Chirality Memory Stored in Magnetic Domain Walls in the Ferromagnetic State of MnP.

Chirality in a helimagnetic structure is determined by the sense of magnetic moment rotation. We found that the chiral information did not disappear even after the phase transition to the high-temperature ferromagnetic phase in a helimagnet MnP. The 2nd harmonic resistivity ρ^{2f}, which reflects the breaking down of mirror symmetry, was found to be almost unchanged after heating the sample above the ferromagnetic transition temperature and cooling it back to the helimagnetic state. The application of a magnetic field along the easy axis in the ferromagnetic state quenched the chirality-induced ρ^{2f}. This indicates that the chirality memory effect originated from the ferromagnetic domain walls.

Elastic stiffness of a Skyrmion crystal.

We observe the elastic stiffness and ultrasonic absorption of a Skyrmion crystal in the chiral-lattice magnet MnSi. The Skyrmion crystal lattice exhibits a stiffness 3 orders of magnitude smaller than that of the atomic lattice of MnSi, being as soft as the flux line lattice in type-II superconductors. The observed anisotropic elastic responses are consistent with the cylindrical shape of the Skyrmion spin texture. Phenomenological analysis reveals that the spin-orbit coupling is responsible for the emergence of anisotropic elasticity in the Skyrmion lattice.

Magnetization control by angular momentum transfer from surface acoustic wave to ferromagnetic spin moments.

Interconversion between electron spin and other forms of angular momentum is useful for spin-based information processing. Well-studied examples of this are the conversion of photon angular momentum and rotation into ferromagnetic moment. Recently, several theoretical studies have suggested that the circular vibration of atoms work as phonon angular momentum; however, conversion between phonon angular momentum and spin-moment has yet to be demonstrated. Here, we demonstrate that the phonon angular momentum of surface acoustic wave can control the magnetization of a ferromagnetic Ni film by means of the phononic-to-electronic conversion of angular momentum in a Ni/LiNbO3 hybrid device. The result clearly shows that the phonon angular momentum is useful for increasing the functionality of spintronic devices.

Electric current control of spin helicity in an itinerant helimagnet.

A helimagnet is a chiral magnet in which the direction of the magnetic moment spatially rotates in a plane perpendicular to the propagation vector. The sense of the rotation known as spin helicity is a robust degree of freedom of matter and may provide a new concept of magnetic memory if it can be electrically controlled and detected. Here we show that the helicity can be controlled by magnetic fields and electric currents in an itinerant helimagnet MnP. Second-harmonic resistivity measurements allow us to read out the controlled helicity. In contract to an insulating multiferroic magnet, in which spin rotation was shown to be controllable by an electric field, we achieve helicity manipulation by using an electric current in the conducting helimagnet. The controllability of the spin helicity may pave the way to new method of realizing magnetic memories based on the spin internal degrees of freedom.

Magnetoelectrical control of nonreciprocal microwave response in a multiferroic helimagnet.

The control of physical properties by external fields is essential in many contemporary technologies. For example, conductance can be controlled by a gate electric field in a field effect transistor, which is a main component of integrated circuits. Optical phenomena induced by an electric field such as electroluminescence and electrochromism are useful for display and other technologies. Control of microwave propagation is also important for future wireless communication technology. Microwave properties in solids are dominated mostly by magnetic excitations, which cannot be easily controlled by an electric field. One solution to this problem is to use magnetically induced ferroelectrics (multiferroics). Here we show that microwave nonreciprocity, that is, different refractive indices for microwaves propagating in opposite directions, could be reversed by an external electric field in a multiferroic helimagnet Ba2Mg2Fe12O22. This approach offers an avenue for the electrical control of microwave properties.

Application of strain to orbital-spin-coupled system MnV2O4 at cryogenic temperatures within a transmission electron microscope.

The impact of mechanical stress on the morphology of crystallographic and magnetic domains in shape-controlled specimens of an orbital-spin-coupled system, MnV2O4, was examined by cryogenic Lorentz microscopy. Because of the difference in thermal expansion coefficients of MnV2O4 and the supporting Mo mesh, compression on the order of 0.01% was applied to the thin-foil specimens near the structural/magnetic phase transformation temperatures. The extent of compression was comparable to the lattice striction associated with the cubic-to-tetragonal phase transformation in MnV2O4 The applied strain thus clearly influenced the morphology of crystallographic domains (i.e. twinning configuration in the tetragonal phase) produced during cooling. The magnetic domain structure was entirely dependent on the configuration of twinning in the tetragonal phase. The observations in this study provided useful information for understanding the relationship between the crystallographic domains and the magnetic domains in MnV2O4.

Critical phenomena of emergent magnetic monopoles in a chiral magnet.

