Transition temperature dependence in perovskite ceramics as a function of grain size

Simple effective field arguments assuming an non isotropic layer of thickness L, covering the ferroelectric bulk grain of perovskite ceramics are used to determine an expression for the transition temperature TJL) as a function of grain linear size L. The surface to volume ratio increases as L decreases reducing the value of TJL). Experimental data for BaTiO₃ ceramics as a function of grain size are described reasonably well by the expression of T_c(L) obtained this way.     

Liquid chromatographic determination of free and total sulphites in fresh sausages

The present work describes a method for the determination of free and total sulphite in fresh sausages and its implementation on 48 samples. The method includes the extraction of sulphite, both free and total, by dissolution of the sample in a suitable solvent and determination by high performance liquid chromatography with electrochemical detection. The method is that previously reported by Kim and Kim (J Food Sci 51 1986 1360–1361) improved by certain modifications the principal of which consists of working atpH 10 for the extraction of total sulphite. Use of this pH permits reversible dissociation of the combined sulphite. In reproducibility assays carried out on sausages, variation coefficients of 3.3 and 5% were obtained for free and total sulphite, respectively. To evaluate recovery, sulphite was added to the samples as hydroxymethylsulphonate. Mean recovery was 86.4% with a variation coefficient of 3.8%. In 62% of the sausages analysed, amounts of total sulphites higher than 450 μ SO₂ g^?1 were found. Among the samples, considerable variation was observed in the distribution of sulphite between the free and combined forms.     

Generalizacion de un S-Juego estrategias finitamente aditivas

Sumario En la primera parte de este trabajo, se estudia la existencia de estrategias óptimas, en el modelo teórico (P_a F, ρ (P_a,f)) (ref. 3), generalización de un S-juego, dondeP _a es un conjunto de probabilidades finitamente aditivas, yF un subconjunto convexo de funciones reales acotadas. A continuación se analizan las clases de estrategias y se obtiene una clase de estrategiasp _a-Bayes, más amplia que la de Bayes β, y Bayes extendida β_o, que tiene la propiedad de contener siempre a la clase de estrategias admisibles. Se demuestra su completitud con hipótesis adicionales, y se obtienen resultados relativos a estrategias σ-aditivas, como casos particulares. Trabajo realizado con la beca March de Matemáticas, convocatoria 1973–74.     

Association of complementary fragments and the elucidation of protein folding pathways

Natural or engineered sites for chemical cleavage can be usedto generate complementary fragments of well characterized proteins.The peptide fragments represent a unique tool for studying earlyevents in protein folding, since these are usually the mostinaccessible to the experimentalist. Analysis of the isolatedfragments in nondenaturing conditions together with the determinationof the structure of the folded non-covalent complexes and, mostimportantly, the kinetic analysis of the resulting second-orderassociation/folding reaction can give a more complete pictureof a folding pathway. The contribution of fragments to the understandingof some well characterized protein folding pathways is discussed.     

Ferroelectric behavior of TAAP single crystal near Tc

Dielectric and hysteresis loop measurements in good quality telluric acid ammonium phosphate from 20 to 50°C with special attention to the behavior in the vicinity of T_c ≈44.80 °C were performed. The effective field higher order parameters characterizing the temperature dependence of the spontaneous polarization were obtained. The main features of the ferroelectric transition in this “hard” ferroelectric have been compared with those of other well known ferroelectric crystals.     

Supertoughness in Polysulfone/Poly(ethylene‐octene) Blends

Summary: Poly(sulfone of Bisphenol A) (PSU) based blends were obtained by melt blending PSU with up to 15 wt.‐% poly(ethylene‐octene) either modified with maleic anhydride (mPEO) or not (PEO). The dispersed particle size was small and similar in blends with PEO or mPEO. These facts indicated respectively that the interfacial tension was low and the lack of compatibilizing effect of mPEO. Some preferential presence of PEO in the outer surface of the specimens was observed, and was attributed to the large viscosity difference between the two components of the blends. This had no effect on the modulus of elasticity, but speeded up both the yield stress and ductility decreases at rubber contents above 3.25 wt.‐%. However, despite the immiscibility of the components, and thanks to the small particle size of the blends, super‐toughness was attained in the unmodified PSU/PEO blends. This was at PEO contents (3.25 wt.‐%) at which the modulus, yield stress and ductility of the blends were almost as good as those of pure PSU. It appeared that a change of the chemical nature of the rubber did not influence by itself super‐toughness, unless it was accompanied by either a morphological or adhesion change.

Impact strength of PSU‐based blends vs. PEO (○) or mPEO (?) content.     

Trihalomethanes in the drinking water of Concepción and Talcahuano,Chile

Formation of trihalomethanes (THMs) during water disinfection has been related to several health problems, although the magnitude of these effects is under discussion. This paper quantifies the THMs in drinking water from the Bío‐Bío Region of central Chile, the first since the modification of the national reference value (Nch 409/05) to include maximal values for THMs. THMs were quantified using a solid phase micro‐extraction (SPME) method and GC‐MS. The concentration ranges were 9.7–111.6, 0.1–1.0 and 0.9–25.5 μg/L for chloroform (CHCl₃), and dibromochloromethane (CHClBr₂) and bromodichloromethane (CHCl₂Br), respectively. Bromoform was not detected in any sample. There were good correlations (R²=0.91–0.98, P<0.001) between the THMs and the residence time of the water, the distance from the treatment plant and an inverse correlation to free chlorine in the water. The Additive Toxicity Index Value (0.07–1.00) showed that all samples were within the Chilean reference value for THMs in drinking water. However, several values were close to exceeding the maximum permitted concentration (200, 100, 100 and 60 μg/L for CHCl₃, CHBr₃, CHClBr₂ and CHCl₂Br, respectively), which may occur when the water demand is low and thus residence times are longer.