The micro-amount of nickel in MnO2, electrolytical and natural both, was determined by differential pulse polarography. NH4OH-NH4Cl was used as supporting electrolyte. It was found that the peak potential of Ni(II) re...The micro-amount of nickel in MnO2, electrolytical and natural both, was determined by differential pulse polarography. NH4OH-NH4Cl was used as supporting electrolyte. It was found that the peak potential of Ni(II) reduction wave is -1.0V (vs. Ag-AgCl electrode). The presence of great amount of Mn(II) does not interfere in the trace nickel determination. the peak current relationship with the Ni2+ concentration presents a quite fine straight line. The differential pulse polarography is proved that it is a simple, reliable and acceptable method for determination of trace Ni in various species of MnO2.展开更多
The polarographic adsorptive complex wave of rare earths (RE) with 1-phenyl-3-methyl-4-benzoylpyrazoione-5 (PMBP) was studied in HAc-NaAc medium at pH=3.80. In the singlesweep polarography, the reduction potential of ...The polarographic adsorptive complex wave of rare earths (RE) with 1-phenyl-3-methyl-4-benzoylpyrazoione-5 (PMBP) was studied in HAc-NaAc medium at pH=3.80. In the singlesweep polarography, the reduction potential of complex wave (-1.16V) is more negative than that of the free ligand. (-1.12V), and the wave was proven to be an adsorptive complex wave by cyclic voltammetry method. This experiment proved that only the complexes of heavy RE ions can be adsorbed on the electrode under the same conditions. So it is a good method to determine heavy rare earths in the presence of light rare earths.展开更多
This paper reports a polarographic catalytic wave of lysozyme (LE) in the presence of KIO3. The mechanism of the catalytic wave was discussed. It is illustrated by the catalytic wave of LE that, besides the Brdicka cu...This paper reports a polarographic catalytic wave of lysozyme (LE) in the presence of KIO3. The mechanism of the catalytic wave was discussed. It is illustrated by the catalytic wave of LE that, besides the Brdicka current, there exists a new kind of catalytic wave of protein.展开更多
The cathodic wave of vitamin C has not been reported in the literature so far.Its E_(1/2)was found at-1.85 volt vs.Ag/AgCl(25℃)in the base solution of 0.1mol/L Bu_4NI.Various electrochemical and spectral techniques w...The cathodic wave of vitamin C has not been reported in the literature so far.Its E_(1/2)was found at-1.85 volt vs.Ag/AgCl(25℃)in the base solution of 0.1mol/L Bu_4NI.Various electrochemical and spectral techniques were used for studying the electrode reaction. They all showed that the electrode reaction was quasi-reversible while C was more than 1.0×10^(-6)mol/L and mainly adsorptive while C was less than 1.0×10^(-6)mol/L at a mercury electrode.The electron transfer number was 2 and the electron transfer coefficient 0.57. Using DPP techniques,the linear response range was 5.0×10^(-7)-2.0×10^(-3)mol/L and the detection limit 1×10^(-7)mol/L.展开更多
The sensitive second derivative waves of Cu(Ⅱ),Pb(Ⅱ),Cd(Ⅱ),Ni(Ⅱ),Zn(Ⅱ),Fe(Ⅱ)and Mn(Ⅱ),forming in the substrate solution(pH=9.26)consisting of ammonia,ammonium chlorid,gelatin and ascorbic acid were researched.T...The sensitive second derivative waves of Cu(Ⅱ),Pb(Ⅱ),Cd(Ⅱ),Ni(Ⅱ),Zn(Ⅱ),Fe(Ⅱ)and Mn(Ⅱ),forming in the substrate solution(pH=9.26)consisting of ammonia,ammonium chlorid,gelatin and ascorbic acid were researched.The peak potentials of the polarographic waves of the seven ions are at about 0.48,0.63,0.79,1.04,1.28,1.44 and 1.60 V respectively.Combining with microwave technique,a new method for the simultaneous determination of the seven trace elements in Chinese traditional medicine was developed.The method is easy to operate,rapid,simple and convenient.When the signal-to-noise rate equals 3,the detection limits of Cu,Pb,Cd,Ni,Zn,Fe and Mn are 4.2×10 3,5.3×10 3,2.1×10 3,5.8×10 4,3.0×10 3,7.7×10 4 and 1.1×10 3 μg/mL respectively.Well linear relationships exist between the concentrations and the peak currents when Cu,Pb,Cd,Ni,Zn,Fe and Mn concentrations are within 8.5×10 3 10,9.7×10 3 10,4.5×10 3 10,1.2×10 3 10,6.4×10 3 10,1.5×10 3 10 and 2.8×10 3 10 μg/mL,respectively.The method has been used to the simultaneous determination of the seven trace elements in Salvia Miltiorrhiza Root and compound Salvia Miltiorrhiza Root injection,the relative standard deviations(RSDs)of the Cu,Pb,Cd,Ni,Zn,Fe and Mn in the two medicines are 3.9% and 5.8%,4.0% and 4.1%,4.3% and 5.7%,4.9% and 5.3%,4.4% and 4.7%,3.5% and 4.0%,0.51% and 2.8%,respectively;the comparisons of the determination results with the values obtained by the standard method indicate that the presented method has very well veracity.展开更多
Polarographic characteristics of Te(Ⅳ)-alkaline dye were investiga- ted at mercury electrode in acidic solution.It was found that the mechanism of the electrode process depended on the concentration of Te(Ⅳ).
