Koji Iwata

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David Pierre Leibovitz

Carleton University

Anna M. Czarnecka

Medical University of Warsaw

Keith Laws

University of Hertfordshire

José María Ruiz-Sánchez de León

Universidad Complutense de Madrid

Peixin Dong

Hokkaido University

Kastytis Šmigelskas

Lithuanian University of Health Sciences

Kenneth Marcu

SUNY: Stony Brook University

Philippos Gourzis

University of Patras

Martin Hunter

Tufts University

Lüder Deecke

Medical University of Vienna

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Papers by Koji Iwata

<title>Energy-dependent quantum detective efficiency (QDE) measurements of a photon-counting CdTe detector array used for the scanning-beam digital x-ray (SBDX) system</title>

Medical Imaging 2003: Physics of Medical Imaging, 2003

The Scanning-Beam Digital X-ray (SBDX) system utilizes a scanning x-ray pencil beam and a small-a... more The Scanning-Beam Digital X-ray (SBDX) system utilizes a scanning x-ray pencil beam and a small-area detector array for low-dose cardiac angiography with tomographic imaging capabilities. For the system to provide adequate signal-to-noise ratios, the multi-element detector must be highly efficient and capable of high photon count rates. Cadmium telluride (CdTe) is well suited to these purposes. The CdTe SBDX detector

Microparticle generation during in vitro platelet activation by anti-CD9 murine monoclonal antibodies

Thrombosis Research, 1991

We used flow cytometry and two anti-CD9 murine monoclonal antibodies (NNKY1-19, MALL13) to invest... more We used flow cytometry and two anti-CD9 murine monoclonal antibodies (NNKY1-19, MALL13) to investigate the glycoprotein composition and the potential functions of microparticles (MP) released by platelets exposed to these antibodies in vitro. NNKY1-19 produced aggregation with characteristics similar to those noted in previous reports. The action of MALL13 on platelets in platelet-rich plasma (PRP), however, differs from that of other anti-CD9 antibodies. The normal fluctuation in the MALL13-induced change in optical density disappeared when complement was present. MALL13-induced effect for platelet in PRP was not inhibited by preincubation with monoclonal anti-GPIIb/IIIa antibody, but was inhibited in washed platelets (WP). Furthermore, following MALL13 stimulation in PRP platelets, the amount of buffer LDH markedly increased and electron microscopy findings showed vacuoles appearing inside the platelets. These results suggest that MALL13 has at least two effects on platelets that differ for PRP platelets and WP. The number of MP released was increased by the addition of anti-CD9 antibodies. MP surfaces were found to be rich in CD9 protein. MALL13 stimulation lead to a significant increase in the binding of C1q and C3 to platelets and caused the production of MP to occur more rapidly than it did the exposure of fibrinogen binding sites in the presence of complement. The analysis of the relationship of MP to anti-CD9 monoclonal antibody may be useful in the investigation of the relationship between platelet function and coagulation regulation.

Effects of ticlopidine on monoclonal anti-CD9 antibody-induced platelet aggregation and microparticle generation

Thrombosis Research, 1992

We analyzed the effects of ticlopidine on platelet aggregation and on microparticle (MP) formatio... more We analyzed the effects of ticlopidine on platelet aggregation and on microparticle (MP) formation when platelets were exposed to a monoclonal anti-CD9 antibody (NNKY1-19) in vitro. Even when NNKY1-19-induced platelet aggregation was completely inhibited by preincubation with anti-GPIIb/IIIa antibody or Arg-Gly-Asp-Ser, or by using washed platelets from a Glanzmann&#39;s thrombasthenia patient, the formation of MP was still observed. Prostaglandin E1 and protein kinase C antagonists (H-7 and staurosporine) inhibited both NNKY1-19-induced aggregation and MP formation. Ticlopidine or aspirin plus apyrase scarcely affected NNKY1-19-induced platelet aggregation, except to prolong the lag time. However, ticlopidine significantly inhibited MP formation (p less than 0.01). These results suggest that ticlopidine inhibits NNKY1-19-induced MP formation by a different mechanism to that of the other antagonists, and that this mechanism is unrelated to the inhibition of platelet aggregation.

