bluuebunny/crossref_metadata_2025 huggingface dataset:
The expression of heat shock protein 70 in the dental pulp following trauma
Authors: Pileggi Roberta , Holland Graham Rex
Published: June 2009

Abstract –  Background/Aim:  Traumatic dental injuries vary in severity from mild concussion to avulsion. All organisms respond to stress by inducing the synthesis of a group of proteins known generically as heat shock proteins. The activation of these proteins is an essential cellular mechanism designed to protect against a variety of environmental stresses. It is probable that the production of these proteins is increased in the cells of the traumatized dental pulp, however, this has not as yet been demonstrated. The degree of heat shock proteins expression may be related to the severity of the trauma such that estimating the extent of heat shock proteins expression may provide a practicable way of quantifying these injuries.

Materials and Methods:  Twenty adult male ferrets were divided into four groups. Each maxillary and mandibular right canine was traumatized with the contralateral canines acting as undamaged controls. The trauma was a simulated concussion injury applied using a uniform force. Animals were killed at 24, 48, 72 and 168 h after the injury. The canines were extracted, sectioned and processed for immunohistochemistry using a mouse monoclonal antibody specific for Hsp70.

Results:  There was a statistically significant difference in Hsp70 staining between traumatized and non‐traumatized teeth only in the group observed 24 h after the trauma. The expression of heat shock proteins form part of the early pulpal response to trauma.
Serum of patients with oral pemphigus vulgaris impairs keratinocyte wound repair in vitro: a time‐lapse study on the efficacy of methylprednisolone and pyridostigmine bromide
Authors: Lanza A , Stellavato A , Heulfe I , Landi C , Gombos F , Cirillo N
Published: June 2009

Objectives:  Pemphigus vulgaris (PV) is an autoimmune blistering disease affecting primarily oral mucosa and skin. Among the drugs used for the therapy of pemphigus, both methylprednisolone (MP) and pyridostigmine bromide (PBr) can prevent acantholysis in vitro. However, their putative therapeutic properties in regenerating PV‐like lesions and promoting the healing process still remain to be demonstrated. To address this issue, here we have developed a model for studying the process of epithelial cleft regeneration in PV by artificially wounding keratinocyte monolayers.

Materials and methods:  The experimental model was established by scratching confluent monolayers to simulate the epithelial cleft; then, wound regeneration in the presence of submaximal concentrations of PV sera was studied by time‐lapse microscopy, with or without the addition of MP and PBr in the culture medium.

Results:  Pemphigus vulgaris serum inhibited epithelial cleft repair of wounded monolayers. Indeed, in the presence of 10% (v/v) PV serum, keratinocytes reached only 2% confluence within 72 h vs an almost complete healing of controls. When administered together with PV sera, MP significantly (P < 0.01) enhanced wound fill by 30% after 72 h. PV‐associated wound repair was significantly (P < 0.05) ameliorated by PBr by 24 h and keratinocytes reached 20% confluence after 72 h. Interestingly, neither MP nor PBr could accelerate wound healing when compared with untreated control monolayers.

Conclusions:  In PV, MP and PBr exert their curative effects in part by enhancing the regeneration properties of keratinocytes. Indeed, our data suggest that both drugs can specifically counterbalance the detrimental effects of PV serum on keratinocyte wound healing. These findings provide an explanation for the efficacy of MP and PBr in the treatment of PV lesions in human skin and oral mucosa.
RHEOLOGICAL AND SENSORY QUALITY OF READY‐TO‐BAKE CHAPATTI DURING FROZEN STORAGE
Authors: YADAV D.N. , PETKI P.E. , SHARMA G.K. , SRIHARI K.A. , HARILAL P.T. , BAWA A.S.
Published: June 2009

The effect of prolonged frozen storage at −18C, on the textural and sensory properties of ready‐to‐bake frozen chapatti (R‐BFC) was evaluated. The R‐BFC samples were prepared from normal‐ (control) and microwave‐treated (18% moisture content for 80 s) wheat grains. Results showed that the extensibility of dough and maximum load for resistance increased gradually in both the samples during frozen storage; however, the increase was lesser in the treated ones. Chapattis prepared from both R‐BFC samples exhibited higher hardness, cohesiveness, chewiness and lower springiness values during frozen storage. Microwave‐treated R‐BFC samples were rated as better retained in color, texture and overall acceptability scores as compared with control, up to 6 months of storage at −18C. Thiamin and riboflavin contents were monitored during frozen storage and a loss of 12.0–14.5% in thiamin and 4–6% in riboflavin after 6 months of frozen storage was recorded.

