The Experts below are selected from a list of 32943 Experts worldwide ranked by ideXlab platform
Wenchang Xiang - One of the best experts on this subject based on the ideXlab platform.
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inclusive diffractive heavy quarkonium Photoproduction including quark subprocesses
Physical Review C, 2021Co-Authors: Yanbing Cai, Wenchang XiangAbstract:To test the contributions of the quark subprocesses to the inclusive diffractive heavy quarkonium Photoproduction, we first investigate the inclusive nondiffractive direct and resolved Photoproduction of $J/\mathrm{\ensuremath{\Psi}}$ in the framework of nonrelativistic quantum chromodynamics (NRQCD). We find that the theoretical total cross section of heavy quarkonium productions are in good agreement with the data available at HERA, once the $\ensuremath{\gamma}q$, $qg$, and $qq$ subprocesses in the heavy quark pair productions are taken into account. Then we predict the inclusive diffractive rapidity and transverse momentum distributions of $J/\mathrm{\ensuremath{\Psi}}$, $\mathrm{\ensuremath{\Psi}}(2S)$, and $\mathrm{\ensuremath{\Upsilon}}(1S)$ in $pp$, $p\mathrm{Pb}$, and $\mathrm{PbPb}$ collisions at the CERN Large Hadron Collider by using our quark improved NRQCD model. We find that the contributions from the quark involved subprocesses to quarkonium Photoproduction are about $6%\text{--}15%$. The numerical results show that the contributions from quark involved subprocesses are significant modification in inclusive diffractive heavy quarkonium Photoproduction.
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inclusive diffractive heavy quarkonium Photoproduction including quark subprocesses
arXiv: High Energy Physics - Phenomenology, 2020Co-Authors: Yanbing Cai, Wenchang XiangAbstract:The inclusive $J/\Psi$, $\Psi(2S)$ and $\Upsilon(1S)$ direct and resolved Photoproduction are investigated by including the quark subprocesses in the framework of non-relativistic quantum chromodynamics (NRQCD). We find that the theoretical total cross section of heavy quarkonium productions are in good agreement with the data available at HERA, once the $\gamma q$, $qg$ and $qq$ subprocesses in the heavy quark pair productions are taken into account. The inclusive diffractive rapidity and transverse momentum distributions of $J/\Psi$, $\Psi(2S)$ and $\Upsilon(1S)$ in $pp$, $pPb$ and $PbPb$ collisions at LHC are also studied by our quark improved NRQCD model combined with the resolved pomeron model. We find that the contributions from the quark involved subprocesses can reach to $8\%$ in the rapidity distribution and $6\%$ in the transverse momentum distribution. The numerical results show that the contributions from quark involved subprocesses are significant in heavy quarkonium photoprodution.
Alice Collaboration - One of the best experts on this subject based on the ideXlab platform.
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Coherent J/ψ and ψ′ Photoproduction at midrapidity in ultra-peripheral Pb–Pb collisions at √sNN = 5.02 TeV
'Springer Science and Business Media LLC', 2021Co-Authors: Alice CollaborationAbstract:The coherent Photoproduction of J/ψ and ψ′ mesons was measured in ultra-peripheral Pb–Pb collisions at a center-of-mass energy √sNN = 5.02 TeV with the ALICE detector. Charmonia are detected in the central rapidity region for events where the hadronic interactions are strongly suppressed. The J/ψ is reconstructed using the dilepton (l+l−) and proton–antiproton decay channels, while for the ψ′ the dilepton and the l+l−π+π− decay channels are studied. The analysis is based on an event sample corresponding to an integrated luminosity of about 233 μb−1. The results are compared with theoretical models for coherent J/ψ and ψ′ Photoproduction. The coherent cross section is found to be in a good agreement with models incorporating moderate nuclear gluon shadowing of about 0.64 at a Bjorken-x of around 6×10−4, such as the EPS09 parametrization, however none of the models is able to fully describe the rapidity dependence of the coherent J/ψ cross section including ALICE measurements at forward rapidity. The ratio of ψ′ to J/ψ coherent Photoproduction cross sections was also measured and found to be consistent with the one for Photoproduction off protons.peerReviewe
