15,610 research outputs found
Splitting of the middle layer of LPW SAFNWC/MSG satellite product in order to improve the monitoring of pre-convective environments
International audienceSeven of the infrared channels from the Spinning Enhanced Visible and Infrared Imagery (SEVIRI) instrument, on board the Meteosat Second Generation (MSG), are used to retrieve Layer Precipitable Water (LPW) and Stability Analysis Imagery (SAI) in the SAFNWC framework. Both products are retrieved using a statistical retrieval based on neural networks; they are routinely generated every fifteen minutes at a satellite horizontal resolution of 3 km in NADIR only in cloud-free areas. Many factors are involved in the development of severe weather and these parameters are only some of the indicators. However, due to the high resolution of these products, the use of them in conjunction with satellite and radar images can help to identify mesoscale features related to convection. The MSG moisture and parcel instability time trend fields are especially useful during the period previous to convection. Once the outbreak of convection occurs, the products calculated in the clear air pixels surrounding the convective system can give us hints to anticipate its evolution. SAFNWC LPW and SAI were analyzed for a severe weather event during August 2004. A thunderstorm over Teruel (Spain) produced intense precipitation and hail; a tornado developed while this thunderstorm was moving towards SE. The pre-convective parcel potential buoyancy and moisture SAFNWC products changed in a way that was consistent with the observed intense convective activity. In previous studies, the atmospheric moisture in medium levels, which has been proven to be relevant in some cases, was represented by only one level parameter (ML: middle layer LPW). However, it was observed that this layer is too thick to do an adequate analysis of moisture available for convection. Hence, an improvement on the LPW algorithm has been carried out by splitting the middle layer into two new sub-layers (approximately separated at 700 hPa) and training two new neural networks. The impact of monitoring moisture in the new sub-layers separately in this severe weather event has been tested, and the improvements achieved have been evaluated
Myristic acid potentiates palmitic acid-induced lipotoxicity and steatohepatitis associated with lipodystrophy by sustaning de novo ceramide synthesis.
Palmitic acid (PA) induces hepatocyte apoptosis and fuels de novo ceramide synthesis in the endoplasmic reticulum (ER). Myristic acid (MA), a free fatty acid highly abundant in copra/palmist oils, is a predictor of nonalcoholic steatohepatitis (NASH) and stimulates ceramide synthesis. Here we investigated the synergism between MA and PA in ceramide synthesis, ER stress, lipotoxicity and NASH. Unlike PA, MA is not lipotoxic but potentiated PA-mediated lipoapoptosis, ER stress, caspase-3 activation and cytochrome c release in primary mouse hepatocytes (PMH). Moreover, MA kinetically sustained PA-induced total ceramide content by stimulating dehydroceramide desaturase and switched the ceramide profile from decreased to increased ceramide 14:0/ceramide16:0, without changing medium and long-chain ceramide species. PMH were more sensitive to equimolar ceramide14:0/ceramide16:0 exposure, which mimics the outcome of PA plus MA treatment on ceramide homeostasis, than to either ceramide alone. Treatment with myriocin to inhibit ceramide synthesis and tauroursodeoxycholic acid to prevent ER stress ameliorated PA plus MA induced apoptosis, similar to the protection afforded by the antioxidant BHA, the pan-caspase inhibitor z-VAD-Fmk and JNK inhibition. Moreover, ruthenium red protected PMH against PA and MA-induced cell death. Recapitulating in vitro findings, mice fed a diet enriched in PA plus MA exhibited lipodystrophy, hepatosplenomegaly, increased liver ceramide content and cholesterol levels, ER stress, liver damage, inflammation and fibrosis compared to mice fed diets enriched in PA or MA alone. The deleterious effects of PA plus MA-enriched diet were largely prevented by in vivo myriocin treatment. These findings indicate a causal link between ceramide synthesis and ER stress in lipotoxicity, and imply that the consumption of diets enriched in MA and PA can cause NASH associated with lipodystrophy
A Simple Method for Tidal Current Prediction in Short Length Convergent Channels An Application to the Vigo and Pontevedra Estuaries
In this paper a simple method for tidal current modelling in short length convergent and elongated channels is presented. The authors have found that for this kind of channels a very suitable approach to tidal current velocity estimation can be obtained through a very simple formula. This method has been developed to obtain reliable tidal current velocity estimations along the channel using as less information as possible. In fact, the only necessary information to apply this method are the harmonic constants of the tidal elevation at any location in the channel and a proper nautical chart. A graphical method is also presented to inquire when the geometrical characteristics of a given channel allow the application of our method. The validation has been performed on two estuaries of the Gallega Estuarine System in Spain
Observational constraints to boxy/peanut bulge formation time
Boxy/peanut bulges are considered to be part of the same stellar structure as
bars and both could be linked through the buckling instability. The Milky Way
is our closest example. The goal of this letter is determining if the mass
assembly of the different components leaves an imprint in their stellar
populations allowing to estimate the time of bar formation and its evolution.
