Hydropower capacity factors trending down in the United States.

The United States hydropower fleet has faced increasing environmental and regulatory pressures over the last half century, potentially constraining total generation. Here we show that annual capacity factor has declined at four fifths of United States hydropower plants since 1980, with two thirds of decreasing trends significant at p < 0.05. Results are based on an analysis of annual energy generation totals and nameplate capacities for 610 plants (>5 megawatt), representing 87% of total conventional hydropower capacity in the United States. On aggregate, changes in capacity factor imply a fleetwide, cumulative generation decrease of 23% since 1980 before factoring in capacity upgrades-akin to retiring a Hoover Dam once every two to three years. Changes in water availability explain energy decline in only 21% of plants, highlighting the importance of non-climatic drivers of generation, including deterioration of plant equipment as well as changes to dam operations in support of nonpower objectives.

Primary venous thromboembolism prophylaxis in ambulatory cancer patients.

OBJECTIVE: To summarize and review current medical literature regarding the efficacy and safety of antithrombotic therapy for primary venous thromboembolism (VTE) prophylaxis in various ambulatory cancer populations. DATA SOURCES: A literature search was conducted in PubMed (1966-September 2012) and International Pharmaceutical Abstracts (1970-September 2012) using the terms venous thromboembolism, primary prophylaxis, anticoagulation, antithrombotic agents, cancer, and ambulatory. The bibliographies of pertinent studies and topic articles were reviewed for additional references. STUDY SELECTION AND DATA EXTRACTION: All English-language articles were evaluated for inclusion. All randomized trials were included in the review. DATA SYNTHESIS: Malignancy has been identified as a major independent risk factor for the development of VTE in the surgical, medically ill, and ambulatory populations. Primary VTE prophylaxis has been identified as an area of great impact in cancer patients because of the difficulties associated with the treatment of VTE and the greater risk for its recurrence in this population. Although primary VTE prophylaxis is recommended in all surgical and hospitalized cancer patients without contraindications to anticoagulants, its role in ambulatory cancer patients is less certain because of varying patient, cancer, and treatment-related factors. Fourteen randomized studies have investigated the use of antithrombotic agents for primary VTE prophylaxis in ambulatory cancer patients. Strong evidence for primary prophylaxis exists for several populations with advanced or metastatic cancer considered to be at high risk, including those with pancreatic cancer, lung cancer, or multiple myeloma. Evidence is inconsistent or lacking for lower risk cancer populations, such as those with breast cancer, or for those with malignant glioma, which carries a high risk for VTE and bleeding relative to the general ambulatory cancer population. CONCLUSIONS: Use of antithrombotic agents has reduced the rate of primary VTE, with minimal increases in bleeding risk in specific ambulatory cancer populations. Further investigation is needed to guide and narrow recommendations for primary VTE prophylaxis in ambulatory cancer patients.

Diversity in reservoir surface morphology and climate limits ability to compare and upscale estimates of greenhouse gas emissions.

Greenhouse gas (GHG) emissions from reservoirs are influenced by many factors, including the reservoir's morphology, watershed, and local climate. Failure to account for diversity in waterbody characteristics contributes to uncertainties in estimates of total waterbody GHG emissions and limits the ability to extrapolate patterns from one set of reservoirs to another. Hydropower reservoirs are of particular interest given recent studies that show variable - and sometimes very high - measurements and estimates of emissions. This study uses characteristics describing reservoir surface morphology and location within the watershed to identify US hydropower reservoir archetypes that represent the diversity of reservoir features relevant to GHG emissions. The majority of reservoirs are characterized by smaller watersheds, smaller surface areas, and lower elevations. Downscaled climate projections of temperature and precipitation mapped onto the archetypes show large variability in hydroclimate stresses (i.e., changes in precipitation and air temperature) within and across different reservoir types. Average air temperatures are projected to increase for all reservoirs by the end of the century, relative to historical conditions, while projected precipitation is much more variable across all archetypes. Variability in projected climate suggests that despite similar morphology-related traits, reservoirs may experience different shifts in climate, potentially resulting in a divergence in carbon processing and GHG emissions from historical conditions. Low representation in published GHG emission measurements among several reservoir archetypes (roughly 14 % of the population of hydropower reservoirs), highlights a potential limit to the generalization of current measurements and models. This multi-dimensional analysis of waterbodies and their local hydroclimate provides valuable context for the growing body of GHG accounting literature and ongoing empirical and modeling studies.

Chest CT for the Diagnosis of Pediatric Esophageal Foreign Bodies.

Foreign body ingestion is a common problem in children. Radiography is the mainstay of imaging, but many radiolucent items go undetected without further imaging by fluoroscopic esophagram. While studies in adults support the use of computed tomography (CT) for esophageal foreign body ingestion, CT has historically not been used in children given the typically higher radiation doses on CT compared with fluoroscopy. In distinction to an esophagram, CT does not require oral contrast nor presence of an onsite radiologist and can be interpreted remotely. At our institution, a dedicated CT protocol has been used for airway foreign bodies since 2015. Given the advantages of CT over esophagram, we retrospectively reviewed institutional radiation dose data from 2017 to 2020 for esophagrams, airway foreign body CT (FB-CT), and routine CT Chest to compare effective doses for each modality. For ages 1+ years, effective dose was lowest using the FB-CT protocol; esophagram mean dose showed the most variability, and was over double the dose of FB-CT for ages 5+ years. Routine CT chest doses were uniformly highest across all age ranges. Given these findings, we instituted a CT foreign body imaging protocol as the first-line imaging modality for radiolucent esophageal foreign body at our institution.