17,456 research outputs found

    Ionosphere/microwave beam interaction study

    Get PDF
    A solar power satellite microwave power density of 20mw sq cm was confirmed as the level where nonlinear interactions may occur in the ionosphere, particularly at 100 km altitude. Radio wave heating at this altitude, produced at the Arecibo Observatory, yielded negative results for radio wave heating of an underdense ionosphere. Overdense heating produced striations in the ionosphere which may cause severe radio frequency interference problems under certain conditions. The effects of thermal self-focusing are shown to be limited severely geographically. The aspect sensitivity of field-aligned striations makes interference-free regions above magnetic latitude about 60 deg. A test program is proposed to simulate the interaction of the SPS beam with the ionosphere, to measure the effects of the interaction on the ionosphere and on communication and navigation systems, and to interpret the results

    History of Montgomery County, Kansas: By Its Own People

    Get PDF
    An excerpt from the History of Montgomery County, Kansas: By Its Own People called Caney and Elk City (pages 136-145), written by Caney Valley lawyer J. R. Charlton. Also included is a news article describing his life.https://digitalcommons.pittstate.edu/caney_books/1019/thumbnail.jp

    History of Montgomery County, Kansas: By Its Own People, 1903

    Get PDF
    An excerpt from the History of Montgomery County, Kansas: By Its Own People called Caney and Elk City (pages 136-145), written by Caney Valley lawyer J. R. Charlton. Also included is a 2002 news article describing his life. The book excerpt is in the public domain although the newspaper clipping is not.https://digitalcommons.pittstate.edu/caney_books/1007/thumbnail.jp

    When can gravitational-wave observations distinguish between black holes and neutron stars?

    Get PDF
    Gravitational-wave observations of compact binaries have the potential to uncover the distribution of masses and angular momenta of black holes and neutron stars in the universe. The binary components' physical parameters can be inferred from their effect on the phasing of the gravitational-wave signal, but a partial degeneracy between the components' mass ratio and their angular momenta limits our ability to measure the individual component masses. At the typical signal amplitudes expected by the Advanced Laser Interferometer Gravitational-wave Observatory (signal-to-noise ratios between 10 and 20), we show that it will in many cases be difficult to distinguish whether the components are neutron stars or black holes. We identify when the masses of the binary components could be unambiguously measured outside the range of current observations: a system with a chirp mass M0.871\mathcal{M} \le 0.871 M_\odot would unambiguously contain the smallest-mass neutron star observed, and a system with \mathcal{M} \ge 2.786 \Msun must contain a black hole. However, additional information would be needed to distinguish between a binary containing two 1.35 M_\odot neutron stars and an exotic neutron-star--black-hole binary. We also identify those configurations that could be unambiguously identified as black-hole binaries, and show how the observation of an electromagnetic counterpart to a neutron-star--black-hole binary could be used to constrain the black-hole spin.Comment: 5 pages, 4 figures. Final version to be published in Ap.J.Let

    Laser spot welding of laser textured steel to aluminium

    Get PDF
    Laser welding of dissimilar metals (steel and aluminium) was investigated with the aim to increase the maximum tensile shear load of the Fe-Al joints. The increase was achieved by texturing the surface of steel prior to the laser spot welding process which was performed in a lap-joint configuration with the steel positioned on top of the aluminium and with a texture faced down to the aluminium surface. This configuration enabled an increase of the bonding area of the joints, because the molten aluminium filled in the gaps of the texture, without the need of increasing the process energy which typically leads to the growth of the intermetallic compounds. Different textures (containing hexagonally arranged craters, parallel lines, grid and spiral patterns) were tested with different laser welding parameters. The Fe-Al joints obtained with the textured steel were found to have up to 25% higher maximum tensile-shear load than the joints obtained with the untextured steel

    Executive function in first-episode schizophrenia

    Get PDF
    BACKGROUND: We tested the hypothesis that schizophrenia is primarily a frontostriatal disorder by examining executive function in first-episode patients. Previous studies have shown either equal decrements in many cognitive domains or specific deficits in memory. Such studies have grouped test results or have used few executive measures, thus, possibly losing information. We, therefore, measured a range of executive ability with tests known to be sensitive to frontal lobe function. METHODS: Thirty first-episode schizophrenic patients and 30 normal volunteers, matched for age and NART IQ, were tested on computerized test of planning, spatial working memory and attentional set shifting from the Cambridge Automated Neuropsychological Test Battery. Computerized and traditional tests of memory were also administered for comparison. RESULTS: Patients were worse on all tests but the profile was non-uniform. A componential analysis indicated that the patients were characterized by a poor ability to think ahead and organize responses but an intact ability to switch attention and inhibit prepotent responses. Patients also demonstrated poor memory, especially for free recall of a story and associate learning of unrelated word pairs. CONCLUSIONS: In contradistinction to previous studies, schizophrenic patients do have profound executive impairments at the beginning of the illness. However, these concern planning and strategy use rather than attentional set shifting, which is generally unimpaired. Previous findings in more chronic patients, of severe attentional set shifting impairment, suggest that executive cognitive deficits are progressive during the course of schizophrenia. The finding of severe mnemonic impairment at first episode suggests that cognitive deficits are not restricted to one cognitive domain

