Search

The coupled Maxwell-Schrodinger equations are used to describe propagation of a pulse in a nonlinear absorbing medium. The absorber is assumed to be comprised of a homogeneously broadened system of two-level atoms that are exactly resonant with the field. Numerical calculations have been performed for incident pulses of hyperbolic-secant shape and of duration that is long compared to the atomic phase-memory time. Selected values of input intensity are considered. For intensities below a certain level the calculations nearly agree with rate-equation predictions, but as the incident intensity is increased we find that optical nutation comes into play. The nutation effect leads to pulse breakup as the packet penetrates into the medium. An analytical calculation, for the case of an applied optical field of step-function form, has been performed in order to provide additional insight about the intensity threshold for nutation.

L'auteur examine comment Formose, au lendemain de la guerre, a réussi à passer du stade d'exportateur de produits primaires à celui d'exportateur de produits manufacturés et finis, ce qui illustre les résultats qu'il est possible d'obtenir en adoptant un système de production répondant à la faible superficie du pays, à la médiocrité de ses ressources naturelles et à l'intensité des pressions démographiques qui s'y exercent. Tout d'abord, grâce à l'agriculture, à l'industrie, à l'infrastructure et au cadre institutionnel relativement bien développés hérités du régime colonial, l'économie, dans les années qui ont suivi la guerre, a pu progresser sur une base solide. Par ailleurs, le fait que l'énorme excédent d'exportation de la balance commerciale ait disparu pour faire place à un déficit important provoqué par la perte du marché japonais jusqu'alors assuré -- facteur auquel il faut ajouter l'immigration massive en provenance de la Chine Continentale les premières années de l'après-guerre -- imposa la nécessité de développer l'industrie pour remplacer les importations. Néanmoins, l'impulsion ainsi imprimée à la croissance industrielle s'était apparemment considérablement ralentie à la fin des années cinquante, ce qui a amené les autorités à réviser les politiques suivies en matière de change et de protection douanière. Les mesures qui furent alors prises ont créé un climat favorable à l'expansion des exportations de produits manufacturés et à une croissance industrielle rapide au cours des années soixante. De l'avis de l'auteur, cette expansion des exportations a été facilitée par le fait que Formose avait déjà atteint un stade intermédiaire de développement, ce qui lui a permis d'entretenir un double courant d'exportations, exportant aux pays moins développés des marchandises dont la production exige un investissement relativement élevé en capital, et aux pays plus développés des articles dont la production nécessite comparativement beaucoup de main-d'Å“uvre. Il est devenu toutefois de plus en plus difficile d'accroître les exportations vers les pays moins développés, ceux-ci ayant eux-mêmes réussi à produire davantage et à importer moins; par ailleurs, les dimensions limitées de l'économie nationale permettent difficilement d'intensifier la production d'articles de base nécessitant des investissements élevés. Il est plus facile d'augmenter les exportations vers les pays développés car celles-ci s'inscrivent dans le cadre de relations commerciales d'un caractère plus complémentaire. Une des conclusions qui se dégagent de cette étude, c'est que les pays ayant des économies du même type que Taïwan ont intérêt comme lui à orienter leur production vers les articles les plus demandés dans les pays développés, de manière à poursuivre leur croissance économique en développant leurs exportations. /// La transformación experimentada por Taiwán--que, de exportador de productos primarios se convirtió en exportador de manufacturas y productos elaborados durante los decenios posteriores a la guerra--se analiza en este trabajo como un ejemplo de selección acertada del patrón de producción que correspondía adoptar en una región pequeña, dotada de recursos naturales limitados y que confronta severas presiones demográficas. En primer lugar, el hecho de que ya se contara con una agricultura relativamente avanzada y con una industria, una infraestructura y un sistema institucional, legados todos del régimen colonial, proporcionó bases firmes para el desarrollo económico de la posguerra. En segundo término, el hecho de que la balanza comercial de Taiwán pasara de un voluminoso superávit de exportación a un déficit considerable al perderse el mercado de exportación que se tenía asegurado en el Japón, así como la densa inmigración proveniente de la China Continental que ocurrió a principios del período posbélico, crearon una oportunidad para la expansión de las actividades fabriles con miras a producir bienes que sustituyesen a las importaciones. Sin embargo, parece que el impulso que adquirió el crecimiento industrial en virtud de este proceso se había perdido en gran parte ya para fines del decenio 1950, y la políticas proteccionistas y cambiarias del país fueron objeto de nuevos análisis. Las políticas que se pusieron en práctica entonces ofrecieron un marco favorable para el aumento de las exportaciones de manufacturas así como para un rápido crecimiento industrial durante el decenio 1960. Se sugiere que la etapa intermedia de desarrollo en que se encontraba Taiwán facilitó la expansión de las exportaciones porque le permitió al país mantener la dualidad de la estructura de éstas, o sea, seguir exportando a los países menos desarrollados bienes cuya producción requiere un coeficiente de capital relativamente alto, y a los países desarrollados bienes que requieren un coeficiente relativamente alto de mano de obra. Sin embargo, se ha tornado cada vez más difícil conseguir que continúen aumentando las exportaciones a los países menos desarrollados, en razón de que dichos países van avanzando en la sustitución de importaciones y porque el desarrollo en Taiwán de industrias de productos básicos que requieren un alto coeficiente de capital se halla obstaculizado por las reducidas dimensiones de la economía. Le expansión de las exportaciones a los países desarrollados, en cambio, resulta más fácil debido a que en las relaciones comerciales con esos países media un mayor grado de complementación recíproca. Esto sugiere, entre otras cosas, que convendría que Taiwán y las economías de índole similar optaran por darle a su producción la configuración que favorezca la elaboración de los productos que son objeto de mayor demanda en los países desarrollados, a fin de mantener el crecimiento económico mediante una expansión de las exportaciones.

