bluuebunny/crossref_metadata_2025 huggingface dataset:
Epidemiology of vitamin D in health and disease
Authors: Wang Sihe
Published: October 2009

Results from ecological, case–control and cohort studies have shown that vitamin D reduces the risk of bone fracture, falls, autoimmune diseases, type 2 diabetes, CVD and cancer. However, there is still epidemic vitamin D insufficiency especially among individuals living at high latitudes or with dark skin. Serum levels of 25-hydroxyvitamin D (25(OH)D) are considered the best biomarker of vitamin D nutritional status. Appropriate sunshine exposure or oral supplementation is necessary to maintain sufficient vitamin D status, which is generally accepted as serum 25(OH)D>75 nmol/l. Immunoassays, especially RIA, have been primarily used to measure serum 25(OH)D while liquid chromatography–MS (LC–MS) is considered the ‘gold standard’. There is significant disparity among the immunoassays, and all immunoassays have considerable bias compared with LC–MS methods. Because of the variations among the results from these different assays, it is necessary that assay-specific reference ranges be established or standardisation of the assays take place. The present review focuses on ecological, case–control, and cohort studies that investigated the role of vitamin D in health and disease. In addition, analytical techniques used in laboratory evaluation of vitamin D nutritional status are also critically reviewed. The majority of the literature included in the present review is selected from that searchable in PubMed up to the end of September 2008.
Analytische und konfigurale Verarbeitung von Objekten im Säuglingsalter
Authors: Schwarzer Gudrun , Jovanovic Bianca , Schum Nina , Dümmler Thomas
Published: October 2009

Zusammenfassung. Bisherige Arbeiten haben dargelegt, dass sich innerhalb des ersten Lebensjahres ein Wechsel von einer analytischen hin zu einer konfiguralen Verarbeitung von Objekten vollzieht. Dieser Wechsel wird im Wesentlichen als von der Komplexität der Objekte und dem Alter der Kinder abhängig gesehen. Im vorliegenden Beitrag wird untersucht, inwieweit auch spezifische Erfahrungen, die Säuglinge im Laufe der Entwicklung machen, relevant sind für die konfigurale Verarbeitung von Objekten. In Experiment 1 wird Evidenz dafür geliefert, dass die Erfahrung 8-monatiger Säuglinge, sich selbst induziert fortzubewegen, eine relevante Bedingung für die konfigurale Objektverarbeitung darstellt. Außerdem wird beschrieben, dass die visuelle und haptische Exploration von Objekten die konfigurale Objektverarbeitung fördert. Darauf aufbauend zeigt Experiment 2, dass 8-monatige Säuglinge die konfigurale Objektverarbeitung, die auf einer visuell-haptischen Exploration beruht, auf die pur visuelle Verarbeitung übertragen können, dass der umgekehrte Transfer jedoch nicht gelingt. Insgesamt bringen die berichteten Befunde somit zum Ausdruck, dass der analytisch-zu-konfigural-Shift nicht nur durch Alter und Objektkomplexität bedingt ist, sondern auch durch spezifische Erfahrungen mit Objekten, die Säuglinge im Laufe des ersten Lebensjahres gesammelt haben.
Planning to reach for a rotating rod
Authors: von Hofsten Claes , Johansson Katarina
Published: October 2009

Abstract. Hand adjustments of 6- and 10-month-old infants and adults were studied as they reach to grasp a rotating rod. It was found that the subjects in all three age groups adjusted the hand prospectively to the rotating rod during the approach of it. They also adjusted the reaches to the rotating rod in such a way that almost all of the grasps were overhand ones as predicted by the endpoint comfort hypothesis. Finally, it was found that the rotation of the hand was made up of movement units as translational movements are, and that the approach units were relatively independent of the rotational ones.
Thickness and production of sea ice in the Okhotsk Sea coastal polynyas from AMSR‐E
Authors: Nihashi Sohey , Ohshima Kay I. , Tamura Takeshi , Fukamachi Yasushi , Saitoh Sei‐ichi
Published: October 2009

From comparisons with thickness of sea ice from Advanced Very High Resolution Radiometer (AVHRR) and ice‐profiling sonar data we have developed an Advanced Microwave Scanning Radiometer‐EOS (AMSR‐E) thin ice thickness algorithm for the Sea of Okhotsk. This algorithm can estimate ice thickness of ≤0.2 m without snow using the polarization ratio of AMSR‐E brightness temperature at a 36.5 GHz channel from a linear relationship with AVHRR ice thickness. When a snow cover exists on the thin ice surface, as occurred a few times in each winter, it is shown that the algorithm cannot detect the thin ice. Sea ice and dense shelf water (DSW) production in coastal polynya are estimated on the basis of heat flux calculation with the daily AMSR‐E ice thickness for three winters (December–March) of 2002–2003 to 2004–2005. The ice production is largest in the northwest shelf (NWS) polynya which accounts for ∼45% of the sum of ice production in major coastal polynyas. The ice production in major coastal polynyas would cover the maximum ice area of the Okhotsk Sea if the average ice thickness is assumed to be 1 m. Variability of the ice production is mainly modulated by air temperature. In the NWS polynya, which is the main DSW production area, the annual DSW formation rate is estimated to be ∼0.36 Sv.
The geodynamic equation of state: What and how
Authors: Connolly J. A. D.
Published: October 2009

