Scintillation efficiency of liquid argon in low energy neutron-argon scattering

Experiments searching for weak interacting massive particles with noble gases such as liquid argon require very low detection thresholds for nuclear recoils. A determination of the scintillation efficiency is crucial to quantify the response of the detector at low energy. We report the results obtained with a small liquid argon cell using a monoenergetic neutron beam produced by a deuterium-deuterium fusion source. The light yield relative to electrons was measured for six argon recoil energies between 11 and 120 keV at zero electric drift field.

Mechanical Degradation of Tungsten Alloys at Extreme Temperatures in Vacuum and Oxidation Atmospheres

Mechanical degradation of tungsten alloys at extreme temperatures in vacuum and oxidation atmospheres.

Máquinas o atmósferas: La estética de la energía en la arquitectura, 1750-2000 = From Machines to Atmospheres: The Aesthetics of Energy in Architecture, 1750-2000

La energía es ya un tema arquitectónico, pero su incorporación al proyecto ha sido hasta ahora fundamentalmente técnica, dando pie a una especie de funcionalismo ecológico cuyo destino es acaso repetir los errores de los viejos funcionalismos en su confianza de encontrar modos ‘objetivos’ de transmutar la energía en forma construida, pero sin que en tal proceso parezca haber hueco para mediaciones de tipo estético. Sin embargo, son precisamente tales mediaciones las que necesitan analizarse para que la adopción de los temas energéticos resulte fructífera en la arquitectura, y asimismo para dar cuenta de otras perspectivas complementarias —filosóficas, científicas, artísticas— que hoy forman el complejo campo semántico de la energía. Partiendo de la fecha de 1750 —que da comienzo simbólicamente al proceso de contaminaciones ‘modernas’ entre la arquitectura y otras disciplinas—, esta tesis analiza los diferentes modos con los que proyectos y edificios han expresado literal y analógicamente ciertos temas o ideales energéticos, demostrando la existencia de una ‘estética de la energía’ en la arquitectura y también de una tradición proyectual e intelectual sostenida en ella. Con este fin, se han seleccionados siete metáforas que vinculan tanto técnica como ideológicamente a la arquitectura con la energía: la metáfora de la máquina, asociada al ideal de movimiento y la autorregulación; las metáforas del arabesco, del cristal y del organismo, afines entre sí en su modo de dar cuenta del principio de la morfogénesis o energía creadora de la naturaleza; la metáfora de la actividad interna de los materiales; la metáfora del gradiente, que expresa la condición térmica y climática de la arquitectura, y, finalmente, la de la atmósfera que, recogiendo los sentidos anteriores, los actualiza en el contexto de la estética contemporánea. La selección de estas siete metáforas se ha llevado a cabo después de un barrido exhaustivo de la bibliografía precedente, y ha estructurado un relato cuyo método combina la perspectiva general —que permite cartografiar las continuidades históricas— con la cercana —que atiende a las problemas específicos de cada tema o metáfora—, complementándolas con una aproximación de sesgo iconográfico cuyo propósito es incidir en los vínculos que se dan entre lo ideológico y lo morfológico. El análisis ha puesto de manifiesto cómo detrás de cada una de estas metáforas se oculta un principio ideológico común —la justificación de la arquitectura desde planteamientos externos procedentes de la ciencia, la filosofía y el arte—, y cómo en cada uno de los casos estudiados las asimilaciones más fructíferas de la energía se han producido según mecanismos de mímesis analógica que inciden más en los procesos que en las formas que estos generan, y que en último término son de índole estética, lo cual constituye un indicio de los métodos de la arquitectura por venir. ABSTRACT Although it is already an architectural theme, the matter of incorporating energy into projects has up to now been mainly technical, giving rise to a kind of ecological functionalism which may be bound to old funcionalist mistakes in hopes of finding “objective” ways of transmuting energy into built forms without aesthetic considerations. However, it is precisely such considerations that need to be analyzed if the adoption of energy issues in architecture is to bear fruit and also to account for other complementary perspectives – philosophical, scientific, artistic – which today form the complex fabric of the energy semantic field. Beginning in 1750 – symbolic start of ‘modern’ contaminations between architecture and other disciplines –, this thesis analyzes the different ways in which projects and buildings have literally and analogically expressed certain subjects or ideals on energy, and demonstrates the existence of an “aesthetics of energy” in architecture, as well as of an intellectual and design tradition based on such aesthetics. For this purpose, seven metaphors are selected to link energy to architecture both technically and ideologically: the machine’s metaphor, associated with the ideal of mouvement and self-regulation; the arabesque, glass and the organism’s metaphors, which account for the morphogenesis principle, i.e. creative energy of nature; the metaphor linked to matter and the ideal of internal activity; the gradient’s metaphor, which expressed the thermal and climatic condition of architecture, and, finally, that of the atmosphere which, collecting the above meanings, updates them in the context of contemporary aesthetics. The selection of these seven metaphors was carried out after a thorough scan of the preceding literature, and has structured a reasoning that combines the overview method – which accounts for historical continuities – with the nearby one – which meets the specifics problems of each theme or metaphor –, both supplemented with an iconographic bias, the purpose of which is to visually express the links existing between the ideological and the morphological. So presented, the analysis shows how, behind each of these metaphors, lies a common ideological principle – the justification of architecture from scientific, philosophical and artistic “external” angles –, and how in each of the studied cases the most successful assimilation of energy were those produced by aesthetic mechanisms of analogical mimesis not focused in forms but in processes that generate them: an indication of the methods of architecture to come.

