The role of newly born magnetars in gamma-ray burst X-ray afterglow emission: Energy injection and internal emission

Swift observations suggest that the central compact objects of some gamma-ray bursts (GRBs) could be newly born millisecond magnetars. Therefore, considering the spin evolution of the magnetars against r-mode instability, we investigate the role of magnetars in GRB X-ray afterglow emission. Besides modifying the conventional energy injection model, we pay particular attention to the internal X-ray afterglow emission, whose luminosity is assumed to track the magnetic dipole luminosity of the magnetars with a certain fraction. Following a comparison between the model and some selected observational samples, we suggest that some so-called canonical X-ray afterglows including the shallow decay, normal decay, and steeper-than-normal decay phases could be internally produced by the magnetars (possibly through some internal dissipations of the magnetar winds), while the (energized) external shocks are associated with another type of X-ray afterglows. If this is true, then from those internal X-ray afterglows we can further determine the magnetic field strengths and the initial spin periods of the corresponding magnetars. © 2010. The American Astronomical Society. All rights reserved.published_or_final_versio

The luminosity function of Swift long gamma-ray bursts

The accumulation of Swift observed gamma-ray bursts (GRBs) has gradually made it possible to directly derive a GRB luminosity function (LF) from the observational luminosity distribution. However, two complexities are involved: (i) the evolving connection between GRB rate and cosmic star formation rate; and (ii) observational selection effects due to telescope thresholds and redshift measurements. With a phenomenological investigation of these two complexities, we constrain and discriminate two popular competing LF models (i.e. the broken-power-law LF and the single-power-law LF with an exponential cut-off at low luminosities). As a result, we find that the broken-power-law LF may be more favoured by observations, with a break luminosity L b= 2.5 × 10 52ergs -1 and prior- and post-break indices ν 1= 1.72 and ν 2= 1.98. Regarding an extra evolution effect expressed by a factor (1 +z) δ, if the metallicity of GRB progenitors is lower than ~0.1Z ⊙ as expected by some collapsar models, then there may be no extra evolution effect other than the metallicity evolution (i.e. δ approaches zero). Alternatively, if we remove the theoretical metallicity requirement, then a relationship between the degenerate parameters δ and Z max can be found, very roughly, δ~ 2.4(Z max/Z ⊙- 0.06). This indicates that extra evolution could become necessary for relatively high metallicities. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.published_or_final_versio

Design of low-threshold compact Au-nanoparticle lasers

2010-2011 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Bardoxolone methyl prevents mesenteric fat deposition and inflammation in high-fat diet mice

Mesenteric fat belongs to visceral fat. An increased deposition of mesenteric fat contributes to obesity associated complications such as type 2 diabetes and cardiovascular diseases. We have investigated the therapeutic effects of bardoxolone methyl (BARD) on mesenteric adipose tissue of mice fed a high-fat diet (HFD). Male C57BL/6J mice were administered oral BARD during HFD feeding (HFD/BARD), only fed a high-fat diet (HFD), or fed low-fat diet (LFD) for 21 weeks. Histology and immunohistochemistry were used to analyse mesenteric morphology and macrophages, while Western blot was used to assess the expression of inflammatory, oxidative stress, and energy expenditure proteins. Supplementation of drinking water with BARD prevented mesenteric fat deposition, as determined by a reduction in large adipocytes. BARD prevented inflammation as there were fewer inflammatory macrophages and reduced proinflammatory cytokines (interleukin-1 beta and tumour necrosis factor alpha). BARD reduced the activation of extracellular signal-regulated kinase (ERK) and Akt, suggesting an antioxidative stress effect. BARD upregulates energy expenditure proteins, judged by the increased activity of tyrosine hydroxylase (TH) and AMP-activated protein kinase (AMPK) and increased peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), and uncoupling protein 2 (UCP2) proteins. Overall, BARD induces preventive effect in HFD mice through regulation of mesenteric adipose tissue. © 2015 Chi H. L. Dinh et al.This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

A New High-Level Reconfigurable Lossless Image Compression System for Space Applications

On board image data compression is an important feature of satellite remote sensing payloads. Reconfigurable Intellectual Property (IP) cores can enable change of functionality or modifications. A new and efficient lossless image compression scheme for space applications is proposed. In this paper, we present a lossless image compression IP core designed using AccelDSP, which gives users high level of flexibility. One typical configuration is implemented and tested on an FPGA prototyping board. Finally, it is integrated successfully into a System-on-Chip platform for payload data processing and control

