Constraints on Supersymmetric Dark Matter for Heavy Scalar Superpartners

We study the constraints on neutralino dark matter in minimal low energy supersymmetry models and the case of heavy lepton and quark scalar superpartners. For values of the Higgsino and gaugino mass parameters of the order of the weak scale, direct detection experiments are already putting strong bounds on models in which the dominant interactions between the dark matter candidates and nuclei are governed by Higgs boson exchange processes, particularly for positive values of the Higgsino mass parameter mu. For negative values of mu, there can be destructive interference between the amplitudes associated with the exchange of the standard CP-even Higgs boson and the exchange of the non-standard one. This leads to specific regions of parameter space which are consistent with the current experimental constraints and a thermal origin of the observed relic density. In this article we study the current experimental constraints on these scenarios, as well as the future experimental probes, using a combination of direct and indirect dark matter detection and heavy Higgs and electroweakino searches at hadron colliders.Comment: 32 pages, 13 figure

Polarisation properties of Milky-Way-like galaxies

(Abridged) We study the polarisation properties, magnetic field strength, and synchrotron emission scale-height of Milky-Way-like galaxies in comparison with other spiral galaxies. We use our 3D-emission model of the Milky Way Galaxy for viewing the Milky Way from outside at various inclinations as spiral galaxies are observed. When seen edge-on the synchrotron emission from the Milky Way has an exponential scale-height of about 0.74 kpc, which is much smaller than the values obtained from previous models. We find that current analysis methods overestimate the scale-height of synchrotron emission of galaxies by about 10% at an inclination of 80 degree and about 40% at an inclination of 70 degree because of contamination from the disk. The observed RMs for face-on galaxies derived from high-frequency polarisation measurements approximate to the Faraday depths (FDs) when scaled by a factor of two. For edge-on galaxies, the observed RMs are indicative of the orientation of the large-scale magnetic field, but are not well related with the FDs. Assuming energy equipartition between the magnetic field and particles for the Milky Way results in an average magnetic-field strength, which is about two times larger than the intrinsic value for a K factor of 100. The number distribution of the integrated polarisation percentages of a large sample of unresolved Milky-Way-like galaxies peaks at about 4.2% at 4.8 GHz and at about 0.8% at 1.4GHz. Integrated polarisation angles rotated by 90 degree align very well with the position angles of the major axes, implying that unresolved galaxies do not have intrinsic RMs.Comment: 10 pages, 11 figures, accepted for publication in A&

Biogeochemical cycling of polybrominated diphenyl ethers (PBDEs) in the Strait of Georgia

The temporal and spatial distribution of dissolved and particulate PBDEs seawater concentration has been monitored in the Strait of Georgia (SoG) since 2013. We aim to determine the sources, sinks and biogeochemical cycling of PBDE congeners in the water column in SoG. Particulate PBDEs concentrations show high temporal and spatial variability, indicating that the outfalls from the waste water treatment plants are major point sources. Changes in congener distributions in relation to total particulate PBDE concentrations suggest that the less brominated congeners desorb from sewage particles and add to the dissolved PBDEs pool more rapidly than the more brominated congeners. We also measured very low particulate PBDE concentrations during phytoplankton blooms, which suggest slow kinetics of adsorption or uptake of dissolved PBDEs by phytoplankton. In contrast, the concentrations of dissolved PBDEs in the SoG are more uniform and indicate that the outfalls from waste water treatment plants are not major direct point sources. Other potential sources include atmospheric deposition and desorption from effluent particles after their dispersion. A depth profile of dissolved PBDEs shows higher concentrations of the BDE-47, 99 and 153 at the surface, indicating contributions from the atmosphere or from the Fraser River. However, their highest concentrations were found at, or above, the buoyancy depth of the outfall plume from the Iona Waste Water Treatment Plant. Results obtained to date suggest a differential partitioning of PBDE congeners after their discharge from waste water treatment plants. Less brominated congeners are preferentially desorbed from sewage particles and are preferentially transported towards the surface by the estuarine circulation of the SoG, while the more brominated congeners predominantly remain associated with particles and accumulate on the seafloor. This working hypothesis will be further tested by measuring the kinetics of adsorption/desorption of PBDEs on phytoplankton and sewage particles using C-14 labelled PBDE congeners

Room-temperature air-stable spin transport in bathocuproine-based spin valves

Organic semiconductors, characterized by weak spin-scattering mechanisms, are attractive materials for those spintronic applications in which the spin information needs to be retained for long times. Prototypical spin-valve devices employing organic interlayers sandwiched between ferromagnetic materials possess a figure of merit (magnetoresistance (MR)) comparable to their fully inorganic counterparts. However, these results are a matter of debate as the conductivity of the devices does not show the expected temperature dependence. Here we show spin valves with an interlayer of bathocuproine in which the transport takes place unambiguously through the organic layer and where the electron spin coherence is maintained over large distances (>60 nm) at room temperature. Additionally, the devices show excellent air stability, with MR values almost unaltered after 70 days of storage under ambient conditions, making bathocuproine an interesting material for future spintronic applications.Fil: Sun, Xiangnan. CIC nanoGUNE; EspañaFil: Gobbi, Marco. Université de Strasbourg; Francia. CIC nanoGUNE; EspañaFil: Bedoya Pinto, Amilcar. CIC nanoGUNE; EspañaFil: Txoperena, Oihana. CIC nanoGUNE; EspañaFil: Golmar, Federico. CIC nanoGUNE; España. Instituto Nacional de Tecnología Industrial; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Llopis, Roger. CIC nanoGUNE; EspañaFil: Chuvilin, Andrey. CIC nanoGUNE; España. Fundación Vasca para la Ciencia; EspañaFil: Casanova, Félix. CIC nanoGUNE; España. Fundación Vasca para la Ciencia; EspañaFil: Hueso, Luis E.. CIC nanoGUNE; España. Fundación Vasca para la Ciencia; Españ

Response of Stomatal Density and Bound Gas Exchange in Leaves of Maize to Soil Water Deficit

Stomatal behavior in response to drought has been the focus of intensive research, but less attention has been paid to stomatal density. In this study, 5-week-old maize seedlings were exposed to different soil water contents. Stomatal density and size as well as leaf gas exchange were investigated after 2-, 4- and 6-weeks of treatment, which corresponded to the jointing, trumpeting, and filling stages of maize development. Results showed that new stomata were generated continually during leaf growth. Reduced soil water content significantly stimulated stomatal generation, resulting in a significant increase in stomatal density but a decrease in stomatal size and aperture. Independent of soil water conditions, stomatal density and length in the trumpeting and filling stages were greater than in the jointing stage. Irrespective of growth stage, severe water deficit significantly reduced stomatal conductance (Gs), decreasing the leaf transpiration rate (Tr) and net photosynthetic rate (Pn). Stomatal density was significantly negatively correlated with both Pn and Tr but more strongly with Tr, so the leaf instantaneous water use efficiency (WUEi) correlated positively with stomatal density. In conclusion, drought led to a significant increase in stomatal density and a reduction in stomatal size and aperture, resulting in decreased Pn and Tr. Because the negative correlation of stomatal density to Tr was stronger than that to Pn, leaf WUEi tended to increase