保费再投资下带干扰的COX风险模型的破产概率

基于经典的风险模型,考虑了对于保费进行稳健投资的情况,同时加入了用布朗运动来描述的干扰因素,引入了保费再投资下带干扰的Cox风险模型.利用鞅方法得到了该模型破产概率的Lundberg不等式.     

顺式二(乙二胺)二硝基合钴(Ⅲ)酒石酸锑盐晶体结构和分子的绝对构型

顺式二(乙二胺)二硝基合钴(Ⅲ)酒石酸锑盐，Δ-cis-［Co(en)₂(NO₂)₂］₂-d-［Sb₂(C₄H₂O_{6)2］·2H2O，是由酒石酸锑钾对外消旋混合物cis-［Co(en)2(NO2)2］Cl进行拆分的产物。标题化合物(Sb2Co2C16N12O22H40)的晶体结构由衍射方法确定。晶体学参数为：正交晶系，空间群P212121,a=10.033(5), b=13.203(2),c=25.928(7)(),V=3434(2)^{3,Z=4,Mr=1114.06, Dc=2.156Mgm-3,μ=21.07 mm-1,F(000)=2208, R=0.072,RW=0.084。结构表明，分子由2个Co(Ⅲ)配离子和一个酒石酸锑阴离子及两个水分子组成，阴离子为一双核螯合离子。Sb原子一对孤对电子与其周围四个配位氧原子形成变形三角双锥结构。通过Co和Sb原子对CuKα射线的反常散射效应确定了分子的绝对构型。二个Co(Ⅲ)离子均为Δ构型，酒石酸锑阴离子为R构型。结构分析表明，标题化合物中三点接触离子对在手性识别中起重要作用。}}     

An advanced automation platform coupled with mass spectrometry for investigating in vitro human skin permeation of UV filters and excipients in sunscreen products

Rationale

Systemic absorption of UV-filtering chemicals following topical application of sunscreens may present a safety concern. The Food and Drug Administration (FDA) had recommended an in vitro skin permeation test (IVPT) to evaluate the potential of this safety risk for the evaluation of sunscreens prior to clinical studies. Therefore, a sensitive and robust bioanalytical method(s) were required for IVPT studies of different topical sunscreen products.

Methods

An analytical procedure to quantitate sunscreen UV-filtering components and excipients in IVPT samples including avobenzone, octocrylene, oxybenzone, ecamsule, methylparaben and propylparaben was developed employing a RapidFire 360 robotic sample delivery system coupled with a triple quadrupole mass spectrometer. The analytical procedure was developed and validated according to the requirements of the FDA Bioanalytical Method Validation Guidance for Industry (2018).

Results

The analytical method provided a turnaround time of 12 seconds per sample and was determined to be accurate, precise, specific, and linear over the corresponding analytical ranges. The validated method was successfully applied for two IVPT studies for evaluating the skin permeation potential of UV-filtering chemicals and assisting with the selection of the sunscreen products for the clinical study conducted by the FDA.

Conclusions

This work highlights the first analytical procedure that has applied a non-chromatographic-MS/MS automation platform to an in vitro biopharmaceutics study. The analytical platform simultaneously quantitated four UV filters and two excipients in complex media to evaluate their permeation in IVPT studies. The sample throughput and analytical performance of advanced automation platforms indicate their analytical procedure has the potential to significantly advance the efficiency of IVPT studies to evaluate permeation of a wide variety of UV chemical filters and excipients for topical OTC sunscreen products.

