Broad area semiconductor laser(BAL)has poor lateral beam quality due to lateral mode competition,which limits its application as a high-power optical source.In this work,the distributed Bragg reflector laser diode wit...Broad area semiconductor laser(BAL)has poor lateral beam quality due to lateral mode competition,which limits its application as a high-power optical source.In this work,the distributed Bragg reflector laser diode with tapered grating(TDBR-LD)is studied.By changing the lateral width,the tapered grating increases the loss of high-order lateral modes,thus improving the lateral characteristics of the laser diode.The measuring results show that the TDBR-LD can achieve a single-lobe output under 0.9 A.In contrast to the straight distributed Bragg reflector laser diode(SDBR-LD),the lateral far field divergence of TDBR-LD is measured to be 5.23°at 1 A,representing a 17%decline.The linewidth of TDBR-LD is 0.4 nm at 0.2 A,which is reduced by nearly 43%in comparison with that of SDBR-LD.Meanwhile,both of the devices have a maximum output power value of approximate 470 mW.展开更多
The brood-parasitic brown-headed cowbird(Molothrus ater)has one of the shortest incubation periods of any bird.Brown-headed cowbird eggs,and those of other avian brood parasites,tend to be more spherical due to their ...The brood-parasitic brown-headed cowbird(Molothrus ater)has one of the shortest incubation periods of any bird.Brown-headed cowbird eggs,and those of other avian brood parasites,tend to be more spherical due to their greater relative width.The traditional explanation for this egg shape is that it,combined with the thicker eggshells,resists host puncture-ejection.However,very few North American hosts of the brownheaded cowbird actually engage in puncture-ejection and therefore wider eggs may instead provide greater contact with a host’s brood patch during incubation,especially in large host nests.We tested whether greater egg width increased mean temperature and reduced temperature variation in brown-headed cowbirds by inserting temperature probes into brown-headed cowbird and house sparrow(Passer domesticus)eggs and placing them into red-winged blackbird(Agelaius phoeniceus)nests.House sparrow eggs are similar in appearance and in length to cowbird eggs,but are not as wide.We found no signifcant relationship between brown-headed cowbird egg width and mean incubation temperature.However,brown-headed cowbird eggs experienced less temperature variation than house sparrow eggs,and within brown-headed cowbird eggs,more spherical eggs experienced less temperature variation when accounting for differences in width.These results suggest that brownheaded cowbirds may have short incubation periods in part because their eggs exhibit less temperature variation over the course of incubation.The brown-headed cowbird’s egg shape may contribute to its accelerated embryonic development rate relative to host eggs of similar size,which explains its ability to hatch in a variety of host nests.展开更多
The application of lead as tem porary w ater - sealing m aterial for the stan dpipes in under ground mine is reported . It is considered that lead is a good w ater - sealing m aterial in un derground mine , especia...The application of lead as tem porary w ater - sealing m aterial for the stan dpipes in under ground mine is reported . It is considered that lead is a good w ater - sealing m aterial in un derground mine , especially for irregular opening with high - pressure rushing w ater . Leadseal is cheap , easy to use and less har m ful to w orkers an d environ m ent and m ay have widerapplication .展开更多
Economic globalizationandknowled ge economy provide newopportunity f or development of Suzhou,a histori-cal city which has traditional intim ate relationship with Shanghai.Thi s paper aims at exploring the chances and...Economic globalizationandknowled ge economy provide newopportunity f or development of Suzhou,a histori-cal city which has traditional intim ate relationship with Shanghai.Thi s paper aims at exploring the chances and chal-lenges faced by Suzhou at the newcent ury and makes the quantitative analy sis of the urban function of the Suzhou Municipali-ty through the studies of the Greater Shanghai Metropolitan Area and the Shanghai-Suzhou relationship.It re aches the conclu-sion that in the new century Suzhou sh all make the integrated development with Shanghai to be built into the pro cessing and manufacturing base with the high and new technology as the mainstay.I n the meantime Suzhou shall also beco me one of the research bases for the advanced technology and the modern tourist city with beautiful eco-environm ent.展开更多
