Photosynthetic reaction center complexes from heliobacteria

The goal of this project is to understand the early evolutionary development of photosynthesis by examining the properties of reaction centers isolated from certain contemporary organisms that appear to contain the simplest photosynthetic reaction centers. The major focus of this project is the family of newly discovered strictly anaerobic photosynthetic organisms known as Heliobacteria. These organisms are the only known photosynthetic organisms that are grouped with the gram-positive phylum of bacteria. The properties of these reaction centers suggest that they might be the decendants of an ancestor that also gave rise to Photosystem 1 found in oxygen-evolving photosynthetic organisms. Photoactive reaction center-core antenna complexes have been isolated from the photosynthetic bacteria Heliobacillus mobilis and Heliobacterium gestii. The absorption and fluorescence properties of membranes and reaction centers are almost identical, suggesting that a single pigment-protein complex serves as both antenna and reaction center. Experiments in progress include sequence determination of the 48,000 Mr reaction center protein, and evolutionary comparisons with other reaction center proteins

Fission product behavior in the Molten Salt Reactor Experiment

Essentially all the fission product data for numerous and varied samples taken during operation of the Molten Salt Reactor Experiment or as part of the examination of specimens removed after particular phases of operation are reported, together with the appropriate inventory or other basis of comparison, and relevant reactor parameters and conditions. Fission product behavior fell into distinct chemical groups. Evidence for fission product behavior during operation over a period of 26 months with $sup 235$U fuel (more than 9000 effective full-power hours) was consistent with behavior during operation using $sup 233$U fuel over a period of about 15 months (more than 5100 effective full- power hours). (auth

Imaging bedrock topography and geological controls on ice streams flowing in the Wilkes Subglacial Basin sector of East Antarctica

The northern Wilkes Subglacial Basin (NWSB) in East Antarctica underlies the catchments of the Matusevich, Cook, Ninnis and Mertz Glaciers, which are largely marine-based and hence particularly sensitive to past and future ocean and climate warming. Here we use airborne radar, aeromagnetic and airborne gravity data to image bedrock topography, subglacial geology and deeper crustal structure and assess its influence on ice sheet dynamics in the NWSB. The previously identified Central Basins extend beneath the fast flowing Cook ice streams, indicating that potential ocean-induced changes could propagate further into the interior of the ice sheet. By analogy with the better exposed Rennick Graben in northern Victoria Land, these deep subglacial basins are interpreted here as grabens that steer fast glacial flow. With the aid of depth to source estimates and forward magnetic and gravity models, we image the 3D variability in geological basal boundary conditions, including Beacon sediments and Jurassic basaltic rocks and uplifted basement blocks within and along the flanks of these grabens. A remarkable contrast in magnetic anomaly signatures is observed over the coastal and inland segments of the Cook ice stream catchment. We model several km thick early Cambrian to late Neoproterozoic sedimentary basins in the basement of the coastal region, in contrast to a prominent Proterozoic basement high at the onset of fast glacial flow further inland. We further hypothesise that this difference affects geothermal heat flux at the base of the ice sheet, which could in turn influence basal melting and subglacial hydrology

The thermodynamic dual structure of linear-dissipative driven systems

The spontaneous emergence of dynamical order, such as persistent currents, is sometimes argued to require principles beyond the entropy maximization of the second law of thermodynamics. I show that, for linear dissipation in the Onsager regime, current formation can be driven by exactly the Jaynesian principle of entropy maximization, suitably formulated for extended systems and nonequilibrium boundary conditions. The Legendre dual structure of equilibrium thermodynamics is also preserved, though it requires the admission of current-valued state variables, and their correct incorporation in the entropy

