Search

We briefly discuss how the wetting properties of a fluid/solid interface can indirectly influence the diffusion properties of fluid confined between two solid walls. This influence is related to the variability of the hydrodynamic boundary conditions at the interface, which correlates to the wetting properties.

Des atomes d'hélium métastables dans l'état 2 3S1sont alignés par pompage optique et soumis à la résonance magnétique. La fréquence du champ de haute fréquence est asservie au champ magnétique à l'aide d'un asservissement numérique. La sensibilité du magnétomètre ainsi réalisé est de l'ordre de 10-10T/$\sqrt{\rm Hz}$.

A simple model of a polyelectrolyte, the charged bead-spring chain, is studied using Monte-Carlo simulations and variational methods. A good quantitative agreement between both approaches is obtained. For bare Coulombic interactions, excellent agreement with the classical “electrostatic blob” picture is found. Screening of the electrostatic interactions causes a crossover to excluded volume behaviour that takes place at scales of the order of the screening length.

The aim of this short chapter is to remind the reader of some of the statistical physics ideas that underlie the use of simulation methods, starting from classical Monte Carlo (MC) and Molecular Dynamics (MD) and extrapolating to more advanced simulation methods that permit an exploration of more sophisticated issues, such as long time scales or spectroscopic response. The objective is not an exhaustive description of the relevant issues, but rather to provide a guide to the relevant litterature – which has now to a large extent appeared in the form of textbooks.

Abstract—The howardite‐eucrite‐diogenite (HED) clan is a group of meteorites that probably originate from the asteroid Vesta. Some of them are complex breccias that contain impact glasses whose compositions mirror that of their source regions. Some K‐rich impact glasses (up to 2 wt% K2O) suggest that in addition to basalts and ultramafic cumulates, K‐rich rocks are exposed on Vesta's surface. One K‐rich glass (up to 6 wt% K2O), with a felsic composition, provides the first evidence of highly differentiated K‐rich rocks on a large asteroid. They can be compared to the rare lunar granites and suggest that magmas generated in a large asteroid are more diverse than previously thought.

Abstract—We report on the major and trace element abundances of 18 diogenites, and O‐isotopes for 3 of them. Our analyses extend significantly the diogenite compositional range, both in respect of Mg‐rich (e.g., Meteorite Hills [MET] 00425, MgO = 31.5 wt%) and Mg‐poor varieties (e.g., Dhofar 700, MgO = 23 wt%). The wide ranges of siderophile and chalcophile element abundances are well explained by the presence of inhomogeneously distributed sulfide or metal grains within the analyzed chips. The behavior of incompatible elements in diogenites is more complex, as exemplified by the diversity of their REE patterns. Apart from a few diogenite samples that contain minute amounts of phosphate, and whose incompatible element abundances are unlike the orthopyroxene ones, the range of incompatible element abundances, and particularly the range of Dy/Yb ratios in diogenites is best explained by the diversity of their parental melts. We estimate that the FeO/MgO ratios of the diogenite parental melts range from about 1.4 to 3.5 and therefore largely overlap the values obtained for non‐cumulate eucrites. Our results rule out the often accepted view that all the diogenites formed from parental melts more primitive than eucrites during the crystallization of a magma ocean. Instead, they point to a more complex history, and suggest that diogenites were derived from liquids produced by the remelting of cumulates formed from the magma ocean.

Abstract—Northwest Africa (NWA) 1670, contains olivines of up to 5 mm in size representing about 30% of the studied section. With subordinate clinopyroxene and chrome‐spinel microphenocrysts (0.2‐0.5 mm), they represent a xenocrystic association. Phenocrysts are surrounded by a groundmass, predominantly comprising bundles of plagioclase and clinopyroxene (typically 20 × 200 μm crystals). Olivine and kirschsteinite are present in the groundmass in lesser amounts. The olivine xenocrysts (Fo90) are significantly fractured and show mosaicism for their major part, the remaining showing faint undulatory extinction. They are surrounded with a rim of 100–200 μm zoned down to Fo80 and overgrown with serrated olivine, Fo80 to Fo60 (about 100 μm). Olivine in the groundmass is zoned from Mg# 0.55 to 0.15; its CaO content ranges 2.0 to 8.4%. Subcalcic kirschsteinite is zoned from Mg# 0.13 to 0.03, CaO increasing from 15.8 to 21.3%. Pyroxenes xenocrysts (Mg# = 0.77) are superseded in the groundmass by less magnesian pyroxenes, Mg# 0.61 to 0.17, with an average FeO/ MnO of 98. Their compositions range from En30Fs22Wo27Al‐Ts28Ti‐Ts2to En2Fs37Wo22Al‐Ts40Ti‐Ts1. Anorthite microcrysts (An99‐100) are restricted to the groundmass. Accessories are pyrrhotite, kamacite, Ca‐phosphate, titanomagnetite, hercynite and Ca‐carbonate.

