Heavy-to-light scalar form factors from Muskhelishvili-Omn\`es dispersion relations

By solving the Muskhelishvili-Omn\`es integral equations, the scalar form factors of the semileptonic heavy meson decays $D\to\pi \bar \ell \nu_\ell$, $D\to \bar{K} \bar \ell \nu_\ell$, $\bar{B}\to \pi \ell \bar\nu_\ell$ and $\bar{B}_s\to K \ell \bar\nu_\ell$ are simultaneously studied. As input, we employ unitarized heavy meson-Goldstone boson chiral coupled-channel amplitudes for the energy regions not far from thresholds, while, at high energies, adequate asymptotic conditions are imposed. The scalar form factors are expressed in terms of Omn\`es matrices multiplied by vector polynomials, which contain some undetermined dispersive subtraction constants. We make use of heavy quark and chiral symmetries to constrain these constants, which are fitted to lattice QCD results both in the charm and the bottom sectors, and in this latter sector to the light-cone sum rule predictions close to $q^2=0$ as well. We find a good simultaneous description of the scalar form factors for the four semileptonic decay reactions. From this combined fit, and taking advantage that scalar and vector form factors are equal at $q^2=0$, we obtain $|V_{cd}|=0.244\pm 0.022$, $|V_{cs}|=0.945\pm 0.041$ and $|V_{ub}|=(4.3\pm 0.7)\times10^{-3}$ for the involved Cabibbo-Kobayashi-Maskawa (CKM) matrix elements. In addition, we predict the following vector form factors at $q^2=0$: $|f_+^{D\to\eta}(0)|=0.01\pm 0.05$, $|f_+^{D_s\to K}(0)|=0.50 \pm 0.08$, $|f_+^{D_s\to\eta}(0)|=0.73\pm 0.03$ and $|f_+^{\bar{B}\to\eta}(0)|=0.82 \pm 0.08$, which might serve as alternatives to determine the CKM elements when experimental measurements of the corresponding differential decay rates become available. Finally, we predict the different form factors above the $q^2-$regions accessible in the semileptonic decays, up to moderate energies amenable to be described using the unitarized coupled-channel chiral approach.Comment: includes further discussions and references; matches the accepted versio

Deterministic ratchet from stationary light fields

Ratchets are dynamic systems where particle transport is induced by zero-average forces due to the interplay between nonlinearity and asymmetry. Generally, they rely on the effect of a strong external driving. We show that stationary optical lattices can be designed to generate particle flow in one direction while requiring neither noise nor driving. Such optical fields must be arranged to yield a combination of conservative (dipole) and nonconservative (radiation pressure) forces. Under strong friction all paths converge to a discrete set of limit periodic trajectories flowing in the same direction.Comment: 6 pages, 4 figure

Classifying BCI signals from novice users with Extreme Learning Machine

Volume 15, Issue 1 Previous ArticleNext Article Classifying BCI signals from novice users with extreme learning machine Germán Rodríguez-Bermúdez / Andrés Bueno-Crespo / F. José Martinez-Albaladejo Published Online: 2017-07-07 | DOI: https://doi.org/10.1515/phys-2017-0056 OPEN ACCESS DOWNLOAD PDF Abstract Brain computer interface (BCI) allows to control external devices only with the electrical activity of the brain. In order to improve the system, several approaches have been proposed. However it is usual to test algorithms with standard BCI signals from experts users or from repositories available on Internet. In this work, extreme learning machine (ELM) has been tested with signals from 5 novel users to compare with standard classification algorithms. Experimental results show that ELM is a suitable method to classify electroencephalogram signals from novice users.Ingeniería, Industria y Construcció

The influence of the powder characteristics on 316L stainless steel coatings sprayed by cold gas spray

Thermally sprayed 316L stainless steel coatings are commonly used on metallic structures due to their corrosion and wear resistance when compared to carbon steel. Cold Gas Spray (CGS) is a convenient thermal spray process to deposit 316L coatings, producing thick and very dense coatings, with almost no deleterious changes on the feedstock properties to the coating condition. The powder characteristics have influence on the microstructure of the coating, such as porosity and oxide contents, which alter its corrosion and wear behavior. CGS is an efficient technique to reduce the problems associated with material melting commonly found in other conventional thermal spray methods. In this work, different 316L powders, produced by different manufacturers, were deposited by CGS, applying the same equipment and parameters, with the objective to evaluate the relation between the powders' characteristics and coating properties. Their microstructure, adherence, hardness, as well as the performance on corrosion and wear testing were evaluated. The water atomized powders presented in general better results than gas atomized powders

Improving the Wear and Corrosion Resistance of Maraging Part Obtained by Cold Gas Spray Additive Manufacturing

The use of the cold gas spray (CGS) process as a metal additive manufacturing (MAM) technique for metallic part production has been deeply studied recently, mainly due to its advantages over other MAM techniques. CGS MAM is a high-productivity technique with a very low level of particle oxidation, microstructural changes, phase transformations, or deleterious residual thermal stresses in the part. The use of CGS MAM to produce maraging parts represents a gain for the industry by saving machining time and preventing raw material waste. Its wear resistance and corrosion behavior were evaluated in this work and were compared with cermet coatings deposited by high-velocity oxy-fuel (HVOF) on the CGS MAM maraging. This work presents the innovative and effective combination of different thermal spraying processes and materials to obtain MAM maraging parts with higher wear resistance, evaluating abrasion, sliding, and water erosion wear type

