5,050 research outputs found
A bilayer Double Semion Model with Symmetry-Enriched Topological Order
We construct a new model of two-dimensional quantum spin systems that
combines intrinsic topo- logical orders and a global symmetry called flavour
symmetry. It is referred as the bilayer Doubled Semion model (bDS) and is an
instance of symmetry-enriched topological order. A honeycomb bi- layer lattice
is introduced to combine a Double Semion Topolgical Order with a global
spin-flavour symmetry to get the fractionalization of its quasiparticles. The
bDS model exhibits non-trival braid- ing self-statistics of excitations and its
dual model constitutes a Symmetry-Protected Topological Order with novel edge
states. This dual model gives rise to a bilayer Non-Trivial Paramagnet that is
invariant under the flavour symmetry and the well-known spin flip symmetry.Comment: revtex4 file, color figure
Career Concerns of Top Executives, Managerial Ownership and CEO Succession
We model the portfolio decisions by managers with career concerns in a context where ownership of the firm's stock can affect the outcome of promotion contests. In addition to their utility from wealth, such managers derive utility from the monetary and non-monetary benefits (prestige) of running a corporation. Our theory predicts that top managers competing for the CEO position will distort their investment decisions away from the optimum portfolio choice in the absence of career concerns. Thus, our model suggests that changing career opportunities can explain portfolio decisions by managers and that insider ownership can help explain the outcomes of promotion contests. Our main testable predictions are that higher ownership by insiders increases their chances of being appointed CEO; that lower ownership by inside managers makes outside CEO appointments more likely; and that a lower probability of CEO turnover (and thus reduced promotion opportunities) leads inside managers to reduce their ownership in the firm and/or to leave the company. Using data on managerial ownership surrounding CEO turnover events, we find evidence supporting the predictions of our model. Overall, our main insight is that insider ownership, the outcome of promotion contests, the choice between inside and outside CEO replacements, and executive departure decisions are all related. Nous développons un modèle de choix de portefeuille des gestionnaires dans un environnement où leurs chances d'être promu PDG sont liées à leur actionnariat dans l'entreprise. Puisque les gestionnaires valorisent leur nomination potentielle au rang de PDG, nous prédisons que leur choix de portefeuille sera biaisé par rapport au choix qu'ils auraient fait en l'absence d'anticipations carriéristes. Notre modèle prédit que des changements dans les chances d'être promu expliquent les choix de portefeuille des gestionnaires. En particulier, nous montrons empiriquement qu'un plus grand actionnariat augmente la chance d'être promu au rang de PDG, réduit la chance qu'un gestionnaire externe à l'entreprise soit nommé. De plus, une réduction dans la possibilité d'être promu réduit l'actionnariat des gestionnaires ou induit leur départ. Nous testons les hypothèses découlant du modèle en utilisant les changements dans l'actionnariat des gestionnaire lors de la démission du PDG. Les hypothèses importantes du modèle sont confirmées.managerial compensation, CEO succession, corporate tournament, portfolio allocation, rémunération des dirigeants, changement de PDG, tournoi corporatif, choix de portefeuille
Strategies for the Integration of quantum networks for a future quantum internet
The great scientific and technological advances that are being carried out in
the field of quantum communications, accompanied by large investment programs
such as EuroQCI, are driving the deployment of quantum network throughout the
world. One of the final long-term objectives is to achieve the development of a
quantum internet that provides greater security in its services and new
functionalities that the current internet does not have. This article analyzes
the possible integration strategies of already deployed networks or in the
process of being deployed in order to reach a future global quantum network.
Two strategies based on the SDN paradigm are proposed, based on a hierarchical
controller scheme and on a distributed model. Each of these approaches shows
pros and cons and could be applicable in different use cases. To define these
strategies, the most relevant deployments of quantum communications networks
carried out to date has been analyzed, as well as the different approaches for
a quantum network architecture and topology, and the various proposed
definitions of what quantum internet is and what are the components that would
make it up in an ideal scenario. Finally, several detected opportunities and
challenges regarding security and technological aspects are presented
Striped superconductors in the extended Hubbard model
We present a minimal model of a doped Mott insulator that simultaneously
supports antiferromagnetic stripes and d-wave superconductivity. We explore the
implications for the global phase diagram of the superconducting cuprates. At
the unrestricted mean-field level, the various phases of the cuprates,
including weak and strong pseudogap phases, and two different types of
superconductivity in the underdoped and the overdoped regimes, find a natural
interpretation. We argue that on the underdoped side, the superconductor is
intrinsically inhomogeneous -- striped coexistence of of superconductivity and
magnetism -- and global phase coherence is achieved through Josephson-like
coupling of the superconducting stripes. On the overdoped side, the state is
overall homogeneous and the superconductivity is of the classical BCS type.Comment: 5 pages, 3 eps figures. Effect of t' on stripe filling + new
references are adde
High prevalence of scrapie in a dairy goat herd: tissue distribution of disease-associated PrP and effect of PRNP genotype and age
Following a severe outbreak of clinical scrapie in 2006–2007, a
large dairy goat herd was culled
and 200 animals were selected for post-mortem examinations in order to
ascertain the prevalence of infection,
the effect of age, breed and PRNP genotype on the susceptibility to scrapie,
the tissue distribution of diseaseassociated
PrP (PrP), and the comparative efficiency of different diagnostic methods.
