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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 1931-1933 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The initial stages of the three-dimensional metal organic vapor phase epitaxy growth of InP/GaAs have been studied by atomic force microscopy and Rutherford backscattering. The results are compared with the predictions of an equilibrium model that predicts an in-plane critical size for island formation. At low growth rates the model fits well the experiments while it needs to be further developed to include kinetic effects at higher growth rates. The experiments indicate a Stranski–Krastanow growth mode with a critical thickness of 2.1 ML. © 1996 American Institute of Physics.
    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 110 (1999), S. 10307-10315 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A high resolution VUV photoabsorption spectrum of ethyl iodide has been recorded between 4 and 10.2 eV (310–120 nm) using synchrotron radiation. The spectrum consists of a broad structureless absorption band centered at 4.78 eV, followed by a region dominated by excitation of Rydberg states. A high resolution photoelectron spectrum (PES) of the lowest energy ionization band has been obtained and provides ionization energies necessary for identification of related Rydberg-excited states. Also, analysis of the vibrational fine structure in the PES has allowed identification of the normal vibrational modes excited and their wave numbers in the ion. These, in turn, have been used in the assignment of the lowest energy photoabsorption bands arising from electron excitation into the 6s Rydberg orbital. An electron energy loss spectrum has also been recorded from 5.8 to 14.2 eV, under electric-dipole conditions. It confirms the magnitude of the photoabsorption cross section values obtained using the synchrotron radiation and extends the differential and optical oscillator strength values up to 14.2 eV. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-4919
    Keywords: WEHI-3B ; L1210 ; murine leukemia ; cholera toxin ; ganglioside ; toxin binding ; cAMP ; growth inhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The murine leukemia cell lines L1210 and WEHI-3B show a very different sensitivity to the cholera toxin (CT). Thein vitro growth of L1210 is completely inhibited by 10−8 M CT, while WEHI-3B growth shows the same inhibition at 10−11 M. The analysis of membrane ganglioside pattern of the two cell lines shows that in L1210 cells the major component is the GM1a ganglioside while the monosialoganglioside fraction from WEHI-3B is entirely composed of gangliosides of the ‘b’ series among which GM1b is the more represented. The total cholera toxin binding capacity of the ganglioside extract from L1210 cells is more than hundred fold higher than that of WEHI-3B and this difference is also confirmed by the number of CT receptors/cell and by the binding of FITC-B subunit of CT on the cells. These surprising data are in conflict with the poor sensitivity to CT evidenced by L1210 compared to WEHI-3B cells. In order to clarify this discrepancy we investigated the cAMP accumulation, the cell viability and the clonogenicity of these two leukemia cell lines following the treatment with CT and forskolin (FRSK). The treatment of WEHI-3B cells with CT induces a dramatic increase of intracellular cAMP which highly correlates with cell death and the decrease of clonogenicity and this result is partially obtained by the treatment with FRSK, L1210 cells do not evidence significant cAMP accumulation neither with CT nor with FRSK treatment. These data suggest that the different inhibiting effect of CT on WEHI-3B and L1210 cells does not correlate with their different pattern of gangliosides and the related toxin binding capacity. Further they indicate that the growth inhibition of WEHI-3B cells is closely related with a cAMP-dependent cell killing mechanism, while the inhibition of L1210 growth (produced by high concentration of CT) is mediated by a cAMP independent mechanism.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Magnetic resonance materials in physics, biology and medicine 4 (1996), S. 241-245 
    ISSN: 1352-8661
    Keywords: vitreous body ; 23na nuclear magnetic resonance ; 23na relaxation times
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics
    Notes: Abstract We have studied the nuclear magnetic resonance (NMR) relaxation behavior, and thus the dynamic properties, of the sodium ion in the vitreous body at different temperatures. The23Na NMR spectrum exhibits a resonance, the intensity of which accounts for an ion visibility of 100%. The23Na longitudinal and transverse relaxation times, at all temperatures but the highest, present two components, suggesting that the sodium ions are present in two states of different mobility, whose populations are in slow exchange on the NMR time scale. The correlation times and quadrupole coupling constants for the two sodium pools have been derived. The faster relaxation of a fraction of the vitreal sodium has tentatively been ascribed to the influence of the macromolecular framework of the vitreous body. The reported information may be of use for the understanding of the diagnostic applications of23Na magnetic resonance imaging of the ocular structures.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1572-9486
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The role that low temperature thermal detectors are going to play in a few relevant subjects of Non Accelerator Physics is briefly reviewed. The use of large arrays of macrobolometers is considered in experiments on Solar Neutrinos, on Double Beta Decay, and on interactions of WIMPS.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-6830
