Chlorination treatment of aqueous samples reduces, but does not eliminate, the mutagenic effect of the azo dyes Disperse Red 1, Disperse Red 13 and Disperse Orange 1

The treatment of textile effluents by the conventional method based on activated sludge followed by a chlorination step is not usually an effective method to remove azo dyes, and can generate products more mutagenic than the untreated dyes. The present work evaluated the efficiency of conventional chlorination to remove the genotoxicity/mutagenicity of the azo dyes Disperse Red 1, Disperse Orange 1, and Disperse Red 13 from aqueous solutions. The comet and micronucleus assays with HepG2 cells and the Salmonella mutagenicity assay were used. The degradation of the dye molecules after the same treatment was also evaluated, using ultraviolet and visible absorption spectrum measurements (UV-vis), high performance liquid chromatography coupled to a diode-array detector (HPLC-DAD), and total organic carbon removal (TOC) analysis. The comet assay showed that the three dyes studied induced damage in the DNA of the HepG2 cells in a dose-dependent manner. After chlorination, these dyes remained genotoxic, although with a lower damage index (DI). The micronucleus test showed that the mutagenic activity of the dyes investigated was completely removed by chlorination, under the conditions tested. The Salmonella assay showed that chlorination reduced the mutagenicity of all three dyes in strain YG1041, but increased the mutagenicity of Disperse Red 1 and Disperse Orange 1 in strain TA98. With respect to chemical analysis, all the solutions showed rapid discoloration and a reduction in the absorbance bands characteristic of the chromophore group of each dye. However, the TOC was not completely removed, showing that chlorination of these dyes is not efficient in mineralizing them. It was concluded that conventional chlorination should be used with caution for the treatment of aqueous samples contaminated with azo dyes. (C) 2010 Elsevier B.V. All rights reserved.

A Comparative Analysis of the Changes During Evaporation of Three Different Commercial Emulsion of Unknown Composition

Optical microscope and centrifugation were used to observe the structure change during evaporation of three different commercial emulsions of unknown composition. The degree of evaporation under an infrared lamp at 70 degrees C was determined from the changed weight of a microscope slide with the emulsion on a defined area and thickness. The results revealed information as to which kind of structure would appear after evaporation.

Compact tiled display with uniform illumination

The demand for more pixels is beginning to be met as manufacturers increase the native resolution of projector chips. Tiling several projectors still offers a solution to augment the pixel capacity of a display. However, problems of color and illumination uniformity across projectors need to be addressed as well as the computer software required to drive such devices. We present the results obtained on a desktop-size tiled projector array of three D-ILA projectors sharing a common illumination source. A short throw lens (0.8:1) on each projector yields a 21-in. diagonal for each image tile; the composite image on a 3×1 array is 3840×1024 pixels with a resolution of about 80 dpi. The system preserves desktop resolution, is compact, and can fit in a normal room or laboratory. The projectors are mounted on precision six-axis positioners, which allow pixel level alignment. A fiber optic beamsplitting system and a single set of red, green, and blue dichroic filters are the key to color and illumination uniformity. The D-ILA chips inside each projector can be adjusted separately to set or change characteristics such as contrast, brightness, or gamma curves. The projectors were then matched carefully: photometric variations were corrected, leading to a seamless image. Photometric measurements were performed to characterize the display and are reported here. This system is driven by a small PC cluster fitted with graphics cards and running Linux. It can be scaled to accommodate an array of 2×3 or 3×3 projectors, thus increasing the number of pixels of the final image. Finally, we present current uses of the display in fields such as astrophysics and archaeology (remote sensing).

Gauge fields, geometric phases, and quantum adiabatic pumps

Quantum adiabatic pumping of charge and spin between two reservoirs (leads) has recently been demonstrated in nanoscale electronic devices. Pumping occurs when system parameters are varied in a cyclic manner and sufficiently slowly that the quantum system always remains in its ground state. We show that quantum pumping has a natural geometric representation in terms of gauge fields (both Abelian and non-Abelian) defined on the space of system parameters. Tunneling from a scanning tunneling microscope tip through a magnetic atom could be used to demonstrate the non-Abelian character of the gauge field.

