bluuebunny/crossref_metadata_2025 huggingface dataset:
Standing (K)in: Street Youth and Street Relatedness in South Africa
Authors: MARGARETTEN EMILY
Published: September 2011

In this article I examine the social attachments of youth living on the streets of Durban, South Africa. I investigate their interactions with one another as friends, kin, and conjugal lovers. As such, I draw attention to the variability and creativity of youth fellowships in the city. My analysis derives from the ethnographic case of Point Place, a condemned apartment complex located in the city center of Durban. Up to a hundred street youth reside here, males and females between the ages of 14 to 29 years. From their narratives of daily survival, I highlight the possible commensalities of the streets. I show how street youth, as articulated in isiZulu, “stand for each other” (ukumelana), not necessarily in violent or coercive formations but in supportive and cooperative companionships. I show how state officials, too, recognize the resourcefulness of these intra‐generational relations. For they allow the Point Place youth “to stand” (ukuma) not only as friends but also as kin, particularly in times of difficulty and distress. With this case study I highlight the critical linkages of belonging on the streets, framed by institutional forces yet also by the interpersonal subjectivities of youth who imaginatively negotiate their relatedness to one another and in the process, their standing in South African society.
Synthesis of Flake‐Shaped NiO–YSZ Particles for High‐Porosity Anode of Solid Oxide Fuel Cell
Authors: Wu Yuzhou , Dong Dehua , Ran Ran , Zeng Yao , Wang Kun , Shao Zongping , Wang Huanting
Published: September 2011

A new synthesis method of using dehydration of sugar (sucrose) with concentrated sulfuric acid was developed to synthesize mixed oxide ceramic particles with flaky shape. The anode disks prepared from flake‐shaped NiO–YSZ particles without a pore‐forming additive exhibited uniform dispersion of NiO and YSZ and a high porosity (45.6%), leading to improved cell performance as compared with an anode prepared from conventional NiO–YSZ powder in Ni–YSZ/YSZ/LSM single cells operated with H2 as the fuel; their maximum power densities were 381 and 300 mW·cm−2 at 850°C, respectively.
Stage of hepatocellular carcinoma is associated with periodontitis
Authors: Tamaki Naofumi , Takaki Akinobu , Tomofuji Takaaki , Endo Yasumasa , Kasuyama Kenta , Ekuni Daisuke , Yasunaka Tetsuya , Yamamoto Kazuhide , Morita Manabu
Published: September 2011

Aim

Periodontitis induces overproduction of reactive oxygen species (ROS). This state increases circulating ROS levels and may affect hepatocellular carcinoma (HCC). The Japan Integrated Stage (JIS) score is a novel staging system for HCC. The objective of the present study was to compare JIS scores in HCC patients with and without periodontitis.

Material and Methods

We recruited 64 HCC patients comprising 31 chronic periodontitis subjects (HCC + P) and 33 periodontally healthy controls (HCC + H). Their JIS scores were recorded. Serum levels of reactive oxygen metabolites (ROM) from HCC + P, HCC + H and healthy age‐ and gender‐matched subjects with healthy gingiva (control, n = 15) were also assessed for circulating ROS levels.

Results

The HCC + P and HCC + H groups had similar body mass index, habitual drinking and tobacco exposure data. The HCC + P group showed higher JIS scores than the HCC + H group (p = 0.027). Both the HCC + P and HCC + H groups had higher serum levels of ROM than controls (p < 0.001), while serum levels of ROM in the HCC + P group were a further 25.8% higher than those in the HCC + H group (p < 0.001).

Conclusion

HCC patients with periodontitis had higher JIS score and circulating ROS level than HCC patients without periodontitis.
Delayed senescence of apple leaves by exogenous melatonin treatment: toward regulating the ascorbate–glutathione cycle
Authors: Wang Ping , Yin Lihua , Liang Dong , Li Chao , Ma Fengwang , Yue Zhiyong
Published: September 2011

Abstract:  The objectives of this study were to test the effects of exogenous melatonin on apple (Malus domestica Borkh. cv. Golden Delicious) leaves and investigate its possible physiological role in delaying leaf senescence. Detached leaves treated with 10 mm melatonin solutions clearly showed a slowing in their process of dark‐induced senescence, as evidenced by both biochemical and molecular parameters. Melatonin delayed the normal reduction in chlorophyll content and maximum potential photosystem II efficiency (Fv/Fm). It also suppressed the transcript levels of a key chlorophyll degradation gene, pheide a oxygenase (PAO), and the senescence‐associated gene 12 (SAG12). This outcome was thought to be because of the enhanced antioxidant capabilities of melatonin. Indeed, H2O2 accumulation was inhibited by exogenous melatonin, which might have resulted from direct reactive oxygen species scavenging by melatonin and a great enhancement of ascorbate peroxidase (APX; EC 1.11.1.11), which acted on both mRNA and protein activity levels. Melatonin treatment led to the maintenance of higher contents of ascorbic acid (AsA) and glutathione (GSH) but less dehydroascorbate (DHA) and oxidized glutathione (GSSG) compared with the control, possibly through its regulation of the AsA–GSH cycle.
Dynamic Imaging of Cell‐Free and Cell‐Associated Viral Capture in Mature Dendritic Cells
Authors: Izquierdo‐Useros Nuria , Esteban Olga , Rodriguez‐Plata Maria T. , Erkizia Itziar , Prado Julia G. , Blanco Julià , García‐Parajo Maria F. , Martinez‐Picado Javier
Published: September 2011

