Luis Izquierdo

Electron microscope observations on the early development of the rat

SummaryThe early development of the rat, from the mature oocyte through fertilization until the 8-cell stage, has been studied with the electron microscope. The fine structure is described and discussed, with particular reference to the following topics. The middle piece of the spermatozoon is found in every stage studied, within the ovum cytoplasm; it is not significantly altered by this situation. The nucleoli are numerous during the 1-cell stage and often present in positions that suggest their extrusion into the cytoplasm; in subsequent stages a branching structure develops around them. The dividing cell presents the mitotic apparatus with its centrioles, hollow looking fibers, chromosomes, but without centromeres; in the cytoplasm the small granules align in rows. Mitochondria are evenly distributed during the 1-cell stage and can be found in the 8-cell stage constricted as if dividing. The “multivesicular bodies” constitute an abundant population of cytoplasmic elements that may be related to the endoplasmic reticulum or the Golgi complex, neither of which is clearly recognizable. In the 8-cell stage the cytoplasm segregates into two zones, one of which contains all the “multivesicular bodies”, while the mitochondria are found in both of them; this distinction provides some basis to adscribe to the “multivesicular bodies” the properties of the so called “metachromatic particles”.

A methodology for estimation of the specific rock energy index using corrected down-the-hole drill monitoring data

Abstract A methodology developed to estimate with accuracy the instantaneous specific rock energy using corrected downthe-hole (DTH) drill monitoring data is presented. A specific rock energy profile can be generated for every hole, and thus a drilling site can be mapped for this index. A special data acquisition system was developed to measure and register the following operational variables: penetration rate, torque, hole depth, pull-down force, air pressure, revolutions per minute (rpm) and the hammer percussion frequency, the latter obtained by sound recording and signal processing. The measured data are fed into two simulation models that estimate the power absorbed by the rock through impact, and then the specific rock energy index. The first of these models simulates the thermodynamic cycle of the DTH hammer, rendering the piston kinetic energy at impact, impact velocity as well as impact frequency. The second model is used for stress wave propagation analysis to estimate the effective energy delivered to the rock. Correlations were found between the specific rock energy and penetration rate, and between the specific rock energy and impact frequency, as well as between the penetration rate and applied torque, and between the penetration rate and impact frequency.

Desde la planta en la arquitectura

En medio de un panorama dominado por la cultura de las imagenes, donde la fotografia de arquitectura y el render se han vuelto los medios de comunicacion predilectos, volvemos por un minuto a detenernos en las plantas de arquitectura. Verdadera huella del edificio sobre el suelo, la planta contiene una parte importante de las claves del proyecto, siendo al mismo tiempo medio de representacion, herramienta de diseno para el arquitecto, patron de trazado e instruccion para el constructor. Aunque la planta se presenta invisible al habitante, ella determina con precision la calidad de los espacios en que vivimos. Sin fotografias, vemos nuevamente en planta.

Izquierdo Lehmann: Edificio Cruz del Sur, Santiago

El proyecto consiste en una torre de oficinas con placa comercial ubicada en el cruce de Avda. Apoquindo, eje principal de Santiago, y Avda. Americo Vespucio, anillo de circunvalacion de la ciudad. A pesar de su importancia urbana, el lugar esta mal conformado por un cruce vial en desnivel y por distintos edificios de diversa altura y calidad, varios de ellos resultantes de una funesta norma de rasantes antigua, apodados lustrines.

Galería Patricia Ready: Vitacura, Chile

Resumen es: Una galeria de arte abierta a la ciudad. Las esculturas se exponen en un patio de acceso para generar la relacion con el contexto inmediato. En el interi...