The mode of abscisic acid （ABA） action, and its relations to drought adaptive responses in particular, has been a captivating area of plant hormone research for much over a decade. The hormone triggers stomatal clos...The mode of abscisic acid （ABA） action, and its relations to drought adaptive responses in particular, has been a captivating area of plant hormone research for much over a decade. The hormone triggers stomatal closure to limit water loss through transpiration, as well as mobilizes a battery of genes that presumably serve to protect the cells from the ensuing oxidative damage in prolonged stress. The signaling network orchestrating these various responses is, however, highly complex. This review summarizes several significant advances made within the last few years. The biosynthetic pathway of the hormone is now almost completely elucidated, with the latest identification of the ABA4 gene encoding a neoxanthin synthase, which seems essential for de novo ABA biosynthesis during water stress. This leads to the interesting question on how ABA is then delivered to perception sites. In this respect, regulated transport has attracted renewed focus by the unexpected finding of a shoot-to-root translocation of ABA during drought response, and at the cellular level, by the identification of a B-galactosidase that releases biologically active ABA from inactive ABA-glucose ester. Surprising candidate ABA receptors were also identified in the form of the Flowering Time Control Protein A （FCA） and the Chloroplastic Magnesium Protoporphyrin-IX Chelatase H subunit （CHLH） in chloroplast-nucleus communication, both of which have been shown to bind ABA in vitro. On the other hand, the protein（s） corresponding to the physiologically detectable cell-surface ABA receptor（s） is （are） still not known with certainty. Genetic and physiological studies based on the guard cell have reinforced the central importance of reversible phosphorylation in modulating rapid ABA responses. Sucrose Non-Fermenting Related Kinases （SnRK）, Calcium-Dependent Protein Kinases （CDPK）, Protein Phosphatases （PP） of the 2C and 2A classes figure as prominent regulators in this single-cell model. Identifying their direct in viv展开更多
AIM:To evaluate the outcome of over-the-scope-clip system(OTSC)for endoscopic treatment of various indications in daily clinical practice in Switzerland.METHODS:This prospective,consecutive case series was conducted a...AIM:To evaluate the outcome of over-the-scope-clip system(OTSC)for endoscopic treatment of various indications in daily clinical practice in Switzerland.METHODS:This prospective,consecutive case series was conducted at a tertiary care hospital from September 2010 to January 2014.Indications for OTSC application were fistulae,anastomotic leakage,perforation,unroofed submucosal lesion for biopsy,refractory bleeding,and stent fixation in the gastrointestinal(GI)tract.Primary technical success was defined as the adequate deployment of the OTSC on the target lesion.Clinical success was defined as resolution of the problem;for instance,no requirement for surgery or further endoscopic intervention.In cases of recurrence,retreatment of a lesion with a second intervention was possible.Complications were classified into those related to sedation,endoscopy,or deployment of the clip.RESULTS:A total of 28 OTSC system applications werecarried out in 21 patients[median age 64 years(range42-85),33%females].The main indications were fistulae(52%),mostly after percutaneous endoscopic gastrostomy tube removal,and anastomotic leakage after GI surgery(29%).Further indications were unroofed submucosal lesions after biopsy,upper gastrointestinal bleeding,or esophageal stent fixation.The OTSC treatments were applied either in the upper(48%)or lower(52%)GI tract.The mean lesion size was 8 mm(range:2-20 mm).Primary technical success and clinical success rates were 85%and 67%,respectively.In53%of cases,the suction method was used without accessories(e.g.,twin grasper or tissue anchor).No endoscopy-related or OTSC-related complications were observed.CONCLUSION:OTSC is a useful tool for endoscopic closure of various GI lesions,including fistulae and leakages.Future randomized prospective multicenter trials are warranted.展开更多
AIM: To evaluate the incidence of late biliary complications in non-resectable alveolar echinococcosis (AE) under long-term chemotherapy with benzimidazoles.
