297 research outputs found
Effective Action for High-Energy Scattering in Gravity
The multi-Regge effective action is derived directly from the linearized
gravity action. After excluding the redundant field components we separate the
fields into momentum modes and integrate over modes which correspond neither to
the kinematics of scattering nor to the one of exchanged particles. The
effective vertices of scattering and of particle production are obtained as
sums of the contributions from the triple and quartic interaction terms and the
fields in the effective action are defined in terms of the two physical
components of the metric fluctuation.Comment: 15 pages, LATE
The Abelian Topological Mass Mechanism From Dimensional Reduction
We show that the abelian topological mass mechanism in four dimensions,
described by the Cremmer-Sherk action, can be obtained from dimensional
reduction in five dimensions. Starting from a gauge invariant action in five
dimensions, where the dual equivalence between a massless vector field and a
massless second-rank antisymmetric field in five dimensions is established, the
dimensional reduction is performed keeping only one massive mode. Furthermore,
the Kalb-Ramond action and the Stuckelberger formulation for massive spin-1 are
recovered.Comment: Three references added, 6 pages, late
Estimating the public health impact of disbanding a government alcohol monopoly: Application of new methods to the case of Sweden
Background: Government alcohol monopolies were created in North America and Scandinavia to limit health and social problems. The Swedish monopoly, Systembolaget, reports to a health ministry and controls the sale of all alcoholic beverages with > 3.5% alcohol/volume for off-premise consumption, within a public health mandate. Elsewhere, alcohol monopolies are being dismantled with evidence of increased consumption and harms. We describe innovative modelling techniques to estimate health outcomes in scenarios involving Systembolaget being replaced by 1) privately owned liquor stores, or 2) alcohol sales in grocery stores. The methods employed can be applied in other jurisdictions and for other policy changes. Methods: Impacts of the privatisation scenarios on pricing, outlet density, trading hours, advertising and marketing were estimated based on Swedish expert opinion and published evidence. Systematic reviews were conducted to estimate impacts on alcohol consumption in each scenario. Two methods were applied to estimate harm impacts: (i) alcohol attributable morbidity and mortality were estimated utilising the International Model of Alcohol Harms and Policies (InterMAHP); (ii) ARIMA methods to estimate the relationship between per capita alcohol consumption and specific types of alcohol-related mortality and crime. Results: Replacing government stores with private liquor stores (Scenario 1) led to a 20.0% (95% CI, 15.3-24.7) increase in per capita consumption. Replacement with grocery stores (Scenario 2) led to a 31.2% (25.1-37.3%) increase. With InterMAHP there were 763 or + 47% (35-59%) and 1234 or + 76% (60-92%) more deaths per year, for Scenarios 1 and 2 respectively. With ARIMA, there were 850 (334-1444) more deaths per year in Scenario 1 and 1418 more in Scenario 2 (543-2505). InterMAHP also estimated 10,859 or + 29% (22-34%) and 16,118 or + 42% (35-49%) additional hospital stays per year respectively. Conclusions: There would be substantial adverse consequences for public health and safety were Systembolaget to be privatised. We demonstrate a new combined approach for estimating the impact of alcohol policies on consumption and, using two alternative methods, alcohol-attributable harm. This approach could be readily adapted to other policies and settings. We note the limitation that some significant sources of uncertainty in the estimates of harm impacts were not modelled
Pseudoclassical theories of Majorana, Weyl and Majorana--Weyl particles
A pseudoclassical theories of Majorana, Weyl and Majorana--Weyl particles in
the space--time dimensions are constructed. The canonical quantization
of these theories is carried out and as a result we obtain the quantum
mechanical description of neutral particle in , Weyl particle in
and neutral Weyl particle in . In dimensional
space--time the description of the neutral particle coincides with the field
theoretical description of the Majorana particle in the Foldy--Wouthuysen
representation. In dimensions the neutral Weyl particle coincides with
the Majorana--Weyl particle in the Foldy--Wouthuysen representation.Comment: LATEX, 17 pages, no figure
Dark Matter Gravitational Interactions
We argue that the conjectured dark mater in the Universe may be endowed with
a new kind of gravitational charge that couples to a short range gravitational
interaction mediated by a massive vector field. A model is constructed that
assimilates this concept into ideas of current inflationary cosmology. The
model is also consistent with the observed behaviour of galactic rotation
curves according to Newtonian dynamics. The essential idea is that stars
composed of ordinary (as opposed to dark matter) experience Newtonian forces
due to the presence of an all pervading background of massive gravitationally
charged cold dark matter. The novel gravitational interactions are predicted to
have a significant influence on pre-inflationary cosmology. The precise details
depend on the nature of a gravitational Proca interaction and the description
of matter. A gravitational Proca field configuration that gives rise to
attractive forces between dark matter charges of like polarity exhibits
homogeneous isotropic eternal cosmologies that are free of cosmological
curvature singularities thus eliminating the horizon problem associated with
the standard big-bang scenario. Such solutions do however admit dense hot
pre-inflationary epochs each with a characteristic scale factor that may be
correlated with the dark matter density in the current era of expansion. The
model is based on a theory in which a modification of Einsteinian gravity at
very short distances can be expressed in terms of the gradient of the Einstein
metric and the torsion of a non-Riemannian connection on the bundle of linear
frames over spacetime. Indeed we demonstrate that the genesis of the model
resides in a remarkable simplification that occurs when one analyses the
variational equations associated with a broad class of non-Riemannian actions.Comment: 40 pages, 4 Postscript figure
Belga B-trees
We revisit self-adjusting external memory tree data structures, which combine
the optimal (and practical) worst-case I/O performances of B-trees, while
adapting to the online distribution of queries. Our approach is analogous to
undergoing efforts in the BST model, where Tango Trees (Demaine et al. 2007)
were shown to be -competitive with the runtime of the best
offline binary search tree on every sequence of searches. Here we formalize the
B-Tree model as a natural generalization of the BST model. We prove lower
bounds for the B-Tree model, and introduce a B-Tree model data structure, the
Belga B-tree, that executes any sequence of searches within a
factor of the best offline B-tree model algorithm, provided .
