Time evolution of charge states in an ECR ion source

The production of high charge-state ions in an ECR ion source has been studied as a function of time using a pulsed NdYAG laser to ablate heavy metal (bismuth) ions into the plasma. The time required to produce a charge state has been measured by observing the arrival time of the ions at a Faraday cup after the source analyzing magnet. The results of these measurements have been compared to a simple sequential ionization model and are found to be in good agreement with the data. The data can be used to characterize the plasma electron density, electron temperature and neutral atom density since these are the only three adjustable parameters in the model and are sufficient to achieve good agreement for the time evolution of all observed charge states

A dynamic ion cooling technique for FTICR mass spectrometry

AbstractA fast dynamic ion cooling technique based upon the adiabatic invariant phenomenon for Fourier transform ion cyclotron resonance mass spectrometry (FTICR) is presented. The method cools ions in the FTICR trap more efficiently, within a few hundred milliseconds without the use of a buffer gas, and results in a substantial signal enhancement. All performance aspects of the FTICR spectrum, e.g., peak intensities, mass resolution, and mass accuracy, improve significantly compared with cooling based on ion–ion interactions. The method may be useful in biological applications of FTICR, such as in proteomic studies involving extended on-line liquid chromatography (LC) separations, in which both the duty cycle and mass accuracy are crucially important

Preliminary Investigation of the Frictional Response of Reptilian Shed Skin

Developing deterministic surfaces relies on controlling the structure of the rubbing interface so that not only the surface is of optimized topography, but also is able to self-adjust its tribological behaviour according to the evolution of sliding conditions. In seeking inspirations for such designs, many engineers are turning toward the biological world to correlate surface structure to functional behavior of bio-analogues. From a tribological point of view, squamate reptiles offer diverse examples where surface texturing, submicron and nano-scale features, achieve frictional regulation. In this paper, we study the frictional response of shed skin obtained from a snake (Python regius). The study employed a specially designed tribo-acoustic probe capable of measuring the coefficient of friction and detecting the acoustical behavior of the skin in vivo. The results confirm the anisotropy of the frictional response of snakes. The coefficient of friction depends on the direction of sliding: the value in forward motion is lower than that in the backward direction. In addition it is shown that the anisotropy of the frictional response may stem from profile asymmetry of the individual fibril structures present within the ventral scales of the reptil

Advances in structure elucidation of small molecules using mass spectrometry

The structural elucidation of small molecules using mass spectrometry plays an important role in modern life sciences and bioanalytical approaches. This review covers different soft and hard ionization techniques and figures of merit for modern mass spectrometers, such as mass resolving power, mass accuracy, isotopic abundance accuracy, accurate mass multiple-stage MS(n) capability, as well as hybrid mass spectrometric and orthogonal chromatographic approaches. The latter part discusses mass spectral data handling strategies, which includes background and noise subtraction, adduct formation and detection, charge state determination, accurate mass measurements, elemental composition determinations, and complex data-dependent setups with ion maps and ion trees. The importance of mass spectral library search algorithms for tandem mass spectra and multiple-stage MS(n) mass spectra as well as mass spectral tree libraries that combine multiple-stage mass spectra are outlined. The successive chapter discusses mass spectral fragmentation pathways, biotransformation reactions and drug metabolism studies, the mass spectral simulation and generation of in silico mass spectra, expert systems for mass spectral interpretation, and the use of computational chemistry to explain gas-phase phenomena. A single chapter discusses data handling for hyphenated approaches including mass spectral deconvolution for clean mass spectra, cheminformatics approaches and structure retention relationships, and retention index predictions for gas and liquid chromatography. The last section reviews the current state of electronic data sharing of mass spectra and discusses the importance of software development for the advancement of structure elucidation of small molecules

Recent developments in ECRIS technology at Argonne National Laboratory and the New ATLAS 14 GHz ECRIS Project

A summary of recent developments in ECRIS technology taking place at Argonne National Laboratory is presented in this paper. A pulsed laser for ablation of solid material into the source plasma has been used online with the ATLAS PII-ECRIS and has allowed direct time measurements to be made which verify and quantify sequential, step-by-step ionization taking place in an ECRIS. In addition, during the course of these laser studies a method was discovered which, from an operational viewpoint, represents an important new method for incorporating solid materials into an ECRIS. We also report on a new 14 GHz ECRIS currently under construction at Argonne. This new ECRIS, along with a new 300 kV high voltage platform and building addition, will further the capabilities of the ATLAS facility by providing the accelerator with a second, independent ECRIS