16,665 research outputs found
The equation of state of neutron matter, symmetry energy, and neutron star structure
We review the calculation of the equation of state of pure neutron matter
using quantum Monte Carlo (QMC) methods. QMC algorithms permit the study of
many-body nuclear systems using realistic two- and three-body forces in a
nonperturbative framework. We present the results for the equation of state of
neutron matter, and focus on the role of three-neutron forces at supranuclear
density. We discuss the correlation between the symmetry energy, the neutron
star radius and the symmetry energy. We also combine QMC and theoretical models
of the three-nucleon interactions, and recent neutron star observations to
constrain the value of the symmetry energy and its density dependence.Comment: 11 pages, 11 figure
Dynamic scaling and universality in evolution of fluctuating random networks
We found that models of evolving random networks exhibit dynamic scaling
similar to scaling of growing surfaces. It is demonstrated by numerical
simulations of two variants of the model in which nodes are added as well as
removed [Phys. Rev. Lett. 83, 5587 (1999)]. The averaged size and connectivity
of the network increase as power-laws in early times but later saturate.
Saturated values and times of saturation change with paramaters controlling the
local evolution of the network topology. Both saturated values and times of
saturation obey also power-law dependences on controlling parameters. Scaling
exponents are calculated and universal features are discussed.Comment: 7 pages, 6 figures, Europhysics Letters for
Comparing persistence diagrams through complex vectors
The natural pseudo-distance of spaces endowed with filtering functions is
precious for shape classification and retrieval; its optimal estimate coming
from persistence diagrams is the bottleneck distance, which unfortunately
suffers from combinatorial explosion. A possible algebraic representation of
persistence diagrams is offered by complex polynomials; since far polynomials
represent far persistence diagrams, a fast comparison of the coefficient
vectors can reduce the size of the database to be classified by the bottleneck
distance. This article explores experimentally three transformations from
diagrams to polynomials and three distances between the complex vectors of
coefficients.Comment: 11 pages, 4 figures, 2 table
Transient jets in V617 Sagittarii
Some of the luminous Compact Binary Supersoft X-Ray sources (CBSS) have shown
indications of jets, also called satellites due to their appearance in the
spectra. In V Sagittae (V Sge) stars, the galactic counterparts of the CBSS,
such features have been reported only for WX Cen. If V Sge stars are indeed the
analogs of CBSS, one may expect transient jet emission in other objects of this
class. Spectroscopic observations of the V Sge star V617 Sgr have been made,
both at high photometric state and at decline. We show that V617 Sgr presents
Halpha satellites at high photometric state with velocities of +/-780 km/s.
This feature confirms, once more, the CBSS nature of the V Sge stars, however
the details of the spectral characteristics also suggest that the two groups of
stars display some intrinsic spectroscopic differences, which are likely to be
due to a selection effect related to chemical abundance.Comment: Four pages, accepted to be published as a Letter in A&
Odour reduction of manure through addition of boracic charcoal
ArticleOdours released during the land application of manure results from different gases
released from the liquid phase. These gases do create objectionable odours in the vicinity of the
land
-
applied manure. In order to reduce the intensity of odour durin
g manure application, we
investigated the effectiveness of combining Borkohle with manure during land application.
Boracic acid is widely used as a flame retardant in cellulose insulation. During demolition of
existing buildings, this insulation is sorted
into its own residual waste fraction. The cellulose
fibres are extracted and pelletized on site. Subsequently, the pellets are charred in a pyrolysis
furnace. The resulting Borkohle
–
charcoal containing boron in various compounds
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can be used
as a soil e
nhancer and provides the trace element Boron to the fields. Furthermore, Borkohle
provides long
-
term storage of carbon in the soil. Initial trials of combining boracic charcoal with
manure additionally showed that odour emissions seemed to be significantly
lower when manure
was combined with
Borkohle.
This work presents methods to quantify the odour reductions resulting from the addition of
Borkohle to manure as well as first results. Parameters like the influence of the amount of charcoal
added and exposur
e time have been investigated.