We have studied thee 4 Compton scattering on targets with arbitrary spin and generalized the low-energy theorems of Cheng, Roy and Singh to higher order in photon energy ω. It is shown that the scattering amplitude has a term ω3 ω whose coefficient is determined entirely by the charge and magnetic moment of the target. In order to derive our theorem, we have evaluated explicitly the Born contribution to the second-order (in ω) terms of thee 2 Compton scattering amplitudes

California University has just completed two buildings at Davis, one of nine storeys, and another smaller one, devoted to offices. Building involved the use of prefabricated, prestressed, load bearing units. The production and placing of these units required a very strict program of control and planning, as each of these operations had very specific features that were not straightforward. The walls, roof and floorings were made of load bearing panels. The lift and stair box was also an important structural element. Both this box and the cross bracing will take up loads arising from possible earthquake effects. As the building is situated on ground with poor resistance, the foundation consists of a number of inverted arches, which float on the soil, and distribute the loads uniformly over a wider area. The lifting of the various units was carried out with two moveable cranes fitted with very long lifting arms, both of which were operated in a closely integrated manner. The final success has been outstanding, both owing to the low cost, the saving in time, and also because it will be easy to extend the project at a later date, by merely moving the position of the lift box, and using the same type of building units.La Universidad de California acaba de construir dos edificios en Davis, uno de nueve plantas, destinado a clases, y otro de menor importancia para oficinas. La construcción debía realizarse con elementos prefabricados, pretensados y autorresistentes. La colocación y preparación de estos elementos se sometió a un estrecho y riguroso programa que se denominó crítico, pues cada una de sus fases presentaba particulares características que la diferenciaba de la siguiente. Los elementos constructivos principales—muros, cubierta y forjados—, debían componerse de paneles autorresistentes. Las cajas de escaleras y ascensores son, asimismo, resistentes; dichas cajas, junto con el arriostramiento general, absorben la mayor parte de las tensiones derivadas de efectos sísmicos. Los cimientos, por hallarse el edificio sobre un suelo poco resistente, se resolvieron con un sistema de arco invertido que flota sobre el terreno y reparte la carga uniformemente sobre el mismo. El montaje se realizó con ayuda de dos grúas móviles, con plumas de gran longitud y maniobrando en estrecha colaboración. El éxito final logrado ha sido notable, tanto en economía financiera como de tiempo de ejecución y, además, se ha dejado el camino expedito a una ampliación futura, para la cual bastará correr la caja de ascensores al nuevo lugar elegido y continuar la reforma con los elementos prefabricados autorresistentes.

