bluuebunny/crossref_metadata_2025 huggingface dataset:
Continental bedrock and riverine fluxes of strontium and neodymium isotopes to the oceans
Authors: Peucker‐Ehrenbrink Bernhard , Miller Mark W. , Arsouze Thomas , Jeandel Catherine
Published: March 2010

Realistic models of past climate and ocean chemistry depend on reconstructions of the Earth's surface environments in the geologic past. Among the critical parameters is the geologic makeup of continental drainage. Here we show, for the present, that the isotope composition of dissolved strontium in rivers increases linearly with the age of bedrock in drainage basins, with the notable exception of the drainage area of Arabia, India, and Southeast Asia that is affected by unusually radiogenic dissolved Sr from the Himalaya. We also demonstrate that the neodymium isotope compositions of suspended matter in rivers as well as clastic sediments deposited along the ocean margins decrease linearly with the bedrock ages of river drainage basins and large‐scale continental drainage regions, as determined from digital geologic maps. These correlations are used to calculate the present‐day input of dissolved Sr (4.7 × 1010 mol yr−1, 87Sr/86Sr of ∼0.7111) and particulate Nd isotopes (ɛNd of approximately −7.3 ± 2.2) to the oceans. The fact that the regionally averaged ɛNd of the global detrital input to the global coastal ocean is identical to globally averaged seawater (ɛNd of −7.2 ± 0.5) lends credence to the importance of “boundary exchange” for the Nd isotope composition of water masses. Regional biases in source areas of detrital matter and runoff are reflected by the observation that the average age of global bedrock, weighted according to the riverine suspended sediment flux, is significantly younger (∼336 Myr) than the age of global bedrock weighted according to water discharge (394 Myr), which is younger than the average bedrock age of the nonglaciated, exorheic portions of the continents (453 Myr). The observation that the bedrock age weighted according to Sr flux is younger (339 Myr) than that weighted according to water flux reflects the disproportionate contribution from young sedimentary and volcanic rocks to the dissolved Sr load. Neither the isotope composition of the dissolved nor the particulate continental inputs to the ocean provide unbiased perspectives of the lithologic makeup of the Earth's surface. Temporal changes in bedrock geology as well as the shifting focal points of physical erosion and water discharge will undoubtedly have exerted strong controls on temporal and spatial changes in the isotope chemistry of past global runoff and thus seawater.
Assessment of the usefulness of lithic clasts from pyroclastic deposits for paleointensity determination
Authors: Paterson Greig A. , Muxworthy Adrian R. , Roberts Andrew P. , Mac Niocaill Conall
Published: March 2010

Paleomagnetic and rock magnetic measurements were carried out on lithic clasts found within pyroclastic deposits to assess their potential for paleointensity determinations. The use of multiple lithologies in a single paleointensity determination would provide confidence that the result is not biased by alteration within one lithology. Lithic clasts were sampled from three historically active volcanoes: Láscar in the Chilean Andes, Mt. St. Helens, United States, and Vesuvius, Italy. At Láscar, triple heating paleointensity experiments allow development of new selection criteria for lithic clasts found within pyroclastic deposits. Using these criteria, the Láscar data yield a mean paleointensity of 24.3 ± 1.3 μT (1σ, N = 26), which agrees well with the expected value of 24.0 μT. This indicates that pyroclastic rocks have promise for paleointensity determinations. Pyroclastics, however, still suffer from the range of problems associated with conventional paleointensity experiments on lava flows. Samples from Mt. St. Helens are strongly affected by multidomain (MD) behavior, which results in all samples failing to pass the paleointensity selection criteria. At Vesuvius, MD grains, magnetic interactions, and chemical remanent magnetizations contributed to failure of all paleointensity experiments. Rock magnetic analyses allow identification of the causes of failure of the paleointensity experiments. However, in this study, they have not provided adequate preselection criteria for identifying pyroclastics that are suitable for paleointensity determination.
Analytical solutions for groundwater flow with arbitrary dimensionality and a finite well radius in fractured rock
Authors: Rehbinder G.
Published: March 2010

The generalized radial flow model describes mathematically nonsteady flow of arbitrary dimensionality from a source in a porous medium. Closed solutions of the corresponding equation have hitherto been considered as impractical except for one simple special case. Two closed solutions of the generalized radial flow equation, corresponding to given head in or given discharge from the source have been derived. The noninteger dimensionality is the only parameter in the problem. The solutions become not valid if the time tends to infinity, such as for 1‐D and 2‐D flows. The influence of a possible noninteger dimensionality has attracted interest in connection with the flow of groundwater in fractured rock, particularly around a repository for nuclear waste or in connection with grouting. In contrast to numerical solutions, the closed solutions offer simple means for evaluation of field tests.
Lava dome collapse detected using passive seismic interferometry
Authors: Baptie B. J.
Published: March 2010

The collapse of the lava dome at the Soufrière Hills Volcano on Montserrat in July 2003 is the largest recorded in historical times. I use noise correlation Green's functions to measure the changes in seismic properties that resulted from this collapse. Continuous three component seismic data recorded at two pairs of stations were cross‐correlated to retrieve three‐component Green's functions along two paths that intersect the volcanic edifice before and after the dome collapse. Particle motion analysis shows that the Green's functions are dominated by Rayleigh waves and are consistent with the expected Green's tensor for a vertical point force source at one station recorded by a three‐component receiver at the other. Following the collapse, there is a clear decorrelation and phase shift in the Green's functions corresponding to a change in velocity of approximately 0.5% that can be interpreted in terms of the unloading of the lava dome.
Caught in the act: Implications for the increasing abundance of mafic enclaves during the recent eruptive episodes of the Soufrière Hills Volcano, Montserrat
Authors: Barclay Jenni , Herd Richard A. , Edwards Ben R. , Christopher Thomas , Kiddle Emma J. , Plail Melissa , Donovan Amy
Published: March 2010

