368 research outputs found
Hurricane Charley Exposure and Hazard of Preterm Delivery, Florida 2004
Objective Hurricanes are powerful tropical storm systems with high winds which influence many health effects. Few studies have examined whether hurricane exposure is associated with preterm delivery. We aimed to estimate associations between maternal hurricane exposure and hazard of preterm delivery. Methods We used data on 342,942 singleton births from Florida Vital Statistics Records 2004–2005 to capture pregnancies at risk of delivery during the 2004 hurricane season. Maternal exposure to Hurricane Charley was assigned based on maximum wind speed in maternal county of residence. We estimated hazards of overall preterm delivery (<37 gestational weeks) and extremely preterm delivery (<32 gestational weeks) in Cox regression models, adjusting for maternal/pregnancy characteristics. To evaluate heterogeneity among racial/ethnic subgroups, we performed analyses stratified by race/ethnicity. Additional models investigated whether exposure to multiples hurricanes increased hazard relative to exposure to one hurricane. Results Exposure to wind speeds ≥39 mph from Hurricane Charley was associated with a 9 % (95 % CI 3, 16 %) increase in hazard of extremely preterm delivery, while exposure to wind speed ≥74 mph was associated with a 21 % (95 % CI 6, 38 %) increase. Associations appeared greater for Hispanic mothers compared to non-Hispanic white mothers. Hurricane exposure did not appear to be associated with hazard of overall preterm delivery. Exposure to multiple hurricanes did not appear more harmful than exposure to a single hurricane. Conclusions Hurricane exposure may increase hazard of extremely preterm delivery. As US coastal populations and hurricane severity increase, the associations between hurricane and preterm delivery should be further studied
Wavelet analysis of epileptic spikes
Interictal spikes and sharp waves in human EEG are characteristic signatures
of epilepsy. These potentials originate as a result of synchronous,
pathological discharge of many neurons. The reliable detection of such
potentials has been the long standing problem in EEG analysis, especially after
long-term monitoring became common in investigation of epileptic patients. The
traditional definition of a spike is based on its amplitude, duration,
sharpness, and emergence from its background. However, spike detection systems
built solely around this definition are not reliable due to the presence of
numerous transients and artifacts. We use wavelet transform to analyze the
properties of EEG manifestations of epilepsy. We demonstrate that the behavior
of wavelet transform of epileptic spikes across scales can constitute the
foundation of a relatively simple yet effective detection algorithm.Comment: 4 pages, 3 figure
Improved constraints on WIMPs from the International Germanium Experiment IGEX
One IGEX 76Ge double-beta decay detector is currently operating in the
Canfranc Underground Laboratory in a search for dark matter WIMPs, through the
Ge nuclear recoil produced by the WIMP elastic scattering. A new exclusion
plot, has been derived for WIMP-nucleon spin-independent interactions. To
obtain this result, 40 days of data from the IGEX detector (energy threshold E
\~ 4 keV), recently collected, have been analyzed. These data improve the
exclusion limits derived from all the other ionization germanium detectors in
the mass region from 20 GeV to 200 GeV, where a WIMP supposedly responsible for
the annual modulation effect reported by the DAMA experiment would be located.
The new IGEX exclusion contour enters, by the first time, the DAMA region by
using only raw data, with no background discrimination, and excludes its upper
left part. It is also shown that with a moderate improvement of the detector
performances, the DAMA region could be fully explored.Comment: 14 pages, 8 figures, submitted to Physics Letters B (revised version
after referee's comments, some figures added
New constraints on WIMPs from the Canfranc IGEX dark matter search
The IGEX Collaboration enriched 76Ge double-beta decay detectors are
currently operating in the Canfranc Underground Laboratory with an overburden
of 2450 m.w.e. A recent upgrade has made it possible to use them in a search
for WIMPs. A new exclusion plot has been derived for WIMP-nucleon
spin-independent interaction. To obtain this result, 30 days of data from one
IGEX detector, which has an energy threshold of ~4 keV, have been considered.
These data improve the exclusion limits derived from other germanium diode
experiments in the ~50 GeV DAMA region, and show that with a moderate
improvement of the background below 10 keV, the DAMA region may be tested with
an additional 1 kg-year of exposure.Comment: 7 pages, 2 figures, submitted to Physics Letter
Charge Transport Through Open, Driven Two-Level Systems with Dissipation
We derive a Floquet-like formalism to calculate the stationary average
current through an AC driven double quantum dot in presence of dissipation. The
method allows us to take into account arbitrary coupling strengths both of a
time-dependent field and a bosonic environment. We numerical evaluate a
truncation scheme and compare with analytical, perturbative results such as the
Tien-Gordon formula.Comment: 14 pages, 6 figures. To appear in Phys. Rev.
A model for net-baryon rapidity distribution
In nuclear collisions, a sizable fraction of the available energy is carried
away by baryons. As the baryon number is conserved, the net-baryon
retains information on the energy-momentum carried by the incoming nuclei. A
simple and consistent model for net-baryon production in high energy
proton-proton and nucleus-nucleus collisions is presented. The basic
ingredients of the model are valence string formation based on standard PDFs
with QCD evolution and string fragmentation via the Schwinger mechanism. The
results of the model are presented and compared with data at different
centre-of-mass energies and centralities, as well as with existing models.
