The potential energy surfaces （PES） of unimolecular dissociation reactions for di-ethyl beryl- lium and di-t-butyl beryllium are investigated by B3LYP, CCSD（T）, and G3B3 approaches. Possible reaction pathways thro...The potential energy surfaces （PES） of unimolecular dissociation reactions for di-ethyl beryl- lium and di-t-butyl beryllium are investigated by B3LYP, CCSD（T）, and G3B3 approaches. Possible reaction pathways through either the radical or transition state （TS） of the molecules are considered. The geometries, vibrational frequencies and relative energies for various sta- tionary points are determined. From the study of energetics, the TS pathways arising from concerted molecular eliminations are indicated to be the main dissociation pathways for both molecules. The PES differences of the dissociation reactions are investigated. The activation energies and rate constants will be helpful for investigating the predictive ability of the reaction in further theoretical and experimental research.展开更多
2,3,5,6-Tetrachloride-quinone was anchored to a gold surfare through the self-assem-bled monolayers of dithiol [DT HS-(CH2).-SH n=2,4,6,8,10]. The surface coverage of the anchoredTQ was esteminated to be 4.0 ×10-...2,3,5,6-Tetrachloride-quinone was anchored to a gold surfare through the self-assem-bled monolayers of dithiol [DT HS-(CH2).-SH n=2,4,6,8,10]. The surface coverage of the anchoredTQ was esteminated to be 4.0 ×10-11 mol’cm-2. The electron transfer rate constant Ket associatedwith the redox process of anchored film decreased from 6.75 s-1 at n=2 to 0.169 s-1 at n=10 withincreasing the chain length of the DT SAMs througth the redox potential of TQ. The turnningbarrier conefficient.(β) of the electron transfer was estimated to be 0.82A-1 from the observed linearrelationship between the Ket and the monolayer chain length.展开更多
The dissociative electron attachment process for CHCl3 at different electric field have been studied with nitrogen as drift and carrier gas using corona discharge ionization source ion mobility spectrometry （CD-IMS）...The dissociative electron attachment process for CHCl3 at different electric field have been studied with nitrogen as drift and carrier gas using corona discharge ionization source ion mobility spectrometry （CD-IMS）. The corresponding electron attachment rate constants varied from 1.26×10-8 cm3/（molecules s） to 8.24×10-9 cm3/（molecules s） as the electric field changed from 200 V/cm to 500 V/cm. At a fixed electric field in the drift region, the attachment rate constants are also detected at different sample concentration. The ionmolecule reaction rate constants for the further reaction between Cl^- and CHCl3 are also detected, which indicates that the technique maybe becomes a new method to research the rate constants between ions and neural molecules. And the reaction rate constants between Cl- and CHCl3 are the first time detected using CD-IMS.展开更多
In many areas of oncology, dynamic contrast-enhanced magnetic resonance imaging(DCE-MRI) has proven to be a clinically useful, non-invasive functional imaging technique to quantify tumor vasculature and tumor perfusio...In many areas of oncology, dynamic contrast-enhanced magnetic resonance imaging(DCE-MRI) has proven to be a clinically useful, non-invasive functional imaging technique to quantify tumor vasculature and tumor perfusion characteristics. Tumor angiogenesis is an essential process for tumor growth, proliferation, and metastasis. Malignant lesions demonstrate rapid extravasation of contrast from the intravascular space to the capillary bed due to leaky capillaries associated with tumor neovascularity. DCE-MRI has the potential to provide information regarding blood flow, areas of hypoperfusion, and variations in endothelial permeability and microvessel density to aid treatment selection, enable frequent monitoring during treatment and assess response to targeted therapy following treatment. This review will discuss the current status of DCE-MRI in cancer imaging, with a focus on its use in imaging prostate malignancies as well as weaknesses that limit its widespread clinical use. The latest techniques for quantification of DCE-MRI parameters will be reviewed and compared.展开更多
The purpose of this review and commentary was to provide an historical and evidence-based account of organic acids and the biochemical and organic chemistry evidence for why cells do not produce metabolites that are a...The purpose of this review and commentary was to provide an historical and evidence-based account of organic acids and the biochemical and organic chemistry evidence for why cells do not produce metabolites that are acids.The scientific study of acids has a long history dating to the 16th and 17th centuries,and the definition of an acid was proposed in 1884 as a molecule that when in an aqueous solution releases a hydrogen ion(H^(+)).There are three common ionizable functional groups for molecules classified as acids:1)the carboxyl group,2)the phos-phoryl group and 3)the amine group.The propensity by which a cation will associate or dissociate with a negatively charged atom is quantified by the equilibrium constant(K_(eq))of the dissociation constant(K_(d))of the ionization(K_(eq)=K_(d)),which for lactic acid(HLa)vs.lactate(La^(-))is expressed as:K_(eq)=K_(d)=[H^(+)][La^(-)]/[HLa]=4677.3514(ionic strength=0.01 Mol⋅L^(-1),T=25℃).The negative log10 of the dissociation pKd reveals the pH at which half of the molecules are ionized,which for HLa=3.67.Thus,knowing the pKd and the pH of the solution at question will reveal the extent of the ionization vs.acidification of molecules that are classified as acids.展开更多
基金ACKNOWLEDGMENTS This work was supported by the NationM Nature Science Foundation of China （No.11104256） and the Open Project of State Key Laboratory Cultivation base for Nonmetal Composites and Functional Mate- rials （No.11zxfk19）. We thank Dr. Shuang-lin Hu from the Chemistry Department of Uppsala University in Sweden for helpful suggestion. We would also thank the Hefei National Laboratory for Physical Sciences at the Microscale in University of Science and Technology of China for the computational facilities （Gaussian 09）.