An exceptional opportunity to sample several large blocks sourced from the same region of the growing Soufrière Hills lava dome has documented a significant increase in the presence of mafic enclaves in the host andesite during the course of a long‐lived eruptive episode with several phases. In 1997 (Phase I) mafic inclusions comprised ∼1 volume percent of erupted material; in 2007 (Phase III) deposits their volumetric abundance increased to 5–7 percent. A broader range of geochemically distinctive types occurs amongst the 2007 enclaves. Crystal‐poor enclaves generally have the least evolved (basaltic) compositions; porphyritic enclaves represent compositions intermediate between basaltic and andesitic compositions. The absence of porphyritic enclaves prior to Phase III magmatism at Soufrière Hills Volcano suggests that a mixing event occurred during the course of the current eruptive episode, providing direct evidence consistent with geophysical observations that the system is continuously re‐invigorated from depth.
Effect of viscoelastic postseismic relaxation on estimates of interseismic crustal strain accumulation at Yucca Mountain, Nevada
Authors: Hammond William C. , Kreemer Corné , Blewitt Geoffrey , Plag Hans‐Peter
Published: March 2010

We estimate the long‐term crustal strain rate at Yucca Mountain (YM), Nevada from GPS velocities taking into account viscoelastic relaxation following recent earthquakes to remove bias associated with transient deformation. The YM data reveal postseismic relaxation in time series non‐linearity and geographic variation of the transient signal. From the data we estimate best‐fitting lower crust and upper mantle viscosities of 1019.5 Pa s and 1018.5 Pa s, respectively. Once the relaxation model predictions are subtracted from the data, the long‐term shear strain accumulation rate is between 16.3 and 25.1 nanostrains/year (ns/yr) to 99% confidence, a range much larger than the formal uncertainties from GPS measurement. We conclude that 1) a Maxwell viscoelastic model cannot explain all the deformation observed at YM, 2) uncertainty in viscosities dominates uncertainty in YM strain rates, and 3) the effects of large, recent earthquakes must be accounted for in seismic hazard studies using GPS.
Coseismic ground deformation of the 6 April 2009 L'Aquila earthquake (central Italy, Mw6.3)
Authors: Boncio P. , Pizzi A. , Brozzetti F. , Pomposo G. , Lavecchia G. , Di Naccio D. , Ferrarini F.
Published: March 2010

We provide field data of coseismic ground deformation related to the 6 April Mw 6.3 L'Aquila normal faulting earthquake. Three narrow fracture zones were mapped: Paganica‐Colle Enzano (P‐E), Mt. Castellano‐Mt. Stabiata (C‐S) and San Gregorio (SG). These zones define 13 km of surface ruptures that strike at 130–140°. We mapped four main types of ground deformation (free faces on bedrock fault scarps, faulting along synthetic splays and fissures with or without slip) that are probably due to the near‐surface lithology of the fault walls and the amount of slip that approached the surface coseismically. The P‐E and C‐S zones are characterized by downthrow to the SW (up to 10 cm) and opening (up to 12 cm), while the SG zone is characterized only by opening. Afterslip throw rates of 0.5–0.6 mm/day were measured along the Paganica fault, where paleoseismic evidence reveals recurring paleo‐earthquakes and post‐24.8 kyr slip‐rate ≥ 0.24 mm/yr.
Average genome size: a potential source of bias in comparative metagenomics
Authors: Beszteri Bánk , Temperton Ben , Frickenhaus Stephan , Giovannoni Stephen J
Published: March 2010

In gene-centric comparative metagenomics, differences in observed relative gene abundances among samples are often assumed to reflect the biological importance of individual genes in different habitats. Statistical tests and data mining for genes that represent habitat-specific adaptations are frequently based on this measure. We demonstrate that this measure is biased by the average genome size of the communities sampled. Average genome sizes can be estimated from the metagenomic data themselves, and taken into account in comparative analyses. We suggest that this would enable ecologically more meaningful comparisons, especially when the average genome sizes of compared communities differ substantially. We illustrate the influence of average genome-size differences on comparative analyses, with an example to highlight the need for further exploration of this bias.
Action Profile of the Antiobesity Drug Candidate Oleoyl‐Estrone in Rats
Authors: Strassburg Sabine , Pfluger Paul T. , Chaudhary Nilika , Tso Patrick , Tschöp Matthias H. , Anker Stefan D. , Nogueiras Ruben , Perez‐Tilve Diego
Published: March 2010

