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31.
We investigated the phase behavior of double-tail lipids, as a function of temperature, headgroup interaction and tail length. At low values of the head-head repulsion parameter a(hh), the bilayer undergoes with increasing temperature the transitions from the subgel phase L(c) via the flat gel phase L(beta) to the fluid phase L(alpha). For higher values of a(hh), the transition from the L(c) to the L(alpha) phase occurs via the tilted gel phase L(beta)(') and the rippled phase P(beta)('). The occurrence of the L(beta)(') phase depends on tail length. We find that the rippled structure (P(beta)(')) occurs if the headgroups are sufficiently surrounded by water and that the ripple is a coexistence between the L(c) or L(beta)(') phase and the L(alpha) phase. The anomalous swelling, observed at the P(beta)(') --> L(alpha) transition, is not directly related to the rippled phase, but a consequence of conformational changes of the tails. 相似文献
32.
Shevchenko A Carter J Fearick RW Förtsch SV Fujita H Fujita Y Kalmykov Y Lacroix D Lawrie JJ von Neumann-Cosel P Neveling R Ponomarev VY Richter A Sideras-Haddad E Smit FD Wambach J 《Physical review letters》2004,93(12):122501
Fine structure in the energy region of the isoscalar giant quadrupole resonance in nuclei is observed in high-resolution proton scattering experiments at iThemba LABS over a wide mass range. A novel method based on wavelet transforms is introduced for the extraction of scales characterizing the fine structure. A comparison with microscopic model calculations including two-particle two-hole (2p2h) degrees of freedom identifies the coupling to surface vibrations as the main source of the observed scales. A generic pattern is also found for the stochastic coupling to the background of the more complex states. 相似文献
33.
Dubbeldam D Calero S Vlugt TJ Krishna R Maesen TL Beerdsen E Smit B 《Physical review letters》2004,93(8):088302
We present a method to determine potential parameters in molecular simulations of confined systems through fitting on experimental isotherms with inflection points. The procedure uniquely determines the adsorbent-adsorbate interaction parameters and is very sensitive to the size parameter. The inflection points in the isotherms are often related to a subtle interplay between different adsorption sites. If a force field can predict this interplay, it also reproduces the remaining part of the isotherm correctly, i.e., the Henry coefficients and saturation loadings. 相似文献
34.
M. I. Lazareva Yu. K. Kryschenko R. Caple W. A. Smit K. A. Lyssenko A. S. Shashkov 《Russian Chemical Bulletin》2000,49(1):85-97
The reaction of the bicyclic thiophanium ions salts, generated by the sequential interaction ofp-TolSCI with dihydropyran or 1-methoxycycloalkene and then with an acyclic alkyl vinyl ether in the presence of a Lewis acid
and with silicon- or tin-capped π-donors, proceeds with high diastereoselectivity at all newly created chiral centers.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 82–94, January, 2000. 相似文献
35.
36.
V. A. Smit S. I. Pogrebnoi Yu. B. Kal'yan M. Z. Krimer 《Russian Chemical Bulletin》1990,39(8):1760-1761
Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1934–1935, August, 1990. 相似文献
37.
38.
R. M. Persoons E. De Grave P. M. A. De Bakker R. E. Vandenberghe H. H. A. Smit 《Hyperfine Interactions》1990,54(1-4):661-666
Spectra for three members of the spinel system Mg1+t
Fe2(1−t)Ti
t
O4, witht=0.5, 0.6 and 0.7, all showing re-entrant spin-glass-like behavior, were collected at temperatures down to 1.6 K and decomposed
in A- and B-site components, both having a broad distribution of hyperfine fields. The numerical results suggest a more pronounced
spin canting on A sites as compared to B sites. From spectra recorded at 4.2 K in an applied field of 6 T, and analysed with
a sum of two bi-dimensional distributions of hyperfine fields and canting angles, the existence of reversed A-site spins is
evidenced. The number of such spins increases with increasing magnetic dilution.
Senior Research Associate at the National Fund for Scientific Research, Belgium 相似文献
39.
DeannaM. D'Alessandro Berend Smit JeffreyR. Long 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2010,122(35):6194-6219
Der stark ansteigende Kohlendioxidgehalt in der Atmosphäre ist eines der drängendsten Umweltprobleme unserer Zeit. Eine Option zur Verringerung anthropogener CO2‐Emissionen ist die Abscheidung und Speicherung von Kohlendioxid (Carbon Capture and Storage, CCS) an Punktquellen wie Kraftwerken. Durch diese Sequestrierung steigt allerdings der Energiebedarf der Kraftwerke um 25–40 %. Wir berichten hier über die Technologien zur Abscheidung, die zur Verringerung der CO2‐Emissionen wahrscheinlich am besten geeignet sind. Dazu zählen Postcombustion‐Verfahren, bei denen die Abscheidung nach der Verbrennung stattfindet (vor allem die CO2/N2‐Separation), Precombustion‐Verfahren, bei denen CO2/H2‐Gemische eingesetzt werden, und die Konditionierung von Erdgas (CO2/CH4). Der Schlüssel zu deutlichen Fortschritten sind bessere Trennmittel zur Separation. Wir werden hier aktuelle Entwicklungen und neuartige Konzepte zur CO2‐Abtrennung durch Lösungsmittel‐Absorption, chemische und physikalische Adsorption und Membranen schildern und besonders auf Fortschritte auf dem wachsenden Gebiet Metall‐organischer Gerüste eingehen. 相似文献
40.
Nico Smit Ruben Musson Fred Romijn Huub Van Rossum Johannes Van Pelt 《Photochemistry and photobiology》2010,86(2):360-366
Calcineurin (Cn) is the target of immunosuppressive drugs used for maintenance therapy of transplant patients. UV radiation is also known to be immunosuppressive and, like the Cn inhibitors, UV has been shown to positively influence various inflammatory skin diseases. Recently, Cn activity has been demonstrated in skin and skin cell cultures. In the present study we have investigated the effects of UV(A-1) irradiation on Cn activity in skin. In total skin we found a significant reduction in Cn activity after exposure to 450 kJ m−2 of UVA-1 (340–400 nm). In repeated experiments cultures of fibroblasts and keratinocytes also showed dose-dependent and selective reduction in Cn activity after UVA-1 irradiation. UVB irradiation caused a decrease in the Cn activity of one of two fibroblast cultures and was ineffective in keratinocytes. In Jurkat cells and PBMC UVA-1 reduced Cn activity and also the production of cytokines such as interleukin (IL)-2, γ-interferon, IL-4 and IL-10 that are controlled by the Ca2+–Cn pathway. These results indicate that UV(A-1) irradiation may lead to inactivation of Cn in the skin and thus suppress the skin immune system in a similar fashion to the Cn inhibitors. 相似文献