403 research outputs found
Toward the estimation of river discharge variations using MODIS data in ungauged basins
This study investigates the capability of the Moderate resolution Imaging Spectroradiometer (MODIS) to estimate river discharge, even for ungauged sites. Because of its frequent revisits (as little as every 3 h) and adequate spatial resolution (250 m), MODIS bands 1 and 2 have significant potential for mapping the extent of flooded areas and estimating river discharge even for medium-sized basins. Specifically, the different behaviour of water and land in the Near Infrared (NIR) portion of the electromagnetic spectrum is exploited by computing the ratio (C/M) of the MODIS channel 2 reflectance values between two pixels located within (M) and outside (C), but close to, the river. The values of C/M increase with the presence of water and, hence, with discharge. Moreover, in order to reduce the noise effects due to atmospheric contribution, an exponential smoothing filter is applied, thus obtaining C/Mâ.
Time series of hourly mean flow velocity and discharge between 2005 and 2011 measured at four gauging stations located along the Po river (Northern Italy) are employed for testing the capability of C/Mâ to estimate discharge/flow velocity. Specifically, the meanders and urban areas are considered the best locations for the position of the pixels M and C, respectively. Considering the optimal pixels, the agreement between C/Mâ and discharge/flow velocity is fairly good with values in the range of 0.65â0.77. Additionally, the application to ungauged sites is tested by deriving a unique regional relationship between C/Mâ and flow velocity valid for the whole Po river and providing only a slight deterioration of the performance. Finally, the sensitivity of the results to the selection of the C and M pixels is investigated by randomly changing their location. Also in this case, the agreement with in situ observations of velocity is fairly satisfactory (r ~ 0.6). The obtained results demonstrate the capability of MODIS to monitor discharge (and flow velocity). Therefore, its application for a larger number of sites worldwide will be the object of future studies
Impact of lysosomal storage disorders on biology of mesenchymal stem cells: Evidences from in vitro silencing of glucocerebrosidase (GBA) and alpha-galactosidase A (GLA) enzymes.
Lysosomal storage disorders (LDS) comprise a group of rare multisystemic diseases resulting from inherited gene mutations that impair lysosomal homeostasis. The most common LSDs, Gaucher disease (GD), and Fabry disease (FD) are caused by deficiencies in the lysosomal glucocerebrosidase (GBA) and alpha-galactosidase A (GLA) enzymes, respectively. Given the systemic nature of enzyme deficiency, we hypothesized that the stem cell compartment of GD and FD patients might be also affected. Among stem cells, mesenchymal stem cells (MSCs) are a commonly investigated population given their role in hematopoiesis and the homeostatic maintenance of many organs and tissues. Since the impairment of MSC functions could pose profound consequences on body physiology, we evaluated whether GBA and GLA silencing could affect the biology of MSCs isolated from bone marrow and amniotic fluid. Those cell populations were chosen given the former's key role in organ physiology and the latter's intriguing potential as an alternative stem cell model for human genetic disease. Our results revealed that GBA and GLA deficiencies prompted cell cycle arrest along with the impairment of autophagic flux and an increase of apoptotic and senescent cell percentages. Moreover, an increase in ataxia-telangiectasia-mutated staining 1âhr after oxidative stress induction and a return to basal level at 48âhr, along with persistent gamma-H2AX staining, indicated that MSCs properly activated DNA repair signaling, though some damages remained unrepaired. Our data therefore suggest that MSCs with reduced GBA or GLA activity are prone to apoptosis and senescence due to impaired autophagy and DNA repair capacity
Maternal ABO Phenotype as a Predictive Factor for Pregnancy Complications Related to Prematurity
Objective: The ABO blood types are associated with cancers, cardiovascular disease, and Type 2 diabetes in adult males and females. Associations of ABO blood type and adverse pregnancy outcomes have not been extensively studied. The purpose of this study was to investigate the relationship with ABO blood groups and risk of adverse pregnancy outcomes contributing to premature birth.Study design: Data on ABO phenotypes and pregnancy outcomes were collected from the medical records of 1,462 premature infants (22-34 weeks). Adverse pregnancy outcomes that were studied in relation to maternal blood type included gestational hypertension (GHTN), preeclampsia (PREE), chorioamnionitis (CA), preterm premature rupture of membranes (PPROM), and intrauterine growth restriction (IUGR)Results: 1,462 charts of mothers with premature infants (22-34 weeks) were studied measuring the relative risk by using standardized statistical software (SPSS).Our study group had 46 mothers with GHTN, 405 with PREE, 282 with CA, 504 with PPROM, and 94 with IUGR. A+ Caucasian mothers had a 28% increased risk of developing preeclampsia (RR= 1.28 (1.09-1.52); 95% CI= .003). B mothers are ata 46% decreased risk of developing chorioamnionitis versus all other blood groups (RR= 0.54, 95% CI= 0.36-0.81; P= .003). Conversely, O+ Caucasian mothers were 2.53 times more likely to develop chorioamnionitis compared to all other blood types (RR=2.53, 95% CI= 1.09-5.88; P= .031).Conclusions: Maternal ABO phenotype significantly influences the incidence of preeclampsia and chorioamnionitis. Pregnancy is a unique antigen-antibody phenomenon with the fetus serving as an antigen to the mother. We postulate that blood group antigen expression at the endothelial level may influence maternal disease states
