Science.gov

Sample records for 4-h virtual farm

  1. The Development of a Virtual Farm for Applications in Elementary Science Education

    ERIC Educational Resources Information Center

    Tarng, Wernhuar; Chang, Mei-Yu; Ou, Kuo-Liang; Yu, Kein-Fu; Hsieh, Kuen-Rong

    2012-01-01

    The goal of this study is to develop a virtual farm for educational applications. Users can play the role of a farmer by planting vegetables and raising poultry on the virtual farm to observe their growth through online learning activities. The virtual farm possesses educational and entertaining functions, and it is designed by simulating the real…

  2. PENG: a neural gas-based approach for pharmacophore elucidation. method design, validation, and virtual screening for novel ligands of LTA4H.

    PubMed

    Moser, Daniel; Wittmann, Sandra K; Kramer, Jan; Blöcher, René; Achenbach, Janosch; Pogoryelov, Denys; Proschak, Ewgenij

    2015-02-23

    The pharmacophore concept is commonly employed in virtual screening for hit identification. A pharmacophore is generally defined as the three-dimensional arrangement of the structural and physicochemical features of a compound responsible for its affinity to a pharmacological target. Given a number of active ligands binding to a particular target in the same manner, it can reasonably be assumed that they have some shared features, a common pharmacophore. We present a growing neural gas (GNG)-based approach for the extraction of the relevant features which we called PENG (pharmacophore elucidation by neural gas). Results of retrospective validation indicate an acceptable quality of the generated models. Additionally a prospective virtual screening for leukotriene A4 hydrolase (LTA4H) inhibitors was performed. LTA4H is a bifunctional zinc metalloprotease which displays both epoxide hydrolase and aminopeptidase activity. We could show that the PENG approach is able to predict the binding mode of the ligand by X-ray crystallography. Furthermore, we identified a novel chemotype of LTA4H inhibitors. PMID:25625859

  3. 4-H and Iowa.

    ERIC Educational Resources Information Center

    Gore, Deborah, Ed.

    1988-01-01

    This issue focuses on Iowa's role in the historical development of the 4-H youth program. "Roots in Iowa" and "Jessie Field Shambaugh: The Mother of 4-H" (J. Friedel) describes the rural Iowan roots of the 4-H program, which today is located in 80 different countries, and give the story of its founder. Jessie Shambaugh, a rural Iowa teacher and…

  4. Design and performance of the virtualization platform for offline computing on the ATLAS TDAQ Farm

    NASA Astrophysics Data System (ADS)

    Ballestrero, S.; Batraneanu, S. M.; Brasolin, F.; Contescu, C.; Di Girolamo, A.; Lee, C. J.; Pozo Astigarraga, M. E.; Scannicchio, D. A.; Twomey, M. S.; Zaytsev, A.

    2014-06-01

    With the LHC collider at CERN currently going through the period of Long Shutdown 1 there is an opportunity to use the computing resources of the experiments' large trigger farms for other data processing activities. In the case of the ATLAS experiment, the TDAQ farm, consisting of more than 1500 compute nodes, is suitable for running Monte Carlo (MC) production jobs that are mostly CPU and not I/O bound. This contribution gives a thorough review of the design and deployment of a virtualized platform running on this computing resource and of its use to run large groups of CernVM based virtual machines operating as a single CERN-P1 WLCG site. This platform has been designed to guarantee the security and the usability of the ATLAS private network, and to minimize interference with TDAQ's usage of the farm. Openstack has been chosen to provide a cloud management layer. The experience gained in the last 3.5 months shows that the use of the TDAQ farm for the MC simulation contributes to the ATLAS data processing at the level of a large Tier-1 WLCG site, despite the opportunistic nature of the underlying computing resources being used.

  5. Individual reactions to a multisensory immersive virtual environment: the impact of a wind farm on individuals.

    PubMed

    Ruotolo, Francesco; Senese, Vincenzo Paolo; Ruggiero, Gennaro; Maffei, Luigi; Masullo, Massimiliano; Iachini, Tina

    2012-08-01

    The aim of this study was to assess the impact of a wind farm on individuals by means of an audio-visual methodology that tried to simulate biologically plausible individual-environment interactions. To disentangle the effects of auditory and visual components on cognitive performances and subjective evaluations, unimodal (Audio or Video) and bimodal (Audio + Video) approaches were compared. Participants were assigned to three experimental conditions that reproduced a wind farm by means of an immersive virtual reality system: bimodal condition, reproducing scenarios with both acoustic and visual stimuli; unimodal visual condition, with only visual stimuli; unimodal auditory condition, with only auditory stimuli. While immersed in the virtual scenarios, participants performed tasks assessing verbal fluency, short-term verbal memory, backward counting, and distance estimations (egocentric: how far is the turbine from you?; allocentric: how far is the turbine from the target?). Afterwards, participants reported their degree of visual and noise annoyance. The results revealed that the presence of a visual scenario as compared to the only availability of auditory stimuli may exert a negative effect on resource-demanding cognitive tasks but a positive effect on perceived noise annoyance. This supports the idea that humans perceive the environment holistically and that auditory and visual features are processed in close interaction. PMID:22806673

  6. Individual reactions to a multisensory immersive virtual environment: the impact of a wind farm on individuals.

    PubMed

    Ruotolo, Francesco; Senese, Vincenzo Paolo; Ruggiero, Gennaro; Maffei, Luigi; Masullo, Massimiliano; Iachini, Tina

    2012-08-01

    The aim of this study was to assess the impact of a wind farm on individuals by means of an audio-visual methodology that tried to simulate biologically plausible individual-environment interactions. To disentangle the effects of auditory and visual components on cognitive performances and subjective evaluations, unimodal (Audio or Video) and bimodal (Audio + Video) approaches were compared. Participants were assigned to three experimental conditions that reproduced a wind farm by means of an immersive virtual reality system: bimodal condition, reproducing scenarios with both acoustic and visual stimuli; unimodal visual condition, with only visual stimuli; unimodal auditory condition, with only auditory stimuli. While immersed in the virtual scenarios, participants performed tasks assessing verbal fluency, short-term verbal memory, backward counting, and distance estimations (egocentric: how far is the turbine from you?; allocentric: how far is the turbine from the target?). Afterwards, participants reported their degree of visual and noise annoyance. The results revealed that the presence of a visual scenario as compared to the only availability of auditory stimuli may exert a negative effect on resource-demanding cognitive tasks but a positive effect on perceived noise annoyance. This supports the idea that humans perceive the environment holistically and that auditory and visual features are processed in close interaction.

  7. Managing 4-H Volunteer Staff: A 4-H Intern Report.

    ERIC Educational Resources Information Center

    Martin, Hope M.

    The 4-H intern report organizes concepts and materials to aid the extension worker in his role as coordinator and trainer of 4-H volunteer staff. A 10-item task analysis of the extension worker--4-H and youth--as volunteer leader coordinator is presented. The importance of managing a volunteer staff is touched upon, and models for job descriptions…

  8. Keeping 4-H Volunteer Leaders.

    ERIC Educational Resources Information Center

    Smith, Keith L.; Bigler, Nancy M.

    1985-01-01

    This study showed that continuing and discontinuing volunteer 4-H Club leaders are significantly different in their geographical location, number of children in family, and number of children in family who have participated in 4-H. These variables may affect the volunteer's decision to continue serving as a 4-H Club leader. (Author/CT)

  9. The gut microbiome as a virtual endocrine organ with implications for farm and domestic animal endocrinology.

    PubMed

    O'Callaghan, T F; Ross, R P; Stanton, C; Clarke, G

    2016-07-01

    The gut microbiome exerts a marked influence on host physiology, and manipulation of its composition has repeatedly been shown to influence host metabolism and body composition. This virtual endocrine organ also has a role in the regulation of the plasma concentrations of tryptophan, an essential amino acid and precursor to serotonin, a key neurotransmitter within both the enteric and central nervous systems. Control over the hypothalamic-pituitary-adrenal axis also appears to be under the influence of the gut microbiota. This is clear from studies in microbiota-deficient germ-free animals with exaggerated responses to psychological stress that can be normalized by monocolonization with certain bacterial species including Bifidobacterium infantis. Therapeutic targeting of the gut microbiota may thus be useful in treating or preventing stress-related microbiome-gut-brain axis disorders and metabolic diseases, much the same way as redirections of metabolopathies can be achieved through more traditional endocrine hormone-based interventions. Moreover, the implications of these findings need to be considered in the context of farm and domestic animal physiology, behavior, and food safety. PMID:27345323

  10. Validation of Individual-Based Markov-Like Stochastic Process Model of Insect Behavior and a "Virtual Farm" Concept for Enhancement of Site-Specific IPM.

    PubMed

    Lux, Slawomir A; Wnuk, Andrzej; Vogt, Heidrun; Belien, Tim; Spornberger, Andreas; Studnicki, Marcin

    2016-01-01

    The paper reports application of a Markov-like stochastic process agent-based model and a "virtual farm" concept for enhancement of site-specific Integrated Pest Management. Conceptually, the model represents a "bottom-up ethological" approach and emulates behavior of the "primary IPM actors"-large cohorts of individual insects-within seasonally changing mosaics of spatiotemporally complex faming landscape, under the challenge of the local IPM actions. Algorithms of the proprietary PESTonFARM model were adjusted to reflect behavior and ecology of R. cerasi. Model parametrization was based on compiled published information about R. cerasi and the results of auxiliary on-farm experiments. The experiments were conducted on sweet cherry farms located in Austria, Germany, and Belgium. For each farm, a customized model-module was prepared, reflecting its spatiotemporal features. Historical data about pest monitoring, IPM treatments and fruit infestation were used to specify the model assumptions and calibrate it further. Finally, for each of the farms, virtual IPM experiments were simulated and the model-generated results were compared with the results of the real experiments conducted on the same farms. Implications of the findings for broader applicability of the model and the "virtual farm" approach-were discussed. PMID:27602000

  11. 4-H Club Goat Guide.

    ERIC Educational Resources Information Center

    Brown, R. Kipp

    This guide provides information for 4-H Club members who have decided on a club goat project. Topics include general information in the following areas: show rules; facilities and equipment (barns/sheds, fences, feeders, water containers, and equipment); selection (structural correctness, muscle, volume and capacity, style and balance, and growth…

  12. Effectiveness of the Indiana 4-H Tractor Program: Alumni Perceptions.

    ERIC Educational Resources Information Center

    Carrabba, James J., Jr.; Talbert, B. Allen; Field, William E.; Tormoehlen, Roger

    2001-01-01

    Responses from Indiana 4-H tractor driving contestants 1982-197 (n=139) showed that 74% were employed on farms; most felt the contests effectively taught tractor safety and made them generally aware of safety. However, many still engaged in risky behaviors such as not wearing seatbelts in tractors with rollover protective structures or allowing…

  13. WNoDeS, a tool for integrated Grid and Cloud access and computing farm virtualization

    NASA Astrophysics Data System (ADS)

    Salomoni, Davide; Italiano, Alessandro; Ronchieri, Elisabetta

    2011-12-01

    INFN CNAF is the National Computing Center, located in Bologna, Italy, of the Italian National Institute for Nuclear Physics (INFN). INFN CNAF, also called the INFN Tier-1, provides computing and storage facilities to the International High-Energy Physics community and to several multi-disciplinary experiments. Currently, the INFN Tier-1 supports more than twenty different collaborations; in this context, optimization of the usage of computing resources is essential. This is one of the main drivers behind the development of a software called WNoDeS (Worker Nodes on Demand Service). WNoDeS, developed at INFN CNAF and deployed on the INFN Tier-1 production infrastructure, is a solution to virtualize computing resources and to make them available through local, Grid or Cloud interfaces. It is designed to be fully integrated with a Local Resource Management System; it is therefore inherently scalable and permits full integration with existing scheduling, policing, monitoring, accounting and security workflows. WNoDeS dynamically instantiates Virtual Machines (VMs) on-demand, i.e. only when the need arises; these VMs can be tailored and used for purposes like batch job execution, interactive analysis or service instantiation. WNoDeS supports interaction with user requests through traditional batch or Grid jobs and also via the Open Cloud Computing Interface standard, making it possible to allocate compute, storage and network resources on a pay-as-you-go basis. User authentication is supported via several authentication methods, while authorization policies are handled via gLite Argus. WNoDeS is an ambitious solution aimed at virtualizing cluster resources in medium or large scale computing centers, with up to several thousands of Virtual Machines up and running at any given time. In this paper, we descrive the WNoDeS architecture.

  14. 4-H in the 70's.

    ERIC Educational Resources Information Center

    Extension Service (USDA), Washington, DC.

    Developed under the leadership of the 1970 and 1971 Extension Committee on Organization and Policy 4-H Youth Subcommittees, the brochure offers a statement of potential and new directions for Extension 4-H youth programs. Opening sections deal with the functions of 4-H and balanced 4-H program expansion to serve seven million youth. Succeeding…

  15. Reaching Migrant Farmworker Youth through 4-H Career and Workforce Programs.

    ERIC Educational Resources Information Center

    Wille, Celina G.

    1999-01-01

    Migrant-farm-worker youth learned about employment and educational opportunities in agriculture through a 4-H-sponsored conference. The conference was developed by a partnership of university extension, community organizations, schools, and private industry. (SK)

  16. Adult 4-H Volunteer Empowerment in 4-H Youth Development Settings

    ERIC Educational Resources Information Center

    Olsen, Pamela

    2009-01-01

    The primary purpose of this study was to determine which factors related to adult 4-H volunteer empowerment in 4-H youth development settings. This study examined the relationship of adult 4-H volunteers' perceived leadership styles of Oregon 4-H Youth Development Educators (YDE) to the adult 4-H volunteer sense of empowerment. In addition,…

  17. Engaging Library Partners in 4-H Programming

    ERIC Educational Resources Information Center

    Fields, Nia Imani; Rafferty, Elizabeth

    2012-01-01

    When most people think about 4-H, they remember county fairs, livestock programs, and agricultural education. While these programs are still prominent, 4-H has grown in order to meet the growing demands of today's youth. The organization has expanded services and programs to serve rural, suburban, and urban youth in every state in the U.S. 4-H is…

  18. Strengthening 4-H by Analyzing Enrollment Data

    ERIC Educational Resources Information Center

    Hamilton, Stephen F.; Northern, Angela; Neff, Robert

    2014-01-01

    The study reported here used data from the ACCESS 4-H Enrollment System to gain insight into strengthening New York State's 4-H programming. Member enrollment lists from 2009 to 2012 were analyzed using Microsoft Excel to determine trends and dropout rates. The descriptive data indicate declining 4-H enrollment in recent years and peak…

  19. Towards more spatially explicit assessments of virtual water flows: linking local water use and scarcity to global demand of Brazilian farming commodities

    NASA Astrophysics Data System (ADS)

    Flach, Rafaela; Ran, Ylva; Godar, Javier; Karlberg, Louise; Suavet, Clement

    2016-07-01

    Global consumption of farming commodities is an important driver of water demand in regions of production. This is the case in Brazil, which has emerged as one of the main producers of globally traded farming commodities. Traditional methods to assess environmental implications of this demand rely on international trade material flows at country resolution; we argue for the need of finer scales that capture spatial heterogeneity in environmental variables in the regions of production, and that account for differential sourcing within the borders of a country of production. To illustrate this, we obtain virtual water flows from Brazilian municipalities to countries of consumption, by allocating high-resolution water footprints of sugarcane and soy production to spatially-explicit material trade flows. We found that this approach results in differences of virtual water use estimations of over 20% when compared to approaches that disregard spatial heterogeneity in sourcing patterns, for three of the main consumers of the analysed crops. This discrepancy against methods using national resolution in trade flows is determined by national heterogeneity in water resources, and differential sourcing. To illustrate the practical implications of this approach, we relate virtual water flows to water stress, identifying where global demand for water coincides with high levels of water stress. For instance, the virtual water flows for Brazilian sugarcane sourced by China were disproportionally less associated to areas with higher water stress when compared to those of the EU, due to EU’s much higher reliance on sugarcane from water scarce areas in Northeast Brazil. Our findings indicate that the policy relevance of current assessments of virtual water flows that rely on trade data aggregated at the national level may be hampered, as they do not capture the spatial heterogeneity in water resources, water use and water management options.

  20. 4-H Clover Awareness Teaching Guide.

    ERIC Educational Resources Information Center

    Rutherford, Barbara; Leach, Jennifer

    The purpose of this teaching guide is to introduce children in grades 1-4 and their parents to the 4-H program without the long-term commitment of the traditional 4-H club. The 4-H Clover Awareness Program was designed as an after-school program; however, it could be used in other settings such as a day camp. In addition to introducing children to…

  1. The Toddler: 4-H Child Development Project.

    ERIC Educational Resources Information Center

    Francis, Connie M.

    Part of a series for 4-H members between 9 and 19 years of age, this age-graded guide is designed to help children and adolescents: (1) understand the toddler's physical, mental, social, and emotional growth; (2) learn to care for a toddler; and (3) choose types of play that toddlers enjoy. Contents include suggestions on projects that 4-H members…

  2. Strengthening 4-H Program Communication through Technology

    ERIC Educational Resources Information Center

    Robideau, Kari; Santl, Karyn

    2011-01-01

    Advances in technology are transforming how youth and parents interact with programs. The Strengthening 4-H Communication through Technology project was implemented in eight county 4-H programs in Northwest Minnesota. This article outlines the intentional process used to effectively implement technology in program planning. The project includes:…

  3. Community Development: A 4-H Intern Report.

    ERIC Educational Resources Information Center

    Scheneman, C. Stephen

    State progress reports on the 4-H/Community Development program, a 1973 nationwide Federally sponsored program facilitating youth in community decision-making processes, indicate that the program appears to be evolving into a viable and integral part of the total 4-H program. Although the report describes unique program features of various States,…

  4. Relationships between 4-H Volunteer Leader Competencies and Skills Youth Learn in 4-H Programs

    ERIC Educational Resources Information Center

    Radhakrishna, Rama; Ewing, John C.

    2011-01-01

    This article examined the relationships between 4-H volunteer leader competencies and skills youth learn in 4-H. Using a descriptive-correlational research, the study reported found significant relationships between leadership competencies and skills youth learn in 4-H. Regression analysis revealed that two variables--skills and…

  5. Middle Childhood: 4-H Child Development Project.

    ERIC Educational Resources Information Center

    Francis, Connie M.

    Part of a series for 4-H members between 9 and 19 years of age, this age-graded guide to the development of 6-, 7-, and 8-year-olds aims to help 4-H members who are children and adolescents themselves: (1) understand the physical, mental, social, and emotional development of children in middle childhood; (2) learn to care for a child in middle…

  6. 4-H Textile Science Beginner Projects.

    ERIC Educational Resources Information Center

    Scholl, Jan

    This packet contains three 4-H projects for students beginning the sewing sequence of the textile sciences area. The projects cover basics of sewing using sewing machines, more difficult sewing machine techniques, and hand sewing. Each project provides an overview of what the student will learn, what materials are needed, and suggested projects…

  7. Multi-state 4-H energy program

    SciTech Connect

    Bakker, U.B.; Garthe, J.W.

    1983-06-01

    Through Agricultural Engineering 4-H Energy Programs, youth can be educated to gain knowledge, increase hands on skills, and incorporate energy-saving techniques into their lifestyle. In a pilot multi-state energy program tested by 13 states, youth increased their energy awareness.

  8. 4-H for Central City Minorities

    ERIC Educational Resources Information Center

    Paige, Joseph C.

    1970-01-01

    Joseph C. Paige is the Dean of Community Education and Director of Cooperative Extension Service of the only urban Land-Grant College, Federal City College, in Washington, D.C. Here he is interviewed about 4-H with children of poor ethnic groups in the District of Columbia. (NL)

  9. The Preschooler: 4-H Child Development Project.

    ERIC Educational Resources Information Center

    Francis, Connie M.

    Intended for 4-H participants who plan and implement activities in the area of child development, this booklet provides a study guide to help young learners: (1) gain understanding of a preschool child's physical, mental, social, and emotional growth; (2) learn to care for a preschooler and promote preschoolers' feelings of security and safety;…

  10. The Infant: 4-H Child Development Project.

    ERIC Educational Resources Information Center

    Francis, Connie M.

    This booklet for 4-H members who elect to undertake projects in child caregiving provides guidelines and information that help children and adolescents between 9 and 19 years of age: (1) understand infants' physical, mental, social, and emotional growth; (2) learn to care for a baby and promote feelings of security and safety; and (3) choose types…

  11. Separates. 4-H Textile Science Advanced Project.

    ERIC Educational Resources Information Center

    Scholl, Jan F.

    This booklet, which was developed for use by 4-H club members in Pennsylvania, contains the information required to sew a two-piece nontailored outfit and/or a one-or two-piece dress. The following are among the topics covered: the difference between a fiber and a fabric; properties of different fibers and fabrics; common jacket, neckline, sleeve,…

  12. 4-H Science Inquiry Video Series

    ERIC Educational Resources Information Center

    Green, Jeremy W.; Black, Lynette; Willis, Patrick

    2013-01-01

    Studies support science inquiry as a positive method and approach for 4-H professionals and volunteers to use for teaching science-based practices to youth. The development of a science inquiry video series has yielded positive results as it relates to youth development education and science. The video series highlights how to conduct science-rich…

  13. Effectiveness of the 4-H Program as Perceived by Parents of 4-H Participants

    ERIC Educational Resources Information Center

    Radhakrishna, Rama; Foley, Caitlin; Ingram, Patreese; Ewing, John C.

    2013-01-01

    The study reported here examined the effectiveness of 4-H program as perceived by parents of program participants. Descriptive-correlational design was employed, with data collected using a mail survey. Parents perceived 4-H as an effective organization in teaching life skills to youth. Significant relationships were found between parents'…

  14. National 4-H Common Measures: Initial Evaluation from California 4-H

    ERIC Educational Resources Information Center

    Lewis, Kendra M.; Horrillo, Shannon J.; Widaman, Keith; Worker, Steven M.; Trzesniewski, Kali

    2015-01-01

    Evaluation is a key component to learning about the effectiveness of a program. This article provides descriptive statistics of the newly developed National 4-H Common Measures (science, healthy living, citizenship, and youth development) based on data from 721 California 4-H youth. The measures were evaluated for their reliability and validity of…

  15. VIBRATIONALLY EXCITED C{sub 4}H

    SciTech Connect

    Cooksy, Andrew L.; Gottlieb, C. A.; Thaddeus, P.; Patel, Nimesh A.; Young, Ken H.; McCarthy, M. C.; Killian, T. C.

    2015-02-01

    Rotational spectra in four new excited vibrational levels of the linear carbon chain radical C{sub 4}H were observed in the millimeter band between 69 and 364 GHz in a low pressure glow discharge, and two of these were observed in a supersonic molecular beam between 19 and 38 GHz. All have rotational constants within 0.4% of the X{sup 2}Σ{sup +} ground vibrational state of C{sub 4}H and were assigned to new bending vibrational levels, two each with {sup 2}Σ and {sup 2}Π vibrational symmetry. The new levels are tentatively assigned to the 1ν{sub 6} and 1ν{sub 5} bending vibrational modes (both with {sup 2}Π symmetry), and the 1ν{sub 6}+1ν{sub 7} and 1ν{sub 5}+1ν{sub 6} combination levels ({sup 2}Σ symmetry) on the basis of the derived spectroscopic constants, relative intensities in our discharge source, and published laser spectroscopic and quantum calculations. Prior spectroscopic constants in the 1ν{sub 7} and 2ν{sub 7} levels were refined. Also presented are interferometric maps of the ground state and the 1ν{sub 7} level obtained with the Submillimeter Array (SMA) near 257 GHz which show that C{sub 4}H is present near the central star in IRC+10216. We found no evidence with the SMA for the new vibrationally excited levels of C{sub 4}H at a peak flux density averaged over a 3{sup ′′} synthesized beam of ⩾0.15 Jy/beam in the 294–296 and 304–306 GHz range, but it is anticipated that rotational lines in the new levels might be observed in IRC+10216 when ALMA attains its full design capability.

  16. Learnings and Recommendations to Advance 4-H Science Readiness

    ERIC Educational Resources Information Center

    Schmitt-McQuitty, Lynn; Carlos, Ramona; Smith, Martin H.

    2014-01-01

    The case study investigation reported here assessed California 4-H professionals' understanding of the essential components of effective 4-H Science programming as established by the National 4-H Science Mission Mandate. Using the 4-H Science Checklist as the basis for defining 4-H Science Readiness, academic and program staff were surveyed…

  17. Thermochemistry of disputed soot formation intermediates C4H3 and C4H5.

    PubMed

    Wheeler, Steven E; Allen, Wesley D; Schaefer, Henry F

    2004-11-01

    Accurate isomeric energy differences and standard enthalpies of formation for disputed intermediates in soot formation, C(4)H(3) and C(4)H(5), have been determined through systematic extrapolations of ab initio energies. Electron correlation has been included through second-order Z-averaged perturbation theory (ZAPT2), and spin-restricted, open-shell coupled-cluster methods through triple excitations [ROCCSD, ROCCSD(T), and ROCCSDT] utilizing the correlation-consistent hierarchy of basis sets, cc-pVXZ (X = D, T, Q, 5, and 6), followed by extrapolations to the complete basis set limit via the focal point method of Allen and co-workers. Reference geometries were fully optimized at the ROCCSD(T) level with a TZ(2d1f,2p1d) basis set. Our analysis finds that the resonance-stabilized i-C(4)H(3) and i-C(4)H(5) isomers lie 11.8 and 10.7 kcal mol(-1) below E-n-C(4)H(3) and E-n-C(4)H(5), respectively, several kcal mol(-1) (more, less) than reported in recent (diffusion Monte Carlo, B3LYP density-functional) studies. Moreover, in these systems Gaussian-3 (G3) theory suffers from large spin contamination in electronic wave functions, poor reference geometries, and anomalous vibrational frequencies, but fortuitous cancellation of these sizable errors leads to isomerization energies apparently accurate to 1 kcal mol(-1). Using focal-point extrapolations for isodesmic reactions, we determine the enthalpies of formation (delta(f)H(0) (composite function)) for i-C(4)H(3), Z-n-C(4)H(3), E-n-C(4)H(3), i-C(4)H(5), Z-n-C(4)H(5), and E-n-C(4)H(5) to be 119.0, 130.8, 130.8, 78.4, 89.7, and 89.1 kcal mol(-1), respectively. These definitive values remove any remaining uncertainty surrounding the thermochemistry of these isomers in combustion models, allowing for better assessment of whether even-carbon pathways contribute to soot formation. PMID:15527344

  18. Thermochemistry of disputed soot formation intermediates C4H3 and C4H5

    NASA Astrophysics Data System (ADS)

    Wheeler, Steven E.; Allen, Wesley D.; Schaefer, Henry F.

    2004-11-01

    Accurate isomeric energy differences and standard enthalpies of formation for disputed intermediates in soot formation, C4H3 and C4H5, have been determined through systematic extrapolations of ab initio energies. Electron correlation has been included through second-order Z-averaged perturbation theory (ZAPT2), and spin-restricted, open-shell coupled-cluster methods through triple excitations [ROCCSD, ROCCSD(T), and ROCCSDT] utilizing the correlation-consistent hierarchy of basis sets, cc-pVXZ (X=D, T, Q, 5, and 6), followed by extrapolations to the complete basis set limit via the focal point method of Allen and co-workers. Reference geometries were fully optimized at the ROCCSD(T) level with a TZ(2d1f,2p1d) basis set. Our analysis finds that the resonance-stabilized i-C4H3 and i-C4H5 isomers lie 11.8 and 10.7 kcal mol-1 below E-n-C4H3 and E-n-C4H5, respectively, several kcal mol-1 (more, less) than reported in recent (diffusion Monte Carlo, B3LYP density-functional) studies. Moreover, in these systems Gaussian-3 (G3) theory suffers from large spin contamination in electronic wave functions, poor reference geometries, and anomalous vibrational frequencies, but fortuitous cancellation of these sizable errors leads to isomerization energies apparently accurate to 1 kcal mol-1. Using focal-point extrapolations for isodesmic reactions, we determine the enthalpies of formation (ΔfH0∘) for i-C4H3, Z-n-C4H3, E-n-C4H3, i-C4H5, Z-n-C4H5, and E-n-C4H5 to be 119.0, 130.8, 130.8, 78.4, 89.7, and 89.1 kcal mol-1, respectively. These definitive values remove any remaining uncertainty surrounding the thermochemistry of these isomers in combustion models, allowing for better assessment of whether even-carbon pathways contribute to soot formation.

  19. Minnesota 4-H Science of Agriculture Challenge: Infusing Agricultural Science and Engineering Concepts into 4-H Youth Development

    ERIC Educational Resources Information Center

    Rice, Joshua E.; Rugg, Bradley; Davis, Sharon

    2016-01-01

    Youth involved in 4-H projects have been engaged in science-related endeavors for years. Since 2006, 4-H has invested considerable resources in the advancement of science learning. The new Minnesota 4-H Science of Agriculture Challenge program challenges 4-H youth to work together to identify agriculture-related issues in their communities and to…

  20. Diversity Inclusion in 4-H Youth Programs: Examining the Perceptions among West Virginia 4-H Youth Professionals

    ERIC Educational Resources Information Center

    LaVergne, Douglas D.

    2013-01-01

    The study reported here sought to examine the perceptions of 4-H youth professionals towards diversity inclusion in 4-H youth programs. A majority of professionals positively reported that there are benefits for youth of color and youth with disabilities in 4-H youth programs. Respondents indicated that the lack of information about 4-H youth…

  1. Curtiss JN-4H Towing Model Wing

    NASA Technical Reports Server (NTRS)

    1921-01-01

    In 1919 the NACA Langley laboratory received its first three research aircraft which were Curtiss JN-4Hs borrowed from the US Army Air Service at Langley Field. One of the first research projects of the laboratory initiated that year was a flight investigation of the lift and drag characteristics of the JN-4H. One of the objectives of the flight tests was to obtain data for correlation with wind-tunnel test results measured at MIT and to aid in the derivation of techniques for extrapolation of model results to full-scale conditions. In a pioneering aeronautical effort in 1920, pressure orifices were installed in the horizontal tail of one of the Jennies and connected to glass manometers for pressure measurements that could be photographed in flight. The NACA also used the aircraft in some of the earliest experiments on maneuverability in 1921. In addition to serving as test subjects, the aircraft were used for measurements of aerodynamic behavior of aircraft components. In this photograph made in 1921, one of the JN- 4Hs is towing a model of an aircraft wing to obtain lift and drag information for comparison to tunnel results. All three Jenny aircraft departed Langley in 1923. Reference: 'Flying the Frontiers: NACA and NASA Experimental Aircraft' by Arthur Pearcy. Naval Institute Press, 1993. ISBN 1-55750-258-7

  2. The Big E (Energy). 4-H Energy Project. 4-H Member's E-Book, Unit 1.

    ERIC Educational Resources Information Center

    Caldwell, William; And Others

    This activity and record book is designed for unit 1 (ages 9-11) of the Nebraska 4-H Energy Project. In this project, members are required to: (1) use energy wisely by closing doors and turning off lights; (2) inspecting homes for energy use at least once; (3) judging the best use of lighting in a home; (4) sharing ideas about energy use in a…

  3. CPR: Purposeful Action. Putting New Life into 4-H.

    ERIC Educational Resources Information Center

    Jones, Deborah A.; Smith, William C.

    1988-01-01

    In Ohio, 4-H professionals found that it is necessary to conduct market research to have an effective program. Cardiopulmonary resuscitation (CPR) training has been successful in strengthening the 4-H position in the marketplace. (JOW)

  4. Hamsters?! What Does 4-H Stand for, Anyway?

    ERIC Educational Resources Information Center

    Grundeen, Brenda

    This paper briefly traces the history of 4-H youth development programs, explains what youth development is, and shows how the experiential learning model is used in 4-H. Begun over 75 years ago as a means of extending the learning of the land-grant university to rural youth, 4-H is part of the Cooperative Extension Service. The curriculum…

  5. The 4-H Club Meeting: An Essential Youth Development Strategy

    ERIC Educational Resources Information Center

    Cassels, Alicia; Post, Liz; Nestor, Patrick I.

    2015-01-01

    The club meeting has served as a key delivery method for 4-H programming across the United States throughout its history. A survey of WV 4-H community club members reinforces the body of evidence that the 4-H club meeting is an effective vehicle for delivering positive youth learning opportunities within the umbrella of the Essential Elements of…

  6. Using Digital Classrooms to Conduct 4-H Club Meetings

    ERIC Educational Resources Information Center

    West, Patricia; Fuhrman, Nicholas E.; Morgan, A. Christian; Duncan, Dennis W.

    2012-01-01

    Using computer technology and digital classrooms to conduct 4-H Club meetings is an efficient way to continue delivering quality 4-H programming during times of limited resources and staff. Nineteen Junior and Senior 4-H'ers participated in seven digital classroom workshops using the Wimba Classroom application. These digital classroom…

  7. Factors Affecting Teen Involvement in Pennsylvania 4-H Programming

    ERIC Educational Resources Information Center

    Gill, Bart E.; Ewing, John C.; Bruce, Jacklyn A.

    2010-01-01

    The study reported here determined the factors that affect teen involvement in 4-H programming. The design of the study was descriptive and correlational in nature. Using a purposive sampling procedure, a survey questionnaire was distributed to all (N=214) 4-H members attending the 4-H State Leadership Conference. The major findings of the study…

  8. Why 4-H Members Leave: A Study of Discontinuance through Both Current 4-H Members and Former Members

    ERIC Educational Resources Information Center

    Chilek, Kevin Dwayne

    2012-01-01

    4-H members quit. It is part of every 4-H program, and according to the research, it is even part of growing up. If only we knew why they quit, we could possibly do something about it. To date, the reasons youth join 4-H have been more thoroughly researched than the reasons they quit. This study explores why youth choose to discontinue membership…

  9. The Oneida County 4-H Conservation Field Days Conflict.

    ERIC Educational Resources Information Center

    Brown, Stephen C.; Vonhof, Sarah; Kelley, Alicia

    2003-01-01

    Examines the various perspectives held by the three major organizations involved (an environmental citizens group, a local sportsmen's club, and the cooperative extension service) regarding a conflict over a 4-H program involving hunting and wildlife management. Discusses why the 4-H program's attempt to build consensus among the organizations was…

  10. Embracing Scientific and Engineering Practices in 4-H

    ERIC Educational Resources Information Center

    Worker, Steven M.

    2013-01-01

    The 4-H Science Initiative has renewed efforts to strengthen 4-H programmatic and evaluation efforts in science and engineering education. A fundamental component of this initiative is to provide opportunities to youth to aid in their development of science process skills; however, emerging research stresses the importance of engaging youth in…

  11. Council of Presidents: A Multifaceted Idea for 4-H

    ERIC Educational Resources Information Center

    Torretta, Alayne

    2015-01-01

    Communication between 4-H professionals and the youth they work with is an important part of a successful 4-H program. By creating a Council of Presidents comprised of officers of all the clubs in your county, you can increase communication while assuring your program addresses all four essential elements. The Council is also as a vehicle for…

  12. 4-H Participation and Science Interest in Youth

    ERIC Educational Resources Information Center

    Heck, Katherine; Carlos, Ramona M.; Barnett, Cynthia; Smith, Martin H.

    2012-01-01

    The study reported here investigated the impacts of participation in 4-H on young people's interest and participation in science. Survey data were collected from relatively large and ethnically diverse samples of elementary and high school-aged students in California. Results indicated that although elementary-grade 4-H members are not more…

  13. Stabilization of 4H hexagonal phase in gold nanoribbons

    PubMed Central

    Fan, Zhanxi; Bosman, Michel; Huang, Xiao; Huang, Ding; Yu, Yi; Ong, Khuong P.; Akimov, Yuriy A.; Wu, Lin; Li, Bing; Wu, Jumiati; Huang, Ying; Liu, Qing; Eng Png, Ching; Lip Gan, Chee; Yang, Peidong; Zhang, Hua

    2015-01-01

    Gold, silver, platinum and palladium typically crystallize with the face-centred cubic structure. Here we report the high-yield solution synthesis of gold nanoribbons in the 4H hexagonal polytype, a previously unreported metastable phase of gold. These gold nanoribbons undergo a phase transition from the original 4H hexagonal to face-centred cubic structure on ligand exchange under ambient conditions. Using monochromated electron energy-loss spectroscopy, the strong infrared plasmon absorption of single 4H gold nanoribbons is observed. Furthermore, the 4H hexagonal phases of silver, palladium and platinum can be readily stabilized through direct epitaxial growth of these metals on the 4H gold nanoribbon surface. Our findings may open up new strategies for the crystal phase-controlled synthesis of advanced noble metal nanomaterials. PMID:26216712

  14. Sodium diffusion in 4H-SiC

    SciTech Connect

    Linnarsson, M. K. Hallén, A.

    2014-09-01

    Sodium diffusion has been studied in p-type 4H-SiC. Heat treatments have been performed from 1200 °C to 1800 °C for 1 min to 4 h. Secondary ion mass spectrometry has been used to measure the sodium distribution. We show that sodium has a considerable mobility at 1200 °C in p-type 4H-SiC. On the other hand for sodium atoms trapped at suitable sites the mobility is limited up to 1800 °C. Trap limited diffusion kinetics is suggested and an effective diffusivity has been extracted with an activation energy of 4 eV for sodium diffusion in p-type 4H-SiC.

  15. Properties of homoepitaxial 4H-SiC and characteristics of Ti/4H-SiC Schottky barrier diodes

    NASA Astrophysics Data System (ADS)

    Chen, G.; Li, Z. Y.; Bai, S.; Han, P.

    2008-02-01

    This paper describes the properties of the homoepitaxial 4H-SiC layer, the fabrication and electrical parameters of Ti/4H-SiC Schottky barrier diode (SBD). The 4H-SiC epitaxial layers, grown on the commercially available 8°off-oriented Si-face(0001) single-crystal 4H-SiC wafers, have been performed at 1550~1600°C by using the step controlled epitaxy with low pressure chemical vapor deposition. X-ray diffraction measurement result indicates the single crystal nature of the epilayer, and Raman spectrum shows the typical 4H-SiC feature peaks. When the off-oriented angle of substrate is 8°, the epitaxial growth perfectly replicates the substrate's polytype. High quality 4H-SiC epilayer has been generated on the 4H-SiC substrate. Ti/4H-SiC SBDs with blocking voltage 1kV have been made on an undoped epilayer with 12um in thick and 3×10 15cm -3 in carrier density. The ideality factor n=1.16 and the effective barrier height φ e=0.9V of the Ti/4H-SiC SBDs are measured with method of forward density-voltage (J-V). The diode rectification ratio of forward to reverse (defined at +/-1V) is over 10 7 at room temperature. By using B + implantation, an amorphous layer as the edge termination is formed. The SBDs have on-state current density of 200A/cm2 at a forward voltage drop of about 2V. The specific on-resistance for the rectifier is found to be as 6.6mΩ•cm2.

  16. Isomer Energy Differences for the C4H3 and C4H5 Isomers UsingDiffusion Monte Carlo

    SciTech Connect

    Domin, D.; Lester Jr., W.A.; Whitesides, R.; Frenklach, M.

    2007-12-01

    A new diffusion Monte Carlo study is performed on the isomers of C{sub 4}H{sub 3} and C{sub 4}H{sub 5} emulating the methodology of a previous study [Int. J. Chem. Kinetics 33, 808 (2001)]. Using the same trial wave function form of the previous study, substantially different isomerization energies were found owing to the use of larger walker populations in the present work. The energy differences between the E and I isomers of C{sub 4}H{sub 3} were found to be 10.5 {+-} 0.5 kcal/mol and for C{sub 4}H{sub 5}, 9.7 {+-} 0.6 kcal/mol. These results are in reasonable accord with recent MRCI and CCSD(T) findings.

  17. Electronic spectra of C4H3Cl+ isomers

    NASA Astrophysics Data System (ADS)

    Chakrabarty, S.; Rudnev, V.; Fulara, J.; Dietsche, R.; Nagy, A.; Garkusha, I.; Mazzotti, F. J.; Rice, C. A.; Maier, J. P.

    2012-12-01

    Two experimental methods were applied to identify the structure and electronic transitions of C4H3Cl+ isomers. The first is a direct absorption technique where mass-selected ions are embedded in 6 K neon matrices using a mass-selected ion beam and absorption spectra of different C4H3Cl+ isomers were thus observed. The second is a gas phase method on ions which have been collisional cooled with cryogenic helium inside of a 22-pole ion trap. The c-type (1)2 A‧ ← X 2 A″ electronic transition of a C4H3Cl+ isomer could then be measured by a one-colour, two-photon technique at 20 and 50 K in the gas phase. The two sets of data, complemented by calculated excitation energies, allowed the assignment of particular isomers. Rotational structure in the gas phase spectra was resolved for C4H3 35Cl+ and C4H3 37Cl+ isomers of cis-1-chlorobutenynylium. The analysis leads to the spectroscopic constants: T 00 = 19 184.680(5), ? , ? , ? , ? , ? and ? (all in cm-1).

  18. On the Ionization Energies of C4H3 Isomers

    SciTech Connect

    Kaiser, Ralf I.; Mebel, Alexander; Kostko, Oleg; Ahmed, Musahid

    2009-09-16

    We have conducted a combined experimental and theoretical study on the formation of distinct isomers of resonantly stabilized free radicals, C4H3, which are important intermediates in the formation of polycyclic aromatic hydrocarbons in combustion flames and possibly in the interstellar medium. Our study utilized laser ablation of graphite in combination with seeding the ablated species in neat methylacetylene gas which also acted as a reagent. Photoionization efficiency (PIE) curves were recorded of the C4H3 isomers at the Advanced Light Source from 8.0 to 10.3 eV. The experimental PIE curve was compared with theoretical ones suggesting the formation of four C4H3 radicals: two acyclic structures i-C4H3 [1] and E/Z-n-C4H3 [2E/2Z]and two cyclic isomers 3 and 4. These molecules are likely formed via an initial addition of ground state carbon atoms to the carbon-carbon triple bond of the methylacetylene molecule followed by isomerization via hydrogen migrations and ring opening and emission of atomic hydrogen from these intermediates.

  19. Density Functional Exploration of C4H3N Isomers.

    PubMed

    Custer, Thomas; Szczepaniak, Urszula; Gronowski, Marcin; Fabisiewicz, Emilia; Couturier-Tamburelli, Isabelle; Kołos, Robert

    2016-07-28

    Molecules having C4H3N stoichiometry are of astrophysical interest. Two of these, methylcyanoacetylene (CH3C3N) and its structural isomer allenyl cyanide (H2CCCHN), have been observed in interstellar space, while several more have been examined in laboratories. Here we describe, for a broad range of C4H3N isomers, density functional calculations (B3LYP/aug-cc-pVTZ) of molecular parameters including the energetics, geometries, rotational constants, electric dipole moments, polarizabilities, vibrational IR frequencies, IR absorption intensities, and Raman activities. Singlet-triplet splittings as well as singlet vertical electronic excitation energies are given for selected species. The identification of less stable C4H3N molecules, generated in ongoing spectroscopic experiments, relies heavily on these quantum chemical predictions. PMID:27341606

  20. The Big E (Energy). 4-H Member Guide, Unit 2.

    ERIC Educational Resources Information Center

    Caldwell, William; And Others

    This activity and record book is designed for unit 2 (ages 12-14) of the Nebraska 4-H Energy Project. Aims, energy attitudes to be developed, and instructions are provided for each activity. Activities include: (1) a word search of energy-related words (with definitions provided); (2) determining fuel waste; (3) reading electric/gas meters and…

  1. Textile Science Leader's Guide. 4-H Textile Science.

    ERIC Educational Resources Information Center

    Scholl, Jan

    This instructor's guide provides an overview of 4-H student project modules in the textile sciences area. The guide includes short notes explaining how to use the project modules, a flowchart chart showing how the project areas are sequenced, a synopsis of the design and content of the modules, and some program planning tips. For each of the…

  2. "Ohio 4-H CARTEENS": Peer Intervention Safety Program.

    ERIC Educational Resources Information Center

    Cropper, Rebecca J.

    1999-01-01

    Ohio 4-H's CARTEENS seeks to reduce juvenile traffic violations in a program designed and presented by teen peer educators with guidance and technical assistance from the state highway patrol. Teens examined court data to determine content, which includes defensive driving, rural road safety, and dealing with peer pressure. (SK)

  3. Fashion Revue. 4-H Textile Science Activity Guide.

    ERIC Educational Resources Information Center

    Scholl, Jan

    This publication was developed to help students participating in Fashion Review, a 4-H event in which students model a clothing outfit and accessories and are judged on their modeling ability, their presentation, and how well the clothing and accessory choices complement the students' skin tones, hair color, figure or physique, personality, and…

  4. Minnesota 4-H Youth Program Quality Improvement Model

    ERIC Educational Resources Information Center

    Herman, Margo; Grant, Samantha

    2015-01-01

    The University of Minnesota Extension Center for Youth Development made an organizational decision in 2011 to invest in a system-wide approach to implement youth program quality into the 4-H program using the Youth Program Quality Assessment (YPQA) tool. This article describes the four key components to the Minnesota Youth Program Quality…

  5. The Big E (Energy). 4-H Member Guide, Unit 3.

    ERIC Educational Resources Information Center

    Caldwell, William; And Others

    This activity and record book is designed for unit 3 (ages 15-19) of the Nebraska 4-H Energy Project. Aims, energy attitudes to be developed, and instructions are provided for each activity. Activities include: (1) determining ways to reduce energy waste with hot water heaters; (2) making personal choices about using appliances; (3) conducting a…

  6. Marketing Strategies for Recruiting 4-H Members in West Virginia.

    ERIC Educational Resources Information Center

    Wingenbach, Gary J.; Nestor, Cheryl; Lawrence, Layle D.; Gartin, Stacy A.; Woloshuk, Jean; Mulkeen, Patricia

    2000-01-01

    According to a survey of 174 West Virginia 4-H members aged 13-18, the Internet and word of mouth were most effective in recruiting new members. Active messages stressing camps, fun, and friendship had the most influence on retention. A statewide marketing plan was recommended. (SK)

  7. Keys To The Kansas Environment. 4-H School Enrichment Program.

    ERIC Educational Resources Information Center

    Kansas State Univ., Manhattan. Extension Service.

    The 4-H Club packet for preschool and elementary school children contains nine "keys", or short learning exercises, designed to enrich science and environmental education both in and out of the classroom. Each "key" includes the purpose of the activity, the intended audience, the best time of the year for the activity, background information,…

  8. Folkpatterns 4-H Leader's Guide: A Cultural Heritage Project.

    ERIC Educational Resources Information Center

    Kozma, LuAnne Gaykowski

    Folkpatterns is a 4-H program in which young people investigate folklore, cultural traditions, and local history. These materials include a leader's guide and Folkpatterns activities. The leader's guide provides information for leading a Folkpatterns project and 12 sample meeting plans to be used with Folkpatterns members or to be adapted for use…

  9. CONSERVING OUR NATURAL RESOURCES, A 4-H LEADER'S GUIDE.

    ERIC Educational Resources Information Center

    AMICK, W. ROBERT; AND OTHERS

    AN EFFECTIVE 4-H CONSERVATION PROGRAM IS DEVELOPED AROUND THE FOLLOWING BASIC CONCEPTS--(1) MAN IS A PART OF THE NATURAL WORLD, IN WHICH THERE ARE MANY VALUABLE MATERIALS, (2) MAN HAS LEARNED TO USE MANY OF THOSE MATERIALS FOR HUMAN SUSTENANCE AND BETTERMENT, AND (3) MAN'S ECONOMIC, SOCIAL, AND GENERAL WELFARE IS LARGELY DEPENDENT UPON THE MANNER…

  10. Self-Protection: A New Approach to 4-H Health.

    ERIC Educational Resources Information Center

    Wright, Sharon K. B.

    This document introduces the issue of self-protection as the Minnesota 4-H Youth Development response to self-destructive behavior among adolescents. It presents findings from a statewide survey of over 36,000 secondary school students using the Minnesota Adolescent Health Survey. Responses are given in the areas of health, school attitudes,…

  11. The Evaluation Attitudes and Practices of 4-H Educators

    ERIC Educational Resources Information Center

    Lekies, Kristi S.; Bennett, Amanda M.

    2011-01-01

    Extension educators are expected to conduct program evaluation. An Internet survey was sent to county 4-H educators in Ohio to examine their evaluation attitudes and practices, as well as barriers to conducting evaluation. Respondents indicated a range of attitudes about evaluation and limited use of different designs and methods. Having enough…

  12. Implementing and Assessing 4-H Educational Activity Kits for Children

    ERIC Educational Resources Information Center

    Scheer, Scott D.; Yeske, Janine; Zimmer, Bruce

    2011-01-01

    Educational activity kits were developed and implemented through a statewide effort for 4-H Youth Development Extension programs serving 5-8 year-old children. The purpose of the kits was to promote life skills in children and assess the learning environment. Data was collected based on the observations of 577 children across 22 counties. Findings…

  13. A Phenomenological Look at 4-H Volunteer Motives for Service

    ERIC Educational Resources Information Center

    Schrock, Jessalyn; Kelsey, Kathleen D.

    2013-01-01

    Volunteers play a vital role in 4-H programs. Without their service, many programs would not be possible. Understanding volunteer motives provides Extension educators with tools for finding high-quality volunteers. The research reported here used McClelland's (1985) framework for motivation (affiliation, achievement, and power) and…

  14. New Jersey 4-H Goat Extravaganza: Efficiently Meeting the Educational Needs of 4-H Goat Project Members, Volunteers, and Parents

    ERIC Educational Resources Information Center

    Ripberger, Chad

    2014-01-01

    The 4-H Goat Extravaganza maximizes limited resources to help youth and adults develop knowledge and skills in goat care and management. It capitalizes on the talents and interests of volunteers to efficiently combine a goat-themed art show, team presentation contest, quiz bowl, skillathon, and adult workshop into 1 day. This article outlines the…

  15. Water Worlds. 4-H Member's Guide M-5-18; 4-H Leaders Guide L-5-18.

    ERIC Educational Resources Information Center

    Hawkes, Janet E.; And Others

    This pocket folder of materials is designed to provide children aged 9 to 12 with an opportunity to explore and observe aquatic environments. The package includes a 4-H Leader's guide, member's guide, and supplementary materials. The leader's guide contains safety considerations, tips and techniques, and additional activities for getting started…

  16. Starting and Maintaining a Marine Aquarium: 4-H Members Guide [and] 4-H Member's Project Record Book.

    ERIC Educational Resources Information Center

    Crenshaw, Neil

    The guide and the project record book included in this document are designed for 4-H members who would like to start a salt-water aquarium project. The guide includes the following topics: (1) general requirements for salt-water aquariums; (2) directions for making an aquarium; (3) suggestions for where to locate it; (4) pros and cons of using…

  17. Farm Living.

    ERIC Educational Resources Information Center

    Marcoux, Mary F.

    1990-01-01

    Described are activities using ants. Ant hunting, a list of books on the topic, information, and ant farming are included. The procedures for assembling and maintenance of an ant farm are presented. (KR)

  18. 4H-SiC detectors for ultraviolet light monitoring

    NASA Astrophysics Data System (ADS)

    Mazzillo, M.; Sciuto, A.; Badalà, P.; Carbone, B.; Russo, A.; Coffa, S.

    2015-02-01

    Silicon Carbide (SiC) provides the unique property of near-perfect visible blindness and very high signal-to-noise ratio due to the high quantum efficiency and low dark current even at high temperature. These features make SiC the best available material for the manufacturing of visible blind semiconductor ultraviolet (UV) light detectors. Thanks to their properties, SiC detectors have been extensively used in fact for flame detection monitoring, UV sterilization and astronomy. Here we report on the electrical and optical performance of patterned thin metal film NiSi/4H-SiC vertical Schottky photodiodes with different semiconductor exposed area suitably designed for UV light monitoring.

  19. Experimental investigations of the hypernucleus Λ4H

    NASA Astrophysics Data System (ADS)

    Achenbach, P.; Schulz, F.; Aulenbacher, S.; Beričič, J.; Bleser, S.; Böhm, R.; Bosnar, D.; Correa, L.; Distler, M. O.; Esser, A.; Fonvieille, H.; Friščić, I.; Fujii, Y.; Fujita, M.; Gogami, T.; Kanda, H.; Kaneta, M.; Kegel, S.; Kohl, Y.; Kusaka, W.; Margaryan, A.; Merkel, H.; Mihovilovič, M.; Müller, U.; Nagao, S.; Nakamura, S. N.; Pochodzalla, J.; Sanchez Lorente, A.; Schlimme, B. S.; Schoth, M.; Sfienti, C.; Širca, S.; Steinen, M.; Takahashi, Y.; Tang, L.; Thiel, M.; Tsukada, K.; Tyukin, A.; Weber, A.

    2016-03-01

    Negatively charged pions from two-body decays of stopped Λ4H hypernuclei were studied in 2012 at the Mainz Microtron MAMI, Germany. The momenta of the decay-pions were measured with unprecedented precision by using high-resolution magnetic spectrometers. A challenge of the experiment was the tagging of kaons from associated K+∧ production off a Be target at very forward angles. In the year 2014, this experiment was continued with a better control of the systematic uncertainties, with better suppression of coincident and random background, improved particle identification, and with higher luminosities. Another key point of the progress was the improvement in the absolute momentum calibration of the magnetic spectrometers.

  20. Extended defects in 4H-silicon carbide homoepitaxial layers

    NASA Astrophysics Data System (ADS)

    Zhang, Xuan

    The purpose of this thesis is to study the structure of extended defects in 4H-SIC homoepitaxial layers, and to identify their nucleation mechanisms. Characteristics of basal plane dislocations in 4H-SiC epilayers were investigated in a comprehensive manner, including their morphologies, Burgers' vectors, positions, and correlation with the extended defects propagating from the substrate. Plan-view transmission x-ray topography was the major characterization technique used in this study. Complementary data was obtained by KOH etching and optical microscopy. Trace of glide was detected on every basal plane dislocation in the entire 3-inch epilayer. In the center area of the epi-wafer, the glide can extend to macroscopic distance and form edge-type dislocations at the epilayer/surface interface. During the motion, dislocation half loop arrays were found to nucleate at the growth front. The magnitude of the resolved shear stress was estimated based on the radius of curvature of the dislocation lines. It surpassed the critical resolved shear stress at the epitaxial growth temperature. The stress was identified to be compressive in the epilayer. Its origin was studied. Nitrogen-doping-difference-induced misfit strain was excluded as the source of the stress. The structures of two morphological defects, 'carrots' and 'arrows', were studied. Cross-section x-ray topography was used to image the structure of carrot defect in whole. The defect was found to nucleate at the epilayer/substrate interface on a threading screw dislocation propagating from the substrate. Its structure was mainly composed of a prismatic stacking fault and a Frank-type basal plane stacking fault. The arrow defect was found to be produced by a spheroid shape inclusion in the volume of the epilayer. Zone axis diffraction pattern under transmission electron microscope identified the nature of the inclusion as 3C-SIC. It was determined to nucleate at the substrate surface contaminations.

