6,595 research outputs found
Quark Masses and Renormalization Constants from Quark Propagator and 3-point Functions
We have computed the light and strange quark masses and the renormalization
constants of the quark bilinear operators, by studying the large-p^2 behaviour
of the lattice quark propagator and 3-point functions. The calculation is
non-perturbatively improved, at O(a), in the chiral limit. The method used to
compute the quark masses has never been applied so far, and it does not require
an explicit determination of the quark mass renormalization constant.Comment: LATTICE99 (Improvement and Renormalization) - 3 pages, 2 figure
The StEllar Counterparts of COmpact high velocity clouds (SECCO) survey. II. Sensitivity of the survey and an Atlas of Synthetic Dwarf Galaxies
SECCO is a survey devoted to the search for stellar counterparts within Ultra
Compact High Velocity Clouds. In this contribution we present the results of a
set of simulations aimed at the quantitative estimate of the sensitivity of the
survey as a function of the total luminosity, size and distance of the stellar
systems we are looking for. For all our synthetic galaxies we assumed an
exponential surface brightness profile and an old and metal-poor population.
The synthetic galaxies are simulated both on the images and on the photometric
catalogs, taking into account all the observational effects. In the fields
where the available observational material is of the top quality we detect
synthetic galaxies as >=5 sigma over-densities of resolved stars down to
muV,h=30.0 mag/arcsec2, for D<=1.5 Mpc, and down to muV,h~29.5 mag/arcsec2, for
D<=2.5 Mpc. In the field with the worst observational material of the whole
survey we detect synthetic galaxies with muV,h<=28.8 mag/arcsec2 out to D<=1.0
Mpc, and those with muV,h<=27.5 mag/arcsec2 out to D<=2.5 Mpc. Dwarf galaxies
with MV=-10, with sizes in the range spanned by known dwarfs, are detected by
visual inspection of the images up to D=5 Mpc independently of the image
quality. In the best quality images dwarfs are partially resolved into stars up
to D=3.0 Mpc, and completely unresolved at D=5 Mpc. As an independent test of
the sensitivity of our images to low surface brightness galaxies we report on
the detection of several dwarf spheroidal galaxies probably located in the
Virgo cluster with MV<=-8.0 and muV,h<=26.8 mag/arcsec2. The nature of the
previously discovered SECCO 1 stellar system, also likely located in the Virgo
cluster, is re-discussed in comparison with these dwarfs. While specific for
the SECCO survey, our study may also provide general guidelines for detection
of faint stellar systems with 8m class telescopes.Comment: accepted for publication on A&
Inferior turbinate osteoma: a rare cause of nasal obstruction
Osteoma of the nose is a rare and benign tumor that develop slowly.
We present an unusula and rare case
The low fertility trap hypothesis: Forces that may lead to further postponement and fewer births in Europe
This paper starts from the assessment that there is no good theory in the social
sciences that would tell us whether fertility in low-fertility countries is likely to
recover in the future, stay around its current level or continue to fall. This
question is key to the discussion whether or not governments should take action
aimed at influencing the fertility rate. To enhance the scholarly discussion in this
field, the paper introduces a clearly defined hypothesis which describes plausible
self-reinforcing mechanisms that would result, if unchecked, in a continued
decrease of the number of births in the countries affected. This hypothesis has
three components: a demographic one based on the negative population growth
momentum, i.e., the fact that fewer potential mothers in the future will result in
fewer births; a sociological one based on the assumption that ideal family size for
the younger cohorts is declining as a consequence of the lower actual fertility they
see in previous cohorts; and an economic one based on the first part of Easterlin\u2019s
(1980) relative income hypothesis, namely, that fertility results from the
combination of aspirations and expected income, and assuming that aspirations of
young adults are on an increasing trajectory while the expected income for the
younger cohorts declines, partly as a consequence of population ageing induced
by low fertility. All three factors would work towards a downward spiral in births
in the future. If there is reason to assume that such mechanisms will indeed be at
work, then this should strengthen the motivation of governments to take