Strigolactones （SLs） are known not only as plant hormones, but also as rhizosphere signals for establishing symbiotic and parasitic interactions. The design of new specific SL analogs is a challenging goal in unders...Strigolactones （SLs） are known not only as plant hormones, but also as rhizosphere signals for establishing symbiotic and parasitic interactions. The design of new specific SL analogs is a challenging goal in understanding the basic plant biology and is also useful to control plant architectures without favoring the development of parasitic plants. Two different molecules （23 （3＇-methyI-GR24）, 31 （thia-3＇-methyl-debranone-like molecule）） already described, and a new one （AR36）, for which the synthesis is presented, are biologically compared with the well-known GR24 and the recently identified CISA-1. These different structures emphasize the wide range of parts attached to the D-ring for the bioactivity as a plant hormone. These new compounds possess a common dimethylbutenolide motif but their structure varies in the ABC part of the molecules： 23 has the same ABC part as GR24, while 31 and AR36 carry, respectively, an aromatic ring and an acyclic carbon chain. Detailed information is given for the bioactivity of such derivatives in strigolactone synthesis or in perception mutant plants （pea rmsl and rms4, Arabidopsis max2 and, max4） for different hormonal functions along with their action in the rhizosphere on arbuscular mycorrhizal hyphal growth and parasitic weed germination.展开更多
(Molecular Plant 14,1864-1880;November 12021)We identified a mistake made when calculating the absolute concentrations of inositol(pyro)phosphates derived from CE-ESl-MS measurements reported in the originally publish...(Molecular Plant 14,1864-1880;November 12021)We identified a mistake made when calculating the absolute concentrations of inositol(pyro)phosphates derived from CE-ESl-MS measurements reported in the originally published version of our manuscript.Due to a calculation error when determining concentrations per fresh biomass,the absolute values shown in the manuscript are approximately 30-fold lower than they should be.This mistake affects Figures 2D,3C,4C,and 7D and Figures S4,S11B,S13,and S15A.Since all conclusions made in the article referred to relative differences between genotypes and treatments,they remained unaffected by these mistakes.展开更多
The use of thiopurines as immunosuppression for the treatment of refractory or chronic active inflammatory bowel disease is established for both Crohn's disease and ulcerative colitis.Nevertheless,many questions r...The use of thiopurines as immunosuppression for the treatment of refractory or chronic active inflammatory bowel disease is established for both Crohn's disease and ulcerative colitis.Nevertheless,many questions remain concerning the optimal treatment regimens of azathioprine,6-mercaptopurine and thioguanine.We will briefly summarize dose recommendations,indications for thiopurine therapy and side effects which are relevant in clinical practice.We discuss some currently debated topics,including the combination of azathioprine and allopurinol,switching of thiopurine therapy in case of side effects,the use of azathioprine in pregnancy,the infection risk using thiopurines and the evidence when to stop thiopurines.Excellent reviews have been published on the thiopurine metabolic pathway which will not be discussed here in detail.展开更多
Dear Editor,Sugarcane mosaic virus （SCMV） causes severe viral diseases in maize worldwide （Fuchs and Gruntzig, 1995）, resulting in significant losses in grain and forage yield in susceptible cultivars of maize and...Dear Editor,Sugarcane mosaic virus （SCMV） causes severe viral diseases in maize worldwide （Fuchs and Gruntzig, 1995）, resulting in significant losses in grain and forage yield in susceptible cultivars of maize and related crops. The most promising solution is to cultivate resistant varieties, which contribute to sustainable crop production. Two epistatically interacting major SCMV resistance loci （Scmvl and Scmv2） are required to confer complete resistance against SCMV in the resistant nearisogenic line F7RPJRR （the letters left of the slash refer to the genotype at Scmv2 on chromosome 3 and those on the right refer to the genotype at Scmvl on chromosome 6, with R indicating a resistance allele and S a susceptibility allele） （Xing et al., 2006）.展开更多
