1,891 research outputs found
Pairing effects in low density domain of nuclear matter
Using equations, governing np pairing correlations in S=1, T=0 pairing
channel (PRC 63 (2001) 021304(R)), it is shown that at low densities equations
for the energy gap in the spectrum of quasiparticles and chemical potentials of
protons and neutrons allow solutions with negative chemical potential. This
corresponds to appearance of Bose--Einstein condensate (BEC) of deuterons in
low density region of nuclear matter.Comment: 4 pages, 3 figure
Quasi-Isotropization of the Inhomogeneous Mixmaster Universe Induced by an Inflationary Process
We derive a ``generic'' inhomogeneous ``bridge'' solution for a cosmological
model in the presence of a real self-interacting scalar field. This solution
connects a Kasner-like regime to an inflationary stage of evolution and
therefore provides a dynamical mechanism for the quasi-isotropization of the
universe. In the framework of a standard Arnowitt-Deser-Misner Hamiltonian
formulation of the dynamics and by adopting Misner-Chitr\`e-like variables, we
integrate the Einstein-Hamilton-Jacobi equation corresponding to a ``generic''
inhomogeneous cosmological model whose evolution is influenced by the coupling
with a bosonic field, expected to be responsible for a spontaneous symmetry
breaking configuration. The dependence of the detailed evolution of the
universe on the initial conditions is then appropriately characterized.Comment: 17 pages, no figure, to appear on PR
On the Relationship Between Photospheric Footpoint Motions and Coronal Heating in Solar Active Regions
PublishedArticleCoronal heating theories can be classified as either direct current (DC) or alternating current (AC) mechanisms, depending on whether the coronal magnetic field responds quasi-statically or dynamically to the photospheric footpoint motions. In this paper we investigate whether photospheric footpoint motions with velocities of 1-2 km sâ1 can heat the corona in active regions, and whether the corona responds quasi-statically or dynamically to such motions (DC versus AC heating). We construct three-dimensional magnetohydrodynamic models for the AlfvĂ©n waves and quasi-static perturbations generated within a coronal loop. We find that in models where the effects of the lower atmosphere are neglected, the corona responds quasi-statically to the footpoint motions (DC heating), but the energy flux into the corona is too low compared to observational requirements. In more realistic models that include the lower atmosphere, the corona responds more dynamically to the footpoint motions (AC heating) and the predicted heating rates due to AlfvĂ©n wave turbulence are sufficient to explain the observed hot loops. The higher heating rates are due to the amplification of AlfvĂ©n waves in the lower atmosphere. We conclude that magnetic braiding is a highly dynamic process
A time series transcriptome analysis of cassava (Manihot esculenta Crantz) varieties challenged with Ugandan cassava brown streak virus
Open Access Journal; Published online: 29 August 2017A time-course transcriptome analysis of two cassava varieties that are either resistant or susceptible to cassava brown streak disease (CBSD) was conducted using RNASeq, after graft inoculation with Ugandan cassava brown streak virus (UCBSV). From approximately 1.92 billion short reads, the largest number of differentially expressed genes (DEGs) was obtained in the resistant (Namikonga) variety at 2 days after grafting (dag) (3887 DEGs) and 5 dag (4911 DEGs). At the same time points, several defense response genes (encoding LRR-containing, NBARC-containing, pathogenesis-related, late embryogenesis abundant, selected transcription factors, chaperones, and heat shock proteins) were highly expressed in Namikonga. Also, defense-related GO terms of âtranslational elongationâ, âtranslation factor activityâ, âribosomal subunitâ and âphosphorelay signal transductionâ, were overrepresented in Namikonga at these time points. More reads corresponding to UCBSV sequences were recovered from the susceptible variety (Albert) (733 and 1660 read counts per million (cpm)) at 45 dag and 54 dag compared to Namikonga (10 and 117âcpm respectively). These findings suggest that Namikongaâs resistance involves restriction of multiplication of UCBSV within the host. These findings can be used with other sources of evidence to identify candidate genes and biomarkers that would contribute substantially to knowledge-based resistance breeding
Identity dynamics as a barrier to organizational change
This article seeks to explore the construction of group and professional identities in situations of organizational change. It considers empirical material drawn from a health demonstration project funded by the Scottish Executive Health Department, and uses insights from this project to discuss issues that arise from identity construction(s) and organizational change. In the course of the project studied here, a new organizational form was developed which involved a network arrangement with a voluntary sector organization and the employment of âlay-workersâ in what had traditionally been a professional setting. Our analysis of the way actors made sense of their identities reveals that characterizations of both self and other became barriers to the change process. These identity dynamics were significant in determining the way people interpreted and responded to change within this project and which may relate to other change-oriented situations
Origin of the shadow Fermi surface in Bi-based cuprates
We used angle-resolved photoemission spectroscopy to study the shadow Fermi
surface in one layer Bi2Sr1.6La0.4CuO6+delta and two layer
(Bi,Pb)2Sr2CaCu2O8+delta. We find the shadow band to have the same peakwidth
and dispersion as the main band. In addition, the shadow band/main band
intensity ratio is found to be binding energy independent. Consequently, it is
concluded that the shadow bands in Bi-based HTSC do not originate from
antiferromagnetic interactions but have a structural origin.Comment: 10 pages, 2 figure
Large closed queueing networks in semi-Markov environment and its application
The paper studies closed queueing networks containing a server station and
client stations. The server station is an infinite server queueing system,
and client stations are single-server queueing systems with autonomous service,
i.e. every client station serves customers (units) only at random instants
generated by a strictly stationary and ergodic sequence of random variables.
