Light-emitting diodes are better illumination sources for biological microscopy than conventional sources.

Light-emitting diodes (LEDs) can be easily and inexpensively integrated into modern light microscopes. There are numerous advantages of LEDs as illumination sources; most notably, they provide brightness and spectral control. We demonstrate that for transmitted light imaging, an LED can replace the traditional tungsten filament bulb while offering longer life; no color temperature change with intensity change; reduced emission in the infrared region, which is important for live cell imaging; and reduced cost of ownership. We show a direct substitution of the typical tungsten bulb with a commercially available LED and demonstrated the color stability by imaging a histology section over a wide range of light intensities. For fluorescent imaging, where the typical illumination sources are mercury or xenon lamps, we demonstrate that LEDs offer advantages of providing a longer lifespan, having a more constant intensity output over time, more homogeneous illumination, and significantly lower photon dose. Our LED equipped system was used to image and deconvolve dual fluorescently labeled cells, as well as image cells undergoing mitosis expressing green fluorescent protein-histone 2B complex. The timing of the stages of mitosis is well established as an indicator of cell viability.     

Construction of spectral sensitivity function using polychromatic UV sources.

A procedure is presented for constructing the spectral sensitivity functions of biological dosimeters, using five polychromatic UV sources possessing different emission spectra. Phage T7 and uracil biological dosimeters have been used for measuring the dose rates of the lamps. Their spectral sensitivity functions consisting of two exponential terms have been constructed. The parameters of the spectral sensitivity functions have been determined by comparing the directly measured and calculated dose-rate values. The parameters of the sensitivity function are accepted as correct values when the deviation of the measured and calculated values is a minimum. Based on the deviations between the constructed and the experimentally determined spectral sensitivities with monochromatic sources, the differences between the measured and calculated results are interpreted. The importance of the correct spectral sensitivity data is demonstrated through the effectiveness spectra of a TL 01 lamp for phage T7 killing, uracil dimerization and erythema induction.     

Purification of alpha-L-fucosidase from various sources by affinity chromatography.

An affinity column for alpha-L-fucosidases was constructed by linking p-amino-phenyl 1-thio-alpha-L-fucopyranoside to Sepharose 4B through linkers of succinyl 3,3'-diamino-dipropylamine. Excellent purification of alpha-L-fucosidase from rat epididymis, Clostridium perfringens and Limulus polyphemus (horse shoecrab) could be effected inone step with good yield. An affinity column purification step can be introduced at any point in published purification procedures. The purified enzyme is essentially free of other glycosidases and proteolytic enzymes. The column material is stable and can be reused for at least two years.     

Carbon sources of natural cyanamide in Vicia villosa subsp. varia

The 13C labels of [13C]carbon dioxide and D-[13C?]glucose were incorporated into cyanamide (NH?CN) when they were administered to Vicia villosa subsp. varia shoots. In contrast, the administration of sodium [2,3-13C?]pyruvate did not affect the relative area of the [M + 1]+ ion of cyanamide in the gas chromatography-mass spectrometry analysis. [2,3-13C?]pyruvate was incorporated into organic acids that are part of the citric acid cycle, such as succinate and fumarate, confirming that the shoots absorbed and metabolised it. These observations demonstrated that the carbon atom of cyanamide is derived from any of the carbohydrates that are present upstream of pyruvate in the metabolic pathway.     

Contributions of A.N. Frumkin and the Frumkin School to power sources research

Journal of Solid State Electrochemistry - The historical interplay between the theoretical researches of the Frumkin School and the development of modern power sources technology is described. We...     

Polycyclic aromatic hydrocarbons in the atmosphere: monitoring, sources, sinks and fate. I: Monitoring and sources

This is the first of a series of two papers intended to review the state-of-the-art knowledge on atmospheric PAHs, concerning their monitoring, sources and transformation processes in the atmosphere. The monitoring section briefly introduces this class of compounds, mainly focusing on the 16 PAHs indicated by the US-EPA as priority pollutants. These compounds undergo partitioning between the gas phase and particulate, which has to be considered in the choice of the sampling methodology. Furthermore, sampling artifacts may arise from further phase transfers inside the sampling device. After sampling, extraction, clean up and detection/quantification procedures will follow. They are closely related since the choice of the extraction technique will heavily condition the clean-up step, and both procedures will place demands on the performance of the detection technique (usually GC-MS or HPLC). This is particularly true in the case of complex samples such as those arising from atmospheric sampling. The sources of atmospheric PAHs are then discussed with a particular focus on receptor models, which can allow the apportionment of PAH sources based on concentration data that can be routinely obtained by pollution control networks.     

Chemical information sources: aids in the review of drug applications.

Applications of computerized databases to the "Chemist's Review" of drug applications are presented with emphasis on the critical topics addressed in the controls review process and the time limitations imposed thereon.     