Oleoyl‐estrone (OE) has been presented as a potential antiobesity therapeutic, but the published series of studies from one laboratory has not yet been independently confirmed, and the exact mechanism of action is unknown. Based on the hypothesis that OE has potential for the treatment of obesity, male and female rats were chronically treated with several doses of OE to evaluate the impact of this compound on energy metabolism. Body weight, body composition, energy balance parameters and the expression of hypothalamic neuropeptides regulating food intake as well as key markers of the reproductive system were examined. OE impressively reduced food consumption and body weight gain in both sexes. Although a major part of the loss in body weight could be explained by decreased fat mass, a substantial loss of lean mass also occurred after OE administration. The loss of weight can be sufficiently explained by the suppression of food consumption, as there were no major changes in energy expenditure, locomotor activity or respiratory quotient. In situ hybridization data showed no significant change in the expression of key neuropeptides and hormone receptors regulating feeding behavior after OE treatment. Cocaine‐amphetamine‐regulated transcript (CART) mRNA levels were decreased in the arcuate nucleus of OE‐treated rats. Hypogonadism and low plasma testosterone levels were found in OE‐treated males, whereas females showed substantially increased liver size. The present data suggest that OE decreases food intake and body weight but also appears to cause a significant impact on the hypothalamus‐pituitary‐reproductive axis.
Food‐Related Odor Probes of Brain Reward Circuits During Hunger: A Pilot fMRI Study
Authors: Bragulat Veronique , Dzemidzic Mario , Bruno Carolina , Cox Cari A. , Talavage Thomas , Considine Robert V. , Kareken David A.
Published: March 2010

Food aromas can be powerful appetitive cues in the natural environment. Although several studies have examined the cerebral responses to food images, none have used naturalistic food aromas to study obesity. Ten individuals (five normal‐weight and five obese) were recruited to undergo 24 h of food deprivation. Subjects were then imaged on a 3T Siemens Trio‐Tim scanner (Siemens, Erlangen, Germany) while smelling four food‐related odors (FRO; two sweet odors and two fat‐related) and four “nonappetitive odors” (NApO; e.g., Douglas fir). Before the imaging session, subjects rated their desire to eat each type of food to determine their most preferred (P‐FRO). Across all 10 subjects, P‐FRO elicited a greater blood oxygenation level dependent (BOLD) response than the NApO in limbic and reward‐related areas, including the bilateral insula and opercular (gustatory) cortex, the anterior and posterior cingulate, and ventral striatum. Obese subjects showed greater activation in the bilateral hippocampus/parahippocampal gyrus, but lean controls showed more activation in the posterior insula. Brain areas activated by food odors are similar to those elicited by cues of addictive substances, such as alcohol. Food odors are highly naturalistic stimuli, and may be effective probes of reward‐related networks in the context of hunger and obesity.
Effects of Weight Reduction on Serum Vaspin Concentrations in Obese Subjects: Modification by Insulin Resistance
Authors: Chang Hye M. , Lee Hea J. , Park Hye S. , Kang Jae H. , Kim Kyung S. , Song Young S. , Jang Yeon J.
Published: March 2010

Visceral adipose tissue‐derived serpin (vaspin) has been regarded as a novel adipokine with potential insulin sensitizing properties. We investigated the changes of serum vaspin concentration in response to weight reduction, and the associations between changes in serum vaspin concentrations and changes of anthropometric and metabolic variables in obese subjects after weight reduction. We performed a longitudinal clinical intervention study on 63 obese persons enrolled in a 12‐week weight reduction program that included lifestyle modification and adjuvant treatment with the antiobesity agent orlistat. Anthropometric variables, lipid profiles, fasting glucose, fasting insulin, and serum vaspin concentrations were measured. Statistical analyses were performed according to the homeostasis model assessment of insulin resistance (HOMAIR). Serum vaspin concentrations decreased significantly in responders (≥2% reduction in baseline weight), but not in nonresponders (<2% reduction in baseline weight). Changes in serum vaspin concentrations were significantly correlated with body weight, BMI, waist circumference, and hip circumference in the higher, but not in the lower, HOMAIR group. In multivariate linear regression analysis, change in serum vaspin concentrations in the higher, but not in the lower, HOMAIR group was positively correlated with change in BMI and negatively correlated with initial HOMAIR level. The associations between changes in serum vaspin concentrations and changes in anthropometric and metabolic parameters differed according to insulin resistance status in obese subjects. These relationships were more prominent in the higher HOMAIR group. Insulin resistance may influence the correlations between changes in serum vaspin concentration and related metabolic variables.
Association Between Obesity, Flow Rate of Whole Saliva, and Dental Caries in Adolescents
Authors: Modéer Thomas , Blomberg Cecilia C. , Wondimu Biniyam , Julihn Annika , Marcus Claude
Published: March 2010

In a cross‐sectional study design, we test the hypothesis whether childhood obesity is associated with reduced flow rate of stimulated whole saliva and dental caries. Obese adolescents (n = 65) with a mean age of 14.5 years and normal weight subjects (n = 65) with a mean age of 14.2 years were clinically examined with respect to dental caries, visible plaque accumulation (visible plaque index (VPI%)), gingival inflammation in terms of bleeding on probing (BOP%) as well as answered a questionnaire concerning medical history, medication, oral hygiene habits, smoking habits, and sociodemographic background. The flow rate of stimulated whole saliva (ml/min) was determined. BMI was calculated and adjusted for age and gender (BMI‐sds). The obese subjects exhibited higher number of decayed surfaces (DS), 0.7 vs. 0.1 (P = 0.008) and lower flow rate of stimulated whole saliva 1.2 vs. 2.0 ml/min (P < 0.001). Of obese patients, 17 subjects had VPI% >25 and 21 had BOP% >25, both compared to only 5 subjects of the normal weight with P values of 0.005 and <0.001, respectively. In a multivariate logistic regression model BMI‐sds was significantly associated with the flow rate of stimulated whole saliva less than the median value 1.5 ml/min (P < 0.001; odds ratio (OR) 1.36) as well as with DS (DS >0) (P = 0.002; OR 1.31) and the associations were not found to be confounded by any of the studied variables. The results indicate that childhood obesity is associated with reduced flow rate of stimulated whole saliva and dental caries and further strengthens obesity's negative effect on children's oral health.
Bioimpedance Analysis Parameters and Epicardial Adipose Tissue Assessed by Cardiac Magnetic Resonance Imaging in Patients With Heart Failure
Authors: Doesch Christina , Suselbeck Tim , Leweling Hans , Fluechter Stephan , Haghi Dariush , Schoenberg Stefan O. , Borggrefe Martin , Papavassiliu Theano
Published: March 2010

