Search Results - (Author, Cooperation:R. Levy)

2012-11-20

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Cephalometry ; Child ; Child Development Disorders, Pervasive/*genetics ; Child, Preschool ; Chromatin Assembly and Disassembly ; Cohort Studies ; DNA Probes ; DNA-Binding Proteins/genetics ; Exome ; Female ; *Genetic Association Studies ; Genetic Predisposition to Disease ; Humans ; Male ; Megalencephaly/genetics ; Microcephaly/genetics ; *Mutation ; Nuclear Proteins/genetics ; PTEN Phosphohydrolase/genetics ; Protein-Serine-Threonine Kinases/genetics ; Protein-Tyrosine Kinases/genetics ; Receptors, Cytoplasmic and Nuclear/genetics ; Receptors, N-Methyl-D-Aspartate/genetics ; Repressor Proteins/genetics ; Sequence Analysis, DNA/*methods ; T-Box Domain Proteins/genetics ; Transcription Factors/genetics ; beta Catenin/genetics/metabolism

2012-04-13

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Autistic Disorder/*genetics ; DNA-Binding Proteins/genetics ; Exome/*genetics ; Exons/*genetics ; GPI-Linked Proteins/genetics ; Genetic Predisposition to Disease/genetics ; Humans ; Laminin/genetics ; NAV1.1 Voltage-Gated Sodium Channel ; Nerve Tissue Proteins/genetics ; Parents ; Point Mutation/*genetics ; Protein Interaction Maps/*genetics ; Receptors, N-Methyl-D-Aspartate/genetics ; Reproducibility of Results ; Siblings ; Signal Transduction ; Sodium Channels/genetics ; Stochastic Processes ; Transcription Factors/genetics ; Tumor Suppressor Protein p53/metabolism ; beta Catenin/metabolism

2013-09-03

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

2018-08-19

MDPI Publishing

2072-4292

Architecture, Civil Engineering, Surveying

Geography

2018-07-27

Sozialwissenschaften, Soziologie ; Social sciences, sociology, anthropology ; Allgemeines zu den Sozialwissenschaften, Entwicklung und Geschichte der Sozialwissenschaften ; Wissenschaftstheorie, Wissenschaftsphilosophie, Wissenschaftslogik, Ethik der Sozialwissenschaften ; General Problems, History of the Social Sciences ; Philosophy of Science, Theory of Science, Methodology, Ethics of the Social Sciences ; historische Entwicklung ; Soziologie ; Schweiz ; Wissenschaftsverständnis ; Interdependenz ; sozioökonomisches System ; Forschung ; Einrichtung ; Sprachbarriere ; soziokulturelle Faktoren ; soziale Funktion ; historical development ; sociology ; Switzerland ; understanding of science ; interdependence ; socioeconomic system ; research ; facility ; language barrier ; sociocultural factors ; social function

Konferenzbeitrag, conference paper

article

1993

Allgemeine Soziologie ; Institutionalisierung ; Sozialstruktur

Behrens, Johann (Hrsg.), Kritische Uebergaenge., Frankfurt, Main: Campus (1993), S. 73-113

German

2018-05-26

BMJ Publishing Group

0022-2593

1468-6244

Medicine

2018-02-16

The American Association for Cancer Research (AACR)

1078-0432

1557-3265

Medicine

2018-04-14

The American Association for Cancer Research (AACR)

1078-0432

1557-3265

Medicine

1471-4159

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Abstract: Previously, opioid peptide analogues, β-endorphin, and synthetic opiates were found to inhibit DNA synthesis in 7-day fetal rat brain cell aggregates via κ-and μ-opioid receptors. Here dynorphins and other endogenous opioid peptides were investigated for their effect on DNA synthesis in rat and guinea pig brain cell aggregates. At 1 µM, all dynorphins tested and β-endorphin inhibited [3H]thymidine incorporation into DNA by 20–38% in 7-day rat brain cell aggregates. The putative ε-antagonist β-endorphin (1–27) did not prevent the effect of β-endorphin, suggesting that the ε-receptor is not involved in opioid inhibition of DNA synthesis. The κ-selective antagonist norbinaltorphimine blocked dynorphin A or B inhibition of DNA synthesis, implicating a κ-opioid receptor. In dose-dependency studies, dynorphin B was three orders of magnitude more potent than dynorphin A in the attenuation of thymidine incorporation, indicative of the mediation of its action by a discrete κ-receptor subtype. The IC50 value of 0.1 nM estimated for dynorphin B is in the physiological range for dynorphins in developing brain. In guinea pig brain cell aggregates, the κ-receptor agonists U50488, U69593, and dynorphin B reduced thymidine incorporation by 40%. When 21-day aggregates were treated with dynorphins, a 33–86% enhancement of thymidine incorporation was observed. Because both 7- and 21-day aggregates correspond to stages in development when glial cell proliferation is prevalent and glia preferentially express κ-receptors in rat brain, these findings support the hypothesis that dynorphins modulate glial DNA synthesis during brain ontogeny.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

We report laser-induced transient grating experiments performed at room temperature on self-supporting p-type porous silicon films with different porosities. With this technique the diffusion of the photocarriers can be studied with a time resolution of some tens of picoseconds. The gratings were created by two interfering pulses of the second-harmonic radiation from an Nd3+:yttrium-aluminum-garnet YAG laser (2.3 eV) and their decay in time was studied by a time-delayed pulse of the fundamental YAG laser frequency (1.15 eV). The observed grating decay time is very fast (hundreds of picoseconds) and shortens with decreasing porosity. Diffusion constants D=45, 24, and 5 cm2 s−1 have been found for the porosities of 64%, 68%, and 73%, respectively. To explain these high values of D we consider a simple kinetic model which takes into account two different types of carriers, delocalized and trapped ones. © 1996 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

