4,723 research outputs found
Geodesics on the Ellipsoid and Monodromy
The equations for geodesic flow on the ellipsoid are well known, and were
first solved by Jacobi in 1838 by separating the variables of the
Hamilton-Jacobi equation. In 1979 Moser investigated the case of the general
ellipsoid with distinct semi-axes and described a set of integrals which
weren't know classically. After reviewing the properties of geodesic flow on
the three dimensional ellipsoid with distinct semi-axes, we investigate the
three dimensional ellipsoid with the two middle semi-axes being equal,
corresponding to a Hamiltonian invariant under rotations. The system is
Liouville-integrable and thus the invariant manifolds corresponding to regular
points of the energy momentum map are 3-dimensional tori. An analysis of the
critical points of the energy momentum maps gives the bifurcation diagram. We
find the fibres of the critical values of the energy momentum map, and carry
out an analysis of the action variables. We show that the obstruction to the
existence of single valued globally smooth action variables is monodromy.Comment: 24 pages, 7 figure
Hydrodynamic theory of quantum fluctuating superconductivity
A hydrodynamic theory of transport in quantum mechanically phase-disordered
superconductors is possible when supercurrent relaxation can be treated as a
slow process. We obtain general results for the frequency-dependent
conductivity of such a regime. With time-reversal invariance, the conductivity
is characterized by a Drude-like peak, with width given by the supercurrent
relaxation rate. Using the memory matrix formalism, we obtain a formula for
this width (and hence also the dc resistivity) when the supercurrent is relaxed
by short range Coulomb interactions. This leads to a new -- effective field
theoretic and fully quantum -- derivation of a classic result on flux flow
resistance. With strong breaking of time-reversal invariance, the optical
conductivity exhibits what we call a `hydrodynamic supercyclotron' resonance.
We obtain the frequency and decay rate of this resonance for the case of
supercurrent relaxation due to an emergent Chern-Simons gauge field. The
supercurrent decay rate in this `topologically ordered superfluid vortex
liquid' is determined by the conductivities of the normal component of the
liquid. Our work gives a controlled framework for low temperature metallic
phases arising from phase-disordered superconductivity.Comment: 1 + 44 pages. 2 figures. v2 discussion improved in places. v3 sign
errors fixed in section
Genome sequence of canine herpesvirus
Canine herpesvirus is a widespread alphaherpesvirus that causes a fatal haemorrhagic disease of neonatal puppies. We have used high-throughput methods to determine the genome sequences of three viral strains (0194, V777 and V1154) isolated in the United Kingdom between 1985 and 2000. The sequences are very closely related to each other. The canine herpesvirus genome is estimated to be 125 kbp in size and consists of a unique long sequence (97.5 kbp) and a unique short sequence (7.7 kbp) that are each flanked by terminal and internal inverted repeats (38 bp and 10.0 kbp, respectively). The overall nucleotide composition is 31.6% G+C, which is the lowest among the completely sequenced alphaherpesviruses. The genome contains 76 open reading frames predicted to encode functional proteins, all of which have counterparts in other alphaherpesviruses. The availability of the sequences will facilitate future research on the diagnosis and treatment of canine herpesvirus-associated disease
Posterior probability intervals in Bayesian wavelet estimation
We use saddlepoint approximation to derive credible intervals for Bayesian wavelet regression estimates. Simulations show that the resulting intervals perform better than the best existing metho
Genome sequences of two pseudorabies virus strains isolated in Greece
Pseudorabies virus (species Suid herpesvirus 1) belongs to the genus Varicellovirus, subfamily Alphaherpesvirinae, family Herpesviridae, and is the causative agent of an acute and frequently fatal disease that affects mainly pigs. Here, we report the genome sequences of two strains of this virus isolated in Greece in 2010
Low-Tech Virtuality: Evidence from SMEs in Hong Kong
Previous research on virtuality has been dominated by discussions of virtual teams, involving either students or organisational employees, with the latter dominated by larger organisations. Little attention has been paid to the SME sector, despite the apparent benefits that could accrue to SMEs that make effective use of virtual collaboration and cooperation technologies. In this paper we report on our investigations into the use of virtual technologies by SMEs in Hong Kong, an economy which is dominated by SMEs (98% of all firms). Drawing on our interviews with nine SMEs, we assessed both their current and likely future usage of virtual technologies. We were surprised to find that most of these SMEs are intentionally low-tech in their attitude towards virtual technologies. We discuss the reasons for and implications of this phenomenon before drawing the paper to a close with a set of recommendations for future research
Using the TIDieR checklist to describe health visitor support for mothers with mental health problems: analysis of a cross-sectional survey
At least half of the 20% of mothers who experience mental health problems (MHPs) during pregnancy or after birth are not receiving the help they need that will lead to recovery. In order to identify where improvements need to be made it is necessary to describe exactly what is being done and the barriers and facilitators that compromise or enhance optimal care. The majority of mothers experience mild to moderate anxiety or depression. The expectation is that primary care professionals, such as health visitors (HVs), can provide the support they need that will lead to recovery. The aim of this study was explore the views of HVs regarding the content and purpose of an intervention to support mothers with MHPs, described as ‘listening visits’ (LVs). A link to an on-line survey was offered to the members and champions of the Institute of Health Visiting (n=9,474) March – May 2016. The survey was completed by 1599 (17%) of the target population, of whom 85% were offering LVs. The Template for Intervention Description and Replication (TIDieR) checklist was used to provide a framework to describe commonalities and variations in practice. There appeared to be a shared understanding of the rationale for LVs but a lack of agreement about what the intervention should be called, the techniques that should be used and the duration, frequency and expected outcomes of the intervention. Contextual factors such as staff shortages; conflicting priorities; the needs and circumstances of mothers; the capability and motivation of HVs; inadequate training and supervision; and absence of clear guidance contributed to variations in perceptions and practice. There are many ways in which the HV contribution to the assessment and management of mothers with MHPs could be improved. The intervention delivered by HVs needs to be more clearly articulated. The contextual factors influencing competent and consistent practice also need to be addressed
- …