SUMMARY An interdisciplinary research project was initiated for systematic, long-term study of employability prognosis of persons with epilepsy. Neurological, psychological, and occupational status variables were investigated in three groups of epileptics: Employed adults, Unemployed adults, and a Prevocational Group of young persons primarily in the 11th and 12th grades. Preliminary results reported showed significant differences between Unemployed and Employed adult epileptics on a substantial number of measures that relate to employability suggesting a continuum of employability from very poor employability prognosis to very good prognosis. Based on the findings presented here, social adaptive abilities appear to be as important as seizure control, and perhaps even more important in the final outcome. In the meantime, increasing evidence does not provide support for the belief that drug therapy and changing employers' attitudes represent a sufficient attack on the employment problems of persons with epilepsy. REASUMEA Un projet de recherche groupant plusieurs disciplines a eAteA mis sur pied. Elle avait pour but d'eAtudier, d'une facLon systeAmatique et sur une longue peAriode, le pronostic de l'emploi d'individus souffrant d'eApilepsie. Plusieurs variables furent exploreAes: neurologique, psychologique et occupationnelle. Trois groupes d'eApileptiques furent examineAs: (1) adultes posseAdant un emploi; (2) adultes sans emploi; (3) jeunes individus en majoriteA dans leur 11e ou 12e anneAe de scolariteA (groupe preA-vocationnel). Les premiers reAsultats deAmontrent qu'il y existe une diffeArence significative entre le groupe des adultes sans emploi et celui des adultes ayant un emploi. De nombreuses mesures portant sur les possibiliteAs d'emploi mirent aG jour ces diffeArences et suggeAreGrent un continuum dans les possibiliteAs d'emploi qui variait d'un pronostic treGs pauvre aG treGs bon. D'apreGs les reAsultats obtenus, les capaciteAs d'adaptation sociale semblent eCtre importantes en tant que meAcanisme de controCle des crises et elles sont possiblement encore plus importantes en ce qui concerne l'issue finale. En attendant, il est de plus en plus eAvident que le traitement meAdicamenteux et le changement d'attitude des employeurs ne s'attaquent pas d'une manieGre suffisante aux probleGmes de l'emploi d'individus souffrant d'eApilepsie.

Ribosomes from soybean root tips were shown to consist of about 75% polyribosomes based on size distribution on sucrose gradients. Electronmicrographs showed the presence of ribosome clusters in normal preparations and only monomers and dimers in ribonuclease-treated preparations. The polyribosome preparations, but not single ribosomes, showed good in vitro amino acid incorporating activity.D-RNA was associated with the ribosome preparations, and preferentially in the polyribosome structure. It is suggested that at least a part of the soybean D-RNA represents a class of messenger RNA.

THE 1971 ACI BUILDING CODE PROVISIONS ARE EXPLAINED FOR MOMENT REDISTRIBUTION IN CONTINUOUS PRESTRESSED CONCRETE BEAMS. BY MEANS OF EXAMPLES, EMPHASIS IS STRESSED FOR WHEN THE SECONDARY MOMENTS DUE TO PRESTRESS FORCE ARE TO BE INCLUDED IN DETERMINING THE ULTIMATE CAPACITY OF CONTINUOUS BEAMS. /AUTHOR/

Basic requirements for the design of concrete buildings for earthquake resistance are given. The elastic behavior of prestressed components and their allowable stresses and load factors are evaluated with respect to earthquake loads. The energy absorption capacity of prestressed members under flexure, shear, combined bending, and shear is reviewed. Prestressing of concrete slabs, shafts, and rigid frames for earthquake resistance in buildings is described. Seismic design of tall buildings for dynamic loads is compared to design for static loads using code values.

The data reported indicate that the oxidation-reduction balance of the ascorbic acid system is not causally related to the auxin-regulation of cell elongation. There was no shift in the ascorbic acid (AA) to dehydroascorbic acid (DHA) ratio with growth-promoting concentration of auxin in several plant tissues. The AA to DHA ratio was experimentally increased without altering the growth rate. Inhibition of growth by supra-optimal auxin was associated with a decrease in the AA to DHA ratio. Since the AA to DHA ratio was lowered by EDTA treatment without altering growth, it seems unlikely that the decrease in the AA to DHA ratio related to the inhibition of growth by high levels of auxin.

