bluuebunny/crossref_metadata_2025 huggingface dataset:
The RanGTP gradient – a GPS for the mitotic spindle
Authors: Kalab Petr , Heald Rebecca
Published: May 2008

The GTPase Ran has a key role in nuclear import and export, mitotic spindle assembly and nuclear envelope formation. The cycling of Ran between its GTP- and GDP-bound forms is catalyzed by the chromatin-bound guanine nucleotide exchange factor RCC1 and the cytoplasmic Ran GTPase-activating protein RanGAP. The result is an intracellular concentration gradient of RanGTP that equips eukaryotic cells with a `genome-positioning system' (GPS). The binding of RanGTP to nuclear transport receptors (NTRs) of the importin β superfamily mediates the effects of the gradient and generates further downstream gradients, which have been elucidated by fluorescence resonance energy transfer (FRET) imaging and computational modeling. The Ran-dependent GPS spatially directs many functions required for genome segregation by the mitotic spindle during mitosis. Through exportin 1, RanGTP recruits essential centrosome and kinetochore components, whereas the RanGTP-induced release of spindle assembly factors (SAFs) from importins activates SAFs to nucleate, bind and organize nascent spindle microtubules. Although a considerable fraction of cytoplasmic SAFs is active and RanGTP induces only partial further activation near chromatin, bipolar spindle assembly is robustly induced by cooperativity and positive-feedback mechanisms within the network of Ran-activated SAFs. The RanGTP gradient is conserved, although its roles vary among different cell types and species, and much remains to be learned regarding its functions.
Micro-elastohydrodynamic lubrication of simple sliding elliptical contacts with sinusoidal roughness
Authors: Kaneta M , Yamada T , Wang J
Published: May 2008

The results of thermal elasthydrodynamic lubrication (EHL) analysis of elliptical contacts between a rough stationary surface and a smooth moving surface are described. The lubricant entrainment is along the major or minor axis of the Hertzian contact ellipse. The equivalent radius in the entrainment direction is assumed to be the same for every elliptical contact. The ridges and the furrows of the sinusoidal roughness are aligned with the arbitrary direction to that of lubricant entrainment. Non-Newtonian fluid flow model (Eyring model) is employed. Obtained results suggest that the rolling contact fatigue is unlikely to occur on the surfaces with longitudinal roughness, and wear or scuffing is likely to occur in elliptical EHL contacts with entrainment along the major contact axis than along the minor contact axis and the origin is at the region where the roughness having orientation angles between 60° and 90° overlaps with macroscopic horseshoe shaped constriction.
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.
Microscopic investigations into lubricated friction pairs in synchronizers
Authors: Poll G , Neudörfer S , Skubacz T
Published: May 2008

An essential component of manually operated vehicle transmissions is the synchronising device. Synchronizers have the task of minimizing the speed difference between the shifted gearwheel and the shaft by means of frictional torque before engaging the gear. Proper operation requires a sufficiently high coefficient of friction. An optimized design of the system with regard to appropriate function and durability on the one hand as well as low cost, low mass, and compact over-all dimensions on the other hand today requires time-consuming and expensive component testing. As it is easier to coat plane surfaces with a friction material than to coat the inner or outer cones of synchronizer rings, this paper investigates if the component tests can be substituted by simpler pin-on-disc type model tests. For this purpose, such model tests and tests with original synchronizers are compared, in particular, regarding the friction characteristics of different materials. Furthermore, a fluorescence-based method is successfully applied to observe the lubricant distribution and the contact conditions during shifts. The investigations reveal that there are limitations to the applicability of tests with plane model pins to real conical component behaviour, which can partly be attributed to differences in drainage efficiency.
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.
A rough surface contact model for anisotropically elastic materials
Authors: Scholz U , Bartel D , Deters L
Published: May 2008

A solution method for three-dimensional isothermal rough surface contact problems of anisotropically elastic materials is outlined. The half-space Fourier response function is calculated numerically by solving a quadratic eigenvalue problem. The surface displacements of an anisotropically elastic half-space due to uniform pressure applied to a rectangular region are obtained by fast Fourier transformation. The surface displacements and sub-surface stresses of the anisotropic half-space due to the normal and tractive contact stress are evaluated by superposition making use of the convolution theorem. The real contact area and the contact pressure are identified by applying multi-grid methods. The material symmetry may be arbitrary. Numerical results for smooth Hertzian contact of cubic and transversely isotropic material agree with the output of analytical models and different methods of numerical solution.
Experimental and theoretical investigation of the asperity flattening process under large bulk strain
Authors: Lu C , Wei D , Jiang Z , Tieu K
Published: May 2008

