profile envelopes with the contact stiffness expressions, yielding the nonlinear stiffness-displacement, and force-displacement relationships for the chosen road-tyre combination. Finally the contact pressure distribution from a steady-state rolling tyre model is applied to the strip profile, via the force-displacement relationship, giving the local tyre displacements on the road texture. This displacement pattern is shown to be proportional to the time and space varying contact pressure, which then is incorporated into a wave equation for rolling contact.

High-precision drop shape analysis (HPDSA) of quasistatic contact angles on silanized silicon wafers with different surface topographies during inclining-plate measurements: Influence of the surface roughness on the contact line dynamics

International Nuclear Information System (INIS)

Heib, F.; Hempelmann, R.; Munief, W.M.; Ingebrandt, S.; Fug, F.; Possart, W.; Groß, K.; Schmitt, M.

2015-01-01

Highlights: • Analysis of the triple line motion on surfaces with nanoscale surface topographies. • Analysis of the triple line motion is performed in sub-pixel resolution. • A special fitting and statistical approach for contact angle analysis is applied. • The analyses result set of contact angle data which is independent of “user-skills”. • Characteristically density distributions in dependence on the surface properties. - Abstract: Contact angles and wetting of solid surfaces are strongly influenced by the physical and chemical properties of the surfaces. These influence quantities are difficult to distinguish from each other if contact angle measurements are performed by measuring only the advancing θ a and the receding θ r contact angle. In this regard, time-dependent water contact angles are measured on two hydrophobic modified silicon wafers with different physical surface topographies. The first surface is nearly atomically flat while the second surface is patterned (alternating flat and nanoscale rough patterns) which is synthesized by a photolithography and etching procedure. The different surface topographies are characterized with atomic force microscopy (AFM), Fourier transform infrared reflection absorption spectroscopy (FTIRRAS) and Fourier transform infrared attenuated total reflection spectroscopy (FTIR-ATR). The resulting set of contact angle data obtained by the high-precision drop shape analysis approach is further analyzed by a Gompertzian fitting procedure and a statistical counting procedure in dependence on the triple line velocity. The Gompertzian fit is used to analyze overall properties of the surface and dependencies between the motion on the front and the back edge of the droplets. The statistical counting procedure results in the calculation of expectation values E(p) and standard deviations σ(p) for the inclination angle φ, contact angle θ, triple line velocity vel and the covered distance of the triple line dis

High-precision drop shape analysis (HPDSA) of quasistatic contact angles on silanized silicon wafers with different surface topographies during inclining-plate measurements: Influence of the surface roughness on the contact line dynamics

Energy Technology Data Exchange (ETDEWEB)

Heib, F., E-mail: f.heib@mx.uni-saarland.de [Department of Physical Chemistry, Saarland University, 66123 Saarbrücken (Germany); Hempelmann, R. [Department of Physical Chemistry, Saarland University, 66123 Saarbrücken (Germany); Munief, W.M.; Ingebrandt, S. [Department of Informatics and Microsystem Technology, University of Applied Sciences, Kaiserslautern, 66482 Zweibrücken (Germany); Fug, F.; Possart, W. [Department of Adhesion and Interphases in Polymers, Saarland University, 66123 Saarbrücken (Germany); Groß, K.; Schmitt, M. [Department of Physical Chemistry, Saarland University, 66123 Saarbrücken (Germany)

2015-07-01

Highlights: • Analysis of the triple line motion on surfaces with nanoscale surface topographies. • Analysis of the triple line motion is performed in sub-pixel resolution. • A special fitting and statistical approach for contact angle analysis is applied. • The analyses result set of contact angle data which is independent of “user-skills”. • Characteristically density distributions in dependence on the surface properties. - Abstract: Contact angles and wetting of solid surfaces are strongly influenced by the physical and chemical properties of the surfaces. These influence quantities are difficult to distinguish from each other if contact angle measurements are performed by measuring only the advancing θ{sub a} and the receding θ{sub r} contact angle. In this regard, time-dependent water contact angles are measured on two hydrophobic modified silicon wafers with different physical surface topographies. The first surface is nearly atomically flat while the second surface is patterned (alternating flat and nanoscale rough patterns) which is synthesized by a photolithography and etching procedure. The different surface topographies are characterized with atomic force microscopy (AFM), Fourier transform infrared reflection absorption spectroscopy (FTIRRAS) and Fourier transform infrared attenuated total reflection spectroscopy (FTIR-ATR). The resulting set of contact angle data obtained by the high-precision drop shape analysis approach is further analyzed by a Gompertzian fitting procedure and a statistical counting procedure in dependence on the triple line velocity. The Gompertzian fit is used to analyze overall properties of the surface and dependencies between the motion on the front and the back edge of the droplets. The statistical counting procedure results in the calculation of expectation values E(p) and standard deviations σ(p) for the inclination angle φ, contact angle θ, triple line velocity vel and the covered distance of the triple

Characterizing the rapid spread of porcine epidemic diarrhea virus (PEDV through an animal food manufacturing facility.

Directory of Open Access Journals (Sweden)

Loni L Schumacher

Full Text Available New regulatory and consumer demands highlight the importance of animal feed as a part of our national food safety system. Porcine epidemic diarrhea virus (PEDV is the first viral pathogen confirmed to be widely transmissible in animal food. Because the potential for viral contamination in animal food is not well characterized, the objectives of this study were to 1 observe the magnitude of virus contamination in an animal food manufacturing facility, and 2 investigate a proposed method, feed sequencing, to decrease virus decontamination on animal food-contact surfaces. A U.S. virulent PEDV isolate was used to inoculate 50 kg swine feed, which was mixed, conveyed, and discharged into bags using pilot-scale feed manufacturing equipment. Surfaces were swabbed and analyzed for the presence of PEDV RNA by quantitative real-time polymerase chain reaction (qPCR. Environmental swabs indicated complete contamination of animal food-contact surfaces (0/40 vs. 48/48, positive baseline samples/total baseline samples, positive subsequent samples/total subsequent samples, respectively; P < 0.05 and near complete contamination of non-animal food-contact surfaces (0/24 vs. 16/18, positive baseline samples/total baseline samples, positive subsequent samples/total subsequent samples, respectively; P < 0.05. Flushing animal food-contact surfaces with low-risk feed is commonly used to reduce cross-contamination in animal feed manufacturing. Thus, four subsequent 50 kg batches of virus-free swine feed were manufactured using the same system to test its impact on decontaminating animal food-contact surfaces. Even after 4 subsequent sequences, animal food-contact surfaces retained viral RNA (28/33 positive samples/total samples, with conveying system being more contaminated than the mixer. A bioassay to test infectivity of dust from animal food-contact surfaces failed to produce infectivity. This study demonstrates the potential widespread viral contamination of

Surface contact stimulates the just-in-time deployment of bacterial adhesins.

Science.gov (United States)

Li, Guanglai; Brown, Pamela J B; Tang, Jay X; Xu, Jing; Quardokus, Ellen M; Fuqua, Clay; Brun, Yves V

2012-01-01

The attachment of bacteria to surfaces provides advantages such as increasing nutrient access and resistance to environmental stress. Attachment begins with a reversible phase, often mediated by surface structures such as flagella and pili, followed by a transition to irreversible attachment, typically mediated by polysaccharides. Here we show that the interplay between pili and flagellum rotation stimulates the rapid transition between reversible and polysaccharide-mediated irreversible attachment. We found that reversible attachment of Caulobacter crescentus cells is mediated by motile cells bearing pili and that their contact with a surface results in the rapid pili-dependent arrest of flagellum rotation and concurrent stimulation of polar holdfast adhesive polysaccharide. Similar stimulation of polar adhesin production by surface contact occurs in Asticcacaulis biprosthecum and Agrobacterium tumefaciens. Therefore, single bacterial cells respond to their initial contact with surfaces by triggering just-in-time adhesin production. This mechanism restricts stable attachment to intimate surface interactions, thereby maximizing surface attachment, discouraging non-productive self-adherence, and preventing curing of the adhesive. © 2011 Blackwell Publishing Ltd.

The role of the roughness spectral breadth in elastic contact of rough surfaces

Science.gov (United States)

Yastrebov, Vladislav A.; Anciaux, Guillaume; Molinari, Jean-François

2017-10-01

We study frictionless and non-adhesive contact between elastic half-spaces with self-affine surfaces. Using a recently suggested corrective technique, we ensure an unprecedented accuracy in computation of the true contact area evolution under increasing pressure. This accuracy enables us to draw conclusions on the role of the surface's spectrum breadth (Nayak parameter) in the contact area evolution. We show that for a given normalized pressure, the contact area decreases logarithmically with the Nayak parameter. By linking the Nayak parameter with the Hurst exponent (or fractal dimension), we show the effect of the latter on the true contact area. This effect, undetectable for surfaces with poor spectral content, is quite strong for surfaces with rich spectra. Numerical results are compared with analytical models and other available numerical results. A phenomenological equation for the contact area growth is suggested with coefficients depending on the Nayak parameter. Using this equation, the pressure-dependent friction coefficient is deduced based on the adhesive theory of friction. Some observations on Persson's model of rough contact, whose prediction does not depend on Nayak parameter, are reported. Overall, the paper provides a unifying picture of rough elastic contact and clarifies discrepancies between preceding results.

Rough surface electrical contact resistance considering scale dependent properties and quantum effects

International Nuclear Information System (INIS)

Jackson, Robert L.; Crandall, Erika R.; Bozack, Michael J.

2015-01-01

The objective of this work is to evaluate the effect of scale dependent mechanical and electrical properties on electrical contact resistance (ECR) between rough surfaces. This work attempts to build on existing ECR models that neglect potentially important quantum- and size-dependent contact and electrical conduction mechanisms present due to the asperity sizes on typical surfaces. The electrical conductance at small scales can quantize or show a stepping trend as the contact area is varied in the range of the free electron Fermi wavelength squared. This work then evaluates if these effects remain important for the interface between rough surfaces, which may include many small scale contacts of varying sizes. The results suggest that these effects may be significant in some cases, while insignificant for others. It depends on the load and the multiscale structure of the surface roughness

Surface topography and contact mechanics of dry and wet human skin

Directory of Open Access Journals (Sweden)

Alexander E. Kovalev

2014-08-01

Full Text Available The surface topography of the human wrist skin is studied by using optical and atomic force microscopy (AFM methods. By using these techniques the surface roughness power spectrum is obtained. The Persson contact mechanics theory is used to calculate the contact area for different magnifications, for the dry and wet skin. The measured friction coefficient between a glass ball and dry and wet skin can be explained assuming that a frictional shear stress σf ≈ 13 MPa and σf ≈ 5 MPa, respectively, act in the area of real contact during sliding. These frictional shear stresses are typical for sliding on surfaces of elastic bodies. The big increase in friction, which has been observed for glass sliding on wet skin as the skin dries up, can be explained as result of the increase in the contact area arising from the attraction of capillary bridges. Finally, we demonstrated that the real contact area can be properly defined only when a combination of both AFM and optical methods is used for power spectrum calculation.

NRC Information No. 88-98: Electrical relay degradation caused by oxidation of contact surfaces

International Nuclear Information System (INIS)

Rossi, C.E.

1992-01-01

The NRC staff was recently informed by Clinton Power Station that a reactor scram on June 24, 1988, was caused by an electrical relay failure from oxide buildup on relay contact surfaces. Other information on relay failure from contact oxidation indicates that this problem may be more prevalent than previously thought. For example, a July 17, 1988, 10 CFR Part 21 report from Palo Verde, Unit 2, reported relay failures from contact oxidation that were due to the low current application of the relays. The relay contact surfaces in both of these examples are silver-nickel alloys, and both applications were for low current (i.e., milli-ampere current). Electrical relay contacts made of silver-nickel or silver-cadmium alloys will oxidize (tarnish) when used in low current applications because of the absence of contact surface sparking from the typical relay contact ''making and breaking'' functions. The sparking in the contact surfaces promotes a self-cleaning mechanism that reduces the tarnish buildup on the silver-nickel or silver-cadmium contacts. Discussions with one relay manufacturer revealed that the normal industry practice for low current circuit applications is either to use a contact surface material that will not oxidize or to compensate for the oxidation by increased maintenance activities to ensure reliability. The applied voltage may also influence contact oxidation

Contact-angle hysteresis on periodic microtextured surfaces: Strongly corrugated liquid interfaces.

Science.gov (United States)

Iliev, Stanimir; Pesheva, Nina

2016-06-01

We study numerically the shapes of a liquid meniscus in contact with ultrahydrophobic pillar surfaces in Cassie's wetting regime, when the surface is covered with identical and periodically distributed micropillars. Using the full capillary model we obtain the advancing and the receding equilibrium meniscus shapes when the cross-sections of the pillars are both of square and circular shapes, for a broad interval of pillar concentrations. The bending of the liquid interface in the area between the pillars is studied in the framework of the full capillary model and compared to the results of the heterogeneous approximation model. The contact angle hysteresis is obtained when the three-phase contact line is located on one row (block case) or several rows (kink case) of pillars. It is found that the contact angle hysteresis is proportional to the line fraction of the contact line on pillars tops in the block case and to the surface fraction for pillar concentrations 0.1-0.5 in the kink case. The contact angle hysteresis does not depend on the shape (circular or square) of the pillars cross-section. The expression for the proportionality of the receding contact angle to the line fraction [Raj et al., Langmuir 28, 15777 (2012)LANGD50743-746310.1021/la303070s] in the case of block depinning is theoretically substantiated through the capillary force, acting on the solid plate at the meniscus contact line.

Bimetallic nanoparticles for surface modification and lubrication of MEMS switch contacts

International Nuclear Information System (INIS)

Patton, Steven T; Hu Jianjun; Slocik, Joseph M; Campbell, Angela; Naik, Rajesh R; Voevodin, Andrey A

2008-01-01

Reliability continues to be a critical issue in microelectromechanical systems (MEMS) switches. Failure mechanisms include high contact resistance (R), high adhesion, melting/shorting, and contact erosion. Little previous work has addressed the lubrication of MEMS switches. In this study, bimetallic nanoparticles (NPs) are synthesized using a biotemplated approach and deposited on Au MEMS switch contacts as a nanoparticle-based lubricant. Bimetallic nanoparticles are comprised of a metallic core (∼10 nm diameter gold nanoparticle) with smaller metallic nanoparticles (∼2-3 nm diameter Pd nanoparticles) populating the core surface. Adhesion and resistance (R) were measured during hot switching experiments at low (10 μA) and high (1 mA) current. The Au/Pd NP coated contacts led to reduced adhesion as compared to pure Au contacts with a compromise of slightly higher R. For switches held in the closed position at low current, R gradually decreased over tens of seconds due to increased van der Waals force and growth of the real area of contact with temporal effects being dominant over load effects. Contact behavior transitioned from 'Pd-like' to 'Au-like' during low current cycling experiments. Melting at high current resulted in rapid formation of large real contact area, low and stable R, and minimal effect of load on R. Durability at high current was excellent with no failure through 10 6 hot switching cycles. Improvement at high current is due to controlled nanoscale surface roughness that spreads current through multiple nanocontacts, which restricts the size of melting regions and causes termination of nanowire growth (prevents shorting) during contact opening. Based on these results, bimetallic NPs show excellent potential as surface modifiers/lubricants for MEMS switch contacts

Dynamics of the contact between a ruthenium surface with a single nanoasperity and a flat ruthenium surface: Molecular dynamics simulations

International Nuclear Information System (INIS)

Barros de Oliveira, Alan; Fortini, Andrea; Buldyrev, Sergey V.; Srolovitz, David

2011-01-01

We study the dynamics of the contact between a pair of surfaces (with properties designed to mimic ruthenium) via molecular dynamics simulations. In particular, we study the contact between a ruthenium surface with a single nanoasperity and a flat ruthenium surface. The results of such simulations suggest that contact behavior is highly variable. The goal of this study is to investigate the source and degree of this variability. We find that during compression, the behavior of the contact force displacement curves is reproducible, while during contact separation, the behavior is highly variable. Examination of the contact surfaces suggests that two separation mechanisms are in operation and give rise to this variability. One mechanism corresponds to the formation of a bridge between the two surfaces that plastically stretches as the surfaces are drawn apart and eventually separate in shear. This leads to a morphology after separation in which there are opposing asperities on the two surfaces. This plastic separation/bridge formation mechanism leads to a large work of separation. The other mechanism is a more brittle-like mode in which a crack propagates across the base of the asperity (slightly below the asperity/substrate junction) leading to most of the asperity on one surface or the other after separation and a slight depression facing this asperity on the opposing surface. This failure mode corresponds to a smaller work of separation. This failure mode corresponds to a smaller work of separation. Furthermore, contacts made from materials that exhibit predominantly brittle-like behavior will tend to require lower work of separation than those made from ductile-like contact materials.

Pressure effects on interfacial surface contacts and performance of organic solar cells

NARCIS (Netherlands)

Agyei-Tuffour, B.; Doumon, Nutifafa Y.; Rwenyagila, E. R.; Asare, J.; Oyewole, O. K.; Shen, Z.; Petoukhoff, C. E.; Zebaze Kana, M. G.; Ocarroll, D. M.; Soboyejo, W. O.

2017-01-01

This paper explores the effects of pressure on the interfacial surface contacts and the performance of organic solar cells. A combination of experimental techniques and analytical/computational models is used to study the evolving surface contacts profiles that occur when compliant, semi-rigid and

Growth of contact area between rough surfaces under normal stress

Science.gov (United States)

Stesky, R. M.; Hannan, S. S.

1987-05-01

The contact area between deforming rough surfaces in marble, alabaster, and quartz was measured from thin sections of surfaces bonded under load with low viscosity resin epoxy. The marble and alabaster samples had contact areas that increased with stress at an accelerating rate. This result suggests that the strength of the asperity contacts decreased progressively during the deformation, following some form of strain weakening relationship. This conclusion is supported by petrographic observation of the thin sections that indicate that much of the deformation was cataclastic, with minor twinning of calcite and kinking of gypsum. In the case of the quartz, the observed contact area was small and increased approximately linearly with normal stress. Only the irreversible cataclastic deformation was observed; however strain-induced birefringence and cracking of the epoxy, not observed with the other rocks, suggests that significant elastic deformation occurred, but recovered during unloading.

Enforcement of the Danish Bisphenol A restriction on Food Contact Materials and Articles for infants

DEFF Research Database (Denmark)

Pedersen, Gitte Alsing; Foverskov, Annie; Petersen, Jens Højslev

In Denmark a national restriction was implemented in 2010 banning the use of bisphenol A (BPA) in any Food Contact Materials intended for children in the age 0-3 years. The ban includes BPA in baby bottles, baby cups, food cans for infant formulas and lids for glass containers with baby food...

Creation of Principally New Generation of Switching Technique Elements (Reed Switches) with Nanostructured Contact Surfaces

Energy Technology Data Exchange (ETDEWEB)

Karabanov S M; Zeltser I A; Maizels R M; Moos E N; Arushanov K A, E-mail: zeltseria@rmcip.ru [Russia, Ryazan, 390027, Novaya Str., 51B, Ryazan Metal Ceramics Instrumentation Plant JSC (Russian Federation)

2011-04-01

The cycle of activities of the creation of principally new generation of reed switches with nanostructured contact surfaces was implemented. Experimental justification of the opportunity of reed switches creation with modified contact surface was given (instead of precious metals-based galvanic coating). Principally new technological process of modification of magnetically operated contacts contacting surfaces was developed, based on the usage of the ion-plasma methods of nanolayers and nanostructures forming having specified contact features.

Bimetallic nanoparticles for surface modification and lubrication of MEMS switch contacts

Energy Technology Data Exchange (ETDEWEB)

Patton, Steven T; Hu Jianjun [University of Dayton Research Institute, Dayton, OH 45469-0168 (United States); Slocik, Joseph M; Campbell, Angela; Naik, Rajesh R; Voevodin, Andrey A [Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, OH 45433-7750 (United States)], E-mail: steve.patton@wpafb.af.mil, E-mail: rajesh.naik@wpafb.af.mil

2008-10-08

Reliability continues to be a critical issue in microelectromechanical systems (MEMS) switches. Failure mechanisms include high contact resistance (R), high adhesion, melting/shorting, and contact erosion. Little previous work has addressed the lubrication of MEMS switches. In this study, bimetallic nanoparticles (NPs) are synthesized using a biotemplated approach and deposited on Au MEMS switch contacts as a nanoparticle-based lubricant. Bimetallic nanoparticles are comprised of a metallic core ({approx}10 nm diameter gold nanoparticle) with smaller metallic nanoparticles ({approx}2-3 nm diameter Pd nanoparticles) populating the core surface. Adhesion and resistance (R) were measured during hot switching experiments at low (10 {mu}A) and high (1 mA) current. The Au/Pd NP coated contacts led to reduced adhesion as compared to pure Au contacts with a compromise of slightly higher R. For switches held in the closed position at low current, R gradually decreased over tens of seconds due to increased van der Waals force and growth of the real area of contact with temporal effects being dominant over load effects. Contact behavior transitioned from 'Pd-like' to 'Au-like' during low current cycling experiments. Melting at high current resulted in rapid formation of large real contact area, low and stable R, and minimal effect of load on R. Durability at high current was excellent with no failure through 10{sup 6} hot switching cycles. Improvement at high current is due to controlled nanoscale surface roughness that spreads current through multiple nanocontacts, which restricts the size of melting regions and causes termination of nanowire growth (prevents shorting) during contact opening. Based on these results, bimetallic NPs show excellent potential as surface modifiers/lubricants for MEMS switch contacts.

Oil Contact Angles in a Water-Decane-Silicon Dioxide System: Effects of Surface Charge.

Science.gov (United States)

Xu, Shijing; Wang, Jingyao; Wu, Jiazhong; Liu, Qingjie; Sun, Chengzhen; Bai, Bofeng

2018-04-19

Oil wettability in the water-oil-rock systems is very sensitive to the evolution of surface charges on the rock surfaces induced by the adsorption of ions and other chemical agents in water flooding. Through a set of large-scale molecular dynamics simulations, we reveal the effects of surface charge on the oil contact angles in an ideal water-decane-silicon dioxide system. The results show that the contact angles of oil nano-droplets have a great dependence on the surface charges. As the surface charge density exceeds a critical value of 0.992 e/nm 2 , the contact angle reaches up to 78.8° and the water-wet state is very apparent. The variation of contact angles can be confirmed from the number density distributions of oil molecules. With increasing the surface charge density, the adsorption of oil molecules weakens and the contact areas between nano-droplets and silicon dioxide surface are reduced. In addition, the number density distributions, RDF distributions, and molecular orientations indicate that the oil molecules are adsorbed on the silicon dioxide surface layer-by-layer with an orientation parallel to the surface. However, the layered structure of oil molecules near the silicon dioxide surface becomes more and more obscure at higher surface charge densities.

Impact of surface coating and food-mimicking media on nanosilver-protein interaction

Energy Technology Data Exchange (ETDEWEB)

Burcza, Anna, E-mail: anna.burcza@mri.bund.de; Gräf, Volker; Walz, Elke; Greiner, Ralf [Max Rubner-Institute, Department of Food Technology and Bioprocess Engineering (Germany)

2015-11-15

The application of silver nanoparticles (AgNPs) in food contact materials has recently become a subject of dispute due to the possible migration of silver in nanoform into foods and beverages. Therefore, the analysis of the interaction of AgNPs with food components, especially proteins, is of high importance in order to increase our knowledge of the behavior of nanoparticles in food matrices. AgPURE™ W10 (20 nm), an industrially applied nanomaterial, was compared with AgNPs of similar size frequently investigated for scientific purposes differing in the surface capping agent (spherical AgNP coated with either PVP or citrate). The interactions of the AgNPs with whey proteins (BSA, α-lactalbumin and β-lactoglobulin) at different pH values (4.2, 7 or 7.4) were investigated using surface plasmon resonance, SDS-PAGE, and asymmetric flow field-flow fractionation. The data obtained by the three different methods correlated well. Besides the nature of the protein and the nanoparticle coating, the environment was shown to affect the interaction significantly. The strongest interaction was obtained with BSA and AgNPs in an acidic environment. Neutral and slightly alkaline conditions however, seemed to prevent the AgNP-protein interaction almost completely. Furthermore, the interaction of whey proteins with AgPURE™ W10 was found to be weaker compared to the interaction with the other two AgNPs under all conditions investigated.

Impact of surface coating and food-mimicking media on nanosilver-protein interaction

International Nuclear Information System (INIS)

Burcza, Anna; Gräf, Volker; Walz, Elke; Greiner, Ralf

2015-01-01

The application of silver nanoparticles (AgNPs) in food contact materials has recently become a subject of dispute due to the possible migration of silver in nanoform into foods and beverages. Therefore, the analysis of the interaction of AgNPs with food components, especially proteins, is of high importance in order to increase our knowledge of the behavior of nanoparticles in food matrices. AgPURE™ W10 (20 nm), an industrially applied nanomaterial, was compared with AgNPs of similar size frequently investigated for scientific purposes differing in the surface capping agent (spherical AgNP coated with either PVP or citrate). The interactions of the AgNPs with whey proteins (BSA, α-lactalbumin and β-lactoglobulin) at different pH values (4.2, 7 or 7.4) were investigated using surface plasmon resonance, SDS-PAGE, and asymmetric flow field-flow fractionation. The data obtained by the three different methods correlated well. Besides the nature of the protein and the nanoparticle coating, the environment was shown to affect the interaction significantly. The strongest interaction was obtained with BSA and AgNPs in an acidic environment. Neutral and slightly alkaline conditions however, seemed to prevent the AgNP-protein interaction almost completely. Furthermore, the interaction of whey proteins with AgPURE™ W10 was found to be weaker compared to the interaction with the other two AgNPs under all conditions investigated

Contact angle determination procedure and detection of an invisible surface film

Science.gov (United States)

Meyer, G.; Grat, R.

1990-01-01

The contact angle value, i.e., the tangent angle of liquid resting on a planar solid surface, is a basic parameter which can be applied to a wide range of applications. The goal is to provide a basic understanding of the contact angle measurement technique and to present a simple illustration that can be applied as a quality control method; namely, detection of a surface contaminant which exists on a surface that appears clean to the unaided eye. The equipment and experimental procedures are detailed.

Elastic–plastic adhesive contact of non-Gaussian rough surfaces

Indian Academy of Sciences (India)

Grinding, milling, honing and abrasion processes produce grooved surfaces with negative ... This may be defined as λ = π2RH4σ/(18K2γ2) where H is the hardness ... The effect of surface roughness on adhesion at the contact of rough solids ...

Effet de la rugosité de surface sur les performances du contact ...

African Journals Online (AJOL)

Effet de la rugosité de surface sur les performances du contact segment- chemise dans un moteur à combustion interne. The effect of surface roughness on the performances of liner-piston ring contact in internal combustion engine. Amar Ayad. *. , Amar Skendraoui & Ammar Haiahem. Laboratoire de Mécanique Industrielle ...

Stability analysis of rough surfaces in adhesive normal contact

Science.gov (United States)

Rey, Valentine; Bleyer, Jeremy

2018-03-01

This paper deals with adhesive frictionless normal contact between one elastic flat solid and one stiff solid with rough surface. After computation of the equilibrium solution of the energy minimization principle and respecting the contact constraints, we aim at studying the stability of this equilibrium solution. This study of stability implies solving an eigenvalue problem with inequality constraints. To achieve this goal, we propose a proximal algorithm which enables qualifying the solution as stable or unstable and that gives the instability modes. This method has a low computational cost since no linear system inversion is required and is also suitable for parallel implementation. Illustrations are given for the Hertzian contact and for rough contact.

Contact mechanics: contact area and interfacial separation from small contact to full contact

International Nuclear Information System (INIS)

Yang, C; Persson, B N J

2008-01-01

We present a molecular dynamics study of the contact between a rigid solid with a randomly rough surface and an elastic block with a flat surface. The numerical calculations mainly focus on the contact area and the interfacial separation from small contact (low load) to full contact (high load). For a small load the contact area varies linearly with the load and the interfacial separation depends logarithmically on the load. For a high load the contact area approaches the nominal contact area (i.e. complete contact), and the interfacial separation approaches zero. The numerical results have been compared with analytical theory and experimental results. They are in good agreement with each other. The present findings may be very important for soft solids, e.g. rubber, or for very smooth surfaces, where complete contact can be reached at moderately high loads without plastic deformation of the solids

Emission of perfluoroalkyl carboxylic acids (PFCA) from heated surfaces made of polytetrafluoroethylene (PTFE) applied in food contact materials and consumer products.

Science.gov (United States)

Schlummer, Martin; Sölch, Christina; Meisel, Theresa; Still, Mona; Gruber, Ludwig; Wolz, Gerd

2015-06-01

Polytetrafluoroethylene (PTFE) has been widely discussed as a source of perfluorooctanoic acid (PFOA), which has been used in the production of fluoropolymers. PTFE may also contain unintended perfluoroalkyl carboxylic acids (PFCAs) caused by thermolysis of PTFE, which has been observed at temperatures above 300°C. Common PTFE coated food contact materials and consumer goods are operated at temperatures above 200°C. However, knowledge on possible emissions of PFCAs is limited. Therefore, it was the aim of this study to investigate and evaluate the emission of PFCAs from PTFE coated products with both, normal use and overheating scenarios. Four pans, claimed to be PFOA free, and nine consumer products were investigated. At normal use conditions (PTFE surfaces were trapped for 1h. Overheating scenarios (>260°C) recorded emissions during a 30min heating of empty pans on a stove. Emissions were analyzed by LC-ESI-MS. Results indicate the emission of PFCAs, whereas no perfluorinated sulfonic acids were traced. At normal use conditions total emissions of PFCAs accounted for 4.75ng per hour. Overheated pans, however, released far higher amounts with up to 12190ng PFCAs per hour at 370°C. Dominating contributors where PFBA and PFOA at normal use and PFBA and PFPeA during overheating. Temperature seems to be the main factor controlling the emission of PFCAs. A worst case estimation of human exposure revealed that emissions of PFCAs from heated PTFE surfaces would be far below the TDI of 1500ng PFOA per kg body weight. Copyright © 2014 Elsevier Ltd. All rights reserved.

Correlations between deformations, surface state and leak rate in metal to metal contact; Correlations entre deformations, etat de surface et debit de fuite au contact metal-metal

Energy Technology Data Exchange (ETDEWEB)

Armand, G; Lapujoulade, J; Paigne, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1963-07-01

The study of metal to metal contact from the stand-point of the leak rate has been carried on a copper ring located between two hard-steel flanges. The analysis of the results confirms the hysteresis phenomenon already seen. Some curves (leak rate versus force and leak rate versus true deformation) in semi-logarithmic coordinates are straight lines. Likewise some curves (electrical contact resistance versus force) in bi-logarithmic coordinates are straight lines. All these results can be understood by looking at the conductance introduced by the deformations of the micro-geometry of the surfaces in contact. Some tests carried out in rising the temperature confirm these hypothesis. (authors) [French] L'etude du contact metal-metal du point de vue debit de fuite a ete poursuivie en utilisant un anneau de cuivre place entre brides d'acier dur. L'analyse des resultats confirme le phenomene d'hysteresis deja constate, montre l'influence de l'etat de surface des brides et du joint. Certaines courbes (debit de fuite/force et debit de fuite/deformation rationnelle), en coordonnees semi-logarithmiques, sont des droites. De meme, certaines courbes (resistance de contact/force) en coordonnees bi-logarithmiques, sont des droites. Ces resultats s'interpretent en considerant la conductance produite par la deformation des microgeometries des surfaces en contact. Quelques essais d'elevation de temperature confirment ces resultats. (auteurs)

Is there a link between blastomere contact surfaces of day 3 embryos and live birth rate?

Directory of Open Access Journals (Sweden)

Paternot Goedele

2012-09-01

Full Text Available Abstract Background Cell-cell communication and adhesion are essential for the compaction process of early stage embryos. The aim of this study was to develop a non-invasive objective calculation system of embryo compaction in order to test the hypothesis that embryos with a larger mean contact surface result in a higher live birth rate compared to embryos with a lower mean contact surface. Methods Multilevel images of 474 embryos transferred on day 3 were evaluated by the Cellify software. This software calculates the contact surfaces between the blastomeres. The primary outcome of this study was live birth. An ideal range of contact surface was determined and the positive and negative predictive value, the sensitivity, the specificity and the area under the curve for this new characteristic were calculated. Results In total, 115 (24% transferred embryos resulted in a live birth. Selection of an embryo for transfer on its mean contact surface could predict live birth with a high sensitivity (80% and high negative predicting value (83% but with a low positive predictive value (27%, a low specificity (31% and low area under the ROC curve (0.56. The mean contact surface of embryos cultured in a single medium was significantly higher compared to the mean contact surface of embryos cultured in a sequential medium (p = 0.0003. Conclusions Neither the mean contact surface nor the number of contact surfaces of a day 3 embryo had an additional value in the prediction of live birth. The type of culture medium, however, had an impact on the contact surface of an embryo. Embryos cultured in a single medium had a significant larger contact surface compared to embryos cultured in the sequential medium.

Asperity interaction in elastic-plastic contact of rough surfaces in presence of adhesion

International Nuclear Information System (INIS)

Sahoo, Prasanta; Banerjee, Atanu

2005-01-01

This paper presents an analysis of the effect of asperity interaction in elastic-plastic contact of rough surfaces in the presence of adhesion. The micro-contact model of asperity interactions, developed by Zhao and Chang (2001 Trans. ASME: J. Tribol. 123 857-64), is integrated into the elastic-plastic contact model developed by Roy Chowdhury and Ghosh (1994 Wear 174 9-19) to allow the asperity interaction and elastic-plastic deformation in the presence of surface forces to be considered simultaneously. The well-established elastic and plastic adhesion indices are used to consider the different conditions that arise as a result of varying load and material parameters. Results show that asperity interaction influences the loading-unloading behaviour in elastic-plastic adhesive contact of rough surfaces and in general asperity interactions reduce the effect of surface forces

Quantitative sub-surface and non-contact imaging using scanning microwave microscopy

International Nuclear Information System (INIS)

Gramse, Georg; Kasper, Manuel; Hinterdorfer, Peter; Brinciotti, Enrico; Rankl, Christian; Kienberger, Ferry; Lucibello, Andrea; Marcelli, Romolo; Patil, Samadhan B.; Giridharagopal, Rajiv

2015-01-01

The capability of scanning microwave microscopy for calibrated sub-surface and non-contact capacitance imaging of silicon (Si) samples is quantitatively studied at broadband frequencies ranging from 1 to 20 GHz. Calibrated capacitance images of flat Si test samples with varying dopant density (10 15 –10 19 atoms cm −3 ) and covered with dielectric thin films of SiO 2 (100–400 nm thickness) are measured to demonstrate the sensitivity of scanning microwave microscopy (SMM) for sub-surface imaging. Using standard SMM imaging conditions the dopant areas could still be sensed under a 400 nm thick oxide layer. Non-contact SMM imaging in lift-mode and constant height mode is quantitatively demonstrated on a 50 nm thick SiO 2 test pad. The differences between non-contact and contact mode capacitances are studied with respect to the main parameters influencing the imaging contrast, namely the probe tip diameter and the tip–sample distance. Finite element modelling was used to further analyse the influence of the tip radius and the tip–sample distance on the SMM sensitivity. The understanding of how the two key parameters determine the SMM sensitivity and quantitative capacitances represents an important step towards its routine application for non-contact and sub-surface imaging. (paper)

Experimental Investigation of Coal Dust Wettability Based on Surface Contact Angle

Directory of Open Access Journals (Sweden)

Gang Zhou

2016-01-01

Full Text Available Wettability is one of the key chemical properties of coal dust, which is very important to dedusting. In this paper, the theory of liquid wetting solid was presented firstly; then, taking the gas coal of Xinglongzhuang coal mine in China as an example, by determination of critical surface tension of coal piece, it can be concluded that only when the surface tension of surfactant solution is less than 45 mN/m can the coal sample be fully wetted. Due to the effect of particle dispersity, compared with the contact angle of milled coal particle, not all the contact angles of screened coal powder with different sizes have a tendency to increase. Furthermore, by the experiments of coal samples’ specific surface areas and porosities, it can be achieved that the volume of single-point total pore decreases with the gradual decreasing of coal’s porosity, while the ultramicropores’ dispersities and multipoint BET specific surface areas increase. Besides, by a series of contact angle experiments with different surfactants, it can be found that with the increasing of porosity and the decreasing of volume percentage of ultramicropore, the contact angle tends to reduce gradually and the coal dust is much easier to get wetted.

Fabrication of surfaces with extremely high contact angle hysteresis from polyelectrolyte multilayer.

