1,497 research outputs found
Design and commissioning of a rotating test facility simulating a LPT hub cavity system for the investigation of cavity flows in aeroengines
Design and commissioning of a rotating test facility simulating a LPT hub cavity system for the investigation of cavity flows in aeroengine
The radiation field in the Gamma Irradiation Facility GIF++ at CERN
The high-luminosity LHC (HL-LHC) upgrade is setting now a new challenge for
particle detector technologies. The increase in luminosity will produce a
particle background in the gas-based muon detectors that is ten times higher
than under conditions at the LHC. The detailed knowledge of the detector
performance in the presence of such a high background is crucial for an
optimized design and efficient operation after the HL-LHC upgrade. A precise
understanding of possible aging effects of detector materials and gases is of
extreme importance. To cope with these challenging requirements, a new Gamma
Irradiation Facility (GIF++) was designed and built at the CERN SPS North Area
as successor of the Gamma Irradiation Facility (GIF) during the Long Shutdown 1
(LS1) period. It features an intense source of 662 keV photons with adjustable
intensity, to simulate continuous background over large areas, and, combined
with a high energy muon beam, to measure detector performance in the presence
of the background. The new GIF++ facility has been operational since spring
2015. In addition to describing the facility and its infrastructure, the goal
of this work is to provide an extensive characterization of the GIF++ photon
field with different configurations of the absorption filters in both the
upstream and downstream irradiation areas. Moreover, the measured results are
benchmarked with Geant4 simulations to enhance the knowledge of the radiation
field. The absorbed dose in air in the facility may reach up to 2.2 Gy/h
directly in front of the irradiator. Of special interest is the low-energy
photon component that develops due to the multiple scattering of photons within
the irradiator and from the concrete walls of the bunker
GRB970228 as a prototype for short GRBs with afterglow
GRB970228 is analyzed as a prototype to understand the relative role of short
GRBs and their associated afterglows, recently observed by Swift and HETE-II.
Detailed theoretical computation of the GRB970228 light curves in selected
energy bands are presented and compared with observational BeppoSAX data.Comment: 2 pages, 1 figure, to appear in the proceedings of "Swift and GRBs",
Venice, 2006, Il Nuovo Cimento, in pres
Conceptual hydrological modeling of the soil-bedrock interface at the bottom of the pyroclastic cover of Cervinara (Italy)
On the basis of the data collected by a monitoring station, a simplified mathematical model of the hydrological behavior of the
layered pyroclastic cover of the slope of Cervinara (southern Apennines) has been developed. The model considers a single homogeneous soil layer, for which effective hydraulic characteristic curves have been defined. The top boundary condition
accounts for the effects of evapotranspiration. The bottom boundary condition conceptually simulates, by means of a linear reservoir model, the hypothesized effects, on the soil water potential at the soil-bedrock interface, of the fluctuations of the water table of an ephemeral aquifer stored in the underlying fractured limestone. Despite its simplifying assumptions, the model satisfactorily reproduces the observed soil water potential at all the monitored depths. The obtained results indicate that even the
highest rainfall intensity can pass through the highly conductive unsaturated soil cover, and leak through the fractured bedrock.
Only when the water level in the underlying aquifer is high, as it happens after long lasting periods of rainfall, the establishment of the vertical water potential gradients, needed for the leakage of high infiltration peaks, leads to soil saturation at the bottom of
the cover. Such a picture provides a possible interpretation of the triggering mechanism of the landside occurred in 1999 along the slope
The Blackholic energy and the canonical Gamma-Ray Burst
We outline the main results of our GRB model, based on the three
interpretation paradigms we proposed in July 2001, comparing and contrasting
them with the ones in the current literature. Thanks to the observations by
Swift and by VLT, this analysis points to a "canonical GRB" originating from
markedly different astrophysical scenarios. The communality is that they are
all emitted in the formation of a black hole with small or null angular
momentum. The following sequence appears to be canonical: the vacuum
polarization process creating an optically thick self accelerating
electron-positron plasma; the engulfment of baryonic mass during the plasma
expansion; the adiabatic expansion of the optically thick "fireshell" up to the
transparency; the interaction of the remaining accelerated baryons with the
interstellar medium (ISM). This leads to the canonical GRB composed of a proper
GRB (P-GRB), emitted at the moment of transparency, followed by an extended
afterglow. The parameters are the plasma total energy, the fireshell baryon
loading and the ISM filamentary distribution around the source. In the limit of
no baryon loading the total energy is radiated in the P-GRB. In this limit, the
canonical GRBs explain as well the short GRBs.Comment: 163 pages, 89 figures, to appear on the "Proceedings of the XIIth
Brazilian School of Cosmology and Gravitation", M. Novello, S.E.
