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Fil: Bertero, Melisa Paola. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Santa Fe. Instituto de Investigaciones en Catalisis y Petroquimica "Ing. Jose Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catalisis y Petroquimica "Ing. Jose Miguel Parera"; Argentina

Pairing a conditioned stimulus (CS) with ethanol generally produces aversion for that CS in adult rodents. However, infant rats (PD1-PD3) exposed to ethanol demonstrate appetitive reinforcement to ethanol (Nizhnikov, Varlinskaya, Petrov, & Spear, 2006; Petrov, Varlinskaya, & Spear, 2003). This sensitivity to the appetitive properties of ethanol during infancy may be transient, as during the second postnatal week rat pups tend to exhibit conditioned aversions to flavors paired with ethanol. The present study examined changes in the motivation properties of ethanol through ontogeny and the neurobiology underlying these changes. Rat pups were exposed to a taste conditioning procedure on PD4 or PD12. Rat pups were intraorally infused with 2.5% of their body weight of saccharin solution (0.1%) and immediately after injected intraperitoneolly (i.p.) with one of six doses of ethanol (0.0-2.0 g/kg). A day later pups were given saccharine infusions and percent body weight gain was used as an index of ethanol's reinforcing effects. PD4 pups expressed appetitive reinforcement to ethanol, as indicated by greater saccharin intake, as compared to control counterparts and to the older PD12 pups. Subsequent experiments revealed that PD4 pups were less sensitive to the aversive properties of the drug than PD12 pups. The older pups found high doses of ethanol aversive while PD4 rat pups did not condition aversions to this dose of ethanol after a single trial. A similar pattern of results was observed between the low doses of ethanol and the highest doses of a kappa opioid agonist. The PD12 animals did not condition to the kappa opioid agonist, while the younger rats expressed an appetitive response. These results illustrate an ontogenetic change in the motivational properties of ethanol, with sensitivity to its appetitive properties declining and responsiveness to the aversive properties increasing with age during early infancy.

AbstractThis paper shows the experimental study of the thermal efficiency of a counter-flow double-pass solar air heater and the theoretical thermal model developed to describe its thermal behavior. The prototype was designed and manufactured at INENCO, Universidad Nacional de Salta, Argentina, The useful collection area is 2m2, and a channel height of 0.025m. The edge and bottom surfaces are thermally insulated with a 0.05 m thick glass wool layer. The air flow is forced by a tangential fan installed in a 0.18m diameter pipe that is connected to the flow outlet. The collector was mounted with a slope of 40° facing north, in order to maximize the intensity of solar irradiance during winter. Experimental outdoor tests were carried out during a winter period, with maximum solar irradiance on the collector plane around 1050W/m2. A semi-empirical thermal model was developed in order to simulate the air temperature at the collector outlet under different outdoor climatic conditions and air flow. Experimental results and the predictions of the theoretical model were found to be in good agreement.

Abstract Two new codes for calculating with space and energy details in the resonance region are presented here: RMET21 and RMET22. The first one is for homogeneous mixtures and pin cells and the second for cluster type fuel elements. The methods used in these codes are based on the solution of the integral form of the Boltzmann transport equation, with first-flight collision probabilities. Resonance profile tabulations are used, constructed from basic evaluated nuclear data files. In the RMET21 program, there is an option to calculate resonance cross-sections with the Breit—Wigner formula, using any set of resonance parameters. This option is useful, e.g. in comparisons with analytical methods and to make sensitivity studies. In the RMET22 code, a new procedure is presented in the resonance region, using collison probabilities, without the approximation of annularization, commonly used to deal with this geometry. In the RMET22 code, the different pins and other regions within a cluster of rods are treated allowing for the details of space and energy. A new method is used to obtain collision probability tables for interpolations and other approximations to speed up the calculations. Comparisons of results obtained by different treatments and experiments are included, showing the accuracy of the methods presented here and their applicability.

Abstract On December 1998, the Endeavour space shuttle launched the Argentine satellite SAC-A. Among several technological experiments, this satellite included a set of crystalline silicon solar cells fabricated in Argentina to test them in the space environment. In this paper, we describe the experiments associated with these solar cells and analyse the corresponding telemetry data received from January to July 1999. Fabrication and characterisation of modules are presented. Some preliminary radiation damage experiments using 10 MeV protons supplied by a cyclotron accelerator were also performed.