Geodynamic models commonly assume equations of state as a function of pressure and temperature. This form is legitimate for homogenous materials, but it is impossible to formulate a general equation of state for a polyphase aggregate, e.g., a rock, as a function of pressure and temperature because these variables cannot distinguish all possible states of the aggregate. In consequence, the governing equations of a geodynamic model based on a pressure‐temperature equation of state are singular at the conditions of low‐order phase transformations. An equation of state as a function of specific entropy, specific volume, and chemical composition eliminates this difficulty and, additionally, leads to a robust formulation of the energy and mass conservation equations. In this formulation, energy and mass conservation furnish evolution equations for entropy and volume and the equation of state serves as an update rule for temperature and pressure. Although this formulation is straightforward, the computation of phase equilibria as a function of entropy and volume is challenging because the equations of state for individual phases are usually expressed as a function of temperature and pressure. This challenge can be met by an algorithm in which continuous equations of state are approximated by a series of discrete states: a representation that reduces the phase equilibrium problem to a linear optimization problem that is independent of the functional form used for the equations of state of individual phases. Because the efficiency of the optimization decays as an exponential function of the dimension of the function to be optimized, direct solution of the linearized optimization problem is impractical. Successive linear programming alleviates this difficulty. A pragmatic alternative to optimization as an explicit function of entropy and volume is to calculate phase relations over the range of pressure‐temperature conditions of interest. Numerical interpolation can then be used to generate tables for any thermodynamic property as a function of any choice of independent variables. Regardless of the independent variables of the governing equations, a consistent definition of pressure, and the coupling of equilibrium kinetics to deformation, is only possible if the continuity equation accounts for dilational strain.
Assimilation of GRACE tide solutions into a numerical hydrodynamic inverse model
Authors: Egbert G. D. , Erofeeva S. Y. , Han S.‐C. , Luthcke S. B. , Ray R. D.
Published: October 2009

We assimilate localized mass anomalies inferred from GRACE ranging measurements into a hydrodynamic model to improve tidal solutions around Antarctica for the M2, S2, and O1 constituents. The variational approach used accounts for the spatial averaging of tidal elevations implicit in the mass anomaly parametrization used for the GRACE tidal analysis, as well as spatial correlation of errors in the resulting estimates. The inverse solution shows better agreement with independent station tide measurements around Antarctica, and it reduces cross‐over residuals for ICESat laser altimeter data over the Filchner, Ronne and Ross Ice Shelves, demonstrating that GRACE data can provide useful constraints for improving hydrodynamic tidal models at high latitudes.
Laboratory studies of products of N2O5 uptake on Cl− containing substrates
Authors: Roberts James M. , Osthoff Hans D. , Brown Steven S. , Ravishankara A. R. , Coffman Derek , Quinn Patricia , Bates Timothy
Published: October 2009

The reaction of dinitrogen pentoxide with chloride‐containing substrates over a concentration range relevant to the atmosphere was examined using cavity ring‐down spectroscopy (CaRDS) and chemical ionization mass spectrometry (CIMS). The main product, nitryl chloride (ClNO2), was formed in efficiencies in the range 0.2 to 0.8 for chloride concentrations of 0.02 to 0.5M. These values are somewhat lower than those from previous, less detailed, measurements carried out mainly at much larger chloride concentrations in NaCl‐water mixtures. Substrates having pH<2 also evolved molecular chlorine (Cl2), with ClNO2 as an intermediate. The ClNO2 yields are compared to recent field measurements of N2O5 and ClNO2 as a function of aerosol chloride concentration and shown to quantitatively explain the observations.
The PPAR-γ Agonist, Darglitazone, Restores Acute Inflammatory Responses to Cerebral Hypoxia–Ischemia in the Diabetic ob/ob Mouse
Authors: Kumari Rashmi , Willing Lisa B , Patel Shyama D , Krady J Kyle , Zavadoski William J , Gibbs E Michael , Vannucci Susan J , Simpson Ian A
Published: October 2009

Diabetes is an increased risk factor for stroke and results in increased brain damage in experimental animals and humans. The precise mechanisms are unclear, but our earlier studies in the db/db mice suggested that the cerebral inflammatory response initiating recovery was both delayed and diminished in the diabetic mice compared with the nondiabetic db/+ mice. In this study, we investigated the actions of the peroxisome proliferator-activated receptor (PPAR)-γ agonist darglitazone in treating diabetes and promoting recovery after a hypoxic-ischemic (H/I) insult in the diabetic ob/ob mouse. Male ob/+ and ob/ob mice received darglitazone (1 mg/kg) for 7 days before induction of H/I. Darglitazone restored euglycemia and normalized elevated corticosterone, triglycerides, and very-low-density lipoprotein levels. Darglitazone dramatically reduced the infarct size in the ob/ob mice at 24 h of recovery compared with the untreated group (30±13% to 3.3±1.6%, n=6 to 8) but did not show any significant effect in the ob/+ mice. Microglial and astrocytic activation monitored by cytokine expression (interleukin-1β and tumor necrosis factor-α) and in situ hybridization studies ( bfl1 and glial fibrillary acidic protein) suggest a biphasic inflammatory response, with darglitazone restoring the compromised proinflammatory response(s) in the diabetic mouse at 4 h but suppressing subsequent inflammatory responses at 8 and 24 h in both control and diabetic mice.
The Relationship of Ectopic Lipid Accumulation to Cardiac and Vascular Function in Obesity and Metabolic Syndrome
Authors: Ruberg Frederick L. , Chen Zhongjing , Hua Ning , Bigornia Sherman , Guo Zifang , Hallock Kevin , Jara Hernan , LaValley Michael , Phinikaridou Alkystis , Qiao Ye , Viereck Jason , Apovian Caroline M. , Hamilton James A.
Published: October 2009

