Orbital ordering and magnetic structures in \LMFO and \LWFO double perovskites

We analyzed the possible magnetic and orbital orderings of double perovskites, using a simple extension of the double exchange model well suited for these compounds. Orbital ordering is favored by the on site repulsion at the Fe ions. We obtain a rich phase diagram, including ferri- and antiferromagnetic phases, which can, in turn, be metallic or insulating, depending on the existence of orbital order.Comment: 6 page

Strain-induced pseudo-magnetic field for novel graphene electronics

Particular strain geometry in graphene could leads to a uniform pseudo-magnetic field of order 10T and might open up interesting applications in graphene nano-electronics. Through quantum transport calculations of realistic strained graphene flakes of sizes of 100nm, we examine possible means of exploiting this effect for practical electronics and valleytronics devices. First, we found that elastic backscattering at rough edges leads to the formation of well defined transport gaps of order 100meV under moderate maximum strain of 10%. Second, the application of a real magnetic field induced a separation, in space and energy, of the states arising from different valleys, leading to a way of inducing bulk valley polarization which is insensitive to short range scattering.Comment: 5 pages, 5 figure

Guinea pigs sublethally infected with aerosolized Legionella pneumophila develop humoral and cell-mediated immune responses and are protected against lethal aerosol challenge. A model for studying host defense against lung infections caused by intracellular pathogens.

We have employed the guinea pig model of L. pneumophila infection, which mimics Legionnaires' disease in humans both clinically and pathologically, to study humoral and cell-mediated immune responses to L. pneumophila and to examine protective immunity after aerosol exposure, the natural route of infection. Guinea pigs exposed to sublethal concentrations of L. pneumophila by aerosol developed strong humoral immune responses. By the indirect fluorescent antibody assay, exposed guinea pigs had a median serum antibody titer (expressed as the reciprocal of the highest positive dilution) of 32, whereas control guinea pigs had a median titer of less than 1. Sublethally infected (immunized) guinea pigs also developed strong cell-mediated immune responses. In response to L. pneumophila antigens, splenic lymphocytes from immunized but not control animals proliferated strongly in vitro, as measured by their capacity to incorporate [3H]thymidine. Moreover, immunized but not control guinea pigs developed strong cutaneous delayed-type hypersensitivity to intradermally injected L. pneumophila antigens. Sublethally infected (immunized) guinea pigs exhibited strong protective immunity to L. pneumophila. In two independent experiments, all 22 immunized guinea pigs survived aerosol challenge with one or three times the lethal dose of L. pneumophila whereas none of 16 sham-immunized control guinea pigs survived (p less than 0.0001 in each experiment). Immunized guinea pigs were not protected significantly from challenge with 10 times the lethal dose. Immunized but not control animals cleared the bacteria from their lungs. This study demonstrates that guinea pigs sublethally infected with L. pneumophila by the aerosol route develop strong humoral immune responses to this pathogen, develop strong cell-mediated immune responses and cutaneous delayed-type hypersensitivity to L. pneumophila antigens, are protected against subsequent lethal aerosol challenge, and are able to clear the bacteria from their lungs. The guinea pig model of L. pneumophila pulmonary infection is as an excellent one for studying general principles of host defense against pulmonary infections caused by intracellular pathogens

New species of Cydistomyia Taylor with notes and collection records for other Tabanidae (Diptera) from New Guinea

Four new species of Cydistomyia Taylor from New Guinea, C. missimiensis, C. madangiensis, C. waigani, and C. moresbyensis, are described and figured. A revised key to the females of New Guinea Cydistomyia and New Guinea collection records for 57 additional species of Tabanidae are provided. A table with the approximate longitudes and latitudes of all but one locality listed is provided

Investment prospects in marine capture fisheries

An examination is made of investment prospects in the Nigerian marine fisheries, considering the following sectors: inshore demersal fishery; inshore pelagic fishery; and the offshore pelagic fishery. The marine fisheries resources of countries with which Nigeria has bilateral fishing rights agreements are discussed, considering Equatorial Guinea, Guinea Conakry, Guinea Bissau, Senegal and Mauritania. Fishing gear and methods for the marine fishery sectors are outlined. Market potentials for fish products and profitability are also examine

Strains and pseudo-magnetic fields in circular graphene rings

We demonstrate that circular graphene ring under a shear stress displays strong pseudo-magnetic fields. We calculate the pseudo-magnetic field both from continuum elasticity theory as well as molecular dynamics simulations. Stable wrinkles are induced by shear deformations and lead to enhancement of the pseudo-magnetic field. The strong pseudo-magnetic field found here can be observed by imaging graphene flake at the atomic level e.g. through scanning tunneling microscope.Comment: 11 pages, 8 figures. (Appendixes A and B are added) To appear in Phys. Rev.

Temperature dependence of the conductivity of graphene on boron nitride

The substrate material of monolayer graphene influences the charge carrier mobility by various mechanisms. At room temperature, the scattering of conduction electrons by phonon modes localized at the substrate surface can severely limit the charge carrier mobility. We here show that for substrates made of the piezoelectric hexagonal boron nitride (hBN), in comparison to the widely used SiO$_2$, this mechanism of remote phonon scattering is --at room temperature-- weaker by almost an order of magnitude, and causes a resistivity of approximately 3\,$\Omega$. This makes hBN an excellent candidate material for future graphene based electronic devices operating at room temperature.Comment: 6 pages, 4 figures, to appear in Phys. Rev.