Hétérocycles contenant du phosphore. XXXII. Etude de l'action des phosphorhydrazides sur les orthoesters,l'anhydride acétique et l'acide formique

The reaction of phosphodi- or trihydrazides with orthoesters affords mainly 2,3,4,5-tetrahydro-1,2,4,5,3-tetrazaphosphorines and sometimes 4-amino-1,2,4,3-triazaphospholidines. These 1,2,4,5,3-tetrazaphosphorines present a prototropy which explains different pathways of the reaction of these derivatives with formaldehyde or acetone, The structure of all heterocycles which were obtained was established by nmr spectra.     

Influence de L’Implantation par Recul et de la Diffusion Sous Irradiation sur L’Exactitude de L’Analyse par Activation Neutronique

A simplified calculation model of the recoil and irradiation enhanced diffusion which occur in neutron activation analysis of metals is proposed. Under usual irradiation conditions, the recoil does not exceed 0.01 μm for n, γ reactions and 2 μm for other reactions; the diffusion does not exceed 1 μm. Examples, in which deep impurity diffusion leading to important analytical errors was put forward, are discussed through this calculation model. In most cases, the observed phenomena are not related to diffusion but to other causes such as unefficient etching of the sample surface.      

An iterative catalytic route to enantiopure deoxypropionate subunits: asymmetric conjugate addition of grignard reagents to alpha,beta-unsaturated thioesters

A highly enantioselective (up to 96% ee) conjugate addition of Grignard reagents, in particular, MeMgBr, to alpha,beta-unsaturated thioesters is provided as well as its application to a diastereo- and enantioselective iterative route to syn- and anti-1,3-dimethyl arrays and deoxypropionate subunits. The versatility of the method is illustrated in the synthesis of (-)-lardolure, a multimethyl-branched insect natural pheromone.     

A study of the extraction of phosphovanadomolybdic acid and application to the neutron activation analysis of phosphorus in steels

Ancient silver-copper-tin alloyed Gaulish coins have been analyzed using 14 MeV neutron activation analysis. The method used takes into account all the differences in composition, geometry, position of irradiation and counting that may exist between the sample and the reference. The results of the analysis are accurate and permit interesting numismatic conclusions.     

Grüneisen gamma of invar-type alloys

Pressure derivatives of elastic constants have been measured for FeNi Invar alloys. Longitudinal and shear mode gamma's are obtained from which the magnetic contributions of intrinsic and non-intrinsic type are extracted; these magnetic Grüneisen gamma's are large and negative.     

Interactions between oscillatory modes near a 2:3 resonant Hopf-Hopf bifurcation

In this paper, the dynamics near a 2:3 resonant Hopf-Hopf bifurcation is studied. The main result is the identification of a distinctive structure connecting 1:2 and 1:3 strong resonances of limit cycles. This structure is found near the Hopf-Hopf point revealing that it may be associated to the resonant case, and may provide useful information about the dynamics generated by this codimension 3 bifurcation.     

Rate Enhancement of the Radical 1,2-Acyloxy Shift (Surzur–Tanner Rearrangement) by Complexation with Lewis Acids

New prospects for synthetic applications are offered by the 1,2-acyloxy shift of β-(acyloxy)alkyl radicals, which proceeds with high yields under Lewis acidic conditions [Eq. (1)]. With the exception of cyclizations, this is the first Lewis acid mediated acceleration of a radical rearrangement.     

Quantitative solid phase microextraction – Gas chromatography mass spectrometry analysis of five megastigmatrienone isomers in aged wine

Megastigmatrienone is a key flavor compound in tobacco. It has also been detected in wine, where it may contribute to a tobacco/incense aroma, but its importance and concentration in wines had never previously been evaluated.     

Dynamic acoustoelastic testing of weakly pre-loaded unconsolidated water-saturated glass beads

Dynamic acoustoelastic testing is applied to weakly pre-loaded unconsolidated water-saturated glass beads. The gravitational acceleration produces, on the probed beads, a static stress of order 130 Pa, thus the granular medium is close to the jamming transition. A low-frequency (LF) acoustic wave gently disturbs the medium, inducing successively slight expansion and compaction of the granular packing expected to modulate the number of contacts between beads. Ultrasound (US) pulses are emitted simultaneously to dynamically detect the induced modification of the granular skeleton. US propagation velocity and attenuation both increase when the LF pressure increases. The quadratic nonlinear elastic parameter β, related to the pressure dependence of US propagation velocity, was measured in the range 60-530 if water-saturated glass beads are considered as an effective medium. A dynamic modification of US scattering induced by beads is proposed to modulate US attenuation. Complex hysteretic behaviors and tension-compression asymmetry are also observed and analyzed by time-domain and spectral analyses. Furthermore acoustic nonlinearities are measured in cases of quasi-static and dynamic variations of the LF wave amplitude, providing quantitatively similar acoustic nonlinearities but qualitatively different.