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The space segment of the Global Navigation Satellite System (GNSS) is equipped with highly stable atomic clocks. In order to use these clocks as references, their time offsets must be estimated from ground measurements as accurately as possible. This work presents a multi-frequency and multi-constellation method for estimating satellite and receiver clock corrections, starting from unambiguous, uncombined, and undifferenced carrier-phase measurements. A byproduct of the estimation process is phase biases (i.e., the hardware delays of the carrier-phase measurements occurring at receivers and satellites). The stability and predictability of our clock estimates for receivers and satellites (GPS and Galileo) are compared with those obtained by the International GNSS Service (IGS), whereas the phase biases are assessed against two independent determinations involving combinations of carrier-phase measurements. We conclude that the method reduces day boundary discontinuities in the clock corrections, and that the estimated phase biases reproduce variabilities already observed by other authors. The present work was supported in part by the Euro-pean Space Agency contract (REL-GAL) N.4000122402/17/NL/IB, by the project RTI2018-094295-B-I00 funded bytheMCIN/AEI10.13039/501100011033whichisco-foundedby the FEDER programme, and by the Horizon 2020 MarieSkłodowska-Curie Individual Global Fellowship 797461NAVSCIN. The authors acknowledge the use of data andproducts provided by the International GNSS Service

The compounds A$_2$Cu$_3$O(SO$_4$)$_3$ (A=Na, K) are characterized by copper hexamers which are weakly coupled to realize antiferromagnetic order below TN=3 K. They constitute novel quantum spin systems with S=1 triplet ground-states. We investigated the energy-level splittings of the copper hexamers by inelastic neutron scattering experiments covering the entire range of the magnetic excitation spectra. The observed transitions are governed by very unusual selection rules which we ascribe to the underlying spin-coupling topology. This is rationalized by model calculations which allow an unambiguous interpretation of the magnetic excitations concerning both the peak assignments and the nature of the spin-coupling parameters., Comment: 17 pages, 4 tables, 9 figures

Optical microcavities are key elements in many photonic devices, and those based on distributed Bragg reflectors (DBRs) enhance dramatically the end reflectivity, allowing for higher quality factors and finesse values. Besides, they allow for wide wavelength tunability, needed for nano-and microscale light sources to be used as photonic building blocks in the micro- and nanoscale. Understanding the complete behavior of light within the cavity is essential to obtaining an optimized design of properties and optical tunability. In this work, focused ion-beam fabrication of high refractive-index contrast DBR-based optical cavities within Ga₂O₃:Cr microwires grown and doped by the vapor-solid mechanism is reported. Room-temperature microphotoluminescence spectra show strong modulations from about 650 nm up to beyond 800 nm due to the microcavity resonance modes. Selectivity of the peak wavelength is achieved for two different cavities, demonstrating the tunability of this kind of optical system. Analysis of the confined modes is carried out by an analytical approximation and by finite-difference-time-domain simulations. A good agreement is obtained between the reflectivity values of the DBRs calculated from the experimental resonance spectra, and those obtained by finite-difference-time-domain simulations. Experimental reflectivities up to 70% are observed in the studied wavelength range and cavities, and simulations demonstrate that reflectivities up to about 90% could be reached. Therefore, Ga₂O₃:Cr high-reflectivity optical microcavities are shown as good candidates for single-material-based, widely tunable light emitters for micro- and nanodevices.

Low-temperature magnetometry, ac susceptibility, and calorimetry have been employed to study Co-based single-chain magnets (SCMs) organized through halogen bonding. Magnetic hysteresis and maxima in the dc and ac susceptibilities, respectively, confirm the SCM behavior of the system. Several characteristic magnetic relaxation regimes are observed at different temperatures, which can be associated with both intra- and interchain exchange interactions. Remarkably, tweaking the rate at which an external magnetic field is swept along the axis of the chains enables a controlled transition between the one- and three-dimensional dynamics. Experiments on an isostructural Co-based SCM system crystallized with different halogens do not show three-dimensional dynamics, illustrating the importance of halogen bonding on the control of interchain interactions., A.A. and E.d.B. acknowledge support from the National Science Foundation (DMR No. 1503627). G.M.E., J.M.C.- J., and E.C. acknowledge the Spanish MINECO (Excellence Unit Maria de Maeztu MDM-2015-0538 and Projects No. MAT2014-56143-R, No. CTQ2014-29509-P, and No. CTQ2014-52758-P, and the excellence network NANOMOLNet on molecular nanoscience, Project No. MAT2014-52919-REDC), the EU (COST Action MOLSPIN), and the Generalidad Valenciana (Prometeo Program). F.L. and M.E. acknowledge funding from the MINECO-FEDER through Grant No. MAT2015-68204-R and from Gobierno de Aragon, Grant No. E98-MOLCHIP.

