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  • 1
    Electronic Resource
    Electronic Resource
    Characterization of the bifurcated structure of the water dimer (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 1825-1828 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The bifurcated structure of the water dimer has been the subject of considerable uncertainty with respect to its vibrational characterization. We have considered this question at the self-consistent-field (SCF) level of theory using finite basis sets that allow a close approach to the Hartree–Fock limit. As one approaches the Hartree–Fock limit, the bifurcated structure is predicted to be a true transition state, with one imaginary vibrational frequency, ω12(B2)∼200i cm−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461030
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  • 2
    Electronic Resource
    Electronic Resource
    Rotational transfer, an angular momentum model (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 4586-4602 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have re-examined critical experiments on collision induced rotational transfer (RT) and conclude that the probability of RT is controlled by the factors that control the probability of angular momentum (AM) change. The probability of energy change seems less important in this respect. In the light of this we suggest a model for RT in which the probability of AM change is calculated directly and present a formalism for this purpose. We demonstrate that such a calculation leads to an exponential-like fall of RT probabilities with transferred AM, a consequence of the radial dependence of the repulsive part of the intermolecular potential. Thus in this AM model, the exponential gap law has a simple physical origin. The AM model we describe may be used as the basis of an inversion routine through which it is possible to convert RT data into a probability density of the repulsive anisotropy. Through this model therefore it is possible to relate experimental RT data directly to the forces that are responsible for rotational transfer. The hard ellipse model is used in this work to relate calculated anisotropies to a form that includes an isotropic component. The result is a representation of the intermolecular potential through which new insights into the RT process are gained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465020
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  • 3
    Electronic Resource
    Electronic Resource
    Environmental isolation platform for microrobot system development (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3492-3498 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Environmental isolation of a microrobot is important to achieve the demanding operating specifications intrinsic to such a system. Our experience with the current generation microrobot, MR1, indicates the next generation microrobot, MR2, will require a high degree of isolation from the mechanical, thermal, electromagnetic, and optical environment of a typical laboratory. Accordingly, this paper presents the design, construction, and isolation test results of an environmental isolation platform built to house MR2 and its many subsystems under development in our laboratory. Our design approach used qualitative estimates of the magnitudes of external environmental noise acceptable to microrobot operation to determine the required attenuation of each noise input. The resulting platform consisted of a custom environmental enclosure mounted on a modified commercial vibration isolation optical table. The performance measurements quantified the attenuation of each unwanted disturbance within the frequency bands of interest and a final test was made with a laser heterodyne interferometer installed on the platform in a typical laboratory environment. The results of this experiment show that the isolation specifications required for microrobot operation were met thereby verifying our platform design. We expect that our design can be used in environmental isolation of not only microrobots but also other sensitive electro-optomechanical instruments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143754
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  • 4
    Electronic Resource
    Electronic Resource
    Characterization and use of a novel optical position sensor for microposition control of a linear motor (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 349-356 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The performance of an optical reflective position sensor is evaluated as the position feedback element in the microposition control of a linear electromagnetic motor. The open loop position sensor characteristics are first measured to determine the analog controller design parameters. The performance of the controller, evaluated using an integrated Michelson interferometer, measures the control loop bidirectional accuracy, hysteresis, long-term stability, and position linearity. Compensation of the small nonlinearity measured required linearization of the input command signal and a practical application is demonstrated with a constant velocity scan of one of the interferometer mirrors. A final result is the submicron square wave modulation of the interferometer output with its scan mirror under closed-loop control using feedback from the reflective position sensor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144256
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  • 5
    Electronic Resource
    Electronic Resource
