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The objective of this study was to make an update on the different strategies in the blood saving in prosthetic primary knee surgery, through a bibliographical review; As well as to know what strategies are followed in different hospitals in our field, through a survey.We carried out a descriptive transversal observational study based on a survey of 64 surgeons and a bibliographical research on the different aspects included in the survey.Surgeons refer that they have presurgical blood-saving protocols implanted in their Hospital at 48.4%. The use of tranexamic acid (ATX) is quite widespread 71.9% of respondents (46/64). It is administered intravenously prior to surgery in 26.6% of cases, intraarticularly by 21.9% and in a combination of both in 23.4%. The preferred time for the placement of ischemia by surgeons is 57.8% prior to painting the field, while a 39.1% prefer to place it in sterile conditions. 3.1% of surgeons claim to implant the prosthesis without using ischemia in surgery.The use of ATX as the primary blood-saving strategy in TKR is being imposed. There is No consensus as to the optimal dose or its route of administration. The efficacy of the ATX is influencing the elimination of post-surgical drainage and the implementation of early rehabilitation programs.El objetivo del presente estudio fue realizar una actualización sobre las diferentes estrategias en el ahorro de sangre en cirugía protésica de rodilla primaria, a través de una revisión bibliográfica; así como conocer qué estrategias se siguen en diferentes centros hospitalarios de nuestro ámbito, mediante un estudio multicéntrico.Se realizó un estudio observacional, transversal, descriptivo, basado en una encuesta hecha a 64 cirujanos y una búsqueda bibliográfica sobre los distintos aspectos incluidos en la encuesta.Los cirujanos refieren que cuentan con protocolos de ahorro sanguíneo prequirúrgicos implantados en su hospital en 48.4% (31/64). La utilización del ácido tranexámico (ATX) es bastante generalizada en 71.9% de los encuestados (46/64). Éste se administra vía endovenosa previa a la cirugía en 26.6% (17/64) de los casos, de manera intraarticular en 21.9% (14/64) y en una combinación de ambas en 23.4% (15/64). El momento preferido para la colocación de la isquemia por los cirujanos es en 57.8% (37/64) previo a preparar el campo, mientras que 39.1% (25/64) prefiere colocarla en estéril. En 3.1% (2/64) de cirujanos afirma implantar las prótesis sin utilizar isquemia en la cirugía.Se está imponiendo la aplicación de ATX como principal estrategia de ahorro de sangre en la artroplastía total de rodilla (ATR). No existe consenso en cuanto a la dosis óptima ni a su vía de administración. La eficacia del ATX está influyendo en la eliminación de los drenajes postquirúrgicos y en la implementación de programas de rehabilitación precoz.

International audience; The fission of uranium dioxide produces gaseous elements degrading nuclear fuel properties. A thorough understanding of the transport and release of gaseous products is thus essential. The present work focuses on xenon and krypton migration mechanism in uranium dioxide. Desorption experiments on ion implanted UO2 were performed at 1300°C. Xe and Kr releases were simulated using a mesoscale model that was developed taking into account single gas atom diffusion and defect traps. We showed that the defects have a high influence on Xe and Kr migration mechanisms and therefore have to be considered to accurately determine diffusion coefficients. We evaluated the diffusion coefficient of Xe and Kr at (1.73 ± 0.15)x10−20 m2/s at 1300°C and we showed that the diffusion of rare gases is subjected to two trapping mechanisms. The first occurs during the ion implantation and the second during high-temperature annealings. The nature of the trapping sites is discussed in the light of the literature on radiation induced defects. This study also consolidates the use of non activated UO2 implanted with heavy ions as a less-hazardeous substitute for irradiated UO2.