Introduction: A great number of software are currently used to digitalize the patient records in order to optimize the quality of services offered to patients. The objective of this study was to evaluate the effects o...Introduction: A great number of software are currently used to digitalize the patient records in order to optimize the quality of services offered to patients. The objective of this study was to evaluate the effects of Electronic Health Records use in Burundi’s hospitals, taking into account the COVID-19 pandemic context. Methods: This was a quasi-experimental study based on difference in difference method. Ten district hospitals were included in the study, five of them had the Electronic Health Records and five of which did not yet have the Electronic Health Records. The hospital’s control group were chosen using the propensity score matching method. The period before the project’s implementation was 2014 and the period after were 2019 and 2020. Results: After 5 years of the Electronic Health Record’s implementation, the results showed an increase in outpatient consultation (70%), deliveries (more than 100%), caesarean sections (56%) and major surgeries (43%) indicators. The overall quality score of hospitals’ care had a regressive effect of 37% and the income from performance-based funding had an increase by 31%. The indicators which were affected by the context of the COVID-19 pandemic were especially outpatient consultation, caesarian section, income from performance-based funding decreased by 3%, 5% and 20% respectively. Conclusion: The effects of Electronic Health Records use are effective. As the COVID-19 pandemic impacted the hospital’s indicators negatively, the resilient strategies alongside the potential shocks are recommended.展开更多
It is reported in this paper a polarographic catalytic double wave of oxygen reduction caused by diphenylamine compounds(diphs).The electrochemical process of the wave includes the polarographic generation of the supe...It is reported in this paper a polarographic catalytic double wave of oxygen reduction caused by diphenylamine compounds(diphs).The electrochemical process of the wave includes the polarographic generation of the superoxide anion O_2^- and the dismutation of O_2^- catalyzed by diphs with redox pseudoreversibility.展开更多
At present, there are many problems in accounting computerization in colleges and universities, such as unreasonable class layout, lack of teachers and weak practical training, which can not adapt to social developmen...At present, there are many problems in accounting computerization in colleges and universities, such as unreasonable class layout, lack of teachers and weak practical training, which can not adapt to social development. Therefore, this paper has certain practical significance for solving the problems related to accounting computerization, training various accounting and electromechanical personnel to meet the social needs and promoting social development.展开更多
Accounting informatization is the combination of accounting and information technology. It is a necessary measure for enterprise financial accounting management to conform to the wave of informatization. It is helpful...Accounting informatization is the combination of accounting and information technology. It is a necessary measure for enterprise financial accounting management to conform to the wave of informatization. It is helpful to enhance the competitiveness of enterprises and solve the "isolated island" phenomenon existing in accounting computerization. In view of this, the article first points out the necessity of the development of enterprise financial accounting informatization, and then expounds the main performance in the development process of enterprise financial accounting informatization, which is helpful for practitioners to understand the realization conditions of enterprise financial accounting informatization. On this basis, the article puts forward the effective countermeasures for the development of enterprise financial accounting computerization to informatization, including establishing the correct cognition and concept of enterprise financial accounting informatization;In order to provide certain reference for the research and practice of practitioners, it is necessary to upgrade and perfect the enterprise financial accounting system in two aspects.展开更多
