Добірка наукової літератури з теми "True/false chirality"

The 1884 suggestion of Pierre Curie (1859–1906) that the type of dissymmetry shown by collinear electric and magnetic fields may induce an enantiomeric excess, in a chemical reaction that would otherwise produce a racemic mixture, is explored in the context of fundamental symmetry arguments. Curie’s arrangement exhibits false chirality (time-noninvariant enantiomorphism), and so it may not induce absolute enantioselection (ae) in a process that has reached thermodynamic equilibrium, since it does not lift the degeneracy of chiral enantiomers. However, it may do so in far-from-equilibrium processes via a breakdown in microscopic reversibility analogous to that observed in elementary particle processes under the influence of CP violation, the associated force possessing false chirality with respect to CP enantiomorphism. In contrast, an influence like circularly polarized light exhibiting true chirality (time-invariant enantiomorphism) lifts the degeneracy of enantiomers, and so may induce ae in all circumstances. Although to date, ae has not been observed under the influence of Curie’s arrangement of collinear electric and magnetic fields, it is argued that two different experiments have now demonstrated ae under a falsely chiral influence in systems far from equilibrium, namely in a spinning sample under a gravitational field, and in the separation of enantiomers at a ferromagnetic surface.

Purpose: Type B aortic dissections propagate with either achiral (nonspiraling) or right-handed chiral (spiraling) morphology, have mobile dissection flaps, and are often treated with thoracic endovascular aortic repair (TEVAR). We aim to quantify cardiac-induced helical deformation of the true lumen of type B aortic dissections before and after TEVAR. Material and Methods: Retrospective cardiac-gated computed tomography (CT) images before and after TEVAR of type B aortic dissections were used to construct systolic and diastolic 3-dimensional (3D) surface models, including true lumen, whole lumen (true+false lumens), and branch vessels. This was followed by extraction of true lumen helicity (helical angle, twist, and radius) and cross-sectional (area, circumference, and minor/major diameter ratio) metrics. Deformations between systole and diastole were quantified, and deformations between pre- and post-TEVAR were compared. Results: Eleven TEVAR patients (59.9±4.6 years) were included in this study. Pre-TEVAR, there were no significant cardiac-induced deformations of helical metrics; however, post-TEVAR, significant deformation was observed for the true lumen proximal angular position. Pre-TEVAR, cardiac-induced deformations of all cross-sectional metrics were significant; however, only area and circumference deformations remained significant post-TEVAR. There were no significant differences of pulsatile deformation from pre- to post-TEVAR. Variance of proximal angular position and cross-sectional circumference deformation decreased after TEVAR. Conclusion: Pre-TEVAR, type B aortic dissections did not exhibit significant helical cardiac-induced deformation, indicating that the true and false lumens move in unison (do not move with respect to each other). Post-TEVAR, true lumens exhibited significant cardiac-induced deformation of proximal angular position, suggesting that exclusion of the false lumen leads to greater rotational deformations of the true lumen and lack of true lumen major/minor deformation post-TEVAR means that the endograft promotes static circularity. Population variance of deformations is muted after TEVAR, and dissection acuity influences pulsatile deformation while pre-TEVAR chirality does not. Clinical Impact Description of thoracic aortic dissection helical morphology and dynamics, and understanding the impact of thoracic endovascular aortic repair (TEVAR) on dissection helicity, are important for improving endovascular treatment. These findings provide nuance to the complex shape and motion of the true and false lumens, enabling clinicians to better stratify dissection disease. The impact of TEVAR on dissection helicity provides a description of how treatment alters morphology and motion, and may provide clues for treatment durability. Finally, the helical component to endograft deformation is important to form comprehensive boundary conditions for testing and developing new endovascular devices.