Effects of Alteplase, a Thrombolytic Agent, in a Rat Photothrombotic Middle Cerebral Artery Occlusion Model

Pathophysiology of Haemostasis and Thrombosis, 2007

In this study, we examined the effects of alteplase, a recombinant tissue-type plasminogen activa... more In this study, we examined the effects of alteplase, a recombinant tissue-type plasminogen activator (t-PA), in a simple and reproducible rat middle cerebral artery (MCA) occlusion model induced by photoillumination with 12 mg/kg of rose bengal. A clinically equivalent dose of alteplase (3 mg/kg), which was administered just after thrombotic occlusion of the MCA, significantly reopened the thrombotic MCA occlusion in 16 of 23 animals (69.6%) when compared with vehicle-treated animals (8 of 22 animals, 36.4%). In addition, alteplase significantly reduced cerebral damage and improved neurological deficits. Although it has been reported that t-PA possesses neurotoxicity, the present findings suggest that alteplase was effective in a rat acute stroke model due to reopening of thrombotic MCA occlusion. This new model is very useful for investigating the efficacy of thrombolytic agents in stroke research, providing a condition similar to the clinical setting.

Advanced creep-fatigue evaluation rule for fast breeder reactor components: generalization of elastic follow-up model

Nuclear Engineering and Design, 1995

High temperature operative conditions of fast breeder reactors (FBRs) cause plastic and creep def... more High temperature operative conditions of fast breeder reactors (FBRs) cause plastic and creep deformations of structures, which lead to the magnification of the creep-fatigue damage of the materials. To take these effects into account, a structural design code for the Japanese prototype FBR "Monju" has adopted an elastic follow-up model. The elastic follow-up model shows a potential for expressing both the plastic and creep behaviors of structures. However, this model has weaknesses which mean that it cannot be used to treat material properties quantitatively and also cannot be adaptive to the existence of stress redistributions. Consequently, we have generalized the elastic follow-up model, by introducing the following concepts: (1) an elastic follow-up model using a power law, for the purpose of the quantitative evaluation of material properties; (2) combined elastic follow-up models, for consideration of stress redistributions; (3) an equivalent elastic follow-up model of Neuber's rule. By applying the generalized elastic follow-up model to structural discontinuity portions, we proposed an advanced creep-fatigue evaluation rule based on elastic analysis. The proposed method is verified through structural strength tests and inelastic finite element calculations. As a result, the design stresses are raised significantly compared with those of the structural design code for "Monju".

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Molecular Sieving Silica Overlayer on γ-Alumina: The Structure and Acidity Controlled by the Template Molecule

Langmuir, 1998

A silica overlayer was prepared on γ-alumina by a method of chemical vapor deposition (CVD) of si... more A silica overlayer was prepared on γ-alumina by a method of chemical vapor deposition (CVD) of silicon alkoxide using preadsorbed benzaldehyde and R-naphthaldehyde as a template. Infrared spectroscopy confirmed that the preadsorbed benzoate anion species remained after the deposition of silica, indicating that silica was deposited on the exposed surface of alumina. On the basis of the adsorption property of modified alumina, it is considered that the silica overlayer had a vacancy whose size was as large as the template molecule. Si NMR spectroscopy showed that the Si species deposited using the template was Si(OAl)1(OSi)1(OH)2 or Si(OAl)2(OSi)1(OH)1, while the deposition without the template formed such a species as Si(OAl)1(OSi)3 and Si(OAl)1(OSi)2(OH)1 bonded via a two-dimensional siloxane network. Lack of activity for double-bond isomerization of 1-butene to 2-butene on the silica overlayer prepared using the template was consistent with the previous results that the two-dimensional network of siloxane on the alumina surface induced Brønsted acidity on the Al-O-Si-OH species. Both the adsorption and acidic properties on silica-deposited alumina using R-naphthaldehyde were different from those on the sample prepared using benzaldehyde, showing that the structure of the silica overlayer was controlled by the template molecules. * Corresponding author. Phone and