espanolAntecedentes: El tromboembolismo es una complicacion de la cirugia de artroplastia total de rodilla. Para su prevencion disponemos de multiples medidas fisicas y farmacologicas.Objetivo:Conocer quemedidas de prevencion tromboembolica son las empleadas por los cirujanos ortopedicos en cirugia protesica de rodilla primaria en diferentes centros hospitalarios de nuestra region.Metodo: Estudio transversal descriptivo observacional basado en encuesta dirigida a especialistas COT de 9 hospitales publicos de la Comunidad Valenciana y busqueda bibliografica.Resultados: Se obtuvieron 64 encuestas. Todos los cirujanos eligen HBPM durante un mes como medida de tromboprofilaxis, descartando anticoagulantes orales o aspirina. El 29% tambien emplea dispositivos de movilizacion pasiva. Conclusiones: Los cirujanos ortopedicos de la comunidad valenciana optan por HBPM conforme a las mejores evidencias. Se estima, que la incidencia de eventos tromboembolicos sintomaticos desciende del 4,3 % al 1,8% con el uso de HBPM. El empleo de dispositivos de movilizacion pasiva y medias de compresion no estan avaladas por las evidencias. La estratificacion preoperatoria del riesgo de tromboembolismo, para emplear acido acetil salicilico asociado a bombas de presion intermitente en caso de no existir alto riesgo es una tendencia cada vez mas aceptada internacionalmente. EnglishBackground: Thromboembolism is one of the Total Knee Arthroplasty risks. For its prevention we have multiple physical and pharmacological measures availables.Objective: To know which thromboembolic prevention measures are those used by orthopedic surgeonsin knee replacement surgery in different hospital centers in our region.Method: Observational descriptive cross-sectional study based on a survey directed at orthopedic surgeons from 9 public hospitals in the Valencian Community and a bibliographic search.Results: 64 completed surveys were obtained. All surgeons choose LMWH for one month as a thromboprophylaxis measure, ruling out oral anticoagulants or aspirin. 29% also employ passive motion devices.Conclusions: Orthopedic surgeons from the Valencian Community opt for LMWH guided by the best evidence. It is estimated that the incidence of symptomatic thromboembolic events drops from 4.3% to 1.8% with the use of LMWH. The use of passive motion devices and graduated compression stockings are not supportedby the evidence. The preoperative stratification of the risk of thromboembolism, to use aspirin associated with intermittent pneumatic compression device in the absence of high risk, is an increasingly internationally accepted trend.

A double focusing sector field mass filter used in Nier-Johnson geometry has been built in order to perform Kr isotope enrichment for 81 Kr and 85 Kr isotopes. The principle consists in implanting Kr+ ions accelerated at 7 keV in Al foils after separation using the magnetic sector. A specific ion source has been designed capable of generating high Kr+ ion beams (>0.5 μA) to transfer into the collecting Al foils in 3 to 5 h significant fractions of large Kr samples (1015 to 1016 atoms) initially introduced in the instrument. Implanted Kr isotopes can be further selectively released from the Al foil by surface ablation using an infrared laser beam. Implantation yields and enrichment factors are measured using a conventional mass spectrometer. Copyright © 2016 John Wiley & Sons, Ltd.

Single crystals of SiC were implanted with heavy inert gases (Xe, Ar) at elevated temperatures (300–800 °C) and for a large range of fluence (1 × 10 12 –1 × 10 15 ions cm −2 ). Thermodesorption measurements suggest that gas is trapped by implantation-induced vacancy-type defects impeding any gas diffusion. The damage accumulation versus dose was studied through the tensile elastic strain determined by using X-ray diffraction. Results show that at low dose the strain is predictable via a thermally activated direct impact model. The low thermal activation energy at saturation suggests a dynamic recovery process dominated by the migration of interstitial-type defects as its relaxation during post thermal annealing. As compared with light-gas implantation the heavy-gas to defect ratio is low enhancing the formation of strongly perturbed zones rather than the formation of bubble precursors.

A new RIS-TOF instrument, called FAKIR (Facility for Analyzing Krypton Isotope Ratios), has been developed at CENBG in order to measure Kr isotope ratios with an extremely high sensitivity. The instrument uses a single color Kr ionization scheme with tunable coherent UV photons near 216.6 nm. A two-photon resonance excitation allows it to reach the 5p[5/2]2 excitation level followed by a single-photon ionization. Krypton ions are accelerated towards an electron multiplier. The instrument includes a cryogenic concentrator that increases the efficiency of the ion source and a new selecting system allowing the deflection of the abundant isotopes before they impact the detector. This device eliminates the blinding effect on the detector that alters the detection of the less abundant Kr isotopes. The current sensitivity of the instrument of ∼6700 atoms has been demonstrated by extracting the gas from 37 mg of the Boguslavka iron meteorite. The associated errors on the 81Kr isotope ratio measurements did not exceed ∼12%. A good agreement is observed with conventional mass spectrometry analysis, which requires several grams of material, by measuring the cosmic ray exposure age of the Boguslavka meteorite.

