The Central Time-of-Flight detector for the Jefferson Laboratory 12-GeV upgrade is being designed with linear-focused photomultiplier tubes that require a robust magnetic shield against the CLAS12 ...main 5-T solenoid fringe fields of 100
mT (1
kG). Theoretical consideration of a ferromagnetic cylinder in an axial field has demonstrated that its shielding capability decreases with increasing length. This observation has been confirmed with finite element analysis using POISSON model software. Several shields composed of coaxial ferromagnetic cylinders have been studied. All difficulties caused by saturation effects were overcome with a novel dynamical shield, which utilizes a demagnetizing solenoid between the shielding cylinders. Basic dynamical shields for ordinary linear-focused 2-in. photomultiplier tubes were designed and tested both with models and experimental prototypes at different external field and demagnetizing current values. Our shield design reduces the 1
kG external axial field by a factor of 5000.
High-precision 1H(e,e'p)pi(0) measurements at Q2 = 0.126 (GeV/c)2 are reported, which allow the determination of quadrupole amplitudes in the gamma*N-->Delta transition; they simultaneously test the ...reliability of electroproduction models. The derived quadrupole-to-dipole ( I = 3/2) amplitude ratios, R(SM) = (-6.5+/-0.2(stat+sys)+/-2.5(mod))% and R(EM) = (-2.1+/-0.2(stat+sys)+/-2.0(mod))%, are dominated by model error. Previous R(SM) and R(EM) results should be reconsidered after the model uncertainties associated with the method of their extraction are taken into account.
This report describes the physics case, the resulting detector requirements, and the evolving detector concepts for the experimental program at the Electron-Ion Collider (EIC). The EIC will be a ...powerful new high-luminosity facility in the United States with the capability to collide high-energy electron beams with high-energy proton and ion beams, providing access to those regions in the nucleon and nuclei where their structure is dominated by gluons. Moreover, polarized beams in the EIC will give unprecedented access to the spatial and spin structure of the proton, neutron, and light ions. The studies leading to this document were commissioned and organized by the EIC User Group with the objective of advancing the state and detail of the physics program and developing detector concepts that meet the emerging requirements in preparation for the realization of the EIC. The effort aims to provide the basis for further development of concepts for experimental equipment best suited for the science needs, including the importance of two complementary detectors and interaction regions. This report consists of three volumes. Volume I is an executive summary of our findings and developed concepts. In Volume II we describe studies of a wide range of physics measurements and the emerging requirements on detector acceptance and performance. Volume III discusses general-purpose detector concepts and the underlying technologies to meet the physics requirements. These considerations will form the basis for a world-class experimental program that aims to increase our understanding of the fundamental structure of all visible matter
The analysis of the nine 1-fold differential cross sections for the γr,vp→π+π−p photo- and electroproduction reactions obtained with the CLAS detector at Jefferson Laboratory was carried out with the ...goal to establish the contributing resonances in the mass range from 1.6 GeV to 1.8 GeV. In order to describe the photo- and electroproduction data with Q2-independent resonance masses and hadronic decay widths in the Q2 range below 1.5 GeV2, it was found that an N′(1720)3/2+ state is required in addition to the already well-established nucleon resonances. This work demonstrates that the combined studies of π+π−p photo- and electroproduction data are vital for the observation of this resonance. The contributions from the N′(1720)3/2+ state and the already established N(1720)3/2+ state with a mass of 1.745 GeV are well separated by their different hadronic decays to the πΔ and ρp final states and the different Q2-evolution of their photo-/electroexcitation amplitudes. The N′(1720)3/2+ state is the first recently established baryon resonance for which the results on the Q2-evolution of the photo-/electrocouplings have become available. These results are important for the exploration of the nature of the “missing” baryon resonances.