A one-dimensional polymeric pyridinium chlorocuprate (HPy)2[Cu3Cl8(H2O)2], an intermediate between (HPy)CuCl3 and CuCl2·2H2O, has been synthesized and characterized by X-ray analysis. The structure contains [Cu3Cl8(H2O)2]n2n- chains in which both square-pyramidal and octahedral CuII exist. The chains are composed of linked [Cu2Cl6]2- dimers and CuCl2(H2O)2 monomeric units. On being heated in the solid state the compound undergoes dehydration followed by dehydrohalogenation to produce a pyridine complex of CuII: [Cu3Py2Cl6]. Magnetic studies reveal ferromagnetic coupling within the chains with an intradimer exchange coupling of 12.1 cm-1 and a dimer-monomer exchange coupling of 1.34 cm-1.

The aim of the present work is to determine the influence of austenitizing temperature holding time and heating velocity on grain size of ferritic-martensitic type 9CrlMoVNb steels developed for Oak Ridge National Laboratories & Combustion Engineering, T91/P91[1] Steels (USA) and X10CrMoVNb 9.1 (Europe). The potential benefits of this material, in term of high resistance, good ductily and oxidation resistance, weldability and in particular good high temperature creep strength, are now widely acknowledged, particulary by supercritical boilers (P = 300 bar, T = 550±50 °C). The studied steels have been produced in, high frecuency induction vacum furnaces and hot-rolled. Se estudia la influencia de la temperatura de austenización, tiempo de permanencia a esta temperatura y velocidad de calentamiento sobre el tamaño de grano de varios aceros ferrítico-martensíticos de última generación del tipo 9CrlMoVNb, desarrollados por Oak Ridge National Laboratories (ORNL) conjuntamente con Combustion Enginering en USA, conocidos por ASME/ASTM por las designaciones T91/P91[1] y en Europa como X10CrMoVNb9.1. Son aceros ductiles y tenaces que presentan muy buenas propiedades de resistencia a fluencia, soldabilidad y conductividad térmica. Son cada vez más utilizados como tubos de alta temperatura (550±50 °C) y presión (300 bar) en calderas supercríticas para centrales térmicas avanzadas. Los aceros estudiados se han fabricado en hornos de inducción de alta frecuencia al vacío y laminados en caliente.

In the present research, high silicon (6.4%) - iron microcrystalline ribbons were obtained by rapid quenching. In this material the incidence of the atmosphere (N2) and the annealing temperature (900-1,100°C) on the micrographic structure, grain size and texture and, as a consequence, in the total core losses ((1.0 T) 10-1000 Hz) were studied. The analysis of the results shows that the core losses are, in all cases, lower than those of the highest grade of conventionally processed nonoriented magnetic steel sheets, this becoming specially noticeable in the frequency range between 50-400 Hz. En el presente trabajo se describe la obtención de cintas microcristalinas Fe - 6,4 % Si por solidificación rápida. Sobre el material así obtenido, se estudió el efecto que la atmósfera (N2) y la temperatura de recocido (900-1100°C) ejercen en la estructura micrográfica, tamaño de grano y textura inducida y, en consecuencia, en la cifra de pérdidas totales ((1,0 T) 10-1000 Hz.). Los resultados obtenidos muestran, en todos los casos, una cifra de pérdidas inferior al mejor grado de la chapa magnética no orientada procesada convencionalmente. Esto adquiere especial relieve en el intervalo de frecuencias comprendido entre 50-400 Hz.

