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Search Results: 1 - 10 of 325504 matches for " S. Schumann "
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Identification of Distant Drug Off-Targets by Direct Superposition of Binding Pocket Surfaces
Marcel Schumann, Roger S. Armen
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0083533
Abstract: Correctly predicting off-targets for a given molecular structure, which would have the ability to bind a large range of ligands, is both particularly difficult and important if they share no significant sequence or fold similarity with the respective molecular target (“distant off-targets”). A novel approach for identification of off-targets by direct superposition of protein binding pocket surfaces is presented and applied to a set of well-studied and highly relevant drug targets, including representative kinases and nuclear hormone receptors. The entire Protein Data Bank is searched for similar binding pockets and convincing distant off-target candidates were identified that share no significant sequence or fold similarity with the respective target structure. These putative target off-target pairs are further supported by the existence of compounds that bind strongly to both with high topological similarity, and in some cases, literature examples of individual compounds that bind to both. Also, our results clearly show that it is possible for binding pockets to exhibit a striking surface similarity, while the respective off-target shares neither significant sequence nor significant fold similarity with the respective molecular target (“distant off-target”).
Production of recombinant proteins in Escherichia coli
Schumann, Wolfgang;Ferreira, Luis Carlos S.;
Genetics and Molecular Biology , 2004, DOI: 10.1590/S1415-47572004000300022
Abstract: attempts to obtain a recombinant protein using prokaryotic expression systems can go from a rewarding and rather fast procedure to a frustrating time-consuming experience. in most cases production of heterologous proteins in escherichia coli k12 strains has remained an empirical exercise in which different systems are tested without a careful insight into the various factors affecting adequate expression of the encoded protein. the present review will deal with e. coli as protein factory and will cover some of the aspects related to transcriptional and translational expression signals, factors affecting protein stability and solubility and targeting of proteins to different cell compartments. based on the knowledge accumulated over the last decade, we believe that the rate of success for those dedicated to expression of recombinant proteins based on the use e. coli strains can still be significantly improved.
Chaotic Quantum Decay in Driven Biased Optical Lattices
S. Mossmann,C. Schumann,H. J. Korsch
Physics , 2005, DOI: 10.1209/epl/i2005-10289-5
Abstract: Quantum decay in an ac driven biased periodic potential modeling cold atoms in optical lattices is studied for a symmetry broken driving. For the case of fully chaotic classical dynamics the classical exponential decay is quantum mechanically suppressed for a driving frequency \omega in resonance with the Bloch frequency \omega_B, q\omega=r\omega_B with integers q and r. Asymptotically an algebraic decay ~t^{-\gamma} is observed. For r=1 the exponent \gamma agrees with $q$ as predicted by non-Hermitian random matrix theory for q decay channels. The time dependence of the survival probability can be well described by random matrix theory. The frequency dependence of the survival probability shows pronounced resonance peaks with sub-Fourier character.
Graphite based Schottky diodes formed on Si, GaAs and 4H-SiC substrates
S. Tongay,T. Schumann,A. F. Hebard
Physics , 2009, DOI: 10.1063/1.3268788
Abstract: We demonstrate the formation of semimetal graphite/semiconductor Schottky barriers where the semiconductor is either silicon (Si), gallium arsenide (GaAs) or 4H-silicon carbide (4H-SiC). Near room temperature, the forward-bias diode characteristics are well described by thermionic emission, and the extracted barrier heights, which are confirmed by capacitance voltage measurements, roughly follow the Schottky-Mott relation. Since the outermost layer of the graphite electrode is a single graphene sheet, we expect that graphene/semiconductor barriers will manifest similar behavior.
Simulating the global atmospheric response to aircraft water vapour emissions and contrails: a first approach using a GCM
M. Ponater,S. Brinkop,R. Sausen,U. Schumann
Annales Geophysicae (ANGEO) , 2003,
Abstract: The effect of contrails and aircraft water vapour emissions on global climate is studied by means of a general circulation model (GCM). In a first approach water vapour emissions and mean contrail coverage within the main flight routes are prescribed according to current observations in a simplified manner. A hierarchic experiment strategy with gradual increase of the forcing is applied to identify the resulting climate signals. The water vapour increase to be expected from air traffic is too small to force a detectable radiative or climatic response. The sensitivity of the model climate to the occurrence of contrails appears to be higher. For mid-latitude summer conditions, the high cloud increase experiments show a consistent temperature response pattern. However, its magnitude is statistically significant only for a mean contrail coverage exceeding present-day amounts. Moreover, the magnitude of the contrail climate signal is highly sensitive to the details of the experimental setup due to several non-linearities of the cloud-radiative interaction. Hence, the prescription of contrails in the GCM has to be as careful as possible for an optimal treatment of the problem. Respective recommendations are given.