Polarographic catalytic wave of chlordiazepoxide in the presence of K 2S 2O 8 was studied in aqueous and DMF/H 2O mixed solutions. The results showed that a single reduction wave in alkaline medium was the reducti...Polarographic catalytic wave of chlordiazepoxide in the presence of K 2S 2O 8 was studied in aqueous and DMF/H 2O mixed solutions. The results showed that a single reduction wave in alkaline medium was the reduction of the N=C bond in 1,2 position of chlordiazepoxide via an intermediate free radical in two one electron successive additions. When K 2S 2O 8 was present, the free radical of the N=C bond was oxidized to regenerate the original, producing a parallel catalytic wave of chlordiazepoxide. It was determined that the apparent rate constant k f of the oxidation reaction was 3.2×10 3 mol -1 ·L·s -1 . Using the catalytic wave the trace of chlordiazepoxide can be determined by linear potential scan polarography. In NH 3/NH 4Cl (pH 10.2±0.1, 0.12 mol/L)/K 2S 2O 8 (0.016 mol/L) supporting electrolyte, the second order derivative peak current of the catalytic wave was rectilinear to chlordiazepoxide concentration in the range of 3.20×10 -8 -1.60×10 -7 , 1.60×10 -7 -1.44×10 -6 and 1.44 ×10 -6 -1.44×10 -5 mol/L, respectively. The limit of detection was 9.0×10 -9 mol/L.展开更多
A new method has been developed to assay poly(ADP-ribose) polymerase (PARP) activity in plant tissues through determining the content of nicotinamide (NIC) produced by enzymatic reaction by linear sweeping polarograph...A new method has been developed to assay poly(ADP-ribose) polymerase (PARP) activity in plant tissues through determining the content of nicotinamide (NIC) produced by enzymatic reaction by linear sweeping polarographic method. The detection limit of NIC was 0.03μmol/L, the calibration graph was linear up to 5μmol/L ( r = 0.999). The recoveries were approximately in the range of 92% to 98% and the relative standard deviations were less展开更多
The polarographic behavior and catalytic wave mechanism of medroprogesterone acetate ( MPA) were studied in both aqueous and DMF media. In 0.2 mol/L acetic acid-sodium acetate ( pH 5 .0 ) buffer solution, the C=C bond...The polarographic behavior and catalytic wave mechanism of medroprogesterone acetate ( MPA) were studied in both aqueous and DMF media. In 0.2 mol/L acetic acid-sodium acetate ( pH 5 .0 ) buffer solution, the C=C bond of MPA first undergoes le,lH+ reduction to form protonated free radical HMPA , the further reduction of HMPA in le,lH + process is simultaneous with the dimerization reaction between HMPA and neutral molecular MPA. In DMF media containing 0.1 mol/ L tetrabutylammonium tetrafluoborate ( TBA ·BF4 ) , the C=C bond of MPA shows two le, 1H+ reduction waves, which are ascribed to the reduction of MPA and free radical MPA' , respectively. Here, no dimerization reaction occurs. These processes produce the reduction wave of MPA. In the presence of oxidant KIO3, a polarographic catalytic wave of MPA is observable due to a chemical reaction between HMPA or MPA ~ and KIO3 as well as its intermediate species to regenerate MPA. The catalytic wave, which is caused by the reduction of organic compound itself and the chemical reaction between oxidant and organic intermediate free radical to regenerate original organic compound, is a new-type wave of organic compound. Under optimum experimental conditions, the sensitivity of MPA catalytic wave in the presence of KIO3 is an order of magnitude higher than that of its reduction wave. The catalytic wave can be used for analytical purpose. The calculated rate constant of catalytic reaction is 1.7 X103mol·-1·S-1 .展开更多
The polarographic catalytic wave of oxygen reduction caused by mefenamic acid (MA) with redox properties was reported in this paper. The electrochemical process of the catalytic wave was proposed that the superoxide a...The polarographic catalytic wave of oxygen reduction caused by mefenamic acid (MA) with redox properties was reported in this paper. The electrochemical process of the catalytic wave was proposed that the superoxide anion O(?) was generated polarographically and the dismutation of the O(?) was catalyzed by MA to reproduce O_2 and H_2O_2. This explained chemically the scavenging of the O_2^- by MA im biomedical area. Based on the catalytic wave, a new method for the determination of MA by single-sweep polarography was developed.展开更多
