The lipases from different sources were screened for their ability to catalyze the resolution of 2-octanol in organic solvents with vinyl acetate as the acylating reagent. The medium effect has been studied on the irr...The lipases from different sources were screened for their ability to catalyze the resolution of 2-octanol in organic solvents with vinyl acetate as the acylating reagent. The medium effect has been studied on the irreversible transesterification with varying water activity(a_w). The influence of vinyl acetate concentration on it has also been investigated. Under the optimal conditions, the enantiomeric ratio(E value) of pseudomonas fluorescence lipase(PFL) exceeded 200 with an enantiomeric excess(e.e.) of S-2-octanol above 99% at a 51% degree of conversion.展开更多
BACKGROUND Neurovascular compression(NVC) is the main cause of primary trigeminal neuralgia(TN) and hemifacial spasm(HFS). Microvascular decompression(MVD) is an effective surgical method for the treatment of TN and H...BACKGROUND Neurovascular compression(NVC) is the main cause of primary trigeminal neuralgia(TN) and hemifacial spasm(HFS). Microvascular decompression(MVD) is an effective surgical method for the treatment of TN and HFS caused by NVC. The judgement of NVC is a critical step in the preoperative evaluation of MVD, which is related to the effect of MVD treatment. Magnetic resonance imaging(MRI) technology has been used to detect NVC prior to MVD for several years. Among many MRI sequences, three-dimensional time-of-flight magnetic resonance angiography(3D TOF MRA) is the most widely used. However, 3D TOF MRA has some shortcomings in detecting NVC. Therefore, 3D TOF MRA combined with high resolution T2-weighted imaging(HR T2WI) is considered to be a more effective method to detect NVC.AIM To determine the value of 3D TOF MRA combined with HR T2WI in the judgment of NVC, and thus to assess its value in the preoperative evaluation of MVD.METHODS Related studies published from inception to September 2022 based on PubMed, Embase, Web of Science, and the Cochrane Library were retrieved. Studies that investigated 3D TOF MRA combined with HR T2WI to judge NVC in patients with TN or HFS were included according to the inclusion criteria. Studies without complete data or not relevant to the research topics were excluded. The Quality Assessment of Diagnostic Accuracy Studies checklist was used to assess the quality of included studies. The publication bias of the included literature was examined by Deeks’ test. An exact binomial rendition of the bivariate mixed-effects regression model was used to synthesize data. Data analysis was performed using the MIDAS module of statistical software Stata 16.0. Two independent investigators extracted patient and study characteristics, and discrepancies were resolved by consensus. Individual and pooled sensitivities and specificities were calculated. The I_(2) statistic and Q test were used to test heterogeneity. The study was registered on the website of PROSERO(registration No. CRD42022357158).RESULTS Our search identified 595 articles, of which 12(including 855 patients) fulfilled the inclusion criteria. Bivariate analysis showed that the pooled sensitivity and specificity of 3D TOF MRA combined with HR T2WI for detecting NVC were 0.96 [95% confidence interval(CI): 0.92-0.98] and 0.92(95%CI: 0.74-0.98), respectively. The pooled positive likelihood ratio was 12.4(95%CI: 3.2-47.8), pooled negative likelihood ratio was 0.04(95%CI: 0.02-0.09), and pooled diagnostic odds ratio was 283(95%CI: 50-1620). The area under the receiver operating characteristic curve was 0.98(95%CI: 0.97-0.99). The studies showed no substantial heterogeneity(I2 = 0, Q = 0.001 P = 0.50).CONCLUSION Our results suggest that 3D TOF MRA combined with HR T2WI has excellent sensitivity and specificity for judging NVC in patients with TN or HFS. This method can be used as an effective tool for preoperative evaluation of MVD.展开更多
（R）-2-Chloro-l-（m-chlorophenyl）ethanol,a precursor of（R）-3-chlorostyrene oxide which is the key chiral intermediate for the preparation of severalβ3-adrenergic receptor agonists was prepared in 40%yield and 99%...（R）-2-Chloro-l-（m-chlorophenyl）ethanol,a precursor of（R）-3-chlorostyrene oxide which is the key chiral intermediate for the preparation of severalβ3-adrenergic receptor agonists was prepared in 40%yield and 99%ee by the Lipozyme TL IM-catalyzed second resolution of the corresponding racemate in the presence of vinyl acetate.展开更多
