bluuebunny/crossref_metadata_2025 huggingface dataset:
Skin layer‐specific transcriptional profiles in normal and recessive yellow (Mc1re/Mc1re) mice
Authors: April Craig S. , Barsh Gregory S.
Published: March 2006

The melanocortin 1 receptor (Mc1r) plays a central role in cutaneous biology, but is expressed at very low levels by a small fraction of cells in the skin. In humans, loss‐of‐function MC1R mutations cause fair skin, freckling, red hair, and increased predisposition to melanoma; in mice, Mc1r loss‐of‐function is responsible for the recessive yellow mutation, associated with pheomelanic hair and a decreased number of epidermal melanocytes. To better understand how Mc1r signaling affects different cutaneous phenotypes, we examined large‐scale patterns of gene expression in different skin components (whole epidermal sheets, basal epidermal cells and whole skins) of neonatal (P2.5) normal and recessive yellow mice, starting with a 26K mouse cDNA microarray. From c. 17 000 genes whose levels could be accurately measured in neonatal skin, we identified 883, 2097 and 552 genes that were uniquely expressed in the suprabasal epidermis, basal epidermis and dermis, respectively; specific biologic roles could be assigned for each class. Comparison of normal and recessive yellow mice revealed 69 differentially expressed genes, of which the majority had not been previously implicated in Mc1r signaling. Surprisingly, many of the Mc1r‐dependent genes are expressed in cells other than melanocytes, even though Mc1r expression in the skin is confined almost exclusively to epidermal melanocytes. These results reveal new targets for Mc1r signaling, and point to a previously unappreciated role for a Mc1r‐dependent paracrine effect of melanocytes on other components of the skin.
Regulation of pigmentation in zebrafish melanophores
Authors: Logan Darren W. , Burn Sally F. , Jackson Ian J.
Published: March 2006

In comparison with the molecular genetics of melanogenesis in mammals, the regulation of pigmentation in poikilothermic vertebrates is poorly understood. Mammals undergo morphological colour change under hormonal control, but strikingly, many lower vertebrates display a rapid physiological colour change in response to the same hormones. The recent provision of extensive genome sequencing data from teleost zebrafish, Danio rerio, provides the opportunity to define the genes and proteins mediating this physiological pigment response and characterise their function biologically. Here, we illustrate the background adaptation process in adults and larvae and describe a novel assay to visualize and directly quantify the rate of zebrafish melanophore pigment translocation in unprecedented detail. We demonstrate the resolution of this assay system; quantifying the zebrafish melanophore response to melanin‐concentrating and melanocyte‐stimulating hormones. Furthermore, we investigate the intracellular signalling downstream of hormone stimulation and the biomechanical processes involved in zebrafish pigment translocation, confirming the importance of cyclic adenosine monophosphate (cAMP) as a mediator of pigment translocation and finding intact microtubules are essential for both melanin dispersion and aggregation in zebrafish, but that microfilament disruption affects aggregation only. In conclusion, we propose these data establish the zebrafish as an experimental model for studying both physiological colour change and the molecular basis of pigment translocation.
Effects of extracts of miswak and derum on proliferation of Balb/C 3T3 fibroblasts and viability of cariogenic bacteria
Authors: Darmani H , Nusayr T , Al‐Hiyasat AS
Published: March 2006

Abstract:  Objectives: This study examined the effects of extracts of two chewing sticks on proliferation of fibroblasts and viability of cariogenic bacteria. Methods: Aqueous extracts of miswak (Salvadora persica; Arak tree) and derum (Juglans regia; walnut tree) were prepared and their effects investigated on growth of Balb/C 3T3 mouse fibroblasts by measuring the mitochondrial succinic dehydrogenase activity. Furthermore, the effects on the viability of various cariogenic bacteria (Streptococcus mutans, Streptococcus salivarius, Lactobacillus casei and Actinomyces viscosus) was also determined. Results: The data revealed that Balb/C 3T3 fibroblasts exposed to aqueous extracts of miswak or derum showed an increase in cell proliferation by 156% and 255%, respectively, in comparison with controls (p<0.0001). Furthermore, extracts from both miswak and derum had adverse effects on the growth of the cariogenic microorganisms, with derum having significantly greater antimicrobial effects than miswak and at much lower concentrations against all the bacteria tested. The most sensitive organisms were A. viscosus, followed by S. mutans, S. salivarius, with L. casei being the most resistant. Conclusion: The results show that aqueous extracts of miswak and derum enhance the growth of fibroblasts and inhibit the growth of cariogenic bacteria, with the derum extract showing greater activity than miswak.
Oral health status in individuals with dementia living in special facilities
Authors: Rejnefelt I , Andersson P , Renvert S
Published: March 2006