Storage of lipid in ectopic depots outside of abdominal visceral and subcutaneous stores, including within the pericardium and liver, has been associated with obesity, insulin resistance, and cardiovascular risk. We sought to determine whether anatomically distinct ectopic depots were physiologically correlated and site‐specific effects upon cardiovascular function could be identified. Obese subjects (n = 28) with metabolic syndrome but without known atherosclerotic disease and healthy controls (n = 18) underwent magnetic resonance imaging (MRI) and proton MR spectroscopy (MRS) to quantify pericardial and periaortic lipid volumes, cardiac function, aortic compliance, and intrahepatic lipid content. Fasting plasma lipoproteins, glucose, insulin, and free‐fatty acids were measured. Pericardial and intrahepatic (P < 0.01) and periaortic (P < 0.05) lipid volumes were increased in obese subjects vs. controls and were strongly and positively correlated (P ≤ 0.01) but independent of BMI (P = NS) among obese subjects. Intrahepatic lipid was associated with insulin resistance (P < 0.01) and triglycerides (P < 0.05), whereas pericardial and periaortic lipid were not (P = NS). Periaortic and pericardial lipid positively correlated to free‐fatty acids (P ≤ 0.01) and negatively correlated to high‐density lipoprotein (HDL) cholesterol (P < 0.05). Pericardial lipid negatively correlated to cardiac output (P = 0.03) and stroke volume (P = 0.01) but not to left ventricular ejection fraction (P = 0.46). None of the ectopic depots correlated to aortic compliance. In conclusion, ectopic storage of lipid in anatomically distinct depots appeared tightly correlated but independent of body size. Site‐specific functional abnormalities were observed for pericardial but not periaortic lipid. These findings underscore the utility of MRI to assess individual differences in ectopic lipid that are not predictable from BMI.
Effect of Glycemic Load on Peptide‐YY Levels in a Biracial Sample of Obese and Normal Weight Women
Authors: Brownley Kimberly A. , Heymen Steve , Hinderliter Alan L. , MacIntosh Beth
Published: October 2009

Black women suffer a disproportionately higher rate of obesity than their white counterparts. Reasons for this racial disparity may reflect underlying differences in the appetite suppressing peptide‐YY (PYY). The PYY response to food is differentially influenced by macronutrient content but the effect of glycemic load on PYY response is unknown. This study examined whether glycemic load influences fasting and postprandial PYY levels and whether fasting and postprandial PYY levels are lower in obese black women compared to normal weight black women and to white women. Data were collected from 40 women (20 black, 20 white; 10 each normal weight vs. obese) at the University of North Carolina Clinical and Translational Research Center (CTRC). Participants completed in counterbalanced order two 4½‐day weight‐maintenance, mixed macronutrient high vs. low glycemic load diets followed by a test meal of identical composition. Total PYY levels were assessed before and after each test meal. Results show no differences in fasting PYY levels but significantly less postprandial PYY area under the curve (PYYAUC) in the group of obese black women compared to each other group (race × obesity interaction, P < 0.04). PYYAUC was positively related to insulin sensitivity (P < 0.004) but was not affected by glycemic load (main and interactive effects, P > 0.27). These findings indicate that postprandial PYY secretion is not affected by glycemic load but is blunted in obese black women compared with normal weight black women and with white women; additionally, they begin to address whether blunted PYY secretion contributes uniquely to the pathogenesis of obesity in black women.
Sleep Duration and Obesity in Middle‐aged Australian Adults
Authors: Magee Christopher A. , Iverson Don C. , Caputi Peter
Published: October 2009

The present study examined the association between sleep duration and obesity in 40,834 middle‐aged Australian adults. Multinomial logistic regression was used to test the relationship between sleep duration and obesity while controlling for important demographic and health covariates; separate models were tested for males and females. Short sleep (i.e., <7 h a night) was found to be independently associated with obesity in males and females. To our knowledge, this is the first study to report an association between short sleep and obesity in Australian adults. Although more research is required, interventions targeting short sleep could aid obesity treatment and prevention.
Childhood and Young Adult Overweight/Obesity and Incidence of Depression in the SUN Project
Authors: Sánchez‐Villegas Almudena , Pimenta Adriano M. , Beunza Juan J. , Guillen‐Grima Francisco , Toledo Estefanía , Martinez‐Gonzalez Miguel A.
Published: October 2009

