509 research outputs found
Status of the standard vector—axial-vector model for nuclear beta decay
The complete set of experimental results on correlations in nuclear beta decay is analyzed in terms of the general Hamiltonian including scalar, vector, axial vector, and tensor interactions with an arbitrary degree of parity violation. It is concluded that the standard vector minus axial-vector model with maximal parity violation (left-handed lepton current) is compatible with the data and rigorous limits are obtained for the values of possible additional coupling constants. In the scalar and tensor case the new constraints are considerably tighter than those published before: |CS / CV| and |CS′ / CV|≤0.2, |(CS+CS′) / CV|≤0.06; |CT / CA| and |CT′ / CA|≤0.09, |(CT+CT′) / CA|≤0.01, all at the 95% confidence level. On the other hand, rather large admixtures of the right-handed lepton currents (CV′ / CV≠1 or CA′ / CA≠1) are allowed by the data. An analysis of the correlations between various coupling constants implied by the data is also performed
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Public health implications of milk fats: the current evidence base and future directions
Equilibrium Configurations of Strongly Magnetized Neutron Stars with Realistic Equations of State
We investigate equilibrium sequences of magnetized rotating stars with four
kinds of realistic equations of state (EOSs) of SLy (Douchin et al.), FPS
(Pandharipande et al.), Shen (Shen et al.), and LS (Lattimer & Swesty).
Employing the Tomimura-Eriguchi scheme to construct the equilibrium
configurations. we study the basic physical properties of the sequences in the
framework of Newton gravity. In addition we newly take into account a general
relativistic effect to the magnetized rotating configurations. With these
computations, we find that the properties of the Newtonian magnetized stars,
e.g., structure of magnetic field, highly depends on the EOSs.
The toroidal magnetic fields concentrate rather near the surface for Shen and
LS EOSs than those for SLy and FPS EOSs. The poloidal fields are also affected
by the toroidal configurations. Paying attention to the stiffness of the EOSs,
we analyze this tendency in detail. In the general relativistic stars, we find
that the difference due to the EOSs becomes small because all the employed EOSs
become sufficiently stiff for the large maximum density, typically greater than
. The maximum baryon mass of the magnetized stars
with axis ratio increases about up to twenty percents for that of
spherical stars. We furthermore compute equilibrium sequences at finite
temperature, which should serve as an initial condition for the hydrodynamic
study of newly-born magnetars. Our results suggest that we may obtain
information about the EOSs from the observation of the masses of magnetars.Comment: submitted to MNRA
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Reformulation initiative for partial replacement of saturated with unsaturated fats in dairy foods attenuates the increase in LDL cholesterol and improves flow-mediated dilatation compared with conventional dairy: the randomized, controlled REplacement of SaturatEd fat in dairy on Total cholesterol (RESET) study
Background
Modifying dairy fat composition by increasing the MUFA content is a potential strategy to reduce dietary SFA intake for cardiovascular disease (CVD) prevention in the population.
Objectives
To determine the effects of consuming SFA-reduced, MUFA-enriched (modified) dairy products, compared with conventional dairy products (control), on the fasting cholesterol profile (primary outcome), endothelial function assessed by flow-mediated dilatation (FMD; key secondary outcome), and other cardiometabolic risk markers.
Methods
A double-blind, randomized, controlled crossover 12-wk intervention was conducted. Participants with a 1.5-fold higher (moderate) CVD risk than the population mean replaced habitual dairy products with study products (milk, cheese, and butter) to achieve a high-fat, high-dairy isoenergetic daily dietary exchange [38% of total energy intake (%TE) from fat: control (dietary target: 19%TE SFA; 11%TE MUFA) and modified (16%TE SFA; 14%TE MUFA) diet].
Results
Fifty-four participants (57.4% men; mean ± SEM age: 52 ± 3 y; BMI: 25.8 ± 0.5 kg/m2) completed the study. The modified diet attenuated the rise in fasting LDL cholesterol observed with the control diet (0.03 ± 0.06 mmol/L and 0.19 ± 0.05 mmol/L, respectively; P = 0.03). Relative to baseline, the %FMD response increased after the modified diet (0.35% ± 0.15%), whereas a decrease was observed after the control diet (−0.51% ± 0.15%; P< 0.0001). In addition, fasting plasma nitrite concentrations increased after the modified diet, yet decreased after the control diet (0.02 ± 0.01 μmol/L and −0.03 ± 0.02 μmol/L, respectively; P = 0.01).