Abstract:  Aim: The aim of this review was to retrieve data describing the oral health status of individuals with dementia living in special facilities. Materials and methods: A literature search on the MEDLINE database (Entrez PubMed) was performed. The literature search yielded 208 papers, of which seven publications were selected for evaluation. Results: From the available studies poorer oral hygiene, decreased saliva flow rates and a higher caries incidence were reported in individuals with dementia living in special facilities when compared with healthy individuals. Oral health problems were more pronounced in the severe stage of the disease. Conclusions: There is limited scientific data describing the oral health status of individuals with dementia living in special facilities. However, available data indicate that individuals with dementia living in special facilities have more oral health problems than individuals without dementia.
Oral health status of vulnerable groups in a village of the Central Highlands, southern Vietnam
Authors: Uetani M , Jimba M , Kaku T , Ota K , Wakai S
Published: March 2006

Abstract:  Objectives: Oral health status of vulnerable people in developing countries tends to be given lower priority than other health issues. Consequently, few studies have examined the oral health status of the poor and minorities in developing countries. We aim to examine the dental caries and periodontal status, and explore the risk indicators of dental caries between two ethnic groups in rural villages in southern Vietnam. Methods: We examined the caries status and its risk indicators of 150 participants (Co‐Ho minority and Kinh majority) living in a hamlet of Dangphuong village in Vietnam. We also assessed periodontal status of the participants aged 14 and over by Community Periodontal Index. Results: We first found that dental caries were highly prevalent among both the Co‐Ho minority and Kinh majority groups. Second, the higher numbers of dental caries among children with primary teeth were associated with a higher frequency of consuming sweets. Third, most people (87%) aged 14 and over had periodontal problems. Finally, the Kinh majority tended to have more dental caries than Co‐Ho among people aged less than 30. Conclusion: Oral health promotion should be considered as a part of the development programmes for vulnerable groups in Vietnam and other developing countries.
Non‐surgical treatment of peri‐implant pathology
Authors: De Araújo Nobre M , Capelas C , Alves A , Almeida T , Carvalho R , Antunes E , Oliveira D , Cardador A , Maló P
Published: March 2006

Abstract:  Introduction: Peri‐implant pathologies consist of an inflammatory process affecting the soft and hard tissues surrounding the implants. Chlorhexidine is considered the gold standard antiseptic, with a large variety of choice in administration. In this study, a protocol for the irrigation of peri‐implant pockets with a chlorhexidine gel, using a plastic needle for the delivery of the product into the peri‐implant pockets is described. Study participants and methods: Nine patients with at least one implant presenting peri‐implant pathology (inflamed soft tissue associated with bone loss around the implant) were enrolled in this prospective clinical study, and followed‐up for 1 year, where clinical parameters such as modified plaque index, modified bleeding index, probing pocket depths, attachment levels were assessed at baseline, 1 month, and 1 year after implementation of the treatment protocol. Results: Treatment success was achieved in eight of the nine patients (and in 11 of the 13 implants) according to the success criteria adopted by the authors of this study. Discussion: Infection control lies at the heart of peri‐implant treatment. The control of three factors such as optimal diagnosis, removal of the aetiological factor of the disease (proper removal of debris and decontamination of the peri‐implant sulcus/pocket) and a good patient's oral hygiene self‐care represents the key to success, resulting in good treatment outcomes when managing peri‐implant pathologies. The protocol used (irrigation of peri‐implant pockets with chlorhexidine gel delivered by a plastic needle) is considered to be of utility.
Isochore structures in the chicken genome
Authors: Gao Feng , Zhang Chun‐Ting
Published: March 2006

The availability of the complete chicken genome sequence provides an unprecedented opportunity to study the global genome organization at the sequence level. Delineating compositionally homogeneous G + C domains in DNA sequences can provide much insight into the understanding of the organization and biological functions of the chicken genome. A new segmentation algorithm, which is simple and fast, has been proposed to partition a given genome or DNA sequence into compositionally distinct domains. By applying the new segmentation algorithm to the draft chicken genome sequence, the mosaic organization of the chicken genome can be confirmed at the sequence level. It is shown herein that the chicken genome is also characterized by a mosaic structure of isochores, long DNA segments that are fairly homogeneous in the G + C content. Consequently, 25 isochores longer than 2 Mb (megabases) have been identified in the chicken genome. These isochores have a fairly homogeneous G + C content and often correspond to meaningful biological units. With the aid of the technique of cumulative GC profile, we proposed an intuitive picture to display the distribution of segmentation points. The relationships between G + C content and the distributions of genes (CpG islands, and other genomic elements) were analyzed in a perceivable manner. The cumulative GC profile, equipped with the new segmentation algorithm, would be an appropriate starting point for analyzing the isochore structures of higher eukaryotic genomes.
NANOGP8 is a retrogene expressed in cancers
Authors: Zhang Jingyu , Wang Xia , Li Meixiang , Han Jin , Chen Bing , Wang Bin , Dai Jianwu
Published: March 2006

Nanog is a transcription factor that plays key roles in the self‐renewal and maintenance of pluripotency in human embryonic stem (ES) cells. Among Nanog's 11 pseudogenes, NANOGP8 theoretically could be a retrogene, but was considered unlikely as it has not been identified in any expressed sequence tags (ESTs). In this study, we found that NANOGP8 was expressed in several cancer cell lines and in all cancer tissues tested. The complete coding sequence was cloned and the sequence is highly homologous to that of Nanog. We were also able to detect its protein expression using anti‐Nanog antibody in recombinant Escherichia coli and some cancer cell lines tested. In addition, expression of NANOGP8 in NIH3T3 cells can promote cell proliferation. The expression of NANOGP8 in cancer cell lines and cancer tissues suggests that NANOGP8 may play important roles in tumorigenesis. This work not only has potential significance in stem cell and cancer research, but it also raises the possibility that some of the human pseudogenes may have regulatory functions.
DNA mismatch repair system
Authors: Jun Sung‐Hoon , Kim Tae Gyun , Ban Changill
Published: March 2006

