Small coin cell batteries are predominantly used for testing lithium-ion batteries(LIBs)in academia because they require small amounts of material and are easy to assemble.However,insufficient attention is given to di...Small coin cell batteries are predominantly used for testing lithium-ion batteries(LIBs)in academia because they require small amounts of material and are easy to assemble.However,insufficient attention is given to difference in cell performance that arises from the differences in format between coin cells used by academic researchers and pouch or cylindrical cells which are used in industry.In this article,we compare coin cells and pouch cells of different size with exactly the same electrode materials,electrolyte,and electrochemical conditions.We show the battery impedance changes substantially depending on the cell format using techniques including Electrochemical Impedance Spectroscopy(EIS)and Galvanostatic Intermittent Titration Technique(GITT).Using full cell NCA-graphite LIBs,we demonstrate that this difference in impedance has important knock-on effects on the battery rate performance due to ohmic polarization and the battery life time due to Li metal plating on the anode.We hope this work will help researchers getting a better idea of how small coin cell formats impact the cell performance and help predicting improvements that can be achieved by implementing larger cell formats.展开更多
The present work aims to demonstrate the capabilities of Laser-induced Breakdown Spectroscopy(LIBS)coupled with a multivariate technique for rapid quantification and classification of old Indian coins made of various ...The present work aims to demonstrate the capabilities of Laser-induced Breakdown Spectroscopy(LIBS)coupled with a multivariate technique for rapid quantification and classification of old Indian coins made of various alloys.Thirteen old Indian coins in different years of circulation,(1922–1986)were selected for the study.The concentrations were determined by Calibration free LIBS(CF-LIBS)method.The concentration of cuprum(Cu)is negligible,and aluminum(Al)is maximum in the first five coins,and vice-versa in the remaining eight coins.Two different multivariate methods,Principal Component Analysis(PCA)and Soft Independent Modelling of Class Analogy(SIMCA)have been used to classify and identify the coins.PCA classified all thirteen samples into four main alloy categories.The discernment of unknown samples to their probable class membership of alloy was performed using SIMCA.The surface hardness(Brinell hardness number)is linearly correlated with the plasma temperature and LIBS intensity ratios.The sample surface of the first and fifth coin belongs to Al-alloy,having the least surface hardness,and it became harder for Cu–Ni alloy,Ni-brass alloy,and bronze alloy.The hardness of the surface is more for bronze sample twelve.It is also observed that the plasma temperature increases monotonically with the Brinell hardness number.This analysis provides valuable information on fabrication methodology and explains large diversification in the elementary composition of old coins.展开更多
As prior researchers have suggested,a firm’s success in an international market depends on how well its strategy fits the nonmarket environment,such as formal institutions.This paper examines the determinants of form...As prior researchers have suggested,a firm’s success in an international market depends on how well its strategy fits the nonmarket environment,such as formal institutions.This paper examines the determinants of formal institutions around new areas of economic activities.Specifically,we propose a framework for understanding how the quality of formal institutions in promoting entrepreneurship drives the focus of such institutions concerning initial coin offering(ICO),which is emerging as a popular fundraising method.The paper uses inductive analysis to examine how nonmarket factors—such as a jurisdiction’s tax haven nature,regulators’perceptions of ICOs as threats to national or political interests,and trade and industry associations—might moderate the relationship between the quality of institutions and the focus of such institutions regarding ICOs.One of this study’s key findings is that an economy’s quality of entrepreneurship-related institutions,perceived threats to national/political interests,and tax haven nature lead to different policy orientations.Consequently,regulators assign different importance when promoting crypto-entrepreneurship and dealing with associated risks.Regulators focusing mainly on promoting crypto-ventures have taken measures to enrich the blockchain ecosystem and provided tax and non-tax incentives to attract such ventures.Regulators focusing mainly on dealing with crypto-venture risks rely on a regulatory sandbox and close regulatory monitoring of such ventures.展开更多
