Influence of the Matrix in Atomic Emission Determination of Impurities in Manganese and Its Compounds

The trend in the change in the intensity of the analytical lines of impurities in the binary system manganese oxide–powdered graphite has been investigated. It has been established that this trend has a complex nonlinear character. Investigations concerned with revealing the factors responsible for the effect observed are reported.     

Laser-ultrasonic generation of Lamb waves in the reaction force range

The Laser-ultrasonic generation of Lamb waves in an elastic plate is investigated theoretically and experimentally for a laser source whose intensity is high enough to create reaction forces (normal tractions) on the illuminated surface of the specimen. The analytical solutions for transient waves are derived using the integral transform method first by considering an arbitrary source shape and time excitation function, and then specifically for circular and line source shapes. The simulation study allows us not only to predict the behavior of individual wave modes but also to construct the overall responses; thus it helps us better understand the wave excitation mechanisms. The dispersive and multi-modal nature of laser-generated Lamb waves is presented by showing the spatiotemporal Fourier transform of displacements obtained by the simulation study. The transform, displayed in the frequency-wave number domain, enunciates the characteristics of the propagating individual Lamb wave modes. The simulation results are then compared with the 2-D Fourier transform of a set of experimental data obtained by scanning an aluminum plate specimen.     

35MeV/u 40Ar+197Au反应中复合核的激发能与温度

利用大面积位置灵敏气体探测器对35MeV/u ⁴⁰Ar+¹⁹⁷Au反应中形成的裂片进行了符合测量,由此得到了裂变复合核的速度分布.在大质量转移假设下扣除前平衡发射粒子的影响,得到复合核的激发能.另外利用望远镜探测器对反应中出射的轻带电粒子也进行了符合测量,并由后角α,p,d,t的能谱提取了复合核的温度.温度与激发能的关系没有表现出理论预言的相变特征.     

Two-dimensional Hadamard spectroscopy

Direct frequency-domain excitation of NMR with an array of different radiofrequencies has been used to speed up two-dimensional NMR experiments by a large factor. Multiplex excitation in the F(1) frequency dimension is restricted to the signal-bearing regions and is encoded according to a Hadamard matrix of dimension N by N, where N is a relatively small number. The detected signals are decoded by reference to the same Hadamard matrix. Alternatively a phase-encoding scheme can be employed. Two-dimensional correlation experiments (COSY and TOCSY) and cross-relaxation measurements (NOESY) implemented on proton systems can be completed in less than a minute in cases where the intrinsic sensitivity is sufficiently high that prolonged multiscan averaging is not required. The results are presented in the form of a high-resolution contour diagram similar to the familiar two-dimensional spectra obtained by Fourier transform methods. Experiments on strychnine demonstrate more than two orders of magnitude improvement in speed compared with the traditional methods.     

Selective excitation in pulsed EPR of a spin-correlated triplet-radical pair

Experiments are described in which a low-amplitude microwave pulse excites only one out of three allowed transitions of the quinone radical (Q(A)(-)) in a spin-correlated triplet-radical pair 3PQ(A)(-) of the bacterial photosynthetic reaction center. A second high-amplitude pulse produces a FID whose temporal shape is strongly modulated with frequencies determined by electron-electron dipolar interaction in the pair. The FID is detected in both the in-phase and the out-of-phase channels. The out-of-phase FID is a result of switching off the magnetic dipolar interaction between 3P and Q(A)(-) due to decay of 3P during the time interval between the two pulses. Refocusing of FID by an additional non-selective pulse allows a dead-time free measurement of this modulation. The influence of the dead-time problem on the distance determination is discussed.     

Multi-Photon Fluorescence Correlation Spectroscopy: a Quantification of Tryptophan Methylester Solutions by Visible Emission

A multi-photon excitation fluorescence correlation system has been developed. The emission from tryptophan methylester solution was observed by this system and analyzed by the intensity correlation function of the visible emission, which originates from the two-photon excitation of photo products generated through a five-photon process. The intensity and the product concentration were proportional to the concentration of tryptophan methylester at a lower concentration range and thus the generation process is a single molecular reaction. The correlation analysis determined the concentration of tryptophan methylester down to 5 μM. The photo product generation from tryptophan solution was enhanced by a potassium iodide addition. These results suggest a new quantification method of tryptophan derivatives.     

Preconditioners Based on Fundamental Solutions

We consider a new preconditioning technique for the iterative solution of linear systems of equations that arise when discretizing partial differential equations. The method is applied to finite difference discretizations, but the ideas apply to other discretizations too. If E is a fundamental solution of a differential operator P, we have E*(Pu) = u. Inspired by this, we choose the preconditioner to be a discretization of an approximate inverse K, given by a convolution-like operator with E as a kernel. We present analysis showing that if P is a first order differential operator, KP is bounded, and numerical results show grid independent convergence for first order partial differential equations, using fixed point iterations. For the second order convection-diffusion equation convergence is no longer grid independent when using fixed point iterations, a result that is consistent with our theory. However, if the grid is chosen to give a fixed number of grid points within boundary layers, the number of iterations is independent of the physical viscosity parameter. AMS subject classification (2000) 65F10, 65N22     

Sharp Estimates for the Size of Balls in the Complement of a Hypersurface

In this paper, we make estimates for the radius of balls contained in some component of the complementary of a complete hypersurface into a space form, generalizing and improving analogous radius estimates for embedded compact hypersurfaces obtained by Blaschke, Koutroufiotis and the authors. The results are obtained using an algebraic lemma and a tangency principle related with the length of the second fundamental form. The algebraic lemma also is used to improve a result for graphs due to Hasanis–Vlachos. The first author dedicates this work to his parents José (in memoriam) and Herondina     

Electronic Excitation Energy Transfer between Different Types of Dye Molecules in a Porous Glass Matrix

The processes of electronic excitation energy transfer (EEET) between different types of dye molecules inserted into the matrix of a porous glass have been investigated. An extreme character of the dependence of the EEET efficiency on the size of pores has been revealed. The dependence of the fractal dimensionality of the distribution of dye molecules on the sizes of the pores has been determined. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 4, pp. 446–449, July–August, 2005.     

Spin Polarization of Fluorine Nuclei in the Si/CaF<Subscript>2</Subscript> Nanostructure Under Optical Excitation

The laws of fluorine nuclear spin polarization in the Si/CaF₂ nanostructure under optical excitation of the charge carriers in it has been considered theoretically. It has been shown that maximum values (up to 3% of the concentration of nuclei in the lattice) are attained under a high rate of optical excitation (>10⁻⁹ sec⁻¹) when the nuclear spin diffusion process and the Auger recombination prevail. In this case, the nuclear relaxation time in an individual layer reaches 100–300 sec and the spin diffusion radius decreases to 0.3 nm. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 3, pp. 397–403, May–June, 2005.