International audience; Boron carbide, B 4 C, is widely used as a neutron absorber in nuclear reactors. Since neutron absorption by 10 B leads to 4 He production, it appears necessary to study He behavior and its possible effects on the B 4 C ceramic. In this study, the diffusion characteristics of ion-implanted He in B 4 C (500 keV, fluences from 1 x 10 +13 to 2 x 10 +15 He.cm-2) were investigated mainly by Thermo-Desorption Spectroscopy (TDS) from 600°C up to B 4 C melting point. The experiments were done on dense B 4 C samples having large grains (30-60 µm) to render grain boundaries effects on He outward diffusion ineffective and thus to access intragranular He diffusion kinetics. From controlled temperature ramp experiments, it was notably observed that He release was realized in two main stages. A first He population was able to exit the material at moderate temperatures by interstitial diffusion. Then a second population was quantitatively released only over 1150°C. This was attributed to He atoms that, in their initial interstitial diffusion course at moderate temperatures from their implantation sites, got trapped in defect aggregates and/or He bubbles. As the nucleations of both these traps are expected to be related to helium and irradiation defect concentrations, the ratio of the two He populations was indeed found to be correlated with the implantation fluence. From the obtained He release curves, the apparent activation energies (E a) of He intragranular diffusion in B 4 C was determined (2.6-3.1 eV) in the 800-1100°C temperature range. This value appears slightly higher than the one determined at lower temperatures, hinting that a change in diffusion mechanism may occur around 800°C. The apparent E a of He detrapping from He bubbles (~2.5 eV) and from defect aggregates (~4 eV) were also determined for temperatures within 1200-1500°C.

The Cluster Dynamics method is assessed for the investigation of fission gas behaviour in a krypton-implanted and annealed UO2sample. The simulation results are then compared to Thermal Desorption Spectroscopy (TDS) data. A release mechanism is proposed: the initial burst is related to krypton migration via an interstitial mechanism, while the second stage of the release process can be accounted for by the diffusion of krypton in a substitutional position. This latter mechanism is compatible with a diffusion coefficient of 4.10-21m²/s.

We measured integral thin target cross sections for the proton-induced production of 3He, 4He, 21Ne, 22Ne, 36Ar and 38Ar from Fe and Ni from the respective reaction thresholds up to 1.6 GeV. The production of noble gas isotopes, especially 4He, from Fe and Ni is of special importance for design studies of accelerator driven systems and/or energy amplifier, because Fe is the main structural material in almost every design study. Furthermore, the cross sections are needed to establish the first physical model calculations for the production of cosmogenic nuclides in iron meteorites. As a result of our new measurements there now exist for both target elements a complete and consistent database for the production of noble gas isotopes. The experimental data are compared to results from the theoretical nuclear model codes INCL4/ABLA and TALYS. This comparison clearly demonstrates again that experimental data are still needed because the predictive power of nuclear model codes, though permanently improving, does still not allow reliably predicting the cross sections needed for most applications and irradiation experiments remain indispensable.

— Two spherical targets made of gabbro with a radius of 25 cm and of steel with a radius of 10 cm were irradiated isotropically with 1600 MeV protons at the SATURNE synchrotron at Laboratoire National Saturne (LNS)/CEN Saclay, in order to simulate the production of nuclides in meteorites induced by galactic cosmic-ray protons in space. These experiments supply depth-dependent production rate data for a wide range of radioactive and stable isotopes in up to 28 target elements. In this paper, we report results for 78Kr, 80–86Kr isotopes in Rb, Sr, Y and Zr and for 124Xe, 126Xe, 128–132Xe, 134Xe, 136Xe isotopes in Ba and La. Krypton and xenon concentrations have been measured at different depths in the spheres by using conventional mass spectrometry. Based on Monte-Carlo techniques, theoretical production rates are calculated by folding depth-dependent spectra of primary and secondary protons and secondary neutrons with the excitation functions of the relevant nuclear reactions. The comparison of the model calculation results with experimental data in the thick target experiments performed at LNS and previously at CERN have allowed adjustments of the poorly known excitation functions of neutron-induced reactions. Thus, for the two experiments at SATURNE, excellent agreement is obtained between experimental and calculated production rates for most Kr and Xe isotopes in all investigated target elements. Only Xe production in Ba in the gabbro is underestimated by the calculations by ˜25%. This work validates the approach of the thin-target model calculations of cosmogenic nuclide production rates in the attempt of modeling the interaction of galactic cosmic-ray protons with stony and iron meteorites in space as well as with lunar samples.