Laser-produced X-ray sources

A formidable array of advanced laser systems are emerging that produce extreme states of light and matter. By irradiating solid and gaseous targets with lasers of increasing energy densities, new physical regimes of radiation effects are being explored for the first time in controlled laboratory settings. One result that is being accomplished or pursued using a variety of techniques, is the realization of novel sources of X-rays with unprecedented characteristics and light–matter interactions, the mechanisms of which are in many cases still being elucidated. Examples include the megajoule class of laser-produced plasmas designed in pursuit of alternative-energy and security applications and the petawatt class of lasers used for fast ignition and X-ray radiographic applications such as medical imaging and real-time imaging of plasma hydrodynamics. As these technologies mature, increased emphasis will need to be placed on advanced instrumentation and diagnostic metrology to characterize the spectra, time structure, and absolute brightness of X-rays emitted by these unconventional sources. Such customized and absolutely calibrated measurement tools will serve as an enabling technology that can help in assessing the overall system performance and progress, as well as identification of the underlying interaction mechanisms of interest to basic and applied strong-field and high-energy-density science.     

Siloxanes as sources of silanones

Pyrolysis of hexamethyldisiloxane (HMDS) and its copyrolysis with chlorotrimethylsilane and tetrachlorosilane were studied. Based on the data of GLC analysis and on the mass spectrum of the condensate obtained after the pyrolysis of HMDS, it was concluded that HMDS acts as a source of dimethylsilanone. The results of the copyrolysis of HMDS with chlorotrimethylsilane used as a trapping reagent indicate that the dimethylsilanone generated from HMDS can be inserted into the Si−Cl and Si−O bonds. In the copyrolysis of HMDS with tetrachlorosilane serving as a trapping reagent for dimethylsilanone, both dimethylsilanone and dichlorosilanone are generated. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1663–1666, September, 1997.     

Bet nitrogen adsorption studies of iron oxides from natural and synthetic sources.

A vacuum microbalance technique has been used to obtain the surface areas and porosities of iron oxyhydroxides derived from Fe(III) and Fe(II) sources. The pore shape of the Fe(III)-derived material was of the wide-bodied, narrow-necked type, whereas the Fe(II)-derived precipitates were composed of parallel plates or slit-shaped pores. The surface area of the Fe(II)-derived material was found to be influenced by the temperature of the precipitate formation. These differences in surface character are discussed in relation to the adsorption of trace constituents at the iron oxyhydroxide-water interface.     

Chromatographic analysis of the neutral and phosphatide glyceryl ethers from various biological sources.

A method of analysis is described which permits the facile evaluation of the neutral glyceryl ether lipids (mild alkaline hydrolysis) and total glyceryl ether lipid (Vitride reduction) thereby allowing an assessment of the phosphatide contribution. The alkyl and alk-enyl glyceryl ethers are chromatographically resolvable on Gelman glass-fiber type SG and Whatman SG-81 and detected by the periodic acid-Schiff and plasmal reaction, respectively. The attending problems and interpretation are discussed with examples from a number of unicellular organisms and animal tissues.     

Chromatography of long chain alcohols (polyprenols) from animal and plant sources.

This paper provides a comprehensive overview of existing chromatographic methods for the analysis of long chain alcohols (polyprenols) from animal and plant sources. After a brief introductory discussion on the biological aspects of the polyprenols, the review focuses on various techniques for the isolation, purification, chromatographic separation and detection of polyprenols.     

Daytime sources of nitrous acid (HONO) in the atmospheric boundary layer.

Nitrous acid (HONO) is an important precursor of the hydroxyl radical (OH), the self-cleaning agent of the atmosphere and a key species in the formation of harmful photooxidants during summer smog. Recent field measurements using very sensitive HONO instruments have shown that daytime HONO concentrations are much higher than has been assumed previously and that the contribution of HONO to the radical formation was underestimated in the past. A strong photochemical HONO source has been proposed, which contributes to the primary OH radical production up to 56 %. These exciting results initiated new laboratory studies, in which new sources of HONO have been identified. It is demonstrated that HONO is photochemically formed 1) on surfaces treated with nitric acid, 2) by reduction of NO(2) on photosensitized organic surfaces like humic acids and c) in the gas phase photolysis of ortho-substituted nitroaromatics. Although significant uncertainties still exist on the exact mechanisms, these additional sources might explain daytime observations in the atmosphere and demonstrate that HONO should be generally measured in field campaigns, besides other radical sources.     

Experimental investigation of chamber-dependent radical sources

While environmental chamber data have been widely used to generate and validate computer models of the chemistry occurring in polluted atmospheres, the effects of the chambers on the gas-phase chemistry being studied have been poorly characterized. In order to investigate such chamber effects, a series of NO_x—air irradiations, with trace levels of organics present to monitor OH radical concentrations, have been carried out in four different environmental chambers (ranging in volume from ～100 to 40,000 L) at varying temperatures, humidities, pressures, and reaction conditions. In addition, a number of control experiments have been carried out to validate the technique for measuring OH radical levels in these irradiations. The data show that unknown sources of OH radicals are present in all of the chambers studied. The data are consistent with the presence of two distinct radical sources: (1) the photolysis of initially present HONO, whose importance increases with increasing NO₂/NO concentration ratios, but which is a minor contributor to the overall radical flux after 30–60 min of irradiation, and (2) a constant (for these NO_x—air irradiations) radical source which dominates beyond approximately the first 60 min of irradiation. The radical input rates, after the first ∽30–60 min of irradiation, are independent of the NO concentration, increase with increasing temperature, humidity, and NO₂ concentration, are proportional to light intensity, and are dependent on the chamber employed. Although the exact nature of this radical source is still undetermined, results of experiments reported here allow a number of possible mechanisms to be ruled, out, and these are discussed.