Rashba Torque Driven Domain Wall Motion in Magnetic Helices

Manipulation of the domain wall propagation in magnetic wires is a key practical task for a number of devices including racetrack memory and magnetic logic. Recently, curvilinear effects emerged as an efficient mean to impact substantially the statics and dynamics of magnetic textures. Here, we demonstrate that the curvilinear form of the exchange interaction of a magnetic helix results in an effective anisotropy term and Dzyaloshinskii--Moriya interaction with a complete set of Lifshitz invariants for a one-dimensional system. In contrast to their planar counterparts, the geometrically induced modifications of the static magnetic texture of the domain walls in magnetic helices offer unconventional means to control the wall dynamics relying on spin-orbit Rashba torque. The chiral symmetry breaking due to the Dzyaloshinskii-Moriya interaction leads to the opposite directions of the domain wall motion in left- or right-handed helices. Furthermore, for the magnetic helices, the emergent effective anisotropy term and Dzyaloshinskii-Moriya interaction can be attributed to the clear geometrical parameters like curvature and torsion offering intuitive understanding of the complex curvilinear effects in magnetism

Curvature effects on phase transitions in chiral magnets

Periodical equilibrium states of magnetization exist in chiral ferromagnetic films, if the constant of antisymmetric exchange (Dzyaloshinskii-Moriya interaction) exceeds some critical value. Here, we demonstrate that this critical value can be significantly modified in curved film. The competition between symmetric and antisymmetric exchange interactions in a curved film can lead to a new type of domain wall which is inclined with respect to the cylinder axis. The wall structure is intermediate between Bloch and N\'eel ones. The exact analytical solutions for phase boundary curves and the new domain wall are obtained

Введення гем-дифлуороциклоалкільних замісників у гетероцикли через стратегію «видалення Нітрогену» Левіна

A series of compounds containing heterocyclic cores and gem-difluorocycloalkyl substituents was obtained under conditions of the parallel synthesis (i.e., simultaneous performance of reaction procedures, treatment of the reaction mixture, and product isolation for a number of similar transformations) using the reductive amination – the “Nitrogen deletion” reaction sequence. The synthesis of the target compounds commenced from heteroaromatic aldehydes and the corresponding gem-difluorocycloalkyl or (gem-difluorocycloalkyl)methyl amines and included the NaBH3CN-mediated reductive amination and “Nitrogen deletion” upon the action of Levin’s anomeric amide. It has been shown that the method can be used to obtain compounds with the aforementioned structural fragments separated by one or two methylene units. The developed protocol allowed for the preparation of a 12-member compound library (67 % synthetic efficiency). Therefore, this novel synthetic methodology is suitable for decorating heterocyclic cores with sp3-enriched substituents that are attractive for medicinal chemistry.В умовах паралельного синтезу (тобто одночасного виконання реакції, оброблення реакційної суміші та виділення продукту для низки споріднених перетворень) із застосуванням послідовності реакції відновного амінування та «видалення Нітрогену» було одержано серію сполук, що містять гетероциклічні фрагменти та гем-дифлуороциклоалкільні замісники. Синтез цільових сполук виходив з гетероароматичних альдегідів і відповідних гем-дифлуороциклоалкіл- або (гем-дифлуороциклоалкіл)метиламінів та передбачав відновне амінування за участі NaBH3CN і «видалення Нітрогену» під дією аномерного аміду Левіна. Доведено, що метод застосовний для одержання сполук із вищезгаданими структурними фрагментами, розділеними однією чи двома метиленовими ланками. Розроблений протокол дозволив одержати бібліотеку сполук із 12 представників (синтетична ефективність 67 %). Отже, ця новітня синтетична методологія є придатною для декорування гетероциклічних систем sp3-збагаченими замісниками, що є привабливими для медичної хімії

Gene Expression and DNA Methylation Alterations During Non-alcoholic Steatohepatitis-Associated Liver Carcinogenesis

Hepatocellular carcinoma (HCC) is one of the most aggressive human cancers. HCC is characterized by an acquisition of multiple abnormal phenotypes driven by genetic and epigenetic alterations, especially abnormal DNA methylation. Most of the existing clinical and experimental reports provide only a snapshot of abnormal DNA methylation patterns in HCC rather than their dynamic changes. This makes it difficult to elucidate the significance of these changes in the development of HCC. In the present study, we investigated hepatic gene expression and gene-specific DNA methylation alterations in mice using the Stelic Animal Model (STAM) of non-alcoholic steatohepatitis (NASH)-derived liver carcinogenesis. Analysis of the DNA methylation status in aberrantly expressed epigenetically regulated genes showed the accumulation of DNA methylation abnormalities during the development of HCC, with the greatest number of aberrantly methylated genes being found in full-fledged HCC. Among these genes, only one gene, tubulin, beta 2B class IIB (Tubb2b), was increasingly hypomethylated and over-expressed during the progression of the carcinogenic process. Furthermore, the TUBB2B gene was also over-expressed and hypomethylated in poorly differentiated human HepG2 cells as compared to well-differentiated HepaRG cells. The results of this study indicate that unique gene-expression alterations mediated by aberrant DNA methylation of selective genes may contribute to the development of HCC and may have diagnostic value as the disease-specific indicator

Rashba torque driven domain wall motion in magnetic helices

Manipulation of the domain wall propagation in magnetic wires is a key practical task for a number of devices including racetrack memory and magnetic logic. Recently, curvilinear effects emerged as an efficient mean to impact substantially the statics and dynamics of magnetic textures. Here, we demonstrate that the curvilinear form of the exchange interaction of a magnetic helix results in an effective anisotropy term and Dzyaloshinskii–Moriya interaction with a complete set of Lifshitz invariants for a one-dimensional system. In contrast to their planar counterparts, the geometrically induced modifications of the static magnetic texture of the domain walls in magnetic helices offer unconventional means to control the wall dynamics relying on spin-orbit Rashba torque. The chiral symmetry breaking due to the Dzyaloshinskii–Moriya interaction leads to the opposite directions of the domain wall motion in left- or right-handed helices. Furthermore, for the magnetic helices, the emergent effective anisotropy term and Dzyaloshinskii–Moriya interaction can be attributed to the clear geometrical parameters like curvature and torsion offering intuitive understanding of the complex curvilinear effects in magnetism