The influence of ionization gauges on gas flow measurements

The pumping speed of BA-gauges using W (thoriated Ir) filaments was measured. It was found to be 0.28 (0.12) litres/s for H₂, 1.5 (0.5) litres/s for O₂; no pumping speed could be detected for CO. Outgassing rates obtained after bakeout for various samples were measured by means of the throughput method. In this work the data obtained are corrected for gauge induced gas reactions.     

Distribution of dispersed droplets in fragmentation of the drop in a high-velocity gas flow

Within the framework of the model of quasicontinuous fragmentation of a drop, the approximate expression for the size distribution function of stripped droplets has been found by the mechanism of gradient instability in high-velocity flows. The intermediate and final distributions obtained for different values of the governing parameters have been given. A comparison to results of calculations performed according to the overall scheme demonstrates good agreement in a wide range of parametric values. Certain general features of the dispersion kinetics have been described.     

The combustion of high-velocity air-propane flow,initiated by a longitudinal-and-transverse DC discharge

Results are given of experimental investigations of the combustion of a supersonic air-propane flow, initiated by a longitudinal-and-transverse dc discharge, in an aerodynamic channel with a backward-facing step. Several modes of combustion are revealed, which depend on the initial conditions associated both with the discharge parameters such as current, duration and so on and with the parameters of supersonic flow such as initial pressures in the systems for delivery of air and propane, initial pressure in the ballast chamber, and the relation between the times of delivery of air and propane.     

Analysis of noncovalent chitinase-chito-oligosaccharide complexes by infrared-matrix assisted laser desorption ionization and nanoelectrospray ionization mass spectrometry

Transferring noncovalently bound complexes from the condensed phase into the gas phase represents a challenging task due to weak intermolecular bonds that have to be maintained during the phase transition. Currently, electrospray ionization (ESI) is the standard mass spectrometric (MS) technique to analyze noncovalent complexes. Although infrared matrix-assisted laser desorption ionization (IR-MALDI)-MS also provides particular soft desorption/ionization conditions, this method has so far hardly been applied for the analysis of noncovalent complexes. In this study, we employed IR-MALDI orthogonal time-of-flight (o-TOF)-MS in combination with the liquid matrix glycerol to characterize the specific complex formation of chito-oligosaccharide (CHOS) ligands with two variants of Chitinase A (ChiA) from Serratia marcescens, the inactive E315Q mutant and the active W167A mutant, respectively. The IR-MALDI-o-TOF-MS results were compared to those obtained using nano-ESI-quadrupole (q)-TOF-MS and ultraviolet (UV)-MALDI-o-TOF-MS. Using IR-MALDI-o-TOF-MS, specific noncovalent complexes between ChiA and CHOS were detected with distributions between enzymes with bound oligosaccharides vs free enzymes that were essentially identical to those obtained by nano-ESI-q-TOF-MS. Chitinase-CHOS complexes were not detected when UV-MALDI was employed for desorption/ionization. The results show that IR-MALDI-MS can be a valuable tool for fast and simple screening of noncovalent enzyme-ligand interactions.     

Increasing the sensitivity of liquid introduction mass spectrometry by combining electrospray ionization and solvent assisted inlet ionization

Combining electrospray ionization (ESI) and solvent assisted inlet ionization (SAII) provides higher ion abundances over a wide range of concentrations for peptides and proteins than either ESI or SAII. In this method, a voltage is applied to a union connector linking tubing from a solvent delivery device and the fused silica capillary, used with SAII, inserted into a heated inlet tube of an Orbitrap Exactive mass spectrometer (MS). The union can be metal or polymeric and the voltage can be applied directly or contactless. Solution flow rates from less than a 1 μL min(-1) to over 100 μL min(-1) can be accommodated. It appears that the voltage is only necessary to provide charge separation in solution, and the hot MS inlet tube and the high velocity of gas through the tube linking atmospheric pressure and vacuum provides droplet formation. As little as 100 V produces an increase in ion abundance for certain compounds using this method relative to no voltage. Interestingly, the total ion current observed with SAII and this electrosprayed inlet ionization (ESII) method are very similar for weak acid solutions, but with voltage on, the ion abundance for peptides and proteins increase as much as 100-fold relative to other compounds in the solution being analyzed. Thus, switching between SAII (voltage off) and ESII (voltage on) provides a more complete picture of the solution contents than either method alone.     

Free-molecule flow of neutral particles with density depleted by ionization

Free-molecule flow of neutral particles is considered in the kinetic approximation under conditions of strong ionization depletion. The problem is solved for an arbitrary semi-isotropic distribution function of particles by velocities at the surface of the emitter. The kinetic effects of preferential depletion of tangentially flying and slow particles are considered. The kinetic equation is solved for the emitter having the forms of a plane, semi-plane, strip, and circle. The average densities, flow densities, and average hydrodynamic velocities are calculated. The expressions for ionization probability of the working gas in channels of Hall thrusters are obtained.     