Bifurcation in growth patterns for arrays of parallel Griffith, edge and sliding cracks

This paper presents the recent finding by Muhlhaus et al [1] that bifurcation of crack growth patterns exists for arrays of two-dimensional cracks. This bifurcation is a result of the nonlinear effect due to crack interaction, which is, in the present analysis, approximated by the dipole asymptotic or pseudo-traction method. The nonlinear parameter for the problem is the crack length/ spacing ratio lambda = a/h. For parallel and edge crack arrays under far field tension, uniform crack growth patterns (all cracks having same size) yield to nonuniform crack growth patterns (i.e. bifurcation) if lambda is larger than a critical value lambda(cr) (note that such bifurcation is not found for collinear crack arrays). For parallel and edge crack arrays respectively, the value of lambda(cr) decreases monotonically from (2/9)(1/2) and (2/15.096)(1/2) for arrays of 2 cracks, to (2/3)(1/2)/pi and (2/5.032)(1/2)/pi for infinite arrays of cracks. The critical parameter lambda(cr) is calculated numerically for arrays of up to 100 cracks, whilst discrete Fourier transform is used to obtain the exact solution of lambda(cr) for infinite crack arrays. For geomaterials, bifurcation can also occurs when array of sliding cracks are under compression.

ESEM observations of SCC initiation for 4340 high strength steel in distilled water

The stress corrosion cracking (SCC) initiation process for 4340 high strength steel in distilled water at room temperature was studied using a new kind of instrument: an environmental scanning electron microscope (ESEM). It was found that the applied stress accelerated oxide film formation which has an important influence on the subsequent SCC initiation. SCC was observed to initiate in the following circumstances: (1) cracking of a thick oxide film leading to SCC initiation along metal grain boundaries, (2) the initiation of pits initiating SCC in the metal and (3) SCC initiating from the edge of the specimen. All these three SCC initiation circumstances are consistent with the following model which couples SCC initiation with cracking of a surface protective oxide. There is a dynamic interaction between oxide formation, the applied stress, oxide cracking, pitting and the initiation of SCC. An aspect of the dynamic interaction is cracks forming in a protective surface oxide because of the applied stress, exposing to the water bare metal at the oxide crack tip, and oxidation of the bare metal causing crack healing. Oxide crack healing would be competing with the initiation of intergranular SCC if an oxide crack meets the metal surface at a grain boundary. If the intergranular SCC penetration is sufficiently fast along the metal grain boundary, then the crack yaws open preventing healing of the oxide crack. If intergranular SCC penetration is not sufficiently fast, then the oxidation process could produce sufficient oxide to fill both the stress corrosion crack and the oxide crack; in this case there would be initiation of SCC but only limited propagation of SCC. Stress-induced cracks in very thin oxide can induce pits which initiate SCC, and under some conditions such stress induced cracks in a thin oxide can directly initiate SCC.

Seven retinal specializations in the tubular eye of the deep-sea pearleye, Scopelarchus michaelsarsi: A case study in visual optimization

