bluuebunny/crossref_metadata_2025 huggingface dataset:
ESCRT‐I Function is Required for Tyrp1 Transport from Early Endosomes to the Melanosome Limiting Membrane
Authors: Truschel Steven T. , Simoes Sabrina , Gangi Setty Subba Rao , Harper Dawn C. , Tenza Danièle , Thomas Penelope C. , Herman Kathryn E. , Sackett Sara D. , Cowan David C. , Theos Alexander C. , Raposo Graça , Marks Michael S.
Published: June 2009

Melanosomes are lysosome‐related organelles that coexist with lysosomes within melanocytes. The pathways by which melanosomal proteins are diverted from endocytic organelles toward melanosomes are incompletely defined. In melanocytes from mouse models of Hermansky‐Pudlak syndrome that lack BLOC‐1, melanosomal proteins such as tyrosinase‐related protein 1 (Tyrp1) accumulate in early endosomes. Whether this accumulation represents an anomalous pathway or an arrested normal intermediate in melanosome protein trafficking is not clear. Here, we show that early endosomes are requisite intermediates in the trafficking of Tyrp1 from the Golgi to late stage melanosomes in normal melanocytic cells. Kinetic analyses show that very little newly synthesized Tyrp1 traverses the cell surface and that internalized Tyrp1 is inefficiently sorted to melanosomes. Nevertheless, nearly all Tyrp1 traverse early endosomes since it becomes trapped within enlarged, modified endosomes upon overexpression of Hrs. Although Tyrp1 localization is not affected by Hrs depletion, depletion of the ESCRT‐I component, Tsg101, or inhibition of ESCRT function by dominant‐negative approaches results in a dramatic redistribution of Tyrp1 to aberrant endosomal membranes that are largely distinct from those harboring traditional ESCRT‐dependent, ubiquitylated cargoes such as MART‐1. The lysosomal protein content of some of these membranes and the lack of Tyrp1 recycling to the plasma membrane in Tsg101‐depleted cells suggests that ESCRT‐I functions downstream of BLOC‐1. Our data delineate a novel pathway for Tyrp1 trafficking and illustrate a requirement for ESCRT‐I function in controlling protein sorting from vacuolar endosomes to the limiting membrane of a lysosome‐related organelle.
Immediate vs late orthodontic extrusion of traumatically intruded teeth
Authors: Medeiros Raquel Bueno , Mucha José Nelson
Published: June 2009

Abstract –  Although the published papers about this matter is limited to clinical case reports, the aim of this review was to quantify the success rate of immediate vs late orthodontic extrusion of traumatically intruded teeth. From 55 reports in a PubMed and Medline computerized search, 13 reported patients involving 22 traumatically intruded anterior upper teeth with orthodontic extrusion were selected. In the sample of 13 patients, six were males and seven females and the average age was 16.4 years old. The selection criteria were patients presenting traumatized anterior upper teeth resulting in intrusive luxation, with at least 1 year follow‐up period. Orthodontic extrusive forces were applied in the immediate group within 10 weeks post‐trauma, while in the late group the forces were applied only after 3 months post‐trauma. Immediate and late orthodontic extrusion was extremely favorable. The success rate (without or with complications) was 95.4% against only 4.5% (1 tooth) because of inflammatory root resorption with rapid progression. All mature teeth (100%) were endodontically treated. Among the 12 immature traumatically intruded teeth, eight were endodontically treated and four were not. A high rate of success was reported in the literature in traumatically intruded teeth orthodontically extruded, either immediate or late.
Are Female Orphans at Risk for Early Marriage, Early Sexual Debut, and Teen Pregnancy? Evidence from Sub‐Saharan Africa
Authors: Palermo Tia , Peterman Amber
Published: June 2009

Female orphans are widely cited as being at risk for early marriage, early childbearing, and risky sexual behavior; however, to date no studies have examined these linkages using population‐level data across multiple countries. This study draws from recent Demographic and Health Surveys from ten sub‐Saharan African countries to examine the relationship between orphanhood status and measures of early marriage, early sexual debut, and teen pregnancy among adolescent girls aged 15 to 17. Results indicate that, overall, little association is found between orphanhood and early marriage or teen pregnancy, whereas evidence from seven countries supports associations between orphanhood and early sexual debut. Findings are sensitive to the use of multivariate models, type of orphan, and country setting. Orphanhood status alone may not be a sufficient targeting mechanism for addressing these outcomes in many countries; a broader, multidimensional targeting scheme including orphan type, schooling, and poverty measures would be more robust in identifying and aiding young women at risk.
Determinants of Contraceptive Acceptance Among Cambodian Abortion Patients
Authors: McDougall Janna , Fetters Tamara , Clark Kathryn Andersen , Rathavy Tung
Published: June 2009