Charcoal was added at concentrations between 5 and 250
g
L
-
1
. While applying typical amounts
of charcoal, a reduction of odour concentration of up to 85% was observed
. A positive correlation
between odour reduction and the amount of charcoal added was observed. Charcoal has a
negligible effect when exposure
times are less than 30 minutes
Possible field-tuned SIT in high-Tc superconductors: implications for pairing at high magnetic fields
The behavior of some high temperature superconductors (HTSC) such as and , at very high
magnetic field, is similar to that of thin films of amorphous InOx near the
magnetic field-tuned superconductor-insulator transition. Analyzing the InOx
data at high fields in terms of persisting local pairing amplitude, we argue by
analogy that local pairing amplitude also persists well into the dissipative
state of the HTSCs, the regime commonly denoted as the "normal state" in very
high magnetic field experiments.Comment: Revised figures and reference
Stellar archeology of the nearby LINER galaxies NGC 4579 and NGC 4736
Stellar archeology of nearby LINER galaxies may reveal if there is a stellar
young population that may be responsible for the LINER phenomenon. We show
results for the classical LINER galaxies NGC 4579 and NGC 4736 and find no
evidence of such populations.Comment: 2 pages, 2 figures, to be published in the Proceedings of the IAU
Symposium no. 26
Mapping low and high density clouds in astrophysical nebulae by imaging forbidden line emission
Emission line ratios have been essential for determining physical parameters
such as gas temperature and density in astrophysical gaseous nebulae. With the
advent of panoramic spectroscopic devices, images of regions with emission
lines related to these physical parameters can, in principle, also be produced.
We show that, with observations from modern instruments, it is possible to
transform images taken from density sensitive forbidden lines into images of
emission from high and low-density clouds by applying a transformation matrix.
In order to achieve this, images of the pairs of density sensitive lines as
well as the adjacent continuum have to be observed and combined. We have
computed the critical densities for a series of pairs of lines in the infrared,
optical, ultraviolet and X-rays bands, and calculated the pair line intensity
ratios in the high and low-density limit using a 4 and 5 level atom
approximation. In order to illustrate the method we applied it to GMOS-IFU data
of two galactic nuclei. We conclude that this method provides new information
of astrophysical interest, especially for mapping low and high-density clouds;
for this reason we call it "the ld/hd imaging method".Comment: 7 pages, 4 figures, accepted for publication on MNRA
Structured education can improve primary-care management of headache: the first empirical evidence, from a controlled interventional study
Headache disorders are under-recognized and under-diagnosed. A principal factor in their suboptimal management is lack of headache-related training among health-care providers, especially in primary care. In Estonia, general practitioners (GPs) refer many headache patients to neurological specialist services, mostly unnecessarily. GPs request diagnostic investigations, which are usually unhelpful and therefore wasteful. GP-made headache diagnoses are often arcane and non-specific, and treatments based on these are inappropriate. The aim of this study was to develop, implement and test an educational model intended to improve headache-related primary health care in Estonia.This was a controlled study consisting of baseline observation, intervention and follow-up observation using the same measures of effect. It involved six GPs in Põlva and the surrounding region in Southern Estonia, together with their future patients presenting consecutively with headache as their main complaint, all with their consent. The primary outcome measure was referral rate (RR) to neurological specialist services. Secondary measures included number of GP-requested investigations, GP-made headache diagnoses and how these conformed to standard terminology (ICD-10), and GP-recommended or initiated treatments.RR at baseline (n = 490) was 39.5 %, falling to 34.7 % in the post-intervention group (n = 295) (overall reduction 4.8 %; p = 0.21). In the large subgroup of patients (88 %) for whom GPs made clearly headache-related ICD-10 diagnoses, RR fell by one fifth (from 40 to 32 %; p = 0.08), but the only diagnosis-related RR that showed a statistically significant reduction was (pericranial) myalgia (19 to 3 %; p = 0.03). There was a significant increase towards use of more specific diagnoses. Use of investigations in diagnosing headache reduced from 26 to 4 % (p < 0.0001). Initiation of treatment by GPs increased from 58 to 81 % (p < 0.0001).These were modest changes in GPs entrenched behaviour. Nevertheless they were empirical evidence that GPs practice in the field of headache could be improved by structured education. Furthermore, the changes were likely to be cost-saving. To our knowledge this study is the first to produce such evidence
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