Observation of nuclear-spin Seebeck effect.

Thermoelectric effects have been applied to power generators and temperature sensors that convert waste heat into electricity. The effects, however, have been limited to electrons to occur, and inevitably disappear at low temperatures due to electronic entropy quenching. Here, we report thermoelectric generation caused by nuclear spins in a solid: nuclear-spin Seebeck effect. The sample is a magnetically ordered material MnCO3 having a large nuclear spin (I = 5/2) of 55Mn nuclei and strong hyperfine coupling, with a Pt contact. In the system, we observe low-temperature thermoelectric signals down to 100 mK due to nuclear-spin excitation. Our theoretical calculation in which interfacial Korringa process is taken into consideration quantitatively reproduces the results. The nuclear thermoelectric effect demonstrated here offers a way for exploring thermoelectric science and technologies at ultralow temperatures.

Observation of Magnon Polarization.

We measure the mode-resolved direction of the precessional motion of the magnetic order, i.e., magnon polarization, via the chiral term of inelastic polarized neutron scattering spectra. The magnon polarization is a unique and unambiguous signature of magnets and is important in spintronics, affecting thermodynamic properties such as the magnitude and sign of the spin Seebeck effect. However, it has never been directly measured in any material until this work. The observation of both signs of magnon polarization in Y_{3}Fe_{5}O_{12} also gives direct proof of its ferrimagnetic nature. The experiments agree very well with atomistic simulations of the scattering cross section.

Observation of a Magnetopiezoelectric Effect in the Antiferromagnetic Metal EuMnBi_{2}.

We have experimentally studied a magnetopiezoelectric effect predicted recently for magnetic metals with low crystal symmetries. In EuMnBi_{2} with antiferromagnetic Mn moments at 77 K, dynamic displacements emerge along the a direction upon application of ac electric fields in the c direction and increase in proportion to the applied electric fields. Such displacements are not observed along the c direction of EuMnBi_{2} or EuZnBi_{2} with nonmagnetic Zn ions. As temperature increases from 77 K, the displacement signals decrease and disappear at about 200 K, above which electric conduction changes from coherent to incoherent. These results demonstrate the emergence of the magnetopiezoelectric effect in a magnetic metal lacking inversion and time-reversal symmetries.

Vortex rectenna powered by environmental fluctuations.

A rectenna, standing for a rectifying antenna, is an apparatus which generates d.c. electricity from electric fluctuations. It is expected to realize wireless power transmission as well as energy harvesting from environmental radio waves. To realize such rectification, devices that are made up of internal atomic asymmetry such as an asymmetric junction have been necessary so far. Here we report a material that spontaneously generates electricity by rectifying environmental fluctuations without using atomic asymmetry. The sample is a common superconductor without lowered crystalline symmetry, but, just by putting it in an asymmetric magnetic environment, it turns into a rectifier and starts generating electricity. Superconducting vortex strings only annihilate and nucleate at surfaces, and this allows the bulk electrons to feel surface fluctuations in an asymmetric environment: a vortex rectenna. The rectification and generation can be switched on and off with only a slight change in temperature or external magnetic fields.

Oscillatory Nernst effect in Pt|ferrite|cuprate-superconductor trilayer films.

Although magnetism and superconductivity hardly coexist in a single material, recent advances in nanotechnology and spintronics have brought to light their interplay in magnetotransport in thin-film heterostructures. Here, we found a periodic oscillation of Nernst voltage with respect to magnetic fields in Pt|LiFe5O8 (Pt|LFO) bilayers grown on a cuprate superconductor YBa2Cu3O7-x (YBCO). At high temperatures above the superconducting transition temperature (T C ) of YBCO, spin Seebeck voltages originating in Pt|LFO layers are observed. As temperature decreases well below T C , the spin Seebeck voltage is suppressed and unconventional periodic voltage oscillation as a function of magnetic fields appears; such an oscillation emerging along the Hall direction in the superconducting state has not been observed yet. Dynamics of superconducting vortices pinned by surface precipitates seems responsible for the oscillatory Nernst effect.

Dispersion-type Hall resistance in InSb|Pt hybrid systems.

In nonmagnetic semiconductors and metals, most of Hall resistance exhibits a linear dependence with applied magnetic fields. In this work, by combining conduction in a metal and a semiconductor under external magnetic fields, we realize a dispersion-type magnetic-field dependence of Hall resistance. The dispersion-type Hall resistance appears in a broad temperature range below 150 K, where quantum linear magnetoresistance is noticeable in the semiconductor substrate. This unconventional Hall response in metal|semiconductor hybrid systems is explained by a change in dominant conduction from the semiconductor to the metal with increasing magnetic field strength.