The deep-sea pearleye, Scopelarchus michaelsarsi (Scopelarchidae) is a mesopelagic teleost with asymmetric or tubular eyes. The main retina subtends a large dorsal binocular field, while the accessory retina subtends a restricted monocular field of lateral visual space. Ocular specializations to increase the lateral visual field include an oblique pupil and a corneal lens pad. A detailed morphological and topographic study of the photoreceptors and retinal ganglion cells reveals seven specializations: a centronasal region of the main retina with ungrouped rod-like photoreceptors overlying a retinal tapetum; a region of high ganglion cell density (area centralis of 56.1x10(3) cells per mm(2)) in the centrolateral region of the main retina; a centrotemporal region of the main retina with grouped rod-like photoreceptors; a region (area giganto cellularis) of large (32.2+/-5.6 mu m(2)), alpha-like ganglion cells arranged in a regular array (nearest neighbour distance 53.5+/-9.3 mu m with a conformity ratio of 5.8) in the temporal main retina; an accessory retina with grouped rod-like photoreceptors; a nasotemporal band of a mixture of rod-and cone-like photoreceptors restricted to the ventral accessory retina; and a retinal diverticulum comprised of a ventral region of differentiated accessory retina located medial to the optic nerve head. Retrograde labelling from the optic nerve with DiI shows that approximately 14% of the cells in the ganglion cell layer of the main retina are displaced amacrine cells at 1.5 mm eccentricity. Cryosectioning of the tubular eye confirms Matthiessen's ratio (2.59), and calculations of the spatial resolving power suggests that the function of the area centralis (7.4 cycles per degree/8.1 minutes of are) and the cohort of temporal alpha-like ganglion cells (0.85 cycles per degree/70.6 minutes of are) in the main retina may be different. Low summation ratios in these various retinal zones suggests that each zone may mediate distinct visual tasks in a certain region of the visual field by optimizing sensitivity and/or resolving power.

Membrane-bounded nucleoids in microbial symbionts of marine sponges

In thin sections of resin-embedded samples of glutaraldehyde- and osmium tetroxide-fixed tissue from five genera of marine sponges, Stromatospongia, Astrosclera, Jaspis, Pseudoceratina and Axinyssa, cells of a bacteria-like symbiont microorganism which exhibit a membrane-bounded nuclear region encompassing the fibrillar nucleoid have been observed within the sponge mesohyl. The nuclear region in these cells is bounded by a single bilayer membrane, so that the cell cytoplasm is divided into two distinct regions. The cell wall consists of subunits analogous to those in walls of some Archaea. Cells of the sponge symbionts observed here are similar to those of the archaeal sponge symbiont Cenarchaeum symbiosum. (C) 1998 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.

The role of parental anxiety in the treatment of childhood anxiety

Sixty-seven children aged 7 to 14 who met diagnostic criteria for an anxiety disorder were assigned to conditions according to parental anxiety level. Within these conditions, children were randomly assigned to I of 2 treatments: child-focused cognitive-behavioral therapy (CBT) or child-focused CBT plus parental anxiety management (CBT + PAM). At posttreatment, results indicated that within the child-anxiety-only condition, 82% of the children in the CBT condition no longer met criteria for an anxiety disorder compared with 80% in the CBT + PAM condition. Within the child + parental anxiety condition, 39% in the CBT condition no longer met criteria compared with 77% in the CBT + PAM condition. At follow-up, these differences were maintained, with some weakening over time. Results were not consistent across outcome measures. The interpretation and potential clinical implications of these findings are discussed.

Evidence of multiple transcription initiation and termination sites within the rDNA intergenic spacer and rRNA readthrough transcription in the urochordate Herdmania curvata

Analysis of the structure of the urochordate Herdmania curvata ribosomal DNA intergenic spacer (IGS) and its role in transcription initiation and termination suggests that rRNA gene regulation in this chordate differs from that in vertebrates. A cloned H, curvata IGS is 1881 bp and composed predominantly of two classes of similar repeat sequences that largely alternate in a tandem array. Southern blot hybridization demonstrates that the IGS length variation within an individual and population is largely the result of changes in internal repeat number. Nuclease S1 mapping and primer extension analyses suggest that there are two transcription initiation sites at the 3' end of the most 3' repetitive element; these sites are 6 nucleotides apart. Unlike mouse, Xenopus, and Drosophila, there is no evidence of transcription starting elsewhere in the IGS. Most sequence differences between the promoter repeat and the other internal repeats are in the vicinity of the putative initiation sites. As in Drosophila, nuclease S1 mapping of transcription termination sites suggest that there is not a definitive stop site and a majority of the pre-rRNAs read through a substantial portion of the IGS. Some transcription appears to proceed completely through the promoter repeat into the adjacent rDNA unit. Analysis of oocyte RNA by reverse transcription-polymerase chain reaction (RT-PCR) confirms that readthrough transcription into the adjacent rDNA unit is occurring in some small IGS length variants; there is no evidence of complete readthrough of IGSs larger than 1.0 kb.