Menthol reacts with phosphorus trichloride to afford menthyl phosphorodichloridite 2, which further reacts with racemic 1, 1-binaphthalene-2, 2-diol to give phosphite (+)-3 in the presence of triethylamine. (+)-3 can ...Menthol reacts with phosphorus trichloride to afford menthyl phosphorodichloridite 2, which further reacts with racemic 1, 1-binaphthalene-2, 2-diol to give phosphite (+)-3 in the presence of triethylamine. (+)-3 can be easily separated by fractional crystallization to form the crystal (+)-(S)-3 and the mother liquor (-)-(R)-3. Then both the crystal and the mother liquor are treated with AcOH-H2O to obtain enantiomeric pure (-)-(S)-1 and (+)-(R)-1 respectively, with enantiomeric excess up to 99.7%.展开更多
Excellent resolution of racemic 2-phenyl-1,1-cyclopropanedicarbonitrile and its nine analogues was accomplished using 100-5CH1-TBB chiral stationary phase under normal-phase HPLC conditions. The influence of mobile ph...Excellent resolution of racemic 2-phenyl-1,1-cyclopropanedicarbonitrile and its nine analogues was accomplished using 100-5CH1-TBB chiral stationary phase under normal-phase HPLC conditions. The influence of mobile phase and the optimum conditions for the resolution of optically active enantiomers were investigated.展开更多
Racemic 2-n-butylbutanedioic acid 4-t-butyl esters were synthesized from methyl hexanoate and t-butyl α-iodoacetate via alkylation and subsequently selective hydrolyzation. The （R）-and （S）-2-n-butylbutanedioic ac...Racemic 2-n-butylbutanedioic acid 4-t-butyl esters were synthesized from methyl hexanoate and t-butyl α-iodoacetate via alkylation and subsequently selective hydrolyzation. The （R）-and （S）-2-n-butylbutanedioic acid 4-t-butyl esters were obtained by the resolution of the above-mentioned racemic compounds with（S）-（ - ） or（R）-（ ＋ ）-α- methylbenzylamine, respectively. The e.e. values of the two optical active products were determined to be above 99% by HPLC after the formation of two pairs of diastereoisomers with（R）-（ ＋ ）-α-methylbenzylamine and（S）- phenylalanine methyl ester.展开更多
A practical synthesis of （S）-N-（2-ethyl-6-methylphenyl）alanine, a key intermediate for （S）-metolachlor, was completed by means of lipase-catalyzed hydrolytic kinetic resolution and chemical racemization of the r...A practical synthesis of （S）-N-（2-ethyl-6-methylphenyl）alanine, a key intermediate for （S）-metolachlor, was completed by means of lipase-catalyzed hydrolytic kinetic resolution and chemical racemization of the remaining ester. The effects of operating temperature and enzyme concentration on the activity and enantioselectivity of enzyme were initially studied, and it was found that the enantioselectivity of CAL-B towards the resolution was not high enough to obtain enantiomerically pure compound（E=12.1）. When diethyl ether（15%, volume fraction） was added in the reaction medium, the lipase gave an excellent enantioselectivity（E=117.8）, which is about 9.7-fold that in pure buffered aqueous solution. For overcoming the limitation of a maximum theoretical yield of 50%, the acid product was separated from the remaining ester by a simple extraction procedure and the remaining ester was racemized with aldehyde and acetic acid under microwave irradiation or conventional heating condition, The results show the microwave irradiation was more effective than the conventional heating method and gave the desired （R,S）-N-（2- ethyl-6-methylphenyl）alanine methyl ester a high yield（92%） with R/S=50/50 in 1 h.展开更多
Regardless of thermodynamic stability, less complex proteome than plasma, convenient and noninvasive sampling of urine, reproducibility and comparability of the data among laboratories are challenges for the urine pro...Regardless of thermodynamic stability, less complex proteome than plasma, convenient and noninvasive sampling of urine, reproducibility and comparability of the data among laboratories are challenges for the urine proteome analysis. Pretreatment of urine with 10 mM EDTA in conjunction with desalting methods to remove interfering molecules significantly improved the presentation of urine proteome on 2-D gels. Statistical analysis of the average ratio of the spot numbers on 2-D gels between EDTA-treated and non-treated samples were 1.35 ± 0.167, 1.26 ± 0.091, and 1.24 ± 0.095 for dialysis, ultrafiltration, and desalting column, respectively, with the p-value of 5.85 × 10–6 for the overall comparison. This result came from the fact that EDTA-treated samples showed better resolutions with less streaks and clearer spots on 2-D gels than the control samples. The results suggest that a simple and non-fractionating EDTA-treatment can be employed to the procedures for the high resolution 2-D gel analysis and other urinary proteomic analysis.展开更多
