bluuebunny/crossref_metadata_2025 huggingface dataset:
Plasma Phospholipid Fatty Acid and Ex Vivo Neutrophil Responses are Differentially Altered in Dogs Fed Fish‐ and Linseed‐Oil Containing Diets at the Same n‐6:n‐3 Fatty Acid Ratio
Authors: Waldron Mark K. , Hannah Steven S. , Bauer John E.
Published: January 2012

The effect of diets containing either 18‐carbon n‐3 fatty acids (FA) or 20/22‐carbon n‐3 FA on canine plasma and neutrophil membrane fatty acid composition, superoxide and leukotriene B4 and B5 production when fed at the same n‐6:n‐3 fatty acid ratio was investigated. Four groups of ten dogs each were fed a low fat basal diet supplemented with safflower oil (SFO), beef tallow (BTO), linseed oil (LSO), or Menhaden fish oil (MHO) for 28 days. Dietary fat provided 40.8% of energy and the n‐6:n‐3 of the diets were ~100:1, 9.7:1, 0.38:1, and 0.34:1 for the SFO, BTO, LSO and MHO groups, respectively. The MHO and LSO groups had increased incorporation of EPA and DPA in both the plasma and neutrophil membranes compared to the BTO and SFO groups. DHA was observed in the MHO but not in the LSO group. Neutrophils from the MHO diet fed dogs had less LTB4 and greater LTB5 than the other three groups. The LSO group also showed a reduction in LTB4 and greater LTB5 production compared to the SFO and BTO groups. Both LSO and MHO groups had lower superoxide production compared to the SFO and BTO groups. Diets containing 18 or 20/22 carbon n‐3 FA fed at the same n‐6:n‐3 resulted in differential incorporation of long chain n‐3 FA into neutrophil membranes. Thus, fatty acid type and chain length individually affect neutrophil membrane structure and function and these effects exist independent of dietary total n‐6:total n‐3 FA ratios.
Fully resolved numerical simulation of particle-laden turbulent flow in a horizontal channel at a low Reynolds number
Authors: Shao Xueming , Wu Tenghu , Yu Zhaosheng
Published: January 2012

A fictitious domain method is used to perform fully resolved numerical simulations of particle-laden turbulent flow in a horizontal channel. The effects of large particles of diameter 0.05 and 0.1 times the channel height on the turbulence statistics and structures are investigated for different settling coefficients and volume fractions (0.79 %–7.08 %) for the channel Reynolds number being 5000. The results indicate the following. (a) When the particle sedimentation effect is negligible (i.e. neutrally buoyant), the presence of particles decreases the maximum r.m.s. of streamwise velocity fluctuation near the wall by weakening the intensity of the large-scale streamwise vortices, while increasing the r.m.s. of the streamwise fluctuating velocity in the region very close to the wall and in the centre region. On the other hand, the particles increase the r.m.s. of transverse and spanwise fluctuating velocities in the near-wall region by inducing the small-scale vortices. (b) When the particle settling effect is so substantial that most particles settle onto the bottom wall and form a particle sediment layer (SL), the SL plays the role of a rough wall and parts of the vortex structures shedding from the SL ascend into the core region and substantially increase the turbulence intensity there. (c) When the particle settling effect is moderate, the effects of particles on the turbulence are a combination of the former two situations, and the Shields number is a good parameter for measuring the particle settling effects (i.e. the particle concentration distribution in the transverse direction). The average velocities of the particle are smaller in the lower half-channel and larger in the upper half-channel compared to the local fluid velocities in the presence of gravity effects. The effects of the smaller particles on the turbulence are found to be stronger at the same particle volume fractions.
Rarefied gas flow around a sharp edge induced by a temperature field
Authors: Taguchi Satoshi , Aoki Kazuo
Published: January 2012

A rarefied gas flow thermally induced around a heated (or cooled) flat plate, contained in a vessel, is considered in two different situations: (i) both sides of the plate are simultaneously and uniformly heated (or cooled); and (ii) only one side of the plate is uniformly heated. The former is known as the thermal edge flow and the latter, typically observed in the Crookes radiometer, may be called the radiometric flow. The steady behaviour of the gas induced in the container is investigated on the basis of the Bhatnagar–Gross–Krook (BGK) model of the Boltzmann equation and the diffuse reflection boundary condition by means of an accurate finite-difference method. The flow features are clarified for a wide range of the Knudsen number, with a particular emphasis placed on the structural similarity between the two flows. The limiting behaviour of the flow as the Knudsen number tends to zero (and thus the system approaches the continuum limit) is investigated for both flows. The detailed structure of the normal stress on the plate as well as the cause of the radiometric force (the force acting on the plate from the hotter to the colder side) is also clarified for the present infinitely thin plate.
Equity Mispricing and Leverage Adjustment Costs
Authors: Warr Richard S. , Elliott William B. , Koëter-Kant Johanna , Öztekin Özde
Published: January 2012

We find that equity mispricing impacts the speed at which firms adjust to their target leverage (TL) and does so in predictable ways depending on whether the firm is over- or underlevered. For example, firms that are above their TL and should therefore issue equity (or retire debt) adjust more rapidly toward their target when their equity is overvalued. However, when a firm is undervalued but needs to reduce leverage, the speed of adjustment is much slower. Our findings support the role of equity mispricing as an important factor that alters the cost of making capital structure adjustments.
Current considerations of the effects of untreated maternal perinatal depression and the National Perinatal Depression Initiative
Authors: Hall P.
Published: January 2012