Surface phonons of NiO(001) ultrathin films grown pseudomorphically on Ag(001)
K. L. Kostov,S. Polzin,F. O. Schumann,W. Widdra
Physics , 2015,
Abstract: For a ultrathin NiO(001) film of 4 monolayers (ML) thickness grown on Ag(001), the vibrational properties have been determined by high-resolution electron energy loss spectroscopy (HREELS). For the well-ordered pseudomorphically grown film, nine phonon modes have been identified and their dispersions have been revealed along the Gamma-X high-symmetry direction. The comparison with phonon data for a 25 ML thick NiO(001) film shows that the NiO (001) phonon properties are already fully developed at 4 ML. Significant differences are found for the surface-localized phonon S6 which has an increased dispersion for the ultrathin film. The dipole-active Fuchs-Kliewer phonon-polariton exhibits a narrower lineshape than the mode found for a single-crystal surface, which might hint to a reduced antiferromagnetic coupling in the ultrathin film.
Distinguishing Kaolinites and Smectite Clays from Central and Eastern Uganda Using Acidity, pH, Colour and Composition  [PDF]
I. Z. Mukasa-Tebandeke, P. J. M. Ssebuwufu, S. A. Nyanzi, A. Schumann, M. Ntale, G. W. Nyakairu, F. Lugolobi
American Journal of Analytical Chemistry (AJAC) , 2015, DOI: 10.4236/ajac.2015.61006
Abstract: The Langmuir isotherms of 1-aminobutane in isohexane slurries showed increase in clay acidity with increase in concentration of mineral acid used to leach the clay as well as the temperature at which the clay was thermally activated prior to experimentation involving adsorption of 1-aminobutane. The values of acidity for Central Uganda were low ranging from 0.07 mol/g to 0.32 mol/g yet those for clays from Eastern Uganda were high ranging from 0.1 mol/g to 1.85 mol/g. Based on acidity, pH, elemental and mineral compositions, the clays from Central Uganda were found to be kaolinites or halloysites, yet Eastern Uganda clays were resolved to contain nontronite and kaolinite.
The Elemental, Mineralogical, IR, DTA and XRD Analyses Characterized Clays and Clay Minerals of Central and Eastern Uganda  [PDF]
I. Z. Mukasa-Tebandeke, P. J. M. Ssebuwufu, S. A. Nyanzi, A. Schumann, G. W. A. Nyakairu, M. Ntale, F. Lugolobi
Advances in Materials Physics and Chemistry (AMPC) , 2015, DOI: 10.4236/ampc.2015.52010
Abstract: The results on the elemental and mineralogical compositions of clays from Central Uganda differed from those from the volcanic sediments of the Mt. Elgon in Eastern Uganda. Utilisation of the two types of clays should be strict after understanding their structural differences. Whereas elemental, mineralogical, DTA, IR, XRD and pH data on selected clays from Kumi, Nakawa, Seeta, Kajansi, Kawuku, Lwanda, Chodah and Umatengah indicated that they were kaolinites. Similar data on clays from Mutufu, Budadiri, Chelel and Siron indicated that they were largely smectites. The IR data accumulated on Kawuku, Kajansi, Lwada, Seeta, Chodah, Umatengah, Kumi and Nakawa clays revealed they were largely kaolinites yet that on Mutufu, Chelel, Budadiri and Siron clays indicated they were smectite-rich.
Adsorption Behavior of Acid-Leached Clays in Bleaching of Oil  [PDF]
I. Z. Mukasa-Tebandeke, P. J. M. Ssebuwufu, S. A. Nyanzi, G. W. Nyakairu, M. Ntale, F. Lugolobi, Schumann Andreas
American Journal of Analytical Chemistry (AJAC) , 2015, DOI: 10.4236/ajac.2015.66049
Abstract: The available data have shown that acid-leached clays had sites for adsorption of impurities in oils. Data obtained on residual impurities in cotton and sunflower-seed oils bleached with the same clay materials produced linear Langmuir and Freundlich isotherms. The increase in constant, k with increase in both temperature of thermal activation and concentration of acid used to leach the clay, suggests that bleaching efficiency increased. The value of n decreased with increase in temperature of activation and concentration of acid used to leach the clay suggesting that bleaching capacity increased. The mineral compositions of the clays influenced their surface, structural and bleaching properties.
A contrail cirrus prediction model
U. Schumann
Geoscientific Model Development (GMD) & Discussions (GMDD) , 2012, DOI: 10.5194/gmd-5-543-2012
Abstract: A new model to simulate and predict the properties of a large ensemble of contrails as a function of given air traffic and meteorology is described. The model is designed for approximate prediction of contrail cirrus cover and analysis of contrail climate impact, e.g. within aviation system optimization processes. The model simulates the full contrail life-cycle. Contrail segments form between waypoints of individual aircraft tracks in sufficiently cold and humid air masses. The initial contrail properties depend on the aircraft. The advection and evolution of the contrails is followed with a Lagrangian Gaussian plume model. Mixing and bulk cloud processes are treated quasi analytically or with an effective numerical scheme. Contrails disappear when the bulk ice content is sublimating or precipitating. The model has been implemented in a "Contrail Cirrus Prediction Tool" (CoCiP). This paper describes the model assumptions, the equations for individual contrails, and the analysis-method for contrail-cirrus cover derived from the optical depth of the ensemble of contrails and background cirrus. The model has been applied for a case study and compared to the results of other models and in-situ contrail measurements. The simple model reproduces a considerable part of observed contrail properties. Mid-aged contrails provide the largest contributions to the product of optical depth and contrail width, important for climate impact.
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