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The GALLEX collaboration aims at the detection of solar neutrinos in a radiochemical experiment employing 30 tons of Gallium in form of concentrated aqueous Gallium-chloride solution. The detector is primarily sensitive to the otherwise inaccessible pp-neutrinos. Details of the experiment have been repeatedly described before [1-7]. Here we report the present status of implementation in the Laboratori Nazionali del Gran Sasso (Italy). So far, 12.2 tons of Gallium are at hand. The present status of development allows to start the first full scale run at the time when 30 tons of Gallium become available. This date is expected to be January, 1990.
The objective of the paper is to determine the stable mechanical equilibrium states of an oblate capsule subjected to a simple shear flow, by positioning its revolution axis initially off the shear plane. We consider an oblate capsule with a strain-hardening membrane and investigate the influence of the initial orientation, capsule aspect ratio
, viscosity ratio
between the internal and external fluids and the capillary number
which compares the viscous to the elastic forces. A numerical model coupling the finite element and boundary integral methods is used to solve the three-dimensional fluid–structure interaction problem. For any initial orientation, the capsule converges towards the same mechanical equilibrium state, which is only a function of the capillary number and viscosity ratio. For
, only four regimes are stable when
: tumbling and swinging in the low and medium
), regimes for which the capsule revolution axis is contained within the shear plane; then wobbling during which the capsule experiences precession around the vorticity axis; and finally rolling along the vorticity axis at high capillary numbers. When
is increased, the tumbling-to-swinging transition occurs for higher
; the wobbling regime takes place at lower
values and within a narrower
, the swinging regime completely disappears, which indicates that the stable equilibrium states are mainly the tumbling and rolling regimes at higher viscosity ratios. We finally show that the
phase diagram is qualitatively similar for higher aspect ratio. Only the
-range over which wobbling is stable increases with
, restricting the stability ranges of in- and out-of-plane motions, although this phenomenon is mainly visible for viscosity ratios larger than 1.
In this contribution, we report progress in the preparation of superconducting materials made by Spark Plasma Sintering (SPS). On the one hand, the fabrication process was optimized in order to improve the texturing of Bi2Ca2Sr2CuO8 superconductor ceramics. The new process is referred to as “Spark Plasma Texturing” (SPT). During SPT, the bulk material is free to deform itself. As a result, an inter-grain preferential crystallographic orientation is generated, while materials processed by conventional SPS are usually quasi-isotropic. The crystallographic orientation causes a strong anisotropy in the magnetic properties of the Bi2Ca2Sr2CuO8 bulk.
On the other hand, superconducting MgB2 discs were consolidated using the rapid SPS process. MgB2 has not been yet been seriously considered as a superconductor that could be used for magnetic levitation. Here we present trapped field measurements as a function of the distance to the superconductor and field cooled levitation force measurements that suggests that it presents interesting characteristics for this application.
The Molène archipelago appears to be particularly rich in Neolithic and Bronze Age remains and an exceptional concentration of megaliths has been brought to light. Several settlements are confirmed by dry-stone structures or by shell middens. These data give precious indications on the occupation chronology of the area. Moreover they allow us, for the first time in Brittany, to reconstruct everyday life during the late Prehistoric period. A prerequisite to this reconstruction was a better understanding of the evolution of the environment during this period, which locally implies a better knowledge of paleogeographic changes related to Holocene sea-level rise as well as on floral and faunal resources.
The results obtained through paleogeographic reconstructions show that the archipelago since 4500 bc was already disconnected from the mainland. The megalithic monuments must therefore have been erected and used by islanders present on the archipelago from the middle of the 5th to the 2nd millennium bc. The distribution of the megalithic tombs reveals landscape occupation strategies which respond to both cultural choices and natural constraints. Throughout the entire period, geographic isolation has continued to increase, although it did not imply strong cultural specificities. Nevertheless, the increasing remoteness of the islands has fostered the search for livelihoods based on the intense exploitation of coastal resources. Despite their focus on the sea, these people did not neglect what inland areas could offer as evidenced by the early agro-pastoral practices in the archipelago.
