bluuebunny/crossref_metadata_2025 huggingface dataset:
The Work‐Up and Management of Patients with Apparent or Subclinical Cardiac Sarcoidosis: With Emphasis on the Associated Heart Rhythm Abnormalities
Authors: SOEJIMA KYOKO , YADA HIROTAKA
Published: January 2009

In patients with newly diagnosed AV block and/or ventricular tachycardia, cardiac sarcoidosis should always be considered in the differential diagnosis. In addition to the pacemaker implant, cardiac resynchronization therapy (CRT) should be selected for severe heart failure patients who have class III or IV heart failure, LVEF ≤35%, and a complete LBBB pattern. If the disease activity is high, corticosteroid therapy is recommended. Patients with extracardiac sarcoidosis need to be closely followed for potential cardiac involvement, as the mortality in sarcoidosis depends on cardiac involvement. Early diagnosis and treatment of cardiac sarcoidosis is essential. Positron emission tomography (PET) and cardiac magnetic resonance imaging (MRI) are considered to have high sensitivity for cardiac involvement, and are the preferred imaging modalities. However, even in the era of new technology, such as PET and cardiac MRI, early diagnosis of cardiac sarcoidosis is still difficult.
MRI assessment of liver iron content in thalassamic patients with three different protocols: comparisons and correlations
Authors: Christoforidis Athanasios , Perifanis Vassilios , Spanos George , Vlachaki Efthimia , Economou Marina , Tsatra Ioanna , Athanassiou‐Metaxa Miranda
Published: January 2009

Our aim was to assess liver iron content, in thalassaemic patients, by using three different MR protocols and compare their data. Ninety‐four thalassaemic patients (44 M and 50 F, mean age 25.82 ± 8.3 yrs), were enrolled in the study. In each patient, three measurements of the liver iron content were performed, with the use of a single imager, equipped with a 1.5 Tesla magnet. Liver R2* was measured on gradient‐echo sequence. Calculation of MR‐HIC values was based on an algorithm using liver to muscle (L/M) ratios in five axial gradient‐echo sequences. Finally, determination of liver R2 employed a 16‐echo, spin‐echo pulse sequence. Additionally, myocardial R2* value was determined for each patient. Results showed that all three magnetic resonance imaging (MRI) methods were highly correlated to each other and significantly correlated to serum ferritin concentrations. Liver R2 method showed an increased sensitivity in detecting liver iron contents in the upper range. No correlation occurred between each liver MRI parameter and myocardial R2* values. Finally, we managed to provide formulae for equating values obtaining with any of these three MRI methods.
Conventional cytogenetics in myelofibrosis: literature review and discussion
Authors: Hussein Kebede , Van Dyke Daniel L. , Tefferi Ayalew
Published: January 2009

The clinical phenotype of myelofibrosis (MF) is recognized either de novo (primary) or in the setting of polycythemia vera (post‐PV) or essential thrombocythemia (post‐ET). Approximately one‐third of patients with primary MF (PMF) present with cytogenetic abnormalities; the most frequent are del(20q), del(13q), trisomy 8 and 9, and abnormalities of chromosome 1 including duplication 1q. Other less frequent lesions include −7/del(7q), del(5q), del(12p), +21 and der(6)t(1;6)(q21;p21.3). In general, cytogenetic abnormalities are qualitatively similar among PMF, post‐ET MF and post‐PV MF although their individual frequencies may differ. Based on prognostic effect, cytogenetic findings in MF are classified as either ‘favorable’ or ‘unfavorable’. The former include normal karyotype or isolated del(20q) or del(13q) and the latter all other abnormalities. Unfavorable cytogenetic profile in both PMF and post‐PV/ET MF confers an independent adverse effect on survival; it is also associated with higher JAK2V617F mutational frequency. In addition to their prognostic value, cytogenetic studies in MF ensure diagnostic exclusion of other myeloid neoplasms that are sometimes associated with bone marrow fibrosis (e.g. BCR‐ABL1‐positive or PDGFRB‐rearranged) and also assist in specific treatment selection (e.g. lenalidomide therapy is active in MF associated with del(5q).
Complex epileptic (Foix–Chavany–Marie like) syndrome in a child with neurofibromatosis type 1 (NF1) and bilateral (opercular and paracentral) polymicrogyria
Authors: Mastrangelo Mario , Mariani Rosanna , Spalice Alberto , Ruggieri Martino , Iannetti Paola
Published: January 2009

The association of brain malformations and symptomatic epilepsy in the setting of neurofibromatosis type 1 (NF1) is rarely reported. When it occurs, patients can present clinically with infantile spasms, focal seizures, generalized tonic clonic seizures or atypical absences. We report on a 10‐year‐old (molecularly proven) NF1 girl manifesting a complex epileptic syndrome resembling the Foix–Chavany–Marie spectrum (also known as opercular syndrome) associated with bilateral (opercular and paracentral lobular) polymicrogyria (PMG). Anecdotal cases of unilateral PMG in the setting of NF1 have been described in association with other‐than‐opercular epileptic syndromes. The typical clinical opercular syndrome consisting in mild mental retardation, epilepsy and pseudobulbar palsy is usually associated to bilateral perisylvian PMG (BPP)

Conclusion: To the best of our knowledge, the complex epileptic syndrome hereby reported has not been previously recorded in the setting of NF1. In addition, the present girl manifested all the clinical features of an opercular syndrome but had an asymmetrical PMG (not a BPP).
Factors associated with sclerema in infants with diarrhoeal disease: a matched case‐control study
Authors: Chisti Mohammod Jobayer , Ahmed Tahmeed , Faruque Abu Syed Golam , Saha Shuvra , Salam Mohammed Abdus , Islam Sufia
Published: January 2009

Aim: To identify clinical and biochemical factors associated with sclerema in infants with diarrhoeal illness, and their outcome.

