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Search Results: 1 - 10 of 402358 matches for " M. Okada "
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Supersymmetric minimal B-L model at the TeV scale with right-handed Majorana neutrino dark matter
Zachary M. Burell,Nobuchika Okada
Physics , 2011, DOI: 10.1103/PhysRevD.85.055011
Abstract: We propose a supersymmetric extension of the minimal $B-L$ model where we consider a new $Z_2$-parity under which one right-handed neutrino is assigned odd parity. When the Majorana Yukawa coupling of a $Z_2$-even right-handed neutrino is large, radiative corrections will drive the mass squared of the corresponding right-handed sneutrino to negative values, breaking the $B-L$ gauge symmetry at the TeV scale in a natural way. Additionally, R-parity is broken and thus the conventional supersymmetric dark matter candidate, the neutralino, is no longer viable. Thanks to the $Z_2$-parity, the $Z_2$-odd right-handed neutrino remains a stable dark matter candidate even in the presence of R-parity violation. We demonstrate that the dark matter relic abundance with an enhanced annihilation cross section by the $B-L$ gauge boson (Z') resonance is in accord with the current observations. Therefore, it follows that the mass of this dark matter particle is close to half of the Z' boson mass. If the Z' boson is discovered at the Large Hadron Collider, it will give rise to novel probes of dark matter: The observed Z' boson mass will delineate a narrow range of allowed dark matter mass. If the Z' boson decays to a pair of dark matter particles, a precise measurement of the invisible decay width can reveal the existence of the dark matter particle.
Friendship Motivation, Aggression, and Self-Esteem in Japanese Undergraduate Students  [PDF]
Ryo Okada
Psychology (PSYCH) , 2012, DOI: 10.4236/psych.2012.31002
Abstract: The purpose of this study was to examine the relationship among self-determined friendship motivation (motivation for friendship formation), aggression, and self-esteem in a sample of 262 Japanese university students. The hypothetical model posited that self-determined friendship motivation predicted lower levels of aggression, which, in turn, predicted lower levels of self-esteem. The results showed that self-determined friendship motivation predicted lower levels of anger, hostility, and physical aggression and that hostility and anger predicted lower levels of self-esteem. Verbal aggression was found to be positively associated with self-determined friendship motivation and self-esteem. The different relationships between self-determined friendship motivation and each facet of aggression are discussed.
Severe brain atrophy in the elderly as a risk factor for lower respiratory tract infection
Okada R, Okada T, Okada A, Muramoto H, Katsuno M, Sobue G, Hamajima N
Clinical Interventions in Aging , 2012, DOI: http://dx.doi.org/10.2147/CIA.S36289
Abstract: e brain atrophy in the elderly as a risk factor for lower respiratory tract infection Original Research (1207) Total Article Views Authors: Okada R, Okada T, Okada A, Muramoto H, Katsuno M, Sobue G, Hamajima N Published Date November 2012 Volume 2012:7 Pages 481 - 487 DOI: http://dx.doi.org/10.2147/CIA.S36289 Received: 23 July 2012 Accepted: 25 September 2012 Published: 12 November 2012 Rieko Okada,1 Takashi Okada,2 Akira Okada,2 Hideyuki Muramoto,3 Masahisa Katsuno,4 Gen Sobue,4 Nobuyuki Hamajima1 1Department of Preventive Medicine, Nagoya University Graduate School of Medicine, 2Okada Medical Clinic, 3Muramoto Clinic, 4Department of Neurology, Nagoya University Graduate School of Medicine, Nagoya, Japan Background: The purpose of this study is to determine whether elderly subjects with severe brain atrophy, which is associated with neurodegeneration and difficulty swallowing (dysphagia), are more susceptible to lower respiratory tract infections (LRTI), including pneumonia. Methods: The severity of brain atrophy was assessed by computed tomography in 51 nursing home residents aged 60–96 years. The incidence of LRTI, defined by body temperature ≥ 38.0°C, presence of two or more respiratory symptoms, and use of antibiotics, was determined over 4 years. The incidence of LRTI was compared according to the severity and type of brain atrophy. Results: The incidence rate ratio of LRTI was significantly higher (odds ratio 4.60, 95% confidence interval 1.18–17.93, fully adjusted P = 0.028) and the time to the first episode of LRTI was significantly shorter (log-rank test, P = 0.019) in subjects with severe brain atrophy in any lobe. Frontal and parietal lobe atrophy was associated with a significantly increased risk of LRTI, while temporal lobe atrophy, ventricular dilatation, and diffuse white matter lesions did not influence the risk of LRTI. Conclusion: Elderly subjects with severe brain atrophy are more susceptible to LRTI, possibly as a result of neurodegeneration causing dysphagia and silent aspiration. Assessing the severity of brain atrophy might be useful to identify subjects at increased risk of respiratory infections in a prospective manner.
Dynamical replica theoretic analysis of CDMA detection dynamics
J. P. L. Hatchett,M. Okada
Physics , 2005, DOI: 10.1088/0305-4470/39/15/003
Abstract: We investigate the detection dynamics of the Gibbs sampler for code-division multiple access (CDMA) multiuser detection. Our approach is based upon dynamical replica theory which allows an analytic approximation to the dynamics. We use this tool to investigate the basins of attraction when phase coexistence occurs and examine its efficacy via comparison with Monte Carlo simulations.
