Arsenic speciation by ion-exchange chromatography with on- line determination by hydride generation: electronic modification of the D.C. plasma by photon counting

A method using L-cysteine for the determination of arsenous acid (As(III)), arsenic acid (As(V)), monomethylarsonic acid (MMAA), and dimethylarsinic acid (DMAA) by hydride generation was demonstrated. The instrument used was a d.c. plasma atomic emission spectrometer (OCP-AES). Complete recovery was reported for As(III), As(V), and DMAA while 86% recovery was reported for MMAA. Detection limits were determined, as arsenic for the species listed previously, to be 1.2, 0.8, 1.1, and 1.0 ngemL-l, respectively. Precision values, at 50 ngemL-1 arsenic concentration, were f.80/0, 2.50/0, 2.6% and 2.6% relative standard deviation, respectively. The L-cysteine reagent was compared directly with the conventional hydride generation technique which uses a potassium iodide-hydrochloric acid medium. Recoveries using L-cysteine when compared with the conventional method provided the following results: similar recoveries were obtained for As(III), slightly better recoveries were obtained for As(V) and MMAA, and significantly better recoveries for DMAA. In addition, tall and sharp peak shapes were observed for all four species when using L-cysteine. The arsenic speciation method involved separation by ion exchange .. high perfonnance liquid chromatography (HPLC) with on-line hydride generation using the L.. cysteine reagent and measurement byOCP-AES. Total analysis time per sample was 12 min while the time between the start of subsequent runs was approximately 20 min. A binary . gradient elution program, which incorporated the following two eluents: 0.01 and 0.5 mM tri.. sodium citrate both containing 5% methanol (v/v) and both at a pH of approximately 9, was used during the separation by HPLC. Recoveries of the four species which were measured as peak area, and were normalized against As(III), were 880/0, 290/0, and 40% for DMAA, MMAA and As(V), respectively. Resolution factors between adjacent analyte peaks of As(III) and DMAA was 1.1; DMAA and MMAA was 1.3; and MMAA and As(V) was 8.6. During the arsenic speciation study, signals from the d.c. plasma optical system were measured using a new photon-signal integrating device. The_new photon integrator developed and built in this laboratory was based on a previously published design which was further modified to reflect current available hardware. This photon integrator was interfaced to a personal computer through an AID convertor. The .photon integrator has adjustable threshold settings and an adjustable post-gain device.

The interpretation of music videos : an interactive relationship between medium and viewer

There is a great deal of evidence to support the examination of an interactive relationship between the medium and the viewer in the interpretation of mainstream media. The exact nature of this relationship, however, is not well understood. The current study was carried out to assess the variables that may help explain why certain people interpret media, such as music videos, differently than others. Jensen's concept of reception analysis describes the relationship between the medium and the audience, and thus remains a strong focus within this study. Differences in the interpretation of music videos were investigated as a function of Absorption, gender role, screen size, age and viewing experience. Multiple regression analyses uncovered independent predictions of sexuality and violence scores by absorption and experience, as well as an interaction between absorption and screen size in the sexuality rating of the music videos.

Weight-preoccupation, personality and depression in university students : an interactionist perspective

