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K Ishii

Publications and source records attributed to K Ishii.

At least 19 recordsLinked to original sources
PubMed2006

Observation and control of transverse energy-transport barrier due to the formation of an energetic-electron layer with sheared ExB flow.

Off-axis electron-cyclotron heating in an axisymmetric barrier mirror produces a cylindrical layer with energetic electrons, which flow through the central cell and into the end region. The layer, producing a localized bumped ambipolar potential Phi(C), forms a strong shear of radial electric fields E(r) and peaked vorticity with the direction reversal of E(r)xB sheared flow near the Phi(C) peak. Intermittent vortexlike turbulent structures near the layer are suppressed in the central cell by this actively produced transverse energy-transport barrier; this results in T(e) and T(i) rises surrounded by the layer.

Journal Article↗
PubMed2006

Surgical outcomes of spinal cord astrocytomas.

STUDY DESIGN: Retrospective case series. OBJECTIVES: To analyze prognostic factors for patients with spinal cord astrocytomas. SETTING: Department of Orthopaedic Surgery, Keio University, Japan. METHODS: Seven patients received total excisions (group T), eight underwent partial excisions (group P), and 15 had excisional biopsies (group B). Impacts of the tumor histological grade, the level of the tumor, the types of surgical interventions, and the use of adjuvant radiotherapies on the survival and functional outcomes of 30 patients (18 in low-grade and 12 high-grade malignancy tumors) were analyzed. RESULTS: The survival rate of the low-grade malignancy group was significantly higher than that of the high-grade group. The survival rate of the patients with thoracic astrocytomas was significantly higher than those with cervical astrocytomas. In both the low- and high-grade groups, the survival rates in groups P/T were significantly higher than those in group B. In the low-grade group, five patients, whose preoperative functional statuses were classified as 'fair' or better, remained 'fair' or better after surgery. In the high-grade group, the postoperative functional statuses were classified as 'no change' or 'aggravated' in all except two patients. No significant difference in the survival rates was detected between patients with and without adjuvant radiotherapy. CONCLUSIONS: The tumor grade and the extent of tumor resection were significant prognostic factors for survival rate. In low-grade malignancy group, good motor function was retained when surgeries were performed before substantial neurological deterioration. The efficacy of postoperative radiotherapy has yet to be determined and needs further study.

Adolescent↗
PubMed2006

Search for the invisible decay of neutrons with KamLAND.

The Kamioka Liquid scintillator Anti-Neutrino Detector is used in a search for single neutron or two-neutron intranuclear disappearance that would produce holes in the -shell energy level of (12)C nuclei. Such holes could be created as a result of nucleon decay into invisible modes (inv), e.g., n--> 3v or nn--> 2v. The deexcitation of the corresponding daughter nucleus results in a sequence of space and time-correlated events observable in the liquid scintillator detector. We report on new limits for one- and two-neutron disappearance: tau(n--> inv) > 5.8 x 10(29) years and tau (nn--> inv) > 1.4 x 10(30) years at 90% C.L. These results represent an improvement of factors of approximately 3 and >10(4) and over previous experiments.

Journal Article↗
PubMed2006

Evaluation of remedial countermeasures using the analytic network process.

The aim of this paper is to present an evaluation method to aid decision makers in the prioritization and selection of appropriate countermeasures at the planning stage of site remediation. We introduced a hierarchical network (hiernet) decision structure and applied the Analytic Network Process (ANP) supermatrix approach to measure the relative desirability of the remedial alternatives using the decision maker's value judgment as input. A simplified illustrative example is presented to elucidate the process, as it is being applied to evaluate the feasible remedial countermeasures of a contaminated site caused by uncontrolled landfill. Four decision models derived from the generalized hiernet were examined to describe the effect of hierarchic functional dependence, inner dependence and feedback cycle on the derivation of the priority weights. The ANP could provide a more flexible analytical framework to break down one's judgment through a more elaborate structure in a systematic way to understand the complexity of the decision problem. The proposed method therefore may not only aid in selecting the best alternative but also may help to facilitate communication to understand why an alternative is preferred over the other alternatives through the analysis of the derived weights and its underlying decision structure.

Conservation of Natural Resources↗
PubMed2006

Resting state glucose utilization and the CERAD cognitive battery in patients with Alzheimer's disease.

