bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of oil rheology and chemistry on journal-bearing friction and wear
Authors: Warrens C , Jefferies A C , Mufti R A , Lamb G D , Guiducci A E , Smith A G 
Published: May 2008

Legislation and market pressures are calling for increased engine power, reduced engine size, and improved fuel consumption. The use of low-viscosity lubricants is considered as a means to enhance fuel economy by reducing viscous friction, particularly in engine bearings. Journal bearings mostly operate under hydrodynamic lubrication with a thin film of oil separating the journal and bearing shell. There are, however, certain conditions, especially under high load or low speed, when the film thickness will be low enough to allow boundary lubrication to occur. In this study, the effect of lubricants with different viscosities, different types of viscosity modifiers, different additives, different types of dispersants, and different lubricant formulations have been studied under hydrodynamic and boundary lubrication regimes. For hydrodynamic conditions, a high-temperature high-shear viscometer, meeting the requirements of ASTM D4741 was used to measure viscosity at 106 s−1. In addition, a new ultra high-shear viscometer, from PCS Instruments, was used to measure viscosity at shear rates near to 107 s−1. Bearing weight loss and load bearing capacity were measured on a rig developed in-house using a specially designed half-bearing shell loaded against a rotating journal. A PCS journal-bearing rig was used to measure the bearing friction under transient load.
A study of the effect of model geometry and lubricant rheology upon the elastohydrodynamic lubrication performance of metal-on-metal hip joints
Authors: Wang W-Z , Jin Z M , Dowson D , Hu Y Z 
Published: May 2008

Lubrication modelling is of great importance in the design of artificial hip joints, especially for the demand of long life expectancy of those joints employing a metal-on-metal bearing. Through lubrication analysis, the dimensions of the head/cup and the clearance between them can be reasonably determined, and thus, if fluid film lubrication can be generated in artificial hip joint replacements, the wear and related failure can be reduced. In the majority of published numerical studies of the lubrication of hip joints, the synovial fluid for the natural joint and bovine serum used for in vitro simulator testing of joint replacements have always been treated as isoviscous, incompressible Newtonian fluids because the viscosity of these lubricants is almost unchanged at high shear rate. However, all these biological lubricants generally exhibit non-Newtonian characteristics of shear thinning, particularly under relatively low shear rates, and display a second Newtonian plateau at high shear rates. In this paper, model geometry is investigated first to show that the ball-on-plane model is a reasonable approximation to a typical metal-on-metal hip joint bearing considered. Then, in order to accurately predict the film thickness and pressure, the Reynolds equation considering the shear thinning effect of biological lubricants is derived, based on the Rabinowitsch model and following Greenwood's approach. The non-Newtonian effect was considered through two effective flow factors in the sliding and leakage directions, respectively. Numerical simulations were conducted on the basis of an equivalent ball-on-plane model with an effective radius determined from the head radius and the radial clearance, showing the influence of the shear thinning effect. The general lubrication model based on the unified Reynolds equations model was solved for the film thickness and pressure distribution, and the FFT-based approach was utilized to speed up the time-consuming calculation of elastic deformation in a fully numerical lubrication analysis. The results showed that the predicted film thickness when considering the shear thinning effect was slightly larger than that from the isoviscous model. It was found, however, that if the viscosity of the lubricant is adopted as the asymptotic value at high shear rate, the isoviscous Newtonian model can also give accurate predictions of film thickness. This is due to the relatively high shear rate in the contact zone.
Effect of albumin adsorption on friction between artificial joint materials
Authors: Chen X M , Jin Z M , Fisher J 
Published: May 2008