PRACTICAL APPLICATIONS

During frozen storage, various physical, rheological and sensory changes occur in the food products, which determine the consumer's acceptability. The results of this study will help to establish quality of the frozen chapattis with respect to texture, color and aroma which will meet the consumer's acceptance. The protocol for the storage of frozen chapattis will help the industry to deliver the product of optimum quality.
Modern Qur’anic Hermeneutics
Authors: Ohlander Erik
Published: June 2009

With an eye towards developments that either depart from or re‐envision Islam's classical exegetical methodologies, this article furnishes a schematic overview of major trends and trajectories in Qur’anic hermeneutics situated across a range of modern Muslim discursivities, paying particular attention to six hermeneutical models that have, some more than others, garnered attention from the mid‐19th century to the present: modernist, Islamist, scientist, translationalist, revisionist, and feminist. As distinct from modern exegetical practice carried out in an established classical idiom, all of these models have engendered debate, controversy, or contestation to one degree or another, being as reflective of the complexity of Muslim engagements with modernity as of the polyvalence of interpretations of the text itself.
The Hasidic Tale as a Historical Source: Historiography and Methodology
Authors: Dynner Glenn
Published: June 2009

A review of the discourse on Hasidic tales reveals a persistent vagueness on the crucial question of how, precisely, historians should read hagiography. Can elements of certain tales stand on their own as historical sources? After a review of the current debates about the historicity of Hasidic tales, this paper introduces several historically oriented redactors whose collections constitute a rich repository of information about events, phenomena, personalities, and what most scholars would consider historical reality. Historians can mine these texts for solid information about Hasidism during its vital phase of growth, expansion, and crystallization.
Information Structure and Syntactic Structure
Authors: Birner Betty J. , Ward Gregory
Published: June 2009

This article explores the interface between syntactic structure and information structure – in particular, the broad generalizations that can be made between certain noncanonical word orders and information‐structural constraints on their use. Various ways of implementing the distinction between ‘given’ and ‘new’ information are described, and several classes of word orders (such as preposings, postposings, argument reversals, and clefts) are discussed in terms of the information‐status constraints to which they are sensitive. It is argued that classes of related word orders share related constraints but that – both cross‐linguistically and within a single language – there are also construction‐specific constraints on the correlation between word order and information status.
Duplication of 7q34 in Pediatric Low‐Grade Astrocytomas Detected by High‐Density Single‐Nucleotide Polymorphism‐Based Genotype Arrays Results in a Novel BRAF Fusion Gene
Authors: Sievert Angela J. , Jackson Eric M. , Gai Xiaowu , Hakonarson Hakon , Judkins Alexander R. , Resnick Adam C. , Sutton Leslie N. , Storm Phillip B. , Shaikh Tamim H. , Biegel Jaclyn A.
Published: June 2009

In the present study, DNA from 28 pediatric low‐grade astrocytomas was analyzed using Illumina HumanHap550K single‐nucleotide polymorphism oligonucleotide arrays. A novel duplication in chromosome band 7q34 was identified in 17 of 22 juvenile pilocytic astrocytomas and three of six fibrillary astrocytomas. The 7q34 duplication spans 2.6 Mb of genomic sequence and contains approximately 20 genes, including two candidate tumor genes, HIPK2 and BRAF. There were no abnormalities in HIPK2, and analysis of two mutation hot‐spots in BRAF revealed a V600E mutation in only one tumor without the duplication. Fluorescence in situ hybridization confirmed the 7q34 copy number change and was suggestive of a tandem duplication. Reverse transcription polymerase chain reaction‐based sequencing revealed a fusion product between KIAA1549 and BRAF. The predicted fusion product includes the BRAF kinase domain and lacks the auto‐inhibitory N‐terminus. Western blot analysis revealed phosphorylated mitogen‐activated protein kinase (MAPK) protein in tumors with the duplication, consistent with BRAF‐induced activation of the pathway. Further studies are required to determine the role of this fusion gene in downstream MAPK signaling and its role in development of pediatric low‐grade astrocytomas.
Detection of Walnut Residues in Foods Using an Enzyme‐Linked Immunosorbent Assay
Authors: Niemann Lynn , Taylor Steve L. , Hefle Susan L.
Published: June 2009

ABSTRACT:  Tree nuts, including walnuts, can be responsible for allergic reactions. Food manufacturers have the responsibility to declare the presence of walnuts on packaged foods even when trace residues may be present from the use of shared equipment or the adventitious contamination of ingredients. The aim of this study was to develop a rapid, sensitive, and specific enzyme‐linked immunosorbent assay (ELISA) method for the detection of walnut protein residues. Mixtures of raw and roasted English walnuts of several varieties were defatted, powdered, and used as separate antigens in sheep and New Zealand white rabbits. An ELISA was developed using the sheep antiroasted walnut serum as the capture reagent and rabbit antiroasted walnut serum as the detector reagent followed by addition of commercial goat anti‐rabbit IgG antibody labeled with alkaline phosphatase and subsequent substrate addition. The performance of the ELISA was validated by testing known amounts of walnut (0 to 100 ppm) either spiked into or manufactured into milk chocolate, cookies, muffins, or ice cream. Recoveries of 1 to 100 ppm walnut‐in‐chocolate ranged from 71.6% to 119%± 7% to 16.5%. The walnut ELISA has a detection limit of 1 ppm (1 μg/g) walnut in several food matrices. Substantial cross‐reactivity was observed with pecan while minimal cross‐reactivity was noted for hazelnut, mustard, mace, and poppy seed among almost 100 foods and food ingredients tested. This walnut ELISA can be used to detect undeclared walnut residues in foods and ingredients and as a tool to validate the effectiveness of allergen control programs for walnuts.
Pasta with Unripe Banana Flour: Physical, Texture, and Preference Study
Authors: Agama‐Acevedo Edith , Islas‐Hernandez José J. , Osorio‐Díaz Perla , Rendón‐Villalobos Rodolfo , Utrilla‐Coello Rubí G. , Angulo Ofelia , Bello‐Pérez Luis A.
Published: June 2009

