22,341 research outputs found
Current trends among pediatric ophthalmologists to decrease myopia progression—an international perspective
Purpose
To explore what the current worldwide preferred practice patterns of pediatric ophthalmologists are to decrease myopia progression among their patients.
Methods
A questionnaire was sent to all members of supranational and national pediatric ophthalmology and strabismus societies.
Results
The questionnaire was fully completed by most respondents 90.10% (847 of 940 responses). Fifty-seven percent (457) routinely treat to decrease myopia progression. The most common parameter to initiate treatment was a myopic increase of 1 diopter/year or more (74.8%, 246). Seventy percent (345) prescribed eye drops. Atropine 0.01% was the most popular (63.4%, 277) followed by atropine 1% (10.9%, 48) and atropine 0.5% (8.9%, 39). Eighty-six percent (394) of the respondents advised to spend more time outdoors, to reduce the amount of time viewing screens (60.2%, 277), and cutback the use of smart phones (63.9%, 294).
Conclusions
Most pediatric ophthalmologists treat to decrease myopia. They employ a wide variety of means to decrease myopia progression. Atropine 0.01% is the most popular and safe modality used similarly to recent reports. However, there is no consensus when treatment should be initiated. Further prospective studies are needed to elucidate the best timing to start treatment and the applicability of recent studies in the Asian population to other ethnic groups. This will improve the ability to update pediatric ophthalmologist with evidenced-based treatment options to counter the myopia epidemic
Minimal Stability in Maximal Supergravity
Recently, it has been shown that maximal supergravity allows for
non-supersymmetric AdS critical points that are perturbatively stable. We
investigate this phenomenon of stability without supersymmetry from the
sGoldstino point of view. In particular, we calculate the projection of the
mass matrix onto the sGoldstino directions, and derive the necessary conditions
for stability. Indeed we find a narrow window allowing for stable SUSY breaking
points. As a by-product of our analysis, we find that it seems impossible to
perturb supersymmetric critical points into non-supersymmetric ones: there is a
minimal amount of SUSY breaking in maximal supergravity.Comment: 27 pages, 1 figure. v2: two typos corrected, published versio
Multifractal detrended fluctuation analysis of rainfall time series in the Guadeloupe archipelago
Due to the vulnerability of the Caribbean islands to the climate change
issue, it is important to investigate the behavior of rainfall. In addition,
the soil of the French West Indies Islands has been contaminated by an
insecticide (Chlordecone) whose decontamination is mainly done by drainage
water. Thus, it is crucial to investigate the fluctuations of rainfall in these
complex environments. In this study, 19 daily rainfall series recorded in
different stations of Guadeloupe archipelago from 2005 to 2014 were analyzed
with the multifractal detrended fluctuation analysis (MF-DFA) method. The aim
of this work is to characterize the long-range correlations and multifractal
properties of the time series and to find geographical patterns over the three
most important islands. This is the first study that addresses the analysis of
multifractal properties of rainfall series in the Caribbean islands. This
region is typically characterized by the almost constant influence of the trade
winds and a high exposure to changes in the general atmospheric circulation. 12
stations exhibit two different power-law scaling regions in rainfall series,
with distinct long-range correlations and multifractal properties for large and
small scales. On the contrary, the rest of stations only show a single region
of scales for relatively small scales. Hurst exponents reveal persistent
long-range correlations. In the most eastern analyzed areas, larger scales
exhibit higher persistence than smaller scales, which suggests a relationship
between persistence and the highest exposure to the trade winds. Stronger
conclusions can be drawn from multifractal spectra, which indicate that most
rainfall series have a multifractal nature with higher complexity and degree of
multifractality at the smallest scales. Furthermore, a clear dependence of
multifractal nature on the latitude is revealed.Comment: 43 pages. 11 figure
Effects of heavy modes on vacuum stability in supersymmetric theories
We study the effects induced by heavy fields on the masses of light fields in
supersymmetric theories, under the assumption that the heavy mass scale is much
higher than the supersymmetry breaking scale. We show that the square-masses of
light scalar fields can get two different types of significant corrections when
a heavy multiplet is integrated out. The first is an indirect level-repulsion
effect, which may arise from heavy chiral multiplets and is always negative.