Rice plays a paramount role in food and nutrition security in many West African countries.Despite the doubling of production during the last decade,rice consumption has grown faster,creating a deficit between the dema...Rice plays a paramount role in food and nutrition security in many West African countries.Despite the doubling of production during the last decade,rice consumption has grown faster,creating a deficit between the demand and supply.Although the West African sub-region remains the main rice-producing centre on the continent,production is severely hampered by biotic and abiotic stresses.Drought is one of the factors that most severely reduce grain yields of rice.Systems of production need to be established in order to mitigate yield loss as a result of drought.This review discusses the effects of drought on rice production in West Africa and its mitigation with an emphasis on the improvement of tolerance to drought stress.Yield stability can be achieved by developing drought-tolerant varieties through several processes encompassing profiling of known QTLs and identification of new ones,marker-assisted selection,genomic selection,and extensive multi-locational yield trials.We suggest a comprehensive strategy for breeding drought-tolerant rice varieties in West Africa.展开更多
BACKGROUND Perianal fistulae strongly impact on quality of life of affected patients.AIM To challenge and novel minimally invasive treatment options are needed.METHODS Patients with Crohn’s disease(CD)in remission an...BACKGROUND Perianal fistulae strongly impact on quality of life of affected patients.AIM To challenge and novel minimally invasive treatment options are needed.METHODS Patients with Crohn’s disease(CD)in remission and patients without inflammatory bowel disease(non-IBD patients)were treated with fistulodesis,a method including curettage of fistula tract,flushing with acetylcysteine and doxycycline,Z-suture of the inner fistula opening,fibrin glue instillation,and Zsuture of the outer fistula opening followed by post-operative antibiotic prophylaxis with ciprofloxacin and metronidazole for two weeks.Patients with a maximum of 2 fistula openings and no clinical or endosonographic signs of a complicated fistula were included.The primary end point was fistula healing,defined as macroscopic and clinical fistula closure and lack of patient reported fistula symptoms at 24 wk.RESULTS Fistulodesis was performed in 17 non-IBD and 3 CD patients,with a total of 22 fistulae.After 24 wk,all fistulae were healed in 4 non-IBD and 2 CD patients(overall 30%)and fistula remained closed until the end of follow-up at 10-25 mo.In a secondary per-fistula analysis,7 out of 22 fistulae(32%)were closed.Perianal disease activity index(PDAI)improved in patients with fistula healing.Low PDAI was associated with favorable outcome(P=0.0013).No serious adverse events were observed.CONCLUSION Fistulodesis is feasible and safe for perianal fistula closure.Overall success rates is at 30%comparable to other similar techniques.A trend for better outcomes in patients with low PDAI needs to be confirmed.展开更多
Root system architecture(RSA)contributes to nitrogen(N)uptake and utilization in maize.In this study,a germplasm enhancement of maize double haploid population of 226 lines genotyped with 61,634 SNPs was used to inves...Root system architecture(RSA)contributes to nitrogen(N)uptake and utilization in maize.In this study,a germplasm enhancement of maize double haploid population of 226 lines genotyped with 61,634 SNPs was used to investigate the genetic basis of RSA under two N levels using a genome-wide association study(GWAS).GLM+PCA,FarmCPU,and MLM models were utilized to balance false positives and false negatives.In total,33 and 51 significant SNP-trait associations were detected under high and low N conditions,respectively.Under high N,SNP S9_2483543 was detected by all models.Linkage disequilibrium(LD)regions of some SNPs overlapped with the intervals of QTL for RSA and N response that were detected in previous studies.In particular,several known genes,Rtcs,Rtcl,Rtcl,and Ms44,were located in the LD regions of S1_9992325,S9_151726472,S9_154381179,and S4_197073985,respectively.Among the candidate genes identified by this study,GRMZM2G139811,GRMZM2G314898,GRMZM2G054050,GRMZM2G173682,GRMZM2G470914,GRMZM2G462325,GRMZM2G416184,and GRMZM2G064302 were involved in seedling,seed,and root system development or N metabolism in Arabidopsis or rice.The markers identified in this study can be used for marker-assisted selection of RSA traits to improve nitrogen use efficiency in maize breeding,and the candidate genes will contribute to further understanding of the genetic basis of RSA under diverse N conditions.展开更多