Dans cet article, nous étudions l'utilisation du flux de lots dans les problèmes de planification de flowhop sans permutation. L'objectif est de minimiser le makepan soumis aux contraintes de flowhop standard, mais où il est maintenant autorisé de réorganiser les tâches entre les machines. En outre, les tâches peuvent être divisées en sous-lots gérables, une stratégie connue sous le nom de flux de lots. Les expériences informatiques montrent que le flux de lots réduit le makepan jusqu'à 43% pour un large éventail de cas par rapport au cas où aucun fractionnement de tâches n'est appliqué. Les avantages augmentent à mesure que le nombre d'étapes du processus de production augmente mais atteignent une limite. Au-delà d'un certain point, la division des tâches en sous-lots supplémentaires n'améliore pas la solution. En este documento investigamos el uso de la transmisión de lotes en problemas de programación de Flowshop sin permutación. El objetivo es minimizar el makepan sujeto a las restricciones estándar de Flowshop, pero donde ahora se permite reordenar trabajos entre máquinas. Además, los trabajos se pueden dividir en sublotes manejables, una estrategia conocida como transmisión de lotes. Los experimentos computacionales muestran que la transmisión de lotes reduce el makepan hasta un 43% para una amplia gama de instancias en comparación con el caso en el que no se aplica la división de trabajos. Los beneficios crecen a medida que aumenta el número de etapas en el proceso de producción, pero alcanzan un límite. Más allá de cierto punto, la división de trabajos en sublotes adicionales no mejora la solución. In this paper we investigate the use of lot streaming in non-permutation flowshop scheduling problems.The objective is to minimize the makespan subject to the standard flowshop constraints, but where it is now permitted to reorder jobs between machines.In addition, the jobs can be divided into manageable sublots, a strategy known as lot streaming.Computational experiments show that lot streaming reduces the makespan up to 43% for a wide range of instances when compared to the case in which no job splitting is applied.The benefits grow as the number of stages in the production process increases but reach a limit.Beyond a certain point, the division of jobs into additional sublots does not improve the solution. في هذه الورقة، نتحقق من استخدام تدفق اللوت في مشاكل جدولة ورشة التدفق غير القابلة للتحويل. الهدف هو تقليل فترة التشغيل وفقًا لقيود ورشة التدفق القياسية، ولكن حيث يُسمح الآن بإعادة ترتيب الوظائف بين الآلات. بالإضافة إلى ذلك، يمكن تقسيم الوظائف إلى أقسام فرعية يمكن التحكم فيها، وهي استراتيجية تعرف باسم تدفق اللوت. تظهر التجارب الحاسوبية أن تدفق اللوت يقلل من فترة التشغيل إلى 43 ٪ لمجموعة واسعة من الحالات عند مقارنتها بالحالة التي لا يتم فيها تطبيق تقسيم الوظائف. تنمو الفوائد مع زيادة عدد المراحل في عملية الإنتاج ولكنها تصل إلى حد. بعد نقطة معينة، لا يؤدي تقسيم الوظائف إلى أقسام فرعية إضافية إلى تحسين الحل.

A number of contingencies simulated during dynamic security assessment do not generate unacceptable values of power system state variables, due to their small influence on system operation. Their exclusion from the set of contingencies to be simulated in the security assessment would achieve a significant reduction in computation time. This paper defines a critical contingencies selection method for on-line dynamic security assessment. The selection method results from an off-line dynamical analysis, which covers typical scenarios and also covers various related aspects like frequency, voltage, and angle analyses among others. Indexes measured over these typical scenarios are used to train neural networks, capable of performing on-line estimation of a critical contingencies list according to the system state.

Resumen: En este trabajo se estudia el desarrollo de materiales cerámicos refractarios de baja densidad utilizando un agente ligante que genere, luego de calcinados, nanoestructuras cerámicas. Además, se adicionaron al sistema fuentes de carbono como agentes formadores de poros con el objetivo de disminuir la densidad final del material. Como materias primas se utilizaron dos arcillas caoliníticas argentinas, gel de fosfato de aluminio que actúan como agentes ligantes y distintas fuentes de carbón (carbón residual de petróleo, carbón vegetal y negro de humo). Se obtuvieron cerámicos con densidades menores a 2 g/cm3 y variada resistencia mecánica a la flexión (8,02-26,87 MPa). Se observó que las propiedades de los materiales cerámicos, para materiales desarrollados bajo iguales condiciones, varían según la fuente de carbono utilizada. Abstract: In this work was studied the development of low density refractory ceramic materials using precursors that produce nanostructured ceramics binders after calcination. Several coal sources were also added as pore forming agent, in order to decrease the final density of the material. As raw material, two Argentine kaolinitic clays, aluminum phosphate gel as binder agent and different coal sources (residual petroleum coal, charcoal and carbon black) were used. Low density ceramic materials were obtained (less than 2 g/cm3) with varied values of flexural strength (from 8.02 to 26.87 MPa). It was also observed that the properties of the ceramic materials obtained, under the same conditions, vary according to the coal source used. Palabras clave: Cerámicos de baja densidad, Agentes ligantes nanoestructurados, Carbón, Arcillas caoliníticas, Keywords: Low density ceramics, Nanostructured binder, Coal, Kaolinitic clays