Bipolaron Localization for Increasing Electron–Phonon Coupling in a Small Cluster

By exact diagonalization of a small cluster, we show that an interplay of electron–phonon and onsite electron–electron interactions results in intersite or onsite two-electron (bipolaronic) solutions of the Holstein–Hubbard model, depending on the strengths of the interactions. On this basis, we argue that the decrease in the superconducting transition temperature of Bi-2212 compounds, following the enhancement of the electron–phonon interaction recently reported by Devereaux et al. [10] might be a consequence of the above mechanism, which leads to a transition from itinerant (intersite) to bound immobile (onsite) bipolarons, thus effectively reducing the number of superconducting carriers.     

Emergence of Pairing Interaction in the Hubbard Model in the Strong Coupling Limit

We implement the rotationally-invariant formulation of the two-dimensional Hubbard model, with nearest-neighbors hopping t, which allows for the analytic study of the system in the low-energy limit. Both U(1) and SU(2) gauge transformations are used to factorize the charge and spin contribution to the original electron operator in terms of the corresponding gauge fields. The Hubbard Coulomb energy U-term is then expressed in terms of quantum phase variables conjugate to the local charge and variable spin quantization axis, providing a useful representation of strongly correlated systems. It is shown that these gauge fields play a similar role as phonons in the BCS theory: they act as the “glue” for fermion pairing. By tracing out gauge degrees of freedom the form of paired states is established and the strength of the pairing potential is determined. It is found that the attractive pairing potential in the effective low-energy fermionic action is non-zero in a rather narrow range of U/t.     

Facebook联手T—Mobile发布免费VoIP应用

T—Mobile美国公司周二联合Facebook椎出了一项免费的VoIp应用Bobsled,允许Facebook用户通过网页给好友打电话。     

High-Entrapment Liposomes for 6-Mercaptopurine—A Prodrug Approach

Low entrapment of drugs into liposomes is a serious challenge in their commercial application. 6-Mercaptopurine (6-MP), an antineoplastic agent, is such a drug with low entrapment efficiency (EE). We devised their lipophilic derivatization as a means of enhancing EE by covalently coupling 6-MP with glyceryl monostearate (GMS) via a succinic anhydride spacer. This prodrug had an improved partition coefficient value of 25.16 compared to 1.22 for free drug, confirming higher lipophilicity. A hydrolysis rate study of prodrug indicated 2.90%, 12.5%, 24.1%, and 25.1% hydrolysis in phosphate buffered saline (PBS) (pH 7.4) and 10%, 20%, and 30% serum, respectively. Liposomes of phosphatidylcholine (PC)/sphingomyelin, cholesterol, and dicetyl phosphate bearing drug or prodrug were prepared by shaking by hand and sonication methods. The EE was found to increase from 1.92% for free drug to 91.8% for drug-conjugate. An in vitro cell line toxicity study on L1210 leukemia cells showed improved performance of liposome-encapsulated drug-conjugate compared to free drug. The plasma drug level profile following administration of free drug and the liposomal formulation containing prodrug (HE liposome) manifested a higher sustained level of the latter, which was further improved in case of sphingomyelin-containing liposomes (STHE liposome). The pharmacokinetic parameters revealed an increase in half-life, from 61 min to 120 min for the HE liposomes and 296 min for the STHE liposomes. Therefore, increased entrapment was made possible through lipophilic derivatization, and it was subsequently tested in vivo.     

Mobile应用开发中的版本控制

Pocket PC和Smartphone设备为软件开发人员和IT管理员提出了有趣的挑战。在整篇本章中。我们提供了代码组织的最佳实践。从台式机编程中借用的总体风格以及如何保持设备程序集始终最新的有用机制。同时。还解释了是什么阻止了您把移动应用程序看作重要的企业级解决方案。     

Windows Mobile 5中的新特性

微软最近推出下一代移动设备操作系统Windows Mobile 5。Windows Mobile 5在用户体验方面做了很多改善，但更多的改进还是在应用程序编程接口方面。在这篇文章中，我们会向您介绍Windows Mobile 5在开发方面的一些新特性，其中包括3D图形编程、新控件、新的API函数等。     

LMS SCADAS Mobile便携式数据采集前端

LMS最新推出的SCADAS Mobile数采前端,完善了移动式振动噪声试验的解决方案,扩展了多领域的测试应用。LMS SCADAS Mobile汇聚了声誉很高的LMS SCADAS系列的优良品质和强大的采集功能,通过紧凑而坚实的设计,赋予它诸多的数据采集和信号调理功能,使得LMS SCADAS Mobile成为同类产品中的佼佼者,其卓越的性能、高精度、设计轻巧、以及长寿命的电池,是移动试验极为理想的数采前端。LMS SCADAS Mobile特点:坚固的外壳设计,胜任恶劣的工作环境先进的热管散热技术,无风扇静音工作模式所有连接和控制开关均集中在前面板单机箱通…     

Approach to the Theoretical Strength of Ti—Ni—Cu Alloy Nanocrystals by Grain Boundary Design

The grain boundary design was used to introduce boride Ti_2B and TiB_2 nanoparticles of 5 nm in size into grain boundaries of nanocrystalline Ti_(50)Ni_(25)Cu_(25) alloy.As a result,the maximum normalized microhardness was increased by 20%and the theoretical limit of hardness is substantially approached.It is proposed that boride nanoparticles suppressed low-temperature grain-boundary sliding and,therefore,shifted the range of the anomalous behavior of Hall-Petch relation toward smaller sizes of the Ti-Ni-Cu nanocrystals.     

