In order to understand whether the ameliorating effect on old ages memory disorder by the root of Salvia miltiorhiza is related to the acetylcholinesterase （ACHE） inhibition, two main ingredients, salvianolic acid B...In order to understand whether the ameliorating effect on old ages memory disorder by the root of Salvia miltiorhiza is related to the acetylcholinesterase （ACHE） inhibition, two main ingredients, salvianolic acid B （1） and rosmarinic acid （2）, which were isolated from S. miltiorhiza water extract, were investigated in vitro by NMR relaxation rate in this work. The results showed that the proton selective relaxation rates and the molecular rotational correlation time of proton pairs for compounds 1 and 2 increased significantly by adding of AChE in mixing solution. The study reveals that the two compounds might bind to the enzyme and have ACHE inhibitory effect, which could contribute to the ameliorating effect at some extent on old ages memory disorder.展开更多
Relaxation rate is a very crucial parameter in physics.For the water surface wave,its relaxation rate is directly relevantto the response time of disturbed spectrum returning back to its quasi-steady state.It is diffi...Relaxation rate is a very crucial parameter in physics.For the water surface wave,its relaxation rate is directly relevantto the response time of disturbed spectrum returning back to its quasi-steady state.It is difficult to be calculated directly asa function of different oceanographic and meteorological parameters.Previous researches were mainly based on experimentalmeasurements or parameterization.In this paper,a method based on the liner array charge-coupled device(CCD)is proposed tomeasure the relaxation rate of the water surface wave.Compared with the traditional methods?it can obtain the information ofsurface wave and current synchronously,and works well under a multi wind-wave environment.Wind wav^tank experimentswere carried out based on this method.The good consistency between the results calculated by this method and the traditionalrelaxation rate models shows the validity of the proposed method.This method can be further used to study the modulation theoryof surface waves by currents.展开更多
Collision-induced re-laxation process of CH(X^(2)Π,v=0)radical in various bath gases He,Ar,and N_(2)has been investigated ex-perimentally under low-temperature(26-52 K)supersonic flow conditions.The CH radicals were ...Collision-induced re-laxation process of CH(X^(2)Π,v=0)radical in various bath gases He,Ar,and N_(2)has been investigated ex-perimentally under low-temperature(26-52 K)supersonic flow conditions.The CH radicals were generat-ed with internal excitation by multiphoton photolysis of CHBr_(3)at 248 nm,and its rotational temperature was found to relax to the flow temperature in a few microseconds by colliding with bath gas.The relaxation rate coefficients for CH(X^(2)Π,v=0)radical in He,Ar,and N_(2)flow were obtained by time-resolved laser-induced fluorescence measurements,ranging from 10^(-12)cm^(3)·molecule^(-1)·s^(-1)to 10^(-11)cm^(3)·molecule^(-1)·s^(-1).The N_(2)flow exhibits the highest relax-ation rate for CH(X^(2)Π)radical due to its additional rovibrational levels,which allow for more efficient energy dissipation during collisions compared to monoatomic gases.The Ar flow shows a larger relaxation rate than He flow due to its greater polarizability and stronger long-range interaction with the CH(X^(2)Π)radical.展开更多
There was a slow-relaxing tail of skeletal muscles in vitro upon the inhibition of Ca2+-pump by cyclopiazonic acid(CPA).Herein,a new linearly-combined bi-exponential model to resolve this slow-relaxing tail from the f...There was a slow-relaxing tail of skeletal muscles in vitro upon the inhibition of Ca2+-pump by cyclopiazonic acid(CPA).Herein,a new linearly-combined bi-exponential model to resolve this slow-relaxing tail from the fast-relaxing phase was investigated for kinetic analysis of the isometric relaxation process of Bufo gastrocnemius in vitro,in comparison to the single exponential model and the classical bi-exponential model.During repetitive stimulations at a 2-s interval by square pulses of a 2-ms duration at 12 V direct currency(DC),the isometric tension of Bufo gastrocnemius was recorded at 100 Hz.The relaxation curve with tensions falling from 90%of the peak to the 15th datum before next stimulation was analyzed by three exponential models using a program in MATLAB 6.5.Both the goodness of fit and the distribution of the residuals for the best fitting sup-ported the comparable validity of this new bi-exponential model for kinetic analysis of the relaxation process of the control muscles.After CPA treatment,however,this new bi-exponential