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  • 1995-1999  (56)
  • 1985-1989  (10)
  • 1840-1849  (3)
  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 114-120 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We report on the design and performance of an atomic force microscope which operates at temperatures down to 20 mK and in magnetic fields up to 9 T. The scan range at low temperatures is 4 μm×4 μm. The instrument features a piezoelectric linear motor for vertical coarse approach, and a horizontal sample translation stage with a 2 mm×2 mm range. A fiber interferometer is used to detect the force-sensing cantilever displacement. The performance demonstrated includes the ability to detect single atomic steps on a graphite surface at 4.2 K and the ability to locate and image nanometer scale electronic devices at millikelvin temperatures. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 7130-7136 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A system of nanometer sized cobalt clusters surrounded by dielectric shells has been investigated by electrical dc conductivity measurements. The cobalt clusters have a diameter of 36 A(ring) and are surrounded by an approximately 12-A(ring)-thick layer of tetra-octyl-ammonium bromide surfactant molecules and poly(phenyl-p-phenylenevinylene). The conductivity σ shows a temperature dependence ln(σ)∝(T0/T)1/2 in the range 100〈T〈240 K. At T(approximately-greater-than)240 K, the temperature dependence of the conductivity demonstrates some peculiarities. Differential scanning analysis suggests that at 240〈T〈350 K phase transitions of the composite material take place. The observed temperature dependence of the conductivity σ for T〈240 K is typical for hopping conduction in granular metallic systems. A theoretical analysis shows that the data are consistent with a hopping model in which the separation between grains is a random variable uncorrelated with the activation energy. The observed nonlinear dependence of the conductivity on the electric field F is interpreted in the framework of the concept of the effective temperature, which suggests that the influence of T and F on σ can be parameterized by a single quantity Teff(T,F). Comparison between the theoretical results and experimental data provides a suitable expression for Teff(T,F). © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 993-995 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have developed an atomic force microscope for the study of mesoscopic samples. The microscope operates at milliKelvin temperatures and in high magnetic fields. Sample images are presented showing atomic steps at 4.2 K and a mesoscopic ring at 30 mK in a 9 T field. Deflection of the force-sensing cantilever is detected via an optical fiber interferometer operating at very low power levels. The microscope is well suited to surface imaging simultaneous with transport measurements at ultralow temperatures, and to the in situ manipulation of sample properties. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Chemistry of materials 1 (1989), S. 412-420 
    ISSN: 1520-5002
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 2520-2527 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The magnetization of stabilized cobalt colloids in tetrahydrofuran has been studied by a superconducting quantum interference device (SQUID) and magnetic balance measurements in dependence of applied magnetic field and temperature. The colloids are generated by a newly developed electrochemical method which allows one to generate clusters containing about 1000 atoms with a narrow size distribution. The final size distribution of the clusters is examined by high resolution transmission electron microscopy and small angle x-ray scattering. The magnetization curves have been determined with special emphasis on changes at the freezing point of the solution. The curves of the liquid phase can be reasonably described by the Langevin function and the magnetic moments of isolated cobalt clusters that have been recently measured by Stern–Gerlach experiments. Deviations that appear at the freezing point can be understood in terms of magnetic anisotropy effects. It is shown that the cluster sizes and the susceptibilities of the dispersions are related. Therefore the growth of the clusters during the electrolysis can be directly observed by measuring the susceptibility in dependence of the charge transport in the cell. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Weed research 37 (1997), S. 0 
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Labonuory bioassay and field experiments were conducted to characterize the dose response of weeds to methyl iodide and methyl bromide as soil fumigants. The patterns in potency of both fumigants and in sensitivity of diffcretit weed species to the fumigants were distinguished with the use of logistic dose-response models. Similar to its response to methyl hromide fumigation. Amaranthus retrofleus L. was the most sensitive to methyl iodide fumigation. Cyperus rotundtis L. was the least sensitive to methyl iodide fumigation, whereas Portuloca oleracea L. was the least sensitive to methyl hromide. Lolium multiflorum Lam. Abutilon theophrasti Medik.Chenopodium album L. P. ateracea. Brassica kaber (D.C.) L.C. Wheeler and Cyperus escuden-tus L. were similar in sensitivity to methyl iodide. Methyl iodide was as potent as methyl bromide for A. retroflexus but more potent than methyl bromide for L. multiflorum, A. theophrasti. C. album. P. oleracea. B. kaber, C. esculentus and C. rotundus. The dose response for weeds in the field was similar to that obtained in laboratory bioassays. Under fieid conditions. 280 kg ha-1 methyl iodide killed all species tested except Solanum nigrum L Methyl iodide appears to be a suitable replacement for meihyl bromide because it can be used in situations simitar to methyl bromide fumigation, has superior efficacy against a broad spectrum of pests and has a low potential for degrading the earth's ozone lavers.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of oral pathology & medicine 24 (1995), S. 0 
    ISSN: 1600-0714
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The immunohistochemical distribution of collagens type I, III, IV, V, VI, of undulin and tenascin. and of integrins α2, α3, α4, α5, α6 and β4, was studied in 14 biopsies of oral lichen planus (OLP), 5 biopsies of orthokeratinized gingiva and 4 biopsies of oral fibrous hyperplasia. The localization of extracellular matrix proteins showed altered expression in OLP when compared to normal oral mucosa, with two principal patterns corresponding to the reticular or atrophic type. Whereas in the reticular type a focal loss of immunoreactivity for collagen types I, III, V, VI and undulin was noted in areas with a cellular infiltrate, in the atrophic variant almost complete loss of immunoreactivity of the subepithelial extracellular matrix was found. There was no clear correlation between the distribution of extracellular matrix proteins and their integrin receptors. The present findings suggest that the autoimmune reaction in OLP might not be primarily targeted to oral keratinocytes but to an unknown antigen in the connective tissue stroma. The changes in the subepithelial extracellular matrix associated with the inflammatory reaction might, especially in the atrophic variant, impair the cross-talk between epithelium and mesenchyme and favour both the loss of barrier function and the development of erosions in the clinical course of the disease.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of oral pathology & medicine 14 (1985), S. 0 
    ISSN: 1600-0714
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Ten teeth of betel chewing P'wo Karen, a hilltribe group of northern Thailand were available for this morphologic study. The structural composition of the black layer on these teeth was studied by light microscopy, microradiography and by electronmicroscopy. Principally, the black layer on the teeth of betel chewers was identical with subgingival calculus which had been colored by specific polyphenols contained in the betel nut. However, a pellicle-like layer forming initially on enamel crystals was also observed, from the morphologic aspect of the black layer a specific anticariogenic property cannot be attested. Further studies on the chemical composition of this black layer may elucidate its probable anticariogenic and its carcinogenic properties relative to oral suhmucous fibrosis.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 44 (1988), S. 1770-1772 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 777 (1996), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Notes: Conscious recall of past events which have specific temporal and spatial contexts, termed episodic memory, is mediated by a system of interrelated brain regions. In Alzheimer's disease (AD) this system breaks down, resulting in an inability to recall events from the immediate past. Studies of normal human auditory-verbal short-term memory suggest that the brain system underlying these processes has distinct components, and the present study utilized the methods of functional brain mapping to determine the nature and extent of the breakdown that occurs in AD. Using subtraction techniques of PET-acquired images of regional cerebral blood flow we demonstrate that AD patients show a compensatory hyperactivation of various regions of cerebral cortex normally involved in these tasks, as well as activation of cortical areas not activated by normal elderly subjects. These results provide clear evidence of functional plasticity in the AD patient's brain even if those changes do not result in normal memory function.
    Type of Medium: Electronic Resource
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