Second-order continuous phase transitions are characterized by symmetry breaking with order parameters. Topological orders of electrons, characterized by the topological index defined in momentum space, provide a distinct perspective for phase transitions, which are categorized as quantum phase transitions not being accompanied by symmetry breaking. However, there are still limited observations of counterparts in real space. Here we show a real-space topological phase transition in a chiral magnet MnGe, hosting a periodic array of hedgehog and antihedgehog topological spin singularities. This transition is driven by the pair annihilation of the hedgehogs and antihedgehogs acting as monopoles and antimonopoles of the emergent electromagnetic field. Observed anomalies in the magnetoresistivity and phonon softening are consistent with the theoretical prediction of critical phenomena associated with enhanced fluctuations of emergent field near the transition. This finding reveals a vital role of topology of the spins in strongly correlated systems.

Uniaxial stress control of skyrmion phase.

Magnetic skyrmions, swirling nanometric spin textures, have been attracting increasing attention by virtue of their potential applications for future memory technology and their emergent electromagnetism. Despite a variety of theoretical proposals oriented towards skyrmion-based electronics (that is, skyrmionics), few experiments have succeeded in creating, deleting and transferring skyrmions, and the manipulation methodologies have thus far remained limited to electric, magnetic and thermal stimuli. Here, we demonstrate a new approach for skyrmion phase control based on a mechanical stress. By continuously scanning uniaxial stress at low temperatures, we can create and annihilate a skyrmion crystal in a prototypical chiral magnet MnSi. The critical stress is merely several tens of MPa, which is easily accessible using the tip of a conventional cantilever. The present results offer a new guideline even for single skyrmion control that requires neither electric nor magnetic biases and consumes extremely little energy.

Does the central sulcus divide motor and sensory functions? Cortical mapping of human hand areas as revealed by electrical stimulation through subdural grid electrodes.

To clarify the exact anatomic relationship of electrically identified hand areas to the central sulcus, we constructed cortical surface renderings of magnetic resonance images (MRI) to locate the central sulcus accurately and measured the distances of stimulated points from the central sulcus and the Sylvian fissure. We obtained hand responses in 33 patients who underwent implantation of subdural grid electrodes for evaluation and surgical treatment of intractable epilepsy and analyzed these responses according to the presence of motor, sensory, mixed motor and sensory, and arrest responses. Hand motor responses occurred not only in the precentral gyrus but also in the postcentral gyrus, with great variability in superior-to-inferior distribution. Sensory responses also occurred in both the precentral and postcentral gyri with a distribution more ventral than that of motor responses. Mixed motor and sensory responses tended to be limited to the middle part of the central sulcus. Sites where electrical stimulation arrested simple hand repetitive voluntary movements occurred widely throughout the premotor and primary sensorimotor cortices. These data indicate a marked variability in the location of the human cortical hand area, and suggest that motor and sensory hand cortices overlap and are not divided in a simple manner by the central sulcus.

Somatosensory evoked potentials to median nerve stimulation after partial section of the corpus callosum.

Cortical somatosensory evoked potentials (SEPs) to electrical stimulation of the median nerve were studied in four patients with intractable epilepsy who had undergone callosotomy and in a patient with infarction in the corpus callosum in order to determine whether the corpus callosum was involved in the generation of ipsilateral frontal components. Both pre- and postoperative SEPs were recorded in three of four epileptic patients. There were no significant differences in the latencies and amplitudes of the bilateral frontal components (P20, N26) between pre- and postoperative recordings. Furthermore, irrespective of the extent of the section or lesion in the corpus callosum, the nature of the impairment and the existence of the disconnection syndrome, the SEP findings showed no significant differences compared with those of normal subjects. It thus appears unlikely that the ipsilateral SEP responses are transmitted from the contralateral hemisphere through at least the anterior portion of the corpus callosum.

Subdivisions of the accessory olfactory bulb, as demonstrated by lectin-histochemistry in the golden hamster.

Lectin-binding patterns in the accessory olfactory bulb (AOB) of the golden hamster were investigated histochemically with 21 biotinylated lectins. The AOB was divided into rostral and caudal halves according to binding patterns of 16 lectins, WGA, s-WGA, LEL, STL, DSL, BSL-II, DBA, SBA, BSL-I, VVA, SJA, PNA, ECL, UEA-I, Con A and PSA. The caudal half of the AOB was further subdivided into anterior 2/3 and posterior 1/3 by 10 lectins, WGA, s-WGA, BSL-II, DBA, SBA, BSL-I, VVA, SJA, PNA and ECL. In addition, the rostral half of the AOB was subdivided into anterior 1/4 and posterior 3/4 by one lectin, PNA. Thus, the AOB of the golden hamster was divided into 4 divisions on the basis of lectin-binding patterns.

