HGG (Hydroxypropyl guar gum) was synthesized by phase transfer catalysis for the first time. The effects of alkalinity, phase transfer catalyst, etherification, pH value, temperature, reaction time and stirring spee...HGG (Hydroxypropyl guar gum) was synthesized by phase transfer catalysis for the first time. The effects of alkalinity, phase transfer catalyst, etherification, pH value, temperature, reaction time and stirring speed were investigated. An optimal synthetic reaction technology was established, namely, dose of guar gum is 100 g, propylene oxide 40-50 g, HTAC (hexadecyl trimethyl ammonium chloride ) 1.3-1.7 g, pH value 10-10.5, temperature 45-50℃, and reaction time 3-4 hours. The result shows that the improved HGG has high viscosity. Its dissolution speed, content of insoluble residue, colloid light transparency and stability are apparently superior to guar flour.展开更多
Current popular deep learning seismic phase pickers like PhaseNet and EQTransformer suffer from performance drop in China.To mitigate this problem,we build a unified set of customized seismic phase pickers for differe...Current popular deep learning seismic phase pickers like PhaseNet and EQTransformer suffer from performance drop in China.To mitigate this problem,we build a unified set of customized seismic phase pickers for different levels of use in China.We first train a base picker with the recently released DiTing dataset using the same U-Net architecture as PhaseNet.This base picker significantly outperforms the original PhaseNet and is generally suitable for entire China.Then,using different subsets of the DiTing data,we fine-tune the base picker to better adapt to different regions.In total,we provide 5 pickers for major tectonic blocks in China,33 pickers for provincial-level administrative regions,and 2 special pickers for the Capital area and the China Seismic Experimental Site.These pickers show improved performance in respective regions which they are customized for.They can be either directly integrated into national or regional seismic network operation or used as base models for further refinement for specific datasets.We anticipate that this picker set will facilitate earthquake monitoring in China.展开更多
The 1-aryloxyacetyl-4-(4-nitrophenyloxyacetyl)-thiosemicarbazides (3a-h) are synthe- sized via reaction of 4-nitrophenyloxyacetyl chloride with ammonium thiocyanate and aryloxyacetic hydrazides (2a-h) under phase tran...The 1-aryloxyacetyl-4-(4-nitrophenyloxyacetyl)-thiosemicarbazides (3a-h) are synthe- sized via reaction of 4-nitrophenyloxyacetyl chloride with ammonium thiocyanate and aryloxyacetic hydrazides (2a-h) under phase transfer catalysis and microwave irradiation in excellent yield.展开更多
Under the condition of solid-liquid phase transfer catalysis, olefins were obtained by the reaction of p-nitrobenzyldibutyltelluronium bromide with aromatic aldehyde.Under the condition of liquid-liquid phase transfer...Under the condition of solid-liquid phase transfer catalysis, olefins were obtained by the reaction of p-nitrobenzyldibutyltelluronium bromide with aromatic aldehyde.Under the condition of liquid-liquid phase transfer catalysis,however,different products were obtained due to the reactivity of different bases or aldehydes.展开更多
Objective:To determine whether a single dose of gonadotropin-releasing hormone(GnRH)agonist administered subcutaneously in addition to the regular progesterone supplementation could provide a better luteal support in ...Objective:To determine whether a single dose of gonadotropin-releasing hormone(GnRH)agonist administered subcutaneously in addition to the regular progesterone supplementation could provide a better luteal support in antagonist protocol fresh embryo transfer cycles.Methods:This prospective,multicentric,cohort study included total 140 women,70 in each group.Controlled ovarian stimulation was carried out as per fixed GnRH antagonist protocol.The trigger was given with hCG.In vitro fertilization/intracytoplasmic sperm injection(IVF/ICSI)was performed and day-3 embryos were transferred.Patients were divided into groups 1 and 2 based on computer generated randomization sheet.Six days following oocyte retrieval,group 1 received 0.2 mg decapeptyl subcutaneously in addition to regular progesterone support while group 2 received progesterone only.Luteal support was given for 14 days to both groups;if pregnancy was