bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigating hypercoagulability during treatment for immune‐mediated thrombocytopenia: a pilot study
Authors: O'Marra Shana K. , Shaw Scott P. , deLaforcade Armelle M.
Published: September 2011

Background

Thromboembolism has recently been described as a complication following treatment for idiopathic thrombocytopenic purpura (ITP). This pilot study was undertaken to determine whether dogs suffering from ITP experience hypercoagulability during treatment and recovery.

Study design

Thromboelastograms (TEG) were performed on dogs with ITP within 24 hours of admission to the hospital, the first day the platelet count exceeded 40 × 109/L (Day 1), and on Days 4, 7, and 14.

Key findings

All dogs had hypocoagulable TEG tracings on initial admission to the hospital, but developed TEG tracings suggestive of hypercoagulability during the study period as indicated by increased maximum amplitude.

Significance

Dogs with ITP developed changes on TEG consistent with hypercoagulability during the study period. Many factors are likely to contribute to these changes. The clinical risk of thrombosis in these patients is unknown.
Cutaneous Collagenous Vasculopathy: Report of the First Pediatric Case
Authors: LLOYD BRENDAN M. , PRUDEN SAMUEL J. , LIND ANNE C. , BERK DAVID R.
Published: September 2011

Abstract:  We describe a 16‐year‐old girl who presented with a 3‐year history of telangiectatic patches on the extremities and trunk. Skin biopsies demonstrated dilated vessels with thickened walls containing hyaline material in the papillary dermis, resembling those seen in systemic amyloidosis, porphyrias, or lipoid proteinosis. A diagnosis of cutaneous collagenous vasculopathy was made. To our knowledge, cutaneous collagenous vasculopathy has previously only been described in adults aged 50 and older.
Alcohol Metabolism in Human Cells Causes DNA Damage and Activates the Fanconi Anemia–Breast Cancer Susceptibility (FA‐BRCA) DNA Damage Response Network
Authors: Abraham Jessy , Balbo Silvia , Crabb David , Brooks Phillip J.
Published: September 2011

Background:  We recently reported that exposure of human cells in vitro to acetaldehyde resulted in the activation of the Fanconi anemia–breast cancer susceptibility (FA‐BRCA) DNA damage response network.

Methods:  To determine whether intracellular generation of acetaldehyde from ethanol metabolism can cause DNA damage and activate the FA‐BRCA network, we engineered HeLa cells to metabolize alcohol by expression of human alcohol dehydrogenase (ADH) 1B.

Results:  Incubation of HeLa‐ADH1B cells with ethanol (20 mM) resulted in acetaldehyde accumulation in the media, which was prevented by co‐incubation with 4‐methyl pyrazole (4‐MP), a specific inhibitor of ADH. Ethanol treatment of HeLa‐ADH1B cells produced a 4‐fold increase in the acetaldehyde–DNA adduct and N2‐ethylidene‐dGuo and also resulted in the activation of the FA‐BRCA DNA damage response network, as indicated by a monoubiquitination of FANCD2 and phosphorylation of BRCA1. Ser 1524 was identified as 1 site of BRCA1 phosphorylation. The increased levels of DNA adducts, FANCD2 monoubiquitination, and BRCA1 phosphorylation were all blocked by 4‐MP, indicating that acetaldehyde, rather than ethanol itself, was responsible for all 3 responses. Importantly, the ethanol concentration we used is within the range that can be attained in the human body during social drinking.

Conclusions:  Our results indicate that intracellular metabolism of ethanol to acetaldehyde results in DNA damage, which activates the FA‐BRCA DNA damage response network.
Using Technology to Encourage Critical Thinking and Optimal Decision Making in Risk Management Education
Authors: Garvey John , Buckley Patrick
Published: September 2011

Abstract

This article draws a link between the risk management failures in the financial services industry and the educational philosophy and teaching constraints at business schools. An innovative application of prediction market technology within business education is proposed as a method that can be used to encourage students to think about risk in an open and flexible way. This article explains how prediction markets also provide students with the necessary experience to critically evaluate and stress‐test quantitative risk modeling techniques later in their academic and professional careers.
Foreign Ownership and Non‐Life Insurer Efficiency in the Japanese Marketplace
Authors: Huang Li‐Ying , Ma Yu‐Luen , Pope Nat
Published: September 2011

Abstract

Traditional shareholding patterns in Japan have experienced significant change beginning in the early 1990s. Since that time, foreign institutional shareholding has increased significantly largely at the expense of domestic financial institution ownership. This article examines whether these changes in ownership patterns share a relationship with insurer performance in the non‐life insurance market. Using data from 1992 to 2005, we assess performance in terms of efficiency measures using data envelopment analyses (DEA) techniques. Our results show that higher levels of domestic financial institution ownership in Japan are associated with insurer inefficiency. Relative to that relationship, the foreign ownership–insurer efficiency relationship is found to be positive. Additionally, we find that the disparity between those relationships has become more acute since 2001 when the Japanese non‐life insurance market experienced significant consolidation.
Improved Structure Stability and Multiferroic Characteristics in CaTiO3‐Modified BiFeO3 Ceramics
Authors: Wang Qing Qing , Wang Zhuo , Liu Xiao Qiang , Chen Xiang Ming
Published: September 2011

