7 research outputs found
Feasibility of an Incoherent-scatter Radar Aboard the Space Shuttle
The results of a preliminary study to investigate the feasibility of conducting an incoherent scatter radar experiment on board the space shuttle are presented. The results indicate that such an experiment is technically feasible. The more difficult questions to answer are whether the system can be made flexible enough to justify the problems and costs involved. The design parameters and the tradeoffs that are available in the consideration of these questions are evaluated. Some of the more serious limitations pertain to: (1) the presence of ground clutter and F region auroral clutter; (2) available average power; (3) weight and volume associated with required antenna size, transmitter, and energy storage devices; and (4) antenna breakdown associated with high power transmitter problems
Plan de ordenaci?n del bosque de la finca "La Selva"
Tesis (M. Sc) -- CATIE, Turrialba (Costa Rica),1956El bosque de la finca "La Selva" cubre una superficie de 603 Ha. Los suelos son de tres clases: una clase de suelo zonal, arcilloso, profundo y bien drenado la segunda clase es intrazonal, con alto nivel de la capa fre?tica, mal drenado y varios grados de gleizaci?n la tercer clase es suelo azonal de aluvi?n reciente y m?s f?rtil que los dem?s suelos. El bosque virgen no ha sido explotado. La masa forestal promedia de todo el bosque con ?rboles de d.a.p. mayores de 20 cm es de 174 m3/Ha, de los cuales 112 m3 pertenecen a 21 especies comerciales. La masa total de las especies comerciales se ha calculado en 67,500 ?? 4,725 m3. De la masa total, el quebracho contiene 39,2 por ciento, cedro macho 6.6 por ciento, y las dem?s 19 especies comerciales son representadas con el 18.3 por ciento. La masa deseada de las especies comerciales se ha fijado en 130 m3/Ha, con un objetivo preliminar. Adem?s, se debe mejorar la forma de los ?rboles. El bosque debe mantenerse con la condici?n mixta no coet?nea. Su tratamieto silvicultural debe seguir las normas del m?todo de selecci?n, con provisiones adecuadas para el mantenimiento de aquellas especies valiosas, que son poco tolerantes. Para estos fines se ha establecido un ciclo de cortas de 10 a?os y se han elaborado las correspondientes reglas de corta y de tratamientos. La posibilidad para los pr?ximos 10 a?os se ha fijado en 1,200 m3 por a?o, ? 2 m3/Ha/a?o, de las especies comerciales. El control del manejo y la determinaci?n del incremento se efectuar? mediante parcelas permanentes de control
Structural adaptation of oxygen tolerance in 4-hydroxybutyrl-CoA dehydratase, a key enzyme of archaeal carbon fixation.
Autotrophic microorganisms that convert inorganic carbon into organic matter were key players in the evolution of life on Earth. As the early atmosphere became oxygenated, microorganisms needed to develop mechanisms for oxygen protection, especially those relying on enzymes containing oxygen-sensitive metal clusters (e.g., Fe-S). Here we investigated how 4-hydroxybutyryl-CoA dehydratase (4HBD) - the key enzyme of the 3-hydroxypropionate/4-hydroxybutyrate (HP/HB) cycle for CO2-fixation - adapted as conditions shifted from anoxic to oxic. 4HBD is found in both anaerobic bacteria and aerobic ammonia-oxidizing archaea (AOA). The oxygen-sensitive bacterial 4HBD and oxygen-tolerant archaeal 4HBD share 59 % amino acid identity. To examine the structural basis of oxygen tolerance in archaeal 4HBD, we determined the atomic resolution structure of the enzyme. Two tunnels providing access to the canonical [4Fe-4S] cluster in oxygen-sensitive bacterial 4HBD were closed with four conserved mutations found in all aerobic AOA and other archaea. Further biochemical experiments and molecular dynamics simulations support our findings that restricting access to the active site is the key to oxygen tolerance, explaining how active site evolution drove a major evolutionary transition. Significance statement Autotrophy (primary production) was the first life strategy on Earth. Before photosynthesis (using solar energy to fix carbon dioxide), life relied on chemical reactions for energy. These chemosynthetic reactions are present in all domains of life, including archaea possessing the most energy-efficient carbon fixation pathway - the 3-hydroxypropionate/4-hydroxybutyrate cycle. This efficiency results from enzyme modifications, including enhanced enzyme stability and catalysis of multiple reactions. We reveal the first structure of aerobic 4-hydroxybutyryl-CoA dehydratase (4HBD) from ammonia-oxidizing archaea. These archaea are among the most abundant organisms on the planet, and their 4HBD active site evolved oxygen tolerance to support aerobic metabolism. This modification can provide further insight into enzyme evolution on early earth, as photosynthesis developed and began oxygenating the atmosphere
Virtual anatomy museum: Facilitating public engagement through an interactive application
Digitisation has become a common practice in the preservation of museum collections. Recent development of photogrammetry techniques allows for more accessible acquisition of three-dimensional (3D) models that serve as accurate representations of their originals. One of the potential applications of this is presenting digital collections as virtual museums to engage the public. Medical museums, particularly, would benefit from digitisation of their collections as many of them are closed to the public.The aim of this project was to design and create an interactive virtual museum which would represent the Anatomy Museum at the University of Glasgow with key specimens digitised using photogrammetry techniques. Members of the general public (25 participants) were asked to evaluate the usability and effectiveness of the interactive application by completing questionnaires.A process to digitise anatomical specimens using photogrammetry and convert them into game-ready 3D models was developed. The results demonstrated successful generation of 3D models of specimens preserved using different techniques, including specimens preserved in fluid and glass jars. User tests and evaluation of the application by members of the general public were positive, with participants agreeing that they would now consider visiting the real museum after using the virtual version