Patents and Competition in the Automobile Industry

Methane (CH4) fluxes from world rivers are still poorly constrained, with measurements restricted mainly to temperate climates. Additional river flux measurements, including spatio-temporal studies, are important to refine extrapolations. Here we assess the spatio-temporal variability of CH4 fluxes from the Amazon and its main tributaries, the Negro, Solimoes, Madeira, Tapajos, Xingu, and Para Rivers, based on direct measurements using floating chambers. Sixteen of 34 sites were measured during low and high water seasons. Significant differences were observed within sites in the same river and among different rivers, types of rivers, and seasons. Ebullition contributed to more than 50% of total emissions for some rivers. Considering only river channels, our data indicate that large rivers in the Amazon Basin release between 0.40 and 0.58 Tg CH4 yr(-1). Thus, our estimates of CH4 flux from all tropical rivers and rivers globally were, respectively, 19-51% to 31-84% higher than previous estimates, with large rivers of the Amazon accounting for 22-28% of global river CH4 emissions.Funding Agencies|FAPESP [08/58089-9, 2011/06609-1, 2011/14502-2, 2012/17359-9]</p

Enhancing the Design and Consistency of an α-particle Irradiator for In Vitro Experiments

https://openworks.mdanderson.org/sumexp23/1033/thumbnail.jp

Combination of ATR Inhibition and X-Ray Irradiation Radiosensitizes Cancer Cells

https://openworks.mdanderson.org/sumexp21/1250/thumbnail.jp

Characterization and Modeling of Relative Luminescence Efficiency of Optically Stimulated Luminescence Detectors Exposed to Heavy Charged Particles

This work investigates the optically stimulated luminescence (OSL) response of carbon-doped aluminum oxide Al 2 O 3 :C detectors exposed to heavy charged particles (HCPs) with energies relevant to radiation protection in space, and cancer therapy. This investigation includes ground-based experiments in accelerators and theoretical studies of the detector's response. These theoretical studies are based on the track structure model (TSM) and require information of the spatial pattern of energy deposition around the HCP path - the radial dose distribution (RDD). Thus, RDDs were obtained using six analytical models, and Monte Carlo (MC) simulations with the code GEANT4. In addition, we propose a modified analytical model to improve the agreement between calculated and experimental efficiency values.Findings and Conclusions: Dose response experiments showed that beta rays and H 1000 MeV radiations produced similar responses in the detectors and we concluded that the H 1000 MeV and beta radiations deposit energy similarly. We observed a common trend of decreasing the relative luminescence efficiency as increasing the unrestricted linear energy transfer in water (LET in water) for all the detectors. For Luxel TM detectors the relative luminescence efficiency was close to unit for particles with LET in water lower than 3 keV/micrometer. TSM using the RDD from Chatterjee and Schaefer, Butts and Katz, Waligorski et al. , Fageeha et al. , Kiefer and Straaten, and Geiss et al. models failed to predict the relative luminescence efficiency values. We proposed a modified version of the RDD from Butts and Katz model, which agreed within 20 % with relative luminescence efficiency experimental data. This was the first time that such agreement was achieved for a wide range of HCPs of different energies. MC simulations with GEANT4 agreed within 35 % with relative luminescence efficiency experimental data. Finally, we suggested a correction method, based on the calculation of the relative luminescence efficiency using the TSM presented in this dissertation, to measure more reliable absorbed doses when using luminescence detectors in complex radiation fields.Department of Physic

Enhancing Anti-Tumor Immunity through High-LET Radiation and Immunotherapy

https://openworks.mdanderson.org/sumexp22/1040/thumbnail.jp

Enhanced Aquatic Respiration Associated With Mixing of Clearwater Tributary and Turbid Amazon River Waters

When water bodies with unique biogeochemical constituents mix together there is potential for diverse responses by aquatic microbial communities and associated ecosystem functions. Here we evaluate bulk respiration under varying mixtures of turbid Amazon River water and two lowland tributaries—the Tapajós and Xingu rivers—based on O2 drawdown in dark rotating incubation chambers. Experiments containing 5, 17, 33, and 50% tributary water mixed with Amazon River water were performed for the Tapajós and Xingu rivers at three different rotation velocities (0, 0.22, and 0.66 m s−1) during the falling water period. Pseudo first order reaction coefficients (k′), a measure of respiration potential, ranged from −0.15 to −1.10 d−1, corresponding to respiration rates from 1.0 to 8.1 mg O2 L d−1. k′-values consistently increased with the rate of chamber rotation, and also was generally higher in the tributary-mainstem mixtures compared to pure endmembers. For both the Tapajós and Xingu rivers, the 17% mixture of tributary water yielded maximal k′-values, which were up to 2.9 and 2.2 times greater than in the tributary endmembers, respectively. The 50% mixtures, on the other hand, did not result in large increases in k′. We hypothesize that enhanced respiration potential after mixing unique water is driven, in part, by microbial priming effects that have been previously identified on a molecular level for these rivers. The results of this study suggest that there may be an optimal mixture for priming effects to occur in terms of the relative abundance of “priming” and “primed” substrates

