Average transmission probability of a random stack

The transmission through a stack of identical slabs that are separated by gaps with random widths is usually treated by calculating the average of the logarithm of the transmission probability. We show how to calculate the average of the transmission probability itself with the aid of a recurrence relation and derive analytical upper and lower bounds. The upper bound, when used as an approximation for the transmission probability, is unreasonably good and we conjecture that it is asymptotically exact.Comment: 10 pages, 6 figure

Electromagnetic Energy, Momentum, and Angular Momentum in an Inhomogeneous Linear Dielectric

In a previous work, Optics Communications 284 (2011) 2460--2465, we considered a dielectric medium with an anti-reflection coating and a spatially uniform index of refraction illuminated at normal incidence by a quasimonochromatic field. Using the continuity equations for the electromagnetic energy density and the Gordon momentum density, we constructed a traceless, symmetric energy--momentum tensor for the closed system. In this work, we relax the condition of a uniform index of refraction and consider a dielectric medium with a spatially varying index of refraction that is independent of time, which essentially represents a mechanically rigid dielectric medium due to external constraints. Using continuity equations for energy density and for Gordon momentum density, we construct a symmetric energy--momentum matrix, whose four-divergence is equal to a generalized Helmholtz force density four-vector. Assuming that the energy-momentum matrix has tensor transformation properties under a symmetry group of space-time coordinate transformations, we derive the global conservation laws for the total energy, momentum, and angular momentum.Comment: added publication informatio

Ideals of womanhood in the literature of Finland and Russia 1894-1914

This study is a literary critical examination of the portrayal of woman in prose and drama, with reference to the themes of political and artistic rebirth which preoccupied writers in Finland and Russia at the turn of the century. The study falls into three sections, each of which represents an aspect of woman's metaphysical condition and for which I have used the categories Action, Voice,a nd Visibility. The first section assesses writers' approach to the issues raised by the woman question, and describes the cultivation of an ideal of politically active, nationally loyal womanhood in the image of the Madonna. The second section demonstrates that woman's silence, a dominant feature of her characterization, signifies both the danger of revolution and the prescription for her social integration. It also includes an analysis of the opportunities and consequences of self-expression for female characters and writers. The third section deals with the view of woman as an embodiment of artistic impulse, especially her idealization as muse, and addresses the issue of pornography in the representation of the female form. The comparison between the two literatures explores the respective national ambitions as well as the concept of the 'new woman'. The image of woman is influenced by contemporary theory of her nature and social function. The literatures contrast most notably in the relationship of the Madonna-like saviour to the political hero, and of the muse to the artist. In Russia, the historic mission of nation and artist is imbued with universal and eternal significance. In Finland, it relates to the immediate, localized ambitions of national selfdetermination. Woman is shown to have a central place in both countries in the process of political and artistic renewal. However, the ideal of womanhood plays upon preconceptions of femininity which preclude the notion of woman's equality and independence at the root of feminist thought. The limitations on woman's existence are observable in the elements of silence and pornography which affect her characterization, erasing her subjective identity and promoting her objectification

Tunable two-dimensional plasmon resonances in an InGaAs/InP high electron mobility transistor

Voltage-tunable plasmon resonances in the two-dimensional electron gas (2DEG) of a high electron mobility transistor (HEMT) fabricated from the InGaAs/InP materials system are reported. The device was fabricated from a commercial HEMT wafer by depositing source and drain contacts using standard photolithography and a semitransparent gate contact that consisted of a 0.5 mu m period transmission grating formed by electron-beam lithography. Narrow-band resonant absorption of terahertz radiation was observed in transmission in the frequency range of 10-50 cm(-1). The resonance frequency depends on the gate-tuned sheet charge density of the 2DEG. The observed separation of resonance fundamental from its harmonics and their shift with gate bias are compared with theory

Oxygen isotopic composition of nitrate and nitrite produced by nitrifying cocultures and natural marine assemblages

Author Posting. © Association for the Sciences of Limnology and Oceanography, 2012. This article is posted here by permission of Association for the Sciences of Limnology and Oceanography for personal use, not for redistribution. The definitive version was published in Limnology and Oceanography 57 (2012): 1361-1375, doi:10.4319/lo.2012.57.5.1361.The δ18O value of nitrate produced during nitrification (δ18ONO3,nit) was measured in experiments designed to mimic oceanic conditions, involving cocultures of ammonia-oxidizing bacteria or ammonia-oxidizing archaea and nitrite-oxidizing bacteria, as well as natural marine assemblages. The estimates of ranged from −1.5‰ ± 0.1‰ to +1.3‰ ± 1.4‰ at δ18O values of water (H2O) and dissolved oxygen (O2) of 0‰ and 24.2‰ vs. Vienna Standard Mean Ocean Water, respectively. Additions of 18O-enriched H2O allowed us to evaluate the effects of oxygen (O) isotope fractionation and exchange on . Kinetic isotope effects for the incorporation of O atoms were the most important factors for setting overall values relative to the substrates (O2 and H2O). These isotope effects ranged from +10‰ to +22‰ for ammonia oxidation (O2 plus H2O incorporation) and from +1‰ to +27‰ for incorporation of H2O during nitrite oxidation. values were also affected by the amount and duration of nitrite accumulation, which permitted abiotic O atom exchange between nitrite and H2O. Coculture incubations where ammonia oxidation and nitrite oxidation were tightly coupled showed low levels of nitrite accumulation and exchange (3% ± 4%). These experiments had values of −1.5‰ to +0.7‰. Field experiments had greater accumulation of nitrite and a higher amount of exchange (22% to 100%), yielding an average value of +1.9‰ ± 3.0‰. Low levels of biologically catalyzed exchange in coculture experiments may be representative of nitrification in much of the ocean where nitrite accumulation is low. Abiotic oxygen isotope exchange may be important where nitrite does accumulate, such as oceanic primary and secondary nitrite maxima.This research was funded by the National Science Foundation Chemical Oceanography grants 05-26277 and 09- 610998 to K.L.C

