Jets from heavy quarks ine + e − annihilation

The quark mass effects in the jet structure ine ⁺ e ^? annihilation into hadrons are studied in the lowest nontrivial O(α _s ) order of QCD perturbation theory.     

Experimental confirmation by galvanomagnetic methods of a complex transport model in In0.53Ga0.47As layers deposited by MBE on SI-InP

At low temperatures In_0.53Ga_0.47As samples show an increase of carrier concentration, which can be explained in terms of a two carriers transport model. This type of problem exists since the beginning of the semiconductor era, dating back to monocrystalline germanium.We propose that in all the investigated layers, there are X atoms or charged dislocations in the region of the first monolayers, which are built in during epitaxial growth. The layers were intentionally undoped. They form an impurity band in which low mobility carriers dominate over the localised electron scattering due to the s-d exchange interaction. These carriers do not freeze out at liquid helium temperature and give rise to two transport media for electrons; a conduction band at higher temperatures and an impurity band at lower temperatures. The electron which fall down onto the previously ionised X atoms, then move by thermally activated hopping. We show that the two carriers model for In_0.53Ga_0.47As epitaxial layers are confirmed by the carrier concentration-temperature, carrier concentration-magnetic field, resistivity-magnetic field behaviour, and also by YKA theory also. The differences between the two transport models are so distinctive that observed phenomena may exist. This paper presents experimental results, which constitute comprehensive evidence for the complicated structure of the semiconductor epitaxial layers on the sample of n-type In_0.53Ga_0.47As/InP layer with n=2.2×10¹⁵/cm³.     

Theoretical study of the influence of laser-induced defects on the adsorption of gases on solid surfaces

Laser treatment of a solid surface was modeled by applying an analytical theory as well as by using Monte Carlo simulations. The crystalline surface was assumed to be initially smooth and chemically uniform, that is free of impurities built into the structure. Creation of surface defects by a laser beam was assumed to have entirely random nature. In particular, the surface was assumed to have been scanned by the beam focused successively on randomly chosen points. In the course of the ablation process, the beam produces a pyramidal crater whose dimensions are proportional to the applied laser power. According to the assumed nature of the scanning procedure, the craters formed by the beam are allowed to overlap. The influence of the number of laser pulses and the crater dimensions on the structural and adsorptive properties of the surface were examined by analysis of the variation of the mean surface depth and the surface width. Changes in the adsorptive properties were also estimated by the calculation of the thermally programmed desorption (TPD) spectra of monomolecular adsorbates desorbed from laser-treated surfaces. Additionally, equilibrium adsorption isotherms were calculated for the obtained surfaces.     

Fast deterministic approximation for the multicommodity flow problem

In this paper we consider an optimization version of the multicommodity flow problem which is known as the maximum concurrent flow problem. We show that an approximate solution to this problem can be computed deterministically using O(k(ε ⁻² + logk) logn) 1-commodity minimum-cost flow computations, wherek is the number of commodities,n is the number of nodes, andε is the desired precision. We obtain this bound by proving that in the randomized algorithm developed by Leighton et al. (1995) the random selection of commodities can be replaced by the deterministic round-robin without increasing the total running time. Our bound significantly improves the previously known deterministic upper bounds and matches the best known randomized upper bound for the approximation concurrent flow problem. A preliminary version of this paper appeared inProceedings of the 6th ACM-SIAM Symposium on Discrete Algorithms, San Francisco CA, 1995, pp. 486–492.     

MR microscopy of water diffusion tensor in biological systems

Diffusion tensor imaging (DTI) of the control and mechanically injured spinal cord of a ratin vitro andin vivo are reported.In vitro experiments were done on a home-built 6.4 T magnetic resonance microscope. Results for formaline-fixed samples show significant differences in diffusion tensor components between gray matter and white matter of the control spinal cord. Moreover, it is shown that already 6–10 min after the injury DTI can detect changes in water diffusion in areas extending far beyond the region of primary tissue damage.In vivo experiments were performed using a 9.4 T Magnex magnet and Bruker Medspec imaging system. Good-quality DTI images, free from motion artifacts were obtained. Results from control samples confirm differences in water diffusion between white matter and gray matter, observedin vitro. In vivo experiments show that characteristic changes in water diffusion observedin vitro 6–10 min after injury are preserved 60–360 min after injury, without significant alteration during this time.     

Heavy metal analysis around Iskenderun Bay in Turkey

The heavy metal analysis around Iskenderun Bay in Turkey was carried out using mosses, soils, mussels, and sediments. This region is one of the most industrial areas of Turkey, including iron–steel plants, beverage, liquefied petroleum gas (LPG) plants, and oil transfer docks. Energy dispersive X‐ray fluorescence spectrometry (Epsilon 5, PANalytical, Almelo, The Netherlands) was used to analyze all samples. V, Cr, Mn, Fe, Ni, Cu, Zn, As, and Pb elements were observed in all samples studied. Although Ce was detected in some mosses and soils, Sn was detected only in some moss samples. Pb concentrations in the moss samples are higher than the soil, the mussel, and the sediment samples. This can be attributed to the mosses that absorb heavy metals such as Pb easily from the air. As the aim of this study was to analyze heavy metals, the evaluation of these elements with their potential hazards for ecology and humans is briefly discussed. Copyright © 2010 John Wiley & Sons, Ltd.     

3D MR imaging of dental cavities-an in vitro study

A 3D spin-echo (3D SE) pulse sequence was used on a 4.7 T research MRI system to produce images of extracted human first molar tooth placed in CuSO4 water solution. The maximal resolution achieved was 35 x 63 x 300 microm3 in read and two phase directions, respectively. The high-intensity signal from water in solution together with the lack of signal from mineralized tooth tissue produce very good contrast allowing to visualize topography of outer and inner surfaces of the tooth. The 3D MR data were median filtered, binarized and then divided into separate segments corresponding to the inner tooth cavities and the hard tooth tissue. The topography of the root canals was visualized and the canals volume was calculated. The presented technique may be used for quantitative analysis of the root canal cavities shape and volume. The results of such an analysis may be applied for estimation of the quality of the impressional mapping methods in restorative dentistry or as an alternative non-impressional 3D mapping method.