immediate action (possibly through policies addressing the tempo effect) in order
to still escape from the expected trap
Observations of one young and three middle-aged -ray pulsars with the Gran Telescopio Canarias
We used the 10.4m Gran Telescopio Canarias to search for the optical
counterparts to four isolated -ray pulsars, all detected in the X-rays
by either \xmm\ or \chan\ but not yet in the optical. Three of them are
middle-aged pulsars -- PSR\, J1846+0919 (0.36 Myr), PSR\, J2055+2539 (1.2 Myr),
PSR\, J2043+2740 (1.2 Myr) -- and one, PSR\, J1907+0602, is a young pulsar
(19.5 kyr). For both PSR\, J1907+0602 and PSR\, J2055+2539 we found one object
close to the pulsar position. However, in both cases such an object cannot be a
viable candidate counterpart to the pulsar. For PSR\, J1907+0602, because it
would imply an anomalously red spectrum for the pulsar and for PSR\, J2055+2539
because the pulsar would be unrealistically bright () for the
assumed distance and interstellar extinction. For PSR\, J1846+0919, we found no
object sufficiently close to the expected position to claim a possible
association, whereas for PSR\, J2043+2740 we confirm our previous findings that
the object nearest to the pulsar position is an unrelated field star. We used
our brightness limits (), the first obtained with a
large-aperture telescope for both PSR\, J1846+0919 and PSR\, J2055+2539, to
constrain the optical emission properties of these pulsars and investigate the
presence of spectral turnovers at low energies in their multi-wavelength
spectra.Comment: 10 pages, 11 figures, accpted for publication in MNRA
A candidate optical counterpart to the middle-aged gamma-ray pulsar PSR J1741-2054
We carried out deep optical observations of the middle-aged -ray
pulsar PSR J1741-2054 with the Very Large Telescope (VLT). We identified two
objects, of magnitudes and , at positions
consistent with the very accurate Chandra coordinates of the pulsar, the
faintest of which is more likely to be its counterpart. From the VLT images we
also detected the known bow-shock nebula around PSR J1741-2054. The nebula is
displaced by \sim 0\farcs9 (at the confidence level) with respect
to its position measured in archival data, showing that the shock propagates in
the interstellar medium consistently with the pulsar proper motion. Finally, we
could not find evidence of large-scale extended optical emission associated
with the pulsar wind nebula detected by Chandra, down to a surface brightness
limit of magnitudes arcsec. Future observations are needed
to confirm the optical identification of PSR J1741-2054 and characterise the
spectrum of its counterpart.Comment: 8 pages, 3 figures, Astrophysical Journal, in pres
Superoxide reductase from Giardia intestinalis: structural characterization of the first sor from a eukaryotic organism shows an iron centre that is highly sensitive to photoreduction
Superoxide reductase (SOR), which is commonly found in prokaryotic organisms, affords protection from oxidative stress by reducing the superoxide anion to hydrogen peroxide. The reaction is catalyzed at the iron centre, which is highly conserved among the prokaryotic SORs structurally characterized to date. Reported here is the first structure of an SOR from a eukaryotic organism, the protozoan parasite Giardia intestinalis (GiSOR), which was solved at 2.0 Å resolution. By collecting several diffraction data sets at 100 K from the same flash-cooled protein crystal using synchrotron X-ray radiation, photoreduction of the iron centre was observed. Reduction was monitored using an online UV-visible microspectrophotometer, following the decay of the 647 nm absorption band characteristic of the iron site in the glutamate-bound, oxidized state. Similarly to other 1Fe-SORs structurally characterized to date, the enzyme displays a tetrameric quaternary-structure arrangement. As a distinctive feature, the N-terminal loop of the protein, containing the characteristic EKHxP motif, revealed an unusually high flexibility regardless of the iron redox state. At variance with previous evidence collected by X-ray crystallography and Fourier transform infrared spectroscopy of prokaryotic SORs, iron reduction did not lead to dissociation of glutamate from the catalytic metal or other structural changes; however, the glutamate ligand underwent X-ray-induced chemical changes, revealing high sensitivity of the GiSOR active site to X-ray radiation damage
A study of rainfall in the Roman area in the years 1951--2000
