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Search Results: 1 - 10 of 19285 matches for " Ricardo;Kitajima "
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A Method for Finding Optimal Parameter Values Using Bifurcation-Based Procedure  [PDF]
Hiroyuki Kitajima, Tetsuya Yoshinaga
International Journal of Modern Nonlinear Theory and Application (IJMNTA) , 2014, DOI: 10.4236/ijmnta.2014.32006

In dynamical systems, the system suddenly becomes unstable due to parameter perturbation which corresponds to environmental changes or major incidents. To avoid such instabilities in engineering systems, tuning system parameters is very important. In this paper, we propose a method for obtaining optimal parameter values in a parameterized dynamical system. Here, the optimal value means the farthest point from the bifurcation curves in a bounded parameter plane. As illustrated examples, we show the results of continuous-time and discrete-time systems. Our algorithm can find the optimal parameter values in both systems.

Suppression of Methane Gas Emissions and Analysis of the Electrode Microbial Community in a Sediment-Based Bio-Electrochemical System  [PDF]
Yoshiyuki Ueno, Yoji Kitajima
Advances in Microbiology (AiM) , 2014, DOI: 10.4236/aim.2014.45032

The effects of bioelectrochemical systems (BESs) for the suppression of methane gas emissions from sediment were examined using a laboratory-scale reactor system. Methane gas emissions from acetate were suppressed by approximately 36% from control based on the installation of a BES in which carbon-graphite electrodes were buried in sediment and arbitrarily set at certain oxidative potentials (+300 mV vs Ag/AgCl) using a potentiostat. Meanwhile, methane gas emissions increased in the BES reactor where the electrode potential was set at -200 mV. Results obtained from pyrotag sequencing analysis of the microbial community on the surface of the buried electrodes targeting 16S rRNA genes demonstrated that the genusGeobacterhad drastically propagated in a sample from the reactor where the electrodes were buried. Quantitative analysis of 16S rRNA genes of archaea also revealed that the archaeal population had decreased to approximately 1/6 of its original level on the electrode of the BES set at +300 mV. This implied that the oxidation-reduction potential (ORP) in the sediment was raised to the inhibition level for methanogenesis in the vicinity of the buried electrode. Analysis of electron flux in the experiment revealed that electrons intrinsically used for methanogenesis were recovered via current generation in the sediment where a potential of +300 mV was set for the electrode, although most electrons donated from acetate were captured by oxygen respiration and other electron-accepting reactions. These results imply that BES technology is suitable for use as a tool for controlling re-dox-dependent reactions in natural environments, and that it also brought about changes in the microbial population structure and methanogenic activity in sediment.

Viróides e virusóides: relíquias do mundo de RNA
Eiras, Marcelo;Daròs, Jose Antonio;Flores, Ricardo;Kitajima, Elliot W.;
Fitopatologia Brasileira , 2006, DOI: 10.1590/S0100-41582006000300001
Abstract: by the middle of the last century, viruses were considered as the simplest biological entities. the discovery of satellite rnas and viroids by 1970 was surprising because it revealed the existence of a novel class of self-replicating molecules even simpler, named subviral agents. there are evidences that viroids and virusoids (a class of satellite rnas) were part of the so-called "rna world" (that preceded our present world based on dna and proteins) and for this reason they can be considered as molecular fossils of this ancient period. the simplicity of these subviral agents and the fact that the rna molecule must interact directly with host factors for completing their infective cycle make these pathogens a model for the study of cellular processes. in the last years, a large number of publications have widened our knowledge of the viroid-host interactions, including pathogenesis mechanisms, movement through the host, gene silencing and ribozyme activity. recent changes have been introduced in the taxonomy of these pathogens, with the creation of families, genera and species, and new viroids have also been found. the purpose of this review is to present the reader with these recent advances in viroid research, mainly on taxonomy, phylogeny and in molecular aspects of the viroid-host interaction. some characteristics of virusoids and their evolutionary relationship with viroids are also included.
