49 research outputs found
Evaluation of the smooth muscle cell component and apoptosis in the varicose vein wall
This study was designed to evaluate the role of the smooth muscle cell and the apoptosis in the pathogenesis of the varicose vein. Segments of saphenous vein were obtained from healthy subjects and from those with varicose veins. The vein specimens were subdivided according to subject age (younger or older than 50 years) and according to the varicose vein source (distal or proximal). Morphological, ultrastructural, cell proliferation (anti-PCNA method) and cell death (TUNEL method) analysis were performed. The walls of healthy, control vein specimens acquired a more collagenous and papillomatous appearance with age. A slight increase in the number of TUNEL-positive cells was also observed in specimens from older subjects. The proportion of apoptotic cells was much greater in the varicose veins than in control specimens. Most cellular alterations were seen in proximal varicose segments obtained from young subjects. These specimens showed hypertrophic areas with a high degree of cellularity (both in the media and in the thickened intima). The highest proportion of apoptotic cells and collagenisation were also observed in these areas. The enhanced number of apoptotic cells in varicose veins observed mainly in proximal/young vein specimens could be responsible, at least in part, for the acceleration of the final fibrosclerotic process characteristic of the varicose vein wall
Reversal of diastereoselectivity in the synthesis of Peptidomimetic 3‑Carboxamide-1,4-benzodiazepin-5-ones
Enantiopure 3-carboxamide-1,4-benzodiazepin-5-ones were synthesized via the Ugi reaction followed by the Staudinger/aza-Wittig or reduction reactions in only two steps. A complete reversal of diastereoselectivity was achieved depending on the cyclization methodology employed. The different orientation of the C3 substituent in our 3-substituted 1,4-benzodiazepin-5-ones with respect to the most studied 1,4-benzodiazepin-2-ones makes them complementary in the development of new drugs because the primary source of binding selectivity of 1,4-benzodiazepines is the selective recognition of ligand conformations by the receptor.Ministerio de Economía y Competitividad, Spain (Project CTQ2012-31611), Junta de Castilla y León, Consejería de Educación y Cultura y Fondo Social Europeo (Project BU246A12-1) and the European Commission, Seventh Framework Programme (Project SNIFFER FP7-SEC-2012-312411)
A search for Very High Energy gamma-ray emission from Scorpius X-1 with the MAGIC telescopes
The acceleration of particles up to GeV or higher energies in microquasars
has been the subject of considerable theoretical and observational efforts in
the past few years. Sco X-1 is a microquasar from which evidence of highly
energetic particles in the jet has been found when it is in the so-called
Horizontal Branch (HB), a state when the radio and hard X-ray fluxes are higher
and a powerful relativistic jet is present. Here we present the first very high
energy gamma-ray observations of Sco X-1 obtained with the MAGIC telescopes. An
analysis of the whole dataset does not yield a significant signal, with 95% CL
flux upper limits above 300 GeV at the level of 2.4x10^{-12} ph/cm^2/s.
Simultaneous RXTE observations were conducted to search for TeV emission during
particular X-ray states of the source. A selection of the gamma-ray data
obtained during the HB based on the X-ray colors did not yield a signal either,
with an upper limit of 3.4x10^{-12} ph/cm^2/s. These upper limits place a
constraint on the maximum TeV luminosity to non-thermal X-ray luminosity of
L_{VHE}/L_{ntX}<0.02, that can be related to a maximum TeV luminosity to jet
power ratio of L_{VHE}/L_{j}<10^{-3}. Our upper limits indicate that the
underlying high-energy emission physics in Sco X-1 must be inherently different
from that of the hitherto detected gamma-ray binaries.Comment: 5 pages, 2 figures, 2 tables. Version as published in ApJ
PG 1553+113: five years of observations with MAGIC
We present the results of five years (2005-2009) of MAGIC observations of the
BL Lac object PG 1553+113 at very high energies (VHEs, E > 100 GeV). Power law
fits of the individual years are compatible with a steady mean photon index
\Gamma = 4.27 0.14. In the last three years of data, the flux level above
150 GeV shows a clear variability (probability of constant flux < 0.001%). The
flux variations are modest, lying in the range from 4% to 11% of the Crab
Nebula flux. Simultaneous optical data also show only modest variability that
seems to be correlated with VHE gamma ray variability. We also performed a
temporal analysis of (all available) simultaneous Fermi/LAT data of PG 1553+113
above 1 GeV, which reveals hints of variability in the 2008-2009 sample.
