Base de dados : MEDLINE
Pesquisa : G01.374.618 [Categoria DeCS]
Referências encontradas : 3253 [refinar]
Mostrando: 1 .. 10   no formato [Longo]

página 1 de 326 ir para página                         

  1 / 3253 MEDLINE  
              next record last record
seleciona
para imprimir
Fotocópia
Texto completo
PMID:28419123
Autor:Darbois Texier B; Ibarra A; Melo F
Endereço:Departamento de Física Universidad de Santiago de Chile, Avenida Ecuador 3493, 9170124 Estación Central, Santiago, Chile.
Título:Low-resistive vibratory penetration in granular media.
Fonte:PLoS One; 12(4):e0175412, 2017.
ISSN:1932-6203
País de publicação:United States
Idioma:eng
Resumo:Non-cohesive materials such as sand, dry snow or cereals are encountered in various common circumstances, from everyday situations to industry. The process of digging into these materials remains a challenge to most animals and machines. Within the animal kingdom, different strategies are employed to overcome this issue, including excavation methods used by ants, the two-anchor strategy employed by soft burrowers such as razor-clams, and undulatory motions exhibited by sandfish lizards. Despite the development of technology to mimic these techniques in diggers and robots, the limitations of animals and machines may differ, and mimicry of natural processes is not necessarily the most efficient technological strategy. This study presents evidence that the resisting force for the penetration of an intruder into a dry granular media can be reduced by one order of magnitude with small amplitude (A ≃ 10 µm) and low frequency (f = 50 - 200 Hz) mechanical vibrations. This observed result is attributed to the local fluidization of the granular bed which induces the rupture of force chains. The drop in resistive force on entering dry granular materials may be relevant in technological development in order to increase the efficiency of diggers and robots.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:0 (Soil); 7631-86-9 (Silicon Dioxide)


  2 / 3253 MEDLINE  
              first record previous record next record last record
seleciona
para imprimir
Fotocópia
Texto completo
PMID:28332407
Autor:Samson M; Bernard A; Monnet T; Lacouture P; David L
Endereço:a P' Institute , CNRS - University of Poitiers - ENSMA , Futuroscope Cedex , France.
Título:Unsteady computational fluid dynamics in front crawl swimming.
Fonte:Comput Methods Biomech Biomed Engin; 20(7):783-793, 2017 May.
ISSN:1476-8259
País de publicação:England
Idioma:eng
Resumo:The development of codes and power calculations currently allows the simulation of increasingly complex flows, especially in the turbulent regime. Swimming research should benefit from these technological advances to try to better understand the dynamic mechanisms involved in swimming. An unsteady Computational Fluid Dynamics (CFD) study is conducted in crawl, in order to analyse the propulsive forces generated by the hand and forearm. The k-ω SST turbulence model and an overset grid method have been used. The main objectives are to analyse the evolution of the hand-forearm propulsive forces and to explain this relative to the arm kinematics parameters. In order to validate our simulation model, the calculated forces and pressures were compared with several other experimental and numerical studies. A good agreement is found between our results and those of other studies. The hand is the segment that generates the most propulsive forces during the aquatic stroke. As the pressure component is the main source of force, the orientation of the hand-forearm in the absolute coordinate system is an important kinematic parameter in the swimming performance. The propulsive forces are biggest when the angles of attack are high. CFD appears as a very valuable tool to better analyze the mechanisms of swimming performance and offers some promising developments, especially for optimizing the performance from a parametric study.
Tipo de publicação: JOURNAL ARTICLE


  3 / 3253 MEDLINE  
              first record previous record next record last record
seleciona
para imprimir
Fotocópia
Texto completo
PMID:28127994
Autor:Zhan JM; Li TZ; Chen XB; Li YS
Endereço:a Department of Applied Mechanics and Engineering , Sun Yat-sen University , Guangzhou , P.R. China.
Título:Hydrodynamic analysis of human swimming based on VOF method.
Fonte:Comput Methods Biomech Biomed Engin; 20(6):645-652, 2017 May.
ISSN:1476-8259
País de publicação:England
Idioma:eng
Resumo:A 3-D numerical model, based on the Navier-Strokes equations and the RNG k-ε turbulence closure, for studying hydrodynamic drag on a swimmer with wave-making resistance taken into account is established. The volume of fluid method is employed to capture the undulation of the free surface. The simulation strategy is evaluated by comparison of the computed results with experimental data. The computed results are in good agreement with data from mannequin towing experiments. The effects of the swimmer's head position and gliding depth on the drag force at different velocities are then investigated. It is found that keeping the head aligned with the body is the optimal posture in streamlined gliding. Also wave-making resistance is significant within 0.3 m depth from the free surface.
Tipo de publicação: JOURNAL ARTICLE


