2,226 research outputs found
Disk formation in the collapse of supramassive neutron stars
Short gamma-ray bursts (sGRBs) show a large diversity in their properties.
This suggests that the observed phenomenon can be caused by different "central
engines" or that the engine produces a variety of outcomes depending on its
parameters, or possibly both. The most popular engine scenario, the merger of
two neutron stars, has received support from the recent Fermi and INTEGRAL
detection of a burst of gamma rays (GRB170817A) following the neutron star
merger GW170817, but at the moment it is not clear how peculiar this event
potentially was. Several sGRBs engine models involve the collapse of a
supramassive neutron star that produces a black hole plus an accretion disk. We
study this scenario for a variety of equations of states both via angular
momentum considerations based on equilibrium models and via fully dynamical
Numerical Relativity simulations. We obtain a broader range of disk forming
configurations than earlier studies but we agree with the latter that none of
these configurations is likely to produce a phenomenon that would be classified
as an sGRB.Comment: accepted by MNRA
Very cold and massive cores near ISOSS J18364-0221: Implications for the initial conditions of high-mass star-formation
We report the discovery of two very cold and massive molecular cloud cores in
the region ISOSS J18364-0221. The object has been identified by a systematic
search for very early evolutionary stages of high-mass stars using the 170
micron ISOPHOT Serendipity Survey (ISOSS). Submm continuum and molecular line
measurements reveal two compact cores within this region. The first core has a
temperature of 16.5 K, shows signs of ongoing infall and outflows, has no NIR
or MIR counterpart and is massive enough (M ~ 75 M_sun) to form at least one O
star with an associated cluster. It is therefore considered a candidate for a
genuine high-mass protostar and a high-mass analog to the Class 0 objects. The
second core has an average gas and dust temperature of only ~ 12 K and a mass
of M ~ 280 M_sun. Its temperature and level of turbulence are below the values
found for massive cores so far and are suggested to represent the initial
conditions from which high-mass star formation occurs.Comment: 9 pages, 6 figures, accepted for publication in the Astrophysical
Journa
Molecular signatures defining proprioceptor muscle-type identity
Proprioception, the sense of body position in space, is critical for generating coordinated
movements and reflexive actions. Proprioceptive sensory neurons (pSN) reside in the dorsal
root ganglia and constantly monitor muscle stretch and tension with their mechanoreceptive
organs (muscle spindles and Golgi-tendon organs) and relay this information to central circuits
that generate coordinated motor actions. In particular, group Ia pSN afferents (muscle spindle)
provide direct sensory feedback to motor neurons controlling the activity of the same muscle
while avoiding motor neurons of antagonistic muscle groups. This precise connectivity pattern
represents the basis of the stretch reflex arc and suggests the existence of proprioceptor
subtypes defined by the muscle they innervate. However, molecular programs controlling
critical aspects of pSN subtype identities, such as the central and peripheral connectivity, are
mainly unknown.
In this study, we devised a single-cell transcriptomic approach that takes advantage of
the topographic organization of the pSN system to reveal molecular features of cardinal
proprioceptor subtypes defined by their connectivity to limb, back, and abdominal muscles.
First, we identified and validated molecular signatures for each pSN muscle-type population.
Second, we found that molecular programs defining these identities are acquired early in
development and maintained until early postnatal stages. Last, we discovered distinct
expression patterns of axon guidance molecules of the ephrin-A/EphA family that distingush
axial- and limb-pSN. In particular, we found that the absence of ephrin-A5 affects the
peripheral connectivity of limb-pSN with specific hindlimb muscles, thus implying an
important role for ephrin-A signaling in controlling the assembly of sensorimotor circuits.
