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  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2017-2019 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The chemisorption of molecular hydrogen onto the Si (100) surface is shown to disrupt the epitaxial growth of silicon and silicon/germanium alloys grown by molecular beam epitaxy. It is only after the substrate temperature is raised above the hydrogen desorption temperature, or the deposition rate is lowered, that high quality single-crystal films can be grown. The results also suggest the surface segregation of hydrogen during growth.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1626-1628 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hydrogen in undoped, unalloyed microcrystalline silicon (μc-Si:H) has been investigated with secondary-ion mass spectrometry (SIMS), Raman spectroscopy, infrared absorption spectroscopy, and nuclear magnetic resonance (NMR). The samples were grown by plasma-enhanced chemical vapor deposition with hydrogen to silane dilution ratios (H2:SiH4) ranging from 0:1 to 98:1. Microcrystallinity is obtained for dilution ratios of 20:1 and greater. The hydrogen concentration is shown to depend nonmonotonically on the degree of hydrogen dilution. The H concentration in the films decreases with dilution for ratios from 0:1 to 10:1 and then increases with greater dilution. This dependence on dilution is established with both NMR and SIMS and suggests the existence of competing processes in the incorporation of hydrogen during deposition. It is further observed that the formation of microcrystallites is accompanied by the appearance of both higher order silicon hydrides and large concentrations of unbound molecular hydrogen.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 4025-4027 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The preparation conditions for the deposition of hydrogenated amorphous silicon-carbon alloys (a-SiC:H) from a glow-discharge plasma have been systematically scanned by changing the starting-gas materials as well as the starting gas to hydrogen dilution ratio. A highly photosensitive alloy showing a photoconductivity to dark conductivity ratio of 107 at a band gap of 2.0 eV was prepared under optimized conditions.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 7689-7698 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a new relativistic formulation for the calculation of nuclear magnetic resonance (NMR) shielding tensors. The formulation makes use of gauge-including atomic orbitals and is based on density functional theory. The relativistic effects are included by making use of the zeroth-order regular approximation. This formulation has been implemented and the 199Hg NMR shifts of HgMe2, HgMeCN, Hg(CN)2, HgMeCl, HgMeBr, HgMeI, HgCl2, HgBr2, and HgI2 have been calculated using both experimental and optimized geometries. For experimental geometries, good qualitative agreement with experiment is obtained. Quantitatively, the calculated results deviate from experiment on average by 163 ppm, which is approximately 3% of the range of 199Hg NMR. The experimental effects of an electron donating solvent on the mercury shifts have been reproduced with calculations on HgCl2(NH3)2, HgBr2(NH3)2, and HgI2(NH3)2. In addition, it is shown that the mercury NMR shieldings are sensitive to geometry with changes for HgCl2 of approximately 50 ppm for each 0.01 Å change in bond length, and 100 ppm for each 10° change in bond angle. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 109 (1987), S. 3050-3057 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 895-905 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A formulation for the calculation of nuclear magnetic resonance (NMR) shielding tensors, based on density functional theory (DFT), is presented. Scalar-relativistic and spin-orbit coupling effects are taken into account, and a Fermi-contact term is included in the NMR shielding tensor expression. Gauge-including atomic orbitals (GIAO) and a frozen-core approximation are used. This formulation has been implemented, and 1H and 13C NMR shifts of hydrogen and methyl halides have been calculated and show good agreement with experiment. 13C NMR shifts of 5d transition metal carbonyls have been calculated and show improved agreement with experiment over previous scalar-relativistic calculations. For the metal carbonyls it is shown explicitly that the combination of spin-orbit coupling and magnetic field mixes spin triplet states into the ground state, inducing a spin density that then interacts with the nuclei of the metal carbonyl via the Fermi-contact term. Results indicate that the Fermi-contact contribution to the 13C NMR of the metal carbonyl ions increases with increasing oxidation state of the ion. It is reasoned that as the oxidation state increases, π back bonding decreases and σ bonding increases, within the metal–carbon bond, thus facilitating a greater transfer of spin density from the metal to the carbon nucleus, and thus increasing the Fermi-contact contribution to the NMR shielding of the carbon. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
