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  • Articles: DFG German National Licenses  (27)
  • 2000-2004  (8)
  • 1995-1999  (17)
  • 1940-1944  (2)
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  • Articles: DFG German National Licenses  (27)
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  • 1
    Electronic Resource
    Electronic Resource
    The effect of physical structure on δI curves of longitudinal thin film (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. 4915-4915 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Conventionally, the simulation of thin films has been carried out using an HCP structure to represent its physical structure. Such an idealized structure has been shown to overestimate the effect of interparticle coupling by using an homogeneous exchange coupling scheme. A more realistic approach to represent physical structure has been undertaken by generating a system of grains which lie on a radially isotropic structure and have a nonuniform volume distribution. Interaction effects can be shown by computing δI curves formed through the comparison of the remanence curves using the Wohlfarth relation. To generate an isothermal remanence curve (IRM), a realistic ac erased state is necessary which has been carried out by using a simulated annealing technique. A comparison has been made to determine the effect of physical structure on the bulk properties by computing hysteresis loops, remanence curves, and δI curves. To reduce statistical error these have been averaged over four different sets of easy axes. The loops indicate that an irregular physical structure leads to an increase in the coercivity and decrease in the squareness. The dc-demagnetization curves show an increase in remanent coercivity; this can be attributed to the random physical structure decreasing the size of magnetically correlated regions within the microstructure. The effect of the physical microstructure on the δI curves will be discussed in full in the paper. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361585
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of work function and surface microstructure on field emission of tetrahedral amorphous carbon (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 6002-6010 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The work function of tetrahedral amorphous carbon (ta-C) has been measured by Kelvin probe to lie in the range 4–5 eV, irrespective of its sp3 content or nitrogen addition. This implies that the surface barrier to emission is dominant and that emission changes caused by sp3 bonding or nitrogen addition are not directly due to changes in work function. Hydrogen, oxygen, and argon plasma treatments are all found to increase the emission of a-C, but hydrogen and argon treatments are found to reduce the work function while oxygen treatment increases it. Detailed studies of the surface with varying plasma treatment conditions suggest that the changes in emission arise mainly from changes in the surface microstructure, such as the formation of sp2 regions within the sp3 bulk. The need for local field enhancement mechanisms to account for emission over the sizeable barrier is emphasized, which may arise from local chemical nonhomogeneity, or formation of nanometer-size sp2 clusters embedded in an sp3 matrix. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1314874
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  • 3
    Electronic Resource
    Electronic Resource
    Stress reduction and bond stability during thermal annealing of tetrahedral amorphous carbon (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 7191-7197 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A comprehensive study of the stress release and structural changes caused by postdeposition thermal annealing of tetrahedral amorphous carbon (ta-C) on Si has been carried out. Complete stress relief occurs at 600–700 °C and is accompanied by minimal structural modifications, as indicated by electron energy loss spectroscopy, Raman spectroscopy, and optical gap measurements. Further annealing in vacuum converts sp3 sites to sp2 with a drastic change occurring after 1100 °C. The field emitting behavior is substantially retained up to the complete stress relief, confirming that ta-C is a robust emitting material. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370531
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  • 4
    Electronic Resource
    Electronic Resource
    Demonstration of a current-controlled three-terminal Nb–InxGa1−xAs/InP Josephson contact (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 2348-2350 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The supercurrent in a Nb–In0.53Ga0.47As/In0.77Ga0.23As/InP weak link structure is controlled by means of a current injected into the two-dimensional electron gas. For small injection currents the critical current to control current ratio is as large as 20. The measured features can be qualitively explained in terms of a modification of the Andreev level occupation by the injected carriers. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122457
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  • 5
    Electronic Resource
    Electronic Resource
    Preparation of regular arrays of antidots in YBa2Cu3O7 thin films and observation of vortex lattice matching effects (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 962-964 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optimized sputtered YBa2Cu3O7 (YBCO) thin films on CeO2-buffered sapphire substrates are patterned into square lattices of submicrometer holes (antidots) with diameters of 250–450 nm and lattice parameters of d=500–1000 nm without deterioration of superconducting properties. In the mixed state, matching effects between the Abrikosov vortex lattice and the artificial antidot lattice are observed. These effects are in the form of peaks or cusps in the critical current density recorded as a function of magnetic induction at integers n and specific rationals k/l of the matching field Bm=(Φ0/d2). The experimental results are discussed in the context of existing theories. The existence of multiquanta vortices confined by the holes in YBCO films are considered. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119701
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  • 6
    Electronic Resource
    Electronic Resource
