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Sample records for subjects wearing pressure

  1. Comparative measurement of intraocular pressure by Icare tonometry and Airpuff tonometry in healthy subjects and patients wearing therapeutic soft contact lenses.

    Science.gov (United States)

    Anton, Alexandra; Neuburger, Matthias; Böhringer, Daniel; Jordan, Jens F

    2013-07-01

    The aim of the present study was to compare the measurement of intraocular pressure (IOP) through a therapeutic soft contact lens with the "native" measurement. We additionally investigate whether a rebound tonometer (RT) or non-contact tonometer (NCT) is more suitable to measure IOP through a bandage contact lens. The IOP was determined using each of the two methods, three times successively with (lens measurement) and without (native measurement) a soft contact lens. The Icare tonometer (Icare® TA01i, Icare Finland Oy, 23 subjects) and the Airpuff tonometer (Nidek NT 53OP, Nidek CO., LTD, Hiroishi Gamagori, Aichi, Japan, 16 subjects) were used. We compared the mean values (validity parameter) and standard deviation (precision parameter) of the three individual measurements in each case using the paired t-test. In addition, we conducted a power analysis to estimate the maximum error in the measurement caused by the contact lens (power level set to 0.8). With the Airpuff tonometer we detected no statistically significant between the lens and the native measurement (15.6 ± 2.6 vs. 15.3 ± 2.6 mmHg; p = 0.42). The power analysis revealed that the maximum error caused by the contact lens was 1.2 mmHg. The Icare tonometry, however, trended toward higher values in the contact lens measurements (17.5 ± 4.3 vs. 16.4 ± 3.5 mmHg in the native measurements; p = 0.05). Interestingly, this difference exhibited a statistically significant correlation with the corneal thickness (0.03 mmHg per μm corneal thickness; p = 0.04). The use of NCT and RT for IOP measurement over a soft contact lens is feasible. The accuracy appears to be sufficient for the most common clinical applications.

  2. Experiment on wear behavior of high pressure gas seal faces

    Science.gov (United States)

    Xu, Jing; Peng, Xudong; Bai, Shaoxian; Meng, Xiangkai; Li, Jiyun

    2014-11-01

    Current researches show that mechanical deformation of seal ring face makes fluid film clearance decrease at high pressure side, thus a divergent clearance is formed and face wear occurs more seriously at the high pressure side than that on the low pressure side. However, there is still lack of published experimental works enough to prove the theoretical results. In this paper, a spiral groove dry gas seal at high pressures is experimentally investigated so as to prove the face wear happened at the high pressure side of seal faces due to the face mechanical deformation, and the wear behavior affected by seal ring structure is also studied. The experimental results show that face wear would occur at the high pressure side of seal faces due to the deformation, thus the leakage and face temperature increase, which all satisfies the theoretical predictions. When sealed pressure is not less than 5 MPa, the pressure can provide enough opening force to separate the seal faces. The seal ring sizes have obvious influence on face wear. Face wear, leakage and face temperature of a dry gas seal with the smaller cross sectional area of seal ring are less than that of a dry gas seal with bigger one, and the difference of leakage rate between these two sizes of seal face width is in the range of 24%-25%. Compared with the effect of seal ring sizes, the effect of secondary O-ring seal position on face deformation and face wear is less. The differences between these two types of dry gas seals with different secondary O-ring seal positions are less than 5.9% when the rotational speed varies from 0 to 600 r/min. By linking face wear and sealing performance changes to the shift in mechanical deformation of seal ring, this research presents an important experimental method to study face deformation of a dry gas seal at high pressures.

  3. Subjective assessment of contact lens wear by army aircrew.

    Science.gov (United States)

    Lattimore, M R; Cornum, R L

    1993-07-01

    Because 23% of Army aviators are ametropic, contact lenses have drawn increased attention as a spectacle substitute to solve system compatibility problems. From November 1988 until October 1991, a series of contact lens research protocols were conducted to develop a comprehensive database on contact lens wear in varied environments. Questionnaires were used to assess suitability and acceptability of routine contact lens wear. Responses from 202 subjects were obtained from September 1989 through September 1991. The questions explored operational and safety of flight issues of contact lens wear. Subjects overwhelmingly approved of contact lens use in all settings: 95% expressed greater combat readiness and effectiveness with contact lenses, 98% felt contact lens use (and maintenance) in the cockpit had no adverse impact on safety of flight, and 98% endorsed the routine use of contact lenses. These data highlight Army aircrew acceptance of contact lens use.

  4. Biomechanics of postoperative shoes: plantar pressure distribution, wearing characteristics and design criteria: a preliminary study.

    Science.gov (United States)

    Schuh, Reinhard; Trnka, Hans-Joerg; Sabo, Anton; Reichel, Martin; Kristen, Karl-Heinz

    2011-02-01

    Modern concepts in the postoperative treatment of first metatarsal osteotomies include special shoes that should decrease stress in the forefoot region. The purpose of this study was to determine plantar pressure distribution, wearing characteristics and stress-reducing effectiveness of five different types of commonly used postoperative shoes. Additionally, we wanted to modify the shoe that revealed the most favourable results in a way that improves forefoot relief as well as provides comfort to the patients. Eight persons consented to participate in the study. Plantar pressure distribution in five different types of postoperative shoes (Rathgeber(®) normal, Rathgeber(®) modified, 4. Darco(®) flat, Darco(®) VFE, Wocker(®)) was assessed using Mediologic(®) insoles. Also, subjective criteria considering wearing comfort, stability and rolling characteristics were evaluated. Based on the postoperative shoe revealing the most favourable results, further prototypes were developed. Each new model was targeted to meet the given requirements, minimal forefoot pressure, in a different way. The Rathgeber(®) modified model revealed the most favourable results concerning plantar pressure distribution as well as subjective wearing characteristics. Therefore, it was chosen for further modifications. After adding an extra layer of high elastic and springy material for shock absorption at the hallux region, forefoot relief and wearing characteristics showed improved results. The results of the present study indicate that damping material in the hallux region of postoperative shoes minimises stress in this region and improves patient's comfort.

  5. Reduction of Erosion Wear of Mean Pressure Cylinder of Steam Turbines Operating Beyond Critical Parameters

    Directory of Open Access Journals (Sweden)

    V. P. Kascheev

    2009-01-01

    Full Text Available The paper considers problems leading to erosion wear of flowing part of a mean pressure turbine cylinder operating beyond critical parameters. Explanation of erosion wear of flowing part of a mean pressure turbine cylinder which is proved in practice and recommendations for wear reduction are given in the paper

  6. Student Pressure Subject of Debate

    Science.gov (United States)

    Gewertz, Catherine

    2006-01-01

    This article discusses student pressure as a subject of debate. The latest debate about schoolwork is being fueled by three recent books: "The Homework Myth" by Alfie Kohn, "The Case Against Homework" by Sara Bennett and Nancy Kalish, and "The Overachievers", by Alexandra Robbins, which depicts overextended high…

  7. The Changes of COP and Foot Pressure after One Hour's Walking Wearing High-heeled and Flat Shoes

    OpenAIRE

    Ko, Dong Yeol; Lee, Han Suk

    2013-01-01

    [Purpose] This study aimed to determine the most appropriate height for shoe heels by measuring the displacement of the COP (center of pressure) and changes in the distribution of foot pressure after walking in flat (0.5 cm), middle-heeled (4 cm), and high-heeled (9 cm) shoes for 1 hour. [Methods] A single-subject design was used, with 15 healthy women wearing shoes with heels of each height in a random order. The foot pressure and displacement of COP before and after walking in an ordinary e...

  8. Intraocular Pressure After 2 Hours of Small-Diameter Scleral Lens Wear.

    Science.gov (United States)

    Nau, Cherie B; Schornack, Muriel M; McLaren, Jay W; Sit, Arthur J

    2016-11-01

    Compression of episcleral veins or deformation of tissue in the Schlemm's canal beneath the landing zone of scleral lenses could elevate intraocular pressure (IOP). We examined the effect of 2 hr of small-diameter scleral lens wear on IOP. Twenty-nine participants, 29 ± 6 years old (mean ± SD) who experienced no history of eye disease or scleral lens wear, were included in the study. Each participant was fitted with a 15-mm Jupiter scleral lens on one eye (study eye). Intraocular pressure was measured in both eyes by pneumatonometry centrally on the cornea and peripherally on the sclera. The lens was then placed on one eye and was worn for 2 hr. Intraocular pressure was remeasured immediately after lens placement, at 1 and 2 hr of lens wear, and immediately after lens removal. Intraocular pressure after removal of the scleral lens was compared with IOP before placing the lens and to IOP in the control eye using paired t tests. Immediately after removing the scleral lens, mean central IOP in the study eye (13.9 ± 3.1 mm Hg) was not different from mean central IOP in the control eye (13.5 ± 2.2 mm Hg, P = 0.4) or in the same eye before lens wear (13.6 ± 1.9 mm Hg, P = 0.6). There were also no differences in IOP measured peripherally at 2 hr of lens wear (P = 0.8). Neophyte scleral lens wear of a 15-mm scleral lens for 2 hr does not increase IOP in healthy eyes.

  9. Pressure fluids of the HFC group and the wear behaviour of positive displacement units

    Energy Technology Data Exchange (ETDEWEB)

    Reichel, J.

    1985-03-01

    In stationary equipment used in coalmining and in diecasting machines the positive displacement units of hydrostatic drives have been operated with HFC fluids for almost 20 years. In tests accompanying development work a large number of pumps and motors were tested on the hydraulic test stand of Bergbau-Forschung GmbH in Essen, at pressures up to 300 bar to establish their wear behaviour with various HFC fluids. The results were confirmed also in controlled operational trials and in the industrial plant in use today. In the selection of the positive displacement units to be used their constructional design and the use of suitable materials or mating materials are substantial prerequisites for favourable wear behaviour in operation with HFC fluids. The recently improved wear protection capacity of these pressure fluids was examined in the test with the vane pump (DIN 51389) and also evaluated in other types of pump. An obvious weak point proved to be roller bearings in axial piston units and radial piston motors. Positive displacement units with hydrostatic balancing and plain bearings can be well adapted to the properties of HFC fluids at working pressures up to 300 bar. The optimum operating temperatures lie between 40 and 50 C; temperatures up to 60 C may be tolerated.

  10. Wear rates of highly cross-linked polyethylene humeral liners subjected to alternating cycles of glenohumeral flexion and abduction.

    Science.gov (United States)

    Peers, Sebastian; Moravek, James E; Budge, Matthew D; Newton, Michael D; Kurdziel, Michael D; Baker, Kevin C; Wiater, J Michael

    2015-01-01

    Although short-term outcomes of reverse total shoulder arthroplasty have been promising, long-term success may be limited due to device-specific complications, including scapular notching. Scapular notching has been explained primarily as mechanical erosion; however, the generation of wear debris may lead to further biologic changes contributing to the severity of scapular notching. A 12-station hip simulator was converted to a reverse total shoulder arthroplasty wear simulator subjecting conventional and highly cross-linked ultra-high-molecular-weight polyethylene humeral liners to 5 million cycles of alternating abduction-adduction and flexion-extension loading profiles. Highly cross-linked polyethylene liners (36.5 ± 10.0 mm(3)/million cycle) exhibited significantly lower volumetric wear rates compared with conventional polyethylene liners (83.6 ± 20.6 mm(3)/million cycle; P linked polyethylene (P linked wear particles had an equivalent circle diameter significantly smaller than wear particles from conventional polyethylene (P linked polyethylene liners significantly reduced polyethylene wear and subsequent particle generation. More favorable wear properties with the use of highly cross-linked polyethylene may lead to increased device longevity and fewer complications but must be weighed against the effect of reduced mechanical properties. Copyright © 2015 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

  11. The Changes of COP and Foot Pressure after One Hour's Walking Wearing High-heeled and Flat Shoes.

    Science.gov (United States)

    Ko, Dong Yeol; Lee, Han Suk

    2013-10-01

    [Purpose] This study aimed to determine the most appropriate height for shoe heels by measuring the displacement of the COP (center of pressure) and changes in the distribution of foot pressure after walking in flat (0.5 cm), middle-heeled (4 cm), and high-heeled (9 cm) shoes for 1 hour. [Methods] A single-subject design was used, with 15 healthy women wearing shoes with heels of each height in a random order. The foot pressure and displacement of COP before and after walking in an ordinary environment for 1 hour were measured using an FDM-S (zebris Medical GmbH, Germany). [Results] The distribution of foot pressure did not change significantly after walking in middle-heeled (4 cm) shoes but did change significantly after walking in either flat (0.5 cm) or high-heeled (9 cm) shoes. Similarly, the COP was not significantly displaced after walking in middle-heeled (4 cm) shoes but was significantly displaced after walking in either flat (0.5 cm) or high-heeled (9 cm) shoes. [Conclusion] Both flat and high-heeled shoes had adverse effects on the body. Middle-heeled (4 cm) shoes are preferable to both flat (0.5 cm) and high-heeled (9 cm) shoes for the health and comfort of the feet.

  12. Effects of long-term soft contact lens wear on the corneal thickness and corneal epithelial thickness of myopic subjects.

    Science.gov (United States)

    Lei, Yulin; Zheng, Xiuyun; Hou, Jie; Xu, Baozeng; Mu, Guoying

    2015-03-01

    To perform safe and successful corneal refractive surgery on myopic patients, corneal thickness (CT) and corneal epithelial thickness (CET) must be accurately measured. Numerous individuals with myopia wear soft contact lenses (SCLs) for the correction of visual acuity but may subsequently undergo corneal refractive surgery. The aim of the present study was therefore to investigate the effects of long-term SCL wear on the CT and the CET of myopic subjects in order to guarantee the safety and accuracy of subsequent corneal refractive surgeries. Fifty-six subjects prepared to receive refractive surgery at Jinan Mingshui Eye Hospital (Zhangqiu, China) from April to July 2013 were included in the study. CT and CET were measured in subjects immediately following discontinued SCL wear (group I, 56 eyes), and subsequently following >two weeks of discontinued SCL wear (group II, 56 eyes). Ninety-four subjects with no history of corneal contact lens wear were enrolled as a control group. The CT and CET were measured at positions with a radius of 0.0‑1.0, 1.0-2.5 (divided into eight quadrants) and 2.5-3.0 mm (divided into eight quadrants) away from the corneal center using the RTVue-100 Fourier-domain anterior segment optical coherence tomography system. A significant decrease in the CT of the subjects in group II was observed, compared with that of group I and the control group (P<0.05). A significant decrease was observed in the CET of groups I and II compared with that of the control group (P<0.05). Following discontinuation of SCL wear, CET increased. However, the increased CET was unable to reach the normal range exhibited by the control group. Edema and thinning of the corneal stroma, as well as thinning of the corneal epithelium were observed in groups I and II. In conclusion, it was proposed that in clinical practice, for myopic patients following long-term SCL wear, CT and CET should be determined ≥ two weeks following discontinuation of SCL wear, once a stable

  13. Does wearing a functional knee brace affect hamstring reflex time in subjects with anterior cruciate ligament deficiency during muscle fatigue?

    Science.gov (United States)

    Lam, Rita Y; Ng, Gabriel Y; Chien, Eric P

    2002-07-01

    To evaluate the effects of wearing a functional knee brace and muscle fatigue on hamstring reflex time in subjects with anterior cruciate ligament (ACL) deficiency. Repeated-measures clinical trial. Outpatient physical therapy department. Sixteen subjects with ACL deficiency. Subjects tested with and without a functional knee brace before and after an exercise protocol designed to fatigue the knee muscles. Latency of hamstring reflex muscle activity after sudden perturbation of the knee. Wearing a knee brace shortened the hamstring reflex latency regardless of fatigue (F(1,15)=20.62, Pknee brace facilitated hamstring muscle reflex, but muscle fatigue lengthened the hamstring reflex latency. Subjects with ACL deficiency should not rely on the knee brace to facilitate hamstring reflex for joint protection during prolonged sporting activities when muscles are fatigued. Copyright 2002 by the American Congress of Rehabilitation Medicine and the American Academy of physical Medicine and Rehabilitation

  14. Epinastine 0.05% ophthalmic solution in contact lens-wearing subjects with a history of allergic conjunctivitis.

    Science.gov (United States)

    Nichols, Kelly K; Morris, Scot; Gaddie, Ian B; Evans, David

    2009-01-01

    To assess the comfort and efficacy of epinastine 0.05% ophthalmic solution in contact lens wearers with a history of allergic conjunctivitis and contact lens intolerance during allergy season. One hundred forty-six subjects were enrolled in a multicenter, open-label study. Enrolled subjects instilled rewetting drops twice a day for a one-week run-in period, then were randomized to epinastine 0.05% twice a day plus rewetting drops as required (n = 75) or rewetting drops alone as required (minimum use twice a day) (n = 71). Subjects recorded the length of time that contact lens wear was comfortable, the total time of wear, ocular itch, overall comfort, and use of rewetting drops during the run-in period, at baseline, and on days 2 to 7 of the treatment period. Subjects averaged 34 years of age; 79% were female. No significant differences were shown at baseline between subjects treated with epinastine 0.05% twice a day plus rewetting drops and control subjects treated with rewetting drops alone. Averaged over the treatment period, epinastine provided significant increases in comfortable wearing time (1.33 +/- 2.89 vs. 0.43 +/- 2.28 hr, P=0.012) and total wearing time (0.35 +/- 1.87 vs. -0.32 +/- 1.81 hr, P=0.008) compared with controls. Epinastine users reported less frequent additional rewetting drop use on average by 0.56 uses per day, which was significantly different than controls (reduction of 0.06 uses per day; P=0.012). Epinastine provided significantly greater improvements from baseline in ocular itch and overall eye comfort compared with rewetting drops alone (Pcontact lens wearers.

  15. An in situ tribometer for measuring friction and wear of polymers in a high pressure hydrogen environment

    Science.gov (United States)

    Duranty, Edward R.; Roosendaal, Timothy J.; Pitman, Stan G.; Tucker, Joseph C.; Owsley, Stanley L.; Suter, Jonathan D.; Alvine, Kyle J.

    2017-09-01

    High pressure hydrogen effects on the friction and wear of polymers are of importance to myriad applications. Of special concern are those used in the infrastructure for hydrogen vehicle refueling stations, including compressor sliding seals, valves, and actuators. While much is known about potentially damaging embrittlement effects of hydrogen on metals, relatively little is known about the effects of high pressure hydrogen on polymers. However, based on the limited results that are published in the literature, polymers also apparently exhibit compatibility issues with hydrogen. An additional study is needed to elucidate these effects to avoid incompatibilities either through design or material selection. As part of this effort, we present here in situ high pressure hydrogen studies of the friction and wear on example polymers. To this end, we have built and demonstrated a custom-built pin-on-flat linear reciprocating tribometer and demonstrated its use with in situ studies of friction and wear behavior of nitrile butadiene rubber polymer samples in 28 MPa hydrogen. Tribology results indicate that friction and wear is increased in high pressure hydrogen as compared both with values measured in high pressure argon and ambient air conditions.

  16. Enhanced computational prediction of polyethylene wear in hip joints by incorporating cross-shear and contact pressure in additional to load and sliding distance: effect of head diameter.

    Science.gov (United States)

    Kang, Lu; Galvin, Alison L; Fisher, John; Jin, Zhongmin

    2009-05-11

    A new definition of the experimental wear factor was established and reported as a function of cross-shear motion and contact pressure using a multi-directional pin-on-plate wear testing machine for conventional polyethylene in the present study. An independent computational wear model was developed by incorporating the cross-shear motion and contact pressure-dependent wear factor into the Archard's law, in additional to load and sliding distance. The computational prediction of wear volume was directly compared with a simulator testing of a polyethylene hip joint with a 28 mm diameter. The effect of increasing the femoral head size was subsequently considered and was shown to increase wear, as a result of increased sliding distance and reduced contact pressure.

  17. Forecast of reliability for mechanical components subjected to wearing; Pronostico de la fiabilidad de componentes mecanicos sometidos a desgaste

    Energy Technology Data Exchange (ETDEWEB)

    Angulo-Zevallos, J.; Castellote-Varona, C.; Alanbari, M.

    2010-07-01

    Generally, improving quality and price of products, obtaining a complete customer satisfaction and achieving excellence in all the processes are some of the challenges currently set up by every company. To do this, knowing frequently the reliability of some component is necessary. To achieve this goal, a research, that contributes with clear ideas and offers a methodology for the assessment of the parameters involved in the reliability calculation, becomes necessary. A parameter closely related to this concept is the probability of product failure depending on the operating time. It is known that mechanical components fail by: creep, fatigue, wear, corrosion, etc. This article proposes a methodology for finding the reliability of a component subject to wear, such as brake pads, grinding wheels, brake linings of clutch discs, etc. (Author)

  18. Tribological performance evaluation of coated steels with TiNbCN subjected to tribo-chemical wear in Ringers solution

    Energy Technology Data Exchange (ETDEWEB)

    Caballero G, J.; Aperador, W. [Universidad Militar Nueva Granada, Volta Research Group, 101-80 Bogota (Colombia); Caicedo, J. C., E-mail: g.ing.materiales@gmail.com [Universidad del Valle, Tribology Polymers, Powder Metallurgy and Processing of Solid Recycled Research Group, Cali (Colombia)

    2016-11-01

    With the aim of generating solutions against the deterioration of the joint prostheses, it was studied the tribo-corrosive behavior of titanium niobium carbonitride (TiNbCN) deposited on stainless steel AISI 316 LVM using the technique of magnetron sputtering physical vapor deposition. The tests were performed in a balanced saline solution (Ringers solution) which represents the characteristics of the body fluids, using an equipment where the micro-abrasive wear is generated by the contact of micro particles in the system; the micro-abrasion-corrosion mechanism is described by means of the incorporation of an electrochemical cell consisting of three electrodes. Both the substrate and the coating, were subjected to micro-abrasive wear simultaneously with the electrochemical tests of Tafel polarization curves and electrochemical impedance spectroscopy (EIS); subsequently of the tests, the specimens were analyzed by optical microscopy and scanning electron microscopy characterizing the surface morphology. It was observed that the coating presents an increase in its corrosion and wear resistance with the presence of a simulated biological fluid. The samples were characterized via X-ray diffraction. (Author)

  19. Wear surface damage of a Stainless Steel EN 3358 aeronautical component subjected to sliding

    Directory of Open Access Journals (Sweden)

    Ferdinando Felli

    2013-01-01

    Full Text Available The present paper describes the failure analysis of an aircraft component subjected to several episodes of in service failure, resulted in loss of the aircraft safety. Modern aircrafts are provided with mechanical systems which have the task to open not pressurized hatches during landing. The components of such systems are subject to considerable mechanical stresses in harsh environment (presence of moisture and pollutants, significant and sudden temperature variations. The system is constituted by a sliding piston, a related nipple and by a locking system consisting of 4 steel spheres which are forced into a countersink machined on the piston when the hatches is open. The whole system is activated by a preloaded spring. The machined parts, nipple and piston, are made of EN3358 steel (X3CrNiMo13-8-2, a precipitation hardening stainless steel with very low content of carbon often used in the aerospace. The samples provided by the manufacturer present different types of damage all referable to phenomena relative to the sliding of the piston inside the nipple. The present paper describes the different damage observed and the microstructure of the material, then are reported the results obtained from the characterization of the material of the samples by means of optical and electronic microscopy, carried out to define the mechanisms involved in the system seizure. In order to define the primary cause of failure and to propose solutions to be adopted, also analyzing the criticality of using this PH stainless steel for this application, the results of different tests were compared with system design and working data.

  20. Wear of components in consumer substation caused by high differential pressure; Slitage av komponenter i FC orsakade av hoega differenstryck

    Energy Technology Data Exchange (ETDEWEB)

    Fransson, Anders [Goeteborg Energi AB (Sweden)

    2005-07-01

    The purpose of this project was to show the consequences in increased wear and decreased lowering of the return temperature in sub stations as a result of changes in the production of district heating, in particular increased differential pressure. It is known that increased differential pressure might lead to; - Noise - Ascending return temperature - Unwanted descending temperatures on the secondary side (i.e. the hot water circuit and the radiator circuit) - Oscillating regulation - Increased wear of the control equipment - Leakage from old heat exchangers There are four areas with in the district heating grid of Goeteborg Energi AB that are studied according to reported faults. Noise: The area which has the highest differential pressure and known variation in differential pressure also has the most problem. It is not possible to make certain statements based on the study. Ascending return temperature: Both areas with higher differential pressure reveals decreased cooling of the primary water and higher overconsumption of primary water according to the principle of overconsumption relatively the other two areas. Unwanted descending temperatures on the secondary side (i.e. the hot water circuit and the radiator circuit) This fault is not found in the study. Oscillating regulation: This fault is not found in the study. Increased wear of the control equipment: The area which has the highest differential pressure also has most problems with wear. Looking at leakage from packing boxes, you will also see a clear effect over time. It is still not possible to make certain statements based on the study. Valves and sometimes the corresponding actuators have been replaced because they were oversized. It is impossible to exclude those replacements completely from the material in the study. Leakage from old heat exchangers: This fault is not found in the study. However it is found more common to find leakage to the surroundings in the areas with higher differential pressure

  1. Objective and subjective assessing efficacy of a lubricating drop in eyes wearing silicone hydrogel contact lenses

    Directory of Open Access Journals (Sweden)

    Amir Asharlous

    2016-06-01

    Conclusion: Our results showed that although the lubricating drop did not improve the tear film stability and optical quality in the silicone hydrogel contact lens wearers, subjects experienced a subjective improvement.

  2. Physical activity after surgically obtained weight loss: study with a SenseWear armband in subjects undergoing biliopancreatic diversion.

    Science.gov (United States)

    Gradaschi, Raffaella; Camerini, Giovanni; Carlini, Flavia; Sukkar, Samyr; Sopinaro, Nicola; Adami, Gian Franco

    2014-02-01

    This study aimed to understand the role of the extra load of body mass in limiting physical activity and in preventing an active lifestyle in severely obese patients. The study was carried out in a University Hospital setting, and investigates severely obese patients, having undergone biliopancreatic diversion (BPD) for obesity and control subjects with a body weight closely similar to that of the BPD subjects; energy intake was evaluated by alimentary interview and energy expenditure was assessed with the Body Media SenseWear® Pro armband (SWA). SWA metabolic efficiency (MET) was negatively associated with body mass index values (ρ = -0.464, p active persons (27% vs. 0 and 7%, respectively) and a lower number of sedentary persons (27% vs. 70 and 43%, respectively) was found (p physical activity and leading to a sedentary lifestyle.

  3. Influence of high sintering pressure on the microhardness and wear resistance of diamond powder and silicon carbide-based composites

    Directory of Open Access Journals (Sweden)

    Osipov Oleksandr Sergueevitch

    2004-01-01

    Full Text Available The work reported on here involved the development of several samples of "diamond-SiC" composite produced under sintering pressures of up to 9.0 GPa at temperatures of up to 1973 7K. The average size of the diamond micropowder crystals used was 40/28 µm. The sintering process was carried out in a 2500-ton hydraulic press equipped with an anvil-type high-pressure device having a toroidal work surface and a central concavity diameter of 20 mm. The microhardness and wear resistance of the samples were found to be dependent on the sintering pressure. The experimental results indicated that the maximum microhardness and minimum wear resistance coefficients of each compact were attained when the pressure applied during sintering exceeded 6.5 GPa. Based on the established values of pressure, this study served to identify the types of devices applicable for the manufacture of composite material inserts for a variety of rock drilling applications.

  4. The Effect of Bias Voltage and Gas Pressure on the Structure, Adhesion and Wear Behavior of Diamond Like Carbon (DLC Coatings With Si Interlayers

    Directory of Open Access Journals (Sweden)

    Liam Ward

    2014-04-01

    Full Text Available In this study diamond like carbon (DLC coatings with Si interlayers were deposited on 316L stainless steel with varying gas pressure and substrate bias voltage using plasma enhanced chemical vapor deposition (PECVD technology. Coating and interlayer thickness values were determined using X-ray photoelectron spectroscopy (XPS which also revealed the presence of a gradient layer at the coating substrate interface. Coatings were evaluated in terms of the hardness, elastic modulus, wear behavior and adhesion. Deposition rate generally increased with increasing bias voltage and increasing gas pressure. At low working gas pressures, hardness and modulus of elasticity increased with increasing bias voltage. Reduced hardness and modulus of elasticity were observed at higher gas pressures. Increased adhesion was generally observed at lower bias voltages and higher gas pressures. All DLC coatings significantly improved the overall wear resistance of the base material. Lower wear rates were observed for coatings deposited with lower bias voltages. For coatings that showed wear tracks considerably deeper than the coating thickness but without spallation, the wear behavior was largely attributed to deformation of both the coating and substrate with some cracks at the wear track edges. This suggests that coatings deposited under certain conditions can exhibit ultra high flexible properties.

  5. Pressure transient analysis of a horizontal well subject to four ...

    African Journals Online (AJOL)

    Reservoir characterization is essential for effective reservoir and wellbore management. But when a horizontal well is subject to constant-pressure external boundaries, the extent of reservoir characterization that is possible depends on the flow regimes that are encountered in a given flow time. In this paper dimensionless ...

  6. Tribological behavior of aeronautical steel under oil–air lubrication containing extreme-pressure and anti-wear additives

    Directory of Open Access Journals (Sweden)

    Wen Guan

    2016-07-01

    Full Text Available If the lubrication system of a helicopter reducer is compromised, its gears and bearings will be in a working state without lubricating oil, which causes the reducer to be damaged in a very short time. Various 2% additives of T307, T321, T202, and T391 were injected and mixed with DOD-L-85734 aeronautical oil to produce 45-min oil–air lubrication experiments performed upon 12Cr2Ni4A aeronautical steel tribo-pairs. The results show that the best anti-wear effect is produced by oil–air lubrication containing T391: its wear width under jetting oil–air just three times and quantity of oil used only 0.015 mL in 45 min was only 421.32 µm but that of dry friction for 48 s was 629.20 µm. The technology of oil–air lubrication that contains an extreme-pressure and anti-wear additive is thus a feasible way to improve the operational ability of a helicopter transmission system that is out of oil.

  7. Home readings of blood pressure in assessment of hypertensive subjects

    DEFF Research Database (Denmark)

    Nielsen, P.E.; Myschetzky, P; Andersen, A R

    1986-01-01

    Out-patient clinic blood pressure (OPC-BP) was compared to home blood pressure (Home-BP) measured three times daily during a two week period in 122 consecutively referred hypertensive subjects. A semi-automatic device (TM-101) including a microphone for detection of Korotkoff-sounds, self......-deflation of cuff pressure and digital display of blood pressure was used. Mean difference between OPC-BP and Home-BP was systolic +13 mm Hg (range -21 - +100 mg Hg) and diastolic +5 mm Hg (range -27 - +36 mm Hg). Although a significant correlation could be demonstrated between Home-BP and OPC-BP, the inter......-individual scatter was pronounced and unpredictable from the hypertensive organ damages. It is argued, that home readings should be used to greater extent in the evaluation of patients with hypertension....

  8. Short-term corneal changes with gas-permeable contact lens wear in keratoconus subjects: a comparison of two fitting approaches.

    Science.gov (United States)

    Romero-Jiménez, Miguel; Santodomingo-Rubido, Jacinto; Flores-Rodríguez, Patricia; González-Méijome, Jose-Manuel

    2015-01-01

    To evaluate changes in anterior corneal topography and higher-order aberrations (HOA) after 14-days of rigid gas-permeable (RGP) contact lens (CL) wear in keratoconus subjects comparing two different fitting approaches. Thirty-one keratoconus subjects (50 eyes) without previous history of CL wear were recruited for the study. Subjects were randomly fitted to either an apical-touch or three-point-touch fitting approach. The lens' back optic zone radius (BOZR) was 0.4mm and 0.1mm flatter than the first definite apical clearance lens, respectively. Differences between the baseline and post-CL wear for steepest, flattest and average corneal power (ACP) readings, central corneal astigmatism (CCA), maximum tangential curvature (KTag), anterior corneal surface asphericity, anterior corneal surface HOA and thinnest corneal thickness measured with Pentacam were compared. A statistically significant flattening was found over time on the flattest and steepest simulated keratometry and ACP in apical-touch group (all pcontact lens wear (all plens wear. Copyright © 2014 Spanish General Council of Optometry. Published by Elsevier Espana. All rights reserved.

  9. Tribological studies of eutectic Aluminum-Silicon alloys used for automotive engine blocks subjected to sliding wear damage

    Science.gov (United States)

    Xue, Guijun

    The microstructures and wear performances of linerless engine cylinder blocks made of two eutectic Al-Si alloys with different Si morphologies were characterized after the engine tests. Overall, both the Al-11 wt. % Si alloy and the Al-12.6 wt. % Si alloy provided similar wear performance. Block-on-ring wear tests were applied to the Al-11% Si alloy. The MW regime in air consisted of two sub-regimes: MW-1 and MW-2. The argon atmosphere produced a 10-fold reduction in wear rates and the formation of LMW regime at loads less than 10 N. The metallic tribolayers formed in the MW under argon atmosphere were uniform and stable, resulting lower wear rates than those in air. The mechanism of material removal under argon atmosphere was delimination. The SW occurring in argon was observed at a relatively low load, compared to an air atmosphere. Wear was also more sensitive to applied load in the argon atmosphere.

  10. Wearing weighted backpack dilates subjective visual duration: The role of functional linkage between weight experience and visual timing

    Directory of Open Access Journals (Sweden)

    Lina eJia

    2015-09-01

    Full Text Available Bodily state plays a critical role in our perception. In the present study, we asked the question whether and how bodily experience of weights influences time perception. Participants judged durations of a picture (a backpack or a trolley bag presented on the screen, while wearing different weight backpacks or without backpack. The results showed that the subjective dura-tion of the backpack picture was dilated when participants wore a medium weighted backpack relative to an empty backpack or without backpack, regardless of identity (e.g., color of the visual backpack. However, the duration dilation was not manifested for the picture of trolley bag. These findings suggest that weight experience modulates visual duration estimation through the linkage between the wore backpack and to-be-estimated visual target. The con-gruent action affordance between the wore backpack and visual inputs plays a critical role in the functional linkage between inner experience and time perception. We interpreted our findings within the framework of embodied time perception.

  11. Contact Pressure and Sliding Velocity Maps of the Friction, Wear and Emission from a Low-Metallic/Cast-Iron Disc Brake Contact Pair

    Directory of Open Access Journals (Sweden)

    J. Wahlström

    2017-12-01

    Full Text Available Particulate matter with an aerodynamic diameter less than 10 µm (PM10 from car disc brakes contribute up to 50% of the total non-exhaust emissions from road transport in the EU. These emissions come from the wear of the pad and rotor contact surfaces. Yet few studies have reported contact pressures and offered sliding speed maps of the friction, wear, and particle emission performance of disc brake materials at a material level. Such maps are crucial to understanding material behaviour at different loads and can be used as input data to numerical simulations. A low-metallic pad and grey cast-iron rotor contact pair commonly used today in passenger car disc brakes was studied using a pin-on-disc tribometer at twelve contact pressure and sliding speed combinations. Maps of the coefficient of friction, specific wear rate, particle number, and mass rate are presented and discussed.

  12. The Effects of Hypoxia Induced by Low Atmospheric Pressure on Soft Contact Lens Wear

    Science.gov (United States)

    1985-06-01

    Ocular Parameters....................o....... 2. Examiner and Subject Grading Scale for Slit-Lamp Findings, Keratometry Reflection Quality, and...Newsom et al. (1969) reported bubble form- ation in 66% of 16 polymethyl methacrylate ( PMMA ) wearers tested (7). With the advent of soft hydrophilic...Four subjects, from whom informed consent had been obtained, participated in the study. All were free of ocular disease and had ocular parameters within

  13. Relationships of contact pressure with subjective experiences of comfort and discomfort in using hand saws

    NARCIS (Netherlands)

    Kuijt-Evers, L.

    2005-01-01

    The relationships of objective measurements (contact pressure and productivity) with subjective experienced comfort and discomfort in using hand saws was examined. Professional carpenters evaluated five different hand saws. The pressure-time integral during the static pressure measurement (beta =

  14. Polymer wear evaluation

    DEFF Research Database (Denmark)

    Lagerbon, Mikkel; Sivebæk, Ion Marius

    2012-01-01

    Polymer wear plays an increasing role in manufacturing of machine parts for e.g. medical devices. Some of these have an expected lifetime of five to eight years during which very little wear of the components is acceptable. Too much wear compromises the dosage accuracy of the device and thereby...... the safety of the patients. Prediction of the wear of polymers is complicated by the low thermal conductivity of this kind of material. It implies that any acceleration of testing conditions by increased contact pressure and/or sliding velocity will make the polymer fail due to exaggerated heat buildup....... This is not the kind of wear observed in medical devices. In the present work a method was developed capable of evaluating the wear progression in polymer-polymer contacts. The configuration of the setup is injection moulded specimens consisting of an upper part having a toroid shape and a lower flat part. The sliding...

  15. Wear and Corrosion Resistance of Thick Ti-6Al-4V Coating Deposited on Ti-6Al-4V Substrate via High-Pressure Cold Spray

    Science.gov (United States)

    Khun, N. W.; Tan, A. W. Y.; Sun, W.; Liu, E.

    2017-08-01

    Ti-6Al-4V (Ti64) coating with a thickness of about 9 mm was deposited on commercial Ti64 substrate via a high-pressure cold spray process. The microstructure, hardness, and wear and corrosion resistance of the Ti64 coating were systematically investigated. The hardness of the Ti64 coating was higher than that of the Ti64 substrate due to the cold-worked microstructure of the coating. The tribological results showed that there was no significant difference in the surface wear rates of the Ti64 coating measured on its different layers while the surface wear resistance of the Ti64 coating was lower than its cross-sectional wear resistance. The corrosion results showed that the Ti64 coating did not effectively prevent its underlying Ti64 substrate from corrosion due to the occurrence of pores in the coating microstructure. It could be concluded that the hardness and wear resistance of the Ti64 coating were comparable to those of the commercial Ti64 substrate.

  16. Blood pressure variations in Subjects with different Haemoglobin ...

    African Journals Online (AJOL)

    Dr Olaleye Samuel

    variations in blood pressures as well as relating the blood pressures in different haemoglobin. (HB) genotypes to each other. Blood pressures in 20 steady and crisis states SCD patients respectively with 40 apparently healthy heterozygous HB AS and HB AA genotype (age and sex –matched). They were aged between 20 ...

  17. Blood pressure variations in Subjects with different Haemoglobin ...

    African Journals Online (AJOL)

    Previous studies on low blood pressure in patients with homozygous sickle cell disease (SCD) have sought various hypotheses on the mechanism of their low blood pressure. However, these studies have not compared the role of the single inheritance of the s-gene in the variations in blood pressures as well as relating the ...

  18. 24-hour intraocular pressure fluctuation monitoring using an ocular telemetry Sensor: tolerability and functionality in healthy subjects.

    Science.gov (United States)

    De Smedt, Stefan; Mermoud, André; Schnyder, Corinne

    2012-01-01

    To evaluate the tolerability, comfort, and reliability of the signal transmission of an ocular Sensor used for 24-hour intraocular pressure fluctuation monitoring in humans. In this uncontrolled open trial involving 10 healthy volunteers, an 8.7-mm radius prototype ocular telemetry Sensor (SENSIMED Triggerfish, Lausanne, Switzerland) and an orbital bandage containing a loop antenna were applied and connected to a portable recorder after full eye examination. Best-corrected visual acuity and position, surface wetting ability, and mobility of the Sensor were assessed after 5 and 30 minutes, 4, 12, and 24 hours. Subjective wearing comfort was scored and activities documented in a logbook. After Sensor removal, a full eye examination was repeated and the recorded signal analyzed. The comfort score was high and did not fluctuate significantly over time. The mobility of the Sensor was limited across follow-up visits and its surface wetting ability remained good. Best-corrected visual acuity was significantly reduced during Sensor wear and immediately after its removal (from 1.07 before, to 0.85 after, P value 0.008). Three subjects developed a mild, transient corneal abrasion. In all but 1 participant, we obtained usable data of a telemetric signal recording with sufficient sensitivity to depict ocular pulsation. This 24-hour trial has encouraging results on the tolerability and functionality of the ocular telemetric Sensor for intraocular pressure fluctuation monitoring. Further studies with different Sensor radii conducted on a larger study population are needed to improve comfort, precision, and interpretation of the telemetric signal.

  19. [Evaluation of total energy expenditure in adult, overweight and free-living subjects. A comparison between two methods: Factorial Method vs SenseWear Armband "Metabolic Holter"].

    Science.gov (United States)

    Giobbi, G

    2008-01-01

    Evaluation of SenseWear Armband functional and structural characteristics and comparison between TEE value from Factorial Method and Metabolic Holter. The study has involved a homogeneous group of 21 adult, overweight (25BMI30 Kg/m(2)) and free-living subjects, 9 men and 12 women, with an average age of 34.9 +/- 14.5 (20-60 years old). TEE valuation has been performed for each subject by means of Factorial Method and, secondly, through the application of SenseWear Armband (Bodymedia Inc., Pittsburgh, PA, USA). Values recorded by Armband overestimate Factorial values of 14%. The Student's t Test has reported significant results (t = 3.540; p = 0.002). Spearman's Correlation has showed the following values of r = 0.696 and p = 0.001. The analysed methods can't be superimposed because the study has showed a signifi cant difference between the reported values. In spite of all that, Spearman study has highlighted a remarkable statistic relation between the techniques. In conclusion, SWA and FM seem to allow a corresponding diagnosis.

  20. Ambulatory blood pressure and urinary albumin excretion in clinically healthy subjects

    DEFF Research Database (Denmark)

    Clausen, Peter Vilhelm; Jensen, J S; Borch-Johnsen, K

    1998-01-01

    UAER. Because 24-hour ambulatory blood pressure is a superior predictor of hypertensive target organ involvement, we aimed to investigate blood pressure profile in clinically healthy subjects with elevated UAER. Ambulatory blood pressure monitoring was performed with a portable recorder in 27 subjects...... with an elevated UAER (>6.6 microg/min, overnight urine collection) and 46 normoalbuminuric control subjects. Mean+/-SD systolic and diastolic ambulatory blood pressures (24-hour) were significantly higher in subjects with elevated UAER than in normoalbuminuric controls (134+/-12 versus 128+/-11 mm Hg and 78...

  1. Evaluation of a new methodology to simulate damage and wear of polyethylene hip replacements subjected to edge loading in hip simulator testing.

    Science.gov (United States)

    Partridge, Susan; Tipper, Joanne L; Al-Hajjar, Mazen; Isaac, Graham H; Fisher, John; Williams, Sophie

    2017-06-29

    Wear and fatigue of polyethylene acetabular cups have been reported to play a role in the failure of total hip replacements. Hip simulator testing under a wide range of clinically relevant loading conditions is important. Edge loading of hip replacements can occur following impingement under extreme activities and can also occur during normal gait, where there is an offset deficiency and/or joint laxity. This study evaluated a hip simulator method that assessed wear and damage in polyethylene acetabular liners that were subjected to edge loading. The liners tested to evaluate the method were a currently manufactured crosslinked polyethylene acetabular liner and an aged conventional polyethylene acetabular liner. The acetabular liners were tested for 5 million standard walking cycles and following this 5 million walking cycles with edge loading. Edge loading conditions represented a separation of the centers of rotation of the femoral head and the acetabular liner during the swing phase, leading to loading of the liner rim on heel strike. Rim damage and cracking was observed in the aged conventional polyethylene liner. Steady-state wear rates assessed gravimetrically were lower under edge loading compared to standard loading. This study supports previous clinical findings that edge loading may cause rim cracking in liners, where component positioning is suboptimal or where material degradation is present. The simulation method developed has the potential to be used in the future to test the effect of aging and different levels of severity of edge loading on a range of cross-linked polyethylene materials. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2017. © 2017 Wiley Periodicals, Inc.

  2. Effects of long-term wearing of high-heeled shoes on the control of the body's center of mass motion in relation to the center of pressure during walking.

    Science.gov (United States)

    Chien, Hui-Lien; Lu, Tung-Wu; Liu, Ming-Wei

    2014-04-01

    High-heeled shoes are associated with instability and falling, leading to injuries such as fracture and ankle sprain. This study investigated the effects of habitual wearing of high-heeled shoes on the body's center of mass (COM) motion relative to the center of pressure (COP) during gait. Fifteen female experienced wearers and 15 matched controls walked with high-heeled shoes (7.3cm) while kinematic and ground reaction force data were measured and used to calculate temporal-distance parameters, joint moments, COM-COP inclination angles (IA) and the rate of IA changes (RCIA). Compared with inexperienced wearers, experienced subjects showed significantly reduced frontal IA with increased ankle pronator moments during single-limb support (pshoes, providing a basis for future design of strategies to minimize the risk of falling during high-heeled gait. Copyright © 2014 Elsevier B.V. All rights reserved.

  3. Physiological and Subjective Responses to Wearing the A/P22P-9(V) helicopter Aircrewman Chemical, Biological Protection Ensemble

    Science.gov (United States)

    1992-04-21

    2. The assembly consists of eight basic components. MK-i Undercoverall 14. The MK-i is a one-piece coverall constructed of a nonwoven nylon fabric...constructed of a nonwoven nylon fabric with a small percentage of viscose rayon. The outside of the garment is treated with a fluorochemical to repel liquids...temperatures was known to produce heat stress. subjects were well-trained on heat-related injuries, their symptoms and remedies . An explanation of heat

  4. Prognostic value of the morning blood pressure surge in 5645 subjects from 8 populations

    DEFF Research Database (Denmark)

    Li, Yan; Thijs, Lutgarde; Hansen, Tine W

    2010-01-01

    Previous studies on the prognostic significance of the morning blood pressure surge (MS) produced inconsistent results. Using the International Database on Ambulatory Blood Pressure in Relation to Cardiovascular Outcome, we analyzed 5645 subjects (mean age: 53.0 years; 54.0% women) randomly...

  5. Eye Wear

    Science.gov (United States)

    Eye wear protects or corrects your vision. Examples are Sunglasses Safety goggles Glasses (also called eyeglasses) Contact ... jobs and some sports carry a risk of eye injury. Thousands of children and adults get eye ...

  6. Sitting and Supine Esophageal Pressures in Overweight and Obese Subjects Authors

    Science.gov (United States)

    Owens, Robert L.; Campana, Lisa M.; Hess, Lauren; Eckert, Danny J.; Loring, Stephen H.; Malhotra, Atul

    2012-01-01

    Esophageal pressure can be used to approximate pleural pressure and might be clinically useful, particularly in the obese e.g to guide mechanical ventilator settings in critical illness. However, mediastinal artifact (the difference between true pleural pressure and esophageal pressure) may limit acceptance of the measurement, and reproducibility of esophageal pressure measurements remains unknown. Therefore, we aimed to assess the effect of body posture on esophageal pressure in a cohort of obese but healthy subjects, some of whom had multiple measurements, to address the clinical robustness of esophageal manometry. Twenty-five overweight and obese subjects (BMI>25kg/m2) and 11 control lean subjects (BMI.1±2.1 vs. −3.3±1.2cmH2O, supine 9.3±3.3 vs. 6.9±2.8cmH2O, respectively). The mean differences between repeated measurements were small (−0.3 ± 1.7cmH2O sitting and −0.1 ± 1.5cmH2O supine). Esophageal pressures correlated with a number of anthropometric and spirometric variables. In conclusion, esophageal pressures are slightly greater in overweight and obese subjects than lean subjects; but changes with position are similar in both groups. These data indicate that mediastinal weight and postural effects on esophageal pressure are within a clinically acceptable range, and suggest that esophageal manometry can be used to inform clinical decision making across wide range of body types. PMID:22695479

  7. The influence of chemistry concentration on the fracture risk of a reactor pressure vessel subjected to pressurized thermal shocks

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Pin-Chiun [Institute of Nuclear Engineering and Science, National Tsing-Hua University, Hsinchu 30013, Taiwan, ROC (China); Chou, Hsoung-Wei, E-mail: hwchou@iner.gov.tw [Institute of Nuclear Energy Research, Taoyuan 32546, Taiwan, ROC (China); Ferng, Yuh-Ming [Institute of Nuclear Engineering and Science, National Tsing-Hua University, Hsinchu 30013, Taiwan, ROC (China)

    2016-02-15

    Highlights: • Probabilistic fracture mechanics method was used to analyze a reactor pressure vessel. • Effects of copper and nickel contents on RPV fracture probability under PTS were investigated and discussed. • Representative PTS transients of Beaver Valley nuclear power plant were utilized. • The range of copper and nickel contents of the RPV materials were suggested. • With different embrittlement levels the dominated PTS category is different. - Abstract: The radiation embrittlement behavior of reactor pressure vessel shell is influenced by the chemistry concentration of metal materials. This paper aims to study the effects of copper and nickel content variations on the fracture risk of pressurized water reactor (PWR) pressure vessel subjected to pressurized thermal shock (PTS) transients. The probabilistic fracture mechanics (PFM) code, FAVOR, which was developed by the Oak Ridge National Laboratory in the United States, is employed to perform the analyses. A Taiwan domestic PWR pressure vessel assumed with varied copper and nickel contents of beltline region welds and plates is investigated in the study. Some PTS transients analyzed from Beaver Valley Unit 1 for establishing the U.S. NRC's new PTS rule are applied as the loading condition. It is found that the content variation of copper and nickel will significantly affect the radiation embrittlement and the fracture probability of PWR pressure vessels. The results can be regarded as the risk incremental factors for comparison with the safety regulation requirements on vessel degradation as well as a reference for the operation of PWR plants in Taiwan.

  8. Subjects with Knee Osteoarthritis Exhibit Widespread Hyperalgesia to Pressure and Cold.

    Directory of Open Access Journals (Sweden)

    Penny Moss

    Full Text Available Hyperalgesia to mechanical and thermal stimuli are characteristics of a range of disorders such as tennis elbow, whiplash and fibromyalgia. This study evaluated the presence of local and widespread mechanical and thermal hyperalgesia in individuals with knee osteoarthritis, compared to healthy control subjects. Twenty-three subjects with knee osteoarthritis and 23 healthy controls, matched for age, gender and body mass index, were recruited for the study. Volunteers with any additional chronic pain conditions were excluded. Pain thresholds to pressure, cold and heat were tested at the knee, ipsilateral heel and ipsilateral elbow, in randomized order, using standardised methodology. Significant between-groups differences for pressure pain and cold pain thresholds were found with osteoarthritic subjects demonstrating significantly increased sensitivity to both pressure (p = .018 and cold (p = .003 stimuli, compared with controls. A similar pattern of results extended to the pain-free ipsilateral ankle and elbow indicating widespread pressure and cold hyperalgesia. No significant differences were found between groups for heat pain threshold, although correlations showed that subjects with greater sensitivity to pressure pain were also likely to be more sensitive to both cold pain and heat pain. This study found widespread elevated pain thresholds in subjects with painful knee osteoarthritis, suggesting that altered nociceptive system processing may play a role in ongoing arthritic pain for some patients.

  9. Radial distribution of esophageal peristaltic pressure in normal subjects and patients with esophageal diverticulum.

    Science.gov (United States)

    Dodds, W J; Stef, J J; Hogan, W J; Hoke, S E; Stewart, E T; Arndorfer, R C

    1975-09-01

    This study was designed to determine the radial profile of peristaltic pressure waves in the esophageal body of normal subjects and patients with isophageal diverticulum. We used a manometric assembly featuring four radial side hole recording orifices oriented at equidistant 90 degree angles. Each recording catheter was infused with water at a rate (6.1 ml per min) which provided high fidelity pressure recording. In normal subjects, the radially recorded peristaltic pressure complexes were similar in peak amplitude and wave form. The range of pressure differences between the four radial recordings averaged 9.0 +/- 4 SD mm Hg A range is less than or greater to 25 mm Hg occurring in 99% of observations. These variations in pressure amplitude showed no consistant spacial orientation. In 5 of the 6 patients with esophageal diverticulum, the range of radial peristaltic pressure differences exceeded 25 mm Hg in the region of the diverticulum, the lowest pressure occurring at the recording orifice facing the diverticulum mouth. In occasional peristaltic sequences abnormal wave forms featuring abrupt onsets or offsets were observed. These bizarre wave forms were probably caused by oralaboral diverticulum movement relative to the recording sensor during peristalsis. Two patients had abnormally high peristaltic pressure amplitudes, greater than 250 mm Hg. This latter finding introduces the possibility that hypertensive peristaltic contractions may contribute to diverticulum production in some patients.

  10. Can subjective comfort be used as a measure of plantar pressure in football boots?

    Science.gov (United States)

    Okholm Kryger, Katrine; Jarratt, Vicky; Mitchell, Séan; Forrester, Steph

    2017-05-01

    Comfort has been shown to be the most desired football boot feature by players. Previous studies have shown discomfort to be related to increased plantar pressures for running shoes which, in some foot regions, has been suggested to be a causative factor in overuse injuries. This study examined the correlation between subjective comfort data and objective plantar pressure for football boots during football-specific drills. Eight male university football players were tested. Plantar pressure data were collected during four football-specific movements for each of three different football boots. The global and local peak pressures based on a nine-sectioned foot map were compared to subjective comfort measures recorded using a visual analogue scale for global discomfort and a discomfort foot map for local discomfort. A weak (rs = -0.126) yet significant (P comfort. The model only significantly predicted (P > 0.001) the outcome for two (medial and lateral forefoot) of the nine foot regions. Subjective comfort data is therefore not a reliable measure of increased plantar pressures for any foot region. The use of plantar pressure measures is therefore needed to optimise injury prevention when designing studded footwear.

  11. Dynamic analysis of an axially moving beam subject to inner pressure using finite element method

    Energy Technology Data Exchange (ETDEWEB)

    Hua, Hongliang; Qiu, Ming; Liao, Zhenqiang [Nanjing University of Science and Technology, Nanjing (China)

    2017-06-15

    A dynamic model of an axially moving flexible beam subject to an inner pressure is present. The coupling principle between a flexible beam and inner pressure is analyzed first, and the potential energy of the inner pressure due to the beam bending is derived using the principle of virtual work. A 1D hollow beam element contain inner pressure is established. The finite element method and Lagrange’s equation are used to derive the motion equations of the axially moving system. The dynamic responses are analyzed by Newmark-β time integration method. Based on the computed dynamic responses, the effects of inner pressure on beam dynamics are discussed. Some interesting phenomenon is observed.

  12. Differences in Blood Pressure Measurements Obtained Using an Automatic Oscillometric Sphygmomanometer Depending on Clothes-Wearing Status

    Science.gov (United States)

    Ki, Ji Hoon; Lee, Soo Hee

    2013-01-01

    Background According to the current guidelines for blood pressure monitoring, clinicians are recommended to measure blood pressure by completely exposing the upper arm. However, it is a common practice that blood pressure is measured with the cuff placed over the sleeve or with the sleeve rolled up. We therefore conducted this study to examine whether there are any differences in blood pressure measurements among the three different settings: the sleeve group, the rolled sleeve group, and the bare arm group. Methods We conducted the current study in 141 male and female adult patients who visited our clinical department. In these patients, we took repeatedly blood pressure measurements using the same automatic oscillometric device on three different settings. Then, we analyzed the results with the use of randomized block design analysis of variance. Results The mean values of systolic blood pressure (SBP) between the first reading and those of the second reading were 128.5 ± 10.6 mm Hg in the sleeve group, 128.3 ± 10.8 mm Hg in the rolled sleeve group, and 128.3 ± 10.7 mm Hg in the bare arm group. These results indicate that there were no significant differences among the three groups (P = 0.32). In addition, the mean values of diastolic blood pressure (DBP) between the first reading and those of the second reading were 80.7 ± 6.1 mm Hg in the sleeve group, 80.7 ± 6.1 mm Hg in the rolled sleeve group, and 80.6 ± 5.9 mm Hg in the bare arm group. These results indicate that there were no significant differences among the three groups (P = 0.77). In addition, based on the age, sex, past or current history of hypertension or diabetes mellitus, the thickness of sleeve, weight, a drinking history, and a smoking history, there were no significant differences in SBP and DBP among the three groups. Conclusion There were no significant differences in blood pressure measurements between the three different settings (the sleeve group, the rolled sleeve group, and the bare

  13. Engineering wear-resistant surfaces in automotive aluminum

    Science.gov (United States)

    Kavorkijan, V.

    2003-02-01

    Inadequate wear resistance and low seizure loads prevent the direct use of aluminum alloys in automotive parts subject to intensive friction combined with high thermal and mechanical loading, such as brake discs, pistons, and cylinder liners. To enable the use of aluminum alloys in the production of automotive brake discs and other wear-resistant products, the insertion of a monolithic friction cladding rather than surface coating has been considered in this work. Three experimental approaches, two based on the pressure-less infiltration of porous ceramic preforms and one based on the subsequent hot rolling of aluminum and metal-matrix composite strips, are currently under investigation.

  14. Wear characteristics in a two-body wear test.

    Science.gov (United States)

    Wassell, R W; McCabe, J F; Walls, A W

    1994-07-01

    A previous report compared spherical steatite (ceramic enamel substitute) abraders with those of natural enamel in a two-body wear test. The wear rates and coefficients of friction of the two abraders against various composites and an amalgam were well correlated although the wear rates were slightly higher with steatite. This report investigates the characteristics of the worn abrader and specimen surfaces. Scanning electron microscopy and laser profilometry were used. Similar wear characteristics were found for the two types of abraders. Adhesive wear was evident for the amalgam, Dispersalloy (Johnson & Johnson), and the heat/pressure-cured microfill composite, Isosit (Ivoclar-Vivadent). Abrasion was seen with the hybrid composite, Occlusin (ICI), and, to a lesser extent, the microfill composite, Heliomolar (Ivoclar-Vivadent). The appearance of the worn small particle hybrid composite, Brilliant Dentin (Coltène), suggested that fatigue and delamination were involved. Laser profilometry showed that the hybrid composites caused much greater wear to the abraders than either the microfill composites or amalgam. The Ra values of the worn abraders and specimens were similar, suggesting conformal contact between them and endorsing the well controlled conditions of the wear test. The results of this and other publications suggest that steatite can be used as an alternative to enamel in performing two-body wear tests on dental composites. This should help significantly in materials evaluation and development.

  15. Tooth wear

    Directory of Open Access Journals (Sweden)

    Tušek Ivan

    2014-01-01

    Full Text Available Tooth wear is the loss of dental hard tissue that was not caused by decay and represents a common clinical problem of modern man. In the etiology of dental hard tissue lesions there are three dominant mechanisms that may act synergistically or separately:friction (friction, which is caused by abrasion of exogenous, or attrition of endogenous origin, chemical dissolution of dental hard tissues caused by erosion, occlusal stress created by compression and flexion and tension that leads to tooth abfraction and microfracture. Wear of tooth surfaces due to the presence of microscopic imperfections of tooth surfaces is clinically manifested as sanding veneers. Tribology, as an interdisciplinary study of the mechanisms of friction, wear and lubrication at the ultrastructural level, has defined a universal model according to which the etiopathogenesis of tooth wear is caused by the following factors: health and diseases of the digestive tract, oral hygiene, eating habits, poor oral habits, bruxism, temporomandibular disorders and iatrogenic factors. Attrition and dental erosion are much more common in children with special needs (Down syndrome. Erosion of teeth usually results from diseases of the digestive tract that lead to gastroesophageal reflux (GER of gastric juice (HCl. There are two basic approaches to the assessment of the degree of wear and dental erosion. Depending on the type of wear (erosion, attrition, abfraction, the amount of calcium that was realised during the erosive attack could be determined qualitatively and quantitatively, or changes in optical properties and hardness of enamel could be recorded, too. Abrasion of teeth (abrasio dentium is the loss of dental hard tissue caused by friction between the teeth and exogenous foreign substance. It is most commonly provoked by prosthetic dentures and bad habits, while its effect depends on the size of abrasive particles and their amount, abrasive particle hardness and hardness of tooth

  16. Structural Stability of a Stiffened Aluminum Fuselage Panel Subjected to Combined Mechanical and Internal Pressure Loads

    Science.gov (United States)

    Rouse, Marshall; Young, Richard D.; Gehrki, Ralph R.

    2003-01-01

    Results from an experimental and analytical study of a curved stiffened aluminum panel subjected to combined mechanical and internal pressure loads are presented. The panel loading conditions were simulated using a D-box test fixture. Analytical buckling load results calculated from a finite element analysis are presented and compared to experimental results. Buckling results presented indicate that the buckling load of the fuselage panel is significantly influenced by internal pressure loading. The experimental results suggest that the stress distribution is uniform in the panel prior to buckling. Nonlinear finite element analysis results correlates well with experimental results up to buckling.

  17. [Influence of gait speed on plantar pressure in subjects with unilateral knee osteoarthritis].

    Science.gov (United States)

    Fernandes, Wagner Costa; Machado, Alvaro; Borella, Caio; Carpes, Felipe P

    2014-01-01

    Changing gait speed is a common strategy to manipulate exercise intensity during physical exercise, but may elicit higher impact forces and consequent joint loading. Here we analyzed the effects of increasing walking velocity on plantar pressure and asymmetries in elderly with knee osteoarthritis (OA). Our hypothesis was that the contralateral limb could receive higher loading compared to the OA limb in the different walking speeds tested. Twelve elderly with unilateral knee OA walked at different self-selected speeds along a 10 m pass way stepping on an instrumented mat for measurement of plantar pressure at preferred, slow and fast gait speeds. Five steps were recorded for each speed. Plantar pressure data were compared between the speeds and legs. speeds were significantly different between them (p<0.05). Mean and peak plantar pressure increased when speed changed from slow to fast (p<0.05). Velocity of the center of pressure increased and the single stance time decreased when walk speed was increased (p<0.05). Any asymmetries were observed. Increasing gait speed from slow to fast in subjects with unilateral knee OA significantly affected variables of plantar pressure, but asymmetries between committed and contralateral leg were not detected. Copyright © 2014 Elsevier Editora Ltda. All rights reserved.

  18. Si{sub 3}N{sub 4} coating for improvement of anti-oxidation and anti-wear properties by low pressure chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seung Yun; Kim, Ok Hee; Park, Chong Ook [Korea Advanced Inst. of Science and Technology, Taejeon (Korea, Republic of); Yeh, Byung Hahn; Jung, Bahl [Agency of Defence Development, Taejon (Korea, Republic of)

    1995-10-01

    The deposition properties of Si{sub 3}N{sub 4} deposited by low pressure chemical vapor deposition were studied to evaluate Si{sub 3}N{sub 4} as part of multi-layer coatings for anti-oxidation and anti-wear coating of graphite in the propellant-burning environment. Si{sub 3}N{sub 4} was deposited on the pack-SiC coated graphite and the tendencies of deposition rate and surface morphology changes with temperatures and reaction gas ratios were investigated. In low deposition temperatures the deposition rate increased with increasing temperature but in high temperatures the deposition rate decreased with increasing temperature. The grain size of Si{sub 3}N{sub 4} decreased with increasing temperature. In condition that the range of reaction gas ratios is 20 {<=} NH{sub 3}/SiH{sub 4} {<=} 40, the deposition rate and surface morphology did not change. The Si{sub 3}N{sub 4} deposited at 800-1300 degree was amorphous, and by post-annealing at 1300 degree in N{sub 2} ambient, the Si{sub 3}N{sub 4} crystallized. (author). 15 refs., 10 figs.

  19. Endothelial dysfunction, ambulatory pulse pressure and albuminuria are associated in Type 2 diabetic subjects

    DEFF Research Database (Denmark)

    Knudsen, Søren Tang; Jeppesen, Peter; Frederiksen, Christian Alcaraz

    2007-01-01

    examined. We examined the relation between PP, markers of endothelial activation and albuminuria in Type 2 diabetic patients. METHODS: In 46 Type 2 diabetic patients and 19 non-diabetic subjects, we performed 24-h ambulatory blood pressure (AMBP) monitoring. Urinary albumin excretion rate was measured......: Increased PP is associated with endothelial activation and albuminuria in Type 2 diabetic patients. Thus, endothelial dysfunction may represent a pathophysiological link between an elevated PP and microvascular complications in these subjects. Prospective studies are needed to further elucidate...

  20. Subjective Mood in Young Unmedicated Depressed Women under High and Low Sleep Pressure Conditions

    Directory of Open Access Journals (Sweden)

    Angelina Birchler-Pedross

    2016-12-01

    Full Text Available Diurnal mood variations are one of the core symptoms in depression, and total sleep deprivation (SD can induce rapid, short-lasting clinical improvement in depressed patients. Here, we investigated if differential sleep pressure conditions impact on subjective mood levels in young women with major depressive disorder (MDD without sleep disturbances, and in healthy controls. Eight healthy and eight MDD women underwent 40-h SD (high sleep pressure and 40-h multiple NAP (low sleep pressure protocols under constant routine conditions during which subjective mood was assessed every 30-min. MDD women rated overall significantly worse mood than controls, with minimal values for both groups during the biological night (ca. 4 a.m., under high and low sleep pressure conditions. During SD, nighttime mood ratings in MDD women were lower than in controls and partially recovered during the second day of SD, but never attained control levels. The degree of this diurnal time-course in mood under SD correlated positively with sleep quality in MDD women. Our data indicate that MDD women without sleep disturbances did not exhibit a SD-induced antidepressant response, suggesting that the mood enhancement response to sleep deprivation might be related to the co-existence of sleep disturbances, which is an association that remains to be fully established.

  1. Subjective Mood in Young Unmedicated Depressed Women under High and Low Sleep Pressure Conditions

    Science.gov (United States)

    Birchler-Pedross, Angelina; Frey, Sylvia; Götz, Thomas; Brunner, Patrick; Knoblauch, Vera; Wirz-Justice, Anna; Chellappa, Sarah L.; Cajochen, Christian

    2016-01-01

    Diurnal mood variations are one of the core symptoms in depression, and total sleep deprivation (SD) can induce rapid, short-lasting clinical improvement in depressed patients. Here, we investigated if differential sleep pressure conditions impact on subjective mood levels in young women with major depressive disorder (MDD) without sleep disturbances, and in healthy controls. Eight healthy and eight MDD women underwent 40-h SD (high sleep pressure) and 40-h multiple NAP (low sleep pressure) protocols under constant routine conditions during which subjective mood was assessed every 30-min. MDD women rated overall significantly worse mood than controls, with minimal values for both groups during the biological night (ca. 4 a.m.), under high and low sleep pressure conditions. During SD, nighttime mood ratings in MDD women were lower than in controls and partially recovered during the second day of SD, but never attained control levels. The degree of this diurnal time-course in mood under SD correlated positively with sleep quality in MDD women. Our data indicate that MDD women without sleep disturbances did not exhibit a SD-induced antidepressant response, suggesting that the mood enhancement response to sleep deprivation might be related to the co-existence of sleep disturbances, which is an association that remains to be fully established. PMID:27941666

  2. FRACTURE MECHANICS UNCERTAINTY ANALYSIS IN THE RELIABILITY ASSESSMENT OF THE REACTOR PRESSURE VESSEL: (2D SUBJECTED TO INTERNAL PRESSURE

    Directory of Open Access Journals (Sweden)

    Entin Hartini

    2016-06-01

    Full Text Available ABSTRACT FRACTURE MECHANICS UNCERTAINTY ANALYSIS IN THE RELIABILITY ASSESSMENT OF THE REACTOR PRESSURE VESSEL: (2D SUBJECTED TO INTERNAL PRESSURE. The reactor pressure vessel (RPV is a pressure boundary in the PWR type reactor which serves to confine radioactive material during chain reaction process. The integrity of the RPV must be guaranteed either  in a normal operation or accident conditions. In analyzing the integrity of RPV, especially related to the crack behavior which can introduce break to the reactor pressure vessel, a fracture mechanic approach should be taken for this assessment. The uncertainty of input used in the assessment, such as mechanical properties and physical environment, becomes a reason that the assessment is not sufficient if it is perfomed only by deterministic approach. Therefore, the uncertainty approach should be applied. The aim of this study is to analize the uncertainty of fracture mechanics calculations in evaluating the reliability of PWR`s reactor pressure vessel. Random character of input quantity was generated using probabilistic principles and theories. Fracture mechanics analysis is solved by Finite Element Method (FEM with  MSC MARC software, while uncertainty input analysis is done based on probability density function with Latin Hypercube Sampling (LHS using python script. The output of MSC MARC is a J-integral value, which is converted into stress intensity factor for evaluating the reliability of RPV’s 2D. From the result of the calculation, it can be concluded that the SIF from  probabilistic method, reached the limit value of  fracture toughness earlier than SIF from  deterministic method.  The SIF generated by the probabilistic method is 105.240 MPa m0.5. Meanwhile, the SIF generated by deterministic method is 100.876 MPa m0.5. Keywords: Uncertainty analysis, fracture mechanics, LHS, FEM, reactor pressure vessels   ABSTRAK ANALISIS KETIDAKPASTIAN FRACTURE MECHANIC PADA EVALUASI KEANDALAN

  3. The prevalence of cervical tooth wear in patients with bruxism and other causes of wear.

    Science.gov (United States)

    Shah, Punit; Razavi, Sheri; Bartlett, David W

    2009-07-01

    The aim of this study was to investigate the prevalence of cervical wear lesions in three groups of patients: bruxists, combined tooth wear, and controls. The hypothesis was that those subjects presenting with bruxism were more likely to develop cervical wear lesions. Of 119 subjects, 31 were bruxists with a mean age 48.7 years [standard deviation (SD): 11.6]; 22 had combined wear, aged 43.5 years (14.2); and 66 controls aged 44.9 years (17.0). The clinical appearance of the tooth wear was used to recruit subjects to the bruxist and combined tooth wear groups. Control subjects were randomly selected from those attending for routine dental examination at two general dental practices. A tooth wear index (TWI) was used by two trained examiners to record the severity of wear in each group. There was a statistically significant difference between the controls and both the bruxist and combined tooth wear groups for wear on all surfaces (p < or = 0.001). There was no significant difference between the bruxist and the combined tooth wear group for wear on any surface. There was a statistically significant difference between the control group and both the bruxist and the combined tooth wear group for the severity of cervical wear (p < or = 0.005), but no difference between the bruxist and combined tooth wear groups. There was also no statistical difference in the number of cervical lesions between the groups. In this study, the likely cause of cervical tooth wear was multifactorial.

  4. Microstructure, Mechanical and Abrasive Wear Behavior of 8.0 wt pct Cr White Iron Subjected to Continuous and Cyclic Annealing Treatment

    Science.gov (United States)

    Mandal, Siddhartha Sankar; Ghosh, K. S.; Mondal, Dipak Kumar

    2017-07-01

    Continuous annealing treatment (austenitization for 4 hours followed by furnace cooling) and cyclic annealing treatment (four cycles of austenitization, each of 0.66 hours duration followed by forced air cooling) of 8.0 wt pct Cr white iron samples are undertaken at 1173 K, 1223 K, 1273 K, 1323 K, and 1373 K (900 °C, 950 °C, 1000 °C, 1050 °C, and 1100 °C) as steps of destabilizing the as-cast structure. Continuous annealing results in precipitation of secondary carbides on a matrix containing mainly pearlite, while cyclic annealing treatment causes similar precipitation of secondary carbides on a matrix containing martensite plus retained austenite. On continuous annealing, the hardness falls below the as-cast value (HV 556), while after cyclic annealing treatment there is about 70 pct increase in hardness, i.e., up to HV 960. Decrease in hardness with increasing annealing temperature is quite common after both heat treatments. The as-cast notched impact toughness (4.0 J) is nearly doubled by increasing to 7.0 J after both continuous and cyclic annealing treatment at 1173 K and 1223 K (900 °C and 950 °C). Cyclic annealing treatment gives rise to a maximum notched impact toughness of 10.0 J at 1373 K (1100 °C). Abrasive wear resistance after continuous annealing treatment degrades exhibiting wear loss greater than that of the as-cast alloy. In contrast, samples with cyclic annealing treatment show reasonably good wear resistance, thereby superseding the wear performance of Ni-Hard IV.

  5. Self-pressurization of a flightweight liquid hydrogen storage tank subjected to low heat flux

    Science.gov (United States)

    Hasan, M. M.; Lin, C. S.; Vandresar, N. T.

    1991-01-01

    Results are presented for an experimental investigation of self-pressurization and thermal stratification of a 4.89 cu m liquid hydrogen (LH2) storage tank subjected to low heat flux (0.35, 2.0, and 3.5 W/sq m) under normal gravity conditions. Tests were performed at fill levels of 83 to 84 percent (by volume). The LH2 tank was representative of future spacecraft tankage, having a low mass-to-volume ratio and high performance multilayer thermal insulation. Results show that the pressure rise rate and thermal stratification increase with increasing heat flux. At the lowest heat flux, the pressure rise rate is comparable to the homogenous rate, while at the highest heat flux, the rate is more than three times the homogeneous rate. It was found that initial conditions have a significant impact on the initial pressure rise rate. The quasi-steady pressure rise rates are nearly independent of the initial condition after an initial transient period has passed.

  6. Airborne Wear Particles Emissions ofCommercial Disc Brake Materials– Disc Brake Test Stand Simulations at LowContact Pressures and Rotors Pre-conditionedwith Rust

    OpenAIRE

    Wahlström, Jens; Olander, Lars; Olofsson, Ulf

    2008-01-01

    Most modern passenger cars have disc brakes on the front wheels, which unlike drum brakes are not sealed off to the ambient air. During braking, there is wear to both the rotor and the pads. This wear process generates particles, which may become airborne. A problem with measuring airborne wear particles in field tests is to distinguish them from the background noise. Therefore, a disc brake laboratory test stand that allows control of the cleanness of the surrounding air is used. With this t...

