218 research outputs found
Biodiversidad del Parque Nacional Pre-Delta (Entre RĂos, Argentina). I) Riqueza del fitoplancton
Mirande, V., S. E. Haleblian, G. A. Barreto & B. C. Tracanna. 2009. Biodiversidad del Parque Nacional Pre-Delta (Entre RĂos, Argentina). I) Riqueza del fitoplancton. Lilloa 46 (1-2). El objetivo del presente trabajo fue contribuir al conocimiento de la riqueza del fitoplancton del Parque Nacional Pre-Delta. Hasta el presente se carece de un relevamiento ambiental y ficoflorĂstico de los cuerpos de agua de este parque, aunque sĂ se dispone de datos geomorfolĂłgicos, faunĂsticos y florĂsticos. Se seleccionaron siete sitios de muestreo correspondientes a ambientes lĂłticos y lenĂticos. Para la extracciĂłn de las muestras cualitativas se filtraron 32 litros de agua a travĂ©s de una red de 20 µm de poro, las cuales fueron fijadas “in situ” con formaldehido al 4%. La comunidad estuvo compuesta por 102 especies pertenecientes a Cyanophyceae, Chlorophyceae, Charophyceae, Dinophyceae, Bacillariophyceae, Chrysophyceae, Xanthophyceae and Euglenophyceae, destacándose una mayor riqueza especĂfica en las lagunas. Los resultados obtenidos evidenciaron a las diatomeas como el grupo que en lĂneas generales más contribuyĂł en especĂmenes. Se citan 26 especies y 3 variedades nuevas para el Noreste Argentino y, además de las mencionadas anteriormente, se aportan otras 18 especies y 6 variedades para la provincia de Entre RĂos. Todas las entidades comentadas son nuevos taxa para el área de estudio
Quantitative plane-resolved crystal growth and dissolution kinetics by coupling in situ optical microscopy and diffusion models : the case of salicylic acid in aqueous solution
The growth and dissolution kinetics of salicylic acid crystals are investigated in situ by focusing on individual microscale crystals. From a combination of optical microscopy and finite element method (FEM) modeling, it was possible to obtain a detailed quantitative picture of dissolution and growth dynamics for individual crystal faces. The approach uses real-time in situ growth and dissolution data (crystal size and shape as a function of time) to parametrize a FEM model incorporating surface kinetics and bulk to surface diffusion, from which concentration distributions and fluxes are obtained directly. It was found that the (001) face showed strong mass transport (diffusion) controlled behavior with an average surface concentration close to the solubility value during growth and dissolution over a wide range of bulk saturation levels. The (1Ě…10) and (110) faces exhibited mixed mass transport/surface controlled behavior, but with a strong diffusive component. As crystals became relatively large, they tended to exhibit peculiar hollow structures in the end (001) face, observed by interferometry and optical microscopy. Such features have been reported in a number of crystals, but there has not been a satisfactory explanation for their origin. The mass transport simulations indicate that there is a large difference in flux across the crystal surface, with high values at the edge of the (001) face compared to the center, and this flux has to be redistributed across the (001) surface. As the crystal grows, the redistribution process evidently can not be maintained so that the edges grow at the expense of the center, ultimately creating high index internal structures. At later times, we postulate that these high energy faces, starved of material from solution, dissolve and the extra flux of salicylic acid causes the voids to close
Composition of the Top Management Team and Firm International Diversification
This study investigates the impact of various top management team characteristics on firm international diversification. Relying on data from 126 firms in the electronics industry, we find that certain top management team characteristics are related to international expansion. Specifically, results indicate that lower average age, higher average tenure, higher average elite education, higher average international experience, and higher tenure heterogeneity are associated with firm international diversification. The study reinforces the importance of top management team composition in internationalization decisions and suggests further research in this context.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline
Risk propensity in the foreign direct investment location decision of emerging multinationals
A distinguishing feature of emerging economy multinationals is their apparent tolerance for host country institutional risk. Employing behavioral decision theory and quasi-experimental data, we find that managers’ domestic experience satisfaction increases their relative risk propensity regarding controllable risk (legally protectable loss), but decreases their tendency to accept non-controllable risk (e.g., political instability). In contrast, firms’ potential slack reduces relative risk propensity regarding controllable risk, yet amplifies the tendency to take non-controllable risk. We suggest that these counterbalancing effects might help explain observation that risk-taking in FDI location decisions is influenced by firm experience and context. The study provides a new understanding of why firms exhibit heterogeneous responses to host country risks, and the varying effects of institutions
Categorization of the main descriptors of different ampicillin crystal habits
With the purpose of enabling the analysis by digital methods of particles of multisource pharmaceutical raw materials, this study analyzed different crystal habits of ampicillin particles, by grouping the external shapes obtained from 3 different solvents (acetonitrile, ethanol, and methanol), thereby reducing the number of descriptors necessary to adequately represent each shape. For this purpose, a selection of morphological descriptors was used including: circularity, roughness, roundness, compactness, aspect ratio, effective diameter, solidity, convexity, fractal dimension, and 10 Complex Fourier descriptors. These measures cover highly diverse morphological properties and define the crystal habit of a particle. Principal Component Analysis (PCA) and the Cluster Analysis (CA) were the grouping techniques used, which demonstrated the possibility of using between 2 and 4 descriptors instead of the 18 proposed initially.Com o objetivo de possibilitar a análise, por meio de mĂ©todos digitais, de partĂculas de matĂ©rias-primas farmacĂŞuticas de mĂşltiplas fontes, analisaram-se diferentes cristais de partĂculas de ampicilina atravĂ©s do agrupamento de formas externas obtidas de trĂŞs diferentes solventes (acetonitrila, etanol e metanol), reduzindo, desse modo, o nĂşmero de descritores necessários para representar adequadamente cada forma. Com esse propĂłsito, utilizou-se seleção de descritores morfolĂłgicos, incluindo: circularidade, aspereza, arredondamento, compactação, relação de aspecto, diâmetro efetivo, solidez, convectividade, dimensĂŁo fractal e 10 descritores complexos de Fourier. Essas medidas cobrem diversas propriedades morfolĂłgicas e definem a cristalinidade de uma partĂcula. As análises do componente principal (PCA) e por grupamento (CA) foram as tĂ©cnicas de agrupamento utilizadas, que demonstraram a possibilidade de utilizar entre 2 e 4 descritores ao invĂ©s dos 18, inicialmente propostos
Learning Sequences: Their Existence, Effect, and Evolution
Much is known about the importance of learning and some of the distinct learning processes that organizations use (e.g., trial-and-error learning, vicarious learning, experimental learning, and improvisational learning). Yet surprisingly little is known about whether these processes combine over time in ordered ways, because most research on learning explores one particular process. Using theory elaboration and theory-building methods and data on the accumulated country entries of entrepreneurial firms, we address this gap. Our core contribution is an emergent theoretical framework that develops the concept of learning sequences. We find that learning sequences exist and are influenced by initial conditions. We also find that learning sequences evolve in fundamentally distinct ways over time and with repeated use. Finally, data show how different learning sequences differentially affect both shorter- and longer-term performance, suggesting that it matters which learning processes are used and when. Overall, our findings on learning sequences have important implications for learning theory, international entrepreneurship, and the growing literature on process management
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