BiFeO3 multiferroic ceramics were modified by introducing CaTiO3. The stability of perovskite BiFeO3 was increased by the present modification, and the single‐phase (Bi1 − xCax)(Fe1 − xTix)O3 solid solutions were obtained when x ≥ 0.15, where the symmetry changed from R3c (x ≤ 0.2) to Pbnm (x ≥ 0.3). The ferroelectric property of BiFeO3 was enhanced by introducing CaTiO3 because of the reduction of leakage current and the increase of resistivity. The increased dielectric constant, decreased dielectric loss, and enhanced remnant magnetization Mr were also obtained. The best combination of multiferroic characteristics were achieved at x = 0.2.
Cell‐mediated immune response to human papillomavirus 16 E7 peptide pools in patients with cervical neoplasia
Authors: LEE YONG SEOK , LEE CHUNG WON , SONG MIN JONG , HO EUN MI , KIM CHAN JOO , PARK TAE CHUL , KIM TAI GYU , PARK JONG SUP
Published: September 2011

Objective. To identify characteristics of the cell‐mediated immune (CMI) response to human papillomavirus‐16 (HPV) E7 viral peptide pools to help the formulation of therapeutic vaccines. Design. Prospective study. Population. Korean women. Setting. University hospital. Methods. From December 2008 to August 2010, 33 HPV‐16‐positive patients, seven patients exhibiting a high‐risk HPV infection other than HPV‐16 with grade 2/3 cervical intraepithelial neoplasm (CIN2/3), and nine healthy control donors were enrolled. Main Outcome Measures. CMI response to synthetic HPV‐16 E7 overlapping peptide pools using the IFN‐γ ELISPOT assay. Results. The E7 sequence comprising amino acids 16–55 was a major immunogenic region. The CMI response to HPV‐16 E7 is highly type‐specific. The follow‐up CMI response may last longer than expected after the lesion is resected. Conclusions. We found that the E7 sequence comprising amino acids 16–55 is a major immunogenic region that is critical for the T‐cell‐mediated immune response with CIN2/3 or cervical cancer. The identification of CMI responses to HPV‐16 E7 peptide pools may provide insight into therapeutic vaccine trials for the control of HPV‐associated diseases.
Content of melatonin and other antioxidants in grape‐related foodstuffs: measurement using a MEPS‐HPLC‐F method
Authors: Mercolini Laura , Mandrioli Roberto , Raggi Maria Augusta
Published: September 2011

Abstract:  The strong antioxidant activity of melatonin is well known and it is important to investigate its presence and levels in different foodstuffs, for the purpose of evaluating their nutraceutical properties. As a contribution towards this goal, an original analytical method has been developed for the simultaneous determination of melatonin and other indolic and phenolic antioxidants (including trans‐ and cis‐resveratrol, ferulic acid, tryptophan, serotonin and 5‐hydroxyindoleacetic acid) in grape‐related foodstuffs and beverages: namely grape, grape juice, must, wine and grappa (Italian pomace brandy). These foodstuffs represent an important part of the diet, both traditionally and in recent times, especially in Mediterranean countries and could be (at least in part) responsible for the beneficial effects involved in the ‘French paradox’. The analytical method is based on high‐performance liquid chromatography coupled to fluorescence detection, exploiting the native fluorescence of the analytes. A C8 column was used as the stationary phase, while the mobile phase was composed of acidic phosphate buffer and acetonitrile; fluorescence intensity was monitored at λ = 386 nm while exciting at λ = 298 nm. The sample pretreatment was carried out by a fast and reliable microextraction by packed sorbent (MEPS) procedure. After validation, the method was applied to the analysis of melatonin and other antioxidants in food and beverages derived from grape, with very good results being obtained. Thus, this methodology may represent a promising tool for the evaluation of the antioxidant properties of nutraceuticals and functional foods.
Description of the constitutive activity of cloned human melatonin receptors hMT1 and hMT2 and discovery of inverse agonists
Authors: Devavry Séverine , Legros Céline , Brasseur Chantal , Delagrange Philippe , Spadoni Gilberto , Cohen William , Malpaux Benoît , Boutin Jean A. , Nosjean Olivier
Published: September 2011

Abstract:  Melatonin receptors have been described to activate different G protein–dependent signaling pathways, both in laboratory, heterologous, cellular models and in physiological conditions. Furthermore, the constitutive activity of G protein–coupled receptors has been shown to be key in physiological and pathological conditions. In the case of melatonin receptors, information is rather scare and concerns only MT1 receptors. In the present report, we show that the G protein–coupled melatonin receptors do have a constitutive, nonmelatonin‐induced signaling activity using two cellular models of different origins, the Chinese hamster ovary cell line and Neuro2A, a neuroblastoma cell line. Furthermore, we show that this constitutive activity involves mainly Gi proteins, which is consistent with the common knowledge on the melatonin receptors. Importantly, we also describe, for the first time, inverse agonist properties for melatonin ligands. Although it is clear than more in‐depth, biochemistry‐based studies will be required to better understand by which pathway(s) the constitutively active melatonin receptors transfer melatonin information into intracellular biochemical events; our data open interesting perspectives for understanding the importance of the constitutive activity of melatonin receptors in physiological conditions.
Assessing the oral health of an ageing population: methods, challenges and predictors of survey participation
Authors: Matthews Debora C. , Brillant Martha G. S. , Clovis Joanne B. , McNally Mary E. , Filiaggi Mark J. , Kotzer Robert D. , Lawrence Herenia P.
Published: September 2011

doi: 10.1111/j.1741‐2358.2011.00540.x

Assessing the oral health of an ageing population: methods, challenges and predictors of survey participation

Objectives:  To examine predictors of participation and to describe the methodological considerations of conducting a two‐stage population‐based oral health survey.