  7. The effect of hyperoxia on central blood pressure in healthy subjects

    Science.gov (United States)

    Siński, Maciej; Dobosiewicz, Anna; Przybylski, Jacek; Abramczyk, Piotr; Gaciong, Zbigniew

    2016-01-01

    Introduction Hyperoxia increases total peripheral resistance by acting locally but also inhibits the activity of carotid body chemoreceptors. We studied the effect of hyperoxia on central pressure in normotensive subjects. Material and methods Medical air followed by 100% oxygen was provided to 19 subjects (12/7 female/male, age 28.2 ±1.1 years) for 15 min through a non-rebreather mask. Central blood pressure was then measured using applanation tonometry. Results After the first 2 min of hyperoxia, heart rate decreased significantly (65 ±2.6 beats/min vs. 61 ±2.1 beats/min, p = 0.0002). Peripheral and central blood pressure remained unchanged, while hemoglobin oxygen saturation and subendocardial viability ratio index increased (97 ±0.4% vs. 99 ±0.2%, p = 0.03; 168 ±8.4% vs. 180 ±8.2%, p = 0.009). After 15 min of 100% oxygen ventilation, heart rate and peripheral and central blood pressures remained unchanged from the first 2 min. The augmentation index, augmentation pressure and ejection duration increased as compared to baseline values and those obtained at 2 min (–5.1 ±2.9% vs. –1.2 ±2.6%, p = 0.005 and –4.6 ±2.7% vs. –1.2 ±2.6%, p = 0.0015; –1.3 ±0.7 mm Hg vs. –0.2 ±1.2 mm Hg, p = 0.003 and –1.1 ±0.7 mm Hg vs. –0.2 ±1.2 mm Hg, p = 0.012; 323 ±3.6 ms vs. 330 ±3.5 ms, p = 0.0002 and 326 ±3.5 ms vs. 330 ±3.5 ms, p = 0.021, respectively). Conclusions The present study shows that hyperoxia does not affect central blood pressure in young healthy subjects and may improve myocardial blood supply estimated indirectly from applanation tonometry. PMID:27695489

  8. Subjectivity

    Directory of Open Access Journals (Sweden)

    Jesús Vega Encabo

    2015-11-01

    Full Text Available In this paper, I claim that subjectivity is a way of being that is constituted through a set of practices in which the self is subject to the dangers of fictionalizing and plotting her life and self-image. I examine some ways of becoming subject through narratives and through theatrical performance before others. Through these practices, a real and active subjectivity is revealed, capable of self-knowledge and self-transformation. 

  9. Relationship Between Simulated Gap Wear and Generalized Wear of Resin Luting Cements.

    Science.gov (United States)

    Tsujimoto, A; Barkmeier, W W; Takamizawa, T; Latta, M A; Miayazaki, M

    The relationship between the simulated gap wear and generalized wear of resin luting cements was investigated. Five resin luting cements, G-Cem LinkForce (GL), Multilink Automix (MA), NX3 Nexus, Panavia V5 (PV), and RelyX Ultimate were evaluated and subsequently subjected to a wear challenge in a Leinfelder-Suzuki (Alabama) wear simulation device. Half of the specimens from each resin luting cement were photo-cured for 40 seconds and the other half were not photo-cured. The simulated gap and generalized wear were generated using a flat-ended stainless steel antagonist. Wear testing was performed in a water slurry of polymethyl methacrylate beads, and the simulated gap and generalized wear were determined using a noncontact profilometer (Proscan 2100) in conjunction with the Proscan and AnSur 3D software. A strong relationship was found between the gap wear and generalized wear simulation models. The simulated gap wear and generalized wear of the resin luting cements followed similar trends in terms of both volume loss and mean depth of wear facets with each curing method. Unlike the simulated gap wear and generalized wear of GL and PV, those of MA, NX, and RU were influenced by the curing method. The results of this study indicate that simulated gap wear of resin luting cements is very similar to simulated generalized wear. In most cases, dual curing appears to ensure greater wear resistance of resin luting cements than chemical curing alone. The wear resistance of some resin luting cements appears to be material dependent and is not influenced by the curing method.

  10. Wear rates of resin composites.

    Science.gov (United States)

    Barkmeier, W W; Erickson, R I; Latta, M A; Wilwerding, T M

    2013-01-01

    SUMMARY A laboratory study was conducted to examine the wear of resin composite materials using a generalized wear simulation model. Ten specimens each of five resin composites (Esthet•X [EX], Filtek Supreme Plus [SP], Filtek Z250 [Z2], Tetric EvoCeram [EC], and Z100 Restorative [Z1]) were subjected to wear challenges of 100,000, 400,000, 800,000, and 1,200,000 cycles. The materials were placed in cylinder-shaped stainless-steel fixtures, and wear was generated using a flat stainless-steel antagonist in a slurry of polymethylmethacrylate beads. Wear (mean facet depth [μm] and volume loss [mm(3)]) was determined using a noncontact profilometer (Proscan 2000) with Proscan and ProForm software. Statistical analysis of the laboratory data using analysis of variance and Tukey's post hoc test showed a significant difference (p<0.05) for mean wear facet depth and volume loss for both the number of cycles and resin composite material. Linear regression analysis was used to develop predictive wear rates and volume loss rates. Linear wear was demonstrated with correlation coefficients (R(2)) ranging from 0.914 to 0.995. Mean wear values (mean facet depth [μm]) and standard deviations (SD) for 1200K cycles were as follows: Z1 13.9 (2.0), Z2 26.7 (2.7), SP 30.1 (4.1), EC 31.8 (2.3), and EX 67.5 (8.2). Volume loss (mm(3)) and SDs for 1200K cycles were as follows: Z1 0.248 (0.036), Z2 0.477 (0.044), SP 0.541 (0.072), EC 0.584 (0.037), and EX 1.162 (0.139). The wear rate (μm) and volume loss rate (mm(3)) per 100,000 cycles for the five resin composites were as follows: wear rate Z1 0.58, EC 1.27, Z2 1.49, SP 1.62, and EX 4.35, and volume loss rate Z1 0.009, EC 0.024, Z2 0.028, SP 0.029, and EX 0.075. The generalized wear model appears to be an excellent method for measuring relative wear of resin composite materials.

  11. Fluoridation and tooth wear in Irish adults.

    LENUS (Irish Health Repository)

    Burke, F M

    2010-10-01

    The aim of this study was to determine the prevalence of tooth wear in adults in Ireland and its relationship with water fluoridation. The National Survey of Adult Oral Health was conducted in 2000\\/2001. Tooth wear was determined using a partial mouth examination assessing the upper and lower anterior teeth. A total of 2456 subjects were examined. In this survey, increasing levels and severity of tooth wear were associated with ageing. Men were more affected by tooth wear and were more likely to be affected by severe tooth wear than women. It was found that age, and gender were significant predictors of tooth wear (P < 0.01). Overall, there was no significant relationship between fluoridation and tooth wear in this study.

  12. Different alternative splicing patterns are subject to opposite selection pressure for protein reading frame preservation

    Directory of Open Access Journals (Sweden)

    Chuang Trees-Juen

    2007-09-01

    Full Text Available Abstract Background Alternative splicing (AS has been regarded capable of altering selection pressure on protein subsequences. Particularly, the frequency of reading frame preservation (FRFP, as a measure of selection pressure, has been reported to be higher in alternatively spliced exons (ASEs than in constitutively spliced exons (CSEs. However, recently it has been reported that different ASE types – simple and complex ASEs – may be subject to opposite selection forces. Therefore, it is necessary to re-evaluate the evolutionary effects of such splicing patterns on frame preservation. Results Here we show that simple and complex ASEs, respectively, have higher and lower FRFPs than CSEs. Since complex ASEs may alter the ends of their flanking exons, the selection pressure on frame preservation is likely relaxed in this ASE type. Furthermore, conservation of the ASE/CSE splicing pattern increases the FRFPs of simple ASEs but decreases those of complex ASEs. Contrary to the well-recognized concept of strong selection pressure on conserved ASEs for protein reading frame preservation, our results show that conserved complex ASEs are relaxed from such pressure and the frame-disrupting effect caused by the insertion of complex ASEs can be offset by compensatory changes in their flanking exons. Conclusion In this study, we find that simple and complex ASEs undergo opposite selection pressure for protein reading frame preservation, with CSEs in-between. Simple ASEs have much higher FRFPs than complex ones. We further find that the FRFPs of complex ASEs coupled with flanking exons are close to those of simple ASEs, indicating that neighboring exons of an ASE may evolve in a coordinated way to avoid protein dysfunction. Therefore, we suggest that evolutionary analyses of AS should take into consideration the effects of different splicing patterns and the joint effects of multiple AS events.

  13. Intraocular pressure following 18 hours of systemic dehydration in ocular normotensive healthy subjects

    Directory of Open Access Journals (Sweden)

    Faustina K. Idu

    2015-03-01

    Full Text Available Aim: To investigate the effect of dehydration on intraocular pressure (IOP. Subjects: The study population comprised 50 subjects (27 men and 23 women with a mean age of 42.84 ± 2.64 years.Method: The subjects dehydrated for 18 hours. IOP was assessed in both eyes using the Perkins handheld applanation tonometer. Baseline measurement of IOP was taken before the subjects dehydrated for 18 hours and repeated after dehydration. Blood samples were taken before and after dehydration for the determination of plasma osmolality and plasma antidiuretic hormone (ADH concentrations.Results: A statistically significant (p < 0.001 reduction in the mean weight of subjects occurred after dehydration. There was a significant reduction in IOP from 16.68 mmHg ± 0.32 mmHg to 13.08 mmHg ± 0.31 mmHg after dehydration (p < 0.001. Mean plasma osmolality showed a statistically significant increase (p < 0.05 from baseline of 290.02 mOsmol/kg ± 1.25 mOsmol/kg to 294.96 mOsmol/kg ± 1.33 mOsmol/kg after dehydration. There was also a significant increase (p < 0.05 in mean plasma ADH concentration from 5.36 pg/mL ± 0.21 pg/mL to 6.40 pg/mL ± 0.20 pg/mL after dehydration. There were no significant differences in both systolic and diastolic blood pressures before and after dehydration.Conclusion: Dehydration decreases IOP in healthy humans; this decrease probably results from an increase in plasma osmolality and plasma ADH concentrations.

  14. Spatial frequency content of plantar pressure and shear profiles for diabetic and non-diabetic subjects.

    Science.gov (United States)

    Berki, Visar; Davis, Brian L

    2016-11-07

    How high does pressure and shear stress sensor resolution need to be in order to reliably measure the plantar pressure and shear profiles (PPSPs) under normal and diabetic feet? In this study, pressure and shear stress data were collected from 26 total diabetic and control subjects using new instrumentation that measures vertical and horizontal force vectors of the plantar contact surface during multiple instances in the gait cycle. The custom built shear-and-pressure-evaluating-camera-system (SPECS) performs simultaneous recordings of pressure and both components of the horizontal force vector (medio-lateral and antero-posterior) at distinctive regions under one׳s foot, at a spatial resolution for each sensor equal to 1.6mm by 1.6mm. A linear interpolation method was used to simulate the effect of increasing sensor size on PPSPs. Ten square-shaped sensors were included in the analysis, having edge lengths of: (1.6mm, 3.2mm, 4.8mm, 6.4mm, 8mm, 9.6mm, 11.2mm, 12.8mm, 14.4mm, and 16mm). A two-dimensional Discrete Fourier Transform was performed on each data set, for each of the ten sensor sizes. To quantify the difference between sensor sizes, a comparison was made using the maximum pressure and shear stress data over the entire plantar contact surface, equivalent to the peak of the spatial frequency spectrum. A reduction of 5% of any component of the stress vector (i.e., pressure, or medio-lateral shear stress, or anter-posterior shear stress) due to an increase in sensor size was deemed significant. The results showed that a sensor measuring 9.6mm by 9.6mm caused meaningful reductions in all three stress components (p<0.001), whereas sensors measuring 1.6mm by 1.6mm, up to 4.8mm by 4.8mm, can capture the full range of spatial frequencies in both pressure and shear stress data. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Boundary-layer transition on a plate subjected to simultaneous spanwise and chordwise pressure gradients

    Science.gov (United States)

    Boldman, D. R.; Brinich, P. F.

    1974-01-01

    The boundary-layer transition on a short plate was studied by means of the china-clay visual technique. The plate model was mounted in a wind tunnel so that it was subjected to small simultaneous spanwise and chordwise pressure gradients. Results of the experimental study, which was performed at three subsonic velocities, indicated that the transition pattern was appreciably curved in the spanwise direction but quite smooth and well behaved. Reasonable comparisons between predictions of transition and experiment were obtained from two finite-difference two-dimensional boundary-layer calculation methods which incorporated transition models based on the concept of a transition intermittency factor.

  16. Investigation of Pull-In Phenomenon of Rectangular Micro-Plate Subjected to Nonlinear Electrostatic Pressure

    Directory of Open Access Journals (Sweden)

    Adel Nabian

    2006-12-01

    Full Text Available In the present work a pull-in voltage of a micro plate subjected to nonlinear electrostatic pressure was studied. The governing equation was derived and in order to linearize the nonlinear governing equation; step-by-step linearization method was used and finite difference method was applied to discretize the linearized equation. The numerical results reveal that the step-by-step linearization method is highly efficient, fast and easiest one to calculate the pull-in voltage. The obtained results for different size of micro plate, initial gap and thickness were shown those effects on the pull-in voltage.

  17. Positive expiratory pressure improves oxygenation in healthy subjects exposed to hypoxia.

    Directory of Open Access Journals (Sweden)

    Hugo Nespoulet

    Full Text Available INTRODUCTION: Positive end-expiratory pressure (PEEP is commonly used in critical care medicine to improve gas exchange. Altitude sickness is associated with exaggerated reduction in arterial oxygenation. We assessed the effect of PEEP and pursed lips breathing (PLB on arterial and tissue oxygenation under normobaric and hypobaric hypoxic conditions. METHODS: Sixteen healthy volunteers were exposed to acute normobaric hypoxia (Laboratory study, FiO₂=0.12. The protocol consisted in 3-min phases with PEEPs of 0, 5 or 10 cmH₂O, PLB or similar ventilation than with PEEP-10, interspaced with 3-min phases of free breathing. Arterial (pulse oximetry and quadriceps (near-infrared spectroscopy oxygenation, ventilation, cardiac function, esophageal and gastric pressures and subjects' subjective perceptions were recorded continuously. In addition, the effect of PEEP on arterial oxygenation was tested at 4,350 m of altitude in 9 volunteers breathing for 20 min with PEEP-10 (Field study. RESULTS: During the laboratory study, PEEP-10 increased arterial and quadriceps oxygenation (arterial oxygen saturation +5.6±5.0% and quadriceps oxyhemoglobin +58±73 µmol.cm compared to free breathing; p0.05 compared to PEEP-0. During the field study, PEEP-10 increased arterial oxygen saturation by +6.7±6.0% after the 3(rd minute with PEEP-10 without further significant increase until the 20(th minute with PEEP-10. Subjects did not report any significant discomfort with PEEP. CONCLUSIONS: These data indicate that 10-cmH₂O PEEP significantly improves arterial and muscle oxygenation under both normobaric and hypobaric hypoxic conditions in healthy subjects. PEEP-10 could be an attractive non-pharmacological tool to limit blood oxygen desaturation and possibly symptoms at altitude.

  18. The effect of single oral doses of duloxetine, reboxetine, and midodrine on the urethral pressure in healthy female subjects, using urethral pressure reflectometry

    DEFF Research Database (Denmark)

    Klarskov, Niels; Cerneus, Dirk; Sawyer, William

    2018-01-01

    AIMS: To evaluate the effect on urethral pressure of reference drugs known to reduce stress urinary incontinence symptoms by different effect size and mechanisms of action on urethral musculature under four test conditions in healthy female subjects using urethral pressure reflectometry. METHODS...

  19. Comparison of two measurement techniques for clinical wear

    DEFF Research Database (Denmark)

    Peters, M C; Delong, R; Pintado, M R

    1999-01-01

    Clinical wear of restorations is generally evaluated by marginal integrity over time. In this study, both a subjective and an objective method for wear assessment are compared, and the relative advantages and disadvantages of each are considered....

  20. Locomotion pattern and foot pressure adjustments during gentle turns in healthy subjects.

    Science.gov (United States)

    Peyer, Kathrin E; Brassey, Charlotte A; Rose, Kayleigh A; Sellers, William I

    2017-07-26

    People suffering from locomotor impairment find turning manoeuvres more challenging than straight-ahead walking. Turning manoeuvres are estimated to comprise a substantial proportion of steps taken daily, yet research has predominantly focused on straight-line walking, meaning that the basic kinetic, kinematic and foot pressure adaptations required for turning are not as well understood. We investigated how healthy subjects adapt their locomotion patterns to accommodate walking along a gently curved trajectory (radius 2.75m). Twenty healthy adult participants performed walking tasks at self-selected speeds along straight and curved pathways. For the first time for this mode of turning, plantar pressures were recorded using insole foot pressure sensors while participants' movements were simultaneously tracked using marker-based 3D motion capture. During the steady-state strides at the apex of the turn, the mean operating point of the inside ankle shifted by 1 degree towards dorsiflexion and that for the outside ankle shifted towards plantarflexion. The largest change in relative joint angle range was an increase in hip rotation in the inside leg (>60%). In addition, the inside foot was subject to a prolonged stance phase and a 10% increase in vertical force in the posteromedial section of the foot compared to straight-line walking. Most of the mechanical change required was therefore generated by the inside leg with hip rotation being a major driver of the gentle turn. This study provides new insight into healthy gait during gentle turns and may help us to understand the mechanics behind some forms of impairment. Copyright © 2017. Published by Elsevier Ltd.

  1. High hydrostatic pressure processing reduces the glycemic index of fresh mango puree in healthy subjects.

    Science.gov (United States)

    Elizondo-Montemayor, Leticia; Hernández-Brenes, Carmen; Ramos-Parra, Perla A; Moreno-Sánchez, Diana; Nieblas, Bianca; Rosas-Pérez, Aratza M; Lamadrid-Zertuche, Ana C

    2015-04-01

    Dietary guidelines recommend the daily consumption of fruits; however, healthy and type 2 diabetes mellitus (T2DM) subjects receive conflicting messages regarding ingestion of fruits, such as mango, because of its sugar content. We investigated the effects of high hydrostatic pressure (HHP) processing of fresh mango puree (MP) on the glycemic indexes (GIs) and postprandial glycemic responses of 38 healthy Mexican subjects in a randomized cross-over clinical trial. Physicochemical characterization of MP included sugar profiles by HPLC-ELSD, starch, fibers, moisture, viscosity, swelling capacity and solubility properties of alcohol insoluble residue (AIR). The mean GI for HHP-MP was significantly lower (32.7 ± 13.4) than that of unprocessed-MP (42.7 ± 19.5). A significantly higher proportion of subjects showed a low GI following the consumption of HHP-MP compared to unprocessed-MP and none of them showed a high GI for the HHP-MP, compared to a significantly higher proportion for the unprocessed-MP. The viscosity and AIR solubility values of HHP-MP samples were significantly higher, which influenced glucose peaking later (Tmax) at 45 minutes and induced 20% lower AUC values than unprocessed-MP, corresponding to greater retardation indexes. The study findings support data stating that low GI fruits are appropriate for glycemic control and that mango may be included as part of healthy subjects' diets and potentially T2DM subjects' diets. Furthermore, HHP processing of mango may offer additional benefits for glycemic control, as its performance regarding GI, AUC and Tmax was significantly better than that of the unprocessed-MP. To our knowledge, this is the first report on the impact of this commercial non-thermal pasteurization technology on glucose metabolism.

  2. Mechanisms underlying center of pressure displacements in obese subjects during quiet stance

    Directory of Open Access Journals (Sweden)

    Priano Lorenzo

    2011-04-01

    Full Text Available Abstract Objective the aim of this study was to assess whether reduced balance capacity in obese subjects is secondary to altered sensory information. Design cross sectional study. Subjects 44 obese (BMI = 40.6 ± 4.6 kg/m2 , age = 34.2 ± 10.8 years, body weight: 114,0 ± 16,0 Kg, body height 167,5 ± 9,8 cm and 20 healthy controls (10 females, 10 males, BMI: 21.6 ± 2.2 kg/m2, age: 30.5 ± 5.5 years, body weight: 62,9 ± 9,3 Kg, body height 170,1 ± 5,8 cm were enrolled. Measurements center of pressure (CoP displacements were evaluated during quiet stance on a force platform with eyes open (EO and closed (EC. The Romberg quotient (EC/EO was computed and compared between groups. Results we found statistically significant differences between obese and controls in CoP displacements (p 0.08. Conclusion the increased CoP displacements in obese subjects do not need an hypothesis about altered sensory information. The integration of different sensory inputs appears similar in controls and obese. In the latter, the increased mass, ankle torque and muscle activity may probably account for the higher CoP displacements.

  3. Isoflavonoids do not inhibit in vivo lipid peroxidation in subjects with high-normal blood pressure.

    Science.gov (United States)

    Hodgson, J M; Puddey, I B; Croft, K D; Mori, T A; Rivera, J; Beilin, L J

    1999-07-01

    The isoflavonoids genistein and daidzein have been shown to have antioxidant activity in vitro, but their effects on in vivo oxidation have not been assessed. The newly described F2-isoprostanes are believed to currently represent the best available marker of in vivo lipid peroxidation. Therefore we have assessed the effects of a 55 mg daily isoflavonoid supplement on urinary F2-isoprostane concentrations in subjects with high-normal blood pressure (BP). A total of 59 subjects completed an 8-week parallel design, randomized, double blind, and placebo-controlled study. F2-isoprostanes, isoflavonoids and creatinine were measured in 24-h urine samples taken at baseline and at the end of the intervention. There were significant increases in urinary excretion of genistein (5.22+/-0.75 mg/day, P genistein and daidzein excretion were not significantly correlated with changes in F2-isoprostanes in the isoflavonoid treatment group. These results are not consistent with the suggestion that the two soy derived isoflavonoids have in vivo antioxidant activity at a level of intake achievable by dietary means and in subjects with high-normal BP.

  4. Intensive blood pressure lowering increases cerebral blood flow in older subjects with hypertension.

    Science.gov (United States)

    Tryambake, Dinesh; He, Jiabao; Firbank, Michael J; O'Brien, John T; Blamire, Andrew M; Ford, Gary A

    2013-06-01

    Hypertension is associated with reduced cerebral blood flow (CBF). Intensive (blood pressure (BP) lowering in older people might give greater reduction in cardiovascular risk, but there are concerns that this might produce hypoperfusion which may precipitate falls and possibly stroke. We determined the effect of intensive compared with usual BP lowering on CBF in hypertensive older subjects. Individuals aged >70 years with a history of systolic hypertension on 1 or no BP lowering drugs were recruited from primary care (n=37; age, 75±4 years; systolic BP, >150 mm Hg) and randomized to receive intensive (target BP, hypertension increases CBF, compared with BP lowering to usual target. These findings suggest hypertension in older people shifts the autoregulatory CBF curve rightward and downward and is reversible with BP lowering.

  5. Nonlinear response of plates subjected to inplane and lateral pressure pulses.

    Science.gov (United States)

    Knapp, L. J.

    1973-01-01

    The nonlinear response of a rectangular plate exposed to a far-field sonic boom disturbance is studied. The plate is subjected to both lateral and in-plane disturbances. The lateral disturbance is in the form of an N-shaped pressure pulse, and the in-plane disturbance is represented by a sinusoidal pulse. The equations of motion are reduced to a set of nonlinear coupled ordinary differential equations using Galerkin's method. These equations are solved numerically using Hamming's (1959) modified predictor-corrector integration method. The effects of in-plane boundary conditions and in-plane inertia are investigated. The nonlinear results, when compared to the linear theory, serve to delineate the realm of validity of the linear theory.

  6. Correlations between subjective treatment responses and plantar pressure parameters of metatarsal pad treatment in metatarsalgia patients: a prospective study

    Directory of Open Access Journals (Sweden)

    Hsi Wei-Li

    2006-12-01

    Full Text Available Abstract Background Metatarsalgia is related to repetitive high-pressure loading under the metatarsal head (MH that causes pain. The high pressure under the MH can be reduced by adequately applying metatarsal pads (MPs. Plantar pressure measurements may provide a method to objectively evaluate pressure loading under the MH. However, it is still unclear if the decrease in plantar pressure under the MH after MP treatment is associated with subjective improvement. This study aims to explore the correlations between subjective pain improvement and outcome rating, and the plantar pressure parameters in metatarsalgia patients treated using MPs. Methods Thirteen patients (a total of 18 feet with secondary metatarsalgia were included in this study. Teardrop-shaped MPs made of polyurethane foam were applied just proximal to the second MH by an experienced physiatrist. Insole plantar pressure was measured under the second MH before and after MP application. Visual analog scale (VAS scores of pain were obtained from all subjects before and after 2 weeks of MP treatment. The subjects rated using four-point subjective outcome scales. The Wilcoxon signed-rank test was used to analyze the difference between the plantar pressure parameters and VAS scores before and after treatment. The Kruskal-Wallis test was applied to compare the plantar pressure parameters in each outcome group. Pearson's correlation was applied to analyze the correlation between the changes in plantar pressure parameters and VAS scores. Statistical significance was set as p Results MP application decreased the maximal peak pressure (MPP and pressure-time integral (PTI under the second MH and also statistically improved subjective pain scores. However, neither the pre-treatment values of the MPP and PTI shift in the position of the MPP after treatment, nor the age, gender and body mass index (BMI of the subjects were statistically correlated with subjective improvement. Declines in the PTI

  7. Beetroot supplementation lowers daily systolic blood pressure in older, overweight subjects.

    Science.gov (United States)

    Jajja, A; Sutyarjoko, A; Lara, J; Rennie, K; Brandt, K; Qadir, O; Siervo, M

    2014-10-01

    Although inorganic nitrate and beetroot juice supplementation are associated with decreased systolic blood pressure (BP), these results have primarily been obtained from short-term trials that focused on healthy young adults. Therefore, we hypothesized that oral supplementation of beetroot juice concentrate would decrease systolic BP in overweight older participants but that the decline in BP would not be sustained after a 1-week interruption of the beetroot juice supplementation. For 3 weeks, 24 participants were randomized to either the beetroot juice concentrate or blackcurrant juice group, with a 1-week postsupplementation phase (week 4). Changes in systolic and diastolic BP were assessed during the supplementation and postsupplementation phases. Blood pressure was measured using 3 different methods: (1) resting clinic BP, (2) 24-hour ambulatory BP monitoring, and (3) home monitoring of daily resting BP. The first 2 methods were applied at baseline and after weeks 3 and 4. Daily measurements were conducted throughout the study, with 21 subjects completing the study (beetroot/blackcurrant = 10/11; male/female = 12/9; age = 62.0 ± 1.4 years; body mass index = 30.1 ± 1.2 kg/m(2)). After 3 weeks, beetroot juice supplementation was not associated with significant changes in resting clinic BP or 24-hour ABPM. Conversely, beetroot juice concentrate reduced daily systolic BP after 3 weeks (-7.3 ± 5.9 mm Hg, P = .02); however, the effect was not maintained after the interruption of the supplementation (week 4, 2.8 ± 6.1 mm Hg, P = .09). In overweight older subjects, beetroot juice concentrate supplementation was associated with beneficial effects on daily systolic BP, although the effects were not significant when measured by 24-hour ABPM or resting clinic BP. Copyright © 2014 Elsevier Inc. All rights reserved.

  8. Fluid-structure interaction analysis for pressurizer surge line subjected to thermal stratification

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Dong Gu [Korea Institute of Nuclear Safety, 19 Guseong-dong, Yuseong-gu, Daejeon 305-338 (Korea, Republic of); Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Jhung, Myung Jo, E-mail: mjj@kins.re.k [Korea Institute of Nuclear Safety, 19 Guseong-dong, Yuseong-gu, Daejeon 305-338 (Korea, Republic of); Chang, Soon Heung [Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)

    2011-01-15

    Research highlights: Temperature of surge line due to stratified flow is defined using CFD analysis. Fluid-structure interaction analysis is performed to investigate the response characteristics due to thermal stress. Fatigue usage factors due to thermal stratification are relatively low. Simplifying temperature distribution in surge line is not always conservative. - Abstract: Serious mechanical damages such as cracks and plastic deformations due to excessive thermal stress caused by thermal stratification have been experienced in several nuclear power plants. In particular, the thermal stratification in the pressurizer surge line has been addressed as one of the significant safety and technical issues. In this study, a detailed unsteady computational fluid dynamics (CFD) analysis involving conjugate heat transfer analysis is performed to obtain the transient temperature distributions in the wall of the pressurizer surge line subjected to stratified internal flows either during out-surge or in-surge operation. The thermal loads from CFD calculations are transferred to the structural analysis code which is employed for the thermal stress analysis to investigate the response characteristics, and the fatigue analysis is ultimately performed. In addition, the thermal stress and fatigue analysis results obtained by applying the realistic temperature distributions from CFD calculations are compared with those by assuming the simplified temperature distributions to identify some requirements for a realistic and conservative thermal stress analysis from a safety point of view.

  9. Induced Opening of the Gastroesophageal Junction Occurs at a Lower Gastric Pressure in Gerd Patients and in Hiatal Hernia Subjects than in Normal Control Subjects

    Directory of Open Access Journals (Sweden)

    Anil Vegesna

    2010-01-01

    Full Text Available Purpose. To determine intragastric pressure threshold for inducing gastroesophageal junction (GEJ opening in normal control subjects with and without hiatal hernia, and in patients with gastroesophageal reflux disease. Methods. This study was performed in 13 normal volunteers, 5 volunteers with hiatal hernia, and 3 patients with gastroesophageal reflux disease. During endoscopy a pressure transducer was used to measure baseline gastric pressures. The pressure in the stomach was measured while air was insufflated into the stomach until the gastroesophageal junction opened on endoscopic view. Results. There were two patterns of GEJ opening in normal volunteers. The mean opening pressure for Gastroesophageal junction in normal pattern-I, normal pattern-II, hiatal hernia, and Gastroesophageal reflux patients was 11.5, 12.6, 3.4, and 1.3 mmHg, respectively. Conclusions. GEJ opening is induced at a significantly lower pressure in subjects with hiatal hernia and in patients with gastroesophageal reflux disease than in normal volunteers.

  10. Correlation between spirometry values and pulmonary artery pressure in young healthy subjects.

    Science.gov (United States)

    Grossman, Alon; Benderly, Michal; Prokupetz, Alex; Gordon, Barak; Kalter-Leibovici, Ofra

    2014-03-01

    Pulmonary hypertension is frequently associated with parenchymal lung disease. We evaluated the association between spirometry values and pulmonary artery systolic pressure (PASP) in young subjects without lung disease : We studied applicants to the Israeli Air Force, who undergo routine evaluation that includes resting spirometry and echocardiography. Applicants with overt lung disease were excluded. All echocardiographic studies performed in the years 1994 through 2010 (n = 6,598) were screened, and files that included PASP and spirometry values were analyzed for the association between PASP and FVC, FEV1, FEV1/FVC, peak expiratory flow, and forced expiratory flow during the middle half of the FVC maneuver. Of the 647 air force applicants who underwent echocardiography in which PASP was measurable and had spirometry data, 607 (94%) were male, and their average age was 18.16 ± 0.73 years. Mean PASP was 26.4 ± 5.2 mm Hg (range 10-41 mm Hg). None of the spirometry values significantly correlated with PASP. PASP in young healthy subjects is not significantly associated with spirometry values. Lung mechanics probably do not contribute significantly to PASP in this population.

  11. Sustainability of Intraocular Pressure Reduction of Travoprost Ophthalmic Solution in Subjects with Normal Tension Glaucoma.

    Science.gov (United States)

    Naito, Tomoko; Okuma, Shinichi; Nagayama, Mikio; Mizoue, Shiro; Ozaki, Mineo; Namiguchi, Koji; Miyamoto, Kazuhisa; Tanito, Masaki; Yoshikawa, Keiji

    2016-03-01

    We examined the sustainability of the intraocular pressure (IOP)-lowering efficacy of travoprost (0.004%) ophthalmic solution in subjects with normal tension glaucoma (NTG). Travoprost ophthalmic solution was given once daily at 9 PM to subjects with newly diagnosed NTG or with NTG who had not received any ocular hypotensives within the previous 30 days. IOP was measured at three time points (9 AM, 1 PM, and 5 PM) at baseline and week 12 visits, and at one time point (9 AM) at week 4 and week 8 visits. Conjunctival hyperemia, superficial punctate keratopathy, and other adverse events were evaluated during the observation period. Thirty subjects (12 males and 18 females; mean age 65.6 years) from 32 subjects enrolled were included in the efficacy analysis. The mean IOPs (±standard deviation) of 16.6 ± 1.4, 15.7 ± 1.8, and 15.7 ± 2.2 mmHg at 9 AM, 1 PM, and 5 PM, respectively, at baseline reduced significantly to the mean IOPs of 13.0 ± 1.8, 12.7 ± 1.8, and 12.8 ± 1.6 mmHg, respectively, at week 12 (P < 0.0001 for every time point). Together with the mean IOPs of 13.4 ± 1.9 mmHg at week 4 and 13.2 ± 1.9 mmHg at week 8, the pooled IOP during the observation period for up to 12 weeks showed a statistically and clinically significant reduction of IOP at 9 AM. (3.4 mmHg or 20.3% reduction from baseline, P < 0.0001). There were no adverse events leading to treatment discontinuation. This multi-center collaborative study suggests that IOP-lowering efficacy of travoprost ophthalmic solution persists during the day at the clinically relevant level in subjects with NTG. Alcon Japan Ltd. University Hospital Medical Information Network, UMIN ID: 000011621.

  12. Noninvasive positive pressure ventilation in subjects with stable COPD: a randomized trial

    Directory of Open Access Journals (Sweden)

    Bhatt SP

    2013-11-01

    Full Text Available Surya P Bhatt,1 Michael W Peterson,2 Jeffrey S Wilson,1 Lakshmi Durairaj1 1Division of Pulmonary, Critical Care, and Occupational Medicine, Department of Internal Medicine, Roy J and Lucille A, Carver College of Medicine, University of Iowa Hospital, Iowa City, IA, USA; 2Department of Medicine, UCSF Fresno Medical Education Program, Fresno, CA, USA Background: The use of domiciliary noninvasive positive pressure ventilation (NPPV in stable chronic obstructive pulmonary disease (COPD with chronic hypercapnic respiratory failure has yielded variable effects on survival, quality of life, and dyspnea. We hypothesized that use of NPPV in stable COPD and partial pressure of carbon dioxide (PaCO2 <52 mmHg might result in improvement in quality of life and dyspnea. Methods: Thirty patients with stable COPD (forced expiratory volume in the first second <50% predicted and PaCO2 <52 mmHg were prospectively randomized to receive domiciliary NPPV (bilevel positive airway pressure, 15/5 cm H2O or usual therapy for 6 months. Measurements were made at baseline, 6 weeks, 3 months, and 6 months. Primary outcomes were quality of life as assessed by the Chronic Respiratory Disease Questionnaire (CRQ, and dyspnea as measured by the Transitional Dyspnea Index (TDI. Results: Fifteen subjects in the NPPV arm and 12 controls completed all the study visits. At 6 weeks and 3 months, the NPPV arm showed significant improvement in TDI total score. However, this effect persisted only in the TDI-Task at 6 months (P=0.03. NPPV use was associated with a small improvement in the CRQ-Mastery domain (0.6 versus –0.1, P=0.04. The arterial partial pressure of oxygen (PaO2 in the control arm worsened over the period of the study, whereas it remained stable in the NPPV arm (change –7.2 mmHg versus +2.1 mmHg, respectively, P=0.02. Conclusion: NPPV resulted in a small improvement in quality of life indices in stable COPD patients with PaCO2 <52 mmHg. Future larger studies will

  13. Wear in human knees

    Directory of Open Access Journals (Sweden)

    M.L. Wang

    2015-06-01

    Full Text Available Wear occurs in natural knee joints and plays a pivotal factor in causing articular cartilage degradation in osteoarthritis (OA processes. Wear particles are produced in the wear process and get involved in inflammation of human knees. This review presents progresses in the mechanical and surface morphological studies of articular cartilages, wear particles analysis techniques for wear studies and investigations of human knee synovial fluid in wear of human knees. Future work is also included for further understanding of OA symptoms and their relations which may shed light on OA causes.

  14. Feasibility study for the non-invasive blood pressure estimation based on ppg morphology: normotensive subject study.

    Science.gov (United States)

    Shin, Hangsik; Min, Se Dong

    2017-01-10

    Blood pressure is a critical bio-signal and its importance has been increased with the aged society and the growth of cardiovascular disease population. However, most of hypertensive patients have been suffered the inconvenience in monitoring blood pressure in daily life because the measurement of the blood pressure depends on the cuff-based technique. Nowadays there are many trials to measure blood pressure without cuff, especially, photoplethysmography (PPG) based research is carried out in various ways. Our research is designed to hypothesis the relationship between vessel wall movement and pressure-flow relationship of PPG and to validate its appropriateness by experimental methods. PPG waveform is simplified by approximate model, and then it is analyzed as the velocity and the acceleration of blood flow using the derivatives of PPG. Finally, we develop pressure index (PI) as an estimation factor of blood pressure by combining of statistically significant segments of photoplethysmographic waveform. Twenty-five subjects were participated in the experiment. As a result of simulation, correlation coefficients between developed PI and blood pressure were represented with R = 0.818, R = 0.827 and R = 0.615 in systolic blood pressure, pulse pressure and mean arterial pressure, respectively, and both of result showed the meaningful statistically significance (P blood pressure but could not find the absolute pressure value. Moreover, proposed index has the limitation of diastolic pressure tracing. However, the result shows that the proposed PI is statistically significantly correlated with blood pressures, and it suggests that the proposed PI as a promising additional parameter for the cuff less blood pressure monitoring.

  15. Perilymphatic pressure dynamics following posture change in patients with Meniere's disease and in normal hearing subjects

    NARCIS (Netherlands)

    Rosingh, HJ; Wit, HP; Albers, FWJ

    The hydrostatic pressure of the inner ear depends on the cerebrospinal fluid pressure through the cochlear aqueduct. The time-course of inner ear pressure change following rapid change in cerebrospinal fluid pressure is related to the aqueduct patency. In this study the patency of the cochlear

  16. Multiscale Modeling of Wear Degradation

    KAUST Repository

    Moraes, Alvaro

    2016-01-06

    Cylinder liners of diesel engines used for marine propulsion are naturally subjected to a wear process, and may fail when their wear exceeds a specified limit. Since failures often represent high economical costs, it is utterly important to predict and avoid them. In this work [4], we model the wear process using a pure jump process. Therefore, the inference goal here is to estimate: the number of possible jumps, its sizes, the coefficients and the shapes of the jump intensities. We propose a multiscale approach for the inference problem that can be seen as an indirect inference scheme. We found that using a Gaussian approximation based on moment expansions, it is possible to accurately estimate the jump intensities and the jump amplitudes. We obtained results equivalent to the state of the art but using a simpler and less expensive approach.

  17. Multiscale Modeling of Wear Degradation

    KAUST Repository

    Moraes, Alvaro

    2015-01-07

    Cylinder liners of diesel engines used for marine propulsion are naturally subjected to a wear process, and may fail when their wear exceeds a specified limit. Since failures often represent high economical costs, it is utterly important to predict and avoid them. In this work [4], we model the wear process using a pure jump process. Therefore, the inference goal here is to estimate: the number of possible jumps, its sizes, the coefficients and the shapes of the jump intensities. We propose a multiscale approach for the inference problem that can be seen as an indirect inference scheme. We found that using a Gaussian approximation based on moment expansions, it is possible to accurately estimate the jump intensities and the jump amplitudes. We obtained results equivalent to the state of the art but using a simpler and less expensive approach.

  18. Multiscale Modeling of Wear Degradation

    KAUST Repository

    Moraes, Alvaro

    2014-01-06

    Cylinder liners of diesel engines used for marine propulsion are naturally subjected to a wear process, and may fail when their wear exceeds a specified limit. Since failures often represent high economical costs, it is utterly important to predict and avoid them. In this work [4], we model the wear process using a pure jump process. Therefore, the inference goal here is to estimate: the number of possible jumps, its sizes, the coefficients and the shapes of the jump intensities. We propose a multiscale approach for the inference problem that can be seen as an indirect inference scheme. We found that using a Gaussian approximation based on moment expansions, it is possible to accurately estimate the jump intensities and the jump amplitudes. We obtained results equivalent to the state of the art but using a simpler and less expensive approach.

  19. Electrocardiographic, echocardiographic, and indirect blood pressure evaluation in dogs subjected to different sedation protocols

    Directory of Open Access Journals (Sweden)

    Helena Mondardo Cardoso

    Full Text Available ABSTRACT: The present study aimed to evaluate the effects of different sedation protocols on blood pressure and echocardiographic and electrocardiographic parameters in dogs. In total, 24 male mixed-breed dogs with a mean weight of 9.87±3.0kg were used.Animals were randomly divided into four groups (n=6, which were subjected to sedation using the following protocols: acepromazine (0.05mgkg-1 and butorphanol (0.3mgkg-1 (AB; acepromazine (0.05mgkg-1and methadone (0.5mgkg-1 (AM; acepromazine (0.03mgkg-1, methadone (0.5mgkg-1, and midazolam (0.3mgkg-1(MAM; and methadone only (0.5mgkg-1 (M. Indirect blood pressure (BP measurements and computerized electrocardiography (ECG and echocardiography (ECO were performed immediately before the application of the sedation protocol (baseline, and the same evaluations were repeated after 15 minutes. BP decreased in groups AB, MAM, and AM compared to baseline values. Electrocardiographic measurements showed decreased heart rates (HRs after sedation in all groups, and bradycardia was observed after sedation in two dogs from group M and one animal from group AM. The P-wave duration increased after sedation in groups AM and M. After sedation, no changes in cardiac dimensions were revealed byECO.Fractional shortening (FS decreased after sedation in the AM group, and dogs from group AB exhibited a smaller decrease in FS compared with the other groups. The cardiac index (CI was lower in groups AM and M than in the other groups. Animals from group AB were less resistant to examination and exhibited the most favorable sedation scores. It was concluded that the combination of acepromazine and butorphanol was the best sedation protocol for performing echocardiogram measurementsbecause dogs were less resistant to examinations and echocardiographic parameters of FS and CI remained stable.

  20. Blood pressure and left ventricular mass in subjects with type 2 diabetes and gingivitis or chronic periodontitis.

    Science.gov (United States)

    Franek, Edward; Napora, Magdalena; Blach, Anna; Budlewski, Tadeusz; Gozdowski, Dariusz; Jedynasty, Krystyna; Krajewski, Jarosław; Gorska, Renata

    2010-10-01

    This study aimed to answer the question of whether chronic periodontitis in subjects with type 2 diabetes mellitus is associated with increased left ventricular mass (LVM) and systemic and central blood pressure (CBP). One hundred and fifty-five subjects with type 2 diabetes (67 F, 88 M, mean age 61.1±6.9 years, BMI 32.7±5.7 kg/m(2)) were divided according to their periodontal status into biofilm-gingival interface - healthy (BGI-H, 14 subjects), BGI-gingivitis (BGI-G, 119 subjects) and BGI-periodontitis (BGI-P, 22 subjects) groups. In all subjects, LVM, systemic and CBP were measured. The LVM index (LVMI) was calculated. (1) BGI-P and BGI-G subjects, respectively, had higher (mean; 95% CI) LVM (238.6 g; 206.6-267.4 and 222.8 g; 207.0-238.2) versus BGI-H subjects (170.3 g; 125.5-217.8).
(2) BGI-P and BGI-G subjects, respectively, had higher (mean; 95% CI) LVM1 (95.2 g/m(2) ; 82.9-107.4) and 87.8 g/m(2) ; 81.5-94.1) versus BGI-H subjects (63.7 g/m(2) ; 45.2-62.3).
(3) BGI-P subjects had higher central and systemic systolic and diastolic blood pressure than subjects from BGI-G and BGI-H groups. In subjects with type 2 diabetes, periodontitis and gingivitis are associated with increased LVM and periodontitis is associated with increased central and systemic blood pressure. © 2010 John Wiley & Sons A/S.

  1. Perilymphatic pressure dynamics following posture change in patients with Menière's disease and in normal hearing subjects.

    Science.gov (United States)

    Rosingh, H J; Wit, H P; Albers, F W

    1998-01-01

    The hydrostatic pressure of the inner ear depends on the cerebrospinal fluid pressure through the cochlear aqueduct. The time-course of inner ear pressure change following rapid change in cerebrospinal fluid pressure is related to the aqueduct patency. In this study the patency of the cochlear aqueduct in 27 patients with Menière's disease (28 affected ears, 16 non-affected ears) and in 12 normal hearing subjects (18 control ears) was assessed non-invasively by means of the MMS-10 Tympanic Displacement Analyser. Following a rapid change in body position, changes in intracranial cerebrospinal fluid pressure were found to influence perilymphatic pressure within 1 min. No significant differences were found among affected ears, non-affected ears and control ears.

  2. Composite Behavior of Insulated Concrete Sandwich Wall Panels Subjected to Wind Pressure and Suction

    Directory of Open Access Journals (Sweden)

    Insub Choi

    2015-03-01

    Full Text Available A full-scale experimental test was conducted to analyze the composite behavior of insulated concrete sandwich wall panels (ICSWPs subjected to wind pressure and suction. The experimental program was composed of three groups of ICSWP specimens, each with a different type of insulation and number of glass-fiber-reinforced polymer (GFRP shear grids. The degree of composite action of each specimen was analyzed according to the load direction, type of the insulation, and number of GFRP shear grids by comparing the theoretical and experimental values. The failure modes of the ICSWPs were compared to investigate the effect of bonds according to the load direction and type of insulation. Bonds based on insulation absorptiveness were effective to result in the composite behavior of ICSWP under positive loading tests only, while bonds based on insulation surface roughness were effective under both positive and negative loading tests. Therefore, the composite behavior based on surface roughness can be applied to the calculation of the design strength of ICSWPs with continuous GFRP shear connectors.

  3. Composite Behavior of Insulated Concrete Sandwich Wall Panels Subjected to Wind Pressure and Suction.

    Science.gov (United States)

    Choi, Insub; Kim, JunHee; Kim, Ho-Ryong

    2015-03-19

    A full-scale experimental test was conducted to analyze the composite behavior of insulated concrete sandwich wall panels (ICSWPs) subjected to wind pressure and suction. The experimental program was composed of three groups of ICSWP specimens, each with a different type of insulation and number of glass-fiber-reinforced polymer (GFRP) shear grids. The degree of composite action of each specimen was analyzed according to the load direction, type of the insulation, and number of GFRP shear grids by comparing the theoretical and experimental values. The failure modes of the ICSWPs were compared to investigate the effect of bonds according to the load direction and type of insulation. Bonds based on insulation absorptiveness were effective to result in the composite behavior of ICSWP under positive loading tests only, while bonds based on insulation surface roughness were effective under both positive and negative loading tests. Therefore, the composite behavior based on surface roughness can be applied to the calculation of the design strength of ICSWPs with continuous GFRP shear connectors.

  4. Leaf expansion of soybean subjected to high and low atmospheric vapour pressure deficits.

    Science.gov (United States)

    Devi, M Jyostna; Taliercio, Earl W; Sinclair, Thomas R

    2015-04-01

    Vapour pressure deficit (VPD) is considered an important environmental factor that might affect leaf expansion and transpiration rate (TR) in plants. Two slow-wilting soybean (Glycine max (L.) Merr.) genotypes PI 416937 and PI 471938 along with commercial cultivar Hutcheson were subjected to low (1.2-1.6 kPa) and high VPD (2.8-3 kPa) environments to study their leaf expansion and TR over five days. Among the three genotypes, PI 416937 had the lowest increase in its TR (34%) at high VPD compared with low VPD and the greatest decrease in leaf area (31%). In contrast, Hutcheson had the highest increase in TR (87%) under high VPD and the lowest decrease in leaf expansion rate (18%). Expansin and extensin genes were isolated in PI 416937 to determine if changes in leaf expansion were associated with changes at the molecular level. The four studied genes were all suppressed after five days in the high VPD environment. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.

  5. Comparative wear mapping techniques

    DEFF Research Database (Denmark)

    Alcock, J.; Sørensen, Ole Toft; Jensen, S.

    1996-01-01

    Pin-on-disc tests of tungsten carbide pins against silicon carbide discs were performed and wear rate, mechanism and friction maps constructed. Correlations were observed between the wear mode and the friction of the pin-disc interface, and between the qualitative incidence of disruptive wear mec...

  6. Blood pressure differences between office and home settings among Japanese normotensive subjects and hypertensive patients.

    Science.gov (United States)

    Mori, Hisao; Ukai, Hiroshi; Yamamoto, Hareaki; Yuasa, Shouhei; Suzuki, Yoshiro; Chin, Keiichi; Katsumata, Takuma; Umemura, Satoshi

    2017-03-01

    This study attempted to clarify the differences in blood pressure (BP) between the office (clinic) and home settings in patients with controlled, sustained, masked or white-coat hypertension. The following formula was used: office mean systolic BP (omSBP)-mean morning home SBP (mmhSBP)/office mean diastolic BP (omDBP)-mean morning home DBP (mmhDBP). The paired t-test was used for statistical analysis. The omSBP-mmhSBP/omDBP-mmhDBP calculation yielded the following results: among normotensive subjects, -1.1±11.2/-1.7±8.5 mm Hg (mean SBP and mean DBP were higher at home than in the office; n=451, P=0.038 in SBP, P=0.000 in DBP); in controlled hypertensive patients, -0.42±10.9/-2.2±8.2 mm Hg (n=1362, P=0.160 in SBP, P=0.000 in DBP); among sustained hypertensive patients, 5.6±14.7/0.048±9.9 mm Hg (n=1370, P=0.000 in SBP, P=0.857 in DBP); in masked hypertensive patients, -15.3±12.9/-9.3±9.5 mm Hg (n=1308, both P=0.000); and among white-coat hypertensive patients, 23.7±13.2/8.2±9.1 mm Hg (n=580, both P=0.000). Our results showed a difference of 5 mm Hg in SBP among sustained hypertensive patients, as recommended by the Japanese Society of Hypertension Guidelines for the Management of Hypertension; however, in other hypertensive patient types, the differences in SBP and DBP between office and home measurements differed by >5 mm Hg. Office and home BP measurements should be interpreted cautiously, keeping in mind the clinical setting.

  7. The impact of increasing body mass on peak and mean plantar pressure in asymptomatic adult subjects during walking

    Directory of Open Access Journals (Sweden)

    Sara Jones

    2010-11-01

    Full Text Available Introduction: The implication of high peak plantar pressure on foot pathology in individuals both with and without diabetes has been recognized. The aim of this study was to investigate and clarify the relationship between increasing body mass and peak and mean plantar pressure in an asymptomatic adult population during walking. Methods: Thirty adults without any relevant medical history, structural foot deformities or foot posture assessed as highly pronated or supinated, and within a normal body mass index range were included in the study. An experimental, same subjects, repeated measures design was used. Peak and mean plantar pressure were evaluated with the F-Scan in-shoe plantar pressure measurement system under four different loading conditions (0, 5, 10, and 15 kg simulated with a weighted vest. Pressure data were gathered from three stances utilizing the mid-gait protocol. Results: There were statistically significant increases in peak pressure between the 10 and 15 kg load conditions compared to the control (0 kg within the heel and second to fifth metatarsal regions. The first metatarsal and hallux regions only displayed statistically significant increases in peak pressure between 15 kg and the control (0 kg. The midfoot and lesser digits regions did not display any statistically significant differences in peak pressure between any load conditions compared to the control (0 kg. The second to fifth metatarsal region displayed statistically significant increases in mean pressure in the 5, 10 and 15 kg groups compared to the control (0 kg. A statistically significant increase in peak pressure between the 15 kg and control (0 kg group was evident in all other regions. Conclusion: The relationship between increasing body mass and peak and mean plantar pressure was dependent upon the plantar region. This study provides more detail outlining the response of peak and mean pressure to different loading conditions than previously reported in the

  8. Changes in body weight and blood pressure: paradoxical outcome events in overweight and obese subjects with cardiovascular disease.

    Science.gov (United States)

    Seimon, R V; Espinoza, D; Ivers, L; Gebski, V; Finer, N; Legler, U F; Sharma, A M; James, W P T; Coutinho, W; Caterson, I D

    2014-09-01

    The Sibutramine Cardiovascular OUTcomes (SCOUT) trial showed a significantly increased relative risk of nonfatal cardiovascular events, but not mortality, in overweight and obese subjects receiving long-term sibutramine treatment with diet and exercise. We examined the relationship between early changes (both increases and decreases) in body weight and blood pressure, and the impact of these changes on subsequent cardiovascular outcome events. A total of 9804 male and female subjects, aged 55 years or older, with a body mass index of 27-45 kg m(-2) were included in this current subanalysis of the SCOUT trial. Subjects were required to have a history of cardiovascular disease and/or type 2 diabetes mellitus with at least one cardiovascular risk factor (hypertension, dyslipidemia, current smoking or diabetic nephropathy) to assess cardiovascular outcomes. Post hoc subgroup analyses of weight change (categories) and blood pressure were performed overall and by treatment group (6-week sibutramine followed by randomized placebo or continued sibutramine). The primary outcome event (POE) was a composite of nonfatal myocardial infarction, nonfatal stroke, resuscitated cardiac arrest or cardiovascular death. Time-to-event analyses of the POE were performed using Cox regression models with factors for treatment, subgroups and interactions. During the initial 6-week sibutramine treatment period, systolic blood pressure decreased progressively with increasing weight loss in hypertensive subjects (-8.1±10.5 mm Hg with <5 kg weight loss to -10.8±11.0 mm Hg with ⩾5 kg weight loss). The highest POE incidence occurred mainly in groups with increases in both weight and blood pressure. However, with long-term sibutramine treatment, a markedly lower blood pressure tended to increase POEs. Modest weight loss and modest lower blood pressure each reduced the incidence of cardiovascular events, as expected. However, the combination of early marked weight loss and rapid

  9. Prognostic value of reading-to-reading blood pressure variability over 24 hours in 8938 subjects from 11 populations

    DEFF Research Database (Denmark)

    Hansen, Tine W; Thijs, Lutgarde; Li, Yan

    2010-01-01

    In previous studies, of which several were underpowered, the relation between cardiovascular outcome and blood pressure (BP) variability was inconsistent. We followed health outcomes in 8938 subjects (mean age: 53.0 years; 46.8% women) randomly recruited from 11 populations. At baseline, we asses...

  10. Non-invasive perilymphatic pressure measurement in normal hearing subjects using the MMS-10 tympanic displacement analyser

    NARCIS (Netherlands)

    Rosingh, HJ; Wit, HP; Albers, FWJ

    The MMS-10 Tympanic Displacement Analyser (TDA) is a new device to measure the perilymphatic pressure of the human inner ear in a non-invasive way. In this study, the instrument was used in 50 normal hearing subjects (100 ears) in three different conditions: i) sitting upright and supine; ii) in the

  11. Water ingestion affects orthostatic challenge-induced blood pressure and heart rate responses in young healthy subjects: gender implications.

    Science.gov (United States)

    Olatunji, L A; Aaron, A O; Micheal, O S; Oyeyipo, I P

    2011-11-23

    Evidence exists that women have lower orthostatic tolerance than men during quiescent standing. Water ingestion has been demonstrated to improve orthostatic tolerance in patients with severe autonomic dysfunction. We therefore sought to test the hypothesis that water ingestion would improve orthostatic tolerance in healthy young women more than in aged-matched men. Thirty seven (22 men and 15 women) healthy subjects aged 22.5± 1.7 and 21.5±1.4 (means±SD) respectively, ingested 50ml (control) and 500ml of water 40min before orthostatic challenge on two separate days of appointment in a randomized controlled, cross-over design. Seated and standing blood pressure and heart rate were determined. Orthostatic tolerance was assessed as the time to presyncope during standing. Ingesting 500ml of water significantly improves orthostatic tolerance by 22% (32.0 ± 5.2 vs 26.2 ± 2.4min; pwater, seated systolic blood pressure, diastolic blood pressure, pulse pressure and mean arterial pressure rose significantly in men while only systolic blood pressure and pulse pressure rose significantly in women. However ingesting 500ml of water did not have significant effect on seated heart rate in both men and women. Ingestion of 500ml of water significantly attenuated both the orthostatic challenge-induced increased heart rate and decreased pulse pressure responses especially in women. Diastolic blood pressure tended to be positively correlated with orthostatic tolerance strongly in men than in women. Pulse pressure correlated positively while heart rate correlated negatively to orthostatic tolerance in women but not in men independent of other correlates. Water ingestion is associated with orthostatic tolerance strongly in women but weakly in men independent of other correlates. In conclusion, the findings in the present study demonstrated that water ingestion caused improvement strongly in young women than in young men. This improvement is associated with increased pulse pressure

  12. Prediction of walking speed using single stance force or pressure measurements in healthy subjects

    NARCIS (Netherlands)

    Keijsers, N.L.W.; Stolwijk, N.M.; Renzenbrink, G.J.; Duysens, J.

    2016-01-01

    Walking speed is one of the best measures of overall walking capacity. In plantar pressure measurements, walking speed can be assessed using contact time, but it is only moderately correlated with walking speed. The center of pressure might be of more value to indicate walking speed since walking

  13. Bicycle saddle pressure: effects of trunk position and saddle design on healthy subjects.

    Science.gov (United States)

    Carpes, Felipe Pivetta; Dagnese, Frederico; Kleinpaul, Julio Francisco; Martins, Elisandro de Assis; Mota, Carlos Bolli

    2009-01-01

    There is a common belief that seat pressure during cycling can compress specific neurovascular tissues over the perineum leading to genital pathologies. This topic has seldom been discussed for women. The present study was conducted to verify the effect of trunk position and saddle design on saddle pressure in both men and women. Recreational cyclists (11 men and 11 women) were evaluated while seated on a bicycle. Saddle pressure was measured with F-scan insoles adapted for two saddle models (with and without a hole), and two trunk positions (upright and forwards). Pressure values were compared between trunk positions and saddles employing ANOVA. There were no statistical differences comparing saddle pressure between the two trunk positions for women. For men a statistical difference between the trunk positions for the saddle with a hole was found. Thus, the trunk forwards shift seems to affect the values of saddle pressure only for men using the 'holed' saddle. Saddle pressure for men was influenced by saddle design and trunk position only. This result indicates that the masculine anatomy may influence saddle pressure during bicycle. (c) 2009 S. Karger AG, Basel.

  14. Effect of respiratory pattern on automated clinical blood pressure measurement: an observational study with normotensive subjects.

    Science.gov (United States)

    Herakova, Natalia; Nwobodo, Nnenna Harmony Nzeribe; Wang, Ying; Chen, Fei; Zheng, Dingchang

    2017-01-01

    It has been reported that deep breathing could reduce blood pressures (BP) in general. It is also known that BP is decreased during inhalation and increased during exhalation. Therefore, the measured BPs could be potentially different during deep breathing with different lengths of inhalation and exhalation. This study aimed to quantitatively investigate the effect of different respiratory patterns on BPs. Forty healthy subjects (20 males and 20 females, aged from 18 to 60 years) were recruited. Systolic and diastolic BPs (SBP and DBP) were measured using a clinically validated automated BP device. There were two repeated measurement sessions for each subject. Within each session, eight BP measurements were performed, including 4 measurements during deep breathing with different respiratory patterns (Pattern 1: 4.5 s vs 4.5 s; Patter 2: 6 s vs 2 s; Pattern 3: 2 s vs 6 s; and Pattern 4: 1.5 s vs 1.5 s, respectively for the durations of inhalation and exhalation) and additional 4 measurements from 1 min after the four different respiratory patterns. At the beginning and end of the two repeated measurement sessions, there were two baseline BP measurements under resting condition. The key experimental results showed that overall automated SBP significantly decreased by 3.7 ± 5.7 mmHg, 3.9 ± 5.2 mmHg, 1.7 ± 5.9 mmHg and 3.3 ± 5.3 mmHg during deep breathing, respectively for Patterns 1, 2, 3 and 4 (all p Pattern 3). Similarly, the automated DBPs during deep breathing in pattern 1, 2 and 4 decreased by 3.7 ± 5.0 mmHg, 3.7 ± 4.9 mmHg and 4.6 ± 3.9 mmHg respectively (all p Pattern 3 with a decrease of 1.0 ± 4.3 mmHg, p = 0.14). Correspondingly, after deep breathing, automated BPs recovered back to normal with no significant difference in comparison with baseline BP (all p > 0.05, except for SBP in Pattern 4). In summary, this study has quantitatively demonstrated that the measured automated BPs decreased

  15. An energy dissipation and cross shear time dependent computational wear model for the analysis of polyethylene wear in total knee replacements.

    Science.gov (United States)

    O'Brien, Sean T; Bohm, Eric R; Petrak, Martin J; Wyss, Urs P; Brandt, Jan-M

    2014-03-21

    The cost and time efficiency of computational polyethylene wear simulations may enable the optimization of total knee replacements for the reduction of polyethylene wear. The present study proposes an energy dissipation wear model for polyethylene which considers the time dependent molecular behavior of polyethylene, aspects of tractive rolling and contact pressure. This time dependent - energy dissipation wear model was evaluated, along with several other wear models, by comparison to pin-on-disk results, knee simulator wear test results under various kinematic conditions and knee simulator wear test results that were performed following the ISO 14243-3 standard. The proposed time dependent - energy dissipation wear model resulted in improved accuracy for the prediction of pin-on-disk and knee simulator wear test results compared with several previously published wear models. Crown Copyright © 2014. Published by Elsevier Ltd. All rights reserved.

  16. Numerical simulations of gun-launched kinetic energy projectiles subjected to asymmetric projectile base pressure

    Energy Technology Data Exchange (ETDEWEB)

    Rabern, D.A.

    1991-12-31

    Three-dimensional numerical simulations were performed to determine the effect of an asymmetric base pressure on kinetic energy projectiles during launch. A matrix of simulations was performed in two separate launch environments. One launch environment represented a severe lateral load environment, while the other represented a nonsevere lateral load environment based on the gun tube straightness. The orientation of the asymmetric pressure field, its duration, the projectile`s initial position, and the tube straightness were altered to determine the effects of each parameter. The pressure asymmetry translates down the launch tube to exit parameters and is washed out by tube profile. Results from the matrix of simulations are presented.

  17. Numerical simulations of gun-launched kinetic energy projectiles subjected to asymmetric projectile base pressure

    Energy Technology Data Exchange (ETDEWEB)

    Rabern, D.A.

    1991-01-01

    Three-dimensional numerical simulations were performed to determine the effect of an asymmetric base pressure on kinetic energy projectiles during launch. A matrix of simulations was performed in two separate launch environments. One launch environment represented a severe lateral load environment, while the other represented a nonsevere lateral load environment based on the gun tube straightness. The orientation of the asymmetric pressure field, its duration, the projectile's initial position, and the tube straightness were altered to determine the effects of each parameter. The pressure asymmetry translates down the launch tube to exit parameters and is washed out by tube profile. Results from the matrix of simulations are presented.

  18. Energetic aspects of boring tools wear

    Directory of Open Access Journals (Sweden)

    Lazarová Edita

    2002-03-01

    Full Text Available In the process of rock desintegration a boring tool is subjected to the wear. From a viewpoint of the bit wear, changes on the contact of operating tool with rock at its one-shot and rerun load or overload by external forces are technically significant. Theis change results in the degradation of bit working properties and the output of desintegration also decreases. In the major part of cases, together with the bit wear, the contact area of a tool with a rock massifs enhanced and this fact causes an increase of fines (dust creation during the desintegration. The wear is always connected with a friction, forces action, deformation, damage, and the increased mechanical work consumption. As to energetic aspects of bit wear, the wear was observed as a function of bore length and in the most of cases as a dependence of the operating time. A linear dependence between the wear intensity (bit wear per unit of bore length and the specific energy of desintegration (energy consumed per volume unit of desintegrated rock was experimentally verified. Thus, the changes of bit wear can be implicitly observed by monitoring the specific energy. At the same time, the specific energy is a function of input parameters of the desintegration process and in the field of applicable external forces it shows an extreme (minimum. Therefore, the specific energy is useful for the extreme optimisation of the rock desintegration process from the viewpoint of the bit wear. It was mathematically proven that the tool output at the desintegration exponentially decreases with the amount of work consumed in the rock desintegration. The derivation of this knowledge comes out from the Krendelev equation.

  19. Negative Pressures and Spallation in Water Drops Subjected to Nanosecond Shock Waves.

    Science.gov (United States)

    Stan, Claudiu A; Willmott, Philip R; Stone, Howard A; Koglin, Jason E; Liang, Mengning; Aquila, Andrew L; Robinson, Joseph S; Gumerlock, Karl L; Blaj, Gabriel; Sierra, Raymond G; Boutet, Sébastien; Guillet, Serge A H; Curtis, Robin H; Vetter, Sharon L; Loos, Henrik; Turner, James L; Decker, Franz-Josef

    2016-06-02

    Most experimental studies of cavitation in liquid water at negative pressures reported cavitation at tensions significantly smaller than those expected for homogeneous nucleation, suggesting that achievable tensions are limited by heterogeneous cavitation. We generated tension pulses with nanosecond rise times in water by reflecting cylindrical shock waves, produced by X-ray laser pulses, at the internal surface of drops of water. Depending on the X-ray pulse energy, a range of cavitation phenomena occurred, including the rupture and detachment, or spallation, of thin liquid layers at the surface of the drop. When spallation occurred, we evaluated that negative pressures below -100 MPa were reached in the drops. We model the negative pressures from shock reflection experiments using a nucleation-and-growth model that explains how rapid decompression could outrun heterogeneous cavitation in water, and enable the study of stretched water close to homogeneous cavitation pressures.

  20. High-sensitivity C-reactive protein is associated with the presence of coronary artery calcium in subjects with normal blood pressure but not in subjects with hypertension.

    Science.gov (United States)

    Sung, Joo-Wook; Lee, Sung Ho; Byrne, Christopher D; Chung, Pil-Wook; Won, Yu Sam; Sung, Ki-Chul

    2014-02-01

    An association has been described between high sensitivity C-reactive protein (hs-CRP) and cardiovascular disease (CVD) in some studies but not in others. This finding may be explained by a differential impact of inflammation according to the absence or presence of certain co-existing risk factors. Because hypertension may be an effect modifier of inflammation on CVD, our aim was to investigate the relationship between hs-CRP and pre-clinical atherosclerosis in subjects with normal blood pressure and hypertension. Data were analyzed from 14,584 Korean subjects. Subjects were stratified according to: a) 6030 (41.3%) patients with normal blood pressure (hypertension (120-139 mmHg and 80-89 mmHg) and c) 2924 (20.0%) patients with hypertension (≥140/90 mmHg). Prevalence and odds ratio for the association between increased hs-CRP (>2 mg/L) and presence of CAC (coronary artery calcium) were calculated. In both normal and pre-hypertensive groups, the prevalence of CAC >0 was higher in subjects with increased hs-CRP concentrations (>2 mg/L). Adjusting for age, sex, cerebrovascular accident, coronary heart disease and diabetes mellitus, lifestyle, obesity, fasting glucose, triglyceride, high-density lipoprotein cholesterol and low-density lipoprotein cholesterol concentrations, there was a significant association between higher hs-CRP levels (>2 mg/L) and CAC score in the normal group (OR 1.55, 95% CI 1.11-2.16; p = 0.010); a borderline significant association in the pre-hypertensive group (OR 1.33, 95% CI 0.99-1.76; p = 0.054); and no association in the hypertensive group (OR 1.01, 95% CI 0.76-1.33; p = 0.94). Higher hs-CRP levels (>2 mg/L) are associated with pre-clinical atherosclerosis in subjects with normal blood pressure but not hypertension. Copyright © 2014 IMSS. Published by Elsevier Inc. All rights reserved.

  1. Nonlinear Response of Thin Cylindrical Shells with Longitudinal Cracks and Subjected to Internal Pressure and Axial compression Loads

    Science.gov (United States)

    Starnes, James H.; Rose, Cheryl A.

    1998-01-01

    The results of an analytical study of the nonlinear response of a thin unstiffened aluminum cylindrical shell with a longitudinal crack are presented. The shell is analyzed with a nonlinear shell analysis code that maintains the shell in a nonlinear equilibrium state while the crack is grown. The analysis accurately accounts for global and local structural response phenomena. Results are presented for internal pressure, axial compression, and combined internal pressure and axial compression loads. The effects of varying crack length on the nonlinear response of the shell subjected to internal pressure are described. The effects of varying crack length on the prebuckling, buckling and postbuckling responses of the shell subjected to axial compression, and subjected to combined internal pressure and axial compression are also described. The results indicate that the nonlinear interaction between the in-plane stress resultants and the out-of-plane displacements near a crack can significantly affect the structural response of the shell. The results also indicate that crack growth instabilities and shell buckling instabilities can both affect the response of the shell as the crack length is increased.

  2. Intraluminal pressure in the sigmoid colon. I. Method and results in normal subjects.

    Science.gov (United States)

    Weinreich, J; Andersen, D

    1976-01-01

    A modified method for measurement of pressure activity in the sigmoid colon is presented, using open-ended tubes and measurement of pressure activity for 30 minutes after intravenous administration of 0.5 mg of neostigmine. The motility index in 12 normal persons was found to have median 597 with a range of 125-1169. Variation among persons exceeded the day-to-day variation significantly. Error in reading the curves was negligible.

  3. The Effect of Topical Anaesthesia on Pressure Pain Thresholds in symptom-free subjects

    OpenAIRE

    Axelsson, Anna; Carlsson, Elsa

    2014-01-01

    Palpation, a standard procedure in the diagnostic process of muscular pain conditions – myalgia, aims to provoke a muscular pain response. The origin of pain elicited by palpation is not fully understood. There is also a possibility that the pressure elicit response from mechanoreceptors in skin, sub mucosal tissue or periosteum, which may affect the validity of the method. The aim of this study was to evaluate the effect of topical anesthesia on pressure pain thresholds at masseter, temporal...

  4. Cerebral artery blood velocity in normal subjects during acute decreases in barometric pressure.

    Science.gov (United States)

    Taubøll, E; Sorteberg, W; Owe, J O; Lindegaard, K F; Rusten, K; Sorteberg, A; Gjerstad, L

    1999-07-01

    To investigate the effect of acute changes in barometric pressure on regional cerebral perfusion we studied the middle cerebral artery (MCA) blood velocity in five healthy male volunteers by means of a low-pressure chamber. The MCA blood velocity, arterial blood and respiratory gases were measured at the barometric pressures of 1, 0.8, 0.65, and 0.5 atmospheres. The observed blood velocity (Vo) showed no systematic changes. Decreases in barometric pressure induced hypoxia and hypocapnia. When normalizing the MCA blood velocity (Vn) to a standard P(CO2) (5.3 kPa), thereby correcting for the hypoxic induced hypocapnia, we obtained an inverse relationship between cerebral artery blood velocity and arterial blood oxygen content (CaO2). The oxygen supply to the brain, estimated as the product of Vo and CaO2, decreased with lowering of the barometric pressure. However, the product of Vn and CaO2 remained constant. This suggests the existence of a regulatory mechanism attempting to maintain a constant oxygen supply to the brain during acute changes in CaO2, if the hyperventilation induced decrease in PCO2 can be omitted. In the artificial situation of a low pressure chamber, our findings are quite similar to those obtained at sea level. This indicates that the underlying mechanisms of control of cerebral blood flow do not change during acute exposure to altitude.

  5. Effect of fatigue induced by strength training on blood pressure response in hypertensive subjects: A systematic review

    Directory of Open Access Journals (Sweden)

    Aluísio Henrique Rodrigues Lima

    2013-04-01

    Full Text Available The objective of this study was to systematically review the literature on blood pressure response after strength training in hypertensive subjects, trying to identify the effect of failure in this response. We performed a literature search in SciELO, LILACS, PubMed / MedLine databases. Out of 9377 studies, only six met the inclusion criteria and were included in the review. Five studies (83.3% reported a reduction in systolic or diastolic blood pressure. Regarding failure, 66.7% (n = 4 of the studies performed the sets until failure while 33.3% (n = 2 interrupted exercise before failure. Out of the four studies that used protocols until failure, 75% (n=3 observed a reduction in blood pressure, and the two studies who discontinued before the series also showed a reduction of failure. The magnitude of blood pressure reduction was similar among studies that employed both protocols. Thus, the results indicated that the reduction in blood pressure after strength training in subjects with hypertension is independent of the occurrence of failure.

  6. Arterial Pressure Variation as a Biomarker of Preload Dependency in Spontaneously Breathing Subjects - A Proof of Principle.

    Science.gov (United States)

    Bronzwaer, Anne-Sophie G T; Ouweneel, Dagmar M; Stok, Wim J; Westerhof, Berend E; van Lieshout, Johannes J

    2015-01-01

    Pulse (PPV) and systolic pressure variation (SPV) quantify variations in arterial pressure related to heart-lung interactions and have been introduced as biomarkers of preload dependency to guide fluid treatment in mechanically ventilated patients. However, respiratory intra-thoracic pressure changes during spontaneous breathing are considered too small to affect preload and stroke volume sufficiently for the detection by PPV and/or SPV. This study addressed the effects of paced breathing and/or an external respiratory resistance on PPV and SPV in detecting preload dependency in spontaneously breathing subjects. In 10 healthy subjects, hemodynamic and respiratory parameters were evaluated during progressive central hypovolemia (head-up tilt). Breathing conditions were varied by manipulating breathing frequency and respiratory resistance. Subjects responding with a reduction in stroke volume index ≥15% were classified as having developed preload dependency. The ability for PPV and SPV to predict preload dependency was expressed by the area under the ROC curve (AUC). A breathing frequency at 6/min increased the PPV (16±5% vs. 10±3%, pvariations in non-ventilated subjects.