model showed an obvious statistical superiority for kinetic analysis of the muscle relaxation process,and it gave the estimated rest tension consistent to that by experimentation,whereas both the classical bi-exponential model and the single exponential model gave biased rest tensions.Moreover,after the treatment of muscles by CPA,both the single exponential model and the classical bi-exponential model yielded lowered relaxation rates,nevertheless,this new bi-exponential model had relaxation rates of negligible changes except much higher rest tensions.These results suggest that this novel linearly-combined bi-exponential model is desirable for kinetic analysis of the relaxation process of muscles with altered Ca2+-pumping activity.展开更多
A plasma screening model that accounts for electronic exchange-correlation effects and ionic nonideality in dense quantum plasmas is proposed.This model can be used as an input in various plasma interaction models to ...A plasma screening model that accounts for electronic exchange-correlation effects and ionic nonideality in dense quantum plasmas is proposed.This model can be used as an input in various plasma interaction models to calculate scattering cross-sections and transport properties.The applicability of the proposed plasma screening model is demonstrated using the example of the temperature relaxation rate in dense hydrogen and warm dense aluminum.Additionally,the conductivity of warm dense aluminum is computed in the regime where collisions are dominated by electron-ion scattering.The results obtained are compared with available theoretical results and simulation data.展开更多
This study employed time-resolved coherent anti-Stokes Raman scattering to investigate the vibrational relaxation mechanism of N_(2)(v=6)molecules in N_(2)-M systems,where M denotes N_(2),O_(2),or CO.At 297 K,the rela...This study employed time-resolved coherent anti-Stokes Raman scattering to investigate the vibrational relaxation mechanism of N_(2)(v=6)molecules in N_(2)-M systems,where M denotes N_(2),O_(2),or CO.At 297 K,the relaxation rate coefficients for collisions between N_(2)(v=6)and N_(2),O_(2),and CO were determined to be(2.85±0.07)×10-14 cm^(3)·s^(-1),(6.29±0.12)×10^(-14)cm^(3)·s^(-1),and(11.21±0.20)×10^(-14)cm^(3)·s^(-1),respectively.The results demonstrated that the relaxation rate coefficient for N_(2)(v=6)-CO collisions was 1.8 times higher than that for N_(2)-O_(2)collisions and 3.9 times greater than that for homonuclear N_(2)-N_(2)collisions,indicating that CO significantly enhances the vibrational relaxation of N_(2)(v=6).Furthermore,by analyzing the time-resolved population evolution of N_(2)(v≤6)in N_(2)-O_(2)and N_(2)-CO systems under varying buffer gas molar ratios and integrating these data with kinetic analysis,the vibrational relaxation mechanism of N_(2)(v=6)in different collisional environments was systematically elucidated.The findings indicate that in the N_(2)-O_(2)system,increasing the molar ratio of acceptor molecules leads to a gradual shift from single-quantum to multi-quantum relaxation dominance,whereas the N_(2)-CO system exhibits a transition from multi-quantum to single-quantum dominance.In addition,a systematic study examined the vibrational relaxation mechanism of N_(2)(v=6)in two gas mixtures between 297 K and 573 K.The results indicate that elevated temperature significantly enhances the efficiency of near-resonance energy transfer associated with the dominant relaxation pathway.展开更多
Brain iron deposition has been proposed to play an important role in the pathophysiology of Alzheimer disease（AD）.The aim of this study was to investigate the correlation of brain iron accumulation with the severity...Brain iron deposition has been proposed to play an important role in the pathophysiology of Alzheimer disease（AD）.The aim of this study was to investigate the correlation of brain iron accumulation with the severity of cognitive impairment in patients with AD by using quantitative MR relaxation rate R2＇ measurements.Fifteen patients with AD,15 age-and sex-matched healthy controls,and 30 healthy volunteers underwent 1.5T MR multi-echo T2 mapping and T2＊ mapping for the measurement of transverse relaxation rate R2＇（R2＇=R2＊-R2）.We statistically analyzed the R2＇ and iron concentrations of bilateral hippocampus（HP）,parietal cortex（PC）,frontal white matter（FWM）,putamen（PU）,caudate nucleus（CN）,thalamus（TH）,red nucleus（RN）,substantia nigra（SN）,and dentate nucleus（DN） of the cerebellum for the correlation with the severity of dementia.Two-tailed t-test,Student-Newman-Keuls test（ANOVA） and linear correlation test were used for statistical analysis.In 30 healthy volunteers,the R2＇ values of bilateral SN,RN,PU,CN,globus