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  • 1
    Electronic Resource
    Electronic Resource
    Glancing-angle diffraction anomalous fine structure of InAs quantum dots and quantum wires (2001)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 8 (2001), S. 536-538 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: We have performed Diffraction Anomalous Fine Structure measurements at the As K-edge of self-growth InAs/InP(001) Quantum Wires and InAs/GaAs(001) Quantum Dots. The samples have been grown by Molecular Beam Epitaxy and their equivalent thickness is of 2.5 monolayers. We have measured the (440) and (420) Bragg reflections in glancing-angle scattering geometry, at incidence angles close to the substrate critical angle. We demonstrate the feasibility of the experiment reporting, for the first time, Diffraction Anomalous Fine Structure spectra of such low coverage epitaxial layers, and we show that the analysis of the Diffraction Anomalous Fine Structure lineshape together with the analysis of oscillatory part of the signal, can provide information about composition and strain of the nanostructures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0909049500016678
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  • 2
    Electronic Resource
    Electronic Resource
    Extented esophago-gastretomy as surgical treatment for carcinoma of the cardia (1981)
    Springer
    Surgery today 11 (1981), S. 311-316 
    Details
    ISSN: 1436-2813
    Keywords: carcinoma of the cardia ; esophagogastrectomy ; isoperistaltic transverse colon interposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract With the object of designing a feasible and more radical surgical intervention for the treatment of carcinoma of the gastric cardia and improving the long term survival of these patients, a procedure was described which entails total esophagogastrectomy and resection of the distal pancreas, spleen and regional lymphnodes. The esophagus was mobilizedvia the diaphragmatic hiatus without thoracotomy. Intestinal continuity, installed isoperistaltically was restituted in the same operation using a segment of transverse and descending colon transferred to the left lateral cervial aspect by way of the posterior mediastinum. The procedure was used in four patients and mortality and serious complications were nil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02468953
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  • 3
    Electronic Resource
    Electronic Resource
    Waste minimization in the Los Alamos Medical Radioisotope Program (1995)
    Springer
    Journal of radioanalytical and nuclear chemistry 195 (1995), S. 287-295 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Since the mid-1970s the Los Alamos Medical Radioisotope Program has been irradiating target materials to produce and recover radioisotopes for applications in medicine, environmental science, biology, physics, materials research, and other disciplines where radiotracers find utility. By necessity, the chemical processing of targets and the isolation of radioisotopes generates radioactive waste materials. In recent years there have been federal mandates requiring us to discontinue the use of hazardous materials and to minimize radioactive waste volumes. As a result, substantial waste reduction measures have been introduced at the irradiation facility, in processing approaches, and even in the ways the product isotopes are supplied to users.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02035968
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  • 4
    Electronic Resource
    Electronic Resource
    Homogeneous and Supported Copper Complexes of Cyclic and Open-Chain Polynitrogenated Ligands as Catalysts of Cyclopropanation Reactions (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2347-2354 
    Details
    ISSN: 1434-1948
    Keywords: Cyclopropanation ; Copper ; N ligands ; Macrocycles ; Supported catalysts ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: CuI and CuII complexes of cyclic and open-chain polyaza compounds have been tested as catalysts in the benchmark cyclopropanation reaction of styrene with ethyl diazoacetate. In general, only small amounts of copper are needed to promote the reaction. The catalytic activity depends on the structure of the ligand, e.g. amine-amides are more efficient than polyamines, and on the oxidation state of copper, CuII being more active than CuI. Given that CuI is the active species, these changes of behavior must be related to the stabilities of the complexes. The nature of the counterion also has a noticeable influence on the catalytic activity, the role of which is discussed. XAS measurements suggest the formation of oligomeric species. Some of the chiral ligands lead to small enantiomeric excesses. Open-chain ligands can easily be supported on organic polymers and their complexes can be used as catalysts. Furthermore, cyclic and acyclic complexes can be supported on clays by cation exchange and the solids obtained tend to promote the reaction with a decrease in the trans/cis ratio.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Potential energy surface for a seven-atom reaction. Thermal rate constants and kinetic isotope effects for CH4+OH (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 5731-5739 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The potential energy surface for the gas-phase CH4+OH→CH3+H2O reaction and its deuterated analogs was constructed with suitable functional forms to represent vibrational modes, and was calibrated by using the experimental thermal rate constants and kinetic isotope effects. On this surface, the forward and reverse thermal rate constants were calculated using variational transition-state theory with semiclassical transmission coefficients over a wide temperature range, 200–2000 K, finding reasonable agreement with the available experimental data. We also calculated six sets of kinetic isotope effects and, in general, the theoretical results underestimate the few available experiments, with exception of the C-13 isotopic effect values which are overestimated. Finally, this surface is also used to analyze dynamical features, such as reaction-path curvature and coupling between the reaction coordinate and vibrational modes. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481148