In this paper, the flattening of the model asperities under large bulk strain has been experimentally and theoretically investigated. The specimens with two types of model asperities (pyramid-shaped asperity and ridge-shaped asperity) on the top surface are compressed by a flat punch. The measured contact ratios are used to validate the theoretical model. The rigid-plastic finite-element method model is developed to analyse the asperity flattening processes under bulk straining. The results show that the contact ratio increases with bulk strain and the contact pressure for both types of asperities. The ridge-shaped asperity exhibits a higher contact ratio than the pyramid-shaped asperity. The contact ratio also increases with the asperity angles in the presence of large bulk deformation.
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.
A new method to evaluate the overall anti-shudder property of automatic transmission fluids – multiple parameters spider chart evaluation
Authors: Zhao H , Neville A , Morina A , Durham J , Vickerman R
Published: May 2008

Formulating automatic transmission fluids (ATFs) can pose some diverse challenges. The friction response should ensure a smooth engagement process with no shudder in the automatic transmission. Friction, as a function of velocity, must show a smooth and positive/plateau curve as velocity increases in the μ− v plots. In this study, the friction behaviour of some basic additive systems for ATFs was assessed by using a variable speed friction test (VSFT) rig. The test was used to mimic the clutch engagement process and to evaluate the friction response of different formulations. The focus was anti-shudder properties of the designated formulations. A new method of evaluating VSFT results was developed to assess the overall ATF friction behaviour in conjunction to the common friction—velocity curve analysis. X-ray photoelectron spectroscopy was used to check the different surface conditions before and after the test.
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.
S. cerevisiae Vts1p induces deadenylation-dependent transcript degradation and interacts with the Ccr4p-Pop2p-Not deadenylase complex
Authors: Rendl Laura M. , Bieman Melissa A. , Smibert Craig A.
Published: May 2008

The Smaug family of sequence-specific RNA binding proteins regulates mRNA translation and degradation by binding to consensus stem–loop structures in target mRNAs. Vts1p is a member of the Smaug protein family that regulates the stability of target transcripts in Saccharomyces cerevisiae. Here we focus on the mechanism of Vts1p-mediated mRNA decay. Using RNA reporters that recapitulate Vts1p-mediated decay in vivo, we demonstrate that Vts1p stimulates mRNA degradation through deadenylation mediated by the Ccr4p-Pop2p-Not deadenylase complex. We also show that Vts1p interacts with the Ccr4p-Pop2p-Not complex suggesting that Vts1p recruits the Ccr4p-Pop2p-Not deadenylase complex to target mRNAs, resulting in transcript decay. Following deadenylation Vts1p target transcripts are decapped and subsequently degraded by the 5′-to-3′ exonuclease Xrn1p. Decapping and 5′-to-3′ decay is thought to occur in foci known as P-bodies, and we provide evidence that Vts1p function may involve P-bodies. Taken together with previous work, these data suggest that Smaug family members employ a conserved mechanism to induce transcript degradation that involves recruitment of the Ccr4-Pop2-Not deadenylase to target mRNAs.
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.
Knowledge Transfer between Multinational Corporations’ Headquarters and Their Subsidiaries: Influences on and Implications for New Product Outcomes
Authors: Lee Ruby P. , Chen Qimei , Kim Daekwan , Johnson Jean L.
Published: May 2008

A multinational corporation's (MNC's) competitive advantage depends increasingly on control over intangible resources, such as knowledge and relational capital. Although prior research has suggested that cross-border knowledge transfer in MNCs is critical to their new product outcomes, the conditions under which such knowledge transfer can serve to induce positive outcomes remain unclear. This study builds on resource-based theory to suggest that knowledge and MNC network strength are the two critical firm resources individually and collectively influencing new product outcomes. Because MNCs are subject to the pressures on various environmental changes, the authors rely on the contingency theory to examine when knowledge transfer works in differential global market and technological turbulence. The results of a survey of MNC headquarters show that the impacts of cross-border knowledge transfer on new product outcomes are not always positive, depending on the levels of network strength and environmental turbulence.
Diffusion of Measurement Invariance Assessment in Cross-National Empirical Marketing Research: Perspectives from the Literature and a Survey of Researchers
Authors: He Yi , Merz Michael A. , Alden Dana L.
Published: May 2008