pallidus（GP）,TH,and FWM were measured.The correlation with the postmortem iron concentration in normal adults was analyzed in order to establish a formula on the relationship between regional R2＇ and brain iron concentration.The iron concentration of regions of interest（ROI） in AD patients and controls was calculated by this formula and its correlation with the severity of AD was analyzed.Regional R2＇ was positively correlated with regional brain iron concentration in normal adults（r=0.977,P0.01）.Iron concentrations in bilateral HP,PC,PU,CN,and DN of patients with AD were significantly higher than those of the controls（P0.05）;Moreover,the brain iron concentrations,especially in parietal cortex and hippocampus at the early stage of AD,were positively correlated with the severity of patients＇ cognitive impairment（P0.05）.The higher the R2＇ and iron concentrations were,the more severe the cognitive impairment was.Regional R2＇ and iron concentration in parietal cortex and hippocampus were positively correlated with the severity of AD patients＇ cognitive impairment,indicating that it may be used as a biomarker to evaluate the progression of AD.展开更多
We study the transient response dynamics of^(87)Rb atomic vapor buffered in 8 torr Ne gas through an electromagnetically induced transparency configured inΛ-scheme.Experimentally,the temporal transmission spectra ver...We study the transient response dynamics of^(87)Rb atomic vapor buffered in 8 torr Ne gas through an electromagnetically induced transparency configured inΛ-scheme.Experimentally,the temporal transmission spectra versus probe detuning by switching on and off the coupling one show complex structures.The transmitted probe light intensity drops to a minimum value when the coupling light turns off,showing a strong absorption.Even at the moment of turning on the coupling light at a subsequent delayed time,the atomic medium shows a fast transient response.To account for the transient switching feature,in the time-dependent optical Bloch equation,we must take the transverse relaxation dephasing process of atomic vapor into account,as well as the fluorescence relaxation along with the optical absorption.This work supplies a technique to quantify the transverse relaxation time scale and to sensitively monitor its variation along the environment by observing the transient dynamics of coherent medium,which is helpful in characterizing the coherent feature of the atomic medium.展开更多
Human mesenchymal stem cells(hMSCs)were labeled with Dotarem or(Gd-DOTA)2-EM7(EM7Gd2)via electroporation(EP).Cellular transmission electron microscopy(TEM)reveals free distribution of Gd agents and formation of EM7Gd2...Human mesenchymal stem cells(hMSCs)were labeled with Dotarem or(Gd-DOTA)2-EM7(EM7Gd2)via electroporation(EP).Cellular transmission electron microscopy(TEM)reveals free distribution of Gd agents and formation of EM7Gd2 clusters in the cytosol.Cellular magnetic resonance imaging(MRI)reveals that the free Gd agents induce MRI signal enhancement effect due to its fast exocytosis and subsequent interaction with intercellular water molecules.The EM7Gd2 clusters exhibits a longer intracellular retention time and induce a persistent MRI signal reduction effect.The cellular MRI results are interpreted by taking into account both T1 and T2 relaxation rates and their correlation with cellular binding structures of Dotarem and EM7Gd2.展开更多
As a promising imaging technology,the low sensitivity of fluorine-19 magnetic resonance imaging(^(19)F MRI)severely hinders its biomedical applications.Herein,we have developed an unprecedented rotaxanebased strategy ...As a promising imaging technology,the low sensitivity of fluorine-19 magnetic resonance imaging(^(19)F MRI)severely hinders its biomedical applications.Herein,we have developed an unprecedented rotaxanebased strategy to improve the sensitivity of^(19)F MRI agents.By threading the fluorinated macrocycle into2-blade pinwheel[2]rotaxanes,the^(19)F longitudinal relaxation rate R1was dramatically increased,resulting in a significant^(19)F MRI signal intensity enhancement of up to 79%.Through comparative molecular dynamics studies using a series of solution and solid-state^(1)H/^(19)F nuclear magnetic resonance(^(1)H/^(19)F NMR)and molecular dynamics simulations,it was found that the formation of mechanical bonds dramatically restricts the motion of the wheel fluorines and thus increasing the R1for higher^(19)F MRI sensitivity.Besides a novel strategy for improving^(19)F MRI sensitivity,this study has established^(19)F NMR/MRI as a valuable technology for monitoring the molecular dynamics of rotaxanes,which may shed new light on high-performance^(19)F MRI agents and molecular devices.展开更多