Supercharged protein and peptide ions formed by electrospray ionization

The multiple charging of large molecules in electrospray ionization provides key advantages for obtaining accurate molecular weights by mass spectrometry and for obtaining structural information by tandem mass spectrometry and MS(n) experiments. Addition of glycerol or m-nitrobenzyl alcohol into the electrospray solutions dramatically increases both the maximum observed charge state and the abundances of the high charge states of protein and peptide ions. Adding glycerol to acidified aqueous solutions of cytochrome c shifts the most abundant charge state from 17+ to 21+, shifts the maximum charge state from 20+ to 23+, and shifts the average charge state from 16.6+ to 20.9+. Much less m-nitrobenzyl alcohol (<1%) is required to produce similar results. With just 0.7% m-nitrobenzyl alcohol, even the 24+ charge state of cytochrome c is readily observed. Similar results are obtained with myoglobin and (Lys)4. For the latter molecule, the 5+ charge state is observed in the electrospray mass spectrum obtained from solutions containing 6.7% m-nitrobenzyl alcohol. This charge state corresponds to protonation of all basic sites in this peptide. Although the mechanism for enhanced charging is unclear, it does not appear to be a consequence of conformational changes of the analyte molecules. This method of producing highly charged protein ions should be useful for improving the performance of mass measurements on mass spectrometers with performances that decrease with increasing m/z. This should also be particularly useful for tandem mass spectrometry experiments, such as electron capture dissociation, for which highly charged ions are desired.     

气相色谱-质谱测定化妆品中的硝基麝香类化合物

建立了化妆品中5种硝基麝香含量的气相色谱-质谱联用检测方法。采用丙酮/正己烷混合液超声提取化妆品中的硝基麝香,提取液经过浓缩,由气相色谱-质谱联用仪检测,以氘代二甲苯麝香内标法定量。该方法对化妆品中5种硝基麝香的加标回收率在85.21%~110.2%之间,相对标准偏差(RSD)不大于7.15%,在50μg/L~5000μg/L范围内呈现良好的线性关系,灵敏度高,最低检测限分别达到20~50μg/kg;选择性好,能有效消除复杂基体干扰。可用于常见化妆品中硝基麝香类化合物含量的检测。     

Solvent assisted inlet ionization: an ultrasensitive new liquid introduction ionization method for mass spectrometry

A new inlet ionization method requiring no voltage or laser, and using water, methanol, or water/organic solvent mixtures, is shown to produce mass spectra similar to those obtained with electrospray ionization (ESI) for small molecules, peptides, and proteins, at least as large as carbonic anhydrase, with sensitivity that surpasses ESI. With the use of wide mass range acquisitions at 100,000 mass resolution on an Orbitrap Exactive, detection limits below parts per trillion are obtained for small molecules such as arginine, ciprofloxacin, and acetaminophen. Low attomoles of bovine insulin consumed produced a multiply charged mass spectrum. Ions are generated, even using pure water as solvent, within the heated inlet tube linking atmospheric pressure with the first vacuum stage of the Orbitrap Exactive. The extremely high sensitivity observed at this early stage of solvent assisted inlet ionization (SAII) development suggests that inlet ionization may surpass nanoelectrospray in sensitivity but without the need for extremely low solvent flows.     

Reactive flow in silicon electrodes assisted by the insertion of lithium

In the search for high-energy density materials for Li-ion batteries, silicon has emerged as a promising candidate for anodes due to its ability to absorb a large number of Li atoms. Lithiation of Si leads to large deformation and concurrent changes in its mechanical properties, from a brittle material in its pure form to a material that can sustain large inelastic deformation in the lithiated form. These remarkable changes in behavior pose a challenge to theoretical treatment of the material properties. Here, we provide a detailed picture of the origin of changes in the mechanical properties, based on first-principles calculations of the atomic-scale structural and electronic properties in a model amorphous silicon (a-Si) structure. We regard the reactive flow of lithiated silicon as a nonequilibrium process consisting of concurrent Li insertion driven by unbalanced chemical potential and flow driven by deviatoric stress. The reaction enables the material to flow at a lower level of stress. Our theoretical model is in excellent quantitative agreement with experimental measurements of lithiation-induced stress on a Si thin film.     

Contrast medium assisted fluid flow measurements

In this paper the development and evaluation of two new approaches for ultrasound time-domain fluid flow measurements by tracking echoes scattered by a contrast agent following injection of a bolus of the contrast agent are described. Their feasibility was investigated by measuring velocity or velocity profile of blood flowing in a mock circulatory loop in vitro. Measurements were made with a one transducer intravessel approach and a two transducer extravessel approach. A hybrid cluster or vector cross-correlation method was used to track the motion of the scatterers in the two transducer time-domain method. This cluster or vector cross correlation method was developed to reduce the ambiguity resulted from misregistration which is a common problem in target tracking by correlating signal patterns. The experimental results show a good agreement between the measured data and those estimated from timing the volume. Although the discussions given in this paper pertain only to blood flow measurements, there is no reason to indicate that these approaches can not be used for fluid flow measurements in an industrial environment if suitable contrast agents can be developed     

Signal processing of ultrasound modulated by gas flow

Ultrasonic measurement of gas flow velocity using cross-correlation functions motivated an intensive investigation of complex modulated signals. The ultrasound signal is modulated in amplitude and also in phase by various physical effects. This paper describes signal demodulation by undersampling and subsequent separation of amplitude and phase modulated parts by the Hilbert-transform. Cross-correlation functions applied to the phase-modulated signal component produce well-defined measurements of flow velocity.     

