First-principles study of electronic properties of biaxially strained silicon: effects on charge carrier mobility

Journal ArticleUsing first-principles method, we calculate the electronic band structure of biaxially strained silicon, from which we analyze the change in electron and hole effective mass as a function of strain and determine the mobility of electrons and holes in the biaxially strained silicon based on Boltzmann transport theory. We found that electron mobility increases with tensile strain and decreases with compressive strain. Such changes are mainly caused by a strain-induced change in electron effective mass, while the suppression of intervalley scattering plays a minor role. On the other hand, the hole mobility increases with both signs of strain and the effect is more significant for compressive strain because the hole effective mass decreases with compressive strain but increases with tensile strain. The strain-induced suppression of interband and intraband scatterings plays also an important role in changing the hole mobility

Method for predicting the formation of silicon nanocrystals in embedded oxide matrices

A method for predicting the formation of silicon nanocrystals in an oxide matrix is disclosed. Initially, fundamental data for a set of microscopic processes that can occur during one or more material processing operations are obtained. Kinetic models are then built by utilizing the fundamental data for a set of reactions that can contribute substantially to the formation of silicon nanocrystals in a silicon oxide matrix. Finally, the kinetic models are applied to predict shape, size distribution, spatial arrangements of silicon nanocrystals.Board of Regents, University of Texas Syste

Elevated CO2 and Warming Altered Grassland Microbial Communities in Soil Top-Layers.

As two central issues of global climate change, the continuous increase of both atmospheric CO2 concentrations and global temperature has profound effects on various terrestrial ecosystems. Microbial communities play pivotal roles in these ecosystems by responding to environmental changes through regulation of soil biogeochemical processes. However, little is known about the effect of elevated CO2 (eCO2) and global warming on soil microbial communities, especially in semiarid zones. We used a functional gene array (GeoChip 3.0) to measure the functional gene composition, structure, and metabolic potential of soil microbial communities under warming, eCO2, and eCO2 + warming conditions in a semiarid grassland. The results showed that the composition and structure of microbial communities was dramatically altered by multiple climate factors, including elevated CO2 and increased temperature. Key functional genes, those involved in carbon (C) degradation and fixation, methane metabolism, nitrogen (N) fixation, denitrification and N mineralization, were all stimulated under eCO2, while those genes involved in denitrification and ammonification were inhibited under warming alone. The interaction effects of eCO2 and warming on soil functional processes were similar to eCO2 alone, whereas some genes involved in recalcitrant C degradation showed no significant changes. In addition, canonical correspondence analysis and Mantel test results suggested that NO3-N and moisture significantly correlated with variations in microbial functional genes. Overall, this study revealed the possible feedback of soil microbial communities to multiple climate change factors by the suppression of N cycling under warming, and enhancement of C and N cycling processes under either eCO2 alone or in interaction with warming. These findings may enhance our understanding of semiarid grassland ecosystem responses to integrated factors of global climate change

Multi-valent Ion Mediated Polyelectrolyte Association and Structure

Polyelectrolytes are commonly used to chelate multi-valent ions in aqueous solutions, playing a critical role in water softening and the prevention of mineralization. At sufficient ionic strength, ion-mediated polyelectrolyte--polyelectrolyte interactions can precipitate polyelectrolyte--ion complexes, a phenomenon known as "like-charge attraction". While the significant influence of small ions on polyelectrolyte solution phase behavior is recognized, the precise molecular mechanisms driving the counterintuitive phenomenon remain largely elusive. In this study, we employ all-atom molecular dynamics simulations to investigate the molecular mechanism of like-charge attraction between two poly(acrylic acid) (PAA) chains in solution. We find that moderate quantities of Ca$^{2+}$ ions induce attraction between PAA chains, facilitated by the formation of PAA--Ca$^{2+}$--PAA bridges and a significant increase in the coordination of Ca$^{2+}$ ions by the PAA chains. At high Ca$^{2+}$ number densities, ion bridges are disfavored due to electrostatic screening, yet the chains are still attracted to each other due to solvent-mediated interactions between the chains and their chelated ions. The insights gleaned from this study not only enrich our understanding of the intricate mechanism of like-charge attraction between polyanions in solution but also illuminate the influence of multi-valent ions on polyelectrolyte interactions.Comment: 15 pages, 6 figure

