Results of the liquid scintillation detector of the Mont Blanc Laboratory

Summary The Liquid Scintillation Detector (LSD experiment) is running since October 1984 in the Mont Blanc Laboratory, with 90 tons of active mass. We discuss here some of the research aims of the experiment, and report the preliminary results on searching for neutrino bursts from collapsing stars and on cosmic-ray muons.

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Riassunto Nell'ottobre 1984 è entrato in misura l'esperimento LSD (Liquid Scintillation Detector) del Laboratorio del Monte Bianco, costituito di 90 tonnellate di rivelatore. In questo lavoro si discutono alcuni degli argomenti di ricerca dell'esperimento e si riportano i risultati preliminari sui burst di neutrini da collassi stellari e sui muoni della radiazione cosmica.

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Резюме Зидкий сцинтилляционный детектор работает с октября 1984 года в лаборатории на Мон Блане. Детектор имеет 90 тонн активной массы. Мы обсуздаем некоторые цели этого эксперимента. Сообщаются предварительные результаты по поиску нейтринных вспышек от коллапсирующих звезд и мюонов в космических лучах.

     

Preparations and spectroscopic studies of organotin complexes of diclofenac

The reactions of the potent and widely used anti-inflammatory drug diclofenac, HL, with diorganotin(IV) oxides were studied. The dimeric tetraorganodistannoxane complexes [Me(2)LSnOSnLMe(2)](2), [Bu(2)LSnOSnLBu(2)](2), [Ph(2)LSnOSnLPh(2)](2) and the dibutyltin complex [Bu(2)SnL(2)], have been prepared and structurally characterized in the solid state by means of vibrational and 119Sn M?ssbauer spectroscopy. Determination of lattice dynamics by temperature-dependent 119Sn M?ssbauer spectroscopy. From the variable-temperature M?ssbauer effect, the Debye temperature was determined. The complexes have been characterized in solution by NMR (1H and 13C) spectroscopy. Vibrational, M?ssbauer, and NMR data are discussed in terms of the proposed structures.     

The 90 ton liquid scintillation detector in the Mont Blanc laboratory

Summary We discuss here the results from calibrating liquid seintillation counters (1.5 m³ each) used in the large-volume neutrino experiment in the Mont Blanc Laboratory. The electronic and recording systems from the 72 counters of the detector are described, and the method to detect low-energy γ pulse from (n, p) reaction by using²⁵²Cf as a neutron source is discussed. Paper presented at the 2° Convegno Nazionale di Fisica Cosmica, held at L'Aquila, 29 May–2 June 1984.     

Sur les égalités du miroir et certaines formes faibles de la conjecture de Greenberg

Let p be an odd prime. For any CM number field K containing a primitive p^th-root of unity, class field theory and Kummer theory put together yield the well known reflection inequality ^+– between the plus and minus parts of the -invariant of K. Greenbergs conjecture asserts that ⁺ is always trivial. We study here a weak form of this conjecture, namely ⁺=^– if and only if ⁺=^–=0.     

Application of Acid and Cold Stresses to Enhance the Production of Clavulanic Acid by Streptomyces clavuligerus

Clavulanic acid (CA) is frequently prescribed for treatment of bacterial infections. Despite the large number of studies concerning CA production, there is still a need to search for more effective and productive processes because it is mainly produced by biochemical route and is chemically unstable. This paper evaluates the influence of acid and cold stresses on CA production by Streptomyces clavuligerus in bench scale stirred tank bioreactor. Four batch cultures were conducted at constant pH (6.8 or 6.3) and temperature (30, 25, or 20 °C) and five batch cultures were performed with application of acid stress (pH reduction from 6.8 to 6.3), cold stress (reduction from 30 to 20 °C), or both. The highest maximum CA concentration (684.4 mg L⁻¹) was obtained in the culture conducted at constant temperature of 20 °C. However, the culture under acid stress, in which the pH was reduced from 6.8 to 6.3 at a rate of 0.1 pH unit every 6 h, provided the most promising result, exhibiting a global yield coefficient of CA relative to cell formation (Y_CA/X) of 851.1 mg_CA g_X⁻¹. High Y_CA/X values indicate that a small number of cells are able to produce a large amount of antibiotic with formation of smaller amounts of side byproducts. This could be especially attractive for decreasing the complexity and cost of the downstream processing, enhancing CA production.