confirmed luteal support was continued till 12 weeks of gestation.The clinical pregnancy rate was the primary outcome.The implantation rate,miscarriage rate,live birth delivery rate,and multiple pregnancy rates were the secondary outcomes.Results:A total of 140 patients were analysed,70 in each group.Clinical pregnancy rates(47.1%vs.35.7%;P=0.17),implantation rates(23.4%vs.18.1%,P=0.24),live birth delivery rates(41.4%vs.27.1%,P=0.08),and multiple pregnancy rates(21.2%vs.16.0%,P=0.74)were higher in group 1 than in group 2.Group 1 had a lower miscarriage rate than group 2(5.7%vs.8.6%;P=0.75).However,these differences were not statistically significant between the two groups.Conclusions:Administration of a single dose of GnRH agonist in addition to regular natural micronized vaginal progesterone as luteal support in GnRH antagonist protocol cycles marginally improves implantation rates,clinical pregnancy rates,and live birth delivery rates.However,more studies with higher sample sizes are needed before any conclusive statements about GnRH agonist as luteal phase support can be made.展开更多
CDMOs are emerging as critical drivers of innovation within the pharmaceutical and biotech industries. As the pharmaceutical industry continues to evolve, we can expect to see CDMOs play an increasingly important role...CDMOs are emerging as critical drivers of innovation within the pharmaceutical and biotech industries. As the pharmaceutical industry continues to evolve, we can expect to see CDMOs play an increasingly important role in drug development and manufacturing. Many companies within these sectors are now leveraging the expertise of CDMOs through technology transfers to foster innovation and enhance the development of new drug products. In the extensive field of drug development, technology transfer plays a crucial role at multiple stages, ranging from preclinical phases to commercialization. By working closely with drug developers, CDMOs can ensure that technologies are transferred seamlessly between phases of drug development, allowing for a more efficient and cost-effective development process. CDMOs also bring a wealth of experience in various areas of drug development, including process development, analytical testing, quality control, and manufacturing. This expertise, combined with a focus on innovation, can help drug developers to overcome technical challenges and optimize their drug development programs. CDMOs can provide drug developers with various manufacturing capabilities, from small-scale clinical trials to large-scale commercial production. This flexibility allows drug developers to focus on their core competencies while relying on CDMOs to provide the necessary infrastructure and support for drug manufacturing. The critical role of CDMOs in advancing pharmaceutical innovation in phase-appropriate technology transfer where there will be a lot of effort and patience with strong technical expertise is required. This article explores the various types of Technology transfer from preclinical to commercial stages and successful strategies to foster innovation.展开更多
Introduction Microwave irradiation has been very widely used in heating, cooking and brewing. Several papers which describe the use of domestic microwave ovens to perform rapid organic synthesis in solution have been ...Introduction Microwave irradiation has been very widely used in heating, cooking and brewing. Several papers which describe the use of domestic microwave ovens to perform rapid organic synthesis in solution have been published. The high heating efficiency gives rise to remarkable rate of reaction and dramatic reduction of reaction time. Nevertheless, its application seems to be limited to these procedures because of展开更多
A series of new diethers were obtained by alkylation of furoin under microwave irradiation (MWI) in phase transfer catalysis (PTC) conditions. The products of alkyl halides were synthesized in good yields (〉75%...A series of new diethers were obtained by alkylation of furoin under microwave irradiation (MWI) in phase transfer catalysis (PTC) conditions. The products of alkyl halides were synthesized in good yields (〉75%) within a few minutes, and the products of dihalides were synthesized in fair yields (about 45%). The yields are dramatically improved compared to conventional heating under the same conditions, in spite of similar profiles of rising in temperature.展开更多