PO-147 Effect of Exercise-induced Fatigue on the Electrical Activity of the External Globus Pallidus Neurons in rats

Objective The motor cortex (MC) stimulation-induced unitary responses of globus pallidus external segment (GPe) neurons in control and exercise induced-fatigue rats were recorded in vivo to examine the role of cortical-striatum-external globus pallidal pathway in the mechanism of central fatigue. Methods 32 Clean healthy male Wistar rats (260~300g), were randomly divided into 4 groups: control group (Control), 1-day fatigue group (1FG), 3-day fatigue group (3FG) and 7-day fatigue group (7FG). Rats were subjected to a 5-day adaptive treadmill training. Modified Bedford treadmill exercise with progressively increasing load was used to creat the exercise fatigue model. （3 levels:8.2 m/min, 15 min; 15m/min, 15 min; 20 m/min, lasting till exhaustion） The spontaneous unit activity and responses to MC stimulation of GPe neurons were recorded by the electrophysiological technique of extracellular recording of glass microelectrodes. Results The results showed that the firing frequency of high-frequency firing with pause (HFP) and low frequency firing with burst (LFB) in the GPe of 1FG was comparable with that of control group (P>0.05). However in 3FG and 7FG , the percentage of HFP neuron was significantly decreased (P<0.05), while the proportion of LFB was significantly increased (P<0.05), and the average firing rate of LFB was higher and inter spike intervals (ISI) was significantly lower than that of the control group. With 200μA electrical stimulation, the explosive discharge of GPe neurons was attenuated after fatigue in rats. The response of GPe neurons to variable frequency stimulation in exhausted model groups was stronger than that of the control group.MC-stimulation typically induced a triphasic response composed of early excitation, inhibition, and late excitation in GPe neurons. The population of neurons showing a short inhibition slightly increased in 3FG and 7FG. Conclusions 1. The results confirmed that GPe is an important nucleus of basal ganglia involved in the regulation of exercise-induced fatigue by the change of spontaneous activity. Electrical stimulation on the cortex can alter response patterns of GPe neurons in exercise-induced fatigue rats, the results confirmed that the Ctx-Str-GPe neural pathway is involved in the regulation of exercise fatigue, and the indirect pathway is over-activated

Dichloroacetate blocks aerobic glycolytic adaptation to attenuated measles virus and promotes viral replication leading to enhanced oncolysis in glioblastoma

Targeting reprogrammed energy metabolism such as aerobic glycolysis is a potential strategy for cancer treatment. However, tumors exhibiting low-rate glycolysis or metabolic heterogeneity might be resistant to such treatment. We hypothesized that a therapeutic modality that drove cancer cells to high-rate glycolysis might sensitize cancer cells to interference directed against metabolic flux. In this study, we found that attenuated oncolytic measles virus Edmonston strain (MV-Edm) caused glioblastoma cells to shift to high-rate aerobic glycolysis; this adaptation was blocked by dichloroacetate (DCA), an inhibitor of glycolysis, leading to profound cell death of cancer cells but not of normal cells. DCA enhanced viral replication by mitigating mitochondrial antiviral signaling protein (MAVS)-mediated innate immune responses. In a subcutaneous glioblastoma (GBM) xenograft mouse model, low-dose MV-Edm and DCA significantly inhibited tumor growth in vivo. We found that DCA impaired glycolysis (blocking bioenergetic generation) and enhanced viral replication (increasing bioenergetic consumption), which, in combination, accelerated bioenergetic exhaustion leading to necrotic cell death. Taken together, oncolytic MV-Edm sensitized cancer cells to DCA, and in parallel, DCA promoted viral replication, thus, improving oncolysis. This novel therapeutic approach should be readily incorporated into clinical trials