Finally, we present a combination of the mean spectrum measured at very high
energies with archival data available for other wavelengths. The mean spectral
energy distribution can be modeled with a one-zone Synchrotron Self Compton
(SSC) model, which gives the main physical parameters governing the VHE
emission in the blazar jet.Comment: 11 pages, 6 figures, accepted for publication in Ap
The 2010 very high energy gamma-ray flare & 10 years of multi-wavelength observations of M 87
Abridged: The giant radio galaxy M 87 with its proximity, famous jet, and
very massive black hole provides a unique opportunity to investigate the origin
of very high energy (VHE; E>100 GeV) gamma-ray emission generated in
relativistic outflows and the surroundings of super-massive black holes. M 87
has been established as a VHE gamma-ray emitter since 2006. The VHE gamma-ray
emission displays strong variability on timescales as short as a day. In this
paper, results from a joint VHE monitoring campaign on M 87 by the MAGIC and
VERITAS instruments in 2010 are reported. During the campaign, a flare at VHE
was detected triggering further observations at VHE (H.E.S.S.), X-rays
(Chandra), and radio (43 GHz VLBA). The excellent sampling of the VHE gamma-ray
light curve enables one to derive a precise temporal characterization of the
flare: the single, isolated flare is well described by a two-sided exponential
function with significantly different flux rise and decay times. While the
overall variability pattern of the 2010 flare appears somewhat different from
that of previous VHE flares in 2005 and 2008, they share very similar
timescales (~day), peak fluxes (Phi(>0.35 TeV) ~= (1-3) x 10^-11 ph cm^-2
s^-1), and VHE spectra. 43 GHz VLBA radio observations of the inner jet regions
indicate no enhanced flux in 2010 in contrast to observations in 2008, where an
increase of the radio flux of the innermost core regions coincided with a VHE
flare. On the other hand, Chandra X-ray observations taken ~3 days after the
peak of the VHE gamma-ray emission reveal an enhanced flux from the core. The
long-term (2001-2010) multi-wavelength light curve of M 87, spanning from radio
to VHE and including data from HST, LT, VLA and EVN, is used to further
investigate the origin of the VHE gamma-ray emission. No unique, common MWL
signature of the three VHE flares has been identified.Comment: 19 pages, 5 figures; Corresponding authors: M. Raue, L. Stawarz, D.
