2,947 research outputs found
Timing of a Young Mildly Recycled Pulsar with a Massive White Dwarf Companion
We report on timing observations of the recently discovered binary pulsar PSR
J1952+2630 using the Arecibo Observatory. The mildly recycled 20.7-ms pulsar is
in a 9.4-hr orbit with a massive, M_WD > 0.93 M_sun, white dwarf (WD)
companion. We present, for the first time, a phase-coherent timing solution,
with precise spin, astrometric, and Keplerian orbital parameters. This shows
that the characteristic age of PSR J1952+2630 is 77 Myr, younger by one order
of magnitude than any other recycled pulsar-massive WD system. We derive an
upper limit on the true age of the system of 50 Myr. We investigate the
formation of PSR J1952+2630 using detailed modelling of the mass-transfer
process from a naked helium star on to the neutron star following a
common-envelope phase (Case BB Roche-lobe overflow). From our modelling of the
progenitor system, we constrain the accretion efficiency of the neutron star,
which suggests a value between 100 and 300% of the Eddington accretion limit.
We present numerical models of the chemical structure of a possible
oxygen-neon-magnesium WD companion. Furthermore, we calculate the past and the
future spin evolution of PSR J1952+2630, until the system merges in about 3.4
Gyr due to gravitational wave emission. Although we detect no relativistic
effects in our timing analysis we show that several such effects will become
measurable with continued observations over the next 10 years; thus PSR
J1952+2630 has potential as a testbed for gravitational theories.Comment: 12 pages, 10 figures, to be published in MNRA
Timing of a Young Mildly Recycled Pulsar with a Massive White Dwarf Companion
We report on timing observations of the recently discovered binary pulsar PSR J1952+2630 using the Arecibo Observatory. The mildly recycled 20.7-ms pulsar is in a 9.4-hr orbit with a massive, M_WD > 0.93 M_sun, white dwarf (WD) companion. We present, for the first time, a phase-coherent timing solution, with precise spin, astrometric, and Keplerian orbital parameters. This shows that the characteristic age of PSR J1952+2630 is 77 Myr, younger by one order of magnitude than any other recycled pulsar-massive WD system. We derive an upper limit on the true age of the system of 50 Myr. We investigate the formation of PSR J1952+2630 using detailed modelling of the mass-transfer process from a naked helium star on to the neutron star following a common-envelope phase (Case BB Roche-lobe overflow). From our modelling of the progenitor system, we constrain the accretion efficiency of the neutron star, which suggests a value between 100 and 300% of the Eddington accretion limit. We present numerical models of the chemical structure of a possible oxygen-neon-magnesium WD companion. Furthermore, we calculate the past and the future spin evolution of PSR J1952+2630, until the system merges in about 3.4 Gyr due to gravitational wave emission. Although we detect no relativistic effects in our timing analysis we show that several such effects will become measurable with continued observations over the next 10 years; thus PSR J1952+2630 has potential as a testbed for gravitational theories
Calculating all elements of minimal index in the infinite parametric family of simplest quartic fields
summary:It is a classical problem in algebraic number theory to decide if a number field is monogeneous, that is if it admits power integral bases. It is especially interesting to consider this question in an infinite parametric family of number fields. In this paper we consider the infinite parametric family of simplest quartic fields generated by a root of the polynomial , assuming that , and has no odd square factors. In addition to generators of power integral bases we also calculate the minimal index and all elements of minimal index in all fields in this family
Regular Consumption of a Flavanol-rich Chocolate can Improve Oxidant Stress in Young Soccer Players
The consumption of a diet rich in certain flavonoids, including the flavanol
sub-class, has been associated with a reduced risk for vascular disease. We
evaluated the effects of the regular consumption (14 d) of a flavanol-containing
milk chocolate (FCMC) or cocoa butter chocolate (CBC) on variables related to
vascular disease risk, oxidative stress and physical activity. Twenty-eight free-living,
young (18–20 years old) male soccer players consumed daily 105 g of FCMC
(168 mg of flavanols) or CBC (<5 mg of flavanols), as part of their normal diet.
The consumption of FCMC was significantly associated with a decrease in diastolic
blood pressure (-5 mm Hg), mean blood pressure (-5 mm Hg), plasma cholesterol
(-11%), LDL-cholesterol (-15%), malondialdehyde (-12%), urate (-11%) and lactate
dehydrogenase (LDH) activity (-11%), and an increase in vitamin E/cholesterol
(+12%). No relevant changes in these variables were associated with CBC
consumption. No changes in the plasma levels of (-)-epicatechin were observed
following analysis of fasting blood samples. In conclusion, FCMC consumption was
associated with changes in several variables often associated with cardiovascular
health and oxidant stress. The presence of significant quantities of
flavanols in FCMC is likely to have been one of the contributing factors to these results
An Eccentric Binary Millisecond Pulsar in the Galactic Plane
Binary pulsar systems are superb probes of stellar and binary evolution and
the physics of extreme environments. In a survey with the Arecibo telescope, we
have found PSR J1903+0327, a radio pulsar with a rotational period of 2.15 ms
in a highly eccentric (e = 0.44) 95-day orbit around a solar mass companion.
Infrared observations identify a possible main-sequence companion star.
