Oxopentanedioic acid isonicotinoyl hydrazone (H_2L) and its five rare earth complexes were synthesized with a view to further investigating MRI activities of the polycarboxylic Schiff base complexes. The complexes wer...Oxopentanedioic acid isonicotinoyl hydrazone (H_2L) and its five rare earth complexes were synthesized with a view to further investigating MRI activities of the polycarboxylic Schiff base complexes. The complexes were characterized on the basis of elemental analyses, IR, UV, (()~1H) NMR spectra and thermal analyses. The general formula of the complexes is [Ln(HL)(H_2O)_2]Cl_2·H_2O (where Ln(Ⅲ)=La, Pr, Nd, Eu and Gd). In addition, the relaxivity ( R _1) of the Gd-complex was determined by INVREC Au program.展开更多
Five neutral macromolecular polyester gadolinium (Ⅲ) complexes with pendant hydrophobic alkyland aromatic functional groups were prepared. The longitudinal relaxation rates of these complexes weremeasured. One of the...Five neutral macromolecular polyester gadolinium (Ⅲ) complexes with pendant hydrophobic alkyland aromatic functional groups were prepared. The longitudinal relaxation rates of these complexes weremeasured. One of these Gd (Ⅲ) complexes was chosen for the acute toxicity test and T_1-weighted imagingmeasurement. Preliminary results showed that. compared with Gd-DTPA. the neutral macromoleculargadolinium (Ⅲ) complexes provide higher T_1 relaxivity enhancement and longer function duration.展开更多
Fifteen new polyester ligands were prepared by copolymerndion Of EDTA(ethylenediaminetetraacetic acid ) dianhydride or DTPA (dikthylenetriaminepenlaacetic acid) dianhydrtde and dihydric alcohol or dihydric phenol. The...Fifteen new polyester ligands were prepared by copolymerndion Of EDTA(ethylenediaminetetraacetic acid ) dianhydride or DTPA (dikthylenetriaminepenlaacetic acid) dianhydrtde and dihydric alcohol or dihydric phenol. Theirparanzagnetic metal complexes were also synthesized. All polyester ligands andmetal complexes were characterized by IHNMR, IR spectra and elemental analyses. Preliminary study showed that the polyester .metal complexes had higher relaxation effectiveness as compared to corresponding small molecular metal complexes.展开更多
Multifunctional lanthanide complexes have been extensively studied in recent years owing to their widespread applications in physics,chemistry and biology,including quantum information processing,molecular spintronics...Multifunctional lanthanide complexes have been extensively studied in recent years owing to their widespread applications in physics,chemistry and biology,including quantum information processing,molecular spintronics and theranostics.The multifunctionality includes chirality,luminescence,magnetism,ferroelectricity,fluorescence/magnetic resonance imaging etc.Although various N-and O-donor ligands have shown the ability to synthesize these complexes,Schiff bases are still the most widely used in constructing air-stable species.Herein,we report the facile gram-level synthesis of three pairs of lanthanide macrocycle enantiomers via an in situ[2+2]imine condensation with a trivalent lanthanide ion as a template.Eu_((III))-based compounds,R/S-Eu and R/S-Eu-Ph_(3)PO,both show efficient circularly polarized luminescence(CPL)with maximum dissymmetry factors(glum)of 0.098 and 0.110,respectively.The latter exhibited stronger emission intensity and a longer luminescence lifetime than the former due to the lower vibrational coordination structures around the Eu_((III))ion.Gd_((III))-based species,R/S-Gd,possess a relatively high relaxivity of up to 35.04 and 34.09 mM^(-1)s^(-1)for R-and S-enantiomers,benefitting from the presence of one coordinated water molecule and abundant intermolecular H-bonds.In addition,the results of the MTT assay and in vitro experiments demonstrated the low toxicity and efficient MRI of Gd_((III))-chelates in A549 cells.展开更多
A homogeneous series of polynuclear structures containing from 2 to 6 GdAAZTA complexes(AAZTA=6-amino-6-methylperhydro-1,4-diazepine tetraacetic acid)were synthesized covering a broad range of molecular weights,ca.120...A homogeneous series of polynuclear structures containing from 2 to 6 GdAAZTA complexes(AAZTA=6-amino-6-methylperhydro-1,4-diazepine tetraacetic acid)were synthesized covering a broad range of molecular weights,ca.1200-6000 Da.A frequency and temperature dependent 1H and 17O NMR relaxometric study on the Gd(III)polynuclear complexes clearly highlights a considerable gain of relaxivity(per Gd)passing from the monomer to the hexanuclear complex,with an enhancement of+370%at 1.5 T and 298 K(+470%at 310 K).In particular,the relaxivity of the hexamer reaches a remarkable value of 28.2 mM^(−1)s^(−1)at 1.5 T and 298 K(23.8 mM^(−1)s^(−1)at 310 K).The NMR study,supported by DFT calculations,allows analysis in detail of the dependence of the rotational dynamics on the size and molecular geometry of the multimers,considering both the global tumbling of the system and the local motions of the monomer units.In addition,T1-weighted phantom MR-images at 1,3 and 7 T on selected polynuclear complexes highlighted the effective signal enhancement of the new MRI probes at clinically relevant magnetic field strengths in comparison with the clinically approved contrast agent ProHance®.Finally,the results obtained enable us to highlight effective strategies for relaxation enhancement,each suitable for a well-defined range of applied magnetic field strength.展开更多