The behavior to hydrogen damage caused by corrosion in a H2S medium is studied in a molded ferrite- austenite (52-48 %) duplex stainless steel 22Cr5NiMoN type (UNS-J9.22.05) under both, static (damaging mechanism called Hydrogen Induced Cracking (HIC)) and sustained load (damaging mechanism called Sulfide Stress Cracking (SSC)), conditions. Se estudia el comportamiento de un mismo acero moldeado inoxidable dúplex austeno-ferrítico (48-52 %) del tipo 22Cr5NiMoN (UNS-J9.22.05) frente al dañado por hidrógeno generado por corrosión en medio H2S, tanto en condiciones estáticas, mecanismo de dañado conocido como HIC (Hydrogen Induced Cracking), como bajo carga de tracción, mecanismo de dañado conocido como SSC (Sulfide Stress Cracking).

Behavior to hydrogen damage caused by stress corrosion in a H2S medium (SSC) and to intergranular corrosion (IGC) in different mediums, such as oxalic acid (C2H2O4-2H20), iron sulphate-50 % sulfuric acid [Fe2(SO4)3-50 % H2SO4], nitric acid (HNO3), copper sulphate-16 % sulfuric acid (CuSO4-5H2O-16 % H2SO4) and cooper sulphate-50 % sulfuric acid (CuSO4-5H2O-50 % H2SO4), is studied in an AISI 347 austenitic stainless steel stabilized with 0.61 mass % Nb and hot rolled to a seamless pipe with 273.1 mm in diameter and 18.2 mm in thickness. Se estudia el comportamiento de un acero inoxidable austenítico del tipo AISI 347 estabilizado con un 0,61 % en masa de Nb, laminado en caliente para producir una tubería sin soldadura de 273,1 mm de diámetro y 18,2 mm de espesor, frente al dañado por hidrógeno generado por tensocorrosión en medio H2S (SSC) y frente a la corrosión intergranular (IGC) en diferentes medios agresivos tales como ácido oxálico (C2H2O4∙2H2O), sulfato de hierro-50% ácido sulfúrico [Fe2 (SO4)3-50 % H2SO4], ácido nítrico (HNO3), sulfato de cobre-16% ácido sulfúrico (CuSO4-5H2O-16 % H2SO4) y sulfato de cobre-50 % ácido sulfúrico (CuSO4-5H2O-50 % H2SO4), respectivamente.

Para prevenir e resolver situações de desmotivação e stresse profissional em profissionais de Educação e de Saúde foi formulado um Programa de Formação Contínua. A versão revista do Programa tem a duração de 50h, distribuídas em onze sessões, dez em sala, centradas nos seguintes aspectos: partilha de experiências profissionais com colegas, identificação de fatores de stresse e estratégias de coping para lidar com eles, substituir crenças irracionais por crenças mais apropriadas, treinar competências de assertividade e de relaxamento. No final, integra um dia de formação no exterior, fora de aula. Comparando os resultados obtidos antes e depois do Programa de Formação, os participantes revelam um aumento significativo da percepção de bem-estar profissional. Palavras-chave: formação contínua; gestão do stresse; bem-estar profissional.

A simple and precise technique to measure the sudden Extreme Ultraviolet (EUV) radiation increase of the Sun, during mid and strong flares, has been formulated and demonstrated for the most active part of the last Solar Cycle. On the one hand, it is based on the short time scale of these events, which allows the validity of a simple global overionization model. And on the other hand on the prompt ionospheric response to the EUV ionization, which signature (in terms of the Global Navigation Satellite Systems -GNSSSolar Flare Activity Indicator, GSFLAI) is accurately measured in real-time from the existing global networks of dual-frequency GNSS receivers, and with a time resolution higher that those of dedicated space probes. Moreover the sensitivity of this approach enables the detection of not only extreme X-class flares, but also the detection of variations of one order of magnitude lower or even smaller (such as for M-class flares): 100% successful detection for all the X-class solar flares during 2000-2006 with registered location outside of the solar limb (i.e. detection of 94% of all of X-class solar-flares) and about 65% for M-class ones, obtained with the associated SISTED detector. In summary, its full availability, continuity, high precision and integrity for mid and high solar flare effects on Ionosphere, can make GSFLAI an useful indicator of potential Space Weather activity for many users in radio propagation. These results, which have been recently published by the authors, are extended in this work up to one complete solar cycle, and using a lower sampling rate (30 seconds), demonstrating the better behaviour of this indirect solar EUV variability proxy (GSFLAI30), when comparisons are made with direct measurements from space probes, providing readings which can be affected by the late enhancement of particles.

