University of Waterloo

About: University of Waterloo is a education organization based out in Waterloo, Ontario, Canada. It is known for research contribution in the topics: Population & Context (language use). The organization has 36093 authors who have published 93906 publications receiving 2948139 citations. The organization is also known as: UW & uwaterloo.

A hydrogen-rich early Earth atmosphere

Abstract: We show that the escape of hydrogen from early Earth's atmosphere likely occurred at rates slower by two orders of magnitude than previously thought. The balance between slow hydrogen escape and volcanic outgassing could have maintained a hydrogen mixing ratio of more than 30%. The production of prebiotic organic compounds in such an atmosphere would have been more efficient than either exogenous delivery or synthesis in hydrothermal systems. The organic soup in the oceans and ponds on early Earth would have been a more favorable place for the origin of life than previously thought.

Gated-SCNN: Gated Shape CNNs for Semantic Segmentation

Abstract: Current state-of-the-art methods for image segmentation form a dense image representation where the color, shape and texture information are all processed together inside a deep CNN. This however may not be ideal as they contain very different type of information relevant for recognition. Here, we propose a new two-stream CNN architecture for semantic segmentation that explicitly wires shape information as a separate processing branch, i.e. shape stream, that processes information in parallel to the classical stream. Key to this architecture is a new type of gates that connect the intermediate layers of the two streams. Specifically, we use the higher-level activations in the classical stream to gate the lower-level activations in the shape stream, effectively removing noise and helping the shape stream to only focus on processing the relevant boundary-related information. This enables us to use a very shallow architecture for the shape stream that operates on the image-level resolution. Our experiments show that this leads to a highly effective architecture that produces sharper predictions around object boundaries and significantly boosts performance on thinner and smaller objects. Our method achieves state-of-the-art performance on the Cityscapes benchmark, in terms of both mask (mIoU) and boundary (F-score) quality, improving by 2% and 4% over strong baselines.

Isolation and Characterization of Mutants of the Plant Growth-Promoting Rhizobacterium Pseudomonas putida GR12-2 That Overproduce Indoleacetic Acid

Abstract: Following transposon Tn5 mutagenesis of the plant growth-promoting rhizobacterium Pseudomonas putida GR12-2, mutants that were able to grow in the presence of the tryptophan analog 5-fluorotryptophan were selected. Seven of the 50 5-fluorotryptophan-resistant mutants overproduced the phytohormone indoleacetic acid (IAA). Of these seven mutants, the highest level of IAA was observed with strain P. putida GR12-2/aux1, which produced four times the amount of indoleacetic acid synthesized by the wild-type strain. Strain P. putida GR12-2/aux1, in contrast to the wild type, lost the ability to stimulate the elongation of the roots of canola seedlings under gnotobiotic conditions. The growth rate, siderophore production, and 1-aminocyclopropane-1-carboxylate deaminase activity of mutant strain P. putida GR12-2/aux1 were identical to those of the wild-type strain. The role of IAA in the mechanism of plant growth stimulation by P. putida GR12-2 and other plant growth-promoting rhizobacteria is discussed.

Carbon isotope fractionation during microbial methane oxidation

Abstract: Methane, a common trace constituent of groundwaters, occasionally makes up more than 20% of the total carbon in groundwaters1,2. In aerobic environments CH4–rich waters can enable microbial food chain supporting a mixed culture of bacteria with methane oxidation as the primary energy source to develop3. Such processes may influence the isotopic composition of the residual methane and because 13C/12C analyses have been used to characterize the genesis of methanes found in different environments, an understanding of the magnitude of such effects is necessary. In addition, carbon dioxide produced by the methane-utilizing bacteria can be added to the inorganic carbon pool of affected groundwaters. We found carbon dioxide experimentally produced by methane-utilizing bacteria to be enriched in 12C by 5.0–29.6‰, relative to the residual methane. Where methane-bearing groundwaters discharged into aerobic environments microbial methane oxidation occurred, with the residual methane becoming progressively enriched in 13C. Various models have been proposed to explain the 13C/12C and 14C content of the dissolved inorganic carbon (DIC) of groundwaters in terms of additions or losses during flow in the subsurface4,5. The knowledge of both stable carbon isotope ratios in various pools and the magnitude of carbon isotope fractionation during various processes allows geochemists to use the 13C/12C ratio of the DIC along with water chemistry to estimate corrected 14C groundwater ages4,5. We show here that a knowledge of the carbon isotope fractionation between CH4 and CO2 during microbial methane-utilization could modify such models for application to groundwaters affected by microbial methane oxidation.