Compounds having an active hydroxy group, such as, acyloins can be easily alkylated by alkyl halides in the presence of a phase transfer catalyst (PTC). The reaction is usually carried out in the presence of con-cen...Compounds having an active hydroxy group, such as, acyloins can be easily alkylated by alkyl halides in the presence of a phase transfer catalyst (PTC). The reaction is usually carried out in the presence of con-centrated aqueous sodium or potassium hydroxide and a phase transfer catalyst, such as, quaternary ammonium salts^[1-3] species, miscible which facilitate the interphase transfer of making reactions between reagents in two im-phases possible. The reaction involves a series of equilibrium and mass-transfer steps.展开更多
A simple and general method for the synthesis of bi(acyl)disulfides is reported.Sulfur is allowed to react with sodium hydroxide to give sodium disulfide at 65℃ under PTC,which can react with acyl halides to afford b...A simple and general method for the synthesis of bi(acyl)disulfides is reported.Sulfur is allowed to react with sodium hydroxide to give sodium disulfide at 65℃ under PTC,which can react with acyl halides to afford bi(acyl)disulfides in good to excellent isolated yields.The effects of solvents and phase transfer catalysts are discussed.展开更多
In order to overcome the difficulty in stripping and reduce the equilibrium time in heavy rare earth separation with acidic organophosphorous extractants, the phase transfer catalysis (PTC) technique was introduced to...In order to overcome the difficulty in stripping and reduce the equilibrium time in heavy rare earth separation with acidic organophosphorous extractants, the phase transfer catalysis (PTC) technique was introduced to the solvent extraction process, especially applied to the stripping section, which was called phase transfer catalysis stripping (PTCS) process. in the PTCS process, an acidic phosphorous extractant was mixed with another extractant which can transfer hydrogen ion from aqueous phase to organic phase and almost does not extract rare earth ions, so that the stripping efficiency can be improved and the stripping extraction equilibrium be accelerated. The reaction mechanism of the PTCS and the requisite properties for a feasible PTCS catalyst in rare earth extraction were studied. We selected D(2)EHPA as the extractant, Alamine 336 as the PTCS catalyst and mixed rare earth chlorides as the feed to test the PTCS phenomenon. Based on the experimental data, the applicability of PTCS technique in rare earth solvent extraction was discussed.展开更多
Seven diaryl ethers were synthesized with potassium fluoride coated alumina as a strong base and the addition of catalytic amount of PTC. The yield of diaryl ethers with addition of PTC was much higher than that witho...Seven diaryl ethers were synthesized with potassium fluoride coated alumina as a strong base and the addition of catalytic amount of PTC. The yield of diaryl ethers with addition of PTC was much higher than that without PTC.A discussion of the catalysis mechanism was given in this paper.展开更多
Cyclopropylamine is synthesized with γ butyrolactone and isopropanol by five steps of ring opening esterification, cyclization, hydrolysis, acylation and Hofmann degradation. Cyclization and hydrolysis are key steps ...Cyclopropylamine is synthesized with γ butyrolactone and isopropanol by five steps of ring opening esterification, cyclization, hydrolysis, acylation and Hofmann degradation. Cyclization and hydrolysis are key steps in the process, and Phase Transfer Catalysis (PTC) is used in the two steps respectively. In the cyclization reaction, because solid liquid PTC, sodium hydroxide is applied instead of expensive sodium alcoholate, the reaction can be carried out in mild conditions. The optimum re action conditions are as follows: 0.03∶1∶1.5 mole ratio of BTEAC to ester to sodium hydroxide, reacting at 50 ℃ for 2 h with yield of 92%. Hydrolysis of isopropyl cyclopropanecarboxylate is accelerated by liquid liquid PTC, and the order of catalytic activity is BTEAC>BTMAC>CTMAB>TBAB. The results show that the new synthesis method is superior to those from literature and feasible for production with simple routes, mild reaction conditions, cheap materials and total yield of 52.6%.展开更多
