3,663 research outputs found
Full counting statistics for voltage and dephasing probes
We present a stochastic path integral method to calculate the full counting
statistics of conductors with energy conserving dephasing probes and
dissipative voltage probes. The approach is explained for the experimentally
important case of a Mach-Zehnder interferometer, but is easily generalized to
more complicated setups. For all geometries where dephasing may be modeled by a
single one-channel dephasing probe we prove that our method yields the same
full counting statistics as phase averaging of the cumulant generating
function.Comment: 4 pages, 2 figure
Star-Forming Galaxies at Cosmic Noon
Ever deeper and wider lookback surveys have led to a fairly robust outline of the cosmic star formation history, which culminated around z~2 -- a period often nicknamed "cosmic noon." Our knowledge about star-forming galaxies at these epochs has dramatically advanced from increasingly complete population censuses and detailed views of individual galaxies. We highlight some of the key observational insights that influenced our current understanding of galaxy evolution in the equilibrium growth picture: ∙ scaling relations between galaxy properties are fairly well established among massive galaxies at least out to z~2, pointing to regulating mechanisms already acting on galaxy growth; ∙ resolved views reveal that gravitational instabilities and efficient secular processes within the gas- and baryon-rich galaxies at z~2 play an important role in the early build-up of galactic structure; ∙ ever more sensitive observations of kinematics at z~2 are probing the baryon and dark matter budget on galactic scales and the links between star-forming galaxies and their likely descendants; ∙ towards higher masses, massive bulges, dense cores, and powerful AGN and AGN-driven outflows are more prevalent and likely play a role in quenching star formation. We outline emerging questions and exciting prospects for the next decade with upcoming instrumentation, including the James Webb Space Telescope and the next generation of Extremely Large Telescopes
Influence of the season on the salicylate and phenolic glycoside contents in the bark of Salix daphnoides, Salix pentandra, and Salix purpurea
Due to the benefits of herbal medicine and their wide range of application for human health, the usage of natural drug products, such as willow bark extract, has increased in the last few years. The principle active compounds of the drugs comprised primarily of willow bark are phenolic glycosides like salicylates. Phenolic glycoside profiles of bark vary among species and between the seasons. To identify and preserve willow clones with high salicylate content for possible commercial usage at a later stage, we have screened three Salix sp. in respect to their chemical profiles. The willow species analysed were: Salix daphnoides, Salix pentandra, and Salix purpurea. These species had distinct phenolic glycoside profiles. The major salicylate of S. daphnoides and S. purpurea clones was salicortin, whereas the main compound of S. pentandra was 2’- O-acetylsalicortin. According to the chemical profiles of 140 clones, seven independent clones of S. daphnoides and S. purpurea as well as four clones of S. pentandra with high phenolic glycoside contents were picked to study seasonal changes in bark chemistry. Overall, the clones of S. daphnoides showed the highest mean salicylate and phenolic glycoside contents, followed by S. pupurea and S. pentandra. The secondary metabolite content of willow bark clones decreased during the vegetative season from March to June 2007 and further from June to July 2007. Our study revealed that for optimum yield of phenolic glycosides the species, the clone, and the time of harvest during the season have to be taken in consideration
Modeling and predicting clogging behavior of the filtration process with fibrous filter media for used engine lube oils
Extremely high magnetoresistance and conductivity in the type-II Weyl semimetals WP2 and MoP2
The peculiar band structure of semimetals exhibiting Dirac and Weyl crossings
can lead to spectacular electronic properties such as large mobilities
accompanied by extremely high magnetoresistance. In particular, two closely
neighbouring Weyl points of the same chirality are protected from annihilation
by structural distortions or defects, thereby significantly reducing the
scattering probability between them. Here we present the electronic properties
of the transition metal diphosphides, WP2 and MoP2, that are type-II Weyl
semimetals with robust Weyl points. We present transport and angle resolved
photoemission spectroscopy measurements, and first principles calculations. Our
single crystals of WP2 display an extremely low residual low-temperature
resistivity of 3 nohm-cm accompanied by an enormous and highly anisotropic
magnetoresistance above 200 million % at 63 T and 2.5 K. These properties are
likely a consequence of the novel Weyl fermions expressed in this compound. We
observe a large suppression of charge carrier backscattering in WP2 from
transport measurements.Comment: Appeared in Nature Communication
Constraints on the assembly and dynamics of galaxies. II. Properties of kiloparsec-scale clumps in rest-frame optical emission of z ~ 2 star-forming galaxies
We study the properties of luminous stellar clumps identified in deep, high
resolution HST/NIC2 F160W imaging at 1.6um of six z~2 star-forming galaxies
with existing near-IR integral field spectroscopy from SINFONI at the VLT.