  1. Intergenerational Panels at Centennial Events: Stimulating Discussion about Continuity and Change in the 4-H Program

    ERIC Educational Resources Information Center

    Kaplan, Matthew S.; Weikert, Ben; Scholl, Jan; Rushton, Mya

    2013-01-01

    This article introduces an intergenerational strategy for organizations planning centennial celebratory events. The methods and findings from the 4-H through the Generations session conducted at the joint 4-H Leadership Conference and 4-H Leaders Forum to celebrate the Pennsylvania 4-H Centennial are reported. Youth and adult participants shared…

  2. North Central Region 4-H Volunteers: Documenting Their Contributions and Volunteer Development

    ERIC Educational Resources Information Center

    Nippolt, Pamela Larson; Pleskac, Sue; Schwartz, Vicki; Swanson, Doug

    2012-01-01

    Documenting volunteer contributions strengthens Extension partnerships with volunteers. A team of North Central Region 4-H volunteer specialists collaborated to conduct a study of 4-H volunteer contributions and impacts related to working with youth within the 4-H program. Over three thousand (3,332) 4-H volunteers from throughout the 12-state…

  3. Farm Team.

    ERIC Educational Resources Information Center

    Gordon, Debra

    2001-01-01

    Describes a Philadelphia high school in which urban students study agricultural sciences to prepare for college and careers. The campus has a complete working farm, and students are exposed to a wide range of agricultural career opportunities while also studying core academic subjects. The school's farm units are real businesses, so students are…

  4. Bittersweet Farms.

    ERIC Educational Resources Information Center

    Kay, Bettye Ruth

    1990-01-01

    The article describes Bittersweet Farms, a rural Ohio farm community for autistic adults. The program is based on the rural, extended family community as a model and includes work components (horticulture, animal care, woodworking and carpentry, maintenance, housekeeping, food preparation), recreational activities, community integration, physical…

  5. Interoperating Cloud-based Virtual Farms

    NASA Astrophysics Data System (ADS)

    Bagnasco, S.; Colamaria, F.; Colella, D.; Casula, E.; Elia, D.; Franco, A.; Lusso, S.; Luparello, G.; Masera, M.; Miniello, G.; Mura, D.; Piano, S.; Vallero, S.; Venaruzzo, M.; Vino, G.

    2015-12-01

    The present work aims at optimizing the use of computing resources available at the grid Italian Tier-2 sites of the ALICE experiment at CERN LHC by making them accessible to interactive distributed analysis, thanks to modern solutions based on cloud computing. The scalability and elasticity of the computing resources via dynamic (“on-demand”) provisioning is essentially limited by the size of the computing site, reaching the theoretical optimum only in the asymptotic case of infinite resources. The main challenge of the project is to overcome this limitation by federating different sites through a distributed cloud facility. Storage capacities of the participating sites are seen as a single federated storage area, preventing the need of mirroring data across them: high data access efficiency is guaranteed by location-aware analysis software and storage interfaces, in a transparent way from an end-user perspective. Moreover, the interactive analysis on the federated cloud reduces the execution time with respect to grid batch jobs. The tests of the investigated solutions for both cloud computing and distributed storage on wide area network will be presented.

  6. The ultraviolet photochemistry of diacetylene - Direct detection of primary products of the metastable C4H2* + C4H2 reaction

    NASA Technical Reports Server (NTRS)

    Bandy, Ralph E.; Lakshminarayan, Chitra; Frost, Rex K.; Zwier, Timothy S.

    1993-01-01

    The products of diacetylene's ultraviolet photochemistry over the 245-220 nm region were directly determined in experiments where C4H2 was excited within a small reaction tube attached to a pulsed nozzle. The products formed in the collisions of C4H2* with C4H2 were subsequently ionized by vacuum UV radiation (at 118 nm) in the ion source of a time-of-flight mass spectrometer. It was found that the reaction of C4H2* with C4H2 produces C6H2 (+C2H2), C8H2 (+2H,H2), and C8H3 (+H), confirming the results of Glicker and Okabe (1987). Under certain conditions, secondary products were observed. Mechanisms for the observed reactions are proposed.

  7. Expression analysis of kenaf cinnamate 4-hydroxylase (C4H) ortholog during developmental and stress responses

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study was conducted to clone and analyze the expression pattern of a C4H gene encoding cinnamate 4-hydroxylase from kenaf (Hibiscus cannabinus L.). A full-length C4H ortholog was cloned using degenerate primers and the RACE (rapid amplification of cDNA ends) method. The full-length C4H ortholog...

  8. Stewardship as a Means to Create Organizational Reform: A View into Minnesota 4-H Youth Development

    ERIC Educational Resources Information Center

    Skuza, Jennifer A.; Freeman, Dorothy M.; Bremseth, Tamara J.; Doering, Shirley A.; Quinlan, Robert B.; Morreim, Patricia A.; Deidrick, James C.

    2010-01-01

    Minnesota 4-H Youth Development (MN 4-H) used stewardship as a means to create organizational reform to address the public use of the 4-H name and emblem in terms of risk management, real estate and equipment, and finances. A task force implemented a participatory process with colleagues and stakeholders to build and implement the reform effort.…

  9. Relationship between Participation in 4-H and Community Leadership in Rural Montana

    ERIC Educational Resources Information Center

    Flynn, Allison; Frick, Martin; Steele, Douglas

    2010-01-01

    Studies on the impact of 4-H on former members generally use alumni as one cohort. In rural states, such as Montana, it is important to understand the impact of 4-H on alumni in these rural areas and the role 4-H plays in community involvement. The study reported here sought to determine the perception of current community leaders in rural Montana…

  10. Perceptions of Missouri 4-H Youth Development Personnel Regarding Interorganizational Cooperative Behavior

    ERIC Educational Resources Information Center

    McKim, Billy R.; Torres, Robert M.

    2011-01-01

    Perceptions of 4-H youth development personnel regarding interorganizational cooperation were studied between the perceived and desired levels of cooperative activities between 4-H youth development personnel and secondary agriculture teachers. Results indicated that 4-H youth development personnel wanted higher levels of coordinated efforts…

  11. Perceptions of Texas 4-H Livestock Ambassadors on Career Development, Higher Education, and Leadership Development

    ERIC Educational Resources Information Center

    Zanolini, William F.; Rayfield, John; Ripley, Jeff

    2013-01-01

    Selected 4-H youth participated in the Texas 4-H Livestock Ambassador program. Forty-five youth participated in the 3-day program delivered by university professors and staff, Texas AgriLife Extension faculty and industry representatives. An instrument was developed and administered to the Texas 4-H Livestock Ambassadors at the end of their first…

  12. Understanding the Knowledge and Use of Experiential Learning within Pennsylvania 4-H Clubs

    ERIC Educational Resources Information Center

    Bechtel, Robyn; Ewing, John C.; Threeton, Mark; Mincemoyer, Claudia

    2013-01-01

    Experiential learning is incorporated into the National 4-H curriculum. However, the state 4-H staff in Pennsylvania is unsure of the current knowledge and use of experiential learning within the local 4-H clubs. An online survey was distributed to Extension educators and volunteer leaders within Pennsylvania to assess the current knowledge and…

  13. Text to Speech: A 4-H Model of Accessibility and Inclusion

    ERIC Educational Resources Information Center

    Green, Jeremy W.

    2012-01-01

    4-H project manuals play an integral part in a youth's ability to achieve mastery in a specific project area. For youth who struggle with reading, written 4-H materials prove inadequate in addressing the needs of the learner. This article proposes a new delivery method of 4-H educational material designed to create a more inclusive and…

  14. Examination of Attitude and Interest Measures for 4-H Science Evaluation

    ERIC Educational Resources Information Center

    Lewis, Kendra M.; Worker, Steven M.

    2015-01-01

    Science education research has demonstrated the influence of affect on learning. The National 4-H Science Logic Model outlines outcomes from youth participation in 4-H science programs, which includes attitude and interest outcomes. The associated measure, the National 4-H Science Common Measure, assesses these attitude constructs and not other…

  15. Synthesis of 4H/fcc-Au@Metal Sulfide Core-Shell Nanoribbons.

    PubMed

    Fan, Zhanxi; Zhang, Xiao; Yang, Jian; Wu, Xue-Jun; Liu, Zhengdong; Huang, Wei; Zhang, Hua

    2015-09-01

    Although great advances on the synthesis of Au-semiconductor heteronanostructures have been achieved, the crystal structure of Au components is limited to the common face-centered cubic (fcc) phase. Herein, we report the synthesis of 4H/fcc-Au@Ag2S core-shell nanoribbon (NRB) heterostructures from the 4H/fcc Au@Ag NRBs via the sulfurization of Ag. Remarkably, the obtained 4H/fcc-Au@Ag2S NRBs can be further converted to a novel class of 4H/fcc-Au@metal sulfide core-shell NRB heterostructures, referred to as 4H/fcc-Au@MS (M = Cd, Pb or Zn), through the cation exchange. We believe that these novel 4H/fcc-Au@metal sulfide NRB heteronanostructures may show some promising applications in catalysis, surface enhanced Raman scattering, solar cells, photothermal therapy, etc.

  16. 4-H PetPALS Juvenile Diversion Program Supports At-Risk Youth and Seniors

    ERIC Educational Resources Information Center

    Goble, Connie L.; Miller, Lucinda B.

    2014-01-01

    The 4-H PetPALS Juvenile Diversion Program provides a partnership opportunity with Extension and the juvenile court system to positively impact lives of at-risk youth. At-risk youth are taught by 4-H PetPALS adult volunteer leaders and 4-H PetPALS members to value and respect the human-animal bond, as well as to understand and empathize with…

  17. Virtual Laboratories and Virtual Worlds

    NASA Astrophysics Data System (ADS)

    Hut, Piet

    2008-05-01

    Since we cannot put stars in a laboratory, astrophysicists had to wait till the invention of computers before becoming laboratory scientists. For half a century now, we have been conducting experiments in our virtual laboratories. However, we ourselves have remained behind the keyboard, with the screen of the monitor separating us from the world we are simulating. Recently, 3D on-line technology, developed first for games but now deployed in virtual worlds like Second Life, is beginning to make it possible for astrophysicists to enter their virtual labs themselves, in virtual form as avatars. This has several advantages, from new possibilities to explore the results of the simulations to a shared presence in a virtual lab with remote collaborators on different continents. I will report my experiences with the use of Qwaq Forums, a virtual world developed by a new company (see http://www.qwaq.com).

  18. Virtual Labs and Virtual Worlds

    NASA Astrophysics Data System (ADS)

    Boehler, Ted

    2006-12-01

    Virtual Labs and Virtual Worlds Coastline Community College has under development several virtual lab simulations and activities that range from biology, to language labs, to virtual discussion environments. Imagine a virtual world that students enter online, by logging onto their computer from home or anywhere they have web access. Upon entering this world they select a personalized identity represented by a digitized character (avatar) that can freely move about, interact with the environment, and communicate with other characters. In these virtual worlds, buildings, gathering places, conference rooms, labs, science rooms, and a variety of other “real world” elements are evident. When characters move about and encounter other people (players) they may freely communicate. They can examine things, manipulate objects, read signs, watch video clips, hear sounds, and jump to other locations. Goals of critical thinking, social interaction, peer collaboration, group support, and enhanced learning can be achieved in surprising new ways with this innovative approach to peer-to-peer communication in a virtual discussion world. In this presentation, short demos will be given of several online learning environments including a virtual biology lab, a marine science module, a Spanish lab, and a virtual discussion world. Coastline College has been a leader in the development of distance learning and media-based education for nearly 30 years and currently offers courses through PDA, Internet, DVD, CD-ROM, TV, and Videoconferencing technologies. Its distance learning program serves over 20,000 students every year. sponsor Jerry Meisner

  19. Virtually Possible

    ERIC Educational Resources Information Center

    Mellon, Ericka

    2011-01-01

    Diane Lewis began building her popular virtual education program in a storage closet. The drab room, just big enough to squeeze in a tiny table, was her office at the headquarters of Seminole County (Florida) Public Schools. She had a computer and a small staff of temporary workers. Lewis, who managed to open two successful virtual schools for…

  20. AB INITIO CHARACTERIZATION OF C{sup -}{sub 4}, C{sub 4}H, AND C{sub 4}H{sup -}

    SciTech Connect

    Senent, M. L.

    2010-01-10

    Using state-of-the-art theoretical methods, we investigate the stable isomers of C{sup -}{sub 4}, C{sub 4}H and C{sub 4}H{sup -}. Three of them are relevant for astrophysics and astrochemistry. These computations are performed using highly correlated ab initio methods and the aug-cc-pVXZ (X = T,Q) basis sets. In addition to the linear isomers, we predict the existence of several cyclic and branched forms for these molecules. For all the molecular species of interest here, sets of spectroscopic parameters are determined with perturbation theory, which compare quite well with experiment. For l - C{sub 4}H{sup -}(X {sup 1}SIGMA{sup +}), the quartic force field is computed at the coupled cluster level of theory. This force field is derived from full nine-dimensional potential energy surface generated close to the equilibrium geometry of this anion. Finally, we treat the thermochemistry of the hydrogen attachment and the electron attachment reactions that may lead to the formation of the C{sub 4}H{sup -} from either C{sup -}{sub 4} or C{sub 4}H.

  1. Molecule intrinsic minimal basis sets. II. Bonding analyses for Si4H6 and Si2 to Si10.

    PubMed

    Lu, W C; Wang, C Z; Schmidt, M W; Bytautas, L; Ho, K M; Ruedenberg, K

    2004-02-01

    The method, introduced in the preceding paper, for recasting molecular self-consistent field (SCF) or density functional theory (DFT) orbitals in terms of intrinsic minimal bases of quasiatomic orbitals, which differ only little from the optimal free-atom minimal-basis orbitals, is used to elucidate the bonding in several silicon clusters. The applications show that the quasiatomic orbitals deviate from the minimal-basis SCF orbitals of the free atoms by only very small deformations and that the latter arise mainly from bonded neighbor atoms. The Mulliken population analysis in terms of the quasiatomic minimal-basis orbitals leads to a quantum mechanical interpretation of small-ring strain in terms of antibonding encroachments of localized molecular-orbitals and identifies the origin of the bond-stretch isomerization in Si4H6. In the virtual SCF/DFT orbital space, the method places the qualitative notion of virtual valence orbitals on a firm basis and provides an unambiguous ab initio identification of the frontier orbitals.

  2. Monolayer growth modes of Re and Nb on 4H -SiC(0001) and 4H-SiC(0001¯)

    NASA Astrophysics Data System (ADS)

    Bryant, K. W.; Bozack, M. J.

    2005-01-01

    Auger electron spectroscopy (AES) and secondary electron emission have been used to specify the room temperature monolayer adsorption characteristics of Re and Nb on the basal, polar surfaces of 4H -SiC. Measurement of the secondary electron emission current relates the absorbed crystal current to the change in AES peak-to-peak signal intensities for both substrate and adsorbate. For the 4H-SiC(0001) Si-face surface, both metals grow by formation of a single monolayer followed by growth of simultaneous monolayers. For the 4H -SiC(0001¯) C-face surface, both metals grow layer by layer (Frank-van der Merwe). Measurements of the coefficient of attenuation, inelastic mean free path, and coverage versus Auger intensities are also reported.

  3. 7 CFR 8.9 - Use in 4-H fund raising.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...-raising programs using the 4-H Name or Emblem may be carried out for specific educational purposes. Such... Research, Education, and Extension Service, United States Department of Agriculture, or a designee, if the fund-raising program is multi-State or Nationwide. (b) When used to promote 4-H educational...

  4. The 4-H Debate Project: Getting Adults and Children Involved in Communication.

    ERIC Educational Resources Information Center

    Atwater, Deborah F.

    Intended to enhance adult leadership skills, the 4-H Debate Project, developed by the 4-H Communication Committee of Delaware County (Pennsylvania), was designed to (1) increase the members' knowledge of library skills through research, (2) make them aware of current issues, (3) help them to become better public speakers and communicators, (4)…

  5. Factors Related to the Developmental Experiences of Youth Serving as 4-H Camp Counselors

    ERIC Educational Resources Information Center

    Carter, David N.; Kotrlik, Joe W.

    2008-01-01

    The purpose of this study was to investigate the developmental experiences of high-school-aged 4-H youth volunteering as counselors at Louisiana 4-H summer camps. A total of 288 counselors from 10 different camping sessions participated in the study. The Youth Experiences Survey 2.0 and the Developmental Experience Survey measured the personal…

  6. The Challenges Associated with Change in 4-H/Youth Development.

    ERIC Educational Resources Information Center

    McKee, Renee K.; Talbert, B. Allen; Barkman, Susan J.

    2002-01-01

    A survey of 97 Indiana 4-H/youth development educators and interviews with staff and volunteer board members indicated that volunteers believe in core 4-H values, recommend reaching more and different youth, and believe that the rural image inhibits progress. Staff interactions with volunteers, lack of parental involvement, group organization and…

  7. Bringing Carnaval Drum and Dance Traditions into 4-H Programming for Latino Youth

    ERIC Educational Resources Information Center

    Conklin-Ginop, Evelyn; Braverman, Marc T.; Caruso, Robyn; Bone, Dennis

    2011-01-01

    4-H Bloco Drum and Dance is an afterschool program that teaches adolescents drumming, dancing, and theater arts in the rich traditions of Brazilian Carnaval. Teens learn to express themselves in a variety of modalities and perform at community events. The program was developed by a community coalition that included 4-H, other youth programs, and…

  8. Cinnamate 4-Hydroxylase (C4H) genes from Leucaena leucocephala: a pulp yielding leguminous tree.

    PubMed

    Kumar, Santosh; Omer, Sumita; Patel, Krunal; Khan, Bashir M

    2013-02-01

    Leucaena leucocephala is a leguminous tree species accounting for one-fourth of raw material supplied to paper and pulp industry in India. Cinnamate 4-Hydroxylase (C4H, EC 1.14.13.11) is the second gene of phenylpropanoid pathway and a member of cytochrome P450 family. There is currently intense interest to alter or modify lignin content of L. leucocephala. Three highly similar C4H alleles of LlC4H1 gene were isolated and characterized. The alleles shared more than 98 % sequence identity at amino acid level to each other. Binding of partial promoter of another C4H gene LlC4H2, to varying amounts of crude nuclear proteins isolated from leaf and stem tissues of L. leucocephala formed two loose and one strong complex, respectively, suggesting that the abundance of proteins that bind with the partial C4H promoter is higher in stem tissue than in leaf tissue. Quantitative Real Time PCR study suggested that among tissues of same age, root tissues had highest level of C4H transcripts. Maximum transcript level was observed in 30 day old root tissue. Among the tissues investigated, C4H activity was highest in 60 day old root tissues. Tissue specific quantitative comparison of lignin from developing seedling stage to 1 year old tree stage indicated that Klason lignin increased in tissues with age. PMID:23070917

  9. 4-H and Forestry Afterschool Clubs: A Collaboration to Foster Stewardship Attitudes and Behaviors in Youth

    ERIC Educational Resources Information Center

    Gupta, Angela S.; Grant, Samantha; Strauss, Andrea Lorek

    2012-01-01

    The University of Minnesota Extension's 4-H and Forestry Afterschool program combined the 4-H structure and various forestry curricula to foster positive attitudes towards the environment and stewardship-related behaviors as these may serve as precursors to later choices that benefit the environment. Evaluation of third through fifth grade…

  10. The Effects of Age, Gender, and 4-H Involvement on Life Skill Development

    ERIC Educational Resources Information Center

    Haas, Bruce E.; Mincemoyer, Claudia C.; Perkins, Daniel F.

    2015-01-01

    The study reported here examined the effects of age, gender, and 4-H involvement in clubs on life skill development of youth ages eight to 18 over a 12-month period. Regression analyses found age, gender, and 4-H involvement significantly influenced life skill development. Results found that females have higher levels of competencies in life…

  11. 4-H and Tech Ed Partnership Gets Students Geeked about STEM

    ERIC Educational Resources Information Center

    Ivey, Debra; Quam, Greg

    2009-01-01

    This article discusses the 4-H Gateway Academies specifically designed to enhance science, technology, engineering, and math (STEM) skills and knowledge in middle school youth. The innovative summer day camps partnered Project Lead the Way--trained teachers with county 4-H staff from University of Wisconsin-Extension (UW-Extension) Cooperative…

  12. Birds in Your Backyard. 4-H Leaders Guide. L-5-17.

    ERIC Educational Resources Information Center

    Hawkes, Janet E.; Held Phillips, Diane

    This pocket folder of instructional materials is designed to introduce youth aged 9 to 12 to ornithology, the study of birds. The package includes a 4-H member's guide and a Leader's guide. The illustrated 4-H member's guide contains information about attracting and feeding birds. It also includes activities for cooking for birds, making bird…

  13. Acquisition, Custody, and Storage of Firearms Used in 4-H Shooting Sports Programs

    ERIC Educational Resources Information Center

    White, David J.; Smith, Jedediah D.

    2014-01-01

    Shooting sports has been a 4-H program offering since the 1930's. Tragic events related to the use of firearms as weapons have caused public and private entities to evaluate and consider the appropriateness of youth access to and usage of firearms. 4-H educators have the primary responsibility for managing the risk associated with shooting…

  14. 4-H and School-Age Care: A Great Combination! Point of View.

    ERIC Educational Resources Information Center

    Vandenbergh, Barbara D.

    1999-01-01

    Discusses the positive relationship between 4-H programs and school-age care programs, advocating the use of 4-H programs as a model for care, or as a source of care, caregiver training, or curriculum. Notes the role of the Cooperative Extension System in training and supporting school-age care providers. (JPB)

  15. Food Challenge: Serving Up 4-H to Non-Traditional Audiences

    ERIC Educational Resources Information Center

    Dodd, Sara; Follmer-Reece, Holly E.; Kostina-Ritchey, Erin; Reyna, Roxanna

    2015-01-01

    This article describes a novel approach for introducing 4-H to non-traditional/diverse audiences using 4-H Food Challenge. Set in a low SES and minority-serving rural school, Food Challenge was presented during the school day to all 7th grade students, with almost half voluntarily participating in an after-school club component. Program design…

  16. College Transition Study Shows 4-H Helps Youth Prepare for and Succeed in College

    ERIC Educational Resources Information Center

    Ratkos, Judy; Knollenberg, Lauren

    2015-01-01

    Many young adults enter college without the knowledge and skills necessary to succeed. The purpose of the study reported here was to determine if 4-H helps develop life skills needed for the transition to college and overall college success. An online survey was sent to college-attending 4-H alumni and a comparison group, with a final sample size…

  17. 4-H Youth Development: The Past, the Present, and the Future

    ERIC Educational Resources Information Center

    Borden, Lynne M.; Perkins, Daniel F.; Hawkey, Kyle

    2014-01-01

    The 4-H Program within Cooperative Extension is more than 100 years old. As we celebrate 100 years of Cooperative Extension, the foundation built by the 4-H Program serves as grounds to meet the needs of today's youth. The diversity of the youth who participate continues to grow, families continue to become less traditional, potential…

  18. 4-H Healthy Living Programs with Impact: A National Environmental Scan

    ERIC Educational Resources Information Center

    Downey, Laura H.; Peterson, Donna J.; LeMenestrel, Suzanne; Leatherman, JoAnne; Lang, James

    2014-01-01

    The 4-H youth development program of the nation's 109 land-grant universities and the Cooperative Extension System is one of the largest youth development organization in the United States serving approximately six million youth. The 4-H Healthy Living initiative began in 2008 to promote achievement of optimal physical, social, and emotional…

  19. Characteristics and Perceptions of 4-H Participants: Gender and Age Differences across Adolescence

    ERIC Educational Resources Information Center

    Bartoszuk, Karin; Randall, Brandy A.

    2011-01-01

    The study reported here examined 367 adolescent 4-H participants in terms of demographic, psychological, behavioral, and relational characteristics, as well as their perceptions and experiences in 4-H. Overall, participants scored high on all outcome variables except having a diverse population in their club. Older participants were more…

  20. Fitting the Framework: The STEM Institute and the 4-H Essential Elements

    ERIC Educational Resources Information Center

    Sallee, Jeff; Peek, Gina G.

    2014-01-01

    Extension and 4-H youth development programs are addressing a shortage of scientists, engineers, and other related professionals by promoting science, technology, engineering, and math (STEM). This case study illustrates how the Oklahoma 4-H Youth Development program trained youth-adult teams to design and implement STEM projects. The STEM…

  1. Global 4-H Network: Laying the Groundwork for Global Extension Opportunities

    ERIC Educational Resources Information Center

    Major, Jennifer; Miller, Rhonda

    2012-01-01

    A descriptive study examining 4-H programs in Africa, Asia, and Europe was conducted to provide understanding and direction in the establishment of a Global 4-H Network. Information regarding structure, organizational support, funding, and programming areas was gathered. Programs varied greatly by country, and many partnered with other 4-H…

  2. Virtual Satellite

    NASA Technical Reports Server (NTRS)

    Hammrs, Stephan R.

    2008-01-01

    Virtual Satellite (VirtualSat) is a computer program that creates an environment that facilitates the development, verification, and validation of flight software for a single spacecraft or for multiple spacecraft flying in formation. In this environment, enhanced functionality and autonomy of navigation, guidance, and control systems of a spacecraft are provided by a virtual satellite that is, a computational model that simulates the dynamic behavior of the spacecraft. Within this environment, it is possible to execute any associated software, the development of which could benefit from knowledge of, and possible interaction (typically, exchange of data) with, the virtual satellite. Examples of associated software include programs for simulating spacecraft power and thermal- management systems. This environment is independent of the flight hardware that will eventually host the flight software, making it possible to develop the software simultaneously with, or even before, the hardware is delivered. Optionally, by use of interfaces included in VirtualSat, hardware can be used instead of simulated. The flight software, coded in the C or C++ programming language, is compilable and loadable into VirtualSat without any special modifications. Thus, VirtualSat can serve as a relatively inexpensive software test-bed for development test, integration, and post-launch maintenance of spacecraft flight software.

  3. Virtual seminars

    NASA Astrophysics Data System (ADS)

    Nelson, H. Roice

    1997-06-01

    A virtual seminar (SM) is an economic and effective instructional tool for teaching students who are at a distance from their instructor. Like conventional class room teaching, a virtual seminar requires an instructor, a student, and a method of communication. Teleconferencing, video conferencing, intranets and the Internet give learners in a Virtual Seminar the ability to interact immediately with their mentors and receive real and relevant answers. This paper shows how industry and academia can benefit from using methods developed and experience gained in presenting the first virtual seminars to academic and petroleum industry participants in mid-1996. The information explosion in industry means that business or technical information is worthless until it is assimilated into a corporate knowledge management system. A search for specific information often turns into a filtering exercise or an attempt to find patterns and classify retrieved material. In the setting of an interactive corporate information system, virtual seminars meet the need for a productive new relationship between creative people and the flux of corporate knowledge. Experience shows that it is more efficient to circulate timesensitive and confidential information electronically through a virtual seminar. Automating the classification of information and removing that task from the usual work load creates an electronic corporate memory and enhances the value of the knowledge to both users and a corporation. Catalogued benchmarks, best-practice standards, and Knowledge Maps (SM) of experience serve as key aids to communicating knowledge through virtual seminars and converting that knowledge into a profit-making asset.

  4. Simple method for the growth of 4H silicon carbide on silicon substrate

    NASA Astrophysics Data System (ADS)

    Asghar, M.; Shahid, M. Y.; Iqbal, F.; Fatima, K.; Nawaz, Muhammad Asif; Arbi, H. M.; Tsu, R.

    2016-03-01

    In this study we report thermal evaporation technique as a simple method for the growth of 4H silicon carbide on p-type silicon substrate. A mixture of Si and C60 powder of high purity (99.99%) was evaporated from molybdenum boat. The as grown film was characterized by XRD, FTIR, UV-Vis Spectrophotometer and Hall Measurements. The XRD pattern displayed four peaks at 2Θ angles 28.550, 32.700, 36.100 and 58.900 related to Si (1 1 1), 4H-SiC (1 0 0), 4H-SiC (1 1 1) and 4H-SiC (2 2 2), respectively. FTIR, UV-Vis spectrophotometer and electrical properties further strengthened the 4H-SiC growth.

  5. Ultra high voltage MOS controlled 4H-SiC power switching devices

    NASA Astrophysics Data System (ADS)

    Ryu, S.; Capell, C.; Van Brunt, E.; Jonas, C.; O'Loughlin, M.; Clayton, J.; Lam, K.; Pala, V.; Hull, B.; Lemma, Y.; Lichtenwalner, D.; Zhang, Q. J.; Richmond, J.; Butler, P.; Grider, D.; Casady, J.; Allen, S.; Palmour, J.; Hinojosa, M.; Tipton, C. W.; Scozzie, C.

    2015-08-01

    Ultra high voltage (UHV, >15 kV) 4H-silicon carbide (SiC) power devices have the potential to significantly improve the system performance, reliability, and cost of energy conversion systems by providing reduced part count, simplified circuit topology, and reduced switching losses. In this paper, we compare the two MOS based UHV 4H-SiC power switching devices; 15 kV 4H-SiC MOSFETs and 15 kV 4H-SiC n-IGBTs. The 15 kV 4H-SiC MOSFET shows a specific on-resistance of 204 mΩ cm2 at 25 °C, which increased to 570 mΩ cm2 at 150 °C. The 15 kV 4H-SiC MOSFET provides low, temperature-independent, switching losses which makes the device more attractive for applications that require higher switching frequencies. The 15 kV 4H-SiC n-IGBT shows a significantly lower forward voltage drop (VF), along with reasonable switching performance, which make it a very attractive device for high voltage applications with lower switching frequency requirements. An electrothermal analysis showed that the 15 kV 4H-SiC n-IGBT outperforms the 15 kV 4H-SiC MOSFET for applications with switching frequencies of less than 5 kHz. It was also shown that the use of a carrier storage layer (CSL) can significantly improve the conduction performance of the 15 kV 4H-SiC n-IGBTs.

  6. Virtual Worlds for Virtual Organizing

    NASA Astrophysics Data System (ADS)

    Rhoten, Diana; Lutters, Wayne

    The members and resources of a virtual organization are dispersed across time and space, yet they function as a coherent entity through the use of technologies, networks, and alliances. As virtual organizations proliferate and become increasingly important in society, many may exploit the technical architecture s of virtual worlds, which are the confluence of computer-mediated communication, telepresence, and virtual reality originally created for gaming. A brief socio-technical history describes their early origins and the waves of progress followed by stasis that brought us to the current period of renewed enthusiasm. Examination of contemporary examples demonstrates how three genres of virtual worlds have enabled new arenas for virtual organizing: developer-defined closed worlds, user-modifiable quasi-open worlds, and user-generated open worlds. Among expected future trends are an increase in collaboration born virtually rather than imported from existing organizations, a tension between high-fidelity recreations of the physical world and hyper-stylized imaginations of fantasy worlds, and the growth of specialized worlds optimized for particular sectors, companies, or cultures.

  7. Wiggles and Wags: Dog 1--Fun Activities for You and Your Dog. 4-H Skills for Life Animal Series. National 4-H Curriculum. BU-08166

    ERIC Educational Resources Information Center

    National 4-H Council, 2005

    2005-01-01

    These guides are activity guides. Several fact-filled books about dogs are listed as resources on this guide. The activities are active, hands-on, and engaging and are guided by the 4-H motto: Learning by Doing. As youth explore a dog project topic of interest to them, they also practice essential life skills. Although a few dog project youth will…

  8. Virtual memory

    NASA Technical Reports Server (NTRS)

    Denning, P. J.

    1986-01-01

    Virtual memory was conceived as a way to automate overlaying of program segments. Modern computers have very large main memories, but need automatic solutions to the relocation and protection problems. Virtual memory serves this need as well and is thus useful in computers of all sizes. The history of the idea is traced, showing how it has become a widespread, little noticed feature of computers today.

  9. Virtual reality and virtual bodies

    NASA Astrophysics Data System (ADS)

    Richards, Catherine; Korba, Larry W.; Shaw, Christopher D.; Green, Mark

    1994-04-01

    There are many ways to produce the sense of `presence' or telepresence in the user of virtual reality. For example attempting to increase the realism of the visual environment is a commonly accepted strategy. In contrast, this paper explores a way for the user to feel present in an unrealistic virtual body. It investigates an unusual approach, proprioceptive illusions. Proprioceptive or body illusions are used to generate and explore the experience of virtuality and presence outside of the normal body limits. These projects are realized in art installations.

  10. Synthesis and characterization of 4-aryl-4H-chromenes from H-cardanol.

    PubMed

    Rao, Hulluru Surya Prakash; Kamalraj, Mani

    2014-09-01

    We have synthesized and characterized a variety of fat-soluble, low-melting and medicinally useful 4-aryl-4H-chromenes from H-cardanol (side-chain perhydrogenated cardanol, 3-pentadecylphenol), a renewable and low-cost product from locally grown cashew nut trees (Anacardium occidentale L.). We incorporated H-cardanol into the aromatic rings of either 4H-chromene or phenol, or both. Substitution of C4SMe in N-methyl-4-(methylthio)-3-nitro-4H-chromene-2-amines with H-cardanol was regio-specific at the C6 position. PMID:25918806

  11. Using Multiple Youth Programming Delivery Modes to Drive the Development of Social Capital in 4-H Participants

    ERIC Educational Resources Information Center

    Kinsey, Sharon

    2013-01-01

    This article focuses on how 4-H youth participants are building social capital, or connections among individuals and community members, through their 4-H experiences. These experiences can be seen through the lens of such 4-H delivery modes as the traditional 4-H club, after-school programs, and school enrichment programs. In addition, other…

  12. Virtual Specimens

    NASA Astrophysics Data System (ADS)

    de Paor, D. G.

    2009-12-01

    Virtual Field Trips have been around almost as long as the Worldwide Web itself yet virtual explorers do not generally return to their desktops with folders full of virtual hand specimens. Collection of real specimens on fields trips for later analysis in the lab (or at least in the pub) has been an important part of classical field geoscience education and research for generations but concern for the landscape and for preservation of key outcrops from wanton destruction has lead to many restrictions. One of the author’s favorite outcrops was recently vandalized presumably by a geologist who felt the need to bash some of the world’s most spectacular buckle folds with a rock sledge. It is not surprising, therefore, that geologists sometimes leave fragile localities out of field trip itineraries. Once analyzed, most specimens repose in drawers or bins, never to be seen again. Some end up in teaching collections but recent pedagogical research shows that undergraduate students have difficulty relating specimens both to their collection location and ultimate provenance in the lithosphere. Virtual specimens can be created using 3D modeling software and imported into virtual globes such as Google Earth (GE) where, they may be linked to virtual field trip stops or restored to their source localities on the paleo-globe. Sensitive localities may be protected by placemark approximation. The GE application program interface (API) has a distinct advantage over the stand-alone GE application when it comes to viewing and manipulating virtual specimens. When instances of the virtual globe are embedded in web pages using the GE plug-in, Collada models of specimens can be manipulated with javascript controls residing in the enclosing HTML, permitting specimens to be magnified, rotated in 3D, and sliced. Associated analytical data may be linked into javascript and localities for comparison at various points on the globe referenced by ‘fetching’ KML. Virtual specimens open up

  13. Fish Farm Challenge Provides STEM Design Experiences for Youth

    ERIC Educational Resources Information Center

    Horton , Robert L.; House, Patty L.

    2015-01-01

    In 2014, Monsanto Corporation partnered with National 4-H Council to help inspire and develop professional skills among young agriculturalists. The Ohio State University created Fish Farm Challenge, which engaged more than 8,000 youth across eight states. Youth were taught about worldwide food insecurity and the importance of aquaculture. They…

  14. Ferromagnetism in proton irradiated 4H-SiC single crystal

    SciTech Connect

    Zhou, Ren-Wei; Wang, Hua-Jie; Chen, Wei-Bin; Li, Fei; Liu, Xue-Chao Zhuo, Shi-Yi; Shi, Er-Wei

    2015-04-15

    Room-temperature ferromagnetism is observed in proton irradiated 4H-SiC single crystal. An initial increase in proton dose leads to pronounced ferromagnetism, accompanying with obvious increase in vacancy concentration. Further increase in irradiation dose lowers the saturation magnetization with the decrease in total vacancy defects due to the defects recombination. It is found that divacancies are the mainly defects in proton irradiated 4H-SiC and responsible for the observed ferromagnetism.

  15. Phosphorus doping of 4H SiC by liquid immersion excimer laser irradiation

    SciTech Connect

    Ikeda, Akihiro; Nishi, Koji; Ikenoue, Hiroshi; Asano, Tanemasa

    2013-02-04

    Phosphorus doping of 4H SiC is performed by KrF excimer laser irradiation of 4H SiC immersed in phosphoric acid. Phosphorus is incorporated to a depth of a few tens of nanometers at a concentration of over 10{sup 20}/cm{sup 3} without generating significant crystal defects. Formation of a pn junction diode with an ideality factor of 1.06 is demonstrated.

  16. Fabrication of High-Q Nanobeam Photonic Crystals in Epitaxially Grown 4H-SiC.

    PubMed

    Bracher, David O; Hu, Evelyn L

    2015-09-01

    Silicon carbide (SiC) is an intriguing material due to the presence of spin-active point defects in several polytypes, including 4H-SiC. For many quantum information and sensing applications involving such point defects, it is important to couple their emission to high quality optical cavities. Here we present the fabrication of 1D nanobeam photonic crystal cavities (PCC) in 4H-SiC using a dopant-selective etch to undercut a homoepitaxially grown epilayer of p-type 4H-SiC. These are the first PCCs demonstrated in 4H-SiC and show high quality factors (Q) of up to ∼7000 as well as low modal volumes of <0.5 (λ/n)(3). We take advantage of the high device yield of this fabrication method to characterize hundreds of devices and determine which PCC geometries are optimal. Additionally, we demonstrate two methods to tune the resonant wavelengths of the PCCs over 5 nm without significant degradation of the Q. Lastly, we characterize nanobeam PCCs coupled to luminescence from silicon vacancy point defects (V1, V2) in 4H-SiC. The fundamental modes of two such PCCs are tuned into spectral overlap with the zero phonon line (ZPL) of the V2 center, resulting in an intensity increase of up to 3-fold. These results are important steps on the path to developing 4H-SiC as a platform for quantum information and sensing.

  17. Synthesis of 4H/fcc Noble Multimetallic Nanoribbons for Electrocatalytic Hydrogen Evolution Reaction.

    PubMed

    Fan, Zhanxi; Luo, Zhimin; Huang, Xiao; Li, Bing; Chen, Ye; Wang, Jie; Hu, Yanling; Zhang, Hua

    2016-02-01

    Noble multimetallic nanomaterials, if only consisting of Au, Ag, Pt, and Pd, typically adopt the high-symmetry face-centered cubic (fcc) structure. Here for the first time, by using the 4H/fcc Au@Ag nanoribbons (NRBs) as seeds, we report the synthesis of 4H/fcc trimetallic Au@PdAg core-shell NRBs via the galvanic reaction method under ambient conditions. Moreover, this strategy can also be used to synthesize 4H/fcc trimetallic Au@PtAg and quatermetallic Au@PtPdAg core-shell NRBs. Impressively, for the first time, these alloy shells, i.e., PdAg, PtAg, and PtPdAg, epitaxially grown on the 4H/fcc Au core with novel 4H hexagonal phase were successfully synthesized. Remarkably, the obtained 4H/fcc Au@PdAg NRBs exhibit excellent electrocatalytic activity toward the hydrogen evolution reaction, which is even quite close to that of the commercial Pt black. We believe that our findings here may provide a novel strategy for the crystal-structure-controlled synthesis of advanced functional noble multimetallic nanomaterials with various promising applications.

  18. The crystal structure of "green" Cs 2[VOF 4(H 2O)] and its relationship to "blue" Cs 2[VOF 4(H 2O)

    NASA Astrophysics Data System (ADS)

    Mattes, Rainer; Foerster, Harry

    1982-11-01

    Crystals of a second, "green" modification of Cs 2[VOF 4(H 2O)] were obtained from aqueous solution. Their crystal structure was studied on the basis of three-dimensional X-ray data. The structure is orthorhombic, a = 8.231(3), b = 10.323(3), c = 8.497(3) Å, V = 722.0Å 3, Z = 4, space group Ccmm. The final R and RW were 0.035 and 0.048, respectively, for 421 independent reflections. As the already known "blue" modification, the present structure contains isolated, highly deformed octahedral [VOF 4(H 2O)] 2- ions with the oxygen atoms in trans positions. The cesium sublattice and the orientation of the anions to each other are completely different in both modifications. uv/VIS reflection, and ir and Raman spectra of both modifications are discussed.

  19. Farm Play Center.

    ERIC Educational Resources Information Center

    Hansen, Linda; And Others

    Because many cultures celebrate a harvest time or festival with which many children can identify, this farm preschool curriculum unit is appropriate for a cross-cultural setting. The farm unit is introduced to children through a field trip to a local farm, with children having the opportunity for experiential learning. The farm may be integrated…

  20. Virtual sound for virtual reality

    SciTech Connect

    Blattner, M.M. ||; Papp, A.L. III |

    1993-02-01

    The computational limitations of real-time interactive computing do not meet our requirements for producing realistic images for virtual reality in a convincing manner. Regardless of the real-time restrictions on virtual reality interfaces, the representations can be no better than the graphics. Computer graphics is still limited in its ability to generate complex objects such as landscapes and humans. Nevertheless, useful and convincing visualizations are made through a variety of techniques. The central theme of this article is that a similar situation is true with sound for virtual reality. It is beyond our abilityto create interactive soundscapes that create a faithful reproduction of real world sounds, however, by choosing one`s application carefully and using sound to enhance a display rather than only mimic real-world scenes, a very effective use of sound can be made.

  1. Virtual sound for virtual reality

    SciTech Connect

    Blattner, M.M. Cancer Center, Houston, TX . Dept. of Biomathematics Lawrence Livermore National Lab., CA California Univ., Davis, CA ); Papp, A.L. III Lawrence Livermore National Lab., CA )

    1993-02-01

    The computational limitations of real-time interactive computing do not meet our requirements for producing realistic images for virtual reality in a convincing manner. Regardless of the real-time restrictions on virtual reality interfaces, the representations can be no better than the graphics. Computer graphics is still limited in its ability to generate complex objects such as landscapes and humans. Nevertheless, useful and convincing visualizations are made through a variety of techniques. The central theme of this article is that a similar situation is true with sound for virtual reality. It is beyond our abilityto create interactive soundscapes that create a faithful reproduction of real world sounds, however, by choosing one's application carefully and using sound to enhance a display rather than only mimic real-world scenes, a very effective use of sound can be made.

  2. Virtualize Me!

    ERIC Educational Resources Information Center

    Waters, John K.

    2009-01-01

    John Abdelmalak, director of technology for the School District of the Chathams, was pretty sure it was time to jump on the virtualization bandwagon last year when he invited Dell to conduct a readiness assessment of his district's servers. When he saw just how little of their capacity was being used, he lost all doubt. Abdelmalak is one of many…

  3. Virtually There.

    ERIC Educational Resources Information Center

    Lanier, Jaron

    2001-01-01

    Describes tele-immersion, a new medium for human interaction enabled by digital technologies. It combines the display and interaction techniques of virtual reality with new vision technologies that transcend the traditional limitations of a camera. Tele-immersion stations observe people as moving sculptures without favoring a single point of view.…

  4. Virtual Labs.

    ERIC Educational Resources Information Center

    Russo, Ruth

    1997-01-01

    Discusses the potential of computers in teaching laboratories to spare the lives of animals; however, it is felt that in areas of physiology education, virtual labs are not as desirable a learning experience for advanced students as live animal labs. (Author/AIM)

  5. Virtual Reality.

    ERIC Educational Resources Information Center

    Newby, Gregory B.

    1993-01-01

    Discusses the current state of the art in virtual reality (VR), its historical background, and future possibilities. Highlights include applications in medicine, art and entertainment, science, business, and telerobotics; and VR for information science, including graphical display of bibliographic data, libraries and books, and cyberspace.…

  6. CFD Growth of 3C-SiC on 4H/6H Mesas

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.; Trunek, Andrew J.; Spry, David J.; Powell, J. Anthony; Du, Hui; Skowronski, Marek; Huang, XianRong; Dudley, Michael

    2006-01-01

    This article describes growth and characterization of the highest quality reproducible 3C-SiC heteroepitaxial films ever reported. By properly nucleating 3C-SiC growth on top of perfectly on-axis (0001) 4H-SiC mesa surfaces completely free of atomic scale steps and extended defects, growth of 3C-SiC mesa heterofilms completely free of extended crystal defects can be achieved. In contrast, nucleation and growth of 3C-SiC mesa heterofilms on top of 4H-SiC mesas with atomic-scale steps always results in numerous observable dislocations threading through the 3C-SiC epilayer. High-resolution X-ray diffraction and transmission electron microscopy measurements indicate non-trivial in-plane lattice mismatch between the 3C and 4H layers. This mismatch is somewhat relieved in the step-free mesa case via misfit dislocations confined to the 3C/4H interfacial region without dislocations threading into the overlying 3C-SiC layer. These results indicate that the presence or absence of steps at the 3C/4H heteroepitaxial interface critically impacts the quality, defect structure, and relaxation mechanisms of single-crystal heteroepitaxial 3C-SiC films.

  7. Self-assembly of C4H-type hydrogenated graphene.

    PubMed

    Liu, Zilong; Xue, Qingzhong; Xing, Wei; Du, Yonggang; Han, Zhide

    2013-11-21

    We demonstrate by molecular dynamic (MD) simulations that patterned partially hydrogenated graphene (C4H) can self-assemble at room temperature. The main driving force of the self-assembly of C4H is due to the one-sided distribution of hydrogen and the corresponding asymmetric orientation of sp(3) bonding, there exists strong electrostatic repulsion between the relatively close H atoms. The simulations show that C4H can self-assemble into various carbon nanoscroll (CNS) structures, this is mainly controlled by its geometry (size and aspect ratio). And the carbon nanotube (CNT) is a good candidate to activate and guide C4H to form CNS, whose core size can be controlled. Meanwhile, a novel CNT/C4H core/shell composite nanostructure is also formed. The theoretical results shed important light on a feasible approach to fabricate high-quality CNS and other novel nanostructures including core/shell structures, which hold great potential applications in optics, optoelectronic devices, hydrogen storage, sensors, and energy storage in supercapacitors or batteries. PMID:24064528

  8. Existence of {sub {lambda}}{sub {lambda}}{sup 4}H: A variational Monte Carlo search

    SciTech Connect

    Shoeb, Mohammad

    2005-02-01

    A variational Monte Carlo (VMC) calculation for the binding energy B{sub {lambda}}{sub {lambda}} of the lightest hypernucleus {sub {lambda}}{sub {lambda}}{sup 4}H has been performed in the four-body {lambda}{lambda}pn model. A range of input {lambda}{lambda} potentials of moderate strength produce a particle-stable {sub {lambda}}{sub {lambda}}{sup 4}H for the simulated NSC97e and f {lambda}N potentials, whereas the phenomenological Minnesota {lambda}N potential needs a much stronger {lambda}{lambda} potential to bind. The VMC results for B{sub {lambda}}{sub {lambda}} agree with the prediction of the stochastic variational model but contradict the recent Faddeev-Yakubovsky calculation. As reported earlier, B{sub {lambda}}{sub {lambda}} is sensitive to the triplet {lambda}N channel for a given {lambda}{lambda} potential. The B{sub {lambda}}{sub {lambda}} of {sub {lambda}}{sub {lambda}}{sup 4}H in the three-body {lambda}{lambda}d cluster model is consistent with but slightly lower than the Faddeev calculation. The VMC method predicts a stable {sub {lambda}}{sub {lambda}}{sup 4}H system in both models and thus offers the possibility of identifying {sub {lambda}}{sub {lambda}}{sup 4}H in a future extension of E906 or of a related experiment at KEK, provided the simulated potentials are true representations of realistic Nijmegen potentials.

  9. CVD Growth of 3C-SiC on 4H/6H Mesas

    SciTech Connect

    Neudeck,P.; Trunek, A.; Spry, D.; Powell, J.; Du, H.; Skowronski, M.; Huang, X.; Dudley, M.

    2006-01-01

    This article describes growth and characterization of the highest quality reproducible 3C-SiC heteroepitaxial films ever reported. By properly nucleating 3C-SiC growth on top of perfectly on-axis (0001) 4H-SiC mesa surfaces completely free of atomic scale steps and extended defects, growth of 3C-SiC mesa heterofilms completely free of extended crystal defects can be achieved. In contrast, nucleation and growth of 3C-SiC mesa heterofilms on top of 4H-SiC mesas with atomic-scale steps always results in numerous observable dislocations threading through the 3C-SiC epilayer. High-resolution X-ray diffraction (HRXRD) and high resolution cross-sectional transmission electron microscopy (HRXTEM) measurements indicate non-trivial, in-plane, lattice mismatch between the 3C and 4H layers. This mismatch is somewhat relieved in the step-free mesa case via misfit dislocations confined to the 3C/4H interfacial region without dislocations threading into the overlying 3C-SiC layer. These results indicate that the presence or absence of steps at the 3C/4H heteroepitaxial interface critically impacts the quality, defect structure, and relaxation mechanisms of single-crystal heteroepitaxial 3C-SiC films.

  10. Effect of neutron irradiation on charge collection efficiency in 4H-SiC Schottky diode

    NASA Astrophysics Data System (ADS)

    Wu, Jian; Jiang, Yong; Lei, Jiarong; Fan, Xiaoqiang; Chen, Yu; Li, Meng; Zou, Dehui; Liu, Bo

    2014-01-01

    The charge collection efficiency (CCE) in 4H-SiC Schottky diode is studied as a function of neutron fluence. The 4H-SiC diode was irradiated with fast neutrons of a critical assembly in Nuclear Physics and Chemistry Institute and CCE for 3.5 MeV alpha particles was then measured as a function of the applied reverse bias. It was found from our experiment that an increase of neutron fluence led to a decrease of CCE. In particular, CCE of the diode was less than 1.3% at zero bias after an irradiation at 8.26×1014 n/cm2. A generalized Hecht's equation was employed to analyze CCE in neutron irradiated 4H-SiC diode. The calculations nicely fit the CCE of 4H-SiC diode irradiated at different neutron fluences. According to the calculated results, the extracted electron μτ product (μτ)e and hole μτ product (μτ)h of the irradiated 4H-SiC diode are found to decrease by increasing the neutron fluence.

  11. Nickel ohmic contacts of high-concentration P-implanted 4H-SiC

    NASA Astrophysics Data System (ADS)

    Chunjuan, Liu; Su, Liu; Jingjing, Feng; Rong, Wu

    2012-03-01

    Different-dose phosphorus ion implantation into 4H-SiC followed by high-temperature annealing was investigated. AlN/BN and graphite post-implantation annealing for ion-implanted SiC at 1650 °C for 30 min was conducted to electrically activate the implanted P+ ions. Ni contacts to the P+-implanted 4H-SiC layers were examined by transmission line model and Hall measurements fabricated on P-implanted (0001). The results indicated that a high-quality ohmic contact and specific contact resistivity of 1.30 × 10-6 Ω · cm2 was obtained for the P+-implanted 4H-SiC layers. The ρC values of the Ni-based implanted layers decreased with increasing P doping concentrations, and a weaker temperature dependence was observed for different samples in the 200-500 K temperature range.

  12. Synthesis, antifungal activity and docking study of 2-amino-4H-benzochromene-3-carbonitrile derivatives

    NASA Astrophysics Data System (ADS)

    Mirjalili, BiBi Fatemeh; Zamani, Leila; Zomorodian, Kamiar; Khabnadideh, Soghra; Haghighijoo, Zahra; Malakotikhah, Zahra; Ayatollahi Mousavi, Seyyed Amin; Khojasteh, Shaghayegh

    2016-07-01

    Pathogenic fungi are associated with diseases ranging from simple dermatosis to life-threatening infections, particularly in immunocompromised patients. During the past two decades, resistance to established antifungal drugs has increased dramatically and has made it crucial to identify novel antimicrobial compounds. Here, we selected 12 new compounds of 2-amino-4H-benzochromene-3-carbonitrile drivetives (C1-C12) for synthesis by using nano-TiCl4.SiO2 as efficient and green catalyst, then nine of synthetic compounds were evaluated against different species of fungi, positive gram and negative gram of bacteria. Standard and clinical strains of antibiotics sensitive and resistant fungi and bacteria were cultured in appropriate media. Biological activity of the 2-amino-4H-benzochromene-3-carbonitrile derivatives against fungi and bacteries were estimated by the broth micro-dilution method as recommended by clinical and laboratory standard institute (CLSI). In addition minimal fangicidal and bactericial concenteration of the compounds were also determined. Considering our results showed that compound 2-amino-4-(4-methyl benzoate)-4H-benzo[f]chromen-3-carbonitrile (C9) had the most antifungal activity against Aspergillus clavatus, Candida glabarata, Candida dubliniensis, Candida albicans and Candida tropicalis at concentrations ranging from 8 to ≤128 μg/mL. Also compounds 2-amino-4-(3,4-dimethoxyphenyl)-4H-benzo[f]chromen-3-carbonitrile (C4) and 2-amino-4-(4-isopropylphenyl)-4H-benzo[f]chromen-3-carbonitrile (C3) had significant inhibitory activities against Epidermophyton floccosum following 2-amino-4-(4-methylbenzoate)-4H-benzo[f]chromen-3-carbonitrile (C9), respectively. Docking simulation was performed to insert compounds C3, C4 and C9 in to CYP51 active site to determine the probable binding model.

