13,058 research outputs found
The Primary Pretenders
We call a composite number q such that there exists a positive integer b with
b^p == b (mod q) a prime pretender to base b. The least prime pretender to base
b is the primary pretender q_b. It is shown that there are only 132 distinct
primary pretenders, and that q_b is a periodic function of b whose period is
the 122-digit number
19568584333460072587245340037736278982017213829337604336734362-
294738647777395483196097971852999259921329236506842360439300.Comment: 7 page
A stochastic template placement algorithm for gravitational wave data analysis
This paper presents an algorithm for constructing matched-filter template
banks in an arbitrary parameter space. The method places templates at random,
then removes those which are "too close" together. The properties and
optimality of stochastic template banks generated in this manner are
investigated for some simple models. The effectiveness of these template banks
for gravitational wave searches for binary inspiral waveforms is also examined.
The properties of a stochastic template bank are then compared to the
deterministically placed template banks that are currently used in
gravitational wave data analysis.Comment: 14 pages, 11 figure
A population-based case-control study on social factors and risk of testicular germ cell tumours
Objectives Incidence rates for testicular cancer have risen over the last few decades. Findings of an association between the risk of testicular cancer and social factors are controversial. The association of testicular cancer and different indicators of social factors were examined in this study.<p></p>
Design Case–control study.<p></p>
Setting Population-based multicentre study in four German regions (city states Bremen and Hamburg, the Saarland region and the city of Essen).<p></p>
Participants The study included 797 control participants and 266 participants newly diagnosed with testicular cancer of which 167 cases were classified as seminoma and 99 as non-seminoma. The age of study participants ranged from 15 to 69 years.<p></p>
Methods Social position was classified by educational attainment level, posteducational training, occupational sectors according to Erikson-Goldthorpe-Portocarrero (EGP) and the socioeconomic status (SES) on the basis of the International SocioEconomic Index of occupational status (ISEI). ORs and corresponding 95% CIs (95% CIs) were calculated for the whole study sample and for seminoma and non-seminoma separately.<p></p>
Results Testicular cancer risk was modestly increased among participants with an apprenticeship (OR=1.7 (95% CI 1.0 to 2.8)) or a university degree (OR=1.6 (95% CI 0.9 to 2.8)) relative to those whose education was limited to school. Analysis of occupational sectors revealed an excess risk for farmers and farm-related occupations. No clear trend was observed for the analyses according to the ISEI-scale.<p></p>
Conclusions Social factors based on occupational measures were not a risk factor for testicular cancer in this study. The elevated risk in farmers and farm-related occupations warrants further research including analysis of occupational exposures.<p></p>
Stacking of large interferometric data sets in the image- and uv-domain -- a comparative study
We present a new algorithm for stacking radio interferometric data in the
uv-domain. The performance of uv-stacking is compared to the stacking of fully
imaged data using simulated Atacama Large Millimeter/sub-millimeter Array
(ALMA) and the Karl G. Jansky Very Large Array (VLA) deep extragalactic
surveys. We find that image- and uv-stacking produce similar results, however,
uv-stacking is typically the more robust method. An advantage of the
uv-stacking algorithm is the availability of uv-data post stacking, which makes
it possible to identify and remove problematic baselines. For deep VLA surveys
uv-stacking yields a signal-to-noise ratio that is up to 20 per cent higher
than image-stacking. Furthermore, we have investigated stacking of resolved
sources with a simulated VLA data set where 1.5" (10-12 kpc at z ~ 1-4) sources
are stacked. We find that uv-stacking, where a model is fitted directly to the
visibilities, significantly improves the accuracy and robustness of the size
estimates. While scientific motivation for this work is studying faint, high-z
galaxies, the algorithm analysed here would also be applicable in other fields
of astronomy. Stacking of radio interferometric data is also expected to play a
big role for future surveys with telescopes such as LOFAR and Square Kilometre
Array (SKA).Comment: 15 pages, 12 figures, accepted for publication in MNRA
Women's Experiences of Preeclampsia: Australian Action on Preeclampsia Survey of Women and Their Confidants
Introduction. The experience of normal pregnancy is often disrupted for women with preeclampsia (PE). Materials and Methods. Postal survey of the 112 members of the consumer group, Australian Action on Pre-Eclampsia (AAPEC). Results. Surveys were returned by 68 women (61% response rate) and from 64 (57%) partners, close relatives or friends. Respondents reported experiencing pre-eclampsia (n = 53), eclampsia (n = 5), and/or Hemolysis, Elevated Liver enzymes, and Low Platelets (HELLP syndrome) (n = 26). Many women had no knowledge of PE prior to diagnosis (77%) and, once diagnosed, did not appreciate how serious or life threatening it was (50%). Women wanted access to information about PE. Their experience contributed substantial anxiety towards future pregnancies. Partners/friends/relatives expressed fear for the woman and/or her baby and had no prior understanding of PE. Conclusions. The PE experience had a substantial effect on women, their confidants, and their babies and affected their approach to future pregnancies. Access to information about PE was viewed as very important
Shear modulus of the hadron-quark mixed phase
Robust arguments predict that a hadron-quark mixed phase may exist in the
cores of some "neutron" stars. Such a phase forms a crystalline lattice with a
shear modulus higher than that of the crust due to the high density and charge
separation, even allowing for the effects of charge screening. This may lead to
strong continuous gravitational-wave emission from rapidly rotating neutron
stars and gravitational-wave bursts associated with magnetar flares and pulsar
glitches. We present the first detailed calculation of the shear modulus of the
mixed phase. We describe the quark phase using the bag model plus first-order
quantum chromodynamics corrections and the hadronic phase using relativistic
mean-field models with parameters allowed by the most massive pulsar. Most of
the calculation involves treating the "pasta phases" of the lattice via
dimensional continuation, and we give a general method for computing
dimensionally continued lattice sums including the Debye model of charge
screening. We compute all the shear components of the elastic modulus tensor
and angle average them to obtain the effective (scalar) shear modulus for the
case where the mixed phase is a polycrystal. We include the contributions from
changing the cell size, which are necessary for the stability of the
lower-dimensional portions of the lattice. Stability also requires a minimum
surface tension, generally tens of MeV/fm^2 depending on the equation of state.
