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  • 1
    Book
    Book
    Ultimate zero and one : computing at the quantum frontier (2000)
    -Verl., New York :Copernicus - Springer,
    Details
    Title: Ultimate zero and one : computing at the quantum frontier
    Author: Williams, Colin P.
    Contributer: Clearwater, Scott H.
    Publisher: -Verl., New York :Copernicus - Springer,
    Year of publication: 2000
    Pages: 250 S.
    Type of Medium: Book
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  • 2
    Book
    Book
    Explorations in quantum computing + CD-ROM (1998)
    New York u. a.; TELOS, :Springer,
    Details
    Title: Explorations in quantum computing + CD-ROM
    Author: Williams, Colin P.
    Contributer: Clearwater, Scott H.
    Publisher: New York u. a.; TELOS, :Springer,
    Year of publication: 1998
    Pages: 307 S.
    Type of Medium: Book
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  • 3
    Electronic Resource
    Electronic Resource
    Glutamate and γ-Aminobutyric Acid Neurotransmitter Systems in the Acute Phase of Maple Syrup Urine Disease and Citrullinemia Encephalopathies in Newborn Calves (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 59 (1992), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Cerebral cortex tissue was obtained at autopsy from neonatal Poll Hereford calves with clinically confirmed maple syrup urine disease (MSUD), neonatal Holstein-Friesian calves with clinically confirmed citrullinemia, and matched controls. From this, synaptosomes were prepared for studies of neurotransmitter amino acid uptake and stimulus-induced release, and synaptic plasma membranes were obtained for studies of associated postsynaptic receptor binding sites. As well as having abnormal brain tissue concentrations of the pathognomic plasma amino acids (markedly increased levels of the branched-chain compounds valine, isoleucine, and leucine in MSUD; marked elevation of citrulline levels in citrullinemia), both groups of diseased animals showed reduced, brain tissue concentrations of each of the transmitter amino acids glutamate, aspartate, and γ-aminobutyric acid (GABA). Nontransmitter amino acids were generally unaffected in either disease. Citrullinemic calves showed a marked increase in brain glutamine concentration; in calves with MSUD, the glutamine concentration was raised, but to a much lesser extent. The Na+-dependent synaptosomal uptake of both glutamate and GABA was markedly reduced (to 〈50% of control values in both cases) in citrullinemic calves but was unaltered in calves with MSUD. Whereas synaptosomes from normal calves showed the expected stimulus-coupled release of transmitter amino acids, especially glutamate and aspartate, and no response to stimulus of nontransmitter amino acids, there was no increased release of transmitter amino acids in response to depolarization in synaptosomes from citrullinemic calves. This was in part because the extracellular concentrations of these compounds in citrullinemic control incubations were already high, especially for glutamate—basal extrasynaptosomal glutamate concentrations were some 20-fold higher than those found with synaptosomes from normal calves—so that further stimuluscoupled enhancement was not possible. Calves with MSUD showed a marked loss in number of postsynaptic GABAA receptors (to ∼-50% of normal values), as assessed from [3H]diazepam binding studies. In contrast, there was no loss of this receptor site in citrullinemic calves. Calves with citrullinemia showed a marked reduction in the affinity and density of postsynaptic glutamate N-methyl-D-aspartate receptors as assessed from [3H]MK-801 binding studies. In contrast, calves with MSUD showed no change in this parameter. These studies show that two major recessively inherited diseases of cattle have similar, but distinct, neurochemical pathologies. The MSUD encephalopathy appears to be driven by a diminution of GABA-mediated inhibitory neurotransmission, whereas in citrullinemia the equivalent proconvulsive state may be driven by a relative increase in glutamate-mediated excitatory activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1992.tb09409.x
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  • 4
    Electronic Resource
    Electronic Resource
    The photodissociation dynamics of CFBr excited into the A˜(1A″) state (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 11789-11797 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dynamics of the photolysis reaction, CFBr+hν→CF+Br, have been investigated for photolysis energies in the range, ν¯=23 500–26 000 cm−1 (λ=385–435 nm). These energies correspond to excitation into the A˜(1A″) state of CFBr with 2500–5000 cm−1 of excess vibrational energy. Following dissociation of jet-cooled CFBr, the internal energy (Ω, Λ, J) of the nascent CF fragments (X 2Π, υ=0) was probed by laser induced fluorescence spectroscopy. Two distinct types of product state distributions were observed. At energies above T00+3360 cm−1 the populations of the 2Π1/2 and 2Π3/2 spin–orbit states of CF were equal, while A″ lambda doublet states were preferred over A′. These populations are consistent with a direct dissociation mechanism on the A˜ state, over a barrier