The molecular mechanisms of the DNA mismatch repair (MMR) system have been uncovered over the last decade, especially in prokaryotes. The results obtained for prokaryotic MMR proteins have provided a framework for the study of the MMR system in eukaryotic organisms, such as yeast, mouse and human, because the functions of MMR proteins have been conserved during evolution from bacteria to humans. However, mutations in eukaryotic MMR genes result in pleiotropic phenotypes in addition to MMR defects, suggesting that eukaryotic MMR proteins have evolved to gain more diverse and specific roles in multicellular organisms. Here, we summarize recent advances in the understanding of both prokaryotic and eukaryotic MMR systems and describe various new functions of MMR proteins that have been intensively researched during the last few years, including DNA damage surveillance and diversification of antibodies.
Binding and activation of nitric oxide synthase isozymes by calmodulin EF hand pairs
Authors: Spratt Donald E. , Newman Elena , Mosher Jennifer , Ghosh Dipak K. , Salerno John C. , Guillemette J. G.
Published: March 2006

Calmodulin (CaM) is a cytosolic Ca2+ signal‐transducing protein that binds and activates many different cellular enzymes with physiological relevance, including the nitric oxide synthase (NOS) isozymes. CaM consists of two globular domains joined by a central linker; each domain contains an EF hand pair. Four different mutant CaM proteins were used to investigate the role of the two CaM EF hand pairs in the binding and activation of the mammalian inducible NOS (iNOS) and the constitutive NOS (cNOS) enzymes, endothelial NOS (eNOS) and neuronal NOS (nNOS). The role of the CaM EF hand pairs in different aspects of NOS enzymatic function was monitored using three assays that monitor electron transfer within a NOS homodimer. Gel filtration studies were used to determine the effect of Ca2+ on the dimerization of iNOS when coexpressed with CaM and the mutant CaM proteins. Gel mobility shift assays were performed to determine binding stoichiometries of CaM proteins to synthetic NOS CaM‐binding domain peptides. Our results show that the N‐terminal EF hand pair of CaM contains important binding and activating elements for iNOS, whereas the N‐terminal EF hand pair in conjunction with the central linker region is required for cNOS enzyme binding and activation. The iNOS enzyme must be coexpressed with wild‐type CaM in vitro because of its propensity to aggregate when residues of the highly hydrophobic CaM‐binding domain are exposed to an aqueous environment. A possible role for iNOS aggregation in vivo is also discussed.
Combined use of selective inhibitors and fluorogenic substrates to study the specificity of somatic wild‐type angiotensin‐converting enzyme
Authors: Jullien Nicolas D. , Cuniasse Philippe , Georgiadis Dimitris , Yiotakis Athanasios , Dive Vincent
Published: March 2006

Somatic angiotensin‐converting enzyme (ACE) contains two homologous domains, each bearing a functional active site. Studies on the selectivity of these ACE domains towards either substrates or inhibitors have mostly relied on the use of mutants or isolated domains of ACE. To determine directly the selectivity properties of each ACE domain, working with wild‐type enzyme, we developed an approach based on the combined use of N‐domain‐selective and C‐domain‐selective ACE inhibitors and fluorogenic substrates. With this approach, marked differences in substrate selectivity were revealed between rat, mouse and human somatic ACE. In particular, the fluorogenic substrate Mca‐Ala‐Ser‐Asp‐Lys‐DpaOH was shown to be a strict N‐domain‐selective substrate of mouse ACE, whereas with rat ACE it displayed marked C‐domain selectivity. Similar differences in selectivity between these ACE species were also observed with a new fluorogenic substrate of ACE, Mca‐Arg‐Pro‐Pro‐Gly‐Phe‐Ser‐Pro‐DpaOH. In support of these results, changes in amino‐acid composition in the binding site of these three ACE species were pinpointed. Together these data demonstrate that the substrate selectivity of the N‐domain and C‐domain depends on the ACE species. These results raise concerns about the interpretation of functional studies performed in animals using N‐domain and C‐domain substrate selectivity data derived only from human ACE.
A potential role for the Src‐like adapter protein SLAP‐2 in signaling by the colony stimulating factor‐1 receptor
Authors: Manes Gael A. , Masendycz Paul , Nguyen Thao , Achuthan Adrian , Dinh Hang , Hamilton John A. , Scholz Glen M.
Published: March 2006