Methods: In this case‐control study, we enrolled 30 infants with clinical sepsis with sclerema (cases) and another 60, age‐ and sex‐matched infants with clinical sepsis but without sclerema (controls) from among those admitted to the special care unit (SCU) and longer stay unit (LSU) of the Dhaka Hospital of International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B) for their diarrhoeal illness from May 2005 through April 2006. Sclerema as the dependant variable while hypoxia, hypothermia, C‐reactive protein (CRP) level, serum total protein and prealbumin level were the major independent variables compared in the analysis. Differences in proportions were compared by the chi‐square test and differences of mean were compared by Student's t‐test or Mann–Whitney test, as appropriate.

Results: The case‐fatality was significantly higher among the cases than the controls (30% vs. 2%, CI 2.9–565.5). After adjusting for confounders, infants with sclerema were more likely to be hypothermic (OR 11.6, 95% CI 1.1–126.5), and have lower serum total protein (OR 1.12, 95% CI 1.04–1.21) and prealbumin (OR 1.5, 95% CI 1.1–2.3).

Conclusion: Diarrhoeal infants having clinical sepsis presenting with hypothermia, lower serum protein and prealbumin are prone to be associated with sclerema.
Comparative analysis of global gene expression profiles between diabetic rat wounds treated with vacuum‐assisted closure therapy, moist wound healing or gauze under suction
Authors: Derrick Kathleen L , Norbury Kenneth , Kieswetter Kris , Skaf Jihad , McNulty Amy K
Published: January 2009

How differential gene expression affects wound healing is not well understood. In this study, Zucker diabetic fatty (fa/fa) male inbred rats were used to investigate gene expression during wound healing in an impaired wound‐healing model. Whole genome microarray surveys were used to gain insight into the biological pathways and healing processes in acute excisional wounds treated with vacuum‐assisted closure (V.A.C.®) Therapy, moist wound healing (MWH) or gauze under suction (GUS). Global gene expression analyses after 2 days of healing indicated major differences with respect to both number of genes showing fold changes and pathway regulation between the three different wound treatments. Statistical analysis of expression profiles indicated that 5072 genes showed a >1·6‐fold change with V.A.C. Therapy compared with 3601 genes with MWH and 3952 genes with GUS. Pathways and related genes associated with the early phases of wound healing diverged between treatment groups. For example, pathways involving angiogenesis, cytoskeletal regulation and inflammation were associated with elevated gene expression following V.A.C. Therapy. This study is the first to assess wound healing by whole genome interrogation in a diabetic rat model treated with different healing modalities.
MENGZI AND RECENT SCHOLARSHIP
Authors: Kline T. C.
Published: January 2009

Book reviewed in this article:

MENCIUS: CONTEXT AND INTERPRETATIONS Edited by Alan K. L. Chan

ESSAYS ON THE MORAL PHILOSOPHY OF MENGZI Edited by Xiusheng Liu and Philip J. Ivanhoe
NISHIDA IN CONTEXT
Authors: McCarrhy Erin
Published: January 2009

Book reviewed in this article:

ZEN AND PHILOSOPHY: AN INTELLECTUAL BIOGRAPHY OF NISHIDA KITARO By Michiko Yusa

PHILOSOPHERS OF NOTHINGNESS: AN ESSAY ON THE KYOTO SCHOOL By James W. Heisig

BEYOND PERSONAL IDENTITY: DOGEN, NISHIDA AND A PHENOMENOLOGY OF NO‐SELF By Gereon Kopf
FROM THEOLOGICAL TO CINEMATIC CRITICISM: EXTRICATING THE STUDY OF RELIGION AND FILM FROM THEOLOGY
Authors: Kraemer Christine Hoff
Published: January 2009

Book reviewed in this article:

RELIGION IN FILM Edited by John R. May and Michael S. Bird Knoxville

NEW IMAGE OF RELIGIOUS FILM Edited by John R. May

SCREENING THE SACRED: RELIGION, MYTH, AND IDEOLOGY IN POPULAR AMERICAN FILM Edited by Joel W. Martin and Conrad Eugene Ostwalt, Jr.

SEEING AND BELIEVING: RELIGION AND VALUES IN THE MOVIES By Margaret Miles

REEL SPIRITUALITY: THEOLOGY AND FILM IN DIALOGUE By Robert K. Johnston Grand

SCREENING SCRIPTURE: INTERTEXTUAL CONNECTIONS BETWEEN SCRIPTURE AND FILM Edited by George Aichele and Richard G. Walsh Harrisburg

HOW HYSTERICAL: IDENTIFICATION AND RESISTANCE IN THE BIBLE AND FILM By Erin Runions

FILM AS RELIGION: MYTHS, MORALS, AND RITUALS By John C. Lyden
THE REDISCOVERY OF AMERICAN SACRED SPACES
Authors: Nelson Louis P.
Published: January 2009

Book reviewed in this article:

THE HERMENEUTICS OF SACRED ARCHITECTURE: EXPERIENCE, INTERPRETATION, COMPARISON (2 volumes) By Lindsay Jones

