Z boson decay to photon plus Kaluza-Klein graviton in large extra dimensions

In the large extra dimensional ADD scenario, Z bosons undergo a one-loop decay into a photon and Kaluza-Klein towers of gravitons/gravi-scalars. We calculate such a decay width, extending previous arguments about the general form of the four-dimensional on-shell amplitude. The amplitudes calculated are relevant to processes in other extra dimensional models where the Standard Model fields are confined to a 4-brane.Comment: 47 pages, uses feynmp for diagrams. v2: typographical corrections for letter-sized paper and to correct feynmf parsing error. v3: minor error in polarisation averaging and reference corrected. v4: reflects changes for published version; arithmetic error corrected and reference updated; section on transversality conditions not present in published version retaine

Etat des connaissances sur la pisciculture en Cote d'Ivoire

La pisciculture a été amorcée en Côte d’Ivoire en 1955. Cependant, la production de l’aquaculture demeure faible. Une enquête a été réalisée sur le profil socio-économique des promoteurs, l’activité piscicole et la production des fermes. Il ressort de cette enquête que la pisciculture en Côte d’Ivoire est pratiquée sur presque toute l’étendue du territoire ivoirien. La majorité des fermes (65,4 %) ont une superficie en eau exploitée inférieure à un hectare. La durée d’existence est inférieure à 10 ans pour 53,8 % des fermes. Les pisciculteurs sont majoritairement des agriculteurs (60,8 %), ivoiriens (87,4 %) de sexe masculin (94,0 %) âgés de plus de 40 ans (83,7 %). Les systèmes d’élevage les plus pratiqués sont le semi-intensif (51,8 %) et l’extensif (42,9 %). Le tilapia Oreochromis niloticus (96,68 % ) et l’hétérotis  Heterotis niloticus (56,81 %) sont les espèces de poissons les plus élevées. Les étangs de dérivation (93,69 %) et les étangs de barrages (47,84 %) sont les principales structures d’élevage. Les aliments utilisés seul ou en association sont les aliments commerciaux (27,57 %), produits par les pisciculteurs eux-mêmes (17,94 %), les sous-produits agroalimentaires (71,10 %) et les aliments non conventionnels (22,26 %). Le développement de la pisciculture en Côte d’Ivoire devrait passer par la promotion de la pisciculture intensive et semi-intensive auprès des salariés et des opérateurs économiques nationaux et internationaux.Mots clés : Pisciculture, pratique, région, production, Côte d’Ivoir

Magnetization reversal and magnetic anisotropy in Co network nanostructures

The magnetization reversal and magnetic anisotropy in Co network structures have been studied using magneto-optic Kerr effect (MOKE). An enhancement of the coercivity is observed in the network structures and is attributed to the pinning of domain walls by the hole edges in the vicinity of which the demagnetizing field spatially varies. We find that the magnetization reversal process is dominated by the intrinsic unaxial anisotropy (2K(u)/M(s)approximate to 200 Oe) in spite of the shape anisotropy induced by the hole edges. The influence of the cross-junction on the competition between the intrinsic uniaxial anisotropy and the induced shape anisotropy is discussed using micromagnetic simulations