Methods:  An observational, cross‐sectional survey (telephone interview and clinical oral examination) of community‐dwelling adults aged 45–64 and ≥65 living in Nova Scotia, Canada was conducted.

Results:  The survey response rate was 21% for the interview and 13.5% for the examination. A total of 1141 participants completed one or both components of the survey. Both age groups had higher levels of education than the target population; the age 45–64 sample also had a higher proportion of females and lower levels of employment than the target population. Completers (participants who completed interview and examination) were compared with partial completers (who completed only the interview), and stepwise logistic regression was performed to examine predictors of completion. Identified predictors were as follows: not working, post‐secondary education and frequent dental visits.

Conclusion:  Recruitment, communications and logistics present challenges in conducting a province‐wide survey. Identification of employment, education and dental visit frequency as predictors of survey participation provide insight into possible non‐response bias and suggest potential for underestimation of oral disease prevalence in this and similar surveys. This potential must be considered in analysis and in future recruitment strategies.
US Retirement Financial Services Advertising's Financial Information Provisions, Communication Strategies and Judgmental Heuristic Cues
Authors: LEE TAEJUN (DAVID) , HALEY ERIC , YUN TAI WOONG , CHUNG WONJUN
Published: September 2011

Retirement savings and investments have been two of the most important financial service vehicles for American consumers' futures in recent years. With this backdrop, policymakers and consumer educators need retirement financial service providers to play the crucial role of helping consumers make economic decisions with regard to retirement plans and ultimately build retirement assets. This research of how retirement financial services advertising attempted to inform, communicate and persuade investors during the past four years (2006–2009) includes two crucial events in the US retirement marketplace—the Pension Protection Act of 2006 and the 2007/2008 US financial crisis. A content analysis examined the type of information, the communication strategies and the judgmental heuristic cues presented in a total of 1,430 retirement financial service advertisements in six national US business‐finance magazines from 2006 to 2009.
Intrinsic Rewards of Work, Future Time Perspective, the Economy in the Future and Retirement Planning
Authors: YANG TING‐YING , DEVANEY SHARON A.
Published: September 2011

This study incorporated intrinsic rewards of work, future time perspective and perspective on the economy in the future to create a model for the psychological mechanism of planning for retirement. The data set included those who were not retired (N = 2,266) in the 1992 Health and Retirement Study. Confirmatory factor analyses and structural equation modeling were used. The analyses were conducted separately on the different types of retirement plans. The results suggest that human resource professionals should (1) encourage employees who perceive high intrinsic rewards of work to plan for their retirement, and (2) remind employees that retirement might be closer than they anticipate.
Parting Perspectives from an Aging Editor (& thanks for all the fish)
Authors: ROTFELD HERBERT JACK
Published: September 2011

Unlike the dolphins in Douglas Adams' Hitchhikers' Guide to the Universe who originally expressed the parenthetical phrase of the title, the editor is not deserting the planet. But becoming a non‐editor means a departure from a special world that filled so much time for so long. And after a long academic life including over 35 years of membership in ACCI, one gets a skeptical perspective to hear young scholars confidently predict the future of consumer issues, which in many ways looks like the past.
Kinetic Analyses of Keap1–Nrf2 Interaction and Determination of the Minimal Nrf2 Peptide Sequence Required for Keap1 Binding Using Surface Plasmon Resonance
Authors: Chen Yu , Inoyama Daigo , Kong Ah‐Ng Tony , Beamer Lesa J. , Hu Longqin
Published: September 2011

The Keap1–Nrf2 interaction plays important roles in regulation of Nrf2 activity and induction of chemopreventive enzymes. To better understand the interaction and to determine the minimal Nrf2 sequence required for Keap1 binding, we synthesized a series of Nrf2 peptides containing ETGE motif and determined their binding affinities to the Kelch domain of Keap1 in solution using a surface plasmon resonance‐based competition assay. The equilibrium dissociation constant for the interaction between 16mer Nrf2 peptide and Keap1 Kelch domain in solution () was found to be 23.9 nm, which is 10× lower than the surface binding constant () of 252 nm obtained for the direct binding of Keap1 Kelch domain to the immobilized 16mer Nrf2 peptide on a surface plasmon resonance sensor chip surface. The binding affinity of Nrf2 peptides to Keap1 Kelch domain was not lost until after deletion of eight residues from the N‐terminus of the 16mer Nrf2 peptide. The 9mer Nrf2 peptide has a moderate binding affinity with a of 352 nm and the affinity was increased 15× upon removal of the positive charge at the peptide N‐terminus by acetylation. These results suggest that the minimal Nrf2 peptide sequence required for Keap1 binding is the 9mer sequence of LDEETGEFL.
Language and Music in the Musician Brain
Authors: Besson Mireille , Chobert Julie , Marie Céline
Published: September 2011