Gadolinium(III)complexes have been employed for more than 30 years as contrast agents in magnetic resonance imaging(MRI).In order to further improve the diagnostic accuracy of enhanced magnetic resonance images or to ...Gadolinium(III)complexes have been employed for more than 30 years as contrast agents in magnetic resonance imaging(MRI).In order to further improve the diagnostic accuracy of enhanced magnetic resonance images or to provide comparable enhancement at a reduced administered dose,current research is focusing on the development of Gd^(Ⅲ)-complexes characterized by higher relaxivity.In this study we describe the synthesis and the equilibrium,kinetic,relaxation and structural properties of two new Gd^(Ⅲ)-complexes based on modified 10-(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid(HP-DO3A)structure which,due to an intramolecular prototropic exchange,display more than two-fold higher relaxivity compared to currently available Gd^(Ⅲ)-based MRI contrast agents.展开更多
Three water-soluble Mn(III)-porphyrin complexes with cationic pyridyl side groups bearing COOH-or OH-terminated carbon chains in the meta or para positions have been synthesized as probes for both magnetic resonance i...Three water-soluble Mn(III)-porphyrin complexes with cationic pyridyl side groups bearing COOH-or OH-terminated carbon chains in the meta or para positions have been synthesized as probes for both magnetic resonance imaging(MRI)and photodynamic therapy(PDT).The complexes Mn-1,Mn-2,and Mn-3 are highly water-soluble,and their relaxivities range between 10 and 15 mM^(-1) s^(-1),at 20-80 MHz and 298 K,2-3 times higher than that of commercial Gd(III)-based agents.The complexes containing carboxylate(Mn-2)or alcoholic(Mn-3)side chains in the para position are endowed with higher relaxivities and have also shown efficient photoinduced DNA cleavage and singlet oxygen(^(1)O_(2))generation.Mn-3 with stronger photoinduced DNA cleavage has also revealed stabilizing and binding activities for G4 DNA,at a similar level as the known G4 binder Mn-TMPyP4.Nevertheless,the G4-binding activity of Mn-3 was nonspecific.Preliminary tests evidenced photocytotoxicity of Mn-3 on HeLa cells without a significant effect in the absence of light.Altogether,these results underline the potential of such water-soluble Mn(III)-porphyrins for the development of multimodal approaches combining MRI and PDT.展开更多
Nuclear magnetic resonance (NMR) relaxation of fluids in porous media is affected by the solid-liquid interface. Quantitative determination of the surface relaxivity is significantly important for both investigation a...Nuclear magnetic resonance (NMR) relaxation of fluids in porous media is affected by the solid-liquid interface. Quantitative determination of the surface relaxivity is significantly important for both investigation and application of relaxation mechanisms in porous media. A method to estimate the surface relaxivity with the combination of relaxation and diffusion measurements is proposed. According to this method, a criterion for testing the current diffusion and relaxation theory for porous media is available.展开更多
Synthesis of ligand, α-oxo-pentanedioic acid benzoyl hydrazone (H2LPB), and its six rare earth (La, Pr, Nd, Sm, Gd and Er) complexes are reported. The composition and the properties of the complexes were characterize...Synthesis of ligand, α-oxo-pentanedioic acid benzoyl hydrazone (H2LPB), and its six rare earth (La, Pr, Nd, Sm, Gd and Er) complexes are reported. The composition and the properties of the complexes were characterized by element analysis, thermal analysis, UV, IR and H NMR spectra. Besides, relaxivity (R1) of Gd-complex has been determined by INVREC.Au program, using inversion recovery pulse sequences, R1=8.05 mmol ·L-1 · s-1. The acute toxicity of Gd-complex in animal has also been tested, and the median lethal dose (LD50) is equal to (468.2±30) mg/kg.展开更多
The fast solution of linear equations has always been one of the hot spots in scientific computing.A kind of the diagonal matrix splitting iteration methods are provided,which is different from the classical matrix sp...The fast solution of linear equations has always been one of the hot spots in scientific computing.A kind of the diagonal matrix splitting iteration methods are provided,which is different from the classical matrix splitting methods.Taking the decomposition of the diagonal elements for coefficient matrix as the key point,some new preconditioners are constructed.Taking the tri-diagonal coefficient matrix as an example,the convergence domains and optimal relaxation factor of the new method are analyzed theoretically.The presented new iteration methods are applied to solve linear algebraic equations,even 2D and 3D diffusion problems with the fully implicit discretization.The results of numerical experiments are matched with the theoretical analysis,and show that the iteration numbers are reduced greatly.The superiorities of presented iteration methods exceed some classical iteration methods dramatically.展开更多