Citrus exocortis viroid and Hop Stunt viroid Doubly infecting grapevines in Brazil
Eiras, Marcelo;Targon, Maria Luisa P.N.;Fajardo, Thor V.M.;Flores, Ricardo;Kitajima, Elliot W.;
Fitopatologia Brasileira , 2006, DOI: 10.1590/S0100-41582006000500002
Abstract: viroids, non-protein-coding small (246-401 nt) circular single-stranded rnas with autonomous replication, are currently classified into two families. within the family pospiviroidae, citrus exocortis viroid (cevd) belongs to the genus pospiviroid while hop stunt viroid (hsvd) is the single member of the genus hostuviroid. these pathogens are distributed worldwide and infect a large number of hosts. in brazil, isolates of cevd and hsvd have been detected in both citrus and grapevine. to characterize and study the genetic variability of these viroids, total rna from leaves of grapevine vitis vinifera 'cabernet sauvignon' and v. labrusca 'niagara rosada' from bento gon?alves, rs, was used as a template for rt-pcr amplification with specific primers for the five viroids described infecting grapevines [hsvd, cevd, grapevine yellow speckle viroid 1 (gysvd-1), grapevine yellow speckle viroid 2 (gysvd-2) and australian grapevine viroid (agvd)]. leaf samples of citrus medica infected with cevd from s?o paulo were also analyzed. the resulting products were separated by agarose gel electrophoresis and dna fragments of the expected size were eluted, cloned and sequenced. the grapevine samples analyzed were doubly infected by cevd and hsvd. a phylogenetic analysis showed that the brazilian grapevine hsvd variants clustered with other grapevine hsvd variants, forming a specific group separated from citrus variants, whereas the brazilian cevd variants clustered with other citrus and grapevine variants.
The Critical Impact of HIF-1a on Gastric Cancer Biology
Yoshihiko Kitajima,Kohji Miyazaki
Cancers , 2013, DOI: 10.3390/cancers5010015
Abstract: Hypoxia inducible factor-1 (HIF-1) monitors the cellular response to the oxygen levels in solid tumors. Under hypoxia conditions, HIF-1a protein is stabilized and forms a heterodimer with the HIF-1β subunit. The HIF-1 complex activates the transcription of numerous target genes in order to adapt the hypoxic environment in human cancer cells. In gastric cancer patients, HIF-1a activation following extended hypoxia strongly correlates with an aggressive tumor phenotype and a poor prognosis. HIF-1a activation has been also reported to occur via hypoxia-independent mechanisms such as PI3K/AKT/mTOR signaling and ROS production. This article argues for the critical roles of HIF-1a in glucose metabolism, carcinogenesis, angiogenesis, invasion, metastasis, cell survival and chemoresistance, focusing on gastric cancer.
Multicanonical Sampling of Rare Trajectories in Chaotic Dynamical Systems
Akimasa Kitajima,Yukito Iba
Physics , 2010, DOI: 10.1016/j.cpc.2010.07.044
Abstract: In chaotic dynamical systems, a number of rare trajectories with low level of chaoticity are embedded in chaotic sea, while extraordinary unstable trajectories can exist even in weakly chaotic regions. In this study, a quantitative method for searching these rare trajectories is developed; the method is based on multicanonical Monte Carlo and can estimate the probability of initial conditions that lead to trajectory fragments of a given level of chaoticity. The proposed method is successfully tested with four-dimensional coupled standard maps, where probabilities as small as $10^{-14}$ are estimated.
Reconstructing Bohr's Reply to EPR in Algebraic Quantum Theory
Masanao Ozawa,Yuichiro Kitajima
Physics , 2011, DOI: 10.1007/s10701-011-9615-7
Abstract: Halvorson and Clifton have given a mathematical reconstruction of Bohr's reply to Einstein, Podolsky and Rosen (EPR), and argued that this reply is dictated by the two requirements of classicality and objectivity for the description of experimental data, by proving consistency between their objectivity requirement and a contextualized version of the EPR reality criterion which had been introduced by Howard in his earlier analysis of Bohr's reply. In the present paper, we generalize the above consistency theorem, with a rather elementary proof, to a general formulation of EPR states applicable to both non-relativistic quantum mechanics and algebraic quantum field theory; and we clarify the elements of reality in EPR states in terms of Bohr's requirements of classicality and objectivity, in a general formulation of algebraic quantum theory.
