Photoluminescence of near-lattice-matched GaN/AlInN quantum wells grown on free-standing GaN and on sapphire substrates

Near-lattice-matched GaN/Al1−xInxN single quantum wells, grown using both free-standing GaN and conventional GaN-on-sapphire substrates, are studied by photoluminescence (PL) and PL excitation spectroscopies. PL spectra distinguish luminescence originating in the wells, barriers, and underlying GaN buffer layers. The spectra also reveal significant differences between structures grown simultaneously on the different substrates. The quantum well transition energy decreases as the well width increases due to the intense in-built electric fields, estimated to be 3.0±0.5 MeV/cm, that persist in strain free GaN/Al1−xInxN. Screening of these fields is studied using the excitation power dependence of the P

Syllinae (Syllidae: polychaeta) from the Mediterranean coast of Egypt with the description of two new species

This is the second paper dealing with the Syllidae collected on soft and hard bottom from the north-western coast of Egypt (Mediterranean Sea) and southern part of the Suez Canal. Eleven species were reported, two of them seem to be new to science, (Syllis sp.1 and Syllissp.2), but need further examination. Six species namely Opisthosyllis brunnea, Syllis columbretensis, Syllis gerlachi, Syllis ergeni, Syllis pulvinata andTrypanosyllis coeliaca were recorded as new for Egyptian waters

Felix Alexandrovich Berezin and his work

This is a survey of Berezin's work focused on three topics: representation theory, general concept of quantization, and supermathematics.Comment: LaTeX, 27 page

Lithium motion in the anode material LiC6 as seen via time-domain 7Li NMR

Since the commercialization of rechargeable lithium-ion energy storage systems in the early 1990s, graphite intercalation compounds (GICs) have served as the number one negative electrode material in most of today's batteries. During charging the performance of a battery is closely tied with facile Li insertion into the graphite host structure. So far, only occasionally time-domain nuclear magnetic resonance (NMR) measurements have been reported to study Li self-diffusion parameters in GICs. Here, we used several NMR techniques to enlighten Li hopping motions from an atomic-scale point of view. Li self-diffusion in the stage-1 GIC LiC6 has been studied comparatively by temperature-variable spin-spin relaxation NMR as well as (rotating frame) spin-lattice relaxation NMR. The data collected yield information on both the relevant activation energies and jump rates, which can directly be transformed into Li self-diffusion coefficients. At room temperature the Li self-diffusion coefficient turns out to be 10−15m2s−1, thus, slightly lower than that for layer-structured cathode materials such as Lix≈0.7TiS2. © 2013 American Physical Society

Charge asymmetry in W + jets production at the LHC

The charge asymmetry in W + jets production at the LHC can serve to calibrate the presence of New Physics contributions. We study the ratio {\sigma}(W^+ + n jets)/{\sigma}(W^- + n jets) in the Standard Model for n <= 4, paying particular attention to the uncertainty in the prediction from higher-order perturbative corrections and uncertainties in parton distribution functions. We show that these uncertainties are generally of order a few percent, making the experimental measurement of the charge asymmetry ratio a particularly useful diagnostic tool for New Physics contributions.Comment: 13 pages, 7 figures. Reference added. Slightly modified tex

100 Gbit/s real-time all-analogue filter bank OFDM based on a gain-switched optical comb

A real-time 5×21.6 Gbit/s WDM electro-optical transceiver is presented. Optical carriers were spaced by 20 GHz and each one transmitted four orthogonally overlapping broadband subcarriers. Only analogue electronics were employed, achieving an unprecedented spectral efficiency in DSP-less SCM links

Two-loop scalar self-energies in a general renormalizable theory at leading order in gauge couplings

I present results for the two-loop self-energy functions for scalars in a general renormalizable field theory, using mass-independent renormalization schemes based on dimensional regularization and dimensional reduction. The results are given in terms of a minimal set of loop-integral basis functions, which are readily evaluated numerically by computers. This paper contains the contributions corresponding to the Feynman diagrams with zero or one vector propagator lines. These are the ones needed to obtain the pole masses of the neutral and charged Higgs scalar bosons in supersymmetry, neglecting only the purely electroweak parts at two-loop order. A subsequent paper will present the results for the remaining diagrams, which involve two or more vector lines.Comment: 26 pages, 4 figures, revtex4, axodraw.sty. Version 2: sentence after eq. (A.13) corrected, references added. Version 3: typos in eqs. (5.17), (5.20), (5.21), (5.32) are corrected. Also, the MSbar versions of eqs. (5.32) and (5.33) are now include

Integral representation of the linear Boltzmann operator for granular gas dynamics with applications

We investigate the properties of the collision operator associated to the linear Boltzmann equation for dissipative hard-spheres arising in granular gas dynamics. We establish that, as in the case of non-dissipative interactions, the gain collision operator is an integral operator whose kernel is made explicit. One deduces from this result a complete picture of the spectrum of the collision operator in an Hilbert space setting, generalizing results from T. Carleman to granular gases. In the same way, we obtain from this integral representation of the gain operator that the semigroup in L^1(\R \times \R,\d \x \otimes \d\v) associated to the linear Boltzmann equation for dissipative hard spheres is honest generalizing known results from the first author.Comment: 19 pages, to appear in Journal of Statistical Physic