Objective:To investigate the differences of apparent diffusion coefficient and transverse relaxation rate(R_(2)^(*))in magnetic resonance imaging(MRI)between micro hepatocellular carcinoma and nodules of cirrhosis.Met...Objective:To investigate the differences of apparent diffusion coefficient and transverse relaxation rate(R_(2)^(*))in magnetic resonance imaging(MRI)between micro hepatocellular carcinoma and nodules of cirrhosis.Method:The clinical data of 68 patients with micro hepatocellular carcinoma(76 lesions)and 45 patients with nodular cirrhosis(48 lesions)were retrospectively analyzed.Diffusion weighted imaging and R_(2)^(*)imaging were performed on all patients.The differences of apparent diffusion coefficient and R_(2)^(*)values in patients with micro hepatocellular carcinoma and nodular cirrhosis were compared.Receiver operating characteristic(ROC)curves were drawn to evaluate the diagnostic efficacy of apparent diffusion coefficient values and R_(2)^(*)values for microhepatocellular carcinoma.Result:Compared with nodules of cirrhosis,the mean apparent diffusion coefficient and R_(2)^(*)value of micro-hepatocellular carcinoma were significantly decreased(P<0.05).The diagnosis threshold of apparent diffusion coefficient is at 1.35×10^(-3)mm^(2)/s,and the sensitivity for the diagnosis of micro-hepatocellular carcinoma was 80.88%,and the specificity was 91.11%,and the corresponding area under the ROC curve was 0.88;The diagnostic threshold for R_(2)^(*)value was at 53.96 Hz,and the sensitivity for the diagnosis of small hepatocellular carcinoma was 91.18%,and the specificity was 77.78%,and the corresponding area under the ROC curve was 0.84.Conclusion:MRI apparent diffusion coefficient value and R_(2)^(*)value can be used to differentiate and diagnose micro hepatocellular carcinoma and nodules of cirrhosis,in which the apparent diffusion coefficient of nodules of cirrhosis was less than 1.35×10^(-3)mm^(2)/s,R_(2)^(*)values were lower than 53.96 Hz may indicate the occurrence of nodular canceration.展开更多
To research the correlation between vibrational energy transition rates and acoustic relaxation processes in excitable gases, the vibrational relaxation theory provided by Tanczos [J. Chem. Phy3. 25, 439 （1956）] is ...To research the correlation between vibrational energy transition rates and acoustic relaxation processes in excitable gases, the vibrational relaxation theory provided by Tanczos [J. Chem. Phy3. 25, 439 （1956）] is applied to calculate the energy transition rates of Vibrational- Vibrational （V-V） and Vibrational-Translational （V-T） energy transfer in gas mixtures. The results of calculation for the multi-relaxation processes in various gas mixtures, consisting of carbon dioxide, methane, chlorine, nitrogen, and oxygen at room temperature, demonstrate that the acoustic energy stagnated in every vibrational mode is coupled with each other through V-V energy exchanges. The vibrational excitation energy will relax through the V-T de-excitation path of the lowest mode because of its fastest V-T transition rate, resulting in that only one absorption peak can be measured for most of excitable gas mixtures. Thus, an effective model is provided to analyze how the vibrational energy transition rates affect the characteristics of acoustic relaxation processes and acoustic propagation in excitable gas mixtures.展开更多
Radiofrequency coil is one of the most important components for a nuclear magnetic resonance(NMR)instrument.In this article,some planar micro coils with an inner diameter of 2 mm and number of turns that varied from 1...Radiofrequency coil is one of the most important components for a nuclear magnetic resonance(NMR)instrument.In this article,some planar micro coils with an inner diameter of 2 mm and number of turns that varied from 1 to 11 were investigated based on the printed circuit board(PCB)technology.The electrical characterization of micro coils show that self-resonant frequencies are larger than 200 MHz.Then,an NMR measurement platform with a static magnetic field of 0.66 T was constructed and the signal to noise ratio(SNR)values of the NMR were analyzed.It was found that the SNR is optimal when the turn number of the micro coils is six and the excitation time of a 90°pulse is 0.8?s.Finally,we used the micro coil with six turns to study the transverse relaxation rate of copper sulfate pentahydrate aqueous solution with different concentrations.It was found that the transverse relaxation rate is proportional to the solution concentration.Results from the micro coil were verified by measurements using a Bruker Minispec MQ60.展开更多
基金The authors are grateful for supports by the National Natural Science Foundation of China （No. 90409015 and 20473013）.