We find that the shear modulus can be a few times 10^33 erg/cm^3, two orders of
magnitude higher than the first estimate, over a significant fraction of the
maximum mass stable star for certain parameter choices.Comment: 22 pages, 12 figures, version accepted by Phys. Rev. D, with the
corrections to the shear modulus computation and Table I given in the erratu
Nonlinear Dynamics of Capacitive Charging and Desalination by Porous Electrodes
The rapid and efficient exchange of ions between porous electrodes and
aqueous solutions is important in many applications, such as electrical energy
storage by super-capacitors, water desalination and purification by capacitive
deionization (or desalination), and capacitive extraction of renewable energy
from a salinity difference. Here, we present a unified mean-field theory for
capacitive charging and desalination by ideally polarizable porous electrodes
(without Faradaic reactions or specific adsorption of ions) in the limit of
thin double layers (compared to typical pore dimensions). We illustrate the
theory in the case of a dilute, symmetric, binary electrolyte using the
Gouy-Chapman-Stern (GCS) model of the double layer, for which simple formulae
are available for salt adsorption and capacitive charging of the diffuse part
of the double layer. We solve the full GCS mean-field theory numerically for
realistic parameters in capacitive deionization, and we derive reduced models
for two limiting regimes with different time scales: (i) In the
"super-capacitor regime" of small voltages and/or early times where the porous
electrode acts like a transmission line, governed by a linear diffusion
equation for the electrostatic potential, scaled to the RC time of a single
pore. (ii) In the "desalination regime" of large voltages and long times, the
porous electrode slowly adsorbs neutral salt, governed by coupled, nonlinear
diffusion equations for the pore-averaged potential and salt concentration
Simulation studies of a phenomenological model for elongated virus capsid formation
We study a phenomenological model in which the simulated packing of hard,
attractive spheres on a prolate spheroid surface with convexity constraints
produces structures identical to those of prolate virus capsid structures. Our
simulation approach combines the traditional Monte Carlo method with a modified
method of random sampling on an ellipsoidal surface and a convex hull searching
algorithm. Using this approach we identify the minimum physical requirements
for non-icosahedral, elongated virus capsids, such as two aberrant flock house
virus (FHV) particles and the prolate prohead of bacteriophage , and
discuss the implication of our simulation results in the context of recent
experimental findings. Our predicted structures may also be experimentally
realized by evaporation-driven assembly of colloidal spheres
Paleoseismicity derived from piston coring methods, Explorer and Juan de Fuca Plate systems, Bristish Columbia
Coring of marine sediments has revealed deposits related to slope instability induced by seismicity on the western margin of Canada. Debris flows and turbidite sequences related to megathrust earthquakes have been recovered in six piston cores on the Juan de Fuca and Explorer tectonic plates, allowing comparison of the response of each plate to shaking during great earthquakes. Analyses of the recovered cores show that turbidite sequences associated with a megathrust quake occur on the Juan de Fuca Plate and do not occur in cores collected 90 km away at a similar site on the Explorer Plate. The record of subduction-related earthquake turbidite sequences is not complete at the Juan de Fuca study area and no reconstruction of megathrust quake periodicity is thus possible using this site alone. These results indicate that strong ground shaking is probably not experienced during large subduction earthquakes on the Explorer Plate
Measurement of Electron Trapping in the CESR Storage Ring
The buildup of low-energy electrons has been shown to affect the performance
of a wide variety of particle accelerators. Of particular concern is the
persistence of the cloud between beam bunch passages, which can impose
limitations on the stability of operation at high beam current. We have
obtained measurements of long-lived electron clouds trapped in the field of a
quadrupole magnet in a positron storage ring, with lifetimes much longer than
the revolution period. Based on modeling, we estimate that about 7% of the
electrons in the cloud generated by a 20-bunch train of 5.3 GeV positrons with
16-ns spacing and population survive longer than 2.3 s in a
quadrupole field of gradient 7.4 T/m. We have observed a non-monotonic
dependence of the trapping effect on the bunch spacing. The effect of a witness
bunch on the measured signal provides direct evidence for the existence of
trapped electrons. The witness bunch is also observed to clear the cloud,
demonstrating its effectiveness as a mitigation technique.Comment: 6 pages, 9 figures, 28 citation
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