Biomedical subjects

Y Rudich

Publications and source records attributed to Y Rudich.

5 recordsLinked to original sources

PubMed2001

Ion motion synchronization in an ion-trap resonator.

Using a new type of ion trap, we demonstrate that the length of a packet of charged particles oscillating between two electrostatic mirrors will remain constant under special conditions. The effect can be understood in terms of phase synchronization, where, in a rather counterintuitive way, the repulsive Coulomb interaction between the ions actually holds the packet together. Application of this effect for mass spectrometry is discussed.

Journal Article↗

PubMed2001

Analysis of semivolatile organic compounds in atmospheric aerosols by direct sample introduction thermal desorption GC/MS.

A technique for identifying trace amounts of semivolatile organic compounds in atmospheric aerosols and in the NIST Urban Dust standard (SRM1649a) is presented. The technique is based on direct sample introduction (DSI) of small samples followed by thermal desorption in a conventional GC injector. The method enables injection of both solid and liquid samples. Validation of the method, including quantitative determination of EPA-targeted polycyclic aromatic hydrocarbons (PAHs), as well as the reproducibility and recovery efficiency tests are presented. The advantages of using aluminum foil as sampling filter are also discussed. Determination of different classes of compounds such as quinolines, methylquinoline isomers, PAHs, and n-monocarboxylic acids in the ambient size-segregated aerosol sample is also performed. The method was directly applied to the determination of C6-C16 n-monocarboxylic acids, eliminating the need for a complex sample preparation procedure. The small quantities needed for the analysis as well as the lack of complicated sample preparation steps enable fast characterization of semivolatile organic species present in time-resolved or size-segregated aerosol samples. Thus, this method can potentially be employed for air quality monitoring and field measurements as well as for fast screening of the organic content of ambient particles.

Aerosols↗

PubMed2001

Desert dust suppressing precipitation: a possible desertification feedback loop.

The effect of desert dust on cloud properties and precipitation has so far been studied solely by using theoretical models, which predict that rainfall would be enhanced. Here we present observations showing the contrary; the effect of dust on cloud properties is to inhibit precipitation. Using satellite and aircraft observations we show that clouds forming within desert dust contain small droplets and produce little precipitation by drop coalescence. Measurement of the size distribution and the chemical analysis of individual Saharan dust particles collected in such a dust storm suggest a possible mechanism for the diminished rainfall. The detrimental impact of dust on rainfall is smaller than that caused by smoke from biomass burning or anthropogenic air pollution, but the large abundance of desert dust in the atmosphere renders it important. The reduction of precipitation from clouds affected by desert dust can cause drier soil, which in turn raises more dust, thus providing a possible feedback loop to further decrease precipitation. Furthermore, anthropogenic changes of land use exposing the topsoil can initiate such a desertification feedback process.

Journal Article↗

PubMed2000

Fourier transform time-of-flight mass spectrometry in an electrostatic ion beam trap

We report on the application of an electrostatic ion beam trap as a mass spectrometer. The instrument is analogous to an optical resonator; ions are trapped between focusing mirrors. The storage time is limited by the residual gas pressure and reaches up to several seconds, resulting in long ion flight paths. The oscillation of ion bunches between the mirrors is monitored by nondestructive image charge detection in a field-free region and mass spectra are obtained via Fourier transform. The principle of operation is demonstrated by measuring the mass spectrum of trapped Ar+ and Xe+ particles, produced by a standard electron impact ion source. Also, mass spectra of heavier PEGnNa+ and bradykinin ions from a pulsed MALDI ion source were obtained. The long ion flight path, combined with mass-independent charge detection, makes this system particularly interesting for the investigation of large molecules.

Journal Article↗

PubMed2000

A comparative study of a liquid and a solid matrix in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and collision cross section measurements.

We present experimental matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) results comparing a liquid (glycerol/K(4)[Fe(CN)(6)]) and a solid matrix (2,5-dihydroxybenzoic acid, DHB) with respect to analyte signal stability and initial ion velocity. For applications requiring stable production of analyte ions over a long period of time, the liquid matrix is superior to the solid matrix. The stable analyte ion signal obtained from a liquid matrix allowed the measurement of collision cross sections of small poly(ethylene glycol) (PEG(n)) adduct ions in the flight tube with good resolution. The initial velocity of these adduct ions was measured. It was found that analyte molecules from the liquid matrix have initial ion velocities significantly smaller than those from the solid matrix. MALDI-TOF measurements for large molecules using a liquid matrix are therefore likely to result in smaller systematic errors in mass calibrations due to initial ion velocity.

Ferrous Compounds↗