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关键词： 35P05   47D06  

摘要： We study the semigroup generated by the hypoelliptic Laplacian on the circle and the maximal bounded holomorphic extension of this semigroup. Using an orthogonal decomposition into harmonic oscillators with complex shifts, we describe the domain of this extension and we show that boundedness in a half plane corresponds to absolute convergence of the expansion of the semigroup in eigenfunctions. This relies on a novel integral formula for the spectral projections which also gives asymptotics for Laguerre polynomials in a large parameter regime.

关键词： directed energy   electric field biophysics   quantitative phase imaging  

摘要： A substantial body of literature exists to study the dynamics of single cells exposed to short duration (<1 mu s), high peak power (similar to 1 MV/m) transient electric fields. Much of this research is limited to traditional fluorescence-based microscopy techniques, which introduce exogenous agents to the culture and are only sensitive to a single molecular target. Quantitative phase imaging (QPI) is a coherent imaging modality which uses optical path length as a label-free contrast mechanism, and has proven highly effective for the study of single-cell dynamics. In this work, we introduce QPI as a useful imaging tool for the study of cells undergoing cytoskeletal remodeling after nanosecond pulsed electric field (nsPEF) exposure. In particular, we use cell swelling, dry mass and disorder strength measurements derived from QPI phase images to monitor the cellular response to nsPEFs. We hope this demonstration of QPI's utility will lead to a further adoption of the technique for the study of directed energy bioeffects. [GRAPHICS] .

关键词： Key Words   completely monotone function   fractional Laplacian   Green function   Jacobi triple product  

摘要： We give a very simple proof of the positivity and unimodality of the Green function for the killed fractional Laplacian on the periodic domain. The argument relies on the Jacobi triple product and a probabilistic representation of the Green function. We also show by a contour integration that the Green function is completely monotone on the positive part of the periodic domain.

关键词： trucking   pricing   spot market   electronic logging device   time series   Almon lag  

摘要： Most truckload freight in the United States is priced using long-term contracts. It is widely recognized in industry that contract prices evolve based on prices shippers pay for one-time spot market transactions. This research examines whether the impact of spot market prices on contract prices has become more pronounced following the start of the electronic logging device (ELD) mandate. We draw on economic theories regarding how firms process information to explain why the ELD mandate, by reducing carriers' ability to artificially adjust capacity up or down as spot prices changed, should strengthen this relationship. To test this prediction, we construct a database that combines monthly proprietary spot market pricing data from DAT Solutions with monthly public contract pricing data from the Bureau of Labor Statistics. We test our predictions using time series regression and evaluate the robustness of our findings using both instrumental variable estimation and seemingly unrelated regression to rule out reverse causality. Consistent with our theorizing, we further this relationship has become more pronounced since the ELD mandate started. We explain the importance of these findings to theory and practice.

关键词： Dry eye   Chronic renal failure   Mass spectrometry   Tear proteomics  

摘要： Ocular surface changes may develop in patients with chronic renal failure (CRF) undergoing hemodialysis. In recent years, an association of CRF with dry eye syndrome has been emphasized. However, tear proteomics of CRF patients has not been analyzed. Here, we performed systematic profiling of the tear film proteins in CRF patients through use of isobaric tags for relative and absolute quantitative (iTRAQ) MS/MS, aiming to identify associations between dry eye symptoms and expression of tear proteomic changes in patients with CRF undergoing hemodialysis. Twenty CRF patients and ten healthy subjects underwent a series of ophthalmic examinations. Tear samples from the participants were analyzed by iTRAQ approach. A total of 1139 tear proteins were screened, and 212 differentially expressed proteins were identified. The pattern changes included 77 whose expression levels were upregulated (fold increase >1.2) whereas 135 others that were downregulated (fold decrease <1/1.2). Bioinformatics analysis showed that these proteins were significantly enriched in lipid metabolism, inflammatory, and immune response pathways. Furthermore, APOA1, APOA4, APOB, APOE, S100A8, S100A9, S100A4, HSP90B and other molecules were significantly changed. Our study elucidated the characteristics of tear dynamics and protein markers in CRF patients undergoing hemodialysis. Significance: Despite the association of chronic renal failure (CRF) with dry eye disease, there are no reports describing potentially important differentially expressed tear proteins in CRF patients undergoing hemodialysis. It is still a challenge to obtain a comprehensive description of the pathogenesis of dry eye in CRF patients which hinders establishing a patient specific therapeutic scheme. Our study is the first iTRAQ proteomics analysis of the tears of patients with CRF, which reveals the changes in the protein expression profile in CRF patients afflicted with dry eye disease. The identity was verified of some relevant