In our previous papers, the isonuclear complexes of RE (Ⅲ)-Ni (Ⅱ) (or Co(Ⅱ))-ALC had been studied by single-sweep polarograph. In the present note, the polarographic adsorptive complex wave of RE (Ⅲ)-Cu (Ⅱ)-ALC i...In our previous papers, the isonuclear complexes of RE (Ⅲ)-Ni (Ⅱ) (or Co(Ⅱ))-ALC had been studied by single-sweep polarograph. In the present note, the polarographic adsorptive complex wave of RE (Ⅲ)-Cu (Ⅱ)-ALC is reported. The mechanisms of the two are different, the former being the reduced wave of ligand (ALC),展开更多
The rare earth ions form complexes with ECAB in 0.1 mol/L NaAc-HAc supporting electrolyte at pH 6. The composition of the complex was determined by spectrophotometric method to be 1: 2. The decrease of SAC peak height...The rare earth ions form complexes with ECAB in 0.1 mol/L NaAc-HAc supporting electrolyte at pH 6. The composition of the complex was determined by spectrophotometric method to be 1: 2. The decrease of SAC peak height of ECAB is proportional to the concentration of rare earth ions in the range of 1×10^(-6)-2×10^(-5) mol/L. The reduction mechanism of ECAB and RE-ECAB is proposed based on the experimental evidence. The complexing group of ECAB with RE ions iust is the redox group, so when RE ions are added, there is no new peak appearing in the polarograms:, the only phenomenon observed is that the peak current of ECAB decreases. The fast protonation of EGAB carbanion formed after the second electron transfer results in the formation of colourless tetrahedral molecules.展开更多
To examine stress redistribution phenomena in bridges subjected to varying operational conditions,this study conducts a comprehensive analysis of three years of monitoring data from a 153-m double-deck road–rail stee...To examine stress redistribution phenomena in bridges subjected to varying operational conditions,this study conducts a comprehensive analysis of three years of monitoring data from a 153-m double-deck road–rail steel arch bridge.An initial statistical comparison of sensor data distributions reveals clear temporal variations in stress redistribution patterns.XGBoost(eXtreme Gradient Boosting),a gradient-boosting machine learning(ML)algorithm,was employed not only for predictive modeling but also to uncover the underlying mechanisms of stress evolution.Unlike traditional numerical models that rely on extensive assumptions and idealizations,XGBoost effectively captures nonlinear and time-varying relationships between stress states and operational/environmental factors,such as temperature,traffic load,and structural geometry.This approach allows for the identification of critical periods and conditions under which stress redistribution becomes significant.Results indicate a clear shift of stress concentrations frombeamends toward mid-span regions following the commencement of metro operations,reflecting both structural adaptation and localized overstress near arch ribs.Furthermore,the model generates robust predictions of stress evolution,demonstrating potential applications in early warning systems and fatigue risk assessment.This work represents the first application of interpretable gradient-boosting techniques to stress redistribution modeling in double-deck bridges.In addition,a Stress Redistribution Index(SRI)is proposed,derived from this monitoring study and finite-element-based transverse load distributions,to quantify temporal stress shifts between midspan and edge beams.The results provide both theoretical contributions and practical guidance for the design,inspection,and maintenance of complex bridge structures.展开更多
文摘The micro-amount of nickel in MnO2, electrolytical and natural both, was determined by differential pulse polarography. NH4OH-NH4Cl was used as supporting electrolyte. It was found that the peak potential of Ni(II) reduction wave is -1.0V (vs. Ag-AgCl electrode). The presence of great amount of Mn(II) does not interfere in the trace nickel determination. the peak current relationship with the Ni2+ concentration presents a quite fine straight line. The differential pulse polarography is proved that it is a simple, reliable and acceptable method for determination of trace Ni in various species of MnO2.
