Lepton spectrum in semileptonic b-decay

We present some results from the computation of the charged lepton energy distribution in the decay b → c + $\text{l}$^? + $\text{ν}$ taking into account first order QCD corrections.     

First evaluation of the thermodynamic properties for spheres to elongated micelles transition of some propanediyl-alpha,omega-bis(dimethylalkylammonium bromide) surfactants in aqueous solution

The apparent and partial molar enthalpies, apparent molar volumes, and adiabatic compressibilities at 298 K of the aqueous solutions of the cationic gemini surfactants propanediyl-alpha,omega-bis(octyldimethylammonium bromide) (8-3-8) and propanediyl-alpha,omega-bis(dodecyldimethylammonium bromide) (12-3-12) have been measured as a function of concentration. The trends of the partial molar enthalpies versus concentration are the first well documented thermodynamic evidence of sphere to rod transition in the micellar phase, involving a detectable quantity of heat, and allow the determination of the change in enthalpy associated with this transition. The changes in enthalpies upon micellization and for the sphere to elongated micelles transition, DeltaH(s)(-->)(r), have been obtained from the experimental data by using a pseudo-phase transition approach: -1.5 kJ mol(-1) for 8-3-8 and -3.9 kJ mol(-1) for 12-3-12. No evidence of the above transition is found in the trends of volumetric properties versus m. The apparent adiabatic molar compressibilities for the compounds under investigation are also reported here for the first time: a negative group contribution for the methylene group is evaluated, when the surfactants are present in solution as a single molecule, reflecting its solvation structure. In the micellar phase, the -CH(2)- group contribution becomes positive. A value of 1.17 x 10(-3) cm(3) bar(-1) mol(-1) for the change in adiabatic molar compressibility upon micellization is obtained. The lower values of the methylene group contributions to the volumetric properties for the monomers support the hypothesis of partial association of the chains before the cmc.     

Synthesis of L-carbafuranomycin, an unnatural analogue of the antibiotic amino acid furanomycin

[reaction: see text] L-(+)-carbafuranomycin is a novel analogue of L-(+)-furanomycin, an unusual antibiotic alpha-amino acid that attracted great interest due to its activity as an isoleucine antagonist. We present here a concise and efficient asymmetric synthesis of this carba-analogue starting with the 1,3-dipolar cycloaddition of a chiral nitrile oxide with cyclopentadiene. Notably, the methyl group was introduced by an S(N)2' cuprate substitution with high stereo- and regioselectivity.     

Supersolids versus phase separation in two-dimensional lattice bosons

We study the nature of the ground state of the two-dimensional extended boson Hubbard model on a square lattice by quantum Monte Carlo methods. We demonstrate that strong but finite on-site interaction U along with a comparable nearest-neighbor repulsion V result in a thermodynamically stable supersolid ground state for densities larger than 1/2, in contrast to fillings less than 1/2 or for very large U, where the checkerboard supersolid is unstable towards phase separation. We discuss the relevance of our results to realizations of supersolids using cold bosonic atoms in optical lattices.     

Sensitivity of a tucuxi (Sotalia fluviatilis guianensis) to airborne sound

Auditory systems of cetaceans are considered highly specialized for underwater sound processing, whereas the extent of their hearing capacity in air is still a point of issue. In this study, the sensitivity to airborne sound in a male tucuxi (Sotalia fluviatilis guianensis) was tested by means of a go/no go response paradigm. Auditory thresholds were obtained from 2 to 31.5 kHz. Compared to the hearing thresholds of other dolphins as well as of amphibian mammals, the sensitivity to airborne sound of the test subject is low from 2 to 8 kHz, with the highest threshold at 4 kHz. Thresholds at 16 and 31.5 kHz reveal a sharp increase in hearing sensitivity. Thus, although not obtained in this study, the upper aerial hearing limit is in the ultrasonic range. A comparison of the present data with the underwater audiogram of the same test subject referred to sound intensity indicates that the sensitivity of Sotalia to underwater sound is generally better than to airborne sound.     

Periodic Solutions for Completely Resonant Nonlinear Wave Equations with Dirichlet Boundary Conditions

We consider the nonlinear string equation with Dirichlet boundary conditions u_tt–u_xx=(u), with (u)=u³+O(u⁵) odd and analytic, 0, and we construct small amplitude periodic solutions with frequency for a large Lebesgue measure set of close to 1. This extends previous results where only a zero-measure set of frequencies could be treated (the ones for which no small divisors appear). The proof is based on combining the Lyapunov-Schmidt decomposition, which leads to two separate sets of equations dealing with the resonant and non-resonant Fourier components, respectively the Q and the P equations, with resummation techniques of divergent powers series, allowing us to control the small divisors problem. The main difficulty with respect to the nonlinear wave equations u_tt–u_xx+Mu=(u), M0, is that not only the P equation but also the Q equation is infinite-dimensional.     

Melting of bosonic stripes

We use quantum Monte Carlo simulations to determine the finite temperature phase diagram and to investigate the thermal and quantum melting of stripe phases in a two-dimensional hard-core boson model. At half filling and low temperatures the stripes melt at a first order transition. In the doped system, the melting transitions of the smectic phase at high temperatures and the superfluid smectic (supersolid) phase at low temperatures are either very weakly first order, or of second order with no clear indications for an intermediate nematic phase.     

Plume separation effect in pulsed laser ablation deposition

The results of a new geometrical configuration of pulsed laser ablation deposition technique that uses a hemi-cylindrical transparent plastic substrate are presented and discussed. With the new arrangement, two distinct components with different material compositions have been clearly observed. While the first component comprises atoms, ions and molecules and constitutes visible or the so-called luminous plume, the second component is formed of fragments, clusters and liquid droplets and is invisible to the naked eye. The latter component constitutes a major part of the ablated material. The luminous plume symmetry axis does not coincide with the mass distribution symmetry axis. In the case of Si ablation and 45° incident beam angle, the maximum deflection angle of the luminous plume reaches 30° with respect to the normal to the target surface, while the deflection angle of the second component is higher than 40°. The change in the target morphology and the dependence of the composition of the ablated material on local fluence, along with the hydrodynamic effects, is sought to explain this previously unexpected and unreported phenomenon. PACS 61.80.Ba; 47.35.+i; 52.38.Mf; 81.15.Fg