In the context of future electron-ion collision experiments,particularly the Electron-Ion Collider(EIC)and the Electron-Ion Collider in China(EicC),investigating exclusive photoproduction processes is of paramount imp...In the context of future electron-ion collision experiments,particularly the Electron-Ion Collider(EIC)and the Electron-Ion Collider in China(EicC),investigating exclusive photoproduction processes is of paramount importance.These processes offer a distinctive opportunity to probe the gluon structure of nuclei across a broad range of Bjorken x,thereby enabling measurements of nuclear shadowing and facilitating the search for gluon saturation and color glass condensates.This study explores the potential of utilizing neutron tagging via the Coulomb excitation of nuclei to precisely determine the impact parameter for exclusive photoproduction in electron-ion collisions.By developing the equivalent photon approximation for fast electrons,this study incorporates a coordinate-space-dependent photon flux distribution to elucidate the relationship between the photon transverse momentum distribution and the collision impact parameter.Furthermore,the differential cross section for Coulomb excitation of nuclei is derived by leveraging the spatial information from the photon flux.Our calculations demonstrate that neutron tagging can significantly alter the impact parameter distributions,thereby providing a robust method for impact parameter manipulation in electron-ion collisions.This study provides valuable insights and strategies for exploring the impact parameter dependence of exclusive photoproduction,offering novel insights for experimental design and data analysis.Ultimately,it enhances our understanding of the gluon distribution within the nucleus.展开更多
Tetracyclines constitute one of the most important antibiotic families and represent a classic example of phototoxicity. The photoproducts of tetracyclines and their parent compounds have potentially adverse effects o...Tetracyclines constitute one of the most important antibiotic families and represent a classic example of phototoxicity. The photoproducts of tetracyclines and their parent compounds have potentially adverse effects on natural ecosystem. In this study, the self-sensitized oxidation products of tetracycline （TC） and oxytetracycline （OTC） were determined and the effects of Ca2＋ and Mg2＋on self-sensitized degradation were investigated. The Ca2＋ and Mg2＋ in the natural water sample accounted for enhancement （pH 7.3） and inhibition （pH 9.0） of photodegradation of TC and OTC due to the formation of metal-ions complexes. The formation of Mg2＋ complexes was unfavorable for the photodegradation of the tetracyclines at both pH values. In contrast, the Ca2＋ complexes facilitated the attack of singlet oxygen （102） arising from self-sensitization at pH 7.3 and enhanced TC photodegradation. For the first time, self- sensitized oxidation products of TC and OTC were verified by quenching experiments and detected by LC/ESI-DAD-MS. The products had a nominal mass 14 Da higher than the parent drugs （designated M＋ 14）, which resulted from the 102 attack of the dimethylamino group on the C-4 atom of the tetracyclines. The presence of Ca2＋ and Mg2＋ also affected the generation of M＋ 14 due to the formation of metal-ions complexes with TC and OTC. The findings suggest that the metal-ion complexation has significant impact on the self- sensitized oxidation processes and the photoproducts of tetracyclines.展开更多
The sunlight photodegradation half-lives of 20 mg/L acetochlor were 151, 154 and 169 days in de-ionized water, river water and paddy water, respectively. When exposed to ultraviolet (UV) light, acetochlor in aqueous s...The sunlight photodegradation half-lives of 20 mg/L acetochlor were 151, 154 and 169 days in de-ionized water, river water and paddy water, respectively. When exposed to ultraviolet (UV) light, acetochlor in aqueous solution was rapidly degraded. The half-lives were 7.1, 10.1, and 11.5 min in de-ionized water, river water and paddy water, respectively. Photoproducts of acetochlor were identified by gas chromatography/mass spectrometry(GC/MS) and found at least twelve photoproducts resulted from dechlorination with subsequent hydroxylation and cyclization processes. The chemical structures of ten photoproducts were presumed on the basis of mass spectrum interpretation and literature data. Photoproducts are identified as 2-ethyl-6-methylaniline; N,N-diethylaniline; 4,8-dimethyl-2-oxo-1,2,3,4- tetrahydroquino-line; 2-oxo-N-(2-ethyl-6-methylphenyl)-N-(ethoxymethyl)acetamide; N-(ethoxymethyl)-2′-ethyl-6′-methylformanilide;1-hydroxyacetyl-2-ethoxyl-7-ethylind ole; 8-ethyl-1-ethoxymethyl-2-oxo-1,2,3,4-tetrahydroquinoline; 4,8-dimethyl-1-ethoxymethyl-2-oxo-1,2,3,4-tetrahydroquinoline; 2-hydroxy-2′-ethyl-6′-methyl-N-(ethoxymethyl)acetanilide and a compound related to acetochlor. The other two photoproducts were detected by GC/MS although their chemical structure was unknown.展开更多
Carbon monoxide(CO) plays a significant role in global warming and atmospheric chemistry. Global oceans are net natural sources of atmospheric CO. CO at surface ocean is primarily produced from the photochemical degra...Carbon monoxide(CO) plays a significant role in global warming and atmospheric chemistry. Global oceans are net natural sources of atmospheric CO. CO at surface ocean is primarily produced from the photochemical degradation of chromophoric dissolved organic matter(CDOM). In this study, the effects of photobleaching, temperature and the origin(terrestrial or marine) of CDOM on the apparent quantum yields(AQY) of CO were studied for seawater samples collected from Jiaozhou Bay. Our results demonstrat that photobleaching, temperature and the origin of CDOM strongly affected the efficiency of CO photoproduction. The concentration, absorbance and fluorescence of CDOM exponentially decreased with increasing light dose. Terrestrial riverine organic matter could be more prone to photodegradation than the marine algae-derived one. The relationships between CO AQY and the dissolved organic carbon-specific absorption coefficient at 254 nm for the photobleaching study were nonlinear, whereas those of the original samples were strongly linear. This suggests that: 1) terrestrial riverine CDOM was more efficient than marine algae-derived CDOM for CO photoproduction; 2) aromatic and olefinic moieties of the CDOM pool were affected more strongly by degradation processes than by aliphatic ones. Water temperature and the origin of CDOM strongly affected the efficiency of CO photoproduction. The photoproduction rate of CO in autumn was estimated to be 31.98 μmol m-2 d-1 and the total DOC photomineralization was equivalent to 3.25%- 6.35% of primary production in Jiaozhou Bay. Our results indicate that CO photochemistry in coastal areas is important for oceanic carbon cycle.展开更多