Individual clumps contribute ~0.5%-15% of the galaxy-integrated rest-frame
~5000A emission, with median of about 2%; the total contribution of clump light
ranges from 10%-25%. The median intrinsic clump size and stellar mass are ~1kpc
and log(Mstar[Msun])~9, in the ranges for clumps identified in rest-UV or line
emission in other studies. The clump sizes and masses in the subset of disks
are broadly consistent with expectations for clump formation via gravitational
instabilities in gas-rich, turbulent disks given the host galaxies' global
properties. By combining the NIC2 data with ACS/F814W imaging available for one
source, and AO-assisted SINFONI Halpha data for another, we infer modest color,
M/L, and stellar age variations within each galaxy. In these two objects, sets
of clumps identified at different wavelengths do not fully overlap;
NIC2-identified clumps tend to be redder/older than ACS- or Halpha-identified
clumps without rest-frame optical counterparts. There is evidence for a
systematic trend of older ages at smaller galactocentric radii among the
clumps, consistent with scenarios where inward migration of clumps transports
material towards the central regions. From constraints on a bulge-like
component at radii <1-3kpc, none of the five disks in our sample appears to
contain a compact massive stellar core, and we do not discern a trend of bulge
stellar mass fraction with stellar age of the galaxy. Further observations are
necessary to probe the build-up of stellar bulges and the role of clumps in
this process.Comment: 29 pages, 11 figures. Revised version accepted for publication in the
Astrophysical Journa
Constraint on the Assembly and Dynamics of Galaxies. II. Properties of Kiloparsec-Scale Clumps in Rest-Frame Optical Emission of z ~ 2 Star-Forming Galaxies
We study the properties of luminous stellar "clumps" identified in deep, high-resolution Hubble Space Telescope NIC2/F160W imaging at 1.6 μm of six z ~ 2 star-forming galaxies with existing near-infrared integral field spectroscopy from SINFONI at the Very Large Telescope. Individual clumps contribute ~0.5%-15% of the galaxy-integrated rest-frame ≈5000 Å emission, with median of ≈2%; the total contribution of clump light ranges from 10% to 25%. The median intrinsic clump size and stellar mass are ~1 kpc and ~10^9 M_☉, in the ranges for clumps identified in rest-UV or line emission in other studies. The clump sizes and masses in the subset of disks are broadly consistent with expectations for clump formation through gravitational instabilities in gas-rich, turbulent disks given the host galaxies' global properties. By combining the NIC2 data with Advanced Camera for Surveys (ACS)/F814W imaging available for one source, and adaptive-optics-assisted SINFONI Hα data for another, we infer modest color, M/L, and stellar age variations within each galaxy. In these two objects, sets of clumps identified at different wavelengths do not fully overlap; NIC2-identified clumps tend to be redder/older than ACS- or Hα-identified clumps without rest-frame optical counterparts. There is evidence for a systematic trend of older ages at smaller galactocentric radii among the clumps, consistent with scenarios where inward migration of clumps transports material toward the central regions. From constraints on a bulge-like component at radii ≾1-3 kpc, none of the five disks in our sample appears to contain a compact massive stellar core, and we do not discern a trend of bulge stellar mass fraction with stellar age of the galaxy. Further observations are necessary to probe the buildup of stellar bulges and the role of clumps in this process
Retinotectal circuitry of larval zebrafish is adapted to detection and pursuit of prey
Retinal axon projections form a map of the visual environment in the tectum. A zebrafish larva typically detects a prey object in its peripheral visual field. As it turns and swims towards the prey, the stimulus enters the central, binocular area, and seemingly expands in size. By volumetric calcium imaging, we show that posterior tectal neurons, which serve to detect prey at a distance, tend to respond to small objects and intrinsically compute their direction of movement. Neurons in anterior tectum, where the prey image is represented shortly before the capture strike, are tuned to larger object sizes and are frequently not direction-selective, indicating that mainly interocular comparisons serve to compute an object's movement at close range. The tectal feature map originates from a linear combination of diverse, functionally specialized, lamina-specific, and topographically ordered retinal ganglion cell synaptic inputs. We conclude that local cell-type composition and connectivity across the tectum are adapted to the processing of locationdependent, behaviorally relevant object features
Difference Equations and Highest Weight Modules of U_q[sl(n)]
The quantized version of a discrete Knizhnik-Zamolodchikov system is solved
by an extension of the generalized Bethe Ansatz. The solutions are constructed
to be of highest weight which means they fully reflect the internal quantum
group symmetry.Comment: 9 pages, LaTeX, no figure
The Optical Structure of the Starburst Galaxy M82. II. Nebular Properties of the Disk and Inner-Wind
(Abridged) In this second paper of the series, we present the results from
optical Gemini-North GMOS-IFU and WIYN DensePak IFU spectroscopic observations
of the starburst and inner wind zones of M82, with a focus on the state of the
T~10^4 K ionized interstellar medium. Our electron density maps show peaks of a
few 1000 cm-3, local small spatial-scale variations, and a fall-off in the
minor axis direction. We discuss the implications of these results with regards
to the conditions/locations that may favour the escape of individual cluster
winds. Our findings imply that the starburst environment is highly fragmented
into a range of clouds from small/dense clumps with low filling factors (<1pc,
n_e>10^4 cm-3) to larger filling factor, less dense gas. The near-constant
state of the ionization state of the ~10^4 K gas throughout the starburst can
be explained as a consequence of the small cloud sizes, which allow the gas
conditions to respond quickly to any changes. We have examined in more detail
both the broad (FWHM 150-350 km/s) line component found in Paper I that we
associated with emission from turbulent mixing layers on the gas clouds, and
the discrete outflow channel identified within the inner wind. The channel
appears as a coherent, expanding cylindrical structure of length >120 pc and
and width 35-50 pc and the walls maintain an approximately constant (but
subsonic) expansion velocity of ~60 km/s. We use the channel to examine further
the relationship between the narrow and broad component emitting gas within the
inner wind. Within the starburst energy injection zone, we find that turbulent
motions (as traced by the broad component) appear to play an increasing role
with height.Comment: 27 pages, 18 figures (13 in colour), accepted for publication in Ap
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