The paper is entitled“Coinage in Akan Among Senior High School Students”.It aims to investigate coinage used by senior high school students.This paper also investigates other word formation processes involved in coi...The paper is entitled“Coinage in Akan Among Senior High School Students”.It aims to investigate coinage used by senior high school students.This paper also investigates other word formation processes involved in coined words and the reasons why the students use them in their everyday conversation.The collected data from direct elicitation and interviews were categorized into the types of coined words and analyzed in terms of their formation processes by using a method of analysis based on theories as proposed by Yule(1985),Potter(1975),O’Grady and Guzman(1996),and Gerber(1968).The findings show that there are 10 groups of word formation processes in this study.This paper presents a qualitative analysis of the findings of a sociolinguistic survey geared towards coinage as used by students of both Osei Tutu Senior High School and Bisease Community/Senior High School speech communities.It is also imperative to state that these two schools are located in typical Akan speaking communities.Osei Tutu Senior High School,situated in Akropong,in the Ashanti region of Ghana,is a single sex school(boys’school)and Bisease Community/Senior High School on the other hand is situated in Ajumako-Bisease in the central region.The latter is a mixed school.展开更多
A capacity increase is often observed in the early stage of Li-ion battery cycling.This study explores the phenomena involved in the capacity increase from the full cell,electrodes,and materials perspective through a ...A capacity increase is often observed in the early stage of Li-ion battery cycling.This study explores the phenomena involved in the capacity increase from the full cell,electrodes,and materials perspective through a combination of non-destructive diagnostic methods in a full cell and post-mortem analysis in a coin cell.The results show an increase of 1%initial capacity for the battery aged at 100%depth of discharge(DOD)and 45℃.Furthermore,large DODs or high temperatures accelerate the capacity increase.From the incremental capacity and differential voltage(IC-DV)analysis,we concluded that the increased capacity in a full cell originates from the graphite anode.Furthermore,graphite/Li coin cells show an increased capacity for larger DODs and a decreased capacity for lower DODs,thus in agreement with the full cell results.Post-mortem analysis results show that a larger DOD enlarges the graphite dspace and separates the graphite layer structure,facilitating the Li+diffusion,hence increasing the battery capacity.展开更多
Foreign body ingestion is a common emergency situation in children with one or a few objects having been ingested. Here we report our experience using endo-scopic retrieval in a female centenarian with dyspnea and for...Foreign body ingestion is a common emergency situation in children with one or a few objects having been ingested. Here we report our experience using endo-scopic retrieval in a female centenarian with dyspnea and foreign bodies in the esophagus. She attempted suicide by swallowing 26 coins and two other foreign bodies. A gastroscope was used to remove all foreign bodies in the lower esophagus. In total, 26 coins, one ferrous ring and one cylindrical plastic object were retrieved. To our knowledge, this is the first clinical report on retrieval of so many foreign bodies in a single case.展开更多
Various adaptive designs have been proposed and applied to clinical trials, bio assay, psychophysics, etc.Adaptive designs are also useful in high cost engineering trials.More and more people have been paying attentio...Various adaptive designs have been proposed and applied to clinical trials, bio assay, psychophysics, etc.Adaptive designs are also useful in high cost engineering trials.More and more people have been paying attention to these design methods. This paper introduces several broad families of designs, such as the play-the-winner rule, randomized play-the-winner rule and its generalization to the multi-arm case, doubly biased coin adaptive design, Markov chain model.展开更多
