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101.
In our work, we will explore the possibility of implementing the well-known Carr–Purcell–Meiboom–Gill pulse sequence to determine the pore size of porous ceramics with magnetic impurities. The proposed approach exploits the diffusion dependence of the spin-echo signal in the presence of internal gradients occurring as a result of susceptibility contrast between the porous matrix and the confined liquid. For calibrating the technique, a comparison of the pore size data with those extracted from the so-called DDIF technique (DDIF, decay due to diffusion in the internal fields) is performed. This approach can be applied for nondestructive in situ characterization of soils, concrete, biological tissues or other structures with micrometer pore size. 相似文献
102.
Conformational transformations of the tetraenic nystatin chromophore under the influence of solvents and UV irradiation have been studied by absorption, fluorescence and wide-line NMR spectroscopy. 相似文献
103.
Rodica Zvoianu Cristina R. Dias M. Farinha Portela 《Reaction Kinetics and Catalysis Letters》2001,72(2):201-208
The acid-base properties of a series of SiO2-supported NiMoO4 catalysts were investigated by temperature-programmed desorption of NH3 and CO2. Results show that supported catalysts with ca. one monolayer of the active phase are less acidic than the unsupported stoichiometric NiMoO4. 相似文献
104.
Ioan Paraschiv Alistair Tomkinson Marcel Giesbers Ernst J. R. Sudh?lter Han Zuilhof Antonius T. M. Marcelis 《Liquid crystals》2013,40(9):1029-1038
The synthesis and thermotropic properties are reported for a series of hexaalkoxytriphenylenes that contain an amide, urea or thiourea group in one of their alkoxy tails. The intermolecular hydrogen bonding abilities of these molecules have a disturbing influence on the formation and stability of the columnar liquid crystalline phases. The stronger the hydrogen bonding the more the liquid crystallinity is suppressed, probably due to disturbance of the π–π stacking of the triphenylene discs. As a direct result, urea‐ and amide‐containing triphenylene derivatives are not liquid crystalline, but several thiourea derivatives show hexagonal columnar mesophases. 相似文献
105.
In this paper the formation mechanism of iron macro-spheres in
a plasma medium is dealt with, including the conditions under which such
spheres are formed. The geometry of the spheres referred to above
depends on the main technological parameters involved in the production
of pores. Conditions under which pores occur within macro-spheres are
also established. The radii of these pores are sensitive to the velocity
distribution within the plasma jet section 相似文献
106.
Carole Fraschini Rodica Plesu Jose‐Ramon Sarasua Robert E. Prud'homme 《Journal of Polymer Science.Polymer Physics》2005,43(22):3308-3315
A polylactide of high optical purity was crystallized between 100 and 140 °C, in‐between two glass slides, and its morphology was investigated by polarizing optical microscopy, scanning electron microscopy, and atomic force microscopy, during subsequent heating and cooling cycles between ?15 °C and the crystallization temperature. It was found that dark circular rings show up on cooling on top of the spherulites and represent cracks of about 300 nm in width. This phenomenon is completely reversible, and the heating–cooling curves are centered at about 56 °C, which coincide with the Tg of polylactide. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3308–3315, 2005 相似文献
107.
108.
Rodica Simion 《Discrete Mathematics》1984,49(1):89-93
In this paper it is shown that the lattice Ln of partitions of n under the dominance ordering is totally asymmetric, except for the cases n = 6 and 7 where the automorphism group is 2 × 2. As a consequence, partition conjugation is the only antiautomorphism of Ln if n ≠ 6, 7. 相似文献
109.
110.
Given a sequence of real or complex coefficients ci and a sequence of distinct nodes ti in a compact interval T, we prove the divergence and the unbounded divergence on superdense sets in the space C(T) of the simple quadrature formulas ∝Tx(t)du(t) = Qn(x) + Rn(x) and ∝Tw(t)x(t)dt = Qn(x) + Rn(x), where Qn(x)=∑i=1mn cix(ti), ε C(T).The divergence (not certainly unbounded) for at most one continuous function of the first simple quadrature formula, with mn = n and u(t) = t, was established by P. J. Davis in 1953. 相似文献