1,240 research outputs found
YAC contigs of the Rab1 and wobbler (wr) spinal muscular atrophy gene region on proximal mouse chromosome 11 and of the homologous region on human chromosome 2p
powerful tool to advance the identi®cation of gene com-Despite rapid progress in the physical characteriza- plexes and of disease genes. In this respect, the analysis tion of murine and human genomes, little molecular in- of human chromosomes 16 and 19 (Nowak, 1995) and formation is available on certain regions, e.g., proximal mouse chromosomes 1 (Hunter et al., 1994) and 17 (Cox mouse chromosome 11 (Chr 11) and human chromosome et al., 1993) as well as of human and murine X chromo-2p (Chr 2p). We have localized the wobbler spinal atrophy somes is particularly far advanced (Hamvas et al., 1993). gene wr to proximal mouse Chr 11, tightly linked toRab1, On the other hand, such extensive information is not a gene coding for a small GTP-binding protein, and Glns- available for mouse proximal chromosome 11 (Chr 11) ps1, an intronless pseudogene of the glutamine synthe- and human chromosome 2p (Chr 2p) (Fig. 1; cf. Berry et tase gene. We have now used these markers to construct al., 1995; Nowak, 1995), known to share at least the genesa 1.3-Mb yeast arti®cial chromosome (YAC) contig of the for the reticuloendotheliosis oncogene (Brownell et al.,Rab1 region on mouse Chr 11. Four YAC clones isolated 1985), for a brain-speci®cb-spectrin isoform (Bloom et al.,from two independent YAC libraries were characterized 1992), and for cytoplasmic malate dehydrogenase (Ball etby rare-cutting analysis, ¯uorescence in situ hybridiza-al., 1994). However, comparing the segregation map oftion (FISH), and sequence-tagged site (STS) isolation and the mouse with the human cytogenetic map, a colinearmapping. Rab1 and Glns-ps1 were found to be only 20
Can we trust elemental abundances derived in late-type giants with the classical 1D stellar atmosphere models?
We compare the abundances of various chemical species as derived with 3D
hydrodynamical and classical 1D stellar atmosphere codes in a late-type giant
characterized by T_eff=3640K, log g = 1.0, [M/H] = 0.0. For this particular set
of atmospheric parameters the 3D-1D abundance differences are generally small
for neutral atoms and molecules but they may reach up to 0.3-0.4 dex in case of
ions. The 3D-1D differences generally become increasingly more negative at
higher excitation potentials and are typically largest in the optical
wavelength range. Their sign can be both positive and negative, and depends on
the excitation potential and wavelength of a given spectral line. While our
results obtained with this particular late-type giant model suggest that 1D
stellar atmosphere models may be safe to use with neutral atoms and molecules,
care should be taken if they are exploited with ions.Comment: Poster presented at the IAU Symposium 265 "Chemical Abundances in the
Universe: Connecting First Stars to Planets", Rio de Janeiro, 10-14 August
2009; 2 pages, 1 figur
Development of a tritium permeation barrier on F82H-mod. Sheets and on MANET tubes by hot dip aluminising and subsequent heat treatment
Entwicklung von Tritiumpermeationshemmenden Schichten auf F82H-mod. Blechen und MANET Rohren nach dem Hot-Dip Aluminierverfahren mit anschließender Wärmebehandlung
In der vorliegenden Arbeit werden die Ergebnisse von tauchaluminierten Blechproben aus F82H-mod. und Rohrproben aus MANET diskutiert. Die anschließende Wärmebehandlung an den getauchten Proben (1040°C, 0.5 h / 750°C, 1 h bzw. 1075°C, 0.5 h / 750°C, 2 h) entspricht der Vergütungsvorschrift für F82H-mod. bzw. der für MANET.
Das Hot-Dip Aluminierverfahren mit anschließender Wärmebehandlung eignet sich als Beschichtungsmethode sowohl für Blechproben als auch für die Innen- und Außenbeschichtung von Rohren. Die Zusammensetzung und Dicke der hergestellten Schichten ist unabhängig vom eingesetzten Stahl. Des weiteren wird gezeigt, daß die hergestellten Aluminidschichten in Pb-17Li beständig sind, der PRF genügend hoch ist und die einzelnen Prozeßschritte mit der ITM Geometrie und der Fabrikationssequenz vereinbar sind
Lower solar atmosphere and magnetism at ultra-high spatial resolution
We present the scientific case for a future space-based telescope aimed at
very high spatial and temporal resolution imaging of the solar photosphere and
chromosphere. Previous missions (e.g., HINODE, SUNRISE) have demonstrated the
power of observing the solar photosphere and chromosphere at high spatial
resolution without contamination from Earth's atmosphere. We argue here that
increased spatial resolution (from currently 70 km to 25 km in the future) and
high temporal cadence of the observations will vastly improve our understanding
of the physical processes controlling solar magnetism and its characteristic
scales. This is particularly important as the Sun's magnetic field drives solar
activity and can significantly influence the Sun-Earth system. At the same time
a better knowledge of solar magnetism can greatly improve our understanding of
other astrophysical objects
Statistical equilibrium of silicon in the solar atmosphere
The statistical equilibrium of neutral and ionised silicon in the solar
photosphere is investigated. Line formation is discussed and the solar silicon
abundance determined. High-resolution solar spectra were used to determine
solar values by comparison with Si line synthesis
based on LTE and NLTE level populations. The results will be used in a
forthcoming paper for differential abundance analyses of metal-poor stars. A
detailed analysis of silicon line spectra leads to setting up realistic model
atoms, which are exposed to interactions in plane-parallel solar atmospheric
models. The resulting departure coefficients are entered into a line-by-line
analysis of the visible and near-infrared solar silicon spectrum. The
statistical equilibrium of \ion{Si}{i} turns out to depend marginally on
bound-free interaction processes, both radiative and collisional. Bound-bound
interaction processes do not play a significant role either, except for
hydrogen collisions, which have to be chosen adequately for fitting the cores
of the near-infrared lines. Except for some near-infrared lines, the NLTE
influence on the abundances is weak. Taking the deviations from LTE in silicon
into account, it is possible to calculate the ionisation equilibrium from
neutral and ionised lines. The solar abundance based on the experimental
-values of Garz corrected for the Becker et al.'s measurement is . Combined with an extended line sample with selected NIST -values, the
solar abundance is , with a nearly perfect ionisation
equilibrium of \Delta\log\epsilon_\odot(\ion{Si}{ii}/\ion{Si}{i}) = -0.01.Comment: 13pages 10 figures. A&A acceptte
CRANKITE: a fast polypeptide backbone conformation sampler
Background: CRANKITE is a suite of programs for simulating backbone conformations of polypeptides and proteins. The core of the suite is an efficient Metropolis Monte Carlo sampler of backbone conformations in continuous three-dimensional space in atomic details.