文摘In order to understand whether the ameliorating effect on old ages memory disorder by the root of Salvia miltiorhiza is related to the acetylcholinesterase （ACHE） inhibition, two main ingredients, salvianolic acid B （1） and rosmarinic acid （2）, which were isolated from S. miltiorhiza water extract, were investigated in vitro by NMR relaxation rate in this work. The results showed that the proton selective relaxation rates and the molecular rotational correlation time of proton pairs for compounds 1 and 2 increased significantly by adding of AChE in mixing solution. The study reveals that the two compounds might bind to the enzyme and have ACHE inhibitory effect, which could contribute to the ameliorating effect at some extent on old ages memory disorder.
基金National Natural Science Foundation of China(No.41276185)
文摘Relaxation rate is a very crucial parameter in physics.For the water surface wave,its relaxation rate is directly relevantto the response time of disturbed spectrum returning back to its quasi-steady state.It is difficult to be calculated directly asa function of different oceanographic and meteorological parameters.Previous researches were mainly based on experimentalmeasurements or parameterization.In this paper,a method based on the liner array charge-coupled device(CCD)is proposed tomeasure the relaxation rate of the water surface wave.Compared with the traditional methods?it can obtain the information ofsurface wave and current synchronously,and works well under a multi wind-wave environment.Wind wav^tank experimentswere carried out based on this method.The good consistency between the results calculated by this method and the traditionalrelaxation rate models shows the validity of the proposed method.This method can be further used to study the modulation theoryof surface waves by currents.
基金supported by the National Natural Science Foundation of China(No.22273103)the National Natural Science Foundation of China(NSFC Center for Chemical Dynamics)(No.22288201)+1 种基金Dalian Institute of Chemical Physics(DICP I202230)the Scientific Instrument Developing Project of the Chinese Academy of Sciences(grant GJJSTD20220001)。
文摘Collision-induced re-laxation process of CH(X^(2)Π,v=0)radical in various bath gases He,Ar,and N_(2)has been investigated ex-perimentally under low-temperature(26-52 K)supersonic flow conditions.The CH radicals were generat-ed with internal excitation by multiphoton photolysis of CHBr_(3)at 248 nm,and its rotational temperature was found to relax to the flow temperature in a few microseconds by colliding with bath gas.The relaxation rate coefficients for CH(X^(2)Π,v=0)radical in He,Ar,and N_(2)flow were obtained by time-resolved laser-induced fluorescence measurements,ranging from 10^(-12)cm^(3)·molecule^(-1)·s^(-1)to 10^(-11)cm^(3)·molecule^(-1)·s^(-1).The N_(2)flow exhibits the highest relax-ation rate for CH(X^(2)Π)radical due to its additional rovibrational levels,which allow for more efficient energy dissipation during collisions compared to monoatomic gases.The Ar flow shows a larger relaxation rate than He flow due to its greater polarizability and stronger long-range interaction with the CH(X^(2)Π)radical.
基金Project supported by the National Natural Science Foundation of China(No.30472139)the Education Commission for the First Batch of Excellent Young Teachers in Universities of Chongqing City,China
文摘There was a slow-relaxing tail of skeletal muscles in vitro upon the inhibition of Ca2+-pump by cyclopiazonic acid(CPA).Herein,a new linearly-combined bi-exponential model to resolve this slow-relaxing tail from the fast-relaxing phase was investigated for kinetic analysis of the isometric relaxation process of Bufo gastrocnemius in vitro,in comparison to the single exponential model and the classical bi-exponential model.During repetitive stimulations at a 2-s interval by square pulses of a 2-ms duration at 12 V direct currency(DC),the isometric tension of Bufo gastrocnemius was recorded at 100 Hz.The relaxation curve with tensions falling from 90%of the peak to the 15th datum before next stimulation was analyzed by three exponential models using a program in MATLAB 6.5.Both the goodness of fit and the distribution of the residuals for the best fitting sup-ported the comparable validity of this new bi-exponential model for kinetic analysis of the relaxation process of the control muscles.After CPA treatment,however,this new bi-exponential model showed an obvious statistical superiority for kinetic analysis of the muscle relaxation process,and it gave the estimated rest tension consistent to that by experimentation,whereas both the classical bi-exponential model and the single exponential model gave biased rest tensions.Moreover,after the treatment of muscles by CPA,both the single exponential model and the classical bi-exponential model yielded lowered relaxation rates,nevertheless,this new bi-exponential model had relaxation rates of negligible changes except much higher rest tensions.These results suggest that this novel linearly-combined bi-exponential model is desirable for kinetic analysis of the relaxation process of muscles with altered Ca2+-pumping activity.