文摘The polarographic adsorptive complex wave of rare earths (RE) with 1-phenyl-3-methyl-4-benzoylpyrazoione-5 (PMBP) was studied in HAc-NaAc medium at pH=3.80. In the singlesweep polarography, the reduction potential of complex wave (-1.16V) is more negative than that of the free ligand. (-1.12V), and the wave was proven to be an adsorptive complex wave by cyclic voltammetry method. This experiment proved that only the complexes of heavy RE ions can be adsorbed on the electrode under the same conditions. So it is a good method to determine heavy rare earths in the presence of light rare earths.
文摘This paper reports a polarographic catalytic wave of lysozyme (LE) in the presence of KIO3. The mechanism of the catalytic wave was discussed. It is illustrated by the catalytic wave of LE that, besides the Brdicka current, there exists a new kind of catalytic wave of protein.
基金Project supported by National Natural Science Foundation of P.R.China and by Foundation of Lab of Electroanalytical Chemistry,Changchun Institute of Applied Chemistry,Academia Sinica
文摘The cathodic wave of vitamin C has not been reported in the literature so far.Its E_(1/2)was found at-1.85 volt vs.Ag/AgCl(25℃)in the base solution of 0.1mol/L Bu_4NI.Various electrochemical and spectral techniques were used for studying the electrode reaction. They all showed that the electrode reaction was quasi-reversible while C was more than 1.0×10^(-6)mol/L and mainly adsorptive while C was less than 1.0×10^(-6)mol/L at a mercury electrode.The electron transfer number was 2 and the electron transfer coefficient 0.57. Using DPP techniques,the linear response range was 5.0×10^(-7)-2.0×10^(-3)mol/L and the detection limit 1×10^(-7)mol/L.
基金Proejcr(20235020) supported by the National Natural Science Foundation of China
文摘The sensitive second derivative waves of Cu(Ⅱ),Pb(Ⅱ),Cd(Ⅱ),Ni(Ⅱ),Zn(Ⅱ),Fe(Ⅱ)and Mn(Ⅱ),forming in the substrate solution(pH=9.26)consisting of ammonia,ammonium chlorid,gelatin and ascorbic acid were researched.The peak potentials of the polarographic waves of the seven ions are at about 0.48,0.63,0.79,1.04,1.28,1.44 and 1.60 V respectively.Combining with microwave technique,a new method for the simultaneous determination of the seven trace elements in Chinese traditional medicine was developed.The method is easy to operate,rapid,simple and convenient.When the signal-to-noise rate equals 3,the detection limits of Cu,Pb,Cd,Ni,Zn,Fe and Mn are 4.2×10 3,5.3×10 3,2.1×10 3,5.8×10 4,3.0×10 3,7.7×10 4 and 1.1×10 3 μg/mL respectively.Well linear relationships exist between the concentrations and the peak currents when Cu,Pb,Cd,Ni,Zn,Fe and Mn concentrations are within 8.5×10 3 10,9.7×10 3 10,4.5×10 3 10,1.2×10 3 10,6.4×10 3 10,1.5×10 3 10 and 2.8×10 3 10 μg/mL,respectively.The method has been used to the simultaneous determination of the seven trace elements in Salvia Miltiorrhiza Root and compound Salvia Miltiorrhiza Root injection,the relative standard deviations(RSDs)of the Cu,Pb,Cd,Ni,Zn,Fe and Mn in the two medicines are 3.9% and 5.8%,4.0% and 4.1%,4.3% and 5.7%,4.9% and 5.3%,4.4% and 4.7%,3.5% and 4.0%,0.51% and 2.8%,respectively;the comparisons of the determination results with the values obtained by the standard method indicate that the presented method has very well veracity.
基金Project Supported by National Natural Scientific Foundation of China
文摘Polarographic characteristics of Te(Ⅳ)-alkaline dye were investiga- ted at mercury electrode in acidic solution.It was found that the mechanism of the electrode process depended on the concentration of Te(Ⅳ).
