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  • 1
    Electronic Resource
    Electronic Resource
    A monolithic polycapillary focusing optic for polychromatic neutron diffraction applications (2002)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 1985-1993 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have conducted measurements at five different thermal neutron wavelengths to determine the transmission characteristics of a tapered monolithic focusing lens with a focal length of 100 mm, suitable for time-of-flight diffraction. Both the width of the focused beam and the intensity gain of the optic increase as a function of wavelength. We have performed similar measurements on a polychromatic beam on a pulsed neutron source, where the results are subject to background from short wavelength neutrons. The use of a beryllium filter shows the increased effective gain for the longer wavelengths at the expense of an increased focused beam width by a factor of 2. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1470236
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  • 2
    Electronic Resource
    Electronic Resource
    A portable time of flight system for thermal and cold neutron applications (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 2770-2774 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A very small Fermi-type neutron chopper fashioned by cutting slots in a boron nitride cylinder was developed for use with a source of thermal and cold (subthermal velocity) neutrons. The original goal was to characterize spectra emerging from glass capillary fibers of less than 1 mm diameter, but other applications became apparent. For approximately 1 m flight paths, conventional nuclear electronics had to be adapted to the millisecond flight times. Both time-to-amplitude converter and multiscaling time-data storage methods were used. Data corrections for the particular geometry are reviewed and applied to the present geometry. Among examples of its potential use, the spectrum of a newly installed cold source was measured. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147106
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  • 3
    Electronic Resource
    Electronic Resource
    Imaging of neutron incoherent scattering from hydrogen in metals (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3669-3674 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Neutron incoherent scattering is a technique that may be used to determine the concentration of hydrogen within various metallic systems. By measuring the scattered neutrons using a position-sensitive detector, we can determine the amount of hydrogen as well as its location in the matrix. Using a slit or aperture in the scattering geometry, we have demonstrated the imaging of hydrogen in layers of polypropylene sandwiched between sets of titanium plates, and also in titanium standards containing known amounts of hydrogen. We have shown the ability to image hydrogen in titanium at the 100 μg/g level as a function of location. Analysis of the images shows that the scattering from the hydrogen increases linearly with its mass fraction within the titanium. We have also investigated the effects on the images of attenuation of the incident beam prior to scattering. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1452769
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  • 4
    Electronic Resource
    Electronic Resource
    A polycapillary bending and focusing lens for neutrons (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 3744-3750 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A glass polycapillary lens that both bends and focuses a cold neutron beam has been designed and constructed. The bender focuser guides part of the incident beam away from its line of sight and focuses it to a spot of width 0.65 mm at a distance 95 mm from the lens exit and 20 mm below the bottom edge of the beam path, with a gain of 20 in neutron current density. The neutron transmission characteristics of the lens have been determined with two types of position-sensitive detectors, a charge injection device, and an imaging plate. The lens has been tested with prompt gamma measurements on a gadolinium shard and titanium foil. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148020
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  • 5
    Electronic Resource
    Electronic Resource
    A basic mathematical model of the immune response (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Chaos 5 (1995), S. 155-161 
    Details
    ISSN: 1089-7682
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Interaction of the immune system with a target population of, e.g., bacteria, viruses, antigens, or tumor cells must be considered as a dynamic process. We describe this process by a system of two ordinary differential equations. Although the model is strongly idealized it demonstrates how the combination of a few proposed nonlinear interaction rules between the immune system and its targets are able to generate a considerable variety of different kinds of immune responses, many of which are observed both experimentally and clinically. In particular, solutions of the model equations correspond to states described by immunologists as "virgin state,'' "immune state'' and "state of tolerance.'' The model successfully replicates the so-called primary and secondary response. Moreover, it predicts the existence of a threshold level for the amount of pathogen germs or of transplanted tumor cells below which the host is able to eliminate the infectious organism or to reject the tumor graft. We also find a long time coexistence of targets and immune competent cells including damped and undamped oscillations of both. Plausibly the model explains that if the number of transformed cells or pathogens exeeds definable values (poor antigenicity, high reproduction rate) the immune system fails to keep the disease under control. On the other hand, the model predicts apparently paradoxical situations including an increased chance of target survival despite enhanced immune activity or therapeutically achieved target reduction. A further obviously paradoxical behavior consists of a positive effect for the patient up to a complete cure by adding an additional target challenge where the benefit of the additional targets depends strongly on the time point and on their amount. Under periodically pulsed stimulation the model may show a chaotic time behavior of both target growth and immune response. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.166098
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  • 6
    Electronic Resource
    Electronic Resource
    Cold neutron incoherent scattering for hydrogen detection in industrial materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 3876-3879 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Neutron incoherent scattering (NIS) is proposed as a method for the rapid detection of hydrogen and corrosion in industrial materials. As an example, we apply the NIS method to the detection of hydrogen in graphite and in titanium alloy, and compare the results with those obtained with the prompt gamma activation analysis (PGAA) method. The scattering cross section for hydrogen is much greater than the capture cross section, which enables the NIS method to have a detection limit and accuracy close to that for PGAA, and allows real time experiments on hydrogen detection to be performed. We report preliminary results on using the NIS method to determine hydrogen in urea [CO(NH2)2]/graphite and in titanium matrices. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366620