A BaF2 time differential perturbed angular distribution spectrometer has been established at the HI-13 tandem accelerator in CIAE. The time resolution of the spectrometer is 195 ps and the nonlinearity is less than 2 ...A BaF2 time differential perturbed angular distribution spectrometer has been established at the HI-13 tandem accelerator in CIAE. The time resolution of the spectrometer is 195 ps and the nonlinearity is less than 2 %. The spectrometer works very stably and no time drift is found over a period of experimelltal ruffs. This spectrometer has been successfully used in the g-factor measurement of 43 Sc (19/2-,3.1232 MeV).展开更多
The 1D τ-p inversion algorithm is widely employed to generate starting models with most computer programs that implement refraction tomography. However, this algorithm emphasizes the vertical resolution of many layer...The 1D τ-p inversion algorithm is widely employed to generate starting models with most computer programs that implement refraction tomography. However, this algorithm emphasizes the vertical resolution of many layers, and as a result, it frequently fails to detect even large lateral variations in seismic velocities, such as the decreases that are indicative of shear zones. This study presents a case that demonstrates the failure of the 1D τ-p inversion algorithm to define or even detect a major shear zone that is 50 m or ten stations wide. Furthermore, the majority of refraction tomography programs parameterize the seismic velocities within each layer with vertical velocity gradients. By contrast, the 2D generalized reciprocal method （GRM） inversion algorithms emphasize the lateral resolution of individual layers. This study demonstrates the successful detection and definition of the 50-m wide shear zone with the GRM inversion algorithms. The existence of the shear zone is corroborated by a 2D analysis of the head wave amplitudes and by numerous closely spaced orthogonal seismic profiles carried out as part of a later 3D refraction investigation. Furthermore, a 1D analysis of the head wave amplitudes indicates that a reversal in the seismic velocities, rather than vertical velocity gradients, occurs in the weathered layers. While all seismic refraction operations should aim to provide as accurate depth estimates as is practical, the major conclusion reached in this study is that refraction inversion algorithms that emphasize the lateral resolution of individual layers generate more useful results for geotechnical and environmental applications. The advantages of the improved lateral resolution are obtained with 2D profiles in which the structural features can be recognized from the magnitudes of the variations in the seismic velocities. Furthermore, the spatial patterns obtained with 3D investigations facilitate the recognition of structural features that do not display any intrinsic variation or ＂signature＂ in seismic velocities.展开更多
RS-3-chloro-2-oxy-propyltrimethylammonium-chloride 1, an important inter- mediate of carnitine and acetylcholine, has been synthesized and resolved by using R,R-tartric acid. Di-(S-3-chloro-2-oxy-propyltrimethylammoni...RS-3-chloro-2-oxy-propyltrimethylammonium-chloride 1, an important inter- mediate of carnitine and acetylcholine, has been synthesized and resolved by using R,R-tartric acid. Di-(S-3-chloro-2-oxy-propyltrimethylammonium)-R,R-tartrate 2, with optical purity of 81.76%, has been obtained. Compound 2 was characterized by IR spectroscopy, MS, NMR and X-ray diffrac- tion, and it crystallizes in orthorhombic, space group P212121, absolute structure parameter 0.56(8), with cell parameters a = 8.323(2), b = 10.203(2), c = 26.178(5) ? C16H34Cl2N2O8, Mr = 453.272, V = 2223.0(8) ?, Z = 4, Dc = 1.354 g/cm3, m = 0.335 mm-1, F(000) = 968, R = 0.0534 and wR = 0.1274 for 4376 observed reflections (I > 2s(I)). The lattice is composed of two S-3-chloro- 2-oxy-propyltrimethylammonium cations and one R,R-tartrate dianion which are arranged in separate stacks linked via hydrogen bonds.展开更多
We report here a generic,green synthesis of 17 valuable syn-aryl-(2S,3R)-2–chloro-3–hydroxy esters(syn-(2S,3R)-1)in 73%-99%isolated yields along with 6.1:1–83:1 dr and 31%~>99%ee,through dynamic reductive kineti...We report here a generic,green synthesis of 17 valuable syn-aryl-(2S,3R)-2–chloro-3–hydroxy esters(syn-(2S,3R)-1)in 73%-99%isolated yields along with 6.1:1–83:1 dr and 31%~>99%ee,through dynamic reductive kinetic resolution of racemic arylα–chloroβ-keto esters(2)catalyzed by an engineered ketoreductase which was obtained via ep PCR-based directed evolution.The hectogram scale synthesis of syn-(2S,3R)-1b at a substrate concentration of 120 g/L showcased the application potential of the biocatalytic method developed presently.展开更多
The optically active R-4-phenyl-2-hydroxy butyrates were prepared by esterification of the racemic acid or transesterification of the racemic ester catalyzed by lipase from Candida cyclindra (CCL) in organic media.
