Interplay between valence and core excitation mechanisms in the breakup of halo nuclei

The phenomenon of core excitation in the breakup of a two-body halo nucleus is investigated. We show that this effect plays a significant role in the reaction dynamics and, furthermore, its interference with the valence excitation mechanism has sizable and measurable effects on the breakup angular distributions. These effects have been studied in the resonant breakup of 11Be on a carbon target, populating the resonances at 1.78 MeV (5/2+) and 3.41 MeV (3/2+). The calculations have been performed using a recently extension of the DWBA method, which takes into account the effect of core excitation in both the structure of the halo nucleus and in the reaction mechanism. The calculated angular distributions have been compared with the available data [Fukuda et al., Phys. Rev. C70,054606]. Although each of these resonances is dominated by one of the two considered mechanisms, the angular patterns of these resonances depend in a very delicate way on the interference between them. This is the first clear evidence of this effect but the phenomenon is likely to occur in other similar reactions.Comment: 5 pages, 2 figures, (Version to appear in Physical Review Letters

Dust outflows and inner gaps generated by massive planets in debris disks

Main sequence stars are commonly surrounded by debris disks, formed by cold far-IR-emitting dust that is thought to be continuously replenished by a reservoir of undetected dust-producing planetesimals. We have investigated the orbital evolution of dust particles in debris disks harboring massive planets. Small dust grains are blown out by radiation pressure, as is well known; in addition, gravitational scattering by the giant planets also creates an outflow of large grains. We describe the characteristics of this large-particle outflow in different planetary architectures and for different particle sizes. In addition, the ejection of particles is responsible for the clearing of dust inside the orbit of the planet. We study the efficiency of particle ejection and the resulting dust density contrast inside and outside the orbit of the planet, as a function of the planet's mass and orbital elements and the particle size. We discuss its implications for exo-planetary debris disks and for the interpretation of in-situ dust detection experiments on space probes traveling in the outer solar system.Comment: 32 pages (pre-print format), including 12 figures. Accepted to ApJ (2005). Due to space constrains Fig. 3-6 are at very low resolutio

Binding-energy independence of reduced spectroscopic strengths derived from (p, 2p) and (p, pn) reactions with nitrogen and oxygen isotopes

A campaign of intermediate energy (300-450 MeV/u) proton-induced nucleon knockout measurements in inverse kinematics has been recently undertaken at the R 3 B/LAND setup at GSI. We present a systematic theoretical analysis of these data with the aim of studying the quenching of the single-particle strengths and its binding-energy dependence. For that, the measured semi-inclusive (p, 2p) and (p, pn) cross sections are compared with theoretical predictions based on single-particle cross sections derived from a novel coupled-channels formalism and shell-model spectroscopic factors. A systematic reduction of about 20-30% is found, with a very limited dependence on proton-neutron asymmetry.Comment: 8 pages, 3 figure

Support Vector Machines (SVM) as a Technique for Solvency Analysis

This paper introduces a statistical technique, Support Vector Machines (SVM), which is considered by the Deutsche Bundesbank as an alternative for company rating. A special attention is paid to the features of the SVM which provide a higher accuracy of company classification into solvent and insolvent. The advantages and disadvantages of the method are discussed. The comparison of the SVM with more traditional approaches such as logistic regression (Logit) and discriminant analysis (DA) is made on the Deutsche Bundesbank data of annual income statements and balance sheets of German companies. The out-of-sample accuracy tests confirm that the SVM outperforms both DA and Logit on bootstrapped samples.Company rating, bankruptcy analysis, support vector machines

Risk factors for central venous catheter-related infections in surgical and intensive care units. The Central Venous Catheter-Related Infections Study Group.

To identify avoidable risk factors for central venous catheter (CVC) infections in patients undergoing short-term catheterization

Determining B(E1)B(E1) distributions of weakly bound nuclei from breakup cross sections using Continuum Discretized Coupled Channels calculations. Application to 11^{11}Be

A novel method to extract the $B(E1)$ strength of a weakly bound nucleus from experimental Coulomb dissociation data is proposed. The method makes use of continuum discretized coupled channels (CDCC) calculations, in which both nuclear and Coulomb forces are taken into account to all orders. This is a crucial advantage with respect to the standard procedure based on the Equivalent Photon Method (EPM) which does not properly take into account nuclear distortion, higher order coupling effects, or Coulomb-nuclear interference terms. The procedure is applied to the $^{11}$Be nucleus using two sets of available experimental data at different energies, for which seemingly incompatible $B(E1)$ have been reported using the EPM. We show that the present procedure gives consistent $B(E1)$ strengths, thus solving the aforementioned long-standing discrepancy between the two measurements.Comment: Submitted for publicatio

Description of the 11^{11}Li(p,d)10(p,d){^{10}}Li transfer reaction using structure overlaps from a full three-body model

Recent data on the differential angular distribution for the transfer reaction $^{11}$Li(p,d)$^{10}$Li at $E/A=5.7$ MeV in inverse kinematics are analysed within the DWBA reaction framework, using the overlap functions calculated within a three-body model of $^{11}$Li. The weight of the different $^{10}$Li configurations in the system's ground state is obtained from the structure calculations unambiguously. The effect of the $^{9}$Li spin in the calculated observables is also investigated. We find that, although all the considered models succeed in reproducing the shape of the data, the magnitude is very sensitive to the content of $p_{1/2}$ wave in the $^{11}$Li ground-state wave function. Among the considered models, the best agreement with the data is obtained when the $^{11}$Li ground state contains a $\sim$31\% of $p_{1/2}$ wave in the $n$-$^9$Li subsystem. Although this model takes into account explicitly the splitting of the $1^+$ and $2^+$ resonances due to the coupling of the $p_{1/2}$ wave to the $3/2^-$ spin of the core, a similar degree of agreement can be achieved with a model in which the $^{9}$Li spin is ignored, provided that it contains a similar p-wave content.Comment: 8 pages, 3 figures. Final versio

Financing SMEs: a model for optimising the capital structure

This paper argues that the existing finance literature is inadequate with respect to its cov-erage of capital structure of small and medium sized enterprises (SMEs). In particular it is argued that the cost of equity (being both conceptually ill defined and empirically non quantifiable) is not applicable to the capital structure decisions for a large proportion of SMEs and the optimal capital structure depends only on the mix of short and long term debt. The paper then presents a model for optimising the debt mix and demonstrates its practical application using an Italian firm’s debt structure as a case study