Baryon pairs production ine + e − annihilation at\sqrt s = 2.4 GeV

Search for baryon pairs production ine ⁺ e ^? annihilation at \(\sqrt s = 2386 MeV\) is reported. The data relate to a luminosity of 161 nb^?1 collected by the DM2 experiment at DCI, the Orsay colliding ring. First measurements of directe ⁺ e ^? annihilation into \(\Lambda \bar \Lambda \) and ofe ⁺ e ^?→ \(p\bar p\) at this energy are presented. First observation of a goode ⁺ e ^?→ \(n\bar n\) candidate is reported and upper limits are given fore ⁺ e ^?→ \(n\bar n, \Lambda \bar \sum ^0 + c.c.\) and \(\Sigma ^0 \bar \Sigma ^0 \) .     

Effectiveness of a Mathematics Methods Course in Reducing Math Anxiety of Preservice Elementary Teachers

In an attempt to find ways of reducing the mathematical anxiety of preservice elementary teachers, three cases were investigated. The first was a section of mathematics for elementary teachers taught in a very traditional manner, and the second was the same course taught in a manner consistent with the recent recommendations of the National Council of Teachers of Mathematics. The third case included two sections of a methods course which covered the same mathematical content, as well as addressing how it should be taught to children. The Mathematics Anxiety Rating Scale for Adults was administered before and after the courses. No significant reduction of anxiety was measured in either mathematics section, but both sections of the methods course showed a significant reduction.     

Study of the Interface Microstructures of CVD Diamond Films by TEM

 The characteristics of the interface microstructures between a CVD diamond film and the silicon substrate have been studied by transmission electron microscopy and electron energy loss spectroscopy. The investigations are performed on plan-view TEM specimens which were intentionally thinned only from the film surface side allowing the overall microstructural features of the interface to be studied. A prominent interfacial layer with amorphous-like features has been directly observed for CVD diamond films that shows a highly twinned defective diamond surface morphology. Similar interfacial layers have also been observed on films with a <100> growth texture but having the {100} crystal faces randomly oriented on the silicon substrate. These interfacial layers have been unambiguously identified as diamond phase carbon by both electron diffraction and electron energy loss spectroscopy. For the CVD diamond films that exhibit heteroepitaxial growth features, with the {100} crystal faces aligned crystallographically on the silicon substrate, such an interfacial layer was not observed. This is consistent with the expectation that the epitaxial growth of CVD diamond films requires diamond crystals to directly nucleate and grow on the substrate surface or on an epitaxial interface layer that has a small lattice misfit to both the substrate and the thin film material.     

New diphosphine ligands based on diphenyl ether for the Pd-catalyzed CO/ethene copolymerization

The catalytic activity and selectivity of palladium(II) complexes of new, flexible bidentate ligands in the CO/ethene copolymerization reaction have been found to change considerably with the steric properties of the ligands.     

Quantitative Conformational Studies on Poly(vinyl Chloride)

Although curve fitting provides a method for obtaining intensity data for the individual components of overlapping band systems, the number of configurational and conformational bands in the C-Cl stretching region of the vibrational spectrum of poly(vinyl chloride) is such that many parameters have to be optimized. It is therefore desirable to impose constraints in the calculations, and prior knowledge of the number of component bands would be valuable. The potential of derivative spectroscopy for obtaining this information has been examined. It is shown that the superior resolution of second and fourth derivative spectra is partially offset by their inferior signal-to-noise ratio, a discriminatory effect against broader bands, and interference by subsidiary derivative peaks. The method has been used to examine the CH₂ deformation and C-Cl stretching modes of three PVC samples of different tacticity. With the former the overlapping system proves to be more complex than hitherto realized; hence, tacticity determinations based on the intensity ratio of two peaks only at 1428 and 1434 cm^?1 must be suspect. With the C-Cl stretching bands second derivatives are more useful than fourth derivatives, and the number and positions of the located bands are in broad agreement with the results from curve fitting, so providing confirmatory evidence for the correctness of the latter.     

Validation of consensus between proteomic and clinical chemistry datasets by applying a new randomisation F-test for generalised procrustes analysis

The use of proteomic data for compound characterisation and toxicity prediction has recently gathered much interest in the pharmaceutical industry, particularly with the development of new high-throughput proteomic techniques such as surface-enhanced laser desorption/ionisation time of flight mass spectrometry (SELDI-ToF) mass spectrometry. To validate these techniques, comparison with established methods such as clinical chemistry endpoints is required; however, there is currently no statistical method available to assess whether the proteomic data describes the same toxicological information as the clinical chemistry data. In this paper, generalised procrustes analysis (GPA) is applied to obtain a consensus between SELDI-ToF data and clinical chemistry data, both obtained from a study of cholestasis in rats. The significance of the consensus and the dimension of the consensus space are diagnosed by a newly developed randomisation F-test method for GPA [Food Qual. Pref. 13 (2002) 191]. Two kinds of matching were considered, using individual animals or treatment groups as samples in GPA. The results show that the SELDI-ToF data has significant consensus with clinical chemistry data, and that the consensus can be visualised in the significant dimensions of group average space.     

Cooperative behavior between oscillatory and excitable units: the peculiar role of positive coupling-frequency correlations

We study the collective dynamics of noise-driven excitable elements, so-called active rotators. Crucially here, the natural frequencies and the individual coupling strengths are drawn from some joint probability distribution. Combining a mean-field treatment with a Gaussian approximation allows us to find examples where the infinite-dimensional system is reduced to a few ordinary differential equations. Our focus lies in the cooperative behavior in a population consisting of two parts, where one is composed of excitable elements, while the other one contains only self-oscillatory units. Surprisingly, excitable behavior in the whole system sets in only if the excitable elements have a smaller coupling strength than the self-oscillating units. In this way positive local correlations between natural frequencies and couplings shape the global behavior of mixed populations of excitable and oscillatory elements.     

Non‐Hydrolytic β‐Lactam Antibiotic Fragmentation by l,d‐Transpeptidases and Serine β‐Lactamase Cysteine Variants

Enzymes often use nucleophilic serine, threonine, and cysteine residues to achieve the same type of reaction; the underlying reasons for this are not understood. While bacterial d,d ‐transpeptidases (penicillin‐binding proteins) employ a nucleophilic serine, l,d ‐transpeptidases use a nucleophilic cysteine. The covalent complexes formed by l,d ‐transpeptidases with some β‐lactam antibiotics undergo non‐hydrolytic fragmentation. This is not usually observed for penicillin‐binding proteins, or for the related serine β‐lactamases. Replacement of the nucleophilic serine of serine β‐lactamases with cysteine yields enzymes which fragment β‐lactams via a similar mechanism as the l,d ‐transpeptidases, implying the different reaction outcomes are principally due to the formation of thioester versus ester intermediates. The results highlight fundamental differences in the reactivity of nucleophilic serine and cysteine enzymes, and imply new possibilities for the inhibition of nucleophilic enzymes.