Proton-coupled electron transfer and tyrosine D of phototsystem II

EPR spectroscopy and isotopic substitution were used to gain increased knowledge about the proton-coupled electron transfer (PCET) mechanism for the reduction of the tyrosine D radical (YD*) in photosystem II. pL dependence (where pL is either pH or pD) of both the rate constant and kinetic isotope effect (KIE) was examined for YD* reduction. Second, the manner in which protons are transferred during the rate-limiting step for YD* reduction at alkaline pL was determined. Finally, high field electron paramagnetic resonance (EPR) spectroscopy was used to study the effect of pH on the environment surrounding both the tyrosine D radical and the tyrosine Z radical (YZ*). At alkaline pL, it was determined that the proton and electron are both transferred in the rate-limiting step of YD* reduction. At acidic pL, the proton transfer occurs first followed by electron transfer. Proton inventory experiments indicate that there is more than one proton donation pathway available to YD* during PCET reduction at alkaline pL. Additionally, the proton inventory experiments indicate that at least one of those pathways is multiproton. High field EPR experiments indicate that both YD* and YZ* are hydrogen bonded to neutral species. The EPR gx component for YD* is invariant with respect to pH. Analysis of the EPR gx component for Yz* indicates that its environment becomes more electropositive as the pH is increased. This is most likely due to changes in the hydrogen bond strengthPh.D.Committee Chair: Bridgette Barry; Committee Member: Ingeborg Schmidt-Krey; Committee Member: Jake Soper; Committee Member: Nils Kroger; Committee Member: Wendy Kell

Threats and Opportunities in the International Economy

The United States remains a military and an economic superpower. But in order to compete in the international economy, Americans need to be a well-educated citizenry.https://openscholarship.wustl.edu/mlw_papers/1067/thumbnail.jp

XBRL And Its Potential Impact On Events Reporting

Financial accounting and reporting has been criticized for producing untimely, periodic, historical-ly-based, and highly-aggregated financial statements that fall far short of meeting the needs of the financial community. Especially recently, the accounting profession has been roundly criticized for its perceived role in highly publicized audit failures including Enron and WorldCom. Proponents of the events reporting paradigm assert that what is needed is an events reporting sys-tem that reports a wider range of relevant and disaggregated events that are free from the biased value judgments and allocations of management. This paper explores the possible role of Extensible Business Reporting Language (XBRL) in the movement toward such an events reporting approach. The web-based XBRL reporting languages allow for the tagging of web-reported business information to provide meaning and context to the information. XBRL pro-vides a platform-independent vehicle for the efficient exchange of business information. Developing XBRL reporting taxonomies will facilitate multi-company financial comparisons and provide a mechanism for obtaining more detail through drill-down analysis

Mixed Infection of Hard Red Winter Wheat with High Plains Virus and Wheat Streak Mosaic Virus from Wheat Curl Mites in Nebraska

A new disease of wheat and corn caused by the High Plains virus (HPV) has been observed in the High Plains region of western United States. HPV is transmitted by the wheat curl mite, Aceria tosichella, which is also the vector of wheat streak mosaic virus (WSMV). In the field it is extremely difficult to visually differentiate plants infected with WSMV from those with HPV. An indirect protein-A sandwich enzyme-linked immunosorbent assay (PAS-ELISA) and Western blot analysis were used to identify WSMV and HPV. Samples of wheat curl mites were collected from arbitrarily chosen sites from commercial wheat plantings in 1995 and 1996 and used to infest caged wheat plants. After 3 weeks, leaf samples were harvested and assayed. Both Western blot analysis and PAS-ELISA were effective at identifying samples positive for WSMV and HPV, both alone and in mixed infections. Western blot results showed that over the 2 years, 65% of the samples were positive for WSMV, 46% were positive for HPV, and mixed infections were found in 40% of the samples. HPV presence was verified with similar results from field collected plant samples. These levels of virus indicate an unexpectedly high incidence of HPV in wheat curl mite populations in Nebraska