Avian brood parasitism is a model system for studies of coevolution and ecological interactions between parasites and their hosts. However, recent work may have led to misconceptions concerning the Brown-headed Cowbir...Avian brood parasitism is a model system for studies of coevolution and ecological interactions between parasites and their hosts. However, recent work may have led to misconceptions concerning the Brown-headed Cowbird (Molothrus ater), the most widely studied brood parasitic bird in the world, and its effects on host species. Potential misconceptions about this species that could affect management issues are as follows: cowbird populations are increasing; cowbirds are relatively new to North America; recently exposed hosts are defenseless against parasitism; cowbirds have caused widespread declines of songbirds; and cowbird control is always effective in increasing the size of endangered host populations. Potential coevolutionary misconceptions are that cowbirds are typically 'host tolerant'; cowbirds evict host nestmates; and the mafia effect is widespread. It is important to clarify these issues because such misconceptions could hinder our understanding of parasite-host interactions, and thus obscure the direction of basic research and of management efforts taken to limit cowbird impacts on endangered species. We discuss these issues and suggest future research directions to enhance our understanding of this fascinating species.展开更多
With the knowledge that cuckoos and cowbirds lay their eggs parasitically,and that some hosts eject parasitic eggs,ornithologists began to ponder the question of how host females discriminate between a foreign egg and...With the knowledge that cuckoos and cowbirds lay their eggs parasitically,and that some hosts eject parasitic eggs,ornithologists began to ponder the question of how host females discriminate between a foreign egg and their own eggs,wondering how hosts 'know' which egg to remove.Results of one of the rst uncontrolled experiments were inappropriately interpreted to imply ejection was based on discordancy,with hosts simply ejecting the egg in the minority,or the 'odd-looking' egg.Controlled experiments eventually revealed that hosts rst learn the appearance of own their eggs and discriminate between them and any odd egg in their nest,regardless of which egg type is in the minority.Recent work has shown that discordancy may play a role in discrimination by males mated successively with females that lay polymorphic eggs.We examine the details of the early experiments,in light of recent advances in studies of egg recognition.An ability to recognize eggs also has been extended,implicitly,to include obligate brood parasites,as it underlies several hypotheses in explanation of the behavior of parasites toward their hosts.Egg recognition in parasites,however,has not been experimentally con rmed,nor has a mechanism been identi ed by which parasites could discriminate between their own eggs and the other eggs in a nest.We review hypotheses(parasite competition,egg removal and multiple parasitism,ma a,farming) that require the ability of obligate brood parasites to discriminate eggs at di erent levels and the potential mechanisms used by parasites to recognize their own eggs and suggest experiments to test for egg discrimination.An assessment of the egg recognition ability of parasites is germane to our understanding of how parasites counteract defenses of hosts.展开更多