The present study examined the cortical functional representation of neuropsychological domains in Alzheimer's disease (AD) using positron emission tomography (PET) and the neuropsychological assessment battery of the Consortium to Establish a Registry of Alzheimer's Disease (CERAD). Thirty patients with clinical probable AD and 10 elderly healthy controls underwent (18)FDG brain PET imaging during a resting state. Correlations between metabolic values and cognitive measures were determined using a region of interest analysis with NEUROSTAT (University of Michigan, USA) and a voxel-based analysis with SPM96 (Wellcome Department, London, UK). Specific correlations were seen between measures of episodic memory, verbal fluency and naming and left hemispheric temporal and prefrontal metabolism. Drawing was correlated with metabolism in left prefrontal and left inferior parietal regions. The presented data support the use of metabolic-cognitive correlations to demonstrate the neuronal substrates of cognitive impairment in AD. Subtests of the CERAD battery give a good representation of left, but not of right hemisphere function in AD.

Aged↗
PubMed2006

Semi-purification of the immunoglobulin E-sweat antigen acting on mast cells and basophils in atopic dermatitis.

BACKGROUND: Sweating aggravates the symptoms of atopic dermatitis (AD). We have recently reported positive skin reactions and histamine release from basophils in response to autologous sweat in patients with AD. OBJECTIVE: To characterize the biochemical and immunological properties of the substance in sweat that evokes histamine release and to study the usability of the basophil-histamine release test with the sweat antigen for AD. METHODS: Sweat collected from healthy volunteers was purified using chromatographies. Serum immunoglobulin (Ig)E of four patients with AD were purified using an affinity-chromatography column with anti-IgE antibodies. The amount of semi-purified sweat antigen (138 ng protein/ml) that induced a half-maximum reaction of basophils of a patient with AD was utilized for the basophil histamine release test. The involvement of specific IgE and high-affinity IgE receptor (FcepsilonRI) in the reactions was examined using basophils of healthy volunteers, a human mast cell line (LAD2), and a rat basophilic leukemia cell line transfected with human alpha-subunit of FcepsilonRI (RBL-48). RESULTS: The semi-purified sweat antigen induced histamine release from the basophils of 47 of 61 (74.6%) patients with AD and four of 46 (8.7%) healthy controls. Both basophils and mast cells sensitized with the patient-derived IgE showed degranulation upon stimulation with the sweat antigen. However, no reaction was observed when cells were sensitized with myeloma IgE or the antigen was treated with proteases. CONCLUSION: The semi-purified standardized sweat antigen consists of a protein that induces degranulation of basophils and mast cells via antigen-specific IgE and FcepsilonRI in patients with AD.

Adolescent↗
PubMed2006

Demonstration of inter- and intracellular distribution of boron and gadolinium using micro-proton-induced X-ray emission (Micro-PIXE).

Micro-proton-induced X-ray emission (Micro-PIXE) was applied to determine inter- and intracellular distribution of boron (10B) and gadolinium (157Gd), the capture atoms used to kill tumor cells in neutron capture therapy (NCT). Cultured 9L gliosarcoma cells on Mylar film were exposed to sodium borocaptate (BSH) and gadobenate dimeglumine (Gd-BOPTA). To analyze the inter- and intracellular distribution of 10B and 157Gd in 9L gliosarcoma cells, the cells were irradiated using a proton beam of 1.7 or 3 MeV energy collimated to 1 microm diameter and emission X-ray was detected. The distribution of 10B and 157Gd in 9L gliosarcoma cells was then examined. In this study, we could directly analyze the inter- and intracellular distribution of 10B and 157Gd elements in 9L gliosarcoma cells directly using Micro-PIXE. This is the first report on the distribution of 10B employing a method to detect gamma-rays resulting from the nuclear reaction of 10B using particle-induced gamma-ray emission (PIGE). These results show that the distribution of 157Gd elements was correctly measured using micro-PIXE. 157Gd should have the same tendency as 10B in cultured 9L gliosarcoma cells and agree with the distribution in 9L gliosarcoma cells. Further investigation is necessary for a higher spatial resolution and optimization of the measurement time or improvement of the sampling method. In the future, it will be possible to employ this method to analyze the intracellular microdistribution of the capture element and in the development of new drugs for NCT.

Boron↗
PubMed2005

Evidence for suppressed screening on the surface of high temperature La(2-x)SrxCuO4 and Nd2(2-x)CexCuO4 superconductors.