Primeiro relato do Tomato spotted wilt virus (TSWV) em Campanula medium L. no Brasil
Gioria, Ricardo;Brunelli, Kátia Regiane;Kobori, Romulo Fujito;Kobori, Márcia Maria Rabelo Guimar?es;Rezende, Jorge Alberto Marques;Kitajima, Elliot Watanabe;
Summa Phytopathologica , 2010, DOI: 10.1590/S0100-54052010000200015
Abstract: plants of bellflower (campanula medium) exhibiting symptoms of mosaic, leaf necrosis and flower ring spot were found in a commercial crop in a greenhouse in atibaia, s?o paulo state. electron microscopy, serology and biological assays indicated the presence of tomato spotted wilt virus (tswv). this is the first report of this pathogen in bellflower plants in brazil.
Happiness and heart rate response: a case of fan services at japanese professional baseball games  [PDF]
Kohzoh Yoshino, Sayaka Matsumoto, Eiichi Someya, Muneo Kitajima
Natural Science (NS) , 2011, DOI: 10.4236/ns.2011.33032
Abstract: The aim of this study was to develop a method for predicting the psychological states of spectators watching professional baseball games at a stadium. This method includes a real time measurement of instantaneous heart rate (i.e., the inverse of the RR interval) without preventing the subject from watching the game and a mathematical procedure used to predict moment by moment psychological states by correlating the degree of a psychological state with the strength of heart rate response, defined as the mean deviation of heart rate variability from a linear regression line from 5 sec before to 25 sec after an event during a baseball game. We recorded the instantaneous heart rates of 10 subjects (total of 27 cases) while they watched Japanese professional baseball games at a stadium and had them subjectively rate the degree of their psychological states in an after-event interview. We identified three psychological states (happiness, excitement, and vigor) whose strength can be predicted from the strength of heart rate response. Analysis of the measured data clarified that heart rate response had a significant correlation with the subjective rating of the intensity of happiness (r = 0.56, p < 0.0001), vigor (r = 0.55, p < 0.0001), and excitement (r = 0.49, p < 0.0001).
A Comt1 Loss of Function Mutation Is Insufficient for Loss of Pungency in Capsicum  [PDF]
Sota Koeda, Kosuke Sato, Yuri Tanaka, Rihito Takisawa, Akira Kitajima
American Journal of Plant Sciences (AJPS) , 2015, DOI: 10.4236/ajps.2015.68127
Abstract: The participation of O-methyltransferase (COMT) in phenylpropanoid-mediated capsaicinoid biosynthesis has long been proposed. Ferulic acid, a phenylpropanoid intermediate, is a precursor of capsaicinoid biosynthesis and is produced from caffeic acid by the action of COMT. As previously reported that silencing Comt expression caused a drastic decrease in capsaicinoid accumulation, it was presumed that a Comt loss-of-function mutation would cause loss of pungency in Capsicum. This hypothesis was tested by cloning Comt1 and Comt2 from the placenta tissue of the pungent cultivar Habanero. The phylogenetic analysis and comparison of critical amino-acid residues for enzyme function showed that the two COMTs had high similarity with the COMTs of other plant species. Moreover, as the two Comts were both expressed in placenta tissue and expressed prior to the accumulation of capsaicinoids, the two genes could be candidates for capsaicinoid biosynthesis. Second, Comt1 loss-of-function mutants were screened from the germplasm. A truncated Comt1 transcript was expressed in non-pungent pepper No.3341 caused by deletion of the genomic region. The predicted No.3341 COMT1 lacked His-265, which was absolutely necessary for enzymatic activity. Contrary to our expectations, the Comt1 mutation was not related to non-pungency of No.3341, as the deletion of Comt1 did not co-segregate with non-pungency in the F2 population obtained from crossing No.3341 with Habanero. This result was confirmed by screening several pungent accessions harboring the same Comt
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