We calculate the centrality dependence of inclusive cross section of large-p _(T )charmed-meson(D^0,D~*,D^(*+),and D_s^+)from heavy quark fragmentation by the hard photoproduction processes in ultrarelativistic heavy ...We calculate the centrality dependence of inclusive cross section of large-p _(T )charmed-meson(D^0,D~*,D^(*+),and D_s^+)from heavy quark fragmentation by the hard photoproduction processes in ultrarelativistic heavy ion collisions.The numerical results indicate that the contribution of the hard photoproduction processes cannot be negligible for the inclusive charmed-meson production in Au-Au collisions at Relativistic Heavy Ion Collider(RHIC)and Pb-Pb collisions at Large Hadron Collider(LHC).展开更多
Under the irradiation of a middle pressure mercury lamp(MPML), we found that the photo lyses of nucleobases, nucleosides and nucleotides were strongly enhanced by phosphates (termed phosphate effect). In order to...Under the irradiation of a middle pressure mercury lamp(MPML), we found that the photo lyses of nucleobases, nucleosides and nucleotides were strongly enhanced by phosphates (termed phosphate effect). In order to explain this phenomenon, the photolytic systems of cytosine in phosphate solutions were selected and studied. Experimental results indicated that the UV irradiation (190-220 nm) in the emission spectra of MPML is responsible for the phosphate effect. Phosphates absorbing the UV (190-220 nm) energy are converted to phosphate radical anions, which react with cytosine, leading to a novel photoproduct with phosphate group (C 4H 6N 3O 5P). It has been isolated, purified and characterized by means of elementary analysis, UV, IR, EI MS, 1H NMR, 13 C NMR and 31 P NMR. The phosphate effect and its formation mechanism have been discussed.展开更多
H2 photoproduction and nitrogenase activities in two strains of Anabaena variabilismarked wild type ATCC 29413 and mutant PK84 exposed to thermal stress (temperature higher than thenormal incubation temperature of 30...H2 photoproduction and nitrogenase activities in two strains of Anabaena variabilismarked wild type ATCC 29413 and mutant PK84 exposed to thermal stress (temperature higher than thenormal incubation temperature of 30℃) were studied. Cultures of both strains collected from any intervalof logarithmic growth phase exhibited high H2 photoproduction and nitrogenase activities when exposed tolimited time heat shock during the assay process. In contrast, the algal H2 photoproduction rate of bothstrains fluctuated with long term thermal stress caused hy increasing the growth temperature from 30℃ to36℃.The changes of nitrogenase (the key H2 photobiosynhetic enzyme) activities in the mutant PK84showed variation tendency similar to that of H2 photoproduction during exposure to thermal stress, indicat-ing that fluctuation of H2 photopnduction in the mutant was mainly due to the variation of nitrogenase ac-tivities. A temporary maximal H2 photoproduction in the mutant PK84 (wild type ATCC29413 ) was ob-served when cells po at 36℃ for 14 (6) days. However, the responses of nitrogenase activities in thewild type to thermal stress were not completely similar to those in the mutant in spite of similar variationsof H2 photoproduction in both strains. The data obtained in these studies suggested tha the activities ofother enzymes (in the wild strain) involved in H2 photoproduction were affected by thermal stress since H2photoporduction maximized or dropped to 0 without variation tendency similar to that of nitrogenase activi-ties.Furthermore, an enhancement of H2 photoproduction speed of the mutant strain cultured in a 4.4 Llaboratory photobioreactor was also observed when it was subjected to short time continuous charge of ar-gon, and temperature rise.All these results indicated that high temperature plays an important role in the photo-autotrophic H2photoproduction, and that long term thermal stress is unfavourable for net H2 phooproduction in bothstrains of A. variabilis though short-time heat shock is conducive to H2 photoproduction.展开更多
Fluctuations of dilepton production from two photon interactionsγγ→l^+l^-are studied in semicentral and peripheral nuclear collisions.Based on the Weizsacker-Williams approach,electromagnetic(EM)fields generated by...Fluctuations of dilepton production from two photon interactionsγγ→l^+l^-are studied in semicentral and peripheral nuclear collisions.Based on the Weizsacker-Williams approach,electromagnetic(EM)fields generated by moving nuclear charges are approximated as quasi-real photons.As fluctuating EM fields in each collision event are hard to be measured directly in experiments due to its short lifetime,we study the dilepton photoproduction with fluctuating EM fields,which are crucial for the EM fields induced chiral and charged particle evolutions,and calculate the relative standard deviation of the dilepton mass spectrum with the event-by-event fluctuating nuclear charge distributions.This fluctuation effect becomes smaller in more peripheral collisions where the shift of proton positions is implicit for EM fields outside the nucleus.The uncertainty of effective impact parameter△b on the standard deviation is also studied,and its effect is around one-third of the effect of nuclear charge fluctuations when△b is taken as^1 fm.展开更多
With a photon spectrum of high energy charged partons, both differential and total cross sections of J/ψ√andΥ(1s) inclusive photoproduction in ultra-peripheral p-Pb Collisions (UPCs) at s=5.5 Te V are given. A dire...With a photon spectrum of high energy charged partons, both differential and total cross sections of J/ψ√andΥ(1s) inclusive photoproduction in ultra-peripheral p-Pb Collisions (UPCs) at s=5.5 Te V are given. A direct photon process and a resolved photon process including fragment and non-fragment contributions are considered. The total cross section is compared to the inelastic production results in coherent p-Pb collisions at the same center-of-mass energy. Our results seem non-negligible.展开更多