Calibration Procedure for Fuel Flow Meters at the Nebraska Tractor Test Lab

Reports in the literature indicated several factors that can influence the accuracy of Coriolis Effect mass flow meters. A Coriolis Effect mass flow meter is used to verify tractor manufacturer’s fuel consumption claims at the Nebraska Tractor Test Laboratory (NTTL). The accuracy requirement placed on the flow meter by the Organization for Economic Co-operation and Development (OECD) in the Code 2 tractor performance test procedure is not clear, but in the most conservative interpretation is ±0.5% of each flow rate measured. Results showed a dynamic weighing calibration method was not accurate enough to obtain a calibration of the flow meter to the desired accuracy level. A static weighing calibration method developed showed no significant difference between the calibration determined by the flow meter’s manufacturer with water and the calibration determined by NTTL with No. 2 diesel fuel. Static weighing calibration tests showed that for flow rates at or above 32 kg/h, the flow meter met the ±0.5% error most conservative interpretation of tolerance on flow rate from OECD Code 2

Testing Fuel Efficiency of a Tractor with a Continuously Variable Transmission

A John Deere 8530 IVT tractor (Waterloo, Iowa) with a continuously variable transmission (CVT) that could be operated in automatic (CVT) or manual (fixed gear ratio) mode was tested for fuel consumption at a setpoint travel speed of 9 km·h‐1 with 17 different drawbar loads. Linear regression analysis results showed that with the throttle set to maximum in both transmission modes, operating the tractor with the transmission in the automatic mode was more fuel efficient than operating with the transmission in the manual mode when the drawbar power was approximately 78%, or less, of maximum power. When load transition portions of the data were filtered out, there was no significant effect of load sequencing in the remaining data. On the other hand, there was a noticeable effect of travel direction which could occur due to a minor slope of the test track in the direction of travel. Testing of more tractor models from different manufacturers and at different travel speeds is needed to determine if these results can be applied to different tractor models produced by the same and/or other manufacturers

Comparative susceptibility of \u3ci\u3eOstrinia furnacalis, Ostrinia nubilalis,\u3c/i\u3e and \u3ci\u3eDiatraea saccharalis\u3c/i\u3e (Lepidoptera: Crambidae) to \u3ci\u3eBacillus thuringiensis\u3c/i\u3e Cry1 toxins

Transgenic corn hybrids that express toxins from Bacillus thuringiensis (Bt) are highly effective against the European corn borer, Ostrinia nubilalis (Hübner), and the closely related Asian corn borer, Ostrinia furnacalis (Guenée). Since the registration of Bt corn hybrids in the U.S. in 1996, there has been a great deal of information generated on O. nubilalis. However, relatively little information exists for O. furnacalis. To help determine whether the information generated for O. nubilalis can be leveraged for decisions regarding the use of transgenic Bt corn against O. furnacalis, experiments were designed to determine whether the pattern of sensitivity to various Bt Cry1 toxins is similar between the two species. Test insects included laboratory-reared O. furnacalis originating from Malaysia, a Bt-susceptible laboratory colony of O. nubilalis maintained at the University of Nebraska-Lincoln (UNL) and an out-group consisting of the sugarcane borer, Diatraea saccharalis (F.), from Louisiana which represents a different genus from the same family. O. furnacalis and O. nubilalis exhibited a similar pattern of susceptibility to all the Cry1 toxins and were highly susceptible to the range of Bt toxins tested including Cry1Aa, Cry1Ab, Cry1Ac and Cry1F. Both of the Ostrinia species were more tolerant to Cry1Ba compared with D. saccharalis, although sensitivity of O. furnacalis was intermediate and did not differ significantly from that of O. nubilalis and D. saccharalis. D. saccharalis was also susceptible to the range of toxins tested but unlike the two Ostrinia species, was more tolerant to Cry1F and more susceptible to Cry1Ba. These results indicate that both of the Ostrinia corn borer species are similar in sensitivity to the Cry1Aa, Cry1Ab, Cry1Ac, Cry1Ba and Cry1F toxins, thus suggesting shared toxin receptors and mechanisms of toxicity for the two species

Comparing the Effects of Two Tillage Operations on Beneficial Epigeal Arthropod Communities and Their Associated Ecosystem Services in Sugar Beets