  7. Nanoclay-Reinforced Glass-Ionomer Cements: In Vitro Wear Evaluation and Comparison by Two Wear-Test Methods

    Directory of Open Access Journals (Sweden)

    Muhammad A. Fareed

    2017-10-01

    Full Text Available Glass ionomer cement (GIC represents a major transformation in restorative dentistry. Wear of dental restoratives is a common phenomenon and the determination of the wear resistance of direct-restorative materials is a challenging task. The aim of this paper was to evaluate the wear resistance of novel glass ionomer cement by two wear-test methods and to compare the two wear methods.The wear resistance of a conventional glass ionomer cement (HiFi Advanced Health Care Kent, UK and cements modified by including various percentages of nanoclays (1, 2 and 4 wt % was measured by a reciprocating wear test (ball-on-flat and Oregon Health and Sciences University’s (OHSU wear simulator. The OHSU wear simulation subjected the cement specimens to three wear mechanisms, namely abrasion, three-body abrasion and attrition using a steatite antagonist. The abrasion wear resulted in material loss from GIC specimen as the steatite antagonist forced through the exposed glass particles when it travelled along the sliding path.The hardness of specimens was measured by the Vickers hardness test. The results of reciprocation wear test showed that HiFi-1 resulted in the lowest wear volume 4.90 (0.60 mm3 (p < 0.05, but there was no significant difference (p > 0.05 in the wear volume in comparison to HiFi, HiFi-2 and HiFi-4. Similarly, the results of OHSU wear simulator showed that the total wear volume of HiFi-4 1.49 (0.24 was higher than HiFi-1 and HiFi-2. However, no significant difference (p > 0.05 was found in the OHSU total wear volume in GICs after nanoclay incorporation. The Vickers hardness (HV of the nanoclay-reinforced cements was measured between 62 and 89 HV. Nanoclay addition at a higher concentration (4% resulted in higher wear volume and wear depth. The total wear volumes were less dependent upon abrasion volume and attrition volume. The total wear depths were strongly influenced by attrition depth and to some extent by abrasion depth. The addition of

  8. Intra-arterial blood pressure response in hypertensive subjects during low- and high-intensity resistance exercise

    Directory of Open Access Journals (Sweden)

    Sandra de Souza Nery

    2010-01-01

    Full Text Available OBJECTIVE: The aim of this study was to describe blood pressure responses during resistance exercise in hypertensive subjects and to determine whether an exercise protocol alters these responses. INTRODUCTION: Resistance exercise has been recommended as a complement for aerobic exercise for hypertensive patients. However, blood pressure changes during this kind of exercise have been poorly investigated in hypertensives, despite multiple studies of normotensives demonstrating significant increases in blood pressure. METHODS: Ten hypertensive and ten normotensive subjects performed, in random order, two different exercise protocols, composed by three sets of the knee extension exercise conducted to exhaustion: 40% of the 1-repetition maximum (1RM with a 45-s rest between sets, and 80% of 1RM with a 90-s rest between sets. Radial intra-arterial blood pressure was measured before and throughout each protocol. RESULTS: Compared with normotensives, hypertensives displayed greater increases in systolic BP during exercise at 80% (+80±3 vs. +62±2 mmHg, P<0.05 and at 40% of 1RM (+75±3 vs. +67±3 mmHg, P<0.05. In both exercise protocols, systolic blood pressure returned to baseline during the rest periods between sets in the normotensives; however, in the hypertensives, BP remained slightly elevated at 40% of 1RM. During rest periods, diastolic blood pressure returned to baseline in hypertensives and dropped below baseline in normotensives. CONCLUSION: Resistance exercise increased systolic blood pressure considerably more in hypertensives than in normotensives, and this increase was greater when lower-intensity exercise was performed to the point of exhaustion.

  9. Capillary viscometer with a pressure sensor: a subject for student projects

    Science.gov (United States)

    Massalha, Taha; Digilov, Rafael M.

    2015-11-01

    We describe a vacuum-based pressure-detecting capillary viscometer for the viscosity determination of Newtonian fluids without known density. The viscometer operates on the principle that the variation in air pressure of the vacuum vessel p≤ft(t\\right) replaces the flow rate and pressure drop measurements which are usually required for the operation of a capillary tube viscometer. The mathematical expression for p≤ft(t\\right), found in the terms of the Lambert-W function, is used to fit the experimental data for viscosity determination. The results for viscosities of distilled water and 50 wt.% glycerol aqueous solution obtained under ambient temperature condition were compared to reference data and a good agreement was observed. The viscometer is suitable for undergraduate laboratories due to its low cost and simplicity in experimental setup. Moreover, the experimental with the vacuum vessel setup provides an in-depth understanding of fluid flow.

  10. Slip behaviour of carbonate-bearing faults subjected to fluid pressure stimulations

    Science.gov (United States)

    Collettini, Cristiano; Scuderi, Marco; Marone, Chris

    2017-04-01

    Earthquakes caused by fluid injection within reservoir have become an important topic of political and social discussion as new drilling and improved technologies enable the extraction of oil and gas from previously unproductive formations. During reservoir stimulation, the coupled interactions of frictional and fluid flow properties together with the stress state control both the onset of fault slip and fault slip behaviour. However, currently, there are no studies under controlled, laboratory conditions for which the effect of fluid pressure on fault slip behaviour can be deduced. To cover this gap, we have developed laboratory experiments where we monitor fault slip evolution at constant shear stress but with increasing fluid pressure, i.e. reducing the effective normal stress. Experiments have been conducted in the double direct shear configuration within a pressure vessel on carbonate fault gouge, characterized by a slightly velocity strengthening friction that is indicative of stable aseismic creep. In our experiments fault slip history can be divided in three main stages: 1) for high effective normal stress the fault is locked and undergoes compaction; 2) when the shear and effective normal stress reach the failure condition, accelerated creep is associated to fault dilation; 3) further pressurization leads to an exponential acceleration during fault compaction and slip localization. Our results indicate that fault weakening induced by fluid pressurization overcomes the velocity strengthening behaviour of calcite gouge, resulting in fast acceleration and earthquake slip. As applied to tectonic faults our results suggest that a larger number of crustal faults, including those slightly velocity strengthening, can experience earthquake slip due to fluid pressurization.

  11. Plasma concentrations of endothelial vasoactive substances in clinically healthy subjects. associations with urinary albumin excretion and ambulatory blood pressure

    DEFF Research Database (Denmark)

    Clausen, P; Jensen, J S; Jensent, G

    2000-01-01

    Elevated urinary albumin excretion (UAE) is a predictor of cardiovascular disease, and one possible explanation is that elevated UAE reflects a generalized vascular dysfunction. The present study tests whether the plasma concentrations of the two main endothelial vasoactive substances (nitric oxide...... and endothelin-1 [ET-1]) are changed in clinically healthy subjects with elevated UAE (>6.6 microg/ min-the 90th percentile in the background population) and to test associations between these concentrations and systemic blood pressure. Twenty-seven subjects with elevated UAE were compared with 46 matched...

  12. Physicochemical characteristics and quality parameters of a beef product subjected to chemical preservatives and high hydrostatic pressure.

    Science.gov (United States)

    Giménez, Belén; Graiver, Natalia; Califano, Alicia; Zaritzky, Noemí

    2015-02-01

    The use of high hydrostatic pressure (HHP) on fresh beef causes a deleterious effect on red colour. A beef product subjected to HHP exhibiting acceptable colour and microbiological stability was developed; the process requires as a first step the immersion in a preservative solution containing ascorbic acid, sodium nitrite, and sodium chloride. Desirability functions were used to optimise the composition of this solution in order to maintain the colour attributes minimising the concentration of sodium nitrite. The product was packed in low gas permeability film before HHP treatment. The effect of the applied pressure (300, 600 MPa) on quality parameters (colour,texture) was analysed. The stability of the product during storage at 4 °C was determined by microbial counts, colour, texture, and exudate. The combination of treatments provided acceptable colour and microbiological stability during four and six weeks of refrigerated storage after the product has been subjected to 300 and 600 MPa, respectively.

  13. Assessment of pre-ejection period in ambulatory subjects using seismocardiogram in a wearable blood pressure monitor.

    Science.gov (United States)

    Guanqun Zhang; Cottrell, Amber C; Henry, Isaac C; McCombie, Devin B

    2016-08-01

    The ability to monitor arterial blood pressure continuously with unobtrusive body worn sensors may provide a unique and potentially valuable assessment of a patient's cardiovascular health. Pulse wave velocity (PWV) offers an attractive method to continuously monitoring blood pressure. However, PWV technologies based on timing measurements between the ECG and a distal PPG suffer from inaccuracies on mobile patients due to the confounding influence of pre-ejection period (PEP). In this paper, we presented a wearable, continuous blood pressure monitor (ViSi Mobile) that can measure and track changes in PEP. PEP is determined from precordial vibrations captured by an accelerometer coupled to the patient's sternum. The performance of the PEP measurements was evaluated on test subjects with postural change and patient activity. Results showed potential to improve cNIBP accuracy in active patients.

  14. Arterial Pressure Variation as a Biomarker of Preload Dependency in Spontaneously Breathing Subjects - A Proof of Principle.

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    Anne-Sophie G T Bronzwaer

    Full Text Available Pulse (PPV and systolic pressure variation (SPV quantify variations in arterial pressure related to heart-lung interactions and have been introduced as biomarkers of preload dependency to guide fluid treatment in mechanically ventilated patients. However, respiratory intra-thoracic pressure changes during spontaneous breathing are considered too small to affect preload and stroke volume sufficiently for the detection by PPV and/or SPV. This study addressed the effects of paced breathing and/or an external respiratory resistance on PPV and SPV in detecting preload dependency in spontaneously breathing subjects.In 10 healthy subjects, hemodynamic and respiratory parameters were evaluated during progressive central hypovolemia (head-up tilt. Breathing conditions were varied by manipulating breathing frequency and respiratory resistance. Subjects responding with a reduction in stroke volume index ≥15% were classified as having developed preload dependency. The ability for PPV and SPV to predict preload dependency was expressed by the area under the ROC curve (AUC.A breathing frequency at 6/min increased the PPV (16±5% vs. 10±3%, p<0.001 and SPV (9±3% vs. 5±2%, p<0.001 which was further enhanced by an expiratory resistance (PPV: 19±3%, p = 0.025 and SPV: 10±2%, p = 0.047. These respiratory modifications, compared to free breathing, enhanced the predictive value of PPV with higher accuracy (AUC: 0.92 vs. 0.46.Under conditions of progressive central hypovolemia, the application of an external respiratory resistance at a breathing frequency of 6/min enhanced PPV and SPV and is worth further study for detection of preload dependency from arterial pressure variations in non-ventilated subjects.

  15. Membrane integrity of Campylobacter jejuni subjected to high pressure is pH-dependent

    Science.gov (United States)

    Lerasle, M.; Guillou, S.; Simonin, H.; Laroche, M.; de Lamballerie, M.; Federighi, M.

    2012-03-01

    Our study focuses on a foodborne pathogen, Campylobacter, which is responsible for the most frequent bacterial enteritis worldwide. Membrane integrity of Campylobacter jejuni NCTC 11168 cells treated at high pressure (300 MPa, 20°C, 10 min) at pH 7.0 and pH 5.6 was measured by fluorescence spectroscopy of propidium iodide (PI) uptake. The percentage of membrane-damaged cells by high pressure, in which PI is allowed to penetrate, was determined using two calibration methods based on the PI fluorescence signal obtained with cells killed either by a heat treatment (80°C for 15 min) or by a pressure treatment (400 MPa, 20°C, 10 min). Both calibrations were shown to be statistically different (P<0.05), particularly at acidic pH, suggesting that a difference in the penetration of PI into bacterial cells might depend on the mode of cell inactivation. These results corroborate the fact that the mechanism of microbial inactivation by high pressure is pH-dependent.

  16. The Difference in Translaminar Pressure Gradient and Neuroretinal Rim Area in Glaucoma and Healthy Subjects

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    Lina Siaudvytyte

    2014-01-01

    Full Text Available Purpose. To assess differences in translaminar pressure gradient (TPG and neuroretinal rim area (NRA in patients with normal tension glaucoma (NTG, high tension glaucoma (HTG, and healthy controls. Methods. 27 patients with NTG, HTG, and healthy controls were included in the prospective pilot study (each group consisted of 9 patients. Intraocular pressure (IOP, intracranial pressure (ICP, and confocal laser scanning tomography were assessed. TPG was calculated as the difference of IOP minus ICP. ICP was measured using noninvasive two-depth transcranial Doppler device. The level of significance P 0.05. The difference between TPG for healthy (5.4(7.7 mmHg and glaucomatous eyes (NTG 6.3(3.1 mmHg, HTG 15.7(7.7 mmHg was statistically significant (P < 0.001. Higher TPG was correlated with decreased NRA (r = −0.83; P = 0.01 in the NTG group. Conclusion. Translaminar pressure gradient was higher in glaucoma patients. Reduction of NRA was related to higher TPG in NTG patients. Further prospective studies are warranted to investigate the involvement of TPG in glaucoma management.

  17. Enzymatically hydrolyzed lactotripeptides do not lower blood pressure in mildly hypertensive subjects

    NARCIS (Netherlands)

    van der Zander, Kim; Bots, Michiel L.; Bak, Annette A. A.; Koning, Mettina M. G.; de Leeuw, Peter W.

    2008-01-01

    Background: Several placebo-controlled clinical studies suggest that products containing isoleucyl-prolyl-proline and valyl-prolylproline are able to lower blood pressure without adverse effects. The most efficient way of producing high concentrations of these lacto-tripeptides (LTPs) is enzymatic

  18. Plasma concentrations of endothelial vasoactive substances in clinically healthy subjects. associations with urinary albumin excretion and ambulatory blood pressure

    DEFF Research Database (Denmark)

    Clausen, P; Jensen, J S; Jensent, G

    2000-01-01

    and endothelin-1 [ET-1]) are changed in clinically healthy subjects with elevated UAE (>6.6 microg/ min-the 90th percentile in the background population) and to test associations between these concentrations and systemic blood pressure. Twenty-seven subjects with elevated UAE were compared with 46 matched...... controls with normoalbuminuria. Plasma concentration of ET-1 was measured using an ELISA method and plasma concentration of nitrate/nitrite using a photometric method. Twenty-four-hour blood pressure was measured using a portable recorder (TM-2421). No significant differences in the concentrations...... of nitrate/nitrite and ET-1 were found between the groups, e.g. 21 (10-105) vs. 18 (11 -152) (p=0.33) and 0.98 (0.58 1.95) vs. 1.10 (0.54 -1.50) (p = 0.27), respectively. However, plasma nitrate/nitrite was significantly positively correlated to systolic and diastolic blood pressure in subjects...

  19. Wavelet coherence analysis of spontaneous oscillations in cerebral tissue oxyhemoglobin concentrations and arterial blood pressure in elderly subjects.

    Science.gov (United States)

    Cui, Ruofei; Zhang, Ming; Li, Zengyong; Xin, Qing; Lu, Liqian; Zhou, Weiei; Han, Qingyu; Gao, Yuanjin

    2014-05-01

    This study aims to assess the relationship between spontaneous oscillations in changes in cerebral tissue oxyhemoglobin concentrations (Delta [HbO2]) and arterial blood pressure (ABP) signals in healthy elderly subjects during the resting state using wavelet coherence analysis. Continuous recordings of near-infrared spectroscopy (NIRS) and ABP signals were obtained from simultaneous measurements in 33 healthy elderly subjects (age: 70.7±7.9 years) and 27 young subjects (age: 25.2±3.7 years) during the resting state. The coherence between Delta [HbO2] and ABP oscillations in six frequency intervals (I, 0.4-2 Hz; II, 0.15-0.4 Hz; III, 0.05-0.15 Hz; IV, 0.02-0.05 Hz, V, 0.005-0.0095 Hz and VI, 0.005-0.0095 Hz) was analyzed using wavelet coherence analysis. In elderly subjects, the Delta [HbO2] and ABP oscillations were significantly wavelet coherent in interval I, and wavelet phase coherent in intervals I, II and IV. The wavelet coherence in interval I was significantly higher (p=0.040), in elderly subjects than in young subjects whereas that in interval V significantly lower (p=0.015). In addition, the wavelet phase coherence in interval IV was significantly higher in elderly subjects than in young subjects (p=0.028). The difference in the wavelet coherence of the elderly subjects and the young subjects indicates an altered cerebral autoregulation caused by aging. This study provides new insight into the dynamics of Delta [HbO2] and ABP oscillations and may be useful in identifying the risk for dynamic cerebral autoregulation processes. Copyright © 2014 Elsevier Inc. All rights reserved.

  20. Prediction of Cone Crusher Performance Considering Liner Wear

    Directory of Open Access Journals (Sweden)

    Yanjun Ma

    2016-12-01

    Full Text Available Cone crushers are used in the aggregates and mining industries to crush rock material. The pressure on cone crusher liners is the key factor that influences the hydraulic pressure, power draw and liner wear. In order to dynamically analyze and calculate cone crusher performance along with liner wear, a series of experiments are performed to obtain the crushed rock material samples from a crushing plant at different time intervals. In this study, piston die tests are carried out and a model relating compression coefficient, compression ratio and particle size distribution to a corresponding pressure is presented. On this basis, a new wear prediction model is proposed combining the empirical model for predicting liner wear with time parameter. A simple and practical model, based on the wear model and interparticle breakage, is presented for calculating compression ratio of each crushing zone along with liner wear. Furthermore, the size distribution of the product is calculated based on existing size reduction process model. A method of analysis of product size distribution and shape in the crushing process considering liner wear is proposed. Finally, the validity of the wear model is verified via testing. The result shows that there is a significant improvement of the prediction of cone crusher performance considering liner wear as compared to the previous model.

  1. Vagal Blocking Improves Glycemic Control and Elevated Blood Pressure in Obese Subjects with Type 2 Diabetes Mellitus

    Directory of Open Access Journals (Sweden)

    S. Shikora

    2013-01-01

    Full Text Available Background. An active device that downregulates abdominal vagal signalling has resulted in significant weight loss in feasibility studies. Objective. To prospectively evaluate the effect of intermittent vagal blocking (VBLOC on weight loss, glycemic control, and blood pressure (BP in obese subjects with DM2. Methods. Twenty-eight subjects were implanted with a VBLOC device (Maestro Rechargeable System at 5 centers in an open-label study. Effects on weight loss, HbA1c, fasting blood glucose, and BP were evaluated at 1 week to 12 months. Results. 26 subjects (17 females/9 males, 51±2 years, BMI 37±1 kg/m2, mean ± SEM completed 12 months followup. One serious adverse event (pain at implant site was easily resolved. At 1 week and 12 months, mean excess weight loss percentages (% EWL were 9±1% and 25±4% (P<0.0001, and HbA1c declined by 0.3±0.1% and 1.0±0.2% (P=0.02, baseline 7.8±0.2%. In DM2 subjects with elevated BP (n=15, mean arterial pressure reduced by 7±3 mmHg and 8±3 mmHg (P=0.04, baseline 100 ± 2 mmHg at 1 week and 12 months. All subjects MAP decreased by 3 ± 2 mmHg (baseline 95 ± 2 mmHg at 12 months. Conclusions. VBLOC was safe in obese DM2 subjects and associated with meaningful weight loss, early and sustained improvements in HbA1c, and reductions in BP in hypertensive DM2 subjects. This trial is registered with ClinicalTrials.gov NCT00555958.

  2. Influence of physical activity and dietary habits on lipid profile, blood pressure and BMI in subjects with metabolic syndrome.

    Science.gov (United States)

    Muros Molina, J J; Oliveras López, Ma J; Mayor Reyes, Ma; Reyes Burgos, T; López García de la Serrana, H

    2011-01-01

    The present study was determined the influence of physical activity and dietary habits on lipid profile, blood pressure (BP) and body mass index (BMI) in subjects with metabolic syndrome (MS). Identify the relationship between physical activity and proper nutrition and the probability of suffering from myocardial infarction (MI). Hundred chronically ill with MS who were active and followed a healthy diet were classified as compliant, while the remaining subjects were classified as non-compliant. The compliant subjects show lower BMI values (30.8±4.9 vs 32.5±4.6), as well as lower levels of triacylglycerol (130.4±48.2 vs 242.1±90.1), total cholesterol (193.5±39 vs 220.2±52.3) and low-density lipoprotein cholesterol (105.2±38.3 vs 139.2±45). They show higher values in terms of high-density lipoprotein cholesterol levels (62.2±20.1 vs 36.6±15.3), with statistically significant differences. In terms of both systolic and diastolic pressure, no differences were revealed between the groups; however, those who maintain proper dietary habits show lower systolic blood pressure levels than the inactive subjects. The probability of suffering from MI greatly increases among the group of non-compliant subjects. Our results demonstrate how performing aerobic physical activity and following an individualized, Mediterranean diet significantly reduces MS indicators and the chances of suffering from MI.

  3. Resistance to Abrasive Wear and Volume Fraction of Carbides in Cast High-manganese Austenitic Steel with Composite Structure

    Directory of Open Access Journals (Sweden)

    Tęcza G.

    2015-12-01

    Full Text Available Cast Hadfield steel is characterised by high abrasion resistance, provided, however, that it is exposed to the effect of dynamic loads. During abrasion without loading, e.g. under the impact of loose sand jet, its wear resistance drops very drastically. To increase the abrasion resistance of this alloy under the conditions where no pressure is acting, primary vanadium carbides are formed in the metallurgical process, to obtain a composite structure after the melt solidification. The primary, very hard, carbides uniformly distributed in the austenitic matrix are reported to double the wear resistance of samples subjected to the effect of a silicon carbide-water mixture.

  4. Influence of prolonged wearing of unstable shoes on upright standing postural control.

    Science.gov (United States)

    Sousa, Andreia S P; Macedo, Rui; Santos, Rubim; Sousa, Filipa; Silva, Andreia; Tavares, João Manuel R S

    2016-02-01

    To study the influence of prolonged wearing of unstable shoes on standing postural control in prolonged standing workers. The participants were divided into two groups: one wore unstable shoes while the other wore conventional shoes for 8weeks. Stabilometry parameters related to centre of pressure (CoP), rambling (RM) and trembling (TR) as well as the total agonist/antagonist muscle activity, antagonist co-activation and reciprocal activation were evaluated during upright standing, before and after the 8weeks period. In both moments, the subjects were evaluated wearing the unstable shoes and in barefoot. The unstable shoe condition presented increased CoP displacement related variables and decreased co-activation command compared to barefoot before and after the intervention. The prolonged wearing of unstable shoes led to: (1) reduction of medial-lateral CoP root mean square and area; (2) decreased anteroposterior RM displacement; (3) increased anteroposterior RM mean velocity and mediolateral RM displacement; (4) decreased anteroposterior TR RMS; and (5) increased thigh antagonist co-activation in the unstable shoe condition. The unstable shoe condition is associated to a higher destabilising effect that leads to a selection of more efficient and accurate postural commands compared to barefoot. Prolonged wearing of unstable shoes provides increased effectiveness and performance of the postural control system, while wearing of unstable shoes in upright standing, that are reflected by changes in CoP related variables and by a reorganisation of postural control commands. Copyright © 2015 Elsevier B.V. All rights reserved.

  5. STUDIES ON TOOL WEAR CONDITION MONITORING

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    Hüseyin Metin ERTUNÇ

    2001-01-01

    Full Text Available In this study, wear mechanisms on cutting tools, especially for the drill bits, during the cutting operation have been investigated. As the importance of full automation in industry has gained substantial importance, tool wear condition monitoring during the cutting operation has been the subject of many investigators. Tool condition monitoring is very crucial in order to change the tool before breakage. Because tool breakage can cause considerable economical damage to both the machine tool and workpiece. In this paper, the studies on the monitoring of drill bit wear in literature have been introduced; the direct/indirect techniques used and sensor fusion techniques have been summarized. The methods which were proposed to determine tool wear evolution as processing the sensor signals collected have been provided and their references have been given for detailed information.

  6. Effect of a Modest Weight Loss in Normalizing Blood Pressure in Obese Subjects on Antihypertensive Drugs.

    Science.gov (United States)

    Gilardini, Luisa; Redaelli, Gabriella; Croci, Marina; Conti, Antonio; Pasqualinotto, Lucia; Invitti, Cecilia

    2016-01-01

    To assess the effect of a lifestyle intervention in lowering/normalizing blood pressure (BP) levels in hypertensive (controlled or not) obese patients. In this prospective observational study, 490 obese hypertensive patients, 389 controlled (BP normalized BP levels (in 49% after a weight loss normalize BP levels avoiding the aggressive use of multiple antihypertensive drugs. © 2016 The Author(s) Published by S. Karger GmbH, Freiburg.

  7. Fluid-Structure Interaction Analysis for Pressurizer Surge Line subjected to Thermal Stratification

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Dong Gu; Jhung, Myung Jo; Yang, Chae Yong [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)

    2012-05-15

    Fluid-Structure Interactions (FSIs) occurring inevitably in operating reactor component systems can cause excessive force or stress to the structures resulting in mechanical damages that may eventually threaten the structural integrity of components. To solve FSI problems, results from one field (fluid-thermal) analysis are applied as loads in other fields (structural) analysis. If two media with different densities flow inside a pipe, thermal stratification can occur. Warm water is lighter than cool water and therefore tends to float on top of the cooler and heavier water, resulting in the upper portion of the pipe being hotter than the lower portion. Under these conditions, differential thermal expansion of the pipe metal can cause the pipe to deflect significantly. Unexpected piping movements are highly undesirable because of potential high piping stress that may exceed design limits for fatigue and stress. In PWRs, there are great possibilities of occurrence of thermal stratification at the feed water lines of the steam generator, at the pressurizer surge line and at the injection pipes of the emergency core cooling systems. The most affected pipe by the thermal stratification is reported to be the pressurizer surge line. Therefore in this study, a thermal-stress simulation is performed using ANSYS FSI. For the pressurizer surge line, thermal loads are transferred from ANSYS CFX to ANSYS Multiphysics in order to determine the heat transfer between the fluid and the solid body. From this information, stresses are determined and ultimately a fatigue analysis is performed

  8. Validation of a miniature thermochron for monitoring thoracolumbosacral orthosis wear time.

    Science.gov (United States)

    Benish, Brian M; Smith, Kristin J; Schwartz, Michael H

    2012-02-15

    Prospective validation study. To establish the accuracy of miniature thermochrons for estimating thoracolumbosacral orthosis (TLSO) wear time in patients with adolescent idiopathic scoliosis. There has been an emphasis in recent years on measuring wear time as opposed to using subjective methods such as relying on the patient or parent estimation. By measuring the amount of time that was spent in the orthosis, uncertainty is reduced and the validity of the research is improved. Several types of devices have been employed for direct monitoring of orthosis wear time including strap tension monitors, pressure sensors, and temperature-time sensors (thermochrons). Direct monitoring studies have shown that relying on patient or parent report is inaccurate; the patient/parent report is clearly biased towards overestimation of wear time. Three miniature thermochrons (DS1922L iButton, Maxim Integrated Products, Inc., Sunnyvale, CA) were mounted underneath padding in the TLSOs of 7 participants diagnosed with adolescent idiopathic scoliosis. The participants wore their TLSO for 1 month. During this time, participants kept meticulous records of wear time in diaries. An algorithm was developed to automatically detect donning/doffing of the orthosis, and the results of the data reduction algorithm were compared with the diary (gold standard). Total wear time accuracy was 98.5% (0.37 hours/day), while the precise timing of donning/doffing was 92% accurate. An inexpensive, commercially available miniature thermochron and a simple robust algorithm can estimate TLSO wear time to a high degree of accuracy. This method is suitable for large-scale prospective studies examining the efficacy of bracing in adolescent idiopathic scoliosis, which remains a topic of controversy.

  9. Effects of a water-loading test on intraocular pressure and corneal hysteresis in young healthy subjects.

    Science.gov (United States)

    Ulaş, Fatih; Balbaba, Mehmet; Celebi, Serdal

    2014-02-01

    To evaluate the influence of a water-loading test on corneal compensated intraocular pressure (IOPcc) and corneal hysteresis (CH) in young healthy subjects. Forty healthy adult subjects (20 female and 20 male), with a mean age of 27.55±2.57 years (range, 24 to 35 y), participated in this prospective study. IOPcc and CH were measured for 1 eye from each participant with an Ocular Response Analyser. These measurements were taken before and 10, 20, and 30 minutes after water loading. Thirty-seven right and 3 left eyes of the 40 subjects fulfilled the study's inclusion criteria. A statistically significant increase in IOPcc was observed between 0 and 10 minutes (P=0.002) and a significant decrease between 10 and 30 minutes (Pcorneal biomechanical properties.

  10. RESTING SYMPATHETIC BAROREFLEX SENSITIVITY IN SUBJECTS WITH LOW AND HIGH TOLERANCE TO CENTRAL HYPOVOLEMIA INDUCED BY LOWER BODY NEGATIVE PRESSURE

    Directory of Open Access Journals (Sweden)

    Carmen eHinojosa-Laborde

    2014-06-01

    Full Text Available Central hypovolemia elicited by orthostasis or hemorrhage triggers sympathetically-mediated baroreflex responses to maintain organ perfusion; these reflexes are less sensitive in patients with orthostatic intolerance, and during conditions of severe blood loss, may result in cardiovascular collapse (decompensatory or circulatory shock. The ability to tolerate central hypovolemia is variable and physiological factors contributing to tolerance are emerging. We tested the hypothesis that resting muscle sympathetic nerve activity (MSNA and sympathetic baroreflex sensitivity (BRS are attenuated in male and female subjects who have low tolerance (LT to central hypovolemia induced by lower body negative pressure (LBNP. MSNA and diastolic arterial pressure (DAP were recorded in 47 human subjects who subsequently underwent LBNP to tolerance (onset of presyncopal symptoms. LT subjects experienced presyncopal symptoms prior to completing LBNP of -60 mm Hg, and subjects with high tolerance (HT experienced presyncopal symptoms after completing LBNP after -60 mmHg. Contrary to our hypothesis, resting MSNA burst incidence was not different between LT and HT subjects, and was not related to time to presyncope. BRS was assessed as the slope of the relationship between spontaneous fluctuations in DAP and MSNA during 5 min of supine rest. MSNA burst incidence/DAP correlations were greater than or equal to 0.5 in 37 subjects (LT: n= 9; HT: n=28, and BRS was not different between LT and HT (-1.8 ± 0.3 vs. -2.2 ± 0.2 bursts•(100 beats-1•mmHg-1, p=0.29. We conclude that tolerance to central hypovolemia is not related to either resting MSNA or sympathetic BRS.

  11. Patient comfort following thirty minutes of lens wear: piggy-back versus conventional rigid-lens wear

    Directory of Open Access Journals (Sweden)

    W. D.H. Gillan

    2014-08-01

    Full Text Available Discomfort when wearing contact lenses, especially rigid contact lenses, is a common complaint amongst neophyte as well as experienced contact lens wearers. Wearing a piggy-back system of contact lenses has been shown to improve comfort and wearing time, especially in keratoconic subjects. Twenty two normal subjects wore a rigid lens or a piggy-back system of lenses for thirty minutes and after a thirty minute break swopped the mode of lens wear and wore the second modality for a thirty minute period. This study suggests that a piggy-back lens system provides improved comfort compared to wearing a rigid lens on its own. The order of lens wear might, however, influence the perceived comfort.

  12. Significantly Reduced Blood Pressure Measurement Variability for Both Normotensive and Hypertensive Subjects: Effect of Polynomial Curve Fitting of Oscillometric Pulses.

    Science.gov (United States)

    Yang, Fangwei; Chen, Fei; Zhu, Mingping; Chen, Aiqing; Zheng, Dingchang

    2017-01-01

    This study aimed to compare within-subject blood pressure (BP) variabilities from different measurement techniques. Cuff pressures from three repeated BP measurements were obtained from 30 normotensive and 30 hypertensive subjects. Automatic BPs were determined from the pulses with normalised peak amplitude larger than a threshold (0.5 for SBP, 0.7 for DBP, and 1.0 for MAP). They were also determined from cuff pressures associated with the above thresholds on a fitted curve polynomial curve of the oscillometric pulse peaks. Finally, the standard deviation (SD) of three repeats and its coefficient of variability (CV) were compared between the two automatic techniques. For the normotensive group, polynomial curve fitting significantly reduced SD of repeats from 3.6 to 2.5 mmHg for SBP and from 3.7 to 2.1 mmHg for MAP and reduced CV from 3.0% to 2.2% for SBP and from 4.3% to 2.4% for MAP (all P oscillometric pulses had the ability to reduce automatic BP measurement variability.

  13. Volatile profile of breast milk subjected to high-pressure processing or thermal treatment.

    Science.gov (United States)

    Contador, R; Delgado, F J; García-Parra, J; Garrido, M; Ramírez, R

    2015-08-01

    The effect of Holder pasteurisation (HoP) (62.5°C for 30 min) or high-pressure treatments (400 or 600 MPa for 3 or 6 min) on the volatile compound profile of human breast milk was evaluated, in order to compare both preservation technologies. A total of 46 different volatile compounds was found in milk samples. The most abundant compounds detected were aliphatic hydrocarbons. In general, the effect of some high-pressure treatments on the volatile profile of human milk was less intense than that caused by HoP. The treatments at 400 and 600 MPa for 3 min maintained the volatile compounds at similar levels to those found in control milk samples. However, the application of 600 MPa for 6 min changed the original volatile compounds of human milk, even more than HoP. Since, HPP at 400 or 600 MPa for 3 min preserved the original volatile compounds of human milk, this novel process may be an alternative to thermal pasteurisation. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Subject Specific Optimisation of the Stiffness of Footwear Material for Maximum Plantar Pressure Reduction.

    Science.gov (United States)

    Chatzistergos, Panagiotis E; Naemi, Roozbeh; Healy, Aoife; Gerth, Peter; Chockalingam, Nachiappan

    2017-08-01

    Current selection of cushioning materials for therapeutic footwear and orthoses is based on empirical and anecdotal evidence. The aim of this investigation is to assess the biomechanical properties of carefully selected cushioning materials and to establish the basis for patient-specific material optimisation. For this purpose, bespoke cushioning materials with qualitatively similar mechanical behaviour but different stiffness were produced. Healthy volunteers were asked to stand and walk on materials with varying stiffness and their capacity for pressure reduction was assessed. Mechanical testing using a surrogate heel model was employed to investigate the effect of loading on optimum stiffness. Results indicated that optimising the stiffness of cushioning materials improved pressure reduction during standing and walking by at least 16 and 19% respectively. Moreover, the optimum stiffness was strongly correlated to body mass (BM) and body mass index (BMI), with stiffer materials needed in the case of people with higher BM or BMI. Mechanical testing confirmed that optimum stiffness increases with the magnitude of compressive loading. For the first time, this study provides quantitative data to support the importance of stiffness optimisation in cushioning materials and sets the basis for methods to inform optimum material selection in the clinic.

  15. Effects of Wearing Different Personal Equipment on Force Distribution at the Plantar Surface of the Foot

    Directory of Open Access Journals (Sweden)

    Christoph Schulze

    2013-01-01

    Full Text Available Background. The wearing of personal equipment can cause specific changes in muscle activity and posture. In the present study, we investigated the influence of differences in equipment related weight loading and load distribution on plantar pressure. In addition, we studied functional effects of wearing different equipment with a particular focus on relevant changes in foot shape. Methods. Static and dynamic pedobarography were performed on 31 male soldiers carrying increasing weights consisting of different items of equipment. Results. The pressure acting on the plantar surface of the foot increased with higher loading, both under static and dynamic conditions (p < 0.05. We observed an increase in the contact area (p < 0.05 and an influence of load distribution through different ways to carry the rifle. Conclusions. The wearing of heavier weights leads to an increase in plantar pressure and contact area. This may be caused by flattening of the transverse and longitudinal arches. The effects are more evident in subjects with flat feet deformities which seem to flatten at an earlier load condition with a greater amount compared to subjects with normal arches. Improving load distribution should be a main goal in the development of military equipment in order to prevent injuries or functional disorders of the lower extremity.

  16. Circadian blood pressure variability in type 1 diabetes subjects and their nondiabetic siblings - influence of erythrocyte electron transfer

    Directory of Open Access Journals (Sweden)

    Masoni Maria

    2010-10-01

    Full Text Available Abstract Background Normotensive non-diabetic relatives of type 1 diabetes (T1D patients have an abnormal blood pressure response to exercise testing that is associated with indices of metabolic syndrome and increased oxidative stress. The primary aim of this study was to investigate the circadian variability of blood pressure and the ambulatory arterial stiffness index (AASI in healthy siblings of T1D patients vs healthy control subjects who had no first-degree relative with T1D. Secondary aims of the study were to explore the influence of both cardiovascular autonomic function and erythrocyte electron transfer activity as oxidative marker on the ambulatory blood pressure profile. Methods Twenty-four hour ambulatory blood pressure monitoring (ABPM was undertaken in 25 controls, 20 T1D patients and 20 siblings. In addition to laboratory examination (including homeostasis model assessment of insulin sensitivity and clinical testing of autonomic function, we measured the rate of oxidant-induced erythrocyte electron transfer to extracellular ferricyanide (RBC vfcy. Results Systolic blood pressure (SBP midline-estimating statistic of rhythm and pulse pressure were higher in T1D patients and correlated positively with diabetes duration and RBC vfcy; autonomic dysfunction was associated with diastolic BP ecphasia and increased AASI. Siblings had higher BMI, lower insulin sensitivity, larger SBP amplitude, and higher AASI than controls. Daytime SBP was positively, independently associated with BMI and RBC vfcy. Among non-diabetic people, there was a significant correlation between AASI and fasting plasma glucose. Conclusions Siblings of T1D patients exhibited a cluster of sub-clinical metabolic abnormalities associated with consensual perturbations in BP variability. Moreover, our findings support, in a clinical setting, the proposed role of transplasma membrane electron transport systems in vascular pathobiology.

  17. Assessment of wear facets produced by the ACTA wear machine

    DEFF Research Database (Denmark)

    Benetti, Ana R; Larsen, Liselotte; Dowling, Adam H

    2016-01-01

    an assessment of the potential of the experimental RBC formulations for clinical usage. CONCLUSION: The 3D technique allowed for the assessment of mean maximum wear depth and mean total volumetric wear which enables tribological analyses of the wear facet and therefore the wear mechanisms operative. Employing...... the 2D profile technique ranks RBC materials in terms of in-vitro wear performance. CLINICAL SIGNIFICANCE: Confidence in the wear volume measurements can only be achieved if the wear facet is analysed with sufficient resolution using a 3D digital measurement technique. However, the employment of 2D...

  18. Gaussian fitting for carotid and radial artery pressure waveforms: comparison between normal subjects and heart failure patients.

    Science.gov (United States)

    Liu, Chengyu; Zheng, Dingchang; Zhao, Lina; Liu, Changchun

    2014-01-01

    It has been reported that Gaussian functions could accurately and reliably model both carotid and radial artery pressure waveforms (CAPW and RAPW). However, the physiological relevance of the characteristic features from the modeled Gaussian functions has been little investigated. This study thus aimed to determine characteristic features from the Gaussian functions and to make comparisons of them between normal subjects and heart failure patients. Fifty-six normal subjects and 51 patients with heart failure were studied with the CAPW and RAPW signals recorded simultaneously. The two signals were normalized first and then modeled by three positive Gaussian functions, with their peak amplitude, peak time, and half-width determined. Comparisons of these features were finally made between the two groups. Results indicated that the peak amplitude of the first Gaussian curve was significantly decreased in heart failure patients compared with normal subjects (PGaussian curves (PGaussian curves (both PGaussian modeling, which should provide essential tools for further understanding the underlying physiological mechanisms of the artery pressure waveform.

  19. Low-fat set yogurt made from milk subjected to combinations of high hydrostatic pressure and thermal processing.

    Science.gov (United States)

    Harte, F; Luedecke, L; Swanson, B; Barbosa-Cánovas, G V

    2003-04-01

    The combined use of high hydrostatic pressure (300 to 676 MPa, 5 min) and thermal treatment (85 degrees C, 30 min) in milk for the manufacture of low-fat yogurt was studied. The objective was to reduce syneresis and improve the rheological properties of yogurt, reducing the need for thickeners and stabilizers. The use of high hydrostatic pressure alone, or after thermal treatment, reduced the lightness and increased the viscosity of skim milk. However, milk recovered its initial lightness and viscosity when thermal treatment was applied after high hydrostatic pressure. The MALDI-TOF spectra of skim milk presented monomers of whey proteins after a treatment of 676 MPa for 5 min. Yogurts made from skim milk subjected to 400 to 500 MPa and thermal treatment showed increased yield stress, resistance to normal penetration, and elastic modulus, while having reduced syneresis when compared to yogurts from thermally treated or raw milks. The combined use of thermal treatment and high hydrostatic pressure assures extensive whey protein denaturation and casein micelle disruption, respectively. Although reaggregation of casein submicelles occurs during fermentation, the net effect of the combined HHP and thermal treatment is the improvement of yogurt yield stress and reduction of syneresis.

  20. Male and female brain evolution is subject to contrasting selection pressures in primates

    Science.gov (United States)

    Dunbar, Robin IM

    2007-01-01

    The claim that differences in brain size across primate species has mainly been driven by the demands of sociality (the "social brain" hypothesis) is now widely accepted. Some of the evidence to support this comes from the fact that species that live in large social groups have larger brains, and in particular larger neocortices. Lindenfors and colleagues (BMC Biology 5:20) add significantly to our appreciation of this process by showing that there are striking differences between the two sexes in the social mechanisms and brain units involved. Female sociality (which is more affiliative) is related most closely to neocortex volume, but male sociality (which is more competitive and combative) is more closely related to subcortical units (notably those associated with emotional responses). Thus different brain units have responded to different selection pressures. PMID:17493267

  1. Male and female brain evolution is subject to contrasting selection pressures in primates

    Directory of Open Access Journals (Sweden)

    Dunbar Robin IM

    2007-05-01

    Full Text Available Abstract The claim that differences in brain size across primate species has mainly been driven by the demands of sociality (the "social brain" hypothesis is now widely accepted. Some of the evidence to support this comes from the fact that species that live in large social groups have larger brains, and in particular larger neocortices. Lindenfors and colleagues (BMC Biology 5:20 add significantly to our appreciation of this process by showing that there are striking differences between the two sexes in the social mechanisms and brain units involved. Female sociality (which is more affiliative is related most closely to neocortex volume, but male sociality (which is more competitive and combative is more closely related to subcortical units (notably those associated with emotional responses. Thus different brain units have responded to different selection pressures.

  2. Effect of wearing a swimsuit on hydrodynamic drag of swimmer

    Directory of Open Access Journals (Sweden)

    Daniel Almeida Marinho

    2012-12-01

    Full Text Available The purpose of this study was to analyse the effect of wearing a swimsuit on swimmer's passive drag. A computational fluid dynamics analysis was carried out to determine the hydrodynamic drag of a female swimmer's model (i wearing a standard swimsuit; (ii wearing a last generation swimsuit and; (iii with no swimsuit, wearing light underwear. The three-dimensional surface geometry of a female swimmer's model with different swimsuit/underwear was acquired through standard commercial laser scanner. Passive drag force and drag coefficient were computed with the swimmer in a prone position. Higher hydrodynamic drag values were determined when the swimmer was with no swimsuit in comparison with the situation when the swimmer was wearing a swimsuit. The last generation swimsuit presented lower hydrodynamic drag values, although very similar to standard swimsuit. In conclusion, wearing a swimsuit could positively influence the swimmer's hydrodynamics, especially reducing the pressure drag component.

  3. Cuff pressure pain detection is associated with both sex and physical activity level in nonathletic healthy subjects

    DEFF Research Database (Denmark)

    Lemming, Dag; Börsbo, Björn; Sjörs, Anna

    2017-01-01

    analogue scale (VAS). The pain detection threshold (PDT) was defined as when the pressure was perceived as painful, and pain tolerance (PTT) was when the subject terminated the cuff inflation. For PTT, the corresponding VAS score was recorded (VAS-PTT). The protocol was repeated with two chambers inflated......PURPOSE : The aim of this study was to evaluate pressure pain sensitivity on leg and arm in 98 healthy persons (50 women) using cuff algometry. Furthermore, associations with sex and physical activity level were investigated. METHOD:  Normal physical activity level was defined as Godin Leisure......-Time Exercise Questionnaire (GLTEQ) score ≤ 45 and high activity level as GLTEQ > 45. A pneumatic double-chamber cuff was placed around the arm or leg where a single chamber was inflated. The cuff inflation rate (1 kPa/s) was constant, and pain intensity was registered continuously on a 10 cm electronic visual...

  4. Relationship between heart rate variability, blood pressure and arterial wall properties during air and oxygen breathing in healthy subjects.

    Science.gov (United States)

    Graff, Beata; Szyndler, Anna; Czechowicz, Krzysztof; Kucharska, Wiesława; Graff, Grzegorz; Boutouyrie, Pierre; Laurent, Stephane; Narkiewicz, Krzysztof

    2013-11-01

    Previous studies reported that normobaric hyperoxia influences heart rate, arterial pressure, cardiac output and systemic vascular resistance, but the mechanisms underlying these changes are still not fully understood. Several factors are considered including degeneration of endothelium-derived nitric oxide by reactive oxygen species, the impact of oxygen-free radicals on tissues and alterations of autonomic nervous system function. Recently, new devices for the detailed non-invasive assessment of large and small arteries have been developed. Therefore, the aim of our study was to assess heart rate variability (HRV) as a potential indicator of autonomic balance and its relation to blood pressure and vascular properties during medical air (MAB) and 100% oxygen breathing (OXB) in healthy volunteers. In 12 healthy subjects we assessed heart rate and blood pressure variability, baroreflex sensitivity, respiratory frequency, common carotid artery diameter and its wall distensibility, as well as changes in the digital artery pulse waveform, stroke index and systemic vascular resistance during MAB and OXB. Mean and systolic blood pressure have increased significantly while digital pulse amplitude and carotid artery diameter were significantly lower during hyperoxia. Heart rate variability measures did not differ during MAB and OXB. However, the correlations between spectral HRV components and those hemodynamic parameters which have changed due to hyperoxia varied substantially during MAB (correlated significantly) and OXB (no significant correlations were noted). Our findings suggest that autonomic nervous system might not be the main mediator of the cardiovascular changes during 100% oxygen breathing in healthy subjects. It seems that the direct vascular responses are initial consequences of hyperoxia and other cardiovascular parameter alterations are secondary to them. Copyright © 2013 Elsevier B.V. All rights reserved.

  5. EFFECTIVE TOOL WEAR ESTIMATION THROUGH ...

    African Journals Online (AJOL)

    using TiN .coated K20 cemented carbide tool inserts to monitor the tool wear. In the early research, tool wear ... deformation, crack initiation, crack propagation and chipping. Such changes in material behavior will ... the coated carbide experienced rapid tool wear (up to a flank wear land of 0.11 Smm), followed by a slow.

  6. The effect of circadian blood pressure pattern on presence of fragmented QRS complexes in hypertensive subjects.

    Science.gov (United States)

    Eyuboglu, Mehmet; Karabag, Yavuz; Karakoyun, Suleyman; Akdeniz, Bahri

    2017-08-01

    The association of deteriorated circadian blood pressure (BP) variability with presence of fragmented QRS (fQRS) on electrocardiography (ECG) is not clear. The present study aims to evaluate the relationship of BP patterns with presence of fQRS on ECG. A total of 338 consecutive newly diagnosed and never treated hypertensive patients who are without left ventricular hypertrophy and underwent 24-hour ambulatory BP monitoring were enrolled. Patients were classified as dippers, nondippers, and reverse dippers according to ambulatory BP monitoring results. The groups were compared regarding frequency of fQRS on ECG. The frequency of fQRS was significantly higher in reverse dippers compared with dippers (37.7% vs. 20.6%, P = .013). In multivariate logistic regression analysis, nighttime systolic BP was found to be an independent predictor of fQRS on ECG (P reverse dipping BP pattern in hypertensive patients (P = .004, odds ratio: 2.416, 95% confidence interval = 1.327-4.396). In conclusion, as a marker of fibrosis and higher fibrotic burden within myocardium, fQRS may be useful to determine the high-risk hypertensive patients in the absence of left ventricular hypertrophy. Copyright © 2017 American Society of Hypertension. Published by Elsevier Inc. All rights reserved.

  7. Friction, Fretting and Wear: Emerging Materials and Technologies

    Indian Academy of Sciences (India)

    wear, erosion, galling, scuffing and damage. Though these issues have been ... applications ranging from pharmaceuticals, dental implants, mining, transportation, space and nuclear medicine underlines the ... of the mechanical behaviour of solids subjected to erosion, abrasion, fretting, fatigue, impact and wear caused by ...

  8. Flow and heat transfer in gas turbine disk cavities subject to nonuniform external pressure field

    Energy Technology Data Exchange (ETDEWEB)

    Roy, R.P.; Kim, Y.W.; Tong, T.W. [Arizona State Univ., Tempe, AZ (United States)

    1995-10-01

    Injestion of hot gas from the main-stream gas path into turbine disk cavities, particularly the first-stage disk cavity, has become a serious concern for the next-generation industrial gas turbines featuring high rotor inlet temperature. Fluid temperature in the cavities increases further due to windage generated by fluid drag at the rotating and stationary surfaces. The resulting problem of rotor disk heat-up is exacerbated by the high disk rim temperature due to adverse (relatively flat) temperature profile of the mainstream gas in the annular flow passage of the turbine. A designer is concerned about the level of stresses in the turbine rotor disk and its durability, both of which are affected significantly by the disk temperature distribution. This distribution also plays a major role in the radial position of the blade tip and thus, in establishing the clearance between the tip and the shroud. To counteract mainstream gas ingestion as well as to cool the rotor and the stator disks, it is necessary to inject cooling air (bled from the compressor discharge) into the wheel space. Since this bleeding of compressor air imposes a penalty on the engine cycle performance, the designers of disk cavity cooling and sealing systems need to accomplish these tasks with the minimum possible amount of bleed air without risking disk failure. This requires detailed knowledge of the flow characteristics and convective heat transfer in the cavity. The flow in the wheel space between the rotor and stator disks is quite complex. It is usually turbulent and contains recirculation regions. Instabilities such as vortices oscillating in space have been observed in the flow. It becomes necessary to obtain both a qualitative understanding of the general pattern of the fluid motion as well as a quantitative map of the velocity and pressure fields.

  9. Environmental Quality and Aquatic Invertebrate Metrics Relationships at Patagonian Wetlands Subjected to Livestock Grazing Pressures.

    Science.gov (United States)

    Epele, Luis Beltrán; Miserendino, María Laura

    2015-01-01

    Livestock grazing can compromise the biotic integrity and health of wetlands, especially in remotes areas like Patagonia, which provide habitat for several endemic terrestrial and aquatic species. Understanding the effects of these land use practices on invertebrate communities can help prevent the deterioration of wetlands and provide insights for restoration. In this contribution, we assessed the responses of 36 metrics based on the structural and functional attributes of invertebrates (130 taxa) at 30 Patagonian wetlands that were subject to different levels of livestock grazing intensity. These levels were categorized as low, medium and high based on eight features (livestock stock densities plus seven wetland measurements). Significant changes in environmental features were detected across the gradient of wetlands, mainly related to pH, conductivity, and nutrient values. Regardless of rainfall gradient, symptoms of eutrophication were remarkable at some highly disturbed sites. Seven invertebrate metrics consistently and accurately responded to livestock grazing on wetlands. All of them were negatively related to increased levels of grazing disturbance, with the number of insect families appearing as the most robust measure. A multivariate approach (RDA) revealed that invertebrate metrics were significantly affected by environmental variables related to water quality: in particular, pH, conductivity, dissolved oxygen, nutrient concentrations, and the richness and coverage of aquatic plants. Our results suggest that the seven aforementioned metrics could be used to assess ecological quality in the arid and semi-arid wetlands of Patagonia, helping to ensure the creation of protected areas and their associated ecological services.

  10. Comparison of intraocular pressure, blood pressure, ocular perfusion pressure and blood flow fluctuations during dorzolamide versus timolol add-on therapy in prostaglandin analogue treated glaucoma subjects.

    Science.gov (United States)

    Januleviciene, Ingrida; Siaudvytyte, Lina; Diliene, Vaida; Barsauskaite, Ruta; Paulaviciute-Baikstiene, Daiva; Siesky, Brent; Harris, Alon

    2012-03-21

    To compare the effects of dorzolamide and timolol add-on therapy in open-angle glaucoma (OAG) patients previously treated with prostaglandin analogue (Pg), by evaluating fluctuations in the intraocular (IOP), blood (BP), ocular perfusion pressures (OPP) and retrobulbar blood flow (RBF) parameters. 35 OAG patients (35 eyes), 31 women (88.6%) age 63.3 (8.9) years were evaluated in a 3 month randomized, cross-over, single-masked study. During the experiments BP, heart rate, IOP and OPP were assessed 4 times per day (8-12-16-20 h). RBF was measured twice per day (8-20 h) using Color Doppler imaging in the ophthalmic (OA), central retinal (CRA), nasal (nSPCA) and temporal (tSPCA) posterior ciliary arteries. In each vessel, peak systolic velocity (PSV) and end-diastolic velocity (EDV) were assessed and vascular resistance (RI) calculated. Both add-on therapies lowered IOP in a statistically significant manner from 15.7 ± 2.4 mmHg at latanoprost baseline to 14.9 ± 2.2 mmHg using dorzolamide (p add-on therapy showed smaller IOP (2.0 ± 1.4), SPP (13.3 ± 7.9), systolic BP (13.5 ± 8.7) and diastolic BP (8.4 ± 5.4) fluctuations as compared to both latanoprost baseline or timolol add-on therapies. Higher difference between morning and evening BP was correlated to decreased evening CRA EDV in the timolol group (c = -0.41; p = 0.01). With increased MAP in the morning or evening hours, we found increased evening OA RI in timolol add-on group (c = 0.400, p = 0.02; c = 0.513, p = 0.002 accordingly). Higher MAP fluctuations were related to impaired RBF parameters during evening hours-decreased CRA EDV (c = -0.408; p = 0.01), increased CRA RI (c = 0.576; p add-on group. OPP fluctuations correlated with increased nSPCA RI (c = 0.453; p = 0.006) in the timolol group. OPP fluctuations were not related to IOP fluctuations in both add-on therapies (p add-on therapies lowered IOP in a statistically significant fashion dorzolamide add-on therapy showed lower fluctuations in IOP, SPP

  11. Immediate effects of hamstring muscle stretching on pressure pain sensitivity and active mouth opening in healthy subjects.

    Science.gov (United States)

    Bretischwerdt, Cristina; Rivas-Cano, Luis; Palomeque-del-Cerro, Luis; Fernández-de-las-Peñas, César; Alburquerque-Sendín, Francisco

    2010-01-01

    This study analyzed the immediate effect of hamstring muscle stretching on pressure pain sensitivity over the masseter and the upper trapezius muscles and maximum active mouth opening in healthy subjects. One hundred twenty volunteers, 70 males and 50 females, between the ages of 22 and 47, were randomly divided into 3 groups: group 1 (control group) that did not receive any intervention, group 2 where a unilateral hamstring muscle stretching was applied, and group 3 where a bilateral stretching was applied. Pressure pain thresholds (PPTs) were bilaterally assessed over the masseter and upper trapezius muscles pre- and 5 minutes posttreatment by an assessor blinded to group assignment. Maximum mouth opening was also assessed pre- and 5 minutes posttreatment. Mixed-model analyses of variance (ANOVAs) were used to examine the effects of the intervention. The primary analysis was the group x time interaction. The ANOVA revealed significant group x time interaction for changes in PPTs over the upper trapezius (F = 4.5; P = .01) and masseter (F = 6.3; P = .002) muscles. Pre-post effect sizes were moderate (0.5 >d > 0.7) for both stretching groups and negative (d 0.7) for both stretching groups and negative (d stretching of the hamstring musculature produced an immediate increase in PPTs over both masseter and upper trapezius muscles in healthy subjects. Copyright 2010 National University of Health Sciences. Published by Mosby, Inc. All rights reserved.

  12. Echocardiographic Measures of Diastolic Function Are Preload Dependent during Triggered Positive Pressure Ventilation: A Controlled Crossover Study in Healthy Subjects

    Directory of Open Access Journals (Sweden)

    Peter Juhl-Olsen

    2012-01-01

    Full Text Available Background. The use of echocardiography in intensive care settings impacts decision making. A prerequisite for the use of echocardiography is relative resistance to changes in volume status and levels of positive pressure ventilation (PPV. Studies on indices of diastolic function report conflicting results with regard to dependence on volume status. Evidence is scarce on PPV. Methods. Ten healthy subjects were exposed to 6 levels of positive end-expiratory pressure (PEEP and pressure support (PS following a baseline reading. All ventilator settings were performed at three positions: horizontal, reverse-Trendelenburg, and Trendelenburg. Echocardiography was performed throughout. Results. During spontaneous breathing, early diastolic transmitral velocity ( changed with positioning (, whereas early diastolic velocity of the mitral annulus ( was independent (. With PPV, and proved preload dependent (. Increases in PEEP, PS, or a combination influenced and in reverse-Trendelenburg- and horizontal positions, but not in the Trendelenburg position. Discussion. The change towards preload dependency of with PPV suggests that PPV increases myocardial preload sensitivity. The susceptibility of and to preload changes during PPV discourages their use in settings of volume shifts or during changes in ventilator settings. Conclusion. Positioning and PPV affect and .

  13. Inspiratory muscle strength in subjects with tetraplegia: viability of evaluation through the measurement of maximal inspiratory pressure

    Directory of Open Access Journals (Sweden)

    Marlene Aparecida Moreno

    Full Text Available Objective To analyze the values of maximal inspiratory pressure (MIP and sniff nasal inspiratory pressure (SNIP and to verify the existence of concordance between the two evaluation methodologies, in subjects with tetraplegia. Materials and methods Cross-sectional study with 17 tetraplegic men, aged 30.42 ± 7.67 years, who underwent MIP and SNIP evaluation using a respiratory pressure meter. Results The MIP and SNIP values obtained showed no difference when compared to each other (88.42 ± 29.39 vs. 86.68 ± 25.40 cmH2O, respectively. They were, however, significantly lower compared to the predicted values (MIP = 128.92 ± 7.18; SNIP = 114.11 ± 3.19 cmH2O, with the MIP values presenting correlation (r2 = 0.94; p < 0.0001 and concordance with those of the SNIP. Conclusions Both the MIP and SNIP values obtained were lower than the predicted values, indicating a reduction in inspiratory muscle strength (IMS. Both techniques showed correlation and concordance, suggesting that MIP can be used as a noninvasive method for IMS evaluation in this population.

  14. Significantly Reduced Blood Pressure Measurement Variability for Both Normotensive and Hypertensive Subjects: Effect of Polynomial Curve Fitting of Oscillometric Pulses

    Directory of Open Access Journals (Sweden)

    Fangwei Yang

    2017-01-01

    Full Text Available This study aimed to compare within-subject blood pressure (BP variabilities from different measurement techniques. Cuff pressures from three repeated BP measurements were obtained from 30 normotensive and 30 hypertensive subjects. Automatic BPs were determined from the pulses with normalised peak amplitude larger than a threshold (0.5 for SBP, 0.7 for DBP, and 1.0 for MAP. They were also determined from cuff pressures associated with the above thresholds on a fitted curve polynomial curve of the oscillometric pulse peaks. Finally, the standard deviation (SD of three repeats and its coefficient of variability (CV were compared between the two automatic techniques. For the normotensive group, polynomial curve fitting significantly reduced SD of repeats from 3.6 to 2.5 mmHg for SBP and from 3.7 to 2.1 mmHg for MAP and reduced CV from 3.0% to 2.2% for SBP and from 4.3% to 2.4% for MAP (all P<0.01. For the hypertensive group, SD of repeats decreased from 6.5 to 5.5 mmHg for SBP and from 6.7 to 4.2 mmHg for MAP, and CV decreased from 4.2% to 3.6% for SBP and from 5.8% to 3.8% for MAP (all P<0.05. In conclusion, polynomial curve fitting of oscillometric pulses had the ability to reduce automatic BP measurement variability.

  15. Law and the Wearing of Religious Symbols: European Bans on the Wearing of Religious Symbols in Education

    Science.gov (United States)

    Howard, Erica

    2011-01-01

    Written in accessible language, Law and the Wearing of Religious Symbols is a comprehensive analysis of a topical subject that is being widely debated across Europe. The book provides an overview of emerging case law from the European Court of Human Rights as well as from national courts and equality bodies in European countries on the wearing of…

  16. Pattern of outsole shoe heel wear in infantry recruits.

    Science.gov (United States)

    Finestone, Aharon S; Petrov, Kaloyan; Agar, Gabriel; Honig, Assaf; Tamir, Eran; Milgrom, Charles

    2012-10-25

    Excessive shoe heel abrasion is of concern to patients, parents and shoe manufacturers, but little scientific information is available. The purpose of this study was to describe the phenomenon in a group of infantry recruits performing similar physical activity, and search for biomechanical factors that might be related. Seventy-six subjects (median age 19) enrolled. Pre-training parameters measured included height, weight, tibial length, foot arch height and foot progression angle. Digital plantar pressure maps were taken to calculate arch indexes. Shoe heel abrasion was assessed manually after 14 weeks of training with different-sized clock transparencies and a calliper. Outsole abrasion was posterolateral, averaging 12 degrees on each shoe. The average heel volume that was eroded was almost 5 cm3. The angle of maximum wear was related to right foot progression angle (r = 0.27, p = 0.02). Recruits with lateral ankle sprains had higher angles of maximal abrasion (17° versus 10°, p = 0.26) and recruits with lateral heel abrasion had more lateral ankle sprains (14% versus 3%, p = 0.12). While shoe heel wear affects many people, very little has been done to measure it. In this study in healthy subjects, we found the main abrasion to be posterolateral. This seems to be related to foot progression angle. It was not related to hindfoot valgus/varus or other factors related to subtalar joint motion. These findings do not warrant modification of subtalar joint motion in order to limit shoe heel abrasion.

  17. IPP-rich milk protein hydrolysate lowers blood pressure in subjects with stage 1 hypertension, a randomized controlled trial

    Directory of Open Access Journals (Sweden)

    Kloek Joris

    2010-11-01

    Full Text Available Abstract Background Milk derived peptides have been identified as potential antihypertensive agents. The primary objective was to investigate the effectiveness of IPP-rich milk protein hydrolysates (MPH on reducing blood pressure (BP as well as to investigate safety parameters and tolerability. The secondary objective was to confirm or falsify ACE inhibition as the mechanism underlying BP reductions by measuring plasma renin activity and angiotensin I and II. Methods We conducted a randomized, placebo-controlled, double blind, crossover study including 70 Caucasian subjects with prehypertension or stage 1 hypertension. Study treatments consisted of daily consumption of two capsules MPH1 (each containing 7.5 mg Isoleucine-Proline-Proline; IPP, MPH2 (each containing 6.6 mg Methionine-Alanine-Proline, 2.3 mg Leucine-Proline-Proline, 1.8 mg IPP, or placebo (containing cellulose for 4 weeks. Results In subjects with stage 1 hypertension, MPH1 lowered systolic BP by 3.8 mm Hg (P = 0.0080 and diastolic BP by 2.3 mm Hg (P = 0.0065 compared with placebo. In prehypertensive subjects, the differences in BP between MPH1 and placebo were not significant. MPH2 did not change BP significantly compared with placebo in stage I hypertensive or prehypertensive subjects. Intake of MPHs was well tolerated and safe. No treatment differences in hematology, clinical laboratory parameters or adverse effects were observed. No significant differences between MPHs and placebo were found in plasma renin activity, or angiotensin I and II. Conclusions MPH1, containing IPP and no minerals, exerts clinically relevant BP lowering effects in subjects with stage 1 hypertension. It may be included in lifestyle changes aiming to prevent or reduce high BP. Trial registration ClinicalTrials.gov NCT00471263

  18. Older age is associated with greater central aortic blood pressure following the exercise stress test in subjects with similar brachial systolic blood pressure.

    Science.gov (United States)

    Kobayashi, Masatake; Oshima, Kazutaka; Iwasaki, Yoichi; Kumai, Yuto; Avolio, Alberto; Yamashina, Akira; Takazawa, Kenji

    2016-08-01

    Brachial systolic pressure (BSP) is often monitored during exercise by the stress test; however, central systolic pressure (CSP) is thought to be a more direct measure of cardiovascular events. Although some studies reported that exercise and aging may play roles in changes of both BSP and CSP, the relationship between BSP and CSP with age following the exercise stress test remains unclear. The aim of this study was to evaluate the effect of age on the relationship between BSP and CSP measured after exercise. Ninety-six subjects underwent the diagnostic treadmill exercise stress test, and we retrospectively divided them into the following 3 groups by age: the younger age group (43 ± 4 years), middle age group (58 ± 4 years), and older age group (70 ± 4 years). Subjects exercised according to the Bruce protocol, to achieve 85 % of their age-predicted maximum heart rate or until the appearance of exercise-associated symptoms. BSP, CSP, and pulse rate (PR) were measured using a HEM-9000AI (Omron Healthcare, Japan) at rest and after exercise. BSP, CSP, and PR at rest were not significantly different among the 3 groups (p = 0.92, 0.21, and 0.99, respectively). BSP and PR immediately after exercise were not significantly different among the groups (p = 0.70 and 0.38, respectively). However, CSP immediately after exercise was 144 ± 18 mmHg (younger age), 149 ± 17 mmHg (middle age), and 158 ± 19 mmHg (older age). CSP in the older age group was significantly higher than that in the younger age group (p age groups after exercise, CSP was higher in the older age group. Therefore, older subjects have a higher CSP after exercise, which is not readily assessed by conventional measurements of BSP.

  19. Effect of wearing a ski helmet on perception and localization of sounds.

    Science.gov (United States)

    Ruedl, G; Kopp, M; Burtscher, M; Zorowka, P; Weichbold, V; Stephan, K; Koci, V; Seebacher, J

    2014-07-01

    Helmet use on ski slopes has steadily increased worldwide over the past years. A common reason reported for helmet non-use, however, is impaired hearing. Therefore, an intra-subject design study was conducted to compare hearing thresholds and sound source localization of 21 adults with normal hearing in an anechoic chamber when wearing a ski helmet and ski goggles or wearing a ski cap and ski goggles to the condition head bare. Hearing thresholds while wearing a ski helmet (6.8 ± 1.6 dB HL) and ski cap (5.5 ± 1.6 dB HL) were significantly different (p = 0.030, d = 0.44). Compared to head bare (2.5 ± 1.2 dB HL), a significant difference was found for the ski helmet only (p = 0.040, d = 1.57). Regarding sound source localization, correct scores in the condition head bare (90%) showed a highly significant difference compared with those of condition cap (65%) and helmet (58%), respectively (p 2.5). Compared to the ski cap, wearing the helmet significantly reduced correct scores (p = 0.020, d = 0.59) irrespective of the tested sound pressure levels. In conclusion, wearing a ski helmet impairs hearing to a small though significantly greater extent compared with a cap, the degree, however, being less than what is termed as a hearing impairment. Compared to the condition head bare, wearing a ski cap or a ski helmet significantly reduced one's ability of sound source localization. © Georg Thieme Verlag KG Stuttgart · New York.

  20. Circadian intraocular pressure patterns in healthy subjects, primary open angle and normal tension glaucoma patients with a contact lens sensor.

    Science.gov (United States)

    Agnifili, Luca; Mastropasqua, Rodolfo; Frezzotti, Paolo; Fasanella, Vincenzo; Motolese, Ilaria; Pedrotti, Emilio; Di Iorio, Angelo; Mattei, Peter A; Motolese, Eduardo; Mastropasqua, Leonardo

    2015-02-01

    To examine the circadian intraocular pressure (IOP) patterns in healthy subjects, in primary open angle and normal tension glaucoma (POAG; NTG) using a contact lens sensor (CLS; Sensimed Triggerfish, Lausanne, Switzerland). This was an observational, nonrandomized study. Ten healthy subjects (Group 1, 10 eyes) and 20 glaucomatous patients [20 eyes, 10 with POAG (Group 2) and 10 with NTG (Group 3)] were enrolled. All patients were controlled with prostaglandin analogues. The 24-hr IOP pattern was the main outcome. The morning (6AM-11AM), afternoon/evening (noon-11PM) and night (midnight-5AM) subperiod patterns, peaks and prolonged peaks (>1 hr) were secondary outcomes. Mean 24-hr IOP pattern showed a nocturnal acrophase in all groups. Patterns were significantly different among groups (p = 0.02), with highest nocturnal IOP values in POAG. Prolonged peaks were more common in patients with glaucoma (70%) than in healthy subjects (33.3%) (p < 0.001). Significant differences were found for Groups 2 and 3 in the morning versus afternoon/evening (p = 0.019 and p = 0.035, Bonferroni correction), morning versus night (p = 0.005 and p < 0.0001) and afternoon/evening versus night periods comparisons (p < 0.0001 for both groups). In Group 1, patterns significantly differed in the morning versus night and afternoon/evening versus night period comparisons (p < 0.0001). Continuous 24-hr IOP monitoring with the CLS revealed a nocturnal acrophase in healthy subjects and, more markedly, in glaucoma. Because the diurnal IOP profile seems not to predict the nocturnal rhythm, the circadian IOP pattern should be evaluated in clinical practice. These findings may be worthwhile for the management of glaucoma. © 2014 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

  1. Effect of Material Parameters on Steady State Creep in a Thick Composite Cylinder Subjected to Internal Pressure

    Directory of Open Access Journals (Sweden)

    Tejeet Singh

    2009-12-01

    Full Text Available The steady state creep in Al- SiCP composite cylinder subjected to internal pressure was investigated. The creep behavior of the material were described by threshold stress based creep law by assuming a stress exponent of 5. The effect of size and content of the reinforcement (SiCP , and operating temperature on the stresses and strain rates in the composite cylinder were investigated. The stresses in the cylinder did not have significant variation with varying size and content of the reinforcement, and operating temperature. However, the tangential as well as radial strain rates in the cylinder could be reduced to a significant extent by decreasing size of SiCP, increasing the content of SiCP and decreasing operating temperature.

  2. Weight loss and blood pressure reduction in obese subjects in response to nutritional guidance using information communication technology.

    Science.gov (United States)

    Ueki, Kanako; Sakurai, Nozomi; Tochikubo, Osamu

    2009-05-01

    The metabolic syndrome caused by visceral-fat obesity is a major risk factor for atherosclerosis. This study used a new information communication technology (ICT) to investigate body weight (BW) and blood pressure (BP) changes in response to nutritional guidance. Obese subjects with hypertension, hyperlipidemia, or impaired glucose tolerance received guidance with the ICT method (n = 13) or face-to-face according to conventional methods (n = 39). The effects of the methods were compared. After 12 weeks, significant weight loss and BP reduction were observed in the ICT group. Also, significant higher improvements were observed in total cholesterol (TC), low-density lipoprotein (LDL) cholesterol, and HbA(1c) in the ICT-group compared with those groups using the conventional method. The effectiveness of the ICT method in reducing BW, BP, total and LDL cholesterol, and HbA(1c) was demonstrated.

  3. Effect of age and gender on sudomotor and cardiovagal function and blood pressure response to tilt in normal subjects

    Science.gov (United States)

    Low, P. A.; Denq, J. C.; Opfer-Gehrking, T. L.; Dyck, P. J.; O'Brien, P. C.; Slezak, J. M.

    1997-01-01

    Normative data are limited on autonomic function tests, especially beyond age 60 years. We therefore evaluated these tests in a total of 557 normal subjects evenly distributed by age and gender from 10 to 83 years. Heart rate (HR) response to deep breathing fell with increasing age. Valsalva ratio varied with both age and gender. QSART (quantitative sudomotor axon-reflex test) volume was consistently greater in men (approximately double) and progressively declined with age for all three lower extremity sites but not the forearm site. Orthostatic blood pressure reduction was greater with increasing age. HR at rest was significantly higher in women, and the increment with head-up tilt fell with increasing age. For no tests did we find a regression to zero, and some tests seem to level off with increasing age, indicating that diagnosis of autonomic failure was possible to over 80 years of age.

  4. Severity of spine malalignment on center of pressure progression during level walking in subjects with adolescent idiopathic scoliosis.

    Science.gov (United States)

    Chern, Jen-Suh; Kao, Chia-Chi; Lai, Po-Lian; Lung, Chi-Wen; Chen, Wen-Jer

    2014-01-01

    Center of pressure (CoP) progression during level walking in subjects with Adolescents Idiopathic Scoliosis (AIS) was measured. Participants were divided into three groups according to scoliosis severity. CoP progression among groups was compared quantitatively and qualitatively. The results showed that scoliosis severity affects CoP progression significantly in the hind-foot and forefoot areas. This result indicated that spine alignment might affect the control of heel, ankle and toe rockers in the ankle-foot complex. The effects of scoliosis severity is mainly on the CoP of right foot plantar surface, indicating asymmetrical influence of IS on bilateral lower limb coordination during walking. These results might contribute to musculoskeletal complains over the apparatus within trunk-foot in the later lives of this population.

  5. Risk Stratification by 24-Hour Ambulatory Blood Pressure and Estimated Glomerular Filtration Rate in 5322 Subjects From 11 Populations

    DEFF Research Database (Denmark)

    Boggia, José; Thijs, Lutgarde; Li, Yan

    2013-01-01

    subjects (median age, 51.8 years; 43.1% women) randomly recruited from 11 populations, who had baseline measurements of 24-hour ambulatory blood pressure (ABP(24)) and eGFR. We computed hazard ratios using multivariable-adjusted Cox regression. Median follow-up was 9.3 years. In fully adjusted models......, which included both ABP(24) and eGFR, ABP(24) predicted (P≤0.008) both total (513 deaths) and cardiovascular (206) mortality; eGFR only predicted cardiovascular mortality (P=0.012). Furthermore, ABP(24) predicted (P≤0.0056) fatal combined with nonfatal events as a result of all cardiovascular causes...... (555 events), cardiac disease (335 events), or stroke (218 events), whereas eGFR only predicted the composite cardiovascular end point and stroke (P≤0.035). The interaction terms between ABP(24) and eGFR were all nonsignificant (P≥0.082). For cardiovascular mortality, the composite cardiovascular end...

