503 research outputs found
Autonomous Systems Validation (SysVal) Environment for Advancing Mission Operations
In order to maintain the health and productivity of satellites, it is crucial to develop a system that can swiftly, accurately, and effectively reproduce the on-orbit workflow and behavior a spacecraft experiences. To achieve this, Planet created the Systems Validation (SysVal) ecosystem; originally developed to validate individual spacecraft subsystem design requirements, and has evolved to encompass satellite concept of operation workflows, innovating test processes while mitigating risks through the ability to rapidly mimic on-orbit activities in a lab environment. SysVal is a fully integrated hardware and software system composed of a ground station network and a mission operations center with multiple integrated satellites, developed in-house by Planet, to assist with operating its Dove constellation of Earth-imaging satellites. Planet’s implementation of agile aerospace has exposed the value of SysVal, which facilitates seamless transitions of operational improvements from development and experimentation to rapid productionalization by incorporating “Test-Like-You-Fly” principles. SysVal utilizes cloned instances of Planet’s operational mission control interfaces and data storage platforms along with fully integrated flight capable satellite hardware, the same build that is flown in space, to test software upgrades before they are deployed on-orbit, reproduce on-orbit issues on the ground, replicate continuous “Day in the Life\u27\u27 satellite operations, examine changes with potential operational impacts, while being easily managed remotely by a distributed team. System autonomy is a principal component of SysVal to alleviate human-in-the-loop decision making, maintenance and resources, and is utilized for quick snapshots of the testbed states, software deploys to match the lab environment to the production environment, automated flashing of lab satellite onboard software images to match on-orbit satellites, as well as autonomous analysis of system-level metrics and daily testbed testing with operator notification. This paper describes the SysVal system utilized by Planet and the latest automations integrated into the ecosystem that assist with the testing and development of operating the world’s largest Earth Observation satellite constellation
A New Timepiece: An Epigenetic Mitotic Clock
A new mitotic clock and mathematical approach that incorporates DNA methylation biology common among human cell types provides a new tool for cancer epigenetics research
Teen smoking, field cancerization, and a "critical period" hypothesis for lung cancer susceptibility.
Cigarette smoking by children and adolescents continues to be prevalent, and this fact represents a major public health problem and challenge. Epidemiologic work has previously suggested that exposure of the lung to tobacco carcinogens at an early age may be an independent risk factor for lung cancer. Recent studies at the molecular and cellular levels are consistent with this, now suggesting that early exposure enhances DNA damage and is associated with the induction of DNA alterations in specific chromosomal regions. In this paper we hypothesize that adolescence, which is known to be the period of greatest development for the lung, may constitute a "critical period" in which tobacco carcinogens can induce fields of genetic alterations that make the early smoker more susceptible to the damaging effects of continued smoking. The fact that lung development differs by sex might also contribute to apparent gender differences in lung cancer susceptibility. Because this hypothesis has important implications for health policy and tobacco control, additional resources need to be devoted to its further evaluation. Targeted intervention in adolescent smoking may yield even greater reductions in lung cancer occurrence than otherwise anticipated
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Absence of an embryonic stem cell DNA methylation signature in human cancer.
BackgroundDifferentiated cells that arise from stem cells in early development contain DNA methylation features that provide a memory trace of their fetal cell origin (FCO). The FCO signature was developed to estimate the proportion of cells in a mixture of cell types that are of fetal origin and are reminiscent of embryonic stem cell lineage. Here we implemented the FCO signature estimation method to compare the fraction of cells with the FCO signature in tumor tissues and their corresponding nontumor normal tissues.MethodsWe applied our FCO algorithm to discovery data sets obtained from The Cancer Genome Atlas (TCGA) and replication data sets obtained from the Gene Expression Omnibus (GEO) data repository. Wilcoxon rank sum tests, linear regression models with adjustments for potential confounders and non-parametric randomization-based tests were used to test the association of FCO proportion between tumor tissues and nontumor normal tissues. P-values of < 0.05 were considered statistically significant.ResultsAcross 20 different tumor types we observed a consistently lower FCO signature in tumor tissues compared with nontumor normal tissues, with 18 observed to have significantly lower FCO fractions in tumor tissue (total n = 6,795 tumor, n = 922 nontumor, P < 0.05). We replicated our findings in 15 tumor types using data from independent subjects in 15 publicly available data sets (total n = 740 tumor, n = 424 nontumor, P < 0.05).ConclusionsThe results suggest that cancer development itself is substantially devoid of recapitulation of normal embryologic processes. Our results emphasize the distinction between DNA methylation in normal tightly regulated stem cell driven differentiation and cancer stem cell reprogramming that involves altered methylation in the service of great cell heterogeneity and plasticity
School Choice and Conflict Narratives: Representative Bureaucracy at the Street Level in East Jerusalem
Ice Layers as an Indicator of Summer Warmth and Atmospheric Blocking in Alaska
Samples were collected from a snow pit and shallow urn core near Kahiltna Pass (2970 m a.s.l.), Denali National Park, Alaska, USA, in May 2008. The record spans autumn 2003 to spring 2008 and reveals clusters of ice layers interpreted as summertime intervals of above-freezing temperatures. High correlation coefficients (0.75-1.00) between annual ice-layer thickness and regional summertime station temperatures for 4 years (n=4) indicate ice-layer thickness is a good proxy for mean and extreme summertime temperatures across Alaska, at least over the short period of record. A Rex-block (aka high-over-low) pattern, a downstream trough over Hudson Bay, Canada, and an upstream trough over eastern Siberia occurred during the three melting events that lasted at least 2 weeks. About half of all shorter melting events were associated with a cut-off low traversing the Gulf of Alaska. We hypothesize that a surface-to-bedrock core extracted from this location would provide a high-quality record of summer temperature and atmospheric blocking variability for the last several hundred years
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