Search for leptoquark pairs decaying into nunu+jets in pp collisions at square root[s] = 1.8 TeV

We present the results of a search for leptoquark (LQ) pairs in (85.2+/-3.7) pb(-1) of pp* collider data collected by the D0 experiment at the Fermilab Tevatron. We observe no evidence for leptoquark production and set a limit on sigma(pp*-->LQLQ-->nunu+jets) as a function of the mass of the leptoquark (m(LQ)). Assuming the decay LQ-->nuq, we exclude scalar leptoquarks for m(LQ) < 98 GeV/c(2), and vector leptoquarks for m(LQ) < 200 GeV/c(2) and coupling which produces the minimum cross section, at a 95% confidence level.     

Rhetsine and rhetsinine The quinazoline alkaloids of Xanthoxylum rhetsa

From the trunk bark of Xanthoxylum rhetsa DC., lupeol and four alkaloids, namely, chelerythrine, rhetine, rhetsine and rhetsinine have been isolated. The constitution of rhetsinine and rhetsine have been established; the former is a new indolequinazoline base, the latter being its desoxy derivative.     

Response of triafol-TN plastic track detectors to238U-ions

Triafol-TN plastic detector foils have been irradiated with²³⁸U ions of energy 16.34 MeV/u and the tracks produced have been observed using the chemical etching technique. The bulk etch rate and track etch rate are determined under successive chemical etching. In our case, the validity of Arrhenius’s law is confirmed by the fact that the same value ofE _a obtained for these different concentrations, within experimental errors. The results show a linear correlation between the measured track etch rate along the track and the corresponding total energy loss rate and a threshold value of ～ 5.0 MeV/(mg/cm²) for track registration was obtained. The maximum etched track length of²³⁸U-ion in triafol-TN has been compared with the theoretically computed range.     

Action of manganese dioxide on carbohydrates—I Some disaccharides

Manganese dioxide degrades 1 → 3, 1 → 4 and 1 → 6 linked hexose disaccharides to, inter alia, 1 → 2, 1 → 3 and 1 → 5 linked hexosyl-pentoses, respectively. The yields (18–31 per cent) compare favourably with those recorded for other degradations. The methods which have been worked out for the isolation of these products are experimentally straightforward, and should be generally applicable to mixtures obtained by oxidation of 3-, 4- and 6-substituted hexoses with manganese dioxide.     

Noether symmetry in the higher order gravity theory

Noether symmetry for scalar tensor theory including curvature quadratic term has been explored, with the introduction of an auxiliary variable. Introduction of an auxiliary variable in the action facilitates in transforming the fourth order field equations to the second order field equations. Introduction of Noether symmetry in the action yield the coupling function () and the potential V(). The application of Noether symmetry further turned out to be powerful tool to find the solution of the field equations. A few physically reasonable solutions like power law inflation are presented.     

Green chemistry approaches to the synthesis of 5-alkoxycarbonyl-4-aryl-3,4- dihydropyrimidin-2(1H)-ones by a three-component coupling of one-pot condensation reaction: comparison of ethanol,water, and solvent-free conditions

A general and practical green chemistry route to the Biginelli cyclocondensation reaction using cerium(III) chloride as the catalyst (25% mol) is described under three different sets of reaction conditions. This method provides an efficient and much improved modification of original Biginelli reaction reported in 1893, in terms of high yields, short reaction times, and simple work-up procedure, and it has the ability to tolerate a wide variety of substitutions in all three components, which is lacking in existing procedures.     

Quantum computing with an always-on Heisenberg interaction

Many promising schemes for quantum computing (QC) involve switching "on" and "off" a physical coupling between qubits. This may prove extremely difficult to achieve experimentally. Here we show that systems with a constant Heisenberg coupling can be employed for QC if we actively "tune" the transition energies of individual qubits. Moreover, we can collectively tune the qubits to obtain an exceptionally simple scheme: computations are controlled via a single "switch" of only six settings. Our schemes are applicable to a wide range of physical implementations, from excitons and spins in quantum dots through to bulk magnets.     

Subsystem purity as an enforcer of entanglement

We show that entanglement can always arise in the interaction of an arbitrarily large system in any mixed state with a single qubit in a pure state. This small initial purity is enough to enforce entanglement even when the total entropy is close to maximum. We demonstrate this feature using the Jaynes-Cummings interaction of a two-level atom in a pure state with a field in a thermal state at an arbitrarily high temperature. We find the time and temperature variation of a lower bound on the amount of entanglement produced and study the classical correlations quantified by the mutual information.