Gel-induced selective crystallization of polymorphs

Although nanoporous materials have been explored for controlling crystallization of polymorphs in recent years, polymorphism in confined environments is still poorly understood, particularly from a kinetic perspective, and the role of the local structure of the substrate has largely been neglected. Herein, we report the use of a novel material, polymer microgels with tunable microstructure, for controlling polymorph crystallization from solution and for investigating systematically the effects of nanoconfinement and interfacial interactions on polymorphic outcomes. We show that the polymer microgels can improve polymorph selectivity significantly. The polymorphic outcomes correlate strongly with the gel-induced nucleation kinetics and are very sensitive to both the polymer microstructure and the chemical composition. Further mechanistic investigations suggest that the nucleation-templating effect and the spatial confinement imposed by the polymer network may be central to achieving polymorph selectivity. We demonstrate polymer microgels as promising materials for controlling crystal polymorphism. Moreover, our results help advance the fundamental understanding of polymorph crystallization at complex interfaces, particularly in confined environments.     

Preparation of true solutions of monomeric amyloidogenic protein/peptide: A critical prerequisite for aggregation kinetic study

Our dynamic laser light scattering(LLS) study shows that the current widely used protocols of dissolving amyloidogenic protein/peptide do not really result in a true solution;namely,there always exist a trace amount of interchain aggregates,which greatly affect the association kinetics,partially explaining why different kinetics were reported even for a solution with identical protein and solvent.Recently,using a combination of the conventional dissolution procedure and our newly developed ultra-filtration method,we have developed a novel protocol to prepare a true solution of amyloidogenic protein/peptide without any interchain aggregates.The resultant solutions remain in their monomeric state for at least one week,which is vitally important for further study of the very initial stage of the interchain association under the physiological conditions because more and more evidence suggests that it is those small oligomers rather than large fabric aggregates that are cytotoxic.In addition,this study shows that combining static and dynamic LLS can lead to more physical and microscopic information about the protein association instead of only the size distribution.     

Observation of a near-threshold enhancement in the omega(phi) mass spectrum from the doubly OZI-suppressed decay J/psi-->gamma(omega)phi

An enhancement near threshold is observed in the omega(phi) invariant mass spectrum from the doubly Okubo-Zweig-Iizuka-suppressed decays of J/psi-->gamma(omega)phi, based on a sample of 5.8 x 10(7) J/psi events collected with the BESII detector. A partial wave analysis shows that this enhancement favors JP=0+, and its mass and width are M=1812(+19)(-26)(stat)+/-18(syst) MeV/c2 and Gamma=105+/-20(stat)+/-28(syst) MeV/c2. The product branching fraction is determined to be B(J/psi-->gammaX)B(X-->omega(phi))=[2.61+/-0.27(stat)+/-0.65(syst)]x10(-4).     

Microstructure and rheological properties of liquid crystallines formed in Brij 97/water/IPM system

The phase diagram of Brij 97/water/IPM systems was determined at 25 degrees C. Rich liquid crystalline phases including Lalpha, H1, and cubic Fd3m phases were identified by means of small angle X-ray scattering (SAXS). Microstructure transitions of liquid crystals with changes in surfactant concentration and oil content are explained qualitatively by the surfactant packing parameter (vL/aSlc). Dynamic rheological results indicate that all three kinds of liquid crystals investigated show high elasticity. The lamellar, Lalpha, phases formed in Brij 97/water with two different oils, oleic acid and geraniol, were also studied in comparison with those of Brij 97/water/IPM systems. The strength of the network of lamellar phases formed in Brij 97/water/oleic acid and Brij 97/water/geraniol systems are appreciably stronger than for Brij 97/water/IPM systems, indicated by the smaller area of surfactant molecules at the interface and the higher moduli (G' and G').     

