Spatially Resolved Magnetic Anisotropy of Cobalt Nanostructures on the Au(111) Surface.

Understanding the origin of perpendicular magnetic anisotropy in surface-supported nanoclusters is crucial for fundamental research as well as data storage applications. Here, we investigate the perpendicular magnetic anisotropy energy (MAE) of bilayer cobalt islands on Au(111) substrate using spin-polarized scanning tunneling microscopy at 4.6 K and first-principles theoretical calculations. Au(111) substrate serves as an excellent model system to study the effect of nucleation site and stacking sequence on MAE. Our measurements reveal that the MAE of bilayer islands depends strongly on the crystallographic stacking of the two Co layers and nucleation of the third layer. Moreover, the MAE of Co atoms on Au(111) is enhanced by a factor of 1.75 as compared to that reported on Cu(111). Our first-principles calculations attribute this enhancement to the large spin-orbit coupling of the Au atoms. Our results highlight the strong impact of nanometer-scale structural changes in Co islands on MAE and emphasize the importance of spatially resolved measurements for the magnetic characterization of surface-supported nanostructures.

Moiré-Assisted Realization of Octahedral MoTe2 Monolayer.

A current key challenge in 2D materials is the realization of emergent quantum phenomena in hetero structures via controlling the moiré potential created by the periodicity mismatch between adjacent layers, as highlighted by the discovery of superconductivity in twisted bilayer graphene. Generally, the lattice structure of the original host material remains unchanged even after the moiré superlattice is formed. However, much less attention is paid for the possibility that the moiré potential can also modify the original crystal structure itself. Here, it is demonstrated that octahedral MoTe2 which is unstable in bulk is stabilized in a commensurate MoTe2 /graphene hetero-bilayer due to the moiré potential created between the two layers. It is found that the reconstruction of electronic states via the moiré potential is responsible for this stabilization, as evidenced by the energy-gap opening at the Fermi level observed by angle-resolved photoemission and scanning tunneling spectroscopies. The present results provide a fresh approach to realize novel 2D quantum phases by utilizing the moiré potential.

Spatially modulated tunnel magnetoresistance on the nanoscale.

We investigate the local tunnel magnetoresistance (TMR) effect within a single Co nanoisland using spin-polarized scanning tunneling microscopy. We observe a clear spatial modulation of the TMR ratio with an amplitude of ~20% and a spacing of ~1.3 nm between maxima and minima around the Fermi level. This result can be ascribed to a spatially modulated spin polarization within the Co island due to spin-dependent quantum interference. Our combined experimental and theoretical study reveals that spin-dependent electron confinement affects all transport properties such as differential conductance, conductance, and TMR. We demonstrate that the TMR within a nanostructured magnetic tunnel junction can be controlled on a length scale of 1 nm through spin-dependent quantum interference.

Robust charge-density wave strengthened by electron correlations in monolayer 1T-TaSe2 and 1T-NbSe2.

Combination of low-dimensionality and electron correlation is vital for exotic quantum phenomena such as the Mott-insulating phase and high-temperature superconductivity. Transition-metal dichalcogenide (TMD) 1T-TaS2 has evoked great interest owing to its unique nonmagnetic Mott-insulator nature coupled with a charge-density-wave (CDW). To functionalize such a complex phase, it is essential to enhance the CDW-Mott transition temperature TCDW-Mott, whereas this was difficult for bulk TMDs with TCDW-Mott < 200 K. Here we report a strong-coupling 2D CDW-Mott phase with a transition temperature onset of ~530 K in monolayer 1T-TaSe2. Furthermore, the electron correlation derived lower Hubbard band survives under external perturbations such as carrier doping and photoexcitation, in contrast to the bulk counterpart. The enhanced Mott-Hubbard and CDW gaps for monolayer TaSe2 compared to NbSe2, originating in the lattice distortion assisted by strengthened correlations and disappearance of interlayer hopping, suggest stabilization of a likely nonmagnetic CDW-Mott insulator phase well above the room temperature. The present result lays the foundation for realizing monolayer CDW-Mott insulator based devices operating at room temperature.

[Neuroradiological study of a possible progressive multifocal leukoencephalopathy using diffusion tensor imaging and proton magnetic resonance spectroscopy].