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Flow-Induced Vibration of Bluff Bodies. Evaluation of Turbulence-Induced Vibration of a Circular Cylinder in Supercritical Reynolds Number Flow

JSME International Journal Series B, 2001

Experiments have been conducted on turbulence-induced vibration of a circular cylinder in water f... more Experiments have been conducted on turbulence-induced vibration of a circular cylinder in water flow with supercritical Reynolds number ranging from 3×105 to 3×106. Based on the power spectral density of cylinder vibrations measured at several Reynolds numbers, fluctuating force coefficients, Strouhal number and correlation length were evaluated. As a result, it was clarified that the prediction method based on the

Addition of serum from patients with collagen diseases increases to cultured human endothelial cells production and release of von willebrand factor

American Journal of Hematology, 1993

The addition of sera from patients with collagen diseases, particularly those with vascular compl... more The addition of sera from patients with collagen diseases, particularly those with vascular complications, to the supernatant of cultured vascular endothellal cells (EC) In vltro significantly Increased the surface and intraceliular amounts of von Wlllebrand factor antigen (vWF:Ag) compared with results obtained with sera from normal healthy subjects. Peak levels of vWF:Ag occurred after 24 h of in vltro culture. Moreover, the amounts of vWF:Ag secreted Into the EC supernatant with patient serum added were significantly higher than the amounts secreted into EC supernatant with control serum added, even after 48 h of In vltro culture.

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Scintillator energy and flux linearity for RbGd2Br7:Ce, LaCl3:Ce, and LaBr3:Ce

The development of scintillator detectors made of dense ionic crystals with high light output and... more The development of scintillator detectors made of dense ionic crystals with high light output and fast response times offers to improve radiation detection systems commonly employed in medical imaging. Three such cerium doped materials, rubidium gadolinium bromide (RbGd2Br7:Ce), lanthanum chloride (LaCl3:Ce), and lanthanum bromide (LaBr3:Ce) show promise as bright, fast scintillators with good energy resolution for gamma rays. To be

Search for Nuclearites using TLS Detector at Sea Level

Nuclear Physics B - Proceedings Supplements, 2006

It is shown that a thermoluminescent sheet stack (TLS) detector, consisting of TL sheets and medi... more It is shown that a thermoluminescent sheet stack (TLS) detector, consisting of TL sheets and medical x-ray films, is an effective nuclearite detector. The TLS can be used for searching lighter nuclearites at sea level owing to the fact that the usual relativistic particles cannot make their tracks in the TLS unless they have a charge of larger than 50. We will report recent results of searching for lighter nuclearites at sea level.

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Dual-modality imaging

Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2001

In comparison to conventional medical imaging techniques, dual-modality imaging offers the advant... more In comparison to conventional medical imaging techniques, dual-modality imaging offers the advantage of correlating anatomical information from X-ray computed tomography (CT) with functional measurements from single-photon emission computed tomography (SPECT) or with positron emission tomography (PET). The combined X-ray/radionuclide images from dual-modality imaging can help the clinician to differentiate disease from normal uptake of radiopharmaceuticals, and to improve diagnosis and

Positron annihilation on large molecules

Physical Review A, 2000

Positron annihilation on molecules is known to depend sensitively on molecular structure. For exa... more Positron annihilation on molecules is known to depend sensitively on molecular structure. For example, in the case of hydrocarbon molecules, modest changes in molecular size produce orders of magnitude changes in the observed annihilation rates. Although this process has been studied for more than three decades, many open questions remain. Experimental studies are described which are designed to test specific

γ-ray spectra from positron annihilation on atoms and molecules

Physical Review A, 1997

γ-ray spectra from positron annihilation on atoms and molecules. Koji Iwata, RG Greaves, and CM S... more