The total number of units in the network is . The expected times between
departures in client stations are . After a service completion
in the server station, a unit is transmitted to the th client station with
probability , and being processed in the th client
station, the unit returns to the server station. The network is assumed to be
in a semi-Markov environment. A semi-Markov environment is defined by a finite
or countable infinite Markov chain and by sequences of independent and
identically distributed random variables. Then the routing probabilities
and transmission rates (which are expressed via
parameters of the network) depend on a Markov state of the environment. The
paper studies the queue-length processes in client stations of this network and
is aimed to the analysis of performance measures associated with this network.
The questions risen in this paper have immediate relation to quality control of
complex telecommunication networks, and the obtained results are expected to
lead to the solutions to many practical problems of this area of research.Comment: 35 pages, 1 figure, 12pt, accepted: Acta Appl. Mat
Towards environments that have a sense of humor
Humans have humorous conversations and interactions. Nowadays our real life existence is integrated with our life in social media, videogames, mixed reality and physical environments that sense our activities and that can adapt appearance and properties due to our activities. There are other inhabitants in these environments, not only human, but also virtual agents and social robots with which we interact and who decide about their participation in activities. In this paper we look at designing humor and humor opportunities in such environments, providing them with a sense of humor, and able to recognize opportunities to generate humorous interactions or events on the fly. Opportunities, made possible by introducing incongruities, can be exploited by the environment itself, or they can be communicated to its inhabitants
Initial-State Interactions in the Unpolarized Drell-Yan Process
We show that initial-state interactions contribute to the
distribution in unpolarized Drell-Yan lepton pair production and , without suppression. The asymmetry is expressed as a
product of chiral-odd distributions , where the quark-transversity function
is the transverse momentum dependent, light-cone
momentum distribution of transversely polarized quarks in an {\it unpolarized}
proton. We compute this (naive) -odd and chiral-odd distribution function
and the resulting asymmetry explicitly in a quark-scalar diquark
model for the proton with initial-state gluon interaction. In this model the
function equals the -odd (chiral-even) Sivers
effect function . This suggests that the
single-spin asymmetries in the SIDIS and the Drell-Yan process are closely
related to the asymmetry of the unpolarized Drell-Yan process,
since all can arise from the same underlying mechanism. This provides new
insight regarding the role of quark and gluon orbital angular momentum as well
as that of initial- and final-state gluon exchange interactions in hard QCD
processes.Comment: 22 pages, 6 figure
Re-Focusing - Building a Future for Entrepreneurial Education & Learning
The field of entrepreneurship has struggled with fundamental
questions concerning the subjectâs nature and purpose. To whom and to
what means are educational and training agendas ultimately directed?
Such questions have become of central importance to policy makers,
practitioners and academics alike. There are suggestions that university
business schools should engage more critically with the lived experiences
of practising entrepreneurs through alternative pedagogical approaches
and methods, seeking to account for and highlighting the social, political
and moral aspects of entrepreneurial practice. In the UK, where funding in
higher education has become increasingly dependent on student fees,
there are renewed pressures to educate students for entrepreneurial
practice as opposed to educating them about the nature and effects of
entrepreneurship. Government and EU policies are calling on business
schools to develop and enhance entrepreneurial growth and skill sets, to
make their education and training programmes more proactive in
providing innovative educational practices which help and facilitate life
experiences and experiential learning. This paper makes the case for
critical frameworks to be applied so that complex social processes
become a source of learning for educators and entrepreneurs and so that
innovative pedagogical approaches can be developed in terms both of
context (curriculum design) and process (delivery methods)
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