The development of macrophages from myeloid progenitor cells is primarily controlled by the growth factor colony stimulating factor‐1 (CSF‐1) and its cognate receptor, a transmembrane tyrosine kinase encoded by the c‐Fms proto‐oncogene. The CSF‐1 receptor exerts its biological effects on cells via a range of signaling proteins including Erk1/2 and Akt. Here we have investigated the potential involvement of the Src‐like adapter protein (SLAP‐2) in signaling by the CSF‐1 receptor in mouse bone marrow‐derived macrophages. RT‐PCR analysis revealed constitutive expression of the SLAP‐2 gene in bone marrow macrophages. Surprisingly, co‐immunoprecipitation and GST binding experiments demonstrated that the CSF‐1 receptor could bind to SLAP‐2 in a ligand‐independent manner. Furthermore, the binding of SLAP‐2 to the CSF‐1 receptor involved multiple domains of SLAP‐2. SLAP‐2 also bound c‐Cbl, with the interaction being mediated, at least in part, by the unique C‐terminal domain of SLAP‐2. Overexpression of SLAP‐2 in bone marrow macrophages partially suppressed the CSF‐1‐induced tyrosine phosphorylation and/or expression level of a ∼ 80 kDa protein without affecting CSF‐1‐induced global tyrosine phosphorylation, or activation of Akt or Erk1/2. Significantly, CSF‐1 stimulation induced serine phosphorylation of SLAP‐2. Pharmacologic inhibition of specific protein kinases revealed that CSF‐1‐induced phosphorylation of SLAP‐2 was dependent on JNK activity. Taken together, our results suggest that SLAP‐2 could potentially be involved in signaling by the CSF‐1 receptor.
Local binding with globally distributed changes in a small protease inhibitor upon enzyme binding
Authors: Gáspári Zoltán , Szenthe Borbála , Patthy András , Westler William M , Gráf László , Perczel András
Published: March 2006

Complexation of the small serine protease inhibitor Schistocerca gregaria chymotrypsin inhibitor (SGCI), a member of the pacifastin inhibitor family, with bovine chymotrypsin was followed by NMR spectroscopy. 1H–15N correlation (HSQC) spectra of the inhibitor with increasing amounts of the enzyme reveal tight and specific binding in agreement with biochemical data. Unexpectedly, and unparalleled among canonical serine protease inhibitors, not only residues in the protease‐binding loop of the inhibitor, but also some segments of it located spatially far from the substrate‐binding cleft of the enzyme were affected by complexation. However, besides changes, some of the dynamical features of the free inhibitor are retained in the complex. Comparison of the free and complexed inhibitor structures revealed that most, but not all, of the observed chemical shift changes can be attributed to minor structural transitions. We suggest that the classical ‘scaffold + binding loop’ model of canonical inhibitors might not be fully valid for the inhibitor family studied. In our view, this feature allows for the emergence of both taxon‐specific and nontaxon‐specific inhibitors in this group of small proteins.
SOLVING THE FAMILY COURT PUZZLE: INTEGRATING RESEARCH, POLICY, AND PRACTICE
Authors: Bridge Hon. Bobbe J.
Published: March 2006

In my opening remarks to the 42nd Annual Conference of the Association of Family and Conciliation Courts, I discuss trends in family law cases from the Supreme Court of Washington and the U.S. Supreme Court. I also review the wide variety of advancements in the way that court systems approach family law cases. Noting a recent emphasis on the fundamental rights of parents, I advocate a new paradigm, moving away from a focus on the parents and toward a focus on the child.
THE EVOLUTION—OR END—OF MARRIAGE?: REFLECTIONS ON THE IMPASSE OVER SAME‐SEX MARRIAGE
Authors: McClain Linda C.
Published: March 2006

The debate over legalizing same‐sex marriage implicates the question of whether doing so would signal the end—or destruction—of the institution of marriage. The appeal to preserving a millennia‐old tradition of marriage against change fails to reckon with the evolution that has already occurred. Invocations of gender complementarity between parents as essential to child well‐being also conflict with growing recognition in family law that children's best interests can be served by gay and lesbian parents. Canada's path toward same‐sex marriage suggests that impasse need not be inevitable. In the United States, this impasse stems in part from the problem that same‐sex marriage serves as an emblem of everything that threatens marriage.
PERMANENCE FOR OLDER FOSTER YOUTH1
Authors: Bussiere Alice
Published: March 2006

I discuss the importance of permanency for older youth in foster care and the limitations of current foster care programs in meeting the permanency needs of these youth. I provide an overview of federal and state policies and describe recent initiatives that are successfully increasing permanence for older foster youth, overcoming barriers to adoption, and using creative strategies to identify alternative permanent arrangements. A key component is inclusion of foster youth in the decisions that affect their lives.
THE COLUMBUS PILOT IN THE FAMILY COURT OF WESTERN AUSTRALIA1
Authors: Pike Lisbeth T. , Murphy Paul T.
Published: March 2006

The Columbus Pilot Project (Columbus) in the Family Court of Western Australia (FCWA) is an early intervention initiative aimed at achieving better outcomes for parents and their children in matters where there have been allegations of domestic violence or child abuse. This article provides an overview of the FCWA, a detailed description of the Columbus process and describes the development of a multimethod longitudinal evaluation model. Quantitative data (including cost/outcome analysis) and qualitative data generated from stakeholder and client interviews suggest that Columbus provides an innovative and effective way of managing these highly conflicted cases.
The Validity of the Reynolds Equation in Modeling Hydrostatic Effects in Gas Lubricated Textured Parallel Surfaces
Authors: Feldman Y. , Kligerman Y. , Etsion I. , Haber S.
Published: March 2006

