Development of a magnetite tracer protocol for seasonal measurement of bed sediment biodiffusion coefficients

This thesis describes the development of a particle tracer technique for making short-term, in situ measurements of aquatic bed sediment biodiffusion coefficients. The bioturbation process in the upper sediment layers of streams, lakes, estuaries, and the marine environment moves particles and porewater. When present, organic chemicals, metals, colloids, etc., are transported across these layers and exchanges may occur at the sediment-water interface. Fickian biodiffusion coefficients that characterize such particle movements, Db (cm2/yr), are used for assessing chemical diagenesis rates and contaminant fluxes and are specific to each site. Chemical Fate and Transport (CFaT) models, developed for tracking contaminants in aquatic environments, require a method of measuring the biodiffusion coefficient at specific locations. This measurement protocol should also be able to detect seasonal or other time dependent variations in the biodiffusion coefficient for improved model predictions. Magnetite, a tracer with a long historical use in scientific studies of porous media, particle transport, etc., was chosen. Unlike most of the other tracers used in this field, magnetite, an inexpensive and naturally occurring iron oxide, is readily obtained from ceramic supply companies and gives reasonable estimations of biodiffusion coefficients from short-term experiments. The steps in the protocol include deployment and retrieval of the tracer, magnetite separation and measurement, math model interpretation, and statistical treatment of data. Application of the technique was tested on South Capitol Lake, a manmade, freshwater lake located in Baton Rouge, Louisiana. The surficial sediment in this lake was found to contain a fairly large population of oligochaete worms in abundances of approximately 18 000 worms/m2. Field deployments of magnetite were conducted in December 2001, January 2002, and February 2002, giving biodiffusion coefficient values of 0.9495 ± 0.2565 cm2/yr, 0.4566 ± 0.3314 cm2/yr, and 0.6591 ± 0.3876 cm2/yr, respectively. Although the protocol was capable of in situ measurements, testing over one or more calendar years at this and other sites will be needed to determine if the magnetite tracer protocol can be used to detect changes in Db with the seasons of the year

Greater Severity of Peanut Challenge Reactions Using a High fat versus Low Fat Matrix Vehicle

Food allergy is a potentially life-threatening disease with a detrimental effect on the quality of life of caregivers and children.(1) Although many different types of food have been identified as potential elicitors of allergic reactions, only a small number of these foods cause the majority of reactions.(2) Food consists of a complex mixture of nutrient and non-nutrient components and their molecular interactions, which are known as the food matrix. Individual matrix components, or the matrix as a whole, may interact with a food allergen and may influence the clinical response to that allergen. This article is protected by copyright. All rights reserved

Can we identify patients at risk of life-threatening allergic reactions to food?

Anaphylaxis has been defined as a “severe, life-threatening generalized or systemic hypersensitivity reaction”. However, data indicate that the vast majority of food-triggered anaphylactic reactions are not life-threatening. Nonetheless, severe life-threatening reactions do occur, and are unpredictable. We discuss the concepts surrounding perceptions of severe, life-threatening allergic reactions to food by different stakeholders, with particular reference to the inclusion of clinical severity as a factor in allergy and allergen risk management. We review the evidence regarding factors which might be used to identify those at most risk of severe allergic reactions to food, and the consequences of misinformation in this regard. For example, a significant proportion of food-allergic children also have asthma, yet almost none will experience a fatal food-allergic reaction; asthma is not, in itself, a strong predictor for fatal anaphylaxis. The relationship between dose of allergen exposure and symptom severity is unclear. While dose appears to be a risk factor in at least a subgroup of patients, studies report that individuals with prior anaphylaxis do not have a lower eliciting dose than those reporting previous mild reactions. It is therefore important to consider severity and sensitivity as separate factors, as a highly sensitive individual will not necessarily experience severe symptoms during an allergic reaction. We identify the knowledge gaps which need to be addressed to improve our ability to better identify those most at risk of severe foodinduced allergic reactions

Energy Guideline Factors Provide a Better Measure of Refinery Energy Performance

Exxon Company, U.S.A. refineries reduced energy consumption by 25% between 1972 and 1978 compared with an 18% reduction for the U.S. Petroleum Refining Industry over the same period. The Exxon approach to conserving energy in petroleum refining operations goes beyond energy conservation housekeeping measures and investments, and uses a comprehensive method to measure energy efficiency rather than energy consumption per barrel. It uses the Exxon Research and Engineering developed energy guideline factors, which are based on energy efficient designs and criteria, to (1) Evaluate the energy efficiency performance of refineries of different complexity in a consistent manner. (2) Compensate for changes in individual process unit throughputs and in unit operating intensity/severity. (3) Identify and quantify areas of energy inefficiency. (4) Regularly monitor and steward energy efficiency performance. Effective conservation also requires the analysis of energy performance and setting goals for future improvement. The paper explains how this can be done

NOVEL SILICON BISALKOXY COMPLEXES WITH A PSEUDO-ATRANE STRUCTURE - SYNTHESIS AND MOLECULAR-STRUCTURES OF 2,6-DI(2-HYDROXY(2-ADAMANTYL))ETHYLPYRIDINE AND 2,6-DI(2-OXY(2-ADAMANTYLIDINE))ETHYLPYRIDINE DIMETHYLSILICON

Reaction of 2,6-lutidine with 2 equivalents of (n)BuLi followed by addition of 2-adamantanone affords the doubly functionalized 2,6-di-(2-oxy(2-adamantylidine))ethylpyridine (2a). Reaction of 2a with Me(2)SiCl(2) gives the pseudo-pentacoordinate 2,6-di-(2-oxy(2-adamantylidine))-ethylpyridinedimethylsilicon (4). The structures of 2a and 4 have been determined by an X-ray diffraction study