Mazin, P. Colin, C. M. Hui, M. Beilicke; Fig. 1 lightcurve data available
online: http://www.desy.de/~mraue/m87
SiPM-matrix readout of two-phase argon detectors using electroluminescence in the visible and near infrared range
Proportional electroluminescence (EL) in noble gases is used in two-phase detectors for dark matter searches to record (in the gas phase) the ionization signal induced by particle scattering in the liquid phase. The “standard” EL mechanism is considered to be due to noble gas excimer emission in the vacuum ultraviolet (VUV). In addition, there are two alternative mechanisms, producing light in the visible and near infrared (NIR) ranges. The first is due to bremsstrahlung of electrons scattered on neutral atoms (“neutral bremsstrahlung”, NBrS). The second, responsible for electron avalanche scintillation in the NIR at higher electric fields, is due to transitions between excited atomic states. In this work, we have for the first time demonstrated two alternative techniques of the optical readout of two-phase argon detectors, in the visible and NIR range, using a silicon photomultiplier matrix and electroluminescence due to either neutral bremsstrahlung or avalanche scintillation. The amplitude yield and position resolution were measured for these readout techniques, which allowed to assess the detection threshold for electron and nuclear recoils in two-phase argon detectors for dark matter searches. To the best of our knowledge, this is the first practical application of the NBrS effect in detection science
Design and construction of a new detector to measure ultra-low radioactive-isotope contamination of argon
Large liquid argon detectors offer one of the best avenues for the detection of galactic weakly interacting massive particles (WIMPs) via their scattering on atomic nuclei. The liquid argon target allows exquisite discrimination between nuclear and electron recoil signals via pulse-shape discrimination of the scintillation signals. Atmospheric argon (AAr), however, has a naturally occurring radioactive isotope, 39Ar, a β emitter of cosmogenic origin. For large detectors, the atmospheric 39Ar activity poses pile-up concerns. The use of argon extracted from underground wells, deprived of 39Ar, is key to the physics potential of these experiments. The DarkSide-20k dark matter search experiment will operate a dual-phase time projection chamber with 50 tonnes of radio-pure underground argon (UAr), that was shown to be depleted of 39Ar with respect to AAr by a factor larger than 1400. Assessing the 39Ar content of the UAr during extraction is crucial for the success of DarkSide-20k, as well as for future experiments of the Global Argon Dark Matter Collaboration (GADMC). This will be carried out by the DArT in ArDM experiment, a small chamber made with extremely radio-pure materials that will be placed at the centre of the ArDM detector, in the Canfranc Underground Laboratory (LSC) in Spain. The ArDM LAr volume acts as an active veto for background radioactivity, mostly γ-rays from the ArDM detector materials and the surrounding rock. This article describes the DArT in ArDM project, including the chamber design and construction, and reviews the background required to achieve the expected performance of the detector
Biblioteca digital Funandi: información sin barreras
La Biblioteca Digital Funandi es una
visualización centralizada de los materiales digitales
disponibles para la docencia y la investigación.
Incluyendo un rango amplio de contenidos para
variados propósitos y usuarios con resultados de
investigaciones tales como artículos de revistas o datos
de investigaciones, tesis, objetos de aprendizaje,
materiales para la enseñanza y datos administrativos.
La biblioteca digital es concebida como un entorno
interoperable dónde fluye información digitalizada y
organizada para su visibilidad en la web, el primer paso
constituye el planeamiento de una metodología para la
creación y el mantenimiento de un repositorio de
publicaciones institucionales y trabajos de grado.
Teniendo en cuenta que “las tecnologías son
instrumentos, las bibliotecas y los centros de
información son servicios”; la función de la Biblioteca
Digital Funandi es brindar a estos la posibilidad de
mejorar los servicios ofrecidos
Evaluation of the smooth muscle cell eomponent and apoptosis in the varicose vein wall
This study was designed to evaluate the role
of the smooth muscle cell and the apoptosis in the
pathogenesis of the varicose vein.
Segments of saphenous vein were obtained from
healthy subjects and from those with varicose veins. The
vein specimens were subdivided according to subject
age (younger or older than 50 years) and according to
the varicose vein source (distal or proximal).
Morphological, ultrastructural, cell proliferation (anti-
PCNA method) and cell death (TUNEL method)
analysis were performed.
The walls of healthy, control vein specimens
acquired a more collagenous and papilomatous
appearance with age. A slight increase in the number of
TUNEL-positive cells was also observed in specimens
from older subjects. The proportion of apoptotic cells
was much greater in the varicose veins than in control
specimens. Most cellular alterations were seen in
proximal varicose segments obtained from young
subjects. These specimens showed hypertrophic areas
with a high degree of cellularity (both in the media and
in the thickened intima). The highest proportion of
apoptotic cells and collagenisation were also observed in
these areas. The enhanced number of apoptotic cells in
varicose veins observed mainly in proximal/young vein
specimens could be responsible, at least in part, for the
acceleration of the final fibrosclerotic process
characteristic of the varicose vein wall