Strong electromagnetic fields produced in the non-central heavy-ion collisions can induce vector meson photoproduction.In this paper,we study the photoproduction J/ψandφmesons in the relativistic heavy-ion collision...Strong electromagnetic fields produced in the non-central heavy-ion collisions can induce vector meson photoproduction.In this paper,we study the photoproduction J/ψandφmesons in the relativistic heavy-ion collision from ultra-peripheral nuclear collisions to peripheral hadronic heavy ion collisions.And then include both initial hadronic production and thermal production in quark-gluon plasma(QGP).We find,for the charm anti-charm bound state J/ψ,the photoproduced J/ψs are mainly in the very low momentum region and clearly exceed the hadronic production.However,considering the thermal production of strange quark anti-quark pairs in QGP produced in relativistic heavy-ion collisions,the photoproducedφis usually smaller than the thermal production and only evident at very peripheral collisions as even their photoproduction is much larger than J/ψ.展开更多
Equilibrium photoproduct of 7r-cyclopentadienyliron dicarbonyl dimer [CpFe（CO）2]2 in non- polar solvent carbon tetrachloride （CC14） is investigated using time-resolved 2D IR spec- troscopy. One of the several poss...Equilibrium photoproduct of 7r-cyclopentadienyliron dicarbonyl dimer [CpFe（CO）2]2 in non- polar solvent carbon tetrachloride （CC14） is investigated using time-resolved 2D IR spec- troscopy. One of the several possible visible-light-driven photoreaction pathways is confirmed and the product is found to contain a di-carbonyl group that exhibits quantum beating be- tween two equivalent transitions in time-resolved 2D IR spectra, which turns out to be the anti-symmetric and symmetric stretching of the terminal carbonyl stretching modes of CpFe（CO）2C1. This is the main product and its reaction pathway involves radical formation, followed by chloride addition. Quantum-chemistry computations support these experimental results. Our results indicate that 2D IR method can be used to identify in situ structures and dynamics of chemical species involved in condensed-phase chemical reactions.展开更多
As a well known DNA photolesion product, the special UV induced pyrimidine dimmer called spore photoproduct （SP）, has aroused strong research interests. The SP formation was reported solely between two adjacent thym...As a well known DNA photolesion product, the special UV induced pyrimidine dimmer called spore photoproduct （SP）, has aroused strong research interests. The SP formation was reported solely between two adjacent thymidine residues. It remains unclear in pervious experimental observations why there is an absence of the cytosine-derived SP-like photoprod- uct formation at the cytosine containing DNA strand, although the cytosine residue holds great similarity to thymine in terms of molecular structure. From a theoretical perspec- tive, we have explored this issue in this work by means of density functional theory at the B3LYP/6-311＋＋G（d,p） //B3LYP/6-31G（d,p） level for the DNA dinucleotide fragment, cy- tosine phosphate thymine （CpT）. Key factors blocking the formation of the SP-like product between two adjacent cytosine and thymidine residues are revealed. Instead of undergoing photochemical SP reaction, a photophysical deactivation pathway back to the ground state turns out to be favorable for the CpT dinucleotide fragment.展开更多
Based on the quark-gluon contents of nucleon and strongly believing that the force mediators,Pomeronand its counterpart in the conventional approach of Regge theory,for high energy diffractive process would be the ten...Based on the quark-gluon contents of nucleon and strongly believing that the force mediators,Pomeronand its counterpart in the conventional approach of Regge theory,for high energy diffractive process would be the tensorglueball and Odderon respectively,we discuss photo-production of vector meson φ off the deuteron at energy less than 3GeV in the QCD inspired model in which the quark gluon degrees of freedom and glueball,Odderon exchange are takeninto account.A calculation is performed for γ + D →φ + D,and the theoretical predictions of the differential crosssection dσ^(γD)) /dt,are presented and compared with available experimental data.Our QCD inspired model reproducesdata quite well in the whole range of the experimental measurements up to |t| ■0.4 GeV.Our results can be used toextract γn→φn data,which cannot be measured in experiment.展开更多
Atorvastatin, widely prescribed hypolipidemic drug, undergoes rapid, probably self-sensitised, degradation (less than 20% left after 25-minute irradiation) if irradiated by wavelengths 300 - 350 nm in aqueous solution...Atorvastatin, widely prescribed hypolipidemic drug, undergoes rapid, probably self-sensitised, degradation (less than 20% left after 25-minute irradiation) if irradiated by wavelengths 300 - 350 nm in aqueous solution. When ferric ions are added to the reaction mixture, the degradation follows first order kinetics with a rate constant of 0.130 min<sup><span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span>1</sup>. Photochemical degradation may thus represent a significant way of environmental transformation of this pharmaceutical. Toxicity testing of atorvastatin and atorvastatin photoproducts performed on the water plant <em>Lemna minor</em> revealed that atorvastatin itself exhibited no observable toxic effect measured as leaf area growth inhibition, while the photoproducts showed a significant toxicity to the plant, which shows the extreme importance of investigating not only toxicity of drugs themselves on aquatic organisms but also effects of their transformation products.展开更多