* The van der Waals radius of Sn was estimated by extrapolation of Pauling's values. International Tables for X-ray Crystallography (1959). Vol. III. Birmingham: Kynoch Press. KASAI, N., YASUDA, K. & OKAWARA, R. (1965). J. Organometal. Chem. 3, 172. LIPPINCOTT, E. R. & SCHROEDER, R. (1955). J. Chem. Phys. 23, 1099. PAULING, L. (1960). The Nature of the Chemical Bond. 3rd ed. Ithaca: Cornell Univ. Press. PHILLIPS, D. C. (1954). Acta Cryst. 7, 746. SCHLEMPER, E. O. • BRITTON, D. (1966). Inorg. Chem. 5, 507. SUTTON, L. E. (1965). Interatomic Distances, Supplement. The Chemical Society, London. THAYER, J. S. & STROMMEN, D. P. (1966). J. Organomet. Chem. 5, 383. THAYER, J. S. & WEST, R. (1964). Inorg. Chem. 3, 889.

The live loading used in designing highway bridges of short and medium spans is standardized by various codes, but the selection of a suitable live loading for long spans has been left to the discr...

The dielectric constants of H–(CH2)n–C(CH3)2–CH2OH with n = 1, 2, 3, 4, 6, and 8 have been measured from about −70° to 100°C with test frequencies 0.05

Polyribosomes of the soybean root rapidly dissociate under energy-depleting conditions, namely anaerobiosis and dinitrophenol treatment. The loss of polyribosomes cannot be attributed to a depletion of messenger RNA, because polyribosomes re-form to about 75% of the original level following restoration of aerobic conditions in the presence of dactinomycin. The dactinomycin treatment resulted in greater than 90% inhibition of RNA synthesis during the aerobic recovery period. Nascent polypeptide is lost from the ribosomes coincident with or during the conversion of polyribosomes to monoribosomes during anaerobiosis. Cycloheximide blocks both the conversion of polyribosomes to monoribosomes and the loss of nascent polypeptide from ribosomes. The results suggest that polyribosome dissociation occurs as a result of completion of read-out and release of polypeptide and monoribosome, coupled with a failure of attachment of ribosomes to messenger RNA and subsequent initiation of new peptide chains.

The controversy as to whether the accessibility of cellulose is a measure of crystal surfaces or of amorphous regions in the cellulose is reviewed. Recent claims that cellulose is composed of completely crystalline elementary fibrils of dimensions 40 × 50 A and that all chemical reactions of cellulose occur on the surface of the fibrils, do not explain many observations which indicate the presence of amorphous structures. Based on X-ray diffraction, chemical hydrolysis, moisture absorption, theoretical calculations of elastic constant, kinetic studies of alkaline degradation, and the lateral-order distribution curve of cellulose, evidence exists favouring the conventional micellar theory. The assumption of a gradual transition between the amorphous and crystalline regions in cellulose offers an explanation of the discrepancies among the accessibility values recorded by different methods.

Summary. Three studies of prediction of academic achievement in introductory psychology courses are reported. The Achiever Personality scale of Fricke's Opinion, Attitude and Interest Survey and Brown and Holtzman's Survey of Study Habits and Attitudes made independent contributions beyond intelligence in the prediction of course grades in two studies. In a third study the Achievement via Independence scale of Gough's California Psychological Inventory was found to contribute to grade prediction.

The recently completed hyperbolic paraboloid concrete shell roof for the Ponce Coliseum in Puerto Rico represents a significant thrust forward in the design of shell structures. The shell roof cantilevers 138 ft (measured along the edge beams) making it the world's longest cantilever shell of the HP type. Post-tensioning was used both in the shell membrane and also along the edge beams to control deflections and stresses. In addition, the piers on opposite sides of the shell were post-tensioned beneath the ground to resist the horizontal thrust. The finite element method was used to analyze the structural behavior and to calculate the moments, stresses, and deflections in the shell and edge beams. This article describes the design and construction techniques used in building this shell roof.

