Magnetic structures and reorientation transitions in noncentrosymmetric uniaxial antiferromagnets

A phenomenological theory of magnetic states in noncentrosymmetric tetragonal antiferromagnets is developed, which has to include homogeneous and inhomogeneous terms (Lifshitz-invariants) derived from Dzyaloshinskii-Moriya couplings. Magnetic properties of this class of antiferromagnets with low crystal symmetry are discussed in relation to its first known members, the recently detected compounds Ba2CuGe2O7 and K2V3O8. Crystallographic symmetry and magnetic ordering in these systems allow the simultaneous occurrence of chiral inhomogeneous magnetic structures and weak ferromagnetism. New types of incommensurate magnetic structures are possible, namely, chiral helices with rotation of staggered magnetization and oscillations of the total magnetization. Field-induced reorientation transitions into modulated states have been studied and corresponding phase diagrams are constructed. Structures of magnetic defects (domain-walls and vortices) are discussed. In particular, vortices, i.e. localized non-singular line defects, are stabilized by the inhomogeneous Dzyaloshinskii-Moriya interactions in uniaxial noncentrosymmetric antiferromagnets.Comment: 18 pages RevTeX4, 13 figure

Effect of Laser Optoperforation of the Zona Pellucida on Mouse Embryo Development in vitro

Laser operations on cells and embryos are an important field of current photobiology and biophotonics. The high power density of tightly focused laser irradiation provides an efficient impact on matter of cells or embryos. Precise focusing of the laser spot allows strictly controlled perforation of the membrane. The present work was devoted to studying the influence of optoperforation of mammalian embryonic zona pellucida with a tightly focused laser beam with 1.48-µm wavelength on further development of the embryo. Such a laser operation was proposed for application in in vitro fertilization (IVF) practice and intracytoplasmic sperm injection into the oocyte (ICSI). For cultured in vitro oocytes and embryos, the process of natural exiting from the zona pellucida ("hatching") is often impaired, which decreases probability of implantation and pregnancy The goals of the present work were to determine the influence of different manipulations on development of embryos in vitro until blastocyst formation and on the ISSN 0006-2979, Biochemistry (Moscow), 2015, Vol. 80, No. 6, pp. 769-775. © Pleiades Publishing, Ltd., 2015. Original Russian Text © E. O. Zakharchenko, A. D. Zalessky, A. A. Osychenko, A. S. Krivokharchenko, A. K. Shakhbazyan, A. V. Ryabova, V. A. Nadtochenko, 2015, published in Biokhimiya, 2015 769 * To whom correspondence should be addressed. Abstract-The effect of laser optical perforation of the zona pellucida on the viability and development of mouse embryos has been studied. Operations of zona pellucida thinning and single or double perforation were carried out on 2-cell embryo, morula, and blastocyst stages with a laser pulse (wavelength 1.48 µm, pulse duration 2 ms). Embryo development up to the blastocyst stage and hatching efficiency were statistically analyzed. It was found that 2-cell or morula stage embryo zona pellucida thinning or single perforation did not affect development to the blastocyst stage and number of hatched embryos, but it accelerated embryo hatching compared to control groups one day earlier in vitro. Double optoperforation on 2-cell embryo or morula stage did not significantly affect development to the blastocyst stage, but it strongly decreased the number of hatched embryos. Also, zona pellucida perforation at the blastocyst stage had a negative effect: hatching did not occur after this manipulation. Blastocyst cell number calculation after single zona pellucida perforation at 2-cell and morula stages showed that cell number of hatching or hatched blastocysts did not differ from the same control groups. This fact points out that the laser single optoperforation method is a useful and safe experimental tool that allows further manipulations within the zona pellucida. Effect of Laser Optoperforation of the Zon

Femtosecond Nanosurgery: Laser Enucleation of Chromatin in the Oocyte

A method for cell enucleation by femtosecond laser nanosurgery has been developed. This enucleation technique allows DNA destruction with high precision and low invasiveness, showing good efficiency. The technology of such operations is of great importance in medical and scientific practice.Работа выполнена при поддержке гранта РНФ № 21-75-10155

