In this study, the mechanical properties of aluminum-5%magnesium doped with rare earth metal neodymium were evaluated. Fuzzy logic (FL) and artificial neural network (ANN) were used to model the mechanical properties ...In this study, the mechanical properties of aluminum-5%magnesium doped with rare earth metal neodymium were evaluated. Fuzzy logic (FL) and artificial neural network (ANN) were used to model the mechanical properties of aluminum-5%magnesium (0-0.9 wt%) neodymium. The single input (SI) to the fuzzy logic and artificial neural network models was the percentage weight of neodymium, while the multiple outputs (MO) were average grain size, ultimate tensile strength, yield strength elongation and hardness. The fuzzy logic-based model showed more accurate prediction than the artificial neutral network-based model in terms of the correlation coefficient values (R).展开更多
It was reported that rare earth elements promote plant growth and other physiological activities. Since the ion radius of Nd3+ is very close to that of Ca2+, the interaction between Nd and Ca might be one of the impor...It was reported that rare earth elements promote plant growth and other physiological activities. Since the ion radius of Nd3+ is very close to that of Ca2+, the interaction between Nd and Ca might be one of the important mechanisms to be understand. Seedlings treated with 3 Umol·T, -1 Nd(NO3)3 in Ca2+ -deficient solution, and the effect of Nd on their membrane damage in oilseed rape(Brassica napus L.) was studied. It shows that the symptom of Ca-starvation is relieved and the peroxidation process in rape is inhibited. It indicates that adding Nd can lower relative permeability of the root and MDA content in leaves and increase CAT, POD, and SOD activities in rape. Likewise, the Nd addition to Hoagland solution shags similar result. The interpretation is that the effect is a consequence of substitution of Nd function for some Ca function through interacting with cellular membrane.展开更多
The effects of carbonate on the exchangeability and the bioavailability of exogenous neodymium in soil were studied by 147 Nd isotopic tracer method. Exchangeable Nd was extracted by 1 mol·L -1 NaAc (pH8 2) in th...The effects of carbonate on the exchangeability and the bioavailability of exogenous neodymium in soil were studied by 147 Nd isotopic tracer method. Exchangeable Nd was extracted by 1 mol·L -1 NaAc (pH8 2) in the experiment. The results indicate that whether carbonate exists in soil or not, beyond 99% of exogenous Nd is adsorbed by soil. Low-concentration carbonate (0 8～1 6 g·kg -1 ) can reduce exchangeable Nd concentration in soil, while high-concentration carbonate (4 0 g·kg -1 ) impacts little on the exchangeable Nd concentration. In addition, carbonate of 0 8～1 6 g·kg -1 in soil can inhibit wheat seedlings to absorb Nd. However, when the carbonate concentration rises to 4 0 g·kg -1 , the inhibition will become indistinct.展开更多
Cholelithiasis is a common and frequently occurring disease in East Asia.Intrahepatic bile duct stone is a benign disease,but the recurrence rate is high.The incidence of postoperative residual stones after traditiona...Cholelithiasis is a common and frequently occurring disease in East Asia.Intrahepatic bile duct stone is a benign disease,but the recurrence rate is high.The incidence of postoperative residual stones after traditional manual stone removal can be30%–96%^([1]).The emergence of endoscopes is therefore a milestone in the treatment of hepatolithiasis.Among the various approaches,choledochoscopy combined with laser lithotripsy has become the main procedure for intrahepatic bile duct stone removal^([2]).Lithotripsy alone has the disadvantages of low stoneremoving efficiency and blurred choledochoscope vision while performing the procedure.Currently,our team has achieved satisfactory results in the removal of intrahepatic bile duct stones with low-pressure pulse flushing and neodymium laser lithotripsy.展开更多
Observation with the transmission electronic microscopy shows that Nd can not enter into the cytoplasm of oilseed rape ( brassica napus L.) in solution culture. It combines with the cell wall or amasses in the interce...Observation with the transmission electronic microscopy shows that Nd can not enter into the cytoplasm of oilseed rape ( brassica napus L.) in solution culture. It combines with the cell wall or amasses in the intercellular space. Nd accumulates in root tip after it enters into the plants, while only a small amount of Nd is transferred to the stem and leaf via apoplasm, and the leaf contains the least of Nd. Such observations are consistent with the analytical results of Nd distribution in rape tissues in soil culture experiment. It suggests that the physiological effects of Nd in plants might mainly function on plasmalemma of root system.展开更多