There is increasing evidence that body composition should be considered as a systemic marker of disease severity in congestive heart failure (CHF). Prior studies established bioelectrical impedance analysis (BIA) as an objective indicator of body composition. Epicardial adipose tissue (EAT) quantified by cardiac magnetic resonance (CMR) is the visceral fat around the heart secreting various bioactive molecules. Our purpose was to investigate the association between BIA parameters and EAT assessed by CMR in patients with CHF. BIA and CMR analysis were performed in 41 patients with CHF and in 16 healthy controls. Patients with CHF showed a decreased indexed EAT (22 ± 5 vs. 34 ± 4 g/m2, P < 0.001) and phase angle (PA) (5.5° vs. 6.4°, P < 0.02) compared to healthy controls. Linear regression analysis showed a significant correlation of CMR indexed EAT with left ventricular ejection fraction (LV‐EF) (r = 0.56, P < 0.001), PA (r = 0.31, P = 0.01), total body muscle mass (TBMM) (r = 0.41, P = 0.001), fat‐free mass (FFM) (r = 0.30, P = 0.02), and intracellular water (ICW) (0.47, P = 0.0003). Multivariable analysis demonstrated that LV‐EF was the only independent determinant of indexed EAT (P < 0.0001). Receiver operating characteristic curve analysis indicated good predictive performance of PA and EAT (area under the curve (AUC) = 0.86 and 0.82, respectively) with respect to cardiac death. After a follow‐up period of 5 years, 8/41 (19.5%) patients suffered from cardiac death. Only indexed EAT <22 g/m2 revealed a statistically significant higher risk of cardiac death (P = 0.02). EAT assessed by CMR correlated with the BIA‐derived PA in patients with CHF. EAT and BIA‐derived PA might serve as additional prognostic indicators for survival in these patients. However, further clinical studies are needed to elucidate the prognostic relevance of these new findings.
Effect of Weight Loss on High‐Molecular Weight Adiponectin in Obese Children
Authors: Martos‐Moreno Gabriel Á. , Barrios Vicente , Martínez Guillermo , Hawkins Federico , Argente Jesús
Published: March 2010

Our aim was to determine the influence of weight reduction on total (T‐) and high‐molecular weight (HMW‐) adiponectin in obese (OB) prepubertal children. Seventy OB prepubertal white patients were followed for 18 months and studied after reducing their BMI by 1 (n = 51) and 2 standard deviation scores (SDS) (n = 21) under conservative treatment, and 6 months after achieving weight loss (n = 44). Body composition dual‐energy X‐ray absorptiometry (DXA) and serum levels of T‐ and HMW‐adiponectin, resistin, leptin, leptin soluble receptor (sOB‐R), tumoral necrosis factor‐α and interleukin‐6 were determined. The control group consisted of 61 healthy prepubertal children. At diagnosis T‐adiponectin was higher (P < 0.01; confidence interval (+0.04) — (+0.15)) and HMW‐adiponectin lower (P < 0.001; confidence interval (−0.45) − (−0.21)) in OB children than in controls. A reduction in body fat increased T‐ and HMW‐adiponectin and sOB‐R (all P < 0.001) and decreased leptin (P < 0.001) and interleukin‐6 levels (P < 0.05). After 6 months of sustained weight reduction a decrease in tumoral necrosis factor‐α (P < 0.01) occurred, whereas weight recovery increased leptin (P < 0.001) and decreased T‐adiponectin (P < 0.05). HMW‐adiponectin levels negatively correlated with homeostasis model assessment (HOMA) index and BMI in the whole cohort (both P < 0.001), as did T‐adiponectin levels and HOMA index in OB patients (P < 0.01), but neither T‐ nor HMW‐adiponectin correlated with body fat content (BFC) in OB children. We conclude that the impairment of T‐ and HMW‐adiponectin levels in childhood obesity is different to that in elder OB patients, showing closer relationship with carbohydrate metabolism parameters than with BFC, but increasing their levels after weight loss and in association with metabolic improvement.
Changing the solvent accessibility of the prion protein disulfide bond markedly influences its trafficking and effect on cell function
Authors: Tabrett Catherine A. , Harrison Christopher F. , Schmidt Bryan , Bellingham Shayne A. , Hardy Tristan , Sanejouand Yves-Henri , Hill Andrew F. , Hogg Philip J.
Published: March 2010

