A first-principles computational method based on the hybrid density functional theory is developed to simulate the electronic transport properties of oligomeric phenylene ethynylene molecular junctions with H2O molecu...A first-principles computational method based on the hybrid density functional theory is developed to simulate the electronic transport properties of oligomeric phenylene ethynylene molecular junctions with H2O molecules accumulated in the vicinity as recently reported by Na et al. [Nanotechnology 18 424001 （2007）]. The numerical results show that the hydrogen bonds between the oxygen atoms of the oligomeric phenylene ethynylene molecule and H2O molecules result in the localisation of the molecular orbitals and lead to the lower transition peaks. The H2O molecular chains accumulated in the vicinity of the molecular junction can not only change the electronic structure of the molecular junctions, but also open additional electronic transport pathways. The obvious influence of H2O molecules on the electronic structure of the molecular junction and its electronic transport properties is thus demonstrated.展开更多
In this paper,shale gas cores from the Lower Silurian Longmaxi Formation in the Zhaotong National Shale Gas Demonstration Area were selected to study the hydration effect of differentfluids on the fracture morphology ...In this paper,shale gas cores from the Lower Silurian Longmaxi Formation in the Zhaotong National Shale Gas Demonstration Area were selected to study the hydration effect of differentfluids on the fracture morphology inside the shale,the rock tensile strength and the Brazilian tensile failure mode.Fresh water and slick water were adopted for hydration pretreatments and the CT technique was used to compare the changes of the fabric in the shale.Then,Brazilian tensile tests were carried out to study the tensile strength and tensile failure modes of the shale specimen after hydration pretreatment.Finally,two horizontal wells in the study area were selected to perform pilot tests of hydration pre-treatment in their fracturing operation sites.And the following research results were obtained.First,in the process of spontaneous imbibition,the hydration effect of fresh water is superior to that of slick water in promoting the fracture complexity of marine shale in the same hydration duration.Second,fresh water has greater surface tension and lower viscosity and its hydration effect can not only promote the propagation of original fractures but induce new micro-fractures or branches,while the hydration effect of slick water mainly promotes the propagation of original fractures.Third,due to hydration effect,marine shale is damaged and its tensile strength is reduced.After the hydration pretreatment by fresh water and slick water,the tensile strength of the shale specimens are reduced by 35.6%and 18.1%,respectively.Fourth,according to the propagation paths of main fractures,the Brazilian tensile failure modes of hydrated shale can be divided into four types(i.e.,step shaped,dog-leg shaped,branching shaped and arc shaped)or their combinations,while the tensile failure mode of unhydrated shale is only a straight line.Fifth,hydration effect can effectively increase the complexity of the hydraulic fractures in marine shale,so if the conditions permit,it is recommended to inject a certain amount of fresh water at a high pumping rate within the limited pressure after perforation and to shut in the well until the hydraulic fracturing operation.And in order to reduce the difficulties of pumping the proppant during the hydraulic fracturing operation,a pumping strategy of“low proppant concentration,large volume of slurries”can be adopted to reach the expected proppant volume.展开更多
The thermal stability of New Zealand culture rabbit muscle aldolase was investigated by differential scanning calorimetry in the water content range 0.23-3.70 g water per g protein.The experimental results showed that...The thermal stability of New Zealand culture rabbit muscle aldolase was investigated by differential scanning calorimetry in the water content range 0.23-3.70 g water per g protein.The experimental results showed that at water contents below 0.47g/g,an endothermic peak was observed and at water contents above 0.57g/g,an endothermic and an exothermic peak were both observed on DSC thermogram.Thermal denaturation result of the enzyme and the relationship between two transition temperatures and water contents were first reported in this paper.Up to now we have not seen any similar reports concerning the exothermic transition.展开更多
The effects of sodium salt of naphthalene formaldehyde sulfonic acid and stearic acid on the hydration of silica fume and Ca(OH)2 have been investigated. The hydration was carried out at 60℃ and W/S ratio of 4 for va...The effects of sodium salt of naphthalene formaldehyde sulfonic acid and stearic acid on the hydration of silica fume and Ca(OH)2 have been investigated. The hydration was carried out at 60℃ and W/S ratio of 4 for various time intervals namely, 1, 3, 7 and 28 days and in the presence of 0, 2% and 5% superplasticizer and stearic acid. The results of the hydration kinetics show that both admixtures accelerate the hydration reaction of silica fume and calcium hydroxide during the first 7 days. Whereas, after 28 days hydration there is no significant effect. Generally, most of free calcium hydroxide seems to be consumed after 28 days. In addition, the phase composition as well as the microstructure of the formed hydrates was examined by using X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM) respectively.展开更多
