The grain size gap and abrupt gravel-sand transitions in rivers due to suspension fallout

Median grain sizes on riverbeds range from boulders in uplands to silt in lowlands; however, rivers with ~1–5 mm diameter bed sediment are rare. This grain size gap also marks an abrupt transition between gravel- and sand-bedded reaches that is unlike any other part of the fluvial network. Abrupt gravel-sand transitions have been attributed to rapid breakdown or rapid transport of fine gravel, or a bimodal sediment supply, but supporting evidence is lacking. Here we demonstrate that rivers dramatically lose the ability to transport sand as wash load where bed shear velocity drops below ~0.1 m/s, forcing an abrupt transition in bed-material grain size. Using thresholds for wash load and initial motion, we show that the gap emerges only for median bed-material grain sizes of ~1–5 mm due to Reynolds number dependencies in suspension transport. The grain size gap, therefore, is sensitive to material properties and gravity, with coarser gaps predicted on Mars and Titan

Mitochondrial management of reactive oxygen species

Mitochondria in aerobic eukaryotic cells are both the site of energy production and the formation of harmful species, such as radicals and other reactive oxygen species, known as ROS. They contain an efficient antioxidant system, including low-molecular-mass molecules and enzymes that specialize in removing various types of ROS or repairing the oxidative damage of biological molecules. Under normal conditions, ROS production is low, and mitochondria, which are their primary target, are slightly damaged in a similar way to other cellular compartments, since the ROS released by the mitochondria into the cytosol are negligible. As the mitochondrial generation of ROS increases, they can deactivate components of the respiratory chain and enzymes of the Krebs cycle, and mitochondria release a high amount of ROS that damage cellular structures. More re-cently, the feature of the mitochondrial antioxidant system, which does not specifically deal with intramitochondrial ROS, was discovered. Indeed, the mitochondrial antioxidant system detoxifies exogenous ROS species at the expense of reducing the equivalents generated in mitochondria. Thus, mitochondria are also a sink of ROS. These observations highlight the importance of the mitochon-drial antioxidant system, which should be considered in our understanding of ROS-regulated pro-cesses. These processes include cell signaling and the progression of metabolic and neurodegenera-tive disease

Setting Sail without a Map: Creative Collaboration for a Multi-Disciplinary Conference

The Art of the Picture Book Conference was launched in May 2006 in Ashland, Ohio. The two-day event drew a total of 158 attendees, featured award-winning authors/ illustrators as keynote speakers, and offered 35 sessions, selected from a total of 45 proposal submissions. By involving co-curricular programs and community partners, such as other departments on campus, the university bookstore, local public libraries and school districts, and regional museums, the conference offered a variety of techniques to develop and enhance literacy in children. Presentation opportunities allowed our university students a venue to showcase their comprehensive information abilities. Crossover into various disciplines created wide interest and networking opportunities, and increased library visibility across campus. Learn how we navigated these murky waters without a map and realized the benefits of venturing beyond the protected waters of the academic library. This session will provide insight into general conference planning skills, such as timelines, schedules, delegation of duties, cross-disciplinary communication, and backup plans. These skills are applicable to workshops and smaller events as well. We will also focus on the unexpected challenges and rewarding opportunities of working closely with university colleagues and with partners outside of the library and academia. Participants will be invited to share their own experiences with conference/workshop planning, and will have an opportunity to brainstorm ideas for new collaborative partnerships on their campuses and within their communities. Timelines and checklists of tasks for successful conference planning will be provided

Editorial: Structural and Dynamic Aspects of Protein Function and Allostery

Editorial on the Research Topi

Role of multidrug-resistant pathogens in health-care-associated pneumonia.

Comment on: Rethinking the concepts of community-acquired and health-care-associated pneumonia. [Lancet Infect Dis. 2010

Chlorella sorokiniana dietary supplementation increases antioxidant capacities and reduces ros release in mitochondria of hyperthyroid rat liver

The ability of aerobic organisms to cope with the attack of radicals and other reactive oxygen species improves by feeding on foods containing antioxidants. Microalgae contain many molecules showing in vitro antioxidant capacity, and their food consumption can protect cells from oxidative insults. We evaluated the capacity of dietary supplementation with 1% dried Chlorella sorokiniana strain 211/8k, an alga rich in glutathione, α-tocopherol, and carotenoids, to counteract an oxidative attack in vivo. We used the hyperthyroid rat as a model of oxidative stress, in which the increase in metabolic capacities is associated with an increase in the release of mitochondrial reactive oxygen species (ROS) and the susceptibility to oxidative insult. Chlorella sorokiniana supplementation prevents the increases in oxidative stress markers and basal oxygen consumption in hyperthyroid rat livers. It also mitigates the thyroid hormone-induced increase in maximal aerobic capacities, the mitochondrial ROS release, and the susceptibility to oxidative stress. Finally, alga influences the thyroid hormone-induced changes in the factors involved in mitochondrial biogenesis peroxisomal proliferator-activated receptor-γ coactivator (PGC1-1) and nuclear respiratory factor 2 (NRF-2). Our results suggest that Chlorella sorokiniana dietary supplementation has beneficial effects in counteracting oxidative stress and that it works primarily by preserving mitochondrial function. Thus, it can be useful in preventing dysfunctions in which mitochondrial oxidative damage and ROS production play a putative role

Harmful and Beneficial Role of ROS

Reactive oxygen species (ROS) are an unavoidable byproduct of oxygen metabolism and their cellular concentrations are determined by the balance between their rates of production and their rates of clearance by various antioxidant compounds and enzymes. For a long time ROS were thought to cause exclusively toxic effects which were associated with various pathologies, including carcinogenesis, neurodegeneration, atherosclerosis, diabetes, and aging. However, to date, it is known that while prolonged exposure to high ROS concentrations may lead to various disorders, low ROS concentrations exert beneficial effects regulating cell signaling cascades