Showing papers by "Tohoku University published in 2001"

Ordered nanoporous arrays of carbon supporting high dispersions of platinum nanoparticles

Abstract: Nanostructured carbon materials are potentially of great technological interest for the development of electronic1,2, catalytic3,4 and hydrogen-storage systems5,6. Here we describe a general strategy for the synthesis of highly ordered, rigid arrays of nanoporous carbon having uniform but tunable diameters (typically 6 nanometres inside and 9 nanometres outside). These structures are formed by using ordered mesoporous silicas as templates, the removal of which leaves a partially ordered graphitic framework. The resulting material supports a high dispersion of platinum nanoparticles, exceeding that of other common microporous carbon materials (such as carbon black, charcoal and activated carbon fibres). The platinum cluster diameter can be controlled to below 3 nanometres, and the high dispersion of these metal clusters gives rise to promising electrocatalytic activity for oxygen reduction, which could prove to be practically relevant for fuel-cell technologies. These nanomaterials can also be prepared in the form of free-standing films by using ordered silica films as the templates.

Color Separation of Galaxy Types in the Sloan Digital Sky Survey Imaging Data

Abstract: We study the optical colors of 147,920 galaxies brighter than g* = 21, observed in five bands by the Sloan Digital Sky Survey (SDSS) over ~100 deg2 of high Galactic latitude sky along the celestial equator. The distribution of galaxies in the g*-r* versus u*-g* color-color diagram is strongly bimodal, with an optimal color separator of u*-r* = 2.22. We use visual morphology and spectral classification of subsamples of 287 and 500 galaxies, respectively, to show that the two peaks correspond roughly to early- (E, S0, and Sa) and late-type (Sb, Sc, and Irr) galaxies, as expected from their different stellar populations. We also find that the colors of galaxies are correlated with their radial profiles, as measured by the concentration index and by the likelihoods of exponential and de Vaucouleurs' profile fits. While it is well known that late-type galaxies are bluer than early-type galaxies, this is the first detection of a local minimum in their color distribution. In all SDSS bands, the counts versus apparent magnitude relations for the two color types are significantly different and demonstrate that the fraction of blue galaxies increases toward the faint end.

Hole-mediated ferromagnetism in tetrahedrally coordinated semiconductors

Abstract: A mean-field model of ferromagnetism mediated by delocalized or weakly localized holes in zinc-blende and wurzite diluted magnetic semiconductors is presented. The model takes into account strong spin-orbit and $k\ensuremath{\cdot}p$ couplings in the valence band as well as the influence of strain upon the hole density of states. Possible effects of disorder and carrier-carrier interactions, particularly near the metal-to-insulator transition, are discussed. A quantitative comparison between experimental and theoretical results for (Ga,Mn)As demonstrates that the theory describes the values of the Curie temperatures observed in the studied systems as well as explaining the directions of the easy axes and the magnitudes of the corresponding anisotropy fields as a function of biaxial strain. Furthermore, the model reproduces the unusual sign, magnitude, and temperature dependence of the magnetic circular dichroism in the spectral region of the fundamental absorption edge. Chemical trends and various suggestions concerning design of ferromagnetic semiconductor systems are described.

Prostaglandin D2 Selectively Induces Chemotaxis in T Helper Type 2 Cells, Eosinophils, and Basophils via Seven-Transmembrane Receptor Crth2

Abstract: Prostaglandin (PG)D2, which has long been implicated in allergic diseases, is currently considered to elicit its biological actions through the DP receptor (DP). Involvement of DP in the formation of allergic asthma was recently demonstrated with DP-deficient mice. However, proinflammatory functions of PGD2 cannot be explained by DP alone. We show here that a seven-transmembrane receptor, CRTH2, which is preferentially expressed in T helper type 2 (Th2) cells, eosinophils, and basophils in humans, serves as the novel receptor for PGD2. In response to PGD2, CRTH2 induces intracellular Ca2+ mobilization and chemotaxis in Th2 cells in a Gαi-dependent manner. In addition, CRTH2, but not DP, mediates PGD2-dependent cell migration of blood eosinophils and basophils. Thus, PGD2 is likely involved in multiple aspects of allergic inflammation through its dual receptor systems, DP and CRTH2.