Bifrontal epidural hematoma after transsphenoidal operation: report of a case with a rare complication.

We report a patient with a growth hormone-secreting adenoma who developed bifrontal epidural hematomas after a transsphenoidal operation. To our knowledge, this is the first report of such a complication.

Translucence stereoscopy of interictal magnetoencephalographic epileptiform discharge.

We have developed a translucence stereoscopy method for displaying the distribution of multiple interictal epileptiform discharges within the intracranial space. The epileptiform discharges, measured using a whole-head magnetoencephalography system, were modeled by a least-squares method to obtain the equivalent current dipoles. The dipoles were located in the stereo pair of intracranial images composed of translucent brain slices at several selected levels. The technique demonstrated clearly the distribution of interictal dipoles within the brain in three patients. Three dimensional understanding of the intracranial distribution of multiple dipoles in one image is valuable in analyzing the intracerebral neurophysiological events in epileptic patients.

Efficacy and toxicity of thromboxane synthetase inhibitor for cerebral vasospasm after subarachnoid hemorrhage.

The efficacy and possible side effects of thromboxane A2 (TXA2) synthetase inhibitor in the treatment of cerebral vasospasm after subarachnoid hemorrhage (SAH) were assessed for 24 patients who presented with grades I to IV of the Hunt and Hess classification. All patients underwent aneurysmal clipping within 48 hours after SAH. Postoperatively, TXA2 synthetase inhibitor, Cataclot [sodium (E)-3-[p-(1H-imidazol-1-ylmethyl)phenyl]-2-propenoate] was administered to 13 patients by continuous drip infusion at a dose of 1 microgram/kg/min for 8 to 14 days (group A). The remaining 11 patients did not receive this drug (group B). Of the 13 patients in group A, seven patients (54%) showed no symptomatic vasospasm after SAH. Four patients (31%) developed a transient deterioration of consciousness and/or motor disturbance. Three of these patients fully recovered, while one of them showed a mild neurological deficit on discharge. One patient (8%) developed permanent dysphasia and hemiparesis as a result of ischemic brain damage due to vasospasm. One patient (8%) died of the side effect. On the other hand, of the 11 patients in group B, only three (27%) showed no symptomatic vasospasm. One (9%) patient presented a transient neurological deficit but fully recovered upon discharge. Four patients (36%) showed permanent neurological deficits, although they all could lead an independent life after discharge. The three remaining patients developed a severe disturbance of consciousness caused by ischemia due to vasospasm, and two of them died within 1 month after the onset of SAH. In the group treated with Cataclot, two patients developed an epidural hematoma late during the administration of the drug. Of these two, one patient died of increased intracranial pressure that was accelerated by the complication. These results indicate that TXA2 synthetase inhibitor is effective in not only decreasing the occurrence of symptomatic vasospasm but also reducing the neurological deterioration due to vasospasm after SAH. However, this drug has a hazardous side effect in that it may promote a tendency to bleed, which caused death in one of our patients.

Cell profile and elastase activity in diffuse panbronchiolitis investigated by bronchoalveolar and bronchial lavage.

To examine the mechanism of tissue damage which causes bronchiolectasis in diffuse panbronchiolitis (DPB), the cellular components, elastase and its main inhibitor, alpha 1-protease inhibitor (alpha 1-PI) were measured in bronchoalveolar and bronchial lavage fluid (BALF and BLF) from 14 DPB patients. A predominant increase in the neutrophil count was observed in DPB. Elastase activity in BALF and BLF was about 1,000-fold higher in the DPB group than in the control group. An inhibitor study and a positive correlation between elastase activity and the neutrophil count in both lavage fluids from the DPB group indicated that the activity was mainly that of neutrophil elastase. Western blot analysis of alpha 1-PI showed that most of the alpha 1-PI in the lavage fluids from DPB group was degraded. These results indicated that neutrophil infiltration increases the level of elastase in the DPB lesions; this increase seems to be closely related to tissue damage.

Enhanced phagocytosis of rat alveolar macrophages by intravenous infusion of an arginine-enriched solution.

Phagocytosis of rat alveolar macrophages (AM) was enhanced by the infusion of arginine-rich solution for 7 days. The enhancement of phagocytosis by arginine-rich solution was due to not the difference in the distribution of AM subpopulations (I to IV) but the difference in phagocytic activity of AM in fraction IV. In the process of phagocytosis, there were no significant differences in the stages of migration, attachment, and digestion between control and arginine-rich solutions, although AM from fraction IV of rats infused with arginine-rich solution showed significantly higher ingestion of opsonized sheep red blood cells (SRBC) compared to that of control group. Furthermore, the production of macrophage-activating factor (MAF) from rat splenocytes was higher in arginine-rich group than that of control group. AM from fraction IV of rats fed a stock diet had a higher arginase activity and showed a significant increase of phagocytosis following in vitro incubation with L-arginine (25 and 50 mM) for 24 h. From these results, the enhanced phagocytosis of AM by arginine-rich solution may be due to the increased phagocytosis of AM from fraction IV, in which the higher sensitivity of AM from fraction IV to arginine and the higher production of MAF from splenocytes following the infusion of arginine-rich solution participate.