Polymerization of 4 vinylpyridine by complex catalyst of neodymium chloride was studied. The influence of Al/Nd(molar ratio), concentration of catalyst, reaction time and temperature on polymerization of 4 vinylpyridi...Polymerization of 4 vinylpyridine by complex catalyst of neodymium chloride was studied. The influence of Al/Nd(molar ratio), concentration of catalyst, reaction time and temperature on polymerization of 4 vinylpyridine was investigated. The results show that different kinds of ligand in the rare earth complex have an effect on the catalytic activity of the complex. The catalytic activity of the rare earth complex is higher than that of simple rare earth chloride. The catalytic activity of polymer supported catalyst is higher than those of the similar small molecular system.展开更多
The title complex [Nd(Gly)(H 2O) 7]Cl 3 was synthesized and its crystal structure was determined by X ray diffraction to obtain a final R value of 0 026 0 and a wR value of 0 086 8. The crystal is of monoclinic system...The title complex [Nd(Gly)(H 2O) 7]Cl 3 was synthesized and its crystal structure was determined by X ray diffraction to obtain a final R value of 0 026 0 and a wR value of 0 086 8. The crystal is of monoclinic system with a space groug Pm . Every two neodymium ions in the crystal are connected with a carboxyl group to form a polymeric chain molecule. And each neodymium ion is further coordinated with seven oxygen atoms from water molecules. The counter ion(Cl -) is non coordinated to fill up the space between the polymeric chains. So the Nd 3+ cation is nine coordinated and the coordination polyhedron is a trigonotetradecahedron. In addition, there exists the mirror symmetry in the complex.展开更多
AIM: To compare surgical peeling and aspiration and neodymium yttrium garnet laser capsulotomy for pearl form of posterior capsule opacification(PCO).METHODS: A prospective, randomized, double blind,study was done at ...AIM: To compare surgical peeling and aspiration and neodymium yttrium garnet laser capsulotomy for pearl form of posterior capsule opacification(PCO).METHODS: A prospective, randomized, double blind,study was done at Rotary Eye Hospital, Maranda,Palampur, India, Santosh Medical College Hospital,Ghaziabad, India and Laser Eye Clinic, Noida India.Consecutive patients with pearl form of PCO following surgery, phacoemulsification, manual small incision cataract surgery and conventional extracapsular cataract extraction(ECCE) for age related cataract, were randomized to have peeling and aspiration or neodymium yttrium garnet laser capsulotomy. Corrected distance visual acuity(CDVA), intra-operative and postoperative complications were compared.RESULTS: A total of 634 patients participated in the study, and 314(49.5%) patients were randomized to surgical peeling and aspiration group and 320(50.5%) to the Nd:YAG laser group. The mean pre-procedural log MAR CDVA in peeling and neodymium: yttrium-aluminium-garnet(Nd:YAG) laser group was 0.80 ±0.25 and 0.86 ±0.22, respectively. The mean final CDVA in peeling group(0.22 ±0.23) was comparable to Nd:YAG group(0.24 ±0.28; t-test, P =0.240). There was a significant improvement in vision after both the procedures(P <0.001). A slightly higher percentage of patients in Nd:YAG laser group(283/88.3%) than in peeling group(262/83.4%) had a CDVA of 0.5(20/63) or better at 9mo(P <0.001). On the contrary, patients havingCDVA worse than 1.00(20/200) was also significantly higher in Nd:YAG laser group as compared to peeling group(25/7.7% vs 15/4.7%, respectively). On application of ANCOVA, there was less than 0.001% risk that PCO thickness and total laser energy had no effect on rate of complications in Nd:YAG laser group and less than 0.001% risk that PCO thickness had no effect on complications in peeling group respectively. Sum of square analysis suggests that in the Nd:YAG laser group,thick PCO had a stronger impact on complications(Fischer test probability, P r <0.0001) than thin PCO and total laser energy(Fischer test probability, P r <0.002),respectively; similarly, in peeling group, thick PCO and preoperative vision had a stronger effect on complications than thin PCO, respectively(Fischer test probability, P r <0.001). The rate of complications like uveitis(P =0.527) and cystoid macular edema(P =0.068),did not differ significantly between both the groups.However, intraocular pressure spikes(P =0.046) and retinal detachment(P<0.001) were significantly higher in Nd:YAG laser group as compared to peeling group.Retinal detachment was more common in patients having degenerative myopia(7/87.5%, P <0.001). Recurrence of pearls was the most common cause of reduction of vision in the peeling group(24/7.6%, P <0.001).CONCLUSION: There is no alternative to Nd:YAG laser capsulotomy for fibrous subtype of PCO. For pearl form of PCO, both techniques are comparable with regard to visual outcomes. Nd:YAG laser capsulotomy has a higher incidence of IOP spikes and retinal detachment whereas recurrence of pearls may occur after successful peeling and aspiration. When posterior capsulotomy is needed in patients with retinal degenerations,retinopathies and pre-existing retinal breaks, the clinician should be cautious about increased risks of possible complications of Nd:YAG laser capsulotomy.展开更多