To this aim we use integral field spectroscopy to derive the stellar age
distributions, SADs, along the bar and disc of NGC 6032. The analysis shows
clearly different SADs for the different bar areas. There is an underlying old
(>=12 Gyr) stellar population for the whole galaxy. The bulge shows star
formation happening at all times. The inner bar structure shows stars of ages
older than 6 Gyrs with a deficit of younger populations. The outer bar region
presents a SAD similar to that of the disc. To interpret our results, we use a
generic numerical simulation of a barred galaxy. Thus, we constrain, for the
first time, the epoch of bar formation, the buckling instability period and the
posterior growth from disc material. We establish that the bar of NGC 6032 is
old, formed around 10 Gyr ago while the buckling phase possibly happened around
8 Gyr ago. All these results point towards bars being long-lasting even in the
presence of gas.Comment: Accepted for publication in MNRAS Letter
Hysteroscopic Management of an Interstitial Ectopic Pregnancy
We report a case of an interstitial ectopic pregnancy successfully managed by hysteroscopy. We highlight the benefits of using hysteroscopy, a non-invasive procedure, to preserve fertility
Novel method for the direct measurement of the tau lepton dipole moments
A novel method for the direct measurement of the elusive magnetic and
electric dipole moments of the tau lepton is presented. The experimental
approach relies on the production of tau+ leptons from Ds+ -> tau+ nu_tau
decays, originated in fixed-target collisions at the LHC. A sample of polarized
tau+ leptons is kinematically selected and subsequently channeled in a bent
crystal. The magnetic and electric dipole moments of the tau+ lepton are
measured by determining the rotation of the spin-polarization vector induced by
the intense electromagnetic field between crystal atomic planes. The
experimental technique is discussed along with the expected sensitivities.Comment: 4 pages, 4 figures, 2 pages supplemental material. Accepted by
Phys.Rev.Let
Hickson-like compact groups inhabiting different environments
Although Compact Groups of galaxies (CGs) have been envisioned as isolated
extremely dense structures in the Universe, it is accepted today that many of
them could be not as isolated as thought. In this work, we study Hickson-like
CGs identified in the Sloan Digital Sky Survey Data Release 16 to analyse these
systems and their galaxies when embedded in different cosmological structures.
To achieve this goal, we identify several cosmological structures where CGs can
reside: Nodes of filaments, Loose Groups, Filaments and cosmic Voids. Our
results indicate that 45 per cent of CGs do not reside in any of these
structures, i.e., they can be considered non-embedded or isolated systems. Most
of the embedded CGs are found inhabiting Loose Groups and Nodes, while there
are almost no CGs residing well inside cosmic Voids. Some physical properties
of CGs vary depending on the environment they inhabit. CGs in Nodes show the
largest velocity dispersions, the brightest absolute magnitude of the
first-ranked galaxy, and the smallest crossing times, while the opposite occurs
in Non-Embedded CGs. When comparing galaxies in all the environments and
galaxies in CGs, CGs show the highest fractions of red/early-type galaxy
members in most of the absolute magnitudes ranges. The variation between
galaxies in CGs inhabiting one or another environment is not as significant as
the differences caused by belonging or not to a CG. Our results suggest a
plausible scenario for galaxy evolution in CGs in which both, large-scale and
local environments play essential roles.Comment: 16 pages, 9 figures, 1 table, accepted for publication in MNRA
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