This study evaluated the impact of biological and environmental factors on the infection of red foxes (Vulpes vulpes)by Echinococcus multilocularisin an endemic area of north-east France. From January 2004 to April 2006, 127 foxes were examined for E. multilocularisand their stomach contents analysed. The effect of year, season, age, sex and urbanisation level on E. multilocularispresence was estimated using a General Linear Model (GLM) with logit link, (i.e. logistic regression). Urbanisation level was the only influencing factor, with a decreasing gradient from rural [54%, CI 95% (40-68)] to peri-urban [31%, CI 95% (15-52)] and urban area [4%, CI 95% (0.7-15)]. The consumption of Arvicola terrestrisand Microtussp., grassland species, the main presumed intermediate hosts of E. multilocularis, was studied by the same approach. The two species were consumed less in the urban area and more in autumn than in spring. Anthropogenic food consumption was linked to urbanisation and to age. The frequency of anthropogenic food consumption decreased in the rural area. A global model explaining the presence of E. multilocularisand including urbanisation level and diet was then elaborated. Independently of urbanisation, there was a suggestion of less E. multilocularisinfection with anthropogenic food consumption. Red foxes consuming Microtussp. and A. terrestrishad higher worm burden than those that did not. The results suggest that the decreasing gradient observed from rural to urban area is linked to behaviour and feeding habits.

Abstract—We report on the petrology and geochemistry of Northwest Africa (NWA) 4215, an unbrecciated diogenite recovered in the Sahara. This single stone, weighing 46.4 g, displays a wellpreserved cumulative texture. It consists of zoned xenomorphic orthopyroxene grains on the order of 500 μm in size, along with a few large chromite crystals (<5 vol%, up to 3 mm). Accessory olivine and scarce diopside grains occur within the groundmass, usually around the chromite crystals. Minor phases are cristobalite, troilite, and metal. Unlike other diogenites, orthopyroxenes (En76.2Wo1.1Fs22.7to En68.6Wo5.5Fs25.9), olivines (Fo76to Fo71), and chromites (Mg# = 14.3 44.0, Cr# = 42.2–86.5) are chemically zoned. The minor element behavior in orthopyroxenes and the intricate chemical profiles obtained in chromites indicate that the zonings do not mirror the evolution of the parental melt. We suggest that they resulted from reaction of the crystals with intercumulus melt. In order to preserve the observed zoning profiles, NWA 4215 clearly cooled significantly faster than other diogenites. Indeed, the cooling rate determined from the diffusion of Cr in olivine abutting chromite is in the order of 10–50 °C/a, suggesting that NWA 4215 formed within a small, shallow intrusion.

Northwest Africa (NWA) 1950 is a new member of the lherzolitic shergottite clan of the Martian meteorites recently found in the Atlas Mountains. The petrological, mineralogical, and geochemical data are very close to those of the other known lherzolitic shergottites. The meteorite has a cumulate gabbroic texture and its mineralogy consists of olivine (Fo66to Fo75), low and high‐Ca pyroxenes (En78Fs19Wo2‐En60Fs26W14; En53Fs16Wo31‐En45Fs14Wo41), and plagioclase (An57Ab41Or1to An40Ab57Or3; entirely converted into maskelynite during intense shock metamorphism). Accessory minerals include phosphates (merrillite), chromite and spinels, sulfides, and a glass rich in potassium. The oxygen isotopic values lie on the fractional line defined by the other SNC meteorites (Δ17O = 0.312 %o). The composition of NWA 1950 is very similar to the other lherzolitic shergottites and suggests an origin from the same magmatic system, or at least crystallization from a close parental melt. Cosmogenic ages indicate an ejection age similar to those of the other lherzolitic shergottites. The intensity of the shock is similar to that observed in other shergottites, as shown by the occurrence of small melt pockets containing glass interwoven with stishovite.

