Detecting the Attenuation of Blazar Gamma-ray Emission by Extragalactic Background Light with GLAST

Gamma rays with energy above 10 GeV interact with optical-UV photons resulting in pair production. Therefore, a large sample of high redshift sources of these gamma rays can be used to probe the extragalactic background starlight (EBL) by examining the redshift dependence of the attenuation of the flux above 10 GeV. GLAST, the next generation high-energy gamma-ray telescope, will have the unique capability to detect thousands of gamma-ray blazars to redshifts of at least z=4, with sufficient angular resolution to allow identification of a large fraction of their optical counterparts. By combining established models of the gamma-ray blazar luminosity function, two different calculations of the high energy gamma-ray opacity due to EBL absorption, and the expected GLAST instrument performance to produce simulated fluxes and redshifts for the blazars that GLAST would detect, we demonstrate that these gamma-ray blazars have the potential to be a highly effective probe of the optical-UV EBL.Comment: 15 pages, AASTeX, 3 eps figures, accepted for publication in Ap

Visualizing evolution in real-time method for strain engineering

The adaptive landscape for an industrially relevant phenotype is determined by the effects of the genetic determinants on the fitness of the microbial system. Identifying the underlying adaptive landscape for a particular phenotype of interest will greatly enhance our abilities to engineer more robust microbial strains. Visualizing evolution in real-time (VERT) is a recently developed method based on in vitro adaptive evolution that facilitates the identification of fitter mutants throughout the course of evolution. Combined with high-throughput genomic tools, VERT can greatly enhance the mapping of adaptive landscapes of industrially relevant phenotypes in microbial systems, thereby expanding our knowledge on the parameters that can be used for strain engineering

Detecting the EBL Attenuation of Blazars with GLAST

The Large Area Telescope (LAT) on board GLAST (Gamma-ray Large Area Space Telescope) due for launch in late 2007 will study the gamma-ray sky in the energy range 20 MeV to >300 GeV. GLAST-LAT's improved sensitivity with respect to previous missions will increase the number of known gamma-ray blazars from about 100 to thousands, with redshifts up to z~3-5. Since gamma rays with energy above 10 GeV interact via pair-production with photons from the Extragalactic Background Light (EBL), the systematic attenuation of GLAST-detected blazars as a function of redshift would constitute and effective and unique probe of the optical-UV EBL density and its evolution over cosmic history. Analysis techniques introduced in this dissertation make use of the large number of blazars detected by GLAST to study the collective behavior of their spectra as a function of redshift. These techniques are shown to offer powerful ways to help separate the common level of attenuation due to the EBL from the intrinsic peculiarities of individual blazars. The capability of GLAST to perform these measurements depends in great measure on the acceptance of the instrument to high energy photons (E > 10 GeV), which in previous space-experiments has been drastically reduced due to backsplash self-veto. This dissertation includes a study of the backsplash effect as measured with flight-like detectors during a beam test of the LAT calibration unit. This analysis was used to verify the capabilities of the GLAST simulations tools to reproduce backsplash effects

Silicon increased the growth, productivity, and nutraceutical quality of tomato (Solanum lycopersicum L.)

Tomato (Solanum lycopersicum L.) is considered one of the most important horticultural crops worldwide due to its nutritional and organoleptic properties. Instead of chemical fertilizers, recent research has shown in several plant species the importance of silicon fertilization. Hence, the present investigation aims to evaluate the effect of three different doses (low, medium, and high dose) of silicon on the growth (stem length and diameter, root length diameter, and stem, leaf and root biomass), productivity (polar and equatorial fruit diameter, number of fruits per bunch and plant, and yield), and nutraceutical quality (total soluble solids, titratable acids, and vitamin C) parameters of tomato. The Si treatment affected the evaluated parameters in a dose dependent way in almost all the parameters evaluated. Despite the tomato is classified as a non-Si accumulator, it has a significant response to Si treatment at a low dose of 0.15 g plant-1, medium dose of 0.25 g plant-1, and high dose of 0.35 g plant-1 after 120 d of transplantation in terms of plant growth, yield, and quality parameters. The effectiveness of Si nutrition is dependent on factors such as element source, plant species, and cultivar, and even, the absorption and bioaccumulation capacity of this element could be different between varieties

Relación entre antecedentes heredofamiliares de Diabetes Mellitus con la presencia de manifestaciones clínicas de resistencia a la insulina (acantosis nigricans)