with a height of 3360 cm−1. The strong state mixing in the vicinity of the barrier ensures a statistical mixture of final spin–orbit states. The preference for the A″ lambda doublet states is consistent with the two lone electrons in in-plane orbitals pairing up in the final CF product, leaving one unpaired electron in an out-of-plane orbital, lying parallel to the J vector of the recoiling fragment. For excitation at energies below T00+3360 cm−1 the ground spin–orbit state of CF (2Π1/2) is preferred, while the lambda doublet populations are equal. The interpretation of these populations is that at these energies A˜ state CFBr is stable with respect to dissociation over the barrier. The molecule crosses to either the X˜ or a˜ state where it encounters a deep attractive potential well. The subsequent slower dissociation rate allows the molecule to follow a more adiabatic pathway producing the lowest spin–orbit state of CF, and for any preference for lambda doublet states to be lost. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479122
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  • 5
    Electronic Resource
    Electronic Resource
    Dynamics of Acetaldehyde Dissociation at 308 nm: Rotational (N, Ka) and Translational Distributions of the HCO Photoproduct (1994)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 98 (1994), S. 10802-10808 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100093a021
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  • 6
    Electronic Resource
    Electronic Resource
    Electronic spectroscopy and ab initio quantum chemical study of the A˜(1A″)−X˜(1A′) transition of CFBr (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 2220-2232 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The A˜(1A″)−X˜(1A′) electronic transition of jet-cooled CFBr has been investigated by spectroscopic and ab initio theoretical methods. Laser induced fluorescence (LIF) excitation spectroscopy was used to explore the rovibronic levels in the A˜ state, and dispersed fluorescence spectroscopy was used to study ground-state vibrations. Analysis of these spectra yielded gas-phase vibrational frequencies and anharmonicity constants in both electronic states. The computed ab initio vibrational frequencies in both X˜ and A˜ states are in good accord with the experimental values. The A˜-state fluorescence lifetimes varied between 100 ns and 3 μs as a function of excited vibronic state. The highest lying levels displayed a shortened fluorescence lifetime, and some vibronic states that involved ν1 (the CF stretch) exhibited shortened lifetimes (300–500 ns) irrespective of the vibrational energy. Vibronic structure in the LIF spectrum disappeared for vibrational energy in excess of 2957 cm−1. Calculations of the A˜-state potential-energy surface show that it has a small barrier to dissociation to CF+Br with a barrier height in good accord with observed termination of fluorescence. The predicted photochemical pathway to production of CF+Br fragments was proven experimentally by detection of CF fragments. The photofragment excitation spectrum showed strong, increasingly broad vibronic structure at higher energies than the LIF spectrum. At lower energy, sharp but weaker vibronic structure was still evident, overlapping the LIF spectrum. There appears to be two photochemical mechanisms to produce CF+Br, one direct and one indirect. We estimate the height of the barrier to direct dissociation to lie 3250±150 cm−1 above the zero-point level of the A˜ state. The asymptotic thermochemical dissociation limit is estimated to lie ≥1100 cm−1 lower. The thermochemical bond dissociation energy for the C–Br bond in CFBr was thereby estimated to be Ediss≤23 180 cm−1, which led to an estimate of the heat of formation for CFBr, ΔfH2980≥86 kJ mol−1. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476790
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  • 7
    Electronic Resource
    Electronic Resource
    HCO (N,Ka,Kc,J) distributions from near-threshold photolysis of H2CO (J,Ka,Kc) (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 3187-3198 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dynamics of the reaction H2CO+hν(λ(approximate)330 nm)→H+HCO have been studied following excitation of formaldehyde into the A˜(1A2) state, just above the dissociation threshold of the X˜(1A1) state. Formaldehyde was excited via specific J, Ka, Kc rotational states and the ensuing rotational distribution of HCO measured by fully resolving N, Ka, Kc, and J=N±S of the fragment. When only the N and Ka quantum numbers of both formaldehyde and the formyl radical are considered, the distributions are generally modeled well by phase space theory (PST). Within (approximate)10 cm−1 of the threshold, however, the PST predictions consistently exceed the experimental populations. This was accounted for by the inclusion of a centrifugal barrier in the PST model. The attractive part of the effective centrifugal potential was modeled by a dipole-induced dipole plus dispersion interaction. The barrier is weak and long range (〉5 Å). Resolution of Kc in the reaction, in both parent and product, gave large deviations from the PST model. The HCO population distributions separate according to whether Kc was the upper- or lower-energy state. Additionally, the upper/lower preference was sensitive to the choice of Kc in the parent. Insufficient data are currently available to quantify this observation. The product state distribution was also found to be independent of the spin–rotation state of HCO. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475736
