The influence of coexisting copper （Cu） ion on the degradation of pesticides pyrethroid cypermethrin and cyhalothrin in soil and photodegradation in water system were studied. Serial concentrations of the pesticides...The influence of coexisting copper （Cu） ion on the degradation of pesticides pyrethroid cypermethrin and cyhalothrin in soil and photodegradation in water system were studied. Serial concentrations of the pesticides with the addition of copper ion were spiked in the soil and incubated for a regular period of time, the analysis of the extracts from the soil was carded out using gas chromatography （GC）. The photodegradation of pyrethroids in water system was conducted under UV irradiation. The effect of Cu^2＋ on the pesticides degradation was measured with half life 00.5） of degradation. It was found that a negative correlation between the degradation of the pyrethroid pesticides in soil and Cu addition was observed. But Cu^2＋ could accelerate photodegradation of the pyrethroids in water. The t0.5 for cyhalothrin extended from 6.7 to 6.8 d while for cypermethrin extended from 8.1 to 10.9 d with the presence of copper ion in soil. As for photodegradation, t0.5 for cyhalothrin reduced from 173.3 to 115.5 min and for cypermethrin from 115.5 to 99.0 min. The results suggested that copper influenced the degradation of the pesticides in soil by affecting the activity of microorganisms. However, it had catalyst tendency for photodegradation in water system. The difference for the degradation efficiency of pyrethroid isomers in soil was also observed. Copper could obviously accelerate the degradation of some special isomers.展开更多
The countries of Central Asia are collectively known as the five "-stans": Uzbekistan, Kyrgyzstan, Turkmenistan, Tajikistan and Kazakhstan. In recent times, the Central Asian region has been affected by the ...The countries of Central Asia are collectively known as the five "-stans": Uzbekistan, Kyrgyzstan, Turkmenistan, Tajikistan and Kazakhstan. In recent times, the Central Asian region has been affected by the shrinkage of the Aral Sea, widespread desertification, soil salinization, biodiversity loss, frequent sand storms, and many other ecological disasters. This paper is a review article based upon the collection, identification and collation of previous studies of environmental changes and regional developments in Central Asia in the past 30 years. Most recent studies have reached a consensus that the temperature rise in Central Asia is occurring faster than the global average. This warming trend will not only result in a higher evaporation in the basin oases, but also to a significant retreat of glaciers in the mountainous areas. Water is the key to sustainable development in the arid and semi-arid regions in Central Asia. The uneven distribution, over consumption, and pollution of water resources in Central Asia have caused severe water supply problems, which have been affecting regional harmony and development for the past 30 years. The widespread and significant land use changes in the 1990 s could be used to improve our understanding of natural variability and human interaction in the region. There has been a positive trend of trans-border cooperation among the Central Asian countries in recent years. International attention has grown and research projects have been initiated to provide water and ecosystem protection in Central Asia. However, the agreements that have been reached might not be able to deliver practical action in time to prevent severe ecological disasters. Water management should be based on hydrographic borders and ministries should be able to make timely decisions without political intervention. Fully integrated management of water resources, land use and industrial development is essential in Central Asia. The ecological crisis should provide sufficient motivation to reach a consensus on u展开更多