Treated FeS2 samples were prepared by natural FeS2 samples which were ground first, heated in nitrogen and then washed in acid. The levels of impurity elements, primarily present as metallic oxides and sulfides, are h...Treated FeS2 samples were prepared by natural FeS2 samples which were ground first, heated in nitrogen and then washed in acid. The levels of impurity elements, primarily present as metallic oxides and sulfides, are higher in the natural FeS2 than those in the treated sample. Scanning electron microscopy shows that the grain sizes of treated FeS2, particles are smaller than those of natural FeS2 particles. The electrochemical performance of Li/treated FeS2 cells is attributed to the smaller grain sizes and higher purity of treated FeS2 particles in comparison to the natural FeS2 sample.展开更多
Objective： The aim of this study was to determine an optimal slice thickness that was efficient in revealing Iobulation of malignant solitary pulmonary nodules （SPNs） on multi-slice spiral computed tomography （MSC...Objective： The aim of this study was to determine an optimal slice thickness that was efficient in revealing Iobulation of malignant solitary pulmonary nodules （SPNs） on multi-slice spiral computed tomography （MSCT） images preliminarily. Methods： Fifty patients with malignant SPNs （diameter -〈 3 cm） underwent multidetector-row computed tomography of the chest in a single-breath-hold technique. The raw data were acquired with a collimation of 0.625 mm. Three sets of contiguous images were reconstructed with 1-, 2-, and 5-ram slice thickness, respectively. The Iobulation sign of SPNs on the computed tomography （CT） images presented in 1-, 2-, and 5-ram slice thickness was compared. Using the 1-mm sections as the gold standard, an optimal slice thickness in revealing Iobulation sign of SPNs was determined. Results： The 1-mm-thick images CT revealed 98 Iobulations （25 with chord distance 〈 1 ram; 30 with chord distance 1-2 ram; 43 with chord distance 〉 2 mm） of 45 malignant SPNs. 18 Iobulations with chord distance 〈 1 mm presented in 2-mm-thick sections were as same as those in I-ram-thick sections. Statistically significant difference in Iobulations number was found between that revealed in 2-ram-thick images and that in I-ram-thick images （P = 0.023 〈 0.05）. 16 Iobulations with chord distance 〈 1 mm presented in 5-mm-thick sections were as same as that in I-ram-thick sections. There was statistically significant difference in Iobulations number between that revealed in 5-mm-thick images and that in I-ram-thick images （P = 0.004 〈 0.05）. The 24 Iobulations with chord distance 1-2 mm presented in 2-ram-thick sections were as same as that in 1-mm-thick sections. No statistically significant difference in Iobulations number were found between that revealed in 2-mm-thick images and that in 1-mm-thick images （P = 0.261 〉 0.05）. 13 Iobulations with chord distance 1-2 mm presented in 5-ram-thick sections were as same as that in 1- mm-thick sections. There was statistically significant difference in Iobulations number between that revealed in 5-ram-thick images and that in I-ram-thick images （P = 0.003 〈 0.05）. 40 Iobulations with chord distance 〉 2 mm presented in 2-ram-thick sections were as same as that in I-ram-thick sections. No statistically significant difference in Iobulations number was found between that revealed in 2-ram-thick images and that in I-ram-thick images （P = 0.631 〉 0.05）. 36 Iobulations with chord distance 〉 2 mm presented in 5-mm-thick sections were as same as that in I-ram-thick sections. There was no statistically significant difference in Iobulations number between that revealed in 5-ram-thick images and that in I-ram-thick images （P = 0.264 〉 0.05）. Conclusion： It is suggested that the use of 1-mm slice thickness is suitable in revealing Iobulations with chord distance 〈 1 ram. A 2-mm slice thickness is suggested to be used in revealing Iobulafions with chord distance 1-2 mm and 5-mm slice thickness to be used in revealing Iobulations with chord distance 〉 2 mm.展开更多
In natural environment, tarnish was observed on the surface of historic and contemporary gold coins in several countries. Few years after the emergence of panda gold coins, several red spots were appeared on the surfa...In natural environment, tarnish was observed on the surface of historic and contemporary gold coins in several countries. Few years after the emergence of panda gold coins, several red spots were appeared on the surface. To identify the stains and to examine the spots, optical microscope （OM）, scanning electron microscope （SEM）, electron microprobe analysis （EMPA）, X-ray photoelectron spectroscopy （XPS）, and X-ray diffraction （XRD） were used. It was found by microscopic observation that the stain has a dark blue central area surrounded by a large area with a nuance of colors from brown to red. Red spots usually contain holes in