Dendritic cells (DCs) capture human immunodeficiency virus (HIV) through a non‐fusogenic mechanism that enables viral transmission to CD4+ T cells, contributing to in vivo viral dissemination. Although previous studies have provided important clues to cell‐free viral capture by mature DCs (mDCs), dynamic and kinetic insight on this process is still missing. Here, we used three‐dimensional video microscopy and single‐particle tracking approaches to dynamically dissect both cell‐free and cell‐associated viral capture by living mDCs. We show that cell‐free virus capture by mDCs operates through three sequential phases: virus binding through specific determinants expressed in the viral particle, polarized or directional movements toward concrete regions of the cell membrane and virus accumulation in a sac‐like structure where trapped viral particles display a hindered diffusive behavior. Moreover, real‐time imaging of cell‐associated viral transfer to mDCs showed a similar dynamics to that exhibited by cell‐free virus endocytosis leading to viral accumulation in compartments. However, cell‐associated HIV type 1 transfer to mDCs was the most effective pathway, boosted throughout enhanced cellular contacts with infected CD4+ T cells. Our results suggest that in lymphoid tissues, mDC viral uptake could occur either by encountering cell‐free or cell‐associated virus produced by infected cells generating the perfect scenario to promote HIV pathogenesis and impact disease progression.
Distinct Subpopulations of Epithelial Ovarian Cancer Cells Can Differentially Induce Macrophages and T Regulatory Cells Toward a Pro‐Tumor Phenotype
Authors: Alvero Ayesha B. , Montagna Michele K. , Craveiro Vinicius , Liu Lanzhen , Mor Gil
Published: September 2011

Citation Alvero AB, Montagna MK, Craveiro V, Liu L, Mor G. Distinct subpopulations of epithelial ovarian cancer cells can differentially induce macrophages and T regulatory cells toward a pro‐tumor phenotype. Am J Reprod Immunol 2012; 67: 256–265

Problem  Presence of immune infiltrates in the tumor does not always correlate with an anti‐tumoral immune response. We previously identified two subpopulations of epithelial ovarian cancer (EOC) cells with differential cytokine profile. We hypothesize that these two subpopulations of EOC cells may differentially regulate the immune phenotype in the tumor microenvironment and therefore affect the immune response.

Method of Study  Macrophages derived from CD14+ monocytes and naive CD4+T cells were treated with conditioned media from two subpopulations of EOC cells. Differentiation markers and phagocytic activity were measured by western blot analysis and flow cytometry. Cytokine levels were quantified using xMAP technology.

Results  Type I EOC cells are able to enhance macrophages’ capacity for tumor repair and renewal by enhancing expression of scavenger receptors and by promoting the secretion of cytokines associated with tissue repair. On the other hand, type II EOC cells are able to create a tolerant microenvironment and prevent an immune response by inducing macrophages’ to secrete IL‐10 and by promoting the generation of T regs.

Conclusion  We demonstrate that each ovarian cancer cell subpopulation can induce a unique phenotype of macrophages and T cells, both associated with tumor‐supportive function.
Elderly complete denture wearers: a social approach to tooth loss
Authors: Papadaki Eftychia , Anastassiadou Vassiliki
Published: September 2011

doi: 10.1111/j.1741‐2358.2011.00550.x

Elderly complete denture wearers: a social approach to tooth loss

Objectives:  To correlate emotional reactions to tooth loss with denture satisfaction attributes in elderly complete denture wearers.

Background:  Total tooth loss is a serious life event, and poor oral health has an impact on daily life. Edentulism treated by rehabilitation with dentures can have a positive effect on patients’ self‐image and social behaviour.

Methods:  A group of 80 edentulous subjects undergoing routine prosthetic care in a Greek Department of Prosthetic Dentistry were interviewed using two structured questionnaires. The first questionnaire explored reactions to tooth loss, whereas the second measured their subjective experience of complete dentures. The responses to both questionnaires were compared using the statistical package spss v.17.

Results:  The results showed significant correlation between aspects of tooth loss experience and complete denture satisfaction. Despite the fact that a substantial proportion of patients were satisfied with their complete dentures, some patients experienced increased social and psychological problems related to their edentulousness and the wearing of complete dentures. The aesthetic and functional aspects of complete dentures affected both patients’ social behaviour and self‐confidence.

