Search Results - (Author, Cooperation:L. Schaefer)

2018-02-23

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Geosciences

Computer Science

Medicine

Natural Sciences in General

Physics

Medicine, Diseases

2018-07-18

National Academy of Sciences

0027-8424

1091-6490

Biology

Medicine

Natural Sciences in General

2015-10-23

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

2018-09-26

National Academy of Sciences

0027-8424

1091-6490

Biology

Medicine

Natural Sciences in General

2011-04-02

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Animals ; *Apoptosis/drug effects ; B-Lymphocytes/metabolism ; Carrier Proteins/metabolism ; Caspase 8/metabolism ; Cells, Cultured ; Dermatitis/genetics/metabolism/pathology ; Fas-Associated Death Domain Protein/metabolism ; Fibroblasts/metabolism ; HEK293 Cells ; HeLa Cells ; Humans ; I-kappa B Kinase/metabolism ; Intracellular Signaling Peptides and Proteins/metabolism ; Macrophages/metabolism ; Mice ; NF-kappa B/*metabolism ; Nerve Tissue Proteins/deficiency/genetics/*metabolism ; Tumor Necrosis Factor-alpha/metabolism/pharmacology ; Ubiquitin/*metabolism ; Ubiquitin-Protein Ligase Complexes/*metabolism ; Ubiquitin-Protein Ligases/metabolism ; Ubiquitination

2018-01-10

Wiley-Blackwell

2049-6060

Geosciences

1089-7550

AIP Digital Archive

Physics

The influence of nitrogen doping on the electrical properties of polycrystalline diamond films has been studied. The films were prepared in a microwave plasma chemical vapor deposition process using a H2/CH4/N2 gas mixture. The CH4 concentration was held constant at 0.5% and the nitrogen to carbon atomic ratio was varied between 0.01 and 0.2. The phase purities, surface morphologies, and the nitrogen contents of the films were analyzed by Raman spectroscopy, scanning electron microscopy, and secondary-ion mass spectroscopy, respectively. From current-voltage characteristics at field strengths up to 106 V cm−1 and in the temperature range between 300 and 800 K the conductivity was determined. The dielectric strength was obtained from the breakdown voltage measured using a voltage ramping rate between 50 and 100 V s−1. A minimum in high field and high-temperature conductivity and a maximum in dielectric strength was found for the samples prepared with a nitrogen to carbon atomic ratio of 0.02. Compared with nitrogen free samples the conductivity is lowered by more than three orders of magnitude and the dielectric strength is enhanced by a factor of two. The results will be discussed in terms of compensation of acceptor states by nitrogen donors and structural changes of the films. © 1995 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

The quantitative determination of atomic hydrogen concentrations cH in the vicinity of hot filaments is performed with two-photon laser-induced fluorescence. The measurements yield atomic hydrogen concentration profiles up to 28 mm from the filament surface with a spatial resolution of about 0.5 mm. The nonequilibrium nature of the hydrogen dissociation on the filament surface results in a saturation of hydrogen concentration profiles cH(r) for gas pressures above 10 mbar. Atomic concentrations in immediate vicinity of the filament are significantly lower than expected from thermodynamical calculations and depend on the filament diameter. Addition of methane results in a decrease of cH by more than 30% near the filament and a steeper cH(r) dependence, demonstrating the accelerated consumption of H atoms by the presence of hydrocarbon species. H concentration profiles for Ta, Ir, and W filaments show a dependence on filament materials which might be taken into account when selecting filament materials for chemical vapor deposition of diamond.

Electronic Resource

0006-291X

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Chemistry and Pharmacology

Physics

Electronic Resource

0885-2006

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Education

Psychology

Electronic Resource

1434-6036

Springer Online Journal Archives 1860-2000

Physics

Abstract We consider instanton-type solutions for a lattice model of the disordered electronic system where both the diagonal and the offdiagonal matrix elements are taken as Gaussian distributed random variables. For a large range of distributions we show that the dominant instanton solution is localized at a single site. This solution is taken as the starting point for a perturbation expansion in powers of 1/E 2 in the region of localized states. This expansion has many features in common with the well-known high-temperature expansions, and we suggest to use it for an estimate of critical exponents. We evaluate the first few terms in the expansions of the density of states, the participation ratio, and the localization length for the case of nearest-neighbour hopping on a simpled-dimensional lattice. The tendency of the numerical results is promising.

