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A. M. Figueiredo Neto

Bio: A. M. Figueiredo Neto is an academic researcher from University of São Paulo. The author has contributed to research in topics: Liquid crystal & Lyotropic. The author has an hindex of 21, co-authored 142 publications receiving 2160 citations. Previous affiliations of A. M. Figueiredo Neto include University of Brasília & University of Paris.


Papers
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Journal ArticleDOI
TL;DR: In this article, the stability of a FF in terms of various forces and torques on the magnetic particles is discussed, as well as the rotational dynamics of the magnetic moments of the particles.
Abstract: Magnetic fluids may be classified as ferrofluids (FF), which are colloidal suspensions of very fine (» 10 nm) magnetic particles, and magnetorheological fluids, which are suspensions of larger, usually non-stable, magnetic particles. We review the general classification and the main properties of FF, some theoretical models and a few applications. We consider the stability of a FF in terms of various forces and torques on the magnetic particles. We discuss thermodiffusion, which is an important phenomenon in FF, and which gives rise to the Soret effect. We also consider the rotational dynamics of the magnetic moments of the particles. A large portion of this review is dedicated to applications of FF, including a few of the many technological applications. Among the uses of a FF in the study of materials, we have selected the doping of liquid crystals. Among the very promising uses in Medicine, we discuss drug targeting, hyperthermia, cell separation, and contrast in magnetic resonance imaging. We also make some comments on directions for future research on the properties of ferrofluids.

463 citations

Book
07 Apr 2005
TL;DR: In this paper, the phase transitions between periodically organized Lyotropic phases are discussed, including the isotropic micellar and bicontinuous phases, the nematic and cholesteric phases, and the one-, two-and three-dimensional ordered phases.
Abstract: 1. Lyotropic systems: main experimental facts and techniques 2. Basic concepts of phase transitions 3. Phase diagrams of lyotropic mixtures 4. Phase transitions between periodically organized lyotropic phases 5. The isotropic micellar and bicontinuous phases 6. The nematic and cholesteric phases 7. The lyotropic one-, two- and three-dimensionally ordered phases 8. Recent developments and related areas

110 citations

Journal ArticleDOI
TL;DR: In this article, high-resolution x-ray measurements have been performed at the synchrotron of LURE (Orsay) to study both uniaxial (discotic and calamitic) and biaaxial nematic lyomesophases of the mixture K•laurate, 1•decanol, and D2O.
Abstract: High‐resolution x‐ray measurements have been performed at the synchrotron of LURE (Orsay) to study both uniaxial (discotic and calamitic) and biaxial nematic lyomesophases of the mixture K‐laurate, 1‐decanol, and D2O. The variations of the densitometric profiles of the diffracted bands are analyzed vs temperature. They are shown to be consistent with the model of similar micellar aggregates in the three nematic phases, undergoing different orientational fluctuations. It is moreover discussed that the micelles have, on the average, the shape of biaxial platelets with a (1/2/3) anisotropy, and that they build the same pseudolamellar structure in each nematic phase.

95 citations

Journal ArticleDOI
TL;DR: In this paper, a first order band and a second order band with spacing ratio 1:2 characteristic of a pseudo-lamellar structure are observed in the three nematic phases.
Abstract: Synchrtron X-ray measurements are performed in both uniaxial (discotic and calamitic) and biaxial nematic lyomesophases of the mixture K-laurate, 1-decanol and D 2 O. A first-order band and a second-order band with spacing ratio 1:2 characteristic of a pseudo-lamellar structure are observed in the three nematic phases. The X-ray diffraction results are interpreted in terms of the orientational fluctuations of intrinsically biaxial correlation volumes. It is argued that the calamitic and discotic phases are not built up of cylindric-like and disk-like micelles, but of aggrgates of statistically biaxial shape, similar in the three nematic phases. The only change at the uniaxial-biaxial nematic transitions is the long-range order Mesures realisees sur un melange de laurate de potassium, decanol-1 et D 2 O. Dans les trois phases discotiques, calomitiques et biaxes, on observe le premier et le second ordre d'une bande de diffraction caracteristique d'une structure pseudo-lamellaire. Les phases calomitiques et discotiques sont composees d'agregats de forme statistiquement biaxe, seul l'ordre a longue distance change aux transitions uniaxes-biaxes

