Superconducting and magnetic properties of ternary silicides in some rare earth-noble metal (Rh or Ir)-silicon systems

New families of ternary silicides have been prepared in the RE - Rh or Ir -Si systems and the crystal structures have been determined: RERh₃Si₂, RE₂Rh₃Si₅, RE₂RhSi₃ (RE = Y, La → Er), RERhSi (Y, La, Gd → Er), REIrSi (RE = La, Ce, Nd), RERhSi₂ and REIrSi₂ (RE = La → Gd). The RE₂RhSi₃ compounds crystallize with a new structural type, the other ones are isostructural with already known silicides or borides. Some of the silicides studied whose rare earths are diamagnetic (Y, La) show superconducting transitions above 1.6 K. They have been compared with other superconducting ternary borides, silicides, germanides and phosphides containing rare earths and noble metals. Except the phases with Y and La which are diamagnetic or show Pauli paramagnetism, the other materials order magnetically at low temperature. The onset of magnetic transitions vs. field has been observed for some compounds below 20 kOe at 4.2 K.     

The borocarbides Mo2−xWxBC (0⩽×⩽1.1), a new family of refractory superconducting materials

Large single crystals of Mo₂BC have been obtained by a Czochralski procedure above 2500 °C. The crystals are characterized by X-ray diffraction, optical metallography, and microprobe analysis. Tungsten substitution in Mo₂BC has been investigated. Resistance to oxidation and microhardness increase with increasing tungsten content in the borocarbides series Mo_2?xW_xBC (0?×?1.1) has been shown. A study of magnetization as a function of the field at different temperatures has been carried out. All borocarbides are type-II superconductors. Both the critical superconductivity temperature T_cr, and critical field,H_c2, decrease with x.     

Development and characterisation of electrochromic devices on polymeric substrates

The development of full solid-state electrochromic (EC) devices on polymeric substrate is underway within a CEC BRITE-EURAM project (Project “FREDOPS”, BE-4137) carried out by four industries, two universities and two research centers from Belgium, Denmark, France, and Italy. The specific goal of this project is to develop a Fast Response Electrochromic Device On Polymeric Substrate (FREDOPS); in order to satisfy the required range of specifications in terms of fast response, long term performance and high contrast ratio, several systems based on different materials have been tested. The full cells consist of an electrochromic material layer and a counter electrode, inserted between two PET/ITO layers and separated by a polymeric electrolyte. Different types of polymeric electrolytes, counter electrodes and electrochromic layers have been developed, studied and checked. Full devices have been assembled using different combinations. Voltammetric and spectrophotometric measurements have been executed to check the electrochromic behaviour of the developed layers in half and full cells. Comparison of the electrochromic performances of different materials based cells has led to the rejection of several solutions due to poor performance and incompatibilities between layers. Considering that the electrochromic devices are finalised for different uses (window, sunroof,…), some performance specifications for each application are defined. A testing bench for cycling and ageing was developed. The present paper discusses these results in order to indicate the best performance.     

Crystal structure of Li2 CaUF8

Compound Li₂CaUF₈ is tetragonal. The unit cell, with $\text{a}\text{=5.2290(12)}\text{A}\text{?}$,$\text{c}\text{=11.0130(18)}\text{A}\text{?}$, contains two formula units and the space group is I$\text{bar}\text{?}$m2. The crystal structure has been solved from single crystal diffractometer data by Patterson and Fourier synthesis and refined by a least-squares method. The final value of R is 0.062 for 602 reflections. The cationic distribution is the same as in the scheelite structure, with an additional cationic ordering. Moreover, we observe that the fluorine atoms are randomly distributed at two half occupied sites.     

Fatty acid and squalene compositions of mediterraneanCentrophorus SPP egg and liver oils in relation to age

The liver oil content of seven MediterraneanCentrophorus spp. were studied together with the oil of one unfertilized egg and one yolk bag. The relative weight of the liver ranges from 15 to 29% of total body weight; 63 to 89% of the liver weight is oil. Squalene, the major component (49–89% in oil) of the unsaponifiable fraction, is directly quantified by GLC following TLC separation. The squalene level increases with the age of the animals. More than 50 fatty acid species were identified. Among them, the most abundant are: 16∶0 (22–27%), 18∶1ω9 (21–36%) and 22∶6ω3 (2–18%). The level of ω3-fatty acids, essential in the fishes, shows a maximum in the egg (26%), decreases to a minimum in the young (5%) and stabilizes to an intermediate level in the adult (12%).     

Measurement of residual stresses in a plate using a vibrationaltechnique-application to electrolytic nickel coatings

A vibration method for the evaluation of the stress in a membrane is presented. The principle is based on the shift of the eigenfrequency of the modes due to the stress. The identification of the modes is obtained by an optical technique. The proposed method is applied to electrolytic nickel coatings. The results are compared with those obtained by X-ray analysis. The application of this type of measurement to other structures is discussed     

Dirofilariasis in France: a case in Languedoc in an HIV-seropositive patient

Dirofilaria repens is an endemic canine parasite in the Mediterranean area. Human infestation is rare. We observed a case in an HIV-positive patient who presented an ocular filaria which was successfully removed under local anesthesia. In man, filariae may be expulsed without a parasite cycle or complete a growth cycle, depending on the individual's immunological status. The disease has been known in southern France for several centuries, mainly in lagoons near the Mediterranean seaside. A review of the literature however shows that observation of clinical cases is rare, only 46 cases having been reported to date. Outcome is favorable.     

Structure,superconductivity and magnetism of new rare earth-rhodium silicides RE2Rh3Si5 of U2Co3Si5-type

New ternary silicides RE₂Rh₃Si₅ (RE = Y, La, Nd, Sm, Gd, Tb, Dy, Ho, Er) have been prepared. They crystalize in the U₂Co₃Si₅-type structure. Only the silicides containing the diamagnetic rare earths Y and La show a superconducting transition at T_Cr = 4.4 ± 0.2K and T_Cr = 2.7 ± 0.1K respectively, those with magnetic rare earths order antiferromagnetically at low temperature.     

Fatty acid and sterol compositions of malagasy tamarind kernel oils

The oil contents of six samples of Malagasy tamarind (Tamarindus indica L.) kernel were determined by hexane extraction (6.0–6.4%) and chloroform/methanol extraction (7.4-9.0%). The protein contents were very low (trace-0.1%). Investigation by gas liquid chromatography revealed 15 fatty acids, mainly palmitic (14–20%), stearic (6–7%), oleic (15–27%), linoleic (36–49%), arachidic (2–4%), behenic (3–5%) and lignoceric (3–8%) acids. Testing for the sterol fraction enabled seven sterols to be separated and quantitatively analyzed by gas liquid chromatography. The main sterols were β-sitosterol (66–72%), campesterol (16–19%) and stigmasterol (11–14%).     

A PM of New Design for High Speed Physics

Total transit time of the order of 1 ns with a standard deviation less than 0.1 ns, IR* better than 0.3 ns FWHM** are typical characteristics of a new type of PM designed and developed at LEP. These performances are obtained with the following applied voltages: between photocathode and oultiplier entrance :1 KV ; across the multiplier: 1 KV to 1.5 KV ; between multiplier output and collector : 2 KV The overall dimensions of the tube are maximum. diameter 40 mm, length 80 mm. The paper explains how these performances are achieved, due to a new design, comapared to the classical approach of PM. The predicted data, deduced from a computer programme (dealing with electron multiplication in channels) are compared to the experimental figures obtained from a coincidence study through a short pulse source, a time to amplitude converter and a multichannel analyzer. Some typical applications are evoked such as : high energy; physics, quantum. electronics.