Conclusions:  Total tooth loss was not only reflected in patient’s social behaviour and self‐image, but it had a complex and multifaceted impact on satisfaction from complete dentures.
Tying the knot: The cystine signature and molecular‐recognition processes of the vascular endothelial growth factor family of angiogenic cytokines
Authors: Iyer Shalini , Acharya K. Ravi
Published: September 2011

The cystine‐knot motif, made up of three intertwined disulfide bridges, is a unique feature of several toxins, cyclotides and growth factors, and occurs in a variety of species, including fungi, insects, molluscs and mammals. Growth factor molecules containing the cystine‐knot motif serve as ligands for a diverse range of receptors and play an important role in extracellular signalling. This superfamily of polypeptides comprises several homodimeric and heterodimeric molecules that are central characters in both health and disease. Amongst these molecules are a group of proteins that belong to the vascular endothelial growth factor (VEGF) subfamily. The members of this family are known angiogenic factors that regulate processes leading to blood vessel formation in physiological and pathological conditions. The focus of the present review is on the structural characteristics of proteins that belong to the VEGF family and on signal‐transduction pathways that become initiated via the VEGF receptors.
Lithium Attenuates Peripheral Neuropathy Induced by Paclitaxel in Rats
Authors: Pourmohammadi Nasir , Alimoradi Houman , Mehr Shahram Ejtemaei , Hassanzadeh Gholamreza , Hadian Mohammad Reza , Sharifzadeh Mohammad , Bakhtiarian Azam , Dehpour Ahmad Reza
Published: September 2011

Abstract:  As a cancer chemotherapeutic agent, paclitaxel (Taxol®) causes dose‐related peripheral neuropathy in human beings. The mechanisms underlying this toxicity are currently unknown, and there are no validated treatments for its prevention or control. To assess whether lithium as a pre‐treatment and at subtherapeutic dose could prevent the peripheral neuropathy produced by it, rats were treated with paclitaxel (2 mg/kg i.p. every other day for a total of 16 times) and/or lithium chloride (300 mg/l) via water supply. General toxicity and body‐weight were measured regularly during the experiment. To evaluate the sensory and motor neuropathy hot‐plate, open‐field test and nerve conduction velocity were used. In rats treated with only paclitaxel, there was behavioural, electrophysiological and histological evidence of a mixed sensorimotor neuropathy after 16 injections. Lithium robustly reduced the rate of mortality and general toxicity. Paclitaxel‐induced sensorimotor neuropathy was significantly improved as indicated by changes in hotplate latency, total distance moved and a significant increase in sciatic, sural and tail sensory or motor nerve conduction velocity. The same results were observed in histopathological examinations; however, dorsal root ganglion neurons did not significantly change in the paclitaxel‐treated groups. These results suggest that lithium, at subtherapeutic doses, can prevent both motor and sensory components of paclitaxel neuropathy in rats. Thus, lithium at these doses, as an inexpensive and relatively safe salt, may be useful clinically in preventing the neuropathy induced by paclitaxel treatment.
Effect of Elevation Resolution on Evapotranspiration Simulations using MODFLOW
Authors: Kambhammettu B.V.N.P. , Schmid Wolfgang , King James P. , Creel Bobby J.
Published: September 2011

Surface elevations represented in MODFLOW head‐dependent packages are usually derived from digital elevation models (DEMs) that are available at much high resolution. Conventional grid refinement techniques to simulate the model at DEM resolution increases computational time, input file size, and in many cases are not feasible for regional applications. This research aims at utilizing the increasingly available high resolution DEMs for effective simulation of evapotranspiration (ET) in MODFLOW as an alternative to grid refinement techniques. The source code of the evapotranspiration package is modified by considering for a fixed MODFLOW grid resolution and for different DEM resolutions, the effect of variability in elevation data on ET estimates. Piezometric head at each DEM cell location is corrected by considering the gradient along row and column directions. Applicability of the research is tested for the lower Rio Grande (LRG) Basin in southern New Mexico. The DEM at 10 m resolution is aggregated to resampled DEM grid resolutions which are integer multiples of MODFLOW grid resolution. Cumulative outflows and ET rates are compared at different coarse resolution grids. Results of the analysis conclude that variability in depth‐to‐groundwater within the MODFLOW cell is a major contributing parameter to ET outflows in shallow groundwater regions. DEM aggregation methods for the LRG Basin have resulted in decreased volumetric outflow due to the formation of a smoothing error, which lowered the position of water table to a level below the extinction depth.
The Value of Retail‐ and Consumer‐Level Fruit and Vegetable Losses in the United States
Authors: BUZBY JEAN C. , HYMAN JEFFREY , STEWART HAYDEN , WELLS HODAN F.
Published: September 2011

Food loss at the retail and consumer levels in the United States includes 14.8 billion pounds of fruit and 23.4 billion pounds of vegetables, valued at $15.1 billion and $27.7 billion, respectively, in 2008 retail market prices. The total value of these losses is $42.8 billion per year, or roughly $141 per capita. To most efficiently reduce the annual food loss, it may be beneficial to focus efforts on the four fruits (fresh apples, grapes, peaches and strawberries) and four vegetables (fresh and canned tomatoes and fresh and frozen potatoes) that have the greatest amount of loss.
Health Risk Factors and Their Effect on Consumers' Use of Nutrition Facts Panels
Authors: COOK LAUREL AYNNE , BURTON SCOT , HOWLETT ELIZABETH
Published: September 2011