The second is a direct coupling contribution, which may arise from heavy vector
multiplets and can have any sign. We then apply these results to the sGoldstino
mass and study the implications for the vacuum metastability condition. We find
that the correction from heavy chiral multiplets is always negative and tends
to compromise vacuum metastability, whereas the contribution from heavy vector
multiplets is always positive and tends on the contrary to reinforce it. These
two effects are controlled respectively by Yukawa couplings and gauge charges,
which mix one heavy and two light fields respectively in the superpotential and
the Kahler potential. Finally we also comment on similar effects induced in
soft scalar masses when the heavy multiplets couple both to the visible and the
hidden sector.Comment: LaTex, 24 pages, no figures; v2 some comments and references adde
Star formation rate indicators in the Sloan Digital Sky Survey
The Sloan Digital Sky Survey (SDSS) first data release provides a database of
106000 unique galaxies in the main galaxy sample with measured spectra. A
sample of star-forming (SF) galaxies are identified from among the 3079 of
these having 1.4 GHz luminosities from FIRST, by using optical spectral
diagnostics. Using 1.4 GHz luminosities as a reference star formation rate
(SFR) estimator insensitive to obscuration effects, the SFRs derived from the
measured SDSS Halpha, [OII] and u-band luminosities, as well as far-infrared
luminosities from IRAS, are compared. It is established that straightforward
corrections for obscuration and aperture effects reliably bring the SDSS
emission line and photometric SFR estimates into agreement with those at 1.4
GHz, although considerable scatter (~60%) remains in the relations. It thus
appears feasible to perform detailed investigations of star formation for large
and varied samples of SF galaxies through the available spectroscopic and
photometric measurements from the SDSS. We provide herein exact prescriptions
for determining the SFR for SDSS galaxies. The expected strong correlation
between [OII] and Halpha line fluxes for SF galaxies is seen, but with a median
line flux ratio F_[OII]/F_Halpha=0.23, about a factor of two smaller than that
found in the sample of Kennicutt (1992). This correlation, used in deriving the
[OII] SFRs, is consistent with the luminosity-dependent relation found by
Jansen et al. (2001). The median obscuration for the SDSS SF systems is found
to be A_Halpha=1.2 mag, while for the radio detected sample the median
obscuration is notably higher, 1.6 mag, and with a broader distribution.Comment: Accepted for publication in ApJ, 40 pages, 26 figure
Cosmological Constant of the -Dimensional World, Embedded in the -Dimensional Bulk Space
In this manuscript we study the cosmological constant of a
-dimensional world, which lives in the higher dimensional bulk space. We
assume the extra dimensions are compact on tori. We consider two cases:
positive and negative bulk cosmological constant. It is pointed out that the
tiny cosmological constant of our world can be obtained by the dynamics of a
scalar field and adjusting the parameters of the model. The cosmological
constant of the dual world also will be discussed. We obtain the Dirac
quantization of these cosmological constants.Comment: 11 pages, Latex, No figure. In the revised version, major changes
have been introduced and also references have been adde
Crystalline Silicate Emission in the Protostellar Binary Serpens--SVS20
We present spatially resolved mid-infrared spectroscopy of the class
I/flat-spectrum protostellar binary system SVS20 in the Serpens cloud core. The
spectra were obtained with the mid-infrared instrument T-ReCS on Gemini-South.
SVS20-South, the more luminous of the two sources, exhibits a mid-infrared
emission spectrum peaking near 11.3 \micron, while SVS20-North exhibits a
shallow amorphous silicate absorption spectrum with a peak optical depth of
. After removal of the the line-of-sight extinction by the
molecular common envelope, the ``protostar-only'' spectra are found to be
dominated by strong amorphous olivine emission peaking near 10 \micron. We also
find evidence for emission from crystalline forsterite and enstatite associated
with both SVS20-S and SVS20-N. The presence of crystalline silicate in such a
young binary system indicates that the grain processing found in more evolved
HAeBe and T Tauri pre-main sequence stars likely begins at a relatively young
evolutionary stage, while mass accretion is still ongoing.Comment: Accepted for publication by The Astrophysical Journa
Influencia del sedentarismo en las desviaciones raquÃdeas de la población escolar de Léon
Nuestra investigación trata de evaluar los hábitos sedentarios, en los escolares de 10 y 14 años de una zona de León, y su influencia en las desviaciones raquÃdeas. Para la obtención de los hábitos nos basamos en el tets de Medoza, R. también se realizó una evaluación fÃsica de los niños para observar las desviaciones raquÃdeas. En el tratamiento de la información se utilizó el análisis de la varianza univariante y multivariante, además del análisis de componentes principales y análisis discriminante. Llegando a la conclusión, respecto al tiempo de televisión que el dÃa de la semana que más tiempo dedican los niños a ver la televisión es discrimante de los escolares que tienen desviación raquÃdea
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