Postnatal and antenatal depression present significant public health concerns. Current opinion on the use of these terms is noted. Previous research findings demonstrate that detrimental effects of untreated maternal depression/anxiety are potentially severe and impact on the whole family; longer-term effects on child development are described. Australia has responded to such overwhelming empirical evidence by the implementation of the National Perinatal Depression Initiative. Key objectives and a brief overview of the work in progress of this Initiative are offered.
Advanced Asian summer monsoon onset in recent decades
Authors: Kajikawa Yoshiyuki , Yasunari Tetsuzo , Yoshida Shuhei , Fujinami Hatsuki
Published: January 2012

In this paper, we first elucidate the significant seasonality in long‐term trends in the Asian monsoon on a monthly mean basis. Advanced monsoon onsets over the Bay of Bengal and the western Pacific were evident in recent decades. Increasing rainfall in May along 10°N reflected the advanced monsoon onset. Decreasing rainfall trends in June along 10°N were also detected. Because the rainfall trends in July and August showed less significance, the monsoon transition phase should be discussed in the context of climate change rather than boreal summer mean field. The advanced monsoon onset and weakening of the monsoon during early summer are most likely to be attributed to the heat contrast between the Asian landmass and the tropical Indian Ocean. The heating trend over the Asian landmass primarily contributes to the heat contrast variability with the persistent SST increase in the Indian Ocean throughout the season.
A comparison of lower thermospheric winds derived from range spread and specular meteor trail echoes
Authors: Li Guozhu , Ning Baiqi , Hu Lianhuan , Chu Yen‐Hsyang , Reid I. M. , Dolman B. K.
Published: January 2012

Interferometry measurements of range spread meteor trail echoes (RSTEs; also known as nonspecular echoes) have provided new insights into both the irregularity structures in meteor trails and lower‐thermospheric winds (LTWs). In this study, we used trail echoes observed with the newly installed Sanya (18.4°N, 109.6°E) 47.5 MHz VHF coherent radar and the Sanya all‐sky meteor radar to estimate instantaneous zonal and hourly averaged meridional winds from RSTEs and hourly averaged zonal and meridional winds from large numbers of specular meteor echoes. The mean height variations in both the zonal and meridional winds estimated from the RSTEs were generally consistent with those estimated from specular meteor echoes below 96 km. This gives validity to the technique proposed recently by Oppenheim et al. (2009) and suggests that RSTE measurements made with a small radar can be used to investigate LTWs, whereas this had previously been limited to larger radars such as the Jicamarca radar. However, some observations show significant differences in wind magnitude at individual heights at times. The results of RSTE measurements show the presence of an intense westward wind with a speed near 100 ms−1. In contrast, the specular meteor zonal winds were generally less than 50 ms−1. On the other hand, the meridional drift of RSTEs derived from the meridional Doppler velocity at higher altitudes shows a very poor correlation with the specular meteor meridional wind. Potential causes for the discrepancy in wind estimates obtained from RSTE and specular meteor trail echoes are discussed.
Unsteady late Pleistocene incision of streams bounding the Colorado Front Range from measurements of meteoric and in situ 10Be
Authors: Dühnforth Miriam , Anderson Robert S. , Ward Dylan J. , Blum Alex
Published: January 2012

Dating of gravel‐capped strath terraces in basins adjacent to western U.S. Laramide Ranges is one approach to document the history of late Cenozoic fluvial exhumation. We use in situ 10Be measurements to date the broad surfaces adjacent to the eastern edge of the Rocky Mountains in Colorado, and compare these calculated ages with results from meteoric 10Be measurements. We analyze three sites near Boulder, Colorado (Gunbarrel Hill, Table Mountain, and Pioneer) that have been mapped as the oldest terrace surfaces with suggested ages ranging from 640 ka to the Plio‐Pleistocene transition. Our in situ 10Be results reveal abandonment ages of 95 ± 129 ka at Table Mountain, 175 ± 27 ka at Pioneer, and ages of 251 ± 10 ka and 307 ± 15 ka at Gunbarrel Hill. All are far younger than previously thought. Inventories of meteoric 10Be support this interpretation, yielding ages that are comparable to Table Mountain and ∼20% lower than Pioneer in situ ages. We argue that lateral beveling by rivers dominated during protracted times of even moderate glacial climate, and that vertical incision rates of several mm/yr likely occurred during times of very low sediment supply during the few interglacials that were characterized by particularly warm climate conditions. In contrast to the traditional age chronology in the area, our ages suggest that the deep exhumation of the western edge the High Plains occurred relatively recently and at an unsteady pace.
Controlled CO2 injection into heterogeneous geologic formations for improved solubility and residual trapping
Authors: Shamshiri Hossein , Jafarpour Behnam
Published: January 2012