To evaluate the accuracy of real-time polymerase chain reaction (PCR) for Clostridium difficile–associated disease (CDAD) detection, after hospital CDAD rates significantly increased following real-time PCR initiation for CDAD diagnosis.
Hospital-wide surveillance study following examination of CDAD incidence density rates by interrupted time series design.
Large university-based hospital.
Hospitalized adult patients.
CDAD rates were compared before and after real-time PCR implementation in a university hospital and in the absence of physician and infection control practice changes. After real-time PCR introduction, all hospitalized adult patients were screened for C. difficile by testing a fecal specimen by real-time PCR, toxin enzyme-linked immunosorbent assay, and toxigenic culture.
CDAD hospital rates significantly increased after changing from cell culture cytotoxicity assay to a real-time PCR assay. One hundred ninety-nine hospitalized subjects were enrolled, and 101 fecal specimens were collected. C. difficile was detected in 18 subjects (18%), including 5 subjects (28%) with either definite or probable CDAD and 13 patients (72%) with asymptomatic C. difficile colonization.
The majority of healthcare-associated diarrhea is not attributable to CDAD, and the prevalence of asymptomatic C. difficile colonization exceeds CDAD rates in healthcare facilities. PCR detection of asymptomatic C. difficile colonization among patients with non-CDAD diarrhea may be contributing to rising CDAD rates and a significant number of CDAD false positives. PCR may be useful for CDAD screening, but further study is needed to guide interpretation of PCR detection of C. difficile and the value of confirmatory tests. A gold standard CDAD diagnostic assay is needed.
The concept of Developmental Origins of Health and Disease initially stemmed from the developmental programming of metabolic diseases. Reproductive functions and fertility in adulthood may also be programmed during foetal development. We studied the impact of dietary-induced maternal hyperlipidaemia and hypercholesterolaemia (HH), administered at 10 weeks of age and throughout the gestation and lactation, on male reproductive functions of rabbit offspring. Male rabbits born to HH dams and fed a control diet had significantly lighter testes and epididymes compared with rabbits born to control dams at adulthood. No significant changes in sperm concentration, sperm DNA integrity and sperm membrane composition were observed, but serum-free testosterone concentrations were decreased in HH males. This study confirms the importance of maternal metabolic status for the development of male reproductive organs.
The objective of this study is to investigate the motion of an ellipsoidal capsule in a simple shear flow when its revolution axis is initially placed off the shear plane. We consider prolate capsules with an aspect ratio of two or three enclosed by a membrane, which is either strain-hardening or strain-softening. We seek the equilibrium motion of the capsule as we increase the capillary number
, which measures the ratio between the viscous and elastic forces. The three-dimensional fluid–structure interaction problem is solved numerically by coupling a boundary integral method (for the internal and external flows) with a finite element method (for the wall deformation). For any initial inclination with the flow vorticity axis, a given capsule converges towards a unique equilibrium configuration which depends on
. At low capillary number, the stable equilibrium motion is the rolling regime: the capsule aligns its long axis with the vorticity axis, while the membrane tank-treads. As
increases, the capsule takes a complex wobbling motion at equilibrium, precessing around the vorticity axis. As
is further increased, the capsule long axis oscillates about the shear plane, while the membrane rotates around a capsule cross-section that also oscillates over time (oscillating–swinging regime). The amplitude of the oscillations about the shear plane decreases as
increases and the capsule finally takes a swinging motion in the shear plane. It is found that the transitions from rolling to wobbling and from wobbling to oscillating–swinging depend on the mean energy stored in the membrane.