Encapsulation of quinine by beta-cyclodextrin: excellent model for mimicking enzyme-substrate interactions

An inclusion complex formed by beta-cyclodextrin and quinine has been investigated in solution and in the solid state, in which the quinoline ring and the aliphatic ring locate in different hydrophobic cavities, respectively. The study on the inclusion geometry and weak interactions shows that the difference in conformation for this complex is a result of three main packing arrangement considerations, which can provide an ideal model mimicking enzyme-substrate interactions.     

On componentwise condition numbers for eigenvalue problems with structured matrices

We give explicit expressions for the componentwise condition number for eigenvalue problems with structured matrices. We will consider only linear structures and show a general result from which expressions for the condition numbers follow. We obtain explicit expressions for the following structures: Toeplitz and Hankel. Details for other linear structures should follow in a straightforward manner from our general result. Copyright © 2008 John Wiley & Sons, Ltd.     

Jones polynomial of knots formed by repeated tangle replacement operations

In this paper, we prove that the Jones polynomial of a link diagram obtained through repeated tangle replacement operations can be computed by a sequence of suitable variable substitutions in simpler polynomials. For the case that all the tangles involved in the construction of the link diagram have at most k crossings (where k is a constant independent of the total number n of crossings in the link diagram), we show that the computation time needed to calculate the Jones polynomial of the link diagram is bounded above by O(nk). In particular, we show that the Jones polynomial of any Conway algebraic link diagram with n crossings can be computed in O(n²) time. A consequence of this result is that the Jones polynomial of any Montesinos link and two bridge knot or link of n crossings can be computed in O(n²) time.     

The Path-Connectivity of s-Elementary Frame Wavelets with Frame MRA

MRA wavelets have been widely studied in recent years due to their applications in signal processing. In order to understand the properties of the various MRA wavelets, it makes sense to study the topological structure of the set of all MRA wavelets. In fact, it has been shown that the set of all MRA wavelets (in any given dimension with a fixed expansive dilation matrix) is path-connected. The current paper concerns a class of functions more general than the MRA wavelets, namely normalized tight frame wavelets with a frame MRA structure. More specifically, it focuses on the parallel question on the topology of the set of all such functions (in the given dimension with a fixed dilation matrix): is this set path-connected? While we are unable to settle this general path-connectivity problem for the set of all frame MRA normalized tight frame wavelets, we show that this holds for a subset of it. An s-elementary frame MRA normalized tight frame wavelets (associated with a given expansive matrix A as its dilation matrix) is a normalized tight frame wavelet whose Fourier transform is of the form $\frac{1}{\sqrt{2\pi}}\chi_{E}$ for some measurable set E?? ^d . In this paper, we show that for any given d×d expansive matrix A, the set of all (A-dilation) s-elementary normalized tight frame wavelets with a frame MRA structure is also path-connected.     

正仲氢催化转化性能低温测试装置设计

液氢在新能源、工业生产等领域有重要的用途.结合液氢生产中正仲氢转化的特点,提出了一种可实现多种转化方式的正仲氢催化转化性能低温测试装置设计.通过液氮预冷和G-M制冷机实现正仲氢转化温度可控、通过设置正仲氢预反应实现入口原料仲氢组分可控,并采用更换可拆卸转化器和热沉方式实现多种正仲氢转化方式.实现不同工况下(等温绝热、连...     

铯原子气室中相干布居俘获的参数依赖关系研究

基于铯原子基态6S_1/2的两个超精细能级（F=3与F=4）与激发态6P_3/2的超精细能级（F′=4）构成的Λ型三能级系统,采用室温下的未充缓冲气体和充有分压为266.6 Pa的氖气作为缓冲气体的铯原子气室对于相干布居俘获（CPT）的参数依赖关系进行了实验研究和理论分析.主要研究了CPT信号的半高全宽和幅度对于频率差为铯原子基态6S_1/2的超精细分裂（9.19263177 GHz）且位相锁定的两激光束的功率、光强比值、光斑直径、磁屏蔽之后的剩余磁场以及是否充缓冲气体等实验参数的依赖关系.在优化的实验参数条件下获得了约340 Hz的CPT信号半高全宽.