Search results for "asma"
showing 10 items of 4204 documents
Internal ion impact ionization for Fourier-transform ion cyclotron resonance
1994
A general scheme for ionization and fragmentation of ions in Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICRMS) is introduced. The technique is based upon excitation of high-frequency (i.e. lowmass) primary ions (e.g. N, Al+, H2O+·) which may be generated by standard ionization methods (e.g. electron ionization or laser desorption) inside the trap. Generation of the primary ions is followed by excitation of their cyclotron motion to high translational energy to serve as projectile ions. The projectiles serve two functions: to ionize neutral gas atoms and/or molecules (secondary ions) within the trap internal ion impact ionization (IIII), and to collisionally activate the…
Low temperature plasma treatment of monomolecular Langmuir-Blodgett films
1993
Abstract The structure of the surface layer of materials is usually quite different from the bulk. Detailed information about the surface structure is often not available. This, together with the complex nature of low temperature plasma treatment, hinders the investigations of plasma chemical processes on solid surfaces. Monomolecular Langmuir-Blodgett (LB) structures offer a unique opportunity to prepare model surfaces with known thickness and molecular architecture. From the data obtained, the depth of the Ar plasma influence on solid organic surfaces was estimated to be about 400–1000 A depending on the nature of the surface layer. An oxygen plasma penetrates deeper with a penetration li…
A critical analysis of the cold plasma induced lipid oxidation in foods
2018
Abstract Background Cold plasma is an emerging, economical and environment-friendly technology with potential applications in food and bioprocessing industry, including microbial decontamination, enzyme inactivation, shelf-life extension, and physicochemical modification. These advantages stem from the cocktail of reactive species and the physical processes that are associated with gaseous electrical discharges. However, when oxygen is present as a component of the gas in which plasma discharges are made, the reactive oxygen species (ROS) could result in decreased food quality. The lipids oxidation induced by an oxygen-containing cold plasma process can eventually affect the acceptability a…
Spark Plasma Sintering (SPS)-Assisted Synthesis and Thermoelectric Characterization of Magnéli Phase V6O11
2018
The Magneli phase V6O11 was synthesized in gram amounts from a powder mixture of V6O11/V7O13 and vanadium metal, using the spark plasma sintering (SPS) technique. Its structure was determined with synchrotron X-ray powder diffraction data from a phase-pure sample synthesized by conventional solid-state synthesis. A special feature of Magneli-type oxides is a combination of crystallographic shear and intrinsic disorder that leads to relatively low lattice thermal conductivities. SPS prepared V6O11 has a relatively low thermal conductivity of κ = 2.72 ± 0.06 W (m K)-1 while being a n-type conductor with an electrical conductivity of σ = 0.039 ± 0.005 (μΩ m)-1, a Seebeck coefficient of α = -(3…
Studies of electron heating on a 6.4 GHz ECR ion source through measurement of diamagnetic current and plasma bremsstrahlung
2011
Diamagnetic current and low energy (2–70 keV) x-ray bremsstrahlung measurements taken on a 6.4 GHz electron cyclotron resonance ion source (ECRIS) are presented as a function of microwave power, neutral gas pressure and magnetic field configuration. X-ray flux from confined electrons and plasma energy density depend logarithmically on microwave power. This result differs from previous studies performed on ECRISs that operate at higher microwave frequencies, in which the x-ray power increases in an essentially linear fashion with the microwave power. X-ray power and plasma energy density both saturate as the neutral pressure is increased beyond a certain value. The gradient of the magnetic f…
Excitation modes for fourier transform-ion cyclotron resonance mass spectrometry.
1992
AbstractVarious geometric configurations for the excitation of coherent ion motion in Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR/MS) are analyzed (in some cases for the first time) with unified notation. The instantaneous power absorption, F·v, in which v is ion velocity and F the force produced by the applied excitation electric field (harmonic, single frequency, on-resonance, in-phase), is time averaged and then set equal to the time rate of change of ion total (cyclotron + magnetron + trapping) energy, to yield a differential equation that is readily solved for the (time-dependent) amplitude of each of the various ion motions. The standard FT-ICR excitation (name…
The elliptical Penning trap: Experimental investigations and simulations
2008
Abstract The application of an additional azimuthal quadrupolar electrostatic field to a Penning trap leads to a field configuration referred to as an elliptical Penning trap. The resulting changes of the radial ion motions have been investigated experimentally and by use of simulations. The eigenfrequencies, i.e., the magnetron frequency ω ˜ − and the reduced cyclotron frequency ω ˜ + , are found to be shifted with respect to those of the standard Penning trap ω − , ω + , respectively. As the shift of the magnetron frequency ω ˜ − is larger than that of the reduced cyclotron frequency ω ˜ + their sum ω ˜ + + ω ˜ − is also a function of the ellipticity and no longer equal to the cyclotron f…
Damping effects in Penning trap mass spectrometry
2011
Abstract Collisions of ions with residual gas atoms in a Penning trap can have a strong influence on the trajectories of the ions, depending on the atom species and the gas pressure. We report on investigations of damping effects in time-of-flight ion-cyclotron resonance mass spectrometry with the Penning trap mass spectrometers ISOLTRAP at ISOLDE/CERN (Geneva, Switzerland) and SHIPTRAP at GSI (Darmstadt, Germany). The work focuses on the interconversion of the magnetron and cyclotron motional modes, in particular the modification of the resonance profiles for quadrupolar excitation due to the damping effect of the residual gas. Extensive experiments have been performed with standard and Ra…
Zur Plasmaproteinbindung von Arzneimitteln
1969
1. Auf Dialyse, Ultrazentrifugation und Sephadexgelfiltration als die gebrauchlichsten Methoden zur quantitativen Bestimmung der Eiweisbindung von Pharmaka wird hingewiesen. 2. Die Wechselwirkung von niedermolekularen Substanzen mit Proteinen folgt dem Massenwirkungsgesetz. Darauf beruht die Formulierung der Ergebnisse von Eiweisbindungsversuchen. Die Darstellung der Ergebnisse nach Scatchard (1949) wird als die wichtigste Methode angesehen. Daneben sind Darstellungsmethoden nach Scholtan (1962) und Kruger-Thiemer (1961) gebrauchlich, die fur bestimmte Fragestellungen Vorteile bieten. 3. Die Bindung von Pharmaka an Plasmaproteine scheint vorwiegend hydrophoben Charakter zu besitzen. Dabei s…
Energy distribution of plasma-assisted electron and ion emission from TGS single crystals
2008
Abstract Electron and ion emission accompanying non-thermal plasma processes, produced at the surface of TGS single crystals under driving ac electric field exceeding 10 3 V/cm, have been carried out. These plasma-assisted emission of electrons and ions were examined by means of time and energy distribution measurements. The intensity of registered charges (electrons and ions) displayed on the 2 ms time scale are represented by two distinct peaks. Time dependent energy spectrum of charges, detected under our experimental conditions, involves electrons and ions with maximum energy up to 30–40 eV for first peaks and up to 70–80 eV for second one. Additionally, the energy of electrons is focu…