Grain boundary,triple junction and quadruple point mobility controlled normal grain growth

Reduction in stored free energy provides the thermodynamic driving force for grain and bubble growth in polycrystals and foams. Evolution of polycrystalline networks exhibit the additional complication that grain growth may be controlled by several kinetic mechanisms through which the decrease in network energy occurs. Polyhedral boundaries, triple junctions (TJs), and quadruple points (QPs) are the geometrically distinct elements of three dimensional networks that follow Plateau’s rules, provided that grain growth is limited by diffusion through, and motion of, cell boundaries. Shvindlerman and co-workers have long recognized the kinetic influences on polycrystalline grain growth of network TJs and QPs. Moreover, the emergence of interesting polycrystalline nanomaterials underscored that TJs can indeed influence grain growth kinetics. Currently there exist few detailed studies concerned either with network distributions of grain size, number of faces per grain, or with ‘grain trajectories’, when grain growth is limited by the motion of its TJs or QPs. By contrast there exist abundant studies of classical grain growth limited by boundary mobility. This study is focused on a topological/geometrical representation of polycrystals to obtain statistical predictions of the grain size and face number distributions, as well as growth ‘trajectories’ during steady-state grain growth. Three limits to grain growth are considered, with grain growth kinetics controlled by boundary, TJ, and QP mobilities.     

Impact of Collection Volume and DNA Extraction Method on the Detection of Biomarkers and HPV DNA in First-Void Urine

The potential of first-void (FV) urine as a non-invasive liquid biopsy for detection of human papillomavirus (HPV) DNA and other biomarkers has been increasingly recognized over the past decade. In this study, we investigated whether the volume of this initial urine stream has an impact on the analytical performance of biomarkers. In parallel, we evaluated different DNA extraction protocols and introduced an internal control in the urine preservative. Twenty-five women, diagnosed with high-risk HPV, provided three home-collected FV urine samples using three FV urine collection devices (Colli-Pee) with collector tubes that differ in volume (4, 10, 20 mL). Each collector tube was prefilled with Urine Conservation Medium spiked with phocine herpesvirus 1 (PhHV-1) DNA as internal control. Five different DNA extraction protocols were compared, followed by PCR for GAPDH and PhHV-1 (qPCR), HPV DNA, and HBB (HPV-Risk Assay), and ACTB (methylation-specific qPCR). Results showed limited effects of collection volume on human and HPV DNA endpoints. In contrast, significant variations in yield for human endpoints were observed for different DNA extraction methods (p < 0.05). Additionally, the potential of PhHV-1 as internal control to monitor FV urine collection, storage, and processing was demonstrated.     

Asymmetric organocatalytic anthrone additions to activated alkenes

Asymmetric organocatalytic additions of anthrones to activated alkenes are discussed. The reaction between anthrone or dithranol and α,β-unsaturated aldehydes is catalyzed by diphenylprolinol trimethylsilyl ether in toluene at −40 °C, giving the Michael adducts with good yields and enantioselectivities. Bifunctional amino-thioureas efficiently catalyze the additions of anthrones to both nitroalkenes and maleimides, and high enantioselectivities can be achieved in both instances at room temperature. In the case of nitroalkenes, a Michael addition takes exclusively place. Anthrone generally gives Diels-Alder cycloadducts in the reaction with maleimides, while dithranol affords the Michael adducts. Transition state working models in which the bifunctional catalyst binds simultaneously to the alkene and to the anthrone enolate account for the stereochemical outcome of these additions.     

Reversing the stereoselectivity of the intermolecular Pauson-Khand reaction: formation of endo-fused norbornadiene adducts

[reaction: see text] An unprecedented endo-selective and regioselective intermolecular Pauson-Khand reaction takes place when heterobimetallic (Mo-Co) complexes derived from N-(2-alkynoyl)oxazolidinones or sultams are heated in the presence of norbornadiene.     

Homogenization of the inviscid incompressible fluid flow through a 2D porous medium

We consider the non-stationary incompressible Euler equations in a 2D porous medium. We suppose a periodic porous medium, with the period proportional to the characteristic pore size and with connected fluid part. The flow is subject to an external force, corresponding to an inflow. We start from an initial irrotational velocity and prove that the effective filtration velocity satisfies a transient filtration law. It has similarities with Darcy's law, but it now connects the time derivative of the filtration velocity with the pressure gradient. The viscosity does not appear in the filtration law any more and the permeability tensor is determined through auxiliary problems of decomposition type. Using the limit problem, we construct the correction for the fluid velocity and prove that -norm of the error is of order . Similarly, we estimate the difference between the fluid pressure and its correction in as .

     

Spectroscopic Study of New Fluorescent Probes

Abstract— Various newly synthesized substances containing the same chromophore as PRODAN were subjected to a spectroscopic study. The new substances, ω-[6-( N -meth-yl- N -alkylamino)naphthoyl]alcanoic acids (MANA), possess polar groups and alkyl chains of variable length that make them potentially useful as fluorescent probes in membrane studies. This paper reports on their spectroscopic properties in various pure solvents. Their Stokes shifts are given and related to different physicochemical properties of the solvents. A theoretical study of the behavior of the new substances is also presented.     

Spectrophotometric determination of cyanide by unsegmented flow methods

Photometric methods for cyanide determination by normal and reversed FIA techniques and by completely continuous monitoring are proposed. The sampling rates for the first two techniques are 20 and 28/hr, respectively, the r.s.d. being less than 0.8% in both cases. A simulation of cyanide control in industrial waste waters shows the usefulness of the continuous monitoring method.     

Scaling exponents and probability distributions of DNA end-to-end distance

The scaling of the average gyration radius of polymers as a function of their length can be experimentally determined from ensemble measurements, such as light scattering, and agrees with analytical estimates. Ensemble techniques, yet, do not give access to the full probability distributions. Single molecule techniques, instead, can deliver information on both average quantities and distribution functions. Here we exploit the high resolution of atomic force microscopy over long DNA molecules adsorbed on a surface to measure the average end-to-end distance as a function of the DNA length, and its full distribution function. We find that all the scaling exponents are close to the predicted 3D values (upsilon=0.589+/-0.006 and delta=2.58+/-0.77). These results suggest that the adsorption process is akin to a geometric projection from 3D to 2D, known to preserve the scaling properties of fractal objects of dimension df<2.