1,526 research outputs found
Aktivität, Populationsdynamik und Diversität Methan oxidierender Bakterien im Reisfeld
Die Methan oxidierenden Bakterien können durch
die Umsetzung von Methan die Emission dieses Treibhausgases aus
gefluteten Reisfeldern deutlich verringern. Um nähere Erkenntnisse
über die Aktivität und Populationsstruktur der Methanotrophen im
Reisfeld zu erhalten, wurden Mikrokosmos- und Feldexperimente
durchgeführt. Die Ergebnisse dieser beiden Systeme waren qualitativ
gut vergleichbar. Der positive Einfluss der Reiswurzel auf die
Methanotrophen war durch die Kompartimentierung im Mikrokosmos
deutlicher nachzuweisen als im Feld. Die insitu Methanoxidation
hatte sowohl im Feld als auch im Mikrokosmos nur während der ersten
Wochen der Vegetationsperiode Einfluss auf die Methanemissionen.
Dagegen blieben die Initialraten in Messungen der potentiellen
Methanoxidation in Bodensuspensionen auch nach Abnahme der
Aktivität in-situ anhaltend hoch. Dies wies auf eine in-situ
Limitierung der Methan oxidierenden Bakterien hin, die auf einen
Mangel an leichtverfügbaren Stickstoffverbindungen zurückgeführt
werden konnte. Die Zellzahl der Methanotrophen nahm während des
Wachstums der Reispflanze besonders in Rhizoplane und Homogenisat
der Wurzel, aber auch im durchwurzelten Boden zu. Im Mikrokosmos
konnte eine in-situ Dominanz der Typ II Methanotrophen in allen
Kompartimenten und über die gesamte Vegetationsperiode nachgewiesen
werden. Die Zahl der Typ I Methanotrophen erreichte nur in der
Rhizoplane Anteile von bis zu 2/3 der Gesamtpopulation. Die Wurzel
ist demnach nicht nur für den Erhalt der Grösse, sondern auch der
Diversität der Population wichtig. Im Feldversuch wurden beide
Familien in vergleichbaren Zellzahlen nachgewiesen. Die
Populationsstruktur wies trotz des Wachstums der Methanotrophen
keine ausgeprägten Änderungen auf. Für Typ II wurden beide
Gattungen (Methylosinus und Methylocystis) nachgewiesen, während
für Typ I nur zur Gattung Methylo-bacter ähnliche Sequenzen
gefunden wurden. Die Dominanz von Methylobacter könnte auf einen
Selektionsvorteil gegenüber anderen Typ I Gattungen zurück-zuführen
sein. Da Reisfelder periodisch trocken gelegt werden, erhalten
diejenigen Bodenbakterien einen Vorteil, die Trocknungsstress
überstehen können. Methylo-bacter ist die einzige Typ I Gattung mit
einem trocknungsresistenten Dauersta-dium und auch beide
nachgewiesenen Typ II Gattungen bilden entsprechende Dauerstadien.
Diese Fähigkeit ermöglichte es ihnen, im Reisfeld zu überdauern und
verdeutlichte so die selektiven Auswirkungen der Physiologie auf
die Populationsstruktur der Methan oxidierenden
Bakterien
Nonmarine Ostracoda as proxies in (geo-)archaeology: a review
Abstract Ostracods as bioindicators are extremely useful for reconstructing palaeoenvironment and palaeoclimate and can also indicate the provenance of sediments and materials, for example, in studies on ancient commercial networks. Ostracods are small crustaceans that live in almost all aquatic habitats, both natural and man-made. Due to their calcitic carapace, they have high fossilization potential, and their use in geoarchaeology has been steadily increasing during the last decades. Their small size needs mean that only small volumes of sediment samples are needed, and species-specific ecological tolerances and preferences allow detailed palaeoenvironmental reconstructions. Typical methods of their application are palaeoecological analyses of associations based on ecological information and taphonomy, morphometric variability and stable isotope and chemistry analyses of their shells. The present paper aims to present an overview of applications of non-marine ostracods in (geo-)archaeological research, recommending sampling and analytical techniques for addressing archaeological research questions on palaeoclimate, habitat and landscape changes, water availability and quality, land use and other anthropogenic impacts, the provenance of materials and commercial networks to promote the application of Ostracoda in geoarchaeology/environmental archaeology.1 Introduction 2 Applications 2.1 short history of ostracod‐based palaeoenvironmental reconstructions 2.2 Palaeoclimate and palaeoenvironmental studies on continental archaeological sites 2.2.1 General palaeoenvironment/landscape reconstructions 2.2.2 Salinity 2.2.3 Temperature 2.2.4 Radiocarbon dating 2.3 Landscape changes by human activity 2.4 Water use and water works 2.5 Provenance studies 3 Methods for sampling and lab analyses 4 Conclusion
Two-component radiation model of the sonoluminescing bubble
Based on the experimental data from Weninger, Putterman & Barber, Phys. Rev.