Based on the quantum chemical descriptors and the activities for isoprene polymerization of 12 neodymium carboxylates obtained by authors’earlier work,statistical analysis of data was made and a QSAR model correlatin...Based on the quantum chemical descriptors and the activities for isoprene polymerization of 12 neodymium carboxylates obtained by authors’earlier work,statistical analysis of data was made and a QSAR model correlating the quantum chemical descriptors and the activity was built with the partial least square(PLS)approach.The model is:A=51602εHOMO+6σ+12546,which indicates that the catalytic activity A is positively correlated with the HOMO energyεHOMOand the ligand polarizabilityσ,with the contribution ofσbeing larger,εHOMO smaller.The model’s coefficient of determination r^2=0.96 and that of cross validation q^2=0.94,both being close to 1,which means that its quality is well and its predictive power is strong.Analysis of the modeling process and the resulted QSAR model,together with the interpretation of the model’s mechanism,also shows that the model obtained from this study is valid and reliable.According to the QSAR model,the mechanism of catalyst activity can be interpreted as that neodymium carboxylates with higher HOMO energy and larger ligand polarizability are easier to react with the co-catalysts so as to produce more active and stable centers of catalyst,resulting in a higher activity.展开更多
The kinetics and the difference for Pr(Ⅲ)and Nd(Ⅲ)extraction from nitrate aqueous solution using trialkylmethylammonium nitrate([A336][NO3])as extractant were investigated by the single drop technique.The dependence...The kinetics and the difference for Pr(Ⅲ)and Nd(Ⅲ)extraction from nitrate aqueous solution using trialkylmethylammonium nitrate([A336][NO3])as extractant were investigated by the single drop technique.The dependence of the extraction rate of Pr(Ⅲ)and Nd(Ⅲ)on the concentrations of free Pr(Ⅲ)and Nd(Ⅲ)ions,the concentrations of Na NO3 and H+in aqueous solutions,and the concentrations of[A336][NO3]in kerosene solutions were discussed and the corresponding extraction rate equations for Pr(Ⅲ)and Nd(Ⅲ)were obtained.These equations demonstrated that the reaction rate constant of Pr(Ⅲ)with[A336][NO3]was double than that of Nd(Ⅲ).The effect of the addition of diethylenetriaminepentaacetic acid(DTPA)on the difference in the extraction rate of Pr(Ⅲ)and Nd(Ⅲ)by[A336][NO3]was also investigated.It was revealed that the difference in the complex formation rates of Pr(Ⅲ)and Nd(Ⅲ)with DTPA made a significant impact on the difference in the extraction rates of Pr(Ⅲ)and Nd(Ⅲ)with[A336][NO3].The ratio of extraction rates of Pr(Ⅲ)to Nd(Ⅲ)with[A336][NO3]was in proportion to the ratio of complex formation rates of Pr(Ⅲ)to Nd(Ⅲ)with DTPA.The extraction rate difference for Pr(Ⅲ)and Nd(Ⅲ)with[A336][NO3]increased due to a higher complex formation rate constant of DTPA with the free and un-complexed Nd(Ⅲ)ions in the aqueous nitrate solution than that with Pr(Ⅲ)ions.Therefore,the addition of DTPA in the aqueous nitrate solution is an effective method to intensify the separation of Pr(Ⅲ)and Nd(Ⅲ)in kinetics.The study on the extraction mechanism indicated that both the extraction of Pr(Ⅲ)and Nd(Ⅲ)by[A336][NO3]were diffusion controlled,and the reactions obeyed SN2 mechanism.The present work highlights a possible approach to strengthen the kinetic separation of Pr(Ⅲ)and Nd(Ⅲ).展开更多
Ring-opening polymerization of trimethylene carbonate (TMC) with a rare earth calixarene compound as catalysthas been studied for the first time. The effect of TMC/Nd (molar ratio) and polymerization conditions were i...Ring-opening polymerization of trimethylene carbonate (TMC) with a rare earth calixarene compound as catalysthas been studied for the first time. The effect of TMC/Nd (molar ratio) and polymerization conditions were investigated indetail. It was found that calix[8]arene-neodymium is a highly effective catalyst for the bulk polymerization of TMC and giveshigh molecular weight (M_v = 60,000) polymer. The optimum conditions of TMC polymerization were found to be asfollows:TMC/Nd (molar ratio) = 2,000, 80℃, 16 h. The polymers were characterized by NMR, GPC and DSC. Studying themechanism by NMR showed that the polymerization of TMC catalyzed by calix[8]arene-neodymium proceeds via a cationicmechanism.展开更多