This study included 11,825 participants of a Spanish dynamic prospective cohort based on former students from University of Navarra, registered professionals from some Spanish provinces, and university graduates from other associations, followed‐up for 6.1 years. We aimed to assess the association between childhood or young adult overweight/obesity and the risk of depression. Participants were asked to select which of nine figures most closely represented their body shape at ages 5 and 20 years. Childhood and young adult overweight/obesity was defined as those cases in which participants reported body shape corresponding to the figures 6–9 (more obese categories) at age 5 or 20, respectively. A subject was classified as incident case of depression if he/she was initially free of depression and reported physician‐made diagnosis of depression and/or the use of antidepressant medication in at least one of biannual follow‐up questionnaires. The association between childhood and young adult overweight/obesity and incidence of depression was estimated by multiple‐adjusted hazard ratio (HR) and its 95% confidence interval (95% CI). Overweight/obesity at age 5 years predicted an increased risk for adult depression (HR = 1.50, 95% CI = 1.06–2.12), and a stronger association was observed at age 20 years ((HR = 2.22, 95% CI = 1.22–4.08), (subjects younger than 30 years at recruitment were excluded from this last analysis)). Childhood or young adult overweight/obesity was associated with elevated risk of adult depression. These results, if causal and confirmed in other prospective studies, support treating childhood and young adult overweight/obesity as part of comprehensive adult depression prevention efforts.
Prevalence of Unhealthy Lifestyle Patterns Among Overweight and Obese Adults
Authors: Kushner Robert F. , Choi Seung W.
Published: October 2009

This study determined the prevalence of unhealthy eating, exercise, and coping pattern traits among a large sample of overweight and obese adults. We analyzed responses to a 53‐item lifestyle pattern questionnaire posted on a commercial weight loss program Web site collected from 2004 through 2008. Subjects included 446,608 healthy weight, overweight, and obese adults, 18–65 years old, average age 31.9 (s.d. = 11.8), average BMI 30.5 kg/m2 (s.d. = 7.5). Categorically, 25.5% were healthy weight, 29.0% were overweight, 33.7% were class I–II obesity, and 11.8% class III obesity. A stratified random sample was used to estimate the prevalence of the 21 lifestyle patterns (7 eating, 7 exercise, and 7 coping) in the general population, and the prevalence of patterns in the complete dataset was further analyzed by gender, age, and BMI. Finally, we analyzed the odds ratio of the pattern prevalence for each BMI category. We found that unhealthy lifestyle patterns in diet, exercise, and coping were highly prevalent among this population. In general, the prevalence of these patterns rose with increasing BMI and is correlated with advancing age. Gender differences were seen with many of the patterns, most noticeably among the coping patterns. The odds ratio for 18 of the 21 patterns was >1.0 and steadily increased with higher BMI categories. We conclude that unhealthy lifestyle patterns in diet, exercise, and coping are highly prevalent among the overweight and obese population. Pattern recognition represents a new method to analyze the cluster of behaviors, attitudes, and traits seen among this population.
Relation of Misperception of Healthy Weight to Obesity in Urban Black Men
Authors: Godino Job G. , Lepore Stephen J. , Rassnick Stefanie
Published: October 2009

This study examined the relation between misperception of healthy weight and obesity, as well as moderators of this relation, in a sample of middle‐aged black men. Survey data from 404 mostly immigrant, black males living in greater New York City were collected as part of a larger randomized controlled trial. Data included measures of health status, BMI, perceived healthy weight, and misperception of healthy weight. Misperception of healthy weight was more frequent among obese men (90.2%) than nonobese men (48.7%) (P < 0.001). Mean level of misperception was also significantly higher in obese men than nonobese men (P < 0.001). Health status moderated the relation between misperception of healthy weight and obesity: obese men who felt healthy or who had fewer comorbid conditions had greater misperception of healthy weight than obese men who felt unhealthy or had relatively more comorbid conditions (P < 0.01). Our findings demonstrate that misperception of healthy weight discriminates between obese and nonobese black men, and the magnitude of this relation is exacerbated in obese men who are relatively healthy. Future studies should determine the prevalence of misperception of healthy weight in more diverse populations and identify potential mediators of the relation between misperception of healthy weight and obesity.
The Effects of Macronutrient Intake on Total and High‐molecular Weight Adiponectin: Results From the OMNI‐Heart Trial
Authors: Yeung Edwina H. , Appel Lawrence J. , Miller Edgar R. , Kao W.H. Linda
Published: October 2009

Higher levels of the adipocyte‐specific hormone adiponectin have been linked to increased high‐density lipoprotein (HDL) and lower insulin resistance. This study was conducted to determine the influence of macronutrient intake on adiponectin levels. One hundred and sixty‐four pre‐ and stage‐1 hypertensive adults participated in the Optimal Macro‐Nutrient Intake Heart (OMNI‐Heart) trial, a crossover feeding study originally testing the effects of macronutrients on blood pressure. Participants underwent three 6‐week feeding periods: one rich in carbohydrates (CARB), one rich in monounsaturated fat (MUFA), and one rich in protein (PROT), while maintaining body weight. Their median plasma high molecular weight (HMW) and total adiponectin levels were 2.3 and 8.2 µg/ml, respectively, resulting in an average of 27% HMW adiponectin. Both HMW and total adiponectin levels decreased after baseline while the percent HMW adiponectin remained unchanged. Between diets, the MUFA diet maintained a higher level of both HMW and total adiponectin levels than either the CARB (HMW: +6.8%, P = 0.02; total: +4.5%, P = 0.001) or PROT (HMW: +8.4%, P = 0.003; total: +5.6%, P < 0.001) diets. Changes in total adiponectin levels were positively correlated to changes in HDL cholesterol irrespective of diets (Spearman r = 0.22–0.40). No correlation was found between changes in lipids, blood pressure, or insulin resistance by the homeostasis model assessment (HOMAIR). Macronutrient intake has effects on HMW and total adiponectin levels independent of weight loss. A diet rich in MUFA was associated with higher levels of total and HMW adiponectin in comparison to a carbohydrate‐ or protein‐rich diet. Effects seen in adiponectin paralleled those found with HDL cholesterol.
Two-dimensional numerical simulation of radio frequency sputter amorphous In–Ga–Zn–O thin-film transistors
Authors: Fung Tze-Ching , Chuang Chiao-Shun , Chen Charlene , Abe Katsumi , Cottle Robert , Townsend Mark , Kumomi Hideya , Kanicki Jerzy
Published: October 2009