Although Cambodia's total fertility rate is declining, limited access to and use of contraceptives has meant that some women rely upon induced abortion, legal since 1997, to achieve their fertility intentions. This study identifies factors that facilitate acceptance of postabortion contraception among women using Cambodia's public health facilities. Data were collected in all of Cambodia's hospitals with obstetric and delivery services (n = 71) and a representative sample of 115 of its 887 health‐care centers, and from women seeking induced abortion or with abortion complications who presented to selected facilities during a three‐week period (n = 933). Weighted data from 316 women who reported not wanting to become pregnant within the next few months and who presented to facilities that provide postabortion contraceptives were analyzed for bivariate and multivariate associations. Approximately 42 percent of women accepted contraceptives at the conclusion of care. After controlling for individual and facility characteristics, women who presented at facilities where a nurse/midwife managed abortion services, where contraceptives and abortions were provided in the same room, and where a larger range of methods were offered had significantly higher odds of contraceptive acceptance following abortion care. Improving contraceptive counseling and training for midwives and physicians, increasing contraceptive choices, and promoting access to contraceptives on site may reduce Cambodian women's risk of unwanted pregnancy and, potentially, unsafe abortion.
Adolescent Reproductive Health in Indonesia: Contested Values and Policy Inaction
Authors: Utomo Iwu Dwisetyani , McDonald Peter
Published: June 2009

This study examines the changing social and political context of adolescent sexual and reproductive health policy in Indonesia. We describe how, in 2001, Indonesia was on the brink of implementing an adolescent reproductive health policy that was consistent with international agreements to which the Indonesian government was a party. Although the health of young Indonesians was known to be at risk, the opportunity for reform passed quickly with the emergence of a new competing force, Middle Eastern fundamentalist Islam. Faced with the risk of regional separatism and competing politico‐religious influences, the Indonesian government retreated to the safety of inaction in this area of policy. In the absence of a supportive and committed political environment that reinforces policy specifically targeted to young people's reproductive health, extremist approaches that involve considerable health risk prevailed. The sexual and reproductive values and behaviors that are emerging among single young people in contemporary Indonesia are conditioned by a political context that allows the conflicting forces of traditional Indonesian values, Westernization, and the strong emerging force of fundamentalist Islam to compete for the allegiance of young people.
Shakespeare in Spain: Current Research Trends
Authors: Calvo Clara
Published: June 2009

This essays aims to offer an overview of recent critical work on the reception of Shakespeare and his works in Spain. It does not offer a history of how Shakespeare fared in Spain across the centuries or a survey of work on Shakespeare by Spanish scholars published in Spain; instead, it takes stock to determine what research trends have prevailed in the last decade and how they have aimed to promote the study of the Shakespeare industry in Spain. It also suggests how current research increasingly regards Shakespeare's reception in Spain as part of a larger picture and a bigger research area, i.e. Shakespeare in Europe. While doing so, it argues that the study of Shakespeare in Spain is still a site displaying a ‘work in progress’ sign – although much has been done recently, the field is slightly behind its counterparts in some European countries. The only possible conclusion, given the state of research in the field, is that there is still ample room for imaginative work in Shakespeare's Spanish afterlives.
Revisiting Post-Ejaculation Refractory Time—What We Know and What We Do Not Know in Males and in Females
Authors: Levin Roy J.
Published: June 2009

Introduction

The post-ejaculation refractory time (PERT), the period after a single ejaculation when further erections and ejaculations are inhibited, has been studied and well-documented in male rats. Since its first attribution in men by Masters and Johnson and its inaccurate delineation in their graphic sexual response model in 1966 it has been infrequently studied whereas scant attention has been paid to any such possible activity in women after female ejaculation.

Aim

To critically review our current knowledge about PERT in rats and humans and describe and correct shortcomings and errors in previous publications and propose corrections.

Methods

Review of published literature.

Main Outcome Measures

Identifying evidence-based data to support authority-based facts.

Results

The review exposes the extremely limited evidence-based data that our knowledge of PERT is based on. The paucity of data for most aspects of human PERT is remarkable; even the generally accepted statement that the duration of PERT increases with age has no published support data.

Conclusions

Despite numerous studies in rats the mechanisms and site(s) of the activity are poorly understood. Dopaminergic and adrenergic pathways are thought to shorten PERT whereas serotonergic pathways lengthen its duration. Raising the brain serotonin levels in men using SSRIs helps reduce early or premature ejaculation. Rats have an absolute PERT (aPERT) during which erection and ejaculation is inhibited and a relative PERT (rPERT) when a stronger or novel stimulus can, whether such phases exist in men is unexamined. Apart from possible depressed activity in the amygdala and penile dorsal nerve and rejection of prolactin as a major factor in PERT little or no significant advance in understanding human male PERT has occurred. No evidence-based data on women’s PERT after female ejaculation exists. New investigations in young and older men utilizing brain imaging and electromagnetic tomography are priority studies to accomplish.
Erectile Function Recovery Rate after Radical Prostatectomy: A Meta-Analysis
Authors: Tal Raanan , Alphs Hannah H. , Krebs Paul , Nelson Christian J. , Mulhall John P.
Published: June 2009

Introduction

Erectile function recovery (EFR) rates after radical prostatectomy (RP) vary greatly based on a number of factors, such as erectile dysfunction (ED) definition, data acquisition means, time-point postsurgery, and population studied.

Aim

To conduct a meta-analysis of carefully selected reports from the available literature to define the EFR rate post-RP.

Main Outcome Measures

EFR rate after RP.

Methods

An EMBASE and MEDLINE search was conducted for the time range 1985–2007. Articles were assessed blindly by strict inclusion criteria: report of EFR data post-RP, study population ≥50 patients, ≥1 year follow-up, nerve-sparing status declared, no presurgery ED, and no other prostate cancer therapy. Meta-analysis was conducted to determine the EFR rate and relative risks (RR) for dichotomous subgroups.

