End effect in MHD ducts with non-conducting partitions

End effect in magnetohydrodynamic ducts with nonconducting partition

Effects of the Zebra Mussel on Nitrogen Dynamics and the Microbial Community at the Sediment-Water Interface

A flow-through experiment was conducted on intact cores of sediments from Saginaw Bay, Lake Huron, to examine how trophic interactions between filter-feeding bivalve mussels and microbial populations could affect nitrogen dynamics at the sediment-water interface. The zebra mussels used in this experiment removed a large proportion of protozoa and phytoplankton from the overlying water, particularly heterotrophic nanoplankton (up to 82%), while bacterial populations showed less change. A 3-fold decrease in the protozoan to bacterial carbon ratio corresponded to a 2.5-fold increase in relative ammonium removal rates as estimated from the dark loss of N-15-ammonium. Excretion by the bivalves also increased net ammonium flux to the water, thus elevating the total calculated areal ammonium removal rates to about B-fold over rates observed in the control treatment. These data suggest that filter-feeding bivalves may significantly affect nitrogen transformation rates near the sediment-water interface by excreting ammonium and altering the microbial food web structure at the sediment-water interface

Valence and sea contributions to the nucleon spin

The first moments of the polarized valence parton distribution functions (PDFs) truncated to the wide Bjorken $x$ region $0.004<x<0.7$ are directly (without any fitting procedure) extracted in the next to leading order (NLO) QCD from both COMPASS and HERMES data on pion production in polarized semi-inclusive DIS (SIDIS) experiments. The COMPASS and HERMES data are combined in two ways and two scenarios for the fragmentation functions (FFs) are considered. Two procedures are proposed for an estimation of light sea quark contributions to the proton spin. Both of them lead to the conclusion that these contributions are compatible with zero within the errors.Comment: 14 pages; added reference

Cold Acclimation Strategy Is Highly Variable among the Sunfishes (Centrarchidae)

We tested the hypothesis that the physiological strategy for acclimating to low body temperature is similar among closely related fish. Largemouth bass (Micropterus salmoides), green sunfish (Lepomis cyanellus), bluegill sunfish (Lepomis macrochirus), black crappie (Pomonix nigromaculatus), and white crappie (Pomonix annularis), all members of the family Centrarchidae, were acclimated to 5° and 25°C. Morphometric variables (total mass, total length, organ masses) and enzyme activities (hexokinase; lactate dehydrogenase; and cytochrome oxidase in heart, liver, and muscle) were measured in 5°C- and 25°C-acclimated fish at 5° and 25°C assay temperatures. Each species displayed a distinct physiological response to cold acclimation that differed among tissues. These data suggest that the response to cold acclimation is highly variable within families. Our findings are consistent with other studies suggesting that acclimation responses are labile and may evolve independently even among closely related species. Reprinted by permission of the publisher

Effect of Shear Modes Interference in Anisotropic Materials

Ultrasonic signals transmitted through a plate by shear waves in weakly anisotropic materials are usually not separable in the time domain and thus interfere at the receiver. The interference signal bears information on material anisotropy due to texture or residual stresses. This dependence of the interference signals on material properties can be utilized practically. Blinka and Sachse [1] used interference of two shear waves to measure stress applied normally to the direction of wave propagation in an aluminum specimen. The phenomenon is also described in [2]. The change of acoustic microscopy contrast is attributed by Dreschler-Krasicka to stress induced interference [3]. Various interference phenomena in crystalline solids are described by Wolfe in [4]

Ultrasonic Characterization of Interfacial Fatigue Damage in Metal Matrix

In recent years there has been significant interest in titanium-based metal-matrix composites for structural applications in airframe and engine components. In many applications, these composites are integrated into structural components by diffusion bonding. Thus the composites are subjected to temperature/time cycles during material processing and to temperature/stress cycles in service. One major effect of these thermomechanical cycles is that they significantly alter the microstructure of the composite constituents and the residual stresses. Even though the changes in microstructure and residual stresses may not affect the composite properties greatly, they often lead to completely different failure mechanisms. Therefore, it is important to understand the role of heat treatment on composite damage development, which can only be done by nondestructively monitoring damage initiation and development during the failure process

“Задонщина”, Рязань и московская великокняжеская семья

This paper is devoted to the history and controversies surrounding the outstanding representative of Russian medieval literature from the late 14th century, the famous Zadonshchina. This work glorifies the military victory of the united forces of the Russian troops, led by Grand Prince Dmitry Donskoy, over the Tatar army on 8 September 1380, at Kulikovo Field near the Don River. This article presents arguments in favor of a Ryazan origin of the Zadonshchina text; furthermore, the article offers an explanation of the presence in the text of two “protagonists,” Grand Prince Dmitry Ivanovich and his cousin, Vladimir Andreyevich the Bold, Prince of Serpukhov. The joint rule of the “brothers” was a result of deaths caused by the plague in the Moscow ruling house, which took the dynasty to the brink of extinction. This feature of the political situation is reflected in the Zadonshchina text.Статья посвящена вопросам истории и происхождения выдающегося памятника литературы Древней Руси — “Задонщины”, воспевающей победу объединенных сил русских князей над Ордой на Куликовом поле 8 сентября 1380 г. Приводятся аргументы в пользу рязанского происхождения текста. Предпринимается попытка аргументированно объяснить наличие в тексте двух “главных героев”, великого князя Дмитрия Ивановича и его двоюродного брата Владимира Андреевича Серпуховского. Формальное соправительство “братьев” стало результатом потерь дома московских князей от чумы, поставивших династию на грань выживания. Эта особенность политической ситуации нашла свое отражение в “Задонщине”

The Effect of Dissolved Polyunsaturated Aldehydes on Microzooplankton Growth Rates in the Chesapeake Bay and Atlantic Coastal Waters

Allelopathy is wide spread among marine phytoplankton, including diatoms, which can produce cytotoxic secondary metabolites such as polyunsaturated aldehydes (PUA). Most studies on diatom-produced PUA have been dedicated to their inhibitory effects on reproduction and development of marine invertebrates. However, little information exists on their impact on key herbivores in the ocean, microzooplankton. This study examined the effects of dissolved 2E,4E-octadienal and 2E,4E-heptadienal on the growth rates of natural ciliate and dinoflagellate populations in the Chesapeake Bay and the coastal Atlantic waters. The overall effect of PUA on microzooplankton growth was negative, especially at the higher concentrations, but there were pronounced differences in response among common planktonic species. For example, the growth of Codonella sp., Leegaardiella sol, Prorodon sp., and Gyrodinium spirale was impaired at 2 nM, whereas Strombidium conicum, Cyclotrichium gigas, and Gymnodinium sp. were not affected even at 20 nM. These results indicate that PUA can induce changes in microzooplankton dynamics and species composition

Nitrogen cycling rates and light effects in tropical Lake Maracaibo, Venezuela

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109860/1/lno19984381814.pd