BACKGROUND:Penehyclidine is a newly developed anticholinergic agent.We aimed to investigate the role of penehyclidine in acute organophosphorus pesticide poisoning(OP)patients.METHODS:We searched the Pubmed,Cochrane l...BACKGROUND:Penehyclidine is a newly developed anticholinergic agent.We aimed to investigate the role of penehyclidine in acute organophosphorus pesticide poisoning(OP)patients.METHODS:We searched the Pubmed,Cochrane library,EMBASE,Chinese National Knowledge Infrastructure(CNKI),Chinese Biomedical literature(CBM)and Wanfang databases.Randomized controlled trials(RCTs)recruiting acute OP patients were identifi ed for meta-analysis.Main outcomes included cure rate,mortality rate,time to atropinization,time to 60%normal acetylcholinesterase(AchE)level,rate of intermediate syndrome(IMS)and rate of adverse drug reactions(ADR).RESULTS:Sixteen RCTs involving 1,334 patients were identifi ed.Compared with the atropineor penehyclidine-alone groups,atropine combined with penehyclidine significantly increased the cure rate(penehyclidine+atropine vs.atropine,0.97 vs.0.86,RR 1.13,95%CI[1.07–1.19];penehyclidine+atropine vs.penehyclidine,0.93 vs.0.80,RR 1.08,95%CI[1.01–1.15])and reduced the mortality rate(penehyclidine+atropine vs.atropine,0.015 vs.0.11,RR 0.17,95%CI[0.06–0.49];penehyclidine+atropine vs.penehyclidine,0.13 vs.0.08,RR 0.23,95%CI[0.04–1.28]).Atropine combined with penehyclidine in OP patients also helped reduce the time to atropinization and AchE recovery,the rate of IMS and the rate of ADR.Compared with a single dose of atropine,a single dose of penehyclidine also signifi cantly elevated the cure rate,reduced times to atropinization,AchE recovery,and rate of IMS.CONCLUSION:Atropine combined with penehyclidine benefi ts OP patients by enhancing the cure rate,mortality rate,time to atropinization,AchE recovery,IMS rate,total ADR and duration of hospitalization.Penehyclidine combined with atropine is likely a better initial therapy for OP patients than atropine alone.展开更多
AIM:To investigate the role of hepatitis B virus (HBV) replication in the development of hepatocellular carcinoma (HCC), a nested case-control study was performed to study the relationship between HBV DNA level and ri...AIM:To investigate the role of hepatitis B virus (HBV) replication in the development of hepatocellular carcinoma (HCC), a nested case-control study was performed to study the relationship between HBV DNA level and risk of HCC. METHODS:One hundred and seventy cases of HCC and 276 control subjects free of HCC and cirrhosis were selected for this study. Serum HBV DNA level was measured using fluorescein quantitative polymerase chain reaction at study entry and the last visit. RESULTS:In a binary unconditional logistic regression analysis adjusted for age, cigarette smoking, alcohol consumption and family history of chronic liver diseases, the adjusted odds ratios (95% confidence intervals) of HCC in patients with increasing HBV DNA level were 2.834 (1.237-6.492), 48.403 (14.392-162.789), 42.252 (14.784-120.750), and 14.819 (6.992-31.411) for HBV DNA levels ≥ 104 to < 105; ≥ 105 to < 106; ≥ 106 to < 107; ≥ 107 copies/mL, respectively. Forty-six HCC cases were selected to compare the serums viral loads of HBV DNA at study entry with those at the last visit. The HBV DNA levels measured at the two time points did not differ significantly.CONCLUSION:The findings of this study provide strong longitudinal evidence of an increased risk of HCC associated with persistent elevation of serum HBV DNA level in the 104-107 range.展开更多
To acquire the synergy effects between Sn and Cu for the jointly high Faradaic efficiency and current density,we develop a novel strategy to design the Sn-Cu alloy catalyst via a decorated co-electrodeposition method ...To acquire the synergy effects between Sn and Cu for the jointly high Faradaic efficiency and current density,we develop a novel strategy to design the Sn-Cu alloy catalyst via a decorated co-electrodeposition method for CO2 electroreduction to formate.The Sn-Cu alloy shows high formate Faradaic efficiency of 82.3%±2.1% and total C1 products Faradaic efficiency of 90.0%±2.7% at^-1.14 V vs.reversible hydrogen electrode(RHE).The current density and mass activity of formate reach as high as(79.0±0.4)mA cm^-2 and(1490.6±7.5)m A mg^-1 at^-1.14 V vs.RHE.Theoretical calculations suggest that Sn-Cu alloy can obtain high Faradaic efficiency for CO2 electroreduction by suppressing the competitive hydrogen evolution reaction and that the formate formation follows the path of CO2→HCOO*→HCOOH.The stepped(211)surface of Sn-Cu alloy is beneficial towards selective formate production.展开更多