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Coherent $\rm{J/\psi}$ and $\rm{\psi'}$ Photoproduction at midrapidity in ultra-peripheral Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}~=~5.02$ TeV
2021Co-Authors: Alice CollaborationAbstract:The coherent Photoproduction of $\rm{J/\psi}$ and $\rm{\psi'}$ mesons was measured in ultra-peripheral Pb-Pb collisions at a center-of-mass energy $\sqrt{s_{\mathrm{NN}}}~=~5.02$ TeV with the ALICE detector. Charmonia are detected in the central rapidity region for events where the hadronic interactions are strongly suppressed. The $\rm{J/\psi}$ is reconstructed using the dilepton ($l^{+} l^{-}$) and proton-antiproton decay channels, while for the $\rm{\psi'}$, the dilepton and the $l^{+} l^{-} \pi^{+} \pi^{-}$ decay channels are studied. The analysis is based on an event sample corresponding to an integrated luminosity of about 233 ${\mu b}^{-1}$. The results are compared with theoretical models for coherent $\rm{J/\psi}$ and $\rm{\psi'}$ Photoproduction. The coherent cross section is found to be in a good agreement with models incorporating moderate nuclear gluon shadowing of about 0.65 at a Bjorken-$x$ of around $6\times 10^{-4}$, such as the EPS09 parametrization, however none of the models is able to fully describe the rapidity dependence of the coherent $\rm{J/\psi}$ cross section including ALICE measurements at forward rapidity. The ratio of $\rm{\psi'}$ to $\rm{J/\psi}$ coherent Photoproduction cross sections was also measured and found to be consistent with the one for Photoproduction off protons.Comment: 28 pages, 6 captioned figures, 4 tables, authors from page 22, submitted to EPJC, figures at http://alice-publications.web.cern.ch/node/677
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Coherent $$\mathrm{J}/\psi $$ J / ψ and $${\uppsi '}$$ ψ ′ Photoproduction at midrapidity in ultra-peripheral Pb–Pb collisions at $$\sqrt{s_{\mathrm {NN}}}~=~5.02$$ s NN = 5.02 TeV
'Springer Science and Business Media LLC', 2021Co-Authors: Alice Collaboration, S. Acharya, D. Adamová, A. Adler, J. Adolfsson, Aglieri G. Rinella, M. Agnello, N. Agrawal, Z. Ahammed, S. AhmadAbstract:Abstract The coherent Photoproduction of $$\mathrm{J}/\psi $$ J / ψ and $${\uppsi '}$$ ψ ′ mesons was measured in ultra-peripheral Pb–Pb collisions at a center-of-mass energy $$\sqrt{s_{\mathrm {NN}}}~=~5.02$$ s NN = 5.02 TeV with the ALICE detector. Charmonia are detected in the central rapidity region for events where the hadronic interactions are strongly suppressed. The $$\mathrm{J}/\psi $$ J / ψ is reconstructed using the dilepton ( $$l^{+} l^{-}$$ l + l - ) and proton–antiproton decay channels, while for the $${\uppsi '}$$ ψ ′ the dilepton and the $$l^{+} l^{-} \pi ^{+} \pi ^{-}$$ l + l - π + π - decay channels are studied. The analysis is based on an event sample corresponding to an integrated luminosity of about 233 $$\mu {\mathrm{b}}^{-1}$$ μ b - 1 . The results are compared with theoretical models for coherent $$\mathrm{J}/\psi $$ J / ψ and $${\uppsi '}$$ ψ ′ Photoproduction. The coherent cross section is found to be in a good agreement with models incorporating moderate nuclear gluon shadowing of about 0.64 at a Bjorken-x of around $$6\times 10^{-4}$$ 6 × 10 - 4 , such as the EPS09 parametrization, however none of the models is able to fully describe the rapidity dependence of the coherent $$\mathrm{J}/\psi $$ J / ψ cross section including ALICE measurements at forward rapidity. The ratio of $${\uppsi '}$$ ψ ′ to $$\mathrm{J}/\psi $$ J / ψ coherent Photoproduction cross sections was also measured and found to be consistent with the one for Photoproduction off protons
Sang Un Ahn - One of the best experts on this subject based on the ideXlab platform.