In this paper, the protein-adsorbing mechanisms on the surface of different artificial joint materials including ultra-high molecular weight polyethylene (UHMWPE), CoCrMo alloy, and Al2O3 ceramic were investigated and the corresponding adsorbing strength was meas-ured. The friction tests between UHMWPE pin-on-CoCrMo plate, UHMWPE pin-on-Al2O3 plate, CoCrMo pin-on-UHMWPE plate, and Al2O3 pin-on-UHMWPE plate were carried out at different sliding speeds and under different stresses. Both dry and lubricated contacts were considered, using pure water, 50 per cent calf bovine serum solution and 50 per cent denatured calf bovine serum solution. The topography of the artificial joint materials before and after treated with 50 per cent calf bovine serum solution as well as the friction test were examined through optical microscope and atomic force microscope. The results indicated that albumin-adsorbing strength on the surface of UHMWPE, CoCrMo alloy, and Al2O3 ceramic was larger than 0.39 MPa. The adsorbed film was found to protect the surfaces of all materials investigated at low sliding speed and low stress, and subsequently to decrease friction. Therefore, at high sliding speed and high stress, the adsorbed albumin film was found to be denatured and desquamated from the bearing surface, which increased friction between the two bearing surfaces. A suitable roughness and surface microtopography may be favourable for retaining the albumin-adsorbed film.
Tribological properties of ionic liquids as lubricants and additives. Part 1: Synergistic tribofilm formation between ionic liquids and tricresyl phosphate
Authors: Fox M F , Priest M 
Published: May 2008

The use of imidazolium tetrafluoroborate, IMM+BF4−, and hexafluorophosphate, IMM+PF6−, ionic liquids as lubricants was investigated at 25 and 100 °C to show lower friction coefficients but higher wear rates than a reference hydrocarbon lubricant. The ionic liquids readily form tribofilms at the lower temperature but have difficulty in forming partial films at the higher temperature. Wear tracks for a Plint TE77 reciprocating ball-on-plate test using ionic liquids show smoother surfaces, with small pits developing, compared to the reference hydrocarbon lubricant test result. Similar ionic liquids not containing fluorine were found to be less effective as lubricants. Addition of ionic liquids to a base grease and a formulated high temperature grease gave surprisingly large increases in the weld load for the Four Ball extreme pressure test. Little difference between base grease and base grease+5 per cent ionic liquid was observed for the TE77 test. There was no clear indication of the effect of alkyl substituent chain length on the imidazolium cation for the Four Ball test wear scar diameter. Addition of 1 per cent tricresyl phosphate (TCP) to ionic liquids rapidly establishes a tribofilm and reduces the wear volume by 64 per cent compared to the same test for the neat ionic liquid or neat TCP. Addition of 1 per cent TCP and 1 per cent ionic liquid to a Group III base oil also establishes a substantial tribofilm and reduces wear volumes compared to the base oil with 1 per cent TCP alone or the base oil with 1 per cent ionic liquid alone. Ionic liquids show promise as neat liquid lubricants by establishing a tribolayer chemically adsorbed to the steel surfaces. They are not as effective as a reference hydrocarbon lubricant in reducing wear of those surfaces by tribocorrosion. The fluorine-free ionic liquids investigated were not as effective as those containing fluorine. The addition of ionic liquids to grease, base or fully formulated, gave a substantial improvement in performance, which indicates a synergistic interaction with the additives present in the formulated grease. There is also clear evidence of a strong synergistic effect between ionic liquids and TCP, both for the neat ionic liquids and for 1 per cent dilution of each respectively in a Group III base oil to give a thick tribofilm and substantially reduced wear in the TE77 ball-on-plate test. The nature of the synergy between ionic liquids and TCP requires further investigation.
The synergistic relationship of perceived autonomy support and structure in the prediction of self‐regulated learning
Authors: Sierens Eline , Vansteenkiste Maarten , Goossens Luc , Soenens Bart , Dochy Filip 
Published: May 2008

Background Self‐determination theory defines two important dimensions of teaching style: autonomy support and structure.Aims The purpose of the present study was to investigate the synergistic relationship of perceived teacher autonomy support and the provision of structure in the prediction of self‐regulated learning.Sample and method Students (N = 526) completed questionnaires assessing perceived autonomy support, structure, and self‐regulated learning.Results First, autonomy support and structure were found to be positively correlated, suggesting that the support of student autonomy generally goes hand in hand with the provision of structure and order in the classroom. Second, moderated regression analyses indicated that structure but not autonomy support yielded a main effect on self‐regulated learning, although this main effect was qualified by a structure by autonomy support interaction.Conclusio The interaction suggests that structure was associated with more self‐regulated learning under conditions of moderate and high autonomy support only. Therefore, when teachers want their students to evaluate themselves, to plan their study activities, and to think about themselves as learners, the teachers are encouraged to provide help, instructions, and expectations in an autonomy‐supportive way.
Hardiness commitment, gender, and age differentiate university academic performance
Authors: Sheard Michael 
Published: May 2008

