An improved method for estimating the neutron background in measurements of neutron capture reactions

The relation between the neutron background in neutron capture measurements and the neutron sensitivity related to the experimental setup is examined. It is pointed out that a proper estimate of the neutron background may only be obtained by means of dedicated simulations taking into account the full framework of the neutron-induced reactions and their complete temporal evolution. No other presently available method seems to provide reliable results, in particular under the capture resonances. An improved neutron background estimation technique is proposed, the main improvement regarding the treatment of the neutron sensitivity, taking into account the temporal evolution of the neutron-induced reactions. The technique is complemented by an advanced data analysis procedure based on relativistic kinematics of neutron scattering. The analysis procedure allows for the calculation of the neutron background in capture measurements, without requiring the time-consuming simulations to be adapted to each particular sample. A suggestion is made on how to improve the neutron background estimates if neutron background simulations are not available.Comment: 11 pages, 9 figure

Nonlocal Treatment of the Buoyancy-Shear-Driven Boundary Layer

Abstract A successful description of a convective boundary layer requires that the model employed takes into account the nonlocal nature of turbulent convection. In this paper new third-order moments (TOMs) are presented and tested. Numerical solutions are obtained using mean flow components and second-order moments as input. The problem of the turbulent damping of the TOMs is considered. The terms in the dynamic equations responsible for the unphysical growth of the TOMs are parameterized, taking into account their dependence on the integral length scale vertical profile. The calculated profiles are presented and tested against large-eddy simulation data and aircraft measurements. In both cases the results compare favorably

Analysis of charged particle emission sources and coalescence in E/A = 61 MeV 36^{36}Ar + 27^{27}Al, 112^{112}Sn and 124^{124}Sn collisions

Single-particle kinetic energy spectra and two-particle small angle correlations of protons ($p$), deuterons ($d$) and tritons ($t$) have been measured simultaneously in 61A MeV $^{36}$Ar + $^{27}$Al, $^{112}$Sn and $^{124}$Sn collisions. Characteristics of the emission sources have been derived from a ``source identification plot'' ($\beta_{source}$--$E_{CM}$ plot), constructed from the single-particle invariant spectra, and compared to the complementary results from two-particle correlation functions. Furthermore, the source identification plot has been used to determine the conditions when the coalescence mechanism can be applied for composite particles. In our data, this is the case only for the Ar + Al reaction, where $p$, $d$ and $t$ are found to originate from a common source of emission (from the overlap region between target and projectile). In this case, the coalescence model parameter, $\tilde{p}_0$ -- the radius of the complex particle emission source in momentum space, has been analyzed.Comment: 20 pages, 5 figures, submitted to Nuclear Physics

The Dynamical Dipole Mode in Fusion Reactions with Exotic Nuclear Beams

We report the properties of the prompt dipole radiation, produced via a collective bremsstrahlung mechanism, in fusion reactions with exotic beams. We show that the gamma yield is sensitive to the density dependence of the symmetry energy below/around saturation. Moreover we find that the angular distribution of the emitted photons from such fast collective mode can represent a sensitive probe of its excitation mechanism and of fusion dynamics in the entrance channel.Comment: 5 pages, 3 figures, to appear in Phys.Rev.

The impact of heavy vehicle traffic trends on the overdesign of flexible asphalt pavements

Given their environmental impact, the careful design of asphalt pavements is crucial. Previous research has highlighted the influence of several parameters on the outputs of different pavement design methods. In this study, the focus is on heavy vehicle trends, considering both the percentage of heavy vehicles in the average traffic flow and its evolution over time, which is usually included as a growth factor in the design inputs. Since these factors are very often assumed to be based on old estimates, the first aim of this study was to update them by exploring a recent series of continuous data collected on the Italian motorway network and showing how to infer estimates from historical traffic data. Subsequently, the variability of these input factors is introduced in standard pavement design methods to assess their influence on the design process and to quantify the risk of overdesign. While the analysis of historical heavy vehicle traffic data may reveal an overall zero-growth traffic tendency, different scenarios should be considered and assessed in cost-benefit analyses given the not negligible influence of growth factors on pavement thicknesses. This influence is shown here in different simulated design conditions, with different initial traffic volumes, share of heavy vehicles, and resilient moduli

The Dynamical Dipole Mode in Dissipative Heavy Ion Collisions

We study the effect of a direct Giant Dipole Resonance ($GDR$) excitation in intermediate dinuclear systems with exotic shape and charge distributions formed in charge asymmetric fusion entrance channels. A related enhancement of the $GDR$ gamma yield in the evaporation cascade of the fused nucleus is expected. The dynamical origin of such $GDR$ extra strength will show up in a characteristic anisotropy of the dipole gamma-emission. A fully microscopic analysis of the fusion dynamics is performed with quantitative predictions of the $GDR$ photon yield based on a dynamics- statistics coupling model. In particular we focus our attention on the energy and mass dependence of the effect. We suggest a series of new experiments, in particular some optimal entrance channel conditions. We stress the importance of using the new available radioactive beams.Comment: 20 pages (Latex), 14 Postscript figure