     

Kinetic study of oxygen adsorption over nanosized Au/γ-Al₂O₃ supported catalysts under selective CO oxidation conditions

O? adsorption is a key process for further understanding the mechanism of selective CO oxidation (SCO) on gold catalysts. Rate constants related to the elementary steps of O? adsorption, desorption and surface bonding, as well as the respective activation energies, over a nanosized Au/γ-Al?O? catalyst, were determined by Reversed-Flow Inverse Gas Chromatography (RF-IGC). The present study, carried-out in a wide temperature range (50-300 °C), both in excess as well as in the absence of H?, resulted in mechanistic insights and kinetic as well as energetic comparisons, on the sorption processes of SCO reactants. In the absence of H?, the rate of O? binding, over Au/γ-Al?O?, drastically changes with rising temperature, indicating possible O? dissociation at elevated temperatures. H? facilitates stronger O? bonding at higher temperatures, while low temperature binding remains practically unaffected. The lower energy barriers observed, under H? rich conditions, can be correlated to O? dissociation after hydrogenation. Although, H? enhances both selective CO reactant's desorption, O? desorption is more favored than that of CO, in agreement with the well-known mild bonding of SCO reactant's at lower temperatures. The experimentally observed drastic change in the strength of CO and O? binding is consistent both with well-known high activity of SCO at ambient temperatures, as well as with the loss of selectivity at higher temperatures.     

The diverse effect of antiplasticizer in the molecular dynamics of an organic dye-doped polymer observed at different motional lengthscales

Complementary thermal analysis techniques were used to study blending-induced perturbations in polymer dynamics pertaining to different motional lengthscales. The antiplasticizing role of common neutral and apolar fluorescent perylimides on the cooperative relaxation dynamics of poly(methyl methacrylate) (PMMA) chain segments is evidenced by a clear rise of both the glass transition (T_g) and liquid-liquid transition (T_LL) temperatures. Simultaneously, the dielectric strength, Δε_β, of the signal ascribed to restricted rotational movements of lateral groups, shows a substantial reduction. Most aspects of the observed behavior bear analogies with recent experimental observations in nanoconfined PMMAs (e.g., PMMA with homogeneously dispersed SiO₂ nanospheres, in-situ polymerized in silica nanopores or in the form of supported ultrathin films), suggesting that a common mechanism is operational. In our mixtures, confinement effects, such as a modification in the macroconformation of the polymer, and changes in the orientation and packing of the polymer random coil, provide a plausible explanation of the observed changes regardless of the motional lengthscale concerned. Consonant with this scenario are reports of advanced optical properties for perylimide + PMMA blends, ascribed to the high rigidity of the matrix together with weak intercomponent interactions.     

High-energy cosmic-ray physics with an EAS array on the top of the Gran Sasso Laboratory

Summary An air shower array on top of the underground Gran Sasso Laboratory (GSL) can give valuable information in the field of high-energy cosmic-ray physics. We discuss the performances of a specific apparatus (EAS-TOP) operating both in coincidence with the underground array (i.e. for measuring the total primary energy of multimuon events) and as an autonomous air shower detector (for studies of ultra-high-energy gamma-ray astronomy, cosmic-ray anisotropies and primary composition).

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Riassunto Un apparato per EAS posto in superficie nella zona sovrastante il laboratorio sotterraneo del Gran Sasso può fornire utili informazioni sulla radiazione cosmica primaria. Qui si presenta un apparato (EAS-TOP) the funzionerà sia in coincidenza con gli apparati posti nel tunnel per misure sull'energia primaria degli eventi multimuonici sia in modo autonomo come rivelatore EAS per ricerche di γ-astronomia ad energie molto elevate, di anisotropia dei raggi cosmici primari, e di composizione primaria.

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Резюме Установка для регистрации ШАЛ над подземной лабораторией Гран Сассо может дать полезную информацию для физики космических лучей высоких энергий. Мы обсуждаем возможности установки EAS-TOP, работающей как в совпадении с подземными детекторами (для измерения полной начальной энергии в многомюинных событиях), так и в автономном режиме—для исследований в области гамма-астрономии сверхвысоких энергий, измерений анизотропии космических лучей и химического состава первичного излучения.

     

EAS-TOP: Results of the gamma-ray astronomy at 1014 eV

Summary The EAS-TOP Extensive Air Shower array, on top of the under-ground Gran Sasso Laboratory, is fully operating as a γ-ray astronomy observatory since the beginning of 1989. After showing the measured angular resolution of the detector, we present the results obtained from the analysis of 280 days of measurements in 1989–1990, with the purpose of investigating possible emission (d.c. and sporadic) from the candidate sources in the Northern hemisphere at an energy, >200 TeV. Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990.