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  • 1
    Electronic Resource
    Electronic Resource
    Exotic Grass Competition in Suppressing Native Shrubland Re-establishment (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Restoration ecology 5 (1997), S. 0 
    Details
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Disturbance of coastal sage scrub in southern California has led to extensive displacement of native shrubs by exotic annual grasses. The initial conversion from shrubland to exotic grassland is typically associated with disturbance caused by intense grazing, high fire frequency, or mechanical vegetation removal. While native shrubs have been shown to recolonize annual grasslands under some conditions, other annual grasslands are persistent and show no evidence of shrub recolonization. This study examined the mechanisms by which annual grasses may exclude native shrubs and persist after release from disturbance. Grass density was manipulated in experimental plots to achieve a series of prescribed densities. Artemisia californica, a dominant native shrub, was seeded or planted into the plots and responses to the grass density treatments were measured over two growing seasons. A. californica germination, first season growth, and survival were all negatively related to the density of neighboring annual grasses. The most probable mechanism underlying the reduction of first season growth and survival was depletion of soil water by the grasses. The effects of the grasses on A. californica were no longer significant in the second season. The results of this study indicate that Mediterranean annual grasses reduce recruitment and can persist by inhibiting post-disturbance establishment of A. californica from seed. Although succession alone may not return disturbed annual grasslands to their former shrubland composition, the results suggest that restoration can be achieved by using container plantings or grass removal followed by seeding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1526-100X.1997.09729.x
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  • 2
    Electronic Resource
    Electronic Resource
    Release of metal impurities from structural defects in polycrystalline silicon (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 1984-1986 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Metal impurity release from structural defects in polycrystalline silicon was studied following thermal treatments, and, in addition, a correlation between impurity distributions and structural defects was established. Impurities were mapped with synchrotron-based x-ray fluorescence in the as-grown state, after rapid thermal annealing and following aluminum gettering treatments. The goal of this work was to determine if impurity release from structural defects limits gettering of metal impurities. The results reveal that nickel and copper metal impurities are primarily found at dislocations in as-grown crystals, and the release of these impurities from defects occurs rapidly with no apparent barrier to dissolution. Gettering treatments dissolved metal impurity precipitates to 〈2–5 nm in radii; however, the material performance was not greatly enhanced. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119762
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  • 3
    Electronic Resource
    Electronic Resource
    Microelectromechanical scanning probe instruments for array architectures (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 4155-4162 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A compact (150 μm×150 μm), electrostatic actuator for out-of-plane (z) actuation of a probe tip has been designed, fabricated, and tested. Static deflections of ±0.7 μm out of the plane of the substrate have been achieved. The device consists of a single crystal silicon tip on a torsional cantilever with out-of-plane interdigitated electrode capacitors. This cantilever and electrode design allows a wide range of stiffnesses, actuator force, and frequency response. Significant improvements in performance (larger tip displacement and increased sense capacitance) and a higher density of devices per unit area can be obtained as the minimum feature size decreases. Applications such as information storage, molecular manipulation, and nanolithography require high density, parallel arrays for reasonable throughput. To demonstrate the suitability of this device for use in such arrays, a 12×12 array of microelectromechanical probe tips with integrated actuators and capacitive sensors for scanning probe microscopy has been fabricated. The size of each array element is about 150 μm by 150 μm with a tip-to-tip spacing in the array of 200 μm. Given these dimensions, the packing density of the devices is about 2500 units/cm2. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148361
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  • 4
    Electronic Resource
    Electronic Resource
    Elderly people from ethnic minorities in Liverpool: mental illness, unmet need and barriers to service use (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Health & social care in the community 5 (1997), S. 0 
    Details
    ISSN: 1365-2524
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The objective of the Health and Ethnicity Project was to identify unmet need and barriers to the use of psychogeriatric and welfare services by ethnic minority older people living in Liverpool's inner-city. The results presented here are the findings of Phase II of the project in which 71 ethnic minority older people aged 65 years and over were interviewed. These respondents had been diagnosed as suffering from dementia or depression earlier in Phase I. They include Black British, Afro Caribbean and Chinese older people. Findings show a low level of service use in spite of considerable unmet need. Only 8% were in institutions and 46% lived alone. For the 17% living alone in sheltered housing, there was evidence of violence towards wardens, wandering, neglect of rooms and occasional fires. Of the 27% living with a family nearly a half of cases also experienced physical disability. Those in institutions were finding language difficulties and problems in obtaining a suitable diet. Using Yeatts et al.'s typology (1992) ‘lack of knowledge’ barriers and ‘lack of intent’ barriers concerned the group as a whole most, i.e. they either did not know of services or perceived them as being culturally inappropriate. Implications for service providers are considerable: to ensure improved access it is necessary not only to invest more in general medical services but to work in partnership with ethnic minority groups to overcome barriers of mistrust and ensure cultural sensitivity in the services offered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2524.1997.tb00112.x
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  • 5
    Electronic Resource
    Electronic Resource