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  • 8
    Electronic Resource
    Electronic Resource
    Characterization of the A˜(1A″) state of HCF by laser induced fluorescence spectroscopy (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 11277-11285 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An extensive experimental exploration of the A˜(1A″)←X˜(1A′) transition of supersonically cooled fluoromethylene has been performed using laser induced fluorescence spectroscopy. Several new bending vibrational bands are reported, which provide the harmonic frequency and anharmonicity constant for this vibration and lead to an estimate of the height of the barrier to linearity as 6400±500 cm−1. Assignment of the vibrational hot-band structure leads to the first measurement of the A˜ state CF stretching frequency as ν3′=1260 cm−1 and tentatively the CH stretching frequency as ν1′=2852 cm−1. The A′ rotational constant increases strongly with increasing quanta of bending vibration, which indicates that the molecular structure is becoming more linear. Consideration of only the average bond angle, calculated from ab initio data for this state, is insufficient to account for the change in A′. The coupling of a-axis rotation with bending vibration must be included. A number of other dynamical effects were observed in the spectra, including lifetime shortening and disappearance of rotational transitions with K′≥1. These were explained in terms of the Renner–Teller interaction between the X˜ and A˜ states. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479068
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  • 9
    Electronic Resource
    Electronic Resource
    The electronic spectroscopy of jet-cooled m-difluorobenzene (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 6426-6439 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The S1(1B2)–S0(1A1) electronic transition of m-difluorobenzene cooled in a supersonic free jet has been investigated in detail by use of laser induced fluorescence excitation and dispersed fluorescence spectroscopy. By analysis of over 50 vibronic transitions we have assigned 16 new S1 vibrational frequencies, and have confirmed seven previous assignments. This advances the total number of known S1 fundamental vibrational frequencies to 23 out of the possible 30. The assignments of two S0 frequencies have also been somewhat modified. Two different types of symmetry-forbidden transitions were identified: transitions involving one-quantum changes in b2 modes were found; and transitions involving combinations of b1 vibrations were observed to be unusually active in the vibronic spectrum. The observation of these forbidden transitions in both the fluorescence excitation and dispersed fluorescence spectra are explored in terms of first- and second-order vibronic coupling. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470421
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  • 10
    Electronic Resource
    Electronic Resource
    Photodissociation dynamics of NO2 at moderately high energy (λ=309.1 nm; Eavail=7222 cm−1) (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 194-204 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dynamics of NO2 dissociation at 309.1 nm have been explored by examining the nascent distribution of NO rotational, vibrational, spin–orbit, and lambda-doublet states. The NO fragment is produced with a monotonically decreasing vibrational distribution over the energetically accessible vibrational states (υ=0–3), and nonstatistical rotational distributions within each vibrational manifold. The distribution within υ=0 and 1 is strongly peaked near J=25.5 with a fairly narrow spread, the distribution within υ=2 is fairly flat, terminating at the limit of available energy, and the υ=3 distribution is oscillatory, also terminating at the limit of available energy. The 2Π1/2 spin–orbit state is more strongly populated than the 2Π3/2 state by a factor of 1.9 for every vibrational state. The differences in lambda-doublet populations are, in general, minor; each Λ state being roughly equally populated, although oscillations are again evident. These results are discussed in relation to results at similar available energy at room temperature and in the free jet at different available energies. It is found that the results are intermediate between the previous data at low excess energy and at high available energy, the distributions showing aspects of both regimes. From the data it is inferred that the dissociation dynamics of NO2 vary continuously from a regime where phase space theory considerations with quantum overtones dominate the product state distributions to the regime where dynamics on the exit channel determine the distributions. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469630
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