The spectral resolution is a main index of evaluating the performance of the designed acousto-optic tunable filter (AOTF). In this letter, an accurate expression of the spectral resolution is presented by considering ...The spectral resolution is a main index of evaluating the performance of the designed acousto-optic tunable filter (AOTF). In this letter, an accurate expression of the spectral resolution is presented by considering both the birefringence and the rotatory property of TeO2 crystal. The deduced expression is significant in improving the accuracy of the design of an AOTF and pushing the development of the high-performance AOTF.展开更多
Using infrared sensors to detect ice clouds in different atmospheric layers is still a challenge.The different scattering and absorption properties of longwave and shortwave infrared channels can be utilized to fulfil...Using infrared sensors to detect ice clouds in different atmospheric layers is still a challenge.The different scattering and absorption properties of longwave and shortwave infrared channels can be utilized to fulfill this purpose.In this study,the release of Suomi-NPP Cross-track Infrared Sounder(Cr IS)full spectrum resolution is used to select and pair channels from longwave(~15μm)and shortwave(~4.3μm)CO2 absorption bands under stricter conditions,so as to better detect ice clouds.Besides,the differences of the weighting function peaks and cloud insensitive level altitudes of the paired channels are both within 50 h Pa so that the variances due to atmospheric conditions can be minimized.The training data of clear sky are determined by Visible Infrared Imaging Radiometer Suite(VIIRS)cloud mask product and used to find the linear relationship between the paired longwave and shortwave CO2 absorption channels.From the linear relationship,the so-called cloud emission and scattering index(CESI)is derived to detect ice clouds.CESI clearly captures the center and the ice cloud features of the Super Typhoon Hato located above 415 h Pa.Moreover,the CESI distributions agree with cloud top pressure from the VIIRS in both daytime and nighttime in different atmospheric layers.展开更多
Soil moisture plays an important role in crop yield estimation,irrigation management,etc.Remote sensing technology has potential for large-scale and high spatial soil moisture mapping.However,offline remote sensing da...Soil moisture plays an important role in crop yield estimation,irrigation management,etc.Remote sensing technology has potential for large-scale and high spatial soil moisture mapping.However,offline remote sensing data processing is time-consuming and resource-intensive,and significantly hampers the efficiency and timeliness of soil moisture mapping.Due to the high-speed computing capabilities of remote sensing cloud platforms,a High Spatial Resolution Soil Moisture Estimation Framework(HSRSMEF)based on the Google Earth Engine(GEE)platform was developed in this study.The functions of the HSRSMEF include research area and input datasets customization,radar speckle noise filtering,optical-radar image spatio-temporal matching,soil moisture retrieving,soil moisture visualization and exporting.This paper tested the performance of HSRSMEF by combining Sentinel-1,Sentinel-2 images and insitu soil moisture data in the central farmland area of Jilin Province,China.Reconstructed Normalized Difference Vegetation Index(NDVI)based on the Savitzky-Golay algorithm conforms to the crop growth cycle,and its correlation with the original NDVI is about 0.99(P<0.001).The soil moisture accuracy of the random forest model(R 2=0.942,RMSE=0.013 m3/m3)is better than that of the water cloud model(R 2=0.334,RMSE=0.091 m3/m3).HSRSMEF transfers time-consuming offline operations to cloud computing platforms,achieving rapid and simplified high spatial resolution soil moisture mapping.展开更多
Objective: This study aimed to investigate the anti-inflammatory and analgesic mechanisms of a breast lump resolution detergent in a rat model of breast hyperplasia. Methods: A rat model of breast hyperplasia was esta...Objective: This study aimed to investigate the anti-inflammatory and analgesic mechanisms of a breast lump resolution detergent in a rat model of breast hyperplasia. Methods: A rat model of breast hyperplasia was established using injections of estradiol benzoate combined with progesterone. The effects of the breast lump resolution detergent on nipple height and diameter in the rat model were observed, along with its impact on serum levels of estradiol (E2), prolactin (PRL), and progesterone (P). Additionally, the study examined the morphological changes in breast tissue. The impact of the breast nodule detergent on blood rheology parameters was also observed. Furthermore, the anti-inflammatory effect of the breast nodule detergent was assessed using the cotton ball granuloma experiment, and the analgesic effect was observed using the writhing test. Results: The breast lump resolution detergent reduced nipple height and diameter in the rat model, decreased serum levels of E2, PRL, and P, and alleviated pathological changes in breast tissue. It also lowered hemorheological parameters