Results

A total of 212 relevant studies were identified; only 22 (10%) met the inclusion criteria and were analyzed (9,965 RPs, EFR data: 4,983 subjects). Mean study population size: 226.5, standard deviation = 384.1 (range: 17–1,834). Overall EFR rate was 58%. Single center series publications (k = 19) reported a higher EFR rate compared with multicenter series publications (k = 3): 60% vs. 33%, RR = 1.82, P = 0.001. Studies reporting ≥18-month follow-up (k = 10) reported higher EFR rate vs. studies with <18-month follow-up (k = 12), 60% vs. 56%, RR = 1.07, P = 0.02. Open RP (k = 16) and laparoscopic RP (k = 4) had similar EFR (57% vs. 58%), while robot-assisted RP resulted in a higher EFR rate (k = 2), 73% compared with these other approaches, P = 0.001. Patients <60 years old had a higher EFR rate vs. patients ≥60 years, 77% vs. 61%, RR = 1.26, P = 0.001.

Conclusions

These data indicate that most of the published literature does not meet strict criteria for reporting post-RP EFR. Single and multiple surgeon series have comparable EFR rates, but single center studies have a higher EFR. Younger men have higher EFR and no significant difference in EFR between ORP and LRP is evident.
The Associations AmongeNOSG894T Gene Polymorphism, Erectile Dysfunction, and Benign Prostate Hyperplasia-Related Lower Urinary Tract Symptoms
Authors: Lee Yung-Chin , Wu Wen-Jeng , Liu Chia-Chu , Wang Chii-Jye , Li Wei-Ming , Huang Chun-Hsiung , Yeh Hsin-Chih , Ke Hung-Lung , Huang Shu-Pin
Published: June 2009

Introduction

A number of literature has now identified the role of impaired nitric oxide synthase/nitric oxide pathway in the endothelium as the central to the development of erectile dysfunction (ED) and benign prostate hyperplasia-related lower urinary tract symptoms (BPH/LUTS). Recently a few studies have reported the associations between endothelial nitric oxide synthase (eNOS) G894T gene polymorphisms and ED. However, there has been no report investigating the eNOS G894T genetic susceptibility factor for both ED and BPH/LUTS.

Aim

To investigate the possible associations among eNOS G894T polymorphism, ED, and BPH/LUTS in a Taiwanese population.

Main Outcome Measures

Patients with ED were defined as those having a 5-item International Index of Erectile Function-5 <21.

Methods

In all, 372 Taiwanese men underwent a free health screening were enrolled. All the men had complete clinical data and questionnaires taken. The eNOS G894T polymorphisms were determined using the polymerase chain reaction-restriction fragment length polymorphism method.

Results

Three hundred seventy-two men had a mean (standard deviation) age of 60.2 (8.8) years. With multivariate analysis, our data identified that aging, diabetes mellitus (DM), and eNOS G894T gene polymorphism were three independent common risk factors for both ED and BPH/LUTS (P < 0.001, P = 0.036, and P = 0.039 for ED; P = 0.034, P = 0.004, and P = 0.016 for BPH/LUTS, respectively). The eNOS 894T allele carriers had significantly higher prevalence of ED (77.9% vs. 60.4%, P = 0.012) and higher International Prostate Symptom score (IPSS) (13.3 ± 10.7 vs. 9.3 ± 7.8, P = 0.001) than G allele carriers.

Conclusions

Our results showed that aging, DM, and eNOS 894T allele carrier gene polymorphism were the three independently common risk factors for both ED and BPH/LUTS in the Taiwanese population. The eNOS 894T allele carriers had significantly higher frequencies of ED and higher IPSS, suggesting that eNOS G894T gene polymorphisms may play an implication as a genetic susceptibility factor for both ED and BPH/LUTS.
Evaluation of Marital and Sexual Interactions of Polish Infertile Couples
Authors: Drosdzol Agnieszka , Skrzypulec Violetta
Published: June 2009

Introduction

The World Health Organization defines infertility as inability to conceive despite regular sexual intercourse sustained for a period exceeding 12 months with no contraceptive methods.

Aim

The aim of this study was to evaluate the effect of infertility on marital and sexual interactions among infertile couples.

Methods

Two hundred six infertile couples were qualified to the study as the research group. The control group consisted of 190 fertile couples.

Main Outcome Measures

A specific questionnaire was used as a research tool in this study. It included the sociodemographic part, infertility status, and validated scales: Polish version of Index of Marital Satisfaction and Index of Sexual Satisfaction. Statistica 6.0 (Medical University of Silesia; Katowice, Poland) was used in the statistical analysis. The statistical analysis made use of: Mann–Whitney U-test, chi-square with Yates’ continuity correction, ancova log-linear analysis of covariance, and logistic regression analysis.

Results

The study showed a significantly better partner relationship in female infertile as compared with female fertile. Clinically significant disorders of partnership stability were observed in 11.65% of studied women and in 20% of controls. Marital adjustment and sexual satisfaction were comparable among male groups. The probability of marital disorders increased with: age above 30 (odds ratio [OR] = 1.6), female sex (OR = 1.5), and lower education (OR = 1.7) among the study population. Diagnosed male factor and infertility duration of 3–6 years were connected with the highest relationship instability and the lowest sexual satisfaction both in female and male infertile.

