Modulation of calcium oxalate crystallization by linear aspartic acid-rich peptides

Calcium oxalate monohydrate (COM) kidney stone formation is prevented in most humans by urinary crystallization inhibitors. Urinary osteopontin (OPN) is a prototype of the aspartic acid-rich proteins (AARP) that modulate biomineralization. Synthetic poly(aspartic acids) that resemble functional domains of AARPs provide surrogate molecules for exploring the role of AARPs in biomineralization. Effects of linear aspartic acid-rich peptides on COM growth kinetics and morphology were evaluated by the combination of constant composition (CC) analysis and atomic force microscopy (AFM). A spacer amino acid (either glycine or serine) was incorporated during synthesis after each group of 3 aspartic acids (DDD) in the 27-mer peptide sequences. Kinetic CC studies revealed that the DDD peptide with serine spacers (DDDS) was more than 30 times more effective in inhibiting COM crystal growth than the DDD peptide with glycine spacers (DDDG). AFM revealed changes in morphology on (010) and (-101) COM faces that were generally similar to those previously described for OPN and citrate, respectively. At comparable peptide levels, the effects of step pinning and reduced growth rate caused by DDDS were remarkably greater. In CC nucleation studies, DDDS caused a greater prolongation of induction periods than DDDG. Thus, nucleation studies link changes in interfacial energy caused by peptide adsorption to COM to the CC growth and AFM results. These studies indicate that, in addition to the number of acidic residues, the contributions of other amino acids to the conformation of DDD peptides are also important determinants of the inhibition of COM nucleation and growth.     

Physically incorporated extraction phase of solid-phase microextraction by sol-gel technology

A sol-gel method for the preparation of solid-phase microextraction (SPME) fiber was described and evaluated. The extraction phase of poly(dimethysiloxane) (PDMS) containing 3% vinyl group was physically incorporated into the sol-gel network without chemical bonding. The extraction phase itself is then partly crosslinked at 320 degrees C, forming an independent polymer network and can withstand desorption temperature of 290 degrees C. The headspace extraction of BTX by the fiber SPME was evaluated and the detection limit of o-xylene was down to 0.26 ng/l. Extraction and determination of organophosphorus pesticides (OPPs) in water, orange juice and red wine by the SPME-GC thermionic specified detector (TSD) was validated. Limits of detection of the method for OPPs were below 10 ng/l except methidathion. Relative standard deviations (RSDs) were in the range of 1-20% for pesticides being tested.     

Controllable size, shape and morphology of molybdic acid self-aggregated with rhodamine B to construct functional material

Controllable size, shape and morphology of rhodamine B/molybdic acid (RBMA) aggregates were prepared from a self-aggregation reaction in a molybdic acid and rhodamine B (RhB) coexisting solution. Nanodisks, as well as microcrystal rods and polyhexagonal microcrystal rods, have been obtained in conventional bulk solutions at different temperatures. Large-sized network microcrystal rods and branched fractal aggregates constructed with nanosubunits after the nucleation duration of an ice-water-cooled process have also been achieved under the evaporation-enhanced conditions on glass substrates. The factors affecting the size, shape and morphology of RBMA aggregates including temperature, nucleation and growth, and processing conditions are discussed. The results show that photofunctional molecules (RhB) modified the surface of the molybdic acid particles and influenced their self-aggregation. The temperature and nucleation play key roles in the formation of RBMA aggregates. The structures of RBMA aggregates were characterized by X-ray diffraction, infrared spectra and elemental dispersive spectroscopy. The results indicate that the aggregates show the characteristics of RhB-mediated hydrated ammonium molybdenum bronze with the metastable hexagonal phase. Visible-light-induced electrons transfer reactions in the RBMA aggregates from rhodamine B molecules to MoO3 matrixes were measured by UV-vis spectra and X-ray photoelectron spectra, and the fluorescent image was observed by laser scanning confocal microscopy.     

Study of conical columns with 10 degrees opening angle for preparative liquid chromatography

The efficiency and sample capacity of conical liquid chromatographic columns with 10 degrees opening angle were studied at different ratio of cross section areas of inlet to outlet (A(in)/A(out)) and column dimension. As the A(in)/A(out) ratio changed from 4 to 2.25, the reduced plate height (h) was reduced and the h value decreased 12% when the column dimension was scaled up proportionally because of relatively smaller dead volume on both end of the column. Compared to cylindrical columns having corresponding lengths and volumes, the conical columns with 10 degrees opening angle were superior in column efficiency, resolution and the maximum peak concentration at column outlet; the loadability of conical column was improved 30-40% on injection volume and 50-60% on sample mass, respectively, over cylindrical columns.     

