Spin-isospin selectivity in three-nucleon forces

Precision data are presented for the break-up reaction, (2)H((p) over right arrow, pp)n, within the framework of nuclear-force studies. The experiment was carried out at KVI using a polarized-proton beam of 190 MeV impinging on a liquid-deuterium target and by exploiting the detector, BINA. Some of the vector-analyzing powers are presented and compared with state-of-the-art Faddeev calculations including three-nucleon forces effect. Significant discrepancies between the data and theoretical predictions were observed for kinematical configurations which correspond to the (2)H((p) over right arrow,(2)He)n channel. These results are compared to the (2)H((p) over right arrow, d)p reaction to test the isospin sensitivity of the present three-nucleon force models. The current modeling of two and three-nucleon forces is not sufficient to describe consistently polarization data for both isospin states. (C) 2010 Elsevier B.V. All rights reserved

Investigation of nuclear forces in d + p elastic and p + d break-up reactions at intermediate energies

In this thesis, the break-up and elastic channels of the reaction at a proton-beam energy of 190~MeV were studied using BINA. After accelerating the polarized-proton beam from POLIS with AGOR, reactions of protons with deuterons from a liquid-deuterium target took place at the center of BINA. The cross section and analyzing powers are measured as a function of the kinematical variable S for different combinations of the polar coordinates of the outgoing particles. As a conclusion and regarding the uncertainties of the data, the deviations between the cross sections and theoretical predictions using solely NN potentials indicate the need for additional ingredients which are presently missing in the nuclear forces or in the framework which provides the predictions for the observables. The effect of 3NFs is predicted to be small and although adding the 3NF to the NN potentials helps to bridge the gap between data and the NN calculations, however, it cannot remedy the discrepancies observed for the cross section. The CDB+Relativistic predictions help to solve the discrepancies between data and theoretical calculations only in part of the phase space. That might be an indication that relativity is playing an important role at energies employed in this experiment, however, the approximations made for these calculations might not be sufficient. The analyzing power does not seem to be sensitive to Coulomb and relativistic effects. This observable is, therefore, a unique probe to study 3NF effects. In particular, at small azimuthal opening angles, 3NF effects can be observed and tested. In this region, however, the experimental data show that the presented 3NF potentials do not resolve the observed discrepancies. On the contrary, the disagreement between data and predictions by the Faddeev calculations increases by including all the 3N potentials.

A system-oriented strategy to enhance electron production of Synechocystis sp. PCC6803 in bio-photovoltaic devices: experimental and modeling insights

Abstract Bio-photovoltaic devices (BPVs) harness photosynthetic organisms to produce bioelectricity in an eco-friendly way. However, their low energy efficiency is still a challenge. A comprehension of metabolic constraints can result in finding strategies for efficiency enhancement. This study presents a systemic approach based on metabolic modeling to design a regulatory defined medium, reducing the intracellular constraints in bioelectricity generation of Synechocystis sp. PCC6803 through the cellular metabolism alteration. The approach identified key reactions that played a critical role in improving electricity generation in Synechocystis sp. PCC6803 by comparing multiple optimal solutions of minimal and maximal NADH generation using two criteria. Regulatory compounds, which controlled the enzyme activity of the key reactions, were obtained from the BRENDA database. The selected compounds were subsequently added to the culture media, and their effect on bioelectricity generation was experimentally assessed. The power density curves for different culture media showed the BPV fed by Synechocystis sp. PCC6803 suspension in BG-11 supplemented with NH4Cl achieved the maximum power density of 148.27 mW m−2. This produced power density was more than 40.5-fold of what was obtained for the BPV fed with cyanobacterial suspension in BG-11. The effect of the activators on BPV performance was also evaluated by comparing their overpotential, maximum produced power density, and biofilm morphology under different conditions. These findings demonstrated the crucial role of cellular metabolism in improving bioelectricity generation in BPVs

Current stage of studies of the star configurations at intermediate energies with the use of the BINA detector

The Space Star Anomaly in proton-deuteron breakup cross-section occurs at energies of about 10 MeV. Data for higher energies are sparse. Therefore, a systematic scan over star configurations in the range of intermediate energies between 50 and 100 MeV/nucleon is carried out on the basis of data collected with the large acceptance BINA detector. The preliminary cross section results for forward star configurations at 80 MeV/nucleon slightly surpass the theoretical calculations, but the systematic uncertainties are still under study. Also, a new variable describing rotation of star configurations is proposed

Determination of phase space region for cross-check validation of the neutron detection in the BINA experiments

Deuteron breakup reactions are basic laboratories for testing nuclear force models. Recent improvements in the data analysis allow for direct identification of neutrons in the BINA detection setup. This opens up the opportunity to study new aspects of few-nucleon system dynamics like charge dependence of nuclear force or Coulomb interaction. In this paper we determine regions along the kinematical curves where differential cross section of deuteron-proton breakup reactions can be measured by the proton-neutron and proton-proton coincidences simultaneously. This is particularly useful for validation of the neutron detection technique