The daily rainfall data collected in the second half of the last century at 31 climatic stations in Lazio, Italy, have been subjected to statistical analysis in order to describe the pluviometric regime of the whole area on a multi-decadal time scale. The stations, for their geographical distribution within the region under study, are apt to represent different climatic zones, namely, a coastal, a rural, a suburban and an urban zone. The data have been treated both as time series and as geographicalstatisticalv
ariates with the double aim, first, to verify if in the area under study any changes in the yearly precipitation rate, frequency and its distribution over different classes of rain intensity, have occurred in the last 50 years; second, to evidence a possible correlation between the intensity of precipitation and any of some environmental variables such as altitude, distance from the coastline and
distance from the urban site. As for the first issue, it can be concluded that the precipitations over the Roman area in the period 1951–2000 show no significant trend; in particular, no trend is visible in any of the single classes of rain intensity, both absolute and percentile-based, considering either their frequency or their percent
contribution to the total. As for the second issue, significant correlations have been found in the spatial distribution of rainfall with any of the relevant environmental variables mentioned above. The results of the analysis also show that in the urban area a less amount of rain seem to fall than in the surroundings zones, a result that seems rather anomalous in consideration of the several known factors that favour the intensification of the rainfall in the city with respect to its surroundings. A detailed statistical characterization of all the single 31 stations over the whole period is also given via a separate study of the durations of droughts and of the statistics of rainy days, using best fits based on the Weibull probability distribution
Effectiveness of communicative and educative strategies in chronic low back pain patients: A systematic review
Objective: To investigate the effectiveness of communicative and educative strategies on 1) patient's low back pain awareness/knowledge, 2) maladaptive behavior modification and 3) compliance with exercise in patients with chronic low back pain. Methods: A systematic review was conducted. Searches were performed on 13 databases. Only randomized controlled trials enrolling patients 65 18 years of age were included. Risk of bias was assessed with the Cochrane Collaboration's tool and interrater agreement between authors for full-texts selection was evaluated with Cohen's Kappa. No meta-analysis was performed and qualitative analysis was conducted. Results: 24 randomized controlled trials which intervention included communicative and educative strategies were selected. Most of the studies were judged as low risk of bias and Cohen's Kappa was excellent ( = 0.822). Interventions addressed were cognitive behavioral therapy as unique treatment or combined with other treatments (multimodal interventions), coaching, mindfulness, pain science education, self-management, graded activity and graded exposure. Conclusions, practice implication: Patient's low back pain awareness/knowledge is still a grey area of literature. Pain science education, graded exposure and multimodal interventions are the most effective for behavior modification and compliance with exercise with benefits also in the long-term, while self-management, graded activity and coaching provide only short-term or no benefits
The distance to the LMC cluster Reticulum from the K-band Period-Luminosity-Metallicity relation of RR Lyrae stars
We present new and accurate Near-Infrared J and Ks-band data of the Large
Magellanic Cloud cluster Reticulum. Data were collected with SOFI available at
NTT and covering an area of approximately (5 x 5) arcmin^2 around the center of
the cluster. Current data allowed us to derive accurate mean K-band magnitudes
for 21 fundamental and 9 first overtone RR Lyrae stars. On the basis of the
semi-empirical K-band Period-Luminosity-Metallicity relation we have recently
derived, we find that the absolute distance to this cluster is 18.52 +- 0.005
(random) +- 0.117 (systematic). Note that the current error budget is dominated
by systematic uncertainty affecting the absolute zero-point calibration and the
metallicity scale.Comment: 14 pages, 2 figures, ApJ accepted. Full resolution figure 1 on
request ([email protected]
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