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  • Elsevier  (27)
  • Springer  (23)
  • Institute of Physics  (2)
  • 1990-1994  (52)
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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Radiation and environmental biophysics 30 (1991), S. 53-70 
    ISSN: 1432-2099
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Physik
    Notizen: Summary Cell survival was studied by analyzing the inactivation probability density function and its fundamental parameters. Mean $$\bar D$$ , varianceσ 2 and modeD mode were evaluated and a set of equations relating these parameters to the usual parameters of the multitarget, multihit and linear-quadratic modelsD o andn, α andβ, k andλ are reported. The multihit equation used was an extension of the usual equation, to allow parameterk to assume values that are not necessarily integers. In the multitarget curve, the mode of inactivation probability density function, proved to be the quasi-threshold doseD q =D o ln(n). Relative variance, degree of asymmetry and degree of peakedness can be calculated from the shape parametersn in the multitarget model,k in the multihit model, and $$\alpha /\sqrt \beta $$ in the linear-quadratic model. From an analysis of eight published cell survival sets of data, on C3H10T1/2 cells exposed to low LET radiations, it was found that $$\bar D$$ ,σ, andSF 2 are the parameters which exhibit the least variation from experiment to experiment and the least variation in selecting the range of data available for estimation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    ISSN: 1432-1424
    Schlagwort(e): epithelial transport ; Na−K−2Cl cotransport ; vasopressin ; Na−Cl transport ; medullary thick ascending limb ; Rb transport
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary Experiments were performed usingin vitro perfused medullary thick ascending limbs of Henle (MTAL) and in suspensions of MTAL tubules isolated from mouse kidney to evaluate the effects of arginine vasopressin (AVP) on the K+ dependence of the apical, furosemide-sensitive Na+:Cl− cotransporter and on transport-related oxygen consumption (QO2). In isolated perfused MTAL segments, the rate of cell swelling induced by removing K+ from, and adding onemm ouabain to, the basolateral solution [ouabain(zero-K+)] provided an index to apical cotransporter activity and was used to evaluated the ionic requirements of the apical cotransporter in the presence and absence of AVP. In the absence of AVP cotransporter activity required Na+ and Cl−, but not K+, while in the presence of AVP the apical cotransporter required all three ions.86Rb+ uptake into MTAL tubules in suspension was significant only after exposure of tubules to AVP. Moreover,22Na+ uptake was unaffected by extracellular K+ in the absence of AVP while after AVP exposure22Na+ uptake was strictly K+-dependent. The AVP-induced coupling of K+ to the Na+:Cl− cotransporter resulted in a doubling in the rate of NaCl absorption without a parallel increase in the rate of cellular22Na+ uptake or transport-related oxygen consumption. These results indicate that arginine vasopressin alters the mode of a loop diuretic-sensitive transporter from Na+:Cl− cotransport to Na+:K+:2Cl− cotransport in the mouse MTAL with the latter providing a distinct metabolic advantage for sodium transport. A model for AVP action on NaCl absorption by the MTAL is presented and the physiological significance of the coupling of K+ to the apical Na+:Cl− cotransporter in the MTAL and of the enhanced metabolic efficiency are discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Il nuovo cimento della Società Italiana di Fisica 14 (1992), S. 1191-1202 
    ISSN: 0392-6737
    Schlagwort(e): Ionizing radiations (X-ray, γ-ray, and particle radiation effect)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Summary There is substantial experimental evidence that protracted exposure to high-LET radiation can have a greated effect than single exposure in inducing cell transformation, the so-called «inverse dose-rate effect». The magnitude of this enhancement is due to the complex interplay between dose, dose rate and radiation quality. We have developed a model that explains the complex trend of the experimental results. This model is based on the assumption that there is a brief period of high sensitivity to transformation in the cell cycle as proposed in the literature and takes into account the saturation observed at high doses in the dose-effect curves. Specific equations are reported for acute, protracted and fractionated irradiation. Findings with C3H10T1/2 cells were analised in the light of this model. Assuming best fitted parameters of the model obtained from acute-irradiation data, tranformation frequencies due to protracted or fractionated exposure were predicted and compared with experimental findings on fission and monoenergetic neutrons and on charged particles of LET between 20 and 150 keV/μm. The model’s predictions were found to be closely consistent with the available experimental data.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Il nuovo cimento della Società Italiana di Fisica 16 (1994), S. 1999-2004 
    ISSN: 0392-6737
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Summary YBCO step-edge junction d.c. SQUIDs have been realized by using the Inverted Cylindrical Magnetron Sputtering (ICMS) technique. This last represents a novel technology for high-T c Josephson junctions (HTSC). Steps are obtained by standard ion milling procedure on LaAlO3 (100) substrates using Nb-masks patterned by reactive ion etching. Measurements of currentvs. voltage, maximum d.c. Josephson currentvs. magnetic field and SQUID voltage response measurements have been performed, also as a function of the temperature. Operating temperature as high as 77K has been achieved. At 4.2K the SQUIDs show a maximum voltage of flux transfer function (∂V/∂ϕ)max=870 μV/Ф0 and a good periodicity of theV-ϕ modulation up to 20Ф0 without any sign of hysteresis. The ratio between the step height (h) and the film thickness (d) seems to play a fundamental role in determining Josephson properties of the bridges, these conditions being more severe with respect to most of the data available in literature.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Astrophysics and space science 169 (1990), S. 125-132 
    ISSN: 1572-946X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Several years of coordinated multifrequency observations of the dwarf nova SS Cygni have been performed in order to study the accretion behaviour of this system in particular, and in general to clarify this crucial problem for the cataclysmic variables. From IUE measurements, together with those from optical and IR ground based telescopes, we have found orbital modulations in the continuum and in the equivalent widths of the emission lines. During quiescent phases the behaviour of SS Cygni are dependent on the type of the preceding outburst (long-type or short-type). In this paper we will discuss the physical implications one can derive from these results.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Journal of electronic testing 4 (1993), S. 215-224 