Nowadays, the measurement and management of color quality of the gonio-apparent materials is complex, but highly demanded in many industrial sectors, as automotive, cosmetics, plastics for consumer electronics, printing inks, architectural coatings, etc. It is necessary to control complex instrumentation and to do visual assessments of texture and color differences to get, for instance, a visual harmony in car bodies; and a profound knowledge of physics and chemistry of special-effect pigments for their optical formulation to obtain attractive visual effects in coatings, plastics, etc, combining among them and with solid pigments. From University of Alicante, for the academic year 2013-14, we are organizing the first MSc degree in Color Technology for the Automotive Sector, with a design of contents embracing CIE colorimetry and visual perception, included the AUDI2000 color difference formula, instrumentation and color management software, fundamentals of coatings and plastics in the automotive sector, and, optical formulation of pigments. The MSc syllabus, with 60 ECTS, is designed to be taught in two semesters: from September to February with on classroom theoretical and practical activities, and, from March to June at virtual level, with internships of training in some companies. Therefore, the MSc Thesis would be the performance report during the internship in companies or research institutions. Some multinational companies, both as car makers and coatings and plastics providers, from European and non-European countries have already shown their support and interest in welcoming students for specific training, even some job offers when the first MSc edition finishes.

Understanding the long-term behaviour of the UO2 spent fuel in terms of helium build-up and oxidation is a very important issue for safety aspects of storage and disposal. Although helium behaviour in stoichiometric UO2 has been studied by many authors, it has not been well established and there is a lack of experimental studies in non-stoichiometric UO2. In this study, an infusion technique was chosen to introduce helium in stoichiometric and hyperstoichiometric single and polycrystalline UO2 and polycrystalline U3O8 samples. Characterization of the samples before and after infusion and after thermal desorption measurements were performed by thermogravimetry, X-ray diffraction, laser flash technique and scanning electron microscopy. It was observed that the increase of stoichiometry in UO2 affects barely the dissolved helium quantity (under the same infusion conditions as in stoichiometric), while it has a more pronounced influence on the helium diffusion. These two effects are much more pronounced for U3O8. (C) 2013 Elsevier Ltd. All rights reserved.

In this work we focus on experiments involving implantation of 500 keV 3He ions in sintered polycrystalline material. Samples are implanted at low fluences (∼2 ×1013 ions/cm2) and subsequently isothermally annealed in a highly sensitive thermal desorption spectrometry (TDS) device PIAGARA (Plateforme Interdisciplinaire pour l’Analyse des GAz Rares en Aquitaine). The helium fluencies studied are two to three orders of magnitude lower than previous Nuclear Reaction Analysis (NRA) experiments carried out on identical samples implanted at identical energies. The fractional release of helium obtained in the TDS experiments is interpreted using a three-dimensional axisymmetric diffusion model which enables results to be quantitatively compared to previous NRA data. The analysis shows that helium behaviour is qualitatively independent of ion fluency over three orders of magnitude: helium diffusion appears to be strongly inhibited below 1273 K within the centre of the grains presumably as a result of helium bubble precipitation. The scenario involving diffusion at grain boundaries and in regions adjacent to them observed at higher fluencies is quantitatively confirmed at much lower doses. The main difference lies in the average width of the region in which uninhibited diffusion occurs.

