Poo Power: Revisiting Biogas Generation Potential on Dairy Farms in Texas

Biogas created from anaerobic digestion on dairy farms can be used to generate electricity, produce coproducts, and reduce reliance on off-farm inputs. We incorporate risk into simulation models representing dairy farms in Texas and demonstrate the profitability of new anaerobic digester installation. Based on this market, results indicate projects that have low investment costs, receive grant support for construction, utilize coproducts, or have some combination of these factors have higher net present value at the end of the study period; however, even with generous grant support and high electricity prices, projects with average investment costs remain unprofitable

Usos actuales de los SIG para la ingeniería civil en Colombia

This document presents and reviews the GIS (Geographic Information System) in Colombia and its possible current uses in civil engineering. Since a model with georeferenced graphic elements (maps) with additional information associated with a database is a very complete design tool, it facilitates engineering analysis to carry out effective construction projects.Este documento presenta y reseña los SIG (Sistema de Información Geográfica) en Colombia y sus posibles usos actuales en la ingeniería civil. Ya que un modelo con elementos gráficos geo referenciados (mapas) que cuenta con información adicional asociada a una base de datos conforma una herramienta de diseño muy completa, la misma facilita a la ingeniería la realización de análisis con el fin de realizar proyectos constructivos efectivos

On the genesis of the Haumea system

The scenarios proposed in the literature for the genesis of the system formed by the dwarf planet 136108 Haumea, its two satellites and a group of some 10 bodies (the family) with semimajor axes, eccentricities and inclinations close to Haumea's values, are analysed against collisional, physical, dynamical and statistical arguments in order to assess their likelihood. All scenarios based on collisional events are reviewed under physical arguments and the corresponding formation probabilities in a collisional environment are evaluated according to the collisional evolution model alicandep. An alternative mechanism is proposed based on the potential possibility of (quasi-) independent origin of the family with respect to Haumea and its satellites. As a general conclusion the formation of the Haumea system is a low-probability event in the currently assumed frame for the evolution of the outer Solar system. However, it is possible that current knowledge is missing some key element in the whole story that may contribute to increase the odds for the formation of such a system.Facultad de Ciencias Astronómicas y Geofísica

The CFEPS Kuiper Belt Survey: Strategy and Pre-survey Results

We present the data acquisition strategy and characterization procedures for the Canada-France Ecliptic Plane Survey (CFEPS), a sub-component of the Canada-France-Hawaii Telescope Legacy Survey. The survey began in early 2003 and as of summer 2005 has covered 430 square degrees of sky within a few degrees of the ecliptic. Moving objects beyond the orbit of Uranus are detected to a magnitude limit of $m_R$=23 -- 24 (depending on the image quality). To track as large a sample as possible and avoid introducing followup bias, we have developed a multi-epoch observing strategy that is spread over several years. We present the evolution of the uncertainties in ephemeris position and orbital elements as the objects progress through the epochs. We then present a small 10-object sample that was tracked in this manner as part of a preliminary survey starting a year before the main CFEPS project. We describe the CFEPS survey simulator, to be released in 2006, which allows theoretical models of the Kuiper Belt to be compared with the survey discoveries since CFEPS has a well-documented pointing history with characterized detection efficiencies as a function of magnitude and rate of motion on the sky. Using the pre-survey objects we illustrate the usage of the simulator in modeling the classical Kuiper Belt.Comment: to be submitted to Icaru

A mid-term astrometric and photometric study of Trans-Neptunian Object (90482) Orcus

From CCD observations of a fixed and large star field that contained the binary TNO Orcus, we have been able to derive high-precision relative astrometry and photometry of the Orcus system with respect to background stars. The RA residuals of an orbital fit to the astrometric data revealed a periodicity of 9.7+-0.3 days, which is what one would expect to be induced by the known Orcus companion. The residuals are also correlated with the theoretical positions of the satellite with regard to the primary. We therefore have revealed the presence of Orcus' satellite in our astrometric measurements. The photocenter motion is much larger than the motion of Orcus around the barycenter, and we show here that detecting some binaries through a carefully devised astrometric technique might be feasible with telescopes of moderate size. We also analyzed the system's mid-term photometry to determine whether the rotation could be tidally locked to the satellite's orbital period. We found that a photometric variability of 9.7+-0.3 days is clear in our data, and is nearly coincident with the orbital period of the satellite. We believe this variability might be induced by the satellite's rotation. There is also a slight hint for an additional small variability in the 10 hr range that was already reported in the literature. This short-term variability would indicate that the primary is not tidally locked and therefore the system would not have reached a double synchronous state. Implications for the basic physical properties of the primary and its satellite are discussed. From angular momentum considerations we suspect that the Orcus satellite might have formed from a rotational fission. This requires that the mass of the satellite would be around 0.09 times that of the primary, close to the value that one derives by using an albedo of 0.12 for the satellite and assuming equal densities for both objects.Comment: in Press at A&