Science.gov (United States)

Wang, Liming; Wei, Jingjing; Su, Zhaohui

2011-12-20

High contact angle hysteresis on polyelectrolyte multilayers (PEMs) ion-paired with hydrophobic perfluorooctanoate anions is reported. Both the bilayer number of PEMs and the ionic strength of deposition solutions have significant influence on contact angle hysteresis: higher ionic strength and greater bilayer number cause increased contact angle hysteresis values. The hysteresis values of ~100° were observed on smooth PEMs and pinning of the receding contact line on hydrophilic defects is implicated as the cause of hysteresis. Surface roughness can be used to further tune the contact angle hysteresis on the PEMs. A surface with extremely high contact angle hysteresis of 156° was fabricated when a PEM was deposited on a rough substrate coated with submicrometer scale silica spheres. It was demonstrated that this extremely high value of contact angle hysteresis resulted from the penetration of water into the rough asperities on the substrate. The same substrate hydrophobized by chemical vapor deposition of 1H,1H,2H,2H-perfluorooctyltriethoxysilane exhibits high advancing contact angle and low hysteresis. © 2011 American Chemical Society

Implementation and applications of a finite-element model for the contact between rough surfaces

DEFF Research Database (Denmark)

Poulios, Konstantinos; Klit, Peder

2013-01-01

Due to the rough nature of real mechanical surfaces, the contact between elastic bodies occurs at several size-scales. Statistical and fractal contact models can take a wide range of roughness wavelengths into account, without additional computational cost. However, deterministic models are more ...... in the examples. Among the presented results one can find the distribution of the contact pressure at the interface and diagrams of the real area of contact as a function of the nominal contact pressure. © 2013 Elsevier B.V.......Due to the rough nature of real mechanical surfaces, the contact between elastic bodies occurs at several size-scales. Statistical and fractal contact models can take a wide range of roughness wavelengths into account, without additional computational cost. However, deterministic models are more...... straightforward to understand and easier to extend to more complex cases like contacting bodies that demonstrate elasto-plastic behavior. This paper presents a finite-element model for studying the frictionless contact between nominally flat rough surfaces. Apart from a description of the model implementation...

Can foot anthropometric measurements predict dynamic plantar surface contact area?

Directory of Open Access Journals (Sweden)

Collins Natalie

2009-10-01

Full Text Available Abstract Background Previous studies have suggested that increased plantar surface area, associated with pes planus, is a risk factor for the development of lower extremity overuse injuries. The intent of this study was to determine if a single or combination of foot anthropometric measures could be used to predict plantar surface area. Methods Six foot measurements were collected on 155 subjects (97 females, 58 males, mean age 24.5 ± 3.5 years. The measurements as well as one ratio were entered into a stepwise regression analysis to determine the optimal set of measurements associated with total plantar contact area either including or excluding the toe region. The predicted values were used to calculate plantar surface area and were compared to the actual values obtained dynamically using a pressure sensor platform. Results A three variable model was found to describe the relationship between the foot measures/ratio and total plantar contact area (R2 = 0.77, p R2 = 0.76, p Conclusion The results of this study indicate that the clinician can use a combination of simple, reliable, and time efficient foot anthropometric measurements to explain over 75% of the plantar surface contact area, either including or excluding the toe region.

Printed paper and board food contact materials as a potential source of food contamination.

Science.gov (United States)

Van Bossuyt, Melissa; Van Hoeck, Els; Vanhaecke, Tamara; Rogiers, Vera; Mertens, Birgit

2016-11-01

Food contact materials (FCM) are estimated to be the largest source of food contamination. Apart from plastics, the most commonly used FCM are made of printed paper and board. Unlike their plastic counterparts, these are not covered by a specific European regulation. Several contamination issues have raised concerns towards potential adverse health effects caused by exposure to substances migrating from printed paper and board FCM. In the current study, an inventory combining the substances which may be used in printed paper and board FCM, was created. More than 6000 unique compounds were identified, the majority (77%) considered non-evaluated in terms of potential toxicity. Based on a preliminary study of their physicochemical properties, it is estimated that most of the non-evaluated single substances have the potential to migrate into the food and become bioavailable after oral intake. Almost all are included in the FACET tool, indicating that their use in primary food packaging has been confirmed by industry. Importantly, 19 substances are also present in one of the lists with substances of concern compiled by the European Chemicals Agency (ECHA). To ensure consumer safety, the actual use of these substances in printed paper and board FCM should be investigated urgently. Copyright © 2016 Elsevier Inc. All rights reserved.

Static or breakloose friction for lubricated contacts: the role of surface roughness and dewetting

International Nuclear Information System (INIS)

Lorenz, B; Persson, B N J; Krick, B A; Sawyer, W G; Rodriguez, N; Mangiagalli, P

2013-01-01

We present experimental data for the static or breakloose friction for lubricated elastomer contacts, as a function of the time of stationary contact. Due to fluid squeeze-out from the asperity contact regions, the breakloose friction force increases continuously with the time of stationary contact. We consider three different cases: (a) PDMS rubber balls against flat smooth glass surfaces, (b) PDMS cylinder ribs against different substrates (glass, smooth and rough PMMA and an inert polymer) and (c) application to syringes. Due to differences in the surface roughness and contact pressures the three systems exhibit very different time dependences of the breakloose friction. In case (a) for rough surfaces the dry contact area A is a small fraction of the nominal contact area A 0 , and the fluid squeeze-out is fast. In case (b) the dry contact area is close to the nominal contact area, A/A 0 ≈ 1, and fluid squeeze-out is very slow due to percolation of the contact area. In this case, remarkably, different fluids with very different viscosities, ranging from 0.005 Pa s (water–glycerol mixture) to 1.48 Pa s (glycerol), give very similar breakloose friction forces as a function of the time of stationary contact. In case (c) the contact pressure and the surface roughness are larger than in case (b), and the squeeze-out is very slow so that even after a very long time the area of real contact is below the percolation threshold. For all cases (a)–(c), the increase in the breakloose friction is mainly due to the increase in the area of real contact with increasing time, because of the fluid squeeze-out and dewetting. (paper)

Static or breakloose friction for lubricated contacts: the role of surface roughness and dewetting.

Science.gov (United States)

Lorenz, B; Krick, B A; Rodriguez, N; Sawyer, W G; Mangiagalli, P; Persson, B N J

2013-11-06

We present experimental data for the static or breakloose friction for lubricated elastomer contacts, as a function of the time of stationary contact. Due to fluid squeeze-out from the asperity contact regions, the breakloose friction force increases continuously with the time of stationary contact. We consider three different cases: (a) PDMS rubber balls against flat smooth glass surfaces, (b) PDMS cylinder ribs against different substrates (glass, smooth and rough PMMA and an inert polymer) and (c) application to syringes. Due to differences in the surface roughness and contact pressures the three systems exhibit very different time dependences of the breakloose friction. In case (a) for rough surfaces the dry contact area A is a small fraction of the nominal contact area A0, and the fluid squeeze-out is fast. In case (b) the dry contact area is close to the nominal contact area, A/A0 ≈ 1, and fluid squeeze-out is very slow due to percolation of the contact area. In this case, remarkably, different fluids with very different viscosities, ranging from 0.005 Pa s (water–glycerol mixture) to 1.48 Pa s (glycerol), give very similar breakloose friction forces as a function of the time of stationary contact. In case (c) the contact pressure and the surface roughness are larger than in case (b), and the squeeze-out is very slow so that even after a very long time the area of real contact is below the percolation threshold. For all cases (a)–(c), the increase in the breakloose friction is mainly due to the increase in the area of real contact with increasing time, because of the fluid squeeze-out and dewetting.

Apparent-contact-angle model at partial wetting and evaporation: impact of surface forces.

Science.gov (United States)

Janeček, V; Nikolayev, V S

2013-01-01

This theoretical and numerical study deals with evaporation of a fluid wedge in contact with its pure vapor. The model describes a regime where the continuous wetting film is absent and the actual line of the triple gas-liquid-solid contact appears. A constant temperature higher than the saturation temperature is imposed at the solid substrate. The fluid flow is solved in the lubrication approximation. The introduction of the surface forces in the case of the partial wetting is discussed. The apparent contact angle (the gas-liquid interface slope far from the contact line) is studied numerically as a function of the substrate superheating, contact line velocity, and parameters related to the solid-fluid interaction (Young and microscopic contact angles, Hamaker constant, etc.). The dependence of the apparent contact angle on the substrate temperature is in agreement with existing approaches. For water, the apparent contact angle may be 20° larger than the Young contact angle for 1 K superheating. The effect of the surface forces on the apparent contact angle is found to be weak.

Normal Contacts of Lubricated Fractal Rough Surfaces at the Atomic Scale

NARCIS (Netherlands)

Solhjoo, Soheil; Vakis, Antonis I.

The friction of contacting interfaces is a function of surface roughness and applied normal load. Under boundary lubrication, this frictional behavior changes as a function of lubricant wettability, viscosity, and density, by practically decreasing the possibility of dry contact. Many studies on

[Role of the EFSA in risk management system regarding food contact materials and articles].

Science.gov (United States)

Cwiek-Ludwicka, Kazimiera; Półtorak, Hanna; Pawlicka, Marzena

2009-01-01

The role of the European Food Safety Authority (EFSA) in the risk management system regarding food contact materials and articles is related with the risk assessment of the substances for the European Commission. General rules for the authorisation of substances used in materials and articles intended to contact with food is established in the Regulation (EC) no 1935/2004. For the evaluation of substances their toxicological properties and magnitude of migration into food simulants is taken into account. Toxicological studies include the mutagenicity tests, oral toxicity studies, carcinogenicity, reproduction and also studies on absorption, distribution, metabolism and excretion of the substance and other studies when needed. The set of the relevant toxicological data for substance depends on the magnitude of migration. In the case of positive opinion by EFSA the substance appears on the Community list of authorised substances. Sometimes, the earlier evaluated and authorized substances must undergo re-evaluation due to their new toxicological properties or as a result of a presence in the food of their earlier unknown decomposition products. Examples of the selected substances which underwent re-evaluation by EFSA in the light of the current toxicological knowledge and the relevant activities undertaken by the European Commission have been presented.

Wettability Control of Gold Surfaces Modified with Benzenethiol Derivatives: Water Contact Angle and Thermal Stability.

Science.gov (United States)

Tatara, Shingo; Kuzumoto, Yasutaka; Kitamura, Masatoshi

2016-04-01

The water wettability of Au surfaces has been controlled using various benzenethiol derivatives including 4-methylbenzenethiol, pentafluorobenzenethiol, 4-flubrobenzenethiol, 4-methoxy-benzenethiol, 4-nitrobenzenethiol, and 4-hydroxybenzenethiol. The water contact angle of the Au surface modified with the benzenethiol derivative was found to vary in the wide range of 30.9° to 88.3°. The contact angle of the modified Au films annealed was also measured in order to investigate their thermal stability. The change in the contact angle indicated that the modified surface is stable at temperatures below about 400 K. Meanwhile, the activation energy of desorption from the modified surface was estimated from the change in the contact angle. The modified Au surface was also examined using X-ray photoelectron spectroscopy.

Determination of Pesticide Dermal Transfer to Operators & Agricultural Workers through Contact with Sprayed Hard Surfaces.

Science.gov (United States)

Tsakirakis, Angelos N; Kasiotis, Konstantinos M; Anastasiadou, Pelagia; Charistou, Agathi N; Gerritsen-Ebben, Rianda; Glass, C Richard; Machera, Kyriaki

2018-05-20

In the present study, the dermal transfer rate of pesticides to agricultural workers occurring via contact with sprayed hard surfaces was investigated. Cotton gloves were used as dosimeters to collect residues from hard surfaces contaminated by pesticides in greenhouses. Dosimeters, either dry or moistened, were in contact with wood, metal and plastic surfaces previously sprayed. The experimental approach applied mimicked the typical hand contact. Moistened cotton gloves were used to simulate hand moisture from dew/condensation or rainfall. The effect of total duration of contact on the final hand exposure via transfer was investigated. The higher duration contact tested (50-sec) resulted in the higher transfer rates for metal and plastic surfaces; no such effect was noted in case of the wood surface. The pesticide amount transferred from the metal and plastic surfaces to wet gloves was greater than the one transferred to dry gloves. Such trend was not observed for the wood surface. Transfer rates varied from 0.46-77.62% and 0.17-16.90% for wet and dry samples, respectively. The current study has generated new data to quantify the proportion of pesticide deposits dislodged from three different non-crop surfaces when in contact with dry or wet gloves. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Surface contact potential patches and Casimir force measurements

International Nuclear Information System (INIS)

Kim, W. J.; Sushkov, A. O.; Lamoreaux, S. K.; Dalvit, D. A. R.

2010-01-01

We present calculations of contact potential surface patch effects that simplify previous treatments. It is shown that, because of the linearity of Laplace's equation, the presence of patch potentials does not affect an electrostatic calibration of a two-plate Casimir measurement apparatus. Using models that include long-range variations in the contact potential across the plate surfaces, a number of experimental observations can be reproduced and explained. For these models, numerical calculations show that if a voltage is applied between the plates which minimizes the force, a residual electrostatic force persists, and that the minimizing potential varies with distance. The residual force can be described by a fit to a simple two-parameter function involving the minimizing potential and its variation with distance. We show the origin of this residual force by use of a simple parallel capacitor model. Finally, the implications of a residual force that varies in a manner different from 1/d on the accuracy of previous Casimir measurements is discussed.

Experimental Study of Static Contact-angle on Peak-like Microstructural Surfaces Produced by PIII Technology

Science.gov (United States)

Yang, Runhua; Yang, Lixin

2018-06-01

Plasma immersion ion implantation (PIII) was used to fabricate micro/nano structures on monocrystalline Si surfaces with different ratios of mixed gases (SF6/O2). The micro/nano structures on the surfaces of the sample were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results showed that with increasing ratio of mixed gases (SF6/O2), the height of the micro/nano structures first increased and then decreased. Contact-angle measurements indicated that the surfaces' micro/nano structures have an obvious effect on the contact-angle, and could cause a change in surface wettability. The theoretical analysis of contact-angle showed that the Wenzel and Cassie theories cannot predict the contact-angle of a roughened surface accurately, and should be corrected for practical applications using an actual model. Moreover, the contact-angle first increased and then decreased with increasing ratio of mixed gases (SF6/O2), which is in accordance with the change of the height of micro/nano structures.

Effect of surface microgeometry on the physical contact formation during pressure welding

Energy Technology Data Exchange (ETDEWEB)

Karakozov, E S; Grigor' evskii, V I; Orlova, L M

1976-01-01

Methods are discussed to analyse both qualitatively and quantitatively the physical contact formation depending upon a microprotrusion height in case of pressure welding. For this purpose VT14 two-phase titanium alloy and in some cases OT4 alloy (for comparison) have been used. Those alloys are of a fine-grained polyhedral structure with a grain size of 8-10 ..mu..m for OT4 alloy and 2-3 ..mu..m for VT14 alloy. The tests have been performed with round specimens with a dia. of 16 mm and a height of 30 mm. The contact surface of one of the samples has been polished, that of the other one had triangular notched microprotrusions with a constant angle ..beta.. equalling 15 deg and a pitch varying in different samples. The specimens have been butt-welded. The surface of the contact formed has been assessed after a break-down of welded joints depending upon the imprint area of the specimen with a polished surface. An assessment of the physical contact surface as well as fractographic and metallographic studies of the break-down surface have been performed with MMI-2, MBS-2 and MIM-8 microscopes. The paper describes results of studies at a welding temperature of 850-950 deg C, with a duration of 20 min specific pressure of 0.2 kgf/sq.mm.

Effect of surface microgeometry on the physical contact formation during pressure welding

International Nuclear Information System (INIS)

Karakozov, Eh.S.; Grigor'evskij, V.I.; Orlova, L.M.

1976-01-01

Methods are discussed to analyse both qualitatively and quantitatively the physical contact formation depending upon a microprotrusion height in case of pressure welding. For this purpose VT14 two-phase titanium alloy and in some cases OT4 alloy (for comparison) have been used. Those alloys are of a fine-grained polyhedral structure with a grain size of 8-10 μm for OT4 alloy and 2-3 μm for VT14 alloy. The tests have been performed with round specimens with a dia. of 16 mm and a height of 30 mm. The contact surface of one of the samples has been polished, that of the other one had triangular notched microprotrusions with a constant angle β equalling 15 deg and a pitch varying in different samples. The specimens have been butt-welded. The surface of the contact formed has been assessed after a break-down of welded joints depending upon the imprint area of the specimen with a polished surface. An assessment of the physical contact surface as well as fractographic and metallographic studies of the break-down surface have been performed with MMI-2, MBS-2 and MIM-8 microscopes. The paper describes results of studies at a welding temperature of 850-950 deg C, with a duration of 20 min specific pressure of 0.2 kgf/sq.mm

Use of nanotechnology in food processing, packaging and safety ...

African Journals Online (AJOL)

Use of nanotechnology in food processing, packaging and safety – review. ... application of nanotechnology in food packaging and food contact materials, ... developing active antimicrobial and antifungal surfaces, and sensing as well as ...

Detailed statistical contact angle analyses; "slow moving" drops on inclining silicon-oxide surfaces.

Science.gov (United States)

Schmitt, M; Groß, K; Grub, J; Heib, F

2015-06-01

Contact angle determination by sessile drop technique is essential to characterise surface properties in science and in industry. Different specific angles can be observed on every solid which are correlated with the advancing or the receding of the triple line. Different procedures and definitions for the determination of specific angles exist which are often not comprehensible or reproducible. Therefore one of the most important things in this area is to build standard, reproducible and valid methods for determining advancing/receding contact angles. This contribution introduces novel techniques to analyse dynamic contact angle measurements (sessile drop) in detail which are applicable for axisymmetric and non-axisymmetric drops. Not only the recently presented fit solution by sigmoid function and the independent analysis of the different parameters (inclination, contact angle, velocity of the triple point) but also the dependent analysis will be firstly explained in detail. These approaches lead to contact angle data and different access on specific contact angles which are independent from "user-skills" and subjectivity of the operator. As example the motion behaviour of droplets on flat silicon-oxide surfaces after different surface treatments is dynamically measured by sessile drop technique when inclining the sample plate. The triple points, the inclination angles, the downhill (advancing motion) and the uphill angles (receding motion) obtained by high-precision drop shape analysis are independently and dependently statistically analysed. Due to the small covered distance for the dependent analysis (contact angle determination. They are characterised by small deviations of the computed values. Additional to the detailed introduction of this novel analytical approaches plus fit solution special motion relations for the drop on inclined surfaces and detailed relations about the reactivity of the freshly cleaned silicon wafer surface resulting in acceleration

Modeling contact angle hysteresis of a liquid droplet sitting on a cosine wave-like pattern surface.

Science.gov (United States)

Promraksa, Arwut; Chen, Li-Jen

2012-10-15

A liquid droplet sitting on a hydrophobic surface with a cosine wave-like square-array pattern in the Wenzel state is simulated by using the Surface Evolver to determine the contact angle. For a fixed drop volume, multiple metastable states are obtained at two different surface roughnesses. Unusual and non-circular shape of the three-phase contact line of a liquid droplet sitting on the model surface is observed due to corrugation and distortion of the contact line by structure of the roughness. The contact angle varies along the contact line for each metastable state. The maximum and minimum contact angles among the multiple metastable states at a fixed viewing angle correspond to the advancing and the receding contact angles, respectively. It is interesting to observe that the advancing/receding contact angles (and contact angle hysteresis) are a function of viewing angle. In addition, the receding (or advancing) contact angles at different viewing angles are determined at different metastable states. The contact angle of minimum energy among the multiple metastable states is defined as the most stable (equilibrium) contact angle. The Wenzel model is not able to describe the contact angle along the three-phase contact line. The contact angle hysteresis at different drop volumes is determined. The number of the metastable states increases with increasing drop volume. Drop volume effect on the contact angles is also discussed. Crown Copyright © 2012. Published by Elsevier Inc. All rights reserved.

The effect of a tribo-modified surface layer on friction in elastomer contacts

OpenAIRE

Mokhtari, Milad

2015-01-01

Friction between rubber and a counter surface has interested many researchers because of its huge practical importance. Rubber components are applied in various industrial applications such as tires, rubber seals, wiper blades, conveyor belts and syringes. The friction between a rubber surface in contact with a rigid surface is still not fully understood. The complexity lies partially in the viscoelastic nature of elastomers next to various parameters such as roughness, contact pressure and s...

Filamentary superhydrophobic Teflon surfaces: Moderate apparent contact angle but superior air-retaining properties.

Science.gov (United States)

Di Mundo, Rosa; Bottiglione, Francesco; Palumbo, Fabio; Notarnicola, Michele; Carbone, Giuseppe

2016-11-15

Micro-scale textured Teflon surfaces, resulting from plasma etching modification, show extremely high water contact angle values and fairly good resistance to water penetration when hit by water drops at medium-high speed. This behavior is more pronounced when these surfaces present denser and smaller micrometric reliefs. Tailoring the top of these reliefs with a structure which further stabilizes the air may further increase resistance to wetting (water penetration) under static and dynamic conditions. Conditions of the oxygen fed plasma were tuned in order to explore the possibility of obtaining differently topped structures on the surface of the polymer. Scanning Electron Microscopy (SEM) was used to explore topography and X-ray Photoelectron Spectroscopy (XPS) to assess chemical similarity of the modified surfaces. Beside the usual advancing and receding water contact angle (WCA) measurements, surfaces were subjected to high speed impacting drops and immersion in water. At milder, i.e. shorter time and lower input power, plasma conditions formation of peculiar filaments is observed on the top of the sculpted reliefs. Filamentary topped surfaces result in a lower WCA than the spherical ones, appearing in this sense less superhydrophobic. However, these surfaces give rise to the formation of a more pronounced air layer when placed underwater. Further, when hit by water drops falling at medium/high speed, they show a higher resistance to water penetration and a sensitively lower surface-liquid contact time. The contact time is as low as previously observed only on heated solids. This behavior may be ascribed to the cavities formed beneath the filaments which, similarly with the salvinia leaf structures, require a surplus of pressure to be filled by water. Also, it suggests a different concept of superhydrophobicity, which cannot be expected on the basis of the conventional water contact angle characterization. Copyright © 2016 Elsevier Inc. All rights reserved.

Dosimetry of skin-contact exposure to tritium gas contaminated surfaces

International Nuclear Information System (INIS)

Legare, M.

1990-12-01

The radiological hazards from tritium are usually associated with exposure to tritium oxide either by inhalation, ingestion or permeation through skin. However, exposure from skin contact with tritium gas contaminated surfaces represents a different radiological hazard in tritium removal facilities and future fusion power plants. Previous experiments on humans and more recent experiments on hairless rats at Chalk River Laboratories have shown that when a tritium gas-contaminated surface is brought into contact with intact skin, high concentrations of organically-bound tritium in urine and skin are observed which were not seen from single tritiated water (liquid or vapour form) contamination. The results of the rat experiments, which involved measurements of tritium activity in urine and skin, after contact with contaminated stainless steel, are described. These results are also compared to previous data from human experiments. The effect of various exposure conditions and different contaminated surfaces such as brass, aluminum and glass are analysed and related to the results from contaminated stainless steel exposure. Dosimetric models are being developed in order to improve the basis for dose assessment for this mode of tritium uptake. The presently studied model is explained along with the assumptions and methods involved in its derivation. The features of 'STELLA', the software program used to implement the model, are discussed. The methods used to estimate skin and whole body dose from a model are demonstrated. Finally, some experiments for improving the accuracy of the model are proposed. Briefly, this study compares the results from animal and human experiments as well as different exposure conditions, and determines the range of whole body and skin dose that may be involved from skin-contact intake. This information is essential for regulatory purposes particularly in the derivation of doses for skin-contact contamination. (15 figs., 7 tabs., 29 refs.)

Beyond Cassie equation: Local structure of heterogeneous surfaces determines the contact angles of microdroplets

Science.gov (United States)

Zhang, Bo; Wang, Jianjun; Liu, Zhiping; Zhang, Xianren

2014-01-01

The application of Cassie equation to microscopic droplets is recently under intense debate because the microdroplet dimension is often of the same order of magnitude as the characteristic size of substrate heterogeneities, and the mechanism to describe the contact angle of microdroplets is not clear. By representing real surfaces statistically as an ensemble of patterned surfaces with randomly or regularly distributed heterogeneities (patches), lattice Boltzmann simulations here show that the contact angle of microdroplets has a wide distribution, either continuous or discrete, depending on the patch size. The origin of multiple contact angles observed is ascribed to the contact line pinning effect induced by substrate heterogeneities. We demonstrate that the local feature of substrate structure near the contact line determines the range of contact angles that can be stabilized, while the certain contact angle observed is closely related to the contact line width. PMID:25059292

Numerical Study for a Large Volume Droplet on the Dual-rough Surface: Apparent Contact Angle, Contact Angle Hysteresis and Transition Barrier.

Science.gov (United States)

Dong, Jian; Jin, Yanli; Dong, He; Liu, Jiawei; Ye, Senbin

2018-06-14

The profile, apparent contact angle (ACA), contact angle hysteresis (CAH) and wetting state transmission energy barrier (WSTEB) are important static and dynamic properties of a large volume droplet on the hierarchical surface. Understanding them can provide us with important insights to functional surfaces and promote the application in corresponding areas. In this paper, we established three theoretical models (Model 1, Model 2 and Model 3) and corresponding numerical methods, which were obtained by the free energy minimization and the nonlinear optimization algorithm, to predict the profile, ACA, CAH and WSTEB of a large volume droplet on the horizontal regular dual-rough surface. In consideration of the gravity, the energy barrier on the contact circle, the dual heterogenous structures and their roughness on the surface, the models are more universal and accurate than previous models. It showed that the predictions of the models were in good agreement with the results from the experiment or literature. The models are promising to become novel design approaches of functional surfaces, which are frequently applied in microfluidic chips, water self-catchment system and dropwise condensation heat transfer system.

A contact mechanics model for ankle implants with inclusion of surface roughness effects

International Nuclear Information System (INIS)

Hodaei, M; Farhang, K; Maani, N

2014-01-01

Total ankle replacement is recognized as one of the best procedures to treat painful arthritic ankles. Even though this method can relieve patients from pain and reproduce the physiological functions of the ankle, an improper design can cause an excessive amount of metal debris due to wear, causing toxicity in implant recipient. This paper develops a contact model to treat the interaction of tibia and talus implants in an ankle joint. The contact model describes the interaction of implant rough surfaces including both elastic and plastic deformations. In the model, the tibia and the talus surfaces are viewed as macroscopically conforming cylinders or conforming multi-cylinders containing micrometre-scale roughness. The derived equations relate contact force on the implant and the minimum mean surface separation of the rough surfaces. The force is expressed as a statistical integral function of asperity heights over the possible region of interaction of the roughness of the tibia and the talus implant surfaces. A closed-form approximate equation relating contact force and minimum separation is used to obtain energy loss per cycle in a load–unload sequence applied to the implant. In this way implant surface statistics are related to energy loss in the implant that is responsible for internal void formation and subsequent wear and its harmful toxicity to the implant recipient. (paper)

A contact mechanics model for ankle implants with inclusion of surface roughness effects

Science.gov (United States)

Hodaei, M.; Farhang, K.; Maani, N.

2014-02-01

Total ankle replacement is recognized as one of the best procedures to treat painful arthritic ankles. Even though this method can relieve patients from pain and reproduce the physiological functions of the ankle, an improper design can cause an excessive amount of metal debris due to wear, causing toxicity in implant recipient. This paper develops a contact model to treat the interaction of tibia and talus implants in an ankle joint. The contact model describes the interaction of implant rough surfaces including both elastic and plastic deformations. In the model, the tibia and the talus surfaces are viewed as macroscopically conforming cylinders or conforming multi-cylinders containing micrometre-scale roughness. The derived equations relate contact force on the implant and the minimum mean surface separation of the rough surfaces. The force is expressed as a statistical integral function of asperity heights over the possible region of interaction of the roughness of the tibia and the talus implant surfaces. A closed-form approximate equation relating contact force and minimum separation is used to obtain energy loss per cycle in a load-unload sequence applied to the implant. In this way implant surface statistics are related to energy loss in the implant that is responsible for internal void formation and subsequent wear and its harmful toxicity to the implant recipient.

Biofilm formation by Staphylococcus aureus from food contact surfaces in a meat-based broth and sensitivity to sanitizers

Directory of Open Access Journals (Sweden)

Evandro Leite de Souza

2014-01-01

Full Text Available This study assessed the capacity of adhesion, the detachment kinetic and the biofilm formation by Staphylococcus aureus isolated from food services on stainless steel and polypropylene surfaces (2 x 2 cm when cultivated in a meat-based broth at 28 and 7 ºC. It was also to study the efficacy of the sanitizers sodium hypochlorite (250 mg/L and peracetic acid (30 mg/L in inactivating the bacterial cells in the preformed biofilm. S. aureus strains adhered in high numbers regardless the assayed surface kind and incubation temperature over 72 h. Cells detachment of surfaces revealed high persistence over the incubation period. Number of cells needed for biofilm formation was noted at all experimental systems already after 3 days. Peracetic acid and sodium hypochlorite were not efficient in completely removing the cells of S. aureus adhered on polypropylene and stainless steel surfaces. From these results, the assayed strains revealed high capacity to adhere and form biofilm on polypropylene and stainless steel surfaces under different growth conditions. Moreover, the cells in biofilm matrix were resistant for total removal when submitted to the exposure to sanitizers.

Attachment behaviour of Escherichia coli K12 and Salmonella Typhimurium P6on food contact surfaces for food transportation

DEFF Research Database (Denmark)

Abban, Stephen; Jakobsen, Mogens; Jespersen, Lene

2012-01-01

The role of cargo container lining materials aluminium, a fibre reinforced plastic (FRP) and stainless steel in bacterial cross contamination during transport was assessed. For this, attachment and detachment of Escherichia coli K12 and Salmonella Typhimurium P6 on the three surfaces in the absence....... Typhimurium P6 respectively. Correlation with roughness average was poor; r = -0.425 and -0.413 respectively for E. coli K12 and S. Typhimurium P6. Presence of residue caused significant reduction (p ... material sections of the same surfaces. We report these observations for the first time for aluminium and the FRP material and in part for stainless steel. The S. Typhimurium P6 strain also had significantly higher level of attachment than the E. coli K12 strain. Our findings show that food residue...

Pseudomonas aeruginosa Survival at Posterior Contact Lens Surfaces after Daily Wear

Science.gov (United States)

Wu, Yvonne T.; Zhu, Lucia S.; Tam, K. P. Connie; Evans, David J.; Fleiszig, Suzanne M. J.

2015-01-01

Purpose Pseudomonas aeruginosa keratitis is a sight-threatening complication of contact lens wear, yet mechanisms by which lenses predispose to infection remain unclear. Here, we tested the hypothesis that tear fluid at the posterior contact lens surface can lose antimicrobial activity over time during lens wear. Methods Daily disposable lenses were worn for 1, 2, 4, 6 or 8 h immediately after removal from their packaging, or after presoaking in sterile saline for 2 days to remove packaging solution. Unworn lenses were also tested, some coated in tears “aged” in vitro for 1 or 8 h. Lenses were placed anterior surface down into tryptic soy agar cradles containing gentamicin (100µg/ml) to kill bacteria already on the lens, and posterior surfaces inoculated with gentamicin-resistant P. aeruginosa for 3 h. Surviving bacteria were enumerated by viable counts of lens homogenates. Results Posterior surfaces of lenses worn by patients for 8 h supported more P. aeruginosa growth than lenses worn for only 1 h, if lenses were presoaked prior to wear (~ 2.4-fold, p = 0.01). This increase was offset if lenses were not presoaked to remove packaging solution (p = 0.04 at 2 h and 4 h). Irrespective of presoaking, lenses worn for 8 h showed more growth on their posterior surface than unworn lenses coated with tear fluid that was “aged” for 8 h vitro (~8.6-fold, presoaked, p = 0.003: ~ 5.4-fold from packaging solution, p = 0.004). Indeed, in vitro incubation did not impact tear antimicrobial activity. Conclusions This study shows that post lens tear fluid can lose antimicrobial activity over time during contact lens wear, supporting the idea that efficient tear exchange under a lens is critical for homeostasis. Additional studies are needed to determine applicability to other lens types, wearing modalities, and relevance to contact lens-related infections. PMID:25955639

[Interlaboratory Study on Evaporation Residue Test for Food Contact Products (Report 2)].

Science.gov (United States)

Ohno, Hiroyuki; Mutsuga, Motoh; Abe, Tomoyuki; Abe, Yutaka; Amano, Homare; Ishihara, Kinuyo; Ohsaka, Ikue; Ohno, Haruka; Ohno, Yuichiro; Ozaki, Asako; Kakihara, Yoshiteru; Kobayashi, Hisashi; Sakuragi, Hiroshi; Shibata, Hiroshi; Shirono, Katsuhiro; Sekido, Haruko; Takasaka, Noriko; Takenaka, Yu; Tajima, Yoshiyasu; Tanaka, Aoi; Tanaka, Hideyuki; Nakanishi, Toru; Nomura, Chie; Haneishi, Nahoko; Hayakawa, Masato; Miura, Toshihiko; Yamaguchi, Miku; Yamada, Kyohei; Watanabe, Kazunari; Sato, Kyoko

2018-01-01

An interlaboratory study was performed to evaluate the equivalence between an official method and a modified method of evaporation residue test using heptane as a food-simulating solvent for oily or fatty foods, based on the Japanese Food Sanitation Law for food contact products. Twenty-three laboratories participated, and tested the evaporation residues of nine test solutions as blind duplicates. In the official method, heating for evaporation was done with a water bath. In the modified method, a hot plate was used for evaporation, and/or a vacuum concentration procedure was skipped. In most laboratories, the test solutions were heated until just prior to dryness, and then allowed to dry under residual heat. Statistical analysis revealed that there was no significant difference between the two methods. Accordingly, the modified method provides performance equal to the official method, and is available as an alternative method. Furthermore, an interlaboratory study was performed to evaluate and compare two leaching solutions (95% ethanol and isooctane) used as food-simulating solvents for oily or fatty foods in the EU. The results demonstrated that there was no significant difference between heptane and these two leaching solutions.

Genotoxicity testing approaches for the safety assessment of substances used in food contact materials prior to their authorization in the European Union.

Science.gov (United States)

Bolognesi, Claudia; Castoldi, Anna F; Crebelli, Riccardo; Barthélémy, Eric; Maurici, Daniela; Wölfle, Detlef; Volk, Katharina; Castle, Laurence

2017-06-01

Food contact materials are all materials and articles intended to come directly or indirectly into contact with food. Before being included in the positive European "Union list" of authorized substances (monomers, other starting substances and additives) for plastic food contact materials, the European Food Safety Authority (EFSA) must assess their safety "in use". If relevant for risk, the safety of the main impurities, reaction and degradation products originating from the manufacturing process is also evaluated. Information on genotoxicity is always required irrespective of the extent of migration and the resulting human exposure, in view of the theoretical lack of threshold for genotoxic events. The 2008 EFSA approach, requiring the testing of food contact materials in three in vitro mutagenicity tests, though still acceptable, is now superseded by the 2011 EFSA Scientific Committee's recommendation for only two complementary tests including a bacterial gene mutation test and an in vitro micronucleus test, to detect two main genetic endpoints (i.e., gene mutations and chromosome aberrations). Follow-up of in vitro positive results depends on the type of genetic effect and on the substance's systemic availability. In this study, we provide an analysis of the data on genotoxicity testing gathered by EFSA on food contact materials for the period 1992-2015. We also illustrate practical examples of the approaches that EFSA took when evaluating "non standard" food contact chemicals (e.g., polymeric additives, oligomer or other reaction mixtures, and nanosubstances). Additionally, EFSA's experience gained from using non testing methods and/or future possibilities in this area are discussed. Environ. Mol. Mutagen. 58:361-374, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

A Mathematical and Numerically Integrable Modeling of 3D Object Grasping under Rolling Contacts between Smooth Surfaces

Directory of Open Access Journals (Sweden)

Suguru Arimoto

2011-01-01

Full Text Available A computable model of grasping and manipulation of a 3D rigid object with arbitrary smooth surfaces by multiple robot fingers with smooth fingertip surfaces is derived under rolling contact constraints between surfaces. Geometrical conditions of pure rolling contacts are described through the moving-frame coordinates at each rolling contact point under the postulates: (1 two surfaces share a common single contact point without any mutual penetration and a common tangent plane at the contact point and (2 each path length of running of the contact point on the robot fingertip surface and the object surface is equal. It is shown that a set of Euler-Lagrange equations of motion of the fingers-object system can be derived by introducing Lagrange multipliers corresponding to geometric conditions of contacts. A set of 1st-order differential equations governing rotational motions of each fingertip and the object and updating arc-length parameters should be accompanied with the Euler-Lagrange equations. Further more, nonholonomic constraints arising from twisting between the two normal axes to each tangent plane are rewritten into a set of Frenet-Serre equations with a geometrically given normal curvature and a motion-induced geodesic curvature.