It is particularly important for consumers with specific diseases to attend to appropriate nutrient data in the Nutrition Facts Panel (NFP). Results for participants 45 years or older show that (1) consumers diagnosed with both high blood pressure and high cholesterol are more likely to access sodium and cholesterol NFP information than consumers with only one or neither condition, and (2) there are few differences in attention to less well‐publicized but relevant nutrients. The results show a greater need for at‐risk consumers to attend to negative (e.g., trans fat) and positive nutrients (fiber) associated with their specific health condition.
Synthesis and Antifungal Activity of 1‐[(2‐Benzyloxy)Phenyl]‐2‐(Azol‐1‐yl)Ethanone Derivatives: Exploring the Scaffold Flexibility
Authors: Emami Saeed , Kazemi‐Najafabadi Motahare , Pashangzadeh Soughra , Foroumadi Alireza , Faramarzi Mohammad Ali , Samadi Nasrin , Falahati Mehraban , Fateh Roohollah , Ashrafi‐Khozani Mahtab
Published: September 2011

Based on the N‐(phenethyl)azole backbone of azole antifungals, we designed 1‐[(2‐benzyloxy)phenyl]‐2‐(azol‐1‐yl)ethanone derivatives 2 and 3, containing benzyloxyphenyl scaffold of croconazole. Also these compounds can be considered as flexible analogs, resulted from C2–C3 disconnection of 3′‐chloro‐3‐imidazolylflavanone 1, recently described as antifungal agent. Thus, in this report, we describe the synthesis of 1‐[(2‐benzyloxy)phenyl]‐2‐(azol‐1‐yl)ethanone derivatives 2 and 3 and their biological evaluation against different pathogenic fungi. By comparing the antifungal activity profile of flexible compounds 2 and 3 with that of rigid analog 1, it can be inferred that lower susceptibilities (higher minimum inhibitory concentrations) were observed with flexible compounds. However, among the synthesized compounds, 1‐[2‐(2,4‐dichlorobenzyloxy)phenyl]‐2‐(1H‐imidazol‐1‐yl)ethanone hydrochloride (2g) showed comparable or more potent antifungal activity in comparison with fluconazole as a standard drug.
Language Ideologies and Policies: Multilingualism and Education
Authors: Farr Marcia , Song Juyoung
Published: September 2011

Educating multilingual students is a great challenge for both teachers and parents in a society in which English is the medium of schooling and of wider communication. Top‐down language policies often overpower teachers’ individual intentions and practices. In this paper, we point out that language ideologies in ‘commonsense’ beliefs and political orientations, rather than pedagogical considerations or research evidence, motivate language policies. We particularly discuss the language ideologies of standardization and monolingualism that underlie bilingual education and English‐only policies in the U.S. and how these policies conflict with the reality of multilingual students’ linguistic and identity practices. We also examine research on bilingual, bidialectal, and plurilingual practices in which multiple languages or varieties within a language co‐exist and are used creatively by speakers for significant social and pragmatic functions, and we highlight the critical gap between top‐down language policies and such ground‐level plurilingualism. Teachers’ knowledge of such plurilingual practices by their students and their deeper understanding of and critical perspective toward language policies can empower them to negotiate top‐down language polices in their classrooms in order to facilitate language and literacy development among their multilingual students.
The Brain Basis of Individual Differences in Language Comprehension Abilities
Authors: Prat Chantel S.
Published: September 2011

Individual differences in language abilities must be manifest by differences in brain functioning. Thus, comprehensive theories of the biological basis of language should account for systematic variability between individuals. This article is divided into two sections summarizing research on individual differences in the language comprehension network and their theoretical implications. The first section reviews research on individual differences in three network‐level characterizations of brain function: neural efficiency, neural adaptability, and functional synchronization. The second section describes some of the implications of this research for theories of language in the brain. The role of the right hemisphere in language comprehension, the brain bases of word knowledge and verbal working‐memory capacity, and potential mechanisms underpinning neural adaptability are discussed.
Adolescent Heritage Speakers of Less Commonly Taught Languages in the United States
Authors: Chhuon Vichet
Published: September 2011

Research has demonstrated that heritage language maintenance can positively contribute to the academic and social lives of immigrant youth in the United States. This review examines the literature regarding adolescent heritage speakers of less commonly taught languages (LCTL). I focus on factors of ethnic identity and family relations and how they interact with language learning opportunities and outcomes for adolescent LCTL heritage learners. Heritage language development can lead to students’ stronger sense of ethnic identity which may serve as an important buffer from discrimination in schools and larger society. Heritage language development can also serve as a supportive mechanism for higher quality adult–child interactions and fewer acculturation‐related conflicts, particularly during adolescence.

In short, researchers and educators must consider how heritage language learning opportunities matter for adolescent LCTL heritage speakers and all diverse students.
Improved methods for predicting trash delivery to culverts protected by trash screens
Authors: Wallerstein N. , Arthur S.
Published: September 2011

The risk of flooding associated with blockage of culverts by natural and anthropogenic debris is often reduced by fitting a trash screen at the structure's inlet. However, screens can actually exacerbate flood risk if not properly designed and maintained. In this paper, findings from a project that has been tasked with developing decision support tools to help the asset manager prioritise screen clearance strategies are explored. The scientific knowledge base surrounding this complex issue has been extended using an empirical approach by correlating the probability of delivery of significant debris loads to trash screens, as determined using data from 140 screen sites in Belfast, Northern Ireland, with pertinent driving variables including channel properties, flows, land use types and the degree of social deprivation. This analysis has enabled fundamental relationships to be developed that, once validated, will help planners to establish the potential loads of debris that may be delivered to screens and will therefore offer a robust means to rank culverts in terms of blockage potential and therefore flood risk.
Mountain City Transit: Management Control and Performance Measurement
Authors: Klassen Mark , Kalagnanam Suresh
Published: September 2011