ABSTRACT: Banana is a starchy food that contains a high proportion of undigestible compounds such as resistant starch and nonstarch polysaccharides. Products with low glycemic response such as pasta are considered favorable to health. The objective of this study was to use unripe banana flour to make spaghetti with low‐carbohydrates digestibility and evaluate its physical and texture characteristics, as well as consumer preference. Formulations with 100% durum wheat semolina (control) and formulations with 3 semolina: banana flour ratios (85: 15, 70: 30, and 55: 45) were prepared for spaghetti processing. The use of banana flour decreased the lightness and diameter of cooked spaghetti, and increased the water absorption of the product. Hardness and elasticity of spaghetti were not affected by banana flour, but adhesiveness and chewiness increased as the banana flour level in the blend rose. Spaghettis prepared in the laboratory (control and those with banana flour) did not show differences in preference by consumers. In general, the preference of spaghettis with different banana flour level was similar. The addition of a source of undigestible carbohydrates (banana flour) to spaghetti is possible without affecting the consumer preference.
Hydrothermal Alteration, Fluid Inclusion and Stable Isotope Studies of the North Roby Zone, Lac des Iles PGE Mine, Ontario, Canada
Authors: Somarin Alireza Karimzadeh , Kissin Stephen A. , Heerema Donald D. , Bihari Daniel J.
Published: June 2009

The Archean mafic–ultramafic complex of Lac des Iles, Ontario, Canada, hosts economic platinum group elements (PGE)‐Au‐Cu‐Ni mineralization in the Roby Zone. All lithologies in the North Roby Zone have been affected by hydrothermal alteration. The alteration products include talc (the most dominant mineral), anthophyllite, serpentine, actinolite, tremolite, chlorite, hornblende, zoisite, clinozoisite, epidote and sericite. In the altered rocks, light rare earth elements (La, Ce, Nd, Sm), Pb, Rb, Ba, Cs, S and possibly Y have been added by hydrothermal solution whereas Eu and heavy rare earth elements (Yb, Gd, Dy, Er) remained immobile. There are five types of fluid inclusions in the pegmatitic plagioclase with homogenization temperature and salinity ranging from 240°C to 445°C and 15.37 to 48.52 wt% equivalent NaCl, respectively. The δ18O and δD of talc range form 6.2‰ to 6.9‰ and −28‰ to −48‰, respectively. δ18O and δD water in equilibrium with talc during the hydrothermal alteration suggest a modified source for the hydrothermal solution. Microthermometry and stable isotope studies suggest that high temperature–high salinity fluid was diluted by, and mixed with, low temperature–low salinity meteoric solution. This mechanism precipitated the hydrothermal assemblage and redistributed trace elements during and after pegmatite formation in the North Ruby Zone.
Mineralogical and Geochemical Characterization of Beryl‐Bearing Granitoids, Eastern Desert, Egypt: Metallogenic and Exploration Constraints
Authors: Abdalla Hamdy M.
Published: June 2009

Mineral chemistry and geochemical characteristics of beryl‐bearing granitoids in Eastern Desert of Egypt, were examined in order to identify the metallogenetic processes of the host granitoids. The investigated Be‐bearing granitoids and type occurrences are classified into two groups: (i) peraluminous, Ta ≥ Nb + Sn + Be ± W‐enriched, Li‐albite granite (e.g. Nuweibi and Abu Dabbab); and (ii) metasomatized, Nb >> Ta + Sn + Be ± W ± Mo‐enriched alkali feldspar granite (i.e. apogranite; e.g. Homr Akarem, Homr Mikpid and Qash Amir). In these two groups, beryl occurs as stockwork greisen veins, greisen bodies, beryl‐bearing cassiterite ± wolframite quartz veins, dissemination, and miarolitic pegmatites. Beryl of the Be‐granitoids, particularly those of miarolitic pegmatites, contains appreciable contents of Fe, Na, and H2O. An important feature of the Be‐apogranites is the occurrence of white mica as the sole mafic mineral in the unaltered alkali feldspar granite in lower zones. Presence of white mica as volatile‐rich pockets suggests that the melt underwent disequilibrium crystallization, rapid nucleation rates, and exsolving and expulsion of volatiles.
Responses of methanogenic archaeal community to oxygen exposure in rice field soil
Authors: Yuan Yanli , Conrad Ralf , Lu Yahai
Published: June 2009

Methanogens are regarded as strict anaerobes and hence sensitive to O2 exposure. It has been demonstrated that CH4 production and emission from rice field soil are substantially reduced when soil is drained or aerated even shortly. However, the response of different methanogenic populations to O2 stress remains unclear. Therefore, we determined CH4 production and structure of the methanogenic community in a Chinese rice field soil after short‐term (24 h) and long‐term (72 h) exposure to O2 under laboratory conditions. O2 stress strongly inhibited CH4 production, and the inhibitory effect increased with the duration of O2 exposure. O2 exposure also resulted in dramatic increase of ferric iron and sulfate concentrations. H2 partial pressures were significantly reduced, most probably due to the competitive consumption by iron and sulfate‐reducing bacteria. However, substrate competition could not explain the inhibition of acetoclastic methanogenesis, since acetate accumulated after O2 exposure compared with the control. Quantitative (real‐time) PCR analyses of both archaeal 16S rRNA and mcrA genes (coding for alpha subunit of the methyl coenzyme M reductase) revealed that growth of the methanogenic populations was suppressed after O2 exposure. However, terminal restriction fragment length polymorphism (T‐RFLP) analyses of both 16S rDNA and 16S rRNA showed that the structure of the methanogenic archaeal community remained remarkably stable, and that acetoclastic Methanosarcinaceae were always dominant whether with or without O2 exposure. Thus, O2 stress apparently did not differentially affect the various methanogenic populations, but instead inhibited CH4 production by enabling competition, generally suppressing growth and differentially affecting existing enzyme activity.
On an Active Control for a Structurally Nonlinear Mechanical System, Taking Into Account an Energy Pumping
Authors: Costa S. N. J. , Balthazar J. M.
Published: June 2009