  4 / 3253 MEDLINE  
              first record previous record next record last record
seleciona
para imprimir
Fotocópia
PMID:28357823
Autor:Frawley L; Devaney B; Tsouras T; Frawley G
Endereço:Department of Intensive Care and Hyperbaric Medicine, The Alfred Hospital, Melbourne, Australia.
Título:Performance of the BBraun perfusor space syringe driver under hyperbaric conditions.
Fonte:Diving Hyperb Med; 47(1):38-43, 2017 03.
ISSN:1833-3516
País de publicação:Australia
Idioma:eng
Resumo:BACKGROUND: The BBraun Perfusor Space™ syringe driver is already in use by ambulance services and retrieval teams but has not previously been assessed for hyperbaric chamber use. METHODS: Pump flow accuracy was tested at rates between 1 and 40 ml· h⁻¹ using three different brands of 50 ml syringe. Function of the occlusion alarms was assessed using the same syringes. The hyperbaric profile involved pressurisation to 284 kPa at 30 kPa· min⁻¹, 30 min at 284 kPa and decompression at 30 kPa· min⁻¹. Output was recorded from differences in weight of collection containers. A single device was tested. RESULTS: Performance was highly dependent on the syringe type used, with two of the three 50 ml syringes used demonstrating 'stiction' at both low and high occlusion pressure alarm settings, most marked during pressurisation. On decompression from 284 kPa all syringes alarmed at significantly lower pressures. Because of the stiction problems only the flow measurements for the BBrown Omni¬ x 50 ml syringes are reported. At a pressure of 284 kPa, the difference between programmed and delivered rates was within the manufacturer's specification of 10%: at 40 ml· h⁻¹ (median variation 1.25%, IQR 0.5-1.7%), 10 ml· h⁻¹ (8.6%, IQR 8-9.2%), 5 ml· h⁻¹ (-8.8%, IQR - 1.6-8.8%) and 1 ml· h⁻¹ (-4%, IQR 4-12%). Pressurisation was associated with significantly lower flow rates whilst decompression was associated with significantly increased rates. Limited testing at 405 kPa was also within the manufacturer's specifications. CONCLUSION: A BBraun Infusor Space syringe driver performed within acceptable performance criteria but is highly dependent on syringe type and flow rates. The potential for the device to under deliver on pressurisation and over deliver on depressurisation, however, suggests vigilance and appropriate rate adjustments may be necessary during these phases.
Tipo de publicação: EVALUATION STUDIES; JOURNAL ARTICLE; TECHNICAL REPORT
Nome de substância:0 (Polymers); 0 (elastomeric)


  5 / 3253 MEDLINE  
              first record previous record next record last record
seleciona
para imprimir
Fotocópia
PMID:28380319
Autor:Kleiner A; Galli M; Franceschini M; De Pandis MF; Stocchi F; Albertini G; de Barros RM
Título:The coefficient of friction in Parkinson's disease gait.
Fonte:Funct Neurol; 32(1):17-22, 2017 Jan/Mar.
ISSN:1971-3274
País de publicação:Italy
Idioma:eng
Resumo:This study aimed to characterize the coefficient of friction (COF) curves of patients with Parkinson's disease (PD) during barefoot gait and to evaluate the relationships between this variable and functional scales. Twenty-two subjects with PD (ON phase of levodopa) and 22 healthy subjects participated in this study. The participants walked barefoot along a pathway that went over two force plates embedded in the floor of the data collection room. The instantaneous COF was calculated as the ratio between the horizontal and vertical components of the ground reaction forces. Two-sample t-tests applied to every 1% of the support phase of the COF curve were used to compare the groups and to identify the phases in which the two groups were different. Specifically, three COF areas were computed: Area 1 (for the loading response phase), Area 2 (for the midstance phase) and Area 3 (for the terminal stance phase). Pearson's tests were applied to assess the associations between the COF curve areas and the clinical scales. The subjects with PD exhibited lower COF values during the loading response and terminal stance phases and higher COF values during the mid-stance phase compared with the control group. A strong positive correlation was observed between Area 1 and the Timed Up and Go Test (90.3%). In conclusion, the patients' COFs exhibited patterns that were different from those of the control group. Moreover, during the loading response phase, these differences were well-correlated with the Timed Up and Go Test scale data; Timed Up and Go Test data can be used to identify the risk of falls among PD patients.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:0 (Antiparkinson Agents); 46627O600J (Levodopa)


