988 resultados para MESON BOUND-STATES
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The quark model successfully describes all ground state bary-ons as members of $SU(N)$ flavour multiplets. For excited baryon states the situation is totally different. There are much less states found in the experiment than predicted in most theoretical calculations. This fact has been known for a long time as the 'missing resonance problem'. In addition, many states found in experiments are only poorly measured up to now. Therefore, further experimental efforts are needed to clarify the situation.rnrnAt mbox{COMPASS}, reactions of a $190uskgigaeVperclight$ hadron beam impinging on a liquid hydrogen target are investigated.rnThe hadron beam contains different species of particles ($pi$, $K$, $p$). To distinguish these particles, two Cherenkov detectors are used. In this thesis, a new method for the identification of particles from the detector information is developed. This method is based on statistical approaches and allows a better kaon identification efficiency with a similar purity compared to the method, which was used before.rnrnThe reaction $pprightarrow ppX$ with $X=(pi^0,~eta,~omega,~phi)$ is used to study different production mechanisms. A previous analysis of $omega$ and $phi$ mesons is extended to pseudoscalar mesons. As the resonance contributions in $peta$ are smaller than in $ppi^0$ a different behaviour of these two final states is expected as a function of kinematic variables. The investigation of these differences allows to study different production mechanisms and to estimate the size of the resonant contribution in the different channels.rnrnIn addition, the channel $pprightarrow ppX$ allows to study baryon resonances in the $pX$ system.rnIn the mbox{COMPASS} energy regime, the reaction is dominated by Pomeron exchange. As a Pomeron carries vacuum quantum numbers, no isospin is transferred between the target proton and the beam proton. Therefore, the $pX$ final state has isospin $textstylefrac{1}{2}$ and all baryon resonances in this channel are $N^ast$ baryons. This offers the opportunity to do spectroscopy without taking $Delta$ resonances into account. rnrnTo disentangle the contributions of different resonances a partial wave analysis (PWA) is used. Different resonances have different spin and parity $J^parity$, which results in different angular distributions of the decay particles. These angular distributions can be calculated from models and then be fitted to the data. From the fit the contributions of the single resonances as well as resonance parameters -- namely the mass and the width -- can be extracted. In this thesis, two different approaches for a partial wave analysis of the reaction $pprightarrow pppi^0$ are developed and tested.
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Na(+)/Ca(2+) exchangers (NCX) constitute a major Ca(2+) export system that facilitates the re-establishment of cytosolic Ca(2+) levels in many tissues. Ca(2+) interactions at its Ca(2+) binding domains (CBD1 and CBD2) are essential for the allosteric regulation of Na(+)/Ca(2+) exchange activity. The structure of the Ca(2+)-bound form of CBD1, the primary Ca(2+) sensor from canine NCX1, but not the Ca(2+)-free form, has been reported, although the molecular mechanism of Ca(2+) regulation remains unclear. Here, we report crystal structures for three distinct Ca(2+) binding states of CBD1 from CALX, a Na(+)/Ca(2+) exchanger found in Drosophila sensory neurons. The fully Ca(2+)-bound CALX-CBD1 structure shows that four Ca(2+) atoms bind at identical Ca(2+) binding sites as those found in NCX1 and that the partial Ca(2+) occupancy and apoform structures exhibit progressive conformational transitions, indicating incremental regulation of CALX exchange by successive Ca(2+) binding at CBD1. The structures also predict that the primary Ca(2+) pair plays the main role in triggering functional conformational changes. Confirming this prediction, mutagenesis of Glu(455), which coordinates the primary Ca(2+) pair, produces dramatic reductions of the regulatory Ca(2+) affinity for exchange current, whereas mutagenesis of Glu(520), which coordinates the secondary Ca(2+) pair, has much smaller effects. Furthermore, our structures indicate that Ca(2+) binding only enhances the stability of the Ca(2+) binding site of CBD1 near the hinge region while the overall structure of CBD1 remains largely unaffected, implying that the Ca(2+) regulatory function of CBD1, and possibly that for the entire NCX family, is mediated through domain interactions between CBD1 and the adjacent CBD2 at this hinge.