The purpose of this work is to investigate the control of the oscillations and the suppression of vibrations in damped and coupled oscillators. In this sense, we look into the potential of using a nonlinear energy sink in combination with an optimal linear control for nonlinear system to suppress structure vibrations under an impact load. As a result, we obtain that the nonlinear energy pumping (a one-way passive and almost irreversible energy flow from a linear main system to a nonlinear attachment that acts as a nonlinear energy sink) can be enhanced with the help of appropriate active control. The numerical results show the effectiveness of the approach presented here.
An Eigenvalue Problem for the Analysis of Variable Topology Mechanical Systems
Authors: Kövecses József , Font-Llagunes Josep M.
Published: June 2009

Mechanical systems with time-varying topology appear frequently in natural or human-made artificial systems. The nature of topology transitions is a key characteristic in the functioning of such systems. In this paper, we discuss a concept that can offer possibilities to gain insight and analyze topology transitions. This approach relies on the use of impulsive constraints and a formulation that makes it possible to decouple the dynamics at topology change. A key point is an eigenvalue problem that characterizes several aspects of energy and momentum transfer at the discontinuous topology transition.
Experiments on Quasiperiodic Wheel Shimmy
Authors: Takács Dénes , Stépán Gábor
Published: June 2009

The lateral vibration of towed wheels—so-called shimmy—is one of the most exciting phenomena of vehicle dynamics. We give a brief description of a simple rig of elastic tire that was constructed for laboratory measurements. A full report is given on the experimental investigation of this rig from the identification of system parameters to the validation of stability boundaries and vibration frequencies of shimmy motion. The experimental results confirm the validity of those tire models that include delay effects. A peculiar quasiperiodic oscillation detected during the experiments is explained by numerical simulations of the nonlinear time-delayed mathematical model.
Grain Boundary Diffusion of Hydrogen in Nano-Structured Pd/Ag Alloy Membranes
Authors: McLeod Logan S. , Degertekin Levent F. , Fedorov Andrei G.
Published: June 2009

Palladium and its alloys have long been used as hydrogen separation membranes due to their extremely high permeability and selectivity to hydrogen over all other gases [1]. The hydrogen permeation process begins with selective chemisorption of the gas onto the metal surface. As the adsorption process is the point in the permeation sequence where the majority of gases become excluded, it follows that a cleverly designed device could be created to take advantage of the so-called ‘fast’ diffusion paths of surface and grain-boundary diffusion to further enhance permeability without sacrificing selectivity. The contribution of grain-boundary diffusion to the overall permeation rate is dependent on the relative volume in the membrane occupied by grain-boundaries versus bulk material. Typically, grain boundaries only make up a miniscule fraction of the overall volume and therefore only contribute an appreciable amount to the overall diffusion process at temperatures low enough to make the bulk diffusion process nearly stagnant. However, in the case of a nanostructured membrane this paradigm is no longer valid. The fabrication methods associated with extremely thin membrane deposition typically lead to highly non-equilibrium microstructure with an average grain size on the order of tens of nanometers [2]. In order to exploit the potential advantages of grain boundary diffusion the nano-scale grains must persist throughout operation. To avoid the tendency for the grain structure to relax to a more equiaxed, coarse-grained morphology the self-diffusion of metal atoms in the film must be minimized by operating the membranes at a temperature much lower than the membrane melting temperature. Figure 1 shows the microstructural changes in a thin, sputtered, Pd/Ag alloy film before and after annealing. The initial fine-grained structure on the bottom surface of the membrane is due to a combination of low substrate temperature during deposition and the Ti adhesion layer onto which the Pd/Ag layer was deposited. After annealing at 400 C the grains have coarsened and the top and bottom structure are identical.
Multiscale Simulations of Thermoelectric Properties of PBTE
Authors: Qiu Bo , Bao Hua , Ruan Xiulin
Published: June 2009

In this paper, thermoelectric properties of bulk PbTe are calculated using first principles calculations and molecular dynamics simulations. The Full Potential Linearized Augmented Plane Wave (FP-LAPW) method is first employed to calculate the PbTe band structure. The transport coefficients (Seebeck coefficient, electrical conductivity, and electron thermal conductivity) are then computed using Boltzmann transport equation (BTE) under the constant relaxation time approximation. Interatomic pair potentials in the Buckingham form are also derived using ab initio effective charges and total energy data. The effective interatomic pair potentials give excellent results on equilibrium lattice parameters and elastic constants for PbTe. The lattice thermal conductivity of PbTe is then calculated using molecular dynamics simulations with the Green-Kubo method. In the end, the figure of merit of PbTe is computed revealing the thermoelectric capability of this material, and the multiscale simulation approach is shown to have the potential to identify novel thermoelectric materials.
Electron-Phonon Interaction and Joule Heating in Nanostructures
Authors: Pop Eric
Published: June 2009