Results of numerous experiments conducted over the past 15 years by using behavioural as well as brain imaging methods have shown that musical expertise influences brain anatomy, brain functions and behaviour. The musician’ brain is thus considered as a very good model of brain plasticity. Moreover, many results have demonstrated that musical expertise not only impacts on music processing but also on several aspects of speech processing including lexical pitch, sentence intonation and the metric structure of words. Conversely, recent results indicated that linguistic expertise with tone or quantity languages such as Mandarin Chinese, Thai, Finnish and Japanese, influences the processing of harmonic tones and musical intervals. We discuss possible interpretations of these findings in terms of common processing of the acoustic parameters involved in music and speech and in terms of bidirectional transfer of training effects between music and speech processing.
Ubiquitin is Associated with Early Truncation of Tau Protein at Aspartic Acid421 during the Maturation of Neurofibrillary Tangles in Alzheimer's Disease
Authors: García‐Sierra Francisco , Jarero‐Basulto Jose J. , Kristofikova Zdena , Majer Emerich , Binder Lester I. , Ripova Daniela
Published: September 2011

Pathological processing of tau protein during the formation and maturation of neurofibrillary tangles (NFTs) includes abnormal phosphorylation, conformational changes and truncation of the C‐terminus at aspartic‐acid421 (apoptotic product) and glutamic‐acid391 residues. Abnormal phosphorylation and misfolding may serve as recognition signals for ubiquitin‐targeting and proteosomal processing. For this reason, we sought to determine whether ubiquitin‐targeting of tau is associated with particular tau modifications that herald specific stages of NFTs maturation in the hippocampus of Alzheimer's disease cases. Using multiple tau antibodies, we found that 30% of the total load of NFTs is ubiquitin‐associated. As reported previously ubiquitin immunoreactivity was associated with markers of phosphorylated tau in certain NFTs; however, a strong association was also found between ubiquitin and the earliest known truncation event at aspartic‐acid421. These findings indicate that tau protein in the NFTs may be dually subjected to both apoptotic and proteosomal processing. By contrast ubiquitin immunoreactivity was poorly associated with truncation of tau at glutamic‐acid391, suggesting that this proteolytic event may be independent of proteosomal activity. It would appear, therefore, that ubiquitin targeting of tau protein occurs at NFTs in the early and intermediate stages of the maturation.
HOW DO THAI PATIENTS WITH END STAGE RENAL DISEASE ADAPT TO BEING DEPENDENT ON HAEMODIALYSIS? A PILOT STUDY
Authors: Yodchai Kantaporn , Dunning Trisha , Hutchinson Alison M. , Oumtanee Areewan , Savage Sally
Published: September 2011

Background: Researchers have explored the experiences of patients on haemodialysis (HD); however, most studies do not include Thai patients. Thus, the way Thai patients experience and adapt to HD is unknown.

Aim: To conduct a pilot study to explore how HD affects Thai patients with end stage renal disease (ESRD) and understand HD patients’ perspectives about adapting to being dependant on HD.

Methods: Data were collected using semi‐structured interviews that focused on problems, feelings, thoughts, attitudes and ways of adapting to HD. Grounded theory (GT) method was selected to guide data collection and analysis.

Findings: Five patients (age range 24–66 years; mean 45.40 years; mode = 24) participated in the study. Four main coping processes emerged during data analysis: planning, adjustment and avoidance, belief in religion and superstition and living with hope. In addition, the patients reported a range of adverse effects of HD including fluid restriction, fatigue, effects on sexual activity, altered body image, fear of dying, stress and depression and suicide.

Conclusion: Thai patients with ESRD felt treatment, including HD, adversely affected their lives and required physical, psychological and social changes to enable them to cope. They reported use of a range of strategies to deal with the adverse effects.
PREVALENCE OF HEPATITIS B IN HAEMODIALYSIS NURSING STAFF IN ATHENS
Authors: Topka Dimitra , Theodosopoulos Labros , Elefsiniotis Ioannis , Saroglou George , Brokalaki Hero
Published: September 2011

Background: Healthcare workers are at high risk of acquiring hepatitis B and particularly haemodialysis staff. The aim of the study was to examine the prevalence of hepatitis B markers in haemodialysis nurses and to explore the determinants of the infection.

Patients and methods: Two hundred and sixteen haemodialysis nurses from 20 haemodialysis units in Athens completed an anonymous questionnaire, their blood samples were taken and tested for hepatitis B virus (HBV) markers.

Results: The prevalence of positive HBsAg among nurses was 0.5%. Anti‐HBc positivity due to past exposure to HBV was 12.5%. A total of 87.5% of the participants had immunity to HBV. Multivariate analysis demonstrated that previous exposure to HBV was related positively with the age of the haemodialysis nursing staff [odd ratios (OR): 1.115, 95% CI: 1.014–1.226, P = 0.025].