文摘Introduction: A great number of software are currently used to digitalize the patient records in order to optimize the quality of services offered to patients. The objective of this study was to evaluate the effects of Electronic Health Records use in Burundi’s hospitals, taking into account the COVID-19 pandemic context. Methods: This was a quasi-experimental study based on difference in difference method. Ten district hospitals were included in the study, five of them had the Electronic Health Records and five of which did not yet have the Electronic Health Records. The hospital’s control group were chosen using the propensity score matching method. The period before the project’s implementation was 2014 and the period after were 2019 and 2020. Results: After 5 years of the Electronic Health Record’s implementation, the results showed an increase in outpatient consultation (70%), deliveries (more than 100%), caesarean sections (56%) and major surgeries (43%) indicators. The overall quality score of hospitals’ care had a regressive effect of 37% and the income from performance-based funding had an increase by 31%. The indicators which were affected by the context of the COVID-19 pandemic were especially outpatient consultation, caesarian section, income from performance-based funding decreased by 3%, 5% and 20% respectively. Conclusion: The effects of Electronic Health Records use are effective. As the COVID-19 pandemic impacted the hospital’s indicators negatively, the resilient strategies alongside the potential shocks are recommended.
文摘It is reported in this paper a polarographic catalytic double wave of oxygen reduction caused by diphenylamine compounds(diphs).The electrochemical process of the wave includes the polarographic generation of the superoxide anion O_2^- and the dismutation of O_2^- catalyzed by diphs with redox pseudoreversibility.
文摘At present, there are many problems in accounting computerization in colleges and universities, such as unreasonable class layout, lack of teachers and weak practical training, which can not adapt to social development. Therefore, this paper has certain practical significance for solving the problems related to accounting computerization, training various accounting and electromechanical personnel to meet the social needs and promoting social development.
文摘Accounting informatization is the combination of accounting and information technology. It is a necessary measure for enterprise financial accounting management to conform to the wave of informatization. It is helpful to enhance the competitiveness of enterprises and solve the "isolated island" phenomenon existing in accounting computerization. In view of this, the article first points out the necessity of the development of enterprise financial accounting informatization, and then expounds the main performance in the development process of enterprise financial accounting informatization, which is helpful for practitioners to understand the realization conditions of enterprise financial accounting informatization. On this basis, the article puts forward the effective countermeasures for the development of enterprise financial accounting computerization to informatization, including establishing the correct cognition and concept of enterprise financial accounting informatization;In order to provide certain reference for the research and practice of practitioners, it is necessary to upgrade and perfect the enterprise financial accounting system in two aspects.
文摘Polarographic catalytic wave of chlordiazepoxide in the presence of K 2S 2O 8 was studied in aqueous and DMF/H 2O mixed solutions. The results showed that a single reduction wave in alkaline medium was the reduction of the N=C bond in 1,2 position of chlordiazepoxide via an intermediate free radical in two one electron successive additions. When K 2S 2O 8 was present, the free radical of the N=C bond was oxidized to regenerate the original, producing a parallel catalytic wave of chlordiazepoxide. It was determined that the apparent rate constant k f of the oxidation reaction was 3.2×10 3 mol -1 ·L·s -1 . Using the catalytic wave the trace of chlordiazepoxide can be determined by linear potential scan polarography. In NH 3/NH 4Cl (pH 10.2±0.1, 0.12 mol/L)/K 2S 2O 8 (0.016 mol/L) supporting electrolyte, the second order derivative peak current of the catalytic wave was rectilinear to chlordiazepoxide concentration in the range of 3.20×10 -8 -1.60×10 -7 , 1.60×10 -7 -1.44×10 -6 and 1.44 ×10 -6 -1.44×10 -5 mol/L, respectively. The limit of detection was 9.0×10 -9 mol/L.
文摘A new method has been developed to assay poly(ADP-ribose) polymerase (PARP) activity in plant tissues through determining the content of nicotinamide (NIC) produced by enzymatic reaction by linear sweeping polarographic method. The detection limit of NIC was 0.03μmol/L, the calibration graph was linear up to 5μmol/L ( r = 0.999). The recoveries were approximately in the range of 92% to 98% and the relative standard deviations were less
基金Project supported by the National Natural Science Foundation of China (Grant No. 29875017).