Mountain City Transit (MCT) is a short in‐class case based on a real‐life city transit department, a context with which students are very familiar. The case allows three delivery options for instructors. A first option is for instructors to use the case to introduce various elements of management control—the case is rich, thereby allowing students to identify multiple issues facing the organization. As a second option, instructors can use it as a performance management case wherein students build a balanced scorecard and receive a completed strategy map to analyze. As a third delivery option, the case can be used twice during the course, both to introduce management control and to discuss performance measurement. Students will also discuss real life implementation challenges that MCT and other organizations face.
Suicide Methods in Singapore (2000–2004): Types and Associations
Authors: Chia Boon‐Hock , Chia Audrey , Ng Wai‐Yee , Tai Bee‐Choo
Published: September 2011

The choice of suicide methods varies between countries. Common methods used in Singapore between 2000 and 2004 were jumping (72.4%), hanging (16.6%), and poisoning (5.9%). Those who jumped were more likely to be young, single, female, and to have had a major mental illness. By comparison, those who hung themselves were more likely to be older (OR 2.68), Indian (OR 2.32), and to leave a suicide note (OR 1.53). Those who used poison were more likely to be married (OR 2.33), to be on antidepressants (OR 2.40), to have previously attempted suicide (OR 2.13), and to leave a letter (OR 2.30). The choice was determined by accessibility, acceptability, generational, gender, and racial factors.
The Stability of Self-Acting Gas Journal Bearings With Noncircular Members and Additional Elements of Flexibility
Authors: Marsh H.
Published: September 2011

The linearized theory for the stability of self-acting gas bearings is extended to include bearing systems with noncircular members or additional elements of flexibility and damping. The theory offers a satisfactory explanation for the unusual behavior of a bearing system with a three-lobed rotor, including the whirl at low speeds and the whirl cessation. A comparison between the theory and experiments for a flexibly mounted bearing system shows that the theory can be applied to predict the stability boundaries of bearing systems with additional elements of flexibility. A new type of bearing apparatus is proposed in which it would be possible to obtain information about bearing stability without operating at the stability boundary.
A Review of Developments in Externally Pressurized Gas Bearing Technology Since 1959
Authors: Gross W. A.
Published: September 2011

The evolution of gas bearing technology during the period since 1959 is reviewed. References to significant literature on externally pressurized gas bearings are cited for the benefit of designers.
Influence of Water on Fatigue-Failure Location and Surface Alteration During Rolling-Contact Lubrication
Authors: Schatzberg P. , Felsen I. M.
Published: September 2011

The influence of dissolved water in the lubricant on fatigue-failure location and surface alteration was determined from experiments conducted with a planetary four-ball machine in the range of 925 to 1300 ksi maximum Hertz compressive stress. The distribution of fatigue spalls on the bearing ball surfaces was influenced by small amounts of water in the hydrocarbon lubricant. In the presence of 0.01 precent water an increase in fatigue-failures occurred on the chemically more reactive portion of the bearing balls. An increase in wear during rolling contact was observed due to the presence of water. This was demonstrated by weight determinations, surface profile measurements and light microscopy.
Effect of Die Surface Composition on Friction and Adhesion in Deformation Processing
Authors: Newnham J. A. , Schey J. A.
Published: September 2011

An experimental investigation was carried out to determine interface friction and adhesion characteristics of workpiece and die materials under pressures and temperatures typical of plastic deformation. Evaluations were made using a twist-compression technique, which provided conditions of enforced sliding, and a ring upsetting technique in which sticking friction was predominant. Hot-rolling tests were performed to correlate the results with conventional metalworking practices. Workpiece materials included aluminum, titanium, and molybdenum alloys, low-alloy steel, and a nickel-base superalloy. Tools were made of die steels, tungsten carbide, and diffusion-coated die materials to evaluate the effects of surface chemistry and hardness in unlubricated contact with the workpiece material. Significant variations in friction due to die surface composition were observed, the effects being more marked with forced interface sliding. The most promising die materials were boronized 4140 steel and titanium carbide-coated 4140 steel. The investigation has shown that with the proper choice of die and workpiece material combinations, friction can be reduced and more importantly, adhesion can be minimized thereby avoiding or delaying catastrophic die failure in the event of lubricant breakdown.
Geometric Optimization of Concentrated Contacts for Minimum Microslips
Authors: Ling F. F. , Wilson E. A. , Peterson M. B.
Published: September 2011

Microslip between concentrated contacts is discussed and design charts are presented for microslips, maximum pressure, closing-in of the contacting bodies, and optimized shapes for minimum microslips. Computer programs for the foregoing are given and they are based on a previous analysis on a generalization of the Hertz problem and that of the Mindlin problem for fourth-order paraboloids in contact. In particular, the microslips and the annulus of slip were sought. To this end an inverse method was devised. Moreover, an optimization procedure was described for finding the geometry for a given loading condition and set of material properties, within the family of paraboloids, which gives minimum slip. It is shown in an example that the annulus of slip may be reduced by 60 percent while the maximum slip may be reduced by 90 percent.
On Temperature Transients at Sliding Interface
Authors: Ling F. F.
Published: September 2011