Conclusion: The prevalence of HBV in the haemodialysis nursing staff in Athens is low, the vaccination coverage and the immunity to HBV are high in comparison to previous reports.
Diagnostic accuracy of α‐fetoprotein and des‐γ‐carboxy prothrombin in screening for hepatocellular carcinoma in liver transplant candidates
Authors: Yamashiki Noriyo , Sugawara Yasuhiko , Tamura Sumihito , Kaneko Junichi , Yoshida Haruhiko , Aoki Taku , Hasegawa Kiyoshi , Akahane Masaaki , Ohtomo Kuni , Fukayama Masashi , Koike Kazuhiko , Kokudo Norihiro
Published: September 2011

Aim:  Although hepatocellular carcinoma (HCC)‐specific serum tumor markers, α‐fetoprotein (AFP) and des‐γ‐carboxy prothrombin (DCP), are used in the screening for HCC, their utility in pre‐transplantation evaluation is not well established. This study aimed to evaluate the accuracy of AFP and DCP measurement for the diagnosis of HCC in liver transplant candidates.

Methods:  A total of 315 consecutive adult patients (174 men and 141 women, mean age 52 years), who were to receive liver transplantation for end‐stage liver diseases, were enrolled. The pre‐transplant levels of AFP and DCP were compared with the histopathology of explanted liver.

Results:  Hepatocellular carcinoma was present in the explanted liver of 106 recipients (median number of nodules 2, mean diameter 2.5 cm). The area under receiver operating characteristic curve for the diagnosis of HCC was 0.83 (95% confidence interval, 0.78–0.88) for AFP and 0.47 (0.41–0.54) for DCP. With the cut‐off value of 100 mAU/mL, 20/106 (18.9%) patients with HCC and 54/194 (27.8%) patients without HCC were positive for DCP. DCP positivity was associated with vascular invasion, tumor differentiation and size among patients with HCC, which was associated with albumin level among patients without HCC. Vitamin K was administered prior to transplantation to 20 patients who were positive for DCP (two with and 18 without HCC), resulting in a decrease in DCP levels in 19 of them.

Conclusions:  Serum DCP levels may be raised in end‐stage liver disease patients without HCC, and cannot be used as a reliable marker for HCC among liver transplant candidates.
Hepatitis B virus drug resistance to current nucleos(t)ide analogs: Mechanisms and mutation sites
Authors: Deng Lihui , Tang Hong
Published: September 2011

Nucleos(t)ide analogs (NAs) have become the mainstream drugs for the treatment of chronic hepatitis B virus infection. Drug resistance to NAs, however, has posed a major obstacle in obtaining sustained viral suppression. Standardized definitions of terms and nomenclature in discussing NAs resistance have been proposed. Drug resistance to NAs is produced by a combination of viral, host and antiviral drug factors. A detailed understanding of the mechanisms and effects of mutation sites that cause resistance to NAs is important for the design of rational treatment and management of patients with existing drug resistance.
Nine lessons and recommendations from the conduct of focus group research in chronic pain samples
Authors: McParland Joanna L. , Flowers Paul
Published: September 2011

Purpose. The view of the patient is central to their care. Focus group methodology has been used in health psychology to capture patient views on health and illness. However, the process of conducting focus group research with patient groups has received scarce attention. The purpose of this paper was to highlight lessons learned from the conduct of focus groups in psychological research with chronic pain samples.

Methods. Lessons were taken from three structured focus groups containing participants recruited from General Practice. Each group contained five, four, and six chronic pain sufferers from upper, middle and lower socioeconomic areas, respectively.

Results. Nine lessons were learned about the conduct of focus group research in general, and also with chronic pain sufferers in particular. The lessons relate to (1) translating study interest into group attendance, (2) ensuring the environment maximizes the opportunity to learn from participants, (3) understanding participant motivations for attendance as well as (4) what participants take from the group, (5) ensuring adequate question specificity, accommodating the needs of particular groups in (6) moderation style and (7) discussion time scales, (8) considering the function of conflict in the group and (9) paying due attention to simultaneous dialogue. Recommendations for addressing the lessons are made.

Conclusion. Patient groups have specific requirements and the conduct of focus groups should be driven by these needs to maximize inclusion and quality contributions in the group. Time, resources, and flexibility are needed to ensure the successful transition of these groups into focus group research.
The Propagation of Disturbances in the Infinitely Wide Foil Bearing
Authors: Eshel A.
Published: September 2011

A technique for the solution of time-dependent foil bearing problems is presented in this report. Solutions obtained for typical disturbances which are introduced into the bearing indicate that they are swept out at a speed of, essentially, U/2. The effects of higher foil stiffness on this phenomenon are found to be small.
Dynamic Behavior of the Spherical Squeeze-Film Hybrid Bearing
Authors: Pan C. H. T. , Chiang T.
Published: September 2011

The stability and vibration response of a spherical squeeze-film hybrid bearing were analyzed theoretically. Since the squeeze frequency is typically much higher than the vibration frequency, the asymptotic analysis for large squeeze number can be applied here. Perturbation solutions about the radially concentric position were obtained for small vibration amplitudes and small radial displacement. There is no limitation, however, in the values of vibration number (so long as it is small in comparison with the squeeze number), compressibility number, axial displacement ratio, and excursion ratio. Dynamic bearing reactions were computed based on the perturbation solutions. Results indicate that a spherical squeeze-film bearing is always stable in the axial direction. In the radial direction, however, instability about the radially concentric position is possible when there is journal rotation, the frequency of instability is exactly one half of the rotational frequency; the system would be stable if the mass is kept below the critical value. The analysis can be readily extended to compute the response to vibratory excitation in either the axial or the radial direction.
Theoretical Flow-Models for Externally Pressurized Gas Bearings
Authors: Mori H. , Miyamatsu Y.
Published: September 2011