Water Contact Angle Dependence with Hydroxyl Functional Groups on Silica Surfaces under CO2 Sequestration Conditions.

Science.gov (United States)

Chen, Cong; Zhang, Ning; Li, Weizhong; Song, Yongchen

2015-12-15

Functional groups on silica surfaces under CO2 sequestration conditions are complex due to reactions among supercritical CO2, brine and silica. Molecular dynamics simulations have been performed to investigate the effects of hydroxyl functional groups on wettability. It has been found that wettability shows a strong dependence on functional groups on silica surfaces: silanol number density, space distribution, and deprotonation/protonation degree. For neutral silica surfaces with crystalline structure (Q(3), Q(3)/Q(4), Q(4)), as silanol number density decreases, contact angle increases from 33.5° to 146.7° at 10.5 MPa and 318 K. When Q(3) surface changes to an amorphous structure, water contact angle increases 20°. Water contact angle decreases about 12° when 9% of silanol groups on Q(3) surface are deprotonated. When the deprotonation degree increases to 50%, water contact angle decreases to 0. The dependence of wettability on silica surface functional groups was used to analyze contact angle measurement ambiguity in literature. The composition of silica surfaces is complicated under CO2 sequestration conditions, the results found in this study may help to better understand wettability of CO2/brine/silica system.

Occupationally related contact dermatitis in North American food service workers referred for patch testing, 1994 to 2010.

Science.gov (United States)

Warshaw, Erin M; Kwon, Gina P; Mathias, C G Toby; Maibach, Howard I; Fowler, Joseph F; Belsito, Donald V; Sasseville, Denis; Zug, Kathryn A; Taylor, James S; Fransway, Anthony F; Deleo, Vincent A; Marks, James G; Pratt, Melanie D; Storrs, Frances J; Zirwas, Matthew J; Dekoven, Joel G

2013-01-01

Contact dermatoses are common in food service workers (FSWs). This study aims to (1) determine the prevalence of occupationally related contact dermatitis among FSWs patch tested by the North American Contact Dermatitis Group (NACDG) and (2) characterize responsible allergens and irritants as well as sources. Cross-sectional analysis of patients patch tested by the NACDG, 1994 to 2010, was conducted. Of 35,872 patients patch tested, 1237 (3.4%) were FSWs. Occupationally related skin disease was significantly more common in FSWs when compared with employed non-FSWs. Food service workers were significantly more likely to have hand (P contact dermatitis in FSWs were 30.6% and 54.7%, respectively. Although the final diagnosis of irritant contact dermatitis was statistically higher in FSWs as compared with non-FSWs, allergic contact dermatitis was lower in FSWs as compared with non-FSWs. The most frequent currently relevant and occupationally related allergens were thiuram mix (32.5%) and carba mix (28.9%). Gloves were the most common source of responsible allergens. The NACDG standard tray missed at least 1 occupationally related allergen in 38 patients (4.3%). Among FSWs patch tested by the NACDG between 1994 and 2010, the most common allergens were thiuram mix and carba mix. Gloves were the most common source of responsible allergens.

[Interlaboratory Study on Evaporation Residue Test for Food Contact Products (Report 1)].

Science.gov (United States)

Ohno, Hiroyuki; Mutsuga, Motoh; Abe, Tomoyuki; Abe, Yutaka; Amano, Homare; Ishihara, Kinuyo; Ohsaka, Ikue; Ohno, Haruka; Ohno, Yuichiro; Ozaki, Asako; Kakihara, Yoshiteru; Kobayashi, Hisashi; Sakuragi, Hiroshi; Shibata, Hiroshi; Shirono, Katsuhiro; Sekido, Haruko; Takasaka, Noriko; Takenaka, Yu; Tajima, Yoshiyasu; Tanaka, Aoi; Tanaka, Hideyuki; Tonooka, Hiroyuki; Nakanishi, Toru; Nomura, Chie; Haneishi, Nahoko; Hayakawa, Masato; Miura, Toshihiko; Yamaguchi, Miku; Watanabe, Kazunari; Sato, Kyoko

2018-01-01

An interlaboratory study was performed to evaluate the equivalence between an official method and a modified method of evaporation residue test using three food-simulating solvents (water, 4% acetic acid and 20% ethanol), based on the Japanese Food Sanitation Law for food contact products. Twenty-three laboratories participated, and tested the evaporation residues of nine test solutions as blind duplicates. For evaporation, a water bath was used in the official method, and a hot plate in the modified method. In most laboratories, the test solutions were heated until just prior to evaporation to dryness, and then allowed to dry under residual heat. Statistical analysis revealed that there was no significant difference between the two methods, regardless of the heating equipment used. Accordingly, the modified method provides performance equal to the official method, and is available as an alternative method.

An adhesive contact mechanics formulation based on atomistically induced surface traction

Energy Technology Data Exchange (ETDEWEB)

Fan, Houfu [Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720 (United States); Ren, Bo [Livermore Software Technology Corporation, 7374 Las Positas Road, Livermore, CA 94551 (United States); Li, Shaofan, E-mail: shaofan@berkeley.edu [Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720 (United States)

2015-12-01

In this work, we have developed a novel multiscale computational contact formulation based on the generalized Derjuguin approximation for continua that are characterized by atomistically enriched constitutive relations in order to study macroscopic interaction between arbitrarily shaped deformable continua. The proposed adhesive contact formulation makes use of the microscopic interaction forces between individual particles in the interacting bodies. In particular, the double-layer volume integral describing the contact interaction (energy, force vector, matrix) is converted into a double-layer surface integral through a mathematically consistent approach that employs the divergence theorem and a special partitioning technique. The proposed contact model is formulated in the nonlinear continuum mechanics framework and implemented using the standard finite element method. With no large penalty constant, the stiffness matrix of the system will in general be well-conditioned, which is of great significance for quasi-static analysis. Three numerical examples are presented to illustrate the capability of the proposed method. Results indicate that with the same mesh configuration, the finite element computation based on the surface integral approach is faster and more accurate than the volume integral based approach. In addition, the proposed approach is energy preserving even in a very long dynamic simulation.

Bacteria hold their breath upon surface contact as shown in a strain of Escherichia coli, using dispersed surfaces and flow cytometry analysis.

Directory of Open Access Journals (Sweden)

Jing Geng

Full Text Available Bacteria are ubiquitously distributed throughout our planet, mainly in the form of adherent communities in which cells exhibit specific traits. The mechanisms underpinning the physiological shift in surface-attached bacteria are complex, multifactorial and still partially unclear. Here we address the question of the existence of early surface sensing through implementation of a functional response to initial surface contact. For this purpose, we developed a new experimental approach enabling simultaneous monitoring of free-floating, aggregated and adherent cells via the use of dispersed surfaces as adhesive substrates and flow cytometry analysis. With this system, we analyzed, in parallel, the constitutively expressed GFP content of the cells and production of a respiration probe--a fluorescent reduced tetrazolium ion. In an Escherichia coli strain constitutively expressing curli, a major E. coli adhesin, we found that single cell surface contact induced a decrease in the cell respiration level compared to free-floating single cells present in the same sample. Moreover, we show here that cell surface contact with an artificial surface and with another cell caused reduction in respiration. We confirm the existence of a bacterial cell "sense of touch" ensuring early signalling of surface contact formation through respiration down modulation.

21 CFR 170.103 - Withdrawal without prejudice of a premarket notification for a food contact substance (FCN).

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Withdrawal without prejudice of a premarket... ADDITIVES Premarket Notifications § 170.103 Withdrawal without prejudice of a premarket notification for a food contact substance (FCN). A manufacturer or supplier may withdraw an FCN without prejudice to a...

A Mathematical Method to Calculate Tumor Contact Surface Area: An Effective Parameter to Predict Renal Function after Partial Nephrectomy.

Science.gov (United States)

Hsieh, Po-Fan; Wang, Yu-De; Huang, Chi-Ping; Wu, Hsi-Chin; Yang, Che-Rei; Chen, Guang-Heng; Chang, Chao-Hsiang

2016-07-01

We proposed a mathematical formula to calculate contact surface area between a tumor and renal parenchyma. We examined the applicability of using contact surface area to predict renal function after partial nephrectomy. We performed this retrospective study in patients who underwent partial nephrectomy between January 2012 and December 2014. Based on abdominopelvic computerized tomography or magnetic resonance imaging, we calculated the contact surface area using the formula (2*π*radius*depth) developed by integral calculus. We then evaluated the correlation between contact surface area and perioperative parameters, and compared contact surface area and R.E.N.A.L. (Radius/Exophytic/endophytic/Nearness to collecting system/Anterior/Location) score in predicting a reduction in renal function. Overall 35, 26 and 45 patients underwent partial nephrectomy with open, laparoscopic and robotic approaches, respectively. Mean ± SD contact surface area was 30.7±26.1 cm(2) and median (IQR) R.E.N.A.L. score was 7 (2.25). Spearman correlation analysis showed that contact surface area was significantly associated with estimated blood loss (p=0.04), operative time (p=0.04) and percent change in estimated glomerular filtration rate (p contact surface area and R.E.N.A.L. score independently affected percent change in estimated glomerular filtration rate (p contact surface area was a better independent predictor of a greater than 10% change in estimated glomerular filtration rate compared to R.E.N.A.L. score (AUC 0.86 vs 0.69). Using this simple mathematical method, contact surface area was associated with surgical outcomes. Compared to R.E.N.A.L. score, contact surface area was a better predictor of functional change after partial nephrectomy. Copyright © 2016 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Statistical contact angle analyses; "slow moving" drops on a horizontal silicon-oxide surface.

Science.gov (United States)

Schmitt, M; Grub, J; Heib, F

2015-06-01

Sessile drop experiments on horizontal surfaces are commonly used to characterise surface properties in science and in industry. The advancing angle and the receding angle are measurable on every solid. Specially on horizontal surfaces even the notions themselves are critically questioned by some authors. Building a standard, reproducible and valid method of measuring and defining specific (advancing/receding) contact angles is an important challenge of surface science. Recently we have developed two/three approaches, by sigmoid fitting, by independent and by dependent statistical analyses, which are practicable for the determination of specific angles/slopes if inclining the sample surface. These approaches lead to contact angle data which are independent on "user-skills" and subjectivity of the operator which is also of urgent need to evaluate dynamic measurements of contact angles. We will show in this contribution that the slightly modified procedures are also applicable to find specific angles for experiments on horizontal surfaces. As an example droplets on a flat freshly cleaned silicon-oxide surface (wafer) are dynamically measured by sessile drop technique while the volume of the liquid is increased/decreased. The triple points, the time, the contact angles during the advancing and the receding of the drop obtained by high-precision drop shape analysis are statistically analysed. As stated in the previous contribution the procedure is called "slow movement" analysis due to the small covered distance and the dominance of data points with low velocity. Even smallest variations in velocity such as the minimal advancing motion during the withdrawing of the liquid are identifiable which confirms the flatness and the chemical homogeneity of the sample surface and the high sensitivity of the presented approaches. Copyright © 2014 Elsevier Inc. All rights reserved.

Surface chemistry and microscopy of food powders

Science.gov (United States)

Burgain, Jennifer; Petit, Jeremy; Scher, Joël; Rasch, Ron; Bhandari, Bhesh; Gaiani, Claire

2017-12-01

Despite high industrial and scientific interest, a comprehensive review of the surface science of food powders is still lacking. There is a real gap between scientific concerns of the field and accessible reviews on the subject. The global description of the surface of food powders by multi-scale microscopy approaches seems to be essential in order to investigate their complexity and take advantage of their high innovation potential. Links between these techniques and the interest to develop a multi-analytical approach to investigate scientific questions dealing with powder functionality are discussed in the second part of the review. Finally, some techniques used in others fields and showing promising possibilities in the food powder domain will be highlighted.

A review of visual cues associated with food on food acceptance and consumption.

Science.gov (United States)

Wadhera, Devina; Capaldi-Phillips, Elizabeth D

2014-01-01

Several sensory cues affect food intake including appearance, taste, odor, texture, temperature, and flavor. Although taste is an important factor regulating food intake, in most cases, the first sensory contact with food is through the eyes. Few studies have examined the effects of the appearance of a food portion on food acceptance and consumption. The purpose of this review is to identify the various visual factors associated with food such as proximity, visibility, color, variety, portion size, height, shape, number, volume, and the surface area and their effects on food acceptance and consumption. We suggest some ways that visual cues can be used to increase fruit and vegetable intake in children and decrease excessive food intake in adults. In addition, we discuss the need for future studies that can further establish the relationship between several unexplored visual dimensions of food (specifically shape, number, size, and surface area) and food intake. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

Interfacial behavior of common food contact polymer additives.

Science.gov (United States)

Heiserman, W M; Can, S Z; Walker, R A; Begley, T H; Limm, W

2007-07-15

Irganox 1076 (IN1076) and Irganox 1010 (IN1010), phenol containing species often used as antioxidant additives in food packaging polymers have both hydrophilic and hydrophobic functional groups. Consequently these additives are likely to absorb to surfaces where their free energy is minimized. Experiments described in this work examine the two-dimensional phase behavior and vibrational structure of IN1076 and IN1010 films adsorbed to the air/water interface. Surface pressure isotherms show that repeated compression of these films leads to continued irreversible loss of molecules and that on a per molecule basis, this loss is more pronounced for IN1076 than for IN1010. Differences in the surface properties of these two antioxidant additives are interpreted based on differences in molecular structure. Surface specific vibrational measurements of these organic films show very little conformational order, implying that even when closely packed, both antioxidant species have little affinity for forming highly organized domains. These findings have important ramifications for mechanisms that reduce antioxidant activity in polymers as well as descriptions of antioxidant blooming on polymer surfaces.

An effect-directed strategy for characterizing emerging chemicals in food contact materials made from paper and board

DEFF Research Database (Denmark)

Rosenmai, Anna Kjerstine; Bengtström, Linda; Taxvig, Camilla

2017-01-01

Food contact materials (FCM) are any type of item intended to come into contact with foods and thus represent a potential source for human exposure to chemicals. Regarding FCMs made of paper and board, information pertaining to their chemical constituents and the potential impacts on human health...... FCMs exhibited activities in at least one assay. As proof-of-principle, FCM samples obtained from a sandwich wrapper and a pizza box were carried through a complete step-by-step multi-tiered approach. The pizza box exhibited ER activity, likely caused by the presence of bisphenol A, dibutyl phthalate......, and benzylbutyl phthalate. The sandwich wrapper exhibited AR antagonism, likely caused by abietic acid and dehydroabietic acid. Migration studies confirmed that the active chemicals can transfer from FCMs to food simulants. In conclusion, we report an effect-directed strategy that can identify hazards posed...

Physicochemical factors influencing bacterial transfer from contact lenses to surfaces with different roughness and wettability.

Science.gov (United States)

Vermeltfoort, Pit B J; van der Mei, Henny C; Busscher, Henk J; Hooymans, Johanna M M; Bruinsma, Gerda M

2004-11-15

The aim of this study was to determine the transfer of Pseudomonas aeruginosa No. 3 and Staphylococcus aureus 835 from contact lenses to surfaces with different hydrophobicity and roughness. Bacteria were allowed to adhere to contact lenses (Surevue, PureVision, or Focus Night & Day) by incubating the lenses in a bacterial suspension for 30 min. The contaminated lenses were put on a glass, poly(methylmethacrylate), or silicone rubber substratum, shaped to mimic the eye. After 2 and 16 h, lenses were separated from the substrata and bacteria were swabbed off from the respective surfaces and resuspended in saline. Appropriate serial dilutions of these suspensions were made, from which aliquots were plated on agar for enumeration. Bacterial transfer varied between 4 and 60%, depending on the combination of strain, contact time, contact lens, and substratum surface. For P. aeruginosa No. 3, transfer was significantly higher after 16 h than after 2 h, whereas less increase with time was seen for S. aureus 835. Bacterial transfer from all tested contact lenses was least to silicone rubber, the most hydrophobic and roughest substratum surface included. (c) 2004 Wiley Periodicals, Inc.

Effects of drop size and measuring condition on static contact angle measurement on a superhydrophobic surface with goniometric technique

International Nuclear Information System (INIS)

Seo, Kwangseok; Kim, Minyoung; Kim, Do Hyun; Ahn, Jeong Keun

2015-01-01

It is not a simple task to measure a contact angle of a water drop on a superhydrophobic surface with sessile drop method, because a roll-off angle is very low. Usually contact angle of a water drop on a superhydrophobic surface is measured by fixing a drop with intentional defects on the surface or a needle. We examined the effects of drop size and measuring condition such as the use of a needle or defects on the static contact angle measurement on superhydrophobic surface. Results showed that the contact angles on a superhydrophobic surface remain almost constant within intrinsic measurement errors unless there is a wetting transition during the measurement. We expect that this study will provide a deeper understanding on the nature of the contact angle and convenient measurement of the contact angle on the superhydrophobic surface.

Contact splitting and the effect of dimple depth on static friction of textured surfaces.

Science.gov (United States)

Greiner, Christian; Schäfer, Michael; Popp, Uwe; Gumbsch, Peter

2014-06-11

The morphological texturing of surfaces has demonstrated its high potential to maximize adhesion as well as to reduce friction and wear. A key to understanding such phenomena is a principle known as contact splitting. Here, we extend this concept to the static friction behavior of dimpled surfaces. Our results indicate that contact splitting does exist for such structures and that with certain dimple sizes and depths static friction values significantly exceeding those of untextured surfaces can be obtained. These results can be applied to all surfaces where friction forces are to be tuned, from nanoelectromechanical systems up to combustion engines.

Nano-indentation at the surface contact level: applying a harmonic frequency for measuring contact stiffness of self-assembled monolayers adsorbed on Au

International Nuclear Information System (INIS)

Chang, C.-W.; Liao, J.-D.

2008-01-01

In this study, the well-ordered alkanethiolate self-assembled monolayers (SAMs) of varied chain lengths and tail groups were employed as examples for nano-characterization on their mechanical properties. A novel nano-indentation technique with a constant harmonic frequency was applied on SAMs chemically adsorbed on Au to explore their contact mechanics, and furthermore to interpret how SAM molecules respond to an infinitesimal oscillation force without pressing them. Experimental results demonstrated that the harmonic contact stiffness along with the measured displacement of SAMs/Au was distinguishable using a dynamic contact modulus with the distinct feature of phase angles. Phase angles resulted from the relaxing continuation of an applied harmonic frequency and mostly influenced by the outermost tail group of SAM molecules. The harmonic contact stiffness of SAM molecules obviously increased with the densely packed alkyl chains and relatively intense agglomeration of the head group at the anchoring site. As a consequence, the result of this work is relevant to contact mechanics at the surface contact level for the distinction of molecular substances attached on a solid surface. Furthermore it is particularly anticipated to identify biological molecules of variable qualities under a fluid-like micro-environment

Nano-indentation at the surface contact level: applying a harmonic frequency for measuring contact stiffness of self-assembled monolayers adsorbed on Au

Energy Technology Data Exchange (ETDEWEB)

Chang, C.-W.; Liao, J.-D. [Department of Materials Science and Engineering, National Cheng Kung University, No. 1, University Road, Tainan 70101, Taiwan (China)], E-mail: jdliao@mail.ncku.edu.tw

2008-08-06

In this study, the well-ordered alkanethiolate self-assembled monolayers (SAMs) of varied chain lengths and tail groups were employed as examples for nano-characterization on their mechanical properties. A novel nano-indentation technique with a constant harmonic frequency was applied on SAMs chemically adsorbed on Au to explore their contact mechanics, and furthermore to interpret how SAM molecules respond to an infinitesimal oscillation force without pressing them. Experimental results demonstrated that the harmonic contact stiffness along with the measured displacement of SAMs/Au was distinguishable using a dynamic contact modulus with the distinct feature of phase angles. Phase angles resulted from the relaxing continuation of an applied harmonic frequency and mostly influenced by the outermost tail group of SAM molecules. The harmonic contact stiffness of SAM molecules obviously increased with the densely packed alkyl chains and relatively intense agglomeration of the head group at the anchoring site. As a consequence, the result of this work is relevant to contact mechanics at the surface contact level for the distinction of molecular substances attached on a solid surface. Furthermore it is particularly anticipated to identify biological molecules of variable qualities under a fluid-like micro-environment.

External Validation of Contact Surface Area as a Predictor of Postoperative Renal Function in Patients Undergoing Partial Nephrectomy.

Science.gov (United States)

Haifler, Miki; Ristau, Benjamin T; Higgins, Andrew M; Smaldone, Marc C; Kutikov, Alexander; Zisman, Amnon; Uzzo, Robert G

2017-09-20

We sought to externally validate a mathematical formula for tumor contact surface area as a predictor of postoperative renal function in patients undergoing partial nephrectomy for renal cell carcinoma. We queried a prospectively maintained kidney cancer database for patients who underwent partial nephrectomy between 2014 and 2016. Contact surface area was calculated using data obtained from preoperative cross-sectional imaging. The correlation between contact surface area and perioperative variables was examined. The correlation between postoperative renal functional outcomes, contact surface area and the R.E.N.A.L. (radius, exophytic/endophytic properties, nearness of tumor to collecting system or sinus, anterior/posterior, location relative to polar lines and tumor touches main renal artery or vein) nephrometry score was also assessed. A total of 257 patients who underwent partial nephrectomy had sufficient data to enter the study. Median contact surface area was 14.5 cm 2 (IQR 6.2-36) and the median nephrometry score was 9 (IQR 7-10). Spearman correlation analysis showed that contact surface area correlated with estimated blood loss (r s = 0.42, p contact surface area and nephrometry score were independent predictors of the absolute change in the estimated glomerular filtration rate (each p contact surface area was a better predictor of a greater than 20% postoperative decline in the estimated glomerular filtration rate compared with the nephrometry score (AUC 0.94 vs 0.80). Contact surface area correlated with the change in postoperative renal function after partial nephrectomy. It can be used in conjunction with the nephrometry score to counsel patients about the risk of renal functional decline after partial nephrectomy. Copyright © 2018 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Certification of contact probe measurement of surface wave of Li jet for IFMIF

Energy Technology Data Exchange (ETDEWEB)

Okita, Takafumi, E-mail: okita@stu.nucl.eng.osaka-u.ac.jp [Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka (Japan); Hoashi, Eiji; Yoshihashi, Sachiko [Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka (Japan); Kondo, Hiroo; Kanemura, Takuji [Japan Atomic Energy Agency, 4002 Narita-cho, Oarai-machi, Higashiibaraki-gun, Ibaraki (Japan); Yamaoka, Nobuo; Horiike, Hiroshi [Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka (Japan)

2015-10-15

Highlights: • We have conducted experiments of liquid lithium free-surface flow for IFMIF. • In the experiment using electro-contact probe apparatus, a droplet of liquid Li on the middle of measurement probe was observed. • Behavior of a droplet and false detections were observed by using HSV camera. • The error of the statistical result was roughly evaluated about 1%. • From results of numerical simulations, we obtained the detailed information about the behavior of a Li droplet. - Abstract: The international fusion material irradiation facility (IFMIF) is a neutron source for developing fusion reactor materials. A liquid lithium (Li) jet with free surface is planned as a target to generate intense neutron field. It is important to obtain information on the surface wave characteristic for safety of the facility and efficient neutron generation. Surface wave characteristics experiment using the liquid Li circulation facility is carried out at Osaka University. In our studies, measurement using an electro-contact probe apparatus is conducted and many data about surface wave height were taken. In this experiment, a liquid Li droplet was observed on the probe. To see effect due to droplets on the probe needle, images near the surface of the Li jet including the Li droplet were taken by HSV camera synchronized with probe contact signals, and correlation between the behavior of the Li droplet and signals was evaluated. From the results, when the droplet on the probe contacts of the droplet with the surface, signals obviously different from the regular signal were observed. The influence on the result of frequency was estimated and is approximately <1%. Accuracy of measurement using probe could be increased by carefully deleting false signals.

Interaction between staining and degradation of a composite resin in contact with colored foods

Directory of Open Access Journals (Sweden)

Debora Soares-Geraldo

2011-08-01

Full Text Available Composite resins might be susceptible to degradation and staining when in contact with some foods and drinks. This study evaluated color alteration and changes in microhardness of a microhybrid composite after immersion in different colored foods and determined whether there was a correlation between these two variables. Eighty composite disks were randomly divided into 8 experimental groups (n = 10: kept dry; deionized water; orange juice; passion fruit juice; grape juice; ketchup; mustard and soy sauce. The disks were individually immersed in their respective test substance at 37 ºC, for a period of 28 days. Superficial analysis of the disk specimens was performed by taking microhardness measurements (Vickers, 50 g load for 45 seconds and color alterations were determined with a spectrophotometer (CINTRA 10- using a CIEL*a*b* system, 400-700 nm wavelength, illuminant d65 and standard observer of 2º at the following times: baseline (before immersion, 1, 7, 14, 21 and 28 days. Results were analyzed by ANOVA and Tukey's test (p < 0.05. Both variables were also submitted to Pearson's correlation test (p < 0.05. The passion fruit group underwent the greatest microhardness change, while the mustard group suffered the greatest color alteration. Significant positive correlation was found between the two variables for the groups deionized water, grape juice, soy sauce and ketchup. Not all color alteration could be associated with surface degradation.

Modelling the static contact between a fingertip and a rigid wavy surface

NARCIS (Netherlands)

Rodriguez Urribarri, Adriana; van der Heide, Emile; Zeng, Xiangqiong; de Rooij, Matthias B.

2016-01-01

Surface topography is one of the major parameters affecting friction during touch and consequently tactility. In order to understand and control friction, fine controlled surfaces with a sinusoidal topography are studied to derive an analytical contact model. The Westergaard model on a

21 CFR 186.1 - Substances added indirectly to human food affirmed as generally recognized as safe (GRAS).

Science.gov (United States)

2010-04-01

... ingredient, one or more of these limited conditions of use, which may include the category of food-contact...(s), it shall be used in food-contact surfaces only within such limitation(s), including the category... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Substances added indirectly to human food affirmed...

Contact angle and local wetting at contact line.

Science.gov (United States)

Li, Ri; Shan, Yanguang

2012-11-06

This theoretical study was motivated by recent experiments and theoretical work that had suggested the dependence of the static contact angle on the local wetting at the triple-phase contact line. We revisit this topic because the static contact angle as a local wetting parameter is still not widely understood and clearly known. To further clarify the relationship of the static contact angle with wetting, two approaches are applied to derive a general equation for the static contact angle of a droplet on a composite surface composed of heterogeneous components. A global approach based on the free surface energy of a thermodynamic system containing the droplet and solid surface shows the static contact angle as a function of local surface chemistry and local wetting state at the contact line. A local approach, in which only local forces acting on the contact line are considered, results in the same equation. The fact that the local approach agrees with the global approach further demonstrates the static contact angle as a local wetting parameter. Additionally, the study also suggests that the wetting described by the Wenzel and Cassie equations is also the local wetting of the contact line rather than the global wetting of the droplet.

A study on the contact angles of a water droplet on smooth and rough solid surfaces

International Nuclear Information System (INIS)

Park, Ju Young; Ha, Man Yeong; Choi, Ho Jin; Hong, Seung Do; Yoon, Hyun Sik

2011-01-01

We investigated the wetting characteristics such as contact angle, wetting radius and topography of water droplets on smooth and random solid surfaces. Molecular dynamic simulation is employed to analyze the wetting behavior of water droplets on smooth and rough surfaces by considering different potential energy models of bond, angle, Lennard-Jones and Coulomb to calculate the interacting forces between water molecules. The Lennard-Jones potential energy model is adopted as an interaction model between water molecules and solid surface atoms. The randomly rough surface is generated by changing the standard deviation of roughness height from 1 A to 3 A with the fixed autocorrelation length. The size of water droplet considered is in the range from 2,000 to 5,000 molecules. The contact angles increase generally with increasing number of water molecules. For a hydrophobic surface whose characteristic energy is 0.1 kcal/mol, the contact angles depend rarely on the standard deviation of the roughness height. However, when the surface energy is 0.5 and 1.0 kcal/mol, the contact angles depend on both the roughness height of surfaces and droplet size

Lubrication of oral surfaces by food emulsions: the importance of surface characteristics

NARCIS (Netherlands)

Hoog, de E.H.A.; Prinz, J.F.; Huntjens, L.; Dresselhuis, D.M.; Aken, van G.A.

2006-01-01

The friction between surfaces in relative motion lubricated by food emulsions has been measured. Different types of surfaces were tested, including metal, glass, rubber, and mucosal surfaces (pig tongue and pig esophagus). We demonstrate that the load-dependent behavior of the coefficient of kinetic

Lubrication of oral surfaces by food emulsions: The importance of surface characteristics

NARCIS (Netherlands)

Hoog, E.H.A. de; Prinz, J.F.; Huntjens, L.; Dresselhuis, D.M.; Aken, G.A. van

2006-01-01

The friction between surfaces in relative motion lubricated by food emulsions has been measured. Different types of surfaces were tested, including metal, glass, rubber, and mucosal surfaces (pig tongue and pig esophagus). We demonstrate that the load-dependent behavior of the coefficient of kinetic

Molecular dynamics study of contact mechanics: contact area and interfacial separation from small to full contact

OpenAIRE

Yang, C.; Persson, B. N. J.

2007-01-01

We report a molecular dynamics study of the contact between a rigid solid with a randomly rough surface and an elastic block with a flat surface. We study the contact area and the interfacial separation from small contact (low load) to full contact (high load). For small load the contact area varies linearly with the load and the interfacial separation depends logarithmically on the load. For high load the contact area approaches to the nominal contact area (i.e., complete contact), and the i...

Primary aromatic amines (PAAs) in black nylon and other food-contact materials, 2004-2009

DEFF Research Database (Denmark)

Trier, Xenia Thorsager; Okholm, B.; Foverskov, Annie

2010-01-01

Primary aromatic amines (PAAs) were analysed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in migrates from 234 samples of food-contact materials, including black nylon (polyamide) kitchen utensils (n = 136), coloured plastics (28), and clear/printed multilayer film/laminates (41......), from retailers, importers, and food producers. A further 29 utensils in use were obtained from colleagues. Very high PAA migration was found from black nylon kitchen utensils to the food simulant 3% acetic acid: the 'non-detectable' limit (20 mu g aniline equivalents kg-1 food) was exceeded by up...... migration test conditions influenced the final test results. Long-term release of PAAs was fitted by diffusion modelling experiments and long-term release was also seen as expected from used utensils. Toxicologists consider these migration levels of the suspected carcinogenic PAAs as a problem of major...

Comparative exposure to DEHP from food contact materials: application of the product intake fraction

DEFF Research Database (Denmark)

Ernstoff, Alexi; Jolliet, Olivier; Fantke, Peter

Quantitative Sustainability Assessment Food contact materials (FCM), e.g. bottles and food handling gloves, can contain potentially endocrine disrupting chemicals, such as di-2-ethylhexyl phthalate(DEHP, CAS: 117-81-7). To investigate the contribution of FCM to dietary DEHP exposure we apply...... thresholds. A hypothetical average PiF for the FCM sector was calculated via production volume and oral exposure doses estimated from NHANES data. In both cases the indication was gloves may contribute more to DEHP exposure when used with certain food items than bottled water. DEHP content in gloves greater...... than 5% would cause exceedance of US EPA threshold when used with certain food items,e.g. radishes based on PiF calculated here. The PiF used in thís context has applications for regulations related to FCM and exposure assessments on a per unit kilo basis....

Investigation of surface porosity measurements and compaction pressure as means to ensure consistent contact angle determinations

DEFF Research Database (Denmark)

Holm, René; Borkenfelt, Simon; Allesø, Morten

2016-01-01

for a compound is determined by its contact angle to a liquid, which in the present study was measured using the sessile drop method applied to a disc compact of the compound. Precise determination of the contact angle is important should it be used to either rank compounds or selected excipients to e.......g. increase the wetting from a solid dosage form. Since surface roughness of the compact has been suggested to influence the measurement this study investigated if the surface quality, in terms of surface porosity, had an influence on the measured contact angle. A correlation to surface porosity was observed......, however for six out of seven compounds similar results were obtained by applying a standard pressure (866MPa) to the discs in their preparation. The data presented in the present work therefore suggest that a constant high pressure should be sufficient for most compounds when determining the contact angle...

Effect of surface tension on the behavior of adhesive contact based on Lennard-Jones potential law

Science.gov (United States)

Zhu, Xinyao; Xu, Wei

2018-02-01

The present study explores the effect of surface tension on adhesive contact behavior where the adhesion is interpreted by long-range intermolecular forces. The adhesive contact is analyzed using the equivalent system of a rigid sphere and an elastic half space covered by a membrane with surface tension. The long-range intermolecular forces are modeled with the Lennard‒Jones (L‒J) potential law. The current adhesive contact issue can be represented by a nonlinear integral equation, which can be solved by Newton‒Raphson method. In contrast to previous studies which consider intermolecular forces as short-range, the present study reveals more details of the features of adhesive contact with surface tension, in terms of jump instabilities, pull-off forces, pressure distribution within the contact area, etc. The transition of the pull-off force is not only consistent with previous studies, but also presents some new interesting characteristics in the current situation.

Recreational Water Contact and Fish Consumption Assessment to Inform Risk Estimates and Evaluate Ecosystem Services

Science.gov (United States)

Background: Surface waters provide invaluable ecosystem services, including drinking water, food, waste water disposal, and recreation. The nature and frequency of recreational contact with surface waters is a critical consideration in evaluating benefits to human well-being (e.g...

Super-mercuryphobic and hydrophobic diamond surfaces with hierarchical structures: Vanishment of the contact angle hysteresis with mercury

International Nuclear Information System (INIS)

Escobar, Juan V.; Garza, Cristina; Alonso, Juan Carlos; Castillo, Rolando

2013-01-01

Increased roughness is known to enhance the natural wetting properties of surfaces, making them either more hydrophobic or more hydrophilic. In this work we study the wetting properties of water and mercury drops in contact with boron doped diamond films with progressively increased surface roughnesses. We show how thermal oxidation of a microcrystalline film creates pyramids decorated with sub-micron protrusions that turn its naturally mercuryphobic surface into super-mercuryphobic. With this liquid, we observe the vanishment of the contact angle hysteresis that is expected for rough surfaces as the contact angle approaches 180, making small drops of mercury roll along out of the surface at an apparent zero tilt-angle. In contrast, the incorporation of nano-globules on the oxidized surface through a silanization process is necessary to increase the hydrophobic properties of the film for which the contact angle with water reaches 138°. The wetting states that dominate in each case are discussed.

Super-mercuryphobic and hydrophobic diamond surfaces with hierarchical structures: Vanishment of the contact angle hysteresis with mercury

Energy Technology Data Exchange (ETDEWEB)

Escobar, Juan V., E-mail: escobar@fisica.unam.mx [Instituto de Física, Universidad Nacional Autónoma de México, PO Box 20-364, DF, México, 01000 (Mexico); Garza, Cristina, E-mail: cgarza@fisica.unam.mx [Instituto de Física, Universidad Nacional Autónoma de México, PO Box 20-364, DF, México, 01000 (Mexico); Alonso, Juan Carlos, E-mail: alonso@unam.mx [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, PO Box 70-360, DF, México, 04510 (Mexico); Castillo, Rolando, E-mail: rolandoc@fisica.unam.mx [Instituto de Física, Universidad Nacional Autónoma de México, PO Box 20-364, DF, México, 01000 (Mexico)

2013-05-15

Increased roughness is known to enhance the natural wetting properties of surfaces, making them either more hydrophobic or more hydrophilic. In this work we study the wetting properties of water and mercury drops in contact with boron doped diamond films with progressively increased surface roughnesses. We show how thermal oxidation of a microcrystalline film creates pyramids decorated with sub-micron protrusions that turn its naturally mercuryphobic surface into super-mercuryphobic. With this liquid, we observe the vanishment of the contact angle hysteresis that is expected for rough surfaces as the contact angle approaches 180, making small drops of mercury roll along out of the surface at an apparent zero tilt-angle. In contrast, the incorporation of nano-globules on the oxidized surface through a silanization process is necessary to increase the hydrophobic properties of the film for which the contact angle with water reaches 138°. The wetting states that dominate in each case are discussed.

Inactivation of avirulent Yersinia pestis on food and food contact surfaces by ultraviolet light and freezing

Science.gov (United States)

Yersinia pestis, the causative agent of plague, can occasionally be contracted as a naso-pharangeal or gastrointestinal illness through consumption of contaminated meat. In this study, the use of 254 nm ultraviolet light (UV-C) to inactivate a multi-isolate cocktail of avirulent Y. pestis on food an...