We reported on a two-dimensional simulation of electrical properties of the radio frequency (rf) sputter amorphous In–Ga–Zn–O (a-IGZO) thin-film transistors (TFTs). The a-IGZO TFT used in this work has the following performance: field-effect mobility (μeff) of ∼12 cm2/V s, threshold voltage (Vth) of ∼1.15 V, subthreshold swing (S) of ∼0.13 V/dec, and on/off ratio over 1010. To accurately simulate the measured transistor electrical properties, the density-of-states model is developed. The donorlike states are also proposed to be associated with the oxygen vacancy in a-IGZO. The experimental and calculated results show that the rf sputter a-IGZO TFT has a very sharp conduction band-tail slope distribution (Ea=13 meV) and Ti ohmic-like source/drain contacts with a specific contact resistance lower than 2.7×10−3 Ω cm2.
Dual folding pathways of an α/β protein from all-atom ab initio folding simulations
Authors: Lei Hongxing , Wang Zhi-Xiang , Wu Chun , Duan Yong
Published: October 2009

Successful ab initio folding of proteins with both α-helix and β-sheet requires a delicate balance among a variety of forces in the simulation model, which may explain that the successful folding of any α/β proteins to within experimental error has yet to be reported. Here we demonstrate that it is an achievable goal to fold α/β proteins with a force field emphasizing the balance between the two major secondary structures. Using our newly developed force field, we conducted extensive ab initio folding simulations on an α/β protein full sequence design (FSD) employing both conventional molecular dynamics and replica exchange molecular dynamics in combination with a generalized-Born solvation model. In these simulations, the folding of FSD to the native state with high population (>64.2%) and high fidelity (Cα-Root Mean Square Deviation of 1.29 Å for the most sampled conformation when compared to the experimental structure) was achieved. The folding of FSD was found to follow two pathways. In the major pathway, the folding started from the formation of the helix. In the minor pathway, however, folding of the β-hairpin started first. Further examination revealed that the helix initiated from the C-terminus and propagated toward the N-terminus. The formation of the hydrophobic contacts coincided with the global folding. Therefore the hydrophobic force does not appear to be the driving force of the folding of this protein.
Influence of ultrathin AlN interlayer on the microstructure and the electrical transport properties of AlxGa1−xN/GaN heterostructures
Authors: Song J. , Xu F. J. , Miao Z. L. , Wang Y. , Wang X. Q. , Shen B.
Published: October 2009

The microstructure and electrical properties of Al0.25Ga0.75N/GaN heterostructures with various AlN thicknesses have been investigated. An optimum thickness of AlN interlayer can remarkably improve the microstructure of Al0.25Ga0.75N barrier with the most uniform strain and the lowest density of threading dislocations, leading to the highest Hall mobility of the two-dimensional electron gas in the heterostructures. Transmission electron microscopy images show that the AlN interlayer with an optimum thickness can make the threading dislocations bend and be annihilated with each other in the vicinity of the heterointerface due to the larger mismatch strain between AlN interlayer and GaN. We believe that such behavior reduces the local strain and improves the uniformity of the strain in the AlxGa1−xN barrier, and thus depresses the scattering induced by the fluctuations of the piezoelectric interface charge owing to the nonuniformity of piezoelectric polarization field in AlxGa1−xN/GaN heterostructures.
Numerical study of self-induced transonic flow oscillations behind a sudden duct enlargement
Authors: Emmert Thomas , Lafon Philippe , Bailly Christophe
Published: October 2009

A sonic flow in a plane duct passing an abrupt increase in cross section is studied using compressible large-eddy simulations. Different flow patterns are likely to appear in this configuration according to the ratio between the downstream ambient pressure and the upstream reservoir pressure. For low pressure ratios, the flow is entirely supersonic in the channel and a steady symmetrical shock pattern is observed. For higher pressure ratios, the flow can be attached to one side of the channel with a jet-like shock cell structure, or can be characterized by strong oscillations of a single normal shock located near the sudden expansion, known as base-pressure oscillations in literature. A hysteresis phenomenon is found experimentally and the state reached by the transonic flow depends on the path followed by the pressure ratio. Moreover, a coupling of these base-pressure oscillations with the quarter-wavelength resonance of the duct can occur. All these regimes are numerically investigated and the results are favorably compared to available experimental data. A case of frequency locking of this self-excited mechanism is also reproduced, in agreement with a modeling of the resonator. The governing equations are solved using high-order central finite differences combined with an overset grid approach. The large-eddy simulations are based on a relaxation filtering and a nonlinear shock-capturing scheme is also implemented for shock waves.
On steady rotational cyclonic flows: The viscous bidirectional vortex
Authors: Majdalani Joseph , Chiaverini Martin J.
Published: October 2009

