Showing papers by "Instituto Politécnico Nacional published in 1969"

Real Gas Effects in Carbon Dioxide Cycles

Abstract: The potential performance of carbon dioxide as working fluid is recognized to be similar to that of steam, which justifies thorough thermodynamic analysis of possible cycles.The substantially better results achievable with CO2 with respect to other gases are due to the real gas behaviour in the vicinity of the Andrews curve. Simple cycles benefit from the reduced compression work, but their efficiency is compromised by significant losses caused by irreversible heat transfer. Their economy, however, is appreciably better than that of perfect gas cycles. More complex cycle arrangements, six of which are proposed and analyzed in detail, reduce heat transfer losses while maintaining the advantage of low compression work and raise cycle efficiency to values attained only by the best steam practice.Some of the cycles presented were conceived to give a good efficiency at moderate pressure which is of particular value in direct-cycle nuclear applications.The favourable influence on heat transfer coefficients of the combined variation with pressure of mechanical, thermal and transport properties, due to real gas effects, is illustrated. Technical aspects as turbo-machines dimensions and heat transfer surfaces needed for regeneration are also considered.Cooling water requirements are found to be not much more stringent than in steam stations.Copyright © 1969 by ASME

Population dynamics and stock assessment for Octopus maya (Cephalopoda: Octopodidae) fishery in the Campeche Bank, Gulf of Mexico.

Abstract: The octopus ( octopus maya ) is one of the most importantfish resources in·the Mexican Gulf of Mexico with a mean annual yield of 9000 ton, and·a "reasonablenumber of jobs created; O. maya represents 80% of the total octopus catch, followed by acto pus vulgaris. There are two artisanal fleets based on actopus maya and a middle-size fleet that covers both species. Catch-at-Iength structured data from the artisanal fleets, for the 1994 season (August 1st to December 15th) were used to analyze the a. maya population dynamics and stock and to estimate the current level of exploitation. Von Bertalanffy growth parameters were: Loo = 252 mm, mantle length; K=1.4 year·1; oscillation parameters C=l.O, WP=O.6; and tz=0.842 years. A rough estimate of natural mortality was M=2.2, total mortality from catch curve Z=8.77, and exploitation rate Frz=O.75. This last value suggests an intensive exploitation, even when yield per recruit analysis indicates both fleets may increase the minimum legal size on about 10% to rncrease yields. The length-based VPA also shows that the stock is being exploited under its maximum acceptable biological limit. These apparently contradictory results are explained by biological and behavioral characteristics of this species. Because most females die after reproduction, a new gross estimation of natural mortality was computed as M=3.3. The new estimate of exploitation rate was FfZ=O.57. This new value coincides with results from the length-VPA and the Thompson and Bell methods, the forrner suggesting that a reduction of 20% infi shing mortality may provide larger yields. Thisfi shery resource is fully exploited and current management measures must be revised to sustain and probably optimize yields.

Sampling Methods and Interpretation of Correlation: A Comparative Analysis of Seven Cross‐Cultural Samples1

Abstract: The degree of agreement between the results of a comparative analysis of seven cross-cultural samples is dependent upon both the nature of the samples and the nature of the variables. All three of the smaller samples examined are demonstrated to be subject to a fatal amount of sampling error. The study incorporates the Tylor-Galton problem and makes an epistemic correlation between the concepts by postulation, historical-diffusional and functional or causal aspects, and the empirical findings of statistical correlation. It speaks in terms of realms of order in sociocultural phenomena and of different degrees of invariant relationship and contingency. Many philosophical puzzles and many problems in theoretical anthropology have, at least in part, empirical solutions. Any theoretical inquiry into questions such as “the nature of culture” should be closely allied with an examination of empirical data. The present approach is an attempt to integrate rational analysis with empirical data.

Enzymic Activity during Growth of Vanilla Fruit 1. Proteinase, Glucosidase, Peroxidase and Polyphenoloxidase

Abstract: SUMMARY —A preliminary study has been made of these enzymic activities along the growth of vanilla pods looking for information about biochemical reactions which lead to the production of the aroma. Proteinase activity decreases with pod age. The activities of glucosidase, peroxidase and polyphenoloxidase increase with stage of growth reaching a maximum near or at ripening. Possibly these enzymes play some role in reactions taking place in curing vanilla, either directly or indirectly supplying the initial products to be transformed into those responsible for color and odor. Partially purified polyphenoloxidase shows a ration catecholase-cresolase activity of 8.9.

Arsenic-Lipid Complex Formation During the Active Transport of Arsenate in Yeast

Abstract: In studying formation of an arsenic-lipid complex during the active transport of 74As-arsenate in yeast, it was found that adaptation of yeast to arsenate resulted in cell populations which showed a deficient inflow of arsenate as compared to the nonadapted yeast. Experiments with both types of cells showed a direct correlation between the arsenate taken up and the amount of As-lipid complex formed. 74As-arsenate was bound exclusively to the phosphoinositide fraction of the cellular lipids. When arsenate transport was inhibited by dinitrophenol and sodium azide, the formation of the As-lipid complex was also inhibited. Phosphate did not interfere with the arsenate transport at a non-inhibitory concentration of external arsenate (10−9m). The As-adapted cells but not the unadapted cells were able to take up phosphate when growing in the presence of 10−2m arsenate.