Electronic Resource

1434-6036

PACS. 83.20.Fk Reptation theories - 83.20.Jp Computer simulation - 83.10.Nn Polymer dynamics

Springer Online Journal Archives 1860-2000

Physics

Abstract: We study the diffusive motion of a (non-selfinteracting) chain through a quenched random environment, constructed such that it influences only the local dynamics but not the equilibrium configuration of the chain. Our Monte Carlo results show that this type of disorder, which we call kinematic, does not ruin reptation. This is in sharp contrast to disorder including also entropic traps and it supports the view that reptation prevails in melts, where in contrast to a gel entropic trapping is absent. Our data show the characteristic features of reptation, irrespective of the dilution or randomness of the kinematic obstacles. Our Monte Carlo results are in quantitative agreement with our recent detailed analytical evaluation of the reptation model (J. Stat. Phys. 90, 1325 (1998)). The analysis suggests that we effectively see reptation of a “blob”-chain, where the size of the blob rapidly increases with decreasing obstacle concentration.

Electronic Resource

0030-4018

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Physics

Electronic Resource

1572-9613

Reptation ; polymer dynamics ; Monte Carlo simulations

Springer Online Journal Archives 1860-2000

Physics

Abstract We present simulation data for the motion of a polymer chain through a regular lattice of impenetrable obstacles (Evans–Edwards model). Chain lengths range from N= 20 to N= 640, and time up to 107Monte Carlo steps. For N≥ 160, for the central segment we find clear t 1/4behavior as an intermediate asymptote. The expected t 1/2range is not yet developed. For the end segment also the t l/4behavior is not reached. All these data compare well to our recent analytical evaluation of the reptation model, which shows that for shorter times (t≲104) the discreteness of the elementary motion cannot be neglected, whereas for longer times and short chains (N≲100) tube renewal plays an essential role also for the central segment. Due to the very broad crossover behavior, both the diffusion coefficient and the reptation time within the range of our simulation do not reach the asymptotic power laws predicted by reptation theory. We present results for the center-of-mass motion, showing the expected intermediate t 1/2behavior, but again only for very long chains. In addition we show results for the motion of the central segment relative to the center of mass, where in some intermediate range we see the expected increase of the effective power beyond the t 1/4law, before saturation sets in. Analysis and simulations agree on defining a new set of criteria as characteristic for reptation of finite chains.

Electronic Resource

1432-0428

Key words IDDM, streptozotocin, tubules, glomeruli, collagenase, gelatinase, cathepsins, hypertrophy.

Springer Online Journal Archives 1860-2000

Medicine

Summary IDDM is associated with an increase in kidney size, which is due to cellular hypertrophy and progressive matrix accumulation within the glomerulus and throughout the tubulointerstitium. The present study addressed the potential role of cysteine and metalloproteinases in renal hypertrophy of short-term diabetes. Three weeks after induction of streptozotocin diabetes in rats, intraglomerular gelatinase activity (streptozotocin: 23±4 vs control: 44±3 mU/µg DNA) and cathepsin L+B activity (streptozotocin: 6.7±0.8 vs control: 9.3±0.7 U/µg DNA) were significantly decreased. Insulin treatment completely prevented the decline in glomerular proteinase activity (gelatinase: 37±6 mU/µg DNA; cathepsin L+B: 9.6±0.9 U/µg DNA). In isolated proximal tubules a similar pattern of enzyme activity could be observed. Three weeks of diabetes caused a significant decline in cathepsin L+B activity (streptozotocin: 28±2 vs control: 37±3 U/µg DNA). Insulin treatment again prevented the decline in these tubular proteinase activities. In parallel, kidney weight increased by 22 % and glomerular protein/DNA ratio rose by 17 % in untreated diabetic rats. Diabetic rats receiving insulin displayed a normal glomerular protein/DNA ratio and the kidney weight was increased by only 5 %. These results show that renal hypertrophy of early diabetes is closely associated with a decline in both glomerular and tubular proteinase activity. Adequate insulin substitution prevented renal hypertrophy and the reduction in proteinase activity. [Diabetologia (1994) 37: 567–571]