This study examined how the signals of interest （SOI） effect on the backscattering measurement numerically based on 3-D finite-difference time-domain （FDTD） method. High resolution microstructure mappings of bovin...This study examined how the signals of interest （SOI） effect on the backscattering measurement numerically based on 3-D finite-difference time-domain （FDTD） method. High resolution microstructure mappings of bovine cancellous bones provided by micro-CT were used as the input geometry for simulations. Backscatter coefficient （BSC）, integrated backscatter coefficient （IBC） and apparent integrated backscatter （AIB） were calculated with changing the start （L1） and duration （L2） of the SOl. The results demonstrated that BSC and IBC decrease as L1 increases, and AIB decreases more rapidly as L1 increases. The backscattering parameters increase with fluctuations as a function of L2 when L2 is less than 6 mm. However, BSC and IBC change little as L2 continues to increase, while AIB slowly decreases as L2 continues to increase. The results showed how the selections of the SOI effect on the backscattering measurement. An explicit standard for SOl selection was proposed in this study and short L1 （about 1.5 mm） and appropriate L2 （6 mm-12 mm） were recommended for the calculations of backscattering parameters.展开更多
Ultrasonic guided waves (GWs) can be used to evaluate long bones effectively because of the ability to provide the information of the whole bone. In this study, a joint spectrogram segmentation and ridge-extraction (J...Ultrasonic guided waves (GWs) can be used to evaluate long bones effectively because of the ability to provide the information of the whole bone. In this study, a joint spectrogram segmentation and ridge-extraction (JSSRE) method was proposed to separate multiple modes in long bones. First, the Gabor time-frequency transform was applied to obtain the spectrogram of multimodal signals. Then, a multi-class image segmentation algorithm was used to find the corresponding region of each mode in the spectrogram, including an improved watershed transform and a region growing procedure. Finally, the ridges were extracted and the time domain signals representing individual modes were reconstructed from these ridges in each region. The validations of this method were discussed by simulated multimodal signals with different signal-to-noise ratios (SNR). The correlation coefficients between the original signals without noise and the reconstructed signals were calculated to analyze the results quantitatively. The results showed that the extracted ridges were in good agreement with generated theoretical dispersion curves, and the reconstructed signals were highly related to the original signals, even under the SNR=3 dB situation.展开更多
Light sources based on reliable and energy-efficient light-emitting diodes (LEDs) are instrumental in the development of solid-statelighting (SSL). Most research efforts in SSL have focused on improving both the intri...Light sources based on reliable and energy-efficient light-emitting diodes (LEDs) are instrumental in the development of solid-statelighting (SSL). Most research efforts in SSL have focused on improving both the intrinsic quantum efficiency (QE) and the stability oflight emitters. For this reason, it is broadly accepted that with the advent of highly efficient (QE close to 1) and stable emitters, thefundamental research phase of SSL is coming to an end. In this study, we demonstrate a very large improvement in SSL emission (above70-fold directional enhancement for p-polarized emission and 60-fold enhancement for unpolarized emission) using nanophotonicstructures. This is attained by coupling emitters with very high QE to collective plasmonic resonances in periodic arrays of aluminumnanoantennas. Our results open a new path for fundamental and applied research in SSL in which plasmonic nanostructures are able tomold the spectral and angular distribution of the emission with unprecedented precision.展开更多
