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Hiroshi Koizumi

Publications and source records attributed to Hiroshi Koizumi.

7 recordsLinked to original sources
PubMed2006

Room-temperature miscibility gap in LixFePO4.

The rechargeable lithium-ion cell is an advanced energy-storage system. However, high cost, safety hazards, and chemical instability prohibit its use in large-scale applications. An alternative cathode material, LiFePO(4), solves these problems, but has a kinetic problem involving strong electron/hole localization. One reason for this is believed to be the limited carrier density in the fixed monovalent Fe(3+)PO(4)/LiFe(2+)PO(4) two-phase electrode reaction in LixFePO4. Here, we provide experimental evidence that LixFePO4, at room temperature, can be described as a mixture of the Fe(3+)/Fe(2+) mixed-valent intermediate LialphaFePO4 and Li1-betaFePO4 phases. Using powder neutron diffraction, the site occupancy numbers for lithium in each phase were refined to be alpha=0.05 and 1-beta=0.89. The corresponding solid solution ranges outside the miscibility gap (0<x<alpha,1-beta<x<1) were detected by the anomaly in the configurational entropy, and also by the deviation of the open-circuit voltage from the constant equilibrium potential. These findings encourage further improvement of this important class of compounds at ambient temperatures.

Journal Article↗
PubMed2006

[A case of recurrent breast cancer with life-threatening multiple lung metastasis markedly responding to CMF as third-line chemotherapy].

A 35-year-old woman with taxane and anthracycline-resistant recurrent breast cancer with multiple lung metastasis and carcinomatous lymphangitis was treated with CMF as third-line chemotherapy. A complete response was achieved,and the toxicities were tolerable. We thought that CMF could be a useful regimen as third-line chemotherapy for metastatic breast cancer.

Adult↗
PubMed2005

Ecosystem development and carbon cycle on a glacier foreland in the high Arctic, Ny-Alesund, Svalbard.

The Arctic terrestrial ecosystem is thought to be extremely susceptible to climate change. However, because of the diverse responses of ecosystem components to change, an overall response of the ecosystem carbon cycle to climate change is still hard to predict. In this review, we focus on several recent studies conducted to clarify the pattern of the carbon cycle on the deglaciated area of Ny-Alesund, Svalbard in the high Arctic. Vegetation cover and soil carbon pools tended to increase with the progress of succession. However, even in the latter stages of succession, the size of the soil carbon pool was much smaller than those reported for the low Arctic tundra. Cryptogams contributed the major proportion of phytomass in the later stages. However, because of water limitation, their net primary production was smaller than that of the vascular plants. The compartment model that incorporated major carbon pools and flows suggested that the ecosystem of the later stages is likely to be a net sink of carbon at least for the summer season. Based on the eco-physiological characteristics of the major ecosystem components, we suggest several possible scenarios of future changes in the ecosystem carbon cycle.

Arctic Regions↗
PubMed2005

[A case of primary small intestinal cancer accompanied by virchow lymph node metastasis undergoing TS-1 treatment].

A 72-year-old female was admitted to our hospital with the complaint of left neck lymph node swelling. Abdominal computed tomography (CT) revealed wall thickening of the small intestine and multiple lymph node metastases. Barium meal study of the small intestine showed circular stenosis. The patient was operated on under a diagnosis of tumor of the small intestine and left neck lymph node swelling. Needle biopsy of the left neck lymph node and partial resection of the small intestine was done without regional lymph node dissection because of Virchow lymph node metastasis. On the resected material a 5 x 4 cm type 2 tumor was identified. Pathological findings included poorly-differentiated adenocarcinoma, si (bladder), n 4, P 0, ly 3, v 3, H 0, M(-), Stage IV. The patient received the chemotherapy with TS-1. TS-1(80 mg/body/day) orally administered for 4 weeks followed by a drug-free 2-week period as one course. CT revealed that the metastatic lesion had shrunk markedly after the second course. A complete response (CR) was observed after one year. There were no drug side effects. At present, 3 years and 9 months after the operation, cervical and abdominal CT reveals no evidence of enlargement of the cervical and intraperitoneal lymph nodes.

Adenocarcinoma↗
PubMed2003

Leaf display and photosynthesis of tree seedlings in a cool-temperate deciduous broadleaf forest understorey.

To examine a possible convergence in leaf photosynthetic characteristics and leaf display responses to light environment in seedlings of three canopy and two shrub tree species in understorey of cool-temperate deciduous broadleaf forest, relationships between light environment, leaf orientation and leaf light-photosynthetic response were measured. Light capture of the seedlings (17-24 individuals with 2-12 leaves for each species) was assessed with a three dimensional geometric modeling program Y-plant. Leaf photosynthetic characteristics of the five species were found to have acclimated to the understorey light environment, i.e., low light compensation point and high apparent quantum yield. In addition, light-saturated photosynthetic rates were higher in seedlings inhabiting microsites with higher light availability. Efficiencies of light capture and carbon gain of the leaf display were evaluated by simulating the directionalities of light capture and daily photosynthesis for each seedling using hemispherical canopy photography. The results showed that most of the seedlings orientated their leaves in a way to increase the daily photosynthesis during the direct light periods (sunflecks) rather than maximize daily photosynthesis by diffuse light. Simulations also showed that daily photosynthesis would increase only 10% of that on actual leaf display when the leaves orientated to maximize the diffuse light interception. Simulations in which leaf orientations were varied showed that when the leaf display fully maximized direct light interception, the time that leaves were exposed to excessive photon flux density of >800 mumol photons m(-2) s(-1) were doubled. The understorey seedlings studied responded to the given light environments in a way to maximize the efficiency of acquisition and use of light during their short (approximately 3 month) seasonal growth period.

Computer Simulation↗
PubMed2002

Effects of light and soil water availability on leaf photosynthesis and growth of Arisaema heterophyllum, a riparian forest understorey plant.

The effects of soil-water availability on leaf light acclimation and whole-plant carbon gain were examined in Arisaema heterophyllum Blume, a riparian deciduous forest understorey plant. Photosynthesis, above-ground morphology and ramet biomass accumulation (relative growth rate: RGR of a corm for a full leaf life-span) were measured on plants raised under three light treatments combined with two soil water conditions. The two higher light treatments during growth (high: max. 550 micro mol photons m(-2) s(-1); medium: 150 micro mol photons m(-2) s(-1)) resulted in a twofold increase in RGRs, 30% higher photosynthetic capacities and 20% less photosynthetic low-light use efficiency than those under a low light condition (50 micro mol photons m(-2) s(-1)). Leaf area was the smallest and leaf mass area ratio was the largest under the high light treatment. Water stress decreased both photosynthetic rate and leaf area and, hence, RGR in all the light regimes. However, water stress did not alter the general patterns of physiological and morphological responses to different light regimes. We estimated that higher photosynthetic low-light use efficiency and larger leaf area in the low light leaf would lead to a threefold carbon gain as compared with the high light leaf under simulated low light conditions. Both experimental and simulation results suggest that the physiological and morphological acclimations tend to be beneficial to carbon gain when light availability is low, whereas they favor increased water use efficiency when light availability is sufficiently high.

Journal Article↗