Is proton radiation more effective than photon radiation at inducing senescence?

https://openworks.mdanderson.org/sumexp21/1158/thumbnail.jp

Terrigenous input off northern South America driven by changes in Amazonian climate and the North Brazil Current retroflection during the last 250 ka

We investigate changes in the delivery and oceanic transport of Amazon sediments related to terrestrial climate variations over the last 250 ka. We present high-resolution geochemical records from four marine sediment cores located between 5 and 12° N a

The Fate of Carbon in Sediments of the Xingu and Tapajós Clearwater Rivers, Eastern Amazon

The Xingu and Tapajós rivers in the eastern Amazon are the largest clearwater systems of the Amazon basin. Both rivers have “fluvial rias” (i.e., lake-like channels) in their downstream reaches as they are naturally impounded by the Amazon mainstem. Fluvial rias are widespread in the Amazon landscape and most of the sedimentary load from the major clearwater and blackwater rivers is deposited in these channels. So far, little is known about the role of Amazon rias as a trap and reactor for organic sediments. In this study, we used organic and inorganic geochemistry, magnetic susceptibility, diatom, and pollen analyses in sediments (suspended, riverbed, and downcore) of the Xingu and Tapajós rias to investigate the effects of hydrologic variations on the carbon budget in these clearwater rivers over the Holocene. Ages of sediment deposition (~100 to 5,500 years) were constrained by optically stimulated luminescence and radiocarbon. Major elements geochemistry and concentration of total organic carbon (TOC) indicate that seasonal hydrologic variations exert a strong influence on riverine productivity and on the input and preservation of organic matter in sediments. Stable carbon isotope data (δ13C from −31.04 to −27.49‰) and pollen analysis indicate that most of the carbon buried in rias is derived from forests. In the Xingu River, diatom analysis in bottom sediments revealed 65 infrageneric taxa that are mostly well-adapted to slack oligotrophic and acidic waters. TOC values in sediment cores are similar to values measured in riverbed sediments and indicate suitable conditions for organic matter preservation in sediments of the Xingu and Tapajós rias at least since the mid-Holocene, with carbon burial rates varying from about 84 g m−2 yr−1 to 169 g m−2 yr−1. However, redox-sensitive elements in sediment core indicate alternation between anoxic/dysoxic and oxic conditions in the water-sediment interface that may be linked to abrupt changes in precipitation. The variation between anoxic/dysoxic and oxic conditions in the water-sediment interface controls organic matter mineralization and methanogenesis. Thus, such changes promoted by hydrological variations significantly affect the capacity of Amazon rias to act either as sources or sinks of carbon

Adjustment of the lateral and longitudinal size of scanned proton beam spots using a pre-absorber to optimize penumbrae and delivery efficiency

In scanned-beam proton therapy, the beam spot properties, such as the lateral and longitudinal size and the minimum achievable range, are influenced by beam optics, scattering media and drift spaces in the treatment unit. Currently available spot scanning systems offer fewoptions for adjusting these properties. We investigated a method for adjusting the lateral and longitudinal spot size that utilizes downstream plastic pre-absorbers located near a water phantom. The spot size adjustment was characterized usingMonte Carlo simulations of a modified commercial scanned-beam treatment head. Our results revealed that the pre-absorbers can be used to reduce the lateral full width at half maximum (FWHM) of dose spots inwater by up to 14 mm, and to increase the longitudinal extent from about 1 mm to 5 mm at residual ranges of 4 cm and less. A large factor in manipulating the lateral spot sizes is the drift space between the preabsorber and the water phantom. Increasing the drift space from 0 cm to 15 cm leads to an increase in the lateral FWHM from 2.15 cm to 2.87 cm, at a waterequivalent depth of 1 cm. These findings suggest that this spot adjustment method may improve the quality of spot-scanned proton treatments. © 2010 Institute of Physics and Engineering in Medicine