Prion diseases are fatal transmissible neurodegenerative diseases that result from structural conversion of the prion protein into a disease-associated isoform. The prion protein contains a single disulfide bond. Our analysis of all NMR structures of the prion protein (total of 440 structures over nine species) containing an explicit disulfide bond reveals that the bond exists predominantly in a stable low-energy state, but can also adopt a high-energy configuration. The side chains of two tyrosine residues and one phenylalanine residue control access of solvent to the disulfide bond. Notably, the side chains rotate away from the disulfide bond in the high-energy state, exposing the disulfide bond to solvent. The importance of these aromatic residues for protein function was analysed by mutating them to alanine residues and analysing the properties of the mutant proteins using biophysical and cell biological approaches. Whereas the mutant protein behaved similarly to wild-type prion protein in recombinant systems, the mutants were retained in the endoplasmic reticulum of mammalian cells and degraded by the proteasomal system. The cellular behaviour of the aromatic residue mutants was similar to the cellular behaviour of a disulfide bond mutant prion protein in which the cysteine residues were replaced with alanine, a result which is consistent with an unstable disulfide bond in the aromatic residue mutants. These observations suggest that the conformation of the prion protein disulfide bond may have implications for correct maturation and function of this protein.
Conductivity mismatch and voltage dependence of magnetoresistance in a semiconductor spin injection device
Authors: Roy Arunanshu M. , Nikonov Dmitri E. , Saraswat Krishna C.
Published: March 2010

Magnetoresistance (MR) in a semiconductor spin injection and detection device is simulated by combining the formalisms for tunneling probabilities and spin polarized carrier diffusion. Thereby dependences of resistance and spin selectivity at the ferromagnet-semiconductor interface on voltage as well as on material parameters are determined. This leads to predicting the voltage dependence of MR of the overall ferromagnet-semiconductor device. It is found to be qualitatively similar to that of a magnetic tunnel junction. Similarly the dependence of the MR on the tunneling barrier height and thickness, and doping density are studied. Optimal material parameters for detection of spin polarized current are thus determined, which are helpful for designing experiments on spin injection into semiconductors.
Burgers equation with a passive scalar: Dissipation anomaly and Colombeau calculus
Authors: Ohkitani Koji , Dowker Mark
Published: March 2010

A connection between dissipation anomaly in fluid dynamics and Colombeau’s theory of products of distributions is exemplified by considering Burgers equation with a passive scalar. Besides the well-known viscosity-independent dissipation of energy in the steadily propagating shock wave solution, the lesser known case of passive scalar subject to the shock wave is studied. An exact dependence of the dissipation rate ϵθ of the passive scalar on the Prandtl number Pr is given by a simple analysis: we show, in particular, ϵθ∝1/Pr for large Pr. The passive scalar profile is shown to have a form of a sum of tanh2n+1 x with suitably scaled x, thereby implying the necessity to distinguish H from Hn when Pr is large, where H is the Heaviside function and n is a positive integer. An incorrect result of ϵθ∝1/Pr would otherwise be obtained. This is a typical example where Colombeau calculus for products of weak solutions is required for a correct interpretation. A Cole–Hopf-type transform is also given for the case of unit Prandtl number.
Activation energy and switching behavior of two interacting identical magnetic particles
Authors: Plamadă Andrei-Valentin , Cimpoesu Dorin , Stancu Alexandru
Published: March 2010

An analytical method to study the magnetization behavior of a system composed of two magnetic particles is presented, when the magnetic field is applied in-plane. The study is based on a single-domain model, assuming that the particles are two ellipsoids with both exchange and magnetostatic coupling. The model is used to study the synthetic antiferromagnetic structure and a pair of particles with only dipolar interaction for bond angles β=0 and π/2. When the magnetic field is applied along the easy axis a complete description for the system’s minima, activation energy, and possible switches is performed.
Simulation of dynamical interaction between dislocations and dipolar loops
Authors: Minárik Vojtěch , Beneš Michal , Kratochvíl Jan
Published: March 2010

The article describes a model of interaction dynamics between a dislocation and dipolar dislocation loops. The interaction is essential for dipolar dislocation structure formation in early stages of a hardening process. For the description of the dislocation curve a direct parametric approach is employed whereas the loops are treated as rigid objects. The model equations are solved approximately by means of the finite-volume method. Physically interesting phenomena can be captured by the model provided the simulation covers long time periods. The strong interaction between the dislocation and the loops causes growing nonuniformity of distribution of discrete nodes along the dislocation curve. This effect is balanced by two proposed types of tangential redistribution of the discrete nodes. The redistribution is tested in simulations of loop clustering.
Nonempirical prediction of impurity segregation in α-Fe from first principles
Authors: Tsuru T. , Suzuki C. , Kaji Y. , Tsukada T.
Published: March 2010

The segregation and clustering of impurities in α-Fe were investigated by first principle density functional theory calculations. The segregation tendencies of various elements observed in reactor pressure vessels were considered and the interaction characteristics between Fe and each impurity element were estimated by mean field approximation. Stable N-atom impurity clusters were subsequently chosen to evaluate the changes in free energy for clustering. These calculations show that Cu and Mn impurities embedded in α-Fe are more stable when they are in the segregated state. Conversely, Nb and Ta are stable in the separately solute state. The present estimates provide reliable suggestions for the segregation characteristics, and the tendencies are in good agreement with the recent atom probe observations. We suggest that the segregation tendency is derived from the d-orbital interaction and that the solubility limit is not necessarily correlated with the tendency of clustering formation.
Voltage tunable surface acoustic wave phase shifter on AlGaN/GaN
Authors: Pedrós J. , Calle F. , Cuerdo R. , Grajal J. , Bougrioua Z.
Published: March 2010

