Improved thermal isolation of silicon suspended platforms for an all-silicon thermoelectric microgenerator based on large scale integration of Si nanowires as thermoelectric material

Special suspended micro-platforms have been designed as a part of silicon compatible planar thermoelectric microgenerators. Bottom-up grown silicon nanowires are going to bridge in the future such platforms to the surrounding silicon bulk rim. They will act as thermoelectric material thus configuring an all-silicon thermoelectric device. In the new platform design other additional bridging elements (usually auxiliary support silicon beams) are substituted by low conductance thin film dielectric membranes in order to maximize the temperature difference developed between both areas. These membranes follow a sieve-like design that allows fabricating them with a short additional wet anisotropic etch step. © Published under licence by IOP Publishing Ltd.Peer ReviewedPostprint (published version

Homogeneous geodesics of non-unimodular Lorentzian Lie groups and naturally reductive Lorentzian spaces in dimension three

We determine, for all three-dimensional non-unimodular Lie groups equipped with a Lorentzian metric, the set of homogeneous geodesics through a point. Together with the results of [C] and [CM2], this leads to the full classification of three-dimensional Lorentzian g.o. spaces and naturally reductive spaces

Fluorescence in quantum dynamics: accurate spectra require post-mean-field approaches

Real time modeling of fluorescence with vibronic resolution entails the representation of the light–matter interaction coupled to a quantum-mechanical description of the phonons and is therefore a challenging problem. In this work, taking advantage of the difference in timescales characterizing internal conversion and radiative relaxation—which allows us to decouple these two phenomena by sequentially modeling one after the other—we simulate the electron dynamics of fluorescence through a master equation derived from the Redfield formalism. Moreover, we explore the use of a recent semiclassical dissipative equation of motion [C. M. Bustamante et al., Phys. Rev. Lett. 126, 087401 (2021)], termed coherent electron electric-field dynamics (CEED), to describe the radiative stage. By comparing the results with those from the full quantum-electrodynamics treatment, we find that the semiclassical model does not reproduce the right amplitudes in the emission spectra when the radiative process involves the de-excitation to a manifold of closely lying states. We argue that this flaw is inherent to any mean-field approach and is the case with CEED. This effect is critical for the study of light–matter interaction, and this work is, to our knowledge, the first one to report this problem. We note that CEED reproduces the correct frequencies in agreement with quantum electrodynamics. This is a major asset of the semiclassical model, since the emission peak positions will be predicted correctly without any prior assumption about the nature of the molecular Hamiltonian. This is not so for the quantum electrodynamics approach, where access to the spectral information relies on knowledge of the Hamiltonian eigenvalues

Prospects for measurement and control of the scattering length of metastable helium using photoassociation techniques

A numerical investigation of two-laser photoassociation (PA) spectroscopy on spin-polarized metastable helium (He*) atoms is presented within the context of experimental observation of the least-bound energy level in the scattering potential and subsequent determination of the s-wave scattering length. Starting out from the model developed by Bohn and Julienne [Phys. Rev. A \textbf{60}, (1999) 414], PA rate coefficients are obtained as a function of the parameters of the two lasers. The rate coefficients are used to simulate one- and two-laser PA spectra. The results demonstrate the feasibility of a spectroscopic determination of the binding energy of the least-bound level. The simulated spectra may be used as a guideline when designing such an experiment, whereas the model may also be employed for fitting experimentally obtained PA spectra. In addition, the prospects for substantial modification of the He* scattering length by means of optical Feshbach resonances are considered. Several experimental issues relating to the numerical investigation presented here are discussed.Comment: 9 pages, 7 figure

Caracterización de placas de yeso con residuos de espuma de poliuretano reforzadas con fibras de polipropileno