Background Intravascular volume expansion represents a beneficial measure against contrast-induced acute kidney injury （CI-AKI） in patients undergoing elective angiographic procedures. However, the efficacy of this ...Background Intravascular volume expansion represents a beneficial measure against contrast-induced acute kidney injury （CI-AKI） in patients undergoing elective angiographic procedures. However, the efficacy of this preventive strategy has not yet been established for patients with ST-elevation-myocardial infarction （STEMI）, who are at higher risk of this complication after primary percutaneous coronary intervention （PCI）. In this randomized study we investigated the possible beneficial role of periprocedural intravenous volume expansion and we compared the efficacy of 2 different hydration strategies in patients with STEMI undergoing primary PCI.展开更多
This study aims at evidencing the effects of lime treatment on the microstructure and hydraulic conductivityof a compacted expansive clay, with emphasis put on the effect of lime hydration and modification.For this pu...This study aims at evidencing the effects of lime treatment on the microstructure and hydraulic conductivityof a compacted expansive clay, with emphasis put on the effect of lime hydration and modification.For this purpose, evolutions of hydraulic conductivity were investigated for both lime-treatedand untreated soil specimens over 7 d after full saturation of the specimens and their microstructureswere observed at the end. Note that for the treated specimen, dry clay powder was mixed with quicklimeprior to compaction in order to study the effect of lime hydration. It is observed that lime hydration andmodification did not affect the intra-aggregate pores but increased the inter-aggregates pores size. Thisincrease gave rise to an increase of hydraulic conductivity. More precisely, the hydraulic conductivity oflime-treated specimen increased progressively during the first 3 d of modification phase and stabilisedduring the next 4 d which correspond to a short period prior to the stabilisation phase. The microstructureobservation showed that stabilisation reactions took place after 7 d. Under the effect of stabilisation,a decreasing hydraulic conductivity can be expected in longer time due to the formation ofcementitious compounds. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.展开更多
The conformations for leucine （Leu） hydrated with one to three water molecules, Leu-（H2O）n （n=1-3）, were carefully searched by considering the trial structures generated by all possible combinations of rotamers ...The conformations for leucine （Leu） hydrated with one to three water molecules, Leu-（H2O）n （n=1-3）, were carefully searched by considering the trial structures generated by all possible combinations of rotamers of Leu combined with all likely hydration modes. The structures were optimized at the BHandHLYP/6-31＋G^＊ level and the single point energies were calculated at the BHandHLYP/6-311＋＋G^＊＊ level. Good correspondence between the conformations of Leu-（H2O）n and bare Leu is found, showing that the conformations of Leu-（H2O）n may be efficiently and reliably determined by the hydration of Leu conformers. The simulated IR spectra of canonical and zwitterionic conformers of Leu-（H2O）n are compared with the experimental result of Leu in aqueous solution. The IR spectrum of zwitterionic Leu- （H2O）3 provides the best description of the experiment. The result demonstrates that the IR spectrum of solute in solution may be simulated by the solute hydrated with an adequate number of water molecules in the gas phase.展开更多
The nature of solid-liquid interfaces is of great significance in lubrication.Remarkable advances have been made in lubrication based on hydration effects.However,a detailed molecular-level understanding is still lack...The nature of solid-liquid interfaces is of great significance in lubrication.Remarkable advances have been made in lubrication based on hydration effects.However,a detailed molecular-level understanding is still lacking.Here,we investigated water molecule behaviors at the TiO2-aqueous interfaces by the sum-frequency generation vibrational spectroscopy(SFG-VS)and atomic force microscope(AFM)to elucidate the fundamental role of solid-liquid interfaces in lubrication.Combined contributions of water structures and hydration effects were revealed,where water structures played the dominant role in lubrication for TiO2 surfaces of varying hydrophilicity,while hydration effects dominated with the increasing of ion concentrations.Superior lubrication is observed on the initial TiO2 surfaces with strongly H-bonded water molecules compared to the hydrophilic TiO2 surfaces with more disordered water.The stable ordered water arrangement with strong hydrogen bonds and the shear plane occurring between the ordered water layer and subsequent water layer may play a significant role in achieving lower friction.More adsorbed hydrated molecules with the increasing ionic concentration perturb ordered water but lead to the enhancement of hydration effects,which is the main reason for the improved lubrication for both TiO2.This work provides more insights into the detailed molecular-level understanding of the mechanism of hydration lubrication.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos.10804064 and 10674084)
文摘A first-principles computational method based on the hybrid density functional theory is developed to simulate the electronic transport properties of oligomeric phenylene ethynylene molecular junctions with H2O molecules accumulated in the vicinity as recently reported by Na et al. [Nanotechnology 18 424001 （2007）]. The numerical results show that the hydrogen bonds between the oxygen atoms of the oligomeric phenylene ethynylene molecule and H2O molecules result in the localisation of the molecular orbitals and lead to the lower transition peaks. The H2O molecular chains accumulated in the vicinity of the molecular junction can not only change the electronic structure of the molecular junctions, but also open additional electronic transport pathways. The obvious influence of H2O molecules on the electronic structure of the molecular junction and its electronic transport properties is thus demonstrated.