Conclusions

The risk factors of marital dissatisfaction in infertility include: female sex, age over 30, lower education level, diagnosis of male infertility, and infertility duration of 3–6 years.
Buddhist Epistemology: The Study of Pram?ṇa
Authors: Stoltz Jonathan
Published: June 2009

Epistemology – the study of the nature and scope of knowledge – has been an integral topic in Indian and Tibetan Buddhist scholastic communities for the past 1500 years. This article provides an overview of the Buddhist epistemological tradition, emphasizing the central role that the concept of pram?ṇa plays in Indian theories of knowledge. After elucidating the two pram?ṇas accepted by the Buddhist epistemological tradition, the article concludes by discussing the relationship between Buddhist epistemology and Buddhist soteriology.
Burmese Monks in Bangkok: Opening an Abhidhamma School and Creating a Lineage
Authors: Meister Kelly
Published: June 2009

In 1951, a small group of Thai monks went to explore the propagation of Buddhism in Burma. After being inspired by the Burmese methods of teaching Buddhist dhamma, the Abhidhamma‐Jotika College was founded by Venerable Sayadaw Saddhammajotika Dhamm?c?riya, a Burmese monk commissioned to initiate Abhidhamma education in Bangkok. In fact, according to the college's history, prior to the founding of the Abhidhamma‐Jotika College, Thailand lacked any formal training institution specifically dedicated to the study of the Abhidhamma, and thus for the means, materials, and teachers to enable the study of this ‘basket’ of the Tipiṭaka, Thais looked to the Burmese. It is common to hear about the negative history of warfare and animosity between the Thai and Burmese.  However, in order to fully understand the relationships between the two, particularly regarding Buddhist practice and study in Thailand, it is crucial to understand the very positive respect given by Thai Buddhists to the Burmese. This paper will look at the Abhidhamma‐Jotika College as an exemplifier of how, through Phra Saddhammajotika, a unique lineage was born in Thailand. Through this lineage the students of the Abhidhamma‐Jotika College continue to identify with the ethnicity of their Burmese founder and, moreover, believe they are participating in ‘something Burmese’.
Association Between Renal Function and Cardiovascular Disease in Patients With Left Ventricular Hypertrophy. VIIDA Study
Authors: Fácila Lorenzo , Bertomeu Vicente , Bertomeu‐González Vicente , Morillas Pedro , Mazón Pilar , González‐Juanatey Jose R. ,   on behalf of the investigators of the VIIDA study
Published: June 2009

The association between renal dysfunction and cardiovascular risk in patients with hypertension and left ventricular hypertrophy (LVH) has not been specifically studied. The aim of this study was to analyze the association between renal function and the presence of cardiovascular disease in this group of patients. Hypertensive patients with electrocardiographic criteria for LVH were recruited in cardiology outpatient clinics from April 2003 until November 2004. Epidemiologic variables were determined, together with an estimation of the glomerular filtration rate by means of the Modification of Diet in Renal Disease (MDRD) and Crockoft‐Gault equations. The population was classified according to the kidney disease stages of the National Kidney Foundation. A total of 3962 patients were included in the study, 47.6% of which were female, with a mean age of 67.2 years. The prevalence of established cardiovascular disease was higher in patients with a depressed glomerular filtration rate (68.3% vs 54.9%; P<.001). After adjusting for age, sex, body mass index, diabetes, smoking habits, and systolic and diastolic blood pressures, the stage of renal function was an independent predictor of the presence of cardiovascular disease (odds ratio, 1.5 [confidence interval, 1.19–2.02]; 2.1 [1.55–2.89]; and 2.6 [1.52–4.42], respectively, for stages 2, 3, 4–5, compared with stage 1). In hypertensive patients with electrocardiographic criteria for LVH, the determination of the glomerular filtration rate by the MDRD or Crockoft equations is easy and identifies a progressive and independent increase in cardiovascular risk.
Pollen morphology supports the reinstatement of Bergera (Rutaceae)
Authors: Mou Feng‐Juan , Zhang Dian‐Xiang
Published: June 2009

Pollen morphology of 11 species of Murraya and Micromelum (Clauseneae: Rutaceae) was investigated using scanning electron microscopy (SEM) and palynological characters including pollen size, aperture number and exine ornamentation were evaluated. The results indicate that species in M. sect. Bergera and sect. Murraya have very distinct pollen morphology. Species in section Bergera have rugulate to foveolate exine, whereas the tectum in section Murraya is cross‐striate. This supports the redefinition of the genus Murraya, retaining only the species of section Murraya, while M. sect. Bergera is better treated as a separate genus. From the palynological point of view, it is suggested that Bergera and Murraya s.s. are not closely related, with the latter being more close to Micromelum and Merrillia, a result in accordance with phytochemical, chromosomal and molecular evidence, thus supporting the reinstatement of the generic name Bergera L.
Therapeutic implications of manipulating and mining the microbiota
Authors: Shanahan Fergus
Published: June 2009

The gut microbiota is increasingly recognized as a health asset but occasionally is a contributor to the pathogenesis of both gastrointestinal and certain extra‐intestinal disorders. This is driving research interest, the pace of which has been greatly facilitated by new molecular technologies for studying mixed microbial populations, including the non‐cultivable sector. In addition, it appears that elements of a modern lifestyle such as diet, domestic hygiene, urbanization, antibiotic usage and family size, may represent proxy markers of environmental influence on the composition of the microbiota colonizing the host in early life. While manipulation of the microbiota has become a therapeutic strategy in certain clinical disorders, the prospect of mining host–microbe–dietary interactions for novel drug discovery may become an even more intriguing reality.
Peripheral sensitisation of nociceptors via G‐proteindependent potentiation of mechanotransduction currents
Authors: Lechner Stefan G. , Lewin Gary R.
Published: June 2009

