ABSTRACTBy combining Monte Carlo simulations and analytical models, we demonstrate and explain how the gas-to-liquid phase transition of colloidal systems confined to a spherical surface depends on the curvature and size of the surface, and on the choice of thermodynamic ensemble. We find that the geometry of the surface affects the shape of the free energy profile and the size of the critical nucleus by altering the perimeter–area ratio of isotropic clusters. Confinement to a smaller spherical surface results in both a lower nucleation barrier and a smaller critical nucleus size. Furthermore, the liquid domain does not grow indefinitely on a sphere. Saturation of the liquid density in the grand canonical ensemble and the depletion of the gas phase in the canonical ensemble lead to a minimum in the free energy profile, with a sharp increase in free energy for additional growth beyond this minimum. 相似文献
Quantum communication provides an enormous advantage over its classical counterpart: security of communications based on the very principles of quantum mechanics. Researchers have proposed several approaches for user identity authentication via entanglement. Unfortunately, these protocols fail because an attacker can capture some of the particles in a transmitted sequence and send what is left to the receiver through a quantum channel. Subsequently, the attacker can restore some of the confidential messages, giving rise to the possibility of information leakage. Here we present a new robust General Nuser authentication protocol based on N-particle Greenberger–Horne–Zeilinger (GHZ) states, which makes eavesdropping detection more effective and secure, as compared to some current authentication protocols. The security analysis of our protocol for various kinds of attacks verifies that it is unconditionally secure, and that an attacker will not obtain any information about the transmitted key. Moreover, as the number of transferred key bits N becomes larger, while the number of users for transmitting the information is increased, the probability of effectively obtaining the transmitted authentication keys is reduced to zero. 相似文献
In reported low-field nuclear magnetic resonance (NMR) measurements using Superconducting Quantum Interference Device (SQUID) detection, the pre-polarizing magnetic field has been usually oriented orthogonal to the measuring field, BpBm. Melton et al. systematically analyzed the consequences of Bp decay in time after turnoff and showed that this decay should be nonadiabatic. We evaluated our measuring procedure in the light of that analysis, and found good quantitative agreement. It was showed that, when the decay time constant is comparable to the precession period of the magnetization of the sample, M, the optimum procedure is to orient Bp parallel to Bm and to apply a π/2 pulse to flip M, similar as in the case of conventional NMR. 相似文献
Molecular Diversity - An elegant, efficient, and highly regioselective approach for the synthesis of novel methyl 5-amino-3-(methylthio)-1-differently substituted-1H-pyrazole-4-carboxylates is... 相似文献
Elimination of toxic organic compounds from wastewater and provision of safe, clean, and cheap water to communities is currently one of the most important global topics in water-pollution control. TiO2 has emerged as one of the most fascinating material in the modern era due to its potential catalytic properties. In spite of extensive efforts to apply TiO2 for environmental remediation, photocatalytic activity in the visible region has remained quite low hence the need to fabricate highly photoactive catalysts through modification of TiO2 and to apply them for water remediation using the abundantly available solar radiation.
Carbon materials are promising candidates for application as functional materials due to their superior physico-chemical properties. This has prompted investigations into their possible application in environmental clean-up. Nanocomposite assemblies composed of different types and proportions of carbon based materials (i.e., carbon nanotubes, graphene, fullerenes, activated carbon, carbon nanofibers) and TiO2 have also found widespread applicability in water decontamination studies using UV or visible light. This article surveys the literature and highlights recent progress in the development of TiO2 and nanocarbon/TiO2 photocatalysts for water decontamination. The nitty-gritties, on-going challenges, areas of controversy, “hotspots” and possible new directions are outlined in this article. 相似文献
The investigations of the crystal and magnetic structures of the Ba Fe12-xAlx O19(x = 0.1–1.2) solid solutions have been performed with powder neutron diffractometry. Magnetic properties of the Ba Fe12-xAlx O19(x = 0.1–1.2) solid solutions have been measured by vibration sample magnetometry at different temperatures under different magnetic fields.The atomic coordinates and lattice parameters have been Rietveld refined. The invar effect is observed in low temperature range(from 4.2 K to 150 K). It is explained by the thermal oscillation anharmonicity of atoms. The increase of microstress with decreasing temperature is found from Rietveld refinement. The Curie temperature and the change of total magnetic moment per formula unit are found for all compositions of the Ba Fe12-xAlx O19(x = 0.1–1.2) solid solutions. The magnetic structure model is proposed. The most likely reasons and the mechanism of magnetic structure formation are discussed. 相似文献
Current--voltage measurements obtained from lead zirconate
titanate/nickel bilayered hollow cylindrical magnetoelectric
composite showed that a sinusoidal current applied to the copper
coil wrapped around the hollow cylinder circumference induces
voltage across the lead zirconate titanate layer thickness. The
current--voltage coefficient and the maximum induced voltage in lead
zirconate titanate at 1~kHz and resonance (60.1~kHz) frequencies
increased linearly with the number of the coil turns and the applied
current. The resonance frequency corresponds to the
electromechanical resonance frequency. The current--voltage
coefficient can be significantly improved by optimizing the
magnetoelectric structure geometry and/or increasing the number of
coil turns. Hollow cylindrical lead zirconate titanate/nickel
structures can be potentially used as current sensors. 相似文献
In III-V and II-VI semiconductors, certain nominally electron-donating impurities do not release electrons but instead form deep electron-traps known as "DX centers." While in these compounds, such traps occur only after the introduction of foreign impurity atoms, we find from first-principles calculations that in ternary I-III-VI2 chalcopyrites like CuInSe2 and CuGaSe2, DX-like centers can develop without the presence of any extrinsic impurities. These intrinsic DX centers are suggested as a cause of the difficulties to maintain high efficiencies in CuInSe2-based thin-film solar-cells when the band gap is increased by addition of Ga. 相似文献
We show that the Coulomb drag effect exhibits saturation at small temperatures, when calculated to the third order in the interlayer interactions. The zero-temperature transresistance is of the order h/(e2g3), where g is the dimensionless sheet conductance. The effect is therefore the strongest in low mobility samples. This behavior should be contrasted with the conventional (second order) prediction that the transresistance scales as a certain power of temperature and is (almost) mobility independent. The result demonstrates that the zero-temperature drag is not an unambiguous signature of a strongly coupled state in double-layer systems. 相似文献