Central Asia(CA)occupies the hinterland of the Eurasian continent,containing the countries of Uzbekistan,Kyrgyzstan,Turkmenistan,Tajikistan,and Kazakhstan[1,2].Being isolated by the Pamir Mountains in Tajikistan,the T...Central Asia(CA)occupies the hinterland of the Eurasian continent,containing the countries of Uzbekistan,Kyrgyzstan,Turkmenistan,Tajikistan,and Kazakhstan[1,2].Being isolated by the Pamir Mountains in Tajikistan,the Tibetan Plateau and the Tian Shan Mountains on the border between China and Kyrgyzstan.展开更多
Highly selective production of value-added multicarbon(C^(2+))products via electrochemical CO_(2) reduction reaction(eCO_(2)RR)on polycrystalline copper(Cu)remains challenging.Herein,the facile surface modification us...Highly selective production of value-added multicarbon(C^(2+))products via electrochemical CO_(2) reduction reaction(eCO_(2)RR)on polycrystalline copper(Cu)remains challenging.Herein,the facile surface modification using poly(α-ethyl cyanoacrylate)(PECA)is presented to greatly enhance the C^(2+)selectivity for eCO_(2)RR over polycrystalline Cu,with Faradaic efficiency(FE)towards C^(2+)products increased from30.1%for the Cu electrode to 72.6%for the obtained Cu-PECA electrode at-1.1 V vs.reversible hydrogen electrode(RHE).Given the well-determined FEs towards C^(2+)products,the partial current densities for C^(2+)production could be estimated to be-145.4 mA cm~(-2)for the Cu-PECA electrode at-0.9 V vs.RHE in a homemade flow cell.In-situ spectral characterizations and theoretical calculations reveal that PECA featured with electron-accepting-C≡N and-COOR groups decorated onto the Cu electrode could inhibit the adsorption of^(*)H intermediates and stabilize the^(*)CO intermediates,given the redistributed interfacial electron density and the raised energy level of d-band center(E_(d))of Cu active sites,thus facilitating the C-C coupling and then the C^(2+)selective production.This study is believed to be guidable to the modification of electrocatalysts and electrodes with polymers to steer the surface adsorption behaviors of reaction intermediates to realize practical eCO_(2)RR towards value-added C^(2+)products with high activity and selectivity.展开更多
The electronic configuration of central metal atoms in single-atom catalysts(SACs)is pivotal in electrochemical CO_(2)reduction reaction(eCO_(2)RR).Herein,chalcogen heteroatoms(e.g.,S,Se,and Te)were incorporated into ...The electronic configuration of central metal atoms in single-atom catalysts(SACs)is pivotal in electrochemical CO_(2)reduction reaction(eCO_(2)RR).Herein,chalcogen heteroatoms(e.g.,S,Se,and Te)were incorporated into the symmetric nickel-nitrogen-carbon(Ni-N4-C)configuration to obtain Ni-X-N3-C(X:S,Se,and Te)SACs with asymmetric coordination presented for central Ni atoms.Among these obtained Ni-X-N3-C(X:S,Se,and Te)SACs,Ni-Se-N3-C exhibited superior eCO_(2)RR activity,with CO selectivity reaching~98%at-0.70 V versus reversible hydrogen electrode(RHE).The Zn-CO_(2)battery integrated with Ni-Se-N3-C as cathode and Zn foil as anode achieved a peak power density of 1.82 mW cm-2 and maintained remarkable rechargeable stability over 20 h.In-situ spectral investigations and theoretical calculations demonstrated that the chalcogen heteroatoms doped into the Ni-N4-C configuration would break coordination symmetry and trigger charge redistribution,and then regulate the intermediate behaviors and thermodynamic reaction pathways for eCO_(2)RR.Especially,for Ni-Se-N3-C,the introduced Se atoms could significantly raise the d-band center of central Ni atoms and thus remarkably lower the energy barrier for the rate-determining step of*COOH formation,contributing to the promising eCO_(2)RR performance for high selectivity CO production by competing with hydrogen evolution reaction.展开更多
基金Project supported by the National Natural Science Foundation of China (No.20677025)Social Development Foundation of Jiangsu Province (No.BS2006052)Social Development Foundation of Zhenjiang City (No.SH2006076)