the center, which are distributed along the forging stress zones formed in the struck process. From the surface analyses using EMPA, sulfur and silver are detected besides gold, and the contents of Ag and S at the tarnish part are higher than those at the other part. Furthermore, distributions of Ag and S are correlated with the morphology of stains. XPS shows that components of stains are Ag2S and Ag2SO4 and the former is much predominant. These results are confirmed using XRD analysis. Accelerated tarnish test of gold in an atmosphere containing sulfur compound proves that the similar phenomenon appears when a small amount of silver is present on the surface of gold. It can be concluded that the occurrence of tarnish stains is caused by the presence of Ag and S.展开更多
A symmetric all-organic non-aqueous redox flow-type battery was investigated employing the neutral small molecule radical 3-phenyl-1,5-di-p-tolylverdazyl,which can be reversibly oxidized and reduced in one-electron pr...A symmetric all-organic non-aqueous redox flow-type battery was investigated employing the neutral small molecule radical 3-phenyl-1,5-di-p-tolylverdazyl,which can be reversibly oxidized and reduced in one-electron processes,as the sole charge storage material.Cyclic voltammetry of the verdazyl radical in 0.5 M tetrabutylammonium hexa fluoro phosphate(TBAPF6)in acetonitrile revealed redox couples at-0.17 V and-1.15 V vs.Ag+/Ag,leading to a theoretical cell voltage of 0.98 V.From the dependence of peak currents on the square root of the scan rate,diffusion coefficients on the order of 4 x 10 6 cm2 s-1 were demonstrated.Cycling performance was assessed in a static cell employing a Tokoyuma AHA anion exchange membrane,with 0.04 M verdazyl as catholyte and anolyte in 0.5 M TBAPF6 in acetonitrile at a current density of 0.12 mA cm-2.Although coulombic efficiencies were good(94%-97%)throughout the experiment,the capacity faded gradually from high initial values of 93%of the theoretical discharge capacity to 35%by the 50th cycle.Voltage and energy efficiencies were 68%and 65%,respectively.Postcycling analysis by cyclic voltammetry revealed that decomposition of the active material with cycling is a leading cause of cell degradation.展开更多
Twenty Yongzheng copper coins were fast dating by X-ray energy dispersive spectrometer with scanning electron microscope (SEM-EDS) according to official ingredient. The 20 coins were classified in two groups according...Twenty Yongzheng copper coins were fast dating by X-ray energy dispersive spectrometer with scanning electron microscope (SEM-EDS) according to official ingredient. The 20 coins were classified in two groups according to the results. Group 1 represents the coins minted before AD 1 728 and group 2 represents the coins minted after AD 1 728. At concentration range (0.00%–5.13%), the distribution of lead is not homogeneous in the coins, and the largest diameter of lead inclusion is less than 15 μm. The official fineness degrade is supported. Key words archaeometry - Yongzheng coins - dating - SEM-EDS CLC number O 69 - K 854.2 Foundation item: Supported by the Project of Instrument Upgraded of Ministry of Science and Technology of ChinaBiography: Lei Jun-feng (1975-), male, Ph. D, research direction: numismatic archaeology and instrument analysis.展开更多
基金funding from the ERC(Consolidator Grant MIGHTY,866005)the Innovate UK(UKRI:104174)Faraday Institution-Future CAT(FIRG017)and Degradation(FIRG001)
文摘Small coin cell batteries are predominantly used for testing lithium-ion batteries(LIBs)in academia because they require small amounts of material and are easy to assemble.However,insufficient attention is given to difference in cell performance that arises from the differences in format between coin cells used by academic researchers and pouch or cylindrical cells which are used in industry.In this article,we compare coin cells and pouch cells of different size with exactly the same electrode materials,electrolyte,and electrochemical conditions.We show the battery impedance changes substantially depending on the cell format using techniques including Electrochemical Impedance Spectroscopy(EIS)and Galvanostatic Intermittent Titration Technique(GITT).Using full cell NCA-graphite LIBs,we demonstrate that this difference in impedance has important knock-on effects on the battery rate performance due to ohmic polarization and the battery life time due to Li metal plating on the anode.We hope this work will help researchers getting a better idea of how small coin cell formats impact the cell performance and help predicting improvements that can be achieved by implementing larger cell formats.