  13. Adult volunteerism in Pennsylvania 4-H natural resources programs for youth

    NASA Astrophysics Data System (ADS)

    Smith, Sanford Sherrick

    2001-07-01

    Pennsylvania's 4-H Youth Development Program relies on adult volunteers to reach youth with educational information and opportunities. Finding adults willing to do this volunteer work is challenging. This study looks at the current status of adult volunteerism with natural resources 4-H projects, and seeks to understand potential volunteers. The literature has much to offer in regards to general volunteer trends, management, motivations, and task preferences; however, few studies focus on volunteers in natural resources or environmental education. A telephone survey conducted with county 4-H agents revealed that only 3.2% of Pennsylvania's 4-H volunteers work with natural resources projects in 56 out of 67 counties, and that very few volunteers have any formal background in natural resources. Semi-structured interviews with 41 adult volunteers currently working with natural resources projects explored volunteer demographics, history, program design preferences, and ideas for seeking more volunteers. Findings from the telephone survey and the semi-structured interviews were used to generate a mail survey with large, random samples from three population groups: (1) 4-H Volunteers, (2) 4-H Parents, and (3) Natural Resources Professionals. Confidence with youth and subject matter, and adult willingness to volunteer was explored for each of the groups in relation to background, demographic characteristics, motivational needs, past and present volunteer activity, personal interests, and program design importance. Natural resources subject matter confidence was shown to be the most significant variable determining willingness to volunteer for all three groups. The variables that contributed to subject matter and youth confidence varied for each population. Key variables effecting willingness to volunteer included outdoor activity level, personal interest in natural resources, the need to fulfill feelings of social responsibility, and confidence with youth. Program design

  14. Anti-reflective nano- and micro-structures on 4H-SiC for photodiodes

    PubMed Central

    2011-01-01

    In this study, nano-scale honeycomb-shaped structures with anti-reflection properties were successfully formed on SiC. The surface of 4H-SiC wafer after a conventional photolithography process was etched by inductively coupled plasma. We demonstrate that the reflection characteristic of the fabricated photodiodes has significantly reduced by 55% compared with the reference devices. As a result, the optical response Iillumination/Idark of the 4H-SiC photodiodes were enhanced up to 178%, which can be ascribed primarily to the improved light trapping in the proposed nano-scale texturing. PMID:21711744

  15. Crystal and molecular structure of 2,4,4-trisubstituted 5-amino-4 H-imidazoles

    NASA Astrophysics Data System (ADS)

    Bellanato, J.; Avendaño, C.; Ramos, M. T.; Smith-Verdier, P.; Florencio, F.; Garcia-Blanco, S.

    Three 5-amino-4 H-imidazole derivatives 2(2-pyridyl) and 2-ethoxycarbonyl-4,4-pentamethylene-5-amino-and 2(2-pyridyl)-4,4-dimethyl-5(2-pyridylamino)4 H-imidazoles have been studied by i.r. and Raman spectroscopy. The crystal structure of one has been determined by X-ray diffraction. The tautomeric amino-imino equilibrium in different working conditions is also studied from spectroscopic data. The amino and the unconjugated imino forms are characterized.

  16. Estimation of negative ions in VHF SiH4/H2 plasma

    NASA Astrophysics Data System (ADS)

    Yamane, Tsukasa; Nakano, Shinya; Nakao, Sachiko; Takeuchi, Yoshiaki; Ichiki, Ryuta; Muta, Hiroshi; Uchino, Kiichiro; Kawai, Yoshinobu

    2014-11-01

    The characteristics of a VHF SiH4/H2 plasma (frequency: 60 MHz) at high pressures were examined as a function of silane concentration with a heated Langmuir probe. Anomalous reductions in electron saturation current were observed, suggesting the existence of many negative ions. An estimation of the concentration of negative ions was attempted using the sheath theory including negative ions. It was found that there exist H- and SiH3- ions as dominant negative ions in the VHF SiH4/H2 plasma. In addition, the measured floating potential agreed with the theoretical value.

  17. Virtual anthropology.

    PubMed

    Weber, Gerhard W

    2015-02-01

    Comparative morphology, dealing with the diversity of form and shape, and functional morphology, the study of the relationship between the structure and the function of an organism's parts, are both important subdisciplines in biological research. Virtual anthropology (VA) contributes to comparative morphology by taking advantage of technological innovations, and it also offers new opportunities for functional analyses. It exploits digital technologies and pools experts from different domains such as anthropology, primatology, medicine, paleontology, mathematics, statistics, computer science, and engineering. VA as a technical term was coined in the late 1990s from the perspective of anthropologists with the intent of being mostly applied to biological questions concerning recent and fossil hominoids. More generally, however, there are advanced methods to study shape and size or to manipulate data digitally suitable for application to all kinds of primates, mammals, other vertebrates, and invertebrates or to issues regarding plants, tools, or other objects. In this sense, we could also call the field "virtual morphology." The approach yields permanently available virtual copies of specimens and data that comprehensively quantify geometry, including previously neglected anatomical regions. It applies advanced statistical methods, supports the reconstruction of specimens based on reproducible manipulations, and promotes the acquisition of larger samples by data sharing via electronic archives. Finally, it can help identify new, hidden traits, which is particularly important in paleoanthropology, where the scarcity of material demands extracting information from fragmentary remains. This contribution presents a current view of the six main work steps of VA: digitize, expose, compare, reconstruct, materialize, and share. The VA machinery has also been successfully used in biomechanical studies which simulate the stress and strains appearing in structures. Although

  18. Virtual impactor

    DOEpatents

    Yeh, Hsu-Chi; Chen, Bean T.; Cheng, Yung-Sung; Newton, George J.

    1988-08-30

    A virtual impactor having improved efficiency and low wall losses in which a core of clean air is inserted into the aerosol flow while aerosol flow is maintained adjacent inner wall surfaces of the focusing portion of the impactor. The flow rate of the core and the length of the throat of the impactor's collection probe, as well as the dimensional relationships of other components of the impactor adjacent the separation region of the impactor, are selected to optimize separation efficiency.

  19. Virtual anthropology.

    PubMed

    Weber, Gerhard W

    2015-02-01

    Comparative morphology, dealing with the diversity of form and shape, and functional morphology, the study of the relationship between the structure and the function of an organism's parts, are both important subdisciplines in biological research. Virtual anthropology (VA) contributes to comparative morphology by taking advantage of technological innovations, and it also offers new opportunities for functional analyses. It exploits digital technologies and pools experts from different domains such as anthropology, primatology, medicine, paleontology, mathematics, statistics, computer science, and engineering. VA as a technical term was coined in the late 1990s from the perspective of anthropologists with the intent of being mostly applied to biological questions concerning recent and fossil hominoids. More generally, however, there are advanced methods to study shape and size or to manipulate data digitally suitable for application to all kinds of primates, mammals, other vertebrates, and invertebrates or to issues regarding plants, tools, or other objects. In this sense, we could also call the field "virtual morphology." The approach yields permanently available virtual copies of specimens and data that comprehensively quantify geometry, including previously neglected anatomical regions. It applies advanced statistical methods, supports the reconstruction of specimens based on reproducible manipulations, and promotes the acquisition of larger samples by data sharing via electronic archives. Finally, it can help identify new, hidden traits, which is particularly important in paleoanthropology, where the scarcity of material demands extracting information from fragmentary remains. This contribution presents a current view of the six main work steps of VA: digitize, expose, compare, reconstruct, materialize, and share. The VA machinery has also been successfully used in biomechanical studies which simulate the stress and strains appearing in structures. Although

  20. Interconversion between Parallel and Antiparallel Conformations of a 4H RNA junction in Domain 3 of Foot-and-Mouth Disease Virus IRES Captured by Dynamics Simulations

    PubMed Central

    Jung, Segun; Schlick, Tamar

    2014-01-01

    RNA junctions are common secondary structural elements present in a wide range of RNA species. They play crucial roles in directing the overall folding of RNA molecules as well as in a variety of biological functions. In particular, there has been great interest in the dynamics of RNA junctions, including conformational pathways of fully base-paired 4-way (4H) RNA junctions. In such constructs, all nucleotides participate in one of the four double-stranded stem regions, with no connecting loops. Dynamical aspects of these 4H RNAs are interesting because frequent interchanges between parallel and antiparallel conformations are thought to occur without binding of other factors. Gel electrophoresis and single-molecule fluorescence resonance energy transfer experiments have suggested two possible pathways: one involves a helical rearrangement via disruption of coaxial stacking, and the other occurs by a rotation between the helical axes of coaxially stacked conformers. Employing molecular dynamics simulations, we explore this conformational variability in a 4H junction derived from domain 3 of the foot-and-mouth disease virus internal ribosome entry site (IRES); this junction contains highly conserved motifs for RNA-RNA and RNA-protein interactions, important for IRES activity. Our simulations capture transitions of the 4H junction between parallel and antiparallel conformations. The interconversion is virtually barrier-free and occurs via a rotation between the axes of coaxially stacked helices with a transient perpendicular intermediate. We characterize this transition, with various interhelical orientations, by pseudodihedral angle and interhelical distance measures. The high flexibility of the junction, as also demonstrated experimentally, is suitable for IRES activity. Because foot-and-mouth disease virus IRES structure depends on long-range interactions involving domain 3, the perpendicular intermediate, which maintains coaxial stacking of helices and thereby

  1. Managing for Motivation: Herzberg's Motivation-Hygiene Theory and Its Application to 4-H Leadership. National Intern Report.

    ERIC Educational Resources Information Center

    Freeman, Walter J.

    A study examined the organizational factors contributing to the motivation of 4-H volunteer leaders. A modified form of Herzberg's Motivation-Hygiene Theory served as the research design of the study. A total of 149 4-H leaders were interviewed regarding thirteen job factors: recognition; personal growth; relationships with other 4-H leaders,…

  2. Maine 4-H Afterschool Academy--A Professional Development Opportunity for Out-of-School-Time Providers

    ERIC Educational Resources Information Center

    Lobley, Jennifer; Ouellette, Kristy L.

    2013-01-01

    The Maine 4-H Afterschool Academy trained 369 after-school and out of school time providers in 2011. This easy-to-adapt professional development opportunity used blended learning, a combination of in-person and Web-based opportunities. Providers successfully learned concepts and practical knowledge regarding 4-H, specifically 4-H Science. In…

  3. Current Practices for Training Staff to Accommodate Youth with Special Health Care Needs in the 4-H Camp Setting

    ERIC Educational Resources Information Center

    Mouton, Lauren; Bruce, Jacklyn

    2013-01-01

    The theory of inclusion is the foundation for the study reported here; inclusion is a focus not only of formal education, but also of nonformal educational settings such as 4-H. Ideally, 4-H camps are designed to serve youth of all backgrounds and abilities. By accommodating youth with special health care needs, 4-H camps are effectively meeting…

  4. E-Learning for 4-H Volunteers: Who Uses It, and What Can We Learn from Them?

    ERIC Educational Resources Information Center

    Ouellette, Kristy L.; Lesmeister, Marilyn K.; Lobley, Jennifer; Gross, Kerry M.

    2014-01-01

    Orienting and training 4-H volunteers are critical to individuals and the organization. The two-part study reported here re-establishes the profile of the 4-H volunteer and evaluates both the format and content of e-Learning for 4-H Volunteers modules launched in 2006. Volunteers from seven states perceived that online modules made learning more…

  5. Farm Parents' Attitudes Towards Farm Safety Experts

    ERIC Educational Resources Information Center

    Neufeld, Steven J.; Cinnamon, Jennifer L.

    2004-01-01

    Using both qualitative and quantitative data, this article analyzes farm parent's attitudes towards the trustworthiness, usefulness, and use of advice from farm safety experts. The article evaluates four different perspectives on trust in expert: the Validity of Knowledge perspective, the Salient Values Similarity perspective, the Diffusion of…

  6. Farm Safety (For Parents)

    MedlinePlus

    ... wheels or blind spots. Because adults who are operating machinery may be unable to see or hear ... a tractor and farm vehicle safety course before operating farm vehicles. Finally, teach older kids how to ...

  7. Middle School Dropout? Enrollment Trends in the California 4-H Youth Development Program

    ERIC Educational Resources Information Center

    Russell, Stephen T.; Heck, Katherine E.

    2008-01-01

    There is a widespread belief that youth drop out of youth development programs during the middle school years. Alternative explanations for the smaller number of adolescent program participants have yet to be explored. We examine age trends in program enrollment using data from over 221,000 youth enrolled in the California 4-H Youth Development…

  8. Promoting the Essential Elements of 4-H Youth Development through an Experiential Learning Model

    ERIC Educational Resources Information Center

    Meyer, Shelley; Jones, Kenneth R.

    2015-01-01

    The purpose of the project reported here was to apply Experiential Learning Theory to a context involving middle and high school aged youth while assessing the four concepts (belonging, mastery, independence, and generosity) in relation to the 4-H youth development essential elements. The conclusions of the project's evaluation suggest…

  9. Performance statistics of the FORTRAN 4 /H/ library for the IBM system/360

    NASA Technical Reports Server (NTRS)

    Clark, N. A.; Cody, W. J., Jr.; Hillstrom, K. E.; Thieleker, E. A.

    1969-01-01

    Test procedures and results for accuracy and timing tests of the basic IBM 360/50 FORTRAN 4 /H/ subroutine library are reported. The testing was undertaken to verify performance capability and as a prelude to providing some replacement routines of improved performance.

  10. A Partnership Model for Training Episodic Environmental Stewardship 4-H Volunteers

    ERIC Educational Resources Information Center

    Young, Jane Chin; Alexander, Janice; Smith, Martin H.

    2013-01-01

    The Marin Environmental Stewardship pilot project demonstrates the potential for a partnership model that brings together external and internal collaborators to recruit and train episodic 4-H volunteers to meet environmental education needs within a community. The clientele served by the volunteers trained through the project was at-risk, urban…

  11. Formation of low-temperature cirrus from H2SO4/H2O aerosol droplets.

    PubMed

    Bogdan, A; Molina, M J; Sassen, K; Kulmala, M

    2006-11-23

    We present experimental results obtained with a differential scanning calorimeter (DSC) that indicate the small ice particles in low-temperature cirrus clouds are not completely solid but rather coated with an unfrozen H2SO4/H2O overlayer. Our results provide a new look on the formation, development, and microphysical properties of low-temperature cirrus clouds.

  12. The Value of 4-H Judging Teams--Missouri Dairy Judging Alumni Survey

    ERIC Educational Resources Information Center

    Deaver, Karla; Probert, Ted

    2016-01-01

    Former Missouri 4-H Dairy Judging Team members responded to a survey about life skills development and the value of the judging team experience. Results of the survey indicate that judging team experience was highly influential in the development of communication, public speaking, and presentation skills. Respondents also indicated that judging…

  13. Children and their 4-H animal projects: How children use science in agricultural activity

    NASA Astrophysics Data System (ADS)

    Emo, Kenneth Roy

    Many children are introduced to science through informal educational programs. 4-H, an educational youth program, has a history of introducing scientific practices into agriculture. The purpose of this ethnographically-driven case study is to examine how science informs the actions of children raising market animals in a 4-H project. For two years the researcher collected data on 4-H children with market animal projects. Observations, interviews, and artifacts gathered are interpreted using the framework of activity theory. This study provides evidence for how the context of an activity system influences individual actions. Rules developed by the organization guide the actions of children to incorporate physical and psychological tools of science into their project to achieve the object: producing animals of proper weight and quality to be competitive in the county fair. Children learn the necessary actions from a community of practitioners through which expertise is distributed. Children's learning is demonstrated by the way their participation in their project changes with time, from receiving assistance from others to developing expertise in which they provide assistance to others. The strength of this educational experience is how children apply specific tools of science in ways that provide meaning and relevancy to their 4-H activity.

  14. Determining Directions for Change in a County 4-H Youth Program: The Role of Evaluation.

    ERIC Educational Resources Information Center

    Braverman, Marc; And Others

    This paper describes the evaluation of the 4-H youth program (serving ages 9 through 19) in Yolo County, California. The paper concentrates on the first component of the evaluation plan, a telephone survey of community needs and perceptions regarding services for youth which was conducted in November, 1984. The originally perceived questions…

  15. The Big E (Energy). 4-H Leader's Guide for Units 2 & 3.

    ERIC Educational Resources Information Center

    Caldwell, William; And Others

    This leader's guide is designed for units 2 and 3 of the Nebraska 4-H Energy Project. The goals of the project are to: (1) help young people understand energy problems related to life styles; (2) use energy resources carefully; (3) guide members in choosing their own energy alternatives; and (4) to enjoy together the challenges and creativity of…

  16. Participant Comfort with and Application of Inquiry-Based Learning: Results from 4-H Volunteer Training

    ERIC Educational Resources Information Center

    Haugen, Heidi; Stevenson, Anne; Meyer, Rebecca L.

    2016-01-01

    This article explores how a one-time training designed to support learning transfer affected 4-H volunteers' comfort levels with the training content and how comfort levels, in turn, affected the volunteers' application of tools and techniques learned during the training. Results of a follow-up survey suggest that the training participants…

  17. Diastereoselectivity in prebiotically relevant 5(4H)-oxazolone-mediated peptide couplings.

    PubMed

    Beaufils, Damien; Danger, Grégoire; Boiteau, Laurent; Rossi, Jean-Christophe; Pascal, Robert

    2014-03-21

    A stereochemical study of a potentially prebiotic peptide-forming reaction was carried out as the first part of a systems chemistry investigation of potential paths for symmetry breaking. Substantial diastereomeric excesses result from a fast epimerization of the 5(4H)-oxazolone intermediate in aqueous solution.

  18. A Beach and Dune Community. 4-H Marine Science. Member's Guide. Activity I. MSp 1.

    ERIC Educational Resources Information Center

    Auburn Univ., AL. Cooperative Extension Service.

    The investigation in this booklet is designed to provide 4-H members with opportunities to identify common plants and animals found on beaches and sand dunes and to determine the role of the plants and animals in this community. Learners are provided with a picture of a hypothetical beach and sand dune and a list of organisms (included in the…

  19. 4-H Tractor Operator Program Teaches Employability Skills and Safety to Youth

    ERIC Educational Resources Information Center

    Barrett, Debra K.

    2013-01-01

    For Michigan State University Extension, the Berrien County 4-H Tractor Operator Program has provided tractor safety education to teens for over 30 years. The certification training satisfies current requirements for operation of a 20 PTO HP or greater agricultural tractor by 14- and 15-year-old youth employed on property "not" owned,…

  20. Bio-Security Proficiencies Project for Beginning Producers in 4-H

    ERIC Educational Resources Information Center

    Smith, Martin H.; Meehan, Cheryl L.; Borba, John A.

    2014-01-01

    Improving bio-security practices among 4-H members who raise and show project animals is important. Bio-security measures can reduce the risk of disease spread and mitigate potential health and economic risks of disease outbreaks involving animal and zoonotic pathogens. Survey data provided statistical evidence that the Bio-Security Proficiencies…

  1. Stakeholder Satisfaction with a 4-H Extension Program for Five- to Eight-Year-Old Children.

    ERIC Educational Resources Information Center

    Scheer, Scott D.; Lafontaine, Kenneth R.

    1999-01-01

    A 4-H K-2 program was evaluated by 277 parents, 144 volunteers, and 44 extension agents. These stakeholders believed the program was beneficial and effective in improving children's life skills (self-esteem, making friends, making choices, learning and physical skills). (SK)

  2. 4-H Chickquest: Connecting Agri-Science with STEM Standards in Urban Schools

    ERIC Educational Resources Information Center

    Horton, Robert L.; Krieger, Jackie; Halasa, Katrina

    2013-01-01

    While young students are more capable of scientific inquiry than previously believed, elementary school teachers are often inexperienced in and lack confidence with teaching science. ChickQuest is a 4-H-created embryology curriculum for third-graders that meets Ohio state science standards, teaches STEM skills, and promotes ongoing interaction…

  3. 4-H Horticulture Project Activity Guides. Leader's Guide and Units 1-3.

    ERIC Educational Resources Information Center

    Illinois Univ., Urbana. Cooperative Extension Service.

    This document, concerning the 4-H horticulture project, includes a leader's guide and three youth activity guides. The leader's guide can be used to plan group project meetings that are both fun and educational. Activities can be adapted to various age groups. The leader's guide includes basic information for growing plants indoors and outdoors,…

  4. The Big E (Energy). 4-H Leader's Guide [for Unit 1].

    ERIC Educational Resources Information Center

    Caldwell, William; And Others

    This guide is designed for leaders of the Nebraska 4-H Energy Project. The goals of the project are to: (1) help young people understand energy problems related to life styles; (2) use energy resources carefully; (3) guide members in choosing their own energy alternatives; and (4) enjoy together the challenges and creativity of finding energy…

  5. Pennsylvania Youth in Action: 4-H Community Development. Adult Leader's Guide.

    ERIC Educational Resources Information Center

    Pennsylvania State Univ., University Park. Dept. of Agricultural and Extension Education.

    Designed to assist leaders in their roles as catalysts, advisors, and resource persons for the Pennsylvania Youth in Action 4-H Community Development program, the guide provides complementary educational, craft, and recreation suggestions to enhance student workbooks for three community development activity units. The first section focuses on the…

  6. County Clustering for the California 4-H Youth Development Program: Impacts and Lessons Learned

    ERIC Educational Resources Information Center

    Subramaniam, Aarti; Dasher, Harry Steve; Young, Jane Chin

    2012-01-01

    In response to budgetary constraints, a new staffing structure, the Pilot Leadership Plan, was proposed for California's 4-H Youth Development Program. County clusters were formed, each led by a coordinator. The plan was piloted for 2 years to provide insight into how county clustering could support Extension staff to increase and enhance…

  7. 4H-SiC photodiode model for DC SPICE circuit simulation

    NASA Astrophysics Data System (ADS)

    Kociubiński, Andrzej; Duk, Mariusz; Korona, Mateusz; Muzyka, Krzysztof

    2015-09-01

    Technology, characterization and in particularly modeling of 4H-SiC photodiode have been presented in this paper. Modeling and simulation has been performed using PSPICE environment. Comparison of simulation with real results for electrical characteristic (I-V) of circular SiC photodiodes has been also presented.

  8. Bufexamac ameliorates LPS-induced acute lung injury in mice by targeting LTA4H

    PubMed Central

    Xiao, Qiang; Dong, Ningning; Yao, Xue; Wu, Dang; Lu, Yanli; Mao, Fei; Zhu, Jin; Li, Jian; Huang, Jin; Chen, Aifang; Huang, Lu; Wang, Xuehai; Yang, Guangxiao; He, Guangyuan; Xu, Yong; Lu, Weiqiang

    2016-01-01

    Neutrophils play an important role in the occurrence and development of acute lung injury (ALI). Leukotriene B4 (LTB4), a hydrolysis product of epoxide leukotriene A4 (LTA4) catalyzed by LTA4 hydrolase (LTA4H), is one of the most potent chemoattractants for neutrophil. Bufexamac is a drug widely used as an anti-inflammatory agent on the skin, however, the mechanism of action is still not fully understood. In this study, we found bufexamac was capable of specifically inhibiting LTA4H enzymatic activity and revealed the mode of interaction of bufexamac and LTA4H using X-ray crystallography. Moreover, bufexamac significantly prevented the production of LTB4 in neutrophil and inhibited the fMLP-induced neutrophil migration through inhibition of LTA4H. Finally, bufexamac significantly attenuated lung inflammation as reflected by reduced LTB4 levels and weakened neutrophil infiltration in bronchoalveolar lavage fluid from a lipopolysaccharide-induced ALI mouse model. In summary, our study indicates that bufexamac acts as an inhibitor of LTB4 biosynthesis and may have potential clinical applications for the treatment of ALI. PMID:27126280

  9. Endocrine Aspects of 4H Leukodystrophy: A Case Report and Review of the Literature

    PubMed Central

    Billington, Emma; Bernard, Geneviève; Gibson, William; Corenblum, Bernard

    2015-01-01

    Introduction. 4H leukodystrophy is an autosomal recessive RNA polymerase III-related leukodystrophy, characterized by hypomyelination, with or without hypodontia (or other dental abnormalities) and hypogonadotropic hypogonadism. Case Presentation. We describe a 28-year-old female who presented with primary amenorrhea at the age of 19. She had a history of very mild neurological and dental abnormalities. She was found to have hypogonadotropic hypogonadism, and magnetic resonance imaging of the brain showed hypomyelination. The diagnosis of 4H leukodystrophy was made. She was subsequently found to have mutations in the POLR3B gene, which encodes the second largest subunit of RNA polymerase III. She wished to become pregnant and failed to respond to pulsatile GnRH but achieved normal follicular growth and ovulation with subcutaneous gonadotropin therapy. Discussion. Patients with 4H leukodystrophy may initially present with hypogonadotropic hypogonadism, particularly if neurological and dental manifestations are subtle. Making the diagnosis has important implications for prognosis and management. Progressive neurologic deterioration is expected, and progressive endocrine dysfunction may occur. Patients with 4H leukodystrophy should be counseled about disease progression and about this disease's autosomal recessive inheritance pattern. In those who wish to conceive, ovulation induction may be achieved with subcutaneous gonadotropin therapy, but pulsatile GnRH does not appear to be effective. PMID:26113998

  10. South Carolina's Model for Initiating Hispanic 4-H Clubs

    ERIC Educational Resources Information Center

    Lippert, Robert; Rembert, Kellye

    2012-01-01

    Over the past 5 years, through the initiative of several county Extension agents, South Carolina 4-H has established a successful model for bringing Hispanic youth into our program. We have found the most effective method is to initiate contact and establish partnerships with the principals and ESOL instructors in the local schools. Through this…

  11. Louisiana 4-H Seeds of Service School Gardens: A Descriptive View

    ERIC Educational Resources Information Center

    Cater, Melissa; Fox, Janet; Fletcher, Bobby Jr.

    2012-01-01

    Louisiana 4-H Seeds of Service School Gardens, a K-12 Learn and Serve Grant program, provides a descriptive view of how school gardens along with classroom instruction link curriculum to outdoor classrooms. The purpose of the process evaluation was to describe curriculum implementation fidelity, reach of the gardening program to participants, use…

  12. Possession, Transportation, and Use of Firearms by Older Youth in 4-H Shooting Sports Programs

    ERIC Educational Resources Information Center

    White, David J.; Williver, S. Todd

    2014-01-01

    Thirty years ago we would think nothing of driving to school with a jackknife in our pocket or rifle in the gun rack. Since then, the practices of possessing, transporting, and using firearms have been limited by laws, rules, and public perception. Despite restrictions on youth, the Youth Handgun Safety Act does afford 4-H shooting sports members…

  13. High efficiency 4H-SiC betavoltaic power sources using tritium radioisotopes

    NASA Astrophysics Data System (ADS)

    Thomas, Christopher; Portnoff, Samuel; Spencer, M. G.

    2016-01-01

    Realization of an 18.6% efficient 4H-silicon carbide (4H-SiC) large area betavoltaic power source using the radioisotope tritium is reported. A 200 nm 4H-SiC P+N junction is used to collect high-energy electrons. The electron source is a titanium tritide (TiH3x) foil, or an integrated titanium tritide region formed by the diffusion of tritium into titanium. The specific activity of the source is directly measured. Dark current measured under short circuit conditions was less than 6.1 pA/cm2. Samples measured with an external tritium foil produced an open circuit voltage of 2.09 V, short circuit current of 75.47 nA/cm2, fill factor of 0.86, and power efficiency of 18.6%. Samples measured with an integrated source produced power efficiencies of 12%. Simulations were done to determine the beta spectrum (modified by self absorption) exiting the source and the electron hole pair generation function in the 4H-SiC. The electron-hole pair generation function in 4H-SiC was modeled as a Gaussian distribution, and a closed form solution of the continuity equation was used to analyze the cell performance. The effective surface recombination velocity in our samples was found to be 105-106 cm/s. Our analysis demonstrated that the surface recombination dominates the performance of a tritium betavoltaic device but that using a thin P+N junction structure can mitigate some of the negative effects.

  14. Experimental Durability Testing of 4H SiC JFET Integrated Circuit Technology at 727 C

    NASA Technical Reports Server (NTRS)

    Spry, David; Neudeck, Phil; Chen, Liangyu; Chang, Carl; Lukco, Dorothy; Beheim, Glenn M

    2016-01-01

    We have reported SiC integrated circuits (IC's) with two levels of metal interconnect that have demonstrated prolonged operation for thousands of hours at their intended peak ambient operational temperature of 500 C [1, 2]. However, it is recognized that testing of semiconductor microelectronics at temperatures above their designed operating envelope is vital to qualification. Towards this end, we previously reported operation of a 4H-SiC JFET IC ring oscillator on an initial fast thermal ramp test through 727 C [3]. However, this thermal ramp was not ended until a peak temperature of 880 C (well beyond failure) was attained. Further experiments are necessary to better understand failure mechanisms and upper temperature limit of this extreme-temperature capable 4H-SiC IC technology. Here we report on additional experimental testing of custom-packaged 4H-SiC JFET IC devices at temperatures above 500 C. In one test, the temperature was ramped and then held at 727 C, and the devices were periodically measured until electrical failure was observed. A 4H-SiC JFET on this chip electrically functioned with little change for around 25 hours at 727 C before rapid increases in device resistance caused failure. In a second test, devices from our next generation 4H-SiC JFET ICs were ramped up and then held at 700 C (which is below the maximum deposition temperature of the dielectrics). Three ring oscillators functioned for 8 hours at this temperature before degradation. In a third experiment, an alternative die attach of gold paste and package lid was used, and logic circuit operation was demonstrated for 143.5 hours at 700 C.

  15. North Carolina Farm Survey.

    ERIC Educational Resources Information Center

    Lilley, Stephen; And Others

    Interviews with 725 North Carolina farm operators revealed: the extent of economic, social, and emotional stresses on farm families; perceptions of the future of agriculture; the degree of reliance on off-farm income; financial management practices; and programs needed from the Agricultural Extension Service. Almost 66% viewed their future in…

  16. Attitudes toward tobacco advertising among Hispanic migrant farm workers.

    PubMed

    LaChausse, R G

    2001-04-01

    The existing literature surrounding the effects of transnational tobacco advertising, advertising near or around U.S. borders, on migrant farm workers have been virtually ignored. The purpose of this study was to determine the media literacy skills among migrant farm workers and gather information regarding attitudes and beliefs surrounding tobacco use. Results indicate that migrant Hispanic farm workers believe that smoking is highly popular in the United States and a necessary part of American culture. The data also revealed low media literacy skills regarding tobacco advertising and pro-tobacco attitudes among Hispanic migrant farm workers. As a result, the current study suggests that this population has specific needs for basic media literacy skills regarding tobacco use. Therefore, health education specialists can develop educational strategies that will address tobacco advertising and media literacy skills among migrant farm workers. PMID:16228794

  17. Human pharmacology of 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) after repeated doses taken 4 h apart Human pharmacology of MDMA after repeated doses taken 4 h apart.

    PubMed

    Farré, Magí; Tomillero, Angels; Pérez-Mañá, Clara; Yubero, Samanta; Papaseit, Esther; Roset, Pere-Nolasc; Pujadas, Mitona; Torrens, Marta; Camí, Jordi; de la Torre, Rafael

    2015-10-01

    3,4-Methylenedioxymethamphetamine (MDMA, ecstasy) is a popular psychostimulant, frequently associated with multiple administrations over a short period of time. Repeated administration of MDMA in experimental settings induces tolerance and metabolic inhibition. The aim is to determine the acute pharmacological effects and pharmacokinetics resulting from two consecutive 100mg doses of MDMA separated by 4h. Ten male volunteers participated in a randomized, double-blind, crossover, placebo-controlled trial. The four conditions were placebo plus placebo, placebo plus MDMA, MDMA plus placebo, and MDMA plus MDMA. Outcome variables included pharmacological effects and pharmacokinetic parameters. After a second dose of MDMA, most effects were similar to those after a single dose, despite a doubling of MDMA concentrations (except for systolic blood pressure and reaction time). After repeated MDMA administration, a 2-fold increase was observed in MDMA plasma concentrations. For a simple dose accumulation MDMA and MDA concentrations were higher (+23.1% Cmax and +17.1% AUC for MDMA and +14.2% Cmax and +10.3% AUC for MDA) and HMMA and HMA concentrations lower (-43.3% Cmax and -39.9% AUC for HMMA and -33.2% Cmax and -35.1% AUC for HMA) than expected, probably related to MDMA metabolic autoinhibition. Although MDMA concentrations doubled after the second dose, most pharmacological effects were similar or slightly higher in comparison to the single administration, except for systolic blood pressure and reaction time which were greater than predicted. The pharmacokinetic-effects relationship suggests that when MDMA is administered at a 4h interval there exists a phenomenon of acute tolerance to its effects.

  18. Taking Science Online: Evaluating Presence and Immersion through a Laboratory Experience in a Virtual Learning Environment for Entomology Students

    ERIC Educational Resources Information Center

    Annetta, Leonard; Klesath, Marta; Meyer, John

    2009-01-01

    A 3-D virtual field trip was integrated into an online college entomology course and developed as a trial for the possible incorporation of future virtual environments to supplement online higher education laboratories. This article provides an explanation of the rationale behind creating the virtual experience, the Bug Farm; the method and…

  19. Virtual impactor

    DOEpatents

    Yeh, H.C.; Chen, B.T.; Cheng, Y.S.; Newton, G.J.

    1988-08-30

    A virtual impactor is described having improved efficiency and low wall losses in which a core of clean air is inserted into the aerosol flow while aerosol flow is maintained adjacent to the inner wall surfaces of the focusing portion of the impactor. The flow rate of the core and the length of the throat of the impactor's collection probe, as well as the dimensional relationships of other components of the impactor adjacent the separation region of the impactor, are selected to optimize separation efficiency. 4 figs.

  20. New insights in the discovery of novel h-MAO-B inhibitors: structural characterization of a series of N-phenyl-4-oxo-4H-chromene-3-carboxamide derivatives

    PubMed Central

    Gomes, Ligia R.; Low, John Nicolson; Cagide, Fernando; Chavarria, Daniel; Borges, Fernanda

    2015-01-01

    Six N-substituted-phenyl 4-oxo-4H-chromene-3-carboxamides, namely N-(2-nitro­phen­yl)-4-oxo-4H-chromene-3-carboxamide, C16H10N2O5 (2b), N-(3-meth­oxy­phen­yl)-4-oxo-4H-chromene-3-carboxamide, C17H13NO4, (3a), N-(3-bromo­phen­yl)-4-oxo-4H-chromene-3-carboxamide, C16H10BrNO3, (3b), N-(4-methoxy­phen­yl)-4-oxo-4H-chromene-3-carboxamide, C17H13NO4, (4a), N-(4-methyl­phen­yl)-4-oxo-4H-chromene-3-carboxamide, C17H13NO3, (4d), and N-(4-hy­droxy­phen­yl)-4-oxo-4H-chromene-3-carboxamide, C16H11NO4, (4e), have been structurally characterized. All compounds exhibit an anti conformation with respect to the C—N rotamer of the amide and a trans-related conformation with the carbonyl groups of the chromone ring of the amide. These structures present an intra­molecular hydrogen-bonded network comprising an N—H⋯O hydrogen bond between the amide N atom and the O atom of the carbonyl group of the pyrone ring, forming an S(6) ring, and a weak Car—H⋯O hydrogen bond in which the carbonyl group of the amide acts as acceptor for the H atom of an ortho-C atom of the exocyclic phenyl ring, which results in another S(6) ring. The N—H⋯O intra­molecular hydrogen bond constrains the carboxamide moiety such that it is virtually coplanar with the chromone ring. PMID:25995877

  1. Virtual screening of virtual libraries.

    PubMed

    Green, Darren V S

    2003-01-01

    Virtual screening of virtual libraries (VSVL) is a rapidly changing area of research. Great efforts are being made to produce better algorithms, selection methods and infrastructure. Yet, the number of successful examples in the literature is not impressive, although the quality of work certainly is high. Why is this? One reason is that these methods tend to be applied at the lead generation stage and therefore there is a large lead-time before successful examples appear in the literature. However, any computational chemist would confirm that these methods are successful and there exists a glut of start-up companies specialising in virtual screening. Moreover, the scientific community would not be focussing so much attention on this area if it were not yielding results. Even so, the paucity of literature data is certainly a hindrance to the development of better methods. The VSVL process is unique within the discovery process, in that it is the only method that can screen the > 10(30) genuinely novel molecules out there. Already, some VSVL methods are evaluating 10(13) compounds, a capacity that high throughput screening can only dream of. There is a huge potential advantage for the company that develops efficient and effective methods, for lead generation, lead hopping and optimization of both potency and ADME properties. To do this, it requires more than the software, it requires confidence to exploit the methodology, to commit synthesis on the basis of it, and to build this approach into the medicinal chemistry strategy. It is a fact that these tools remain quite daunting for the majority of scientists working at the bench. The routine use of these methods is not simply a matter of education and training. Integration of these methods into accessible and robust end user software, without dilution of the science, must be a priority. We have reached a coincidence, where several technologies have the required level of maturity predictive computational chemistry

  2. Thermodynamic calculations in the system CH4-H2O and methane hydrate phase equilibria

    USGS Publications Warehouse

    Circone, S.; Kirby, S.H.; Stern, L.A.

    2006-01-01

    Using the Gibbs function of reaction, equilibrium pressure, temperature conditions for the formation of methane clathrate hydrate have been calculated from the thermodynamic properties of phases in the system CH4-H 2O. The thermodynamic model accurately reproduces the published phase-equilibria data to within ??2 K of the observed equilibrium boundaries in the range 0.08-117 MPa and 190-307 K. The model also provides an estimate of the third-law entropy of methane hydrate at 273.15 K, 0.1 MPa of 56.2 J mol-1 K-1 for 1/n CH4??H 2O, where n is the hydrate number. Agreement between the calculated and published phase-equilibria data is optimized when the hydrate composition is fixed and independent of the pressure and temperature for the conditions modeled. ?? 2006 American Chemical Society.

  3. Detection of minority carrier traps in p-type 4H-SiC

    SciTech Connect

    Alfieri, G.; Kimoto, T.

    2014-03-03

    Contrarily to the case of n-type 4H-SiC, very little is known about the presence of minority carrier traps in p-type epilayers. In this study, we performed the electrical characterization of as-grown, electron irradiated, and thermally oxidized p-type 4H-SiC, by using minority carrier transient spectroscopy. Four minority carrier traps are reported in 1.6–2.3 eV energy range above the valence band edge (E{sub V}). Particular emphasis is given to the mid-gap minority carrier trap (EH{sub 6∕7}) and to its correlation to an energetically close mid-gap majority carrier trap (HK4)

  4. Magnesium chloride tetrahydrate, MgCl2·4H2O.

    PubMed

    Schmidt, Horst; Hennings, Erik; Voigt, Wolfgang

    2012-01-01

    The title compound, MgCl(2)·4H(2)O, was crystallized at 403 K and its structure determined at 200 K. The structure is built up from MgCl(2)(H(2)O)(4) octahedra with a trans configuration. Each complex is situated on a crystallographic twofold axis, with the rotation axis aligned along one H(2)O-Mg-OH(2) axis. They are connected by a complex network of O-H···Cl hydrogen bonds. The structure contains two-dimensional sections that are essentially identical to those in the reported tetrahydrates of CrCl(2), FeCl(2), FeBr(2) and CoBr(2), but they are stacked in a different manner in MgCl(2)·4H(2)O compared with the transition metal structures.

  5. A 4H Silicon Carbide Gate Buffer for Integrated Power Systems

    SciTech Connect

    Ericson, N; Frank, S; Britton, C; Marlino, L; Ryu, SH; Grider, D; Mantooth, A; Francis, M; Lamichhane, R; Mudholkar, M; Shepherd, P; Glover, M; Valle-Mayorga, J; McNutt, T; Barkley, A; Whitaker, B; Cole, Z; Passmore, B; Lostetter, A

    2014-02-01

    A gate buffer fabricated in a 2-mu m 4H silicon carbide (SiC) process is presented. The circuit is composed of an input buffer stage with a push-pull output stage, and is fabricated using enhancement mode N-channel FETs in a process optimized for SiC power switching devices. Simulation and measurement results of the fabricated gate buffer are presented and compared for operation at various voltage supply levels, with a capacitive load of 2 nF. Details of the design including layout specifics, simulation results, and directions for future improvement of this buffer are presented. In addition, plans for its incorporation into an isolated high-side/low-side gate-driver architecture, fully integrated with power switching devices in a SiC process, are briefly discussed. This letter represents the first reported MOSFET-based gate buffer fabricated in 4H SiC.

  6. The C4H radical and the diffuse interstellar bands. An ab initio study

    NASA Technical Reports Server (NTRS)

    Kolbuszewski, Marcin

    1994-01-01

    An ab initio study of the low-lying electronic states of C4H has been presented where the species studied has a chi(2)sigma(+) ground state and two low lying pi states. Based on the vertical and adiabatic excitation energies between those states it is suggested that the 4428 A diffuse interstellar band is not carried by C4H. The application of the particle in a box model shows strong coincidences between the strong DIB's and predicted wavelengths of pi-pi transitions in C(2n)H series. Based on those coincidences, it is suggested the C(2n)H species as good candidates for carriers of diffuse interstellar bands.

  7. Donor-acceptor-pair emission in fluorescent 4H-SiC grown by PVT method

    SciTech Connect

    Liu, Xi Zhuo, Shi-Yi; Gao, Pan; Huang, Wei; Yan, Cheng-Feng; Shi, Er-Wei

    2015-04-15

    Fluorescent SiC, which contains donor and acceptor impurities with optimum concentrations, can work as a phosphor for visible light emission by donor-acceptor-pair (DAP) recombination. In this work, 3 inch N-B-Al co-doped fluorescent 4H-SiC crystals are prepared by PVT method. The p-type fluorescent 4H-SiC with low aluminum doping concentration can show intensive yellow-green fluorescence at room temperature. N-B DAP peak wavelength shifts from 578nm to 525nm and weak N-Al DAP emission occurred 403/420 nm quenches, when the temperature increases from 4K to 298K. The aluminum doping induces higher defect concentration in the fluorescent crystal and decreases optical transmissivity of the crystal in the visible light range. It triggers more non-radiative recombination and light absorption losses in the crystal.

  8. Characteristic morphologies of triangular defects on Si-face 4H-SiC epitaxial films

    NASA Astrophysics Data System (ADS)

    Yamashita, T.; Naijo, T.; Matsuhata, H.; Momose, K.; Osawa, H.; Okumura, H.

    2016-01-01

    Triangular defects with a characteristic morphology consisting of a 3C-type structure were investigated on Si-face 4H-SiC epitaxial films using electron microscopy. Two types of triangular defects were investigated: one with a single valley on the surface along the [ 11 2 bar 0 ] direction and another with several parallel ridges and valleys called "washboard-like defects". The defects with a single valley had a characteristic domain structure consisting of four 3C crystals, which is similar to that of previously reported comet-shaped defects on the C-face. It is shown that the 3C domain in the washboard-like defect is covered by 4H layers with a washboard-like morphology.

  9. Electric-field dependence of electron drift velocity in 4H-SiC

    NASA Astrophysics Data System (ADS)

    Ivanov, P. A.; Potapov, A. S.; Samsonova, T. P.; Grekhov, I. V.

    2016-09-01

    Room temperature isothermal forward current-voltage characteristics of mesa-epitaxial 4H-SiC Schottky diodes were measured at high electric fields (beyond 105 V/cm) in the 34-μm thick n-base doped at 1 × 1015 cm-3. The effect of diode self-heating on current was minimized when using single 4-ns pulses. The analytical formula was derived for the dependence of electron drift velocity on electric field along c-axis.

  10. Enantioselective synthesis of 4H-pyranonaphthoquinones via sequential squaramide and silver catalysis.

    PubMed

    Kaya, Uğur; Chauhan, Pankaj; Hack, Daniel; Deckers, Kristina; Puttreddy, Rakesh; Rissanen, Kari; Enders, Dieter

    2016-01-28

    An enantioselective one-pot Michael addition/hydroalkoxylation reaction between 2-hydroxy-1,4-naphthoquinones and alkyne-tethered nitroalkenes catalyzed by a cinchona-derived squaramide and a silver(I) salt has been developed. The sequential protocol provides a direct access to 4H-pyranonaphthoquinones in moderate to very good yields and good to excellent enantioselectivities at a very low catalyst loading (0.5 mol%) of the squaramide.

  11. Resistance of 4H-SiC Schottky barriers at high forward-current densities

    SciTech Connect

    Ivanov, P. A. Samsonova, T. P.; Il’inskaya, N. D.; Serebrennikova, O. Yu.; Kon’kov, O. I.; Potapov, A. S.

    2015-07-15

    The resistance of Schottky barriers based on 4H-SiC is experimentally determined at high forward-current densities. The measured resistance is found to be significantly higher than the resistance predicted by classical mechanisms of electron transport in Schottky contacts. An assumption concerning the crucial contribution of the tunnel-transparent intermediate oxide layer between the metal and semiconductor to the barrier resistance is proposed and partially justified.

  12. Polarographic study of cadmium 5-hydroxy 2-(hydroxymethyl) 4H-pyran-4-one complex

    NASA Technical Reports Server (NTRS)

    Wilson, Ray F.; Daniels, Robert C.

    1989-01-01

    A polarographic study was performed on the products formed in the interaction of cadmium (II) with a 5-hydroxy 2-(hydroxymethyl) 4H-Pyran-4-one, using varying conditions of pH, supporting electrolytes, and concentrations. Measurements using the differential pulse method show that cadmium (II) exhibits a molar combining ratio of complexing agents to cation ranging from 1 to 1 to 3 to 1 depending on the pH and the supporting electrolyte employed.

  13. Enantioselective synthesis of 4H-pyranonaphthoquinones via sequential squaramide and silver catalysis.

    PubMed

    Kaya, Uğur; Chauhan, Pankaj; Hack, Daniel; Deckers, Kristina; Puttreddy, Rakesh; Rissanen, Kari; Enders, Dieter

    2016-01-28

    An enantioselective one-pot Michael addition/hydroalkoxylation reaction between 2-hydroxy-1,4-naphthoquinones and alkyne-tethered nitroalkenes catalyzed by a cinchona-derived squaramide and a silver(I) salt has been developed. The sequential protocol provides a direct access to 4H-pyranonaphthoquinones in moderate to very good yields and good to excellent enantioselectivities at a very low catalyst loading (0.5 mol%) of the squaramide. PMID:26660230

  14. High Resolution Topography Analysis on Threading Edge Dislocations in 4H-SiC Epilayers

    SciTech Connect

    Kamata, I.; Nagano, M; Tsuchida, H; Chen, Y; Dudley, M

    2009-01-01

    Threading edge dislocations (TEDs) in a 4H-SiC epitaxial layer are investigated using high-resolution synchrotron topography. Six types of TED image are confirmed to correspond to the Burgers vector directions by a comparison of computer simulated images and observed topography images in crystal boundaries. Using a mapping method, a wide spatial distribution of the six types of TED is examined in a quarter section of a 2-inch wafer.

  15. Theoretical microwave spectral constants for C3H/+/ and C4H/+/

    NASA Technical Reports Server (NTRS)

    Wilson, S.; Green, S.

    1980-01-01

    A number of linear conjugated carbon chain molecules have been observed in the interstellar gas. It has been suggested that ion molecule chemistry schemes may explain the formation of these compounds. In the present paper, theoretical bond lengths and rotation constants are obtained for C3H(+) and C4H(+). Calculations for C3 are used to assess the accuracy of the former. Recent results for C2H(+) are examined.

  16. Carbon-antisite vacancy defect in 4H silicon carbide for realizing solid state qubit

    NASA Astrophysics Data System (ADS)

    Gali, Adam; Szász, Krisztián; Ivády, Viktor; Abrikosov, Igor; Bockstedte, Michel; Janzén, Erik

    2015-03-01

    Dopants in solids are promising candidates for implementations of quantum bits for quantum computing. Silicon carbide (SiC) with engineered point defects is considered as very promising material for the next generation devices, with applications ranging from electronics and photonics to quantum computing. Employing density functional theory and many body perturbation theory, we show that the neutral carbon antisite-vacancy pair (CAV) has high spin ground state, and that its spin may be coherently manipulated by optical excitation in n-type 4H SiC. As the positively charged CAV defect in 4H SiC has been recently engineered to act as single photon source, our finding brings a hope that optically addressed quantum bits can be realized by the neutral CAV defects in 4H SiC, and provide an additional target for researchers seeking for solid state single color centers for quantum information processes and metrology. The calculated zero-phonon line of the optically excited state is about 1550 nm (0.8 eV) which perfectly fits to the telecom wavelengths, that makes this qubit candidate very promising for integration of quantum optics devices with existing fiber optics technology. Lendület program of Hungarian Academy of Sciences, the Knut & Alice Wallenberg Foundation, Swedish Research Council, US DoE.

  17. Combustion of CH4/H2/air mixtures in catalytic microreactors.

    PubMed

    Specchia, Stefania; Vella, Luigi D; Burelli, Sara; Saracco, Guido; Specchia, Vito

    2009-03-23

    The combustion of CH(4)/H(2)/HC mixtures in a very small space represents an alternative, innovative way to produce thermal/electrical energy. Pd/NiCrO(4) catalysts are lined on SiC monoliths via in situ solution combustion synthesis (SCS), and the monoliths are then tested by feeding CH(4), H(2), and lean CH(4)/H(2) mixtures into a lab-scale test rig at an output thermal power of 7.6 MW(th) m(-3). In all cases, the combustion temperature shifts to values lower than those observed in non-catalytic combustion. When the power density is kept constant (by adding H(2) to the gas mixture), the value of CH(4)-T(50) (the half-conversion temperature of CH(4)) decreases relative to that of pure CH(4), and the slope of the conversion curve becomes steeper. The higher the H(2) concentration is, the higher the reactivity of the mixture towards CH(4) oxidation-probably due to a higher production of H(2) reactive radicals (OH).

  18. Demonstration of the First 4H-SiC EUV Detector with Large Detection Area

    NASA Technical Reports Server (NTRS)

    Xin, Xiaobin; Yan, Feng; Koeth, Timothy W.; Hu, Jun; Zhao, Jian H.

    2005-01-01

    Ultraviolet (UV) and Extreme Ultraviolet (EUV) detectors are very attractive in astronomy, photolithography and biochemical applications. For EUV applications, most of the semiconductor detectors based on PN or PIN structures suffer from the very short penetration depth. Most of the carries are absorbed at the surface and recombined there due to the high surface recombination before reach the depletion region, resulting very low quantum efficiency. On the other hand, for Schottky structures, the active region starts from the surface and carriers generated from the surface can be efficiently collected. 4H-Sic has a bandgap of 3.26eV and is immune to visible light background noise. Also, 4H-Sic detectors usually have very good radiation hardness and very low noise, which is very important for space applications where the signal is very weak. The E W photodiodes presented in this paper are based on Schottky structures. Platinum (Pt) and Nickel (Ni) are selected as the Schottky contact metals, which have the highest electron work functions (5.65eV and 5.15eV, respectively) among all the known metals on 4H-Sic.

  19. Laboratory detection of the C3N an C4H free radicals

    NASA Technical Reports Server (NTRS)

    Gottlieb, C. A.; Gottlieb, E. W.; Thaddeus, P.; Kawamura, H.

    1983-01-01

    The millimeter-wave spectra of the linear carbon chain free radicals C3N and C4H, first identified in IRC + 10216 and hitherto observed only in a few astronomical sources, have been detected with a Zeeman-modulated spectrometer in laboratory glow discharges through low pressure flowing mixtures of N2 + HC3N and He + HCCH, respectively. Four successive rotational transitions between 168 and 198 GHz have been measured for C3N, and five rotational transitions between 143 and 200 GHz for C4H; each is a well-resolved spin doublet owing to the unpaired electron present in both species. Precise values for the rotational, centrifugal distortion, and spin doubling constants have been obtained, which, with hyperfine constants derived from observations of the lower rotational transitions in the astronomical source TMC 1, allow all the rotational transitions of C3N and C4H at frequencies less than 300 GHz to be calculated to an absolute accuracy exceeding 1 ppm.

  20. A remarkable activity of human leukotriene A4 hydrolase (LTA4H) toward unnatural amino acids.

    PubMed

    Byzia, Anna; Haeggström, Jesper Z; Salvesen, Guy S; Drag, Marcin

    2014-05-01

    Leukotriene A4 hydrolase (LTA4H--EC 3.3.2.6) is a bifunctional zinc metalloenzyme, which processes LTA4 through an epoxide hydrolase activity and is also able to trim one amino acid at a time from N-terminal peptidic substrates via its aminopeptidase activity. In this report, we have utilized a library of 130 individual proteinogenic and unnatural amino acid fluorogenic substrates to determine the aminopeptidase specificity of this enzyme. We have found that the best proteinogenic amino acid recognized by LTA4H is arginine. However, we have also observed several unnatural amino acids, which were significantly better in terms of cleavage rate (k cat/K m values). Among them, the benzyl ester of aspartic acid exhibited a k cat/K m value that was more than two orders of magnitude higher (1.75 × 10(5) M(-1) s(-1)) as compared to L-Arg (1.5 × 10(3) M(-1) s(-1)). This information can be used for design of potent inhibitors of this enzyme, but may also suggest yet undiscovered functions or specificities of LTA4H.

  1. Extended charge accumulation in ruthenium-4H-imidazole-based black absorbers: a theoretical design concept.

    PubMed

    Kupfer, Stephan

    2016-05-11

    A theoretical-guided design concept aiming to achieve highly efficient unidirectional charge transfer and multi-charge separation upon successive photoexcitation for light-harvesting dyes in the scope of supramolecular photocatalysts is presented. Four 4H-imidazole-ruthenium(ii) complexes incorporating a biimidazole-based electron-donating ligand sphere have been designed based on the well-known 4H-imidazole-ruthenium(ii) polypyridyl dyes. The quantum chemical evaluation, performed at the density functional and time-dependent density functional level of theory, revealed extraordinary unidirectional charge transfer bands from the near-infrared to the ultraviolet region of the absorption spectrum upon multi-photoexcitation. Spectro-electrochemical simulations modeling photoexcited intermediates determined the outstanding multi-electron storage capacity for this novel class of black dyes. These remarkable photochemical and photophysical properties are found to be preserved upon site-specific protonation rendering 4H-imidazole-ruthenium(ii) biimidazole dyes ideal for light-harvesting applications in the field of solar energy conversion. PMID:27121270

  2. Interfacial atomic site characterization by photoelectron diffraction for 4H-AlN/4H-SiC(11\\bar{2}0) heterojunction

    NASA Astrophysics Data System (ADS)

    Maejima, Naoyuki; Horita, Masahiro; Matsui, Hirosuke; Matsushita, Tomohiro; Daimon, Hiroshi; Matsui, Fumihiko

    2016-08-01

    The interfacial atomic structure of an AlN thin film on a nonpolar 4H-SiC(11\\bar{2}0) substrate grown by atomic Al and N plasma deposition was studied by photoelectron diffraction and spectroscopy. The epitaxial growth of the thin film was confirmed by the comparison of element-specific photoelectron intensity angular distributions (PIADs). Depth profiles were analyzed by angle-resolved constant-final-state-mode X-ray photoelectron spectroscopy (AR-XPS). No polar angular dependence was observed in Al 2p spectra, while an additional intermixing component was found in interface-sensitive N 1s spectra. The site-specific N 1s PIADs for the AlN film and an intermixing component were derived from two N 1s PIADs with different binding energies. We attributed the intermixing component to SiN interfacial layer sites. In order to prevent SiN growth at the interface, we deposited Al on the SiC(11\\bar{2}0) substrate prior to the AlN growth. A significant reduction in the amount of intermixing components at the AlN/SiC interface was confirmed by AR-XPS.