Theoretical study on photophysical and charge transport properties of 1,6-bis(2-hydroxyphenol)pyridylboron bis(4-n-butylphenyl)phenyleneamine compound

The absorption and emission spectra of 1,6-bis(2-hydroxyphenol)pyridylboron bis(4-n-butylphenyl)phenyleneamine were systematically calculated by time-dependent density functional theory (TD-DFT) level. These results are in good agreement with experiment ones. The charge transport properties were investigated within the framework of the charge hopping model. The results show that 1,6-bis(2-hydroxyphenyl)pyridineboron ((dppy)BF) functions as a electron transport group and triphenylamine as a hole transport group; the charge transport ability for the two types of carriers is not only high but also nearly balanced, which explains why it is an efficient single-layer electroluminescent device. On the basis of the large second-order polarizability value and high transparency, this compound has the possibility to be an excellent second-order nonlinear optical material. The main origin of this large second-order nonlinear optical response is charge transfer from the triphenylamine group to (dppy)BF.     

HPLC method for the determination and pharmacokinetic studies on geniposide in rat serum after oral administration of traditional Chinese medicinal preparation Yin-Zhi-Ku decoction

A new HPLC method for the determination of geniposide in rat serum with solid-phase extraction (SPE) for preconcentration is described. Geniposide and an internal standard (paeoniflorin) were extracted from serum by SPE using C18 cartridges. Analysis of the extract was then performed on a reversed-phase C18 column using acetonitrile-water (16:84, v/v) as the eluting solvent system, and UV detection at 238 nm was used to measure the analyte with a limit of quantitation about 0.1 microg/mL. The calibration curve for geniposide was linear (r = 0.9993) in the concentration range 0.1-16.0 microg/mL. The intra- and inter-day precision of the geniposide were determined and their RSD did not exceed 10%. The validated method has been successfully applied for pharmacokinetic studies of geniposide from rat serum after oral administration of Yin-Zhi-Ku decoction.     

南海夏季风与登陆我国大陆初旋的关系

利用1948---2009年南海夏季风指数、NCEP/NCAR月平均再分析位势高度场、风场资料, 首次分析了南海夏季风与每年登陆中国大陆的首个热带气旋(初旋)的关系. 结果表明: 初旋的登陆日、登陆纬度、生成纬度与当年登陆中国大陆热带气旋的频数、活动期、强度等相关性较好; 强(弱)南海夏季风指数年份, 登陆大陆热带气旋数偏多(少)、初旋登陆日偏迟(早)、初旋登陆点偏南(北). 从流场上看, 强(弱)南海夏季风指数年份, 对应的季风槽偏强(弱), 其异常风场和初旋路径也截然不同. 从年际变化上看, 南海夏季风指数明显呈减弱趋势, 而初旋登陆点则有一定北移.     

On Higher Order Pyramidal Finite Elements

In this paper we first prove a theorem on the nonexistence of pyramidal polynomial basis functions. Then we present a new symmetric composite pyramidal finite element which yields a better convergence than the nonsymmetric one. It has fourteen degrees of freedom and its basis functions are incomplete piecewise triquadratic polynomials. The space of ansatz functions contains all quadratic functions on each of four sub-tetrahedra that form a given pyramidal element.     

Generation of minimally persistent circle formation for a multi-agent system

In this paper, two methods of generating minimally persistent circle formation are presented. The proposed methods adopt a leader-follower strategy and all followers are firstly motivated to move into the leader＇s interaction range. Based on the information about relative angle and relative distance, two numbering schemes are proposed to generate minimally persistent circle formation. Distributed control laws are also designed to maintain the desired relative distance between agents. The distinctive features of the proposed methods are as follows. First, only 2n - 3 unilateral communication links for n agents are needed during the circle formation process and thus the communication complexity can be reduced. In addition, the formation topology is kept fixed for the whole motion and achieves a self-stability property. Finally, each follower keeps a regualr interval with its neighbors and the formation converges to a uniform circle formation. Simulation results are also provided to demonstrate the effectiveness of the proposed methods.     

A study on coherent structures and drag-reduction in the wall turbulence with polymer additives by TRPIV

An experimental measurement was performed using time-resolved particle image velocimetry (TRPIV) to investigate the spatial topological character of coherent structures in wall-bounded turbulence of polymer additive solution. The fully developed near-wall turbulent flow fields with and without polymer additives at the same Reynolds number were measured by TRPIV in a water channel. The comparisons of turbulent statistics confirm that due to viscoelastic structure of long-chain polymers, the wall-normal velocity fluctuation and Reynolds shear stress in the near-wall region are suppressed significantly. Furthermore, it is noted that such a behavior of polymers is closely related to the decease of the motion of the second and forth quadrants, i.e., the ejection and sweep events, in the near-wall region. The spatial topological mode of coherent structures during bursts has been extracted by the new mu-level criteria based on locally averaged velocity structure function. Although the general shapes of coherent structures are unchanged by polymer additives, the fluctuating velocity, velocity gradient, velocity strain rate and vorticity of coherent structures during burst events are suppressed in the polymer additive solution compared with that in water. The results show that due to the polymer additives the occurrence and intensity of coherent structures are suppressed, leading to drag reduction.