In order to make clear the characteristics of externally pressurized gas bearings, several mathematical flow-models are constructed by making proper chains of fundamental and elemental flow-patterns and pressure changes for circular thrust bearings with single central supply hole. The suggested flow-models, which are the combination of rather simple elements to make the mathematical analysis easy, are quite effective to explain the pressure distributions, the load capacity, and the rate of flow observed experimentally over wide operating conditions. And also, these flow-models make it possible to understand the effects of the inherent compensation, the so-called restrictions in series and the occurrence of shock wave.
Foil Bearings
Authors: Wildmann M.
Published: September 2011

A general description of the behavior of foil bearings is given. This description summarizes and interprets the work of various authors in the field of foil bearings, with particular emphasis on recent publications.
Higher Order Approximations in the Asymptotic Solution of the Reynolds Equation for Slider Bearings at High Bearing Numbers
Authors: DiPrima R. C.
Published: September 2011

The methods of matched asymptotic expansions are used in a systematic manner to obtain the load-carrying capacity of an infinitely long slider bearing correct through terms 0 (1/Λ) where Λ is the bearing number. The expression for the load is extremely simple. It is shown that the error is 0 (1/Λ2), and the procedure for obtaining higher order terms is discussed. Results are given for the case of a converging film thickness with a parabolic shape and for a partial arc journal bearing.
Performance Characteristics of Spiral-Groove and Shrouded Rayleigh Step Profiles for High-Speed Noncontacting Gas Seals
Authors: Cheng H. S. , Castelli V. , Chow C. Y.
Published: September 2011

Current methods in gas lubrication have been used in this paper to analyze the gas-film characteristics in a high-speed, face-type gas seal. Detailed analyses are presented for two different surface geometries, the spiral-groove-orifice seal and the shrouded Rayleigh step seal. Results are presented in three parts. The first part shows the performance of a spiral-groove seal without the orifices, and also the difference in performance when the grooves are located at the high pressure, low pressure, or both sides. The second part gives typical performance of a nonparallel film profile for the spiral-groove-orifice seal as well as for the shrouded Rayleigh step seal. In the last part, a comparison is made between the two seal geometries on their tolerance to coning or dishing under a constant seal load.
On the Local Compressibility Effect in Spiral-Groove Bearings
Authors: Constantinescu V. N. , Castelli V.
Published: September 2011

In order to determine the qualitative effect of lubricant compressibility in groove bearings, the Whipple’s method already used in several papers references [1–8]1 is employed, but eliminating, however, certain approximations, especially the consideration of constant pressure gradients perpendicular to the groove edge. Under these conditions one shows that the analysis is consistent with the normal limiting solution of ph = const, which takes place when the compressibility number increases indefinitely. Grooved bearings behave thus similarly to the usual step bearings, but they operate at a much smaller local compressibility number. Some considerations concerning the values of the compressibility number at which the compressibility effect must be taken into account are given. An exact solution obtained by numerical methods over a no-throughflow groove-ridge pair with cyclic conditions is presented over the entire range of compressibility numbers of interest to show the actual influence of local compressibility.
Contact Conformity Effects on Spinning Torque and Friction
Authors: Dietrich M. W. , Parker R. J. , Zaretsky E. V. , Anderson W. J.
Published: September 2011

Lubricated and unlubricated tests were conducted in the NASA spinning friction apparatus with SAE 52100 steel specimens with ball-race conformities of infinity (a ball on a flat), 60, 55, and 51-percent. For a constant conformity under lubricated conditions, the coefficient of spinning friction decreased from approximately 0.5 to 0.05 with increasing load and stress. At a constant stress, the coefficient of spinning friction increased with decreasing conformity (increasing percent conformity). Under unlubricated conditions, the coefficient of spinning friction remained relatively constant regardless of load, stress, or conformity, having values within a scatter band of 2.5 to 6.0. For a constant stress under both lubricated and unlubricated conditions, the greater the conformity (the smaller the percent conformity), the higher the torque.
Compression of a Thin Plastic Mass Between Two Elastic Cylinders
Authors: Wilson E. A.
Published: September 2011

This work presents an analytical investigation of a plastic mass being compressed between the ends of two elastic circular cylinders. A special function recently tabulated by the author is used to find the deformation of the elastic cylinders due to the pressure distribution caused by the compression of the plastic mass. Based on the deformed shape of the cylinders found by the iterative solution using the special function, the author presents a simplified approximate method for finding the pressure distribution on the cylinders when given the edge separation of the cylinders and the ratio of the shear strength of the plastic mass to the modulus of elasticity in shear of the cylinders.
A Test of Molybdenum Disulfide Lubricants in Radiation and Vacuum Environments
Authors: Lewis J. H. , McDaniel R. H.
Published: September 2011