TEMPLES OF GRACE: THE MATERIAL TRANSFORMATION OF CONNECTICUT'S CHURCHES, 1790–1840 By Gretchen Buggeln

WHEN CHURCH BECAME THEATRE: THE TRANSFORMATION OF EVANGELICAL ARCHITECTURE AND WORSHIP IN THE NINETEENTH‐CENTURY AMERICA By Jeanne Kilde

PRAYERS IN STONE: CHRISTIAN SCIENCE ARCHITECTURE IN THE UNITED STATES, 1894–1930 By Paul Eli Ivey

SHUL WITH A POOL: THE “SYNAGOGUE‐CENTER” IN AMERICAN JEWISH HISTORY By David Kaufman

MYTHS IN STONE: RELIGIOUS DIMENSIONS OF WASHINGTON, D.C. By Jeffrey F. Meyer

UGLY AS SIN: WHY THEY CHANGED OUR CHURCHES FROM SACRED PLACES TO MEETING SPACES AND HOW WE CAN CHANGE THEM BACK AGAIN By Michael S. Rose

BUILDING FROM BELIEF: ADVANCE, RETREAT, AND COMPROMISE IN THE REMAKING OF CATHOLIC CHURCH ARCHITECTURE By Michael E. DeSanctis

ARCHITECTURE IN COMMUNION: IMPLEMENTING THE SECOND VATICAN COUNCIL THROUGH LITURGY AND ARCHITECTURE By Steven J. Schloeder
Erythrocyte 2,3‐DPG, PO250% and available O2 during the early post‐natal fall in hemoglobin in rabbits
Authors: HOLTER P. H. , HALVORSEN S. , REFSUM H. E.
Published: January 2009

Erythrocyte 2,3‐DPG, PO250%, whole blood hemoglobin and available O2, and fixed acid Bohr effect were studied during the first 10 days after birth in rapidly growing suckling rabbits. The post‐natal fall in hemoglobin concentration was accompanied by a marked rise in erythrocyte 2,3‐DPG and a gradual increase in PO250%. The rise in PO250% was sufficient to keep the available O2 of the blood unchanged throughout the observation period. The observations show that a 2,3‐DPG mediated rise in PO250% very effectively contributes to maintenance of adequate tissue oxygenation during the post‐natal fall in hemoglobin. The rise in 2,3‐DPG and PO250% may be due to the ordinary hypoxia‐induced shift to the right of the hemoglobin O2 dissociation curve, as observed under other circumstances when blood hemoglobin is rapidly reduced, but the very marked rise in 2,3‐DPG and the very low Δ PO250%/Δ 2,3‐DPG ratio suggest that the rise may as well be due to hypoxia independent, pre‐programmed processes. The fixed acid Bohr effect was essentially the same in newborn and adult rabbits, and was uninfluenced by large variations in 2,3‐DPG.
Blood‐brain barrier permeability and immobilization stress
Authors: BELOVA T. I. , JONSSON G.
Published: January 2009

The regional capacity of the blood‐brain barrier (BBB) has been investigated in rat brain during normal conditions and after acute immobilization (IMO). The BBB function was monitored by fluorescence microscopical localization of systemically administered vital dye (trypan blue) and by studying the ability of the brain capillaries to decarboxylate and trap injected L‐DOPA. The results demonstrated clear signs of dye penetration into the parenchyma of certain brain regions (area preoptica, some hypothalamic nuclei, area ventralis tegmenti and ventral part of the pons and medulla oblongata) in addition to the areas known to be ‘outside the BBB’ (the circumventricular organ). There was an apparent increase in dye penetration in these regions after IMO, most pronounced in the reticular formation of the brain stem. In the mesencephalic reticular formation ruptures of a substantial number of vessels occurred after IMO leading to massive leakage of dye into surrounding brain parenchyma. The main finding after L‐DOPA administration was indications of a more efficient decarboxylation and trapping of L‐DOPA in most brain regions after IMO. The findings of dye penetration in certain brain regions, which are known to be involved in autonomic regulation, may reflect possible ways of chemical communication between the circulation and neuronal structures in these regions and/or possibly constitute the basis for inactivation processes for transport of substances outwards from the brain as well as potential loci for adverse effects and development of pathological conditions.
Importance of zinc for human sperm head‐tail connection
Authors: BJÖRNDAHL LARS , KVIST ULRIK
Published: January 2009

Head‐tail detachment of ejaculated human spermatozoa was studied with phase contrast microscopy. The frequency of head‐tail detachment was assessed after sperm exposure to the anionic detergent sodium dodecyl sulfate (SDS) for 60 min at 22°C. Decapitation was enhanced by EDTA. Zinc reversibly inhibited native as well as EDTA induced head‐tail disconnection. Still a certain proportion of spermatozoa were resistant to EDTA‐treatment and this proportion significantly increased upon 24 h of saline storage. The development of EDTA resistance was enhanced by EDTA treatment before storage. A physiological role for zinc as a preserver of an inherent mechanism for head‐tail detachment is suggested.
Improvement of reading speed after providing of low vision aids in patients with age‐related macular degeneration
Authors: Nguyen Nhung Xuan , Weismann Malte , Trauzettel‐Klosinski Susanne
Published: January 2009

Purpose:  Age‐related macular degeneration (AMD) is the most common cause of severe visual impairment, including loss of reading ability, among elderly persons in developed countries. The aim of the present study was to evaluate reading ability before and after providing of appropriate low vision aids.

