Orientation dependence of the NMR signal of deformed NaCl single crystals

The ²³Na signal of different deformed NaCl crystals was measured as function of the angle of rotation of the crystal with respect to the static magnetic field. The second moment of the NMR line is changed periodically determined by the slip mechanism. It is shown that the measured second moment can be obtained by a superposition of the parts originating from two-fold and four fold slip, respectively. The portion of the two slip mechanisms can be calculated quantitatively by fitting the experimental points.     

Porous Media Characterization Using Minkowski Functionals: Theories,Applications and Future Directions

An elementary question in porous media research is in regard to the relationship between structure and function. In most fields, the porosity and permeability of porous media are properties of key interest. There is, however, no universal relationship between porosity and permeability since not only does the fraction of void space matter for permeability but also the connectivity of the void fraction. With the evolution of modern day X-ray microcomputed tomography (micro-CT) and advanced computing, it is now possible to visualize porous media at an unprecedented level of detail. Approaches in analyzing micro-CT data of porous structures vary in the literature from phenomenological characterization to network analysis to geometrical and/or topological measurements. This leads to a question about how to consistently characterize porous media in a way that facilitates theoretical developments. In this effort, the Minkowski functionals (MF) emerge from the field of statistical physics where it is evident that many physical processes depend on the geometry and topology of bodies or multiple bodies in 3D space. Herein we review the theoretical basis of the MF, mathematical theorems and methods necessary for porous media characterization, common measurement errors when using micro-CT data and recent findings relating the MF to macroscale porous media properties. This paper is written to provide the basics necessary for porous media characterization and theoretical developments. With the wealth of information generated from 3D imaging of porous media, it is necessary to develop an understanding of the limitations and opportunities in this exciting area of research.

     

Assignment of aluminum corroles absorption bands to electronic transitions by femtosecond polarization resolved VIS-pump IR-probe spectroscopy

We combine femtosecond polarization resolved VIS-pump IR-probe spectroscopy with DFT and TD-DFT calculations to identify and assign absorption bands to electronic transitions for corroles. These macrocycles and their corresponding metal complexes are receiving great attention because of their utility in many fields, while many of their spectroscopic features have not yet been fully described. Analysis of the perturbed free induction decay provides information about the bleaching signal at time zero and allows for determination of overlapping excited state and bleaching signal amplitudes. The S(0) → S(1) and S(0) → S(2) transitions in the Q-band of the hexacoordinated Al(tpfc)(py)(2) and Br(8)Al(tpfc)(py)(2) absorption spectra are explicitly assigned. Angles between these electronic transition dipole moments (tdms) with a single vibrational transition dipole moment of (53 ± 2)° and (34 ± 2)° when excited at 580 and 620 nm for hexacoordinated Al(tpfc)(py)(2) and (51 ± 2)° and (43 ± 2)° when excited at 590 and 640 nm for hexacoordinated Br(8)Al(tpfc)(py)(2) were determined. The relative angles between the two lowest electronic tdms are (90 ± 8)° and (94 ± 3)° for Al(tpfc)(py)(2) and Br(8)Al(tpfc)(py)(2), respectively. Angles are determined before time zero by polarization resolved perturbed free induction decay and after time zero by polarization resolved transients. Comparison of corrole's wave functions with those of porphine show that the reduced symmetry in the corrole molecules results in lifting of Q-band degeneracy and major reorientation of the electronic transition dipole moments within the molecular scaffold. This information is necessary in designing optimal corrole-based electron and energy transfer complexes.     

Approximation algorithms for free-label maximization

Inspired by air-traffic control and other applications where moving objects have to be labeled, we consider the following (static) point-labeling problem: given a set P of n points in the plane and labels that are unit squares, place a label with each point in P in such a way that the number of free labels (labels not intersecting any other label) is maximized. We develop efficient constant-factor approximation algorithms for this problem, as well as PTASs, for various label-placement models.     