80 citations

Journal ArticleDOI
TL;DR: In this paper, a review of experimental data on the nonlinear optical properties of thermotropic and lyotropic liquid crystals probed by the Z-scan technique is presented, and the physical processes associated with nonlinear response in thermotropics are not completely understood.
Abstract: We present a review of experimental data on the nonlinear optical properties of thermotropic and lyotropic liquid crystals probed by the Z-scan technique. Depending on the time scale, different processes originate a nonlinear optical response. Particularly, at nanosecond range, the physical processes associated with the nonlinear response in thermotropics are not completely understood. In lyotropics, the nonlinear response at ms time scale is from thermal origin and depends on the particular mesophase, relative concentration of the components, and temperature.

76 citations


Cited by
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01 Jan 2016
TL;DR: In this paper, the authors present the principles of optics electromagnetic theory of propagation interference and diffraction of light, which can be used to find a good book with a cup of coffee in the afternoon, instead of facing with some infectious bugs inside their computer.
Abstract: Thank you for reading principles of optics electromagnetic theory of propagation interference and diffraction of light. As you may know, people have search hundreds times for their favorite novels like this principles of optics electromagnetic theory of propagation interference and diffraction of light, but end up in harmful downloads. Rather than enjoying a good book with a cup of coffee in the afternoon, instead they are facing with some infectious bugs inside their computer.

2,213 citations

Dissertation
01 Oct 1948
TL;DR: In this article, it was shown that a metal should be superconductive if a set of corners of a Brillouin zone is lying very near the Fermi surface, considered as a sphere, which limits the region in the momentum space completely filled with electrons.
Abstract: IN two previous notes1, Prof. Max Born and I have shown that one can obtain a theory of superconductivity by taking account of the fact that the interaction of the electrons with the ionic lattice is appreciable only near the boundaries of Brillouin zones, and particularly strong near the corners of these. This leads to the criterion that the metal should be superconductive if a set of corners of a Brillouin zone is lying very near the Fermi surface, considered as a sphere, which limits the region in the momentum space completely filled with electrons.

2,042 citations

Journal ArticleDOI
TL;DR: A comprehensive overview of the progress that has been made within the context of 1D ZnO nanostructures synthesized via wet chemical methods can be found in this paper, where the synthetic methodologies and corresponding growth mechanisms, different structures, doping and alloying, position-controlled growth on substrates, and finally, their functional properties as catalysts, hydrophobic surfaces, sensors, and in nanoelectronic, optical, optoelectronics, and energy harvesting devices.
Abstract: One-dimensional (1D) ZnO nanostructures have been studied intensively and extensively over the last decade not only for their remarkable chemical and physical properties, but also for their current and future diverse technological applications. This article gives a comprehensive overview of the progress that has been made within the context of 1D ZnO nanostructures synthesized via wet chemical methods. We will cover the synthetic methodologies and corresponding growth mechanisms, different structures, doping and alloying, position-controlled growth on substrates, and finally, their functional properties as catalysts, hydrophobic surfaces, sensors, and in nanoelectronic, optical, optoelectronic, and energy harvesting devices.

1,247 citations

Journal ArticleDOI
TL;DR: In this article, structural and properties of liquid crystalline phases formed by bent-core molecules are reviewed and the most attractive properties of this new class of liquid crystals are in polarity and chirality, despite being formed from achiral molecules.
Abstract: Structures and properties of liquid crystalline phases formed by bent-core molecules are reviewed. At least eight phases designated as B1–B8 have been found, being unambiguously distinguished from phases formed by usual calamitic molecules due to a number of remarkable peculiarities. In addition to B1–B8 phases, smectic A-like phases and biaxial nematic phases formed by bent-core molecules are also reviewed. The most attractive aspects of this new class of liquid crystals are in polarity and chirality, despite being formed from achiral molecules. The bent-core mesogens are the first ferroelectric and antiferroelectric liquid crystals realized without introducing chirality. Spontaneous chiral deracemization at microscopic and macroscopic levels occurs and is controllable. Moreover, achiral bent-core molecules enhance system chirality. The interplay between polarity and chirality provides chiral nonlinear optic effects. Further interesting phenomena related to polarity and chirality are also reviewed.

713 citations