  6 / 3253 MEDLINE  
              first record previous record next record last record
seleciona
para imprimir
Fotocópia
Texto completo
PMID:28193469
Autor:Mann BF; Makarov AA; Wang H; Welch CJ
Endereço:Merck & Co., Inc., MRL, Department of Process Research & Development, Rahway, NJ 07065, USA. Electronic address: ben.mann@gmail.com.
Título:Effects of pressure and frictional heating on protein separation using monolithic columns in reversed-phase chromatography.
Fonte:J Chromatogr A; 1489:58-64, 2017 Mar 17.
ISSN:1873-3778
País de publicação:Netherlands
Idioma:eng
Resumo:Pressure is not typically controlled or adjusted independently of flow rate during method development in reversed-phase LC (RPLC). However, it has been shown that pressure has an effect on analyte molecular molar volume, and the magnitude of this effect is greater for proteins and ionizable compounds than neutral small molecules. This phenomenon has received attention recently in the context of porous sub-2-micron particle packed columns. The present study surveys the effect of pressure and frictional heating on RPLC separations using commercially-available monolithic columns at constant flow rate and with controlled external temperature. Because the current monoliths cannot be operated at high pressures, all experiments were conducted with pressures at or below 200bar. Nonetheless, substantial changes in retention were still observed; for example, an increase in pressure of 75bar shifted the retention factor for bovine insulin from 1.27 to 1.78, a 40% increase, while a similar experiment with the neutral small molecule, toluene, showed no change in retention. Results are presented from investigations of model peptides and proteins ranging in size from 1kDa to 30kDa, as well as experiments performed with a silica-based C18 monolith and a polystyrene divinylbenzene monolith functionalized with a phenyl stationary phase. This work indicates that protein separations in monoliths are highly pressure sensitive, and pressure should therefore be considered as an additional parameter in method development for optimizing retention and selectivity. Given these findings, and the ever-increasing importance of chromatographic separations of proteins in both industrial and academic laboratories, improved instrumentation and mechanisms for directly controlling system backpressure could be of great practical value.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:0 (Insulin); 0 (Peptides); 0 (Proteins)


  7 / 3253 MEDLINE  
              first record previous record next record last record
seleciona
para imprimir
Fotocópia
Texto completo
PMID:27987761
Autor:Aminzahed I; Mashhadi MM; Sereshk MR
Endereço:Department of Mechanical Engineering, University of Tehran, Tehran, Iran. Electronic address: iaminzahed@ut.ac.ir.
Título:Investigation of holder pressure and size effects in micro deep drawing of rectangular work pieces driven by piezoelectric actuator.
Fonte:Mater Sci Eng C Mater Biol Appl; 71:685-689, 2017 Feb 01.
ISSN:1873-0191
País de publicação:Netherlands
Idioma:eng
Resumo:Micro forming is a manufacturing process to fabricate micro parts with high quality and a cost effective manner. Deep drawing could be a favorable method for production of complicated parts in macro and micro sizes. In this paper piezoelectric actuator is used as a novel approach in the field of micro manufacturing. Also, in current work, investigations are conducted with four rectangular punches and blanks with various thicknesses. Blank holder pressure effects on thickness distributions, punch force, and springback are studied. According to the results of this work, increasing of blank holder pressure in scaled deep drawing, in contrast to thickness of drawn part, leads to decrease in the punch forces and springback. Furthermore, it is shown that in micro deep drawing, the effects of holder pressure on mentioned parameters can be ignored.
Tipo de publicação: JOURNAL ARTICLE


  8 / 3253 MEDLINE  
              first record previous record next record last record
seleciona
para imprimir
Fotocópia
Texto completo
PMID:27987740
Autor:Cui W; Qin G; Duan J; Wang H
Endereço:Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Material Science and Engineering, Northeastern University, Shenyang 110819, China.
Título:A graded nano-TiN coating on biomedical Ti alloy: Low friction coefficient, good bonding and biocompatibility.
Fonte:Mater Sci Eng C Mater Biol Appl; 71:520-528, 2017 Feb 01.
ISSN:1873-0191
País de publicação:Netherlands
Idioma:eng
Resumo:In order to solve wear resistance of Ti alloy biomaterials, the concept of a graded nano-TiN coating has been proposed. The coating was prepared on Ti-6Al-4V bio-alloy by DC reactive magnetron sputtering. The wear performance of the coated specimens was measured in Hank's solution under the load of 10N, and the biocompatibility was evaluated according to ISO-10993-4 standard. The results show that the gradient coating exhibits a gradual change in compositions and microstructures along the direction of film growth. Nano-TiN with the size of several to dozens nanometers and Ti N transitional phase with variable composition form a graded composite structure, which significantly improves adhesion strength (L =80N, L =120N), hardness (21GPa) and anti-wear performance (6.2×10 mm /Nm). The excellent bonding and wear resistance result from a good match of mechanical properties at substrate/coating interface and the strengthening and toughening effects of the nanocrystalline composite. The nano-TiN coating has also been proved to have good biocompatibility through in-vitro cytotoxicity, hemocompatibility and general toxicity tests. And thus, the proposed graded nano-TiN coating is a good candidate improving wear resistance of many implant medical devices.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:0 (Coated Materials, Biocompatible); 12743-70-3 (titanium alloy (TiAl6V4)); 6RW464FEFF (titanium nitride); D1JT611TNE (Titanium)