Methods:  Five hundred and thirty patients with different stages of AMD (age 82 ± 8 years) were included in this retrospective study. All patients underwent a standardized ophthalmological examination including evaluation of magnification requirement and careful providing of low vision aids. Before and after the provision of low vision aids, reading speed [words per minute (wpm)] was evaluated using standardized reading texts.

Results:  For the whole group, the average best‐corrected distance visual acuity of the better eye was 0.18 ± 0.15, with 69% of patients having visual acuity of 0.1 (20/200) or better. The mean magnification requirement was 7.4 ± 6.3‐fold (range 2–25). Visual rehabilitation was achieved with optical visual aids in 58% of patients, whereas 42% of patients needed electronically closed‐circuit TV systems. Mean reading speed was 20 ± 33 wpm before and increased significantly to 72 ± 35 (p < 0.0001) after the provision of low vision aids for the whole group. Between patients with visual acuity < 0.1 and patients with visual acuity of 0.1 or better, there are highly significant differences in reading speed before (0.4 ± 3.8 versus 20 ± 28 wpm, p ≤ 0.0001) and after providing of visual aids (40 ± 13 versus 84 ± 30 wpm, p ≤ 0.0001). Patients with severe visual impairment (visual acuity ≤ 0.1) showed significantly lower improvement of reading speed compared to patients with visual acuity of 0.1 or better following rehabilitation (p ≤ 0.0001). Before providing of low vision aids, only 16% of patients were able to read; in contrast, reading ability was achieved in 94% of patients after the provision of low vision aids for the whole group.

Conclusion:  Our results indicate the great value of low vision rehabilitation through adequate providing of vision aids for the improvement of reading ability, with a highly significant increase of reading speed without training of eccentric viewing in patients with retained central fixation. The prompt implementation of low vision aids in patients with macular degeneration will help them to maintain and regain their reading ability, which can lead to an increase in independence, communication, mental agility and quality of life.
Optic nerve hypoplasia in North America: a re‐appraisal of perinatal risk factors
Authors: Garcia‐Filion Pamela , Fink Cassandra , Geffner Mitchell E. , Borchert Mark
Published: January 2009

Purpose:  The purpose of this study is to describe and clarify the birth and prenatal characteristics of a large cohort of children with optic nerve hypoplasia.

Methods:  This is a descriptive report of 204 patients aged ≤ 36 months and enrolled in a prospective study at the Children’s Hospital Los Angeles. Birth characteristics, including complications, were abstracted from study files and medical records. Systematic maternal interviews were conducted to obtain detailed prenatal histories. National birth data were used for comparison with birth findings.

Results:  Birth characteristics were unremarkable for birthweight and gestation, but significant for increased frequency of caesarean delivery and fetal and neonatal complications. Young maternal age and primaparity were dominating maternal features. Preterm labour, gestational vaginal bleeding, low maternal weight gain and weight loss during pregnancy were prevalent.

Conclusions:  These findings confirm young maternal age and primaparity as associated risk factors, challenge many other suggested factors such as alcohol and drug abuse, and introduce potentially significant prenatal characteristics such as maternal weight loss and early gestational vaginal bleeding as aetiological correlates.
Comparison and Optimization of Heliostat Canting Methods
Authors: Buck R. , Teufel E.
Published: January 2009

Heliostat canting (alignment of mirror facets) is known to have a major influence on the optical efficiency of heliostat fields and therefore on the power output of solar tower plants. In recent years several canting concepts were used, mainly on- and off-axis canting. Several new canting concepts, such as stretched-parabolic or target-aligned canting, were proposed in order to improve the performance of heliostats. As solar power plants become economically more attractive, knowledge about the influence of canting becomes more important. In this context, the influence of several factors on the canting method is discussed and optimal canting strategies are described. The considered factors comprise plant power level, heliostat position in the field, heliostat area, receiver dimension, and site latitude. It is concluded that the target-aligned tracking method is superior to all other variants in the majority of cases. As for the standard azimuth-elevation tracking methods, not one of these exhibits a clear advantage. It is only the on-axis method that performs worst in all cases.
The Actuator Surface Model: A New Navier–Stokes Based Model for Rotor Computations
Authors: Shen Wen Zhong , Zhang Jian Hui , Sørensen Jens Nørkær
Published: January 2009

This paper presents a new numerical technique for simulating two-dimensional wind turbine flow. The method, denoted as the 2D actuator surface technique, consists of a two-dimensional Navier–Stokes solver in which the pressure distribution is represented by body forces that are distributed along the chord of the airfoils. The distribution of body force is determined from a set of predefined functions that depend on angle of attack and airfoil shape. The predefined functions are curve fitted using pressure distributions obtained either from viscous-inviscid interactive codes or from full Navier–Stokes simulations. The actuator surface technique is evaluated by computing the two-dimensional flow past a NACA 0015 airfoil at a Reynolds number of 106 and an angle of attack of 10deg and by comparing the computed streamlines with the results from a traditional Reynolds-averaged Navier–Stokes computation. In the last part, the actuator surface technique is applied to compute the flow past a two-bladed vertical axis wind turbine equipped with NACA 0012 airfoils. Comparisons with experimental data show an encouraging performance of the method.
Imbalance Estimation Without Test Masses for Wind Turbines
Authors: Ramlau Ronny , Niebsch Jenny
Published: January 2009