Review of the superconducting properties of MgB2

Abstract: This review paper illustrates the main normal and superconducting state properties of magnesium diboride, a material known since the early 1950s but only recently discovered to be superconductive at a remarkably high critical temperature Tc = 40 K for a binary compound. What makes MgB2 so special? Its high Tc, simple crystal structure, large coherence lengths, high critical current densities and fields, and transparency of grain boundaries to current promise that MgB2 will be a good material for both large-scale applications and electronic devices. During the last seven months, MgB2 has been fabricated in various forms: bulk, single crystals, thin films, tapes and wires. The largest critical current densities, greater than 10 MA cm−2, and critical fields, 40 T, are achieved for thin films. The anisotropy ratio inferred from upper critical field measurements is yet to be resolved as a wide range of values have been reported, γ = 1.2–9. Also, there is no consensus on the existence of a single anisotropic or double energy gap. One central issue is whether or not MgB2 represents a new class of superconductors, which is the tip of an iceberg awaiting to be discovered. To date MgB2 holds the record for the highest Tc among simple binary compounds. However, the discovery of superconductivity in MgB2 revived the interest in non-oxides and initiated a search for superconductivity in related materialss; several compounds have since been announced to be superconductive: TaB2, BeB2.75, C–S composites, and the elemental B under pressure.

Rapidly Solidified Powder Metallurgy Mg97Zn1Y2Alloys with Excellent Tensile Yield Strength above 600 MPa

Abstract: Nanocrystalline magnesium alloys having high tensile strength, high elevated-temperature tensile strength, high-strain-rate superplasticity and high thermal stability have been developed in Mg 97 Zn 1 Y 2 (at% I alloy by rapidly solidified powder metallurgy (RS P/M) processing. The tensile yield strength and elongation that were dependent on the consolidation temperature were in the ranges of 480 to 610MPa and 5 to 16%, respectively. Young's modulus of the RS P/M alloy was 45 GPa. The specific tensile yield strength was four times as high as that of a commercial AZ91-T6 alloy, and was higher than those of conventional titanium (Ti-6Al-4V) and aluminum (7075-T6) alloys. The RS P/M alloys exhibited excellent elevated-temperature yield strength that was 510 MPa at 423 K. The RS P/M alloy also exhibited high-strain-rate superplasticity at a wide strain-rate range from I × 10 - to I × 10 0 s -1 and at a low temperature of 623 K. It is expected that the Mg 97 Zn 1 Y 2 RS P/M alloy can he applied in some fields that requires simultaneously the high specific strength at ambient and elevated temperatures and high workability.

Review of superconducting properties of MgB2

Abstract: This review paper illustrates the main normal and superconducting state properties of magnesium diboride, a material known since early 1950's, but recently discovered to be superconductive at a remarkably high critical temperature Tc=40K for a binary compound. What makes MgB2 so special? Its high Tc, simple crystal structure, large coherence lengths, high critical current densities and fields, transparency of grain boundaries to current promises that MgB2 will be a good material for both large scale applications and electronic devices. During the last seven month, MgB2 has been fabricated in various forms, bulk, single crystals, thin films, tapes and wires. The largest critical current densities >10MA/cm2 and critical fields 40T are achieved for thin films. The anisotropy ratio inferred from upper critical field measurements is still to be resolved, a wide range of values being reported, between 1.2 and 9. Also there is no consensus about the existence of a single anisotropic or double energy gap. One central issue is whether or not MgB2 represents a new class of superconductors, being the tip of an iceberg who awaits to be discovered. Up to date MgB2 holds the record of the highest Tc in its class. However, the discovery of superconductivity in MgB2 revived the interest in non-oxides and initiated a search for superconductivity in related materials, several compounds being already announced to become superconductive: TaB2, BeB2.75, C-S composites, and the elemental B under pressure.

