Formation of disubstituted beta-lactones using bifunctional catalysis

[reaction: see text] Acid chlorides and aromatic aldehydes react in the presence of a stoichiometric amount of a tertiary amine and catalytic amounts of a cinchona alkaloid derivative and a Lewis acid to produce beta-lactones in high diastereo- and enantioselectivity. The sense of the diastereoselectivity depends on the substitution of the acid chloride, with the reactions of aliphatic acid chlorides giving predominantly the trans-isomer and those of alkoxyacetyl chlorides favoring formation of the cis-isomer.     

Study of the energy stability of ultra-short pulses from an yttrium-aluminium garnet laser

The energy stability of ultra-short pulses (USPs) from an yttrium-aluminium garnet laser with passive mode locking (PML) has been investigated. Experimental results of passive mode locking based on solutions of widely used dyes are given for comparison. Using these saturable absorbers we found that the energy distribution of USP did not depend on the laser working frequency nor on the duration of the experiment.     

Beta decay of <Superscript>115</Superscript>In to the first excited level of <Superscript>115</Superscript>Sn: Potential outcome for neutrino mass

Recent observation of β decay of ¹¹⁵In to the first excited level of ¹¹⁵Sn with an extremely low Q _β value (Q _β ≤ O(1) [keV]) could be used to set a limit on neutrino mass. To give a restriction potentially competitive with those extracted from experiments with ³H (≃2 eV) and ¹⁸⁷Re (≃15 eV), the atomic mass difference between ¹¹⁵In and ¹¹⁵Sn and energy of the first ¹¹⁵Sn level should be remeasured with higher accuracy (possibly of the order of ∼1 eV). The text was submitted by the authors in English.     

Lagrangian of two charged gravitating bodies in the second post-Newton approximation

On the basis of a Lagrangian formulation of Relativistic theory of direct interparticle interactions, a post-Newton correction (of order c^–4) is found to the Bazaski lagrangian in the problem of two gravitating bodies.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 31–36, July, 1990.     

THE EFFECT OF ACIDS ON THE INFRARED SPECTRA OF SCHIFF BASES—II. IMINES CONTAINING THE C=C-C=N AND C=C-C=C-C=N UNITS

Abstract— The Fourier-transform infrared spectra of chloroform-d solutions of conjugated imines CH₃CH=CHCH=NCH(CH₃)₂ and CH₃CH₂CH=CHCH=CHCH=NCH(CH₃)₂ and the related protonated species with HCl, HBr, HI, trichloro, dichloro, monobromo and monochloroacetic acids or propionic acid are presented. The effects of conjugation and protonation are examined. The results show that conjugation slightly increases the basicity of the Schiff bases. HCl, HBr and HI protonate the Schiff bases completely. The carboxylic acids protonate partially depending on their p K _a, values. When the Schiff base contains two (or more) C=C bonds conjugated with C=N, the main C=C stretching band undergoes a strong intensification showing that sizeable dipole moment variations occur along the conjugated chain.     

Testing the Pauli exclusion principle with the NEMO-2 detector

The Pauli Exclusion Principle (PEP) was tested with the NEMO-2 detector. Limits at the 90% C.L. on the violation of PEP for p-shell nucleons in ¹²C were obtained. Specifically, transitions to the fully occupied 1s _1/2-shell yielded a limit of 4.2 · 10²⁴ y for the process with emission of a γ-quantum. Similarly limits of 3.1 · 10²⁴ y for β⁻ and 2.6 · 10²⁴ y for β⁺ Pauli-forbidden transitions of ¹²C →¹²?¹²B) are reported here. Received: 25 August 1999     

A search for spontaneous emission of heavy clusters in the 127I nuclide

The results of an experimental search for spontaneous cluster decay in ¹²⁷I are presented. Several possible channels have been investigated considering an exposure of 33834 kg ^. day collected by a large-mass highly radiopure NaI(Tl) set-up deep underground in the Gran Sasso National Laboratory of the INFN. New lower limits on the lifetime of ²⁴₁₀Ne, ²⁸₁₂Mg, ³⁰₁₂Mg, ³²₁₄Si, ³⁴₁₄Si, ⁴⁸₂₀Ca, ⁴⁹₂₁Sc cluster radioactivity in ¹²⁷I have been achieved.     

Estimation ofv μ→v τ oscillation parameters in the E-564 hybrid experiment

The limits on the parameters of thev _μ→v _τ oscillations are obtained in the E-564 hybrid experiment: Δm ²≦4.5 eV² and sin²(2θ)≦6.0·10^?2 (90% CL). A possibility of direct observation of τ-lepton decays in the nuclear emulsion vertex detector allowed the sensitivity of this experiment to the parameters of the oscillations to be increased.