11,987 research outputs found
Variational Bayes model averaging for graphon functions and motif frequencies inference in W-graph models
W-graph refers to a general class of random graph models that can be seen as
a random graph limit. It is characterized by both its graphon function and its
motif frequencies. In this paper, relying on an existing variational Bayes
algorithm for the stochastic block models along with the corresponding weights
for model averaging, we derive an estimate of the graphon function as an
average of stochastic block models with increasing number of blocks. In the
same framework, we derive the variational posterior frequency of any motif. A
simulation study and an illustration on a social network complete our work
Impact of Interatomic Electronic Decay Processes on Xe 4d Hole Decay in the Xenon Fluorides
A hole in a 4d orbital of atomic xenon relaxes through Auger decay after a
lifetime of 3 fs. Adding electronegative fluorine ligands to form xenon
fluoride molecules, results in withdrawal of valence-electron density from Xe.
Thus, within the one-center picture of Auger decay, a lowered Xe 4d Auger width
would be expected, in contradiction, however, with experiment. Employing
extensive ab initio calculations within the framework of many-body Green's
functions, we determine all available decay channels in XeFn and characterize
these channels by means of a two-hole population analysis. We derive a relation
between two-hole population numbers and partial Auger widths. On this basis,
interatomic electronic decay processes are demonstrated to be so strong in the
xenon fluorides that they overcompensate the reduction in intra-atomic Auger
width and lead to the experimentally observed trend. The nature of the relevant
processes is discussed. These processes presumably underlie Auger decay in a
variety of systems.Comment: 11 pages, 5 figures, 3 tables, RevTeX4, extensively revised, the
discussion of single ionization of XeFn was published separately: J. Chem.
Phys. 119, 7763--7771 (2003), preprint arXiv: physics/030612
The thermal Hall effect of spin excitations in a Kagome magnet
At low temperatures, the thermal conductivity of spin excitations in a
magnetic insulator can exceed that of phonons. However, because they are charge
neutral, the spin waves are not expected to display a thermal Hall effect in a
magnetic field. Recently, this semiclassical notion has been upended in quantum
magnets in which the spin texture has a finite chirality. In the Kagome
lattice, the chiral term generates a Berry curvature. This results in a thermal
Hall conductivity that is topological in origin. Here we report
observation of a large in the Kagome magnet Cu(1-3, bdc) which
orders magnetically at 1.8 K. The observed undergoes a remarkable
sign-reversal with changes in temperature or magnetic field, associated with
sign alternation of the Chern flux between magnon bands. We show that thermal
Hall experiments probe incisively the effect of Berry curvature on heat
transport.Comment: 6 pages, 3 figure
Detection of a branched alkyl molecule in the interstellar medium: iso-propyl cyanide
The largest non-cyclic molecules detected in the interstellar medium (ISM)
are organic with a straight-chain carbon backbone. We report an interstellar
detection of a branched alkyl molecule, iso-propyl cyanide (i-C3H7CN), with an
abundance 0.4 times that of its straight-chain structural isomer. This
detection suggests that branched carbon-chain molecules may be generally
abundant in the ISM. Our astrochemical model indicates that both isomers are
produced within or upon dust grain ice mantles through the addition of
molecular radicals, albeit via differing reaction pathways. The production of
iso-propyl cyanide appears to require the addition of a functional group to a
non-terminal carbon in the chain. Its detection therefore bodes well for the
presence in the ISM of amino acids, for which such side-chain structure is a
key characteristic.Comment: This is the author's version of the work. It is posted here by
permission of the AAAS for non-commercial use. The definitive version was
published in Science 345, 1584 (2014), doi:10.1126/science.125667
Special Issue: Evolutionary perspectives on salmonid conservation and management
This special issue of Evolutionary Applications comprises 15 papers that illustrate how evolutionary principles can inform the conservation and management of salmonid fishes. Several papers address the past evolutionary history of salmonids to gain insights into their likely plastic and genetic responses to future environmental change. The remaining papers consider potential evolutionary responses to climate warming, biological invasions, artificial propagation, habitat alteration, and harvesting. All of these papers consider how such influences might alter selective regimes, which should then favour plastic or genetic responses. Some of the papers then go on to document such responses, at least some of which are genetically based and adaptive. Despite the different approaches and target species, all of the papers argue for the importance of evolutionary considerations in the conservation and management of salmonids
Breathing mode for systems of interacting particles
We study the breathing mode in systems of trapped interacting particles. Our
approach, based on a dynamical ansatz in the first equation of the
Bogolyubov-Born-Green-Kirkwood-Yvon (BBGKY) hierarchy allows us to tackle at
once a wide range of power law interactions and interaction strengths, at
linear and non linear levels. This both puts in a common framework various
results scattered in the literature, and by widely generalizing these,
emphasizes universal characters of this breathing mode. Our findings are
supported by direct numerical simulations.Comment: 4 pages, 4 figure
Fine mapping of rice drought QTL and study on combined effect of QTL for their physiological parameters under moisture stress condition
The present investigation was undertaken to study the effect of different yield QTL (DTY2.2, DTY3.1 and DTY8.1) under drought and their physiological response to drought stress. Backcross Inbred Lines (BILs) of IR64 (CB-193 and CB-229) along with IR64, APO and the traditional rice variety Norungan were raised in green house condition under water stress and control to evaluate the effect of the QTL on grain yield. The BIL CB-193 recorded higher photosynthetic rate (22.051), transpiration rate (7.152) and Ci/Ca ratio (0.597) whereas the BIL CB-229 recorded high relative water content (80.76%). It was found that the combination of three QTL (CB-229) performed better than the susceptible parent and the line with two QTL (CB-193 Fine-mapping of two QTLs viz., qDTY2.2 and qDTY8.1, for grain yield (GY) were conducted using backcross derived lines. Composite interval mapping analyses resolved the originally identified qDTY2.2 region of 6.7 cM into a segment of 2.1 cM and two sub QTLs at region between RM23132 and RM1578 (75.75 cM- 77.66 cM), RM515 and RM1578 (75.11 cM-77.66 cM) were identified in qDTY8.1 region. However this study provides a unique opportunity to breeders to introgress such regions together as a unit into high-yielding drought-susceptible varieties through MAS
Poor electronic screening in lightly doped Mott insulators observed with scanning tunneling microscopy
The effective Mott gap measured by scanning tunneling microscopy (STM) in the
lightly doped Mott insulator differs
greatly from values reported by photoemission and optical experiments. Here, we
show that this is a consequence of the poor electronic screening of the
tip-induced electric field in this material. Such effects are well known from
STM experiments on semiconductors, and go under the name of tip-induced band
bending (TIBB). We show that this phenomenon also exists in the lightly doped
Mott insulator and that, at doping
concentrations of , it causes the measured energy gap in the sample
density of states to be bigger than the one measured with other techniques. We
develop a model able to retrieve the intrinsic energy gap leading to a value
which is in rough agreement with other experiments, bridging the apparent
contradiction. At doping we further observe circular features
in the conductance layers that point to the emergence of a significant density
of free carriers in this doping range, and to the presence of a small
concentration of donor atoms. We illustrate the importance of considering the
presence of TIBB when doing STM experiments on correlated-electron systems and
discuss the similarities and differences between STM measurements on
semiconductors and lightly doped Mott insulators.Comment: 9 pages, 5 figure
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