Mechanical stimuli impinging on the skin are converted into electrical signals by mechanically gated ion channels located at the peripheral nerve endings of dorsal root ganglion (DRG) neurons. Under inflammatory conditions sensory neurons are commonly sensitised to mechanical stimuli; a putative mechanism that may contribute to such sensitisation of sensory neurons is enhanced responsiveness of mechanotransduction ion channels. Here we show that the algogens UTP and ATP potentiate mechanosensitive RA currents in peptidergic nociceptive DRG neurons and reduce thresholds for mechanically induced action potential firing in these neurones. Pharmacological characterisation suggests that this effect is mediated by the Gq‐coupled P2Y2nucleotide receptor. Moreover, using thein vitroskin nerve technique, we show that UTP also increases action potential firing rates in response to mechanical stimuli in a subpopulation of skin C‐fibre nociceptors. Together our findings suggest that UTP sensitises a subpopulation of cutaneous C‐fibre nociceptors via a previously undescribed G‐protein‐dependent potentiation of mechanically activated RA‐type currents.
Near-Field Radiation Between a Sphere and Substrates of Different Materials
Authors: Shen Sheng , Narayanaswamy Arvind , Chen Gang
Published: June 2009

In order to measure the near-field radiative heat transfer between a microsphere and a substrate, we have developed a sensitive technique using a bi-material atomic force microscope (AFM) cantilever. In this paper, we use this technique to measure the near-field radiation between a silica microsphere and substrates made of different materials (semiconductor, metal and polar dielectric materials). The resulting “Conductance-distance” curves show the presence of the near-field radiation enhancement caused by surface phonon-polaritons.
Modeling and Designing a Device Using MuGFETs
Authors: Lamba V. K. , Engles Derick , Malik S. S.
Published: June 2009

This work describes computer simulations of various, Silicon on Insulator (SOI) Metal Oxide Semiconductor Field Effect Transistor (MOSFETs) with double and triple-gate structures, as well as gate-all-around devices. To explore the optimum design space for four different gate structures, simulations were performed with four variable device parameters: gate length, channel width, doping concentration, and silicon film thickness. The efficiency of the different gate structures is shown to be dependent of these parameters. Here short-channel properties of multi-gate SOI MOSFETs (MuGFETs) are studied by numerical simulation. The evolution of characteristics such as Drain induced barrier lowering (DIBL), sub-threshold slope, and threshold voltage roll-off is analyzed as a function of channel length, silicon film or fin thickness, gate dielectric thickness and dielectric constant, and as a function of the radius of curvature of the corners. The notion of an equivalent gate number is introduced. As a general rule, increasing the equivalent gate number improves the short-channel behavior of the devices. Similarly, increasing the radius of curvature of the corners improves the control of the channel region by the gate.
A Two-Temperature Model of Narrow-Body Silicon Transistors Under Steady State and Transient Operation
Authors: Ong Zhun-Yong , Pop Eric
Published: June 2009

We present a simple theory of diffusive phonon heat transport in silicon thin films using the Two-Temperature Model (TTM). In silicon thin films, boundary scattering reduces the lifetime and hence, the mean free path of acoustic phonons. As acoustic phonons are responsible for heat transport in silicon, the latter effect leads to a reduction in the lattice thermal conductivity. However, optical phonons are unaffected by boundary scattering. As the boundary scattering rate exceeds the inverse lifetime of acoustic phonons and the energy relaxation rate between optical and acoustic phonons, it results in an energy transfer bottleneck. The reduced lattice thermal conductivity from boundary scattering and the energy transfer bottleneck are taken into account in the TTM. We apply the TTM to find the steady temperature distribution in a 2D model of a silicon-on-insulator (SOI) device. The numerical results are in good agreement with those obtained from the more sophisticated full dispersion model of the Boltzmann Transport Equation (BTE). We apply the TTM to calculate the steady state and transient temperature distributions in a simplified 1D model of a SOI device.
Nano-Droplet Impact on a Homogenous Surface Using Molecular Dynamics
Authors: Maroo Shalabh C. , Chung Jacob N.
Published: June 2009

Impact of argon nano-droplet on homogeneous platinum wall is simulated using molecular dynamics. Wall temperature (90 K, 300 K) and surface wettability (high, low based on εAr–Pt parameter) are varied to study four cases. An external force is applied on the drop for a short time period to achieve velocities in the range of 13 m/s – 15 m/s. Interface markers, interfacial fit and contact angles are evaluated. Complete spreading is obtained on the high wettable surface, whereas drop oscillations are seen for the low wettable surface for wall temperatures of 90 K. Liedenfrost effect is observed for wall temperature of 300 K for both cases of surface wettability.
Structural and Electrochemical Studies on Thin-Film Yttria-Doped Zirconia Electrolytes for Microscale Solid Oxide Fuel Cells
Authors: Johnson Alex C. , Ramanathan Shriram
Published: June 2009

