Evaluating experiential education through an intertidal ecology field trip.

*Background/Question/Methods*

Stanford SEEDS and the Jasper Ridge Biological Preserve have worked together with Redwood High School to implement an experiential ecology education program. The Redwood Environmental Academy of Leadership(REAL) is designed to bring underserved high school students out of the classroom and into the outdoors to create a unique and effective learning experience. Though the program focuses on riparian ecosystem restoration, the course curriculum is interdisciplinary and designed to inspire continuation high school students to attend college or pursue environmental careers. Through a SEEDS special grant, REAL students were taken to Fitzgerald Marine Reserve in Half Moon Bay, California, to learn about marine ecology and intertidal ecosystems at a minus tide. Redwood High School students were joined by their teachers and Stanford faculty and students to study the adaptations of intertidal organisms to their harsh environment.

*Results/Conclusions*

SEEDS and REAL were able to evaluate the success of the field trip by comparing the students’ knowledge of intertidal habitat, the nature of the ocean ecosystems, plants, animals, and reproduction both before and after the trip. This opportunity provides insight into the effectiveness of experiential education for the REAL program and recommendations for future ecology outreach programs

Development of a 1000V, 200A, low-loss, fast-switching, gate-assisted turn-off thyristor

Feasibility was demonstrated for a thyristor that blocks 1000V forward and reverse, conducts 200A, and turns on in little more than 2 microsec with only 2A of gate drive. Its features include a turn-off time of 3 microsec achieved with 2A of gate assist current of a few microseconds duration and an energy dissipation of only 12 mJ per pulse for a 20 microsec half sine wave, 200A pulse. Extensive theoretical and experimental study of the electrical behavior of thyristors having a fast turn-off time have significantly improved the understanding of the physics of turning thyristor off. Thyristors of two new designs were fabricated and evaluated. The high speed and low power were achieved by a combination of gate amplification, cathode shunting, and gate-assisted turn-off. Two techniques for making this combination practical are described

Plume mapping and isotopic characterisation of anthropogenic methane sources

Methane stable isotope analysis, coupled with mole fraction measurement, has been used to link isotopic signature to methane emissions from landfill sites, coal mines and gas leaks in the United Kingdom. A mobile Picarro G2301 CRDS (Cavity Ring-Down Spectroscopy) analyser was installed on a vehicle, together with an anemometer and GPS receiver, to measure atmospheric methane mole fractions and their relative location while driving at speeds up to 80 kph. In targeted areas, when the methane plume was intercepted, air samples were collected in Tedlar bags, for delta C-13-CH4 isotopic analysis by CF-GC-IRMS (Continuous Flow Gas Chromatography-Isotope Ratio Mass Spectrometry). This method provides high precision isotopic values, determining delta C-13-CH4 to +/- 0.05 per mil. The bulk signature of the methane plume into the atmosphere from the whole source area was obtained by Keeling plot analysis, and a delta C-13 -CH4 signature, with the relative uncertainty, allocated to each methane source investigated. Both landfill and natural gas emissions in SE England have tightly constrained isotopic signatures. The averaged delta C-13-CH4 for landfill sites is -58 +/- 3%o. The delta C-13-CH4 signature for gas leaks is also fairly constant around -36 +/- 2 parts per thousand, a value characteristic of homogenised North Sea supply. In contrast, signatures for coal mines in N. England and Wales fall in a range of -51.2 +/- 0.3 parts per thousand to 30.9 +/- 1.4 parts per thousand, but can be tightly constrained by region. The study demonstrates that CRDS-based mobile methane measurement coupled with off-line high precision isotopic analysis of plume samples is an efficient way of characterising methane sources. It shows that iiotopic measurements allow type identification, and possible location of previously unknown methane sources. In modelling studies this measurement provides an independent constraint to determine the contributions of different sources to the regional methane budget and in the verification of inventory source distribution. (C) 2015 Elsevier Ltd. All rights reserved

Space Station long term lubrication analysis. Phase 1 preliminary tribological survey