Gypsum plasterboard that incorporates various combinations of polyurethane foam waste and polypropylene fibers in its matrix is studied. The prefabricated material was characterized in a series of standardized tests: bulk density, maximum breaking load under flexion stress, total water absorption, surface hardness, thermal properties, and reaction to fire performance. Polypropylene fibers were added to the polyurethane gypsum composites to improve the mechanical behavior of the plasterboard under loading. The results indicate that increased quantities of polymer waste led to significant reductions in the weight/surface ratio, the mechanical strength and the surface hardness of the gypsum, as well as improving its thermal resistance. The polypropylene fibers showed good adhesion to the polymer and the gypsum matrix, which enhanced the mechanical performance and the absorption capacity of these compounds. The non-combustibility test demonstrated the potential of the new material for use in internal linings.Este artículo presenta un estudio experimental basado en la reutilización de residuos de poliuretano en una matriz de yeso para elaborar una placa de yeso laminado. Las placas fueron caracterizadas mediante los ensayos normalizados de densidad aparente, carga de rotura máxima a flexión, absorción total de agua, dureza superficial y reacción al fuego. Se han introducido fibras de polipropileno en la matriz con el objetivo de aumentar la resistencia mecánica del material. Los resultados muestran que el incremento de residuo polimérico en el material implica importantes reducciones de peso, resistencia mecánica y dureza superficial, a la par que se mejora su resistencia térmica consiguiéndose valores similares a los comerciales. Las fibras de polipropileno mostraron una buena adhesión con el polímero, mejorando el comportamiento mecánico y la capacidad de absorción. El ensayo de reacción al fuego confirmó que los residuos de poliuretano pueden ser empleados en la fabricación de placas de yeso laminado en cumplimiento con la normativa

Antiviral Activity of Reagents in Mouth Rinses against SARS-CoV-2.

The oral cavity, an essential part of the upper aerodigestive tract, is believed to play an important role in the pathogenicity and transmission of SARS-CoV-2. The identification of targeted antiviral mouth rinses to reduce salivary viral load would contribute to reducing the COVID-19 pandemic. While awaiting the results of significant clinical studies, which to date do not exist, the commercial availability of mouth rinses leads us to search among them for reagents that would have specific antiviral properties with respect to SARS-CoV-2. The challenges facing this target were examined for 7 reagents found in commercially available mouth rinses and listed on the ClinicalTrials.gov website: povidone-iodine, chlorhexidine, hydrogen peroxide, cyclodextrin, Citrox, cetylpyridinium chloride, and essential oils. Because SARS-CoV-2 is an enveloped virus, many reagents target the outer lipid membrane. Moreover, some of them can act on the capsid by denaturing proteins. Until now, there has been no scientific evidence to recommend mouth rinses with an anti-SARS-CoV-2 effect to control the viral load in the oral cavity. This critical review indicates that current knowledge of these reagents would likely improve trends in salivary viral load status. This finding is a strong sign to encourage clinical research for which quality protocols are already available in the literature

The Second Wind in McArdle Patients: Fitness Matters

Glucogenosis tipo 5; Deficiencia de miofosforilasa; Umbral de ventilaciónGlycogenosis type 5; Myophosphorylase deficiency; Ventilatory thresholdGlucogenosi tipus 5; Deficiència de miofosforilasa; Llindar ventilatoriBackground: The “second wind” (SW) phenomenon—commonly referring to both an initial period of marked intolerance to dynamic exercise (e.g., brisk walking) that is not followed by perceived improvement and disappearance of previous tachycardia (i.e., the actual “SW”) until 6–10 min has elapsed—is an almost unique feature of McArdle disease that limits adherence to an active lifestyle. In this regard, an increase in the workload eliciting the SW could potentially translate into an improved patients’ exercise tolerance in daily life. We aimed to determine whether aerobic fitness and physical activity (PA) levels are correlated with the minimum workload eliciting the SW in McArdle patients—as well as with the corresponding heart rate value. We also compared the SW variables and aerobic fitness indicators in inactive vs. active patients. Methods: Fifty-four McArdle patients (24 women, mean ± SD age 33 ± 12 years) performed 12-min constant-load and maximum ramp-like cycle-ergometer tests for SW detection and aerobic fitness [peak oxygen uptake (VO2peak) and workload and ventilatory threshold] determination, respectively. They were categorized as physically active/inactive during the prior 6 months (active = reporting ≥150 min/week or ≥75 min/week in moderate or vigorous-intensity aerobic PA, respectively) and were also asked on their self-report of the SW. Results: Both peak and submaximal indicators of aerobic fitness obtained in the ramp tests were significantly correlated with the workload of the SW test, with a particularly strong correlation for the VO2peak and peak workload attained by the patients (both Pearson’s coefficients > 0.70). Twenty (seven women) and 24 patients (18 women) were categorized as physically active and inactive, respectively. Not only the aerobic fitness level [∼18–19% higher values of VO2peak (ml⋅kg–1⋅min–1)] but also the workload of the SW tests was significantly higher in active than in inactive patients. All the inactive patients reported that they experienced the SW during walking/brisk walking in daily life, whereas active patients only reported experiencing this phenomenon during more strenuous activities (very brisk walking/jogging and bicycling). Conclusion: A higher aerobic fitness and an active lifestyle are associated with a higher workload eliciting the so-called SW phenomenon in patients with McArdle disease, which has a positive impact on their exercise tolerance during daily living.Research by AL, CF-L, GN-G, MM, and TP was funded by the Instituto de Salud Carlos III (ISCIII) and Fondos Feder (grants PI18/00139, PI20/00645, PI18/00713, PI17/00093, and PI19/01313). CF-L and GN-G were supported by Miguel Servet contracts (CP18/00034 and CPII19/00021, respectively) from ISCIII. The funders had no role in study design; in the collection, analysis, and interpretation of data; in the writing of the report; or in the decision to submit the manuscript for publication