  6. The effect of welding on the strength of aluminium stiffened plates subject to combined uniaxial compression and lateral pressure

    Directory of Open Access Journals (Sweden)

    Pedram Masoud

    2014-03-01

    Full Text Available Nowadays aluminum stiffened plates are one of the major constituents of the marine structures, espe¬cially high-speed vessels. On one hand, these structures are subject to various forms of loading in the harsh sea envi¬ronment, like hydrostatic lateral pressures and in-plane compression. On the other hand, fusion welding is often used to assemble those panels. The common marine aluminum alloys in the both 5,000 and 6,000 series, however, lose a re¬markable portion of their load carrying capacity due to welding. This paper presents the results of sophisticated finite-element investigations considering both geometrical and mechanical imperfections. The tested models were those pro¬posed by the ultimate strength committee of 15th ISSC. The presented data illuminates the effects of welding on the strength of aluminum plates under above-mentioned load conditions.

  7. The evaluation of the elasto-plastic behavior in case of the honed steel pipes subjected to variable internal pressure

    Science.gov (United States)

    Steigmann, R.; Stanciu, M. D.; Szasz, M.; Curtu, I.; Sturzu, T.; Savin, A.

    2016-08-01

    The paper analyses the elasto-plastic behavior of ten samples of E355 steel pipe of the same inner diameter, but with wall thickness ranging between 1.100 and 2.500 mm and length about 100 mm. The samples were subjected to variable internal pressure which was increased from 0 to 600-800 bar (up to the breaking of the pipe), being used the hydraulic oil, type HM46. The outer diameter of the tested pipes was measured successive for each increase of pressure with 100 bars, thus being determined the flow curve of the pipe material characterized by the elasto-plastic behavior and a tenacious failure. It was found that thin pipes, with the ratio between the inner and outer diameter less than 1.1, shows a different flow curve compare to pipes with thick walls, having the ratio between the inner and outer diameter greater than 1.1, the deformations being about two times higher. The rheological models of each type of pipes were identified.

  8. Simulated Wear of Self-Adhesive Resin Cements.

    Science.gov (United States)

    Takamizawa, T; Barkmeier, W W; Latta, M A; Berry, T P; Tsujimoto, A; Miyazaki, M

    2016-01-01

    One of the primary areas of concern with luting agents is marginal gap erosion and attrition. The purpose of this laboratory study was to evaluate bulk and marginal slit (gap) generalized wear of self-adhesive resin cements. Three self-adhesive resin cements were used in this study: G-CEM LinkAce (LA), Maxcem Elite (ME), and RelyX Unicem2 Automix (RU). A custom stainless-steel fixture with a cavity 4.5 mm in diameter and 4 mm deep was used for simulated generalized (bulk) wear. For simulated marginal gap wear, a two-piece stainless-steel custom fixture was designed with a slit (gap) 300 μm wide and 3 mm in length. For both wear models, 20 specimens each for each of the three adhesive cements were made for both light-cure and chemical-cure techniques. The cured cements were polished with a series of carbide papers to a 4000-grit surface and subjected to 100,000 cycles using the slit (gap) wear model and 400,000 cycles for generalized (bulk) wear in a Leinfelder-Suzuki (Alabama machine) wear simulator (maximum load of 78.5 N). Flat-ended stainless-steel antagonists were used in a water slurry of poly(methylmethacrylate) beads for simulation of generalized contact-free area wear with both wear models. Before and after the wear challenges, the specimens were profiled with a Proscan 2100 noncontact profilometer, and wear (volume loss [VL] and mean facet depth [FD]) was determined using AnSur 3D software. Two-way analysis of variance (ANOVA) and Tukey post hoc tests were used for data analysis for the two wear models. Scanning electron microscopy (SEM) was used to examine polished surfaces of the resin cements and the worn surfaces after the wear challenges. The two-way ANOVA of VL using the generalized (bulk) wear model showed a significant effect among the three resin cement materials for the factor of resin cement (pcement and cure method (pcement (pcement and cure method (pcements and the resultant effect of the wear challenges. The worn surfaces of each cement were

  9. The Devil Wears Prada

    African Journals Online (AJOL)

    Adele

    The film is based on the book. The Devil Wears Prada written by Lauren Weisberger, ... image and power driven industry that is haute couture and fashion today. Although Andrea's experience is the main ... creations not fit even for Halloween, designer and brand name jewellery and other fashion accessories. Anything from ...

  10. Comparative wear mapping techniques

    DEFF Research Database (Denmark)

    Alcock, J.; Sørensen, Ole Toft; Jensen, S.

    1996-01-01

    Pin surfaces were analysed by laser profilometry. Two roughness parameters, R(a) and the fractal dimension, were investigated as a first step towards methods of quantitative wear mechanism mapping. Both parameters were analysed for their relationship to the severity and prevalence of a mechanism....

  11. Are blood pressure and diabetes additive or synergistic risk factors? outcome in 8494 subjects randomly recruited from 10 populations

    DEFF Research Database (Denmark)

    Sehestedt, Thomas; Hansen, Tine W; Li, Yan

    2011-01-01

    It remains unknown whether diabetes and high blood pressure (BP) are simply additive risk factors for cardiovascular outcome or whether they act synergistically and potentiate one another. We performed 24-h ambulatory BP monitoring in 8494 subjects (mean age, 54.6 years; 47.0% women; 6.9% diabetic...... as the reference group, the adjusted hazard ratios for the cardiovascular endpoint were 1.35 (95% confidence interval (CI), 0.87-2.11) for white-coat hypertension, 1.78 (95% CI, 1.22-2.60) for masked hypertension and 2.44 (95% CI, 1.92-3.11) for sustained hypertension. The hazard ratios for non-diabetic subjects...... were not different from those of diabetic patients (P-values for interaction, 0.09¿P¿0.72). In conclusion, in a large international population-based database, both diabetes mellitus and BP contributed equally to the risk of cardiovascular complications without evidence for a synergistic effect.Hypertension...

  12. [Ambulatory blood pressure in normotensive subjects. Definition of reference values as a function of age by the Spacelabs instrument].

    Science.gov (United States)

    Pagny, J Y; Delva, R; Aouizerate, M; Chatellier, G; Battaglia, C; Devriès, C; Plouin, P F; Corvol, P; Ménard, J

    1987-10-10

    For a finer assessment, by repeated blood pressure (BP) measurements, of the cardiovascular risk associated with BP levels, new instruments have been developed which provide multiple reading during periods of activity. However, the lack of epidemiological studies makes it necessary to determine reference ambulatory BP levels by another method. Twelve-hour recordings were taken with the Spacelabs instrument in 130 volunteers (45% males) aged from 20 to 90 years during their various activities. Mean systolic and diastolic BP values +/- SD were calculated per age-groups of 10 years each. That this sample was representative of the general population was confirmed by the fact that BP fluctuations and variations according to age and sex in these 130 subjects were identical with those observed in the population of an entire town (Framingham). The concept of hypertension, as defined by ambulatory BP recordings, is discussed. This study provides, for the first time, reference ambulatory BP values according to age and sex, measured in normotensive subjects with the Spacelabs instrument. These values constitute a preliminary step indispensable to evaluate this technique in hypertensive patients.

  13. Autonomic neuropathy in nondiabetic offspring of type 2 diabetic subjects is associated with urinary albumin excretion rate and 24-h ambulatory blood pressure: the Fredericia Study

    DEFF Research Database (Denmark)

    Foss, Anne-Catherine; Vestbo, Else; Frøland, Anders

    2001-01-01

    The aim of this study was to examine the impact of parental type 2 diabetes on the autonomic nervous system and to determine whether autonomic neuropathy is present and associated with changes in 24-h ambulatory blood pressure (AMBP) and urinary albumin excretion rate (UAER) in nondiabetic subjects...... offspring with parental type 2 diabetes (6.7%) was significantly (P pressure...... UAER, fasting insulin level, and 24-h AMBP and a reduced diurnal blood pressure variation. This study indicates that parental type 2 diabetes has an impact on the cardiac autonomic function in nondiabetic subjects....

  14. Substantial Inter-Subject Variability in Blood Pressure Responses to Glucose in a Healthy, Non-obese Population

    Directory of Open Access Journals (Sweden)

    Cathriona R. Monnard

    2017-07-01

    Full Text Available Aim: A large inter-subject variability in the blood pressure (BP response to glucose drinks has been reported. However, the underlying factors remain elusive and we hypothesized that accompanying changes in glucose metabolism affect these BP responses.Methods: Cardiovascular and glycemic changes in response to a standard 75 g oral-glucose-tolerance-test were investigated in 30 healthy, non-obese males. Continuous cardiovascular monitoring, including beat-to-beat BP, electrocardiographically deduced heart rate and impedance cardiography, was performed during a 30 min baseline and continued up to 120 min after glucose ingestion. Blood samples were taken at baseline, 30, 60, 90, and 120 min for the assessment of glucose, insulin and c-peptide. Additionally, we evaluated body composition by using validated bioelectrical impedance techniques.Results: Individual overall changes (i.e., averages over 120 min for systolic BP ranged from −4.9 to +4.7 mmHg, where increases and decreases were equally distributed (50%. Peak changes (i.e., peak averages over 10 min intervals for systolic BP ranged from −1.3 to +9.5 mmHg, where 93% of subjects increased systolic BP above baseline values (similar for diastolic BP whilst 63% of subjects increased peak systolic BP by more than 4 mmHg. Changes in peak systolic BP were negatively associated with the calculated Matsuda-index of insulin sensitivity (r = −0.39, p = 0.04 but with no other evaluated parameter including body composition. Moreover, besides a trend toward an association between overall changes in systolic BP and total fat mass percentage (r = +0.32, p = 0.09, no association was found between other body composition parameters and overall BP changes.Conclusion: Substantial inter-subject variability in BP changes was observed in a healthy, non-obese subpopulation in response to an oral glucose load. In 63% of subjects, peak systolic BP increased by more than a clinically relevant 4 mmHg. Peak systolic

  15. The Fluctuation of Intraocular Pressure Measured by a Contact Lens Sensor in Normal-Tension Glaucoma Patients and Nonglaucoma Subjects.

    Science.gov (United States)

    Tojo, Naoki; Abe, Shinya; Ishida, Masaaki; Yagou, Takaaki; Hayashi, Atsushi

    2017-03-01

    We compared the fluctuation of intraocular pressure (IOP) in normal-tension glaucoma (NTG) patients and individuals with nonglaucoma eyes. We obtained continuous IOP values using a SENSIMED Triggerfish contact lens sensor. The eyes of 12 nonglaucoma subjects and 14 NTG patients were examined. In all 26 subjects, the IOP fluctuation was measured continuously for 24 hours with a contact lens sensor. We evaluated the range of IOP fluctuations over the 24-hour period separately for diurnal IOP and nocturnal IOP and identified each subject's maximum value. The range of IOP fluctuation were analyzed, cutoff level of IOP fluctuation was calculated using receiver operating characteristic curve analyses. The mean IOP in the NTG eyes was 11.5±2.4 mm Hg and that in the nonglaucoma eyes was 12.7±2.0 mm Hg, a nonsignificantly difference (P=0.175). The 24-hour range of IOP fluctuations in the NTG group was significantly larger than that of the nonglaucoma group (P=0.007). The percentage of NTG patients who had the peak time of IOP fluctuation during nocturnal sleep was 57.1%, whereas the corresponding rate for the nonglaucoma eyes was 91.7%. The cutoff level of IOP fluctuation for glaucoma was 442 mVeq (sensitivity=1.00; specificity=0.571). The range of IOP fluctuation was larger in the eyes with NTG than in the nonglaucoma eyes. This larger fluctuation might be one of the reasons underlying the aggravation of the visual field by NTG. Measurements of 24-hour continuous IOP might be one of the useful methods to distinguish NTG from nonglaucoma eyes.

  16. Spectral components of laser Doppler flowmetry signals recorded in healthy and type 1 diabetic subjects at rest and during a local and progressive cutaneous pressure application: scalogram analyses

    Energy Technology Data Exchange (ETDEWEB)

    Humeau, Anne [Groupe ISAIP-ESAIP, 18 rue du 8 mai 1945, BP 80022, 49180 Saint Barthelemy d' Anjou cedex (France); Koitka, Audrey [Laboratoire de Physiologie et d' Explorations Vasculaires, Centre Hospitalier Universitaire d' Angers, 49033 Angers cedex 01 (France); Abraham, Pierre [Laboratoire de Physiologie et d' Explorations Vasculaires, Centre Hospitalier Universitaire d' Angers, 49033 Angers cedex 01 (France); Saumet, Jean-Louis [Laboratoire de Physiologie et d' Explorations Vasculaires, Centre Hospitalier Universitaire d' Angers, 49033 Angers cedex 01 (France); L' Huillier, Jean-Pierre [Ecole Nationale Superieure d' Arts et Metiers (ENSAM), Laboratoire Procedes-Materiaux-Instrumentation (LPMI), 2 boulevard du Ronceray, BP 3525, 49035 Angers cedex (France)

    2004-09-07

    A significant transient increase in laser Doppler flowmetry (LDF) signals is observed in response to a local and progressive cutaneous pressure application in healthy subjects. This reflex may be impaired in diabetic patients. The work presents a signal processing providing the clarification of this phenomenon. Scalogram analyses of LDF signals recorded at rest and during a local and progressive cutaneous pressure application are performed on healthy and type 1 diabetic subjects. Three frequency bands, corresponding to myogenic, neurogenic and endothelial related metabolic activities, are studied. The results show that, at rest, the scalogram energy of each frequency band is significantly lower for diabetic patients than for healthy subjects, but the scalogram relative energies do not show any statistical difference between the two groups. Moreover, the neurogenic and endothelial related metabolic activities are significantly higher during the progressive pressure than at rest, in healthy and diabetic subjects. However, the relative contribution of the endothelial related metabolic activity is significantly higher during the progressive pressure than at rest, in the interval 200-400 s following the beginning of the pressure application, but only for healthy subjects. These results may improve knowledge on cutaneous microvascular responses to injuries or local pressures initiating diabetic complications.

  17. Reducing dropout of contact lens wear with Biotrue multipurpose solution

    Directory of Open Access Journals (Sweden)

    Rah MJ

    2014-01-01

    Full Text Available Marjorie J Rah, Mohinder M Merchea, Marianne Q DoktorBausch & Lomb Incorporated, Rochester, NY, USAPurpose: To evaluate whether the use of Biotrue multipurpose solution (MPS could significantly reduce the likelihood with which patients drop out of using daily wear contact lenses (CLs amongst 18–44-year-old frequent replacement CL wearers.Methods: Daily wear CL subjects habitually using MPSs (other than Biotrue MPS who reported an intent to imminently drop out of CL wear because of comfort and dryness complaints were recruited to participate in this investigation. Subjects were switched to Biotrue MPS and continued to use habitual CL types with the new MPS for 2 weeks. Subjects completed an online satisfaction questionnaire at baseline and after 2 weeks to assess the change in symptoms and the intent to drop out of CL wear. Six months after completion of the initial study, a follow-up survey was administered to a subset of the initial participants.Results: A total of 153 daily wear (silicone hydrogel and hydrogel subjects completed this 2-week study with Biotrue MPS. When measuring those with the highest propensity to drop out of lens wear (n=93 after switching to Biotrue MPS, 90% of subjects significantly reduced their likelihood of dropping out of CL wear (P<0.0001. Online interviews were conducted with 73 of the study participants 6 months after completion of the initial study. A total of 93% of participants responded that they were still wearing CLs at least once per week. Of the 7% of respondents who were not currently wearing lenses 6 months after the initial study, two had dropped out of lens wear completely, and three still wore lenses less than once per week.Conclusion: Patients intending to drop out of CL wear due to discomfort and dryness significantly reduced their propensity of discontinuing lens wear following use of Biotrue MPS. Six months after completion of the study, 93% of patients were still wearing CLs at least once per

  18. Corneal response to different oxygen levels during extended wear.

    Science.gov (United States)

    Rivera, R K; Polse, K A

    1991-04-01

    In this study we explored the relationship between hypoxic exposure level and corneal response by assuming that the partial pressure of oxygen (PO2) under a contact lens during eye closure is directly related to oxygen transmissibility (Dk/L). To study this relationship, we monitored a group of subjects who wore RGP lenses of various Dk/L values on an extended wear basis. The results revealed that as Dk/L increases, there is a substantial decrease in overnight corneal edema and epithelial microcysts. However, other responses seemingly related to purely mechanical properties (e.g., lens adherence, corneal topographical changes, and 3-9 limbal superficial punctate keratitis) appear to be independent of Dk/L. Results also suggest that sufficient PO2 levels under a contact lens can minimize endothelial morphological changes associated with hypoxia. We conclude that metabolically driven complications accompanying RGP extended wear can be substantially eliminated with lenses having Dk/L values of 80 x 10(-9) (cm x mL O2)/(sec x mL x mm Hg) or greater.

  19. Hybrid equation/agent-based model of ischemia-induced hyperemia and pressure ulcer formation predicts greater propensity to ulcerate in subjects with spinal cord injury.

    Directory of Open Access Journals (Sweden)

    Alexey Solovyev

    Full Text Available Pressure ulcers are costly and life-threatening complications for people with spinal cord injury (SCI. People with SCI also exhibit differential blood flow properties in non-ulcerated skin. We hypothesized that a computer simulation of the pressure ulcer formation process, informed by data regarding skin blood flow and reactive hyperemia in response to pressure, could provide insights into the pathogenesis and effective treatment of post-SCI pressure ulcers. Agent-Based Models (ABM are useful in settings such as pressure ulcers, in which spatial realism is important. Ordinary Differential Equation-based (ODE models are useful when modeling physiological phenomena such as reactive hyperemia. Accordingly, we constructed a hybrid model that combines ODEs related to blood flow along with an ABM of skin injury, inflammation, and ulcer formation. The relationship between pressure and the course of ulcer formation, as well as several other important characteristic patterns of pressure ulcer formation, was demonstrated in this model. The ODE portion of this model was calibrated to data related to blood flow following experimental pressure responses in non-injured human subjects or to data from people with SCI. This model predicted a higher propensity to form ulcers in response to pressure in people with SCI vs. non-injured control subjects, and thus may serve as novel diagnostic platform for post-SCI ulcer formation.

  20. Beneficial Effects of Long-Term CPAP Treatment on Sleep Quality and Blood Pressure in Adherent Subjects With Obstructive Sleep Apnea.

    Science.gov (United States)

    Yang, Mei-Chen; Huang, Yi-Chih; Lan, Chou-Chin; Wu, Yao-Kuang; Huang, Kuo-Feng

    2015-12-01

    Obstructive sleep apnea (OSA) is associated with increased risk of cardiovascular diseases. Although CPAP is the first treatment choice for moderate-to-severe OSA, acceptance of and adherence to CPAP remain problematic. High CPAP adherence is generally defined as ≥4 h of use/night for ≥70% of the nights monitored. We investigated the long-term beneficial effects of CPAP on sleep quality and blood pressure in subjects with moderate-to-severe OSA according to high or low CPAP adherence. We retrospectively analyzed 121 subjects with moderate-to-severe OSA from August 2008 to July 2012. These subjects were divided into 3 groups: (1) no CPAP treatment (n = 29), (2) low CPAP adherence (n = 28), and (3) high CPAP adherence (n = 64). All subjects were followed up for at least 1 y. The 3 groups were compared regarding anthropometric and polysomnographic variables, presence of cardiovascular comorbidities, and blood pressure at baseline and at the last follow-up. The no-treatment group showed significant increases in oxygen desaturation index and blood pressure. The high-adherence group showed significant improvement in daytime sleepiness, apnea-hypopnea index (AHI), oxygen desaturation index, and blood pressure. Although the AHI was also significantly decreased after CPAP treatment in the low-adherence group, blood pressure remained unchanged. CPAP treatment had beneficial effects on both sleep quality and blood pressure only in subjects with OSA and high CPAP adherence who used CPAP for ≥4 h/night for ≥70% of nights monitored. Subjects with low CPAP adherence received beneficial effects on AHI, but not blood pressure. Copyright © 2015 by Daedalus Enterprises.

  1. Vegetarian diets and blood pressure among white subjects: results from the Adventist Health Study-2 (AHS-2)

    Science.gov (United States)

    Pettersen, Betty J; Anousheh, Ramtin; Fan, Jing; Jaceldo-Siegl, Karen; Fraser, Gary E

    2012-01-01

    Objective Previous work studying vegetarians has often found that they have lower blood pressure (BP). Reasons may include their lower BMI and higher intake levels of fruit and vegetables. Here we seek to extend this evidence in a geographically diverse population containing vegans, lacto-ovo vegetarians and omnivores. Design Data are analysed from a calibration sub-study of the Adventist Health Study-2 (AHS-2) cohort who attended clinics and provided validated FFQ. Criteria were established for vegan, lacto-ovo vegetarian, partial vegetarian and omnivorous dietary patterns. Setting Clinics were conducted at churches across the USA and Canada. Dietary data were gathered by mailed questionnaire. Subjects Five hundred white subjects representing the AHS-2 cohort. Results Covariate-adjusted regression analyses demonstrated that the vegan vegetarians had lower systolic and diastolic BP (mmHg) than omnivorous Adventists (β =−6·8, Pvegans) were also less likely to be using antihypertensive medications. Defining hypertension as systolic BP > 139 mmHg or diastolic BP > 89 mmHg or use of antihypertensive medications, the odds ratio of hypertension compared with omnivores was 0·37 (95 % CI 0·19, 0·74), 0·57 (95 % CI 0·36, 0·92) and 0·92 (95 % CI 0·50, 1·70), respectively, for vegans, lacto-ovo vegetarians and partial vegetarians. Effects were reduced after adjustment for BMI. Conclusions We conclude from this relatively large study that vegetarians, especially vegans, with otherwise diverse characteristics but stable diets, do have lower systolic and diastolic BP and less hypertension than omnivores. This is only partly due to their lower body mass. PMID:22230619

  2. Comparison of plantar pressure distribution in subjects with normal and flat feet during gait DOI: 10.5007/1980-0037.2010v12n4p290

    Directory of Open Access Journals (Sweden)

    Patrik Felipe Nazario

    2010-01-01

    Full Text Available The aim of this study was to determine the possible relationship between loss of the normal medial longitudinal arch measured by the height of the navicular bone in a static situation and variables related to plantar pressure distribution measured in a dynamic situation. Eleven men (21 ± 3 years, 74 ± 10 kg and 175 ± 4 cm participated in the study. The Novel Emed-AT System was used for the acquisition of plantar pressure distribution data (peak pressure, mean pressure, contact area, and relative load at a sampling rate of 50 Hz. The navicular drop test proposed by Brody (1982 was used to assess the height of the navicular bone for classification of the subjects. The results were compared by the Mann-Whitney U test, with the level of significance set at p ≤ 0.05. Differences were observed between the two groups in the mid-foot region for all variables studied, with the observation of higher mean values in subjects with flat feet. There were also significant differences in contact area, relative load, peak pressure, and mean pressure between groups. The present study demonstrates the importance of paying attention to subjects with flat feet because changes in plantar pressure distribution are associated with discomfort and injuries.

  3. Office blood pressure is a predictor of aortic elastic properties and urinary protein excretion in subjects with white coat hypertension.

    Science.gov (United States)

    Aznaouridis, Konstantinos; Vlachopoulos, Charalambos; Masoura, Konstantina; Pietri, Panagiota; Vyssoulis, Gregory; Ioakeimidis, Nikolaos; Stefanadis, Christodoulos; Tousoulis, Dimitrios

    2016-01-15

    White coat hypertension (WCH) is related to target organ damage and increased cardiovascular risk. Arterial elastic properties and urinary protein excretion are determinants of cardiovascular performance and predictors of outcomes. We investigated whether office blood pressure (BP) is a better determinant of arterial and renal function than the ambulatory BP in WCH patients. We studied 440 consecutive untreated non-diabetic patients with WCH (office BP >140/90 mmHg, mean daytime ambulatory BP 0.5). Hierarchical multilevel linear regression analysis showed that office systolic BP is an independent determinant of cfPWV (P=0.050), AIx (P=0.029), albumin (P=0.002) and ACR (P=0.001) and has a borderline association with α1-microglobulin (P=0.088). In non-diabetic WCH individuals, office systolic BP is an independent predictor of aortic elastic properties and urinary protein excretion, whereas ambulatory BP is not. This finding suggests that office BP may be a marker of cardiovascular risk in subjects with WCH. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  4. Consumption of a Polyphenol-Rich Grape-Wine Extract Lowers Ambulatory Blood Pressure in Mildly Hypertensive Subjects

    Directory of Open Access Journals (Sweden)

    Richard Draijer

    2015-04-01

    Full Text Available Polyphenols in grape and wine have been suggested to contribute to the cardiovascular health benefits of the Mediterranean lifestyle. The reported effects of grape products on blood pressure (BP remain, however, equivocal. In a double-blind placebo controlled crossover study, the effect of two grape extracts on BP and vascular function was assessed in 60 untreated, mildly hypertensive subjects after four weeks intervention. Both extracts (grape-red wine and grape alone had high concentrations of anthocyanins and flavonols, but the grape alone was relatively poor in catechins and procyanidins. Parameters measured included ambulatory and office BP, flow-mediated vasodilation, arterial distensibility, platelet function and plasma lipoproteins. Results showed that 24-hour ambulatory systolic/diastolic BPs were significantly lower in the grape-wine extract intervention (135.9 ± 1.3/84.7 ± 0.8 mmHg; mean ± SEM compared to placebo (138.9 ± 1.3/86.6 ± 1.2 mmHg, predominantly during daytime. Plasma concentrations of the vasoconstrictor endothelin-1 decreased by 10%, but other measures of vascular function were not affected. Grape juice extract alone had no effect on BP or any measures of vascular function. Polyphenol-rich food products, and may be specifically catechins and procyanidins, may thus help sustain a healthy BP and contribute to the healthy Mediterranean lifestyle.

  5. Effects of positive expiratory pressure on chest wall volumes in subjects with stroke compared to healthy controls: a case-control study.

    Science.gov (United States)

    Cabral, Elis E A; Resqueti, Vanessa R; Lima, Illia N D F; Gualdi, Lucien P; Aliverti, Andrea; Fregonezi, Guilherme A F

    2017-07-08

    Alterations in respiratory system kinematics in stroke lead to restrictive pattern associated with decreased lung volumes. Chest physical therapy, such as positive expiratory pressure, may be useful in the treatment of these patients; however, the optimum intensity to promote volume and motion changes of the chest wall remains unclear. To assess the effect of different intensities of positive expiratory pressure on chest wall kinematics in subjects with stroke compared to healthy controls. 16 subjects with chronic stroke and 16 healthy controls matched for age, gender, and body mass index were recruited. Chest wall volumes were assessed using optoelectronic plethysmography during quiet breathing, 5 minutes, and recovery. Three different intensities of positive expiratory pressure (10, 15, and 20cmH2O) were administered in a random order with a 30 minutes rest interval between intensities. During positive expiratory pressure, tidal chest wall expansion increased in both groups compared to quiet breathing; however, this increase was not significant in the subjects with stroke (0.41 vs. 1.32L, 0.56 vs. 1.54L, 0.52 vs. 1.8L, at 10, 15, 20cmH2O positive expiratory pressure, for stroke and control groups; p<0.001). End-expiratory chest wall volume decreased in controls, mainly due to the abdomen, and increased in the stroke group, mainly due the pulmonary rib cage. Positive expiratory pressure administration facilitates acute lung expansion of the chest wall and its compartments in restricted subjects with stroke. Positive expiratory pressure intensities above 10cmH2O should be used with caution as the increase in end-expiratory volume led to hyperinflation in subjects with stroke. Copyright © 2017 Associação Brasileira de Pesquisa e Pós-Graduação em Fisioterapia. Publicado por Elsevier Editora Ltda. All rights reserved.

  6. Study on prestressed concrete reactor vessel structures. II-5: Crack analysis by three dimensional finite elements method of 1/20 multicavity type PCRV subjected to internal pressure

    Science.gov (United States)

    1978-01-01

    A three-dimensional finite elements analysis is reported of the nonlinear behavior of PCRV subjected to internal pressure by comparing calculated results with test results. As the first stage, an analysis considering the nonlinearity of cracking in concrete was attempted. As a result, it is found possible to make an analysis up to three times the design pressure (50 kg/sqcm), and calculated results agree well with test results.

  7. How experienced alpine-skiers cope with restrictions of ankle degrees-of-freedom when wearing ski-boots in postural exercises.

    Science.gov (United States)

    Noé, Frédéric; Amarantini, David; Paillard, Thierry

    2009-04-01

    The present study investigates the mechanisms underlying changes in postural strategy that occur to compensate for mechanical ankle joint restrictions induced by wearing ski-boots during postural exercises. Fourteen experienced skiers were asked to stand as still as possible in a stable (STA) posture and in 2 postures with instability in the medio/lateral and antero/posterior (ML and AP postures) direction. Postural tasks were performed with eyes open or closed and while wearing or not wearing ski-boots. The electromyographic (EMG) activity of representative lower limb muscles and positions of centre-of-foot pressure (COP) were recorded and analyzed. Our results illustrated enhanced postural performances with ski-boots in the STA posture, whereas postural performances remained unchanged when wearing ski-boots in the ML and AP postures. Analysis of COP sways in the frequency domain did not illustrate any modification in the contribution of different neuronal loops when the study subjects wore ski-boots. EMG showed that the mechanical effects of wearing ski-boots were compensated by changes in postural strategy through the reorganization of muscle coordination, made possible by inherent redundancies in the human body. The preservation of postural performances, despite restrictions of ankle degrees-of-freedom induced by ski-boots, emphasizes the subjects' capacity to exploit the additional support provided by ski-boots by adequately adjusting muscle coordination to control posture in different balance conditions.

  8. Friction and wear behaviour of self lubricating bearing liners

    Science.gov (United States)

    Gay, Russell

    The thesis describes a numerical model for evaluating the variation of friction and wear of a self lubricating bearing liner over its useful wear life. Self-lubricating bearings have been in widespread use since the mid-1950s, particularly in the aerospace industry where they have the advantage of being low maintenance components. They are commonly used in relatively low speed, reciprocating applications such as control surface actuators, and usually consist of a spherical bearing with the inner and outer elements separated by a composite textile resin-bonded liner. A finite element model has been developed to predict the local stiffness of a particular liner at different states of wear. Results obtained using the model were used to predict the overall friction coefficient as it evolves due to wear, which is a novel approach. Experimental testing was performed on a bespoke flat-on-flat wear test rig with a reciprocating motion to validate the results of the friction model.. These tests were carried out on a commercially-available bearing liner, predominantly at a high contact pressure and an average sliding speed of 0.2 ms-1. Good agreement between predicted and experimentally measured wear was obtained when appropriate coefficients of friction were used in the friction model, and when the reciprocating sliding distance was above a critical value. A numerical wear model was also developed to predict the trend of backlash development in real bearing geometries using a novel approach. Results from the wear model were validated against full-scale bearing tests carried out elsewhere by the sponsoring company. Good agreement was obtained between the model predictions and the experimental results for the first 80% of the bearing wear life, and explanations for the discrepancy during the last 20% of the wear life have been proposed..

  9. Passenger comfort on high-speed trains: effect of tunnel noise on the subjective assessment of pressure variations.

    Science.gov (United States)

    Sanok, Sandra; Mendolia, Franco; Wittkowski, Martin; Rooney, Daniel; Putzke, Matthias; Aeschbach, Daniel

    2015-01-01

    When passing through a tunnel, aerodynamic effects on high-speed trains may impair passenger comfort. These variations in atmospheric pressure are accompanied by transient increases in sound pressure level. To date, it is unclear whether the latter influences the perceived discomfort associated with the variations in atmospheric pressure. In a pressure chamber of the DLR-Institute of Aerospace Medicine, 71 participants (M = 28.3 years ± 8.1 SD) rated randomised pressure changes during two conditions according to a crossover design. The pressure changes were presented together with tunnel noise such that the sound pressure level was transiently elevated by either +6 dB (low noise condition) or +12 dB (high noise condition) above background noise level (65 dB(A)). Data were combined with those of a recent study, in which identical pressure changes were presented without tunnel noise (Schwanitz et al., 2013, 'Pressure Variations on a Train - Where is the Threshold to Railway Passenger Discomfort?' Applied Ergonomics 44 (2): 200-209). Exposure-response relationships for the combined data set comprising all three noise conditions show that pressure discomfort increases with the magnitude and speed of the pressure changes but decreases with increasing tunnel noise. Practitioner Summary: In a pressure chamber, we systematically examined how pressure discomfort, as it may be experienced by railway passengers, is affected by the presence of tunnel noise during pressure changes. It is shown that across three conditions (no noise, low noise (+6 dB), high noise (+12 dB)) pressure discomfort decreases with increasing tunnel noise.

  10. Phenomenological modeling of abradable wear in turbomachines

    Science.gov (United States)

    Berthoul, Bérenger; Batailly, Alain; Stainier, Laurent; Legrand, Mathias; Cartraud, Patrice

    2018-01-01

    Abradable materials are widely used as coatings within compressor and turbine stages of modern aircraft engines in order to reduce operating blade-tip/casing clearances and thus maximize energy efficiency. However, rubbing occurrences between blade tips and coating liners may lead to high blade vibratory levels and endanger their structural integrity through fatigue mechanisms. Accordingly, there is a need for a better comprehension of the physical phenomena at play and for an accurate modeling of the interaction, in order to predict potentially unsafe events. To this end, this work introduces a phenomenological model of the abradable coating removal based on phenomena reported in the literature and accounting for key frictional and wear mechanisms including plasticity at junctions, ploughing, micro-rupture and machining. It is implemented within an in-house software solution dedicated to the prediction of full three-dimensional blade/abradable coating interactions within an aircraft engine low pressure compressor. Two case studies are considered. The first one compares the results of an experimental abradable test rig and its simulation. The second one deals with the simulation of interactions in a complete low-pressure compressor. The consistency of the model with experimental observations is underlined, and the impact of material parameter variations on the interaction and wear behavior of the blade is discussed. It is found that even though wear patterns are remarkably robust, results are significantly influenced by abradable coating material properties.

  11. Vegetarian diets and blood pressure among white subjects: results from the Adventist Health Study-2 (AHS-2).

    Science.gov (United States)

    Pettersen, Betty J; Anousheh, Ramtin; Fan, Jing; Jaceldo-Siegl, Karen; Fraser, Gary E

    2012-10-01

    Previous work studying vegetarians has often found that they have lower blood pressure (BP). Reasons may include their lower BMI and higher intake levels of fruit and vegetables. Here we seek to extend this evidence in a geographically diverse population containing vegans, lacto-ovo vegetarians and omnivores. Data are analysed from a calibration sub-study of the Adventist Health Study-2 (AHS-2) cohort who attended clinics and provided validated FFQ. Criteria were established for vegan, lacto-ovo vegetarian, partial vegetarian and omnivorous dietary patterns. Clinics were conducted at churches across the USA and Canada. Dietary data were gathered by mailed questionnaire. Five hundred white subjects representing the AHS-2 cohort. Covariate-adjusted regression analyses demonstrated that the vegan vegetarians had lower systolic and diastolic BP (mmHg) than omnivorous Adventists (β = -6.8, P vegetarians (β = -9.1, P vegetarians (mainly the vegans) were also less likely to be using antihypertensive medications. Defining hypertension as systolic BP > 139 mmHg or diastolic BP > 89 mmHg or use of antihypertensive medications, the odds ratio of hypertension compared with omnivores was 0.37 (95 % CI 0.19, 0.74), 0.57 (95 % CI 0.36, 0.92) and 0.92 (95 % CI 0.50, 1.70), respectively, for vegans, lacto-ovo vegetarians and partial vegetarians. Effects were reduced after adjustment for BMI. We conclude from this relatively large study that vegetarians, especially vegans, with otherwise diverse characteristics but stable diets, do have lower systolic and diastolic BP and less hypertension than omnivores. This is only partly due to their lower body mass.

  12. Wear of polymers and composites

    CERN Document Server

    Abdelbary, Ahmed

    2015-01-01

    In the field of tribology, the wear behaviour of polymers and composite materials is considered a highly non-linear phenomenon. Wear of Polymers and Composites introduces fundamentals of polymers and composites tribology. The book suggests a new approach to explore the effect of applied load and surface defects on the fatigue wear behaviour of polymers, using a new tribometer and thorough experiments. It discusses effects of surface cracks, under different static and cyclic loading parameters on wear, and presents an intelligent algorithm, in the form of a neural network, to map the relations

  13. Friction and wear calculation methods

    CERN Document Server

    Kragelsky, I V; Kombalov, V S

    1981-01-01

    Friction and Wear: Calculation Methods provides an introduction to the main theories of a new branch of mechanics known as """"contact interaction of solids in relative motion."""" This branch is closely bound up with other sciences, especially physics and chemistry. The book analyzes the nature of friction and wear, and some theoretical relationships that link the characteristics of the processes and the properties of the contacting bodies essential for practical application of the theories in calculating friction forces and wear values. The effect of the environment on friction and wear is a

  14. Mechanical modelling of tooth wear.

    Science.gov (United States)

    Karme, Aleksis; Rannikko, Janina; Kallonen, Aki; Clauss, Marcus; Fortelius, Mikael

    2016-07-01

    Different diets wear teeth in different ways and generate distinguishable wear and microwear patterns that have long been the basis of palaeodiet reconstructions. Little experimental research has been performed to study them together. Here, we show that an artificial mechanical masticator, a chewing machine, occluding real horse teeth in continuous simulated chewing (of 100 000 chewing cycles) is capable of replicating microscopic wear features and gross wear on teeth that resemble wear in specimens collected from nature. Simulating pure attrition (chewing without food) and four plant material diets of different abrasives content (at n = 5 tooth pairs per group), we detected differences in microscopic wear features by stereomicroscopy of the chewing surface in the number and quality of pits and scratches that were not always as expected. Using computed tomography scanning in one tooth per diet, absolute wear was quantified as the mean height change after the simulated chewing. Absolute wear increased with diet abrasiveness, originating from phytoliths and grit. In combination, our findings highlight that differences in actual dental tissue loss can occur at similar microwear patterns, cautioning against a direct transformation of microwear results into predictions about diet or tooth wear rate. © 2016 The Author(s).

  15. Analysis of an Aircraft Honeycomb Sandwich Panel with Circular Face Sheet/Core Disbond Subjected to Ground-Air Pressurization

    Science.gov (United States)

    Rinker, Martin; Krueger, Ronald; Ratcliffe, James

    2013-01-01

    The ground-air pressurization of lightweight honeycomb sandwich structures caused by alternating pressure differences between the enclosed air within the honeycomb core and the ambient environment is a well-known and controllable loading condition of aerospace structures. However, initial face sheet/core disbonds intensify the face sheet peeling effect of the internal pressure load significantly and can decrease the reliability of the sandwich structure drastically. Within this paper, a numerical parameter study was carried out to investigate the criticality of initial disbonds in honeycomb sandwich structures under ground-air pressurization. A fracture mechanics approach was used to evaluate the loading at the disbond front. In this case, the strain energy release rate was computed via the Virtual Crack Closure Technique. Special attention was paid to the pressure-deformation coupling which can decrease the pressure load within the disbonded sandwich section significantly when the structure is highly deformed.

  16. Dynamic plantar pressure measurement for the normal subject: Free-mapping model for the analysis of pediatric foot deformities.

    Science.gov (United States)

    Liu, Xue C; Thometz, John G; Tassone, Channing; Barker, Brady; Lyon, Roger

    2005-01-01

    In measuring plantar pressures during gait, prior methods have divided the foot into five regions and neglected forefoot alignment as it is involved in intoeing and outtoeing. The authors' proposed free-mapping method divides the foot into nine regions and incorporates a pedobarograph foot progression angle. The purpose of the study was to provide normal pressure parameter data during stance phase using a free-mapping model. Sixty-six normal children, ages 6 to 16 years, were recruited and walked along the 5-m walkway at self-selected speeds. The mean and standard deviation for the plantar contact area, contact time, peak pressure, maximal mean pressure, pressure-time integral, force-time integral, instant of peak pressure, and instant of maximum force in nine foot regions are reported. These normative data will provide a basis with which assessment of foot deformities involved in clubfoot, pes planus, and cavus foot will be more accurately defined.

  17. Comparison of two rocket sled slipper materials for resistance to wear

    Science.gov (United States)

    Liu, Jun; Wang, Weihua; Zhao, Feng; Gong, Mingsheng

    2017-10-01

    The wear loss amount directly affects rocket sled's working speed and safety. The paper evaluates the wear resistance of two materials, 0Cr18Ni9Ti and T250. Wear loss under different working conditions are tested using pin-on-disk experiment for both materials, and an equivalent conversion method to evaluate the slipper wear loss in lab experiment was established. Results show that T250 possesses better wear resistance property than 0Cr18Ni9Ti especially in high pressure and velocity. Above Pv value of 8×107Pa.m/s, the wear loss of 0Cr18Ni9Ti increases exponentially, comparing with a steady wear amount of approximately 0.5g for that of T250. The results provide a reliable reference for the choice of rocket sled slipper material in different range of speed and load.

  18. Disposable contact lenses vs. contact lens maintenance for extended wear.

    Science.gov (United States)

    Josephson, J E; Caffery, B E; Campbell, I; Slomovic, A R

    1990-01-01

    We compared a disposable extended wear contact lens modality with conventional extended wear over a 6-week period. To do so, we refit 31 patients who had successfully worn conventional extended wear contact lenses for more than 1 year. One eye was fit with the AcuvueR disposable contact lens, and a new extended wear lens of the type the patient had been wearing was placed on the other eye. At weekly intervals the disposable lens was discarded and a new disposable lens inserted. At the same time, the conventional lens on the fellow eye was cleaned, disinfected, and reinserted. After 6 weeks the ocular response, subjective impressions, and condition of the lenses in the two eyes were compared. Both lenses were then cultured. Three subjects had to discontinue disposable lens wear because of adverse reactions to trapped cellular debris and corneal microcysts. Although the results were not statistically significant, the Acuvue lens appeared to perform better than or equal to the conventional lens in biomicroscopic observation, visual acuity measurement, and subjective patient preference. Eighty-seven percent of patients preferred to continue with the disposable system. There were no differences found in the type or degree of microbial contamination of the lenses.

  19. Pure mechanical wear loss measurement in corrosive wear

    Indian Academy of Sciences (India)

    Unknown

    Abstract. The method for the measurement of the pure mechanical wear loss for 321 stainless steel, 1045 steel and pure iron in the study of the synergy between corrosion and wear was studied. The methods studied included the measurement in distilled water, by cathodic protection and by adding inhibitor KI, and all were.

  20. Pure mechanical wear loss measurement in corrosive wear

    Indian Academy of Sciences (India)

    The method for the measurement of the pure mechanical wear loss for 321 stainless steel, 1045 steel and pure iron in the study of the synergy between corrosion and wear was studied. The methods studied included the measurement in distilled water, by cathodic protection and by adding inhibitor KI, and all were ...

  1. Pattern of outsole shoe heel wear in infantry recruits

    Directory of Open Access Journals (Sweden)

    Finestone Aharon S

    2012-10-01

    Full Text Available Abstract Background Excessive shoe heel abrasion is of concern to patients, parents and shoe manufacturers, but little scientific information is available. The purpose of this study was to describe the phenomenon in a group of infantry recruits performing similar physical activity, and search for biomechanical factors that might be related. Methods Seventy-six subjects (median age 19 enrolled. Pre-training parameters measured included height, weight, tibial length, foot arch height and foot progression angle. Digital plantar pressure maps were taken to calculate arch indexes. Shoe heel abrasion was assessed manually after 14 weeks of training with different-sized clock transparencies and a calliper. Results Outsole abrasion was posterolateral, averaging 12 degrees on each shoe. The average heel volume that was eroded was almost 5 cm3. The angle of maximum wear was related to right foot progression angle (r = 0.27, p = 0.02. Recruits with lateral ankle sprains had higher angles of maximal abrasion (17° versus 10°, p = 0.26 and recruits with lateral heel abrasion had more lateral ankle sprains (14% versus 3%, p = 0.12. Conclusion While shoe heel wear affects many people, very little has been done to measure it. In this study in healthy subjects, we found the main abrasion to be posterolateral. This seems to be related to foot progression angle. It was not related to hindfoot valgus/varus or other factors related to subtalar joint motion. These findings do not warrant modification of subtalar joint motion in order to limit shoe heel abrasion.

  2. Role of 5-hydroxytryptamine mechanisms in mediating the effects of small intestinal glucose on blood pressure and antropyloroduodenal motility in older subjects

    NARCIS (Netherlands)

    Gentilcore, Diana; Little, Tanya J.; Feinle-Bisset, Christine; Samsom, Melvin; Smout, Andre J. P. M.; Horowitz, Michael; Jones, Karen L.

    2007-01-01

    5-hydroxytryptamine mechanisms in mediating the effects of small intestinal glucose on blood pressure and antropyloroduodenal motility in older subjects. Am J Physiol Gastrointest Liver Physiol 293: G692-G698, 2007. First published August 9, 2007; doi:10.1152/ajpgi.00199.2007.-Postprandial

  3. A comparison of spectacle and contact lens wearing times in the ACHIEVE study.

    Science.gov (United States)

    Jones-Jordan, Lisa A; Chitkara, Monica; Coffey, Bradley; Jackson, John Mark; Manny, Ruth E; Rah, Marjorie J; Walline, Jeffrey J

    2010-05-01

    The aim was to compare vision correction wearing time between myopic children and teenagers in a clinical trial of contact lenses and spectacles. Parents of subjects in the Adolescent and Child Health Initiative for Vision Empowerment (ACHIEVE) study provided wearing times for spectacle and contact lens wear. Hours wearing primary correction and total correction were compared between the two treatment groups. Other factors hypothesised to be associated with wearing time were analysed. The average wearing time of the primary correction differed significantly with the wearing time for the spectacles group being 91.5 hours per week compared to 80.3 hours per week for the contact lens wearers (p lenses less than young spectacle wearers and older contact lens wearers. Low scores on an appearance quality-of-life scale were associated with longer wearing time in spectacle wearers compared to the low- and high-scoring contact lens wearers. Gender, spectacle satisfaction and activities were not related to wearing time. While contact lens wearers, on average, wear their contact lenses less than spectacle wearers, they spend roughly the same amount of time wearing a refractive correction. Higher refractive error resulted in longer wearing times for both spectacle and contact lens wearers. Younger contact lens wearers wore their contact lenses for shorter periods than the spectacle wearers, but still wore them, on average, 74.4 hours per week (about 10 hours per day), suggesting that contact lenses are a viable alternative mode of correction for children.

  4. INTRAOCULAR PRESSURE, MEAN ARTERIAL BLOOD PRESSURE AND PUPILLARY DIAMETER IN RABBITS ( (Oryctolagus cuniculus SUBJECTED TO RETROBULBAR BLOCK WITH DIFFERENT ANESTHETIC PROTOCOLS

    Directory of Open Access Journals (Sweden)

    Renata Maria Monção da Silva

    2015-10-01

    Full Text Available The aim of this study was to evaluate four protocols of loco regional anesthesia for ophthalmic procedures that could provide safety and life support, in addition to maintain intraocular pressure stable, with eye centralization and eyelid akinesia. 20 New Zealand rabbits were used to perform local anesthesia by retrobulbar block with four protocols: 2% lidocaine with epinephrine, 2% lidocaine without epinephrine associated with tramadol, 1% ropivacaine and bupivacaine 0.5 %. Each animal received an anesthetic volume of 1 mL. All anesthetic protocols used promoted eyelid akinesia and centralization of the eye during the assessment period. The retrobulbar block with the proposed anesthetic protocols proved to be feasible and safe for the maintenance of intraocular pressure, invasive blood pressure and pupillary diameter and can be used in intraocular surgeries, respecting the time of action of each anesthetic. All protocols showed an excellent blockage action but bupivacaine promoted the highest pupil diameter compared to the other drugs tested.

  5. Tyre and road wear prediction

    NARCIS (Netherlands)

    Lupker, H.A.

    2003-01-01

    Both tyre wear and road polishing are complex phenomenon, which are obviously strongly related; the energy that polishes the road is the energy that wears the tyre. The both depend non-linearly on numerous parameters, like materials used, vehicle and road usage, environmental conditions (i.e.

  6. The influence of laser line hardening of carbon steel AISI 1045 on the lubricated wear against steel AISI 52100

    NARCIS (Netherlands)

    Visscher, H.; de Rooij, Matthias B.; Vroegop, P.H.; Schipper, Dirk J.

    1995-01-01

    To diminish wear in tribological systems it is not always necessary to provide the entire surface with a wear resistant layer. Depending on the application it is sufficient to harden locally the load carrying areas which are subjected to wear. Such areas can be treated properly by a laser, either

  7. Switch wear leveling

    Science.gov (United States)

    Wu, Hunter; Sealy, Kylee; Gilchrist, Aaron

    2015-09-01

    An apparatus for switch wear leveling includes a switching module that controls switching for two or more pairs of switches in a switching power converter. The switching module controls switches based on a duty cycle control technique and closes and opens each switch in a switching sequence. The pairs of switches connect to a positive and negative terminal of a DC voltage source. For a first switching sequence a first switch of a pair of switches has a higher switching power loss than a second switch of the pair of switches. The apparatus includes a switch rotation module that changes the switching sequence of the two or more pairs of switches from the first switching sequence to a second switching sequence. The second switch of a pair of switches has a higher switching power loss than the first switch of the pair of switches during the second switching sequence.

  8. Prediction of Polyethylene Wear Rates from Gait Biomechanics and Implant Positioning in Total Hip Replacement.

    Science.gov (United States)

    Ardestani, Marzieh M; Amenábar Edwards, Pedro P; Wimmer, Markus A

    2017-08-01

    Patient-specific gait and surgical variables are known to play an important role in wear of total hip replacements (THR). However a rigorous model, capable of predicting wear rate based on a comprehensive set of subject-specific gait and component-positioning variables, has to our knowledge, not been reported. (1) Are there any differences between patients with high, moderate, and low wear rate in terms of gait and/or positioning variables? (2) Can we design a model to predict the wear rate based on gait and positioning variables? (3) Which group of wear factors (gait or positioning) contributes more to the wear rate? Data on patients undergoing primary unilateral THR who performed a postoperative gait test were screened for inclusion. We included patients with a 28-mm metal head and a hip cup made of noncrosslinked polyethylene (GUR 415 and 1050) from a single manufacturer (Zimmer, Inc). To calculate wear rates from radiographs, inclusion called for patients with a series of standing radiographs taken more than 1 year after surgery. Further, exclusion criteria were established to obtain reasonably reliable and homogeneous wear readings. Seventy-three (83% of included) patients met all criteria, and the final dataset consisted of 43 males and 30 females, 69 ± 10 years old, with a BMI of 27.3 ± 4.7 kg/m(2). Wear rates of these patients were determined based on the relative displacement of the femoral head with regard to the cup using a validated computer-assisted X-ray wear-analysis suite. Three groups with low ( 0.2 mm/year) wear were established. Wear prediction followed a two-step process: (1) linear discriminant analysis to estimate the level of wear (low, moderate, or high), and (2) multiple linear and nonlinear regression modeling to predict the exact wear rate from gait and implant-positioning variables for each level of wear. There were no group differences for positioning and gait suggesting that wear differences are caused by a combination of wear

  9. The wearing of hydrophilic contact lenses aboard a commercial jet aircraft: I. Humidity effects on fit.

    Science.gov (United States)

    Eng, W G; Harada, L K; Jagerman, L S

    1982-03-01

    The increasing use of hydrophilic (soft) lenses in the United States hs prompted interest in the clinical investigation of these lenses under various wearing conditions. Any factor causing lens dehydration during wear may affect lens performance and ultimately cause eye discomfort. The purpose of this study was to evaluate the environmental conditions in the aircraft cabin and to observe any changes in the fit of the hydrophilic lenses that might occur during flight. A "laboratory" for testing was set up aboard a World Airways DC-10 on a scheduled round trip between Oakland, California and Honolulu, Hawaii. A keratometer was used to assess lens fit of seven subjects who were wearing hydrophilic lenses. The efficacy of using a soft lens hydrating solution on the fit of the lens was evaluated, but will also be evaluated in a future paper. Atmospheric pressure, humidity, and temperature measurements were recorded throughout the inflight study. The results showed that a decline in cabin humidity from at least 47% to 11% occurred within 30 min of takeoff. Although previous reports have indicated that there are a number of environmental factors in the aircraft that contribute to eye discomfort for lens wearers, this study indicates that low cabin humidity is possibly the most significant factor.

  10. Maximal stress test performance while wearing a self-contained breathing apparatus

    Energy Technology Data Exchange (ETDEWEB)

    Raven, P.B.; Davis, T.O.; Shafer, C.L.; Linnebur, A.C.

    1977-12-01

    Fifteen adult male volunteers (mean age = 31.0 years; eight non-smokers and seven smokers) carried out a Bruce protocol maximal treadmill stress test under four separate conditions. These four conditions were (1) without Scott Air Pak (SAP) respirator; (2) with SAP respirator apparatus but not wearing face mask; (3) with SAP apparatus, wearing face mask in ''demand'' breathing mode; and (4) with SAP respirator apparatus, wearing face mask in ''pressure-demand'' breathing mode. The data indicate that the overriding factor in the approximately 20% decrement in work performance during conditions 2, 3, and 4 was related to the weight of the SAP respirator (15.8 kg), P < 0.05. Only during condition 3 did eight of 15 subjects report lack of air as one reason for termination. Conditions 3 and 4 resulted in a significant decrease in T/sub Fore/ (2.5/sup 0/C) and was primarily related to the decreased T/sub insp/ which reached a maximum decrement of 9.7/sup 0/C. Under all conditions the smokers' work time was significantly less than nonsmokers, P < 0.05.

  11. Prolonging contact lens wear and making contact lens wear safer.

    Science.gov (United States)

    Foulks, Gary N

    2006-02-01

    To summarize the present status of safety and efficacy of contact lens wear. Literature review. Ovid Medline searches were performed on records from 1966 through 2005 using keywords: keratitis, contact lens complications, extended-wear contact lenses, and silicone-hydrogel contact lenses. Patients desire comfort, clarity of vision, and prolonged contact lens wear when contact lenses are used to correct refractive error. Practitioners desire patient satisfaction but also require maintenance of the integrity of the eye and no complications that jeopardize vision or health of the eye. Improvements in the oxygen permeability of the contact lens materials, design of the contact lens and its surface, and solutions for the maintenance of the lens have reduced but not eliminated the risks of infection, inflammation, and conjunctival papillary reaction associated with contact lens wear. The lessons of past and recent history suggest that patient education and practitioner participation in the management of contact lens wear continue to be critical factors for patient satisfaction and safety in the extended wear of contact lenses. The availability of highly oxygen permeable contact lenses has increased the tolerance and safety of extended contact lens wear, but patient instruction and education in proper use and care of lenses is required and caution is advised.

  12. Wear model of an excavator bucket

    Science.gov (United States)

    Sarychev, Vladimir D.; Granovskii, Alexey Yu.; Nevskii, Sergey A.; Konovalov, Sergey V.; Gromov, Victor E.

    2017-12-01

    A mathematical model describing wear of the interior faces of the excavator bucket during the long-termed operation is proposed. The model is based on the Navier-Stocks equation and boundary conditions. The bucket was modeled as a rectangular parallelepiped; one of its faces is permeable for a granular material, whereas the others meet the conditions of impermeability and adhesion. In the approximation of viscous fluid, motion equations of a granular material in the excavator bucket were solved by the finite elements method. The velocity distribution curves of material particles along the bucket surface are obtained. A vortex structure is revealed at the bottom-back wall edge of the bucket, and it is thought to be the reason for high wear in these zones. As shown by the granular material pressure distributed along the bucket walls, its maximum is at the bottom-back wall edge of the excavator bucket. It is considered to be the reason for high wear in the operation process. Therefore, the bottom and back walls of the excavator bucket should be coated with a composite armouring mesh via arc surfacing.

  13. Proteolytic activity of protease produced by Pseudomonas fluorescens IB 2312 in skimmed milk subject to the process of high pressure homogenization

    Directory of Open Access Journals (Sweden)

    Claudia Regina Gonçalves Pinho

    2014-08-01

    Full Text Available The presence of thermoresistant proteases produced by psychrotrophic microorganisms have been identified as a limiting factor of the UHT milk shelflife, causing undesirable changes in milk products. High pressure homogenization (HPH processing is a non-thermal method of food preservation, able to promotes the microbiological safety and inactivation of some enzymes. Thus, this work assessed the proteolytic activity of protease produced by Pseudomonas fluorescens in skim milk subjected to high pressure homogenization process. The milk samples were added by the protease enzymatic extract (10% v/v and subjected to pressures up to 300 MPa. The assays showed that pressures on the order of 300 MPa caused a 72.5% reduction in proteolytic activity. Therefore, the process at high pressures resulted in significant inactivation of this thermoresistent enzyme, which possibly favors the shelf-life extension of the UHT milk and also limits the yield and quality loss of cheeses due to undesirable sensory changes in flavor and texture caused by this enzyme.

  14. Low friction wear resistant graphene films

    Science.gov (United States)

    Sumant, Anirudha V.; Berman, Diana; Erdemir, Ali

    2017-02-07

    A low friction wear surface with a coefficient of friction in the superlubric regime including graphene and nanoparticles on the wear surface is provided, and methods of producing the low friction wear surface are also provided. A long lifetime wear resistant surface including graphene exposed to hydrogen is provided, including methods of increasing the lifetime of graphene containing wear surfaces by providing hydrogen to the wear surface.

  15. Demographic Factors Affect Ocular Comfort Ratings During Contact Lens Wear.

    Science.gov (United States)

    Naduvilath, Thomas; Papas, Eric B; Lazon de la Jara, Percy

    2016-08-01

    To determine if rating of ocular comfort during soft contact lens wear is affected by demographic factors. Retrospective analysis of ocular comfort ratings during soft contact lens wear extracted from 44 nonrandomized similar clinical trials (n = 986). Subjects wore one of seven daily wear silicone hydrogels (SiHy) in combination with one of nine lens care products (LCP), and two daily disposables lenses. The effects on comfort rating of demographic factors were examined after adjusting for lens and LCP effects using general linear model. Males reported lower comfort on insertion than females (7.9 ± 1.6 vs. 8.1 ± 1.6, p = 0.001). Over 45 years old had higher comfort ratings than those between 26 and 45 or gender, lens wear experience, ethnicity, and refractive status can influence the rating of ocular comfort in clinical studies. The confounding effects of such demographic factors can be controlled by implementing randomization and appropriate multivariable statistical analysis.

  16. Analysis of polymerization time on abrasive wear of dental resins

    Directory of Open Access Journals (Sweden)

    Eduardo Carlos Bianchi

    2010-03-01

    Full Text Available An evaluation was made of the abrasive wear of six composite thermofixed dental resins subjected to different polymerization times. The method of evaluation was based on sharpness measurements to quantify the abrasive wear resistance of the resins. To this end, a test bench was built, consisting of a rotating porcelain cylinder that wears out a resin-coated cylinder placed above it, thus causing vertical displacement of the contact as the wear progresses. The values of vertical displacement, i.e., the input variables, were read and recorded by means of a computer program to obtain the sharpness values. These data indicated that the resins displayed different behaviors as a function of the polymerization times applied, reinforcing the importance of using a practical and rapid method of analysis in order to ensure that the behavior of new materials is fully understood before they are launched on the market.

  17. Gastric bypass surgery is followed by lowered blood pressure and increased diuresis - long term results from the Swedish Obese Subjects (SOS study.

    Directory of Open Access Journals (Sweden)

    Peter Hallersund

    Full Text Available OBJECTIVE: To compare two bariatric surgical principles with regard to effects on blood pressure and salt intake. BACKGROUND: In most patients bariatric surgery induces a sustained weight loss and a reduced cardiovascular risk profile but the long-term effect on blood pressure is uncertain. METHODS: Cohort study with data from the prospective, controlled Swedish Obese Subjects (SOS study involving 480 primary health care centres and 25 surgical departments in Sweden. Obese patients treated with non-surgical methods (Controls, n = 1636 and n = 1132 at 2 y and 10 y follow up, respectively were compared to patients treated with gastric bypass (GBP, n = 245 and n = 277, respectively or purely restrictive procedures (vertical banded gastroplasty or gastric banding; VBG/B, n = 1534 and n = 1064, respectively. RESULTS: At long-term follow-up (median 10 y GBP was associated with lowered systolic (mean: -5.1 mm Hg and diastolic pressure (-5.6 mmHg differing significantly from both VBG/B (-1.5 and -2.1 mmHg, respectively; p<0.001 and Controls (+1.2 and -3.8 mmHg, respectively; p<0.01. Diurnal urinary output was +100 ml (P<0.05 and +170 ml (P<0.001 higher in GBP subjects than in weight-loss matched VBG/B subjects at the 2 y and 10 y follow-ups, respectively. Urinary output was linearly associated with blood pressure only after GBP and these patients consumed approximately 1 g salt per day more at the follow-ups than did VBG/B (P<0.01. CONCLUSIONS: The purely restrictive techniques VBG/B exerted a transient blood pressure lowering effect, whereas gastric bypass was associated with a sustained blood pressure reduction and an increased diuresis. The daily salt consumption was higher after gastric bypass than after restrictive bariatric surgery.

  18. INTRAOCULAR PRESSURE, MEAN ARTERIAL BLOOD PRESSURE AND PUPILLARY DIAMETER IN RABBITS ( (Oryctolagus cuniculus) ) SUBJECTED TO RETROBULBAR BLOCK WITH DIFFERENT ANESTHETIC PROTOCOLS

    OpenAIRE

    Renata Maria Monção da Silva; Francisco de Assis Dórea Neto; Vivian Fernanda Barbosa; Newton Nunes; Emanoel Ferreira Martins Filho; Arianne Pontes Oria

    2015-01-01

    The aim of this study was to evaluate four protocols of loco regional anesthesia for ophthalmic procedures that could provide safety and life support, in addition to maintain intraocular pressure stable, with eye centralization and eyelid akinesia. 20 New Zealand rabbits were used to perform local anesthesia by retrobulbar block with four protocols: 2% lidocaine with epinephrine, 2% lidocaine without epinephrine associated with tramadol, 1% ropivacaine and bupivacaine 0.5 %. Each animal recei...

  19. Diabetic Foot Prevention: Repeatability of the Loran Platform Plantar Pressure and Load Distribution Measurements in Nondiabetic Subjects during Bipedal Standing—A Pilot Study

    Directory of Open Access Journals (Sweden)

    Martha Zequera

    2011-01-01

    Full Text Available This study was designed to assess the repeatability of the Loran Platform and evaluate the variability of plantar pressure and postural balance, during barefoot standing in nondiabetic subjects, for future diabetic foot clinical evaluation. Measurements were taken for eight nondiabetic subjects (4 females, 4 males, aged 47±7.2 years who had no musculoskeletal symptoms. Five variables were measured with the platform in the barefoot standing position. Ten measurements were taken using two different techniques for feet and posture positioning, during three sessions, once a week. For most measurements, no significant effect over time was found with Student's t-test (P<.000125. The ANOVA test of statistical significance confirmed that measurement differences between subjects showed higher variations than measurements taken from the same subject (P<.001. The measurements taken by the Loran Platform system were found to be repeatable.

  20. Clinical measurement of tooth wear: Tooth Wear Indices

    OpenAIRE

    J. López Frías; Castellanos Cosano, Lizett; Martín González, Jenifer; Llamas Carreras, José María; Segura-Egea, Juan J.

    2012-01-01

    Attrition, erosion, and abrasion result in alterations to the tooth and manifest as tooth wear. Each classification corresponds to a different process with specific clinical features. Classifications made so far have no accurate prevalence data because the indexes do not necessarily measure a specific etiology, or because the study populations can be diverse in age and characteristics. Tooth wears (attrition, erosion and abrasion) is perceived internationally as a growing problem. However, th...

  1. Effects of absorbent incontinence pads on pressure management mattresses.

    Science.gov (United States)

    Fader, Mandy; Bain, Duncan; Cottenden, Alan

    2004-12-01

    The aim of this paper is to report a study to determine the effects of absorbent pads on the pressure-relieving properties of 'standard' and pressure management mattresses. Pressure ulcers and incontinence often co-exist. There is a strong association between poor mobility and continence problems and patients using pressure management products are therefore also likely to be using absorbent pads. An instrumented articulated anthropometric phantom with simulated soft body 'tissues' in the gluteal and sacral areas was used as the 'subject'. The phantom was raised and lowered on to three mattresses (standard foam, visco-elastic foam and surface-cut foam) in three states: naked, wearing a dry pad (Tena Super, SCA Hygiene AB) and wearing a wet pad. The pressure mapping device Xsensor was used to record the distribution of pressure over the sacral and ischial areas of the phantom. Peak pressure was used as the primary outcome variable and 10 repeats were made on each mattress under each condition. There were substantial and significant differences for all three mattresses in recorded peak pressures between the naked buttocks and the buttocks wearing a dry pad. There were no significant differences between measurements made using the dry vs. wet pad. Peak pressures frequently occurred over areas of pad folds. Additional testing showed that pads that were 'smoothed' by hand had significantly lower peak pressures than 'unsmoothed' pads. Absorbent pads have a substantial adverse effect on the pressure redistribution properties of mattresses. Pad folds appear to contribute to this effect, which can be ameliorated slightly by smoothing. Absorbent pad manufacturers should consider engineering pads that minimize disruption to pressure management. Further examination of continence and pressure management products is necessary to establish optimum combinations for nursing care.

  2. Analysis of Impact of Chosen Parameters on the Wear of Camshft

    Directory of Open Access Journals (Sweden)

    Burdzik R.

    2014-10-01

    Full Text Available The paper provides an analysis of the reasons for excessive wear of the camshafts system components based on models developed to describe the impact of selected material, technological and operational factors. The subject of the research was wear of camshaft cams studied in accordance with results of operation tests. Based on the said tests, the dependence of wear intensity of cams from their angular position was established. The respective calculation results enabled the function of cam fallibility to be determined.

  3. Efficacy of multiwavelength light therapy in the treatment of pressure ulcers in subjects with disorders of the spinal cord: A randomized double-blind controlled trial.

    Science.gov (United States)

    Taly, Arun B; Sivaraman Nair, Krishan P; Murali, Thyloth; John, Archana

    2004-10-01

    To study the efficacy of multiwavelength light therapy in the treatment of pressure ulcers in subjects with spinal cord disorders. Randomized controlled trial. Neurologic rehabilitation ward of a referral center in India. Thirty-five subjects with spinal cord injury, with 64 pressure ulcers (stage 2, n=55; stage 3, n=8; stage 4, n=1), were randomized into treatment and control groups. One subject refused consent. Mean duration of ulcers in the treatment group was 34.2+/-45.5 days and in the control group, 57.1+/-43.5 days. Treatment group received 14 sessions of multiwavelength light therapy, with 46 probes of different wavelengths from a gallium-aluminum-arsenide laser source, 3 times a week. Energy used was 4.5 J/cm(2). Ulcers in the control group received sham treatment. Healing of the ulcer, defined as the complete closure of the wound with healthy scar tissue, time taken for the ulcer to heal, and stage of the ulcer and Pressure Sore Status Tool score 14 days after last treatment. There was no significant difference in healing between the treatment and control groups. Eighteen ulcers in treatment group and 14 in control group healed completely ( P =.802). Mean time taken by the ulcers to heal was 2.45+/-2.06 weeks in the treatment group and 1.78+/-2.13 weeks in the control group ( P =.330). Time taken for stage 3 and 4 ulcers to reach stage 2 was 2.25+/-0.5 weeks in treatment group and 4.33+/-1.53 weeks in control group ( P =.047). Multiwavelength light therapy from a gallium-aluminum-arsenide laser source did not influence overall healing pressure ulcers. Limited evidence suggested that it improved healing of stage 3 and 4 pressure ulcers.

  4. Phenomenological description of the association of protein subunits subjected to conformational drift. Effects of dilution and of hydrostatic pressure.

    Science.gov (United States)

    Weber, G

    1986-06-17

    The native conformation of oligomers may be expected to undergo reversible changes when they separate upon dissociation of the original aggregate. When these changes are slow in comparison with the time of an association-dissociation (AD) cycle, they give rise to characteristic effects in the dependence of the dissociation: upon dilution, at constant pressure, and upon the applied pressure, at constant concentration. The phenomenological description of these effects is examined by comparing two possible models: The first model assumes a continuous loss in free energy of association with the extent of dissociation; the second supposes the existence of two or more distinct aggregates differing in subunit affinity and present in proportions that vary with the extent of dissociation. The latter model fits better the experimental data available, with regard to both the concentration and the pressure dependence of the association, and gives a particularly simple explanation of the hysteresis phenomena observed in several oligomeric proteins after application of pressure. The validity of the principle of detailed balance, often assumed in dealing with complex equilibria, is discussed in detail as it does not appear possible to reconcile it with some of the experimental observations or with the proposed model.

  5. Effects of cimetidine and ranitidine on interdigestive and postprandial lower esophageal sphincter pressures and plasma gastrin levels in normal subjects

    NARCIS (Netherlands)

    Smout, A. J.; Bogaard, J. W.; van Hattum, J.; Akkermans, L. M.

    1985-01-01

    The purpose of this study was to investigate the effects of cimetidine and ranitidine on human lower esophageal sphincter pressure (LESP) and plasma levels of gastrin in all phases of the interdigestive motor complex and after a test meal. In a random, double-blind manner, placebo, cimetidine (1.0

  6. Consumption of a polyphenol-rich grape-wine extract lowers ambulatory blood pressure in mildly hypertensive subjects

    NARCIS (Netherlands)

    Draijer, Richard; de Graaf, Young; Slettenaar, Marieke; de Groot, Eric; Wright, Chris I.

    2015-01-01

    Polyphenols in grape and wine have been suggested to contribute to the cardiovascular health benefits of the Mediterranean lifestyle. The reported effects of grape products on blood pressure (BP) remain, however, equivocal. In a double-blind placebo controlled crossover study, the effect of two

  7. Fully Hydro-Mechanically Coupled Experiments and Simulations on Rough Fractures Subjected to High-Pressure Fluid Injection

    Science.gov (United States)

    Vogler, D.; Settgast, R.; Annavarapu, C.; Madonna, C.; Bayer, P.; Amann, F.

    2016-12-01

    This work presents fully hydro-mechanically coupled experiments and simulations in heterogeneous fractures. Cylindrical specimens with an artificial fracture normal to the cylinder axis were axially loaded to evaluate: (i) fracture normal closure; (ii) fracture contact stress evolution; and (iii) fracture normal closure and fluid injection pressure response. The laboratory experiments were simulated with the GEOS framework, which captures the non-linear behavior of fracture normal closure and fluid pressure response. To apply the developed model on the field scale, a heterogeneous fracture aperture field is created from aperture data recorded under zero-stress on natural tensile fractures from the Grimsel Test Site (GTS), Switzerland. The field stresses measured in the GTS are applied on the model domain, yielding the unique aperture distribution and stress perturbations in the rock mass associated with the applied stress state. Next, fluid is injected into the fracture center and tortuous flow channeling is observed. Increasing fluid injection pressures result in localized fracture opening, which leads to an increasingly non-linear relationship between fluid injection flow rate and pressure.

  8. Effect of lingual plates on generating intra-oral pressure during swallowing: an experimental study in healthy subjects.

    Science.gov (United States)

    Hori, Kazuhiro; Srinivasan, Murali; Barbezat, Cindy; Tamine, Ken-ichi; Ono, Takahiro; Müller, Frauke

    2013-07-01

    Although palatal augmentation prostheses (PAPs) can improve dysphagia, their application is compromised in the absence of maxillary abutment teeth. Experimental lingual plates (ELPs) used for raising the tongue may be employed as alternative to PAPs. Influence of different ELP designs, plateau (P-type) and drop-shaped (D-type), on the intra-oral pressure during swallowing were tested. Eleven healthy dentate volunteers, with a mean age of 35.5±10.5 years, participated in this study. Tongue pressure on the hard palate was measured using an ultra-thin sensor sheet with five measuring points, whilst performing dry, 5-ml and 15-ml water swallows, with and without the ELPs in situ. Additional pressure sensors were installed in the lingual aspects of the ELPs, and on the vestibular aspect of the lower molars for measuring sublingual and oral vestibule pressures, respectively. Each measurement was recorded thrice. A repeated measures ANOVA was employed to verify differences in duration, maximal magnitude and integrated value for the different experimental situations. Tukey's post hoc test was performed for comparison testing. Statistical significance was set at prationale of using ELPs for the treatment of dysphagia; hence a rather biologically designed piezographic lingual plate may be more appropriate.

  9. Skeletal adaptation to intramedullary pressure-induced interstitial fluid flow is enhanced in mice subjected to targeted osteocyte ablation.

    Directory of Open Access Journals (Sweden)

    Ronald Y Kwon

    Full Text Available Interstitial fluid flow (IFF is a potent regulatory signal in bone. During mechanical loading, IFF is generated through two distinct mechanisms that result in spatially distinct flow profiles: poroelastic interactions within the lacunar-canalicular system, and intramedullary pressurization. While the former generates IFF primarily within the lacunar-canalicular network, the latter generates significant flow at the endosteal surface as well as within the tissue. This gives rise to the intriguing possibility that loading-induced IFF may differentially activate osteocytes or surface-residing cells depending on the generating mechanism, and that sensation of IFF generated via intramedullary pressurization may be mediated by a non-osteocytic bone cell population. To begin to explore this possibility, we used the Dmp1-HBEGF inducible osteocyte ablation mouse model and a microfluidic system for modulating intramedullary pressure (ImP to assess whether structural adaptation to ImP-driven IFF is altered by partial osteocyte depletion. Canalicular convective velocities during pressurization were estimated through the use of fluorescence recovery after photobleaching and computational modeling. Following osteocyte ablation, transgenic mice exhibited severe losses in bone structure and altered responses to hindlimb suspension in a compartment-specific manner. In pressure-loaded limbs, transgenic mice displayed similar or significantly enhanced structural adaptation to Imp-driven IFF, particularly in the trabecular compartment, despite up to ∼50% of trabecular lacunae being uninhabited following ablation. Interestingly, regression analysis revealed relative gains in bone structure in pressure-loaded limbs were correlated with reductions in bone structure in unpressurized control limbs, suggesting that adaptation to ImP-driven IFF was potentiated by increases in osteoclastic activity and/or reductions in osteoblastic activity incurred independently of

  10. Surface roughness and wear of resin cements after toothbrush abrasion

    Directory of Open Access Journals (Sweden)

    Sérgio Kiyoshi ISHIKIRIAMA

    2015-01-01

    Full Text Available Increased surface roughness and wear of resin cements may cause failure of indirect restorations. The aim of this study was to evaluate quantitatively the surface roughness change and the vertical wear of four resin cements subjected to mechanical toothbrushing abrasion. Ten rectangular specimens (15 × 5 × 4 mm were fabricated according to manufacturer instructions for each group (n = 10: Nexus 3, Kerr (NX3; RelyX ARC, 3M ESPE (ARC; RelyX U100, 3M ESPE (U100; and Variolink II, Ivoclar/Vivadent (VL2. Initial roughness (Ra, µm was obtained through 5 readings with a roughness meter. Specimens were then subjected to toothbrushing abrasion (100,000 cycles, and further evaluation was conducted for final roughness. Vertical wear (µm was quantified by 3 readings of the real profile between control and brushed surfaces. Data were subjected to analysis of variance, followed by Tukey’s test (p < 0.05. The Pearson correlation test was performed between the surface roughness change and wear (p < 0.05. The mean values of initial/final roughness (Ra, µm/wear (µm were as follows: NX3 (0.078/0.127/23.175; ARC (0.086/0.246/20.263; U100 (0.296/0.589/16.952; and VL2 (0.313/0.512/22.876. Toothbrushing abrasion increased surface roughness and wear of all resin cements tested, although no correlation was found between those variables. Vertical wear was similar among groups; however, it was considered high and may lead to gap formation in indirect restorations.

