Charge and angular distributions and secondary fission of deep inelastic products from the reaction 197Au + 979 MeV 136Xe 1443 08

Kinetic energy spectra, charge and angular distributions are presented for over 40 elements (Z = 27?68). The kinetic energy spectra show two distinct components: a deep inelastic one and another from secondary fission of the target-like product. The charge distribution widths are comparable to those observed in Kr bombardments, the angular distributions, however, are more extensively side peaked.     

High efficient system for studying multiphoton absorption

An optical arrangement for studying two-photon absorption in liquids is presented. The main feature of this new arrangement is fuller utilization of fluorescence light. This makes possible application of very low power cw laser in such experiments.     

Evidence against non-asymptotically-free theories of strong interactions

It is shown that ultraviolet finite fixed point theories of strong interactions are incompatible with the pattern of scaling deviations in deep inelastic lepton-hadron processes.     

A modified analytical method for total antioxidant potential assay using RP-HPLC with electrochemical detection and its application for pro- and antioxidative properties of dopamine measurement

Total antioxidant potential (TAP) is usually measured using photometric or fluorometric assays. Preliminary results of a reversed-phase high-performance liquid chromatography--electrochemical detection assay are given. The method is based on the generation of hydroxyl radicals in a Fenton reaction and analysis of the product of their interaction with p-hydroxybenzoic acid (3,4-dihydroxybenzoic acid). The method is applied to estimate the TAP of dopamine. As a result, depending on the concentration, dopamine is pro- or antioxidant. The results are compared with TAP measurements using a standard photometric method.     

The problem of the 27Al neutron spin-dependent scattering length

Early measurements of the neutron spin-dependent scattering length of ²⁷Al by neutron precession have given two values, consistent within the limits of accuracy, whose mean value is b₊?b_? = + 0.52 ± 0.02 fm. The positive sign was recently put in doubt from known values of neutron resonance parameters. New experiments were undertaken on a sample of ²⁷Al, a compound sample of ²⁷Al and ⁴⁵Sc, together with a redetermination of the sign of the ²⁷Al gyromagnetic ratio. These experiments confirmed in sign and magnitude the b₊?b_? value previously found. We have so far no explanation of the discrepancy.     

A model calculation in a new approach to the three-body problem

A method to calculate the binding energy of a system of three identical particles is proposed. The kernel of a previously derived integral equation in two variables is replaced by an approximation of finite rank. It turns out that a one term approximation is already sufficient to determine the binding energy very well.     

The Exact Three-Dimensional Half-Shell t-Matrix for a Sharply Cut-off Coulomb Potential in the Screening Limit

The screening limit of the three-dimensional half-shell t-matrix for a sharply cut-off Coulomb potential is analytically derived without reference to partial wave expansion. The numerical solutions of the three-dimensional Lippmann–Schwinger equation for increasing cut-off radii provide half-shell t-matrices which are in quite a good agreement with the asymptotic values.     

Sequences of bias-adjusted covariance matrix estimators under heteroskedasticity of unknown form

The linear regression model is commonly used by practitioners to model the relationship between the variable of interest and a set of explanatory variables. The assumption that all error variances are the same, known as homoskedasticity, is oftentimes violated when cross sectional data are used. Consistent standard errors for the ordinary least squares estimators of the regression parameters can be computed following the approach proposed by White (Econometrica 48:817–838, 1980). Such standard errors, however, are considerably biased in samples of typical sizes. An improved covariance matrix estimator was proposed by Qian and Wang (J Stat Comput Simul 70:161–174, 2001). In this paper, we improve upon the Qian–Wang estimator by defining a sequence of bias-adjusted estimators with increasing accuracy. The numerical results show that the Qian–Wang estimator is typically much less biased than the estimator proposed by Halbert White and that our correction to the former can be quite effective in small samples. Finally, we show that the Qian–Wang estimator can be generalized into a broad class of heteroskedasticity-consistent covariance matrix estimators, and our results can be easily extended to such a class of estimators.