This study is focused on the tangential boundary layers of a bidirectional vortex, specifically those forming at the core and the sidewall of a swirl-driven cyclonic chamber. Our analysis is based on the regularized, tangential momentum equation which is rescaled in a manner to capture the forced vortex near the chamber axis and the no slip requirement at the sidewall. After identifying the coordinate transformations needed to resolve the rapid changes in the regions of nonuniformity, two inner expansions are constructed. These expansions are then matched with the outer, free vortex solution that is sandwiched between the core and the hard wall. By combining inner and outer expansions, uniformly valid approximations are subsequently obtained for the swirl velocity, vorticity, and pressure. These are shown to be strongly influenced by a dimensionless grouping that we refer to as the vortex Reynolds number, V. This keystone parameter appears as a ratio of the mean flow Reynolds number and the product of the swirl number and the chamber aspect ratio. Based on V, several fundamental features of the bidirectional vortex are quantified. Among them are the thicknesses of the viscous core and sidewall boundary layers; these decrease with V1/2 and V, respectively. The converse may be said of the peak velocity which increases with V1/2. In the same vein, the angular speed of the rigid-body rotation of the forced vortex is found to be linearly proportional to V. Our laminar swirl velocity is reminiscent of Sullivan’s two-cell vortex except for its additional dependence on the aspect ratio of the chamber. For the purpose of verification, theoretical predictions are compared to particle image velocimetry measurements and Navier–Stokes simulations at high vortex Reynolds numbers. By properly accounting for the turbulent eddy viscosity in the analytical model, local agreement is obtained with both laboratory measurements and computer simulations.
Compressive creep behavior of an electric brush-plated nanocrystalline Cu at room temperature
Authors: Wang Guoyong , Lian Jianshe , Jiang Zhonghao , Qin Liyuan , Jiang Qing
Published: October 2009

Creep tests were conducted on a nanocrystalline Cu at room temperature. The results at very low strain rates (<4×10−8 s−1) are consistent with Coble creep. An overall view of stress-strain rate behavior of this nanocrystalline Cu indicates that as the strain rate decreases, the deformation mechanism transition from predominantly dislocation activity to diffusion Coble creep, as evidenced by the strain rate sensitivity on stress trending to m=1 and activation volume trending to υ=1.5b3. The typical strain rate sensitivity of m=0.5 for surperplasticity can hardly be obtained at such low homogenous temperature.
Generalized form of anhysteretic magnetization function for Jiles–Atherton theory of hysteresis
Authors: Raghunathan A. , Melikhov Y. , Snyder J. E. , Jiles D. C.
Published: October 2009

A generalized form of anhysteretic magnetization function to extend Jiles–Atherton theory to different forms of anisotropy has been derived. The general equation for the function has been compared with those of calculations made on the basis of known equations for specific cases: axially anisotropic (one-dimensional), planar anisotropic (two-dimensional), and isotropic (three-dimensional). The Jiles–Atherton model using the proposed functional form of generalized anhysteretic magnetization function for anisotropy dependence has been validated and the necessary equations derived. It has been shown in this work that this functional form of anhysteretic magnetization with necessary boundary conditions can be reduced to the familiar specific model equations in the particular cases.
Explicit pure-state density operator structure for quantum tomography
Authors: Fan Hong-yi , Lv Cui-hong
Published: October 2009

The formulation of region operators named by D. Ellinas and A. J. Bracken [Phys. Rev. A 78, 052106 (2008)], which appears as the phase-space integration corresponding to the straight line over the Wigner operator, is manifestly improved and generalized. By virtue of the technique of integration within ordered (both normally ordered and Weyl ordered) product of operators, we show that the integration involved in the generalized region operator can be directly carried through to completion that leads to the explicit pure-state density operator |u⟩λ,τλ,τ⟨u|, where |u⟩λ,τ makes up the coordinate-momentum intermediate representation. This directly results in that the tomogram of a quantum state |ψ⟩ is just proportional to |⟨u|ψ⟩λ,τ|2, where ⟨u|ψ⟩λ,τ is the wave function of |ψ⟩ in the coordinate-momentum intermediate representation.
Optical Thomson scatter from a laser-ablated magnesium plume
Authors: Delserieys A. , Khattak F. Y. , Lewis C. L. S. , Riley D.
Published: October 2009

We have carried out an optical Thomson scatter study of a KrF laser-ablated Mg plume. The evolution of the electron temperature and density at distances 2–5mm from the target surface has been studied. We have observed that the electron density falls more rapidly than the atomic density and believe that this is a result of rapid dielectronic recombination. A comparison of the electron density profile and evolution with simple hydrodynamic modeling indicates that there is a strong absorption of the laser in the plasma vapor above the target, probably due to photoionization. We also conclude that an isothermal model of expansion better fits the data than an isentropic expansion model. Finally, we compared data obtained from Thomson scatter with those obtained by emission spectroscopy under similar conditions. The two sets of data have differences but are broadly consistent.
Influence of thin metal nanolayers on the photodetective properties of ZnO thin films
Authors: Liu K. W. , Liu B. , Wang S. J. , Wei Z. P. , Wu T. , Cong C. X. , Shen Z. X. , Sun X. W. , Sun H. D.
Published: October 2009

