26,887 research outputs found
An early warning indicator for atmospheric blocking events using transfer operators
The existence of persistent midlatitude atmospheric flow regimes with
time-scales larger than 5-10 days and indications of preferred transitions
between them motivates to develop early warning indicators for such regime
transitions. In this paper, we use a hemispheric barotropic model together with
estimates of transfer operators on a reduced phase space to develop an early
warning indicator of the zonal to blocked flow transition in this model. It is
shown that, the spectrum of the transfer operators can be used to study the
slow dynamics of the flow as well as the non-Markovian character of the
reduction. The slowest motions are thereby found to have time scales of three
to six weeks and to be associated with meta-stable regimes (and their
transitions) which can be detected as almost-invariant sets of the transfer
operator. From the energy budget of the model, we are able to explain the
meta-stability of the regimes and the existence of preferred transition paths.
Even though the model is highly simplified, the skill of the early warning
indicator is promising, suggesting that the transfer operator approach can be
used in parallel to an operational deterministic model for stochastic
prediction or to assess forecast uncertainty
K_l3 form factor with two-flavors of dynamical domain-wall quarks
We report on our calculation of K \to \pi vector form factor by numerical
simulations of two-flavor QCD on a 16^3x32x12 lattice at a \simeq 0.12 fm using
domain-wall quarks and DBW2 glue. Our preliminary result at a single sea quark
mass correponding to m_PS/m_V \simeq 0.53 shows a good agreement with previous
estimate in quenched QCD and that from a phenomenological model.Comment: 6 pages, 5 figures, poster presented at Lattice2005 (Weak matrix
elements); v2: a reference adde
Sunyaev-Zel'dovich Effects from Quasars in Galaxies and Groups
The energy fed by active galactic nuclei to the surrounding diffuse baryons
changes their amount, temperature, and distribution; so in groups and in member
galaxies it affects the X-ray luminosity and also the Sunyaev-Zel'dovich
effect. Here we compute how the latter is enhanced by the transient blastwave
driven by an active quasar, and is depressed when the equilibrium is recovered
with a depleted density. We constrain such depressions and enhancements with
the masses of relic black holes in galaxies and the X-ray luminosities in
groups. We discuss how all these linked observables can tell the quasar
contribution to the thermal history of the baryons pervading galaxies and
groups.Comment: 4 pages, 3 figures, uses REVTeX4 and emulateapj.cls. Accepted by ApJ
Simulating Impacts of Extreme Weather Events on Urban Transport Infrastructure in the UK
Urban areas face many risks from future climate change and their infrastructure will be placed under more pressure
due to changes in climate extremes. Using the Tyndall Centre Urban Integrated Assessment Framework, this paper
describes a methodology used to assess the impacts of future climate extremes on transport infrastructure in
London. Utilising high-resolution projections for future climate in the UK, alongside stochastic weather generators
for downscaling, urban temperature and flooding models are used to provide information on the likelihood of future
extremes. These are then coupled with spatial network models of urban transport infrastructure and, using thresholds
to define the point at which systems cease to function normally, disruption to the networks can be simulated.
Results are shown for both extreme heat and urban surface water flooding events and the impacts on the travelling
population, in terms of both disruption time and monetary cost
Twisted semilocal strings in the MSSM
The standard electroweak model is extended by means of a second
Brout-Englert-Higgs-doublet. The symmetry breaking potential is chosen is such
a way that (i) the Lagrangian possesses a custodial symmetry, (ii) a
stationary, axially symmetric ansatz of the bosonic fields consistently reduces
the Euler-Lagrange equations to a set of differential equations. The potential
involves, in particular, a direct interaction between the two doublets.
