7,861 research outputs found
DEVELOPMENT OF AMINE OXIDASE-CONTAINING PEROXISOMES IN YEASTS DURING GROWTH ON GLUCOSE IN THE PRESENCE OF METHYLAMINE AS THE SOLE SOURCE OF NITROGEN
Development and Breakdown of Peroxisomes in the Yeast Hansenula polymorpha in Response to a Changing Environment
Development and Breakdown of Peroxisomes in the Yeast Hansenula polymorpha in Response to a Changing Environment
Spectral irradiance variations: Comparison between observations and the SATIRE model on solar rotation time scales
Aims: We test the reliability of the observed and calculated spectral
irradiance variations between 200 and 1600 nm over a time span of three solar
rotations in 2004.
Methods: We compare our model calculations to spectral irradiance
observations taken with SORCE/SIM, SoHO/VIRGO and UARS/SUSIM. The calculations
assume LTE and are based on the SATIRE (Spectral And Total Irradiance
REconstruction) model. We analyse the variability as a function of wavelength
and present time series in a number of selected wavelength regions covering the
UV to the NIR. We also show the facular and spot contributions to the total
calculated variability.
Results: In most wavelength regions, the variability agrees well between all
sets of observations and the model calculations. The model does particularly
well between 400 and 1300 nm, but fails below 220 nm as well as for some of the
strong NUV lines. Our calculations clearly show the shift from
faculae-dominated variability in the NUV to spot-dominated variability above
approximately 400 nm. We also discuss some of the remaining problems, such as
the low sensitivity of SUSIM and SORCE for wavelengths between approximately
310 and 350 nm, where currently the model calculations still provide the best
estimates of solar variability.Comment: 15 pages, 11 figures, accepted by A&
Tilt Texture Domains on a Membrane and Chirality induced Budding
We study the equilibrium conformations of a lipid domain on a planar fluid
membrane where the domain is decorated by a vector field representing the tilt
of the stiff fatty acid chains of the lipid molecules, while the surrounding
membrane is fluid and structureless. The inclusion of chirality in the bulk of
the domain induces a novel budding of the membrane, which preempts the budding
induced by a decrease in interfacial tension.Comment: 5 pages, 3 figure
Non-equilibrium dynamics and floral trait interactions shape extant angiosperm diversity.
Why are some traits and trait combinations exceptionally common across the tree of life, whereas others are vanishingly rare? The distribution of trait diversity across a clade at any time depends on the ancestral state of the clade, the rate at which new phenotypes evolve, the differences in speciation and extinction rates across lineages, and whether an equilibrium has been reached. Here we examine the role of transition rates, differential diversification (speciation minus extinction) and non-equilibrium dynamics on the evolutionary history of angiosperms, a clade well known for the abundance of some trait combinations and the rarity of others. Our analysis reveals that three character states (corolla present, bilateral symmetry, reduced stamen number) act synergistically as a key innovation, doubling diversification rates for lineages in which this combination occurs. However, this combination is currently less common than predicted at equilibrium because the individual characters evolve infrequently. Simulations suggest that angiosperms will remain far from the equilibrium frequencies of character states well into the future. Such non-equilibrium dynamics may be common when major innovations evolve rarely, allowing lineages with ancestral forms to persist, and even outnumber those with diversification-enhancing states, for tens of millions of years
Analysis of strain and stacking faults in single nanowires using Bragg coherent diffraction imaging
Coherent diffraction imaging (CDI) on Bragg reflections is a promising
technique for the study of three-dimensional (3D) composition and strain fields
in nanostructures, which can be recovered directly from the coherent
diffraction data recorded on single objects. In this article we report results
obtained for single homogeneous and heterogeneous nanowires with a diameter
smaller than 100 nm, for which we used CDI to retrieve information about
deformation and faults existing in these wires. The article also discusses the
influence of stacking faults, which can create artefacts during the
reconstruction of the nanowire shape and deformation.Comment: 18 pages, 6 figures Submitted to New Journal of Physic
Denominators of Eisenstein cohomology classes for GL_2 over imaginary quadratic fields
We study the arithmetic of Eisenstein cohomology classes (in the sense of G.
Harder) for symmetric spaces associated to GL_2 over imaginary quadratic
fields. We prove in many cases a lower bound on their denominator in terms of a
special L-value of a Hecke character providing evidence for a conjecture of
Harder that the denominator is given by this L-value. We also prove under some
additional assumptions that the restriction of the classes to the boundary of
the Borel-Serre compactification of the spaces is integral. Such classes are
interesting for their use in congruences with cuspidal classes to prove
connections between the special L-value and the size of the Selmer group of the
Hecke character.Comment: 37 pages; strengthened integrality result (Proposition 16), corrected
statement of Theorem 3, and revised introductio
The HERMES Back Drift Chambers
The tracking system of the HERMES spectrometer behind the bending magnet
consists of two pairs of large planar 6-plane drift chambers. The design and
performance of these chambers is described. This description comprises details
on the mechanical and electronical design, information about the gas mixture
used and its properties, results on alignment, calibration, resolution, and
efficiencies, and a discussion of the experience gained through the first three
years of operation.Comment: 21 pages, LaTex, 16 figures include
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