1,709 research outputs found
CAD-integrierte Isogeometrische Analyse und Entwurf leichter Tragwerke
Isogeometric methods are extended for the parametric design process of complex lightweight structures. Three novel methods for the coupling of different structural elements are proposed: rotational coupling, implicit geometry description, and frictionless sliding contact. Moreover, the necessary steps for the integration of the numerical analysis, including pre- and post-processing, in CAD are investigated. It is possible to base several different analyses on each other in order to parametrically represent a construction process with multiple steps.Die isogeometrischen Methoden werden zur Anwendung im parametrischen Entwurfsprozess von komplexen Leichtbaustrukturen erweitert. Hierzu werden drei neue Methoden zur Kopplung unterschiedlicher Strukturelemente vorgeschlagen: Rotationskopplung, implizite Geometriebeschreibung und reibungsfreier Gleitkontakt. Ferner werden die nötigen Schritte zur Einbindung von Pre- und Postprocessing für numerische Simulationen in CAD untersucht. Mehrere unterschiedliche Analysen können auf einander folgen und werden verlinkt, um den Aufbauprozess in mehreren Schritten vollparametrisch abzubilden
Guidelines and recommendations on yeast cell death nomenclature
Elucidating the biology of yeast in its full complexity has major implications
for science, medicine and industry. One of the most critical processes
determining yeast life and physiology is cellular demise. However, the
investigation of yeast cell death is a relatively young field, and a widely
accepted set of concepts and terms is still missing. Here, we propose unified
criteria for the definition of accidental, regulated, and programmed forms of
cell death in yeast based on a series of morphological and biochemical
criteria. Specifically, we provide consensus guidelines on the differential
definition of terms including apoptosis, regulated necrosis, and autophagic
cell death, as we refer to additional cell death routines that are relevant
for the biology of (at least some species of) yeast. As this area of
investigation advances rapidly, changes and extensions to this set of
recommendations will be implemented in the years to come. Nonetheless, we
strongly encourage the authors, reviewers and editors of scientific articles
to adopt these collective standards in order to establish an accurate
framework for yeast cell death research and, ultimately, to accelerate the
progress of this vibrant field of research
Transcriptome analysis of Aspergillus niger xlnR and xkiA mutants grown on corn Stover and soybean hulls reveals a highly complex regulatory network.
BACKGROUND:Enzymatic plant biomass degradation by fungi is a highly complex process and one of the leading challenges in developing a biobased economy. Some industrial fungi (e.g. Aspergillus niger) have a long history of use with respect to plant biomass degradation and for that reason have become 'model' species for this topic. A. niger is a major industrial enzyme producer that has a broad ability to degrade plant based polysaccharides. A. niger wild-type, the (hemi-)cellulolytic regulator (xlnR) and xylulokinase (xkiA1) mutant strains were grown on a monocot (corn stover, CS) and dicot (soybean hulls, SBH) substrate. The xkiA1 mutant is unable to utilize the pentoses D-xylose and L-arabinose and the polysaccharide xylan, and was previously shown to accumulate inducers for the (hemi-)cellulolytic transcriptional activator XlnR and the arabinanolytic transcriptional activator AraR in the presence of pentoses, resulting in overexpression of their target genes. The xlnR mutant has reduced growth on xylan and down-regulation of its target genes. The mutants therefore have a similar phenotype on xylan, but an opposite transcriptional effect. D-xylose and L-arabinose are the most abundant monosaccharides after D-glucose in nearly all plant-derived biomass materials. In this study we evaluated the effect of the xlnR and xkiA1 mutation during growth on two pentose-rich substrates by transcriptome analysis. RESULTS:Particular attention was given to CAZymes, metabolic pathways and transcription factors related to the plant biomass degradation. Genes coding for the main enzymes involved in plant biomass degradation were down-regulated at the beginning of the growth on CS and SBH. However, at a later time point, significant differences were found in the expression profiles of both mutants on CS compared to SBH. CONCLUSION:This study demonstrates the high complexity of the plant biomass degradation process by fungi, by showing that mutant strains with fairly straightforward phenotypes on pure mono- and polysaccharides, have much less clear-cut phenotypes and transcriptomes on crude plant biomass
Cool, Luminous, and Highly Variable Stars in the Magellanic Clouds from ASAS-SN: Implications for Thorne-\.Zytkow Objects and Super-Asymptotic Giant Branch Stars
Stars with unusual properties can provide a wealth of information about rare
stages of stellar evolution and exotic physics. However, determining the true
nature of peculiar stars is often difficult. In this work, we conduct a
systematic search for cool and luminous stars in the Magellanic Clouds with
extreme variability, motivated by the properties of the unusual SMC star and
Thorne-\.Zytkow Object (T\.ZO) candidate HV2112. Using light curves from
ASAS-SN we identify 38 stars with surface temperatures T 4800K,
luminosities (L/L) 4.3, variability periods 400 days, and
variability amplitudes V 2.5 mag. Eleven of these stars possess the
distinctive double-peaked light curve morphology of HV2112. We use the
pulsation properties and derived occurrence rates for these 12 objects to
constrain their nature. From comparisons to stellar populations and models, we
find that one star may be a red supergiant with large amplitude pulsations. For
the other 11 stars we derive current masses of 5-10 M, below
the theoretical minimum mass of 15 M for T\.ZOs to be stable,
casting doubt on this interpretation. Instead, we find that the temperatures,
luminosities, mass-loss rates, and periods of these stars are consistent with
predictions for super-Asymptotic Giant Branch (s-AGB) stars that have begun
carbon burning but have not reached the superwind phase. We infer lifetimes in
this phase of 17) 10 years, also consistent with an
s-AGB interpretation. If confirmed, these objects would represent the first
identified population of s-AGB stars, illuminating the transition between low-
and high-mass stellar evolution.Comment: 29 pages, 14 figures, 4 tables, plus Appendix. Accepted for
publication in the Astrophysical Journa
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