Conclusions
In adults at moderate CVD risk, consumption of a high-fat diet containing SFA-reduced, MUFA-enriched dairy products for 12 wk showed beneficial effects on fasting LDL cholesterol and endothelial function compared with conventional dairy products. Our findings indicate that fatty acid modification of dairy products may have potential as a public health strategy aimed at CVD risk reduction. This trial was registered at clinicaltrials.gov as NCT02089035
Maximum gravitational-wave energy emissible in magnetar flares
Recent searches of gravitational-wave (GW) data raise the question of what
maximum GW energies could be emitted during gamma-ray flares of highly
magnetized neutron stars (magnetars). The highest energies (\sim 10^{49} erg)
predicted so far come from a model [K. Ioka, Mon. Not. Roy. Astron. Soc. 327,
639 (2001)] in which the internal magnetic field of a magnetar experiences a
global reconfiguration, changing the hydromagnetic equilibrium structure of the
star and tapping the gravitational potential energy without changing the
magnetic potential energy. The largest energies in this model assume very
special conditions, including a large change in moment of inertia (which was
observed in at most one flare), a very high internal magnetic field, and a very
soft equation of state. Here we show that energies of 10^{48}-10^{49} erg are
possible under more generic conditions by tapping the magnetic energy, and we
note that similar energies may also be available through cracking of exotic
solid cores. Current observational limits on gravitational waves from magnetar
fundamental modes are just reaching these energies and will beat them in the
era of advanced interferometers.Comment: 16 pages, 5 figures, 1 tabl
Are there any stable magnetic fields in barotropic stars?
We construct barotropic stellar equilibria, containing magnetic fields with
both poloidal and toroidal field components. We extend earlier results by
exploring the effect of different magnetic field and current distributions. Our
results suggest that the boundary treatment plays a major role in whether the
poloidal or toroidal field component is globally dominant. Using time
evolutions we provide the first stability test for mixed poloidal-toroidal
fields in barotropic stars, finding that all these fields suffer instabilities
due to one of the field components: these are localised around the pole for
toroidal-dominated equilibria and in the closed-field line region for
poloidal-dominated equilibria. Rotation provides only partial stabilisation.
There appears to be very limited scope for the existence of stable magnetic
fields in barotropic stars. We discuss what additional physics from real stars
may allow for stable fields.Comment: 16 pages, 11 figures. Some minor revision from v1, including a new
figure; results unchanged. Now published in MNRA
On non-axisymmetric magnetic equilibria in stars
In previous work stable approximately axisymmetric equilibrium configurations
for magnetic stars were found by numerical simulation. Here I investigate the
conditions under which more complex, non-axisymmetric configurations can form.
I present numerical simulations of the formation of stable equilibria from
turbulent initial conditions and demonstrate the existence of non-axisymmetric
equilibria consisting of twisted flux tubes lying horizontally below the
surface of the star, meandering around the star in random patterns. Whether
such a non-axisymmetric equilibrium or a simple axisymmetric equilibrium forms
depends on the radial profile of the strength of the initial magnetic field.
The results could explain observations of non-dipolar fields on stars such as
the B0.2 main-sequence star tau-Sco or the pulsar 1E 1207.4-5209. The secular
evolution of these equilibria due to Ohmic and buoyancy processes is also
examined.Comment: 13 pages, 12 figures. Accepted by MNRA
Evolution of low-mass star and brown dwarf eclipsing binaries
We examine the evolution of low-mass star and brown dwarf eclipsing binaries.
These objects are rapid rotators and are believed to shelter large magnetic
fields. We suggest that reduced convective efficiency, due to fast rotation and
large field strengths, and/or to magnetic spot coverage of the radiating
surface significantly affect their evolution, leading to a reduced heat flux
and thus larger radii and cooler effective temperatures than for regular
objects. We have considered such processes in our evolutionary calculations,
using a phenomenological approach. This yields mass-radius and effective
temperature-radius relationships in agreement with the observations. We also
reproduce the effective temperature ratio and the radii of the two components
of the recently discovered puzzling eclipsing brown dwarf system. These
calculations show that fast rotation and/or magnetic activity may significantly
affect the evolution of eclipsing binaries and that the mechanical and thermal
properties of these objects depart from the ones of non-active low-mass
objects. We find that, for internal field strengths compatible with the
observed surface value of a few kiloGauss, convection can be severely
inhibited. The onset of a central radiative zone for rapidly rotating active
low-mass stars might thus occur below the usual \sim 0.35 \msol limit.Comment: to appear in A&A Letter
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