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  • American Institute of Physics (AIP)  (4)
  • Blackwell Science Ltd  (3)
  • 1995-1999  (7)
  • 1
    Electronic Resource
    Electronic Resource
    Dynamics of hydrogen-bonded liquids confined to mesopores: A dielectric and neutron spectroscopy study (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 2016-2024 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this paper we present and discuss experimental results on molecular mobility in propylene glycol and its three oligomers confined to the ∼100 A(ring) pores of a controlled porous glass. The objective is to elucidate the finite size effects on the dynamics of hydrogen-bonded liquids of different molecular weights but identical chemical composition. The methods of dielectric and neutron spectroscopy have been employed to investigate both the low- and high-frequency features as a function of temperature. We find that all fluids in pores separate into two distinct liquid phases. (i) molecules physisorbed at the surface which exhibit a dramatic frustration of their mobility related to a substantial positive shift of the glass transition temperature Tg by up to ΔTg≈+47 K; and (ii) relatively "free'' molecules in the inner pore space subject to only moderate retardation of the α and normal mode relaxation and substantial broadening of the distribution of relaxation times. The shift in Tg for the α process with ΔTg≈+5 K is maximal for the monomer liquid and gradually diminishes with increasing molecular weight or decreasing intermolecular hydrogen bonding. The inelastic neutron spectrum of confined propylene glycol shows the boson peak as expected in bulk strong and intermediate glass formers in the vicinity of Tg. This effect can be attributed to the finite-size induced crossover from long wave vibrations characteristic of a continuous medium to localized vibrations in a confined geometry. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469728
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  • 2
    Electronic Resource
    Electronic Resource
    The electron cyclotron absorption diagnostic at the Rijnhuizen tokamak project (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 4439-4447 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new 20-channel electron cyclotron absorption diagnostic has been developed at the Rijnhuizen tokamak project. It is the first time the electron pressure profile in a tokamak plasma can be measured directly with a time resolution of 1 ms. The diagnostic measures simultaneously the emission and absorption of the second harmonic electron cyclotron frequencies. Microwaves are injected from the high field side and detected at the low field side in the equatorial midplane. The transmitted power is measured after a single pass through the plasma column. The absorption measurements are complicated by nonresonant losses: refraction of the injected microwaves (losses up to 100%), and scattering of microwaves by density fluctuations (losses 2%–3%). A fast algorithm has been developed to obtain a quantitative measure for these nonresonant losses. This calculation method is based on a parametrization of the experimental data. Combining the electron cyclotron absorption (ECA) measurements and the parametrization provides a reliable tool for determining the optical depth, the electron temperature, and the electron pressure. A good agreement was found between pressure and temperature profiles, measured with ECA and other diagnostics. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148411
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  • 3
    Electronic Resource
    Electronic Resource
    Elastomeric binary phase gratings for measuring acceleration, displacement, strain, and stress (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 3310-3319 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This article describes the fabrication and operating principles of a device suitable for measuring displacements, stresses, strains, accelerations, and forces. The device consists of an elastomeric material with a surface relief diffraction grating embossed on its surface. Mechanical compression of this element changes the way that it diffracts light. This article also describes designs and performance characteristics of simple accelerometers and pressure sensors based on these devices. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147413
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  • 4
    Electronic Resource
    Electronic Resource
    Investigation of ion sawtooth activity by Rutherford scattering : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 327-329 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The Rutherford scattering diagnostic at TEXTOR has been used to investigate the time evolution of the ion velocity distribution during sawtooth activity. Coherent averaging techniques have been employed to obtain better statistics. The time evolutions of central ion and electron density were found to be strongly correlated in four out of five cases. In one case, where saturation of the sawteeth occurred, a discrepancy between the two has been found, which could be attributed to an influx of impurities towards the end of the sawtooth. Changes of about 20% in the central toroidal rotation of the bulk ions have been found during sawtooth crashes of neutral beam injected discharges, whereas no changes were found in the ohmic case. No statistically reliable statements can be made about changes in the ion temperature. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146401
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  • 5
    Electronic Resource