The electron-phonon energy dissipation bottleneck is examined in silicon and carbon nanoscale devices. Monte Carlo simulations of Joule heating are used to investigate the spectrum of phonon emission in bulk and strained silicon. The generated phonon distributions are highly non-uniform in energy and momentum, although they can be approximately grouped into one third acoustic (AC) and two thirds optical phonons (OP) at high electric fields. The phonon dissipation is markedly different in strained silicon at low electric fields, where certain relaxation mechanisms are blocked by scattering selection rules. In very short (∼10 nm) silicon devices, electron and phonon transport is quasi-ballistic, and the heat generation domain is much displaced from the active device region, into the contact electrodes. The electron-phonon bottleneck is more severe in carbon nanotubes, where the optical phonon energy is three times higher than in silicon, and the electron-OP interaction is entirely dominant at high fields. Thus, persistent hot optical phonons are easily generated under Joule heating in single-walled carbon nanotubes suspended between two electrodes, in vacuum. This leads to negative differential conductance at high bias, light emission, and eventual breakdown. Conversely, optical and electrical measurements on such nanotubes can be used to gauge their thermal properties. The hot optical phonon effects appear less pronounced in suspended nanotubes immersed in an ambient gas, suggesting that phonons find relaxation pathways with the vibrational modes of the ambient gas molecules. Finally, hot optical phonons are least pronounced for carbon nanotube devices lying on dielectrics, where the OP modes can couple into the vibrational modes of the substrate. Such measurements and modeling suggest very interesting, non-equilibrium coupling between electrons and phonons in solid-state devices at nanometer length and picoseconds time scales.
Surface-Plasmon Enhanced Near-Bandgap Light Absorption in Silicon Photovoltaics
Authors: Hu Lu , Chen Xiaoyuan , Chen Gang
Published: June 2009

One key challenge for silicon-based solar cells is the weak absorption of long-wavelength photons near the bandgap (1.1eV) due to the indirect bandgap of silicon. A large fraction of the AM 1.5 solar spectrum falls into a regime (0.7 μm – 1.1 μm) where silicon does not absorb light well. The capture of these long-wavelength photons imposes a particular problem to the thin-film silicon solar cells. For this reason, thin-film silicon solar cells often incorporate some forms of light trapping mechanisms.
Enhancement of Pt-Based Catalysts via N-Doped Carbon Supports
Authors: O’Hayre Ryan , Zhou Yingke , Pasquarelli Robert , Berry Joe , Ginley David
Published: June 2009

This study experimentally examines the enhancement of carbon supported Pt-based catalysts systems via nitrogen doping. It has been reported that nitrogen-containing carbons promote significant enhancement in Pt/C catalyst activity and durability with respect to the methanol oxidation and oxygen reduction reactions. In order to systematically investigate the effect of N-doping, in this work we have developed geometrically well-defined model catalytic systems consisting of tunable assemblies of Pt catalyst nanoparticles deposited onto both N-doped and undoped highly-oriented pyrolytic graphite (HOPG) substrates. N-doping was achieved via ion beam implantation, and Pt was electrodeposited from solutions of H2PtCl6 in aqueous HClO4. Morphology from scanning electron microscopy (SEM) and catalytic activity measurement from aqueous electrochemical analysis were utilized to examine the N-doping effects. The results strongly support the theory that doping nitrogen into a graphite support significantly affects both the morphology and behavior of the overlying Pt nanoparticles. In particular, nitrogen-doping was observed to cause a significant decrease in the average Pt nanoparticle size, an increase in the Pt nanoparticle dispersion, and a significant increase in catalytic activity for both methanol oxidation and oxygen reduction.
Stiffness Optimization of Hollow Cylindrical Rolling Element Bearing
Authors: Darji P. H. , Vakharia D. P.
Published: June 2009

Since being originally introduced, cylindrical rolling element bearings have been significantly improved, in terms of their performance and working life. A major objective has been to decrease the Hertz contact stresses at the roller–raceway interfaces, because these are the most heavily stressed areas in a bearing. It has been shown that bearing life is inversely proportional to the stress raised to the ninth power (even higher). Investigators have proposed that under large normal loads a hollow element with a sufficiently thin wall thickness will deflect appreciably more than a solid element of the same size. An improvement in load distribution and thus load capacity may be realized, as well as contact stress is also reduced considerably by using a bearing with hollow rolling elements. Since for hollow rolling element no method is available for the calculation of contact stresses and deformation. The contact stresses in hollow members are often calculated by using the same equations and procedures as for solid specimens. This approach seems to be incorrect. Recently, the Finite Element Analysis (FEA) has been successfully used to evaluate contact problems for the roller bearings. Investigations have been made for hollow rollers in pure normal loading. Different hollowness percentages ranging from 0% to 90% have been analysed in FEA software to find the optimum percentage hollowness which gives minimum stress and finally longest fatigue life.
Numerical Simulation of Touchdown/Takeoff Hysterisis of Spherical Pad Slider by Considering the Liquid Bridge Between the Slider and Lubricant-Disk
Authors: Li Hui , Li Jianhua , Xu Junguo , Shimizu Yuki , Ono Kyosuke , Yoshida Shinobu
Published: June 2009