  11. Intraexaminer and interexaminer reliability of manual palpation and pressure algometry of the lower limb nerves in asymptomatic subjects.

    Science.gov (United States)

    Fingleton, Caitriona P; Dempsey, Lucy; Smart, Keith; Doody, Catherine M

    2014-02-01

    Nerve palpation is a method of clinically identifying mechanosensitivity of neural tissue by means of pressure algometry and manual palpation. There are few investigations of the reliability of lower limb nerve palpation, and femoral nerve palpation has never been previously reported. The aim of this study was to investigate the reliability of nerve palpation of the femoral, sciatic, tibial, and common peroneal nerves and to report normative values for the femoral nerve. The 4 lower limb nerves were palpated in 39 healthy volunteers using pressure algometry and manual digital palpation. Measurements were taken twice by 1 rater (intrarater reliability) and once by a second rater (interrater reliability). Intraclass correlation coefficients for pressure pain thresholds (PPTs) via pressure algometry of the femoral, common peroneal, tibial, and sciatic nerves were 0.69, 0.84, 0.64, and 0.9 for intrarater reliability, respectively, and 0.82, 0.7, 0.56, and 0.75 for interrater reliability. κ Values for manual palpation were 0.59, 0.55, 0.42, and 0.60 for intrarater reliability and 0.30, 0.49, 0.37, and 0.60 for interrater reliability. Males demonstrated significantly higher PPTs than females for the femoral, sciatic, and tibial nerves, and differences in PPTs were present between right and left sides. Nerve palpation of the femoral, common peroneal, and sciatic nerves using pressure algometry demonstrated good to excellent reliability, whereas the tibial nerve PPTs showed moderate to good reliability. Manual palpation measurements demonstrated fair to moderate reliability. Copyright © 2014 National University of Health Sciences. Published by Mosby, Inc. All rights reserved.

  12. The Effect of Low Volume Interval Training on Resting Blood Pressure in Pre-hypertensive Subjects: A Preliminary Study.

    Science.gov (United States)

    Skutnik, Benjamin C; Smith, Joshua R; Johnson, Ariel M; Kurti, Stephanie P; Harms, Craig A

    2016-01-01

    Clinically pre-hypertensive adults are at a greater risk of developing hypertension, stiffened arteries, and other cardiovascular risks. Endurance exercise training has been shown to improve elevated resting blood pressure and C-reactive protein (CRP) levels. However, a primary barrier preventing individuals from engaging in regular physical activity is a lack of time. The purpose of our study was to determine if a high-intensity interval training (HIIT) protocol would be as effective as continuous aerobic endurance training (ET) on resting blood pressure in pre-hypertensive participants. Additionally, this study investigated the effects of HIIT vs. ET on CRP. Twelve pre-hypertensive participants (33.3±6.1 yrs; 3M/9W) participated in 8 weeks of cycle ergometer exercise training. The ET exercised for 30 continuous min/day, 4 days/week at 40% VO2max reserve. The HIIT exercised at a 1:1 work-to-rest for 20 min/day, 3 days/week at 60% peak power. Resting mean arterial pressure and CRP were compared throughout the study. Both groups showed decreases (p<0.001) in mean arterial pressure (ET: -11.5 ± 5.9 mmHg; HIIT: -8.6 ± 4.8 mmHg) following the 8 weeks. For CRP, there was a significant decrease (p=0.014) as a main effect of time. VO2max increased (p<0.001) approximately 25% for both HIIT and ET. These preliminary data suggest HIIT and ET similarly decreased resting blood pressure and increased VO2max.

  13. Evaluation of hardness and wear resistance of interim restorative materials.

    Science.gov (United States)

    Savabi, Omid; Nejatidanesh, Farahnaz; Fathi, Mohamad Hossein; Navabi, Amir Arsalan; Savabi, Ghazal

    2013-03-01

    The interim restorative materials should have certain mechanical properties to withstand in oral cavity. The aim of this study was to evaluate the hardness and wear resistance of interim restorative materials. Fifteen identical rectangular shape specimens with dimensions of 2 mm × 10 mm × 30 mm were made from 7 interim materials (TempSpan, Protemp 3 Garant, Revotek, Unifast LC, Tempron, Duralay, and Acropars). The Vickers hardness and abrasive wear of specimens were tested in dry conditions and after 1 week storage in artificial saliva. The depth of wear was measured using surface roughness inspection device. Data were subjected to Kruskal-Wallis and Mann-Whitney tests. The Pearson correlation coefficient was used to determine the relationship between hardness and wear (α =0.05). TempSpan had the highest hardness. The wear resistance of TempSpan (in dry condition) and Revotek (after conditioning in artificial saliva) was significantly higher (P materials (P = 0.281, r = -0.31). Hardness and wear resistance of interim resins are material related rather than category specified.

  14. Wear behaviour of Al 261

    Directory of Open Access Journals (Sweden)

    N. Mathan Kumar

    2016-03-01

    Full Text Available Al 2618 matrix material was mixed with the Silicon Nitride (Si3N4, Aluminium Nitride (AlN and Zirconium Boride (ZrB2 reinforced particles. AMC was synthesized successfully by the stir casting method with the various X-wt.% of reinforcements (X = 0,2,4,6,8. Tribological behaviour was studied in this composite with various temperature conditions. The working conditions were Temperature (°C, Load (N, Velocity (m/s and Sliding Distances (m. Before wear testing the mechanical behaviour has been analysed. EDAX was confirmed by the matrix material composition. The Al 2618 alloy and the reinforcement mixers were confirmed by the X-ray Diffraction analysis. Wear rate (mm3/m, Wear resistance (m/mm3, Specific Wear rate (m/Nm and Co-efficient of friction (μ were analysed with various conditions. The worn surfaces were analysed before and after wear testing by Scanning Electron Microscope (SEM. Influence of process parameters and Percentage of contribution were analysed by Taguchi and Analysis of Variance (ANOVA methods. Genetic Algorithm (GA was adopted for optimizing the best and mean of the wear rate and to identify the exact influence of input parameters.

  15. Tool Wear in Friction Drilling

    Energy Technology Data Exchange (ETDEWEB)

    Miller, Scott F [ORNL; Blau, Peter Julian [ORNL; Shih, Albert J. [University of Michigan

    2007-01-01

    This study investigated the wear of carbide tools used in friction drilling, a nontraditional hole-making process. In friction drilling, a rotating conical tool uses the heat generated by friction to soften and penetrate a thin workpiece and create a bushing without generating chips. The wear of a hard tungsten carbide tool used for friction drilling a low carbon steel workpiece has been investigated. Tool wear characteristics were studied by measuring its weight change, detecting changes in its shape with a coordinate measuring machine, and making observations of wear damage using scanning electron microscopy. Energy dispersive spectroscopy was applied to analyze the change in chemical composition of the tool surface due to drilling. In addition, the thrust force and torque during drilling and the hole size were measured periodically to monitor the effects of tool wear. Results indicate that the carbide tool is durable, showing minimal tool wear after drilling 11000 holes, but observations also indicate progressively severe abrasive grooving on the tool tip.

  16. Gear Tooth Wear Detection Algorithm

    Science.gov (United States)

    Delgado, Irebert R.

    2015-01-01

    Vibration-based condition indicators continue to be developed for Health Usage Monitoring of rotorcraft gearboxes. Testing performed at NASA Glenn Research Center have shown correlations between specific condition indicators and specific types of gear wear. To speed up the detection and analysis of gear teeth, an image detection program based on the Viola-Jones algorithm was trained to automatically detect spiral bevel gear wear pitting. The detector was tested using a training set of gear wear pictures and a blind set of gear wear pictures. The detector accuracy for the training set was 75 percent while the accuracy for the blind set was 15 percent. Further improvements on the accuracy of the detector are required but preliminary results have shown its ability to automatically detect gear tooth wear. The trained detector would be used to quickly evaluate a set of gear or pinion pictures for pits, spalls, or abrasive wear. The results could then be used to correlate with vibration or oil debris data. In general, the program could be retrained to detect features of interest from pictures of a component taken over a period of time.

  17. Hemodynamic mechanisms of the attenuated blood pressure response to mental stress after a single bout of maximal dynamic exercise in healthy subjects

    Directory of Open Access Journals (Sweden)

    F.J. Neves

    2012-07-01

    Full Text Available To determine the hemodynamic mechanisms responsible for the attenuated blood pressure response to mental stress after exercise, 26 healthy sedentary individuals (age 29 ± 8 years underwent the Stroop color-word test before and 60 min after a bout of maximal dynamic exercise on a treadmill. A subgroup (N = 11 underwent a time-control experiment without exercise. Blood pressure was continuously and noninvasively recorded by infrared finger photoplethysmography. Stroke volume was derived from pressure signals, and cardiac output and peripheral vascular resistance were calculated. Perceived mental stress scores were comparable between mental stress tests both in the exercise (P = 0.96 and control (P = 0.24 experiments. After exercise, the blood pressure response to mental stress was attenuated (pre: 10 ± 13 vs post: 6 ± 7 mmHg; P 0.05. In conclusion, a single bout of maximal dynamic exercise attenuates the blood pressure response to mental stress in healthy subjects, along with lower stroke volume and cardiac output, denoting an acute modulatory action of exercise on the central hemodynamic response to mental stress.

  18. Effects of the amount of rice in meals on postprandial blood pressure in older people with postprandial hypotension: a within-subjects design.

    Science.gov (United States)

    Son, Jung Tae; Lee, Eunjoo

    2015-08-01

    To determine the effect of the amount of rice carbohydrates consumed during mealtime on the extent of decrease in postprandial blood pressure in older people with postprandial hypotension. The incidence of postprandial hypotension is as high as 74% in older people with hypertension. A within-subjects repeated measures design was used. Thirty-nine older people in nursing homes received a full serving and a half-serving of rice on two separate days, in random order blood pressure and heart rate were measured before each meal and every 15 minutes for a total of 120 minutes after each meal. Data were analysed using repeated measures analysis of variance and the paired t-test with a Bonferroni adjustment using IBM spss version 19.0. The control and intervention conditions yielded significantly different patterns in systolic blood pressure and diastolic blood pressure. Postprandial hypotension was less frequent under the intervention condition; however, decrease in rice intake did not significantly affect heart rate. Reducing the amount of rice intake per meal prevents postprandial blood pressure decreases in the older people. Small and frequent meals with decreased carbohydrate content are recommended to prevent postprandial hypotension and its complications in the older people. Patients, dieticians and caregivers of older patients should be aware of the importance of diet, especially of decreasing the amount of carbohydrate in a meal. Smaller and more frequent meals are recommended for older people to slow gastric emptying. © 2015 John Wiley & Sons Ltd.

  19. Intraexaminer and interexaminer reliability of manual palpation and pressure algometry of the lower limb nerves in asymptomatic subjects.

    LENUS (Irish Health Repository)

    Fingleton, Caitriona P

    2014-02-01

    Nerve palpation is a method of clinically identifying mechanosensitivity of neural tissue by means of pressure algometry and manual palpation. There are few investigations of the reliability of lower limb nerve palpation, and femoral nerve palpation has never been previously reported. The aim of this study was to investigate the reliability of nerve palpation of the femoral, sciatic, tibial, and common peroneal nerves and to report normative values for the femoral nerve.

  20. Heart Rate Variability during Simulated Hemorrhage with Lower Body Negative Pressure in High and Low Tolerant Subjects

    Science.gov (United States)

    2011-11-01

    rate, respiration rate, and pulse character do not consistently change until hemorrhage has progressed to the point of decompensation (i.e., hemodynamic...Absolute Aliens, Turku, Finland). Beat-to-beat stroke volume was derived from the arterial pressure waveform using the pulse contour method (Jansen et...notion that the magni- tude of tachycardia reflects the degree of hypovolemia. However, the reliability of tachycardia in response to hypovolemia has

  1. Non-dipping pattern in ambulatory blood pressure monitoring is associated with metabolic abnormalities in a random sample of middle-aged subjects.

    Science.gov (United States)

    Ukkola, Olavi; Vasunta, Riitta-Liisa; Kesäniemi, Y Antero

    2009-11-01

    A reduction in the blood pressure decline at night (pattern') is associated with cardiovascular morbidity. Our aim was to evaluate whether ABPM characteristics are associated with metabolic abnormalities in subjects without known hypertension or type 2 diabetes mellitus (T2DM). This is a cross-sectional population-based study on middle-aged subjects (n=462). Two distinct definitions of metabolic syndrome (MetS) were used: National Cholesterol Education Program-Third Adult Treatment Panel (NCEP-ATPIII) and International Diabetes Federation (IDF) criteria. Results suggested that subjects characterized by non-dipping in 24 h ABPM were more obese (P=0.014). After adjustment for body mass index, age and sex, non-dippers had higher very-low-density lipoprotein (VLDL)-cholesterol (P=0.003), total (P=0.029)-and VLDL-triglycerides (P=0.026) and oral glucose tolerance test 2 h blood glucose (P=0.027) compared with dippers. Non-dipping status was more common among subjects with MetS (Ppattern. The percentage decline in blood pressure from day to night decreased with the number of metabolic abnormalities (P=0.012). In conclusion, ABPM non-dipping status is an independent predictor of glucose intolerance. It is also associated with several other metabolic abnormalities. Whether non-dipping pattern is causally related to these metabolic aberrations remains to be explored in a future prospective follow-up of this cohort.

  2. Round-robin pretest analyses of a 1:6-scale reinforced concrete containment model subject to static internal pressurization

    Energy Technology Data Exchange (ETDEWEB)

    Clauss, D.B. (ed.)

    1987-05-01

    Analyses of a 1:6-scale reinforced concrete containment model that will be tested to failure at Sandia National Laboratories in the spring of 1987 were conducted by the following organizations in the United States and Europe: Sandia National Laboratories (USA), Argonne National Laboratory (USA), Electric Power Research Institute (USA), Commissariat a L'Energie Atomique (France), HM Nuclear Installations Inspectorate (UK), Comitato Nazionale per la ricerca e per lo sviluppo dell'Energia Nucleare e delle Energie Alternative (Italy), UK Atomic Energy Authority, Safety and Reliability Directorate (UK), Gesellschaft fuer Reaktorsicherheit (FRG), Brookhaven National Laboratory (USA), and Central Electricity Generating Board (UK). Each organization was supplied with a standard information package, which included construction drawings and actual material properties for most of the materials used in the model. Each organization worked independently using their own analytical methods. This report includes descriptions of the various analytical approaches and pretest predictions submitted by each organization. Significant milestones that occur with increasing pressure, such as damage to the concrete (cracking and crushing) and yielding of the steel components, and the failure pressure (capacity) and failure mechanism are described. Analytical predictions for pressure histories of strain in the liner and rebar and displacements are compared at locations where experimental results will be available after the test. Thus, these predictions can be compared to one another and to experimental results after the test.

  3. Critical component wear in heavy duty engines

    CERN Document Server

    Lakshminarayanan, P A

    2011-01-01

    The critical parts of a heavy duty engine are theoretically designed for infinite life without mechanical fatigue failure. Yet the life of an engine is in reality determined by wear of the critical parts. Even if an engine is designed and built to have normal wear life, abnormal wear takes place either due to special working conditions or increased loading.  Understanding abnormal and normal wear enables the engineer to control the external conditions leading to premature wear, or to design the critical parts that have longer wear life and hence lower costs. The literature on wear phenomenon r

  4. Resting Sympathetic Baroreflex Sensitivity in Subjects with Low and High Tolerance to Central Hypovolemia Induced by Lower Body Negative Pressure

    Science.gov (United States)

    2014-06-01

    Subjects were positioned supine within an airtight chamber that was sealed at the level of the iliac crest by a neoprene skirt, and allowed to acclimate to...Common syndromes of orthostatic intolerance. Pediattics 131, 968–980. doi: 10.1542/peds.2012-2610 Sundlof, G., and Wallin, B. G. (1978). Effect of lower

  5. Oral magnesium supplements decrease high blood pressure (SBP>155 mmHg) in hypertensive subjects on anti-hypertensive medications: a targeted meta-analysis.

    Science.gov (United States)

    Rosanoff, Andrea; Plesset, Michael R

    2013-01-01

    Previously, we examined 44 human studies involving oral magnesium (Mg) supplementation for hypertension (HT), sorting them according to HT status, Mg dose and anti-hypertensive medication usage. We found that while some studies reported a significant lowering of blood pressure with Mg supplementation, others did not. We present here our first meta-analysis of a uniform subset from this series of studies. Seven studies, involving 135 hypertensive subjects on anti-hypertensive medication continuously for at least six months, with no more than a two-week washout and with a mean starting systolic blood pressure (SBP)>155 mmHg, demonstrated a mean change of -18.7 mmHg [95% CI=-14.95 to -22.45] p155 mmHg starting SBP values or not complying as regards anti-hypertensive medication usage, showed mean changes in both SBP and DBP with oral Mg that, while not approaching the high-responder values of the present study, appeared to include some high-responder subjects combined with low- or non-responder subjects. This uniform subset of seven studies showed a strong effect of Mg treatment in hypertension, which is in stark contrast to results of three other meta-analyses. Using non-uniform sets of studies, the small effects reported in previous meta-analyses may reflect a blending of dissimilar studies, which acted to seriously underestimate the potential of Mg in hypertension in some (but not all) subjects. Within studies, blending of non-, moderate and highresponder subjects in any one study might mask strong effects of Mg treatment in some subjects.

  6. The effects of increasing heel height on forefoot peak pressure.

    Science.gov (United States)

    Mandato, M G; Nester, E

    1999-02-01

    The purpose of this study was to determine the effect of increasing heel height on peak forefoot pressure. Thirty-five women were examined while wearing sneakers and shoes with 2-inch and 3-inch heels. An in-shoe pressure-measurement system was used to document the magnitude and location of plantar peak pressures. Pressure under the forefoot was found to increase significantly with increasing heel height. As the heel height increased, the peak pressure shifted toward the first metatarsal and the hallux. The reproducibility of data obtained with the in-shoe pressure-measurement system was tested in five subjects; the data were found to be reproducible to within approximately 3% of measured pressures.

  7. Abrasive wear behavior of heat-treated ABC-silicon carbide

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiao Feng; Lee, Gun Y.; Chen, Da; Ritchie, Robert O.; De Jonghe, Lutgard C.

    2002-06-17

    Hot-pressed silicon carbide, containing aluminum, boron, and carbon additives (ABC-SiC), was subjected to three-body and two-body wear testing using diamond abrasives over a range of sizes. In general, the wear resistance of ABC-SiC, with suitable heat treatment, was superior to that of commercial SiC.

  8. Tear film inflammatory mediators during continuous wear of contact lenses and corneal refractive therapy

    OpenAIRE

    González-Pérez, Javier; Villa-Collar, César; Sobrino Moreiras, Tomás; Lema Gesto, Isabel; González-Méijome, José Manuel; Rodríguez Ares, María T.; Parafita, Manuel A.

    2012-01-01

    OBJECTIVES: To study changes in tear film inflammatory mediators following continuous wear of silicone-hydrogel lenses and corneal refractive therapy with reverse geometry contact lenses. DESIGN: A prospective, case-control study. METHODS: Twenty-eight subjects had worn silicone-hydrogel lenses on a 30-night continuous wear basis. Thirty-two subjects had worn corneal refractive therapy lenses on an overnight basis. Thirty-two matched control subjects were also recruited. Tear samples ...

  9. Objective measurement of spectacle wear with a temperature sensor data logger.

    Science.gov (United States)

    Lentsch, Matthew J; Marsack, Jason D; Anderson, Heather A

    2017-11-08

    This study seeks to establish the utility of the SmartButton Data Logger (www.acrsystems.com) to monitor spectacle wear for research and clinical applications. Fifty adults wore a thermosensor on their spectacles for 2 weeks for each of two mount types while keeping wear-time logs. Temperatures during reported spectacle wear (ON) were compared to temperatures during non-wear (OFF) with repeated measures analysis of variance (ANOVA). In addition, two strategies to approximate spectacle wear from temperature data were evaluated: (1) Filtering data based on temperature ranges to identify spectacle wear (either group mean ON temperature, or an individual's mean ON temperature), and (2) Separate examiners inspecting temperature against time plots to identify spectacle wear. The success of these methods to approximate wear time was evaluated by per cent error with respect to subject reported wear time. Group mean ON (31.8 [0.6]°Celsius [°C]) and OFF (24.7 [1.5]°C) temperatures differed significantly (F1,47  = 471.2, p spectacle compliance in patients with all approximation methods evaluated providing less than 10% median per cent error in wear time. © 2017 The Authors Ophthalmic & Physiological Optics © 2017 The College of Optometrists.

  10. Cerebral autoregulation in response to posture change in elderly subjects-assessment by wavelet phase coherence analysis of cerebral tissue oxyhemoglobin concentrations and arterial blood pressure signals.

    Science.gov (United States)

    Gao, Yuanjin; Zhang, Ming; Han, Qingyu; Li, Wenhao; Xin, Qing; Wang, Yan; Li, Zengyong

    2015-02-01

    This study aims to assess the dynamic cerebral autoregulation (dCA) in response to posture change using wavelet phase coherence (WPCO) of cerebral tissue oxyhemoglobin concentrations (Delta [HbO2]) and arterial blood pressure (ABP) signals in healthy elderly subjects. Continuous recordings of near-infrared spectroscopy (NIRS) and ABP signals were obtained from simultaneous measurements in 16 healthy elderly subjects (age: 68.9±7.1 years) and 19 young subjects (age: 24.9±3.2 years). The phase coherence between Delta [HbO2] and ABP oscillations in six frequency intervals (I, 0.6-2 Hz; II, 0.15-0.6 Hz; III, 0.05-0.15 Hz; IV, 0.02-0.05 Hz, V, 0.0095-0.02 Hz and VI, 0.005-0.0095 Hz) was analyzed using WPCO. The sit-to-stand posture change induces significantly lower WPCO in interval III (F=5.50 p=0.025) in the elderly subjects than in the young subjects. However, the stand-to-sit posture change induces higher WPCO in intervals II (F=5.25 p=0.028) and V (F=6.22 p=0.018) in the elderly subjects than in the young subjects. The difference of WPCO in response to posture change between the elderly and the young subjects indicates an altered CA due to aging. This study provides new insight into the dynamics of CA and may be useful in identifying the risk for dCA processes. Copyright © 2014 Elsevier B.V. All rights reserved.

  11. Reference values of one-point carotid stiffness parameters determined by carotid echo-tracking and brachial pulse pressure in a large population of healthy subjects.

    Science.gov (United States)

    Vriz, Olga; Aboyans, Victor; Minisini, Rosalba; Magne, Julien; Bertin, Nicole; Pirisi, Mario; Bossone, Eduardo

    2017-07-01

    Arterial stiffness can predict cardiovascular events, and the aim of this study was to produce age- and sex-specific reference values for echo-tracking carotid stiffness in healthy subjects. A total of 900 subjects (500 males, mean age 45.8±19 years) were enrolled. Common carotid artery stiffness and compliance, using a high-definition echo-tracking ultrasound system, were evaluated. To compare stiffness parameters across the different age groups, individual scores were transformed into T-scores, indicating how many standard deviation (s.d.) units an individual's score was above or below the mean that was observed in the group including same-sex individuals aged 36 to 44 years. Carotid stiffness was similar among genders, except compliance, which was lower in women (Pparameters increased significantly with age, but the opposite occurred for compliance. The T-score was found to increase significantly across all age groups, with a steeper increase in stiffness around the age of 60 years in women. For each T-score s.d., the corresponding carotid absolute values for arterial stiffness and compliance were obtained. In a multivariate model, carotid stiffness parameters were constantly and independently associated with age, mean arterial pressure, pulse pressure, heart rate and body mass index. Our study provides a normogram of carotid arterial stiffness and compliance indices obtained with the echo-tracking method in a large population of healthy subjects stratified by gender and age that can be used in clinical practice.

  12. Mirtogenol® potentiates latanoprost in lowering intraocular pressure and improves ocular blood flow in asymptomatic subjects

    Directory of Open Access Journals (Sweden)

    Robert D Steigerwalt Jr

    2010-05-01

    Full Text Available Robert D Steigerwalt Jr1, Gianni Belcaro1, Paolo Morazzoni2, Ezio Bombardelli2, Carolina Burki3, Frank Schönlau4 1Department of Biomedical Sciences, University of Chieti-Pescara, San Valentino, Italy; 2Indena S.p.A. Scientific Department, Milan, Italy; 3Horphag Research (UK Ltd., Geneva, Switzerland; 4Horphag Research (UK Ltd. South Kensington, London UKPurpose: The dietary supplement Mirtogenol® was previously shown to lower elevated intraocular pressure (IOP. We here present the effects of this supplement on IOP in comparison as well as in combination with latanoprost eye drops. Methods: Seventy-nine patients with asymptomatic ocular hypertension were randomly assigned to three groups receiving either the supplement, or latanoprost eye drops, or both in combination. Intraocular pressure and retinal blood flow were investigated in monthly intervals over 24 weeks.Results: Mirtogenol alone lowered IOP from baseline 38.1 to 29.0 mmHg after 16 weeks, with little further improvement during the following eight weeks. Latanoprost rapidly lowered IOP from baseline 37.7 to 27.2 mmHg within four weeks, without further effects thereafter. The combination of the supplement and latanoprost lowered IOP from 38.0 to 27.3 mmHg after four weeks, and further decreased IOP to 24.2 mmHg after six weeks. After 24 weeks IOP with the combination treatment (23.0 mmHg was significantly lower than with latanoprost alone (27.2 mmHg. Mirtogenol and latanoprost individually showed comparable effects for gradually increasing central artery blood flow with treatment duration. Combination treatment showed higher systolic blood flow velocity throughout the trial period. The diastolic blood flow velocity gradually increased with treatment duration in all three groups. From twelve weeks onwards, the diastolic component with combination treatment was higher than with individual treatments.Conclusions: Mirtogenol lowered elevated IOP in patients almost as effectively as

  13. The response of polymethyl methacrylate (PMMA) subjected to large strains, high strain rates, high pressures, a range in temperatures, and variations in the intermediate principal stress

    Science.gov (United States)

    Holmquist, T. J.; Bradley, J.; Dwivedi, A.; Casem, D.

    2016-05-01

    This article presents the response of polymethyl methacrylate (PMMA) subjected to large strains, high strain rates, high pressures, a range in temperatures, and variations in the intermediate principal stress. Laboratory data from the literature, and new test data provided here, are used in the evaluation. The new data include uniaxial stress compression tests (at various strain rates and temperatures) and uniaxial stress tension tests (at low strain rates and ambient temperatures). The compression tests include experiments at ˙ɛ = 13,000 s-1, significantly extending the range of known strain rate data. The observed behavior of PMMA includes the following: it is brittle in compression at high rates, and brittle in tension at all rates; strength is dependent on the pressure, strain, strain rate, temperature, and the intermediate principal stress; the shear modulus increases as the pressure increases; and it is highly compressible. Also presented are novel, high velocity impact tests (using high-speed imaging) that provide insight into the initiation and evolution of damage. Lastly, computational constitutive models for pressure, strength, and failure are presented that provide responses that are in good agreement with the laboratory data. The models are used to compute several ballistic impact events for which experimental data are available.

  14. Comparison of the compressive strength of impregnated and nonimpregnated eucalyptus subjected to two different pressures and impregnation times

    Directory of Open Access Journals (Sweden)

    Waldemir Rodrigues

    2004-06-01

    Full Text Available The durability of wood is affected by several factors. For this reason, much research has been done on a variety of chemical compounds for impregnating wood, aimed at preserving it while simultaneously improving its properties. Recent studies of the properties of impregnated wood have demonstrated the possibility of substantially improving its mechanical characteristics. Thus, the purpose of this work was to compare the strength to parallel compression of wooden fibers (Eucalyptus grandis, both nonimpregnated and impregnated with a monocomponent resin, from the standpoint of pressure and impregnation time, aiming at its structural utilization. The results demonstrate that the compressive strength of impregnated test specimens is greater than that of nonimpregnated ones, indicating that monocomponent polyurethane resin can be considered suitable for impregnating wood, since it increases the compressive strength of eucalyptus.

  15. Study on Abrasive Wear of Brake Pad in the Large-megawatt Wind Turbine Brake Based on Deform Software

    Science.gov (United States)

    Zhang, Shengfang; Hao, Qiang; Sha, Zhihua; Yin, Jian; Ma, Fujian; Liu, Yu

    2017-12-01

    For the friction and wear issues of brake pads in the large-megawatt wind turbine brake during braking, this paper established the micro finite element model of abrasive wear by using Deform-2D software. Based on abrasive wear theory and considered the variation of the velocity and load in the micro friction and wear process, the Archard wear calculation model is developed. The influence rules of relative sliding velocity and friction coefficient in the brake pad and disc is analysed. The simulation results showed that as the relative sliding velocity increases, the wear will be more serious, while the larger friction coefficient lowered the contact pressure which released the wear of the brake pad.

  16. Rigid gas-permeable vs. hydrogel contact lenses for extended wear.

    Science.gov (United States)

    Fonn, D; Holden, B A

    1988-07-01

    A clinical trial was conducted to compare the extended wear performance of rigid gas-permeable (RGP) contact lenses with that of soft lenses. Subjects were fitted with a RGP lens (Boston IV) in one eye and a soft lens (Bausch & Lomb "O" series) in the other eye, and wore them on an extended wear basis for up to 3 months. No subjects developed any acute adverse reactions in the RGP lens-wearing eye. After the initial adaptation period, subject acceptance of RGP extended wear in terms of vision and comfort was superior. The RGP lenses also induced less chronic hypoxic stress than hydrogel lenses of comparable Dk/L, as evidenced by the presence of epithelial microcysts. Several complications of RGP extended wear were observed including lens binding, blepharoptosis, transient pupil size increases, and corneal staining. As hypoxia-induced corneal changes, such as microcysts and striae, were observed in the RGP lens-wearing eyes, we consider that these particular RGP lenses do not have adequate oxygen transmissibility for successful long-term extended wear. However, if RGP lens materials of higher oxygen transmissibility and better designs can be attained, the potential of RGP extended wear would appear promising.

  17. 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.

  18. Detailed study of oxidation/wear mechanism in lox turbopump bearings

    Science.gov (United States)

    Chase, T. J.; McCarty, J. P.

    1993-12-01

    Wear of 440C angular contact ball bearings of the phase 2 high pressure oxygen turbopump (HPOTP) of the space shuttle main engine (SSME) has been studied by means of various advanced nondestructive techniques (NDT) and modeled with reference to all known material, design, and operation variables. Three modes dominating the wear scenario were found to be the adhesive/sheer peeling (ASP), oxidation, and abrasion. Bearing wear was modeled in terms of the three modes. Lacking a comprehensive theory of rolling contact wear to date, each mode is modeled after well-established theories of sliding wear, while sliding velocity and distance are related to microsliding in ball-to-ring contacts. Microsliding, stress, temperature, and other contact variables are evaluated with analytical software packages of SHABERTH(TM)/SINDA(TM) and ADORE(TM). Empirical constants for the models are derived from NIST experiments by applying the models to the NIST wear data. The bearing wear model so established precisely predicts quite well the average ball wear rate for the HPOTP bearings. The wear rate has been statistically determined for the entire population of flight and development bearings based on Rocketdyne records to date. Numerous illustrations are given.

  19. Influence of shoe midsole hardness on plantar pressure distribution in four basketball-related movements.

    Science.gov (United States)

    Lam, Wing-Kai; Ng, Wei Xuan; Kong, Pui Wah

    2017-01-01

    This study examined how shoe midsole hardness influenced plantar pressure in basketball-related movements. Twenty male university basketball players wore customized shoes with hard and soft midsoles (60 and 50 Shore C) to perform four movements: running, maximal forward sprinting, maximal 45° cutting and lay-up. Plantar loading was recorded using an in-shoe pressure measuring system, with peak pressure (PP) and pressure time integral (PTI) extracted from 10 plantar regions. Compared with hard shoes, subjects exhibited lower PP in one or more plantar regions when wearing the soft shoes across all tested movements (Ps basketball players.

  20. Factors Affecting the Wear Resistance of Forging Tools

    Directory of Open Access Journals (Sweden)

    Zwierzchowski M.

    2017-09-01

    Full Text Available The durability of forging tools is a function of many variables: tool heat treatment, surface quality, temperature, pressure, number of forgings, diffusion layers (nitriding and many others. The objective of study was to analyze and compare the working conditions of forging tools. For the analysis of selected flat surfaces of tools. Analyzed forging dies subjected to normal use. Presented results of laboratory tests . The effect of temperature and time on the properties of the surface layer of forging tools. The results were compared with the literature data. This article shows the results of microhardness tests for forging dies which have forged the corresponding number of forgings. The results of laboratory studies on microhardness of hot working steel 1.2344 in the furnace at various temperatures and time are also presented. The working conditions of the forging tools are very complex. The most often described in the literature are: thermal fatigue, abrasive wear, mechanical fatigue and cracks. The article discusses the effects of increased temperature on the surface properties of forging tools. Forging dies were made of hot work tool steel 1.2344. FEM modeling of changes in the surface layer should take into account changes in tool hardness as a function of time (number of forgings.

  1. Experimental and analytical program to determine strains in 737 LAP splice joints subjected to normal fuselage pressurization loads

    Energy Technology Data Exchange (ETDEWEB)

    Roach, D.P. [Sandia National Labs., Albuquerque, NM (United States); Jeong, D.Y. [Department of Transportation, Cambridge, MA (United States). John A. Volpe National Transportation Systems Center

    1996-02-01

    The Federal Aviation Administration Technical Center (FAATC) has initiated several research projects to assess the structural integrity of the aging commercial aircraft fleet. One area of research involves the understanding of a phenomenon known as ``Widespread Fatigue Damage`` or WFD, which refers to a type of multiple element cracking that degrades the damage tolerance capability of an aircraft structure. Research on WFD has been performed both experimentally and analytically including finite element modeling of fuselage lap splice joints by the Volpe Center. Fuselage pressurization tests have also been conducted at the FAA`s Airworthiness Assurance NDI Validation Center (AANC) to obtain strain gage data from select locations on the FAA/AANC 737 Transport Aircraft Test Bed. One-hundred strain channels were used to monitor five different lap splice bays including the fuselage skin and substructure elements. These test results have been used to evaluate the accuracy of the analytical models and to support general aircraft analysis efforts. This paper documents the strain fields measured during the AANC tests and successfully correlates the results with analytical predictions.

  2. A systematic review of the effect of paracetamol on blood pressure in hypertensive and non-hypertensive subjects

    Science.gov (United States)

    Turtle, Emma J; Dear, James W; Webb, David J

    2013-01-01

    Aim To review current evidence on the effect of paracetamol on blood pressure (BP), the quality of the previous studies and the validity of the results, and to summarize these findings. Methods A systematic literature review was performed by searching PubMed, the Cochrane library and EMBASE for publications between the years 1963 and 2012. Results We identified three case reports, seven prospective observational trials, six randomized controlled trials, one commentary and two reviews. Some, but not all, of the observational studies, which included over 147 000 patients, showed an increased risk of hypertension with paracetamol use. The randomized studies were generally small and the results were inconsistent. Three studies, which included 104 patients, showed an increase of systolic BP by ∼4 mmHg, two studies, which included 27 patients, reported no change in BP and one study, which included 21 patients, reported a fall in BP although no placebo arm was included for comparison. Conclusions The overall effect of paracetamol on BP is unclear. Given that paracetamol is often suggested as a safer alternative to non-steroidal anti-inflammatory drugs (NSAIDs), it would seem that further prospective evidence is now needed to address the effect of paracetamol on BP. This would be best done with larger studies in relevant cohorts using BP measured by ambulatory BP monitoring as the primary endpoint. PMID:23145789

  3. Influence of Blood Pressure and Other Clinical Variables on Long-Term Mortality in a Cohort of Elderly Subjects with Type 2 Diabetes.

    Science.gov (United States)

    Tessier, Daniel M; Meneilly, Graydon S; Moleski, Luc; Trottier, Lise; Lanthier, Luc

    2016-02-01

    Diabetes mellitus and high blood pressure (HBP) are commonly associated conditions in the elderly population. An effect of treatments, biologic and anthropometric variables on long-term mortality is unknown in this population. To determine the prevalence of HBP control in a sample of elderly patients with type 2 diabetes with office blood pressure (BP) readings and ambulatory blood pressure monitoring (ABPM) and evaluate the influence of BP, anthropometric and laboratory variables on long term mortality. Cohort study in patients living at home in the area of Sherbrooke, ≥65 years old, receiving reimbursement for antidiabetic medication. The study included medical history, 2 sets of BP measurements, 2 24-hour urinary collections for microalbuminuria, 1 24-hour ABPM, blood level of creatinine and glycosylated hemoglobin. Charts were reanalyzed 8 years later for analysis of cardiovascular and total mortality cases. 198 patients were initially recruited. By history, 83% of the subjects had diagnoses and treatments for high blood pressure. In multivariate analysis, factors associated with an 8-year increased risk for cardiovascular mortality were creatinine ≥84 µmol/L, office seated systolic blood pressure ≤130 and diastolic BP ≤67.6 over 24 hours. Factors associated with total mortality were lower waist circumference, serum creatinine ≥84 and diastolic BP ≤67.6 over 24 hours. Lower systolic and diastolic BP (office and ABPM), lower waist circumference and higher creatinine values are associated with an increased mortality risk. This suggests that a lower BP, declining kidney function and frailty are factors associated with this observation. Copyright © 2015 Canadian Diabetes Association. Published by Elsevier Inc. All rights reserved.

  4. Lens adherence and postlens tear film changes in closed-eye wear of hydrogel lenses.

    Science.gov (United States)

    Bruce, A S; Mainstone, J C

    1996-01-01

    Lens adherence and a reduced postlens tear film circulation have been suggested as factors contributing to some adverse reactions in extended wear of hydrogel contact lenses. In this study, we determined lens fitting and postlens tear film characteristics during closed-eye wear. Twenty subjects wore hydrogel lenses for 3 h of eye closure, followed by 30 min of open-eye wear. Lens movement was measured with a video biomicroscope. Postlens tear film appearances in specular reflection were classified as either amorphous, or as one of four color intensity grades, where a colored appearance was taken as indicative of a depleted postlens tear film. All subjects showed lens adherence (movement colored postlens tear film patterns of any intensity. Closed-eye wear was invariably associated with the onset of lens adherence and postlens tear film depletion. This finding emphasizes the need for adequate lens movement during the open-eye phase of extended wear.

  5. Cell counts and survival to vitrification of bovine in vitro produced blastocysts subjected to sublethal high hydrostatic pressure.

    Science.gov (United States)

    Trigal, B; Muñoz, M; Gómez, E; Caamaño, J N; Martin, D; Carrocera, S; Casais, R; Diez, C

    2013-04-01

    This work analyses the effects of a high hydrostatic pressure (HHP) treatment on in vitro survival of in vitro produced (IVP) bovine embryos vitrified with the Cryologic Vitrification Method (CVM). Consequences on embryo quality in terms of cell proliferation and differentiation, and levels of embryonic Heat Shock Protein 70 (Hsp-70) were also examined. Day 7 and 8 bovine in vitro-produced blastocysts were submitted to an HHP treatment (60 MPa, at 32 °C for 1 h) and allowed to recover for 1 or 2 h in culture medium. The HHP treatment did not improve blastocyst survival rates after vitrification/warming. Survival (24 h post-warming) and hatching (48 h post-warming) rates were 79.3 ± 4.9 and 51.8 ± 4.2 vs 73.9 ± 4.2 and 44.7 ± 4.1 for untreated controls and HHP-treated embryos, respectively. Total cell numbers measured in fresh embryos were reduced after 1 h at 32 °C, with or without HHP treatment, indicating that cell proliferation was stopped as a result of stress. Vitrified HHP-treated embryos that hatched at 48 h after warming showed increased cell numbers in their ICM compared with untreated controls (50.2 ± 3.1 vs 38.8 ± 2.7), indicating higher embryo quality. Treatment of blastocysts with HHP did not alter the level of the Hsp-70 protein. In our conditions, HHP treatment did not affect the cryoresistance of these embryos. However, combination of HHP treatment and vitrification in fibreplugs resulted in an increase in the ICM cell number of hatched embryos 48 h post-warming. © 2012 Blackwell Verlag GmbH.

  6. Lumbar spine orthosis wearing. I. Restriction of gross body motions.

    Science.gov (United States)

    Lantz, S A; Schultz, A B

    1986-10-01

    The effects of wearing commonly prescribed low-back braces and corsets on restriction of gross body motions were investigated. A lumbosacral corset, a chairback brace, and a molded plastic thoracolumbosacral orthosis (TLSO) were studied. Four trunk movements (flexion, extension, lateral bending, and twisting) were examined in five healthy adult men when standing and sitting. All three orthoses restricted at least some gross body motion to approximately two thirds to one half of no-orthosis values. All three orthoses failed to provide restrictions of at least 10% in at least one motion. Mean motion restriction across all eight movements studied in all five subjects were largest when wearing the TLSO and least when wearing the corset. Gross body motion restrictions relieve lumbar trunk muscle and spine loads.

  7. Juice Powder Concentrate and Systemic Blood Pressure, Progression of Coronary Artery Calcium and Antioxidant Status in Hypertensive Subjects: A Pilot Study

    Directory of Open Access Journals (Sweden)

    M. C. Houston

    2007-01-01

    Full Text Available Because micronutrients from plants may have beneficial cardiovascular effects, the hypothesis that an encapsulated juice powder concentrate might affect several measures of vascular health was tested in free living adults at low cardiovascular risk. Blood pressure, vascular compliance, lipid and antioxidant markers, and serial electron beam tomography (to calculate a coronary artery calcium score as a measure of atherosclerosis burden, were monitored in 51 pre-hypertensive and hypertensive subjects over 2 years. By the end of follow-up, systolic and diastolic blood pressure decreased significantly (−2.4 ± 1.0 mmHg, P < 0.05 and −2.2 ± 0.6 mmHg, P < 0.001, and large artery compliance improved significantly (1.9 ± 0.6 ml mmHg−1 × 100, P < 0.01. The progression of coronary artery calcium score was smaller than expected compared with a historical database (P < 0.001. Laboratory testing showed a significant decrease in homocysteine (P = 0.05, HDL cholesterol (P = 0.025 and Apo A (P = 0.004, as well as a significant increase in β-carotene, folate, Co-Q10 and α-tocopherol (all P < 0.001. The phytonutrient concentrate we utilized induced several favorable modifications of markers of vascular health in the subjects. This study supports the notion that plant nutrients are important components of a heart healthy diet.

  8. Automotive brake wear: a review.

    Science.gov (United States)

    Wahid, Syed M S

    2018-01-01

    Road transport systems generate toxic particulate matter (PM) when in motion, that ultimately finds its way to the atmosphere. The PM produced by road transport systems can be broadly classified as exhaust and non-exhaust emissions. Exhaust emission is primarily due to product of combustion, as is the case of internal combustion engines and the PM is released to the atmosphere through the tail. Non-exhaust PM sources can be classified as sources such as emissions due to brake wear, tyre wear, road surface wear and resuspension. Both exhaust and non-exhaust sources generate PM of various sizes and shapes that has an impact on our health. Strict legislations by authorities have led to reduced exhaust emissions; however, due to the nature of complexity of PM generation by non-exhaust sources, effective control of non-exhaust emission still needs to be developed. Thus, as exhaust emissions are being controlled, non-exhaust is becoming a significant source of PM emission. The present paper reviews work done by previous researchers on non-exhaust PM and specifically, brake wear from road transport systems as this is one of the most important non-exhaust source of PM in the environment. The finding of the paper would be beneficial to policy makers and researchers.

  9. Should School Nurses Wear Uniforms?

    Science.gov (United States)

    Journal of School Health, 2001

    2001-01-01

    This 1958 paper questions whether school nurses should wear uniforms (specifically, white uniforms). It concludes that white uniforms are often associated with the treatment of ill people, and since many people have a fear reaction to them, they are not necessary and are even undesirable. Since school nurses are school staff members, they should…

  10. A CFD Case Study of a Fan Stage with Split Flow Path Subject to Total Pressure Distortion Inflow

    Science.gov (United States)

    To, Wai-Ming

    2017-01-01

    This report is the documentation of the work performed under the Hypersonic Project of the NASA's Fundamental Aeronautics Program. It was funded through Task Number NNC10E444T under GESS-2 Contract NNC06BA07B. The objective of the task is to develop advanced computational tools for the simulation of multi-stage turbomachinery in support of aeropropulsion. This includes work elements in extending the TURBO code and validating the multi-stage URANS (Unsteady Reynolds Averaged Navier Stokes) simulation results with the experimental data. The unsteady CFD (Computation Fluid Dynamics) calculations were performed in full wheel mode with and without screen generated total pressure distortion at the computational inflow boundary, as well as in single passage phase lag mode for uniform inflow. The experimental data were provided by NASA from the single stage RTA (Revolutionary Turbine Accelerator) fan test program.Significant non-uniform flow condition at the fan-face of the aeropropulsion system is frequentlyencountered in many of the advanced aerospace vehicles. These propulsion systems can be eithera podded or an embedded design employed in HWB (Hybrid Wing Body) airframe concept. It isalso a topic of interest in military applications, in which advanced air vehicles have already deployedsome form of embedded propulsion systems in their design because of the requirementsof compact and low observable inlets. Even in the conventional airframe/engine design, the fancould operate under such condition when the air vehicle is undergoing rapid maneuvering action.It is believed that a better understanding of the fan’s aerodynamic and aeromechanical responseto this type of operating condition or off design operation would be beneficial to designing distortiontolerant blades for improved engine operability.The objective for this research is to assess the capability of turbomachinery code as an analysistool in understanding the effects and evaluating the impact of flow distortion

  11. Wear performance of laser processed tantalum coatings

    Energy Technology Data Exchange (ETDEWEB)

    Dittrick, Stanley; Balla, Vamsi Krishna; Bose, Susmita; Bandyopadhyay, Amit, E-mail: amitband@wsu.edu

    2011-12-01

    This first generation investigation evaluates the in vitro tribological performance of laser-processed Ta coatings on Ti for load-bearing implant applications. Linear reciprocating wear tests in simulated body fluid showed one order of magnitude less wear rate, of the order of 10{sup -4} mm{sup 3}(N.m){sup -1}, for Ta coatings compared to Ti. Our results demonstrate that Ta coatings can potentially minimize the early-stage bone-implant interface micro-motion induced wear debris generation due to their excellent bioactivity comparable to that of hydroxyapatite (HA), high wear resistance and toughness compared to popular HA coatings. Highlights: {yields} In vitro wear performance of laser processed Ta coatings on Ti was evaluated. {yields} Wear tests in SBF showed one order of magnitude less wear for Ta coatings than Ti. {yields} Ta coatings can minimize early-stage micro-motion induced wear debris generation.

  12. Estimation of tool wear during CNC milling using neural network-based sensor fusion

    Science.gov (United States)

    Ghosh, N.; Ravi, Y. B.; Patra, A.; Mukhopadhyay, S.; Paul, S.; Mohanty, A. R.; Chattopadhyay, A. B.

    2007-01-01

    Cutting tool wear degrades the product quality in manufacturing processes. Monitoring tool wear value online is therefore needed to prevent degradation in machining quality. Unfortunately there is no direct way of measuring the tool wear online. Therefore one has to adopt an indirect method wherein the tool wear is estimated from several sensors measuring related process variables. In this work, a neural network-based sensor fusion model has been developed for tool condition monitoring (TCM). Features extracted from a number of machining zone signals, namely cutting forces, spindle vibration, spindle current, and sound pressure level have been fused to estimate the average flank wear of the main cutting edge. Novel strategies such as, signal level segmentation for temporal registration, feature space filtering, outlier removal, and estimation space filtering have been proposed. The proposed approach has been validated by both laboratory and industrial implementations.

  13. The Delamination Theory of Wear - III

    Science.gov (United States)

    1977-12-01

    approximate, it shows excellent agreement with the above postulate and with experimental observations of wear. It was shown that void nucleation is...purposes: to predict wear arnd to reduce wear, Mathematical modelo are necessary in order to predict wear 40 qualitatively. They are also useful in the...the substrate and on the physical and chemical properties of the materials involved, There are a number of excellent references on coating techniques

  14. Complications Caused by Contact Lens Wearing

    OpenAIRE

    Beljan, Jasna; Beljan, Kristina; Beljan, Zdravko

    2013-01-01

    Complications in wearing contact lenses are very rare and caused by poor maintenance, over-extended wear and wearing of contact lenses in a polluted environment. Regular control by a professional person can efficiently reduce the number of complications. This paper describes the most common risks factors for complications, and complications of wearing contact lenses with the classification according to the anatomic parts of the eye: eyelids, tear film, limbus, corneal epithelium, corneal stro...

  15. Weight loss approach during routine follow-up is effective for obstructive sleep apnea hypopnea syndrome subjects receiving nasal continuous positive airway pressure treatment.

    Science.gov (United States)

    Fujii, Hiroko; Miyamoto, Masayuki; Miyamoto, Tomoyuki; Muto, Takashi

    2010-01-01

    The present study investigated the effectiveness of a weight loss program during routine medical follow-up with regularity on promoting weight reduction in obese obstructive sleep apnea hypopnea syndrome (OSAHS) subjects receiving continuous positive airway pressure treatment (CPAP). A total of 10 male obese OSAHS subjects treated with CPAP were enrolled in the present study that was an intervention study without a control and had a pre-post test study design. The age was 50.7 (7.8) (mean (SD)) years, and body mass index was 30.7 (2.5) kg/m(2). A 4-month weight loss program was developed, using a combined approach of diet and physical activity based on individual counseling with behavioral approach. At 4 months, weight was significantly decreased compared with the baseline value (88.4 (8.9) kg to 86.9 (8.8) kg, p=0.005), and the mean weight loss was a 1.7% decrease from the baseline. There was significantly higher percent weight loss in the group with a CPAP duration or = 30 months (2.7 (1.6) % vs. 0.6 (0.5) %, p=0.032). The present study shows that a weight loss program may be useful in reducing weight for male obese OSAHS subjects treated with CPAP.

  16. Needs and challenges in precision wear measurement

    Energy Technology Data Exchange (ETDEWEB)

    Blau, P.J.

    1996-01-10

    Accurate, precise wear measurements are a key element in solving both current wear problems and in basic wear research. Applications range from assessing durability of micro-scale components to accurate screening of surface treatments and thin solid films. Need to distinguish small differences in wear tate presents formidable problems to those who are developing new materials and surface treatments. Methods for measuring wear in ASTM standard test methods are discussed. Errors in using alterate methods of wear measurement on the same test specimen are also described. Human judgemental factors are a concern in common methods for wear measurement, and an experiment involving measurement of a wear scar by ten different people is described. Precision in wear measurement is limited both by the capabilities of the measuring instruments and by the nonuniformity of the wear process. A method of measuring wear using nano-scale indentations is discussed. Current and future prospects for incorporating advanced, higher-precision wear measurement methods into standards are considered.

  17. Heart rate and pulmonary function while wearing the launch-entry crew escape suit (LES) during + Gx acceleration and simulated Shuttle launch

    Science.gov (United States)

    Krutz, Robert W., Jr.; Bagian, James P.; Burton, Russell R.; Meeker, Larry J.

    1990-01-01

    Space shuttle crewmembers have been equipped with a launch-entry crew escape system (LES) since the Challenger accident in 1986. Some crewmembers, wearing the new pressure suit, have reported breathing difficulties and increased effort to achieve the desired range of motion. This study was conducted to quantify the reported increased physical workloads and breathing difficulty associated with wearing the LES. Both veteran astronauts and centrifuge panel members were exposed to various + Gx profiles (including simulated shuttle launch) + Gx on the USAF School of Aerospace Medicine (USAFSAM) human-use centrifuge. Maximum heart rate data showed no increased workload associated with arm and head movement in the LES when compared to the flight suit/helmet ensemble (LEH). However, the LES did impose a significant increase in breathing difficulty beginning at +2.5 Gx which was demonstrated by a decrease in forced vital capacity and subjected questionnaries.

  18. Response of right ventricular size, function, and pressure to supine exercise: a comparison of patients with chronic obstructive lung disease and normal subjects

    Energy Technology Data Exchange (ETDEWEB)

    Slutsky, R.; Hooper, W.; Ackerman, W.; Moser, K.

    1982-12-01

    The response of right ventricular ejection fraction (RVEF) and right ventricular end-diastolic volume (RVEDV) to exercise was studied in 11 patients with severe (FEV/sub 25/sub(%)sub(-)/sub 75/sub(%)=0.32+-0.13, mean+-SD) chronic obstructive pulmonary disease (COPD). Using gated radionuclide cardiac blood pool imaging techniques, the response of the patients with COPD was compared with that of 15 control subjects. Arterial blood gases, pulmonary arterial pressures, wedge pressure, and right ventricular pressures also were monitored in patients with COPD. The resting RVEF was lower and the resting RVEDV was higher in patients with COPD than in normals (both, P<0.01). Two of the 11 COPD patients had a RVEF during rest that was below lower limits, while 10 of 11 patients had RV dilation. Right ventricular end-diastolic pressure, measured during rest in patients with COPD, was normal (6.1+-2.1 mm Hg) and cardiac index was within normal limits (3.55+-0.82 l/min/m/sup 2/). With exercise this cardiac index rose to 5.52+-1.7/min/m/sup 2/(P<0.01) due to the increase in heart rate (83+-18 to 125+-25 beats/min; P<0.01) while stroke volume did not significantly change. During exercise, normal subjects showed an increase in RVEF while RVEDV did not change; in patients with COPD, the RVEF fell and the RVEDV increased. In the patients with COPD, mild resting arterial hypoxemia and hypercapnia were both exaggerated during exercise; and mild resting pulmonary arterial hypertension (PAm=24.3+-7.65 mm Hg) also worsened with exercise (PAm=41+-19 mm Hg, P<0.01). Correlation between change in RVEF and PAm was -0.58, and between change in RVEDV and PAm was 0.63. We conclude that patients with severe COPD often have right ventricular dilation at rest and commonly respond to supine exercise with a fall in FV ejection fraction and further dilation of the right ventricle.

  19. Feasibility and antihypertensive effect of replacing regular salt with mineral salt -rich in magnesium and potassium- in subjects with mildly elevated blood pressure

    Directory of Open Access Journals (Sweden)

    Sarkkinen Essi S

    2011-09-01

    Full Text Available Abstract Background High salt intake is linked to hypertension whereas a restriction of dietary salt lowers blood pressure (BP. Substituting potassium and/or magnesium salts for sodium chloride (NaCl may enhance the feasibility of salt restriction and lower blood pressure beyond the sodium reduction alone. The aim of this study was to determine the feasibility and effect on blood pressure of replacing NaCl (Regular salt with a novel mineral salt [50% sodium chloride and rich in potassium chloride (25%, magnesium ammonium potassium chloride, hydrate (25%] (Smart Salt. Methods A randomized, double-blind, placebo-controlled study was conducted with an intervention period of 8-weeks in subjects (n = 45 with systolic (SBP 130-159 mmHg and/or diastolic (DBP 85-99 mmHg. During the intervention period, subjects consumed processed foods salted with either NaCl or Smart Salt. The primary endpoint was the change in SBP. Secondary endpoints were changes in DBP, daily urine excretion of sodium (24-h dU-Na, potassium (dU-K and magnesium (dU-Mg. Results 24-h dU-Na decreased significantly in the Smart Salt group (-29.8 mmol; p = 0.012 and remained unchanged in the control group: resulting in a 3.3 g difference in NaCl intake between the groups. Replacement of NaCl with Smart Salt resulted in a significant reduction in SBP over 8 weeks (-7.5 mmHg; p = 0.016. SBP increased (+3.8 mmHg, p = 0.072 slightly in the Regular salt group. The difference in the change of SBP between study groups was significant (p Conclusions The substitution of Smart Salt for Regular salt in subjects with high normal or mildly elevated BP resulted in a significant reduction in their daily sodium intake as well as a reduction in SBP. Trial Registration ISRCTN: ISRCTN01739816

  20. Effect of Wearing the Elevation Training Mask on Aerobic Capacity, Lung Function, and Hematological Variables.

    Science.gov (United States)

    Porcari, John P; Probst, Lauren; Forrester, Karlei; Doberstein, Scott; Foster, Carl; Cress, Maria L; Schmidt, Katharina

    2016-06-01

    Altitude training and respiratory muscle training (RMT) have been reported to improve performance in elite and well-trained athletes. Several devices (altitude and RMT) have been developed to help athletes gain the competitive edge. The Elevation Training Mask 2.0 (ETM) purportedly simulates altitude training and has been suggested to increase aerobic capacity (VO2max), endurance performance, and lung function. Twenty-four moderately trained subjects completed 6 weeks of high-intensity cycle ergometer training. Subjects were randomized into a mask (n = 12) or control (n = 12) group. Pre and post-training tests included VO2max, pulmonary function, maximal inspiration pressure, hemoglobin and hematocrit. No significant differences were found in pulmonary function or hematological variables between or within groups. There was a significant improvement in VO2max and PPO in both the control (13.5% and 9.9%) and mask (16.5% and 13.6%) groups. There was no difference in the magnitude of improvement between groups. Only the mask group had significant improvements in ventilatory threshold (VT) (13.9%), power output (PO) at VT (19.3%), respiratory compensation threshold (RCT) (10.2%), and PO at RCT (16.4%) from pre to post-testing. The trends for improvements in VT and PO at VT between groups were similar to improvements in RCT and PO at RCT, but did not reach statistical significance (VT p = 0.06, PO at VT p = 0.170). Wearing the ETM while participating in a 6-week high-intensity cycle ergometer training program does not appear to act as a simulator of altitude, but more like a respiratory muscle training device. Wearing the ETM may improve specific markers of endurance performance beyond the improvements seen with interval training alone. Key pointsWearing the ETM during a 6-week high-intensity cycle ergometer training program may improve performance variables, such as VO2max, PPO, VT, PO at VT, RCT and PO at RCT.Wearing the ETM did not improve lung function, inspiratory

  1. Fundamental study of the effect of high-salinity brines on the friction and wear properties of stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Pearsall, K.J.; Govin, G.; Eliezer, Z.; Bebout, D.G.; Bachman, A.L. (eds.)

    1981-01-01

    Friction and corrosive wear experiments were performed in a geothermal-geopressured brine and in a 3% NaCl solution in a friction and wear electrolytic cell. The formation of a passive film on 304 stainless steel has a beneficial effect on the magnitude of the coefficient of friction. When pits are electrochemically introduced in the passive film, the friction coefficient becomes even lower than the passive coefficient of friction in the 3% NaCl, but does not significantly change for the brine. The effect of corrosive wear on the surface film is more difficult to assess. Auger spectroscopy was performed on wear surfaces (subjected to both electrochemical and mechanical action) and non-wear surfaces (subjected only to electrochemical action). The surface films formed in 3% NaCl in the non-wear and wear areas including pits consisted of Cr, Fe and Ni in ratios consistent to the bulk material plus 0. In brine the surface film consists of the same elements as above; however, the surface film associated with the non-wear area and the wear area pit show a Cr depletion. Yet, the wear area film is consistent with bulk as in the case of the 3% NaCl.

  2. Cocoa extract intake for 4 weeks reduces postprandial systolic blood pressure response of obese subjects, even after following an energy-restricted diet

    Directory of Open Access Journals (Sweden)

    Idoia Ibero-Baraibar

    2016-03-01

    Full Text Available Background: Cardiometabolic profile is usually altered in obesity. Interestingly, the consumption of flavanol-rich foods might be protective against those metabolic alterations. Objective: To evaluate the postprandial cardiometabolic effects after the acute consumption of cocoa extract before and after 4 weeks of its daily intake. Furthermore, the bioavailability of cocoa extract was investigated. Design: Twenty-four overweight/obese middle-aged subjects participated in a 4-week intervention study. Half of the volunteers consumed a test meal enriched with 1.4 g of cocoa extract (415 mg flavanols, while the rest of the volunteers consumed the same meal without the cocoa extract (control group. Glucose and lipid profile, as well as blood pressure and cocoa metabolites in plasma, were assessed before and at 60, 120, and 180 min post-consumption, at the beginning of the study (Postprandial 1 and after following a 4-week 15% energy-restricted diet including meals containing or not containing the cocoa extract (Postprandial 2. Results: In the Postprandial 1 test, the area under the curve (AUC of systolic blood pressure (SBP was significantly higher in the cocoa group compared with the control group (p=0.007, showing significant differences after 120 min of intake. However, no differences between groups were observed at Postprandial 2. Interestingly, the reduction of postprandial AUC of SBP (AUC_Postprandial 2-AUC_Postprandial 1 was higher in the cocoa group (p=0.016. Furthermore, cocoa-derived metabolites were detected in plasma of the cocoa group, while the absence or significantly lower amounts of metabolites were found in the control group. Conclusions: The daily consumption of cocoa extract within an energy-restricted diet for 4 weeks resulted in a greater reduction of postprandial AUC of SBP compared with the effect of energy-restricted diet alone and independently of body weight loss. These results suggest the role of cocoa flavanols on

  3. Cocoa extract intake for 4 weeks reduces postprandial systolic blood pressure response of obese subjects, even after following an energy-restricted diet

    Science.gov (United States)

    Ibero-Baraibar, Idoia; Suárez, Manuel; Arola-Arnal, Anna; Zulet, M. Angeles; Martinez, J. Alfredo

    2016-01-01

    Background Cardiometabolic profile is usually altered in obesity. Interestingly, the consumption of flavanol-rich foods might be protective against those metabolic alterations. Objective To evaluate the postprandial cardiometabolic effects after the acute consumption of cocoa extract before and after 4 weeks of its daily intake. Furthermore, the bioavailability of cocoa extract was investigated. Design Twenty-four overweight/obese middle-aged subjects participated in a 4-week intervention study. Half of the volunteers consumed a test meal enriched with 1.4 g of cocoa extract (415 mg flavanols), while the rest of the volunteers consumed the same meal without the cocoa extract (control group). Glucose and lipid profile, as well as blood pressure and cocoa metabolites in plasma, were assessed before and at 60, 120, and 180 min post-consumption, at the beginning of the study (Postprandial 1) and after following a 4-week 15% energy-restricted diet including meals containing or not containing the cocoa extract (Postprandial 2). Results In the Postprandial 1 test, the area under the curve (AUC) of systolic blood pressure (SBP) was significantly higher in the cocoa group compared with the control group (p=0.007), showing significant differences after 120 min of intake. However, no differences between groups were observed at Postprandial 2. Interestingly, the reduction of postprandial AUC of SBP (AUC_Postprandial 2-AUC_Postprandial 1) was higher in the cocoa group (p=0.016). Furthermore, cocoa-derived metabolites were detected in plasma of the cocoa group, while the absence or significantly lower amounts of metabolites were found in the control group. Conclusions The daily consumption of cocoa extract within an energy-restricted diet for 4 weeks resulted in a greater reduction of postprandial AUC of SBP compared with the effect of energy-restricted diet alone and independently of body weight loss. These results suggest the role of cocoa flavanols on postprandial blood

  4. Effects of sintering temperatures on microstructure and wear resistance of iron-silica composite

    Science.gov (United States)

    Amir, Adibah; Mamat, Othman

    2015-07-01

    Ceramic particle reinforced into metal base matrix composite has been reported to produce higher strength and wear resistance than its alloys because the ceramic phases can strongly resist abrasion. In this study the iron matrix was reinforced with two compositions of 20 and 25 wt. % fine silica particles. The compacts were produced by using powder metallurgy fabrication technique and sintered at three sintering temperatures: 1000, 1100 and 1200°C. Effects of various sintering temperatures on microstructures and the composite's wear resistance were evaluated via optical and SEM microscopy. Both compositions were also subjected to ball-on-disk wear test. The results showed the reinforcement weight fraction of 20 wt.% of silica and sintering temperature at 1100°C exhibited better result, in all aspects. It possessed higher mechanical properties, it's microstructure revealed most intact reinforcing region and it displayed higher wear resistance during wear test.

  5. Wear resistance of hydrophobic surfaces

    Science.gov (United States)

    Martinez, MA; Abenojar, J.; Pantoja, M.; López de Armentia, S.

    2017-05-01

    Nature has been an inspiration source to develop artificial hydrophobic surfaces. During the latest years the development of hydrophobic surfaces has been widely researched due to their numerous ranges of industrial applications. Industrially the use of hydrophobic surfaces is being highly demanded. This is why many companies develop hydrophobic products to repel water, in order to be used as coatings. Moreover, these coating should have the appropriated mechanical properties and wear resistance. In this work wear study of a hydrophobic coating on glass is carried out. Hydrophobic product used was Sika Crystal Dry by Sika S.A.U. (Alcobendas, Spain). This product is currently used on car windshield. To calculate wear resistance, pin-on-disk tests were carried out in dry and water conditions. The test parameters were rate, load and sliding distance, which were fixed to 60 rpm, 5 N and 1000 m respectively. A chamois was used as pin. It allows to simulate a real use. The friction coefficient and loss weight were compared to determinate coating resistance

  6. Dual factor pulse pressure: body mass index and outcome in type 2 diabetic subjects on maintenance  hemodialysis. A longitudinal study 2003–2006

    Directory of Open Access Journals (Sweden)

    Lydia Foucan

    2008-12-01

    Full Text Available Lydia Foucan1,2, Kheira Hue3, Jocelyn Inamo1, Jacqueline Deloumeaux1,2, Anne Blanchet-Deverly, et al1Research group Clinical Epidemiology and Medicine of the University of Antilles and Guyane, French West Indies; 2Department of Medical Information and Public Health; 3Nephrology and hemodialysis Unit; 4Cardiology Unit, CHU of Pointe-à-Pitre, Guadeloupe, French West Indies; 5Hemodialysis Unit, Clinic of Choisy Sainte Anne, Guadeloupe, French West IndiesBackground: Inverse associations between risk factors and mortality have been reported in epidemiological studies of patients on maintenance hemodialysis (MHD.Objective: The aim of this prospective study was to estimate the effect of the dual variable pulse pressure (PP – body mass index (BMI on cardiovascular (CV events and death in type 2 diabetic (T2D subjects on MHD in a Caribbean population.Methods: Eighty Afro-Caribbean T2D patients on MHD were studied prospectively from 2003 to 2006. Proportional-hazard modeling was used.Results: Of all, 23.8% had a high PP (PP ≥ 75th percentile, 76.3% had BMI < 30 Kg/m2, 21.3% had the dual factor high PP – absence of obesity. During the study period, 23 patients died and 13 CV events occurred. In the presence of the dual variable and after adjustment for age, gender, duration of MHD, and pre-existing CV complications, the adjusted hazard ratio (HR (95% CI of CV events and death were respectively 2.7 (0.8–8.3; P = 0.09 and 2.4 (1.1–5.9; P = 0.04.Conclusions: The dual factor, high PP – absence of obesity, is a prognosis factor of outcome. In type 2 diabetics on MHD, a specific management strategy should be proposed in nonobese subjects with wide pulse pressure in order to decrease or prevent the incidence of fatal and nonfatal events.Keywords: dual factor, pulse pressure, body mass index, type 2 diabetes, outcome

  7. Conjunctival epithelial flap in continuous contact lens wear.

    Science.gov (United States)

    Graham, Andrew D; Truong, Tan N; Lin, Meng C

    2009-04-01

    Composed of sheets of cells detached from the underlying conjunctiva, conjunctival epithelial flap (CEF) is a recently reported phenomenon associated with contact lens wear with potential consequences for ocular health. Although CEF is generally asymptomatic, it is not known to what extent it might increase the longer-term risk of discomfort, inflammatory response, or infection. In this study, we use survival analysis methods to obtain unbiased estimates of the probability of developing CEF, the mean survival time free of CEF, and the effects of age, gender, ethnicity, and contact lens type. Two hundred four subjects were recruited for a continuous wear (CW) study of silicone hydrogel (SiH) and gas permeable (GP) contact lenses. Subjects were examined by optometrists throughout contact lens adaptation and CW periods. Statistical methods included the Kaplan-Meier nonparametric estimator of the survival function and the Cox proportional hazards model for estimating the relative effects of covariates. Of the 204 subjects, 72 (35%) developed CEF. In 64% of cases, CEFs were observed bilaterally. The majority of cases (90.3%) presented with CEF in the superior conjunctiva. Mean survival time free of CEF was longer for GP lenses (94.3 days) than for SiH lenses (76.5 days), and the probability of developing CEF was significantly greater for SiH lenses (p = 0.002). Although there was some evidence that women and non-Asians remain free of CEF longer, the effects of age, gender, and ethnicity were not statistically significant. There was a significantly increased risk of CEF in subjects wearing SiH lenses, compared with GP lenses. Subjects wearing SiH lenses remained free of CEF for a shorter time on average. Further study is needed to determine whether the increased incidence of CEF in CW with SiH lenses poses an increased risk of adverse ocular response or infection.

  8. Predicting extended wear complications from overnight corneal swelling.

    Science.gov (United States)

    Graham, A D; Fusaro, R E; Polse, K A; Lin, M C; Giasson, C J

    2001-12-01

    To examine the hypothesis that the corneal overnight swelling response (ONSR) is a predictor of ocular complications in contact lens extended wear (EW). The Berkeley Contact Lens Extended Wear Study (CLEWS) was a randomized, concurrently controlled clinical trial in which more than 200 subjects in EW with rigid gas-permeable (RGP) lenses were observed for 1 year. After adapting to EW, subjects were randomized to either medium or high oxygen-permeable (Dk) RGP lenses and underwent clinical assessments, keratometry, and corneal pachometry at 3-month intervals. The ONSR was directly related to lens Dk (P = 0.01) and exhibited substantial variability across subjects. The probability of remaining free of complications over time was not significantly lower for subjects with a mild ONSR compared with those with greater edema (P = 0.84). The risk of development of keratopathy was not significantly related to the ONSR (relative risk = 1.00). The corneal ONSR is not a good predictor of ocular complications in 1 year of RGP EW. Lenses that cause little or no corneal edema are not necessarily safer for overnight wear.

  9. Modeling of Complex Wear Behavior Associated with Grid-to-Rod Fretting in Light Water Nuclear Reactors

    Science.gov (United States)

    Blau, P. J.; Qu, J.; Lu, R.

    2016-11-01

    Fretting wear damage to fuel cladding from flow-induced vibrations can be a significant concern in the operation of light water nuclear reactors. For years, research on the grid-to-rod fretting (GTRF) phenomena has been underway in countries where nuclear power production is a significant industry. Under the auspices of the U.S. Department of Energy Consortium for Advanced Simulation of Light Water Reactors, an effort has been underway to develop and test an engineering wear model for zirconium alloy fuel rod cladding against a supporting grid. The multi-stage model accounts for oxide layers and wear rate transitions. This paper describes the basis for a GTRF engineering wear model, the physical significance of the wear factor it contains, and recent progress toward model validation based on a fretting wear testing apparatus that accounts for coolant temperature, pressure, and the presence of periodic impacts (gaps) in grid/rod contact.

  10. Analysing a Relationship Between Wheel Wear and Cutting Forces During Diamond Grinding

    Directory of Open Access Journals (Sweden)

    M. A. Shavva

    2014-01-01

    Full Text Available In diamond grinding cutting forces affect the quality of the machined surface. We can estimate a wear rate of the diamond wheel by the magnitude of the forces and promptly resort to the restoration of its cutting properties. To solve this problem it is necessary to define a relationship between grinding wheel wear and cutting forces. There was no this dependence found in the sources of literature.The forces acting on a single worn diamond grain are considered to find the relationship between wheel wear and cutting forces. The main forces acting on the diamond grain are such as a reaction force of machining material, a frictional force over a worn place of the grain, and a total pressure on the contact surface of the grain and machining material. According to calculation results, in grinding the cutting forces are proportional to the hardness of machining material, and depend on the grain wear, as well as on the process operation conditions.The paper presents a technique for calculating the number of cutting (active grains per unit surface of diamond wheel to determine a total cutting force in grinding. The number of cutting grains depends on the properties of diamond wheel and on the operation conditions of grinding process.During grinding a total cutting force is calculated through the single grain cutting force, the number of cutting grains per unit surface of the grinding wheel and the contact area between the wheel and the work piece. Theoretical calculation of the forces is based on the condition that protrusions of all cutting grains are identical and all grains have a maximum wear, i.e. maximum worn place of grain.Calculations based on proposed theoretical formulas are compared with the calculations from the empirical formulas given in the literature. Varying the operation conditions of grinding makes the comparison. Convergence of results in the range of 5-20% is regarded as acceptable.On the BMSTU base flat diamond grinding of tungsten

  11. Ambulatory Arterial Stiffness Index (AASI) is Unable to Estimate Arterial Stiffness of Hypertensive Subjects: Role of Nocturnal Dipping of Blood Pressure.