Rotor imbalances of a wind turbine can cause severe damage of the turbine or its components and thus reduce the lifespan and security of the turbine significantly. At present, balancing of the rotor is a time consuming and expensive process due to the necessity of mounting test weights to measure a reference imbalance state. We describe a new method for the detection and reconstruction of imbalances in the rotor of a wind turbine avoiding test weight measurements. The method is based on a wind turbine model, which is derived by the finite element method. In some respect, the model information replaces the information of a reference imbalance state. A mathematical equation linking imbalances and the resulting vibrations is derived using the model. Thus the inverse problem of computing an imbalance from vibration measured at the nacelle is solvable with the usual techniques for ill-posed problems. We show that our model for a wind turbine can be used to predict the vibrations for a given imbalance distribution. In particular, it can be used to reconstruct the imbalance distribution of a wind turbine from noisy measurements in real time, which is verified both for artificial and real data. Also, an optimization strategy is presented in order to adapt the model to the wind turbine at hand. The new method requires a simple model of a wind turbine under consideration but reduces the measuring effort for the computation of balancing weights. It can be implemented into a condition monitoring system (CMS). For the first time, there can be not only an alarm generation but also the actual imbalance and balancing weights and positions can be computed directly from the observed CMS data.
Experimental and Numerical Study of Mixing in a Hot-Water Storage Tank
Authors: Aviv A. , Blyakhman Y. , Beeri O. , Ziskind G. , Letan R.
Published: January 2009

Thermal mixing and stratification are explored numerically and experimentally in a cylindrical tank, which simulates a storage of water heated by a solar collector. The tank is 70cm in height and 24cm in diameter. The inlet and outlet are vertical and located off the centerline of the tank. The study is conducted in a transient mode, namely, the tank is filled with hot water, and as the hot water is being withdrawn, the tap water replaces it in a stratified way or by mixing. The flowrates of 2l∕min, 3l∕min, 5l∕min and 7l∕min, which correspond to superficial velocities of 4.35cm∕min, 6.52cm∕min, 10.87cm∕min, and 15.2cm∕min, are explored. Temperature of hot water ranges within 40–50°C, while the tap water is about 25–27°C. Installation of one and two horizontal baffles above the inlet is examined. Simultaneous experimental and numerical investigations are performed. In the experiment, both flow visualization and temperature measurements are used. Three-dimensional transient numerical simulations are done using the FLUENT 6 software. Validation of the numerical model is achieved by comparison with the experimental results. Then, the numerical model is applied to a study of various possible changes in the system. The results show that at low flowrates, up to a superficial velocity of about 11cm∕min through the tank, the baffles have no effect on tap water mixing with the stored hot water. At higher flowrates, a single horizontal baffle prevents the mixing and preserves the desired stratified temperature distribution in the storage tank.
Asymmetric Asperity Height Distributions in a Scale-Dependent Model for Contact and Friction
Authors: Adams George G. , Mu¨ftu¨ Sinan
Published: January 2009

The effect of an asymmetric distribution of asperity heights is accounted for in a recently developed scale-dependent multi-asperity model of contact and friction. A Weibull distribution of asperity heights is used which allows the skew and kurtosis to be varied, but not independently of each other. The contact and friction model used includes the effects of adhesion and of scale-dependent friction. The results obtained demonstrate that positive/negative skew decreases/increases both the friction coefficient and its dependence on the magnitude of the normal load.
Finite Element Simulation of Dynamic Instabilities in Frictional Sliding Contact
Authors: Baillet L. , Linck V. , D’Errico S. , Laulagnet B. , Berthier Y.
Published: January 2009

This paper describes tools for numerical modelisation which enable the understanding of the appearance of the vibration of structure generated by the frictional contact between two bodies (the excitation source being friction). The dynamic finite element code PLASTD is used to reproduce transitory phenomena generated at the contact interface. This code includes contact and friction algorithms based upon the formulation of Lagrange multipliers. A numerical study of the dynamic response of a 2D mechanical model composed of a deformable plane in relative translation and unilateral contact with Coulomb friction with a rigid surface is presented. The steady sliding solution is generically unstable and leads to a dynamic response which leads to the generation of instabilities characterized by the appearance of sliding-sticking or sliding-sticking-separation waves. It is important to notice that those instabilities appear even with a constant friction coefficient. These simulations have permitted to obtain the local contact conditions (kinematics, tribological state, contact stresses, etc). The kinematics shows the existence of local impacts and sliding at high frequencies. Furthermore, local normal pressure is much higher than that expected for a smooth surface. Finally, a 3D simulation of braking is carried out. We focused on the vibration of the disc and the brake pad which caused noises due to the generation of interface instabilities.
Understanding the Effects of Friction and Surface Roughness on Noise Generation From Elastic Components in Sliding Contact
Authors: Soom Andres , Dargush Gary F. , Serpe Catalin I.
Published: January 2009

One type of troublesome friction-induced noise, common in brakes, clutches and mechanical seals, is high frequency chirp or squeal. The frequencies at which these noises and underlying vibrations occur typically range from around 1 kHz to more than 10 kHz. We have found that the essential physical ingredients needed to model this problem are two finite elastic systems coupled by friction and a distributed interfacial contact stiffness, transverse to the direction of sliding. The contact stiffness is associated with the roughness of the sliding surfaces and, sometimes, with the presence of wear particles within the contact. Our approach is to perform an eigenvalue analysis, using finite elements, of pairs of coupled sliding elastic rings. Due to the presence of friction, the stiffness matrix is asymmetric and mode coupling or mode splitting can occur. Typically ten per cent of the first forty or so vibratory modes are potentially unstable. Generally one or two of these appear as instabilities in the actual physical system being modeled. No stick-slip action needs to be invoked and these instabilities can occur with a single constant coefficient of friction.
Friction Induced Transverse Vibrations of an Axially Accelerating String
Authors: Zen Giampaolo , Mu¨ftu¨ Sinan
Published: January 2009