文摘The potential energy surfaces （PES） of unimolecular dissociation reactions for di-ethyl beryl- lium and di-t-butyl beryllium are investigated by B3LYP, CCSD（T）, and G3B3 approaches. Possible reaction pathways through either the radical or transition state （TS） of the molecules are considered. The geometries, vibrational frequencies and relative energies for various sta- tionary points are determined. From the study of energetics, the TS pathways arising from concerted molecular eliminations are indicated to be the main dissociation pathways for both molecules. The PES differences of the dissociation reactions are investigated. The activation energies and rate constants will be helpful for investigating the predictive ability of the reaction in further theoretical and experimental research.
文摘2,3,5,6-Tetrachloride-quinone was anchored to a gold surfare through the self-assem-bled monolayers of dithiol [DT HS-(CH2).-SH n=2,4,6,8,10]. The surface coverage of the anchoredTQ was esteminated to be 4.0 ×10-11 mol’cm-2. The electron transfer rate constant Ket associatedwith the redox process of anchored film decreased from 6.75 s-1 at n=2 to 0.169 s-1 at n=10 withincreasing the chain length of the DT SAMs througth the redox potential of TQ. The turnningbarrier conefficient.(β) of the electron transfer was estimated to be 0.82A-1 from the observed linearrelationship between the Ket and the monolayer chain length.
基金ACKNOWLEDGMENTS The work was support by the National Natural Science Foundation of China （No.20707025 and No.20907054） and the Excellent Youth Foundation of Anhui Province Scientific Committee （No.06045098）.
文摘The dissociative electron attachment process for CHCl3 at different electric field have been studied with nitrogen as drift and carrier gas using corona discharge ionization source ion mobility spectrometry （CD-IMS）. The corresponding electron attachment rate constants varied from 1.26×10-8 cm3/（molecules s） to 8.24×10-9 cm3/（molecules s） as the electric field changed from 200 V/cm to 500 V/cm. At a fixed electric field in the drift region, the attachment rate constants are also detected at different sample concentration. The ionmolecule reaction rate constants for the further reaction between Cl^- and CHCl3 are also detected, which indicates that the technique maybe becomes a new method to research the rate constants between ions and neural molecules. And the reaction rate constants between Cl- and CHCl3 are the first time detected using CD-IMS.
文摘In many areas of oncology, dynamic contrast-enhanced magnetic resonance imaging(DCE-MRI) has proven to be a clinically useful, non-invasive functional imaging technique to quantify tumor vasculature and tumor perfusion characteristics. Tumor angiogenesis is an essential process for tumor growth, proliferation, and metastasis. Malignant lesions demonstrate rapid extravasation of contrast from the intravascular space to the capillary bed due to leaky capillaries associated with tumor neovascularity. DCE-MRI has the potential to provide information regarding blood flow, areas of hypoperfusion, and variations in endothelial permeability and microvessel density to aid treatment selection, enable frequent monitoring during treatment and assess response to targeted therapy following treatment. This review will discuss the current status of DCE-MRI in cancer imaging, with a focus on its use in imaging prostate malignancies as well as weaknesses that limit its widespread clinical use. The latest techniques for quantification of DCE-MRI parameters will be reviewed and compared.
文摘The purpose of this review and commentary was to provide an historical and evidence-based account of organic acids and the biochemical and organic chemistry evidence for why cells do not produce metabolites that are acids.The scientific study of acids has a long history dating to the 16th and 17th centuries,and the definition of an acid was proposed in 1884 as a molecule that when in an aqueous solution releases a hydrogen ion(H^(+)).There are three common ionizable functional groups for molecules classified as acids:1)the carboxyl group,2)the phos-phoryl group and 3)the amine group.The propensity by which a cation will associate or dissociate with a negatively charged atom is quantified by the equilibrium constant(K_(eq))of the dissociation constant(K_(d))of the ionization(K_(eq)=K_(d)),which for lactic acid(HLa)vs.lactate(La^(-))is expressed as:K_(eq)=K_(d)=[H^(+)][La^(-)]/[HLa]=4677.3514(ionic strength=0.01 Mol⋅L^(-1),T=25℃).The negative log10 of the dissociation pKd reveals the pH at which half of the molecules are ionized,which for HLa=3.67.Thus,knowing the pKd and the pH of the solution at question will reveal the extent of the ionization vs.acidification of molecules that are classified as acids.
