Switching magnetic vortex core by a single nanosecond current pulse

In a ferromagnetic nanodisk, the magnetization tends to swirl around in the plane of the disk and can point either up or down at the center of this magnetic vortex. This binary state can be useful for information storage. It is demonstrated that a single nanosecond current pulse can switch the core polarity. This method also provides the precise control of the core direction, which constitutes fundamental technology for realizing a vortex core memory.Comment: 13 pages, 4 figure

Histological Observation of the Development of Follicles and Follicular Atresia in Immature Rat Ovaries

To clarify the development of follicular growth and atresia in the immature ovary, rats. ovaries and blood were removed at fixed points during the period from 0 to 35 days after birth (Day 0 to Day 35). The ovaries were immunohistochemically examined, and blood concentrations of serum follicle-stimulating hormone (FSH) and estrogen (E) were measured. We investigated how time-course changes in follicular cell proliferation, estrogen receptor β (ERβ), apoptosis, and FSH and E concentrations are connected with follicular growth and atresia. Apoptosis was found in the ova from Day 0 to Day 3. On Day 15, apoptosis occurred in some granulosa cell nuclei in some follicles, but BrdU uptake and the presence of cyclin D2 and ER β could be observed in other granulosa cells. From Day 17, apoptosis increased in the follicular granulosa cells, and BrdU uptake and the presence of cyclin D2 and ERβ were decreased. Follicular atresia continued, reaching a peak on Day 30. Serum FSH and E concentrations increased until Day 15, then markedly decreased after Day 17. The mechanism of apoptosis in the ova from Day 0 to 3 has not been clarified. However, the onset of follicular atresia was caused by apoptotic degeneration from Days 15 to 17. These results showed that the oocytes were selected by apoptosis at 2 points in the time-course of the maturation of the ovary

Direct withdrawal of zones during preparative capillary type isotachophoresis.

This study used a Shimadzu IP-1B capillary type isotachophoretic apparatus with a potential gradient detector. An ipp-1 withdrawal cell was fitted to this and a technique for withdrawing individual components directly through this port was developed using a microsyringe. The recovery rate was up to 45% for individual target components. When 100% withdrawal of the target component was attempted by withdrawing a volume four times the calculated volume (so that the zones both before and after the target component were also included), the best recovery rate was only 78%. In all cases, the results varied less than 3%. The limit for analysis of individual components of a 0.01 M solution was around 3 microliters. If this volume was exceeded, the ion quantity was too large for the volume of the microcapillary tube and mixed zones formed such that complete separation and analysis of individual components became impossible.</p

Quantification of PERF 15 mRNA in Tissue Sections from Rat Testes

We previously conducted basic research to quantify in situ hybridization (ISH) signals in rat testes. In this experimental model, we selected ribosomal RNA (rRNA) as the hybridizable RNA in paraffin sections, since it allowed us to easily analyze ISH signals expressed with digoxygenin (DIG)-labeled probes quantitatively through “posterization” of the images. We applied this method to analyze the quantification of transcript, PERF 15 mRNA. PERF 15 is expressed specifically in the testes and localized in the rigid cytoskeletal structure of the sperm head, and has been considered to be involved in the apoptotic process of spermatogenic cells. Quantification of the signals may help to clarify the detailed function of PERF 15. We further analyzed the signals concomitant with a confocal laser scanning microscope. The peak of PERF 15 mRNA expression was found in diplotene spermatocytes, and the amount of PERF 15 mRNA was greatest in late pachytene and diplotene spermatocytes and early spermatids, followed by early pachytene spermatocytes, and then late spermatids. PERF 15 may be involved in the events leading to meiotic division, in which apoptosis is also involved. The present study may help to determine the concentration of mRNA in tissue sections

Differential, histochemical and immunohistochemical changes in rat hepatocytes after isoflurane or sevoflurane exposure.

Differential, histochemical and immunohistochemical changes were observed in hepatocytes from immediately to 7 days after isoflurane or sevoflurane exposure (at H 0 to on Day 7) to study the process of development and recovery in anesthetic-induced hepatic injury. A total of 570 7-week-old male Sprague-Dawley rats with or without phenobarbital treatment were exposed to isoflurane or sevoflurane in 100%, 21%, or 10% oxygen, or to 10% oxygen alone for 2h. In phenobarbital-treated rats, hepatocytes both with and without anesthetic exposure markedly changed in 10% oxygen at H 0. Glycogen and ribosomal ribonucleic acid (rRNA) disappeared at H 0 and at H 6, respectively, and at H 6, AST levels in the blood rose. From H 6 to Day 1, necrosis developed more markedly and widely in zone 3 hepatocytes exposed to anesthetics in 10% oxygen than in those exposed to oxygen alone. All degenerated tissues had returned to normal levels by day 7. Recovery of the hepatolobular structure may be attributed to rearrangement of remaining hepatocytes in the portal vein area. Both the disappearance of glycogen and rRNA and the increase in blood AST levels after exposure to isoflurane or sevoflurane are considered to be factors contributing to the induction of necrosis around the central vein. The grade of isoflurane-induced hepatic injury was found to be significantly higher than that of sevoflurane.</p

X-ray imaging of vortex cores in confined magnetic structures

Cores of magnetic vortices in micron-sized NiFe disk structures, with thicknesses between 150 and 50 nm, were imaged and analysed by high resolution magnetic soft X-ray microscopy. A decrease of the vortex core radius was observed, from #24; ~38 to 18 nm with decreasing disk thickness. By comparing with full 3D micromagnetic simulations showing the well-known barrel structure, we obtained excellent agreement taking into account instrumental broadening and a small perpendicular anisotropy. The proven magnetic spatial resolution of better than 25 nm was sufficient to identify a negative dip close to the vortex core, originating from stray fields of the core. Magnetic vortex structures can serve as test objects for evaluating sensitivity and spatial resolution of advanced magnetic microscopy techniques

Probing the spin polarization of current by soft X-ray imaging of current-induced magnetic vortex dynamics

Time-resolved soft X-ray transmission microscopy is applied to image the current-induced resonant dynamics of the magnetic vortex core realized in a micronsized Permalloy disk. The high spatial resolution better than 25 nm enables us to observe the resonant motion of the vortex core. The result also provides the spin polarization of the current to be 0.67 +/-0.16 for Permalloy by fitting the experimental results with an analytical model in the framework of the spin-transfer torque.Comment: 13 pages, 3 figure