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Search Results: 1 - 10 of 1072 matches for " Kei Wagatsuma "
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Natural Postoperative Bone Metabolic Changes after Total Knee Arthroplasty Determined by Positron Emission Tomography Scans  [PDF]
Masakazu Kanetaka, Soichiro Kaneko, Kei Wagatsuma, Kenji Ishii, Kimiteru Ito, Shinya Nakamura, Hiroshi Hamaji, Yukimasa Yamato, Yorito Anamizu, Fumiaki Tokimura, Tsuyoshi Miyazaki
Open Journal of Orthopedics (OJO) , 2018, DOI: 10.4236/ojo.2018.812046
Abstract: Artificial joint replacement surgery is the orthopedic procedure of choice to relieve pain, correct joint deformities, and help patients resume everyday activities. However, the detailed mechanisms regulating peri-implant bone remodeling at the bone-prosthesis interface remain elusive. To address this gap in knowledge, we evaluated the natural postoperative course of bone metabolism by using [18F] NaF positron emission tomography (PET)/computed tomography in 57 patients (104 joints) who underwent asymptomatic total knee arthroplasty (TKA). First, we measured total tracer uptake around TKA to determine the total bone metabolism (TBM) and used the ischial tuberosity as the reference tissue for normalization of PET images. Second, we calculated the TBM ratio (TBMR) by dividing the TBM by tracer uptake in the reference tissue. A moderate increase in TBMR was observed 4 - 5 days after implantation, and its intensity reached the maximum on the seventh postoperative day. The TBMR showed no differences until 12 weeks, after which it decreased slowly and returned to the basal levels. The new parameter TBMR and the unique pattern of postoperative metabolic changes in the bone around the prosthesis may help set accurate interpretation criteria to diagnose complications such as loosening or infections.
Measuring Conditions for the Determination of Lead in Iron-Matrix Samples Using Graphite Atomizers with/without a Platform in Graphite Furnace Atomic Absorption Spectrometry  [PDF]
Syun Morimoto, Tetsuya Ashino, Kazuaki Wagatsuma
American Journal of Analytical Chemistry (AJAC) , 2011, DOI: 10.4236/ajac.2011.26081
Abstract: In graphite furnace atomic absorption spectrometry (GF-AAS), the atomization process of lead occurring in graphite atomizers with/without a platform plate was investigated when palladium was added to an iron-matrix sample solution containing trace amounts of lead. Absorption profiles of a lead line were meas- ured at various compositions of iron and palladium. Variations in the gas temperature were also estimated with the progress of atomization, by using a two-line method under the assumption of a Boltzmann distribu- tion. Each addition of iron and palladium increased the lead absorbance in both the atomizers, indicating that iron or palladium became an effective matrix modifier for the determination of lead. Especially, palladium played a significant role for controlling chemical species of lead at the charring stage in the platform-type atomizer, to change several chemical species to a single species and eventually to yield a dominant peak of the lead absorbance at the atomizing stage. Furthermore, the addition of palladium delayed the peak after the gas atmosphere in the atomizer was heated to a higher temperature. These phenomena would be because the temperature of the platform at the charring stage was elevated more slowly compared to that of the furnace wall, and also because a thermally-stable compound, such as a palladium-lead solid solution, was produced by their metallurgical reaction during heating of the charring stage. A platform-type atomizer with palladium as the matrix modifier is recommended for the determination of lead in GF-AAS. The optimum condition for this was obtained in a coexistence of 1.0 × 10–2 g/dm3 palladium, when the charring at 973 K and then the atomizing at 3073 K were conducted.