The present research was designed to examine Beck's (1983; 1987) cognitive diathesis-stress model of depression in a new context. Specifically, this cross-sectional study investigated whether Beck's cognitive-personality traits of sociotropy and autonomy interacted with a specific daily hassle/stressor, weightpreoccupation, in the prediction of depressed mood in women and men. Weightpreoccupation was chosen as the particular daily stressor, because, according to Kanner, Coyne, Schaeffer, and Lazarus (1981). concern about weight and physical appearance were two of the most troublesome daily hassles among university students. ContraIy to current stereotypes, men also express concerns with weight and appearance (Cash, Winstead, &, landi, 1986), in both the direction of weight loss and weight/muscle gain (Drewnowski &, Yee, 1987). Thus, unique to this study was the examination of weight-preoccupation in men, not only in the direction of weight loss, but also in the direction of weight and muscle gain. Two hundred and fifty-one undergraduates were administered the revised SociotropyAutonomy Scale (SAS), the Beck Depression Inventory (BDij, the Hassles and Uplifts Scale, the Eating Disorders Inventory (EDI), and the Restraint Scale (RS). Through a process of model building, a final model was devised in which depression (ie., BDI total scores) was regressed on personality (Le., SAS Sociotropy) and weight-preoccupation (i.e., Drive for Thinness, Body Dissatisfaction, and the Restraint Scale). Separate hierarchical multiple regression analyses, with BDI as the dependent variable, were carried out for each of the 2 3 weight-preoccupation variables. Results revealed a specific congruent interaction between weight,..preoccupation and personality. Specifically, drive for thinness and body dissatisfaction interacted with sociotropy to predict depressed mood in both women and men, but the interaction between sociotropy and the Restraint Scale was marginal. Findings suggested that weight-preoccupied women and men experienced depressed mood to the extent that they were characterized as more highly sociotropic. As predicted, personality (i.e., sociotropy), moderated the relationship between daily stress (i.e., weight-preoccupation) and depression. Thus, results revealed that the proposed diathesis-stress model seemed to operate in the same manner for women and men. Moreover, the examination of weightpreoccupation among men (i.e., in the direction of both weight loss and weight/muscle gain) further revealed that, when curvilinearity was taken into account, highly sociotropic men, who had a low desire to gain weight and muscle mass (i.e., most likely those who desired to lose weight), experienced higher levels of depressed mood than those who had a "medium" desire for weight and muscle gain. However, the highest levels of depressed mood was experienced by highly sociotropic men who were highly weight-preoccupied in the direction of wanting to gain weight and muscle mass. In addition, possible reasons for the present fmdings, as wen as iimitations and impiicalions for future research are discussed.

The effects of plants(Typha Latifolia)and root-bed medium on the treatment of domestic sewage within a vertical flow constructed wetland /

The effect that plants {Typha latifolia) as well as root-bed medium physical and chemical characteristics have on the treatment of primary treated domestic wastewater within a vertical flow constructed wetland system was investigated. Five sets of cells, with two cells in each set, were used. Each cell was made of concrete and measured 1 .0 m X 1 .0 m and was 1.3 m deep. Four different root-bed media were tested : Queenston Shale, Fonthill Sand, Niagara Shale and a Michigan Sand. Four of the sets contained plants and a single type of root-bed medium. The influence of plants was tested by operating a Queenston Shale set without plants. Due to budget constraints no replicates were constructed. All of the sets were operated independently and identically for twenty-eight months. Twelve months of data are presented here, collected after 16 months of continuous operation. Root-bed medium type did not influence BOD5 removal. All of the sets consistently met Ontario Ministry of Environment (MOE) requirements (<25 mg/L) for BOD5 throughout the year. The 12 month average BOD5 concentration from all sets with plants was below 2.36 mg/L. All of the sets were within MOE discharge requirements (< 25 mg/L) for suspended solids with set effluent concentrations ranging from 1.53 to 14.80 mg/L. The Queenston Shale and Fonthill Sand media removed the most suspended solids while the Niagara Shale set produced suspended solids. The set containing Fonthill Sand was the only series to meet MOE discharge requirements (< Img/L) for total phosphorus year-round with a twelve month mean effluent concentration of 0.23 mg/L. Year-round all of the root-bed media were well below MOE discharge requirements (< 20mg/L in winter and < 10 mg/L in sumnner) for ammonium. The Queenston Shale and Fonthill Sand sets removed the most total nitrogen. Plants had no effect on total nitrogen removal, but did influence how nitrogen was cycled within the system. Plants increased the removal of suspended solids by 14%, BOD5 by 10% and total phosphorus by 22%. Plants also increased the amount of dissolved oxygen that entered the system. During the plant growing season removal of total phosphorus was better in all sets with plants regardless of media type. The sets containing Queenston Shale and Fonthill Sand media achieved the best results and plants in the Queenston Shale set increased treatment efficiency for every parameter except nitrogen. Vertical flow wetland sewage treatment systems can be designed and built to consistently meet MOE discharge requirements year-round for BOD5, suspended solids, total phosphorus and ammonium. This system Is generally superior to the free water systems and sub-surface horizontal flow systems in cold climate situations.