Short-term variability of a sample of 29 trans-Neptunian objects and Centaurs

We present results of 6 years of observations, reduced and analyzed with the same tools in a systematic way. We report completely new data for 15 objects, for 5 objects we present a new analysis of previously published results plus additional data and for 9 objects we present a new analysis of data already published. Lightcurves, possible rotation periods and photometric amplitudes are reported for all of them. The photometric variability is smaller than previously thought: the mean amplitude of our sample is 0.1mag and only around 15% of our sample has a larger variability than 0.15mag. The smaller variability than previously thought seems to be a bias of previous observations. We find a very weak trend of faster spinning objects towards smaller sizes, which appears to be consistent with the fact that the smaller objects are more collisionally evolved, but could also be a specific feature of the Centaurs, the smallest objects in our sample. We also find that the smaller the objects, the larger their amplitude, which is also consistent with the idea that small objects are more collisionally evolved and thus more deformed. Average rotation rates from our work are 7.5h for the whole sample, 7.6h for the TNOs alone and 7.3h for the Centaurs. All of them appear to be somewhat faster than what one can derive from a compilation of the scientific literature and our own results. Maxwellian fits to the rotation rate distribution give mean values of 7.5h (for the whole sample) and 7.3h (for the TNOs only). Assuming hydrostatic equilibrium we can determine densities from our sample under the additional assumption that the lightcurves are dominated by shape effects, which is likely not realistic. The resulting average density is 0.92g/cm^3 which is not far from the density constraint that one can derive from the apparent spin barrier that we observe.Comment: Accepted for publication in A&

Novel Automation of an Enzyme-Linked Immunosorbent Spot Assay Testing Method: Comparable Diagnostic Performance of the T-SPOT.TB Test Using Manual Density Gradient Cell Isolation versus Automated Positive Selection with the T-Cell Select Kit

The diagnosis of latent tuberculosis (TB) infection (LTBI) is critical to improve TB treatment and control, and the T-SPOT.TB test is a commercial enzyme-linked immunosorbent spot assay used for this purpose. The objective of the study was to increase automation and extend the time between blood collection and processing for the T-SPOT.TB test from 0 to 8 h to 0 to 54 h. The previous maximum time between blood collection and processing for the T-SPOT.TB test is 32 h using T-Cell Xtend. For this, we compared the T-SPOT.TB test using manual peripheral blood mononuclear cell (PBMC) isolation by density gradient separation at 0 to 8 h (reference method, control arm) to an automated PBMC isolation method using magnetic beads (T-Cell Select kit) at 0 to 55 h postcollection. A total of 620 subjects were enrolled from 4 study sites, and blood samples were collected from each volunteer, comprising 1,850 paired samples in total. Overall agreement between both methods was 96.8% (confidence interval [CI], 95.9 to 97.6%), with 95.8% (CI, 93.5 to 97.5%) positive and 97.1% negative agreement (CI, 96.1 to 97.9%). In summary, there was a strong overall agreement between the automated and manual T-SPOT.TB test processing methods. The results suggest that the T-SPOT.TB test can be processed using automated positive selection with magnetic beads using T-Cell Select to decrease hands-on time. Also, this cell isolation method allowed for the time between blood collection and processing to range from 0 to 55 h. Additional studies in larger and diverse patient populations including immunocompromised and pediatric patients are needed

Rotational fission of Trans-Neptunian Objects. The case of Haumea

We present several lines of evidence based on different kinds of observations to conclude that rotational fission has likely occurred for a fraction of the known Trans-Neptunian Objects (TNOs). It is also likely that a number of binary systems have formed from that process in the trans-neptunian belt. We show that Haumea is a potential example of an object that has suffered a rotational fission. Its current fast spin would be a slight evolution of a primordial fast spin, rather than the result of a catastrophic collision, because the percentage of objects rotating faster than 4 hours would not be small in a maxwellian distribution of spin rates that fits the current TNO rotation database. On the other hand, the specific total angular momentum of Haumea and its satellites falls close to that of the high size ratio asteroid binaries, which are thought to be the result of rotational fissions or mass shedding. We also present N-body simulations of rotational fissions applied to the case of Haumea, which show that this process is feasible, might have generated satellites, and might have even created a "family" of bodies orbitally associated to Haumea. The orbitally associated bodies may come from the direct ejection of fragments according to our simulations, or through the evolution of a proto-satellite formed during the fission event. Also, the disruption of an escaped fragment after the fission might create the orbitally related bodies. If any of those mechanisms are correct, other rotational fission families may be detectable in the trans-neptunian belt in the future, and perhaps even TNO pairs might be found (pairs of bodies sharing very similar orbital elements, but not bound together)

Anatomic alterations and prevalence of high myopia

El objetivo de esta revisión fue describir las alteraciones anatómicas características del ojo con miopía alta e identificar la prevalencia de esta condición en diferentes poblaciones. La miopía alta se caracteriza por el alargamiento del globo ocular. La elongación del polo posterior causa complicaciones en la esclera, la coroides y la retina, y amenaza la visión central, por lo que es causa importante de baja visión y ceguera prevenible en el mundo. El continente con mayor prevalencia de miopía alta es Asia, por lo que la raza se considera un factor importante. La revisión realizada indica que existen diferencias en la definición de miopía alta que utilizan los estudios, así como en el método que aplican para la medición refractiva y para la clasificación patológica.The purpose of this review was to describe the characteristic anatomic alterations in the eye with high myopia and to identify the prevalence of this condition in different populations. High myopia is characterized by elongation of the eyeball. The elongation of the posterior pole causes complications in the sclera, choroid and retina, and threatens central vision, which is why it is an important cause of low vision and preventable blindness in the world. Asia is the continent with the highest prevalence of high myopia; therefore, race is considered an important factor. This review indicates that there are differences in the definition of high myopia between studies, as well as in the method used for refractive measurement and for pathological classification