Molecular Mechanisms for Age-Associated Mitochondrial Deficiency in Skeletal Muscle
Akira Wagatsuma,Kunihiro Sakuma
Journal of Aging Research , 2012, DOI: 10.1155/2012/768304
Abstract: The abundance, morphology, and functional properties of mitochondria decay in skeletal muscle during the process of ageing. Although the precise mechanisms remain to be elucidated, these mechanisms include decreased mitochondrial DNA (mtDNA) repair and mitochondrial biogenesis. Mitochondria possess their own protection system to repair mtDNA damage, which leads to defects of mtDNA-encoded gene expression and respiratory chain complex enzymes. However, mtDNA mutations have shown to be accumulated with age in skeletal muscle. When damaged mitochondria are eliminated by autophagy, mitochondrial biogenesis plays an important role in sustaining energy production and physiological homeostasis. The capacity for mitochondrial biogenesis has shown to decrease with age in skeletal muscle, contributing to progressive mitochondrial deficiency. Understanding how these endogenous systems adapt to altered physiological conditions during the process of ageing will provide a valuable insight into the underlying mechanisms that regulate cellular homeostasis. Here we will summarize the current knowledge about the molecular mechanisms responsible for age-associated mitochondrial deficiency in skeletal muscle. In particular, recent findings on the role of mtDNA repair and mitochondrial biogenesis in maintaining mitochondrial functionality in aged skeletal muscle will be highlighted. 1. Introduction Mitochondria are ubiquitous membrane-bound organelles that are a defining and unique feature of the eukaryotic cell [1]. Mitochondria produce about 90% of the energy necessary for cellular function via oxidative phosphorylation (OXPHOS) [2]. Additionally, mitochondria play central roles in metabolism, signaling, and programmed cell death [3]. Mitochondrial deficiency has been shown in neuromuscular diseases, neurodegenerative diseases, type 2 diabetes, ageing, and sarcopenia [4–8]. During the process of ageing, the abundance, morphology, and functional properties of mitochondria decay in several tissues including skeletal muscle [9–12]. Among all cell types, the skeletal muscle possesses the unique ability to increase metabolic rate nearly 100-fold during the transition form a basal resting state to near-maximal contractile activity [11]. Thus, it is easy to assume that skeletal muscle is profoundly affected by age-associated mitochondrial deficiency. Despite age-associated mitochondrial deficiency being extensively investigated, the precise mechanisms remain to be elucidated. However, these mechanisms include at least decreased mitochondrial DNA (mtDNA) repair, defective
Numerical Study on Nonlinear Sound Propagation for Parametric Array  [PDF]
Kei Fujisawa
Journal of Flow Control, Measurement & Visualization (JFCMV) , 2014, DOI: 10.4236/jfcmv.2014.23014
Abstract: This paper presents the numerical study on the nonlinear sound propagation for the parametric array using the compressible form of Navier-Stokes equations combined with the mass and energy conservation equations and the state equation. These governing equations are solved by finite difference time domain (FDTD) based method. The numerical result is shown for the parametric sound propagation in the near field of the sound source in cylindrical coordinate. The result indicates the generation of low-frequency unsteady beat by the interaction of two frequency sound waves in the near field, which grows to a difference frequency sound in the far field.
Determinants of Health Expenditures: Stylized Facts and a New Signal  [PDF]
Kei Hosoya
Modern Economy (ME) , 2014, DOI: 10.4236/me.2014.513109
Abstract: This article further investigates the determinants of health expenditures by using aggregate data. Specifically, a panel data analysis of 25 OECD countries reveals that under several model specifications, the proxy for population ageing has no effect on health costs in accordance with recent findings. In contrast to this well-known result, an additional estimation conducted to check robustness revealed that the ageing variable becomes positive and significant. The significant effect may provide a new signal for a determinant of health expenditures. This result suggests that ageing is an important factor that cannot be ignored when considering variations in health expenditures.
Seeking a Better Recovery Process from Major Natural Disasters: A Lesson from Several Growth Models with Multiple Equilibria  [PDF]
Kei Hosoya
Theoretical Economics Letters (TEL) , 2017, DOI: 10.4236/tel.2017.75103
Abstract: Based on several existing growth models with multiple steady states, this paper examines economic conditions that enable recovery from major natural disasters. We focus on recovery from the 2011 Great East Japan Earthquake and Tsunami. More concretely, we survey three recently released studies, which indicate that the sense of direction for expectation formation has the potential to play an important role in recovering from large natural disasters. We also find an inference that the big-push development scenarios that traditionally appear in developing economies have a low affinity with disaster reconstruction in developed countries. After a discussion of these equilibrium selections, this paper makes further reference to economic environments needed for a sustainable recovery path toward a superior long-run, steady-state equilibrium. This equilibrium allows interpreting the terminal of a series of recovery programs in our context.