This work carries on a numerical simulation of the touchdown/takeoff (TD/TO) hysterisis of the spherical pad slider. It numerically studies the meniscus bridge’s formation and meniscus force interaction between the spherical pad and lubricant over the disk surface. It proposes a geometry model for the lubricant bridge, and correspondingly, a force model for the meniscus force acting on the spherical pad slider due to the lubricant bridge. By solving the liquid balance state at the meniscus boundary, it obtains the geometry of the liquid bridge. A parametric study is done to study the effects of the geometry of spherical pad, Hamaker constant of lubricant-disk, and surface energy of lubricant on the formation of the liquid bridge. The overflow phenomenon is analyzed to find out the acceptable dimension of the spherical pad design. Moreover, a three-dimensional (3D) model of spherical pad slider/disk interface is built to study the steady-state flying of the spherical pad slider. The different parameters are analyzed to study their effects on the TD/TO hysteresis.
The Effect of Boron Nitride Lubricant Thickness and Steel Surface Condition on Tribological Behavior of P20 Steel/5083 Aluminum Sliding Pairs at High Temperature
Authors: Hanna M. David , Franetovic Vjekoslav
Published: June 2009

The tribological behavior of AA5083 aluminum sheet sliding against tool steel impacts the quality of components manufactured with the Quick Plastic Forming (QPF) process. The effect of boron nitride lubricant thickness on the tribological performance of different coated steel/AA5083 pairs utilizing a recently developed reciprocating flat-on-flat tribological test technique was investigated. In most cases of coated and uncoated steel, the time-to-contact increased by a factor of ten when the BN thickness was increased from 8.4 μm to 14.5 μm. The tribological tests with a low sliding speed method (0.1 Hz) confirmed the previous observations conducted at 0.5 Hz in which nitrocarburizing of the tool surface decreased adhesion of aluminum to the steel during sliding contact.
Synergistic Antiwear Effects of Zinc Dialkyl Dithiophosphate and Different Detergents
Authors: Pennecot G. , Komvopoulos K. , Yamaguchi E. S.
Published: June 2009

The effectiveness of blends consisting of base oil, some secondary zinc dialkyl dithiophosphate (ZDDP), and different detergents to form antiwear tribofilms on steel surfaces sliding in the boundary lubrication regime was investigated in the temperature range of 105–125°C. The efficacy of the tribofilms formed from these blends was evaluated in terms of contact voltage and wear rate measurements. The best antiwear performance was demonstrated by the tribofilm formed from the blend containing sulphonate detergent. The results of this study provide insight into competing effects between ZDDP and different detergents that affect significantly the antiwear performance of the formed tribofilms.
Understanding to Read/Write Signal Modulation Due to Lube Droplet at Head Disk Interface
Authors: Li Jianhua , Xu Junguo
Published: June 2009

To understand the cause of read/write error due to lube accumulation, a model to simulate the slider’s response to “soft contact”, which can occur between a lubricant droplet on the disk and a slider, was developed. The contact impact model is based on the water-hammer pressure model with an additional damping force, where the wave-shock pressure is assumed to function as the soft contact pressure, and the damping force defines the damping characteristics of the impact which are due to the lubricant’s high viscosity. This modeling and simulation are helpful to us in understanding the read/write signal loss due to a lube droplet at head disk interface.
Oilflow Interaction of Engine Bearings
Authors: Backhaus Katja , Knoll Gunter
Published: June 2009

To improve calculation of the oil supply to the main and conrod bearings in the combustion engine, it is possible to simulate plain bearings on a coupled elasto-hydrodynamic basis while allowing for partial-fill states. In an effort to advance the extended simulation technique, software has been developed by the Institute for Machine Components and Design (IMK) at the University of Kassel and validated in experiments. This paper describes the simulation software that has been developed, including the resultant findings on the lubricating oil requirement.
A Simple Model of the Entrainment of Particles in a Gap Considering Elasticity
Authors: Zhong Zhenyuan , Zhang Youyun , Han Haiyan
Published: June 2009

Many researches are conducted on the effect of particles on lubricated friction and wear of contact surfaces, which shows that particles between two contact surfaces increase lubricated friction and do a great effect to the wear of two sliding surfaces. Similar phenomena also occur when a hard containment particle is being entrained into the lubricated contact. This paper presents a simple two dimensional model which describes the entrainment of particles in a gap. Considering elasticity of the sliding surfaces, the model treats conditions under which a spherical particle of size d can be entrained into a gap between a sliding surface and a fixed plane surface. These conditions are determined by size of the particles, d, and friction coefficients between the particle and the sliding surface, and the particle and the plane, denoted by μs and μp respectively. For the particles to be entrained into the contact, this model predicts the maximum of particles size and the relationship of μs and μp.
An Overview of Passive Magnetic Bearings
Authors: Samanta Pranab , Hirani Harish
Published: June 2009

This paper describes different passive magnetic bearing configurations and associated pros and cons. It details the techniques used by different inventors to overcome the limitations of passive magnetic bearing, such as low damping, low stiffness and its inherent instability. To overcome these limitations different hybridization techniques used by different researchers have been illustrated. Finally, a new hybrid bearing configuration invented by the authors has been described.
Lubricating Characteristics of Fluorine Grease Containing Silica Nanoparticles
Authors: Hokao Michita , Yokouchi Atsushi
Published: June 2009