— The L/LL5 chondrite Knyahinya had an approximately spherical shape, and as it experienced a single stage exposure history, it represents a very interesting object to study depth profiles of cosmic-ray-produced nuclide concentrations. Such data are required to improve and to validate model calculations of production rates. We report Ne, Ar, Kr and Xe isotopic abundances in five bulk samples. The adopted procedure of noble gas extraction included two pyrolysis steps at 450 °C and 650 °C, respectively, followed by a combustion step in pure O2 at 650 °C before melting the sample. This procedure allows for the separation of a significant fraction of the trapped Kr and Xe, leading to an enrichment of the cosmic-ray produced component, which is released in the melting step. The isotopic composition of the trapped Xe component measured in the combustion step is found to be identical with the OC-Xe composition (Lavielle and Marti, 1992) and supports the suggestion that ordinary chondrites formed in a homogeneous trapped noble gas reservoir. Cosmic-ray produced Kr and Xe components and depth profiles were measured, including for the first time a 81Kr profile. The calculated exposure age of 39.5 ± 1.0 Ma, based on the 81Kr-Kr method, is found to be in excellent agreement with previous determinations. The concentrations of trapped and fissiogenic noble gas components are clearly lower than those generally observed in type 5 ordinary chondrites and may suggest diffusion losses before a meter-sized object was exposed to the cosmic radiation.

The purpose of this work is to study the diffusion properties in an argillaceous formation and how these properties change after the excavation of galleries, over a long period. The Tournemire Underground Research Laboratory (URL) located in Aveyron (France) offers the unique opportunity to investigate different stages of the evolution of the so-called Excavation Damaged Zone (EDZ) over a period of about 124 a. Four horizontal boreholes parallel to the bedding and one vertical borehole were drilled in order to study diffusion transport in the EDZ in both directions in galleries excavated 124, 13, 6, and 1 a ago, respectively. Noble gases dissolved in the pore water of 47 core samples were extracted in order to establish precise depth profiles. Mainly produced in situ by decay of U and Th, radiogenic He accumulates in the pore water of rocks and escapes toward the gallery, allowing a characterization of the diffusive transport in the EDZ and its evolution with time. For the oldest gallery (1882–1888), core mapping reveals an EDZ well developed with fractures up to a depth of 1.8 m. In this zone, all radiogenic He has been lost and at the same time heavy noble gases are trapped in the rock with an enrichment of Xe relative to Kr and of Kr relative to Ar. From 1.8 m, He concentration increases with depth to reach a plateau at about 3.5 m corresponding to a concentration normally found in the unaltered zone. Considering diffusive transport of the radiogenic He to the EDZ, model calculations allowed proposing transport properties in the unfractured and undisturbed zone (UZ) with a pore diffusion coefficient Dp of 1 × 10 −10 m 2 /s deduced from the best-fit curve to experimental data and a mean porosity of 0.1 obtained form petrophysical measurements. The most recent gallery (2008) did not show any evidence of EDZ at depths greater than 7.5 cm. A fracture located around 0.75 m, possibly of tectonic origin, induced large advection and diffusion losses of He on both sides in the next 50 cm. Excesses of Ar, Kr and Xe are found, suggesting diffusion of air from the gallery associated with He losses. The 6-a-old gallery is clearly influenced by fractures of tectonic origin increasing the EDZ thickness of 0.7 m up to a Damaged Zone of 1.8 m. Based on the He concentration profile, the 13-a-old gallery (1996) has a net EDZ of 1.2 m, larger than the 0.7 m deduced from the structural analysis by core mapping, followed by a disturbed zone of up to 3.5 m that could represent an intermediate stage before the development of fractures in the EDZ. The vertical borehole drilled in the same gallery shows a less extensive damaged zone (1.4 m) and allows the determination of a Dp of 3 × 10 −11 m 2 /s taking into account the anisotropy relative to the stratification plane. The rare gas analysis has, therefore, enabled confirmation and better description of the net time-dependent evolution of the EDZ around drifts in the argillaceous Tournemire site: no obvious EDZ for the 1-a gallery (2008), 1.2 m width for the 13-a-old gallery (1996), and 2 m width for the century-old tunnel. The occurrence of a disturbed and unfractured zone (dZ) around the 13-a-old gallery undetected by structural studies and geophysical methods clearly demonstrates the power of radiogenic He in assessing the transport properties around drifts excavated at different ages in compacted clay rocks.