Light and heavy transfer products in Xe 136 + U 238 multinucleon transfer reactions

A. Vogt et al.; 12 pags.; 14 figs.; PACS number(s): 24.10.−i, 25.70.Hi, 29.30.Aj, 29.40.Gx© 2015 American Physical Society. ©2015 American Physical Society. Background: Multinucleon transfer reactions (MNT) are a competitive tool to populate exotic neutron-rich nuclei in a wide region of nuclei, where other production methods have severe limitations or cannot be used at all. Purpose: Experimental information on the yields of MNT reactions in comparison with theoretical calculations are necessary to make predictions for the production of neutron-rich heavy nuclei. It is crucial to determine the fraction of MNT reaction products which are surviving neutron emission or fission at the high excitation energy after the nucleon exchange. Method: Multinucleon transfer reactions in Xe136+U238 have been measured in a high-resolution γ-ray/particle coincidence experiment. The large solid-angle magnetic spectrometer PRISMA coupled to the high-resolution Advanced Gamma Tracking Array (AGATA) has been employed. Beamlike reaction products after multinucleon transfer in the Xe region were identified and selected with the PRISMA spectrometer. Coincident particles were tagged by multichannel plate detectors placed at the grazing angle of the targetlike recoils inside the scattering chamber. Results: Mass yields have been extracted and compared with calculations based on the grazing model for MNT reactions. Kinematic coincidences between the binary reaction products, i.e., beamlike and targetlike nuclei, were exploited to obtain population yields for nuclei in the actinide region and compared to x-ray yields measured by AGATA. Conclusions: No sizable yield of actinide nuclei beyond Z=93 is found to perform nuclear structure investigations. In-beam γ-ray spectroscopy is feasible for few-neutron transfer channels in U and the -2p channel populating Th isotopes.The research leading to these results has received funding from the German Bundesministerium fur Bildung ¨ und Forschung (BMBF) under Contract No. 05P12PKFNE TP4, the European Union Seventh Framework Programme (FP7/2007-2013) under Grant No. 262010-ENSAR, and the Spanish Ministerio de Ciencia e Innovacion under Contract ´ No. FPA2011-29854-C04. A.V. thanks the Bonn-Cologne Graduate School of Physics and Astronomy (BCGS) for financial support. One of the authors (A. Gadea) was supported by MINECO, Spain, under Grants No. FPA2011-29854-C04 and No. FPA2014-57196-C5, Generalitat Valenciana, Spain, under Grant No. PROMETEOII/2014/019, and EU under the FEDER program.Peer Reviewe

Vibronic coupling and core-hole localization in K-shell excitations of ethylene

A new high-resolution measurement of the C 1s near-edge photoabsorption spectrum of the ethylene molecule is reported. An analysis of the vibrational structure in the C 1s-π* band indicates strong excitation of non-totally-symmetry modes and the importance of vibronic coupling. The latter phenomenon provides a mechanism for core-hole localization in the final state