Distribution of Spectral Lags in Gamma Ray Bursts

Using the data acquired in the Time To Spill (TTS) mode for long gamma-ray bursts (GRBs) collected by the Burst and Transient Source Experiment on board the Compton Gamma Ray Observatory (BATSE/CGRO), we have carefully measured spectral lags in time between the low (25-55 keV) and high (110-320 keV) energy bands of individual pulses contained in 64 multi-peak GRBs. We find that the temporal lead by higher-energy gamma-ray photons (i.e., positive lags) is the norm in this selected sample set of long GRBs. While relatively few in number, some pulses of several long GRBs do show negative lags. This distribution of spectral lags in long GRBs is in contrast to that in short GRBs. This apparent difference poses challenges and constraints on the physical mechanism(s) of producing long and short GRBs. The relation between the pulse peak count rates and the spectral lags is also examined. Observationally, there seems to be no clear evidence for systematic spectral lag-luminosity connection for pulses within a given long GRB.Comment: 20 pages, 4 figure

Higgs algebraic symmetry of screened system in a spherical geometry

The orbits and the dynamical symmetries for the screened Coulomb potentials and isotropic harmonic oscillators have been studied by Wu and Zeng [Z. B. Wu and J. Y. Zeng, Phys. Rev. A 62,032509 (2000)]. We find the similar properties in the responding systems in a spherical space, whose dynamical symmetries are described by Higgs Algebra. There exists a conserved aphelion and perihelion vector, which, together with angular momentum, constitute the generators of the geometrical symmetry group at the aphelia and perihelia points $(\dot{r}=0)$.Comment: 8 pages, 1 fi

Inflation and nonequilibrium renormalization group

We study de spectrum of primordial fluctuations and the scale dependence of the inflaton spectral index due to self-interactions of the field. We compute the spectrum of fluctuations by applying nonequilibrium renormalization group techniques.Comment: 6 pages, 1 figure, submitted to J. Phys.

Genetic incorporation of the protein transduction domain of Tat into Ad5 fiber enhances gene transfer efficacy

<p>Abstract</p> <p>Background</p> <p>Human adenovirus serotype 5 (Ad5) has been widely explored as a gene delivery vector for a variety of diseases. Many target cells, however, express low levels of Ad5 native receptor, the Coxsackie-Adenovirus Receptor (CAR), and thus are resistant to Ad5 infection. The Protein Transduction Domain of the HIV Tat protein, namely PTD_tat, has been shown to mediate protein transduction in a wide range of cells. We hypothesize that re-targeting Ad5 vector via the PTD_tatmotif would improve the efficacy of Ad5-mediated gene delivery.</p> <p>Results</p> <p>In this study, we genetically incorporated the PTD_tatmotif into the knob domain of Ad5 fiber, and rescued the resultant viral vector, Ad5.PTD_tat. Our data showed the modification did not interfere with Ad5 binding to its native receptor CAR, suggesting Ad5 infection via the CAR pathway is retained. In addition, we found that Ad5.PTD_tatexhibited enhanced gene transfer efficacy in all of the cell lines that we have tested, which included both low-CAR and high-CAR decorated cells. Competitive inhibition assays suggested the enhanced infectivity of Ad5.PTD_tatwas mediated by binding of the positively charged PTD_tatpeptide to the negatively charged epitopes on the cells' surface. Furthermore, we investigated <it>in vivo </it>gene delivery efficacy of Ad5.PTD_tatusing subcutaneous tumor models established with U118MG glioma cells, and found that Ad5.PTD_tatexhibited enhanced gene transfer efficacy compared to unmodified Ad5 vector as analyzed by a non-invasive fluorescence imaging technique.</p> <p>Conclusion</p> <p>Genetic incorporation of the PTD_tatmotif into Ad5 fiber allowed Ad5 vectors to infect cells via an alternative PTD_tattargeting motif while retaining the native CAR-mediated infection pathway. The enhanced infectivity was demonstrated in both cultured cells and in <it>in vivo </it>tumor models. Taken together, our study identifies a novel tropism expanded Ad5 vector that may be useful for clinical gene therapy applications.</p

Patterns and Variation in the Sex Ratio at Birth in the Republic of Korea

In this paper, we examine sex ratio patterns at birth (SRB) among sub-areas of South Korea during the 1990s. We report higher than biologically normal SRBs at varying levels of geography, for three years in the 1990s. These high SRBs are mainly due to prenatal sex identification followed by female-specific induced abortion. This strategy has been implemented in the Republic of Korea following the country's dramatic reduction in fertility. Higher than biologically normal sex ratios at birth carry important implications for the society's males and females, particularly a few decades after their births, when young people begin to exercise marriage options. We estimate that approximately 25 years after 1990, around 2015, approximately 10 to 13 percent of marriage-age males in South Korea will be unsuccessful in their courtship pursuits. In 2015, there could be as many as 400,000 South Korean men of marriageable ages unable to find wives. We explore implications of this unbalanced marriage market for South Korea and its excess male population

Parametrization for the Scale Dependent Growth in Modified Gravity

We propose a scale dependent analytic approximation to the exact linear growth of density perturbations in Scalar-Tensor (ST) cosmologies. In particular, we show that on large subhorizon scales, in the Newtonian gauge, the usual scale independent subhorizon growth equation does not describe the growth of perturbations accurately, as a result of scale-dependent relativistic corrections to the Poisson equation. A comparison with exact linear numerical analysis indicates that our approximation is a significant improvement over the standard subhorizon scale independent result on large subhorizon scales. A comparison with the corresponding results in the Synchronous gauge demonstrates the validity and consistency of our analysis.Comment: 10 pages, 5 figures. Minor modifications and references added to match published versio

Recent progress in mesoporous titania materials: adjusting morphology for innovative applications

This review article summarizes recent developments in mesoporous titania materials, particularly in the fields of morphology control and applications. We first briefly introduce the history of mesoporous titania materials and then review several synthesis approaches. Currently, mesoporous titania nanoparticles (MTNs) have attracted much attention in various fields, such as medicine, catalysis, separation and optics. Compared with bulk mesoporous titania materials, which are above a micrometer in size, nanometer-sized MTNs have additional properties, such as fast mass transport, strong adhesion to substrates and good dispersion in solution. However, it has generally been known that the successful synthesis of MTNs is very difficult owing to the rapid hydrolysis of titanium-containing precursors and the crystallization of titania upon thermal treatment. Finally, we review four emerging fields including photocatalysis, photovoltaic devices, sensing and biomedical applications of mesoporous titania materials. Because of its high surface area, controlled porous structure, suitable morphology and semiconducting behavior, mesoporous titania is expected to be used in innovative applications