基金funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan Grant No.AP19678033“The study of the transport and optical properties of hydrogen at high pressure.”。
文摘A plasma screening model that accounts for electronic exchange-correlation effects and ionic nonideality in dense quantum plasmas is proposed.This model can be used as an input in various plasma interaction models to calculate scattering cross-sections and transport properties.The applicability of the proposed plasma screening model is demonstrated using the example of the temperature relaxation rate in dense hydrogen and warm dense aluminum.Additionally,the conductivity of warm dense aluminum is computed in the regime where collisions are dominated by electron-ion scattering.The results obtained are compared with available theoretical results and simulation data.
基金Project supported by the Natural Science Foundation of Xinjiang Uygur Autonomous Region of China(Grant No.2024D01C51)。
文摘This study employed time-resolved coherent anti-Stokes Raman scattering to investigate the vibrational relaxation mechanism of N_(2)(v=6)molecules in N_(2)-M systems,where M denotes N_(2),O_(2),or CO.At 297 K,the relaxation rate coefficients for collisions between N_(2)(v=6)and N_(2),O_(2),and CO were determined to be(2.85±0.07)×10-14 cm^(3)·s^(-1),(6.29±0.12)×10^(-14)cm^(3)·s^(-1),and(11.21±0.20)×10^(-14)cm^(3)·s^(-1),respectively.The results demonstrated that the relaxation rate coefficient for N_(2)(v=6)-CO collisions was 1.8 times higher than that for N_(2)-O_(2)collisions and 3.9 times greater than that for homonuclear N_(2)-N_(2)collisions,indicating that CO significantly enhances the vibrational relaxation of N_(2)(v=6).Furthermore,by analyzing the time-resolved population evolution of N_(2)(v≤6)in N_(2)-O_(2)and N_(2)-CO systems under varying buffer gas molar ratios and integrating these data with kinetic analysis,the vibrational relaxation mechanism of N_(2)(v=6)in different collisional environments was systematically elucidated.The findings indicate that in the N_(2)-O_(2)system,increasing the molar ratio of acceptor molecules leads to a gradual shift from single-quantum to multi-quantum relaxation dominance,whereas the N_(2)-CO system exhibits a transition from multi-quantum to single-quantum dominance.In addition,a systematic study examined the vibrational relaxation mechanism of N_(2)(v=6)in two gas mixtures between 297 K and 573 K.The results indicate that elevated temperature significantly enhances the efficiency of near-resonance energy transfer associated with the dominant relaxation pathway.
基金supported by grants from the National Natural Science Foundation of China (No. 30870702 and No.30570531)863 Project of China (No. 2006AA02Z4A1)
文摘Brain iron deposition has been proposed to play an important role in the pathophysiology of Alzheimer disease（AD）.The aim of this study was to investigate the correlation of brain iron accumulation with the severity of cognitive impairment in patients with AD by using quantitative MR relaxation rate R2＇ measurements.Fifteen patients with AD,15 age-and sex-matched healthy controls,and 30 healthy volunteers underwent 1.5T MR multi-echo T2 mapping and T2＊ mapping for the measurement of transverse relaxation rate R2＇（R2＇=R2＊-R2）.We statistically analyzed the R2＇ and iron concentrations of bilateral hippocampus（HP）,parietal cortex（PC）,frontal white matter（FWM）,putamen（PU）,caudate nucleus（CN）,thalamus（TH）,red nucleus（RN）,substantia nigra（SN）,and dentate nucleus（DN） of the cerebellum for the correlation with the severity of dementia.Two-tailed t-test,Student-Newman-Keuls test（ANOVA） and linear correlation test were used for statistical analysis.In 30 healthy volunteers,the R2＇ values of bilateral SN,RN,PU,CN,globus pallidus（GP）,TH,and FWM were measured.The correlation with the postmortem iron concentration in normal adults was analyzed in order to establish a formula on the relationship between regional R2＇ and brain iron concentration.The iron concentration of regions of interest（ROI） in AD patients and controls was calculated by this formula and its correlation with the severity of AD was analyzed.Regional R2＇ was positively correlated with regional brain iron concentration in normal adults（r=0.977,P0.01）.Iron concentrations in bilateral HP,PC,PU,CN,and DN of patients with AD were significantly higher than those of the controls（P0.05）;Moreover,the brain iron concentrations,especially in parietal cortex and hippocampus at the early stage of AD,were positively correlated with the severity of patients＇ cognitive impairment（P0.05）.The higher the R2＇ and iron concentrations were,the more severe the cognitive impairment was.Regional R2＇ and iron concentration in parietal cortex and hippocampus were positively correlated with the severity of AD patients＇ cognitive impairment,indicating that it may be used as a biomarker to evaluate the progression of AD.
