Condensation of a supersaturated vapor. V. The nucleating effects of ultraviolet light on vapors containing very low concentrations of o‐tolualdehyde

1981 ◽  
Vol 75 (3) ◽  
pp. 1459-1474 ◽  
Author(s):  
Joseph L. Katz ◽  
Timothy McLaughlin ◽  
F. C. Wen
Keyword(s):  
Ultraviolet Light ◽  
Supersaturated Vapor ◽  
Low Concentrations

Concentrations of Endotoxins in Waters Around the Island of Montreal, and Treatment Options

2008 ◽  
Vol 43 (4) ◽  
pp. 291-303 ◽  
Author(s):  
Ronald Gehr ◽  
Santiago Parent Uribe ◽  
Isabel Fatima Da Silva Baptista ◽  
Bruce Mazer
Keyword(s):  
Ultraviolet Light ◽  
Contact Time ◽  
Treatment Options ◽  
Test Methods ◽  
Water Disinfection ◽  
Gram Negative Bacteria ◽  
Limulus Amebocyte Lysate ◽  
Low Concentrations ◽  
Drinking Water Disinfection ◽  
Factor C

Abstract Endotoxins are a component of most Gram negative bacteria, and some cyanobacteria. They may be toxic to humans when inhaled or injected, but the effects are unclear when they are ingested. In fact, low concentrations may protect children against certain allergies. Data for endotoxins in Quebec waters are unavailable, hence this study mapped levels in the waters around Montreal, using two commercial test methods. The recently developed factor C method had a greater linear range and was more convenient to use than the widely used Limulus amebocyte lysate (LAL) method. Although the methods gave endotoxin values of the same order, a consistent relationship between the two could not be established. Endotoxin concentrations in the untreated waters varied from 32 to 1,188 EU/mL, comparable in the literature from pristine waters to wastewaters. Values were generally lower in the summer. Filtration is known to be partially effective at removing endotoxins, but the effects of disinfection are not well established. Accordingly, chlorination, ozonation, and ultraviolet light were tested for the destruction of endotoxins in water, at doses found during drinking water disinfection. While chlorine and ultraviolet light had minimal effects on endotoxin levels, ozone could achieve up to 60% reductions at Ct values (concentration x contact time) as low as 2.5 mg•min/L.

Regulation of Anthocyanin Synthesis in Apple Skin. I. Comparison of the Effects of Cycloheximide, Ultraviolet Light, Wounding and Maturity

1977 ◽  
Vol 4 (1) ◽  
pp. 111 ◽  
Author(s):  
DJ Chalmers ◽  
JD Faragher
Keyword(s):  
Ultraviolet Light ◽  
Specific Treatment ◽  
Primary Effect ◽  
Anthocyanin Synthesis ◽  
Secondary Effect ◽  
Anthocyanin Accumulation ◽  
Fruit Tissue ◽  
Anthocyanin Formation ◽  
Low Concentrations ◽  
Fruit Maturity

Cycloheximide applied to apple skin discs inhibited anthocyanin synthesis even at very low concentrations (0.01 �g ml-1) but stimulated accumulation in whole apple skin at concentrations between 0.05 and 30 �g ml-1. When cycloheximide was applied as a drop to whole fruit, anthocyanin synthesis was inhibited in the zone of application. A region of enhanced synthesis surrounded the inhibited area when the concentration was 1 �g ml-1 or higher. Inhibition appears to be the primary effect, while stimulation is a secondary effect of the application of cycloheximide. Similarly, exposure to u.v. light for 5-60 min promoted anthocyanin accumulation. Wounding of fruit tissue, as a specific treatment or while preparing skin discs, increased the level of anthocyanin in the skin and replaced the stimulating effect on anthocyanin formation of applied u.v. light or cycloheximide. The effects of wounding and cycloheximide decreased with increasing fruit maturity. The data suggested that wounding, u.v. light, maturity and cycloheximide act through a common effector, perhaps ethylene.