  9 / 3253 MEDLINE  
              first record previous record next record last record
seleciona
para imprimir
Fotocópia
Texto completo
PMID:27987696
Autor:Amanov A; Lee SW; Pyun YS
Endereço:Department of Mechanical Engineering, Sun Moon University, Asan 31460, South Korea. Electronic address: aamanov@outlook.com.
Título:Low friction and high strength of 316L stainless steel tubing for biomedical applications.
Fonte:Mater Sci Eng C Mater Biol Appl; 71:176-185, 2017 Feb 01.
ISSN:1873-0191
País de publicação:Netherlands
Idioma:eng
Resumo:We propose herein a nondestructive surface modification technique called ultrasonic nanocrystalline surface modification (UNSM) to increase the strength and to improve the tribological performance of 316L stainless steel (SS) tubing. Nanocrystallization along nearly the complete tube thickness of 200µm was achieved by UNSM technique that was confirmed by electron backscatter diffraction (EBSD). Nano-hardness of the untreated and UNSM-treated specimens was measured using a nanoindentation. Results revealed that a substantial increase in hardness was obtained for the UNSM-treated specimen that may be attributed to the nanocrystallization and refined grains. Stress-strain behavior of the untreated and UNSM-treated specimens was assessed by a 3-point bending test. It was found that the UNSM-treated specimen exhibited a much higher strength than that of the untreated specimen. In addition, the tribological behavior of the untreated and UNSM-treated specimens with an outer diameter (OD) of 1.6mm and an inner diameter (ID) of 1.2mm was investigated using a cylinder-on-cylinder (crossed tubes of equal radius) tribo-tester against itself under dry conditions at ambient temperature. The friction coefficient and wear resistance of the UNSM-treated specimen were remarkably improved compared to that of the untreated specimen. The significant increase in hardness after UNSM treatment is responsible for the improved friction coefficient and wear resistance of the tubing. Thus, the UNSM technique was found to be beneficial to improving the mechanical and tribological properties of 316L SS tubing for various potential biomedical applications, in particular for coronary artery stents.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:12597-68-1 (Stainless Steel)


  10 / 3253 MEDLINE  
              first record previous record
seleciona
para imprimir
Fotocópia
Texto completo
PMID:27835815
Autor:Raj A; Wang M; Zander T; Wieland DC; Liu X; An J; Garamus VM; Willumeit-Römer R; Fielden M; Claesson PM; Dedinaite A
Endereço:KTH Royal Institute of Technology, School of Chemical Sciences and Engineering, Department of Chemistry, Surface and Corrosion Science, Drottning Kristinas Väg 51, SE-10044 Stockholm, Sweden. Electronic address: rajaka@kth.se.
Título:Lubrication synergy: Mixture of hyaluronan and dipalmitoylphosphatidylcholine (DPPC) vesicles.
Fonte:J Colloid Interface Sci; 488:225-233, 2017 Feb 15.
ISSN:1095-7103
País de publicação:United States
Idioma:eng
Resumo:Phospholipids and hyaluronan have been implied to fulfil important roles in synovial joint lubrication. Since both components are present in synovial fluid, self-assembly structures formed by them should also be present. We demonstrate by small angle X-ray scattering that hyaluronan associates with the outer shell of dipalmitoylphophatidylcholine (DPPC) vesicles in bulk solution. Further, we follow adsorption to silica from mixed hyaluronan/DPPC vesicle solution by Quartz Crystal Microbalance with Dissipation measurements. Atomic Force Microscope imaging visualises the adsorbed layer structure consisting of non-homogeneous phospholipid bilayer with hyaluronan/DPPC aggregates on top. The presence of these aggregates generates a long-range repulsive surface force as two such surfaces are brought together. However, the aggregates are easily deformed, partly rearranged into multilayer structures and partly removed from between the surfaces under high loads. These layers offer very low friction coefficient (<0.01), high load bearing capacity (≈23MPa), and self-healing ability. Surface bound DPPC/hyaluronan aggregates provide a means for accumulation of lubricating DPPC molecules on sliding surfaces.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:0 (Lipid Bilayers); 0 (Solutions); 2644-64-6 (1,2-Dipalmitoylphosphatidylcholine); 7631-86-9 (Silicon Dioxide); 9004-61-9 (Hyaluronic Acid)



página 1 de 326 ir para página                         
   


Refinar a pesquisa
  Base de dados : MEDLINE Formulário avançado   

    Pesquisar no campo  
1  
2
3
 
           



Search engine: iAH v2.6 powered by WWWISIS

BIREME/OPAS/OMS - Centro Latino-Americano e do Caribe de Informação em Ciências da Saúde