     

激光辐照对MgB2超导体电子结构的影响

研究了光辐照对MgB2超导体电子结构的影响。对MgB2超导体进行不同时间的激光照射后,利用正电子湮没技术对光照样品进行了研究,根据正电子寿命谱参数的变化情况,对光辐照后MgB2超导体样品中缺陷及电子结构的变化进行了讨论。实验表明:MgB2超导体中的平均电子浓度对激光的照射十分敏感,并随光照时间的增加而增加。     

n型掺杂GaAs中重空穴的飞秒动力学

本文采用fs脉冲饱和吸收光谱技术研究了室温下Si掺杂GaAs在电子激发态处于费密面附近时重空穴的超快弛豫特性。测量到重空穴的热化时间约为300fs,与理论计算结果一致,表明重空穴-光学声子散射是主要的热化途径,并得到光学形变势常数d₀为31eV.     

Tunable fiber-tip lens based on thermo-optic effect of amorphous silicon

We theoretically demonstrate a compact all-dielectric metasurface fiber-tip lens composed of sub-wavelength amorphous silicon on the end face of a multimode fiber.The full 2πphase control was realized by varying the widths of resonant units.The tunable focal length is achieved by using the thermal-optic effect of amorphous silicon.The focal length increases from 309μm to 407μm when the temperature changes by 300 K.The temperature controlled all-fiber integrated lens is compact and with high efficiency and provides an excellent platform of a fiber-tip lab.Meanwhile,the proposed fiber lens does not have any structural changes during dynamic tuning,which improves the durability and repeatability of the devices.     

Surrogate model‐based strategy for cryogenic cavitation model validation and sensitivity evaluation

The study of cavitation dynamics in cryogenic environment has critical implications for the performance and safety of liquid rocket engines, but there is no established method to estimate cavitation‐induced loads. To help develop such a computational capability, we employ a multiple‐surrogate model‐based approach to aid in the model validation and calibration process of a transport‐based, homogeneous cryogenic cavitation model. We assess the role of empirical parameters in the cavitation model and uncertainties in material properties via global sensitivity analysis coupled with multiple surrogates including polynomial response surface, radial basis neural network, kriging, and a predicted residual sum of squares‐based weighted average surrogate model. The global sensitivity analysis results indicate that the performance of cavitation model is more sensitive to the changes in model parameters than to uncertainties in material properties. Although the impact of uncertainty in temperature‐dependent vapor pressure on the predictions seems significant, uncertainty in latent heat influences only temperature field. The influence of wall heat transfer on pressure load is insignificant. We find that slower onset of vapor condensation leads to deviation of the predictions from the experiments. The recalibrated model parameters rectify the importance of evaporation source terms, resulting in significant improvements in pressure predictions. The model parameters need to be adjusted for different fluids, but for a given fluid, they help capture the essential fluid physics with different geometry and operating conditions. Copyright © 2008 John Wiley & Sons, Ltd.     

25kW氩壁稳电弧离子体LTE性的光谱学实验研究

本文利用光谱学诊断方法对25kW氩壁稳电弧等离子体的LTE性进行了实验研究.结果发现在实验条件下等离子体至少是PLTE的,压力高于0.05MPa、电流大于50A时,基本上是LTE的,谱线半宽度与等离子状态无关,只取决于电子密度.     

Steric effects on diffusion of associated molecules in acetone

The effects due to steric hindrance on solute-solvent interactions and on diffusion of associated molecules were found by comparing the diffusion coefficients of different aromatic isomers in acetone at 298.2 K; there exists a correlation between the isomeric effects of intermolecular association on diffusion and the molecular scales of overall hydrogen-bond acidity of the isomers studied.     

An efficient direct approach for computing shortest rectilinear paths among obstacles in a two-layer interconnection model

In this paper, we present a direct approach for routing a shortest rectilinear path between two points among a set of rectilinear obstacles in a two-layer interconnection model that is used for VLSI routing applications. The previously best known direct approach for this problem takes O(nlog²n) time and O(nlogn) space, where n is the total number of obstacle edges. By using integer data structures and an implicit graph representation scheme (i.e., a generalization of the distance table method), we improve the time bound to O(nlog^3/2n) while still maintaining the O(nlogn) space bound. Comparing with the indirect approach for this problem, our algorithm is simpler to implement and is probably faster for a quite large range of input sizes.