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  • 1
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Some cases of autosomal-dominant familial amyotrophic lateral sclerosis (FALS) have been associated with mutations in SOD1, the gene that encodes Cu/Zn superoxide dismutase (Cu/Zn SOD). We determined the concentrations (µg of Cu/Zn SOD/mg of total protein), specific activities (U/µg of total protein), and apparent turnover numbers (U/µmol of Cu/Zn SOD) of Cu/Zn SOD in erythrocyte lysates from patients with known SOD1 mutations. We also measured the concentrations and activities of Cu/Zn SOD in FALS patients with no identifiable SOD1 mutations, sporadic ALS (SALS) patients, and patients with other neurologic disorders. The concentration and specific activity of Cu/Zn SOD were decreased in all patients with SOD1 mutations, with mean reductions of 51 and 46%, respectively, relative to controls. In contrast, the apparent turnover number of the enzyme was not altered in these patients. For the six mutations studied, there was no correlation between enzyme concentration or specific activity and disease severity, expressed as either duration of disease or age of onset. No significant alterations in the concentration, specific activity, or apparent turnover number of Cu/Zn SOD were detected in the FALS patients with no identifiable SOD1 mutations, SALS patients, or patients with other neurologic disorders. That Cu/Zn SOD concentration and specific activity are equivalently reduced in erythrocytes from patients with SOD1 mutations suggests that mutant Cu/Zn SOD is unstable in these cells. That concentration and specific activity do not correlate with disease severity suggests that an altered, novel function of the enzyme, rather than reduction of its dismutase activity, may be responsible for the pathogenesis of FALS.
    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 104 (1996), S. 2557-2565 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: For diffusion-controlled reactions in three dimensions, continuum mechanics provides a quantitative relation between the steady-state reaction rate constant k and the diffusion coefficient D. However, this approach fails in two dimensions, where no steady-state solution exists on an infinite domain. Using both Monte Carlo methods and analytical techniques, we show that previous attempts to circumvent this problem fail under real laboratory conditions, where fractional coverages often exceed 10−3. Instead, we have developed a rigorous and general relation between k and D for all coverages on a square lattice for the reaction A+A→A2. For short times or high coverages, the relation k=πD/γ holds exactly, where γ denotes the two-dimensional packing fraction. For lower coverages, however, k depends on time in both constant-coverage (adsorption allowed) and transient-coverage (adsorption forbidden) regimes. In both cases, k decreases in response to the evolution of nonrandom adsorbate configurations on the surface. These results indicate that diffusion-limited surface reactions may be identified unambiguously in the laboratory and also provide a quantitative link between diffusion parameters and experimentally determined recombination rate parameters. Practical experimental methods highlighting such effects are outlined. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Clinical psychology 5 (1998), S. 0 
    ISSN: 1468-2850
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Psychology
    Notes: This article reviews the evidence regarding the effects of parental death on children's acute and long-term psychological adjustment, as well as the clinical literature describing interventions for bereaved families. The risk of adjustment difficulties for bereaved children has shown no consistent relation to complications of grieving, but is instead largely accounted for by an increased probability of inadequate care following the loss of a parent. The literature describing interventions for bereaved families offers little formal evaluation, and reflects our incomplete understanding of children's grief responses, and thus of appropriate treatment goals. Further research should focus on more molecular analysis of grief processes, including grief-related interactions between children and parents, and should take into account developmental variation in children's needs and experiences. The use of multiple informants of child and parent behavior is strongly recommended, and the unique contributions of longitudinal research in understanding children's adjustment to loss are highlighted.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Langmuir 11 (1995), S. 186-190 
    ISSN: 1520-5827
