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  • 1
    Electronic Resource
    Electronic Resource
    Selective excitation of high vibrational states using Raman chirped adiabatic passage (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 4229-4237 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Calculations indicate that high vibrational states of oxygen and chlorine can be excited using a series of nonresonant Raman pulses, where both the pump and the Stokes pulses are chirped with linear frequency sweeps. Most of the previously reported coherent processes (such as simple adiabatic passage) are seriously degraded when rotational effects are included. However, we find that the laser pulse parameters (intensity and bandwidth) required to invert population into high vibrational states via Raman chirped adiabatic passage are achievable using technology that is currently available. Applications to homonuclear diatomic molecules are discussed in detail. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478305
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  • 2
    Electronic Resource
    Electronic Resource
    Molecularly chemisorbed intermediates to oxygen adsorption on Pt(111): A molecular beam and electron energy-loss spectroscopy study (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 3696-3704 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: High translational energy adsorption of oxygen on the (111) surface of platinum was examined with electron energy loss spectroscopy (EELS) and molecular beam techniques. EEL spectra indicate that over an incident energy range of 0.2–1.37 eV and on a Pt(111) surface held at 77 K, oxygen adsorbs in an associative chemisorbed state—yielding to the dissociated state only after sufficient substrate heating. Simple direct dissociation appears negligible for all incident kinetic energies studied. At near-zero surface coverages, exclusive population of the peroxolike molecular precursor is observed for adsorption at these high translational energies, while both superoxolike and peroxolike forms are detected for low energy adsorption (0.055 eV). This peculiarity represents evidence that translational energy is effective in differentially populating reaction intermediates and provides better quantification of potential energy barriers to dissociation. We estimate the activation barrier for dissociation from the peroxolike precursor to be approximately 0.29 eV. Initial adsorption probability measurements over a wide range of surface temperatures and high incident kinetic energies corroborate a molecular chemisorption mediated mechanism. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479649
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  • 3
    Electronic Resource
    Electronic Resource
    3He refrigerator based very low temperature scanning tunneling microscope (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 1459-1463 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe the design and development of a scanning tunneling microscope (STM) which can operate at temperatures down to 240 mK and in magnetic fields up to 7 T with high spatial and energy resolution. The compact and rigid STM head is mounted directly on a low vibration, single shot, 3He refrigerator. This refrigerator can be operated at its base temperature continuously for several days before the 3He needs to be recondensed. The system is equipped with a sample transport manipulator from room temperature, and a cleavage device at low temperature, so that the cryogenic ultrahigh vacuum condition inside the cryostat can be utilized. A superconducting magnet provides a magnetic field of up to 7 T at the sample along the STM tip direction. Test results have shown that, at the base temperature, this instrument has better than 0.5 pm z-direction resolution in imaging mode, and better than 20 μV energy resolution in spectroscopy mode. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149605
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  • 4
    Electronic Resource
    Electronic Resource
    Geographical distribution of Erwinia salicis strains, the cause of watermark disease of willows (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Forest pathology 29 (1999), S. 0 
    Details
    ISSN: 1439-0329
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Eighty-six isolates of Erwinia salicis, the causal agent of watermark disease of willow, were obtained from culture collections and collected from various willow plantations in south-east England. These isolates were characterized by their reaction in a competitive enzyme-linked immunosorbent assay, by enzyme electrophoresis, and for lysis by a panel of five bacteriophage. Eighty-one isolates had similar characteristics and clustered at a level of similarity of at least 60%. Five isolates were found to have less than 20% similarity to the other E. salicis. Antiserum raised against E. salicis (NCPPB 2535) was found to be specific to E. salicis and did not cross-react with other bacteria tested. No geographical clustering of electrotypes was found: however, Dutch and English isolates could be distinguished by bacteriophage typing. The local distribution of electrotypes collected from diseased trees suggests that the bacterium is spread via the propagating material and that tree to tree spread is rare.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1439-0329.1999.00167.x
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  • 5
    Electronic Resource
    Electronic Resource
    Manipulating the intensity of near-bed turbulence in rivers: effects on benthic invertebrates (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 42 (1999), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Flow conditions were modified over patches of river bed in three rivers in south-western Australia to determine the effects of turbulence on benthic invertebrate communities.2. Artificial structures to increase downstream turbulence were developed in a laboratory flume. In the field, these increased turbulence intensity by 35% for a 20% reduction in velocity.3. Patches of gravel were placed in each river and turbulence-generating structures allocated randomly to half of these, creating treatment patches. An acoustic Doppler velocimeter was used to measure flow conditions over both treatment and control patches at several heights above the bed. After 6 weeks, the invertebrate fauna of the gravel patches were sampled to examine the response to modified flow conditions.4. The treatments increased relative turbulence intensity twofold for a reduction in velocity of between 3 and 5 cm s−1, but turbulence intensity was significantly higher in only one of the three rivers.5. There were no significant effects of increased relative turbulence intensity on any aspect of the invertebrate assemblage. This may be a result of the fairly small increase in relative turbulence intensity created during the experiment, the spatial scale of the manipulation or the types of stream community studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.1999.00506.x
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  • 6
    Electronic Resource
    Electronic Resource
    AusRivAS: using macroinvertebrates to assess ecological condition of rivers in Western Australia (1999)
    Oxford, UK : Blackwell Science, Ltd