including whole blood high, medium, and low shear viscosity, plasma viscosity, red blood cell hematocrit, red blood cell aggregation index, red blood cell deformability index, red blood cell electrophoresis time, and erythrocyte sedimentation rate in the acute “blood stasis” rat model. The detergent reduced the weight of cotton ball granulomas in mice and decreased the number of writhing episodes caused by acetic acid. Conclusion: The breast lump resolution detergent demonstrates favorable therapeutic effects in treating breast hyperplasia, promoting blood circulation and removing blood stasis, exerting anti-inflammatory properties, and providing analgesic effects. The downregulation of serum E2 and PRL levels and the upregulation of P levels may be critical mechanisms underlying its efficacy.展开更多
High-resolution atomic-beam laser spectroscopy has been performed to study Stark effect of Ba atom. Stark spectra have been observed at various electric fields for Ba highly excited states. The scalar polarizability o...High-resolution atomic-beam laser spectroscopy has been performed to study Stark effect of Ba atom. Stark spectra have been observed at various electric fields for Ba highly excited states. The scalar polarizability of the transition from 6s5d3D2 to 5d6p3F3 at 728.0 nm and the tensor polarizability of the 3F3 level have been determined for the first time, to be αs = -89.8 (12) kHz/(kV/cm)2 and αt = -133.7 (20) kHz/(kV/cm)2, respectively.展开更多
基金Supported by the National Natural Science Foundation of China(No.2 0 0 72 0 11and2 0 2 72 0 17)
文摘The lipases from different sources were screened for their ability to catalyze the resolution of 2-octanol in organic solvents with vinyl acetate as the acylating reagent. The medium effect has been studied on the irreversible transesterification with varying water activity(a_w). The influence of vinyl acetate concentration on it has also been investigated. Under the optimal conditions, the enantiomeric ratio(E value) of pseudomonas fluorescence lipase(PFL) exceeded 200 with an enantiomeric excess(e.e.) of S-2-octanol above 99% at a 51% degree of conversion.
基金Supported by the Key Research and Development Plan of Shaanxi Province,No.2021SF-298.
文摘BACKGROUND Neurovascular compression(NVC) is the main cause of primary trigeminal neuralgia(TN) and hemifacial spasm(HFS). Microvascular decompression(MVD) is an effective surgical method for the treatment of TN and HFS caused by NVC. The judgement of NVC is a critical step in the preoperative evaluation of MVD, which is related to the effect of MVD treatment. Magnetic resonance imaging(MRI) technology has been used to detect NVC prior to MVD for several years. Among many MRI sequences, three-dimensional time-of-flight magnetic resonance angiography(3D TOF MRA) is the most widely used. However, 3D TOF MRA has some shortcomings in detecting NVC. Therefore, 3D TOF MRA combined with high resolution T2-weighted imaging(HR T2WI) is considered to be a more effective method to detect NVC.AIM To determine the value of 3D TOF MRA combined with HR T2WI in the judgment of NVC, and thus to assess its value in the preoperative evaluation of MVD.METHODS Related studies published from inception to September 2022 based on PubMed, Embase, Web of Science, and the Cochrane Library were retrieved. Studies that investigated 3D TOF MRA combined with HR T2WI to judge NVC in patients with TN or HFS were included according to the inclusion criteria. Studies without complete data or not relevant to the research topics were excluded. The Quality Assessment of Diagnostic Accuracy Studies checklist was used to assess the quality of included studies. The publication bias of the included literature was examined by Deeks’ test. An exact binomial rendition of the bivariate mixed-effects regression model was used to synthesize data. Data analysis was performed using the MIDAS module of statistical software Stata 16.0. Two independent investigators extracted patient and study characteristics, and discrepancies were resolved by consensus. Individual and pooled sensitivities and specificities were calculated. The I_(2) statistic and Q test were used to test heterogeneity. The study was registered on the website of PROSERO(registration No. CRD42022357158).RESULTS Our search identified 595 articles, of which 12(including 855 patients) fulfilled the inclusion criteria. Bivariate analysis showed that the pooled sensitivity and specificity of 3D TOF MRA combined with HR T2WI for detecting NVC were 0.96 [95% confidence interval(CI): 0.92-0.98] and 0.92(95%CI: 0.74-0.98), respectively. The pooled positive likelihood ratio was 12.4(95%CI: 3.2-47.8), pooled negative likelihood ratio was 0.04(95%CI: 0.02-0.09), and pooled diagnostic odds ratio was 283(95%CI: 50-1620). The area under the receiver operating characteristic curve was 0.98(95%CI: 0.97-0.99). The studies showed no substantial heterogeneity(I2 = 0, Q = 0.001 P = 0.50).CONCLUSION Our results suggest that 3D TOF MRA combined with HR T2WI has excellent sensitivity and specificity for judging NVC in patients with TN or HFS. This method can be used as an effective tool for preoperative evaluation of MVD.