A simple stochastic model of interface temperature of solids in sliding contact, introduced earlier, has been extended. An experimental investigation has also been carried out, the result of which seems to lend credence to the theoretical model. The model led to the observation that, statistically, there are two temperatures at the interface, both being transients. The first is the average over the geometric contact area at all times, the temperature that is most likely to be measured by dynamic thermocouple method. The second is the time and space average over the instantaneous contacts. It is suggested that, as often as not, it is the latter which should be the reference temperature level upon which activities at the interface depend.
Reversed Flow in Face Seals
Authors: Sneck H. J.
Published: September 2011

The stream surfaces for laminar and turbulent flow in parallel surface seals are analytically determined for the cases where the fluid separates from one of the solid boundaries. These stream surfaces are used to determine when there is an exchange of external fluid across the seal land as well as the rate of these exchanges.
Measurement and Prediction of Viscosity-Pressure Characteristics of Liquids
Authors: Fresco G. P. , Klaus E. E. , Tewksbury E. J.
Published: September 2011

The successful application of a precision capillary-type pressure viscometer in the measurement of viscosity-pressure characteristics of a variety of fluids over the range of 0 to 10,000 psig is demonstrated. A number of pressure-viscosity values determined for about ten different chemical types of fluids provides the basis for the development of a graphical relationship involving the logarithm of viscosity, the pressure coefficient, and the viscosity temperature properties (ASTM slope) of the fluid. A second-degree polynomial equation in conjunction with a digital computer program allows one to calculate the pressure coefficient and, therefore, the viscosity values of fluids at 100 deg F and pressures up to 10,000 psig. The derivation of an exponent for the pressure coefficient extends the ability to calculate values over a range of temperatures. Primary data from three sources are used to compare and contrast these methods with those proposed by several other investigators.
Inertia Effects in MHD Hydrostatic Thrust Bearing
Authors: Kamiyama S.
Published: September 2011

An approximate analytical study is made of inertia effects in magnetohydrodynamic lubrication flow between two parallel disks, one of which rotates at a constant angular velocity in an axial magnetic field. Fairly good accuracy of the approximate solution is confirmed in the special limiting case of zero rotating speed. By the numerical examples, the inertia effects on pressure distribution, load capacity, and frictional torque of the bearing are clearly shown.
An Analysis of Self-Energized Hydrostatic Shaft Seals
Authors: Adams M. L. , Colsher R. J.
Published: September 2011

An analysis of a self-energized hydrostatic shaft seal operating with incompressible fluid in the laminar regime is presented. Dimensionless results are optimized for maximum stiffness. Comparisons are made between full annulus and sectored annulus recess configurations. It is shown that translational and torsional stiffnesses are critically dependent upon orifice size. A sample problem is included to demonstrate use of equations, design curves and criteria developed.
Development of a Liquid Dynamic Seal to Vacuum
Authors: Schnetzer E. , Rossbach R. J.
Published: September 2011

In the development of the advanced Rankine space power system technology the rotating machinery is to run on potassium-lubricated bearings. The alternator rotor cavity is evacuated either by venting to space or through artificial means. This reduces rotor windage losses to an acceptable level from the standpoint of alternator efficiency and rotor cooling. The problem investigated was the dynamic seal between the pressurized liquid potassium in the bearing cavity and the vacuum in the alternator rotor cavity. No rubbing seals are permitted because of the high rubbing speeds and the design life in excess of three years. In such a seal there must be a liquid-vapor interface. The objective was to keep the leakage rate at this interface below 10 lb/yr. The experimental development of two dynamic seals meeting the leakage tolerance objective is described. Easily resolved was the problem of maintaining a significant pressure difference across the seal. In the first development the main accomplishment was to solve the problem associated with the breakdown of the liquid-vapor interface which resulted in “sputtering”, an intermittent leakage of liquid droplets. The main accomplishment of the second development was a significant reduction in power consumption by the seal.
Investigations Into the Detergent Action of Additives for Motor Oils in the Presence of an Electric Field
Authors: Zaslavsky Yu. S. , Shor G. I. , Morosova I. A. , Lapin V. P.
Published: September 2011

The report deals with the results of the investigation into the detergent action of additives for motor oils in the presence of an electric field. It has been experimentally established that an electromotive force of the order of 1 v arises between two different metals separated with a motor oil layer. When using a nonpolar paraffin-naphthenic fraction of the same oil no electromotive force is created. The experiments were carried out with a motor oil with various detergent additives using an aluminum electrode in combination with duralumin, iron, copper, lead, bronze, and tin electrodes. The ability of various detergent additives to wash deposits from the metal surface or to prevent their formation under the action of an electric field has been studied using radioactive carbon black.
The Axisymmetric, Perfectly Flexible Foil Bearing With Porous Inlet Restrictor
Authors: Barlow E. J. , Wildmann M.
Published: September 2011

The equations for the axisymmetric, perfectly flexible foil bearing are solved for the case of an externally pressurized foil with porous inlet restriction. The results are presented in graphical form for design use. For comparison, results for the axisymmetric, perfectly flexible foil bearing with discrete inlet restrictors are also given.
Stability Considerations for a Gas-Lubricated Tilting-Pad Journal Bearing—Part 1: Analytical Methods
Authors: Chu T. Y. , McCabe J. T. , Elrod H. G.
Published: September 2011