    Freshwater biology 41 (1999), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. AusRivAS (Australian River Assessment Scheme) models were developed, using macroinvertebrates as indicators, to assess the ecological condition of rivers in Western Australia as part of an Australia-wide program. The models were based on data from 188 minimally disturbed reference sites and are similar to RIVPACS models used in Britain. The major habitats in the rivers (macrophyte, channel) were sampled separately and macroinvertebrates collected were identified to family level.2. Laboratory sorting of preserved macroinvertebrate samples recovered about 90% of families present when 150 animals were collected, whereas live picking in the field recovered only 76%.3. Reference sites clustered into five groups on the basis of macroinvertebrate families present. Using seven physical variables, a discriminant function allocated 73% of sites to the correct classification group. A discriminant function based on seven physical and two chemical variables allocated 81% of sites to the correct group. However, when the same reference sites were re-sampled the following year, the nine variable discriminant function misallocated more sites than the seven variable function, owing to annual fluctuations in water chemistry that were not accompanied by changes in fauna.4. In preliminary testing, the wet season channel model correctly assessed 80% of reference sites as undisturbed in the year subsequent to model building (10% of sites were expected to rate as disturbed because the 10th percentile was used as the threshold for disturbance). Nine sites from an independent data set, all thought to be disturbed, were assessed as such by the model. Results from twenty test sites, chosen because they represented a wide range of ecological condition, were less clear-cut. In its current state the model reliably distinguishes undisturbed and severely disturbed sites. Subtle impacts are either detected inconsistently or do not affect ecological condition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.1999.00430.x
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  • 7
    Electronic Resource
    Electronic Resource
    Patterns of distribution of macroinvertebrate families in rivers of north-western Australia (1999)
    Oxford, UK : Blackwell Science, Ltd
    Freshwater biology 41 (1999), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. The northern half of Western Australia is a large, sparsely populated area with a climate that ranges from monsoonal in the Kimberley to arid in the Gascoyne and Pilbara regions. The aquatic invertebrate fauna is poorly known.2. Fifty-one sites located on 14 river systems were sampled three times between August 1994 and October 1995. A total of 90 taxa, most identified to family level, were collected. The fauna was dominated by insects, which constituted 74% of the total number of taxa collected.3. Major habitats at each site were sampled separately and sites with more habitats tended to have a richer fauna. All habitats showed significant differences in taxonomic richness between regions. Family richness decreased with increasing latitude, being highest in the Kimberley region and lowest in the Gascoyne.4. Despite the differences in taxon richness between regions, community composition of the aquatic invertebrate fauna at the family level did not differ greatly. Four major groups of sites were identified by cluster analysis, based on the invertebrate families present at each site, but differences between groups were small.5. Significant temporal variation in taxon richness was found in channel habitat but not the three other habitats sampled (riffle, macrophyte, pool-rocks). Community composition in channel habitat varied temporally among groups of sites identified by cluster analysis but the pattern was not consistent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.1999.00432.x
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  • 8
    Electronic Resource
    Electronic Resource
    Ethnic, Anthropometric, and Lifestyle Associations with Regional Variations in Peak Bone Mass (1999)
    Springer
    Calcified tissue international 65 (1999), S. 100-105 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Bone density — Bone mineral content — Anthropometry — Lifestyle — Ethnicity.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. The study investigated the ability of ethnicity and anthropometric and lifestyle factors to account for differences within subjects in bone mass at different skeletal sites. The subjects were young, adult, Japanese, Filipino, Hawaiian, and white women ages 25–34. In the preliminary analyses, they were divided into thirds based on their BMD z-scores. Thirty-five percent exhibited high variability in bone mass: they were in the upper third at one or more bone sites and in the lower third at one or more sites. Other women had more generalized low bone mass: 25% were in the lowest third for two or more sites, and there were no sites with low bone mass in the upper third. In subsequent analyses, ethnicity, anthropometry, and lifestyle influences were examined as possible predictors of differences in bone mineral content (BMC) between bone sites in bone-size adjusted models. White women had greater BMC at the proximal radius and calcaneus than at the distal radius compared with other ethnic groups. This may be explained by the fact that they had exceptionally wide bone widths at the distal radius. Of the anthropometric variables, fat mass was associated with higher bone mass at sites with higher proportions of cancellous tissue (calcaneus 〉 spine 〉 radius sites). Muscle mass was associated with greater bone mass at the calcaneus and proximal radius than at the spine. For the lifestyle variables, women with greater milk consumption between the ages of 10–24 years had higher spine bone mass than expected from their measurements at the proximal radius. Women 12–17 years of age who had been more active in sports had higher calcaneous bone mass than expected from their spine measurements. As the study participants were still young women, the results suggest that regional differences in bone mass may partly derive from anthropometric and lifestyle influences during skeletal maturation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900664
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  • 9
    Electronic Resource
    Electronic Resource
    Reply Josephson effect and a π-state in superfluid 3 He (1999)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 397 (1999), S. 485-485 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Backhaus et al. reply — Avenel et al. have suggested a mechanism that might explain the recently discovered metastable π-state in a superfluid 3He weak-link array. We are pleased that our experiment is leading to new ideas that may extend the understanding of weak-link ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/17251
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  • 10
    Electronic Resource
    Electronic Resource
    GIXAFS study of Fe3+ sorption and precipitation on natural quartz surfaces (1999)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 6 (1999), S. 615-617 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0909049599001764
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