基金the National Natural Science Foundation of China(Grant Nos.12074388 and 12004393)。
文摘We study the transient response dynamics of^(87)Rb atomic vapor buffered in 8 torr Ne gas through an electromagnetically induced transparency configured inΛ-scheme.Experimentally,the temporal transmission spectra versus probe detuning by switching on and off the coupling one show complex structures.The transmitted probe light intensity drops to a minimum value when the coupling light turns off,showing a strong absorption.Even at the moment of turning on the coupling light at a subsequent delayed time,the atomic medium shows a fast transient response.To account for the transient switching feature,in the time-dependent optical Bloch equation,we must take the transverse relaxation dephasing process of atomic vapor into account,as well as the fluorescence relaxation along with the optical absorption.This work supplies a technique to quantify the transverse relaxation time scale and to sensitively monitor its variation along the environment by observing the transient dynamics of coherent medium,which is helpful in characterizing the coherent feature of the atomic medium.
基金the Natural Science Foundation of China(21673281,31870982)a National Key R&D Program from MOST of China(2017YFA0104301).
文摘Human mesenchymal stem cells(hMSCs)were labeled with Dotarem or(Gd-DOTA)2-EM7(EM7Gd2)via electroporation(EP).Cellular transmission electron microscopy(TEM)reveals free distribution of Gd agents and formation of EM7Gd2 clusters in the cytosol.Cellular magnetic resonance imaging(MRI)reveals that the free Gd agents induce MRI signal enhancement effect due to its fast exocytosis and subsequent interaction with intercellular water molecules.The EM7Gd2 clusters exhibits a longer intracellular retention time and induce a persistent MRI signal reduction effect.The cellular MRI results are interpreted by taking into account both T1 and T2 relaxation rates and their correlation with cellular binding structures of Dotarem and EM7Gd2.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB0540000)the National Key R&D Program of China(No.2018YFA0704000)+2 种基金the National Natural Science Foundation of China(Nos.22327901,22077098,U21A20392,21921004,and 82127802)the Knowledge Innovation Program of WuhanBasic Research(No.2022020801010137)support from the Youth Innovation Promotion Association and the Young Top-notch Talent Cultivation Program。
文摘As a promising imaging technology,the low sensitivity of fluorine-19 magnetic resonance imaging(^(19)F MRI)severely hinders its biomedical applications.Herein,we have developed an unprecedented rotaxanebased strategy to improve the sensitivity of^(19)F MRI agents.By threading the fluorinated macrocycle into2-blade pinwheel[2]rotaxanes,the^(19)F longitudinal relaxation rate R1was dramatically increased,resulting in a significant^(19)F MRI signal intensity enhancement of up to 79%.Through comparative molecular dynamics studies using a series of solution and solid-state^(1)H/^(19)F nuclear magnetic resonance(^(1)H/^(19)F NMR)and molecular dynamics simulations,it was found that the formation of mechanical bonds dramatically restricts the motion of the wheel fluorines and thus increasing the R1for higher^(19)F MRI sensitivity.Besides a novel strategy for improving^(19)F MRI sensitivity,this study has established^(19)F NMR/MRI as a valuable technology for monitoring the molecular dynamics of rotaxanes,which may shed new light on high-performance^(19)F MRI agents and molecular devices.
