194 research outputs found

    Los cuerpos indígenas entre textos y silencios. El caso de una niña Aché

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    The organization of collections of human remains of different “races”, during the end of the XIX century and the beginning of the XX century, was associated with archival work that enabled to certificate the authenticity of the specimens. These files contain individual data, such as the origin, sex, age and name, but also data about the collector or donor. This study analyses the different material and textual strategies carried out on a young Aché indigenous woman by the German anthropologist Robert Lehmann-Nitsche (1872-1938), responsible of the Sección Antropológica of the Museo de La Plata (Argentina); strategies through which the anthropologist built the epistemological value of the indigenous body and his own scientific authority. We also discuss how certain practices were inspired in written and non-written instructions, but sometimes personal motivations interrupted procedures for elaborate scientific objects, leaving “silences” that can only recently be interpreted in light of the claims existing over museums that house human remains.La formación de colecciones de restos humanos de distintas “razas”, hacia fines del siglo XIX y comienzos del XX, se asoció con la elaboración de un corpus documental que permitiese acreditar la autenticidad de los especímenes. En estos archivos constan datos individuales, como la procedencia, sexo, edad y el nombre, pero también sobre el colector o donante. A partir de las prácticas materiales y textuales efectuadas sobre una joven indígena Aché por el antropólogo alemán Robert Lehmann-Nitsche (1872-1938), jefe de la Sección Antropológica del Museo de La Plata (Argentina), este trabajo analiza las distintas estrategias para otorgar valor epistemológico al cuerpo indígena y la autoridad científica del propio investigador. Se discute además cómo algunas prácticas estuvieron inspiradas en instrucciones escritas o no escritas, pero a veces las motivaciones personales condujeron a interrumpir los procedimientos de producción de objetos de estudio, dejando “silencios” que solo recientemente pueden ser interpretados a la luz de los cuestionamientos que existen sobre los museos que albergan restos humanos

    Theory for Cavity Cooling of Levitated Nanoparticles via Coherent Scattering: Master Equation Approach

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    We develop a theory for cavity cooling of the center-of-mass motion of a levitated nanoparticle through coherent scattering into an optical cavity. We analytically determine the full coupled Hamiltonian for the nanoparticle, cavity, and free electromagnetic field. By tracing out the latter, we obtain a Master Equation for the cavity and the center of mass motion, where the decoherence rates ascribed to recoil heating, gas pressure, and trap displacement noise are calculated explicitly. Then, we benchmark our model by reproducing published experimental results for three-dimensional cooling. Finally, we use our model to demonstrate the possibility of ground-state cooling along each of the three motional axes. Our work illustrates the potential of cavity-assisted coherent scattering to reach the quantum regime of levitated nanomechanics.Comment: 27 pages (18 main text + 9 Appendices), 12 figures, 3 table

    Estructura hidrográfica de la Bahía de Bluefields, Nicaragua

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    In March and October of 2000, under the DIPAL II project (Proyecto para el Desarrollo Integral de la Pesca Artesanal en la Región Autónoma del Atlántico Sur), two hydrographic surveys were carried out in the Bay of Bluefields to study their hydrography during the dry and rainy seasons. Water temperature, salinity and turbidity were determined both at the surface and the bottom of the bay. The results obtained are consistent with previous studies carried out in this area. In March, water temperature and salinity were lower and higher, respectively, than in October. Water turbidity increased with increased fresh water input as a result of a greater movement of suspended sediments and organic matter into the water body. Saline wedges were observed in deep strata during the two months of sampling in the adjacent areas to the bars of The Bluff and Hone Sound. In the first case the wedge extended to the northwest up to the area of Bluefields, while in the second case it extended to the west reaching the western coast of the bay. The vertical gradient of salinity was stronger in October, when the superficial flow of fresh water in the whole bay was more intense. A circulation pattern related to the salinity field was recognised: fresh water introduced by the Caño Negro and Escondido rivers moves along the western coast of the bay, while sea water enters the bay towards the northwest, throughout the whole water column, at the bars of The Bluff and Hone Sound. Fresh water introduced by the River Torsuani moves along the eastern coast towards the open sea at the southern end of the bay

    Higgs particle detection using jets

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    We study the possibility of detecting the Higgs boson in the intermediate mass range via its two jet channel. We consider only Higgs bosons produced in association with a ttˉt \bar{t} pair. Both tt and tˉ\bar{t} are required to decay semileptonically to reduce the QCD background. The signal is compared with the main background, ttˉ+2t \bar{t} + 2 jets, after appropriate cuts. A sizable signal above background is seen in our simulation at the parton level. Use of the ttˉZt\bar{t}Z channel with Z Z decaying to l+ll^+ l^- is suggested for eliminating theoretical uncertainties in determining the ttˉHt \bar{t}H signal.Comment: 10 pages, Fig.1 a,b,c,d(surve on request), plain tex, PVAM-HEP-93-

    Woolliness assessment in peaches (Cv. Springcrest) by sensory and instrumental means.