Toxicity, Analysis, and Production of Aspergillic Acid and its Analogues

1973 ◽  
Vol 51 (9) ◽  
pp. 1311-1315 ◽  
Author(s):  
J. C. MacDonald
Keyword(s):  
Ultraviolet Light ◽  
Aspergillus Flavus ◽  
Yeast Extract ◽  
Separate Study ◽  
Differential Analysis ◽  
Liquid Media ◽  
Low Concentrations ◽  
Toxicity Analysis

A differential analysis, utilizing the decomposition of 3,6-disubstituted-1-hydroxy-2(1H) pyrazinones (HPYs) by ultraviolet light, was developed to measure low concentrations of total HPYs (aspergillic acid and/or its analogues) in cultures.Two strains of Aspergillus flavus were found to differ in their ability to produce aflatoxins and HPYs on liquid media composed of 2% yeast extract and varying amounts of sucrose. Production of HPYs by both strains was best in the absence of sucrose and production of aflatoxins was best on media containing 10–20% sucrose. The better producer of HPYs was strain PRL 932, but when it was grown on moist seeds of peas, barley, maize, or wheat, it produced only traces of these compounds.In a separate study, two analogues of aspergillic acid were tested for toxicity in mice. The toxicity of a novel analogue, 3-(2-(methylthio)-ethyl)-6-sec-butyl-1-hydroxy-2(1H) pyrazinone, was the same as that of a more common analogue, neoaspergillic acid.

scholarly journals Influence of Polyphosphates on the Physicochemical Properties of Poly (Vinyl Chloride) after Irradiation with Ultraviolet Light

Polymers ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 193 ◽  
Author(s):  
Gamal A. El-Hiti ◽  
Dina S. Ahmed ◽  
Emad Yousif ◽  
Mohammad Hayal Alotaibi ◽  
Hind A. Satar ◽  
...  
Keyword(s):  
Surface Morphology ◽  
Ultraviolet Light ◽  
Vinyl Chloride ◽  
Phosphate Ester ◽  
Optical Scanning ◽  
Atomic Force ◽  
Poly Vinyl Chloride ◽  
Low Concentrations ◽  
Ft Ir ◽  
Acidic Conditions

Three new polyphosphates were synthesized in good yields by reacting diethylenetriamine with the appropriate phosphate ester in ethanol under acidic conditions. The polyphosphate structures were determined using FT-IR and 1H-NMR spectroscopies, and their elemental compositions were confirmed by EDX spectroscopy. Polyphosphates were added to poly(vinyl chloride) (PVC) at low concentrations to fabricate thin films. The PVC films were irradiated with ultraviolet light for long periods, and the effect of polyphosphates as the photostabilizer was investigated by determining changes in the infrared spectra (intensity of specific functional group peaks), reduction in molecular weight, weight loss, and surface morphology. Minimal changes were seen for PVC films containing polyphosphate compared to that for the blank film. In addition, optical, scanning electron, and atomic force microscopies were used to inspect the surface morphology of films. Undesirable changes due to photodegradation were negligible in PVC films containing additives compared to films containing no additives. In addition, the surfaces were smoother and more homogeneous. Polyphosphates, and in particular ones that contain an ortho-geometry, act as efficient photostabilizers to reduce the rate of photodegradation. Polyphosphates absorb ultraviolet light, chelate with polymeric chains, scavenge radical moieties, and decompose peroxide residues.

scholarly journals Some fluorescent counterstains for neuroanatomical studies.

1982 ◽  
Vol 30 (2) ◽  
pp. 123-128 ◽  
Author(s):  
L C Schmued ◽  
L W Swanson ◽  
P E Sawchenko
Keyword(s):  
Ultraviolet Light ◽  
Ethidium Bromide ◽  
Green Light ◽  
Neural Tissue ◽  
Neutral Red ◽  
Retrograde Tracer ◽  
Fluorescent Markers ◽  
Cell Counts ◽  
Low Concentrations ◽  
Nissl Stain

