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排序方式: 共有185条查询结果,搜索用时 31 毫秒
81.
Mangiapia G Ricciardi R Auriemma F Rosa CD Celso FL Triolo R Heenan RK Radulescu A Tedeschi AM D'Errico G Paduano L 《The journal of physical chemistry. B》2007,111(9):2166-2173
The structure of poly(vinyl alcohol) (PVA) hydrogels formed as a result of freeze/thaw treatments of aqueous solutions of the polymer (11 wt % PVA) in the freshly prepared state is analyzed through the combined use of small (SANS) and ultrasmall (USANS) angle neutron scattering techniques. The structure of these hydrogels may be described in terms of polymer rich regions, with dimensions of the order of 1-2 microm, dispersed in a water rich phase, forming two bicontinuous phases. The PVA chains in the polymer rich phase form a network where the cross-linking points are mainly crystalline aggregates of PVA having average dimensions of approximately 45 A. The structural organization of freeze/thaw PVA hydrogel membranes does not change either after rehydration of dried gels or in the presence of a tensile force. Finally, addition of surfactant micelles inside the gel provides a formulation with both hydrophobic and hydrophilic regions, which demonstrates the potential of the system for drug delivery. Both SANS and EPR measurements show that sodium decylsulfate (C10OS) micelles do not significantly interact with the PVA gel. Variation of the gel structure by the number of freeze/thaw cycles should modulate the rate of release of an active constituent, for example, in a dermal patch. 相似文献
82.
We present the first model-independent comparison of recent measurements of the entropy and of the critical temperature of a unitary Fermi gas, performed by Luo et al., with the most complete results currently available from finite temperature Monte Carlo calculations. The measurement of the critical temperature in a cold fermionic atomic cloud is consistent with a value T(c) = 0.23(2)epsilon(F) in the bulk, as predicted by the present authors in their Monte Carlo calculations. 相似文献
83.
Aurel Bejancu 《General Relativity and Gravitation》2013,45(11):2291-2308
Based on the new point of view on space–time–matter theory developed in our paper (Bejancu, Gen Rel Grav, 2013), we obtain the $4D$ 4 D Einstein equations in a general $5D$ 5 D Kaluza–Klein space with electromagnetic potentials. In particular, we recover the $4D$ 4 D Einstein equations obtained by Wesson and Ponce de Leon (J Math Phys 33:3883, 1992) in case the electromagnetic potentials vanish identically on $\bar{M}$ M ¯ . The Riemannian horizontal connection and the $4D$ 4 D tensor calculus on $\bar{M}$ M ¯ , are the main tools in the study. 相似文献
84.
Daniel Gherca Aurel Pui Nicoleta Cornei Alina Cojocariu Valentin Nica Ovidiu Caltun 《Journal of magnetism and magnetic materials》2012
We focused on obtaining MFe2O4 nanoparticles using ricin oil solution as surfactant and on their structural characterization and magnetic properties. The annealed samples at 500 °C in air for 6 h were analyzed for the crystal phase identification by powder X-ray diffraction using CuKα radiation. The particle size, the chemical composition and the morphology of the calcinated powders were characterized by scanning electron microscopy. All sintered samples contain only one phase, which has a cubic structure with crystallite sizes of 12–21 nm. From the infrared spectra of all samples were observed two strong bands around 600 and 400 cm−1, which correspond to the intrinsic lattice vibrations of octahedral and tetrahedral sites of the spinel structure, respectively, and characteristic vibration for capping agent. The magnetic properties of fine powders were investigated at room temperature by using a vibrating sample magnetometer. The room temperature M–H hysteresis loops show ferromagnetic behavior of the calcined samples, with specific saturation magnetization (Ms) values ranging between 11 and 53 emu/g. 相似文献
85.
Catalin Tanase Aurel Pui Adrian Oprea Karin Popa 《Journal of Radioanalytical and Nuclear Chemistry》2009,281(3):563-567
The present study follows the extent of translocation radioactivity from the substrates of the Crucea uranium mining area
to the macromycetes spontaneously occurred during June–October 2008. To this end, radioactivity measurements (gross α + β
and 137Cs) on both macromycetes and their substrates were made. The resultants obtained were confirmed by FT-IR spectroscopy, evidencing
the presence of characteristic bands around of 910 cm−1, corresponding to the asymmetric stretching vibration of the uranyl unit and to the interaction between the UO2
2+ ions and the group belonging to various cellular components. 相似文献
86.
The first-order moments and two families of commutators are proven to determine uniquely the moments of a probability measure
on ℝ
d
. These families are the commutators between the annihilation and creation operators, and the commutators between the annihilation
and preservation operators. An explicit method for recovering the moments from these commutators and first-order moments is
presented.
相似文献
87.
We present a parallel solver for second order scalar PDE called The Parallel Toolbox. We investigate certain performance issues which arise when high performance compute nodes with a relatively slow network interconnect are used. These performance issues motivate the introduction of block methods which reduce network usage and thus increase parallel performance. First benchmarks computed on a GPU cluster evaluate the success of this attempt. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
88.
We study, in a fully nonperturbative calculation, a dilute system of spin 1/2 interacting fermions, characterized by an infinite scattering length at finite temperatures. Various thermodynamic properties and the condensate fraction are calculated and we also determine the critical temperature for the superfluid-normal phase transition in this regime. The thermodynamic behavior appears as a rather surprising and unexpected mélange of fermionic and bosonic features. The thermal response of a spin 1/2 fermion at the BCS-BEC crossover should be classified as that of a new type of superfluid. 相似文献
89.
For a system of charged Fermions interacting with an electromagnetic field, we derive a non-Markovian master equation in the second-order approximation of the weak dissipative coupling. A complex dissipative environment including Fermions, Bosons and the free electromagnetic field is taken into account. Besides the well-known Markovian term of Lindblad’s form, that describes the decay of the system by correlated transitions of the system and environment particles, this equation includes new Markovian and non-Markovian terms proceeding from the fluctuations of the self-consistent field of the environment. These terms describe fluctuations of the energy levels, transitions among these levels stimulated by the fluctuations of the self-consistent field of the environment, and the influence of the time-evolution of the environment on the system dynamics. We derive a complementary master equation describing the environment dynamics correlated with the dynamics of the system. As an application, we obtain non-Markovian Maxwell-Bloch equations and calculate the absorption spectrum of a field propagation mode transversing an array of two-level quantum dots. 相似文献
90.
Zeitschrift für Physik D Atoms,Molecules and Clusters - When the cluster excitation energy is such that the hopping between different isomers becomes energetically allowed, the power spectrum... 相似文献