Solar 8B and hep Neutrino Measurements from 1258 Days of Super-Kamiokande Data

Abstract: Solar neutrino measurements from 1258days of data from the Super-Kamiokande detector are presented. The measurements are based on recoil electrons in the energy range 5.0{endash}20.0MeV. The measured solar neutrino flux is 2.32{+-}0.03(stat){sup +0.08}{sub {minus}0.07}(syst){times}10{sup 6} cm{sup {minus}2}s{sup {minus}1} , which is 45.1{+-}0.5(stat ){sup +1.6}{sub {minus}1.4}(syst) % of that predicted by the BP2000 SSM. The day vs night flux asymmetry ({Phi}{sub n}{minus}{Phi}{sub d})/ {Phi}{sub average} is 0.033{+-}0.022(stat){sup +0.013}{sub {minus}0.012}(syst) . The recoil electron energy spectrum is consistent with no spectral distortion. For the hep neutrino flux, we set a 90% C.L.upper limit of 40{times}10{sup 3} cm{sup {minus}2}s{sup {minus}1} , which is 4.3times the BP2000 SSM prediction.

Revascularization of an immature permanent tooth with apical periodontitis and sinus tract.

Abstract: A necrotic immature mandibular second premolar with periapical involvement in a 13-year-old patient was treated. Instead of the standard root canal treatment protocol and apexification, antimicrobial agents were used in the canal, after which the canal was left empty. Radiographic examination showed the start of apical closure 5 months after the completion of the antimicrobial protocol. Thickening of the canal wall and complete apical closure was confirmed 30 months after the treatment, indicating the revascularization potential of a young permanent tooth pulp into a bacteria-free root canal space.

Strengthening Mechanisms of Creep Resistant Tempered Martensitic Steel

Abstract: The creep deformation resistance and rupture life of high Cr ferritic steel with a tempered martensitic lath structure are critically reviewed on the basis of experimental data. Special attention is directed to the following three subjects: creep mechanism of the ferritic steel, its alloy design for further strengthening, and loss of its creep rupture strength after long-term use. The high Cr ferritic steel is characterized by its fine subgrain structure with a high density of free dislocations within the subgrains. The dislocation substructure is the most densely distributed obstacle to dislocation motion in the steel. Its recovery controls creep rate and rupture life at elevated temperatures. Improvement of creep strength of the steel requires a fine subgrain structure with a high density of free dislocations. A sufficient number of pinning particles (MX particles in subgrain interior and M 23 C 6 particles on sub-boundaries) are necessary to cancel a large driving force for recovery due to the high dislocation density. Coarsening and agglomeration of the pinning particles have to be delayed by an appropriate alloy design of the steel. Creep rupture strength of the high Cr ferritic steel decreases quickly after long-term use. A significant improvement of creep rupture strength can be achieved if we can prevent the loss of rupture strength. In the steel tempered at high temperature, enhanced recovery of the subgrain structure along grain boundaries is the cause of the premature failure and the consequent loss of rupture strength. However, the scenario is not always applicable. Further studies are needed to solve this important problem of high Cr ferritic steel. MX particles are necessary to retain a fine subgrain structure and to achieve the excellent creep strength of the high Cr ferritic steel. Strengthening mechanism of the MX particles is another important problem left unsolved.

Proliferative activity of intratumoral CD8(+) T-lymphocytes as a prognostic factor in human renal cell carcinoma: clinicopathologic demonstration of antitumor immunity.

Abstract: Tumor-infiltrating lymphocytes, particularly CD8(+) T cells, could be a manifestation of antitumor immunity. We clinicopathologically analyzed the biological significance of tumor-infiltrating lymphocytes in 221 patients with renal cell carcinoma without preoperative treatments. More abundant infiltration of tumor tissue not only by CD8(+) but also CD4(+) T cells was associated with shorter survival of the patients, because of the positive correlation between the number of lymphocytes and representative tumor grade factors. This suggests that immune cell reactions are more pronounced as the tumor grade/biological malignancy progresses, probably because of increased antigenicity of tumor cells. We next analyzed the proliferative activity of CD8(+) T cells that infiltrated in tumor cell nests, which could also reflect antitumor immunity. Higher labeling index of Ki-67, a proliferation-associated antigen, among CD8(+) T cells in contact to tumor cells was associated with a longer survival by both uni- and multivariate analyses. Our data in human renal cell carcinoma suggest that infiltration of tumor tissue by T cells itself does not denote the efficacy of antitumor immunity because of its dependence on the biological malignancy of tumor cells, but infiltration of tumor tissue by CD8(+) T cells bearing more pronounced proliferative activity could reflect effective antitumor immunity. This concept would be important for future immunotherapy of human cancer.