The authors examine (1) the extent to which cross-national marketing scholars report measurement invariance (MI) assessment results and (2) what cross-national marketing scholars think about MI assessment in general. In Study 1, the authors analyze all cross-national empirical articles (243) published in 15 well-respected and peer-reviewed marketing journals from 2000 to 2005. Although the results indicate a steady growth of published cross-national empirical marketing research and assessment of MI, only 28% of the studies undertook the procedure. In Study 2, the authors analyze responses from 86 cross-national empirical marketing scholars regarding their knowledge about, attitudes toward, and use of MI assessment. The results indicate that the relatively low utilization of MI assessment is due to low MI knowledge and the sophistication of the techniques. The authors conclude with suggested implications for the field of international marketing and a discussion of future research directions.
Patronesses and “Mothers” of RomanCollegia
Authors: Hemelrijk Emily
Published: May 2008

This paper studies the meaning and function of the titles “patroness” and “mother” of collegia in Italy and the Latin-speaking provinces of the Roman Empire in the first three centuries CE. It is investigated why some collegia co-opted female patrons or appointed “mothers.” What was expected from these women and was there any difference between a “mother” and a patroness of a collegium? On the basis of epigraphic evidence it is argued that patrona collegii and mater collegii were no empty titles but denoted distinct functions exercised by different classes of women. Whereas patronesses were, as a rule, outsiders to the collegium they patronized, “mothers” were mostly social climbers from within the ranks of the collegia. Though both types of women acted on behalf of the collegia, they did so in a different way. Moreover, they were honored differently. Collegia, therefore, had good reasons to distinguish between the titles they gave them.
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

Objective

Osteoporosis (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.

Design

We performed a genotype–phenotype association study at a university hospital.

Methods

A 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.

Results

SNP 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.

Conclusions

We 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.
Spatiotemporal expression pattern of progranulin in embryo implantation and placenta formation suggests a role in cell proliferation, remodeling, and angiogenesis
Authors: Desmarais Joëlle A , Cao Mingju , Bateman Andrew , Murphy Bruce D
Published: May 2008

Embryo implantation in the mink is preceded by a variable but obligate period of delay in development. Under the influence of progesterone and unknown luteal factors, the mink embryo implants 11–13 days following its exit from diapause. Recent work suggests that progranulin, a growth factor and secreted glycoprotein, is involved in trophoblast proliferation, placental development and endometrial differentiation in the mouse. Using the mink model of delayed implantation and endotheliochorial placentation, we examined the spatiotemporal distribution of progranulin in trophoblast and endometrium during pre- and early post-implantation gestation in vivo. A partial sequence of the mink progranulin gene was cloned and sequenced. Comparative sequence analysis revealed that exons 1 and 2 of mink progranulin share 86.6, 82.4, and 94.9% of nucleic acid sequence identity with the human, mouse, and dog sequences respectively, and indicated that the invariable residues of the cysteine-rich motifs of progranulin are well conserved in the mink sequence. By in situ hybridization, we show that mink progranulin transcript is present in the cytotrophoblast and in epithelial and stromal endometrial cells at the site of implantation and during early placental formation. Immunohistochemistry revealed the progranulin protein to be strongly expressed in endometrial luminal and glandular epithelium around the time of implantation. In the incipient labyrinth, progranulin expression is localized to cytotrophoblasts and fetal capillaries, as well as to the hypertrophied maternal endothelial cells. This study demonstrates that high levels of progranulin expression correspond to active cell proliferation, remodeling, and angiogenesis occurring during the establishment of the placenta in the mink.
Expression of growth differentiation factor 9, bone morphogenetic protein 15, and anti-Müllerian hormone in cultured mouse primary follicles
Authors: Sadeu J C , Adriaenssens T , Smitz J
Published: May 2008