文摘The influence of coexisting copper （Cu） ion on the degradation of pesticides pyrethroid cypermethrin and cyhalothrin in soil and photodegradation in water system were studied. Serial concentrations of the pesticides with the addition of copper ion were spiked in the soil and incubated for a regular period of time, the analysis of the extracts from the soil was carded out using gas chromatography （GC）. The photodegradation of pyrethroids in water system was conducted under UV irradiation. The effect of Cu^2＋ on the pesticides degradation was measured with half life 00.5） of degradation. It was found that a negative correlation between the degradation of the pyrethroid pesticides in soil and Cu addition was observed. But Cu^2＋ could accelerate photodegradation of the pyrethroids in water. The t0.5 for cyhalothrin extended from 6.7 to 6.8 d while for cypermethrin extended from 8.1 to 10.9 d with the presence of copper ion in soil. As for photodegradation, t0.5 for cyhalothrin reduced from 173.3 to 115.5 min and for cypermethrin from 115.5 to 99.0 min. The results suggested that copper influenced the degradation of the pesticides in soil by affecting the activity of microorganisms. However, it had catalyst tendency for photodegradation in water system. The difference for the degradation efficiency of pyrethroid isomers in soil was also observed. Copper could obviously accelerate the degradation of some special isomers.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences, Pan-Third Pole Environment Study for a Green Silk Road (XDA20060303)the Xinjiang Key Research and Development Program (2016B02017-4)+1 种基金the National Nature Science Foundation of China-United Nations Environment Programme (NSFC-UNEP, 41361140361)the ''High-level Talents Project'' (Y871171) of Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences
文摘The countries of Central Asia are collectively known as the five "-stans": Uzbekistan, Kyrgyzstan, Turkmenistan, Tajikistan and Kazakhstan. In recent times, the Central Asian region has been affected by the shrinkage of the Aral Sea, widespread desertification, soil salinization, biodiversity loss, frequent sand storms, and many other ecological disasters. This paper is a review article based upon the collection, identification and collation of previous studies of environmental changes and regional developments in Central Asia in the past 30 years. Most recent studies have reached a consensus that the temperature rise in Central Asia is occurring faster than the global average. This warming trend will not only result in a higher evaporation in the basin oases, but also to a significant retreat of glaciers in the mountainous areas. Water is the key to sustainable development in the arid and semi-arid regions in Central Asia. The uneven distribution, over consumption, and pollution of water resources in Central Asia have caused severe water supply problems, which have been affecting regional harmony and development for the past 30 years. The widespread and significant land use changes in the 1990 s could be used to improve our understanding of natural variability and human interaction in the region. There has been a positive trend of trans-border cooperation among the Central Asian countries in recent years. International attention has grown and research projects have been initiated to provide water and ecosystem protection in Central Asia. However, the agreements that have been reached might not be able to deliver practical action in time to prevent severe ecological disasters. Water management should be based on hydrographic borders and ministries should be able to make timely decisions without political intervention. Fully integrated management of water resources, land use and industrial development is essential in Central Asia. The ecological crisis should provide sufficient motivation to reach a consensus on u