A voltage tunable surface acoustic wave (SAW) phase shifter on a two-dimensional electron gas (2DEG) AlGaN/GaN heterostructure has been developed. The acoustoelectric interaction is field-effect modulated by means of an insulated gate placed in the acoustic path of a SAW delay line. The phase velocity under the gate is tuned by modifying the conductance of the 2DEG with a dc bias, while the insulating layer prevents the screening of the SAW piezoelectric fields by the gate. The device is compatible with the nitride transistor technology for signal processing and frequency control applications.
Structure and dynamics of the protic ionic liquid monomethylammonium nitrate ([CH3NH3][NO3]) from ab initio molecular dynamics simulations
Authors: Zahn Stefan , Thar Jens , Kirchner Barbara
Published: March 2010

The dynamics of the protic ionic liquid monomethylammonium nitrate is investigated by Car–Parrinello molecular dynamics simulations. On average, 1.8 of 3 possible hydrogen bond contacts are formed. Therefore, one hydrogen bond acceptor and one donor site in each ion pair of monomethylammonium nitrate remains free, which is similar to water. Furthermore, like water, monomethylammonium nitrate exhibits a fast fluctuating hydrogen bond network. The comparable hydrogen bond network and dynamics of both liquids might explain the similar impact on reactivity and selectivity found for chemical reactions. However, the hydrogen bond network of monomethylammonium nitrate and water show some structural differences. While the hydrogen bonds in water arrange in parallel fashion, the hydrogen bonds of monomethylammonium nitrate prefer angles of 0°, 90°, and 180°. The ion dynamics of monomethylammonium nitrate indicate that at about 85% of the ion pairs are still connected after 14.5 ps. A closer inspection of the first solvation shell dynamics of one cation reveals that after 11 ps the current ion pair conformation is independent of the initial ion pair conformation because the ion pairs lose their information of the initial ion pair conformation much faster than the time needed to escape from their solvent cage. The ion dynamics of monomethylammonium nitrate can be described by the following model: There are ions rattling in long living cages which are formed by long living ion pairs.
An experimental investigation on the performance of conical nozzles for argon cluster formation in supersonic jets
Authors: Lu Haiyang , Ni Guoquan , Li Ruxin , Xu Zhizhan
Published: March 2010

This work intends to get a better understanding of cluster formation in supersonic nozzles of different geometries. The throat diameters d are within 0.26 mm≤d≤0.62 mm, the half-opening-angle α within 4.2°≤α≤11.3°, and the length L of the conical section is 17.5 mm (eight nozzles) or 12 mm (two nozzles). Thus the so-called “equivalent sonic-nozzle diameter deq” for these conical nozzle geometries, defined by deq=0.74 d/tan α (for monatomic gases), is in the range of 1.59 mm≤deq≤5.21 mm. Source temperature for the clustering experiments was T0=298 K, and the backing pressure P0 was between 0.5 and 30 bars. The (average) cluster sizes observed for these conical nozzles deviate from the predictions of the simple stream-tube-model. These deviations are accounted for by introducing the so-called “effective equivalent sonic-nozzle diameter deq∗,” defined as the product of the equivalent sonic-nozzle diameter deq and a new parameter δ, deq∗=δdeq. The parameter δ serves to modify the equivalent diameters deq of the conical nozzles, which are applied in the idealized cases where the gas flows are suggested to be formed through free jet expansion. Then, δ represents the deviation of the performance in cluster formation of the practical conical nozzles from those predicted based on the idealized picture. The experimental results show that the values of δ can be described by an empirical formula, depending on the gas backing pressure P0 and the parameter deq of the conical nozzles. The degradation of the performance of the present conical nozzles was found with the increase in P0 and the larger deq. It was revealed that δ is inversely proportional to a fractional power (∼0.5–0.6) of the molecular density nmol in the gas flows under the present experimental conditions. The boundary layers effects are considered to be mainly responsible for the restriction of the performance of the conical nozzles in cluster formation.
Optical coherence tomography for process control of laser micromachining
Authors: Wiesner Markus , Ihlemann Jürgen , Müller Heike H. , Lankenau Eva , Hüttmann Gereon
Published: March 2010

In situ surface imaging for nondestructive evaluation (NDE) by optical coherence tomography (OCT) before, during, and after ablative laser processing is presented. Furthermore, it is shown that the ability of in situ characterization is beneficial for samples such as optical fibers, which are difficult to handle in the standard analysis. Surface images taken by the OCT are compared with these common analysis tools such as scanning electron microscopy (SEM), reflected-light, and confocal microscopy. An axial resolution of ∼126 nm for surface detection and a lateral resolution <2.5 μm are obtained and the potential of the setup to imaging structures with high aspect ratio is demonstrated.
Development of multiwavelength-range fine-resolution spectrometer for hydrogen emissions and its application to large helical device periphery plasmas
Authors: Fujii K. , Mizushiri K. , Nishioka T. , Shikama T. , Iwamae A. , Goto M. , Morita S. , Kado S , Sawada K. , Hasuo M.
Published: March 2010

