Possibilities for gamma-ray stimulated emissionexperiments

We show that gamma-ray stimulated emission experiments are comparatively easy and inexpensive. The registration of a double- (N_2γ/N_γ) and a triple-energy peak (N_3γ/N_γ) is possible and the relation between their intensities permits the calculation of the recoilles factor f_s (stimulated) and making a conclusion about constructing a working gamma-ray laser. This revised version was published online in August 2006 with corrections to the Cover Date.     

Unusual mode of reactivity of 2-alkylidene-4-oxothiazolidine S-oxides under the Pummerer reaction conditions

The reactivity of 2-alkylidene-4-oxothiazolidine S-oxides under the Pummerer reaction conditions, using Ac₂O, TFAA, SOCl₂ and SOBr₂ as initiators, has been examined. Almost all reactions proceeded with absolute regioselectivity yielding α-substituted sulfides or vinyl-chloro derivatives. The mechanism for the formation of the latter products was postulated and proved experimentally.     

Fabrication of Pascal-triangle Lattice of Proteins by Inducing Ligand Strategy

A protein Pascal triangle has been constructed as new type of supramolecular architecture by using the inducing ligand strategy that we previously developed for protein assemblies. Although mathematical studies on this famous geometry have a long history, no work on such Pascal triangles fabricated from native proteins has been reported so far due to their structural complexity. In this work, by carefully tuning the specific interactions between the native protein building block WGA and the inducing ligand R-SL , a 2D Pascal-triangle lattice with three types of triangular voids has been assembled. Moreover, a 3D crystal structure was obtained based on the 2D Pascal triangles. The distinctive carbohydrate binding sites of WGA and the intralayer as well as interlayer dimerization of RhB was the key to facilitate nanofabrication in solution. This strategy may be applied to prepare and explore various sophisticated assemblies based on native proteins.     

High regioselectivity in the heterocyclization of β-oxonitriles to 4-oxothiazolidines: X-ray structure proof

Base-catalyzed reactions of β-oxonitriles 1 with diethyl mercaptosuccinate favour heterocyclization to afford 2-alkylidene-4-oxothiazolidines 3, rather than 2-alkylidene-4-oxo-1,3-thiazinanes 4. The observed regioselectivity is based on spectroscopic and experimental evidence, including a single-crystal X-ray structure determination.     

The Generalized Cross Entropy Method, with Applications to Probability Density Estimation

Nonparametric density estimation aims to determine the sparsest model that explains a given set of empirical data and which uses as few assumptions as possible. Many of the currently existing methods do not provide a sparse solution to the problem and rely on asymptotic approximations. In this paper we describe a framework for density estimation which uses information-theoretic measures of model complexity with the aim of constructing a sparse density estimator that does not rely on large sample approximations. The effectiveness of the approach is demonstrated through an application to some well-known density estimation test cases.     

Modeling of aortic valve dynamics in a lumped parameter model of left ventricular-arterial coupling

A lumped parameter model of the sub-system of left ventricle, aortic valve, systemic arteries, systemic capillaries and systemic veins was considered during systole. A model of aortic valve dynamics based solely on geometrical and kinematical consideration is defined. The model is described by two geometrical parameters of aortic valve and a few kinematical relationships. The proposed model mimics the incisures in the aortic flow and aortic pressure very well. We showed that the dicrotic notch could be explained by aortic valve closing in terms of a lumped parameter model, without a need for any wave reflection theory. According to the proposed model the effects of aortic valve dynamics on the aortic flow and pressure are mainly limited to the valve opening and closing periods. The model offers a new paradigm for defining a more realistic left ventricle model.      

125m Te (109.3 keV) stimulated emission and gamma lasers

Summary Proceeding from the drastic discrepancy between experimental data and theory, we show (contrary to other authors) that the relations between the Einstein's coefficients are true for transitions from any of the excited levels and theground state of the quantum system only. The relations connecting those coefficients are derived for transitions betweenany two states; the corresponding cross-sections are calculated and it is shown (contrary to other authors) that the stimulated emission cross-section may be large enough for the creation of gamma lasers. The new relation for Einstein's coefficients (and the corresponding cross-sections) are fundamentally different from those known so far (74 years after Einstein). The results are compared with experiment and the coincidence is very good. These investigations can lead to progress in the study of physical processes in star atmospheres. The author of this paper has agreed to not receive the proofs for correction.     

Highly Dispersible Hexagonal Carbon–MoS2–Carbon Nanoplates with Hollow Sandwich Structures for Supercapacitors

MoS₂, a typical layered transition-metal dichalcogenide, is promising as an electrode material in supercapacitors. However, its low electrical conductivity could lead to limited capacitance if applied in electrochemical devices. Herein, a new nanostructure composed of hollow carbon–MoS₂–carbon was successfully synthesized through an l -cysteine-assisted hydrothermal method by using gibbsite as a template and polydopamine as a carbon precursor. After calcination and etching of the gibbsite template, uniform hollow platelets, which were made of a sandwich-like assembly of partial graphitic carbon and two-dimensional layered MoS₂ flakes, were obtained. The platelets showed excellent dispersibility and stability in water, and good electrical conductivity due to carbon provided by the calcination of polydopamine coatings. The hollow nanoplate morphology of the material provided a high specific surface area of 543 m² g⁻¹, a total pore volume of 0.677 cm³ g⁻¹, and fairly small mesopores (≈5.3 nm). The material was applied in a symmetric supercapacitor and exhibited a specific capacitance of 248 F g⁻¹ (0.12 F cm⁻²) at a constant current density of 0.1 A g⁻¹; thus suggesting that hollow carbon–MoS₂–carbon nanoplates are promising candidate materials for supercapacitors.     

An extraction system for low-energy hydrogen ions formed by electron impact

A system has been developed for extracting near-zero kinetic energy H⁻ and D⁻ ions formed by dissociative electron attachment. It is the essential part of a new set-up for vibrational spectroscopy of hydrogen molecules. A magnetic field is used to collimate the probing electron beam. Ions produced by electron collision with the target molecules are collected by the combined action of this field and an electrostatic field penetrating into the interaction region. Highly effective extraction is achieved by taking into account the correct out-of plane displacement of ion trajectories which is usually neglected in similar arrangements. The extraction conditions are mass dependent so that by proper tuning, mass selection of detected ions is achieved. The new system is also used for detecting positive ions created by electron collisions with hydrogen atoms and molecules.