Probing the heavy Higgs mass by the measurement of the Higgs decay branching ratios in the minimal supersymmetric standard model
J. Kamoshita,Y. Okada,M. Tanaka
Physics , 1995, DOI: 10.1016/S0370-2693(96)01457-8
Abstract: We examine whether the parameters in the Higgs sector of the minimal supersymmetric standard model can be determined by detailed study of production cross section and decay branching ratios of the Higgs particle. Assuming that the lightest CP-even Higgs boson ($h$) is observed at a future $e^+ e^-$ linear collider with $\sqrt{s}=300\sim500$GeV, we show that the value of CP-odd scalar mass is determined from the ratio of the two branching ratios, $Br(h\to b\bar{b})$ and $Br(h\to c\bar{c})+Br(h\to gg)$, almost independently of the stop mass scale.
Retrieval Properties of Hopfield and Correlated Attractors in an Associative Memory Model
T. Uezu,A. Hirano,M. Okada
Physics , 2004, DOI: 10.1143/JPSJ.73.867
Abstract: We examine a previouly introduced attractor neural network model that explains the persistent activities of neurons in the anterior ventral temporal cortex of the brain. In this model, the coexistence of several attractors including correlated attractors was reported in the cases of finite and infinite loading. In this paper, by means of a statistical mechanical method, we study the statics and dynamics of the model in both finite and extensive loading, mainly focusing on the retrieval properties of the Hopfield and correlated attractors. In the extensive loading case, we derive the evolution equations by the dynamical replica theory. We found several characteristic temporal behaviours, both in the finite and extensive loading cases. The theoretical results were confirmed by numerical simulations.
Time reversal violation in $K^+ \to μ^+ νγ$ decay and three Higgs model
M. Kobayashi,T. -T. Lin,Y. Okada
Physics , 1995, DOI: 10.1143/PTP.95.361
Abstract: Transverse muon polarization in the $K^+ \rightarrow \mu^+ \nu \gamma$ decay is calculated in the model with scalar and pseudo scalar four-Fermi interactions. Combined with a similar calculation in the $K^+ \rightarrow \mu^+ \nu \pi^0$ decay, a possible constraint on parameters in the three-Higgs model is obtained assuming sensitivity of the up-coming KEK experiment. It is pointed out that the predictions for the two polarizations are strongly correlated in the three Higgs model.
The fate of the B ball
Junji Hisano,Mihoko M. Nojiri,Nobuchika Okada
Physics , 2001, DOI: 10.1103/PhysRevD.64.023511
Abstract: The gauge-mediated SUSY-breaking (GMSB) model needs entropy production at a relatively low temperature in the thermal history of the Universe for the unwanted relics to be diluted. This requires a mechanism for the baryogenesis after the entropy production, and the Affleck and Dine (AD) mechanism is a promising candidate for it. The AD baryogenesis in the GMSB model predicts the existence of the baryonic Q ball, that is the B ball, and this may work as the dark matter in the Universe. In this article, we discuss the stability of the B ball in th presence of baryon-number violating interactions. We find that the evaporation rate increases monotonically with the B-ball charge because the large field value inside the B ball enhances the effect of the baryon-number-violating operators. While there are some difficulties to evaluate the evaporation rate of the B ball, we derive the evaporation time (lifetime) of the B ball for the mass-to-charge ratio $\omega_0\gsim 100 \MEV$. The lifetime of the B ball and the distortion of the cosmic ray positron flux and the cosmic background radiation from the B ball evaporation give constraints on the baryon number of the B ball and the interaction, if the B ball is the dark matter. We also discuss some unresolved properties of the B ball.
Search for optimal measure for discriminating spike trains with different randomness
K. Miura,M. Okada,S. Shinomoto
Quantitative Biology , 2005,
Abstract: We wish to discriminate spike sequences based on the degree of irregularity. For this purpose, we search for a rational expressions of quadratic functions of consecutive interspike intervals that efficiently measures spiking irregularity. Under natural assumptions, the functional form of the coefficient can be parameterized by a single parameter. The parameter is determined so as to maximize the mutual information between the distributions of coefficients computed for spike sequences derived from different renewal point processes. We find that the local variation of interspike intervals, LV (Neural Comput. Vol. 15, pp. 2823-42, 2003), is nearly optimal for whose intrinsic irregularity is close to that of experimental data.
Factors Influencing the Development of “Purpose in Life”and Its Relationship to Coping with Mental Stress  [PDF]
Riichiro Ishida, Masahiko Okada
Psychology (PSYCH) , 2011, DOI: 10.4236/psych.2011.21005
Abstract: Factors influencing the development of purpose in life (PIL) were examined. Methods: We recruited 67 healthy students of Niigata University (34 males and 33 females, 18-35 years of age). PIL and approval motivation (AM), and memories of experiences (IME) were measured using the PIL test, Martin-Larsen Approval Motivation Scale (MLAM), and the Early Life and Youth Experiences Inventory. Confusion, heart rate, systolic blood pressure, and thumb-tip temperature were measured before and during “Evaluating-Integrating Words Task (EIWT).” Results: In the Profile of Mood States (POMS) tests, changes in the confusion scores were significantly higher in the weak PIL compared to the firm PIL group. The scores were significantly higher for the firm AM compared to the weak AM group. Changes in heart rate were significantly higher in the weak PIL compared to the firm PIL group. IME scores for memories of the beauty of nature, empathetic listening from parents and teachers were positively or negatively correlated with PIL test scores or MLAM scores for life stages: infancy, junior high school, and university. Conclusion: PIL and AM seemed to grow through the experiences of the beauty of nature and empathic understanding by parents and teachers during various developmental stages. Purpose in life had greater influence on emotional response and the autonomic nervous system response during psychological stress compared to approval motivation
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