The purpose of this study is to investigate the dynamic response of axially translating continua undergoing both the effect of friction and axial acceleration. The axially moving continuum is initially modeled as a string, neglecting its flexural stiffness; the response, with particular interest given to transverse vibrations and dynamic stability, is studied through numerical methods. A finite element method is employed to discretize the space domain and an implicit α–method is employed to integrate the resulting matrix equation in the time domain. Results are given through time history diagrams and stability considerations.
Friction Modeling of a Free-Spinning Bicycle Wheel
Authors: Huang Shuguang , Nagurka Mark
Published: January 2009

An experiment is conducted in which a free-standing bicycle wheel is given an initial angular speed and then allowed to slow down to rest. Measurements of the wheel speed, using a magnetic sensor, during the decay are compared to predictions from a model accounting for a combination of viscous and dry friction at the wheel bearing. The time history data indicate two dynamic regimes: (i) a higher speed phase corresponding to the first part of the motion for which a simple viscous friction model applies, and (ii) a slower speed phase corresponding to low speed to stop behavior for which a model involving both viscous and dry friction is proposed. A method is presented for finding the viscous and dry friction coefficients of the two phases.
Stiction Suppression in High Volume MEMS Products
Authors: Martin Jack
Published: January 2009

Analog Devices has shipped over 120 million MEMS inertial sensors (accelerometers and gyros). Most are used in automotive air bag systems so high reliability is absolutely critical. the DMD die used in the Texas Instruments’ DLP image projection systems have up to 1.3 million micromirrors on each die that are designed to touch and release. the DLP product line also has a well-established record of high reliability. Clearly, both Companies have solved the problem of MEMS stiction to the extent that it no longer impacts field reliability. However, stiction remains a primary cause of failure in other micromachined products that are produced on less mature processes than those employed by high volume manufacturers like ADI and TI. This paper discusses the fundamental causes of stiction and the techniques that commercial MEMS suppliers use to suppress it.
A Cylindrical Contact Model for Two-Dimensional Multiasperity Profiles
Authors: Jagodnik John J. , Mu¨ftu¨ Sinan
Published: January 2009

In practice, multi-asperity contact problems are often solved as two dimensional (2D) plane problems rather than true three dimensional (3D) problems. This is accomplished by assuming that each peak on a 2D scanned profile is the pinnacle of a half sphere. Hertz contact equations are then used to solve for the radius of contact and pressure profile. In reality, the local maximum in the plane may not be the maximum in the unmeasured depth direction, creating inherent errors in the contact model. This error is shown to be significant in contact problems when estimating the area of contact and total contact force over a single asperity. The pressure corrected Sternberg-Turteltaub model is introduced, in which a cylinder is used to model a sphere in a plane. This model is shown to improve the contact area and total force estimates for a range contact parameters.
Pressure Distribution in a Hertz Circular Contact Affected by a Central, Circular Dent
Authors: Diaconescu Emanuel N. , Cerlinca Delia F.
Published: January 2009

Rolling contact fatigue is strongly influenced either by subsurface imperfections or by surface defects. The latter tend to become the major factor influencing contact fatigue. The first step to assess the effect of these defects upon contact fatigue life is to find the pressure distribution alterations they generate. This paper investigates the pressure riser effect around a circular dent placed centrally in a Hertz circular contact. The solutions of Erdogan are used as a start point. The superposition principle for the half-space is applied to these solutions to find the pressure distribution. The involved integrals are evaluated numerically. The dent affects the Hertz pressure only in its immediate neighborhood. It produces significant pressure risers near the outer edge of the dent and a central circular region free of pressure inside. In comparison to the case of smooth surfaces, the outer radius of the contact extends by a very small amount dependent on dent geometry. Calculations evidence the influence of dent geometry upon pressure riser effect.
Nanoindentations on SrTiO3 Substrates: Effects of Fractal Roughness on Contact Mechanics
Authors: Buzio Renato , Malyska Karolina , Rymuza Zygmunt , Boragno Corrado , Buatier de Mongeot Francesco , Valbusa Ugo
Published: January 2009

The non-stationary character of roughness is a widely recognized property of surface morphology and suggests modelling several solid surfaces by fractal geometry. In the field of contact mechanics this demands for novel investigations attempting to clarify the role of multi-scale roughness during physical contact. Here we propose an experimental investigation of the mechanical response of SrTiO3 substrates probed by a commercial nanoindentor. Load-displacement curves have been acquired respectively on well-defined crystalline surfaces and on mechanically lapped surfaces. We observe the first-loading cycles to be considerably affected by surface roughness whenever the penetration depth is kept below the interface width. The obtained results are analyzed within an elasto-plastic deformation model for fractal surfaces and a picture is developed to describe the deformation process with respect to surface roughness and structural parameters.
Thermal Stability of Z-Type Perfluoro Poly Ether Lubricant Polymers: A Combined Thermogravimetric and Temperature Programmed Desorption Study
Authors: Jones Paul M. , Li Lei , Hsia Yiao-Tee
Published: January 2009

