8,508 research outputs found
Constraining the general reheating phase in the -attractor inflationary cosmology
In this paper we constrain some aspects of the general postinflationary phase
in the context of superconformal -attractor models of inflation. In
particular, we provide constraints on the duration of the reheating process,
, and on the reheating temperature, , simulating possible and
future results given by the next-generation of cosmological missions. Moreover,
we stress what kinds of equation-of-state parameter, , are favored for
different scenarios. The analysis does not depend on the details of the
reheating phase and it is performed assuming different measurements of the
tensor-to-scalar ratio .Comment: 8 pages, 2 figure
Analysis of heat transfer in different CPC solar collectors: A CFD approach
In this paper a methodology is proposed to estimate thermal heat losses inside compound parabolic collectors (CPC) to be used in designing and validating new collectors' concepts and materials. CFD simulations were carried out on different CPCs, taking into account the effective working conditions and the presence of radiative heat transfer as well as the absence of adiabatic walls. The CFD model was validated considering a previous work reported in literature. The results were employed to develop some correlations by interpolation of numerical data, to express the Nusselt number on the receiver. We used these correlations to calculate heat losses of the receiver and to show the influence of different parameters such as the shape of receiver itself, tilt angle and concentration ratio. The variation of terms of the correlation as a function of characteristic length and concentration was studied. These results might be employed for a preliminary estimation procedure of a CPC collector efficiency and to propose sizing criteria of general validity for this class of devices
Budget impact analysis of apixaban to treat and prevent venous thromboembolism in Italy
BACKGROUND: Venous thromboembolism (VTE), a collective term for deep vein thrombosis (DVT) and pulmonary embolism (PE), is a serious vascular condition associated to high economic and clinical burden. Apixaban, a Novel Oral Anticoagulant (NOAC) has shown non-inferiority efficacy versus the current standard of care (low molecular weight heparin [LMWH]/vitamin K antagonist [VKA]) in the acute treatment and prevention of VTE and a significant reduction in the risk of bleeding.AIM: Evaluate the economic impact of the use of apixaban for treatment and prevention of DVT and PE from the perspective of the Italian National Health System (NHS).METHODS: A budget impact model was adapted in order to compare clinical outcomes and economic consequences associated to apixaban vs. LMWH/VKA and others NOACs over a three-year time horizon in the Italian setting. In the analysis two scenario were compared: status quo scenario without apixaban and an alternative scenario with apixaban. Only direct healthcare costs have been considered.RESULTS: Assuming a population of patients receiving apixaban over the first 3 years equal to 20,957, the introduction of apixaban is associated to an incremental saving of ⏠821,748 in the first years, ⏠1,250,454 in the second year, and ⏠1,866,466 in the third year. The total net saving over the 3-year period is ⏠3,938,668, which is a 2.47% decrease from the total budget for the status quo scenario without apixaban. This saving is mainly due to reduced VTE events and bleeds by apixaban. Indeed apixaban is associated with less VTE events (both fatal and non-fatal), less major bleeding and less Clinical Relevant Non Major (CRNM) bleeding with a total of 52 fatal events avoided.CONCLUSIONS: The listing of apixaban for the treatment of VTE (both DVT and PE) and the prevention of recurrent VTE provides both significant clinical advantages, in terms of deaths and events avoided, and economical advantages, consisting in a reduction in the total expenditure on the Italian NHS
MarciaTesta: An Automatic Generator of Test Programs for Microprocessors' Data Caches
SBST (Software Based Self-Testing) is an effective solution for in-system testing of SoCs without any additional hardware requirement. SBST is particularly suited for embedded blocks with limited accessibility, such as cache memories. Several methodologies have been proposed to properly adapt existing March algorithms to test cache memories. Unfortunately they all leave the test engineers the task of manually coding them into the specific Instruction Set Architecture (ISA) of the target microprocessor. We propose an EDA tool for the automatic generation of assembly cache test program for a specific architectur
Validation & Verification of an EDA automated synthesis tool
