Variabilidad en el tamaño de ovocitos y fecundidad parcial de anchoveta (Engraulis ringens, Jenyns 1842) en dos áreas de desove de la costa de Chile

Utilising histological preparations of ovaries from Engraulis ringens females collected in two contrasting spawning habitats along the Chilean coast, we assess the variability in oocyte size and batch fecundity during the peak spawning seasons in three years. The effects of female size (length and weight), batch fecundity and mean sea surface temperature on oocyte size were also examined. Results showed larger oocytes and lower batch fecundity in females from the southern area. Oocyte volume differences persisted inter-annually and were not explained by differences in female sizes. Since ovary weight was similar between areas, the cost of producing larger oocytes in the south population seems to be a fecundity reduction. The latitudinal variations in oocyte number and size seem to be determined by the predominant environmental conditions in each habitat. Hence, female E. ringens seem to adapt their reproductive tactics by producing eggs sizes and quantities that favour survival of their offspring under the environmental conditions in which they are to develop.Utilizando preparaciones histológicas de ovarios de anchovetas (Engraulis ringens) colectadas en dos hábitats contrastantes a lo largo de la costa de Chile, se estudia la variabilidad en tamaño de ovocitos y fecundidad parcial en la estación de máximo desove durante tres años. Los efectos de tamaño de hembra (longitud total y peso total), fecundidad parcial y temperatura superficial del mar sobre el tamaño de los ovocitos, también fueron investigados. Los resultados mostraron ovocitos más grandes y menor fecundidad en hembras de la zona sur. Las diferencias en volumen de ovocitos persistieron inter-anualmente y no fueron explicadas por diferencias en el tamaño de las hembras. Dado que los pesos de los ovarios fueron similares entre zonas, el coste de producir ovocitos más grandes en la población del sur sería la reducción en la fecundidad. Las variaciones latitudinales en número y tamaño de ovocitos parecen ser determinadas por las condiciones ambientales predominantes en cada hábitat de desove. De este modo, las hembras de E. ringens adaptarían sus tácticas reproductivas produciendo tamaño y cantidades de huevos que favorezcan la supervivencia de sus descendientes a las condiciones ambientales en las que se desarrollarán

Recombination dynamics in ZnO nanowires: Surfaces states versus mode quality factor

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Lett. 97, 133116 (2010) and may be found at https://doi.org/10.1063/1.3496444.In this work, we investigate the influence of finite size on the recombinations dynamics of ZnO nanowires. We demonstrate that diameter as well as length of nanowires determine the lifetime of the neutral donor bound excitons. Our findings suggest that while the length is mainly responsible for different mode quality factors of the cavity-like nanowires, the diameter determines the influence of surface states as alternative recombinations channels for the optical modes trapped in the nanocavity. In addition, comparing nanowires grown using different catalyst we show that the surfaces states strongly depend on each precursor characteristics.DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, BauelementeDFG, 53182490, EXC 314: Unifying Concepts in Catalysi

Structural studies of two Tinuvin® P analogs: 2-(2,4-Dimethylphenyl)- 2H-benzotriazole and 2-phenyl-2H-benzotriazole

2-(2,4-Dimethylphenyl)-2H-benzotriazole (1) has been synthesized in a three step procedure starting from 2,4-dimethyl-N-(2-nitrophenyl)benzamide via a 5-(2,4-dimethylphenyl)-1-(2-nitrophenyl)-1H-tetrazole intermediate. Its structure and those of Tinuvin® P and 2-phenyl-2H-benzotriazole (5) have been studied by multinuclear NMR (1H-, 13C- and 15N-) in solution and in the solid state. X-ray diffraction analysis of 1 and 5 allowed to us establish the molecular conformation around the single bond connecting the two aromatic systems, in agreement with the conclusions drawn from the NMR study. In the case of 1 ab initio geometry optimization was achieved at the Hartree-Fock HF/6-31G** and DFT B3LYP/6-31G ** levels. © 2007 by MDPI.Peer Reviewe

Advanced measurement techniques for the characterization of ReRAM devices

In some Resistive Random Access Memories (ReRAM), which could become the next generation of non-volatile memories [1], the voltage-controlled high and low resistance states (HRS and LRS, respectively) are associated to the creation (Set) and disruption (Reset) of a conductive filament (CF) that locally connects (LRS) or disconnects (HRS) the electrodes [2]. Usually, a current limit (CL) must be fixed during the Set process. Typically, these devices are characterized using source measurement units (SMU) to measure the current through the device. However, most of the SMU have a low sampling rate (around 1sample/1ms) and the current limitation mechanism used by the equipment is not well understood. To overcome these limitations, in this work, a low-cost setup with large sampling rate (larger than 1sample/10μs) is presented which, in addition, includes a well-controlled wide-range current limiting unit, CLCU (Fig. 1). The system is suitable to capture fast transients during the Set/Reset processes (Fig. 2) and to detect HRS Random Telegraph Noise (RTN) unresolvable by SMUs (Fig. 3) [3]. These device-level measurements can be combined with a Conductive Atomic Force Microscope, to get information on CF properties that cannot be directly measured at device level, as, for example, the spatial distribution of current in the CF at LRS and HRS (Fig. 4) [4]. Please click Additional Files below to see the full abstract

¿La neurociencia puede explicar el funcionamiento global del cerebro?

El Proyecto Cerebro Humano es una iniciativa europea de investigación del cerebro para el avance de la neurociencia y para elaborar tecnología inspirada en la información cerebral. Es posible que las funciones superiores de la persona queden explicadas neurobiológicamente, aunque siga en pie la cuestión relevante ¿soy yo quien activa su cerebro o es el cerebro que me activa a mí? Una comprensión integral del cerebro requiere una visión profunda de esta estructura y de su organización que va desde el estudio genético hasta todo el conjunto del órgano y no puede dirigirse únicamente a un solo nivel. Muchos autores han puesto de relieve diferentes ideas acerca del funcionamiento cerebral. A pesar de este esfuerzo tan importante, se plantea la incógnita de si la neurociencia actual tiene las herramientas óptimas para explicar de manera pormenorizada el funcionamiento del cerebro humano. Para ello se analizan una serie de aspectos que se integran en los denominados procesos mentales. Actualmente la neurociencia no da razón de como es el funcionamiento global de nuestro cerebro. Necesariamente será imprescindible un trabajo interdisciplinar