Tests have been conducted on two MoS2-base solid-film lubricants, one containing gold and sodium silicate and the other containing bismuth and aluminum phosphate, having potential for application under severe environmental conditions. The lubricant with gold was applied to test races of 440 C steel and Rene´ 41 and exposed with a reactor to 1.5 × 1011 ergs/g(C) of gamma and 8.2 × 1016 neutrons/cm2 (E > 0.1 MeV). The test specimens were subsequently evaluated in sliding-wear tests at temperatures as high as 1200 deg F. Both lubricants were tested in vacuum (∼10−6 torr) and in air on size R-3 ball bearings, which were run at 6000 rpm in servomotors. No significant radiation effects were detected with the MoS2:Au lubricant on 440 C steel in tests at room temperature and 600 deg F. In tests at room temperature, 600 deg F, and 1200 deg F on Rene´ 41, the data indicated a possible radiation effect at 600 deg F but not at the other temperatures. In two vacuum tests on bearings, the MoS2:Au lubricant gave a mean running time of about 110 h. The MoS2:Bi film gave a mean life of 96 h in the first test and 853 h in the second test.
A Numerical Solution for the Incompressible Hybrid Journal Bearing With Cavitation
Authors: Heller Stanley , Shapiro Wilbur
Published: September 2011

A numerical solution is presented for determining performance for hybrid journal bearings with arbitrary clearance distribution and cavitation. Regions of cavitation are determined by solution of the incompressible Reynolds’ equation. The pressures in the cavitated regions are immediately adjusted to a specified vapor pressure with zero pressure gradient. The continuity of mass equation permits coupling the influence of the external supply circuit and the methods of recess compensation to the Reynolds’ equation. Results are presented for geometrically similar hydrodynamic, hydrostatic, and hybrid bearings. Favorable comparisons are made with previously published results for the hydrodynamic bearing.
Optimum Design of Hydrodynamic Journal Bearings
Authors: Seireg A. , Ezzat H.
Published: September 2011

This paper presents an automated system for the selection of the length, clearance, and lubricant viscosity which optimize the performance of a hydrodynamic journal bearing, under specified values or ranges of load and speed. The study illustrates the feasibility of applying optimal programming techniques for the development of bearing design systems.
The Effects of Forced-Feed Lubrication on Performance Characteristics of Full Finite Journal Bearings
Authors: Servaes H.
Published: September 2011

The purpose of this paper is to facilitate the analysis and design of pressure fed journal bearings. Numerical solutions of Reynolds’ equation are obtained for full finite journal bearings for the widely used case of L/D = 1. It is found that the performance characteristics of the bearing, mainly the side flow, depend not only on the Sommerfeld number but also on the groove dimensions and on the oil supply pressure. The calculated characteristics are compared with experimental measurements. Correlation is good, leading to the conclusion that the theoretical data are effective for design analysis of pressure fed journal bearings.
The Dynamic Stiffness of Controlled Hydrostatic Bearings
Authors: Mohsin M. E. , Morsi S. A.
Published: September 2011

The first part of this paper is concerned with the theoretical analysis of the dynamic behavior of externally pressurized bearings compensated by constant resistance as well as controlled restrictors. The response of the bearing to harmonic and step function loads is considered and perturbation solutions are obtained. The effect of the different bearing design parameters on its dynamic stiffness is studied and recommendations are suggested. The second part of the paper includes a description of an experimental investigation supporting the theoretical analysis. Experiments were conducted on a single bearing as well as on a scale-model machine table supported on four bearings. Results obtained for different types of bearing compensation and loading are described and discussed. Moreover, the effect of oil aeration on the dynamic stiffness of hydrostatic bearings is investigated.
Investigation of the Step-Thrust Gas Bearing Without Feed Grooves for Two Directions of Shaft Rotation
Authors: Rood L. H.
Published: September 2011

The step-thrust self-acting gas bearing was investigated for an application where equal load support was required for both directions of rotation. A method of computer analysis by James and Potter [1] shows characteristics of the support for geometric, gas and speed parameters. Support of this step bearing is shown to be about one fifth of a good spiral-groove thrust bearing (spiral-groove bearings are limited to one direction of rotation). For comparison, a good thrust plate of unidirectional design would have the following parameters: groove width ratio ∼0.5, groove depth ratio ∼3, spiral angle ∼70 deg, and a radius ratio (R1/R0) ∼0.62. Two test models were built and evaluated to confirm the computer analysis. Dynamic responses to vibration loads were also tested.
Turborotor Instability: Effect of Initial Transients on Plane Motion
Authors: Badgley R. H. , Booker J. F.
Published: September 2011

The rigid-body dynamics of rotors supported in plain, cylindrical, cavitated, fluid-film journal bearings are investigated numerically by Runge-Kutta extrapolation techniques. Expressions for journal force due to the fluid-film are developed for the short-bearing (Ocvirk), long-bearing (Sommerfeld), and finite-length-bearing (Warner) approximate solutions to the Reynolds equation. Stability of plane motion is investigated for each solution under the assumption of light initial impact. The long-bearing solution appears to be most conservative (that is, it predicts the onset of instability at lower angular velocity ratios than the other solutions) for static eccentricity ratios between 0 and 0.5, while the finite-bearing solution, with bearing length-to-diameter ratio L/D equal to 1, appears most conservative at higher static eccentricity ratios. Variations in L/D between 0.5 and 2.0 appear not to affect journal path shapes appreciably. Variations in initial journal center velocity are found to be important, at least with the short-bearing solution: large initial velocities are observed to produce instability for certain parameter combinations which are stable under small initial position or velocity disturbances. In all cases investigated, instability is not observed above static eccentricity ratios of 0.83.
Method for Solution of Lubrication Problems With Temperature and Elasticity Effects: Application to Sector, Tilting-Pad Bearings
Authors: Castelli V. , Malanoski S. B.
Published: September 2011