STUDY OF THE POSSIBILITIES OF USING FEMTOSECOND LASER NANO SURGERY TO OBTAIN PLANT HYBRIDS

Femtosecond laser nanosurgery can be a very convenient selection tool. The method of laser nanosurgery allows working with individual organelles without damaging or killing a cell. Studying the interaction of a laser pulse with a biological material will greatly simplify the selection.Работа выполнена при поддержке гранта Российского фонда фундаментальных исследований 19-53-52007, а также при поддержке Государственного задания ФИЦ ХФ РАН АААА-А19-119012990175-9 с использованием оборудования ЦКП ФИЦ ХФ им. Н. Н. Семенова (№506694)

Changes to the Fossil Record of Insects through Fifteen Years of Discovery

The first and last occurrences of hexapod families in the fossil record are compiled from publications up to end-2009. The major features of these data are compared with those of previous datasets (1993 and 1994). About a third of families (>400) are new to the fossil record since 1994, over half of the earlier, existing families have experienced changes in their known stratigraphic range and only about ten percent have unchanged ranges. Despite these significant additions to knowledge, the broad pattern of described richness through time remains similar, with described richness increasing steadily through geological history and a shift in dominant taxa, from Palaeoptera and Polyneoptera to Paraneoptera and Holometabola, after the Palaeozoic. However, after detrending, described richness is not well correlated with the earlier datasets, indicating significant changes in shorter-term patterns. There is reduced Palaeozoic richness, peaking at a different time, and a less pronounced Permian decline. A pronounced Triassic peak and decline is shown, and the plateau from the mid Early Cretaceous to the end of the period remains, albeit at substantially higher richness compared to earlier datasets. Origination and extinction rates are broadly similar to before, with a broad decline in both through time but episodic peaks, including end-Permian turnover. Origination more consistently exceeds extinction compared to previous datasets and exceptions are mainly in the Palaeozoic. These changes suggest that some inferences about causal mechanisms in insect macroevolution are likely to differ as well

Revealing nucleoplasm mechanics by optical trapping and Brownian motion of nucleolus within mouse GV-oocytes in vivo

Abstract Optical trapping of nucleoli within nucleoplasm of living oocytes as unique model system provides non-invasive technique for investigation of nuclear environment. We employed methods of active and passive rheology to characterize rheological properties of the nucleoplasm of GV-oocytes (germinal vesicle stage) with main types of chromatin distribution in the nucleus (NSN, SN). By using of single beam optical trap, formed by a tightly focused laser radiation at 790 nm wavelength, we performed subsequent stress-relaxation tests series of nucleoli in various directions and with different amplitudes. Nucleolus of the oocyte was employed as a microprobe due to its large size and spherical shape. The characteristic nucleolus relaxation times were obtained for two types of chromatin distribution, which can subsequently be used to evaluate the viscoelastic properties of the nuclear material within oocytes with different physiological states. Motion activity of nucleoli was also extracted to evaluate local forces, acting within nucleolar environment and facilitating chromatin redistribution.</jats:p

The use of optical chopper increases the efficiency of femtosecond laser-induced cell fusion

Abstract Artificial cell fusion is a widely used approach in cell biology and biomedicine. Femtosecond laser-induced cell fusion is considered to be a precise and low-invasive tool for the cell fusion. However, the percentage of somatic cell fusion remains not very high, and the use of polyethylene glycol is often required. In our research we propose the use of rotating optical chopper to produce ultra-short trains of femtosecond pulses (up to 1 ms) for decreasing the laser impact. It helps to control the appearance and size of gas-vapor bubbles, avoiding cell destruction. We achieved the cell fusion efficiency of 45% without the use of polyethylene glycol, but only in freshly thawed cells. Continuously cultured cells completely failed to fuse.</jats:p