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Coherent J/$\psi$ and $\psi'$ Photoproduction at midrapidity in ultra-peripheral Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV
2021Co-Authors: Acharya Shreyasi, Adamova Dagmar, Adler Alexander, Adolfsson Jonatan, Aglieri Rinella Gianluca, Agnello Michelangelo, Agrawal Neelima, Ahammed Zubayer, Ahmad Shakeel, Sang Un AhnAbstract:The coherent Photoproduction of J/$\psi$ and $\psi'$ mesons was measured in ultra-peripheral Pb-Pb collisions at a center-of-mass energy $\sqrt{s_{\rm NN}}$ = 5.02 TeV with the ALICE detector. Charmonia are detected in the central rapidity region for events where the hadronic interactions are strongly suppressed. The J/$\psi$ is reconstructed using the dilepton ($e^{+} e^{-}$) and proton-antiproton decay channels, while for the $\psi'$, the dilepton and the $e^{+} e^{-} \pi^{+} \pi^{-}$ decay channels are studied. The analysis is based on an event sample corresponding to an integrated luminosity of about 233 ${\mu b}^{-1}$. The results are compared with theoretical models for coherent J/$\psi$ and $\psi'$ Photoproduction. The coherent cross section is found to be in a good agreement with models incorporating moderate nuclear gluon shadowing of about 0.65 at a Bjorken-$x$ of around $6\times 10^{-4}$, such as the EPS09 parametrization, however none of the models is able to fully describe the rapidity dependence of the coherent J/$\psi$ cross section including ALICE measurements at forward rapidity. The ratio of $\psi'$ to J/$\psi$ coherent Photoproduction cross sections was also measured and found to be consistent with the one for Photoproduction off protons.The coherent Photoproduction of $\rm{J/\psi}$ and $\rm{\psi'}$ mesons was measured in ultra-peripheral Pb-Pb collisions at a center-of-mass energy $\sqrt{s_{\mathrm{NN}}}~=~5.02$ TeV with the ALICE detector. Charmonia are detected in the central rapidity region for events where the hadronic interactions are strongly suppressed. The $\rm{J/\psi}$ is reconstructed using the dilepton ($l^{+} l^{-}$) and proton-antiproton decay channels, while for the $\rm{\psi'}$, the dilepton and the $l^{+} l^{-} \pi^{+} \pi^{-}$ decay channels are studied. The analysis is based on an event sample corresponding to an integrated luminosity of about 233 ${\mu b}^{-1}$. The results are compared with theoretical models for coherent $\rm{J/\psi}$ and $\rm{\psi'}$ Photoproduction. The coherent cross section is found to be in a good agreement with models incorporating moderate nuclear gluon shadowing of about 0.65 at a Bjorken-$x$ of around $6\times 10^{-4}$, such as the EPS09 parametrization, however none of the models is able to fully describe the rapidity dependence of the coherent $\rm{J/\psi}$ cross section including ALICE measurements at forward rapidity. The ratio of $\rm{\psi'}$ to $\rm{J/\psi}$ coherent Photoproduction cross sections was also measured and found to be consistent with the one for Photoproduction off protons
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Coherent $\rm{J/\psi}$ and $\rm{\psi'}$ Photoproduction at midrapidity in ultra-peripheral Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}~=~5.02$ TeV