Geologic CO2 storage (GCS) has been proposed as a potentially viable climate change mitigation option. Among the trapping mechanisms known for permanent CO2 storage in saline aquifers, solubility and residual trapping are important for safe short‐term entrapment. These storage mechanisms are hampered by density‐driven upward CO2 movement that inhibits the lateral migration of the plume, leaving a large portion of the aquifer volume unexposed to CO2 and unavailable for storage. Heterogeneity of aquifer hydraulic properties and high horizontal/vertical hydraulic conductivity ratio of geologic formations are two competing mechanisms that can hinder upward CO2 migration. Postinjection displacement of free‐phase CO2 is somewhat controlled by the heterogeneity in rock permeability and porosity distributions. In particular, low permeability shale layers that act as vertical flow barrier and high‐permeability horizontal channels that form flow conduits can spread the CO2 plume laterally in the aquifer. In this paper, we consider CO2 storage in heterogeneous saline aquifers and propose controlled CO2 injection, based on existing knowledge of heterogeneity, to increase CO2 contact with brine and improve the solubility and residual trapping and the overall aquifer storage potential. We examine two optimization methods: directly maximizing the total stored gas in the aquifer, and maximizing the sweep efficiency of the CO2 flood to promote uniform displacement in all directions. We consider the effect of geologic uncertainty on the performance of the controlled injection schemes by using an ensemble of model realizations to represent the uncertainty in aquifer property distribution. We also show how a controlled injection can be used to mitigate the risk of leakage from potential pathways, such as an abandoned well, by restricting CO2 movement toward the leakage zone. Our results suggest that controlled injection can lead to substantial improvements in residual and dissolution trapping and can be used to divert a CO2 plume from approaching sensitive zones or leakage pathways.
An algorithm for treating flat areas and depressions in digital elevation models using linear interpolation
Authors: Pan Feifei , Stieglitz Marc , McKane Robert B.
Published: January 2012

Digital elevation model (DEM) data are essential to hydrological applications and have been widely used to calculate a variety of useful topographic characteristics, e.g., slope, flow direction, flow accumulation area, stream channel network, topographic index, and others. Except for slope, none of the other topographic characteristics can be calculated until the flow direction at each pixel within a DEM is determined. However, flow direction cannot be accurately calculated until depressions and flat areas within a DEM have been rectified. This is a routine problem in hydrologic modeling, because virtually all DEMs contain flat and sink pixels, both real and artifactual, that if left untreated will prevent accurate simulation of hydrologic flow paths. Although a number of algorithms are available for rectifying flat and sink pixels in DEM data, treatment of flat areas and depressions and calculation of flow direction remain problematic for reasons of complexity and uncertainty. A new algorithm that effectively rectifies flat and sink pixels was developed and tested. The approach is to use linear interpolation between low elevation grid cells on the edge of each flat area or depression defined as outlets and higher elevation grid cells on the opposite side defined as inflow pixels. The implementation requires an iterative solution to accommodate the irregular geometry of flat areas or depressions and exceptions that arise. Linear interpolation across flat areas or depressions provides a natural way to scale elevation adjustments based on the vertical scale of the surrounding topography, thereby avoiding the addition or subtraction of arbitrary small numbers that we regard as a disadvantage in some prior techniques. Tests for two virtual terrains and one real terrain show that our algorithm effectively rectifies flat areas and depressions, even in low‐relief terrain, and produces realistic patterns of flow accumulation and extracted channel networks.
Salt marsh ecohydrological zonation due to heterogeneous vegetation–groundwater–surface water interactions
Authors: Moffett Kevan B. , Gorelick Steven M. , McLaren Robert G. , Sudicky Edward A.
Published: January 2012

Vegetation zonation and tidal hydrology are basic attributes of intertidal salt marshes, but specific links among vegetation zonation, plant water use, and spatiotemporally dynamic hydrology have eluded thorough characterization. We developed a quantitative model of an intensively studied salt marsh field site, integrating coupled 2‐D surface water and 3‐D groundwater flow and zonal plant water use. Comparison of model scenarios with and without heterogeneity in (1) evapotranspiration rates and rooting depths, according to mapped vegetation zonation, and (2) sediment hydraulic properties from inferred geological heterogeneity revealed the coupled importance of both sources of ecohydrological variability at the site. Complex spatial variations in root zone pressure heads, saturations, and vertical groundwater velocities emerged in the model but only when both sources of ecohydrological variability were represented together and with tidal dynamics. These regions of distinctive root zone hydraulic conditions, caused by the intersection of vegetation and sediment spatial patterns, were termed “ecohydrological zones” (EHZ). Five EHZ emerged from different combinations of sediment hydraulic properties and evapotranspiration rates, and two EHZ emerged from local topography. Simulated pressure heads and groundwater dynamics among the EHZ were validated with field data. The model and data showed that hydraulic differences between EHZ were masked shortly after a flooding tide but again became prominent during prolonged marsh exposure. We suggest that ecohydrological zones, which reflect the combined influences of topographic, sediment, and vegetation heterogeneity and do not emphasize one influence over the others, are the fundamental spatial habitat units comprising the salt marsh ecosystem.
Can Stereotype Threat Explain the Gender Gap in Mathematics Performance and Achievement?
Authors: Stoet Gijsbert , Geary David C.
Published: January 2012

Men and women score similarly in most areas of mathematics, but a gap favoring men is consistently found at the high end of performance. One explanation for this gap, stereotype threat, was first proposed by Spencer, Steele, and Quinn (1999) and has received much attention. We discuss merits and shortcomings of this study and review replication attempts. Only 55% of the articles with experimental designs that could have replicated the original results did so. But half of these were confounded by statistical adjustment of preexisting mathematics exam scores. Of the unconfounded experiments, only 30% replicated the original. A meta-analysis of these effects confirmed that only the group of studies with adjusted mathematics scores displayed the stereotype threat effect. We conclude that although stereotype threat may affect some women, the existing state of knowledge does not support the current level of enthusiasm for this as a mechanism underlying the gender gap in mathematics. We argue there are many reasons to close this gap, and that too much weight on the stereotype explanation may hamper research and implementation of effective interventions.
The interplay between endoplasmic reticulum stress and inflammation
Authors: Hasnain Sumaira Z , Lourie Rohan , Das Indrajit , Chen Alice C‐H , McGuckin Michael A
Published: January 2012