4-dimethylammo-4'-cyanostilbene and selectively bridged model compounds are investigated using ps-time-resolved absorption and fluorescence measurements. The formation kinetics of a bicimer species are compared in homologous alcohol solvents at ambient pressure and as a function of high pressure, and the viscosity dependences are discussed.

Several selectively bridged 4-(dimethylamino)-4'-cyanostilbenes are investigated. All of them show strongly red-shifted fluorescence spectra connected with a considerable dynamical Stokes shift in polar solvents. Bridging, however, photophysics (fluorescence quantum yields and lifetimes) dramatically. Blocking of the double bond twist by a sufficiently rigid bridge (-CH 2 -) leads to quantum yields near 1, although the anilino group is free to rotate

Several selectively bridged 4-(dimethylamino)-4'-cyanostilbenes are investigated. All of them show strongly red-shifted fluorescence spectra connected with a considerable dynamical Stokes shift in polar solvents. Bridging, however, photophysics (fluorescence quantum yields and lifetimes) dramatically. Blocking of the double bond twist by a sufficiently rigid bridge (-CH 2 -) leads to quantum yields near 1, although the anilino group is free to rotate

Sn ← S1 transient-absorption and gain spectra in the picosecond time range of three benzoxazole derivatives are reported. These are two symmetric molecules, 2,5-bis-(benzoxazolyl)-hydroquinone and 3,6-bis-(benzoxazolyl)-pyrocatechol undergoing single and double proton transfer (PT), respectively, and 2,5-bis-(benzoxazolyl)-4-methoxyphenol, a compound with one reaction center excluded by OH → OCH3 substitution. Transient spectra are interpreted by comparison with a model structure (phenanthrenequinone) and quantum-chemical calculations; kinetics of the PT process in the last molecule are directly observed by the determination of the rise of the gain band situated in the spectral region of the photoautomeric fluorescence. From the temperature dependence of the rise time, it is concluded that the intramolecular PT is an activated process. The proton-transfer rate constant is of the order of 1010 s−1. A previously proposed mechanism is confirmed.

International audience; This study deals with the behaviour of helium in a molybdenum liner dedicated to the retention of fission products. More precisely this work contributes to evaluate the release of implanted helium when the gas has precipitated into nanometric bubbles close to the free surface. A simple model dedicated to calculate the helium release in such a condition is presented. The specificity of this model lays on the assumption that the gas is in equilibrium with a simple distribution of growing bubbles. This effort is encouraging since the calculated helium release fits an experimental dataset with a set of parameters in good agreement with the literature.

$\beta$-Thorium phosphate diphosphate polycrystalline ceramic is considered as a promising candidate for the immobilization of actinides in the field of a long-term storage. In order to study the behavior of the ceramic in relation with the evacuation of helium produced by actinides and daughters disintegrations, the release of radiogenic helium from a sintered pellet aged over an about six year period was studied by thermal desorption and high resolution mass spectrometry. The apparent diffusion coefficients are determined for different annealing sequences and are approximately the same for zircon and britholite at low temperature and uranium dioxide ceramic at high temperature. The apparent diffusion coefficients are found to be (7 ± 3) x 10^-22 m^2 s^-1 and (1.5 ± 0.5) · 10^-20 m^2 s^-1 at 20 °C and 120°C, respectively. The activation energy for the apparent diffusion process encompassing both volume and inter-granular diffusion is estimated at 45 ± 15 kJ mol^-1 in the studied temperature range (20–1020° C).

A simple picosecond time-resolved spectrometer allowing recording of absorption and emission spectra of short-lived species is described. For absorption measurements it uses the pump-probe method and for emission measurements the optical Kerr effect shutter. It allows recording of full spectra in the range 4000–8000A with a time resolution of 10 ps. Applications to the study of conformational changes of solvent cage and intramolecular twisting of excited organic compounds in solution are presented.

We measured integral thin target cross sections for the proton-induced production of He-, Ne-, and Ar- isotopes from Fe and Ni and of He-, Ne-, Ar-, Kr-, and Xe-isotopes from Bi from the respective reaction thresholds up to 2.6GeV. Iron and Ni are important structural materials for the planned ADS/EA systems and Bi is a major constituent for planned spallation neutron sources. In addition, we give new data for the production of 3 He from Mg, Al, Si, and Pb by revising earlier data and considering now 3 Hd iffusive losses and new information for the 3 H/ 3 He branching ratios. The data are compared to results from theoretical nuclear model codes.

