Application of matrix-assisted laser desorption/ionization to on-line aerosol time-of-flight mass spectrometry

Matrix-assisted laser desorption/ionization (MALDI) mass spectra were obtained from single biological aerosol particles using an aerosol time-of-flight mass spectrometer (ATOFMS). The inlet to the ATOFMS was coupled with an evaporation/condensation flow cell that allowed the aerosol to be coated with matrix material as the sampled stream entered the spectrometer. Mass spectra were generated from aerosol composed either of gramicidin-S or erythromycin, two small biological molecules, or from aerosolised spores of Bacillus subtilis var niger. Three different matrices were used: 3-nitrobenzyl alcohol, picolinic acid and sinapinic acid. A spectrum of gramicidin-S was generated from approximately 250 attomoles of material using a molar ratio of 3-nitrobenzyl alcohol to analyte of approximately 20:1. A single peak, located at 1224 Da, was obtained from the bacterial spores. The washing liquid and extract solution from the spores were analyzed using electrospray mass spectrometry and subsequent MS/MS product ion experiments. This independent analysis suggests that the measured species represents part of the B. subtilis peptidoglycan. The on-line addition of matrix allows quasi-real-time chemical analysis of individual, aerodynamically sized particles, with an overall system residence time of less than 5 seconds. These results suggest that a MALDI-ATOFMS can provide nearly real-time identification of biological aerosols. Copyright 2000 John Wiley & Sons, Ltd.     

Topology of the polypeptide chain in the complex of agglutinin from castor bean seeds with β-D-galactose in the crystalline state

The three-dimensional structure of the complex of agglutinin from Ricinus communis with β-D-galactose was established and refined at 2.5 Å resolution by X-ray structure analysis. Biocrystals were obtained using dialysis through a semipermeable membrane. X-ray intensity data (R _merge = 4.6%) were collected from one crystal at 100 K using synchrotron radiation at the DESY outstation [European Molecular Biology Laboratory (EMBL), Hamburg, Germany]. The initial phases were calculated by the molecular replacement method. The atoms of both protein and sugar molecules were localized. Unlike ricin, the ricinlike heterodimer RcA contains only one galactose-binding center in the region of the Asn46-Gly25-Trp37-Lys40 site in the first domain of the B subunit, whereas the second galactose-binding site of the B subunit is lost. One functionally important water molecule, which is bound to the residues Tyr123-Glu176-Arg179-Glu207, was revealed in the region of the active center in the A subunit.     

International linear collider simulations using BDSIM

Power loss simulations for the 2, 14, and 20 mrad extraction line designs using the BDSIM toolkit are presented. A preliminary study on the backgrounds from the beam losses along the extraction line in the case of 20 mrad with high luminosity parameters is also given.      

(∈, ∈∨q)-fuzzy subnear-rings and (∈, ∈∨q)-fuzzy ideals of near-rings

In this paper, we introduce the notions of (∈, ∈∨q)-fuzzy subnear-ring, (∈, ∈∨q)-fuzzy ideal and (∈, ∈∨q)-fuzzy quasi-ideal of near-rings and find more generalized concepts than those introduced by others. The characterization of such (∈, ∈ ∨q)-fuzzy ideals are also obtained.     

SEM diagnostics of the surface of MK-40 and MA-40 heterogeneous ion-exchange membranes in the swollen state after thermal treatment

The morphology of the surface of MK-40 and MA-40 ion-exchange membranes in the swollen state after chemical and thermal treatment is studied using scanning electron microscopy. The distribution of portions of the ion exchanger on the surface of heterogeneous membranes is found to be of a complex stochastic nature; their sizes for the MK-40 and MA-40 membranes are 5–30 and 8–40 μm, respectively, while the sizes typical for the secondary porous structure are 2–8 μm. An increase in the share of the ion-exchange component of the surface (by 20–40%), the sizes of the ion-exchange portions (by 20%), and the surface porosity (by two-three times) in the samples subjected to thermal treatment is revealed.     

A technology for the calculation and manufacture of devices for shaping a proton beam in radiotherapy

A therapeutic proton beam for an actual irradiation procedure is shaped using customized collimator leaves made out of Cerrobend, while to make the proton-beam depth-dose distribution conformal to the target volume, so-called boluses (compensators) with sophisticated shapes are calculated and then fabricated to compensate for the heterogeneities of a patient??s tissues and organs in the beam path. This article describes the main stages of testing a technology for manufacturing bolus from industrial wax which was developed at the Medico-Technical Complex (MTC) at the Dzelepov Laboratory of Nuclear Problems, Joint Institute for Nuclear Research (DLNP JINR), by comparing the spatial dose distributions obtained under a computer simulation of proton irradiation and the actually measured ones under the experiment.     

Optical characteristics of porous silicon structures

Morphology, composition, and optical properties of porous silicon on single-crystal-silicon substrates and p-n junctions are studied. Substrate orientation, type of conduction, and composition of etching agent are varied to obtain nano-, meso-, and microporous silicon and multilayer porous structures. A correlation of the photoluminescence intensity and intensity of the IR absorption band peaking at 616 cm^?1 is related to the presence of Si-Si bonds.