The multiplicity of parameters associated with a tilting-pad journal bearing demands that special consideration be given to the selection of an analytical method for stability prediction. The classical Frequency Response (small perturbation) method and the Nonlinear Orbit method (a direct numerical integration of all governing differential equations) are discussed and evaluated. A new approach for the determination of film response called the “Step-Jump” method is here extended to the tilting-pad bearing. Three means of utilizing the film response functions in the dynamical equations are outlined and compared. The relationship of the Frequency Response method to the Step-Jump method is explained and a comparison of the Step-Jump results with the Nonlinear Orbit approach is made. One of the techniques for applying the Step-Jump response functions, called the “Characteristic Equation” method, is shown to be most suitable for parametric studies of stability thresholds.
Steady-State and Dynamic Properties of the Floating-Ring Journal Bearing
Authors: Orcutt F. K. , Ng C. W.
Published: September 2011

Calculated data on steady-state and dynamic properties of the plain cylindrical floating-ring bearing with pressurized lubricant supply are given. The data are for a bearing with L/D of 1, and values of the ratio of inner to outer film clearances of 0.7 and 1.3. One value of dimensionless supply pressure parameter is covered. Experimental results are presented which verify the calculated results and which supplement them, particularly with respect to stability characteristics of the bearing.
Mechanisms of Wear in Misaligned Splines
Authors: Weatherford W. D. , Valtierra M. L. , Ku P. M.
Published: September 2011

Experimental results are presented on the wear behavior of misaligned splines operating without lubrication and with either grease or oil lubrication, in various environmental atmospheres. On the basis of the observed results, it appears that protection from rapid wear stems from conditions which inhibit oxidation of the stressed metal surfaces. This inhibition process can be obtained by both physical and chemical means. The physical means include exclusion of oxygen from the contact region, and the chemical means include the use of lubricant additives. It was found that once the lubricant loses its ability to inhibit the oxidation reactions, continuous moderate wear results from oxidative attack, even if enough liquid lubricant is present to allow the debris particles to move away from the stressed surfaces. With grease lubricant, the abrasive wear debris is retained in the contact region, thus continued rapid wear ensues after the lubricant loses its ability to inhibit oxidation reactions.
Criteria of Ductile Fracture Initiated by a Pressurized Penny-Shaped Crack
Authors: Wnuk Milosz
Published: September 2011

The mechanism of ductile fracture is discussed by means of an analysis of energy balance at fracture of an ideally elastic-plastic solid containing a pressurized penny-shaped crack. According to the present model, the solid should satisfy an additional requirement that the yielded zone be localized in a narrow layer preceding the crack tip. The critical load determined by a maximum on the potential energy curve, is compared with that which follows from the ultimate plastic strain criterion for fracture. The results are also compared with the predictions of the theory of elasticity (Griffith, Sneddon, Sack). It is pointed out that the loading scheme has an important influence on the way in which fracture occurs. The equations obtained may be helpful in the studies of surface wear of hydrodynamically lubricated surfaces, weakened by flaws or cracks. Cracking in this case is attached to the notch brittleness effect, which is shown to be considerable for a pressurized crack.
The Consequences of Spline Friction in Multiple Disk Brake and Clutch Packs
Authors: Finkin E. F.
Published: September 2011

A mathematical analysis is offered showing the various consequences of spline friction in multiple disk systems. Included are equations for the load variation through a multiple disk pack, the effect of interfacial pressure distribution on this load variation, the torque variation through a pack, and the total torque carried by a pack. The relation between friction and velocity is taken into account. The coefficient of friction determined from the data of a multiple disk test apparatus, ignoring spline friction, is shown to be significantly in error and an equation is derived for calculating the true coefficients of friction. Examples of the load variation in a pack are derived and the results plotted.
The Role of Lubrication in Propagation of Contact Fatigue Cracks
Authors: Littmann W. E. , Widner R. L. , Wolfe J. O. , Stover J. D.
Published: September 2011

Comparative life tests of tapered roller bearings in mineral oils and synthetic fluids, Mil L-7808-F and Mil L-23699, demonstrate a strong influence of lubrication upon bearing life and failure characteristics. The inclusion origin mode of failure propagates very rapidly and takes on the macroscopic appearance of the point surface origin mode when fatigue cracks interact with a lubricant having low viscosity at the operating temperature. Observations indicate that bruises from debris in the lubricant are stress raisers of severity equivalent to nonmetallic inclusions in bearing materials for nucleation of contact fatigue cracking. Surface fatigue by “peeling” or superficial pitting can also act as the nucleus of fatigue cracks which propagate in the same manner as the point surface origin mode. In general, any surface stress concentration in combination with low lubricant film thickness promotes surface origin modes of contact fatigue and low lubricant viscosity at the operating temperature promotes rapid propagation by a hydraulic pressure mechanism.
Cavitation in Mechanical Face Seals
Authors: Findlay J. A.
Published: September 2011

