1,402 research outputs found
Distribution and pattern of moraines in far ne Russia reveal former glacial extent
Here we present a series of six maps illustrating the distribution of end moraines in Far NE Russia. The maps are the first to systematically document the distribution of moraines across this region from the Verkhoyansk Mountains at the westernmost limit of our study area to the Chukchi Peninsula in the NE and to Kamchatka in the south, covering almost 4 million km 2 . Moraines were identified and mapped from analysis of satellite images and digital elevation model data. A total of 2173 moraines are identified, and we highlight some 197 more speculative features (perhaps moraines) that require further investigation. The distribution of moraines indicates that much of the region, now largely ice-free, was formerly occupied by glaciers centred upon the region's uplands and that glacier outlets were typically < 200 km in length. The maps demonstrate the usefulness of remote sensing to derive an improved understanding of the glacial history of this vast and isolated region, and we present them to stimulate further work and act as a systematic framework for targeted geochronometric dating
The anomalous U(1) global symmetry and flavors from an SU(5) x SU(5) GUT in orbifold compactification
In string compactifications, frequently there appears the anomalous U(1)
gauge symmetry which belonged to E8E8 of the heterotic string. This
anomalous U(1) gauge boson obtains mass at the compactification scale, just
below GeV, by absorbing one pseudoscalar (corresponding to the
model-independent axion) from the second rank anti-symmetric tensor field
.
Below the compactification scale, there results a global symmetry U(1) whose charge is the original gauge U(1) charge. This is
the most natural global symmetry, realizing the "invisible" axion. This global
symmetry U(1) is suitable for a flavor symmetry. In the simplest
compactification model with the flipped SU(5) grand unification, we calculate
all the low energy parameters in terms of the vacuum expectation values of the
standard model singlets.Comment: 18 pages, 4 figur
Axion Protection from Flavor
The QCD axion fails to solve the strong CP problem unless all explicit PQ
violating, Planck-suppressed, dimension n<10 operators are forbidden or have
exponentially small coefficients. We show that all theories with a QCD axion
contain an irreducible source of explicit PQ violation which is proportional to
the determinant of the Yukawa interaction matrix of colored fermions.
Generically, this contribution is of low operator dimension and will
drastically destabilize the axion potential, so its suppression is a necessary
condition for solving the strong CP problem. We propose a mechanism whereby the
PQ symmetry is kept exact up to n=12 with the help of the very same flavor
symmetries which generate the hierarchical quark masses and mixings of the SM.
This "axion flavor protection" is straightforwardly realized in theories which
employ radiative fermion mass generation and grand unification. A universal
feature of this construction is that the heavy quark Yukawa couplings are
generated at the PQ breaking scale.Comment: 16 pages, 2 figure
Medical causes of admissions to hospital among adults in Africa: a systematic review.
BACKGROUND: Despite the publication of several studies on the subject, there is significant uncertainty regarding the burden of disease among adults in sub-Saharan Africa (sSA). OBJECTIVES: To describe the breadth of available data regarding causes of admission to hospital, to systematically analyze the methodological quality of these studies, and to provide recommendations for future research. DESIGN: We performed a systematic online and hand-based search for articles describing patterns of medical illnesses in patients admitted to hospitals in sSA between 1950 and 2010. Diseases were grouped into bodily systems using International Classification of Disease (ICD) guidelines. We compared the proportions of admissions and deaths by diagnostic category using χ2. RESULTS: Thirty articles, describing 86,307 admissions and 9,695 deaths, met the inclusion criteria. The leading causes of admission were infectious and parasitic diseases (19.8%, 95% confidence interval [CI] 19.6-20.1), respiratory (16.2%, 95% CI 16.0-16.5) and circulatory (11.3%, 95% CI 11.1-11.5) illnesses. The leading causes of death were infectious and parasitic (17.1%, 95% CI 16.4-17.9), circulatory (16%, 95% CI 15.3-16.8) and digestive (16.2%, 95% CI 15.4-16.9). Circulatory diseases increased from 3.9% of all admissions in 1950-59 to 19.9% in 2000-2010 (RR 5.1, 95% CI 4.5-5.8, test for trend p<0.00005). The most prevalent methodological deficiencies, present in two-thirds of studies, were failures to use standardized case definitions and ICD guidelines for classifying illnesses. CONCLUSIONS: Cardiovascular and infectious diseases are currently the leading causes of admissions and in-hospital deaths in sSA. Methodological deficiencies have limited the usefulness of previous studies in defining national patterns of disease in adults. As African countries pass through demographic and health transition, they need to significantly invest in clinical research capacity to provide an accurate description of the disease burden among adults for public health policy
Exotic particles below the TeV from low scale flavour theories
A flavour gauge theory is observable only if the symmetry is broken at
relatively low energies. The intrinsic parity-violation of the fermion
representations in a flavour theory describing quark, lepton and higgsino
masses and mixings generically requires anomaly cancellation by new fermions.
