Sporadic Bovine Encephalomyelitis

The infectious agent of sporadic bovine encephalomyelitis has now been propagated for nearly three years in developing chick embryos.This has afforded a convenient method of propagation while studying the causal agent. It is interesting that during all of this time in chick embryos, which represents more than 135 passages in series, there has been no apparent variation in the character of the infectious agent. It is as pathogenic for guinea pigs and cattle as when first isolated. Failure to recognize anything in the tissues of affected animals that would indicate the exact nature of the entity which causes the disease, led to an extension of the histological study to infected chick embryos, especially their membranes and yolk sacs

Parasite infections in a social carnivore: Evidence of their fitness consequences and factors modulating infection load

There are substantial individual differences in parasite composition and infection load in wildlife populations. Few studies have investigated the factors shaping this heterogeneity in large wild mammals or the impact of parasite infections on Darwinian fitness, particularly in juveniles. A host's parasite composition and infection load can be shaped by factors that determine contact with infective parasite stages and those that determine the host's resistance to infection, such as abiotic and social environmental factors, and age. Host–parasite interactions and synergies between coinfecting parasites may also be important. We test predictions derived from these different processes to investigate factors shaping infection loads (fecal egg/oocyte load) of two energetically costly gastrointestinal parasites: the hookworm Ancylostoma and the intracellular Cystoisospora, in juvenile spotted hyenas (Crocuta crocuta) in the Serengeti National Park, in Tanzania. We also assess whether parasite infections curtail survival to adulthood and longevity. Ancylostoma and Cystoisospora infection loads declined as the number of adult clan members increased, a result consistent with an encounter‐reduction effect whereby adults reduced encounters between juveniles and infective larvae, but were not affected by the number of juveniles in a clan. Infection loads decreased with age, possibly because active immune responses to infection improved with age. Differences in parasite load between clans possibly indicate variation in abiotic environmental factors between clan den sites. The survival of juveniles (<365 days old) to adulthood decreased with Ancylostoma load, increased with age, and was modulated by maternal social status. High‐ranking individuals with low Ancylostoma loads had a higher survivorship during the first 4 years of life than high‐ranking individuals with high Ancylostoma loads. These findings suggest that high infection loads with energetically costly parasites such as hookworms during early life can have negative fitness consequences

Exchange bias and interface electronic structure in Ni/Co3O4(011)

A detailed study of the exchange bias effect and the interfacial electronic structure in Ni/Co3O4(011) is reported. Large exchange anisotropies are observed at low temperatures, and the exchange bias effect persists to temperatures well above the Neel temperature of bulk Co3O4, of about 40 K: to ~80 K for Ni films deposited on well ordered oxide surfaces, and ~150 K for Ni films deposited on rougher Co3O4 surfaces. Photoelectron spectroscopy measurements as a function of Ni thickness show that Co reduction and Ni oxidation occur over an extended interfacial region. We conclude that the exchange bias observed in Ni/Co3O4, and in similar ferromagnetic metallic/Co3O4 systems, is not intrinsic to Co3O4 but rather due to the formation of CoO at the interface.Comment: 8 pages, 6 figures. Accepted for publication in Physical Review B

Spin Polarization and Magneto-Coulomb Oscillations in Ferromagnetic Single Electron Devices

The magneto-Coulomb oscillation, the single electron repopulation induced by external magnetic field, observed in a ferromagnetic single electron transistor is further examined in various ferromagnetic single electron devices. In case of double- and triple-junction devices made of Ni and Co electrodes, the single electron repopulation always occurs from Ni to Co electrodes with increasing a magnetic field, irrespective of the configurations of the electrodes. The period of the magneto-Coulomb oscillation is proportional to the single electron charging energy. All these features are consistently explained by the mechanism that the Zeeman effect induces changes of the Fermi energy of the ferromagnetic metal having a non-zero spin polarizations. Experimentally determined spin polarizations are negative for both Ni and Co and the magnitude is larger for Ni than Co as expected from band calculations.Comment: 4 pages, 3 figures, uses jpsj.sty, submitted to J. Phys. Soc. Jp

