Investigating Instabilities with HEC-RAS Unsteady Flow Modeling for Regulated Rivers at Low Flow Stages

Dams are used throughout the United States for generation of electricity and flood control. The Tennessee River Valley’s regulated river system extends through Tennessee and parts of Kentucky, Mississippi, Alabama, Georgia, North Carolina, South Carolina, and Virginia. Of the dams in this area, 49 are managed by the Tennessee Valley Authority (TVA). The TVA forecasts and monitors the activities related to these dams and others in the area on an around-the-clock basis to ensure maximum generation potential is attained and to prevent flooding of the surrounding cities. To best forecast hydrology for the regulated river system, the TVA chose to upgrade the forecasting center to include HEC-RAS models for high and low flow simulations. These simulations can better guide TVA engineers to the best route when releasing water from the dam in the case of an emergency flooding situation or on a daily basis. Building a HEC-RAS model for the TVA reservoir system is a large undertaking and model stability issues arise from different possible causes. In this paper, the best methods of stabilizing modeled reaches on a regulated river system during low flows were compiled in logic flow charts, which can be of general assistance to modelers when stabilizing HEC-RAS simulations for regulated river systems. The flow charts were created and explained, with multiple options for stability described and analyzed throughout the creation process. They were based on results where stability issues were regularly due to cross sectional spacing and the addition of base flow through the upstream boundary and lateral inflows. Other potential methods were also considered for applicability in a model such as this, including the addition of pilot channels and increasing the theta weighting factor. Using the flow charts created, HEC-RAS modelers should gain a better understanding of stability issues in a river system and what causes these problems

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field