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  • 7
    Electronic Resource
    Electronic Resource
    Efficacy and tolerability of multiple-dose SDZ IMM 125 in patients with severe psoriasis (1995)
    Oxford, UK : Blackwell Publishing Ltd
    British journal of dermatology 133 (1995), S. 0 
    Details
    ISSN: 1365-2133
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Although cyclosporin is effective in immunosuppression following organ transplantation and in the treatment of psoriasis, its use is limited by its side-effects, notably impaired renal function and hypertension. As SDZ IMM 125, a new derivative of the cyclosporin family, showed considerable immunosuppressive activity in experimental studies, with less effect on renal function, it was considered a potential successor to cyclosporin for both indications. In this multicentre, double-blind, placebo-controlled study, the efficacy and tolerability of 40, 100, 200 and 400mg SDZ IMM 125 daily were studied in 59 patients with psoriasis. Patients were followed for a period of 5 weeks (4 weeks treatment, and 1 week post-treatment observation). A dose-dependent effect of SDZ IMM 125 was observed. A significant correlation was found between the dose of SDZ IMM 125 and changes in the sum of severity scores of three indicator plaques. There was a significant decrease in the body surface area affected by psoriasis in the 400-mg group (P 〈 0.01), whereas a decrease of the global psoriasis severity was observed in the 200-mg (P 〈 0.01) and the 400-mg groups (P 〈 0.001). No serious adverse events occurred during the 4 weeks of treatment. Three patients discontinued treatment because of adverse events (one sore throat, two influenza). Clinical adverse events were similar to those reported with cyclosporin, the most frequent being gastrointestinal disturbances. Estimation of renal function indices showed that increases from baseline values were dose dependent, and appeared to be similar to those seen with cyclosporin. Changes in liver function tests showed a clearcut dose-dependent increase of some liver enzymes, principally alanine aminotransferase (ALAT). SDZ IMM 125 is effective in clearing psoriasis. However, long-term studies comparing the efficacy and safety of SDZ IMM 125 and cyclosporin must be performed, to determine whether SDZ IMM 125 has a better risk-benefit ratio than cyclosporin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2133.1995.tb02500.x
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  • 8
    Electronic Resource
    Electronic Resource
    Carbon and oxygen isotope composition of organic compounds in the phloem sap provides a short-term measure for stomatal conductance of European beech (Fagus sylvatica L.) (2003)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 26 (2003), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: At eight different dates during the 2000 growing season, δ13C and δ18O were determined in the phloem of adult beech trees growing in natural beech stands in south-west Germany differing in stand density and local climate. In addition, stand transpiration, precipitation, photosynthetic active radiation, relative air humidity, water pressure deficit of the air, air and soil temperature, soil water potential, and sugar concentration of the phloem sap were determined directly and evaporation and canopy stomatal conductance were modelled. All parameters were related to δ13C. The study aimed to identify the time integral within which the δ13C of organic compounds transported in the phloem is an indicative measure of these environmental influences. δ13C of soluble carbon transported in the phloem was well correlated with mean stomatal conductance in a two-day integral prior to phloem sampling but did not depend on either light intensity or soil water availability. A strong positive relationship between δ13C and δ18O pointed to observed variation in δ13C of phloem sap being a result of variation in stomatal conductance. Bulk leaf δ13C was a poor indicator of changes in environmental conditions during the growing season. From these results we conclude that the analysis of δ13C in soluble carbon transported in the phloem is a reliable indicator of short-term changes in Ci/Ca. In contrast, the δ13C of structural carbon in beech foliage represents an integration of a range of factors that mask short-term influences responsible for Ci/Ca.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2003.01040.x
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  • 9
    Electronic Resource
    Electronic Resource
    NEAR-THRESHOLD FATIGUE CRACK GROWTH IN A12O3 PARTICLE REINFORCED 6061 ALUMINIUM ALLOY (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 18 (1995), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The influence of Al2O3 particle reinforcement on the fatigue crack growth properties of 6061-T6 aluminium alloy in the near threshold regime has been investigated at a load ratio of R=– 1 using an alloy with 15 vol.% fine particles (6061/Al2O3/15p) and one with 21 vol.% coarser particles (6061/Al2O3/21p). The Al2O3 particles act as obstacles for fatigue crack growth and are especially effective at very low cyclic loads. For the reinforced alloy with fine particles the threshold of the stress intensity amplitude is higher than that for the alloy containing coarse particles, and the lowest threshold value of Kmax was obtained for pure 6061-T6. Fracture of ceramic particles and interfaces between matrix and Al2O3 particles, both more frequent for coarser particles, may serve as an explanation for the more effective improvement of fatigue crack growth properties by fine particles. At maximum stress intensity factors above 6.5 MPa√m, fatigue crack growth in the particle reinforced alloys is faster than in the unreinforced alloy 6061-T6, which is attributed to more frequent particle and interface fracturing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1995.tb01190.x
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  • 10
    Electronic Resource
    Electronic Resource
    INFLUENCE OF TRANSFORMATION-INDUCED CRACK CLOSURE ON SLOW FATIGUE CRACK GROWTH UNDER VARIABLE AMPLITUDE LOADING (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 18 (1995), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Fatigue crack growth under constant and random loading conditions was investigated for a metastable austenitic-bainitic steel in comparison with a ferritic chromium steel at very low crack growth rates. Experimentally determined random crack growth was compared with linear Miner calculations on the basis of constant amplitude results. It was found that the measured crack growth rates in transforming material are a factor of 10 lower than the calculated values, whereas the difference is only a factor of 2 for the ferritic steel. The reason for the pronounced crack growth retardation in the metastable alloy is transformation of part of the austenitic phase into martensite in the stress field of the crack tip, accompanied by a volume increase and, consequently, residual compressive stresses. Rare high load cycles in the random sequence increase the closure level, which then leads to pronounced retardation of fatigue crack growth for the numerous successive low amplitude cycles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1995.tb00918.x
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