Conventional binary stellar evolution models predict neither large orbital
eccentricities nor main-sequence companions around millisecond pulsars.
Alternative formation scenarios involve recycling a neutron star in a globular
cluster then ejecting it into the Galactic disk or membership in a hierarchical
triple system. A relativistic analysis of timing observations of the pulsar
finds its mass to be 1.74+/-0.04 Msun, an unusually high value.Comment: 28 pages, 4 figures inc Supplementary On-Line Material. Accepted for
publication in Science, published on Science Express: 10.1126/science.115758
AGATA, Technical Proposal for an Advanced Gamma Tracking Array for the European Gamma Spectroscopy Community
International audienceAn Advanced GAmma-ray Tracking Array, AGATA, is proposed for high-resolution γ-ray spectroscopy with exotic beams. AGATA will employ highly segmented Ge detectors as well as fully digital electronics and relies on newly developed pulse-shape analysis and tracking methods. The array is being designed in a way that it provides optimal properties for nuclear structure experiments in a wide range of beam velocities (from stopped to v/c ≈ 50%), almost independent of beam quality and background conditions. Selectivity and sensitivity of AGATA will be superior to any existing γ-array by several orders of magnitude. Hence, it will be for a long time a rich source for nuclear structure physics providing the means for new discoveries and opening challenging new perspectives. This document is the initial proposal sent to the European Commission to obtain the necessary funds for the project
Emotions and Digital Well-being. The rationalistic bias of social media design in online deliberations
In this chapter we argue that emotions are mediated in an incomplete way in online social media because of the heavy reliance on textual messages which fosters a rationalistic bias and an inclination towards less nuanced emotional expressions. This incompleteness can happen either by obscuring emotions, showing less than the original intensity, misinterpreting emotions, or eliciting emotions without feedback and context. Online interactions and deliberations tend to contribute rather than overcome stalemates and informational bubbles, partially due to prevalence of anti-social emotions. It is tempting to see emotions as being the cause of the problem of online verbal aggression and bullying. However, we argue that social media are actually designed in a predominantly rationalistic way, because of the reliance on text-based communication, thereby filtering out social emotions and leaving space for easily expressed antisocial emotions. Based on research on emotions that sees these as key ingredients to moral interaction and deliberation, as well as on research on text-based versus non-verbal communication, we propose a richer understanding of emotions, requiring different designs of online deliberation platforms. We propose that such designs should move from text-centred designs and should find ways to incorporate the complete expression of the full range of human emotions so that these can play a constructive role in online deliberations
Sensitive Search for a Permanent Muon Electric Dipole Moment
We are proposing a new method to carry out a dedicated search for a permanent
electric dipole moment (EDM) of the muon with a sensitivity at a level of
10^{-24} e cm. The experimental design exploits the strong motional electric
field sensed by relativistic particles in a magnetic storage ring. As a key
feature, a novel technique has been invented in which the g-2 precession is
compensated with radial electric field. This technique will benefit greatly
when the intense muon sources advocated by the developers of the muon storage
rings and the muon colliders become available.Comment: 16 pages, 3 figures. Submitted for publication in Proceedings of the
International Workshop on High Intensity Muon Sources (HIMUS99), KEK, Japan,
December 1-4 199
Formation of plasma around a small meteoroid: 1. Kinetic theory
This article is a companion to Dimant and Oppenheim [2017] https://doi.org/10.1002/2017JA023963.This paper calculates the spatial distribution of the plasma responsible for radar head echoes by applying the kinetic theory developed in the companion paper. This results in a set of analytic expressions for the plasma density as a function of distance from the meteoroid. It shows that at distances less than a collisional mean free path from the meteoroid surface, the plasma density drops in proportion to 1/R where R is the distance from the meteoroid center; and, at distances much longer than the mean‐free‐path behind the meteoroid, the density diminishes at a rate proportional to 1/R2. The results of this paper should be used for modeling and analysis of radar head echoes.This work was supported by NSF grant AGS-1244842. (AGS-1244842 - NSF
Fenestration of the vertebrobasilar junction detected with multidetector computed tomography angiography
The complex embryonic origin of the vertebrobasilar system may result in a wide range of anatomical variations. It has been hypothesized that the formation of fenestrations are likely to occur due to the failure of regression of the bridging arteries that connect the longitudinal neural arteries during embryogenesis. Fenestration of the vertebrobasilar system is a rare anatomical variation that involves a luminal division of the artery, that has a single origin into two separate and parallel channels which are rejoined distally. Fenestrations are important anatomical variants in patients undergoing endovascular and invasive intracranial interventions. Vascular fenestration has been associated with aneurysms, arteriovenous malformations, neuralgia, and vertebrobasilar ischaemia. We report on 3 cases of fenestration at the vertebrobasilar junction in 1 female and 2 male patients, respectively, using multidetector computed tomography angiography. The length of the fenestrated segment of the artery measured 4.41 mm, 3.90 mm, and 5.90 mm, respectively in the patients. Our report is clinically important as the presence of this anatomical variation may influence the management of cervical and intracranial pathologies. Increased awareness of the prevalence of anatomic variations contributes to the advancement of noninvasive imaging capabilities
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