Polymerization of styrene and 1,3-butadiene were performed by calix[4]arene neodymium complexes using di-n-butylmagnesium and tri-iso-butylaluminum as cocatalyst respectively. The effect of the substituent groups in c...Polymerization of styrene and 1,3-butadiene were performed by calix[4]arene neodymium complexes using di-n-butylmagnesium and tri-iso-butylaluminum as cocatalyst respectively. The effect of the substituent groups in calix[4]arene on the catalytic activity was first investigated.展开更多
The neodymium electrolysis produces unnecessary high emission of CF4 and C2F6. These perfluorocarbons (PFCs) are potent greenhouse gases and are not filtered or destroyed in the off-gas. A process control in analogy t...The neodymium electrolysis produces unnecessary high emission of CF4 and C2F6. These perfluorocarbons (PFCs) are potent greenhouse gases and are not filtered or destroyed in the off-gas. A process control in analogy to the aluminum electrolysis can reduce the PFC emission to a great extend and keep the process in a green process window. Therefore, a theoretical analysis is done of the cell voltage of the industrial neodymium electrolysis in dependence on the neodymium oxide concentration in the electrolyte. The analysis shows the different contributions to the cell voltage focusing on the impact of the anodic overvoltage on the cell voltage, by which the electrolysis process can be controlled. The model of the cell voltage is evaluated by laboratory neodymium electrolysis with a similar setup as the industrial cell. The relation of the oxide concentration, the anodic current density and the cell voltage with the cell resistance are measured. The continuous off-gas measurements show the gas concentration and PFC emissions. The effect of Nd2O3 feeding on the galvanostatic electrolysis is analyzed as well. Based on the results a process control strategy is proposed similar to the aluminum electrolysis strategy. The green process window is in a narrow oxide concentration range, making a continuous and precise oxide feeding essential.展开更多
The cyclic voltammetry was used to investigate the electrode processes of Nd(Ⅲ)reduced on iron electrode and Nd(Ⅲ),Fe(Ⅱ)reduced on molybdenum electrode in molten chlorides.The Nd-Fe and Nd-rich RE-Fe alloys contain...The cyclic voltammetry was used to investigate the electrode processes of Nd(Ⅲ)reduced on iron electrode and Nd(Ⅲ),Fe(Ⅱ)reduced on molybdenum electrode in molten chlorides.The Nd-Fe and Nd-rich RE-Fe alloys contained rare earth up to90wt% were prepared by consumable cathode and electrolytic codeposition.The mechanism of electrochemical formation ofNd-Fe alloy had been discussed.展开更多
The nonrelativistic DV-X<sub>α</sub>-SCC method was used to study the electronic structure and chemi-cal bonding of tetranuclear neodymium complex Nd<sub>4</sub>O（OR）<sub>4</sub>...The nonrelativistic DV-X<sub>α</sub>-SCC method was used to study the electronic structure and chemi-cal bonding of tetranuclear neodymium complex Nd<sub>4</sub>O（OR）<sub>4</sub>（NR′<sub>2</sub>）<sub>6</sub>,with emphasis on the bonding charac-ter of the central μ<sub>4</sub>-O atom and the four Nd atoms.The results of calculation show that the μ<sub>4</sub>-O atom usesits sp<sup>3</sup> valence orbitals to contribute four O-Nd bonding MOs with character of multicenter bond apparent-ly.The Mulliken population analysis shows that the overlap population between Nd atoms is almost equal tozero,therefore there is no direct metal-metal bond between Nd atoms.The coordination number of Nd in thecomplex is discussed briefly.展开更多
In view of the problems of slower precipitation rate and lower recovery rate in the traditional preparation process of neodymium fluoride, the process of conversion with ammonia bicarbonate and adding macromolecular p...In view of the problems of slower precipitation rate and lower recovery rate in the traditional preparation process of neodymium fluoride, the process of conversion with ammonia bicarbonate and adding macromolecular precipitant aid to prepare neodymium fluoride was studied. The effect of HF amount, reaction temperature, rare earth concentrations and macromolecular precipitating aid on the recovery rate of rare earth and its precipitation rate were investigated. The particulate size, morphology and composition of NdF3 were analyzed by TEM, XRD, etc. A feasible process to produce good crystal degree neodymium fluoride with rapid precipitation and higher recovery rate was obtained.展开更多