Hard x-ray photoemission spectroscopy (PES) of Cu core electronic states, with a probing depth of approximately 60 A, is used to show that the Zhang-Rice singlet feature is present in La2CuO4 but is absent in Nd2CuO4. Hole and electron doping in La(2-x)SrxCuO4 (LSCO) and Nd(2-x)CexCuO4 (NCCO) result in new well-screened features which are missing in soft x-ray PES. Impurity Anderson model calculations establish screening from doped states as its origin, which is strongly suppressed within 15 A of the surface. Complemented with x-ray absorption spectroscopy, the small chemical-potential shift in core levels (approximately 0.2 eV) are shown to be consistent with modifications of valence and conduction band states spanning the band gap (approximately 1 eV) upon hole and electron doping in LSCO and NCCO.

Journal Article↗
PubMed2005

Experimental investigation of geologically produced antineutrinos with KamLAND.

The detection of electron antineutrinos produced by natural radioactivity in the Earth could yield important geophysical information. The Kamioka liquid scintillator antineutrino detector (KamLAND) has the sensitivity to detect electron antineutrinos produced by the decay of 238U and 232Th within the Earth. Earth composition models suggest that the radiogenic power from these isotope decays is 16 TW, approximately half of the total measured heat dissipation rate from the Earth. Here we present results from a search for geoneutrinos with KamLAND. Assuming a Th/U mass concentration ratio of 3.9, the 90 per cent confidence interval for the total number of geoneutrinos detected is 4.5 to 54.2. This result is consistent with the central value of 19 predicted by geophysical models. Although our present data have limited statistical power, they nevertheless provide by direct means an upper limit (60 TW) for the radiogenic power of U and Th in the Earth, a quantity that is currently poorly constrained.

Journal Article↗
PubMed2005

Momentum dependence of charge excitations in the electron-doped superconductor Nd1.85 Ce0.15 CuO4: a resonant inelastic x-ray scattering study.

We report a resonant inelastic x-ray scattering (RIXS) study of charge excitations in the electron-doped high-T(c) superconductor Nd1.85 Ce0.15 CuO4. The intraband and interband excitations across the Fermi energy are separated for the first time by tuning the experimental conditions properly to measure charge excitations at low energy. A dispersion relation with q-dependent width emerges clearly in the intraband excitation, while the intensity of the interband excitation is concentrated around 2 eV near the zone center. The experimental results are consistent with theoretical calculation of the RIXS spectra based on the Hubbard model.

Journal Article↗
PubMed2005

Mott gap excitations in twin-free YBa2Cu3O7-delta (Tc=93 K) studied by resonant inelastic x-ray scattering.

Mott gap excitations in the optimally doped high-T(c) superconductor YBa(2)Cu(3)O(7-delta) (T(c)=93 K) have been studied by the resonant inelastic x-ray scattering method. Anisotropic spectra in the ab plane are observed in a twin-free crystal. The excitation from the one-dimensional CuO chain is enhanced at 2 eV near the zone boundary of the b* direction, while the excitation from the CuO2 plane is broad at 1.5-4 eV and almost independent of the momentum transfer. Theoretical calculations based on the one-dimensional and two-dimensional Hubbard model reproduces the observed spectra when different values of the on-site Coulomb energy are assumed. The Mott gap of the CuO chain site is found to be much smaller than that of the CuO2 plane site.

Journal Article↗
PubMed2005

Observation of the effects of radially sheared electric fields on the suppression of turbulent vortex structures and the associated transverse loss in GAMMA 10.

Vortexlike turbulent structures in hot-ion mode plasmas with several keV are observed in the case with a radially produced weak shear of electric fields E(r). However, a strong E(r) shear formation due to a high ion-confining potential phi(c) production clears up these vortices together with plasma-confinement improvement and disappearance of both drift-wave and turbulencelike Fourier spectral signals. These findings are based on three-time progress in phi(c) in comparison to phi(c) attained 1992-2002. The significant advance of phi(c) is well extended in line with proposed potential-formation physics scalings.

Journal Article↗
PubMed2005

Measurement of neutrino oscillation with KamLAND: evidence of spectral distortion.