    Science.gov (United States)

    Di Raimondo, Domenico; Casuccio, Alessandra; Di Liberti, Rosangela; Musiari, Gaia; Zappulla, Valentina; D'Angelo, Alessandra; Pinto, Antonio

    2017-01-01

    Ambulatory Arterial Stiffness Index (AASI) has been proposed as an indirect and simpler method to estimate the Arterial Stiffness (AS). AASI, calculated from a set of data collected during a 24-hours ambulatory blood pressure monitoring (ABPM), is defined as 1 minus the regression slope of diastolic on systolic blood pressure (BP) values. For a given increase in diastolic BP, the increase in systolic BP is smaller in a compliant compared to a stiff artery; the stiffer the arterial tree, the closer AASI is to 1. AASI was demonstrated to predict cardiovascular mortality, cerebrovascular events and to be associated with target organ damage. Taking into account the almost complete absence of data regarding the ability of AASI to predict the different degree of AS when hypertensives are divided into four classes of dipping in relation to the extent of the nocturnal reduction of BP (extreme dippers, dippers, mild dippers and reverse dippers) aim to clarify the ability of AASI to estimate the different degree of AS of hypertensive subjects with different nocturnal BP profile and resulting in different extent of organ damage. We enrolled 816 subjects (403 men and 413 women) with essential hypertension, referred to the U.O.C of Medicina Interna e Cardioangiologia of the University of Palermo; 173 subjects (71 men and 102 women, mean age 44.4 ± 14.6 years) without a history of hypertension were enrolled as controls. The analysis of data was performed by dividing the population into four categories in relation to the extent of the nocturnal decline of BP: 124 extreme dipper (mean age 54,8 ± 12,4 years, men 46.8 %); 287 dipper (mean age 55,9 ± 14,2 years, men 54,0 %); 271 mild dipper (mean age 61,5 ± 14,7 years, men 52,0 %); 134 reverse dipper (mean age 61,5 ± 14,7 years, men 33.6 %). The mean value of AASI was significantly higher for mild and reverse dippers versus control patients and versus the other categories of dipping. The multiple regression analysis with AASI as

  12. Effect of Febuxostat on Ambulatory Blood Pressure in Subjects With Hyperuricemia and Hypertension: A Phase 2 Randomized Placebo-Controlled Study.

    Science.gov (United States)

    Gunawardhana, Lhanoo; McLean, Lachy; Punzi, Henry A; Hunt, Barbara; Palmer, Robert N; Whelton, Andrew; Feig, Daniel I

    2017-11-04

    Hyperuricemia is associated with hypertension, with elevated serum uric acid levels postulated to have a causal role in the development of hypertension. Consequently, serum uric acid reduction may help lower blood pressure (BP). A Phase 2, double-blind, placebo-controlled trial was conducted to assess the potential BP-lowering effects of the xanthine oxidase inhibitor febuxostat in subjects with hypertension and hyperuricemia (serum uric acid ≥0.42 mmol/L [≥7.0 mg/dL]). Subjects (n=121) were randomized 1:1 to febuxostat 80 mg once daily or to placebo. The primary end point was change from baseline to Week 6 in 24-hour mean ambulatory systolic BP (SBP). Additional end points included the following: change from baseline to Week 3 in 24-hour mean SBP and changes from baseline to Weeks 3 and 6 in 24-hour mean ambulatory diastolic BP, serum uric acid, mean daytime and nighttime ambulatory SBP/diastolic BP, and clinic SBP/diastolic BP. For the overall study population, there were no significant differences between febuxostat and placebo for changes from baseline to Weeks 3 or 6 in ambulatory, daytime or nighttime, or clinic SBP or diastolic BP. However, in a preplanned subgroup analysis, there was a significant decrease in SBP from baseline to Week 6 in subjects with normal renal function (estimated glomerular filtration rate ≥90 mL/min) treated with febuxostat versus placebo; least squares mean difference, -6.7; 95% confidence interval -13.3 to -0.0; P=0.049. This study suggests that febuxostat may lower BP in hyperuricemic patients with hypertension and normal renal function; further studies should be conducted to confirm this finding. URL: http://www.clinicaltrials.gov. Unique identifier: NCT01496469. © 2017 The Authors and Takeda Pharmaceuticals. Published on behalf of the American Heart Association, Inc., by Wiley.

  13. Wear resistance of four types of vacuum-formed retainer materials: a laboratory study.

    Science.gov (United States)

    Raja, Taiyub A; Littlewood, Simon J; Munyombwe, Theresa; Bubb, Nigel L

    2014-07-01

    To investigate the resistance to wear of four different vacuum-formed retainer (VFR) materials: Essix C+, Essix ACE, Duran, and Tru-Tain. Essix C+ is a polypropylene polymer; the other materials are polyethylene co-polymers. The study was undertaken at the Leeds Dental Institute, Leeds, UK, with 26 samples in each group. The specimens were vacuum-formed according to the manufacturers' guidelines, and a custom-made wear-simulation machine was used to conduct the test. Each specimen was subjected to 1000 cycles of the wear simulation, with steatite balls as the antagonist material. The resistance to wear of the VFR materials was evaluated by measuring the maximum wear depth using noncontact, three-dimensional surface profilometry. The wear depth was given in micrometers. The median wear depth was 63.20 µm for the Essix C+ group, 7.88 µm for the Essix ACE group, 9.75 µm for the Duran group, and 12.08 µm for the Tru-Tain group. The Kruskal-Wallis test to compare the four VFR materials detected a statistically significant difference between the groups (P materials-Essix ACE, Duran, and Tru-Tain-exhibited significantly less wear than the polypropylene material, Essix C+.

  14. Evaluation of the wear resistance of new nanocomposite resin restorative materials.

    Science.gov (United States)

    Yesil, Zeynep Duymus; Alapati, Satish; Johnston, William; Seghi, Robert R

    2008-06-01

    The use of composite resins for the restoration of posterior teeth is popular because of the improved performance and appearance of these materials. Wear resistance continues to be of particular importance when restoring large occlusal areas in posterior teeth. The purpose of this study was to evaluate the relative wear characteristics of 2 recently introduced nanofiller-based composite resins (Filtek Supreme, Premise) and compare them to the more traditional microhybrid (Point 4) and microfill (Heliomolar RO) materials that have been used for many years. Six specimens (2 mm thick and 15 mm in diameter) of each material were subjected to 3-body wear tests using the Oregon Health Sciences University Oral Wear Simulator to produce abrasive wear and attrition for all specimens using human enamel as the opposing cusp. Profilometric tracings of the worn surfaces were used to determine the relative abrasive wear, attrition wear, and roughness (Ra) of the composite resin substrate. The mean diameter of the antagonist enamel wear facets was determined under a measuring microscope. Qualitative SEM analysis was also used to assess the surface appearance of the resulting enamel and composite resin wear facets. The data were analyzed by 1-way ANOVA and Tukey's multiple range post hoc test (alpha=.05). The results indicated that the composite resin type did not significantly affect the amount of measured attrition (P=.15) but did significantly affect abrasive wear (P=.02). The conventional microfill composite resin (Heliomolar RO) exhibited significantly less abrasive wear than the nanohybrid material (Premise). There was no significant difference in the average size of the opposing enamel wear facet generated by the different composite resin materials. Heliomolar RO resulted in a significantly rougher surface within the wear track than either nanohybrid composite resin (Premise) or microhybrid composite resin (Point 4) but was not significantly different than nanofilled

  15. Dynamic and kinematic effects in the friction and wear of rubber

    Science.gov (United States)

    Gerrard, David Peter

    Research is presented which focuses on the micro-mechanical processes that dominate the friction and wear of rubber. New test concepts and equipment were developed to study the dynamic and kinematic effects involved in these processes. Several new analytical tools were presented to explain the observed results in quantifiable terms. Experiments conducted on filled NR confirmed that a transition in wear behavior does not occur across a wide range of power inputs. Examination of the debris distributions across the contact revealed that an agglomeration process of intrinsic particles occurs, the extent of which is purely a function of distance from the contact's leading edge. This revelation is used to explain the commonly reported bimodal size distribution of debris generated during rubber wear and to expose the mechanical process that generates intrinsic debris as the primary cause of wear. The effect of contact length (i.e. extent of agglomeration) on corresponding friction and wear levels was studied. The effects of dynamically changing slip orientation on the properties of a coated abrasive and the friction and wear of a filled SBR were studied. The process of removal of intrinsic debris from a rubber surface was described in terms of a micro-mechanical fatigue fracture process that occurs at varying rates that are dependent on the frictional work acting on the average intrinsic nodule. The model was successfully tested against previously published data and new data and was shown to account for pressure and abrasive effects with one set of two constants. The potential effects of pattern morphologies on rubber friction and wear were examined as well. The wear patterns showed a clear tendency to roll up as opposed to peeling back. The intrinsic wear model was then applied to a description of pattern wear by assuming that the rate of intrinsic abrasion across a pattern is simply a function of the local pressure distribution which varies from the front to the back

  16. The measurement of enamel wear by four toothpastes.

    Science.gov (United States)

    Joiner, A; Pickles, M J; Lynch, S; Cox, T F

    2008-02-01

    To determine the enamel abrasivity of three whitening toothpastes and a silica toothpaste and to measure the brushing forces used. Polished human enamel blocks were indented with a Knoop diamond and attached to dentures of adult volunteers. The blocks were brushed ex vivo, twice per day with either a whitening toothpaste containing Perlite (White System), a commercial whitening toothpaste (A and B) or a silica toothpaste. After four and twelve-weeks, one block per subject was removed and the Knoop indent remeasured. From the changes in the indent length, the amount of enamel wear was calculated. The mean enamel wear (sd) for White System, silica toothpaste, whitening toothpaste A and B after four-weeks was 0.14 (0.15), 0.09 (0.16), 0.14 (0.12) and 0.89 (0.93) and after twelve-weeks was 0.24 (0.21), 0.37 (0.73), 0.36 (0.52) and 1.04 (0.98) microm respectively. After four-weeks, the differences in enamel wear between whitening toothpaste B and all other toothpastes were of statistical significance (p whitening toothpastes did not give significantly more enamel wear than a silica toothpaste after twelve-weeks in situ with ex vivo brushing.

  17. A Multi-Stage Wear Model for Grid-to-Rod Fretting of Nuclear Fuel Rods

    Energy Technology Data Exchange (ETDEWEB)

    Blau, Peter Julian [ORNL

    2014-01-01

    The wear of fuel rod cladding against the supporting structures in the cores of pressurized water nuclear reactors (PWRs) is an important and potentially costly tribological issue. Grid-to-rod fretting (GTRF), as it is known, involves not only time-varying contact conditions, but also elevated temperatures, flowing hot water, aqueous tribo-corrosion, and the embrittling effects of neutron fluences. The multi-stage, closed-form analytical model described in this paper relies on published out-of-reactor wear and corrosion data and a set of simplifying assumptions to portray the conversion of frictional work into wear depth. The cladding material of interest is a zirconium-based alloy called Zircaloy-4, and the grid support is made of a harder and more wear-resistant material. Focus is on the wear of the cladding. The model involves an incubation stage, a surface oxide wear stage, and a base alloy wear stage. The wear coefficient, which is a measure of the efficiency of conversion of frictional work into wear damage, can change to reflect the evolving metallurgical condition of the alloy. Wear coefficients for Zircaloy-4 and for a polyphase zirconia layer were back-calculated for a range of times required to wear to a critical depth. Inputs for the model, like the friction coefficient, are taken from the tribology literature in lieu of in-reactor tribological data. Concepts of classical fretting were used as a basis, but are modified to enable the model to accommodate the complexities of the PWR environment. Factors like grid spring relaxation, pre-oxidation of the cladding, multiple oxide phases, gap formation, impact, and hydrogen embrittlement are part of the problem definition but uncertainties in their relative roles limits the ability to validate the model. Sample calculations of wear depth versus time in the cladding illustrate how GTRF wear might occur in a discontinuous fashion during months-long reactor operating cycles. A means to account for grid/rod gaps

  18. Changes in pressure-pain thresholds of the jaw muscles during a natural stressful condition in a group of symptom-free subjects.

    Science.gov (United States)

    Michelotti, A; Farella, M; Tedesco, A; Cimino, R; Martina, R

    2000-01-01

    To investigate the effects of a natural emotional stressor on pressure-pain thresholds (PPTs) of the masticatory muscles of symptom-free subjects. Sixteen healthy dental students were selected before they undertook an academic examination. Sixteen gender-matched students who were not exposed to an examination served as controls. The 2 groups of students were monitored in parallel on 5 separate days over a 1-month period: 2 days before the examination (T1), on the day of the examination (T2), 2 days after (T3), 1 month after (T4), and again after another 2 days (T5). On the day of the examination (T2), the control students were only required to complete a brief, non-demanding questionnaire. On each day, the following parameters were assessed: PPTs of the masseter, the anterior temporalis, and the Achilles tendon; state anxiety; and present stress (measured on a visual analog scale [VAS]). Furthermore, in the students undergoing the examination, venous blood samples for assessment of beta-endorphin levels were obtained at T2 and T5. In the stressed students, the PPTs of the masticatory muscles and the Achilles tendon were significantly lower (analysis of variance [ANOVA], P exam (T1, T3), and state anxiety and present stress were significantly higher (ANOVA, P 0.05). In the control group, PPTs, state anxiety, and present stress did not change significantly (ANOVA, P > 0.05). The results support a relationship between psychologic stress and pressure-pain sensitivity of the masticatory muscles.

  19. Radial artery pulse pressure variation correlates with brachial artery peak velocity variation in ventilated subjects when measured by internal medicine residents using hand-carried ultrasound devices.

    Science.gov (United States)

    Brennan, J Matthew; Blair, John E A; Hampole, Chetan; Goonewardena, Sascha; Vasaiwala, Samip; Shah, Dipak; Spencer, Kirk T; Schmidt, Gregory A

    2007-05-01

    Rapid prediction of the effect of volume expansion is crucial in unstable patients receiving mechanical ventilation. Both radial artery pulse pressure variation (DeltaPP) and change of aortic blood flow peak velocity are accurate predictors but may be impractical point-of-care tools. We sought to determine whether respiratory changes in the brachial artery blood flow velocity (DeltaVpeak-BA) as measured by internal medicine residents using a hand-carried ultrasound (HCU) device could provide an accurate corollary to DeltaPP in patients receiving mechanical ventilation. Thirty patients passively receiving volume-control ventilation with preexisting radial artery catheters were enrolled. The brachial artery Doppler signal was recorded and analyzed by blinded internal medicine residents using a HCU device. Simultaneous radial artery pulse wave and central venous pressure recordings (when available) were analyzed by a blinded critical care physician. A Doppler signal was obtained in all 30 subjects. The DeltaVpeak-BA correlated well with DeltaPP (r = 0.84) with excellent agreement (weighted kappa, 0.82) and limited intraobserver variability (2.8 +/- 2.8%) [mean +/- SD]. A DeltaVpeak-BA cutoff of 16% was highly predictive of DeltaPP > or = 13% (sensitivity, 91%; specificity, 95%). A poor correlation existed between the CVP and both DeltaVpeak-BA (r = - 0.21) and DeltaPP (r = - 0.16). The HCU Doppler assessment of the DeltaVpeak-BA as performed by internal medicine residents is a rapid, noninvasive bedside correlate to DeltaPP, and a DeltaVpeak-BA cutoff of 16% may prove useful as a point-of-care tool for the prediction of volume responsiveness in patients receiving mechanical ventilation.

  20. Evaluation of tribological wear and corrosion in coatings of diamalloy 4060NS deposited by thermal spray

    Science.gov (United States)

    Acuña R, S. M.; Moreno T, C. M.; Espinosa C, E. J.

    2017-12-01

    Surface engineering seeks the development of new techniques to improve the performance and life of components of machines or industrial facilities, always looking for low costs and the least possible environmental damage. Thermal projection is one of the techniques that is based on the projection of particles of compounds and alloys on properly prepared and heated substrates, these particles are driven by a stream of air passing through an oxyacetylene flame which gives the energy to the process; These coatings give the possibility to improve the properties of the materials or the maintenance of components to maximize the availability of service. In order to reduce the damage caused by wear and corrosion of a low carbon AISI 1020 steel, they were coated with a metal based alloy, studying the effect of the cobalt-chromium-silicon-tungsten carbide alloy coating (DIAMALLLOY 4060 NS). The coating was deposited with two different pressures in the gases supplied to the torch, obtaining two flames and working three thicknesses of coating that oscillate between 100-500μm, according to the number of deposited layers, making use of a projection gun Castolin Eutectic. Powder and substrate characterization was performed using X-Ray Diffraction (XRD) techniques, X-Ray Fluorescence (XRF), Scanning Electron Microscopy (SEM), spark emission spectroscopy and metallographic analysis. The results confirm the chemical nature and structure of the powder of the alloy and the substrate to be used, in addition, the thermal stability of the system was verified. The evaluation of the adhesion of the deposited layers was carried out by the implementation of pull-off tests according to ASTM D4541, in order to determine the type of failure that is presented. Mechanical wear was determined using a MT/60/NI microtest tribometer while electrochemical tests were performed using a suitable experimental unit for this purpose, confirming that the substrate exhibits lower wear levels when coated with

  1. Role of plastic deformation in wear of copper and copper - 10-percent-aluminum alloy in cryogenic fuels

    Science.gov (United States)

    Bill, R. C.; Wisander, D. W.

    1973-01-01

    High-purity copper specimens and a copper-aluminum (10%) alloy specimen were subjected to sliding against Type 440 C in cryogenic fuel environments. It was found that virtually all wear occurred by the plastic deformation of a recrystallized layer extending to about 10 micrometers below the wear scar surface of the copper or copper alloy. The wear debris was in the form of a layered structure adhering to the exit region of the wear scar. Measurements on the high purity copper specimens indicated that the wear rate was proportional to the applied load and to the sliding velocity squared. A physical model of the wear process is proposed to account for these observations.

  2. Effects of low-fat dairy intake on blood pressure, endothelial function, and lipoprotein lipids in subjects with prehypertension or stage 1 hypertension

    Directory of Open Access Journals (Sweden)

    Maki KC

    2013-07-01

    Full Text Available Kevin C Maki,1 Tia M Rains,1 Arianne L Schild,1 Mary R Dicklin,1 Keigan M Park,2 Andrea L Lawless,1 Kathleen M Kelley1 1Biofortis Clinical Research, Addison, IL, USA; 2Dairy Research Institute/National Dairy Council, Rosemont, IL, USA Objective: This randomized crossover trial assessed the effects of 5 weeks of consuming low-fat dairy (one serving/day each of 1% fluid milk, low-fat cheese, and low-fat yogurt versus nondairy products (one serving/day each of apple juice, pretzels, and cereal bar on systolic and diastolic blood pressures (SBP and DBP, vascular function (reactive hyperemia index [RHI] and augmentation index, and plasma lipids. Methods: Patients were 62 men and women (mean age 54.5 years, body mass index 29.2 kg/m2 with prehypertension or stage 1 hypertension (mean resting SBP/DBP 129.8 mmHg/80.8 mmHg while not receiving antihypertensive medications. A standard breakfast meal challenge including two servings of study products was administered at the end of each treatment period. Results: Dairy and nondairy treatments did not produce significantly different mean SBP or DBP in the resting postprandial state or from premeal to 3.5 hours postmeal (SBP, 126.3 mmHg versus 124.9 mmHg; DBP, 76.5 mmHg versus 75.7 mmHg, premeal (2.35 versus 2.20 or 2 hours postmeal (2.33 versus 2.30 RHI, and premeal (22.5 versus 23.8 or 2 hours postmeal (12.4 versus 13.2 augmentation index. Among subjects with endothelial dysfunction (RHI ≤ 1.67; n = 14 during the control treatment, premeal RHI was significantly higher in the dairy versus nondairy condition (2.32 versus 1.50, P = 0.002. Fasting lipoprotein lipid values were not significantly different between treatments overall, or in subgroup analyses. Conclusion: No significant effects of consuming low-fat dairy products, compared with low-fat nondairy products, were observed for blood pressures, measures of vascular function, or lipid variables in the overall sample, but results from subgroup analyses

  3. Consideration of Wear Rates at High Velocity

    Science.gov (United States)

    2010-03-01

    Ayers and Second Lieutenant Julius Puentes pro- vided excellent support with dynamic model data, and slipper/rail specimens. Mr. Larry Perkins, Mr...Wear Research . . . . . . . . . . . . . . . . 29 1.10 Key Concepts from the Literature Search . . . . . . . . . 30 II. Metallographic Analysis...to AFIT for physical on-site investigation. 1.4 Description of Wear The literature search revealed that there are many different definitions of wear

  4. The Wear of the Focusing Tube and the Cut-Surface Quality

    Directory of Open Access Journals (Sweden)

    B. Nedic

    2010-06-01

    Full Text Available The wear of the focusing tube is a very important feature of the abrasive water jet machining. Of all rejected focusing tubes, 85% are worn. Similarly, the age of focusing tube influences the cut geometry and quality of machined surface. With regard to the stated, wearing of the focusing tube is subject of this paper. Focusing tube outlet diameter was measured as well as its influence on the surface quality.

  5. Effect of surface treatment on wear behavior of magnesium alloy AZ31

    Directory of Open Access Journals (Sweden)

    Y. Fouad

    2011-03-01

    Full Text Available In the present study, wear test has been performed on wrought magnesium alloy AZ31 samples. The test samples were in different conditions as; in the as cast alloy or after undergoing different surface treatment of the wrought alloy. The surface treatments included ball burnishing, swaging and shot peening. The shot peening is done at two main pressure loads; 0.1 and 0.3 bars, while other parameters are held constant. The test results show that the wear worst results were observed in the as cast sample at pressure load 0.3 bars, while the shot peening sample has the worst wear rate among all samples at pressure load of 0.1 bars. On the other hand, the hardness test showed that the swaged sample has the highest hardness value among all samples.

  6. Wear Characteristics of Polymer -Based Composites

    Science.gov (United States)

    Şahin, Y.; Mirzayev, H.

    2015-11-01

    The dry wear of polytetrafluoroethylene (PTFE)-based composites, including bronze-filled composites (B60), glass-filled composites (G15), and carbon-filled composites (C25), produced by the mold casting method were investigated under different sliding conditions. The Taguchi L27 method and the analysis of variance were used to identify the effect of process parameters on the wear of tested materials. Experimental results showed that the wear resistance of G15 polymer composites was better than those of C25 and B60 ones. The specific wear rate decreased with increasing sliding distance and load, but partly decreased with increasing tensile strength.

  7. Wear Behaviour of Iron Matrix Composite Reinforced by ZTA Particles in Impact Abrasion

    Science.gov (United States)

    Qiu, B.; Xing, S. M.; Dong, Q.

    2017-11-01

    Zirconia toughened alumina (ZTA) particles reinforced high chromium cast iron composites (ZTA/Iron composites) were prepared by a two-step processing method, i.e. mixing particles by the molten metal and cohering by high pressure, which based on the squeeze casting process. The impact wear resistance under different impact energies were investigated using dynamically loaded abrasive wear tester at room temperature. For comparison, the wear tests of high chromium cast iron were also carried out under the same conditions. Worn surfaces of the samples were observed under scanning electron microscopy equipped with an energy dispersive detector. The results showed that the composites have better impact wear resistance than that of high Cr cast iron regardless of impact energy level, and the wear resistance of the two materials all decrease with the increase of the impact energy. The main wear mechanisms of the high Cr cast iron were micro-cutting and fatigue peeling, while the wear of composites occurred through micro-cutting of the matrix (lower impact energy) and breaking and shedding of the reinforced particles (higher impact energy).

  8. Wear resistance of alloy вт-22 with non-ferrous alloys at reverse

    Directory of Open Access Journals (Sweden)

    А.М. Хімко

    2010-01-01

    Full Text Available  The article presents the results of tests of non hardened titanium alloy ВТ-22 with aviation non-ferrous alloys in reverse sliding friction. The main objective of the work is the selection of the optimum combination of materials depending on changes in loading conditions. Study of alloy ВТ-22 wear resistance was carried out in pairs with БрОФ-10-1, БрБ2, БрАЖ-9-4, ВТ-22, МЛ5, Д16Т, 7Х21ГАН5Ш and 95Х18Ш. The dependencies of the materials wear at pressures 10, 20 and 30 Mpa we determined. The linear nature of titanium alloy wear curves indicates that the change in the wear mechanism occurs gradually. The histograms of non-ferrous materials wear and the total wear of the friction pair are presented. It is established that the bronze БрАЖ-9-4 is the most preferable material for contact with non hardened titanium alloy ВТ-22, the least wear among the tested materials. The established coefficients of the titanium alloy ВТ-22 friction in pair with aviation structural non-ferrous alloys are presented. The results of research will be relevant for the engineering industry, where non hardened titanium alloy ВТ-22 in pair with non-ferrous alloys is applied.

  9. A comparative study on the wear behavior of a polymer infiltrated ceramic network (PICN) material and tooth enamel.

    Science.gov (United States)

    Xu, Zhou; Yu, Ping; Arola, Dwayne D; Min, Jie; Gao, Shanshan

    2017-09-20

    To investigate the wear mechanisms of a polymer infiltrated ceramic network (PICN) material, to compare its wear behavior with that of tooth enamel, and to provide evidence relevant to its clinical use. The Vickers hardness (HV) and elastic modulus (E) of a commercial PICN material (ENAMIC) and enamel were measured. Reciprocating wear tests were performed under a ball-on-flat configuration. Three wear pairs were explored including ENAMIC and enamel subjected to Si3N4 ball antagonists and ENAMIC subjected to enamel cusp antagonists. The coefficients of Friction (CoFs) were monitored continuously to 5×104 cycles. The wear depth of ENAMIC, enamel specimens and enamel cusps were quantified using white light interferometry, and the wear morphologies were examined using scanning electron microscopy (SEM) to distinguish the wear mechanisms. The HV of ENAMIC is similar to tooth enamel but the E is much lower. For both materials, the CoFs increased sharply in the early stage and then reached plateaus in the later phase. Throughout the cyclic loading history, ENAMIC exhibited larger wear depths than enamel. However, the damage evolution in ENAMIC was similar to that of enamel as the polymer phase was worn preferentially similar to inter-rod enamel, and then the ceramic phase exfoliated from the wear surface akin to enamel rods. The SEM images showed evidence of few cracks within wear tracks of ENAMIC, in comparison to numerous cracks in tooth enamel. ENAMIC has lower wear resistance than tooth enamel, but it exhibits a wear damage mode similar to tooth enamel. Copyright © 2017. Published by Elsevier Ltd.

  10. Average Ambulatory Measures of Sound Pressure Level, Fundamental Frequency, and Vocal Dose Do Not Differ Between Adult Females With Phonotraumatic Lesions and Matched Control Subjects.

    Science.gov (United States)

    Van Stan, Jarrad H; Mehta, Daryush D; Zeitels, Steven M; Burns, James A; Barbu, Anca M; Hillman, Robert E

    2015-11-01

    Clinical management of phonotraumatic vocal fold lesions (nodules, polyps) is based largely on assumptions that abnormalities in habitual levels of sound pressure level (SPL), fundamental frequency (f0), and/or amount of voice use play a major role in lesion development and chronic persistence. This study used ambulatory voice monitoring to evaluate if significant differences in voice use exist between patients with phonotraumatic lesions and normal matched controls. Subjects were 70 adult females: 35 with vocal fold nodules or polyps and 35 age-, sex-, and occupation-matched normal individuals. Weeklong summary statistics of voice use were computed from anterior neck surface acceleration recorded using a smartphone-based ambulatory voice monitor. Paired t tests and Kolmogorov-Smirnov tests resulted in no statistically significant differences between patients and matched controls regarding average measures of SPL, f0, vocal dose measures, and voicing/voice rest periods. Paired t tests comparing f0 variability between the groups resulted in statistically significant differences with moderate effect sizes. Individuals with phonotraumatic lesions did not exhibit differences in average ambulatory measures of vocal behavior when compared with matched controls. More refined characterizations of underlying phonatory mechanisms and other potentially contributing causes are warranted to better understand risk factors associated with phonotraumatic lesions. © The Author(s) 2015.

  11. Cross friction algometry (CFA): Comparison of pressure pain thresholds between patients with chronic non-specific low back pain and healthy subjects.

    Science.gov (United States)

    Farasyn, Andre; Lassat, Bert

    2016-04-01

    Palpation is widely used to assess muscular sensitivity in clinical settings but still remains a subjective evaluation. This cross-sectional study assessed a newly developed cross-friction algometry making palpation measurable. The objective was to investigate the reliability of pressure pain thresholds obtained using Cross-Friction Algometry (CFA-PPTs) measured at the level of Erector spinae and Gluteus maximus central muscle parts, and to compare the CFA-PPTs between patients with chronic nonspecific low back pain (nCLBP) and matching healthy subjects. Patients presenting nCLBP to GP's and send into a Pain Center and healthy subjects recruited via university ad valvas & flyers distribution. 30 patients with nCLBP were measured for cross-friction algometry. Other evaluations consisted of the Visual Analogue Scale (VAS) and the Oswestry Disability Index (ODI). The inter- and intra-reliability were tested and found to be sufficient. The mean CFA-PPT values of the Erector spinae at levels T8, T10, L1 & L3 and the Gluteus maximus of the nCLBP group were significantly lower (p ≤ 0.001) when compared to the CFA-PPT values of the healthy group. The greatest difference (-58%) was found at L1 Erector spinae level and at the superior part of the Gluteus maximus measuring point (-59%). Within the group of patients with nCLBP it was surprising to notice that there was no significant correlation between all the reference points measured using CFA-PPTs and the outcomes of the VAS and ODI scores. With the aid of CFA, the importance of local muscular disorder in the lumbar part of the Erector spinae and Gluteus maximus in patients with nCLBP is obviously demonstrated, but also reveals the very large inter-individual differences in muscular fibrosis sensitivity and/or pain behavior in daily life. This possibly re-opens the debate on which influences can be put forward as the most important: the central or the peripheral sensitization system. Copyright © 2015 Elsevier Ltd. All

  12. Long-term clinical results: 3 years of up to 30-night continuous wear of lotrafilcon A silicone hydrogel and daily wear of low-Dk/t hydrogel lenses.

    Science.gov (United States)

    Bergenske, Peter; Long, Bill; Dillehay, Sally; Barr, Joseph T; Donshik, Peter; Secor, Glenda; Yoakum, John; Chalmers, Robin L

    2007-03-01

    To summarize results of a 3-year clinical trial assessing subjective and objective experience with lotrafilcon A silicone hydrogel (SH) lenses for up to 30 nights of continuous wear or low-Dk/t daily-wear (LDW) hydrogel lenses. Nineteen sites dispensed SH lenses to 317 subjects (286 current wearers and 31 new wearers) and 2-week replacement LDW lenses to 81 new wearers in a 3-year study. For the SH cohort, limbal redness, conjunctival redness, and corneal neovascularization improved among 23%, 21%, and 13% of eyes, respectively (PDk/t hydrogel lenses. Many biomicroscopy signs and symptoms worsened among neophytes wearing daily-wear low-Dk/t hydrogel lenses. The use of lotrafilcon A lenses may minimize many ocular changes from soft contact lens wear.

  13. Effect of Wearing the Elevation Training Mask on Aerobic Capacity, Lung Function, and Hematological Variables

    Directory of Open Access Journals (Sweden)

    John P. Porcari, Lauren Probst, Karlei Forrester, Scott Doberstein, Carl Foster, Maria L. Cress, Katharina Schmidt

    2016-06-01

    Full Text Available Altitude training and respiratory muscle training (RMT have been reported to improve performance in elite and well-trained athletes. Several devices (altitude and RMT have been developed to help athletes gain the competitive edge. The Elevation Training Mask 2.0 (ETM purportedly simulates altitude training and has been suggested to increase aerobic capacity (VO2max, endurance performance, and lung function. Twenty-four moderately trained subjects completed 6 weeks of high-intensity cycle ergometer training. Subjects were randomized into a mask (n = 12 or control (n = 12 group. Pre and post-training tests included VO2max, pulmonary function, maximal inspiration pressure, hemoglobin and hematocrit. No significant differences were found in pulmonary function or hematological variables between or within groups. There was a significant improvement in VO2max and PPO in both the control (13.5% and 9.9% and mask (16.5% and 13.6% groups. There was no difference in the magnitude of improvement between groups. Only the mask group had significant improvements in ventilatory threshold (VT (13.9%, power output (PO at VT (19.3%, respiratory compensation threshold (RCT (10.2%, and PO at RCT (16.4% from pre to post-testing. The trends for improvements in VT and PO at VT between groups were similar to improvements in RCT and PO at RCT, but did not reach statistical significance (VT p = 0.06, PO at VT p = 0.170. Wearing the ETM while participating in a 6-week high-intensity cycle ergometer training program does not appear to act as a simulator of altitude, but more like a respiratory muscle training device. Wearing the ETM may improve specific markers of endurance performance beyond the improvements seen with interval training alone.

  14. Problems of locomotive wheel wear in fleet replacement

    Directory of Open Access Journals (Sweden)

    L.P. Lingaytis

    2013-08-01

    Full Text Available Purpose. To conduct a research and find out the causes of defects appearing on the wheel thread of freight locomotives 2М62 and SIEMENS ER20CF. Methodology. To find the ways to solve this problem comparing the locomotive designs and their operating conditions. Findings. After examining the nature of the wheel wear the main difference was found: in locomotives of the 2M62 line wears the wheel flange, and in the locomotives SIEMENS ER20CF – the tread surface. After installation on the 2M62 locomotive the lubrication system of flanges their wear rate significantly decreased. On the new freight locomotives SIEMENS ER20CF the flange lubrication systems of the wheel set have been already installed at the factory, however the wheel thread is wearing. As for locomotives 2M62, and on locomotives SIEMENS ER20CF most wear profile skating wheels of the first wheel set. On both locomotive lines the 2М62 and the SIEMENS ER20CF the tread profile of the first wheel set most of all is subject to the wear. After reaching the 170 000 km run, the tread surface of some wheels begins to crumble. There was a suspicion that the reason for crumb formation of the wheel surface may be insufficient or excessive wheel hardness or its chemical composition. In order to confirm or deny this suspicion the following studies were conducted: the examination of the rim surface, the study of the wheel metal hardness and the document analysis of the wheel production and their comparison with the results of wheel hardness measurement. Practical value. The technical condition of locomotives is one of the bases of safety and reliability of the rolling stock. The reduction of the wheel wear significantly reduces the operating costs of railway transport. After study completion it was found that there was no evidence to suggest that the ratio of the wheel-rail hardness could be the cause of the wheel surface crumbling.

  15. Wear monitoring of single point cutting tool using acoustic emission ...

    Indian Academy of Sciences (India)

    was carried out to study the wear monitoring in single point cutting tool using acoustic emission techniques. 2. Propagation of stress wave due to crater wear and flank wear. Figure 1 show the crater wear occurred on the rake face of the tool. This crater wear emits stress wave, which propagates as spherical wave front and ...

  16. Microtomography evaluation of dental tissue wear surface induced by in vitro simulated chewing cycles on human and composite teeth

    Directory of Open Access Journals (Sweden)

    Rossella Bedini

    2012-01-01

    Full Text Available In this study a 3D microtomography display of tooth surfaces after in vitro dental wear tests has been obtained. Natural teeth have been compared with prosthetic teeth, manufactured by three different polyceramic composite materials. The prosthetic dental element samples, similar to molars, have been placed in opposition to human teeth extracted by paradontology diseases. After microtomography analysis, samples have been subjected to in vitro fatigue test cycles by servo-hydraulic mechanical testing machine. After the fatigue test, each sample has been subjected again to microtomography analysis to obtain volumetric value changes and dental wear surface images. Wear surface images were obtained by 3D reconstruction software and volumetric value changes were measured by CT analyser software. The aim of this work has been to show the potential of microtomography technique to display very clear and reliable wear surface images. Microtomography analysis methods to evaluate volumetric value changes have been used to quantify dental tissue and composite material wear.

  17. Effects of low-fat dairy intake on blood pressure, endothelial function, and lipoprotein lipids in subjects with prehypertension or stage 1 hypertension

    Science.gov (United States)

    Maki, Kevin C; Rains, Tia M; Schild, Arianne L; Dicklin, Mary R; Park, Keigan M; Lawless, Andrea L; Kelley, Kathleen M

    2013-01-01

    Objective This randomized crossover trial assessed the effects of 5 weeks of consuming low-fat dairy (one serving/day each of 1% fluid milk, low-fat cheese, and low-fat yogurt) versus nondairy products (one serving/day each of apple juice, pretzels, and cereal bar) on systolic and diastolic blood pressures (SBP and DBP), vascular function (reactive hyperemia index [RHI] and augmentation index), and plasma lipids. Methods Patients were 62 men and women (mean age 54.5 years, body mass index 29.2 kg/m2) with prehypertension or stage 1 hypertension (mean resting SBP/DBP 129.8 mmHg/80.8 mmHg) while not receiving antihypertensive medications. A standard breakfast meal challenge including two servings of study products was administered at the end of each treatment period. Results Dairy and nondairy treatments did not produce significantly different mean SBP or DBP in the resting postprandial state or from premeal to 3.5 hours postmeal (SBP, 126.3 mmHg versus 124.9 mmHg; DBP, 76.5 mmHg versus 75.7 mmHg), premeal (2.35 versus 2.20) or 2 hours postmeal (2.33 versus 2.30) RHI, and premeal (22.5 versus 23.8) or 2 hours postmeal (12.4 versus 13.2) augmentation index. Among subjects with endothelial dysfunction (RHI ≤ 1.67; n = 14) during the control treatment, premeal RHI was significantly higher in the dairy versus nondairy condition (2.32 versus 1.50, P = 0.002). Fasting lipoprotein lipid values were not significantly different between treatments overall, or in subgroup analyses. Conclusion No significant effects of consuming low-fat dairy products, compared with low-fat nondairy products, were observed for blood pressures, measures of vascular function, or lipid variables in the overall sample, but results from subgroup analyses were consistent with the hypothesis that dairy foods might improve RHI in those with endothelial dysfunction. PMID:23901280

  18. Changes in the Eye Microbiota Associated with Contact Lens Wearing

    Directory of Open Access Journals (Sweden)

    Hakdong Shin

    2016-03-01

    Full Text Available Wearing contact lenses has been identified as a risk factor for the development of eye conditions such as giant papillary conjunctivitis and keratitis. We hypothesized that wearing contact lenses is associated with changes in the ocular microbiota. We compared the bacterial communities of the conjunctiva and skin under the eye from 58 subjects and analyzed samples from 20 subjects (9 lens wearers and 11 non-lens wearers taken at 3 time points using a 16S rRNA gene-based sequencing technique (V4 region; Illumina MiSeq. We found that using anesthetic eye drops before sampling decreases the detected ocular microbiota diversity. Compared to those from non-lens wearers, dry conjunctival swabs from lens wearers had more variable and skin-like bacterial community structures (UniFrac; P value = 3.0. The results indicate that wearing contact lenses alters the microbial structure of the ocular conjunctiva, making it more similar to that of the skin microbiota. Further research is needed to determine whether the microbiome structure provides less protection from ocular infections.

  19. Sliding wear resistance of iron aluminides

    Indian Academy of Sciences (India)

    Unknown

    ordered intermetallic alloy (Johnson et al 1990, 1994,. 1996; Maupin et al 1992, 1993; Tu and Liu 1997; Kim and Kim 1998). Maupin et al (1992, 1993) had shown that the Fe3Al alloy having DO3 structure possesses mar- ginally lower wear rate than those with B2 structure. The wear resistance of Fe3Al alloy was found to ...

  20. Effective tool wear estimation through multisensory information ...

    African Journals Online (AJOL)

    Effective tool wear estimation through multisensory information fusion using Artificial Neural Network. ... On-line tool wear monitoring plays a significant role in industrial automation for higher productivity and product quality. In addition, an intelligent system is required to make a timely decision for tool change in machining ...

  1. Truck tyre wear assessment and prediction

    NARCIS (Netherlands)

    Lupker, H.A.; Montanaro, F.; Donadio, D.; Gelosa, E.; Vis, M.A.

    2002-01-01

    Tyre wear is a complex phenomenon. It depends non-linearly on numerous parameters, like tyre compound and design, vehicle type and usage, road conditions and road surface characteristics, environmental conditions (e.g., temperature) and many others. Yet, tyre wear has many economic and ecological

  2. Asphalt wear and pollution transport

    Energy Technology Data Exchange (ETDEWEB)

    Lindgren, Asa [Division of Traffic Engineering, Lulea University of Technology Lulea (Sweden)

    1996-09-06

    Studded tires cause extensive wear of road surfaces during winter producing small particles. Besides transporting different adsorbed pollutants these particles also discharge metal ions by their own natural content. The major part (95%) of the asphalt is composed of stone fractions. The rest consists mainly of bitumen, which contains trace quantities of metals. Laboratory studies in this study have demonstrated different adsorbing properties of metal ions, as well as differences in adsorption when comparing stone materials. Two stone materials, a gabbro and a porphyry, have been tested for their adsorption properties concerning Pb, Cu, Zn and Cd. The gabbro showed better adsorption capacity than the porphyry. Gabbro has coarser grains, it is softer, and also has a higher content of most metals compared to the porphyry. In all tests lead and copper are more adsorbed than zinc and cadmium. All metal ions are released at about the same pH ({approx}4)

  3. Sympathetic Activation Does Not Affect the Cardiac and Respiratory Contribution to the Relationship between Blood Pressure and Pial Artery Pulsation Oscillations in Healthy Subjects.

    Directory of Open Access Journals (Sweden)

    Pawel J Winklewski

    Full Text Available Using a novel method called near-infrared transillumination backscattering sounding (NIR-T/BSS that allows for the non-invasive measurement of pial artery pulsation (cc-TQ and subarachnoid width (sas-TQ in humans, we assessed the influence of sympathetic activation on the cardiac and respiratory contribution to blood pressure (BP cc-TQ oscillations in healthy subjects.The pial artery and subarachnoid width response to handgrip (HGT and cold test (CT were studied in 20 healthy subjects. The cc-TQ and sas-TQ were measured using NIR-T/BSS; cerebral blood flow velocity (CBFV was measured using Doppler ultrasound of the left internal carotid artery; heart rate (HR and beat-to-beat mean BP were recorded using a continuous finger-pulse photoplethysmography; respiratory rate (RR, minute ventilation (MV, end-tidal CO2 (EtCO2 and end-tidal O2 (EtO2 were measured using a metabolic and spirometry module of the medical monitoring system. Wavelet transform analysis was used to assess the relationship between BP and cc-TQ oscillations.HGT evoked an increase in BP (+15.9%; P<0.001, HR (14.7; P<0.001, SaO2 (+0.5; P<0.001 EtO2 (+2.1; P<0.05 RR (+9.2%; P = 0.05 and MV (+15.5%; P<0.001, while sas-TQ was diminished (-8.12%; P<0.001, and a clear trend toward cc-TQ decline was observed (-11.0%; NS. CBFV (+2.9%; NS and EtCO2 (-0.7; NS did not change during HGT. CT evoked an increase in BP (+7.4%; P<0.001, sas-TQ (+3.5%; P<0.05 and SaO2(+0.3%; P<0.05. HR (+2.3%; NS, CBFV (+2.0%; NS, EtO2 (-0.7%; NS and EtCO2 (+0.9%; NS remained unchanged. A trend toward decreased cc-TQ was observed (-5.1%; NS. The sas-TQ response was biphasic with elevation during the first 40 seconds (+8.8% vs. baseline; P<0.001 and subsequent decline (+4.1% vs. baseline; P<0.05. No change with respect to wavelet coherence and wavelet phase coherence was found between the BP and cc-TQ oscillations.Short sympathetic activation does not affect the cardiac and respiratory contribution to the relationship

  4. Complications caused by contact lens wearing.

    Science.gov (United States)

    Beljan, Jasna; Beljan, Kristina; Beljan, Zdravko

    2013-04-01

    Complications in wearing contact lenses are very rare and caused by poor maintenance, over-extended wear and wearing of contact lenses in a polluted environment. Regular control by a professional person can efficiently reduce the number of complications. This paper describes the most common risks factors for complications, and complications of wearing contact lenses with the classification according to the anatomic parts of the eye: eyelids, tear film, limbus, corneal epithelium, corneal stroma and corneal endothelium. Every complication has been described by the characteristic signs and symptoms, etiology and pathology, as well as therapy and prognosis. The paper describes how to select adequate customers as contact lens users, with proper education in order to ensure minimal incidence of complications due to contact lens wear, thus attracting a lot of satisfied and healthy customers.

  5. Biologically Based Restorative Management of Tooth Wear

    Directory of Open Access Journals (Sweden)

    Martin G. D. Kelleher

    2012-01-01

    Full Text Available The prevalence and severity of tooth wear is increasing in industrialised nations. Yet, there is no high-level evidence to support or refute any therapeutic intervention. In the absence of such evidence, many currently prevailing management strategies for tooth wear may be failing in their duty of care to first and foremost improve the oral health of patients with this disease. This paper promotes biologically sound approaches to the management of tooth wear on the basis of current best evidence of the aetiology and clinical features of this disease. The relative risks and benefits of the varying approaches to managing tooth wear are discussed with reference to long-term follow-up studies. Using reference to ethical standards such as “The Daughter Test”, this paper presents case reports of patients with moderate-to-severe levels of tooth wear managed in line with these biologically sound principles.

  6. Two-body wear performance of dental colored zirconia after different surface treatments.

    Science.gov (United States)

    Bai, Yunyang; Zhao, Jing; Si, Wenjie; Wang, Xinzhi

    2016-10-01

    Colored zirconia is widely used in dental clinical practice; however, data pertaining to its wear resistance after different surface treatments are sparse. The purpose of this in vitro study was to evaluate the 2-body wear resistance of dental colored zirconia after different glazing and polishing treatments. Standardized specimens were prepared from dental zirconia (internal and external staining and no staining) and subjected to different surface treatments. The stained zirconia and control ceramics were polished with a Robinson brush and polishing paste or polishing kits, while the nonstained zirconia was airborne-particle abraded and glazed. The specimens were then abraded against steatite antagonists using a pin-on-disk wear tester. The wear depth for the specimens was measured using confocal microscopy. Wear areas on the steatite antagonists were measured by using an optical microscope. Scanning electron microscopy (SEM) was used to evaluate the wear pattern of the zirconia specimens. All data were statistically analyzed with 1-way ANOVA and the Tamhane test for post hoc analysis (α=.05). The surfaces polished using the Robinson brush and paste showed no wear. The wear depth of the unglazed surfaces was 42.27 ±3.21 ∼84.15 ±2.57 μm and 87.75 ±9.36 and 91.76 ±13.58 μm for the glazed surfaces. The antagonist wear area was 1.79 ±0.21 ∼2.69 ±0.34 mm 2 (unglazed) and 3.34 ±0.29 ∼4.51 ±0.88 mm 2 (glazed). SEM revealed chipping fractures, and peeling cracks were observed on the glazed zirconia surfaces, indicating a combination of fatigue and abrasive wear. The results of this in vitro study suggest that highly polished zirconia shows the least wear, including antagonist wear. Furthermore, glazed zirconia can be significantly more abrasive than polished zirconia. The wear properties of internally and externally stained zirconia are similar. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All

  7. Effect of tolvaptan on renal water and sodium excretion and blood pressure during nitric oxide inhibition: a dose-response study in healthy subjects.

    Science.gov (United States)

    Al Therwani, Safa; Rosenbæk, Jeppe Bakkestrøm; Mose, Frank Holden; Bech, Jesper Nørgaard; Pedersen, Erling Bjerregaard

    2017-03-13

    Tolvaptan is a selective vasopressin receptor antagonist. Nitric Oxide (NO) promotes renal water and sodium excretion, but the effect is unknown in the nephron's principal cells. In a dose-response study, we measured the effect of tolvaptan on renal handling of water and sodium and systemic hemodynamics, during baseline and NO-inhibition with L-NMMA (L-NG-monomethyl-arginine). In a randomized, placebo-controlled, double blind, cross over study, 15 healthy subjects received tolvaptan 15, 30 and 45 mg or placebo. L-NMMA was given as a bolus followed by continuous infusion during 60 min. We measured urine output (UO), free water clearance (CH2O), fractional excretion of sodium (FENa), urinary aquaporin-2 channels (u-AQP2) and epithelial sodium channels (u-ENaCγ), plasma vasopressin (p-AVP) and central blood pressure (cBP). During baseline, FENa was unchanged. Tolvaptan decreased u-ENaCγ dose-dependently and increased p-AVP threefold, whereas u-AQP2 was unchanged. During tolvaptan with NO-inhibition, UO and CH2O decreased dose-dependently. FENa decreased dose-independently and u-ENaCγ remained unchanged. Central BP increased equally after all treatments. During baseline, fractional excretion of sodium was unchanged. During tolvaptan with NO-inhibition, renal water excretion was reduced dose dependently, and renal sodium excretion was reduced unrelated to the dose, partly via an AVP dependent mechanism. Thus, tolvaptan antagonized the reduction in renal water and sodium excretion during NO-inhibition. Most likely, the lack of decrease in AQP2 excretion by tolvaptan could be attributed to a counteracting effect of the high level of p-AVP. Clinical Trial no: NCT02078973 . Registered 1 March 2014.

  8. Dynamic SEM wear studies of tungsten carbide cermets. [friction and wear experiments

    Science.gov (United States)

    Brainard, W. A.; Buckley, D. H.

    1975-01-01

    Dynamic friction and wear experiments were conducted in a scanning electron microscope. The wear behavior of pure tungsten carbide and composite with 6 and 15 weight percent cobalt binder was examined, and etching of the binder was done to selectively determine the role of the binder in the wear process. Dynamic experiments were conducted as the tungsten carbide (WC) and bonded WC cermet surfaces were transversed by a 50 micron radiused diamond stylus. These studies show that the predominant wear process in WC is fracture initiated by plastic deformation, and the wear of the etched cermets is similar to pure WC. The presence of the cobalt binder reduces both friction and wear. The cementing action of the cobalt reduces granular separation, and promotes a dense polished layer because of its low shear strength film-forming properties. The wear debris generated from unetched surface is approximately the same composition as the bulk.

  9. Model development of work roll wear in hot strip mill

    Science.gov (United States)

    Liu, Ziying; Guan, Yingping; Wang, Fengqin

    2017-06-01

    This paper, based on the analysis of the main factors(specific roll force, mean roll surface temperature, irregular edge wear and contact arc length) affecting roll wear, designed a new work roll wear model, the test data shows that the model can more accurately reflect the work roll wear, can be on-line prediction of work roll wear. The roll wear curve, including constant wear and irregular edge wear, presents a box shape, and the reasons also are showed in this paper. The top roll wear and bottom roll wear in the same mill are inconsistent, and the reasons are also analysed in this paper. Results show that the construction of the work roll mathematical model accords with the general law of work roll wear and tear; it can more accurately forecast roll wear online.

  10. Adhesive Wear of Rollers in Vacuum

    Science.gov (United States)

    Shaeef, Iqbal; Krantz, Timothy L.

    2012-01-01

    This work was done to support NASA's James Webb Space Telescope that is equipped with a Near Infrared Camera and Spectrograph and Micro Shutter Assembly (MSA). A MSA mechanism's qualification test in cryogenic vacuum at 30deg K for 96K cycles resulted in roller wear and formation of some debris. Lab tests in vacuum were conducted at NASA Glenn Research Center (GRC) to understand the wear of Ti6Al4V mated with 440F steel rollers. Misalignment angle was found to have the most significant effect on debris formation. At misalignment angle of 1.4deg, significant amount of wear debris were formed within 50,000 cycles. Very few wear particles were found for a zero misalignment angle, and the total wear was small even after 367,000 cycles. The mode of wear in all the tests was attributed to adhesion, which was clearly evident from video records as well as the plate-like amalgamated debris material from both rollers. The adhesive wear rate was found to be approximately proportional to the misalignment angle. The wear is a two-way phenomenon, and the mixing of both roller materials in wear debris was confirmed by x-ray fluorescence (XRF) and EDX spectra. While there was a net loss of mass from the steel rollers, XRF and energy dispersive x-ray (EDX) spectra showed peaks of Ti on steel rollers, and peaks of Fe on Ti rollers. These results are useful for designers in terms of maintaining appropriate tolerances to avoid misalignment of rolling elements and the resulting severe wear

  11. Delamination and adhesive wear behavior of alpha-tocopherol-stabilized irradiated ultrahigh-molecular-weight polyethylene.

    Science.gov (United States)

    Wannomae, Keith K; Christensen, Steven D; Micheli, Brad R; Rowell, Shannon L; Schroeder, Dave W; Muratoglu, Orhun K

    2010-06-01

    Wear and delamination of conventional ultrahigh-molecular-weight polyethylene (UHMWPE) components used in total knee arthroplasty can compromise long-term performance. Radiation cross-linking and melt-annealing reduced wear and increased delamination resistance of UHMWPE. An alternative material is the alpha-tocopherol-stabilized irradiated UHMWPE (alphaTPE), with improved mechanical and fatigue properties vs irradiated and melted UHMWPE. We studied the wear and delamination resistance of alphaTPE and conventional UHMWPE (direct compression molded GUR 1050 and Himont 1900) under reciprocating unidirectional motion. Wear resistance was improved, and no delamination was observed in alphaTPE. Accelerated aging did not alter the wear and delamination behavior of alphaTPE. The GUR 1050 UHMWPE showed delamination and pitting when subjected to unidirectional reciprocating motion after accelerated aging. Himont 1900 UHMWPE showed no delamination when subjected to unidirectional reciprocating motion after accelerated aging. alpha-Tocopherol-stabilized irradiated UHMWPE is advanced for use in total knee arthroplasty due to its high resistance to wear, delamination, and oxidation. Copyright 2010 Elsevier Inc. All rights reserved.

  12. Surface Modification by Friction Stir Processing of Low-Carbon Steel: Microstructure Investigation and Wear Performance

    Science.gov (United States)

    Sattari, Behnoosh; Shamanian, Morteza; Salimijazi, Farshid; Salehi, Mehdi

    2018-01-01

    A low-carbon steel sheet with a thickness of 5 mm was subjected to friction stir processing (FSP) by one to four different passes. The microstructures of different regions were characterized using the optical microscopy and electron backscatter diffraction. The Vickers micro-harness was measured at the distance of 200 μm below the processed surfaces. The influence of pass numbers (PNs) on wear resistance was studied in terms of coefficients of friction (CoFs), weight losses and wear rates. SEM topographies of the worn surfaces were also studied to evaluate the wear mechanisms. Microstructure observations showed that Widmänstatten ferrite plates were formed in stir zones (SZs) and heat affected zones. As PN increased, these grains were widened due to the increment of the carbon diffusivity and lengthened because of the high heat input and microstructure anisotropy. Besides, increasing the PN causes increasing of the hardness and wear resistance, simultaneously. Specifically, the wear rate in the SZ was reduced from 2.8 × 10-2 mm3 m-1 in base metal to 0.3 × 10-2 mm3 m-1 in sample which was subjected to 4 FSP passes. However, variation in PN had no considerable effect on CoFs. Oxidative wear mechanism was observed on the worn surface of the steel and the FSPed samples while more debris was formed by increasing the PNs.

  13. ANALYTICAL MODEL OF CALCULUS FOR INFLUENCE THE TRANSLATION GUIDE WEAR OVER THE MACHINING ACCURACY ON THE MACHINE TOOL

    Directory of Open Access Journals (Sweden)

    Ivona PETRE

    2010-10-01

    Full Text Available The wear of machine tools guides influences favorably to vibrations. As a result of guides wear, the initial trajectory of cutting tools motion will be modified, the generating dimensional accuracy discrepancies and deviations of geometrical shape of the work pieces. As it has already been known, the wear of mobile and rigid guides is determined by many parameters (pressure, velocity, friction length, lubrication, material. The choice of one or another analytic model and/or the experimental model of the wear is depending by the working conditions, assuming that the coupling material is known.The present work’s goal is to establish an analytic model of calculus showing the influence of the translation guides wear over the machining accuracy on machine-tools.

  14. "Kicking Up Some Dust": An Experimental Investigation Relating Lunar Dust Erosive Wear to Solar Power Loss

    Science.gov (United States)

    Mpagazehe, Jeremiah N.; Street, Kenneth W., Jr.; Delgado, Irebert R.; Higgs, C. Fred, III

    2013-01-01

    The exhaust from retrograde rockets fired by spacecraft landing on the Moon can accelerate lunar dust particles to high velocities. Information obtained from NASA's Apollo 12 mission confirmed that these high-speed dust particles can erode nearby structures. This erosive wear damage can affect the performance of optical components such as solar concentrators. Solar concentrators are objects which collect sunlight over large areas and focus the light into smaller areas for purposes such as heating and energy production. In this work, laboratory-scale solar concentrators were constructed and subjected to erosive wear by the JSC-1AF lunar dust simulant. The concentrators were focused on a photovoltaic cell and the degradation in electrical power due to the erosive wear was measured. It was observed that even moderate exposure to erosive wear from lunar dust simulant resulted in a 40 percent reduction in power production from the solar concentrators.

  15. Quantifying Cutting and Wearing Behaviors of TiN- and CrNCoated AISI 1070 Steel

    Directory of Open Access Journals (Sweden)

    Ahmet Cakan

    2008-11-01

    Full Text Available Hard coatings such as titanium nitride (TiN and chromium nitride (CrN are widely used in cutting and forming tools against wear and corrosion. In the present study, hard coating films were deposited onto AISI 1070 steels by a cathodic arc evaporation plating (CAVP technique. These samples were subjected to wear in a conventional lathe for investigating the tribological behaviour of coating structure, and prenitrided subsurface composition was characterized using scanning electron microscopy (SEM, line scan analyses and X-ray diffraction (XRD. The wear properties of TiN- and CrNcoated samples were determined using an on-line monitoring system. The results show that TiN-coated samples demonstrate higher wear resistance than CrN-coated samples.

  16. Do daily wear opaquely tinted hydrogel soft contact lenses affect contrast sensitivity function at one meter?

    Science.gov (United States)

    Ozkagnici, Ahmet; Zengin, Nazmi; Kamiş, Omit; Gündüz, Kemal

    2003-01-01

    To investigate the effects of daily wear opaquely tinted hydrogel soft contact lenses on contrast sensitivity functions, as measured using the Pelli-Robson chart viewed at 1 meter. Contrast sensitivity was measured in 48 healthy individuals before and 6 hours after soft contact lens wear. Twenty-four subjects used clear soft contact lenses and 24 used tinted soft contact lenses. The contrast sensitivity scores were significantly decreased monocularly and binocularly (P = 0.000 and P = 0.002, respectively) in the colored contact lens group whereas there were no significant changes in the clear contact lens group (P = 0.317 and P = 0.317, respectively). Color-tinted contact lenses were associated with a reduction of contrast sensitivity function. Therefore, those who wear colored contact lenses should be informed about the possible consequences of tinted contact lens wearing.

  17. Peripheral refraction in myopic children wearing orthokeratology and gas-permeable lenses.

    Science.gov (United States)

    Kang, Pauline; Swarbrick, Helen

    2011-04-01

    To investigate changes in peripheral refraction after orthokeratology (OK) and rigid gas-permeable (GP) lens wear in progressing myopic children and to compare these peripheral defocus changes with reported changes in adults wearing OK. Sixteen myopic children subjects were fitted with an OK lens in one eye for overnight wear and a GP lens in the other eye for daily wear. Central and peripheral refraction were measured at baseline and then after 3 mo of lens wear. At baseline, myopic children showed relative peripheral hyperopia compared with central refraction at and beyond 20° in the temporal visual field (VF) and 30° in the nasal VF. Three months of OK lens wear produced hyperopic shifts in refraction between 30° in the temporal VF and 20° in the nasal VF. Peripheral refraction was similar to center at all positions in the temporal VF while remaining significantly myopic at all locations in the nasal VF. No change in either central or peripheral refraction was found after 3 mo in the eye assigned for GP lens wear. OK significantly reduced myopia in the central 20° VF in myopic children, converting relative peripheral hyperopia measured at baseline to relative peripheral myopia. These changes in children are similar to changes reported in myopic adults wearing OK lenses. No change in either central or peripheral refraction was found after 3 mo of daily GP lens wear. OK lenses can be used to induce myopic defocus in the periphery in myopic children and may thus provide a potential mechanism for myopia control.

  18. Tear film inflammatory mediators during continuous wear of contact lenses and corneal refractive therapy.

    Science.gov (United States)

    González-Pérez, Javier; Villa-Collar, César; Sobrino Moreiras, Tomás; Lema Gesto, Isabel; González-Méijome, José Manuel; Rodríguez-Ares, María Teresa; Parafita, Manuel

    2012-08-01

    To study changes in tear film inflammatory mediators following continuous wear of silicone-hydrogel lenses and corneal refractive therapy with reverse geometry contact lenses. A prospective, case-control study. Twenty-eight subjects had worn silicone-hydrogel lenses on a 30-night continuous wear basis. Thirty-two subjects had worn corneal refractive therapy lenses on an overnight basis. Thirty-two matched control subjects were also recruited. Tear samples were obtained 12 months after initial fitting and assayed using ELISA for cytokines (interleukin (IL)-6 and IL-8), matrix metalloproteinase 9 (MMP-9) and epidermal growth factor (EGF). EGF was significantly increased 12 months after both interventions. IL-6, IL-8 and MMP-9 were significantly increased only after corneal refractive therapy. The inflammatory response for the corneal refractive therapy patients was found to be associated with the degree of myopia corrected and the presence of corneal staining. Moreover, an increased level of MMP-9 and EGF was found to be associated with the presence of corneal-pigmented arc in the corneal refractive therapy group. This research showed long-term increased tear levels of inflammatory markers in subjects wearing corneal refractive therapy lenses when compared with continuous wear of silicone-hydrogel lenses or no lens wear.

  19. Tolerability of 24-hour intraocular pressure monitoring of a pressure-sensitive contact lens.

    Science.gov (United States)

    Lorenz, Katrin; Korb, Christina; Herzog, Nicola; Vetter, Jan M; Elflein, Heike; Keilani, Munir M; Pfeiffer, Norbert

    2013-01-01

    To investigate tolerability and safety of a new diagnostic device for 24-hour intraocular pressure monitoring in healthy subjects and age-matched glaucoma patients. Twenty healthy subjects (group 1) and 20 age-matched glaucoma patients (group 2) were included in this prospective, single-center, open, observational parallel group study. The SENSIMED Triggerfish Sensor is a soft disposable contact lens embedding a telemetry chip and strain gauge sensor for continuous intraocular pressure monitoring. The Sensor was placed in 1 eye for 24 hours. Tolerability was evaluated using a visual analog scale (range, 0 to 100; 0=no discomfort; 100=very severe discomfort). Safety parameters included best corrected visual acuity, pachymetry, epithelial defects, conjunctival erythema, and corneal topography. Mean age was 61.7 years in group 1 and 65.0 years in group 2. Nineteen healthy subjects and 19 glaucoma patients (95%) completed the 24-hour wearing period. Early discontinuation resulted from pain (n=1) or inappropriate fitting of the sensor due to steep corneal radii (n=1). Mean tolerability was 21.8 in group 1 (range, 7 to 67) and 26.8 in group 2 (range, 0 to 71). Corneal epithelial staining (Modified Oxford scale, grade 0 to 4) changed from 0.4 (group 1) and 1.0 (group 2) at baseline to 1.8 (group 1) and 2.8 (group 2) after monitoring. No statistically significant differences could be detected between both groups. This new pressure-sensitive contact lens is tolerable and safe over a 24-hour wearing period in healthy subjects and glaucoma patients. Both normals and glaucoma patients had a similar safety and tolerability profile.

  20. Use of microhardness as a simple means of estimating relative wear resistance of carbide thermal spray coatings: Part 2. wear resistance of cemented carbide coatings

    Science.gov (United States)

    Factor, Michael; Roman, Itzhak

    2002-12-01

    A selection of WC-Co and Cr3C2-25%NiCr coatings produced by plasma spray and high velocity oxygen fuel (HVOF) deposition techniques were subjected to various wear tests designed to simulate abrasion, cavitation, sliding, and particle erosion type wear mechanisms. All of the coatings were at least 200 µm thick and were deposited onto stainless steel substrates. In Part 1 of this contribution, the microstructures of the coatings were characterized and their mechanical properties were assessed using microindentation procedures. In this second part of the article, the behavior of the coatings when subjected to the various wear tests is reported and the utility of microhardness testing as an indication of relative wear resistance is discussed. It is shown that correctly performed, appropriate microhardness measurements are a good indication of abrasion resistance and sliding wear resistance, and also correlate well with cavitation resistance in Cr3C2-NiCr. The measurements were less useful for predicting erosion resistance for both Cr3C2-NiCr and WC-Co, however, and for abrasion resistance when WC-Co was ground against SiC. Here the contribution of micromechanisms involving fracturing and brittle failure is greater than that indicated by the coating microhardness, which is essentially a measurement of resistance to plastic deformation under equilibrium conditions.

  1. Risk factors for contact lens bacterial contamination during continuous wear.

    Science.gov (United States)

    Szczotka-Flynn, Loretta B; Bajaksouzian, Saralee; Jacobs, Michael R; Rimm, Alfred

    2009-11-01

    Microbial contamination of contact lenses is associated with corneal infection and inflammation. This study determined the microbiological, clinical, and demographic factors that are associated with bacterial contamination of a silicone hydrogel contact lens when worn for continuous wear (CW). Two hundred five healthy subjects were enrolled in the Longitudinal Analysis of Silicone Hydrogel Contact Lens Study and were fitted with lotrafilcon A lenses for monthly CW and followed for 1 year. Lenses were aseptically removed after 1 week and 4 months of wear and cultured using an agar sandwich technique. Lids and conjunctiva were routinely cultured at baseline and after 1 week and 4 months of CW. Lenses and ocular sites were considered to have substantial microbial bioburden when they harbored pathogenic organisms or high levels of commensal organisms. Univariate and multivariate logistic regression analyses were conducted to examine whether substantial conjunctival or lid bioburden, subject demographics, lens-wearing history, symptoms, and biomicroscopic signs were associated with lens bioburden. About one third (32.4%) of subjects had substantial bacterial bioburden in either eye across multiple visits. Over half (53.2%) and about one tenth (11.7%) of subjects had substantial lid and conjunctival bioburden, respectively, and 11.2% discontinued because of discomfort. The adjusted odds ratios (and 95% confidence intervals) for presence of substantial lens bioburden were 2.49 (1.17-5.30), 4.24 (1.45-12.40), and 4.11 (1.17-14.46) for substantial lid bioburden, substantial conjunctival bioburden, and lens discomfort, respectively. Bacterial contamination of silicone hydrogel contact lenses is common during CW. Substantial lens bioburden is associated with discomfort precluding successful CW. The presence of substantial lid and conjunctival bioburden is associated with a 2.5-fold and more than fourfold greater risk of substantial lens bioburden and is likely the major route

  2. Crystal Orientation Dependence of Gallium Nitride Wear.

    Science.gov (United States)

    Zeng, Guosong; Sun, Wei; Song, Renbo; Tansu, Nelson; Krick, Brandon A

    2017-10-26

    We explore how crystallographic order and orientation affect the tribological (friction and wear) performance of gallium nitride (GaN), through experiments and theory. Friction and wear were measured in every direction on the c-plane of GaN through rotary wear experiment. This revealed a strong crystallographic orientation dependence of the sliding properties of GaN; a 60° periodicity of wear rate and friction coefficient was observed. The origin of this periodicity is rooted in the symmetry presented in wurtzite hexagonal lattice structure of III-nitrides. The lowest wear rate was found as 0.6 × 10 -7 mm 3 /Nm with , while the wear rate associated with had the highest wear rate of 1.4 × 10 -7 mm 3 /Nm. On the contrary, higher friction coefficient can be observed along while lower friction coefficient always appeared along . We developed a simple molecular statics approach to understand energy barriers associated with sliding and material removal; this calculated change of free energy associated with sliding revealed that there were smaller energy barriers sliding along as compared to the direction.

  3. Wear Characteristics of Metallic Biomaterials: A Review

    Directory of Open Access Journals (Sweden)

    Mohamed A. Hussein

    2015-05-01

    Full Text Available Metals are extensively used in a variety of applications in the medical field for internal support and biological tissue replacements, such as joint replacements, dental roots, orthopedic fixation, and stents. The metals and alloys that are primarily used in biomedical applications are stainless steels, Co alloys, and Ti alloys. The service period of a metallic biomaterial is determined by its abrasion and wear resistance. A reduction in the wear resistance of the implant results in the release of incompatible metal ions into the body that loosen the implant. In addition, several reactions may occur because of the deposition of wear debris in tissue. Therefore, developing biomaterials with high wear resistance is critical to ensuring a long life for the biomaterial. The aim of this work is to review the current state of knowledge of the wear of metallic biomaterials and how wear is affected by the material properties and conditions in terms of the type of alloys developed and fabrication processes. We also present a brief evaluation of various experimental test techniques and wear characterization techniques that are used to determine the tribological performance of metallic biomaterials.

  4. Heterogeneous structure and mechanical hardness of biomedical β-type Ti-29Nb-13Ta-4.6Zr subjected to high-pressure torsion.

    Science.gov (United States)

    Yilmazer, H; Niinomi, M; Nakai, M; Hieda, J; Todaka, Y; Akahori, T; Miyazaki, T

    2012-06-01

    A novel β-type titanium alloy, Ti-29Nb-13Ta-4.6Zr (TNTZ), has been developed as a candidate for biomedical applications. TNTZ exhibits non-toxicity and a low Young's modulus close to that of bone (10-30 GPa). Such a low Young's modulus of this alloy is achieved by comprising a single metastable β phase. Greater mechanical biocompatibility, which implies higher mechanical strength and hardness while maintaining a low Young's modulus, has been aimed for TNTZ. Therefore, strengthening by grain refinement and increasing dislocation density is expected to provide TNTZ high mechanical strength while keeping a low Young's modulus because they keep the original β phase. In this case, high-pressure torsion (HPT) processing is one of the effective ways to obtain these properties simultaneously in TNTZ. Thus, in this study, the effect of HPT processing on the microstructure and mechanical hardness of TNTZ was systematically investigated at rotation numbers (N) of 1 to 20 under a pressure of around 1.25 GPa at room temperature. On the cross sections of TNTZ subjected to HPT processing (TNTZ(HPT)) after cold rolling (TNTZ(CR)) at any rotation number, a heterogeneous microstructure consisting of a matrix and a non-etched band, which is not corroded by etching solution, can be observed. The thickness of non-etched band increases as rotation number and distance from specimen center increase. Both matrix and non-etched band comprise a single β phase, but their grain geometries are different each other. Equiaxed grains and elongated grains are observed in the matrix and the non-etched band, respectively. The equiaxed grain diameter, which is ranged from 155 nm to 44 nm, in the matrix decreases with increasing rotation number. Contrastingly, the elongated grains with a length of around 300 nm and a width of 30 nm, which are nearly constant with rotation number, are observed in the non-etched band. The mechanical hardness of TNTZ(HPT) is consistently much higher than that of

  5. Paleo-tribology: development of wear measurement techniques and a three-dimensional model revealing how grinding dentitions self-wear to enable functionality

    Science.gov (United States)

    Erickson, Gregory M.; Sidebottom, Mark A.; Curry, John F.; Kay, David Ian; Kuhn-Hendricks, Stephen; Norell, Mark A.; Sawyer, W. Gregory; Krick, Brandon A.

    2016-06-01

    In most mammals and a rare few reptilian lineages the evolution of precise dental occlusion led to the capacity to form functional chewing surfaces due to pressures generated while feeding. The complex dental architectures of such teeth and the biomechanics of their self-wearing nature are poorly understood. Our research team composed of paleontologists, evolutionary biologists, and engineers have developed a protocol to: (1) determine the histological make-up of grinding dentitions in extant and fossil taxa; (2) ascertain wear-relevant material properties of the tissues; (3) determine how those properties relate to inter-tissue-biomechanics leading the dental functionality using a three-dimensional Archard’s wear model developed specifically for dental applications; (4) analyze those data in phylogenetic contexts to infer evolutionary patterns as they relate to feeding. Finally we discuss industrial applications that are emerging from our paleontologically-inspired research.

  6. Influence of Lubricant Additives on Friction and Wear Characteristics of Compressor parts under the Alternative Refrigerant

    Science.gov (United States)

    Yamaguchi, Hidehiro; Imai, Hachiro; Yamamoto, Tetsuya; Yamamoto, Tsutomu; Ueki, Yutaka; Takizawa, Kikuo; Fukushima, Kiyoshi

    From the standpoint of lubricative deficit under the alternative refrigerant/lubricants coexistence, the influence of additives on friction and wear characteristics for compressor parts have been investigated by the wear tester reappeared on friction condition similarly to actual compressor. It has been shown that an ester type base oil containing TCP (tricresyl phosphate) as an extreme pressure agents indicates satisfactory lubrication because of its EP effect. However owning to the deterioration of base oil caused by a cresol which is a reactant of TCP, a hydrolysis inhibitor must be necessary. The results indicates that a hydrolysis inhibitor added to POE is able to not only prevent the base oil from deteriorating but also feed the strength into oil films. On the other hands, in such a case that TCP concentration added in an alkylbenzen type base oil is excess or wear track temperature is higher, wear amounts of compressor parts are increased on account of corrosion wear. The reactivity of TCP depends on wear track temperature and its concentration. Consequently, it is possible that EP effect of TCP has been considered in terms of its concentration and temperature to be appropriated.

