Observations of HNO3, ΣAN, ΣPN and NO2 fluxes: evidence for rapid HOx chemistry within a pine forest canopy

Measurements of exchange of reactive nitrogen oxides between the atmosphere and a ponderosa pine forest in the Sierra Nevada Mountains are reported. During winter, we observe upward fluxes of NO₂, and downward fluxes of total peroxy and peroxy acyl nitrates (ΣPNs), total gas and particle phase alkyl and multifunctional alkyl nitrates (ΣANs_(g+p)), and the sum of gaseous HNO₃ and semi-volatile NO₃^− particles (HNO_3(g+p)). We use calculations of the vertical profile and flux of NO, partially constrained by observations, to show that net midday ΣNO_yi fluxes in winter are –4.9 ppt m s^−1. The signs and magnitudes of these wintertime individual and ΣNO_yi fluxes are in the range of prior measurements. In contrast, during summer, we observe downward fluxes only of ΣANs_(g+p), and upward fluxes of HNO_3(g+p), ΣPNs and NO₂ with signs and magnitudes that are unlike most, if not all, previous observations and analyses of fluxes of individual nitrogen oxides. The results imply that the mechanisms contributing to NO_y fluxes, at least at this site, are much more complex than previously recognized. We show that the observations of upward fluxes of HNO_3(g+p) and σPNs during summer are consistent with oxidation of NO₂ and acetaldehyde by an OH x residence time of 1.1×10¹⁰ molec OH cm^−3 s, corresponding to 3 to 16×10⁷ molecules cm^−3 OH within the forest canopy for a 420 to 70 s canopy residence time. We show that ΣAN_(g+p) fluxes are consistent with this range in OH if the reaction of OH with ΣANs produces either HNO₃ or NO₂ with a 6–30% yield. Calculations of NO fluxes constrained by the NO₂ observations and the inferred OH indicate that NO_x fluxes are downward into the canopy because of the substantial conversion of NO_x to HNO₃ and σPNs in the canopy. Even so, we derive that NO_x emission fluxes of ~15 ng(N) m^−2 s^−1 at midday during summer are required to balance the NO_x and NO_y flux budgets. These fluxes are partly explained by estimates of soil emissions (estimated to be between 3 and 6 ng(N) m^−2 s^-1). One possibility for the remainder of the NO_x source is large HONO emissions. Alternatively, the 15 ng(N) m^−2 s^−1 emission estimate may be too large, and the budget balanced if the deposition of HNO₃ and σPNs is slower than we estimate, if there are large errors in either our understanding of peroxy radical chemistry, or our assumptions that the budget is required to balance because the fluxes do not obey similarity theory

Development of a three-dimensional time-dependent flow field model

A three-dimensional, time-dependent mathematical model to represent Mobile Bay was developed. Computer programs were developed which numerically solve the appropriate conservation equations for predicting bay and estuary flow fields. The model is useful for analyzing the dispersion of sea water into fresh water and the transport of sediment, and for relating field and physical model data

Random polynomials, random matrices, and LL-functions

We show that the Circular Orthogonal Ensemble of random matrices arises naturally from a family of random polynomials. This sheds light on the appearance of random matrix statistics in the zeros of the Riemann zeta-function.Comment: Added background material. Final version. To appear in Nonlinearit

Effects of Neutron Irradiation on Carbon Doped MgB2 Wire Segments

We have studied the evolution of superconducting and normal state properties of neutron irradiated Mg(B$_{.962}$C$_{.038}$)$_2$ wire segments as a function of post exposure annealing time and temperature. The initial fluence fully suppressed superconductivity and resulted in an anisotropic expansion of the unit cell. Superconductivity was restored by post-exposure annealing. The upper critical field, H$_{c2}$(T=0), approximately scales with T$_c$ starting with an undamaged T$_c$ near 37 K and H$_{c2}$(T=0) near 32 T. Up to an annealing temperature of 400 $^ o$C the recovery of T$_c$ tends to coincide with a decrease in the normal state resistivity and a systematic recovery of the lattice parameters. Above 400 $^ o$C a decrease in order along the c- direction coincides with an increase in resistivity, but no apparent change in the evolution of T$_c$ and H$_{c2}$. To first order, it appears that carbon doping and neutron damaging effect the superconducting properties of MgB$_2$ independently