Increases in the size, complexity, and life requirements of satellites and space vehicles have put increasing demands on the lubrication requirements for trouble-free service. Since the development costs of large systems are high, long lives with minimum maintenance are dictated. The Space Station represents the latest level of size and complexity in satellite development; it will be nearly 100 meters in major dimensions and will have a life requirement of thirty years. It will have numerous mechanisms critical to its success, some of which will be exposed to the space environment. Designing long-life lubrication systems and choosing appropriate lubricants for these systems will be necessary for their meeting the requirements and for avoiding failures with associated dependent mechanisms. The purpose of this program was to identify the various critical mechanisms and review their designs during the overall design and development stage so that problem areas could be avoided or minimized prior to the fabrication of hardware. The specific objectives were fourfold: (1) to perform a tribology survey of the Space Station for the purpose of documenting each wear point as to materials involved, environmental conditions, and operating characteristics; (2) to review each wear point (point of relative motion) as to the lubrication used and substrate materials selected in the context of its operating characteristics and the environmental conditions imposed; (3) to make recommendations for improvement in areas where the lubricant chosen and/or where the substrate (materials of the wear couple) are not considered optimum for the application; and (4) to make or recommend simulated or full scale tests in tribological areas where the state-of-the-art is being advanced, in areas where new designs are obviously being employed and a critical review would indicate that problems are a strong possibility, and/or where excessive wear, a malfunction, or excessive leakage would create fluid systems problems or contamination of exposed optical equipment

Development of a 1000V, 200A, low-loss, fast-switching, gate-assisted turn-off thyristor

The results of a program to develop a fast high power thyristor that can operate in switching circuits at frequencies of 10 to 20 kHz with very low power loss are given. Feasibility was demonstrated for a thyristor that blocks 1000V forward and reverse, conducts 200A, turns on in little more than 2 more microseconds with only 2A of gate drive, turns off in 3 microseconds with 2A of gate assist current and has an energy dissipation of only 12 mJ per pulse for a 20 microsecond half sine wave 200A pulse. Data were generated that clearly showed the tradeoffs that can be made between the turn off time and forward drop. The understanding of this relationship is necessary in the selection of deliverable thyristors with turn off times up to 7 microseconds to give improved efficiency in a series resonant dc to dc inverter application

Design, Fabrication and Test of Composite Curved Frames for Helicopter Fuselage Structure

Aspects of curved beam effects and their importance in designing composite frame structures are discussed. The curved beam effect induces radial flange loadings which in turn causes flange curling. This curling increases the axial flange stresses and induces transverse bending. These effects are more important in composite structures due to their general inability to redistribute stresses by general yielding, such as in metal structures. A detailed finite element analysis was conducted and used in the design of composite curved frame specimens. Five specimens were statically tested and compared with predicted and test strains. The curved frame effects must be accurately accounted for to avoid premature fracture; finite element methods can accurately predict most of the stresses and no elastic relief from curved beam effects occurred in the composite frames tested. Finite element studies are presented for comparative curved beam effects on composite and metal frames

-OH No! hiPSCs Misplace Their 5hmCs

hiPSCs and hESCs are thought to display subtle genetic and epigenetic variability. Recently in Nature Cell Biology, Wang et al. (2013) demonstrated a role for TET1 during reprogramming of human cells and showed that hiPSCs lack appropriate 5hmC marks in subtelomeric regions, contributing to epigenetic variation common to hiPSCs

Magnetic resonance studies of reactively sputtered amorphous silicon-hydrogen alloys

Proton magnetic resonance and electron paramagnetic resonance measurement results are presented for several reactively sputtered amorphous silicon-hydrogen alloys and for a few amorphous silicon-hydrogen-deuterium alloys. Proton NMR absorption measurements made on a series of samples with controlled and varied amounts of hydrogen have been interpreted as evidence for significant inhomogeneity in the local hydrogen density: there is a phase of the material, in which the hydrogen bonded to Si is randomly distributed with average local density 3.39 x 10(\u2721) cm(\u27-3); there is a hydrogen cluster defect with average local hydrogen density 4.34 x 10(\u2722) cm(\u27-3); in the lower hydrogen samples there is a third phase of the material which has no H;Proton NMR spin-lattice relaxation measurements as a function of both temperature and H concentration have been interpreted, consistent with the above conclusions. The mechanism of spin-lattice relaxation in both cases involves spin diffusion to relaxation centers. In the low H concentration samples the relaxation centers are dangling bond electrons, while the centers in the high H samples appear to be three-center Si-H-Si bonds;EPR measurements on the dangling bond electrons are consistent with all of the above conclusions. Furthermore, a new very broad ((TURN).1 Tesla) resonance has been detected in all of the samples. It is tentatively interpreted in support of the existence of three-center bonds;The implications these results may have for the electronic device properties of this material are discussed