Metal-free diastereoselective synthesis of diaza-bicyclo[3.2.0]heptan-7-one and its transformation to functionalized proline esters

A metal-free diastereoselective synthesis of novel 4-halo-3,6-di-aryl-2,6-diaza-bicyclo[3.2.0]heptan-7-one by intramolecular endo-trig haloamination of 3-amino-2-azetidinone is reported. The amidiolytic ring opening of diaza-bicyclo[3.2.0]heptan-7-one with sodium methoxide provides an easy access to previously unknown 4-halo-3-aryl amino-pyrrolidine-2-carboxylic acid methyl esters in good yields.     

Thermophysical properties of binary mixtures of odichlorobenzene and o-chlorophenol with diethyl ether, tetrahydrofuran, cyclohexane and anisole

Measurement of density and viscosity has been used for evaluating derived parameters for binary system of o-dichlorobenzene and o-chlorophenol with diethyl ether, tetrahydrofuran, cyclohexane and anisole at the different temperatures and at atmospheric pressure. From these, excess parameters have been calculated over entire range of composition. The variation of derived parameters as well as the sign and magnitude of corresponding excess functions has been used to investigate the type and extent of interaction between the component molecules of the binary mixture.     

Structure and rheology of fiber-laden membranes via integration of nematodynamics and membranodynamics

This paper presents a study of the structure and dynamics of rigid fiber-laden deformable curved fluid membranes based on an viscoelastic model that integrates the statics of anisotropic membranes, the planar nematodynamics of fibers and the dynamics of isotropic membranes. Fiber-laden membranes arise frequently in biological systems, such as the plant cell wall and in protein–lipid bilayers. Based on the membrane's force and torque balance equations and the fiber's balance of molecular fields, a viscoelastic anisotropic model that provides the governing equations for the membrane's velocity and curvature and the fiber structure (fiber orientation and order) is found. A Helmholtz free energy that incorporates the tension/bending/and torsion membrane elasticity, the Landau–de Gennes fiber ordering, and fiber order-membrane curvature interactions is used to derive elastic moments, torques, and stresses. The corresponding viscous stresses and moments include the Boussinesq–Scriven contributions as well as bending, torsion, and rotational dissipation. A spectral decomposition leads to the main viscoelastic material functions for anisotropic fluid membranes. Applications of the rheological model to cylindrical growth and cylindrical axial stretching show that competing curvo-phobic, curvo-philic interactions under extensional flow predict transitions between axial and azimuthal fiber arrangements, of interest to cellulose fiber orientation in plant morphogenesis.     

Hyper-aging dynamics of nanoclay suspension

Aqueous suspension of nanoclay Laponite undergoes structural evolution as a function of time, which enhances its elasticity and relaxation time. In this work, we employ an effective time approach to investigate long-term relaxation dynamics by carrying out creep experiments. Typically, we observe that the monotonic evolution of elastic modulus shifts to lower aging times, while maxima in viscous moduli get progressively broader for experiments carried out on a later date after preparation (idle time) of the nanoclay suspension. Application of effective time theory produces a superposition of all the creep curves irrespective of their initial state. The resulting dependence of the relaxation time on aging time shows very strong hyper-aging dynamics at short idle times, which progressively weakens to demonstrate a linear dependence in the limit of very long idle times. Remarkably, this behavior of nanoclay suspensions is akin to that observed for polymeric glasses. Consideration of aging as a first-order process suggests that continued hyper-aging dynamics causes cessation of aging. The dependence of relaxation time on aging time, therefore, must attenuate eventually producing linear or weaker dependence on time in order to approach a progressively low-energy state in the limit of very long times as observed experimentally. We also develop a simple scaling model based on a concept of aging of an energy well, which qualitatively captures various experimental observations very well, leading to profound insight into the hyper-aging dynamics of nanoclay suspensions.     

驱动模式对具有库源平衡的黏性流体中空间反射时间反演联合对称性的影响

满足空间反射时间反演parity and time-reversal(PT)联合对称性的库源平衡宏观开放系统近几年成为一个研究热点.本文将PT对称性引入到动力学系统,用格子玻尔兹曼方法求解Navier-Stokes方程,发现在二维黏性流体中,如果进口和出口的条件完全等同,在低雷诺数流动中,流场的PT对称函数(ρ)随雷诺数(Re)的增高以ρn～Ren指数增长.用三种不同的速度剖面来驱动流体,计算流场达到稳定状态时的PT对称性.结果发现,进出口平衡的黏性管流中,ρn～Ren的规律在三种驱动模式中出现,表明流场的PT对称性是由流体本身决定的,与驱动模式没有关系,从此论证所得到的指数率的谱适性.     

White Luminescence from Multiple‐Dye‐Doped Electrospun DNA Nanofibers by Fluorescence Resonance Energy Transfer

A DNA spin‐off : Electrospinning of DNA complexes gives nanofibers with a highly ordered morphology that allows homogeneous distribution of encapsulated multiple chromophores. The emission color can be controlled by suitable choice of the donor–acceptor pair and the doping ratio. Pure white‐light emission from nanofibers is demonstrated (see picture).

     

Regioselective enzymatic acylation of beta-L-2'-deoxynucleosides: application in resolution of beta-D/L-2'-deoxynucleosides

[reaction: see text] A practical synthesis of beta-L-3'- and beta-L-5'-O-levulinyl-2'-deoxynucleosides has been described for the first time through enzymatic acylation and/or hydrolysis processes. It is noteworthy that the different behavior exhibited by Pseudomonas cepacia lipase in the acylation of D- and L-nucleosides allows the parallel kinetic resolution of D/L-nucleosides.     

Nodal Cooper-pair stabilized phase dynamics in granular d-wave superconductors

Scanning tunneling microscope measurements on single crystals of Bi2Sr2CaCu2O8+x materials have shown that the d-wave superconductivity in cuprates has nanoscale inhomogeneities and is still robust in spite of their presence. We study the dynamics of Josephson coupling between such granular d-wave superconductors, focusing on the effect of nodal Cooper pairs and disorder. We find that the nodal Cooper pairs give rise to a power-law Josephson coupling which leads to the stabilization of the superconducting phase. Our findings suggest that the d-wave superconductivity in an array of grains is unexpectedly robust against a disordering transition, as observed in the experiments. Furthermore, we predict the existence of a planar Josephson-plasmon mode with characteristic frequency that decreases with temperature.     

RLIP76, a non-ABC transporter,and drug resistance in epilepsy

Background  

Permeability of the blood-brain barrier is one of the factors determining the bioavailability of therapeutic drugs and resistance to chemically different antiepileptic drugs is a consequence of decreased intracerebral accumulation. The ABC transporters, particularly P-glycoprotein, are known to play a role in antiepileptic drug extrusion, but are not by themselves sufficient to fully explain the phenomenon of drug-resistant epilepsy. Proteomic analyses of membrane protein differentially expressed in epileptic foci brain tissue revealed the frequently increased expression of RLIP76/RALBP1, a recently described non-ABC multi-specific transporter. Because of a significant overlap in substrates between P-glycoprotein and RLIP76, present studies were carried out to determine the potential role of RLIP76 in AED transport in the brain.