39K and 77Se NMR study of the paraelectric-to-incommensurate phase transition of K2SeO4

Topic B, von Kienlin A, Gölzhäuser A, Haeberlin U, Blinc R. 39K and 77Se NMR study of the paraelectric-to-incommensurate phase transition of K2SeO4. Physical Review, B. 1988;38(13):8625-8632.The 39K quadrupole-coupling and chemical-shift tensors have been determined from the angular dependences of the 39K line shifts of the 39K±(1/2 ± 1) / 2 central NMR transitions in the paraelectric (P) and incommensurate (I) phases of K2SeO4. The main effect of the P-I phase transition on these tensors is the appearance of nonzero off-diagonal elements Vab and Vbc which reflects the destruction of mirror planes by frozen-in soft-mode displacements along the b axis. From the angular dependences of the 77Se line shifts the 77Se chemical-shift tensor has been determined in the paraelectric phase of K2SeO4. In contrast to the 39K quadrupole-coupling and chemical-shift tensors it remains unaffected on going through TI and changes only slightly at TC

Evaluación de impacto socioeconómico de la tecnología generada en fríjol en las provincias de Guanenta y Comuneros, Santander :(informe final)

El presente trabajo tiene como objetivo evaluar el impacto socioeconómico de la tecnología generada en frijol en las Provincias Guanentá y Comuneros, con énfasis en las variedades ICA - CORPOICA Guanentá y CORPOICA Froilán, que fueron entregadas a los agricultores en los años de 1994 y 1997, respectivamente. La zona de estudio se concentró en los municipios de Villanueva, San Gil, Barichara y Curití, que representan el 79.6% del área cultivada en frijol en estas Provincias. La información de campo se obtuvo mediante consenso con productores y a través de una encuesta aplicada a una muestra de 81 agricultores, para lo cual se utilizó la técnica de muestreo aleatorio estratificado con afijación proporcional simple. Las características sobresalientes de las nuevas variedades son la resistencia a la Antracnosis (Colletotricum Lindemu Thianum), uno de los mayores limitantes de la producción, y el aumento de la productividad física por hectárea. Se encontró que el 40% de los productores consultados utilizan en sus predios las dos variedades simultáneamente; en la actualidad el 79% de ellos utilizan la variedad Froilán y el 49.4% continúan usando la variedad Guanentá. La rentabilidad mensual para las variedades Guanentá y Froilán es de 8.9 y 12% respectivamente, muy superior al costo de oportunidad del capital en la zona. Así mismo, la Tasa Interna de Retomo Social de la investigación en frijol en el Creced es de 64%, lo que demuestra que los recursos públicos dedicados a esta investigación tienen alta rentabilidad social.Fríjol-Phaseolus vulgarisCorpoica Froilán: variedad de frijol tipo radical para clima medio para las subregiones naturales Montaña Santandereana y Valle de los ríos Chicamocha, Suárez y Fonc

Advanced Technologies for Oral Controlled Release: Cyclodextrins for oral controlled release

Cyclodextrins (CDs) are used in oral pharmaceutical formulations, by means of inclusion complexes formation, with the following advantages for the drugs: (1) solubility, dissolution rate, stability and bioavailability enhancement; (2) to modify the drug release site and/or time profile; and (3) to reduce or prevent gastrointestinal side effects and unpleasant smell or taste, to prevent drug-drug or drug-additive interactions, or even to convert oil and liquid drugs into microcrystalline or amorphous powders. A more recent trend focuses on the use of CDs as nanocarriers, a strategy that aims to design versatile delivery systems that can encapsulate drugs with better physicochemical properties for oral delivery. Thus, the aim of this work was to review the applications of the CDs and their hydrophilic derivatives on the solubility enhancement of poorly water soluble drugs in order to increase their dissolution rate and get immediate release, as well as their ability to control (to prolong or to delay) the release of drugs from solid dosage forms, either as complexes with the hydrophilic (e.g. as osmotic pumps) and/ or hydrophobic CDs. New controlled delivery systems based on nanotechonology carriers (nanoparticles and conjugates) have also been reviewed

Temperature-dependent tensile properties of polyamide 12 for the use in percutaneous transluminal coronary angioplasty balloon catheters

BACKGROUND: Percutaneous transluminal coronary angioplasty (PTCA) balloon catheters must withstand high pressures required for the lesion treatment, pushing loads during insertion, and pulling loads during withdrawal. These loads pose a challenge especially for polymeric tubular shafts with small cross sections. In order to enable new design innovations and to better understand the mechanics of current catheter technologies, the tensile properties of polyamide (PA) 12 were investigated. PA 12 dog bone specimens and medical PA 12 tubes were either stored at ambient temperature and humidity or conditioned in water, and subjected to tensile loads at different temperatures. In addition, the effect on the tensile properties of the necking process, a forming process to reduce the wall thickness of the tubes, was determined. RESULTS: The tested tubes showed a reduction in both Young’s Modulus (− 41.5%) and yield stress (− 29.2%) compared to standardized specimens. Furthermore, an increase in temperature and water absorption softens the material and reduces the mechanical properties like the Young’s Modulus and the yield stress. It was found that the material strengthens during the necking process. Likely due to the orientation of the polymers chain molecules in load direction (Rösler et al., 2007), the Young’s Modulus of the material could be increased by 43.5%. Furthermore, the absence of a yield point after necking allows for a greater loading capacity of the material without unstable neck growth. Besides the strengthening, the ultimate strain is reduced by 50%. This indicates that the necking process induces plastic deformation. CONCLUSION: The investigation showed that the environmental conditions like temperature and humidity can influence mechanical properties. It could also be shown that pre-forming processes such as necking can enhance the mechanical properties, such as the Young’s Modulus, while reducing the wall thickness. These findings suggest possible further development of catheters with a small cross section and higher mechanical strength and highlight the importance to account for the targeted operating temperature during the design process

Differenz als Konstitutionsproblem der Sonderpädagogik

Dieser Beitrag analysiert die Funktion von Differenz in der Sonderpädagogik. Für die Sonderpädagogik gilt der Differenzbegriff „Behinderung“ funktional, d. h. inhaltlich und sozial, als systemkonstituierend, als Gestaltungselement der Differenz von Gleichheit und Anderssein. Diese Perspektive bildet hier (… die) Analysefolie. In einem einleitenden Abschnitt wird dies erläutert. Der zweite Teil beschreibt aus dieser Blickrichtung die Entwicklung der Sonderpädagogik entlang ihrer inhaltlichen Auseinandersetzung mit sonderpädagogischen Problemstellungen. Im dritten Teil wenden (…sich die Autoren) der Funktion der Sonderpädagogik unter dem Gesichtspunkt der sozialen Integration zu. Abschließend werden vor diesem Hintergrund Forderungen an die sonderpädagogische Theoriebildung formuliert. (DIPF/ Orig.