We report in-plane and through-plane conductivity measurements of dense YSZ films varying in thickness from 20 to 200 nm. In-plane measurements were performed on YSZ films grown on silicon wafers coated with SiO2 or Si3N4. Micro-fabricated strips with Pt electrodes in various geometries were used to obtain conductivity as a function of temperature from 200 – 600 °C in a custom-designed micro-probe station. These films have activation energies, which vary from 0.77 to 1.09 eV. Their absolute conductivity is lower compared with other reports. Through-plane and fuel cell measurements were performed by depositing YSZ on a nitrided silicon wafer, then etching through the wafer and depositing porous platinum electrodes on both sides [6,7]. We discuss the electrochemical conduction studies in detail along with fuel cell performance and correlation with electrode microstructure.
Molecular Dynamics Simulation of Interfacial Thermal Resistance of Nanofins
Authors: Singh Navdeep , Unnikrishnan V. U. , Reddy J. N. , Banerjee Debjyoti
Published: June 2009

In this study molecular dynamic (MD) simulations are performed to study the interfacial thermal resistance between a nanofin and a working fluid. A (5, 5) carbon nanotube (CNT) of diameter 6.78 Å and various lengths are immersed in different fluids in these analyses. For this simulation the total numbers of the fluid molecules, and the breath and the height of the cell are kept constant. In these simulations, the nanotube is placed at the centre of the cell and the matrix molecules surround the nanotube. Periodic boundary conditions are applied in all the directions. So the system under consideration is array of long nanotubes aligned in the horizontal direction. Simulation procedure consists of first minimizing the system. During the minimization the system is allowed to relax. During the simulations, nanotube and water molecules are allowed to move but the cell size remains constant. After minimization, NVT process is performed for 10ps to scale the velocities so that the average temperature of the cell is 300K. After the ensemble is equilibrated to the base temperature of 300K, the temperature of the nanotube is raised to 750K, by scaling the velocities of the carbon atoms. In the next step the system is allowed to relax under constant energy. This is done by performing the NVE equilibration for 10ps. The difference in the temperature of the carbon nanotube and the matrix is then calculated and plotted against the equilibration time. For the all three matrix, the temperature decreases exponentially with time as predicted by various researchers in the literature. From the graphs the interfacial resistance for water, ethyl alcohol and 1-Hexene is found to be 7.76×10-8, 6.76×10-8 and 35.1×10-8 W/m2K. The value of interfacial resistance for water is consistent with results in the literature.
Thermal Modeling of Atomic-Scale Three-Dimensional Phononic Crystals for Thermoelectric Applications
Authors: Gillet Jean-Numa , Chalopin Yann , Volz Sebastian
Published: June 2009

Extensive research on semiconducting superlattices with a very low thermal conductivity was performed to fabricate thermoelectric materials. However, as nanowires, superlattices affect heat transfer in only one main direction, and often show dislocations owing to lattice mismatches when they are made up of a periodic repetition of two materials with different lattice constants. This reduces their electrical conductivity. Therefore it is challenging to obtain a thermoelectric figure of merit ZT superior to unity with the superlattices. Self-assembly with lithographic patterning and/or liquid precursors is a major epitaxial technology to fabricate ultradense arrays of germaniums quantum dots (QDs) in silicon for many promising electronic and photonic applications as quantum computing where accurate QD positioning and low degree of dislocations are required. We theoretically demonstrate that high-density three-dimensional (3-D) arrays of self-assembled Ge nanoparticles, with a size of some nanometers, in Si can also show a very low thermal conductivity in the three spatial directions. This property can now be considered to design new thermoelectric devices, which are compatible with new complementary metal-oxide-semiconductor (CMOS) processes. To obtain a computationally manageable model of these nanomaterials, we simulate their thermal behavior with atomic-scale 3-D phononic crystals. A phononic-crystal period or supercell consists of diamond-like Si cells. At each supercell center, we substitute Si atoms by Ge atoms in a given number of cells to form a box-like nanoparticle. According to our model, in an example 3-D phononic crystal, the thermal conductivity can be reduced to a value lower than only 0.2 W/mK or by a factor of at least 750 compared to bulk Si at 300 K. This value is five times smaller than the Einstein Limit of single-crystalline bulk Si. We considered the flat dispersion curves computed by lattice dynamics to obtain this huge decrease. However, we did not consider multiple-scattering effects as multiple reflections and diffusions of the phonons between the Ge nanoparticles. We expect a larger decrease of the real thermal conductivity owing to the reduction of the phonon mean free paths from these collective effects. We hope to obtain a large ZT in these self-assembled Ge nanoparticle arrays in Si. Indeed, they are crystalline with an electrical conductivity that can be also increased by doping using CMOS processes, which is not possible with other recently proposed materials.
A Molecular Dynamics Study on Effects of Nanostructural Clearances on Thermal Resistance at an Interface Between Liquid and Solid
Authors: Shibahara Masahiko , Takeuchi Kiyoshi
Published: June 2009