  3. Virtual Reality and the Virtual Library.

    ERIC Educational Resources Information Center

    Oppenheim, Charles

    1993-01-01

    Explains virtual reality, including proper and improper uses of the term, and suggests ways that libraries might be affected by it. Highlights include elements of virtual reality systems; possible virtual reality applications, including architecture, the chemical industry, transport planning, armed forces, and entertainment; and the virtual…

  4. Farm Health and Safety

    MedlinePlus

    ... jobs in the United States. Farms have many health and safety hazards, including Chemicals and pesticides Machinery, ... equipment can also reduce accidents. Occupational Safety and Health Administration

  5. The Research of Computer Aided Farm Machinery Designing Method Based on Ergonomics

    NASA Astrophysics Data System (ADS)

    Gao, Xiyin; Li, Xinling; Song, Qiang; Zheng, Ying

    Along with agricultural economy development, the farm machinery product type Increases gradually, the ergonomics question is also getting more and more prominent. The widespread application of computer aided machinery design makes it possible that farm machinery design is intuitive, flexible and convenient. At present, because the developed computer aided ergonomics software has not suitable human body database, which is needed in view of farm machinery design in China, the farm machinery design have deviation in ergonomics analysis. This article puts forward that using the open database interface procedure in CATIA to establish human body database which aims at the farm machinery design, and reading the human body data to ergonomics module of CATIA can product practical application virtual body, using human posture analysis and human activity analysis module to analysis the ergonomics in farm machinery, thus computer aided farm machinery designing method based on engineering can be realized.

  6. Ultra-High Voltage 4H-SiC Bi-Directional Insulated Gate Bipolar Transistors

    NASA Astrophysics Data System (ADS)

    Chowdhury, Sauvik

    4H- Silicon Carbide (4H-SiC) is an attractive material for power semiconductor devices due to its large bandgap, high critical electric field and high thermal conductivity compared to Silicon (Si). For ultra-high voltage applications (BV > 10 kV), 4H-SiC Insulated Gate Bipolar Transistors (IGBTs) are favored over unipolar transistors due to lower conduction losses. With improvements in SiC materials and processing technology, promising results have been demonstrated in the area of conventional unidirectional 4H-SiC IGBTs, with breakdown voltage ratings up to 27 kV. This research presents the experimental demonstration of the world's first high voltage bi-directional power transistors in 4H-SiC. Traditionally, four (two IGBTs and two diodes) or two (two reverse blocking IGBTs) semiconductor devices are necessary to yield a bidirectional switch. With a monolithically integrated bidirectional switch as presented here, the number of semiconductor devices is reduced to only one, which results in increased reliability and reduced cost of the overall system. Additionally, by using the unique dual gate operation of BD-IGBTs, switching losses can be reduced to a small fraction of that in conventional IGBTs, resulting in increased efficiency. First, the performance limits of SiC IGBTs are calculated by using analytical methods. The performance benefits of SiC IGBTs over SiC unipolar devices and Si IGBTs are quantified. Numerical simulations are used to optimize the unit cell and edge termination structures for a 15 kV SiC BD-IGBT. The effect of different device parameters on BD-IGBT static and switching performance are quantified. Second, the process technology necessary for the fabrication of high voltage SiC BD-IGBTs is optimized. The effect of different process steps on parameters such as breakdown voltage, carrier lifetime, gate oxide reliability, SiO2-SiC interface charge density is quantified. A carrier lifetime enhancement process has been optimized for lightly doped

  7. Atomistic Simulations of Epitaxial Recrystallization in 4H-SiC along the [0001] Direction

    SciTech Connect

    Gao, Fei; Zhang, Yanwen; Devanathan, Ram; Posselt, Matthias; Weber, William J.

    2007-02-16

    Molecular dynamics (MD) methods have been employed to study the epitaxail recrystallization and amorphous-to-crystalline (a-c) transition in 4H-SiC, with simulation times of up to a few hundred ns and at temperatures of 1500 and 2000 K. Three nano-sized amorphous layers with the normal of a-c interfaces along the [-12-10 ], [-1010] and [0001] directions, respectively, were created within a crystalline cell to investigate the anisotropies of recrystallization processes. The recovery of bond defects at the interfaces is an important process driving the initial epitaxial recrystallization of the amorphous layers. The amorphous layers with the a-c interface normal along the [-12-10] direction can be completely recrystallized at the temperatures of 1500 and 2000 K, and along the [0001] direction at 2000 K. However, the recrystallized region is defected with dislocations and stacking faults. The temperatures required for complete recrystallization are in good agreement with those observed in experiments. On the other hand, the recrystallization processes for the a-c interface normal along [-1010] direction are hindered by the nucleation of polycrystalline phases. These secondary ordered phases have been identified as 4H- and 3C-SiC with different crystallographic orientations to the original 4H-SiC. The bond mismatches at the interfaces between different microcrystals result in the formation of a number of stacking faults. The temperature is an important parameter to control the nucleation of the secondary ordered phase, whereas the size of amorphous region has a significant effect on their growth. These results are in good agreement with the previous experimental observations.

  8. Virtual Worlds, Real Learning

    ERIC Educational Resources Information Center

    Meyers, Eric M.

    2009-01-01

    Many children between the ages of four and twelve log in to Web-based virtual play spaces each day, and these virtual worlds are quickly becoming an important aspect of their out-of-school lives. Consequently, educators' challenge is to see how they can leverage virtual spaces, such as the virtual play spaces, for learning and literacy. Over the…

  9. Rethinking Virtual School

    ERIC Educational Resources Information Center

    Schomburg, Gary; Rippeth, Michelle

    2009-01-01

    Virtual schooling has been touted as one of the best ways to meet the needs of at-risk students, but what happens when a district's virtual education program is unsuccessful? That was the problem in Eastern Local School District, a small rural district in Beaver, Ohio. The district contracted virtual school services and used the virtual school for…

  10. High responsivity 4H-SiC based metal-semiconductor-metal ultraviolet photodetectors

    NASA Astrophysics Data System (ADS)

    Yang, Weifeng; Zhang, Feng; Liu, Zhuguang; Lü, Ying; Wu, Zhengyun

    2008-11-01

    4H-SiC based metal-semiconductor-metal (MSM) photodetectors with diverse spacing were designed, fabricated, and characterized, in which nickel Schottky contacts were needed. Current-voltage and spectral responsivity measurements were carried out at room temperature. The fabricated 4 μm-spacing device showed a very low dark current (0.25 pA at 5 V bias voltage), a typical responsivity of 0.103 A/W at 20 V, and a peak response wavelength at 290 nm. The fabricated devices held a high DUV to visible rejection ratio of >103.

  11. Transient collector modulation of 4H-SiC BJTs during switch-on process

    NASA Astrophysics Data System (ADS)

    Yuferev, Valentin S.; Levinshtein, Michael E.; Ivanov, Pavel A.; Zhang, Jon Q.; Palmour, John W.

    2016-09-01

    Main physical features of the collector resistance modulation processes have been studied via a one-dimensional simulation for n+-p-n0-n+ 4H-SiC bipolar junction transistor. The motion dynamics of minority carriers (holes) across the n0 collector layer during the switch-on process is traced. It is demonstrated that the effective modulation of the collector resistance is only possible in the case of a rather fast transistor switch-on. A necessary condition for the fast switch-on is the large amplitude and short leading edge of the base current pulse.

  12. Hydrogen Gas Sensors Fabricated on Atomically Flat 4H-SiC Webbed Cantilevers

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.; Spry, David J.; Trunek, Andrew J.; Evans, Laura J.; Chen, Liang-Yu; Hunter, Gary W.; Androjna, Drago

    2007-01-01

    This paper reports on initial results from the first device tested of a "second generation" Pt-SiC Schottky diode hydrogen gas sensor that: 1) resides on the top of atomically flat 4H-SiC webbed cantilevers, 2) has integrated heater resistor, and 3) is bonded and packaged. With proper selection of heater resistor and sensor diode biases, rapid detection of H2 down to concentrations of 20 ppm was achieved. A stable sensor current gain of 125 +/- 11 standard deviation was demonstrated during 250 hours of cyclic test exposures to 0.5% H2 and N2/air.

  13. 4H-SiC Schottky photodiodes for ultraviolet flame detection

    NASA Astrophysics Data System (ADS)

    Mazzillo, M.; Sciuto, A.

    2015-10-01

    In the last few years silicon carbide (SiC) has emerged as an appropriate material for the detection of very low ultraviolet photon fluxes even at elevated temperatures. In this paper we report on the electro-optical characteristics of large area interdigit Ni2Si/4H-SiC photodiodes in TO metal can package with a suitable molded cap quartz window with high transmission in the ultraviolet wavelength range. The detectors have been tested for the detection of the ultraviolet component of the yellow flame emitted by a small candle, showing good sensitivity for very weak photon fluxes notwithstanding the linear operation condition of the photodiodes.

  14. Dynamic characteristics of 4H-SiC drift step recovery diodes

    SciTech Connect

    Ivanov, P. A. Kon’kov, O. I.; Samsonova, T. P.; Potapov, A. S.; Grekhov, I. V.

    2015-11-15

    The dynamic characteristics of 4H-SiC p{sup +}–p–n{sub 0}–n{sup +} diodes are experimentally studied in the pulsed modes characteristic of the operation of drift step recovery diodes (DSRD-mode). The effect of the subnanosecond termination of the reverse current maintained by electron-hole plasma preliminarily pumped by a forward current pulse is analyzed in detail. The influence exerted on the DSRD effect by the amplitude of reverse-voltage pulses, the amplitude and duration of forward-current pulses, and the time delay between the forward and reverse pulses is demonstrated and accounted for.

  15. 4H-SiC JFET Multilayer Integrated Circuit Technologies Tested Up to 1000 K

    NASA Technical Reports Server (NTRS)

    Spry, D. J.; Neudeck, P. G.; Chen, L.; Chang, C. W.; Lukco, D.; Beheim, G. M.

    2015-01-01

    Testing of semiconductor electronics at temperatures above their designed operating envelope is recognized as vital to qualification and lifetime prediction of circuits. This work describes the high temperature electrical testing of prototype 4H silicon carbide (SiC) junction field effect transistor (JFET) integrated circuits (ICs) technology implemented with multilayer interconnects; these ICs are intended for prolonged operation at temperatures up to 773K (500 C). A 50 mm diameter sapphire wafer was used in place of the standard NASA packaging for this experiment. Testing was carried out between 300K (27 C) and 1150K (877 C) with successful electrical operation of all devices observed up to 1000K (727 C).

  16. Atomic oxidation of large area epitaxial graphene on 4H-SiC(0001)

    SciTech Connect

    Velez-Fort, E.; Ouerghi, A.; Silly, M. G.; Sirtti, F.; Eddrief, M.; Marangolo, M.; Shukla, A.

    2014-03-03

    Structural and electronic properties of epitaxial graphene on 4H-SiC were studied before and after an atomic oxidation process. X-ray photoemission spectroscopy indicates that oxygen penetrates into the substrate and decouples a part of the interface layer. Raman spectroscopy demonstrates the increase of defects due to the presence of oxygen. Interestingly, we observed on the near edge x-ray absorption fine structure spectra a splitting of the π* peak into two distinct resonances centered at 284.7 and 285.2 eV. This double structure smears out after the oxidation process and permits to probe the interface architecture between graphene and the substrate.

  17. Development of 17 kV 4H-SiC PiN diode

    NASA Astrophysics Data System (ADS)

    Runhua, Huang; Yonghong, Tao; Ling, Wang; Gang, Chen; Song, Bai; Rui, Li; Yun, Li; Zhifei, Zhao

    2016-08-01

    The design, fabrication, and electrical characteristics of a 4H-SiC PiN diode with breakdown voltage higher than 17 kV are presented. The three-zone JTE has been used in the fabrication. Numerical simulations have been performed to optimize the parameters of the edge termination technique. The epilayer properties of the N-type are 175 μm with a doping of 2 × 1014 cm-3. With the three-zone JTE, a typical breakdown voltage of 17 kV has been achieved. Project supported by the National High Technology Research and Development Program of China (No. 2014AA041401).

  18. Development of 17 kV 4H-SiC PiN diode

    NASA Astrophysics Data System (ADS)

    Runhua, Huang; Yonghong, Tao; Ling, Wang; Gang, Chen; Song, Bai; Rui, Li; Yun, Li; Zhifei, Zhao

    2016-08-01

    The design, fabrication, and electrical characteristics of a 4H-SiC PiN diode with breakdown voltage higher than 17 kV are presented. The three-zone JTE has been used in the fabrication. Numerical simulations have been performed to optimize the parameters of the edge termination technique. The epilayer properties of the N-type are 175 μm with a doping of 2 × 1014 cm‑3. With the three-zone JTE, a typical breakdown voltage of 17 kV has been achieved. Project supported by the National High Technology Research and Development Program of China (No. 2014AA041401).

  19. Virtual courseware for geoscience education: Virtual Earthquake and Virtual Dating

    NASA Astrophysics Data System (ADS)

    Novak, Gary A.

    1999-05-01

    Virtual courseware developed for introductory-level, on-line geology labs is an interactive teaching/learning model that has an enormous pedagogical potential for making Web sites places where students learn by doing. Virtual Earthquake and Virtual Dating are modest examples of the `virtual courseware' paradigm. Virtual Earthquake helps students explore the techniques of how an earthquake's epicenter is located and how its Richter magnitude is determined. Virtual Dating models the theory and techniques of the radiometric age determination of rocks and minerals. Virtual courseware applications offer several advantages over traditional floppy disk or CD ROM-based courseware, the most significant being the ease of dissemination. The author's experience with bringing these two virtual applications on-line suggests that there is a need for interactive geology labs on-line and that the approach will be received with enthusiasm by the educational community. The widespread implementation and adoption of virtual courseware can bring meaningful educational content and interactivity for the geosciences that goes beyond multimedia on the World-Wide-Web.

  20. Virtual button interface

    DOEpatents

    Jones, Jake S.

    1999-01-01

    An apparatus and method of issuing commands to a computer by a user interfacing with a virtual reality environment. To issue a command, the user directs gaze at a virtual button within the virtual reality environment, causing a perceptible change in the virtual button, which then sends a command corresponding to the virtual button to the computer, optionally after a confirming action is performed by the user, such as depressing a thumb switch.

  1. Virtual button interface

    DOEpatents

    Jones, J.S.

    1999-01-12

    An apparatus and method of issuing commands to a computer by a user interfacing with a virtual reality environment are disclosed. To issue a command, the user directs gaze at a virtual button within the virtual reality environment, causing a perceptible change in the virtual button, which then sends a command corresponding to the virtual button to the computer, optionally after a confirming action is performed by the user, such as depressing a thumb switch. 4 figs.

  2. Complete genome sequence of the marine, cellulose and xylan degrading bacterium Glaciecola sp. 4H-3-7+YE-5

    SciTech Connect

    Klippel, Dr Barbara; Bruce, David; Davenport, Karen W.; Goodwin, Lynne A.; Han, James; Han, Shunsheng; Land, Miriam L; Mikhailova, Natalia; Nolan, Matt; Pennacchio, Len; Pitluck, Sam; Tapia, Roxanne; Woyke, Tanja; Wiebusch, Sigrid; Basner, Alexander; Abe, Fumiyoshi; Horikoshi, Koki; Antranikian, Garabed

    2011-01-01

    Glaciecola sp. 4H-3-7+YE-5 was isolated from deep sea sediments at Suruga Bay in Japan and is capable of efficiently hydrolyzing cellulose and xylan. The complete genome sequence of Glaciecola sp. 4H-3-7+YE-5 revealed several genes encoding putatively novel glycoside hydrolases associated with plant biomass degradation.

  3. A Mixed Method Study of Positional Leadership of North Dakota 4-H Ambassador and State FFA Officer Alumni

    ERIC Educational Resources Information Center

    Peterson, Nels Milan

    2010-01-01

    The purpose of this mixed method study was to determine the positional leadership of North Dakota 4-H and FFA leadership alumni. This study determined the influence of youth development programs on statewide leadership alumni (those who served from 1970 to 2000) and community leadership roles as adults. Former North Dakota 4-H Ambassador Alumni…

  4. Understanding Life Skills Gained from and Reasons for Youth Participation in the Tennessee 4-H Sheep Skillathon

    ERIC Educational Resources Information Center

    Davis, Terra Kimes; Stripling, Christopher T.; Stephens, Carrie A.; Loveday, H. Dwight

    2016-01-01

    The high number of U.S. youth exhibiting at-risk behavior points to a lack of life skills development. We determined the effects of participating in one state's 4-H sheep skillathon on youths' life skills development and the youths' reasons for participating. The target population was 2014 Tennessee 4-H Sheep Skillathon participants (N = 153), and…

  5. Eat, Grow, Lead 4-H: An Innovative Approach to Deliver Campus- Based Field Experiences to Pre-Entry Extension Educators

    ERIC Educational Resources Information Center

    Weeks, Penny Pennington; Weeks, William G.

    2012-01-01

    Eat, Grow, Lead 4-H Club was created as a pilot program for college students seeking to gain experience as non-formal youth educators, specifically serving pre-entry level Extension educators through a university-based 4-H club. Seventeen student volunteers contributed an estimated 630 hours of service to the club during spring 2011. The club…

  6. Family Diversity in a Youth Organization: Involvement of Single-Parent Families and Stepfamilies in 4-H.

    ERIC Educational Resources Information Center

    Ganong, Lawrence H.

    1993-01-01

    Evaluated involvement of children from single-parent and stepparent households in 4-H clubs. Used case study approach, with data collected via written materials; interviews with 4-H staff; and mailed questionnaires from professional staff, paraprofessionals, and parents. Children from single-parent households were found to be underrepresented, as…

  7. Virtual goods recommendations in virtual worlds.

    PubMed

    Chen, Kuan-Yu; Liao, Hsiu-Yu; Chen, Jyun-Hung; Liu, Duen-Ren

    2015-01-01

    Virtual worlds (VWs) are computer-simulated environments which allow users to create their own virtual character as an avatar. With the rapidly growing user volume in VWs, platform providers launch virtual goods in haste and stampede users to increase sales revenue. However, the rapidity of development incurs virtual unrelated items which will be difficult to remarket. It not only wastes virtual global companies' intelligence resources, but also makes it difficult for users to find suitable virtual goods fit for their virtual home in daily virtual life. In the VWs, users decorate their houses, visit others' homes, create families, host parties, and so forth. Users establish their social life circles through these activities. This research proposes a novel virtual goods recommendation method based on these social interactions. The contact strength and contact influence result from interactions with social neighbors and influence users' buying intention. Our research highlights the importance of social interactions in virtual goods recommendation. The experiment's data were retrieved from an online VW platform, and the results show that the proposed method, considering social interactions and social life circle, has better performance than existing recommendation methods. PMID:25834837

  8. Virtual goods recommendations in virtual worlds.

    PubMed

    Chen, Kuan-Yu; Liao, Hsiu-Yu; Chen, Jyun-Hung; Liu, Duen-Ren

    2015-01-01

    Virtual worlds (VWs) are computer-simulated environments which allow users to create their own virtual character as an avatar. With the rapidly growing user volume in VWs, platform providers launch virtual goods in haste and stampede users to increase sales revenue. However, the rapidity of development incurs virtual unrelated items which will be difficult to remarket. It not only wastes virtual global companies' intelligence resources, but also makes it difficult for users to find suitable virtual goods fit for their virtual home in daily virtual life. In the VWs, users decorate their houses, visit others' homes, create families, host parties, and so forth. Users establish their social life circles through these activities. This research proposes a novel virtual goods recommendation method based on these social interactions. The contact strength and contact influence result from interactions with social neighbors and influence users' buying intention. Our research highlights the importance of social interactions in virtual goods recommendation. The experiment's data were retrieved from an online VW platform, and the results show that the proposed method, considering social interactions and social life circle, has better performance than existing recommendation methods.

  9. Virtual Goods Recommendations in Virtual Worlds

    PubMed Central

    Chen, Kuan-Yu; Liao, Hsiu-Yu; Chen, Jyun-Hung; Liu, Duen-Ren

    2015-01-01

    Virtual worlds (VWs) are computer-simulated environments which allow users to create their own virtual character as an avatar. With the rapidly growing user volume in VWs, platform providers launch virtual goods in haste and stampede users to increase sales revenue. However, the rapidity of development incurs virtual unrelated items which will be difficult to remarket. It not only wastes virtual global companies' intelligence resources, but also makes it difficult for users to find suitable virtual goods fit for their virtual home in daily virtual life. In the VWs, users decorate their houses, visit others' homes, create families, host parties, and so forth. Users establish their social life circles through these activities. This research proposes a novel virtual goods recommendation method based on these social interactions. The contact strength and contact influence result from interactions with social neighbors and influence users' buying intention. Our research highlights the importance of social interactions in virtual goods recommendation. The experiment's data were retrieved from an online VW platform, and the results show that the proposed method, considering social interactions and social life circle, has better performance than existing recommendation methods. PMID:25834837

  10. Effect of Doping Concentration Variations in PVT-Grown 4H-SiC Wafers

    NASA Astrophysics Data System (ADS)

    Yang, Yu; Guo, Jianqiu; Goue, Ouloide; Raghothamachar, Balaji; Dudley, Michael; Chung, Gil; Sanchez, Edward; Quast, Jeff; Manning, Ian; Hansen, Darren

    2016-04-01

    Synchrotron white beam x-ray topography studies carried out on 4H-SiC wafers characterized by locally varying doping concentrations reveals the presence of overlapping Shockley stacking faults generated from residual surface scratches in regions of higher doping concentrations after the wafers have been subjected to heat treatment. The stacking faults are rhombus-shaped and bound by Shockley partial dislocations. The fault generation process is driven by the fact that in regions of higher doping concentrations, a faulted crystal containing double Shockley faults is more stable than a perfect 4H-SiC crystal at the high temperatures (>1000°C) that the wafers are subject to during heat treatment. We have developed a model for the formation mechanism of the rhombus-shaped stacking faults. Our studies show that during heat treatment of the wafer, such double Shockley faults can be generated in regions where dislocation sources are presents (e.g. scratches or low-angle boundaries) and when the nitrogen doping concentration exceeds a certain level.

  11. Evaluation of 4H-SiC Thermal Oxide Reliability Using Area-Scaling Method

    NASA Astrophysics Data System (ADS)

    Senzaki, Junji; Shimozato, Atsushi; Okamoto, Mitsuo; Kojima, Kazutoshi; Fukuda, Kenji; Okumura, Hajime; Arai, Kazuo

    2009-08-01

    The reliability of thermal oxides grown on an n-type 4H-SiC(0001) was investigated using an area-scaling method, and the influence of dislocation defects on the time-dependent dielectric breakdown characteristics of thermal oxides was examined. A thermal oxide was grown by dry oxidation at 1200 °C followed by nitrogen post-oxidation annealing. Using the area-scaling method, the time-to-breakdown (tBD) distribution curves of metal-oxide-semiconductor (MOS) capacitors with different gate area sizes were converged to a single one. It was clearly shown that origins of dielectric breakdown are edge breakdown and dislocation-related breakdown for steep and gradual slopes of the area-scaling normalized tBD distribution curve, respectively. In addition, a yield analysis of MOS capacitors quantitatively indicated that both threading screw dislocation and basal plane dislocation are predominant killer defects for the dielectric breakdown of thermal oxides on the 4H-SiC(0001) face.

  12. Characterization of V-shaped defects in 4H-SiC homoepitaxial layers

    DOE PAGES

    Zhang, Lihua; Su, Dong; Kisslinger, Kim; Stach, Eric; Chung, Gil; Zhang, Jie; Thomas, Bernd; Sanchez, Edward K; Mueller, Stephan G.; Hansen, Darren; et al

    2014-12-04

    Synchrotron white beam x-ray topography images show that faint needle-like surface morphological features observed on the Si-face of 4H-SiC homoepitaxial layers using Nomarski optical microscopy are associated with V shaped stacking faults in the epilayer. KOH etching of the V shaped defect reveals small oval pits connected by a shallow line which corresponding to the surface intersections of two partial dislocations and the stacking fault connecting them. Transmission electron microscopy (TEM) specimens from regions containing the V shaped defects were prepared using focused ion beam milling, and stacking sequences of (85), (50) and (63) are observed at the faulted regionmore » with high resolution TEM. In order to study the formation mechanism of V shaped defect, low dislocation density 4H-SiC substrates were chosen for epitaxial growth, and the corresponding regions before and after epitaxy growth are compared in SWBXT images. It is found that no defects in the substrate are directly associated with the formation of the V shaped defect. Simulation results of the contrast from the two partial dislocations associated with V shaped defect in synchrotron monochromatic beam x-ray topography reveals the opposite sign nature of their Burgers vectors. Therefore, a mechanism of 2D nucleation during epitaxy growth is postulated for the formation of the V shaped defect, which requires elimination of non-sequential 1/4[0001] bilayers from the original structure to create the observed faulted stacking sequence.« less

  13. Characterization of V-shaped defects in 4H-SiC homoepitaxial layers

    SciTech Connect

    Zhang, Lihua; Su, Dong; Kisslinger, Kim; Stach, Eric; Chung, Gil; Zhang, Jie; Thomas, Bernd; Sanchez, Edward K; Mueller, Stephan G.; Hansen, Darren; Loboda, Mark J.; Wu, Fangzhen; Wang, Huanhuan; Raghothamachar, Balaji; Dudley, Michael

    2014-12-04

    Synchrotron white beam x-ray topography images show that faint needle-like surface morphological features observed on the Si-face of 4H-SiC homoepitaxial layers using Nomarski optical microscopy are associated with V shaped stacking faults in the epilayer. KOH etching of the V shaped defect reveals small oval pits connected by a shallow line which corresponding to the surface intersections of two partial dislocations and the stacking fault connecting them. Transmission electron microscopy (TEM) specimens from regions containing the V shaped defects were prepared using focused ion beam milling, and stacking sequences of (85), (50) and (63) are observed at the faulted region with high resolution TEM. In order to study the formation mechanism of V shaped defect, low dislocation density 4H-SiC substrates were chosen for epitaxial growth, and the corresponding regions before and after epitaxy growth are compared in SWBXT images. It is found that no defects in the substrate are directly associated with the formation of the V shaped defect. Simulation results of the contrast from the two partial dislocations associated with V shaped defect in synchrotron monochromatic beam x-ray topography reveals the opposite sign nature of their Burgers vectors. Therefore, a mechanism of 2D nucleation during epitaxy growth is postulated for the formation of the V shaped defect, which requires elimination of non-sequential 1/4[0001] bilayers from the original structure to create the observed faulted stacking sequence.

  14. Exploration of Defects in 4H-SiC MOSFETs via Spin Dependent Charge Pumping

    NASA Astrophysics Data System (ADS)

    Anders, Mark; Lenahan, Patrick; Lelis, Aivars

    4H-SiC MOSFETs have great promise for use in high temperature and high voltage applications. Unfortunately, defects at the SiC/SiO2 interface reduce the performance of these devices. Previously, our group utilized electrically detected magnetic resonance (EDMR) detected via spin dependent recombination (SDR) to identify such SiC/SiO2 interface defects utilizing the bipolar amplification (BAE) biasing scheme; we observed SiC silicon vacancies, E-prime centers, and hydrogen complexed E-prime centers. All of these defects must have levels around the middle of the SiC band gap because they are effective recombination centers. We expanded our studies to include EDMR detection via spin dependent charge pumping (SDCP) at low field, X band, and K band, allowing EDMR exploration of nearly the entire 4H-SiC band gap. Perhaps the most important finding of the (nearly) full band gap measurements is the absence of the carbon dangling bond spectrum in the SDCP. Additionally, in nMOSFETs, we observe an SDCP EDMR spectrum dominated by a silicon vacancy, whereas in pMOSFETs, we also observe a strong, nearly isotropic single line spectrum with g = 2.00244 and 2.00248 when the c-axis is nearly parallel and perpendicular to the magnetic field, respectively. The results suggest that silicon vacancy centers dominate nMOSFET interfaces whereas additional defects clearly play important roles in pMOSFETs.

  15. n-ZnO/p-4H-SiC diode: Structural, electrical, and photoresponse characteristics

    SciTech Connect

    Guziewicz, M. Jung, W.

    2015-09-07

    Epitaxial n-type ZnO film has been grown, on a commercial 5 μm thick p-type 4H-SiC(00.1) Al doped epilayer, by atomic layer deposition. A full width at half maximum of the ZnO 00.2 diffraction peak rocking curve of 0.34°{sup  }± 0.02° has been measured. Diodes formed on the n-ZnO/p-4H-SiC heterostructure show rectifying behavior with a forward to reverse current ratio at the level of 10{sup 9} at ±4 V, a leakage current density of ∼6 × 10{sup −8} A/cm{sup 2}, and a low ideality factor equal to 1.17 ± 0.04. In addition, the diodes exhibit selective photoresponse with a maximum at 367 nm, and with a current increase of ∼10{sup 3} under illuminations with respect to the dark value, which makes such devices prospective candidates for ultraviolet light sensors.

  16. Comprehensive study of a 4H-SiC MES-MOSFET

    NASA Astrophysics Data System (ADS)

    Jamali Mahabadi, S. E.; Amini Moghadam, Hamid

    2015-11-01

    In this paper, we studied the enhancement of the breakdown voltage in the 4H-SiC MESFET-MOSFET (MES-MOSFET) structure which we have proposed in our previous work. We compared this structure with Conventional Bulk-MOSFET (CB-MOSFET) and Field plated Conventional Bulk-MOSFET (FCB-MOSFET) structures. The 4H-SiC MES-MOSFET structure consists of two additional schottky buried gates which behave like a Metal on Semiconductor (MES) at the interface of the active region and substrate. The motivation for this structure was to enhance the breakdown voltage by introducing a new technique of utilizing the reduced surface field (RESURF) concept. In our comparison and investigation we used a two-dimensional device simulator. Our simulation results show that the breakdown voltage of the proposed structure is 3.7 and 2.9 times larger than CB-MOSFET and FCB-MOSFET structures, respectively. We also showed that the threshold voltage and the slope of drain current (ID) as a function of drain-source voltage (VDS) for all the structures is the same.

  17. Characterization of the Minimum Energy Paths for the Ring Closure Reactions of C4H3 with Acetylene

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.

    1995-01-01

    The ring closure reaction of C4H3 with acetylene to give phenyl radical is one proposed mechanism for the formation of the first aromatic ring in hydrocarbon combustion. There are two low-lying isomers of C4H3; 1-dehydro-buta-l-ene-3-yne (n-C4H3) and 2-dehydro-buta-l-ene-3-yne (iso-C4H3). It has been proposed that only n-C4H3 reacts with acetylene to give phenyl radical, and since iso-C4H3 is more stable than n-C4H3, formation of phenyl radical by this mechanism is unlikely. We report restricted Hartree-Fock (RHF) plus singles and doubles configuration interaction calculations with a Davidson's correction (RHF+1+2+Q) using the Dunning correlation consistent polarized valence double zeta basis set (cc-pVDZ) for stationary point structures along the reaction pathway for the reactions of n-C4H3 and iso-C4H3 with acetylene. n-C4H3 plus acetylene (9.4) has a small entrance channel barrier (17.7) (all energetics in parentheses are in kcal/mol with respect to iso-C4H3 plus acetylene) and the subsequent closure steps leading to phenyl radical (-91.9) are downhill with respect to the entrance channel barrier. Iso-C4H3 Plus acetylene also has an entrance channel barrier (14.9) and there is a downhill pathway to 1-dehydro-fulvene (-55.0). 1-dehydro-fulvene can rearrange to 6-dehydro-fulvene (-60.3) by a 1,3-hydrogen shift over a barrier (4.0), which is still below the entrance channel barrier, from which rearrangement to phenyl radical can occur by a downhill pathway. Thus, both n-C4H3 and iso-C4H3 can react with acetylene to give phenyl radical with small barriers.

  18. Biotechnology on the farm

    SciTech Connect

    Tangley, L.

    1986-10-01

    A new genetically engineered growth hormone promises to boost milk yields for dairy farms. Larger milk yields would worsen economic problems facing dairy farmers especially owners of small farms. The conflicts between new technologies and US agricultural policy are discussed here.

  19. Not Your Family Farm

    ERIC Educational Resources Information Center

    Tenopir, Carol; Baker, Gayle; Grogg, Jill E.

    2007-01-01

    The information industry continues to consolidate, just as agribusiness has consolidated and now dominates farming. Both the family farm and the small information company still exist but are becoming rarer in an age of mergers, acquisitions, and increased economies of scale. Small companies distinguish themselves by high quality, special themes,…

  20. Migrant Farm Workers.

    ERIC Educational Resources Information Center

    Slesinger, Doris P.; Pfeffer, Max J.

    This paper documents migrant farm workers as being among the most persistently underprivileged groups in American society. Migrant farm workers typically receive low wages from irregular employment and live in poverty with access to only substandard housing and inadequate health care. The lack of economic improvement stems from a number of…

  1. Occupations and the Farm.

    ERIC Educational Resources Information Center

    Ewert-Krocker, Laurie

    2001-01-01

    Describes "occupation" as a Montessori term, which the Hershey Montessori Farm School, in Huntsburg, Ohio, has adopted for any task arising from the needs of the farm that then generates a scientific or historic study. Includes lists of occupations pursued during 2000-2001 and samples of record forms students used to manage their work. (Author/KB)

  2. Occupational Hazards of Farming

    PubMed Central

    White, Gill; Cessna, Allan

    1989-01-01

    A number of occupational hazards exist for the farmer and farm worker. They include the hazards of farm machinery, biologic and chemical hazards, and social and environmental stresses. Recognizing of these hazards will help the family physician care for farmers and their families. PMID:21248929

  3. Virtual PCR

    SciTech Connect

    Gardner, S N; Clague, D S; Vandersall, J A; Hon, G; Williams, P L

    2006-02-23

    The polymerase chain reaction (PCR) stands among the keystone technologies for analysis of biological sequence data. PCR is used to amplify DNA, to generate many copies from as little as a single template. This is essential, for example, in processing forensic DNA samples, pathogen detection in clinical or biothreat surveillance applications, and medical genotyping for diagnosis and treatment of disease. It is used in virtually every laboratory doing molecular, cellular, genetic, ecologic, forensic, or medical research. Despite its ubiquity, we lack the precise predictive capability that would enable detailed optimization of PCR reaction dynamics. In this LDRD, we proposed to develop Virtual PCR (VPCR) software, a computational method to model the kinetic, thermodynamic, and biological processes of PCR reactions. Given a successful completion, these tools will allow us to predict both the sequences and concentrations of all species that are amplified during PCR. The ability to answer the following questions will allow us both to optimize the PCR process and interpret the PCR results: What products are amplified when sequence mixtures are present, containing multiple, closely related targets and multiplexed primers, which may hybridize with sequence mismatches? What are the effects of time, temperature, and DNA concentrations on the concentrations of products? A better understanding of these issues will improve the design and interpretation of PCR reactions. The status of the VPCR project after 1.5 years of funding is consistent with the goals of the overall project which was scoped for 3 years of funding. At half way through the projected timeline of the project we have an early beta version of the VPCR code. We have begun investigating means to improve the robustness of the code, performed preliminary experiments to test the code and begun drafting manuscripts for publication. Although an experimental protocol for testing the code was developed, the preliminary

  4. Virtual Flow Simulator

    SciTech Connect

    Calderer, Antoni; Yang, Xiaolei; Angelidis, Dionysios; Khosronejad, Ali; Le, Trung; Kang, Seokkoo; Gilmanov, Anvar; Ge, Liang; Borazjani, Iman

    2015-10-05

    Virtual Flow Simulator (VFS) is a state-of-the-art computational fluid mechanics (CFD) package that is capable of simulating multi-physics/multi-phase flows with the most advanced turbulence models (RANS, LES) over complex terrains. The flow solver is based on the Curvilinear Immersed Boundary (CURVIB) method to handle geometrically complex and moving domains. Different modules of the VFS package can provide different simulation capabilities for specific applications ranging from the fluid-structure interaction (FSI) of solid and deformable bodies, the two-phase free surface flow solver based on the level set method for ocean waves, sediment transport models in rivers and the large-scale models of wind farms based on actuator lines and surfaces. All numerical features of VFS package have been validated with known analytical and experimental data as reported in the related journal articles. VFS package is suitable for a broad range of engineering applications within different industries. VFS has been used in different projects with applications in wind and hydrokinetic energy, offshore and near-shore ocean studies, cardiovascular and biological flows, and natural streams and river morphodynamics. Over the last decade, the development of VFS has been supported and assisted with the help of various United States companies and federal agencies that are listed in the sponsor lists. In this version, VFS-Wind contains all the necessary modeling tools for wind energy applications, including land-based and offshore wind farms. VFS is highly scalable to run on either desktop computers or high performance clusters (up to 16,000 CPUs). This released version comes with a detailed user’s manual and a set of case studies designed to facilitate the learning of the various aspects of the code in a comprehensive manner. The included documentation and support material has been elaborated in a collaboration effort with Sandia National Labs under the contract DE-EE0005482. The VFS

  5. Virtual Flow Simulator

    2015-10-05

    Virtual Flow Simulator (VFS) is a state-of-the-art computational fluid mechanics (CFD) package that is capable of simulating multi-physics/multi-phase flows with the most advanced turbulence models (RANS, LES) over complex terrains. The flow solver is based on the Curvilinear Immersed Boundary (CURVIB) method to handle geometrically complex and moving domains. Different modules of the VFS package can provide different simulation capabilities for specific applications ranging from the fluid-structure interaction (FSI) of solid and deformable bodies, themore » two-phase free surface flow solver based on the level set method for ocean waves, sediment transport models in rivers and the large-scale models of wind farms based on actuator lines and surfaces. All numerical features of VFS package have been validated with known analytical and experimental data as reported in the related journal articles. VFS package is suitable for a broad range of engineering applications within different industries. VFS has been used in different projects with applications in wind and hydrokinetic energy, offshore and near-shore ocean studies, cardiovascular and biological flows, and natural streams and river morphodynamics. Over the last decade, the development of VFS has been supported and assisted with the help of various United States companies and federal agencies that are listed in the sponsor lists. In this version, VFS-Wind contains all the necessary modeling tools for wind energy applications, including land-based and offshore wind farms. VFS is highly scalable to run on either desktop computers or high performance clusters (up to 16,000 CPUs). This released version comes with a detailed user’s manual and a set of case studies designed to facilitate the learning of the various aspects of the code in a comprehensive manner. The included documentation and support material has been elaborated in a collaboration effort with Sandia National Labs under the contract DE-EE0005482

  6. Plasma ignition and steady state simulations of the Linac4 H{sup −} ion source

    SciTech Connect

    Mattei, S. Lettry, J.; Grudiev, A.; Ohta, M.; Yasumoto, M.; Hatayama, A.

    2014-02-15

    The RF heating of the plasma in the Linac4 H{sup −} ion source has been simulated using a particle-in-cell Monte Carlo collision method. This model is applied to investigate the plasma formation starting from an initial low electron density of 10{sup 12} m{sup −3} and its stabilization at 10{sup 18} m{sup −3}. The plasma discharge at low electron density is driven by the capacitive coupling with the electric field generated by the antenna, and as the electron density increases the capacitive electric field is shielded by the plasma and induction drives the plasma heating process. Plasma properties such as e{sup −}/ion densities and energies, sheath formation, and shielding effect are presented and provide insight to the plasma properties of the hydrogen plasma.

  7. Evaluation of MOS structures processed on 4H SiC layers grown by PVT epitaxy

    NASA Astrophysics Data System (ADS)

    Ciechonski, R. R.; Syväjärvi, M.; Wahab, Q.; Yakimova, R.

    2005-12-01

    MOS capacitors have been fabricated on 4H-SiC epilayers grown by physical vapor transport (PVT) epitaxy. The properties were compared with those on similar structures based on chemical vapor deposition (CVD) layers. Capacitance-voltage ( C- V) and conductance measurements ( G- V) were performed in the frequency range of 1 kHz to 1 MHz and also at temperatures up to 475 K. Detailed investigations of the PVT structures indicate a stable behaviour of the interface traps from room temperature up to 475 K. The amount of positive oxide charge QO is 6.83 × 10 9 cm -2 at room temperature and decreases with temperature increase. This suggests that the processed devices are temperature stable. The density of interface states Dit obtained by Nicollian-Brews conductance method is lower in the structure based on the PVT grown sample.

  8. Band gap states of Ti, V, and Cr in 4H-silicon carbide

    NASA Astrophysics Data System (ADS)

    Achtziger, Norbert; Witthuhn, Wolfgang

    1997-07-01

    Band gap states of Ti, V, and Cr in n-type 4H-SiC were investigated by radiotracer deep level transient spectroscopy (DLTS). Doping with the radioactive isotopes 48V and 51Cr was done by recoil implantation followed by annealing (1600 K). Repeated DLTS measurements during the elemental transmutation of these isotopes to 48Ti and 51V, respectively, reveal the corresponding concentration changes of band gap states. Thus, six levels are identified in the band gap: Cr levels at 0.15, 0.18, and 0.74 eV, one V level at 0.97 eV, and two Ti levels at 0.13 and 0.17 eV below the conduction band edge.

  9. 4H-SiC UV Photo Detector with Large Area and Very High Specific Detectivity

    NASA Technical Reports Server (NTRS)

    Yan, Feng; Shahid, Aslam; Franz, David; Xin, Xiaobin; Zhao, Jian H.; Zhao, Yuegang; Winer, Maurice

    2004-01-01

    Pt/4H-SiC Schottky photodiodes have been fabricated with the device areas up to 1 sq cm. The I-V characteristics and photo-response spectra have been measured and analyzed. For a 5 mm x 5 mm area device leakage current of 1 x 10(exp 15)A at zero bias and 1.2 x 10(exp 14)A at -IV have been established. The quantum efficiency is over 30% from 240nm to 320nm. The specific detectivity, D(sup *), has been calculated from the directly measured leakage current and quantum efficiency data and are shown to be higher than 10(exp 15) cmHz(sup 1/2)/W from 210nm to 350nm with a peak D(sup *) of 3.6 x 10(exp 15)cmH(sup 1/2)/W at 300nm.

  10. Excess leakage currents in high-voltage 4H-SiC Schottky diodes

    SciTech Connect

    Ivanov, P. A. Grekhov, I. V.; Potapov, A. S.; Samsonova, T. P.; Il'inskaya, N. D.; Kon'kov, O. I.; Serebrennikova, O. Yu.

    2010-05-15

    The high-voltage 4H-SiC Schottky diodes are fabricated with a nickel barrier and a guard system in the form of 'floating' planar p-n junctions. The analysis of I-V characteristics measured in a wide temperature range shows that the forward current is caused by thermionic emission; however, the current is 'excessive' in the reverse direction. It is assumed that the reverse current flows locally through the points of the penetrating-dislocation outcrop to the Ni-SiC interface. The shape of reverse I-V characteristics makes it possible to conclude that the electron transport is governed by the monopolar-injection mechanism (the space-charge limited current) with participation of capture traps.

  11. Characterization and Modeling of 4H-SiC Lateral MOSFETs for Integrated Circuit Design

    SciTech Connect

    Mudholkar, M; Mantooth, HA

    2013-06-01

    A new process in 4H-SiC is developed that features n-type buried and inversion channel lateral MOSFETs that are fabricated with several different channel lengths (2-8 mu m) and widths (8-32 mu m) and characterized over a wide temperature range (25 degrees C-225 degrees C). It is shown that the on-resistance of enhancement-mode SiC MOSFETs reduces with temperature despite a reduction in inversion mobility because of the interaction of interface states with temperature. To enable integrated circuit development using the developed MOSFETs, their electrical characteristics are modeled over geometry and temperature using the industry standard PSP MOSFET model. A new mathematical formulation to describe the presence of the interface states is also developed and implemented in the PSP model, and excellent agreement is shown between measurement and simulation using the modified PSP model.

  12. Evidence for near-infrared photoluminescence of nitrogen vacancy centers in 4 H -SiC

    NASA Astrophysics Data System (ADS)

    Zargaleh, S. A.; Eble, B.; Hameau, S.; Cantin, J.-L.; Legrand, L.; Bernard, M.; Margaillan, F.; Lauret, J.-S.; Roch, J.-F.; von Bardeleben, H. J.; Rauls, E.; Gerstmann, U.; Treussart, F.

    2016-08-01

    We present evidence of near-infrared photoluminescence (PL) signature of nitrogen vacancy centers (NCVSi) - in silicon carbide (SiC). This center exhibits an S =1 ground state spin similar to the NV- center in diamond. We have performed photoluminescence excitation measurements at cryogenic temperature and demonstrated efficient photoexcitation of distinct photoluminescence from (NCVSi)- in 4 H -SiC. Furthermore, by correlating the energies of measured zero phonon lines (ZPLs) with theoretical values derived from hybrid density functional theory each of the ZPLs has been associated to the respective occupation of hexagonal (h ) and quasicubic (k ) lattice sites in close analogy to neutral divacancy centers (VCVSi) 0 in the same material. Finally, with the appropriate choice of excitation energy we demonstrated the selective excitation of (NCVSi) - PL with no contamination by (VCVSi) 0 PL, thereby opening the way towards the optical detection of (NCVSi) - electron spin resonance.

  13. Irradiation of 4H-SiC UV detectors with heavy ions

    SciTech Connect

    Kalinina, E. V. Lebedev, A. A.; Bogdanova, E.; Berenquier, B.; Ottaviani, L.; Violina, G. N.; Skuratov, V. A.

    2015-04-15

    Ultraviolet (UV) photodetectors based on Schottky barriers to 4H-SiC are formed on lightly doped n-type epitaxial layers grown by the chemical vapor deposition method on commercial substrates. The diode structures are irradiated at 25°C by 167-MeV Xe ions with a mass of 131 amu at a fluence of 6 × 10{sup 9} cm{sup −2}. Comparative studies of the optical and electrical properties of as-grown and irradiated structures with Schottky barriers are carried out in the temperature range 23–180°C. The specific features of changes in the photosensitivity and electrical characteristics of the detector structures are accounted for by the capture of photogenerated carriers into traps formed due to fluctuations of the conduction-band bottom and valence-band top, with subsequent thermal dissociation.

  14. An Integrated Gate Driver in 4H-SiC for Power Converter Applications

    SciTech Connect

    Ericson, Milton Nance; Frank, Steven Shane; Britton, Charles; Janke, Devon D; Ezell, N Dianne Bull; Ryu, Sei_Hyung; Mantooth, Alan; Francis, Dr. Matt; Lanmichhane, Dr. Ranjan; Shepherd, Dr. Paul; Glover, Dr. Michael; Whitaker, Mr. Bret; Cole, Mr. Zach; Passmore, Mr. Brandon; Mcnutt, Tyler

    2014-01-01

    A gate driver fabricated in a 2-um 4H silicon carbide (SiC) process is presented. This process was optimized for vertical power MOSFET fabrication but accommodated integration of a few low-voltage device types including N-channel MOSFETs, resistors, and capacitors. The gate driver topology employed incorporates an input level translator, variable power connections, and separate power supply connectivity allowing selection of the output signal drive amplitude. The output stage utilizes a source follower pull-up device that is both overdriven and body source connected to improve rise time behavior. Full characterization of this design driving a SiC power MOSFET is presented including rise and fall times, propagation delays, and power consumption. All parameters were measured to elevated temperatures exceeding 300 C. Details of the custom test system hardware and software utilized for gate driver testing are also provided.

  15. Detection of powder formation in SiH4/H2 glow discharges

    NASA Astrophysics Data System (ADS)

    Alexiou, G.; Tsigaras, G.; Amanatides, E.; Mataras, D.

    2016-03-01

    Time-resolved self-bias voltage measurements and spatiotemporal resolved optical emission spectroscopy were used in order to monitor particle formation and instabilities in the initial stage of 13.56 MHz SiH4/H2. The effect of total gas pressure on the particles formation and the time required for the plasma to reach steady state was investigated. Both techniques were very sensitive in monitoring the nucleation and coagulation phase of particles formation. The characteristic times required for reaching steady state were similar for both techniques indicating that electrical properties and chemical kinetics are affected in a similar way from particle formation. The increase of pressure resulted in a significant shortening of the instability period and this can be a significant advantage in the deposition of device grade silicon thin films.

  16. Characterization of N-doped multilayer graphene grown on 4H-SiC (0001)

    NASA Astrophysics Data System (ADS)

    Arezki, Hakim; Ho, Kuan-I.; Jaffré, Alexandre; Alamarguy, David; Alvarez, José; Kleider, Jean-Paul; Lai, Chao-Sung; Boutchich, Mohamed

    2015-02-01

    Large-area graphene film doped with hetero-atoms is of great interest for a wide spectrum of nanoelectronics applications, such as field effect devices, super capacitors, fuel cells among many others. Here, we report the structural and electronic properties of nitrogen doped multilayer graphene on 4H-SiC (0001). The incorporation of nitrogen during the growth causes an increase in the D band on the Raman signature indicating that the nitrogen is creating defects. The analysis of micro-Raman mapping of G, D, 2D bands shows a predominantly trilayer graphene with a D band inherent to doping and inhomogeneous dopant distribution at the step edges. Ultraviolet photoelectron spectroscopy (UPS) indicates an n type work function (WF) of 4.1 eV. In addition, a top gate FET device was fabricated showing n-type I-V characteristic after the desorption of oxygen with high electron and holes mobilities.

  17. Charcot-Marie-Tooth Disease Type 4H Resulting from Compound Heterozygous Mutations in FGD4 from Nonconsanguineous Korean Families.

    PubMed

    Hyun, Young Se; Lee, Jinho; Kim, Hye Jin; Hong, Young Bin; Koo, Heasoo; Smith, Alec S T; Kim, Deok-Ho; Choi, Byung-Ok; Chung, Ki Wha

    2015-11-01

    Charcot-Marie-Tooth disease type 4H (CMT4H) is an autosomal recessive demyelinating subtype of peripheral enuropathies caused by mutations in the FGD4 gene. Most CMT4H patients are in consanguineous Mediterranean families characterized by early onset and slow progression. We identified two CMT4H patients from a Korean CMT cohort, and performed a detailed genetic and clinical analysis in both cases. Both patients from nonconsanguineous families showed characteristic clinical manifestations of CMT4H including early onset, scoliosis, areflexia, and slow disease progression. Exome sequencing revealed novel compound heterozygous mutations in FGD4 as the underlying cause in both families (p.Arg468Gln and c.1512-2A>C in FC73, p.Met345Thr and c.2043+1G>A (p.Trp663Trpfs*30) in FC646). The missense mutations were located in highly conserved RhoGEF and PH domains which were predicted to be pathogenic in nature by in silico modeling. The CMT4H occurrence frequency was calculated to 0.7% in the Korean demyelinating CMT patients. This study is the first report of CMT4H in Korea. FGD4 assay could be considered as a means of molecular diagnosis for sporadic cases of demyelinating CMT with slow progression.

  18. Measurement of Optical, Mechanical and Transport properties of the hexagonal closed packed 4H polytype of metallic silver

    NASA Astrophysics Data System (ADS)

    Chakraborty, Indrani; Shirodkar, Sharmila N.; Gohil, Smita; Waghmare, Umesh; Ayyub, Pushan

    2013-03-01

    Optical, mechanical and transport property measurements were done on the hexagonal closed packed (hcp) 4H polytype of Ag with stacking sequence ABCBABCB.. grown as bulk films on Al2O3 substrates. Diffused reflectance measurements done on the 4H films showed a general loss of reflectivity amounting to a decrease of 35% as compared to normal fcc (3C) Ag near 500 nm with a blueshift of 5nm in the bulk plasmon frequency, possibly due to the modified electronic structure of the hcp form. Raman spectroscopic measurements showed the appearance of a peak at 64.3 cm-1 at 4K which underwent ``Mode softening,'' that is shifted to lower wave numbers with increase of temperature and disappeared above 350K. Low temperature transport measurements done on 4H films gave the in-plane resistivity value to be 39 times higher than that of a similarly synthesized fcc Ag film at 295 K. Vicker's microhardness measurements done on the 4H films showed that the 4H samples to be almost 5 times harder than the 3C Ag. Density functional theory simulations were done to obtain the phonon dispersion, band structure and nature of Fermi surface for the 4H Ag which corroborated with the experimental observations. The 4H form appears to be a much less metallic, darker and harder form of Ag.