  7. Dynamic simulation of a displacement-controlled total knee replacement wear tester.

    Science.gov (United States)

    Lanovaz, J L; Ellis, R E

    2008-07-01

    This paper presents a dynamic finite element method (FEM) model of a commercial displacement-controlled total knee replacement (TKR) wear tester. The first goal of the study was to validate the model, which included both the wear tester and the TKR components. Convergence simulations and experimental testing were performed. These included a novel experimental determination of the coefficient of friction and an evaluation of predicted joint contact areas by comparing simulation results with experimental data collected using pressure-sensitive film. The second goal of this study was to develop a procedure for implementing force-based testing protocols on a displacement-controlled TKR wear tester. A standard force-based cyclic wear-testing protocol was simulated using the FEM model and resulting displacement waveforms were extracted. These were used as control inputs to the physical wear tester and an experimental wear test was performed. Reaction loads on the tibial components were measured and compared with the simulated results. The model was capable of accurately predicting the tibial loads throughout the test cycle, verifying the model's contact mechanics. The study demonstrated the use of computational modelling to convert a force-based testing protocol into displacement-based control parameters for use in a displacement-controlled mechanical testing system.

  8. Effect of revised high-heeled shoes on foot pressure and static balance during standing.

    Science.gov (United States)

    Bae, Young-Hyeon; Ko, Mansoo; Park, Young-Soul; Lee, Suk-Min

    2015-04-01

    [Purpose] The purpose of this study was to investigate the effects of revised high-heeled shoes on the foot pressure ratio and static balance during standing. [Subjects and Methods] A single-subject design was used, 15 healthy women wearing revised high-heeled shoes and general high-heeled shoes in a random order. The foot pressure ratio and static balance scores during standing were measured using a SpaceBalance 3D system. [Results] Forefoot and rearfoot pressures were significantly different between the 2 types of high-heeled shoes. Under the 3 conditions tested, the static balance score was higher for the revised high-heeled shoes than for the general high-heeled shoes, but this difference was not statistically significant. [Conclusion] Revised high-heeled shoes are preferable to general high-heeled shoes, as they result in normalization of normalized foot pressure and a positive effect on static balance.

  9. Rolling Contact Fatigue and Wear Behavior of High-Performance Railway Wheel Steels Under Various Rolling-Sliding Contact Conditions

    Science.gov (United States)

    Faccoli, Michela; Petrogalli, Candida; Lancini, Matteo; Ghidini, Andrea; Mazzù, Angelo

    2017-07-01

    An experimental investigation was carried out to study and compare the response to cyclic loading of the high-performance railway wheel steels ER8 EN13262 and SUPERLOS®. Rolling contact tests were performed with the same contact pressure, rolling speed and sliding/rolling ratio, varying the lubrication regime to simulate different climatic conditions. The samples, machined out of wheel rims at two depths within the reprofiling layer, were coupled with UIC 900A rail steel samples. The wear rates, friction coefficients and hardness were correlated with the deformation beneath the contact surface. The crack morphology was studied, and the damage mechanisms were identified. The distribution of crack length and depth at the end of the dry tests was analyzed to quantify the damage. The main difference between the steels lies in the response of the external samples to dry contact: SUPERLOS® is subjected to a higher wear and lower friction coefficient than ER8, and this reduces the density of surface cracks that can propagate under wet contact conditions. The analysis of feedback data from in-service wheels confirmed the experimental results.

  10. Prediction of Wear in Crosslinked Polyethylene Unicompartmental Knee Arthroplasty

    Directory of Open Access Journals (Sweden)

    Jonathan Netter

    2015-05-01

    Full Text Available Wear-related complications remain a major issue after unicompartmental arthroplasty. We used a computational model to predict knee wear generated in vitro under diverse conditions. Inverse finite element analysis of 2 different total knee arthroplasty designs was used to determine wear factors of standard and highly crosslinked polyethylene by matching predicted wear rates to measured wear rates. The computed wear factor was used to predict wear in unicompartmental components. The articular surface design and kinematic conditions of the unicompartmental and tricompartmental designs were different. Predicted wear rate (1.77 mg/million cycles was very close to experimental wear rate (1.84 mg/million cycles after testing in an AMTI knee wear simulator. Finite element analysis can predict experimental wear and may reduce the cost and time of preclinical testing.

  11. Clinical and Wear Analyses of 9 Large Metal-on-Metal Total Hip Prostheses.

    Science.gov (United States)

    Koper, M C; Mathijssen, N M C; Witt, F; Morlock, M M; Vehmeijer, S B W

    2016-01-01

    Metal-on-Metal (MoM) total hip arthroplasties (THA) are associated with pseudotumor formation and high revision rates. This prospective study analysed the clinical and wear analyses of 9 large Metal-on-Metal (MoM) total hip arthroplasties (THA) to understand the underlying mechanisms of failure. The MoM bearings were revised for multiple reasons; the main reason was pseudotumor formation. From 2006 till 2010 the Reinier de Graaf Hospital implanted 160 large head M2a-Magnum™ (Biomet Inc. Warsaw, Indiana, USA) THAs in 150 patients. The first year, 9 bearings were revised and analysed at the Biomechanics Section, Hamburg University of Technology, Germany. We performed clinical (Harris Hip Score, radiographic analysis, blood cobalt and chromium) and wear analysis (implant, tissue and fluid) of the 9 bearings. Since this study did not fall under the scope of the Medical Research Involving Human Subjects Act in The Netherlands, no ethical approval was necessary. In this prospective study all patient details were anonymized by the corresponding author, all other authors were blinded during the research and wear analyses. Patients with bilateral MoM implants were excluded. The 9 bearings had a median (IQR) survival of 41.0 (25) months in situ. From these bearings, three showed no noticeable wear. The median (IQR) head wear volume was 3.2 (3.6) mm3 and maximum wear depth 0.02 (0.02) mm. For the cup the median (IQR) wear volume was 0.23 (0.3) mm3 with a maximum wear depth of 0.03 (0.05) mm. An early identification of parameters related to failure of the MoM THA, such as pain, decreased range of motion, radiographic changes and high levels of blood cobalt and chromium is of great importance for patient's quality of life. Especially now patients and surgeons face the long term effects of all these bearings still in situ. This study reports the clinical and wear analyses of 9 MoM THA. In the majority of this group the reason for revision was pseudotumor formation. Most

  12. Multiscale Modeling of Wear Degradation in Cylinder Liners

    KAUST Repository

    Moraes, Alvaro

    2014-03-20

    Every mechanical system is naturally subjected to some kind of wear process that, at some point, will cause failure in the system if no monitoring or treatment process is applied. Since failures often lead to high economical costs, it is essential both to predict and to avoid them. To achieve this, a monitoring system of the wear level should be implemented to decrease the risk of failure. In this work, we take a first step into the development of a multiscale indirect inference methodology for state-dependent Markovian pure jump processes. This allows us to model the evolution of the wear level and to identify when the system reaches some critical level that triggers a maintenance response. Since the likelihood function of a discretely observed pure jump process does not have an expression that is simple enough for standard nonsampling optimization methods, we approximate this likelihood by expressions from upscaled models of the data. We use the Master Equation (ME) to assess the goodness-of-fit and to compute the distribution of the hitting time to the critical level.

  13. Predicting the Wear of High Friction Surfacing Aggregate

    Directory of Open Access Journals (Sweden)

    David Woodward

    2017-05-01

    Full Text Available High friction surfacing (HFS is a specialist type of road coating with very high skid resistance. It is used in the UK at locations where there is significant risk of serious or fatal accidents. This paper considers the aggregate used in HFS. Calcined bauxite is the only aggregate that provides the highest levels of skid resistance over the longest period. No naturally occurring aggregate has been found to give a comparable level of in-service performance. This paper reviews the historical development of HFS in the UK relating to aggregate. In-service performance is predicted in the laboratory using the Wear test which subjects test specimens to an estimated 5–8 years simulated trafficking. Examples are given of Wear test data. They illustrate why calcined bauxite performs better than natural aggregate. They show how the amount of calcined bauxite can be reduced by blending with high skid resistant natural aggregates. Data from the Wear test can be related to every HFS laboratory experiment and road trial carried out in the UK for over the last 50 years. Anyone considering the prediction of HFS performance needs to carefully consider the data given in this paper with any other test method currently being considered or used to investigate HFS.

  14. Investigation into Transient Flow in a Centrifugal Pump with Wear Ring Clearance Variation

    Directory of Open Access Journals (Sweden)

    Houlin Liu

    2014-04-01

    Full Text Available The leakage flow paths in the sidewall gaps of centrifugal pumps are of significant importance for numbers of effects. The paper is concerned with the transient flow in the leakage flow paths with wear ring clearance variation. For this purpose, numerical simulations of the whole pump were carried out. The grid dependence and yplus check were performed first. Additionally, experimental data of performance characteristic and pressure fluctuation inside the sidewall gap was used to validate the numerical results. The transient velocity fields inside the sidewall gaps during one blade passage period were simulated. And the leakage through the wear ring gap was obtained for all operating points investigated. To have a better idea of attenuation and propagation of pressure inside the sidewall gap, the unsteady pressure distributions in the gap were calculated. Additionally, the surfaces of the impeller were divided into four parts. The fluid force on each part was expressed as a percentage of the total radial force. Through comparing the flow fields, the pressure distributions, and the radial force between the pumps with different wear ring clearances, the effects of the wear ring clearance were discussed in detail. The results can be used to guide the optimum design of the pump sidewall gaps.

  15. Impact of NiB Coating on the Efficiency, Scuffing, and Wear of Gear Contacts

    Science.gov (United States)

    2013-05-01

    nozzle. The loading arm applied a normal force through a controlled proportional valve leading to a pneumatic cylinder. The pressure regulator...million cycles, while in certain tests this was reduced to every 2 million cycles to more accurately document the wear rate. A suspension criterion

  16. The measurement of enamel wear of two toothpastes.

    Science.gov (United States)

    Joiner, Andrew; Weader, Elizabeth; Cox, Trevor F

    2004-01-01

    The aim of this study was to compare the enamel abrasivity of a whitening toothpaste with a standard silica toothpaste. Polished human enamel blocks (4 x 4 mm) were indented with a Knoop diamond. The enamel blocks were attached to the posterior buccal surfaces of full dentures and worn by adult volunteers for 24 hours per day. The blocks were brushed ex vivo for 30 seconds, twice per day with the randomly assigned toothpaste (n = 10 per treatment). The products used were either a whitening toothpaste containing Perlite or a standard silica toothpaste. After four, eight and twelve weeks, one block per subject was removed and the geometry of each Knoop indent was re-measured. From the baseline and post-treatment values of indent length, the amount of enamel wear was calculated from the change in the indent depth. The mean enamel wear (sd) for the whitening toothpaste and the standard silica toothpaste after four weeks was 0.20 (0.11) and 0.14 (0.10); after 8 weeks was 0.44 (0.33) and 0.18 (0.17), and after 12 weeks was 0.60 (0.72) and 0.67 (0.77) microns respectively. After four, eight and twelve weeks, the difference in enamel wear between the two toothpastes was not of statistical significance (p > 0.05, 2 sample t-test) at any time point. The whitening toothpaste did not give a statistically significantly greater level of enamel wear as compared to a standard silica toothpaste over a 4-, 8- and 12-weeks period.

  17. Wear and Life Characteristics of Microwave-Sintered Copper-Graphite Composite

    Science.gov (United States)

    Rajkumar, K.; Aravindan, S.; Kulkarni, M. S.

    2012-11-01

    Copper-graphite composite is an important tribological material used in electrical sliding contact applications like electrical brushes in motors and generators. The electrical sliding contact experiences multiple stresses such as mechanical pressure and temperature. Traditional life tests under normal operating condition would be a time-consuming process due to the longer expected life of the composite. Accelerated wear testing was carried out to evaluate the life characteristics of the composite. This work focuses on evaluation of tribological performance of microwave-sintered copper-graphite composite using accelerated wear testing methodology using high temperature pin-on-disc tribometer. Microstructural studies of worn out surfaces were carried out using SEM with EDAX. Reliability and analysis on life characteristics were performed on the time-to-failure data using temperature-nonthermal-accelerated life-stress model. The obtained times-to-failure data from the accelerated wear testing was extrapolated to normal usage condition. Temperature and pressure are significantly affecting the wear performance. Self-lubricating action of graphite and improvement in wear resistance is helpful in extending the life of copper graphite composite. The life of the composite obtained through testing at mean and 99% reliability are 18,725 and 16,950 h, respectively.

  18. Risk factors for contact lens-induced papillary conjunctivitis associated with silicone hydrogel contact lens wear.

    Science.gov (United States)

    Tagliaferri, Angela; Love, Thomas E; Szczotka-Flynn, Loretta B

    2014-05-01

    Contact lens-induced papillary conjunctivitis (CLPC) continues to be a major cause of dropout during extended wear of contact lenses. This retrospective study explores risk factors for the development of CLPC during extended wear of silicone hydrogel lenses. Data from 205 subjects enrolled in the Longitudinal Analysis of Silicone Hydrogel Contact Lens study wearing lotrafilcon A silicone hydrogel lenses for up to 30 days of continuous wear were used to determine risk factors for CLPC in this secondary analysis of the main cohort. The main covariates of interest included substantial lens-associated bacterial bioburden and topographically determined lens base curve-to-cornea fitting relationships. Additional covariates of interest included history of adverse events, time of year, race, education level, gender, and other subject demographics. Statistical analyses included univariate logistic regression to assess the impact of potential risk factors on the binary CLPC outcome and Cox proportional hazards regression to describe the impact of those factors on time-to-CLPC diagnosis. Across 12 months of follow-up, 52 subjects (25%) experienced CLPC. No associations were found between the CLPC development and the presence of bacterial bioburden, lens-to-cornea fitting relationships, history of adverse events, gender, or race. Contact lens-induced papillary conjunctivitis development followed the same seasonal trends as the local peaks in environmental allergens. Lens fit and biodeposits, in the form of lens-associated bacterial bioburden, were not associated with the development of CLPC during extended wear with lotrafilcon A silicone hydrogel lenses.

  19. The effects of daily wear contact lenses on goblet cell density.

    Science.gov (United States)

    Connor, C G; Campbell, J B; Steel, S A; Burke, J H

    1994-11-01

    Some patients can wear contact lenses with a low tear breakup time while others with an identical tear breakup time cannot wear lenses. This suggests the current method of tear film assessment is inadequate at differentiating between these two types of patients. The study attempts to expand our knowledge of the tear film with special attention directed to a critical yet little studied component: mucin. Mucin is vital to maintenance of the tear film and functions as a tear film stabilizer. The condition of the precorneal tear film is a major determinant in the success of contact lens wear. Eighteen subjects free of ocular surface disease who had never worn contact lenses had the goblet cell density of their inferior bulbar conjunctiva determined by impression cytology. The subjects were then fit in a 38 percent water polymacon lens and their goblet cell density determined on a monthly basis for 6 months. Nearly a 2-fold increase in goblet cell density was observed in 88 percent of the subjects over the 6-month period. The first statistically significant increase occurred 5 months after the initiation of lens wear when the goblet cell density rose from 4.19-7.84 percent. We speculate the increase in goblet cells is an adaptive response of the ocular surface to a coated daily wear contact lens.

  20. A Numerical Study on Contact Condition and Wear of Roller in Cold Rolling

    Directory of Open Access Journals (Sweden)

    Qichao Jin

    2017-09-01

    Full Text Available An accurate determination of the contact pressure and local sliding in a cold rolling process is an essential step towards the prediction of the roller’s life due to wear damage. This investigation utilized finite element analysis to quantify the local contact pressure and local sliding over the rolling bite in a plate cold rolling process. It was the first study to quantify the local sliding distance in a rolling process using the Finite Element Analysis (FEA. The numerical results indicate that the local contact pressure over the rolling bite demonstrates a hill profile, and the peak coincides with the neutral plane. The local sliding distance over the rolling bite demonstrates a double-peak profile with the two peaks appearing at the forward slip and backward slip zones respectively. The amplitude of sliding distance in the backward slip zone is larger than that in the forward slip zone. A stick zone was confirmed between the forward slip and backward slip zones. According to a parametric study, the local contact pressure and sliding distance decrease when the thickness reduction is reduced or the diameter of the roller is decreased. The location of the neutral plane always presents at the rolling exit side of the rolling bite’s center. The size of the stick zone enlarges and the sizes of slip zones shrink significantly when the friction coefficient is increased. Finally, a novel concept of wear intensity was defined to examine the wear of the roller based on the local contact pressure and local sliding distance. The results show that a two-peak wear response exists in the backward and forward slip zones. The magnitude of the wear in the backward slip zone is larger than that in the forward slip zone. For a given roller and blank material combination, using a smaller thickness reduction, a smaller diameter roller and a higher friction coefficient condition can reduce the wear of the roller for a single rolling cycle. The current paper

  1. How Chronic Fatigue Syndrome Wears Patients Out

    Science.gov (United States)

    ... https://medlineplus.gov/news/fullstory_167452.html How Chronic Fatigue Syndrome Wears Patients Out Study suggests body amplifies fatigue ... what it's like for those who struggle with chronic fatigue syndrome, and researchers suggest in a new report that ...

  2. Wear and repair of stainless steel crowns

    National Research Council Canada - National Science Library

    Yilmaz, Y; Kara, N Belduz; Yilmaz, A; Sahin, H

    2011-01-01

    The purpose of this study was to determine the wear of stainless steel crowns (SSCs) in children, and compare the extent of microleakage in SSCs that had been repaired using either a cermet glass-ionomer cement...

  3. Implant wear mechanisms-basic approach

    Energy Technology Data Exchange (ETDEWEB)

    Bhatt, Himanshu; Goswami, Tarun [Department of Biomedical, Industrial and Human Factors Engineering, Wright State University, Dayton, OH 45435 (United States)

    2008-12-15

    Numerous parameters control the long-term performance of a total hip joint arthroplasty. The articulating motions between the femoral and the acetabular components produce wear debris in a hip implant. Surface roughness, clearance, coefficient of friction and sliding distance are found to be contributing parameters that affect wear rates. Wear produced in a hip implant leads to the loosening of a hip prosthesis and thus failure of the hip implant. Ultra-high-molecular-weight polyethylene (UHMWPE) has been successfully used as an acetabular weight bearing component in the THR applications. Cross-linked UHMWPE was found to improve the lifespan of an artificial hip. A gradient cross-linking of UHMWPE has been observed to be a recent development in implant bearing materials. During in vitro studies, gradient cross-linked UHMWPE showed nearly undetectable wear rates. (topical review)

  4. Mammalian dental function and wear: A review

    Directory of Open Access Journals (Sweden)

    Peter S. Ungar

    2015-03-01

    Full Text Available This paper presents a brief synopsis of work on relationships between mammalian tooth form and function, and considers the role of dental wear in studies of mammal teeth. Mammalian teeth function both as guides for chewing and as tools for initiating and propagating cracks through food items. They tend to vary in form and structure with the mechanical properties of foods a species has evolved to eat; and we can learn a lot about relationships between teeth and diet by comparing species. One area of special interest is tooth wear. Dental structure and chemistry combine in ways that lead wear to sculpt occlusal surfaces so a tooth can develop or maintain its functional efficiency. Dental wear, especially that on microscopic scales, can also serve as a proxy for diet in fossil species, as specific types of food leave distinctive patterns.

  5. Prediction of wear rates in comminution equipment

    DEFF Research Database (Denmark)

    Jensen, Lucas Roald Dörig; Fundal, Erling; Møller, Per

    2010-01-01

    Raw material comminution equipment may be exposed to excessive wear, which makes it difficult to operate minerals processing plants continuously because lengthy and unplanned shut-downs interrupt the overall process. In general, most comminution equipment is fine-tuned to operate at low vibrations...... and to achieve guaranteed performance. From an economical point of view, it is always preferred to replace all worn parts during the planned maintenance shutdowns. When operating comminution equipment, the wear rate receives little attention and is considered a secondary matter. However, experience shows......-resistant high chromium white cast iron (21988/JN/HBW555XCr21), a heat-treated wear resistant steel (Hardox 400) and a plain carbon construction steel (S235). Quartz, which accounts for the largest wear loss in the cement industry, was chosen as abrasive. Other process parameters such as velocity (1–7 m...

  6. The effect of clothes on sphygmomanometric blood pressure measurement in hypertensive patients.

    Science.gov (United States)

    Pinar, Rukiye; Ataalkin, Sıddıka; Watson, Roger

    2010-07-01

    To test whether there is any difference between blood pressure readings with patients wearing clothes under the manometer's cuff and not wearing clothes. The few studies published on this subject have shown that blood pressure measurements give similar results whether the patients' arm is covered by clothing or not. However, it has not been clarified whether this is also true in hypertensive patients. Blood pressure was measured on non-sleeved arm, sleeved arm and again on non-sleeved arm in 258 hypertensive patients using a mercury-filled column sphygmomanometer. Three nurses who were experienced and specially trained for the study performed blood pressure measurements. They were unaware of the purpose of the research. Measuring blood pressure with the manometer's cuff over participant's sleeved arm did not differ significantly from non-sleeved arm measurements. Sleeves have no effect on blood pressure results. Blood pressure readings taken over the sleeves will be much more practical and time saving in busy departments like emergency rooms, during disasters like earthquake where decisions have to make in minutes. Additionally, it will be time saving for general health screening surveys. Finally, it may have preferable because of hygiene concerns, patient privacy and religious beliefs. © 2010 Blackwell Publishing Ltd.

  7. Effect of Wearing Socks, Stockings and Leather Shoe on Shoe Microclimate and Wear Comfort

    OpenAIRE

    三ツ井, 紀子; Michiko, Mitsui

    2001-01-01

    The effects of socks, stockings and leather shoe on wear comfort and microclimate between shoe and skin while exercising has been studied by seven women under laboratory conditions. Temperature and absolute humidity in wearing socks or stockings were higher than barefooted. Further under wearing shoes and socks or stockings they are increased. Temperature and absolute humidity at the measuring point were the highest between the first and the second toes. Inside socks or stockings with shoes a...

  8. Accommodation in young adults wearing aspheric multifocal soft contact lenses

    Science.gov (United States)

    Lindskoog Pettersson, Anna; Wahlberg Ramsay, Marika; Lundström, Linda; Rosén, Robert; Nilsson, Maria; Unsbo, Peter; Brautaset, Rune

    2011-11-01

    The aim of the present project was to investigate accommodative behavior in young adults and adolescents fitted with an aspheric multifocal (center distance) contact lens with focus on evaluating whether these lenses can be an alternative treatment for subjects in which a reduced level of blur and thereby accommodation in near vision is aimed at. Twenty normal subjects aged between 21 and 35 years participated in the study. Aberrometry was perfomed using a Zywave™ aberrometer, first on the uncorrected eyes of all subjects, and again while the subjects wore a multifocal contact lens with a +1.00 add. A Shin-Nippon N Vision-K 5001 Autoref-Keratometer was used to measure accommodative response with two different refractive corrections: (1) habitual spectacle correction only, and (2) habitual correction and a aspheric multifocal (center distance) contact lens. Four hours of adaptation to the lens was allowed. The lag when wearing only the habitual spectacles was compared with the lag while wearing both the habitual spectacles and the aspheric multifocal contact lens. The mean lag of accommodation for the subject group was 0.85 D (±0.57 SD) and 0.75 D (±0.52 SD) without and with the multifocal lens, respectively. Statistical analyses showed no difference in lag (t = 0.8479, p = 0.407) with and without the lens. In conclusion, young normal subjects do not relax accommodation when fitted with aspheric multifocal center distance lenses when the addition is +1.00. It is therefore unlikely that subjects with accommodative ability, in whom the treatment purpose is to reduce blur and thereby accommodation, can be effectively treated with such lenses.

  9. Third abrasive wear mode: is it possible?

    Directory of Open Access Journals (Sweden)

    Ronaldo Câmara Cozza

    2014-04-01

    Full Text Available The objective of this paper is to propose an initial discussion on the characterization of a third abrasive wear mode. The results obtained in a previous work [1] under different test conditions revealed the occurrence of the superposition of the “rolling” and “grooving” abrasive wear modes. This phenomenon was denoted “micro-rolling abrasion” due to the observation that “rolling abrasion” was found to act on “grooving abrasion”.

  10. [Study on friction and wear properties of dental zirconia ceramics processed by microwave and conventional sintering methods].

    Science.gov (United States)

    Guoxin, Hu; Ying, Yang; Yuemei, Jiang; Wenjing, Xia

    2017-04-01

    This study evaluated the wear of an antagonist and friction and wear properties of dental zirconia ceramic that was subjected to microwave and conventional sintering methods. Ten specimens were fabricated from Lava brand zirconia and randomly assigned to microwave and conventional sintering groups. A profile tester for surface roughness was used to measure roughness of the specimens. Wear test was performed, and steatite ceramic was used as antagonist. Friction coefficient curves were recorded, and wear volume were calculated. Finally, optical microscope was used to observe the surface morphology of zirconia and steatite ceramics. Field emission scanning electron microscopy was used to observe the microstructure of zirconia. Wear volumes of microwave and conventionally sintered zirconia were (6.940±1.382)×10⁻², (7.952±1.815) ×10⁻² mm³, respectively. Moreover, wear volumes of antagonist after sintering by the considered methods were (14.189±4.745)×10⁻², (15.813±3.481)×10⁻² mm³, correspondingly. Statistically significant difference was not observed in the wear resistance of zirconia and wear volume of steatite ceramic upon exposure to two kinds of sintering methods. Optical microscopy showed that ploughed surfaces were apparent in zirconia. The wear surface of steatite ceramic against had craze, accompanied by plough. Scanning electron microscopy showed that zirconia was sintered compactly when subjected to both conventional sintering and microwave methods, whereas grains of zirconia sintered by microwave alone were smaller and more uniform. Two kinds of sintering methods are successfully used to produce dental zirconia ceramics with similar friction and wear properties.
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  11. Contoured, prefabricated foot orthoses demonstrate comparable mechanical properties to contoured, customised foot orthoses: a plantar pressure study.

    Science.gov (United States)

    Redmond, Anthony C; Landorf, Karl B; Keenan, Anne-Maree

    2009-06-16

    Foot orthoses have been demonstrated to be effective in the management of a range of conditions, but there is debate as to the benefits of customised foot orthoses over less expensive, prefabricated devices. In a randomised, cross-over trial, 15 flat-footed participants aged between 18 and 45 years were provided with semi-rigid, customised orthoses and semi-rigid, contoured, prefabricated orthoses. Pressures and forces were measured using an in-shoe system with subjects wearing shoes alone, wearing customised orthoses, and again when wearing contoured prefabricated orthoses. Two weeks acclimatisation was included between cross-over of therapy. Repeated measures ANOVA models with post-hoc, pair-wise comparisons were used to test for differences. When compared to wearing shoes alone, wearing either the customised orthoses or the prefabricated orthoses was associated with increases in force and force time integrals in the midfoot region. Peak and maximum mean pressure and pressure-time, and force-time integrals were reduced in both the medial and lateral forefoot. There were, however, no significant differences between the customised orthoses and the prefabricated orthoses at any site. There was a similar change in loading with both the semi-rigid customised and the semi-rigid prefabricated orthoses when compared to the shoe alone condition. However, while customised devices offered minor differences over prefabricated orthoses in some variables, these were not statistically significant. The results suggest that there may be only minor differences in the effects on plantar pressures between the customised and the less expensive prefabricated orthoses tested in this study, however further research is warranted.

  12. Acanthamoeba keratitis and contact lens wear: static or increasing problem?

    Science.gov (United States)

    Foulks, Gary N

    2007-11-01

    The occurrence of Acanthamoeba keratitis is increasing in the United States because of an expanding population at risk of infection and sporadic outbreaks of infection. Such outbreaks are the result of lapses in contact lens wear and care and of alterations in water quality and water treatment procedures. Although improved techniques in diagnosis are available, better identification of infection alone does not explain an increase in the observed occurrence of the disease. Likewise, there does not appear to be an increase in the virulence or infectivity of the amoebae. Strategies for prevention, including patient education, improved decontaminating agents, maintenance of water treatment standards, and possible immunization of subjects at risk, are needed.

  13. Contact lens wear and the development of squamous metaplasia of the surface cells of the conjunctiva.

    Science.gov (United States)

    Doughty, Michael J

    2011-09-01

    To review the reported effects of contact lens wear on the surface epithelial cells of the human conjunctiva as assessed by conjunctival impression cytology (CIC). A literature search was undertaken to identify reports on the conjunctival health after contact lens wear, principally as assessed using CIC. Of 26 reports identified, 22 examined the bulbar conjunctiva, and 2 examined the tarsal conjunctiva. Just 16 reports provided data from which mean squamous metaplasia grades could be calculated, with the overall grade being just 0.7 on a 0 to 3 scale. Only 13 of these studies provided unambiguous data on the duration of contact lens wear, and only an apparent trend was evident in that grades of squamous metaplasia increased over early years of lens wear. Such a trend was not statistically significant either up to 6 years of average lens wear (P>0.05) or over all studies (P>0.5). The estimated variability in squamous metaplasia was substantially greater when low grades were reported, an observation that either reflects the heterogeneity in the cell response or highlights the difficulty in assigning low grades to cell samples. Based on subjective grading, CIC studies reveal no clearly definable relationship between the duration of contact lens wear and the extent of development of conjunctival squamous metaplasia. Logically, therefore, objective methods to assess squamous metaplasia are needed. Various options for quantitative CIC are discussed, including the use of in vivo confocal microscopy.

  14. Three-dimensional in vitro measurements of tooth wear using fluoridated dentifrices.

    Science.gov (United States)

    Al-Mashhadani, A; Plygkos, I; Bozec, L; Rodriguez, J M

    2016-09-01

    The aim of this study was to compare differences in wear of human enamel and dentine in vitro using a 3D measurement method comparing silica versus non-silica containing fluoridated dentifrices (Colgate Total(™) [CT] or Fluor Protector Gel(™) [FPG]). Mounted native enamel (n = 36) and polished dentine (n = 36) samples were subjected to 10 wear cycles. Each cycle consisted of: (1) 1 hour remineralization in artificial saliva (AS); (2) 10 minute erosion (0.3% citric acid; pH = 2.8); (3) 2 minute toothbrush abrasion in AS (G1, control) or a slurry of 3:1 by weight of AS:dentifrice (G2 = CT; G3 = FPG) under a load of 2 N. Each group contained 12 enamel and 12 dentine samples. Paired pre- and post-wear scans made with a contacting scanner were digitally superimposed using ball bearings as datum. Mean and (SD) enamel wear was G1 = 21.9 μm (6.4); G2 = 15.2 μm (2.8); G3 = 16.9 μm (3.2). Enamel wear was not different between dentifrices (p = 0.99). Both dentifrices resulted in less enamel wear compared to the control (p Dental Association.

  15. Pseudomembranous candidiasis in patient wearing full denture

    Directory of Open Access Journals (Sweden)

    Nurdiana Nurdiana

    2009-06-01

    Full Text Available Background: Oral candidiasis is a common opportunistic infection of the oral cavity caused by an overgrowth of Candida species, the commonest being Candida albicans. Candida albicans is a harmless commensal organism inhabiting the mouths but it can change into pathogen and invade tissue and cause acute and chronic disease. Dentures predispose to infection with Candida in as many as 65% of elderly people wearing full upper dentures. Purpose: The purpose of this case report is to discuss thrush in patient wearing full denture which rapidly developed. Case: This paper report a case of 57 year-old man who came to the Oral Medicine Clinic Faculty of Dentistry Airlangga University with clinical appearance of pseudomembranous candidiasis (thrush. Case Management: Diagnosis of this case is confirmed with microbiology examination. Patient was wearing full upper dentures, and from anamnesis known that patient wearing denture for 24 hours and he had poor oral hygiene. Patient was treated with topical (nystatin oral suspension and miconazole oral gel and systemic (ketoconazole antifungal. Patient also instructed not to wear his denture and cleaned white pseudomembrane on his mouth with soft toothbrush. Conclusion: Denture, habit of wearing denture for 24 hours, and poor oral hygiene are predisposing factors of thrush and it can healed completely after treated with topical and systemic antifungal.

  16. Development and Performance Evaluation of an Abrasive Wear ...

    African Journals Online (AJOL)

    The wear of tillage tools is a major source of economic constraints to local farmers. Estimating wear in the field is time consuming and expensive. Abrasive wear testing machines developed in advanced countries are not available in Ghana. This makes the study of wear related problems at laboratory levels difficult in the ...

  17. Detection and Monitoring of Wear Using Imaging Methods

    NARCIS (Netherlands)

    Zhang, Jindang

    2006-01-01

    Wear is traditionally measured offline. A new methodology for online detection and monitoring of wear has been investigated in this thesis. This methodology consists of design of an online wear testing apparatus and development of techniques for online wear detection and monitoring using imaging

  18. Minimal graphene thickness for wear protection of diamond

    Directory of Open Access Journals (Sweden)

    M. M. van Wijk

    2015-01-01

    Full Text Available We show, by means of molecular dynamics simulations, that the transformation from diamond to amorphous carbon occurring while sliding under pressure can be prevented by having at least two graphene layers between the diamond slabs. The resulting reduction of wear makes this combination of materials suitable for new coatings and micro- and nanoelectromechanical devices. Grain boundaries, vacancies and steps on the diamond surface do not change this prediction. We attribute this behavior to the bonding in layered materials like graphene. The strong in-plane bonding and the weak interlayer interaction that evolves to a strong interlayer repulsion under pressure prevent the transition to amorphous carbon when more than one layer is present.

  19. Wear-resistance of Aluminum Matrix Microcomposite Materials

    Directory of Open Access Journals (Sweden)

    M. Kandeva

    2011-03-01

    Full Text Available A procedure is developed for the study of wear of aluminum alloys AlSi7 obtained by casting, reinforced by TiC microparticles, before and after heat treatment. Tribological study is realized under conditions of friction on counterbody with fixed abrasive. Experimental results were obtained for mass wear, wear rate, wear intensity and wear-resistance of the alloys with different wt% of microparticles.

  20. Effect of wearing fingers rings on the behavioral and psychological symptoms of dementia: An exploratory study.

    Science.gov (United States)

    Yokoi, Teruo; Okamura, Hitoshi; Yamamoto, Tomoka; Watanabe, Katsuya; Yokoi, Shigeko; Atae, Hitoshi; Ueda, Masayuki; Kuwayama, Takahiro; Sakamoto, Shigekazu; Tomino, Saaya; Fujii, Hideo; Honda, Takefumi; Morita, Takayosi; Yukawa, Takafumi; Harada, Nobuko

    2017-01-01

    This study was conducted to examine the effects of an approach that wears finger rings on elderly females with behavioral and psychological symptoms of dementia. The subjects were seven Japanese dementia patients living in elderly nursing homes. A single-case experimental design was adopted for the study. Each study subject was asked to put rings on her finger (from 9:00 to 19:00) for 7 days. The Neuropsychiatric Inventory, scenes of behavioral and psychological symptoms of dementia, interest in wearing rings, self-awareness, and overall profile were determined to assess the effect on the patients of wearing rings. The majority of nursing care providers stated, based on their assessment, that the "irritability/lability" that was noted during the baseline period disappeared during the ring-wearing intervention period in the three patients who displayed an interest in rings. In the assessment of the self-awareness ability, these three women were aware themselves of their intellect collapsing and were capable of conjecturing their own and others' minds. It was commonly seen that the nursing staff, even though they had not been asked to do so by the researchers, told the patients, "Mrs. XX, you look so beautiful" when they found a patient wearing rings. Individuals with low self-esteem are inclined to get angry and display aggression. In subjects with low self-esteem, anger and aggression readily arise when they are slighted by others. Self-esteem is low in those women who are aware of their own status of collapsing intellect. It is concluded that the words of conjuration, "you look so beautiful," which the wearing of the ring per se by the patient elicited from the caregivers heightened the self-esteem and alleviated "irritability/lability" in the study subjects.

  1. The Long-Term Effects of Silicone Hydrogel Contact Lens Wear on Corneal Morphology

    Directory of Open Access Journals (Sweden)

    Yelda Yıldız

    2012-03-01

    Full Text Available Pur po se: To evaluate the effects of silicone hydrogel contact lenses (SHCL on central corneal thickness (CCT, corneal endothelial cell morphology, and tear functions. Ma te ri al and Met hod: Fifty-five eyes of 28 SHCL wearers (Group 1 and 52 eyes of 26 healthy subjects (Group 2 were included in this study’. According to their contact lens wearing time, the contact lens wearing subjects were divided into 2 groups: Group 1a - wearing time less than 1 year and Group 1b - wearing time more than 1 year. CCT, epithelial thickness, corneal endothelial cell morphology, ocular surface disease index score (OSDI, and tear break-up time (TBUT were evaluated. Re sults: In Group 1 and Group 2, the mean CCT was 561.85±39.98 µm and 537.25±27.12 µm, respectively (p: 0.001.The epithelial thickness was 50.38±5.41 µm and 55.64±5.32 µm, respectively (p: 0.001. In Group 1a and Group1 b, the mean CCT was 573.39±33.86 µm and 546.96±42.98 µm (p: 0.014 and the epithelial thickness was 49.51±4.78 µm and 51.50±6.04 µm (p>0.05, respectively. In Group 1, the percentage of endothelial cells larger than 700µ was low, while the percentage of endothelial cells between 200 and 400µ was high (p<0,05. Dis cus si on: With SHCL wear, the corneal morphology is more affected in the short-term period. During long-term contact lens wear, the cornea enters an adaptation period and shows near-normal morphology. Tear functions are not affected by short- or long-term SHCL wear. (Turk J Ophthalmol 2012; 42: 91-6

  2. An approach to understanding tribological behaviour of dental composites through volumetric wear loss and wear mechanism determination; beyond material ranking.

    Science.gov (United States)

    Altaie, Asmaa; Bubb, Nigel L; Franklin, Paul; Dowling, Adam H; Fleming, Garry J P; Wood, David J

    2017-04-01

    To investigate the fundamental wear mechanisms of six resin-based composite (RBC) formulations during short-term in vitro wear testing. RBC materials were condensed into rectangular bar-shaped specimens and light irradiated using the ISO 4049 specimen manufacture and irradiation protocol. Wear testing (n=10 specimens for each RBC) was performed on a modified pin-on-plate wear test apparatus and wear facets were analysed for wear volume loss using a white light profilometer. The wear tested RBC specimens and their corresponding antagonists were analysed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), respectively to determine the wear mechanism. Data generated using the profilometer showed variations in the mean total wear volume (mm(3)) between the RBCs tested (psystem rather than relying on a simple wear ranking for the RBC materials as is routinely the case in dental research studies. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. REDUCED ENGINE FRICTION AND WEAR

    Energy Technology Data Exchange (ETDEWEB)

    Ron Matthews

    2005-05-01

    This Final Technical Report discusses the progress was made on the experimental and numerical tasks over the duration of this project regarding a new technique for decreasing engine friction and wear via liner rotation. The experimental subtasks involved quantifying the reduction in engine friction for a prototype rotating liner engine relative to a comparable baseline engine. Both engine were single cylinder conversions of nominally identical production four-cylinder engines. Hot motoring tests were conducted initially and revealed that liner rotation decreased engine friction by 20% under motoring conditions. A well-established model was used to estimate that liner rotation should decrease the friction of a four-cylinder engine by 40% under hot motoring conditions. Hot motoring tear-down tests revealed that the crankshaft and valve train frictional losses were essentially the same for the two engines, as expected. However, the rotating liner engine had much lower (>70%) piston assembly friction compared to the conventional engine. Finally, we used the Instantaneous IMEP method to compare the crank-angle resolved piston assembly friction for the two engines. Under hot motoring conditions, these measurements revealed a significant reduction in piston assembly friction, especially in the vicinity of compression TDC when the lubrication regime transitions from hydrodynamic through mixed and into boundary friction. We have some remaining problems with these measurements that we expect to solve during the next few weeks. We will then perform these measurements under firing conditions. We also proposed to improve the state-of-the-art of numerical modeling of piston assembly friction for conventional engines and then to extend this model to rotating liner engines. Our research team first modeled a single ring in the Purdue ring-liner test rig. Our model showed good agreement with the test rig data for a range of speeds and loads. We then modeled a complete piston

  4. Renin-angiotensin-aldosterone responsiveness to low sodium and blood pressure reactivity to angiotensin-II are unrelated to cholesteryl ester transfer protein mass in healthy subjects

    NARCIS (Netherlands)

    Krikken, Jan A.; Dallinga-Thie, Geesje M.; Navis, Gerjan; Dullaart, Robin P. F.

    2008-01-01

    Background: The blood pressure increase associated with the cholesteryl ester transfer protein (CETP) inhibitor, torcetrapib is probably attributable to an off-target effect but it is unknown whether activation of the renin-angiotensin-aldosterone system (RAAS) may be related to variation in the

  5. Influence of Shot Peening on Abrasion Wear in Real Conditions of Ni-Cu-Ausferritic Ductile Iron

    Directory of Open Access Journals (Sweden)

    Wieczorek A. N.

    2016-12-01

    Full Text Available The paper presents results of the wear tests of chain wheels made of austempered ductile iron with various content of residual austenite. The aim of this study was to demonstrate the impact of the dynamic surface treatment (shot peening on wear properties of surface layers of the chain wheels tested that were subjected to the action of quartz abrasive. Apart from determining the value of the abrasive wear, examinations of the magnetic phase content in the microstructure were carried out and plots of hardness of the surface layer as a function of the distance from the surface and microstructure of the materials were prepared. Based on the results, the following was found: an increase in the abrasive wear and a reduction in the hardness of the surface layer of chain wheels subjected to shot peening, as well as reduction of susceptibility to negative action of the shot for cast irons with the structure of upper ausferrite.

  6. Effect of deep cryogenic treatment on the microstructure and wear performance of Cr-Mn-Cu white cast iron grinding media

    Science.gov (United States)

    Vidyarthi, M. K.; Ghose, A. K.; Chakrabarty, I.

    2013-12-01

    The phase transformation and grinding wear behavior of Cr-Mn-Cu white cast irons subjected to destabilization treatment followed by air cooling or deep cryogenic treatment were studied as a part of the development program of substitute alloys for existing costly wear resistant alloys. The microstructural evolution during heat treatment and the consequent improvement in grinding wear performance were evaluated with optical and scanning electron microscopy, X-ray diffraction analysis, bulk hardness, impact toughness and corrosion rate measurements, laboratory ball mill grinding wear test etc. The deep cryogenic treatment has a significant effect in minimizing the retained austenite content and converts it to martensite embedded with fine M7C3 alloy carbides. The cumulative wear losses in cryotreated alloys are lesser than those with conventionally destabilized alloys followed by air cooling both in wet and dry grinding conditions. The cryotreated Cr-Mn-Cu irons exhibit comparable wear performance to high chromium irons.

  7. Influence of the Lactotripeptides Isoleucine-Proline-Proline and Valine-Proline-Proline on Systolic Blood Pressure in Japanese Subjects: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

    Directory of Open Access Journals (Sweden)

    Aurelie Chanson-Rolle

    Full Text Available The lactotripeptides isoleucine-proline-proline (IPP and valine-proline-proline (VPP have been shown to decrease systolic blood pressure (SBP in several populations, but the size of the effect varies among studies. We performed a meta-analysis including all published studies to evaluate the SBP-lowering effect of IPP/VPP in Japanese subjects more comprehensively.Eligible randomized controlled trials were searched for within four bibliographic databases, including two Japanese ones. Eighteen studies (including a total of 1194 subjects were included in the meta-analysis. A random effect model using the restricted maximum likelihood (REML estimator was used for the analysis. The analysis showed that consumption of IPP/VPP induced a significant reduction in SBP as compared with placebo in Japanese subjects, with an estimated effect of -5.63 mm Hg (95% CI, -6.87 to -4.39, P<0.0001 and no evidence of publication bias. A significant heterogeneity between series was evident, which could be explained by a significant influence of the baseline blood pressure status of the subjects, the effect of IPP/VPP on SBP being stronger in hypertensive subjects (-8.35 mm Hg, P<0.0001 than in non-hypertensive subjects (-3.42mm Hg, P<0.0001. Furthermore, the effect of IPP/VPP on SBP remained significant when limiting the analysis to series that tested the usual doses of IPP/VPP consumed daily (below 5 mg/d, with estimated effects of -6.01 mm Hg in the overall population and -3.32 mm Hg in non-hypertensive subjects.Results from this meta-analysis show that IPP/VPP lactotripeptides can significantly reduce office SBP in Japanese subjects with or without overt hypertension, and for doses that can potentially be consumed as an everyday supplement. This suggests that these peptides could play a role in controlling blood pressure in Japanese subjects. The systematic review protocol was published on the PROSPERO register (CRD42014014322.

  8. Automatic ultrasonic inspection system for wear determination in calandria tubes of Embalse Nuclear Power Plant

    Energy Technology Data Exchange (ETDEWEB)

    Katchadjian, Pablo, E-mail: katcha@cnea.gov.ar; Desimone, Carlos, E-mail: katcha@cnea.gov.ar; Garcia, Alejandro, E-mail: katcha@cnea.gov.ar [Comisión Nacional de Energía Atómica, Depto. ENDE - INEND, Av. Gral. Paz 1499, Buenos Aires (Argentina); Antonaccio, Carlos; Schroeter, Fernando; Molina, Héctor [Nucleoeléctrica Argentina-SA, Arribeños 3619, Buenos Aires (Argentina)

    2015-03-31

    Embalse Nuclear Power Plant (CNE) (CANDU design) is reaching its end of life and due to elapsed operating time the problem of deformation by accelerated creep occurs in the pressure tubes (PT), leading to a possible contact between calandria tubes (CT), concentric to the PT, and some Liquid Injection Shutdown System (LISS) nozzles that pass underneath them. With determination of CT wear, after the predicted contact occurs, the wear rate of the TC could be determined and thus take less conservative measures over the remaining life of the component. This paper presents the development of an ultrasonic technique for measuring wear in CT, with nominal thickness of 1.34 mm. Because the only access is through the interior of PT, to perform this measurement it is necessary to pass through three different interfaces.

  9. Modeling of wear behavior of Al/B{sub 4}C composites produced by powder metallurgy

    Energy Technology Data Exchange (ETDEWEB)

    Sahin, Ismail; Bektas, Asli [Gazi Univ., Ankara (Turkey). Dept. of Industrial Design Engineering; Guel, Ferhat; Cinci, Hanifi [Gazi Univ., Ankara (Turkey). Dept. of Materials and Metallurgy Engineering

    2017-06-01

    Wear characteristics of composites, Al matrix reinforced with B{sub 4}C particles percentages of 5, 10,15 and 20 produced by the powder metallurgy method were studied in this study. For this purpose, a mixture of Al and B{sub 4}C powders were pressed under 650 MPa pressure and then sintered at 635 C. The analysis of hardness, density and microstructure was performed. The produced samples were worn using a pin-on-disk abrasion device under 10, 20 and 30 N load through 500, 800 and 1200 mesh SiC abrasive papers. The obtained wear values were implemented in an artificial neural network (ANN) model having three inputs and one output using feed forward backpropagation Levenberg-Marquardt algorithm. Thus, the optimum wear conditions and hardness values were determined.

  10. Suppressing Nanoscale Wear by Graphene/Graphene Interfacial Contact Architecture: A Molecular Dynamics Study.

    Science.gov (United States)

    Xu, Qiang; Li, Xin; Zhang, Jie; Hu, Yuanzhong; Wang, Hui; Ma, TianBao

    2017-11-07

    Nanoscale wear is one of the key factors hindering the performance and lifetime of micro- and nanosystems, such as the scanning tip wear in atomic force microscopy (AFM), the head-disk interface in magnetic storage system, and the moving components in micro- or nanoelectromechanical systems (MEMS/NEMS). Here, we propose to construct the graphene/graphene interfacial architecture to suppress the nanoscale wear. Molecular dynamics simulations show that the atomic roughness of the sliding surfaces with either stepped or amorphous structure can lead to strong inhomogeneity of the local contact pressure distribution. By coating graphene on both sides of the frictional surfaces, the local contact pressure fluctuations due to the atomic roughness are suppressed. Moreover, this trend is more evident with the increasing layer number of the graphene coating. Furthermore, the nanoscratching simulation suggests that the rupture of graphene is driven by the inhomogeneous pressure distribution-induced lateral atomic interlocking between the rough tip and substrate and the consequent in-plane lattice deformation and C-C bond breaking during sliding. By coating graphene on the rough amorphous carbon tip, the critical normal load for wear failure of graphene is significantly increased, due to the weakening effect of the atomic interlocking by improving the contact conditions with atomically smooth graphene/graphene sliding interface. This investigation reveals a strategy for reducing nanowear by suppressing the local contact pressure fluctuations via graphene/graphene sliding interface architecture, which provides a theoretical guidance for designing wear-resistant coatings for the longevity of AFM probes and MEMS/NEMS systems.

  11. A WEAR MODEL FOR DIESEL ENGINE EXHAUST VALVES

    Energy Technology Data Exchange (ETDEWEB)

    Blau, Peter Julian [ORNL

    2009-11-01

    The work summarized here comprises the concluding effort of a multi-year project, funded by the U.S. Department of Energy, Office of Vehicle Technologies. It supports the development of a better understanding of advanced diesel engine designs in which enhanced power density, energy efficiency, and emissions control place increasing demands upon the durability of engine materials. Many kinds of metallic alloys are used in engines depending on the operating stresses, temperatures, and chemical environments. Exhaust valves, for example, are subjected to high temperatures and repetitive surface contacts that place demands on durability and frictional characteristics of the materials. Valves must continue to seal the combustion chamber properly for thousands of hours of cyclic engine operation and under varying operating conditions. It was the focus of this effort to understand the wear processes in the valve-seat area and to develop a model for the surface deformation and wear of that important interface. An annotated bibliography is provided to illustrate efforts to understand valve wear and to investigate the factors of engine operation that affect its severity and physical manifestation. The project for which this modeling effort was the final task, involved construction of a high-temperature repetitive impact test system as well as basic tribology studies of the combined processes of mechanical wear plus oxidation at elevated temperatures. Several publications resulted from this work, and are cited in this report. The materials selected for the experimental work were high-performance alloys based on nickel and cobalt. In some cases, engine-tested exhaust valves were made available for wear analysis and to ensure that the modes of surface damage produced in experiments were simulative of service. New, production-grade exhaust valves were also used to prepare test specimens for experimental work along with the other alloy samples. Wear analysis of valves and seats

  12. Incisor wear and age in Yellowstone bison

    Science.gov (United States)

    Christianson, D.A.; Gogan, P.J.P.; Podruzny, K.M.; Olexa, E.M.

    2005-01-01

    Biologists commonly use tooth eruption and wear patterns or cementum annuli techniques to estimate age of ungulates. However, in some situations the accuracy or sampling procedures of either approach are undesirable. We investigated the progression of several quantitative measures of wear with age, using permanent first incisors from Yellowstone bison (Bison bison), and tested for differences between sexes and herds. We further investigated the relationship of wear and age to explore an age-estimation method. Labial-lingual width (LLW) correlated best with assigned age (r2=0.66, males; r2=0.76 females). Labial-lingual width differed between sexes, with females showing ∼0.2 mm more wear than males. Additionally, differences in rate of wear existed between bison of the northern and central Yellowstone herds (1.2 and 0.9 mm/year, respectively). We developed a regression formula to test the power of LLW as an estimator of Yellowstone bison age. Our method provided estimated ages within 1 year of the assigned age 73% and 82% of the time for female and male bison, respectively.

  13. Investigation on wear characteristic of biopolymer gear

    Science.gov (United States)

    Ghazali, Wafiuddin Bin Md; Daing Idris, Daing Mohamad Nafiz Bin; Sofian, Azizul Helmi Bin; Basrawi, Mohamad Firdaus bin; Khalil Ibrahim, Thamir

    2017-10-01

    Polymer is widely used in many mechanical components such as gear. With the world going to a more green and sustainable environment, polymers which are bio based are being recognized as a replacement for conventional polymers based on fossil fuel. The use of biopolymer in mechanical components especially gear have not been fully explored yet. This research focuses on biopolymer for spur gear and whether the conventional method to investigate wear characteristic is applicable. The spur gears are produced by injection moulding and tested on several speeds using a custom test equipment. The wear formation such as tooth fracture, tooth deformation, debris and weight loss was observed on the biopolymer spur gear. It was noted that the biopolymer gear wear mechanism was similar with other type of polymer spur gears. It also undergoes stages of wear which are; running in, linear and rapid. It can be said that the wear mechanism of biopolymer spur gear is comparable to fossil fuel based polymer spur gear, thus it can be considered to replace polymer gears in suitable applications.

  14. Dental Wear: A Scanning Electron Microscope Study

    Directory of Open Access Journals (Sweden)

    Luca Levrini

    2014-01-01

    Full Text Available Dental wear can be differentiated into different types on the basis of morphological and etiological factors. The present research was carried out on twelve extracted human teeth with dental wear (three teeth showing each type of wear: erosion, attrition, abrasion, and abfraction studied by scanning electron microscopy (SEM. The study aimed, through analysis of the macro- and micromorphological features of the lesions (considering the enamel, dentin, enamel prisms, dentinal tubules, and pulp, to clarify the different clinical and diagnostic presentations of dental wear and their possible significance. Our results, which confirm current knowledge, provide a complete overview of the distinctive morphology of each lesion type. It is important to identify the type of dental wear lesion in order to recognize the contributing etiological factors and, consequently, identify other more complex, nondental disorders (such as gastroesophageal reflux, eating disorders. It is clear that each type of lesion has a specific morphology and mechanism, and further clinical studies are needed to clarify the etiological processes, particularly those underlying the onset of abfraction.

  15. Randomized Trial of the Effect of Contact Lens Wear on Self-Perception in Children

    NARCIS (Netherlands)

    Walline, J.J.; Jones, L.A.; Sinnott, L.; Chitkara, M.; Coffey, B.; Jackson, J.M.; Manny, R.E.; Rath, M.J.; Prinstein, M.J.

    2009-01-01

    Purpose. To determine whether contact lens wear affects children's self-perceptions. Methods. The Adolescent and Child Health Initiative to Encourage Vision Empowerment Study was a randomized, single-masked trial conducted at five clinical centers in the United States. Subjects were 8- to

  16. The interactions between attrition, abrasion and erosion in tooth wear.

    Science.gov (United States)

    Shellis, R Peter; Addy, Martin

    2014-01-01

    Tooth wear is the result of three processes: abrasion (wear produced by interaction between teeth and other materials), attrition (wear through tooth-tooth contact) and erosion (dissolution of hard tissue by acidic substances). A further process (abfraction) might potentiate wear by abrasion and/or erosion. Knowledge of these tooth wear processes and their interactions is reviewed. Both clinical and experimental observations show that individual wear mechanisms rarely act alone but interact with each other. The most important interaction is the potentiation of abrasion by erosive damage to the dental hard tissues. This interaction seems to be the major factor in occlusal and cervical wear. The available evidence is insufficient to establish whether abfraction is an important contributor to tooth wear in vivo. Saliva can modulate erosive/abrasive tooth wear, especially through formation of pellicle, but cannot prevent it. © 2014 S. Karger AG, Basel.

  17. Temperature effect on IG-11 graphite wear performance

    Energy Technology Data Exchange (ETDEWEB)

    Luo Xiaowei [Institute of Nuclear Energy and New Energy Technology, Tsinghua University, Beijing 100084 (China)]. E-mail: xwluo@mail.tsnghua.edu.cn; Yu Suyuan [Institute of Nuclear Energy and New Energy Technology, Tsinghua University, Beijing 100084 (China); Sheng Xuanyu [Institute of Nuclear Energy and New Energy Technology, Tsinghua University, Beijing 100084 (China); He Shuyan [Institute of Nuclear Energy and New Energy Technology, Tsinghua University, Beijing 100084 (China)

    2005-10-01

    IG-11 graphite, used in the 10 MW high temperature gas-cooled test reactor (HTR-10), was tested under different temperatures on an SRV standard wear performance tester. The experiment temperatures were room temperature, 100, 200, 300 and 400 deg C. According to the reactor structure, the experiments were designed to test graphite-graphite and graphite-stainless steel wear. The wear debris was collected, and the worn surfaces and debris were observed under scanning electronic microscope (SEM). It was found that there were different wear mechanisms at different temperatures. The main wear mechanism at room temperature was abrasive wear; at 200 deg C, it was fatigue wear; at 400 deg C, adhesive wear was observed. This difference was mainly due to the change of stress distribution at the contact area. The distribution of wear debris was also analyzed by EDX particle analysis software.

  18. Wear behavior of contacting between thin film coating on SKD11 ball and 304 stainless steel disk

    Directory of Open Access Journals (Sweden)

    Sriprasird, J.

    2007-11-01

    Full Text Available Wear is a well known problem in metal stamping die, especially on the die working with stainless steel workpiece, in which wear rate is severe. This research considered various types of material coating on tool surface which were regularly practised in modern stamping industry due to the ability to increase wear resistance. The model study of friction "Ball-on-disk" technique was employed throughout this work. The disk was made from stainless steel austenitic grade (SUS304. The ball was made from cold work tool steel, SKD11 (JIS and was hardened to 60±2 HRC. Ball surface conditions selected for this work were non-coated, coated by TiC-CVD, TiCN (TiC/TiCN/TiN Multilayer-CVD and TiCN (TiN/TiCN Double layer-PVD, and treated by VC-TD. Tests were carried out without lubricant. The results show that the coating film and the surface treatment has no effect on the friction coefficient but it can reduce wear rate by 64.1-99.7% at contact pressure condition less than 1,100 MPa. At the higher level of contact pressure, only 2 types of coating, TiCN (Multilayer-CVD and TiC-CVD, can reduce wear rate. The other two, which are TiCN (Double layer-PVD coating film and a surface treatment by VC-TD process, on the contrary increase the rate of wear significantly. This is due to delamination of coating film at high contact pressure. The coating particles of high hardness accelerate wear phenomenon on the tool surface. Therefore, proper selection of tool surface condition depends on level of contact pressure generated in the process.

  19. Experimental study and modelling of the effect of microstructure on friction and wear mechanisms of low alloy steel

    Science.gov (United States)

    Trevisiol, C.; Jourani, A.; Bouvier, S.

    2017-12-01

    Few models are focused on the combined effects of microstructure and roughness on the tribological behavior of materials. Hardness is the material property mainly used in the tribological models which are usually at a macroscopic scale. For a dual-phase steel, experimental and predicted values of friction coefficients and specific wear resistances are compared. The investigated models are declined into two pressure distribution modes between the phases. Friction tests are performed between steel pins composed of a ferrite-martensite dual-phase microstructure against abrasive papers with various abrasive particle sizes ranging from 15 µm to 200 µm. By using heat treatments on a low alloy steel, dual-phase microstructures with various martensite volume fractions, ranging from 45% to 100%, are generated. As martensite volume fraction increases, the experimental and predicted results show that the specific wear resistance increases whereas the friction coefficient decreases. Furthermore, the latter evolutions depend on roughness. For a predominance of abrasive wear mechanisms generated by coarse abrasive particles (~200 µm), the experimental tribological parameters tend to follow the predicted ones associated to the mode characterized by equal pressures between the phases. Then, as the abrasive particle size decreases, abrasive wear mechanisms reduce whereas adhesive wear mechanisms increase and the experimental tribological parameters tend to follow the predicted ones associated to the mode characterized by equal wear rate between the phases.

  20. Quantitative wear particle analysis for osteoarthritis assessment.

    Science.gov (United States)

    Guo, Meizhai; Lord, Megan S; Peng, Zhongxiao

    2017-12-01

    Osteoarthritis is a degenerative joint disease that affects millions of people worldwide. The aims of this study were (1) to quantitatively characterise the boundary and surface features of wear particles present in the synovial fluid of patients, (2) to select key numerical parameters that describe distinctive particle features and enable osteoarthritis assessment and (3) to develop a model to assess osteoarthritis conditions using comprehensive wear debris information. Discriminant analysis was used to statistically group particles based on differences in their numerical parameters. The analysis methods agreed with the clinical osteoarthritis grades in 63%, 50% and 61% of particles for no osteoarthritis, mild osteoarthritis and severe osteoarthritis, respectively. This study has revealed particle features specific to different osteoarthritis grades and provided further understanding of the cartilage degradation process through wear particle analysis - the technique that has the potential to be developed as an objective and minimally invasive method for osteoarthritis diagnosis.

  1. Friction and Wear Processes – Thermodynamic Approach

    Directory of Open Access Journals (Sweden)

    M. Banjac

    2014-12-01

    Full Text Available Tribology, as the scientific and professional discipline within the mechanical engineering, studies phenomena and processes on the interacting surfaces, in direct and indirect contact and in relative motion. It includes the study and application of the principles of friction, wear and lubrication, as well as phenomena connected with these processes. Given that a process involving friction is always accompanied by transformation of energy, more precisely an energy dissipation process which generates entropy, the concept of thermodynamic entropy production analysis represents one of appropriate tools for studying and analysing the behaviour of complex friction and wear processes. This paper presents a review of published works in which the thermodynamic approach was used in analysing the friction and wear processes in tribosystems.

  2. Adhesion and wear resistance of materials

    Science.gov (United States)

    Buckley, D. H.

    1986-01-01

    Recent studies into the nature of bonding at the interface between two solids in contact or a solid and deposited film have provided a better understanding of those properties important to the adhesive wear resistance of materials. Analytical and experimental progress are reviewed. For simple metal systems the adhesive bond forces are related to electronic wave function overlap. With metals in contact with nonmetals, molecular-orbital energy, and density of states, respectively can provide insight into adhesion and wear. Experimental results are presented which correlate adhesive forces measured between solids and the electronic surface structures. Orientation, surface reconstruction, surface segregation, adsorption are all shown to influence adhesive interfacial strength. The interrelationship between adhesion and the wear of the various materials as well as the life of coatings applied to substrates are discussed. Metallic systems addressed include simple metals and alloys and these materials in contact with themselves, both oxide and nonoxide ceramics, diamond, polymers, and inorganic coating compounds, h as diamondlike carbon.

  3. Wear Resistant Amorphous and Nanocomposite Coatings

    Energy Technology Data Exchange (ETDEWEB)

    Racek, O

    2008-03-26

    Glass forming materials (critical cooling rate <10{sup 4}K.s{sup -1}) are promising for their high corrosion and wear resistance. During rapid cooling, the materials form an amorphous structure that transforms to nanocrystalline during a process of devitrification. High hardness (HV 1690) can be achieved through a controlled crystallization. Thermal spray process has been used to apply coatings, which preserves the amorphous/nanocomposite structure due to a high cooling rate of the feedstock particles during the impact on a substrate. Wear properties have been studied with respect to process conditions and feedstock material properties. Application specific properties such as sliding wear resistance have been correlated with laboratory tests based on instrumented indentation and scratch tests.

  4. Blood Pressure Is the Determinant for the Increased Risk for Intracranial Arterial Stenosis in Subjects with Elevated Glycated Hemoglobin Levels: The Kangbuk Samsung Health Study.

    Science.gov (United States)

    Oh, Hyung-Geun; Rhee, Eun-Jung

    2016-11-01

    Ischemic stroke is known to be an important vascular complication of diabetes. Intracranial arterial stenosis (ICAS) is considered as an important cause of stroke in Asians. We aimed to analyze the risk for ICAS assessed by transcranial Doppler (TCD) ultrasonography in different groups of young Korean subjects divided by glycated hemoglobin (HbA1c) levels. This study included 10,437 participants without history of cardiovascular diseases (81.3% men, mean age 43 years) from a health screening program, in whom TCD ultrasonography was used to detect greater than 50% ICAS based on criteria modified from the SONIA (Stroke Outcomes and Neuroimaging of Intracranial Atherosclerosis) trial. The subjects were divided into 3 groups according to HbA1c levels: HbA1c < 5.7%, 5.7 ≤ HbA1c < 6.5%, and HbA1c ≥ 6.5% or under medication for diabetes. Among the participants, 3.0% of the subjects had ICAS. The subjects with ICAS tended to have higher mean HbA1c level compared with those without ICAS (5.8 ± .8 versus 5.7 ± .6, P = .063). The proportion of subjects with ICAS significantly increased as the HbA1c increased from the first to the third group (2.8%, 3.0%, 4.6%, P for linear trend = .022). In logistic regression analysis with ICAS as the dependent variable, the group with HbA1c ≥ 6.5% showed significantly increased odds ratio for ICAS with subjects with HbA1c < 5.7% as the reference after adjustment for confounding variables (1.575, 95% confidence interval 1.056-2.347). However, this significance disappeared with inclusion of presence of hypertension in the model. The risk for ICAS assessed by TCD was increased in young Korean subjects with HbA1c ≥ 6.5%. However, this significance was attenuated after adjustment for presence of hypertension, suggesting the importance of hypertension in ICAS. Copyright © 2016 National Stroke Association. Published by Elsevier Inc. All rights reserved.

  5. Influence of wearing an unstable shoe construction on compensatory control of posture.

    Science.gov (United States)

    Sousa, Andreia S P; Macedo, Rui; Santos, Rubim; Tavares, João Manuel R S

    2013-12-01

    This study investigated the influence of wearing unstable shoe construction (WUS) on compensatory postural adjustments (CPA) associated with external perturbations. Thirty-two subjects stood on a force platform resisting an anterior-posterior horizontal force applied to a pelvic belt via a cable, which was suddenly released. They stood under two conditions: barefoot and WUS. The electromyographic (EMG) activity of gastrocnemius medialis, tibialis anterior, rectus femoris, biceps femoris, rectus abdominis, and erector spinae muscles and the center of pressure (CoP) displacement were acquired to study CPA. The EMG signal was used to assess individual muscle activity and latency, antagonist co-activation and reciprocal activation at joint and muscle group levels. Compared to barefoot, WUS led to: (1) increased gastrocnemius medialis activity, (2) increased total agonist activity, (3) decreased antagonist co-activation at the ankle joint and muscle group levels, (4) increased reciprocal activation at the ankle joint and muscle group levels, and (5) decrease in all muscle latencies. No differences were observed in CoP displacement between conditions. These findings demonstrate that WUS led to a reorganization of the postural control system associated to improved performance of some components of postural control responses. Copyright © 2013 Elsevier B.V. All rights reserved.

  6. Investigation of the Wear and Hardness Behaviour of Aluminium Alloy Coated Using the Powder Flame Spraying Method

    Directory of Open Access Journals (Sweden)

    Nurullah KIRATLI

    2009-03-01

    Full Text Available In this study, the wear behavior of aluminum alloy AL 5754 ( Etial 53 coated with powders of 10Al-Cu alloy (RotoTec® 19850 and 15Cr7Fe-Ni alloy (RotoTec® 19985 using powder flame spraying method has been investigated. To avoid thermal expansions between substrate and coating materials, Ni-Al RotoTec® 51000 was used as binding material. The wear test was performed on a pin-on-disc test apparatus. As an abrasive material, a SiC, 800 sandpaper was used. The wear tests of coated materials were carried out at room temperature and at 1.0m/s sliding speed with 0.35 and 0.70MPa pressures. To characterize coated specimens, they have been examined with optical microscope. As a result, it is found that the both coating materials have improved wear resistance.

  7. Surface engineering for enhanced performance against wear

    CERN Document Server

    2013-01-01

    Surface Engineering constitutes a variety of processes and sub processes. Each chapter of this work covers specific processes by experts working in the area. Included for each topic are tribological performances for each process as well as results of recent research. The reader also will benefit from in-depth studies of diffusion coatings, nanocomposite films for wear resistance, surfaces for biotribological applications, thin-film wear, tribology of thermal sprayed coatings, hardfacing, plating for tribology and high energy beam surface modifications. Material scientists as well as engineers working with surface engineering for tribology will be particularly interested in this work.

  8. Wear Analysis of Wind Turbine Gearbox Bearings

    Energy Technology Data Exchange (ETDEWEB)

    Blau, Peter Julian [ORNL; Walker, Larry R [ORNL; Xu, Hanbing [ORNL; Parten, Randy J [ORNL; Qu, Jun [ORNL; Geer, Tom [ORNL

    2010-04-01

    The objective of this effort was to investigate and characterize the nature of surface damage and wear to wind turbine gearbox bearings returned from service in the field. Bearings were supplied for examination by S. Butterfield and J. Johnson of the National Wind Technology Center (NREL), Boulder, Colorado. Studies consisted of visual examination, optical and electron microscopy, dimensional measurements of wear-induced macro-scale and micro-scale features, measurements of macro- and micro-scale hardness, 3D imaging of surface damage, studies of elemental distributions on fracture surfaces, and examinations of polished cross-sections of surfaces under various etched and non-etched conditions.

  9. The effect of microstructure on abrasive wear of steel

    Science.gov (United States)

    Kešner, A.; Chotëborský, R.; Linda, M.

    2017-09-01

    Abrasive wear of agricultural tools is one of the biggest problems in currently being. The amount of abrasive wear, depending on the microstructure, has been investigated in this work. Steels 25CrMo4 and 51CrV4 were used in this work to determine the effect of the microstructure on the abrasive wear. These steels are commonly used for components that have to withstand abrasive wear.SEM analysis was used to detect the microstructure. The standardized ASTM G65 method was used to compare the abrasive wear of steels. The results show that the abrasive wear depends on the microstructure of steels.

  10. Comparative in vitro wear resistance of CAD/CAM composite resin and ceramic materials.

    Science.gov (United States)

    Zhi, Li; Bortolotto, Tissiana; Krejci, Ivo

    2016-02-01

    Composite resin is a promising option in computer-aided design and computer-aided manufacturing (CAD/CAM) dentistry; however, the wear resistance of composite resin remains a primary concern. The purpose of this in vitro study was to evaluate the wear resistance of 5 CAD/CAM materials (n=10), consisting of 4 composite resins (3M Lava Ultimate, Kerr experimental composite resin material, Vita Enamic, 3M Paradigm MZ100) and 1 ceramic (Vita Mark II) in contact with natural human enamel cusps. Specimens were loaded into a computer-controlled mastication simulator and subjected to 200000 mechanical cycles (49 N) against natural human enamel simultaneously with 500 thermal cycles (5°C to 50°C to 5°C). The wear resistance was analyzed by measuring the vertical substance loss (the maximum depth of the worn area) in the contact point area of the specimen. The worn surfaces were observed by scanning electron microscopy to determine the wear patterns. Vita Mark II exhibited the best wear resistance among the tested materials, followed by 3M Lava Ultimate, Vita Enamic, and 3M Paradigm MZ100. The Kerr experimental material exhibited the lowest wear resistance, yet its results were not significantly different from those of the 3 other composite resin blocks (P>.05). Within the limitations of this in vitro study, the wear resistance of composite resin blocks in contact with enamel cusps was significantly lower than that of a ceramic block. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  11. Wear and Degradation Modes in Selected Vehicle Tribosystems

    Directory of Open Access Journals (Sweden)

    G. Pantazopoulos

    2015-03-01

    Full Text Available The wear and degradation mechanisms of two principle vehicle tribosystems are presented to elucidate the main causes of their premature failure. The first case study concerns the malfunction of an automotive cast iron pressure plate operated in an automobile clutch system. The second is related to the unexpected failure of a stainless steel brake disk of a high performance motorcycle. Both components are designed to function under sliding friction conditions that lead to the severe wear of consumable non-metallic parts of the tribosystems: the clutch disk and the brake pad, respectively. However, in both cases it was the unexpected failure of the conjugate metallic parts that resulted in terminal system damage. The experimental approach to identify the root cause of failure involved both microstructure characterization, as well as observations of the metallic contact surfaces by means of optical and scanning electron microscopy, in conjunction with microhardness and surface topography measurements. For the case of the stainless steel brake disk in particular, Finite Element Analysis was employed to simulate the operating tribosystem, identify the site(s prone for crack initiation and validate the failure mechanisms hypotheses.

  12. Effects of Load and Speed on Wear Rate of Abrasive Wear for 2014 Al Alloy

    Science.gov (United States)

    Odabas, D.

    2018-01-01

    In this paper, the effects of the normal load and sliding speed on wear rate of two-body abrasive wear for 2014 Al Alloy were investigated in detail. In order to understand the variation in wear behaviour with load and speed, wear tests were carried out at a sliding distance of 11 m, a speed of 0.36 m/s, a duration of 30 s and loads in the range 3-11 N using 220 grit abrasive paper, and at a speed range 0.09-0.90 m/s, a load of 5 N and an average sliding distance of 11 m using abrasive papers of 150 grit size under dry friction conditions. Before the wear tests, solution treatment of the 2014 Al alloy was carried out at temperatures of 505 and 520 °C for 1 h in a muffle furnace and then quenched in cold water at 15 °C. Later, the ageing treatment was carried out at 185 °C for 8 h in the furnace. Generally, wear rate due to time increased linearly and linear wear resistance decreased with increasing loads. However, the wear rate was directly proportional to the load up to a critical load of 7 N. After this load, the slope of the curves decreased because the excessive deformation of the worn surface and the instability of the abrasive grains began to increase. When the load on an abrasive grain reaches a critical value, the groove width is about 0.17 of the abrasive grain diameter, and the abrasive grains begin to fail. The wear rate due to time increased slightly as the sliding speed increased in the range 0.09-0.90 m/s. The reason for this is that changes arising from strain rate and friction heating are expected with increasing sliding speeds.

  13. The inter-relationship between dietary and environmental properties and tooth wear: comparisons of mesowear, molar wear rate, and hypsodonty index of extant Sika deer populations.

    Directory of Open Access Journals (Sweden)

    Mugino Ozaki Kubo

    Full Text Available In reference to the evolutionary trend of increasing cheek tooth height in herbivorous ungulates, the causes of dental abrasion have long been debated. Interspecific comparisons of extant ungulates have revealed that both phytoliths in grass and external abrasive matter may play important roles. Using analysis of extant sika deer living in various environments and showing continuous latitudinal variation in food habits from northern grazing to southern browsing, we quantitatively evaluated the influence of dietary and environmental properties on three dental variables: mesowear score (MS, molar wear rate, and M3 hypsodonty index. We used 547 skulls and 740 mandibles from 16 populations of sika deer to obtain the dental measurements. We found that only graminoid proportion in diet correlated with MS and the molar wear rate, implying that phytoliths in grass abrade dental tissues. In contrast, annual precipitation in habitat was not correlated with any of the dental variables. We also found a significant correlation between the molar wear rate (selective pressure for high-crowned molars and the M3 hypsodonty index of extant sika deer, implying an evolutionary increment in molar height corresponding to the molar wear rate. Our intraspecific comparative analyses provide further support for use of mesowear analysis as a paleodiet estimation method; it not only reveals staple food types (graminoids or dicots but also implies regional or seasonal variation in the diet of the species.