The classical molecular dynamics simulation was conducted in order to clarify the effects of the surface structural clearances in nanometer scale on thermal resistance at a liquid-solid interface as well as static and dynamic behaviours of fluid molecules in the vicinity of the surface. A liquid molecular region confined between the solid walls, of which the interparticle potential was Lennard-Jones type, was employed as a calculation system. The thermal resistance between the liquid molecular region and the solid walls with nanostructures was calculated by the heat flux and the temperature jump obtained in the molecular dynamics simulations. With changing the surface structural clearances from 0 to 2.81 nm the thermal resistance between the liquid molecular region and the solid walls with nanostructures once decreased and became the minimum value when the structural clearances were about 0.7 nm. Surface area in molecular scale and fluid density at the interface were dependent on the surface structural clearances and the thermal resistance index calculated by the relative surface area in molecular scale and the relative fluid density at the interface could predict thermal resistance change depending on the nanostructural clearances. Surface nanostructural clearances affected the fluid molecular motions along the heat transfer direction only when the molecular velocity was averaged over a specific characteristic time. Surface nanostructural clearances affected the diffusion behaviours of fluid molecules in the vicinity of the surface too.
Water-Evaporation Characteristics of Nano-Structure Surface
Authors: Satake Shin-Ichi , Taniguchi Jun
Published: June 2009

The characteristics of water-evaporation from a glassy carbon (GC) plate with nano-structure surface were investigated. The nano-scale structures on the carbon plate are made by Oxygen ion beam process. In changing the exposure time in the Ion beam process, it can be changed as for the pitch and diameter of nano-structure with conical structures. The experiment measured the temperature of GC plate and weight of a water-droplet while the droplet evaporates on the heating carbon plate. Consequently, special evaporation appeared when the pitch of nano-structure with the conical structures was larger than 80 nm.
Influence of Lubricant and Operating Characteristics on EHD Lubrication in Hypoid Gears
Authors: Simon Vilmos
Published: June 2009

The full thermal EHD lubrication analysis is applied, therefore, the oil viscosity variation with respect to pressure and temperature and the density variation with respect to pressure are included. By using the corresponding computer program, the influence of oil viscosity, pressure-viscosity and temperature-viscosity exponents, supplied oil temperature, speed and minimum oil film thickness on maximum oil film pressure and temperature, EHD load carrying capacity, and on power losses in the oil film is investigated. Small part of the obtained results is presented and discussed.
Thermal and Roughness Effects in a Slider Bearing Considering Conduction Through Both the Pad and the Slider
Authors: Sinha Prawal , Adamu Getachew
Published: June 2009

This paper analyses the thermal and roughness effects on different characteristics of an infinitely long tilted pad slider bearing considering heat conduction through both the pad and slider. The roughness is assumed to be stochastic, Gaussian randomly distributed. Density and viscosity are assumed to be temperature dependent. The irregular domain of the fluid due to roughness is mapped to a regular domain so that the numerical method can be easily applied. The modified Reynolds equation, momentum equation, continuity equation, energy equation and the heat conduction equations on the pad and slider are coupled and solved using finite difference method to yield various bearing characteristics. The solutions with respect to different pad and slider boundary conditions are elaborated through tables and figures.
Technical Development Path for Foil Gas Bearings
Authors: DellaCorte Christopher
Published: June 2009

Foil gas bearings are in widespread commercial use in air cycle machines, turbocompressors and microturbine generators and are emerging in more challenging applications such as turbochargers, auxiliary power units and propulsion gas turbines. Though not well known, foil bearing technology is well over fifty years old. Recent technological developments indicate that their full potential has yet to be realized. This paper investigates the key technological developments that have characterized foil bearing advances. It is expected that a better understanding of foil gas bearing development path will aid in future development and progress towards more advanced applications.
Experimental Study of a Creeping Polymer Sphere in Contact With a Rigid Flat
Authors: Ovcharenko Andrey , Halperin Gregory , Etsion Izhak
Published: June 2009

The creep of a polymer sphere contacting a rigid flat under a constant normal load is investigated experimentally. An optical technique is used to observe in situ the evolution of the contact area while the increase of contact interference is measured simultaneously. The experimental results obtained with PTFE spheres of different diameters pressed against a sapphire flat under different normal loads are presented and the effect of sphere diameter and normal load on the creep of the contact parameters is discussed. The present experimental study validate recently published theoretical results of a contact model for a creeping sphere and a rigid flat showing that a universal similarity solution exists for the dimensionless creep interference and dimensionless creep contact area as functions of the dimensionless time.
The Synergistic Antioxidation Effects of Molybdenum Dialkydithiocarbamate With Arylamine Antioxidants
Authors: Hu Jian-Qiang , Zeng Xian-Jun , Zhang Wei , Shang Ben-Ke
Published: June 2009

The antioxidation properties of molybdenum dialkyldithiocarbamate (M 807)- and p, p-dioctyldiphenylalmine (V 81)- or mixed octylated and butylated diphenylalmines (V 961)-containing poly-α-olefin (PAO)-derived lubricants were evaluated by differential scanning calorimetry (DSC) and modified penn state micro-oxidation test (PMOT). DSC test measures incipient oxidation temperature (OT) and oxidation induction time (IT) of the lubricant at high temperatures and the oxidation stability of oil weight loss is measured by PMOT test. DSC test shows that OT and IT of V 81-or V 961-containing PAO were improved significantly by M 807 addition. PMOT test indicates that when combining with V 81 antioxidants, M 807 can also effectively reduce the increase in weight loss of PAO and deposits formed in oils. These results suggest that the M 807 shows a good antioxidative synergism with alkylated diphenylamine antioxidants. In addition, FTIR results from PMOT test confirm that addition of M 807 can significantly enhance the oxidation induction time of oils containing V 81 and inhibit formation of oxidation products including carbonyl bonds or hydroxyl group.
An Experimental Investigation Into the Effect of Lubricant on the Local Film Thickness of Artificial Roughness Features
Authors: Furtuna M. D. , Glovnea R. P.
Published: June 2009