    Electronic Resource
    Deregulation of gluconeogenic structural genes by variants of the transcriptional activator Cat8p of the yeast Saccharomyces cerevisiae (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In the yeast Saccharomyces cerevisiae, growth with a non-fermentable carbon source requires co-ordinate transcriptional activation of gluconeogenic structural genes by an upstream activation site (UAS) element, designated CSRE (carbon source-responsive element). The zinc cluster protein encoded by CAT8 is necessary for transcriptional derepression mediated by a CSRE. Expression of CAT8 as well as transcriptional activation by Cat8p is regulated by the carbon source, requiring a functional Cat1p (= Snf1p) protein kinase. The importance of both regulatory levels was investigated by construction of CAT8 variants with a constitutive transcriptional activation domain (INO2TAD) and/or a carbon source-independent promoter (MET25 ). Whereas a reporter gene driven by a CSRE-dependent synthetic minimal promoter showed a 40-fold derepression with wild-type CAT8, an almost constitutive expression was found with a MET25–CAT8–INO2TAD fusion construct due to a dramatically increased gene activation under conditions of glucose repression. Similar results were obtained with the mRNA of the isocitrate lyase gene ICL1 and at the level of ICL enzyme activity. Taking advantage of a Cat8p size variant, we demonstrate its binding to the CSRE. Our data show that carbon source-dependent transcriptional activation by Cat8p is the most important mechanism affecting the regulated expression of gluconeogenic structural genes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1999.01588.x
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  • 6
    Electronic Resource
    Electronic Resource
    The product of the SNF2/SWI2 paralogue INO80 of Saccharomyces cerevisiae required for efficient expression of various yeast structural genes is part of a high-molecular-weight protein complex (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 32 (1999), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Structural genes of phospholipid biosynthesis in the yeast Saccharomyces cerevisiae are activated by the Ino2p/Ino4p transcription factor that binds to ICRE promoter motifs and mediates maximal gene expression in the absence of inositol. We identified the ino80 mutation causing inositol auxotrophy as a result of a defect in ICRE-dependent gene activation. The product of the corresponding wild-type gene INO80 (= YGL150C) shows significant similarity to the Snf2p family of DNA-dependent ATPases. Nevertheless, SNF2 in increased gene dosage did not suppress ino80 mutant phenotypes. Mutation of the Ino80p lysine residue corresponding to the NTP binding site of Snf2p led to a non-functional protein. In ino80 null mutants, gene activation mediated by an ICRE decreased to 16% of the wild-type level. Maximal expression of PHO5, GAL1, CYC1 and ICL1 was also significantly reduced. Thus, Ino80p affects several transcription factors involved in unrelated pathways. As demonstrated by gel filtration, Ino80p is part of a high-molecular-weight complex of more than 1 MDa. Similar to what was found for Snf2p, the Ino80p-containing complex may influence the transcriptional level of several unrelated structural genes by functioning as an ATPase that possibly acts on chromatin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1999.01390.x
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  • 7
    Electronic Resource
    Electronic Resource
    Transcriptional control of the yeast acetyl-CoA synthetase gene, ACS1, by the positive regulators CAT8 and ADR1 and the pleiotropic repressor UME6 (1997)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 26 (1997), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The ACS1 gene, encoding one out of two acetyl-CoA synthetase isoenzymes of Saccharomyces cerevisiae, is strictly regulated at the transcriptional level by the carbon source of the medium. While ACS1 is poorly expressed in the presence of a high glucose concentration, a several hundred-fold derepression occurs with ethanol as the sole carbon source or under conditions of sugar limitation. The molecular mechanism responsible for the carbon source control of ACS1 turned out to be highly complex. A carbon source-responsive element (CSRE), previously identified upstream of gluconeogenic structural genes, and a binding site of the alcohol dehydrogenase regulator, Adr1p, together mediate about 80% of the derepressed gene activity. Binding of Adr1p synthesized by Escherichia coli to the ACS1 control region was shown by an electrophoretic mobility shift assay. In addition to these activating elements, two URS1 motifs confer negative control on the ACS1 promoter. The URS1 element was found to be a constitutive repression site, which is most effective from a downstream position with respect to an upstream activation site (UAS). In a mutant lacking the URS1-binding factor, Ume6p, ACS1 expression was partially glucose insensitive. Ume6p must counteract transcription factors that are constitutively active. Site-directed mutagenesis of Abf1p binding sites in the ACS1 promoter significantly reduced gene expression in the ume6 mutant, grown under repressing conditions. Thus, a functional balance of the pleiotropic positive factor Abf1p and the negative factor Ume6p is in part responsible for glucose repression of ACS1. The combined influence of the regulated UAS elements, CSRE and Adr1p binding site, mediates a strong increase in ACS1 expression under derepressing conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1997.5611937.x
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