Isotopic Composition of Fragments in Nuclear Multifragmentation

The isotope yields of fragments, produced in the decay of the quasiprojectile in Au+Au peripheral collisions at 35 MeV/nucleon and those coming from the disassembly of the unique source formed in Xe+Cu central reactions at 30 MeV/nucleon, were measured. We show that the relative yields of neutron-rich isotopes increase with the excitation energy in multifragmentation reaction. In the framework of the statistical multifragmentation model which fairly well reproduces the experimental observables, this behaviour can be explained by increasing N/Z ratio of hot primary fragments, that corresponds to the statistical evolution of the decay mechanism with the excitation energy: from a compound-like decay to complete multifragmentation.Comment: 10 pages. 4 Postscript figures. Submitted to Physical Review C, Rapid Communicatio

On the optimal energy of epithermal neutron beams for BNCT

The optimal neutron energy for the treatment of deep-seated tumours using boron neutron capture therapy is studied by analysing various figures of merit. In particular, analysis of the therapeutic gain as a function of the neutron energy indicates that, with the currently available 10 B carriers, the most useful neutrons for the treatment of deep-seated tumours, in particular glioblastoma multiforme, are those with an energy of a few keV. Based on the results of the simulations, a method is presented which allows us to evaluate the quality of epithermal neutron beams of known energy spectrum, thus allowing us to compare different neutron-producing reactions and beam-shaping assembly configurations used for accelerator-based neutron sources

Data from a multidisciplinary poll of 178 expert physicians on the usage of non-vitamin K Oral Anticoagulants in patients with atrial fibrillation and venous thromboembolism

This data article contains data from a multidisciplinary questionnaires filled in by 178 expert physicians on the usage of non-vitamin K Oral Anticoagulants in patients with atrial fibrillation (AF) and for the treatment of patients with venous thromboembolism (VTE). The questionnaire consists of 9 statements of clinical complex AF and VTE cases and informative campaign on antithrombotic therapy for stroke prevention in AF. The data are potentially valuable for the scientific community, showing the doubts of different specialists (Internists, Pneumologists, Geriatricians, Cardiologists and Neurologists) with a large experience in prescribing oral anticoagulation in difficult AF and VTE cases (see full list of participants provided). The data obtained in some particular clinical cases such as CHA2DS2-VASc=1, comorbid coronary artery disease, frailty, advanced age, risk of falling and prior haemorrhagic stroke, can be compared with indications from published guidelines and recommendations for future insight and to be considered as a benchmark for future trials in the area or oral anticoagulation for AF and VTE.The data concerning informative campaign on antithrombotic therapy for stroke prevention showed the expert panel agreement on the inclusion of self monitoring of heart rhythm by pulse taking in subjects older than 64 years of age (81% agreement, item 3); knowledge that the risk of stroke associated with AF is almost twice the risk associated with hypertension (95% agreement, item 4); knowledge that the CHA2DS2-VASc score exerts a higher influence on stroke risk compared to AF duration (92% agreement, item 5); knowledge that stroke prevention in AF with a NOAC is more effective, does not cause any higher bleeding risk, and is equally simple compared to aspirin treatment (91% agreement, item 6).Data on strategies to optimise appropriate prescription of antithrombotic therapy showed agreement on the utility of short television advertisements about the risks of stroke associated with AF (79% agreement, item 8), on a campaign encouraging regular control of cardiac rhythm by pulse taking (77% agreement, item 1), on a campaign reporting the advantages of anticoagulation over no antithrombotic therapy (98% agreement, item 2) or of NOACs over aspirin (96% agreement, item 3) or on the practical use of NOAC (93% agreement, item 6) or on stroke and bleeding risk scores (87% agreement, item 7). See Colonna et al. (2017) [1] for further interpretation and discussion

Low-cost smartphone-based speed surveying methods in proximity to traffic calming devices

The study is aimed at investigating the effectiveness of two smartphone applications for surveying speeds of moving objects. These applications are used for urban speed measurements. Once the most reliable application was selected among the available ones, its outputs were calibrated by using the speed from the GPS system mounted on the test vehicle as a benchmark. Thereafter, an experimental test was conducted for monitoring the influence of a raised crossing on the vehicle speeds in the urban environment, by using the selected smartphone application