Finite temperature QCD in the presence of dynamical quarks

By using Monte Carlo (MC) methods we study the deconfining transition of QCD with color group SU(3) at finite temperature. The fermion polarization effects are kept in account by implementing the pseudo-fermion method. We use two different lattice volumes (6³ × 4, 8³ × 4) to check finite size effects. Even in the presence of light quarks we find a discontinuous transition. The existence of this transition is observed both creating metastable states and using mixed phase runs.     

Some results for secondary processes generated by a poisson process

We obtain the moment structure of a general class of random variables generated by a Poisson process. We then apply these relationships to several applied probability models. Among these are queues, counter models and low density traffic flow.     

Optimization studies of CVD growth of GaAs0.6P0.4

CVD growth conditions, particularly growth temperature and partial pressures of the reactant gases, strongly affect the growth characteristics and properties of GaAs_0.6P_0.4 epitaxial layers grown on GaAs substrates. For LED’s the most important properties of the material are B/J (brightness per unit current density) and surface morphology. This paper presents the results of a systematic study of the effect of temperature and reactant gas partial pressure (at a fixed III/V ratio) on B/J, surface morphology, growth rate, impurity doping and layer composition. Growth conditions which yield the optimum properties for LED’s are determined. The results are interpreted on the basis of kinetic and thermodynamic mechanisms controlling the growth process under various growth conditions. At constant temperature and constant III/V ratio, increasing the partial pressures causes the growth process to change from mass transport limited, where the growth rate increases with increasing partial pressures, to kinetically limited, where the growth rate is independent of partial pressures. Good morphology layers are obtained over a range of partial pressures around the transition from mass transport limited to kinetically limited growth. The B/J peaks at a value of partial pressure in the kinetically limited regime at which good morphology layers are obtained. Although B/J increases with increasing growth rate in the mass transport regime, the maximum B/J occurs in the region where growth rate is independent of partial pressures so that growth rate alone is not sufficient to determine B/J. In contrast to the “parabolic≓ dependence of growth rate on growth temperature, caused by the transition from the mass transport regime to the kinetic regime, the relative incorporation of As, P, and Te varies with temperature in the manner predicted from thermodynamics in both regimes. This behavior is consistent with the growth rate in the kinetic regime being limited by the desorption of chlorine atoms from the growth surface, with the reaction of As, P, and Te with the Ga proceeding thermodynamically at all temperatures.     

Some variational aspects of an automatic control problem

Techniques of the calculus of variations are used in order to examine a two-point boundary value problem whose boundary condition depends on the value of the solution at an interior point.The author wishes to express his deep appreciation to the referee for his suggestion of a much briefer and more elegant proof of Theorem 2.1 than that originally given.     

Vibrational excitation of deuterium fluoride and hydrogen fluoride by atomic and diatomic species

The vibrational excitation of HF and DF and the energy transfer efficiencies for various collision partners were investigated over the temperature and pressure ranges of 1400°K to 4100°K and 0.1 to 0.3 atm, respectively. The extent of excitation was determined as a function of time by continuously monitoring the infrared emission intensity at the center of the 1–0 vibration-rotation band of the molecule. Collisional efficiencies of HF, N₂, O₂, F, Cl, and DF in relaxing HF and of DF, HF, and N₂ in relaxing DF are reported. A comparison with relaxation data for pure HF taken at lower temperature suggests that long-range attractive forces are mechanistically of major importance in the relaxation process. The relatively high efficiency of atomic chlorine in relaxing HF, i.e., (τP)_HF–HF/(τP)_HF–C1 ≥ 5 at 3000°K is discussed in terms of our previous result for atomic fluorine, i.e., (τP)_HF–HF/(τP)_HF–F = 18.     

Deformed Bosons: Combinatorics of Normal Ordering

We solve the normal ordering problem for (A A) ⁿ where A and A are one mode deformed ([A,A ] = [N+1] – [N]) bosonic ladder operators. The solution generalizes results known for canonical bosons. It involves combinatorial polynomials in the number operator N for which the generating function and explicit expressions are found. Simple deformations provide examples of the method.     

Oxygen activation by the noncoupled binuclear copper site in peptidylglycine alpha-hydroxylating monooxygenase. Reaction mechanism and role of the noncoupled nature of the active site

Reaction thermodynamics and potential energy surfaces are calculated using density functional methods to investigate possible reactive Cu/O(2) species for H-atom abstraction in peptidylglycine alpha-hydroxylating monooxygenase (PHM), which has a noncoupled binuclear Cu active site. Two possible mononuclear Cu/O(2) species have been evaluated, the 2-electron reduced Cu(II)(M)-OOH intermediate and the 1-electron reduced side-on Cu(II)(M)-superoxo intermediate, which could form with comparable thermodynamics at the catalytic Cu(M) site. The substrate H-atom abstraction reaction by the Cu(II)(M)-OOH intermediate is found to be thermodynamically accessible due to the contribution of the methionine ligand, but with a high activation barrier ( approximately 37 kcal/mol, at a 3.0-A active site/substrate distance), arguing against the Cu(II)(M)-OOH species as the reactive Cu/O(2) intermediate in PHM. In contrast, H-atom abstraction from substrate by the side-on Cu(II)(M)-superoxo intermediate is a nearly isoenergetic process with a low reaction barrier at a comparable active site/substrate distance ( approximately 14 kcal/mol), suggesting that side-on Cu(II)(M)-superoxo is the reactive species in PHM. The differential reactivities of the Cu(II)(M)-OOH and Cu(II)(M)-superoxo species correlate to their different frontier molecular orbitals involved in the H-atom abstraction reaction. After the H-atom abstraction, a reasonable pathway for substrate hydroxylation involves a "water-assisted" direct OH transfer to the substrate radical, which generates a high-energy Cu(II)(M)-oxyl species. This provides the necessary driving force for intramolecular electron transfer from the Cu(H) site to complete the reaction in PHM. The differential reactivity pattern between the Cu(II)(M)-OOH and Cu(II)(M)-superoxo intermediates provides insight into the role of the noncoupled nature of PHM and dopamine beta-monooxygenase active sites, as compared to the coupled binuclear Cu active sites in hemocyanin, tyrosinase, and catechol oxidase, in O(2) activation.