In the carrying out of this work of enlarging the San Francisco International Airport, a criterion has been maintained which has allowed a series of interesting results to be obtained. The building technique is very unusual, giving it the mark of innovation. This technique has made use of prestressed, prefabricated parts, thus reducing by about 40 % the amount of materials that ordinary building methods would have required, lightening the loads, and keeping as far as possible within the limitations imposed by traffic and the terrain. And all without detriment to a considerable aesthetic effect.En la realización de esta obra para la ampliación del aeropuerto internacional de San Francisco se ha mantenido un criterio que ha permitido obtener una serie de resultados interesantes. Presenta un carácter innovador, ya que la técnica constructiva es muy poco habitual. Dicha técnica ha facilitado emplear elementos prefabricados pretensados, reducir en un 40 % la cantidad de materiales que hubieran sido necesarios de haber utilizado una técnica de construcción normal, aligerar las cargas y ceñirse al máximo a una serie de limitaciones impuestas por el tráfico y la naturaleza del terreno; todo ello sin detrimento de obtener un efecto estético considerable.

This bibliography (1963-1967) lists 1300 articles and 170 patents, supplementing an earlier one (-1963) which contains 735 articles and 60 patents.

The Cross method of distributing fixed-end moments in the analysis of continuous frames has become recognized as such a convenient tool of structural design that it is unnecessary to state its impo...

Describes the construction of a 480-ft long precast, post-tensioned concrete, inverted suspension bridge which was recently constructed near San Jose, Costa Rica. This functional and economically built bridge shows how, with some ingenuity, the principles of suspension, arch, and cantilever theory can be applied with relatively simple construction techniques to span a deeply inclined canyon in remote and very rugged terrain. Initially, the piers of the bridge were built vertically. They were then rotated 30 deg so that they could provide beneficial arch and cantilever action and also to insure a safe foundation. Precast concrete segments form the soffit along the suspended cables. In turn, the soffit was used as a working platform on which precast bents and roadway beams were erected. This article describes the construction sequence of the bridge erection with the aid of diagrams and photographs.

A liquid flow recorder of simple design which can be easily constructed with readily obtainable material at low cost is described. It is used with a piston recorder and a time interval marking clock to measure the rate of liquid flow over a range of a few drops to 50 ml/min.

California University has constructed a two storey garage, with a prestressed concrete structure, at Berkeley. A particular feature of this building is that on the roof a soil layer, 0.45 cm in depth, has been laid, on which there is a grass lawn. The structure consists of a framework of beams, of 7.30 m span, in one direction, and 19 m in the other: this being the maximum separation of the columns in one elevation. Consequently the flooring is made of slabs spanning the shorter 7.30 m distance. The roof slab has been prestressed in two mutually perpendicular directions, hence it is practically impossible for it to develop cracks. This arrangement renders the slab watertight and implies a saving in the cost of applying waterproofing treatment. As the building is surrounded on three sides by three contention walls, advantage has been taken of this to transmit to these the horizontal thrusts due to windage and seismic forces. Most of the structural elements, excepting the flooring, have been prestressed and prefabricated at a workshop 80 Km. away from the site. Many of the constructional units have additional reinforcement, which can be post-tensioned after erection at the working site.La Universidad de California ha construido un garaje, de dos plantas, de hormigón pretensado, en Berkeley, que presenta la particularidad de utilizar la parte superior de su cubierta para colocar sobre ella una capa de tierra, de 0,45 metros de espesor, coronada por un manto de césped. La estructura resistente está constituida por un reticulado de vigas formando crujías de 7,30 m de luz y apoyos espaciados a 19 m. Por tanto, las losas que forman los forjados salvan una, luz de 7,30 m, mientras que las vigas forman pórticos de 19 m de luz máxima. La losa de cubierta se ha pretensado en dos direcciones normales entre sí y, como consecuencia de ello, al hallarse debidamente comprimida en el sentido de estas dos direcciones es prácticamente imposible la presencia de grietas. Esta disposición en el trazado de los cables del pretensado asegura la impermeabilización del hormigón e introduce ventajas económicas, ya que hace innecesaria toda capa de impermeabilización. Como el edificio se halla rodeado en tres de sus fachadas por otros tantos muros de contención, se ha sacado partido de esta circunstancia para arriostrar los forjados sobre estos muros y transmitir sobre ellos los efectos del viento y sísmicos, en una dirección, mientras que, en la normal a ella, estos efectos son transmitidos al terreno por el intermedio de los soportes. La mayoría de los elementos estructurales, a excepción de las losas para forjados, han sido prefabricados y pretensados en un taller situado a unos 80 km de distancia de la obra. Muchos de los elementos cuentan con armaduras complementarias para el postensado después de haber sido colocados en obra.