Astrometric Effects of a Stochastic Gravitational Wave Background

A stochastic gravitational wave background causes the apparent positions of distant sources to fluctuate, with angular deflections of order the characteristic strain amplitude of the gravitational waves. These fluctuations may be detectable with high precision astrometry, as first suggested by Braginsky et al. in 1990. Several researchers have made order of magnitude estimates of the upper limits obtainable on the gravitational wave spectrum \Omega_gw(f), at frequencies of order f ~ 1 yr^-1, both for the future space-based optical interferometry missions GAIA and SIM, and for VLBI interferometry in radio wavelengths with the SKA. For GAIA, tracking N ~ 10^6 quasars over a time of T ~ 1 yr with an angular accuracy of \Delta \theta ~ 10 \mu as would yield a sensitivity level of \Omega_gw ~ (\Delta \theta)^2/(N T^2 H_0^2) ~ 10^-6, which would be comparable with pulsar timing. In this paper we take a first step toward firming up these estimates by computing in detail the statistical properties of the angular deflections caused by a stochastic background. We compute analytically the two point correlation function of the deflections on the sphere, and the spectrum as a function of frequency and angular scale. The fluctuations are concentrated at low frequencies (for a scale invariant stochastic background), and at large angular scales, starting with the quadrupole. The magnetic-type and electric-type pieces of the fluctuations have equal amounts of power.Comment: 23 pages, 2 figures, references added and minor text correction

Redox-Active Nanomaterials For Nanomedicine Applications

Nanomedicine utilizes the remarkable properties of nanomaterials for the diagnosis, treatment, and prevention of disease. Many of these nanomaterials have been shown to have robust antioxidative properties, potentially functioning as strong scavengers of reactive oxygen species. Conversely, several nanomaterials have also been shown to promote the generation of reactive oxygen species, which may precipitate the onset of oxidative stress, a state that is thought to contribute to the development of a variety of adverse conditions. As such, the impacts of nanomaterials on biological entities are often associated with and influenced by their specific redox properties. In this review, we overview several classes of nanomaterials that have been or projected to be used across a wide range of biomedical applications, with discussion focusing on their unique redox properties. Nanomaterials examined include iron, cerium, and titanium metal oxide nanoparticles, gold, silver, and selenium nanoparticles, and various nanoscale carbon allotropes such as graphene, carbon nanotubes, fullerenes, and their derivatives/variations. Principal topics of discussion include the chemical mechanisms by which the nanomaterials directly interact with biological entities and the biological cascades that are thus indirectly impacted. Selected case studies highlighting the redox properties of nanomaterials and how they affect biological responses are used to exemplify the biologically-relevant redox mechanisms for each of the described nanomaterials

Mercados Informales y Control Vertical: Comercialización de Pesca Artesanal Perecible

This paper offers an in-depth case study analysis about institutional changes occurring since the late 1990s at the Chilean Austral Hake artisanal fishery. This high-value exporting fishery, specialized on selling fresh-chilled products, represents a pioneering example of self-government developments within artisanal fishermen's communities exploiting mobile marine resources in Chile. Despite entry restrictions and global catch quotas, this fishery faced a productivity crisis from the late 1980s up to the second half of the 1990s. As a response to this, fishermen initiated talks with the Government in order to introduce new management rules. After gradual evolution, today there prevails a well-developed system of de facto individual non-transferable quotas subject to a high degree of self-management by fishermen organizations. We discuss industrial organization issues which condition the exchange solutions found at this fishery. In particular, we discuss incentives derived from industrial concentration and buyer power, vertical integration and other strategies of vertical control between transacting parties at this industry; namely, between wholesale marketing brokers, exporters, processors, direct buyers of the catch and fishermen. Contractual issues of relevancy are: the use of informal markets; multi-dimensional contracting; temporal specificity due to product perishability; the use of different instruments for vertical control; and the influence of increasing degrees of industrial concentration as we advance through the wholesale commercialization channel, moving closer to the retailing stages at final export markets.Producción y comercialización de Alimentos; Cadenas de producción; Control y Coordinación Vertical; Pesca Artesanal en Chile; Merluza Austral.

Thirty Meter Telescope Site Testing I: Overview

As part of the conceptual and preliminary design processes of the Thirty Meter Telescope (TMT), the TMT site testing team has spent the last five years measuring the atmospheric properties of five candidate mountains in North and South America with an unprecedented array of instrumentation. The site testing period was preceded by several years of analyses selecting the five candidates, Cerros Tolar, Armazones and Tolonchar in northern Chile; San Pedro Martir in Baja California, Mexico and the 13 North (13N) site on Mauna Kea, Hawaii. Site testing was concluded by the selection of two remaining sites for further consideration, Armazones and Mauna Kea 13N. It showed that all five candidates are excellent sites for an extremely large astronomical observatory and that none of the sites stands out as the obvious and only logical choice based on its combined properties. This is the first article in a series discussing the TMT site testing project.Comment: Accepted for publication in PASP, April 2009 issu

Design, navigation, and structure of a hypermedia application for the teaching–learning of pneumatic engineering design drawing

This article presents a hypermedia application used to study pneumatics that serves to support the lecturer in the lecture hall and as a self-study tool for the student. The reason behind the creation of this application is as follows: currently, there is no application in the market, which is equipped with a navigational system to guide the student through this subject matter, which has a system for self-assessment, and a system to identify those concepts that are of greatest interest or difficulty for the student. The proposed system monitors the time each user spends studying each section, as well as the dates on which each one was studied. Moreover, students are able to monitor their progress in learning the subject matter and identify those areas in which they have to improve. They are also able to simulate any pneumatic circuit in order to check its feasibility or detect any errors. The application has an open, modular structure, which enables changes to be made without its structure being affected. Use of the hypermedia application has supported the tutorial work of lecturers and reduced time spent elaborating on subject matter in the lecture hall, at the same time as facilitating its study

Prevalencia serológica de tenosinovitis infecciosa (artritis viral) en los principales planteles de reproducción avícola del país.