Methods: In contrast to other programs relying on local Metropolis moves in the space of dihedral angles, our sampler utilizes local crankshaft rotations of rigid peptide bonds in Cartesian space.
Results: The sampler allows fast simulation and analysis of secondary structure formation and conformational changes for proteins of average length
Expansion of magnetic flux concentrations: a comparison of Hinode SOT d ata and models
Context: The expansion of network magnetic fields with height is a
fundamental property of flux tube models. A rapid expansion is required to form
a magnetic canopy. Aims: We characterize the observed expansion properties of
magnetic network elements and compare them with the thin flux tube and sheet
approximations, as well as with magnetoconvection simulations. Methods: We used
data from the Hinode SOT NFI NaD1 channel and spectropolarimeter to study the
appearance of magnetic flux concentrations seen in circular polarization as a
function of position on the solar disk. We compared the observations with
synthetic observables from models based on the thin flux tube approximation and
magnetoconvection simulations with two different upper boundary conditions for
the magnetic field (potential and vertical). Results: The observed circular
polarization signal of magnetic flux concentrations changes from unipolar at
disk center to bipolar near the limb, which implies an expanding magnetic
field. The observed expansion agrees with expansion properties derived from the
thin flux sheet and tube approximations. Magnetoconvection simulations with a
potential field as the upper boundary condition for the magnetic field also
produce bipolar features near the limb while a simulation with a vertical field
boundary condition does not. Conclusions: The near-limb apparent bipolar
magnetic features seen in high-resolution Hinode observations can be
interpreted using a simple flux sheet or tube model. This lends further support
to the idea that magnetic features with vastly varying sizes have similar
relative expansion rates. The numerical simulations presented here are less
useful in interpreting the expansion since the diagnostics we are interested in
are strongly influenced by the choice of the upper boundary condition for the
magnetic field in the purely photospheric simulations.Comment: accepted for publication in A&
Development of a tritium permeation barrier on MANET II steel by hot dip aluminising and subsequent heat treatment
Entwicklung von Tritiumpermeationshemmenden Schichten auf MANET II Stahl nach dem Hot-Dip Aluminierverfahren mit anschließender Wärmebehandlung
In der vorliegenden Arbeit werden die Ergebnisse von MANET Blech- und Rohrproben diskutiert, die bei 700 °C, 30 s aluminiert wurden. Das Hot-Dip Aluminierverfahren ist sowohl für die Beschichtung von Blechen als auch für die Innen- und Außenbeschichtung von Rohren geeignet. Die gebildete (Fe,Cr)2Al5 Schicht hat bei Blechen eine Dicke von 15 - 20 µm, bei Rohren von 8 - 12 µm.
Die anschließende Wärmebehandlung von 950 °C, 2 h und 750 °C, 2 h bzw. 1075 °C, 0.5 h und 750 °C, 2 h, entspricht der Vergütungsvorschrift für MANET. Während der Wärmebehandlung wird die harte (Fe,Cr)2Al5 Schicht in zwei weniger spröde Phasen umgewandelt. Die dabei entstandene obere Schicht, (Fe,Cr)Al, ist ca. 20 - 30 µm dick, die untere, -Fe(Cr,Al), ca. 70 - 110 µm. Die beiden Schichten sind durch ein Porenband voneinander getrennt
Irreversible impact of chronic hepatitis C virus infection on human natural killer cell diversity
Diversity is crucial for the immune system to efficiently combat infections. Natural killer (NK) cells are innate cytotoxic lymphocytes that contribute to the control of viral infections. NK cells were for long thought to be a homogeneous population of cells. However, recent work has instead revealed NK cells to represent a highly diverse population of immune cells where a vast number of subpopulations with distinct characteristics exist across tissues. However, the degree to which a chronic viral infection affects NK cell diversity remains elusive. Hepatitis C virus (HCV) is effective in establishing chronic infection in humans. During the last years, new direct-acting antiviral drugs (DAA) have revolutionized treatment of chronic hepatitis C, enabling rapid cure in the majority of patients. This allows us to study the influence of a chronic viral infection and its subsequent elimination on the NK cell compartment with a focus on NK cell diversity. In our recent study (Nat Commun, 9:2275), we show that chronic HCV infection irreversibly impacts human NK cell repertoire diversity
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