Mercury(Hg)is extremely toxic,and continues to cause major threats to aquatic life,human health and the environment.Hg^2+mainly derives from seawater as a product of atmospheric deposition,therefore there is great dem...Mercury(Hg)is extremely toxic,and continues to cause major threats to aquatic life,human health and the environment.Hg^2+mainly derives from seawater as a product of atmospheric deposition,therefore there is great demand for sensing approaches that can detect Hg^2+in seawater samples.Herein,we demonstrate that the peroxidase-mimicking activity of gold nanoparticles(AuNPs)or so-called nanozymes,can be exploited for the detection of Hg^2+ions in various water samples.In a high electrolyte environment,the catalytic activity for the oxidation of 3,3’,5,5’-tetramethylbenzidine(TMB)was significantly diminished due to poor stability of the bare-AuNPs.This activity was reduced by-73.7%when the NaCl concentration was higher than 1.168%,which is much lower than that of seawater(-3.5%),thus presenting its unsuitability for detecting Hg^2+in harsh water matrices.To overcome this limitation,AuNPs were first functionalized with oligo-ethylene glycol(OEG),of which their colloidal form presented high stability in NaCl concentrations up to 20%and across a wide range of pHs from 1-14.Interestingly,the catalytic activity of OEG-AuNPs for the oxidation of TMB was strongly suppressed by the coating,but enhanced upon formation of Au-Hg amalgamation.This novel finding underlies a straightforward,sensitive,and highly selective detection platform for Hg^2+in water samples.The approach could detect the exposure limit level for Hg^2+in drinking water(i.e.,2 ppb for tap and bottled water)as set by the United States Environmental Protection Agency(EPA)and the World Health Organization(WHO).When Hg^2+was spiked into a 3.5%saline solution and a coastal seawater certified reference material(CRM),the detection limits were found to be 10 ancM 3 ppb,respectively,which exceed the Hg^2+concentrations commonly found within seawater(-60-80 ppb).The whole procedure takes less than 45 min to conduct,providing a highly innovative,rapid and low-cost approach for detecting Hg^2+in complex water matrices.展开更多
Development of efficient non-precious catalysts for seawater electrolysis is of great significance but challenging due to the sluggish kinetics of oxygen evolution reaction(OER)and the impairment of chlorine electroch...Development of efficient non-precious catalysts for seawater electrolysis is of great significance but challenging due to the sluggish kinetics of oxygen evolution reaction(OER)and the impairment of chlorine electrochemistry at anode.Herein,we report a heterostructure of Ni_(3)S_(2)nanoarray with secondary Fe-Ni(OH)_(2)lamellar edges that exposes abundant active sites towards seawater oxidation.The resultant Fe-Ni(OH)_(2)/Ni_(3)S_(2)nanoarray works directly as a free-standing anodic electrode in alkaline artificial seawater.It only requires an overpotential of 269 mV to afford a current density of 10 mA·cm^(-2)and the Tafel slope is as low as 46 m V·dec^(-1).The 27-hour chronopotentiometry operated at high current density of 100 mA·cm^(-2)shows negligible deterioration,suggesting good stability of the Fe-Ni(OH)_(2)/Ni_(3)S_(2)@NF electrode.Faraday efficiency for oxygen evolution is up to〜95%,revealing decent selectivity of the catalyst in saline water.Such desirable catalytic performance could be benefitted from the introduction of Fe activator and the heterostructure that offers massive active and selective sites.The density functional theory(DFT)calculations indicate that the OER has lower theoretical overpotential than Cl_(2) evolution reaction in Fe sites,which is contrary to that of Ni sites.The experimental and theoretical study provides a strong support for the rational design of high-performance Fe-based electrodes for industrial seawater electrolysis.展开更多
基金Project supported by theScienceand Technology Development Plan of Jilin Province,China(Grant Nos.20210201030GX and 20210201089GX).
文摘Broad area semiconductor laser(BAL)has poor lateral beam quality due to lateral mode competition,which limits its application as a high-power optical source.In this work,the distributed Bragg reflector laser diode with tapered grating(TDBR-LD)is studied.By changing the lateral width,the tapered grating increases the loss of high-order lateral modes,thus improving the lateral characteristics of the laser diode.The measuring results show that the TDBR-LD can achieve a single-lobe output under 0.9 A.In contrast to the straight distributed Bragg reflector laser diode(SDBR-LD),the lateral far field divergence of TDBR-LD is measured to be 5.23°at 1 A,representing a 17%decline.The linewidth of TDBR-LD is 0.4 nm at 0.2 A,which is reduced by nearly 43%in comparison with that of SDBR-LD.Meanwhile,both of the devices have a maximum output power value of approximate 470 mW.