    AN ECONOMIC ANALYSIS OF THE NORTH DAKOTA CATTLE INDUSTRY

    Get PDF
    The analysis was conducted to evaluate the impacts of both the Federal Agricultural Improvement and Reform Act of 1996 (FAIR) and the cattle cycle on the livestock enterprises. The North Dakota Representative Farm and Ranch Model, which uses the Food and Agricultural Policy Research Institute price projections as an input, was developed and used for this analysis. Net farm income and farm debt-to-asset ratios for the average and large beef cattle farms were analyzed. The U.S. cattle industry has been characterized by cyclical variations in production and prices. It appears that the current cattle cycle is in the final stages of expansion. Cattle numbers continued to increase during 1995, but at a slow rate. Industry estimates are that the bottom of cattle prices will occur in late 1996 or 1997. Price recovery is projected to start sometime in 1998 as inventory numbers decline. Prices are forecast to rise through 2002. Net farm income for the representative beef cattle farms is projected to follow the cattle cycle with the lowest net incomes during 1997- 1999. Net farm income for most representative beef cattle farms recovers by 2002-2003. The debt-to-asset ratios for the representative beef cattle farms will likely rise throughout the forecast period. FAPRI Note: Figures are not included in the machine readable copy--contact the authors for more information.livestock, representative farms, cattle cycle, Production Economics,

    A photoelectron diffraction investigation of vanadyl phthalocyanine on Au(1 1 1)

    Get PDF
    Scanned-energy mode photoelectron diffraction using the O 1s and V 2p emission perpendicular to the surface has been used to investigate the orientation and internal conformation of vanadyl phthalocyanine (VOPc) adsorbed on Au(1 1 1). The results confirm earlier indications from scanning tunnelling microscopy that the Vdouble bond; length as m-dashO vanadyl bond points out of, and not into, the surface. The Vdouble bond; length as m-dashO bondlength is 1.60 ± 0.04 Å, not significantly different from its value in bulk crystalline VOPc. However, the V atom in the adsorbed molecule is almost coplanar with the surrounding N atoms and is thus pulled down into the approximately planar region defined by the N and C atoms by 0.52 (+0.14/−0.10) Å, relative to its location in crystalline VOPc. This change must be attributed to the bonding interaction between the molecule and the underlying metal surface

    Environmental pollutants from the Scott and Shackleton expeditions during the ‘Heroic Age’ of Antarctic exploration

    Get PDF
    Early explorers to Antarctica built wooden huts and brought huge quantities of supplies and equipment to support their geographical and scientific studies for several years. When the expeditions ended and relief ships arrived, a rapid exodus frequently allowed only essential items to be taken north. The huts and thousands of items were left behind. Fuel depots with unused containers of petroleum products, asbestos materials, and diverse chemicals were also left at the huts. This investigation found high concentrations of polyaromatic hydrocarbons in soils under and around the historic fuel depots, including anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, chrysene, fluorene, and pyrene, as well as benzo[a]anthracene, benzo[a]pyrene, and fluoranthene, which are recognized carcinogens. Asbestos materials within the huts have been identified and extensive amounts of fragmented asbestos were found littering the ground around the Cape Evans hut. These materials are continually abraded and fragmented as tourists walk over them and the coarse scoria breaks and grinds down the materials. A chemical spill, within the Cape Evans hut, apparently from caustic substances from one of the scientific experiments, has caused an unusual deterioration and defibration on affected woods. Although these areas are important historic sites protected by international treaties, the hazardous waste materials left by the early explorers should be removed and remedial action taken to restore the site to as pristine a condition as possible. Recommendations are discussed for international efforts to study and clean up these areas, where the earliest environmental pollution in Antarctica was produced

    Experimental investigation of high-dimensional quantum key distribution protocols with twisted photons

    Get PDF
    Quantum key distribution is on the verge of real world applications, where perfectly secure information can be distributed among multiple parties. Several quantum cryptographic protocols have been theoretically proposed and independently realized in different experimental conditions. Here, we develop an experimental platform based on high-dimensional orbital angular momentum states of single photons that enables implementation of multiple quantum key distribution protocols with a single experimental apparatus. Our versatile approach allows us to experimentally survey different classes of quantum key distribution techniques, such as the 1984 Bennett \& Brassard (BB84), tomographic protocols including the six-state and the Singapore protocol, and to investigate, for the first time, a recently introduced differential phase shift (Chau15) protocol using twisted photons. This enables us to experimentally compare the performance of these techniques and discuss their benefits and deficiencies in terms of noise tolerance in different dimensions.Comment: 13 pages, 4 figures, 1 tabl
    corecore