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A search for excited states of the B ± c meson is performed using 4.9 fb −1 of 7 TeV and 19.2 fb −1 of 8 TeV pp collision data collected by the ATLAS experiment at the LHC. A new state is observed through its hadronic transition to the ground state, with the latter detected in the decay B ± c →J/ψπ ± . The state appears in the m(B ± c π + π − )−m(B ± c )−2m(π ± ) mass difference distribution with a significance of 5.2 standard deviations. The mass of the observed state is 6842±4±5 MeV , where the first error is statistical and the second is systematic. The mass and decay of this state are consistent with expectations for the second S -wave state of the B ± c meson, B ± c (2S) .
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Weak radiative decays of the B mesons belong to the most important flavor changing processes that provide constraints on physics at the TeV scale. In the derivation of such constraints, accurate standard model predictions for the inclusive branching ratios play a crucial role. In the current Letter we present an update of these predictions, incorporating all our results for the O(α2s) and lower-order perturbative corrections that have been calculated after 2006. New estimates of nonperturbative effects are taken into account, too. For the CP- and isospin-averaged branching ratios, we find Bsγ=(3.36±0.23)×10−4 and Bdγ=(1.73+0.12−0.22)×10−5, for Eγ>1.6 GeV. Both results remain in agreement with the current experimental averages. Normalizing their sum to the inclusive semileptonic branching ratio, we obtain Rγ≡(Bsγ+Bdγ)/Bcℓν=(3.31±0.22)×10−3. A new bound from Bsγ on the charged Higgs boson mass in the two-Higgs-doublet-model II reads MH±>480 GeV at 95% C.L.
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Between the 1990 and 2000 Censuses, the Latino population accounted for 40% of the increase in the nation’s total population. The growing population of Latinos underscores the importance for understanding factors that influence whether and how Latinos take care of their health. According to the U.S. Department of Human Health Service’s Office of Minority Health (OMH), Latinos are at greater risk for health disparities (2003). Factors such as lack of health insurance and access to preventive care play a major role in limiting Latino use of primary health care (Institute of Medicine, 2005). Other significant barriers to preventive health care maintenance behaviors have been identified in current literature such as primary care physician interaction, self-perceived health status, and socio-cultural beliefs and traditions (Rojas-Guyler, King, Montieth and 2008; Meir, Medina, and Ory, 2007; Black, 1999). Despite these studies, there remains less information regarding interpersonal perceptions, environmental dynamics and individual and cultural attitudes relevant to utilization of healthcare (Rojas-Guyler, King, Montieth and 2008; Aguirre-Molina, Molina and Zambrana, 2001). Understanding the perceptions of Latinos and the barriers to health care could directly affect healthcare delivery. Improved healthcare utilization among Latinos could reduce the long term health consequences of many preventable and manageable diseases. The purpose of this study was to explore Latino perceptions of U.S. health care and desired changes by Latinos in the U.S. healthcare system. The study had several objectives, including to explore perceived barriers to healthcare utilization and the resulting effects on health among Latinos, to describe culturally influenced attitudes about health care and use of health care services among Latinos, and to make recommendations for reducing disparities by improving healthcare and its utilization. The current study utilized data that were collected as part of a larger study to examine multidimensional, cross-cultural issues relevant to interactions between healthcare consumers and providers. Qualitative methods were used to analyze four Spanish-language focus group transcripts to interpret cultural influences on perceptions and beliefs among Latinos. Direct coding of transcript content was carried out by two reviewers, who conducted independent reviews of each transcript. Team members developed and refined thematic categories, positive and negative cases, and example text segments for each theme and sub-theme. Incongruities of interpretations were resolved through extensive discussion. Study participants included 44 self-identified Latino adults (16 male, 28 female) between age 18 and 64 years. Thirty seven (84.1%) of the participants were immigrants. The study population comprised eight ethnic subgroups. While 31% of the participants reported being employed on a full-time basis, only 18.4% had medical insurance that was private or employee sponsored. Five major themes regarding the perceptions and healthcare utilization behaviors of Latinos were consistent across all focus groups and were identified during the analysis. These were: (1) healthcare utilization, experience, and access; (2) organizational and institutional systems; (3) communication and interpersonal interactions between healthcare provider, staff, and patient; (4) Latinos’ perception of their own health