Microdimples generated by laser surface texturing (LST) can be used to enhance performance in hydrostatic gas-lubricated tribological components with parallel surfaces. The pressure distribution and load carrying capacity for a single three-dimensional dimple, representing the LST, were obtained via two different methods of analysis: a numerical solution of the exact full Navier-Stokes equations, and an approximate solution of the much simpler Reynolds equation. Comparison between the two solution methods illustrates that, despite potential large differences in local pressures, the differences in load carrying capacity, for realistic geometrical and physical parameters, are small. Even at large clearances of 5% of the dimple diameter and pressure ratios of 2.5 the error in the load carrying capacity is only about 15%. Thus, for a wide range of practical clearances and pressures, the simpler, approximate Reynolds equation can safely be applied to yield reasonable predictions for the load carrying capacity of dimpled surfaces.
Frequency Dependency of Measured and Predicted Rotordynamic Coefficients for a Load-On-Pad Flexible-Pivot Tilting-Pad Bearing
Authors: Rodriguez Luis E. , Childs Dara W.
Published: March 2006

Experimental dynamic-stiffness-coefficient results are presented for a high-speed, lightly loaded, load-on-pad, flexible-pivot tilting-pad (FPTP) bearing. Results show that the real parts of the direct dynamic-stiffness are quadratic functions of the excitation frequency. Frequency independent [M], [K], and [C] matrices can be used in place of frequency dependent [K] and [C] matrices to model the FPTP bearing for the conditions tested. The model reduction that results in moving from twelve degrees of freedom (three degrees of freedom for each of four pads) to two degrees of freedom in the bearing reaction model seems to account for most of the observed and predicted frequency dependency. Predictions indicate that pad and fluid inertia have a secondary impact for excitation frequencies out to synchronous frequency. Experimental results are compared to numerical predictions from models based on: (i) The Reynolds equation, and (ii) a Navier-Stokes (NS) equations bulk-flow model that retains the temporal and convective fluid inertia terms. The NS bulk-flow model results correlate better with experimental dynamic stiffness results, including added-mass terms. Both models underestimate the measured added-mass coefficients for the full excitation range; however, they do an adequate job for excitation frequencies up to synchronous frequency. The advantage of using a frequency-independent [M]-[K]-[C] model is that rotordynamic stability calculations become noniterative and much quicker than for a frequency dependent [K]-[C] model. However, these results only apply to this bearing at the conditions tested. Conventional tilting pad and/or FPTP bearings with different geometry and operating conditions (or even this FPTP bearing at higher loads) may require a frequency-dependent [K]-[C] model.
Modeling and Parametric Study of Torque in Open Clutch Plates
Authors: Aphale Chinar R. , Cho Jinhyun , Schultz William W. , Ceccio Steven L. , Yoshioka Takao , Hiraki Henry
Published: March 2006

The relative motion of the friction and separator plates in wet clutches during the disengaged mode causes viscous shear stresses in the fluid passing through the 100microns gap. This results in a drag torque on both the disks that wastes energy and decreases fuel economy. The objective of the study is to develop an accurate mathematical model for the above problem with verification using FLUENT and experiments. Initially we two consider flat disks. The mathematical model calculates the drag torque on the disks and the 2D axisymmetric solver verifies the solution. The surface pressure distribution on the plates is also verified. Then, 3D models of one grooved and one flat disk are tested using CFD, experiments and an approximate 3D mathematical model. The number of grooves, depth of groove and clearance between the disks are studied to understand their effect on the torque. The study determines the pressure field that eventually affects aeration incipience (not studied here). The results of the model, computations and experiments corroborate well in the single-phase regime.
Bio-Ferrography to Capture and Separate Polyethylene Wear Debris from Hip Simulator Fluid and Compared with Conventional Filter Method
Authors: Meyer Donna M. , Tillinghast Adam , Hanumara Nevan C. , Franco Ana
Published: March 2006

This paper describes an experimental method, bio-ferrography, to separate ultrahigh molecular weight polyethylene (UHMWPE) wear debris, generated in hip simulators, from bovine serum lubricating fluid. A total of 54 experiments were performed in which an enzyme digestion “cocktail” was developed and used to clean the bovine serum samples of extraneous sugars, proteins, and lipids that interfere with the UHMWPE particle separation. Erbium chloride was used to marginally magnetize particles in the fluid prior to passing through the ferrographic device. The particles were captured and separated from the fluid by traversing the treated serum across a magnetic gap of a bio-ferrograph. Morphology of the captured and separated wear debris was compared with particles from samples of fluid filtered through a paper sieve arrangement with pores of 0.05micrometers in diameter. The UHMWPE wear debris collected using the described experimental method, were found to be between 0.1 and 20micrometers in diameter with spherical and pill-shaped particles. The filtered UHMWPE particles were in the same size range as the debris separated using bio-ferrography. To show that the experimental method captured UHMWPE particles, the spectra of the chemical composition of UHMWPE from an acetabular cup insert of a hip implant and of UHMWPE particles separated using bio-ferrography were compared and found to be the same. To further demonstrate that polyethylene could be captured and separated through the experimental method, manufactured polyethylene microspheres in the diameter range of 3-45micrometers, were captured and separated using the bio-ferrographic process.
Experimental Study of a Squeeze Film Damper With Eccentric Circular Orbits
Authors: Adiletta Giovanni , Della Pietra Lelio
Published: March 2006

