Self-beating instabilities in bistable devices

Since the observation of optical bistability by Gibbs et al., optical bistability has been the field where researchers from many fields have found a common place to work. More recently, when Ikeda and co-workers discussed the effect of a delayed feedback on instability of a ring cavity containing a non linear dielectric medium, and pointed out that the transmitted light from the ring cavity can be periodic or chaotic in time under a certain condition, optical bistable devices have shown new possibilities to be applied in many different fields. The novel phenomenon has been predicted to be observed in the hybrid optical device and has been confirmed by Gibbs et al. Moreover, as we have shown, a similar effect can be obtained when liquid crystal cells are employed as non linear element

Structural Extremes in a Cretaceous Dinosaur

Fossils of the Early Cretaceous dinosaur, Nigersaurus taqueti, document for the first time the cranial anatomy of a rebbachisaurid sauropod. Its extreme adaptations for herbivory at ground-level challenge current hypotheses regarding feeding function and feeding strategy among diplodocoids, the larger clade of sauropods that includes Nigersaurus. We used high resolution computed tomography, stereolithography, and standard molding and casting techniques to reassemble the extremely fragile skull. Computed tomography also allowed us to render the first endocast for a sauropod preserving portions of the olfactory bulbs, cerebrum and inner ear, the latter permitting us to establish habitual head posture. To elucidate evidence of tooth wear and tooth replacement rate, we used photographic-casting techniques and crown thin sections, respectively. To reconstruct its 9-meter postcranial skeleton, we combined and size-adjusted multiple partial skeletons. Finally, we used maximum parsimony algorithms on character data to obtain the best estimate of phylogenetic relationships among diplodocoid sauropods. Nigersaurus taqueti shows extreme adaptations for a dinosaurian herbivore including a skull of extremely light construction, tooth batteries located at the distal end of the jaws, tooth replacement as fast as one per month, an expanded muzzle that faces directly toward the ground, and hollow presacral vertebral centra with more air sac space than bone by volume. A cranial endocast provides the first reasonably complete view of a sauropod brain including its small olfactory bulbs and cerebrum. Skeletal and dental evidence suggests that Nigersaurus was a ground-level herbivore that gathered and sliced relatively soft vegetation, the culmination of a low-browsing feeding strategy first established among diplodocoids during the Jurassic

Regulation of pituitary hormones and cell proliferation by components of the extracellular matrix

The extracellular matrix is a three-dimensional network of proteins, glycosaminoglycans and other macromolecules. It has a structural support function as well as a role in cell adhesion, migration, proliferation, differentiation, and survival. The extracellular matrix conveys signals through membrane receptors called integrins and plays an important role in pituitary physiology and tumorigenesis. There is a differential expression of extracellular matrix components and integrins during the pituitary development in the embryo and during tumorigenesis in the adult. Different extracellular matrix components regulate adrenocorticotropin at the level of the proopiomelanocortin gene transcription. The extracellular matrix also controls the proliferation of adrenocorticotropin-secreting tumor cells. On the other hand, laminin regulates the production of prolactin. Laminin has a dynamic pattern of expression during prolactinoma development with lower levels in the early pituitary hyperplasia and a strong reduction in fully grown prolactinomas. Therefore, the expression of extracellular matrix components plays a role in pituitary tumorigenesis. On the other hand, the remodeling of the extracellular matrix affects pituitary cell proliferation. Matrix metalloproteinase activity is very high in all types of human pituitary adenomas. Matrix metalloproteinase secreted by pituitary cells can release growth factors from the extracellular matrix that, in turn, control pituitary cell proliferation and hormone secretion. In summary, the differential expression of extracellular matrix components, integrins and matrix metalloproteinase contributes to the control of pituitary hormone production and cell proliferation during tumorigenesis