    Keywords: brain gliomas ; ceramide ; ganglioside ; malignancy ; 1H NMR spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. The high-resolution 1H NMR (MRS) spectra of human brain tumor homogenates revealed a broad resonance at 5.3–5.4 ppm in glioblastoma multiforme (N = 16) and brain metastases (N = 2). The broad resonance was identified as ceramide, a sphingosine–fatty acid combination portion of ganglioside, indicating an elevated abundance of monounsaturated fatty acids. GLC analysis of gangliosides in the highly malignant glioblastoma multiforme revealed that the elevated monounsaturated fatty acid is oleic acid (C18:1). The resonance at 5.3–5.4 ppm region was not detectable in normal human brain (N = 2), in meningiomas (N = 2), or in low-grade astrocytomas (N = 12). In normal human brain the abundance of monounsaturated fatty acid is minimal. 2. This investigation was made possible because the method of producing homogenate resulted in (i) no loss of lipids during the process and (ii) a well-homogenised sample, with (iii) no loss in chemical integrity. 3. The properties of tumor gangliosides include antigenic specificity and immunosuppresive activity and the ceramide, a sphingosine–fatty acid combination, noticeably influences the ganglioside immunosuppressive activity. 4. The observation of 1H NMR ceramide resonance in high-malignant brain tumors emphasizes the dramatic role of aberrant gangliosides and ceramide precursors on the grade of malignancy and invasiveness. 5. Further insight into the specific nature of the ceramide portion of gangliosides in grading the malignancy of brain tumors should be investigated further.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0044-2313
    Keywords: Tin complexes ; thiolated ligands ; 119Sn Mössbauer spectra ; molecular dynamics ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zinn(IV)-, Monomethylzinn(IV)- und Dimethylzinn(IV)-Komplexe mit Thiolschwefel- und heterocyclischen Stickstoff-Donatoren: Moleküldynamik und Struktur bei 119Sn-Mössbauer-SpektrenDie Moleküldynamik der Komplexe Sn(SPyN)4 (1), SnCl2(SPyN)2 (2), MeSn(SPy)3 (3), MeSnCl(SPyN)2 (4), Me2Sn(TCy)2 (5), Me2SnCl(TOx) (6) und Me2Sn(TUr) (7) (HSPy = 2-Mercaptopyridin; HSPyN = 2-Mercaptopyrimidin; HTCy = 2-Thiocytosin; HTOx = 8-Thiochinolin; H2TUr = 2-Thiouracil) wurde mit 119Sn-Mössbauer-Spektroskopie bei verschiedenen Temperaturen untersucht. Die Flächen unter den Resonanzlinien wurden als Funktion der Temperatur bestimmt und daraus die Debye-Temperaturen, die cut-off-Frequenzen wie auch die rückstoßfreien Anteile (Lamb-Mössbauer-Faktor) und die mittleren quadratischen Auslenkungen der 119Sn-Atome berechnet. Durch Fingerprintvergleiche auf Grund von Literaturdaten wurden monomere Strukturen den Komplexen (1) bis (4) und (6) zugeordnet, während (5) und (7) an der Grenze monomer eindimensionaler Polymerer liegen. Die Ergebnisse werden auf der Basis bekannter Kristall- und Molekülstrukturen diskutiert. Die Umgebung der Zinnatome wird durch Punktladungsmodell-Berechnungen von Kernquadrupolaufspaltungs-Parametern simuliert; Molekülstrukturen für die Komplexe (5) bis (7), von denen keine Röntgendaten verfügbar sind, werden vorgeschlagen.
    Notes: The molecular dynamics of the complexes Sn(SPyN)4 (1), SnCl2(SPyN)2 (2), MeSn(SPy)3 (3), MeSnCl(SPyN)2 (4), Me2Sn(TCy)2 (5), Me2SnCl(TOx) (6), and Me2Sn(TUr) (7) [HSPy = 2-mercaptopyridine; HSPyN = 2-mercaptopyrimidine; HTCy = 2-thiocytosine; HTOx = 8-thioquinoline; H2TUr = 2-thiouracil] has been investigated by variable temperature 119Sn Mössbauer spectroscopy. The area under the resonant peaks has been determined as function of temperature, from which Debye temperatures and cut-off frequencies, as well as recoil-free fractions (Lamb Mössbauer factor) and mean square displacements of 119Sn, have been calculated. By fingerprint procedures on the basis of literature data, monomeric structures are attributed to complexes (1)-(4) and (6), while (5) and (7) lie in the borderline monomersmonodimensional polymers. The results are discussed on the basis of known crystal and molecular structures. The nature of the environment of tin atoms has been simulated by point-charge model calculations of nuclear quadrupole splitting parameters; molecular structures are proposed for complexes (5)-(7), where no X-ray diffractometric data are available.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0268-2605
    Keywords: organotin(IV) ; porphine ; Mössbauer ; NMR ; development ; Ascidiaceae ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Diorgano- and triorgano-tin(IV) derivatives of meso-tetra(4-sulfonatophenyl)porphine (H4TPPS) with general formula (R2Sn)2TPPS and (R3Sn)4TPPS (TPPS4-=[meso-tetra(4-sulfonatophenyl)porphinate]4-, R=Me, Bu, Ph) have been obtained and their solid-state configuration inferred on the basis of IR and Mössbauer spectroscopy, while solution-phase studies have been carried out by 1H and 13C NMR in DMSO-d6, together with determination of the in vivo cytotoxicity of the new derivatives towards embryonic development of Ciona intestinalis. In particular, octahedral and trigonal-bipyramidal eq-R3Sn polymeric configurations are proposed, in the solid state, respectively for (R2Sn)2TPPS and (R3Sn)4TPPS complexes, with the arylsulfonate groups behaving as monoanionic bidentate bridging ligands.The 1H and 13C NMR data lead to the conclusion that the metal-to-ligand ratio (2:1 or 4:1), binding site (the sulfonato-group oxygens), and the coordination polyhedron around the metal (trans-octahedral or trigonal-bipyramidal) found in the solid state are preserved in solution. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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