Evaluación de la pesquería de Lutjanus peru (Pisces: Lutjanidae) de . Guerrero, México

Abstract: Red snapper ( Lutjanus peru ) fishery was analyzed from landings and catch records. Stock age structure was reconstructed after the parameter values of the von Bertalanffy growth model, the length-weight relationship, ages and the natural mortality coefficient through each of nine years of cateh records. The Pisat software package was applied to assess population parameters, whose estimates are, for the von Bertalanffy growth model, K = 0. 1 442 to 0.38; lo = -0.2; L = 87 cm; W = 9.4 Kg, and the natural mortality coefficient (M) afier several methods (0. 14 to 0.38). Cohort size was assessed by the virtual population analysis (VPA), estlmating population size in 5.2* 1 06 fish with a biomass of 8 454 tonnes. Current fishing mortality P, ranges from 0.06 to 1 . 1 3, depending upon the chosen M value; according to this, when the M value used is low, the results suggest that the stock is nnderexploited, and vice versa. The yield per recruit model applied suggests improvements to the management strategy. The model indicates recruit overfishing because very small fish are the main target (te

Periodo reproductivo y talla de madurez masiva del camarón de roca Sicyonia penicillata (Decapoda: Sicyoniidae) en Bahía Kino, Sonora, México

Abstract: Se estudia el periodo reproductivo del camaron de roca Sicyonia penicillata en el area de Bahia Kino, Sonora, de enero a diciembre de 1996 mediante muestreos quincenales efectuados a bordo de embarcaciones de la flota camaronera comercial y un crucero de investigacion durante julio. La actividad reproductiva de la especie inicia a partir de los 25 mm de longitud abdominal, pero la talla de madurez sexual masiva de la especie se ubico en 55 mm de longitud abdominal. Se encontraron organismos maduros todo el ano, pero el patron de reclutamiento indica que existe un periodo reproductivo masivo de agosto a enero; un segundo periodo, menos intenso ocurre en marzo y abril. Estos resultados son coincidentes para los meses en los que se cuenta con datos de madurez gonadica. Se postula la idea de un posible patron de migracion de juveniles hacia areas someras de Bahia Kino.

The Dependence of Power Cycles’ Performance on Their Location Relative to the Andrews Curve

Abstract: The adoption of the closed cycle and of working fluids other than steam or air gives the possibility of utilizing for power cycles regions of the temperature-entropy diagram which are inaccessible when the working media are water or combustion products and which enjoy some useful peculiarities. A number of fluids are presented which are suitable for industrial applications and which allow the organization of power cycles covering the liquid, gaseous, and hypercritical regions of the state diagram of a typical substance. Efficiency, specific work, heat transfer surfaces, dimensions of turbomachines, distribution of losses among the various components relating to different fluids and cycles are analyzed and reported. The results strongly support the conclusion that the nature of the working fluid is a powerful tool to adapt the characteristics of power cycles to the widely differing requirements encountered in technical applications.Copyright © 1969 by ASME

On the physiology of dendrites.

Abstract: Extra- and intracellular unitary potentials were recorded in the exposed spinal cord of cats These potentials are attributed to the activity of dendrites It is suggested that they contribute to the slow components of the spinal cord potentials The moloncuron excitabiiity was studied during the development of spinal responses to activation from differerent pathways The correlation observed between the excitability changes with the different components of the extracellular spinal potentials is considered as evidence of the important role of dendrites in modulating the ability of cell firing The possible mechanisms involved are the electrotonic effects and the influence of the large electrical fields created

Identidades, aprendizagem e mediação intercultural: uma análise antropológica

Abstract: In this text it is discussed the problem of plural identities and its reconstruction in contexts of school education and non school education. It is discussed the construction and incorporation of multicultural, intercultural and monocultural attitudes on the part of the self and it reconceptualizes the concept of cultural metissage as capable to handle the complexity of the identity of the subjects of contemporary times where intercultural and sociopedagogical mediation appear as fundamental instruments to the hospitality of the cultures and of the subjects who inhabit them and (re) construct. Through the processes of teaching and learning, we all end up by having a multiplicity of cultures, language codes, more restricted, more elaborate, more locals, more universal, beliefs, values, knowledge, etc. being increasingly culturally more mestizos. In the type of reconstruction of the personal identity, the intercultural mediator has a relevant role, as we will try to show throughout this trial.

Biodegradación de queroseno en la rizósfera de gramíneas en condiciones de invernadero

Abstract: Kerosene affects in a negative way the soil biological activity, also the growth and development of the plant. To examine the aforesaid, this contaminant was evaluated in oats plants (Avena sativa), barley (Hordeum vulgare), grass (Chloris gayana) and wheat (Triticum aestivum), in the microbial populations of the rizosphere and rhizoplane. Also determined was the contaminant’s degradation percentage in the rizospheric soil of the different grasses. A completely at random experimental design with a 2x4 factorial arrangement, was used, with 8 treatments and 5 repetitions each. The factors were kerosene doses (0 and 2000 mg.kg -1) and plant species. At 56 days after establishment of the experiment, the contaminated soil reduced significantly (p≤0.05), the foliar area, the total dry matter and the root volume of the 4 grasses, compared to those established in soil without contamination. In the contaminated soil the total microbial populations in the rhizoplane and the plant rizosphere increased; while those that used the hydrocarbon as carbon source increased in the rhizoplane. The mycorrhizal colonization went from 28.8 to 15.7%, and when the soil was contaminated it was reduced from 11.4 to 5%; however, the endomycorrizal fungus performed its functions even with the hydrocarbon present in the soil. The oats rizosphere allowed a kerosene degradation of 84.4%, while that of the grass only 39.6%. It is convenient to expand the rizospheric studies with another organic contaminant, to determine the oats’ rizospheric effectiveness and to evaluate if the hydrocarbon is accumulated in its tissues.