The acetylated xylo-and arabinopyranosyl esters(1-8) were obtained in high yields with stereoselectivity by phase-transfer catalyzed (PTC) synthesis, and their structures were confirmed by elemental analysis and I...The acetylated xylo-and arabinopyranosyl esters(1-8) were obtained in high yields with stereoselectivity by phase-transfer catalyzed (PTC) synthesis, and their structures were confirmed by elemental analysis and IR,;H-NMR spectral data.展开更多
We demonstrate coherent optical frequency dissemination over a distance of 972 km by cascading two spans where the phase noise is passively compensated for.Instead of employing a phase discriminator and a phase lockin...We demonstrate coherent optical frequency dissemination over a distance of 972 km by cascading two spans where the phase noise is passively compensated for.Instead of employing a phase discriminator and a phase locking loop in the conventional active phase control scheme,the passive phase noise cancellation is realized by feeding double-trip beat-note frequency to the driver of the acoustic optical modulator at the local site.This passive scheme exhibits fine robustness and reliability,making it suitable for long-distance and noisy fiber links.An optical regeneration station is used in the link for signal amplification and cascaded transmission.The phase noise cancellation and transfer instability of the 972-km link is investigated,and transfer instability of 1.1×10^(-19)at 10^(4)s is achieved.This work provides a promising method for realizing optical frequency distribution over thousands of kilometers by using fiber links.展开更多
Ethyl N-cyanomethytbenzenecarboximidate reacted with aliphatic aldehydes under the solid-liquid PTC condition to gire a-ethoxyphenylmethylene- aminoacrylonitrile derivatives and oxazoline derivatives.It is a convenien...Ethyl N-cyanomethytbenzenecarboximidate reacted with aliphatic aldehydes under the solid-liquid PTC condition to gire a-ethoxyphenylmethylene- aminoacrylonitrile derivatives and oxazoline derivatives.It is a convenient and new method for synthesis of β,β'-dihyroxy-a-amino acids by hydrolysis of the oxazoline derivatives.展开更多
p nitrophenol is synthesized using p nitrochlorobenzene and sodium hydroxide with phase transfer catalyst. Several reaction factors, such as catalyst type, the amounts of catalysts and sodium hydroxide, the concentrat...p nitrophenol is synthesized using p nitrochlorobenzene and sodium hydroxide with phase transfer catalyst. Several reaction factors, such as catalyst type, the amounts of catalysts and sodium hydroxide, the concentration of sodium hydroxide solution as well as reaction time, affect greatly the yield of p nitrophenol. The optimum reaction conditions are as follows: A 1 used as phase transfer catalyst whose consumption is 6% (mole fraction) of p nitrochlorobenzene; the molar ratio of sodium hydroxide to p nitrochlorobenzene is 3:1; the concentration of sodium hydroxide solution is 50% (mass fraction). Nitrobenzene, whose molar amount is 2.45 times as much as that of p nitrochlorobenzene; reaction time is 7 h at 140 ℃ under normal pressure. The final yield of p nitrophenol is 83.6%.展开更多
Using galvinoxyl as catalyst, the phase transfer catalyzed method of oxidation of primary amines to symmetrical azobenzenes with a saturated solution of potassium ferricyanide in 2 mom aqueous potassium hydroxide and ...Using galvinoxyl as catalyst, the phase transfer catalyzed method of oxidation of primary amines to symmetrical azobenzenes with a saturated solution of potassium ferricyanide in 2 mom aqueous potassium hydroxide and dichloromethane is described. The reaction has intimate relation with Hammett substituent constants. This report offers an efficient and rapid method to prepare azobenzenes and a possible mechanism is also suggested.展开更多
文摘HGG (Hydroxypropyl guar gum) was synthesized by phase transfer catalysis for the first time. The effects of alkalinity, phase transfer catalyst, etherification, pH value, temperature, reaction time and stirring speed were investigated. An optimal synthetic reaction technology was established, namely, dose of guar gum is 100 g, propylene oxide 40-50 g, HTAC (hexadecyl trimethyl ammonium chloride ) 1.3-1.7 g, pH value 10-10.5, temperature 45-50℃, and reaction time 3-4 hours. The result shows that the improved HGG has high viscosity. Its dissolution speed, content of insoluble residue, colloid light transparency and stability are apparently superior to guar flour.