Altogether, this work reveals the molecular foundation of pSN muscle-type identity and paves
the way for studying the development and function of muscle-specific sensory feedback
circuits
Influence of Internal Climate Variability on Estuarine Sediment Dynamics
Mini-Symposium: Impacts of Climate Chang
Influence of fermentation temperature and duration on survival and biocontrol efficacy of Pseudomonas fluorescens Pf153 freeze‐dried cells
Aim: The aim of this paper was to determine whether the quality of formulated Pseudomonas fluorescens Pf153 can be influenced by changes in fermentation conditions. In this study, the influence of the fermentation temperature on the growth and its consequence on shelf life, viability and biocontrol efficacy of freeze-dried cells of P. fluorescens Pf153 was investigated. Methods and Results: Cells of P. fluorescens Pf153 were grown at 20 and 28°C in flasks and fermenter and harvested in the mid-log and the beginning of the stationary phase. The survival during storage of freeze-dried cells was tested at 25°C. Cells fermented at 20°C survived in storage better than those grown at 28°C, irrespective of the harvesting time. Compared to the untreated control, in in vitro tests Pf153 was in all production temperature/duration combinations significantly effective against all tested Botrytis cinerea strains. But no differences between temperature/duration combinations were found. In bioassay on detached Vicia faba leaves, it was found that young cells, when fermented at 28°C had a significant positive influence on the biocontrol efficacy. Conclusions: These results demonstrate that fermentation parameters have an influence on the performance and quality of a formulated product. Significance and Impact of the Study: Only limited numbers of biocontrol products based on antagonistic pseudomonads are on the market. This can be attributed to the lack of suitable formulated products with high numbers of viable cells and a good shelf life. Currently, only limited information on the influence of the fermentation on subsequent downstreaming process is available. Within this study, we focused on the influence of the two important parameters fermentation temperature and harvest time on survival, shelf life and biocontrol efficacy of P. fluorescens Pf153.Lincoln University
http://dx.doi.org/10.13039/100007032Peer Reviewe
Einsatz mikrobiologischer Präparate zur Regulierung von Schadinsekten und Krankheiten an Erdbeeren
Im organischen Erdbeeranbau sind bodenbürtige Krankheiten, z. B. Verticillium-Welke und Rhizomfäule, ein wachsendes Problem. Auch im konventionellen Anbau ist eine Bekämpfung der Verticillium-Welke nur bedingt möglich, da keine effizienten Pflanzenschutzmittel verfügbar sind. Aus diesem Grund sollte untersucht werden, ob Mikroorganismen zur Regulierung von bodenbürtigen Krankheiten an Erdbeeren verwendet werden können.
Hierfür wurden 98 Mikroorganismen, davon 68 Bakterien und 26 Pilze, in in vitro Tests gegen die Verticillium-Welke (V. albo-atrum, V. dahliae), die Rhizomfäule (Phytophthora cactorum) und die Rote Wurzelfäule getestet. In einem mehrstufigen Selektionsprozess wurden von den 98 Mikroorganismen 15 Mikroorganismen für weitere Laborversuche ausgewählt. Als Selektionskriterien wurden u.a. das antagonistische Potential, die Kombinierbarkeit und die Marktverfügbarkeit berücksichtigt.
Die fünfzehn Mikroorganismen, die die vorgegebenen Kriterien erfüllten, wurden in weiteren Kompatibilitätstest getestet. Anschließend wurden vier Mikroorganismen ausgewählt: zwei Trichoderma (T. atroviride P1 und T. harzianum T58), ein entomopathogener Pilz (Metarhizium anisopliae Ma43) und ein Bakterium (Bacillus subtilis FZB24). Diese Antagonisten wurden in Gewächshaus- und Freilandversuche an zwei Erdbeersorten (Honeoye und Sonata) in mit V. dahliae und P. cactorum inokulierter Erde getestet.
Weder in Gewächshaus- noch in Freilandversuchen konnten auch nach künstlicher Inokulation des Bodens mit den zwei Pathogenen reproduzierbare Krankheitssymptome hervorgerufen werden. Damit konnte keine klare Aussage zur befallsreduzierenden Wirkung der antagonistischen Mikroorganismen getroffen werden.
Allerdings wurde in Gewächshausversuchen mit V. dahliae inokulierter Erde bei der Sorte Honeoye ein positiver Einfluss der Antagonisten auf unterschiedliche Wachstumsparameter beobachtet. Die Ergebnisse zum Einfluss der Antagonisten auf die Mikrosklerotien, die Überdauerungsformen von V. dahliae, waren widersprüchlich. Nur in Freilandversuchen wurde eine Reduktion der Mikrosklerotien durch pilzliche Antagonisten erreicht
- …