1,059 research outputs found
An Analysis of \pi\pi-Scattering Phase Shift and Existence of \sigma(555) particle
In most of the Nambu:Jona-Lasinio(NJL)-type models, realizing the hidden
chiral symmetry, the existence of a scalar particle \sigma is needed with a
mass m_\sigma=2 m_q, as a partner of the Nambu-Goldstone boson \pi. However,
the results of many analyses on \pi\pi phase-shift thus far made have been
negative for its existence. In this paper we re-analyze the phase-shift,
applying a new method, the interfering amplitude method, which treats the
T-matrix directly and describes multi-resonances in conformity with the
unitarity. As a result, the existence of \sigma has been strongly suggested
from the behavior of the \pi\pi-->\pi\pi phase shift between the \pi\pi- and
the KK- thresholds, with mass = 553.3 +- 0.5_{st} MeV and width= 242.6 +-
1.2_{st} MeV. The most crucial point in our analysis is the introduction of a
negative background phase, possibly reflecting a ``repulsive core" in \pi\pi
interactions. The properties of f_0(980) are also investigated from data
including those over the KK threshold. Its mass is obtained as 993.2 +-
6.5_{st} +- 6.9_{sys} MeV. Its width is about a hundred MeV, although this
depends largely on the treatment of the elasticity and the \pi\pi-->KK phase
shift, both of which may have large experimental uncertainties.Comment: 22 pages, Latex with Prog. Theor. Phys. format PTPTEX.sty, 4 EPS
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pi^0 pi^0 Scattering Amplitudes and Phase Shifts Obtained by the pi^- P Charge Exchange Process
The results of the analysis of the pi^0 pi^0 scattering amplitudes obtained
with pi^- P charge exchange reaction, pi^- P --> pi^0 pi^0 n, data at 9 GeV/c
are presented. The pi^0 pi^0 scattering amplitudes show clear f_0(1370) and
f_2(1270) signals in the S and D waves, respectively. The pi^0 pi^0 scattering
phase shifts have been obtained below Kbar K threshold and been analyzed by the
Interfering Amplitude method with introduction of negative background phases.
The results show a S wave resonance, sigma. Its Breit-Wigner parameters are in
good agreement with those of our previous analysis on the pi^+ pi^- phase shift
data.Comment: 4 pages, 4 figures. Proceedings of the int. conf. Hadron'99 at
Beijing, Aug. 1999. Presented for the collaboration of A.M.Ma, K.Takamatsu,
M.Y.Ishida, S.Ishida, T.Ishida, T. Tsuru and H. Shimizu, and the E135
collaboration. For our activities on sigma, visit
http://amaterasu.kek.jp/sigm
DETERMINATION OF BODY SEGMENT INERTIA PARAMETERS USING 3D HUMAN BODY SCANNER AND 3D CAD SOFTWARE
In the field of sports biomechanics, a human body is often treated as a linkage model to investigate various kinds of human movement. This modeling requires body segment inertia parameters (BSPs) such as masses, centers of mass, and moments of inertia. As the quality of motion capture system increases, more accurate BSPs are also needed to get accurate inverse dynamics results. Advanced technology has enabled us to obtain three-dimensional coordinates of the entire body surface. A 3D CAD software has also been able to be applied to measure the human body. It was hypothesized that BSPs with high accuracy could be determined by the combination of a 3D body scanner and a 3D CAD software. The purposes of this study are, first, to introduce a new method of measuring subject-specific BSPs and, second, to compare the BSPs from this study with those from an existing mathematical model in order to
show that the proposed method can be used to produce more accurate BSPs
Direct patterning of organic conductors on knitted textiles for long-term electrocardiography.
Wearable sensors are receiving a great deal of attention as they offer the potential to become a key technological tool for healthcare. In order for this potential to come to fruition, new electroactive materials endowing high performance need to be integrated with textiles. Here we present a simple and reliable technique that allows the patterning of conducting polymers on textiles. Electrodes fabricated using this technique showed a low impedance contact with human skin, were able to record high quality electrocardiograms at rest, and determine heart rate even when the wearer was in motion. This work paves the way towards imperceptible electrophysiology sensors for human health monitoring
Avaliação da avifauna em sistemas agroflorestais com dendĂȘ (Elaeis guianeensis) no municĂpio de TomĂ©-Açu (PA).
Ă apresentada uma comparação entre a composição da avifauna de sistemas agroflorestais (SAF) com dendĂȘ, copoeiras e uma monocultura de dendĂȘ ao longo de dois anos no intuito de relatar a funcionalidade dos SAFs na manutenção de aves amazĂŽnicas. Foram registradas 196 espĂ©cies, destas 88 encontradas nos SAFs, 120 na capoeira e 63 na monocultura. Foi observada a ausĂȘncia de espĂ©cies florestais das famĂlias, Thamnophilidae, Furnaridae e Tyrannidae no SAF e na monocultura de dendĂȘ, presentes na capoeira. O Ăndice de similaridade de Morisita mostra que os SAFs se assemelham mais Ă s monoculturas do que Ă s capoeiras, possivelmente devido ao tempo recente de plantio, onde os SAFs ainda nĂŁo apresentam uma estrutura florestal mais complexa com sub-bosque e dossel. Foi observado um aumento na riqueza de espĂ©cies frutĂvoras e nectarĂvoras e na diversidade dos SAFs, possivelmente refletindo o contĂnuo desenvolvimento e estruturação deste sistema. Os resultados apresentados mostram que apesar de os SAFs apresentarem uma comunidade de aves em geral distinta da comunidade encontrada nas capoeiras, estas apresentam Ăndices de diversidade e riqueza de espĂ©cies semelhantes. A monocultura de dendĂȘ apresentou a menor riqueza e Ăndices de diversidade, alĂ©m de apresentar principalmente espĂ©cies insetĂvoras, onĂvoras e granĂvoras na composição de sua avifauna, configurando um ambiente pouco diverso na estrutura da vegetação. Sistemas agroflorestais de dendĂȘ podem vir a contribuir na manutenção da diversidade local de aves florestais amazĂŽnicas, contudo os resultados apontam a necessidade de mais tempo para um melhor desenvolvimento do sistema.Editores tĂ©cnicos: Roberto Porro, Milton Kanashiro, Maria do Socorro Gonçalves Ferreira, Leila Sobral Sampaio e Gladys Ferreira de Sousa
Enhanced Hyperthermia Induced by MDMA in Parkin Knockout Mice
MDMA (3,4-methylenedioxymethamphetamine) is reportedly severely toxic to both dopamine (DA) and serotonin neurons. MDMA significantly reduces the number of DA neurons in the substantia nigra, but not in the nucleus accumbens, indicating that MDMA causes selective destruction of DA neurons in the nigrostriatal pathway, sparing the mesolimbic pathway. Parkinsonâs disease (PD) is a neurodegenerative disorder of multifactorial origin. The pathological hallmark of PD is the degeneration of DA neurons in the nigrostriatal pathway. Mutations in the parkin gene are frequently observed in autosomal recessive parkinsonism in humans. Parkin is hypothesized to protect against neurotoxic insult, and we attempted to clarify the role of parkin in MDMA-induced hyperthermia, one of the causal factors of neuronal damage, using parkin knockout mice. Body temperature was measured rectally before and 15, 30, 45, and 60 min after intraperitoneal injection of MDMA (30 mg/kg) at an ambient temperature of 22 ± 2°C. Significantly enhanced hyper-thermia after MDMA injection was observed in heterozygous and homozygous parkin knockout mice compared with wildtype mice, suggesting that parkin plays a protective role in MDMA neurotoxicity
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