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Obsidian is volcanic glass that results from the rapid cooling of silica-rich melt. Nanoscale crystallites precipitate out of the melt prior to solidification and remain embedded in the amorphous matrix. These crystallites provide information on the flow kinetics and composition of the melt. Due to the sparsity and size of nanolites, studies often focus on supramicron crystallites. This research takes advantage of the conchoidal fracture of obsidian by knapping samples with nanometer-thin edges for transmission electron microscopy characterization. Nanolites in the amorphous matrix are studied using energy-dispersive spectroscopy (EDS) and electron diffraction. Certain alkali and alkaline-earth cations exhibit patterns of depletion near Fe-oxide nanolites. EDS is used to identify nanolites and variations in the composition of the matrix. Parallel beam diffraction and radial distribution function analysis of nearest-neighbor distances determine average bond lengths in the matrix near nanolites, showing that nanolites influence the nearby short-range ordering and atomic character of the matrix. Analysis reveals decreased mean nearest-neighbor distances in the matrix adjacent to nanolites compared to the bulk. Our methods exhibit the required sensitivity to detect variations in the composition and structure near nanolites, and our findings indicate that obsidian nanolites contribute to quantifiable localized changes in the amorphous structure.
Scanning transmission electron microscopy (STEM) allows for imaging, diffraction, and spectroscopy of materials on length scales ranging from microns to atoms. By using a high-speed, direct electron detector, it is now possible to record a full two-dimensional (2D) image of the diffracted electron beam at each probe position, typically a 2D grid of probe positions. These 4D-STEM datasets are rich in information, including signatures of the local structure, orientation, deformation, electromagnetic fields, and other sample-dependent properties. However, extracting this information requires complex analysis pipelines that include data wrangling, calibration, analysis, and visualization, all while maintaining robustness against imaging distortions and artifacts. In this paper, we present py4DSTEM, an analysis toolkit for measuring material properties from 4D-STEM datasets, written in the Python language and released with an open-source license. We describe the algorithmic steps for dataset calibration and various 4D-STEM property measurements in detail and present results from several experimental datasets. We also implement a simple and universal file format appropriate for electron microscopy data in py4DSTEM, which uses the open-source HDF5 standard. We hope this tool will benefit the research community and help improve the standards for data and computational methods in electron microscopy, and we invite the community to contribute to this ongoing project.
In recent years there has been a rapid growth of interest in exploring the relationship between nutritional therapies and the maintenance of cognitive function in adulthood. Emerging evidence reveals an increasingly complex picture with respect to the benefits of various food constituents on learning, memory and psychomotor function in adults. However, to date, there has been little consensus in human studies on the range of cognitive domains to be tested or the particular tests to be employed. To illustrate the potential difficulties that this poses, we conducted a systematic review of existing human adult randomised controlled trial (RCT) studies that have investigated the effects of 24 d to 36 months of supplementation with flavonoids and micronutrients on cognitive performance. There were thirty-nine studies employing a total of 121 different cognitive tasks that met the criteria for inclusion. Results showed that less than half of these studies reported positive effects of treatment, with some important cognitive domains either under-represented or not explored at all. Although there was some evidence of sensitivity to nutritional supplementation in a number of domains (for example, executive function, spatial working memory), interpretation is currently difficult given the prevailing ‘scattergun approach’ for selecting cognitive tests. Specifically, the practice means that it is often difficult to distinguish between a boundary condition for a particular nutrient and a lack of task sensitivity. We argue that for significant future progress to be made, researchers need to pay much closer attention to existing human RCT and animal data, as well as to more basic issues surrounding task sensitivity, statistical power and type I error.
Few prearranged events provide better opportunities for emergency health system coordination and planned disaster management than does medical coverage of a major city marathon. No guidelines exist as to the appropriate level of care that should be provided for such an event.
The medical coverage for 2,900 marathon runners and an estimated 500,000 spectators along a 26.2-mile course over city streets for the 1986 Pittsburgh Marathon was examined prospectively. Support groups included physicians, nurses, and medical students from area hospitals and emergency departments and podiatrists, physical therapists, athletic trainers, and massage therapists from the Pittsburgh area. Emergency medical services were provided by city and county advanced life support (ALS) and basic life support (BLS) units, the American Red Cross, and the Salvation Army. A total of 641 medical volunteers participated in the coverage. Data were collected by volunteers as to acute medical and sports medical complaints of all patients, their vital signs, and the treatment provided. Medical care was provided at 20 field aid-stations along the race route (including a station every mile afier the 12-mile mark, and at four stations at the finish line).
Race day weather conditions were unusually warm with a high temperature of 86°F (30°C), relative humidity of 64%, partly sunny with little ambient wind, and a high wet bulb-globe temperature of 78°F (25.6°C). Records were obtained on 658/2,900 (25%) runner-patients of which 52 (8%) required transportation to area hospitals after evaluation at aid-stations: three were admitted to intensive care units. Analysis showed that 379/658 (58%) of the patients were treated at the finish line medical areas, and of the remaining 279 patients treated on the course, 218/279 (78%) were seen at seven, mile-aid-stations between 16.2 and 22.8 miles. The conditions of heat and humidity constitute a near “worst-case” scenario and the numbers of medical personnel that should be available to deliver acute care of hyperthermia/hypothermia and fluid/electrolyte disorders are recommended. Also it is recommended that approximately 50% of medical personnel and equipment should be deployed in the finish line area and that 80% of the remaining resources on the race course be deployed in aid-stations located every mile between miles 16 and 23.
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