EB surface sterilization of food material

International Nuclear Information System (INIS)

Kaneko, H.; Mizutani, A.; Kato, K.; Nishikimi, T.; Taniguchi, S.

2001-01-01

In this paper, we introduce a food irradiation with low energetic, lower than 300keV, electrons (so-called SOFT ELECTRON) as a rather new method of food sterilization. It is also a physical sterilization method, and free from the problems mentioned above. Low energetic electrons have small penetration power (50-200micron) through raw materials, and by selecting a proper energy of electrons we can sterilize only the surfaces or skins of target materials

Pinning of the Contact Line during Evaporation on Heterogeneous Surfaces: Slowdown or Temporary Immobilization? Insights from a Nanoscale Study.

Science.gov (United States)

Zhang, Jianguo; Müller-Plathe, Florian; Leroy, Frédéric

2015-07-14

The question of the effect of surface heterogeneities on the evaporation of liquid droplets from solid surfaces is addressed through nonequilibrium molecular dynamics simulations. The mechanism behind contact line pinning which is still unclear is discussed in detail on the nanoscale. Model systems with the Lennard-Jones interaction potential were employed to study the evaporation of nanometer-sized cylindrical droplets from a flat surface. The heterogeneity of the surface was modeled through alternating stripes of equal width but two chemical types. The first type leads to a contact angle of 67°, and the other leads to a contact angle of 115°. The stripe width was varied between 2 and 20 liquid-particle diameters. On the surface with the narrowest stripes, evaporation occurred at constant contact angle as if the surface was homogeneous, with a value of the contact angle as predicted by the regular Cassie-Baxter equation. When the width was increased, the contact angle oscillated during evaporation between two boundaries whose values depend on the stripe width. The evaporation behavior was thus found to be a direct signature of the typical size of the surface heterogeneity domains. The contact angle both at equilibrium and during evaporation could be predicted from a local Cassie-Baxter equation in which the surface composition within a distance of seven fluid-particle diameters around the contact line was considered, confirming the local nature of the interactions that drive the wetting behavior of droplets. More importantly, we propose a nanoscale explanation of pinning during evaporation. Pinning should be interpreted as a drastic slowdown of the contact line dynamics rather than a complete immobilization of it during a transition between two contact angle boundaries.

Radiation-heterogeneous processes on the surface of stainless steel in contact with water

International Nuclear Information System (INIS)

Garibov, A.; Agayev, T.N.; Velibekova, G.Z.; Ismayilov, Sh.S.; Aliyev, A.G.

2003-01-01

Full text: Stainless steels are one of prevailing materials of nuclear power engineering. Under operating conditions in real systems they are exposed to influence of ionizing radiation in contact with various environments. Therefore in the processes of corrosion and destruction of stainless steels special significance takes on surface processes and subsequent heterogeneous processes with their participation. In this report the results of research of nuclear-heterogeneous processes regularities in contact with stainless steel of nuclear reactors with water under influence of γ-quanta in the temperature range 300-573 K are given. Radiolytic processes in water are investigated comprehensively and therefore it was taken as modelling system for titration of surface defects and secondary electrons, emitted from metal. It was determined, that radiation processes in stainless steel give rise to the increasing of energy output of molecular hydrogen at water radiolysis from 0.45 molecule/100 eV at pure water radiolysis at 296 K up to 3.4 molecule/100 eV at the presence of stainless steel at 300 K. With increase of temperature the output of molecular hydrogen increases up to 8.2 molecule/100 eV at 573 K. Processes of lattice damage in samples of stainless steel under influence of γ-rays were investigated by electrophysical method. Influence of γ-radiation on stainless steel in contact with water at temperatures T ≤ 423 K and initial values of radiation dose D ≤ 200 kGy given rise to the reduction of electrical resistivity of samples. At doses D≥200 kGy electrical resistivity is increased. Increase of temperature from 333 K up to 423 K lead to the reduction of dose value, at which the transition to resistance increase, from 200 kGy up to 100 kGy occurs. At T≥523 K insoluble oxide phase is formed on a surface of metal which give rise to the increase of electrical resistivity of stainless steel samples. Surface oxide film formed in contact of stainless steel + H 2 O

Drop deposition on surfaces with contact-angle hysteresis: Liquid-bridge stability and breakup

OpenAIRE

Akbari, Amir; Hill, Reghan J.

2015-01-01

We study the stability and breakup of liquid bridges with a free contact line on a surface with contact-angle hysteresis under zero-gravity conditions. Theoretical predictions of the stability limits are validated by experimental measurements. Experiments are conducted in a water-methanol-silicon oil system where the gravity force is offset by buoyancy. We highlight cases where stability is lost during the transition from a pinned-pinned to pinned-free interface when the receding contact angl...

Evidence of bad recycling practices: BFRs in children's toys and food-contact articles.

Science.gov (United States)

Guzzonato, A; Puype, F; Harrad, S J

2017-07-19

Brominated flame retardants (BFRs) have been used intentionally in a wide range of plastics, but are now found in an even wider range of such materials (including children's toys and food contact articles) as a result of recycling practices that mix BFR-containing waste plastics with "virgin" materials. In this study Br was quantified in toy and food contact samples on the assumption that its concentration can be used as a metric for BFR contamination. Subsequently, compound specific determination of BFRs was performed to evaluate the validity of the aforementioned assumption, crucial to render rapid, inexpensive, in situ Br determination in non-laboratory environments (such as waste handling facilities) a viable option for sorting wastes according to their BFR content. We report semi-quantitative compound specific BFR concentrations to give an overview of the distribution of individual BFRs in the analyzed samples. Finally, we evaluated the correlations between waste electrical and electronic equipment (WEEE) related substances (Ca, Sb and rare earth elements (REEs)) and Br as a proxy for identifying poor sorting practices in different waste streams. 26 samples of toys, food-contact articles and WEEE were analyzed with a suite of different techniques in order to obtain comprehensive information about their elemental and molecular composition. The information obtained from principal component analysis about WEEE-related compounds provides new insights into the influence of sorting practices on the extent of products' contamination and bringing out polymer-related trends in the pollutants' signature. 61% of all samples were Br positive: of these samples, 45% had decaBDE concentrations exceeding the concentration limits for PBDEs and their main constituent polymer was - according to the REE signature of such samples - Acrylonitrile Butadiene Styrene (ABS), uses of which include copying equipment, laptops and computers. The ability to better track chemicals of concern

Pizza makers' contact dermatitis.

Science.gov (United States)

Lembo, Serena; Lembo, Claudio; Patruno, Cataldo; Balato, Anna; Balato, Nicola; Ayala, Fabio

2014-01-01

Contact eczema to foods, spices, and food additives can occur in occupational and nonoccupational settings in those who grow, handle, prepare, or cook food. Pizza is one of the most eaten foods in every continent, and pizza making is a common work in many countries. We aimed to evaluate the occurrence and the causes of contact dermatitis in pizza makers in Naples. We performed an observational study in 45 pizza makers: all the enrolled subjects had to answer a questionnaire designed to detect personal history of respiratory or cutaneous allergy, atopy; work characteristics and timing were also investigated. Every subject attended the dermatology clinic for a complete skin examination, and when needed, patients were patch tested using the Italian baseline series of haptens integrated with an arbitrary pizza makers series. Our results reported that 13.3% of the enrolled pizza makers (6/45) presented hand eczema, and that 8.9% (4/45) were affected by occupational allergic contact dermatitis. Diallyl disulfide and ammonium persulfate were the responsible substances. Performing patch tests in pizza makers and food handlers affected by hand contact dermatitis is useful. We propose a specific series of haptens for this wide working category.

Food packing optimization

Science.gov (United States)

The development of a universal closure lid for the space shuttle food package is reported. The revised lid needs a folded configuration which, when unfolded, fully conforms to the interior surfaces of the food cup. Experimental thermoform molds were fabricated and test lids formed. The lid material not in contact with the food conformed to the cup interior without wrinkles, permitting full nesting of the cups. The final lid design was established and thermoform tooling designed and fabricated. Lids formed on these molds were tested for strength. The heating elements were replaced and repositioned to eliminate any hot spots which may cause warpage.

Investigation of surface porosity measurements and compaction pressure as means to ensure consistent contact angle determinations.

Science.gov (United States)

Holm, René; Borkenfelt, Simon; Allesø, Morten; Andersen, Jens Enevold Thaulov; Beato, Stefania; Holm, Per

2016-02-10

Compounds wettability is critical for a number of central processes including disintegration, dispersion, solubilisation and dissolution. It is therefore an important optimisation parameter both in drug discovery but also as guidance for formulation selection and optimisation. Wettability for a compound is determined by its contact angle to a liquid, which in the present study was measured using the sessile drop method applied to a disc compact of the compound. Precise determination of the contact angle is important should it be used to either rank compounds or selected excipients to e.g. increase the wetting from a solid dosage form. Since surface roughness of the compact has been suggested to influence the measurement this study investigated if the surface quality, in terms of surface porosity, had an influence on the measured contact angle. A correlation to surface porosity was observed, however for six out of seven compounds similar results were obtained by applying a standard pressure (866 MPa) to the discs in their preparation. The data presented in the present work therefore suggest that a constant high pressure should be sufficient for most compounds when determining the contact angle. Only for special cases where compounds have poor compressibility would there be a need for a surface-quality-control step before the contact angle determination. Copyright © 2015 Elsevier B.V. All rights reserved.

How to make sticky surfaces slippery: Contact angle hysteresis in electrowetting with alternating voltage

NARCIS (Netherlands)

Li, F.; Li, F.; Mugele, Friedrich Gunther

2008-01-01

Contact angle hysteresis caused by random pinning forces is a major obstacle in moving small quantities of liquid on solid surfaces. Here, we demonstrate that the contact angle hysteresis for sessile drops in electrowetting almost disappears with increasing alternating voltage, whereas for direct

Studies of non-contact methods for roughness measurements on wood surfaces

International Nuclear Information System (INIS)

Lundberg, I.A.S.; Porankiewicz, B.

1995-01-01

The quality of wood surfaces after different kinds of machining processes is a property of great importance for the wood processing industries. Present work is a study, whose objective was to evaluate different non-contact methods, for measurement of the quality of the wood surfaces by correlating them with stylus tracing. A number of Scots Pine samples were prepared by different kinds of wood machining processing. Surface roughness measurements were performed, utilizing two optical noncontact methods. The results indicate that the laser scan method can measure surface roughness on sawn wood with a sufficient degree of accuracy. (author) [de

Evolution of the Contact Area with Normal Load for Rough Surfaces: from Atomic to Macroscopic Scales.

Science.gov (United States)

Huang, Shiping

2017-11-13

The evolution of the contact area with normal load for rough surfaces has great fundamental and practical importance, ranging from earthquake dynamics to machine wear. This work bridges the gap between the atomic scale and the macroscopic scale for normal contact behavior. The real contact area, which is formed by a large ensemble of discrete contacts (clusters), is proven to be much smaller than the apparent surface area. The distribution of the discrete contact clusters and the interaction between them are key to revealing the mechanism of the contacting solids. To this end, Green's function molecular dynamics (GFMD) is used to study both how the contact cluster evolves from the atomic scale to the macroscopic scale and the interaction between clusters. It is found that the interaction between clusters has a strong effect on their formation. The formation and distribution of the contact clusters is far more complicated than that predicted by the asperity model. Ignorance of the interaction between them leads to overestimating the contacting force. In real contact, contacting clusters are smaller and more discrete due to the interaction between the asperities. Understanding the exact nature of the contact area with the normal load is essential to the following research on friction.

A highly accurate dynamic contact angle algorithm for drops on inclined surface based on ellipse-fitting.

Science.gov (United States)

Xu, Z N; Wang, S Y

2015-02-01

To improve the accuracy in the calculation of dynamic contact angle for drops on the inclined surface, a significant number of numerical drop profiles on the inclined surface with different inclination angles, drop volumes, and contact angles are generated based on the finite difference method, a least-squares ellipse-fitting algorithm is used to calculate the dynamic contact angle. The influences of the above three factors are systematically investigated. The results reveal that the dynamic contact angle errors, including the errors of the left and right contact angles, evaluated by the ellipse-fitting algorithm tend to increase with inclination angle/drop volume/contact angle. If the drop volume and the solid substrate are fixed, the errors of the left and right contact angles increase with inclination angle. After performing a tremendous amount of computation, the critical dimensionless drop volumes corresponding to the critical contact angle error are obtained. Based on the values of the critical volumes, a highly accurate dynamic contact angle algorithm is proposed and fully validated. Within nearly the whole hydrophobicity range, it can decrease the dynamic contact angle error in the inclined plane method to less than a certain value even for different types of liquids.

Investigation of Thermostressed State of Coating Formation at Electric Contact Surfacing of “Shaft” Type Parts

Directory of Open Access Journals (Sweden)

Olena V. Berezshnaya

2016-01-01

Full Text Available The forming of coating at electric contact surfacing is considered. The mathematical model of the coating formation is developed. The method of numerical recurrent solution of the finite-difference form of static equilibrium conditions of the selected elementary volume of coating is used. This model considers distribution of thermal properties and geometric parameters along the thermal deformation zone during the process of electric contact surfacing by compact material. It is found that the change of value of speed asymmetry factor leads to increasing of the friction coefficient in zone of surfacing. This provides the forming of the coating of higher quality. The limitation of the technological capabilities of equipment for electric contact surfacing is related to the size of recoverable parts and application of high electromechanical powers. The regulation of the speed asymmetry factor allows for expanding the technological capabilities of equipment for electric contact surfacing. The nomograms for determination of the stress on the roller electrode and the finite thickness of the coating as the function of the initial thickness of the compact material and the deformation degree are shown.

3D finite element model of elastoplastic contact on the double sinus rough surface

International Nuclear Information System (INIS)

Hagege, H; Bouvier, S; Mazeran, P-E; Bigerelle, M

2011-01-01

One of the objectives in the field of tribology is to solve the mechanical stress-displacement problem involved by rough contacts. In our approach, the surface chosen is a 256-256 μm 2 3D sinusoidal shape (amplitude 4.5μm, wavelength 50μm) with an elastoplastic constitutive behaviour. The constitutive law combines isotropic and kinematic hardening and is experimentally identified from 316L steel sheets. The FEM deformable surface is crushed then uncrushed by a rigid flat surface: stresses, contact pressure and plastic cumulated strain are computed. We investigate the results sensitivity with respect to the level of in-plane refinement. At last, we conclude on some guidelines for 3D finite elements modelling of rough surfaces.

Type conversion, contacts, and surface effects in electroplated CdTe films

International Nuclear Information System (INIS)

Basol, B.M.; Ou, S.S.; Stafsudd, O.M.

1985-01-01

Efficient electroplated CdS/CdTe solar cells can be fabricated by heat treating and type-converting the n-CdTe films deposited on CdS layers. In this paper, various mechanisms which may give rise to the conversion of electroplated CdTe films from n to p type are investigated. It is concluded that Cd-vacancy generation is the main mechanism of type conversion. Possible effects of oxygen on this mechanism are also discussed. Evaporated Au contacts to electroplated p-CdTe films were studied. It was found that the Au contacts depleted the excess Te present on the surface of Br 2 -methanol etched p-CdTe films. Oxygen was found to affect the electrical characteristics of such contacts

Contact angle and surface tension measurements of a five-ring polyphenyl ether

Science.gov (United States)

Jones, W. R., Jr.

1986-01-01

Contact angle measurements were performed for a five-ring polyphenyl ether isomeric mixture on M-50 steel in a dry nitrogen atmosphere. Two different techniques were used: (1) a tilting plate apparatus, and (2) a sessile drop apparatus. Measurements were made for the temperature range 25 to 190 C. Surface tension was measured by a differential maximum bubble pressure technique over the range 23 to 220 C in room air. The critical surface energy of spreading (gamma /sub c/) was determined for the polyphenyl ether by plotting the cosine of the contact angle (theta) versus the surface tension (gamma /sub LV/). The straight line intercept at cosine theta = 1 is defined as gamma (sub c). Gamma (sub c) was found to be 30.1 dyn/cm for the tilting plate technique and 31.3 dyn/cm for the sessile drop technique. These results indicate that the polyphenyl ether is inherently autophobic (i.e., it will not spread on its own surface film until its surface tension is less than gamma /sub c/). This phenomenon is discussed in light of the wettability and wear problems encountered with this fluid.

Correlation of Cell Surface Biomarker Expression Levels with Adhesion Contact Angle Measured by Lateral Microscopy.

Science.gov (United States)

Walz, Jenna A; Mace, Charles R

2018-06-05

Immunophenotyping is typically achieved using flow cytometry, but any influence a biomarker may have on adhesion or surface recognition cannot be determined concurrently. In this manuscript, we demonstrate the utility of lateral microscopy for correlating cell surface biomarker expression levels with quantitative descriptions of cell morphology. With our imaging system, we observed single cells from two T cell lines and two B cell lines adhere to antibody-coated substrates and quantified this adhesion using contact angle measurements. We found that SUP-T1 and CEM CD4+ cells, both of which express similar levels of CD4, experienced average changes in contact angle that were not statistically different from one another on surfaces coated in anti-CD4. However, MAVER-1 and BJAB K20 cells, both of which express different levels of CD20, underwent average changes in contact angle that were significantly different from one another on surfaces coated in anti-CD20. Our results indicate that changes in cell contact angles on antibody-coated substrates reflect the expression levels of corresponding antigens on the surfaces of cells as determined by flow cytometry. Our lateral microscopy approach offers a more reproducible and quantitative alternative to evaluate adhesion compared to commonly used wash assays and can be extended to many additional immunophenotyping applications to identify cells of interest within heterogeneous populations.

Nanoscale Coloristic Pigments: Upper Limits on Releases from Pigmented Plastic during Environmental Aging, In Food Contact, and by Leaching

DEFF Research Database (Denmark)

Neubauer, Nicole; Scifo, Lorette; Navratilova, Jana

2017-01-01

The life cycle of nanoscale pigments in plastics may cause environmental or human exposure by various release scenarios. We investigated spontaneous and induced release with mechanical stress during/after simulated sunlight and rain degradation of polyethylene (PE) with organic and inorganic...... pigments. Additionally, primary leaching in food contact and secondary leaching from nanocomposite fragments with an increased surface into environmental media was examined. Standardized protocols/methods for release sampling, detection, and characterization of release rate and form were applied......: Transformation of the bulk material was analyzed by Scanning Electron Microscopy (SEM), X-ray-tomography and Fourier-Transform Infrared spectroscopy (FTIR); releases were quantified by Inductively Coupled Plasma Mass Spectrometry (ICP-MS), single-particle-ICP-MS (sp-ICP-MS), Transmission Electron Microscopy (TEM...

Investigation of the primary plasticisers present in polyvinyl chloride (PVC) products currently authorised as food contact materials.

Science.gov (United States)

Carlos, Katherine S; de Jager, Lowri S; Begley, Timothy H

2018-03-15

PVC is a common food contact material that is usually plasticised to increase its flexibility. Phthalates are one class of chemical compounds that are often used as plasticisers in PVC in a wide range of industries. They may be used in packaging materials for foods and can also be found in components of certain food processing equipment such as conveyor belts and tubing. Transfer of plasticisers from packaging to foods can occur. In recent years, there has been increased interest in understanding the health effects of phthalates, as well as the possible human exposure levels. However, there is limited information available about the routes of exposure to phthalates. In July 2014, the Chronic Hazard Advisory Panel (CHAP) produced a report for the U.S. Consumer Product Safety Commission detailing the potential health hazards of phthalates and phthalate alternatives. This report listed diet as one factor contributing greater than or equal to 10% of total phthalate exposure. As a result of this report, the U.S. Food and Drug Administration (FDA) is interested in determining the types of the primary plasticiser present in food packaging and processing materials as well as their concentrations. An investigation was conducted of 56 different samples of PVC food packaging and food processing materials available in the US market using a solvent extraction and GC-MS analysis. Nine different plasticisers including three phthalates, di(2-ethylhexyl) phthalate, diisononyl phthalate and diisodecyl phthalate, were identified in the products tested. The plasticiser concentrations ranged from 1 to 53% depending on the types of food contact materials and the type of plasticiser. Overall, it appears that manufacturers are switching away from phthalates as their primary plasticiser to alternate compounds such as ESBO, ATBC, DEHT, DINCH, DEHA and DINA.

Surface mobility and structural transitions of poly(n-alkyl methacrylates) probed by dynamic contact angle measurements

NARCIS (Netherlands)

van Damme, H.S.; Hogt, A.H.; Feijen, Jan

1986-01-01

Dynamic contact angles and contact-angle hysteresis of a series of poly(n-alkyl methacrylates) (PAMA) were investigated using the Wilhelmy plate technique. The mobility of polymer surface chains, segments, and side groups affected the measured contact angles and their hysteresis. A model is

Elastic-plastic adhesive contact of rough surfaces using n-point asperity model

International Nuclear Information System (INIS)

Sahoo, Prasanta; Mitra, Anirban; Saha, Kashinath

2009-01-01

This study considers an analysis of the elastic-plastic contact of rough surfaces in the presence of adhesion using an n-point asperity model. The multiple-point asperity model, developed by Hariri et al (2006 Trans ASME: J. Tribol. 128 505-14) is integrated into the elastic-plastic adhesive contact model developed by Roy Chowdhury and Ghosh (1994 Wear 174 9-19). This n-point asperity model differs from the conventional Greenwood and Williamson model (1966 Proc. R. Soc. Lond. A 295 300-19) in considering the asperities not as fixed entities but as those that change through the contact process, and hence it represents the asperities in a more realistic manner. The newly defined adhesion index and plasticity index defined for the n-point asperity model are used to consider the different conditions that arise because of varying load, surface and material parameters. A comparison between the load-separation behaviour of the new model and the conventional one shows a significant difference between the two depending on combinations of mean separation, adhesion index and plasticity index.

Colored Contact Lens Dangers

Medline Plus

Full Text Available ... One Use Facts About Colored Contacts and Halloween Safety Colored Contact Lens Facts Over-the-Counter Costume ... use of colored contact lenses , from the U.S. Food and Drug Administration (FDA). Are the colored lenses ...

Contact angle studies on PDMS surfaces fouled by bovine serum albumin

CSIR Research Space (South Africa)

Windvoel, VT

2010-01-01

Full Text Available Polydimethylsiloxane (PDMS) has a hydrophobic surface, forming a contact angle of around 110º with deionised water. It is due to its hydrophobic nature that the elastomer is prone to bio-fouling, such as non-specific adsorption of biomaterials like...

Evaluating non-stick properties of different surface materials for contact frying

DEFF Research Database (Denmark)

Ashokkumar, Saranya; Adler-Nissen, Jens

2011-01-01

to evaluate non-stick and cleaning properties of the coatings. In accordance with industry standards pancake was selected as the food model for the non-stick properties. The performance of different frying surfaces (stainless steel, aluminium, PTFE (polytetrafluoroethylene) and three ceramic coatings with two...... on their non-stick properties, so that the smoother surfaces gave a higher force of adhesion between pancake and surface....

ER-mitochondria contacts control surface glycan expression and sensitivity to killer lymphocytes in glioma stem-like cells.

Science.gov (United States)

Bassoy, Esen Yonca; Kasahara, Atsuko; Chiusolo, Valentina; Jacquemin, Guillaume; Boydell, Emma; Zamorano, Sebastian; Riccadonna, Cristina; Pellegatta, Serena; Hulo, Nicolas; Dutoit, Valérie; Derouazi, Madiha; Dietrich, Pierre Yves; Walker, Paul R; Martinvalet, Denis

2017-06-01

Glioblastoma is a highly heterogeneous aggressive primary brain tumor, with the glioma stem-like cells (GSC) being more sensitive to cytotoxic lymphocyte-mediated killing than glioma differentiated cells (GDC). However, the mechanism behind this higher sensitivity is unclear. Here, we found that the mitochondrial morphology of GSCs modulates the ER-mitochondria contacts that regulate the surface expression of sialylated glycans and their recognition by cytotoxic T lymphocytes and natural killer cells. GSCs displayed diminished ER-mitochondria contacts compared to GDCs. Forced ER-mitochondria contacts in GSCs increased their cell surface expression of sialylated glycans and reduced their susceptibility to cytotoxic lymphocytes. Therefore, mitochondrial morphology and dynamism dictate the ER-mitochondria contacts in order to regulate the surface expression of certain glycans and thus play a role in GSC recognition and elimination by immune effector cells. Targeting the mitochondrial morphology, dynamism, and contacts with the ER could be an innovative strategy to deplete the cancer stem cell compartment to successfully treat glioblastoma. © 2017 The Authors.

Study on the surface of fluorosilicone acrylate RGP contact lens treated by low-temperature nitrogen plasma

International Nuclear Information System (INIS)

Ren Li; Yin Shiheng; Zhao Lianna; Wang Yingjun; Chen Hao; Qu Jia

2008-01-01

In order to improve the surface hydrophilicity of fluorosilicone acrylate rigid gas permeable (RGP) contact lens, low temperature nitrogen plasma was used to modify the lens surface. Effects of plasma conditions on the surface structures and properties were investigated. Results indicated that the surface hydrophilicity of RGP contact lens was significantly improved after treatment. X-ray photoelectron spectroscopy (XPS) results showed that the nitrogen element was successfully incorporated into the surface. Furthermore, some new bonds such as N-C=O, F - and silicate were formed on the lens surface after nitrogen plasma treatment, which could result in the improvement of the surface hydrophilicity. Scanning electronic microscope (SEM) results indicated that nitrogen plasma with moderate power could make the surface smoother in some degree, while plasma with higher power could etch the surface

Incorporating contact angles in the surface tension force with the ACES interface curvature scheme

Science.gov (United States)

Owkes, Mark

2017-11-01

In simulations of gas-liquid flows interacting with solid boundaries, the contact line dynamics effect the interface motion and flow field through the surface tension force. The surface tension force is directly proportional to the interface curvature and the problem of accurately imposing a contact angle must be incorporated into the interface curvature calculation. Many commonly used algorithms to compute interface curvatures (e.g., height function method) require extrapolating the interface, with defined contact angle, into the solid to allow for the calculation of a curvature near a wall. Extrapolating can be an ill-posed problem, especially in three-dimensions or when multiple contact lines are near each other. We have developed an accurate methodology to compute interface curvatures that allows for contact angles to be easily incorporated while avoiding extrapolation and the associated challenges. The method, known as Adjustable Curvature Evaluation Scale (ACES), leverages a least squares fit of a polynomial to points computed on the volume-of-fluid (VOF) representation of the gas-liquid interface. The method is tested by simulating canonical test cases and then applied to simulate the injection and motion of water droplets in a channel (relevant to PEM fuel cells).

Experimental determination of the thermal contact conductance between two solid surfaces by the energy pulse technique

International Nuclear Information System (INIS)

Rubin, Gerson Antonio

1979-01-01

An experimental procedure for the determination of the thermal contact conductance between two solid surfaces as a function of the contact pressure and the energy of the laser radiation has been developed using the laser pulse method. A rubi laser with variable energy levels was employed as a radiating pulse energy source. The laser beam was allowed to impinge perpendicularly on the front face of a electrolytic iron 73 4 . The temperature fluctuations resulting on the back surface of the sample was detected by a thermocouple, which Is coupled to a PDP-11/45 Computer 32 Kbytes of memory, through a Analog-Digital Converter. A theoretical function, derived exclusively for the problem mentioned in this work, was adjusted by a method of least square fitting of experimental results. This adjustment yielded the value of a parameter related to the contact conductance between two surfaces. The experimental error obtained for the thermal contact conductance was +- 4.9%. (author)

Preparation of electrodes on cfrp composites with low contact resistance comprising laser-based surface pre-treatment

KAUST Repository

Almuhammadi, Khaled Hamdan

2016-12-29

Various examples are provided related to the preparation of electrodes on carbon fiber reinforced polymer (CFRP) composites with low contact resistance. Laser-based surface preparation can be used for bonding to CFRP composites. In one example, a method includes preparing a pretreated target area on a CFRP composite surface using laser pulsed irradiation and bonding an electrode to exposed fibers in the pretreated target area. The surface preparation can allow the electrode to have a low contact resistance with the CFRP composite.

Adsorption of natural surfactants present in sea waters at surfaces of minerals: contact angle measurements

Directory of Open Access Journals (Sweden)

Katarzyna Boniewicz-Szmyt

2009-09-01

Full Text Available The wetting properties of solid mineral samples (by contact angles in original surfactant-containing sea water (Gulf of Gdańsk, Baltic were characterised under laboratory conditions on a large set (31 samples of well-classified stones of diverse hydrophobicity using the sessile drop (ADSA-P approach, captive bubble and inclined plate methods. An experimental relation between the static contact angle θeq and stone density ρ was obtained in the form θeq = Bρ + C, where B = 12.23 ± 0.92, C = - (19.17 ± 0.77, and r2 = 0.92. The histogram of θeq distribution for polished stone plates exhibited a multimodal feature indicating that the most abundant solid materials (hydrophilic in nature have contact angles θeq = 7.2, 10.7, 15.7 and 19.2º, which appear to be applicable to unspecified field stones as well. The contact angle, a pH-dependent quantity, appears to be a sensitive measure of stone grain size, e.g. granite. The captive bubble method gives reproducible results in studies of porous and highly hydrophilic surfaces such as stones and wood. The authors consider the adsorption of natural sea water surfactants on stone surfaces to be the process responsible for contact angle hysteresis. In the model, an equation was derived for determining the solid surface free energy from the liquid's surface tension γLV it also enabled the advancing θA and receding θR contact angles of this liquid to be calculated. Measurements of contact angle hysteresis Δθ (=θA - θR with surfactant-containing sea water and distilled water (reference on the same stone surfaces allowed the film pressure ΔΠ (1.22 to 8.80 mJ m-2, solid surface free energy ΔγS (-17.03 to -23.61 mJ m-2 and work done by spreading ΔWS (-1.23 to -11.52 mJ m-2 to be determined. The variability in these parameters is attributed to autophobing, an effect operative on a solid surface covered with an adsorptive layer of surfactants. The wetting behaviour of solid particles is of great

An energy-based equilibrium contact angle boundary condition on jagged surfaces for phase-field methods.

Science.gov (United States)

Frank, Florian; Liu, Chen; Scanziani, Alessio; Alpak, Faruk O; Riviere, Beatrice

2018-08-01

We consider an energy-based boundary condition to impose an equilibrium wetting angle for the Cahn-Hilliard-Navier-Stokes phase-field model on voxel-set-type computational domains. These domains typically stem from μCT (micro computed tomography) imaging of porous rock and approximate a (on μm scale) smooth domain with a certain resolution. Planar surfaces that are perpendicular to the main axes are naturally approximated by a layer of voxels. However, planar surfaces in any other directions and curved surfaces yield a jagged/topologically rough surface approximation by voxels. For the standard Cahn-Hilliard formulation, where the contact angle between the diffuse interface and the domain boundary (fluid-solid interface/wall) is 90°, jagged surfaces have no impact on the contact angle. However, a prescribed contact angle smaller or larger than 90° on jagged voxel surfaces is amplified. As a remedy, we propose the introduction of surface energy correction factors for each fluid-solid voxel face that counterbalance the difference of the voxel-set surface area with the underlying smooth one. The discretization of the model equations is performed with the discontinuous Galerkin method. However, the presented semi-analytical approach of correcting the surface energy is equally applicable to other direct numerical methods such as finite elements, finite volumes, or finite differences, since the correction factors appear in the strong formulation of the model. Copyright © 2018 Elsevier Inc. All rights reserved.

Exposure to lead and cadmium released from ceramics and glassware intended to come into contact with food.

Science.gov (United States)

Rebeniak, Małgorzata; Wojciechowska-Mazurek, Maria; Mania, Monika; Szynal, Tomasz; Strzelecka, Agnieszka; Starska, Krystyna

2014-01-01

The dietary intake of harmful elements, particularly lead and cadmium constitutes a health threat and essential measures should be undertaken to reduce consumer exposure. The latest risk assessments by the European Food Safety Authority (EFSA) and Joint FAO/WHO Expert Committee on Food Additives (JECFA) have indicated that the Provisional Tolerable Weekly Intake (PTWI) for lead and cadmium do not ensure health safety and their review had to be undertaken. Migration from ceramics and glassware intended for food contact is an important source of lead and cadmium intake. To study the release of lead and cadmium from ceramics and glassware (including decorated products) intended for food contact that are available on the Polish market and to assess the resulting health risk to the consumer. Ceramics and glassware (mainly decorated) were sampled from the Polish market during 2010- 2012 throughout the country by staff of the Sanitary-Epidemiological Stations in accordance with monitoring procedures and guidelines designed by the National Institute of Public Health-National Institute of Hygiene. Migration of lead and cadmium was measured by incubating the samples with 4% acetic acid for 24 hours at a temperature of 22±2ºC in the dark. Flame Atomic Absorption Spectrometry (FAAS) was used to measure these elements in food simulant according to a validated and accredited method (PN-EN ISO/IEC 17025). 1273 samples of ceramics and glass wares were analysed in 2010-2012. Lead and cadmium release were usually found to be below analytical detection limits. Permissible migration limits (as prescribed by the legislation) of these metals were rarely exceeded and were reported mainly in articles imported from outside the EU. Two imported and decorated ceramic flat plates released lead at 0.9 and 11.9 mg/dm2 (limit 0.8 mg/dm2) and 5 imported deep plates gave migration values of 4.7 mg/L, 4.9 mg/L, 5.6 mg/L, 6.1 mg/L, 8.6 mg/L (limit 4.0 mg/L). Lead migrations from ceramic ware rims

Estrogen Receptor Binding Affinity of Food Contact Material Components Estimated by QSAR.

Science.gov (United States)

Sosnovcová, Jitka; Rucki, Marián; Bendová, Hana

2016-09-01

The presented work characterized components of food contact materials (FCM) with potential to bind to estrogen receptor (ER) and cause adverse effects in the human organism. The QSAR Toolbox, software application designed to identify and fill toxicological data gaps for chemical hazard assessment, was used. Estrogen receptors are much less of a lock-and-key interaction than highly specific ones. The ER is nonspecific enough to permit binding with a diverse array of chemical structures. There are three primary ER binding subpockets, each with different requirements for hydrogen bonding. More than 900 compounds approved as of FCM components were evaluated for their potential to bind on ER. All evaluated chemicals were subcategorized to five groups with respect to the binding potential to ER: very strong, strong, moderate, weak binder, and no binder to ER. In total 46 compounds were characterized as potential disturbers of estrogen receptor. Among the group of selected chemicals, compounds with high and even very high affinity to the ER binding subpockets were found. These compounds may act as gene activators and cause adverse effects in the organism, particularly during pregnancy and breast-feeding. It should be considered to carry out further in vitro or in vivo tests to confirm their potential to disturb the regulation of physiological processes in humans by abnormal ER signaling and subsequently remove these chemicals from the list of approved food contact materials. Copyright© by the National Institute of Public Health, Prague 2016

Stick-Slip Motion of Moving Contact Line on Chemically Patterned Surfaces

KAUST Repository

Wu, Congmin; Lei, Siulong; Qian, Tiezheng; Wang, Xiaoping

2009-01-01

Based on our continuum hydrodynamic model for immiscible two-phase flows at solid surfaces, the stick-slip motion has been predicted for moving contact line at chemically patterned surfaces [Wang et al., J. Fluid Mech., 605 (2008), pp. 59-78]. In this paper we show that the continuum predictions can be quantitatively verified by molecular dynamics (MD) simulations. Our MD simulations are carried out for two immiscible Lennard-Jones fluids confined by two planar solid walls in Poiseuille flow geometry. In particular, one solid surface is chemically patterned with alternating stripes. For comparison, the continuum model is numerically solved using material parameters directly measured in MD simulations. From oscillatory fluid-fluid interface to intermittent stick-slip motion of moving contact line, we have quantitative agreement between the continuum and MD results. This agreement is attributed to the accurate description down to molecular scale by the generalized Navier boundary condition in our continuum model. Numerical results are also presented for the relaxational dynamics of fluid-fluid interface, in agreement with a theoretical analysis based on the Onsager principle of minimum energy dissipation. © 2010 Global-Science Press.

Suitability of polystyrene as a functional barrier layer in coloured food contact materials.

