The influence of oxidation reduction potential and water treatment processes on quartz lamp sleeve fouling in ultraviolet disinfection reactors

Ultraviolet (UV) disinfection systems are incorporated into drinking water production facilities because of their broad-spectrum antimicrobial capabilities, and the minimal disinfection by-product formation that generally accompanies their use. Selection of an optimal location for a UV system within a drinking water treatment facility depends on many factors; a potentially important consideration is the effect of system location on operation and maintenance issues, including the potential for fouling of quartz surfaces. To examine the effect of system location on fouling, experiments were conducted at a groundwater treatment facility, wherein aeration, chlorination, and sand filtration were applied sequentially for treatment. In this facility, access to the water stream was available prior to and following each of the treatment steps. Therefore, it was possible to examine the effects of each of these unit operations on fouling dynamics within a UV system. Results indicated zero-order formation kinetics for the fouling reactions at all locations. Increases in oxidation reduction potential, caused by water treatment steps such as aeration and chlorination, increased the rate of sleeve fouling and the rate of irradiance loss within the reactor. Analysis of metals in the sleeve foulant showed that calcium and iron predominate, and relative comparisons of foulant composition to water chemistry highlighted a high affinity for incorporation into the foulant matrix for both iron and manganese, particularly after oxidizing treatment steps. Fouling behavior was observed to be in qualitative agreement with representations of the degree of saturation, relative to the metal:ligand combinations that are believed to comprise a large fraction of the foulants that accumulate on the surfaces of quartz jackets in UV systems used to treat water.     

Saving Sergeant Buske. An account of remarkable valor and amazing survival from the records of the 65th General Hospital, a Duke University Army Reserve Unit of World War II

BACKGROUND: Attentional processes are assumed to play an important role in the maintenance of illness anxiety, although empirical support is relatively scarce. METHODS: The present study explores the relationship between selective attention (i.e. private body consciousness and symptom reporting), intensive concentration (i.e. attentional control and sustained attention), and illness anxiety in 57 non-clinical subjects. RESULTS: Zero-order and multiple correlations suggest that illness anxiety is significantly related to cognitive failures in everyday life and private body consciousness and to a lesser extent to symptom reporting. CONCLUSION: It is concluded that illness anxiety can be partly predicted from specific attentional variables. However, specific operationalizations of attentional parameters seems to determine the existence and magnitude of these relations.     

Magnetic response of a hollow ellipsoid

The response of a ferrous ellipsoidal target in the presence of an applied magnetic field is studied. The ellipsoid is allowed to have two layers of contrasting magnetic permeability, and the frequency is assumed low enough to neglect any eddy currents. Because of its versatile geometry, the ellipsoid can represent several common shapes, such as discs, pancakes, cigars, and vertical or horizontal plates. Several special cases are considered in detail, including a hollow ellipsoid made of a thin, highly permeable shell. It is shown that the cross-polar component of the scattered field bears information about the ellipsoid's location     

Note on the impedance of a wire grid parallel to homogeneousinterface

Numerical data are provided for the correction factor that is used to calculate the impedance of a planar wire grid parallel to the interface between two dielectric half-spaces. Comparisons with earlier investigations clarify, extend, and supersede previous computations. The authors show more clearly the significant influence of the interface on the equivalent grid impedance     

Factors affecting the reliability and precision of the spectroscopic determination of vitamin A

Summary By means of simple statistical methods the effects of technique, laboratory equipment, solvents, temperature, and instruments on the precision and accuracy of the determination of the extinction coefficient at 328 mμ of fish liver oils are outlined. Methyl, ethyl, propyl and butyl alcohols give successively lower E-values. As the temperature increases, Beckman spectrophotometers tend to give lower values. The cells used to hold the solutions to be measured need to be individually checked. No suitable standards for spectrophotometers are yet available, but potassium nitrate, potassium chromate, and Bureau of Standard glasses are useful. By careful observance of all the variations discussed the determination of the E-value may be made with considerable precision; the value of σ, the standard deviation, is 0.22%. Communication No. 82 from the Laboratories of Distillation Products, Inc.     