The importance of temperature and elasticity effects in bearings have been demonstrated by several authors. This paper offers an efficient method for the simultaneous solution of the Reynolds and energy equations and their coupling with elastic deformation results obtained by variational techniques. Results are presented for centrally pivoted, tilting-pad, sector, thrust bearings.
Rayleigh Step Journal Bearing, Part II—Incompressible Fluid
Authors: Hamrock B. J. , Anderson W. J.
Published: September 2011

A theoretical analysis of the pressure distribution, load, capacity, and attitude angle for a single-step concentric as well as a multistep infinite length eccentric Rayleigh step journal bearing is performed. The results from the single-step concentric analysis indicated that the maximum load capacity is obtained when the film thickness ratio is 1.7 and the ratio of the angle subtended by the ridge to the angle subtended by the pad is 0.35. The results from the infinite length eccentric analysis indicated that one step placed around the journal was optimal. For eccentricity ratios greater than or equal to 0.2 the maximum load occurred for a bearing without a step or a Sommerfeld bearing. For eccentricity ratios less than 0.2 the optimal film thickness ratio is 1.7 while there are three optimal ratios of angle subtended by the ridge to the angle subtended by the pad of 0.4, 0.45, and 0.5 depending on whether load capacity or stability or both load capacity and stability is more important in the application being considered.
The Misaligned, Eccentric Face Seal
Authors: Sneck H. J.
Published: September 2011

The analytical investigation of a misaligned face seal shows that eccentricity will cause a component of the total leakage to be inward or outward depending on the phase angle between the eccentricity and the misalignment.
Theory of the Mechanism of Sealing with Application to Face Seals
Authors: Kuzma Dennis C.
Published: September 2011

A theory of the mechanism of sealing is presented. This theory accounts for the load carrying capacity of the seal and allows a pressure gradient to be maintained across the seal with no leakage. The theory is applied to a simple face seal. The results agree with many experimentally observed phenomena.
Effects of Viscoelastic Lubricant on Squeeze Film Lubrication Between Impinging Spheres
Authors: Mow V. C.
Published: September 2011

An asymptotic solution is obtained for squeeze film flow between impinging spheres. The lubricant is assumed to be a four-constant, nonlinear, viscoelastic liquid. The pressure peak in the lubricant is very sensitive to the values of viscoelastic constants. The results agree qualitatively with those observed experimentally.
Asymptotic Methods for an Infinitely Long Slider Squeeze-Film Bearing
Authors: DiPrima R. C.
Published: September 2011

The application of the techniques of singular perturbation theory (boundary layer theory) to several problems in gas bearing lubrication is discussed. The leading terms in asymptotic expansions for the pressure are obtained for the cases: A slider bearing with large bearing number, a squeeze-film thrust bearing with large squeeze number, and a combined slider squeeze-film bearing with large bearing number and/or large squeeze number. For the latter problem it is necessary to distinguish several cases depending upon the relative rate at which the bearing number and squeeze number approach infinity
Solving the Incompressible and Isothermal Problem in Elastohydrodynamic Lubrication Through an Integral Equation
Authors: Herrebrugh K.
Published: September 2011

It will be shown that the hydrodynamic and elasticity equations in elastohydrodynamic lubrication can be coupled to one single integral equation of the following form: H(x)=f(x)−T∫abK(x,ξ)F{H(ξ)}dξ in which f(x) and K(x, ξ) are both known analytic functions inside [a, b], and F(H) is in general a nonlinear function of the dimensionless film thickness. A numerical solution of this integral equation for constant viscosity is presented for a large range of loading conditions.
Forced Cooling of a Slider Bearing With Wedge Film
Authors: Tahara H.
Published: September 2011

This paper deals with the forced cooling problem of a slider bearing with wedge film of finite length, where most of the heat generated in the lubricant film is removed by a coolant which flows under the surface of the bearing pad. Analysis was made on the generalized Reynolds’ equation, including viscosity variations with temperature throughout the film and the energy equation. Simultaneous solutions of these equations seemed to be supported by experiments. From the analysis, calculations were made on the heat flow rate into the coolant, the temperature difference between slider and pad surfaces, bearing characteristics using the representative viscosity, and the mean heat transfer coefficient of the wedge film.
Considerations of Flow Across a Bearing Groove
Authors: Ettles C. M. M. , Cameron A.
Published: September 2011

It is known that the majority of heat lost from small bearings is by conduction through the bearing surfaces. A lower proportion is assumed lost by convection from the film. However, it is shown that between 60 and 95 percent of the connected heat re-enters the film on the opposite side of the groove. This proportion of heat carried over is largely unaffected by speed, film thickness, or groove width. Due to the formation of a boundary layer within the groove, a ram pressure is generated at the pad leading edge. Approximate analyses are given for the boundary-layer formation, ram pressure, and heat carried over. Fair agreement is obtained with experimental results.