The neodymium complexes with crosslinked polystyrene containing —CH 2SH and —CH 2SOCH 3 groups, P—CH 2SH·NdCl 3 and P—CH 2SOCH 3·NdCl 3, were prepared. P—CH 2SH·NdCl 3 shows no catalytic activity f...The neodymium complexes with crosslinked polystyrene containing —CH 2SH and —CH 2SOCH 3 groups, P—CH 2SH·NdCl 3 and P—CH 2SOCH 3·NdCl 3, were prepared. P—CH 2SH·NdCl 3 shows no catalytic activity for butadiene polymerization, while P—CH 2SOCH 3·NdCl 3 can catalyze the polymerization of butadiene. The content of cis 1,4 polybutadiene is more than 95%.展开更多
The title compound, [Nd(dmso) 7Cl][Bph 4] 2(dmso=dimethylsulfoxide, Bph 4=tetraphenylboron anion) was synthesized in organic solvent acetone/EtOH and the structure was determined by single crystal X ray diffraction. T...The title compound, [Nd(dmso) 7Cl][Bph 4] 2(dmso=dimethylsulfoxide, Bph 4=tetraphenylboron anion) was synthesized in organic solvent acetone/EtOH and the structure was determined by single crystal X ray diffraction. The crystal is triclinic with space group P 1, and the crystal data are as follows: a =1 2554(1) nm, b = 1 2799(1) nm, c =2 4598(3) nm; α =93 53(1)°, β =104 50(1)°, γ =112 77(1)°, V =3 4722(6) nm 3, Z =2, M r=1365 01, D c=1 306 g·cm -3 . The crystal is composed of a big cation [Nd(dmso) 7Cl] 2+ and two big anions [BPh 4] -. The Nd 3+ is coordinated by a chlorine atom and seven oxygen atoms from seven dimethylsulfoxides forming a distorted square antiprism coordination polyhedron,while the BPh - 4 anion is charge equilibrium ion.展开更多
文摘In this study, the mechanical properties of aluminum-5%magnesium doped with rare earth metal neodymium were evaluated. Fuzzy logic (FL) and artificial neural network (ANN) were used to model the mechanical properties of aluminum-5%magnesium (0-0.9 wt%) neodymium. The single input (SI) to the fuzzy logic and artificial neural network models was the percentage weight of neodymium, while the multiple outputs (MO) were average grain size, ultimate tensile strength, yield strength elongation and hardness. The fuzzy logic-based model showed more accurate prediction than the artificial neutral network-based model in terms of the correlation coefficient values (R).
基金the National Natural Science Foundation of China!39670422
文摘It was reported that rare earth elements promote plant growth and other physiological activities. Since the ion radius of Nd3+ is very close to that of Ca2+, the interaction between Nd and Ca might be one of the important mechanisms to be understand. Seedlings treated with 3 Umol·T, -1 Nd(NO3)3 in Ca2+ -deficient solution, and the effect of Nd on their membrane damage in oilseed rape(Brassica napus L.) was studied. It shows that the symptom of Ca-starvation is relieved and the peroxidation process in rape is inhibited. It indicates that adding Nd can lower relative permeability of the root and MDA content in leaves and increase CAT, POD, and SOD activities in rape. Likewise, the Nd addition to Hoagland solution shags similar result. The interpretation is that the effect is a consequence of substitution of Nd function for some Ca function through interacting with cellular membrane.
文摘The effects of carbonate on the exchangeability and the bioavailability of exogenous neodymium in soil were studied by 147 Nd isotopic tracer method. Exchangeable Nd was extracted by 1 mol·L -1 NaAc (pH8 2) in the experiment. The results indicate that whether carbonate exists in soil or not, beyond 99% of exogenous Nd is adsorbed by soil. Low-concentration carbonate (0 8～1 6 g·kg -1 ) can reduce exchangeable Nd concentration in soil, while high-concentration carbonate (4 0 g·kg -1 ) impacts little on the exchangeable Nd concentration. In addition, carbonate of 0 8～1 6 g·kg -1 in soil can inhibit wheat seedlings to absorb Nd. However, when the carbonate concentration rises to 4 0 g·kg -1 , the inhibition will become indistinct.
基金This study was supported by grants from the National Nat-ural Science Foundation of China(81872237)the Science Tech-nology Program of Zhejiang Province on the Scientific Re-search Project(LGF19H160018,LQ18H160028 and LY17H160069)Zhejiang Provincial Health Department Project(2017KY161 and 2015KYB434)。
文摘Cholelithiasis is a common and frequently occurring disease in East Asia.Intrahepatic bile duct stone is a benign disease,but the recurrence rate is high.The incidence of postoperative residual stones after traditional manual stone removal can be30%–96%^([1]).The emergence of endoscopes is therefore a milestone in the treatment of hepatolithiasis.Among the various approaches,choledochoscopy combined with laser lithotripsy has become the main procedure for intrahepatic bile duct stone removal^([2]).Lithotripsy alone has the disadvantages of low stoneremoving efficiency and blurred choledochoscope vision while performing the procedure.Currently,our team has achieved satisfactory results in the removal of intrahepatic bile duct stones with low-pressure pulse flushing and neodymium laser lithotripsy.