Perez-Bergliaffa (editors), AIP, in pres
Nanofabrication strategies for influencing biomolecule behavior
In recent years, nanofabrication techniques have shown themselves to have the most promising potential for innovative research
on crucial biomolecules for life sciences, such as DNA and RNA. Two main examples are: Firstly, large-scale nanostructuring,
effective for engineering innovative biosensors; and secondly, nanopores, intensively exploited for developing fast and inexpensive
technologies for DNA sequencing, a major research challenge in the field of biomedicine. In addition to nanopores, nanoslits and
nanochannels allow interesting functionalities for the study, processing and sorting of DNA. For example, when a long DNA chain
is forced to enter a nanochannel, it stretches, thus acquiring a conformation which allows its genetic information to be optically
read. Herein, we have focused on various geometry-based strategies, involving short and long channels, as well as funnels and a
series of pit nanostructures, integrated into polymeric lab-on-a-chip models. We have implemented these miniaturized systems in
order to study, at single molecule level, the typical conformations of DNA chains in various nano-confinement conditions whilst also
observing the dynamic behavior of the long strands in crossing structures with different cross sections. In fact, by taking advantage
of polydimethylsiloxane's elasticity, we have developed a strategy for modulating the translocation dynamics of single molecules
crossing a nanochannel. Lastly, we have investigated on important applications for life and material sciences of the recent innovative
tool which counts and recognizes nanoparticles through a new simultaneous optical and electrical sensing method
Impact of Isolated Tricuspid Valve Repair on Right Ventricular Remodelling in an Adult Congenital Heart Disease Population
BackgroundSurgical repair of isolated congenital tricuspid valve (TV) disease is rare with no well-defined indication and outcomes. Moreover, the role of right ventricle (RV) in this context has not yet been investigated.ObjectivesWe sought to assess the impact of congenital TV repair on cardiac remodelling and clinical–functional status and the importance of the RV function in an adult congenital heart disease (ACHD) population.Methods and resultsFrom January 2005 to December 2015, 304 patients underwent TV surgery in our centre. Of these, 27 (ACHD) patients had isolated TV repair. Patients were evaluated with preoperative and postoperative transthoracic echocardiogram. Survival rate has been investigated with a mean clinical follow-up (FU) of 3.7 ± 2.3 years, whereas the mean echocardiographic FU was 2.9 ± 1.8 years. The clinical and functional status of patients showed a statistically significant improvement after the surgical repair in terms of New York Heart Association class (66.7 vs 7.4%; p < 0.01), clinical signs of heart failure (29.6 vs 7.4%; p < 0.01), and left ventricular function (14.8 vs 7.4%; p < 0.01). The RV and right atrium diameter were significantly reduced after surgery (5.15 ± 1.21 vs 4.32 ± 1.16; p < 0.01) and (44.7 ± 16.7 vs 26.7 ± 9.2; p < 0.01), respectively. The degree of postoperative pulmonary hypertension was also significantly reduced (40.7 vs 7.4%; p < 0.01). The survival rate was 96.3% at 1 year and 93.7% at 5 years. One patient (3.7%) had early failure of the tricuspid repair requiring a reoperation.ConclusionIsolated TV repair for adult congenital disease significantly improved patients’ clinical and functional status and allowed right ventricular remodelling and functional improvement
- …