  19. Clinical spectrum of 4H leukodystrophy caused by POLR3A and POLR3B mutations

    PubMed Central

    Vanderver, Adeline; van Spaendonk, Rosalina M.L.; Schiffmann, Raphael; Brais, Bernard; Bugiani, Marianna; Sistermans, Erik; Catsman-Berrevoets, Coriene; Kros, Johan M.; Pinto, Pedro Soares; Pohl, Daniela; Tirupathi, Sandya; Strømme, Petter; de Grauw, Ton; Fribourg, Sébastien; Demos, Michelle; Pizzino, Amy; Naidu, Sakkubai; Guerrero, Kether; van der Knaap, Marjo S.; Bernard, Geneviève

    2014-01-01

    Objective: To study the clinical and radiologic spectrum and genotype–phenotype correlation of 4H (hypomyelination, hypodontia, hypogonadotropic hypogonadism) leukodystrophy caused by mutations in POLR3A or POLR3B. Methods: We performed a multinational cross-sectional observational study of the clinical, radiologic, and molecular characteristics of 105 mutation-proven cases. Results: The majority of patients presented before 6 years with gross motor delay or regression. Ten percent had an onset beyond 10 years. The disease course was milder in patients with POLR3B than in patients with POLR3A mutations. Other than the typical neurologic, dental, and endocrine features, myopia was seen in almost all and short stature in 50%. Dental and hormonal findings were not invariably present. Mutations in POLR3A and POLR3B were distributed throughout the genes. Except for French Canadian patients, patients from European backgrounds were more likely to have POLR3B mutations than other populations. Most patients carried the common c.1568T>A POLR3B mutation on one allele, homozygosity for which causes a mild phenotype. Systematic MRI review revealed that the combination of hypomyelination with relative T2 hypointensity of the ventrolateral thalamus, optic radiation, globus pallidus, and dentate nucleus, cerebellar atrophy, and thinning of the corpus callosum suggests the diagnosis. Conclusions: 4H is a well-recognizable clinical entity if all features are present. Mutations in POLR3A are associated with a more severe clinical course. MRI characteristics are helpful in addressing the diagnosis, especially if patients lack the cardinal non-neurologic features. PMID:25339210

  20. Development of 4H-pyridopyrimidines: a class of selective bacterial protein synthesis inhibitors

    PubMed Central

    2012-01-01

    Background We have identified a series of compounds that inhibit protein synthesis in bacteria. Initial IC50's in aminoacylation/translation (A/T) assays ranged from 3 to14 μM. This series of compounds are variations on a 5,6,7,8-tetrahydropyrido[4,3-d]pyrimidin-4-ol scaffold (e.g., 4H-pyridopyrimidine). Methods Greater than 80 analogs were prepared to investigate the structure-activity relationship (SAR). Structural modifications included changes in the central ring and substituent modifications in its periphery focusing on the 2- and 6-positions. An A/T system was used to determine IC50 values for activity of the analogs in biochemical assays. Minimum inhibitory concentrations (MIC) were determined for each analog against cultures of Enterococcus faecalis, Moraxella catarrhalis, Haemophilus influenzae, Streptococcus pneumoniae, Staphylococcus aureus, Escherichia coli tolC mutants and E. coli modified with PMBN. Results Modifications to the 2-(pyridin-2-yl) ring resulted in complete inactivation of the compounds. However, certain modifications at the 6-position resulted in increased antimicrobial potency. The optimized compounds inhibited the growth of E. faecalis, M. catarrhalis, H. influenzae, S. pneumoniae, S. aureus, E. coli tolC, mutants and E. coli modified with PMBN with MIC values of 4, ≤ 0.12, 1, 2, 4, 1, 1 μg/ml, respectively. IC50 values in biochemical assay were reduced to mid-nanomolar range. Conclusion 4H-pyridopyrimidine analogs demonstrate broad-spectrum inhibition of bacterial growth and modification of the compounds establishes SAR. PMID:22373064

  1. Connecting Kids To The Universe: Partnering With 4-H Youth Development To Pilot 'Afterschool Universe' In New York

    NASA Astrophysics Data System (ADS)

    Schaff, Nancy

    2008-05-01

    4-H Youth Development - as the youth program of the Cooperative Extension system associated with the land grant university in every state - is an ideal partner for statewide dissemination of EPO programs. With funding from a Chandra Cycle 9 EPO grant we are piloting `Afterschool Universe’ in five urban locations in New York State. `Afterschool Universe’ is an education/outreach effort sponsored by NASA's Beyond Einstein program and was developed in partnership with the Imagine the Universe EPO program. The program is targeted at middle school students in out-of-school-time settings and explores basic astronomy concepts focused on the Universe beyond the solar system. Consisting of 12 sessions of engaging hands-on activities, the flexibly structured program can be used in a variety of settings, including astronomy days, youth groups, summer camps, and afterschool programs. Partnering with 4-H Youth Development helps us reach large numbers of underserved and underrepresented minority youth and girls in widely dispersed areas of New York and fits ideally with the current national 4-H SET (science, engineering, and technology) initiative and emphasis on 4-H afterschool programming. The pilot program provides teaching kits and workshops for program leaders. Our 4-H county partners recruit afterschool program staff, science center staff, 4-H volunteers, 4-H teens, and other youth group leaders as workshop participants. The 4-H program will house and loan the kit to trained leaders. By providing kits and training in 2008, we are gearing up for International Year of Astronomy programs in 2009 in out-of-school settings. Based on pilot results, we will seek additional funding to expand the program. The poster will discuss kit development, 4-H partnership, workshops, participating organizations, target audiences, successes, and challenges.

  2. White meat-Green farm: case study of Brinson Farms

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Comprehensive on-farm resource utilization and renewable energy generation at the farm scale are not new concepts. However, truly encompassing implementation of these ideals is lacking. Brinson Farms operates 10 commercial broiler houses. The farm generates heat for its houses using biomass boile...

  3. People on the Farm: Corn and Hog Farming.

    ERIC Educational Resources Information Center

    Department of Agriculture, Washington, DC. Office of Governmental and Public Affairs.

    This booklet provides information on corn and hog farming on a small farm through a profile of a farm family. According to the profile, John and Mary Miller and their three children are a comfortable family operating a corn and hog farm in Iowa. John, the principal farmer, uses a variety of skills in management, veterinary science, soil science,…

  4. Synthesis of N-Aryl-3,5-dichloro-4H-1,2,6-thiadiazin-4-imines from 3,4,4,5-Tetrachloro-4H-1,2,6-thiadiazine.

    PubMed

    Kalogirou, Andreas S; Manoli, Maria; Koutentis, Panayiotis A

    2015-08-21

    Condensation of 3,4,4,5-tetrachloro-4H-1,2,6-thiadiazine with a range of anilines gave 22 N-aryl-3,5-dichloro-4H-1,2,6-thiadiazin-4-imines in 43-96% yields. The scope and limitations of this condensation are briefly investigated. Furthermore, mono- and bis-substitution of the C-3 and C-5 chlorines of 3,5-dichloro-N-phenyl-4H-1,2,6-thiadiazin-4-imine by amine and alkoxide nucleophiles is explored. Finally, Stille coupling chemistry is used to prepare several N-phenyl-3,5-diaryl-4H-1,2,6-thiadiazin-4-imines. PMID:26261875

  5. Intelligent Virtual Station (IVS)

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The Intelligent Virtual Station (IVS) is enabling the integration of design, training, and operations capabilities into an intelligent virtual station for the International Space Station (ISS). A viewgraph of the IVS Remote Server is presented.

  6. Farm accidents in children.

    PubMed

    Cogbill, T H; Busch, H M; Stiers, G R

    1985-10-01

    During a 6 1/2 year period, 105 children were admitted to the hospital as the result of trauma that occurred on farms. The mechanism of injury was animal related in 42 (40%), tractor or wagon accident in 28 (26%), farm machinery in 21 (20%), fall from farm building in six (6%), and miscellaneous in eight (8%). Injury Severity Score was calculated for each patient. An Injury Severity Score of greater than or equal to 25 was determined for 11 children (11%). Life-threatening injuries, therefore, are frequently the result of childhood activities that take place in agricultural environments. The most common injuries were orthopedic, neurologic, thoracoabdominal, and maxillofacial. There was one death in the series, and only one survivor sustained major long-term disability. Such injuries are managed with optimal outcome in a regional trauma center. Educational programs with an emphasis on prevention and safety measures may reduce the incidence of farm accidents. PMID:4047799

  7. Tifft Farm Nature Preserve.

    ERIC Educational Resources Information Center

    Benjamin, Thomas B.; Gannon, David J.

    1980-01-01

    Described are the creation, development, activities, and programs of Tifft Farm, a 264-acre nature preserve and environmental education center in Buffalo, New York, constructed on a sanitary landfill. (BT)

  8. The effect of CH4/H2 ratio on the surface properties of HDPE treated by CHx ion beam bombardment

    NASA Astrophysics Data System (ADS)

    Ding, Wanyu; Guo, Yuanyuan; Ju, Dongying; Sato, Susumu; Tsunoda, Teruo

    2016-06-01

    The surface of high density polyethylene (HDPE) substrate was bombarded by the CHx group ion beam, which was generated by the mixture of CH4/H2. Varying the CH4/H2 ratio, HDPE surfaces with different chemical bond structures and properties were obtained. Raman and XPS results show that sp2 and sp3 bond structures are formed at HDPE surface bombarded by CHx group ions. The sp3 bond fraction at bombarded HDPE surface depends on the H2 ratio in CH4/H2 mixture, because the H ion/atom/molecule can improve the growth of sp3 bond structure. For HDPE surface bombarded by CH4/H2 = 50/50, sp3 bond fraction reaches the maximum of 30.5%, the surface roughness decreases to 17.04 nm, and the static contact angle of polar H2O molecule increased to 140.2∘.

  9. Virtual Worlds? "Outlook Good"

    ERIC Educational Resources Information Center

    Kelton, AJ

    2008-01-01

    Many people believed that virtual worlds would end up like the eight-track audiotape: a memory of something no longer used (or useful). Yet today there are hundreds of higher education institutions represented in three-dimensional (3D) virtual worlds such as Active Worlds and Second Life. The movement toward the virtual realm as a viable teaching…

  10. Virtual Reality: An Overview.

    ERIC Educational Resources Information Center

    Franchi, Jorge

    1994-01-01

    Highlights of this overview of virtual reality include optics; interface devices; virtual worlds; potential applications, including medicine and archaeology; problems, including costs; current research and development; future possibilities; and a listing of vendors and suppliers of virtual reality products. (Contains 11 references.) (LRW)

  11. Optical triggering of high-voltage (18 kV-class) 4H-SiC thyristors

    NASA Astrophysics Data System (ADS)

    Rumyantsev, S. L.; Levinshtein, M. E.; Shur, M. S.; Cheng, L.; Agarwal, A. K.; Palmour, J. W.

    2013-12-01

    Optical triggering of high-voltage (18 kV-class) 4H-SiC thyristors with a single amplification step (pilot thyristor) is reported. It is demonstrated that the switch-on processes in such high-voltage structures are quite different from the switch-on processes in 12 kV 4H-SiC thyristors. In particular, the switch-on process occurs in two stages even at maximum light pulse energy and rather high anode biases.

  12. Are HO radicals produced in the reaction of O(3P) with 1-C4H8 ?

    NASA Technical Reports Server (NTRS)

    Luria, M.; Simonaitis, R.; Heicklen, J.

    1972-01-01

    The reaction of O(3P) with 1-C4H8 was examined in the presence of CO which scavenges HO radicals to produce CO2. From the CO2 quantum yield, an upper limit to the efficiency of HO production in the reaction of O(3P) with 1-C4H8 was found to be 0.020 at both 298 and 473 K.

  13. Evolution of extended defects in PVT-grown 4H-silicon carbide single crystals

    NASA Astrophysics Data System (ADS)

    Lee, Jaewon

    The purpose of this thesis is to identify the origin and evolution of two types of extended defects frequently observed in physical vapor transport (PVT) grown hexagonal SiC bulk crystals. They are basal plane dislocations and threading edge dislocations. PVT-grown 4H-SiC single crystals were investigated using high-resolution x-ray diffraction, defect selective etching, and transmission electron microscopy. The (0008) diffraction peak position shifted about 2.5° along the 3 inch crystal diameter indicating the bending of the basal plane. Transmission electron microscopy revealed that the bending is due to deformation-induced basal plane dislocations with at least a partial edge character. The basal plane dislocations had a non-zero net Burgers vector with the net extra half plane pointing toward the seed side of the investigated crystals, and thus caused the basal plane to bend concave toward the growth direction. Approximately parallel basal plane dislocation arrays were shown to correspond to basal plane slip bands. The bending of entire boules and the global distribution of the slip bands indicated that the basal plane slip system was activated by the macroscopic shear stress resulting from the thermal gradient imposed on the crystal during the PVT growth. The fine structure of the 'star defect' in PVT-grown 4H-SiC single crystals was investigated using molten KOH etching, transmission x-ray topography, and transmission electron microscopy. The star defect is one of the macroscopic extended defects consisting of the defect center and symmetric dislocation arrays extending along six equivalent <11-20> directions. The <11-20> arms of the star defect were shown to consist of polygonized threading edge dislocation arrays, which correspond to prismatic slip bands. Transmission electron microscopy revealed that Burgers vectors of the dislocations are anti-parallel to corresponding arm directions, and the extra half planes of the dislocations extend toward the

  14. Enhancement of atmospheric H2SO4 / H2O nucleation: organic oxidation products versus amines

    NASA Astrophysics Data System (ADS)

    Berndt, T.; Sipilä, M.; Stratmann, F.; Petäjä, T.; Vanhanen, J.; Mikkilä, J.; Patokoski, J.; Taipale, R.; Mauldin, R. L., III; Kulmala, M.

    2014-01-01

    Atmospheric H2SO4 / H2O nucleation influencing effects have been studied in the flow tube IfT-LFT (Institute for Tropospheric Research - Laminar Flow Tube) at 293 ± 0.5 K and a pressure of 1 bar using synthetic air as the carrier gas. The presence of a possible background amine concentration in the order of 107-108 molecule cm-3 throughout the experiments has to be taken into account. In a first set of investigations, ozonolysis of olefins (tetramethylethylene, 1-methyl-cyclohexene, α-pinene and limonene) for close to atmospheric concentrations, served as the source of OH radicals and possibly other oxidants initiating H2SO4 formation starting from SO2. The oxidant generation is inevitably associated with the formation of organic oxidation products arising from the parent olefins. These products (first generation mainly) showed no clear effect on the number of nucleated particles within a wide range of experimental conditions for H2SO4 concentrations higher than ~107 molecule cm-3. Also the early growth process of the nucleated particles was not significantly influenced by the organic oxidation products in line with the expected growth by organic products using literature data. An additional, H2SO4-independent process of particle (nano-CN) formation was observed in the case of α-pinene and limonene ozonolysis for H2SO4 concentrations smaller than ~107 molecule cm-3. Furthermore, the findings confirm the appearance of an additional oxidant for SO2 beside OH radicals, very likely stabilized Criegee Intermediates (sCI). A second set of experiments has been performed in the presence of added amines in the concentrations range of a few 107-1010 molecule cm-3 applying photolytic OH radical generation for H2SO4 production without addition of other organics. All amines showed significant nucleation enhancement with increasing efficiency in the order pyridine < aniline < dimethylamine < trimethylamine. This result supports the idea of H2SO4 cluster stabilization by

  15. Contaminant exposures at the 4H shell mounds in the Santa Barbara Channel.

    PubMed

    Phillips, Charles R; Salazar, Michael H; Salazar, Sandra M; Snyder, Barry J

    2006-12-01

    Remobilization, bioavailability, and potential toxicity of chemical contaminants were evaluated at the 4H shell mounds - the site of abandoned offshore oil and gas production platforms in the Santa Barbara Channel region of the Southern California Bight. Evaluations used a weight-of-evidence approach based on results from bulk phase chemical analyses and laboratory toxicity testing of shell mound cores, in situ field bioassays using caged mussels, and surficial sediment chemistry. Shell mound cores contained elevated concentrations of metals associated with drilling wastes (e.g., Ba, Cr, Pb, and Zn), as well as monocyclic and polycyclic aromatic hydrocarbons (PAHs). The highest concentrations along with pockets of free oil were associated with the middle "cuttings" stratum. Sediments composited from all core strata caused significant acute toxicity and bioaccumulation of Ba and PAHs in test organisms during laboratory exposures. In contrast, caged mussels placed at each of the shell mounds for a period of 57-58 days had greater than 90% survival, and there were no significant differences in survival of mussels placed at the shell mounds and corresponding reference sites. While all mussel samples exhibited increases in shell length, whole animal weight, and tissue lipid content, in some cases growth metrics for the shell mound mussels were significantly higher than those for the reference sites. Concentrations of metals, PAHs, and polychlorinated biphenyls (PCBs) in tissues of the shell mound mussels were not significantly different from those at reference sites. The presence of labile aromatic hydrocarbons in shell mound cores and absence of significant contaminant accumulation of tissues of caged mussels indicated that chemical contaminants are not being remobilized from the 4H shell mounds. Surficial bottom sediments near the shell mounds contained elevated Ba concentrations that probably were associated with drilling wastes. However, concentrations did not

  16. Contaminant exposures at the 4H shell mounds in the Santa Barbara Channel.

    PubMed

    Phillips, Charles R; Salazar, Michael H; Salazar, Sandra M; Snyder, Barry J

    2006-12-01

    Remobilization, bioavailability, and potential toxicity of chemical contaminants were evaluated at the 4H shell mounds - the site of abandoned offshore oil and gas production platforms in the Santa Barbara Channel region of the Southern California Bight. Evaluations used a weight-of-evidence approach based on results from bulk phase chemical analyses and laboratory toxicity testing of shell mound cores, in situ field bioassays using caged mussels, and surficial sediment chemistry. Shell mound cores contained elevated concentrations of metals associated with drilling wastes (e.g., Ba, Cr, Pb, and Zn), as well as monocyclic and polycyclic aromatic hydrocarbons (PAHs). The highest concentrations along with pockets of free oil were associated with the middle "cuttings" stratum. Sediments composited from all core strata caused significant acute toxicity and bioaccumulation of Ba and PAHs in test organisms during laboratory exposures. In contrast, caged mussels placed at each of the shell mounds for a period of 57-58 days had greater than 90% survival, and there were no significant differences in survival of mussels placed at the shell mounds and corresponding reference sites. While all mussel samples exhibited increases in shell length, whole animal weight, and tissue lipid content, in some cases growth metrics for the shell mound mussels were significantly higher than those for the reference sites. Concentrations of metals, PAHs, and polychlorinated biphenyls (PCBs) in tissues of the shell mound mussels were not significantly different from those at reference sites. The presence of labile aromatic hydrocarbons in shell mound cores and absence of significant contaminant accumulation of tissues of caged mussels indicated that chemical contaminants are not being remobilized from the 4H shell mounds. Surficial bottom sediments near the shell mounds contained elevated Ba concentrations that probably were associated with drilling wastes. However, concentrations did not

  17. Discovery and Analysis of 4H-Pyridopyrimidines, a Class of Selective Bacterial Protein Synthesis Inhibitors▿

    PubMed Central

    Ribble, Wendy; Hill, Walter E.; Ochsner, Urs A.; Jarvis, Thale C.; Guiles, Joseph W.; Janjic, Nebojsa; Bullard, James M.

    2010-01-01

    Bacterial protein synthesis is the target for numerous natural and synthetic antibacterial agents. We have developed a poly(U) mRNA-directed aminoacylation/translation protein synthesis system composed of phenyl-tRNA synthetases, ribosomes, and ribosomal factors from Escherichia coli. This system, utilizing purified components, has been used for high-throughput screening of a small-molecule chemical library. We have identified a series of compounds that inhibit protein synthesis with 50% inhibitory concentrations (IC50s) ranging from 3 to 14 μM. This series of compounds all contained the same central scaffold composed of tetrahydropyrido[4,3-d]pyrimidin-4-ol (e.g., 4H-pyridopyrimidine). All analogs contained an ortho pyridine ring attached to the central scaffold in the 2 position and either a five- or a six-member ring tethered to the 6-methylene nitrogen atom of the central scaffold. These compounds inhibited the growth of E. coli, Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis, with MICs ranging from 0.25 to 32 μg/ml. Macromolecular synthesis (MMS) assays with E. coli and S. aureus confirmed that antibacterial activity resulted from specific inhibition of protein synthesis. Assays were developed for the steps performed by each component of the system in order to ascertain the target of the compounds, and the ribosome was found to be the site of inhibition. PMID:20696870

  18. Discovery and analysis of 4H-pyridopyrimidines, a class of selective bacterial protein synthesis inhibitors.

    PubMed

    Ribble, Wendy; Hill, Walter E; Ochsner, Urs A; Jarvis, Thale C; Guiles, Joseph W; Janjic, Nebojsa; Bullard, James M

    2010-11-01

    Bacterial protein synthesis is the target for numerous natural and synthetic antibacterial agents. We have developed a poly(U) mRNA-directed aminoacylation/translation protein synthesis system composed of phenyl-tRNA synthetases, ribosomes, and ribosomal factors from Escherichia coli. This system, utilizing purified components, has been used for high-throughput screening of a small-molecule chemical library. We have identified a series of compounds that inhibit protein synthesis with 50% inhibitory concentrations (IC(50)s) ranging from 3 to 14 μM. This series of compounds all contained the same central scaffold composed of tetrahydropyrido[4,3-d]pyrimidin-4-ol (e.g., 4H-pyridopyrimidine). All analogs contained an ortho pyridine ring attached to the central scaffold in the 2 position and either a five- or a six-member ring tethered to the 6-methylene nitrogen atom of the central scaffold. These compounds inhibited the growth of E. coli, Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis, with MICs ranging from 0.25 to 32 μg/ml. Macromolecular synthesis (MMS) assays with E. coli and S. aureus confirmed that antibacterial activity resulted from specific inhibition of protein synthesis. Assays were developed for the steps performed by each component of the system in order to ascertain the target of the compounds, and the ribosome was found to be the site of inhibition.

  19. Surface Al doping of 4H-SiC via low temperature annealing

    NASA Astrophysics Data System (ADS)

    Park, Junbo; Kim, Ki-hwan; Park, Young-rak; Kim, Minki; Lee, Hyungseok; Jun, Chi-Hoon; Koo, Sangmo; Ko, Sang Choon

    2016-07-01

    We present a method of forming shallow p-doping on a 4H-SiC surface by depositing a thin Al layer (d = 5 nm) and then thermally annealing it at 1000 °C for 10 min. A secondary ion mass spectrometry analysis of the annealed Al/SiC sample reveals an Al concentration in excess of 1017 cm-3 up to a depth of d ≤ 250 nm. I-V measurements and CV characterizations of Ti-SiC Schottky barrier diodes (SBDs) fabricated on a n-type SiC epi-wafer indicate that the shallow Al doping increases the built-in potential of the junction and the barrier height by Δ V b i = 0.51 eV and Δ ϕ B = 0.26 eV , respectively. Assuming a rectangular doping profile, calculations of the built-in voltage shift and the Schottky barrier height indicate that partial dopant activation (activation ratio ˜2%) can induce the observed barrier height shift. The shallow doping method was then used to fabricate junction terminations in SBDs which increased the breakdown voltage and reduced the reverse leakage current. Technology CAD simulations of the SBD with and without doping verify that a reduction of peak electric field can explain the improvement of the breakdown voltage.

  20. A novel double-recessed 4H-SiC MESFET with partly undoped space region

    NASA Astrophysics Data System (ADS)

    Orouji, Ali A.; Aminbeidokhti, Amirhossein

    2011-12-01

    In this paper, a novel double-recessed 4H-SiC metal semiconductor field effect transistor (MESFET) with partly undoped space region (DRUS-MESFET) is introduced. The key idea in this work is to improve the DC and RF characteristics of the device by introducing an undoped space region. Using two-dimensional and two-carrier device simulation, we demonstrate that breakdown voltage ( VBR) increases from 109 V in conventional double recessed MESFET (DR-MESFET) structure to 144.5 V in the DRUS-MESFET structure due to the modified channel electric field distribution of the proposed structure. The maximum output power density of the DRUS-MESFET structure is about 25.4% larger than that of the DR-MESFET structure. Furthermore, lower gate-drain capacitance ( CGD), higher cut-off frequency ( fT), larger maximum available gain (MAG), and higher maximum oscillation frequency ( fmax) are achieved for the DRUS-MESFET structure. The results show that the fmax and fT of the proposed structure improve 95.6% and 13.07% respectively, compared with that of the DR-MESFET structure. Also, the MAG of the DRUS-MESET is 4.5 dB higher than that of the DR-MESFET structure at 40 GHz. The results show that the DRUS-MESFET structure has superior electrical characteristics and performances in comparison with the DR-MESFET structure.

  1. Prediction of 4H-SiC betavoltaic microbattery characteristics based on practical Ni-63 sources.

    PubMed

    Gui, Gui; Zhang, Kan; Blanchard, James P; Ma, Zhenqiang

    2016-01-01

    We have investigated the performance of 4H-SiC betavoltaic microbatteries under exposure to the practical Ni-63 sources using the Monte Carlo method and Synopsys® Medici device simulator. A typical planar p-n junction betavoltaic device with the Ni-63 source of 20% purity on top is modeled in the simulation. The p-n junction structure includes a p+ layer, a p- layer, an n+ layer, and an n- layer. In order to obtain an accurate and valid predication, our simulations consider several practical factors, including isotope impurities, self-absorption, and full beta energy spectra. By simulating the effects of both the p-n junction configuration and the isotope source thickness on the battery output performance, we have achieved the optimal design of the device and maximum energy conversion efficiency. Our simulation results show that the energy conversion efficiency increases as the doping concentration and thickness of the p- layer increase, whereas it is independent of the total depth of the p-n junction. Furthermore, the energy conversion efficiency decreases as the thickness of the practical Ni-63 source increases, because of self-absorption in the isotope source. Therefore, we propose that a p-n junction betavoltaic cell with a thicker and heavily doped p- layer under exposure to a practical Ni-63 source with an appreciable thickness could produce the optimal energy conversion efficiency. PMID:26583261

  2. Nitrogen doping of chemical vapor deposition grown graphene on 4H-SiC (0001)

    SciTech Connect

    Urban, J. M.; Binder, J.; Wysmołek, A.; Dąbrowski, P.; Strupiński, W.; Kopciuszyński, M.; Jałochowski, M.; Klusek, Z.

    2014-06-21

    We present optical, electrical, and structural properties of nitrogen-doped graphene grown on the Si face of 4H-SiC (0001) by chemical vapor deposition method using propane as the carbon precursor and N{sub 2} as the nitrogen source. The incorporation of nitrogen in the carbon lattice was confirmed by X-ray photoelectron spectroscopy. Angle-resolved photoemission spectroscopy shows carrier behavior characteristic for massless Dirac fermions and confirms the presence of a graphene monolayer in the investigated nitrogen-doped samples. The structural and electronic properties of the material were investigated by Raman spectroscopy. A systematical analysis of the graphene Raman spectra, including D, G, and 2D bands, was performed. In the case of nitrogen-doped samples, an electron concentration on the order of 5–10 × 10{sup 12} cm{sup −2} was estimated based upon Raman and Hall effect measurements and no clear dependence of the carrier concentration on nitrogen concentration used during growth was observed. This high electron concentration can be interpreted as both due to the presence of nitrogen in graphitic-like positions of the graphene lattice as well as to the interaction with the substrate. A greater intensity of the Raman D band and increased inhomogeneity, as well as decreased electron mobility, observed for nitrogen-doped samples, indicate the formation of defects and a modification of the growth process induced by nitrogen doping.

  3. Electrical Characterization of High Energy Electron Irradiated Ni/4 H-SiC Schottky Barrier Diodes

    NASA Astrophysics Data System (ADS)

    Paradzah, A. T.; Omotoso, E.; Legodi, M. J.; Auret, F. D.; Meyer, W. E.; Diale, M.

    2016-08-01

    The effect of high energy electron irradiation on Ni/4 H-SiC Schottky barrier diodes was evaluated by current-voltage ( I- V) and capacitance-voltage ( C- V) measurements at room temperature. Electron irradiation was achieved by using a radioactive strontium source with peak emission energy of 2.3 MeV. Irradiation was performed in fluence steps of 4.9 × 1013 cm-2 until a total fluence of 5.4 × 1014 cm-2 was reached. The Schottky barrier height determined from I- V measurements was not significantly changed by irradiation while that obtained from C- V measurements increased with irradiation. The ideality factor was obtained before irradiation as 1.05 and this value did not significantly change as a result of irradiation. The series resistance increased from 47 Ω before irradiation to 74 Ω after a total electron fluence of 5.4 × 1014 cm-2. The net donor concentration decreased with increasing irradiation fluence from 4.6 × 1014 cm-3 to 3.0 × 1014 cm-3 from which the carrier removal rate was calculated to be 0.37 cm-1.

  4. Identification of antisite carbon split-interstitial defects in 4H-SiC

    SciTech Connect

    Steeds, J. W.; Sullivan, W.

    2008-05-15

    A rich variety of optical centers with high energy local vibrational modes has been found in electron-irradiated 4H-SiC in both the as-irradiated and annealed states. These energies have been measured and the annealing dependence of the optical centers has been investigated by low-temperature photoluminescence spectroscopy. In view of the relatively high energies of these modes, it is anticipated that they involve carbon interstitials and a detailed correlation has therefore been undertaken, in selected cases, between the experimentally observed energies and those calculated by recent local density approximation, i.e., ab initio methods for atomic arrangements involving carbon interstitials. When satisfactory agreement has been achieved, the annealing behavior is compared to the calculated stabilities of the defects concerned. As a result, different configurations of carbon antisite defects are identified together with their spatial distributions with respect to the irradiated areas and their sequences of appearance and disappearance on annealing. These findings significantly add to the understanding of the radiation damage process and its subsequent development and recovery on annealing. Some of the optical centers that have well-defined local vibrational modes remain to be identified in the future.

  5. Influence of growth pressure on filling 4H-SiC trenches by CVD method

    NASA Astrophysics Data System (ADS)

    Ji, Shiyang; Kojima, Kazutoshi; Kosugi, Ryoji; Saito, Shingo; Sakuma, Yuuki; Tanaka, Yasunori; Yoshida, Sadafumi; Himi, Hiroaki; Okumura, Hajime

    2016-01-01

    To construct a superjunction structure consisting of p/n columns, narrow stripe-shaped trenches (∼1.5 µm wide and ∼4.7 µm deep) preformed on an n+ 4H-SiC substrate were filled by the hot-wall CVD method using a conventional gas reaction system, SiH4:C3H8:H2. The influences of growth pressure on the coverage distribution of epilayers and the corresponding filling efficiency (the thickness ratio of epilayers on trench bottom and mesa top) were investigated. Two benefits of increasing the growth pressure from 10 to 38 kPa were found: one is the reduced growth around the mesa surface, which lessens the risk of void formation; the other is a high filling rate as well as an improved filling efficiency up to ∼7. By supplying source gases at high flow rates, a void-free trench filling with a filling rate of ∼1.3 µm/h was successfully achieved at 38 kPa.

  6. Raman spectra of the different phases in the CaSO4-H2O system.

    PubMed

    Prieto-Taboada, Nagore; Gómez-Laserna, Olivia; Martínez-Arkarazo, Irantzu; Olazabal, María Ángeles; Madariaga, Juan Manuel

    2014-10-21

    Although it is known that the CaSO4/H2O system is formed by at least five different phases, this fact is not correctly documented in Raman spectroscopy studies. The main problem detected in the literature was the incorrect definition of the anhydrite, which produced the assignation of different spectra for a single compound. In this sense, two different spectra were clearly identified from the bibliography, which showed different main Raman bands at 1017 or 1025 cm(-1), although anhydrite could be present even as three different polymorphous species with different structures. A better understanding of the whole system obtained from a review of the literature allowed new conclusions to be established. Thanks to that revision and the development of different thermodynamical experiments by Raman spectroscopy, the Raman spectra of each phase were successfully identified for the first time. In this way, the main Raman bands of gypsum, bassanite, anhydrite III, anhydrite II and anhydrite I were identified at 1008, 1015, 1025, 1017 and 1017 cm(-1), respectively. To conclude this work, the contradictions found in literature were critically summarized. PMID:25226433

  7. Control of electric field in 4H-SiC UMOSFET: Physical investigation

    NASA Astrophysics Data System (ADS)

    Jozi, Mohammad; Orouji, Ali A.; Fathipour, Morteza

    2016-09-01

    In this paper, we show how breakdown voltage (VBR) and the specific on-resistance (Ron) can be improved simply by controlling of the electric field in a power 4H-SiC UMOSFET. The key idea in this work is increasing the uniformity of the electric field profile by inserting a region with a graded doping density (GD region) in the drift region. The doping density of inserted region is decreased gradually from top to bottom, called Graded Doping Region UMOSFET (GDR-UMOSFET). The GD region results in a more uniform electric field profile in comparison with a conventional UMOSFET (C-UMOSFET) and a UMOSFET with an accumulation layer (AL-UMOSFET). This in turn improves breakdown voltage. Using two-dimensional two-carrier simulation, we demonstrate that the GDR-UMOSFET shows higher breakdown voltage and lower specific on-resistance. Our results show the maximum breakdown voltage of 1340 V is obtained for the GDR-UMOSFET with 10 μm drift region length, while at the same drift region length and approximated doping density, the maximum breakdown voltages of the C-UMOSFET and the AL-UMOSFET structures are 534 V and 703 V, respectively.

  8. Microscopic origin of the prolonged coherence in 4H-SiC divacancy spin qubits

    NASA Astrophysics Data System (ADS)

    Seo, Hosung; Falk, Abram; Klimov, Paul; Christle, David; Awschalom, David; Galli, Giulia

    Long coherence times of quantum bits (qubits) is a key prerequisite for quantum computing and quantum metrology. Recently, electronic spin qubits localized to divacancies in 4H-SiC were found to have a long spin coherence time (T2) exceeding 1 ms, which is longer than that of the nitrogen-vacancy (NV) center in chemically but not isotopically purified diamond. In this talk, we discuss the microscopic origin behind the prolonged divacancy coherence. By using optically detected magnetic resonance (ODMR), we show that the divacancy T2 rapidly increases as a function of magnetic field, saturating at 1.3 ms at T = 20 K. We used a quantum-bath model combined with a cluster correlation expansion technique to calculate the divacancy coherence function and found an excellent agreement between theory and experiment. We show that an effective decoupling of the 29Si and 13C nuclear spins due to their gyromagnetic ratio difference is one of the key reasons responsible for suppressing the decoherence of the divacancy qubits in SiC under magnetic fields larger than 100G. We gratefully acknowledge financial support from the National Science Foundation through the University of Chicago MRSEC under Award Number DMR-1420709.

  9. High-voltage (3.3 kV) 4H-SiC JBS diodes

    SciTech Connect

    Ivanov, P. A. Grekhov, I. V.; Il'inskaya, N. D.; Kon'kov, O. I.; Potapov, A. S.; Samsonova, T. P.; Serebrennikova, O. U.

    2011-05-15

    High-voltage 4H-SiC junction-barrier Schottky (JBS) diodes have been fabricated and studied. The working area of the diodes (anode contact area) is 1.44 mm{sup 2}. At currents in the range from 10{sup -11} to 1.5 A, the forward current-voltage characteristic of the diodes is described in terms of the thermionic emission model, with the series resistance taken into account: Schottky barrier height {Phi}{sub B} = 1.16 eV, ideality factor n = 1.01, and series resistance R{sub s} = 2.2 {Omega} (32 m{Omega} cm{sup 2}). The value of R{sub s} is governed by the resistance of the blocking epitaxial n-base (impurity concentration N = 9 Multiplication-Sign 10{sup 14} cm{sup -3}, n-layer thickness d = 34 {mu}m). The diodes can block a reverse voltage of at least 3.3 kV (with a leakage current at room temperature on the order of 1 {mu}A). It is suggested that the leakage mechanism is associated with crystal lattice defects (dislocations) in SiC. It is shown that the reverse-recovery characteristics of the diodes are determined by the flow of a purely capacitive reverse current.

  10. Transport and photoconduction characteristics of metal-graphene-4H-SiC(0001) heterojunction devices

    SciTech Connect

    Hosseini, T.; Kouklin, N.; Tomer, D.; Rajput, S.; Li, L.

    2014-12-01

    Vertically integrated graphene-semiconductor systems remain of significant technological importance for their promise to captivate new device physics and propel the development of advanced carbon-based opto-electronic devices. In this study, we carry out a series of bias-dependent transport, gate-dependent transport, and photoconduction measurements to probe the opto-electronic characteristics of metal-graphene-4H-SiC (0001) (Si-face) heterojunctions. The forward bias transport is found to deviate strongly from thermionic emission one as being controlled by the device circuitry and minority carrier injection mechanisms. An improved analytical model is offered and used to extract key junction parameters including series resistance of ∼80 kΩ, interface barrier height of ∼0.6 eV, and ideality factor of ∼6.1. The results of the photocurrent tests point to a light-assisted minority carrier injection as a key mechanism behind the photoconductive gain obtained in the devices subject to a weak, sub-bandgap cw-excitation.

  11. From the Au nano-clusters to the nanoparticles on 4H-SiC (0001)

    PubMed Central

    Li, Ming-Yu; Zhang, Quanzhen; Pandey, Puran; Sui, Mao; Kim, Eun-Soo; Lee, Jihoon

    2015-01-01

    The control over the configuration, size, and density of Au nanoparticles (NPs) has offered a promising route to control the spatial confinement of electrons and photons, as a result, Au NPs with a various configuration, size and density are witnessed in numerous applications. In this work, we investigate the evolution of self-assembled Au nanostructures on 4H-SiC (0001) by the systematic variation of annealing temperature (AT) with several deposition amount (DA). With the relatively high DAs (8 and 15 nm), depending on the AT variation, the surface morphology drastically evolve in two distinctive phases, i.e. (I) irregular nano-mounds and (II) hexagonal nano-crystals. The thermal energy activates adatoms to aggregate resulting in the formation of self-assembled irregular Au nano-mounds based on diffusion limited agglomeration at comparatively low annealing temperature, which is also accompanied with the formations of hillocks and granules due to the dewetting of Au films and surface reordering. At high temperature, hexagonal Au nano-crystals form with facets along {111} and {100} likely due to anisotropic distribution of surface energy induced by the increased volume of NPs. With the small DA (3 nm), only dome shaped Au NPs are fabricated along with the variation of AT from low to elevated temperature. PMID:26354098

  12. Synthesis, molecular docking and biological evaluation of new steroidal 4H-pyrans

    NASA Astrophysics Data System (ADS)

    Uzzaman, Shams; Dar, Ayaz Mahmood; Sohail, Aamir; Bhat, Sheraz; mustafa, Mir Faisal; Khan, Yusuf

    2014-01-01

    A series of new steroidal 4H-pyrans (4-6) have been synthesized from steroidal α, β-unsaturated ketones (1-3). The products (4-6) were characterized by IR, 1H NMR, 13C NMR, MS and analytical data. The interaction studies of compounds (4-6) with DNA were carried out by employing gel electrophoresis, UV-vis and fluorescence spectroscopy. The gel electrophoresis pattern revealed that compounds (4-6) bind to DNA and also demonstrated that the compound 6 alone or in presence of Cu (II) causes the nicking of supercoiled pBR322. The compounds 4 and 5 bind to DNA preferentially through electrostatic and hydrophobic interactions with Kb values found to be 5.3 × 103 and 3.7 × 103 M-1, respectively, indicating the higher binding affinity of compound 4 towards DNA. The docking study suggested the intercalation of compounds in between the nucleotide base pairs. The cytotoxicity and genotoxicity of the newly synthesized compounds were checked by MTT and comet assay, respectively during which compound 6 showed potential behaviour.

  13. Silicon vacancy center in 4 H -SiC: Electronic structure and spin-photon interfaces

    NASA Astrophysics Data System (ADS)

    Soykal, Ö. O.; Dev, Pratibha; Economou, Sophia E.

    2016-02-01

    Defects in silicon carbide are of intense and increasing interest for quantum-based applications due to this material's properties and technological maturity. We calculate the multiparticle symmetry-adapted wave functions of the negatively charged silicon vacancy defect in hexagonal silicon carbide via use of group theory and density functional theory and find the effects of spin-orbit and spin-spin interactions on these states. Although we focused on VSi- in 4 H -SiC because of its unique fine structure due to the odd number of active electrons, our methods can be easily applied to other defect centers of different polytypes, especially to the 6 H -SiC. Based on these results, we identify the mechanism that polarizes the spin under optical drive, obtain the ordering of its dark doublet states, point out a path for electric field or strain sensing, and find the theoretical value of its ground-state zero-field splitting to be 68 MHz, in good agreement with experiment. Moreover, we present two distinct protocols of a spin-photon interface based on this defect. Our results pave the way toward quantum information and quantum metrology applications with silicon carbide.

  14. Dicarbon antisite defect in n -type 4H-SiC

    NASA Astrophysics Data System (ADS)

    Umeda, T.; Isoya, J.; Morishita, N.; Ohshima, T.; Janzén, E.; Gali, A.

    2009-03-01

    We identify the negatively charged dicarbon antisite defect ( C2 core at silicon site) in electron-irradiated n -type 4H-SiC by means of combined electron paramagnetic resonance (EPR) measurements and first-principles calculations. The HEI5 and HEI6 EPR centers ( S=1/2 ; C1h symmetry) are associated with cubic and hexagonal dicarbon antisite defects, respectively. This assignment is based on a comparison of the measured and calculated hyperfine tensors of C13 and S29i atoms as far as the second neighborhood around the defects. Theoretically, the dicarbon antisites are stable in a single negative charge state under a wide range of n -type samples. We found that the defects can be created under a wide range of irradiation conditions, and our measurements strongly suggest the existence of carbon antisite defects in the as-grown samples. Annealing studies revealed several atomistic processes such as recombination of carbon interstitials with vacancies and formation of carbon aggregates. These processes were activated at about 1000°C , and as theoretically predicted, the dicarbon antisite is much more stable than the dicarbon interstitial defect ( C2 core at carbon site). The measured activation temperature is consistent with the temperature range for forming various carbon aggregate-related photoluminescence centers.

  15. Can the bis(diboranyl) structure of B(4)H(10) be observed? The story continues.

    PubMed

    Ramakrishna, Vinutha; Duke, Brian J

    2004-12-13

    Pathways for the conversion of the unknown bis(diboranyl) isomer of tetraborane(10) (B(4)H(10)) to the known arachno isomer have been determined for the first time with the use of an electron correlation ab initio quantum chemical method and without the use of constraints in determination of the transition structures. Two isomers of tetraborane(10), one new, with a pentacoordinated boron atom have been found on the theoretical potential energy surface. Several other pathways for molecular rearrangement of tetraborane(10) have also been characterized. The theoretical method was MP2 theory with the 6-31G(d,p) basis set. The most likely pathway for the conversion of the bis(diboranyl) isomer of tetraborane(10) to the arachno isomer is a concerted pathway with two pentacoordinated intermediates. The highest energy transition state for this pathway lies 27.7 kcal/mol above the bis(diboranyl) isomer. At the same level of the theory, the bis(diboranyl) isomer lies 9.2 kcal/mol above the known arachno isomer. The two isomers with a pentacoordinated boron atom lie 12.5 and 13.1 kcal/mol above the arachno isomer.

  16. Incorporating isolated molybdenum (Mo) atoms into Bilayer Epitaxial Graphene on 4H-SiC(0001)

    NASA Astrophysics Data System (ADS)

    Huang, Han; Wan, Wen; Li, Hui; Wong, Swee Liang; Lv, Lu; Gao, Yongli; Wee, Andrew T. S.

    2014-03-01

    The atomic structures and electronic properties of isolated Mo atoms in bilayer epitaxial graphene (BLEG) on 4H-SiC(0001) are investigated by low temperature scanning tunneling microscopy (LT-STM). LT-STM results reveal that isolated Mo dopants prefer to substitute C atoms at α-sites, and preferentially locate between the graphene bilayers. First-principles calculations confirm that the embedding of single Mo dopants within BLEG is energetically favorable as compared to monolayer graphene. The calculated bandstructures show that Mo-doped BLEG is n-doped, and each Mo atom introduces a local magnetic moment of 1.81 μB. Our findings demonstrate a simple and stable method to incorporate single transition metal dopants into the graphene lattice to tune its electronic and magnetic properties for possible use in graphene spin devices. NRF-CRP (Singapore) grants R-143-000-360-281and R-144-000-295-281. ``Shenghua Professorship'' startup funding from CSU and the support from the NSF of China (Grant No.11304398).

  17. Current gain of 4H SiC high-voltage BJTs at reduced temperatures

    NASA Astrophysics Data System (ADS)

    Ivanov, P. A.; Levinshtein, M. E.; Palmour, J. W.; Agarwal, A. K.; Krishnaswami, S.

    2007-06-01

    The dependences of the common-emitter current gain β on the collector current IC have been measured at reduced temperatures in 3 kV 4H-SiC epitaxial-emitter npn bipolar junction transistors with implanted p+ base contact and base-emitter distances Lbe ranging from 3 to 15 µm. The collector-emitter voltage was fixed (at 100 V) to provide the active operation mode at any collector current in a wide range from 80 mA to 10 A (current densities of 3.5-445 A cm-2). The maximum current gain steadily grows with Lbe from 8 (Lbe = 3 µm) to 21 (Lbe = 15 µm) at room temperature. For all values of Lbe, β steadily increases as the temperature becomes lower; however, the smaller Lbe is, the weaker the effect produced by temperature lowering. As, for example, the temperature is lowered to -42 °C, β increases from 8 to 9 for structures with Lbe = 3 µm and from 21 to 31 for structures with Lbe = 15 µm. The phenomena observed have been accounted for by recombination at the p+-p base boundary.

  18. From the Au nano-clusters to the nanoparticles on 4H-SiC (0001).

    PubMed

    Li, Ming-Yu; Zhang, Quanzhen; Pandey, Puran; Sui, Mao; Kim, Eun-Soo; Lee, Jihoon

    2015-01-01

    The control over the configuration, size, and density of Au nanoparticles (NPs) has offered a promising route to control the spatial confinement of electrons and photons, as a result, Au NPs with a various configuration, size and density are witnessed in numerous applications. In this work, we investigate the evolution of self-assembled Au nanostructures on 4H-SiC (0001) by the systematic variation of annealing temperature (AT) with several deposition amount (DA). With the relatively high DAs (8 and 15 nm), depending on the AT variation, the surface morphology drastically evolve in two distinctive phases, i.e. (I) irregular nano-mounds and (II) hexagonal nano-crystals. The thermal energy activates adatoms to aggregate resulting in the formation of self-assembled irregular Au nano-mounds based on diffusion limited agglomeration at comparatively low annealing temperature, which is also accompanied with the formations of hillocks and granules due to the dewetting of Au films and surface reordering. At high temperature, hexagonal Au nano-crystals form with facets along {111} and {100} likely due to anisotropic distribution of surface energy induced by the increased volume of NPs. With the small DA (3 nm), only dome shaped Au NPs are fabricated along with the variation of AT from low to elevated temperature.

  19. Spectral broadening induced by intense ultra-short pulse in 4H-SiC crystals

    NASA Astrophysics Data System (ADS)

    Chun-hua, Xu; Teng-fei, Yan; Gang, Wang; Wen-jun, Wang; Jing-kui, Liang; Xiao-long, Chen

    2016-06-01

    We report the observation of spectral broadening induced by 200 femtosecond laser pulses with the repetition rate of 1 kHz at the wavelength of 532 nm in semi-insulating 4H-SiC single crystals. It is demonstrated that the full width at half maximum of output spectrum increases linearly with the light propagation length and the peak power density, reaching a maximum 870 cm-1 on a crystal of 19 mm long under an incident laser with a peak power density of 60.1 GW/cm2. Such spectral broadening can be well explained by the self-phase modulation model which correlates time-dependent phase change of pulses to intensity-dependent refractive index. The nonlinear refractive index n 2 is estimated to be 1.88×10-15 cm2/W. The intensity-dependent refractive index is probably due to both the nonlinear optical polarizability of the bound electrons and the increase of free electrons induced by the two-photon absorption process. Super continuum spectra could arise as crystals are long enough to induce the self-focusing effect. The results show that SiC crystals may find applications in spectral broadening of high power lasers. Project supported by the National High Technology Research and Development Program of China (Grant No. 2014AA041402) and the National Natural Science Foundation of China (Grant Nos. 51272276 and 51322211).

  20. Fast Turn-Off Times Observed in Experimental 4H SiC Thyristors

    NASA Technical Reports Server (NTRS)

    Niedra, Janis M.

    2006-01-01

    Room temperature measurements of the turn-off time (t(sub q)) are reported for several packaged, npnp developmental power thyristors based on 4H-type SiC and rated 400 V, 2 A. Turn-off is effected by a 50 V pulse of applied reverse voltage, from a state of a steady 1 A forward current. Plots of t(sub q) against the ramp rate (dV(sub AK)/dt) of reapplied forward voltage are presented for preset values of limiting anode-to-cathode voltage (V(sub AK,max)). The lowest t(sub q) measured was about 180 ns. A rapid rise of these t(sub q) curves was observed for values of V(sub AK,max) that are only about a fifth of the rated voltage, whereas comparative t(sub q) plots for a commercial, fast turn-off, Si-based thyristor at a proportionately reduced V(sub AK,max) showed no such behavior. Hence these SiC thyristors may have problems arising from material defects or surface passivation. The influence the R-C-D gate bypass circuit that was used is briefly discussed.

  1. Concentration of point defects in 4H-SiC characterized by a magnetic measurement

    NASA Astrophysics Data System (ADS)

    Peng, B.; Jia, R. X.; Wang, Y. T.; Dong, L. P.; Hu, J. C.; Zhang, Y. M.

    2016-09-01

    A magnetic method is presented to characterize the concentration of point defects in silicon carbide. In this method, the concentration of common charged point defects, which is related to the density of paramagnetic centers, is determined by fitting the paramagnetic component of the specimen to the Brillouin function. Several parameters in the Brillouin function can be measured such as: the g-factor can be obtained from electron spin resonance spectroscopy, and the magnetic moment of paramagnetic centers can be obtained from positron lifetime spectroscopy combined with a first-principles calculation. To evaluate the characterization method, silicon carbide specimens with different concentrations of point defects are prepared with aluminum ion implantation. The fitting results of the densities of paramagnetic centers for the implanted doses of 1 × 1014 cm-2, 1 × 1015 cm-2 and 1 × 1016 cm-2 are 6.52 × 1014/g, 1.14 × 1015/g and 9.45 × 1014/g, respectively. The same trends are also observed for the S-parameters in the Doppler broadening spectra. It is shown that this method is an accurate and convenient way to obtain the concentration of point defects in 4H-SiC.

  2. A novel 4H-SiC MESFET with ultrahigh upper gate

    NASA Astrophysics Data System (ADS)

    Jia, Hujun; Zhang, Hang; Xing, Ding; Luo, Yehui; Duan, Baoxing

    2015-10-01

    A novel 4H-SiC metal semiconductor field effect transistor with ultrahigh upper gate (UU-MESFET) by depletion layer variation and electric field modulation is proposed in this paper for the first time. The prominent merits in the proposed structure are the smaller gate depletion layer and the higher electric field peak produced by the electric field modulation due to ultrahigh upper gate. A higher electric field peak is introduced by ultrahigh upper gate at lower gate corner instead of upper gate corner, which leads to electric field breakdown. Using ISE simulation, the breakdown voltage of the UU-MESFET is improved by 55% and the drain saturation current is increased by 15% than those of the conventional DR-MESFET, which means that the UU-MESFET has an improvement of about 78% in the maximum output power density compared to the DR-MESFET. Furthermore, the gate-source capacitance of the proposed structure is about 17% smaller than that of the DR-MESFET. Therefore the proposed structure has fantastic DC performance and in the meanwhile possesses better RF characteristics.

  3. Structural transformations in femtosecond laser-processed n-type 4H-SiC

    NASA Astrophysics Data System (ADS)

    Rehman, Z. U.; Janulewicz, K. A.

    2016-11-01

    We present a comprehensive study of morphological modification induced on and below the surface of n-type 4H-SiC by irradiation with femtosecond laser pulses under tight focusing condition. Spectroscopic investigation of local electronic and structural transformations in SiC-micro/nanostructures suggested bond breaking i.e. transformation of crystalline SiC to amorphous silicon (a-Si) and amorphous carbon (a-C). These observations were augmented by investigations applying atomic force microscopy (AFM), micro-photoluminescence (PL) spectroscopy, and high resolution X-ray diffraction (HRXRD). A high-resolution cross-sectional study of laser-modified region with transmission electron microscope (TEM) showed a thin amorphous layer in the vicinity of the geometrical focus with deformations and stacking faults in the sub-surface area. Having considered the existing ablation theories, a complex interplay of fast laser heating followed by melting and rapid re-solidification as well as dynamic relaxation of the laser-induced stresses seems to be responsible for formation of the observed structural changes.

  4. Plasma Etching of n-Type 4H-SiC for Photoconductive Semiconductor Switch Applications

    NASA Astrophysics Data System (ADS)

    Ekinci, Huseyin; Kuryatkov, Vladimir V.; Mauch, Daniel L.; Dickens, James C.; Nikishin, Sergey A.

    2015-05-01

    Photoconductive semiconductor switches (PCSS) fabricated on high-purity semi-insulating 4H-SiC substrates (000) are capable of switching high currents in compact packages with long device lifetimes. A heavily doped n-type SiC epitaxial layer of appropriate thickness is required to form low-resistance ohmic contacts with these devices. In addition, to enhance the performance of the PCSSs, the SiC surface between the ohmic contacts must be extremely smooth. We report a chlorine-based, inductively coupled plasma reactive ion-etching process yielding n-type SiC epitaxial layers with the required smoothness. The rate of etching and post-etching surface morphology were dependent on plasma conditions. We found that the surface smoothness of epitaxial layers can be improved by including BCl3 in the argon-chlorine mixture. The optimum etching process yielded very smooth surfaces (˜0.3 nm RMS) at a relatively high rate of etching of ˜220 nm/min. This new fabrication approach significantly reduced the on-state resistance of the PCSS device and improved its durability of operation.

  5. From the Au nano-clusters to the nanoparticles on 4H-SiC (0001).

    PubMed

    Li, Ming-Yu; Zhang, Quanzhen; Pandey, Puran; Sui, Mao; Kim, Eun-Soo; Lee, Jihoon

    2015-01-01

    The control over the configuration, size, and density of Au nanoparticles (NPs) has offered a promising route to control the spatial confinement of electrons and photons, as a result, Au NPs with a various configuration, size and density are witnessed in numerous applications. In this work, we investigate the evolution of self-assembled Au nanostructures on 4H-SiC (0001) by the systematic variation of annealing temperature (AT) with several deposition amount (DA). With the relatively high DAs (8 and 15 nm), depending on the AT variation, the surface morphology drastically evolve in two distinctive phases, i.e. (I) irregular nano-mounds and (II) hexagonal nano-crystals. The thermal energy activates adatoms to aggregate resulting in the formation of self-assembled irregular Au nano-mounds based on diffusion limited agglomeration at comparatively low annealing temperature, which is also accompanied with the formations of hillocks and granules due to the dewetting of Au films and surface reordering. At high temperature, hexagonal Au nano-crystals form with facets along {111} and {100} likely due to anisotropic distribution of surface energy induced by the increased volume of NPs. With the small DA (3 nm), only dome shaped Au NPs are fabricated along with the variation of AT from low to elevated temperature. PMID:26354098

  6. Certified safe farm: identifying and removing hazards on the farm.

    PubMed

    Rautiainen, R H; Grafft, L J; Kline, A K; Madsen, M D; Lange, J L; Donham, K J

    2010-04-01

    This article describes the development of the Certified Safe Farm (CSF) on-farm safety review tools, characterizes the safety improvements among participating farms during the study period, and evaluates differences in background variables between low and high scoring farms. Average farm review scores on 185 study farms improved from 82 to 96 during the five-year study (0-100 scale, 85 required for CSF certification). A total of 1292 safety improvements were reported at an estimated cost of $650 per farm. A wide range of improvements were made, including adding 9 rollover protective structures (ROPS), 59 power take-off (PTO) master shields, and 207 slow-moving vehicle (SMV) emblems; improving lighting on 72 machines: placing 171 warning decals on machinery; shielding 77 moving parts; locking up 17 chemical storage areas, adding 83 lockout/tagout improvements; and making general housekeeping upgrades in 62 farm buildings. The local, trained farm reviewers and the CSF review process overall were well received by participating farmers. In addition to our earlier findings where higher farm review scores were associated with lower self-reported health outcome costs, we found that those with higher farm work hours, younger age, pork production in confinement, beef production, poultry production, and reported exposure to agrichemicals had higher farm review scores than those who did not have these characteristics. Overall, the farm review process functioned as expected. encouraging physical improvements in the farm environment, and contributing to the multi-faceted CSF intervention program.