Stationary, axially-symmetric solutions of the classical equations are
constructed. Some of them can be assimilated to embedded Nielsen-Olesen
strings. From these solutions there are bifurcations and new solutions appear
which exhibit the characteristics of the recently constructed twisted semilocal
strings. A special emphasis is set on "doubly-twisted" solutions for which the
two doublets present different time-dependent phase factors. They are regular
and have a finite energy which can be lower than the energy of the embedded
twisted solution. Electric-type solutions, such that the fields oscillate
asymptotically far from the symmetry-axis, are also reported.Comment: 17 pages, 11 figures, discussion extended, new solutions obtaine
Evidence to inform education, training and supportive work environments for midwives involved in the care of women with female genital mutilation
Female genital mutilation (FGM) is a practice that is carried out on young girls and women in 29 countries in Africa and the Middle East, as well as some Asian countries (WHO, 2008). Migration from these countries to Australia has led to an increasing number of midwives caring for women with FGM and educating families in order to prevent this harmful and illegal practice. However very little is known about the challenges midwives face in delivering care and education and what professional development and workplace strategies might better support midwives. This presentation reports on a synthesis of the peer reviewed literature published between 2004 and 2014 undertaken to identify the knowledge, experiences and needs of midwives globally with respect to FGM. This review forms part of a larger research project funded by the Department of Health and Aging to examine the obstetric outcomes of women who have FGM and midwives experiences in Australia. Ten papers were included in the review, two from lower-middle income counties and eight from high income countries. The findings indicate that midwives lack technical knowledge and cultural competency to adequately care for women. Midwives, particularly those in lower-middle income counties where FGM was traditionally practiced were found to face significant challenges in their efforts to advocate for the abandonment of the practice. Training for midwives in the area of FGM was limited. Only one study reported the outcomes of an education initiative that was found to be beneficial. Professional education and training, a working environment supported by guidelines and responsive policy and community education, were suggested are necessary to enable midwives to improve the care of women with FGM and advocate against the practice. Implications for midwifery in NSW include the need for specialised education and training for midwives on FGM, alongside opportunities for collaborative practice in contexts that support the effective reporting of FGM to authorities. Our research project will seek to further examine the implications of this review through a nation-wide survey of Australian midwives and focus group discussions with midwives in selected hospital s in NSW
Sphaleron-Bisphaleron bifurcations in a custodial-symmetric two-doublets model
The standard electroweak model is extended by means of a second
Brout-Englert-Higgs-doublet. The symmetry breaking potential is chosen is such
a way that (i) the Lagrangian possesses a custodial symmetry, (ii) a static,
spherically symmetric ansatz of the bosonic fields consistently reduces the
Euler-Lagrange equations to a set of differential equations. The potential
involves, in particular, products of fields of the two doublets, with a
coupling constant .Static, finite energy solutions of the classical
equations are constructed. The regular, non-trivial solutions having the lowest
classical energy can be of two types: sphaleron or bisphaleron, according to
the coupling constants. A special emphasis is put to the bifurcation between
these two types of solutions which is analyzed in function of the different
constants of the model,namely of .Comment: 10 pages, 3 figure
Scalar meson in dynamical and partially quenched two-flavor QCD: lattice results and chiral loops
This is an exploratory study of the lightest non-singlet scalar
state on the lattice with two dynamical quarks. Domain Wall fermions are used
for both sea and valence quarks on a 16^3*32 lattice with an inverse lattice
spacing of 1.7 GeV. We extract the scalar meson mass 1.58(34) GeV from the
exponential time-dependence of the dynamical correlators with
and N_f=2. Since this statistical error-bar from dynamical correlators is
rather large, we analyze also the partially quenched lattice correlators with
not equal . They are positive for and
negative for . In order to understand this striking effect of
partial quenching, we derive the scalar correlator within the Partially
Quenched ChPT and find it describes lattice correlators well. The leading
unphysical contribution in Partially Quenched ChPT comes from the exchange of
the two pseudoscalar fields and is also positive for and
negative for at large t. After the subtraction of this
unphysical contribution from the partially quenched lattice correlators, the
correlators are positive and exponentially falling. The resulting scalar meson
mass 1.51(19) GeV from the partially quenched correlators is consistent with
the dynamical result and has appreciably smaller error-bar.Comment: 23 pages, 8 figure
QCD Corrections to Production of Higgs Pseudoscalars
Models of electroweak symmetry breaking with more than a single doublet of
Higgs scalars contain a neutral pseudoscalar boson. The production of such a
pseudoscalar in hadron collisions proceeds primarily via gluon fusion through a
top-quark loop (except for those models in which the pseudoscalar coupling to
bottom quarks is strongly enhanced). We compute the QCD corrections to this
process in the heavy-quark limit, using an effective Lagrangian derived from
the axial anomaly.Comment: 9 pages, (BNL number added, 1 typo corrected, PHYZZX format, 4
figures not included, available on request), BNL-4906
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