基金support from the National Natural Science Foundation of China(No20672110)
文摘（R）-2-Chloro-l-（m-chlorophenyl）ethanol,a precursor of（R）-3-chlorostyrene oxide which is the key chiral intermediate for the preparation of severalβ3-adrenergic receptor agonists was prepared in 40%yield and 99%ee by the Lipozyme TL IM-catalyzed second resolution of the corresponding racemate in the presence of vinyl acetate.
基金Financial Support by the National Natural Science Foundation of China (No.29872016) the Hong Kong Polytechnic University ASD Fund are gratefully acknowledged.
文摘Menthol reacts with phosphorus trichloride to afford menthyl phosphorodichloridite 2, which further reacts with racemic 1, 1-binaphthalene-2, 2-diol to give phosphite (+)-3 in the presence of triethylamine. (+)-3 can be easily separated by fractional crystallization to form the crystal (+)-(S)-3 and the mother liquor (-)-(R)-3. Then both the crystal and the mother liquor are treated with AcOH-H2O to obtain enantiomeric pure (-)-(S)-1 and (+)-(R)-1 respectively, with enantiomeric excess up to 99.7%.
文摘Excellent resolution of racemic 2-phenyl-1,1-cyclopropanedicarbonitrile and its nine analogues was accomplished using 100-5CH1-TBB chiral stationary phase under normal-phase HPLC conditions. The influence of mobile phase and the optimum conditions for the resolution of optically active enantiomers were investigated.
基金Supported by the National Basic Research Priority Program(No. 2003CCA027).
文摘Racemic 2-n-butylbutanedioic acid 4-t-butyl esters were synthesized from methyl hexanoate and t-butyl α-iodoacetate via alkylation and subsequently selective hydrolyzation. The （R）-and （S）-2-n-butylbutanedioic acid 4-t-butyl esters were obtained by the resolution of the above-mentioned racemic compounds with（S）-（ - ） or（R）-（ ＋ ）-α- methylbenzylamine, respectively. The e.e. values of the two optical active products were determined to be above 99% by HPLC after the formation of two pairs of diastereoisomers with（R）-（ ＋ ）-α-methylbenzylamine and（S）- phenylalanine methyl ester.
基金Supported by the National Natural Science Foundation of China(No.20802025)the Hi-Tech Research and Development Program of China(No.2007AA021306)Jilin Provincial Science & Technology Sustentation Program,China(No.20070553)
文摘A practical synthesis of （S）-N-（2-ethyl-6-methylphenyl）alanine, a key intermediate for （S）-metolachlor, was completed by means of lipase-catalyzed hydrolytic kinetic resolution and chemical racemization of the remaining ester. The effects of operating temperature and enzyme concentration on the activity and enantioselectivity of enzyme were initially studied, and it was found that the enantioselectivity of CAL-B towards the resolution was not high enough to obtain enantiomerically pure compound（E=12.1）. When diethyl ether（15%, volume fraction） was added in the reaction medium, the lipase gave an excellent enantioselectivity（E=117.8）, which is about 9.7-fold that in pure buffered aqueous solution. For overcoming the limitation of a maximum theoretical yield of 50%, the acid product was separated from the remaining ester by a simple extraction procedure and the remaining ester was racemized with aldehyde and acetic acid under microwave irradiation or conventional heating condition, The results show the microwave irradiation was more effective than the conventional heating method and gave the desired （R,S）-N-（2- ethyl-6-methylphenyl）alanine methyl ester a high yield（92%） with R/S=50/50 in 1 h.
文摘Regardless of thermodynamic stability, less complex proteome than plasma, convenient and noninvasive sampling of urine, reproducibility and comparability of the data among laboratories are challenges for the urine proteome analysis. Pretreatment of urine with 10 mM EDTA in conjunction with desalting methods to remove interfering molecules significantly improved the presentation of urine proteome on 2-D gels. Statistical analysis of the average ratio of the spot numbers on 2-D gels between EDTA-treated and non-treated samples were 1.35 ± 0.167, 1.26 ± 0.091, and 1.24 ± 0.095 for dialysis, ultrafiltration, and desalting column, respectively, with the p-value of 5.85 × 10–6 for the overall comparison. This result came from the fact that EDTA-treated samples showed better resolutions with less streaks and clearer spots on 2-D gels than the control samples. The results suggest that a simple and non-fractionating EDTA-treatment can be employed to the procedures for the high resolution 2-D gel analysis and other urinary proteomic analysis.