Endoplasmic reticulum (ER) stress may be both a trigger and consequence of chronic inflammation. Chronic inflammation is often associated with diseases that arise because of primary misfolding mutations and ER stress. Similarly, ER stress and activation of the unfolded protein response (UPR) is a feature of many chronic inflammatory and autoimmune diseases. In this review, we describe how protein misfolding and the UPR trigger inflammation, how environmental ER stressors affect antigen presenting cells and immune effector cells, and present evidence that inflammatory factors exacerbate protein misfolding and ER stress. Examples from both animal models of disease and human diseases are used to illustrate the complex interactions between ER stress and inflammation, and opportunities for therapeutic targeting are discussed. Finally, recommendations are made for future research with respect to the interaction of ER stress and inflammation.
CX3CR1 Deficiency Does Not Influence Trafficking of Adipose Tissue Macrophages in Mice With Diet‐Induced Obesity
Authors: Morris David L. , Oatmen Kelsie E. , Wang Tianyi , DelProposto Jennifer L. , Lumeng Carey N.
Published: January 2012

Adipose tissue macrophages (ATMs) accumulate in fat during obesity and resemble foam cells in atherosclerotic lesions, suggesting that common mechanisms underlie both inflammatory conditions. CX3CR1 and its ligand fractalkine/CX3CL1 contribute to macrophage recruitment and inflammation in atherosclerosis, but their role in obesity‐induced adipose tissue inflammation is unknown. Therefore, we tested the hypothesis that CX3CR1 regulates ATM trafficking to epididymal fat and contributes to the development of adipose tissue inflammation during diet‐induced obesity. Cx3cl1 and Cx3cr1 expression was induced specifically in epididymal fat from mice fed a high‐fat diet (HFD). CX3CR1 was detected on multiple myeloid cells within epididymal fat from obese mice. To test the requirement of CX3CR1 for ATM trafficking and obesity‐induced inflammation, Cx3cr1+/GFP and Cx3cr1GFP/GFP mice were fed a HFD. Ly‐6cLow monocytes were reduced in lean Cx3cr1GFP/GFP mice; however, HFD‐induced monocytosis was comparable between strains. Total ATM content, the ratio of type 1 (CD11c+) to type 2 (CD206+) ATMs, expression of inflammatory markers, and T‐cell content were similar in epididymal fat from obese Cx3cr1+/GFP and Cx3cr1GFP/GFP mice. Cx3cr1 deficiency did not prevent the development of obesity‐induced insulin resistance or hepatic steatosis. In summary, our data indicate that CX3CR1 is not required for the recruitment or retention of ATMs in epididymal adipose tissue of mice with HFD‐induced obesity even though CX3CR1 promotes foam cell formation. This highlights an important point of divergence between the mechanisms regulating monocyte trafficking to fat with obesity and those that contribute to foam cell formation in atherogenesis.
The guanine-nucleotide-exchange factor P-Rex1 is activated by protein phosphatase 1α
Authors: Barber Mark A. , Hendrickx Annick , Beullens Monique , Ceulemans Hugo , Oxley David , Thelen Sylvia , Thelen Marcus , Bollen Mathieu , Welch Heidi C. E.
Published: January 2012

P-Rex1 is a GEF (guanine-nucleotide-exchange factor) for the small G-protein Rac that is activated by PIP3 (phosphatidylinositol 3,4,5-trisphosphate) and Gβγ subunits and inhibited by PKA (protein kinase A). In the present study we show that PP1α (protein phosphatase 1α) binds P-Rex1 through an RVxF-type docking motif. PP1α activates P-Rex1 directly in vitro, both independently of and additively to PIP3 and Gβγ. PP1α also substantially activates P-Rex1 in vivo, both in basal and PDGF (platelet-derived growth factor)- or LPA (lysophosphatidic acid)-stimulated cells. The phosphatase activity of PP1α is required for P-Rex1 activation. PP1β, a close homologue of PP1α, is also able to activate P-Rex1, but less effectively. PP1α stimulates P-Rex1-mediated Rac-dependent changes in endothelial cell morphology. MS analysis of wild-type P-Rex1 and a PP1α-binding-deficient mutant revealed that endogenous PP1α dephosphorylates P-Rex1 on at least three residues, Ser834, Ser1001 and Ser1165. Site-directed mutagenesis of Ser1165 to alanine caused activation of P-Rex1 to a similar degree as did PP1α, confirming Ser1165 as a dephosphorylation site important in regulating P-Rex1 Rac-GEF activity. In summary, we have identified a novel mechanism for direct activation of P-Rex1 through PP1α-dependent dephosphorylation.
Arterialized cephalic vein as a femoropopliteal bypass graft: A case report
Authors: Stefanov Georgi , Cheshmedzhiev Michail , Andreev Andreia , Denchev Borislav , Bachvarov Chavdar , Yordanov Miroslav , Velinov Tihomir , Peev Veselin
Published: January 2012

G Stefanov, M Cheshmedzhiev, A Andreev, et al. Arterialized cephalic vein as a femoropopliteal bypass graft: A case report. Int J Angiol 2007;16(4):146-148.