We investigate the photoconductivity properties of ZnO thin films prepared by pulsed laser deposition with and without metals (Au or Pt) on the surface. The covering of nanostructured metals can largely enhance the photocurrent. Meanwhile, the dark currents have been increased significantly due to the increase in carrier concentration and mobility near the surface of ZnO thin film. Although plasmonic effect was observed by the photoluminescence enhancement, the main mechanism of the increase in the dark current and photoresponsivity for ZnO photoconductors has been interpreted by surface states, interface states, and persistent photoconductivity.
Resistance of diamond (100) to hyperthermal atomic oxygen attack
Authors: Shpilman Z. , Gouzman I. , Grossman E. , Shen L. , Minton T. K. , Hoffman A.
Published: October 2009

The morphology of polycrystalline chemical vapor deposited (CVD) diamond films following the interaction with hyperthermal (∼5 eV) atomic oxygen (AO) was studied by atomic force microscopy. Selective etching of the (111) diamond facets occurred, while the (100) facets showed high endurance. The observed phenomenon is associated with the AO chemisorption energies on the various diamond facets. Only facets having an AO chemisorption energy lower than that of the incident AO were etched. AO is the dominant neutral component of the low-Earth-orbital environment; therefore, highly durable materials for space applications may be produced by utilizing diamond directional growth.
Selected Values of Critical Supersaturation for Nucleation of Liquids from the Vapor
Authors: Pound G. M.
Published: October 2009

Selected values of critical supersaturations for homogeneous nucleation of droplets from the vapor and for heterogeneous nucleation of droplets on the natural stationary concentration of gaseous ions are tabulated and plotted, and a rationale is given for selection of these data.
Investigation of high Curie temperature (1−x)BiSc1−yFeyO3–xPbTiO3 piezoelectric ceramics
Authors: Sterianou I. , Sinclair D. C. , Reaney I. M. , Comyn T. P. , Bell A. J.
Published: October 2009

Ceramics around the morphotropic phase boundary (MPB) in the (1−x)BiSc1−yFeyO3–xPbTiO3 solid solution were fabricated. For y=0.5, ceramics were single phase, and piezoelectric coefficients (d33) and electromechanical coupling coefficients (kp) for MPB compositions were 300 pC/N and 0.49, respectively; a level of piezoelectric activity similar to that of hard, lead zirconate titanate compositions but with TC∼60 °C higher at ∼440 °C. For ceramics with y≥0.7, dielectric measurements in combination with diffraction contrast transmission electron microscopy revealed the existence of two ferroelectric phases for most PbTiO3 contents studied. The presence of two ferroelectric phases was associated with a decrease in piezoelectric activity and although raw materials costs for y=0.7 and 0.8 with respect to y=0 were significantly lower (less Sc2O3) and TC greater (∼500 °C), d33 (∼100 pC/N) and kp (0.18) were too low to be commercially useful for actuator applications.
Comparison of the recently proposed super-Marx generator approach to thermonuclear ignition with the deuterium-tritium laser fusion-fission hybrid concept by the Lawrence Livermore National Laboratory
Authors: Winterberg F.
Published: October 2009

The recently proposed super-Marx generator pure deuterium microdetonation ignition concept is compared to the Lawrence Livermore National Ignition Facility (NIF) Laser deuterium-tritium fusion-fission hybrid concept (LIFE). In a super-Marx generator, a large number of ordinary Marx generators charge up a much larger second stage ultrahigh voltage Marx generator from which for the ignition of a pure deuterium microexplosion an intense GeV ion beam can be extracted. Typical examples of the LIFE concept are a fusion gain of 30 and a fission gain of 10, making up a total gain of 300, with about ten times more energy released into fission as compared to fusion. This means the substantial release of fission products, as in fissionless pure fission reactors. In the super-Marx approach for the ignition of pure deuterium microdetonation, a gain of the same magnitude can, in theory, be reached. If feasible, the super-Marx generator deuterium ignition approach would make lasers obsolete as a means for the ignition of thermonuclear microexplosions.
Electronegativity equalization model for interface barrier formation at reactive metal/organic contacts
Authors: Tang J. X. , Li Y. Q. , Wang S. D. , Lee C. S. , Lee S. T.
Published: October 2009

A general model based on electronegativity equalization method (EEM) is proposed for a quantitative formulation of barrier formation at reactive metal/organic interfaces. The present model predicts for molecular bonding formation a linear dependence of barrier heights on the degree of partial charge transfer, which is determined by the electronegativity difference between metals and molecules. Also, the calculated barrier heights show good agreement with the empirical values. It suggests that the EEM-based electronegativity model has captured the essence of barrier formation at reactive metal/organic interfaces, and that electronegativity is a fundamental factor in characterizing the chemical trend of barrier heights.
Dynamics of self-assembled droplet etching
Authors: Heyn Ch. , Stemmann A. , Hansen W.
Published: October 2009

We study the self-assembled local droplet etching of nanoholes in AlGaAs surfaces with Ga droplets. The data establish an unexpected delay of both the hole drilling process as well as the removal of the liquid material after etching. Furthermore, coarsening by Ostwald ripening is found to reduce the droplet density before drilling. Basing on these findings, we propose a growth, coarsening, drilling, and removal mechanism for the droplet etching process.
Ab initio-derived correlations for defect-dopant interactions in electronic materials
Authors: Haran Mohit , Clancy Paulette
Published: October 2009