文摘Observation with the transmission electronic microscopy shows that Nd can not enter into the cytoplasm of oilseed rape ( brassica napus L.) in solution culture. It combines with the cell wall or amasses in the intercellular space. Nd accumulates in root tip after it enters into the plants, while only a small amount of Nd is transferred to the stem and leaf via apoplasm, and the leaf contains the least of Nd. Such observations are consistent with the analytical results of Nd distribution in rape tissues in soil culture experiment. It suggests that the physiological effects of Nd in plants might mainly function on plasmalemma of root system.
文摘Polymerization of 4 vinylpyridine by complex catalyst of neodymium chloride was studied. The influence of Al/Nd(molar ratio), concentration of catalyst, reaction time and temperature on polymerization of 4 vinylpyridine was investigated. The results show that different kinds of ligand in the rare earth complex have an effect on the catalytic activity of the complex. The catalytic activity of the rare earth complex is higher than that of simple rare earth chloride. The catalytic activity of polymer supported catalyst is higher than those of the similar small molecular system.
文摘The title complex [Nd(Gly)(H 2O) 7]Cl 3 was synthesized and its crystal structure was determined by X ray diffraction to obtain a final R value of 0 026 0 and a wR value of 0 086 8. The crystal is of monoclinic system with a space groug Pm . Every two neodymium ions in the crystal are connected with a carboxyl group to form a polymeric chain molecule. And each neodymium ion is further coordinated with seven oxygen atoms from water molecules. The counter ion(Cl -) is non coordinated to fill up the space between the polymeric chains. So the Nd 3+ cation is nine coordinated and the coordination polyhedron is a trigonotetradecahedron. In addition, there exists the mirror symmetry in the complex.
文摘AIM: To compare surgical peeling and aspiration and neodymium yttrium garnet laser capsulotomy for pearl form of posterior capsule opacification(PCO).METHODS: A prospective, randomized, double blind,study was done at Rotary Eye Hospital, Maranda,Palampur, India, Santosh Medical College Hospital,Ghaziabad, India and Laser Eye Clinic, Noida India.Consecutive patients with pearl form of PCO following surgery, phacoemulsification, manual small incision cataract surgery and conventional extracapsular cataract extraction(ECCE) for age related cataract, were randomized to have peeling and aspiration or neodymium yttrium garnet laser capsulotomy. Corrected distance visual acuity(CDVA), intra-operative and postoperative complications were compared.RESULTS: A total of 634 patients participated in the study, and 314(49.5%) patients were randomized to surgical peeling and aspiration group and 320(50.5%) to the Nd:YAG laser group. The mean pre-procedural log MAR CDVA in peeling and neodymium: yttrium-aluminium-garnet(Nd:YAG) laser group was 0.80 ±0.25 and 0.86 ±0.22, respectively. The mean final CDVA in peeling group(0.22 ±0.23) was comparable to Nd:YAG group(0.24 ±0.28; t-test, P =0.240). There was a significant improvement in vision after both the procedures(P <0.001). A slightly higher percentage of patients in Nd:YAG laser group(283/88.3%) than in peeling group(262/83.4%) had a CDVA of 0.5(20/63) or better at 9mo(P <0.001). On the contrary, patients havingCDVA worse than 1.00(20/200) was also significantly higher in Nd:YAG laser group as compared to peeling group(25/7.7% vs 15/4.7%, respectively). On application of ANCOVA, there was less than 0.001% risk that PCO thickness and total laser energy had no effect on rate of complications in Nd:YAG laser group and less than 0.001% risk that PCO thickness had no effect on complications in peeling group respectively. Sum of square analysis suggests that in the Nd:YAG laser group,thick PCO had a stronger impact on complications(Fischer test probability, P r <0.0001) than thin PCO and total laser energy(Fischer test probability, P r <0.002),respectively; similarly, in peeling group, thick PCO and preoperative vision had a stronger effect on complications than thin PCO, respectively(Fischer test probability, P r <0.001). The rate of complications like uveitis(P =0.527) and cystoid macular edema(P =0.068),did not differ significantly between both the groups.However, intraocular pressure spikes(P =0.046) and retinal detachment(P<0.001) were significantly higher in Nd:YAG laser group as compared to peeling group.Retinal detachment was more common in patients having degenerative myopia(7/87.5%, P <0.001). Recurrence of pearls was the most common cause of reduction of vision in the peeling group(24/7.6%, P <0.001).CONCLUSION: There is no alternative to Nd:YAG laser capsulotomy for fibrous subtype of PCO. For pearl form of PCO, both techniques are comparable with regard to visual outcomes. Nd:YAG laser capsulotomy has a higher incidence of IOP spikes and retinal detachment whereas recurrence of pearls may occur after successful peeling and aspiration. When posterior capsulotomy is needed in patients with retinal degenerations,retinopathies and pre-existing retinal breaks, the clinician should be cautious about increased risks of possible complications of Nd:YAG laser capsulotomy.
