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Search Results: 1 - 10 of 401240 matches for " M. Wurm "
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CHO Quasispecies—Implications for Manufacturing Processes
Florian M. Wurm
Processes , 2013, DOI: 10.3390/pr1030296
Abstract: Chinese hamster ovary (CHO) cells are a source of multi-ton quantities of protein pharmaceuticals. They are, however, immortalized cells, characterized by a high degree of genetic and phenotypic diversity. As is known for any biological system, this diversity is enhanced by selective forces when laboratories (no sharing of gene pools) grow cells under (diverse) conditions that are practical and useful. CHO cells have been used in culture for more than 50 years, and various lines of cells are available and have been used in manufacturing. This article tries to represent, in a cursory way, the history of CHO cells, particularly the origin and subsequent fate of key cell lines. It is proposed that the name CHO represents many different cell types, based on their inherent genetic diversity and their dynamic rate of genetic change. The continuing remodeling of genomic structure in clonal or non-clonal cell populations, particularly due to the non-standardized culture conditions in hundreds of different labs renders CHO cells a typical case for “quasispecies”. This term was coined for families of related (genomic) sequences exposed to high mutation rate environments where a large fraction of offspring is expected to carry one or more mutations. The implications of the quasispecies concept for CHO cells used in protein manufacturing processes are significant. CHO genomics/transcriptomics may provide only limited insights when done on one or two “old” and poorly characterized CHO strains. In contrast, screening of clonal cell lines, derived from a well-defined starting material, possibly within a given academic or industrial environment, may reveal a more narrow diversity of phenotypes with respect to physiological/metabolic activities and, thus, allow more precise and reliable predictions of the potential of a clone for high-yielding manufacturing processes.
Symmetries and the conductance of graphene nanoribbons with long-range disorder
J. Wurm,M. Wimmer,K. Richter
Physics , 2011, DOI: 10.1103/PhysRevB.85.245418
Abstract: We study the conductance of graphene nanoribbons with long-range disorder. Due to the absence of intervalley scattering from the disorder potential, time-reversal symmetry (TRS) can be effectively broken even without a magnetic field, depending on the type of ribbon edge. Even though armchair edges generally mix valleys, we show that metallic armchair nanoribbons possess a hidden pseudovalley structure and effectively broken TRS. In contrast, semiconducting armchair nanoribbons inevitably mix valleys and restore TRS. As a result, in strong disorder metallic armchair ribbons exhibit a perfectly conducting channel, but semiconducting armchair ribbons ordinary localization. TRS is also effectively broken in zigzag nanoribbons in the absence of valley mixing. However, we show that intervalley scattering in zigzag ribbons is significantly enhanced and TRS is restored even for smooth disorder, if the Fermi energy is smaller than the potential amplitude. The symmetry properties of disordered nanoribbons are also reflected in their conductance in the diffusive regime. In particular, we find suppression of weak localization and an enhancement of conductance fluctuations in metallic armchair and zigzag ribbons without valley mixing. In contrast, semiconducting armchair and zigzag ribbons with valley mixing exhibit weak localization behavior.
Flood risks in urbanized areas – multi-sensoral approaches using remotely sensed data for risk assessment
H. Taubenb?ck,M. Wurm,M. Netzband,H. Zwenzner
Natural Hazards and Earth System Sciences (NHESS) & Discussions (NHESSD) , 2011, DOI: 10.5194/nhess-11-431-2011
Abstract: Estimating flood risks and managing disasters combines knowledge in climatology, meteorology, hydrology, hydraulic engineering, statistics, planning and geography – thus a complex multi-faceted problem. This study focuses on the capabilities of multi-source remote sensing data to support decision-making before, during and after a flood event. With our focus on urbanized areas, sample methods and applications show multi-scale products from the hazard and vulnerability perspective of the risk framework. From the hazard side, we present capabilities with which to assess flood-prone areas before an expected disaster. Then we map the spatial impact during or after a flood and finally, we analyze damage grades after a flood disaster. From the vulnerability side, we monitor urbanization over time on an urban footprint level, classify urban structures on an individual building level, assess building stability and quantify probably affected people. The results show a large database for sustainable development and for developing mitigation strategies, ad-hoc coordination of relief measures and organizing rehabilitation.
Odorant Binding Proteins of the Red Imported Fire Ant, Solenopsis invicta: An Example of the Problems Facing the Analysis of Widely Divergent Proteins
Dietrich Gotzek,Hugh M. Robertson,Yannick Wurm,DeWayne Shoemaker
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0016289
Abstract: We describe the odorant binding proteins (OBPs) of the red imported fire ant, Solenopsis invicta, obtained from analyses of an EST library and separate 454 sequencing runs of two normalized cDNA libraries. We identified a total of 18 putative functional OBPs in this ant. A third of the fire ant OBPs are orthologs to honey bee OBPs. Another third of the OBPs belong to a lineage-specific expansion, which is a common feature of insect OBP evolution. Like other OBPs, the different fire ant OBPs share little sequence similarity (~20%), rendering evolutionary analyses difficult. We discuss the resulting problems with sequence alignment, phylogenetic analysis, and tests of selection. As previously suggested, our results underscore the importance for careful exploration of the sensitivity to the effects of alignment methods for data comprising widely divergent sequences.