Spin-electricity conversion induced by spin injection into topological insulators.

We report successful spin injection into the surface states of topological insulators by using a spin pumping technique. By measuring the voltage that shows up across the samples as a result of spin pumping, we demonstrate that a spin-electricity conversion effect takes place in the surface states of bulk-insulating topological insulators Bi(1.5)Sb(0.5)Te(1.7)Se(1.3) and Sn-doped Bi(2)Te(2)Se. In this process, the injected spins are converted into a charge current along the Hall direction due to the spin-momentum locking on the surface state.

Paramagnetic spin pumping.

We have demonstrated spin pumping from a paramagnetic state of an insulator La2NiMnO6 into a Pt film. Single-crystalline films of La2NiMnO6 which exhibit a ferromagnetic order at TC≈270 K were grown by pulsed laser deposition. The inverse spin Hall voltage induced by spin-current injection has been observed in the Pt layer not only in the ferromagnetic phase of La2NiMnO6, but also in a wide temperature range above TC. The efficient spin pumping in the paramagnetic phase is ascribable to ferromagnetic correlation, not to ferromagnetic order.

Extremely high electron mobility in a phonon-glass semimetal.

The electron mobility is one of the key parameters that characterize the charge-carrier transport properties of materials, as exemplified by the quantum Hall effect as well as high-efficiency thermoelectric and solar energy conversions. For thermoelectric applications, introduction of chemical disorder is an important strategy for reducing the phonon-mediated thermal conduction, but is usually accompanied by mobility degradation. Here, we show a multilayered semimetal ß-CuAgSe overcoming such a trade-off between disorder and mobility. The polycrystalline ingot shows a giant positive magnetoresistance and Shubnikov de Haas oscillations, indicative of a high-mobility small electron pocket derived from the Ag s-electron band. Ni doping, which introduces chemical and lattice disorder, further enhances the electron mobility up to 90,000 cm(2) V(-1) s(-1) at 10 K, leading not only to a larger magnetoresistance but also a better thermoelectric figure of merit. This Ag-based layered semimetal with a glassy lattice is a new type of promising thermoelectric material suitable for chemical engineering.

Longitudinal spin Seebeck effect free from the proximity Nernst effect.

This Letter provides evidence for intrinsic longitudinal spin Seebeck effects (LSSEs) that are free from the anomalous Nernst effect (ANE) caused by an extrinsic proximity effect. We report the observation of LSSEs in Au/Y(3)Fe(5)O(12) (YIG) and Pt/Cu/YIG systems, showing that the LSSE appears even when the mechanism of the proximity ANE is clearly removed. In the conventional Pt/YIG structure, furthermore, we separate the LSSE from the ANE by comparing the voltages in different magnetization and temperature-gradient configurations; the ANE contamination was found to be negligibly small even in the Pt/YIG structure.

Hall effect of spin-chirality origin in a triangular-lattice helimagnet Fe{1.3}Sb.

We report on a topological Hall effect possibly induced by scalar spin chirality in a quasi-two-dimensional helimagnet Fe{1+δ}Sb. In the low-temperature region where the spins on interstitial-Fe (concentration δ∼0.3) intervening the 120° spin-ordered triangular planes tend to freeze, a nontrivial component of Hall resistivity with opposite sign of the conventional anomalous Hall term is observed under magnetic field applied perpendicular to the triangular-lattice plane. The observed unconventional Hall effect is ascribed to the scalar spin chirality arising from the heptamer spin clusters around the interstitial-Fe sites, which can be induced by the spin modulation by the Dzyaloshinsky-Moriya interaction.

Observation of the magnon Hall effect.

The Hall effect usually occurs in conductors when the Lorentz force acts on a charge current in the presence of a perpendicular magnetic field. Neutral quasi-particles such as phonons and spins can, however, carry heat current and potentially exhibit the thermal Hall effect without resorting to the Lorentz force. We report experimental evidence for the anomalous thermal Hall effect caused by spin excitations (magnons) in an insulating ferromagnet with a pyrochlore lattice structure. Our theoretical analysis indicates that the propagation of the spin waves is influenced by the Dzyaloshinskii-Moriya spin-orbit interaction, which plays the role of the vector potential, much as in the intrinsic anomalous Hall effect in metallic ferromagnets.