BackgroundThe increasing diversity of students, particularly in age, attending university has seen a concomitant interest in factors predicting academic success.AimsThis 2‐year correlational study examined whether age, gender (demographic variables), and hardiness (cognitive/emotional variable) differentiate and predict university final degree grade point average (GPA) and final‐year dissertation mark.SampleData are reported from a total of 134 university undergraduate students.MethodParticipants provided baseline data in questionnaires administered during the first week of their second year of undergraduate study and gave consent for their academic progress to be tracked. Final degree GPA and dissertation mark were the academic performance criteria.ResultsMature‐age students achieved higher final degree GPA compared to young undergraduates. Female students significantly outperformed their male counterparts in each measured academic assessment criteria. Female students also reported a significantly higher mean score on hardinesscommitmentcompared to male students.Commitmentwas the most significant positive correlate of academic achievement. Final degree GPA and dissertation mark were significantly predicted bycommitment, andcommitmentand gender, respectively.ConclusionsThe findings have implications for universities targeting academic support services to maximize student scholastic potential. Future research should incorporate hardiness, gender, and age with other variables known to predict academic success.
Single nucleotide polymorphisms in new candidate genes are associated with bone mineral density and fracture risk
Authors: Lazáry Áron , Kósa János P , Tóbiás Bálint , Lazáry Judit , Balla Bernadett , Bácsi Krisztián , Takács István , Nagy Zsolt , Mező Tibor , Speer Gábor , Lakatos Péter 
Published: May 2008

ObjectiveOsteoporosis (OP) is a multifactorial disease with high heritability but its exact genetic background is still poorly understood. We examined the effect of 24 single nucleotide polymorphisms (SNPs) located in five genes – alkaline phosphatase, matrix metalloproteinase-2, tissue inhibitor of metalloproteases-2 (TIMP2), fibroblast growth factor receptor-1 (FGFR1), and fatty acid-binding protein-3 (FABP3) – previously not associated with OP.DesignWe performed a genotype–phenotype association study at a university hospital.MethodsA total of 360 Hungarian postmenopausal women were involved in the study. Bone mineral density (BMD) was determined at spine, hip, and distal radius. Genomic DNA was extracted from venous blood samples and a high-throughput genotyping method based on single-based primer extension was applied for allelic discrimination. Robust statistical tools were utilized for multiplex data analysis.ResultsSNP rs6996321 in FGFR1 was significantly related to spine BMD (P=0.002) and rs10914367 in FABP3 was associated with hip BMD (P=0.028). Non-vertebral fracture risk was significantly increased in carriers of ‘A’ allele of rs9900972 in TIMP2 (odds ratio=2.06, P=0.0187). We could also identify validated gene–gene interactions significantly affecting BMD and fracture risk.ConclusionsWe identified two previously unreported SNPs in FGFR1 and FABP3 associated with BMD and a third SNP in TIMP2 related to risk for non-vertebral osteoporotic fractures. This is the first report about the association between these allelic variants and the phenotypes of postmenopausal OP. Further studies need to clarify the role of these genes and their polymorphisms in the process of bone loss.
Codeswitching on the Web. English and Jamaican Creole in e-mail communication. Lars Hinrichs (2006)
Authors: Bartens Angela 
Published: May 2008

Codeswitching on the Web. English and Jamaican Creole in e-mail communication. Lars Hinrichs (2006) (Pragmatics and Beyond Volume 147) Amsterdam and Philadelphia: John Benjamins. pp. ix + 301. ISBN 978 90 272 5390 3
Accumulation of Malignant Renal Stem Cells Is Associated with Epigenetic Changes in Normal Renal Progenitor Genes
Authors: Metsuyanim Sally , Pode-Shakked Naomi , Schmidt-Ott Kai M. , Keshet Gilmor , Rechavi Gideon , Blumental Danith , Dekel Benjamin 
Published: May 2008