A pilot study of lithium carbonate plus divalproex sodium for the continuation and maintenance treatment of patients with bipolar I disorder

PURPOSE OF STUDY: To assess whether selected periapical radiographs, taken according to High Yield Criteria, can reveal as much intra-osseous pathology as universal panoramic screening. POPULATION STUDIED: The records of 1101 RAF recruits enlisted in 1988-89, average age 19 years (range 16-26). METHODS: The clinical records and bitewing radiographs of the recruits were examined and the requirement for periapical radiographs determined according to high yield criteria. A template, cut out to simulate the area covered by a periapical bitewing radiograph, was placed over the suspect region on the panoramic film and any findings found within the template recorded. The entire dental panoramic tomograph was then examined on a masked screen under 2X magnification and any further findings recorded. FINDINGS: There was a considerable number of findings reported, including three large isolated radiolucent areas, 75 periradicular radiolucent areas, four probable cysts and 1187 unerupted mandibular third molars. However, when the clinical significance of these 'lesions' was assessed only those related to dental causes appeared to have significant clinical implications and the results indicated that these could have been detected by selective radiology. CONCLUSION: This study showed that the only pathology which occurs frequently enough to justify radiographic screening of the jaws in young adults is related to teeth. It seems probable that this type of pathology can be at least as well detected by selective periapical screening, using high yield criteria, as is possible by universal panoramic screening.     

Glutathione synthetase is dispensable for growth under both normal and oxidative stress conditions in the yeast Saccharomyces cerevisiae due to an accumulation of the dipeptide gamma-glutamylcysteine

Glutathione (GSH) synthetase (Gsh2) catalyzes the ATP-dependent synthesis of GSH from gamma-glutamylcysteine (gamma-Glu-Cys) and glycine. GSH2, encoding the Saccharomyces cerevisiae enzyme, was isolated and used to construct strains that either lack or overproduce Gsh2. The identity of GSH2 was confirmed by the following criteria: 1) the predicted Gsh2 protein shared 37-39% identity and 58-60% similarity with GSH synthetases from other eukaryotes, 2) increased gene dosage of GSH2 resulted in elevated Gsh2 enzyme activity, 3) a strain deleted for GSH2 was dependent on exogenous GSH for wild-type growth rates, and 4) the gsh2 mutant lacked GSH and accumulated the dipeptide gamma-Glu-Cys intermediate in GSH biosynthesis. Overexpression of GSH2 had no effect on cellular GSH levels, whereas overexpression of GSH1, encoding the enzyme for the first step in GSH biosynthesis, lead to an approximately twofold increase in GSH levels, consistent with Gsh1 catalyzing the rate-limiting step in GSH biosynthesis. In contrast to a strain deleted for GSH1, which lacks both GSH and gamma-Glu-Cys, the strain deleted for GSH2 was found to be unaffected in mitochondrial function as well as resistance to oxidative stress induced by hydrogen peroxide, tert-butyl hydroperoxide, and the superoxide anion. Furthermore, gamma-Glu-Cys was at least as good as GSH in protecting yeast cells against an oxidant challenge, providing the first evidence that gamma-Glu-Cys can act as an antioxidant and substitute for GSH in a eukaryotic cell. However, the dipeptide could not fully substitute for the essential function of GSH in the cell as shown by the poor growth of the gsh2 mutant on minimal medium. We suggest that this function may be the detoxification of harmful intermediates that are generated during normal cellular metabolism.     

HF ground wave propagation over sea ice for a spherical Earth model

Calculations of the field strength at 10 MHz are reported for a ground wave signal where the path is sea water covered by a uniform layer of sea ice. It is shown that a surface wave type mode may dominate the conventional ground wave modes at the shorter ranges (i.e., < 10 km). At larger ranges the field strength due to the ice layer may be seriously degraded.     

Radiation from a spherical aperature antenna immersed in a compressible plasma

The exterior boundary-value problem for a sphere immersed in a compressible plasma medium is solved. The model is a perfectly conducting sphere excited by an aperture, in its surface, which has a specified distribution of the tangential electric field. The configuration is such that Maxwell's equations, when combined with the continuum theory of fluid dynamics, are separable. The sheath at the interface with the plasma is characterized by an absorptive boundary condition which assumes a linear relationship between the pressure and the mean velocity of the electrons. It is shown that the TM (transverse magnetic) waves are coupled with the electroacoustic waves, while the TE (transverse electric) waves are decoupled. Some numerical results are presented which show, in quantitative manner, the relative fraction of the total power which is radiated in the form of electroacoustic waves.