    Fluorescence excitation spectroscopy of the Ar–HCO(X˜ 2A′,B˜ 2A′) van der Waals complex (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 680-690 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The fluorescence excitation spectrum of the Ar–HCO van der Waals complex in the vicinity of the B˜ 2A′–X˜ 2A′ 000 band of free HCO is reported. At least eight bands associated with the complex have been detected. From the spectral shift of the lowest energy Ar–HCO band from the origin of the free HCO transition, we estimate the Ar–HCO binding energy in the excited electronic state to be at least 13 cm−1 greater than that in the ground state. Rotational analysis of some of the bands has been carried out, and average Ar–HCO separations (∼3.7 Å) in both electronic states determined. Several of the bands were assigned as hot bands from the first excited bend–stretch level (K″=1) in the ground electronic state. From the derived A rotational constants, we conclude that the ArCO framework has an approximately T-shaped geometry in both electronic states. The decay lifetime of the upper state of the strongest Ar–HCO band was measured and was found to be somewhat smaller than those previously measured for low rotational levels of free HCO. With the high signal-to-noise ratio in this study, it was also possible to observe transitions in the free H13CO isotopomer. A rotational analysis of the B˜ 2A′–X˜ 2A′ 000 band of the H13CO isotopomer was carried out. The isotopic shifts of the origins of the 301 and 201 bands were also measured, and a normal mode analysis of HCO(B˜) was carried out. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474469
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  • 6
    Electronic Resource
    Electronic Resource
    Rotational analysis of the B˜2A′′−X˜2A′′ origin band of the CH2CFO radical (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 9755-9758 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The laser fluorescence excitation spectrum of the origin band of an electronic transition in the CH2CFO radical was recorded with partial rotational resolution using a supersonic, rotationally cold beam. The radical was prepared in a pulsed free jet by 193 nm photolysis of acetyl fluoride diluted in helium or argon. The rotational structure of the band is consistent with an in-plane electronic transition of this near oblate rotor. In analogy with the vinoxy radical, this transition is designated as B˜2A′′−X˜2A′′. Spectroscopic constants were derived from a fit to the assigned rotational transitions. The lower state rotational constants agree with those calculated from an ab initio CH2CFO equilibrium structure [M. Furubayashi, I. Bridier, S. Inomata, N. Washida, and K. Yamashita, J. Chem. Phys. 106, 6302 (1997)]. The present study thus provides confirmation of the assignment of the molecular carrier as CH2CFO and eliminates the alternative assignment to FCO [B. A. Williams and J. W. Fleming, J. Chem. Phys. 106, 4376 (1997)]. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475272
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  • 7
    Electronic Resource
    Electronic Resource
    Nonlinear dynamics of torsion–rotation interactions: A model study of toluene (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 6646-6658 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The internal rotation, or torsion, of a methyl group has been implicated in the acceleration of intramolecular vibrational redistribution (IVR) in numerous experimental studies. In the present work, we investigate its interaction with overall molecular rotation. To isolate the effects of torsion–rotation coupling, a simple two-degree-of-freedom model, including only torsion and three-dimensional rotation, is constructed and its dynamics at j=45 for several energies are studied. Investigation of other values of angular momentum indicate that the results reported are largely independent of j. Two primary effects are observed: (i) a shifting of the stable and unstable axes of rotation due to free methyl torsion, and (ii) a limited degree of weakly chaotic dynamics for trajectories whose torsional energy is near the top of its barrier. Chaos is first observed at the lowest energy at which torsion can surmount its barrier, but then disappears from the system at higher energies. Model toluene exhibits only narrow, high-order nonlinear resonances due to the frequency disparity between torsion and rotation, and these resonances are reduced in number by "selection rules" that arise in part from the symmetry of the Hamiltonian. These observations are analyzed in depth and simple, but quantitative, models are proposed to explain the magnitude of the rotational axis shift, the limited extent of chaos, and the resonance selection rules. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474907
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  • 8
    Electronic Resource
    Electronic Resource
    Cultures, Identities, and Dress: A Renewed Sociological Interest (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Sociological inquiry 67 (1997), S. 0 
    Details
    ISSN: 1475-682X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Sociology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-682X.1997.tb01098.x
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  • 9
    Electronic Resource
    Electronic Resource
    Repetitive sequences found in the chromosome of the myxobacterium Nannocystisexedens are similar to msDNA: a possible retrotransposition event in bacteria (1997)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 23 (1997), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The first reverse transcriptase (RT) to be found in a prokaryotic cell is encoded by an element called a retron which resides in the chromosome of many different bacteria. In addition, all retrons code for a functionally obscure RNA–DNA satellite molecule called msDNA. msDNA is synthesized from an RNA template by the retron-encoded RT. An unusual retron element is described here from the myxobacterium Nannocystis exedens. This retron does not appear to have a typical RT gene in close proximity (1 kb) to the gene msd (which encodes the DNA strand of msDNA). The gene msr (which encodes the RNA strand of msDNA) appears to be duplicated and flanks both sides of the msd gene. Also discovered throughout the chromosome of this bacterium is a set of repeated sequences related to msDNA. These repeat sequences match only part of the sequence of msDNA and may have become incorporated into the chromosome of this bacterium by reverse transcription.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1997.2671627.x
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  • 10
    Electronic Resource
    Electronic Resource
    Female rainbow trout urine contains a pheromone which causes a rapid rise in plasma 17,20β-dihydroxy-4-pregnen-3-one levels and milt amounts in males (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 50 (1997), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Previous studies have shown that spermiating male rainbow trout respond to the presence of female urine in the water with significant increases in plasma levels of gonadotrophin II, 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) and testosterone. The present results show that males only need a single brief exposure to female urine in order to respond; levels of 17,20β-P rise significantly within 1 h of exposure, and peak between 3 and 4 h. Also, milt amounts increase significantly following exposure of males to female urine. Levels of 17,20β-P are also related positively to the amount of female urine to which the males are exposed. Furthermore, when live females are placed, out of physical and visual contact, in the same tank as males, levels of 17,20β-P rise in the same way as in males which are exposed to female urine. However, if females are fitted with urinary catheters (which drain the urine outside the tank), males respond more slowly. These results indicate that urine is the main source of the male ‘priming’ pheromone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1997.tb01343.x
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