The overall therapeutic strategy in patients with diabetes mellitus and peripheral arterial disease affecting several arterial segments is problematic. Usually, the greater saphenous vein (GSV) is the gold standard for bypass. However, alternative venous grafts may be necessary when the GSV is not available. The superficial veins of the arm are not suitable for bypass operations in most cases because of anatomical variations, inadequate diameter or very thin walls. However, arterialization of the cephalic vein can dilate and strengthen the walls, thus avoiding postoperative complications.

The present patient, whose case was followed for 20 months postoperatively, suffered both from diabetes and peripheral arterial disease in a setting of gangrene and a lack of the GSV. The treament of the patient and the problems it incurred are discussed. The advantages of preoperative temporary arteriovenous shunting to improve the quality of the cephalic vein as an alternative autogenous graft are analyzed. Currently, the patient has excellent postoperative results, with healing of the ulcers and preserved peripheral pulses.
Chronic mesenteric artery insufficiency produces hyperplasia of the intestine - case report
Authors: Wang ZhongGao , Yu HenXi , Gu YongQuan , Li JianXin , Zhang Jian , Li Zhen
Published: January 2012

ZG Wang, HX Yu, YQ Gu, JX Li, J Zhang, Z Li. Chronic mesenteric artery insufficiency produces hyperplasia of the intestine - case report. Int J Angiol 2007;16(4):149-151.

Chronic ischemia produces corresponding tissue hypoplasia. However, the present paper reports a distinctive hypertrophy of the intestine due to chronic mesenteric artery insufficiency. Two patients with chronic mesentery artery insufficiency confirmed by angiography are presented. The first patient demonstrated marked hypertrophy of the intestine, while the second patient was remarkable for pronounced hypoplasia. During the surgery of the first patient, an ileum approximately 60 cm long with a sausage-like consistency and cyanosis was identified proximal to the cecum; wall-attached thromboembolism material and the hypertrophic segment of ileum were removed. In the other patient, the intestine wall was paper thin; after the aortomesen- teric bypass, the intestine wall grew thicker. Postoperative recovery of both patients was uneventful. The commonly observed situation after a longstanding hypoxic insult in a setting of chronic mesenteric ischemia is that the target tissue will, at least, develop slight hypoplasia. However, the cases presented here had either pronounced hyperplasia or severe hypoplasia. The authors find this observation so interesting that they report it in the hope that an explanation for this conundrum may come forth.
Understanding the EF-hand closing pathway using non-biased interatomic potentials
Authors: Dupuis L. , Mousseau Normand
Published: January 2012

The EF-hand superfamily of proteins is characterized by the presence of calcium binding helix-loop-helix structures. Many of these proteins undergo considerable motion responsible for a wide range of properties upon binding but the exact mechanism at the root of this motion is not fully understood. Here, we use an unbiased accelerated multiscale simulation scheme, coupled with two force fields — CHARMM-EEF1 and the extended OPEP — to explore in details the closing pathway, from the unbound holo state to the closed apo state, of two EF-hand proteins, the Calmodulin and Troponin C N-terminal nodules. Based on a number of closing simulations for these two sequences, we show that the EF-hand β-scaffold, identified as crucial by Grabarek for the EF-hand opening driven by calcium binding, is also important in closing the EF-hand. We also show the crucial importance of the phenylalanine situated at the end of first EF-hand helix, and identify an intermediate state modulating its behavior, providing a detailed picture of the closing mechanism for these two representatives of EF-hand proteins.
Reynolds number effects on scale energy balance in wall turbulence
Authors: Saikrishnan Neelakantan , De Angelis Elisabetta , Longmire Ellen K. , Marusic Ivan , Casciola Carlo M. , Piva Renzo
Published: January 2012

The scale energy budget utilizes a modified version of the classical Kolmogorov equation of wall turbulence to develop an evolution equation for the second order structure function [R. J. Hill, “Exact second-order structure-function relationships,” J. Fluid Mech. 468, 317 (2002)]. This methodology allows for the simultaneous characterization of the energy cascade and spatial fluxes in turbulent shear flows across the entire physical domain as well as the range of scales. The present study utilizes this methodology to characterize the effects of Reynolds number on the balance of energy fluxes in turbulent channel flows. Direct numerical simulation data in the range Reτ = 300–934 are compared to previously published results at Reτ = 180 [N. Marati, C. M. Casciola, and R. Piva, “Energy cascade and spatial fluxes in wall turbulence,” J. Fluid Mech. 521, 191 (2004)]. The present results show no Reynolds number effects in the terms of the scale energy budget in either the viscous sublayer or buffer regions of the channel. In the logarithmic layer, the transfer of energy across scales clearly varies with Reynolds number, while the production of turbulent kinetic energy is not dependent on Reynolds number. An envelope of inverse energy cascade is quantified in the buffer region within which energy is transferred from small to larger scales. This envelope is observed in the range 6 < y+ < 37, where all scales except the smallest scales display characteristics of an inverse energy cascade. The cross-over scale lc+, which indicates the transition between production dominated and scale transfer dominated regimes, increases with Reynolds number, implying a larger range of transfer dominated scales, before the dominant mechanism switches to production. At higher Reynolds numbers, two distinct regimes of lc+ as a function of wall-normal location are observed, which was not captured at Reτ = 180. The variations of lc+ match the trends of the shear scale, which is a representation of the mean shear in the flow. Thus, this study demonstrates the utility and importance of the use of higher Reynolds number data in order to accurately characterize and understand the energy dynamics of various scales across the entire boundary layer.
Real-time x-ray diffraction at the impact surface of shocked crystals
Authors: Turneaure Stefan J. , Gupta Y. M.
Published: January 2012