HAL CCSD, 2021Co-Authors: Acharya Shreyasi, Adamova Dagmar, Adler Alexander, Adolfsson Jonatan, Aglieri Rinella Gianluca, Agnello Michelangelo, Agrawal Neelima, Ahammed Zubayer, Ahmad Shakeel, Sang Un AhnAbstract:The coherent Photoproduction of $\rm{J/\psi}$ and $\rm{\psi'}$ mesons was measured in ultra-peripheral Pb-Pb collisions at a center-of-mass energy $\sqrt{s_{\mathrm{NN}}}~=~5.02$ TeV with the ALICE detector. Charmonia are detected in the central rapidity region for events where the hadronic interactions are strongly suppressed. The $\rm{J/\psi}$ is reconstructed using the dilepton ($l^{+} l^{-}$) and proton-antiproton decay channels, while for the $\rm{\psi'}$, the dilepton and the $l^{+} l^{-} \pi^{+} \pi^{-}$ decay channels are studied. The analysis is based on an event sample corresponding to an integrated luminosity of about 233 ${\mu b}^{-1}$. The results are compared with theoretical models for coherent $\rm{J/\psi}$ and $\rm{\psi'}$ Photoproduction. The coherent cross section is found to be in a good agreement with models incorporating moderate nuclear gluon shadowing of about 0.65 at a Bjorken-$x$ of around $6\times 10^{-4}$, such as the EPS09 parametrization, however none of the models is able to fully describe the rapidity dependence of the coherent $\rm{J/\psi}$ cross section including ALICE measurements at forward rapidity. The ratio of $\rm{\psi'}$ to $\rm{J/\psi}$ coherent Photoproduction cross sections was also measured and found to be consistent with the one for Photoproduction off protons
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Coherent $J/ \psi$ and $\phi$' Photoproduction at midrapidity in ultra-peripheral Pb–Pb collisions at $\sqrt {s_{NN}}$ = 5.02 TeV
'Springer Science and Business Media LLC', 2021Co-Authors: Acharya Shreyasi, Adamova Dagmar, Adler Alexander, Adolfsson Jonatan, Aglieri Rinella Gianluca, Agnello Michelangelo, Agrawal Neelima, Ahammed Zubayer, Ahmad Shakeel, Sang Un AhnAbstract:International audienceThe coherent Photoproduction of $\rm{J/\psi}$ and $\rm{\psi'}$ mesons was measured in ultra-peripheral Pb-Pb collisions at a center-of-mass energy $\sqrt{s_{\mathrm{NN}}}~=~5.02$ TeV with the ALICE detector. Charmonia are detected in the central rapidity region for events where the hadronic interactions are strongly suppressed. The $\rm{J/\psi}$ is reconstructed using the dilepton ($l^{+} l^{-}$) and proton-antiproton decay channels, while for the $\rm{\psi'}$, the dilepton and the $l^{+} l^{-} \pi^{+} \pi^{-}$ decay channels are studied. The analysis is based on an event sample corresponding to an integrated luminosity of about 233 ${\mu b}^{-1}$. The results are compared with theoretical models for coherent $\rm{J/\psi}$ and $\rm{\psi'}$ Photoproduction. The coherent cross section is found to be in a good agreement with models incorporating moderate nuclear gluon shadowing of about 0.65 at a Bjorken-$x$ of around $6\times 10^{-4}$, such as the EPS09 parametrization, however none of the models is able to fully describe the rapidity dependence of the coherent $\rm{J/\psi}$ cross section including ALICE measurements at forward rapidity. The ratio of $\rm{\psi'}$ to $\rm{J/\psi}$ coherent Photoproduction cross sections was also measured and found to be consistent with the one for Photoproduction off protons
Acharya Shreyasi - One of the best experts on this subject based on the ideXlab platform.