High-frequency switching of power transistors in power electronic systems can cause electromagnetic emissions.Simple approaches for reducing high-frequency disturbances,such as inserting an additional gate resistor,le...High-frequency switching of power transistors in power electronic systems can cause electromagnetic emissions.Simple approaches for reducing high-frequency disturbances,such as inserting an additional gate resistor,lead to increased power losses.This makes achieving both electromagnetic compatibility and power efficiency difficult.Active gate drivers help to find a trade-off between these two.Typically,only narrow-band disturbances must be reduced.Accordingly,a target signal with a spectrum notched at some frequencies can be defined.The target signal can be reached by a target-signal-oriented control of the transistor’s gate.This leads to steeper switching slopes,such that the power losses are less increased.Generating arbitrary target signals is impossible.The transistor signal exhibits some physical limitations.A constraint satisfaction problem must be solved,and the gate drive signal must be optimized by applying a residual and Newton’s method.The proposed optimization process in the frequency domain is based on the circuit simulation method named“harmonic balance”.Measurements on a DC/DC converter exhibit the benefits of this method.展开更多
Water oxidation, as a mandatory reaction of solar fuels conversion systems, requires the use of light absorbers with electronic properties that are well matched with those of the multi-electron catalyst in order to ac...Water oxidation, as a mandatory reaction of solar fuels conversion systems, requires the use of light absorbers with electronic properties that are well matched with those of the multi-electron catalyst in order to achieve high efficiency. Molecular light absorbers offer flexibility in fine tuning of orbital energetics,and metal oxide nanoparticles have emerged as robust oxygen evolving catalysts. Hence, these material choices offer a promising approach for the development of photocatalytic systems for water oxidation.However, efficient charge transfer coupling of molecular light absorbers and metal oxide nanoparticle catalysts has proven a challenge. Recent new approaches toward the efficient coupling of these components based on synthetic design improvements combined with direct spectroscopic observation and kinetic evaluation of charge transfer processes are discussed.展开更多
文摘The mode of abscisic acid （ABA） action, and its relations to drought adaptive responses in particular, has been a captivating area of plant hormone research for much over a decade. The hormone triggers stomatal closure to limit water loss through transpiration, as well as mobilizes a battery of genes that presumably serve to protect the cells from the ensuing oxidative damage in prolonged stress. The signaling network orchestrating these various responses is, however, highly complex. This review summarizes several significant advances made within the last few years. The biosynthetic pathway of the hormone is now almost completely elucidated, with the latest identification of the ABA4 gene encoding a neoxanthin synthase, which seems essential for de novo ABA biosynthesis during water stress. This leads to the interesting question on how ABA is then delivered to perception sites. In this respect, regulated transport has attracted renewed focus by the unexpected finding of a shoot-to-root translocation of ABA during drought response, and at the cellular level, by the identification of a B-galactosidase that releases biologically active ABA from inactive ABA-glucose ester. Surprising candidate ABA receptors were also identified in the form of the Flowering Time Control Protein A （FCA） and the Chloroplastic Magnesium Protoporphyrin-IX Chelatase H subunit （CHLH） in chloroplast-nucleus communication, both of which have been shown to bind ABA in vitro. On the other hand, the protein（s） corresponding to the physiologically detectable cell-surface ABA receptor（s） is （are） still not known with certainty. Genetic and physiological studies based on the guard cell have reinforced the central importance of reversible phosphorylation in modulating rapid ABA responses. Sucrose Non-Fermenting Related Kinases （SnRK）, Calcium-Dependent Protein Kinases （CDPK）, Protein Phosphatases （PP） of the 2C and 2A classes figure as prominent regulators in this single-cell model. Identifying their direct in viv