AbstractRecent studies indicate a dual epigenetic role of the Polycomb group (PcG) proteins in self-renewal of stem cells and oncogenesis. Their elevation in our previous human kidney microarray screen led us examine whether they participate in processes involving normal and malignant renal progenitors. We therefore analyzed the expression of the PcG genes (EZH2, BMI-1, EED, SUZ12) in relation to that of the nephric-progenitor genes (WT1, PAX2, SALL1, SIX2, CITED1) using real-time polymerase chain reaction and methylation assays during renal development, regeneration, and tumorigenesis. Although all of the nephric-progenitor genes were shown to be developmentally regulated, analysis of polycomb gene expression during murine nephrogenesis and in an in vitro induction model of the nephrogenic mesenchyme indicated dynamic regulation only for EZH2 in the normal renal progenitor population. In contrast, induction of adult kidney regeneration by ischemia/reperfusion injury resulted primarily in rapid elevation of BMI-1, whereas EZH2 was silenced. Analysis of renal tumorigenesis in stem cell-like tumor xenografts established by serial passage of Wilms' tumor (WT) in immunodeficient mice showed cooperative upregulation of all PcG genes. This was accompanied by upregulation of WT1, PAX2, and SALL1 but downregulation of SIX2. Accordingly, methylation-specific quantitative polymerase chain reaction demonstrated promoter hypomethylation of WT1, PAX2, and SIX2 in primary WT and fetal kidneys, whereas progressive WT xenografts showed hypermethylation of SIX2, possibly leading to loss of renal differentiation. PcG genes vary in expression during renal development, regeneration, and tumorigenesis. We suggest a link between polycomb activation and epigenetic alterations of the renal progenitor population in initiation and progression of renal cancer.Disclosure of potential conflicts of interest is found at the end of this article.
Efficient Production of Mice from Embryonic Stem Cells Injected into Four- or Eight-Cell Embryos by Piezo Micromanipulation
Authors: Huang Junjiu , Deng Kai , Wu Haojia , Liu Zhong , Chen Zhisheng , Cao Shanbo , Zhou Lingjun , Ye Xiaoying , Keefe David L. , Liu Lin 
Published: May 2008

Abstract
The conventional method for producing embryonic stem (ES) cell-derived knockout or transgenic mice involves injection of ES cells into normal, diploid blastocysts followed by several rounds of breeding of resultant chimeras and thus is a time-consuming and inefficient procedure. F0 ES cell pups can also be derived directly from tetraploid embryo complementation, which requires fusion of two-cell embryos. Recently, F0 ES cell pups have been produced by injection of ES cells into eight-cell embryos using a laser-assisted micromanipulation system. We report a simple method for producing F0 ES cell germline-competent mice by piezo injection of ES cells into four- or eight-cell embryos. The efficiency of producing live, transgenic mice by this method is higher than that with the tetraploid blastocyst complementation method. This efficient and economical technique for directly producing F0 ES cell offspring can be applicable in many laboratories for creating genetically manipulated mice using ES cell technology and also for stringent testing of the developmental potency of new ES cell or other types of pluripotent stem cell lines.
Disclosure of potential conflicts of interest is found at the end of this article.
Costimulation Blockade Induces Tolerance to HESC Transplanted to the Testis and Induces Regulatory T-Cells to HESC Transplanted into the Heart
Authors: Grinnemo Karl-Henrik , Genead Rami , Kumagai-Braesch Makiko , Andersson Agneta , Danielsson Christian , Månsson-Broberg Agneta , Dellgren Göran , Strömberg Anne-Marie , Ekberg Henrik , Hovatta Outi , Sylvén Christer , Corbascio Matthias 
Published: May 2008

Abstract
In order to study the ability of costimulation blockade to induce tolerance to human embryonic stem cells (HESC), severe combined immunodeficient (SCID), and immunocompetent C57BL/6 mice treated with costimulation blockade received intratesticular and intramyocardial HESC transplants. All SCID mice with intratesticular HESC transplants developed teratoma. When SCID mice were transplanted intramyocardially, only two of five mice developed teratoma-like tumors. C57BL/6 mice transplanted intratesticularly and treated with costimulation blockade all developed teratoma and were surrounded by CD4+CD25+Foxp3+ T-cells, while isotype control treated recipients rejected their grafts. Most C57BL/6 mice transplanted intramyocardially and treated with costimulation blockade demonstrated lymphocytic infiltrates 1 month after transplantation, whereas one maintained its graft. Isolation of regulatory T-cells from intramyocardial transplanted recipients treated with costimulation blockade demonstrated specificity toward undifferentiated HESC and down-regulated naive T-cell activation toward HESC. These results demonstrate that costimulation blockade is sufficiently robust to induce tolerance to HESC in the immune-privileged environment of the testis. HESC specific regulatory T-cells developed to HESC transplanted to the heart and the success of transplantation was similar to that seen in SCID mice.
Disclosure of potential conflicts of interest is found at the end of this article.
Partial Resistance to Peroxisome Proliferator–Activated Receptor-α Agonists in ZDF Rats Is Associated With Defective Hepatic Mitochondrial Metabolism
Authors: Satapati Santhosh , He TianTeng , Inagaki Takeshi , Potthoff Matthew , Merritt Matthew E. , Esser Victoria , Mangelsdorf David J. , Kliewer Steven A. , Browning Jeffrey D. , Burgess Shawn C. 
Published: May 2008