Although veterinary authorities aim to limit persistence of classical swine fever (CSF) in wild boar (Sus scrofa), to avoid potential transmission to pigs, factors influencing CSF transmission and persistence are not clearly understood. Here we analyse incidence and persistence in a CSF epidemic that occurred in the French Vosges Forest. Higher incidence was found in large forests compared to smaller isolated ones, being highest near the starting point of the epidemic, but poorly related to the local density. We hypothesize that the spatial and social structure of wild boar populations may be responsible for this variability of incidence over space. Persistence was highest near the starting point of the epidemic and where initial density was highest. We hypothesize that persistence was favoured by the abundance of young wild boar, itself encouraged by CSF. Our results allow us to propose management measures aimed at limiting CSF persistence.

Abstract—We report on a new angrite, Northwest Africa (NWA) 1296, a fine‐grained rock with a magmatic texture of rapid cooling. Dendritic olivine (≅Fo50) crystallized first in association with anorthite microcrysts (An98–100) forming composite chains separated from one another by intergrown Al‐Fe diopside‐hedenbergite pyroxenes. In addition, some olivines with lower Mg# and increased CaO (up to 12%) are found between the chains as equant microphenocrysts. Pyroxenes and olivines are both normally zoned from Mg# = 0.52 to less than 0.01 in the rims. Ca‐rich olivines are surrounded by, intergrown with, or replaced by subcalcic kirschsteinite. They appear after plagioclase crystallization stopped, at the end of the crystallization sequence. Minor phases are pyrrhotite, F‐apatite, and titanomagnetite. Pyroxene is the last silicate phase to grow, interstitial to idiomorphic olivine‐kirschsteinite. Numerous small vesicles and some channels are filled with microcristalline carbonate. The mode (vol%) is about 28% olivine, 3% kirschsteinite, 32% anorthite, 34% pyroxene, and 3% of the minor phases—close to that reported previously for D'Orbigny and Sahara (SAH) 99555. The bulk chemical composition of NWA 1296 is similar to D'Orbigny and SAH 99555; NWA 1296 differs by its texture and mineralogy, which are interpreted as resulting from rapid crystallization—an evidence of impact melting. Angrites cannot be produced by partial melting of a CV source because segregation of a “planetary” core is necessary to explain the low FeO/MgO ratio of magnesian olivines. Neither the odd Ca/Al ratio nor the very low SiO2content can be explained by conventional partial melting scenarios. We suggest that carbonate is the key to angrite genesis. This is supported by the striking similarities with terrestrial melilitites (low SiO2, superchondritic Ca/Al ratio, presence of carbonate). The lack of alkalies could be the result of either loss after impact melting or absence of alkalies in the source.

We examine the static and dynamic properties of polymer chains in a melt in the presence of a solid surface. A molecular dynamics simulation is carried out using a coarse-grained bead−spring model of polymer chains. Both attractive and repulsive interactions between surface and monomers are examined. Static conformations are characterized in terms of trains of attached monomers and detached loops and tails. We compare these conformations to a random walk model. Chain desorption rates are measured in order to calculate characteristic desorption times. We distinguish between chains which desorb rapidly after arriving at the surface and chains which reach a relaxed state at the surface and then desorb at a constant rate. A kinetic model is developed as a means to predict desorption rates and late time chain conformations.

Abstract—We report on the discovery of a new shergottite from South Morocco. This single stone weighing 320 g is referenced as Northwest Africa (NWA) 856 with Djel Ibone as a synonymous name. It is a fresh, fine‐grained basaltic rock consisting mainly of two pyroxenes (total ˜68 vol%: 45% pigeonite, En61‐16Wo9–22Fs26–68; 23% augite, En46‐26Wo34‐29Fs21–43) and plagioclase converted to maskelynite (˜23 vol%, Ab43–57Or1–5An54‐36). Accessory minerals include merrillite, Cl‐apatite, pyrrhotite, ilmenite, ulvöspinel, silica (stishovite and glass), amorphous K‐feldspar and baddeleyite. Amorphous mixtures of maskelynite and silica occur most commonly as median layers inside maskelynite laths. In addition, melt pockets (˜2 vol%) were recognized with relics of maskelynite, pyroxene and both dense silica glass and stishovite occurring as both grains and submicrometer needles. The compositions of the melt pockets are consistent with mixtures of maskelynite and pyroxenes with an average of ˜50 vol% maskelynite. The meteorite is highly fractured at all scales.