The lubrication of rough surfaces has been a focus of researchers in the field for many years now. A good deal of work has been carried out either on the experimental or on the theoretical sides of the research. From the experimental point of view it is obviously more convenient to study the lubrication of artificial roughness features such as ridges, bumps or dents rather than real, random roughness. The advantage of model roughness features is that they are well individualized, located, and characterized, thus a comparison of the surfaces geometry inside and outside an elastohydrodynamic contact can be made. The studies carried out so far have focused on the effect of the geometry of the features and that of the entrainment speed. No detailed experimental work on the effect of the lubricant properties on the behavior of the EHD films has been performed, to the authors’ knowledge. The present study uses the optical interferometry method to measure the EHD film thickness between a flat disc and a ball on which artificial ridges have been sputtered. Two lubricants, with different viscosity and pressure/viscosity coefficient are used in a range of pressures and entrainment speeds.
Soft EHL Analysis of a Reciprocating Hydraulic Step Seal
Authors: Yang Bo , Salant Richard F.
Published: June 2009

A numerical soft EHL (elastohydrodynamic lubrication) model of a reciprocating hydraulic step seal has been used to analyze seal performance. The model consists of coupled steady state fluid mechanics, deformation mechanics, contact mechanics and thermal analyses, with an iterative computational procedure. Results for a typical step seal are compared with those of a double lip U-cup seal.
Evaluation of Vapor Pressure and Ultra-High Vacuum Tribological Properties of Ionic Liquids (2) Mixtures and Additives
Authors: Morales Wilfredo , Street Kenneth W. , Koch Victor R. , Richard Ryan M.
Published: June 2009

Ionic liquids are salts, many of which are typically viscous fluids at room temperature. The fluids are characterized by negligible vapor pressures under ambient conditions. These properties have led us to study the effectiveness of ionic liquids containing both organic cations and anions for use as space lubricants. In the previous paper we have measured the vapor pressure and some tribological properties of two distinct ionic liquids under simulated space conditions. In this paper we will present vapor pressure measurements for two new ionic liquids and friction coefficient data for boundary lubrication conditions in a spiral orbit tribometer using stainless steel tribocouples. In addition we present the first tribological data on mixed ionic liquids and an ionic liquid additive. Post mortem infrared and Raman analysis of the balls and races indicates the major degradation pathway for these two organic ionic liquids is similar to those of other carbon based lubricants, i.e. deterioration of the organic structure into amorphous graphitic carbon. The coefficients of friction and lifetimes of these lubricants are comparable to or exceed these properties for several commonly used space oils.
Tribological Understanding of Polymer Lapped Surfaces
Authors: Mandel K. , Chen W. W. , Ren N. , Graham M. , Chung Y. W. , Wang Q.
Published: June 2009

Polymer lapping may significantly remove secondary roughness and result in smoothened topography that helps improve the tribological performance of surfaces. Reported in this paper are studies of topographic, mechanical and tribological characteristics of a lapped surface. The effects of secondary roughness on contact and lubrication are explored.
Viscosity and Tribology of Copper Oxide Nanofluids
Authors: Hernandez Battez A. , Viesca Rodriguez J. L. , Gonzalez Rodriguez R. , Fernandez Rico J. E.
Published: June 2009

Nanofluids, a term proposed by Choi in 1995 [1], are composites consisting of solid nanoparticles with sizes varying generally from 1 to 100 nm dispersed in a liquid. Numerous nanoparticles used as oil additives have been investigated in recent years [2–7]. Results show that they deposit on the rubbing surface and improve the tribological properties of the base oil, displaying good friction and wear reduction characteristics even at concentrations below 2%wt.
A New Technique for the Investigation of Tribological Behavior of Sliding Pairs Used in Hot Forming Processes
Authors: Franetovic Vjekoslav
Published: June 2009

Hot forming of aluminum sheet is highly influenced by the tribological behavior of the interacting surfaces of sliding pairs. Here we describe a new technique to investigate tribo-pair candidates for Quick Plastic Forming (QPF) and warm forming processes. This technique represents a bench type simulation of the real forming process where the sheet and tool interact by sliding against each other in a single motion (slide/stroke).
Rolling/Sliding Wear Behavior of High Carbon Steel Wire Rod (HSWR) of Traction Machine
Authors: Jang Beom-Taek , Kim Seock-Sam
Published: June 2009

Steel wires are critical load-bearing components in a wide range of applications such as elevator, cranes, mine haulage etc. The traction machine of elevator which transmits power to wire rope causes micro-slip between wire rope and sheave during reciprocating action. The lubrication condition of wire rope is also changed due to the lack of grease. This study focuses on the wear behavior of steel wire and effect of both dry and grease conditions by using the rolling/sliding contact wear tester done under various slip ratios and rolling speeds. The experimental results of the wear volume curve against the number of revolutions under the grease condition are compared with the results under dry condition. The worn surface of steel wire and the size of wear particles were observed by SEM. In order to quantify the wear amount of steel wire we established an equation and finally obtained the wear coefficient.