Beneficial arthropods provide important ecosystem services in terms of arthropod pest and weed management, but these services can be adversely affected by farming practices such as tillage. This study investigated the impact of two tillage operations (zone tillage and moldboard plow) on the activity density of several beneficial, epigeal arthropod taxa, and postdispersal weed seed and prey removal in sugar beet agroecosystems. In addition, four omnivorous ground beetle species were selected for a weed-seed choice feeding assay, whereas a single species was selected for a weed-seed age preference assay. Ground beetles were the most commonly collected taxon (via pitfall sampling), with only a few dominant species. Tillage operation did not affect ground beetle activity density; however, spider, centipede, and rove beetle activity densities were higher in the reduced-tillage treatment. Live prey consumption was similar between tillage practices, with more prey consumed during nocturnal hours. More weed seeds were consumed in the reduced-tillage treatment, whereas weed-seed preference differed between the four weed species tested [Setaria pumila (Poir.) Roem. & Schult., Echinochloa crus-galli (L.), Kochia scoparia (L.), and Chenopodium album (L.)]. In the weed-seed choice feeding assay, significantly more broad-leaf weed seeds (C. album and K. scoparia) were consumed compared with grassy weed seeds (E. crus-galli and S. pumila). No preference for seed age was detected for E. crus-galli, but Harpalus pensylvanicus (De Geer) preferred old C. album seeds over fresh seeds. Zone tillage is compatible with ecosystem services, providing critical habitat within agricultural ecosystems needed to conserve beneficial, edaphic arthropods

Comparing the Effects of Two Tillage Operations on Beneficial Epigeal Arthropod Communities and Their Associated Ecosystem Services in Sugar Beets

Published ArticleBeneficial arthropods provide important ecosystem services in terms of arthropod pest and weed management, but these services can be adversely affected by farming practices such as tillage. This study investigated the impact of two tillage operations (zone tillage and moldboard plow) on the activity density of several beneficial, epigeal arthropod taxa, and postdispersal weed seed and prey removal in sugar beet agroecosystems. In addition, four omnivorous ground beetle species were selected for a weed-seed choice feeding assay, whereas a single species was selected for a weed-seed age preference assay. Ground beetles were the most commonly collected taxon (via pitfall sampling), with only a few dominant species. Tillage operation did not affect ground beetle activity density; however, spider, centipede, and rove beetle activity densities were higher in the reduced-tillage treatment. Live prey consumption was similar between tillage practices, with more prey consumed during nocturnal hours. More weed seeds were consumed in the reduced-tillage treatment, whereas weed-seed preference differed between the four weed species tested [Setaria pumila (Poir.) Roem. & Schult., Echinochloa crus-galli (L.), Kochia scoparia (L.), and Chenopodium album (L.)]. In the weed-seed choice feeding assay, significantly more broad-leaf weed seeds (C. album and K. scoparia) were consumed compared with grassy weed seeds (E. crus-galli and S. pumila). No preference for seed age was detected for E. crus-galli, but Harpalus pensylvanicus (De Geer) preferred old C. album seeds over fresh seeds. Zone tillage is compatible with ecosystem services, providing critical habitat within agricultural ecosystems needed to conserve beneficial, edaphic arthropods

Distribution of entanglement in light-harvesting complexes and their quantum efficiency

Recent evidence of electronic coherence during energy transfer in photosynthetic antenna complexes has reinvigorated the discussion of whether coherence and/or entanglement has any practical functionality for these molecular systems. Here we investigate quantitative relationships between the quantum yield of a light-harvesting complex and the distribution of entanglement among its components. Our study focusses on the entanglement yield or average entanglement surviving a time scale comparable to the average excitation trapping time. As a prototype system we consider the Fenna-Matthews-Olson (FMO) protein of green sulphur bacteria and show that there is an inverse relationship between the quantum efficiency and the average entanglement between distant donor sites. Our results suggest that longlasting electronic coherence among distant donors might help modulation of the lightharvesting function.Comment: Version accepted for publication in NJ