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Coherent J/$\psi$ and $\psi'$ Photoproduction at midrapidity in ultra-peripheral Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV
2021Co-Authors: Acharya Shreyasi, Adamova Dagmar, Adler Alexander, Adolfsson Jonatan, Aglieri Rinella Gianluca, Agnello Michelangelo, Agrawal Neelima, Ahammed Zubayer, Ahmad Shakeel, Sang Un AhnAbstract:The coherent Photoproduction of J/$\psi$ and $\psi'$ mesons was measured in ultra-peripheral Pb-Pb collisions at a center-of-mass energy $\sqrt{s_{\rm NN}}$ = 5.02 TeV with the ALICE detector. Charmonia are detected in the central rapidity region for events where the hadronic interactions are strongly suppressed. The J/$\psi$ is reconstructed using the dilepton ($e^{+} e^{-}$) and proton-antiproton decay channels, while for the $\psi'$, the dilepton and the $e^{+} e^{-} \pi^{+} \pi^{-}$ decay channels are studied. The analysis is based on an event sample corresponding to an integrated luminosity of about 233 ${\mu b}^{-1}$. The results are compared with theoretical models for coherent J/$\psi$ and $\psi'$ Photoproduction. The coherent cross section is found to be in a good agreement with models incorporating moderate nuclear gluon shadowing of about 0.65 at a Bjorken-$x$ of around $6\times 10^{-4}$, such as the EPS09 parametrization, however none of the models is able to fully describe the rapidity dependence of the coherent J/$\psi$ cross section including ALICE measurements at forward rapidity. The ratio of $\psi'$ to J/$\psi$ coherent Photoproduction cross sections was also measured and found to be consistent with the one for Photoproduction off protons.The coherent Photoproduction of $\rm{J/\psi}$ and $\rm{\psi'}$ mesons was measured in ultra-peripheral Pb-Pb collisions at a center-of-mass energy $\sqrt{s_{\mathrm{NN}}}~=~5.02$ TeV with the ALICE detector. Charmonia are detected in the central rapidity region for events where the hadronic interactions are strongly suppressed. The $\rm{J/\psi}$ is reconstructed using the dilepton ($l^{+} l^{-}$) and proton-antiproton decay channels, while for the $\rm{\psi'}$, the dilepton and the $l^{+} l^{-} \pi^{+} \pi^{-}$ decay channels are studied. The analysis is based on an event sample corresponding to an integrated luminosity of about 233 ${\mu b}^{-1}$. The results are compared with theoretical models for coherent $\rm{J/\psi}$ and $\rm{\psi'}$ Photoproduction. The coherent cross section is found to be in a good agreement with models incorporating moderate nuclear gluon shadowing of about 0.65 at a Bjorken-$x$ of around $6\times 10^{-4}$, such as the EPS09 parametrization, however none of the models is able to fully describe the rapidity dependence of the coherent $\rm{J/\psi}$ cross section including ALICE measurements at forward rapidity. The ratio of $\rm{\psi'}$ to $\rm{J/\psi}$ coherent Photoproduction cross sections was also measured and found to be consistent with the one for Photoproduction off protons
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Coherent $\rm{J/\psi}$ and $\rm{\psi'}$ Photoproduction at midrapidity in ultra-peripheral Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}~=~5.02$ TeV
HAL CCSD, 2021Co-Authors: Acharya Shreyasi, Adamova Dagmar, Adler Alexander, Adolfsson Jonatan, Aglieri Rinella Gianluca, Agnello Michelangelo, Agrawal Neelima, Ahammed Zubayer, Ahmad Shakeel, Sang Un AhnAbstract:The coherent Photoproduction of $\rm{J/\psi}$ and $\rm{\psi'}$ mesons was measured in ultra-peripheral Pb-Pb collisions at a center-of-mass energy $\sqrt{s_{\mathrm{NN}}}~=~5.02$ TeV with the ALICE detector. Charmonia are detected in the central rapidity region for events where the hadronic interactions are strongly suppressed. The $\rm{J/\psi}$ is reconstructed using the dilepton ($l^{+} l^{-}$) and proton-antiproton decay channels, while for the $\rm{\psi'}$, the dilepton and the $l^{+} l^{-} \pi^{+} \pi^{-}$ decay channels are studied. The analysis is based on an event sample corresponding to an integrated luminosity of about 233 ${\mu b}^{-1}$. The results are compared with theoretical models for coherent $\rm{J/\psi}$ and $\rm{\psi'}$ Photoproduction. The coherent cross section is found to be in a good agreement with models incorporating moderate nuclear gluon shadowing of about 0.65 at a Bjorken-$x$ of around $6\times 10^{-4}$, such as the EPS09 parametrization, however none of the models is able to fully describe the rapidity dependence of the coherent $\rm{J/\psi}$ cross section including ALICE measurements at forward rapidity. The ratio of $\rm{\psi'}$ to $\rm{J/\psi}$ coherent Photoproduction cross sections was also measured and found to be consistent with the one for Photoproduction off protons