  7. Certified safe farm: identifying and removing hazards on the farm.

    PubMed

    Rautiainen, R H; Grafft, L J; Kline, A K; Madsen, M D; Lange, J L; Donham, K J

    2010-04-01

    This article describes the development of the Certified Safe Farm (CSF) on-farm safety review tools, characterizes the safety improvements among participating farms during the study period, and evaluates differences in background variables between low and high scoring farms. Average farm review scores on 185 study farms improved from 82 to 96 during the five-year study (0-100 scale, 85 required for CSF certification). A total of 1292 safety improvements were reported at an estimated cost of $650 per farm. A wide range of improvements were made, including adding 9 rollover protective structures (ROPS), 59 power take-off (PTO) master shields, and 207 slow-moving vehicle (SMV) emblems; improving lighting on 72 machines: placing 171 warning decals on machinery; shielding 77 moving parts; locking up 17 chemical storage areas, adding 83 lockout/tagout improvements; and making general housekeeping upgrades in 62 farm buildings. The local, trained farm reviewers and the CSF review process overall were well received by participating farmers. In addition to our earlier findings where higher farm review scores were associated with lower self-reported health outcome costs, we found that those with higher farm work hours, younger age, pork production in confinement, beef production, poultry production, and reported exposure to agrichemicals had higher farm review scores than those who did not have these characteristics. Overall, the farm review process functioned as expected. encouraging physical improvements in the farm environment, and contributing to the multi-faceted CSF intervention program. PMID:20503809

  8. Non-Micropipe Dislocations in 4H-SiC Devices: Electrical Properties and Device Technology Implications

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.; Huang, Wei; Dudley, Michael; Fazi, Christian

    1998-01-01

    It is well-known that SiC wafer quality deficiencies are delaying the realization of outstandingly superior 4H-SiC power electronics. While efforts to date have centered on eradicating micropipes (i.e., hollow core super-screw dislocations with Burgers vectors greater than or equal to 2c), 4H-SiC wafers and epilayers also contain elementary screw dislocations (i.e., Burgers vector = 1c with no hollow core) in densities on the order of thousands per sq cm, nearly 100-fold micropipe densities. While not nearly as detrimental to SiC device performance as micropipes, it has recently been demonstrated that elementary screw dislocations somewhat degrade the reverse leakage and breakdown properties of 4H-SiC p(+)n diodes. Diodes containing elementary screw dislocations exhibited a 5% to 35% reduction in breakdown voltage, higher pre-breakdown reverse leakage current, softer reverse breakdown I-V knee, and microplasmic breakdown current filaments that were non-catastrophic as measured under high series resistance biasing. This paper details continuing experimental and theoretical investigations into the electrical properties of 4H-SiC elementary screw dislocations. The nonuniform breakdown behavior of 4H-SiC p'n junctions containing elementary screw dislocations exhibits interesting physical parallels with nonuniform breakdown phenomena previously observed in other semiconductor materials. Based upon experimentally observed dislocation-assisted breakdown, a re-assessment of well-known physical models relating power device reliability to junction breakdown has been undertaken for 4H-SiC. The potential impact of these elementary screw dislocation defects on the performance and reliability of various 4H-SiC device technologies being developed for high-power applications will be discussed.

  9. Chloride-based fast homoepitaxial growth of 4H-SiC films in a vertical hot-wall CVD

    NASA Astrophysics Data System (ADS)

    Guoguo, Yan; Feng, Zhang; Yingxi, Niu; Fei, Yang; Xingfang, Liu; Lei, Wang; Wanshun, Zhao; Guosheng, Sun; Yiping, Zeng

    2016-06-01

    Chloride-based fast homoepitaxial growth of 4H-SiC epilayers was performed on 4° off-axis 4H-SiC substrates in a home-made vertical hot-wall chemical vapor deposition (CVD) system using H2‑SiH4‑C2H4‑HCl. The effect of the SiH4/H2 ratio and reactor pressure on the growth rate of 4H-SiC epilayers has been studied successively. The growth rate increase in proportion to the SiH4/H2 ratio and the influence mechanism of chlorine has been investigated. With the reactor pressure increasing from 40 to 100 Torr, the growth rate increased to 52 μm/hand then decreased to 47 μm/h, which is due to the joint effect of H2 and HCl etching as well as the formation of Si clusters at higher reactor pressure. The surface root mean square (RMS) roughness keeps around 1 nm with the growth rate increasing to 49 μm/h. The scanning electron microscope (SEM), Raman spectroscopy and X-ray diffraction (XRD) demonstrate that 96.7 μm thick 4H-SiC layers of good uniformity in thickness and doping with high crystal quality can be achieved. These results prove that chloride-based fast epitaxy is an advanced growth technique for 4H-SiC homoepitaxy. Project supported by the National High Technology R&D Program of China (No. 2014AA041402), the National Natural Science Foundation of China (Nos. 61474113, 61274007, 61574140), the Beijing Natural Science Foundation of China (Nos. 4132076, 4132074), the Program of State Grid Smart Grid Research Institute (No. SGRI-WD-71-14-004), and the Youth Innovation Promotion Association of CAS.

  10. Chloride-based fast homoepitaxial growth of 4H-SiC films in a vertical hot-wall CVD

    NASA Astrophysics Data System (ADS)

    Guoguo, Yan; Feng, Zhang; Yingxi, Niu; Fei, Yang; Xingfang, Liu; Lei, Wang; Wanshun, Zhao; Guosheng, Sun; Yiping, Zeng

    2016-06-01

    Chloride-based fast homoepitaxial growth of 4H-SiC epilayers was performed on 4° off-axis 4H-SiC substrates in a home-made vertical hot-wall chemical vapor deposition (CVD) system using H2-SiH4-C2H4-HCl. The effect of the SiH4/H2 ratio and reactor pressure on the growth rate of 4H-SiC epilayers has been studied successively. The growth rate increase in proportion to the SiH4/H2 ratio and the influence mechanism of chlorine has been investigated. With the reactor pressure increasing from 40 to 100 Torr, the growth rate increased to 52 μm/hand then decreased to 47 μm/h, which is due to the joint effect of H2 and HCl etching as well as the formation of Si clusters at higher reactor pressure. The surface root mean square (RMS) roughness keeps around 1 nm with the growth rate increasing to 49 μm/h. The scanning electron microscope (SEM), Raman spectroscopy and X-ray diffraction (XRD) demonstrate that 96.7 μm thick 4H-SiC layers of good uniformity in thickness and doping with high crystal quality can be achieved. These results prove that chloride-based fast epitaxy is an advanced growth technique for 4H-SiC homoepitaxy. Project supported by the National High Technology R&D Program of China (No. 2014AA041402), the National Natural Science Foundation of China (Nos. 61474113, 61274007, 61574140), the Beijing Natural Science Foundation of China (Nos. 4132076, 4132074), the Program of State Grid Smart Grid Research Institute (No. SGRI-WD-71-14-004), and the Youth Innovation Promotion Association of CAS.

  11. Farm accidents in children.

    PubMed Central

    Cameron, D.; Bishop, C.; Sibert, J. R.

    1992-01-01

    OBJECTIVE--To examine the problem of accidental injury to children on farms. DESIGN--Prospective county based study of children presenting to accident and emergency departments over 12 months with injuries sustained in a farm setting and nationwide review of fatal childhood farm accidents over the four years April 1986 to March 1990. SETTING--Accident and emergency departments in Aberystwyth, Carmarthen, Haverfordwest, and Llanelli and fatal accidents in England, Scotland, and Wales notified to the Health and Safety Executive register. SUBJECTS--Children aged under 16. MAIN OUTCOME MEASURE--Death or injury after farm related accidents. RESULTS--65 accidents were recorded, including 18 fractures. Nine accidents necessitated admission to hospital for a mean of two (range one to four) days. 13 incidents were related to tractors and other machinery; 24 were due to falls. None of these incidents were reported under the statutory notification scheme. 33 deaths were notified, eight related to tractors and allied machinery and 10 related to falling objects. CONCLUSIONS--Although safety is improving, the farm remains a dangerous environment for children. Enforcement of existing safety legislation with significant penalties and targeting of safety education will help reduce accident rates further. PMID:1638192

  12. Enhancement of atmospheric H2SO4/H2O nucleation: organic oxidation products versus amines

    NASA Astrophysics Data System (ADS)

    Berndt, T.; Sipilä, M.; Stratmann, F.; Petäjä, T.; Vanhanen, J.; Mikkilä, J.; Patokoski, J.; Taipale, R.; Mauldin, R. Lee, III; Kulmala, M.

    2013-06-01

    Atmospheric H2SO4/H2O nucleation influencing effects have been studied in the flow tube IfT-LFT (Institute for Tropospheric Research - Laminar Flow Tube) at 293 ± 0.5 K and a pressure of 1 bar using synthetic air as the carrier gas. The presence of a~possible background amine concentration in the order of 107-108 molecule cm-3 throughout the experiments has to be taken into account. In a first set of investigations, ozonolysis of olefins (tetramethylethylene, 1-methyl-cyclohexene, α-pinene and limonene) for close to atmospheric concentrations, served as the source of OH radicals and possibly other oxidants initiating H2SO4 formation starting from SO2. The oxidant generation is inevitably associated with the formation of a series of organic oxidation products arising from the parent olefins. These products (first generation mainly) showed no clear effect on the number of nucleated particles within a wide range of experimental conditions for H2SO4 concentrations higher than ~107 molecule cm-3. A comparison of the results of two different particle counters (50% cut-off size: about 1.5 nm or 2.5-3 nm) suggested that the early growth process of the nucleated particles was not significantly influenced by the organic oxidation products. An additional, H2SO4-independent process of particle (nano-CN) formation was observed in the case of α-pinene and limonene ozonolysis for H2SO4 concentrations smaller than ~10 7 molecule cm-3. Furthermore, the findings confirm the existence of an additional oxidant for SO2 beside OH radicals, very likely stabilized Criegee Intermediate (sCI). In the case of the ozonolysis of tetramethylethylene, the H2SO4 measurements in the absence and presence of an OH radical scavenger were well described by modelling using recently obtained kinetic data for the sCI reactivity in this system. A second set of experiments has been performed in the presence of added amines (trimethylamine, dimethylamine, aniline and pyridine) in the concentration range

  13. Temperature dependence of damage formation in Ag ion irradiated 4H-SiC

    NASA Astrophysics Data System (ADS)

    Wendler, E.; Bierschenk, Th.; Wesch, W.; Friedland, E.; Malherbe, J. B.

    2010-10-01

    Rutherford backscattering spectrometry (RBS) in channelling mode was used to study the defect formation in silver (Ag) ion irradiated silicon carbide (SiC). The 4H-SiC samples were irradiated with 360 keV Ag ions at different temperatures (15, 295, 375, 475, 625 and 875 K) over a wide range of fluences ( 1×1011 to 2×1016 cm, depending on the irradiation temperature). The results can be divided into two groups: (i) for irradiation temperatures between 15 and 475 K amorphisation of the implanted layers is reached for ion fluences between 7×1013 and 3×1014 cm. The over-all cross-section of defect production at very low ion fluences which comprises the formation of point defects and of amorphous clusters, is almost identical for all data sets measured in this temperature range. Differences in the damage evolution which occur at higher ion fluences, suggest that the relative contribution of amorphous clusters within single ion impacts in crystalline material decreases with rising temperature. (ii) For irradiations performed at 625 and 875 K no amorphisation is found for ion fluences as high as 2×1016 cm. With increasing ion fluence the defect concentration exhibits a distinctive plateau due to the balance between formation and recombination of point defects before increasing up to a saturation level well below amorphisation. For this final stage our results indicate a mixture of point defect clusters and extended defects most probably dislocations. A comparison with data from the literature suggests that the damage evolution for implantation at 625 and 875 K is strongly influenced by the mobility of vacancies starting at around 600 K.

  14. Virtual annotation: Verbal communication in virtual reality

    NASA Astrophysics Data System (ADS)

    Verlinden, Jouke C.; Bolter, Jay David; Vandermast, Charles

    A system that was developed to explore communication in virtual reality and which offers a simple and powerful method to embed verbal communication in simulations and visualizers by means of voice annotation is described. The prototype demonstrates that the addition of verbal communication opens up a range of new uses for virtual environments. A similar voice annotation facility is easily added to existing visualizers and simulations, and it enables reading, writing and communicating.

  15. Synthesis and antifungal activity of 2H-1,4-benzoxazin-3(4H)-one derivatives.

    PubMed

    Śmist, Małgorzata; Kwiecień, Halina; Krawczyk, Maria

    2016-01-01

    A series of 2-alkyl-2H-1,4-benzoxazin-3(4H)-ones (4a-l) was easily synthesized by two-step process involving O-alkylation of 2-nitrophenols with methyl 2-bromoalkanoates and next "green" catalytic reductive cyclization of the obtained 2-nitro ester intermediates (3a-l). Further, 6,7-dibromo (5a-c) and N-acetyl (6) derivatives were prepared by bromination and acetylation of unsubstituted 2-alkyl-2H-1,4-benzoxazin-3(4H)-ones (4a-c). The novel compounds (3a-l, 4d-l, 5a-c and 6) were fully characterized by spectroscopic methods (MS, (1)H and (13)C NMR). 2-Alkyl-2H-1,4-benzoxazin-3(4H)-ones (4a-l, 5a-c and 6) were screened for antifungal activity. Preliminary assays were performed using two methods: in vitro against seven phytopathogenic fungi-Botrytis cinerea, Phythophtora cactorum, Rhizoctonia solani, Phoma betae, Fusarium culmorum, Fusarium oxysporum and Alternaria alternata-and in vivo against barley powdery mildew Blumeria graminis. The tested compounds displayed moderate to good antifungal activity at high concentration (200 mg L(-1)). The most potent compounds were 2-ethyl-2H-1,4-benzoxazin-3(4H)-one (4a), 2-ethyl-7-fluoro-2H-1,4-benzoxazin-3(4H)-one (4g) and 4-acetyl-2-ethyl-2H-1,4-benzoxazin-3(4H)-one (6), which completely inhibited the mycelial growth of seven agricultural fungi at the concentration of 200 mg L(-1) in the in vitro tests. Moreover, 2-ethyl-2H-1,4-benzoxazin-3(4H)-one (4a) and 4-acetyl-2-ethyl-2H-1,4-benzoxazin-3(4H)-one (6) were also screened for antifungal activity at concentrations of 100 mg L(-1) and 20 mg L(-1). In the concentration of 100 mg L(-1), the N-acetyl derivative (6) completely inhibited the growth of three strains of fungi (F. culmorum, P. cactorum and R. solani), while 2-ethyl-2H-1,4-benzoxazin-3(4H)-one (4a) completely inhibited only R. solani strain. At the concentration of 20 mg L(-1), compound 6 showed good activity only against P. cactorum strain (72%). PMID:26963527

  16. Pressure-induced superconductivity in H2-containing hydride PbH4(H2)2

    PubMed Central

    Cheng, Ya; Zhang, Chao; Wang, Tingting; Zhong, Guohua; Yang, Chunlei; Chen, Xiao-Jia; Lin, Hai-Qing

    2015-01-01

    High pressure structure, stability, metallization, and superconductivity of PbH4(H2)2, a H2-containing compound combining one of the heaviest elements with the lightest element, are investigated by the first-principles calculations. The metallic character is found over the whole studied pressure range, although PbH4(H2)2 is metastable and easily decompose at low pressure. The decomposition pressure point of 133 GPa is predicted above which PbH4(H2)2 is stable both thermodynamically and dynamically with the C2/m symmetry. Interestedly, all hydrogen atoms pairwise couple into H2 quasi-molecules and remain this style up to 400 GPa in the C2/m structure. At high-pressure, PbH4(H2)2 tends to form the Pb-H2 alloy. The superconductivity of Tc firstly rising and then falling is observed in the C2/m PbH4(H2)2. The maximum of Tc is about 107 K at 230 GPa. The softening of intermediate-frequency phonon induced by more inserted H2 molecules is the main origin of the high Tc. The results obtained represent a significant step toward the understanding of the high pressure behavior of metallic hydrogen and hydrogen-rich materials, which is helpful for obtaining the higher Tc. PMID:26559369

  17. Temperature-dependent analysis of conduction mechanism of leakage current in thermally grown oxide on 4H-SiC

    SciTech Connect

    Sometani, Mitsuru; Takei, Manabu; Okamoto, Dai; Harada, Shinsuke; Ishimori, Hitoshi; Takasu, Shinji; Hatakeyama, Tetsuo; Yonezawa, Yoshiyuki; Fukuda, Kenji; Okumura, Hajime

    2015-01-14

    The conduction mechanism of the leakage current of a thermally grown oxide on 4H silicon carbide (4H-SiC) was investigated. The dominant carriers of the leakage current were found to be electrons by the carrier-separation current-voltage method. The current-voltage and capacitance-voltage characteristics, which were measured over a wide temperature range, revealed that the leakage current in SiO{sub 2}/4H-SiC on the Si-face can be explained as the sum of the Fowler-Nordheim (FN) tunneling and Poole-Frenkel (PF) emission leakage currents. A rigorous FN analysis provided the true barrier height for the SiO{sub 2}/4H-SiC interface. On the basis of Arrhenius plots of the PF current separated from the total leakage current, the existence of carbon-related defects and/or oxygen vacancy defects was suggested in thermally grown SiO{sub 2} films on the Si-face of 4H-SiC.

  18. Wind Farm Recommendation Report

    SciTech Connect

    John Reisenauer

    2011-05-01

    On April 21, 2011, an Idaho National Laboratory (INL) Land Use Committee meeting was convened to develop a wind farm recommendation for the Executive Council and a list of proposed actions for proceeding with the recommendation. In terms of land use, the INL Land Use Committee unanimously agrees that Site 6 is the preferred location of the alternatives presented for an INL wind farm. However, further studies and resolution to questions raised (stated in this report) by the INL Land Use Committee are needed for the preferred location. Studies include, but are not limited to, wind viability (6 months), bats (2 years), and the visual impact of the wind farm. In addition, cultural resource surveys and consultation (1 month) and the National Environmental Policy Act process (9 to 12 months) need to be completed. Furthermore, there is no documented evidence of developers expressing interest in constructing a small wind farm on INL, nor a specific list of expectations or concessions for which a developer might expect INL to cover the cost. To date, INL assumes the National Environmental Policy Act activities will be paid for by the Department of Energy and INL (the environmental assessment has only received partial funding). However, other concessions also may be expected by developers such as roads, fencing, power line installation, tie-ins to substations, annual maintenance, snow removal, access control, down-time, and remediation. These types of concessions have not been documented, as a request, from a developer and INL has not identified the short and long-term cost liabilities for such concessions should a developer expect INL to cover these costs. INL has not identified a go-no-go funding level or the priority this Wind Farm Project might have with respect to other nuclear-related projects, should the wind farm remain an unfunded mandate. The Land Use Committee recommends Legal be consulted to determine what, if any, liabilities exist with the Wind Farm Project and

  19. Long Island Solar Farm

    SciTech Connect

    Anders, R.

    2013-05-01

    The Long Island Solar Farm (LISF) is a remarkable success story, whereby very different interest groups found a way to capitalize on unusual circumstances to develop a mutually beneficial source of renewable energy. The uniqueness of the circumstances that were necessary to develop the Long Island Solar Farm make it very difficult to replicate. The project is, however, an unparalleled resource for solar energy research, which will greatly inform large-scale PV solar development in the East. Lastly, the LISF is a superb model for the process by which the project developed and the innovation and leadership shown by the different players.

  20. First estimation of C4-H bond dissociation energies of NADH and its radical cation in aqueous solution.

    PubMed

    Zhu, Xiao-Qing; Yang, Yuan; Zhang, Min; Cheng, Jin-Pei; Zhang, Ming

    2003-12-17

    The heterolytic and homolytic C4-H bond dissociation energies of NADH and its radical cation (NADH*+) in aqueous solution were estimated according to the reaction of NADH with N,N,N',N'-tetramethyl-p-phenylenediamine radical cation perchlorate (TMPA*+) in aqueous solution. The results show that the values of the heterolytic and homolytic C4-H bond dissociation energies of NADH in aqueous solution are 53.6 and 79.3 kcal/mol, respectively; the values of the heterolytic and homolytic C4-H bond dissociation energies of NADH*+*+ in aqueous solution are 5.1 and 36.3 kcal/mol, respectively, which, to our knowledge, is first reported. This energetic information disclosed in the present work should be believed to furnish hints to the understanding of the mechanisms for the redox interconversions of coenzyme couple NADH/NAD+ in vivo.

  1. MITRE's virtual model shop

    NASA Astrophysics Data System (ADS)

    Wingfield, Michael A.

    1995-04-01

    The exploration of visual data and the use of visual information during the design process can be greatly enhanced by working within the virtual environment where the user is closely coupled to the data by means of immersive technologies and natural user interfaces. Current technology enables us to construct a virtual environment utilizing 3D graphics projection, object generated stereo sound, tactile feedback, and voice command input. Advances in software architectures and user interfaces enable us to focus on enhancing the design process within the virtual environment. These explorations at MITRE have evolved into an application which focuses on the ability to create, manipulate, and explore photo and audio realistic 3D models of work spaces, office complexes, and entire communities in real-time. This application, the Virtual Interactive Planning System, is a component of the MITRE virtual model shop, a suite of applications which permits the user to design and manipulate computer graphics models within the virtual environment.

  2. Agreements in Virtual Organizations

    NASA Astrophysics Data System (ADS)

    Pankowska, Malgorzata

    This chapter is an attempt to explain the important impact that contract theory delivers with respect to the concept of virtual organization. The author believes that not enough research has been conducted in order to transfer theoretical foundations for networking to the phenomena of virtual organizations and open autonomic computing environment to ensure the controllability and management of them. The main research problem of this chapter is to explain the significance of agreements for virtual organizations governance. The first part of this chapter comprises explanations of differences among virtual machines and virtual organizations for further descriptions of the significance of the first ones to the development of the second. Next, the virtual organization development tendencies are presented and problems of IT governance in highly distributed organizational environment are discussed. The last part of this chapter covers analysis of contracts and agreements management for governance in open computing environments.

  3. Efficiency and impacts of hythane (CH4+H2) underground storage

    NASA Astrophysics Data System (ADS)

    Sáinz-García, Alvaro; Abarca, Elena; Grandia, Fidel

    2016-04-01

    The foreseen increase share of renewable energy production requires energy storage to mitigate shortage periods of energy supply. Hydrogen is an efficient energy carrier that can be transported and storage. A very promising way to store large amounts of hydrogen is underground geological reservoirs. Hydrogen can be stored, among other options, as a mixture of natural gas and less than 20% of hydrogen (hythane) to avoid damages on the existing infrastructure for gas transport. This technology is known as power-to-gas and is being considered by a number of European countries (Simon et al., 2015). In this study, the feasibility of a deep aquifer to store CH4-H2 mixtures in the Lower Triassic of the Paris Basin is numerically analyzed. The solubility of gas mixture in the groundwater is extremely low (Panfilov, 2015) and, therefore, gas and water are considered immiscible and non-reactive. An immiscible multiphase flow model is developed using the coefficient-form PDE interface of the finite element method code, COMSOL Multiphysics. The modelled domain is a 2D section of 2500 x 290 m resembling the Lower Triassic aquifer of the Paris basin, consisting of 2 layers of sandstone separated by a layer of conglomerates. The domain dips 0.5% from east to west. The top of the aquifer is 500 m-deep and the lateral boundaries are assumed to be open. This case is considered conservative compared to a dome-like geological trap, which could be more favorable to retain higher gas concentration. A number of cycles of gas production and injection were modelled. An automatic shut-down of the pump is implemented in case pressure on the well exceeds an upper or lower threshold. The influence of the position of the well, the uncertain residual gas saturation and the regional flow are studied. The model shows that both gas and aquifer properties have a significant impact on storage. Due to its low viscosity, the mobility of the hythane is quite high and gas expands significantly, reducing

  4. ZC4H2, an XLID gene, is required for the generation of a specific subset of CNS interneurons

    PubMed Central

    May, Melanie; Hwang, Kyu-Seok; Miles, Judith; Williams, Charlie; Niranjan, Tejasvi; Kahler, Stephen G.; Chiurazzi, Pietro; Steindl, Katharina; Van Der Spek, Peter J.; Swagemakers, Sigrid; Mueller, Jennifer; Stefl, Shannon; Alexov, Emil; Ryu, Jeong-Im; Choi, Jung-Hwa; Kim, Hyun-Taek; Tarpey, Patrick; Neri, Giovanni; Holloway, Lynda; Skinner, Cindy; Stevenson, Roger E.; Dorsky, Richard I.; Wang, Tao; Schwartz, Charles E.; Kim, Cheol-Hee

    2015-01-01

    Miles–Carpenter syndrome (MCS) was described in 1991 as an XLID syndrome with fingertip arches and contractures and mapped to proximal Xq. Patients had microcephaly, short stature, mild spasticity, thoracic scoliosis, hyperextendable MCP joints, rocker-bottom feet, hyperextended elbows and knees. A mutation, p.L66H, in ZC4H2, was identified in a XLID re-sequencing project. Additional screening of linked families and next generation sequencing of XLID families identified three ZC4H2 mutations: p.R18K, p.R213W and p.V75in15aa. The families shared some relevant clinical features. In silico modeling of the mutant proteins indicated all alterations would destabilize the protein. Knockout mutations in zc4h2 were created in zebrafish and homozygous mutant larvae exhibited abnormal swimming, increased twitching, defective eye movement and pectoral fin contractures. Because several of the behavioral defects were consistent with hyperactivity, we examined the underlying neuronal defects and found that sensory neurons and motoneurons appeared normal. However, we observed a striking reduction in GABAergic interneurons. Analysis of cell-type-specific markers showed a specific loss of V2 interneurons in the brain and spinal cord, likely arising from mis-specification of neural progenitors. Injected human wt ZC4H2 rescued the mutant phenotype. Mutant zebrafish injected with human p.L66H or p.R213W mRNA failed to be rescued, while the p.R18K mRNA was able to rescue the interneuron defect. Our findings clearly support ZC4H2 as a novel XLID gene with a required function in interneuron development. Loss of function of ZC4H2 thus likely results in altered connectivity of many brain and spinal circuits. PMID:26056227

  5. Skynet Junior Scholars: From Idea to Enactment--Tales from the Trenches I. Implementation in 4-H settings.

    NASA Astrophysics Data System (ADS)

    Burnside, Jason; Feldman, Lynn; Gurton, Suzanne; Heatherly, Sue Ann; Hoette, Vivian L.; Murray, Jenny; Zastrow, Ginger

    2016-01-01

    The creators of Skynet Junior Scholars were ambitious to say the least when they set out to:- Develop online tools that enable middle school and high school aged youth to use robotic optical and radio telescopes to do astronomy- Create an inquiry-based curriculum that promotes critical thinking and scientific habits of mind- Proactively incorporate Principles of Universal Design in all SJS development tasks to ensure access by blind/low vision and deaf/hard of hearing youth- Prepare 180 adult youth leaders from diverse backgrounds including museum educators, amateur astronomers, teachers 4-H leaders to facilitate SJS activities in a variety of settings.After 3 years of development SJS is in full implementation mode. As of August, 2015, 105 youth leaders and leader supervisors from 24 states have completed professional development and many have formed SJS youth groups. In this paper we describe what it takes for a successful implementation of Skynet Junior Scholars in a 4-H setting, from the viewpoint of adult leaders in the trenches who have created novel implementation models to make SJS work in diverse environments from monthly 4-H meetings to immersive residential camps.4-H is the nation's largest positive youth development organization, with a membership of more than six million young people in the U.S. In 2003 the national organization formed a strong commitment to STEM education with the goal to "to engage one million new youth in a dynamic process of discovery and exploration in science, engineering and technology to prepare them to meet the challenges of the 21st century". Skynet Junior Scholars has formed a strong and growing partnership with state 4-H agencies in West Virginia and Wisconsin, with a goal of establishing SJS as a national 4-H curriculum.Skynet Junior Scholars is supported by the National Science Foundation under Grant Numbers 1223687, 1223235 and 1223345.

  6. Spectroscopic and Rheokinetic Properties of [(C4H9O)3P=O]2ZnCl2

    NASA Astrophysics Data System (ADS)

    Volkova, E. R.; Karmanov, V. I.; Tereshatov, V. V.

    2013-09-01

    The complex [(C4H9O)3P=O]2ZnCl2 was synthesized. Its effects on urethane-formation kinetics via reaction of hydroxyl-containing oligomers and isocyanates were studied by IR spectroscopy; on polyurethane curing kinetics, by a rheological method. It was established that [(C4H9O)3P=O]2ZnCl2 was an effective catalyst that accelerated the initial step of regular structure formation during the synthesis of multi-component polyurethanes with low curing temperatures.

  7. Microwave spectra of the SiH4-H2O complex: A new sort of intermolecular interaction

    NASA Astrophysics Data System (ADS)

    Kawashima, Yoshiyuki; Suenram, Richard D.; Hirota, Eizi

    2016-09-01

    Microwave spectral patterns observed for the silane-water complex were found much different from those of the methane-water complex. The SiH4-H2O complex is likely to have a tightly bound structure. The effective rotational and centrifugal distortion constants: B = 3621.1193 (45) MHz and DJ = 49.84 (30) kHz led to the distance between the Si and O atoms in the complex to be 3.3 Å, much shorter than the C and O separation in the CH4-H2O of 3.7 Å, and to the silane-water stretching force constant and stretching frequency to be 2.88 N/m and 65 cm-1, respectively, which are to be compared with 1.52 N/m and 55 cm-1 of the CH4-H2O. The characteristic features of the spectra observed for the main species 28SiH4-H2O are common to those of isotopic species: 29SiH4-H2O, 30SiH4-H2O, 28SiH4-H218O, 28SiH4-D2O, 29SiH4-D2O, 30SiH4-D2O, 28SiH4-HDO, 29SiH4-HDO, 30SiH4-HDO, 28SiD4-H2O, 28SiD4-D2O, and 28SiD4-HDO. The observed spectra also indicate that the silane executes a threefold internal rotation about one of its four Si-H bonds, while the C2 symmetry axis of the water is bent away from the internal-rotation axis. An internal axis method analysis yielded an estimate of the internal-rotation potential barrier V3 to be 140 ± 50 cm-1, and those based on diagonalization of a principal axis method Hamiltonian matrix and on the extended internal axis method resulted in V3 ranging from 180 to 100 cm-1, depending on the isotopic species studied. All the measurements were done by using a pulsed nozzle Fourier transform microwave spectrometer, and the spectral assignments were made with the aid of the Stark effect, which yielded the dipole moment to be 1.730 (10) D. Transitions in higher energy states of the SiH4 internal rotation were observed, clearly resolved from the main lines, when the carrier gas was replaced from Ar to Ne.

  8. Hog Farms in Pennsylvania.

    ERIC Educational Resources Information Center

    Shannon, Patrick

    2003-01-01

    Discusses a community's opinion and reaction to corporate hog farms. Acknowledges the vivid demonstration of literacy in these communities. Considers how these citizens use their literacy as political agents--just like they were taught to do in civics classes in high school--to participate in decisions affecting their lives. Considers the…

  9. Farming the Sea

    ERIC Educational Resources Information Center

    Morgan, William

    1971-01-01

    Florida has initiated a training program in an entirely new dimension--Sea Farming. Presented is a description of the vocational agriculture program designed to teach propagation, cultivation, harvesting, marketing, and conservation practices related to production of oysters, shrimp, scallops, crabs, and fin fishes. (Editor/GB)

  10. FARM LABOR MARKET DEVELOPMENT.

    ERIC Educational Resources Information Center

    Department of Labor, Washington, DC.

    PART ONE OF THE REPORT CONSISTED OF AN ANALYSIS OF TRENDS BETWEEN 1960 AND 1961 IN WAGES OF UNITED STATES FARM WORKERS IN MAJOR AREAS USING MEXICAN NATIONALS. THE DATA WERE DERIVED FROM PREVAILING-WAGE REPORTS RECEIVED BY THE BUREAU OF EMPLOYMENT SECURITY FROM AFFILIATED STATE EMPLOYMENT SECURITY AGENCIES. THE SURVEY RATES WERE USED BY THE…

  11. Cryptosporidiois in farmed animals

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The disease, cryptosporidiosis, has been identified in humans and animals in 106 countries and has been attributed to 26 species of Cryptosporidium and several additional genotypes. The specific farmed animals discussed in this chapter include cattle, sheep, goats, water buffaloes, deer, camels, lla...

  12. Agriculture Education. Farm Machinery.

    ERIC Educational Resources Information Center

    Stuttgart Public Schools, AR.

    This curriculum guide is designed for group instruction of secondary agricultural education students enrolled in one or two semester-long courses in farm machinery. The guide presents units of study in the following areas: (1) small gas engines, (2) job opportunities, (3) tractors, (4) engines, (5) hydraulics, (6) electrical system, (7) combine…

  13. Modelling Farm Animal Welfare

    PubMed Central

    Collins, Lisa M.; Part, Chérie E.

    2013-01-01

    Simple Summary In this review paper we discuss the different modeling techniques that have been used in animal welfare research to date. We look at what questions they have been used to answer, the advantages and pitfalls of the methods, and how future research can best use these approaches to answer some of the most important upcoming questions in farm animal welfare. Abstract The use of models in the life sciences has greatly expanded in scope and advanced in technique in recent decades. However, the range, type and complexity of models used in farm animal welfare is comparatively poor, despite the great scope for use of modeling in this field of research. In this paper, we review the different modeling approaches used in farm animal welfare science to date, discussing the types of questions they have been used to answer, the merits and problems associated with the method, and possible future applications of each technique. We find that the most frequently published types of model used in farm animal welfare are conceptual and assessment models; two types of model that are frequently (though not exclusively) based on expert opinion. Simulation, optimization, scenario, and systems modeling approaches are rarer in animal welfare, despite being commonly used in other related fields. Finally, common issues such as a lack of quantitative data to parameterize models, and model selection and validation are discussed throughout the review, with possible solutions and alternative approaches suggested. PMID:26487411

  14. Content Priorities for Farm Mechanics

    ERIC Educational Resources Information Center

    Knotts, C. Don; Webb, Earl S.

    1974-01-01

    Fifty successful young Texas farmers evaluated agricultural mechanics skills (in the broad areas of farm power and machinery, farm shop, farm electricity, buildings and conveniences, and soil and water management) in terms of their importance. Teachers can use the findings to plan course content relevant to their students' needs. (AJ)

  15. Farm Education at Stony Kill.

    ERIC Educational Resources Information Center

    Parisio, Richard

    1986-01-01

    Describes typical winter farm lessons for students visiting Stony Kill Farm Environmental Education Center located 70 miles north of New York City: butter and corncake making, soil erosion experiments, dissecting and growing seeds. Emphasizes major theme of conservation of farmland from destructive farming practices and careless development. (NEC)

  16. Cinnamic acid 4-hydroxylase of sorghum [Sorghum biocolor (L.) Moench] gene SbC4H1 restricts lignin synthesis in Arabidopsis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cinnamic acid 4-hydroxylase (C4H) is the first hydroxylase enzyme of the phenylpropanoid pathway, and its content and activity affects the lignin synthesis. In this study, we isolated a C4H gene SbC4H1 from the suppression subtractive hybridization library of brown midrib (bmr) mutants of Sorghum b...

  17. Synthesis of a Biologically Active Oxazol-5-(4H)-One via an Erlenmeyer-Plo¨chl Reaction

    ERIC Educational Resources Information Center

    Rodrigues, Catarina A. B.; Martinho, Jose´ M. G.; Afonso, Carlos A. M.

    2015-01-01

    The synthesis of (Z)-4-(4-nitrobenzylidene)-2- phenyloxazol-5(4"H")-one, which is a potent immunomodulator and tyrosinase inhibitor, is described as an experiment for an upper-division undergraduate organic chemistry laboratory course. This compound is produced via an Erlenmeyer-Plo¨chl reaction in the absence of any additional solvents…

  18. Blue Sky Below My Feet. Adventures in Space Technology, Forces, Fibers, Foods. 4-H Leader/Teacher Handbook.

    ERIC Educational Resources Information Center

    Manholt, Donna; And Others

    This teaching guide for 4th through 6th grade classes integrates science, language arts, and math concepts into ready-to-use space and space technology lessons. Significant learning outcomes for this curriculum are linked to Ohio's educational objectives for science in an at-a-glance curriculum matrix. A summary of the significant 4-H life skills…

  19. On the relationship between radiation-stimulated photoluminescence and nitrogen atoms in p-4 H-SiC

    NASA Astrophysics Data System (ADS)

    Lebedev, A. A.; Ber, B. Ya.; Bogdanova, E. V.; Seredova, N. V.; Kazantsev, D. Yu.; Kozlovski, V. V.

    2015-12-01

    Photoluminescence (PL) appearing in p-4 H-SiC upon its electron irradiation has been studied. A model that accounts for the dependence of the PL intensity on the irradiation dose is suggested. The conclusion is drawn that nitrogen-radiation defect donor-acceptor pairs are PL activators.

  20. Factors Influencing Food Choices of 4-H Club Members in Williamson County, Tennessee. A Research Summary of a Graduate Study.

    ERIC Educational Resources Information Center

    Geary, Virginia Ruth; And Others

    A study was conducted to identify some of the eating habits and factors influencing food choices of selected junior (9 to 13 years old) and senior (14 to 19 years old) 4-H club members enrolled in Williamson County, Tennessee, in 1968. Data were collected through group interviews with 200 juniors and 70 seniors--116 boys and 154 girls.…

  1. Fowler-Nordheim electron tunneling mechanism in Ni/SiO2/n-4H SiC MOS devices

    NASA Astrophysics Data System (ADS)

    Kodigala, Subba Ramaiah; Chattopadhyay, S.; Overton, C.; Ardoin, I.

    2015-12-01

    The Ni/SiO2/n-type 4H SiC MOS devices have been fabricated for microelectronic device applications. The SiO2 layer employed in the MOS devices is grown by wet thermal oxidation process. The current-field characteristics of Ni/SiO2/n-type 4H SiC MOS devices are quiet interestingly studied by employing Fowler Nordheim (FN) conduction tunneling model, which is verified by theoretical simulation. It is learnt that the tunneling current through the barrier in the MOS devices promptly obeys the FN conduction tunneling mechanism. The simulation results show that the current in the MOS device increases and barrier height decreases with increasing temperature and internal electric field. Therefore, the correction factor for the barrier height of n-type 4H SiC/SiO2 MOS device due to the influence of both the temperature and internal electric field is employed. The barrier height observed by the experiments is apparently smaller than the simulated one of an ideal MOS device. However, after employing all the correction factors to the barrier height, the simulated current-field curves fairly coincide with the experimental results. The reason for obtaining smaller experimental barrier height for MOS devices is substantially explored with the support of current-field (J-F) analysis. On the other hand, this article comprehensively addresses the effects of quantum mechanical, interface trap density and thickness of 4H-SiC on the barrier height.

  2. From Threshers to Thrashers: In Montana, 4-H Takes a Modern Spin To Engage "Blue-Ribbon Kids."

    ERIC Educational Resources Information Center

    Linik, Joyce Riha

    2002-01-01

    A 4-H skateboard club in Bozeman, Montana offers kids community service and educational opportunities as well as something to do after school. Adult and college-student volunteers teach a skateboarding curriculum and help kids fix boards and design ramps. Club members have learned public speaking, fundraising, city planning, and civic involvement…

  3. The reaction H + C4H2 - Absolute rate constant measurement and implication for atmospheric modeling of Titan

    NASA Technical Reports Server (NTRS)

    Nava, D. F.; Mitchell, M. B.; Stief, L. J.

    1986-01-01

    The absolute rate constant for the reaction H + C4H2 has been measured over the temperature (T) interval 210-423 K, using the technique of flash photolysis-resonance fluorescence. At each of the five temperatures employed, the results were independent of variations in C4H2 concentration, total pressure of Ar or N2, and flash intensity (i.e., the initial H concentration). The rate constant, k, was found to be equal to 1.39 x 10 to the -10th exp (-1184/T) cu cm/s, with an error of one standard deviation. The Arrhenius parameters at the high pressure limit determined here for the H + C4H2 reaction are consistent with those for the corresponding reactions of H with C2H2 and C3H4. Implications of the kinetic carbon chemistry results, particularly those at low temperature, are considered for models of the atmospheric carbon chemistry of Titan. The rate of this reaction, relative to that of the analogous, but slower, reaction of H + C2H2, appears to make H + C4H2 a very feasible reaction pathway for effective conversion of H atoms to molecular hydrogen in the stratosphere of Titan.

  4. Regionalization of the Washington State University Extension 4-H Youth Development Program: Employee Awareness, Buy-In, and Communication

    ERIC Educational Resources Information Center

    White, Alison J.; Teuteberg, Dan

    2015-01-01

    Washington's 4-H program is transitioning from a predominately single-county faculty model to a regional system. This article highlights survey results regarding the level of awareness and buy-in that Extension administration, faculty, and staff have concerning the regional model and how communication about the model took place. While most…

  5. Wetlands Are Wonderlands. Leader/Teacher Guide and Member/Youth Guide. 4-H Marine Education Series-1.

    ERIC Educational Resources Information Center

    Meenen, Kimberly, Ed.; Goettel, Robin G., Ed.

    This guide, for a 4-H wetlands project, is designed for sixth to eighth grade youth and their leaders interested in learning and doing aquatic science activities that can help the environment. The project provides basic wetland information with one or more activities for each of six sections: (1) What is a wetland?; (2) value of wetlands; (3)…

  6. [Nebraska 4-H Wheat Science School Enrichment Project, Teacher/Leader Guides 213-222 and 227.

    ERIC Educational Resources Information Center

    Nebraska Univ., Lincoln. Inst. of Agriculture and Natural Resources.

    Through the 4-H Wheat Science project, students learn the importance of wheat from the complete process of growing wheat to the final product of bread. The curriculum is designed to include hands-on experiences in science, consumer education, nutrition, production economics, vocabulary, and applied mathematics. Teachers can select those units out…

  7. Nationwide Participation in 4-H during the 1980s: Information from the Office of Education NELS:88 Study.

    ERIC Educational Resources Information Center

    Steele, Sara M.; And Others

    A study examined national participation in 4-H Club activities during the 1980s. The study population was a carefully drawn sample of 24,500 eighth graders from more than 1,000 public and private schools throughout the country as well as their parents and teachers. The study established that, as of 1988, about one of every six eighth-grade…

  8. The Impact of Raising and Exhibiting Selected 4-H Livestock Projects on the Development of Life and Project Skills.

    ERIC Educational Resources Information Center

    Rusk, Clinton P.; Summerlot-Early, Jill M.; Machtmes, Krisanna L.; Talbert, B. Allen; Balschweid, Mark A.

    2003-01-01

    Responses from 176 of 420 4-H members involved in livestock projects showed they were able to accomplish skills in sportsmanship, safety, and animal grooming and selection but were less confident about animal health care. The sense of responsibility acquired from these projects was applied to homework, punctuality, and care for younger siblings.…

  9. Does Study Abroad Make a Difference? An Impact Assessment of the International 4-H Youth Exchange Program.

    ERIC Educational Resources Information Center

    Boyd, Barry L.; Giebler, Christie; Hince, Matthew; Liu, Yaru; Mehta, Neha; Rash, Ryan; Rowald, Jennifer; Saldana, Carlos; Yanta, Yvonne

    2001-01-01

    A survey of 28 participants in the International 4-H Youth Exchange program, 16 family members/ friends, and 60 extension agents indicated that participants expanded awareness of global issues, developed cultural sensitivity, and increased community involvement. Barriers such as money and lack of program knowledge can be overcome by seeking…

  10. Living the Dream of Green Acres: Boy with Autism Finds Acceptance and Success Thanks to 4-H

    ERIC Educational Resources Information Center

    Richardson, Ginny

    2006-01-01

    Twelve-year-old Aaron Zibricky, a member of the Lucky Clovers 4-H Club, entered his prize sheep, Star, in the 2005 Will County Fair in Illinois. Zibricky, who is diagnosed with autism, had worked and strived for this moment, putting in long hours feeding, cleaning and shearing the sheep and learning showmanship skills. No one was more elated at…

  11. Land Use for Marsh Beach. 4-H Marine Science Simulation Game. Member's Guide [and] Agent's Supplement. MSp 5 [and] 6.

    ERIC Educational Resources Information Center

    Auburn Univ., AL. Cooperative Extension Service.

    A six-part marine science simulation game for 4-H members concerning land use in a hypothetical community is provided. The major problem is to decide what are some possible uses of a three-mile (1,250 acre) Marsh Beach which the city recently purchased. Members assume the roles of decision-makers in the simulated environment and compete for…

  12. Improving Healthy Living Youth Development Program Outreach in Extension: Lessons Learned from the 4-H Health Rocks! Program

    ERIC Educational Resources Information Center

    Kumaran, Muthusami; Fogarty, Kate; Fung, Whitney M.; Terminello, Amanda

    2015-01-01

    This article discusses a qualitative evaluation of the Florida 4-H Health Rocks! program aimed at youth alcohol, tobacco, and other drug use prevention. A questionnaire was distributed to Extension professionals across Florida to gain insight into the strengths and barriers they faced with programming. Programmatic strengths included targeting a…

  13. A Virtual Good Idea

    ERIC Educational Resources Information Center

    Bolch, Matt

    2009-01-01

    School districts across the country have always had to do more with less. Funding goes only so far, leaving administrators and IT staff to find innovative ways to save money while maintaining a high level of academic quality. Creating virtual servers accomplishes both tasks, district technology personnel say. Virtual environments not only allow…

  14. 10 Myths of Virtualization

    ERIC Educational Resources Information Center

    Schaffhauser, Dian

    2012-01-01

    Half of servers in higher ed are virtualized. But that number's not high enough for Link Alander, interim vice chancellor and CIO at the Lone Star College System (Texas). He aspires to see 100 percent of the system's infrastructure requirements delivered as IT services from its own virtualized data centers or other cloud-based operators. Back in…

  15. Virtual Worlds for Educators

    ERIC Educational Resources Information Center

    Dembo, Steve

    2008-01-01

    This article describes an online experience that has not only created a fantasy world for the general public but has enabled some tech-savvy educators to create virtual educational opportunities. Second Life, or SL, is a 3-D Internet-based virtual world created by Linden Lab and populated by nearly 1,000,000 active users worldwide since 2003.…

  16. Virtual Peace Education

    ERIC Educational Resources Information Center

    Firer, Ruth

    2008-01-01

    This article is based on the convictions that peace education is the basis for any sustainable non-violent relations between parties in a conflict, and that virtual peace education is almost the only feasible way to practise peace education in an open violent conflict as is the current Israeli/Palestinians one. Moreover, virtual peace education…

  17. Digging the Virtual Past

    ERIC Educational Resources Information Center

    Polymeropoulou, Panagiota

    2014-01-01

    In this paper we will investigate the way that the technological progress and the Informatics contributed greatly to the field of Archaeology. There will be analyzed the terms of virtual archaeology and virtual reality in archaeology and there will be an extended reference to the applications and the computer graphics that archaeologists could use…

  18. Virtual School Counseling

    ERIC Educational Resources Information Center

    Osborn, Debra S.; Peterson, Gary W.; Hale, Rebecca R.

    2015-01-01

    The advent of virtual schools opens doors to opportunity for delivery of student services via the Internet. Through the use of structured interviews with four practicing Florida virtual school counselors, and a follow-up survey, the authors examined the experiences and reflections of school counselors who are employed full time in a statewide…

  19. Virtual Schools. Literature Review

    ERIC Educational Resources Information Center

    Blazer, Christie

    2009-01-01

    The majority of school districts in the U.S. are providing some form of online learning for their students. In the past, virtual schools primarily targeted advanced students who didn't have access to certain courses in their regular schools. Recently, however, many virtual schools have shifted their focus to credit recovery as a way to provide…

  20. Rethinking the Virtual

    ERIC Educational Resources Information Center

    Burbules, Nicholas C.

    2004-01-01

    The author builds theoretically off an alternative conception of the virtual, through a series of steps. First, he explores four processes of engagement through which immersion happens (interest, involvement, imagination and interaction); these will prove especially important for understanding the educational potential of virtuality. Second, he…

  1. Virtual Learning Environments.

    ERIC Educational Resources Information Center

    Follows, Scott B.

    1999-01-01

    Illustrates the possibilities and educational benefits of virtual learning environments (VLEs), based on experiences with "Thirst for Knowledge," a VLE that simulates the workplace of a major company. While working in this virtual office world, students walk through the building, attend meetings, read reports, receive e-mail, answer the telephone,…

  2. Preparation of floating microspheres for fish farming.

    PubMed

    Nepal, Pushp R; Chun, Myung-Kwan; Choi, Hoo-Kyun

    2007-08-16

    The aim of this study was to develop floating microspheres with practical applications to fish farming. Each microsphere with a central hollow cavity was prepared using a solvent diffusion and evaporation method with Eudragit E100. Various manufacturing parameters were investigated by single factor method. The macrolide antibiotic josamycin was selected as a model drug. The loading efficiency of the drug in the microspheres was 64.7%. In the release study, virtually none of the drug was released into the fresh water whereas the entire drug was released from the josamycin-loaded microspheres into the simulated gastric fluid of rainbow trout (pH 2.7). The buoyancy was excellent with approximately 90% of the microspheres still floating after 24h.

  3. Temperature dependence of current-and capacitance-voltage characteristics of an Au/4H-SiC Schottky diode

    NASA Astrophysics Data System (ADS)

    Gülnahar, Murat

    2014-12-01

    In this study, the current-voltage (I-V) and capacitance-voltage (C-V) measurements of an Au/4H-SiC Schottky diode are characterized as a function of the temperature in 50-300 K temperature range. The experimental parameters such as ideality factor and apparent barrier height presents to be strongly temperature dependent, that is, the ideality factor increases and the apparent barrier height decreases with decreasing temperature, whereas the barrier height values increase with the temperature for C-V data. Likewise, the Richardson plot deviates at low temperatures. These anomaly behaviors observed for Au/4H-SiC are attributed to Schottky barrier inhomogeneities. The barrier anomaly which relates to interface of Au/4H-SiC is also confirmed by the C-V measurements versus the frequency measured in 300 K and it is interpreted by both Tung's lateral inhomogeneity model and multi-Gaussian distribution approach. The values of the weighting coefficients, standard deviations and mean barrier height are calculated for each distribution region of Au/4H-SiC using the multi-Gaussian distribution approach. In addition, the total effective area of the patches NAe is obtained at separate temperatures and as a result, it is expressed that the low barrier regions influence meaningfully to the current transport at the junction. The homogeneous barrier height value is calculated from the correlation between the ideality factor and barrier height and it is noted that the values of standard deviation from ideality factor versus q/3kT curve are in close agreement with the values obtained from the barrier height versus q/2kT variation. As a result, it can be concluded that the temperature dependent electrical characteristics of Au/4H-SiC can be successfully commented on the basis of the thermionic emission theory with both models.

  4. Breakdown degradation associated with elementary screw dislocations in 4H-SiC p +n junction rectifiers

    NASA Astrophysics Data System (ADS)

    Neudeck, P. G.; Huang, W.; Dudley, M.

    1998-12-01

    It is well-known that SiC wafer quality deficiencies are delaying the realization of outstandingly superior 4H-SiC power electronics. While efforts to date have centered on eradicating micropipes (i.e., hollow core super-screw dislocations with Burgers vector>2 c), 4H-SiC wafers and epilayers also contain elementary screw dislocations (i.e., Burgers vector=1 c with no hollow core) in densities on the order of thousands per cm 2, nearly 100-fold micropipe densities. This paper describes an initial study into the impact of elementary screw dislocations on the reverse-bias current-voltage ( I- V) characteristics of 4H-SiC p +n diodes. First, synchrotron white beam X-ray topography (SWBXT) was employed to map the exact locations of elementary screw dislocations within small-area 4H-SiC p +n mesa diodes. Then the high-field reverse leakage and breakdown properties of these diodes were subsequently characterized on a probing station outfitted with a dark box and video camera. Most devices without screw dislocations exhibited excellent characteristics, with no detectable leakage current prior to breakdown, a sharp breakdown I- V knee, and no visible concentration of breakdown current. In contrast, devices that contained at least one elementary screw dislocation exhibited 5-35% reduction in breakdown voltage, a softer breakdown I- V knee, and visible microplasmas in which highly localized breakdown current was concentrated. The locations of observed breakdown microplasmas corresponded exactly to the locations of elementary screw dislocations identified by SWBXT mapping. While not as detrimental to SiC device performance as micropipes, the undesirable breakdown characteristics of elementary screw dislocations could nevertheless adversely affect the performance and reliability of 4H-SiC power devices.

