Coherent single pion production by antineutrino charged current interactions and test of PCAC

The cross section for coherent production of a single π^? meson in charged current antineutrino interactions on neon nuclei has been measured in BEBC to be (175±25) 10^?40 cm²/neon nucleus, averaged over the energy spectrum of the antineutrino wide band beam at the CERN SPS; this corresponds to (0.9±0.1) % of the total charged current \(\bar v_\mu \) cross section. The distributions of kinematical variables are in agreement with theoretical predictions based on the PCAC hypothesis and the meson dominance model; in particular, theQ ² dependence is well described by a propagator containing a massm=(1.35±0.18) GeV. The absolute value of the cross section is also in agreement with the model. This analysis thus provides a test of the PCAC hypothesis in the antineutrino energy range 5–150 GeV.     

Reaction of a stable aminoarylcarbene with 2-chloroacrylonitrile: dearomatizing cyclization rather than cyclopropanation

The reaction of a stable aminoarylcarbene with 2-chloroacrylonitrile is reported. The resulting 1/1 adduct has been spectroscopically and structurally characterized. The initial Michael addition is not followed by cyclopropane formation but by a dearomatizing cyclization affording an original bicyclic structure.     

Multiparametric microsensor chips for screening applications

The identification of drug targets for pharmaceutical screening can be greatly accelerated by gene databases and expression studies. The identification of leading compounds from growing libraries is realized by high throughput screening platforms. Subsequently, for optimization and validation of identified leading compounds studies of their functionality have to be carried out, and just these functionality tests are a limiting factor. A rigorous preselection of identified compounds by in vitro cellular screening is necessary prior to using the drug candidates for the further time consuming and expensive stage, e.g. in animal models. Our efforts are focused to the parallel development, adaptation and integration of different microelectronic sensors into miniaturized biochips for a multiparametric, functional on-line analysis of living cells in physiologically environments. Parallel and on-line acquisition of data related to different cellular targets is required for advanced stages of drug screening and for economizing animal tests.     

黄原胶以三价铬交联的水凝胶的脱水行为

对黄原胶／三价铬水凝胶在７０，８０和９０℃下的脱水行为进行了研究．脱水与凝胶的交联密度即参与交联反应的三价铬的含量有密切联系．突发脱水之后的过程可以用一级反应动力学描述，反应速度常数随三价铬的浓度和温度的增高而增大，活化能为３４．５ｋｃａｌ／ｍｏｌ．一价盐（ＮａＣｌ）的含量对脱水过程没有影响．     

Dielectric relaxation of polystyrene with side-chain- and chain-end-labels

Polystyrenes with different concentrations of side groups with cyano groups were prepared and complex dielectric constants were measured in the range of the glass transition temperature and the frequency range of 10^–2–10⁷ Hz.The GPC and DSC measurements showed that the molecular weight of these polystyrenes was about 10500 g/mole and the glass transition temperatures were 89.5°C for all samples.The dielectric relaxation spectra obtained for the side group polystyrene labels and also the chain-end polystyrene labels prepared before [9] were analyzed to find out the degree of coupling of the chain-end and side-group labels with the cooperative reorientation of the polymeric matrix. The analysis of the spectra was carried out using the analysis method developed by Mansour and Stoll [6].The results obtained showed that both end- and side-group labels are strongly coupled with the segmental reorientation and relax with relaxation times longer than that of the segments.The value of logf _m = (logf _m(label)) – logf _m(matrix)) was obtained from the recently designed comparison diagram suggested by Mansour and Stoll [6, 14]. The value of logf _m depends on the label length in the case of chain-end labels.It was surprising to find that the side groups relax slower than the segments by only 0.9 decades. These results obtained implied that the label relaxes through a multistep relaxation mechanism of the side and end groups and not through a diffusion mechanism of the whole chain. In addition, the effective lengths of the relaxing units were determined using the empirical equation obtained before in the case of rodlike molecules in polyisoprene [7].     