文摘AIM:To evaluate the outcome of over-the-scope-clip system(OTSC)for endoscopic treatment of various indications in daily clinical practice in Switzerland.METHODS:This prospective,consecutive case series was conducted at a tertiary care hospital from September 2010 to January 2014.Indications for OTSC application were fistulae,anastomotic leakage,perforation,unroofed submucosal lesion for biopsy,refractory bleeding,and stent fixation in the gastrointestinal(GI)tract.Primary technical success was defined as the adequate deployment of the OTSC on the target lesion.Clinical success was defined as resolution of the problem;for instance,no requirement for surgery or further endoscopic intervention.In cases of recurrence,retreatment of a lesion with a second intervention was possible.Complications were classified into those related to sedation,endoscopy,or deployment of the clip.RESULTS:A total of 28 OTSC system applications werecarried out in 21 patients[median age 64 years(range42-85),33%females].The main indications were fistulae(52%),mostly after percutaneous endoscopic gastrostomy tube removal,and anastomotic leakage after GI surgery(29%).Further indications were unroofed submucosal lesions after biopsy,upper gastrointestinal bleeding,or esophageal stent fixation.The OTSC treatments were applied either in the upper(48%)or lower(52%)GI tract.The mean lesion size was 8 mm(range:2-20 mm).Primary technical success and clinical success rates were 85%and 67%,respectively.In53%of cases,the suction method was used without accessories(e.g.,twin grasper or tissue anchor).No endoscopy-related or OTSC-related complications were observed.CONCLUSION:OTSC is a useful tool for endoscopic closure of various GI lesions,including fistulae and leakages.Future randomized prospective multicenter trials are warranted.
基金Supported by The Foundation for Medical Research and Development(Winterthur,Switzerland),the Gebert-Ruef Foundation(Zurich,Switzerland)the Baugarten-Foundation(Zurich,Switzerland)+3 种基金the OPO-Foundation(Zurich,Switzerland)the Caritative Foundation Gerberten Bosch(Zurich Switzerland)the UBS(Zurich,Switzerland)acting on behalf of a major anonymous sponsorandSwiss National Science Foundation Grants NO.320000-114009/3 and NO.32473B_135694/1(Vavricka SR)
文摘AIM: To evaluate the incidence of late biliary complications in non-resectable alveolar echinococcosis (AE) under long-term chemotherapy with benzimidazoles.
文摘Strigolactones （SLs） are known not only as plant hormones, but also as rhizosphere signals for establishing symbiotic and parasitic interactions. The design of new specific SL analogs is a challenging goal in understanding the basic plant biology and is also useful to control plant architectures without favoring the development of parasitic plants. Two different molecules （23 （3＇-methyI-GR24）, 31 （thia-3＇-methyl-debranone-like molecule）） already described, and a new one （AR36）, for which the synthesis is presented, are biologically compared with the well-known GR24 and the recently identified CISA-1. These different structures emphasize the wide range of parts attached to the D-ring for the bioactivity as a plant hormone. These new compounds possess a common dimethylbutenolide motif but their structure varies in the ABC part of the molecules： 23 has the same ABC part as GR24, while 31 and AR36 carry, respectively, an aromatic ring and an acyclic carbon chain. Detailed information is given for the bioactivity of such derivatives in strigolactone synthesis or in perception mutant plants （pea rmsl and rms4, Arabidopsis max2 and, max4） for different hormonal functions along with their action in the rhizosphere on arbuscular mycorrhizal hyphal growth and parasitic weed germination.
