579 research outputs found

    Confocal Microscopy of Plant Cells

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    The increasing availability of confocal microscopy has begun a revolution in plant biology in which microscopy has again become a powerful tool for understanding structure and function. Examples of applications include: three dimensional (3D) reconstruction of the interphase microtubule array in large vacuolated epidermal cells (1); measuring cytoplasmic free calcium changes in whole maize coleoptile segments in response to phototropic and gravitropic stimuli (2); and studying symplastic phloem connections in intact Arabidopsis roots (3). The major reason for this revolution is the ability to collect clear images in three dimensions due to the lack of image degradation caused by out-of-focus light. Plant cells can attain very large sizes (hundreds of micrometers, in some cases) and are very thick. Thus the ability of the confocal microscope to obtain optical sections of tissues from which 3D reconstructions can be made surpasses the limitations of conventional “wide-field” microscopic techniques where microtome sectioning is often required and cells must be viewed as flat, two-dimensional objects. Furthermore, the reduction in out-of-focus flare increases depth discriminatio

    Understanding predictive uncertainty in hydrologic modeling: The challenge of identifying input and structural errors

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    Meaningful quantification of data and structural uncertainties in conceptual rainfall-runoff modeling is a major scientific and engineering challenge. This paper focuses on the total predictive uncertainty and its decomposition into input and structural components under different inference scenarios. Several Bayesian inference schemes are investigated, differing in the treatment of rainfall and structural uncertainties, and in the precision of the priors describing rainfall uncertainty. Compared with traditional lumped additive error approaches, the quantification of the total predictive uncertainty in the runoff is improved when rainfall and/or structural errors are characterized explicitly. However, the decomposition of the total uncertainty into individual sources is more challenging. In particular, poor identifiability may arise when the inference scheme represents rainfall and structural errors using separate probabilistic models. The inference becomes ill‐posed unless sufficiently precise prior knowledge of data uncertainty is supplied; this ill‐posedness can often be detected from the behavior of the Monte Carlo sampling algorithm. Moreover, the priors on the data quality must also be sufficiently accurate if the inference is to be reliable and support meaningful uncertainty decomposition. Our findings highlight the inherent limitations of inferring inaccurate hydrologic models using rainfall‐runoff data with large unknown errors. Bayesian total error analysis can overcome these problems using independent prior information. The need for deriving independent descriptions of the uncertainties in the input and output data is clearly demonstrated.Benjamin Renard, Dmitri Kavetski, George Kuczera, Mark Thyer, and Stewart W. Frank

    Behavioral Health and Performance Operations During the Space Shuttle Program

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    Prior to the Columbia STS 107 disaster in 2003, the Johnson Space Center s Behavioral Health and Performance Group (BHP) became involved in Space Shuttle Operations on an as needed basis, occasionally acting as a consultant and primarily addressing crew-crew personality conflicts. The BHP group also assisted with astronaut selection at every selection cycle beginning in 1991. Following STS 107, an event that spawned an increased need of behavioral health support to STS crew members and their dependents, BHP services to the Space Shuttle Program were enhanced beginning with the STS 114 Return to Flight mission in 2005. These services included the presence of BHP personnel at STS launches and landings for contingency support, a BHP briefing to the entire STS crew at L-11 months, a private preflight meeting with the STS Commander at L-9 months, and the presence of a BHP consultant at the L-1.5 month Family Support Office briefing to crew and family members. The later development of an annual behavioral health assessment of all active astronauts also augmented BHP s Space Shuttle Program specific services, allowing for private meetings with all STS crew members before and after each mission. The components of each facet of these BHP Space Shuttle Program support services will be presented, along with valuable lessons learned, and with recommendations for BHP involvement in future short duration space mission

    NASA's Astronant Family Support Office

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    During the NASAMir program of the 1990s and due to the challenges inherent in the International Space Station training schedule and operations tempo, it was clear that a special focus on supporting families was a key to overall mission success for the ISS crewmembers pre, in and postflight. To that end, in January 2001 the first Family Services Coordinator was hired by the Behavioral Health and Performance group at NASA JSC and matrixed from Medical Operations into the Astronaut Office's organization. The initial roles and responsibilities were driven by critical needs, including facilitating family communication during training deployments, providing missionspecific and other relevant trainings for spouses, serving as liaison for families with NASA organizations such as Medical Operations, NASA management and the Astronaut Office, and providing assistance to ensure success of an Astronaut Spouses Group. The role of the Family Support Office (FSO) has modified as the ISS Program matured and the needs of families changed. The FSO is currently an integral part of the Astronaut Office's ISS Operations Branch. It still serves the critical function of providing information to families, as well as being the primary contact for US and international partner families with resources at JSC. Since crews launch and return on Russian vehicles, the FSO has the added responsibility for coordinating with Flight Crew Operations, the families, and their guests for Soyuz launches, landings, and Direct Return to Houston postflight. This presentation will provide a summary of the family support services provided for astronauts, and how they have changed with the Program and families the FSO serves. Considerations for future FSO services will be discussed briefly as NASA proposes one year missions and beyond ISS missions. Learning Objective: 1) Obtain an understanding of the reasons a Family Support Office was important for NASA. 2) Become familiar with the services provided for astronauts and their families and how they changed with the Program and family needs

    NASA Astronaut Selection 2009: Behavioral Overview

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    NASA's multi-phase U.S. astronaut selection process seeks to identify the most qualified astronaut candidates from a large number of applicants. With the approaching retirement of the Space Shuttle, NASA focused on selecting those individuals who were most suited to the unique demands of long-duration spaceflight. In total, NASA received 3,535 applications for the 2009 astronaut selection cycle. Of these, 123 were invited to NASA Johnson Space Center (JSC) for Round 1 initial screening and interviews, which consisted of an Astronaut Selection Board (ASB) preliminary interview, medical review, and psychological testing. Of these, 48 individuals were invited to return for Round 2. This round consisted of medical testing, further behavioral assessments, and a second ASB interview. Following this, nine astronaut candidates (ASCANs) were ultimately chosen to go forward to basic training. The contents, benefits, and lessons learned from implementing this phased process will be discussed. The lessons learned can benefit the future selection of space flyers, whether they are NASA or commercial. Learning Objective: 1) Familiarization with the 2009 NASA behavioral screening process for astronaut applicants
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