Correlation between bulk and surface properties in Cd–X (X = Hg,Mg) liquid alloys

A theoretical investigation of the energetics and its effect on the alloying behaviour of Cd–Hg and Cd–Mg liquid alloys have been carried out with the aim of correlating their bulk and surface phenomena. Using the Quasi-chemical approximation for regular solution model, our results indicate that Cd–Hg and Cd–Mg are weakly heterocoordinated both in the bulk and on the surface. We observed that the degree of chemical order in Cd–Mg liquid alloy is more than that of Cd–Hg liquid alloy.     

The quark-nucleon phase diagram and quantum chromodynamics

The temperature dependence of a conjectured first-order phase transition between nuclear matter and quark-gluon matter is calculated for temperatures below T = 200 MeV. On the nuclear side a rather successful meson-nucleon mean field theory is applied while quark-gluon matter at large densities and finite temperatures is described perturbatively by quantum chromodynamics. Outside the finite volume of hot and dense quark-gluon matter the physical vacuum is characterized, by the newly determined bag parameter Λ_B = 235 MeV. We observe a dramatic drop in the density of nuclear matter at the phase transition point as the temperature increases, if the scale parameter Λ of QCD is chosen as Λ = 100 MeV. For larger values of Λ the effect is less pronounced. Further work is required to settle this problem.     

The quark bag model

The quark bag model is reviewed here with particular emphasis on spectroscopic applications and the discussion of exotic objects as baryonium, gluonium, and the quark phase of matter. The physical vacuum is pictured in the model as a two-phase medium. In normal phase of the vacuum, outside hadrons, the propagation of quark and gluon fields is forbidden. When small bubbles in a second phase are created in the medium of the normal phase with a characteristic size of one fermi, the hadron constituent fields may propagate inside the bubbles in normal manner. The bubble (bag) is stabilized against the pressure of the confined hadron constituent fields by vacuum pressure and surface tension. Inside the bag the colored quarks and gluons are governed by the equations of quantum chromodynamics.     

Kinetics of thermal decomposition of 4-carboxyl-2,6-dinitrobenzenediazonium ion (CDNBD)

The kinetics of thermal decomposition of 4-carboxyl-2,6-dinitrobenzenediazonium ion (CDNBD), an arenediazonium ion newly developed as a derivatizing reagent for drug analysis, are described. The arenediazonium ion, in an optimized concentrated sulfuric acid/orthophosphoric acid medium, was incubated for various time intervals at 30 degrees, 45 degrees, 55 degrees , 65 degrees , 75 degrees, and 85 degrees C. The amount of ion left after each time interval was quantified selectively by colorimetric assay at 490 nm, using mefenamic acid as a model diazo-coupling component. The rate constants for the decomposition were determined graphically. An Arrhenius plot was used to delineate the dependence of the rate constant on temperature and to predict the half-life at 25 degrees C and lower temperatures. The diazonium ion decomposed by first-order kinetics. The rate constants of decomposition, which increased progressively with temperature, were 3.18 +/- 0.41 x 10(-5), 1.19 +/- 0.07 x 10(-4), 4.87 +/- 0.15 x 10(-4), 12.88 +/- 0.73 x 10(-4), and 21.32 +/- 2.74 x 10(-4) (s(-1)) with corresponding half-lives of 363, 97.06, 23.72, 8.97, and 5.42 min at 30 degrees, 45 degrees, 55 degrees, 65 degrees, and 75 degrees C, respectively. CDNBD is highly stable in concentrated acid medium, with half-life values of about 10 h, 10 days, and 7.3 months at 25 degrees, 0 degrees, and -20 degrees C, respectively. The reagent stability profile shows that it could be readily adapted for routine applications in instrumental chemical analysis.     

Can the nearly conformal sextet gauge model hide the Higgs impostor?

New results are reported from large scale lattice simulations of a frequently discussed strongly interacting gauge theory with a fermion flavor doublet in the two-index symmetric (sextet) representation of the SU(3) color gauge group. We find that the chiral condensate and the mass spectrum of the sextet model are consistent with chiral symmetry breaking in the limit of vanishing fermion mass. In contrast, sextet fermion mass deformations of spectral properties are not consistent with leading conformal scaling behavior near the critical surface of a conformal theory. A recent paper could not resolve the conformal fixed point of the gauge coupling from the slowly walking scenario of a very small nearly vanishing β-function (DeGrand et al. [3]). It is argued that overall consistency with our new results is resolved if the sextet model is close to the conformal window, staying outside with a very small non-vanishing β-function. The model would exhibit then the simplest composite Higgs mechanism leaving open the possibility of a light scalar state with quantum numbers of the Higgs impostor. It would emerge as the pseudo-Goldstone dilaton state from spontaneous symmetry breaking of scale invariance. We will argue that even without association with the dilaton, the scalar Higgs-like state can be light very close to the conformal window. A new Higgs project of sextet lattice simulations is outlined to resolve these important questions.     

Nearly conformal gauge theories in finite volume

We report new results on nearly conformal gauge theories with fermions in the fundamental representation of the SU(3)$\mathit{SU}(3)$ color gauge group as the number of fermion flavors is varied in the Nf=4–16$N_f=4\text{–}16$ range. To unambiguously identify the chirally broken phase below the conformal window we apply a comprehensive lattice tool set in finite volumes which includes the test of Goldstone pion dynamics, the spectrum of the fermion Dirac operator, and eigenvalue distributions of random matrix theory. We also discuss the theory inside the conformal window and present our first results on the running of the renormalized gauge coupling and the renormalization group beta function. The importance of understanding finite volume zero momentum gauge field dynamics inside the conformal window is illustrated. Staggered lattice fermions are used throughout the calculations.