The characteristics of mechanical face seals operating with hydrodynamic films containing gas cavities were studied. Solutions to Reynolds’ equation for hydrodynamic lubrication were obtained using both the short bearing approximation and numerical iterative methods. These two methods of solution satisfy continuity of flow throughout the seal film. Leakage rates and seal hydrodynamic loads were calculated. Some computed cavity shapes are also given.
Positive Action Seals in Europe
Authors: Jagger E. T.
Published: September 2011

Positive Action seals have been known and used in Europe for more than 20 years. Early designs used the “Threaded Bush” principle, but this was developed into the “Spiral Groove” principle in order to achieve the advantages of economic production along with positive action sealing. The paper presents a historical survey of these developments and outlines the current situation. Reference is also made to “Duo-Positive” seals (i.e. Positive Action seals which operate equally effectively for both directions of shaft rotation).
Gradient and Time Dependence of Viscosity of Polymer Solutions in Very Viscous Solvents
Authors: Peterlin A.
Published: September 2011

Solutions of high molecular weight linear polymers in very viscous solvents exhibit two peculiar effects even at rather low concentrations. With increasing gradient the viscosity first drops to a minimum and then increases over a wide gradient range. Moreover, prolonged shearing at constant gradient induces an increase of viscosity which dependent on concentration and gradient either continues with steadily decreasing slope or after a while turns over into a gradual decrease with a finite limit not much different from the starting value. The first effect is partly due to an actual increase of intrinsic viscosity with increasing gradient and partly to the time effect. The former contribution is proportional to the concentration, the latter to the second or higher power of concentration. Both effects occur with the polymer improved lubricating oils.
Air-Bearing Applications to Machine Tools and Measuring Instruments
Authors: Wunsch H. L.
Published: September 2011

This paper attempts to illustrate the advantages and limitations of air bearings in the machine-tool and measuring instrument field by reference to actual industrial applications. It also indicates likely future developments.
A Study of High Speed Machines With Rubber Stabilized Air Bearings
Authors: Powell J. W. , Tempest M. C.
Published: September 2011

This paper discusses the influence of rubber properties on the ability of rubber “O” rings to suppress the self-excited whirl of rotors supported in resiliently mounted air bearings.
A Survey of Gas-Lubricated Porous Bearings
Authors: Sneck H. J.
Published: September 2011

A review of the literature pertaining to the theory of porous gas bearings, their experimentally observed behavior, and their applications.
Developments in Supercleaning and Boundary Lubrication for Gas-Bearing Gyros Related to Surface Phenomena
Authors: Galvin G. D. , Morecroft D. W. , Patterson A. G.
Published: September 2011

British aerodynamic gas-bearing gyros of the highest precision for use in Naval equipment are required to have long durability of low starting friction for the brief periods of rubbing contact before the rotor becomes gas-borne. Start failures in service have caused the Navy Department to initiate a two-phase programme of investigation and research into the problem. The first phase, intended to enable production to continue and reasonable performance to be obtained, is reported in references [1, 2]. The second phase, described herein, has been of a more fundamental nature and has been intended to amend hitherto empirical processes to a sound scientific basis and to gain understanding of bearing surface behavior. The paper describes trials and results of experiments carried out jointly by Admiralty Compass Observatory and Shell Research Ltd. on various aspects of bearing cleaning, boundary-lubricant behavior, and bearing surface materials. Glow discharge cleaning, examined by radiotracer technique, has been found to be very much more efficient than organic solvents, as well as permitting a big reduction in process time. Proposals for a simplified and more effective cleaning process and for boundary lubrication with a fatty acid are given. Examinations of surface films by friction machine, radiotracer techniques, electron diffraction, and ellipsometry have established that chemical bonding occurs between bearing surfaces and boundary lubricant and have enabled film thicknesses of molecular proportions and molecular orientations to be determined. Preliminary work is reported on the effects of processes described on ceramic bearing materials.
A Theoretical Analysis of Whirl Instability and Pneumatic Hammer for a Rigid Rotor in Pressurized Gas Journal Bearings
Authors: Lund J. W.
Published: September 2011

A theoretical analysis is presented for the threshold of instability for a rigid rotor supported in hydrostatic gas journal bearings. Both rotationally induced instability (hybrid instability) and pneumatic hammer are considered. The analysis is based on a first-order perturbation with respect to the eccentricity ratio (i.e., the results are limited to small eccentricity ratios) and makes use of the linearized Ph-method [2, 5, 8]. The pressurized gas is supplied to the bearing through restricted feeding holes in the center plane of the bearing and the analysis takes into account the discreteness of the feeding holes, the feeder hole time constant, and inherent compensation effects. Numerical results are given in form of 16 graphs, showing the threshold of instability as a function of supply pressure ratio, feeding parameter and eccentricity ratio. Also, the effect of the feeder hole time constant is investigated with respect to pneumatic hammer.
Complex Variable Analysis for Stepped Thrust Bearings
Authors: Tanner R. I.
Published: September 2011

It is shown how simple series solutions can be found for the bearing characteristics of stepped thrust bearings with curved steps. Loads are shown to be higher than with straight steps. The simplicity of the form of the solution allows optimal parameters to be determined readily. Detailed results to illustrate the use of the solution are given for annular and square pads. It is noted that the rear “corners” of square pads could be deleted with advantage.