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71.
In situ pulsed force mode scanning force microscopy (PFM-SFM) images of phase separated solid-supported lipid bilayers are discussed with the help of computer simulations. Simultaneous imaging of material properties and topography in a liquid environment by means of PFM-SFM is severely hampered by hydrodynamic damping of the cantilever. Stiffness and adhesion images of solid-supported membranes consisting of cholesterol, sphingomyelin, and 1,2-dioleyl-phosphatidylcholine obtained in aqueous solution exhibit contrast inversion of adhesion and stiff. ness images depending on parameters such as driving frequency, amplitude, and trigger setting. Simulations using a simple harmonic oscillator model explain experimental findings and give a deeper insight into the way PFM-SFM experiments have to be performed in order to obtain interpretable results and hence pave the way for reliable material contrast imaging at high speed. 相似文献
72.
W. Krätschmer 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,19(4):405-408
At the beginning two remarks. One to the nomenclature: Fullerite does not name a specific substance; it names a solid entirely consisting of fullerenes, i.e. closed-cage all-carbon molecules. When our method of synthesis is applied, a solid is obtained in which C60 is the most abundant species. This material may thus be called C60-fullerite. The other remark regarding the production of fullerite: in view of the ease with which this could be achieved, I have the feeling that fullerene molecules must belong to a very frequently overlooked molecular species in carbon chemistry. Since the synthesis is simple and does not require many words to be described, I thought it might be interesting to tell how we came to make fullerite. 相似文献
73.
Bandyopadhyay S Chakraborty S Balasubramanian S Bagchi B 《Journal of the American Chemical Society》2005,127(11):4071-4075
The structure and dynamics of water around a protein is expected to be sensitive to the details of the adjacent secondary structure of the protein. In this article, we explore this sensitivity by calculating both the orientational dynamics of the surface water molecules and the equilibrium solvation time correlation function of the polar amino acid residues in each of the three helical segments of the protein HP-36, using atomistic molecular dynamics simulations. The solvation dynamics of polar amino acid residues in helix-2 is found to be faster than that of the other two helices (the average time constant is smaller by a factor of 2), although the interfacial water molecules around helix-2 exhibit much slower orientational dynamics than that around the other two helices. A careful analysis shows that the origin of such a counterintuitive behavior lies in the dependence of the solvation time correlation function on the surface exposure of the probe-the more exposed is the probe, the faster the solvation dynamics. We discuss that these results are useful in explaining recent solvation dynamics experiments. 相似文献
74.
G. Basar H-D Kronfeldt S. Kröger 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1996,36(1):35-39
The hyperfine structure of the odd configurations 5d 96p and 5d 86s6p was studied with laser optogalvanic spectroscopy and high resolution interferometry in a platinum hollow cathode. A parametric hyperfine structure analysis for the configurations (5d+6s)96p with 10 excited odd-parity levels was performed for195Pt. We obtained one-electron hfs parameters,a 5d 01 =1160(320) MHz,a 6s 10 =35600(5300) MHz anda 6p 01 =1300(780) MHz for the configuration 5d 86s6p. The corresponding $\left\langle {r^{ - 3} } \right\rangle _{nl}^{k_s k_l } $ values are compared with those known for other 5d-elements. 相似文献
75.
Zusammenfassung Das Verhalten von Polypropylen im elektrischen Wechselfeld wurde im Frequenzbereich von 0,15 kHz bis 300 kHz und im Temperaturbereich von –75 C bis +140 C untersucht. Es konnte sowohl ein Tieftemperaturdispersionsgebiet —-Absorption — als auch ein Hochtemperaturdispersionsgebiet —-Absorption — beobachtet werden. Die Untersuchungsergebnisse wurden, um die Breite des Dispersionsgebietes und die zugehörigen -Stufen zu bestimmen, nach demCole-Cole-Kreisbogengesetz analysiert. Aus dem Anstieg der Geraden: logf
max 1/T
K wurden sowohl für die- als auch fur die-Absorption die experimentellen Aktivierungsenergien berechnet. Eine Deutung der Ergebnisse wurde versucht. 相似文献
76.
Marian Čerňanský Přemysl Vaněk Karel Král Radmila Krupková 《Monatshefte für Chemie / Chemical Monthly》2002,133(6):799-806
Summary. In this investigation the crystallization of PbTiO3 upon annealing of pure nanopowders and PbTiO3–SiO2 (1:1 v/v) nanocomposite powders prepared by the sol-gel technique was studied. Using X-ray diffraction phase analysis, the
start of PbTiO3 crystallization in pure PbTiO3 powders was detected at 400°C. Distinct crystallization of PbTiO3 in PbTiO3–SiO2 nanocomposites starts at 700°C, whereas SiO2 remains amorphous. There are indications that an interface interaction between the PbTiO3 and the SiO2 phase plays an important role in hindering the crystallization of PbTiO3. The particle size (size of coherently scattering regions) was estimated from the broadening of the X-ray diffraction line
profiles. The average size of PbTiO3 nanocrystallites increases with temperature and time of annealing, the influence of temperature being more significant than
that of the annealing time. Differential scanning calorimetry confirmed the results of the X-ray diffraction with respect
to the start of the crystallization. Laser beam scattering and scanning electron microscopy provided the statistical distribution
of the grain size and the morphology of the powder grains, showing that each grain of the powders contains several nanocrystallites
(coherently scattering regions).
Received October 4, 2001. Accepted (revised) December 14, 2001 相似文献
77.
Schwenninger R Schlögl J Maynollo J Gruber K Ochsenbein P Bürgi HB Konrat R Kräutler B 《Chemistry (Weinheim an der Bergstrasse, Germany)》2001,7(12):2676-2686
Representative metal complexes of a biconcave D4-symmetric porphyrin were synthesised by metalion insertion into the porphyrin ligand 1. The NMR spectra suggested D4-symmetry for the ZnII and dioxo-RuVI complexes of 1 and C4-symmetry for the unsymmetrically ligated RuII and RhIII complexes. Metal complexes of 1 proved to be versatile chiral 1H NMR shift agents for a broad spectrum of organic amines, alcohols, carboxylic acids, esters, nitriles and nonpolar fullerene derivatives. A practical analysis of chiral substrates with 1 covers enantiomeric excesses beyond 99%. An X-ray structure of (1:1)-cocrystals of an achiral, biconcave CoII porphyrinate and C60 provided the first detailed insights into the structure of such a biconcave metallo-porphyrinate. It also showed remarkable packing of the carbon sphere against the main concave units of the porphyrin and gave clues about the relevant interactions between biconcave porphyrins and fullerenes. 相似文献
78.
Using both spreading techniques — mixed spreading and separate spreading- and, simultaneously, film pressure and film potential measurements, the mixing behavior of the following five binary systems was investigated and compared: 1) system 1,2-dilauroyl-phosphatidylethanolamine/cholesterol; 2) system 1,2-dimyristoyl-phosphatidylethanolamine/cholesterol; 3) system 1,2-dipalmitoyl-phosphatidylethanolamine/cholesterol; 4) system Na-eicosyl sulphate/hexadecanol; 5) system phosphatidic acid/1,2-dimyristoyl-phosphatidylethanolamine.Analyzing the time and concentration dependence of the /a isotherms and v/a isotherms (s = film pressure, v
s potential,a=average area per molecule in mixed films in the monolayers) of the binary monolayers it can be concluded that the components of the binary systems 1–4 are complete miscible in the monolayers. On the other hand the components of the system 5 are probably partially miscible only. 相似文献
79.
80.
Królikowski W 《Physical review D: Particles and fields》1992,46(11):5188-5191