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  • 1
    Electronic Resource
    Electronic Resource
    Structure and phase behavior of a model clay dispersion: A molecular-dynamics investigation (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 311-322 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Reversible molecular-dynamics (MD) simulations have been carried out on simple models for dispersions of circular Laponite clay platelets to investigate the local structure on a mesoscopic scale. The platelets carry discrete charged sites interacting via a screened Coulomb potential. In model A all surface sites have identical negative charge, while model B also includes rim charges of opposite sign. These two models were used in a series of simulations in the semidilute regime, and for three values of the Debye screening length. The structure of the dispersions is characterized by translational and orientational pair distribution functions, and by the corresponding structure factors. Qualitative differences in the pair structure arising from variations in concentration and screening length lead to a tentative identification of sol, gel, and crystal phases. The rim charges have a dramatic effect on the local structure in the strong screening regime, leading to T-shaped pair configuration and clustering of the platelets at low clay concentrations, and at higher concentrations to a space-filling "house-of-cards" structure. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480582
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  • 2
    Electronic Resource
    Electronic Resource
    Soft x-ray imaging for spheromak-like plasmas (abstract) : Papers from the thirteenth topical conference on high temperature plasma diagnostics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 742-742 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A pinhole soft x-ray imaging camera is being developed for use on the Caltech solar prominence simulation experiment and also the Caltech spheromak experiment. The camera is based upon a commercial gated intensifier which produces an image on a phosphor screen. Moderate signal level, excellent time resolution, and reasonable imaging have been obtained, but there has not been any determination of the x-ray energy spectrum. An estimation of the spectrum is now underway using filtered AXUV diodes and it is expected that knowledge of the x-ray energy will enable further optimization of the camera.© 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1323484
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  • 3
    Electronic Resource
    Electronic Resource
    Si self-interstitial injection from Sb complex formation in Si (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 3254-3259 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It has recently been established that Si self-interstitials are generated during annealing of high-concentration Sb layers in Si. In the present work, we make use of samples grown with molecular-beam epitaxy. We monitor, at different times and temperatures, the diffusion enhancement or retardation of deep B or Sb marker layers next to a 1.1×1020 cm−3 Sb box, as well as the formation of Sb precipitates within the box. It is concluded that the interstitials are not associated with precipitate growth, but that they are generated from formation of Sb-vacancy complexes, primarily involving 2 Sb atoms. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1289234
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  • 4
    Electronic Resource
    Electronic Resource
    Accurate effective pair potentials for polymer solutions (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 4296-4311 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Dilute or semidilute solutions of nonintersecting self-avoiding walk (SAW) polymer chains are mapped onto a fluid of "soft" particles interacting via an effective pair potential between their centers of mass. This mapping is achieved by inverting the pair distribution function of the centers of mass of the original polymer chains, using integral equation techniques from the theory of simple fluids. The resulting effective pair potential is finite at all distances, has a range of the order of the radius of gyration, and turns out to be only moderately concentration-dependent. The dependence of the effective potential on polymer length is analyzed in an effort to extract the scaling limit. The effective potential is used to derive the osmotic equation of state, which is compared to simulation data for the full SAW segment model, and to the predictions of renormalization group calculations. A similar inversion procedure is used to derive an effective wall–polymer potential from the center of mass density profiles near the wall, obtained from simulations of the full polymer segment model. The resulting wall–polymer potential turns out to depend strongly on bulk polymer concentration when polymer–polymer correlations are taken into account, leading to a considerable enhancement of the effective repulsion with increasing concentration. The effective polymer–polymer and wall–polymer potentials are combined to calculate the depletion interaction induced by SAW polymers between two walls. The calculated depletion interaction agrees well with the "exact" results from much more computer-intensive direct simulation of the full polymer-segment model, and clearly illustrates the inadequacy—in the semidilute regime—of the standard Asakura–Oosawa approximation based on the assumption of noninteracting polymer coils. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1344606
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  • 5
    Electronic Resource
    Electronic Resource
    Self-assembly of epitaxially grown Ge/Si quantum dots enhanced by As ion implantation (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 4025-4027 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ge/Si islands, grown using molecular-beam epitaxy on a Si/Si0.5Ge0.5 buffer structure modified with in situ ion implantation of 1 keV As+, are investigated by transmission electron microscopy (TEM), photoluminiscence (PL), and Raman spectroscopy. Vertically correlated Ge islands are observed by TEM as a result of the implantation. A 0.8 μm PL peak is detected from the layers of self-assembled Ge quantum dots. A nonhomogeneous distribution of strain around the Ge/Si islands is deduced from the Raman scattering data. This strain is assumed to be responsible for the PL emission. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1425955
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  • 6
    Electronic Resource
    Electronic Resource
    Self-organization of GeAs nanodots in relaxed Si0.5Ge0.5 alloys (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 3494-3496 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the bimodal distribution and long-range ordering of GeAs nanodots obtained in strain-relaxed epitaxial Si0.5Ge0.5 alloy layers after arsenic implantation and rapid thermal annealing. GeAs dots of two different average sizes around 15 and 55 nm are found after high temperature rapid thermal annealing. The larger dots are of elliptical shape and located at the surface region; they are distributed preferably along 〈110〉 directions which correlates well with the observed cross-hatch pattern. The origin of the bimodal precipitate distribution as well as of the long-range ordering effect of the GeAs nanodots is discussed in terms of strain-induced nucleation and diffusion-limited growth. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1418262
