Biodegradable Silicon-Containing Elastomers for Tissue Engineering Scaffolds and Shape Memory Polymers

Commonly used thermoplastic biodegradable polymers are generally brittle and lack appreciable elasticity at physiological temperature and thereby fail to mimic the elastic nature of many human soft tissues such as blood vessels. Thus, there is a need for biomaterials which exhibit elasticity. Biodegradable elastomers are promising candidates whose elasticity more closely parallels that of soft tissues. In this research, we developed hybrid biodegradable elastomers comprised of organic and inorganic polymer components in a block copolymer system: poly(e-caprolactone) (PCL) and poly(dimethylsiloxane) (PDMS), respectively. A block structure maintains the distinct properties of the PCL and PDMS components. These elastomers may be useful for the tissue engineering of soft tissues as well as for shape memory polymer (SMP) devices. Tri-block macromers of the form PCLn-block-PDMSm-block-PCLn were developed to permit systematic variations to key features including: PDMS block length, PCL block length, PDMS:PCL ratio, and crosslink density. The macromer was capped with acrylating groups (AcO) to permit their photochemical cure to form elastomers. Thus, a series of biodegradable elastomers were prepared by photocrosslinking a series of macromers in which the PCL blocks varied (n = 5, 10, 20, 30, and 40) and the PDMS block was maintained (m = 37). All elastomers displayed hydrophobic surface properties and high thermal stability. These elastomers demonstrated systematic tuning of mechanical properties as a function of PCL block length or crosslink density. Notable was strains at break as high as 814% making them suitable for elastomeric bioapplications. Elastomers with a critical PCL block length (n = 30 or 40) exhibited shape memory properties. Shape memory polymers based on an organic-inorganic, photocurable silicon-containing polymer system is a first of its kind. This SMP demonstrated strain fixity of 100% and strain recovery near 100% after the third thermomechanical cycle. Transition from temporary to permanent shape was quite rapid (2 sec) and at temperatures near body temperature (60 degrees C). Lastly, porous analogues of the biodegradable elastomers were created using a novel porogen - salt leaching technique. Resulting porous elastomers were designed for tissue engineering scaffolds or shape memory foams

SUSTRACCIÓN Y RESTITUCIÓN DE MENORES EN EL DERECHO INTERNACIONAL Y EN EL DERECHO CONSTITUCIONAL MEXICANO

El tema de la sustracción de menores, obliga a hacer referencia a la guarda y custodia, derivada de la figura de la patria potestad, la que vinculada a la organización de la familia, ha sufrido, como esta, importantes variaciones en las últimas décadas, ante lo vertiginoso de los desplazamientos de personas a lo largo y ancho del mundo, con fines laborales, profesionales, académicos, artísticos, financieros, turísticos, empresariales, energéticos, inclusive delincuenciales, -por ejemplo, los terroristas-, y un largo etcétera, provocando la creación de relaciones de todo tipo, en el ámbito familiar: conyugales, concubinarias, de filiación y parentesco, entre personas de diferente nacionalidad, con las consecuencias legales inherentesEl presente capítulo de libro titulado ¨SUSTRACCIÓN Y RESTITUCIÓN DE MENORES EN EL DERECHO INTERNACIONAL Y EN EL DERECHO CONSTITUCIONAL MEXICANO¨ desarrolla una explicación acerca de los menores, abarcando desde el momento en que adquieren la protección del orden jurídico, asi, como quienes lo protegerán en ese orden jurídico, es decir, los padres que ejercen la patria potestad, otorgando de estos últimos una descripción explicativa de la potestad jurídica que se les otorg

Reconstructed Dynamics of Rapid Extinctions of Chaparral-Requiring Birds in Urban Habitat Islands

The distribution of native, chaparral-requiring bird species was determined for 37 isolated fragments of canyon habitat ranging in size from 0.4 to 104 hectares in coastal, urban San Diego County, California The area of chaparral habitat and canyon age (time since isolation of the habitat fragment) explains most of the variation in the number of chaparral-requiring bird species. In addition, the distribution of native predators may influence species number. There is statistical evidence that coyotes control the populations of smaller predators such as foxes and domestic cats. The absence of coyotes may lead to higher levels of predation by a process of mesopredator release. The distance of canyons from other patches of chaparral habitat does not add significantly to the explained variance in chaparral-requiring species number–probably because of the virtual inability of most chaparral-requiring species to disperse through developed areas and nonscrub habitats. These results and other lines of evidence suggest that chaparral-requiring birds in isolated canyons have very high rates of extinction, in part because of their low vagility. The best predictors of vulnerability of the individual species are their abundances (densities) in undisturbed habitat and their body sizes; together these two variables account for 95 percent of the variation in canyon occupancy. A hypothesis is proposed to account for the similarity between the steep slopes of species-area curves for chaparral-requiring birds and the slopes for some forest birds on small islands or in habitat fragments. The provision of corridors appears to be the most effective design and planning feature for preventing the elimination of chaparral-requiring species in a fragmented landscape.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74761/1/j.1523-1739.1988.tb00337.x.pd

Shape memory polymer scaffolds for tissue defects

A method of making a shape memory polymer (SMP) tissue scaffold includes forming a salt template and adding a macromer solution to the salt template. The macromer solution may include a photoinitiator solution. The method includes drying the SMP scaffold and leaching salt from the SMP scaffold. A coating is then applied to the SMP scaffold. The coating may be applied either before or after heating the SMP scaffold.U