Electrospray ionization-voltage sweep-Ion mobility spectrometry for biomolecules and complex samples

Voltage Sweep Ion Mobility Spectrometry (VSIMS) has been applied to complex samples using electrospray ionization (ESI). The usable range of VSIMS has been extended from that obtained in previous studies where only volatile compounds were investigated. Using ESI, VSIMS was evaluated with compounds with reduced mobility values as low as 0.3 V²cm^?1 s^?1. The primary advantage of VSIMS is to enable a drift time ion mobility spectrometer (DTIMS) to detect both fast and slow moving ions at optimal resolving power, thus improving the peak capacity. In this work ESI-VSIMS was applied to a series of small peptides and drugs spanning a large range of reduced mobility values in order to demonstrate ESI-VSIMS to separation. To demonstrate improved peak capacity of IMS with voltage scan operation, oligomers of silicone oil provided a series of evenly-spaced peaks, ranging in reduced mobility values from 0.85 to 0.3 V²cm^?1 s^?1. The peak capacity of 61 for a standard IMS was improved to 102 when voltage sweep operation was employed. In addition, VSIMS increased the average resolving power of the DTIMS from 66 to 106 for silicone oil.     

Accurate zero-field mobilities of atomic ions in the rare gases for calibration of ion mobility spectrometers

The zero-field mobilities of many atomic ions in rare gases are calculated from highly accurate, ab initio potential energy curves. They are expected to be accurate to at least 0.05%, thus allowing them to be used to calibrate mobility measurements in different drift-tube and ion mobility mass spectrometers.     

Domain walls in modulated systems

The properties of discommensurations in modulated phases of the ANNNI-(Axial Next Nearest Neighbour Interaction) model are described. A method is presented for deriving wall profiles, free energies, and interaction energies from a fixed point expansion of the 4d mapping representing the MFA equilibrium equations. Implications for the characteristics of phase diagrams and transitions are discussed.     

The influence of defect site statistics on ferroelectric properties

Averaged Green's functions are determined for lattices containing point defects with given site-correlations by extending existing averaging procedures. The anharmonicity of ferroelectric crystals is treated in SCPA. The results show a strong influence of the correlations on ferroelectric properties. For comparison MD calculations were performed which show a good agreement with the analytic approximations.     

An envelopment-analysis approach to measuring the managerial efficiency of banks

The dramatic rise in bank failures over the last decade has led to a search for leading indicators so that costly bailouts might be avoided. While the quality of a bank's management is generally acknowledged to be a key contributor to institutional collapse, it is usually excluded from early warning models for lack of a metric. This paper presents a new approach for quantifying a bank's managerial efficiency, using a data-envelopment-analysis model that combines multiple inputs and outputs to compute a scalar measure of efficiency and quality. An analysis of 930 banks over a five-year period shows significant differences in management-quality scores between surviving and failing institutions. These differences are detectable long before failure occurs and increase as the failure date approaches. Hence this new metric provides an important, yet previously missing, modelling element for the early identification of troubled banks.     

Construction and characterization of a high-flow, high-resolution ion mobility spectrometer for detection of explosives after personnel portal sampling

A novel analysis of explosives via the coupling of an airline passenger personnel portal with a high-flow (HF), high-resolution (HR) ion mobility spectrometry (IMS) was shown for the first time. The HF-HR-IMS utilized a novel ion aperture grid design with a (63)Ni ionization source while operating at ambient pressure in the positive ion mode at 200 degrees C. The HF-HR-IMS response characteristics of 2,4,6-trinitrotoluene (TNT), 4,6-dinitro-o-cresol (4,6DNOC), and cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX) were investigated. Modifications made to the HF-HR-IMS exhaust and ionization source created an 800% increase in the total ion current (TIC), from 0.85 to 6.8 nA. This translated into a 65% ion response increase for TNT when compared with a traditional IMS. A mixture of TNT and (4,6DNOC) was used to successfully demonstrate the resolving power of the species with similar reduced mobility constants (K(o)), 1.54 and 1.59, respectively. The reactant ion (H(2)O)(n)H(+), peak was also used to measure the resolving power of the spectrometer while varying the internal diameter of three different aperture openings from 1.00 to 3.54cm. This provided a resolving power range of 50-60, double that typically achievable by commercial IMS instruments. Most important, these changes made in this new instrumental design can be implemented to all existing and future IMS's to greatly enhance the achievable IMS resolving power.     

Raman and resonance-Raman spectra of CsI/I−3

Raman and resonance-Raman spectra of the I^?₃ ion isolated within CsI crystals have been studied using 647 nm and 488 nm exciting radiation. Sample temperatures between 300 and 20 K have been used. Eleven overtones of the symmetric stretching mode (nν₁) have been observed in the resonance-Raman spectrum excited by the 488 nm Ar⁺ laser line. Bands centred at 153, 170, 264 and 304 cm^?1 have been assigned as ν₃, 2ν₂, ν₁+ν₃ and 2ν₃(Σ⁺) respectively. The remaining structure between the nν₁ lines has been assigned as due to combinations of these lines with the lattice vibrations of the CsI crystal.     

Application of reversed-phase and ion-pair HPLC for investigation of nucleotide metabolism in erythrocytes,reticulocytes and tumour cells

Summary The determination of nucleotides, nucleosides, and nucleobases was carried out in cells of different metabolic complexity: in mature and immature red blood cells, in Ehrlich ascites tumour cells from different proliferation stages, and in other tumour cells. The maturation of reticulocytes to erythrocytes is accompanied by loss of organelles and energy-requiring processes as well as the switch from aerobic to anaerobic ATP production. The profile of purine nucleotides, nucleosides, bases, and pyridine dinucleotides, by reversed-phae HPLC, shows large concentration changes during the maturation of red blood cells. The concentrations of purine mono and triphosphates are two to four times greater in reticulocytes in comparison with erythrocytes; the difference in the concentrations of nucleosides and nucleobases between reticulocytes and erythrocytes is even greater. Application of ion-pair HPLC showed that the Ehrlich ascites cells loose major portions of purine mono-, diand triphosphates between the 7th and 11th day after inoculation. Fast growing solid sarcoma tumours of rats (MV 202 Ner) contain higher amounts of nucleotides than slowly growing tumours of identical cell type.     

Schraubenversetzungen in zylindrischen Körpern

The stress field and the energy of straight screw dislocations lying parallel to the axis of cylindrical specimens with various cross sections are calculated. The method employs results of the theory of complex functions. An extension of the isotropic theory to dislocations in the hexagonal basal plane is given. The application of the method to dislocation configurations observed in the electron microscope is described. Finally the connection with the method of image dislocations is discussed.