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 2374-2376 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: State-filling spectroscopy is used to study the effects of alloy intermixing in quantum-dot (QD) ensembles having well-defined electronic shells. Rapid thermal annealing is performed on samples of self-assembled QDs grown with different intersublevel energy spacings. For InAs/GaAs QDs, the intersublevel is tuned between ∼90 and 25 meV. The intense and sharp shell structures observed in photoluminescence indicate unambiguously that the QDs retained their zero-dimensional density of states after the diffusion of the potential, which also causes strong blueshifts (up to ∼200 meV) and a pronounced narrowing of the inhomogeneously broadened emission (down to ∼12 meV). © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 12 (2000), S. 1087-1100 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Within the context of the rotating shallow water equations, it is shown how initially unbalanced states possessing certain symmetries dynamically evolve to lose those symmetries during nonlinear geostrophic adjustment. Using conservation law methods, it is demonstrated that the adjustment of equal and opposite (circular) mass imbalances results in a balanced end state where cyclones are stronger than anticyclones; the reverse holds true for momentum imbalances. In both cases, the degree of this asymmetry is shown to be directly proportional to the amount of initial imbalance (a measure of the nonlinearity occurring during time-dependent adjustment). On the other hand, the degree of asymmetry is maximal for imbalances of Rossby deformation scale. As for the potential vorticity, it is shown that its final profile can be noticeably different from its initial one; from an Eulerian perspective, this rearrangement is not confined to uniform shifts of potential vorticity fronts. Direct 2D numerical initial value problems confirm the asymmetry in the predicted final states and establish a relatively fast time scale for adjustment to complete. The robustness of these results is confirmed by studying, in addition, the adjustment of elliptical mass imbalances. The numerical integrations reveal that, during geostrophic adjustment, potential vorticity rearrangement occurs irreversibly on a fast wave time scale. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 2701-2703 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We study how the optical properties of InAs self-assembled quantum dots (QDs) grown on GaAs substrate are affected when using AlGaAs barriers to increase the carrier confinement. The inhomogeneous broadening of the QD ensemble is found to increase when ternary aluminum alloys are used next to or within the QDs. By growing thin GaAs spacers to separate the QDs from the AlGaAs barriers, we obtain QD ensembles which exhibit little photoluminescence quenching and well-defined excited states up to room temperature. Postgrowth rapid thermal annealing is then used to intermix these InAs/GaAs/AlGaAs QDs and diffuse the Al towards the QDs. In contrast with QDs having thick binary GaAs barriers, the inhomogeneous broadening of QDs with nearby AlGaAs barriers is not decreased with intermixing, leading to unresolved excited state peaks when the interdiffusion length becomes comparable to the GaAs spacer thickness. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 3583-3585 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Laser annealing of InAs/GaAs quantum-dot (QD) microstructures has been investigated for selective area tuning of their electronic shell structure. Extensive blueshifts of the QD excited states were observed following 20–40 s laser irradiation. In the most extreme case, we were able to shift the position of the ground state transition by 298 meV, i.e., to the spectral region where the photoluminescence signal originates from the as-grown InAs wetting layer. A reduction from ∼50 to 8 meV of the full width at half maximum of the PL peak corresponding to this transition indicates a drastic change in the structural characteristics of the investigated QD ensemble. The attractive feature of the laser-QD-intermixing technique is that it offers the possibility of obtaining targeted blueshifts and inter-sublevel energy spacing on the lateral scale required in the fabrication of QD-based integrated optoelectronic devices and, possibly, photonic band gap crystals. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 986-988 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Quantum-dot laser diodes with up to five well-defined electronic shells are fabricated using self-assembled quantum dots (QDs) grown by molecular-beam epitaxy. Shape-engineered stacks of self-aligned QDs with improved uniformity are used to increase the gain in the active region. Lasing is observed in the upper QD shells for small-gain media, and progresses towards the QD ground states for longer cavity lengths. We obtained at 77 K thresholds of Jth=15 A/cm2 for a 2 mm cavity lasing in the first excited state (p shell), and Jth=125 A/cm2 for a 1 mm cavity lasing in n=3 (d shell). At 300 K for a 1 mm cavity, Jth is 490 A/cm2 with lasing in n=4 (f shell). © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 2611-2613 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Effects of 1 MeV electron irradiation on Xe precipitates in Al, formed by ion implantation, have been observed in situ by high-voltage transmission electron microscopy. Individual Xe precipitates undergo melting and recrystallization, migration which leads to coalescence, and shape changes. These processes are driven by the production of defects without either cascade defect production or the introduction of additional Xe atoms. Precipitate migration is due to an irradiation-induced surface diffusion process on the Xe/Al interfaces. Coalescence of close precipitates is enhanced by directed motion as a result of the net displacement of Al atoms out of the volume between them. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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