Improvement of reproduction in dairy cows has become a major challenge in dairy production. We have recently shown that dairy cows carrying the ‘fertil−’ haplotype for one quantitative trait locus (QTL), affecting female fertility and located on the bovine chromosome 3, had a significantly lower conception rate after the first artificial insemination than cows carrying the ‘fertil+’ haplotype. The objective of this paper was to study other phenotypic modifications linked to this QTL. In the present study, 23 ‘fertil+’ and 18 ‘fertil−’ cows were characterized for live weight, milk production, food intake, eating behaviour and plasma metabolites. These parameters were measured during the first lactation, from calving to 40 weeks postpartum (wkpp). In the first 7 weeks of lactation, ‘fertil+’ primiparous cows had a significantly higher live BW and milk production than ‘fertil−’ cows. Dry matter intake tended to be slightly higher for ‘fertil+’ than for ‘fertil−’ primiparous cows in this period. However, energy balance was similar for the two haplotypes in the whole lactation, except in the first wkpp, and consequently, could not explain their different fertility. The major observation concerned the eating behaviour. ‘Fertil+’ primiparous cows had a significantly lower eating rate than ‘fertil−’ cows during the 40 weeks of lactation. In parallel, ‘fertil+’ cows spent significantly more time at the feeder for a similar number of visits than ‘fertil−’ cows. Furthermore, no differences in plasma concentrations of non-esterified fatty acids and insulin were observed between the two haplotypes. Plasma glucose was significantly lower in ‘fertil+’ than in ‘fertil−’ cows in the second wkpp. Taken together, our results show that ‘fertil+’ and ‘fertil−’ dairy cows, with different fertility, have also different eating behaviour without any variation in energy balance, except in the first week of lactation.
The diagnosis of cows' milk protein allergy (CMPA) requires first the suspicion of diagnosis based on symptoms described in the medical history, and, second, the elimination of cows' milk proteins (CMP) from the infant's diet. Without such rigorous analysis, the elimination of CMP is unjustified, and sometimes harmful. The elimination diet should be strictly followed, at least until 9–12 months of age. If the child is not breast fed or the mother cannot or no longer wishes to breast feed, the first choice is an extensively hydrolysed formula (eHF) of CMP, the efficacy of which has been demonstrated by scientifically sound studies. If it is not tolerated, an amino acid-based formula is warranted. A rice protein-based eHF can be an alternative to a CMP-based eHF. Soya protein-based infant formulae are also a suitable alternative for infants >6 months, after establishing tolerance to soya protein by clinical challenge. CMPA usually resolves during the first 2–3 years. However, the age of recovery varies depending on the child and the type of CMPA, especially whether it is IgE-mediated or not, with the former being more persistent. Once the child reaches the age of 9–12 months, an oral food challenge is carried out in the hospital ward to assess the development of tolerance and, if possible, to allow for the continued reintroduction of CMP at home. Some children with CMPA will tolerate only a limited daily amount of CMP. The current therapeutic options are designed to accelerate the acquisition of tolerance thereof, which seems to be facilitated by repeated exposure to CMP.
Porous silicon formed in p+ single crystal silicon is an interesting material for the study of the behavior of a fluid confined in mesoporous media, because it is a simple system of non interconnected straight pores, all perpendicular to the substrate and it can be well characterized by different methods. Moreover, the pores may be closed at one end when the porous layer is supported by the substrate or opened at both ends when the layer is removed from the substrate. Surprising results have been obtained. A hysteresis loop of type H2 (IUPAC classification), which is generally obtained for highly interconnected porous material, is also observed. Furthermore, a hysteresis of same type is also observed in pores closed at one end which is in contradiction with the Cohan model. The steep desorption process does not account for the large pore size distribution extracted from transmission electronic microscopy study. It is believed that, during the desorption process, the presence of an adsorbed layer on the external surface of the pores and/or the coupling between the pores via the silicon walls must be taken into account.
