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  • 1
    Electronic Resource
    Electronic Resource
    Perturbed-angular-correlation studies of In-vacancy pairs in Hg1−xCdxTe (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 3576-3583 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The interaction of vacancies with 111In atoms is studied in Hg1−xCdxTe compounds via perturbed-angular correlation (PAC) experiments, for x=0.065, 0.21, 0.44, and 0.95. In the low-x (Hg-rich) compounds, Hg vacancies are created by heating in vacuum. For the x=0.21 alloy, we have previously shown that InC-vacC pairs (A centers consisting of an In atom on a cation site and a vacancy at a neighboring cation site) are abundant after quenching from elevated temperatures. These defects are characterized by two PAC signals with quadrupole interaction frequencies νQ1=83 MHz and νQ2=92 MHz, and asymmetry parameters η1=η2=0.08. For the x=0.065–0.44 alloys, the data presented in this article show that the fractions f1 and f2 of In atoms associated with these two frequencies vary with x according to whether one or two Hg atoms are nearest neighbors to the Te atom that is bound to the In atom and the vacancy. The data are explained by the polarizable point-ion model. For the x=0.95 compound, PAC signals are observed only when stable In is added to the compound, indicating that the presence of In creates vacancies, and that self-compensation via A centers is dominant. In this case, the well-known frequencies νQ4=100 MHz and νQ5=112 MHz are seen for samples quenched from several different temperatures between 325 and 525 °C, or slow cooled from 475 °C or below. In contrast, for a sample slowly cooled from 525 °C, the frequency νQ6=60 MHz was dominant. This signal could be due to InC−vacC pairs in which the vacancy is singly charged, or to In-group I pairs. We attribute the frequencies νQ4=100 MHz and νQ5=112 MHz, like νQ1 and νQ2, to InC-vacC pairs having doubly charged vacancies. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371261
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  • 2
    Electronic Resource
    Electronic Resource
    Doping of diamond by coimplantation of carbon and boron (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1397-1399 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have implanted boron ions into insulating natural diamonds which were predamaged by carbon ion implantation in order to enhance the doping efficiency. All implantations were performed at liquid-nitrogen temperature. Subsequent rapid thermal annealing at 1100 °C produced strong new optical absorption bands near 1060 cm−1, and a sharp absorption at 2962 cm−1 (0.37 eV) which is close to that attributed to substitutional boron in type IIB diamond. We obtained resistivity of the order of 100 Ω cm and carrier activation energy of 0.1 eV for a sample implanted with 2×1015 C and 3×1014 B per cm2 , indicating a high substitutional fraction of boron atoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101605
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  • 3
    Electronic Resource
    Electronic Resource
    In situ doping by As ion implantation of silicon grown by molecular-beam epitaxy (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 3938-3944 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The incorporation and electrical activation of As, implanted in situ during molecular-beam epitaxial growth of epilayers on Si(100), is reported. Parameters varied included growth temperature (460–700 °C), implantation energy (500–1000 eV), and concentration (1017→〉1020/cm3 ). In general, the material was excellent with 100% activation and bulk mobilities for concentrations up to the equilibrium solid solubility limit and carrier densities in excess of five times this limit in highly doped samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341350
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  • 4
    Electronic Resource
    Electronic Resource
    Surface alloying in stainless steel and Ni-20% Fe by pulsed laser irradiation (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3061-3070 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Surface alloys have been produced by pulsed laser irradiation of thin metal overlayers (Au and Mo) on austenitic stainless steel and Ni-20% Fe. The structure and composition of the surface alloys have been characterized by Rutherford backscattering and ion channeling. The stainless-steel alloy has a thin surface layer with nonsubstitutional Au or Mo on top of the substitutional alloy. Metastable solid solutions of gold are formed with concentration levels as high as 5 at. % in stainless steel and 28 at. % in Ni-20% Fe. The laser alloying process involves surface melting and, in some cases, the formation of ∼1-μm-high ridges. The quality of the epitaxial regrowth, as seen in the channeling spectra, ranges from good to very poor. Dechanneling in the alloyed surface has a complex behavior and is dependent on the energy density used for the irradiation. It is also important whether or not the irradiation is carried out in air or in flowing helium. The use of flowing helium instead of air has a striking reverse effect on the two alloy systems; it reduces the lattice disorder of alloys formed by Au and stainless steel, while an increase in disorder is seen when Au is alloyed with Ni-20% Fe.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337858