Nonliposomal Approach—A Study of Preparation of Egg Albumin Nanospheres Containing Amphotericin-B

The stability of liposomes after introduction into the body is presently being discussed and needs thorough understanding. Hence, as a nonliposomal approach, egg albumin nanospheres were prepared by the pH-coacervation method, and a preliminary study was carried out of the influence of process variables on the size and shape of nanospheres by changing the pH of the albumin solution, concentration of albumin solution, and volume of cross-linking agent. The batch prepared with an albumin medium of pH 9, 2% concentration, and 100 μl of 4% glutaraldehyde-ethanol solution was found to have a spherical uniform shape with an average size of 497.6 nm. The ideal batch was loaded with the systemic antifungal drug amphotericin-B. Drug-loaded nanospheres were evaluated to study their in vitro release. They were found to exhibit a biphasic pattern with a cumulative percentage release of 97.7%.     

A Combined Convex Approximation—Interior Point Approach for Large Scale Nonlinear Programming

The method of moving asymptotes (MMA) and its globally convergent extension SCP (sequential convex programming) are known to work well in the context of structural optimization. The two main reasons are that the approximation scheme used for the objective function and the constraints fits very well to these applications and that at an iteration point a local optimization model is used such that additional expensive function and gradient evaluations of the original problem are avoided. The subproblems that occur in both methods are special nonlinear convex programs and have traditionally been solved using a dual approach. This is now replaced by an interior point approach. The latter one is more suitable for large problems because sparsity properties of the original problem can be preserved and the separability property of the approximation functions is exploited. The effectiveness of the new method is demonstrated by a few examples dealing with problems of structural optimization.     

Multi-Gaussian Ultrasonic Beam Modeling for Multiple Curved Interfaces—an ABCD Matrix Approach

ABSTRACT

A multi-Gaussian beam model uses a superposition of Gaussian beams to simulate the waves radiated from an ultrasonic transducer. We show that propagation and reflection/transmission laws for Gaussian beams in fluids and elastic solids can be written in the form of A , B , C , D matrices that are analogous to the A, B, C, D scalars used in Gaussian optics. This representation leads to simple expressions for a Gaussian beam even after that beam has been transmitted or reflected at multiple curved interfaces and produces a highly modular multi-Gaussian beam model that is also computationally very efficient. Some examples of the use of this model for both planar and curved interfaces are given.     

用GAPI开发Windows Mobile手机游戏

目前mobile phone游戏API简称GAPI为手机上的游戏开发者提供了强有力的高效率的编程接口，当然GAPI不仅仅使用在游戏方面，需要高效率图形显示处理的地方都可以使用GAPI。     

Mobile IP切换的实验研究

首先简要介绍了Mobile IP及其切换原理，然后通过具体实验分析了Mobile IP切换对传输层协议（TCP和UDP）造成的影响。实验主要测试了切换对TCP造成的影响，并由此类推出对UDP的影响。最后讨论了可行的改进措施，重点讨论了如何减少Mobile IP切换时的分组丢失和时延。     

Windows Mobile中的Web Service应用

Web Serivce对于开发者来说已经不再是一个陌生概念了，Web Service允许应用程序通过Internet进行通讯和数据交换。随着微软NET战略的推行，选种可编程的、通过SOAP协议、基于XML的网络协议已经赢得了开发者的心。     

from Clothes Manufacturing Big Country to Strong Country

日前,在北京闭幕的第十二届中国国际服装博览会,在充分表现中国世界服装大国地位的同时,也显露出我国服装业与世界服装强国之间的差距。专家分析,中国服装产业要想从大到强必须要解决如下两个问题。才能真正进入世界服装强国之列。     

Electro-Discharge Machining–A Qualitative Approach

The complex and stochastic nature of Electro-Discharge Machining (EDM) has drawn numerous investigations to establish control over the quality related characteristics such as better surface finish, smaller heat-affected zone including minimized recast layer without compromising the productivity of the machining process. The present paper proposes a three-dimensional transient heat conduction model where the growth of the plasma channel is considered. The temperature distribution function is used to compute the depth of the crater that defines the surface roughness (Ry) and depth of the heat-affected zone at different pulse duration. Further, experiments are conducted to measure the depth of the crater and the depth of the heat-affected zone. The experimental and theoretical results show significant similarity.     

Producing Ceramic High Tc Superconductors for Strong Current Applications

Strong current and large-scale application is the most important prospect of high Tc superconductors (HTS).Practical HTS samples, both in forms of wire and bulk, have been produced with high critical currents operated at economic cryogenic temperatures, and studied for engineering applications with various prototype devices. The applicable HTS materials produced are introduced in this paper with regard to processing, characterization and application.     

Application of General Fractal Dimension to Coupling Fault Diagnosis

This paper presents the coucept of general and sensitive dimension,and also proposes the calculation formula of the general dimension least squares method.By calculating and analyzing the power spectrum and general dimension grom the fault sample,the relationship is achieved between sample status and the general simension from vibration signals of the equipment so as to provide reference to fault diagnosis.Furthermore,a correlation function of general dimension is proposed,and calculations are carried out for a monitor signal and samples signal.The diagnosis method based on fractal theory is effective through the concrete examples of the steam-electric generating set fault diagnosis,and the correlation coefficient of general dimension between a monitor signal and samples signal can improve the accuracy for fault diagnosis.