文摘Objective:To investigate the differences of apparent diffusion coefficient and transverse relaxation rate(R_(2)^(*))in magnetic resonance imaging(MRI)between micro hepatocellular carcinoma and nodules of cirrhosis.Method:The clinical data of 68 patients with micro hepatocellular carcinoma(76 lesions)and 45 patients with nodular cirrhosis(48 lesions)were retrospectively analyzed.Diffusion weighted imaging and R_(2)^(*)imaging were performed on all patients.The differences of apparent diffusion coefficient and R_(2)^(*)values in patients with micro hepatocellular carcinoma and nodular cirrhosis were compared.Receiver operating characteristic(ROC)curves were drawn to evaluate the diagnostic efficacy of apparent diffusion coefficient values and R_(2)^(*)values for microhepatocellular carcinoma.Result:Compared with nodules of cirrhosis,the mean apparent diffusion coefficient and R_(2)^(*)value of micro-hepatocellular carcinoma were significantly decreased(P<0.05).The diagnosis threshold of apparent diffusion coefficient is at 1.35×10^(-3)mm^(2)/s,and the sensitivity for the diagnosis of micro-hepatocellular carcinoma was 80.88%,and the specificity was 91.11%,and the corresponding area under the ROC curve was 0.88;The diagnostic threshold for R_(2)^(*)value was at 53.96 Hz,and the sensitivity for the diagnosis of small hepatocellular carcinoma was 91.18%,and the specificity was 77.78%,and the corresponding area under the ROC curve was 0.84.Conclusion:MRI apparent diffusion coefficient value and R_(2)^(*)value can be used to differentiate and diagnose micro hepatocellular carcinoma and nodules of cirrhosis,in which the apparent diffusion coefficient of nodules of cirrhosis was less than 1.35×10^(-3)mm^(2)/s,R_(2)^(*)values were lower than 53.96 Hz may indicate the occurrence of nodular canceration.
基金supported by the National Natural Science Foundation of China(61461008,61371139,61571201,61540051)the China Scholarship Council Project(201708525058)+1 种基金the National Science Foundation of Guizhou Province,China(Qian Ke He J Zi[2015]2065),Qian Ke He LH Zi[2014]7361)the Recruitment Program of Guizhou Institute of Technology(XJGC20140601,XJGC20150107)
文摘To research the correlation between vibrational energy transition rates and acoustic relaxation processes in excitable gases, the vibrational relaxation theory provided by Tanczos [J. Chem. Phy3. 25, 439 （1956）] is applied to calculate the energy transition rates of Vibrational- Vibrational （V-V） and Vibrational-Translational （V-T） energy transfer in gas mixtures. The results of calculation for the multi-relaxation processes in various gas mixtures, consisting of carbon dioxide, methane, chlorine, nitrogen, and oxygen at room temperature, demonstrate that the acoustic energy stagnated in every vibrational mode is coupled with each other through V-V energy exchanges. The vibrational excitation energy will relax through the V-T de-excitation path of the lowest mode because of its fastest V-T transition rate, resulting in that only one absorption peak can be measured for most of excitable gas mixtures. Thus, an effective model is provided to analyze how the vibrational energy transition rates affect the characteristics of acoustic relaxation processes and acoustic propagation in excitable gas mixtures.
基金supported by the National Natural Science Foundation of China(Grant No.51175083)the Jiangsu Province University Industry Cooperation Innovation Foundation-Prospective Study of China(Grant No.BY 2011135)
文摘Radiofrequency coil is one of the most important components for a nuclear magnetic resonance(NMR)instrument.In this article,some planar micro coils with an inner diameter of 2 mm and number of turns that varied from 1 to 11 were investigated based on the printed circuit board(PCB)technology.The electrical characterization of micro coils show that self-resonant frequencies are larger than 200 MHz.Then,an NMR measurement platform with a static magnetic field of 0.66 T was constructed and the signal to noise ratio(SNR)values of the NMR were analyzed.It was found that the SNR is optimal when the turn number of the micro coils is six and the excitation time of a 90°pulse is 0.8?s.Finally,we used the micro coil with six turns to study the transverse relaxation rate of copper sulfate pentahydrate aqueous solution with different concentrations.It was found that the transverse relaxation rate is proportional to the solution concentration.Results from the micro coil were verified by measurements using a Bruker Minispec MQ60.