文摘BACKGROUND:Penehyclidine is a newly developed anticholinergic agent.We aimed to investigate the role of penehyclidine in acute organophosphorus pesticide poisoning(OP)patients.METHODS:We searched the Pubmed,Cochrane library,EMBASE,Chinese National Knowledge Infrastructure(CNKI),Chinese Biomedical literature(CBM)and Wanfang databases.Randomized controlled trials(RCTs)recruiting acute OP patients were identifi ed for meta-analysis.Main outcomes included cure rate,mortality rate,time to atropinization,time to 60%normal acetylcholinesterase(AchE)level,rate of intermediate syndrome(IMS)and rate of adverse drug reactions(ADR).RESULTS:Sixteen RCTs involving 1,334 patients were identifi ed.Compared with the atropineor penehyclidine-alone groups,atropine combined with penehyclidine significantly increased the cure rate(penehyclidine+atropine vs.atropine,0.97 vs.0.86,RR 1.13,95%CI[1.07–1.19];penehyclidine+atropine vs.penehyclidine,0.93 vs.0.80,RR 1.08,95%CI[1.01–1.15])and reduced the mortality rate(penehyclidine+atropine vs.atropine,0.015 vs.0.11,RR 0.17,95%CI[0.06–0.49];penehyclidine+atropine vs.penehyclidine,0.13 vs.0.08,RR 0.23,95%CI[0.04–1.28]).Atropine combined with penehyclidine in OP patients also helped reduce the time to atropinization and AchE recovery,the rate of IMS and the rate of ADR.Compared with a single dose of atropine,a single dose of penehyclidine also signifi cantly elevated the cure rate,reduced times to atropinization,AchE recovery,and rate of IMS.CONCLUSION:Atropine combined with penehyclidine benefi ts OP patients by enhancing the cure rate,mortality rate,time to atropinization,AchE recovery,IMS rate,total ADR and duration of hospitalization.Penehyclidine combined with atropine is likely a better initial therapy for OP patients than atropine alone.
基金The National High Technology Research and Development Program of China 863 Project, No. 2006AA02Z4C5
文摘AIM:To investigate the role of hepatitis B virus (HBV) replication in the development of hepatocellular carcinoma (HCC), a nested case-control study was performed to study the relationship between HBV DNA level and risk of HCC. METHODS:One hundred and seventy cases of HCC and 276 control subjects free of HCC and cirrhosis were selected for this study. Serum HBV DNA level was measured using fluorescein quantitative polymerase chain reaction at study entry and the last visit. RESULTS:In a binary unconditional logistic regression analysis adjusted for age, cigarette smoking, alcohol consumption and family history of chronic liver diseases, the adjusted odds ratios (95% confidence intervals) of HCC in patients with increasing HBV DNA level were 2.834 (1.237-6.492), 48.403 (14.392-162.789), 42.252 (14.784-120.750), and 14.819 (6.992-31.411) for HBV DNA levels ≥ 104 to < 105; ≥ 105 to < 106; ≥ 106 to < 107; ≥ 107 copies/mL, respectively. Forty-six HCC cases were selected to compare the serums viral loads of HBV DNA at study entry with those at the last visit. The HBV DNA levels measured at the two time points did not differ significantly.CONCLUSION:The findings of this study provide strong longitudinal evidence of an increased risk of HCC associated with persistent elevation of serum HBV DNA level in the 104-107 range.
基金supported by the National Key R&D Program of China(2017YFA0700102)the National Natural Science Foundation of China(21573222,91545202,21802124,91945302 and 91845103)+6 种基金Dalian National Laboratory for Clean Energy(DNL180404)Dalian Institute of Chemical Physics(DICP DMTO201702)Dalian Outstanding Young Scientist Foundation(2017RJ03)Liaoning Revitalization Talents Program(XLYC1907099)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB17020200)the financial support from CAS Youth Innovation Promotion(2015145)the financial support from the China Postdoctoral Science Foundation(2018M630307 and 2019T120220)。
文摘To acquire the synergy effects between Sn and Cu for the jointly high Faradaic efficiency and current density,we develop a novel strategy to design the Sn-Cu alloy catalyst via a decorated co-electrodeposition method for CO2 electroreduction to formate.The Sn-Cu alloy shows high formate Faradaic efficiency of 82.3%±2.1% and total C1 products Faradaic efficiency of 90.0%±2.7% at^-1.14 V vs.reversible hydrogen electrode(RHE).The current density and mass activity of formate reach as high as(79.0±0.4)mA cm^-2 and(1490.6±7.5)m A mg^-1 at^-1.14 V vs.RHE.Theoretical calculations suggest that Sn-Cu alloy can obtain high Faradaic efficiency for CO2 electroreduction by suppressing the competitive hydrogen evolution reaction and that the formate formation follows the path of CO2→HCOO*→HCOOH.The stepped(211)surface of Sn-Cu alloy is beneficial towards selective formate production.