文摘The present work aims to demonstrate the capabilities of Laser-induced Breakdown Spectroscopy(LIBS)coupled with a multivariate technique for rapid quantification and classification of old Indian coins made of various alloys.Thirteen old Indian coins in different years of circulation,(1922–1986)were selected for the study.The concentrations were determined by Calibration free LIBS(CF-LIBS)method.The concentration of cuprum(Cu)is negligible,and aluminum(Al)is maximum in the first five coins,and vice-versa in the remaining eight coins.Two different multivariate methods,Principal Component Analysis(PCA)and Soft Independent Modelling of Class Analogy(SIMCA)have been used to classify and identify the coins.PCA classified all thirteen samples into four main alloy categories.The discernment of unknown samples to their probable class membership of alloy was performed using SIMCA.The surface hardness(Brinell hardness number)is linearly correlated with the plasma temperature and LIBS intensity ratios.The sample surface of the first and fifth coin belongs to Al-alloy,having the least surface hardness,and it became harder for Cu–Ni alloy,Ni-brass alloy,and bronze alloy.The hardness of the surface is more for bronze sample twelve.It is also observed that the plasma temperature increases monotonically with the Brinell hardness number.This analysis provides valuable information on fabrication methodology and explains large diversification in the elementary composition of old coins.
文摘As prior researchers have suggested,a firm’s success in an international market depends on how well its strategy fits the nonmarket environment,such as formal institutions.This paper examines the determinants of formal institutions around new areas of economic activities.Specifically,we propose a framework for understanding how the quality of formal institutions in promoting entrepreneurship drives the focus of such institutions concerning initial coin offering(ICO),which is emerging as a popular fundraising method.The paper uses inductive analysis to examine how nonmarket factors—such as a jurisdiction’s tax haven nature,regulators’perceptions of ICOs as threats to national or political interests,and trade and industry associations—might moderate the relationship between the quality of institutions and the focus of such institutions regarding ICOs.One of this study’s key findings is that an economy’s quality of entrepreneurship-related institutions,perceived threats to national/political interests,and tax haven nature lead to different policy orientations.Consequently,regulators assign different importance when promoting crypto-entrepreneurship and dealing with associated risks.Regulators focusing mainly on promoting crypto-ventures have taken measures to enrich the blockchain ecosystem and provided tax and non-tax incentives to attract such ventures.Regulators focusing mainly on dealing with crypto-venture risks rely on a regulatory sandbox and close regulatory monitoring of such ventures.
文摘The paper is entitled“Coinage in Akan Among Senior High School Students”.It aims to investigate coinage used by senior high school students.This paper also investigates other word formation processes involved in coined words and the reasons why the students use them in their everyday conversation.The collected data from direct elicitation and interviews were categorized into the types of coined words and analyzed in terms of their formation processes by using a method of analysis based on theories as proposed by Yule(1985),Potter(1975),O’Grady and Guzman(1996),and Gerber(1968).The findings show that there are 10 groups of word formation processes in this study.This paper presents a qualitative analysis of the findings of a sociolinguistic survey geared towards coinage as used by students of both Osei Tutu Senior High School and Bisease Community/Senior High School speech communities.It is also imperative to state that these two schools are located in typical Akan speaking communities.Osei Tutu Senior High School,situated in Akropong,in the Ashanti region of Ghana,is a single sex school(boys’school)and Bisease Community/Senior High School on the other hand is situated in Ajumako-Bisease in the central region.The latter is a mixed school.
基金supported by a grant from the China Scholarship Council(202006370035 and 202006220024)supported by the National Natural Science Foundation of China(52107229)。
文摘A capacity increase is often observed in the early stage of Li-ion battery cycling.This study explores the phenomena involved in the capacity increase from the full cell,electrodes,and materials perspective through a combination of non-destructive diagnostic methods in a full cell and post-mortem analysis in a coin cell.The results show an increase of 1%initial capacity for the battery aged at 100%depth of discharge(DOD)and 45℃.Furthermore,large DODs or high temperatures accelerate the capacity increase.From the incremental capacity and differential voltage(IC-DV)analysis,we concluded that the increased capacity in a full cell originates from the graphite anode.Furthermore,graphite/Li coin cells show an increased capacity for larger DODs and a decreased capacity for lower DODs,thus in agreement with the full cell results.Post-mortem analysis results show that a larger DOD enlarges the graphite dspace and separates the graphite layer structure,facilitating the Li+diffusion,hence increasing the battery capacity.