Methods for counterstaining neural tissue that contains fluorescent markers have been developed. Acridine orange is useful for localizing cells that are retrogradely labelled with the fluorescent tracers true blue, bisbenzimide, and nuclear yellow because at low concentrations it yields a green Nissl stain when excited with blue, but not with ultraviolet, light; since the tracers fluoresce only when exposed to ultraviolet light, they are not masked by the counterstain. In addition, counterstaining at pH 2 increases bisbenzimide fluorescence considerably. Ethidium bromide is useful for immunohistochemistry (IHC) because it yields a bright red Nissl counterstain when excited by green light, and is only faintly visible when the fluorescein marker is excited with blue light, or when ultraviolet excitation is used. Ethidium bromide is therefore a good counterstain for fluorescent retrograde tracer and for combined IHC-retrograde tracer studies as well. Certain dyes are also useful for studies of the normal morphology of neural tissue. For example, bisbenzimide and nuclear yellow at low concentrations produce a brilliant Nissl stain at pH 2, and stain only nuclei at pH 7.2. The latter procedure may be particularly useful for cell counts. Finally, neutral red, astrazone red, and safranin-O differentially stain cells amd myelinated fibers, producing fluorescence analogs of the Klüver-Barrera stain.

Research on Photolysis of Steroid Estrogens in Aquatic System

2011 ◽  
Vol 343-344 ◽  
pp. 241-245 ◽  
Author(s):  
Ya Qin He ◽  
Gang Xu ◽  
Liang Tang ◽  
Dong Ying Qian ◽  
Lai Tang Ren ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Ultraviolet Light ◽  
Biologically Active ◽  
Endocrine Function ◽  
Xenon Lamp ◽  
Degradation Mechanisms ◽  
Synthetic Compounds ◽  
Low Concentrations ◽  
17Β Estradiol ◽  
Steroid Estrogens

Estrogens such as estrone (E1), 17β-estradiol (E2) and estriol (E3) which are excreted by humans and animals or synthetic compounds such as 17α-ethinylestradiol (EE2) are a group of biologically active compounds that are synthesized from cholesterol and have a steroid ring in common. Steroid estrogens harm to organisms at very low concentrations with much more endocrine function than other EDCs. Obviously, it is an important issue to explore their degradation mechanisms and effective methods. In the present studies, 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) were used as target compounds, and the photodegradation of them were investigated in aqueous solution using natural sunlight produced using a xenon lamp, or ultraviolet light via a Hg lamp.

Microtubule nucleation sequence studied by time-resolved x-ray scattering and electron microscopy

1983 ◽  
Vol 41 ◽  
pp. 766-767
Author(s):  
Eva-Maria Mandelkow ◽  
Eckhard Mandelkow ◽  
Joan Bordas
Keyword(s):  
Electron Microscopy ◽  
Dynamic Equilibrium ◽  
Time Resolved ◽  
X Ray ◽  
Additional Information ◽  
X Ray Scattering ◽  
Low Concentrations ◽  
Microtubule Growth ◽  
Ray Patterns ◽  
Ray Scattering

When a solution of microtubule protein is changed from non-polymerising to polymerising conditions (e.g. by temperature jump or mixing with GTP) there is a series of structural transitions preceding microtubule growth. These have been detected by time-resolved X-ray scattering using synchrotron radiation, and they may be classified into pre-nucleation and nucleation events. X-ray patterns are good indicators for the average behavior of the particles in solution, but they are difficult to interpret unless additional information on their structure is available. We therefore studied the assembly process by electron microscopy under conditions approaching those of the X-ray experiment. There are two difficulties in the EM approach: One is that the particles important for assembly are usually small and not very regular and therefore tend to be overlooked. Secondly EM specimens require low concentrations which favor disassembly of the particles one wants to observe since there is a dynamic equilibrium between polymers and subunits.

