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  • Articles  (58)
  • 1995-1999  (58)
  • 1970-1974
  • 1997  (58)
  • Chemistry and Pharmacology  (50)
  • Mathematics  (4)
  • Energy, Environment Protection, Nuclear Power Engineering  (4)
Collection
  • Articles  (58)
Years
  • 1995-1999  (58)
  • 1970-1974
Year
Journal
  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 9286-9296 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have calculated a two-dimensional (2D) potential energy surface (PES) for H2 interacting with a Pd(111) surface. The geometry considered is for H2 approaching a bridge site and dissociating into neighboring hollow sites and the subsurface sites directly below these. Density functional calculations were performed using both the local density approximation (LDA) and the generalized gradient approximation (GGA). The LDA PES gives the usual overbinding and shows no barrier (relative to the bottom of the H2 potential) to subsurface absorption, while the GGA PES agrees with the experimental adsorption energies and has a large barrier. We have performed quantum mechanical wave packet calculations on the GGA PES to obtain the direct subsurface absorption probability. We have also calculated the barrier height's dependence on a coordinate that can be associated with a local surface vibrational mode and the results suggest that this degree of freedom should be taken into account in the dynamical calculations. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 10652-10661 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Based on density functional theory (DFT) within the generalized gradient approximation (GGA) we have calculated a three-dimensional (3D) potential energy surface (PES) for H2+Pd(111), depending on two hydrogen molecular degrees of freedom and one palladium surface degree of freedom. The PES is then used in 3D quantum mechanical wave packet calculations to investigate the effect of the surface motion on the direct subsurface absorption. We also compare the full 3D calculations to calculations where the surface motion is included through the sudden approximation. The calculations show a large downward shift of the onset energy for direct subsurface absorption upon inclusion of palladium surface motion (from 0.74 eV to 0.40 eV for H2). The use of the sudden approximation works well at collision energies greater than 1.3 eV (for H2), but leads to a significant underestimation of the direct subsurface absorption probability at lower energies. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of mathematical biology 59 (1997), S. 197-204 
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1122
    Keywords: Key words:Foreign exchange rates, intra-daily, heterogeneous, distribution ¶JEL classification:F31, G15, E44 ¶Mathematics Subject Classification (1991):90-02, 62-07, 62P20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract. This paper presents stylized facts concerning the spot intra-daily foreign exchange markets. It first describes intra-daily data and proposes a set of definitions for the variables of interest. Empirical regularities of the foreign exchange intra-daily data are then grouped under three major topics: the distribution of price changes, the process of price formation and the heterogeneous structure of the market. The stylized facts surveyed in this paper shed new light on the market structure that appears composed of heterogeneous agents. It also poses several challenges such as the definition of price and of the time-scale, the concepts of risk and efficiency, the modeling of the markets and the learning process.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 97 (1997), S. 125-135 
    ISSN: 1432-2234
    Keywords: Key words: Relativistic two-component quantum chemical methods ; Complete-active-space-SCF theory ; Spin-orbit coupling ; Spin-dependent one-particle bases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract. Detailed formulae for the implementation of the multi-configuration SCF spinor optimization in a basis of Kramers pair 2-spinors – i.e. exploiting time-reversal symmetry – are presented. Full expressions for the spinor gradient and spinor Hessian elements are given in abstract form as well as within the usual CASSCF subspace division. As far as possible, the resulting terms are grouped to relativistic inactive and active Fock matrices, which have been introduced previously. Approximations for the Hessian are introduced so as to initialize it in an inverse Hessian update algorithm for a diagonal first approximation within the standard quasi-Newton-Raphson procedure. The effects of double group symmetry arising from spin dependence on Fock matrices and therefore gradient and Hessian are discussed and a group scheme for the implementation is proposed.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 97 (1997), S. 301-312 
    ISSN: 1432-2234
    Keywords: Key words: Spin-orbit coupling ; Determinant configuration interaction ; Time-reversal symmetry ; Relativistic configuration interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract. A general configuration interaction (CI) algorithm incorporating one- and two-electron spin-orbit operators is presented. The algorithm is determinant based and enables the use of highly vectorized non-relativistic algorithms in the most operation-intensive part. Excitations between α and β spin orbitals are avoided in the time consuming parts by performing separate S + and S − operations. The relativistic CI expansions are often very large, so the algorithms require only the presence of segments of vectors in memory. Double-group symmetry is fully accounted for and time-reversal symmetry is exploited for both even and odd numbers of electrons.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Environmental and ecological statistics 4 (1997), S. 93-94 
    ISSN: 1573-3009
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Environmental and ecological statistics 4 (1997), S. 167-180 
    ISSN: 1573-3009
    Keywords: cause-effect ; forest ; Forest Health Monitoring (FHM) ; Forest Inventory and Analysis (FIA) ; monitoring design ; National Resource Inventory (NRI) ; natural resource surveys ; rangeland ; status ; trends
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Our objective is to present a perspective on large-scale natural resource monitoring when cause-effect is a potential issue. We believe that the approach of designing a survey to meet traditional commodityproduction and resource state descriptive objectives is too restrictive and unnecessarily limits theability to investigate cause-effect issues. We only consider terrestrial natural resources, focusing on forests and rangeland. A large institutionalized programme is required to establish cause-effect relationships when monitoring terrestrial resources. This is justified based on the growing concerns about our natural resources. A long-term vision of a desirable future terrestrial monitoring system, realizing that it is not clear yet what key variables should be measured, will increase the chances that decisions on current designs will ultimately lead to better systems in the future. We propose a pronounced shift in the designs applied to forest and range, specifically, the NationalResources Inventory (NRI), the Forest Inventory and Analysis (FIA), and the Forest Health Monitoring (FHM) programmes. The designs must not only address simple status and trends estimation but also give emphasis to identifying interesting changes occurring in the sampled populations thus facilitating identification and establishment of possible cause-effect relationships. We propose an integrated design consisting of a large-scale, long-term ongoing survey as the core design accompanied by supplemental experimental design studies or analytic survey. Continuous inventory involving annual measurement of a subset of the sample from selected populations should be implemented: inventorying a population every five years (as with NRI) or every ten years (as with FIA) is insufficient. FHM, FIA, and NRI should collect a subset of variables in common. Complementarity of data collected would make it more likely to identify promising cause-effect relationships for a wider range of resource variables. At this stage we recommend focusing on the mortality of trees, shrubs, forbs, and grasses as the key indicator of forest and range health. Mortality is objectively measurable and can often be detected by remote sensing. When possible, follow-up observational studies to document cause-effect relationships should be limited to public lands because of concern of infringing on the personal rights of landowners. This may not be possible if unrepresentative populations result because of this. If studies are designed properly, we could achieve our objectives yet tie such studies to current natural resource inventory systems.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 16 (1997), S. 69-71 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The management of safety, quality and environmental issues covers a complex set of interrelated issues of concern to society and industry. Traditionally an engineering approach has been adopted for the management of risk; the development of technical standards, operations and requirements. Recently, industry leaders have begun to realize that real progress will be made only throgh effective risk management systems. This paper presents a few of the key requirements for improving risk management and risk analysis. By improving the way risk analysis is used for decision support, improving hazard identification exercise, while incorporating site specific properties of design, condition, operation and management into an analysis, it is possible to improve the value of current risk management techniques.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Publication Date: 1997-10-01
    Print ISSN: 0163-3864
    Electronic ISSN: 1520-6025
    Topics: Chemistry and Pharmacology
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