An experiment was carried out to investigate the distribution of oil pressure within a squeeze film damper. The damper was made so that its operation turned out to be as simple as possible, in order to highlight the main causes of practical deviation from theoretical prediction, with particular reference to cavitating mechanisms and regardless of inertia effects. The journal of the damper was given an eccentric orbital precession, with adoption of two distinct values of the offset. A groove placed laterally to the film secured the oil feeding. An outlet plenum at the opposite side of the film was operated with two different levels of exposure to the ambient air. Observation of the oil pressure was restricted to the film section midway between the inlet and outlet border, by means of three piezoelectric transducers plus a strain gauge sensor. Theoretical prediction with a simple isoviscous short bearing uncavitated model was shown to be a significant reference for the experimental data. Analysis of the pressure levels and shape of the pressure waves made it possible to recognize operating conditions with the presence of tensile stresses and rupture of the film. The latter conditions were chiefly due to vapor cavitation. In many circumstances, spikes with tensile strength preceded the ruptured region. Air entrainment and its effects proved to be restricted at high frequency regimes with very low supply pressures and coexisted with vapor cavitation. The influence of moderate orbital distortion on pressure signals was highlighted. Significant differences in the pressure behavior from one sensor location to the other, for the same operating conditions, were frequently observed.
An Approximate Analytical Model for the Separation of a Sphere From a Flat in the Presence of a Liquid
Authors: Streator J. L.
Published: March 2006

An approximate analytical model is proposed to describe the process of separating a sphere from a flat in the presence of a Newtonian liquid, under conditions of constant force. The model is based on consideration of the effects of sphere inertia in characterizing the critical point of separation—namely, that there is a sudden onset of significant sphere acceleration. Good agreement is found between the predictions of the analytical model with those of a full numerical simulation.
Elastic-Plastic Contact Behavior Considering Asperity Interactions for Surfaces With Various Height Distributions
Authors: Jeng Yeau-Ren , Peng Shin-Rung
Published: March 2006

This study investigates the effects of asperity interactions on the mean surface separation and the real contact area for rough surfaces with non-Gaussian height distributions. The effects of the asperity interactions on the local deformation behavior of a given microcontact are modeled using the Saint Venant principle and Love’s formula. The non-Gaussian rough surfaces are described by the Johnson translatory system. The results indicate that asperity interactions can significantly affect the mean separation of surfaces with non-Gaussian height distributions. The findings also reveal that the contact load and the real contact area of surfaces with non-Gaussian height distributions are significantly different from those of surfaces with Gaussian height distributions. This study uncovers that skewed surfaces tend to deform more elastically, which provides underlying physics for the long-time conventional wisdom and recent experimental data [Y. R. Jeng, 1996, Tribol. Trans., 39, 354–361;Y. R. Jeng, Z. W. Lin, and S. H. Shyo, 2004, ASME J. Tribol., 126, 620–625] that running-in surfaces have better wear resistance.
Design of Optimized Opposed Slider Air Bearings for High-Speed Recording on a Metal Foil Disk
Authors: White James
Published: March 2006

A metal foil disk offers some of the best characteristics of both the hard disk and floppy disk for digital data storage. The current work defines an opposed slider air-bearing arrangement that provides advantages when used with a high-speed metal foil disk in either a fixed or removable format. Use is made of the fact that the opposing sliders interact through their influence on the flexible disk that is sandwiched between them. Asymmetry of opposing air bearings is created by etching the air-bearing pad opposite the recording element pad to a depth sufficient that the flying height and air film stiffness of the opposing pad reach desired levels. The result is an air-bearing interface with low flying height and high stiffness over the recording element directly opposed by a high flying height and low stiffness on the other side of the disk. This air-bearing interface was found to provide an enhanced dynamic flexibility to the metal foil disk when it is subjected to mechanical shock. As a result, the opposed slider arrangement with metal foil disk is able to avoid contact and impact when subjected to substantial levels of mechanical shock. Thus, wear and damage to slider and disk surfaces are reduced as well as the possibility of lost recorded data. This should make the metal foil disk a strong candidate as a rotating storage medium for mobile and portable applications where a shock environment is common. Computer simulation of the new air-bearing configuration will be presented and discussed. The current work is related to but distinct from that reported recently by White (2005, ASME J. Tribol., 127, pp. 522–529) for a Mylar disk.
Finite Element Analysis of the Coupled Journal and Thrust Bearing in a Computer Hard Disk Drive
Authors: Jang G. H. , Lee S. H. , Kim H. W.
Published: March 2006