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Effects of in-plane magnetic field direction on the nuclear-spin relaxation in the quantum Hall state

Physica E: Low-dimensional Systems and Nanostructures, 2008

ABSTRACT We investigated effects of the direction of in-plane magnetic field B∥ on the phase tran... more ABSTRACT We investigated effects of the direction of in-plane magnetic field B∥ on the phase transition in the quantum Hall ferromagnet at Landau-level filling factor ν=23 by the nuclear-spin relaxation measurements. We controlled the angle φ between the direction of B∥ and a current I; when B∥ is parallel (perpendicular) to I, φ=0∘(φ=90∘). We found that the nuclear spin relaxation rate T1-1 at φ=0∘ is about twice as much as that at φ=90∘. We discuss the anisotropic behavior of T1-1 in term of a suppression of low-frequency electron spin fluctuations by B∥ at φ=90∘.

CdZnTe detector for combined X-ray CT and SPECT

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1999

A medical imaging system providing both X-ray transmission and radionuclide measurements would al... more A medical imaging system providing both X-ray transmission and radionuclide measurements would allow correlation of structural and functional information. We therefore are evaluating a pixellated CdZnTe detector for combined X-ray computed tomography (CT) and single photon emission computed tomography (SPECT) imaging. Gamma-ray spectra of 57Co measured using NIM electronics (2μs shaping time) and multichannel fast photon-counting electronics (50ns shaping time) produced energy resolutions of 6.5keV FWHM and 17keV FWHM, respectively, at 122keV. Fast photon-counting electronics achieved linear X-ray count-rate response up to 4×105cps in comparison to 1.5×108cps achieved with digital readout electronics based on a variable rate ΣΔ ADC in current mode. Results suggest that the CdZnTe detector is capable of performing both X-ray CT and SPECT with the fast photon-counting electronics, and X-ray CT in current mode with the digital readout electronics.

A single CdZnTe detector for simultaneous CT/SPECT imaging

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2003

Clinical CT/SPECT systems acquire CT and SPECT data sequentially using different detectors in clo... more Clinical CT/SPECT systems acquire CT and SPECT data sequentially using different detectors in close proximity to minimise patient movement and interscan delay. We have developed a prototype simultaneous CT/SPECT imager, using a single CdZnTe detector, with the goal of improving image coregistration and decreasing scan time. A 16-pixel CdZnTe detector was operated in pulse-counting mode with 50ns shaping time. Energy

Annihilation in low-energy positron - helium scattering

Journal of Physics B: Atomic, Molecular and Optical Physics, 1996

ABSTRACT

An ultra high resolution ECG-gated myocardial imaging system for small animals

IEEE Transactions on Nuclear Science, 1999

Standard radionuclide imaging systems are of limited use due to their inability to resolve struct... more

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Ab initio study of surface structural changes during methanol synthesis over Zn/Cu(111)

Chemical Physics Letters, 1999

We have studied the adsorption state of formate on clean and Zn-deposited Cu 111 surfaces by usin... more We have studied the adsorption state of formate on clean and Zn-deposited Cu 111 surfaces by using a DFT-GGA-Ž . pseudopotential method. We show that, although the deposited Zn alone is substitutionally adsorbed on the Cu 111 surface, the formate stabilizes the Zn atom sitting on the Cu surface and forms a tilted bidentate formate bound to the Zn and Cu atoms. Our results suggest that the adsorption state of Zn changes from the substitutional to on-surface adsorption by co-adsorption with the formate. q

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Design and utility of a small animal CT/SPECT system

… Record, 2001 IEEE, 2002

Design and Utility of a Small Animal CT/SPECT System Koji Iwata, Andrew B. Hwang, Max C. Wu, H. R... more

<title>Energy-dependent quantum detective efficiency (QDE) measurements of a photon-counting CdTe detector array used for the scanning-beam digital x-ray (SBDX) system</title>

Medical Imaging 2003: Physics of Medical Imaging, 2003