da Vinci fluids,catch-up dynamics and dense granular flow

We introduce and study a da Vinci fluid, a fluid whose dissipation is dominated by solid friction. We analyse the flow rheology of a discrete model and then coarse-grain it to the continuum. We find that the model gives rise to behaviour that is characteristic of dense granular fluids. In particular, it leads to plug flow. We analyse the nucleation mechanism of plugs and their development. We find that plug boundaries generically expand and we calculate the growth rate of plug regions. In systems whose internal effective dynamic and static friction coefficients are relatively uniform we find that the linear size of plug regions grows as (time)^1/3 . The suitability of the model to granular materials is discussed.     

Failure of Russell-Saunders coupling in the 5f states of plutonium

Using high energy-electron energy loss spectroscopy, transmission electron microscopy, and synchrotron-radiation-based x-ray absorption spectroscopy, we provide the first experimental evidence that Russell-Saunders (LS) coupling fails for the 5f states of Pu. These results support the assumption that only the use of jj or intermediate coupling is appropriate for the 5f states of Pu. High energy-electron energy loss spectroscopy experiments were performed by use of a transmission electron microscope and are coupled with image and diffraction data; therefore, the measurements are completely phase specific.     

Observation of B(s)(0) → D(s)(*)+ D(s)(*)- using e+ e- collisions and a determination of the B(s)-B(s) width difference ΔΓ(s)

We have made the first observation of B(s)(0)→D(s)(*)+ D(s)(*)- decays using 23.6 fb(-1) of data recorded by the Belle experiment running on the Υ(5S) resonance. The branching fractions are measured to be B(B(s)(0)→D(s)+ D(s)-)=(1.03(-0.32-0.25)(+0.39+0.26))%, B(B(s)(0)→D(s)(*±) D(s)(?))=(2.75(-0.71)(+0.83)±0.69)%, and B(B(s)(0)→D(s)*+ D(s)*-)=(3.08(-1.04-0.86)(+1.22+0.85))%; the sum is B[B(s)(0)→D(s)(*)+ D(s)(*)-]=(6.85(-1.30-1.80)(+1.53+1.79))%. Assuming B(s)(0)→D(s)(*)+ D(s)(*)- saturates decays to CP-even final states, the branching fraction determines the ratio ΔΓ(s)/cosφ, where ΔΓ(s) is the difference in widths between the two B(s)-B(s) mass eigenstates, and φ is a CP-violating weak phase. Taking CP violation to be negligibly small, we obtain ΔΓ(s)/Γ(s)=0.147(-0.030)(+0.036)(stat)(-0.041)(+0.042)(syst), where Γ(s) is the mean decay width.     

A propos de conjectures de Serre et Sullivan

Summary We first give a new proof of a conjecture of J.-P. Serre on the homotopy of finite complexes, which was recently proved by C. McGibbon and J. Neisendorfer. The emphasis is on a property of the mod. 2 homology of certain spaces: their quasi-boundedness as right modules over the Steenrod algebra. This property is preserved when one goes from a simply connected space to its loop space and also when one takes a covering of anH-space. Then we show that this notion of quasi-boundedness simplifies H. Miller's proof of D. Sullivan's conjecture on the contractibility of the space of pointed maps from the classifying space of the groupe /2 into a finite complex.     

Rare-earth valence-state studies of the series RIn3 and RSn3 derived from quadrupole coupling constants

Time-differential perturbed angular correlation was applied to measure the quadrupole coupling constants of¹¹¹Cd (247 keV) at the In and Sn sites for rare-earth compounds of the series RIn₃ and RSn₃ that have the AuCu₃ structure. Definitive evidence was found for Yb and Eu having lower valence states relative to the assumed value of +3 for the other rare earths. Measurements at liquid helium temperatures and pressures to 18.5 kbar indicate that the room temperature valencies of CeSn₃, YbSn₃, and YbIn₃ have not changed.Work done under the auspices of the US Energy Research and Development Administration     

Analysis of matrix nuclei spin flip satellite lines in EPR spectra: Application to trapped hydrogen atoms

The relative intensities and energy separation of allowed EPR lines of a paramagnetic species and partially forbidden spin flip satellite lines due to dipole-dipole coupling between the paramagnetic species and the matrix nuclei have been analyzed in a new way. The analysis allows one to determine both the distance to and the number of matrix nuclei that contribute to a given satellite transition. For hydrogen atoms trapped in a gamma-irradiated sulphuric acid glass at 77 K the analysis indicates that interaction occurs with four matrix protons at a distance of 2.15 Å. For trapped hydrogen atoms in phosphoric acid glass the analysis indicates interaction with four matrix protons at 2.37 Å.     

Chemical investigation of three plutonium–beryllium neutron sources

Thorough physical and chemical characterization of plutonium–beryllium (PuBe) neutron sources is an important capability with applications ranging from material accountancy to nuclear forensics. Characterization of PuBe sources is not trivial owing to range of existing source designs and the need for adequate infrastructure to deal with radiation and protect the analyst. This study demonstrates a method for characterization of three PuBe sources that includes physical inspection and imaging followed by controlled disassembly and destructive analysis.     

Cathode-catalyzed transesterification of alkylphosphonates

The cathodic electrolysis of aliphatic alcohols and alkylphosphonates in acetonitrile with 0.5 N Et₄NClO₄ as the base electrolyte leads to mono- and ditransesterified phosphonates. The yield and ratio of these products is a function of the nature of the starting reagents and amount of current passed.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 200–204, January, 1991.