X-ray diffraction (XRD) measurements at the impact surface, rather than the rear surface, of a shocked crystal have two important advantages: time-dependent material response can be directly monitored and the shocked crystal may be examined in a constant state over a continuous range of peak stresses. Methods for obtaining XRD data at the impact surface of crystals impacting an x-ray window are presented. Quantitative accuracy of the impact surface XRD method was established using Si(100) shocked elastically to 5.4 GPa. For Si(100) shocked inelastically to 12.2 GPa, partial strength loss occurred and the lattice strain and orientation became quite heterogeneous.
Fluctuation modes of nanoconfined DNA
Authors: Karpusenko Alena , Carpenter Joshua H. , Zhou Chunda , Lim Shuang Fang , Pan Junhan , Riehn Robert
Published: January 2012

We report an experimental investigation of the magnitude of length and density fluctuations in DNA that has been stretched in nanofluidic channels. We find that the experimental data can be described using a one-dimensional overdamped oscillator chain with nonzero equilibrium spring length and that a chain of discrete oscillators yields a better description than a continuous chain. We speculate that the scale of these discrete oscillators coincides with the scale at which the finite extensibility of the polymer manifests itself. We discuss how the measurement process influences the apparent measured dynamic properties, and outline requirements for the recovery of true physical quantities.
Evolution of laser-fired aluminum-silicon contact geometry in photovoltaic devices
Authors: Raghavan A. , Palmer T. A. , DebRoy T.
Published: January 2012

The evolution of temperature and velocity fields during laser processing of solar cells to produce an ohmic contact between an aluminum thin film and a silicon wafer is studied using a transient numerical heat transfer and liquid metal flow model. Since small changes in pulse duration, power, and power density can result in significant damage to the substrate and, in extreme cases, expulsion of droplets from the molten zone, the selection of optimal laser processing parameters is critical. The model considers the unusually large heat of fusion of the Al-Si alloy formed during processing and the large composition-dependent two phase region. The calculated size and shape of the fusion zone were in good agreement with the corresponding experimental data, indicating the validity of the model and providing a basis for using the model to develop a better understanding of the laser-assisted fabrication of contacts for solar cell devices. The transient changes in the composition of the Al-Si molten region are found to have a major impact on the heat transfer during the formation of the contact. Consideration of the time-dependent concentration of Al in the molten region is also essential to achieve good agreement between the experimental and computed molten pool sizes. Process maps showing peak temperatures and the depth and width of the molten pool are presented in order to assist users in the selection of safe process parameters for the rapid fabrication of these silicon-based photovoltaic devices.
Circular multilayer zone plate for high-energy x-ray nano-imaging
Authors: Koyama Takahisa , Takano Hidekazu , Konishi Shigeki , Tsuji Takuya , Takenaka Hisataka , Ichimaru Satoshi , Ohchi Tadayuki , Kagoshima Yasushi
Published: January 2012

A circular multilayer zone plate (MZP) was fabricated and its focusing performance was evaluated using 20-keV x-rays. MoSi2 and Si layers were alternately deposited by DC magnetron sputtering on a wire core; all the interfaces satisfied the Fresnel zone condition. The measured line spread function was converted to a point spread function by tomographic reconstruction. The results suggest that the MZP has the potential to realize the diffraction-limited resolving power, which is calculated to be 35 nm using the diffraction integral. Furthermore, scanning transmission microscopy using the MZP could resolve a 50-nm line-and-space pattern.
Repetitive impact loading causes local plastic deformation in wood
Authors: Salmi Ari , Salminen Lauri I. , Engberg Birgitta A. , Björkqvist Tomas , Hæggström Edward
Published: January 2012

The relationship between the impactor velocity and the amount of strain localization in a single impact compression of cellular solids is known. However, few studies report on the effects of repeated high frequency compression. We therefore studied the mechanical behavior of Norway spruce, a cellular viscoelastic material, before, during, and after cyclic high frequency, high strain rate, compression. A custom made device applied 5000-20 000 unipolar (constrained compression and free relaxation) fatigue cycles with a 0.75 mm peak-to-peak amplitude at 500 Hz frequency. The consequences of this treatment were quantified by pitch-catch ultrasonic measurements and by dynamic material testing using an encapsulated Split-Hopkinson device that incorporated a high-speed camera. The ultrasonic measurements quantified a stiffness modulus drop and revealed the presence of a fatigued low modulus layer near the impacting surface. Such a localized plastic deformation is not predicted by classical mechanics. We introduce a simple model that explains several changes in the mechanical properties caused by fatiguing. The high speed images indicated pronounced strain localization in the weakest (thinnest walls) parts of the earlywood layers, and revealed strain propagation as a function of time. We present a hypothesis explaining why there is a fatigued layer formed in a piece of wood that has sustained cyclic compression and free relaxation.
Electrostatic interaction of neutral semi-permeable membranes
Authors: Vinogradova Olga I. , Bocquet Lyderic , Bogdanov Artem N. , Tsekov Roumen , Lobaskin Vladimir
Published: January 2012