    Rapid Communication: A cis-Acting Element, Tα-1, in the Upstream Region of Rod α-Transducin Gene that Binds a Developmentally Regulated Retina-Specific Nuclear Factor (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 62 (1994), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The G protein transducin (T) is an integral component of the signal transduction pathway in photoreceptors. We have identified a cis-acting element, Ta-1, in the upstream region of the mouse rod a-T (Trα) gene that may be important for tissue-specific expression. Tα-1 binds a retina-specific nuclear factor of apparent molecular mass of 90 kDa. Binding to the Tα-1 site is developmentally regulated and peaks between postnatal days 6 and 9. This corresponds to the time of rod photoreceptor maturation and the rise in Trα gene expression. The sequence of Tα-1 shows homology with RET-1, a cis-acting element in the proximal promoter of opsin gene that binds a distinct retina-specific factor. Tα-1 and RET-1 sequences may have been derived from a prototype Tα-1/RET-1 sequence, evolved to confer photoreceptor specificity on retina-specific genes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1994.62010396.x
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  • 6
    Electronic Resource
    Electronic Resource
    Homocysteine potentiates copper- and amyloid beta peptide-mediated toxicity in primary neuronal cultures: possible risk factors in the Alzheimer's-type neurodegenerative pathways (2001)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 76 (2001), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Oxidative stress may have an important role in the progression of neurodegenerative disorders such as Alzheimer's disease (AD) and prion diseases. Oxidative damage could result from interactions between highly reactive transition metals such as copper (Cu) and endogenous reducing and/or oxidizing molecules in the brain. One such molecule, homocysteine, a thiol-containing amino acid, has previously been shown to modulate Cu toxicity in HeLa and endothelial cells in vitro. Due to a possible link between hyperhomocysteinemia and AD, we examined whether interaction between homocysteine and Cu could potentiate Cu neurotoxicity. Primary mouse neuronal cultures were treated with homocysteine and either Cu (II), Fe (II or III) or Zn (II). Homocysteine was shown to selectively potentiate toxicity from low micromolar concentrations of Cu. The toxicity of homocysteine/Cu coincubation was dependent on the ability of homocysteine to reduce Cu (II) as reflected by the inhibition of toxicity with the Cu (I)-specific chelator, bathocuproine disulphonate. This was supported by data showing that homocysteine reduced Cu (II) more effectively than cysteine or methionine but did not reduce Fe (III) to Fe (II). Homocysteine also generated high levels of hydrogen peroxide in the presence of Cu (II) and promoted Aβ/Cu-mediated hydrogen peroxide production and neurotoxicity. The potentiation of metal toxicity did not involve excitotoxicity as ionotropic glutamate receptor antagonists had no effect on neurotoxicity. Homocysteine alone also had no effect on neuronal glutathione levels. These studies suggest that increased copper and/or homocysteine levels in the elderly could promote significant oxidant damage to neurons and may represent additional risk factor pathways which conspire to produce AD or related neurodegenerative conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.2001.00178.x
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  • 7
    Electronic Resource
    Electronic Resource
    Substrate-Bound β-Amyloid Peptides Inhibit Cell Adhesion and Neurite Outgrowth in Primary Neuronal Cultures (2000)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 74 (2000), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Accumulation of theβ-amyloid protein (Aβ) in the brain is an important step in the pathogenesis of Alzheimer's disease. However, the mechanism of Aβ toxicity remains unclear. Aβ can bind to the extracellular matrix, a structure that regulates adhesive events such as neurite outgrowth and synaptogenesis. The binding of Aβ to the extracellular matrix suggests that Aβ may disrupt cell-substrate interactions. Therefore, the effect of substrate-bound Aβ on the growth of isolated chick sympathetic and mouse cortical neurons was examined. Aβ1-40 and Aβ1-42 had dose-dependent effects on cell morphology. When tissue culture plates were coated with 0.1-10 ng/well Aβ, neurite outgrowth increased. Higher amounts of Aβ peptides (≥μg/well) inhibited outgrowth. The inhibitory effect was related to aggregation of the peptide, as preincubation of Aβ1-40 for 24 h at 37 °C (a process known to increase amyloid fibril formation) was necessary for inhibition of neurite outgrowth. Aβ29-42, but not Aβ1-28, also inhibited neurite outgrowth at high concentrations, demonstrating that the inhibitory domain is located within the hydrophobic C-terminal region. Aβ1-40, Aβ1-42, and Aβ29-42 also inhibited cell-substrate adhesion, indicating that the effect on neurite outgrowth may have been due to inhibition of cell adhesion. The results suggest that accumulation of Aβ may disrupt cell-adhesion mechanisms in vivo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.2000.741122.x
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  • 8
    Electronic Resource
    Electronic Resource
    Molecular structure of chromyl nitrate (CrO2(NO3)2) in the gas phase: a novel form of coordination for chromium? (1991)
    s.l. : American Chemical Society
    Inorganic chemistry 30 (1991), S. 4761-4766 
    Details
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ic00025a016
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  • 9
    Electronic Resource
    Electronic Resource
    The Perturbation of the Ultraviolet Spectrum of Nitromethane in Mixed Solvents, with a Note on Complex Formation (1955)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 77 (1955), S. 3959-3963 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja01620a005
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  • 10
    Electronic Resource
    Electronic Resource
    Importance of domain closure for homotropic cooperativity in Escherichia coli aspartate transcarbamylase (1990)
    s.l. : American Chemical Society
    Biochemistry 29 (1990), S. 1444-1451 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00458a015
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