Parity violation at neutron p-wave resonances of238U and232Th and related questions

Parity violation effects have been studied at 40 neutron p-wave resonances of the even-even nuclei²³⁸U and²³²Th. Of these 11 show parity violation effects larger than 2 standard deviations, making parity violation a rather common phenomenon. Parity mixing up to 10% has been found. The root-mean squared matrix elements for parity violation derived from these resonances are M=0.58 (+0.50/-0.25) meV for²³⁸U, respectively 1.39 (+0.35/-0.38) meV for²³²Th.     

Dynamical theory of an atom with two or three levels interacting with quantized cavity fields

We review the dynamical interaction of an atom with radiation in the framework of models of the Jaynes-Cummings type. The atom is restricted to a few energy levels and the radiation consists of quantized near-resonant loss-free modes. A general formalism is presented that allows a compact discussion of atom and field dynamics without approximations. Quantum wave packet collapse and revival phenomena, coherent trapping states, and some experimental prospects for two-level and three-level atoms are treated in detail, and some related effects are discussed more briefly.     

The electronic properties of [CH(FeCl4)0.061]x

The temperature dependence of d.c. conductivity, thermopower and electron paramagnetic resonance (EPR) results on [CH(FeCl₄)_0.061]_x are reported. The d.c. conductivity and thermopower measurements indicate metallic charge transport along the polyacetylene chain interrupted by the interfibril contact resistances and also ‘dragged’ primarily by the dopant ions. The initial measurements of EPR show Dysonian lineshape with very broad linewidth (ΔH ≈ 600 G at room temperature). The temperature dependence of EPR absorption intensity implies that there exist localized magnetic moments. The observed g value (g ≈ 2.03) suggests the dopant anion is in a form of (FeCl₄)^-.     

Low-Reynolds-number modelling of flows over a backward-facing step

The complex turbulent flow behind a backward-facing step is modelled using a full Reynolds stress closure. In order to develop a closure model that can resolve the complex near-wall flow in the recirculation region and in the recovery region downstream of the reattachment point, the performance of a low and a high Reynolds number version of the full Reynolds stress closure is examined and compared. Furthermore, the effects of redistribution modelling on the calculated flow is studied by comparing the performance of three redistribution models: one return-to-isotropy model and two with mean-strain effects. The results are grid independent and show that the flow downstream of the step is best described by a low-Reynolds-number model that does not depend on the conventional wall function assumption. However, the skin friction behavior is correctly predicted by the stipulation of a wall function. Of the three redistribution models examined, the return-to-isotropy model gives results that are in excellent agreement with measurements. Finally, the calculated results are adversely affected by refining the redistribution models to include meanstrain effects.     

A non-separable solution of the diffusion equation based on the Galerkin’s method using cubic splines

The two dimensional diffusion equation of the form is considered in this paper. We try a bi-cubic spline function of the form as its solution. The initial coefficients C_i,j(0) are computed simply by applying a collocation method; C_i,j = f(x_i, y_j) where f(x, y) = u(x, y, 0) is the given initial condition. Then the coefficients C_i,j(t) are computed by X(t) = e^tQX(0) where X(t) = (C_0,1, C_0,1, C_0,2, … , C_0,N, C_1,0, … , C_N,N) is a one dimensional array and the square matrix Q is derived from applying the Galerkin’s method to the diffusion equation. Note that this expression provides a solution that is not necessarily separable in space coordinates x, y. The results of sample calculations for a few example problems along with the calculation results of approximation errors for a problem with known analytical solution are included.     