  5. Monolayer compression induces fluidization in binary system of partially fluorinated alcohol (F4H11OH) with DPPC.

    PubMed

    Nakahara, Hiromichi; Ohmine, Aya; Kai, Shoko; Shibata, Osamu

    2013-01-01

    A two-component Langmuir monolayer consisting of (perfluorobutyl)undecanol (F4H11OH) and dipalmitoylphosphatidylcholine (DPPC), a major component of pulmonary surfactants in mammals, has been investigated at the air-water interface. The binary monolayer has been systematically examined from both thermodynamic and morphological perspectives. The excess Gibbs free energy of mixing has been calculated from surface pressure (π)-molecular area (A) isotherms, and the results indicate that the miscibility of the two-component system shows a maximum in thermodynamical stability when the mole fraction (X(F4H11OH)) is 0.3. Results from a two-dimensional phase diagram (π vs. X(F4H11OH)) are consistent with these findings and depict the degree of miscibility resulting from the variation in the transition and collapse pressures relative to the concentration of X(F4H11OH). The miscibility is also supported by in situ Brewster angle microscopy and fluorescence microscopy, as well as ex situ atomic force microscopy for the system after transfer onto a mica substrate. Aside from temperature, a known driving force for the fluidization of DPPC monolayers is a change in surface composition caused by the addition of additive molecules. In the present study, however, the fluidization is driven by increasing surface pressures even at constant X(F4H11OH). Such a fluidization is a fascinating property when looked at in context of its potential implications for pulmonary replacement therapy, and hence, this study provides a fundamental insight into designing fluorinated materials for biomedical use.

  6. Breakdown Degradation Associated with Elementary Screw Dislocations in 4H-SiC P(+)N Junction Rectifiers

    NASA Technical Reports Server (NTRS)

    Neudeck, P. G.; Huang, W.; Dudley, M.

    1998-01-01

    It is well-known that SiC wafer quality deficiencies are delaying the realization of outstandingly superior 4H-SiC power electronics. While efforts to date have centered on eradicating micropipes (i.e., hollow core super-screw dislocations with Burgers vector greater than 2c), 4H-SiC wafers and epilayers also contain elementary screw dislocations (i.e., Burgers vector = lc with no hollow core) in densities on the order of thousands per sq cm, nearly 100-fold micropipe densities. This paper describes an initial study into the impact of elementary screw dislocations on the reverse-bias current-voltage (I-V) characteristics of 4H-SiC p(+)n diodes. First, Synchrotron White Beam X-ray Topography (SWBXT) was employed to map the exact locations of elementary screw dislocations within small-area 4H-SiC p(+)n mesa diodes. Then the high-field reverse leakage and breakdown properties of these diodes were subsequently characterized on a probing station outfitted with a dark box and video camera. Most devices without screw dislocations exhibited excellent characteristics, with no detectable leakage current prior to breakdown, a sharp breakdown I-V knee, and no visible concentration of breakdown current. In contrast devices that contained at least one elementary screw dislocation exhibited a 5% to 35% reduction in breakdown voltage, a softer breakdown I-V knee, and visible microplasmas in which highly localized breakdown current was concentrated. The locations of observed breakdown microplasmas corresponded exactly to the locations of elementary screw dislocations identified by SWBXT mapping. While not as detrimental to SiC device performance as micropipes, the undesirable breakdown characteristics of elementary screw dislocations could nevertheless adversely affect the performance and reliability of 4H-SiC power devices.

  7. Reversible Photoinduced Reductive Elimination of H2 from the Nitrogenase Dihydride State, the E(4)(4H) Janus Intermediate.

    PubMed

    Lukoyanov, Dmitriy; Khadka, Nimesh; Yang, Zhi-Yong; Dean, Dennis R; Seefeldt, Lance C; Hoffman, Brian M

    2016-02-01

    We recently demonstrated that N2 reduction by nitrogenase involves the obligatory release of one H2 per N2 reduced. These studies focus on the E4(4H) "Janus intermediate", which has accumulated four reducing equivalents as two [Fe-H-Fe] bridging hydrides. E4(4H) is poised to bind and reduce N2 through reductive elimination (re) of the two hydrides as H2, coupled to the binding/reduction of N2. To obtain atomic-level details of the re activation process, we carried out in situ 450 nm photolysis of E4(4H) in an EPR cavity at temperatures below 20 K. ENDOR and EPR measurements show that photolysis generates a new FeMo-co state, denoted E4(2H)*, through the photoinduced re of the two bridging hydrides of E4(4H) as H2. During cryoannealing at temperatures above 175 K, E4(2H)* reverts to E4(4H) through the oxidative addition (oa) of the H2. The photolysis quantum yield is temperature invariant at liquid helium temperatures and shows a rather large kinetic isotope effect, KIE = 10. These observations imply that photoinduced release of H2 involves a barrier to the combination of the two nascent H atoms, in contrast to a barrierless process for monometallic inorganic complexes, and further suggest that H2 formation involves nuclear tunneling through that barrier. The oa recombination of E4(2H)* with the liberated H2 offers compelling evidence for the Janus intermediate as the point at which H2 is necessarily lost during N2 reduction; this mechanistically coupled loss must be gated by N2 addition that drives the re/oa equilibrium toward reductive elimination of H2 with N2 binding/reduction.

  8. Synthesis of 4H/fcc-Au@M (M = Ir, Os, IrOs) Core-Shell Nanoribbons For Electrocatalytic Oxygen Evolution Reaction.

    PubMed

    Fan, Zhanxi; Luo, Zhimin; Chen, Ye; Wang, Jie; Li, Bing; Zong, Yun; Zhang, Hua

    2016-08-01

    The high-yield synthesis of 4H/face-centered cubic (fcc)-Au@Ir core-shell nanoribbons (NRBs) is achieved via the direct growth of Ir on 4H Au NRBs under ambient conditions. Importantly, this method can be used to synthesize 4H/fcc-Au@Os and 4H/fcc-Au@IrOs core-shell NRBs. Significantly, the obtained 4H/fcc-Au@Ir core-shell NRBs demonstrate an exceptional electrocatalytic activity toward the oxygen evolution reaction under acidic condition, which is much higher than that of the commercial Ir/C catalyst.

  9. Intelligent virtual teacher

    NASA Astrophysics Data System (ADS)

    Takács, Ondřej; Kostolányová, Kateřina

    2016-06-01

    This paper describes the Virtual Teacher that uses a set of rules to automatically adapt the way of teaching. These rules compose of two parts: conditions on various students' properties or learning situation; conclusions that specify different adaptation parameters. The rules can be used for general adaptation of each subject or they can be specific to some subject. The rule based system of Virtual Teacher is dedicated to be used in pedagogical experiments in adaptive e-learning and is therefore designed for users without education in computer science. The Virtual Teacher was used in dissertation theses of two students, who executed two pedagogical experiments. This paper also describes the phase of simulating and modeling of the theoretically prepared adaptive process in the modeling tool, which has all the required parameters and has been created especially for the occasion. The experiments are being conducted on groups of virtual students and by using a virtual study material.

  10. 29 CFR 780.142 - Practices on a farm not related to farming operations.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 3 2011-07-01 2011-07-01 false Practices on a farm not related to farming operations. 780... FAIR LABOR STANDARDS ACT General Scope of Agriculture âsuch Farming Operationsâ-on the Farm § 780.142 Practices on a farm not related to farming operations. Practices performed on a farm in connection...

  11. 29 CFR 780.142 - Practices on a farm not related to farming operations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 3 2010-07-01 2010-07-01 false Practices on a farm not related to farming operations. 780... FAIR LABOR STANDARDS ACT General Scope of Agriculture âsuch Farming Operationsâ-on the Farm § 780.142 Practices on a farm not related to farming operations. Practices performed on a farm in connection...

  12. 29 CFR 780.142 - Practices on a farm not related to farming operations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 29 Labor 3 2014-07-01 2014-07-01 false Practices on a farm not related to farming operations. 780... FAIR LABOR STANDARDS ACT General Scope of Agriculture âsuch Farming Operationsâ-on the Farm § 780.142 Practices on a farm not related to farming operations. Practices performed on a farm in connection...

  13. 29 CFR 780.142 - Practices on a farm not related to farming operations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 29 Labor 3 2013-07-01 2013-07-01 false Practices on a farm not related to farming operations. 780... FAIR LABOR STANDARDS ACT General Scope of Agriculture âsuch Farming Operationsâ-on the Farm § 780.142 Practices on a farm not related to farming operations. Practices performed on a farm in connection...

  14. 29 CFR 780.142 - Practices on a farm not related to farming operations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 29 Labor 3 2012-07-01 2012-07-01 false Practices on a farm not related to farming operations. 780... FAIR LABOR STANDARDS ACT General Scope of Agriculture âsuch Farming Operationsâ-on the Farm § 780.142 Practices on a farm not related to farming operations. Practices performed on a farm in connection...

  15. Designing the automatic milking farm in a hot climate.

    PubMed

    Halachmi, I

    2004-03-01

    A mathematical simulation model was used to assist 5 farmers in developing design criteria for inclusion of robotic milking systems in each farm situation. The barn layout influences arrivals of cows to the milking robot as well as other cow traffic and must be carefully planned. Each farmer had individual objectives and consequently unique design criteria that determined the optimal solution. Planning factors addressed by simulations on these farms included: 1) optimal cow cooling locations; 2) optimal facility allocation in expanding dairies; 3) concentrate feeder locations and feeding management; 4) number of feeders--based on expected rations; 5) use of a robot in an open cowshed without free stalls; 6) number of robots needed, currently and in the future; 7) eight robots working in harmony; 8) robot locations that allow for expansion; 9) floor space needed in each barn section including maternity and veterinary treatment areas; 10) location of bottlenecks that limit efficiency or expansion; and 11) cow traffic routine as affected by management practices, feed allocation, and farm layout. The simulation allowed farmers to receive a course in managing a "virtual robotic milking farm" before installation of the barn. Therefore, each could be more confident that his future barn would work properly under his unique local conditions and management practices. One farm checked 2 yr after construction achieved an average daily robot utilization of 84%, nearly matching the 85% projected before the barn was built. Important variables considered in the simulations were facility allocation, cow space needed in each farm area, robot utilization, number of cows, milk yield, milk flow rate, feeding method and timing, robot location and orientation, and farm physical layout.

  16. Farm Work-Related Asthma Among US Primary Farm Operators

    PubMed Central

    Mazurek, Jacek M.; White, Gretchen E.; Rodman, Chad; Schleiff, Patricia L.

    2015-01-01

    The objective of this study was to estimate the prevalence of current asthma and the proportion of current asthma that is related to work on the farm among primary farm operators. The 2011 Farm and Ranch Safety Survey data were used to produce estimates and prevalence odds ratios. An estimated 5.1% of farm operators had asthma. Of these, 15.4% had farm work-related asthma. Among operators with farm work-related asthma, 54.8% (95% confidence interval [CI]: 41.8%–68.2%) had an asthma attack in the prior 12 months and 33.3% (95% CI: 21.2%–45.4%) had an asthma attack that occurred while doing farm work. Of those who had an asthma attack that occurred while doing farm work, 65.0% associated their asthma attack with plant/tree materials. This study provides updated information on asthma and the proportion of current asthma that is related to work on the farm and identifies certain groups of farm operators that might benefit from workplace asthma prevention intervention. PMID:25635741

  17. Transgenic Farm Animals

    NASA Astrophysics Data System (ADS)

    Solomon, Morse B.; Eastridge, Janet S.; Paroczay, Ernest W.

    Conventional science to improve muscle and meat parameters has involved breeding strategies, such as selection of dominant traits or selection of preferred traits by cross breeding, and the use of endogenous and exogenous hormones. Improvements in the quality of food products that enter the market have largely been the result of postharvest intervention strategies. Biotechnology is a more extreme scientific method that offers the potential to improve the quality, yield, and safety of food products by direct genetic manipulation. In the December 13, 2007 issue of the Southeast Farm Press, an article by Roy Roberson pointed out that biotechnology is driving most segments of U.S. farm growth. He indicated that nationwide, the agriculture industry is booming and much of that growth is the result of biotechnology advancements.

  18. Virtual Worlds, Virtual Literacy: An Educational Exploration

    ERIC Educational Resources Information Center

    Stoerger, Sharon

    2008-01-01

    Virtual worlds enable students to learn through seeing, knowing, and doing within visually rich and mentally engaging spaces. Rather than reading about events, students become part of the events through the adoption of a pre-set persona. Along with visual feedback that guides the players' activities and the development of visual skills, visual…

  19. Software for batch farms

    SciTech Connect

    Ian Bird; Bryan Hess; Andy Kowalski

    2000-02-01

    Over the past few years, LSF has become a standard for job management on batch farms. However, there are many instances where it cannot be deployed for a variety of reasons. In large farms the cost may be prohibitive for the set of features actually used; small university groups who wish to clone the farms and software of larger laboratories often have constraints which preclude the use of LSF. This paper discusses a generic interface developed at Jefferson Lab to provide a set of common services to the user, while using any one of a variety of underlying batch management software products. Initially the system provides an interface to LSF and an alternative--Portable Batch System (PBS) developed by NASA and freely available in source form. It is straightforward to extend this to other systems. Such a generic interface allows users to move from one location to another and run their jobs with no modification, and by extension provides a framework for a ''global'' batch system where jobs submitted at one site may be transparently executed at another. The interface also provides additional features not found in the underlying batch software. Being written in Java, the client can be easily installed anywhere and allows for authenticated remote job submission and manipulation, including a web interface. This paper will also discuss the problem of keeping a large batch farm occupied with work without waiting for slow tape access. The use of file caching, pre-staging of files from tape and the interconnection with the batch system will be discussed. As well as automated techniques, the provision of appropriate information to the user to allow optimization should not be overlooked.

  20. Synthesis of 5,6-dihydro-4H-benzo[d]isoxazol-7-one and 5,6-dihydro-4H-isoxazolo[5,4-c]pyridin-7-one derivatives as potential Hsp90 inhibitors.

    PubMed

    Musso, Loana; Cincinelli, Raffaella; Giannini, Giuseppe; Manetti, Fabrizio; Dallavalle, Sabrina

    2015-11-01

    A novel class of 5,6-dihydro-4H-benzo[d]isoxazol-7-ones and 5,6-dihydro-4H-isoxazolo[5,4-c]pyridin-7-ones was designed, synthesized, and assayed to investigate the affinity toward Hsp90 protein. The synthetic route was based on a 1,3-dipolar cycloaddition of nitriloxides, generated in situ from suitable benzaldoximes, with 2-bromocyclohex-2-enones or 3-bromo-5,6-dihydro-1H-pyridin-2-ones. Whereas all the compounds bearing a benzamide group on the bicyclic scaffold were devoid of activity, the derivatives carrying a resorcinol-like fragment showed a remarkable inhibitory effect on Hsp90. Docking calculations were performed to investigate the orientation of the new compounds within the binding site of the enzyme.

  1. Synthesis of 5,6-dihydro-4H-benzo[d]isoxazol-7-one and 5,6-dihydro-4H-isoxazolo[5,4-c]pyridin-7-one derivatives as potential Hsp90 inhibitors.

    PubMed

    Musso, Loana; Cincinelli, Raffaella; Giannini, Giuseppe; Manetti, Fabrizio; Dallavalle, Sabrina

    2015-11-01

    A novel class of 5,6-dihydro-4H-benzo[d]isoxazol-7-ones and 5,6-dihydro-4H-isoxazolo[5,4-c]pyridin-7-ones was designed, synthesized, and assayed to investigate the affinity toward Hsp90 protein. The synthetic route was based on a 1,3-dipolar cycloaddition of nitriloxides, generated in situ from suitable benzaldoximes, with 2-bromocyclohex-2-enones or 3-bromo-5,6-dihydro-1H-pyridin-2-ones. Whereas all the compounds bearing a benzamide group on the bicyclic scaffold were devoid of activity, the derivatives carrying a resorcinol-like fragment showed a remarkable inhibitory effect on Hsp90. Docking calculations were performed to investigate the orientation of the new compounds within the binding site of the enzyme. PMID:25855505

  2. Wind farm electrical system

    DOEpatents

    Erdman, William L.; Lettenmaier, Terry M.

    2006-07-04

    An approach to wind farm design using variable speed wind turbines with low pulse number electrical output. The output of multiple wind turbines are aggregated to create a high pulse number electrical output at a point of common coupling with a utility grid network. Power quality at each individual wind turbine falls short of utility standards, but the aggregated output at the point of common coupling is within acceptable tolerances for utility power quality. The approach for aggregating low pulse number electrical output from multiple wind turbines relies upon a pad mounted transformer at each wind turbine that performs phase multiplication on the output of each wind turbine. Phase multiplication converts a modified square wave from the wind turbine into a 6 pulse output. Phase shifting of the 6 pulse output from each wind turbine allows the aggregated output of multiple wind turbines to be a 24 pulse approximation of a sine wave. Additional filtering and VAR control is embedded within the wind farm to take advantage of the wind farm's electrical impedence characteristics to further enhance power quality at the point of common coupling.

  3. Virtual Machine Logbook - Enabling virtualization for ATLAS

    NASA Astrophysics Data System (ADS)

    Yao, Yushu; Calafiura, Paolo; Poffet, Julien; Cavalli, Andrea; Leggett, Charles; Frédéric, Bapst

    2010-04-01

    ATLAS software has been developed mostly on CERN linux cluster lxplus or on similar facilities at the experiment Tier 1 centers. The fast rise of virtualization technology has the potential to change this model, turning every laptop or desktop into an ATLAS analysis platform. In the context of the CernVM project we are developing a suite of tools and CernVM plug-in extensions to promote the use of virtualization for ATLAS analysis and software development. The Virtual Machine Logbook (VML), in particular, is an application to organize work of physicists on multiple projects, logging their progress, and speeding up "context switches" from one project to another. An important feature of VML is the ability to share with a single "click" the status of a given project with other colleagues. VML builds upon the save and restore capabilities of mainstream virtualization software like VMware, and provides a technology-independent client interface to them. A lot of emphasis in the design and implementation has gone into optimizing the save and restore process to makepractical to store many VML entries on a typical laptop disk or to share a VML entry over the network. At the same time, taking advantage of CernVM's plugin capabilities, we are extending the CernVM platform to help increase the usability of ATLAS software. For example, we added the ability to start the ATLAS event display on any computer running CernVM simply by clicking a button in a web browser. We want to integrate seamlessly VML with CernVM unique file system design to distribute efficiently ATLAS software on every physicist computer. The CernVM File System (CVMFS) download files on-demand via HTTP, and cache it locally for future use. This reduces by one order of magnitude the download sizes, making practical for a developer to work with multiple software releases on a virtual machine.

  4. The ferrimagnetic compounds CoM[Mscript(EDTA)]2 . 4H2O(M,Mscript=Co,Ni): Magnetic characterization of CoCo[Ni(EDTA)2] . 4H2O

    NASA Astrophysics Data System (ADS)

    Sapiña, F.; Coronado, E.; Gomez-Romero, P.; Beltran, D.; Burriel, R.; Carlin, R. L.

    1990-05-01

    We report on the magnetic properties of the ordered bimetallic compound CoCo(NiEDTA)2ṡ4H2O (abbreviated as [CoCoNi]). The structure consists of ordered bimetallic layers formed by alternating octahedral sites of Co and Ni(II); tetrahedral Co sites connect different Co-Ni layers. We discuss the low-dimensional ferrimagnetic behavior of this compound in terms of a model that assumes three spin sublattices exchange coupled by an Ising interaction.

  5. Virtual Human Project

    SciTech Connect

    Ward, RD

    2001-06-12

    This paper describes the development of a comprehensive human modeling environment, the Virtual Human, which will be used initially to model the human respiratory system for purposes of predicting pulmonary disease or injury using lung sounds. The details of the computational environment, including the development of a Virtual Human Thorax, a database for storing models, model parameters, and experimental data, and a Virtual Human web interface are outlined. Preliminary progress in developing this environment will be presented. A separate paper at the conference describes the modeling of sound generation using computational fluid dynamics and the modeling of sound propagation in the human respiratory system.

  6. Virtual slit scanning microscopy.

    PubMed

    Fiolka, Reto; Stemmer, Andreas; Belyaev, Yury

    2007-12-01

    We present a novel slit scanning confocal microscope with a CCD camera image sensor and a virtual slit aperture for descanning that can be adjusted during post-processing. A very efficient data structure and mathematical criteria for aligning the virtual aperture guarantee the ease of use. We further introduce a method to reduce the anisotropic lateral resolution of slit scanning microscopes. System performance is evaluated against a spinning disk confocal microscope on identical specimens. The virtual slit scanning microscope works as the spinning disk type and outperforms on thick specimens. PMID:17891411

  7. Regioisomer-Free C 4h β-Tetrakis(tert-butyl)metallo-phthalocyanines: Regioselective Synthesis and Spectral Investigations.

    PubMed

    Iida, Norihito; Tanaka, Kenta; Tokunaga, Etsuko; Takahashi, Hiromi; Shibata, Norio

    2015-04-01

    Metal β-tetrakis(tert-butyl)phthalocyanines are the most commonly used phthalocyanines due to their high solubility, stability, and accessibility. They are commonly used as a mixture of four regioisomers, which arise due to the tert-butyl substituent on the β-position, and to the best of our knowledge, their regioselective synthesis has yet to be reported. Herein, the C 4h -selective synthesis of β-tetrakis(tert-butyl)metallophthalocyanines is disclosed. Using tetramerization of α-trialkylsilyl phthalonitriles with metal salts following acid-mediated desilylation, the desired metallophthalocyanines were obtained in good yields. Upon investigation of regioisomer-free zinc β-tetrakis(tert-butyl)phthalocyanine using spectroscopy, the C 4h single isomer described here was found to be distinct in the solid state to zinc β-tetrakis(tert-butyl)phthalocyanine obtained by a conventional method.

  8. Synthesis, spectral characterization, and pharmacological importance of new 4H-1,4-benzothiazines, their sulfone analogues, and ribofuranosides.

    PubMed

    Gautam, Naveen; Garg, Ankita; Gautam, Dinesh Chand

    2015-01-01

    The present article describes the synthesis of new 4H-1,4-benzothiazines via condensation and oxidative cyclization of substituted 2-aminobenzenethiols with compounds containing active methylene groups. It is believed that the reaction proceeds via intermediary of the enaminoketone system. The sulfone derivatives were synthesized by oxidation of 4H-1,4-benzothiazines using 30% hydrogen peroxide in glacial acetic acid. Benzothiazines were used as bases to prepare ribofuranosides by treatment with a sugar derivative (β-D-ribofuranosyl-1-acetate-2,3,5-tribenzoate). The pharmacological importance of the synthesized compounds was evaluated by their, antimicrobial properties against various bacterial strains and fungal species. The structures of the compounds have been confirmed by spectral and chemical analysis. PMID:25513863

  9. High rate dry etching of (BiSb)2Te3 film by CH4/H2-based plasma

    NASA Astrophysics Data System (ADS)

    Song, Junqiang; Shi, Xun; Chen, Lidong

    2014-10-01

    Etching characteristics of p-type (BiSb)2Te3 films were studied with CH4/H2/Ar gas mixture using an inductively coupled plasma (ICP)-reactive ion etching (RIE) system. The effects of gas mixing ratio, working pressure and gas flow rate on the etch rate and the surface morphology were investigated. The vertical etched profile with the etch rate of 600 nm/min was achieved at the optimized processing parameters. X-ray photoelectron spectroscopy (XPS) analysis revealed the non-uniform etching of (BiSb)2Te3 films due to disparate volatility of the etching products. Micro-masking effects caused by polymer deposition and Bi-rich residues resulted in roughly etched surfaces. Smooth surfaces can be obtained by optimizing the CH4/H2/Ar mixing ratio.

  10. Chloride-based SiC growth on a-axis 4H-SiC substrates

    NASA Astrophysics Data System (ADS)

    Booker, Ian D.; Farkas, Ildiko; Ivanov, Ivan G.; Hassan, Jawad ul; Janzén, Erik

    2016-01-01

    SiC has, during the last few years, become increasingly important as a power-device material for high voltage applications. The thick, low-doped voltage-supporting epitaxial layer is normally grown by CVD on 4° off-cut 4H-SiC substrates at a growth rate of 5 - 10 μm / h using silane (SiH4) and propane (C3H8) or ethylene (C2H4) as precursors. The concentrations of epitaxial defects and dislocations depend to a large extent on the underlying substrate but can also be influenced by the actual epitaxial growth process. Here we will present a study on the properties of the epitaxial layers grown by a Cl-based technique on an a-axis (90° off-cut from c-direction) 4H-SiC substrate.

  11. Melting of H2SO4·4H2O Particles upon Cooling: Implications for Polar Stratospheric Clouds

    PubMed

    Koop; Carslaw

    1996-06-14

    Polar stratospheric clouds (PSCs) are important for the chemical activation of chlorine compounds and subsequent ozone depletion. Solid PSCs can form on sulfuric acid tetrahydrate (SAT) (H2SO4·4H2O) nuclei, but recent laboratory experiments have shown that PSC nucleation on SAT is strongly hindered. A PSC formation mechanism is proposed in which SAT particles melt upon cooling in the presence of HNO3 to form liquid HNO3-H2SO4-H2O droplets 2 to 3 kelvin above the ice frost point. This mechanism offers a PSC formation temperature that is defined by the ambient conditions and sets a temperature limit below which PSCs should form.

  12. Low resistance Ti Ohmic contacts to 4H-SiC by reducing barrier heights without high temperature annealing

    SciTech Connect

    Huang Lingqin; Liu Bingbing; Zhu Qiaozhi; Chen Suhua; Gao Mingchao; Wang Dejun; Qin Fuwen

    2012-06-25

    Ti Ohmic contacts to relatively highly doped (1 Multiplication-Sign 10{sup 18} cm{sup -3}) n-type 4H-SiC have been produced, without high temperature annealing, by means of low temperature electronic cyclotron resonance microwave hydrogen plasma pre-treatment (HPT) of the SiC surface. The as-deposited Ti/4H-SiC contacts show Ohmic properties, and the specific contact resistance obtained is as low as 2.07 Multiplication-Sign 10{sup -4}{Omega}{center_dot}cm{sup 2} after annealing at low temperatures (400 Degree-Sign C). This is achieved by low barrier height at Ti/SiC interface, which could be attributed to decrease of surface states density by the HPT releasing Fermi level pinning, and to band-gap narrowing, image-force, and thermionic-field emission at high doping.

  13. Synthesis, bioassay, and QSAR study of bronchodilatory active 4H-pyrano[3,2-c]pyridine-3-carbonitriles.

    PubMed

    Girgis, Adel S; Saleh, Dalia O; George, Riham F; Srour, Aladdin M; Pillai, Girinath G; Panda, Chandramukhi S; Katritzky, Alan R

    2015-01-01

    A statistically significant QSAR model describing the bioactivity of bronchodilatory active 4H-pyrano[3,2-c]pyridine-3-carbonitriles (N = 41, n = 8, R(2) = 0.824, R(2)cv = 0.724, F = 18.749, s(2) = 0.0018) was obtained employing CODESSA-Pro software. The bronchodilatory active 4H-pyrano[3,2-c]pyridine-3-carbonitriles 17-57 were synthesized through a facile approach via reaction of 1-alkyl-4-piperidones 1-4 with ylidenemalononitriles 5-16 in methanol in the presence of sodium. The bronchodilation properties of 17-57 were investigated in vitro using isolated guinea pig tracheal rings pre-contracted with histamine (standard method) and compared with theophylline (standard reference). Most of the compounds synthesized exhibit promising bronchodilation properties especially, compounds 25 and 28. PMID:25462283

  14. Surface-state dependent optical properties of OH-, F-, and H-terminated 4H-SiC quantum dots.

    PubMed

    Rashid, Marzaini; Tiwari, Amit K; Goss, J P; Rayson, M J; Briddon, P R; Horsfall, A B

    2016-08-01

    Density functional calculations are performed for OH-, F- and H-terminated 4H-SiC 10-20 Å diameter clusters to investigate the effect of surface species upon the optical absorption properties. H-termination results in a pronounced size-dependent quantum-confinement in the absorption, whereas F- and OH-terminations exhibit much reduced size dependent absorption due to surface states. Our findings are in good agreement with recent experimental studies, and are able to explain the little explored dual-feature photoluminescence spectra of SiC quantum dots. We propose that along with controlling the size, suitable surface termination is the key for optimizing optical properties of 4H-SiC quantum structures, such as might be exploited in optoelectronics, photovoltaics and biological applications. PMID:27430278

  15. The urban stormwater farm.

    PubMed

    Liebman, M B; Jonasson, O J; Wiese, R N

    2011-01-01

    Currently more than 3 billion people live in urban areas. The urban population is predicted to increase by a further 3 billion by 2050. Rising oil prices, unreliable rainfall and natural disasters have all contributed to a rise in global food prices. Food security is becoming an increasingly important issue for many nations. There is also a growing awareness of both 'food miles' and 'virtual water'. Food miles and virtual water are concepts that describe the amount of embodied energy and water that is inherent in the food and other goods we consume. Growing urban agglomerations have been widely shown to consume vast quantities of energy and water whilst emitting harmful quantities of wastewater and stormwater runoff through the creation of massive impervious areas. In this paper it is proposed that there is an efficient way of simultaneously addressing the problems of food security, carbon emissions and stormwater pollution. Through a case study we demonstrate how it is possible to harvest and store stormwater from densely populated urban areas and use it to produce food at relatively low costs. This reduces food miles (carbon emissions) and virtual water consumption and serves to highlight the need for more sustainable land-use planning.

  16. The urban stormwater farm.

    PubMed

    Liebman, M B; Jonasson, O J; Wiese, R N

    2011-01-01

    Currently more than 3 billion people live in urban areas. The urban population is predicted to increase by a further 3 billion by 2050. Rising oil prices, unreliable rainfall and natural disasters have all contributed to a rise in global food prices. Food security is becoming an increasingly important issue for many nations. There is also a growing awareness of both 'food miles' and 'virtual water'. Food miles and virtual water are concepts that describe the amount of embodied energy and water that is inherent in the food and other goods we consume. Growing urban agglomerations have been widely shown to consume vast quantities of energy and water whilst emitting harmful quantities of wastewater and stormwater runoff through the creation of massive impervious areas. In this paper it is proposed that there is an efficient way of simultaneously addressing the problems of food security, carbon emissions and stormwater pollution. Through a case study we demonstrate how it is possible to harvest and store stormwater from densely populated urban areas and use it to produce food at relatively low costs. This reduces food miles (carbon emissions) and virtual water consumption and serves to highlight the need for more sustainable land-use planning. PMID:22053481

  17. Working Group Reports and Presentations: Virtual Worlds and Virtual Exploration

    NASA Technical Reports Server (NTRS)

    LAmoreaux, Claudia

    2006-01-01

    Scientists and engineers are continually developing innovative methods to capitalize on recent developments in computational power. Virtual worlds and virtual exploration present a new toolset for project design, implementation, and resolution. Replication of the physical world in the virtual domain provides stimulating displays to augment current data analysis techniques and to encourage public participation. In addition, the virtual domain provides stakeholders with a low cost, low risk design and test environment. The following document defines a virtual world and virtual exploration, categorizes the chief motivations for virtual exploration, elaborates upon specific objectives, identifies roadblocks and enablers for realizing the benefits, and highlights the more immediate areas of implementation (i.e. the action items). While the document attempts a comprehensive evaluation of virtual worlds and virtual exploration, the innovative nature of the opportunities presented precludes completeness. The authors strongly encourage readers to derive additional means of utilizing the virtual exploration toolset.

  18. Characterization of tungsten-nickel simultaneous Ohmic contacts to p- and n-type 4H-SiC

    NASA Astrophysics Data System (ADS)

    Kragh-Buetow, K. C.; Okojie, R. S.; Lukco, D.; Mohney, S. E.

    2015-10-01

    Ohmic contacts to p- and n-type 4H-SiC using refractory alloyed W:Ni thin films were investigated. Transfer length measurement test structures to p-type 4H-SiC (NA = 3 × 1020 cm-3) revealed Ohmic contacts with specific contact resistances, ρc, of ˜10-5 Ω cm2 after 0.5 h annealing in argon at temperatures of 1000 °C, 1100 °C, 1150 °C, and 1200 °C. Contacts fabricated on n-type 4H-SiC (ND = 2 × 1019 cm-3) by similar methods were shown to have similar specific contact resistance values after annealing, demonstrating simultaneous Ohmic contact formation for W:Ni alloys on 4H-SiC. The lowest ρc values were (7.3 ± 0.9) × 10-6 Ω cm2 for p-SiC and (6.8 ± 3.1) × 10-6 Ω cm2 for n-SiC after annealing at 1150 °C. X-ray diffraction shows a cubic tungsten-nickel-carbide phase in the Ohmic contacts after annealing as well as WC after higher temperatures. Auger electron spectroscopy depth profiles support the presence of metal carbide regions above a nickel and silicon-rich region near the interface. X-ray energy dispersive spectroscopy mapping showed tungsten-rich and nickel-rich regions after annealing at 1100 °C and above. W:Ni alloys show promise as simultaneous Ohmic contacts to p- and n-SiC, offering low and comparable ρc values along with the formation of WxNiyC.

  19. Organocatalyzed enantioselective synthesis of 2-amino-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carboxylates

    PubMed Central

    Ramireddy, Naresh; Abbaraju, Santhi; Zhao, Cong-Gui

    2011-01-01

    The organocatalyzed enantioselective synthesis of biologically active 2-amino-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carboxylate derivatives was achieved using bifunctional cinchona alkaloids as the catalysts. Using quinine thiourea as the catalyst, the tandem Michael addition-cyclization reaction between 1,3-cyclohexanediones and alkylidenecyanoacetate derivatives gives the desired products in high yields (up to 92%) and good ee values (up to 82%). PMID:22081731

  20. Interfaces between 4H-SiC and SiO2: Microstructure, nanochemistry, and near-interface traps

    NASA Astrophysics Data System (ADS)

    Pippel, Eckhard; Woltersdorf, Jörg; Ólafsson, Halldor Ö.; Sveinbjörnsson, Einar Ö.

    2005-02-01

    We report on electrical and microscopic investigations aimed to clarify the origin of near-interface traps (NITs) in metal-silicon dioxide-4H-silicon carbide structures. Using capacitance-voltage and thermal dielectric relaxation current (TDRC) analysis we investigated NITs close to the 4H-SiC conduction-band edge in differently prepared thermal and deposited oxides and found that the traps give rise to two characteristic TDRC signatures belonging to two groups of trap levels. The total trapped charge exceeds 1×1013cm-2. The observed density and energy distribution of these traps are nearly identical in all thermal and deposited oxides investigated, suggesting that the NITs belong to intrinsic defects at the SiO2/SiC interface which are readily formed during oxide deposition or thermal oxidation of 4H-SiC. Using high-resolution electron microscopy combined with nanochemical analysis (electron energy-loss near-edge spectroscopy and energy-filtered transmission electron microscopy) we investigated the SiO2/SiC interface in samples receiving reoxidation and did not find any indication of graphitic regions at or near the SiO2/SiC interface or in the bulk silicon dioxide within a detection limit of 0.7nm. In addition, no amorphous carbon accumulation was observed near the SiO2/SiC interface. The overall results strongly suggest that the NITs near the 4H-SiC conduction band are not related to carbon structures in the SiO2/SiC interlayer.

  1. Electron paramagnetic resonance and theoretical studies of Nb in 4H- and 6H-SiC

    NASA Astrophysics Data System (ADS)

    Tien Son, Nguyen; Thang Trinh, Xuan; Gällström, Andreas; Leone, Stefano; Kordina, Olof; Janzén, Erik; Szász, Krisztián; Ivády, Viktor; Gali, Adam

    2012-10-01

    High purity silicon carbide (SiC) materials are of interest from high-power high temperature applications across recent photo-voltaic cells to hosting solid state quantum bits, where the tight control of electrically, optically, and magnetically active point defects is pivotal in these areas. 4H- and 6H-SiC substrates are grown at high temperatures and the incorporation of transition metal impurities is common. In unintentionally Nb-doped 4H- and 6H-SiC substrates grown by high-temperature chemical vapor deposition, an electron paramagnetic resonance (EPR) spectrum with C1h symmetry and a clear hyperfine (hf) structure consisting of ten equal intensity hf lines was observed. The hf structure can be identified as due to the interaction between the electron spin S = 1/2 and the nuclear spin of 93Nb. Additional hf structures due to the interaction with three Si neighbors were also detected. In 4H-SiC, a considerable spin density of ˜37.4% was found on three Si neighbors, suggesting the defect to be a complex between Nb and a nearby carbon vacancy (VC). Calculations of the 93Nb and 29Si hf constants of the neutral Nb on Si site, NbSi0, and the Nb-vacancy defect, NbSiVC0, support previous reported results that Nb preferentially forms an asymmetric split-vacancy (ASV) defect. In both 4H- and 6H-SiC, only one Nb-related EPR spectrum has been observed, supporting the prediction from calculations that the hexagonal-hexagonal defect configuration of the ASV complex is more stable than others.

  2. Simulation of Intra- or transboundary surface-water-rights hierarchies using the farm process for MODFLOW-2000

    USGS Publications Warehouse

    Schmid, W.; Hanson, R.T.

    2007-01-01

    Water-rights driven surface-water allocations for irrigated agriculture can be simulated using the farm process for MODFLOW-2000. This paper describes and develops a model, which simulates routed surface-water deliveries to farms limited by streamflow, equal-appropriation allotments, or a ranked prior-appropriation system. Simulated diversions account for deliveries to all farms along a canal according to their water-rights ranking and for conveyance losses and gains. Simulated minimum streamflow requirements on diversions help guarantee supplies to senior farms located on downstream diverting canals. Prior appropriation can be applied to individual farms or to groups of farms modeled as "virtual farms" representing irrigation districts, irrigated regions in transboundary settings, or natural vegetation habitats. The integrated approach of jointly simulating canal diversions, surface-water deliveries subject to water-rights constraints, and groundwater allocations is verified on numerical experiments based on a realistic, but hypothetical, system of ranked virtual farms. Results are discussed in light of transboundary water appropriation and demonstrate the approach's suitability for simulating effects of water-rights hierarchies represented by international treaties, interstate stream compacts, intrastate water rights, or ecological requirements. ?? 2007 ASCE.

  3. Electrical and optical properties of stacking faults introduced by plastic deformation in 4H-SiC

    NASA Astrophysics Data System (ADS)

    Pichaud, B.; Regula, G.; Yakimov, E. B.

    2014-02-01

    The electrical and optical properties of stacking faults (SFs) introduced by plastic deformation in 4H-SiC were studied by Electron Beam Induced Current (EBIC) and cathodoluminescence (CL) methods. Partial dislocations and stacking faults in the (0001) glide planes perpendicular to the surface were introduced in n-type 4H-SiC under a well-controlled state of stress by cantilever bending at 550°C. CL measurements allow determining the multiplicity of the SFs (single or double). It is observed that the overwhelming majority of stacking faults are double Shockley type SFs (CL emission at 504 nm) that correlates well with previously published high resolution transmission electron microscopy (HRTEM) investigations. However, single Shockley type SFs (CL emission at 422 nm) of much smaller lengths are also observed in some areas near the scratched region from where the defects are nucleated. This suggests that the velocity of partial dislocation pairs under a given applied stress could be higher than that of single partial dislocations. It is also shown that in the EBIC mode, SFs produce a strong bright contrast, which can be explained by considering the SFs in 4H-SiC to be quantum wells of II type.

  4. Growth and surface analysis of SiO2 on 4H-SiC for MOS devices

    NASA Astrophysics Data System (ADS)

    Kodigala, Subba Ramaiah; Chattopadhyay, Somnath; Overton, Charles; Ardoin, Ira; Gordon, B. J.; Johnstone, D.; Roy, D.; Barone, D.

    2015-03-01

    The SiO2 layers have been grown onto C-face and Si-face 4H-SiC substrates by two different techniques such as wet thermal oxidize process and sputtering. The deposition recipes of these techniques are carefully optimized by trails and error method. The growth effects of SiO2 on the C-face and Si-face 4H-SiC substrates are thoroughly investigated by AFM analysis. The growth mechanism of different species involved in the growth process of SiO2 by wet thermal oxide is now proposed by adopting two body classical projectile scattering. This mechanism drives to determine growth of secondary phases such as α-CH nano-islands in the grown SiO2 layer. The effect of HF etchings on the SiO2 layers grown by both techniques and on both the C-face and Si-face substrates are legitimately studied. The thicknesses of the layers determined by AFM and ellipsometry techniques are widely promulgated. The MOS capacitors are made on the Si-face 4H-SiC wafers by wet oxidation and sputtering processes, which are studied by capacitance versus voltage (CV) technique. From CV measurements, the density of trap states with variation of trap level for MOS devices is estimated.

  5. Electrical and optical properties of stacking faults introduced by plastic deformation in 4H-SiC

    SciTech Connect

    Pichaud, B.; Regula, G.; Yakimov, E. B.

    2014-02-21

    The electrical and optical properties of stacking faults (SFs) introduced by plastic deformation in 4H-SiC were studied by Electron Beam Induced Current (EBIC) and cathodoluminescence (CL) methods. Partial dislocations and stacking faults in the (0001) glide planes perpendicular to the surface were introduced in n-type 4H-SiC under a well-controlled state of stress by cantilever bending at 550°C. CL measurements allow determining the multiplicity of the SFs (single or double). It is observed that the overwhelming majority of stacking faults are double Shockley type SFs (CL emission at 504 nm) that correlates well with previously published high resolution transmission electron microscopy (HRTEM) investigations. However, single Shockley type SFs (CL emission at 422 nm) of much smaller lengths are also observed in some areas near the scratched region from where the defects are nucleated. This suggests that the velocity of partial dislocation pairs under a given applied stress could be higher than that of single partial dislocations. It is also shown that in the EBIC mode, SFs produce a strong bright contrast, which can be explained by considering the SFs in 4H-SiC to be quantum wells of II type.

  6. Evaluation of sintering effects on SiC incorporated UO2 kernels under Ar and Ar-4%H2 environments

    SciTech Connect

    Silva, Chinthaka M; Lindemer, Terrence; Hunt, Rodney Dale; Collins, Jack Lee; Terrani, Kurt A; Snead, Lance Lewis

    2013-01-01

    Silicon carbide (SiC) is suggested as an oxygen getter in UO2 kernels used for TRISO particle fuels to lower oxygen potential and prevent kernel migration during irradiation. Scanning electron microscopy and X-ray diffractometry analyses performed on sintered kernels verified that internal gelation process can be used to incorporate SiC in urania fuel kernels. Sintering in either Ar or Ar-4%H2 at 1500 C lowered the SiC content in the UO2 kernels to some extent. Formation of UC was observed as the major chemical phase in the process, while other minor phases such as U3Si2C2, USi2, U3Si2, and UC2 were also identified. UC formation was presumed to be occurred by two reactions. The first was the SiC reaction with its protective SiO2 oxide layer on SiC grains to produce volatile SiO and free carbon that subsequently reacted with UO2 to form UC. The second process was direct UO2 reaction with SiC grains to form SiO, CO, and UC, especially in Ar-4%H2. A slightly higher density and UC content was observed in the sample sintered in Ar-4%H2, but the use of both atmospheres produced kernels with ~95% of theoretical density. It is suggested that incorporating CO in the sintering gas would prevent UC formation and preserve the initial SiC content.

  7. The Virtual Reference Librarian's Handbook.

    ERIC Educational Resources Information Center

    Lipow, Anne Grodzins

    This book is a practical guide to librarians and their administrators who are thinking about or in the early stages of providing virtual reference service. Part 1, "The Decision to Go Virtual," provides a context for thinking about virtual reference, including the benefits and problems, getting in the virtual frame of mind, and shopping for…

  8. Jefferson Lab Virtual Tour

    SciTech Connect

    2013-07-13

    Take a virtual tour of the campus of Thomas Jefferson National Accelerator Facility. You can see inside our two accelerators, three experimental areas, accelerator component fabrication and testing areas, high-performance computing areas and laser labs.

  9. Nuevo Observatorio Virtual Argentino

    NASA Astrophysics Data System (ADS)

    Tissera, P. B.

    We summarized the main events in the creation of the Nuevo Observatorio Virtual Argentino (NOVA) and its objectives. We also discuss the present advances and the goals for the near future. FULL TEXT IN SPANISH

  10. Virtual Organizations: An Overview

    NASA Astrophysics Data System (ADS)

    Nami, Mohammad Reza

    The need to remain competitive in the open market forces companies to concentrate on their core competencies while searching for alliances when additional skills or resources are needed to fulfill business opportunities. The changing business situation of companies and customer needs have motivated researchers to introduce Virtual Organization (VO) idea. A Virtual Organization is always a form of partnership and managing partners and handling partnerships are crucial. Virtual organizations are defined as a temporary collection of enterprises that cooperate and share resources, knowledge, and competencies to better respond to business opportunities. This paper presents base concepts of virtual organizations including properties, management concepts, operational concepts, and main issues in collaboration such as security and authentication.

  11. ISIS Workshops Using Virtualization

    NASA Astrophysics Data System (ADS)

    Becker, K. J.; Becker, T. L.

    2015-06-01

    ISIS workshops are now using virtualization technology to improve the user experience and create a stable, consistent and useful ISIS installation for educational purposes as well as future processing needs.

  12. Going Virtual, Getting Real.

    ERIC Educational Resources Information Center

    Alford, Randall J.

    1999-01-01

    Presents an account of how one company went completely virtual--no office at all--and reaped the eventual rewards. Describes implementation processes, communication challenges, and customer reactions. (JOW)

  13. Jefferson Lab Virtual Tour

    ScienceCinema

    None

    2016-07-12

    Take a virtual tour of the campus of Thomas Jefferson National Accelerator Facility. You can see inside our two accelerators, three experimental areas, accelerator component fabrication and testing areas, high-performance computing areas and laser labs.

  14. Virtual Reality Lab Assistant

    NASA Technical Reports Server (NTRS)

    Saha, Hrishikesh; Palmer, Timothy A.

    1996-01-01

    Virtual Reality Lab Assistant (VRLA) demonstration model is aligned for engineering and material science experiments to be performed by undergraduate and graduate students in the course as a pre-lab simulation experience. This will help students to get a preview of how to use the lab equipment and run experiments without using the lab hardware/software equipment. The quality of the time available for laboratory experiments can be significantly improved through the use of virtual reality technology.

  15. NASA New Virtual Airport

    NASA Technical Reports Server (NTRS)

    1995-01-01

    NASA's Virtual Airport Tower is located at the Ames Research Center, Moffett Field, California. The Virtual Airport Tower's two-story structure is a full-scale, highly sophisticated simulation facility that will emulate Level 5 air traffic control towers and the busiest airports. It provides the platform to conduct in-depth human factors studies with quantifiable results using actual air traffic controllers, airline dispatchers and airport managers.

  16. 29 CFR 780.156 - Transportation of farm products from the fields or farm.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... on a farm as an incident to or in conjunction with the farming operations of that farmer or that farm...” farming operations are also within section 3(f). These principles have been recognized by the courts...

  17. 29 CFR 780.156 - Transportation of farm products from the fields or farm.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... on a farm as an incident to or in conjunction with the farming operations of that farmer or that farm...” farming operations are also within section 3(f). These principles have been recognized by the courts...

  18. The Virtual Observatory: I

    NASA Astrophysics Data System (ADS)

    Hanisch, R. J.

    2014-11-01

    The concept of the Virtual Observatory arose more-or-less simultaneously in the United States and Europe circa 2000. Ten pages of Astronomy and Astrophysics in the New Millennium: Panel Reports (National Academy Press, Washington, 2001), that is, the detailed recommendations of the Panel on Theory, Computation, and Data Exploration of the 2000 Decadal Survey in Astronomy, are dedicated to describing the motivation for, scientific value of, and major components required in implementing the National Virtual Observatory. European initiatives included the Astrophysical Virtual Observatory at the European Southern Observatory, the AstroGrid project in the United Kingdom, and the Euro-VO (sponsored by the European Union). Organizational/conceptual meetings were held in the US at the California Institute of Technology (Virtual Observatories of the Future, June 13-16, 2000) and at ESO Headquarters in Garching, Germany (Mining the Sky, July 31-August 4, 2000; Toward an International Virtual Observatory, June 10-14, 2002). The nascent US, UK, and European VO projects formed the International Virtual Observatory Alliance (IVOA) at the June 2002 meeting in Garching, with yours truly as the first chair. The IVOA has grown to a membership of twenty-one national projects and programs on six continents, and has developed a broad suite of data access protocols and standards that have been widely implemented. Astronomers can now discover, access, and compare data from hundreds of telescopes and facilities, hosted at hundreds of organizations worldwide, stored in thousands of databases, all with a single query.

  19. VIRTUAL FRAME BUFFER INTERFACE

    NASA Technical Reports Server (NTRS)

    Wolfe, T. L.

    1994-01-01

    Large image processing systems use multiple frame buffers with differing architectures and vendor supplied user interfaces. This variety of architectures and interfaces creates software development, maintenance, and portability problems for application programs. The Virtual Frame Buffer Interface program makes all frame buffers appear as a generic frame buffer with a specified set of characteristics, allowing programmers to write code which will run unmodified on all supported hardware. The Virtual Frame Buffer Interface converts generic commands to actual device commands. The virtual frame buffer consists of a definition of capabilities and FORTRAN subroutines that are called by application programs. The virtual frame buffer routines may be treated as subroutines, logical functions, or integer functions by the application program. Routines are included that allocate and manage hardware resources such as frame buffers, monitors, video switches, trackballs, tablets and joysticks; access image memory planes; and perform alphanumeric font or text generation. The subroutines for the various "real" frame buffers are in separate VAX/VMS shared libraries allowing modification, correction or enhancement of the virtual interface without affecting application programs. The Virtual Frame Buffer Interface program was developed in FORTRAN 77 for a DEC VAX 11/780 or a DEC VAX 11/750 under VMS 4.X. It supports ADAGE IK3000, DEANZA IP8500, Low Resolution RAMTEK 9460, and High Resolution RAMTEK 9460 Frame Buffers. It has a central memory requirement of approximately 150K. This program was developed in 1985.

  20. Farm-Size Structure and Off-Farm Income and Employment Generation in the North Central Region.

    ERIC Educational Resources Information Center

    Heady, Earl O.; Sonka, Steven T.

    The relationship between size of farm and the welfare of farm and nonfarm society was examined in terms of total income in the farm sector, the number and size of farms, income per farm, secondary income generation, and consumer food costs using four alternative farm structures: large farm (gross farm sales of at least $40,000); medium farm (gross…

  1. Whole Farm Nutrient Balance Calculator for New York Dairy Farms

    ERIC Educational Resources Information Center

    Soberon, Melanie A.; Ketterings, Quirine M.; Rasmussen, Caroline N.; Czymmek, Karl J.

    2013-01-01

    Nutrient loss and accumulation as well as associated environmental degradation have been a concern for animal agriculture for many decades. Federal and New York (NY) regulations apply to Concentrated Animal Feeding Operations and a comprehensive nutrient management plan (CNMP) is required for regulated farms. The whole farm nutrient mass balance…

  2. Economic Indicators of the Farm Sector. Farm Sector Review, 1985.

    ERIC Educational Resources Information Center

    Economic Research Service (USDA), Washington, DC.

    Farm production rose 6 percent in 1985 due to record high yields in corn, soybeans, cotton, and several other crops. While United States consumption increased slightly, exports of farm products fell 23 percent in value and 19 percent in volume. Net cash income increased 12 percent due to increased output, lower cash expenses, and unusually high…

  3. In Uzbekistan, Is It Farm Management or FARM "Management?"

    ERIC Educational Resources Information Center

    Long, James S.; Luery, Andrea

    A broad spectrum of stakeholders in Uzbekistan were interviewed to identify areas in which Winrock International's Farmer-to-Farmer program volunteers could be targeted to help Uzbeks complete the transition to privatized farms. The interviews revealed that Uzbeks have a much broader conception of the "farm" than do people in Western countries and…

  4. Farm Household Survival Strategies and Diversification on Marginal Farms

    ERIC Educational Resources Information Center

    Meert, H.; Van Huylenbroeck, G.; Vernimmen, T.; Bourgeois, M.; van Hecke, E.

    2005-01-01

    On marginal farms, and in agriculture in general, sustainability is largely guaranteed by a broad range of survival strategies, closely interlinked and embedded in the household structure of typical family farms. This paper reports results of a socio-economic study carried out among Belgian farmers, focusing specifically on the opportunities…

  5. Wind Farm Feasibility Study

    SciTech Connect

    Richard Curry; Erik Foley; DOE Project Officer - Keith Bennett

    2007-07-11

    Saint Francis University has assessed the Swallow Farm property located in Shade Township, Somerset County, Pennsylvania as a potential wind power development site. Saint Francis worked with McLean Energy Partners to have a 50-meter meteorological tower installed on the property in April 2004 and continues to conduct a meteorological assessment of the site. Results suggest a mean average wind speed at 80 meters of 17 mph with a net capacity factor of 31 - 33%. Approximate electricity generation capacity of the project is 10 megawatts. Also, the University used matching funds provided by the federal government to contract with ABR, Inc. to conduct radar studies of nocturnal migration of birds and bats during the migrations seasons in the Spring and Fall of 2005 with a mean nocturnal flight altitude of 402 meters with less than 5% of targets at altitudes of less than 125 meters. The mean nocturnal passage rate was 166 targets/km/h in the fall and 145 targets/km/h in the spring. Lastly, University faculty and students conducted a nesting bird study May - July 2006. Seventy-three (73) species of birds were observed with 65 determined to be breeding or potentially breeding species; this figure represents approximately 30% of the 214 breeding bird species in Pennsylvania. No officially protected avian species were determined to be nesting at Swallow Farm.

  6. Part-time Farming: Saving the Farm or Saving the Life-style?

    ERIC Educational Resources Information Center

    Barlett, Peggy F.

    1986-01-01

    Study of part-time farmers in a Georgia county examines mobility patterns, economic circumstances, scale of farming, reasons for part-time farming, commitment to farm, household division of labor, and impact of current farm crisis. Finds most part-time farmers obtained stable off-farm jobs, then added farms later in their adult years. (LFL)

  7. Virtual water balance estimation in Tunisia

    NASA Astrophysics Data System (ADS)

    Stambouli, Talel; Benalaya, Abdallah; Ghezal, Lamia; Ali, Chebil; Hammami, Rifka; Souissi, Asma

    2015-04-01

    concept integration in the production systems choice and policies affecting the use of water is very useful to save over this scarce resource and to support farmers in their production activities and maintaining the sustainability of farms. Keywords: Virtual water, water balance, irrigation, Tunisia

  8. Visit a Farm? Surely Not!

    ERIC Educational Resources Information Center

    Graham, Bill

    2012-01-01

    Popular myth has it that visiting a farm can be dangerous, but there are only a few occasions when children have become ill during a school visit to a farm. Simple, sensible precautions, including wearing appropriate clothing, such as trousers and wellington boots (if wet) or sensible shoes, and careful hand-washing, are all that is required. The…

  9. Electrocution Hazards on the Farm

    MedlinePlus

    ... by overhead power lines, standby generators, and general operating procedures of electrical systems at the farm work site. Electrocution hazards The ... electricity generated by a farm operation’s emergency power system from entering the ... operating precautions, equipment can come in contact with electrical ...

