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  • 1
    Electronic Resource
    Electronic Resource
    The construction of a gas aggregation source for the preparation of size-selected nanoscale transition metal clusters (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 3178-3183 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The design and operation of a gas aggregation source is described. The source combines the attributes of high-temperature operation (enabling preparation of transition metal clusters), mass selection, ultrahigh vacuum compatibility, and transportability. This makes it ideally suited to in situ studies such as scanning tunneling microscope or synchrotron radiation experiments. Data are presented to illustrate the performance of the source; recent results obtained in synchrotron radiation studies are highlighted. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1304868
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  • 2
    Electronic Resource
    Electronic Resource
    Tobacco use by university students, Lebanon, 2001 (2003)
    Oxford, UK : Blackwell Science Ltd
    Addiction 98 (2003), S. 0 
    Details
    ISSN: 1360-0443
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Notes: Aims  The objective was to determine the prevalence of smoking [cigarettes and/or narghile (i.e. water-pipe)] among university students and to examine multiple correlates.Design  Cross-sectional.Setting  Beirut, Lebanon.Participants  A proportionate random sample of 1964 students from public and private universities in Beirut, Lebanon.Measurements  Participants completed a self-administered anonymous questionnaire that included demographic and scholastic items and health behavioral aspects, including smoking, alcohol, physical activity, weight control measures and seat belt use.Findings  The overall prevalence of smoking was 40% (21.1%, 7.6% and 11.3% of the students were smoking only narghile, only cigarettes and both cigarettes and narghile, respectively). Regression analyses showed that males, those of non-Lebanese origin, pursuing undergraduate degrees, performing risky weight control measures and drinking excessive amounts of alcohol had increased odds of smoking cigarettes. Also, age, high level of paternal education and field of study were significant predictors. Narghile smoking was significantly higher among males who drank excessive alcohol.Conclusions  The authors advocate a collaborative effort to alleviate the consequences of smoking among university students.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1360-0443.2003.00413.x
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  • 3
    Electronic Resource
    Electronic Resource
    Absorption spectra of 2-styryl-4-phenyl-thiazole ethiodides in organic solvents of varying polarities and determination of the formation constant of the charge transfer complex formed (1980)
    Springer
    Monatshefte für Chemie 111 (1980), S. 1213-1224 
    Details
    ISSN: 1434-4475
    Keywords: Charge transfer complexes ; Solvent effects ; Thermodynamic parameters ; UV-Vis. spectra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Elektronenanregungsspektren einiger substituierter 2-Styryl-4-phenyl-thiazol-ethiodide wurden in einigen Lösungsmitteln unterschiedlicher Polarität untersucht. Die Absorption bei kürzerer Wellenlänge wird einem intramolekularen Charge-Transfer (CT)-Übergang zugeordnet, die langwellige Bande einem intermolekularen CT-Übergang (Jodid—organ. Kation). Die Diskussion erfolgt basierend auf Substitutions-, Lösungsmittel-, Konzentrations-, und Temperatur-Effekten. Die Komplexbildungskonstanten und die thermodynamischen Parameter ΔH o, ΔG o und ΔS o werden angegeben.
    Notes: Abstract The electronic absorption spectra of some 2-styryl-4-phenyl-thiazole ethiodides are studied in organic solvents of different polarities. The shorter wavelength band appearing in the visible region is assigned to an intramolecular charge transfer (CT)-transition originating from the phenyl moiety to the positively charged hetero ring, while the longer wavelength one is due to an intermolecular CT-transition from the iodide ion to the 2-styryl-4-phenyl-thiazolinium cation. These assignments are based on the nature of the aldehydic residue and effects of solvent, concentration, and temperature on both the position and absorptivity of the CT complex-band. It is concluded that the CT complex formed will be highly solvated inDMF, DMSO, ethanol and methanol relative to in CHCl3, dioxane and acetone. The formation constant of the CT complex in solutions of different polarities is determined at different temperatures. Furthermore, the thermodynamic parameters ΔH o, ΔG o and ΔS o for complex formation are calculated and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00909679
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  • 4
    Electronic Resource
    Electronic Resource
    Mutation of the surface valine residues 8 and 44 in the rubredoxin from Clostridium pasteurianum : solvent access versus structural changes as determinants of reversible potential (2000)
    Springer
    JBIC 5 (2000), S. 75-84 
    Details
    ISSN: 1432-1327
    Keywords: Key words Reduction potential ; Rubredoxin ; Square wave voltammetry ; X-ray crystallography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  The Pri sidechains of two adjacent valine residues, V8 and V44, define the surface of the rubredoxin from Clostridium pasteurianum and control access to its Fe(S-Cys)4 active site. To assess the effect of systematic change of the steric bulk of the alkyl sidechains, eight single and three double mutant proteins have been isolated which vary G (H), A (Me), V (Pri), L (Bui) and I (Bus) at those positions. X-ray crystal structures of the FeIII forms of the V44A and V44I proteins are reported. Positive shifts in reversible potential of up to 116 mV are observed and attributed to increased polarity around the Fe(S-Cys)4 site induced by (1) changes in protein backbone conformation driven by variation of the steric demands of the sidechain substituents and (2) changes in solvent access to the sidechains of ligands C9 and C42. Data for the V44A mutant show that a minor change in the steric requirements of a surface residue can introduce a NH···Sγ hydrogen bond at the active site and lead to a shift in potentialof +50 mV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00010656
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  • 5
    Electronic Resource
    Electronic Resource
    Giant distal humeral geode (2000)
    Springer
    Skeletal radiology 29 (2000), S. 165-167 
    Details
    ISSN: 1432-2161
    Keywords: Key words Rheumatoid arthritis ; Geode ; Pathological fracture ; Humerus ; X-ray ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We describe the imaging features of a giant geode of the distal humerus in a patient with rheumatoid arthritis, which presented initially as a pathological fracture. The value of magnetic resonance imaging in establishing this diagnosis is emphasized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002560050587