Hydrothermal Synthesis of Metal Oxide Nanoparticles at Supercritical Conditions

Abstract: Hydrothermal synthesis of CeO2 and AlO(OH) were conducted using a flow type apparatus over the range of temperature from 523 to 673 K at 30 MPa. Nanosize crystals were formed at supercritical conditions. The mechanism of nanoparticle formation at supercritical conditions was discussed based on the metal oxide solubility and kinetics of the hydrothermal synthesis reaction. The reaction rate of Ce(NO3)3 and Al(NO3)3 was evaluated using a flow type reactor. The Arrhenius plot of the first order rate constant fell on a straight line in the subcritical region, while it deviated from the straight line to the higher values above the critical point. The solubility of Ce(OH)3 and AlO(OH) was estimated by using a modified HKF model in a wide range of pH and temperature. In acidic conditions, where hydrothermal synthesis reaction is concerned, solubility gradually decreased with increasing temperature and then drastically dropped above the critical point. The trend of the solubility and the kinetics around the critical point could be explained by taking account of the dielectric constant effect on the reactions. There are two reasons why nanoparticle are formed at supercritical conditions. Larger particles are produced at subcritical conditions due to Ostwald ripening; that could not be observed in supercritical water because of the extremely low solubility. Second reason is the faster nucleation rate in supercritical water because of the lower solubility and the extremely fast reaction rate.

Cutting Edge: The Common γ-Chain Is an Indispensable Subunit of the IL-21 Receptor Complex

Abstract: The common γ-chain (γc) is an indispensable subunit of the functional receptor complexes for IL-4, IL-7, IL-9, and IL-15 as well as IL-2. Here we show that the γc is also shared with the IL-21R complex. Although IL-21 binds to the IL-21R expressed on γc-deficient ED40515− cells, IL-21 is unable to transduce any intracytoplasmic signals. However, in EDγ-16 cells, a γc-transfected ED40515− cell line, IL-21 binds to the IL-21R and can activate Janus kinase (JAK)1, JAK3, STAT1, and STAT3. The chemical cross-linking study reveals the direct binding of IL-21 to the γc. These data clearly demonstrate that the γc is an indispensable subunit of the functional IL-21R complex.

Expression of Osteoprotegerin, Receptor Activator of NF-κB Ligand (Osteoprotegerin Ligand) and Related Proinflammatory Cytokines During Fracture Healing

Abstract: Fracture healing is a unique biological process regulated by a complex array of signaling molecules and proinflammatory cytokines. Recent evidence for the role of tumor necrosis family members in the coupling of cellular functions during skeletal homeostasis suggests that they also may be involved in the regulation of skeletal repair. The expression of a number of cytokines and receptors that are of functional importance to bone remodeling (osteoprotegerin [OPG], macrophage colony-stimulating factor [M-CSF], and osteoprotegerin ligand [receptor activator of NF-kappaB ligand (RANKL)]), as well as inflammation (tumor necrosis factor alpha [TNF-alpha] and its receptors, and interleukin-1alpha [IL-1alpha] and -beta and their receptors) were analyzed over a 28-day period after the generation of simple transverse fractures in mouse tibias. OPG was expressed constitutively in unfractured bones and elevated levels of expression were detected throughout the repair process. It showed two distinct peaks of expression: the first occurring within 24 h after fracture and the second at the time of peak cartilage formation on day 7. In contrast, the expression of RANKL was nearly undetectable in unfractured bones but strongly induced throughout the period of fracture healing. The peak in expression of RANKL did not correlate with that of OPG, because maximal levels of expression were seen on day 3 and day 14, when OPG levels were decreasing. M-CSF expression followed the temporal profile of RANKL but was expressed at relatively high basal levels in unfractured bones. TNF-alpha, lymphotoxin-beta (LT-beta), IL-1alpha, and IL-1beta showed peaks in expression within the first 24 h after fracture, depressed levels during the period of cartilage formation, and increased levels of expression on day 21 and day 28 when bone remodeling was initiated. Both TNF-alpha receptors (p55 and p75) and the IL-1RII receptor showed identical patterns of expression to their ligands, while the IL-1R1 was expressed only during the initial period of inflammation on day 1 and day 3 postfracture. Both TNF-alpha and IL-1alpha expression were localized primarily in macrophages and inflammatory cells during the early periods of inflammation and seen in mesenchymal and osteoblastic cells later during healing. TNF-alpha expression also was detected at very high levels in hypertrophic chondrocytes. These data imply that the expression profiles for OPG, RANKL, and M-CSF are tightly coupled during fracture healing and involved in the regulation of both endochondral resorption and bone remodeling. TNF-alpha and IL-1 are expressed at both very early and late phases in the repair process, which suggests that these cytokines are important in the initiation of the repair process and play important functional roles in intramembraneous bone formation and trabecular bone remodeling.