A series of direct carotid end-to-end laser anastomosis vs. direct manual suture was carried out on a series of 70 Wistar rats (mean weight 260 g). Both common carotids (0.8-1.2 mm) were sectioned and repaired. The left side (n = 70) was submitted to laser-assisted microvascular anastomosis (LAMA) performed by means of a diode laser device (wavelength 830 nm and power output 3 W in continuous wave) without chromophore. The right side (n = 70) underwent a control manual suture (CMA). The diode laser energy was delivered into a micromanipulator coupled to a Zeiss operating microscope with a focused spot of 300 mum in diameter. After placement of three 10.0 stitches for edge coaptation, the LAMA was achieved using laser shots (average 3) of 500 mW power, 4.5 s duration, and 700 W/cm2 irradiance each. The CMA was performed by means of six 10.0 stitches. The good vascular flow was confirmed by Doppler spectral analysis (n = 466) carried out from day 0 to day 90. Light and scanning electron microscopy (n = 82) showed that re-endothelialization after LAMA was gaining ground on day 3, whereas collagenous network developed in the media scar by day 10. In contrast, after CMA the arterial repair was delayed on day 20, inducing a media fibrotic scar. The patency rate was 93% in both anastomoses. The shorter operating time (13 min for LAMA vs. 22 min for CMA) and the noncontact laser technique are the main intraoperative advantages. The technical benefits of the diode laser are pointed out. (C) 1994 Wiley-Liss, Inc.

This work introduces a novel ionospheric activity indicator useful for identifying disturbed periods affecting performance for GNSS users, at regional level. This indicator is based in the “Along Arc TEC Rate (AATR) and can be easily computed from GNSS data. The AATR indicator has been assessed over more than one Solar Cycle (2002-2013) involving 140 receivers distributed world-wide. Results show that it is well correlated with the ionospheric activity and, unlike other global indicators linked to the geomagnetic activity (i.e. DST, Ap), it is sensitive to regional behaviour the ionosphere and identifies specific effects on GNSS users. Moreover from a devoted analysis of EGNOS performances in different ionospheric conditions, it follows that the AATR indicator is able to predict SBAS user availability anomalies linked to the ionosphere. The AATR indicator has been chosen as the metric to characterise the ionosphere operational conditions in the frame of EGNOS activities. This indicator has been also proposed for joint analysis in the International SBAS-Ionosphere Working Group.

In this work the characterization of the superelastic effect in three different Cu-Al-Ni samples elaborated by power metallurgy is presented. Specifically, the maximum values of superelasticity and the shape of the stress-strain curves have been studied for the different samples. Moreover, the Clausius-Clapeyron curve for each sample has been obtained carrying out superelastic curves at different temperatures. The differences observed in the parameters studied in each sample have been related to the differences in the microstructure of each sample, generated by the changes introduced in the elaboration process. En este trabajo se presenta la caracterización del efecto superelástico de tres muestras diferentes de Cu-Al-Ni que han sido elaboradas mediante el método pulvimetalúrgico. En concreto, se han caracterizado los valores máximos de superelasticidad para cada una de ellas, así como la forma de la curva tensión-deformación. Además, mediante la realización de ciclos superelásticos a diferentes temperaturas se han obtenido las curvas de Clausius- Clapeyron para cada una de las muestras. Las diferencias observadas en los parámetros estudiados se han relacionado con las diferentes microestructuras de las muestras, causadas por las diferencias en el proceso de elaboración de las mismas.