This paper proposes a method to calculate the characteristics of a coupled fluid dynamic journal and thrust bearing of a hard disk drive (HDD) spindle motor. The governing equations for the journal and thrust bearings are the two-dimensional Reynolds equations in the θz and rθ planes, respectively. The finite element method is appropriately applied to analyze the coupled bearing under the conditions of the continuity of mass and pressure at the interface between the journal and thrust bearings. The pressure in the coupled bearing was calculated by applying the Reynolds boundary condition. The validity of this application was verified by comparing the analytical results of the flying height at various rotating speeds with experimental results. The characteristics of the coupled journal and thrust bearing were also investigated due to the Reynolds and Half-Sommerfeld boundary conditions and the coupled and separate analysis. This research demonstrates that the proposed method can accurately and realistically describe the coupled fluid dynamic bearing in a HDD system.
Influence of Inlet Oil Temperature on the Instability Threshold of Rotor-Bearing Systems
Authors: Wang J. K. , Khonsari M. M.
Published: March 2006

The existing literature contains a number of disparities in assessing the effect of inlet oil temperature on the instability threshold speed in hydrodynamic journal bearings. Specifically, some papers have presented evidence that lowering the inlet oil temperature tends to have a stabilizing effect, whereas others have shown the opposite. No clear explanation has been offered for this phenomenon. This paper presents the results of a series of experiments that explain the nature of these disparities and sheds light on the effect of the inlet oil temperature on the instability threshold in hydrodynamic journal bearings.
Elastic-Plastic Contact Between Rough Surfaces: Proposal for a Wear or Running-In Model
Authors: Nélias D. , Boucly V. , Brunet M.
Published: March 2006

A semi-analytical thermo-elastic-plastic contact model has been recently developed and presented in a companion paper. The main advantage of this approach over the classical finite element method (FEM) is the treatment of transient problems with the use of fine meshing and the possibility of studying the effect of a surface defect on the surface deflection as well as on subsurface stress state. A return-mapping algorithm with an elastic predictor/plastic corrector scheme and a von Mises criterion is now used, which improves the plasticity loop. This improvement in the numerical algorithm increases the computing speed significantly and shows a much better convergence and accuracy. The contact model is validated through a comparison with the FEM results of Kogut and Etsion (2002, J. Appl. Mech., 69, pp. 657–662) which correspond to the axisymmetric contact between an elastic-perfectly plastic sphere and a rigid flat. A model for wear prediction based on the material removal during cyclic loading is then proposed. Results are presented, first, for initially smooth surfaces and, second, for rough surfaces. The effects of surface shear stress and hardening law are underlined.
Lubricating Properties of Water in Oil Emulsions
Authors: Benner James J. , Sadeghi Farshid , Hoeprich Michael R. , Frank Mark C.
Published: March 2006

In this study the effect of water as a contaminant in lubricated contacts was analytically and experimentally investigated. A steel ball on glass disc apparatus was used to measure lubricant film thickness of pure oil and water in oil emulsions under various operating conditions. A steel ball on steel disc rig was used to measure friction as a function of various loads, slide to roll ratios and water in oil emulsions. A finite difference numerical model was developed using the continuum theory of mixtures and results were corroborated with the experimental measurements. Numerical results are in excellent agreement with the experimental results and indicate that water will flow around the contact. The experimental and analytical results suggest that for heavily loaded contacts water-in-oil emulsions perform essentially the same as pure oils.
Thermal and Non-Newtonian Numerical Analyses for Starved EHL Line Contacts
Authors: Yang P. , Wang J. , Kaneta M.
Published: March 2006

This paper focuses on the mechanism of starvation and the thermal and non-Newtonian behavior of starved elastohydrodynamic lubrication (EHL) in line contacts. It has been found that for a starved EHL line contact if the position of the oil-air meniscus is given as input parameter, the effective thickness of the available lubricant layers on the solid surfaces can be solved easily from the mass continuity condition, alternatively, if the later is given as input parameter, the former can also be determined easily. Numerical procedures were developed for both situations, and essentially the same solution can be obtained for the same parameters. In order to highlight the importance of the available oil layers, isothermal and Newtonian solutions were obtained first with multi-level techniques. The results show that as the inlet meniscus of the film moves far away from the contact the effective thickness of the oil layers upstream the meniscus gently reaches a certain value. This means very thin layers (around 1μm in thickness) of available lubricant films on the solid surfaces, provided the effective thickness is equal to or larger than this limitation, are enough to fill the gap downstream the meniscus and makes the contact work under a fully flooded condition. The relation between the inlet meniscus and the effective thickness of the available lubricant layers was further investigated by thermal and non-Newtonian solutions. For these solutions the lubricant was assumed to be a Ree-Eyring fluid. The pressures, film profiles and temperatures under fully flooded and starved conditions were obtained with the numerical technique developed previously. The traction coefficient of the starved contact is found to be larger than that of the fully flooded contact, the temperature in the starved EHL film, however, is found to be lower than the fully flooded contact. Some non-Newtonian results were compared with the corresponding Newtonian results.
A Lattice-Based Cellular Automata Modeling Approach for Granular Flow Lubrication
Authors: Jasti Venkata K. , Higgs C. Fred
Published: March 2006