(E), 54, R2205 (1996), we offer an alternative interpretation of their
experimetal results. A model of sonoluminescing bubble which proposes that the
electromagnetic radiation originates from two sources: the isotropic black body
or bramsstrahlung emitting core and dipole radiation-emitting shell of
accelerated electrons driven by the liquid-bubble interface is outlined.Comment: 5 pages Revtex, submitted to Phys. Rev.
Supply Current Diagnosis in VLSI
This paper presents a technique based upon the power supply current signature (cd) which allows for the testing of mixed-signal systems, in situ. Through experiments with a microprocessor, the cd is shown to contain important information concerning the operational status of the system which may be easily extracted using approaches based on statistical signal detection theory. The fault-detection performance of these techniques is compared to that achieved through auto-regressive modeling of the cd
Nonradiative Electronic Deexcitation Time Scales in Metal Clusters
The life-times due to Auger-electron emission for a hole on a deep electronic
shell of neutral and charged sodium clusters are studied for different sizes.
We consider spherical clusters and calculate the Auger-transition probabilities
using the energy levels and wave functions calculated in the
Local-Density-Approximation (LDA).
We obtain that Auger emission processes are energetically not allowed for
neutral and positively charged sodium clusters. In general, the Auger
probabilities in small Na clusters are remarkably different from the
atomic ones and exhibit a rich size dependence.
The Auger decay times of most of the cluster sizes studied are orders of
magnitude larger than in atoms and might be comparable with typical
fragmentation times.Comment: 11 pages, 4 figures. Accepted for publication in Phys. Rev.
СУТНІСТЬ ТА ПРОЦЕС ФОРМУВАННЯ ІНТЕГРОВАНИХ МАРКЕТИНГОВИХ КОМУНІКАЦІЙ
Проаналізовано сутність, характеристика, принципи інтегрованих комунікацій та розкрито особливості процесу їх формування на підприємствах України.; The essence, characteristics and principles of integrated communications are analyzed. The peculiarities of the process of their formation on the enterprises are discovered
Gauge Theories with Cayley-Klein and Gauge Groups
Gauge theories with the orthogonal Cayley-Klein gauge groups and
are regarded. For nilpotent values of the contraction
parameters these groups are isomorphic to the non-semisimple Euclid,
Newton, Galilei groups and corresponding matter spaces are fiber spaces with
degenerate metrics. It is shown that the contracted gauge field theories
describe the same set of fields and particle mass as gauge
theories, if Lagrangians in the base and in the fibers all are taken into
account. Such theories based on non-semisimple contracted group provide more
simple field interactions as compared with the initial ones.Comment: 14 pages, 5 figure
Mechanisms for Stable Sonoluminescence
A gas bubble trapped in water by an oscillating acoustic field is expected to
either shrink or grow on a diffusive timescale, depending on the forcing
strength and the bubble size. At high ambient gas concentration this has long
been observed in experiments. However, recent sonoluminescence experiments show
that in certain circumstances when the ambient gas concentration is low the
bubble can be stable for days. This paper presents mechanisms leading to
stability which predict parameter dependences in agreement with the
sonoluminescence experiments.Comment: 4 pages, 3 figures on request (2 as .ps files
Stress-induced activation of the proline biosynthetic pathway in Bacillus subtilis:A population-wide and single-cell study of the osmotically controlled proHJ promoter
Bacillus subtilis, in its natural habitat, is regularly exposed to rapid changes in the osmolarity of its surrounding. As its primary survival strategy, it accumulates large amounts of the compatible solute proline by activating the de novo proline biosynthesis pathway and exploiting the glutamate pools. This osmotically-induced biosynthesis requires activation of a SigA-type promoter that drives the expression of the proHJ operon. Population-wide studies have shown that the activity of the proHJ promoter correlates with the increased osmotic pressure of the environment. Therefore, the activation of the proHJ transcription should be an adequate measure of the adaptation to osmotic stress through proline synthesis in the absence of other osmoprotectants. In this study, we investigate the kinetics of the proHJ promoter activation and the early adaptation to mild osmotic upshift at the single-cell level. Under these conditions, we observed a switching point and heterogeneous proline biosynthesis gene expression, where the subpopulation of cells showing active proHJ transcription is able to continuously divide, and those unresponsive to osmotic stress remain dormant. Additionally, we demonstrate that bactericidal antibiotics significantly upregulate proHJ transcription in the absence of externally imposed osmotic pressure, suggesting that the osmotically-controlled proline biosynthesis pathway is also involved in the antibiotic-mediated stress response
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