文摘The brood-parasitic brown-headed cowbird(Molothrus ater)has one of the shortest incubation periods of any bird.Brown-headed cowbird eggs,and those of other avian brood parasites,tend to be more spherical due to their greater relative width.The traditional explanation for this egg shape is that it,combined with the thicker eggshells,resists host puncture-ejection.However,very few North American hosts of the brownheaded cowbird actually engage in puncture-ejection and therefore wider eggs may instead provide greater contact with a host’s brood patch during incubation,especially in large host nests.We tested whether greater egg width increased mean temperature and reduced temperature variation in brown-headed cowbirds by inserting temperature probes into brown-headed cowbird and house sparrow(Passer domesticus)eggs and placing them into red-winged blackbird(Agelaius phoeniceus)nests.House sparrow eggs are similar in appearance and in length to cowbird eggs,but are not as wide.We found no signifcant relationship between brown-headed cowbird egg width and mean incubation temperature.However,brown-headed cowbird eggs experienced less temperature variation than house sparrow eggs,and within brown-headed cowbird eggs,more spherical eggs experienced less temperature variation when accounting for differences in width.These results suggest that brownheaded cowbirds may have short incubation periods in part because their eggs exhibit less temperature variation over the course of incubation.The brown-headed cowbird’s egg shape may contribute to its accelerated embryonic development rate relative to host eggs of similar size,which explains its ability to hatch in a variety of host nests.
文摘The application of lead as tem porary w ater - sealing m aterial for the stan dpipes in under ground mine is reported . It is considered that lead is a good w ater - sealing m aterial in un derground mine , especially for irregular opening with high - pressure rushing w ater . Leadseal is cheap , easy to use and less har m ful to w orkers an d environ m ent and m ay have widerapplication .
文摘Economic globalizationandknowled ge economy provide newopportunity f or development of Suzhou,a histori-cal city which has traditional intim ate relationship with Shanghai.Thi s paper aims at exploring the chances and chal-lenges faced by Suzhou at the newcent ury and makes the quantitative analy sis of the urban function of the Suzhou Municipali-ty through the studies of the Greater Shanghai Metropolitan Area and the Shanghai-Suzhou relationship.It re aches the conclu-sion that in the new century Suzhou sh all make the integrated development with Shanghai to be built into the pro cessing and manufacturing base with the high and new technology as the mainstay.I n the meantime Suzhou shall also beco me one of the research bases for the advanced technology and the modern tourist city with beautiful eco-environm ent.
文摘Avian brood parasitism is a model system for studies of coevolution and ecological interactions between parasites and their hosts. However, recent work may have led to misconceptions concerning the Brown-headed Cowbird (Molothrus ater), the most widely studied brood parasitic bird in the world, and its effects on host species. Potential misconceptions about this species that could affect management issues are as follows: cowbird populations are increasing; cowbirds are relatively new to North America; recently exposed hosts are defenseless against parasitism; cowbirds have caused widespread declines of songbirds; and cowbird control is always effective in increasing the size of endangered host populations. Potential coevolutionary misconceptions are that cowbirds are typically 'host tolerant'; cowbirds evict host nestmates; and the mafia effect is widespread. It is important to clarify these issues because such misconceptions could hinder our understanding of parasite-host interactions, and thus obscure the direction of basic research and of management efforts taken to limit cowbird impacts on endangered species. We discuss these issues and suggest future research directions to enhance our understanding of this fascinating species.
基金funded chiefly by grants from the Natural Sciences and Engineering Research Council of Canada
文摘With the knowledge that cuckoos and cowbirds lay their eggs parasitically,and that some hosts eject parasitic eggs,ornithologists began to ponder the question of how host females discriminate between a foreign egg and their own eggs,wondering how hosts 'know' which egg to remove.Results of one of the rst uncontrolled experiments were inappropriately interpreted to imply ejection was based on discordancy,with hosts simply ejecting the egg in the minority,or the 'odd-looking' egg.Controlled experiments eventually revealed that hosts rst learn the appearance of own their eggs and discriminate between them and any odd egg in their nest,regardless of which egg type is in the minority.Recent work has shown that discordancy may play a role in discrimination by males mated successively with females that lay polymorphic eggs.We examine the details of the early experiments,in light of recent advances in studies of egg recognition.An ability to recognize eggs also has been extended,implicitly,to include obligate brood parasites,as it underlies several hypotheses in explanation of the behavior of parasites toward their hosts.Egg recognition in parasites,however,has not been experimentally con rmed,nor has a mechanism been identi ed by which parasites could discriminate between their own eggs and the other eggs in a nest.We review hypotheses(parasite competition,egg removal and multiple parasitism,ma a,farming) that require the ability of obligate brood parasites to discriminate eggs at di erent levels and the potential mechanisms used by parasites to recognize their own eggs and suggest experiments to test for egg discrimination.An assessment of the egg recognition ability of parasites is germane to our understanding of how parasites counteract defenses of hosts.
