1,232 research outputs found
H-alpha features with hot onsets. II. A contrail fibril
The solar chromosphere observed in H-alpha consists mostly of narrow fibrils.
The longest typically originate in network or plage and arch far over adjacent
internetwork. We use data from multiple telescopes to analyze one well-observed
example in a quiet area. It resulted from the earlier passage of an
accelerating disturbance in which the gas was heated to high temperature as in
the spicule-II phenomenon. After this passage a dark H-Halpha fibril appeared
as a contrail. We use Saha-Boltzmann extinction estimation to gauge the onset
and subsequent visibilities in various diagnostics and conclude that such
H-alpha fibrils can indeed be contrail phenomena, not indicative of the
thermodynamic and magnetic environment when they are observed but of more
dynamic happenings before. They do not connect across internetwork cells but
represent launch tracks of heating events and chart magnetic field during
launch, not at present.Comment: Accepted for Astronomy & Astrophysic
Germinant receptor diversity and germination responses of four strains of the Bacillus cereus group
Four strains of the Bacillus cereus group were compared for their germinant receptor composition and spore germination capacity. Phylogenetic analysis of the germinant receptor encoding operons of the enterotoxic strains B. cereus ATCC 14579 and ATCC 10987, the emetic strain AH187, and the psychrotolerant strain Bacillus weihenstephanensis KBAB4, indicated a core group of five germinant receptor operons to be present in the four strains, with each strain containing one to three additional receptors. Using quantitative PCR, induction of expression during sporulation was confirmed for all identified germinant receptor operons in these strains. Despite the large overlap in receptors, diversity in amino acid-induced germination capacity was observed, with six out of 20 amino acids, serving as germinants for spores of all four strains. Each strain showed unique features: efficient germination of strain KBAB4 spores required non-inducing amounts of inosine as the co-germinant, strain ATCC 10987 spores germinated only efficiently after heat activation. Furthermore, strain ATCC 14579 and AH187 spores germinated without heat activation or inosine, with strain ATCC 14579 spores being triggered by all amino acids except phenylalanine and strain AH187 spores being specifically triggered efficiently only by phenylalanine. Analysis of all germination data did not reveal strict linkages between specific germinants and germinant receptors. Finally, the diversity in nutrient-induced germination capacity was also reflected in the diverse germination responses of heat-activated spores of the four B. cereus strains in food matrices, such as milk, rice water and meat bouillon, indicating that amino acid composition and/or availability of inosine are important germination determinants in foods. Keywords: Ger operon; Food preservation; B. weihenstephanensis; Sporulatio
Dynamics of the solar magnetic bright points derived from their horizontal motions
The sub-arcsec bright points (BP) associated with the small scale magnetic
fields in the lower solar atmosphere are advected by the evolution of the
photospheric granules. We measure various quantities related to the horizontal
motions of the BPs observed in two wavelengths, including the velocity
auto-correlation function. A 1 hr time sequence of wideband H
observations conducted at the \textit{Swedish 1-m Solar Telescope}
(\textit{SST}), and a 4 hr \textit{Hinode} \textit{G}-band time sequence
observed with the Solar Optical telescope are used in this work. We follow 97
\textit{SST} and 212 \textit{Hinode} BPs with 3800 and 1950 individual velocity
measurements respectively. For its high cadence of 5 s as compared to 30 s for
\textit{Hinode} data, we emphasize more on the results from \textit{SST} data.
The BP positional uncertainty achieved by \textit{SST} is as low as 3 km. The
position errors contribute 0.75 km s to the variance of the observed
velocities. The \textit{raw} and \textit{corrected} velocity measurements in
both directions, i.e., , have Gaussian distributions with standard
deviations of and km s respectively. The BP
motions have correlation times of about s. We construct the power
spectrum of the horizontal motions as a function of frequency, a quantity that
is useful and relevant to the studies of generation of Alfv\'en waves.
Photospheric turbulent diffusion at time scales less than 200 s is found to
satisfy a power law with an index of 1.59.Comment: Accepted for publication in The Astrophysical Journal. 24 pages, 9
figures, and 1 movie (not included
De gevangene gevangen
Het lijkt in te zijn tegenwoordig: ontsnappen uit zwaar bewaakte gevangenissen. Als ware professionals gebruiken de inmates de spectaculairste middelen en weten de heren Gevangenisdirecteuren zich steeds weer geconfronteerd met de "boze buitenwereld". De nood is de vader aller commissies. Helaas blijkt hij maar al te vruchtbaar. Als een ware Athena ontsprong de commissie Hoekstra aan het brein van Kosto
Biologische teelt en certificatie in de landbouw
Een teler kan volgens allerlei kwaliteitskeurmerken produceren. Er is bij een aantal certificeringsystemen overlap. Deze overlap kan met referentietabellen in beeld worden gebracht.Dit rapport bevat een inventarisatie van normen en keurmerken diein de open teelten van toepassing kunnen zijn. In deze inventarisatie is gekeken op welke doelen het kwaliteitssysteem zich hoofdzakelijk richt. Ook is gekeken of de eisen voor certificering gericht zijn op procesmatige beheersing of op controle vangebruikte productiemethode en middelen. Tenslotte is aangegeven in welke sectoren de diverse systemen worden gebruikt en of een keurmerk aan het systeem verbonden is. Deze inventarisatie is gebruikt om te bepalen naast welke kwaliteitszorgsystemen in ditonderzoek het biologische productiecertificaat gezet kan worden
Meningococcal; septic shock in children: clinical and laboratory features, outcome and edevelopment of a prognostic score
Energetics of magnetic transients in a solar active region plage
Densely packed coronal loops are rooted in plages in the vicinity of active
regions on the Sun. The photospheric magnetic features underlying these plages
are patches of mostly unidirectional magnetic field extending several arcsec on
the solar surface. We aim to explore the transient nature of the magnetic
field, its mixed-polarity characteristics, and the associated energetics in
plages using high resolution observations and simulations. We used photospheric
Fe I 6173 {\AA} spectropolarimetric observations of a decaying active region
obtained from the SST. These data were inverted to retrieve the photospheric
magnetic field underlying the plage as identified in the EUV emission maps
obtained from the SDO/AIA. To obtain better insight into the evolution of
plages, we performed 3D radiation magnetohydrodynamic simulations of
magnetoconvection using the MURaM code. The observations show transient
magnetic flux emergence and cancellation events within the plage on timescales
of a few 100 s and on spatial scales comparable to granules. These transient
events occur at the footpoints of active region plage loops. In one case the
coronal response at the footpoints of these loops is clearly associated with
the underlying transient. The simulations also reveal similar magnetic flux
emergence and cancellation events that extend to even smaller spatial and
temporal scales. Individual simulated transient events transfer an energy flux
in excess of 1 MW m through the photosphere. We suggest that the
magnetic transients could play an important role in the energetics of active
region plage. Both in observations and simulations, the opposite-polarity
magnetic field brought up by transient flux emergence cancels with the
surrounding plage field. Magnetic reconnection associated with such transient
events likely conduits magnetic energy to power the overlying chromosphere and
coronal loops.Comment: Published in A&A (abridged abstract
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