We report a possible case of progressive multifocal leukoencephalopathy (PML) that was attempted to evaluate the pathogenesis by a novel brain MRI techniques. A 72-year-old woman had developed subacute visual disturbance, right hemiparesis and sensory disturbance. Laboratory examinations revealed liver dysfunction and pancytopenia due to liver cirrhosis (type C) and preclinical status of multiple myeloma. Thus, this patient had these two underlying diseases, while anti-HIV antibody was negative. She was suspected with PML by detection of JCV-DNA in cerebrospinal fluid using with PCR. MRI showed multifocal T2-high signals in the bilateral parieto-occipital deep white matter, basal ganglia and right cerebellar hemisphere. No gadolinium enhancement was found. On FLAIR and diffusion weighted images (DWI), the lesion showed hyperintensity. The hyperintense areas on DWI showed various pattern on apparent diffusion coefficient (ADC) and fractional anisotropy (FA). In particular white matter changes, the course of FA reflected the clinical course more than ADC. Proton magnetic resonance spectroscopy (1H-MRS) in deep brain white matter showed ratios of reduced N-acetyl aspartate (NAA) and increased choline (Cho) to creatine. 1H-MRS by chemical shift imaging were undergone three times between 4 and 6 months after the onset. The change of these chemical markers correlated with her clinical course. We conclude that the approach of diffusion tensor imaging (DTI) and 1H-MRS are useful for evaluating neuropathologic observations and clinical course.

Drip-and-Ship Thrombolytic Therapy Supported by the Telestroke System for Acute Ischemic Stroke Patients Living in Medically Under-served Areas.

There are a few stroke specialists in medically under-served areas in Japan. Consequently, in remote area patients may not receive thrombolysis with intravenous recombinant tissue plasminogen activator (iv rt-PA), the standard treatment for acute ischemic stroke. Using a mobile telestroke support system (TSS) that accesses the internet via a smart phone, we implemented iv rt-PA infusion therapy under a drip-and-ship protocol to treat the stroke patients in medically under-served areas. The physicians at the Tokushima Prefectural Kaifu Hospital (TPKH), located in rural Japan, can relay CT or MRI scans and other patient data via their smart phone to off-site stroke specialists. In the course of 34 months, we used the TSS in 321 emergencies. A total of 9 of 188 (4.8%) with acute ischemic stroke, received iv rt-PA infusion therapy using a mobile TSS; in 5 among these (55.6%), we obtained partial or complete recanalization of occluded arteries. None suffered post-treatment hemorrhage and their average NIH stroke score fell from 14.6 at the time of admission to 6.8 at 24 h post-infusion. The drip-and-ship protocol contributed to the safe and effective treatment of the stroke patients living in medically under-served rural areas.

The impact of structural relaxation on spin polarization and magnetization reversal of individual nano structures studied by spin-polarized scanning tunneling microscopy.

The application of low temperature spin-polarized scanning tunneling microscopy and spectroscopy in magnetic fields for the quantitative characterization of spin polarization, magnetization reversal and magnetic anisotropy of individual nano structures is reviewed. We find that structural relaxation, spin polarization and magnetic anisotropy vary on the nm scale near the border of a bilayer Co island on Cu(1 1 1). This relaxation is lifted by perimetric decoration with Fe. We discuss the role of spatial variations of the spin-dependent electronic properties within and at the edge of a single nano structure for its magnetic properties.

Remora technique to approach the affected, difficult to approach sinus at transvenous embolization for dural arteriovenous fistulae: case report.

BACKGROUND AND IMPORTANCE: We describe a novel technique that uses a goose neck snare for microcatheterization at transvenous embolization (TVE) for dural arteriovenous fistulae (dAVF). We have named our method the "remora technique." CLINICAL PRESENTATION: A 48-year-old man reported with dizziness. Angiography disclosed a transverse-sigmoid sinus (T-SS) dAVF with proximal sigmoid sinus occlusion, an open distal transverse sinus, narrow multiple divided confluence sinus, and multiple retrograde leptomeningeal venous drainage. We attempted TVE via the confluence sinus from the contralateral open side; it was narrow, steep, and divided into cavities, rendering the procedure very difficult. Although we were able to pass a 0.035-inch guidewire to the affected transverse sinus, we could not advance via the same route with the microguidewire. One month later we attempted transfemoral TVE again using the remora technique. We caught the 0.035-inch guidewire in the left internal jugular vein with a goose neck micro snare bearing a microcatheter. By advancing the 0.035-inch wire across the confluence sinus to the affected sinus, we were able to pass the microcatheter through the lesion using the snare like a remora. We then performed transvenous coil packing. CONCLUSION: In TVE for dAVF, passage of the microguidewire is often difficult. Even if the affected sinus can be reached with the stiff 0.035-inch guidewire, it may not be possible to follow with the microguidewire. We report on a patient with T-SS dAVF who underwent successful microcatheterization in which we used our remora technique with a goose neck snare.

Traumatic pseudoaneurysm of superficial temporal artery.

An 83-year-old man reported falling and bumping his right lateral forehead on the ground 3 weeks previously. Physical examination revealed a soft, reddish swelling on the lateral forehead. Computed tomography confirmed a hematoma of the right lateral forehead. On the seventh hospital day, the swelling showed slight enlargement. Re-examination revealed a pulsatile mass with a palpable thrill and systolic bruit. Doppler echo showed pulsation of the swelling, which disappeared with compression of the anterior branch of the superficial temporal artery (STA). Surgical exploration was performed, and the pseudoaneurysm was resected. Pathological findings confirm a pseudoaneurysm.