Electrical motor bearings for use in automotive control units are sometimes exposed to high-temperature operating conditions. Therefore, these bearings are sometimes packed with fluorine grease in order to meet the demand for long service life performance. In recent years, there is growing demand for lower initial torque in these same bearings without sacrificing service life performance. This paper describes the effects of fluorine grease containing silica nanoparticles on initial bearing torque of electrical motor bearings. Silica nanoparticles are effective in helping to reduce amounts of initial bearing torque and help stabilize bearing torque due to improved channeling characteristics.
Optimization of Groove Geometry for Thrust Air Bearing According to Various Objective Functions
Authors: Hashimoto Hiromu , Ochiai Masayuki , Namba Tadashi
Published: June 2009

Grooved thrust air bearings are widely used to support high-speed, low-loaded shafts in many rotating systems because of their low friction, noiseless operation, and simple structure. Several types of groove geometries, such as straight line, spiral, and herringbone, are commonly used in actual applications. Among them the spiral groove is mainly used. However, as far as the authors know, there is no theoretical evidence that the spiral groove is an optimized groove geometry in all possible groove geometries. This paper describes the optimum design for the groove geometry of thrust air bearings according to various objective functions, such as air film thickness, bearing torque, dynamic stiffness of air film, and combinations of same. In an optimum design, groove geometries are expressed by the third degrees of spline function, and sequential quadratic programming is used as the optimization method. We found that groove geometry optimizing air film thickness or friction torque takes the form of a spiral groove. The geometry optimizing the dynamic stiffness is the modified spiral groove. Some numerical results are compared with the measured data, and good agreements can be seen between them.
An Experimental Investigation on Friction Coefficient in Plain Journal Bearings During Start-Up
Authors: Bouyer J. , Fillon M.
Published: June 2009

The start-up friction coefficient is a parameter which is very useful for engineers who design hydrodynamic bearings. It is most often issued from an approximation. Several studies can be found in the literature on this topic but most of them are concerned with air bearings or are only numerical. Some studies are more general and deal with the transient thermal behaviour in journal bearings as well as in thrust bearings. Other studies deal with the friction coefficient during running, at a fixed rotational speed. The aim of this study is to provide experimental measurements of the bush torque during start-up of plain journal bearings, varying the specific pressure. Thus, the friction coefficient at start-up (deduced from measurements) is obtained for four different bearings varying feeding conditions, radial clearance and length.
Contact Mechanism of Tribological Coatings With Columnar Microstructure
Authors: Kang Young Sup , Evans Ryan D. , Doll Gary L.
Published: June 2009

Tribological coatings for mechanical components such as bearings and gears can experience failure occurring at the surface for highly localized contact conditions. In the present study, a finite element analysis (FEA) model was developed to study the stress distribution and deformation of tungsten carbide reinforced amorphous hydrocarbon coatings with and without columnar microstructures under nanoindentation. Results show that the microstructure of these tribological coatings significantly influences the stress distribution and deformation under heavily loaded conditions.
Frictional Characteristics of Polytetrafluoroethylene (PTFE) Thin Films Deposited by Hot Filament – Chemical Vapor Deposition (HFCVD)
Authors: Karnath Michael A. , White Aleksandr J. , Mu¨ftu¨ Sinan
Published: June 2009

Frictional characteristics of PTFE films deposited by HFCVD method on glass substrates were determined using ball-on-flat and ball-on-disk configurations. Optical microscopy was used to examine the surface profile of the PTFE films left by the UMT after the tests. In general, the COF of the HFCVD-PTFE thin films on glass decreases at low sliding speeds and high loads. Limited number of durability tests show that the COF stabilizes to a fixed value different than the initial one. Based on the results of the tests conducted in this work, it is concluded that the PTFE films deposited by HFCVD display the similar properties to bulk PTFE.
Numerical Analysis on Lubrication Characteristics of Nanometer Gas Film in Hard Disk Drive
Authors: Yao Hua-Ping , Wu Yan-Hua , Ping Huang
Published: June 2009

In this paper, a new numerical scheme to analyze the characteristics of the nanometer gas film in hard disk drive is presented based on the modified Reynolds equation with the FK-Boltzmann modified modeling. It is well known that the great high bearing number can lead to divergence in the conventional finite difference method. As to the existence of the variable pressure in the Couette flow terms in the equation, it was proposed to discretize equation by taking the Couette flow term as the dominating ones in iterative process. In addition, a special treatment by using weighting flow factor for the abrupt change of film thickness was proposed. It was presented that the result using this new scheme was close to the analytic solution. Using this new method to analyze several sliders, the pressure distribution of every slider can be successfully obtained with well convergence property, which indicated that this new scheme is a correct and stable numerical method.
Nanorheological Measurement of Monolayer Lubricant Films Using the Oscillating Optical Fiber Probe
Authors: Hamamoto Yuya , Itoh Shintaro , Fukuzawa Kenji , Zhang Hedong
Published: June 2009

We achieved a viscoelastic measurement of monolayer lubricant films using the fiber wobbling method, which is the highly sensitive shear force measuring method that we have developed. In order to make the measurement possible, we attained the accurate determination of nanometer-sized gap widths between sliding surfaces. In addition, we developed a new method to align the parallelism between the sliding surfaces. We observed the differences in the mechanical responses of sheared lubricant films due to their adsorptivity to the substrate surfaces.
Anisotropic Frictional Behavior of Nanotextured Surfaces
Authors: Zhang H.-S. , Komvopoulos K.
Published: June 2009