文摘A BaF2 time differential perturbed angular distribution spectrometer has been established at the HI-13 tandem accelerator in CIAE. The time resolution of the spectrometer is 195 ps and the nonlinearity is less than 2 %. The spectrometer works very stably and no time drift is found over a period of experimelltal ruffs. This spectrometer has been successfully used in the g-factor measurement of 43 Sc (19/2-,3.1232 MeV).
文摘The 1D τ-p inversion algorithm is widely employed to generate starting models with most computer programs that implement refraction tomography. However, this algorithm emphasizes the vertical resolution of many layers, and as a result, it frequently fails to detect even large lateral variations in seismic velocities, such as the decreases that are indicative of shear zones. This study presents a case that demonstrates the failure of the 1D τ-p inversion algorithm to define or even detect a major shear zone that is 50 m or ten stations wide. Furthermore, the majority of refraction tomography programs parameterize the seismic velocities within each layer with vertical velocity gradients. By contrast, the 2D generalized reciprocal method （GRM） inversion algorithms emphasize the lateral resolution of individual layers. This study demonstrates the successful detection and definition of the 50-m wide shear zone with the GRM inversion algorithms. The existence of the shear zone is corroborated by a 2D analysis of the head wave amplitudes and by numerous closely spaced orthogonal seismic profiles carried out as part of a later 3D refraction investigation. Furthermore, a 1D analysis of the head wave amplitudes indicates that a reversal in the seismic velocities, rather than vertical velocity gradients, occurs in the weathered layers. While all seismic refraction operations should aim to provide as accurate depth estimates as is practical, the major conclusion reached in this study is that refraction inversion algorithms that emphasize the lateral resolution of individual layers generate more useful results for geotechnical and environmental applications. The advantages of the improved lateral resolution are obtained with 2D profiles in which the structural features can be recognized from the magnitudes of the variations in the seismic velocities. Furthermore, the spatial patterns obtained with 3D investigations facilitate the recognition of structural features that do not display any intrinsic variation or ＂signature＂ in seismic velocities.
文摘RS-3-chloro-2-oxy-propyltrimethylammonium-chloride 1, an important inter- mediate of carnitine and acetylcholine, has been synthesized and resolved by using R,R-tartric acid. Di-(S-3-chloro-2-oxy-propyltrimethylammonium)-R,R-tartrate 2, with optical purity of 81.76%, has been obtained. Compound 2 was characterized by IR spectroscopy, MS, NMR and X-ray diffrac- tion, and it crystallizes in orthorhombic, space group P212121, absolute structure parameter 0.56(8), with cell parameters a = 8.323(2), b = 10.203(2), c = 26.178(5) ? C16H34Cl2N2O8, Mr = 453.272, V = 2223.0(8) ?, Z = 4, Dc = 1.354 g/cm3, m = 0.335 mm-1, F(000) = 968, R = 0.0534 and wR = 0.1274 for 4376 observed reflections (I > 2s(I)). The lattice is composed of two S-3-chloro- 2-oxy-propyltrimethylammonium cations and one R,R-tartrate dianion which are arranged in separate stacks linked via hydrogen bonds.
基金The National Key Research and Development Program of China(Nos.2021YFA0911400 and 2021YFF0600704)the National Natural Science Foundation of China(Nos.22071033 and 21801047)are acknowledged for the financial supports。
文摘We report here a generic,green synthesis of 17 valuable syn-aryl-(2S,3R)-2–chloro-3–hydroxy esters(syn-(2S,3R)-1)in 73%-99%isolated yields along with 6.1:1–83:1 dr and 31%~>99%ee,through dynamic reductive kinetic resolution of racemic arylα–chloroβ-keto esters(2)catalyzed by an engineered ketoreductase which was obtained via ep PCR-based directed evolution.The hectogram scale synthesis of syn-(2S,3R)-1b at a substrate concentration of 120 g/L showcased the application potential of the biocatalytic method developed presently.
文摘The optically active R-4-phenyl-2-hydroxy butyrates were prepared by esterification of the racemic acid or transesterification of the racemic ester catalyzed by lipase from Candida cyclindra (CCL) in organic media.
文摘The spectral resolution is a main index of evaluating the performance of the designed acousto-optic tunable filter (AOTF). In this letter, an accurate expression of the spectral resolution is presented by considering both the birefringence and the rotatory property of TeO2 crystal. The deduced expression is significant in improving the accuracy of the design of an AOTF and pushing the development of the high-performance AOTF.