Electronic Resource

1432-0428

IDDM ; streptozotocin ; tubules ; glomeruli ; collagenase ; gelatinase ; cathepsins ; hypertrophy

Springer Online Journal Archives 1860-2000

Medicine

Summary IDDM is associated with an increase in kidney size, which is due to cellular hypertrophy and progressive matrix accumulation within the glomerulus and throughout the tubulointerstitium. The present study addressed the potential role of cysteine and metalloproteinases in renal hypertrophy of short-term diabetes. Three weeks after induction of streptozotocin diabetes in rats, intraglomerular gelatinase activity (streptozotocin: 23±4 vs control: 44±3 mU/μg DNA) and cathepsin L + B activity (streptozotocin: 6.7±0.8 vs control: 9.3±0.7 U/μg DNA) were significantly decreased. Insulin treatment completely prevented the decline in glomerular proteinase activity (gelatinase: 37±6 mU/μg DNA; cathepsin L + B: 9.6±0.9 U/μg DNA). In isolated proximal tubules a similar pattern of enzyme activity could be observed. Three weeks of diabetes caused a significant decline in cathepsin L + B activity (streptozotocin: 28±2 vs control: 37±3 U/μg DNA). Insulin treatment again prevented the decline in these tubular proteinase activities. In parallel, kidney weight increased by 22% and glomerular protein/DNA ratio rose by 17% in untreated diabetic rats. Diabetic rats receiving insulin displayed a normal glomerular protein/DNA ratio and the kidney weight was increased by only 5%. These results show that renal hypertrophy of early diabetes is closely associated with a decline in both glomerular and tubular proteinase activity. Adequate insulin substitution prevented renal hypertrophy and the reduction in proteinase activity.

Electronic Resource

1432-0428

Keywords Glomerulosclerosis ; matrix metalloproteinase ; tissue inhibitor of metalloproteinases ; obese Zucker rat.

Springer Online Journal Archives 1860-2000

Medicine

Summary The obese Zucker rat represents a model of obesity combined with insulin resistance and hyperlipidaemia, which over a period of several months develops spontaneous glomerulosclerosis. The present study addressed the question as to whether glomerular sclerosis was associated with alterations in the degradation of matrix components. In the early phase (up to 6 months) glomeruli from obese rats displayed increased total collagen content (+ 64 %) and decreased gelatinolytic activity (− 34 %) as compared to lean control animals. This decline in glomerular gelatinolytic activity was due to a reduction in gelatinase B [matrix metalloproteinase (MMP)-9]. Glomerular MMP-9 mRNA was reduced 4.6 ± 0.6-fold (n = 3; p 〈 0.05), MMP-9 protein was not detectable by Western blotting and MMP-9 activity was considerably suppressed in gelatin zymograms. MMP-2, in terms of mRNA expression and activity, was unchanged. Tissue inhibitor of metalloproteinases (TIMP)-1 mRNA expression, TIMP-1 protein (immunohistochemistry) and TIMP-1 activity (reverse zymography) were enhanced in glomeruli from obese rats, while TIMP-2 mRNA remained unchanged. Moreover, mRNA for the α1 IV collagen chain was 2.1 ± 0.8-fold higher in glomeruli isolated from obese animals (n = 3; p 〈 0.05). These findings indicate that matrix expansion in glomeruli from obese Zucker rats is due to both enhanced synthesis of matrix components as well as reduced degradation by matrix metalloproteinases. Apparently the latter effect is based on a reduction in MMP-9 and up-regulation of its inhibitor TIMP-1. [Diabetologia (1997) 40: 1035–1043]