Effects of pH variation and NaCl on in vitro digestibility of cow's milk proteins in commercially available infant formulas.

Allergenicity and antigenicity of food proteins are generally dependent on their heat-stability and resistance to digestive enzymes. Using the methods of SDS-PAGE and immunoblots, we assessed peptic-digestibility of major milk proteins (casein, beta-lactoglobulin and alpha-lactalbumin) in commercially available infant formulas in acidic pH range (pH 1.5 to 4.0), and we also investigated the effect of NaCl on peptic-digestibility of cow's milk proteins at pH 2.0. The profile of peptic-digestion of casein was similar at pH range from 1.5 to 3.5 where the intact protein of casein rapidly disappeared, whereas slow digestibility of the protein was found at pH 4.0. Beta-lactoglobulin and alpha-lactalbumin were digested at pH range from 1.5 to 2.5 and were almost entirely resistant to peptic digestion at over pH 3.0. In the presence of NaCl at pH 2.0, casein showed a good digestibility by pepsin similar to that in the absence of NaCl, in contrast to beta-lactoglobulin and alpha-lactalbumin both having their peptic-digestibility decreased in the presence of 0.2 M NaCl. As the state of the stomach in new born infants shows low amounts of secretary pepsin and out of optimum pH of peptic activity, low digestibility of beta-lactoglobulin and alpha-lactalbumin in cow's milk based infant formulas at over pH 3.0 is supposed to be responsible for their allergenicity.

Partial callosotomy for Lennox-Gastaut syndrome--first cases in Japan.

Corpus callosotomy is a well established procedure for the treatment of intractable epilepsy. However, this is the first clinical report of surgical division of the corpus callosum in Japan. Four patients with refractory seizures suffering from Lennox-Gastaut syndrome underwent anterior partial corpus callosotomy. Their seizures consisted of absences, tonic, atonic, tonic-clonic attacks and were characterized by frequent falls. Electroencephalograms showed paroxysms of bilateral synchrony of slow spike and wave complexes. Postoperative follow-up during 12-27 months showed that partial callosotomy reduced the frequency and severity of seizures in all the patients, although they still require antiepileptic medication. This procedure was effective even in patients with mixed cerebral dominance and also in a patient with low intelligence quotient. Postoperatively, disconnection syndrome developed in three patients, which was transient in one and lasting in two.

Purine catabolites in cerebral interstitial fluid during progression of and recovery from ischemia.

The concentrations of purine catabolites in the cerebral interstitial fluid during progression of and recovery from ischemia were studied using brain microdialysis and high-performance liquid chromatography. Sealed 0.5-mm hollow dialysis fibers were stereotactically implanted into either the cerebral cortex or hippocampus of ketamine anesthetized gerbils and perfused with artificial cerebrospinal fluid at 2 microliters/min. Cerebral ischemia was induced by occlusion of the bilateral common carotid arteries. The reflectance spectra of oxy- and deoxyhemoglobin at the brain surface were monitored over the scalp to assess ischemia and confirm recirculation. Ischemia caused a rapid, 4.8-fold increase in the extracellular concentration of adenosine. The progressive increase in the concentration of adenosine, inosine, and hypoxanthine soon after recirculation is particularly interesting. The subsequent decrease in purine compound concentration was rapid for adenosine but more gradual for inosine and hypoxanthine. Calculated K values for adenosine deaminase and purine nucleoside phosphorylase were 0.045/min and 0.016/min, respectively. However, no xanthine, uric acid, or purine nucleotides were found in the perfusate. These observations indicated the presence of purine catabolites in the cerebral interstitial space as well as consecutive degradation and recycling involving the interconversion of purine compounds by biochemical metabolic pathways.

Nodding attacks (infantile spasms) associated with temporal lobe astrocytoma--case report.

A 2-year-old boy suffered nodding attacks (infantile spasms) that were refractory to anticonvulsants. Computed tomography showed a mass with cystic components in the right temporal lobe, and electroencephalography (EEG) disclosed polyspike and wave discharges in the bilateral temporoparietal regions. At surgery, a firm, gray, well circumscribed tumor was radically removed. The nodding attacks disappeared immediately after surgery and EEG improved gradually. The pathological diagnosis was grade 1 astrocytoma with abundant capillaries and calcospherites. He remained free of seizures during the following 6 years.