    Josephson effect in Nb/two-dimensional electron gas structures using a pseudomorphic InxGa1−xAs/InP heterostructure (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 3575-3577 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Superconducting Nb–In0.53Ga0.47As/In0.77Ga0.23As/InP–Nb contacts with an electrode separation of 450 nm were fabricated. Due to the high mobility of the two-dimensional electron gas, the current transport can be described within the clean limit regime. At 0.3 K a critical current of 3.8 μA was obtained for 6 μm wide contacts leading to a characteristic voltage of 190 μV. The decrease of the critical current with increasing temperature can be explained by a theory developed by A. Chrestin, T. Matsuyama, and U. Merkt [Phys. Rev. B 49, 498 (1994)], which takes δ-shaped barriers at the superconductor/semiconductor interfaces into account. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120410
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  • 7
    Electronic Resource
    Electronic Resource
    Field emission from tetrahedral amorphous carbon as a function of surface treatment and substrate material (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 1594-1596 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: To understand the mechanism of electron field emission from diamond-like carbon, tetrahedral amorphous carbon (ta-C) films were subjected to Ar, H2, and O2 plasma treatments to change their surface condition and were deposited on substrates of different work function. The threshold fields and current densities for undoped ta-C are found to be significantly improved by the plasma treatments, largely due to an increase in emission site density, while little dependence was found on work function of substrate. This suggests that the main barrier to emission from ta-C is at the front surface. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123627
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  • 8
    Electronic Resource
    Electronic Resource
    Field emission from tetrahedral amorphous carbon (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 1430-1432 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Field emission has been measured from a series of tetrahedrally bonded amorphous carbon (ta-C) films produced by the filtered cathodic vacuum arc. The threshold field and current densities achievable have been studied as a function of their sp3 content and of nitrogen incorporation. Typical undoped ta-C films are found to have a threshold field of 10–20 V/μm, decreasing with increasing sp3 content, and optimally nitrogen doped films exhibit threshold fields as low as 3–5 V/μm. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119915
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  • 9
    Electronic Resource
    Electronic Resource
    Azathioprine dose escalation in inflammatory bowel disease (2004)
    Oxford, UK : Blackwell Science Ltd
    Alimentary pharmacology & therapeutics 20 (2004), S. 0 
    Details
    ISSN: 1365-2036
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background : Forty per cent of patients with inflammatory bowel disease fail to respond to standard dose azathioprine (2 mg/kg/day).Aims : To evaluate the efficacy and safety of increasing the azathioprine dose according to a fixed schedule and guided by clinical response and adverse effects.Methods : We reviewed the records of all patients with inflammatory bowel disease treated by a single clinician over 6 years, unresponsive to at least 3 months treatment with standard dose azathioprine, and whose dose was subsequently increased.Results : Forty patients (27 male; 24 Crohn's, 16 ulcerative colitis) with chronic active disease or recurrent flares despite standard dose azathioprine for a median 8 months (range 3–114) increased their dose from a median 2.02 (1.61–3.19) mg/kg/day to 2.72 (2.37–3.99) mg/kg/day in one to four increments of 0.5 mg/kg/day, and were followed over a median6 (0.5–54) months. Eleven of the 40 patients (seven Crohn's, four ulcerative colitis) responded or had reduced frequency of flare-ups at the end of follow-up, while 17 of the 40 patients had no benefit. Response was more likely for maximum doses ≤2.5 mg/kg/day (six of 11 patients) than for doses 〉2.5 mg/kg/day (five of 29 patients) (P = 0.042). Twelve patients (11 of whom received maximum doses 〉2.5 mg/kg/day) were unable to maintain an increased azathioprine dose because of leukopenia in eight, nausea in three, and raised liver enzymes in one (all transient and reversible).Conclusions : Increasing the azathioprine dose up to 2.5 mg/kg/day appears beneficial in patients who have not responded to 2 mg/kg/day. Further increase above 2.5 mg/kg/day is less likely to be efficacious, and is associated with a substantial risk of adverse reactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2036.2004.02009.x
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  • 10
    Electronic Resource
    Electronic Resource
    The role of the gut flora in health and disease, and its modification as therapy (2002)
    Oxford, UK : Blackwell Science Ltd
    Alimentary pharmacology & therapeutics 16 (2002), S. 0 
    Details
    ISSN: 1365-2036
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The gut flora is a vast interior ecosystem whose nature is only beginning to be unravelled, due to the emergence of sophisticated molecular tools. Techniques such as 16S ribosomal RNA analysis, polymerase chain reaction amplification and the use of DNA microarrays now facilitate rapid identification and characterization of species resistant to conventional culture and possibly unknown species. Life-long cross-talk between the host and the gut flora determines whether health is maintained or disease intervenes. An understanding of these bacteria–bacteria and bacteria–host immune and epithelial cell interactions is likely to lead to a greater insight into disease pathogenesis. Studies of single organism–epithelial interactions have revealed the large range of metabolic processes that gut bacteria may influence. In inflammatory bowel diseases, bacteria drive the inflammatory process, and genetic predisposition to disease identified to date, such as the recently described NOD2/CARD15 gene variants, may relate to altered bacterial recognition. Extra-intestinal disorders, such as atopy and arthritis, may also have an altered gut milieu as their basis. Clinical evidence is emerging that the modification of this internal environment, using either antibiotics or probiotic bacteria, is beneficial in preventing and treating disease. This natural and apparently safe approach holds great appeal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2036.2002.01310.x
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