8,752 research outputs found
A Double-Mode RR Lyrae Star with a Strong Fundamental Mode Component
NSVS 5222076, a thirteenth magnitude star in the Northern Sky Variability
Survey, was identified by Oaster as a possible new double-mode RR Lyrae star.
We confirm the double-mode nature of NSVS 5222076, supplementing the survey
data with new V band photometry. NSVS 5222076 has a fundamental mode period of
0.4940 day and a first overtone period of 0.3668 day. Its fundamental mode
light curve has an amplitude twice as large as that of the first overtone mode,
a ratio very rarely seen. Data from the literature are used to discuss the
location in the Petersen diagram of double-mode RR Lyrae stars having strong
fundamental mode pulsation. Such stars tend to occur toward the short period
end of the Petersen diagram, and NSVS 5222976 is no exception to this rule.Comment: 14 pages, 4 figures, To be published in the March, 2006, issue of
PAS
Mortality due to cardiovascular disease, respiratory disease and cancer in adults with cerebral palsy
Aim: To compare mortality rates for cardiovascular disease, cancer, and respiratory disease between adults with cerebral palsy (CP) and the general population.
Method: A cohort study was conducted using data from adults with CP in England, identified through a primary care dataset (the Clinical Practice Research Datalink), with linked data on death registrations from the Office for National Statistics. Cause of death was categorised according to ICD codes. Standardised mortality ratios were calculated to compare mortality rates between adults with CP and the general population, adjusted for age, sex, and calendar-year.
Results: 958 adults with CP were identified (median age at start of follow-up 31 yr; 52.5% males) and followed for a total of 7693 person-years. 142 patients (15%) died during follow-up. Adults with CP had an increased risk of death due to cardiovascular disease (SMR: 3.19, 95% CI 2.20 to 4.62) and respiratory disease (SMR: 13.59, 95% CI to 18.67), but not from malignant neoplasms (SMR: 1.42, 95% CI 0.83 to 2.45).
Interpretation: We found that adults with CP in England have increased risk of death due to diseases of the circulatory and respiratory systems, supporting findings from two studies that compared cause-specific mortality rates between adults with CP in the US and the general population. Further research is required into primary and secondary prevention of cardiovascular and respiratory disease in people with CP worldwide. </p
A systematic study of the sensitivity of triangular flow to the initial state fluctuations in relativistic heavy-ion collisions
Experimental data from the Relativistic Heavy Ion Collider (RHIC) suggests
that the quark gluon plasma behaves almost like an ideal fluid. Due to its
short lifetime, many QGP properties can only be inferred indirectly through a
comparison of the final state measurements with transport model calculations.
Among the current phenomena of interest are the interdependencies between two
collective flow phenomena, elliptic and triangular flow. The former is mostly
related to the initial geometry and collective expansion of the system whereas
the latter is sensitive to the fluctuations of the initial state. For our
investigation we use a hybrid transport model based on the Ultra-relativistic
Quantum Molecular Dynamics (UrQMD) transport approach using an ideal
hydrodynamic expansion for the hot and dense stage. Using UrQMD initial
conditions for an Au-Au collision, particles resulting from a collision are
mapped into an energy density distribution that is evolved event-by-event with
a hydrodynamic calculation. By averaging these distributions over different
numbers of events, we have studied how the granularity/smoothness of the
distribution affects the initial eccentricity, the initial triangularity, and
the resulting flow components. The average elliptic flow in non central
collisions is not sensitive to the granularity, while triangular flow is. The
triangularity might thus provide a good measure of the amount of initial state
fluctuations that is necessary to reproduce the experimental data.Comment: 10 pages, 7 figure
The Economic Resource Receipt of New Mothers
U.S. federal policies do not provide a universal social safety net of economic support for women during pregnancy or the immediate postpartum period but assume that employment and/or marriage will protect families from poverty. Yet even mothers with considerable human and marital capital may experience disruptions in employment, earnings, and family socioeconomic status postbirth. We use the National Survey of Families and Households to examine the economic resources that mothers with children ages 2 and younger receive postbirth, including employment, spouses, extended family and social network support, and public assistance. Results show that many new mothers receive resources postbirth. Marriage or postbirth employment does not protect new mothers and their families from poverty, but education, race, and the receipt of economic supports from social networks do
A comparision of GHG emissions from UK field crop production under selected arable systems with reference to disease control