Taking into account the effects of shadowing and jet quenching, the large transverse momentum distribution of K＋, π＋ and K＋/π＋ ratios at s = 200 GeV originating from resolved photoproduction processes is calcula...Taking into account the effects of shadowing and jet quenching, the large transverse momentum distribution of K＋, π＋ and K＋/π＋ ratios at s = 200 GeV originating from resolved photoproduction processes is calculated based on perturbative quantum chromodynamics. It is found that the contribution of K＋ and π＋ produced by photoproduction processes is evident. The K＋ /π＋ ratios in Au-Au collisions show an obvious enhancement compared with p p collisions. The numerical results indicate that the photoproduetion processes are good modification for kaon and pion production.展开更多
Hard photoproduction of J/ψ and T at large hadron collider(LHC)Pb-Pb collisionswith CMS energy 6300 GeV/u is discussed in the process Pb+Pb→Pb+J/ψ+X with threetypes of equivalent photon spectrum functions.It turns ...Hard photoproduction of J/ψ and T at large hadron collider(LHC)Pb-Pb collisionswith CMS energy 6300 GeV/u is discussed in the process Pb+Pb→Pb+J/ψ+X with threetypes of equivalent photon spectrum functions.It turns out that the hard photoproductionprocesses can be used to probe several important problems such as the gluon distribution in thenucleus,gluon and heavy q.uark fragmentation of J/ψ,et al.In addition,the process alsoprovides a new way of testing the EMC effects.展开更多
We study the inelastic charmonium(J/ψ,ψ(2S))and bottomonium(Υ(nS))photoproduction and fragmentation processes in p-p and Pb-Pb collisions at LHC energies,where the ultra-incoherent photon emission is included.Using...We study the inelastic charmonium(J/ψ,ψ(2S))and bottomonium(Υ(nS))photoproduction and fragmentation processes in p-p and Pb-Pb collisions at LHC energies,where the ultra-incoherent photon emission is included.Using the NRQCD factorization approach,an exact treatment is developed.This approach recovers the Weizs?cker-Williams approximation(WWA)near the Q^(2)~0region,where the Martin-Ryskin and BCCKL methods are used to avoid double counting.We calculated the Q^(2),y,z,√s and p_(T)dependent and total cross sections.Inelastic photoproduction and fragmentation were observed to contribute to heavy quarkonium production,particularly at large p_(T).In addition,the contribution of the ultra-incoherent photon channel,which increases rapidly with quarkonium mass,is significant and begins to dominate the photoproduction processes for large p_(T).We also obtained the complete WWA validity scopes of inelastic heavy quarkonium photoproduction in heavy-ion collisions.The WWA had high accuracy at high energies and for Pb-Pb collisions.However,current photon spectra are derived beyond the WWA scope,and double counting can occur when considering different channels simultaneously.展开更多
We present a comprehensive analysis of near-threshold photoproduction ofρ^(0),ω,andΦmesons on a deuterium target,utilizing published datasets from DESY and SLAC forρ^(0)andωproduction,as well as data from the LEP...We present a comprehensive analysis of near-threshold photoproduction ofρ^(0),ω,andΦmesons on a deuterium target,utilizing published datasets from DESY and SLAC forρ^(0)andωproduction,as well as data from the LEPS and CLAS Collaborations forΦproduction.In extracting the deuteron mass radius,we adopt a dipole parameterization for the scalar gravitational form factor,which effectively captures the|t|-dependence of the differential cross sections associated with vector meson photoproduction.In addition,results from alternative commonly used form factor parameterizations are considered and compared.By employing the vector meson dominance(VMD)framework and invoking low-energy Quantum Chromodynamics(QCD)theorems,we extract the deuteron mass radius from near-threshold photoproduction data ofρ^(0),ω,andΦmesons.The mass radii obtained from the various datasets are found to be consistent within statistical uncertainties,yielding an average value of 2.03±0.13 fm under the dipole form assumption.We also provide a detailed discussion of the sensitivity of the extracted radius to the choice of gravitational form factor models.Our result represents a significant improvement in precision compared to earlier estimates based solely onΦmeson photoproduction,offering new constraints for theoretical models of nuclear structure and deepening our understanding of the mass distribution within the deuteron.展开更多
The photoproduction of the f1(1285)meson off the proton target is investigated within an effective Lagrangian approach.The t-channelρ-andω-exchange diagrams,u-channel nucleon-exchange diagram,generalized contact ter...The photoproduction of the f1(1285)meson off the proton target is investigated within an effective Lagrangian approach.The t-channelρ-andω-exchange diagrams,u-channel nucleon-exchange diagram,generalized contact term,and s-channel pole diagrams of the nucleon and a minimal number of nucleon resonances are taken into account in constructing the reaction amplitudes to describe the experimental data.Three different models,that is,the Feynman,Regge,and interpolated Regge models,are employed,where the t-channel reaction amplitudes are constructed in Feynman,Regge,and interpolated Regge types,respectively.The results show that neither the Feynman model with two nucleon resonances nor the interpolated Regge model with one nucleon resonance can satisfactorily reproduce the available data forγp→f1(1285)p.Nevertheless,in the Regge model,when any one of the N(1990)7/2^(+),N(2000)5/2^(+),N(2040)3/2^(+),N(2060)5/2^(-),N(2100)1/2^(+),N(2120)3/2^(-),N(2190)7/2^(-),N(2300)1/2^(+),and N(2570)5/2^(-)resonances is considered,the data can be well described.The resulting resonance parameters are consistent with those advocated in the Particle Data Group(PDG)review.Further analysis shows that,in the high-energy region,the peaks of γp→f1(1285)p differential cross sections at forward angles are dominated by the contributions from t-channelρ-andω-exchange diagrams,while in low-energy region,the s-channel pole diagrams of resonances also provide significant contributions to theγp→f1(1285)p cross sections.展开更多
基金supported in part by the National Key Research and Development Program of China under Contract No.2022YFA1604900the National Natural Science Foundation of China(NSFC)under Contract No.12175223 and 12005220+1 种基金W.Zha is supported by Anhui Provincial Natural Science Foundation No.2208085J23Youth Innovation Promotion Association of Chinese Academy of Science.