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    Mealiness is a negative attribute of sensory texture, characterised by the lack of juiciness without variation of total water content in the tissues. In peaches, mealiness is also known as "woolliness" and "leatheriness". This internal disorder is characterised by the lack of juiciness and flavour. In peaches, it is associated with interna browning near the stone and the incapacity of ripening although there is externa ripe appearance. Woolliness is associated with inadequate cold storage and is considered as a physiological disorder that appears in stone fruits when an unbalanced pectolitic enzyme activity during storage occurs (Kailasapathy and Melton, 1992). Many attempts have been carried out to identify and measure mealiness and woolliness in fruits. The texture of a food product is composed by a wide spectrum of sensory attributes. Consumer defines the texture integrating simultaneously all the sensory attributes. However, an instrument assesses one or several parameters related to a fraction of the texture spectrum (Kramer, 1973). The complexity of sensory analysis by means of trained panels to assess the quality of some producing processes, supports the attempt to estimate texture characteristics by instrumental means. Some studies have been carried out comparing sensory and instrumental methods to assess mealiness and woolliness. The current study is centered on analysis and evaluation of woolliness in peaches and is part of the European project FAIR CT95 0302 "Mealiness in fruits: consumer perception and means for detection". The main objective of this study was to develop procedures to detect woolly peaches by sensory and by instrumental means, as well as to compare both measuring procedures

    Superradiance mediated by Graphene Surface Plasmons

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    We demonstrate that the interaction between two emitters can be controlled by means of the efficient excitation of surface plasmon modes in graphene. We consider graphene surface plasmons supported by either two-dimensional graphene sheets or one-dimensional graphene ribbons, showing in both cases that the coupling between the emitters can be strongly enhanced or suppressed. The super- and subradiant regimes are investigated in the reflection and transmission configurations. Importantly, the length scale of the coupling between emitters, which in vacuum is fixed by the free space wavelength, is now determined by the wavelength of the graphene surface plasmons that can be extremely short and be tuned at will via a gate voltage

    Suppressing Recoil Heating in Levitated Optomechanics using Squeezed Light

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    We theoretically show that laser recoil heating in free-space levitated optomechanics can be arbitrarily suppressed by shining squeezed light onto an optically trapped nanoparticle. The presence of squeezing modifies the quantum electrodynamical light-matter interaction in a way that enables us to control the amount of information that the scattered light carries about a given mechanical degree of freedom. Moreover, we analyze the trade-off between measurement imprecision and back-action noise and show that optical detection beyond the standard quantum limit can be achieved. We predict that, with state-of-the-art squeezed light sources, laser recoil heating can be reduced by at least 60% by squeezing a single Gaussian mode with an appropriate incidence direction, and by 98% by squeezing a properly mode-matched mode. Our results, which are valid both for motional and librational degrees of freedom, will lead to improved feedback cooling schemes as well as boost the coherence time of optically levitated nanoparticles in the quantum regime.Comment: 16 pages, 5 figure

    Selecting cash management models from a multiobjective perspective

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    [EN] This paper addresses the problem of selecting cash management models under different operating conditions from a multiobjective perspective considering not only cost but also risk. A number of models have been proposed to optimize corporate cash management policies. The impact on model performance of different operating conditions becomes an important issue. Here, we provide a range of visual and quantitative tools imported from Receiver Operating Characteristic (ROC) analysis. More precisely, we show the utility of ROC analysis from a triple perspective as a tool for: (1) showing model performance; (2) choosingmodels; and (3) assessing the impact of operating conditions on model performance. We illustrate the selection of cash management models by means of a numerical example.Work partially funded by projects Collectiveware TIN2015-66863-C2-1-R (MINECO/FEDER) and 2014 SGR 118.Salas-Molina, F.; Rodríguez-Aguilar, JA.; Díaz-García, P. (2018). 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