基金the National Key R&D Program of China(No.2021YFC3000700)the Special Fund of the Institute of Geophysics,China Earthquake Administration(Nos.DQJB22X08 and DQJB21Z05).
文摘Current popular deep learning seismic phase pickers like PhaseNet and EQTransformer suffer from performance drop in China.To mitigate this problem,we build a unified set of customized seismic phase pickers for different levels of use in China.We first train a base picker with the recently released DiTing dataset using the same U-Net architecture as PhaseNet.This base picker significantly outperforms the original PhaseNet and is generally suitable for entire China.Then,using different subsets of the DiTing data,we fine-tune the base picker to better adapt to different regions.In total,we provide 5 pickers for major tectonic blocks in China,33 pickers for provincial-level administrative regions,and 2 special pickers for the Capital area and the China Seismic Experimental Site.These pickers show improved performance in respective regions which they are customized for.They can be either directly integrated into national or regional seismic network operation or used as base models for further refinement for specific datasets.We anticipate that this picker set will facilitate earthquake monitoring in China.
基金Technological Innovation Engineering of Northwest Normal University (NWNU-KJCXGC-218) Natural Science Foundation of Gansu Province and Youth Foundation of Northwest Normal University.
文摘The 1-aryloxyacetyl-4-(4-nitrophenyloxyacetyl)-thiosemicarbazides (3a-h) are synthe- sized via reaction of 4-nitrophenyloxyacetyl chloride with ammonium thiocyanate and aryloxyacetic hydrazides (2a-h) under phase transfer catalysis and microwave irradiation in excellent yield.
文摘Under the condition of solid-liquid phase transfer catalysis, olefins were obtained by the reaction of p-nitrobenzyldibutyltelluronium bromide with aromatic aldehyde.Under the condition of liquid-liquid phase transfer catalysis,however,different products were obtained due to the reactivity of different bases or aldehydes.
文摘Objective:To determine whether a single dose of gonadotropin-releasing hormone(GnRH)agonist administered subcutaneously in addition to the regular progesterone supplementation could provide a better luteal support in antagonist protocol fresh embryo transfer cycles.Methods:This prospective,multicentric,cohort study included total 140 women,70 in each group.Controlled ovarian stimulation was carried out as per fixed GnRH antagonist protocol.The trigger was given with hCG.In vitro fertilization/intracytoplasmic sperm injection(IVF/ICSI)was performed and day-3 embryos were transferred.Patients were divided into groups 1 and 2 based on computer generated randomization sheet.Six days following oocyte retrieval,group 1 received 0.2 mg decapeptyl subcutaneously in addition to regular progesterone support while group 2 received progesterone only.Luteal support was given for 14 days to both groups;if pregnancy was confirmed luteal support was continued till 12 weeks of gestation.The clinical pregnancy rate was the primary outcome.The implantation rate,miscarriage rate,live birth delivery rate,and multiple pregnancy rates were the secondary outcomes.Results:A total of 140 patients were analysed,70 in each group.Clinical pregnancy rates(47.1%vs.35.7%;P=0.17),implantation rates(23.4%vs.18.1%,P=0.24),live birth delivery rates(41.4%vs.27.1%,P=0.08),and multiple pregnancy rates(21.2%vs.16.0%,P=0.74)were higher in group 1 than in group 2.Group 1 had a lower miscarriage rate than group 2(5.7%vs.8.6%;P=0.75).However,these differences were not statistically significant between the two groups.Conclusions:Administration of a single dose of GnRH agonist in addition to regular natural micronized vaginal progesterone as luteal support in GnRH antagonist protocol cycles marginally improves implantation rates,clinical pregnancy rates,and live birth delivery rates.However,more studies with higher sample sizes are needed before any conclusive statements about GnRH agonist as luteal phase support can be made.