Predictors of Virologic Failure in HIV‐1–Infected Adults Receiving First‐Line Antiretroviral Therapy in 8 Provinces in China

Despite poor primary healthcare systems, free antiretroviral therapy (ART) has been available in China for over 5 years. Virologic outcomes of Chinese patients receiving ART have not been described at a national level

Magnetic Graphene Nanohole Superlattices

We investigate the magnetic properties of nano-holes (NHs) patterned in graphene using first principles calculations. We show that superlattices consisting of a periodic array of NHs form a new family of 2D crystalline "bulk" magnets whose collective magnetic behavior is governed by inter-NH spin-spin interaction. They exhibit long-range magnetic order well above room temperature. Furthermore, magnetic semiconductors can be made by doping magnetic NHs into semiconducting NH superlattices. Our findings offer a new material system for fundamental studies of spin-spin interaction and magnetic ordering in low dimensions, and open up the exciting opportunities of making engineered magnetic materials for storage media and spintronics applications

Decreasing Excess Mortality of HIV-Infected Patients Initiating Antiretroviral Therapy: Comparison with Mortality in General Population in China, 2003–2009

To evaluate excess mortality across calendar time comparing HIV-infected patients receiving cART with the general Chinese population

Particular distribution and expression pattern of endoglin (CD105) in the liver of patients with hepatocellular carcinoma

<p>Abstract</p> <p>Background</p> <p>Endoglin (CD105) has been considered a prognostic marker for hepatocellular carcinoma (HCC), and widely used as an appropriate targeting for antiangenesis therapy in some cancers. Our aim was to evaluate the distribution and expression of CD105 in the liver of patients with HCC, and to discuss whether CD105 may be used as an appropriate targeting for antiangenesis therapy in HCC.</p> <p>Methods</p> <p>Three parts of liver tissues from each of 64 patients with HCC were collected: tumor tissues (TT), adjacent non-tumor (AT) liver tissues within 2 cm, and tumor free tissues (TF) 5 cm far from the tumor edge. Liver samples from 8 patients without liver diseases served as healthy controls (HC). The distribution and expression of CD105 in tissues were evaluated by immunohistochemistry, Western blotting analysis, and real-time PCR. HIF-1alpha and VEGF₁₆₅protein levels in tissues were analyzed by Immunohistochemistry and Western blotting analysis or ELISA.</p> <p>Results</p> <p>CD105 was positively stained mostly in a subset of microvessels 'endothelial sprouts' in TT of all patients while CD105 showed diffuse positive staining, predominantly on hepatic sinus endothelial cells in the surrounding of draining veins in TF and AT. The mean score of MVD-CD105 (mean ± SD/0.74 mm²) was 19.00 ± 9.08 in HC, 153.12 ± 53.26 in TF, 191.12 ± 59.17 in AT, and 85.43 ± 44.71 in TT, respectively. Using a paired <it>t </it>test, the expression of CD105 in AT and TF was higher than in TT at protein (MVD, <it>p </it>= 0.012 and <it>p </it>= 0.007, respectively) and mRNA levels (<it>p </it>< 0.001 and <it>p </it>= 0.009, respectively). Moreover, distribution and expression of CD105 protein were consistent with those of HIF-1alpha and VEGF₁₆₅protein in liver of patients with HCC. The level of <it>CD105 </it>mRNA correlated with VEGF₁₆₅level in TF (r = 0.790, <it>p </it>= 0.002), AT (r = 0.723, <it>p </it>< 0.001), and TT (r = 0.473, <it>p </it>= 0.048), respectively.</p> <p>Conclusion</p> <p>It is demonstrated that CD105 was not only present in neovessels in tumor tissues, but also more abundant in hepatic sinus endothelium in non-tumor tissues with cirrhosis. Therefore, CD105 may not be an appropriate targeting for antiangenesis therapy in HCC, especially with cirrhosis.</p