  10. Food and farm products surveillance

    SciTech Connect

    Poston, T.M.

    1995-06-01

    This section of the 1994 Hanford Site Environmental Report summarizes the radiological analyses performed on food and farm samples collected during 1994. The food and farm sampling design addresses the potential influence of Hanford Site releases. Details of the sampling design and radionuclides analyzed are included in this section.

  11. Virtual data in CMS production

    SciTech Connect

    Arbree, A. et al.

    2004-08-26

    Initial applications of the GriPhyN Chimera Virtual Data System have been performed within the context of CMS Production of Monte Carlo Simulated Data. The GriPhyN Chimera system consists of four primary components: (1) a Virtual Data Language, which is used to describe virtual data products, (2) a Virtual Data Catalog, which is used to store virtual data entries, (3) an Abstract Planner, which resolves all dependencies of a particular virtual data product and forms a location and existence independent plan, (4) a Concrete Planner, which maps an abstract, logical plan onto concrete, physical grid resources accounting for staging in/out files and publishing results to a replica location service. A CMS Workflow Planner, MCRunJob, is used to generate virtual data products using the Virtual Data Language. Subsequently, a prototype workflow manager, known as WorkRunner, is used to schedule the instantiation of virtual data products across a grid.

  12. Etching Characteristics of ZnO and Al-Doped ZnO in Inductively Coupled Cl2/CH4/H2/Ar and BCl3/CH4/H2/Ar Plasmas

    NASA Astrophysics Data System (ADS)

    Lee, Hack Joo; Kwon, Bong Soo; Kim, Hyun Woo; Kim, Seon Il; Yoo, Dong-Geun; Boo, Jin-Hyo; Lee, Nae-Eung

    2008-08-01

    ZnO and Al-doped ZnO (AZO) were etched in Cl2/CH4/H2/Ar (Cl2-based) and BCl3/CH4/H2/Ar (BCl3-based), inductively coupled plasmas (ICPs) and their etching characteristics were compared by varying the Cl2/(Cl2+CH4) and BCl3/(BCl3+CH4) flow ratios, top electrode power and dc self-bias voltage (Vdc). The etch rates of both ZnO and AZO layers were higher in the Cl2-based chemistry than in the BCl3-based chemistry. The AZO and ZnO etch rates were increased and decreased, respectively, with increasing Cl2 or BCl3 flow ratio. Optical emission measurements of the radical species in the plasma and surface binding states by optical emission spectroscopy (OES) and X-ray photoelectron spectroscopy (XPS), respectively, indicated that, with increasing Cl2 or BCl3 flow ratio; the effective removal of Al in the AZO enhanced the AZO etch rate, whereas the reduced removal of Zn by the Zn(CHx)y products reduced the ZnO etch rate.

  13. Verification of Fowler-Nordheim electron tunneling mechanism in Ni/SiO2/n-4H SiC and n+ poly-Si/SiO2/n-4H SiC MOS devices by different models

    NASA Astrophysics Data System (ADS)

    Kodigala, Subba Ramaiah

    2016-11-01

    This article emphasizes verification of Fowler-Nordheim electron tunneling mechanism in the Ni/SiO2/n-4H SiC MOS devices by developing three different kinds of models. The standard semiconductor equations are categorically solved to obtain the change in Fermi energy level of semiconductor with effect of temperature and field that extend support to determine sustainable and accurate tunneling current through the oxide layer. The forward and reverse bias currents with variation of electric field are simulated with help of different models developed by us for MOS devices by applying adequate conditions. The latter is quite different from former in terms of tunneling mechanism in the MOS devices. The variation of barrier height with effect of quantum mechanical, temperature, and fields is considered as effective barrier height for the generation of current-field (J-F) curves under forward and reverse biases but quantum mechanical effect is void in the latter. In addition, the J-F curves are also simulated with variation of carrier concentration in the n-type 4H SiC semiconductor of MOS devices and the relation between them is established.

  14. Structure, ferroelectric ordering, and semiempirical quantum calculations of lanthanide based metal-organic framework: [Nd(C4H5O6)(C4H4O6)][3H2O

    NASA Astrophysics Data System (ADS)

    Ahmad, Bhat Zahoor; Want, Basharat

    2016-04-01

    We investigate the structure and ferroelectric behavior of a lanthanide based metal-organic framework (MOF), [Nd(C4H5O6)(C4H4O6)][3H2O]. X-ray crystal structure analyses reveal that it crystallizes in the P41212 space group with Nd centres, coordinated by nine oxygen atoms, forming a distorted capped square antiprismatic geometry. The molecules, bridged by tartrate ligands, form a 2D chiral structure. The 2D sheets are further linked into a 3D porous framework via strong hydrogen-bonding scheme (O-H…O ≈ 2.113 Å). Dielectric studies reveal two anomalies at 295 K and 185 K. The former is a paraelectric-ferroelectric transition, and the later is attributed to the freezing down of the motion of the hydroxyl groups. The phase transition is of second order, and the spontaneous polarization in low temperature phase is attributed to the ordering of protons of hydroxyl groups. The dielectric nonlinearity parameters have been calculated using Landau- Devonshire phenomenological theory. In addition, the most recent semiempirical models, Sparkle/PM7, Sparkle/RM1, and Sparkle/AM1, are tested on the present system to assay the accuracy of semiempirical quantum approaches to predict the geometries of solid MOFs. Our results show that Sparkle/PM7 model is the most accurate to predict the unit cell structure and coordination polyhedron geometry. The semiempirical methods are also used to calculate different ground state molecular properties.

  15. Livestock farming and atmospheric emissions.

    PubMed

    Zicari, Giuseppe; Soardo, Vincenzo; Rivetti, Daniela; Cerrato, Elena; Russo, Domenico

    2013-01-01

    Livestock farming produces atmospheric emissions that may pose a risk to workers and a disturbance to the population. Emissions into the atmosphere produced by livestock farming consist of gases such as ammonia, dust, compounds such as aliphatic hydrocarbons and bio-aerosols formed by microorganisms. Some gases, such as ammonia and hydrogen sulphide, have foul odours and are thus potentially annoying to the population. Gaseous or volatile molecules produced by livestock installations and related activities may have several adverse effects on health and environment. The most significant exposure certainly relates to workers in the confined spaces of farms, rather than to residents in the surrounding areas. In this article we examine potential hazards to farm workers and to the population living in the vicinity of livestock farms, arising from emissions into the atmosphere.

  16. Varieties of virtualization

    NASA Technical Reports Server (NTRS)

    Ellis, Stephen R.

    1991-01-01

    Natural environments have a content, i.e., the objects in them; a geometry, i.e., a pattern of rules for positioning and displacing the objects; and a dynamics, i.e., a system of rules describing the effects of forces acting on the objects. Human interaction with most common natural environments has been optimized by centuries of evolution. Virtual environments created through the human-computer interface similarly have a content, geometry, and dynamics, but the arbitrary character of the computer simulation creating them does not insure that human interaction with these virtual environments will be natural. The interaction, indeed, could be supernatural but it also could be impossible. An important determinant of the comprehensibility of a virtual environment is the correspondence between the environmental frames of reference and those associated with the control of environmental objects. The effects of rotation and displacement of control frames of reference with respect to corresponding environmental references differ depending upon whether perceptual judgement or manual tracking performance is measured. The perceptual effects of frame of reference displacement may be analyzed in terms of distortions in the process of virtualizing the synthetic environment space. The effects of frame of reference displacement and rotation have been studied by asking subjects to estimate exocentric direction in a virtual space.

  17. Coniochaetones E-I, new 4H-chromen-4-one derivatives from the Cordyceps-colonizing fungus Fimetariella sp.

    PubMed

    Deng, Lianwu; Niu, Shubing; Liu, Xingzhong; Che, Yongsheng; Li, Erwei

    2013-09-01

    Five new 4H-chromen-4-one derivatives coniochaetones E-I (1-5), along with the known compounds coniochaetones B (6) and A (7) have been isolated from solid cultures of the Cordyceps-colonizing fungus Fimetariella sp. Their structures were elucidated primarily by NMR spectroscopy and the absolute configurations of compounds 1-3 were assigned using the modified Mosher's method. Compound 4 showed weak cytotoxic activity against HeLa cells with IC50 values of 72.8 μM. The co-isolated known compound 6 showed modest inhibitory effects against Aspergilus fumigates, Fusarium oxysporum and Fusarium nivale. PMID:23685047

  18. Report on the 4-h rule and National Emergency Access Target (NEAT) in Australia: time to review.

    PubMed

    Staib, Andrew; Sullivan, Clair; Griffin, Bronwyn; Bell, Anthony; Scott, Ian

    2016-06-01

    Objective The aim of the present study was to provide a summary of a systematic review of literature reporting benefits and limitations of implementing National Emergency Access Target (NEAT), a target stipulating that a certain proportion of patients presenting to hospital emergency departments are admitted or discharged within 4h of presentation. Methods A systematic review of published literature using specific search terms, snowballing techniques applied to retrieved references and Google searches was performed. Results are presented as a narrative synthesis given the heterogeneity of included studies. Results Benefits of a time-based target for emergency care are improved timeliness of emergency care and reduced in-hospital mortality for emergency admissions to hospital. Limitations centre on using a process measure (time) alone devoid of any monitoring of patient outcomes, the threshold nature of a time target and the fact that currently NEAT combines the measurement of clinical management of two very different patient cohorts seeking emergency care: less acute patients discharged home and more acute patients admitted to hospital. Conclusions Time-based access targets for emergency presentations are associated with significant improvements in in-hospital mortality for emergency admissions. However, other patient-important outcomes are deserving of attention, choice of targets needs to be validated by empirical evidence of patient benefit and single targets need to be partitioned into separate targets pertaining to admitted and discharged patients. What is known about the topic? Time targets for emergency care originated in the UK. The introduction of NEAT in Australia has been controversial. NEAT directs that a certain proportion of patients will be admitted or discharged from an emergency department (ED) within 4h. Recent dissolution of the Australian National Partnership Agreement (which provided hospitals with financial incentives for achieving NEAT

  19. Infrared band extinctions and complex refractive indices of crystalline C2H2 and C4H2

    NASA Technical Reports Server (NTRS)

    Khanna, R. K.; Ospina, Mario J.; Zhao, Guizhi

    1988-01-01

    Thermal IR absorption intensities are obtained for thin films of crystalline C2H2 and C4H2 at 70 K, and their n and k complex refractive indices are ascertained by separating true film absorption from interface reflection on the basis of an analysis of the transmission spectrum ratio for two sample thicknesses. This method significantly simplifies the n and k iteration process. The n and k values determined in the laboratory will in most cases reproduce a given sample thickness' observed transmission to within + or - 5 percent.

  20. Calorimetric and computational study of 2H-1, 4-benzoxazin-3(4H)-one and of related species

    NASA Astrophysics Data System (ADS)

    Agostinha, M.; Matos, R.; Miranda, Margarida S.; Morais, Victor M. F.; Liebman, Joel F.

    The standard molar enthalpy of formation in the gas phase of 2H-1,4-benzoxazin-3(4H)-one was derived from the standard energy of combustion determined by static bomb combustion calorimetry in oxygen atmosphere and from the standard sublimation enthalpy determined by Calvet microcalorimetry. In addition, we report the results of a systematic theoretical study of the keto and enol tautomers in benzoxazinones and diones using density functional theory. The keto tautomers are computed to be more stable than the enols. Tautomerization energies are reported.

  1. Tunneling Atomic Force Microscopy Studies on Surface Growth Pits Due to Dislocations in 4H-SiC Epitaxial Layers

    NASA Astrophysics Data System (ADS)

    Ohtani, Noboru; Ushio, Shoji; Kaneko, Tadaaki; Aigo, Takashi; Katsuno, Masakazu; Fujimoto, Tatsuo; Ohashi, Wataru

    2012-08-01

    The morphological and electrical properties of surface growth pits caused by dislocations in 4H-SiC epitaxial layers were characterized using tunneling atomic force microscopy. The characteristic distribution of the tip current between the metal-coated atomic force microscopy tip and the SiC was observed within a large surface growth pit caused by a threading screw dislocation. The current was highly localized inside the pit and occurred only on the inclined surface in the up-step direction near the pit bottom. This paper discusses the causes and possible mechanisms of the observed tip current distribution inside surface growth pits.

  2. Electrical Characteristics of Ni-CNT-SiO2-SiC Structured 4H-SiC MIS Capacitors.

    PubMed

    Lee, Taeseop; Kang, Min-Seok; Ha, Tae-Jun; Koo, Sang-Mo

    2015-10-01

    In this study, the electrical characteristics of Ni-CNT-SiO2-SiC structured 4H-SiC MIS capacitors were investigated. The effect of CNTs in the gate/insulator interface have been characterized by C-V measurement at 300 to 500K and J-V have also been measured. The experimental flat-band voltage tends to change with or without CNTs. Current densities of both devices are observed a negligible difference up to 3 V. It has been found that adding CNTs and/or change of temperature can help to control the positive and/or negative flat-band voltage shift.

  3. Growth of Shockley type stacking faults upon forward degradation in 4H-SiC p-i-n diodes

    NASA Astrophysics Data System (ADS)

    Tanaka, Atsushi; Matsuhata, Hirofumi; Kawabata, Naoyuki; Mori, Daisuke; Inoue, Kei; Ryo, Mina; Fujimoto, Takumi; Tawara, Takeshi; Miyazato, Masaki; Miyajima, Masaaki; Fukuda, Kenji; Ohtsuki, Akihiro; Kato, Tomohisa; Tsuchida, Hidekazu; Yonezawa, Yoshiyuki; Kimoto, Tsunenobu

    2016-03-01

    The growth of Shockley type stacking faults in p-i-n diodes fabricated on the C-face of 4H-SiC during forward current operation was investigated using Berg-Barrett X-ray topography and photoluminescence imaging. After forward current experiment, Shockley type stacking faults were generated from very short portions of basal plane dislocations lower than the conversion points to threading edge dislocations in the epitaxial layer. The growth behavior of Shockley type stacking faults was discussed. Growth of stacking faults in the substrates was not observed.

  4. High current (1300 A) optical triggering of a 12 kV 4H-SiC thyristor

    NASA Astrophysics Data System (ADS)

    Rumyantsev, S. L.; Levinshtein, M. E.; Shur, M. S.; Cheng, L.; Agarwal, A. K.; Palmour, J. W.

    2013-04-01

    Optical triggering of a high-voltage (12 kV class) 4H-SiC thyristor to a current Imax = 1300 A is demonstrated. An amplification step (pilot thyristor) and a mixed resistive-inductive load are used to reduce the current ramp dI/dt. The results obtained show that a decrease in the current density at the end of the first, fastest phase of the switch-on process can be achieved either by improving the homogeneity of the initially turned-on region or by introducing additional amplification steps.

  5. Characterization of 100 mm Diameter 4H-Silicon Carbide CrystalsWith Extremely Low Basal Plane Dislocation Density

    SciTech Connect

    M Dudley; N Zhang; Y Zhang; B Raghothamachar; S Byrappa; G Choi; E Drachev; M Loboda

    2011-12-31

    Synchrotron White Beam X-ray Topography (SWBXT) studies are presented of basal plane dislocation (BPD) configurations and behavior in a new generation of 100mm diameter, 4H-SiC wafers with extremely low BPD densities (3-4 x 10{sup 2} cm{sup -2}). The conversion of non-screw oriented, glissile BPDs into sessile threading edge dislocations (TEDs) is observed to provide pinning points for the operation of single ended Frank-Read sources. In some regions, once converted TEDs are observed to re-convert back into BPDs in a repetitive process which provides multiple BPD pinning points.

  6. Electrical Characterization of 4H-SiC JFET Wafer: DC Parameter Variations for Extreme Temperature IC Design

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.; Chen, Liangyu; Spry, David J.; Beheim, Glenn M.; Chang, Carl W.

    2014-01-01

    This work reports DC electrical characterization of a 76 mm diameter 4H-SiC JFET test wafer fabricated as part of NASA's on-going efforts to realize medium-scale ICs with prolonged and stable circuit operation at temperatures as high as 500 degC. In particular, these measurements provide quantitative parameter ranges for use in JFET IC design and simulation. Larger than expected parameter variations were observed both as a function of position across the wafer as well as a function of ambient testing temperature from 23 degC to 500 degC.

  7. Design and fabrication of a 3.3 kV 4H-SiC MOSFET

    NASA Astrophysics Data System (ADS)

    Runhua, Huang; Yonghong, Tao; Song, Bai; Gang, Chen; Ling, Wang; Ao, Liu; Neng, Wei; Yun, Li; Zhifei, Zhao

    2015-09-01

    A 4H-SiC MOSFET with breakdown voltage higher than 3300 V has been successfully designed and fabricated. Numerical simulations have been performed to optimize the parameters of the drift layer and DMOSFET cell structure of active area. The n-type epilayer is 33 μm thick with a doping of 2.5 × 1015 cm-3. The devices were fabricated with a floating guard ring edge termination. The drain current Id = 5 A at Vg = 20 V, corresponding to Vd = 2.5 V. Project supported by the National High Technology Research and Development Program of China (No. 2014AA052401).

  8. Effect of 3.0 MeV helium implantation on electrical characteristics of 4H-SiC BJTs

    NASA Astrophysics Data System (ADS)

    Usman, Muhammad; Hallén, Anders; Ghandi, Reza; Domeij, Martin

    2010-11-01

    Degradation of 4H-SiC power bipolar junction transistors (BJTs) under the influence of a high-energy helium ion beam was studied. Epitaxially grown npn BJTs were implanted with 3.0 MeV helium in the fluence range of 1010-1011 cm-2. The devices were characterized by their current-voltage (I-V) behaviour before and after the implantation, and the results showed a clear degradation of the output characteristics of the devices. Annealing these implanted devices increased the interface traps between passivation oxide and the semiconductor, resulting in an increase of base current in the low-voltage operation range.

  9. Dry etching of CdTe/GaAs epilayers using CH{sub 4}H{sub 2} gas mixtures

    SciTech Connect

    Neswal, M.; Gresslehner, K.H.; Lischka, K.

    1993-05-01

    A CH{sub 4}/H{sub 2} gas mixture has been used for the dry etching of (100) and (111) oriented CdTe epilayers in a barrel reactor. The effects of various process parameters on etch rate and surface morphology were studied with special attention paid to the gas composition and the total chamber pressure as well as the crystallographic orientation of the sample. Clear evidence is found for both isotropic and preferential etching along crystalolographic planes depending on the set of etch parameters used. 14 refs., 7 figs.

  10. Farm Hall: The Play

    NASA Astrophysics Data System (ADS)

    Cassidy, David C.

    2013-03-01

    It's July 1945. Germany is in defeat and the atomic bombs are on their way to Japan. Under the direction of Samuel Goudsmit, the Allies are holding some of the top German nuclear scientists-among them Heisenberg, Hahn, and Gerlach-captive in Farm Hall, an English country manor near Cambridge, England. As secret microphones record their conversations, the scientists are unaware of why they are being held or for how long. Thinking themselves far ahead of the Allies, how will they react to the news of the atomic bombs? How will these famous scientists explain to themselves and to the world their failure to achieve even a chain reaction? How will they come to terms with the horror of the Third Reich, their work for such a regime, and their behavior during that period? This one-act play is based upon the transcripts of their conversations as well as the author's historical work on the subject.

  11. High efficiency virtual impactor

    DOEpatents

    Loo, B.W.

    1980-03-27

    Environmental monitoring of atmospheric air is facilitated by a single stage virtual impactor for separating an inlet flow (Q/sub 0/) having particulate contaminants into a coarse particle flow (Q/sub 1/) and a fine particle flow (Q/sub 2/) to enable collection of such particles on different filters for separate analysis. An inlet particle acceleration nozzle and coarse particle collection probe member having a virtual impaction opening are aligned along a single axis and spaced apart to define a flow separation region at which the fine particle flow (Q/sub 2/) is drawn radially outward into a chamber while the coarse particle flow (Q/sub 1/) enters the virtual impaction opening.

  12. Intraoperative virtual brain counseling

    NASA Astrophysics Data System (ADS)

    Jiang, Zhaowei; Grosky, William I.; Zamorano, Lucia J.; Muzik, Otto; Diaz, Fernando

    1997-06-01

    Our objective is to offer online real-tim e intelligent guidance to the neurosurgeon. Different from traditional image-guidance technologies that offer intra-operative visualization of medical images or atlas images, virtual brain counseling goes one step further. It can distinguish related brain structures and provide information about them intra-operatively. Virtual brain counseling is the foundation for surgical planing optimization and on-line surgical reference. It can provide a warning system that alerts the neurosurgeon if the chosen trajectory will pass through eloquent brain areas. In order to fulfill this objective, tracking techniques are involved for intra- operativity. Most importantly, a 3D virtual brian environment, different from traditional 3D digitized atlases, is an object-oriented model of the brain that stores information about different brain structures together with their elated information. An object-oriented hierarchical hyper-voxel space (HHVS) is introduced to integrate anatomical and functional structures. Spatial queries based on position of interest, line segment of interest, and volume of interest are introduced in this paper. The virtual brain environment is integrated with existing surgical pre-planning and intra-operative tracking systems to provide information for planning optimization and on-line surgical guidance. The neurosurgeon is alerted automatically if the planned treatment affects any critical structures. Architectures such as HHVS and algorithms, such as spatial querying, normalizing, and warping are presented in the paper. A prototype has shown that the virtual brain is intuitive in its hierarchical 3D appearance. It also showed that HHVS, as the key structure for virtual brain counseling, efficiently integrates multi-scale brain structures based on their spatial relationships.This is a promising development for optimization of treatment plans and online surgical intelligent guidance.

  13. A Study of Changes in Dental Health Care Behavior of 4-H Youth in Selected Louisiana Parishes. R and T--Summary 51.

    ERIC Educational Resources Information Center

    Jones, Michael Alan

    The effectiveness of the Dental Hygiene Education Program in changing the dental health care practices of 4-H club youth in four Louisiana parishes and youth knowledge of dental care principles were studied in this before-after experimental design. The study sample consisted of 258 youth from 10 4-H clubs. Subjects completed a four-item…

  14. Development and Evaluation of an On-Line Educational Module for Volunteer Leaders on Bio-Security in Washington State 4-H Livestock Projects

    ERIC Educational Resources Information Center

    Stevenson, Jill L.; Moore, Dale A.; Newman, Jerry; Schmidt, Janet L.; Smith, Sarah M.; Smith, Jean; Kerr, Susan; Wallace, Michael; BoyEs, Pat

    2011-01-01

    A module on disease prevention was created for 4-H volunteer leaders who work with livestock projects in Washington to better prepare them to teach youth about bio-security and its importance in 4-H livestock projects. Evaluation of the module and usage statistics since the module's debut were collected and evaluated. The module increases…

  15. Development and Evaluation of an On-Line Educational Module for Volunteer Leaders on Bio-Security in Washington State 4-H Livestock Projects

    ERIC Educational Resources Information Center

    Stevenson, Jill L.; Moore, Dale A.; Newman, Jerry; Schmidt, Janet L.; Smith, Sarah M.; Smith, Jean; Kerr, Susan; Wallace, Michael; BoyEs, Pat

    2011-01-01

    An on-line module on disease prevention was created for 4-H volunteer leaders who work with livestock projects in Washington to better prepare them to teach youth about bio-security and its importance in 4-H livestock projects. Evaluation of the module and usage statistics since the module's debut were collected and evaluated. The module increases…

  16. Social Background, Personality and Attitudinal Factors Influencing the Decision to Volunteer and Level of Involvement among Adult 4-H Leaders. Summary of Research 39.

    ERIC Educational Resources Information Center

    Rohs, Frederick R.; Warmbrod, J. Robert

    A study was conducted to investigate, using a portion of Smith's Sequential Specificity Model, the relationship between social background, personality, and attitudinal factors and the participation of adult volunteers in the 4-H program in Ohio. Data were collected from a sample of 300 adult 4-H volunteers in Ohio through a mailed questionnaire; a…

  17. A Mixed Methods Case Study: Understanding the Experience of Nebraska 4-H Participants Relative to Their Transition and Adaptation to College

    ERIC Educational Resources Information Center

    Walahoski, Jill

    2013-01-01

    This mixed methods case study was designed to assess the preparedness of former Nebraska 4-H participants to successfully transition and adjust to college. The study also sought to understand the way that students' experiences in Nebraska 4-H may have influenced their readiness to transition to college. The initial quantitative stage of this…

  18. Carbon nanoscroll from C4H/C4F-type graphene superlattice: MD and MM simulation insights.

    PubMed

    Liu, Zilong; Xue, Qingzhong; Tao, Yehan; Li, Xiaofang; Wu, Tiantian; Jin, Yakang; Zhang, Zhongyang

    2015-02-01

    Morphology manipulation opens up a new avenue for controlling and tailoring the functional properties of graphene, enabling the exploration of graphene-based nanomaterials. Through mixing single-side-hydrogenated graphene (C4H) with fluorinated graphene (C4F) on one single sheet, the C4H/C4F-type graphene superlattices can self-scroll at room temperature. We demonstrate using molecular dynamic (MD) simulations that different proportions, sizes, directions of hydrogenation and fluorination, and geometry of graphene have a great influence on the self-scrolling of superlattices into a variety of well-defined carbon nanoscrolls (CNSs), thus providing a controllable approach to tune their structures. Based on molecular mechanics (MM) simulations, the CNSs bear more than eight times the radial pressure than that of their multiwalled carbon nanotube (MWNT) counterparts, and an excellent radial elasticity of CNSs is also shown. Compared with conventional CNSs, these novel CNSs are endowed with more ample and flexible heterogeneous structures due to the on-demand hydrogenation and fluorination. Besides, this work provides a feasible route to achieve the necessary electronic and optical changes to be applied in graphene device applications. PMID:25531924

  19. Nitrogen bridgehead compounds. 44. New antiallergic 4H-pyrido[1,2-a]pyrimidin-4-ones. 4.

    PubMed

    Hermecz, I; Horváth, A; Mészáros, Z; De Vos, C; Rodriguez, L

    1984-10-01

    The weak antiallergic activity of 6-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3-carbox yli c acid (1) in the rat reaginic passive cutaneous anaphylaxis test was enhanced by the introduction of an (arylamino)methylene moiety into position 9 of the pyridopyrimidine ring. Compound 34, (+)-6(S)-methyl-9-[(m-methylphenyl)-hydrazono]-4-oxo-4H-pyrido[1,2 -a] pyrimidine-3-carboxylic acid, displayed about 10 000 times the activity of the starting compound 1. A structure-activity relationship study of 9-[(arylamino)methylene]tetrahydropyridopyrimidine-3-carb ox ylic acids resulted in conclusions similar to those found for the 9-(arylhydrazono)tetrahydro-and 9-(arylamino)dihydropyridopyrimidine series. Replacement of the 3-carboxy group of 9-(phenylhydrazono)-tetrahydropyridopyrimidin-4-ones with an acrylic acid moiety caused slight increases in potency. In the 6-methyl-substituted series, a high stereospecificity was observed between the enantiomers with 6S and 6R absolute configurations, the former being responsible for the antiallergic activity. The effects of some 9-[(arylamino)-methylene]tetrahydropyridopyrimidine-3-car box ylic acids on the rat passive peritoneal anaphylaxis test were also investigated.

  20. Nitrogen bridgehead compounds. 38. New antiallergic 4H-pyrido[1,2-a]pyrimidin-4-ones. 3.

    PubMed

    Hermecz, I; Breining, T; Vasvári-Debreczy, L; Horváth, A; Mészáros, Z; Bitter, I; DeVos, C; Rodriguez, L

    1983-10-01

    The weak antiallergic activity of 6-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3-carboxylic acid (4) on the rat reaginic passive cutaneous anaphylaxis test was enhanced by the introduction of appropriate functional groups into position 9 of the pyridopyrimidine ring. The most active 9-substituted pyridopyrimidinecarboxylic acids contained an oxime, a phenylamino, or a (phenylamino)thioxomethyl group in position 9. The 9-phenylcarboxamido and 9-phenylhydrazono moieties may be regarded as bioisosteric groups in the pyridopyrimidinone series. In the series of 9-(arylamino)dihydropyridopyrimidines, the structure-activity relationship study revealed similar relationships as found for the 9-(arylhydrazono)tetrahydropyridopyrimidines. The biological activity was due to the 6S enantiomers. A monosubstituted arylamino moiety in position 9 was necessary for the intravenous activity. The most active compound, 9-[(3-acetylphenyl)amino]-6-methyl-4-oxo-6,7,8,9-tetrahydro-4H- pyrido[1,2-a]pyrimidine-3-carboxylic acid (40) was three times as active as the reference sodium chromoglycate (DSCG) in the passive cutaneous anaphylaxis (PCA) test.

  1. Investigation of current transport parameters of Ti/4H-SiC MPS diode with inhomogeneous barrier

    NASA Astrophysics Data System (ADS)

    Song, Qing-Wen; Zhang, Yu-Ming; Zhang, Yi-Men; Chen, Feng-Ping; Tang, Xiao-Yan

    2011-05-01

    The current transport parameters of 4H-SiC merged PiN Schottky (MPS) diode are investigated in a temperature range of 300-520 K. Evaluation of the experimental current-voltage (I—V) data reveals the decrease in Schottky barrier height Φb but an increase in ideality factor n, with temperature decreasing, which suggests the presence of an inhomogeneous Schottky barrier. The current transport behaviours are analysed in detail using the Tung's model and the effective area of the low barrier patches is extracted. It is found that small low barrier patches, making only 4.3% of the total contact, may significantly influence the device electrical characteristics due to the fact that a barrier height of 0.968 eV is much lower than the average barrier height 1.39 eV. This shows that ion implantation in the Schottky contact region of MPS structure may result in a poor Ti/4H-SiC interface quality. In addition, the temperature dependence of the specific on-resistance (Ron—sp), T2.14, is determined between 300 K and 520 K, which is similar to that predicted by a reduction in electron mobility.

  2. Synthesis, in vitro and in silico antimalarial activity of 7-chloroquinoline and 4H-chromene conjugates.

    PubMed

    Parthiban, A; Muthukumaran, J; Manhas, Ashan; Srivastava, Kumkum; Krishna, R; Rao, H Surya Prakash

    2015-10-15

    A new series of chloroquinoline-4H-chromene conjugates incorporating piperizine or azipane tethers were synthesized and their anti-malarial activity were evaluated against two Plasmodium falciparum strains namely 3D7 chloroquine sensitive (CQS) and K1 chloroquine resistant (CQR). Chloroquine was used as the standard and also reference for comparison. The conjugates exhibit intense UV absorption with λmax located at 342 nm (log ε=4.0), 254 nm (log ε=4.2), 223 nm (log ε=4.4) which can be used to spectrometrically track the molecules even in trace amounts. Among all the synthetic compounds, two molecules namely 6-nitro and N-piperazine groups incorporated 7d and 6-chloro and N-azapane incorporated 15b chloroquinoline-4H-chromene conjugates showed significant anti-malarial activity against two strains (3D7 and K1) of P. falciparum. These values are lesser than the values of standard antimalarial compound. Molecular docking results suggested that these two compounds showing strong binding affinity with P. falciparum lactate dehydrogenase (PfLDH) and also they occupy the co-factor position which indicated that they could be the potent inhibitors for dreadful disease malaria and specifically attack the glycolytic pathway in parasite for energy production. PMID:26338359

  3. Phospho-silicate glass gated 4H-SiC metal-oxide-semiconductor devices: Phosphorus concentration dependence

    NASA Astrophysics Data System (ADS)

    Jiao, C.; Ahyi, A. C.; Xu, C.; Morisette, D.; Feldman, L. C.; Dhar, S.

    2016-04-01

    The correlation between phosphorus concentration in phospho-silicate glass (PSG) gate dielectrics and electrical properties of 4H-SiC MOS devices has been investigated. Varying P uptake in PSG is achieved by changing the POCl3 post-oxidation annealing temperature. The density of interface traps (Dit) at the PSG/4H-SiC interface decreases as the amount of interfacial P increases. Most significantly, the MOSFET channel mobility does not correlate with Dit for all samples, which is highly unusual for SiC MOSFETs. Further analysis reveals two types of field-effect mobility (μfe) behavior, depending on the annealing temperature. Annealing at 1000 °C improves the channel mobility most effectively, with a peak value ˜105 cm2 V-1 s-1, and results in a surface phonon scattering limited mobility at high oxide field. On the other hand, PSG annealed at other temperatures results in a surface roughness scattering limited mobility at similar field.

  4. Effect of substitution group on dielectric properties of 4H-pyrano [3, 2-c] quinoline derivatives thin films

    NASA Astrophysics Data System (ADS)

    H, M. Zeyada; F, M. El-Taweel; M, M. El-Nahass; M, M. El-Shabaan

    2016-07-01

    The AC electrical conductivity and dielectrical properties of 2-amino-6-ethyl-5-oxo-4-(3-phenoxyphenyl)-5,6-dihydro-4H-pyrano[3, 2-c]quinoline-3-carbonitrile (Ph-HPQ) and 2-amino-4-(2-chlorophenyl)-6-ethyl-5-oxo-5,6-dihydro-4H-pyrano [3, 2-c] quinoline-3-carbonitrile (Ch-HPQ) thin films were determined in the frequency range of 0.5 kHz–5 MHz and the temperature range of 290–443 K. The AC electrical conduction of both compounds in thin film form is governed by the correlated barrier hopping (CBH) mechanism. Some parameters such as the barrier height, the maximum barrier height, the density of charges, and the hopping distance were determined as functions of temperature and frequency. The phenoxyphenyl group has a greater influence on those parameters than the chlorophenyl group. The AC activation energies were determined at different frequencies and temperatures. The dielectric behaviors of Ph-HPQ and Ch-HPQ were investigated using the impedance spectroscopy technique. The impedance data are presented in Nyquist diagrams for different temperatures. The Ch-HPQ films have higher impedance than the Ph-HPQ films. The real dielectric constant and dielectric loss show a remarkable dependence on the frequency and temperature. The Ph-HPQ has higher dielectric constants than the Ch-HPQ.

  5. Assessment of 4H-SiC epitaxial layers and high resistivity bulk crystals for radiation detectors

    NASA Astrophysics Data System (ADS)

    Mandal, Krishna C.; Muzykov, Peter G.; Chaudhuri, Sandeep K.; Terry, J. R.

    2012-10-01

    We present results of structural, electrical, and defect characterization of 4H-SiC epitaxial layers and bulk crystals and show performance of the radiation detectors fabricated from these materials. The crystal quality was evaluated by x-ray diffraction (XRD) rocking curve measurements, electron beam induced current (EBIC) imaging, and defect delineating etching in conjunction with optical microscopy and scanning electron microscopy (SEM). Studies of the electrically active intrinsic defects and impurities were conducted using thermally stimulated current (TSC) measurements in a wide temperature range of 94 - 750K. The results are correlated with the capability of bulk crystals and epitaxial layers for the detection of α-particles, low to high energy x-rays and gamma rays. High barrier rectifying Schottky diodes have been fabricated and tested. The epitaxial 4H-SiC radiation detectors exhibited low leakage current (< 1 nA) at ~ 200 V operating voltage up to 200 C. The soft x-ray responsivity measurements performed at the National Synchrotron Light Source (NSLS) at Brookhaven National Lab (BNL) showed significantly improved characteristics compared to commercially-available SiC UV photodiode detectors.

  6. Communication: Ab initio study of O{sub 4}H{sup +}: A tracer molecule in the interstellar medium?

    SciTech Connect

    Xavier, George D.; Bernal-Uruchurtu, Margarita I.; Hernández-Lamoneda, Ramón

    2014-08-28

    The structure and energetics of the protonated molecular oxygen dimer calculated via ab initio methods is reported. We find structures that share analogies with the eigen and zundel forms for the protonated water dimer although the symmetrical sharing of the proton is more prevalent. Analysis of different fragmentation channels show charge transfer processes which indicate the presence of conical intersections for various states including the ground state. An accurate estimate for the proton affinity of O{sub 4} leads to a significantly larger value (5.6 eV) than for O{sub 2} (4.4 eV), implying that the reaction H{sub 3}{sup +} + O{sub 4} → O{sub 4}H{sup +} + H{sub 2} is exothermic by 28 Kcal/mol as opposed to the case of O{sub 2} which is nearly thermoneutral. This opens up the possibility of using O{sub 4}H{sup +} as a tracer molecule for oxygen in the interstellar medium.

  7. Effect of substitution group on dielectric properties of 4H-pyrano [3, 2-c] quinoline derivatives thin films

    NASA Astrophysics Data System (ADS)

    H, M. Zeyada; F, M. El-Taweel; M, M. El-Nahass; M, M. El-Shabaan

    2016-07-01

    The AC electrical conductivity and dielectrical properties of 2-amino-6-ethyl-5-oxo-4-(3-phenoxyphenyl)-5,6-dihydro-4H-pyrano[3, 2-c]quinoline-3-carbonitrile (Ph-HPQ) and 2-amino-4-(2-chlorophenyl)-6-ethyl-5-oxo-5,6-dihydro-4H-pyrano [3, 2-c] quinoline-3-carbonitrile (Ch-HPQ) thin films were determined in the frequency range of 0.5 kHz-5 MHz and the temperature range of 290-443 K. The AC electrical conduction of both compounds in thin film form is governed by the correlated barrier hopping (CBH) mechanism. Some parameters such as the barrier height, the maximum barrier height, the density of charges, and the hopping distance were determined as functions of temperature and frequency. The phenoxyphenyl group has a greater influence on those parameters than the chlorophenyl group. The AC activation energies were determined at different frequencies and temperatures. The dielectric behaviors of Ph-HPQ and Ch-HPQ were investigated using the impedance spectroscopy technique. The impedance data are presented in Nyquist diagrams for different temperatures. The Ch-HPQ films have higher impedance than the Ph-HPQ films. The real dielectric constant and dielectric loss show a remarkable dependence on the frequency and temperature. The Ph-HPQ has higher dielectric constants than the Ch-HPQ.

  8. High growth rate 4H-SiC epitaxial growth using dichlorosilane in a hot-wall CVD reactor

    NASA Astrophysics Data System (ADS)

    Chowdhury, Iftekhar; Chandrasekhar, M. V. S.; Klein, Paul B.; Caldwell, Joshua D.; Sudarshan, Tangali

    2011-02-01

    Thick, high quality 4H-SiC epilayers have been grown in a vertical hot-wall chemical vapor deposition system at a high growth rate on (0 0 0 1) 8° off-axis substrates. We discuss the use of dichlorosilane as the Si-precursor for 4H-SiC epitaxial growth as it provides the most direct decomposition route into SiCl 2, which is the predominant growth species in chlorinated chemistries. A specular surface morphology was attained by limiting the hydrogen etch rate until the system was equilibrated at the desired growth temperature. The RMS roughness of the grown films ranged from 0.5-2.0 nm with very few morphological defects (carrots, triangular defects, etc.) being introduced, while enabling growth rates of 30-100 μm/h, 5-15 times higher than most conventional growths. Site-competition epitaxy was observed over a wide range of C/Si ratios, with doping concentrations <1×10 14 cm -3 being recorded. X-ray rocking curves indicated that the epilayers were of high crystallinity, with linewidths as narrow as 7.8 arcsec being observed, while microwave photoconductive decay (μPCD) measurements indicated that these films had high injection (ambipolar) carrier lifetimes in the range of 2 μs.

  9. Reassessment of HLA-G isoform specificity of MEM-G/9 and 4H84 monoclonal antibodies.

    PubMed

    Zhao, L; Teklemariam, T; Hantash, B M

    2012-09-01

    Human leukocyte antigen (HLA)-G is a non-classical HLA class I molecule thought to play a key role in maternal-fetal tolerance. Although initial studies suggested that HLA-G expression is restricted to extravillous cytotrophoblasts, expression was subsequently reported in a wide variety of other human tissues and tumor cells. However, consensus as to the validity of these collective findings has proven difficult because the antibodies used to define the temporal and spatial expression patterns of HLA-G remain incompletely characterized. The aim of our study was to reassess two of the most widely used HLA-G antibodies (MEM-G/9 and 4H84) in HLA-G-positive (JEG-3 and HLA-G transduced) and -negative (dermal fibroblast, mesenchymal stem cell, K562, and Jurkat) lines using flow cytometry, immunofluorescence, and western blotting. We found that MEM-G/9 recognized HLA-G3 by flow cytometry, indicating that its epitope is present on the α1 domain of HLA-G. Although 4H84 preferably recognized unfolded HLA-G-free chains, it showed strong non-specificity under certain methodological conditions.

  10. New Mononuclear Cu(II) Complexes and 1D Chains with 4-Amino-4H-1,2,4-triazole

    PubMed Central

    Dîrtu, Marinela M.; Boland, Yves; Gillard, Damien; Tinant, Bernard; Robeyns, Koen; Safin, Damir A.; Devlin, Eamonn; Sanakis, Yiannis; Garcia, Yann

    2013-01-01

    The crystal structures of two mononuclear Cu(II) NH2trz complexes [Cu(NH2trz)4(H2O)](AsF6)2 (I) and [Cu(NH2trz)4(H2O)](PF6)2 (II) as well as two coordination polymers [Cu(μ2-NH2trz)2Cl]Cl·H2O (III) and [Cu(μ2-NH2trz)2Cl] (SiF6)0.5·1.5H2O (IV) are presented. Cationic 1D chains with bridging bis-monodentate μ2-coordinated NH2trz and bridging μ2-coordinated chloride ligands are present in III and IV. In these coordination polymers, the Cu(II) ions are strongly antiferromagnetically coupled with J = −128.4 cm−1 for III and J = −143 cm−1 for IV (H = −J∑SiSi+1), due to the nature of the bridges between spin centers. Inter-chain interactions present in the crystal structures were taken into consideration, as well as g factors, which were determined experimentally, for the quantitative modeling of their magnetic properties. PMID:24300095

  11. Raman spectral characterization of NH4H2PO4 single crystals: Effect of pH on microstructure

    NASA Astrophysics Data System (ADS)

    Zhou, Hailiang; Wang, Fang; Xu, Mingxia; Liu, Baoan; Liu, Fafu; Zhang, Lisong; Xu, Xinguang; Sun, Xun; Wang, Zhengping

    2016-09-01

    Single crystals of ammonium dihydrogen phosphate (NH4H2PO4, ADP) were grown from aqueous solutions using "point seeds" method. The Raman spectra of the NH4H2PO4 single crystals were recorded as a function of pH. The band intensities and frequencies were monitored to determine the diagnostic bands for the crystals grown from the solutions of different pH values of aqueous solution. In the Raman spectra of ADP crystal samples at different pH, the position and intensity of the peaks in the range 300-900 cm-1 did not change; the peaks in the range 1400-1700 cm-1 shifted their position, although they had the same intensity. This indicates that the structure of (PO4) 3 - did not change with pH, whereas the structure of NH4+ changed with pH. In the Raman study in the range 1700-4000 cm-1, the primary discrimination occurred for the intensity of the peaks at 3050 cm-1 and 3147 cm-1, which is attributed to the vibration of O-H⋯O hydrogen bond, it can be inferred that pH slightly affected the O-H⋯O hydrogen bonding. This Raman spectral characterization may help to better understand the microstructural change under different conditions and optimize the growth and property of this type of material.

  12. Carbon nanoscroll from C4H/C4F-type graphene superlattice: MD and MM simulation insights.

    PubMed

    Liu, Zilong; Xue, Qingzhong; Tao, Yehan; Li, Xiaofang; Wu, Tiantian; Jin, Yakang; Zhang, Zhongyang

    2015-02-01

    Morphology manipulation opens up a new avenue for controlling and tailoring the functional properties of graphene, enabling the exploration of graphene-based nanomaterials. Through mixing single-side-hydrogenated graphene (C4H) with fluorinated graphene (C4F) on one single sheet, the C4H/C4F-type graphene superlattices can self-scroll at room temperature. We demonstrate using molecular dynamic (MD) simulations that different proportions, sizes, directions of hydrogenation and fluorination, and geometry of graphene have a great influence on the self-scrolling of superlattices into a variety of well-defined carbon nanoscrolls (CNSs), thus providing a controllable approach to tune their structures. Based on molecular mechanics (MM) simulations, the CNSs bear more than eight times the radial pressure than that of their multiwalled carbon nanotube (MWNT) counterparts, and an excellent radial elasticity of CNSs is also shown. Compared with conventional CNSs, these novel CNSs are endowed with more ample and flexible heterogeneous structures due to the on-demand hydrogenation and fluorination. Besides, this work provides a feasible route to achieve the necessary electronic and optical changes to be applied in graphene device applications.

  13. Study of surface potential variation in p-/n-type 4H-SiC using scanning kelvin probe microscopy

    NASA Astrophysics Data System (ADS)

    Ahn, Jung-Joon; You, Lin; Yu, Liangchun; Koo, Sang-Mo; Kopanski, Joseph

    2013-03-01

    We report surface potential images of p-n junctions in 4H-SiC measured using scanning kelvin probe microscopy (SKPM) and relate them to the local dopant concentration. SKPM has been demonstrated on various semiconductor materials to examine crystalline defects and doping profiles. SKPM measured surface potential depends on the local dopant concentration and clearly differentiates between n-type and p-type materials. As opposed to scanning capacitance microscopy, which requires a good quality surface insulating layer, SKPM requires a clean surface and the lack of a screening oxide might result in higher spatial resolution. For the measurement, partially de-processed SiC high power LMOSFETS were used. The p-n junctions were formed from 4H-SiC wafers having a p-epilayer on p-substrate that was ion-implanted with nitrogen and annealed to build a shallow n-type region. The samples were observed in plan-view and in cross-section. Amplitude modulated, double pass SKPM was implemented with a commercial AFM. We conducted a detailed study of various data acquisition parameters and it seems that the lateral resolution of the potential difference can be enhanced by applying higher ac modulation amplitude and small tip-sample scanning height.

  14. Theoretical study of radiative electron attachment to CN, C{sub 2}H, and C{sub 4}H radicals

    SciTech Connect

    Douguet, Nicolas; Fonseca dos Santos, S.; Orel, Ann E.; Raoult, Maurice; Dulieu, Olivier

    2015-06-21

    A first-principle theoretical approach to study the process of radiative electron attachment is developed and applied to the negative molecular ions CN{sup −}, C{sub 4}H{sup −}, and C{sub 2}H{sup −}. Among these anions, the first two have already been observed in the interstellar space. Cross sections and rate coefficients for formation of these ions by direct radiative electron attachment to the corresponding neutral radicals are calculated. For the CN molecule, we also considered the indirect pathway, in which the electron is initially captured through non-Born-Oppenheimer coupling into a vibrationally resonant excited state of the anion, which then stabilizes by radiative decay. We have shown that the contribution of the indirect pathway to the formation of CN{sup −} is negligible in comparison to the direct mechanism. The obtained rate coefficients for the direct mechanism at 30 K are 7 × 10{sup −16} cm{sup 3}/s for CN{sup −}, 7 × 10{sup −17} cm{sup 3}/s for C{sub 2}H{sup −}, and 2 × 10{sup −16} cm{sup 3}/s for C{sub 4}H{sup −}. These rates weakly depend on temperature between 10 K and 100 K. The validity of our calculations is verified by comparing the present theoretical results with data from recent photodetachment experiments.

  15. New X-ray insight into oxygen intercalation in epitaxial graphene grown on 4H-SiC(0001)

    SciTech Connect

    Kowalski, G. Tokarczyk, M.; Dąbrowski, P.; Ciepielewski, P.; Możdżonek, M.; Strupiński, W.; Baranowski, J. M.

    2015-03-14

    Efficient control of intercalation of epitaxial graphene by specific elements is a way to change properties of the graphene. Results of several experimental techniques, such as X-ray photoelectron spectroscopy, micro-Raman mapping, reflectivity, attenuated total reflection, X-ray diffraction, and X-ray reflectometry, gave a new insight into the intercalation of oxygen in the epitaxial graphene grown on 4H-SiC(0001). These results confirmed that oxygen intercalation decouples the graphene buffer layer from the 4H-SiC surface and converts it into the graphene layer. However, in contrast to the hydrogen intercalation, oxygen does not intercalate between carbon planes (in the case of few layer graphene) and the interlayer spacing stays constant at the level of 3.35–3.32 Å. Moreover, X-ray reflectometry showed the presence of an oxide layer having the thickness of about 0.8 Å underneath the graphene layers. Apart from the formation of the nonuniform thin oxide layer, generation of defects in graphene caused by oxygen was also evidenced. Last but not least, water islands underneath defected graphene regions in both intercalated and non-intercalated samples were most probably revealed. These water islands are formed in the case of all the samples stored under ambient laboratory conditions. Water islands can be removed from underneath the few layer graphene stacks by relevant thermal treatment or by UV illumination.

  16. First-principles study on reconstruction of 4H-SiC(0001) and (000 1 bar)

    NASA Astrophysics Data System (ADS)

    Kaneko, Tomoaki; Yamasaki, Takahiro; Tajima, Nobuo; Ohno, Takahisa

    2016-05-01

    We have found that 4H-SiC(0001) and (000 1 bar) surfaces can reconstruct to stable (2 × 1) π-bonded chain structures, which are the same kind of structure that was predicted by Pandey for Si(111) surface (K. C. Pandey, 1981) but have not been examined for the SiC surfaces so far. Their relative energy gain on (0001) and (000 1 bar) surfaces to the ideal spin non-polarized surfaces are 0.275-0.298 eV/(1 × 1) and 0.378-0.441 eV/(1 × 1), respectively. The band gaps of the π-bonded chain models for 4H-SiC(0001) and (000 1 bar) are 1.34-1.36 eV and 1.92-2.46 eV, respectively, which are much larger than that for Si(111) due to difference between energy levels of p-orbitals of Si and C atoms.

  17. Sodium alginate: An efficient biopolymeric catalyst for green synthesis of 2-amino-4H-pyran derivatives.

    PubMed

    Dekamin, Mohammad G; Peyman, S Zahra; Karimi, Zahra; Javanshir, Shahrzad; Naimi-Jamal, M Reza; Barikani, Mehdi

    2016-06-01

    Sodium alginate, a naturally occurring macromolecule, in its granular form and without any post-modification was found to be an efficient and recoverable bifunctional heterogeneous organocatalyst for the domino synthesis of various 2-amino-3-cyano-4H-pyran annulated derivatives through three-component condensation of different aldehydes, malononitrile and diverse 1,3-dicarbonyl compounds under mild conditions. Corresponding 4H-pyran derivatives were obtained in high to excellent yields after 25-150min stirring in 2mL EtOH under reflux conditions in the presence of 10mol% of sodium alginate, equimolar amounts of aldehydes, malononitrile and 1,3-dicarbonyl compounds. The catalyst was easily separated from the reaction mixture to obtain desired products in excellent purity as shown by FTIR and (1)H NMR spectroscopic methods. Avoiding the use of any transition metal, one-pot and multi-component procedure catalyzed by a renewable biopolymer, the reusability of the catalyst, broad substrate scope and operational simplicity are important features of this methodology for preparation of medicinally important compounds. PMID:26845480

  18. Formation of amorphous alloys on 4H-SiC with NbNi film using pulsed-laser annealing

    NASA Astrophysics Data System (ADS)

    De Silva, Milantha; Ishikawa, Seiji; Miyazaki, Takamichi; Kikkawa, Takamaro; Kuroki, Shin-Ichiro

    2016-07-01

    Amorphous alloys containing Ni-Si-Nb-C were formed on 4H-SiC creating a low resistance Ohmic contact electrode. In a conventional nickel silicide (NiSi) electrode on SiC, a carbon agglomeration at the silicide/SiC interface occurs, and contact resistance between NiSi and SiC substrate becomes larger. For carbon agglomeration suppression, nanosecond non-equilibrium laser annealing was introduced, and to form metal carbides, carbon-interstitial type metals Nb and Mo were introduced. Ni, Nb, Mo, Nb/Ni, Mo/Ni multilayer contacts, and NbNi mixed contact were formed on the C-face side of n-type 4H-SiC wafers. The electrical contact properties were investigated after a 45 ns pulse laser annealing in N2 ambient. As a result, with NbNi film, an amorphous alloy with Ni-Si-Nb-C was formed, and a low specific contact resistance of 5.3 × 10-4 Ω cm2 was realized.

  19. Dwornikite, (Ni,Fe)SO4.H2O, a member of the kieserite group from Minasragra, Peru.

    USGS Publications Warehouse

    Milton, C.; Evans, H.T.; Johnson, R.G.

    1982-01-01

    A new nickel sulphate monohydrate is described from V-sulphide ore from Minasragra; it occurs associated with patronite (VS2) with various sulphates, sulphur and bitumen. Dwornikite forms fine-grained white aggregates mixed with other oxidation products. Indexed X-ray powder data are tabulated; strongest lines 3.342(100) , 4.732(70), 3.024(70), 4.754(50), 3.293(35), 2.491(35) A; a 6.839, b 7.582, c 7.474 A, beta 117.85o; space group C2/c. XRF gave NiO 39.0, FeO 9.3, SO3 42.4, = 90.7; Dcalc. 3.34 g/cm3; mean refr. ind. approx 1.63. Unit-cell data for the synthetic end-member compounds NiSO4.H2O and FeSO4.H2O and new X-ray powder data for retgersite (NiSO4.6H2O) are given. The name is for E. J. Dwornik, mineralogist with the U.S. Geological Survey.-R.A.H.

  20. Using queuing theory to analyse the government's 4-H completion time target in accident and emergency departments.

    PubMed

    Mayhew, L; Smith, D

    2008-03-01

    This paper uses a queuing model to evaluate completion times in Accident and Emergency (A&E) departments in the light of the Government target of completing and discharging 98% of patients inside 4 h. It illustrates how flows though an A&E can be accurately represented as a queuing process, how outputs can be used to visualise and interpret the 4-h Government target in a simple way and how the model can be used to assess the practical achievability of A&E targets in the future. The paper finds that A&E targets have resulted in significant improvements in completion times and thus deal with a major source of complaint by users of the National Health Service in the U.K. It suggests that whilst some of this improvement is attributable to better management, some is also due to the way some patients in A&E are designated and therefore counted through the system. It finds for example that the current target would not have been possible without some form of patient re-designation or re-labelling taking place. Further it finds that the current target is so demanding that the integrity of reported performance is open to question. Related incentives and demand management issues resulting from the target are also briefly discussed. PMID:18390164