文摘CDMOs are emerging as critical drivers of innovation within the pharmaceutical and biotech industries. As the pharmaceutical industry continues to evolve, we can expect to see CDMOs play an increasingly important role in drug development and manufacturing. Many companies within these sectors are now leveraging the expertise of CDMOs through technology transfers to foster innovation and enhance the development of new drug products. In the extensive field of drug development, technology transfer plays a crucial role at multiple stages, ranging from preclinical phases to commercialization. By working closely with drug developers, CDMOs can ensure that technologies are transferred seamlessly between phases of drug development, allowing for a more efficient and cost-effective development process. CDMOs also bring a wealth of experience in various areas of drug development, including process development, analytical testing, quality control, and manufacturing. This expertise, combined with a focus on innovation, can help drug developers to overcome technical challenges and optimize their drug development programs. CDMOs can provide drug developers with various manufacturing capabilities, from small-scale clinical trials to large-scale commercial production. This flexibility allows drug developers to focus on their core competencies while relying on CDMOs to provide the necessary infrastructure and support for drug manufacturing. The critical role of CDMOs in advancing pharmaceutical innovation in phase-appropriate technology transfer where there will be a lot of effort and patience with strong technical expertise is required. This article explores the various types of Technology transfer from preclinical to commercial stages and successful strategies to foster innovation.
文摘Introduction Microwave irradiation has been very widely used in heating, cooking and brewing. Several papers which describe the use of domestic microwave ovens to perform rapid organic synthesis in solution have been published. The high heating efficiency gives rise to remarkable rate of reaction and dramatic reduction of reaction time. Nevertheless, its application seems to be limited to these procedures because of
基金Natural Science Foundation of Jilin Province, China (No. 1999010540).
文摘A series of new diethers were obtained by alkylation of furoin under microwave irradiation (MWI) in phase transfer catalysis (PTC) conditions. The products of alkyl halides were synthesized in good yields (〉75%) within a few minutes, and the products of dihalides were synthesized in fair yields (about 45%). The yields are dramatically improved compared to conventional heating under the same conditions, in spite of similar profiles of rising in temperature.
基金Supported by the Natural Science Foundation of Jilin Province,China(No.1999010540).
文摘Compounds having an active hydroxy group, such as, acyloins can be easily alkylated by alkyl halides in the presence of a phase transfer catalyst (PTC). The reaction is usually carried out in the presence of con-centrated aqueous sodium or potassium hydroxide and a phase transfer catalyst, such as, quaternary ammonium salts^[1-3] species, miscible which facilitate the interphase transfer of making reactions between reagents in two im-phases possible. The reaction involves a series of equilibrium and mass-transfer steps.
文摘A simple and general method for the synthesis of bi(acyl)disulfides is reported.Sulfur is allowed to react with sodium hydroxide to give sodium disulfide at 65℃ under PTC,which can react with acyl halides to afford bi(acyl)disulfides in good to excellent isolated yields.The effects of solvents and phase transfer catalysts are discussed.
文摘In order to overcome the difficulty in stripping and reduce the equilibrium time in heavy rare earth separation with acidic organophosphorous extractants, the phase transfer catalysis (PTC) technique was introduced to the solvent extraction process, especially applied to the stripping section, which was called phase transfer catalysis stripping (PTCS) process. in the PTCS process, an acidic phosphorous extractant was mixed with another extractant which can transfer hydrogen ion from aqueous phase to organic phase and almost does not extract rare earth ions, so that the stripping efficiency can be improved and the stripping extraction equilibrium be accelerated. The reaction mechanism of the PTCS and the requisite properties for a feasible PTCS catalyst in rare earth extraction were studied. We selected D(2)EHPA as the extractant, Alamine 336 as the PTCS catalyst and mixed rare earth chlorides as the feed to test the PTCS phenomenon. Based on the experimental data, the applicability of PTCS technique in rare earth solvent extraction was discussed.
文摘Seven diaryl ethers were synthesized with potassium fluoride coated alumina as a strong base and the addition of catalytic amount of PTC. The yield of diaryl ethers with addition of PTC was much higher than that without PTC.A discussion of the catalysis mechanism was given in this paper.
