Warped compactification to de Sitter space

We explore in detail the prospects of obtaining a four-dimensional de Sitter universe in classical supergravity models with warped and time-independent extra dimensions, presenting explicit cosmological solutions of the (4+n)$(4+n)$-dimensional Einstein equations with and without a bulk cosmological constant term. For the first time in the literature we show that there may exist a large class of warped supergravity models with a noncompact extra dimension which lead to a finite 4D Newton constant as well as a massless 4D graviton localized on an inflating four-dimensional FLRW universe. This result helps establish that the ‘no-go’ theorem forbidding acceleration in ‘standard’ compactification of string/M-theory on physically compact spaces should not apply to a general class of warped supergravity models that allows at least one noncompact direction. We present solutions for which the size of the radial dimension takes a constant value in the large volume limit, providing an explicit example of spontaneous compactification.     

Theoretical investigation on thermal lensing effects of Yb:KY(WO4)2 in diode-pumped lasers

Based on the features of laser diode end-pumped lasers, a thermal model of Yb:KY(WO₄)₂(Yb:KYW) with square cross-section was established. Considering the heat transfer on side faces, the anisotropic of thermal conductivity and the latest reports about thermo-optic coefficient, thermal expansion coefficient and thermal conductivity, temperature distribution, end-pumped face distortion and thermal lens focal length of Yb:KYW were more precisely obtained using finite difference method to solve Poisson equation in a rectangular Cartesian coordinate for the first time. At the pump power of 14 W, the highest temperature located at the center of end-pumped face was 243.8 °C, the highest distortion was 0.28 μm, and the thermal lens focal length was 5.4 cm along z-axis and −4.9 cm along x-axis. The results show that thermal lensing effects in the b-cut Yb:KYW were mainly determined by the anisotropic thermal expansion of Yb:KYW, and further present thermal lensing effects become weaker after considering the heat transfer. This work is significant for compensating the thermal lensing effect and improving the resonator stability of diode-pumped anisotropy crystal lasers.     

A DC current–voltage model for organic thin film transistor for circuit design

Organic integrated circuits based on organic thin film transistors (OTFT) are gaining more and more attention nowadays, the availability of accurate spice-like device model for OTFTs suitable for Electronic design automation (EDA) applications is particularly attractive. In this paper, we demonstrate the applicability of the accurate direct-current (DC) model for OTFTs suitable for EDA, the parameters in the unified model all can be extracted in a simple and direct way from the experimental measurements. Two types of top source and drain contact (TC) pentacene TFTs with different gate dielectrics are researched on, simulation results based Simulation Program with Integrated Circuit Emphasis (SPICE) are obtained with this model and parameters extracted, which show a very good agreement with measured curves in both transfer and output characteristics, so the DC model and the extracted parameters are verified.     

The lexicographically smallest universal cycle for binary strings with minimum specified weight

H. Fredricksen, I.J. Kessler and J. Maiorana discovered a simple but elegant construction of a universal cycle for binary strings of length n: Concatenate the aperiodic prefixes of length n binary necklaces in lexicographic order. We generalize their construction to binary strings of length n whose weights are in the range $c,c+1,\dots ,n$ by simply omitting the necklaces with weight less than c. We also provide an efficient algorithm that generates the universal cycles in constant amortized time per bit using $O(n)$ space. Our universal cycles have the property of being the lexicographically smallest universal cycle for the set of binary strings of length n with weight ≥c.     

Discovery of dipeptidyl peptidase Ⅳ(DPP4) inhibitors based on a novel indole scaffold

Dipeptidyl peptidase Ⅳ(DPP4) inhibitors are proven in the treatment of type 2 diabetes.We designed and synthesized a series of novel indole compounds that selectively inhibit the activity of DPP4 over dipeptidyl peptidase 9(DPP9)(200 fold).We further co-crystallized DPP4 with indole sulfonamide(compound 1) to confirm a proposed binding mode.Good metabolic stability of the indole compounds represents another positive attribute for further development.     

HSSPME-GC-MS联用分析墨吉对虾储藏过程挥发性有机物特征的变化

建立了顶空固相微萃取-气相色谱-质谱联用分析墨吉对虾挥发性有机物(VOCs)的方法,结合化学计量学方法解析了墨吉对虾储藏过程中VOCs特征的变化,初步研究了VOCs特征变化与其鲜度的关系.采用上述方法,在新鲜和变质墨吉对虾样品中分别检测到22种和16种VOCs组分.采用主成分分析解析新鲜、储藏过程及变质阶段对虾样品的VOCs色谱特征,结果表明墨吉对虾变质前后VOCs特征有明显不同的聚类规律,且对虾样品储藏过程中VOCs特征从新鲜到变质状态呈现逐步过渡的趋势,对虾储藏过程VOCs特征的变化可以提供更加准确的鲜度变化预警信息.最后,采用共有模式统计对比了新鲜和变质墨吉对虾VOCs特征聚类数据,获得对样品变质前后VOCs特征差异贡献前5位VOCs,可作为潜在的鲜度判别预警VOCs标志物.