文摘The polarographic behavior and catalytic wave mechanism of medroprogesterone acetate ( MPA) were studied in both aqueous and DMF media. In 0.2 mol/L acetic acid-sodium acetate ( pH 5 .0 ) buffer solution, the C=C bond of MPA first undergoes le,lH+ reduction to form protonated free radical HMPA , the further reduction of HMPA in le,lH + process is simultaneous with the dimerization reaction between HMPA and neutral molecular MPA. In DMF media containing 0.1 mol/ L tetrabutylammonium tetrafluoborate ( TBA ·BF4 ) , the C=C bond of MPA shows two le, 1H+ reduction waves, which are ascribed to the reduction of MPA and free radical MPA' , respectively. Here, no dimerization reaction occurs. These processes produce the reduction wave of MPA. In the presence of oxidant KIO3, a polarographic catalytic wave of MPA is observable due to a chemical reaction between HMPA or MPA ~ and KIO3 as well as its intermediate species to regenerate MPA. The catalytic wave, which is caused by the reduction of organic compound itself and the chemical reaction between oxidant and organic intermediate free radical to regenerate original organic compound, is a new-type wave of organic compound. Under optimum experimental conditions, the sensitivity of MPA catalytic wave in the presence of KIO3 is an order of magnitude higher than that of its reduction wave. The catalytic wave can be used for analytical purpose. The calculated rate constant of catalytic reaction is 1.7 X103mol·-1·S-1 .
文摘The polarographic catalytic wave of oxygen reduction caused by mefenamic acid (MA) with redox properties was reported in this paper. The electrochemical process of the catalytic wave was proposed that the superoxide anion O(?) was generated polarographically and the dismutation of the O(?) was catalyzed by MA to reproduce O_2 and H_2O_2. This explained chemically the scavenging of the O_2^- by MA im biomedical area. Based on the catalytic wave, a new method for the determination of MA by single-sweep polarography was developed.
基金Project supported by the National Natural Science Foundation of China
文摘In our previous papers, the isonuclear complexes of RE (Ⅲ)-Ni (Ⅱ) (or Co(Ⅱ))-ALC had been studied by single-sweep polarograph. In the present note, the polarographic adsorptive complex wave of RE (Ⅲ)-Cu (Ⅱ)-ALC is reported. The mechanisms of the two are different, the former being the reduced wave of ligand (ALC),
基金Project supported by the National Natural Science Foundation of China
文摘The rare earth ions form complexes with ECAB in 0.1 mol/L NaAc-HAc supporting electrolyte at pH 6. The composition of the complex was determined by spectrophotometric method to be 1: 2. The decrease of SAC peak height of ECAB is proportional to the concentration of rare earth ions in the range of 1×10^(-6)-2×10^(-5) mol/L. The reduction mechanism of ECAB and RE-ECAB is proposed based on the experimental evidence. The complexing group of ECAB with RE ions iust is the redox group, so when RE ions are added, there is no new peak appearing in the polarograms:, the only phenomenon observed is that the peak current of ECAB decreases. The fast protonation of EGAB carbanion formed after the second electron transfer results in the formation of colourless tetrahedral molecules.
基金supported by the Key Technologies Research and Development Program under Grant 2021YFB1600300.
文摘To examine stress redistribution phenomena in bridges subjected to varying operational conditions,this study conducts a comprehensive analysis of three years of monitoring data from a 153-m double-deck road–rail steel arch bridge.An initial statistical comparison of sensor data distributions reveals clear temporal variations in stress redistribution patterns.XGBoost(eXtreme Gradient Boosting),a gradient-boosting machine learning(ML)algorithm,was employed not only for predictive modeling but also to uncover the underlying mechanisms of stress evolution.Unlike traditional numerical models that rely on extensive assumptions and idealizations,XGBoost effectively captures nonlinear and time-varying relationships between stress states and operational/environmental factors,such as temperature,traffic load,and structural geometry.This approach allows for the identification of critical periods and conditions under which stress redistribution becomes significant.Results indicate a clear shift of stress concentrations frombeamends toward mid-span regions following the commencement of metro operations,reflecting both structural adaptation and localized overstress near arch ribs.Furthermore,the model generates robust predictions of stress evolution,demonstrating potential applications in early warning systems and fatigue risk assessment.This work represents the first application of interpretable gradient-boosting techniques to stress redistribution modeling in double-deck bridges.In addition,a Stress Redistribution Index(SRI)is proposed,derived from this monitoring study and finite-element-based transverse load distributions,to quantify temporal stress shifts between midspan and edge beams.The results provide both theoretical contributions and practical guidance for the design,inspection,and maintenance of complex bridge structures.