— The Campos Sales meteorite fell close to the town of Campos Sales in the northeastern Brazilian state of Ceara (7°2′ S, 40°10′ W) on 1991 January 31 at 10:00 P.M. (local time). Several fragments were recovered from an area estimated to be 1 × 3 km. The stone is an ordinary L5 chondrite (Fa25.0 and FS21.6) and is lightly shocked (S1). Metal phases present are kamacite, tetrataenite, and antitaenite. Noble gases He, Ne, Ar, Kr, and Xe have been analyzed in two bulk samples of Campos Sales. All exposure ages based on determination of cosmogenic 3He, 21Ne, 38Ar, 83Kr, and 126Xe abundances and on the cosmogenic 81Kr/83Kr ratio agree well, which suggests no gas loss during cosmic-ray exposure. The cosmic-ray exposure age is 23.3 ± 1.0 Ma, which falls in the range observed for L5 chondrites (20–30 Ma). The gas-retention ages indicate He loss that must have occurred prior to or during ejection from the L-chondrite parent body.

Time-resolved emission spectroscoy of “push—pull” stilbene derivatives has revealed the presence of an anomalous emission band appearing in the 5200–5600 A spectral range. This anomalous band appears only in derivatives where the donor group is able to twist and depends on the solvent polarity, concentration and intensity excitation. This band, correlated to the presence of excited TICT states, is attributed to the emission of a “bicimer” species formed by the association of a pair of electronically excited state with large dipole moments.

Using an optical Kerr shutter and sophisticated automatization procedure, we have shown that it is possible to record routinely, with a good accuracy, and in an experiment consuming a comfortable time, time‐resolved emission spectra of short‐lived species in the time scale of 10 ps and in the spectral range 3900–9000 A. This system will allow us to obtain a better understanding of ultrafast dynamics in solution, where time spectral changes provide new insight.

The presence of two time-resolved emission bands is observed in trans-4-dimethylamino-4′-cyanostilbene dissolved in polar solvents using picosecond time-resolved spectroscopy. In a non-polar solvent, only the presence of a single emission band is observed at any temperature. A precursor-successor relationship occurs between the two species responsible for the two emission bands. It is concluded that the formation of a twisted intramolecular charge transfer (TICT) exicted state may explain these experimental results.

A simple picosecond time-resolved fluorescence spectrometer is developped using the optical Kerr effect. It allows to obtain whole time-resolved emission spectra between 4uuO and b000 A. Applications to the study of conformational changes of solvent cage and intramolecular twisting in solutions of organic compounds are presented.

International audience; Thermo-Desorption Spectrometry (TDS) was employed to study the release of fission gases from a Kr implanted UO2+x during 1050–1300 °C isotherms. The stoichiometry of the sample has been regularly increased by O2 additions in the vacuum setup to cover an hyperstoichiometry x range from ∼1 × 10−6 to ∼0.1. We used an analytical model based on Fick's second law to determine krypton diffusion kinetics (DKr) from the Kr cumulated release profiles. We demonstrate that even little x deviations from stoichiometric UO2 down to the 10−6 order are sufficient to quantitatively enhance fission gas diffusion. This likely explains a fair amount of data scatter in literature for experimental fission gases diffusion rates in (supposedly) perfectly stoichiometric UO2. A model was developed from the experimental results and well-accepted data for UO2 to estimate DKr (and DXe equivalently) as a function of T and x in the ranges of the present study. For moderate hyperstoichiometries, the present results suggest a fission gas diffusion mechanism identical (or similar to the very least) to that largely accepted for stoichiometric UO2, with the increased concentration of oxygen interstitials in the material kinetically enhancing Kr diffusion. At x ≈ 0.001 the diffusion-limiting mechanism changes, materialized by an increase of the activation energy (Ea). This Ea increase seemingly rules out a diffusion of fission gases controlled by VU (U vacancies). Instead, the rise of oxygen interstitial clusters, becoming the dominant type of defects in UO2+x for similar x ≥ 0.001 threshold, makes these defects prime suspects in controlling Kr (and Xe) diffusion in hyperstoichiometric uranium dioxide.