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Coherent $J/ \psi$ and $\phi$' Photoproduction at midrapidity in ultra-peripheral Pb–Pb collisions at $\sqrt {s_{NN}}$ = 5.02 TeV
'Springer Science and Business Media LLC', 2021Co-Authors: Acharya Shreyasi, Adamova Dagmar, Adler Alexander, Adolfsson Jonatan, Aglieri Rinella Gianluca, Agnello Michelangelo, Agrawal Neelima, Ahammed Zubayer, Ahmad Shakeel, Sang Un AhnAbstract:International audienceThe coherent Photoproduction of $\rm{J/\psi}$ and $\rm{\psi'}$ mesons was measured in ultra-peripheral Pb-Pb collisions at a center-of-mass energy $\sqrt{s_{\mathrm{NN}}}~=~5.02$ TeV with the ALICE detector. Charmonia are detected in the central rapidity region for events where the hadronic interactions are strongly suppressed. The $\rm{J/\psi}$ is reconstructed using the dilepton ($l^{+} l^{-}$) and proton-antiproton decay channels, while for the $\rm{\psi'}$, the dilepton and the $l^{+} l^{-} \pi^{+} \pi^{-}$ decay channels are studied. The analysis is based on an event sample corresponding to an integrated luminosity of about 233 ${\mu b}^{-1}$. The results are compared with theoretical models for coherent $\rm{J/\psi}$ and $\rm{\psi'}$ Photoproduction. The coherent cross section is found to be in a good agreement with models incorporating moderate nuclear gluon shadowing of about 0.65 at a Bjorken-$x$ of around $6\times 10^{-4}$, such as the EPS09 parametrization, however none of the models is able to fully describe the rapidity dependence of the coherent $\rm{J/\psi}$ cross section including ALICE measurements at forward rapidity. The ratio of $\rm{\psi'}$ to $\rm{J/\psi}$ coherent Photoproduction cross sections was also measured and found to be consistent with the one for Photoproduction off protons
Sergey Kosourov - One of the best experts on this subject based on the ideXlab platform.
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water oxidation by photosystem ii is the primary source of electrons for sustained h2 Photoproduction in nutrient replete green algae
Proceedings of the National Academy of Sciences of the United States of America, 2020Co-Authors: Sergey Kosourov, Valeria Nagy, Dmitry Shevela, Martina Jokel, Johannes Messinger, Yagut AllahverdiyevaAbstract:The unicellular green alga Chlamydomonas reinhardtii is capable of photosynthetic H2 production. H2 evolution occurs under anaerobic conditions and is difficult to sustain due to 1) competition between [FeFe]-hydrogenase (H2ase), the key enzyme responsible for H2 metabolism in algae, and the Calvin–Benson–Bassham (CBB) cycle for photosynthetic reductants and 2) inactivation of H2ase by O2 coevolved in photosynthesis. Recently, we achieved sustainable H2 Photoproduction by shifting algae from continuous illumination to a train of short (1 s) light pulses, interrupted by longer (9 s) dark periods. This illumination regime prevents activation of the CBB cycle and redirects photosynthetic electrons to H2ase. Employing membrane-inlet mass spectrometry and H 2 18 O , we now present clear evidence that efficient H2 Photoproduction in pulse-illuminated algae depends primarily on direct water biophotolysis, where water oxidation at the donor side of photosystem II (PSII) provides electrons for the reduction of protons by H2ase downstream of photosystem I. This occurs exclusively in the absence of CO2 fixation, while with the activation of the CBB cycle by longer (8 s) light pulses the H2 Photoproduction ceases and instead a slow overall H2 uptake is observed. We also demonstrate that the loss of PSII activity in DCMU-treated algae or in PSII-deficient mutant cells can be partly compensated for by the indirect (PSII-independent) H2 Photoproduction pathway, but only for a short (