基金Finacial support from the National Natural Science Foundation of China(21676139)。
文摘Based on the quantum chemical descriptors and the activities for isoprene polymerization of 12 neodymium carboxylates obtained by authors’earlier work,statistical analysis of data was made and a QSAR model correlating the quantum chemical descriptors and the activity was built with the partial least square(PLS)approach.The model is:A=51602εHOMO+6σ+12546,which indicates that the catalytic activity A is positively correlated with the HOMO energyεHOMOand the ligand polarizabilityσ,with the contribution ofσbeing larger,εHOMO smaller.The model’s coefficient of determination r^2=0.96 and that of cross validation q^2=0.94,both being close to 1,which means that its quality is well and its predictive power is strong.Analysis of the modeling process and the resulted QSAR model,together with the interpretation of the model’s mechanism,also shows that the model obtained from this study is valid and reliable.According to the QSAR model,the mechanism of catalyst activity can be interpreted as that neodymium carboxylates with higher HOMO energy and larger ligand polarizability are easier to react with the co-catalysts so as to produce more active and stable centers of catalyst,resulting in a higher activity.
基金financially supported by the National Natural Science Foundation of China(Nos.51574213,51074150)the Key Project of Chinese National Programs for Fundamental Research and Development(973 Program No.2012CBA01203)。
文摘The kinetics and the difference for Pr(Ⅲ)and Nd(Ⅲ)extraction from nitrate aqueous solution using trialkylmethylammonium nitrate([A336][NO3])as extractant were investigated by the single drop technique.The dependence of the extraction rate of Pr(Ⅲ)and Nd(Ⅲ)on the concentrations of free Pr(Ⅲ)and Nd(Ⅲ)ions,the concentrations of Na NO3 and H+in aqueous solutions,and the concentrations of[A336][NO3]in kerosene solutions were discussed and the corresponding extraction rate equations for Pr(Ⅲ)and Nd(Ⅲ)were obtained.These equations demonstrated that the reaction rate constant of Pr(Ⅲ)with[A336][NO3]was double than that of Nd(Ⅲ).The effect of the addition of diethylenetriaminepentaacetic acid(DTPA)on the difference in the extraction rate of Pr(Ⅲ)and Nd(Ⅲ)by[A336][NO3]was also investigated.It was revealed that the difference in the complex formation rates of Pr(Ⅲ)and Nd(Ⅲ)with DTPA made a significant impact on the difference in the extraction rates of Pr(Ⅲ)and Nd(Ⅲ)with[A336][NO3].The ratio of extraction rates of Pr(Ⅲ)to Nd(Ⅲ)with[A336][NO3]was in proportion to the ratio of complex formation rates of Pr(Ⅲ)to Nd(Ⅲ)with DTPA.The extraction rate difference for Pr(Ⅲ)and Nd(Ⅲ)with[A336][NO3]increased due to a higher complex formation rate constant of DTPA with the free and un-complexed Nd(Ⅲ)ions in the aqueous nitrate solution than that with Pr(Ⅲ)ions.Therefore,the addition of DTPA in the aqueous nitrate solution is an effective method to intensify the separation of Pr(Ⅲ)and Nd(Ⅲ)in kinetics.The study on the extraction mechanism indicated that both the extraction of Pr(Ⅲ)and Nd(Ⅲ)by[A336][NO3]were diffusion controlled,and the reactions obeyed SN2 mechanism.The present work highlights a possible approach to strengthen the kinetic separation of Pr(Ⅲ)and Nd(Ⅲ).
基金This work was supported by the National Natural Science Foundation of China (No. 29674027, No. 29844002), the Ministry of National Education (G98402) and Organometallic Laboratory of Institute of Organic Chemistry of Chinese Academy of Sciences.
文摘Ring-opening polymerization of trimethylene carbonate (TMC) with a rare earth calixarene compound as catalysthas been studied for the first time. The effect of TMC/Nd (molar ratio) and polymerization conditions were investigated indetail. It was found that calix[8]arene-neodymium is a highly effective catalyst for the bulk polymerization of TMC and giveshigh molecular weight (M_v = 60,000) polymer. The optimum conditions of TMC polymerization were found to be asfollows:TMC/Nd (molar ratio) = 2,000, 80℃, 16 h. The polymers were characterized by NMR, GPC and DSC. Studying themechanism by NMR showed that the polymerization of TMC catalyzed by calix[8]arene-neodymium proceeds via a cationicmechanism.