Abstract—North West Africa (NWA) 480 is a new martian meteorite of 28 g found in the Moroccan Sahara in November 2000. It consists mainly of large gray pyroxene crystals (the largest grains are up to 5 mm in length) and plagioclase converted to maskelynite. Excluding the melt pocket areas, modal analyses indicate the following mineral proportions: 72 vol% pyroxenes extensively zoned, 25% maskelynite, 1% phosphates (merrillite and chlorapatite), 1% opaque oxides (ilmenite, ulvöspinel and chromite) and sulfides, and 1% others such as silica and fayalite. The compositional trend of NWA 480 pyroxenes is similar to that of Queen Alexandra Range (QUE) 94201 but in NWA 480 the pyroxene cores are more Mg‐rich (En77‐En65). Maskelynites display a limited zoning (An42–50Ab54‐48Or2–4). Our observations suggest that NWA 480 formed from a melt with a low nuclei density at a slow cooling rate. The texture was achieved viaa single‐stage cooling where pyroxenes grew continuously. A similar model was previously proposed for QUE 94201 by McSween et al.(1996). NWA 480 is an Al‐poor ferroan basaltic rock and resembles Zagami or Shergotty for major elements and compatible trace element abundances. The bulk rock analysis for oxygen isotopes yields Δ17O = +0.42%, a value in agreement at the high margin, with those measured on other shergottites (Clayton and Mayeda, 1996; Romanek et al., 1998; Franchi et al., 1999). Its CI‐normalized rare earth element pattern is similar to those of peridotitic shergottites such as Allan Hills (ALH)A77005, suggesting that these shergottites shared a similar parent liquid, or at least the same mantle source.

Abstract—We report on major and trace element analyses obtained by, respectively, inductively coupled plasma‐atomic emission spectrometry (ICP‐AES) and inductively coupled plasma‐mass spectrometry (ICP‐MS) of three different aliquots of the new Saharan shergottite Dar al Gani (DaG) 476. The new analyses are in excellent agreement with previous data (Zipfel et al., 2000). Ba, Sr and U abundances, together with the presence of carbonate, suggest that the sample has been significantly weathered. Three rare earth element (REE) patterns (normalized to CI) determined on three different aliquots of the sample all show similar shapes. The heavy REEs are flat with a slight depletion at the heavy end and a strong depletion from Dy to Pr. All of the patterns display an upturn to La which we interpret as being caused by the introduction of a terrestrial component. Taking the terrestrial contamination into account, this study demonstrates that DaG 476 is one of the most depleted of the shergottites, and, just like Queen Alexandra Range (QUE) 94201 (Dreibus et al., 1996), displays very low Zr/Hf ratios. It appears that the Zr/Hf ratios of shergottites are not uniform, and have been significantly fractionated by martian mantle processes.

Abstract—We report on major and trace element analyses of 17 eucrites, including three cumulate eucrites (Binda, Moore County, and Serra de Magé), determined by, respectively, inductively‐coupled plasma atomic emission spectrometry and inductively‐coupled plasma mass spectrometry. The results obtained for Binda and Moore County are consistent with the model of Treiman (1997) for the formation of cumulate eucrites, which holds that these meteorites were produced from a eucritic melt. Our sample of Serra de Magé contains unusually large amounts of pyroxene and probably an accessory phase rich in heavy rare earth elements and is therefore not representative of this eucrite as known from literature data.