Science.gov (United States)

Genualdi, Susan; Addo Ntim, Susana; Begley, Timothy

2015-01-01

Functional barriers in food contact materials (FCMs) are used to prevent or reduce migration from inner layers in multilayer structures to food. The effectiveness of functional barrier layers was investigated in coloured polystyrene (PS) bowls due to their intended condition of use with hot liquids such as soups or stew. Migration experiments were performed over a 10-day period using USFDA-recommended food simulants (10% ethanol, 50% ethanol, corn oil and Miglyol) along with several other food oils. At the end of the 10 days, solvent dyes had migrated from the PS bowls at 12, 1 and 31,000 ng cm(-)(2) into coconut oil, palm kernel oil and Miglyol respectively, and in coconut oil and Miglyol the colour change was visible to the human eye. Scanning electron microscope (SEM) images revealed that the functional barrier was no longer intact for the bowls exposed to coconut oil, palm kernel oil, Miglyol, 10% ethanol, 50% ethanol and goat's milk. Additional tests showed that 1-dodecanol, a lauryl alcohol derived from palm kernel oil and coconut oil, was present in the PS bowls at an average concentration of 11 mg kg(-1). This compound is likely to have been used as a dispersing agent for the solvent dye and aided the migration of the solvent dye from the PS bowl into the food simulant. The solvent dye was not found in the 10% ethanol, 50% ethanol and goat's milk food simulants above their respective limits of detection, which is likely to be due to its insolubility in aqueous solutions. A disrupted barrier layer is of concern because if there are unregulated materials in the inner layers of the laminate, they may migrate to food, and therefore be considered unapproved food additives resulting in the food being deemed adulterated under the Federal Food Drug and Cosmetic Act.

Spread of Staphylococcus aureus between medical staff and high-frequency contact surfaces in a large metropolitan hospital

Directory of Open Access Journals (Sweden)

Li-sha Shi

2015-12-01

Conclusion: Cross-contamination of S. aureus or MRSA on medical workers' hands and contact surfaces was demonstrated within and between departments of a large metropolitan hospital. Improvements are needed in medical staff hygiene habits and in the cleaning of high-frequency contact surfaces to help prevent and control nosocomial infections.

Effect of solution and leaf surface polarity on droplet spread area and contact angle.

Science.gov (United States)

Nairn, Justin J; Forster, W Alison; van Leeuwen, Rebecca M

2016-03-01

How much an agrochemical spray droplet spreads on a leaf surface can significantly influence efficacy. This study investigates the effect solution polarity has on droplet spreading on leaf surfaces and whether the relative leaf surface polarity, as quantified using the wetting tension dielectric (WTD) technique, influences the final spread area. Contact angles and spread areas were measured using four probe solutions on 17 species. Probe solution polarity was found to affect the measured spread area and the contact angle of the droplets on non-hairy leaves. Leaf hairs skewed the spread area measurement, preventing investigation of the influence of surface polarity on hairy leaves. WTD-measured leaf surface polarity of non-hairy leaves was found to correlate strongly with the effect of solution polarity on spread area. For non-polar leaf surfaces the spread area decreases with increasing solution polarity, for neutral surfaces polarity has no effect on spread area and for polar leaf surfaces the spread area increases with increasing solution polarity. These results attest to the use of the WTD technique as a means to quantify leaf surface polarity. © 2015 Society of Chemical Industry. © 2015 Society of Chemical Industry.

A novel safety assessment strategy for non-intentionally added substances (NIAS) in carton food contact materials

NARCIS (Netherlands)

Koster, S.; Rennen, M.; Leeman, W.; Houben, G.; Muilwijk, B.; Acker, F. van; Krul, L.

2014-01-01

One of the main challenges in food contact materials research is to prove that the presence of non-intentionally added substances (NIAS) is not a safety issue. Migration extracts may contain many unknown substances present at low concentrations. It is difficult and time-consuming to identify all

Genotoxicity of styrene oligomers extracted from polystyrene intended for use in contact with food

Directory of Open Access Journals (Sweden)

Makoto Nakai

2014-01-01

Full Text Available Here, we conducted in vitro genotoxicity tests to evaluate the genotoxicity of styrene oligomers extracted from polystyrene intended for use in contact with food. Styrene oligomers were extracted with acetone and the extract was subjected to the Ames test (OECD test guideline No. 471 and the in vitro chromosomal aberration test (OECD test guideline No. 473 under good laboratory practice conditions. The concentrations of styrene dimers and trimers in the concentrated extract were 540 and 13,431 ppm, respectively. Extraction with acetone provided markedly higher concentrations of styrene oligomers compared with extraction with 50% ethanol aqueous solution, which is the food simulant currently recommended for use in safety assessments of polystyrene by both the United States Food and Drug Administration and the European Food Safety Authority. And these high concentrations of styrene dimers and trimers were utilized for the evaluation of genotoxicity in vitro. Ames tests using five bacterial tester strains were negative both in the presence or absence of metabolic activation. The in vitro chromosomal aberration test using Chinese hamster lung cells (CHL/IU was also negative. Together, these results suggest that the risk of the genotoxicity of styrene oligomers that migrate from polystyrene food packaging into food is very low.

Robust and general method for determining surface fluid flow boundary conditions in articular cartilage contact mechanics modeling.

Science.gov (United States)

Pawaskar, Sainath Shrikant; Fisher, John; Jin, Zhongmin

2010-03-01

Contact detection in cartilage contact mechanics is an important feature of any analytical or computational modeling investigation when the biphasic nature of cartilage and the corresponding tribology are taken into account. The fluid flow boundary conditions will change based on whether the surface is in contact or not, which will affect the interstitial fluid pressurization. This in turn will increase or decrease the load sustained by the fluid phase, with a direct effect on friction, wear, and lubrication. In laboratory experiments or clinical hemiarthroplasty, when a rigid indenter or metallic prosthesis is used to apply load to the cartilage, there will not be any fluid flow normal to the surface in the contact region due to the impermeable nature of the indenter/prosthesis. In the natural joint, on the other hand, where two cartilage surfaces interact, flow will depend on the pressure difference across the interface. Furthermore, in both these cases, the fluid would flow freely in non-contacting regions. However, it should be pointed out that the contact area is generally unknown in advance in both cases and can only be determined as part of the solution. In the present finite element study, a general and robust algorithm was proposed to decide nodes in contact on the cartilage surface and, accordingly, impose the fluid flow boundary conditions. The algorithm was first tested for a rigid indenter against cartilage model. The algorithm worked well for two-dimensional four-noded and eight-noded axisymmetric element models as well as three-dimensional models. It was then extended to include two cartilages in contact. The results were in excellent agreement with the previous studies reported in the literature.

Characterisation of silica surfaces III: Characterisation of aerosil samples through ethanol adsorption and contact angle studies

Directory of Open Access Journals (Sweden)

M.S. Nadiye–Tabbiruka

2009-12-01

Full Text Available Aerosil samples, heat treated and then silylated with various silanes at various temperatures have been characterised by adsorption of ethanol at 293 K. Adsorption isotherms were plotted and the BET specific surface areas were determined. Contact angles were measured by the captive bubble method at the three phase contact line in ethanol, on glass slides similarly modified. Silylation was found to alter the ethanol adsorptive properties on aerosil and increase the contact angles on the glass slides to extents that depend on the silane used as well as the concentration of residual silanols and that of surface silyl groups.

Bacterial desorption from food container and food processing surfaces.

Science.gov (United States)

McEldowney, S; Fletcher, M

1988-03-01

The desorption ofStaphylococcus aureus, Acinetobacter calcoaceticus, and a coryneform from the surfaces of materials used for manufacturing food containers (glass, tin plate, and polypropylene) or postprocess canning factory conveyor belts (stainless steel and nylon) was investigated. The effect of time, pH, temperature, and adsorbed organic layers on desorption was studied.S. aureus did not detach from the substrata at any pH investigated (between pH 5 and 9).A. calcoaceticus and the coryneform in some cases detached, depending upon pH and substratum composition. The degree of bacterial detachment from the substrata was not related to bacterial respiration at experimental pH values. Bacterial desorption was not affected by temperature (4-30°C) nor by an adsorbed layer of peptone and yeast extract on the substrata. The results indicate that bacterial desorption, hence bacterial removal during cleaning or their transfer via liquids flowing over colonized surfaces, is likely to vary with the surface composition and the bacterial species colonizing the surfaces.

Silver deposition on stainless steel container surfaces in contact with disinfectant silver aqueous solutions

International Nuclear Information System (INIS)

Petala, M.; Tsiridis, V.; Mintsouli, I.; Pliatsikas, N.; Spanos, Th.; Rebeyre, P.; Darakas, E.; Patsalas, P.; Vourlias, G.; Kostoglou, M.; Sotiropoulos, S.; Karapantsios, Th.

2017-01-01

Highlights: • Silver is one of the biocides of water consumed in the International Space Station. • Ionic silver is depleted from potable water when in contact with stainless steel (SS). • SEM and XPS analysis reveal a uniform silver deposition over the SS surface. • Silver deposits in its metallic form, in line with a galvanic deposition mechanism. • Evidence is provided that Cr and/ or Ni oxide builds-up on SS surfaces. - Abstract: Silver is the preservative used on the Russian segment of the International Space Station (ISS) to prevent microbial proliferation within potable water supplies. Yet, in the frame of the European Automated Transfer Vehicle (ATV) missions to ISS, silver depletion from water has been detected during ground transportation of this water to launch site, thereby indicating a degradation of water quality. This study investigates the silver loss from water when in contact with stainless steel surfaces. Experiments are conducted with several types of stainless steel surfaces being exposed to water containing 10 or 0.5 mg/L silver ions. Results show that silver deposits on stainless steel surfaces even when a passivation layer protects the metallic surface. The highest protection to silver deposition is offered by acid passivated and electropolished SS 316L. SEM and XPS experiments were carried out at several locations of the sample area that was in contact with the Ag solution and found similar morphological (SEM) and compositional (sputter-etch XPS) results. The results reveal that silver deposits uniformly across the wetted surface to a thickness larger than 3 nm. Moreover, evidence is provided that silver deposits in its metallic form on all stainless steel surfaces, in line with a galvanic deposition mechanism. Combination of ICP-MS and XPS results suggests a mechanism for Ag deposition/reduction with simultaneous substrate oxidation resulting in oxide growth at the exposed stainless steel surface.

Silver deposition on stainless steel container surfaces in contact with disinfectant silver aqueous solutions

Energy Technology Data Exchange (ETDEWEB)

Petala, M., E-mail: petala@civil.auth.gr [Department of Civil Engineering, Aristotle University of Thessaloniki, Thessaloniki, 54124 (Greece); Tsiridis, V. [Department of Civil Engineering, Aristotle University of Thessaloniki, Thessaloniki, 54124 (Greece); Mintsouli, I. [Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki, 54124 (Greece); Pliatsikas, N. [Department of Physics, Aristotle University of Thessaloniki, Thessaloniki, 54124 (Greece); Spanos, Th. [Department of Petroleum and Mechanical Engineering Sciences, Eastern Macedonia and Thrace Institute of Technology, Kavala, 65404 (Greece); Rebeyre, P. [ESA/ESTEC, P.O.Box 299, 2200 AG, Noordwijk (Netherlands); Darakas, E. [Department of Civil Engineering, Aristotle University of Thessaloniki, Thessaloniki, 54124 (Greece); Patsalas, P.; Vourlias, G. [Department of Physics, Aristotle University of Thessaloniki, Thessaloniki, 54124 (Greece); Kostoglou, M.; Sotiropoulos, S.; Karapantsios, Th. [Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki, 54124 (Greece)

2017-02-28

Highlights: • Silver is one of the biocides of water consumed in the International Space Station. • Ionic silver is depleted from potable water when in contact with stainless steel (SS). • SEM and XPS analysis reveal a uniform silver deposition over the SS surface. • Silver deposits in its metallic form, in line with a galvanic deposition mechanism. • Evidence is provided that Cr and/ or Ni oxide builds-up on SS surfaces. - Abstract: Silver is the preservative used on the Russian segment of the International Space Station (ISS) to prevent microbial proliferation within potable water supplies. Yet, in the frame of the European Automated Transfer Vehicle (ATV) missions to ISS, silver depletion from water has been detected during ground transportation of this water to launch site, thereby indicating a degradation of water quality. This study investigates the silver loss from water when in contact with stainless steel surfaces. Experiments are conducted with several types of stainless steel surfaces being exposed to water containing 10 or 0.5 mg/L silver ions. Results show that silver deposits on stainless steel surfaces even when a passivation layer protects the metallic surface. The highest protection to silver deposition is offered by acid passivated and electropolished SS 316L. SEM and XPS experiments were carried out at several locations of the sample area that was in contact with the Ag solution and found similar morphological (SEM) and compositional (sputter-etch XPS) results. The results reveal that silver deposits uniformly across the wetted surface to a thickness larger than 3 nm. Moreover, evidence is provided that silver deposits in its metallic form on all stainless steel surfaces, in line with a galvanic deposition mechanism. Combination of ICP-MS and XPS results suggests a mechanism for Ag deposition/reduction with simultaneous substrate oxidation resulting in oxide growth at the exposed stainless steel surface.

A Simple Approach for Local Contact Angle Determination on a Heterogeneous Surface

KAUST Repository

Wu, Jinbo; Zhang, Mengying; Wang, Xiang; Li, Shunbo; Wen, Weijia

2011-01-01

We report a simple approach for measuring the local contact angle of liquids on a heterogeneous surface consisting of intersected hydrophobic and hydrophilic patch arrays, specifically by employing confocal microscopy and the addition of a very low

Evaluation of surface characteristics under fretting of electrical contacts: Removal behaviour of hot dipped tin coating

International Nuclear Information System (INIS)

Park, Young Woo; Ramesh Bapu, G.N.K.; Lee, Kang Yong

2009-01-01

The fretting corrosion behaviour of hot dipped tin coating is investigated at low fretting cycles at ±25 μm displacement amplitude, 0.5N normal load, 3 Hz frequency, 45-50% relative humidity, and 25 ± 1 deg. C temperature. The typical characteristics of the change in contact resistance with fretting cycles are explained. The fretted surface is examined using laser scanning microscope, scanning electron microscope and energy dispersive X-ray analysis to assess the surface profile, extent of fretting damage, extent of oxidation and elemental distribution across the contact zone. The interdependence of extent of wear and oxidation increases the complexity of the fretting corrosion behaviour of tin coating. The variation of contact resistance clearly revealed the fretting of tin coating from 50 to 1200 cycles and the fretting of the substrate above 1200 cycles. The observed low and stable contact resistance region and the fluctuating resistance region at various fretting cycles are explained and substantiated with Scanning electron microscopy (SEM), laser scanning microscope (LSM) and energy dispersive analysis of X-rays (EDAX) analysis results of the fretted surface.

Physicochernical factors influencing bacterial transfer from contact lenses to surfaces with different roughness and Wettability

NARCIS (Netherlands)

Vermeltfoort, PBJ; van der Mei, HC; Busscher, HJ; Hooymans, JMM; Bruinsma, GM

2004-01-01

The aim of this study was to determine the transfer of Pseudomonas aeruginosa No. 3 and Staphylococcus aureus 835 from contact lenses to surfaces with different hydrophobicity and roughness. Bacteria were allowed to adhere to contact lenses (Surevue, PureVision, or Focus Night & Day) by incubating

Water in contact with extended hydrophobic surfaces: Direct evidence of weak dewetting

International Nuclear Information System (INIS)

Jensen, Torben R.; Kjaer, Kristian; Oestergaard Jensen, Morten; Peters, Guenther H.; Reitzel, Niels; Balashev, Konstantin; Bjoernholm, Thomas

2003-01-01

X-ray reflectivity measurements reveal a significant dewetting of a large hydrophobic paraffin surface floating on water. The dewetting phenomenon extends less than 15 A into the bulk water phase and results in an integrated density deficit of about one water molecule per 25-30 A 2 of water in contact with the paraffin surface. The results are supported by molecular dynamics simulations and related to the hydrophobic effect

PFAS in paper and board for food contact - options for risk management of poly- and perfluorinated substances

DEFF Research Database (Denmark)

Trier, Xenia; Taxvig, Camilla; Rosenmai, Anna Kjerstine

Poly- and perfluorinated alkyl substances (PFAS) are used in paper and board food contact materials (FCMs) and they have been found to be highly persistent, bioaccumulative and toxic. The purpose of the Nordic workshop and of this report is to:* create an overview of the use of PFAS in FCMs...... for analysing and regulating the substances are available* discuss the possibility and structure of national regulations or Nordic recommendations for PFAS in FCMs of paper and board. Risk management to reduce the total content of organically bound fluorine in paper and board FCMs is supported. The given report...... is published in continuation of a Nordic workshop on January 28th -29th 2015 on poly- and perfluorinated substances (PFAS) in food contact materials. Representatives from EU MS countries, US FDA, Canada and China, as well as manufacturers, retailers, compliance testing laboratories and academia were present...

Contact Angle and Adhesion Dynamics and Hysteresis on Molecularly Smooth Chemically Homogeneous Surfaces.

Science.gov (United States)

Chen, Szu-Ying; Kaufman, Yair; Schrader, Alex M; Seo, Dongjin; Lee, Dong Woog; Page, Steven H; Koenig, Peter H; Isaacs, Sandra; Gizaw, Yonas; Israelachvili, Jacob N

2017-09-26

Measuring truly equilibrium adhesion energies or contact angles to obtain the thermodynamic values is experimentally difficult because it requires loading/unloading or advancing/receding boundaries to be measured at rates that can be slower than 1 nm/s. We have measured advancing-receding contact angles and loading-unloading adhesion energies for various systems and geometries involving molecularly smooth and chemically homogeneous surfaces moving at different but steady velocities in both directions, ±V, focusing on the thermodynamic limit of ±V → 0. We have used the Bell Theory (1978) to derive expressions for the dynamic (velocity-dependent) adhesion energies and contact angles suitable for both (i) dynamic adhesion measurements using the classic Johnson-Kendall-Roberts (JKR, 1971) theory of "contact mechanics" and (ii) dynamic contact angle hysteresis measurements of both rolling droplets and syringe-controlled (sessile) droplets on various surfaces. We present our results for systems that exhibited both steady and varying velocities from V ≈ 10 mm/s to 1 nm/s, where in all cases but one, the advancing (V > 0) and receding (V contact angles converged toward the same theoretical (thermodynamic) values as V → 0. Our equations for the dynamic contact angles are similar to the classic equations of Blake & Haynes (1969) and fitted the experimental adhesion data equally well over the range of velocities studied, although with somewhat different fitting parameters for the characteristic molecular length/dimension or area and characteristic bond formation/rupture lifetime or velocity. Our theoretical and experimental methods and results unify previous kinetic theories of adhesion and contact angle hysteresis and offer new experimental methods for testing kinetic models in the thermodynamic, quasi-static, limit. Our analyses are limited to kinetic effects only, and we conclude that hydrodynamic, i.e., viscous, and inertial effects do not play a role at the

Control of Listeria species food safety at a poultry food production facility.

Science.gov (United States)

Fox, Edward M; Wall, Patrick G; Fanning, Séamus

2015-10-01

Surveillance and control of food-borne human pathogens, such as Listeria monocytogenes, is a critical aspect of modern food safety programs at food production facilities. This study evaluated contamination patterns of Listeria species at a poultry food production facility, and evaluated the efficacy of procedures to control the contamination and transfer of the bacteria throughout the plant. The presence of Listeria species was studied along the production chain, including raw ingredients, food-contact, non-food-contact surfaces, and finished product. All isolates were sub-typed by pulsed-field gel electrophoresis (PFGE) to identify possible entry points for Listeria species into the production chain, as well as identifying possible transfer routes through the facility. The efficacy of selected in-house sanitizers against a sub-set of the isolates was evaluated. Of the 77 different PFGE-types identified, 10 were found among two or more of the five categories/areas (ingredients, food preparation, cooking and packing, bulk packing, and product), indicating potential transfer routes at the facility. One of the six sanitizers used was identified as unsuitable for control of Listeria species. Combining PFGE data, together with information on isolate location and timeframe, facilitated identification of a persistent Listeria species contamination that had colonized the facility, along with others that were transient. Copyright © 2015 Elsevier Ltd. All rights reserved.

Contact Angle of Drops Measured on Nontransparent Surfaces and Capillary Flow Visualized

Science.gov (United States)

Chao, David F.; Zhang, Nengli

2003-01-01

The spreading of a liquid on a solid surface is important for various practical processes, and contact-angle measurements provide an elegant method to characterize the interfacial properties of the liquid with the solid substrates. The complex physical processes occurring when a liquid contacts a solid play an important role in determining the performance of chemical processes and materials. Applications for these processes are in printing, coating, gluing, textile dyeing, and adhesives and in the pharmaceutical industry, biomedical research, adhesives, flat panel display manufacturing, surfactant chemistry, and thermal engineering.

Transfer, attachment, and formation of biofilms by Escherichia coli O157:H7 on meat-contact surface materials.

Science.gov (United States)

Simpson Beauchamp, Catherine; Dourou, Dimitra; Geornaras, Ifigenia; Yoon, Yohan; Scanga, John A; Belk, Keith E; Smith, Gary C; Nychas, George-John E; Sofos, John N

2012-06-01

Studies examined the effects of meat-contact material types, inoculation substrate, presence of air at the liquid-solid surface interface during incubation, and incubation substrate on the attachment/transfer and subsequent biofilm formation by Escherichia coli O157:H7 on beef carcass fabrication surface materials. Materials studied as 2 × 5 cm coupons included stainless steel, acetal, polypropylene, and high-density polyethylene. A 6-strain rifampicin-resistant E. coli O157:H7 composite was used to inoculate (6 log CFU/mL, g, or cm²) tryptic soy broth (TSB), beef fat/lean tissue homogenate (FLH), conveyor belt-runoff fluids, ground beef, or beef fat. Coupons of each material were submerged (4 °C, 30 min) in the inoculated fluids or ground beef, or placed between 2 pieces of inoculated beef fat with pressure (20 kg) applied. Attachment/transfer of the pathogen was surface material and substrate dependent, although beef fat appeared to negate differences among surface materials. Beef fat was the most effective (P transfer and subsequent biofilm formation by E. coli O157:H7. The results highlight the importance of thoroughly cleaning soiled surfaces to remove all remnants of beef fat or other organic material that may harbor or protect microbial contaminants during otherwise lethal antimicrobial interventions. © 2012 Institute of Food Technologists®

Surface analysis of CdTe after various pre-contact treatments

Energy Technology Data Exchange (ETDEWEB)

Waters, D.M. [Univ. of California, Santa Cruz, CA (United States). Dept. of Physics; Niles, D.; Gessert, T.A.; Albin, D.; Rose, D.H.; Sheldon, P. [National Renewable Energy Lab., Golden, CO (United States)

1998-09-01

The authors present surface analysis of close-spaced sublimated (CSS) CdTe after various pre-contact treatments. Methods include Auger electron spectroscopy (AES), x-ray photoelectron spectroscopy (XPS), and grazing-incidence x-ray diffraction (GI-XRD). XPS and GI-XRD analyses of the surface residue left by the solution-based CdCl{sub 2} treatment do not indicate the presence of a significant amount of CdCl{sub 2}. In addition, the solubility properties and relatively high thermal stability of the residue suggest the presence of the oxychloride Cd{sub 3}Cl{sub 2}O{sub 2} rather than CdCl{sub 2} as the major chlorine-containing component. Of the methods tested for their effectiveness in removing the residue, only HNO{sub 3} etches removed all detectable traces of chlorine from the surface.

Isolation of Arcobacter butzleri in environmental and food samples collected in industrial and artisanal dairy plants

Directory of Open Access Journals (Sweden)

Federica Giacometti

2013-10-01

Full Text Available This study investigated the presence of Arcobacter species in two cheese factories; a total of 22 environmental samples and 10 food samples were collected from an artisanal and an industrial cheese factory; Arcobacter species were isolated after enrichment, and isolates were identified at species level by multiplex-polymerase chain reaction (PCR assay. In the artisanal cheese factory, Arcobacter spp. were isolated from several environmental samples, cow and water buffalo raw milk and ricotta cheese. In the industrial plant, Arcobacter spp. were isolated from surfaces not in contact with food and from a cleaned surface in contact with food; no Arcobacter spp. was isolated from food. All isolates were identified as A. butzleri. We report of the presence of A. butzleri in a ready-to-eat cheese produced for retail. In addition, the isolation of A. butzleri in food processing surfaces in the two cheese factories could be assessed as a source of potential contamination for cheeses

Tyre contact length on dry and wet road surfaces measured by three-axial accelerometer

Science.gov (United States)

Matilainen, Mika; Tuononen, Ari

2015-02-01

We determined the tyre contact length on dry and wet roads by measuring the accelerations of the inner liner with a three-axial accelerometer. The influence of the tyre pressure, driving velocity, and tread depth on the contact length was studied in both types of road surface conditions. On dry asphalt the contact length was almost constant, regardless of the driving velocity. On wet asphalt the presence of water could be detected even at low driving velocities (e.g. 20 km/h for a worn tyre) as the contact length began to decrease from that found in the dry asphalt situation. In addition to improving the performance of active safety systems and driver warning systems, the contact length information could be beneficial for classifying and studying the aquaplaning behaviour of tyres.

Relationship between healthcare worker surface contacts, care type and hand hygiene: an observational study in a single-bed hospital ward.

Science.gov (United States)

King, M-F; Noakes, C J; Sleigh, P A; Bale, S; Waters, L

2016-09-01

This study quantifies the relationship between hand hygiene and the frequency with which healthcare workers (HCWs) touch surfaces in patient rooms. Surface contacts and hand hygiene were recorded in a single-bed UK hospital ward for six care types. Surface contacts often formed non-random patterns, but hygiene before or after patient contact depends significantly on care type (P=0.001). The likelihood of hygiene correlated with the number of surface contacts (95% confidence interval 1.1-5.8, P=0.002), but not with time spent in the room. This highlights that a potential subconscious need for hand hygiene may have developed in HCWs, which may support and help focus future hygiene education programmes. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Computational Sensing of Staphylococcus aureus on Contact Lenses Using 3D Imaging of Curved Surfaces and Machine Learning.

Science.gov (United States)

Veli, Muhammed; Ozcan, Aydogan

2018-03-27

We present a cost-effective and portable platform based on contact lenses for noninvasively detecting Staphylococcus aureus, which is part of the human ocular microbiome and resides on the cornea and conjunctiva. Using S. aureus-specific antibodies and a surface chemistry protocol that is compatible with human tears, contact lenses are designed to specifically capture S. aureus. After the bacteria capture on the lens and right before its imaging, the captured bacteria are tagged with surface-functionalized polystyrene microparticles. These microbeads provide sufficient signal-to-noise ratio for the quantification of the captured bacteria on the contact lens, without any fluorescent labels, by 3D imaging of the curved surface of each lens using only one hologram taken with a lens-free on-chip microscope. After the 3D surface of the contact lens is computationally reconstructed using rotational field transformations and holographic digital focusing, a machine learning algorithm is employed to automatically count the number of beads on the lens surface, revealing the count of the captured bacteria. To demonstrate its proof-of-concept, we created a field-portable and cost-effective holographic microscope, which weighs 77 g, controlled by a laptop. Using daily contact lenses that are spiked with bacteria, we demonstrated that this computational sensing platform provides a detection limit of ∼16 bacteria/μL. This contact-lens-based wearable sensor can be broadly applicable to detect various bacteria, viruses, and analytes in tears using a cost-effective and portable computational imager that might be used even at home by consumers.

Moving contact lines on vibrating surfaces

Science.gov (United States)

Solomenko, Zlatko; Spelt, Peter; Scott, Julian

2017-11-01

Large-scale simulations of flows with moving contact lines for realistic conditions generally requires a subgrid scale model (analyses based on matched asymptotics) to account for the unresolved part of the flow, given the large range of length scales involved near contact lines. Existing models for the interface shape in the contact-line region are primarily for steady flows on homogeneous substrates, with encouraging results in 3D simulations. Introduction of complexities would require further investigation of the contact-line region, however. Here we study flows with moving contact lines on planar substrates subject to vibrations, with applications in controlling wetting/dewetting. The challenge here is to determine the change in interface shape near contact lines due to vibrations. To develop further insight, 2D direct numerical simulations (wherein the flow is resolved down to an imposed slip length) have been performed to enable comparison with asymptotic theory, which is also developed further. Perspectives will also be presented on the final objective of the work, which is to develop a subgrid scale model that can be utilized in large-scale simulations. The authors gratefully acknowledge the ANR for financial support (ANR-15-CE08-0031) and the meso-centre FLMSN for use of computational resources. This work was Granted access to the HPC resources of CINES under the allocation A0012B06893 made by GENCI.

Tribological Behavior of Oil-Lubricated Laser Textured Steel Surfaces in Conformal Flat and Non-Conformal Contacts

Energy Technology Data Exchange (ETDEWEB)

Kovalchenko, A. M. [Inst. for Problems of Materials Science, Dept. 7, 3 Krzhizhanovsky Street, Kyiv 03142, UA (Corresponding author), e-mail: andrii.kovalchenko@gatech.edu; Erdemir, A. [Argonne National Lab., Energy Systems Division, 9700 South Cass Avenue, Argonne, IL 60439 US; Ajayi, O. O. [Argonne National Lab., Energy Systems Division, 9700 South Cass Avenue, Argonne, IL 60439 US; Etsion, I. [Technion-Israel Inst. of Technology, Dept. of Mechanical Engineering, Haifa 32000, IL

2017-01-30

Changing the surface texture of sliding surfaces is an effective way to manipulate friction and wear of lubricated surfaces. Having realized its potential, we have done very extensive studies on the effects of laser surface texturing (LST, which involves the creation of an array of microdimples on a surface) on friction and wear behavior of oil-lubricated steel surfaces in the early 2000s. In this paper, we reviewed some of our research accomplishments and assessed future directions of the laser texturing field in many diverse industrial applications. Our studies specifically addressed the impact of laser texturing on friction and wear of both the flat conformal and initial non-conformal point contact configurations using a pin-on-disk test rig under fully-flooded synthetic oil lubricants with different viscosities. Electrical resistance measurement between pin and LST disks was also used to determine the operating lubrication regimes in relation to friction. In conformal contact, we confirmed that LST could significantly expand the operating conditions for hydrodynamic lubrication to significantly much higher loads and slower speeds. In particular, with LST and higher viscosity oils, the low-friction full hydrodynamic regime was shifted to the far left in the Stribeck diagram. Overall, the beneficial effects of laser surface texturing were more pronounced at higher speeds and loads and with higher viscosity oil. LST was also observed to reduce the magnitude of friction coefficients in the boundary regime. For the non-conformal contact configuration, we determined that LST would produce more abrasive wear on the rubbing counterface compared to the untreated surfaces due to a reduction in lubricant fluid film thickness, as well as the highly uneven and rough nature of the textured surfaces. However, this higher initial wear rate has led to faster generation of a conformal contact, and thus transition from the high-friction boundary to lower friction mixed

Neutron activation analysis of recycled paper and board in contact with food

International Nuclear Information System (INIS)

Parry, S.J.

2001-01-01

Recycling of wastepaper has been shown to increase the concentration of metals in the product. Although it is generally assumed that there is no risk of migration of chemical contaminants from recycled paper and board into food, the UK Food Standards Agency has identified limited evidence of such migration. Therefore, it is important to carry out research to establish the concentration of metals in recycled paper and board in contact with food. A previous study at Imperial College had resulted in the development of a neutron activation analysis method to determine trace metals in plastic packaging. An initial study is described to establish whether the same methodology could be applied to paper and board and to carry out a preliminary investigation into a small range of recycled paper and board products. The study was made on 22 elements in 17 products including pizza boxes, fries boxes, kitchen towel, table napkins, greaseproof paper, tea bags and cake cases. Elevated levels of some elements including barium (69 mg/kg in pizza bases) and chromium (5 mg/kg in napkins, 50 mg/kg in greaseproof paper, 2 mg/kg in cake cases, 90 mg/kg in baking parchment, 5 mg/kg in fries boxes and 5 mg/kg in pizza bases) have been shown. (author)

Non-contact adhesion to self-affine surfaces: A theoretical model

Energy Technology Data Exchange (ETDEWEB)

Makeev, Maxim A., E-mail: makeev@umich.edu

2013-11-22

Strength of adhesion between materials is known to be strongly influenced by interface irregularities. In this work, I devise a perturbative approach to describe the effect of self-affine roughness on non-contact adhesive interactions. The hierarchy of the obtained analytical solutions is the following. First, analytical formulae are deduced to describe roughness corrections to the van der Waals interaction energies between a hemi-space adherend, bounded by a self-affine surface, and a point-like adherent. Second, the problem of two hemi-spaces, one of which has a planar surface, and the other is bounded by a self-affine surface, is solved analytically. In the latter case, a numerical analysis is performed to delineate the behavior of the roughness corrections as a function of the parameters, characterizing self-affine fractal surface roughness. The problem of two hemi-spaces, both bounded by self-affine fractal surfaces, is also addressed in this work. The model's predictions are compared with previously reported theoretical results and available experimental data.

Free surface modeling of contacting solid metal flows employing the ALE formulation

NARCIS (Netherlands)

van der Stelt, A.A.; Bor, Teunis Cornelis; Geijselaers, Hubertus J.M.; Akkerman, Remko; Huetink, Han; Merklein, M.; Hagenah, H.

2012-01-01

In this paper, a numerical problem with contacting solid metal flows is presented and solved with an arbitrary Lagrangian-Eulerian (ALE) finite element method. The problem consists of two domains which mechanically interact with each other. For this simulation a new free surface boundary condition

Phthalates in soft PVC products used in food production equipment and in other food contact materials on the Danish and the Nordic Market 2013-2014

DEFF Research Database (Denmark)

Petersen, Jens Højslev; Jensen, Lisbeth Krüger

2016-01-01

they were well-known endocrine disruptors. Results of the Danish Food Authorities control in 2008 and 2009 showed 23 % non-compliant samples. Critical FCMs turned out to be those made from plasticised PVC and sold as suitable for contact with fatty foodstuffs. Targeted follow up control campaigns were...

The mechanism and universal scaling law of the contact line friction for the Cassie-state droplets on nanostructured ultrahydrophobic surfaces.

Science.gov (United States)

Zhao, Lei; Cheng, Jiangtao

2018-04-05

Besides the Wenzel state, liquid droplets on micro/nanostructured surfaces can stay in the Cassie state and consequently exhibit intriguing characteristics such as a large contact angle, small contact angle hysteresis and exceptional mobility. Here we report molecular dynamics (MD) simulations of the wetting dynamics of Cassie-state water droplets on nanostructured ultrahydrophobic surfaces with an emphasis on the genesis of the contact line friction (CLF). From an ab initio perspective, CLF can be ascribed to the collective effect of solid-liquid retarding and viscous damping. Solid-liquid retarding is related to the work of adhesion, whereas viscous damping arises from the viscous force exerted on the liquid molecules within the three-phase (liquid/vapor/solid) contact zone. In this work, a universal scaling law is derived to generalize the CLF on nanostructured ultrahydrophobic surfaces. With the decreasing fraction of solid-liquid contact (i.e., the solid fraction), CLF for a Cassie-state droplet gets enhanced due to the fact that viscous damping is counter-intuitively intensified while solid-liquid retarding remains unchanged. Nevertheless, the overall friction between a Cassie-state droplet and the structured surface is indeed reduced since the air cushion formed in the interstices of the surface roughness underneath the Cassie-state droplet applies negligible resistance to the contact line. Our results have revealed the genesis of CLF from an ab initio perspective, demonstrated the effects of surface structures on a moving contact line and justified the critical role of CLF in the analysis of wetting-related situations.

Verification of aspheric contact lens back surfaces.

Science.gov (United States)

Dietze, Holger H; Cox, Michael J; Douthwaite, William A

2003-08-01

To suggest a tolerance level for the degree of asphericity of aspheric rigid gas-permeable contact lenses and to find a simple method for its verification. Using existing tolerances for the vertex radius, tolerance limits for eccentricity and p values and were calculated. A keratometer-based method and a method based on sag measurements were used to measure the vertex radius and eccentricity of eight concave progressively aspheric surfaces and six concave ellipsoidal surfaces. The results were compared with a gold standard measurement made using a high-precision mechanical instrument (Form Talysurf). The suggested tolerance for eccentricity and p value and is +/-0.05. The keratometer method was very accurate and precise at measuring the vertex radius (mean deviation +/- SD from Talysurf results, -0.002 +/- 0.008 mm). The keratometer was more precise than and similar in accuracy to the sag method for measurement of asphericity (mean deviation of keratometer method results from Talysurf results, 0.017 +/- 0.018; mean deviation of sag method results from Talysurf results using five semichords, -0.016 +/- 0.032). Neither method was precise enough to verify the asphericity within the suggested tolerance. The keratometer can be efficiently used to verify the back vertex radius within its International Organization for Standardization tolerance and the back surface asphericity within an eccentricity/p value tolerance of +/-0.1. The method is poor for progressive aspheres with large edge blending zones. Deriving the eccentricity from sag measurements is a potential alternative if the mathematical description of the surface is known. The limiting factor of this method is the accuracy and precision of individual sag measurements.

21 CFR 178.3910 - Surface lubricants used in the manufacture of metallic articles.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Surface lubricants used in the manufacture of... lubricants used in the manufacture of metallic articles. The substances listed in this section may be safely used in surface lubricants employed in the manufacture of metallic articles that contact food, subject...