We developed a spectrometer specialized for simultaneous observation of the hydrogen Balmer-α, -β, -γ lines and the Fulcher-α v′=v″=2 rovibronic transition band. The spectrometer was optimized for the light input coupled by nine optical fibers having 400 μm core diameters. The spectral resolutions were 0.02–0.03 nm for these wavelength ranges at the entrance slit width of 20 μm. The polarization resolved spectra of these emissions from the peripheral region of large helical device (LHD) plasmas were measured simultaneously and showed the polarization dependence coming from the magnetic field in the LHD plasma.
Compression of 1.8 μm laser pulses to sub two optical cycles with bulk material
Authors: Schmidt Bruno E. , Béjot Pierre , Giguère Mathieu , Shiner Andrew D. , Trallero-Herrero Carlos , Bisson Éric , Kasparian Jérôme , Wolf Jean-Pierre , Villeneuve David M. , Kieffer Jean-Claude , Corkum Paul B. , Légaré François
Published: March 2010

We demonstrate a simple scheme to generate 0.4 mJ 11.5 fs laser pulses at 1.8 μm. Optical parametrically amplified pulses are spectrally broadened by nonlinear propagation in an argon-filled hollow-core fiber and subsequently compressed to 1.9 optical cycles by linear propagation through bulk material in the anomalous dispersion regime. This pulse compression scheme is confirmed through numerical simulations.
Effect of removing the no-virtual pair approximation on the correlation energy of the He isoelectronic sequence. II. Point nuclear charge model
Authors: Watanabe Yoshihiro , Nakano Haruyuki , Tatewaki Hiroshi
Published: March 2010

The correlation energies (CEs) of the He isoelectronic sequence Z=2–116 with a point nuclear charge model were investigated with the four component relativistic configuration interaction method. We obtained CEs with and without the virtual pair approximation which are close to the values from Pestka et al.’s Hylleraas-type configuration interaction calculation. We also found that the uniform charge and point charge models for the nucleus differ substantially for Z≥100.
Vibrational dynamics of permanently densified GeO2 glasses: Densification-induced changes in the boson peak
Authors: Orsingher L. , Fontana A. , Gilioli E. , Carini G. , Carini G. , Tripodo G. , Unruh T. , Buchenau U.
Published: March 2010

Vitreous GeO2, one of the main prototypes of strong glasses, was densified at several pressures up to 6 GPa, achieving more than 20% of densification. The density dependence of the vibrational density of states and of the low temperature properties of these glasses was investigated by means of inelastic neutron scattering and calorimetric measurements. With increasing density, both the boson peak and the bump in cp/T3 versus T plot exhibit variations which are stronger than the elastic medium expectation. If one reduces the measured spectra to a common master curve, one finds that this is only possible for the densified samples; the first densification step has an additional effect, similar to other cases in the literature. Nevertheless, the existence of a master curve for the three densified samples proves that the total number of excess modes remains constant on further densification. The experimental data are discussed in the framework of different theoretical models.
A wideband magnetic energy harvester
Authors: Zhang C. L. , Chen W. Q.
Published: March 2010

A wideband magnetic energy harvester is proposed by using a number of multiferroic composite fibers of different lengths which are connected in parallel or series. The structural theory is employed to characterize the magnetoelectroelastic behavior of the fibers. A global circuit analysis is then performed. It is shown that such a structure of energy harvester is capable of collecting the ambient magnetic energy over a wide frequency range.
Cross sections for the valence shell excitations of nitrous oxide studied by fast electron impact
Authors: Wang You-Yan , Sun Jian-Min , Zhu Lin-Fan
Published: March 2010

The generalized oscillator strengths, differential cross sections, as well as the integral cross sections for electron impact excitation of the B Δ1, C Π1, and D Σ1+ states of N2O have been determined at an incident electron energy of 2500 eV. A generalized oscillator strength analysis reveals that the B Δ1←X Σ1+ transition is dominated by the quadrupolar component. From the comparison to the previous experimental results, it is found that the first Born approximation is not satisfied for the C Π1 excitation while it is valid for the D Σ1+ excitation at an incident electron energy of 200 eV. The BE-scaled integral cross section for the B Δ1 excitation from its threshold to 5000 eV was calculated based on its generalized oscillator strength, and the present integral cross sections for the excitation of the C Π1 and D Σ1+ states are in good agreement with the calculations using the BEf-scaling approach.
Analysis of electrowetting-driven spreading of a drop in air
Authors: Oh Jung Min , Ko Sung Hee , Kang Kwan Hyoung
Published: March 2010

A set of shape mode equations is derived to describe unsteady motions of a sessile drop actuated by electrowetting. The unsteady, axially symmetric, and linearized flow field is analyzed by expressing the shape of a drop using the Legendre polynomials. A modified boundary condition is obtained by combining the contact angle model and the normal stress condition at the surface. The electrical force is assumed to be concentrated on one point (i.e., three-phase contact line) rather than distributed on the narrow surface of the order of dielectric layer thickness near the contact line. Then, the delta function is used to represent the wetting tension, which includes the capillary force, electrical force, and contact line friction. In previous work [J. M. Oh et al., Langmuir 24, 8379 (2008)], the capillary forces of the air-substrate and liquid-substrate interfaces were neglected, together with the contact-line friction. The delta function is decomposed into a weighted sum of the Legendre polynomials so that each component becomes a forcing term that drives a shape mode of motion. The shape mode equations are nonlinearly coupled between modes due to the contact line friction. The equilibrium contact angle of electrowetting predicted by the present method shows a good agreement with the Lippmann–Young equation and with our experimental results. The present theoretical model is also validated by predicting the spreading of a drop for step input voltages. It shows qualitative agreement with experimental results in temporal evolution of drop shape.
Configurational and residual entropies of nonergodic crystals and the entropy’s behavior on glass formation
Authors: Johari G. P.
Published: March 2010