Abstract:: By means of molecular dynamics computer simulations we investigate the out of equilibrium relaxation dynamics of a simple glass former, a binary Lennard-Jones system, after a quench to low temperatures. We find that one-time quantities, such as the energy or the structure factor, show only a weak time dependence. By comparing the out of equilibrium structure factor with equilibrium data we find evidence that during the aging process the system remains in that part of phase space that mode-coupling theory classifies as liquid like. Two-times correlation functions show a strong time and waiting time dependence. For large and times corresponding to the early -relaxation regime the correlators approach the Edwards-Anderson value by means of a power-law in time. For large but fixed values of the relaxation dynamics in the -relaxation regime seems to be independent of the observable and temperature. The -relaxation shows a power-law dependence on time with an exponent which is independent of but depends on the observable. We find that at long times the correlation functions can be expressed as and compute the function h(t). This function is found to show a t-dependence which is a bit stronger than a logarithm and to depend on the observable considered. If the system is quenched to very low temperatures the relaxation dynamics at long times shows fast drops as a function of time. We relate these drops to relatively local rearrangements in which part of the sample relaxes its stress by a collective motion of 50-100 particles. Finally we discuss our measurements of the time dependent response function. We find that at long times the correlation functions and the response are not related by the usual fluctuation dissipation theorem but that this relation is similar to the one found for spin glasses with one step replica symmetry breaking.

Abstract—Comparison between clasts of the Tatahouine diogenite, collected the day of the fall in 1931 and 63 years later in 1994, allows the evaluation of mineralogical and chemical effects of terrestrial residence on meteorites. Secondary minerals are found in the 1994 samples: iron stains and carbonate rosettes. Major and trace element abundances have been determined on fallen and found clasts. No significant differences have been observed for most elements with the exception of Rb, Sr, and (in a single case) the light rare earth elements (LREE). In this case, the REE pattern of a 1994 clast displays a weak positive Ce anomaly, probably linked to the presence of iron hydroxide. The contents of Rb and Sr are significantly higher in the 1994 samples than in the 1931 clasts and reflect the formation of calcite inside some of the clast fractures. These results demonstrate that weathering processes may change the chemistry of meteorites in a very short time.

During a serosurvey of domestic dogs in Tanzania, a rapid fluorescent focus inhibition test (RFFIT) and a liquid-phase blocking ELISA (LPBE) were used to measure rabies antibodies in vaccinated and unvaccinated dogs. Post-vaccination titres measured by LPBE correlated closely with those found by RFFIT. Of 567 unvaccinated dogs tested using the LPBE, 42 (7·4%) were seropositive, with titres exceeding 32. Of this group, 233 dogs were tested using the RFFIT and 115 (49·4%) were seropositive, with titres exceeding 0·5 IU/ml. Two lines of evidence pointed to the greater specificity of the LPBE when measuring rabies antibodies induced by natural infections: (a) no seropositive dogs were detected among the 162 unvaccinated dogs from the rabies-free island of Pemba, Tanzania, when using LPBE, whereas 15/145 (10·3%) dogs of the same group were seropositive using RFFIT; (b) among Tanzanian dogs there was a close association between the location of rabies cases and location of seropositive dogs when using LPBE, but not when using RFFIT. These results suggest that LPBE may be of value in rabies seroepidemiological studies and could be developed as a reference technique for the detection of rabies antibody in domestic dogs.

Abstract: We study the relaxation to equilibrium of two dimensional islands containing up to 20 000 atoms by Kinetic Monte Carlo simulations. We find that the commonly assumed relaxation mechanism - curvature-driven relaxation via atom diffusion - cannot explain the results obtained at low temperatures, where the island edges consist in large facets. Specifically, our simulations show that the exponent characterizing the dependence of the equilibration time on the island size is different at high and low temperatures, in contradiction with the above cited assumptions. Instead, we propose that - at low temperatures - the relaxation is limited by the nucleation of new atomic rows on the large facets: this allows us to explain both the activation energy and the island size dependence of the equilibration time.

Abstract: The response function of domain growth processes, and in particular the violation of the fluctuation-dissipation theorem, are studied both analytically and numerically. In the asymptotic limit of large times, the fluctuation-dissipation ratio X, which quantifies this violation, tends to one if C > m 2 and to zero if C < m 2, corresponding to the fast (“bulk”) and slow (“domain-wall”) responses, respectively. In this paper, we focus on the pre-asymptotic behavior of the domain-wall response. This response is shown to scale with the typical domain length L(t) as 1/L(t) for dimension d > 2, and as ln(L(t))/L(t) for d = 2. Numerical results confirming this analysis are presented.