Reliability and correctness are two mandatory features for automated synthesis tools. To reach the goals several campaigns of Validation and Verification (V&V) are needed. The paper presents the extensive efforts set up to prove the correctness of a newly developed EDA automated synthesis tool. The target tool, MarciaTesta, is a multi-platform automatic generator of test programs for microprocessors' caches. Getting in input the selected March Test and some architectural details about the target cache memory, the tool automatically generates the assembly level program to be run as Software Based Self-Testing (SBST). The equivalence between the original March Test, the automatically generated Assembly program, and the intermediate C/C++ program have been proved resorting to sophisticated logging mechanisms. A set of proved libraries has been generated and extensively used during the tool development. A detailed analysis of the lessons learned is reporte
Magnesium isotopes: a tool to understand self-enrichment in Globular Clusters
A critical issue in the asymptotic giant branch (AGB) self-enrichment
scenario for the formation of multiple populations in Globular Clusters (GCs)
is the inability to reproduce the magnesium isotopic ratios, despite the model
in principle can account for the depletion of magnesium. In this work we
analyze how the uncertainties on the various p-capture cross sections affect
the results related to the magnesium content of the ejecta of AGB stars. The
observed distribution of the magnesium isotopes and of the overall Mg-Al trend
in M13 and NGC 6752 are successfully reproduced when the proton-capture rate by
25Mg at the temperatures 100 MK, in particular the 25Mg(p, gamma)26Alm channel,
is enhanced by a factor 3 with respect to the most recent experimental
determinations. This assumption also allows to reproduce the full extent of the
Mg spread and the Mg-Si anticorrelation observed in NGC 2419. The uncertainties
in the rate of the 25Mg(p,gamma)26Alm reaction at the temperatures of interest
here leave space for our assumption and we suggest that new experimental
measurements are needed to settle this problem. We also discuss the competitive
model based on the super massive star nucleosynthesis.Comment: accepted for publication on MNRA
Compensating the Noise of a Communication Channel via Asymmetric Encoding of Quantum Information
An asymmetric preparation of the quantum states sent through a noisy channel
can enable a new way to monitor and actively compensate the channel noise. The
paradigm of such an asymmetric treatment of quantum information is the Bennett
1992 protocol, in which the ratio between conclusive and inconclusive counts is
in direct connection with the channel noise. Using this protocol as a guiding
example, we show how to correct the phase drift of a communication channel
without using reference pulses, interruptions of the quantum transmission or
public data exchanges.Comment: 5 pages, 3 figure
Stars caught in the braking stage in young Magellanic Clouds clusters
The color-magnitude diagrams of many Magellanic Cloud clusters (with ages up
to 2 billion years) display extended turnoff regions where the stars leave the
main sequence, suggesting the presence of multiple stellar populations with
ages which may differ even by hundreds million years (Mackey et al. 2008,
Milone et al. 2009, Girardi et al. 2011). A strongly debated question is
whether such an extended turnoff is instead due to populations with different
stellar rotations (Girardi et al. 2011, Goudfrooij et al. 2011, Rubele et al.
2013, Li et al. 2014). The recent discovery of a `split' main sequence in some
younger clusters (about 80--400Myr) added another piece to this puzzle. The
blue (red) side of the main sequence is consistent with slowly (rapidly)
rotating stellar models (D'Antona et al. 2015, Milone et al. 2016, Correnti et
al. 2017, Milone et al 2016), but a complete theoretical characterization of
the observed color-magnitude diagram appeared to require also an age spread
(Correnti et al. 2017). We show here that, in three clusters so far analyzed,
if the blue main sequence stars are interpreted with models that have been
always slowly rotating, they must be about 30% younger than the rest of the
cluster. If they are instead interpreted as stars initially rapidly rotating,
but that have later slowed down, the age difference disappears, and "braking"
also helps to explain the apparent age differences of the extended turnoff. The
age spreads in Magellanic Cloud clusters are a manifestation of rotational
stellar evolution. Observational tests are suggested.Comment: Accepted for publication and in state of Advance Online Publication
(from 24 July 2017) on Nature Astronom
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