Opposite sign dimuon events produced in narrow band neutrino and antineutrino beams

On the basis of 315 dimuon events of opposite sign for which the nature (and energy) of the incident neutrino is known, and the momenta and hadronic shower energy are measured, we find a) very similar production by neutrinos and antineutrinos, and therefore confirmation of the GIM model for semileptonic weak interactions, b) energy spectra, excitation functions, angular correlations and transverse momentum distributions which are in remarkable agreement with the hypothesis of charm production and decay, c) evidence against models for which the second muon has a heavy lepton as origin, d) evidence against “bottom” quark production by antineutrinos, e) the amount and the structure function for the strange quark-antiquark sea, and f) an approximate branching ratio, of 0.15 for the muonic decay of the semistable charmed meson.     

Preparation of polymer nanocomposites with “ultrahigh” refractive index

Nanocomposites of lead sulfide and several polymers, especially poly(ethyleneoxide), were prepared by coprecipitation of lead sulfide and polymer, followed by a drying and pressing procedure. Such nanocomposites consist of ca. 90% w/w (or ca. 50% v/v) lead sulfide, of particle dimensions of 2–40 nm. The refractive index of these materials is on the order of 3 and therefore, to the authors' best knowledge, is the highest reported for any polymer composite.     

Role of host layer flexibility in DNA guest intercalation revealed by computer simulation of layered nanomaterials

Layered double hydroxides (LDHs) have been shown to form staged intermediate structures in experimental studies of intercalation. However, the mechanism by which staged structures are produced remains undetermined. Using molecular dynamics simulations, we show that LDHs are flexible enough to deform around bulky intercalants such as deoxyribonucleic acid (DNA). The flexibility of layered materials has previously been shown to affect the pathway by which staging occurs. We explore three possible intermediate structures which may form during intercalation of DNA into Mg2Al LDHs and study how the models differ energetically. When DNA strands are stacked directly on top of each other, the LDH system has a higher potential energy than when they are stacked in a staggered or interstratified structure. It is generally thought that staged intercalation occurs through a Daumas-Herold or a Rudorff model. We find, on average, greater diffusion coefficients for DNA strands in a Daumas-Herold configuration compared to a Rudorff model and a stage-1 structure. Our simulations provide evidence for the presence of peristaltic modes of motion within Daumas-Herold configurations. This is confirmed by spectral analysis of the thickness variation of the basal spacing. Peristaltic modes are more prominent in the Daumas-Herold structure compared to the Rudorff and stage-1 structures and support a mechanism by means of which bulky intercalated molecules such as DNA rapidly diffuse within an LDH interlayer.     

Observation of the ground-state geometric phase in a Heisenberg XY model

Geometric phases play a central role in a variety of quantum phenomena, especially in condensed matter physics. Recently, it was shown that this fundamental concept exhibits a connection to quantum phase transitions where the system undergoes a qualitative change in the ground state when a control parameter in its Hamiltonian is varied. Here we report the first experimental study using the geometric phase as a topological test of quantum transitions of the ground state in a Heisenberg XY spin model. Using NMR interferometry, we measure the geometric phase for different adiabatic circuits that do not pass through points of degeneracy.     

Suppression of stimulated brillouin scattering by increased landau damping in multiple-ion-species hohlraum plasmas

We demonstrate that multiple-ion-species plasmas greatly reduce stimulated Brillouin scattering (SBS) in high-electron temperature inertial confinement fusion hohlraums. Landau damping is increased by adding hydrogen to a CO(2) gas filled hohlraum. We find that the SBS reflectivity decreases monotonically with increasing hydrogen fraction from 18% to 3% with a simultaneous increase of laser beam transmission. Detailed simulations with a 3D laser-plasma interaction code are in agreement with the experimentally observed reduction in backscattered light.