Para determinar la prevalencia serológica de la artritis viral o tenosinovitis infecciosa, se estudiaron mediante la prueba de difusión doble en agar, un total de 19 planteles avícolas de reproducción (95 por ciento) ubicados en 6 departamentos. Los antígenos y sueros utilizados fueron suministrados por los laboratorios Sterwin Millsboro (Delaware, Canadá), las muestras fueron seleccionadas por la aplicación de un modelo aleatorio simple. Se encontró evidencia serológica para la enfermedad en 17 de los 19 planteles estudiados (89.5 por ciento), determinándose que la prevalencia es del 25,40 por ciento y que se encuentra dentro de un intervalo de confianza no mayor del 30,48 por ciento, o que estaría entre 20,32 por ciento y 25,40 por ciento. Los resultados sugieren la presencia de la enfermedad o bien del contacto de los animales con antígeno vacunal o con otras vacunas aviares contaminadas con el agente. Se sugieren futuras medidas para la prevención y control y se recomiendan otros estudios sobre la mismaAvicultur

Implications of the Cosmic Background Imager Polarization Data

We present new measurements of the power spectra of the E-mode of CMB polarization, the temperature T, the cross-correlation of E and T, and upper limits on the B-mode from 2.5 years of dedicated Cosmic Background Imager (CBI) observations. Both raw maps and optimal signal images in the uv-plane and real space show strong detections of the E-mode (11.7 sigma for the EE power spectrum overall) and no detection of the B-mode. The power spectra are used to constrain parameters of the flat tilted adiabatic Lambda-CDM models: those determined from EE and TE bandpowers agree with those from TT, a powerful consistency check. There is little tolerance for shifting polarization peaks from the TT-forecast locations, as measured by the angular sound crossing scale theta = 100 ell_s = 1.03 +/- 0.02 from EE and TE cf. 1.044 +/- 0.005 with the TT data included. The scope for extra out-of-phase peaks from subdominant isocurvature modes is also curtailed. The EE and TE measurements of CBI, DASI and BOOMERANG are mutually consistent, and, taken together rather than singly, give enhanced leverage for these tests.Comment: 15 pages, 9 figures, submitted to ApJ -- Accepted version. The fine-bin spectrum, covariance matrix, and window functions are now available on the web (suitable for use in COSMOMC) at: http://www.astro.caltech.edu/~tjp/CBI/data2006/index.html The pipeline in the previous version inadvertently omitted one antenna, so the new spectrum contains ~15% more data. We emphasize that previous results were in no way biased, and that the (small) changes to the spectrum solely reflect the inclusion of the additional data. Numbers and figures in the paper have been updated correspondingly. All maps now have color bar

Prevalencia serológica de la bursitis viral o enfermedad de gumboro en un plantel de pavos de reproducción.

Se estudió la prevalencia serológica de la bursitis viral (enfermedad de gumboro) en un plantel de pavos de reproducción localizados en el Departamento de Cundinamarca, mediante la prueba de precipitación doble en agar, los antígenos utilizados fueron enviados por el laboratorio de Weybridge (Inglaterra). Los sueros a examinar fueron obtenidos al azar y el tamaño de la muestra se obtuvo por la aplicación de un modelo binomial. No se encontró evidencia serológica para la enfermedad en el plantel en estudio (p menor que 0,05), lo que indica que los animales no han estado en contacto con el virus causal. Se sugieren medidas para la prevención de la enfermedad y se recomienda realizar otros estudiosAvicultur

The wideband backend at the MDSCC in Robledo. A new facility for radio astronomy at Q- and K- bands

The antennas of NASA's Madrid Deep Space Communications Complex (MDSCC) in Robledo de Chavela are available as single-dish radio astronomical facilities during a significant percentage of their operational time. Current instrumentation includes two antennas of 70 and 34 m in diameter, equipped with dual-polarization receivers in K (18 - 26 GHz) and Q (38 - 50 GHz) bands, respectively. We have developed and built a new wideband backend for the Robledo antennas, with the objectives (1) to optimize the available time and enhance the efficiency of radio astronomy in MDSCC; and (2) to tackle new scientific cases impossible to that were investigated with the old, narrow-band autocorrelator. The backend consists of an IF processor, a FFT spectrometer (FFTS), and the software that interfaces and manages the events among the observing program, antenna control, the IF processor, the FFTS operation, and data recording. The whole system was end-to-end assembled in August 2011, at the start of commissioning activities, and the results are reported in this paper. Frequency tunings and line intensities are stable over hours, even when using different synthesizers and IF channels; no aliasing effects have been measured, and the rejection of the image sideband was characterized. The first setup provides 1.5 GHz of instantaneous bandwidth in a single polarization, using 8192 channels and a frequency resolution of 212 kHz; upgrades under way include a second FFTS card, and two high-resolution cores providing 100 MHz and 500 MHz of bandwidth, and 16384 channels. These upgrades will permit simultaneous observations of the two polarizations with instantaneous bandwidths from 100 MHz to 3 GHz, and spectral resolutions from 7 to 212 kHz.Comment: 9 pages, 8 figures. Accepted to Astronomy and Astrophysic