Nitrogen cycling in the secondary nitrite maximum of the eastern tropical North Pacific off Costa Rica

Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 29 (2015): 2061–2081, doi:10.1002/2015GB005187.Nitrite is a central intermediate in the marine nitrogen cycle and represents a critical juncture where nitrogen can be reduced to the less bioavailable N2 gas or oxidized to nitrate and retained in a more bioavailable form. We present an analysis of rates of microbial nitrogen transformations in the oxygen deficient zone (ODZ) within the eastern tropical North Pacific Ocean (ETNP). We determined rates using a novel one-dimensional model using the distribution of nitrite and nitrate concentrations, along with their natural abundance nitrogen (N) and oxygen (O) isotope profiles. We predict rate profiles for nitrate reduction, nitrite reduction, and nitrite oxidation throughout the ODZ, as well as the contributions of anammox to nitrite reduction and nitrite oxidation. Nitrate reduction occurs at a maximum rate of 25 nM d−1 at the top of the ODZ, at the same depth as the maximum rate of nitrite reduction, 15 nM d−1. Nitrite oxidation occurs at maximum rates of 10 nM d−1 above the secondary nitrite maximum, but also in the secondary nitrite maximum, within the ODZ. Anammox contributes to nitrite oxidation within the ODZ but cannot account for all of it. Nitrite oxidation within the ODZ that is not through anammox is also supported by microbial gene abundance profiles. Our results suggest the presence of nitrite oxidation within the ETNP ODZ, with implications for the distribution and physiology of marine nitrite-oxidizing bacteria, and for total nitrogen loss in the largest marine ODZ.National Science Foundation. Grant Numbers OCE 05-26277, OCE 09-610998; WHOI Coastal Ocean Institute2016-06-1

Search for Magnetic Monopoles Trapped in Matter

There have been many searches for magnetic monopoles in flight, but few for monopoles in matter. We have searched for magnetic monopoles in meteorites, schists, ferromanganese nodules, iron ores and other materials. The detector was a superconducting induction coil connected to a SQUID (Superconducting Quantum Interference Device) with a room temperature bore 15 cm in diameter. We tested a total of more than 331 kg of material including 112 kg of meteorites. We found no monopole and conclude the overall monopole/nucleon ratio in the samples is $<1.2 \times 10^{-29}$ with a 90\% confidence level.Comment: 6 pages, rev tex, no figure

Isotopic constraints on nitrogen transformation rates in the deep sedimentary marine biosphere

Author Posting. © American Geophysical Union,2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Isotopic constraints on nitrogen transformation rates in the deep sedimentary marine biosphere. Global Biogeochemical Cycles, 32, (2018):1688–1702., doi: 10.1029/2018GB005948.Little is known about the nature of microbial community activity contributing to the cycling of nitrogen in organic-poor sediments underlying the expansive oligotrophic ocean gyres. Here we use pore water concentrations and stable N and O isotope measurements of nitrate and nitrite to constrain rates of nitrogen cycling processes over a 34-m profile from the deep North Atlantic spanning fully oxic to anoxic conditions. Using a 1-D reaction-diffusion model to predict the distribution of nitrogen cycling rates, results converge on two distinct scenarios: (1) an exceptionally high degree of coupling between nitrite oxidation and nitrate reduction near the top of the anoxic zone or (2) an unusually large N isotope effect (~60‰) for nitrate reduction that is decoupled from the corresponding O isotope effect, which is possibly explained by enzyme-level interconversion between nitrite and nitrate.Samples analyzed for this study were collected during the final expedition of the RV Knorr, KN223. The expedition would not have been possible without the captain and crew of the RV Knorr and the efforts of the shipboard science party. We would like to acknowledge Robert Pockalny for planning and facilitating the expedition. Inorganic geochemistry sample collection, processing, and analysis were performed shipboard by Arthur Spivack,Dennis Graham, Chloe Anderson, Emily Estes, Kira Homola, Claire McKinley, Theodore Present, and Justine Sauvage. Coring capabilities were provided by the Oregon State University and Woods Hole Oceanographic Institute Coring Facilities, directed and funded by the U. S. National Science Foundation (NSF) Ship Facilities Program. The cored materials and discrete samples from the expedition are curated and stored by the Marine Geological Samples Laboratory at the University of Rhode Island, codirected by Rebecca Robinson and Katherine Kelly and funded by the NSF Ocean Sciences Division. The nutrient and isotope data from pore waters in this study will be available at The Biological and Chemical Data Management Office (https://www.bcodmo.org/project/567401). This project was partially funded by an NSF CDEBI postdoctoral fellowship to C. Buchwald. Portions of this material are based upon work supported while R. W. M. was serving at the National Science Foundation.2019-04-1