We consider an osmotic equilibrium between bulk solutions of polyelectrolyte bounded by semi-permeable membranes and separated by a thin film of salt-free liquid. Although the membranes are neutral, the counter-ions of the polyelectrolyte molecules permeate into the gap and lead to a steric charge separation. This gives rise to a distance-dependent membrane potential, which translates into a repulsive electrostatic disjoining pressure. From the solution of the nonlinear Poisson–Boltzmann equation, we obtain the distribution of the potential and of ions. We then derive an explicit formula for the pressure exerted on the membranes and show that it deviates from the classical van't Hoff expression for the osmotic pressure. This difference is interpreted in terms of a repulsive electrostatic disjoining pressure originating from the overlap of counterion clouds inside the gap. We also develop a simplified theory based on a linearized Poisson–Boltzmann approach. A comparison with simulation of a primitive model for the electrolyte is provided and does confirm the validity of the theoretical predictions. Beyond the fundamental result that the neutral surfaces can repel, this mechanism not only helps to control the adhesion and long-range interactions of living cells, bacteria, and vesicles, but also allows us to argue that electrostatic interactions should play enormous role in determining behavior and functions of systems bounded by semi-permeable membranes.
Dissociative photoionization of methyl chloride studied with threshold photoelectron-photoion coincidence velocity imaging
Authors: Tang Xiaofeng , Zhou Xiaoguo , Wu Manman , Liu Shilin , Liu Fuyi , Shan Xiaobin , Sheng Liusi
Published: January 2012

Utilizing threshold photoelectron-photoion coincidence (TPEPICO) velocity imaging, dissociation of state-selected CH3Cl+ ions was investigated in the excitation energy range of 11.0–18.5 eV. TPEPICO time-of-flight mass spectra and three-dimensional time-sliced velocity images of CH3+ dissociated from CH3Cl+(A2A1 and B2E) ions were recorded. CH3+ was kept as the most dominant fragment ion in the present energy range, while the branching ratio of CH2Cl+ fragment was very low. For dissociation of CH3Cl+(A2A1) ions, a series of homocentric rings was clearly observed in the CH3+ image, which was assigned as the excitation of umbrella vibration of CH3+ ions. Moreover, a dependence of anisotropic parameters on the vibrational states of CH3+(11A′) provided a direct experimental evidence of a shallow potential well along the C–Cl bond rupture. For CH3Cl+(B2E) ions, total kinetic energy released distribution for CH3+ fragmentation showed a near Maxwell-Boltzmann profile, indicating that the Cl-loss pathway from the B2E state was statistical predissociation. With the aid of calculated Cl-loss potential energy curves of CH3Cl+, CH3+ formation from CH3Cl+(A2A1) ions was a rapid direct fragmentation, while CH3Cl+(B2E) ions statistically dissociated to CH3+ + Cl via internal conversion to the high vibrational states of X2E.
Simultaneous observation of magnetostatic backward volume waves and surface waves in single crystal barium ferrite platelets with in-plane easy axis
Authors: Popov M. A. , Zavislyak I. V. , Srinivasan G.
Published: January 2012

Resonances corresponding to backward volume magnetostatic waves as well as magnetostatic surface waves have been observed in single crystal barium hexaferrite rectangular platelets with in-plane easy axis. Samples placed directly on waveguide wall or on a quartz substrate show a surface mode. A series of backward volume wave modes in the U-band are observed, with the sample placed on quartz showing a relatively few modes. Data on H-dependence of the mode frequency have been obtained for both kinds of magnetostatic waves and theoretical estimates of the mode frequencies are in reasonable agreement with the data. Quality-factor for the modes is in the range 400-750. The results are of interest for non-reciprocal ferrite devices in the U-band.
Note: Thermal conductivity measurement of individual poly(ether ketone)/carbon nanotube fibers using a steady-state dc thermal bridge method
Authors: Moon Jaeyun , Weaver Keith , Feng Bo , Gi Chae Han , Kumar Satish , Baek Jong-Beom , Peterson G. P.
Published: January 2012

Customized engineered fibers are currently being used extensively in the aerospace and automobile industries due to the ability to “design in” specific engineering characteristics. Understanding the thermal conductivity of these new fibers is critical for thermal management and design optimization. In the current investigation, a steady-state dc thermal bridge method (DCTBM) is developed to measure the thermal conductivity of individual poly(ether ketone) (PEK)/carbon nanotube (CNT) fibers. For non-conductive fibers, a thin platinum layer was deposited on the test articles to serve as the heater and temperature sensor. The effect of the platinum layer on the thermal conductivity is presented and discussed. DCTBM is first validated using gold and platinum wires (25 μm in diameter) over a temperature ranging from room temperature to 400 K with ±11% uncertainty, and then applied to PEK/CNT fibers with diverse CNT loadings. At a 28 wt. % CNT loading, the thermal conductivity of fibers at 390 K is over 27 Wm−1K−1, which is comparable to some engineering alloys.
Improved self-consistent and resolution-of-identity approximated Becke'05 density functional model of nondynamic electron correlation
Authors: Proynov Emil , Liu Fenglai , Shao Yihan , Kong Jing
Published: January 2012