As determined by immunohistochemical (IHC) examinations with Bar224 PrP antibody, the
prevalence of preclinical infection
was very high (72/200; 36.0%), with most infected animals being positive
for PrP in lymphoreticular system
(LRS) tissues (68/72; 94.4%) compared to those that were positive in
brain samples (38/72; 52.8%). The
retropharyngeal lymph node and the palatine tonsil showed the highest
frequency of PrP accumulation (87.3%
and 84.5%, respectively), while the recto-anal mucosa-associated lymphoid
tissue (RAMALT) was positive in
only 30 (41.7%) of the infected goats. However, the efficiency of rectal
and palatine tonsil biopsies taken
shortly before necropsy was similar. The probability of brain and RAMALT
being positive directly
correlated with the spread of PrP within the LRS. The prevalence of
infection was influenced by PRNP
genetics at codon 142 and by the age of the goats: methionine carriers older
than 60 months showed a much
lower prevalence of infection (12/78; 15.4%) than those younger than 60 months (20/42; 47.6%); these last
showed prevalence values similar to isoleucine homozygotes of any age
(40/80; 50.0%). Two of seven goats
with definite signs of scrapie were negative for PrP in brain but positive
in LRS tissues, and one goat showed
biochemical and IHC features of PrP different from all other infected
goats. The results of this study have
implications for surveillance and control policies for scrapie in goats
Atomistic modeling and simulation of long-term transport phenomena in nanomaterials
In the past two decades, extensive research has been conducted towards developing nanomaterials with superior transport properties, such as heat conductivity and mass diffusivity, for applications in various industries including, but not limited to,energy storage and microelectronics. In terms of modeling and simulation, along-standing difficulty lies in the separation of temporal and spatial scales. Indeed, many transport phenomena in nanomaterials are characterized by slow kinetic processes with time scale of the order of seconds, hours, or even years, far beyond the time windows of existing simulation technologies such as molecular dynamics (MD)and Monte Carlo (MC) methods. We have developed a novel deformation-diffusion coupled computational framework that allows long-term simulation of such slow processes, while at the same time maintains a strictly atomistic description of the material. Ournon-equilibrium statistical thermo-dynamics model includes discrete kinetic laws, which govern mass diffusion and head conductionion at atomic scale. In this work, we explore the capabilities and performance of this computational framework through its application to heat conduction problems
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De-novo transcriptome assembly for gene identification, analysis, annotation, and molecular marker discovery in Onobrychis viciifolia
Background
Sainfoin (Onobrychis viciifolia) is a highly nutritious tannin-containing forage legume. In the diet of ruminants sainfoin can have anti-parasitic effects and reduce methane emissions under in vitro conditions. Many of these benefits have been attributed to condensed tannins or proanthocyanidins in sainfoin. A combination of increased use of industrially produced nitrogen fertilizer, issues with establishment and productivity in the first year and more reliable alternatives, such as red clover led to a decline in the use of sainfoin since the middle of the last century. In recent years there has been a resurgence of interest in sainfoin due to its potential beneficial nutraceutical and environmental attributes. However, genomic resources are scarce, thus hampering progress in genetic analysis and improvement. To address this we have used next generation RNA sequencing technology to obtain the first transcriptome of sainfoin. We used the library to identify gene-based simple sequence repeats (SSRs) and potential single nucleotide polymorphisms (SNPs).
Results
One genotype from each of five sainfoin accessions was sequenced. Paired-end (PE) sequences were generated from cDNA libraries of RNA extracted from 7 day old seedlings. A combined assembly of 92,772 transcripts was produced de novo using the Trinity programme. About 18,000 transcripts were annotated with at least one GO (gene ontology) term. A total of 63 transcripts were annotated as involved in the tannin biosynthesis pathway. We identified 3786 potential SSRs. SNPs were identified by mapping the reads of the individual assemblies against the combined assembly. After stringent filtering a total of 77,000 putative SNPs were identified. A phylogenetic analysis of single copy number genes showed that sainfoin was most closely related to red clover and Medicago truncatula, while Lotus japonicus, bean and soybean are more distant relatives.
Conclusions
This work describes the first transcriptome assembly in sainfoin. The 92 K transcripts provide a rich source of SNP and SSR polymorphisms for future use in genetic studies of this crop. Annotation of genes involved in the condensed tannin biosynthesis pathway has provided the basis for further studies of the genetic control of this important trait in sainfoin
Negative time delay for wave reflection from a one-dimensional semi-harmonic well
It is reported that the phase time of particles which are reflected by a
one-dimensional semi-harmonic well includes a time delay term which is negative
for definite intervals of the incoming energy. In this interval, the absolute
value of the negative time delay becomes larger as the incident energy becomes
smaller. The model is a rectangular well with zero potential energy at its
right and a harmonic-like interaction at its left.Comment: 6 pages, 5 eps figures. Talk presented at the XXX Workshop on
Geometric Methods in Physics, Bialowieza, Poland, 201
Boltzmann equation and hydrodynamic fluctuations
We apply the method of invariant manifolds to derive equations of generalized
hydrodynamics from the linearized Boltzmann equation and determine exact
transport coefficients, obeying Green-Kubo formulas. Numerical calculations are
performed in the special case of Maxwell molecules. We investigate, through the
comparison with experimental data and former approaches, the spectrum of
density fluctuations and address the regime of finite Knudsen numbers and
finite frequencies hydrodynamics.Comment: This is a more detailed version of a related paper: I.V. Karlin, M.
Colangeli, M. Kroger, PRL 100 (2008) 214503, arXiv:0801.2932. It contains
comparison between predictions and experiment, in particular. 11 pages, 6
figures, 2 table
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