基金Project supported by the National Major Science and Technology Project“Zhaotong Shale Gas Exploration and Development Demonstration Project”(No.2017ZX05063)the Science and Technology Project of CNPC Chuanqing Drilling Engineering Company Limited“Study and Application of Hydration Mechanism of Shale Reservoir”(No.CQ2018B-23-1-4).
文摘In this paper,shale gas cores from the Lower Silurian Longmaxi Formation in the Zhaotong National Shale Gas Demonstration Area were selected to study the hydration effect of differentfluids on the fracture morphology inside the shale,the rock tensile strength and the Brazilian tensile failure mode.Fresh water and slick water were adopted for hydration pretreatments and the CT technique was used to compare the changes of the fabric in the shale.Then,Brazilian tensile tests were carried out to study the tensile strength and tensile failure modes of the shale specimen after hydration pretreatment.Finally,two horizontal wells in the study area were selected to perform pilot tests of hydration pre-treatment in their fracturing operation sites.And the following research results were obtained.First,in the process of spontaneous imbibition,the hydration effect of fresh water is superior to that of slick water in promoting the fracture complexity of marine shale in the same hydration duration.Second,fresh water has greater surface tension and lower viscosity and its hydration effect can not only promote the propagation of original fractures but induce new micro-fractures or branches,while the hydration effect of slick water mainly promotes the propagation of original fractures.Third,due to hydration effect,marine shale is damaged and its tensile strength is reduced.After the hydration pretreatment by fresh water and slick water,the tensile strength of the shale specimens are reduced by 35.6%and 18.1%,respectively.Fourth,according to the propagation paths of main fractures,the Brazilian tensile failure modes of hydrated shale can be divided into four types(i.e.,step shaped,dog-leg shaped,branching shaped and arc shaped)or their combinations,while the tensile failure mode of unhydrated shale is only a straight line.Fifth,hydration effect can effectively increase the complexity of the hydraulic fractures in marine shale,so if the conditions permit,it is recommended to inject a certain amount of fresh water at a high pumping rate within the limited pressure after perforation and to shut in the well until the hydraulic fracturing operation.And in order to reduce the difficulties of pumping the proppant during the hydraulic fracturing operation,a pumping strategy of“low proppant concentration,large volume of slurries”can be adopted to reach the expected proppant volume.
基金Supported by National Natural Science Fundation of China
文摘The thermal stability of New Zealand culture rabbit muscle aldolase was investigated by differential scanning calorimetry in the water content range 0.23-3.70 g water per g protein.The experimental results showed that at water contents below 0.47g/g,an endothermic peak was observed and at water contents above 0.57g/g,an endothermic and an exothermic peak were both observed on DSC thermogram.Thermal denaturation result of the enzyme and the relationship between two transition temperatures and water contents were first reported in this paper.Up to now we have not seen any similar reports concerning the exothermic transition.
文摘The effects of sodium salt of naphthalene formaldehyde sulfonic acid and stearic acid on the hydration of silica fume and Ca(OH)2 have been investigated. The hydration was carried out at 60℃ and W/S ratio of 4 for various time intervals namely, 1, 3, 7 and 28 days and in the presence of 0, 2% and 5% superplasticizer and stearic acid. The results of the hydration kinetics show that both admixtures accelerate the hydration reaction of silica fume and calcium hydroxide during the first 7 days. Whereas, after 28 days hydration there is no significant effect. Generally, most of free calcium hydroxide seems to be consumed after 28 days. In addition, the phase composition as well as the microstructure of the formed hydrates was examined by using X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM) respectively.