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  • 5
    Electronic Resource
    Electronic Resource
    STABILITY OF THE BRAIN FATTY ACID PATTERN IN ADULT RATS DURING EXTREME STARVATION (1974)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Adult rats were denied food for 7 days. As compared with a control group, this severe starvation reduced the mean total body weight by 44 per cent, the weight of the diaphragm by 33 per cent and liver by 67 per cent, the total lipid content of the diaphragm by 57 per cent and liver by 69 per cent, and the total lipid phosphorus content of the diaphragm by 19 per cent and liver by 68 per cent. The decrease in lipid phosphorus contents indicates that the diaphragm and liver catabolized membrane phospholipids as well as triglycerides. In contrast, the fresh weight of the brain and the total lipid content of the brain were not significantly altered by starvation. The fatty acid patterns of the total lipid of the diaphragm and liver (determined by GLC) were grossly altered by starvation. In the brain, however, 17 of the 21 fatty acids measured did not change significantly (P 〉 0.05) and the remaining four changed, with borderline statistical significance, by only 2 to 13 per cent. There was no significant effect of starvation of the pattern of the brain polyunsaturated fatty acids when measured by alkali isomerization. In contrast to the liver and diaphragm, the brain is apparently unable to utilize its lipids appreciably as an energy source. Presumably the lipids of the brain are preserved to permit this organ to function properly, even in the last stages of starvation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1974.tb06911.x
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  • 6
    Electronic Resource
    Electronic Resource
    Single-crystal diamond plate liftoff achieved by ion implantation and subsequent annealing (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 3124-3126 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We describe a new method for removing thin, large area sheets of diamond from bulk or homoepitaxial diamond crystals. This method consists of an ion implantation step, followed by a selective etching procedure. High energy (4–5 MeV) implantation of carbon or oxygen ions creates a well-defined layer of damaged diamond that is buried at a controlled depth below the surface. For C implantations, this layer is graphitized by annealing in vacuum, and then etched in either an acid solution, or by heating at 550–600 °C in oxygen. This process successfully lifts off the diamond plate above the graphite layer. For O implantations of a suitable dose (3×1017 cm−2 or greater), the liftoff is achieved by annealing in vacuum or flowing oxygen. In this case, the O required for etching of the graphitic layer is also supplied internally by the implantation. This liftoff method, combined with well-established homoepitaxial growth processes, has considerable potential for the fabrication of large area single crystalline diamond sheets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107981
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  • 7
    Electronic Resource
    Electronic Resource
    Indium-Hg vacancy interactions in Hg1−xCdxTe measured by perturbed angular correlation (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 938-940 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The interaction of mercury vacancies with dopant indium atoms in Hg0.79Cd0.21Te was studied using the perturbed γγ angular correlation (PAC) technique. Two dominant PAC signals, characterized by quadrupole interaction strengths νQ1=83 MHz and νQ2= 91 MHz and asymmetry parameters η1=η2=0.08, were observed and attributed to one or more In-VHg complexes. The complexes appeared after annealing doped samples at T≥350 °C in vacuum and quenching. The fraction of In atoms associated with vacancies was increased further by annealing at 80 °C for (approximately-greater-than)10 h. The In-vacancy complexes vanished on annealing in a Hg-saturated atmosphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106307
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  • 8
    Electronic Resource
    Electronic Resource
    LEGIONELLA PNEUMOPHILA PATHOGENESIS: A Fateful Journey from Amoebae to Macrophages (2000)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Microbiology 54 (2000), S. 567-613 