This letter describes a parameter-free, simulation-free route to predict dopant-defect energetics under given hydrostatic strained silicon lattices using readily available physical constants such as electronegativity and size, and dimensionless correlations derived from density functional theory calculations. Illustration of the effectiveness of these correlations to predict the behavior of dopant materials is shown for strained SiGe materials. As a more stringent test of the reliability of the correlations and their ability to extend beyond the SiGe materials, we also demonstrate the accuracy of these correlations for the prediction of dopant energetics for other classes of electronic materials, such as the III/V material, GaAs.
Improved model for the angular dependence of excimer laser ablation rates in polymer materials
Authors: Pedder J. E. A. , Holmes A. S. , Dyer P. E.
Published: October 2009

Measurements of the angle-dependent ablation rates of polymers that have applications in microdevice fabrication are reported. A simple model based on Beer’s law, including plume absorption, is shown to give good agreement with the experimental findings for polycarbonate and SU8, ablated using the 193 and 248 nm excimer lasers, respectively. The modeling forms a useful tool for designing masks needed to fabricate complex surface relief by ablation.
Short range ordering in Fe–Ge and Fe–Ga single crystals
Authors: Huang Mianliang , Lograsso Thomas A.
Published: October 2009

We report on the nature of short range ordering (SRO) in slow cooled (100) and (111) Fe81.6Ga18.4 and Fe81Ge9 single crystals determined by x-ray θ-2θ scans. The SRO of the Ga atoms has at least some D03 character. In contrast Ge atoms only exhibit B2 chemical ordering symmetries in the short range order. It has been proposed that the D03 character in the SRO is important for the enhancement in magnetoelasticity in Fe-based alloys; however the presence of B2 character in Fe–Ge alloys suggest that the SRO is not of primary importance in increasing the magnetostriction.
Thermal convection of a viscoplastic liquid with high Rayleigh and Bingham numbers
Authors: Vikhansky A.
Published: October 2009

We consider the effect of yield stress on the Rayleigh–Bénard convection of a viscoplastic material. First we consider the model problem of convection in a differentially heated loop, which is described by the (modified) Lorenz equations. The presence of the yield stress significantly alters the dynamics of the system. In particular, the chaotic motion can stop suddenly (sometimes, after a period of chaotic oscillations). Guided by the model equations we performed direct numerical simulations of convection of the Bingham liquid in a square cavity heated from bellow. Our interest has been concentrated on the situation when both buoyancy and plastic forces are large. The obtained results are in a reasonable agreement with the predictions by the Lorenz equations.
Magnetic remanent states and quasistatic switching behavior of Fe split-rings for spin field-effect-transistor applications
Authors: Lee J. H. , Holmes S. N. , Hong B. , Roy P. E. , Mascaro M. D. , Hayward T. J. , Anderson D. , Cooper K. , Jones G. A. C. , Vickers M. E. , Ross C. A. , Barnes C. H. W.
Published: October 2009

The magnetic remanent states and switching behavior of Fe thin-film split-rings are investigated using magnetic force microscopy, magnetoresistance measurements, and micromagnetic simulations in order to assess their suitability as spin-filter contacts for spin field-effect-transistors. The gaps between the two halves of each ring are found to absorb then emit domain walls and act as pinning sites for “virtual” domain walls so that the observed switching mechanisms are similar to those of continuous rings. It is shown that these rings offer advantages over rectangular spin-filter contacts owing to their reduced stray fields and easy accessibility of the necessary magnetic states.
Increases in effective head field gradients in exchange spring media
Authors: Lee Jehyun , Suess Dieter , Schrefl Thomas , Dean Julian , Fidler Josef
Published: October 2009

Finite head field gradients in combination with switching field distribution of individual grains lead to transition jitter in granular recording media. We studied the effective head field gradients in various recording media structures using finite element micromagnetics. Inhomogeneous reversal was strongly induced in exchange spring structures that had a hard layer at the bottom. Due to the inhomogeneous reversal mode the effective head field gradient increases. As a result the transition jitter that is caused by an anisotropy distribution was reduced by more than 50% in exchange spring media compared to single phase media.
Observation of buried water molecules in phospholipid membranes by surface sum-frequency generation spectroscopy
Authors: Sovago Maria , Vartiainen Erik , Bonn Mischa
Published: October 2009

We investigate the structure and orientation of water molecules at the water-lipid interface, using vibrational sum-frequency generation in conjunction with a maximum entropy phase retrieval method. We find that interfacial water molecules have an orientation opposite to that predicted by electrostatics and thus are likely localized between the lipid headgroup and its apolar alkyl chain. This type of water molecule is observed for phospholipids but not for structurally simpler surfactants.
Microwave energy absorption driven by dynamic structural and magnetization states in Fe85B15 metallic glass ribbons
Authors: Nicula R. , Ishizaki K. , Stir M. , Catala-Civera J.-M. , Vaucher S.
Published: October 2009

The kinetics of the microwave crystallization of Fe85B15 metallic glasses was investigated in situ using the time-resolved x-ray diffraction method. It is shown that the recorded thermal profile during the microwave exposure of the ribbons bears a close relationship with the dynamic magnetization state during the decomposition of the amorphous phase into nanocrystalline α-Fe and Fe3B phases.