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.     

Two-dimensional microfabricated sources for nanoelectrospray

The idea of a novel two-dimensional (2D) nanoelectrospray ionization emitter tip with the shape of a nib is explored here. This novel planar design is studied as an alternative to the needle-like standard emitter tips that suffer from a lack of reproducibility and robustness and from an inherent incompatibility with high-throughput analysis. The composition of the micro-nib sources is analogous to the working of a simple fountain pen, with a liquid reservoir linked to a micro-nib tip from which the sample is electrosprayed via a capillary slot. The micro-nib prototypes described here were fabricated using microtechnology techniques and using the epoxy-based negative photoresist SU-8. The resulting free-standing micro-nib structure was supported by a silicon wafer. We present here two series of such micro-nib sources, the latter series exhibiting improved characteristics such as a 8 micro m source width of the nib tip. They were tested in mass spectrometry experiments on an ion trap mass spectrometer (LCQ Deca XP+, Thermo Finnigan) using standard peptide samples having concentrations down to 1 micro M and with a high voltage (HV) supply around 1 kV for the second series of micro-nib sources. In addition to the stability of the spray, the obtained mass spectra showed the reliability of these sources for peptide analysis; the signal of the spectra was as intense and the signal-to-noise ratio (S/N) as high as that obtained with the use of standard emitter tips.     

Radioisotope sources for X-ray fluorescence analysis

Problems involved in developing radioisotope sources and the characteristics of potentially useful radioisotopes for X-ray fluorescence analysis are presented. Some of the isotopes, which are not in use but look very promising, are indicated.     

Comparison of combustion sources for sulfur chemiluminescence detection

Three different types of SCD combustion source have been evaluated for use in the chromatographic analysis of atmospheric sulfur compounds. The conventional FID source and the newer inverted burner source were found to be less sensitive and less stable than the flameless design. Overall, the flameless source was superior for use with HRGC-SCD.     

Conditions of use for sealed cobalt 60 sources

Conditions of use specifications define suitable operating environments for sealed radioactive sources. There are minor differences between manufacturer’s specifications. The basis for these differences is explored and the results of recent water quality surveillance presented. It is concluded that the specifications are readily achievable and that gamma irradiation continues to be a safe and reliable technology.     

Microfluidic discharge-based optical sources for detection of biochemicals

This paper reports a discharge-based optical source for fluorescence of biochemicals in microfluidic systems. Its efficacy is demonstrated using a stacked microchip that integrates a microfluidic wavelength-tunable optical source, a biochemical sample reservoir and optical filters. It is shown to excite fluorescence in l-tryptophan and DNA samples labeled by SYBR green dye. The discharge is struck in ambient air, between a metal anode and a cathode cavity that is filled with an aqueous solution, which is doped with a metal salt selected for its emission characteristics. The characteristic line spectra, which arise from energetic transitions of the metal ions that are sputtered into the glow region of the discharge, are optically filtered and guided to the biochemical sample that resides in a separate on-chip reservoir. For DNA fluorescence, a barium chloride solution is used to emit light at 454 and 493 nm. For tryptophan fluorescence, the cathode contains lead (ii) nitrate solution to provide a 280 nm emission. The resulting fluorescence from the DNA and tryptophan samples is compared to reference data. This technique can also be used to excite other fluorophores by using appropriately doped liquid cathodes having the desired emission characteristics.     

Estimation of true coincidence corrections for voluminous sources

To analyze a voluminous radioactive source with the highest possible sensitivity, it is necessary to use both a high efficiency detector and an optimal measurement geometry. The optimal geometry implies positioning the source as close to the detector as possible. It also implies selection of the shape of the source in order to reach the highest efficiency possible (e.g., Marinelli beaker). Under such conditions of measurements, true coincidences may cause systematic errors that can reach levels of more than ten percent for some radionuclides. A method for estimation of the effect of these coincidences was developed. It is based on direct computation of the effect by means of integration of a function which involves the experimentally obtained detection efficiency for the place around the detector. It was found that for the tested detector with a relative efficiency of 15%, the so-called intrinsic peak-to-total calibration may be used in the course of such an integration: It has been shown that theP/T-ratio for the given energy in the working space around the detector may be considered a constant value. Some results from a peak-to-total calibration study in the presence of scattering material are also given.The main part of the material has been presented at the Third International Meeting Nuclear Methods for Protection of the Environment, May 1995, Dubna, Russia.     

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.     

Alternative sources of syngas for hydroformylation of unsaturated compounds

Russian Chemical Bulletin - Hydroformylation reactions and related tandem reactions (hydroformylation—hydrogenation, hydroaminomethylation) proceeding without introduction of syngas were...     

Screening for novel plant sources of prenyloxyanthraquinones: Senna alexandrina Mill. and Aloe vera (L.) Burm. F.

As a continuation of our ongoing studies aimed to reveal the presence of oxyprenylated anthraquinones in plants claimed to have a laxative effect, in this article, we describe the extraction and HPLC separation of madagascin (3-isopentenyloxyemodin) and 3-geranyloxyemodine from dried leaves and fruits of Senna alexandrina Mill. (Leguminosae) and leaves and gel of Aloe vera (L.) Burm. F. (Xanthorrhoeaceae). Both compounds are described herein for the first time as components of extracts of the title plants.     

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.     

Laser sources for precision spectroscopy on atomic strontium

We present a new laser setup designed for high-precision spectroscopy on laser cooled atomic strontium. The system, which is entirely based on semiconductor laser sources, delivers 200 mW at 461 nm for cooling and trapping atomic strontium from a thermal source, 4 mW at 497 nm for optical pumping from the metastable P23 state, 12 mW at 689 nm on linewidth less than 1 kHz for second-stage cooling of the atomic sample down to the recoil limit, 1.2 W at 922 nm for optical trapping close to the "magic wavelength" for the 0-1 intercombination line at 689 nm. The 689 nm laser was already employed to perform a frequency measurement of the 0-1 intercombination line with a relative accuracy of 2.3 x 10(-11), and the ensemble of laser sources allowed the loading in a conservative dipole trap of multi-isotopes strontium mixtures. The simple and compact setup developed represents one of the first steps towards the realization of a transportable optical standards referenced to atomic strontium.