Lithium sulfate: Calorimetric determination of the temperatures and enthalpies of high-temperature phase transitions

Using a high-temperature Calvet calorimeter as a differential enthalpic analyser Li₂SO₄ was investigated in the temperature range 800–1200 K. One transformation in the solid state was observed at 847 K with a corresponding enthalpy increment of 24.2 kJ mol^?1. The solid-liquid transition was found to occur at 1131 K with an enthalpy of fusion of 7.74 kJ mol^?1. Furthermore, the analysis of the corresponding thermograms supports the presence of the premelting effect which was evidenced by other techniques. A critical comparison with previous results in the literature is given.     

Thermodynamic Study of the Molten Salt Binary System KHSO4−NaHSO4

The partial molar enthalpies of mixing of NaHSO₄ and KHSO₄ have been measured at 528 K by dropping samples of pure compounds into molten mixtures of NaHSO₄ and KHSO₄ in Calvet calorimeter. From these values the molar enthalpy of mixing has been deduced. The same method has been used for the determination of the heat capacity of the two pure compounds in the solid and liquid states. The phase diagram of this system has been confirmed by conductometric and thermal analysis methods. By an optimization method the excess entropy of the liquid mixtures was also calculated. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis and Reactions of 3‐Methylthiazolo[3,2‐a]Benzimidazole‐2‐Carboxylic Acid Hydrazide: Synthesis of Some New Pyrazole, 1,3‐Thiazoline, 1,2,4‐Triazole and 1,2,4‐Triazolo[3,4‐b]‐1,3,4‐Thiadiazine Derivatives Pendant to Thiazolo[3,2‐a]Benzimidazole Moiety

The reaction of 3‐methylthiazolo[3,2‐a]benzimidazole‐2‐carboxylic acid ethyl ester (1) with hydrazine hydrate gives the hydrazide 2 which reacts with CS₂/KOH to afford the potassium salt 3. Treatment of 3 with l‐aryl‐2‐bromoethanones 4a,b afforded the 1,3‐thiazoline derivatives 6a,b, respectively, while the reaction of 3 with hydrazine hydrate afforded 1,2,4‐triazole‐3‐thione derivative 9. The reaction of 9 with l‐aryl‐2‐bromoethanones 4a,b and with hydrazonyl chlorides 11a,b gave the 1,2,4‐triazolo[3,4‐b]‐1,3,4‐thiadiazine derivatives 10a,b and 12a,b, respectively. Treatment of hydrazide 2 with phenyl isothiocyanate in refluxing benzene gave the thiosemicarbazide derivative 16. The latter reaction gave 1,3,4‐oxadiazole derivative 17 when benzene was replaced by DMF. Cyclization of the thiosemicarbazide derivative 16 with NaOH resulted in the formation of the 1,2,4‐triazole‐3‐thione derivative 18.     

Optimal estimates for blowup rate and behavior for nonlinear heat equations

We first describe all positive bounded solutions of where \input amstex \loadmsbm $(y,s)\in \Bbb R^N\times \Bbb R$ , 1 < p, and (N − 2)p ≤ N + 2. We then obtain for blowup solutions u(t) of uniform estimates at the blowup time and uniform space-time comparison with solutions of u′ = u^p. © 1998 John Wiley & Sons, Inc.     

Chemical vapour etching for double-sided buried metallic contacts in polycrystalline silicon solar cells processing

In this paper, we investigate the effect of double-sided buried metallicontacts (BMCs) on the photovoltaic performances of polycrystalline-silicon (pc-Si) solar cells. Prior to junction formation, groove patterns were achieved on both surface sides of the pc-Si wafers using a chemical vapour etching-based technique. The BMCs were realized onto the grooved areas using the screen printing technique. Once the BMCs were formed, we point out a significant increase of the spectral response in the 400-1100 nm wavelength range, particularly at short and long wavelengths. These results were attributed to an enlargement of the contact areas in both emitter and base regions of the cells, leading to a reduction of their effective thickness and to an enhancement of the minority carrier collection. The dark I-V characteristics of BMCs-based pc-Si cells show a significant reduction of the reverse current together with an improvement of the rectifying behaviour. The I-V characteristic under AM1.5 illumination shows that the introduction of BMCs in polycrystalline silicon solar cells processing improves the conversion efficiency by about 2.5-3.5%.     

Determination of the blow-up rate for a critical semilinear wave equation

In this paper, we determine the blow-up rate for the semilinear wave equation with critical power nonlinearity related to the conformal invariance.Mathematics Subject classification (2000): 35L05, 35L67Membre de lInstitut Universitaire de France     

Fission fragment track etching modelling for the cellular localisation of Neptunium-237 nuclei in rat tissues

Heavy ion recording in dielectric isotropic detectors has a wide range of applications in uranium cartography or dating. In this study, solid state nuclear tracks detectors (SSNTDs) have been applied to localise neptunium-237, in vivo, by means of the neutron-induced fission cartography of neptunium-237 nuclei in organ sections. At the cellular level, a precise localisation can only be achieved with a good understanding of the etch pit evolution during the chemical etching process.

A tailor-made software for modelling the etching process has been developed to simulate the profile of an etched track produced by a neutron-induced fission fragment. This software is based on a model that considers the evolution of the track etching velocity along the damage trail in order to perfectly model the shape of the track.     

Synthesis of some new benzofuran‐based thiophene, 1,3‐oxathiole and 1,3,4‐oxa(thia)diazole derivatives

Treatment of 3‐(3‐methylbenzofuran‐2‐yl)‐3‐oxopropanenitrile ( 1 ) with phenyl isothiocyanate afforded the thioacetanilide derivative 3 , which when reacted with α‐haloketones, α‐halodiketones, and hydrazonoyl chlorides gives thiophene, 1,3‐oxathiole, and 1,3,4‐thiadiazole derivatives 6a,b, 10a,b and 14a–g , respectively. Treatment of 3‐methyl‐2‐benzofurancarboxylic acid hydrazide ( 15 ) with benzaldehyde followed by bromine afforded the 1,3,4‐oxadiazole derivative 18 . Treatment of the acid hydrazide 15 with phenyl isothiocyanate gave the thiosemicarbazide 20 . Compound 20 could be converted into 1,3,4‐oxadiazole, 1,2,4‐triazole‐3‐thione, and 1,3,4‐thiadiazole derivatives 21, 22 , and 23 , respectively. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:294–300, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20298