We also show how to transform any static BST into a static B-tree which is
faster by a factor; the transformation is randomized and we
show that randomization is necessary to obtain any significant speedup
Building capacity for HIV/AIDS program leadership and management in Uganda through mentored Fellowships
Background: Around the world, health professionals and program managers are leading and managing public and private health organizations with little or no formal management and leadership training and experience. Objective: To describe an innovative 2-year, long-term apprenticeship Fellowship training program implemented by Makerere University School of Public Health (MakSPH) to strengthen capacity for leadership and management of HIV/AIDS programs in Uganda. Implementation process: The program, which began in 2002, is a 2-year, full-time, non-degree Fellowship. It is open to Ugandan nationals with postgraduate training in health-related disciplines. Enrolled Fellows are attached to host institutions implementing HIV/AIDS programs and placed under the supervision of host institution and academic mentors. Fellows spend 75% of their apprenticeship at the host institutions while the remaining 25% is dedicated to didactic short courses conducted at MakSPH to enhance their knowledge base. Achievements: Overall, 77 Fellows have been enrolled since 2002. Of the 57 Fellows who were admitted between 2002 and 2008, 94.7% (54) completed the Fellowship successfully and 50 (92.3%) are employed in senior leadership and management positions in Uganda and internationally. Eighty-eight percent of those employed (44/54) work in institutions registered in Uganda, indicating a high level of in-country retention. Nineteen of the 20 Fellows who were admitted between 2009 and 2010 are still undergoing training. A total of 67 institutions have hosted Fellows since 2002. The host institutions have benefited through staff training and technical expertise from the Fellows as well as through grant support to Fellows to develop and implement innovative pilot projects. The success of the program hinges on support from mentors, stakeholder involvement, and the hands-on approach employed in training. Conclusion: The Fellowship Program offers a unique opportunity for hands-on training in HIV/AIDS program leadership and management for both Fellows and host institutions
Palaeozoic giant dragonfies were hawker predators
The largest insects to have ever lived were the giant meganeurids of the Late Palaeozoic, ancient
stem relatives of our modern dragonfies. With wingspans up to 71cm, these iconic insects have been
the subject of varied documentaries on Palaeozoic life, depicting them as patrolling for prey through
coal swamp forests amid giant lycopsids, and cordaites. Such reconstructions are speculative as few
defnitive details of giant dragonfy biology are known. Most specimens of giant dragonfies are known
from wings or isolated elements, but Meganeurites gracilipes preserves critical body structures, most
notably those of the head. Here we show that it is unlikely it thrived in densely forested environments
where its elongate wings would have become easily damaged. Instead, the species lived in more
open habitats and possessed greatly enlarged compound eyes. These were dorsally hypertrophied, a
specialization for long-distance vision above the animal in fight, a trait convergent with modern hawker
dragonfies. Sturdy mandibles with acute teeth, strong spines on tibiae and tarsi, and a pronounced
thoracic skewness are identical to those specializations used by dragonfies in capturing prey while
in fight. The Palaeozoic Odonatoptera thus exhibited considerable morphological specializations
associated with behaviours attributable to âhawkersâ or âperchersâ among extant Odonata.This work benefted from a grant of the French âAgence Nationale de la Rechercheâ via the program âInvestissements dâavenirâ (ANR-11-INBS-0004-RECOLNAT)JP and MP gratefully acknowledge research support from the Grant Agency of the Czech Republic No. 18-03118 SThe work of MSE was supported by US National Science Foundation grant DEB-114416
Alcohol consumption and the physical availability of take-away alcohol: systematic reviews and meta-analyses of the days and hours of sale and outlet density.
OBJECTIVE: Systematic reviews and meta-analyses were completed studying the effect of changes in the physical availability of take-away alcohol on per capita alcohol consumption. Previous reviews examining this topic have not focused on off-premise outlets where take-away alcohol is sold and have not completed meta-analyses. METHOD: Systematic reviews were conducted separately for policies affecting the temporal availability (days and hours of sale) and spatial availability (outlet density) of take-away alcohol. Studies were included up to December 2015. Quality criteria were used to select articles that studied the effect of changes in these policies on alcohol consumption with a focus on natural experiments. Random-effects meta-analyses were applied to produce the estimated effect of an additional day of sale on total and beverage-specific consumption. RESULTS: Separate systematic reviews identified seven studies regarding days and hours of sale and four studies regarding density. The majority of articles included in these systematic reviews, for days/hours of sale (7/7) and outlet density (3/4), concluded that restricting the physical availability of take-away alcohol reduces per capita alcohol consumption. Meta-analyses studying the effect of adding one additional day of sale found that this was associated with per capita consumption increases of 3.4% (95% CI [2.7, 4.1]) for total alcohol, 5.3% (95% CI [3.2, 7.4]) for beer, 2.6% (95% CI [1.8, 3.5]) for wine, and 2.6% (95% CI [2.1, 3.2]) for spirits. The small number of included studies regarding hours of sale and density precluded meta-analysis. CONCLUSIONS: The results of this study suggest that decreasing the physical availability of take-away alcohol will decrease per capita consumption. As decreasing per capita consumption has been shown to reduce alcohol-related harm, restricting the physical availability of take-away alcohol would be expected to result in improvements to public health
'Clinical triad' findings in pediatric Klippel-Feil patients
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