The thermal stability of Zdol 4000, 7800 and Ztetraol perfluoropolyethers (PFPE) have been studied in both the bulk with thermogravimetric analysis (TGA) and in thin film form with temperature programmed desorption spectroscopy (TPD). The TGA results have been interpreted to yield an evaporation activation energy for both Zdol 4000 (13 kcal/mole) and Zdol 7800 (19 kcal/mole). A larger activation energy is also found for all three samples investigated that is consistent with polymer decomposition (22, 27 and 21 kcal/mole respectively). The TPD threshold has been found to be approximately similar all three samples (∼500 K). The temperature of decomposition was also found to be similar for all three samples and was dominated by the CF2O+ mass fragment at ∼660 K. Two desorption maximums were observed for both Zdol 4000 and Ztetraol indicating the similarity in their decomposition chemistry. In contrast only one desorption peak was observed from Zdol 7800 (675 K). A CF3+ fragment was not observed in any of the TPD spectra indicating the absence an acidic decomposition path for all of the Fomblin Z polymers studied.
Thermal Analysis for the Protrusion of Magnetic Head
Authors: Xu Junguo , Kurita Masayuki , Saegusa Shozo
Published: January 2009

The thermal protrusion of a magnetic head was investigated through, first a high-resolution measurement of temperature distribution over the air bearing surface (ABS) and head coil and, second, a numerical calculation of the head protrusion. It was found that the temperature on the ABS results in a “butterfly”-shaped distribution. It was also found that an eddy current induced by high frequency write-current significantly increases the temperature of read/write elements. Moreover, the point of maximum temperature changed from the head core to the write gap when the applied current was switched from DC to AC. It was also found that a write-current induced head protrusion caused more deformation of the alumina over coat in the horizontal direction and that an ambient-temperature-induced head protrusion caused more deformation around the read-write elements. Furthermore, it is clarified that film materials with higher elastic modulus, lower expansion rate, and higher thermal conductivity reduce the head thermal protrusion. Finally, to reduce write-current-induced head protrusion, a novel thermally improved head structure is proposed.
Thermal Effects and Self-Heating Time Constant for GMR Recording Heads
Authors: Baril Lydia , Schreck Erhard , Wallash Al
Published: January 2009

An understanding of the temperature of the GMR reader element used in disk drives during operating and non-operating condition is critical to optimize its performance. Self-heating and/or external heat sources will cause an increase in the temperature of the GMR sensor. In this work we concentrate on the self-heating effect due to bias current. Experiments that monitored the resistance change during very short current pulses showed that state-of-the-art GMR sensors have an extremely short time-constant that is less than 2 ns. This work is applicable to the current transients that the GMR head experiences during electrical crosstalk, electrostatic discharge and thermal asperities.
Head Wear in Contact Recording Systems
Authors: Kawakubo Youichi , Kobatake Shinichi , Miyazawa Shunichi , Nakazawa Shinichi
Published: January 2009

The possibility of disk failure, a common failure mode conventional HDDs, was studied in conditions supposed contact recording systems. For this purpose, transparent pin-on-disk wear tests were performed on thin-film magnetic disks with sliding load less than 5 mN. We found that visible wear scar did not appear on disk surfaces. Wear debris were found be buried on the disk surfaces. This showed that the reduction of head wear and vibration are two main problems to be solve for future hard disk drives. We then studied effects of disk lubricant and tape burnishing of disk surface on pin wear. The results showed the higher the molecular weight of lubricants, the lower the pin wear, and tape burnishing reduced pin wear.
Optimization of Air Bearing Contours for Shock Performance of a Hard Disk Drive
Authors: Jayson Eric M. , Talke Frank E.
Published: January 2009

Hard disk drives must be designed to withstand shock during operation. Large movements of the slider during shock impulse can cause reading and writing errors, track misregistration, or in extreme cases, damage to the magnetic material and loss of data. The design of the air bearing contour determines the steady state flying conditions of the slider as well as dynamic flying conditions, including shock response. In this paper a finite element model of the hard disk drive mechanical components was developed to determine the time dependent forces and moments applied to the slider during a shock event. The time dependent forces and moments are applied as external loads in a solution of the dynamic Reynolds equation to determine the slider response to a shock event. The genetic algorithm was then used to optimize the air bearing contour for optimum shock response while keeping the steady flying conditions constant. The results show substantial differences in the spacing modulation of the head/disk interface after a shock as a function of the design of the air bearing contour.
Measurements of Thickness, Surface Roughness and Corrosion Performance of 1-10 nm Thick CNx Films
Authors: Li Dejun , Chen Yanfeng , Chung Yip-Wah
Published: January 2009

Nitrogenated carbon (CNx) films were synthesized by using pulsed dc magnetron sputtering. When grown with substrate tilt of 45° and rotation speed of 20–25 rpm, the root-mean-square surface roughness is ∼0.3 nm when sampled over 20×20 μm2 areas, increasing to ∼0.4 nm when sampled over ∼0.05×3 cm2 using x-ray reflectivity measurements. X-ray reflectivity measurements showed that the mass density of these CNx films is ∼2.0 gm/cc, independent of film thickness from ∼1 to 10 nm, consistent with ion beam analysis. CNx films deposited with substrate tilt of 45° and rotation speed of 20–25 rpm have about 1/3 fewer corrosion spots per unit area than those without. Reducing CNx thickness from 3 to 1 nm results in marked increase in corrosion currents.
Numerical Modeling of a Turbulent Gas Jet Flame in a Swirling Air Stream
Authors: Qubbaj Ala R. , Gollahalli S. R. , Villarreal John
Published: January 2009

