Chiral 1,4-Benzodiazepines. X. Further Investigations of Configurational Stability of the Chiral Centre C(3)

For various at C(3)-chiral 1,4-benzodiazepin-2-ones rate determinations of racemisation (ka.- for C(3)-0CH3 derivative ( + )-1), degenerate nucleophilic exchange (k0 - for rac. 1 and rac. 2), and solvolysis (k5 - for C(3)-hemisuccinyl derivative 4) have been performed. These investigations revealed; (a) retention of .configuration during methanolysis of ( + )-3, (b) slow racemisation of ( + )-1 during solvolytic degenerate nucleophilic substitution (kefko. - - 4), (c} no participation of SNl retentive reaction, possible via intramolecular transfer of the methoxy group within intermediary compounds 4-6, (d) thermodi:namic parameters for racemisation of ( + )-1 between 20-40 °c; liH"" = 18.0 ± 0.8 kcal/moll**, liS"" = = - 7.2 ± 2.5 e. u.*** Mechanistic scheme is offered which accounts for all experimental results. The effect of the electrocyclic equilibrium on the electronic structure of N(4) protonated benzodiazepines, and its possible consequences for their mechanisms of biological activity on the central nervous system (CNS), have briefly been discussed

Transitions and Probes in Turbulent Helium

Previous analysis of a Paris turbulence experiment \cite{zoc94,tab95} shows a transition at the Taylor Reynolds number \rel \approx 700. Here correlation function data is analyzed which gives further evidence for this transition. It is seen in both the power spectrum and in structure function measurements. Two possible explanations may be offered for this observed transition: that it is intrinsic to the turbulence flow in this closed box experiment or that it is an effect of a change in the flow around the anemometer. We particularly examine a pair of ``probe effects''. The first is a thermal boundary layer which does exist about the probe and does limit the probe response, particularly at high frequencies. Arguments based on simulations of the response and upon observations of dissipation suggests that this effect is only crucial beyond \rel\approx 2000. The second effect is produced by vortex shedding behind the probe. This has been seen to produce a large modification in some of the power spectra for large \rel. It might also complicate the interpretation of the experimental results. However, there seems to be a remaining range of data for \rel < 1300 uncomplicated by these effects, and which are thus suggestive of an intrinsic transition.Comment: uuencoded .ps files. submitted to PRE. 12 figures are sent upon request to jane wang ([email protected]

Probability Density Function of Longitudinal Velocity Increment in Homogeneous Turbulence

Two conditional averages for the longitudinal velocity increment u_r of the simulated turbulence are calculated: h(u_r) is the average of the increment of the longitudinal Laplacian velocity field with u_r fixed, while g(u_r) is the corresponding one of the square of the difference of the gradient of the velocity field. Based on the physical argument, we suggest the formulae for h and g, which are quite satisfactorily fitted to the 512^3 DNS data. The predicted PDF is characterized as (1) the Gaussian distribution for the small amplitudes, (2) the exponential distribution for the large ones, and (3) a prefactor before the exponential function for the intermediate ones.Comment: 4 pages, 4 figures, using RevTeX3.

PECULIARITIES OF MANUFACTURING AND APPLICATION OF MIXED EXPLOSIVES OF ANFO TYPE AT MINING ENTERPRISES OF MONGOLIA

The article describes problems of blasting operations carried out at an industrial scale using ammonia-nitrate explosives. Based on experimental studies conducted by the authors, it was determined that for use in mining enterprises in Mongolia, primarily in coal mines, the most rational and effective explosives are mixed ones based on ammonium nitrate in the solid state with various liquid as well as solid dispersed fuels additives - ANFO mixtures. The temperature boundaries for the phase transitions of ammonium nitrate in open areas for the period of three months for different humidity values have been determined. The indicators of oil absorption are identified depending on the cycle of phase transitions for ammonium nitrate

Influenza della cicloeximide, della DL-etionina, della L-andrenalina e del cortisolo sulla biosintesi della glicerina e dell'acetoina da parte di Kloeckera apiculata

Nella fermentazione alcolica del mosto d'uva con Kl. apiculata, la cicloeximide (acticlione) inibiva parzialmente la formazione della glicerina e clell'acetoina. L'inibizione della formazione della glicerina era parzialmente contrastata dalla L-adrenalina, mentre la DL-etionina e il cortisolo contrastavano quella dell'acetoina. La cicloeximide causava anche un aumento del rendimento in alcole. L'etionina attivava tanto la formazione della glicerina quanto quella dell'acetoina. L'adrenalina non influiva sulla formazione della glicerina, ma inibiva fortemente quella dell'acetoina. In presenza di cortisolo avveniva il contrario. I risultati sono discussi in relazione alla possibilità di variare i rapporti fra i prodotti secondari della fermentazione con l'aiuto di sostanze endogene o esogene ai mosti.Einfluß von Cycloheximid, DL-Aethionin, L-Adrenalin und Cortisol auf die von Kloeckera apiculata verursachte Biosynthese des Glycerin und des AcetoinIn der von Kloeckera apiculata verursachten alkoholischen Gärung des Traubenmostes hemmte Cycloheximid (Actidion) die Glyzerin- und Acetoinbildung teilweise. Die Hemmung der Glycerinbildung wurde zum Teil von L-Adrenalin aufgehoben, während DL-Aethionin und Cortisol der Hemmung der Acetoinbildung entgegenwirkten. Cycloheximid verursachte auch eine Zunahme der Alkoholbildung während der Gärung.Die Glyzerin- und Acetoinbildung wurde von DL-Aethionin aktiviert. L-Adrenalin übte keine Wirkung auf die Glyzerinbildung aus, hemmte jedoch die Acetoinbildung. In Anwesenheit von Cortisol erfolgte das Gegenteil.Die Ergebnisse wurden hinsichtlich der Möglichkeit erörtert, die Anteile der sekundären Gärungsprodukte mit Hilfe endogener oder exogener Stoffe zu verändern