文摘In the context of future electron-ion collision experiments,particularly the Electron-Ion Collider(EIC)and the Electron-Ion Collider in China(EicC),investigating exclusive photoproduction processes is of paramount importance.These processes offer a distinctive opportunity to probe the gluon structure of nuclei across a broad range of Bjorken x,thereby enabling measurements of nuclear shadowing and facilitating the search for gluon saturation and color glass condensates.This study explores the potential of utilizing neutron tagging via the Coulomb excitation of nuclei to precisely determine the impact parameter for exclusive photoproduction in electron-ion collisions.By developing the equivalent photon approximation for fast electrons,this study incorporates a coordinate-space-dependent photon flux distribution to elucidate the relationship between the photon transverse momentum distribution and the collision impact parameter.Furthermore,the differential cross section for Coulomb excitation of nuclei is derived by leveraging the spatial information from the photon flux.Our calculations demonstrate that neutron tagging can significantly alter the impact parameter distributions,thereby providing a robust method for impact parameter manipulation in electron-ion collisions.This study provides valuable insights and strategies for exploring the impact parameter dependence of exclusive photoproduction,offering novel insights for experimental design and data analysis.Ultimately,it enhances our understanding of the gluon distribution within the nucleus.
基金supported by the National Natural Science Foundation of China (No. 21007018,51078161)the Natural Science Foundation of Hubei Province (No. 2010CDB01104)+1 种基金the Research Fund for the Doctoral Program of Higher Education of China (No. 20100142120004)the 11th Five-year Plan of National Water Environmental Special Program of China (No. 2008ZX07211-10-02)
文摘Tetracyclines constitute one of the most important antibiotic families and represent a classic example of phototoxicity. The photoproducts of tetracyclines and their parent compounds have potentially adverse effects on natural ecosystem. In this study, the self-sensitized oxidation products of tetracycline （TC） and oxytetracycline （OTC） were determined and the effects of Ca2＋ and Mg2＋on self-sensitized degradation were investigated. The Ca2＋ and Mg2＋ in the natural water sample accounted for enhancement （pH 7.3） and inhibition （pH 9.0） of photodegradation of TC and OTC due to the formation of metal-ions complexes. The formation of Mg2＋ complexes was unfavorable for the photodegradation of the tetracyclines at both pH values. In contrast, the Ca2＋ complexes facilitated the attack of singlet oxygen （102） arising from self-sensitization at pH 7.3 and enhanced TC photodegradation. For the first time, self- sensitized oxidation products of TC and OTC were verified by quenching experiments and detected by LC/ESI-DAD-MS. The products had a nominal mass 14 Da higher than the parent drugs （designated M＋ 14）, which resulted from the 102 attack of the dimethylamino group on the C-4 atom of the tetracyclines. The presence of Ca2＋ and Mg2＋ also affected the generation of M＋ 14 due to the formation of metal-ions complexes with TC and OTC. The findings suggest that the metal-ion complexation has significant impact on the self- sensitized oxidation processes and the photoproducts of tetracyclines.
文摘The sunlight photodegradation half-lives of 20 mg/L acetochlor were 151, 154 and 169 days in de-ionized water, river water and paddy water, respectively. When exposed to ultraviolet (UV) light, acetochlor in aqueous solution was rapidly degraded. The half-lives were 7.1, 10.1, and 11.5 min in de-ionized water, river water and paddy water, respectively. Photoproducts of acetochlor were identified by gas chromatography/mass spectrometry(GC/MS) and found at least twelve photoproducts resulted from dechlorination with subsequent hydroxylation and cyclization processes. The chemical structures of ten photoproducts were presumed on the basis of mass spectrum interpretation and literature data. Photoproducts are identified as 2-ethyl-6-methylaniline; N,N-diethylaniline; 4,8-dimethyl-2-oxo-1,2,3,4- tetrahydroquino-line; 2-oxo-N-(2-ethyl-6-methylphenyl)-N-(ethoxymethyl)acetamide; N-(ethoxymethyl)-2′-ethyl-6′-methylformanilide;1-hydroxyacetyl-2-ethoxyl-7-ethylind ole; 8-ethyl-1-ethoxymethyl-2-oxo-1,2,3,4-tetrahydroquinoline; 4,8-dimethyl-1-ethoxymethyl-2-oxo-1,2,3,4-tetrahydroquinoline; 2-hydroxy-2′-ethyl-6′-methyl-N-(ethoxymethyl)acetanilide and a compound related to acetochlor. The other two photoproducts were detected by GC/MS although their chemical structure was unknown.