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  • 6
    Electronic Resource
    Electronic Resource
    The SiH4+H→SiH3+H2 reaction: Potential energy surface, rate constants, and kinetic isotope effects (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 466-473 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The potential energy surface for the gas-phase SiH4+H→SiH3+H2 reaction and its deuterated analogs was constructed with suitable functional forms to represent the stretching and bending modes, and using as calibration criterion the reactant and product experimental properties and the ab initio saddle point properties. Using this surface, the rate constants were calculated with variational transition-state theory over the temperature range 200–1000 K, finding good agreement with experiments. We also provide a detailed analysis of the kinetic isotope effects and a comparison with the scarce experimental results. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476581
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  • 7
    Electronic Resource
    Electronic Resource
    Extended x-ray-absorption fine-structure study of InAs/InP and GaAs/InP strained heterostructures (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 62-65 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Extended x-ray-absorption fine-structure measurements have been performed at the As K edge of GaAs/InP and InAs/InP strained single heterostructures grown by molecular-beam epitaxy. The results show a substantial conservation of the bond length in the strained epitaxial layers with respect to the corresponding bulk materials. The measures point out the formation of a thick InAsP (or InGaAsP) layer at the GaAs/InP interface. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359355
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  • 8
    Electronic Resource
    Electronic Resource
    Cathodoluminescence and photoluminescence in the core region of Bi12GeO20 and Bi12SiO20 crystals (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 7186-7190 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Cathodoluminescence and photoluminescence of Bi12SiO20 and Bi12GeO20 samples are studied. Both kinds of samples show a dark orange central part or core. Emissions in the blue, green, and red spectral regions are observed. The 640 nm band is the predominant feature in the core emission. The evolution of this band during electron irradiation suggests possible emission mechanisms. In addition, two infrared emissions at about 915 and 1390 nm are detected. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361434
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  • 9
    Electronic Resource
    Electronic Resource
    Correlation between magnetovolume and giant magnetoresistance effects in doped La2/3Ca1/3MnO3 perovskites : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5175-5177 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: La0.62Tb0.05Ca0.33MnO3 and La0.6Y0.07Ca0.33MnO3 have been studied in order to probe into the mechanisms responsible for the giant magnetoresistance ratios observed in this kind of compound. The experiments have shown a strong connection between the magnetotransport and magnetovolume properties. A large volume effect appears above Tc which collapses with applied magnetic field or when the long range magnetic order sets in. Above Tc the magnetostriction and magnetoresistance isotherms are highly correlated. Charge localization with local distortion appears to be responsible for the transport and volume properties at zero field. Charge mobility and a more normal volume dependence on temperature are restored by applying high enough magnetic fields. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361544
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  • 10
    Electronic Resource
    Electronic Resource
    Pressure effect on the resistivity in GMR La0.60Y0.07Ca0.33MnO3 compound (abstract) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5178-5178 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The substitution of La+3 by smaller Y+3 ions in mixed valence Mn+3–Mn+4 perovskites La0.67−xYxCa0.33MnO3 gives rise to a decrease of the order temperature (Tc=160±5 K for x=0.07 and Tc=240 K for x=0). One of the most relevant features found in this compound was the extremely large magnetoresistance observed in bulk polycrystals (≈−10 000%) near Tc. This huge effect was associated with the reduction of the lattice parameter. In order to have an insight into the influence of volume change on transport properties in this compound, we have performed measurement of the thermal dependence of the resistivity under hydrostatic pressure up to 8 kbar. At ambient pressure a peaklike anomaly in the resistivity is observed at Tc. Under the former assumptions, one would expect an increase of the resistivity value at the maximum as well as a decrease of Tc. However, we have found a shift toward higher temperatures and a drastic decreasing of the maximum in the resistivity for increasing pressures. At a pressure of 7.5 kbar the anomaly in the resistivity almost disappears and consequently the GMR effect. As a consequence, the effect of pressure seems to be identical to the effect of the applied magnetic field. Ibarra et al. recently observed a large spontaneous magnetovolume effect at Tc with an extra contribution to the lattice thermal expansion. This extra contribution was found to be suppressed by an applied magnetic field. From these preliminary results it seems that the interplay between magnetostrictive deformations and the shrinkage of the lattice by external pressure could be in the origin of the observed behavior. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361330
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