Disintegration of carbon steel by high-velocity plasma jets

The disintegration of steel targets by high-velocity concentrated plasma jets is analyzed. The effects of carbon content, heat treatment, and specimen temperature on the disintegration pattern are revealed as a result.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 24, No. 4, pp. 627–631, April, 1973.     

Damage evaluation of concrete plates by high-velocity impact

This paper describes the evaluation of the local damage of concrete plates by the impact of high-velocity rigid projectiles. A new launching system of mushroom-shaped projectiles has been developed. Impact tests for concrete plates have been conducted by using the system to examine failure modes of the local damage of concrete plates. The damage or failure behavior has been discussed on the basis of the failure process captured by a high speed video camera and the strain histories obtained by strain gauges on the concrete plate. Numerical simulations have been also carried out in order to explain the mechanism of the local damage observed by the experiment. A reasonable numerical model has been discussed in terms of a constitutive model and strain rate effect of concrete material. Mechanism of the local damage of concrete plates has been illustrated schematically.     

High-pressure gas phase femtosecond laser ionization mass spectrometry

We describe a novel ion source for analytical mass spectrometry based on femtosecond laser ionization at pressures at and above atmospheric and characterize its performance when coupled to a tandem quadrupole/time-of-flight mass spectrometer. We assess source saturation limits, ionization and sampling efficiencies, the effective ionization volume, and limits of detection. We demonstrate 100% efficient ionization for a set of organic compounds and show that the degree of ion fragmentation over a range of laser powers is favorable compared to electron impact ionization, especially in that a substantial parent ion signal is always observed. We show how collisional cooling plays a role in controlling fragmentation at high pressures and address how ion-molecule chemistry can be controlled or exploited. High-pressure femtosecond laser ionization will allow "universal" and efficient ionization, presenting a research direction that will broaden the options for gas phase analysis beyond the capabilities of electron impact ionization.     

The flow of a fluid film entrained by a supersonic flow of gas

We have conducted an experimental study into the flow of a high-viscosity fluid directed through an orifice of small diameter onto the surface of a body contained within a supersonic flow of air.Notation M Mach number for the outlet cross section of the nozzle - Re_D Reynolds number calculated from the parameters of the unperturbed flow at the outlet section of the nozzle and from the diameter of model rounding - P₀ total pressure in the pressure chamber of the wind tunnel, Pa - T₀ deceleration temperature - sweepback angle of leading edge of plate (between the normal to the direction of the unperturbed flow and the generatrix of the leading edge), deg - d orifice diameter, mm - angle between direction of unperturbed flow and radius vector of orifice, deg - frictional stress at boundary separating fluid and gas, Pa - Q volumetric fluid flow rate, cm³/sec - kinematic viscosity of fluid, cSt - q /q_g ratio of the velocity head of the fluid at the outlet from the orifice to the local velocity head of the gas - thickness of fluid film, mm - b width of fluid film, mm - angle between tangents to the side boundaries of the fluid film, deg - s coordinate calculated from the center of the orifice along the midline of the film or along the axis of wedge symmetry, mm - z coordinate calculated along the normal to the axis, mm Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 59, No. 2, pp. 181–186, August, 1990.     

Characterization of nanoparticle flow produced by gas aggregation source

A simple and compact gas aggregation cluster and nanoparticle source based on a planar magnetron (Haberland type) without mass separation was characterized. Such source produces a beam of neutral, positively and negatively charged particles that are dragged by a buffer gas expanding from the aggregation chamber. Sizes, speeds and charges of nanoparticles have been determined using a combination of TEM micrographs, electrostatic deflection setup and numeric modeling. The strong dependence of the velocity of the nanoparticles on their size was confirmed both experimentally and by modeling.     

Electron-impact ionization of sulfur in the gas phase

The procedure and results of studying the yield of positive ions formed via electron-impact dissociative ionization of sulfur are described. The ionization energy of the ground molecule and appearance energies of fragmentary ions are derived from the ionization efficiency curves. The dynamics of formation of molecular sulfur ions in the temperature range of 300–670 K are studied. The energy dependences of the efficiency of formation of ions S _n for n = 1–6 are analyzed, and the appearance energies are determined. The total ionization cross section of sulfur is determined using a monoenergetic electron beam.     

Theory and experiment in the problem of the interaction of high-velocity gas flows with materials

An analysis is made of the intensive thermal action of a gas flow on a body in the flow. An examination is made of features of failure of such bodies and the difference between the melting and vaporization points of glass-plastics in a turbulent boundary layer compared to a laminar boundary layer.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 5, pp. 765–774, November, 1987.