In a recent letter [E. Proynov, Y. Shao, and J. Kong, Chem. Phys. Lett. 493, 381 (2010)10.1016/j.cplett.2010.05.029], Becke's B05 model of nondynamic electron correlation in density functional theory was implemented self-consistently with computational efficiency (the “SCF-RI-B05” scheme). Important modifications of the algorithm were done in order to make the self-consistency feasible. In the present work, we give a complete account of the SCF-RI-B05 algorithm, including all the formulae for the analytical representation of the B05 functional and for its self-consistent field (SCF) potential. The average performance of the SCF-RI-B05 method reported in the above letter was somewhat less accurate, compared to the original B05 implementation, mainly because the parameters of the original B05 model were optimized with post-local-spin-density calculations. In this work, we report improved atomization energies with SCF-RI-B05, based on a SCF re-optimization of its four linear parameters. The re-optimized SCF-RI-B05 scheme is validated also on reaction barriers, and on the subtle energetics of NO dimer, an exemplary system of strong nondynamic correlation. It yields both the binding energy and the singlet-triplet splitting of the NO dimer correctly, and close to the benchmarks reported in the literature.
Magnetodielectric effect in Z-type hexaferrite
Authors: Zhang X. , Zhao Y. G. , Cui Y. F. , Ye L. D. , Wang J. W. , Zhang S. , Zhang H. Y. , Zhu M. H.
Published: January 2012

The authors report on the magnetodielectric (MD) effect of Z-type hexaferrite Sr3Co2Fe24O41 at various temperatures and frequencies. A fairly large negative MD effect was observed with a peak near room temperature and a maximum at low frequencies. Analysis suggests that the MD effect shows a quadratic dependence on magnetization. The results were discussed by considering the magnetic field induced change of transverse conical spin structure and spin-phonon coupling. This work is helpful for understanding the MD effect in materials with complicated spin structures.
Categorical perception effects for facial identity in robustly represented familiar and self-faces: The role of configural and featural information
Authors: Keyes Helen
Published: January 2012

Categorical perception of robustly represented faces (self, friend) and unfamiliar faces is investigated, and the relative roles of configural and featural information are examined. Participants performed identification and discrimination tasks on morph series containing the self-face and a friend's face (self–Friend 1), two friends' faces (Friend 2–Friend 3), and two unfamiliar faces (Unfamiliar 1–Unfamiliar 2), presented in upright and inverted orientations. For upright faces, categorical perception effects were observed for both familiar morph series but not for the unfamiliar morph series, suggesting that robust representation is a requirement for categorical perception in facial identity. For inverted faces, categorical perception was observed for the self–Friend 1 morph series only. This suggests that categorical perception is tied to configural processing for familiar non-self-faces, but can be observed for self-faces during featural processing—consistent with evidence that self-face representations contain strong configural and featural components. Finally, categorical perception is not enhanced by the presence of the self-face relative to other familiar faces when upright, but shows a trend of being enhanced for self-faces when inverted, adding to the debate on the ways in which robustly represented faces can elicit categorical perception.
Sequential class switching is required for the generation of high affinity IgE antibodies
Authors: Xiong Huizhong , Dolpady Jayashree , Wabl Matthias , Curotto de Lafaille Maria A. , Lafaille Juan J.
Published: January 2012

IgE antibodies with high affinity for their antigens can be stably cross-linked at low concentrations by trace amounts of antigen, whereas IgE antibodies with low affinity bind their antigens weakly. In this study, we find that there are two distinct pathways to generate high and low affinity IgE. High affinity IgE is generated through sequential class switching (μ→γ→ε) in which an intermediary IgG phase is necessary for the affinity maturation of the IgE response, where the IgE inherits somatic hypermutations and high affinity from the IgG1 phase. In contrast, low affinity IgE is generated through direct class switching (μ→ε) and is much less mutated. Mice deficient in IgG1 production cannot produce high affinity IgE, even after repeated immunizations. We demonstrate that a small amount of high affinity IgE can cause anaphylaxis and is pathogenic. Low affinity IgE competes with high affinity IgE for binding to Fcε receptors and prevents anaphylaxis and is thus beneficial.
Age, microbiota, and T cells shape diverse individual IgA repertoires in the intestine
Authors: Lindner Cornelia , Wahl Benjamin , Föhse Lisa , Suerbaum Sebastian , Macpherson Andrew J. , Prinz Immo , Pabst Oliver
Published: January 2012

Intestinal immunoglobulin A (IgA) ensures host defense and symbiosis with our commensal microbiota. Yet previous studies hint at a surprisingly low diversity of intestinal IgA, and it is unknown to what extent the diverse Ig arsenal generated by somatic recombination and diversification is actually used. In this study, we analyze more than one million mouse IgA sequences to describe the shaping of the intestinal IgA repertoire, its determinants, and stability over time. We show that expanded and infrequent clones combine to form highly diverse polyclonal IgA repertoires with very little overlap between individual mice. Selective homing allows expanded clones to evenly seed the small but not large intestine. Repertoire diversity increases during aging in a dual process. On the one hand, microbiota-, T cell–, and transcription factor RORγt–dependent but Peyer’s patch–independent somatic mutations drive the diversification of expanded clones, and on the other hand, new clones are introduced into the repertoire of aged mice. An individual’s IgA repertoire is stable and recalled after plasma cell depletion, which is indicative of functional memory. These data provide a conceptual framework to understand the dynamic changes in the IgA repertoires to match environmental and intrinsic stimuli.