Binding states of Ga and Sn on W and Mo: Structures,evaporation field and its temperature dependence

Binding states of deposited Ga and Sn on the W and Mo substrates were studied by measuring the evaporation fields of the deposited metal atoms at various temperatures. Ga and Sn form two layers: an overlayer and an underneath pseudomorphic layer which directly contacts the substrate surface. The evaporation fieds of the overlayer Ga and Sn atoms were found to be the same on various crystal planes and significantly lower than that of the pseudomorphic Ga and Sn atoms, indicating that the binding between the overlayer atoms and the pseudomorphic atoms is much weaker than that between the pseudomorphic atoms and the substrate W and Mo atoms. The finding that the evaporation field of the pseudomorphic atoms on W is very close to that on Mo while the evaporation field of W is significantly higher than that of Mo was unexpected. Another interesting finding is that the field emission current from the (011) plane is not noticeably affected by the coverage of the mono-atomic Ga layer arranged in the superstructure while the current from other crystal planes covered by the pseudomorphic layer having the same atomic arrangement with the substrate surface is minimized. Furthermore, it has been found that the evaporation field of the Ga overlayer is lower than that of Sn, while the Ga pseudomorph is more stable than Sn pseudomorph on W surface at temperatures below about 100 K. The temperature dependence of the evaporation field was also examined and compared with existing models.     

Jet calculus: A simple algorithm for resolving QCD jets

It is argued that, in the leading logarithm approximation (LLA) of asymptotically free quantum chromodynamics (QCD), a simple algorithm (jet calculus) can be justified for computing a large number of quantities related to the longitudinal and transverse structure of quark and gluon jets.We formulate the rules of jet calculus in two variables, x and y which are related to longitudinal (energy) and transverse momentum respectively. Throughout the paper, quark and gluon jets are contrasted. After reviewing what has been done on longitudinal spectra, we turn to the transverse structure of jets down to relative transverse momenta of the order of a few GeV (independently of the total energy). The relation of our work to that of Dokshitzer, D'Yakonov and Troyan is elucidated. We also study jets generated by (almost) real photons and compare both with standard “final” parton jets.We also discuss calorimeter measured quantities, compare our results with those of other authors and propose a new and easy way for measuring QCD-predictable anomalous dimensions.We finally give a Lagrangian formulation of jet calculus, as a non-local theory in 1 + 1 dimensions to be solved in the tree approximation.     

Asymptotic expansions for the distributions of functions of a correlation matrix

This paper deals with asymptotic expansions for the non-null distributions of certain test statistics concerning a correlation matrix in a multivariate normal distribution. For this purpose an asymptotic expansion is given for the distribution of a function of the sample correlation matrix. As special cases of the resulting expansion, asymptotic expansions for the distributions of the sample correlation coefficient, Fisher's z-transformation and arcsine transformation are also given.     

θ problem and composite quarks

It is argued that a wide class of composite models of quarks and leptons contain an automatic solution of the strong P and CP problem, having an axion of the type of Kim and Shifman, Vainshtein and Zakharov.     

Crystallinity of bulk polyacetylene

The fine structure of bulk trans-polyacetylene (PA) was investigated by x-ray diffraction. The degree of crystallinity 0.81, determined by Ruland's method, was significantly higher than the value for linear polyethylene. The disorder parameter k was 5, which is much larger than the value for polyethylene. These results led us to propose that PA crystals are more disordered than PE crystals owing to the higher rigidity of PA chains. Small-angle x-ray diffraction indicated that the crystal morphology is of the extended-chain type rather than lamellar. All results obtained in this work showed that the fine structure of PA bulk is such as to facilitate electrical conduction of bulk PA.