In order to determine the third order of the nonlinear susceptibility χ(3) of GaN, we perform degenerate four-wave mixing measurements in a two-beam configuration at low temperature on a GaN epilayer on sapphire substrate. We measure the excitation spectrum of χ(3) close to the exciton resonances. Besides the χ(3) contribution, higher orders of the nonlinear susceptibility show already up around 10 kW cm−2, leading to a saturation of the signal. Results are complemented by a study of the influence of a band-to-band excitation ((h-dash-bar)ωP=4.02 eV) on the nonlinear susceptibility. © 1999 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

The roughening kinetics of copper films synthesized by low pressure chemical vapor deposition (LPCVD) on Si(100) substrates was investigated by scanning tunneling microscopy (STM). By applying the dynamic scaling theory to the STM images, a steady growth roughness exponent α=0.81±0.05 and a dynamic growth roughness exponent β=0.62±0.09 were determined. The value of α is consistent with growth model predictions incorporating surface diffusion. The value of β, while higher than expected from these models, can be related to LPCVD processing conditions favoring growth instabilities. © 1996 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Bulk Cd1−xZnxTe ternary compounds are studied through nonlinear optical pump and probe experiments for different zinc concentrations x. These measurements, similar to excitation spectra, enable us to determine the frequency dependence of the optical nonlinearity. It is attributed to the presence of impurity levels in the material. The two-photon absorption through these states gives rise to a high induced absorption. © 1997 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

The microstructure of amorphous hydrogenated boron nitride films, with nominal composition B3N:H, is characterized with respect to hydrogen bonding and distribution by combined application of nuclear-magnetic-resonance (NMR) spectroscopy, electron-spin-resonance spectroscopy, and evolved gas analysis. Previous infrared studies on annealed films suggest that hydrogen is present in multiple configurations; qualitatively, low-temperature anneals (∼600 °C) deplete N-H moieties whereas B-H configurations are depleted at higher temperatures (∼1050 °C). Gas analysis corroborates these results, showing H2 peaks at ∼570 and ∼950 °C. From an analysis of nuclear dipolar couplings extracted from the 1H NMR spectra, it is concluded that the hydrogen is essentially randomly distributed as monohydrides; other configurations, such as dihydrides and monohydride clusters, are estimated to be less than 20% total. Furthermore, the 1H NMR spectra show no evidence of molecular H2 trapped in the films. In a film exposed to a high x-ray dose (∼30 kJ cm−3), it was determined that the damage was equivalent to 1 unpaired electron spin per 175 B3N:H units. The 1H NMR linewidth did not change after irradiation, which suggests that the hydrogen spatial distribution was unaffected.

Electronic Resource

1471-0528

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

A case of retroperitoneal ectopic pregnancy is described.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We study the optical nonlinear properties of bulk Cd0.13Zn0.87Te monocrystals at room temperature near the band gap. In time-resolved test and pump experiments, they manifest themselves by a defocalization and an induced absorption of the test beam in the presence of the pump beam. By measuring the spatial intensity profile of the test pulse transmitted through the sample, we determine the real and the imaginary parts of the refractive index as functions of the photon energy and time delay between pump and test pulses.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We report nonlinear absorption around the Z3 exciton in CuCl microcrystallites embedded in a glass matrix. Our experiments are performed in a test-pump configuration with picosecond pulses at low temperature. In addition to a shift and a bleaching of the excitonic resonance, induced absorption on the high-energy side is found. The nonlinear index changes induced per exciton per unit volume of CuCl quantum dot could be determined by Kramers–Kronig transformations.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Persistent spectral-holes (p-SH) are burned in the Z1,2 excitonic band of CuBr nanocrystals by a pulsed laser excitation. The annealing of p-SH is studied by three types of hole-filling (HF) experiments: (i) the spontaneous HF, (ii) thermally-induced HF, and (iii) the laser-induced HF. Results are compared to the well developed theory of the persistent spectral hole-burning (p-SHB) in the system of molecules in amorphous matrices. Both p-SHB and HF phenomena can be explained within the framework of a photochemical reaction like the photoionization of nanocrystals. The potential application of p-SHB to the frequency-domain optical data storage is discussed. © 1997 American Institute of Physics.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

We investigate the nonlinear absorption of C60-doped porous sol-gel glasses by single- and double-pulse pump–probe experiments. We find that the reverse saturable absorption (RSA) of these samples can be explained in the frame of a five level system as it is commonly used for C60 solutions. We observe a strong saturation of the RSA at high fluences, especially if the molecules are prepared in the triplet state. In a double-pulse pump–probe experiment we measure the triplet quantum yield for C60 solutions (0.8) and doped glasses (0.25) and the singlet and triplet absorption cross sections. In the first excited singlet state (S1) lifetimes of 1 ns and 65 ps are determined in solutions and glasses, respectively. We find that the dynamics of both depopulation processes, direct S1–S0 relaxation, and intersystem crossing is faster in glasses than in the case where C60 is in solution in a liquid aromatic solvent. We tentatively explain these findings by the absence of a stabilizing solvent and a perturbation of the molecular energy levels due to interaction with the solid glass matrix. We finally determine the lifetime of the triplet states in our glass samples to 2 μs. © 1999 American Institute of Physics.

Electronic Resource