文摘(Molecular Plant 14,1864-1880;November 12021)We identified a mistake made when calculating the absolute concentrations of inositol(pyro)phosphates derived from CE-ESl-MS measurements reported in the originally published version of our manuscript.Due to a calculation error when determining concentrations per fresh biomass,the absolute values shown in the manuscript are approximately 30-fold lower than they should be.This mistake affects Figures 2D,3C,4C,and 7D and Figures S4,S11B,S13,and S15A.Since all conclusions made in the article referred to relative differences between genotypes and treatments,they remained unaffected by these mistakes.
文摘The use of thiopurines as immunosuppression for the treatment of refractory or chronic active inflammatory bowel disease is established for both Crohn's disease and ulcerative colitis.Nevertheless,many questions remain concerning the optimal treatment regimens of azathioprine,6-mercaptopurine and thioguanine.We will briefly summarize dose recommendations,indications for thiopurine therapy and side effects which are relevant in clinical practice.We discuss some currently debated topics,including the combination of azathioprine and allopurinol,switching of thiopurine therapy in case of side effects,the use of azathioprine in pregnancy,the infection risk using thiopurines and the evidence when to stop thiopurines.Excellent reviews have been published on the thiopurine metabolic pathway which will not be discussed here in detail.
文摘Dear Editor,Sugarcane mosaic virus （SCMV） causes severe viral diseases in maize worldwide （Fuchs and Gruntzig, 1995）, resulting in significant losses in grain and forage yield in susceptible cultivars of maize and related crops. The most promising solution is to cultivate resistant varieties, which contribute to sustainable crop production. Two epistatically interacting major SCMV resistance loci （Scmvl and Scmv2） are required to confer complete resistance against SCMV in the resistant nearisogenic line F7RPJRR （the letters left of the slash refer to the genotype at Scmv2 on chromosome 3 and those on the right refer to the genotype at Scmvl on chromosome 6, with R indicating a resistance allele and S a susceptibility allele） （Xing et al., 2006）.
基金supported by the Federal Ministry of Education and Research of Germany through the West African Science Service Center on Climate Change and Adapted Land Use
文摘Rice plays a paramount role in food and nutrition security in many West African countries.Despite the doubling of production during the last decade,rice consumption has grown faster,creating a deficit between the demand and supply.Although the West African sub-region remains the main rice-producing centre on the continent,production is severely hampered by biotic and abiotic stresses.Drought is one of the factors that most severely reduce grain yields of rice.Systems of production need to be established in order to mitigate yield loss as a result of drought.This review discusses the effects of drought on rice production in West Africa and its mitigation with an emphasis on the improvement of tolerance to drought stress.Yield stability can be achieved by developing drought-tolerant varieties through several processes encompassing profiling of known QTLs and identification of new ones,marker-assisted selection,genomic selection,and extensive multi-locational yield trials.We suggest a comprehensive strategy for breeding drought-tolerant rice varieties in West Africa.
文摘BACKGROUND Perianal fistulae strongly impact on quality of life of affected patients.AIM To challenge and novel minimally invasive treatment options are needed.METHODS Patients with Crohn’s disease(CD)in remission and patients without inflammatory bowel disease(non-IBD patients)were treated with fistulodesis,a method including curettage of fistula tract,flushing with acetylcysteine and doxycycline,Z-suture of the inner fistula opening,fibrin glue instillation,and Zsuture of the outer fistula opening followed by post-operative antibiotic prophylaxis with ciprofloxacin and metronidazole for two weeks.Patients with a maximum of 2 fistula openings and no clinical or endosonographic signs of a complicated fistula were included.The primary end point was fistula healing,defined as macroscopic and clinical fistula closure and lack of patient reported fistula symptoms at 24 wk.RESULTS Fistulodesis was performed in 17 non-IBD and 3 CD patients,with a total of 22 fistulae.After 24 wk,all fistulae were healed in 4 non-IBD and 2 CD patients(overall 30%)and fistula remained closed until the end of follow-up at 10-25 mo.In a secondary per-fistula analysis,7 out of 22 fistulae(32%)were closed.Perianal disease activity index(PDAI)improved in patients with fistula healing.Low PDAI was associated with favorable outcome(P=0.0013).No serious adverse events were observed.CONCLUSION Fistulodesis is feasible and safe for perianal fistula closure.Overall success rates is at 30%comparable to other similar techniques.A trend for better outcomes in patients with low PDAI needs to be confirmed.