The Use of Styrenes as Embedding Media for Electron Microscopy

1971 ◽  
Vol 29 ◽  
pp. 488-489
Author(s):  
Edward D. De-Lamater ◽  
Eric Johnson ◽  
Thad Schoen ◽  
Cecil Whitaker
Keyword(s):  
Electron Microscopy ◽  
Surface Tension ◽  
Ultraviolet Light ◽  
Methyl Ethyl Ketone Peroxide ◽  
Methyl Ethyl ◽  
Styrene Polymerization ◽  
Radical Initiation ◽  
Tertiary Butyl ◽  
Low Viscosity ◽  
Free Radical Initiation

Monomeric styrenes are demonstrated as excellent embedding media for electron microscopy. Monomeric styrene has extremely low viscosity and low surface tension (less than 1) affording extremely rapid penetration into the specimen. Spurr's Medium based on ERL-4206 (J.Ultra. Research 26, 31-43, 1969) is viscous, requiring gradual infiltration with increasing concentrations. Styrenes are soluble in alcohol and acetone thus fitting well into the usual dehydration procedures. Infiltration with styrene may be done directly following complete dehydration without dilution.Monomeric styrenes are usually inhibited from polymerization by a catechol, in this case, tertiary butyl catechol. Styrene polymerization is activated by Methyl Ethyl Ketone peroxide, a liquid, and probably acts by overcoming the inhibition of the catechol, acting as a source of free radical initiation.Polymerization is carried out either by a temperature of 60°C. or under ultraviolet light with wave lengths of 3400-4000 Engstroms; polymerization stops on removal from the ultraviolet light or heat and is therefore controlled by the length of exposure.

Resolution in photoelectron microscopy

1991 ◽  
Vol 49 ◽  
pp. 458-459
Author(s):  
G. F. Rempfer
Keyword(s):  
Electron Microscopy ◽  
Electric Field ◽  
Ultraviolet Light ◽  
Uniform Field ◽  
Virtual Image ◽  
Lens System ◽  
Photoemission Electron Microscopy ◽  
Planar Electrode ◽  
Electron Lens ◽  
Photoemission Electron

In photoelectron microscopy (PEM), also called photoemission electron microscopy (PEEM), the image is formed by electrons which have been liberated from the specimen by ultraviolet light. The electrons are accelerated by an electric field before being imaged by an electron lens system. The specimen is supported on a planar electrode (or the electrode itself may be the specimen), and the accelerating field is applied between the specimen, which serves as the cathode, and an anode. The accelerating field is essentially uniform except for microfields near the surface of the specimen and a diverging field near the anode aperture. The uniform field forms a virtual image of the specimen (virtual specimen) at unit lateral magnification, approximately twice as far from the anode as is the specimen. The diverging field at the anode aperture in turn forms a virtual image of the virtual specimen at magnification 2/3, at a distance from the anode of 4/3 the specimen distance. This demagnified virtual image is the object for the objective stage of the lens system.

Ultrastructural Changes in Three Different Mammalian Cells Following Ultraviolet Laser Irradiation

1972 ◽  
Vol 30 ◽  
pp. 350-351
Author(s):  
K. Shankar Narayan ◽  
Kailash C. Gupta ◽  
Tohru Okigaki
Keyword(s):  
Ultraviolet Light ◽  
Mammalian Cells ◽  
Biological Effects ◽  
Survival Rates ◽  
Chinese Hamster ◽  
Cell Types ◽  
Differential Sensitivity ◽  
Ultrastructural Changes ◽  
Ultraviolet Laser

The biological effects of short-wave ultraviolet light has generally been described in terms of changes in cell growth or survival rates and production of chromosomal aberrations. Ultrastructural changes following exposure of cells to ultraviolet light, particularly at 265 nm, have not been reported.We have developed a means of irradiating populations of cells grown in vitro to a monochromatic ultraviolet laser beam at a wavelength of 265 nm based on the method of Johnson. The cell types studies were: i) WI-38, a human diploid fibroblast; ii) CMP, a human adenocarcinoma cell line; and iii) Don C-II, a Chinese hamster fibroblast cell strain. The cells were exposed either in situ or in suspension to the ultraviolet laser (UVL) beam. Irradiated cell populations were studied either "immediately" or following growth for 1-8 days after irradiation.Differential sensitivity, as measured by survival rates were observed in the three cell types studied. Pattern of ultrastructural changes were also different in the three cell types.

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