Evaluation of the risk of contamination by pesticides

Pesticides have the particularity of accumulating mainly in aquatic  ecosystems. The concentration of pesticides in such contaminated  ecosystems appears to be a potential health risk resulting from the human consumption of fish from these ecosystems. The aim of this study is to determine the pesticide residue levels of Chrysichthys nigrodigitatus and Tilapia zilli × Tilapia guinensis. 120 samples of each species, distributed from 96 samples for sector IV and 24 samples for sector V, were collected from February 2014 to January 2015. These were analyzed by gas chromatography coupled to a spectrometer of mass (GC / MS), after extraction and purification respectively by accelerated solvent extraction (ASE) and by adsorption chromatography on Oasis HLB Plus cartridges. Pesticide concentrations detected in fish muscle ranged from 0 to 40.66 ìg / kg in the study area. All values found for the health risk index (HI) in Chrysichthys nigrodigitatus and Tilapia hybrid muscles are well below 1 (HI < 1). Pesticide residues detected in both fish species do not pose a potential risk to human health.Keywords: Contamination, pesticides, Chrysichthys nigrodigitatus, Tilapia, risk. French Title: Evaluation du risque de contamination par les pesticidesLes pesticides ont la particularité de s’accumuler principalement dans les écosystèmes aquatiques. La concentration de pesticides dans de tels écosystèmes contaminés apparaît comme un risque potentiel pour la santé résultant de la consommation humaine de poissons de ces écosystèmes. Cette étude a pour objectif de déterminer la concentration de résidus de pesticides chez Chrysichthys nigrodigitatus et Tilapia zilli × Tilapia guinensis. 120 échantillons de chaque espèce, repartis en raison de 96 échantillons pour le secteur IV et 24 échantillons pour le secteur V, ont été collectés de février 2014 à janvier 2015. Ceux-ci ont été analysés par chromatographie en phase gazeuse couplée à un spectromètre de masse (GC / MS), après Extraction et purification respectivement par ExtractionAccélérée par Solvant (ASE) et par chromatographie d’adsorption sur cartouches Oasis HLB Plus. Les concentrations de pesticides quantifiés et non détectés dans les muscles des poissons variaient entre 0 et 40,66 ìg/kg dans la zone d’étude. Toutes les valeurs trouvées pour l’indice de risque pour la santé (HI) dans les muscles de Chrysichthys nigrodigitatus et de Tilapia hybride sont nettement inférieures à 1 (HI <1). Les résidus de pesticides détectés chez les deux espèces de poisson ne présentent pasde risque potentiel pour la santé humaine.Mots-clés : Contaminations, pesticides, Chrysichthys nigrodigitatus, Tilapia, risque

Contact-induced spin polarization in carbon nanotubes

Motivated by the possibility of combining spintronics with molecular structures, we investigate the conditions for the appearance of spin-polarization in low-dimensional tubular systems by contacting them to a magnetic substrate. We derive a set of general expressions describing the charge transfer between the tube and the substrate and the relative energy costs. The mean-field solution of the general expressions provides an insightful formula for the induced spin-polarization. Using a tight-binding model for the electronic structure we are able to estimate the magnitude and the stability of the induced moment. This indicates that a significant magnetic moment in carbon nanotubes can be observed.Comment: To appear in Phys. Rev. B (2003

Large Thermoelectric Power Factor in TiS2 Crystal with Nearly Stoichiometric Composition

A TiS$_{2}$ crystal with a layered structure was found to have a large thermoelectric power factor.The in-plane power factor $S^{2}/ \rho$ at 300 K is 37.1~$\mu$W/K$^{2}$cm with resistivity ($\rho$) of 1.7 m$\Omega$cm and thermopower ($S$) of -251~$\mu$V/K, and this value is comparable to that of the best thermoelectric material, Bi$_{2}$Te$_{3}$ alloy. The electrical resistivity shows both metallic and highly anisotropic behaviors, suggesting that the electronic structure of this TiS$_{2}$ crystal has a quasi-two-dimensional nature. The large thermoelectric response can be ascribed to the large density of state just above the Fermi energy and inter-valley scattering. In spite of the large power factor, the figure of merit, $ZT$ of TiS$_{2}$ is 0.16 at 300 K, because of relatively large thermal conductivity, 68~mW/Kcm. However, most of this value comes from reducible lattice contribution. Thus, $ZT$ can be improved by reducing lattice thermal conductivity, e.g., by introducing a rattling unit into the inter-layer sites.Comment: 11 pages, 4 figures, to be published in Physical Review

Wedgebox analysis of four-lepton events from neutralino pair production at the LHC

`Wedgebox' plots constructed by plotting the di-electron invariant mass versus the di-muon invariant mass from pp -> e^+e^- mu^+ mu^- + missing energy signature LHC events. Data sets of such events are obtained across the MSSM input parameter space in event-generator simulations, including cuts designed to remove SM backgrounds. Their study reveals several general features: (1)Regions in the MSSM input parameter space where a sufficient number of events are expected so as to be able to construct a clear wedgebox plot are delineated. (2)The presence of box shapes on a wedgebox plot either indicates the presence of heavy Higgs bosons decays or restricts the location to a quite small region of low \mu and M_2 values \lsim 200 GeV, a region denoted as the `lower island'. In this region, wedgebox plots can be quite complicated and change in pattern rather quickly as one moves around in the (\mu, M_2) plane. (3)Direct neutralino pair production from an intermediate Z^{0*} may only produce a wedge-shape since only \widetilde{\chi}_2^0\widetilde{\chi}_3^0 decays can contribute significantly. (4)A double-wedge or wedge-protruding-from-a-box pattern on a wedgebox plot, which results from combining a variety of MSSM production processes, yields three distinct observed endpoints, almost always attributable to \widetilde{\chi}_{2,3,4}^0 \to \widetilde{\chi}_1^0 \ell^+\ell^- decays, which can be utilized to determine a great deal of information about the neutralino and slepton mass spectra and related MSSM input parameters. Wedge and double-wedge patterns are seen in wedgebox plots in another region of higher \mu and M_2 values, denoted as the`upper island.' Here the pattern is simpler and more stable as one moves across the (\mu, M_2) input parameter space.Comment: 28 pages (LaTeX), 8 figures (encapsulated postscript