A numerical study of large sparse matrix exponentials arising in Markov chains

Krylov subspace techniques have been shown to yield robust methods for the numerical computation of large sparse matrix exponentials and especially the transient solutions of Markov Chains. The attractiveness of these methods results from the fact that they allow us to compute the action of a matrix exponential operator on an operand vector without having to compute, explicitly, the matrix exponential in isolation. In this paper we compare a Krylov-based method with some of the current approaches used for computing transient solutions of Markov chains. After a brief synthesis of the features of the methods used, wide-ranging numerical comparisons are performed on a power challenge array supercomputer on three different models. (C) 1999 Elsevier Science B.V. All rights reserved.AMS Classification: 65F99; 65L05; 65U05.

Temperature-induced bleaching of corals begins with impairment of the CO2 fixation mechanism in zooxanthellae

The early effects of heat stress on the photosynthesis of symbiotic dinoflagellates (zooxanthellae) within the tissues of a reef-building coral were examined using pulse-amplitude-modulated (PAM) chlorophyll fluorescence and photorespirometry. Exposure of Stylophora pistillata to 33 and 34 degrees C for 4 h resulted in (1) the development of strong non-photochemical quenching (qN) of the chlorophyll fluorescence signal, (2) marked decreases in photosynthetic oxygen evolution, and (3) decreases in optimal quantum yield (F-v/F-m) of photosystern II (PSII), Quantum yield decreased to a greater extent on the illuminated surfaces of coral branches than on lower (shaded) surfaces, and also when high irradiance intensities were combined with elevated temperature (33 degrees C as opposed to 28 degrees C), qN collapsed in heat-stressed samples when quenching analysis was conducted in the absence of oxygen, Collectively, these observations are interpreted as the initiation of photoprotective dissipation of excess absorbed energy as heat (qN) and O-2-dependent electron flow through the Mehler-Ascorbate-Peroxidase cycle (MAP-cycle) following the point at which the rate of light-driven electron transport exceeds the capacity of the Calvin cycle. A model for coral bleaching is proposed whereby the primary site of heat damage in S, pistillata is carboxylation within the Calvin cycle, as has been observed during heat damage in higher plants, Damage to PSII and a reduction in F-v/F-m (i.e. photoinhibition) are secondary effects following the overwhelming of photoprotective mechanisms by light. This secondary factor increases the effect of the primary variable, temperature. Potential restrictions of electron flow in heat-stressed zooxanthellae are discussed with respect to Calvin cycle enzymes and the unusual status of the dinoflagellate Rubisco, Significant features of our model are that (1) damage to PSII is not the initial step in the sequence of heat stress in zooxanthellae, acid (2) light plays a key secondary role in the initiation of the bleaching phenomena.

Self-efficacy for refusal mediated by outcome expectancies in the prediction of alcohol-dependence amongst young adults

The present study examined the relative importance of outcome expectancies and self-efficacy [1] in the prediction of alcohol dependence [2] and alcohol consumption in a sample of young adult drinkers drawn from a milieu previously reported as supportive of risky drinking. In predicting alcohol dependence, outcome expectancies were found to mediate self-efficacy and the same pattern was found for both males and females. This suggests that male and female drinkers may become more similar as they progress along the drinking continuum from risky drinking to dependent drinking. However, in women, in comparison to men, a greater array of expectancies and self-efficacy scales were found to predict heavy drinking, as measured by quantity and frequency. These results suggest that heavy drinking women are particularly at risk of developing drinking related complications and that preventative education needs to take into account gender differences.