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  • 7
    Electronic Resource
    Electronic Resource
    Identifying responders to acid suppression in dyspepsia using a random starting day trial (2000)
    Oxford UK : Blackwell Science Ltd
    Alimentary pharmacology & therapeutics 14 (2000), S. 0 
    Details
    ISSN: 1365-2036
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Functional dyspepsia is a heterogeneous condition and a uniform response to drug treatment is not likely. This may be the reason for the general failure of acid suppression in clinical trials in these patients. It may be more rewarding to identify true responders to drug treatment by a single subject trial.〈section xml:id="abs1-2"〉〈title type="main"〉Aim:To develop and to test a novel single subject trial design (random starting day trial) in dyspeptic patients.〈section xml:id="abs1-3"〉〈title type="main"〉Patients and methods:A total of 301 dyspeptic patients entered a 16-day trial. All patients received placebo for the first 4 days and switched to omeprazole at a randomized and blinded day between day 5 and day 14. Response was defined as a sustained ≥ 50% decrease in symptom score occurring in relation to drug shifting.〈section xml:id="abs1-4"〉〈title type="main"〉Results:Spontaneous response varied between 0.3% and 10.6% per day, uniformly distributed over time. Overall, 53–61% of patients with organic dyspepsia had a symptom response in relation to shifting to active treatment, compared to only 23% of patients with functional dyspepsia. The only predictor of response was symptoms suggesting gastro-oesophageal reflux.〈section xml:id="abs1-5"〉〈title type="main"〉Conclusions:A random starting day trial may be a valuable tool to identify response to acid suppression in dyspeptic patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2036.2000.00866.x
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  • 8
    Electronic Resource
    Electronic Resource
    Monomeric immunoglobulin E stabilizes FcεRIα from the human basophil cell line KU812 by protecting it from natural turnover (2003)
    Oxford, UK : Blackwell Science Ltd
    Clinical & experimental allergy 33 (2003), S. 0 
    Details
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background The high affinity IgE receptor (FcεRI) on mast cells and basophils is up-regulated by its own ligand IgE; however, the mechanism is unknown.Objective To study the IgE-mediated effect on FcεRI on basophils by using the human basophilic cell line KU812.Methods Expression of cell surface FcεRI was assessed by flow cytometry. Western blot technique was used to illustrate tyrosine-phosphorylation and the Ca2+ level in KU812 was measured by fluorescence of Fura-2. Soluble specimens of the α-chain from FcεRI (FcεRIα) were obtained by lysing 107 KU812 pr. mL. FcεRIα was detected by a sandwich immunoradiometric assay employing the IgE-binding capacity of FcεRIα in conjunction with a monoclonal antibody. Polyclonal rabbit anti-FcεRIα was used for detection of FcεRIα by Western blotting.Results We found that monomeric IgE did not induce tyrosine-phosphorylation in KU812, which was the case when stimulating with IgE cross-linked by anti-IgE binding. Further, only cross-linking of IgE, but not monomeric IgE, increased the Ca2+ level. Using the immunoradiometric assay, we found a temperature dependent reduction in the amount of FcεRIα. Samples incubated at 37 °C for 5 h displayed a 16-fold decrease in the FcεRIα level compared with samples incubated at 4 °C. In the presence of IgE the reduction at 37°C was only threefold.Conclusion These results indicate that IgE does not induce intracellular signals in KU812, i.e., tyrosine-phosphorylation or Ca2+ release. Instead it appears that FcεRIα is an unstable protein that IgE stabilizes and thereby protects from a temperature dependent turnover.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2222.2003.01653.x
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  • 9
    Electronic Resource
    Electronic Resource
    Efficiency of a nature-like bypass channel for sea trout (Salmo trutta) ascending a small Danish stream studied by PIT telemetry (2003)
    Oxford, UK : Blackwell Science, Ltd
    Ecology of freshwater fish 12 (2003), S. 0 
    Details
    ISSN: 1600-0633
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract – Upstream passage of adult sea trout (Salmo trutta) in a nature-like bypass channel was investigated in the Tirsbæk brook, Denmark, in autumn and winter 1999/2000. Sea trout were caught by electrofishing up- and downstream of the weir at which the bypass was situated. Fish were tagged with passive integrated transponder (PIT) tags and released downstream of the weir. Automatic PIT-tag logging stations were positioned downstream, in the lower part, and at the upstream exit of the bypass to investigate the passage success of the fish. The bypass was neither size- nor sex-selective in the size ranges investigated. The majority (68%) of fish approached the bypass at night. Over 90% of tagged upstream-searching fish located and entered the bypass channel, but only about half of them passed through. The inefficiency is suggested to be because of a combination of the length of the bypass channel and inadequate flow in the bypass channel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1600-0633.2003.00028.x
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  • 10
    Electronic Resource
    Electronic Resource
    Structure and low-temperature thermal relaxation of ion-implanted germanium (2001)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 8 (2001), S. 773-775 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The structure of implantation-induced damage in Ge has been investigated using high resolution extended X-ray absorption fine structure spectroscopy(EXAFS). EXAFS data analysis was performed with the Cumulant Method. For the crystalline-to-amorphous transformation, a progressive increase in bond-length was observed without the presence of an asymmetry in interatomic distance distribution (RDF). Beyond the amorphization threshold the RDF was dose dependent and asymmetric, where the bond-length and asymmetry increased as functions of ion dose. Such an effect was attributed to the formation of three- and five-fold coordinated atoms within the a morphous phase. Low-temperature thermal annealing resulted in structural relaxation of the amorphous phase as evidenced by a reduction in the centroid ,asymmetry and width of the RDF, as consistent with a reduction in the fraction of non four-fold coordinated atoms.The results have been compared to other EXAFS studies of amorphous Ge, and it issuggested thatthe range of bond-lengths reported therein is related to the sample preparation method and state of relaxation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0909049500012620
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