We use thermodynamics of lattice vacancies to test the merits of the view that (i) statistical entropy, kB ln Ω, vanishes on vitrification of a liquid and hence there is no residual entropy and (ii) kB ln Ω of a nonergodic state would increase with time t as its structure relaxes. We argue that this view conflicts with the precepts of the configurational entropy of a crystal, −R[x ln x+(1−x)ln(1−x)], where x is the fractional population of vacancies, and with the observed decrease in x with t on structural relaxation. The issue of whether the entropy of a kinetically arrested crystal state is equal to kB ln Ω or equal to −R[x ln x+(1−x)ln(1−x)] can be resolved by measuring the vapor pressure, the emf of an electrolytic cell, and by scanning calorimetry. We also consider how the energy landscapes of a crystal and liquid differ, and point out that since crystals are in a nonequilibrium state, their thermodynamic data are inappropriate for testing the validity of the third law.
Physics-based analysis of the hydrodynamic stress in a fluid-particle system
Authors: Zhang Quan , Prosperetti Andrea
Published: March 2010

The paper begins by showing how standard results on the average hydrodynamic stress in a uniform fluid-particle system follow from a direct, elementary application of Cauchy’s stress principle. The same principle applied to the angular momentum balance proves the emergence, at the mesoscale, of an antisymmetric component of the volume-averaged hydrodynamic stress irrespective of the particle Reynolds number. Several arguments are presented to show the physical origin of this result and to explain how the averaging process causes its appearance at the mesoscale in spite of the symmetry of the microscale stress. Examples are given for zero and finite Reynolds number, and for potential flow. For this last case, the antisymmetric stress component vanishes, but the Cauchy principle proves nevertheless useful to derive in a straightforward way known results and to clarify their physical nature.
Assessing the thermodynamic signatures of hydrophobic hydration for several common water models
Authors: Ashbaugh Henry S. , Collett Nicholas J. , Hatch Harold W. , Staton Jennifer A.
Published: March 2010

Following the conclusions of an information theory analysis that hydrophobic hydration is dictated by the equation of state of liquid water, we perform simulations of ten different water models to examine the correlation between the fidelity of each model to the experimental density of liquid water and the accuracy of its description of methane hydration. We find that the three- and five-point water models provide an inferior description of both the liquid density and methane solubility compared to the four-point water models. Of the four-point water models, TIP4P/2005 provides the best description of both the aqueous equation-of-state and methane hydration thermodynamics. When the optimized potentials for liquid simulation united-atom description for methane is used, we find that while the entropy and heat capacity of methane hydration are in excellent agreement with experiment, the chemical potential and enthalpy are systematically shifted upwards. We subsequently reoptimize the methane interaction to accurately reproduce the experimental solubilities as a function of temperature by accounting for missing attractive interactions.
Thermospin effects of a quasi-one-dimensional system in the presence of spin-orbit interaction
Authors: Lü Hai-Feng , Zhu Liang-Chen , Zu Xiao-Tao , Zhang Huai-Wu
Published: March 2010

The authors investigate the effect of Rashba spin-orbit interaction (SOI) and external magnetic field on the thermospin properties of a quasi-one-dimensional ballistic electron system. Spin analogs to the thermoelectric Seebeck coefficient and figure of merit (FOM) are defined and studied. Sign reversal and oscillation of spin Seebeck coefficient are indicated as a function of junction parameters. With the increase of SOI strength, the spin Seebeck coefficient oscillates more rapidly and the intervals between adjacent peaks are narrowed. Because large thermal conductance is induced by the more conducting paths, spin-FOM in the presence system is smaller than that of a quantum dot device.
Colossal electroresistance and colossal magnetoresistance in spinel multiferroic CdCr2S4
Authors: Sun C. P. , Huang C. L. , Lin C. C. , Her J. L. , Ho C. J. , Lin J.-Y. , Berger H. , Yang H. D.
Published: March 2010

Colossal magnetoresistance (CMR) and colossal electroresistance (CER) induced by the electric field in spinel multiferroic CdCr2S4 are reported. It is found that a metal-insulator transition in CdCr2S4 is triggered by the electrical field. In magnetic fields, the resistivity ρ of CdCr2S4 responds similarly to that of CMR manganites. Combing previous reports, these findings make CdCr2S4 the unique compound to possess all four properties of the colossal magnetocapacitive, colossal electrocapacitive, CER, and CMR. The present results open a new venue for searching new materials to show CMR by tuning electric and magnetic fields.
Heterojunction of Fe(Se1−xTex) superconductor on Nb-doped SrTiO3
Authors: Wu C. T. , Chang H. H. , Luo J. Y. , Chen T. J. , Hsu F. C. , Chen T. K. , Wang M. J. , Wu M. K.
Published: March 2010

We report the fabrication of heterojunctions formed by the FeSe0.5Te0.5 (FeSeTe) superconductor and Nb-doped SrTiO3 semiconducting substrate and their properties. At high temperature when FeSeTe is in its normal state, the forward bias I−V curves behave like a metal-semiconductor junction with a low Schottky barrier. Direct tunneling through the thin depletion layer of the junction dominates the reverse bias I−V curves. When FeSeTe film becomes superconducting at low temperature, we observed that the Schottky barrier height of the junction increased but was suppressed by an external magnetic field. This deviation provides an estimate of the superconducting energy gap of the FeSeTe film.