基金The author N.L.and C.M.thank the PhD studentship support from the D epartm ent of Employment and Learning for Northern Ireland(DEL)C.C.thanks the strong support from the Central Research Support Funds of Queens University Belfast via a start-up grant.
文摘Mercury(Hg)is extremely toxic,and continues to cause major threats to aquatic life,human health and the environment.Hg^2+mainly derives from seawater as a product of atmospheric deposition,therefore there is great demand for sensing approaches that can detect Hg^2+in seawater samples.Herein,we demonstrate that the peroxidase-mimicking activity of gold nanoparticles(AuNPs)or so-called nanozymes,can be exploited for the detection of Hg^2+ions in various water samples.In a high electrolyte environment,the catalytic activity for the oxidation of 3,3’,5,5’-tetramethylbenzidine(TMB)was significantly diminished due to poor stability of the bare-AuNPs.This activity was reduced by-73.7%when the NaCl concentration was higher than 1.168%,which is much lower than that of seawater(-3.5%),thus presenting its unsuitability for detecting Hg^2+in harsh water matrices.To overcome this limitation,AuNPs were first functionalized with oligo-ethylene glycol(OEG),of which their colloidal form presented high stability in NaCl concentrations up to 20%and across a wide range of pHs from 1-14.Interestingly,the catalytic activity of OEG-AuNPs for the oxidation of TMB was strongly suppressed by the coating,but enhanced upon formation of Au-Hg amalgamation.This novel finding underlies a straightforward,sensitive,and highly selective detection platform for Hg^2+in water samples.The approach could detect the exposure limit level for Hg^2+in drinking water(i.e.,2 ppb for tap and bottled water)as set by the United States Environmental Protection Agency(EPA)and the World Health Organization(WHO).When Hg^2+was spiked into a 3.5%saline solution and a coastal seawater certified reference material(CRM),the detection limits were found to be 10 ancM 3 ppb,respectively,which exceed the Hg^2+concentrations commonly found within seawater(-60-80 ppb).The whole procedure takes less than 45 min to conduct,providing a highly innovative,rapid and low-cost approach for detecting Hg^2+in complex water matrices.
基金the National Natural Science Foundation of China(No.91963113).
文摘Development of efficient non-precious catalysts for seawater electrolysis is of great significance but challenging due to the sluggish kinetics of oxygen evolution reaction(OER)and the impairment of chlorine electrochemistry at anode.Herein,we report a heterostructure of Ni_(3)S_(2)nanoarray with secondary Fe-Ni(OH)_(2)lamellar edges that exposes abundant active sites towards seawater oxidation.The resultant Fe-Ni(OH)_(2)/Ni_(3)S_(2)nanoarray works directly as a free-standing anodic electrode in alkaline artificial seawater.It only requires an overpotential of 269 mV to afford a current density of 10 mA·cm^(-2)and the Tafel slope is as low as 46 m V·dec^(-1).The 27-hour chronopotentiometry operated at high current density of 100 mA·cm^(-2)shows negligible deterioration,suggesting good stability of the Fe-Ni(OH)_(2)/Ni_(3)S_(2)@NF electrode.Faraday efficiency for oxygen evolution is up to〜95%,revealing decent selectivity of the catalyst in saline water.Such desirable catalytic performance could be benefitted from the introduction of Fe activator and the heterostructure that offers massive active and selective sites.The density functional theory(DFT)calculations indicate that the OER has lower theoretical overpotential than Cl_(2) evolution reaction in Fe sites,which is contrary to that of Ni sites.The experimental and theoretical study provides a strong support for the rational design of high-performance Fe-based electrodes for industrial seawater electrolysis.