Stochastic Optimal Control to Minimize State Uncertainty

In many spacecraft control scenarios, the standard design procedure begins with a deterministic propellant minimization that does not consider random errors due to navigation uncertainty, control noise, unknown parameters, or mismodeled dynamics. However, these random errors can render a deterministic trajectory infeasible or result in large state deviations that are resource-intensive to correct. Therefore, a deterministic design is followed by feasibility studies to ensure that potential errors will not compromise the mission performance. Alternatively, this dissertation investigates the more direct approach of stochastic optimal control. Stochastic control techniques include uncertainty within the optimization process such that error statistics can be minimized or constrained directly. Two novel stochastic control problems are investigated in this dissertation: 1) open-loop multi-objective trajectory optimization to minimize state error covariance and control energy using indirect methods and 2) closed-loop guidance to minimize mean squared error using dynamic programming. These techniques may be employed independently or in tandem to improve mission robustness. Both approaches consider control-dependent noise that is proportional to the magnitude of the nominal control (a structure that is common in spacecraft thrusters). The stochastic control methods in this dissertation are demonstrated for various mission scenarios including asteroid orbits in microgravity and multi-body orbits in the Earth-Moon system. Moreover, the growth of state uncertainty over time is dependent on the dynamical system in question, with the degree of nonlinearity playing an important role. This dissertation also studies the relationship between uncertainty and nonlinearity and proposes a semianalytical measure of nonlinearity that is based on the eigenpairs of higher-order tensors. The nonlinearity measure can be used to identify regions of strong nonlinearity, estimate the size of the ``linear'' region about a nominal trajectory, and inform navigation and control algorithms. Collectively, this research results in a generalized guidance and control framework that facilitates robust performance.</p

Notes--\u3ci\u3eNebraska Bird Review\u3c/i\u3e (March 1982)

Notes contain stories of Cattle Egrets viewed on Prairie Dog Waterfowl Production Area near Axtell; Wood Duck broods on Carter Lake in Omaha; a first-year Thayer’s Gull on Lake North near Columbus; a variety of birds (Swamp Sparrow, Great Horned Owl, Cliff Swallows, Savannah Sparrows, Grasshopper Sparrows, Purple Martins, Carolina Wren, Great Blue Heron, Western Kingbird, Prairie Chicken, Sprague’s Pipits, and more) seen in and around the Minden area; and a Scissor-tailed Flycatcher at Verdon Lake in Richardson County

Religiosity, Delinquency, and the Deterrent Effects of Informal Sanctions

Past research in deterrence theory suggests that informal social sanctions intervene in the effect of religiosity on criminal and delinquent behavior, such that more religious individuals tend to perceive stronger informal sanctions (Grasmick, Bursik and Cochran 1991a; Grasmick, Kinsey and Cochran 1991b). This study examines the influence of religiosity and social deterrence on college students\u27 delinquent behavior, as measured by anticipated violation of a university\u27s alcohol policy. Data were collected through a survey of undergraduate students (n = 484) at a large South-Midwestern public university that instituted a campus alcohol ban. The survey took place three months after the ban was implemented and asked students about religiosity, perceptions of informal deterrence, and expectations of violating the policy. Results partially support the hypothesis that religiosity predicts conformity primarily through the deterrent threat of informal sanctions. Religiosity increased perceived threats of shame and embarrassment, which in turn reduced the likelihood of anticipated policy violation. When controlling for demographics, college lifestyle, attitudes, and past drinking behavior, shame remained a significant predictor of expected policy violation, but embarrassment did not. Also, contrary to expectations, one measure of fundamentalist religiosity (biblical literalness) retained a direct main effect on intended compliance, even when taking informal sanctions into account. Theoretical, methodological, and policy implications are discussed

Scalar Field Quantum Inequalities in Static Spacetimes

We discuss quantum inequalities for minimally coupled scalar fields in static spacetimes. These are inequalities which place limits on the magnitude and duration of negative energy densities. We derive a general expression for the quantum inequality for a static observer in terms of a Euclidean two-point function. In a short sampling time limit, the quantum inequality can be written as the flat space form plus subdominant correction terms dependent upon the geometric properties of the spacetime. This supports the use of flat space quantum inequalities to constrain negative energy effects in curved spacetime. Using the exact Euclidean two-point function method, we develop the quantum inequalities for perfectly reflecting planar mirrors in flat spacetime. We then look at the quantum inequalities in static de~Sitter spacetime, Rindler spacetime and two- and four-dimensional black holes. In the case of a four-dimensional Schwarzschild black hole, explicit forms of the inequality are found for static observers near the horizon and at large distances. It is show that there is a quantum averaged weak energy condition (QAWEC), which states that the energy density averaged over the entire worldline of a static observer is bounded below by the vacuum energy of the spacetime. In particular, for an observer at a fixed radial distance away from a black hole, the QAWEC says that the averaged energy density can never be less than the Boulware vacuum energy density.Comment: 27 pages, 2 Encapsulated Postscript figures, uses epsf.tex, typeset in RevTe