Electronic Resource

1432-0851

Springer Online Journal Archives 1860-2000

Medicine

Summary Thymosin, fraction V, a partially purified extract of calf thymus, was administered to 14 patients with disseminated, far-advanced malignant disease. It increased the number of positive delayed-type hypersensitivity skin tests in 69% of the patients and the number of recall KLH responses in 85% of the subjects. Thymosin significantly increased T-lymphocyte rosettes in the group of patients with percentages originally less than 50%. Thymosin administration resulted in no toxic manifestations aside from local cutaneous hypersensitivity in one subject. Suggestive evidence of thymosin clinical activity was detected in three subjects. Thymosin's activity in these patients is compatible with and complementary to results obtained in vitro, in animals, and in children with certain primary immunodeficiency diseases. Thymosin may prove to be a major addition to the group of agents effective in the immunorestoration and immunotherapy of immunodeficient cancer patients.

Electronic Resource

1432-1289

Schlüsselwörter Azidose ; Alkalose ; pH-Wert ; PCO2 ; Bicarbonat

Springer Online Journal Archives 1860-2000

Medicine

Zum Thema Bei den Störungen des Säure-Basen-Haushalts wird zwischen Alkalosen (pH 〉7,44) und Azidosen (pH 〈7,36) unterschieden. Je nach zugrundeliegender Pathogenese unterteilt man beide Zustände nochmals in metabolische bzw. respiratorische Formen. Finden sich Änderungen in der Bikarbonat-Konzentration oder beim pCO2 und ist der pH-Wert dabei noch innerhalb des Normbereichs, so spricht man von einer kompensierten, ansonsten von einer dekompensierten Störung. Primär respiratorische Störungen werden mit einer metabolischen Gegenreaktion beantwortet, während primär metabolische Störungen zu einer respiratorischen Kompensation führen. Diese kompensatorischen Vorgänge erschweren häufig die Interpretation von Störungen des Säure-Basen-Haushalts, da es in praxi sehr schwierig sein kann, die adäquate Kompensation von einer gemischten Säure-Basen-Störung zu unterscheiden.

Electronic Resource

1432-1246

Springer Online Journal Archives 1860-2000

Medicine

Zusammenfassung Im Vergleich zu früheren Tierversuchen mit grobkörnigem Getreideund in einer Vibratommühle auf kleinste Korngrößen gebrachtem Bagassestaub wurden in dieser Versuchsreihe 60 Ratten feinkörniger Getreidestaub und grobkörniger Staub von zwei Bagassearten, teilweise nach vorhergehender Sterilisation, in physiologischer Kochsalzlösung aufgeschwemmt, injiziert. Nach verschiedenen Zeitabständen (maximal 395 Tage) wurden die Tiere untersucht. Die Ergebnisse stimmen im wesentlichen mit denen der früheren Versuchsreihen überein. So zeigen auch diesmal die Lungen Bildung von Schaumzellen in den Alveolen und Bronchien, Bronchitiden und Bronchopneumonien und als relativ charakteristische Veränderungen bronchiektatische Kavernen sowie ausgedehnte Lungenabscesse und Fremdkörpergranulome. Es wird in Übereinstimmung mit unseren früheren Untersuchungen festgestellt, daß auch der sterilisierte Staub schwerste entzündliche Veränderungen hervorruft. Gewisse Unterschiede bei den Lungenbefunden gegenüber früheren Experimenten, so z. B. das häufige Auftreten bestimmter Veränderungen und deren andersartige Verteilung auf das Lungenparenchym, finden in der unterschiedlichen Staubkorngröße ihre Erklärung. Es hat den Anschein, als führe der Bagassestaub häufiger und schneller zur Bildung von Fremdkörpergranulomen als der Getreidestaub. Eine silikogene Wirkung der Stäube ist auch diesmal nicht nachzuweisen.

Electronic Resource