CLIMATE CHAGE IMPACTS OF RURAL SOCIETIES: STAKEHOLDERS PERCEPTIONS AND ADAPTATION STRATEGIES IN BUENOS AIRES, ARGENTINA

N° ISBN - 978-2-7380-1284-5International audienceHeavily dependent on agriculture, Argentinean stakeholders must prepare to adapt their activities to a different climate. However, the country does not have an agricultural adaptation plan. A space of joint discussion and participatory planning among farmers, scientific researchers, firm managers and government representatives can increase the preparedness to cope with the impacts of climate change. This research uses individual and group interviews to identify perceptions about climate change and possible adaptation strategies suitable for different types of stakeholders of the district of Balcarce. Relatively homogeneous groups of stakeholders perceive an array of weather changes and identify a range of adaptation strategies. This rich set of perceptions and strategies constitute an excellent starting point to define priorities in research and in policy making to implement national, regional, or firm- level adaptation strategies. Genetic techniques, specific scientific knowledge and land-use planning are viewed as promising sources of adaptation and coordination mechanisms. One common request from stakeholders is the coordination between, and within, public and private organizations. Effective adaptation strategies require the implementation multi-level governance and policy integration. However, these integrations will generate benefits in any type of future climate

Dimensional structure of the oral health-related quality of life in healthy Spanish workers

<p>Abstract</p> <p>Background</p> <p>Oral health-related quality of life (OHQoL) is conceived as a multidimensional construct. Here our aim was to investigate the dimensional structure of OHQoL as measured by the Spanish versions of the Oral Impacts on Daily Performance (OIDP) and the Oral Health Impact Profile (OHIP-14) questionnaires applied simultaneously.</p> <p>Methods</p> <p>We recruited a consecutive sample of 270 healthy Spanish workers visiting the Employment Risk Prevention Centre for a routine medical check-up. OHIP-14 was self-completed by participants but the OIDP was completed in face-to-face interviews. An Exploratory Factor Analysis (EFA) was performed to identify the underlying dimensions of the OHQoL construct assessed by both instruments. This factorial structure was later confirmed by Confirmatory Factor Analysis (CFA) using several estimators of goodness of fit indices.</p> <p>Results</p> <p>EFA and the CFA identified and respectively confirmed a set of 3 underlying factors in both questionnaires that could be interpreted as functional limitation, pain-discomfort, and psychosocial impacts. The model achieved was seen to fit properly for both instruments, but the factorial structure was clearer for the OIDP.</p> <p>Conclusions</p> <p>The results provide evidence for construct equivalence in the latent factors assessed by both OIDP and OHIP-14, suggesting that OHQoL is a three-dimensional construct. The prevalence of impact on these three factors was coherent between both indicators, pain-discomfort having the highest prevalence, followed by psycho-social impact, and functional limitation.</p

Strong magnetic response of submicron Silicon particles in the infrared

High-permittivity dielectric particles with resonant magnetic properties are being explored as constitutive elements of new metamaterials and devices in the microwave regime. Magnetic properties of low-loss dielectric nanoparticles in the visible or infrared are not expected due to intrinsic low refractive index of optical materials in these regimes. Here we analyze the dipolar electric and magnetic response of loss-less dielectric spheres made of moderate permittivity materials. For low material refractive index there are no sharp resonances due to strong overlapping between different multipole contributions. However, we find that Silicon particles with refractive index 3.5 and radius approx. 200nm present a dipolar and strong magnetic resonant response in telecom and near-infrared frequencies, (i.e. at wavelengths approx. 1.2-2 micrometer). Moreover, the light scattered by these Si particles can be perfectly described by dipolar electric and magnetic fields, quadrupolar and higher order contributions being negligible.Comment: 10 pages, 5 figure

Computerized Generation and Finite Element Stress Analysis of Endodontic Rotary Files

Introduction: The finite element method has been extensively used to analyze the mechanical behavior of endodontic rotary files under bending and torsional conditions. This methodology requires elevated computer-aided design skills to reproduce the geometry of the endodontic file, and also mathematical knowledge to perform the finite element analysis. In this study, an automated procedure is proposed for the computerized generation and finite element analysis of endodontic rotary files under bending and torsional conditions. Methods: An endodontic rotary file with a 25mm total length, 0.25mm at the tip, 1.20mm at 16mm from the tip, 2mm pitch and squared cross section was generated using the proposed procedure and submitted for analysis under bending and torsional conditions by clamping the last 3mm of the endodontic rotary file and applying a transverse load of 0.1N and a torsional moment of 0.3N.cm. Results: The results of the finite element analyses showed a maximum von Mises stress of 398MPa resulting from the bending analysis and a maximum von Mises stress of 843MPa resulting from the torsional analysis, both of which are next to the encastre point. Conclusions: The automated procedure allows an accurate description of the geometry of the endodontic file to be obtained based on its design parameters as well as a finite element model of the endodontic file from the previously generated geometry

Metal Knitting: A New Strategy for Cold Gas Spray Additive Manufacturing

Cold Spray Additive Manufacturing (CSAM) is an emergent technique to produce parts by the additive method, and, like other technologies, it has pros and cons. Some advantages are using oxygen-sensitive materials to make parts, such as Ti alloys, with fast production due to the high deposition rate, and lower harmful residual stress levels. However, the limitation in the range of the parts' geometries is a huge CSAM con. This work presents a new conceptual strategy for CSAM spraying. The controlled manipulation of the robot arm combined with the proper spraying parameters aims to optimize the deposition efficiency and the adhesion of particles on the part sidewalls, resulting in geometries from thin straight walls, less than 5 mm thick, up to large bulks. This new strategy, Metal Knitting, is presented regarding its fundamentals and by comparing the parts' geometries produced by Metal Knitting with the traditional strategy. The Metal Knitting described here made parts with vertical sidewalls, in contrast to the 40 degrees of inclination obtained by the traditional strategy. Their mechanical properties, microstructures, hardness, and porosity are also compared for Cu, Ti, Ti6Al4V, 316L stainless steel, and Al