Silicon wafers were exposed to an oblique Ar+ ion beam to create arrays of surface ripples. Atomic force microscope (AFM) imaging revealed that the rippled (textured) surfaces exhibited highly anisotropic morphologies. Nanoscale friction experiments performed with different diamond tips illustrated a dependence of the coefficient of friction on tip radius, normal load, and sliding direction. Changes in the coefficient of friction are interpreted in terms of the applied normal load and varying contributions of the adhesion friction mechanism.
Misalignment Effect on Cement Kiln Support Bearing
Authors: Samanta P. , Chakrabarti Barun , Herwadkar S. V.
Published: June 2009

This paper illustrates the effect of misalignment on performance of cement kiln partial journal bearing. The performance parameters include minimum film thickness, load carrying capacity, power loss and dynamic coefficients such as elastic coefficients and damping coefficients. The bearing analyses have been carried out using a commercial rotor dynamics software package.
Dynamic Analysis of Minimally Lubricated Ball Bearings for Space Applications
Authors: Nogi T. , Maniwa K. , Obara S.
Published: June 2009

A computer program for dynamic analysis of ball bearings, in which a simple mixed lubrication model for the retainer/race and retainer/ball contact is incorporated, is developed and retainer instability in reaction wheel bearings is investigated. Results show that an increase in the amount of oil promotes the instability and that a retainer with rectangular pockets is more stable than one with circular pockets.
Prototype Design of a High-Speed Viscous Air Spindle
Authors: Delhaes Guido M. J. , van Beek Anton , van Ostayen Ron A. J. , Munnig Schmidt Robert H.
Published: June 2009

In this paper an innovative air driven spindle for micro cutting applications is presented. The spindle uses a viscous traction concept which has the advantage that the viscous traction forces can act directly on the cylindrical part of the tool, which makes the tool-holder redundant. Furthermore, the tool can be actuated in the axial direction within the housing. In this paper the concept of the viscous turbine, a design of a prototype spindle along with the traction and load-capacity of the spindle are discussed.
Determination of the Corrosiveness of a Lubricating Oil by a Corrosion Sensor
Authors: Schneidhofer C. , Doerr N. , Jakoby B.
Published: June 2009

The degree of acidification is considered a crucial property of lubricating oils for some applications, e.g. gas engines, as corrosive wear of machine components may be caused by acidic contaminations. For this reason, a sensor concept using the effect of material loss of a thin metal film due to corrosion is proposed. The corrosion of these films prepared from lead has been monitored electrically. In laboratory tests, the sensors were immersed in a series of oils characterized by different types and amounts of acidic components. The usefulness of the proposed sensor concept is also illustrated by corrosion tests with used oil samples taken from engines. The experiments clearly showed a correlation of corrosion rate with acidification expressed as TAN.
Optimization of Hydrodynamic Sliders for Multiple Operating Conditions
Authors: van Ostayen Ron A. J. , van Beek Anton , Munnig Schmidt Robert H.
Published: June 2009

We present a new method to determine the film height distribution of the load-optimal hydrodynamic slider for multiple operating conditions. The use of the method is demonstrated in two examples, the second of which is based on the load conditions in an artificial hip-joint during a standard walking cycle. The results of this optimization may lead to an improved design of the replacement hip-joint, resulting in less wear and an improved lifespan.
Environmental Performance Limits of Ultrananocrystalline Diamond Films
Authors: Hamilton Matthew A. , Konicek Andrew R. , Grierson David S. , Sumant A. V. , Auciello Orlando , Sawyer W. Gregory , Carpick Robert W.
Published: June 2009

Recent improvements in growth methodologies have decreased the grain sizes and thicknesses of polycrystalline diamond films to the nanometer range, while also increasing the film uniformity and growth rate and preserving the outstanding mechanical properties of diamond. This is rendering such films more technologically and commercially viable. Ultrananocrystalline diamond (UNCD) are the thinnest (<200 nm) and smoothest (Rq < 10 nm) diamond films available.[1] These films demonstrated self-mated friction coefficients as low as near frictionless carbon (μ < 0.007) in environments with sufficient humidity, and the corresponding wear rates could not be measured using scanning white-light interferometry. However, their response to environmental conditions (e.g. relative humidity, ambient species, velocity, and temperature) had not been systematically explored in the past. This study focused on identifying conditions that contribute to favorable tribological performance. We find low friction performance at humidity levels below 1.5% in both nitrogen and argon environments.
Contact Hysteresis Design Considerations of High Thermal Actuation Efficiency Sliders
Authors: Kim Dongman , Sullivan Michael T. , Zhang Shuyu
Published: June 2009

Pushing recording density toward 1TB/in2 and beyond requires a stable head disk magnetic recording system with 3–4nm head disk spacing. Air bearing design strategy with respect to thermally actuated writer / reader elements is investigated in this work. The goal is to significantly increase stability of the head-disk spacing for ultra-low flying height recording systems. Investigations presented in this paper indicate that placement of the air bearing pressure concentration location is an effective approach for achieving flying height stability. Proper placement can reduce the disturbance due to short range interaction forces. It was also found that lower viscosity lubricant systems exhibit less interaction disturbance during contact hysteresis characterization while controlling ambient air pressure.