基金National Key R&D Program(2018YFC1506904)Natural Science Foundation of China(41590873,41705089)。
文摘Using infrared sensors to detect ice clouds in different atmospheric layers is still a challenge.The different scattering and absorption properties of longwave and shortwave infrared channels can be utilized to fulfill this purpose.In this study,the release of Suomi-NPP Cross-track Infrared Sounder(Cr IS)full spectrum resolution is used to select and pair channels from longwave(~15μm)and shortwave(~4.3μm)CO2 absorption bands under stricter conditions,so as to better detect ice clouds.Besides,the differences of the weighting function peaks and cloud insensitive level altitudes of the paired channels are both within 50 h Pa so that the variances due to atmospheric conditions can be minimized.The training data of clear sky are determined by Visible Infrared Imaging Radiometer Suite(VIIRS)cloud mask product and used to find the linear relationship between the paired longwave and shortwave CO2 absorption channels.From the linear relationship,the so-called cloud emission and scattering index(CESI)is derived to detect ice clouds.CESI clearly captures the center and the ice cloud features of the Super Typhoon Hato located above 415 h Pa.Moreover,the CESI distributions agree with cloud top pressure from the VIIRS in both daytime and nighttime in different atmospheric layers.
基金Under the auspices of National Key Research and Development Project of China(No.2021YFD1500103)Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA28100500)+2 种基金National Natural Science Foundation of China(No.4197132)Science and Technology Development Plan Project of Jilin Province(No.20210201044GX)Land Observation Satellite Supporting Platform of National Civil Space Infrastructure Project(No.CASPLOS-CCSI)。
文摘Soil moisture plays an important role in crop yield estimation,irrigation management,etc.Remote sensing technology has potential for large-scale and high spatial soil moisture mapping.However,offline remote sensing data processing is time-consuming and resource-intensive,and significantly hampers the efficiency and timeliness of soil moisture mapping.Due to the high-speed computing capabilities of remote sensing cloud platforms,a High Spatial Resolution Soil Moisture Estimation Framework(HSRSMEF)based on the Google Earth Engine(GEE)platform was developed in this study.The functions of the HSRSMEF include research area and input datasets customization,radar speckle noise filtering,optical-radar image spatio-temporal matching,soil moisture retrieving,soil moisture visualization and exporting.This paper tested the performance of HSRSMEF by combining Sentinel-1,Sentinel-2 images and insitu soil moisture data in the central farmland area of Jilin Province,China.Reconstructed Normalized Difference Vegetation Index(NDVI)based on the Savitzky-Golay algorithm conforms to the crop growth cycle,and its correlation with the original NDVI is about 0.99(P<0.001).The soil moisture accuracy of the random forest model(R 2=0.942,RMSE=0.013 m3/m3)is better than that of the water cloud model(R 2=0.334,RMSE=0.091 m3/m3).HSRSMEF transfers time-consuming offline operations to cloud computing platforms,achieving rapid and simplified high spatial resolution soil moisture mapping.
文摘Objective: This study aimed to investigate the anti-inflammatory and analgesic mechanisms of a breast lump resolution detergent in a rat model of breast hyperplasia. Methods: A rat model of breast hyperplasia was established using injections of estradiol benzoate combined with progesterone. The effects of the breast lump resolution detergent on nipple height and diameter in the rat model were observed, along with its impact on serum levels of estradiol (E2), prolactin (PRL), and progesterone (P). Additionally, the study examined the morphological changes in breast tissue. The impact of the breast nodule detergent on blood rheology parameters was also observed. Furthermore, the anti-inflammatory effect of the breast nodule detergent was assessed using the cotton ball granuloma experiment, and the analgesic effect was observed using the writhing test. Results: The breast lump resolution detergent reduced nipple height and diameter in the rat model, decreased serum levels of E2, PRL, and P, and alleviated pathological changes in breast tissue. It also lowered hemorheological parameters including whole blood high, medium, and low shear viscosity, plasma viscosity, red blood cell hematocrit, red blood cell aggregation index, red blood cell deformability index, red blood cell electrophoresis time, and erythrocyte sedimentation rate in the acute “blood stasis” rat model. The detergent reduced the weight of cotton ball granulomas in mice and decreased the number of writhing episodes caused by acetic acid. Conclusion: The breast lump resolution detergent demonstrates favorable therapeutic effects in treating breast hyperplasia, promoting blood circulation and removing blood stasis, exerting anti-inflammatory properties, and providing analgesic effects. The downregulation of serum E2 and PRL levels and the upregulation of P levels may be critical mechanisms underlying its efficacy.
文摘High-resolution atomic-beam laser spectroscopy has been performed to study Stark effect of Ba atom. Stark spectra have been observed at various electric fields for Ba highly excited states. The scalar polarizability of the transition from 6s5d3D2 to 5d6p3F3 at 728.0 nm and the tensor polarizability of the 3F3 level have been determined for the first time, to be αs = -89.8 (12) kHz/(kV/cm)2 and αt = -133.7 (20) kHz/(kV/cm)2, respectively.