A factorization ansatz for the triplet direction correlation function c(3) is combined with the exact relation between c(3) and the derivative of the pair function c(2) with respect to density to derive a simple and tractable approximation for c(3) in dense, classical fluids. The predictions of this approximation are found to be in good agreement with the results of 'exact' molecular dynamics simulations for the 'soft sphere' model near freezing. The approximate c(3) is then used to derive an improved integral equation for the pair correlation function which is found to yield satisfactory results. In another application, the third order term in the density functional theory of freezing is systematically evaluated for the first time and is found to lead to significant improvement over the usual second order theory, particularly for soft interatomic repulsions.

A simple model of a polyelectrolyte, the charged bead-spring chain, is studied using Monte-Carlo simulations and variational methods. A good quantitative agreement between both approaches is obtained. For bare Coulombic interactions, excellent agreement with the classical ?electrostatic blob? picture is found. Screening of the electrostatic interactions causes a crossover to excluded volume behaviour that takes place at scales of the order of the screening length. Nous ?tudions par des simulations Monte-Carlo et des m?thodes variationnelles un mod?le simple de poly?lectrolyte, la cha?ne gaussienne charg?e. Un bon accord quantitatif entre les deux approches utilis?es est obtenu. Pour des interactions de Coulomb non ?crant?es, les r?sultats sont en excellent accord avec le mod?le classique du ?blob ?lectrostatique?. Lorsque les interactions ?lectrostatiques sont ?crant?es, on observe aux ?chelles de longueur plus grandes que la longueur d'?cran le d?but d'une transition vers un r?gime de volume exclus ?lectrostatique.

Metastable 2 3S1He atoms are aligned by optical pumping and submitted to magnetic resonance. The frequency of the radio-frequency field is locked to the static magnetic field through numerical control. The sensitivity of this magnetometer is of the order of 10-10T/?(Hz). Des atomes d'h?lium m?tastables dans l'?tat 2 3S1sont align?s par pompage optique et soumis ? la r?sonance magn?tique. La fr?quence du champ de haute fr?quence est asservie au champ magn?tique ? l'aide d'un asservissement num?rique. La sensibilit? du magn?tom?tre ainsi r?alis? est de l'ordre de 10-10T/?(Hz).

For thirty years now, linear or macrocyclic gadolinium-based contrast agents (GBCAs) have been routinely used in MRI. They were initially assumed to have virtually no side effects, but gadolinium can accumulate in tissue, bone and brain. Moreover, linear GBCAs can cause nephrogenic systemic fibrosis, a debilitating and potentially life-threatening disease, for patients with kidney failure. Thus, the use of some linear GBCAs has been reduced over the last decade, and has even been stopped in Europe.

Three groups of 10 foxes were vaccinated by the direct oral instillation of 2 ml of SAG1 rabies virus vaccine containing 106MICLD50 (107TCID50/ml) infectious viral particles/ml. SAG1 is a natural variant of the attenuated rabies vaccine strain SAD Bern and was selected in the presence of monoclonal antibodies. The strain is devoid of residual pathogenicity for the fox and the highly susceptible adult laboratory mouse by the oral, intramuscular and intracerebral routes. The foxes were challenged six, 12 and 18 months later with a virulent vulpine street rabies virus (GS 7‐1‐1). They all survived, whereas seven of eight unvaccinated control foxes died.

Among the various autoantibodies commonly found in women with systemic lupus erythematosus, the so-called lupus anticoagulant has been described in association with fetal losses. Recently, women with repeated spontaneous abortions and lupus anticoagulant, but no apparent systemic lupus erythematosus have been described. We have studied prospectively the possible connections between fetal losses and autoimmunity in a large control study of 130 idiopathic habitual aborters. These non-pregnant patients without any antecedent autoimmune disease were explored for the presence for autoantibodies especially lupus anticoagulant. Ten percent of the patients exhibit an antithromboplastin antibody (lupus anticoagulant) and half of this group possesses a striking association of biological manifestations of autoimmunity. In conclusion, two points appear: firstly, statistical correlation is demonstrated between antithromboplastin antibody and habitual abortion; secondly, doubt remains about the significance of the association between autoimmunity, fetal losses and antithromboplastin: beginning of systemic lupus erythematosus or new autoimmune entity with gynaeco-obstetrical expression.