This report describes the physics case, the resulting detector requirements, and the evolving detector concepts for the experimental program at the Electron-Ion Collider (EIC). The EIC will be a ...powerful new high-luminosity facility in the United States with the capability to collide high-energy electron beams with high-energy proton and ion beams, providing access to those regions in the nucleon and nuclei where their structure is dominated by gluons. Moreover, polarized beams in the EIC will give unprecedented access to the spatial and spin structure of the proton, neutron, and light ions. The studies leading to this document were commissioned and organized by the EIC User Group with the objective of advancing the state and detail of the physics program and developing detector concepts that meet the emerging requirements in preparation for the realization of the EIC. The effort aims to provide the basis for further development of concepts for experimental equipment best suited for the science needs, including the importance of two complementary detectors and interaction regions.
This report consists of three volumes. Volume I is an executive summary of our findings and developed concepts. In Volume II we describe studies of a wide range of physics measurements and the emerging requirements on detector acceptance and performance. Volume III discusses general-purpose detector concepts and the underlying technologies to meet the physics requirements. These considerations will form the basis for a world-class experimental program that aims to increase our understanding of the fundamental structure of all visible matter.
Enzymatic synthesis optimization of isoamyl butyrate Anschau, Andréia; Aragão, Vitor C.; Porciuncula, Barbara D. A. ...
Journal of the Brazilian Chemical Society,
11/2011, Letnik:
22, Številka:
11
Journal Article
Recenzirano
Odprti dostop
Lipozyme TL IM was used to catalyse the esterification of isoamyl alcohol and butyric acid. A fractional factorial design was employed to evaluate the effects of temperature (30, 40, 50 °C), ...alcohol:acid molar ratio (1:1, 2:1, 3:1), enzyme concentration (0.003, 0.0115, 0.020 g mL-1), butyric acid concentration (0.1, 0.3, 0.5 mol L-1) and shaking rate (50, 115, 180 rpm) on the ester yield. With these results, the levels were redefined to a 2³ factorial design. The maximum yield of ester was obtained at 30 ºC, 180 rpm, alcohol:acid molar ratio of 1:1, enzyme concentration of 0.021 g mL-1 and butyric acid concentration of 0.5 mol L-1. Under the optimal conditions, 92% esterification was attained with an ester concentration of 0.9 mol L-1. Isoamyl alcohol from fusel oil was used under the same conditions and resulted in 93% esterification and an ester concentration of 1.0 mol L-1.
The first CLAS12 experiments will provide high-precision data on inclusive electron scattering observables at a photon virtuality Q2 ranging from 0.05 to 12GeV2 and center-of-mass energies W up to 4 ...GeV. In view of this endeavor, we present the modeling of the resonant contributions to the inclusive electron scattering observables. As input, we use the existing CLAS electrocoupling results obtained from exclusive meson electroproduction data off protons, and evaluate for the first time the resonant contributions based on the experimental results on the nucleon resonance electroexcitation. The uncertainties are given by the data and duly propagated through a Monte Carlo approach. In this way, we obtain estimates for the resonant contributions, important for insight into the nucleon parton distributions in the resonance region and for the studies of quark-hadron duality.
Recent results in electromagnetic excitation of nucleon resonance are presented, and confronted with theoretical predictions. Preliminary data in the search for missing states are discussed as well. ...Resonance electroproduction has rich applications in nucleon structure studies at intermediate and large distances. Resonances play an important role in understanding the spin structure of the nucleon. More than 80% of the helicity-dependent integrated total photoabsorption cross-section difference (GDH integral) is a result of the excitation of the {Delta}(1232). At Q{sup 2} = 1 GeV{sup 2}, about 40% of the first moment {Lambda}{sub 1}{sup P}(Q{sup 2}) = {integral}{sub 0}{sup 1} g{sub 1}(x, Q{sup 2})dx for the proton is due to contributions of the resonance region at W < 2 GeV. Conclusions regarding the nucleon spin structure for Q{sup 2} < 2 GeV{sup 2} must therefore be regarded with some scepticism if contributions of baryon resonances are not taken into account.
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