基金China Scholarship Council(CSC)for Langlang Ma’s fundingUSDA’s National Institute of Food and Agriculture(IOW04314,IOW01018)+1 种基金Hatch Multistate Project NC-007the R.F.Baker Center for Plant Breeding at Iowa State University,for supporting this work.
文摘Root system architecture(RSA)contributes to nitrogen(N)uptake and utilization in maize.In this study,a germplasm enhancement of maize double haploid population of 226 lines genotyped with 61,634 SNPs was used to investigate the genetic basis of RSA under two N levels using a genome-wide association study(GWAS).GLM+PCA,FarmCPU,and MLM models were utilized to balance false positives and false negatives.In total,33 and 51 significant SNP-trait associations were detected under high and low N conditions,respectively.Under high N,SNP S9_2483543 was detected by all models.Linkage disequilibrium(LD)regions of some SNPs overlapped with the intervals of QTL for RSA and N response that were detected in previous studies.In particular,several known genes,Rtcs,Rtcl,Rtcl,and Ms44,were located in the LD regions of S1_9992325,S9_151726472,S9_154381179,and S4_197073985,respectively.Among the candidate genes identified by this study,GRMZM2G139811,GRMZM2G314898,GRMZM2G054050,GRMZM2G173682,GRMZM2G470914,GRMZM2G462325,GRMZM2G416184,and GRMZM2G064302 were involved in seedling,seed,and root system development or N metabolism in Arabidopsis or rice.The markers identified in this study can be used for marker-assisted selection of RSA traits to improve nitrogen use efficiency in maize breeding,and the candidate genes will contribute to further understanding of the genetic basis of RSA under diverse N conditions.
文摘High-frequency switching of power transistors in power electronic systems can cause electromagnetic emissions.Simple approaches for reducing high-frequency disturbances,such as inserting an additional gate resistor,lead to increased power losses.This makes achieving both electromagnetic compatibility and power efficiency difficult.Active gate drivers help to find a trade-off between these two.Typically,only narrow-band disturbances must be reduced.Accordingly,a target signal with a spectrum notched at some frequencies can be defined.The target signal can be reached by a target-signal-oriented control of the transistor’s gate.This leads to steeper switching slopes,such that the power losses are less increased.Generating arbitrary target signals is impossible.The transistor signal exhibits some physical limitations.A constraint satisfaction problem must be solved,and the gate drive signal must be optimized by applying a residual and Newton’s method.The proposed optimization process in the frequency domain is based on the circuit simulation method named“harmonic balance”.Measurements on a DC/DC converter exhibit the benefits of this method.
基金supported by the Director,Office of Science,Office of Basic Energy Sciences,Division of Chemical,Geological and Biosciences of the U.S.Department of Energy under Contract No.DE-AC02-05CH11231
文摘Water oxidation, as a mandatory reaction of solar fuels conversion systems, requires the use of light absorbers with electronic properties that are well matched with those of the multi-electron catalyst in order to achieve high efficiency. Molecular light absorbers offer flexibility in fine tuning of orbital energetics,and metal oxide nanoparticles have emerged as robust oxygen evolving catalysts. Hence, these material choices offer a promising approach for the development of photocatalytic systems for water oxidation.However, efficient charge transfer coupling of molecular light absorbers and metal oxide nanoparticle catalysts has proven a challenge. Recent new approaches toward the efficient coupling of these components based on synthetic design improvements combined with direct spectroscopic observation and kinetic evaluation of charge transfer processes are discussed.