Benchmark supersymmetric flavour models are built and studied to argue that: i)
the flavour symmetry breaking should be about three orders of magnitude above
the higgsino mass, enough also to efficiently suppress FCNC and CP violations
coming from higher-dimensional operators; ii) new fermions with exotic decays
into lighter particles are typically required at scales of the order of the
higgsino mass.Comment: 19 pages, references added, one comment and one footnote added,
results unchange
The Impact of Flavour Changing Neutral Gauge Bosons on B->X_s gamma
The branching ratio of the rare decay B->X_s gamma provides potentially
strong constraints on models beyond the Standard Model. Considering a general
scenario with new heavy neutral gauge bosons, present in particular in Z' and
gauge flavour models, we point out two new contributions to the B->X_s gamma
decay. The first one originates from one-loop diagrams mediated by gauge bosons
and heavy exotic quarks with electric charge -1/3. The second contribution
stems from the QCD mixing of neutral current-current operators generated by
heavy neutral gauge bosons and the dipole operators responsible for the B->X_s
gamma decay. The latter mixing is calculated here for the first time. We
discuss general sum rules which have to be satisfied in any model of this type.
We emphasise that the neutral gauge bosons in question could also significantly
affect other fermion radiative decays as well as non-leptonic two-body B
decays, epsilon'/epsilon, anomalous (g-2)_mu and electric dipole moments.Comment: 31 pages, 5 figures; version published on JHEP; added magic QCD
numbers for flavour-violating Z gauge boson contribution to B -> X_s gamm
Gastroesophageal reflux symptoms in infants in a rural population: longitudinal data over the first six months
<p>Abstract</p> <p>Background</p> <p>Increasing numbers of infants are receiving prescription medications for symptoms associated with gastroesophageal reflux. Our aim was to prospectively measure reported gastroesophageal reflux symptoms in healthy term infants for the first six months of life.</p> <p>Methods</p> <p>In a prospective cohort study in the rural Upper Peninsula of Michigan, 128 consecutive maternal-infant pairs were followed for six months and administered the Infant Gastroesophageal Reflux Questionnaire Revised (I-GERQ-R) at the one-month, two-month, four-month, and six-month well-child visits.</p> <p>Results</p> <p>The I-GERQ-R scores decreased with age. Average scores were 11.74 (SE = 5.97) at one-month, 9.97(4.92) at two-months, 8.44(4.39) at four-months, and 6.97(4.05) at six months. Symptoms associated with colic were greatest at one month of age.</p> <p>Conclusion</p> <p>Symptoms of gastroesophageal reflux as measured by the I-GERQ-R decrease with age in the first six months of life in otherwise healthy infants; however the I-GERQ-R may have difficulty differentiating gastroesophageal reflux disease from colic in those under 3 months of age.</p
Incidence and duration of total occlusion of the radial artery in newborn infants after catheter removal
The incidence and duration of total occlusion of the radial artery after catheter removal was determined using repeated Doppler flow measurements. Thirty-two newborn infants with birthweights ranging from 945 g to 3890 g (median 1935 g) and gestational age ranging from 26 to 40 weeks (median 32 weeks) were studied. In 20 out of 32 infants (63%), complete occlusion of the radial artery occurred. The number of occlusions were not related to birthweight, gestational age or duration of cannulation. In all infants, blood flow in the radial artery resumed within 1-29 days after catheter removal. The duration of occlusion was directly related to the duration of cannulation and inversely related to birthweight. This study demonstrates a high frequency of total occlusion of the radial artery in newborn infants after percutaneous radial artery cannulation. In the majority of infants with a radial artert catheter, blood flow to the tissue distal to the cannulation site is dependent solely on the existence of an adequate arterial palmar collateral circulation
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Search for gravitational waves from Scorpius X-1 in the second Advanced LIGO observing run with an improved hidden Markov model
We present results from a semicoherent search for continuous gravitational
waves from the low-mass X-ray binary Scorpius X-1, using a hidden Markov model
(HMM) to track spin wandering. This search improves on previous HMM-based
searches of LIGO data by using an improved frequency domain matched filter, the
-statistic, and by analysing data from Advanced LIGO's second
observing run. In the frequency range searched, from to
, we find no evidence of gravitational radiation. At
, the most sensitive search frequency, we report an upper
limit on gravitational wave strain (at 95\% confidence) of when marginalising over source inclination angle. This is the
most sensitive search for Scorpius X-1, to date, that is specifically designed
to be robust in the presence of spin wandering
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The Pandora multi-algorithm approach to automated pattern recognition of cosmic-ray muon and neutrino events in the MicroBooNE detector.
The development and operation of liquid-argon time-projection chambers for neutrino physics has created a need for new approaches to pattern recognition in order to fully exploit the imaging capabilities offered by this technology. Whereas the human brain can excel at identifying features in the recorded events, it is a significant challenge to develop an automated, algorithmic solution. The Pandora Software Development Kit provides functionality to aid the design and implementation of pattern-recognition algorithms. It promotes the use of a multi-algorithm approach to pattern recognition, in which individual algorithms each address a specific task in a particular topology. Many tens of algorithms then carefully build up a picture of the event and, together, provide a robust automated pattern-recognition solution. This paper describes details of the chain of over one hundred Pandora algorithms and tools used to reconstruct cosmic-ray muon and neutrino events in the MicroBooNE detector. Metrics that assess the current pattern-recognition performance are presented for simulated MicroBooNE events, using a selection of final-state event topologies
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