Colored Contact Lens Dangers

Medline Plus

Full Text Available ... contact lenses , from the U.S. Food and Drug Administration (FDA). Are the colored lenses you are considering ... Follow The Academy Professionals: Education Guidelines News Multimedia Public & Patients: Contact Us About the Academy Jobs at ...

An adaptive EFG-FE coupling method for elasto-plastic contact of rough surfaces

International Nuclear Information System (INIS)

Liu Lan; Liu Geng; Tong Ruiting; Jin Saiying

2010-01-01

Differing from Finite Element Method, the meshless method does not need any mesh information and can arrange nodes freely which is perfectly suitable for adaptive analysis. In order to simulate the contact condition factually and improve computational efficiency, an adaptive procedure for Element-free Galerkin-Finite Element (EFG-FE) coupling contact model is established and developed to investigate the elastoplastic contact performance for engineering rough surfaces. The local adaptive refinement strategy combined with the strain energy gradient-based error estimation model is employed. The schemes, including principle explanation, arithmetic analysis and programming realization, are introduced and discussed. Furthermore, some related parameters on adaptive convergence criterion are researched emphatically, including adaptation-stop criterion, refinement or coarsening criterion which are guided by the relative error in total strain energy with two adjacent stages. Based on pioneering works of the EFG-FE coupling method for contact problems, an adaptive EFG-FE model for asperity contact is studied. Compared with the solutions obtained from the uniform refinement model, the adaptation results indicate that the adaptive method presented in this paper is capable of solving asperity contact problems with excellent calculation accuracy and computational efficiency.

Exploring the sensitivity of the zone of inhibition test for leachable biocides from paper and board food contact materials, and improvements thereof.

Science.gov (United States)

Castle, L; Kelly, J; Jickells, S M; Johns, S M; Mountfort, K A

2012-01-01

The zone of inhibition method to test the release of biocides from paper and board food contact materials was evaluated. The method tests the paper by placing a small specimen directly onto culture plates of Bacillus subtilis and Aspergillus niger. The principle is that any extractable biocide will diffuse from the paper into the surrounding nutrient medium and so inhibit growth of the microorganism in the vicinity. The test was found to have insufficient sensitivity for assuring food safety, where detection limits for migration at or below the mg l(-1) (parts per million) level are needed. Also, the test does not mimic the actual or foreseeable conditions of use since most paper/board materials are not intended for direct contact with an aqueous medium for up to 3 days at 30°C (B. subtilis) or 25°C (A. niger), which are the incubation conditions used. The sensitivity of the test was increased approximately 100-fold by preparing a concentrated extract of the paper to be tested and applying this extract to the assay via a blank paper carrier. This was done using methanol as a good solvent for most biocides, as a proof of principle. Other solvents or food simulants could be used to mimic the conditions of use intended for the particular paper/board samples under examination, e.g. contact with dry, fatty, aqueous or acidic foods, hot or cold. Twenty-four plain (unconverted) paper and board samples and 100 food packaging samples were evaluated using the modified procedure. The results revealed that the method has been developed to the stage where background cytotoxic action of normal paper constituents gives a weak response. Unlike the original method, therefore, the modified method with its improved sensitivity and the facility to link with the intended food contact conditions may be considered a suitable bioassay screening test to complement chemical analysis of paper/board for composition and migration.

Thermal Diffusion Processes in Metal-Tip-Surface Interactions: Contact Formation and Adatom Mobility

DEFF Research Database (Denmark)

Sørensen, Mads Reinholdt; Jacobsen, Karsten Wedel; Jonsson, Hannes

1996-01-01

and the surface can occur by a sequence of atomic hop and exchange processes which become active on a millisecond time scale when the tip is about 3-5 Angstrom from the surface. Adatoms on the surface are stabilized by the presence of the tip and energy barriers for diffusion processes in the region under the tip......We have carried out computer simulations to identify and characterize various thermally activated atomic scale processes that can play an important role in room temperature experiments where a metal tip is brought close to a metal surface. We find that contact formation between the tip...

Functional parameter screening for predicting durability of rolling sliding contacts with different surface finishes

Science.gov (United States)

Dimkovski, Z.; Lööf, P.-J.; Rosén, B.-G.; Nilsson, P. H.

2018-06-01

The reliability and lifetime of machine elements such as gears and rolling bearings depend on their wear and fatigue resistance. In order to screen the wear and surface damage, three finishing processes: (i) brushing, (ii) manganese phosphating and (iii) shot peening were applied on three disc pairs and long-term tested on a twin-disc tribometer. In this paper, the elastic contact of the disc surfaces (measured after only few revolutions) was simulated and a number of functional and roughness parameters were correlated. The functional parameters consisted of subsurface stresses at different depths and a new parameter called ‘pressure spikes’ factor’. The new parameter is derived from the pressure distribution and takes into account the proximity and magnitude of the pressure spikes. Strong correlations were found among the pressure spikes’ factor and surface peak/height parameters. The orthogonal shear stresses and Von Mises stresses at the shallowest depths under the surface have shown the highest correlations but no good correlations were found when the statistics of the whole stress fields was analyzed. The use of the new parameter offers a fast way to screen the durability of the contacting surfaces operating at similar conditions.

Adaptive local surface refinement based on LR NURBS and its application to contact

Science.gov (United States)

Zimmermann, Christopher; Sauer, Roger A.

2017-12-01

A novel adaptive local surface refinement technique based on Locally Refined Non-Uniform Rational B-Splines (LR NURBS) is presented. LR NURBS can model complex geometries exactly and are the rational extension of LR B-splines. The local representation of the parameter space overcomes the drawback of non-existent local refinement in standard NURBS-based isogeometric analysis. For a convenient embedding into general finite element codes, the Bézier extraction operator for LR NURBS is formulated. An automatic remeshing technique is presented that allows adaptive local refinement and coarsening of LR NURBS. In this work, LR NURBS are applied to contact computations of 3D solids and membranes. For solids, LR NURBS-enriched finite elements are used to discretize the contact surfaces with LR NURBS finite elements, while the rest of the body is discretized by linear Lagrange finite elements. For membranes, the entire surface is discretized by LR NURBS. Various numerical examples are shown, and they demonstrate the benefit of using LR NURBS: Compared to uniform refinement, LR NURBS can achieve high accuracy at lower computational cost.

AFM-based tribological study of nanopatterned surfaces: the influence of contact area instabilities.

Science.gov (United States)

Rota, A; Serpini, E; Gazzadi, G C; Valeri, S

2016-04-06

Although the importance of morphology on the tribological properties of surfaces has long been proved, an exhaustive understanding of nanopatterning effects is still lacking due to the difficulty in both fabricating 'really nano-' structures and detecting their tribological properties. In the present work we show how the probe-surface contact area can be a critical parameter due to its remarkable local variability, making a correct interpretation of the data very difficult in the case of extremely small nanofeatures. Regular arrays of parallel 1D straight nanoprotrusions were fabricated by means of a low-dose focused ion beam, taking advantage of the amorphization-related swelling effect. The tribological properties of the patterns were detected in the presence of air and in vacuum (dry ambient) by atomic force microscopy. We have introduced a novel procedure and data analysis to reduce the uncertainties related to contact instabilities. The real time estimation of the radius of curvature of the contacting asperity enables us to study the dependence of the tribological properties of the patterns from their geometrical characteristics. The effect of the patterns on both adhesion and the coefficient of friction strongly depends on the contact area, which is linked to the local radius of curvature of the probe. However, a detectable hydrophobic character induced on the hydrophilic native SiO2 has been observed as well. The results suggest a scenario for capillary formation on the patterns.

AFM-based tribological study of nanopatterned surfaces: the influence of contact area instabilities

International Nuclear Information System (INIS)

Rota, A; Serpini, E; Gazzadi, G C; Valeri, S

2016-01-01

Although the importance of morphology on the tribological properties of surfaces has long been proved, an exhaustive understanding of nanopatterning effects is still lacking due to the difficulty in both fabricating ‘really nano-’ structures and detecting their tribological properties. In the present work we show how the probe–surface contact area can be a critical parameter due to its remarkable local variability, making a correct interpretation of the data very difficult in the case of extremely small nanofeatures. Regular arrays of parallel 1D straight nanoprotrusions were fabricated by means of a low-dose focused ion beam, taking advantage of the amorphization-related swelling effect. The tribological properties of the patterns were detected in the presence of air and in vacuum (dry ambient) by atomic force microscopy. We have introduced a novel procedure and data analysis to reduce the uncertainties related to contact instabilities. The real time estimation of the radius of curvature of the contacting asperity enables us to study the dependence of the tribological properties of the patterns from their geometrical characteristics. The effect of the patterns on both adhesion and the coefficient of friction strongly depends on the contact area, which is linked to the local radius of curvature of the probe. However, a detectable hydrophobic character induced on the hydrophilic native SiO 2 has been observed as well. The results suggest a scenario for capillary formation on the patterns. (paper)

An effective medium approach to predict the apparent contact angle of drops on super-hydrophobic randomly rough surfaces.

Science.gov (United States)

Bottiglione, F; Carbone, G

2015-01-14

The apparent contact angle of large 2D drops with randomly rough self-affine profiles is numerically investigated. The numerical approach is based upon the assumption of large separation of length scales, i.e. it is assumed that the roughness length scales are much smaller than the drop size, thus making it possible to treat the problem through a mean-field like approach relying on the large-separation of scales. The apparent contact angle at equilibrium is calculated in all wetting regimes from full wetting (Wenzel state) to partial wetting (Cassie state). It was found that for very large values of the roughness Wenzel parameter (r(W) > -1/ cos θ(Y), where θ(Y) is the Young's contact angle), the interface approaches the perfect non-wetting condition and the apparent contact angle is almost equal to 180°. The results are compared with the case of roughness on one single scale (sinusoidal surface) and it is found that, given the same value of the Wenzel roughness parameter rW, the apparent contact angle is much larger for the case of a randomly rough surface, proving that the multi-scale character of randomly rough surfaces is a key factor to enhance superhydrophobicity. Moreover, it is shown that for millimetre-sized drops, the actual drop pressure at static equilibrium weakly affects the wetting regime, which instead seems to be dominated by the roughness parameter. For this reason a methodology to estimate the apparent contact angle is proposed, which relies only upon the micro-scale properties of the rough surface.

THE DYNAMIC INTERACTION OF THE MOVING CONTACTING SURFACES AT THE EXAMPLE OF THE ELECTRIC ROLLING STOCK CURRENT COLLECTOR

Directory of Open Access Journals (Sweden)

M. O. Babiak

2009-07-01

Full Text Available The process of mutual moving and contacting of surfaces of current collecting pantograph elements and contact network is considered taking into account the particularities of inf1uence of speed and acceleration parameters, determination of which will allow to forecast mathematically the wear-out degree of contacting elements.

The effects of electron beam irradiation on additives present in food-contact polymers

International Nuclear Information System (INIS)

Crowson, Andrew.

1991-09-01

A range of additives (Irganox 1010, Irganox 1076, Irganox 1330, Irgafos 168 and Tinuvin 622) has been incorporated into a variety of food-contact polymers including polypropylene and low density polyethylene. Samples of these stabilized polymers were subjected to electron-beam or gamma irradiation to receive doses of 1,5,10,25 and 50 kGy. The effects of electron-beam irradiation on the amount of extractable antioxidant in polymers were determined. Using hplc techniques it was found that there was a dose-related reduction in the amount of extractable antioxidant similar to that caused by gamma irradiation. The magnitude of this reduction was found to be dependent upon the nature of both the antioxidant and the polymer type. Electron-beam irradiation was also found to cause a dose-related reduction in the levels of the antioxidants Irganox 1010 and Irganox 1076 migrating from polymers into a food simulant. This effect was similar to that caused by gamma irradiation. (author)

On crack growth in molar teeth from contact on the inclined occlusal surface.

Science.gov (United States)

Chai, Herzl

2015-04-01

Extracted human molar teeth are indented by hard balls laid at the central fossa, sectioned, and their interior examined for damage. Contact on the fissured enamel coat generally occurs on three distinct spots. The main forms of damage are radial cracks growing from the DEJ to the occlusal surface and median radial and cylindrical cracks growing from a contact spot to the DEJ. For large balls failure by edge chipping near a cusp apex may occur. The median cracks tend to run unstably to the DEJ upon reaching the middle part of the enamel coat. The corresponding load, PFM, and the load needed to initiate radial cracks at the DEJ, PFR, are taken to signal crown failure. The mean values of PFM and PFR are on the order of 1000N. A conical bilayer model defined by thickness d, inclination angle θ, failure stress σF and toughness KC of the enamel coat is developed to assess crown failure. The analytical predictions for PFR and PFM agree well with the tests. The results indicate that enamel thickness is so designed as to ensure that PFR and PFM just exceed the maximum bite force under normal conditions while the choice of θ seems to reflect a compromise between needs to resist crown failure and break hard food particles. Both PFR and PFM are greatly reduced with reducing d, which points to the danger posed by tooth wear. The analytical expressions for PFR and PFM may also apply to other multi-cusp mammalian or prosthetic molar crowns. Cone cracking, suppressed in the anisotropic tooth enamel, may be an important failure mode in prosthetic crowns. Copyright © 2014 Elsevier Ltd. All rights reserved.

Evaluation of the hygiene of ready-to-eat food preparation areas and practices in mobile food vendors in the UK.

Science.gov (United States)

Little, Christine; Sagoo, Satnam

2009-12-01

This study was undertaken to assess the cleanliness of food preparation areas, cleaning methods used, and the microbiological quality of water used by 1258 mobile food vendors in the UK. Samples collected included potable water (1102), cleaning cloths (801) and environmental swabs from food preparation surfaces (2704). Cleaning cloths were more heavily contaminated with Aerobic Colony Counts, Enterobacteriaceae, Escherichia coli, and Staphylococcus aureus compared to surfaces sampled. Surfaces that were visually dirty, wet, and chopping boards that were plastic or damaged also had high levels of these bacteria. Fifty-four percent of potable water samples were of poor microbiological quality; i.e. contained coliforms, E. coli and/or enterococci. A documented food safety management system was only evident in 40.1% of vendors and cleaning schedules were only used by 43.6%. Deficiencies in the correct use of cleaning materials, such as dilution factors and the minimum contact time for disinfectants, were identified.

Experimental studies of contact angle hysteresis phenomena on polymer surfaces – Toward the understanding and control of wettability for different applications.

Science.gov (United States)

Grundke, K; Pöschel, K; Synytska, A; Frenzel, R; Drechsler, A; Nitschke, M; Cordeiro, A L; Uhlmann, P; Welzel, P B

2015-08-01

Contact angle hysteresis phenomena on polymer surfaces have been studied by contact angle measurements using sessile liquid droplets and captive air bubbles in conjunction with a drop shape method known as Axisymmetric Drop Shape Analysis - Profile (ADSA-P). In addition, commercially available sessile drop goniometer techniques were used. The polymer surfaces were characterized with respect to their surface structure (morphology, roughness, swelling) and surface chemistry (elemental surface composition, acid-base characteristics) by scanning electron microscopy (SEM), scanning force microscopy (SFM), ellipsometry, X-ray photoelectron spectroscopy (XPS) and streaming potential measurements. Heterogeneous polymer surfaces with controlled roughness and chemical composition were prepared by different routes using plasma etching and subsequent dip coating or grafting of polymer brushes, anodic oxidation of aluminium substrates coated with thin polymer films, deposition techniques to create regular patterned and rough fractal surfaces from core-shell particles, and block copolymers. To reveal the effects of swelling and reorientation at the solid/liquid interface contact angle hysteresis phenomena on polyimide surfaces, cellulose membranes, and thermo-responsive hydrogels have been studied. The effect of different solutes in the liquid (electrolytes, surfactants) and their impact on contact angle hysteresis were characterized for solid polymers without and with ionizable functional surface groups in aqueous electrolyte solutions of different ion concentrations and pH and for photoresist surfaces in cationic aqueous surfactant solutions. The work is an attempt toward the understanding of contact angle hysteresis phenomena on polymer surfaces aimed at the control of wettability for different applications. Copyright © 2014 Elsevier B.V. All rights reserved.

[Determination of bisphenol A from toys and food contact materials by derivatization and gas chromatography-mass spectrometry].

Science.gov (United States)

Gao, Yonggang; Zhang, Yanyan; Gao, Jianguo; Zhang, Huiling; Zheng, Lisha; Chen, Jing

2012-10-01

A method was developed for the determination of bisphenol A (BPA) in toys and food contact materials. The BPA was extracted with Soxhlet extraction method from the sample and reacted with acetic anhydride. The final product was determined by gas chromatography-mass spectrometry (GC-MS). To achieve the optimum derivatization performance, the derivatization time and dosage of derivatization reagent etc. were investigated. Under the optimized experimental conditions, the final product was stable and the peak shape was good. The linearity of the derivative was good in the range of 0.05 to 50 mg/L with the correlation coefficient (r2) above 0.999. The recoveries ranged from 80% to 93% at the spiked levels of 0.05, 1.00, 10.00 mg/kg with the relative standard deviations (RSDs) less than 3.7%. The limit of detection (S/N = 3) was 10 microg/kg. The method is accurate and has high recovery. The method is suitable for the inspection of bisphenol A in toys and food contact materials.

EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids (CEF); Scientific Opinion on Flavouring Group Evaluation 309 (FGE.309): Sodium Diacetate

DEFF Research Database (Denmark)

Larsen, John Christian; Nørby, Karin Kristiane; Beltoft, Vibe Meister

The Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids of the European Food Safety Authority was requested to evaluate sodium diacetate [FL-no: 16.073] in the Flavouring Group Evaluation 309, using the Procedure in Commission Regulation (EC) No 1565/2000. However, although...

Effects of vacuum heat treatment on the photoelectric work function and surface morphology of multilayered silver–metal electrical contacts

International Nuclear Information System (INIS)

Akbi, Mohamed; Bouchou, Aïssa; Zouache, Noureddine

2014-01-01

Contact materials used for electrical breakers are often made with silver alloys. Mechanical and thermodynamical properties as well as electron emission of such complicated alloys present a lack of reliable and accurate experimental data. This paper deals mainly with electron work function (EWF) measurements about silver–metal (Ag–Me) electrical contacts (Ag–Ni (60/40) and Ag–W (50/50)), before and after surface heat treatments at 513 K–873 K, under UHV conditions (residual gas pressure of 1.4 × 10 −7 mbar). The electron work function (EWF) of silver alloyed contacts was measured photoelectrically, using both Fowler's method of isothermal curves and linearized Fowler plots. An interesting fact brought to light by this investigation is that after vacuum heat treatments, the diffusion and/or evaporation phenomena, affecting the atomic composition of the alloy surface, somehow confine the EWF of the silver–nickel alloy, Φ(Ag–Ni), determined at room temperature in interval]Φ(Ag), Φ(Ni) [=] 4.26 eV, 4.51 eV[. Surface analysis of two specimens before and after heating showed a significant increase of tungsten atomic proportion on the contact surface for Ag–W contacts after VH treatments. A multilayer model, taking into account the strong intergranular and volume segregation gives a good interpretation of the obtained results.

Cohesive delamination and frictional contact on joining surface via XFEM

Directory of Open Access Journals (Sweden)

Francesco Parrinello

2018-02-01

Full Text Available In the present paper, the complex mechanical behaviour of the surfaces joining two differentbodies is analysed by a cohesive-frictional interface constitutive model. The kinematical behaviouris characterized by the presence of discontinuous displacement fields, that take place at the internalconnecting surfaces, both in the fully cohesive phase and in the delamination one. Generally, in order tocatch discontinuous displacement fields, internal connecting surfaces (adhesive layers are modelled bymeans of interface elements, which connect, node by node, the meshes of the joined bodies, requiringthe mesh to be conforming to the geometry of the single bodies and to the relevant connecting surface.In the present paper, the Extended Finite Element Method (XFEM is employed to model, both fromthe geometrical and from the kinematical point of view, the whole domain, including the connectedbodies and the joining surface. The joining surface is not discretized by specific finite elements, butit is defined as an internal discontinuity surface, whose spatial position inside the mesh is analyticallydefined. The proposed approach is developed for two-dimensional composite domains, formed by twoor more material portions joined together by means of a zero thickness adhesive layer. The numericalresults obtained with the proposed approach are compared with the results of the classical interfacefinite element approach. Some examples of delamination and frictional contact are proposed withlinear, circular and curvilinear adhesive layer.

Elastohydrodynamic lubrication in point contact on the surfaces of particle-reinforced composite

Science.gov (United States)

Chen, Keying; Zeng, Liangcai; Wu, Zhenpeng; Zheng, Feilong

2018-04-01

Appreciable friction and serious wear are common challenges in the operation of advanced manufacturing equipment, and friction pairs may be susceptible to damage even with oil lubrication when point contact exists. In this study, a type of particle-reinforced composite material is introduced for one of the components of a heavy-load contact pair, and the performance improvement of elastohydrodynamic lubrication (EHL) is analyzed considering the rheological properties of non-Newtonian fluids. The Ree-Eyring EHL model is used considering the surface of the particle-reinforced composite, in which the film thickness includes the particle-induced elastic deformation. The problem of inclusions with different eigenstrains is solved by using Galerkin vectors. The influences of particle properties, size, burial depth, and interparticle distance on point-contact EHL are investigated. Furthermore, using several cases, the structural parameters of the particles in the composites are optimized, and an appropriate parameter range is obtained with the goal of reducing friction. Finally, the results for the EHL traction coefficient demonstrate that appropriate particle properties, size, burial depth, and interparticle distance can effectively reduce the traction coefficient in heavy-load contact.

Piercing the water surface with a blade: Singularities of the contact line

Energy Technology Data Exchange (ETDEWEB)

Alimov, Mars M. [Kazan Federal University, Kazan 420008 (Russian Federation); Kornev, Konstantin G. [Department of Materials Science & Engineering, Clemson University, Clemson, South Carolina 29634 (United States)

2016-01-15

An external meniscus on a narrow blade with a slit-like cross section is studied using the hodograph formulation of the Laplace nonlinear equation of capillarity. On narrow blades, the menisci are mostly shaped by the wetting and capillary forces; gravity plays a secondary role. To describe a meniscus in this asymptotic case, the model of Alimov and Kornev [“Meniscus on a shaped fibre: Singularities and hodograph formulation,” Proc. R. Soc. A 470, 20140113 (2014)] has been employed. It is shown that at the sharp edges of the blade, the contact line makes a jump. In the wetting case, the contact line sitting at each side of the blade is lifted above the points where the meniscus first meets the blade edges. In the non-wetting case, the contact line is lowered below these points. The contours of the constant height emanating from the blade edges generate unusual singularities with infinite curvatures at some points at the blade edges. The meniscus forms a unique surface made of two mirror-symmetric sheets fused together. Each sheet is supported by the contact line sitting at each side of the blade.

Piercing the water surface with a blade: Singularities of the contact line

International Nuclear Information System (INIS)

Alimov, Mars M.; Kornev, Konstantin G.

2016-01-01

An external meniscus on a narrow blade with a slit-like cross section is studied using the hodograph formulation of the Laplace nonlinear equation of capillarity. On narrow blades, the menisci are mostly shaped by the wetting and capillary forces; gravity plays a secondary role. To describe a meniscus in this asymptotic case, the model of Alimov and Kornev [“Meniscus on a shaped fibre: Singularities and hodograph formulation,” Proc. R. Soc. A 470, 20140113 (2014)] has been employed. It is shown that at the sharp edges of the blade, the contact line makes a jump. In the wetting case, the contact line sitting at each side of the blade is lifted above the points where the meniscus first meets the blade edges. In the non-wetting case, the contact line is lowered below these points. The contours of the constant height emanating from the blade edges generate unusual singularities with infinite curvatures at some points at the blade edges. The meniscus forms a unique surface made of two mirror-symmetric sheets fused together. Each sheet is supported by the contact line sitting at each side of the blade

Preferences of lame cows for type of surface and level of social contact in hospital pens

DEFF Research Database (Denmark)

Jensen, Margit Bak; Herskin, Mette S; Thomsen, Peter T.

2015-01-01

To investigate preferences of lame cows for flooring and level of social contact, 37 lame, lactating dairy cows (diagnosed with sole ulcer or white line disease) were housed individually for 6 d in experimental hospital pens, where they could choose between 2 equally sized areas (6m × 4.5m......) with either deep-bedded sand or a rubber surface. On both surfaces, cows could choose between 2 equally sized areas either near or away from heifers in a neighboring group pen. Cows spent more time lying on the deep-bedded sand than on the rubber surface (870 vs. 71min/d), whereas they spent less time upright...... (standing or walking) on the sand than on the rubber surface (180 vs. 319min/d). In addition, cows spent less time self-grooming on the sand than on the rubber surface (2.2 vs. 4.7% of time spent upright). With regard to level of social contact, cows spent more time near the neighboring heifers than away...

Polímeros reciclados para contato com alimentos Recycled polymers for food contact

Directory of Open Access Journals (Sweden)

Sandra A. Cruz

2011-01-01

Full Text Available Os resíduos sólidos urbanos (RSUs são atualmente um dos maiores problemas ambientais, por serem gerados em grande quantidade e ocuparem extensos espaços por um longo período, resultando na diminuição do tempo de vida útil dos aterros sanitários. Os polímeros constituem um grande percentual da composição do RSUs, sendo que as embalagens plásticas contribuem com maior volume e massa. Apesar da reciclagem de polímeros estarem se consolidando no Brasil, graças ao seu mercado ascendente e promissor, existem ainda restrições quanto a sua utilização em contato com alimentos devido aos eventuais processos de migração de contaminantes que podem ocorrer da resina reciclada para o alimento. Por outro lado, dados recentes do setor indicam que a maior parte do consumo de resina virgem é destinada, justamente, para o mercado de embalagens alimentícias. Assim, o desenvolvimento e o gerenciamento de tecnologias que possibilitem o retorno destes materiais a sua aplicação original é de grande importância para sociedade contemporânea. Em um panorama geral, este trabalho aborda as exigências e limitações do uso de polímeros reciclados para contato com alimentos.Municipal solid waste has recently become one of the severest environmental problems. This is because it is generated on a large scale and occupies large spaces for long periods resulting in a decrease in the useful life of landfills. Polymers comprise a large percentage of municipal solid waste and polymer packaging is responsible for the large mass and volume amount. Despite the consolidation of polymer recycling in Brazil, due to the promising and growing market, there are still restrictions concerning to its application for food contact due to eventual migration process that might occur from the recycled resin into the food. On the other hand, recent data of the sector indicates that food packaging market is responsible for the highest consumption of the produced amount of

A new theory for the static contact between rough, unmated surfaces in non-elastically deforming rock and its implications for rock friction

Science.gov (United States)

Stesky, R. M.; Hannan, S. S.

The closure behavior of fractures in marble and alabaster is markedly different from that in quartzite. The aperture decreases considerably more under normal stress and remains permanently reduced, for the same ratio of normal stress to unconfined compressive strength. Also, a larger permanent relative contact area develops between the surfaces of marble and alabaster than it does between surfaces of quartzite. The permanent contact area increases at an increasing rate with normal stress in marble and alabaster, unlike the nearly linear increase in quartzite. The failure of surface asperities of calcite and gypsum during closure accounts for these differences. We modeled this process by considering the surfaces to consist of paraboloids lying on a flat plane and having a range of initial heights. Closure occurs by pressing a plane rigid surface against the 'hills', flattening their peaks, keeping the base area of the hills constant. To allow for a changing resistance to deformation, the contact stress is assumed to vary linearly with the shortening strain, to a first approximation. This model was tested against measurements of fracture closure and contact area of rough surfaces of calcite marble with a known initial height distribution of surface peaks. The fit to the data is quite good. In all cases, the model shows that closure is accompanied by a decrease in contact strength of deforming asperities, suggested also by the cataclastic deformation observed petrographically. The number of contact spots and the total length of contact seen in profile are also reasonably well modeled. These results have important implications for our understanding of frictional strength of fractures. The overall resistance to shear along rough surfaces depends upon the product of the shear strength and true area of the contacts, both of which are affected by normal stress. Application of this model approach shows that the initial frictional resistance of some fractures in ductile

Wear of Polished Steel Surfaces in Dry Friction Linear Contact on Polimer Composites with Glass Fibres

Directory of Open Access Journals (Sweden)

D. Rus

2013-12-01

Full Text Available It is generally known that the friction and wear between polymers and polished steel surfaces has a special character, the behaviour to friction and wear of a certain polymer might not be valid for a different polymer, moreover in dry friction conditions. In this paper, we study the reaction to wear of certain polymers with short glass fibres on different steel surfaces, considering the linear friction contact, observing the friction influence over the metallic surfaces wear. The paper includes also its analysis over the steel’s wear from different points of view: the reinforcement content influence and tribological parameters (load, contact pressure, sliding speed, contact temperature, etc.. Thus, we present our findings related to the fact that the abrasive component of the friction force is more significant than the adhesive component, which generally is specific to the polymers’ friction. Our detections also state that, in the case of the polyamide with 30% glass fibres, the steel surface linear wear rate order are of 10-4 mm/h, respectively the order of volumetric wear rate is of 10-6 cm3 /h. The resulting volumetric wear coefficients are of the order (10-11 – 10-12 cm3/cm and respectively linear wear coefficients of 10-9 mm/cm.

Role of Ag-alloy in the thermal stability of Ag-based ohmic contact to GaN(0 0 0 1) surface

International Nuclear Information System (INIS)

Xiong, Zhihua; Qin, Zhenzhen; Zhao, Qian; Chen, Lanli

2015-01-01

First-principles calculations are performed to study Ag and Ag-alloy adsorption stability on GaN(0 0 0 1) surface. We find Ag only contact to GaN surface is unstable under high temperature. While Ag-alloy adsorption exhibits better adsorption stability and electronic properties than that of the Ag only contact,due to the enhanced interaction between Ag-alloy and GaN(0 0 0 1) surface. The Ag-alloy, particularly AgNi, is proposed to be used as very promising ohmic contact to GaN for practical applications

Colored Contact Lens Dangers

Medline Plus

Full Text Available ... eye-care team . Consumer warning about the improper use of colored contact lenses , from the U.S. Food and Drug Administration (FDA). Are the colored lenses you are considering buying approved by the FDA? Check the FDA's database of approved contact lenses . Related Stories Prevent Infection ...

Applicability of contact angle techniques used in the analysis of contact lenses, part 1: comparative methodologies.

Science.gov (United States)

Campbell, Darren; Carnell, Sarah Maria; Eden, Russell John

2013-05-01

Contact angle, as a representative measure of surface wettability, is often employed to interpret contact lens surface properties. The literature is often contradictory and can lead to confusion. This literature review is part of a series regarding the analysis of hydrogel contact lenses using contact angle techniques. Here we present an overview of contact angle terminology, methodology, and analysis. Having discussed this background material, subsequent parts of the series will discuss the analysis of contact lens contact angles and evaluate differences in published laboratory results. The concepts of contact angle, wettability and wetting are presented as an introduction. Contact angle hysteresis is outlined and highlights the advantages in using dynamic analytical techniques over static methods. The surface free energy of a material illustrates how contact angle analysis is capable of providing supplementary surface characterization. Although single values are able to distinguish individual material differences, surface free energy and dynamic methods provide an improved understanding of material behavior. The frequently used sessile drop, captive bubble, and Wilhelmy plate techniques are discussed. Their use as both dynamic and static methods, along with the advantages and disadvantages of each technique, is explained. No single contact angle technique fully characterizes the wettability of a material surface, and the application of complimenting methods allows increased characterization. At present, there is not an ISO standard method designed for soft materials. It is important that each contact angle technique has a standard protocol, as small protocol differences between laboratories often contribute to a variety of published data that are not easily comparable.

Tissue Engineering at the Blood-Contacting Surface: A Review of Challenges and Strategies in Vascular Graft Development.

Science.gov (United States)

Radke, Daniel; Jia, Wenkai; Sharma, Dhavan; Fena, Kemin; Wang, Guifang; Goldman, Jeremy; Zhao, Feng

2018-05-07

Tissue engineered vascular grafts (TEVGs) are beginning to achieve clinical success and hold promise as a source of grafting material when donor grafts are unsuitable or unavailable. Significant technological advances have generated small-diameter TEVGs that are mechanically stable and promote functional remodeling by regenerating host cells. However, developing a biocompatible blood-contacting surface remains a major challenge. The TEVG luminal surface must avoid negative inflammatory responses and thrombogenesis immediately upon implantation and promote endothelialization. The surface has therefore become a primary focus for research and development efforts. The current state of TEVGs is herein reviewed with an emphasis on the blood-contacting surface. General vascular physiology and developmental challenges and strategies are briefly described, followed by an overview of the materials currently employed in TEVGs. The use of biodegradable materials and stem cells requires careful control of graft composition, degradation behavior, and cell recruitment ability to ensure that a physiologically relevant vessel structure is ultimately achieved. The establishment of a stable monolayer of endothelial cells and the quiescence of smooth muscle cells are critical to the maintenance of patency. Several strategies to modify blood-contacting surfaces to resist thrombosis and control cellular recruitment are reviewed, including coatings of biomimetic peptides and heparin. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Intelligent tires for identifying coefficient of friction of tire/road contact surfaces using three-axis accelerometer

International Nuclear Information System (INIS)

Matsuzaki, Ryosuke; Kamai, Kazuto; Seki, Ryosuke

2015-01-01

Intelligent tires equipped with sensors as well as the monitoring of the tire/road contact conditions are in demand for improving vehicle control and safety. With the aim of identifying the coefficient of friction of tire/road contact surfaces during driving, including during cornering, we develop an identification scheme for the coefficient of friction that involves estimation of the slip angle and applied force by using a single lightweight three-axis accelerometer attached on the inner surface of the tire. To validate the developed scheme, we conduct tire-rolling tests using an accelerometer-equipped tire with various slip angles on various types of road surfaces, including dry and wet surfaces. The results of these tests confirm that the estimated slip angle and applied force are reasonable. Furthermore, the identified coefficient of friction by the developed scheme agreed with that measured by standardized tests. (paper)

Effects of materials containing antimicrobial compounds on food hygiene.

Science.gov (United States)

Møretrø, Trond; Langsrud, Solveig

2011-07-01

Surfaces with microorganisms may transfer unwanted microorganisms to food through cross-contamination during processing and preparation. A high hygienic status of surfaces that come in contact with food is important in order to reduce the risk of cross-contamination. During the last decade, products containing antimicrobial compounds, such as cutting boards, knives, countertops, kitchen utensils, refrigerators, and conveyor belts, have been introduced to the market, claiming hygienic effects. Such products are often referred to as "treated articles." Here we review various aspects related to treated articles intended for use during preparation and processing of food. Regulatory issues and methods to assess antibacterial effects are covered. Different concepts for treated articles as well as their antibacterial activity are reviewed. The effects of products with antimicrobials on food hygiene and safety are discussed. Copyright ©, International Association for Food Protection

Dynamics of liquid nitrogen cooling process of solid surface at wetting contact coefficient

International Nuclear Information System (INIS)

Smakulski, P; Pietrowicz, S

2015-01-01

Liquid cryogens cooling by direct contact is very often used as a method for decreasing the temperature of electronic devices or equipment i.e. HTS cables. Somehow, cooldown process conducted in that way could not be optimized, because of cryogen pool boiling characteristic and low value of the heat transfer coefficient. One of the possibilities to increase the efficiency of heat transfer, as well as the efficiency of cooling itself, it is to use a spray cooling method. The paper shows dynamics analysis of liquid nitrogen cooling solid surface process. The model of heat transfer for the single droplet of liquid nitrogen, which hits on a flat and smooth surface with respect to the different Weber numbers, is shown. Temperature profiles in calculation domains are presented, as well as the required cooling time. The numerical calculations are performed for different initial and boundary conditions, to study how the wetting contact coefficient is changing, and how it contributed to heat transfer between solid and liquid cryogen. (paper)

CONTACT RESISTANCE MODELING

Directory of Open Access Journals (Sweden)

S. V. LOSKUTOV

2018-05-01

Full Text Available Purpose. To determine the contribution of the real contact spots distribution in the total conductivity of the conductors contact. Methodology. The electrical contact resistance research was carried out on models. The experimental part of this work was done on paper with a graphite layer with membranes (the first type and conductive liquids with discrete partitions (the second type. Findings. It is shown that the contact electrical resistance is mainly determined by the real area of metal contact. The experimental dependence of the electrical resistance of the second type model on the distance between the electrodes and the potential distribution along the sample surface for the first type model were obtained. The theoretical model based on the principle of electric field superposition was considered. The dependences obtained experimentally and calculated by using the theoretical model are in good agreement. Originality. The regularity of the electrical contact resistance formation on a large number of membranes was researched for the first time. A new model of discrete electrical contact based on the liquid as the conducting environment with nuclear membrane partitions was developed. The conclusions of the additivity of contact and bulk electrical resistance were done. Practical value. Based on these researches, a new experimental method of kinetic macroidentation that as a parameter of the metal surface layer deformation uses the real contact area was developed. This method allows to determine the value of average contact stresses, yield point, change of the stress on the depth of deformation depending on the surface treatment.