We report here on thin films proton-working electrochromic devices based on the wellknown tungsten oxide as the coloring electrode, and Antimony Tin Oxide (ATO) as the ionstorage counter-electrode. We show that films deposited by Pulsed Laser Deposition (PLD) technique have an apparent Sb solubility up to 70 at %, and exhibit unusual electrochromic properties. Through potentiostatic tests we'll demonstrate that depending on the composition which influences film morphology, the Sn-Sb-O films could either present a faradic or a capacitive-like behavior, associated to a color or a neutral switching over a wide range of potentials, respectively. The structural properties of ATO films are characterized by X-ray diffraction and transmission electron microscopy (TEM). Electrochromic behavior is studied by means of cyclic voltamperometry coupled with ex situ optical transmittance measurements in the visible range. The maximum proton-storage capacity is observed for ATO films containing 40–50 at % Sb, while being quasi-neutral when switching over a wide range of potentials. These compositions are finally retained for the assembly of our WO3/proton-electrolyte/ATO devices, whose performances are reported.
Yttria stabilized zirconia (YSZ) films have been characterized. The refractive index measured by ellipsometry is about 2.1. The breakdown electric field is greater than 4MV/cm for small area capacitors with a decrease for large area capacitors. This dielectric strength is weakly dependent on the film thickness within the range 0.2-1.lμm. The analysis of the 1MHz C(V) curves by the Terman method leads to a density of interface states of the order of 1012cm−2eV−1 in the middle of the bandgap with an increase near the conduction and the valence bands. The sensitivity of zirconia to the irradiations has been characterized by analysing 1MHz C(V). With or without electric field applied during the irradiations, the Flat-Band voltage shifts are lower for YSZ films than for thermal silicon dioxide films (2 times smaller).
Thin films of indium zinc oxide so called IZO were prepared with pulsed laser deposition. It was found that the crystalline structure, the composition and the morphology of the films as well as the optical and electrical properties were quite sensitive to the deposition conditions namely to the temperature and oxygen pressure. The crystallinity of the ZnkIn2O3+k (k from 1 to 5) thin films increases as the substrate temperature increases. An average transmittance of 85 % in the visible region was obtained for any k values. Optical measurements show a continuous decrease of the band gap as the zinc amount increases. The highest conductivity reported is for the ZnIn2O4, thin films deposited at 300 °C (σ = 1.2 103 S/cm). Increasing the amount of Zn (i.e. k value) was found to result in a conductivity decrease. Finally, a good correlation between the electric mobility and the optical mobility is obtained.
The “1:2” family of A2+(B2+1/3B+5+2/3)O3 (e.g. B2+ = Mg, Ni, Zn; B5+ = Nb, Ta) mixed metal perovskites typically adopt a 1:2 layered ordered structure when A = Ba and Sr, and a 1:1 ordered doubled perovskite structure for A = Pb. To understand the stability of the cation order in these systems and explore how the different cation correlations affect their dielectric and ferroelectric properties, the response of several members of this family of perovskites to a series of chemical substitutions and thermal treatments have been explored. In this paper we present results for a system where the divalent A cation is replaced by a 1:1 mixture of Na+ and La3+. At all temperatures this substitution stabilizes 1:1 B-site ordering. Below ~ 950°C an additional ordering reaction occurs on the A sub-lattice with Na and La occupying alternate layers along the c axis. The formation of different orientational variants of the A-site ordered phase produces a twinned nano-domain structure which in turn perturbs the length-scale, but not the symmetry, of the order on the B-site lattice. The presence of (Na1/2La1/2) on the A-site is apparently effective in destabilizing the 1:2 layering of the B-site cations observed in alkaline earth systems, possibly through unfavorable local charge imbalances.
Germanium nitride (Ge3N4) was examined as a potential negative electrode material for Li-ion batteries. The electrochemistry of Ge3N4 versus Li showed high reversible capacity (500mAh/g) and good capacity retention during cycling. A combination of ex-situ and in-situ x-ray diffraction (XRD), ex-situ transmission electron microscopy (TEM) and ex-situ selective area electron diffraction (SAED) analyses revealed evidence supporting the conversion of a layer of Ge3N4 crystal into an amorphous Li3N+LixGe nanocomposite during the first lithiation. The nanocomposite was electrochemically active via a reversible Li-Ge alloying reaction while a core of unreacted Ge3N4 crystal remained inactive. The lithium/metal nitride conversion reaction process was kinetically hindered resulting in limited capacity. Mechanical milling was found to improve the material capacity.