These results show that a good description of the main features of net-baryon
data is possible in the framework of a simplistic model, with the advantage of
making the fundamental production mechanisms manifest.Comment: 9 pages, 12 figures; in fig. 11 a) the vertical scale was correcte
Association Between Gestational Diabetes and Incident Maternal CKD: The Coronary Artery Risk Development in Young Adults (CARDIA) Study
Background Gestational diabetes mellitus (GDM) is associated with increased risk for diabetes mellitus, metabolic syndrome, and cardiovascular disease. We evaluated whether GDM is associated with incident chronic kidney disease (CKD), controlling for prepregnancy risk factors for both conditions. Study Design Prospective cohort. Setting & Participants Of 2,747 women (aged 18-30 years) enrolled in the Coronary Artery Risk Development in Young Adults (CARDIA) Study in 1985 to 86, we studied 820 who were nulliparous at enrollment, delivered at least 1 pregnancy longer than 20 weeks’ gestation, and had kidney function measurements during 25 years of follow-up. Predictor GDM was self-reported by women for each pregnancy. Outcomes CKD was defined as the development of estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m2 or urine albumin-creatinine ratio ≥ 25 mg/g at any one CARDIA examination in years 10, 15, 20, or 25. Measurements HRs for developing CKD were estimated for women who developed GDM versus women without GDM using complementary log-log models, adjusting for prepregnancy age, systolic blood pressure, dyslipidemia, body mass index, smoking, education, eGFR, fasting glucose concentration, physical activity level (all measured at the CARDIA examination before the first pregnancy), race, and family history of diabetes. We explored for an interaction between race and GDM. Results During a mean follow-up of 20.8 years, 105 of 820 (12.8%) women developed CKD, predominantly increased urine albumin excretion (98 albuminuria only, 4 decreased eGFR only, and 3 both). There was evidence of a GDM-race interaction on CKD risk (P = 0.06). Among black women, the adjusted HR for CKD was 1.96 (95% CI, 1.04-3.67) in GDM compared with those without GDM. Among white women, the HR was 0.65 (95% CI, 0.23-1.83). Limitations Albuminuria was assessed by single untimed measurements of urine albumin and creatinine. Conclusions GDM is associated with the subsequent development of albuminuria among black women in CARDIA
Scale-free memory model for multiagent reinforcement learning. Mean field approximation and rock-paper-scissors dynamics
A continuous time model for multiagent systems governed by reinforcement
learning with scale-free memory is developed. The agents are assumed to act
independently of one another in optimizing their choice of possible actions via
trial-and-error search. To gain awareness about the action value the agents
accumulate in their memory the rewards obtained from taking a specific action
at each moment of time. The contribution of the rewards in the past to the
agent current perception of action value is described by an integral operator
with a power-law kernel. Finally a fractional differential equation governing
the system dynamics is obtained. The agents are considered to interact with one
another implicitly via the reward of one agent depending on the choice of the
other agents. The pairwise interaction model is adopted to describe this
effect. As a specific example of systems with non-transitive interactions, a
two agent and three agent systems of the rock-paper-scissors type are analyzed
in detail, including the stability analysis and numerical simulation.
Scale-free memory is demonstrated to cause complex dynamics of the systems at
hand. In particular, it is shown that there can be simultaneously two modes of
the system instability undergoing subcritical and supercritical bifurcation,
with the latter one exhibiting anomalous oscillations with the amplitude and
period growing with time. Besides, the instability onset via this supercritical
mode may be regarded as "altruism self-organization". For the three agent
system the instability dynamics is found to be rather irregular and can be
composed of alternate fragments of oscillations different in their properties.Comment: 17 pages, 7 figur
The Majorana neutrino masses, neutrinoless double beta decay and nuclear matrix elements
The effective Majorana neutrino mass is evaluated by using the latest results
of neutrino oscillation experiments. The problems of the neutrino mass
spectrum,absolute mass scale of neutrinos and the effect of CP phases are
addressed. A connection to the next generation of the neutrinoless double beta
decay (0nbb-decay) experiments is discussed. The calculations are performed for
76Ge, 100Mo, 136Xe and 130Te by using the advantage of recently evaluated
nuclear matrix elements with significantly reduced theoretical uncertainty. An
importance of observation of the 0nbb-decay of several nuclei is stressed.Comment: 29 pages, 5 figures, EXO (10 t) experiment considere
Learning to look : evaluating the student experience of an interactive image appraisal activity
Introduction: Student radiographers have expressed difficulty in performing image appraisal tasks. The purpose of this study was to investigate the value of a workshop delivered to level 4 undergraduate students. All students completed an image appraisal activity, inputting their appraisal into software that displayed their response alongside an expert opinion. They were asked to identify and discuss any discrepancy.
Methods: All Level 4 students participated in an image appraisal workshop and were subsequently invited to take part in a focus group immediately after the activity. Twenty-three students took part in three focus groups (n = 7; n = 8; n = 8). A thematic analysis of transcripts was performed alongside validation from observations during the image appraisal activity.
Results: Findings demonstrate that despite teaching and resources being available, students had focused on learning a generic checklist for image appraisal, had not appreciated the application of projection specific criteria and felt underprepared. The use of specific criteria and repetition within the task was considered useful. They identified learning needs and misconceptions through peer discussion and via the expert opinion, highlighting the value of feedback. Students enjoyed the workshop and made suggestions for implementation into the curriculum.
Conclusion: Educators must not assume that the provision of resources will result in students developing deep knowledge. Teaching and learning strategies that are task specific are recommended to avoid a surface approach to learning. Time, repetition and appropriate feedback are essential to enable learners to develop competence and confidence for complex visual tasks, such as image appraisal
- …