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141.
J. F. Nagle 《Journal of statistical physics》1995,78(1-2):549-561
Personal recollections give a sampling of some of Onsager's later interests in ice and biomembranes. The author's involvement in these topics led to modeling a particular biomembrane phase transition using dimer models. Recent work is described for a particularly rich dimer model which is isomorphic to the F-model in three kinds of fields (direct, staggered, and quarter). New results for the full three-dimensional phase diagram show (1) how the anomalous OK multicritical point is destroyed by a direct field, and (2) how a new line of critical points must be added to the phase diagram in direct and staggered fields obtained previously by Baxter, due to diverging susceptibilities in the quarter field. 相似文献
142.
B. Lacaze 《Waves in Random and Complex Media》2006,16(1):69-74
Backscattering of radar waves on the sea takes place even when there is no target. It appears as a noise which it is necessary to study in decision problems. Today, the model of a mixing of Gaussian for spectra seems widely agreed. In this paper, we show that it is equivalent to a mixing of monochromatic waves whose trajectories are time perturbed by Gaussian processes. In addition, this model explains linear variations of Doppler shifts and spectral widths with the emitted frequencies. 相似文献
143.
Alan M. Davies 《国际流体数值方法杂志》1985,5(5):405-425
A three dimensional hydrodynamic sea model of an arbitrary sea area is formulated using sigma co-ordinates in the vertical. The solution of the equations using finite difference grids in the horizontal and the vertical is described. Discretization of the vertical viscosity term in the hydrodynamic equations using the DuFort-Frankel and Saul'ev methods is developed. Some numerical instabilities occur with the DuFort-Frankel method which can be overcome by splitting the hydrodynamic equations into equations describing the mean flow and equations describing the deviations from it. The computational advantages of solving these equations with different time steps are discussed. The accuracy and stability of the various methods is demonstrated for wind induced flow in a simple rectangular basin having dimensions representing the North Sea. 相似文献
144.
Seong‐Chan Park Dr. Joon‐Ki Kim Chang‐Woo Lee Eui‐Seong Moon Heon Kang Prof. Dr. 《Chemphyschem》2007,8(17):2520-2525
Proton transfer from the hydronium ion to NH3, CH3NH2, and (CH3)2NH is examined at the surface of ice films at 60 K. The reactants and products are quantitatively monitored by the techniques of Cs+ reactive‐ion scattering and low‐energy sputtering. The proton‐transfer reactions at the ice surface proceed only to a limited extent. The proton‐transfer efficiency exhibits the order NH3>(CH3)NH2=(CH3)2NH, which opposes the basicity order of the amines in the gas phase or aqueous solution. Thermochemical analysis suggests that the energetics of the proton‐transfer reaction is greatly altered at the ice surface from that in liquid water due to limited hydration. Water molecules constrained at the ice surface amplify the methyl substitution effect on the hydration efficiency of the amines and reverse the order of their proton‐accepting abilities. 相似文献
145.
Alexander Goodwin Craig E. Banks Dario Omanovi? Richard G. Compton 《Analytica chimica acta》2005,533(2):141-145
Cathodic stripping voltammetry at a boron-doped diamond electrode utilising an insonated accumulation protocol is shown to be possible for the on-site trace detection of free manganese in seawater samples. No sample pre-treatment is required with the application of ultrasound providing a sensitive and selective protocol for the analysis of manganese. The protocol is used in the evaluation of manganese in seawater samples taken near the site of a former ferromanganese factory in the town Šibenik, Croatia. 相似文献
146.
We prepared thin molecular films of ethanol and 2-methylpropan-2-ol on Ru(001) substrates at temperature of 100-150 K and examined their reactivity toward HBr. The reaction intermediates and products formed at the surfaces were unambiguously identified by the techniques of Cs(+) reactive ion scattering (RIS) and low-energy sputtering. The reaction on the ethanol surface produced protonated ethanol, which is stabilized on the surface and does not proceed to further reactions. On the 2-methylpropan-2-ol surface, protonated alcohol [(CH(3))(3)COH(2) (+)] and carbocation [(CH(3))(3)C(+)] were formed with the respective yield of 20 and 78 %. Alkyl bromides, which are the final products of the corresponding reactions in liquid solvents, have extremely small yields on these surfaces (< 0.3 % for ethyl bromide and 2 % for tert-butyl bromide). The results indicate that the reactions on frozen films are characterized by kinetic control, stabilization of ionic intermediates (protonated alcohols and tert-butyl cation), and effective blocking of the charge recombination steps in S(N)1 and S(N)2 paths. The implication of these findings for the molecular evolution process in interstellar medium is also discussed. 相似文献
147.
A new analytical method based on the cloud-point extraction (CPE) methodology combined with high-performance liquid chromatography is used in this study for the extraction and quantification of polychlorinated dibenzo-p-dioxins. These compounds are extracted by using the non-ionic surfactant polyoxyethylene 10 lauryl ether (POLE) from different aqueous systems: fresh, brackish and sea waters. After the cloud-point extraction, which also allowed a preconcentration of the PCDDs being studied, the samples were analysed using a HPLC–UV system under the optimum chromatographic conditions. The proposed method showed very satisfactory recovery percentages for the PCDDs under study and standard deviation values lower than 2%.
The results obtained were finally compared with those found using the traditional liquid–liquid extraction method. 相似文献
148.
The effects of poly(vinyl alcohol) (PVA) on the Ostwald ripening of polycrystalline ice samples are studied. At -6 degrees C, ice recrystallization in sucrose solutions is inhibited at PVA concentrations down to 0.005 mg mL(-1), with a recrystallization inhibition constant of 48.9 mL mg(-1). Ice growth-habit experiments reveal molecular recognition of the arrangement of water molecules in the ice by PVA molecules, and indicate that PVA molecules adsorb to the primary and secondary prism faces of hexagonal ice, Ih. Based on these observations, together with an analysis of the O-atom pattern in ice and the conformation of OH groups in PVA, an adsorption model is proposed. We suggest that PVA segments adsorb to the primary and secondary prism faces of ice parallel to the c axis with a linear misfit parameter of only 2.7 %, most likely via multiple hydrogen bonds. The proposed adsorption mechanism is discussed in the light of recent thermal hysteresis and scanning tunneling microscopy experiments. 相似文献
149.
Hiroharu Yui Toshinori Morisaku Akira Suzuki 《Surface and interface analysis : SIA》2019,51(1):136-140
Phase transition of water confined in nanospaces with charged inner-surfaces was investigated by vibrational spectroscopy. Aerosol sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles give a series of spherical nanospaces with controlled inner-radius (Rw) with nanometer-scale precision. Successive spectroscopic measurements of the confined water with decreasing temperature revealed that the water freezes to metastable cubic ice (Ic) coexisting with super-cooled water or unstable amorphous ice at the Rw ranging from 1.0 to 2.0 nm. When Rw exceeded 2.0 nm, stable hexagonal ice (Ih) dominated. The drastic change of the dominant ice structure with the increase of 1 nm in Rw shows that the thickness of water layers affected by the inner surface can be estimated to be ~1 nm, where three or four layers of water hydrated to the surface. It is worth noting that the clear phase transition behavior of the confined water vanishes at Rw = 1.2 nm and that the gradual formation of Ic and coexistence of super-cooled water or glassy state of water are detected. The range of the effective interaction between interfacial water and the charged inner surfaces and the mechanism of the extremely slow phase transition were also discussed. 相似文献
150.