Quantifying the Likelihood of Regional Cimate Change: A hybridized Approach

The growing need for risk-based assessments of impacts and adaptation to climate change calls for increased capability in climate projections: the quantification of the likelihood of regional outcomes and the representation of their uncertainty. Herein, we present a technique that extends the latitudinal projections of the 2-D atmospheric model of the MIT Integrated Global System Model (IGSM) by applying longitudinally resolved patterns from observations, and from climate-model projections archived from exercises carried out for the 4th Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC). The method maps the IGSM zonal means across longitude using a set of transformation coefficients, and we demonstrate this approach in application to near-surface air temperature and precipitation, for which high-quality observational datasets and model simulations of climate change are available. The current climatology of the transformation coefficients is observationally based. To estimate how these coefficients may alter with climate, we characterize the climate models’ spatial responses, relative to their zonal mean, from transient increases in trace-gas concentrations and then normalize these responses against their corresponding transient global temperature responses. This procedure allows for the construction of meta-ensembles of regional climate outcomes, combining the ensembles of the MIT IGSM—which produce global and latitudinal climate projections, with uncertainty, under different global climate policy scenarios—with regionally resolved patterns from the archived IPCC climate-model projections. This approach also provides a hybridization of the climate-model longitudinal projections with the global and latitudinal patterns projected by the IGSM, and can be applied to any given state or flux variable that has the sufficient observational and model-based information.U.S. Department of Energy’s Abrupt Climate Change program, grant # DE-FG02-08ER64597

The Elections of 2000: Politics, Culture and Economics in North America

The essays in this collection are the product of a conversation among scholars, spanning national borders and disciplinary boundaries, about the increasing integration of Canada, Mexico, and the United States and the development of a “continental perspective.” This conversation has been underway for some time, reflecting the causes, challenges, and consequences of economic, cultural, and political integration in North America. The conjunction of national elections in all three of the great North American democracies in 2000 offered us the opportunity to deepen this conversation and engage in scholarly discourse from a “continental perspective.” Taken together, the essays in this book provide a vivid portrait of North American democracies at the turn of the century.https://ideaexchange.uakron.edu/elections_of_2000/1000/thumbnail.jp

Information Flow through a Chaotic Channel: Prediction and Postdiction at Finite Resolution

We reconsider the persistence of information under the dynamics of the logistic map in order to discuss communication through a nonlinear channel where the sender can set the initial state of the system with finite resolution, and the recipient measures it with the same accuracy. We separate out the contributions of global phase space shrinkage and local phase space contraction and expansion to the uncertainty in predicting and postdicting the state of the system. Thus, we determine how the amplification parameter, the time lag, and the resolution influence the possibility for communication. A novel representation for real numbers is introduced that allows for a visualization of the flow of information between scales.Comment: 14 pages, 13 figure

Statistical Properties of Share Volume Traded in Financial Markets

We quantitatively investigate the ideas behind the often-expressed adage `it takes volume to move stock prices', and study the statistical properties of the number of shares traded $Q_{\Delta t}$ for a given stock in a fixed time interval $\Delta t$. We analyze transaction data for the largest 1000 stocks for the two-year period 1994-95, using a database that records every transaction for all securities in three major US stock markets. We find that the distribution $P(Q_{\Delta t})$ displays a power-law decay, and that the time correlations in $Q_{\Delta t}$ display long-range persistence. Further, we investigate the relation between $Q_{\Delta t}$ and the number of transactions $N_{\Delta t}$ in a time interval $\Delta t$, and find that the long-range correlations in $Q_{\Delta t}$ are largely due to those of $N_{\Delta t}$. Our results are consistent with the interpretation that the large equal-time correlation previously found between $Q_{\Delta t}$ and the absolute value of price change $| G_{\Delta t} |$ (related to volatility) are largely due to $N_{\Delta t}$.Comment: 4 pages, two-column format, four figure

On the Floquet Theory of Delay Differential Equations

We present an analytical approach to deal with nonlinear delay differential equations close to instabilities of time periodic reference states. To this end we start with approximately determining such reference states by extending the Poincar'e Lindstedt and the Shohat expansions which were originally developed for ordinary differential equations. Then we systematically elaborate a linear stability analysis around a time periodic reference state. This allows to approximately calculate the Floquet eigenvalues and their corresponding eigensolutions by using matrix valued continued fractions