Constraints on neutrino oscillations using 1258 days of Super-Kamiokande solar neutrino data.

Abstract: We report the result of a search for neutrino oscillations using precise measurements of the recoil electron energy spectrum and zenith angle variations of the solar neutrino flux from 1258 days of neutrino-electron scattering data in Super-Kamiokande The absence of significant zenith angle variation and spectrum distortion places strong constraints on neutrino mixing and mass difference in a flux-independent way Using the Super-Kamiokande flux measurement in addition, two allowed regions at large mixing are found

Real-time difference imaging analysis of moa galactic bulge observations during 2000

Abstract: We describe observations carried out by the MOA group of the Galactic bulge during 2000 that were designed to detect efficiently gravitational microlensing of faint stars in which the magnification is high and/or of short duration. These events are particularly useful for studies of extrasolar planets and faint stars. Approximately 17 deg2 were monitored at a sampling rate of up to six times per night. The images were analysed in real time using a difference imaging technique. 20 microlensing candidates were detected, of which eight were alerted to the microlensing community whilst in progress. Approximately half of the candidates had high magnifications (≳10), at least one had very high magnification (≳50), and one exhibited a clear parallax effect. The details of these events are reported here, together with details of the on-line difference imaging technique. Some nova-like events were also observed and these are described, together with one asteroid.

Heme mediates derepression of Maf recognition element through direct binding to transcription repressor Bach1.

Abstract: Heme controls expression of genes involved in the synthesis of globins and heme. The mammalian transcription factor Bach1 functions as a repressor of the Maf recognition element (MARE) by forming antagonizing hetero-oligomers with the small Maf family proteins. We show here that heme binds specifically to Bach1 and regulates its DNA-binding activity. Deletion studies demonstrated that a heme-binding region of Bach1 is confined within its C-terminal region that possesses four dipeptide cysteine–proline (CP) motifs. Mutations in all of the CP motifs of Bach1 abolished its interaction with heme. The DNA-binding activity of Bach1 as a MafK hetero-oligomer was markedly inhibited by heme in gel mobility shift assays. The repressor activity of Bach1 was lost upon addition of hemin in transfected cells. These results suggest that increased levels of heme inactivate the repressor Bach1, resulting in induction of a host of genes with MAREs.

A Calcium-Dependent Feedback Mechanism Participates in Shaping Single NMDA Miniature EPSCs

Abstract: NMDA receptors (NMDARs) are highly calcium-permeable and are negatively regulated by intracellular calcium during prolonged exposure to agonist. We have investigated whether calcium-mediated feedback occurs during transient exposure to glutamate during single synaptic events. Examination of miniature EPSCs (mEPSCs) indicated that the decay kinetics of the NMDAR component was markedly slowed by the intracellular perfusion of exogenous calcium buffers (BAPTA or Fluo-3). In contrast, the AMPA receptor component of the miniature EPSC was unaffected. Slow on-rate calcium buffers, such as EGTA, did not alter kinetics of the NMDAR component of the mEPSC. Addition of exogenous fast calcium buffers did not slow the decay kinetics of glutamate-evoked currents mediated by NR1/NR2A heteromers expressed in HEK 293 cells, suggesting that the effect we observed in neurons may be specific to processes associated with synaptically activated receptors. Trial-to-trial amplitude variability of miniature calcium transients mediated by NMDARs increased with the injection of exogenous calcium buffers, suggesting that the amplitude of synaptic calcium transients are maintained at a rather constant level by a calcium-mediated feedback mechanism.