Graphene Rings in Magnetic Fields: Aharonov-Bohm Effect and Valley Splitting
J. Wurm,M. Wimmer,H. U. Baranger,K. Richter
Physics , 2009, DOI: 10.1088/0268-1242/25/3/034003
Abstract: We study the conductance of mesoscopic graphene rings in the presence of a perpendicular magnetic field by means of numerical calculations based on a tight-binding model. First, we consider the magnetoconductance of such rings and observe the Aharonov-Bohm effect. We investigate different regimes of the magnetic flux up to the quantum Hall regime, where the Aharonov-Bohm oscillations are suppressed. Results for both clean (ballistic) and disordered (diffusive) rings are presented. Second, we study rings with smooth mass boundary that are weakly coupled to leads. We show that the valley degeneracy of the eigenstates in closed graphene rings can be lifted by a small magnetic flux, and that this lifting can be observed in the transport properties of the system.
Aktuell: Reduction of ischemic sequelae following spontaneous subarachnoid hemorrhage: a double-blind, randomized comparison of enoxaparin versus placebo
Wurm G
Journal für Neurologie, Neurochirurgie und Psychiatrie , 2004,
Kleene Algebras, Regular Languages and Substructural Logics
Christian Wurm
Computer Science , 2014, DOI: 10.4204/EPTCS.161.7
Abstract: We introduce the two substructural propositional logics KL, KL+, which use disjunction, fusion and a unary, (quasi-)exponential connective. For both we prove strong completeness with respect to the interpretation in Kleene algebras and a variant thereof. We also prove strong completeness for language models, where each logic comes with a different interpretation. We show that for both logics the cut rule is admissible and both have a decidable consequence relation.
Synchronous Subsequentiality and Approximations to Undecidable Problems
Christian Wurm
Computer Science , 2015, DOI: 10.4204/EPTCS.193.5
Abstract: We introduce the class of synchronous subsequential relations, a subclass of the synchronous relations which embodies some properties of subsequential relations. If we take relations of this class as forming the possible transitions of an infinite automaton, then most decision problems (apart from membership) still remain undecidable (as they are for synchronous and subsequential rational relations), but on the positive side, they can be approximated in a meaningful way we make precise in this paper. This might make the class useful for some applications, and might serve to establish an intermediate position in the trade-off between issues of expressivity and (un)decidability.
A search for neutrino-antineutrino mass inequality by means of sterile neutrino oscillometry
M. V. Smirnov,K. K. Loo,Yu. N. Novikov,W. H. Trzaska,M. Wurm
Physics , 2015, DOI: 10.1016/j.nuclphysb.2015.09.003
Abstract: The investigation of the oscillation pattern induced by the sterile neutrinos might determine the oscillation parameters, and at the same time, allow to probe CPT symmetry in the leptonic sector through neutrino-antineutrino mass inequality. We propose to use a large scintillation detector like JUNO or LENA to detect electron neutrinos and electron antineutrinos from MCi electron capture or beta decay sources. Our calculations indicate that such an experiment is realistic and could be performed in parallel to the current research plans for JUNO and RENO. Requiring at least 5$\sigma$ confidence level and assuming the values of the oscillation parameters indicated by the current global fit, we would be able to detect neutrino-antineutrino mass inequality of the order of 0.5% or larger, which would imply a signal of CPT anomalies.
Sociogenomics of Cooperation and Conflict during Colony Founding in the Fire Ant Solenopsis invicta
Fabio Manfredini ,Oksana Riba-Grognuz,Yannick Wurm,Laurent Keller,DeWayne Shoemaker,Christina M. Grozinger
PLOS Genetics , 2013, DOI: 10.1371/journal.pgen.1003633
Abstract: One of the fundamental questions in biology is how cooperative and altruistic behaviors evolved. The majority of studies seeking to identify the genes regulating these behaviors have been performed in systems where behavioral and physiological differences are relatively fixed, such as in the honey bee. During colony founding in the monogyne (one queen per colony) social form of the fire ant Solenopsis invicta, newly-mated queens may start new colonies either individually (haplometrosis) or in groups (pleometrosis). However, only one queen (the “winner”) in pleometrotic associations survives and takes the lead of the young colony while the others (the “losers”) are executed. Thus, colony founding in fire ants provides an excellent system in which to examine the genes underpinning cooperative behavior and how the social environment shapes the expression of these genes. We developed a new whole genome microarray platform for S. invicta to characterize the gene expression patterns associated with colony founding behavior. First, we compared haplometrotic queens, pleometrotic winners and pleometrotic losers. Second, we manipulated pleometrotic couples in order to switch or maintain the social ranks of the two cofoundresses. Haplometrotic and pleometrotic queens differed in the expression of genes involved in stress response, aging, immunity, reproduction and lipid biosynthesis. Smaller sets of genes were differentially expressed between winners and losers. In the second experiment, switching social rank had a much greater impact on gene expression patterns than the initial/final rank. Expression differences for several candidate genes involved in key biological processes were confirmed using qRT-PCR. Our findings indicate that, in S. invicta, social environment plays a major role in the determination of the patterns of gene expression, while the queen's physiological state is secondary. These results highlight the powerful influence of social environment on regulation of the genomic state, physiology and ultimately, social behavior of animals.
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