Students’ Perceptions of School-Based Agricultural Education Through an Initial Early Field Experience

The purpose of this study was to identify the perception of students enrolled in an initial early field experience (EFE) in relation to the components of the agricultural education model. The students enrolled in the initial field experience were freshmen and sophomore students. The initial field experience course consisted of four face-to-face class meetings and a 12-hour initial field experience observation. Students’ photographed their perceptions of each component in the agricultural education model (classroom, SAE, FFA). The coding of reflective captions led to themes in three areas of the agricultural education model: (a) classroom themes were active learning, collaboration and facilities, (b) FFA themes were activities and opportunities, and (c) SAE themes were school based projects, awards/degrees, and the smallest circle. Overall, the EFE students used their photographs and descriptions to describe the learner-centered nature of the program. The EFE students described how the three components of the agricultural education model worked together to help school-based agricultural education (SBAE) students gain knowledge and experience. It is recommended that teacher educators incorporate photovoice in EFE programs to facilitate discussion of the initial perceptions of students

Some 5-13 micrometer airborne observations of Comet Wilson 1986l: Preliminary results

Comet Wilson was observed from the Kuiper Airborne Observatory approximately 23.6 and 25.7 Apr. 1987, UT (approx. 3 to 5 days after perihelion) using the NASA-Ames Faint Object Grating Spectrometer. Spectrophotometric data were observed with a 21 inch aperture between 5 and 13 micrometer and with a spectral resolution of 50 to 100. Spectra of the inner coma and nucleus reveal a fairly smooth continuum with little evidence of silicate emission. The 5 to 8 micrometer color temperature of the comet was 300 + or - 15 K, approx. 15 percent higher than the equilibrium blackbody temperature. All three spectra of the nucleus show a new emission feature at approx. 12.25 micrometer approx. two channels (.22 micrometer) wide. Visual and photographic observations made during the time of these observations showed a broad faint, possible two component tail. No outburst activity was observed

COMPTEL’s solar flare catalog

COMPTEL, the imaging gamma‐ray telescope, capable of detecting gamma rays in the range of 0.1–30 MeV, is one of four instruments aboard NASA’s Compton Gamma‐Ray Observatory. The Comptel burst detectors (single Defector Mode) have a field of view of ∼2.5 π sr. These detectors of COMPTEL permit measurements of energy spectra and time histories of solar flare gamma‐ray emission. A search through the Single Detector Mode’s data is being conducted. We summarize the preliminary results of this search

COMPTEL gamma ray and neutron measurements of solar flares

COMPTEL on the Compton Gamma Ray Observatory has measured the flux of x‐rays and neutrons from several solar flares. These data have also been used to image the Sun in both forms of radiation. Unusually intense flares occurred during June 1991 yielding data sets that offer some new insight into of how energetic protons and electrons are accelerated and behave in the solar environment. We summarize here some of the essential features in the solar flare data as obtained by COMPTEL during June 1991

Infrared receivers for low background astronomy: Incoherent detectors and coherent devices from one micrometer to one millimeter

The status of incoherent detectors and coherent receivers over the infrared wavelength range from one micrometer to one millimeter is described. General principles of infrared receivers are included, and photon detectors, bolometers, coherent receivers, and important supporting technologies are discussed, with emphasis on their suitability for low background astronomical applications. Broad recommendations are presented and specific opportunities are identified for development of improved devices

Neutron and gamma‐ray measurements of the solar flare of 1991 June 9

The COMPTEL Imaging Compton Telescope on‐board the Compton Gamma Ray Observatory measured significant neutron and γ‐ray fluxes from the solar flare of 9 June 1991. The γ‐ray flux had an integrated intensity (≳1 MeV) of ∼30 cm−2, extending in time from 0136 UT to 0143 UT, while the time of energetic neutron emission extended approximately 10 minutes longer, indicating either extended proton acceleration to high energies or trapping and precipitation of energetic protons. The production of neutrons without accompanying γ‐rays in the proper proportion indicates a significant hardening of the precipitating proton spectrum through either the trapping or extended acceleration process

Accelerated Ru-Cu Trinuclear Cooperative C−H Bond Functionalization of Carbazoles : A Kinetic and Computational Investigation

The mechanism of a trinuclear cooperative dehydrogenative C−N bond-forming reaction is investigated in this work, which avoids the use of chelate-assisting directing groups. Two new highly efficient Ru/Cu co-catalyzed systems were identified, allowing orders of magnitude greater TOFs than the previous state of the art. In-depth kinetic studies were performed in combination with advanced DFT calculations, which reveal a decisive rate-determining trinuclear Ru-Cu cooperative reductive elimination step (CRE)

Comparative Analysis of Tandem Repeats from Hundreds of Species Reveals Unique Insights into Centromere Evolution

Centromeres are essential for chromosome segregation, yet their DNA sequences evolve rapidly. In most animals and plants that have been studied, centromeres contain megabase-scale arrays of tandem repeats. Despite their importance, very little is known about the degree to which centromere tandem repeats share common properties between different species across different phyla. We used bioinformatic methods to identify high-copy tandem repeats from 282 species using publicly available genomic sequence and our own data. The assumption that the most abundant tandem repeat is the centromere DNA was true for most species whose centromeres have been previously characterized, suggesting this is a general property of genomes. Our methods are compatible with all current sequencing technologies. Long Pacific Biosciences sequence reads allowed us to find tandem repeat monomers up to 1,419 bp. High-copy centromere tandem repeats were found in almost all animal and plant genomes, but repeat monomers were highly variable in sequence composition and in length. Furthermore, phylogenetic analysis of sequence homology showed little evidence of sequence conservation beyond ~50 million years of divergence. We find that despite an overall lack of sequence conservation, centromere tandem repeats from diverse species showed similar modes of evolution, including the appearance of higher order repeat structures in which several polymorphic monomers make up a larger repeating unit. While centromere position in most eukaryotes is epigenetically determined, our results indicate that tandem repeats are highly prevalent at centromeres of both animals and plants. This suggests a functional role for such repeats, perhaps in promoting concerted evolution of centromere DNA across chromosomes