Endophytic Colonization and In Planta Nitrogen Fixation by a Herbaspirillum sp. Isolated from Wild Rice Species

Abstract: Nitrogen-fixing bacteria were isolated from the stems of wild and cultivated rice on a modified Rennie medium. Based on 16S ribosomal DNA (rDNA) sequences, the diazotrophic isolates were phylogenetically close to four genera: Herbaspirillum, Ideonella, Enterobacter, and Azospirillum. Phenotypic properties and signature sequences of 16S rDNA indicated that three isolates (B65, B501, and B512) belong to the Herbaspirillum genus. To examine whether Herbaspirillum sp. strain B501 isolated from wild rice, Oryza officinalis, endophytically colonizes rice plants, the gfp gene encoding green fluorescent protein (GFP) was introduced into the bacteria. Observations by fluorescence stereomicroscopy showed that the GFP-tagged bacteria colonized shoots and seeds of aseptically grown seedlings of the original wild rice after inoculation of the seeds. Conversely, for cultivated rice Oryza sativa, no GFP fluorescence was observed for shoots and only weak signals were observed for seeds. Observations by fluorescence and electron microscopy revealed that Herbaspirillum sp. strain B501 colonized mainly intercellular spaces in the leaves of wild rice. Colony counts of surface-sterilized rice seedlings inoculated with the GFP-tagged bacteria indicated significantly more bacterial populations inside the original wild rice than in cultivated rice varieties. Moreover, after bacterial inoculation, in planta nitrogen fixation in young seedlings of wild rice, O. officinalis, was detected by the acetylene reduction and 15N2 gas incorporation assays. Therefore, we conclude that Herbaspirillum sp. strain B501 is a diazotrophic endophyte compatible with wild rice, particularly O. officinalis.

Observation of a 6∧∧ He double hypernucleus

Abstract: A double-hyperfragment event has been found in a hybrid-emulsion experiment. It is identified uniquely as the sequential decay of ${}_{\ensuremath{\Lambda}\ensuremath{\Lambda}}^{6}\mathrm{He}$ emitted from a ${\ensuremath{\Xi}}^{\ensuremath{-}}$ hyperon nuclear capture at rest. The mass of ${}_{\ensuremath{\Lambda}\ensuremath{\Lambda}}^{6}\mathrm{He}$ and the $\ensuremath{\Lambda}\ensuremath{-}\ensuremath{\Lambda}$ interaction energy $\ensuremath{\Delta}{B}_{\ensuremath{\Lambda}\ensuremath{\Lambda}}$ have been measured for the first time devoid of the ambiguities due to the possibilities of excited states. The value of $\ensuremath{\Delta}{B}_{\ensuremath{\Lambda}\ensuremath{\Lambda}}$ is $1.01\ifmmode\pm\else\textpm\fi{}{0.20}_{\ensuremath{-}0.11}^{+0.18}\phantom{\rule{0ex}{0ex}}\mathrm{MeV}$. This demonstrates that the $\ensuremath{\Lambda}\ensuremath{-}\ensuremath{\Lambda}$ interaction is weakly attractive.

The gene mutated in ataxia-ocular apraxia 1 encodes the new HIT/Zn-finger protein aprataxin

Abstract: The newly recognized ataxia-ocular apraxia 1 (AOA1; MIM 208920) is the most frequent cause of autosomal recessive ataxia in Japan and is second only to Friedreich ataxia in Portugal. It shares several neurological features with ataxia-telangiectasia, including early onset ataxia, oculomotor apraxia and cerebellar atrophy, but does not share its extraneurological features (immune deficiency, chromosomal instability and hypersensitivity to X-rays). AOA1 is also characterized by axonal motor neuropathy and the later decrease of serum albumin levels and elevation of total cholesterol. We have identified the gene causing AOA1 and the major Portuguese and Japanese mutations. This gene encodes a new, ubiquitously expressed protein that we named aprataxin. This protein is composed of three domains that share distant homology with the amino-terminal domain of polynucleotide kinase 3'- phosphatase (PNKP), with histidine-triad (HIT) proteins and with DNA-binding C2H2 zinc-finger proteins, respectively. PNKP is involved in DNA single-strand break repair (SSBR) following exposure to ionizing radiation and reactive oxygen species. Fragile-HIT proteins (FHIT) cleave diadenosine tetraphosphate, which is potentially produced during activation of the SSBR complex. The results suggest that aprataxin is a nuclear protein with a role in DNA repair reminiscent of the function of the protein defective in ataxia-telangiectasia, but that would cause a phenotype restricted to neurological signs when mutant.