文摘Foreign body ingestion is a common emergency situation in children with one or a few objects having been ingested. Here we report our experience using endo-scopic retrieval in a female centenarian with dyspnea and foreign bodies in the esophagus. She attempted suicide by swallowing 26 coins and two other foreign bodies. A gastroscope was used to remove all foreign bodies in the lower esophagus. In total, 26 coins, one ferrous ring and one cylindrical plastic object were retrieved. To our knowledge, this is the first clinical report on retrieval of so many foreign bodies in a single case.
文摘Various adaptive designs have been proposed and applied to clinical trials, bio assay, psychophysics, etc.Adaptive designs are also useful in high cost engineering trials.More and more people have been paying attention to these design methods. This paper introduces several broad families of designs, such as the play-the-winner rule, randomized play-the-winner rule and its generalization to the multi-arm case, doubly biased coin adaptive design, Markov chain model.
基金SUPPORTED BY NATIONAL NATURAL SCIENCE FOUNDATION OF CHINA( NO. 20273047)DOCTOR FOUNDATION OF MINISTRY OF EDUCATION ( NO. 20020056045).
文摘Treated FeS2 samples were prepared by natural FeS2 samples which were ground first, heated in nitrogen and then washed in acid. The levels of impurity elements, primarily present as metallic oxides and sulfides, are higher in the natural FeS2 than those in the treated sample. Scanning electron microscopy shows that the grain sizes of treated FeS2, particles are smaller than those of natural FeS2 particles. The electrochemical performance of Li/treated FeS2 cells is attributed to the smaller grain sizes and higher purity of treated FeS2 particles in comparison to the natural FeS2 sample.
文摘Objective： The aim of this study was to determine an optimal slice thickness that was efficient in revealing Iobulation of malignant solitary pulmonary nodules （SPNs） on multi-slice spiral computed tomography （MSCT） images preliminarily. Methods： Fifty patients with malignant SPNs （diameter -〈 3 cm） underwent multidetector-row computed tomography of the chest in a single-breath-hold technique. The raw data were acquired with a collimation of 0.625 mm. Three sets of contiguous images were reconstructed with 1-, 2-, and 5-ram slice thickness, respectively. The Iobulation sign of SPNs on the computed tomography （CT） images presented in 1-, 2-, and 5-ram slice thickness was compared. Using the 1-mm sections as the gold standard, an optimal slice thickness in revealing Iobulation sign of SPNs was determined. Results： The 1-mm-thick images CT revealed 98 Iobulations （25 with chord distance 〈 1 ram; 30 with chord distance 1-2 ram; 43 with chord distance 〉 2 mm） of 45 malignant SPNs. 18 Iobulations with chord distance 〈 1 mm presented in 2-mm-thick sections were as same as those in I-ram-thick sections. Statistically significant difference in Iobulations number was found between that revealed in 2-ram-thick images and that in I-ram-thick images （P = 0.023 〈 0.05）. 16 Iobulations with chord distance 〈 1 mm presented in 5-mm-thick sections were as same as that in I-ram-thick sections. There was statistically significant difference in Iobulations number between that revealed in 5-mm-thick images and that in I-ram-thick images （P = 0.004 〈 0.05）. The 24 Iobulations with chord distance 1-2 mm presented in 2-ram-thick sections were as same as that in 1-mm-thick sections. No statistically significant difference in Iobulations number were found between that revealed in 2-mm-thick images and that in 1-mm-thick images （P = 0.261 〉 0.05）. 13 Iobulations with chord distance 1-2 mm presented in 5-ram-thick sections were as same as that in 1- mm-thick sections. There was statistically significant difference in Iobulations number between that revealed in 5-ram-thick images and that in I-ram-thick images （P = 0.003 〈 0.05）. 40 Iobulations with chord distance 〉 2 mm presented in 2-ram-thick sections were as same as that in I-ram-thick sections. No statistically significant difference in Iobulations number was found between that revealed in 2-ram-thick images and that in I-ram-thick images （P = 0.631 〉 0.05）. 36 Iobulations with chord distance 〉 2 mm presented in 5-mm-thick sections were as same as that in I-ram-thick sections. There was no statistically significant difference in Iobulations number between that revealed in 5-ram-thick images and that in I-ram-thick images （P = 0.264 〉 0.05）. Conclusion： It is suggested that the use of 1-mm slice thickness is suitable in revealing Iobulations with chord distance 〈 1 ram. A 2-mm slice thickness is suggested to be used in revealing Iobulafions with chord distance 1-2 mm and 5-mm slice thickness to be used in revealing Iobulations with chord distance 〉 2 mm.