Antifatigue Effect of Millettiae speciosae Champ (Leguminosae) Extract in Mice

Purpose: To evaluate whether Millettiae Speciosae Champ. (Leguminosae) can enhance exercise performance as well as ascertain if it a potential functional food material.Methods: The extract of Millettia speciosa Champ. (MSE) was orally administered to mice in 500, 1000, 2000 mg/kg doses to investigate its anti-fatigue effect in both forced swimming and climbing tests. Glycogen, triglyceride (TG), blood urea nitrogen (BUN) and creatine phosphokinase (CK) levels in plasma which can indicate alterations in energy utilization during exercise performance, were determined to analyze the operating exercise mechanisms.Results: The results showed that swimming time to exhaustion was longer in all treated groups (41.06 ± 1.92, 47.84 ± 1.60, 54.00 ± 2.45 min for 500, 10000 and 2000 mg/kg doses, respectively) than for control (19.45 ± 0.62 min, p < 0.05). The middle and high doses of MSE-treated groups significantly prolonged the climbing time compared with control (p < 0.05). Furthermore, MSE reduced the content of TG significantly by increasing fat utilization, delayed the accumulation of BUN and decreased the level of CK (p < 0.05). In addition, administration of MSE significantly protected the depletion of muscle glycogen when compared with control (p < 0.05).Conclusion: The results show for the first time that Millettia speciosa Champ. (Leguminosae) has significant anti-fatigue activity, and also suggest that it is a potential functional food material.Keywords: Radix millettiae speciosae, Anti-fatigue activity, Exercise performance, Serum urea nitrogen, Gastrocnemius muscle glycogen, Triglyceride, Functional foo

Central inflammation and leptin resistance are attenuated by ginsenoside Rb1 treatment in obese mice fed a high-fat diet

A low-grade pro-inflammatory state is at the pathogenic core of obesity and type 2 diabetes. We tested the hypothesis that the plant terpenoid compound ginsenoside Rb1 (Rb1), known to exert anti-inflammatory effects, would ameliorate obesity, obesity-associated inflammation and glucose intolerance in the high-fat diet-induced obese mouse model. Furthermore, we examined the effect of Rb1 treatment on central leptin sensitivity and the leptin signaling pathway in the hypothalamus. We found that intraperitoneal injections of Rb1 (14 mg/kg, daily) for 21 days significantly reduced body weight gain, fat mass accumulation, and improved glucose tolerance in obese mice on a HF diet compared to vehicle treatment. Importantly, Rb1 treatment also reduced levels of pro-inflammatory cytokines (TNF-α, IL-6 and/or IL-1β) and NF-κB pathway molecules (p-IKK and p-IκBα) in adipose tissue and liver. In the hypothalamus, Rb1 treatment decreased the expression of inflammatory markers (IL-6, IL-1β and p-IKK) and negative regulators of leptin signaling (SOCS3 and PTP1B). Furthermore, Rb1 treatment also restored the anorexic effect of leptin in high-fat fed mice as well as leptin pSTAT3 signaling in the hypothalamus. Ginsenoside Rb1 has potential for use as an anti-obesity therapeutic agent that modulates obesity-induced inflammation and improves central leptin sensitivity in HF diet-induced obesity. © 2014 Public Library of ScienceAcquired from the Public Library of Science. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. 2014 Wu et al

Correlation between promoter methylation of p14ARF, TMS1/ASC, and DAPK, and p53 mutation with prognosis in cholangiocarcinoma

<p>Abstract</p> <p>Background</p> <p>To study the methylation status of genes that play a role in the p53-Bax mitochondrial apoptosis pathway and its clinical significance in cholangiocarcinoma.</p> <p>Patients and Methods</p> <p>Out of 36 cases cholangiocarcinoma patients from April 2000 to May 2005 were collected.Promoter hypermethylation of <it>DAPK</it>, <it>p14^ARF</it>, and <it>ASC </it>were detected by methylation-specific PCR on cholangiocarcinoma and normal adjacent tissues samples. Mutation of the p53 gene was examined by automated sequencing. Correlation between methylation of these genes and/or <it>p53 </it>mutation status with clinical characteristics of patients was investigated by statistical analysis.</p> <p>Results</p> <p>We found 66.7% of 36 cholangiocarcinoma patients had methylation of at least one of the tumor suppressor genes analyzed. <it>p53 </it>gene mutation was found in 22 of 36 patients (61.1%). Combined <it>p53 </it>mutation and <it>DAPK, p14^ARF, and/or ASC </it>methylation was detected in 14 cases (38.9%). There were statistically significant differences in the extent of pathologic biology, differentiation, and invasion between patients with combined <it>p53 </it>mutation and <it>DAPK, p14^ARF, and/or ASC </it>methylation compared to those without (P < 0.05). The survival rate of patients with combined <it>DAPK, p14^ARF, and ASC </it>methylation and <it>p53 </it>mutation was poorer than other patients (<it>P </it>< 0.05).</p> <p>Conclusion</p> <p>Our study indicates that methylation of <it>DAPK, p14^ARF, and ASC </it>in cholangiocarcinoma is a common event. Furthermore, <it>p53 </it>mutation combined with <it>DAPK, p14^ARF, and/or ASC </it>methylation correlates with malignancy and poor prognosis.</p