Light Vector Mesons in the Nuclear Medium
The light vector mesons (, , and ) were produced in
deuterium, carbon, titanium, and iron targets in a search for possible
in-medium modifications to the properties of the meson at normal nuclear
densities and zero temperature. The vector mesons were detected with the CEBAF
Large Acceptance Spectrometer (CLAS) via their decays to . The rare
leptonic decay was chosen to reduce final-state interactions. A combinatorial
background was subtracted from the invariant mass spectra using a
well-established event-mixing technique. The meson mass spectrum was
extracted after the and signals were removed in a nearly
model-independent way. Comparisons were made between the mass spectra
from the heavy targets () with the mass spectrum extracted from the
deuterium target. With respect to the -meson mass, we obtain a small
shift compatible with zero. Also, we measure widths consistent with standard
nuclear many-body effects such as collisional broadening and Fermi motion.Comment: 15 pages, 18 figures, 3 table
First measurement of direct photoproduction on the proton
We report on the results of the first measurement of exclusive
meson photoproduction on protons for GeV and GeV. Data were collected with the CLAS detector at the Thomas
Jefferson National Accelerator Facility. The resonance was detected via its
decay in the channel by performing a partial wave analysis of the
reaction . Clear evidence of the meson
was found in the interference between and waves at GeV. The -wave differential cross section integrated in the mass range of
the was found to be a factor of 50 smaller than the cross section
for the meson. This is the first time the meson has been
measured in a photoproduction experiment
First measurement of coherent -meson photoproduction on deuteron at low energies
The cross section and decay angular distributions for the coherent \phi meson
photoproduction on the deuteron have been measured for the first time up to a
squared four-momentum transfer t =(p_{\gamma}-p_{\phi})^2 =-2 GeV^2/c^2, using
the CLAS detector at the Thomas Jefferson National Accelerator Facility. The
cross sections are compared with predictions from a re-scattering model. In a
framework of vector meson dominance, the data are consistent with the total
\phi-N cross section \sigma_{\phi N} at about 10 mb. If vector meson dominance
is violated, a larger \sigma_{\phi N} is possible by introducing larger t-slope
for the \phi N \to \phi N process than that for the \gamma N \to \phi N
process. The decay angular distributions of the \phi are consistent with
helicity conservation.Comment: 6 page
Exclusive electroproduction on the proton at CLAS
The reaction has been measured, using the 5.754
GeV electron beam of Jefferson Lab and the CLAS detector. This represents the
largest ever set of data for this reaction in the valence region. Integrated
and differential cross sections are presented. The , and
dependences of the cross section are compared to theoretical calculations based
on -channel meson-exchange Regge theory on the one hand and on quark handbag
diagrams related to Generalized Parton Distributions (GPDs) on the other hand.
The Regge approach can describe at the 30% level most of the features
of the present data while the two GPD calculations that are presented in this
article which succesfully reproduce the high energy data strongly underestimate
the present data. The question is then raised whether this discrepancy
originates from an incomplete or inexact way of modelling the GPDs or the
associated hard scattering amplitude or whether the GPD formalism is simply
inapplicable in this region due to higher-twists contributions, incalculable at
present.Comment: 29 pages, 29 figure
Electroproduction of mesons at GeV measured with the CLAS spectrometer
Electroproduction of exclusive vector mesons has been studied with the
CLAS detector in the kinematical range GeV,
GeV, and GeV. The
scaling exponent for the total cross section as was
determined to be . The slope of the four-momentum transfer
distribution is GeV. Under the assumption of
s-channel helicity conservation (SCHC), we determine the ratio of longitudinal
to transverse cross sections to be . A 2-gluon exchange model
is able to reproduce the main features of the data.Comment: Phys Rev C, 15 pages, 18 figure
Search for medium modification of the meson
The photoproduction of vector mesons on various nuclei has been studied using
the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Laboratory. The
vector mesons, , , and , are observed via their decay to
, in order to reduce the effects of final state interactions in the
nucleus. Of particular interest are possible in-medium effects on the
properties of the meson. The spectral function is extracted from
the data on various nuclei, carbon, iron, and titanium, and compared to the
spectrum from liquid deuterium, which is relatively free of nuclear effects. We
observe no significant mass shift for the meson; however, there is some
widening of the resonance in titanium and iron, which is consistent with
expected collisional broadening.Comment: 8 pages, 4 figure
- âŠ