Water Quality Criteria for Water Bodies in Urban Areas and Accompanying Changes in Surrounding and In-Situ Vegetation: Considerations from the Landscape Aspect of Planning Water Recreational Areas  [PDF]
Shigeki Harada, Risa Wagatsuma, Tatsunari Koseki, Toshiaki Aoki, Taisuke Hashimoto
Journal of Water Resource and Protection (JWARP) , 2013, DOI: 10.4236/jwarp.2013.52017
Abstract:

Water bodies in urban areas are important as recreational areas. Thus, management plans that maintain high water quality are quite important. At the Hatadate Water Park adjacent to Miyagi University, water quality parameters such as visibility, COD, TOC, and TN were monitored at a small pond and the inflowing stream from August to December in 2011, and photographs were taken of these sites. Variations in COD and TOC were highly related to changes in the physical appearance, especially changes in vegetation. These findings suggest: 1) the importance of management of vegetation for water quality control; and 2) the importance of collecting photographic records of sites for research purposes of interpreting data and even as a data point of water quality. Together with the water quality goals for water bodies in urban areas proposed by Sudo et al. [1], these water quality criteria were assessed, and it was notable that COD often exceeded the set goal. These results suggest that the maintenance of vegetation is more important than controlling incoming TN for primary production in the pond. Seasonal variations in COD and TOC were plotted for surface water of Kamafusa and Okura dams, both are important lakes in Miyagi area and the catchments of both lakes are mainly hilly area, using published water quality reports. Similar annual-cycle changing patterns were shown both for the dams, implying that some kinds of ecological factors in the catchments are affecting the water qualities of the dam, even at those

Dissolution of Rare Earth Elements from Coal Fly Ash Particles in a Dilute H2SO4 Solvent  [PDF]
Shunsuke Kashiwakura, Yuichi Kumagai, Hiroshi Kubo, Kazuaki Wagatsuma
Open Journal of Physical Chemistry (OJPC) , 2013, DOI: 10.4236/ojpc.2013.32009
Abstract:

Recently, the worldwide supply of rare earth element (REE) resources will be severely restricted. On the other hand, coal fly ash particles emitted from coal-fired electric power plants contain relatively high concentrations of REEs. The contents of REEs in coal fly ash are regularly several hundreds of ppmw. In order to extract and recover REEs from coal fly ash particles, as a first step, we have investigated their dissolution behavior in a dilute H2SO4 solvent. The REE content of coal fly ash specimens has been precisely determined, and their presence in the ash component of the original coal and their enrichment in coal fly ash particles during coal combustion have been suggested. REEs in coal fly ash dissolve gradually in H2SO4 over time, and this implies two types of occurrences of the REEs in coal fly ash particles. By applying the unreacted core model to the dissolution behavior of REEs in a H2SO4 solvent, we can explain both types of occurrences.

Layer-Dependent Attentional Processing by Top-down Signals in a Visual Cortical Microcircuit Model
Nobuhiko Wagatsuma,Tobias C. Potjans
Frontiers in Computational Neuroscience , 2011, DOI: 10.3389/fncom.2011.00031
Abstract: A vast amount of information about the external world continuously flows into the brain, whereas its capacity to process such information is limited. Attention enables the brain to allocate its resources of information processing to selected sensory inputs for reducing its computational load, and effects of attention have been extensively studied in visual information processing. However, how the microcircuit of the visual cortex processes attentional information from higher areas remains largely unknown. Here, we explore the complex interactions between visual inputs and an attentional signal in a computational model of the visual cortical microcircuit. Our model not only successfully accounts for previous experimental observations of attentional effects on visual neuronal responses, but also predicts contrasting differences in the attentional effects of top-down signals between cortical layers: attention to a preferred stimulus of a column enhances neuronal responses of layers 2/3 and 5, the output stations of cortical microcircuits, whereas attention suppresses neuronal responses of layer 4, the input station of cortical microcircuits. We demonstrate that the specific modulation pattern of layer-4 activity, which emerges from inter-laminar synaptic connections, is crucial for a rapid shift of attention to a currently unattended stimulus. Our results suggest that top-down signals act differently on different layers of the cortical microcircuit.
Is Consumption in the United States and Japan Too Much or Too Little?  [PDF]
Yutaka Kurihara, Kei Tomimura
iBusiness (IB) , 2012, DOI: 10.4236/ib.2012.43029
Abstract: This article reports on the results of an empirical examination of whether consumption in the United States and Japan is too much or too little relative to productivity in these countries (1993-2011). Findings reveal some clear and common characteristics of both countries for the sample period. The most typical one occurred during financial crises around 2008, which is often called the Lehman shock. In both countries, consumers had considerably reduced consumption around that period. The IT boom collapse at the beginning of the 2000s also diminished consumption in the United States. This paper examines impulse responses to trace the effect of a productivity shock to one of the innovations on the current and future value of consumption. Findings indicate that the effect of the shock of productivity on consumption is long both countries
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