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a truncated antenna mutant of chlamydomonas reinhardtii can produce more hydrogen than the parental strain
International Journal of Hydrogen Energy, 2011Co-Authors: Sergey Kosourov, Maria L Ghirardi, Michael SeibertAbstract:Abstract Photoproduction of H2 gas was examined in the Chlamydomonas reinhardtii tla1 strain, CC-4169, containing a truncated light-harvesting antenna, along with its parental CC-425 strain. Although enhanced photosynthetic performance of truncated antenna algae has been demonstrated previously (Polle et al. Planta 2003; 217:49–59), improved H2 Photoproduction has yet to be reported. Preliminary experiments showed that sulfur-deprived, suspension cultures of the tla1 mutant could not establish anaerobiosis in a photobioreactor, and thus, could not photoproduce H2 gas under conditions typical for the sulfur-deprived wild-type cells (Kosourov et al. Biotech Bioeng 2002; 78:731–40). However, they did produce H2 gas when deprived of sulfur and phosphorus after immobilization within thin (∼300 μm) alginate films. These films were monitored for long-term H2 Photoproduction activity under light intensities ranging from 19 to 350 μE m−2 s−1 PAR. Both the tla1 mutant and the CC-425 parental strain produced H2 gas for over 250 h under all light conditions tested. Relative to the parental strain, the CC-4169 mutant had lower maximum specific rates of H2 production at low and medium light intensities (19 and 184 μE m−2 s−1), but it exhibited a 4-times higher maximum specific rate at 285 μE m−2 s−1 and an 8.5-times higher rate at 350 μE m−2 s−1 when immobilized at approximately the same cell density as the parental strain. As a result, the CC-4169 strain accumulated almost 4-times more H2 than CC-425 at 285 μE m−2 s−1 and over 6-times more at 350 μE m−2 s−1 during 250-h experiments. These results are the first demonstration that truncating light-harvesting antennae in algal cells can increase the efficiency of H2 Photoproduction in mass culture at high light intensity.
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effects of extracellular ph on the metabolic pathways in sulfur deprived h2 producing chlamydomonas reinhardtii cultures
Plant and Cell Physiology, 2003Co-Authors: Sergey Kosourov, Michael Seibert, Maria L GhirardiAbstract:;Sustained Photoproduction of H 2 by the green alga, Chlamydomonas reinhardtii, can be obtained by incubating cells in sulfur-deprived medium [Ghirardi et al. (2000b) Trends Biotechnol. 18: 506; Melis et al. (2000) Plant Physiol. 122: 127]. The current work focuses on (a) the effects of different initial extracellular pHs on the inactivation of photosystem II (PSII) and O2-sensitive H2-production activity in sulfur-deprived algal cells and (b) the relationships among H2-production, photosynthetic, aerobic and anaerobic metabolisms under different pH regimens. The maximum rate and yield of H2 production occur when the pH at the start of the sulfur deprivation period is 7.7 and decrease when the initial pH is lowered to 6.5 or increased to 8.2. The pH profile of hydrogen Photoproduction correlates with that of the residual PSII activity (optimum pH 7.3–7.9), but not with the pH profiles of photosynthetic electron transport through photosystem I or of starch and protein degradation. In vitro hydrogenase activity over this pH range is much higher than the actual in situ rates of H 2 production, indicating that hydrogenase activity per se is not limiting. Starch and protein catabolisms generate formate, acetate and ethanol; contribute some reductant for H 2 Photoproduction, as indicated by 3-(3,4-dichlorophenyl)1,1-dimethylurea and 2,5-dibromo-6-isopropyl-3-methyl-1,4benzoquinone inhibition results; and are the primary sources of reductant for respiratory processes that remove photosynthetically generated O2. Carbon balances demonstrate that alternative metabolic pathways predominate at different pHs, and these depend on whether residual photosynthetic activity is present or not.