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    London : Periodicals Archive Online (PAO)
    Journal of adolescence. 10:2 (1987:June) 105 
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  • 8
    ISSN: 1432-1432
    Keywords: Pongidae ; Chromosome ; Karyotype ; Restriction enzymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The pattern of banding induced by five restriction enzymes in the chromosome complement of chimpanzee, gorilla, and orangutan is described and compared with that of humans. The G banding pattern induced by Hae III was the only feature common to the four species. Although hominid species show almost complete chromosomal homology, the restriction enzyme C banding pattern differed among the species studied. Hinf I did not induce banding in chimpanzee chromosomes, and Rsa I did not elicit banding in chimpanzee and orangutan chromosomes. Equivalent amounts of similar satellite DNA fractions located in homologous chromosomes from different species or in nonhomologous chromosomes from the same species showed different banding patterns with identical restriction enzymes. The great variability in frequency of restriction sites observed between homologous chromosome regions may have resulted from the divergence of primordial sequences changing the frequency of restriction sites for each species and for each chromosomal pair. A total of 30 patterns of banding were found informative for analysis of the hominid geneaalogical tree. Using the principle of maximum parsimony, our data support a branching order in which the chimpanzee is more closely related to the gorilla than to the human.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Archives of orthopaedic and trauma surgery 119 (1999), S. 267-270 
    ISSN: 1434-3916
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A prospective randomized trial in 42 patients undergoing elective total hip or knee arthroplasty under general anaesthesia was carried out to evaluate the efficacy of patient-controlled analgesia (PCA) versus demanded conventional pain therapy (CPT) for controlling postoperative pain. Four patients had to be excluded from the study (2 postoperative confusion, 1 elevated piritramid dosage caused by chronic pain therapy, 1 stressed by PCA pump handling). PCA group (n = 19) received piritramid via PCA pump, CPT group (n = 19) received tramadol (oral or intramuscularly) or piritramid intravenously. PCA or CPT was started in the intensive care unit. Pain was measured with a standard 100 mm visual analogue scale (VAS) for 60 h postoperatively. Over this period of time, no significant differences were found in the pain score of both groups, nor did the incidence of side-effects differ significantly. The PCA group required on average twice as much piritramid-equivalent than the CPT group (P 〈 0.001). Patient satisfaction was good in both groups, but significantly better in the PCA group (P 〈 0.01), although the measured postoperative individual pain scores were above the preoperatively determined individual subjective pain threshold in the majority of both groups. From these results we draw the conclusion that even if the patients feel satisfied by the pain therapy administered, the majority are objectively treated below their individual subjective pain threshold.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Cancer chemotherapy and pharmacology 19 (1987), S. 246-249 
    ISSN: 1432-0843
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary VP-16-213 (Etoposide) is an active antineoplastic agent which has undergone extensive evaluation of clinical dose escalation. To corroborate a putative dose-response relationship, we studied, in a modified clonogenic assay, various doses and durations of exposure. VP-16-213 at doses of 0.01, 0.05, 0.10, 0.50, 1.0, 5.0 and 10.0 μg/ml, each with exposure durations of 1, 3, 18, and 30 h, was studied in vitro against two human tumor cell lines, MOLT and 9812. The doses and durations of exposure were chosen to approximate some of the pharmacokinetic values achievable in either standard-dose or high-dose clinical studies. The results, summarized as linear regression lines, demonstrate with statistical significance (p〈0.03) that there is correlation between dose and cytotoxicity and between dose x duration of exposure (representing the area under the concentration-time curve) and cytotoxicity. Our in vitro data thus support the concept of intensive use of VP-16-213 to maximize antitumor activity. However, how best to accomplish the manipulation of dose and duration of exposure is not yet clear and will be the subject of future clinical investigations.
    Type of Medium: Electronic Resource
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