  14. The inter-relationship between dietary and environmental properties and tooth wear: comparisons of mesowear, molar wear rate, and hypsodonty index of extant Sika deer populations.

    Science.gov (United States)

    Kubo, Mugino Ozaki; Yamada, Eisuke

    2014-01-01

    In reference to the evolutionary trend of increasing cheek tooth height in herbivorous ungulates, the causes of dental abrasion have long been debated. Interspecific comparisons of extant ungulates have revealed that both phytoliths in grass and external abrasive matter may play important roles. Using analysis of extant sika deer living in various environments and showing continuous latitudinal variation in food habits from northern grazing to southern browsing, we quantitatively evaluated the influence of dietary and environmental properties on three dental variables: mesowear score (MS), molar wear rate, and M3 hypsodonty index. We used 547 skulls and 740 mandibles from 16 populations of sika deer to obtain the dental measurements. We found that only graminoid proportion in diet correlated with MS and the molar wear rate, implying that phytoliths in grass abrade dental tissues. In contrast, annual precipitation in habitat was not correlated with any of the dental variables. We also found a significant correlation between the molar wear rate (selective pressure for high-crowned molars) and the M3 hypsodonty index of extant sika deer, implying an evolutionary increment in molar height corresponding to the molar wear rate. Our intraspecific comparative analyses provide further support for use of mesowear analysis as a paleodiet estimation method; it not only reveals staple food types (graminoids or dicots) but also implies regional or seasonal variation in the diet of the species.

  15. Simulation and experiment of the effect of clearance of impeller wear-rings on the performance of centrifugal pump

    Science.gov (United States)

    Chen, S. X.; Pan, Z. Y.; Wu, Y. L.; Zhang, D. Q.

    2012-11-01

    The effect of clearance of impeller wear-rings on the performance of a centrifugal pump was investigated numerically and experimentally. The whole flow field model including front and back shrouds of pump was designed so as to accurately calculate the head and efficiency of the centrifugal pump. Based on RNG k-ε turbulence model, three wear-rings schemes were established, and the effects of clearance of impeller wear-rings on the hydraulic efficiency and mechanical efficiency of the centrifugal pump was analyzed, chiefly from the turbulent kinetic energy, vorticity and radial force angles. According to the results, it can be drawn that the head and total efficiency of the centrifugal pump increase as the clearance value of wear-rings narrows. The following reasons may account for it: firstly, as the clearance value of wear-rings declines, the turbulent kinetic energy and energy dissipation decrease within the impeller, and the impact of secondary flow at the inlet of impeller on the mainstream weakens slowly, which leads to a lower hydraulic loss, thus a higher hydraulic efficiency; secondly, radial force decreases with the clearance value of wear-rings, so the eccentric whirl of centrifugal pump is dampened, which results in a lower mechanical loss and a higher mechanical efficiency; thirdly, the front shroud leakage diminishes with the clearance value of wear-rings, therefore, the volume loss is reduced and volume efficiency improved. Finally, the first wear-ring scheme of impeller is adopted after comprehensive comparison of these three wear-ring schemes, because its efficiency is highest and it satisfies the requirements of the engineering application.

  16. Wear resistance analysis of the aluminum 7075 alloy and the nanostructured aluminum 7075 - silver nanoparticles composites

    Directory of Open Access Journals (Sweden)

    Estrada-Ruiz R.H.

    2016-01-01

    Full Text Available Nanostructured composites of the aluminum 7075 alloy and carbon-coated silver nanoparticles were synthetized by the mechanical milling technique using a high-energy mill SPEX 8000M; the powders generated were compacted, sintered and hot-extruded to produce 1 cm-diameter bars. The composites were then subjected to a wear test using a pin-on-disc device to validate the hypothesis that second phase-ductile nanometric particles homogenously distributed throughout the metalmatrix improve the wear resistance of the material. It was found that silver nanoparticles prevent the wear of the material by acting as an obstacle to dislocations movement during the plastic deformation of the contact surface, as well as a solid lubricant when these are separated from the metal-matrix.

  17. Wear and corrosion performances of new friction materials for automotive industry

    Directory of Open Access Journals (Sweden)

    R. Samur

    2012-01-01

    Full Text Available In this study, after a NiCr bond layer was deposited on a pearlitic, grey cast iron rotor disc of the kind used in a production passenger car (Toyota Corolla 1600 cc, Cr3C2-NiCr and Al2O3-TiO2powders were sprayed using High Velocity Oxygen Fuel(HVOF and plasma spray processes, respectively. The discs were subjected to cosmetic corrosion test according to SAE J2334 test standard. Additionally, wear tests were carried out using a reciprocating wear tester by rubbing a 10 mm diameter Al2O3 ball on the specimens machined from rotor discs in salt solution. It was found that the Cr3C2-NiCr coating (HSCN sprayed using HVOF method exhibited highest hardness and highest corrosion and wear resistances.

  18. Refractive behavior changes with six months daily wear of high and low oxygen permeability hydrogel contact lenses

    Directory of Open Access Journals (Sweden)

    W.D.H. Gillan

    2006-01-01

    Full Text Available Introduction: The investigation of myopia and soft contact lenses is not new. Many reports show  that  the  wearing  of  silicone  hydrogel lenses as opposed to conventional disposable hydrogel lenses results in little progression of myopia in the eyes wearing silicone hydrogels. Method: Six subjects wore a silicone hydro-gel lens on one eye while the other eye wore a habitual disposable hydrogel lens for six months of daily wear. Fifty measurements of refractive state in each eye were taken prior to the subjects wearing a silicone lens in one eye and a conven-tional hydrogel lens in the other eye. After six months of daily wear another fifty measurements of refractive state were taken for each subject. Results:  Although  there  is  no  statisti-cal  support  for  the  findings  of  this  study, comet stereo-pairs are used to show the chang-es in refractive state for each subject. Four of  the  six  subjects  showed  an  increase  in myopia in the eye wearing the silicone lens. Discussion:  The  increase  in  myopia in eyes wearing a silicone hydrogel lens is contrary  to  the  findings  of  other  studies.

  19. Sliding wear of conventional and nanostructured cemented carbides

    Energy Technology Data Exchange (ETDEWEB)

    Jia, K. [Stevens Inst. of Tech., Hoboken, NJ (United States). Dept. of Materials Science and Engineering; Fischer, T.E. [Stevens Inst. of Tech., Hoboken, NJ (United States). Dept. of Materials Science and Engineering

    1997-03-01

    The sliding wear mechanisms of cemented carbide and the effects of the microstructure scale on the wear resistance were investigated by performing a series of unlubricated sliding wear tests in air with pins of WC-Co composites sliding against silicon nitride disks. In the first approximation, the wear rate is proportional to the hardness with a wear coefficient k=6.9x10{sup -6} for all materials. In the conventional cermets, the wear coefficient k also depends on the grain size; materials with smaller WC grains exhibit a smaller wear resistance. This reduction, however, does not extend to the nanostructured materials which exhibit the above value for k: Their wear resistance is higher than that of conventional cermets in proportion to their hardness. The data can also be expressed in terms of cobalt content: The lower the cobalt content, the lower the wear; but two different such dependencies exist, one for the conventional and one for the nanostructured materials with lower wear. The sliding wear of WC-Co composites occurs on a very small scale: The worn surfaces show no evidence of fracture of plastic deformation. This wear behavior is explained by the hexagonal structure and the anisotropic mechanical behavior of the WC grains that are capable of shear in a limited number of planes but are not capable of triaxial deformation. The higher wear resistance of the nanostructured composites is related to their hardness which decreases the real area of contact. (orig.)

  20. Wear Improvement of Tools in the Cold Forging Process for Long Hex Flange Nuts

    Directory of Open Access Journals (Sweden)

    Shao-Yi Hsia

    2015-09-01

    Full Text Available Cold forging has played a critical role in fasteners and has been widely used in automotive production, manufacturing, aviation and 3C (Computer, Communication, and Consumer electronics. Despite its extensive use in fastener forming and die design, operator experience and trial and error make it subjective and unreliable owing to the difficulty of controlling the development schedule. This study used finite element analysis to establish and simulate wear in automotive repair fastener manufacturing dies based on actual process conditions. The places on a die that wore most quickly were forecast, with the stress levels obtained being substituted into the Archard equation to calculate die wear. A 19.87% improvement in wear optimization occurred by applying the Taguchi quality method to the new design. Additionally, a comparison of actual manufacturing data to simulations revealed a nut forging size error within 2%, thereby demonstrating the accuracy of this theoretical analysis. Finally, SEM micrographs of the worn surfaces on the upper punch indicate that the primary wear mechanism on the cold forging die for long hex flange nuts was adhesive wear. The results can simplify the development schedule, reduce the number of trials and further enhance production quality and die life.

  1. EFFECT OF SOLUTIONIZING ON DRY SLIDING WEAR OF AL2024-BERYL METAL MATRIX COMPOSITE

    Directory of Open Access Journals (Sweden)

    Abdul Sharief

    2012-12-01

    Full Text Available In the present investigation, Al2024–Beryl particulate composites were fabricated by stir casting by varying the weight percentage of beryl particulates from 0 wt% to 10 wt% in steps of 2 wt%. The cast Al2024 alloy and its composites have been subjected to solutionizing treatment at a temperature of 495°C for 2 hrs, followed by ice quenching. Microstructural studies were carried out to determine the nature of the structure. The Brinell hardness test was conducted on both the Al2024 alloy and its composites before and after solutionizing. Pin-on disc wear tests were conducted to examine the wear behavior of the Al2024 alloy and its composites. Sliding wear tests were conducted at various applied loads, sliding velocities and sliding distances. The results reveal that the wear rate of the composites is lower than that of the matrix alloy. The wear rate increased with an increasing applied load and sliding distance, and decreased with increasing sliding velocity.

  2. Corneo-scleral limbal changes following short-term soft contact lens wear.

    Science.gov (United States)

    Consejo, Alejandra; Bartuzel, Maciej M; Iskander, D Robert

    2017-10-01

    To assess whether short-term soft contact lens wear alters the anterior eye surface. Twenty-two neophyte subjects wore soft contact lenses for a period of five hours. Topography based corneo-scleral limbal radius estimates were derived from height measurements acquired with a corneo-scleral profilometer. Additionally, central corneal thickness (CCT), anterior chamber depth (ACD), corneal curvature radius (R) and white-to-white (WTW) diameter were acquired with an OCT-assisted biometer. Measurements were obtained without lens wear (baseline), immediately after lens removal following five hours of wear and three hours after lens removal. Short-term soft contact lens wear significantly modifies corneo-scleral limbal radius (mean±SD: 130±74μm, p < 0.001) and the changes are repeatable. In contrast, the WTW diameter and R were not modified. ACD and CCT were significantly affected but no significant correlations were found between the increment of the limbal radius and the decrease in ACD and CCT. Limbal radius increment was reversed three hours after lens removal for 68% of the subjects but the time course of this reversal was not uniform. It is possible to accurately quantify limbal radius changes as a consequence of soft contact lens wear. The increment in the limbal diameter could reach over 0.5mm but that alteration does not correspond to changes in WTW diameter and it was not observable to the examiner using a slit lamp. Assessing topographical limbus after contact lens wear could be a tool to optimize the selection of the contact lens, from the perspective of anterior eye surface changes. Copyright © 2017 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

  3. Mask-wearing and respiratory infection in healthcare workers in Beijing, China

    Directory of Open Access Journals (Sweden)

    Peng Yang

    Full Text Available OBJECTIVES: The aim of the study was to determine rates of mask-wearing, of respiratory infection and the factors associated with mask-wearing and of respiratory infection in healthcare workers (HCWs in Beijing during the winter of 2007/2008. METHODS: We conducted a survey of 400 HCWs working in eight hospitals in Beijing by face to face interview using a standardized questionnaire. RESULTS: We found that 280/400 (70.0% of HCWs were compliant with mask-wearing while in contact with patients. Respiratory infection occurred in 238/400 (59.5% subjects from November, 2007 through February, 2008. Respiratory infection was higher among females (odds ratio [OR], 2.00 [95% confidence interval {CI}, 1.16-3.49] and staff working in larger hospitals (OR, 1.72 [95% CI, 1.092.72], but was lower among subjects with seasonal influenza vaccination (OR, 0.46 [95% CI, 0.280.76], wearing medical masks (reference: cotton-yarn; OR, 0.60 [95% CI, 0.39-0.91] or with good mask-wearing adherence (OR, 0.60 [95% CI, 0.37-0.98]. The risk of respiratory infection of HCWs working in low risk areas was similar to that of HCWs in high risk area. CONCLUSION: Our data suggest that female HCWs and staffs working in larger hospitals are the focus of prevention and control of respiratory infection in Beijing hospitals. Mask-wearing and seasonal influenza vaccination are protective for respiratory infection in HCWs; the protective efficacy of medical masks is better than that of cotton yarn ones; respiratory infection of HCWs working in low risk areas should also be given attention.

  4. Physiological responses wearing MOPP-IV after atropine and pralidoxime administration in warm and cool environments

    Energy Technology Data Exchange (ETDEWEB)

    Kolka, M.A.; Cadarette, B.S.

    1988-04-01

    The effect of cholinolytic and oxime (2 mg atropine + 600 mg pralidoxime) therapy on temperature regulation was evaluated in 8 subjects wearing chemical warfare protective clothing (MOPP-level IV). Subjects were tested in two environments: 35 c, 60% rh and 13 C, 44% rh during very light physical activity (1-2 Met) over a six-hour period. Sweating was suppressed approximately 40% by atropine and pralidoxime, and heart rate increased approximately 30 beats/min with drug treatment. At 13 C, all eight subjects completed 350 minutes of exposure in both drug and control experiments. Rectal temperature (t sub re) averaged 38.24 C in both treatments when subjects terminated their exposure at 35 C. Mean skin temperature averaged 37.42 C for both groups at termination. The treatment of subjects with atropine and pralidoxime when wearing chemical protective clothing does not adversely affect the length of time individuals can remain in a cool environment during very light work. However, the wearing of chemical protective clothing will decrease exposure time significantly (approx. 40%) in both control and drug treated subjects in a warm environment.

  5. Healthy Contact Lens Wear and Care

    Centers for Disease Control (CDC) Podcasts

    2014-02-04

    In this podcast, CDC’s Dr. Jennifer Cope explains some basic steps for proper wear and care of soft contact lenses.  Created: 2/4/2014 by National Center for Emerging and Zoonotic Infectious Diseases (NCEZID).   Date Released: 2/4/2014.

  6. Friction measurement in a hip wear simulator.

    Science.gov (United States)

    Saikko, Vesa

    2016-05-01

    A torque measurement system was added to a widely used hip wear simulator, the biaxial rocking motion device. With the rotary transducer, the frictional torque about the drive axis of the biaxial rocking motion mechanism was measured. The principle of measuring the torque about the vertical axis above the prosthetic joint, used earlier in commercial biaxial rocking motion simulators, was shown to sense only a minor part of the total frictional torque. With the present method, the total frictional torque of the prosthetic hip was measured. This was shown to consist of the torques about the vertical axis above the joint and about the leaning axis. Femoral heads made from different materials were run against conventional and crosslinked polyethylene acetabular cups in serum lubrication. Regarding the femoral head material and the type of polyethylene, there were no categorical differences in frictional torque with the exception of zirconia heads, with which the lowest values were obtained. Diamond-like carbon coating of the CoCr femoral head did not reduce friction. The friction factor was found to always decrease with increasing load. High wear could increase the frictional torque by 75%. With the present system, friction can be continuously recorded during long wear tests, so the effect of wear on friction with different prosthetic hips can be evaluated. © IMechE 2016.

  7. Illumination methods for optical wear detection

    NARCIS (Netherlands)

    Zhang, Jindang; Regtien, Paulus P.L.

    2007-01-01

    The paper presents some results of a study on optical wear detection. The focus of the paper is on the illumination, to optimize the contrast of the images. Various illumination methods are compared: bright field versus dark field illumination, and various kind of light sources: laser light, diffuse

  8. Tribology: Friction, lubrication, and wear technology

    Science.gov (United States)

    Blau, Peter J.

    1993-06-01

    The topics are presented in viewgraph form and include the following: introduction and definitions of terms; friction concepts; lubrication technology concepts; wear technology concepts; and tribological transitions. This document is designed for educators who seek to teach these concepts to their students.

  9. Childhood intelligence and early tooth wear patterns.

    Science.gov (United States)

    Heikkinen, Tuomo; Rusanen, Jaana; Sato, Koshi; Pesonen, Paula; Harila, Virpi; Alvesalo, Lassi

    2017-02-20

    The aim of this study is to explore the relationships between early dental wear patterns and preschool IQ (Intelligence Quotient, by Stanford-Binet) of the child to illuminate the historic relationship of mental queries and bruxism. The dental study participants were 864 Euro-American preschool and school children whose IQs were tested for school maturity purposes at the age of 4 years, followed by dental data in a cross-sectional manner at the mean age of 7.8 years. Worn dentitions were classified as "symmetric" or "right-" and "left-sided," based on the faceting of the teeth. In general, the relationships of tooth wear and intelligence were scarce, reflecting social background factors. Statistically significant results between asymmetric wear and gender groups suggest that direction of jaw function has a role in the regulation of processes responsible for individual mental performance in childhood. Increased left-side tooth wear and early advantage in the intelligence test in girls is intriguing due to the fact that they reach maturity earlier than boys in verbal articulation, controlled in most cases by the limited area on the left side of the brain.

  10. ERRATUM: Work smart, wear your hard hat

    CERN Multimedia

    2003-01-01

    An error appeared in the article «Work smart, wear your hard hat» published in Weekly Bulletin 27/2003, page 5. The impact which pierced a hole in the hard hat worn by Gerd Fetchenhauer was the equivalent of a box weighing 5 kg and not 50 kg.

  11. Saliva Parameters and Erosive Wear in Adolescents

    NARCIS (Netherlands)

    Zwier, N.; Huysmans, M. C. D. N. J. M.; Jager, D. H. J.; Ruben, J.; Bronkhorst, E. M.; Truin, G. J.

    2013-01-01

    The aim of this study was to investigate the relationship between several parameters of saliva and erosive wear in adolescents. (Un-)stimulated saliva was collected from 88 adolescents with erosion and 49 controls (age 16 +/- 1 years). Flow rate, pH and buffer capacity were determined immediately.

  12. Wear-Out Sensitivity Analysis Project Abstract

    Science.gov (United States)

    Harris, Adam

    2015-01-01

    During the course of the Summer 2015 internship session, I worked in the Reliability and Maintainability group of the ISS Safety and Mission Assurance department. My project was a statistical analysis of how sensitive ORU's (Orbital Replacement Units) are to a reliability parameter called the wear-out characteristic. The intended goal of this was to determine a worst case scenario of how many spares would be needed if multiple systems started exhibiting wear-out characteristics simultaneously. The goal was also to determine which parts would be most likely to do so. In order to do this, my duties were to take historical data of operational times and failure times of these ORU's and use them to build predictive models of failure using probability distribution functions, mainly the Weibull distribution. Then, I ran Monte Carlo Simulations to see how an entire population of these components would perform. From here, my final duty was to vary the wear-out characteristic from the intrinsic value, to extremely high wear-out values and determine how much the probability of sufficiency of the population would shift. This was done for around 30 different ORU populations on board the ISS.

  13. Tribology: Friction, lubrication, and wear technology

    Science.gov (United States)

    Blau, Peter J.

    1993-01-01

    The topics are presented in viewgraph form and include the following: introduction and definitions of terms; friction concepts; lubrication technology concepts; wear technology concepts; and tribological transitions. This document is designed for educators who seek to teach these concepts to their students.

  14. The Influence of the Thermomechanical Processing Regime on the Structural Evolution of Mo-Nb-Ti-V Microalloyed Steel Subjected to High-Pressure Torsion

    Science.gov (United States)

    Astafurova, Elena; Maier, Galina; Melnikov, Eugene; Naydenkin, Eugene; Smirnov, Aleksander; Bataev, Vladimir; Odessky, Pavel; Dobatkin, Sergey; Maier, Hans J.

    2017-07-01

    In the present study the effect of the thermal-mechanical processing regime—cold high-pressure torsion (HPT) at room temperature, cold HPT followed by annealing at 773 K (500 °C), and warm HPT at 723 K (450 °C)—on the peculiarities of the microstructure and microhardness of a Mo-Nb-Ti-V-0.08C microalloyed steel was analyzed. HPT processing resulted in high deformation and refinement of the initial structure and produced an ultrafine-grained microstructure featuring different morphologies with fine (partial recovery of the structure occurred, but the average size of the structural elements and their distribution varied only slightly whereas the microhardness increased to 642 HV. The variations in the microhardness with the processing regime were correlated to changes in microstructural parameters (grain size, dislocation density and precipitation strengthening).

  15. Long-term Efficacy of Orthokeratology Contact Lens Wear in Controlling the Progression of Childhood Myopia.

    Science.gov (United States)

    Santodomingo-Rubido, Jacinto; Villa-Collar, César; Gilmartin, Bernard; Gutiérrez-Ortega, Ramón; Sugimoto, Keiji

    2017-05-01

    The primary outcome of this study is to compare the axial length growth of white European myopic children wearing orthokeratology contact lenses (OK) to a control group (CT) over a 7-year period. Subjects 6-12 years of age with myopia -0.75 to -4.00DS and astigmatism ≤1.00DC were prospectively allocated OK or distance single-vision spectacles (SV) correction. Measurements of axial length (Zeiss IOLMaster), corneal topography, and cycloplegic refraction were taken at 6-month intervals over a 2-year period. Subjects were invited to return to the clinic approximately 5 years later (i.e., 7 years after the beginning of the study) for assessment of their ocular refractive and biometric components. The CT consisted of 4 SV and 12 subjects who switched from SV to soft contact lens wear after the initial 2 years of SV lens wear. Changes in axial length relative to baseline over a 7-year period were compared between groups. Fourteen and 16 subjects from the OK and CT groups, respectively, were examined 6.7 ± 0.5 years after the beginning of the study. Statistically significant changes in the axial length were found over time and between groups (both p < 0.001), but not for the time*group interaction (p = 0.125). The change in the axial length for the OK group was 22% (p = 0.328), 42% (p = 0.007), 40% (p = 0.020), 41% (p = 0.013), and 33% (p = 0.062) lower than the CT group following 6, 12, 18, 24, and 84 months of lens wear, respectively. A trend toward a reduction in the rate of axial elongation of the order of 33% was found in the OK group in comparison to the CT group following 7 years of lens wear.

  16. Instagram Shows How Diabetics Really Wear a Glucose Monitor

    Science.gov (United States)

    ... page: https://medlineplus.gov/news/fullstory_167648.html Instagram Shows How Diabetics Really Wear a Glucose Monitor ... and her colleagues searched the social media site Instagram. They found 353 posts featuring people wearing Dexcom ...

  17. Corrosive wear. Evaluation of wear and corrosive resistant materials; Noetningskorrosion. Utvaerdering av noetnings- och korrosionsbestaendiga material

    Energy Technology Data Exchange (ETDEWEB)

    Persson, H.; Hjertsen, D.; Waara, P.; Prakash, B.; Hardell, J.

    2007-12-15

    With a new purchase of a waste conveyer screw at hand, for the 'A-warehouse' at the combined power and heating plant at E.ON Norrkoeping, the request for improved construction materials was raised. The previous screw required maintenance with very short intervals due to the difficult operation conditions. With the new screw the expectation is to manage 6 months of operation without interruption. The environment for the screw has two main components that sets the demand on the materials, on one hand the corrosive products that comes along and which forms at digestion of the waste and on the other hand the abrasive content in the waste. The term of the mechanism is wear-corrosion and can give considerably higher material loss than the two mechanisms wear and corrosion separately. Combination of a strong corrosive environment together with extensive wear is something that we today have limited knowledge about. The overall objective of the project has been to establish better wear and corrosive resistant construction materials for a waste conveyer screw that will lead to reduced operational disturbance costs. The evaluation has been performed in both controlled laboratory environments and in field tests, which has given us a better understanding of what materials are more suitable in this tough environment and has given us a tool for future predictions of the wear rate of the different material. The new conveyer screw, installed in February 2007 and with which the field test have been performed, has considerably reduced the wear of the construction and the target of 6 month maintenance-free operation is met with this screw for all the evaluated materials. The wear along the screw varies very much and with a clear trend for all the materials to increase towards the feeding direction of the screw. As an example, the wear plate SS2377 (stainless duplex steel) has a useful life at the most affected areas that is calculated to be 1077 days of operation with the

  18. Impaired fasting glucose as an independent risk factor for hypertension among healthy middle-aged Japanese subjects with optimal blood pressure: the Yuport Medical Checkup Centre retrospective cohort study.

    Science.gov (United States)

    Morio, Masaaki; Inoue, Machiko; Inoue, Kazuo; Akimoto, Kimihiko

    2013-12-20

    This study aimed at investigating whether impaired fasting glucose (IFG) is an independent risk factor for incident hypertension among middle-aged Japanese subjects with optimal blood pressure (OBP). This retrospective cohort study was conducted in 2943 non-diabetic and non-hypertensive subjects aged 40-64 years, who participated in a voluntary health check-up program during the baseline (1998-2002) and follow-up periods (2002-2006). A multiple logistic regression model was utilized to calculate the odds ratio (OR) of incident hypertension among men and women with IFG and OBP. OBP was defined as systolic blood pressure (SBP) <120 mmHg and diastolic blood pressure (DBP) <80 mmHg, with no known history of hypertension. In this study, hypertension was defined as SBP ≥140 mmHg and DBP ≥90 mmHg or by a self-reported clinical diagnosis of hypertension. After the mean follow-up period of 5.6 years, the incidence of hypertension in men and women was 5.7% (73/1270) and 3.8% (62/1673), respectively. The age-adjusted ORs for incident hypertension in men and women with IFG were 1.95 (95% CI, 1.21-3.15) and 3.54 (95% CI, 2.00-6.27), respectively. After adjusting for age, systolic blood pressure, body mass index, total cholesterol, triglyceride, high-density lipoprotein cholesterol, and uric acid, the ORs for hypertension were 1.66 (95% CI; 1.02-2.70) for men and 2.62 (95% CI, 1.45-4.73) for women. The study results show that IFG may act as an independent risk factor for developing hypertension in individuals with OBP.

  19. QUALITY EVALUATION OF THE TPP POWER GENERATING UNITS WEAR RECONDITIONING

    Directory of Open Access Journals (Sweden)

    E. M. Farhadzadeh

    2016-01-01

    Full Text Available Reconditioning of the power generating unit worn equipment and devices is conducted during the scheduled repair period. Quality of wear reconditioning is evaluated by technical state and repair work implementation. Quality of the repair work execution characterizes logistical activities of the power station and the repair services and is rated by a five-grade scale. There are three technical conditions: adequate, subject to reservations, falling short of the technical standard documentation requirements. In practical work these constraints give place to essential ambiguity of the decision. Further to regulating techniques by way of informational support, the authors propose conducting the wear-reconditioning quality evaluation (repair quality accordingly the technical-and-economic indexes pattern of change. The paper recommends applying similarly the fivegrade system in evaluating the power generating unit technical state and distinguishes intolerable, dissatisfactory, fair, good and model estimates. The study demonstrates the assessment criteria dependence on the character of reliability and economical efficiency of performance variation after the repair with increase or decrease of the technical-and-economic indexes in reference to their mean, minimum and maximum values before the repair. The cases ascribed to intolerable quality of the wear reconditioning are those with one or more technical-and-economic indexes that not only failed to improve their values but deteriorated, and at that they became the worst amongst observable values. The model quality estimate of the wear reconditioning is allotted under condition that the power unit technical-and-economic index valuations after the repair not merely improved but also exceeded the best among those under observation. The developed method and algorithm for quality evaluation of the scheduled repair implementation contribute to practical realization of the independent monitoring. This monitoring

  20. Occlusion and temporomandibular function among subjects with mandibular distal extension removable partial dentures

    NARCIS (Netherlands)

    Creugers, N.H.J.; Witter, D.J.; Spijker, A. van 't; Gerritsen, A.E.; Kreulen, C.M.

    2010-01-01

    Objective. To quantify effects on occlusion and temporomandibular function of mandibular distal extension removable partial dentures in shortened dental arches. Methods. Subjects wearing mandibular extension removable partial dentures (n = 25) were compared with subjects with shortened dental arches

  1. From observation to understanding: Approach to analysis of wear mechanisms, Case of RCCAs and CRDM latch arms

    Energy Technology Data Exchange (ETDEWEB)

    Hertz, D. [Framatome ANP, 10, rue Juliette Recamier, 69456 Lyon Cedex 06 (France)

    2004-07-01

    Component wear can affect the ability of a component to fulfill its required function. For a designer or user, it is reasonable to expect possible wear occurrence as soon as parts are in relative motion. It is less obvious to extend this possibility to motions with small or very small amplitudes and loads. However, it has to be admitted that such cases exist. It then becomes imperative to determine the wear mechanisms so that the lifetime of the components and the optimum date of their replacement can be predicted or the degradation can be remedied. For this purpose, standard and widely accepted practice is to carry out simulator tests. Through examples of wear from nuclear reactor components such as the RCCAs (Rod Cluster Control Assembly) and the CRDM (Control Rod Drive Mechanism) latch arms, an approach for understanding the wear mechanisms and controlling their effects can be undertaken. Cases of wear have been observed on real-life parts, but the first simulator tests have shown deviations from in-reactor behaviour. Comparative examination of the wear facies of actual parts which have operated in reactor or simulators, both control rods and CRDM latch arms, was the key starting point for a new analytical approach, incorporating the formulation of wear mechanism hypotheses which can account for the observed facies. Expert assessment thus highlighted the importance of the environment by revealing that the wear featured a large component linked to friction-assisted corrosion. By including this tribo-corrosion aspect, it became possible to reach understanding of the mechanisms and account for the wear observed in reactor and on simulators. Further well-controlled simulator tests then made it possible to verify the importance of the tribo-corrosion processes in a pressurized water medium. Analysis of the physical chemical behaviour of the original materials (austenitic stainless steel) also explains why these surface modifications limit or remedy wear

  2. Measurement and Evaluation of Wear Frogs Switches ŽSR

    Directory of Open Access Journals (Sweden)

    Urda Ján

    2014-05-01

    Full Text Available This paper deals with the measurement and evaluation of wear frogs switches ZSR. One of the main problems is the oversize wear. The possibilities analysis of this problem is offered through a set of switches and monitoring of selected parameters. One of these parameters is also monitoring the vertical wear

  3. 46 CFR 169.825 - Wearing of safety belts.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Wearing of safety belts. 169.825 Section 169.825 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) NAUTICAL SCHOOLS SAILING SCHOOL VESSELS Operations § 169.825 Wearing of safety belts. The master of each vessel shall ensure that each person wears...

  4. Load application for the contact mechanics analysis and wear prediction of total knee replacement.

    Science.gov (United States)

    Zhang, Jing; Chen, Zhenxian; Wang, Ling; Li, Dichen; Jin, Zhongmin

    2017-05-01

    Tibiofemoral contact forces in total knee replacement have been measured at the medial and lateral sites respectively using an instrumented prosthesis, and predicted from musculoskeletal multibody dynamics models with a reasonable accuracy. However, it is uncommon that the medial and lateral forces are applied separately to replace a total axial load according to the ISO standard in the majority of current finite element analyses. In this study, we quantified the different effects of applying the medial and lateral loads separately versus the traditional total axial load application on contact mechanics and wear prediction of a patient-specific knee prosthesis. The load application position played an important role under the medial-lateral load application. The loading set which produced the closest load distribution to the multibody dynamics model was used to predict the contact mechanics and wear for the prosthesis and compared with the total axial load application. The medial-lateral load distribution using the present method was found to be closer to the multibody dynamics prediction than the traditional total axial load application, and the maximum contact pressure and contact area were consistent with the corresponding load variation. The predicted total volumetric wear rate and area were similar between the two load applications. However, the split of the predicted wear volumes on the medial and the lateral sides was different. The lateral volumetric wear rate was 31.46% smaller than the medial from the traditional load application prediction, while from the medial-lateral load application, the lateral side was only 11.8% smaller than the medial. The medial-lateral load application could provide a new and more accurate method of load application for patient-specific preclinical contact mechanics and wear prediction of knee implants.

  5. Sleep bruxism in individuals with and without attrition-type tooth wear: An exploratory matched case-control electromyographic study.

    Science.gov (United States)

    Jonsgar, Christine; Hordvik, Paul-Arne; Berge, Morten E; Johansson, Ann-Katrin; Svensson, Peter; Johansson, Anders

    2015-12-01

    To examine if there is a difference in possible sleep bruxism activity (SB) in subjects with or without attrition-type tooth wear. Sixteen individuals with pronounced attritional-type tooth wear were compared with sex and aged matched controls without tooth wear by means of measurement of electromyographic (EMG) activity during a minimum of four consecutive nights of sleep. Mean age and range for the study- and control- group was 23.7 years (range 19.9-28.5) and 23.6 years (range 20.3-27.9), respectively. There were 11 females and five males in each of the two groups. The attrition group presented incisal/occlusal attrition wear into dentin and matching wear facets between opposing anterior teeth. The controls had negligible signs of incisal/occlusal wear and a minimal number of matching wear facets. The prevalence of both self-reported and partner-reported SB was significantly more common in the attrition group compared to the controls (P=0.04 and P=0.007, respectively). Self-reported morning facial pain was similarly more common in the attrition group (P=0.014). Maximum opening capacity, number of muscles painful to palpation, salivary flow rate and buffering capacity were not significantly different between the groups. Interestingly, none of the measures of jaw muscle EMG activity during sleep, as recorded by the portable EMG equipment, differed significantly between the attrition group and the matched controls (P>0.05). The results from this exploratory study suggest that there is no difference in EMG activity between subjects with and without attrition-type tooth wear. Further research is needed in order to substantiate these preliminary findings. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

  6. Pattern of tongue pressure on hard palate during swallowing.

    Science.gov (United States)

    Ono, Takahiro; Hori, Kazuhiro; Nokubi, Takashi

    2004-01-01

    Contact of the tongue against the hard palate plays an important role in swallowing. This study aimed to clarify the pattern of contact between the tongue and hard palate by analyzing tongue pressure produced in swallowing 15 ml of water by healthy subjects wearing an experimental palatal plate with seven pressure sensors. Tongue pressure was generated initially by close contact with the anteriomedian part of the hard palate, then with the circumferential part, and finally softly with the posteriomedian part. Tongue pressure reached a peak quickly, then decreased gradually before disappearing almost simultaneously at each measured part of the hard palate. Magnitude and duration were significantly larger in the anteriomedian part compared to the other six parts measured, and was significantly smaller in the posteriomedian part. No laterality was found in tongue pressure produced at the circumferential parts of the hard palate. Our findings indicate that the order of tongue contact against each part of the hard palate as well as duration and magnitude of tongue pressure are coordinated precisely during swallowing. These findings could aid assessment of the tongue movement of dysphagic patients during rehabilitation.

  7. Organic carbon, and major and trace element dynamic and fate in a large river subjected to poorly-regulated urban and industrial pressures (Sebou River, Morocco).

    Science.gov (United States)

    Hayzoun, H; Garnier, C; Durrieu, G; Lenoble, V; Le Poupon, C; Angeletti, B; Ouammou, A; Mounier, S

    2015-01-01

    An annual-basis study of the impacts of the anthropogenic inputs from Fez urban area on the water geochemistry of the Sebou and Fez Rivers was conducted mostly focusing on base flow conditions, in addition to the sampling of industrial wastewater characteristic of the various pressures in the studied environment. The measured trace metals dissolved/particulate partitioning was compared to the ones predicted using the WHAM-VII chemical speciation code. The Sebou River, upstream from Fez city, showed a weakly polluted status. Contrarily, high levels of major ions, organic carbon and trace metals were encountered in the Fez River and the Sebou River downstream the Fez inputs, due to the discharge of urban and industrial untreated and hugely polluted wastewaters. Trace metals were especially enriched in particles with levels even exceeding those recorded in surface sediments. The first group of elements (Al, Fe, Mn, Ti, U and V) showed strong inter-relationships, impoverishment in Fez particles/sediments and stable partition coefficient (Kd), linked to their lithogenic origin from Sebou watershed erosion. Conversely, most of the studied trace metals/metalloids, originated from anthropogenic sources, underwent significant changes of Kd and behaved non-conservatively in the Sebou/Fez water mixing. Dissolved/particulate partitioning was correctly assessed by WHAM-VII modeling for Cu, Pb and Zn, depicting significant differences in chemical speciation in the Fez River when compared to that in the Sebou River. The results of this study demonstrated that a lack of compliance in environmental regulations certainly explained this poor status. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. A study on the physical fitness index, heart rate and blood pressure in different phases of lunar month on male human subjects

    Science.gov (United States)

    Chakraborty, Ujjwal; Ghosh, Tusharkanti

    2013-09-01

    The gravitational pull of the moon on the earth is not the same in all phases of the lunar month, i.e. new moon (NM), first quarter (FQ), full moon (FM) and third quarter (TQ), and as a result the amplitude of tide differs in different phases. The gravitational pull of the moon may have effects on the fluid compartments of the human body and hence the cardiovascular system may be affected differentially in the different phases of the lunar month. In the present study resting heart rate (HR) and blood pressure (BP), physical fitness index (PFI), peak HR and BP immediately after step test, and recovery HR and BP after step test were measured during different phases of the lunar month in 76 male university students (age 23.7 ± 1.7 years). At rest, both systolic and mean arterial BP were ˜5 mmHg lower in NM and FM compared to FQ and TQ, but resting HR was not significantly different between phases. Further, peak HR and peak systolic BP after step test were lower (˜4 beat/min and ˜5 mmHg, respectively) in NM and FM compared to FQ and TQ. PFI was also higher (˜5) in NM and FM compared to FQ and TQ. Recovery of HR after step test was quicker in NM and FM compared to that of FQ and TQ. It appears from this study that gravitational pull of the moon may affect the cardiovascular functions of the human body. Moreover, the physical efficiency of humans is increased in NM and FM due to these altered cardiovascular regulations.

  9. Obstructive sleep apnea is independently associated with inflammation and insulin resistance, but not with blood pressure, plasma catecholamines, and endothelial function in obese subjects.

    Science.gov (United States)

    Araújo, Luciene da Silva; Fernandes, Julia Freitas Rodrigues; Klein, Márcia Regina Simas Torres; Sanjuliani, Antonio Felipe

    2015-01-01

    Obstructive sleep apnea (OSA) is associated with an increased risk of cardiovascular disease (CVD). Several of the proposed mechanisms for the development of CVD in OSA are similar to those proposed for the increased risk of CVD in obesity, so that it is difficult to determine the influence of OSA on these pathogenic mechanisms in obese individuals. The aim of this study was to evaluate the relationship of OSA with endothelial function, oxidative stress, inflammatory biomarkers, metabolic profile, sympathetic nervous system activity, and blood pressure (BP) in obese individuals. This cross-sectional study included 53 obese adults (28 women). Sleep study was performed with WatchPAT 200 (Itamar Medical, Caesarea, Israel) and the diagnosis of OSA was made when apnea-hypopnea index (AHI) ≥5 events/h (n = 33). All participants underwent evaluation of: body adiposity, BP, plasma catecholamines, high sensitivity C-reactive protein (hs-CRP), adiponectin, malondialdehyde, glucose, insulin, lipid profile, and endothelial function (EndoPAT 2000). In univariate analysis, participants with OSA compared with those without OSA exhibited higher values of neck circumference, glucose, noradrenaline, and systolic BP. After adjustment for confounders, including adiposity, only glucose and hs-CRP were significantly higher in OSA patients. In correlation analysis, after controlling for confounders, AHI was positively and significantly associated with neck circumference and hs-CRP, while minimum O2 saturation was associated negatively and significantly with neck circumference, insulin and homeostatic model assessment-insulin resistance (HOMA-IR). The present study suggests that in obese individuals OSA is independently associated with inflammation and insulin resistance, but not with BP, plasma catecholamines and endothelial function. Copyright © 2015 Elsevier Inc. All rights reserved.

  10. Short-term effects of sports taping on navicular height, navicular drop and peak plantar pressure in healthy elite athletes: A within-subject comparison.

    Science.gov (United States)

    Kim, Taegyu; Park, Jong-Chul

    2017-11-01

    Medial tibial stress syndrome (MTSS) is one of the most common exercise-induced leg pain. The navicular drop (ND) was identified as a risk factor for MTSS. This study aimed to evaluate the short-term effects of sports taping applied to the supporting lower leg during sitting, standing, walking, and jogging to restrict the ND in healthy elite athletes.Twenty-four healthy elite athletes without a history of exercise-induced pain or injuries in the lower limbs participated in this study (median age: 21.00 years; 1st--3rd quartiles; 19.25-22.00). The 4 taping conditions were used: rigid taping (RT), kinesiology taping (KT), placebo taping (PT), and non-taping (NT). The order of taping techniques was randomly assigned. Normalized navicular height (NH), ND, and normalized ND evaluated using 3-dimensional motion analysis, and normalized peak plantar pressure (PP) were compared in 4 taping conditions during sitting, standing, walking, and jogging.During sitting, the normalized NH of RT is higher than that of NT, KT, and PT (χ = 17.30, P = .001), while during jogging, the normalized NH of RT is higher than that of NT and PT (χ = 10.55, P = .014). The normalized peak PP of NT is higher than that of PT (χ = 8.871, P = .031) in the lateral midfoot region.This study showed the RT technique maintained NH during sitting and jogging, and the RT technique could be an effective preventive and treatment strategy for MTSS.

  11. Predicting success with orthokeratology lens wear: a retrospective analysis of ocular characteristics.

    Science.gov (United States)

    Carkeet, N L; Mountford, J A; Carney, L G

    1995-12-01

    Orthokeratology procedures suffer from lack of predictability in the response of individuals. To identify factors contributing to this, we have retrospectively studied a range of ocular parameters in patients with varying outcomes from orthokeratology lens wear. Three groups were studied: an experimental group (9 subjects wearing Contex OK-3 design orthokeratology contact lenses), and 2 control groups [10 rigid gas permeable (RGP) contact lens wearers and 10 non-contact lens wearers]. Three categories were identified among the orthokeratology group: those responding well, moderately, or poorly to orthokeratology lens wear. Measurements included subjective refraction, intraocular distances, corneal thickness, ocular rigidity, and epithelial fragility. When comparing the three orthokeratology categories, there was no significant difference for central and peripheral epithelial fragility and ocular rigidity. There was also no significant difference for any of the biometric characteristics measured. The prefitting spherical equivalent power was found to be significantly different between categories of responders (p = 0.0228), with the poor responders having the highest initial level of myopia. None of the measured characteristics differed significantly among the orthokeratology group and the two control groups. In this pilot study, the success of orthokeratology lens wear was not related to ocular biomechanical or biometric attributes, but it was related to prefitting refractive error.

  12. Pressure sensor

    Science.gov (United States)

    Mee, David K.; Ripley, Edward B.; Nienstedt, Zachary C.; Nienstedt, Alex W.; Howell, Jr., Layton N.

    2015-09-29

    Disclosed is a passive, in-situ pressure sensor. The sensor includes a sensing element having a ferromagnetic metal and a tension inducing mechanism coupled to the ferromagnetic metal. The tension inducing mechanism is operable to change a tensile stress upon the ferromagnetic metal based on a change in pressure in the sensing element. Changes in pressure are detected based on changes in the magnetic switching characteristics of the ferromagnetic metal when subjected to an alternating magnetic field caused by the change in the tensile stress. The sensing element is embeddable in a closed system for detecting pressure changes without the need for any penetrations of the system for power or data acquisition by detecting changes in the magnetic switching characteristics of the ferromagnetic metal caused by the tensile stress.

  13. Tribology of Si/SiO2 in humid air: transition from severe chemical wear to wearless behavior at nanoscale.

    Science.gov (United States)

    Chen, Lei; He, Hongtu; Wang, Xiaodong; Kim, Seong H; Qian, Linmao

    2015-01-13

    Wear at sliding interfaces of silicon is a main cause for material loss in nanomanufacturing and device failure in microelectromechanical system (MEMS) applications. However, a comprehensive understanding of the nanoscale wear mechanisms of silicon in ambient conditions is still lacking. Here, we report the chemical wear of single crystalline silicon, a material used for micro/nanoscale devices, in humid air under the contact pressure lower than the material hardness. A transmission electron microscopy (TEM) analysis of the wear track confirmed that the wear of silicon in humid conditions originates from surface reactions without significant subsurface damages such as plastic deformation or fracture. When rubbed with a SiO2 ball, the single crystalline silicon surface exhibited transitions from severe wear in intermediate humidity to nearly wearless states at two opposite extremes: (a) low humidity and high sliding speed conditions and (b) high humidity and low speed conditions. These transitions suggested that at the sliding interfaces of Si/SiO2 at least two different tribochemical reactions play important roles. One would be the formation of a strong "hydrogen bonding bridge" between hydroxyl groups of two sliding interfaces and the other the removal of hydroxyl groups from the SiO2 surface. The experimental data indicated that the dominance of each reaction varies with the ambient humidity and sliding speed.

  14. Is tooth wear in the primary dentition predictive of tooth wear in the permanent dentition? Report from a longitudinal study.

    LENUS (Irish Health Repository)

    Harding, M A

    2010-03-01

    To determine the prevalence of tooth wear in the permanent dentition of a sample of 12-year-old school children and establish whether an association exists between tooth wear recorded now and tooth wear recorded in their primary dentition at age five.

  15. Investigation of the influence of process parameters on adhesive wear under hot stamping conditions

    Science.gov (United States)

    Schwingenschlögl, P.; Weldi, M.; Merklein, M.

    2017-09-01

    Current challenges like increasing safety standards and reducing fuel consumption motivate lightweight construction in modern car bodies. Besides using lightweight workpiece materials like aluminum, hot stamping has been established as a key technology for producing safety relevant components. Producing hot stamped parts out of ultra-high strength steels offers the possibility to improve the crash performance. At the same time the weight of car structure is reduced by using thinner sheet thicknesses. In order to avoid oxide scale formation and ensure corrosion protection, AlSi coatings are commonly deposited on the sheet surfaces used for direct hot stamping. This workpiece coating has a critical impact on the tribological conditions within the forming process and, as a consequence, influences the quality of hot stamped parts as well as tool wear. AlSi coatings have been identified as major reason for adhesive wear, which represents the main wear mechanism in hot stamping. Within this study, the influence of the process parameters on adhesive wear are investigated in dependency of workpiece and tool temperatures, drawing velocities and contact pressures. The tribological behavior is analyzed based on strip drawing experiments under direct hot stamping conditions. The experiments are performed with AlSi coated 22MnB5 in contact with the hot working tool steel 1.2367. For analyzing the amount of adhesion on the friction jaws, the surfaces are characterized by optical measurements. The experiments indicate that higher workpiece temperatures cause severe adhesive wear on the tool surface, while an increase of drawing velocity or contact pressure led to reduced adhesion. The measured friction coefficients decreased with rising amount of adhesion and remained at a constant level after a certain adhesive layer was built up on the tool surface.

  16. Aluminum nanocomposites having wear resistance better than stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    An, Linan [University of Central Florida; Qu, Jun [ORNL; Luo, Jinsong [Chinese Academy of Sciences; Fan, Yi [Chinese Academy of Sciences; Zhang, Ligong [University of Central Florida; Liu, Jinling [University of Central Florida; Xu, Chengying [University of Central Florida; Blau, Peter Julian [ORNL

    2011-01-01

    Tribological behavior of alumina-particle-reinforced aluminum composites made by powder metallurgy process has been investigated. The nanocomposite containing 15 vol% of Al2O3 nanoparticles exhibits excellent wear resistance by showing significantly low wear rate and abrasive wear mode. The wear rate of the nanocomposite is even lower than stainless steel. We have also demonstrated that such excellent wear resistance only occurred in the composite reinforced with the high volume fraction of nanosized reinforcing particles. The results were discussed in terms of the microstructure of the nanocomposite.

  17. Finger wear detection for production line battery tester

    Science.gov (United States)

    Depiante, Eduardo V.

    1997-01-01

    A method for detecting wear in a battery tester probe. The method includes providing a battery tester unit having at least one tester finger, generating a tester signal using the tester fingers and battery tester unit with the signal characteristic of the electrochemical condition of the battery and the tester finger, applying wavelet transformation to the tester signal including computing a mother wavelet to produce finger wear indicator signals, analyzing the signals to create a finger wear index, comparing the wear index for the tester finger with the index for a new tester finger and generating a tester finger signal change signal to indicate achieving a threshold wear change.

  18. Organic carbon, and major and trace element dynamic and fate in a large river subjected to poorly-regulated urban and industrial pressures (Sebou River, Morocco)

    Energy Technology Data Exchange (ETDEWEB)

    Hayzoun, H. [Université de Toulon, PROTEE, EA 3819, 83957 La Garde (France); LIMOM, Faculté des Sciences Dhar El Mehraz, Université Sidi Mohamed Ben Abdellah, Dhar El Mehraz B.P. 1796 Atlas, Fès 30000 (Morocco); Garnier, C., E-mail: cgarnier@univ-tln.fr [Université de Toulon, PROTEE, EA 3819, 83957 La Garde (France); Durrieu, G.; Lenoble, V.; Le Poupon, C. [Université de Toulon, PROTEE, EA 3819, 83957 La Garde (France); Angeletti, B. [Centre Européen de Recherche et d' Enseignement de Géosciences de l' Environnement UMR 6635 CNRS — Aix-Marseille Université, FR ECCOREV, Europôle Méditerranéen de l' Arbois, 13545 Aix-en-Provence (France); Ouammou, A. [LIMOM, Faculté des Sciences Dhar El Mehraz, Université Sidi Mohamed Ben Abdellah, Dhar El Mehraz B.P. 1796 Atlas, Fès 30000 (Morocco); Mounier, S. [Université de Toulon, PROTEE, EA 3819, 83957 La Garde (France)

    2015-01-01

    An annual-basis study of the impacts of the anthropogenic inputs from Fez urban area on the water geochemistry of the Sebou and Fez Rivers was conducted mostly focusing on base flow conditions, in addition to the sampling of industrial wastewater characteristic of the various pressures in the studied environment. The measured trace metals dissolved/particulate partitioning was compared to the ones predicted using the WHAM-VII chemical speciation code. The Sebou River, upstream from Fez city, showed a weakly polluted status. Contrarily, high levels of major ions, organic carbon and trace metals were encountered in the Fez River and the Sebou River downstream the Fez inputs, due to the discharge of urban and industrial untreated and hugely polluted wastewaters. Trace metals were especially enriched in particles with levels even exceeding those recorded in surface sediments. The first group of elements (Al, Fe, Mn, Ti, U and V) showed strong inter-relationships, impoverishment in Fez particles/sediments and stable partition coefficient (Kd), linked to their lithogenic origin from Sebou watershed erosion. Conversely, most of the studied trace metals/metalloids, originated from anthropogenic sources, underwent significant changes of Kd and behaved non-conservatively in the Sebou/Fez water mixing. Dissolved/particulate partitioning was correctly assessed by WHAM-VII modeling for Cu, Pb and Zn, depicting significant differences in chemical speciation in the Fez River when compared to that in the Sebou River. The results of this study demonstrated that a lack of compliance in environmental regulations certainly explained this poor status. - Highlights: • Pristine status of the Sebou River, Morrocco's main river, upstream Fez (1 M inhabitants) • The Fez River collecting Fez's urban/industrial wastewaters is heavily polluted. • The Fez discharge into the Sebou induces an increase of contaminant levels. • Change in partitioning and chemical speciation of

  19. Vascular Response to Graded Angiotensin II Infusion in Offspring Subjected to High-Salt Drinking Water during Pregnancy: The Effect of Blood Pressure, Heart Rate, Urine Output, Endothelial Permeability, and Gender

    Directory of Open Access Journals (Sweden)

    Zahra Pezeshki

    2014-01-01

    Full Text Available Introduction. Rennin-angiotensin system and salt diet play important roles in blood pressure control. We hypothesized that the high-salt intake during pregnancy influences the degree of angiotensin-dependent control of the blood pressure in adult offspring. Methods. Female Wistar rats in two groups (A and B were subjected to drink tap and salt water, respectively, during pregnancy. The offspring were divided into four groups as male and female offspring from group A (groups 1 and 2 and from group B (groups 3 and 4. In anesthetized matured offspring mean arterial pressure (MAP, heart rate and urine output were measured in response to angiotensin II (AngII (0-1000 ng/kg/min, iv infusion. Results. An increase in MAP was detected in mothers with salt drinking water (P<0.05. The body weight increased and kidney weight decreased significantly in male offspring from group 3 in comparison to group 1 (P<0.05. MAP and urine volume in response to AngII infusion increased in group 3 (P<0.05. These findings were not observed in female rats. Conclusion. Salt overloading during pregnancy had long-term effects on kidney weight and increased sex-dependent response to AngII infusion in offspring (adult that may reveal the important role of diet during pregnancy in AngII receptors.

  20. Exposure and risks from wearing asbestos mitts

    Directory of Open Access Journals (Sweden)

    Tindall Matthew

    2005-10-01

    Full Text Available Abstract Background Very high fibre inhalation exposure has been measured while people were wearing personal protective equipment manufactured from chrysotile asbestos. However, there is little data that relates specifically to wearing asbestos gloves or mitts, particularly when used in hot environments such as those found in glass manufacturing. The aim of this study was to assess the likely personal exposure to asbestos fibres when asbestos mitts were used. Results Three types of work activity were simulated in a small test room with unused mitts and artificially aged mitts. Neither pair of mitts were treated to suppress the dust emission. The measured respirable fibre exposure levels ranged from Conclusion People who wore asbestos mitts were likely to have been exposed to relatively low levels of airborne chrysotile asbestos fibres, certainly much lower than the standards that were accepted in the 1960's and 70's. The cancer risks from this type of use are likely to be very low.

  1. Risk factors and causative organisms in microbial keratitis in daily disposable contact lens wear.

    Science.gov (United States)

    Stapleton, Fiona; Naduvilath, Thomas; Keay, Lisa; Radford, Cherry; Dart, John; Edwards, Katie; Carnt, Nicole; Minassian, Darwin; Holden, Brien

    2017-01-01

    This study investigated independent risk factors and causative organisms in microbial keratitis in daily disposable contact lens (CL)-wearers. A multisite prospective case-control study was undertaken. Cases were daily disposable CL-wearers attending Moorfields Eye Hospital with microbial keratitis and those reported through a one-year surveillance study in Australia and in New Zealand. A population-based telephone survey identified daily disposable CL-wearing controls. Subjects completed a questionnaire describing CL-wear history, hygiene and demographics. The sample used for risk factor analysis was weighted in proportion to the CL-wearing population at each location. Corneal scrape results were accessed. Independent risk factors were determined using multiple binary logistic regression. Causative organisms in different CL-wear modalities were compared using a chi-squared test. 963 daily disposable CL-wearers were identified, from which 67 cases and 374 controls were sampled. Independent risk factors were; wearing CLs every day compared with less frequent use (OR 10.4x; 95% CI 2.9-56.4), any overnight wear (OR 1.8x; 95% CI 1.6-2.1), less frequent hand washing (OR 1.8x; 95% CI 1.6-2.0), and smoking (OR 1.3x; 95% CI 1.1-1.6). Certain daily disposable CLs (OR 0.2x; 95% CI 0.1-0.2) had protective effects. Environmental organisms were less frequently recovered with daily disposable CLs (20%), compared with other modalities (36%; pkeratitis with daily disposable CLs. Risk varied with daily disposable CL type. The profile of causative organisms is consistent with less severe disease.

  2. Tooth wear and feeding ecology in mountain gorillas from Volcanoes National Park, Rwanda.

    Science.gov (United States)

    Galbany, Jordi; Imanizabayo, Olive; Romero, Alejandro; Vecellio, Veronica; Glowacka, Halszka; Cranfield, Michael R; Bromage, Timothy G; Mudakikwa, Antoine; Stoinski, Tara S; McFarlin, Shannon C

    2016-03-01

    Ecological factors have a dramatic effect on tooth wear in primates, although it remains unclear how individual age contributes to functional crown morphology. The aim of this study is to determine how age and individual diet are related to tooth wear in wild mountain gorillas (Gorilla beringei beringei) from Volcanoes National Park, Rwanda. We calculated the percent of dentine exposure (PDE) for all permanent molars (M1-M3) of known-age mountain gorillas (N = 23), to test whether PDE varied with age using regression analysis. For each molar position, we also performed stepwise multiple linear regression to test the effects of age and percentage of time spent feeding on different food categories on PDE, for individuals subject to long-term observational studies by the Dian Fossey Gorilla Fund International's Karisoke Research Center. PDE increased significantly with age for both sexes in all molars. Moreover, a significant effect of gritty plant root consumption on PDE was found among individuals. Our results support prior reports indicating reduced tooth wear in mountain gorillas compared to western gorillas, and compared to other known-aged samples of primate taxa from forest and savanna habitats. Our findings corroborate that mountain gorillas present very low molar wear, and support the hypothesis that age and the consumption of particular food types, namely roots, are significant determinants of tooth wear variation in mountain gorillas. Future research should characterize the mineral composition of the soil in the Virunga habitat, to test the hypothesis that the physical and abrasive properties of gritty foods such as roots influence intra- and interspecific patterns of tooth wear. © 2015 Wiley Periodicals, Inc.

  3. SYNTHESIS OF FUNCTIONALLY GRADED ALUMINIUM COMPOSITE AND INVESTIGATION ON ITS ABRASION WEAR BEHAVIOUR

    Directory of Open Access Journals (Sweden)

    N. RADHIKA

    2017-05-01

    Full Text Available Functionally graded aluminium (Al-Si5Cu3 metal matrix composite reinforced with 10 wt-percent of boron carbide particles having average size of 33 µm was synthesized through horizontal centrifugal casting method. The specimen of length 150 mm and outer diameter of 154 mm with the thickness of 20 mm was produced under the centrifuging speed of 1000 rpm. Composite specimens were prepared as per ASTM standards from the casting and subjected to microstructural evaluation, hardness testing and three body abrasion wear test. The microstructural observation was done on the surfaces at the distance of 1, 2.5, 10 and 15 mm from the outer periphery of the casting and the result shows that larger amount of particles observed at distance of 2.5 mm and very less particles observed at the distance of 15 mm. The hardness test was conducted on the different surfaces in the radial direction from the outer periphery and found decrease in hardness from 2.5 to 15 mm. The abrasion wear test was conducted using dry abrasion tester for various loads of 28, 40 and 52 N at different distances from the outer periphery of the casting and the results revealed that wear rate gradually increases when moving towards the inner periphery and also with the increasing load. Therefore higher wear resistance was observed at the outer periphery and the lower wear resistance was obtained at the inner periphery. This property makes them suitable for using in wear applications such as in cylinder liners.

  4. Wear performance of monolithic dental ceramics with different surface treatments.

    Science.gov (United States)

    Preis, Verena; Weiser, Felix; Handel, Gerhard; Rosentritt, Martin

    2013-05-01

    To investigate the two-body wear performance of monolithic dental ceramics with different surface treatments. Standardized specimens (n = 8/ series) were fabricated from three monolithic dental ceramics (experimental translucent zirconia, experimental shaded zirconia, lithium disilicate). Four groups of each material were defined according to clinically relevant surface treatments: polished, polishedground, polished-ground-repolished, glazed. Two-body wear tests with steatite antagonists were performed in a chewing simulator. Surface roughness (R(a)) was controlled, and wear depths of specimens and antagonistic wear areas were calculated in relation to human enamel as reference. Statistical analysis of wear data was carried out using one-way ANOVA and Bonferroni multiple comparison test for post hoc analysis (α = .05). Scanning electron microscopy was applied for evaluating wear performance of ceramics and antagonists. Polished, ground, and repolished zirconia showed no wear, while glaze was abraded. Irrespective of the surface treatment, wear depth of lithium disilicate was significantly (P grinding and glazing. Steatite surfaces were smooth when opposed to polished/ground/repolished zirconia, and ploughed when opposed to glaze and lithium disilicate. Translucent and shaded experimental zirconia yielded superior wear behavior and lower antagonistic wear compared to lithium disilicate. A trend to higher ceramic and antagonistic wear was shown after grinding and glazing.

  5. Wirelessly Interrogated Wear or Temperature Sensors

    Science.gov (United States)

    Woodard, Stanley E.; Taylor, Bryant D.

    2010-01-01

    Sensors for monitoring surface wear and/or temperature without need for wire connections have been developed. Excitation and interrogation of these sensors are accomplished by means of a magnetic-field-response recorder. In a sensor of the present type as in the previously reported ones, the capacitance and, thus, the resonance frequency, varies as a known function of the quantity of interest that one seeks to determine. Hence, the resonance frequency is measured and used to calculate the quantity of interest.

  6. Contact Thermal Analysis and Wear Simulation of a Brake Block

    Directory of Open Access Journals (Sweden)

    Nándor Békési

    2013-01-01

    Full Text Available The present paper describes an experimental test and a coupled contact-thermal-wear analysis of a railway wheel/brake block system through the braking process. During the test, the friction, the generated heat, and the wear were evaluated. It was found that the contact between the brake block and the wheel occurs in relatively small and slowly moving hot spots, caused by the wear and the thermal effects. A coupled simulation method was developed including numerical frictional contact, transient thermal and incremental wear calculations. In the 3D simulation, the effects of the friction, the thermal expansion, the wear, and the temperature-dependent material properties were also considered. A good agreement was found between the results of the test and the calculations, both for the thermal and wear results. The proposed method is suitable for modelling the slowly oscillating wear caused by the thermal expansions in the contact area.

  7. Postmarket surveillance of Menicon Z rigid gas-permeable contact lenses for up to 30 days continuous wear in the United States.

    Science.gov (United States)

    Albright, Roger A; Venuti, Beverley D; Ichijima, Hideji; Nyunt, Aung Kyaw; Cavanagh, H Dwight

    2010-09-01

    To evaluate the incidence of microbial keratitis associated with the use of the Menicon Z rigid gas-permeable (RGP) contact lenses (CLs) for up to 30 days continuous wear (CW). For this study, CW was defined as wearing CLs in an extended-wear modality with an average wearing time of 22 days or more. Microbial keratitis was the sole endpoint of the study safety evaluation. Subjects who were interested in RGP lens CW were recruited for the study through 33 investigational practices. To be eligible for the study, subjects must have worn the Menicon Z lens for CW for at least 1.5 months with an average CW time of 22 days or more. Eligible wearers were then contacted at 6-month intervals for up to 24 months after enrollment to determine their typical wearing schedules and continuance of wear and to detect any problems that would be indicative of microbial keratitis. Discontinuation from the study was defined as a discontinuation of contact with or CL wear by the study participants. Study volunteers could be discontinued from the study at 6, 12, 18, or 24 months if they could not be contacted (lost to follow-up); if they were not wearing their CL for CW; or at their own request. Wearing time data collected for individuals discontinued from the study was included in the wearing time analysis. The study population included 507 participants, of whom 173 had discontinued by the end of study at 24 months. Lack of 22 days or more of CW was the most frequently cited reason for discontinuation and accounted for 121 of the 173 subject discontinuations. Lost to follow-up, study participant choice, and other reasons accounted for the remaining 52 subject discontinuations. Of the reported wearing times over the duration of the study, 1,275 of the 1,527 contacts resulted in reported wearing times of 22 days or more of CW. There were no findings of microbial keratitis during the study. Overall, there was a low reported rate of complications for the enrolled study participants. On the

  8. Wear Resistance Assessment of Fluoropolymer Coated Gears

    Directory of Open Access Journals (Sweden)

    Lidia Nedeloni

    2017-11-01

    Full Text Available Power transmissions that incorporate gears dissipate a significant amount of energy and noise. Thus, any improvement in their performance contributes to reducing energy consumption and noise pollution. In recent years, the opportunities offered by conventional technologies to increase gear performance have been fully exploited. Therefore, surface depositions on gear teeth have become increasingly important technologies in achieving objectives such as: improving energy performance, providing greater protection against superficial defects, increasing load capacity and reducing acoustic emissions generated during operation. However, gear coating technologies have begun to be developed, but the investigations are still insufficient. In this study, we carried out wear resistance investigations performed on fluoropolymer coatings for different working speeds, loads and lubrication conditions. The results point out that the deterioration rate of the coating increases with the increase of the working speed and the applied load. In addition, a slight lubrication, applied at the start of testing, leads to a noticeable improvement in wear behaviour. This study represents one step further in understanding the wear process of fluoropolymer coated gears

  9. Corrosion and wear in plasma electrosurgical devices

    Science.gov (United States)

    Gaspredes, J.; Ryan, T. P.; Stalder, K. R.; Woloszko, J.

    2017-02-01

    Data were previously reported on studies of the effects of electrical discharges on the corrosion and wear of simple, single-wire test devices immersed in isotonic saline 1 . This work showed that there are a wide variety of mechanisms that can explain various aspects of electrode mass loss, even with very simple electrode geometries and operating conditions. It was found that the electrode material composition played an important role. Subsequently, our studies were expanded to include more realistic device geometries and operating conditions. This paper shows the results of studies on wear characteristics of electrodes made from a variety of highly corrosion resistant metals and alloys, including Waspaloy, Hastelloy, Inconel, Havar, Monel, and other pure metals such as Hafnium. All of these metals underwent wear testing under clinically relevant conditions. Depending on the operating conditions, multiple discrete physical and chemical effects were observed at different locations on the surface of an individual millimeter-scale device electrode. Scanning electron microscope (SEM) micrographs, Energy-dispersive X-ray spectroscopy (EDS) and area loss data will be presented for a variety of test conditions and electrode materials.

  10. Effects of local fatigue on myoelectrical activity of erector spine muscles and the center for pressure displacement of the feet during balance recovery following postural perturbation in kyphotic subjects

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    Rooholah Rezaee

    2014-07-01

    Full Text Available Background: kyphosis deformity affects postural control. Muscular fatigue is one of the factors that can impair the mechanism of body balance. The aim of this study was to determine the effects of local fatigue on the myoelectrical activity of erector spine muscles and the center for pressure displacement of the feet during balance recovery following postural perturbation in kyphotic subjects. Methods: In this quasi-experimental study, 12 male students with>40 degrees thoracic kyphosis and 12 controls were selected to participate in the study. A flexible ruler was used to measure thoracic kyphosis. For postural control assessment, each subject underwent unexpected, forward-backward perturbations while standing on a foot scan mounted on a movable plate triggered by a weight equivalent to 10% of the subjects’ body weight. Experimental procedure was measured before (3 trails and after (3 trials the fatigue protocol. The myoelectric activity of the erector spine and multi fidus was compared in the groups using repeated measures of ANOVA and independent t-test (P<0.05. Results: There was no significant difference in the foot center of pressure displacement in both groups after muscular fatigue. After fatigue, there was an increase in the activity of longissimus thoracis (P=0.001 and iliocostalis thoracis (P= 0.001 in control group, while no significant difference was reported for the muscular activity of multifidus (p=0.084. The activity of langisimus thoracis was significantly increased (P=0.028 in kyphtic group after fatigue. Conclusion: erector spine muscles fatigue could not significantly affect the postural control in both groups, but the electrical activity of erector spine muscles during balance recovery following postural perturbation in kyphotic subjects was different than the controls.

  11. Comparison of pattern of failure of resin composite restorations in non-carious cervical lesions with and without occlusal wear facets.

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    Oginni, Adeleke Oke; Adeleke, Adeyinka Adedayo

    2014-07-01

    Many studies have reported the clinical problems associated with resin composite restorations in NCCLs. None has compared these clinical problems in NCCLs with and without occlusal wear facets. The present study sets out to determine the proportion of NCCLs that presents occlusal wear facets, and to compare the failure pattern of resin composite restorations in NCCLs with and without occlusal wear facets. Teeth with NCCLs were classified into two groups, those with and without occlusal wear facets. Both groups were restored using micro hybrid resin composite. The restorations were evaluated at the end of 2 years concerning post-operative sensitivity, retention, marginal integrity, marginal discolouration, wear, and secondary caries, using the USPHS criteria. Statistical analysis compared the ratings of each criterion between the two groups using Pearson's χ(2) or Fisher's exact test. About one-third (33.8%) of teeth with NCCLs presented with occlusal wear facets, more NCCLs with occlusal wear facets in mandibular teeth (44.7%) than maxillary teeth (24.5%). Retention rate of composite resin restorations in NCCLs with and without occlusal wear facets was 63.9% and 74.4% respectively at the end of 2 years. More marginal discolouration and defects were observed in restorations in NCCLs with occlusal wear facets, the differences were not statistically significant (p>0.05). The decline in ratings of marginal discolouration and defects, and the lower retention rate of restorations in NCCLs with occlusal wear facets may support the role of occlusal stress and tooth flexure as a cause of failure of restorations in NCCLs. The ability to distinguish between stress induced lesions (with occlusal wear facets) and other cervical lesions will have important ramifications for the success of their restorations because they are not subjected to the same physical forces that are responsible for the deterioration of the restoration. Copyright © 2014 Elsevier Ltd. All rights reserved.

  12. Relations between a novel, reliable, and rapid index of arterial compliance (PP-HDI) and well-established inidices of arterial blood pressure (ABP) in a sample of hypertensive elderly subjects.

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    Bergamini, L; Finelli, M E; Bendini, C; Ferrari, E; Veschi, M; Neviani, F; Manni, B; Pelosi, A; Rioli, G; Neri, M

    2009-01-01

    Hypertension is a risk factor for a long-lasting arterial wall-remodelling leading to stiffness. The rapid method measuring the pulse pressure (PP) by means of the tool of Hypertension Diagnostic Instruments (HDI) called PP-HDI, overcomes some of the problems arising with more-time consuming methods, like ambulatory blood pressure monitoring (ABPM), and give information about the elasticity of the arterial walls. We studied the relationship between the PP-HDI, the large artery compliance (LA-C) and small artery compliance (SA-C) and few well-established indices of arterial blood pressure (ABP) in a sample of 75 hypertensive subjects, aged 65 years and over. Significant correlations between LA-C and heart rate (HR), PP-ABPM and PP-HDI were found. SA-C relates with HR and systolic blood pressure (SBP) measured in lying and standing positions. Applying a stepwise regression analysis, we found that LA-C variance stems from PP-HDI and HR, while SA-C variance stems from SBP in lying position. Receiver operator characteristic (ROC) curves for thresholds of PP showed that PP-HDI reached levels of sensitivity/specificity similar to PP-ABPM. In conclusion, surveillance of ABP through hemo-dynamic indices, in particular of SBP, is essential, nevertheless the advantage of this control is not known in an elderly population where the organ damage is already evident. PP needs necessarily an instrumental measurement. The PP-HDI result is similar in reliability with respect to PPABPM, but is more rapid and well applicable in an elderly population.

  13. Operation-Oriented Studies on Wear Properties of Surface-Hardened Alloy Cast Steels Used in Mining in the Conditions of the Combined Action of Dynamic Forces and an Abrasive Material

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    Wieczorek A.N.

    2017-12-01

    Full Text Available This paper presents the results of wear tests of shot-peened and not shot-peened cast steels used in the mining machinery industry, in particular in the construction of chain drums for armoured face conveyors. Wear tests were carried out in the conditions corresponding to the real operating conditions of armoured face conveyors during drifting work in rocks such as sandstone. The operating factors subjected to the analyses included the presence of quartz abrasive and the impact of external dynamic forces. On the basis of the wear tests as well as the microhardness and microstructure examinations performed, it has been found that the action of an additional dynamic force has a synergistic impact on the process of abrasive wear in loose quartz abrasive. It has been further found that the value of abrasive wear of chain wheels operated in the conditions of a combined action of abrasive and a dynamic force depends on whether the area of mating of wheels with the chain was shot-peened or not before the wear tests – an increase in the abrasive wear was observed for the wheels made of cast steel subjected to shot peening in the area of mating with the chain. Lower resistance to abrasive wear of the cast steels subjected to shot peening before the wear tests could result from the formation of cracks in the surface layer caused by the action of shot.

  14. Performance of Zinc-Difattyalkyldithyocarbamate as Anti-Friction/Anti-Wear Lubricant Additives

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    Komar Sutriah

    2014-03-01

    Full Text Available Dithyocarbamate is an organosulphur compound that has long been known and widely applied in various fields, including in agriculture and industry. Several variants of synthesized vegetable oil-based Zinc-difattyalkyldithyocarbamate were tested its anti-friction/anti-wear performance on four ball machine using the method of ASTM-D2783. Anti-friction/anti-wear test to six of additive variants of Zinc-difattyalkyldithyocarbamate at doses of 1.2% indicated that all variants of the product has welding point value higher than the lube base oil lubricant HVI 60, and from US Steel 136 standard for Hydraulic lubricants, but only two additive variants of Zinc-bis(lauryl palmityldithyocarbamate and Zinc-bis(lauryl oleyldithyocarbamate which has a larger load wear index value than the standard, and meet the criteria as an additive extreme pressure according to US steel 136 standard. Zinc-bis(lauryl palmityldithyocarbamate is an additive variant with the best performance, meet bi-functional lubricant additives criteria, as anti-friction/anti-wear and antioxidant additive.

  15. Modelling of tunnelling processes and rock cutting tool wear with the particle finite element method

    Science.gov (United States)

    Carbonell, Josep Maria; Oñate, Eugenio; Suárez, Benjamín

    2013-09-01

    Underground construction involves all sort of challenges in analysis, design, project and execution phases. The dimension of tunnels and their structural requirements are growing, and so safety and security demands do. New engineering tools are needed to perform a safer planning and design. This work presents the advances in the particle finite element method (PFEM) for the modelling and the analysis of tunneling processes including the wear of the cutting tools. The PFEM has its foundation on the Lagrangian description of the motion of a continuum built from a set of particles with known physical properties. The method uses a remeshing process combined with the alpha-shape technique to detect the contacting surfaces and a finite element method for the mechanical computations. A contact procedure has been developed for the PFEM which is combined with a constitutive model for predicting the excavation front and the wear of cutting tools. The material parameters govern the coupling of frictional contact and