Lorenz number determination of the dissipationless nature of the anomalous Hall effect in itinerant ferromagnets.

We have measured the thermal Hall conductivity for ferromagnetic Ni and Ni0.97Cu0.03. In the low temperature region ( less, similar 100 K), we show for the first time that the Wiedemann-Franz law is satisfied even for the anomalous Hall current. While the Hall Lorenz number for the normal part decreases rapidly with temperature, that for the anomalous part shows much less deviation from the free-electron Lorenz number. This evidences the dissipationless nature of the anomalous Hall effect.

Case report: internal and external jugular vein thrombosis with marked accumulation of FDG.

We report an unusual case of idiopathic internal and external jugular vein thrombosis. Positron emission tomography (PET) using (18)F-fluoro-2-deoxy-D-glucose (FDG), which was conducted to assess subclinical malignancy, revealed intense uptake of FDG, corresponding to thrombus within the left internal and external jugular veins. Although FDG-PET is widely used in differentiating between malignant and benign diseases, we should bear in mind that this benign entity can demonstrate high accumulation of FDG.

Cytokine production inhibitors produced by a fungus, Oidiodendron griseum.

A series of diterpenes were isolated from the fermentation broth of a fungus, Oidiodendron griseum CL37215. The diterpenes were identified as LL-Z1271alpha, LL-Z1271gamma, CJ-14,445, PR 1388, CJ-14,604 and a new diterpene, CJ-14,515. They inhibited both lipopolysaccharide-induced interleukin-1beta and tumor necrosis factor-alpha production in human whole blood with IC50s of the range from 0.049 to 100 microM.

Novel cytokine production inhibitors produced by a basidiomycete, Marasmiellus sp.

New cytokine production inhibitors, CJ-14,877 (I) and CJ-14,897 (II), were isolated from the fermentation broth of a basidiomycete, Marasmiellus sp. CL21624. Their structures were determined to be methyl-(7S,8S)-5-(7,8-dihydroxypropyl)pyridine-2-carboxylate and methyl-(7S,8S)-5-(8-acetoxy-7-hydroxypropyl)pyridine-2-carboxylate [corrected], respectively, by spectroscopic analyses. These compounds showed inhibitory activities for lipopolysaccharide-induced production of interleukin-1beta and tumor necrosis factor-alpha in human whole blood with IC50 values of the range from 0.059 to 2.6 microM.

Hearing impairment in a patient with unilateral narrowing of the internal auditory canal--a case report.

A 9-year-old boy complaining of left hearing loss with unknown date of onset visited our clinic. The pure tone audiogram showed profound hearing loss in the left ear, while normal in the right ear. Computed tomography and magnetic resonance imaging showed narrowing of the left internal auditory canal (IAC) in contrast with the right IAC. Distortion Product Otoacoustic Emissions of the left ear were not present above the background noise at any frequency tested in contrast to the right one. A retrocochlear lesion might be accompanied, while the profound hearing loss was thought to be caused mainly by a cochlear lesion.

A large outbreak of foodborne infection attributed to Providencia alcalifaciens.

The enteropathogenicity of Providencia alcalifaciens, a member of the family Enterobacteriaceae, has not yet been well established. In November 1996, a large outbreak of foodborne infection occurred in Fukui, Japan. In this study, the etiology of the outbreak was investigated. No other recognized enteropathogens were detected in patient fecal samples, but P. alcalifaciens was detected in 7 of 18 samples. The isolates were found to be clonal by pulsed-field gel electrophoresis. The patients who presented with gastroenteritis had elevated levels of specific antibody against the isolated P. alcalifaciens. The isolates showed invasion of Caco-2 cells and fluid accumulation in rabbit ileal loops. This study strongly suggests that the outbreak was caused by P. alcalifaciens. This is the first report of a large outbreak of foodborne infection attributed to the organism and provides definitive evidence that P. alcalifaciens is a causative agent of gastroenteritis.

Atlantoaxial subluxation in an adult secondary to retropharyngeal abscess.

Atlantoaxial subluxation secondary to a retropharyngeal abscess is well described in children, but very rare in adults. Only two adult cases have been reported in the literature. We present a case of severe atlantoaxial subluxation in an adult secondary to retropharyngeal abscess. His atlas-dens interval was very large, up to 10 mm in flexion. We tried external fixation with a neck collar initially, but for remaining instability, surgical fusion was performed. The mechanism of subluxation is attributed to softening of the ligament allowing greater mobility at the joint. The etiology of this process is speculative.