status; (5) cultural influences on healthcare utilization, which included an innovation termed culturally-bound locus of control. Healthcare utilization was directly influenced by healthcare experience, access, current health status, and cultural factors and indirectly influenced by organizational systems. There was a strong interdependence among the main themes. The ability to communicate and interact effectively with healthcare providers and navigate healthcare systems (organizational and institutional access) significantly influenced the participant’s health care experience, most often (indirectly) impacting utilization negatively. ^ Research such as this can help to identify those perceptions and attitudes held by Latinos concerning utilization or underutilization of healthcare systems. These data suggest that for healthcare utilization to improve among Latinos, healthcare systems must create more culturally competent environments by providing better language services at the organizational level and more culturally sensitive providers at the interpersonal level. Better understanding of the complex interactions between these impediments can aid intervention developments, and help health providers and researchers in determining appropriate, adequate, and effective measurers of care to better increase overall health of Latinos.^
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Ultrafiltration with tagged atoms was used to study physicochemical states (dissolved, colloidal, suspended) of Mn, Co, Ni, Zn, and Ce in bottom and interstitial waters collected in two areas of the Pacific Ocean with Fe-Mn nodules of different size, shape, structure and origin in different abundances. Use of filters with pore diameter of 0.05 ?m allowed to identify colloidal forms of the metals in bottom sediments and interstitial waters. It was demonstrated experimentally that differences in physicochemical situation in the studied areas could result in formation of nodules by different mechanisms, producing characteristic differences that were observed.
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Let D be a link diagram with n crossings, sA and sB be its extreme states and |sAD| (respectively, |sBD|) be the number of simple closed curves that appear when smoothing D according to sA (respectively, sB). We give a general formula for the sum |sAD| + |sBD| for a k-almost alternating diagram D, for any k, characterizing this sum as the number of faces in an appropriate triangulation of an appropriate surface with boundary. When D is dealternator connected, the triangulation is especially simple, yielding |sAD| + |sBD| = n + 2 - 2k. This gives a simple geometric proof of the upper bound of the span of the Jones polynomial for dealternator connected diagrams, a result first obtained by Zhu [On Kauffman brackets, J. Knot Theory Ramifications6(1) (1997) 125–148.]. Another upper bound of the span of the Jones polynomial for dealternator connected and dealternator reduced diagrams, discovered historically first by Adams et al. [Almost alternating links, Topology Appl.46(2) (1992) 151–165.], is obtained as a corollary. As a new application, we prove that the Turaev genus is equal to the number k of dealternator crossings for any dealternator connected diagram
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Thermomechanical relaxation events and different water states in cottonseed protein bioplastics are presented whilst investigating the effects of aldehyde cross-linking agents. Thermomechanical relaxation of cottonseed protein bioplastics associated with protein denaturation, moisture absorption and broad glass transitions (Tg) were observed from DSC and DMA measurements. It was shown that variation of the aldehyde influences the storage modulus at very low temperature (below Tg). From measurements of the water fusion point, enthalpy, vaporisation, and weight loss, three water states in the water-absorbed bioplastics are suggested; namely strongly-bound-to-polymer, weakly-bound-to-polymer and bulk-like water. The water content and unreacted cross-linking agents are influential factors in controlling formation of the different water states, whilst the selection of different aldehydes was found to be negligible. These results could be valuable for adjusting the thermomechanical relaxations of protein based bioplastics, and tailoring their properties in wet environments.
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Opinions concerning the 7th article of the treaty.
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Mode of access: Internet.
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Bound in green cloth; stamped in gold and blind.
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A second copy bound with: Report on the geology, mineralogy, botany, and zoology of Massachusetts / by Edward Hitchcock -- Report on a re-examination of the economical geology of Massachusetts / by Edward Hitchcock -- First report on the geology of the public lands in the state of Maine / by Charles T. Jackson.
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Includes index.
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"Printed by A. Strahan ... London" -- Colophon