文摘Polymerization of styrene and 1,3-butadiene were performed by calix[4]arene neodymium complexes using di-n-butylmagnesium and tri-iso-butylaluminum as cocatalyst respectively. The effect of the substituent groups in calix[4]arene on the catalytic activity was first investigated.
文摘The neodymium electrolysis produces unnecessary high emission of CF4 and C2F6. These perfluorocarbons (PFCs) are potent greenhouse gases and are not filtered or destroyed in the off-gas. A process control in analogy to the aluminum electrolysis can reduce the PFC emission to a great extend and keep the process in a green process window. Therefore, a theoretical analysis is done of the cell voltage of the industrial neodymium electrolysis in dependence on the neodymium oxide concentration in the electrolyte. The analysis shows the different contributions to the cell voltage focusing on the impact of the anodic overvoltage on the cell voltage, by which the electrolysis process can be controlled. The model of the cell voltage is evaluated by laboratory neodymium electrolysis with a similar setup as the industrial cell. The relation of the oxide concentration, the anodic current density and the cell voltage with the cell resistance are measured. The continuous off-gas measurements show the gas concentration and PFC emissions. The effect of Nd2O3 feeding on the galvanostatic electrolysis is analyzed as well. Based on the results a process control strategy is proposed similar to the aluminum electrolysis strategy. The green process window is in a narrow oxide concentration range, making a continuous and precise oxide feeding essential.
基金Project supported by the Science Fund of the Chinese Academy of Sciences.
文摘The cyclic voltammetry was used to investigate the electrode processes of Nd(Ⅲ)reduced on iron electrode and Nd(Ⅲ),Fe(Ⅱ)reduced on molybdenum electrode in molten chlorides.The Nd-Fe and Nd-rich RE-Fe alloys contained rare earth up to90wt% were prepared by consumable cathode and electrolytic codeposition.The mechanism of electrochemical formation ofNd-Fe alloy had been discussed.
基金The project supported by the National Natural Science Foundation of China
文摘The nonrelativistic DV-X<sub>α</sub>-SCC method was used to study the electronic structure and chemi-cal bonding of tetranuclear neodymium complex Nd<sub>4</sub>O（OR）<sub>4</sub>（NR′<sub>2</sub>）<sub>6</sub>,with emphasis on the bonding charac-ter of the central μ<sub>4</sub>-O atom and the four Nd atoms.The results of calculation show that the μ<sub>4</sub>-O atom usesits sp<sup>3</sup> valence orbitals to contribute four O-Nd bonding MOs with character of multicenter bond apparent-ly.The Mulliken population analysis shows that the overlap population between Nd atoms is almost equal tozero,therefore there is no direct metal-metal bond between Nd atoms.The coordination number of Nd in thecomplex is discussed briefly.
文摘In view of the problems of slower precipitation rate and lower recovery rate in the traditional preparation process of neodymium fluoride, the process of conversion with ammonia bicarbonate and adding macromolecular precipitant aid to prepare neodymium fluoride was studied. The effect of HF amount, reaction temperature, rare earth concentrations and macromolecular precipitating aid on the recovery rate of rare earth and its precipitation rate were investigated. The particulate size, morphology and composition of NdF3 were analyzed by TEM, XRD, etc. A feasible process to produce good crystal degree neodymium fluoride with rapid precipitation and higher recovery rate was obtained.
文摘The neodymium complexes with crosslinked polystyrene containing —CH 2SH and —CH 2SOCH 3 groups, P—CH 2SH·NdCl 3 and P—CH 2SOCH 3·NdCl 3, were prepared. P—CH 2SH·NdCl 3 shows no catalytic activity for butadiene polymerization, while P—CH 2SOCH 3·NdCl 3 can catalyze the polymerization of butadiene. The content of cis 1,4 polybutadiene is more than 95%.
文摘The title compound, [Nd(dmso) 7Cl][Bph 4] 2(dmso=dimethylsulfoxide, Bph 4=tetraphenylboron anion) was synthesized in organic solvent acetone/EtOH and the structure was determined by single crystal X ray diffraction. The crystal is triclinic with space group P 1, and the crystal data are as follows: a =1 2554(1) nm, b = 1 2799(1) nm, c =2 4598(3) nm; α =93 53(1)°, β =104 50(1)°, γ =112 77(1)°, V =3 4722(6) nm 3, Z =2, M r=1365 01, D c=1 306 g·cm -3 . The crystal is composed of a big cation [Nd(dmso) 7Cl] 2+ and two big anions [BPh 4] -. The Nd 3+ is coordinated by a chlorine atom and seven oxygen atoms from seven dimethylsulfoxides forming a distorted square antiprism coordination polyhedron,while the BPh - 4 anion is charge equilibrium ion.