文摘In natural environment, tarnish was observed on the surface of historic and contemporary gold coins in several countries. Few years after the emergence of panda gold coins, several red spots were appeared on the surface. To identify the stains and to examine the spots, optical microscope （OM）, scanning electron microscope （SEM）, electron microprobe analysis （EMPA）, X-ray photoelectron spectroscopy （XPS）, and X-ray diffraction （XRD） were used. It was found by microscopic observation that the stain has a dark blue central area surrounded by a large area with a nuance of colors from brown to red. Red spots usually contain holes in the center, which are distributed along the forging stress zones formed in the struck process. From the surface analyses using EMPA, sulfur and silver are detected besides gold, and the contents of Ag and S at the tarnish part are higher than those at the other part. Furthermore, distributions of Ag and S are correlated with the morphology of stains. XPS shows that components of stains are Ag2S and Ag2SO4 and the former is much predominant. These results are confirmed using XRD analysis. Accelerated tarnish test of gold in an atmosphere containing sulfur compound proves that the similar phenomenon appears when a small amount of silver is present on the surface of gold. It can be concluded that the occurrence of tarnish stains is caused by the presence of Ag and S.
基金supported by the Natural Sciences and Engineering Research Council (NSERC) of Canada (C. A. D.: DG, 04279 J. B. G.: DG, 435675 and S. M. B.: CGS D scholarship)+1 种基金support form the Canada Foundation for Innovation (CFI) the New Brunswick Innovation Foundation (NBIF)the University of New Brunswick. J. B. G. would like to thank the University of Western Ontario for support
文摘A symmetric all-organic non-aqueous redox flow-type battery was investigated employing the neutral small molecule radical 3-phenyl-1,5-di-p-tolylverdazyl,which can be reversibly oxidized and reduced in one-electron processes,as the sole charge storage material.Cyclic voltammetry of the verdazyl radical in 0.5 M tetrabutylammonium hexa fluoro phosphate(TBAPF6)in acetonitrile revealed redox couples at-0.17 V and-1.15 V vs.Ag+/Ag,leading to a theoretical cell voltage of 0.98 V.From the dependence of peak currents on the square root of the scan rate,diffusion coefficients on the order of 4 x 10 6 cm2 s-1 were demonstrated.Cycling performance was assessed in a static cell employing a Tokoyuma AHA anion exchange membrane,with 0.04 M verdazyl as catholyte and anolyte in 0.5 M TBAPF6 in acetonitrile at a current density of 0.12 mA cm-2.Although coulombic efficiencies were good(94%-97%)throughout the experiment,the capacity faded gradually from high initial values of 93%of the theoretical discharge capacity to 35%by the 50th cycle.Voltage and energy efficiencies were 68%and 65%,respectively.Postcycling analysis by cyclic voltammetry revealed that decomposition of the active material with cycling is a leading cause of cell degradation.
文摘Twenty Yongzheng copper coins were fast dating by X-ray energy dispersive spectrometer with scanning electron microscope (SEM-EDS) according to official ingredient. The 20 coins were classified in two groups according to the results. Group 1 represents the coins minted before AD 1 728 and group 2 represents the coins minted after AD 1 728. At concentration range (0.00%–5.13%), the distribution of lead is not homogeneous in the coins, and the largest diameter of lead inclusion is less than 15 μm. The official fineness degrade is supported. Key words archaeometry - Yongzheng coins - dating - SEM-EDS CLC number O 69 - K 854.2 Foundation item: Supported by the Project of Instrument Upgraded of Ministry of Science and Technology of ChinaBiography: Lei Jun-feng (1975-), male, Ph. D, research direction: numismatic archaeology and instrument analysis.