Growth differentiation factor 9 (GDF9), bone morphogenetic protein 15 (BMP15), and anti-Müllerian hormone (AMH) play an important role in the primary to secondary follicle transition and follicle activation in vivo. In organ culture of neonatal mouse ovaries, it was observed that significantly fewer primary follicles develop to the secondary stage. The objectives of this study were: (1) to compare ovarian follicular populations between organ-cultured neonatal mouse ovaries and freshly isolated age-matched control ovaries; (2) to quantify RNA levels of Gdf9, Bmp15, and Amh in cultured primary follicles; and (3) to immunolocalize GDF9 and AMH in cultured ovaries. Ovaries from 3-day-old (PND 3) mice were cultured for 7 or 10 days in the absence or presence of FSH. Follicular populations were counted in freshly isolated 13-day-old (PND 13) ovaries and organ-cultured ovaries. Transcripts were quantified in isolated primary follicles using real-time RT-PCR, and protein expressions were localized using immunohistochemistry. The number of secondary follicles in organ-cultured ovaries was significantly lower than in vivo controls. Gdf9 and Bmp15 mRNA expression levels were similar as in controls. Amh mRNA levels were significantly (P<0.05) lower after day 10 of culture in the absence of FSH. GDF9 and AMH proteins were respectively detected in the oocytes and the granulosa cells (GC) beginning at the primary and primordial stages onward. GDF9 and BMP15 production in cultured primary follicles are not different from in vivo controls; hence abnormal early follicular growth was not related to a deficient transcription of these factors.
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
Inmigración y aprendizaje de lenguas en un contexto bilingüe. Amaia Ibarraran, David Lasagabaster y Juan Manuel Sierra (2007)
Authors: Safont Jordà Maria Pilar
Published: May 2008

Inmigración y aprendizaje de lenguas en un contexto bilingüe. Amaia Ibarraran, David Lasagabaster y Juan Manuel Sierra (2007) Bilbao: LETE argitaletxea , 242pp ISBN 978-84-611-4249-1
Research on politeness in the Spanish-speaking world. María Elena Placencia and Carmen García (eds) (2007)
Authors: Sykes Julie M , Klee Carol A
Published: May 2008

Research on politeness in the Spanish-speaking world. María Elena Placencia and Carmen García (eds) (2007) Mahwah, NJ: Lawrence Erlbaum Associates, pp. v + 442 ISBN 0–8058–5227–1
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

Recent 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

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

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.
Traffic crashes at toll plazas in Hong Kong
Authors: Sze N. N. , Wong S. C. , Chan W. F.
Published: May 2008

Poisson regression was used to identify the significant contributory factors to traffic crashes at toll plaza areas in Hong Kong. Information on the crash incidences and traffic volume at the toll plaza areas of ten tolled roads in Hong Kong during 1998–2003 were obtained from the traffic accident database system and annual traffic census of the Transport Department of the Government of Hong Kong Special Administrative Region. These data, together with the geometric and operational characteristics, including toll plaza width, carriageway width, degree of road curvature, road gradient, and toll booth configuration, were incorporated into two aggregated crash predictive models for different traffic directions. The results revealed that the crash likelihood of inbound traffic was increased significantly with downward slope and the crash likelihood of outbound traffic increased with the degree of road curvature.
Potassium Release in Representative Maize‐Producing Soils of Thailand
Authors: Nilawonk Weena , Attanandana Tasnee , Phonphoem Anan , Yost Russell , Shuai Xiufu
Published: May 2008

Ammonium acetate K does not adequately measure available K in the mineralogically diverse maize (Zea mays L.)‐producing soils of Thailand. The objective of this study was to understand the causes of this problem and propose a solution using laboratory and greenhouse experiments to examine the release patterns and the availability of exchangeable and nonexchangeable K. Eight kaolinitic and smectitic soils were examined for the release of K in each soil fraction (sand, silt, and clay) using the Ca‐resin successive extraction method. The data were fitted using parabolic diffusion, power function, and segmented straight line regression models. The power function and the segmented regression model fitted the data well. All soils were exhaustively cropped with maize in the greenhouse until the soils became K deficient. The results indicated that a segmented regression model described nonexchangeable K release to the Ca resin and to plants in a way that seemed to correspond with earlier predictions. According to the model, there were two fractions of nonexchangeable K, which were released at distinctly different rates. The greenhouse study yielded fast and slow K release rates from the nonexchangeable K pool of 0.45 to 0.85 and 0 mg kg−1 d−1, respectively, in kaolinitic soils and 1.60 to 1.98 and 0.27 to 0.52 mg kg−1 d−1, respectively, in smectitic soils. Our results suggested that NH4OAc‐extractable K was suitable and sufficient to determine plant‐available K in kaolinitic soils. In contrast, a successive Ca‐resin extraction characterization plus NH4OAc‐extractable K was required to determine plant‐available K in smectitic soils.
Influence of Soil Characteristics and Formulation on Alachlor Dissipation in Soil
Authors: Sopeña Fátima , Maqueda Celia , Morillo Esmeralda
Published: May 2008

Alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl)acetamide] is one of the most commonly found herbicides in surface and groundwaters of the United States and Europe, and it contaminates these environments even when it is used according to the manufacturer's instructions for conventional formulations. To determine how its persistence in soil is affected by herbicide formulation and soil type, alachlor was applied to several soils in different formulations: technical grade (AT), a commercial formulation (CF), and different ethylcellulose microencapsulated formulations (MEFs). The results show that MEFs provided a prolonged release of the herbicide into the soil solution and protected against its dissipation in soil more than AT or the CF. The half‐life in soil (t1/2) for the AT, CF, and MEFs was up to 2.7, 6.4, and 32.54 d, respectively. The lowest herbicide loss was observed in MEFs prepared using a lower stirring speed or a higher ethylcellulose viscosity during the microencapsulation process. As with AT and the CF, the microencapsulated alachlor persisted longer in the soils with low pH and high clay content. In the soil where alachlor showed the least persistence, MEFs reduced the herbicide loss by 54% compared with the CF. The use of MEFs extended the alachlor concentration in the soil, thereby avoiding the need for using high herbicide application rates and decreasing the risk of environmental contamination.
Soil Mineralogy of Mangrove Forests from the State of São Paulo, Southeastern Brazil
Authors: Souza-Júnior V. S. , Vidal-Torrado P. , Garcia-Gonzaléz M. T. , Otero X. L. , Macías F.
Published: May 2008

The minerals of the clay fraction in estuarine plains are mainly detrital, being a mixture of marine and continental sediments, but can also be authigenic. Because of the importance of mangrove ecosystems in tropical estuarine areas and the relatively few existing studies of the mineralogical composition of soils in these environments, the aim of this study was to determine the mineralogical assemblage and identify potential contrasts along the coast of the State of São Paulo. Soils from 11 mangroves distributed along the coastal plain of the State of São Paulo were sampled at depths of 0 to 20 and 60 to 80 cm, and samples of suspended sediments from the Ribeira do Iguape River were collected for analysis. Mineralogical analyses were performed on the clay and silt fractions by x‐ray diffraction (XRD) and transmission electron microscopy, and fresh soil samples were analyzed by scanning electron microscopy–energy dispersive spectrometry and suspended sediments by XRD. The silt fraction contained quartz, feldspars, gibbsite, kaolinite, illite, and vermiculite, and the clay fraction contained smectite, kaolinite, illite, gibbsite, quartz, and feldspars. Locally, vermiculite, biotite, anatase, halloysite, and goethite may occur because of recent transport of sediments to the system. Pyrite was identified in fresh samples. The allochthonous minerals found either were terrestrial and transported by rivers or had originated from the continental platform by past transgressive events. We suggest that the neoformation of smectite and kaolinite occurs in mangrove soils. Different geomorphological settings along the São Paulo coast appear to regulate mineral distribution in mangrove soils.
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

Ion 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

We 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.
Calculation of the mean long-term service speed of transport ship: Part II Service speed of ship sailing on regular shipping route in real weather conditions
Authors: Szelangiewicz Tadeusz , Żelazny Katarzyna
Published: May 2008

Calculation of the mean long-term service speed of transport ship: Part II Service speed of ship sailing on regular shipping route in real weather conditions

Service speed obtainable by a ship in real weather conditions when sailing on a given shipping route, is one of the major parameters which have great impact on ship operation costs. The so far used, very approximate method of service speed prediction based on "service margin", is very little exact. In this paper a new method based on additional ship resistance dependent on mean statistical parameters of wave and wind occurring on a given shipping route, is presented. The mean long-term service speed is calculated on the basis of the calculated additional resistance and the screw propeller and propulsion engine parameters. Also, a new definition of service margin and a way of its calculation is presented apart from the results of the mean service speed calculation depending on ship's type and size and shipping route.