Sparticle Spectra and LHC Signatures for Large Volume String Compactifications

We study the supersymmetric particle spectra and LHC collider observables for the large-volume string models with a fundamental scale of 10^{11} GeV that arise in moduli-fixed string compactifications with branes and fluxes. The presence of magnetic fluxes on the brane world volume, required for chirality, perturb the soft terms away from those previously computed in the dilute-flux limit. We use the difference in high-scale gauge couplings to estimate the magnitude of this perturbation and study the potential effects of the magnetic fluxes by generating many random spectra with the soft terms perturbed around the dilute flux limit. Even with a 40% variation in the high-scale soft terms the low-energy spectra take a clear and predictive form. The resulting spectra are broadly similar to those arising on the SPS1a slope, but more degenerate. In their minimal version the models predict the ratios of gaugino masses to be M_1 : M_2 : M_3=(1.5 - 2) : 2 : 6, different to both mSUGRA and mirage mediation. Among the scalars, the squarks tend to be lighter and the sleptons heavier than for comparable mSUGRA models. We generate 10 fb^{-1} of sample LHC data for the random spectra in order to study the range of collider phenomenology that can occur. We perform a detailed mass reconstruction on one example large-volume string model spectrum. 100 fb^{-1} of integrated luminosity is sufficient to discriminate the model from mSUGRA and aspects of the sparticle spectrum can be accurately reconstructed.Comment: 42 pages, 21 figures. Added references and discussion for section 3. Slight changes in the tex

Looking for magnetic monopoles at LHC with diphoton events

Magnetic monopoles have been a subject of interest since Dirac established the relation between the existence of monopoles and charge quantization. The intense experimental search carried thus far has not met with success. The Large Hadron Collider is reaching energies never achieved before allowing the search for exotic particles in the TeV mass range. In a continuing effort to discover these rare particles we propose here other ways to detect them. We study the observability of monopoles and monopolium, a monopole-antimonopole bound state, at the Large Hadron Collider in the $\gamma \gamma$ channel for monopole masses in the range 500-1000 GeV. We conclude that LHC is an ideal machine to discover monopoles with masses below 1 TeV at present running energies and with 5 fb$^{-1}$ of integrated luminosity.Comment: This manuscript contains information appeared in Looking for magnetic monopoles at LHC, arXiv:1104.0218 [hep-ph] and Monopolium detection at the LHC.,arXiv:1107.3684 [hep-ph] by the same authors, rewritten for joint publication in The European Physica Journal Plus. 26 pages, 22 figure

A geological and geophysical context for the Wenchuan earthquake of 12 May 2008, Sichuan, People's Republic of China

On 12 May 2008, a magnitude 7.9 earthquake ruptured the Longmen Shan margin of the eastern Tibetan plateau. This event occurred within the context of long-term uplift and eastward enlargement of the plateau. The area has numerous geological features not typical of active convergent mountain belts, including the presence of a steep mountain front (>4 km relief) but an absence of large-magnitude low-angle thrust faults; young high topography (post ca. 15 Ma) and thickened crust but low global positioning system (GPS) shortening rates (<3 mm/yr); and no coeval foreland subsidence. In our interpretation, crustal thickening beneath the eastern Tibetan plateau occurred without large-scale shortening of the upper crust but instead is caused by ductile thickening of the deep crust in a weak (low-viscosity) layer. Late Cenozoic shortening across the Longmen Shan could be as little as 10-20 km, with folding and faulting mainly accommodating differential surface uplift between the plateau and the Sichuan Basin. The earthquake of 12 May probably reflects long-term uplift with slow convergence and right-slip, of the eastern plateau relative to the Sichuan Basin. GPS-determined rates in the vicinity of the 12 May event suggest an average recurrence interval of ∼2,000-10,000 yr