Simultaneous qualitative and quantitative method using liquid chromatography selected reaction monitoring-triggered quantitation-enhanced data-dependent tandem mass spectrometry for the identification and classification of amphetamine-type stimulant abusers in human urine

Amphetamine (AP) and amphetamine‐type stimulants, methamphetamine (MA) and N,N‐dimethylamphetamine (DMA), are known as central nervous system stimulants, and their abuse throughout the world has recently increased. Since it is difficult to physically distinguish among AP, MA and DMA, analysts may not be aware of what abusers have administered. In this study, following the detection of specific metabolites of AP, MA and DMA as biomarkers in abuser urines, a rapid and sensitive method was developed for the identification and classification of AP‐type stimulants abusers. After the simple filtration of the urine samples, the samples were directly analyzed using a liquid chromatography/tandem mass spectrometry system with selected reaction monitoring (SRM)‐triggered quantitation‐enhanced data‐dependent MS/MS (QED‐MS/MS) for the simultaneous qualitative and quantitative analysis of p‐hydroxy AP, p‐hydroxy MA, p‐hydroxy DMA, AP, MA, DMA and DMA N‐oxide. The determination of p‐hydroxy AP, p‐hydroxy MA, AP, MA, DMA and DMA N‐oxide was accurate and reproducible, with the limits of quantitation of 5 ng/mL in urine. When applied to the urine samples of suspected AP‐type stimulants abusers, the abused drugs were precisely identified between MA and DMA abusers. Copyright © 2010 John Wiley & Sons, Ltd.     

On the path-dependence of the open-cell voltage of a galvanic cell involving a ternary or multinary compound with multiple mobile ionic species under multiple chemical potential gradients

It is well known that the open-cell voltage (U) of a galvanic cell involving a binary compound, or a multinary compound with a single kind of mobile ionic species, is a state property under a gradient of chemical potential of the mobile component. It is not so transparent, however, whether U is still a state property when involving a ternary or multinary compound with two or more kinds of mobile ions under multiple chemical potential gradients of those mobile components. We clarify this issue with a multinary oxide that conducts oxide ions, protons and electron holes and is exposed to the chemical potential gradients of both water and oxygen. We show that U is path- and history-dependent, and manifests itself along the diffusion paths of the two mobile components H and O under given boundary conditions.     

Microwave assisted synthesis of bridgehead alkenes

A new, concise method to synthesize triene precursors for the type 2 intramolecular Diels-Alder reaction has been developed. Microwave irradiation of the trienes provides a convenient method for the synthesis of bridgehead alkenes. Higher yields, shorter reaction times, and lower reaction temperatures provide a general and efficient route to this interesting class of molecules.     

Control of on-off or off-on fluorescent and optical [Cu²⁺] and [Hg²⁺] responses via formal Me/H substitution in fully characterized thienyl "scorpionate"-like BODIPY systems

One 8-phenyl and two 8-mesityl-substituted "scorpionate"-like BODIPY-type species of the formula [3,4,4-tris(5-R-(2-thienyl))-8-(2,4,6-R'-phenyl)-4-bora-3a,4a-diaza-s-indacene (R = H, R' = H, 3a; R, = H, R' = Me, 2a; R, = Me, R' = Me, 2b)] have been synthesized and fully characterized. Importantly, differences in their solution (MeCN) optical Cu(2+) and Hg(2+) probing capacity via SSS-chelation were investigated. Compounds 2a-3a were prepared from the requisite 8-substituted BODIPY complexes. They were characterized first by complete (1)H, (11)B and (13)C NMR spectroscopic assignments (CD(3)Cl or CD(3)C(O)CD(3)); the molecular structures of 2a and 3a were determined by X-ray crystallography. Compounds 2a-3a were studied by UV-vis and fluorescence spectroscopy [Φ(F) = 0.27 ± 0.013 (2a); 0.024 ± 0.0016 (2b); 0.0034 ± 0.00047 (3a)]. Importantly, low [Cu(2+)] with 3a (<3.0 × 10(-5) M) gave rise to an increase of fluorescence intensity (off-on; 6.3-fold), whereas with 2a it decreased (on-off). When [Hg(2+)] (<3.0 × 10(-5) M) was added to 2b, the λ(em,max) value increased (off-on; 3.2-fold), and for 2a, it decreased (on-off). The association constant (K(a)) for Hg(2+)·2a was determined to be 3120 ± 307 M(-1). An approximate stoichiometric 1:1 binding determined by Job plot analysis is in line with successful DFT modeling of SSS-Cu(2+) binding for this system type. (1)H NMR spectroscopy also revealed tentative sets of product complex peaks. These simple differences caused by formal ligand Me-group incorporation are the first for any related fluorophores, to the best of our knowledge.