基金financially supported by the National Natural Science Foundation of China (No. 40976043)the Science and Technology Key Project of Shandong Province (2006GG2205024)+2 种基金the Changjiang Scholars Program, Ministry of Education of Chinathe Taishan Scholars Program of Shandong Provincethe Scholar Foundation of Qingdao Agricultural University (631102)
文摘Carbon monoxide(CO) plays a significant role in global warming and atmospheric chemistry. Global oceans are net natural sources of atmospheric CO. CO at surface ocean is primarily produced from the photochemical degradation of chromophoric dissolved organic matter(CDOM). In this study, the effects of photobleaching, temperature and the origin(terrestrial or marine) of CDOM on the apparent quantum yields(AQY) of CO were studied for seawater samples collected from Jiaozhou Bay. Our results demonstrat that photobleaching, temperature and the origin of CDOM strongly affected the efficiency of CO photoproduction. The concentration, absorbance and fluorescence of CDOM exponentially decreased with increasing light dose. Terrestrial riverine organic matter could be more prone to photodegradation than the marine algae-derived one. The relationships between CO AQY and the dissolved organic carbon-specific absorption coefficient at 254 nm for the photobleaching study were nonlinear, whereas those of the original samples were strongly linear. This suggests that: 1) terrestrial riverine CDOM was more efficient than marine algae-derived CDOM for CO photoproduction; 2) aromatic and olefinic moieties of the CDOM pool were affected more strongly by degradation processes than by aliphatic ones. Water temperature and the origin of CDOM strongly affected the efficiency of CO photoproduction. The photoproduction rate of CO in autumn was estimated to be 31.98 μmol m-2 d-1 and the total DOC photomineralization was equivalent to 3.25%- 6.35% of primary production in Jiaozhou Bay. Our results indicate that CO photochemistry in coastal areas is important for oceanic carbon cycle.
基金Supported by the National Natural Science Foundation of China under Grant No.11847207the International Postdoctoral Exchange Fellowship Program of China under Grant No.20180010the China Postdoctoral Science Foundation funded project No.2017M610663
文摘We calculate the centrality dependence of inclusive cross section of large-p _(T )charmed-meson(D^0,D~*,D^(*+),and D_s^+)from heavy quark fragmentation by the hard photoproduction processes in ultrarelativistic heavy ion collisions.The numerical results indicate that the contribution of the hard photoproduction processes cannot be negligible for the inclusive charmed-meson production in Au-Au collisions at Relativistic Heavy Ion Collider(RHIC)and Pb-Pb collisions at Large Hadron Collider(LHC).
文摘Under the irradiation of a middle pressure mercury lamp(MPML), we found that the photo lyses of nucleobases, nucleosides and nucleotides were strongly enhanced by phosphates (termed phosphate effect). In order to explain this phenomenon, the photolytic systems of cytosine in phosphate solutions were selected and studied. Experimental results indicated that the UV irradiation (190-220 nm) in the emission spectra of MPML is responsible for the phosphate effect. Phosphates absorbing the UV (190-220 nm) energy are converted to phosphate radical anions, which react with cytosine, leading to a novel photoproduct with phosphate group (C 4H 6N 3O 5P). It has been isolated, purified and characterized by means of elementary analysis, UV, IR, EI MS, 1H NMR, 13 C NMR and 31 P NMR. The phosphate effect and its formation mechanism have been discussed.
文摘H2 photoproduction and nitrogenase activities in two strains of Anabaena variabilismarked wild type ATCC 29413 and mutant PK84 exposed to thermal stress (temperature higher than thenormal incubation temperature of 30℃) were studied. Cultures of both strains collected from any intervalof logarithmic growth phase exhibited high H2 photoproduction and nitrogenase activities when exposed tolimited time heat shock during the assay process. In contrast, the algal H2 photoproduction rate of bothstrains fluctuated with long term thermal stress caused hy increasing the growth temperature from 30℃ to36℃.The changes of nitrogenase (the key H2 photobiosynhetic enzyme) activities in the mutant PK84showed variation tendency similar to that of H2 photoproduction during exposure to thermal stress, indicat-ing that fluctuation of H2 photopnduction in the mutant was mainly due to the variation of nitrogenase ac-tivities. A temporary maximal H2 photoproduction in the mutant PK84 (wild type ATCC29413 ) was ob-served when cells po at 36℃ for 14 (6) days. However, the responses of nitrogenase activities in thewild type to thermal stress were not completely similar to those in the mutant in spite of similar variationsof H2 photoproduction in both strains. The data obtained in these studies suggested tha the activities ofother enzymes (in the wild strain) involved in H2 photoproduction were affected by thermal stress since H2photoporduction maximized or dropped to 0 without variation tendency similar to that of nitrogenase activi-ties.Furthermore, an enhancement of H2 photoproduction speed of the mutant strain cultured in a 4.4 Llaboratory photobioreactor was also observed when it was subjected to short time continuous charge of ar-gon, and temperature rise.All these results indicated that high temperature plays an important role in the photo-autotrophic H2photoproduction, and that long term thermal stress is unfavourable for net H2 phooproduction in bothstrains of A. variabilis though short-time heat shock is conducive to H2 photoproduction.
基金supported by NSFC Grant No.11705125,11547043the Sino-Germany(CSC-DAAD)Postdoc Scholarshipsupport by the AI grant of SAMSON AG,Frankfurt.