基金The Science and Research Foundation of Education Commission of Hunan Province
文摘Cyclopropylamine is synthesized with γ butyrolactone and isopropanol by five steps of ring opening esterification, cyclization, hydrolysis, acylation and Hofmann degradation. Cyclization and hydrolysis are key steps in the process, and Phase Transfer Catalysis (PTC) is used in the two steps respectively. In the cyclization reaction, because solid liquid PTC, sodium hydroxide is applied instead of expensive sodium alcoholate, the reaction can be carried out in mild conditions. The optimum re action conditions are as follows: 0.03∶1∶1.5 mole ratio of BTEAC to ester to sodium hydroxide, reacting at 50 ℃ for 2 h with yield of 92%. Hydrolysis of isopropyl cyclopropanecarboxylate is accelerated by liquid liquid PTC, and the order of catalytic activity is BTEAC>BTMAC>CTMAB>TBAB. The results show that the new synthesis method is superior to those from literature and feasible for production with simple routes, mild reaction conditions, cheap materials and total yield of 52.6%.
文摘The acetylated xylo-and arabinopyranosyl esters(1-8) were obtained in high yields with stereoselectivity by phase-transfer catalyzed (PTC) synthesis, and their structures were confirmed by elemental analysis and IR,;H-NMR spectral data.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12103059,12033007,12303077,and 12303076)the Fund from the Xi’an Science and Technology Bureau,China(Grant No.E019XK1S04)the Fund from the Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.1188000XGJ).
文摘We demonstrate coherent optical frequency dissemination over a distance of 972 km by cascading two spans where the phase noise is passively compensated for.Instead of employing a phase discriminator and a phase locking loop in the conventional active phase control scheme,the passive phase noise cancellation is realized by feeding double-trip beat-note frequency to the driver of the acoustic optical modulator at the local site.This passive scheme exhibits fine robustness and reliability,making it suitable for long-distance and noisy fiber links.An optical regeneration station is used in the link for signal amplification and cascaded transmission.The phase noise cancellation and transfer instability of the 972-km link is investigated,and transfer instability of 1.1×10^(-19)at 10^(4)s is achieved.This work provides a promising method for realizing optical frequency distribution over thousands of kilometers by using fiber links.
基金The project supported by the National Natural Science Foundation of China.Present Address:Shanghai Institute of Organic Chemistry,Academia Sinica.
文摘Ethyl N-cyanomethytbenzenecarboximidate reacted with aliphatic aldehydes under the solid-liquid PTC condition to gire a-ethoxyphenylmethylene- aminoacrylonitrile derivatives and oxazoline derivatives.It is a convenient and new method for synthesis of β,β'-dihyroxy-a-amino acids by hydrolysis of the oxazoline derivatives.
文摘p nitrophenol is synthesized using p nitrochlorobenzene and sodium hydroxide with phase transfer catalyst. Several reaction factors, such as catalyst type, the amounts of catalysts and sodium hydroxide, the concentration of sodium hydroxide solution as well as reaction time, affect greatly the yield of p nitrophenol. The optimum reaction conditions are as follows: A 1 used as phase transfer catalyst whose consumption is 6% (mole fraction) of p nitrochlorobenzene; the molar ratio of sodium hydroxide to p nitrochlorobenzene is 3:1; the concentration of sodium hydroxide solution is 50% (mass fraction). Nitrobenzene, whose molar amount is 2.45 times as much as that of p nitrochlorobenzene; reaction time is 7 h at 140 ℃ under normal pressure. The final yield of p nitrophenol is 83.6%.
文摘Using galvinoxyl as catalyst, the phase transfer catalyzed method of oxidation of primary amines to symmetrical azobenzenes with a saturated solution of potassium ferricyanide in 2 mom aqueous potassium hydroxide and dichloromethane is described. The reaction has intimate relation with Hammett substituent constants. This report offers an efficient and rapid method to prepare azobenzenes and a possible mechanism is also suggested.