Future Evolution of Greenland\u27s Marine-Terminating Outlet Glaciers

Mass loss from the Greenland ice sheet (GrIS) has increased over the last two decades in response to changes in global climate, motivating the scientific community to question how the GrIS will contribute to sea-level rise on timescales that are relevant to coastal communities. Observations also indicate that the impact of a melting GrIS extends beyond sea-level rise, including changes to ocean properties and circulation, nutrient and sediment cycling, and ecosystem function. Unfortunately, despite the rapid growth of interest in GrIS mass loss and its impacts, we still lack the ability to confidently predict the rate of future mass loss and the full impacts of this mass loss on the globe. Uncertainty in GrIS mass loss projections in part stems from the nonlinear response of the ice sheet to climate forcing, with many processes at play that influence how mass is lost. This is particularly true for outlet glaciers in Greenland that terminate in the ocean because their flow is strongly controlled by multiple processes that alter their boundary conditions at the ice-atmosphere, ice-ocean, and ice-bed interfaces. Many of these processes change on a range of overlapping timescales and are challenging to observe, making them difficult to understand and thus missing in prognostic ice sheet/climate models. For example, recent (beginning in the late 1990s) mass loss via outlet glaciers has been attributed primarily to changing ice-ocean interactions, driven by both oceanic and atmospheric warming, but the exact mechanisms controlling the onset of glacier retreat and the processes that regulate the amount of retreat remain uncertain. Here we review the progress in understanding GrIS outlet glacier sensitivity to climate change, how mass loss has changed over time, and how our understanding has evolved as observational capacity expanded. Although many processes are far better understood than they were even a decade ago, fundamental gaps in our understanding of certain processes remain. These gaps impede our ability to understand past changes in dynamics and to make more accurate mass loss projections under future climate change. As such, there is a pressing need for (1) improved, long-term observations at the ice-ocean and ice-bed boundaries, (2) more observationally constrained numerical ice flow models that are coupled to atmosphere and ocean models, and (3) continued development of a collaborative and interdisciplinary scientific community

Magneto-Coulomb Oscillation in Ferromagnetic Single Electron Transistors

The mechanism of the magneto-Coulomb oscillation in ferromagnetic single electron transistors (SET's) is theoretically considered. Variations in the chemical potentials of the conduction electrons in the ferromagnetic island electrode and the ferromagnetic lead electrodes in magnetic fields cause changes in the free energy of the island electrode of the SET. Experimental results of the magneto-Coulomb oscillation in a Ni/Co/Ni ferromagnetic SET are presented and discussed. Possible applications of this phenomenon are also discussed.Comment: 24 pages Latex, 5 figures in GIF files, style files included. Revised version: some errors are corrected and further discussions are added. To be published in J. Phys. Soc. Jpn. Vol.67 (1998) No.

Micro-fading spectrometry: investigating the wavelength specificity of fading

A modified microfading spectrometer incorporating a linear variable filter is used to investigate the wavelength dependence of fading of traditional watercolour pigments, dosimeters and fading standards at a higher spectral resolution and/or sampling than had previously been attempted. While the wavelength dependence of photochemical damage was largely found to correlate well with the absorption spectra of each material, exceptions were found in the case of Prussian blue and Prussian green pigments (the latter includes Prussian blue), for which an anti-correlation between the spectral colour change and the absorption spectrum was found

Direct observation of a highly spin-polarized organic spinterface at room temperature

The design of large-scale electronic circuits that are entirely spintronics-driven requires a current source that is highly spin-polarised at and beyond room temperature, cheap to build, efficient at the nanoscale and straightforward to integrate with semiconductors. Yet despite research within several subfields spanning nearly two decades, this key building block is still lacking. We experimentally and theoretically show how the interface between Co and phthalocyanine molecules constitutes a promising candidate. Spin-polarised direct and inverse photoemission experiments reveal a high degree of spin polarisation at room temperature at this interface. We measured a magnetic moment on the molecules's nitrogen pi orbitals, which substantiates an ab-initio theoretical description of highly spin-polarised charge conduction across the interface due to differing spinterface formation mechanims in each spin channel. We propose, through this example, a recipe to engineer simple organic-inorganic interfaces with remarkable spintronic properties that can endure well above room temperature

An asymptotic form of the reciprocity theorem with applications in x-ray scattering

The emission of electromagnetic waves from a source within or near a non-trivial medium (with or without boundaries, crystalline or amorphous, with inhomogeneities, absorption and so on) is sometimes studied using the reciprocity principle. This is a variation of the method of Green's functions. If one is only interested in the asymptotic radiation fields the generality of these methods may actually be a shortcoming: obtaining expressions valid for the uninteresting near fields is not just a wasted effort but may be prohibitively difficult. In this work we obtain a modified form the reciprocity principle which gives the asymptotic radiation field directly. The method may be used to obtain the radiation from a prescribed source, and also to study scattering problems. To illustrate the power of the method we study a few pedagogical examples and then, as a more challenging application we tackle two related problems. We calculate the specular reflection of x rays by a rough surface and by a smoothly graded surface taking polarization effects into account. In conventional treatments of reflection x rays are treated as scalar waves, polarization effects are neglected. This is a good approximation at grazing incidence but becomes increasingly questionable for soft x rays and UV at higher incidence angles. PACs: 61.10.Dp, 61.10.Kw, 03.50.DeComment: 19 pages, 4 figure