We present results of a study of neutrino oscillation based on a 766 ton/year exposure of KamLAND to reactor antineutrinos. We observe 258 nu (e) candidate events with energies above 3.4 MeV compared to 365.2+/-23.7 events expected in the absence of neutrino oscillation. Accounting for 17.8+/-7.3 expected background events, the statistical significance for reactor nu (e) disappearance is 99.998%. The observed energy spectrum disagrees with the expected spectral shape in the absence of neutrino oscillation at 99.6% significance and prefers the distortion expected from nu (e) oscillation effects. A two-neutrino oscillation analysis of the KamLAND data gives Deltam(2)=7.9(+0.6)(-0.5)x10(-5) eV(2). A global analysis of data from KamLAND and solar-neutrino experiments yields Deltam(2)=7.9(+0.6)(-0.5)x10(-5) eV(2) and tan((2)theta=0.40(+0.10)(-0.07), the most precise determination to date.

Journal Article↗
PubMed2005

Early surgery for ruptured cerebral arteriovenous malformations.

Acute surgery on cerebral arteriovenous malformations (AVMs) has seldom been reported or used. We reviewed 49 patients of ages 2 months to 78 years (mean 32.8 years), 32 male (65%) and 17 female (35%), treated acutely (within 4 days of bleed) in Helsinki Neurosurgery during 1997-2002. The following variables were assessed in regards to the outcome (Glasgow outcome score; GOS; 2-3 months after bleed): age, sex, Hunt and Hess Grade (HH), Spetzler-Martin Grade (SMG), location of AVM, size of intraparenchymal haematoma (ICH), and presence of intraventricular haemorrhage (IVH). Most of the patients were in a poor clinical condition on admission (two thirds were HH 4-5). 45 (92%) patients underwent extirpation of AVM and evacuation of ICH, within 4 days after bleed. Over 55% had good functional outcome. GOS correlated significantly with HH (p = 0.001), age (p = 0.006), and IVH (p = 0.049). On the other hand, SMG, location of AVM, and size of haematoma did not significantly predict the outcome. Microneurosurgery with preoperative embolization has made possible the excision of 90% of AVMs. It is our experience that it can be done acute and early, and it saves lives as compared to natural history of cerebral AVMs or late surgery, and accelerates rehabilitation of the patients.

Adolescent↗
PubMed2005

Lateral supraorbital approach as an alternative to the classical pterional approach.

OBJECTIVE: The standard pterional approach has been used to approach aneurysms of the anterior circulation and the basilar tip, suprasellar tumors, cavernous lesions. The senior author (JH) established a lateral supraorbital approach as an alternative to the pterional approach after continuous trial and error. We describe the techniques of this approach based on clinical experiences. METHODS: The lateral supraorbital approach is more subfrontal and anterior than the pterional approach. This approach has been regularly used by the senior author (JH) in the last decade in more than 2000 operations for mostly aneurysms of anterior circulation, but also for tumors of the anterior fossa and parasellar area as well as the sphenoid wing area. RESULTS: This approach can be used to operate on most cases, in which the classical pterional approach would be used. There are almost no craniotomy-related complications with this approach. This approach is not suitable in certain lesions which need to be exposed from a more temporal perspective. CONCLUSION: This approach is simpler, faster, safer and less invasive than the classical pterional approach.

Humans↗
PubMed2005

Subtemporal approach to basilar bifurcation aneurysms: advanced technique and clinical experience.

OBJECTIVE: The surgical treatment of basilar bifurcation aneurysms is challenging, and many of these aneurysms are currently treated by endovascular means. However, the complete closure of the aneurysm by surgical clipping still remains the best and most permanent cure for the aneurysm. The "gold standard", subtemporal approach was established and introduced by Drake and it has been adapted by the senior author Hernesniemi. We describe our present modified technique of this approach based on clinical experience. METHODS: The subtemporal approach to basilar bifurcation aneurysms has been regularly used by the senior author Hernesniemi in recent 15 years in over 200 operations in Kuopio and Helsinki, Finland. RESULTS: This approach is suitable in most basilar bifurcation aneurysms except for those high above the posterior clinoid process. To avoid temporal lobe damage, cerebrospinal fluid drainage is necessary. Benefits of subtemporal approach are short operative and retraction times, and no need for skull base resection. CONCLUSION: The subtemporal approach is simple and safe in experienced hands, and should be considered the standard method to approach most basilar bifurcation aneurysms.

Basilar Artery↗