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991.
T. Schubert G. Steinhoff H. -G. von Ribbeck M. Stutzmannn M. Eickhoff M. Tanaka 《The European physical journal. E, Soft matter》2009,30(2):233-238
We report on the deposition of planar lipid bilayers (supported membranes) on gallium nitride (GaN) electrodes for potential
applications as membrane-based biosensors. The kinetics of the lipid membrane formation upon vesicle fusion were monitored
by simultaneous measurements of resistance and capacitance of the membrane using AC impedance spectroscopy in the frequency
range between 50mHz and 50kHz. We could identify a two-step process of membrane spreading and self-healing. Despite its relatively
low resistance, the membrane can be modeled by a parallel combination of an ideal resistor and capacitor, indicating that
the membrane efficiently blocks the diffusion of ions. 相似文献
992.
A. Magnus G. Carvalho F. Garcia P.J. von Ranke G.D. Loula A.A. Coelho F.C.G. Gandra 《Journal of magnetism and magnetic materials》2009,321(19):3014-3018
In this work, we report the theoretical and experimental investigations on the magnetic and magnetocaloric properties for Gd0.5Pr0.5Al2 compound in different magnetic fields. The magnetization features indicate that Gd0.5Pr0.5Al2 is ferrimagnetic at low temperatures. We also present data from X-ray magnetic circular dichroism (XMCD) experiments for this compound, with which we have confirmed that the magnetic moments of the Pr ions are antiparallel to the magnetic moments of the Gd ions. The magnetocaloric parameters, ΔTS and ΔST, were obtained from calorimetric data and both curves present normal and inverse magnetocaloric effect. A theoretical model for ferrimagnetic coupling, including the crystalline electrical field anisotropy, was used to describe the ΔTS and ΔST experimental results. 相似文献
993.
Investigation on the magnetocaloric effect in DyNi2, DyAl2 and Tb1−nGdnAl2 (n=0, 0.4, 0.6) compounds
V.S.R. de Sousa E.J.R. Plaza B.P. Alho S. Gama P.J. von Ranke 《Journal of magnetism and magnetic materials》2009,321(20):3462-3465
The magnetocaloric effect (MCE) in the DyNi2, DyAl2 and Tb1−nGdnAl2 (n=0, 0.4, 0.6) was theoretically investigated in this work. The DyNi2 and DyAl2 compounds are described considering a model Hamiltonian which includes the crystalline electrical field anisotropy. The anisotropic MCE was calculated changing the magnetic field direction from 〈1 1 1〉 to 〈0 0 1〉 in DyNi2 and from 〈1 0 0〉 to 〈0 1 1〉 in DyAl2. The influence of the second- and first-order spin-reorientation phase transitions on the MCE that occurs in these systems is discussed. For the calculations of the MCE thermodynamic quantities in the Tb1−nGdnAl2 systems we take into account a two sites magnetic model, and good agreement with the available experimental data was obtained. 相似文献
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997.
Carina Schönherr Sounia Touchene Gaston Wilser Regine Peschka-Süss Giancarlo Francese 《Journal of chromatography. A》2009,1216(5):781-786
In recent decades the use of liposomal preparations as drug delivery systems has become very attractive in pharmaceutical development. Therefore, thorough characterization and quantification of the lipids which form liposomes is wished from both investigators and regulatory authorities when the application in humans is being considered. In this study a new HPLC method for the detection of lipids in liposomal formulations was established using corona charged aerosol detection (CAD) which has the advantage to be independent of the chemical properties of the analytes. The superiority of this method over UV detection was demonstrated. Compared to UV detection no absorption effects of the organic solvent in the mobile phase interfering with the lipid signals were observed with CAD. CAD showed good linearity (R2 > 0.990) for all liposomal compounds. The acceptance criteria for precision including repeatability were met. The average recovery for each of the excipients of the liposomal formulation was in the range of 90.0–110%. 相似文献
998.
Based on the extra-ligand addition effect, the principles of targeted self-assembly of nanosized multiporphyrin complexes
of various types with controllable geometry and composition (up to 8 tetrapyrroles) and heterogeneous composites based on
trioctylphosphine oxide-stabilized CdSe/ZnS semiconductor nanocrystals and organic compounds were developed. The dynamics
and mechanisms of energy and charge transfer (including electron tunneling) in such systems were studied by continuous, picosecond
fluorescence (Δ1/2 ≈ 30 ps), and femtosecond transient (Δ1/2 ≈ 120 fs) spectroscopy with varying the quantitative and qualitative constitution of the composites, the temperature, and
the polarity of the medium. 相似文献
999.
Gökhan Baykut Oliver von Halem Oliver Raether 《Journal of the American Society for Mass Spectrometry》2009,20(11):2070-2081
A dynamic method is applied to measure the mobility of gas-phase ions in the dual ion funnel interface of the electrospray
source of a quadrupole orthogonal time-of-flight mass spectrometer. In a new operational mode, a potential barrier was formed
in the second ion funnel of the mass spectrometer and then progressively increased. In this region, a flow of gas drags the
ions into the mass spectrometer while the electric force applied by the potential barrier decelerates them. Ions with lower
mobility can be carried by the gas flow more easily than those with high mobility. Thus, electrical forces can block the more
mobile ions more easily. Hence, the electric barrier formed in the ion funnel permits only ions below a certain mobility threshold
to enter the mass spectrometer. When the barrier voltage is increased, this threshold moves from high to low mobilities. Ions
with mobilities above the threshold cannot enter the mass spectrometer, and their signal decreases to zero. Thus, in a barrier
voltage scan, mass spectrometric signals of ions sequentially disappear. Differentiation of these decreasing ion signal curves
produces peaks from which an ion mobility spectrum can be reconstructed. Blocking voltages, i.e., the positions of the peaks
on the barrier voltage scale are directly related to the mobility of these ions. An internal calibration using ions with known
mobility values helps determine the unknown ion mobilities and allows calculation of ionic cross sections. 相似文献
1000.
Christoph Bttcher Edda von Roepenack‐Lahaye Jürgen Schmidt Stephan Clemens Dierk Scheel 《Journal of mass spectrometry : JMS》2009,44(4):466-476
Total phenolic choline ester fractions prepared from seeds of Arabidopsis thaliana and Brassica napus were analyzed by capillary LC/ESI‐QTOF‐MS and direct infusion ESI‐FTICR‐MS. In addition to the dominating sinapoylcholine, 30 phenolic choline esters could be identified based on accurate mass measurements, interpretation of collision‐induced dissociation (CID) mass spectra, and synthesis of selected representatives. The compounds identified so far include substituted hydroxycinnamoyl‐ and hydroxybenzoylcholines, respective monohexosides as well as oxidative coupling products of phenolic choline esters and monolignols. Phenolic choline esters are well separable by reversed‐phase liquid chromatography and sensitively detectable using electrospray ionization mass spectrometry in positive ion mode. CID mass spectra obtained from molecular ions facilitate the characterization of both the type and substitution pattern of such compounds. Therefore, LC/ESI‐MS/MS represents a valuable tool for comprehensive qualitative and quantitative analysis of this compound class. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献