    Details
    ISSN: 0066-4227
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Legionella pneumophila first commanded attention in 1976, when investigators from the Centers for Disease Control and Prevention identified it as the culprit in a massive outbreak of pneumonia that struck individuals attending an American Legion convention (84). It is now clear that this gram-negative bacterium flourishes naturally in fresh water as a parasite of amoebae, but it can also replicate within alveolar macrophages. L. pneumophila pathogenesis is discussed using the following model as a framework. When ingested by phagocytes, stationary-phase L. pneumophila bacteria establish phagosomes which are completely isolated from the endosomal pathway but are surrounded by endoplasmic reticulum. Within this protected vacuole, L. pneumophila converts to a replicative form that is acid tolerant but no longer expresses several virulence traits, including factors that block membrane fusion. As a consequence, the pathogen vacuoles merge with lysosomes, which provide a nutrient-rich replication niche. Once the amino acid supply is depleted, progeny accumulate the second messenger guanosine 3',5'-bispyrophosphate (ppGpp), which coordinates entry into the stationary phase with expression of traits that promote transmission to a new phagocyte. A number of factors contribute to L. pneumophila virulence, including type II and type IV secretion systems, a pore-forming toxin, type IV pili, flagella, and numerous other factors currently under investigation. Because of its resemblance to certain aspects of Mycobacterium, Toxoplasma, Leishmania, and Coxiella pathogenesis, a detailed description of the mechanism used by L. pneumophila to manipulate and exploit phagocyte membrane traffic may suggest novel strategies for treating a variety of infectious diseases. Knowledge of L. pneumophila ecology may also inform efforts to combat the emergence of new opportunistic macrophage pathogens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.micro.54.1.567
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  • 9
    Electronic Resource
    Electronic Resource
    Transition between Ge segregation and trapping during high-pressure oxidation of GexSi1−x/Si (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 4750-4755 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A transition from Ge segregation to trapping during high-pressure oxidation of GexSi1−x alloys has been observed. The atomic fraction x of Ge was varied from 0.4% to 26%, and oxidations were performed at 740 °C under 102 atm of dry O2. It was observed that the effect of oxidation on the Ge distribution could be divided into three stages. In the initial stage of the oxidation, Ge was segregated from the growing oxide and accumulated in a Ge-rich layer at the oxide/alloy interface. For alloys with high Ge content this initial stage was very short. In the second stage of oxidation, after a critical quantity of Ge had accumulated at the interface, there was a transition from segregation to trapping of Ge in the oxide. In the third stage, the critical amount of Ge remained segregated at the interface, and the final oxide layer was Ge free. A kinetic model based on a steady-state equilibrium between the diffusive flux of Si across the Ge-rich layer and the rate of Si consumption by the oxidation reaction predicts, with reasonable agreement, the critical quantity of segregated Ge for the onset of trapping.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354345
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  • 10
    Electronic Resource
    Electronic Resource
    Perturbed angular correlation studies of dopant atom interactions in silicon (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 3026-3037 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The perturbed γγ angular correlation (PAC) technique was used to study the interaction of implanted 111 In probe atoms with the donor atoms P, As, and Sb in Si. Nearest-neighbor pairs of In-P, In-As, and In-Sb atoms, characterized by νQ1 =179(1), 229(1), and 271(1) MHz, respectively, and having trigonal symmetry about a 〈111〉 axis (η1 =0), were observed after annealing the samples between 540 and 1170 K. These results indicate a strong interaction between acceptor and donor atoms in Si, thus explaining the present and earlier Rutherford backscattering-channeling results that the In atom solubility in Si was enhanced by the addition of As. The In-donor atom binding energy was about 0.5 eV. For increasing As concentrations, PAC data showed the appearance of small In-As atom clusters characterized by νQ2 (As)=238(1) MHz, η2 = 0.65(1); they were probably In-As2 complexes produced when mobile In atoms were trapped by As2 pairs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344188
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