Sonic anemometry of planetary atmospheres

The application of a recently developed model of sonic anemometers measuring process has revealed that these sensors cannot be considered as absolute ones when measuring spectral characteristics of turbulent wind speed since it is demonstrated that the ratios of measured to real spectral density functions depend on the composition and temperature of the considered planetary atmosphere. The new model of the measuring process of sonic anemometers is applied to describe the measuring characteristics of these sensors as fluid/flow dependent (against the traditional hypothesis of fluid/flow independence) and hence dependent on the considered planetary atmosphere. The influence of fluid and flow characteristics (quantified via the Mach number of the flow) and the influence of the design parameters of sonic anemometers (mainly represented by time delay between pulses shots and geometry) on turbulence measurement are quantified for the atmospheres of Mars, Jupiter, and Earth. Important differences between the behavior of these sensors for the same averaged wind speed in the three considered atmospheres are detected in terms of characteristics of turbulence measurement as well as in terms of optimum values of anemometer design parameters for application on the different considered planetary atmospheres. These differences cannot be detected by traditional models of sonic anemometer measuring process based on line averaging along the sonic acoustic paths.

Glycolytic Flux Is Adjusted to Nitrogenase Activity in Nodules of Detopped and Argon-Treated Alfalfa Plants1

To investigate the short-term (30–240 min) interactions among nitrogenase activity, NH4+ assimilation, and plant glycolysis, we measured the concentrations of selected C and N metabolites in alfalfa (Medicago sativa L.) root nodules after detopping and during continuous exposure of the nodulated roots to Ar:O2 (80:20, v/v). Both treatments caused an increase in the ratios of glucose-6-phosphate to fructose-1,6-bisphosphate, fructose-6-phosphate to fructose-1,6-bisphosphate, phosphoenolpyruvate (PEP) to pyruvate, and PEP to malate. This suggested that glycolytic flux was inhibited at the steps catalyzed by phosphofructokinase, pyruvate kinase, and PEP carboxylase. In the Ar:O2-treated plants the apparent inhibition of glycolytic flux was reversible, whereas in the detopped plants it was not. In both groups of plants the apparent inhibition of glycolytic flux was delayed relative to the decline in nitrogenase activity. The decline in nitrogenase activity was followed by a dramatic increase in the nodular glutamate to glutamine ratio. In the detopped plants this was coincident with the apparent inhibition of glycolytic flux, whereas in the Ar:O2-treated plants it preceded the apparent inhibition of glycolytic flux. We propose that the increase in the nodular glutamate to glutamine ratio, which occurs as a result of the decline in nitrogenase activity, may act as a signal to decrease plant glycolytic flux in legume root nodules.

On the Electric Breakdown in Liquid Argon at Centimeter Scale

We present a study on the dependence of electric breakdown discharge properties on electrode geometry and the breakdown field in liquid argon near its boiling point. The measurements were performed with a spherical cathode and a planar anode at distances ranging from 0.1 mm to 10.0 mm. A detailed study of the time evolution of the breakdown volt-ampere characteristics was performed for the first time. It revealed a slow streamer development phase in the discharge. The results of a spectroscopic study of the visible light emission of the breakdowns complement the measurements. The light emission from the initial phase of the discharge is attributed to electro-luminescence of liquid argon following a current of drifting electrons. These results contribute to set benchmarks for breakdown-safe design of ionization detectors, such as Liquid Argon Time Projection Chambers (LAr TPC).

(Table 1) Argon dating of ash layers from DSDP Hole 18-178

Ash layers from Deep Sea Drilling Project site 178 in the northeast Pacific Ocean have been dated by the 40Ar-39Ar stepwise heating technique to resolve published discrepancies concerning the length of time explosive volcanism has affected the eastern Aleutian arc and Alaskan Peninsula. The results of the investigation indicate that the record of ash-fall deposition at site 178 extends back at least 6.5 m.y. Assuming that 6.5 m.y. ago marks the onset of renewed calc-alkalic volcanism of the volcanic arc, proposed models of continuous and discontinuous motion between the Pacific and North American lithospheric plates can be evaluated. If appreciable time elapsed between the onset of subduction and the onset of arc volcanism, the 6.5-m.y. record of ash-fall deposition in the north-east Pacific is most compatible with models of continuous plate motion throughout late Cenozoic time.

Evaluation of Horizons, Inc. Th metal powder : progress report no. 1 for February 18, 1954-March 4, 1954 /

Three samples of thorium powder as supplied by Horizons, Inc. of Cleveland, Ohio were compared. The powder was processed entirely without the use of protective atmospheres with the exception of the sintering which was performed in a tank argon atmosphere with a dew point of approximately -80°C and the hot-pressing which was carried out in vacuum. The equipment and procedures used for cold-pressing and sintering were identical to those used in the evaluation of Sylvania produced thorium powders. The hot-pressing was done with standard uranium hot-pressing equipment.

A technical report on analytical-experimental correlation of radiation loss from an argon arcjet.

At head of title: Dept. of the Air Force. Office of Aerospace Research. Aeronautical Research Laboratory. Thermomechanics Branch. Contract AF 33(657)-9962.