文摘Fluctuations of dilepton production from two photon interactionsγγ→l^+l^-are studied in semicentral and peripheral nuclear collisions.Based on the Weizsacker-Williams approach,electromagnetic(EM)fields generated by moving nuclear charges are approximated as quasi-real photons.As fluctuating EM fields in each collision event are hard to be measured directly in experiments due to its short lifetime,we study the dilepton photoproduction with fluctuating EM fields,which are crucial for the EM fields induced chiral and charged particle evolutions,and calculate the relative standard deviation of the dilepton mass spectrum with the event-by-event fluctuating nuclear charge distributions.This fluctuation effect becomes smaller in more peripheral collisions where the shift of proton positions is implicit for EM fields outside the nucleus.The uncertainty of effective impact parameter△b on the standard deviation is also studied,and its effect is around one-third of the effect of nuclear charge fluctuations when△b is taken as^1 fm.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11465021,11065010
文摘With a photon spectrum of high energy charged partons, both differential and total cross sections of J/ψ√andΥ(1s) inclusive photoproduction in ultra-peripheral p-Pb Collisions (UPCs) at s=5.5 Te V are given. A direct photon process and a resolved photon process including fragment and non-fragment contributions are considered. The total cross section is compared to the inelastic production results in coherent p-Pb collisions at the same center-of-mass energy. Our results seem non-negligible.
文摘Strong electromagnetic fields produced in the non-central heavy-ion collisions can induce vector meson photoproduction.In this paper,we study the photoproduction J/ψandφmesons in the relativistic heavy-ion collision from ultra-peripheral nuclear collisions to peripheral hadronic heavy ion collisions.And then include both initial hadronic production and thermal production in quark-gluon plasma(QGP).We find,for the charm anti-charm bound state J/ψ,the photoproduced J/ψs are mainly in the very low momentum region and clearly exceed the hadronic production.However,considering the thermal production of strange quark anti-quark pairs in QGP produced in relativistic heavy-ion collisions,the photoproducedφis usually smaller than the thermal production and only evident at very peripheral collisions as even their photoproduction is much larger than J/ψ.
文摘Equilibrium photoproduct of 7r-cyclopentadienyliron dicarbonyl dimer [CpFe（CO）2]2 in non- polar solvent carbon tetrachloride （CC14） is investigated using time-resolved 2D IR spec- troscopy. One of the several possible visible-light-driven photoreaction pathways is confirmed and the product is found to contain a di-carbonyl group that exhibits quantum beating be- tween two equivalent transitions in time-resolved 2D IR spectra, which turns out to be the anti-symmetric and symmetric stretching of the terminal carbonyl stretching modes of CpFe（CO）2C1. This is the main product and its reaction pathway involves radical formation, followed by chloride addition. Quantum-chemistry computations support these experimental results. Our results indicate that 2D IR method can be used to identify in situ structures and dynamics of chemical species involved in condensed-phase chemical reactions.
文摘As a well known DNA photolesion product, the special UV induced pyrimidine dimmer called spore photoproduct （SP）, has aroused strong research interests. The SP formation was reported solely between two adjacent thymidine residues. It remains unclear in pervious experimental observations why there is an absence of the cytosine-derived SP-like photoprod- uct formation at the cytosine containing DNA strand, although the cytosine residue holds great similarity to thymine in terms of molecular structure. From a theoretical perspec- tive, we have explored this issue in this work by means of density functional theory at the B3LYP/6-311＋＋G（d,p） //B3LYP/6-31G（d,p） level for the DNA dinucleotide fragment, cy- tosine phosphate thymine （CpT）. Key factors blocking the formation of the SP-like product between two adjacent cytosine and thymidine residues are revealed. Instead of undergoing photochemical SP reaction, a photophysical deactivation pathway back to the ground state turns out to be favorable for the CpT dinucleotide fragment.
基金Supported by National Natural Science Foundation of China under Grant Nos.10647002 and 10565001
文摘Based on the quark-gluon contents of nucleon and strongly believing that the force mediators,Pomeronand its counterpart in the conventional approach of Regge theory,for high energy diffractive process would be the tensorglueball and Odderon respectively,we discuss photo-production of vector meson φ off the deuteron at energy less than 3GeV in the QCD inspired model in which the quark gluon degrees of freedom and glueball,Odderon exchange are takeninto account.A calculation is performed for γ + D →φ + D,and the theoretical predictions of the differential crosssection dσ^(γD)) /dt,are presented and compared with available experimental data.Our QCD inspired model reproducesdata quite well in the whole range of the experimental measurements up to |t| ■0.4 GeV.Our results can be used toextract γn→φn data,which cannot be measured in experiment.
文摘Atorvastatin, widely prescribed hypolipidemic drug, undergoes rapid, probably self-sensitised, degradation (less than 20% left after 25-minute irradiation) if irradiated by wavelengths 300 - 350 nm in aqueous solution. When ferric ions are added to the reaction mixture, the degradation follows first order kinetics with a rate constant of 0.130 min<sup><span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span>1</sup>. Photochemical degradation may thus represent a significant way of environmental transformation of this pharmaceutical. Toxicity testing of atorvastatin and atorvastatin photoproducts performed on the water plant <em>Lemna minor</em> revealed that atorvastatin itself exhibited no observable toxic effect measured as leaf area growth inhibition, while the photoproducts showed a significant toxicity to the plant, which shows the extreme importance of investigating not only toxicity of drugs themselves on aquatic organisms but also effects of their transformation products.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11065010 and 11465021
文摘Taking into account the effects of shadowing and jet quenching, the large transverse momentum distribution of K＋, π＋ and K＋/π＋ ratios at s = 200 GeV originating from resolved photoproduction processes is calculated based on perturbative quantum chromodynamics. It is found that the contribution of K＋ and π＋ produced by photoproduction processes is evident. The K＋ /π＋ ratios in Au-Au collisions show an obvious enhancement compared with p p collisions. The numerical results indicate that the photoproduetion processes are good modification for kaon and pion production.