基金supported by the National Natural Science Foundation of China(Grant No. 11174060)the Ph.D. Programs Foundation of the Ministry of Education of China(Grant Nos. 20090071110066,20110071130004)+1 种基金the Key Science and Technology Program of Shanghai(Grant No. 09441900400)the Program for New Century Excellent Talents in University(Grant No. NCET-10-0349)
文摘This study examined how the signals of interest （SOI） effect on the backscattering measurement numerically based on 3-D finite-difference time-domain （FDTD） method. High resolution microstructure mappings of bovine cancellous bones provided by micro-CT were used as the input geometry for simulations. Backscatter coefficient （BSC）, integrated backscatter coefficient （IBC） and apparent integrated backscatter （AIB） were calculated with changing the start （L1） and duration （L2） of the SOl. The results demonstrated that BSC and IBC decrease as L1 increases, and AIB decreases more rapidly as L1 increases. The backscattering parameters increase with fluctuations as a function of L2 when L2 is less than 6 mm. However, BSC and IBC change little as L2 continues to increase, while AIB slowly decreases as L2 continues to increase. The results showed how the selections of the SOI effect on the backscattering measurement. An explicit standard for SOl selection was proposed in this study and short L1 （about 1.5 mm） and appropriate L2 （6 mm-12 mm） were recommended for the calculations of backscattering parameters.
基金supported by the National Natural Science Foundation of China(Grant No. 11174060)the PhD Programs Foundation of the Ministry of Education of China(Grant Nos. 20090071110066 and 20110071130004)the New Century Excellent Talents of the Ministry of Education of China(Grant No. NCET-10-0349)
文摘Ultrasonic guided waves (GWs) can be used to evaluate long bones effectively because of the ability to provide the information of the whole bone. In this study, a joint spectrogram segmentation and ridge-extraction (JSSRE) method was proposed to separate multiple modes in long bones. First, the Gabor time-frequency transform was applied to obtain the spectrogram of multimodal signals. Then, a multi-class image segmentation algorithm was used to find the corresponding region of each mode in the spectrogram, including an improved watershed transform and a region growing procedure. Finally, the ridges were extracted and the time domain signals representing individual modes were reconstructed from these ridges in each region. The validations of this method were discussed by simulated multimodal signals with different signal-to-noise ratios (SNR). The correlation coefficients between the original signals without noise and the reconstructed signals were calculated to analyze the results quantitatively. The results showed that the extracted ridges were in good agreement with generated theoretical dispersion curves, and the reconstructed signals were highly related to the original signals, even under the SNR=3 dB situation.
基金This work is part of the research program of the Foundation for Fundamental Research on Matter(FOM),which is financially supported by the Netherlands Organization for Fundamental Research(NWO)It is also part of an industrial partnership program between Philips and FOM.It is supported by NanoNextNL of the Government of the Netherlands and 130 partners.