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  • 6
    Electronic Resource
    Electronic Resource
    Mean-square helical hydrophobic moments in partially ordered proteins (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1057-1066 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Helical hydrophobic moment ratios, 〈h2〉/〈H2〉, have been evaluated for 34 polypeptides under conditions where the helix content is dictated solely by the short-range interactions operative in aqueous media. The mean-square helical hydrophobic moment is denoted by 〈h2〉, and 〈H2〉 is the averaged of the squared hydrophobicites. This ratio would be one in absence of any correlation in the hydrophobicities of amino acid residues in helices. The 〈h2〉/〈H2〉 tend to be substantially larger than values of the analogous ratio formulated for the mean-square dipole moments of typical synthetic polymers. For 24 of the 34 polypeptide chains considered, 〈h2〉/〈H2〉 is found to be greater than one, indicating a tendency to form helices with amphiphilic character. The ratio is exceptionally large in the case of the δ-hemolysins. It is also large for two other surface-active peptides, for two of the four apolipoproteins examined, and for myohemerythrin. A much smaller 〈h2〉/〈H2〉 is found for melittins. If melittins is to form helices with large 〈h2〉/〈H2〉, the configurational statistics must be governed by effects in addition to those short-range interactions that occur when water is the solvent.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230607
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  • 7
    Electronic Resource
    Electronic Resource
    Mean-square hydrophobic moment for partially helical polypeptides (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 201-212 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A mean-square helical hydrophobic moment, 〈h2〉, is defined for polypeptides in analogy to the mean-square dipole moment, 〈μ2〉, for polymer chains. For a freely jointed polymer chain, 〈μ2〉 is given by Σmi2, where mi denotes the dipole moment associated with bond i. In the absence of any correlations in the hydrophobic moments of individual amino acid residues in the helix, 〈h2〉 is specified by ΣHi2, where Hi denotes the hydrophobicity of residue i. The tendency for correlations in orientations of residue hydrophobic moments in helices therefore dictates the size of 〈h2〉/〈H2〉, where 〈H2〉 denotes the average value of ΣHi2 for all helices. The value of 〈h2〉/〈H2〉 will be greater than one in amphiphilic helices. A necessary prerequisite for this diagnostic usage of 〈h2〉/〈H2〉 is that the residue hydrophobic moment be oriented prependicular to the principal axis of the helix. Matrix-generation schemes are formulated that permit rapid evaluation of 〈h2〉 and 〈H2〉. The behavior of 〈h2〉/〈H2〉 is illustrated by calculations performed for model sequential copolypeptides.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230204
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  • 8
    Electronic Resource
    Electronic Resource
    Molecular orbital treatment of phenylfurans and bifurans (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 383-399 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecule-in-molecule method of computation has been applied in a SCF study of the electronic absorption spectra of 2- and 3-phenylfurans and 2,2′- and 3,3′-bifurans. The computed values for the transition energies and band intensities differ for the different isomers and help one to assign the preferred conformer of the studied molecules. Computations were performed on planar as well as nonplanar conformers. The calculated parameters as well as the interaction energy suggest all-planar configuration for the studied molecules. A model potential for the sigma framework for the ortho-hydrogens is considered. The calculated steric repulsion energy is negligible compared to the π delocalization. The height of the rotational barrier was larger for 2-phenylfuran than for 3-phenylfuran, and larger for 2,2′-bifuran than for 3,3′-bifuran. This result is in accord with predictions based on the extent of “π” conjugation in these molecules.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560190303
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  • 9
    Electronic Resource
    Electronic Resource
    Behavior of amphipathic helices on analysis via matrix methods, with application to glucagon, secretin, and vasoactive intestinal peptide (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 1003-1021 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A configuration partition function, which incorporates concepts embodied in the amphipathic helix hypothesis, has been formulated for a polypeptide in the presence of zwitterionic phospholipid. An enhanced probability is assigned to helix formation in any region of the polypeptide chain where side chains bearing charges of opposite sign will be situated on the same side of the α-helix but displaced from one another by one turn. This situation will arise when residues i - 4 (or i - 3) and i bear charges of opposite sign and residue i - 4 (or i - 3) through i are in a helical state. Illustrative calculations are performed for polypeptide chains in which the generalized nonionic amino acid residue serving as host has Zimm-Bragg parameters of σ = 10-4, s = 1. These calculations define conditions under which two interacting charged pairs can cooperate in a synergistic helix augmentation even when the two pairs are separated by significantly more than four generalized nonionic amino acid residues. Furthermore, the two interacting charged pairs, as well as the intervening amino acid residues, may become helical as one unit. Significant augmentation in helicity is observed with plausible values for the enhanced probablity assigned to helix formation for an interacting pair. This model predicts correctly that glucagon and secretin, but not vasoactive intestinal peptide, undergo a coil-to-helix trnsition in the presence of zwitterionic phospholipid. This prediction is made with plausible values for the parameter used to express the helicity enhancement. The experimental observation with zwitterionic phospholipids is the direct opposite of that seen for these three peptides in the presence of anionic lipids and detergents. In anionic lipids the amount of induced helicity is in the following order: glucagon 〈 secretin 〈 vasoactive intestinal peptide. Results obtained with these three peptides demonstrate that the nature of the head group of the lipid is important for lipid-protein interaction and that the resulting conformational changes can be rationalized by matrix methods.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360220317
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