文摘Hard photoproduction of J/ψ and T at large hadron collider(LHC)Pb-Pb collisionswith CMS energy 6300 GeV/u is discussed in the process Pb+Pb→Pb+J/ψ+X with threetypes of equivalent photon spectrum functions.It turns out that the hard photoproductionprocesses can be used to probe several important problems such as the gluon distribution in thenucleus,gluon and heavy q.uark fragmentation of J/ψ,et al.In addition,the process alsoprovides a new way of testing the EMC effects.
基金Supported in part by the National Natural Science Foundation of China(12305092,12233006,12150013)the Xingdian Talent Support Program for Youth Project+1 种基金by the Yunnan Fundamental Research Projects(202401AU070206)supported by the Scientific Research and Innovation Project of Postgraduate Students in the Academic Degree of Yun Nan University(KC-242410212)。
文摘We study the inelastic charmonium(J/ψ,ψ(2S))and bottomonium(Υ(nS))photoproduction and fragmentation processes in p-p and Pb-Pb collisions at LHC energies,where the ultra-incoherent photon emission is included.Using the NRQCD factorization approach,an exact treatment is developed.This approach recovers the Weizs?cker-Williams approximation(WWA)near the Q^(2)~0region,where the Martin-Ryskin and BCCKL methods are used to avoid double counting.We calculated the Q^(2),y,z,√s and p_(T)dependent and total cross sections.Inelastic photoproduction and fragmentation were observed to contribute to heavy quarkonium production,particularly at large p_(T).In addition,the contribution of the ultra-incoherent photon channel,which increases rapidly with quarkonium mass,is significant and begins to dominate the photoproduction processes for large p_(T).We also obtained the complete WWA validity scopes of inelastic heavy quarkonium photoproduction in heavy-ion collisions.The WWA had high accuracy at high energies and for Pb-Pb collisions.However,current photon spectra are derived beyond the WWA scope,and double counting can occur when considering different channels simultaneously.
基金Supported by the National Natural Science Foundation of China(12305127)the International Partnership Program of the Chinese Academy of Sciences(016GJHZ2022054FN)National Key R&D Program of China(2024YFE0109800,2024YFE0109802)。
文摘We present a comprehensive analysis of near-threshold photoproduction ofρ^(0),ω,andΦmesons on a deuterium target,utilizing published datasets from DESY and SLAC forρ^(0)andωproduction,as well as data from the LEPS and CLAS Collaborations forΦproduction.In extracting the deuteron mass radius,we adopt a dipole parameterization for the scalar gravitational form factor,which effectively captures the|t|-dependence of the differential cross sections associated with vector meson photoproduction.In addition,results from alternative commonly used form factor parameterizations are considered and compared.By employing the vector meson dominance(VMD)framework and invoking low-energy Quantum Chromodynamics(QCD)theorems,we extract the deuteron mass radius from near-threshold photoproduction data ofρ^(0),ω,andΦmesons.The mass radii obtained from the various datasets are found to be consistent within statistical uncertainties,yielding an average value of 2.03±0.13 fm under the dipole form assumption.We also provide a detailed discussion of the sensitivity of the extracted radius to the choice of gravitational form factor models.Our result represents a significant improvement in precision compared to earlier estimates based solely onΦmeson photoproduction,offering new constraints for theoretical models of nuclear structure and deepening our understanding of the mass distribution within the deuteron.
基金Partially supported by the National Natural Science Foundation of China(12175240,12147153,11635009,12305097,12305137)the Fundamental Research Funds for the Central Universitiesthe China Postdoctoral Science Foundation(2021M693141,2021M693142)。
文摘The photoproduction of the f1(1285)meson off the proton target is investigated within an effective Lagrangian approach.The t-channelρ-andω-exchange diagrams,u-channel nucleon-exchange diagram,generalized contact term,and s-channel pole diagrams of the nucleon and a minimal number of nucleon resonances are taken into account in constructing the reaction amplitudes to describe the experimental data.Three different models,that is,the Feynman,Regge,and interpolated Regge models,are employed,where the t-channel reaction amplitudes are constructed in Feynman,Regge,and interpolated Regge types,respectively.The results show that neither the Feynman model with two nucleon resonances nor the interpolated Regge model with one nucleon resonance can satisfactorily reproduce the available data forγp→f1(1285)p.Nevertheless,in the Regge model,when any one of the N(1990)7/2^(+),N(2000)5/2^(+),N(2040)3/2^(+),N(2060)5/2^(-),N(2100)1/2^(+),N(2120)3/2^(-),N(2190)7/2^(-),N(2300)1/2^(+),and N(2570)5/2^(-)resonances is considered,the data can be well described.The resulting resonance parameters are consistent with those advocated in the Particle Data Group(PDG)review.Further analysis shows that,in the high-energy region,the peaks of γp→f1(1285)p differential cross sections at forward angles are dominated by the contributions from t-channelρ-andω-exchange diagrams,while in low-energy region,the s-channel pole diagrams of resonances also provide significant contributions to theγp→f1(1285)p cross sections.