Depth profiling of porcine adipose tissue by Raman spectroscopy

Raman spectroscopy was applied on a depth profile of porcine adipose tissue (from skin to meat) with the purpose of (1) discriminating between fat layers and (2) estimating the variation in fatty acid composition as a function of fat depth and fat layer: total degree of unsaturation (iodine value), fractions of saturated, and monounsaturated and polyunsaturated fatty acids. The thickness and composition of the outer layer of porcine adipose tissue influences the final quality of backfat. A too‐thick outer layer is associated with problems such as oily appearance, rancidity development, and difficulties in separating muscle and adipose tissue when cutting. From principal component analysis on standard normal variate preprocessed Raman spectra (1800–800 cm^–1), it was possible to discriminate between the outer and the inner backfat layer. Principal component analysis loadings showed that the separation of layer was mainly explained by variation in the bands originating from vibration of double bond C = C stretching plus = C–H twisting and rocking. In the prediction of iodine value a three‐component partial least squares regression model based on full range Raman spectra showed a root mean square error of cross validation of 2.00 and R² = 0.69. Applying Cauchy–Lorentz band fitting proved that information regarding fat unsaturation was found not only in band intensity, but also in band parameters such as location and width. The results suggest Raman spectroscopy as a potential measurement technique for rapid grading of pork carcasses. Copyright © 2011 John Wiley & Sons, Ltd.     

Complete Monotonicity of a Difference Between the Exponential and Trigamma Functions and Properties Related to a Modified Bessel Function

In the paper, the authors find necessary and sufficient conditions for a difference between the exponential function αe ^β/t , α, β > 0, and the trigamma function ψ′(t) to be completely monotonic on (0, ∞). While proving the complete monotonicity, the authors discover some properties related to the first order modified Bessel function of the first kind I ₁, including inequalities, monotonicity, unimodality, and convexity.     

Periodicity of some classes of holomorphic difference equations

In this paper, we investigate the periodicity character of some classes of difference equations. Among other results, we give a simpler proof of an Open Problem addressed in Csörnyei and Laczkovich, 2001, “Some periodic and non-periodic recursions”, Monath. Math., 132, 215–236. We also consider Open Problem 2.8 in Grove and Ladas, 2005, Periodicities in Nonlinear Difference Equations, (Chapman and Hall/CRC), and the case when a difference equation has periodic solutions depending on arbitrary parameters.     

First Precision Spectroscopy of Pionic Atoms at RI Beam Factory

We conducted an inclusive missing-mass spectroscopy of ¹²²Sn (d, ³He) reaction near the π¯ emission threshold at an incident energy of T _d = 250 MeV/nucleon. The experiment sets its goals to the research and development of the high precision spectroscopy of pionic atoms at the RI beam factory (RIBF) of RIKEN, which precedes a new project, pionic atom factory project (piAF), to observe pionic atoms systematically. Here, we report the preliminary results of the pilot experiment.     

Ab Initio Calculations and Raman and SERS Spectral Analyses of Amphetamine Species

Abstract

For the first time, the differences between the spectra of amphetamine and amphetamine-H⁺ and between different conformers are thoroughly studied by ab initio model calculations, and Raman and surface-enhanced Raman spectroscopy (SERS) spectra are measured for different species of amphetamine. The spectra of amphetamine and amphetamine-H⁺ samples were obtained and assigned according to a comparison of the experimental spectra and the ab initio MO calculations, performed using the Gaussian 03W program (Gaussian, Inc., Pittsburgh, PA). The analyses were based on complete geometry minimization of the conformational energy of the S-plus-amphetamine molecule and the S-plus-amphetamine-H⁺ ion. The harmonic frequency calculations provide information about the characteristic features of the Raman spectra and the nature of the bonding in the molecule. It is concluded that vibrational bands from salt anions with internal bonds (sulfates, hydrogen phosphates, etc.) need to be taken into account when employing these spectra for identification purposes. These results also show how Raman spectroscopy can assist the forensic community in drug profiling studies. Furthermore, because their spectra are different, discrimination between the free and protonated forms of amphetamine salts can be observed. Here, we provide evidence for this difference and show experimentally how it has been overseen.