Crop disease not only threatens global food security by reducing crop production at a time of growing demand, but also contributes to greenhouse gas (GHG) emissions by reducing efficiency of N fertiliser use and farm operations and by driving land use change. GHG emissions associated with adoption of reduced tillage, organic and integrated systems of field crop production across the UK and selected regions are compared with emissions from conventional arable farming to assess their potential for climate change mitigation. The reduced tillage system demonstrated a modest (<20%) reduction in emissions in all cases, although in practice it may not be suitable for all soils and it is likely to cause problems with control of diseases spread on crop debris. There were substantial increases in GHG emissions associated with the organic and integrated systems at national level, principally due to soil organic carbon losses from land use change. At a regional level the integrated system shows the potential to deliver significant emission reductions. These results indicate that the conventional crop production system, coupled to reduced tillage cultivation where appropriate, is generally the best for producing high yields to minimise greenhouse gas emissions and contribute to global food security, although there may be scope for use of the integrated system on a regional basis. The control of crop disease will continue to have an essential role in both maintaining productivity and decreasing GHG emissions.Peer reviewe
Tectonic structure, evolution, and the nature of oceanic core complexes and their detachment fault zones (13°20′N and 13°30′N, Mid Atlantic Ridge)
Microbathymetry data, in situ observations, and sampling along the 138200N and 138200N oceanic
core complexes (OCCs) reveal mechanisms of detachment fault denudation at the seafloor, links between tectonic
extension and mass wasting, and expose the nature of corrugations, ubiquitous at OCCs. In the initial
stages of detachment faulting and high-angle fault, scarps show extensive mass wasting that reduces their
slope. Flexural rotation further lowers scarp slope, hinders mass wasting, resulting in morphologically complex
chaotic terrain between the breakaway and the denuded corrugated surface. Extension and drag along the fault
plane uplifts a wedge of hangingwall material (apron). The detachment surface emerges along a continuous
moat that sheds rocks and covers it with unconsolidated rubble, while local slumping emplaces rubble ridges
overlying corrugations. The detachment fault zone is a set of anostomosed slip planes, elongated in the alongextension
direction. Slip planes bind fault rock bodies defining the corrugations observed in microbathymetry
and sonar. Fault planes with extension-parallel stria are exposed along corrugation flanks, where the rubble cover
is shed. Detachment fault rocks are primarily basalt fault breccia at 138200N OCC, and gabbro and peridotite
at 138300N, demonstrating that brittle strain localization in shallow lithosphere form corrugations, regardless of
lithologies in the detachment zone. Finally, faulting and volcanism dismember the 138300N OCC, with widespread
present and past hydrothermal activity (Semenov fields), while the Irinovskoe hydrothermal field at the
138200N core complex suggests a magmatic source within the footwall. These results confirm the ubiquitous
relationship between hydrothermal activity and oceanic detachment formation and evolution
Structural Analysis of Biodiversity
Large, recently-available genomic databases cover a wide range of life forms, suggesting opportunity for insights into genetic structure of biodiversity. In this study we refine our recently-described technique using indicator vectors to analyze and visualize nucleotide sequences. The indicator vector approach generates correlation matrices, dubbed Klee diagrams, which represent a novel way of assembling and viewing large genomic datasets. To explore its potential utility, here we apply the improved algorithm to a collection of almost 17000 DNA barcode sequences covering 12 widely-separated animal taxa, demonstrating that indicator vectors for classification gave correct assignment in all 11000 test cases. Indicator vector analysis revealed discontinuities corresponding to species- and higher-level taxonomic divisions, suggesting an efficient approach to classification of organisms from poorly-studied groups. As compared to standard distance metrics, indicator vectors preserve diagnostic character probabilities, enable automated classification of test sequences, and generate high-information density single-page displays. These results support application of indicator vectors for comparative analysis of large nucleotide data sets and raise prospect of gaining insight into broad-scale patterns in the genetic structure of biodiversity
Constraining the initial state granularity with bulk observables in Au+Au collisions at GeV
In this paper we conduct a systematic study of the granularity of the initial
state of hot and dense QCD matter produced in ultra-relativistic heavy-ion
collisions and its influence on bulk observables like particle yields,
spectra and elliptic flow. For our investigation we use a hybrid transport
model, based on (3+1)d hydrodynamics and a microscopic Boltzmann transport
approach. The initial conditions are generated by a non-equilibrium hadronic
transport approach and the size of their fluctuations can be adjusted by
defining a Gaussian smoothing parameter . The dependence of the
hydrodynamic evolution on the choices of
and is explored by means of a Gaussian emulator.
To generate particle yields and elliptic flow that are compatible with
experimental data the initial state parameters are constrained to be
fm and fm. In addition, the influence of changes in the
equation of state is studied and the results of our event-by-event calculations
are compared to a calculation with averaged initial conditions. We conclude
that even though the initial state parameters can be constrained by yields and
elliptic flow, the granularity needs to be constrained by other correlation and
fluctuation observables.Comment: 14 pages, 8 figures, updated references, version to appear in J.
Phys.
- …