Shewanella putrefaciens adhesion and biofilm formation on food processing surfaces

DEFF Research Database (Denmark)

Bagge, Dorthe; Hjelm, M.; Johansen, C.

2001-01-01

Laboratory model systems were developed for studying Shewanella putrefaciens adhesion and biofilm formation under batch and flow conditions. S. putrefaciens plays a major role in food spoilage and may cause microbially induced corrosion on steel surfaces. S. putrefaciens bacteria suspended in buf...... from surfaces, and indirect conductometry and found this combination sufficient to quantify bacteria on surfaces...

Electrical characterization and nanoscale surface morphology of optimized Ti/Al/Ta/Au ohmic contact for AlGaN/GaN HEMT.

Science.gov (United States)

Wang, Cong; Kim, Nam-Young

2012-02-07

Good ohmic contacts with low contact resistance, smooth surface morphology, and a well-defined edge profile are essential to ensure optimal device performances for the AlGaN/GaN high electron mobility transistors [HEMTs]. A tantalum [Ta] metal layer and an SiNx thin film were used for the first time as an effective diffusion barrier and encapsulation layer in the standard Ti/Al/metal/Au ohmic metallization scheme in order to obtain high quality ohmic contacts with a focus on the thickness of Ta and SiNx. It is found that the Ta thickness is the dominant factor affecting the contact resistance, while the SiNx thickness affects the surface morphology significantly. An optimized Ti/Al/Ta/Au ohmic contact including a 40-nm thick Ta barrier layer and a 50-nm thick SiNx encapsulation layer is preferred when compared with the other conventional ohmic contact stacks as it produces a low contact resistance of around 7.27 × 10-7 Ω·cm2 and an ultra-low nanoscale surface morphology with a root mean square deviation of around 10 nm. Results from the proposed study play an important role in obtaining excellent ohmic contact formation in the fabrication of AlGaN/GaN HEMTs.

Measuring contact area in a sliding human finger-pad contact.

Science.gov (United States)

Liu, X; Carré, M J; Zhang, Q; Lu, Z; Matcher, S J; Lewis, R

2018-02-01

The work outlined in this paper was aimed at achieving further understanding of skin frictional behaviour by investigating the contact area between human finger-pads and flat surfaces. Both the static and the dynamic contact areas (in macro- and micro-scales) were measured using various techniques, including ink printing, optical coherence tomography (OCT) and Digital Image Correlation (DIC). In the studies of the static measurements using ink printing, the experimental results showed that the apparent and the real contact area increased with load following a piecewise linear correlation function for a finger-pad in contact with paper sheets. Comparisons indicated that the OCT method is a reliable and effective method to investigate the real contact area of a finger-pad and allow micro-scale analysis. The apparent contact area (from the DIC measurements) was found to reduce with time in the transition from the static phase to the dynamic phase while the real area of contact (from OCT) increased. The results from this study enable the interaction between finger-pads and contact object surface to be better analysed, and hence improve the understanding of skin friction. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

A Simple Approach for Local Contact Angle Determination on a Heterogeneous Surface

KAUST Repository

Wu, Jinbo

2011-05-17

We report a simple approach for measuring the local contact angle of liquids on a heterogeneous surface consisting of intersected hydrophobic and hydrophilic patch arrays, specifically by employing confocal microscopy and the addition of a very low concentration of Rhodamine-B (RB) (2 × 10 -7 mol/L). Interestingly, RB at that concentration was found to be aggregated at the air-liquid and solid (hydrophobic patch only)-liquid interfaces, which helps us to distinguish the liquid and solid interfaces as well as hydrophobic and hydrophilic patches by their corresponding fluorescent intensities. From the measured local contact angles, the line tension can be easily derived and the value is found to be (-2.06-1.53) × 10-6 J/m. © 2011 American Chemical Society.

On the nature of surface roughness with application to contact mechanics, sealing, rubber friction and adhesion

International Nuclear Information System (INIS)

Persson, B N J; Albohr, O; Tartaglino, U; Volokitin, A I; Tosatti, E

2005-01-01

Surface roughness has a huge impact on many important phenomena. The most important property of rough surfaces is the surface roughness power spectrum C(q). We present surface roughness power spectra of many surfaces of practical importance, obtained from the surface height profile measured using optical methods and the atomic force microscope. We show how the power spectrum determines the contact area between two solids. We also present applications to sealing, rubber friction and adhesion for rough surfaces, where the power spectrum enters as an important input. (topical review)

In vitro genotoxicity assessment of MTES, GPTES and TEOS, three precursors intended for use in food contact coatings.

Science.gov (United States)

Lionti, Krystelle; Séverin, Isabelle; Dahbi, Laurence; Toury, Bérangère; Chagnon, Marie-Christine

2014-03-01

Organoalkoxysilanes are precursors that are used increasingly in the synthesis of food contact coatings. To comply with the EU regulation, their potential toxicity must be assessed, and very little information is known. The genotoxicity of three common precursors was studied, namely, tetraethylorthosilicate (TEOS), methyltriethoxysilane (MTES) and 3-glycidyloxypropyltriethoxysilane (GPTES). By the Ames test, MTES and TEOS were not mutagenic for bacteria. A significant positive response was observed with GPTES in the TA100 and TA1535 strains. The mutagenic effect was more pronounced in the presence of the exogenous metabolic activation system with an increase of the induction factor (ten-fold higher for the TA1535 strain). In the micronucleus assay performed with a human hepatoma cell line (HepG2 cells), GPTES gave negative results even in the presence of an exogenous activation system. To ascertain the possibility of using this precursor in food contact material, its migration must be monitored according to the coating formulation because migration might result in hazardous human exposure. Copyright © 2014. Published by Elsevier Ltd.

A novel in-vitro method for assessing contact lens surface dewetting: Non-invasive keratograph dry-up time (NIK-DUT).

Science.gov (United States)

Marx, Sebastian; Sickenberger, Wolfgang

2017-12-01

This study was designed to develop a novel technique called non-invasive keratograph dry-up time (NIK-DUT), which used an adapted corneal topographer, to analyse in-vitro contact lens surface dewetting and the effects of combinations of lenses and lens care solutions on dewetting. Variables were assessed to optimise sensitivity and reproducibility. To validate the method, in-vitro dewetting of silicone hydrogel contact lenses (balafilcon A, comfilcon A, lotrafilcon A, lotrafilcon B and senofilcon A) was tested. All lens types were soaked in OPTI-FREE ® PureMoist ® Multipurpose Disinfecting Solution (OFPM) and Sensitive Eyes ® Saline Solution. The mean NIK-DUT, defined as drying of 25% of the placido ring measurement segments (NIK-DUT_S25), was calculated for each lens/lens solution combination and a visual map constructed representing the time and location of the dry-up event. Optimal conditions for NIK-DUT measurement included mounting onto a glass stage with a surface geometry of r=8.5mm, e=0, and measuring with high intensity red or white illumination. This method detected significant differences in contact lens dewetting with different lens soaking solutions. NIK-DUT_S25 for all lenses was longer when pre-soaked in OFPM versus saline. Visual analysis showed that dewetting of contact lenses was not uniform across surfaces and differed between test solutions. NIK-DUT is suitable for detecting differences in dewetting among various contact lenses and lens-care combinations. NIK-DUT can quantify the dewetting of large areas of lens surfaces with little subjective influence. Lens care solutions containing surface-active wetting agents were found to delay surface dewetting of silicone hydrogel lenses. Copyright © 2017. Published by Elsevier Ltd.

High-precision drop shape analysis on inclining flat surfaces: introduction and comparison of this special method with commercial contact angle analysis.

Science.gov (United States)

Schmitt, Michael; Heib, Florian

2013-10-07

Drop shape analysis is one of the most important and frequently used methods to characterise surfaces in the scientific and industrial communities. An especially large number of studies, which use contact angle measurements to analyse surfaces, are characterised by incorrect or misdirected conclusions such as the determination of surface energies from poorly performed contact angle determinations. In particular, the characterisation of surfaces, which leads to correlations between the contact angle and other effects, must be critically validated for some publications. A large number of works exist concerning the theoretical and thermodynamic aspects of two- and tri-phase boundaries. The linkage between theory and experiment is generally performed by an axisymmetric drop shape analysis, that is, simulations of the theoretical drop profiles by numerical integration onto a number of points of the drop meniscus (approximately 20). These methods work very well for axisymmetric profiles such as those obtained by pendant drop measurements, but in the case of a sessile drop onto real surfaces, additional unknown and misunderstood effects on the dependence of the surface must be considered. We present a special experimental and practical investigation as another way to transition from experiment to theory. This procedure was developed to be especially sensitive to small variations in the dependence of the dynamic contact angle on the surface; as a result, this procedure will allow the properties of the surface to be monitored with a higher precession and sensitivity. In this context, water drops onto a 111 silicon wafer are dynamically measured by video recording and by inclining the surface, which results in a sequence of non-axisymmetric drops. The drop profiles are analysed by commercial software and by the developed and presented high-precision drop shape analysis. In addition to the enhanced sensitivity for contact angle determination, this analysis technique, in

A Facile All-Solution-Processed Surface with High Water Contact Angle and High Water Adhesive Force.

Science.gov (United States)

Chen, Mei; Hu, Wei; Liang, Xiao; Zou, Cheng; Li, Fasheng; Zhang, Lanying; Chen, Feiwu; Yang, Huai

2017-07-12

A series of sticky superhydrophobicity surfaces with high water contact angle and high water adhesive force is facilely prepared via an all-solution-processed method based on polymerization-induced phase separation between liquid crystals (LCs) and epoxy resin, which produces layers of epoxy microspheres (EMSs) with nanofolds on the surface of a substrate. The morphologies and size distributions of EMSs are confirmed by scanning electron microscopy. Results reveal that the obtained EMS coated-surface exhibits high apparent contact angle of 152.0° and high water adhesive force up to 117.6 μN. By varying the composition of the sample or preparing conditions, the sizes of the produced EMSs can be artificially regulated and, thus, control the wetting properties and water adhesive behaviors. Also, the sticky superhydrophobic surface exhibits excellent chemical stability, as well as long-term durability. Water droplet transportation experiments further prove that the as-made surface can be effectively used as a mechanical hand for water transportation applications. Based on this, it is believed that the simple method proposed in this paper will pave a new way for producing a sticky superhydrophobic surface and obtain a wide range of use.

Inspection Method for Contact Condition of Soil on the Surface of Underground Pipe Utilizing Resonance of Transverse Lamb Wave

Science.gov (United States)

Tanigawa, Hiroshi; Seno, Hiroaki; Watanabe, Yoshiaki; Nakajima, Koshiro

1998-05-01

A nondestructive inspection method to estimate the contact condition of soil on the surface of an underground pipe, utilizing the resonance of a transverse Lamb wave circulating along the pipe wall is proposed.The Q factor of the resonance is considered and measured under some contact conditions by sweeping the vibrating frequency in a 150-mm-inner diameter Fiberglass Reinforced Plastic Mortar (FRPM) pipe. It is confirmed that the Q factor shows a clear response to the change in the contact conditions. For example, the Q factor is 8.4 when the pipe is in ideal contact with the soil plane and goes up to 19.2 when a 100-mm-diameter void is located at the contact surface of the soil.The spatial resolution of the proposed inspection method is also measured by moving the sensing point along the direction of laying the length of the pipe into a 85-mm-diameter void. The resolution of the proposed method is estimated at about 50 mm.

Contact Angle Goniometer

Data.gov (United States)

Federal Laboratory Consortium — Description:The FTA32 goniometer provides video-based contact angle and surface tension measurement. Contact angles are measured by fitting a mathematical expression...

Migration of fluorochemical paper additives from food-contact paper into foods and food simulants.

Science.gov (United States)

Begley, T H; Hsu, W; Noonan, G; Diachenko, G

2008-03-01

Fluorochemical-treated paper was tested to determine the amount of migration that occurs into foods and food-simulating liquids and the characteristics of the migration. Migration characteristics of fluorochemicals from paper were examined in Miglyol, butter, water, vinegar, water-ethanol solutions, emulsions and pure oil containing small amounts of emulsifiers. Additionally, microwave popcorn and chocolate spread were used to investigate migration. Results indicate that fluorochemicals paper additives do migrate to food during actual package use. For example, we found that microwave popcorn contained 3.2 fluorochemical mg kg(-1) popcorn after popping and butter contained 0.1 mg kg(-1) after 40 days at 4 degrees C. Tests also indicate that common food-simulating liquids for migration testing and package material evaluation might not provide an accurate indication of the amount of fluorochemical that actually migrates to food. Tests show that oil containing small amounts of an emulsifier can significantly enhance migration of a fluorochemical from paper.

Bacteriophages and Their Role in Food Safety

Directory of Open Access Journals (Sweden)

Sanna M. Sillankorva

2012-01-01

Full Text Available The interest for natural antimicrobial compounds has increased due to alterations in consumer positions towards the use of chemical preservatives in foodstuff and food processing surfaces. Bacteriophages fit in the class of natural antimicrobial and their effectiveness in controlling bacterial pathogens in agro-food industry has led to the development of different phage products already approved by USFDA and USDA. The majority of these products are to be used in farm animals or animal products such as carcasses, meats and also in agricultural and horticultural products. Treatment with specific phages in the food industry can prevent the decay of products and the spread of bacterial diseases and ultimately promote safe environments in animal and plant food production, processing, and handling. This is an overview of recent work carried out with phages as tools to promote food safety, starting with a general introduction describing the prevalence of foodborne pathogens and bacteriophages and a more detailed discussion on the use of phage therapy to prevent and treat experimentally induced infections of animals against the most common foodborne pathogens, the use of phages as biocontrol agents in foods, and also their use as biosanitizers of food contact surfaces.

Tribological behavior of micro/nano-patterned surfaces in contact with AFM colloidal probe

International Nuclear Information System (INIS)

Zhang Xiaoliang; Wang Xiu; Kong Wen; Yi Gewen; Jia Junhong

2011-01-01

In effort to investigate the influence of the micro/nano-patterning or surface texturing on the nanotribological properties of patterned surfaces, the patterned polydimethylsiloxane (PDMS) surfaces with pillars were fabricated by replica molding technique. The surface morphologies of patterned PDMS surfaces with varying pillar sizes and spacing between pillars were characterized by atomic force microscope (AFM) and scanning electron microscope (SEM). The AFM/FFM was used to acquire the friction force images of micro/nano-patterned surfaces using a colloidal probe. A difference in friction force produced a contrast on the friction force images when the colloidal probe slid over different regions of the patterned polymer surfaces. The average friction force of patterned surface was related to the spacing between the pillars and their size. It decreased with the decreasing of spacing between the pillars and the increasing of pillar size. A reduction in friction force was attributed to the reduced area of contact between patterned surface and colloidal probe. Additionally, the average friction force increased with increasing applied load and sliding velocity.

Tribological behavior of micro/nano-patterned surfaces in contact with AFM colloidal probe

Energy Technology Data Exchange (ETDEWEB)

Zhang Xiaoliang; Wang Xiu; Kong Wen [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Graduate University of Chinese Academy of Sciences, Beijing 100049 (China); Yi Gewen [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Jia Junhong, E-mail: jhjia@licp.cas.cn [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)

2011-10-15

In effort to investigate the influence of the micro/nano-patterning or surface texturing on the nanotribological properties of patterned surfaces, the patterned polydimethylsiloxane (PDMS) surfaces with pillars were fabricated by replica molding technique. The surface morphologies of patterned PDMS surfaces with varying pillar sizes and spacing between pillars were characterized by atomic force microscope (AFM) and scanning electron microscope (SEM). The AFM/FFM was used to acquire the friction force images of micro/nano-patterned surfaces using a colloidal probe. A difference in friction force produced a contrast on the friction force images when the colloidal probe slid over different regions of the patterned polymer surfaces. The average friction force of patterned surface was related to the spacing between the pillars and their size. It decreased with the decreasing of spacing between the pillars and the increasing of pillar size. A reduction in friction force was attributed to the reduced area of contact between patterned surface and colloidal probe. Additionally, the average friction force increased with increasing applied load and sliding velocity.

Effect of Spreading Time on Contact Angle of Nanofluid on the Surface of Stainless Steel AISI 316 and Zircalloy 4

Science.gov (United States)

Prajitno, D. H.; Trisnawan, V.; Syarif, D. G.

2017-05-01

The solid surface tension plays an important role in the heat and mass transfer system for heat exchanger equipment. In the nuclear power plant industry, the stainless steel AISI 316 and Zircalloy 4 have been used for long time as structure materials. The purpose of the experimental is to study solid state surface tension behavior by measure contact angle Nano fluid contain nano particle alumina on metal surface of stainless steel AISI 316 and Zircalloy 4 by sessile drop method. The experiment is to measure the static contact angle and drop nano fluid contains nano particle alumina on stainless steel 316 and zircalloy 4 with different spreading time from 1 to 30 minute. It was observed that stainless steel 316 and zircalloy 4 lose their hydrophobic properties with increasing elapsed time during drop of nano fluid on the surface of alloy. As a result the contact angle of nano fluid on surface of metal is decrease with increasing elapsed time. While the magnitude diameter of drop nano fluid and wetting surface is increase with increasing elapsed time on the surface of the stainless steel SS 316 and Zircalloy 4.

Point contact tunneling spectroscopy apparatus for large scale mapping of surface superconducting properties

Energy Technology Data Exchange (ETDEWEB)

Groll, Nickolas; Pellin, Michael J. [Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439 (United States); Zasadzinksi, John F. [Illinois Institute of Technology, Chicago, Illinois 60616 (United States); Proslier, Thomas, E-mail: prolier@anl.gov [Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439 (United States); High Energy Physics Division, Argonne National Laboratory, Lemont, Illinois 60439 (United States)

2015-09-15

We describe the design and testing of a point contact tunneling spectroscopy device that can measure material surface superconducting properties (i.e., the superconducting gap Δ and the critical temperature T{sub C}) and density of states over large surface areas with size up to mm{sup 2}. The tip lateral (X,Y) motion, mounted on a (X,Y,Z) piezo-stage, was calibrated on a patterned substrate consisting of Nb lines sputtered on a gold film using both normal (Al) and superconducting (PbSn) tips at 1.5 K. The tip vertical (Z) motion control enables some adjustment of the tip-sample junction resistance that can be measured over 7 orders of magnitudes from a quasi-ohmic regime (few hundred Ω) to the tunnel regime (from tens of kΩ up to few GΩ). The low noise electronic and LabVIEW program interface are also presented. The point contact regime and the large-scale motion capabilities are of particular interest for mapping and testing the superconducting properties of macroscopic scale superconductor-based devices.

Soft electron processor for surface sterilization of food material

International Nuclear Information System (INIS)

Baba, Takashi; Kaneko, Hiromi; Taniguchi, Shuichi

2004-01-01

As frozen or chilled foods have become popular nowadays, it has become very important to provide raw materials with lower level microbial contamination to food processing companies. Consequently, the sterilization of food material is one of the major topics for food processing. Dried materials like grains, beans and spices, etc., are not typically deeply contaminated by microorganisms, which reside on the surfaces of materials, so it is very useful to take low energetic, lower than 300 keV, electrons with small penetration power (Soft-Electrons), as a sterilization method for such materials. Soft-Electrons is researched and named by Dr. Hayashi et al. This is a non-thermal method, so one can keep foods hygienic without serious deterioration. It is also a physical method, so is free from residues of chemicals in foods. Recently, Nissin-High Voltage Co., Ltd. have developed and manufactured equipment for commercial use of Soft-Electrons (Soft Electron Processor), which can process 500 kg/h of grains. This report introduces the Soft Electron Processor and shows the results of sterilization of wheat and brown rice by the equipment

PREFACE: Non-contact AFM Non-contact AFM

Science.gov (United States)

Giessibl, Franz J.; Morita, Seizo

2012-02-01

This special issue is focussed on high resolution non-contact atomic force microscopy (AFM). Non-contact atomic force microscopy was established approximately 15 years ago as a tool to image conducting and insulating surfaces with atomic resolution. Since 1998, an annual international conference has taken place, and although the proceedings of these conferences are a useful source of information, several key developments warrant devoting a special issue to this subject. In the theoretic field, the possibility of supplementing established techniques such as scanning tunneling microscopy (STM) and Kelvin probe microscopy with atomically resolved force micrsoscopy poses many challenges in the calculation of contrast and contrast reversal. The surface science of insulators, self-assembled monolayers and adsorbates on insulators is a fruitful field for the application of non-contact AFM: several articles in this issue are devoted to these subjects. Atomic imaging and manipulation have been pioneered using STM, but because AFM allows the measurement of forces, AFM has had a profound impact in this field as well. Three-dimensional force spectroscopy has allowed many important insights into surface science. In this issue a combined 3D tunneling and force microscopy is introduced. Non-contact AFM typically uses frequency modulation to measure force gradients and was initially used mainly in a vacuum. As can be seen in this issue, frequency modulation is now also used in ambient conditions, allowing better spatial and force resolution. We thank all of the contributors for their time and efforts in making this special issue possible. We are also very grateful to the staff of IOP Publishing for handling the administrative aspects and for steering the refereeing process. Non-contact AFM contents Relation between the chemical force and the tunnelling current in atomic point contacts: a simple model Pavel Jelínek, Martin Ondrácek and Fernando Flores Theoretical simulation of

Influence of day and night wear on surface properties of silicone hydrogel contact lenses and bacterial adhesion.

Science.gov (United States)

Vermeltfoort, Pit B J; Rustema-Abbing, Minie; de Vries, Joop; Bruinsma, Gerda M; Busscher, Henk J; van der Linden, Matthijs L; Hooymans, Johanna M M; van der Mei, Henny C

2006-06-01

The aim of this study was to determine the effect of continuous wear on physicochemical surface properties of silicone hydrogel (S-H) lenses and their susceptibility to bacterial adhesion. In this study, volunteers wore 2 pairs of either "lotrafilcon A" or "balafilcon A" S-H contact lenses. The first pair was worn continuously for a week and the second pair for 4 weeks. One lens of each pair was used for surface characterization and the other one for bacterial adhesion experiments. Lens surfaces were characterized by examination of their wettability, roughness, elemental composition, and proteins attached to their surfaces. Adhesion of Staphylococcus aureus 835 and Pseudomonas aeruginosa #3 to a lens was studied using a parallel plate flow chamber. Before use, the lotrafilcon A lens was rougher than the balafilcon A lens and had a lower water contact angle and a higher affinity for S. aureus 835. After wear, both lens types had similar water contact angles, whereas the differences in elemental surface composition decreased as well. S. aureus 835 adhered in higher numbers to worn balafilcon A lenses, whereas the opposite was seen for P. aeruginosa #3. The initial deposition rates of both bacterial strains to lotrafilcon A lenses decreased by wearing and were found to correlate significant (P lenses. In this study, the differences in surface properties between 2 types of S-H lenses were found to change after 1 week of continuous wear. Generally, bacteria adhered in lower numbers and less tenaciously to worn lenses, except S. aureus 835, adhering in higher numbers to worn balafilcon A lenses.

Non-Contact Surface Roughness Measurement by Implementation of a Spatial Light Modulator

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Laura Aulbach

2017-03-01

Full Text Available The surface structure, especially the roughness, has a significant influence on numerous parameters, such as friction and wear, and therefore estimates the quality of technical systems. In the last decades, a broad variety of surface roughness measurement methods were developed. A destructive measurement procedure or the lack of feasibility of online monitoring are the crucial drawbacks of most of these methods. This article proposes a new non-contact method for measuring the surface roughness that is straightforward to implement and easy to extend to online monitoring processes. The key element is a liquid-crystal-based spatial light modulator, integrated in an interferometric setup. By varying the imprinted phase of the modulator, a correlation between the imprinted phase and the fringe visibility of an interferogram is measured, and the surface roughness can be derived. This paper presents the theoretical approach of the method and first simulation and experimental results for a set of surface roughnesses. The experimental results are compared with values obtained by an atomic force microscope and a stylus profiler.

Listeria monocytogenes contamination of the environment and surfaces of the equipment in the meat processing facilities in republic of Macedonia

Directory of Open Access Journals (Sweden)

Dean Jankuloski

2007-11-01

Full Text Available Listeria monocytogenes contamination of the environment and surfaces of the equipment was examined in seven meat processing facilities. Up to date prevalence of this foodborn pathogen in meat processing facilities facilities in Republic of Macedonia was unknown. Biofilms are composed from food spoilage microorganisms and food born pathogens. They are located on the surfaces of the equipment that come in contact with food and in facilities environment. Microorganisms in biofilm presenting micro eco system and are source of dissemination and contamination of food born pathogens in final meat products. During the preparation of this study we have covered a 7 meat processing facilities and we took a total of 39 swabs from surfaces that come in direct or indirect contact with food. Listeria monocytogenes was discovered in 10 (25,64% swabs (locations. Prevalence of other Listeria spp. compared with total number of taken samples was 15 (38,46% Listeria innocua, 3 (7,69% Listeria welshimeri and 1 (2,65% isolate Listeria seeligeri.

Ocular surface and tear film status among contact lens wearers and non-wearers who use VDT at work: comparing three different lens types.

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Tauste, Ana; Ronda, Elena; Baste, Valborg; Bråtveit, Magne; Moen, Bente E; Seguí Crespo, María-Del-Mar

2018-04-01

To analyze differences in the ocular surface appearance and tear film status of contact lens wearers and non-wearers in a group of visual display terminals (VDT) workers and additionally to assess differences between lens materials. Cross-sectional study of 236 office workers, of whom 92 were contact lens wearers. Workers provided information on their contact lenses (conventional hydrogel, silicone hydrogel or rigid gas permeable lenses) and exposure to VDT at work. Ocular surface and tear film status were determined by the presence of bulbar, limbal and lid redness, lid roughness and corneal staining type, and by Schirmer's and tear break-up time tests (TBUT). A generalized linear model was used to calculate the crude (cRR) and age- and sex-adjusted (aRR) relative risk to measure the association between ocular surface and tear film abnormalities and contact lens use and type. The aRR of ocular surface abnormalities was higher in contact lens wearers compared to non-wearers: bulbar redness (aRR 1.69; 95% CI 1.25-2.30), limbal redness (aRR 2.87; 1.88-4.37), lid redness (aRR 2.53; 1.35-4.73) and lid roughness (aRR 7.03; 1.31-37.82). VDT exposure > 4 h/day increased wearers' risk of limbal and lid redness. Conventional hydrogel wearers had the highest risk of ocular surface abnormalities, followed by silicone hydrogel wearers. Both contact and non-contact lens wearers had a high prevalence of altered TBUT (77.3 and 75.7% respectively) and Schirmer (51.8 and 41.3%). Regular contact lens use during VDT exposure at work increases risk of bulbar, limbal and lid redness, and lid roughness, especially in soft contact lens wearers. The high prevalence of altered TBUT and Schirmer's results in all participants suggests that VDT use greatly affects tear film characteristics.

An observational study of frequency of provider hand contacts in child care facilities in North Carolina and South Carolina.

Science.gov (United States)

Fraser, Angela; Wohlgenant, Kelly; Cates, Sheryl; Chen, Xi; Jaykus, Lee-Ann; Li, You; Chapman, Benjamin

2015-02-01

Children enrolled in child care are 2.3-3.5 times more likely to experience acute gastrointestinal illness than children cared for in their own homes. The purpose of this study was to determine the frequency surfaces were touched by child care providers to identify surfaces that should be cleaned and sanitized. Observation data from a convenience sample of 37 child care facilities in North Carolina and South Carolina were analyzed. Trained data collectors used iPods (Apple, Cupertino, CA) to record hand touch events of 1 child care provider for 45 minutes in up to 2 classrooms in each facility. Across the 37 facilities, 10,134 hand contacts were observed in 51 classrooms. Most (4,536) were contacts with porous surfaces, with an average of 88.9 events per classroom observation. The most frequently touched porous surface was children's clothing. The most frequently touched nonporous surface was food contact surfaces (18.6 contacts/observation). Surfaces commonly identified as high-touch surfaces (ie, light switches, handrails, doorknobs) were touched the least. General cleaning and sanitizing guidelines should include detailed procedures for cleaning and sanitizing high-touch surfaces (ie, clothes, furniture, soft toys). Guidelines are available for nonporous surfaces but not for porous surfaces (eg, clothing, carpeting). Additional research is needed to inform the development of evidence-based practices to effectively treat porous surfaces. Copyright © 2015 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

Resonant characteristics and sensitivity dependency on the contact surface in QCM-micropillar-based system of coupled resonator sensors

International Nuclear Information System (INIS)

Kashan, M A M; Kalavally, V; Ramakrishnan, N; Lee, H W

2016-01-01

We report the characteristics and sensitivity dependence over the contact surface in coupled resonating sensors (CRSs) made of high aspect ratio resonant micropillars attached to a quartz crystal microbalance (QCM). Through experiments and simulation, we observed that when the pillars of resonant heights were placed in maximum displacement regions the resonance frequency of the QCM increased following the coupled resonance characteristics, as the pillar offered elastic loading to the QCM surface. However, the same pillars when placed in relatively lower displacement regions, in spite of their resonant dimension, offered inertial loading and resulted in a decrease in QCM resonance frequency, as the displacement amplitude was insufficient to couple the vibrations from the QCM to the pillars. Accordingly, we discovered that the coupled resonance characteristics not only depend on the resonant structure dimensions but also on the contact regions in the acoustic device. Further analysis revealed that acoustic pressure at the contact surface also influences the resonance frequency characteristics and sensitivity of the CRS. To demonstrate the significance of the present finding for sensing applications, humidity sensing is considered as the example measurand. When a sensing medium made of resonant SU-8 pillars was placed in a maximum displacement region on a QCM surface, the sensitivity increased by 14 times in comparison to a resonant sensing medium placed in a lower displacement region of a QCM surface. (paper)

Poly(styrene-co-butadiene) random copolymer thin films and nanostructures on a mica surface: morphology and contact angles of nanodroplets.

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McClements, Jake; Buffone, Cosimo; Shaver, Michael P; Sefiane, Khellil; Koutsos, Vasileios

2017-09-20

The self-assembly of poly(styrene-co-butadiene) random copolymers on mica surfaces was studied by varying solution concentrations and polymer molecular weights. Toluene solutions of the poly(styrene-co-butadiene) samples were spin coated onto a mica surface and the resulting polymer morphology was investigated by atomic force microscopy. At higher concentrations, thin films formed with varying thicknesses; some dewetting was observed which depended on the molecular weight. Total dewetting did not occur despite the polymer's low glass transition temperature. Instead, partial dewetting was observed suggesting that the polymer was in a metastable equilibrium state. At lower concentrations, spherical cap shaped nanodroplets formed with varying sizes from single polymer chains to aggregates containing millions of chains. As the molecular weight was increased, fewer aggregates were observed on the surface, albeit with larger sizes resulting from increased solution viscosities and more chain entanglements at higher molecular weights. The contact angles of the nanodroplets were shown to be size dependent. A minimum contact angle occurs for droplets with radii of 100-250 nm at each molecular weight. Droplets smaller than 100 nm showed a sharp increase in contact angle; attributed to an increase in the elastic modulus of the droplets, in addition, to a positive line tension value. Droplets larger than 250 nm also showed an increased contact angle due to surface heterogeneities which cannot be avoided for larger droplets. This increase in contact angle plateaus as the droplet size reaches the macroscopic scale.

Receding and advancing (CO_2 + brine + quartz) contact angles as a function of pressure, temperature, surface roughness, salt type and salinity

International Nuclear Information System (INIS)

Al-Yaseri, Ahmed Z.; Lebedev, Maxim; Barifcani, Ahmed; Iglauer, Stefan

2016-01-01

Highlights: • (Water + CO_2) contact angle on quartz increases substantially with pressure and salinity. • (Water + CO_2) contact angle on quartz increases slightly with temperature. • Surface roughness has only a minor influence on (water + CO_2 + quartz) contact angles. - Abstract: The wetting characteristics of CO_2 in rock are of vital importance in carbon geo-storage as they determine fluid dynamics and storage capacities. However, the current literature data has a high uncertainty, which translates into uncertain predictions in terms of containment security and economic project feasibility. We thus measured contact angles for the CO_2/water/quartz system at relevant reservoir conditions, and analysed the effects of pressure (0.1 to 20) MPa, temperature (296 to 343) K, surface roughness (56 to 1300) nm, salt type (NaCl, CaCl_2, and MgCl_2) and brine salinities (0 to 35) wt%. Water contact angles decreased with surface roughness, but increased with pressure, temperature, and brine salinity. Overall the contact angles were significantly increased at storage conditions (∼50°) when compared to ambient conditions (always 0°). Consequently quartz is weakly water-wet (not completely water-wet) at storage conditions, and structural and residual trapping capacities are reduced accordingly.

Effects of laser shock peening with contacting foil on micro laser texturing surface of Ti6Al4V

Science.gov (United States)

Dai, Fengze; Zhang, Zidong; Ren, Xudong; Lu, Jinzhong; Huang, Shu

2018-02-01

Ti6Al4V samples with micro-dimple arrays were subjected to laser shock peening in contact with foil (HCLSP). The surface roughness, micro-hardness, the residual stress distribution and the surface morphology of the micro-dimple arrays were studied to evaluate the effects of HCLSP. Moreover, the surface topography of the foils in contact was also analyzed. The gap existence between the foil and the to-be treated surface led the mechanism of HCLSP to be different compared to regular laser shock peening. The surface roughness reduction, the work-hardening effects, the compressive residual stress and the micro crack enclosure were achieved. A simplified ball-hitting-surface model was utilized to analyze the HCLSP impact. The model could well explain the experimental results. When treated by the HCLSP with H62 foil at the laser power density of 4.24 GW/cm2, the Ti6Al4V samples with micro-dimple arrays exhibit well surface topography and mechanical performance.

On a free-surface problem with moving contact line: From variational principles to stable numerical approximations

Science.gov (United States)

Fumagalli, Ivan; Parolini, Nicola; Verani, Marco

2018-02-01

We analyze a free-surface problem described by time-dependent Navier-Stokes equations. Surface tension, capillary effects and wall friction are taken into account in the evolution of the system, influencing the motion of the contact line - where the free surface hits the wall - and of the dynamics of the contact angle. The differential equations governing the phenomenon are first derived from the variational principle of minimum reduced dissipation, and then discretized by means of the ALE approach. The numerical properties of the resulting scheme are investigated, drawing a parallel with the physical properties holding at the continuous level. Some instability issues are addressed in detail, in the case of an explicit treatment of the geometry, and novel additional terms are introduced in the discrete formulation in order to damp the instabilities. Numerical tests assess the suitability of the approach, the influence of the parameters, and the effectiveness of the new stabilizing terms.

Aberration changes of the corneal anterior surface following discontinued use of rigid gas permeable contact lenses.

Science.gov (United States)

Yu, Qing; Wu, Jiang-Xiu; Zhang, He-Ning; Ye, Sheng; Dong, Shi-Qi; Zhang, Chen-Hao

2013-01-01

To record aberrations with a corneal topographic device on the anterior surface of the cornea at different time-points prior to wearing and following discontinued use of rigid gas permeable (RGP) contact lenses. The effect of wearing RGP on the anterior surface of the cornea was discussed to provide guidance for clinical refractive error correction. The study objects were 24 eyes from 24 patients. All patients underwent identical examination procedures prior to lens use, as well as afterwards, including slit-lamp examination, non-contact tonometer measurement, computer optometry and corneal curvature measurement, subjective refraction test, and corneal topography analysis. The patients wore contact lenses everyday for 1 month and then discontinued. Corneal topographies were recorded at certain time points of 30 minutes, 1 day, 3, 7 and 14 days following use. Total corneal aberration at each time point following discontinued use of RGP contact lenses was less than the time point prior to use. Detailed results were as follows: root mean square (RMS) (pre)=(1.438±0.328)µm, RMS (30 minutes)=(1.076±0.355)µm, RMS (1 day)=(1.362±0.402)µm, RMS (3 days)=(1.373±0.398)µm, RMS (7 days)=(1.387±0.415)µm, and RMS (14 days)=(1.430±0.423)µm. Results showed that at 30 minutes after discontinued use of RGP contact lenses, almost all 2(nd)- and 3(rd)-order aberrations change. Quadrafoil Z10 and spherical Z12 of the 4(th)-order were also changed. Alterations to Z5, Z6, and Z12 at 1 day after discontinued use were significant differences compared with the time period prior to RGP use: Z5 and Z6 decreased, and Z12 increased slightly. Z5 and Z6 remained decreased at 3 days after discontinued use, but Z9 and Z10 continued to increase and Z12 returned to levels prior to RGP use. At 14 days after discontinued use, all aberrations were not significantly different from the values prior to use. The use RGP contact lenses greatly reduced total aberration of the anterior surface of

Surface potential measurement on contact resistance of amorphous-InGaZnO thin film transistors by Kelvin probe force microscopy

Science.gov (United States)

Han, Zhiheng; Xu, Guangwei; Wang, Wei; Lu, Congyan; Lu, Nianduan; Ji, Zhuoyu; Li, Ling; Liu, Ming

2016-07-01

Contact resistance plays an important role in amorphous InGaZnO (a-IGZO) thin film transistors (TFTs). In this paper, the surface potential distributions along the channel have been measured by using Kelvin probe force microscopy (KPFM) on operating a-IGZO TFTs, and sharp potential drops at the edges of source and drain were observed. The source and drain contact resistances can be extracted by dividing sharp potential drops with the corresponding drain to source current. It is found that the contact resistances could not be neglected compared with the whole channel resistances in the a-IGZO TFT, and the contact resistances decrease remarkably with increasing gate biased voltage. Our results suggest that the contact resistances can be controlled by tuning the gate biased voltage. Moreover, a transition from gradual channel approximation to space charge region was observed through the surface potential map directly when TFT operating from linear regime to saturation regime.

