Following the early prediction of the skyrmion lattice (SkL)--a periodic array of spin vortices--it has been observed recently in various magnetic crystals mostly with chiral structure. Although ...non-chiral but polar crystals with Cnv symmetry were identified as ideal SkL hosts in pioneering theoretical studies, this archetype of SkL has remained experimentally unexplored. Here, we report the discovery of a SkL in the polar magnetic semiconductor GaV4S8 with rhombohedral (C3v) symmetry and easy axis anisotropy. The SkL exists over an unusually broad temperature range compared with other bulk crystals and the orientation of the vortices is not controlled by the external magnetic field, but instead confined to the magnetic easy axis. Supporting theory attributes these unique features to a new Néel-type of SkL describable as a superposition of spin cycloids in contrast to the Bloch-type SkL in chiral magnets described in terms of spin helices.
Magnetic skyrmions in chiral magnets are nanoscale, topologically protected magnetization swirls that are promising candidates for spintronics memory carriers. Therefore, observing and manipulating ...the skyrmion state on the surface level of the materials are of great importance for future applications. Here, we report a controlled way of creating a multidomain skyrmion state near the surface of a Cu2OSeO3 single crystal, observed by soft resonant elastic X-ray scattering. This technique is an ideal tool to probe the magnetic order at the L 3 edge of 3d metal compounds giving an average depth sensitivity of ∼50 nm. The single-domain 6-fold-symmetric skyrmion lattice can be broken up into domains, overcoming the propagation directions imposed by the cubic anisotropy by applying the magnetic field in directions deviating from the major cubic axes. Our findings open the door to a new way to manipulate and engineer the skyrmion state locally on the surface or on the level of individual skyrmions, which will enable applications in the future.
•CA of a Fe3O4 ferronanofluid and water on Cu and Al substrates is measured.•Two instant effects of a magnetic field on a ferronanofluid droplet are found.•For Bom < 2.5, the pinning-fixed regime is ...present.•For Bom > 2.5, metastable state is achieved, in which de-pinning regime may occur.•Magnetic field aligns cracks in its direction and decreases their number.
The unique magnetic properties of ferronanofluids distinguish them from the rest of the nanofluids group. To discover their full potential, their thermophysical properties have to be investigated. The aim of this study is to provide more insight into ferronanofluid wettability, including the contact angle on copper and aluminium surfaces. The presence of a ferronanofluid droplet in a magnetic field causes an interaction. The effect of this interplay is depicted by droplet side profile photographs and microscope imaging of a dried deposit. Two regimes of a droplet deformation due to this interplay are identified: pinning-fixed and de-pinning regime. In the first one, the droplet contact line is maintained, while the contact angle is increased. In the de-pinning regime, the droplet starts to flow, elongating its contact line and decreasing the contact angle. The regime transition occurs at a magnetic Bond number of 2.5. Cracking of the ferronanofluid deposit is also observed. Drying the droplet under the magnetic field affects the crack pattern by changing the alignment of cracks to match the direction of the magnetic field and reducing the number of cracks. This shows the influence of the ferronanoparticles ordering, and therefore of the magnetic stress, on the material fracture.
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BACKGROUND: It is of fundamental importance for IVF clinics to determine the most viable embryos for transfer. The challenge for ART clinics is to transfer fewer embryos, thereby minimizing the risk ...of multiple‐infant births, while still maintaining the greatest chance of pregnancy for their patients. In this study, an investigation was made to determine if developmental markers on the day of fertilization (day 1) can predict good subsequent blastocyst development. METHODS AND RESULTS: A total of 1550 individually cultured 2PN embryos from 191 patients undergoing IVF/ICSI treatment at the Yale University Center for Reproductive Medicine and Infertility from February to December 2001 was included. The results showed a significant positive relationship between early‐cleaving 2‐cell embryos and subsequent good quality ≥4‐cell, ≥7‐cell and blastocyst development (P < 0.05). PN symmetry (the relative size of the PN to each other), when checked at the time fertilization, is also a significant indictor of good quality ≥4‐cell, ≥7‐cell stage embryos and blastocysts. Combined, a developing embryo showing PN symmetry with early cleavage and subsequent good ≥4‐cell and ≥7‐cell cleavage, has a one in two chance of developing into a good‐quality blastocyst. CONCLUSION: Early embryo assessment can be used as an indicator of subsequent good blastocyst development.
Primates that are identical in both nuclear and cytoplasmic components have not been produced by current cloning strategies, yet such identicals represent the ideal model for investigations of human ...diseases. Here, genetically identical nonhuman embryos were produced as twin and larger sets by separation and reaggregation of blastomeres of cleavage-stage embryos. A total of 368 multiples were created by the splitting of 107 rhesus embryos with four pregnancies established after 13 embryo transfers (31% versus 53% in vitro fertilization controls). The birth of Tetra, a healthy female cloned from a quarter of an embryo, proves that this approach can result in live offspring.
Programmed cell death (apoptosis) characteristically affects the single cells of blastocysts whereas necrosis affects cluster of cells in both the inner cell mass (ICM) and the trophectoderm (TE). ...This study uses the trophectodermrminal deoxynucleotidyl transferase (TdT) mediated dUTP nick-end labeling (TUNEL) assay as a way of evaluating the proportion of apoptotic cells and, thus, bovine blastocyst quality during in vitro culture at Days 6, 7, and 8. Furthermore, parthenogenetic blastocysts were compared to in vitro fertilized blastocysts at Day 7. Confocal microscopy was used to generate three-dimensional reconstructions of the blastocysts.
Apoptosis was observed in both early (Day 6) and late (Day 8) developing blastocysts. The dead cell index (DCI, total number of apoptotic nuclei/total number of nuclei) tend to increase as the in vitro culture time increases, and apoptosis is proportionately higher in the ICM than in the TE. The ratio of ICM to TE cells remains relatively constant even as the blastocysts cell number increases (Day 6=11.9±2.2, Day 7=11.2±0.5, Day 8=11.7±0.4). The overall cell number is significantly reduced in parthenogenetic blastocysts compared to Day 7 in vitro produced blastocysts (
P=0.037). The parthenogenetic blastocysts also show an increase of apoptosis over Day 7 controls. The decrease in cell number in the parthenogenetic blastocysts may be due to the increase of apoptotic nuclei observed.
Based on these results we found the TUNEL assay to be a useful method for evaluating in vitro culture conditions of pre-implantation bovine embryos.
This study compares failed fertilization oocytes from patients participating in an in-vitro fertilization (IVF) programme with failed fertilization oocytes from B6SJLF1/J mice, in order to ...characterize and describe the distribution of DNA in oocytes that do not undergo normal fertilization. Our goal is to evaluate the mouse IVF system as a model to gain insight into reasons for human fertilization failures. All oocytes were stained with the vital fluorescent dye, Hoechst 33342, which rapidly stains double-stranded DNA. Of the 237 human oocytes that had been scored as failed fertilization by brightfield microscopy, 61 (25.7%) showed the presence of at least one spermatozoon within the oocyte cytoplasm. In contrast, out of 69 failed fertilization mouse oocytes, only one oocyte showed the presence of a spermatozoon within its cytoplasm. Mouse failed fertilization oocytes exhibited a significantly lower internal sperm rate (P < 0.0001) than human failed fertilization oocytes. Human failed fertilization oocytes show a higher incidence of sperm penetration, but the cytoplasm fails to support pronuclear development, whereas, at least in this strain, mouse failed fertilization oocytes arise from an inability of the spermatozoa to penetrate the oocyte. This study suggests that the mouse is not a clinically relevant model for human fertilization failures.
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