文摘Background Intravascular volume expansion represents a beneficial measure against contrast-induced acute kidney injury （CI-AKI） in patients undergoing elective angiographic procedures. However, the efficacy of this preventive strategy has not yet been established for patients with ST-elevation-myocardial infarction （STEMI）, who are at higher risk of this complication after primary percutaneous coronary intervention （PCI）. In this randomized study we investigated the possible beneficial role of periprocedural intravenous volume expansion and we compared the efficacy of 2 different hydration strategies in patients with STEMI undergoing primary PCI.
基金the French National Research Agency for funding the present study within the project-TERDOUEST "Sustainable earthworks involving treated soils"
文摘This study aims at evidencing the effects of lime treatment on the microstructure and hydraulic conductivityof a compacted expansive clay, with emphasis put on the effect of lime hydration and modification.For this purpose, evolutions of hydraulic conductivity were investigated for both lime-treatedand untreated soil specimens over 7 d after full saturation of the specimens and their microstructureswere observed at the end. Note that for the treated specimen, dry clay powder was mixed with quicklimeprior to compaction in order to study the effect of lime hydration. It is observed that lime hydration andmodification did not affect the intra-aggregate pores but increased the inter-aggregates pores size. Thisincrease gave rise to an increase of hydraulic conductivity. More precisely, the hydraulic conductivity oflime-treated specimen increased progressively during the first 3 d of modification phase and stabilisedduring the next 4 d which correspond to a short period prior to the stabilisation phase. The microstructureobservation showed that stabilisation reactions took place after 7 d. Under the effect of stabilisation,a decreasing hydraulic conductivity can be expected in longer time due to the formation ofcementitious compounds. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.
基金V. ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.11074233） the National Basic Research Program of China （No.2012CB215405）, and the Specialized Research Fund for the Doctoral Program of Higher Education （No.20113402110038）.
文摘The conformations for leucine （Leu） hydrated with one to three water molecules, Leu-（H2O）n （n=1-3）, were carefully searched by considering the trial structures generated by all possible combinations of rotamers of Leu combined with all likely hydration modes. The structures were optimized at the BHandHLYP/6-31＋G^＊ level and the single point energies were calculated at the BHandHLYP/6-311＋＋G^＊＊ level. Good correspondence between the conformations of Leu-（H2O）n and bare Leu is found, showing that the conformations of Leu-（H2O）n may be efficiently and reliably determined by the hydration of Leu conformers. The simulated IR spectra of canonical and zwitterionic conformers of Leu-（H2O）n are compared with the experimental result of Leu in aqueous solution. The IR spectrum of zwitterionic Leu- （H2O）3 provides the best description of the experiment. The result demonstrates that the IR spectrum of solute in solution may be simulated by the solute hydrated with an adequate number of water molecules in the gas phase.
基金supported by the National Natural Science Foundation of China(51922058).
文摘The nature of solid-liquid interfaces is of great significance in lubrication.Remarkable advances have been made in lubrication based on hydration effects.However,a detailed molecular-level understanding is still lacking.Here,we investigated water molecule behaviors at the TiO2-aqueous interfaces by the sum-frequency generation vibrational spectroscopy(SFG-VS)and atomic force microscope(AFM)to elucidate the fundamental role of solid-liquid interfaces in lubrication.Combined contributions of water structures and hydration effects were revealed,where water structures played the dominant role in lubrication for TiO2 surfaces of varying hydrophilicity,while hydration effects dominated with the increasing of ion concentrations.Superior lubrication is observed on the initial TiO2 surfaces with strongly H-bonded water molecules compared to the hydrophilic TiO2 surfaces with more disordered water.The stable ordered water arrangement with strong hydrogen bonds and the shear plane occurring between the ordered water layer and subsequent water layer may play a significant role in achieving lower friction.More adsorbed hydrated molecules with the increasing ionic concentration perturb ordered water but lead to the enhancement of hydration effects,which is the main reason for the improved lubrication for both TiO2.This work provides more insights into the detailed molecular-level understanding of the mechanism of hydration lubrication.