    ISSN: 1573-0727
    Schlagwort(e): Constant tetability ; fault detection ; fault location ; FFT ; testing
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract This article presents new approaches for testing VLSI array architectures used in the computation of the complexN-point Fast Fourier Transform. Initially, an unrestricted single cell-level fault model is considered. The first proposed approach is based on a process whose complexity is independent (or C- as constant) of the number of cells in the FFT architecture. This is accomplished by showing a topological equivalence between the FFT array and a linear (one-dimensional) array. The process of fault location is also analyzed. The second proposed method is based on a testing process whose complexity is linear with respect to the number of stages (columns) of the FFT array. A component-level fault model is also proposed and analyzed. The implications of this model on the C-testability process are fully described.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Journal of electronic testing 1 (1990), S. 43-57 
    ISSN: 1573-0727
    Schlagwort(e): diagnosis ; redundant memory ; repair ; WSI ; yield
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract In this article, yield enhancement and manufacturing throughput of large repairable memories are analyzed. These objectives are met by repairability/unrepairability detection. Initially two new techniques for detection of memory chips with redundancy are presented. Initially, a heuristic, yet efficient approach is proposed. This first approach is based on finding a very good approximation to the minimum covering set. An algorithm, which executes in quadratic time with respect to the largest dimension of the memory, is presented. This algorithm is executed off-line, that is, when the memory has been fully diagnosed. New conditions for detection are presented and fully analyzed. These are based on a more accurate estimation of the regions of repairability and unrepairability. Hence, this results in a reduction of the uncertainty region, where the status of a memory cannot be established without executing a fully exhaustive search algorithm. The second approach to repairability/unrepairability detection is based on a more complex covering relationship, namely the generalized leading element. A model for manufacturing throughput of large repairable memories is presented. A new repair algorithm which utilizes a ternary tree approach, is also presented. This repair algorithm is perfect in the sense that it finds the optimal repair-solution (whenever one exists) after the memory has not been diagnosed unrepairable. Illustrative examples and simulation results show that considerable improvements for average and the worst-case analysis over existing techniques can be achieved.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Research in engineering design 2 (1991), S. 239-253 
    ISSN: 1435-6066
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Technik allgemein
    Notizen: Abstract A study has been carried out on the use of knowledge-based computer-aided design methodology for the design of thermal systems. An expert system is developed using a Prolog-based front end, where the design rules, material databases, computational procedures, and the relevant expert knowledge are implemented. A combination of quantitative and heuristic inputs are employed in the design process. The basic approach employs an iterative redesign strategy, starting with an initial design obtained from the available knowledge base, and the design parameters are iteratively varied until the specified design rules and constraints are satisfied. The general approach can be employed for a variety of thermal systems. The application to a practical system is demonstrated by the design of an electrical furnace used in the thermal processing of materials. The results from the numerical simulation and design of this system are presented to indicate the basic features and the versatility of the expert system.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    ISSN: 1432-1211
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Among the HLA-DR-specific monoclonal antibodies (mAbs) that have been characterized previously, there is a marked shortage of DRα chain-specific mAbs which stain unfixed cells. This may result from the high degree of sequence similarity between the α1 domains of HLA-DR and H-2E leading to a state of cross-tolerance to DRα in H-2-expressing mice. BALB/b (E-negative) mice were immunized with DR1-transfected mouse L cells. The chain specificity of the resulting DR-specific mAb was determined using a panel of transfectants expressing hybrid mouse/human class II heterodimers. A DRα-specific mAb was generated which was capable of immunoprecipitating DRαβ dimers and inhibiting the anti-DR alloresponse of human T-cell clones. The present study demonstrates that, with the selection of suitable recipient strain, transfectants can be useful in the generation and definition of chain-specific mouse mAbs.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    ISSN: 1432-1211
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The regions of the HLA-A2 molecule controlling anti-A2 alloreactivity were explored using naturally occurring allelic variants of HLA-A, and a panel of transfectants expressing the products of A2.1 genes that had been mutated at multiple positions encoding residues in the α2 domain α-helix. As a means of detecting distant conformational effects, these altered A2.1 molecules were also examined serologically. Amino acid substitutions at the carboxy-terminal end of the α2 domain α-helix led to diminished staining with the monoclonal antibody (mAb) MA2.1. The epitope for this antibody has previously been mapped to the α1 domain α-helix (residues 62–65). This suggests that interdomain contacts may cause conformational alteration, and that mutants can have distant, as well as local effects. Of the 24 positions where substitutions were made, only six led to loss of the anti-A2 alloresponse by the three clones and three lines that were tested. In addition, the mutations that altered the MA2.1 epitope, located on the α1 domain α-helix, did not inhibit allorecognition. This suggests that a limited number of regions on the A2.1 molecule are responsible for allodeterminant expression. The most influential substitutions were those at positions 152, 154, 162, and 166. It is notable that three of these are predicted to be T-cell receptor (Tcr)-contacting residues, and one (152) to contribute to peptide binding. These results suggest that the specificity of alloreactive T cells is determined by exposed polymorphisms, directly contacted by the Tcr, and by concealed polymorphisms which influence peptide binding.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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