Anomalous barium filling fraction and n-type thermoelectric performance of BayCo4Sb12

Abstract: Barium-filled skutterudites BayCo4Sb12 with an anomalously large filling fraction of up to y=0.44 have been synthesized. The lattice parameters increase linearly with Ba content. Magnetic susceptibility data show that Ba0.44Co4Sb12 is paramagnetic, which implies that some of the Co atoms in BayCo4Sb12 have acquired a magnetic moment. The presence of the two different valence states of Co (Co3+ and Co2+) leads to the anomalously large barium filling fraction even without extra charge compensation. All samples show n-type conduction. The electrical conductivity increases with increasing the Ba filling fraction. The lattice thermal conductivity of BayCo4Sb12 is significantly depressed as compared to unfilled Co4Sb12. The dimensionless thermoelectric figure of merit, ZT, increases with increasing temperature reaching a maximum value of 1.1 for Ba0.24Co4Sb12 at 850 K.

Mixed spinel structure in nanocrystalline NiFe 2 O 4

Abstract: Nanocrystalline ${\mathrm{NiFe}}_{2}{\mathrm{O}}_{4}$ spinel has been synthesized with various grain sizes by high-energy ball milling. From the high-field magnetization studies and extended x-ray-absorption fine-structure, and M\"ossbauer measurements in an external magnetic field of 5 T applied parallel to the direction of gamma rays, we could observe that ${\mathrm{Ni}}^{2+}$ ions occupy tetrahedral sites on grain-size reduction due to milling. The ${\mathrm{Fe}}^{3+}$ spins have a canted structure and the canting angle increases with grain-size reduction. It is possible that the core ${\mathrm{Fe}}^{3+}$ spins are also canted because of the magnetocrystalline anisotropy introduced by the occupancy of the ${\mathrm{Ni}}^{2+}$ ions in the tetrahedral sites.

Sequential organization of multiple movements : Involvement of cortical motor areas

Abstract: Much of our normal behavior depends on the sequential execution of multiphased movements, or the execution of multiple movements arranged in a correct temporal order. This article deals with the issue of motor selection to arrange multiple movements in an appropriate temporal order, rather than the issue of constructing spatio-temporal structures in a single action. Planning, generating, and controlling the sequential motor behavior involves multiple cortical and subcortical neural structures. Studies on human subjects and nonhuman primates, however, have revealed that the medial motor areas in the frontal cortex and the basal ganglia play particularly important roles in the temporal sequencing of multiple movements. Cellular activity observed in the supplementary and presupplementary motor areas while performing specifically designed motor tasks suggests the way in which these areas take part in constructing the time structure for the sequential execution of multiple movements.

Novel ultra high density flash memory with a stacked-surrounding gate transistor (S-SGT) structured cell

Abstract: In order to overcome the limitation of cell area of 4F/sup 2/ per bit in conventional NAND flash memory cells, stacked-surrounding gate transistor (S-SGT) structured cell is proposed. This newly structured cell achieves a cell area of 4F/sup 2//N per bit, where N is the number of stacked memory cells in one silicon pillar, without using multibit per memory cell technology. The S-SGT structured cell consisting of two stacked memory cells in one silicon pillar achieves a cell area per bit of less than 50% of the smallest reported NAND structured cell. The novel S-SGT structured cells are fabricated by vertical self-aligned processes using a 0.2 /spl mu/m design rule. The S-SGT structured cell can be programmed and erased by uniform injection and uniform emission of Fowler-Nordheim (F-N) tunneling electrons over the whole channel area of the memory cell, respectively, which is the same program and erase mechanism as in conventional NAND structured cell. This high performance S-SGT structured cell is applicable to high-density nonvolatile memories for 16 G/64 G bit Flash memories and beyond.