OBJECTIVE—Fluxes through mitochondrial pathways are defective in insulin-resistant skeletal muscle, but it is unclear whether similar mitochondrial defects play a role in the liver during insulin resistance and/or diabetes. The purpose of this study is to determine whether abnormal mitochondrial metabolism plays a role in the dysregulation of both hepatic fat and glucose metabolism during diabetes.RESEARCH DESIGN AND METHODS—Mitochondrial fluxes were measured using 2H/13C tracers and nuclear magnetic resonance spectroscopy in ZDF rats during early and advanced diabetes. To determine whether defects in hepatic fat oxidation can be corrected by peroxisome proliferator–activated receptor (PPAR-)-α activation, rats were treated with WY14,643 for 3 weeks before tracer administration.RESULTS—Hepatic mitochondrial fat oxidation in the diabetic liver was impaired twofold secondary to decreased ketogenesis, but tricarboxylic acid (TCA) cycle activity and pyruvate carboxylase flux were normal in newly diabetic rats and elevated in older rats. Treatment of diabetic rats with a PPAR–α agonist induced hepatic fat oxidation via ketogenesis and hepatic TCA cycle activity but failed to lower fasting glycemia or endogenous glucose production. In fact, PPAR-α agonism overstimulated mitochondrial TCA cycle flux and induced pyruvate carboxylase flux and gluconeogenesis in lean rats.CONCLUSIONS—The impairment of certain mitochondrial fluxes, but preservation or induction of others, suggests a complex defect in mitochondrial metabolism in the diabetic liver. These data indicate an important codependence between hepatic fat oxidation and gluconeogenesis in the normal and diabetic state and potentially explain the sometimes equivocal effect of PPAR-α agonists on glycemia.
On the possible methods for the mathematical description of the ball and chain model of ion channel inactivation
Authors: Małysiak Krzysztof , Grzywna Zbigniew 
Published: May 2008

AbstractIon channels are large transmembrane proteins that are able to conduct small inorganic ions. They are characterized by high selectivity and the ability to gate, i.e. to modify their conductance in response to different stimuli. One of the types of gating follows the ball and chain model, according to which a part of the channel’s protein forms a ball connected with the intracellular side of the channel by a polypeptide chain. The ball is able to modify the conductance of the channel by properly binding to and plugging the channel pore. In this study, the polypeptide ball is treated as a Brownian particle, the movements of which are limited by the length of the chain. The probability density of the ball’s position is resolved by different diffusional operators — parabolic (including the case with drift), hyperbolic, and fractional. We show how those different approaches shed light on different aspects of the movement. We also comment on some features of the survival probabilities (which are ready to be compared with electrophysiological measurements) for issues based on the above operators.
On the role of ball and chain interactions in recovery from the inactivation of the shaker potassium channel
Authors: Borys Przemysław , Grzywna Zbigniew 
Published: May 2008

AbstractWe describe a new factor in the recovery from inactivation in the ball and chain model. We propose a model in which the tension from the chain may help pull the ball away from its binding site, reducing the duration of the inactivation period. A corresponding model was built and analysed.
Investigations of influence of screw propeller operation on water flow around stern part of ship hull
Authors: Koronowicz Tadeusz , Krzemianowski Zbigniew 
Published: May 2008

Investigations of influence of screw propeller operation on water flow around stern part of ship hull
This paper presents results of measurements of velocity field in before- the - propeller flow in presence of a ship model hull of two configurations, as well as comparative calculations of velocity field on a full-scale ship. Analysis of the research results showed that input data to Biot-Savart formula should be modified in the case of calculations of propeller-induced velocities on ship hull surface.