AbstractChirality is a manifestation of the asymmetry inherent in nature. It has been defined as the symmetry breaking of the parity of static objects, and the definition was extended to dynamic motion such that true and false chiralities were distinguished. Recently, rotating, yet not propagating, atomic motions were predicted and observed in two-dimensional materials, and they were referred to as ‘chiral phonons’. A natural development would be the discovery of truly chiral phonons that propagate while rotating in three-dimensional materials. Here we used circularly polarized Raman scattering and first-principles calculations to identify truly chiral phonons in chiral bulk crystals. This approach enabled us to determine the chirality of a crystal in a non-contact and non-destructive manner. In addition, we demonstrated that the law of the conservation of pseudo-angular momentum holds between circularly polarized photons and chiral phonons. These findings are expected to help develop ways for transferring the pseudo-angular momentum from photons to electron spins via propagating chiral phonons in opto-phononic-spintronic devices.

L’énantioséparation de précision est essentielle pour les industries pharmaceutiques et alimentaires. Les techniques conventionnelles de séparation chirale offrent un large éventail de méthodes, qui reposent toutes sur des sélecteurs chiraux - des phases stationnaires ou des molécules qui distinguent les énantiomères par une interaction stéréospécifique. Malgré le grand nombre de sélecteurs naturels et synthétiques actuellement utilisés, la demande croissante d’énantiopurité stimule la recherche de nouvelles méthodes polyvalentes.Le but de cette thèse est d'étudier des méthodes alternatives de séparation chirale impliquant l'application de champs magnétiques dans diverses configurations. Une idée est centrée sur le concept de vraie et fausse chiralité, introduit par L. Barron pour les systèmes dynamiques d'objets individuels et de grandeurs physiques vectorielles. Sa discussion indique explicitement que ni les champs magnétiques ni électriques statiques, ni aucune combinaison de ceux-ci, ne possèdent une véritable chiralité, la caractéristique requise pour induire une discrimination énantiomérique. Cependant, sa théorie suggère l’existence d’un analogue moléculaire de l’effet Faraday bien connu sous forme de l’application colinéaire d’un champ magnétique à un flux moléculaire.Alternativement, une configuration perpendiculaire au flux moléculaire impliquant un substrat ferromagnétique a démontré des interactions de spin énantiospécifiques, également connues sous le nom d'effet CISS. À cet égard, notre objectif principal était d’explorer une telle interaction dans des conditions dynamiques d’électrophorèse capillaire, qui permet une détection simple et rapide, tout en introduisant des substrats de Ni le long du flux de molécules et en appliquant un champ magnétique orthogonal.Enfin, la configuration orthogonale du champ magnétique a été exploitée pour étudier le comportement dynamique d'objets électropolarisés. Il a été démontré que la rotation présenté par différents objets sous l'effet magnétohydrodynamique induit par la force de Lorentz dépendent de la polarité du champ magnétique. Leur comportement dynamique en fonction du temps ressemble à celui de systèmes faussement chiraux
High-purity enantioseparation is essential for the pharmaceutical and food industries. Conventional chiral separation techniques provide a wide range of methods, all of which rely on chiral selectors - stationary phases or molecules that discriminate enantiomers through stereospecific interaction. Despite the vast number of natural and synthetic selectors currently in use, the increasing demand for enantiopurity is driving research for new and versatile methods.The aim of this thesis is to investigate alternative methods of chiral separation that involve the application of magnetic fields in various configurations. One idea centers around the concept of true and false chirality, which was introduced by L. Barron for dynamic systems of individual objects and physical vector quantities. His discussion explicitly states that neither static magnetic nor electric fields, nor any combination of those, possess true chirality, the feature required to induce enantiomeric discimination. However, his theory suggests a molecular analog of the well-known Faraday effect based on the collinear application of magnetic field to a molecular flow.Alternatively, a perpendicular configuration with the molecular flow involving a ferromagnetic substrate has demonstrated enantiospecific spin interactions, otherwise known as the CISS effect. In this regard, our main objective was the further exploration of such interactions in dynamic conditions of capillary electrophoresis, which provides simple and fast detection, while introducing Ni substrates along the flow of molecules and applying an orthogonal magnetic field.Lastly, the orthogonal configuration of the magnetic field was exploited to study the dynamic behavior of electropolarized objects. The patterns of the resulting rotation, exhibited by different objects under the influence of a magnetohydrodynamic effect, originating from the induced Lorentz force, are shown to be dependent on magnetic field polarity. Their dynamic behavior as a function of time resembles those of falsely chiral systems