We have developed an experimental apparatus combining an ion mobility spectrometer and a tandem reflectron time-of-flight mass spectrometer for size- and isomer-selected cluster ion beam formation. By using this apparatus, we have succeeded in observing photoinduced dissociation and collision-induced dissociation reactions of selected ions of carbon and silicon clusters, Cn+ and Sin+. We have discussed the parent-isomer dependence of the observed fragment-ion distributions. Future studies are also mentioned in the last section, including the application of isomer-resolved photoelectron spectroscopy of cluster negative ions.
Recent development of ion mobility mass spectrometry (IM-MS) with electrospray ionization (ESI) has enabled the characterization of protein assemblies which play important roles in various events in living cells. Some proteins change their conformations by target recognition. Therefore, the conformational analysis with a small amount of proteins is helpful to understand the mechanism of biological events. By IM-MS, proteins with the same masses but different conformations can be separated, and the information on the shape of analyte ions can be obtained even for the protein assemblies. In this article, an overview of traveling-wave IM-MS for biomolecules is described, showing an example of IM-MS for a globular protein, bovine Ubiquitin. In addition, application of IM-MS to characterize the structure of an intrinsically disordered protein complex, Swi5-Sfr1, is demonstrated.
Differential mobility analyzer (DMA) is recognized as one of the most reliable aerosol size classifier using the principle that electrical mobility of charged particles is dependent upon their size. Now, smaller and more complex nanoparticles have attracted more interest, and thus more careful, reliable, and high functional size classifier is being required. Recently, we proposed a novel double-layer differential mobility analyzer (DLDMA), composed of two parallel-plate DMAs connected in tandem with minimum distance. The DLDMA is capable of revealing rapid size changes during the mobility measurements and select the size of stable nanoparticles among unstable aerosol. The potentiality of aerosol size-selection by the DLDMA will be described.
In our previous study (Sato et al., 2011), we observed that the charged fractions of 241Am neutralizers deviated from those calculated by Wiedensohler (1988) under some conditions. Inspired by the work by Nagato and Ogawa (1998), in which they observed the mobility of positive ions decreased sharply in a time scale of tens to hundreds of milliseconds after the ions were generated by radioactive ionization of 241Am, while the mobility of negative ions did not change in the same time scale, we developed a method to calculate positive ion mobilities from the observed deviations of charged fractions. The positive ion mobilities thus obtained were compared to and found to agree well with those by Nagato and Ogawa (1998). In this article, the above method of calculating the positive ion mobility is reviewed first, and then the method was applied to a new data set that we recently obtained. The positive ion mobilities for the new data set agreed well again with those by Nagato and Ogawa (1998). The agreement implies that the change of the charged fractions observed in our studies may be associated with changes of the mobility of positive ions in the neutralizer.
Measurements of sulfate particles using a commercial sulfate monitor were performed in Imizu City, Toyama Prefecture in the summer of 2009 and at Bijodaira (altitude, 977 m) on the western slope of Mt. Tateyama in the autumn of 2008 and 2010. Concentrations of sulfate had a good correlation with those of PM2.5 in Imizu City. The highest concentrations of PM2.5 and sulfate during the observation period were measured during 27-29 June, 2009. The diurnal variations of PM2.5 and sulfate were unclear in Imizu City. The temporal variations of sulfate were similar to those of the number concentrations of the fine particles at Bijodaira, however, the diurnal variations of sulfate were different from those of the number concentrations. High concentrations of sulfate and the number concentrations of particles associated with the increase of O3 and SO2 were often observed. The high concentrations of sulfate may be due to the long-range transport of air pollutants from the Asian continent.
While airborne emission of radioactive cesium (Cs) from contaminated biomass by fire has been studied, only few data is publicly available with regard to the transfer of Cs in tobacco leaf to tobacco smoke. The purpose of this study was to investigate the fate of Cs during cigarette smoking, utilizing stable cesium isotope (133Cs) which is naturally contained in tobacco leaf. In order to calculate the transfer rate, mainstream and sidestream smoke from four brand styles of commercial cigarettes were collected with a machine-smoking method. Ash and butts from the smoked cigarettes of two out of the four brand styles were also collected for the estimation of mass balance. After digestion, those collected samples were analyzed with ICP-MS to determine the amount of 133Cs, and the amounts were compared with the original concentration in the cigarettes examined. The transfer rates of 133Cs into the mainstream smoke were proportional to the tar-level of each cigarette, whereas those into sidestream smoke were almost similar among the brand styles investigated. The maximum transfer rates into mainstream and sidestream smoke were 0.35% and 0.57%, respectively, and almost all 133Cs in tobacco was retained in ash and cigarette butts.
Rapid expansion of liquid carbon dioxide through a nozzle can result in the production of dry ice particles by the Joule Thomson effect. Dry ice jets formed by this method are employed in various industrial fields because of their advantageous properties such as lower temperature and sublimated dry ice particles. However, fundamental knowledge on the production of dry ice particles in an expanded jet flow is still insufficient. The state of dry ice particles changes rapidly with time; therefore, dynamic analysis of particle production is essential. The present paper reviews research on dry ice jets and their applications, and then presents the latest findings obtained through in-situ observations and measurements. Finally, the paper addresses in detail dry surface cleaning using a dry ice jet, which has attracted research attention as an alternative method to conventional wet surface cleaning.