摘要： 本文简介了电荷流、极化电流与自旋流，自旋流产生和检测之机制以及自旋电荷转换等自旋电子学重要观念，并介绍了一个新颖的材料：拓朴绝缘体。我们在拓朴绝缘体异质结构中在调整费米能阶位置调控自旋电荷之转换。通过自旋帮浦测量分析，揭示了自旋电荷转换与拓朴绝缘体的费米能阶高度的相依关系。结果显示，当费米能接近狄拉克点时，自旋流可在最大程度上转化为电荷流。我们的研究工作提供了一种新方法，可以通过控制拓朴绝缘体的费米能阶来实现有效的自旋电荷转换。而自旋电荷转换对於自旋电子元件中的读写功能，以及对低能耗高速元件的研发都是非常重要的课题与关键技术。

关键词： PT-symmetric quantum mechanics   Superconducting qubits  

摘要： We study the dynamics of a driven non-Hermitian superconducting qubit which is perturbed by quantum jumps between energy levels, a purely quantum effect with no classical correspondence. The quantum jumps mix the qubit states leading to decoherence. We observe that this decoherence rate is enhanced near the exceptional point, owing to the cube-root topology of the non-Hermitian eigenenergies. Together with the effect of non-Hermitian gain or loss, quantum jumps can also lead to a breakdown of adiabatic evolution under the slow-driving limit. Our study shows the critical role of quantum jumps in generalizing the applications of classical non-Hermitian systems to open quantum systems for sensing and control.

摘要： 纯自旋电流在携带极少或甚至没有电荷载子的情况下，可以更有效地传递的自旋角动量，因此最近自旋电子现象的探索和自旋电子学元件的研究与进展已经由利用自旋极化电流演变为纯自旋电流。在本文中，我们的工作证明了自旋玻璃系统中的自旋涨落可以用来增强纯自旋电流。此外，我们还发现样品的形状和去磁效应会强烈影响纯自旋电流的行为。

关键词： Free energy   Peptides and proteins   QM/MM   Chemical reactions   Chemical calculations  

摘要： Increasing demands for efficient and versatile chemical reactions have prompted innovations in enzyme engineering. A major challenge in engineering alpha-ketoglutarate-dependent oxygenases is to develop a rational strategy which can be widely used for directly evolving the desired mutant to generate new products. Herein, we report a strategy for rational redesign of a model enzyme, 4-hydroxyphenylpyruvate dioxygenase (HPPD), based on quantum mechanics/molecular mechanics (QM/MM) calculation and molecular dynamic simulations. This strategy enriched our understanding of the HPPD catalytic reaction pathway and led to the discovery of a series of HPPD mutants producing hydroxyphenylacetate (HPA) as the alternative product other than the native product homogentisate. The predicted HPPD-Fe(IV)=O-HPA intermediate was further confirmed by the crystal structure of Arabidopsis thaliana HPPD/S267W complexed with HPA. These findings not only provide a good understanding of the structure-function relationship of HPPD but also demonstrate a generally applicable platform for the development of biocatalysts.

关键词： defect capturing   charging dynamics   magneto-transport   quantum wells   energy balance   energy-relaxation  

摘要： The calculated defect corrections to the polarization and dielectric functions for Bloch electrons in quantum wells are presented. These results were employed to derive the first two moment equations from the Boltzmann transport theory and then applied to explore the role played by defects on the magneto-transport of Bloch electrons. Additionally, we have derived analytically the inverse momentum-relaxation time and mobility tensor for Bloch electrons by making use of the screened defect-corrected polarization function. Based on quantum-statistical theory, we have investigated the defect capture and charging dynamics by employing a parameterized physics-based model for defects to obtain defect wave functions. Both capture and relaxation rates, as well as the density for captured Bloch electrons, were calculated self-consistently as functions of temperature, doping density and chosen defect parameters. By applying the energy-balance equation, the number of occupied energy levels and the chemical potential of defects were determined, with which the transition rate for defect capturing was obtained. By applying these results, the defect energy-relaxation, capture and escape rates, and Bloch-electron chemical potential were calculated self-consistently for a non-canonical subsystem of Bloch electrons. At the same time, the energy- and momentum-relaxation rates of Bloch electrons, as well as the current suppression factor, were also investigated quantitatively. By combining all these results, the temperature dependence of the Hall and longitudinal mobilities was presented for Bloch electrons in either single- or multi-quantum wells.