Efficacy of a Food-grade Mixture of Volatile Compounds to Reduce Salmonella Levels on Food Contact Surfaces

Science.gov (United States)

Introduction: Volatile organic compounds (VOCs) released from an endophytic fungus, Muscodor crispans, have been shown to have antimicrobial activity against many fungal and bacterial species. These VOCs have been synthesized into a commercial mixture called “B-23”, which may be a useful surface san...

Food nanotechnology: water is the key to lowering the energy density of processed foods.

Science.gov (United States)

Robson, A A

2011-01-01

It is crucial that emergent technologies create foods that help prevent the causal mechanisms of the diet induced disease epidemic. Food nanotechnology could create modem convenience foods that mimic and improve on the nutritional value of the most nutritious cooked wild foods for humans. Structuring a solid processed food similar to a celery stalk using self-assembled, water-filled, edible nanocells or nanotubes would substantially lower its energy density (Food technologists could harness the natural turgor force to produce a firm chocolate bar, biscuit or breakfast cereal with a good bite, without altering the appearance or taste of the product. Water carries flavour with few calories, and taste sensation per mouthful could be improved by processing food on the nanoscale to increase the surface area that is in contact with taste and smell receptors. The bioavailable nutrient content (including cofactors) of processed foods could be increased by existing bioactive nanoencapsulation. This would allow people to continue to consume modern convenience food on a mass scale, while simultaneously and significantly increasing nutrient intake and reducing energy intake per day. Thus, helping to reduce mental ill health, obesity and other postprandial insults.

Surface Tension Flows inside Surfactant-Added Poly(dimethylsiloxane Microstructures with Velocity-Dependent Contact Angles

Directory of Open Access Journals (Sweden)

Jyh Jian Chen

2014-03-01

Full Text Available Filling of liquid samples is realized in a microfluidic device with applications including analytical systems, biomedical devices, and systems for fundamental research. The filling of a disk-shaped polydimethylsiloxane (PDMS microchamber by liquid is analyzed with reference to microstructures with inlets and outlets. The microstructures are fabricated using a PDMS molding process with an SU-8 mold. During the filling, the motion of the gas-liquid interface is determined by the competition among inertia, adhesion, and surface tension. A single ramp model with velocity-dependent contact angles is implemented for the accurate calculation of surface tension forces in a three-dimensional volume-of-fluid based model. The effects of the parameters of this functional form are investigated. The influences of non-dimensional parameters, such as the Reynolds number and the Weber number, both determined by the inlet velocity, on the flow characteristics are also examined. An oxygen-plasma-treated PDMS substrate is utilized, and the microstructure is modified to be hydrophilic. Flow experiments are conducted into both hydrophilic and hydrophobic PDMS microstructures. Under a hydrophobic wall condition, numerical simulations with imposed boundary conditions of static and dynamic contact angles can successfully predict the moving of the meniscus compared with experimental measurements. However, for a hydrophilic wall, accurate agreement between numerical and experimental results is obvious as the dynamic contact angles were implemented.

Contact pin-printing of albumin-fungicide conjugate for silicon nitride-based sensors biofunctionalization: Multi-technique surface analysis for optimum immunoassay performance

Energy Technology Data Exchange (ETDEWEB)

Gajos, Katarzyna, E-mail: katarzyna.gajos@doctoral.uj.edu.pl [M. Smoluchowski Institute of Physics, Jagiellonian University, Łojasiewicza, 11, 30-348 Kraków (Poland); Budkowski, Andrzej [M. Smoluchowski Institute of Physics, Jagiellonian University, Łojasiewicza, 11, 30-348 Kraków (Poland); Tsialla, Zoi; Petrou, Panagiota [Institute of Nuclear & Radiological Sciences & Technology, Energy & Safety, NCSR Demokritos, P. Grigoriou & Neapoleos St., Aghia Paraksevi 15310, Athens (Greece); Awsiuk, Kamil; Dąbczyński, Paweł [M. Smoluchowski Institute of Physics, Jagiellonian University, Łojasiewicza, 11, 30-348 Kraków (Poland); Bernasik, Andrzej [Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Mickiewicza 30, 30-059 Kraków (Poland); Academic Centre for Materials and Nanotechnology, AGH University of Science and Technology, Mickiewicza 30, 30-059 Kraków (Poland); Rysz, Jakub [M. Smoluchowski Institute of Physics, Jagiellonian University, Łojasiewicza, 11, 30-348 Kraków (Poland); Misiakos, Konstantinos; Raptis, Ioannis [Department of Microelectronics, Institute of Nanoscience and Nanotechnology, NCSR Demokritos, P. Grigoriou & Neapoleos St., Aghia Paraksevi 15310, Athens (Greece); Kakabakos, Sotirios [Institute of Nuclear & Radiological Sciences & Technology, Energy & Safety, NCSR Demokritos, P. Grigoriou & Neapoleos St., Aghia Paraksevi 15310, Athens (Greece)

2017-07-15

Highlights: • Contact pin-printing of overlapping probe spots and spotting by hand are compared. • Contact pin-printing favors probe immobilization with two-fold higher surface density. • Incomplete monolayer develops to bilayer as printing solution concentration increases. • Blocking molecules complete probe monolayer but reduce probe bilayer. • Surface immunoreaction increases with probe concentration in printing solution. - Abstract: Mass fabrication of integrated biosensors on silicon chips is facilitated by contact pin-printing, applied for biofunctionalization of individual Si{sub 3}N{sub 4}-based transducers at wafer-scale. To optimize the biofunctionalization for immunochemical (competitive) detection of fungicide thiabendazole (TBZ), Si{sub 3}N{sub 4} surfaces are modified with (3-aminopropyl)triethoxysilane and examined after: immobilization of BSA-TBZ conjugate (probe) from solutions with different concentration, blocking with bovine serum albumin (BSA), and immunoreaction with a mouse monoclonal antibody against TBZ. Nanostructure, surface density, probe composition and coverage uniformity of protein layers are evaluated with Atomic Force Microscopy, Spectroscopic Ellipsometry, Time-of-Flight Secondary Ion Mass Spectrometry and X-ray Photoelectron Spectroscopy. Contact pin-printing of overlapping probe spots is compared with hand spotted areas. Contact pin-printing resulted in two-fold increase of immobilized probe surface density as compared to hand spotting. Regarding BSA-TBZ immobilization, an incomplete monolayer develops into a bilayer as the concentration of BSA-TBZ molecules in the printing solution increases from 25 to 100 μg/mL. Upon blocking, however, a complete protein monolayer is formed for all the BSA-TBZ concentrations used. Free surface sites are filled with BSA for low surface coverage with BSA-TBZ, whereas loosely bound BSA-TBZ molecules are removed from the BSA-TBZ bilayer. As a consequence immunoreaction efficiency

Impact of recess etching and surface treatments on ohmic contacts regrown by molecular-beam epitaxy for AlGaN/GaN high electron mobility transistors

Energy Technology Data Exchange (ETDEWEB)

Joglekar, S.; Azize, M.; Palacios, T. [Microsystems Technology Laboratories, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States); Beeler, M.; Monroy, E. [Université Grenoble-Alpes, 38000 Grenoble (France); CEA Grenoble, INAC-PHELIQS, 38000 Grenoble (France)

2016-07-25

Ohmic contacts fabricated by regrowth of n{sup +} GaN are favorable alternatives to metal-stack-based alloyed contacts in GaN-based high electron mobility transistors. In this paper, the influence of reactive ion dry etching prior to regrowth on the contact resistance in AlGaN/GaN devices is discussed. We demonstrate that the dry etch conditions modify the surface band bending, dangling bond density, and the sidewall depletion width, which influences the contact resistance of regrown contacts. The impact of chemical surface treatments performed prior to regrowth is also investigated. The sensitivity of the contact resistance to the surface treatments is found to depend upon the dangling bond density of the sidewall facets exposed after dry etching. A theoretical model has been developed in order to explain the observed trends.

Effects of gamma irradiation on food contact polyethylene, polypropylene and polystyrene. Volatiles

International Nuclear Information System (INIS)

Kawamura, Yoko; Sayama, Kayo; Yamada, Takashi

2000-01-01

The effects of gamma irradiation on the generation of volatiles from food contact polyethylene and polypropylene were investigated using head space (HS)/GC/MS. All samples generated volatiles such as acetic acid, propionic acid, butanoic acid, 2,2-dimethylpropionic acid, acetone, 2-butanone, 2-propanol, 2-methyl-2-propanol, hydrocarbons, etc., due to the gamma irradiation. Especially, acetic acid and acetone were formed in greatest amounts. Since these volatiles did not exist before irradiation and their amounts increased with increasing irradiation dose, they should be degradation products from the polymer or additives by irradiation. Polypropylene generated more kinds and larger amounts of volatiles than polyethylene, which showed that polypropylene is more sensitive to irradiation. Polystyrene contained styrene and ethylbenzene as monomers before irradiation and their amounts decreased after irradiation. Polystyrene generated few degradation products during the irradiation. (author)

High-throughput dietary exposure predictions for chemical migrants from food contact substances for use in chemical prioritization.

Science.gov (United States)

Biryol, Derya; Nicolas, Chantel I; Wambaugh, John; Phillips, Katherine; Isaacs, Kristin

2017-11-01

Under the ExpoCast program, United States Environmental Protection Agency (EPA) researchers have developed a high-throughput (HT) framework for estimating aggregate exposures to chemicals from multiple pathways to support rapid prioritization of chemicals. Here, we present methods to estimate HT exposures to chemicals migrating into food from food contact substances (FCS). These methods consisted of combining an empirical model of chemical migration with estimates of daily population food intakes derived from food diaries from the National Health and Nutrition Examination Survey (NHANES). A linear regression model for migration at equilibrium was developed by fitting available migration measurements as a function of temperature, food type (i.e., fatty, aqueous, acidic, alcoholic), initial chemical concentration in the FCS (C 0 ) and chemical properties. The most predictive variables in the resulting model were C 0 , molecular weight, log K ow , and food type (R 2 =0.71, pchemicals identified via publicly-available data sources as being present in polymer FCSs were predicted for 12 food groups (combinations of 3 storage temperatures and food type). The model was parameterized with screening-level estimates of C 0 based on the functional role of chemicals in FCS. By combining these concentrations with daily intakes for food groups derived from NHANES, population ingestion exposures of chemical in mg/kg-bodyweight/day (mg/kg-BW/day) were estimated. Calibrated aggregate exposures were estimated for 1931 chemicals by fitting HT FCS and consumer product exposures to exposures inferred from NHANES biomonitoring (R 2 =0.61, pchemicals), they can provide critical refinement to aggregate exposure predictions used in risk-based chemical priority-setting. Published by Elsevier Ltd.

Occupational protein contact dermatitis.

Science.gov (United States)

Barbaud, Annick; Poreaux, Claire; Penven, Emmanuelle; Waton, Julie

2015-01-01

Occupational contact dermatitis is generally caused by haptens but can also be induced by proteins causing mainly immunological contact urticaria (ICU); chronic hand eczema in the context of protein contact dermatitis (PCD). In a monocentric retrospective study, from our database, only 31 (0.41%) of patients with contact dermatitis had positive skin tests with proteins: 22 had occupational PCD, 3 had non-occupational PCD, 5 occupational ICU and 1 cook had a neutrophilic fixed food eruption (NFFE) due to fish. From these results and analysis of literature, the characteristics of PCD can be summarized as follows. It is a chronic eczematous dermatitis, possibly exacerbated by work, suggestive if associated with inflammatory perionyxix and immediate erythema with pruritis, to be investigated when the patient resumes work after a period of interruption. Prick tests with the suspected protein-containing material are essential, as patch tests have negative results. In case of multisensitisation revealed by prick tests, it is advisable to analyse IgE against recombinant allergens. A history of atopy, found in 56 to 68% of the patients, has to be checked for. Most of the cases are observed among food-handlers but PCD can also be due to non-edible plants, latex, hydrolysed proteins or animal proteins. Occupational exposure to proteins can thus lead to the development of ICU. Reflecting hypersensitivity to very low concentrations of allergens, investigating ICU therefore requires caution and prick tests should be performed with a diluted form of the causative protein-containing product. Causes are food, especially fruit peel, non-edible plants, cosmetic products, latex, animals.

Surface modification of blood-contacting biomaterials by plasma-polymerized superhydrophobic films using hexamethyldisiloxane and tetrafluoromethane as precursors

Energy Technology Data Exchange (ETDEWEB)

Hsiao, Chaio-Ru [Department of Materials Science and Engineering, Feng Chia University, No. 100, Wenhwa Rd., Seatwen District, Taichung City 40724, Taiwan (China); Lin, Cheng-Wei [Department of Dental Technology and Materials Science, Central Taiwan University of Science and Technology, No. 666, Buzih Rd., Beitun District, Taichung City 40601, Taiwan (China); Chou, Chia-Man, E-mail: cmchou@vghtc.gov.tw [Department of Surgery, Taichung Veterans General Hospital, No. 1650, Sec. 4, Taiwan Boulevard, Seatwen District, Taichung City 40705, Taiwan (China); Department of Medicine, National Yang-Ming University, No. 155, Sec. 2, Linong Street, Beitou District, Taipei City 11221, Taiwan (China); Chung, Chi-Jen, E-mail: cjchung@seed.net.tw [Department of Dental Technology and Materials Science, Central Taiwan University of Science and Technology, No. 666, Buzih Rd., Beitun District, Taichung City 40601, Taiwan (China); He, Ju-Liang [Department of Materials Science and Engineering, Feng Chia University, No. 100, Wenhwa Rd., Seatwen District, Taichung City 40724, Taiwan (China)

2015-08-15

Highlights: • Biomaterials modified by nanoparticle-containing plasma polymerized films. • A superhydrophoic film was obtained, and the properties of the coating were examined. • In vitro blood compatibility tests revealed neither platelet adhesion nor fibrinogen adsorption. • Surface modification technology of medical devices: non-cytotoxic and no blood clot formation. - Abstract: This paper proposes a plasma polymerization system that can be used to modify the surface of the widely used biomaterial, polyurethane (PU), by employing low-cost hexamethyldisiloxane (HMDSO) and tetrafluoromethane (CF{sub 4}) as precursors; this system features a pulsed-dc power supply. Plasma-polymerized HMDSO/CF{sub 4} (pp-HC) with coexisting micro- and nanoscale morphology was obtained as a superhydrophobic coating material by controlling the HMDSO/CF{sub 4} (f{sub H}) monomer flow ratio. The developed surface modification technology can be applied to medical devices, because it is non-cytotoxic and has favorable hemocompatibility, and no blood clots form when the device surface direct contacts. Experimental results reveal that the obtained pp-HC films contained SiO{sub x} nanoparticles randomly dispersed on the micron-scale three-dimensional network film surface. The −CF functional group, −CF{sub 2} bonding, and SiO{sub x} were detected on the film surface. The maximal water contact angle of the pp-HC coating was 161.2°, apparently attributable to the synergistic effect of the coexisting micro- and nanoscale surface morphology featuring a low surface-energy layer. The superhydrophobic and antifouling characteristics of the coating were retained even after it was rubbed 20 times with a steel wool tester. Results of in vitro cytotoxicity, fibrinogen adsorption, and platelet adhesion tests revealed favorable myoblast cell proliferation and the virtual absence of fibrinogen adsorption and platelet adhesion on the pp-HC coated specimens. These quantitative findings imply

Mixed Lubricated Line Contacts

NARCIS (Netherlands)

Faraon, I.C.

2005-01-01

The present work deals with friction in mixed lubricated line contacts. Components in systems are becoming smaller and due to, for instance power transmitted, partial contact may occur. In industrial applications, friction between the moving contacting surfaces cannot be avoided, therefore it is

Detection of microbial biofilms on food processing surfaces: hyperspectral fluorescence imaging study

Science.gov (United States)

Jun, Won; Kim, Moon S.; Chao, Kaunglin; Lefcourt, Alan M.; Roberts, Michael S.; McNaughton, James L.

2009-05-01

We used a portable hyperspectral fluorescence imaging system to evaluate biofilm formations on four types of food processing surface materials including stainless steel, polypropylene used for cutting boards, and household counter top materials such as formica and granite. The objective of this investigation was to determine a minimal number of spectral bands suitable to differentiate microbial biofilm formation from the four background materials typically used during food processing. Ultimately, the resultant spectral information will be used in development of handheld portable imaging devices that can be used as visual aid tools for sanitation and safety inspection (microbial contamination) of the food processing surfaces. Pathogenic E. coli O157:H7 and Salmonella cells were grown in low strength M9 minimal medium on various surfaces at 22 +/- 2 °C for 2 days for biofilm formation. Biofilm autofluorescence under UV excitation (320 to 400 nm) obtained by hyperspectral fluorescence imaging system showed broad emissions in the blue-green regions of the spectrum with emission maxima at approximately 480 nm for both E. coli O157:H7 and Salmonella biofilms. Fluorescence images at 480 nm revealed that for background materials with near-uniform fluorescence responses such as stainless steel and formica cutting board, regardless of the background intensity, biofilm formation can be distinguished. This suggested that a broad spectral band in the blue-green regions can be used for handheld imaging devices for sanitation inspection of stainless, cutting board, and formica surfaces. The non-uniform fluorescence responses of granite make distinctions between biofilm and background difficult. To further investigate potential detection of the biofilm formations on granite surfaces with multispectral approaches, principal component analysis (PCA) was performed using the hyperspectral fluorescence image data. The resultant PCA score images revealed distinct contrast between

Gallate Contact Dermatitis: Product Update and Systematic Review.

Science.gov (United States)

Holcomb, Zachary E; Van Noord, Megan G; Atwater, Amber Reck

Allergic contact dermatitis related to cosmetic use can result from allergens not routinely evaluated by standard patch test protocols. Propyl, octyl, and dodecyl gallates are commonly used antioxidant preservatives with reports of associated allergic contact dermatitis in the literature. The objectives of this review were to investigate the role of gallates in allergic contact dermatitis and to explore products containing these preservatives. A systematic review of the literature through April 2016 was performed to explore cases of reported gallate allergy. Food and cosmetic product databases were searched for products containing gallates. Seventy-four cases of gallate contact allergy have been reported. In addition, a variety of commercially available cosmetic products and foods contain gallate chemicals. Propyl gallate is the most commonly reported gallate contact allergen and often causes facial and/or hand dermatitis.

Analysis of melamine migration from melamine food contact articles.

Science.gov (United States)

Chik, Z; Haron, D E Mohamad; Ahmad, E D; Taha, H; Mustafa, A M

2011-01-01

Migration of melamine has been determined for 41 types of retail melamine-ware products in Malaysia. This study was initiated by the Ministry of Health, Malaysia, in the midst of public anxiety on the possibility of melamine leaching into foods that come into contact with the melamine-ware. Thus, the objective of this study was to investigate the level of melamine migration in melamine utensils available on the market. Samples of melamine tableware, including cups and plates, forks and spoons, tumblers, bowls, etc., were collected from various retail outlets. Following the test guidelines for melamine migration set by the European Committee for Standardisation (CEN 2004) with some modifications, the samples were exposed to two types of food simulants (3% acetic acid and distilled water) at three test conditions (25°C (room temperature), 70 and 100°C) for 30 min. Melamine analysis was carried out using LC-MS/MS with a HILIC column and mobile phase consisting of ammonium acetate/formic acid (0.05%) in water and ammonium acetate/formic acid (0.05%) in acetonitrile (95 : 5, v/v). The limit of quantification (LOQ) was 5 ng/ml. Melamine migration was detected from all samples. For the articles tested with distilled water, melamine migration were [median (interquartile range)] 22.2 (32.6), 49.3 (50.9), 84.9 (89.9) ng/ml at room temperature (25°C), 70 and 100°C, respectively. In 3% acetic acid, melamine migration was 31.5 (35.7), 81.5 (76.2), 122.0 (126.7) ng/ml at room temperature (25°C), 70 and 100°C, respectively. This study suggests that excessive heat and acidity may directly affect melamine migration from melamine-ware products. However the results showed that melamine migration in the tested items were well below the specific migration limit (SML) of 30 mg/kg (30,000 ng/ml) set out in European Commission Directive 2002/72/EC.

Estimating the Contact Endurance of the AISI 321 Stainless Steel Under Contact Gigacycle Fatigue Tests

Science.gov (United States)

Savrai, R. A.; Makarov, A. V.; Osintseva, A. L.; Malygina, I. Yu.

2018-02-01

Mechanical testing of the AISI 321 corrosion resistant austenitic steel for contact gigacycle fatigue has been conducted with the application of a new method of contact fatigue testing with ultrasonic frequency of loading according to a pulsing impact "plane-to-plane" contact scheme. It has been found that the contact endurance (the ability to resist the fatigue spalling) of the AISI 321 steel under contact gigacycle fatigue loading is determined by its plasticity margin and the possibility of additional hardening under contact loading. It is demonstrated that the appearance of localized deep and long areas of spalling on a material surface can serve as a qualitative characteristic for the loss of the fatigue strength of the AISI 321 steel under impact contact fatigue loading. The value of surface microhardness measured within contact spots and the maximum depth of contact damages in the peripheral zone of contact spots can serve as quantitative criteria for that purpose.

Comparative analysis of biofilm formation by Bacillus cereus reference strains and undomesticated food isolates and the effect of free iron

NARCIS (Netherlands)

Hayrapetyan, H.; Muller, L.K.; Tempelaars, M.H.; Abee, T.; Nierop Groot, M.N.

2015-01-01

Biofilm formation of Bacillus cereus reference strains ATCC 14579 and ATCC 10987 and 21 undomesticated food isolates was studied on polystyrene and stainless steel as contact surfaces. For all strains, the biofilm forming capacity was significantly enhanced when in contact with stainless steel (SS)

The influence of surface chemistry and topography on the contact guidance of MG63 osteoblast cells.

Science.gov (United States)

Ismail, F S Magdon; Rohanizadeh, R; Atwa, S; Mason, R S; Ruys, A J; Martin, P J; Bendavid, A

2007-05-01

The purpose of the present study was to determine in vitro the effects of different surface topographies and chemistries of commercially pure titanium (cpTi) and diamond-like carbon (DLC) surfaces on osteoblast growth and attachment. Microgrooves (widths of 2, 4, 8 and 10 microm and a depth of 1.5-2 microm) were patterned onto silicon (Si) substrates using microlithography and reactive ion etching. The Si substrates were subsequently vapor coated with either cpTi or DLC coatings. All surfaces were characterized using atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and contact angle measurements. Using the MG63 Osteoblast-Like cell line, we determined cell viability, adhesion, and morphology on different substrates over a 3 day culture period. The results showed cpTi surfaces to be significantly more hydrophilic than DLC for groove sizes larger than 2 microm. Cell contact guidance was observed for all grooved samples in comparison to the unpatterned controls. The cell viability tests indicated a significantly greater cell number for 8 and 10 microm grooves on cpTi surfaces compared to other groove sizes. The cell adhesion study showed that the smaller groove sizes, as well as the unpatterned control groups, displayed better cell adhesion to the substrate.

Clostridium difficile from food and surface samples in a Belgian nursing home: an unlikely source of contamination.

Science.gov (United States)

Rodriguez, C; Korsak, N; Taminiau, B; Avesani, V; Van Broeck, J; Brach, P; Delmée, M; Daube, G

2015-04-01

This study investigates the contamination of foods and surfaces with Clostridium difficile in a single nursing home. C. difficile PCR-ribotype 078 was found in one food sample and in none of the tested surfaces. These results indicate that food and surfaces are an unlikely source of C. difficile infection in this setting. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effect of implanted doses of N+-ions on the contact resistance of copper contacts

International Nuclear Information System (INIS)

Dubravec, B.; Kovac, P.; Lipka, F.; Padysak, M.

1997-01-01

The paper deals with the effect of implanted doses of N + ions on the contact resistance. Dependencies of the contact resistance versus contact force R c =f(F c ) and microhardness of implanted surfaces were measured for three implanted profiles. The influence of the aggressive environs on the contact resistance of implanted contact is given too

Quasi-static motion of microparticles at the depinning contact line of an evaporating droplet on PDMS surface

Science.gov (United States)

Yu, Ying-Song; Xia, Xue-Lian; Zheng, Xu; Huang, Xianfu; Zhou, Jin-Zhi

2017-09-01

In this paper, evaporation of sessile water droplets containing fluorescent polystyrene (PS) microparticles on polydimethylsiloxane (PDMS) surfaces with different curing ratios was studied experimentally using laser confocal microscopy. At the beginning, there were some microparticles located at the contact line and some microparticles moved towards the line. Due to contact angle hysteresis, at first both the contact line and the microparticles were pinned. With the depinning contact line, the microparticles moved together spontaneously. Using the software ImageJ, the location of contact lines at different time were acquired and the circle centers and radii of the contact lines were obtained via the least square method. Then the average distance of two neighbor contact lines at a certain time interval was obtained to characterize the motion of the contact line. Fitting the distance-time curve at the depinning contact line stage with polynomials and differentiating the polynomials with time, we obtained the velocity and acceleration of both the contact line and the microparticles located at the line. The velocity and the maximum acceleration were, respectively, of the orders of 1 μm/s and 20-200 nm/s2, indicating that the motion of the microparticles located at the depinning contact line was quasi-static. Finally, we presented a theoretical model to describe the quasi-static process, which may help in understanding both self-pinning and depinning of microparticles.

Microbial control of food-related surfaces: Na-Chlorophyllin-based photosensitization.

Science.gov (United States)

Luksiene, Zivile; Paskeviciute, Egle

2011-10-05

The aim of this study was to evaluate efficiency of photosensitization as surface sanitation alternative using model systems when food pathogens, their spores and biofilms were attached to the food-related surface (polyolefine). In addition it was important to compare antibacterial efficiency of Na-Chlorophyllin (Na-Chl)-based photosensitization with conventional sanitizers. Obtained results indicate that Bacilluscereus ATCC 12826 and Listeriamonocytogenes ATCC 7644 as well as their thermoresistant strains B.cereus SV90 and L.monocytogenes 56LY were effectively inactivated (7 log) by Na-Chl-based photosensitization in vitro. Inactivation rate of thermoresistant strains was slower. The number of attached to the surface B.cereus ATCC 12826 and L.monocytogenes ATCC 7644 was reduced from 4-4.5 log to 0 log after photosensitization treatment. To achieve adequate inactivation of thermoresistant strains the higher Na-Chl concentration and longer illumination times had to be used. Comparison of different surface decontamination treatments reveal that photosensitization is much more effective against all surface-attached B.cereus and L.monocytogenes strains than washing with water or 200 ppm Na-hypochlorite. It is important to note, that surface-attached B.cereus spores and L.monocytogenes biofilms can be eliminated from it by photosensitization as well. Our data support the idea that Na-Chlorophyllin-based photosensitization has high antibacterial potential which may serve in the future for the development of human and environment friendly, non-thermal surface decontamination technique. Copyright © 2011 Elsevier B.V. All rights reserved.

Segmental equivalent temperature determined by means of a thermal manikin: A method for correcting errors due to incomplete contact of the body with a surface

DEFF Research Database (Denmark)

Melikov, Arsen Krikor; Janieas, N.R.D.J.; Silva, M.C.G.

2004-01-01

of the thermal manikins used at present is not as flexible as the human body and is divided into body segments with a surface area that differs from that of the human body in contact with a surface. The area of the segment in contact with a surface will depend on the shape and flexibility of the surface...

Mathematical Modeling of Contact Problems of Elasticity Theory with Continuous Unilateral Contact

Directory of Open Access Journals (Sweden)

I. V. Stankevich

2015-01-01

Full Text Available The work [1] presents the formulation and numerical solution of the problem concerning the unilateral discrete contact interaction of an elastic body and a rigid half-space. However, many parts and components of engineering structures have a pronounced continuous contact within a given surface [2, 3]. In this paper we consider a special case of this option of contact interaction when, the elastic body of finite size, subjected to external forces, is based on a rigid half-space. Contact occurs through a dedicated contact surface, which in general can change their sizes.Developed to solve this problem, a numerical algorithm is a further adaptation and development of the approaches described in [1]. The paper shows results of solving the model problem of the elasticity theory with and without taking friction into account. In the latter case, were additionally obtained numerical data characterizing the convergence of the solution.

Biofilm Formation of Listeria monocytogenes on Various Surfaces

Directory of Open Access Journals (Sweden)

M Mahdavi

2007-10-01

Full Text Available Introduction & Objective: Listeria monocytogenes is considered as a ubiquitous foodborne pathogen which can lead to serious infections, especially in newborns, elderly, pregnant, and immunocompromised people. The organism has been isolated from many foods and may cause meningitis, septicemia and abortion in pregnant women. Also L. monocytogenes forms biofilms on many food contact surface materials and medical devices. Development of biofilms on many surfaces is a potential source of contamination of foods that may lead to spoilage or transmission of foodborne pathogens. Materials & Methods: Biofilm formation of L. monocytogenes (RITCC 1293 serotype 4a was investigated. Hydrophobicity of L. monocytogenes was measured by MATH method. Then biofilm formation of the organism was assessed at 2, 4, 8, 16 and 20 hours on stainless steel (type 304 no 2B, polyethylene and glass by drop plate method. Results: Results indicated that L. monocytogenes with 85% of hydrophobicity formed biofilm on each of three surfaces. Biofilm formation on stainless steel surfaces was significantly more than other surfaces (p<0.05. Conclusion: The ability of biofilm formation of L. monocytogenes on medical devices and food containers is very important as far as hygiene and disease outbreaks are concerned.

Elastic contact mechanics: percolation of the contact area and fluid squeeze-out.

Science.gov (United States)

Persson, B N J; Prodanov, N; Krick, B A; Rodriguez, N; Mulakaluri, N; Sawyer, W G; Mangiagalli, P

2012-01-01

The dynamics of fluid flow at the interface between elastic solids with rough surfaces depends sensitively on the area of real contact, in particular close to the percolation threshold, where an irregular network of narrow flow channels prevails. In this paper, numerical simulation and experimental results for the contact between elastic solids with isotropic and anisotropic surface roughness are compared with the predictions of a theory based on the Persson contact mechanics theory and the Bruggeman effective medium theory. The theory predictions are in good agreement with the experimental and numerical simulation results and the (small) deviation can be understood as a finite-size effect. The fluid squeeze-out at the interface between elastic solids with randomly rough surfaces is studied. We present results for such high contact pressures that the area of real contact percolates, giving rise to sealed-off domains with pressurized fluid at the interface. The theoretical predictions are compared to experimental data for a simple model system (a rubber block squeezed against a flat glass plate), and for prefilled syringes, where the rubber plunger stopper is lubricated by a high-viscosity silicon oil to ensure functionality of the delivery device. For the latter system we compare the breakloose (or static) friction, as a function of the time of stationary contact, to the theory prediction.

Order of 12 August 1986 on treatment by ionizing radiation of material and objects in contact with foods and beverages

International Nuclear Information System (INIS)

1986-01-01

This Order applies to packaging material and articles in contact with foods and beverages, when they are treated by cobalt 60 or caesium 137 gamma rays, accelerated electrons of the energy lower than or equal to 10 MeV and X rays of the energy lower than or equal to 10 MeV. (NEA) [fr

Preparation of electrodes on cfrp composites with low contact resistance comprising laser-based surface pre-treatment

KAUST Repository

Almuhammadi, Khaled Hamdan; Lubineau, Gilles; Alfano, Marco Francesco; Buttner, Ulrich

2016-01-01

Various examples are provided related to the preparation of electrodes on carbon fiber reinforced polymer (CFRP) composites with low contact resistance. Laser-based surface preparation can be used for bonding to CFRP composites. In one example, a

Exploring surface cleaning strategies in hospital to prevent contact transmission of methicillin-resistant Staphylococcus aureus.

Science.gov (United States)

Lei, Hao; Jones, Rachael M; Li, Yuguo

2017-01-18

Cleaning of environmental surfaces in hospitals is important for the control of methicillin-resistant Staphylococcus aureus (MRSA) and other hospital-acquired infections transmitted by the contact route. Guidance regarding the best approaches for cleaning, however, is limited. In this study, a mathematical model based on ordinary differential equations was constructed to study MRSA concentration dynamics on high-touch and low-touch surfaces, and on the hands and noses of two patients (in two hospitals rooms) and a health care worker in a hypothetical hospital environment. Two cleaning interventions - whole room cleaning and wipe cleaning of touched surfaces - were considered. The performance of the cleaning interventions was indicated by a reduction in MRSA on the nose of a susceptible patient, relative to no intervention. Whole room cleaning just before first patient care activities of the day was more effective than whole room cleaning at other times, but even with 100% efficiency, whole room cleaning only reduced the number of MRSA transmitted to the susceptible patient by 54%. Frequent wipe cleaning of touched surfaces was shown to be more effective that whole room cleaning because surfaces are rapidly re-contaminated with MRSA after cleaning. Wipe cleaning high-touch surfaces was more effective than wipe cleaning low-touch surfaces for the same frequency of cleaning. For low wipe cleaning frequency (≤3 times per hour), high-touch surfaces should be targeted, but for high wipe cleaning frequency (>3 times per hour), cleaning should target high- and low-touch surfaces in proportion to the surface touch frequency. This study reproduces the observations from a field study of room cleaning, which provides support for the validity of our findings. Daily whole room cleaning, even with 100% cleaning efficiency, provides limited reduction in the number of MRSA transmitted to susceptible patients via the contact route; and should be supplemented with frequent targeted

Aberration changes of the corneal anterior surface following discontinued use of rigid gas permeable contact lenses

Directory of Open Access Journals (Sweden)

Shi-Qi Dong

2013-04-01

Full Text Available AIM: To record aberrations with a corneal topographic device on the anterior surface of the cornea at different time-points prior to wearing and following discontinued use of rigid gas permeable (RGP contact lenses. The effect of wearing RGP on the anterior surface of the cornea was discussed to provide guidance for clinical refractive error correction. METHODS: The study objects were 24 eyes from 24 patients. All patients underwent identical examination procedures prior to lens use, as well as afterwards, including slit-lamp examination, non-contact tonometer measurement, computer optometry and corneal curvature measurement, subjective refraction test, and corneal topography analysis. The patients wore contact lenses everyday for 1 month and then discontinued. Corneal topographies were recorded at certain time points of 30 minutes, 1 day, 3, 7 and 14 days following use. RESULTS: Total corneal aberration at each time point following discontinued use of RGP contact lenses was less than the time point prior to use. Detailed results were as follows:root mean square (RMS (pre=(1.438±0.328μm, RMS (30 minutes=(1.076±0.355μm, RMS (1 day=(1.362±0.402μm, RMS (3 days=(1.373±0.398μm, RMS (7 days=(1.387±0.415μm, and RMS (14 days=(1.430±0.423μm. Results showed that at 30 minutes after discontinued use of RGP contact lenses, almost all 2nd- and 3rd-order aberrations change. Quadrafoil Z10 and spherical Z12 of the 4th-order were also changed. Alterations to Z5, Z6, and Z12 at 1 day after discontinued use were significant differences compared with the time period prior to RGP use:Z5 and Z6 decreased, and Z12 increased slightly. Z5 and Z6 remained decreased at 3 days after discontinued use, but Z9 and Z10 continued to increase and Z12 returned to levels prior to RGP use. At 14 days after discontinued use, all aberrations were not significantly different from the values prior to use. CONCLUSION: The use RGP contact lenses greatly reduced total

Pinus sylvestris L. needle surface wettability parameters as indicators of atmospheric environment pollution impacts: Novel contact angle hysteresis methodology