Liquid lubricants break down at extreme temperatures and promote stiction in micro-/nanoscale environments. Consequently, using flows of solid granular particles as a “dry” lubrication mechanism in sliding contacts was proposed because of their ability to carry loads and accommodate surface velocities. Granular flows are highly complex flows that in many ways act similar to fluids, yet are difficult to predict because they are not well understood. Granular flows are composed of discrete particles that display liquid and solid lubricant behavior with time. This work describes the usefulness of employing lattice-based cellular automata (CA), a deterministic rule-based mathematics approach, as a tool for modeling granular flows in tribological contacts. In the past work, granular flows have been modeled using the granular kinetic lubrication (GKL) continuum modeling approach. While the CA modeling approach is constructed entirely from rules, results are in good agreement with results from the GKL model benchmark results. Velocity results of the CA model capture the well-known slip behavior of granular flows near boundaries. Solid fraction results capture the well-known granular flow characteristic of a highly concentrated center region. CA results for slip versus roughness also agree with GKL theory.
Vibration Response of Rolling Element Bearings in a Rotor Bearing System to a Local Defect Under Radial Load
Authors: Choudhury A. , Tandon N.
Published: March 2006

In the present investigation, a theoretical model has been developed to obtain the vibration response due to a localized defect in various bearing elements in a rotor-bearing system under radial load conditions. The rotor-bearing system has been modeled as a three degrees-of-freedom system. The model predicts significant components at the harmonics of characteristic defect frequency for a defect on the particular bearing element. In the case of a defect on the inner race or a rolling element, the model predicts sidebands about the peaks at defect frequencies, at multiples of shaft and cage frequencies, respectively. The model has also predicted some additional components at harmonics of shaft and cage frequencies due to a local defect on the inner race and a rolling element, respectively. The expressions for all these spectral components have also been derived. Typical numerical results for an NJ 204 bearing have been obtained and plotted. The amplitude of the component at defect frequency, for an outer race defect, is found to be much higher as compared to those due to inner race defect or a rolling element defect of the same size and under similar conditions of load and speed. The results of vibration measurements on roller bearings with simulated local defects have also been presented to experimentally validate the theoretical model proposed. It can be observed from the results that the spectral components predicted by the theoretical model find significant presence in the experimental spectra. Comparison of the normalized analytical values of the spectral components with their experimental values shows fair agreement for most of the cases considered. Probable area of the generated excitation pulses has been calculated and the effects of pulse area variation on the experimental results have been studied.
Rotordynamic-Coefficients and Static (Equilibrium Loci and Leakage) Characteristics for Short, Laminar-flow Annular Seals
Authors: Childs Dara W. , Rodriguez Luis E. , Cullotta Vito , Al-Ghasem Adnan , Graviss Matthew
Published: March 2006

Test results are presented for laminar-flow seals that are representative of buffered-flow oil seals in centrifugal compressors. The seals are short (L∕D≅0.21), with a diameter of 117mm and a clearance-to-radius ratio 0.0007. A smooth seal, a seal with one central groove, and a seal with three grooves were tested. Groove geometries employed are representative of industrial practice for compressors with a groove-depth to clearance ratio on the order of 6. Tests were conducted at 4000, 7000, and 10,000rpm shaft speed with delta pressures across the seals of 21, 45, and 69bars. For all cases, the flow was laminar. The seals were tested from a centered position out to an eccentricity ratio of 0.7. Static data included leakage and equilibrium loci for a range of loads. Direct and cross-coupled stiffness and damping coefficients and direct mass coefficients were determined from dynamic tests. For the smooth seal, comparisons between measurements and predictions were reasonable for the direct and cross-coupled stiffness and damping coefficients; however, measured added mass coefficients were roughly ten times larger than predicted. Predictions for the grooved seals from a “deep-groove” model that assumed zero pressure oscillations in the grooves greatly over predicted the influence of the grooves. In a centered position, smooth and grooved seals had comparable leakage performance. At higher eccentricity ratios, the grooved seals leaked modestly more. For eccentricity ratios less than approximately 0.3, the grooved seals and the smooth seal had qualitatively similar static and dynamic characteristics. In terms of cross-coupled stiffness coefficients, the grooved seals were less stable than the smooth seal at eccentricity ratios greater than approximately 0.5 but had significantly lower cross-coupled coefficients at reduced eccentricity ratios between zero and 0.3. A grooved centered seal is more stable than a smooth centered seal. The smooth seal had higher damping than the grooved seals and had moderately better centering capabilities.
Numerical Modelling of High Pressure Gas Face Seals
Authors: Thomas Sébastien , Brunetière Noël , Tournerie Bernard
Published: March 2006

An axisymetric numerical model of face seals operating with compressible fluids at high pressure is presented. Inertia terms are included using an averaged method and thermal effects are considered. The real behavior of gases at high pressure is taken into account. An original exit boundary condition is used to deal with choked flow. The model is validated by comparison with experimental data and analytical solutions. Finally, the influence of the operating conditions on the performance of a high-pressure gas face seal is analyzed. It is shown that when the flow is choked, the mass flow rate is reduced and the behavior of the seal becomes unstable.