To establish the relationship between hereditary family history and the presence of acanthosis nigricans (AN) in order to determine its possible influence on the development of Type 2 Diabetes Mellitus. Material and methods: an analytical, observational, cross-sectional study was carried out. . The study population consisted of 40 patients between 18 and 25 years of age treated in the outpatient clinic of the General Hospital of Minatitlán and General Hospital of Oluta who presented Acanthosis Nigricans. Results: The prevalence of AN was 25%, with a female predominance of 88.8%. The most frequent site where it occurred was the neck with 50%. The prevalence of hereditary family history was 83%. AN is a factor associated with a family history of Diabetes Mellitus. (p<0.05). It was found that there is a relationship between family history of diabetes mellitus and the presence of clinical manifestations of insulin resistance (acanthosis nigricans) in patients at the General Hospital of Minatitlán and the General Hospital of Oluta, Veracruz.Establecer la relación de los antecedentes heredo familiares con la presencia de acantosis nigricans (AN) con el objetivo de determinar su posible influencia en el desarrollo de Diabetes Mellitus Tipo 2. Material y métodos: se llevó a cabo un estudio analítico, observacional, seccional transversal. La población de estudio estuvo constituida por 40 pacientes de 18 a 25 años de edad atendidos en la consulta externa del Hospital General de Minatitlán y Hospital General de Oluta que presentaran Acantosis Nigricans. Resultados: La prevalencia de AN fue de 25%, con una predominancia del género femenino de un 88.8%. El sitio más frecuente donde se presentó fue el cuello con un 50%. La prevalencia de antecedentes heredofamiliares fue de un 83%. La AN es factor asociado a antecedentes heredofamiliares de Diabetes Mellitus. (p<0.05). Se comprobó que existe relación entre antecedentes heredofamiliares de diabetes mellitus con la presencia de manifestaciones clínicas de resistencia a la insulina (acantosis nigricans) en pacientes del Hospital General de Minatitlán y el Hospital General de Oluta, Veracruz

Physiological Responses of Species to Microclimate Help explain Population Dynamics along Succession in a Tropical Dry Forest of Yucatan, Mexico

We investigated relationships between population dynamics and microclimate, physiology, and the degree of mycorrhizal colonization, for three species (Piscidia piscipula L.(Sarg.)) (Fabaceae), Bunchosia swartzianaGriseb. (Malpighiaceae) and Psidium sartorianum (Bergius) Nied. (Myrtaceae)) of a tropical sub deciduous forest in Yucatan, Mexico that were growing in plots of different successional ages. We hypothesized that abundance and persistence were related to increased plasticity in CO2assimilation. We found that Piscidia piscipula had greater abundance in intermediate plots (18 to 21 years), presented higher levels of plasticity in CO2 assimilation (greater variability among individuals, plots, and seasons), presented the highest CO2 assimilation rates, and presented greater drought resistance (higher water potentials and capacitance). Conversely, Psidium sartorianum had greater abundance in older plots (more than 50 years of secondary succession), lower assimilation rates, and low levels of plasticity in CO2 assimilation. Bunchosia had intermediate values. Locally, the degree of mycorrhizal colonization was consistent with abundance across plots. Regionally (but not locally), plasticity in CO2 assimilation was consistent with abundance. We found differences in microclimates among plots and within plots among species. Physiological adjustments appeared to play an important role in the capacity to regenerate and in the successional persistence of these species in this tropical dry forest

Surface Screening in the Casimir Force

We calculate the corrections to the Casimir force between two metals due to the spatial dispersion of their response functions. We employ model-independent expressions for the force in terms of the optical coefficients. We express the non-local corrections to the Fresnel coefficients employing the surface $d_\perp$ parameter, which accounts for the distribution of the surface screening charge. Within a self-consistent jellium calculation, spatial dispersion increases the Casimir force significatively for small separations. The nonlocal correction has the opposite sign than previously predicted employing hydrodynamic models and assuming abruptly terminated surfaces.Comment: 5 pages, 2 figure

Functional Diversity of Small and Large Trees Along Secondary Succession in a Tropical Dry Forest

Functional Diversity is considered an important driver of community assembly in environmental and successional gradients. To understand tree assembly processes in a semideciduous tropical forest, we analyzed the variation of Functional Richness (FRic), Functional Divergence (FDiv), and Functional Evenness (FEve) of small vs. large trees in relation to fallow age after slash-and-burn agriculture and topographical position (flat sites vs. hills). FRic of small trees was lower than null model predicted values across the successional gradient, and decreased unexpectedly in older successional ages. FRic of large trees was higher than null model predictions early in succession and lower in late-successional stands on hills. Dominant species were more similar (low FDiv) in early and intermediate successional stands for small trees, and on hills for large trees, suggesting that species that are best adapted to harsh conditions share similar traits. We also found evidence of competitive exclusion among similar species (high FEve) for small trees in early successional stands. Overall, our results indicate that community assembly of small trees is strongly affected by the changing biotic and abiotic conditions along the successional and topographical gradient. For large trees, hills may represent the most stressful conditions in this landscape