A numerical simulation of a turbulent natural gas jet diffusion flame at a Reynolds number of 9000 in a swirling air stream is presented. The numerical computations were carried out using the commercially available software package CFDRC. The instantaneous chemistry model was used as the reaction model. The thermal, composition, flow (velocity), as well as stream function fields for both the baseline and airswirling flames were numerically simulated in the near-burner region, where most of the mixing and reactions occur. The results were useful to interpret the effects of swirl in enhancing the mixing rates in the combustion zone as well as in stabilizing the flame. The results showed the generation of two recirculating regimes induced by the swirling air stream, which account for such effects. The present investigation will be used as a benchmark study of swirl flow combustion analysis as a step in developing an enhanced swirl-cascade burner technology.
Submerged Gas Injection in Microgravity
Authors: Carrera J. , Parthasarathy R. N. , Gollahalli S. R.
Published: January 2009

The effects of buoyancy on the flow regimes of submerged gas injection were studied in this investigation. A capillary tube submerged in water was used for gas injection in microgravity and terrestrial conditions, and the resulting flow regimes and bubble sizes were documented. The effects of liquid co-flow and reduced surface tension were also analyzed. Under reduced gravity, three flow regimes were observed over the range of conditions tested. At low gas flow rates, the bubbles did not detach from the injector, forming an interconnected bubble cluster that adhered to the injector. Single bubbles started detaching and moving away from the injector when the Weber number reached a value around 3. At gas flow rates corresponding to a Weber number value of 10, the bubble coalescence regime was observed near the injector. It was found that the absence of buoyancy prevented the formation of the jetting regime. For all gas throughputs, the co-flowing liquid aided the detachment of the bubbles, resulting in the generation of more uniform bubbles than in quiescent liquids. The presence of co-flow resulted in a smaller bubble size accompanied by an increased frequency of bubble formation. Reduced surface tension produced a similar effect, resulting in smaller bubbles.
Examination of the Flame Blowout Characteristics of a Jet Diffusion Flames Burner in Co- and Cross-Flowing Air
Authors: Kibrya M. G. , Karim G. A.
Published: January 2009

The blowout limit of a jet diffusion flame was shown experimentally to improve significantly through the introduction of an auxiliary fuel in the surrounding air. A small experimental burner was devised so that the auxiliary fuel could be introduced and controlled independently of the main jet fuel, through a number of small pilot jets uniformly distributed around the main central fuel jet. This burner arrangement eliminated the likelihood of a flame flashing back into the surrounding atmosphere and some fuel escaping combustion. The burner was tested with methane as the fuel both for the main jet and the auxiliary side jets. Tests were made for both co-flow and cross-flow air streams of uniform velocity. It is shown that the arrangement adopted for auxiliary fuel introduction produced improvements in the flame blowout limits of the burner under both types of surrounding flow conditions. For the conditions considered, the blowout limits were of higher values in cross flow than for the corresponding co-flowing air streams.
The Mechanism of Flue Gas Injection for Enhanced Light Oil Recovery
Authors: Shokoya O. S. , Mehta S. A. , Moore R. G. , Maini B. B. , Pooladi-Darvish M. , Chakma A. K.
Published: January 2009

Flue gas injection into light oil reservoirs could be a cost-effective gas displacement method for enhanced oil recovery, especially in low porosity and low permeability reservoirs. The flue gas could be generated in situ as obtained from the spontaneous ignition of oil when air is injected into a high temp erature reservoir, or injected directly into the reservoir from some surface source. When operating at high pressures commonly found in deep light oil reservoirs, the flue gas may become miscible or near miscible with the reservoir oil, thereby displacing it more efficiently than an immiscible gas flood. Some successful high pressure air injection (HPAI) projects have been reported in low permeability and low porosity light oil reservoirs. Spontaneous oil ignition was reported in these projects, at least from laboratory experiments; however, the mechanism by which the generated flue gas displaces the oil has not been discussed in clear terms in the literature. An experimental investigation was carried out to study the mechanism by which flue gases displace light oil at a reservoir temperature of 116 °C and typical reservoir pressures ranging from 4,028 psi (27.77 MPa) to 6,680 psi (46.06 MPa). The results showed that the flue gases displaced the oil in a forward contacting process resembling a combined vaporizing and condensing multi-contact gas drive mechanism. The flue gases also became near-miscible with the oil at elevated pressures, an indication that high pressure flue gas (or air) injection is a cost-effective process for enhanced recovery of light oils, compared to rich gas or water injection, with the potential of sequestering greenhouse gases.
The Catalytic Oxidation of Heated Lean Homogeneously Premixed Gaseous-Fuel Air Streams
Authors: Depiak A. , Wierzba I.
Published: January 2009

Results are presented of an experimental laboratory investigation of the oxidation reactions of heated low velocity streams of homogeneous lean fuel-air mixtures within a packed bed tubular reactor at atmospheric pressure in the presence of non-noble metal oxides catalysts. The main fuel considered was methane, however, other common gaseous fuels, i.e. propane, carbon monoxide, hydrogen and ethylene were also examined for comparative purposes. It was shown that binary cobalt oxide/chromium oxide catalysts can be effective in the oxidation of very lean fuel-air mixtures. Furthermore, there is an optimum value of their mass ratio that could produce a significant improvement to the low temperature oxidation of the lean mixtures examined and the corresponding resulting emissions.