Enthalpies of solution and of crystallization of lithium nitrate and of lithium nitrate trihydrate in water at 25°C

The enthalpies of crystallization of LiNO₃ and LiNO₃–3H₂O from aqueous solutions at 25°C, measured by a calorimetric method and determined from the previously published data on the concentration dependence of the enthalpy of solution, are reported. The results are compared with the values obtained from the concentration dependences of the activity coefficients and from the temperature dependences of the solubilities. The enthalpy of solution at infinite dilution and the enthalpy of hydration are given.     

Destabilized carbenium ions: Secondary and tertiary α-carbomethoxybenzyl cations

The secondary α-carbomethoxybenzyl cations a and the tertiary α-carbomethoxybenzyl cations d have been generated by electron impact-induced fragmentation from appropriately α-substituted methyl phenylacetate and 2-phenylpropionates 1–4. The ions a and d are further examples of destabilized carbenium ions with a push–pull substitution at the carbenium ion centre. The characteristic reaction of these ions is a rearrangement by a 1,2-shift of the methoxy group concomitant to the elimination of CO. This rearrangement reaction is associated with a very large and non-statistical kinetic energy release (a : T ₅₀ = 570 meV; d : T ₅₀ = 760 meV), which is attributed to tight transition states along the reaction coordinates corresponding to the three-membered cyclic oxonium ions b and h, respectively. The tertiary ion d can be distinguished from its more stable isomers f and g by the mass-analysed ion kinetic energy and collisional activation spectra. The investigation of specifically deuterated analogues of ions d and g reveals an isomerization of d to g via a species protonated at the phenyl group but no equilibration between d and g. This isomerization exhibits a large isotope effect for the hydrogen transfer, indicating similar energy barriers for the isomerization and for the CO elimination of d.     

Pyridazines: (thiényl-2)-3 pyridazine,quelques (thiényl-2)-3 pyridazines substituées en 6 et systèmes à noyaux condensés dérivés

We describe the synthesis of 3-(2-thienyl)pyridazine and of some of its derivatives substituted on the 6 position eg., ethoxy, hydrazino and azido. Some of these compounds have lead to condensed rings systems, namely, triazolo- and tetrazolopyridazines.     

Sedimentation of dissolved macromolecules in the vicinity of the consolute point 1. Strictly binary systems and kinetic considerations

This paper analyzes the effect of gravity on polymer solutions near the consolute point. Calculations are carried out for monodisperse polystyrene in cyclohexane using the Flory-Huggins expression with a concentration-dependent interaction parameter for the free energy of mixing. Depending on molecular weight and distance to the demixing temperature, the influence of gravity leads to non-negligible gradients of the volume fraction in the one-phase region as well as in the two-phase region. In particular, the effect of gravity on the measurement of the coexistence curve in a finite sample is calculated explicitly.In contrast to theory, experiments show that the concentration remains constant throughout the sample over a period of days as long as the system is kept in the homogenous region. Pronounced concentration gradients, however, are established in the twophase region within approximately one day. These findings are discussed with respect to sedimentation kinetics in terms of the droplet model of critical fluids.     

Theoretical and experimental reevaluation of the basicity of lambda3-phosphinine

We have investigated the basicity of phosphinine (C5H5P, phosphabenzene) in reevaluating its proton affinity (PA) and gas-phase basicity (GB) and the pK(a) value of its protonated form. As a necessary step, we have first determined its gas-phase proton affinity. Using both mass spectrometric and quantum chemical methods, we have obtained the values PA(C5H5P) = 195.8 +/- 1.0 kcal mol(-1) and GB(298)(C5H5P) = 188.1 +/- 1.0 kcal mol(-1), in good agreement with previous results. We then derived a value of pK(a)(C5H6P+) = -16.1 +/- 1.0 in aqueous solution using three different approaches: the latter markedly differs from the currently available value of -10. The reason for such a discrepancy in the pK(a) of protonated phosphinine in solution is discussed. In the theoretical determination of PAs, evaluation of the basis set superposition error (BSSE) showed that this effect is quite small, being 0.1-0.2 kcal mol(-1) for phosphinine, when a density functional theory (DFT) method in conjunction with a large basis set were used.