The reversible Li-driven copper extrusion/insertion mechanism into Cu2.33V4O11 electrode has been studied and a new ion-exchanged assisted electrochemical process was unravelled. This process, entails during the charging of “Lix V4O11 + Cu0” composite electrodes vs. Li, the oxidation of Cu metal into copper ions that concomitantly exchanged for lithium ions to produce back Cu2.33V4O11. The electrochemical performances of such cells, namely in terms of capacity retention and power rates, are explained on the basis of the electrochemically generated Cu ions that can either being ion-exchanged with Li within the Li-V-O host or released in the solution. When the former does occur we show, owing to excellent kinetic of both, the ion-exchanged reaction between Cu2+ and Li+ together with a fast charge transfer between Cu0 and Cu2+, that high rate performances electrodes can be achieved whereas when the latter prevails the cells rapidly fail. It appears then that Cu+ ions should be removed. Thus, a new copper vanadate Cu1.1V4O11 phase has been isolated by both chemical and electrochemical removal of Cu from the mother Cu2.33V4O11 phase, and its electrochemical performance in Li cells studied. The removal of copper was shown to occur in a topotactic manner resulting in a stacking of [V4O11]n layers linked by differently coordinated copper ions. This new phase reversibly reacts with 5 Li, leading to a capacity of about 260 mAh/g, through a process involving a reversible displacement reaction entailing to the growth/disappearance of Cu dendrites.
The impact of capacitive coupling effects increases with scaling down the dimensions and towards higher performances. For bipolar technologies, the introduction of deep trench isolation gives a substantial reduction in the collector substrate capacitance. In this paper a method for the formation of airgap deep trenches (with 1μm – depth 6 μm) is presented. The method is fully compatible with standard CMOS Shallow Trench Isolation (STI) and does not require additional masking steps. The approach is based on a partial removal of the poly-Si filling in the trench. Subsequently, inside D-shape oxide spacers are formed narrowing the opening of the trench down. An SF6 plasma is used to convert the nearly completely incorporated poly-Si to volatile SiF4, such that it desorbs through the opening. In the following steps the opening is sealed by depositing SiO2 resulting in the formation of an airgap (patent pending). The normal module for STI formation continues without any adaptation of the process steps. In total four standard additional process steps are needed.
The absence of the common oxide/poly filling in the deep trench decreases the peripheral collector substrate capacitance with an order of magnitude to a value of 0.02fF/μm. As a consequence the low power available bandwidth is improved with 90%.
In order to investigate the possibility of modelling plant motion at the landscape scale, an equation for crop plant motion, forced by an instantaneous velocity field, is introduced in a large-eddy simulation (LES) airflow model, previously validated over homogeneous and heterogeneous canopies. The canopy is simply represented as a poroelastic continuous medium, which is similar in its discrete form to an infinite row of identical oscillating stems. Only one linear mode of plant vibration is considered. Two-way coupling between plant motion and the wind flow is insured through the drag force term. The coupled model is validated on the basis of a comparison with measured movements of an alfalfa crop canopy. It is also compared with the outputs of a linear stability analysis. The model is shown to reproduce the well-known phenomenon of ‘honami’ which is typical of wave-like crop motions on windy days. The wavelength of the main coherent waving patches, extracted using a bi-orthogonal decomposition (BOD) of the crop velocity fields, is in agreement with that deduced from video recordings. The main spatial and temporal characteristics of these waving patches exhibit the same variation with mean wind velocity as that observed with the measurements. However they differ from the coherent eddy structures of the wind flow at canopy top, so that coherent waving patches cannot be seen as direct signatures of coherent eddy structures. Finally, it is shown that the impact of crop motion on the wind dynamics is negligible for current wind speed values. No lock-in mechanism of coherent eddy structures on plant motion is observed, in contradiction with the linear stability analysis. This discrepancy may be attributed to the presence of a nonlinear saturation mechanism in LES.