文摘Light sources based on reliable and energy-efficient light-emitting diodes (LEDs) are instrumental in the development of solid-statelighting (SSL). Most research efforts in SSL have focused on improving both the intrinsic quantum efficiency (QE) and the stability oflight emitters. For this reason, it is broadly accepted that with the advent of highly efficient (QE close to 1) and stable emitters, thefundamental research phase of SSL is coming to an end. In this study, we demonstrate a very large improvement in SSL emission (above70-fold directional enhancement for p-polarized emission and 60-fold enhancement for unpolarized emission) using nanophotonicstructures. This is attained by coupling emitters with very high QE to collective plasmonic resonances in periodic arrays of aluminumnanoantennas. Our results open a new path for fundamental and applied research in SSL in which plasmonic nanostructures are able tomold the spectral and angular distribution of the emission with unprecedented precision.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA20060303)the Fund“Light of West China”Program of Chinese Academy of Sciences(2018-XBQNXZ-B-017)+1 种基金the High-level Talents Project in Xinjiang(Y942171)“One Hundred Person Project of Chinese Academy of Sciences”(Y931201)。
文摘Central Asia(CA)occupies the hinterland of the Eurasian continent,containing the countries of Uzbekistan,Kyrgyzstan,Turkmenistan,Tajikistan,and Kazakhstan[1,2].Being isolated by the Pamir Mountains in Tajikistan,the Tibetan Plateau and the Tian Shan Mountains on the border between China and Kyrgyzstan.
基金supported by the National Natural Science Foundation of China(52225606,52488201)the Fundamental Research Funds for the Central UniversitiesThe Youth Innovation Team of Shaanxi Universities。
文摘Highly selective production of value-added multicarbon(C^(2+))products via electrochemical CO_(2) reduction reaction(eCO_(2)RR)on polycrystalline copper(Cu)remains challenging.Herein,the facile surface modification using poly(α-ethyl cyanoacrylate)(PECA)is presented to greatly enhance the C^(2+)selectivity for eCO_(2)RR over polycrystalline Cu,with Faradaic efficiency(FE)towards C^(2+)products increased from30.1%for the Cu electrode to 72.6%for the obtained Cu-PECA electrode at-1.1 V vs.reversible hydrogen electrode(RHE).Given the well-determined FEs towards C^(2+)products,the partial current densities for C^(2+)production could be estimated to be-145.4 mA cm~(-2)for the Cu-PECA electrode at-0.9 V vs.RHE in a homemade flow cell.In-situ spectral characterizations and theoretical calculations reveal that PECA featured with electron-accepting-C≡N and-COOR groups decorated onto the Cu electrode could inhibit the adsorption of^(*)H intermediates and stabilize the^(*)CO intermediates,given the redistributed interfacial electron density and the raised energy level of d-band center(E_(d))of Cu active sites,thus facilitating the C-C coupling and then the C^(2+)selective production.This study is believed to be guidable to the modification of electrocatalysts and electrodes with polymers to steer the surface adsorption behaviors of reaction intermediates to realize practical eCO_(2)RR towards value-added C^(2+)products with high activity and selectivity.
文摘The electronic configuration of central metal atoms in single-atom catalysts(SACs)is pivotal in electrochemical CO_(2)reduction reaction(eCO_(2)RR).Herein,chalcogen heteroatoms(e.g.,S,Se,and Te)were incorporated into the symmetric nickel-nitrogen-carbon(Ni-N4-C)configuration to obtain Ni-X-N3-C(X:S,Se,and Te)SACs with asymmetric coordination presented for central Ni atoms.Among these obtained Ni-X-N3-C(X:S,Se,and Te)SACs,Ni-Se-N3-C exhibited superior eCO_(2)RR activity,with CO selectivity reaching~98%at-0.70 V versus reversible hydrogen electrode(RHE).The Zn-CO_(2)battery integrated with Ni-Se-N3-C as cathode and Zn foil as anode achieved a peak power density of 1.82 mW cm-2 and maintained remarkable rechargeable stability over 20 h.In-situ spectral investigations and theoretical calculations demonstrated that the chalcogen heteroatoms doped into the Ni-N4-C configuration would break coordination symmetry and trigger charge redistribution,and then regulate the intermediate behaviors and thermodynamic reaction pathways for eCO_(2)RR.Especially,for Ni-Se-N3-C,the introduced Se atoms could significantly raise the d-band center of central Ni atoms and thus remarkably lower the energy barrier for the rate-determining step of*COOH formation,contributing to the promising eCO_(2)RR performance for high selectivity CO production by competing with hydrogen evolution reaction.