A novel ligand of DTPA-dihydropyridine derivative was synthesized by reaction of DTPA-dianhydride with 4-aniline-1,4-dihydropyridine. Its complexes of gadolinium, manganese and iron were prepared. Their spin-lattice r...A novel ligand of DTPA-dihydropyridine derivative was synthesized by reaction of DTPA-dianhydride with 4-aniline-1,4-dihydropyridine. Its complexes of gadolinium, manganese and iron were prepared. Their spin-lattice relaxivities (T1) were investigated. The results show that the NMR T1 relaxivitives (R1) for complexes of Fe(Ⅲ), Mn(Ⅱ) are less than that of Gd(Ⅲ) complex,which has a high relaxivity (R1) on the surrounding water protons, indicating that the Gd(Ⅲ) complex possesses the precondition to be contrast agents for magnetic resonance imaging.展开更多
X-ray single crystal analysis of a new paramagnetic manganese（Ⅱ） complex with DTPA-BpABA （a DTPAbisamide derivative）, Mn（DTPA-BpABA）·4H2O, shows that four oxygen atoms and three nitrogen atoms from the lig...X-ray single crystal analysis of a new paramagnetic manganese（Ⅱ） complex with DTPA-BpABA （a DTPAbisamide derivative）, Mn（DTPA-BpABA）·4H2O, shows that four oxygen atoms and three nitrogen atoms from the ligand coordinate to Mn（Ⅱ） cation, forming a seven-coordinate distorted pentagonal bipyramid polyhedron. In the crystal, the carboxyl groups and the nitrogen atoms extensively form hydrogen bonds with the lattice water molecules, building a 3D-network. The relaxometric study indicates that the R1 value of the paramagnetic manganese（Ⅱ）complex is 5.12 mmol·L·s^-1. The higher R1 value means that this complex may find an application in magnetic resonance imaging （MRI） technique.展开更多
It’s never too early in the year to start planning a break from the stress of city life,and southwest China’s charming Guizhou Province is a destination that should be right at the top of your list.
In order to enable wing morphing(e.g.change in camber or folds)without incurring additional weight to the aircraft,lightweight flexible materials such as membrane are needed.However,the research on fluid-structure cou...In order to enable wing morphing(e.g.change in camber or folds)without incurring additional weight to the aircraft,lightweight flexible materials such as membrane are needed.However,the research on fluid-structure coupling of membranes has mainly focused on parachutes in low-speed conditions,while that in supersonic flow conditions is lacking.Here,the degraded shell method is proposed to study membrane deformation by using shell element,which is more effective than using membrane elements directly.A fluid-structure interaction computational framework is proposed,whereby the aerodynamic module is composed of either the piston theory or computational fluid dynamics.A rectangular membrane of length 0.4 m and width 0.6 m is investigated in supersonic conditions.The characteristics of the limit cycle and steady deformation are analyzed,considering the effects of angle of attack and dynamic pressure.It is found that the structural response exhibits significant differences under various angles of attack.Furthermore,initial relaxation of membrane has significant influence on the structural deformation.Finally,the aeroelastic scaling method for membrane structures is derived,providing guidance for the design of wind tunnel models.This study provides a theoretical foundation for the analysis and application of membrane structures under supersonic conditions in future research.展开更多
The photovoltaic performance of metal halide perovskite solar cells often respond divergently to environmental conditions during storage.In particular,light exposure can either enhance or degrade device efficiency,yet...The photovoltaic performance of metal halide perovskite solar cells often respond divergently to environmental conditions during storage.In particular,light exposure can either enhance or degrade device efficiency,yet the mechanisms underlying these antithetical behaviors are still under investigation.In this study,we explore the modulation of the open-circuit voltage(Voc)in triple-cation mixed-halide perovskite solar cells by systematically controlling storage environments.While light intensity exhibits minimal impact during storage,the spectral composition of illumination selectively enhances Voc comprising reversible and irreversible contributions.Structural characterization reveals that prolonged storage degrades the quality of perovskite crystals in the upper region of the perovskite layer,whereas light storage promotes the relaxation of microstrain at the buried interface with a p-type organic layer.This structural reorganization at the interface,accompanied by lattice expansion,accounts for suppressed nonradiative recombination and a corresponding increase in quasi-Fermi level splitting.Consequently,devices fabricated without chemical defect passivation achieve a power conversion efficiency of higher than 40%under indoor lighting conditions after preconditioned by continuous exposure to ambient light during storage.These findings highlight the critical role of controlled light exposure during storage not only in enhancing efficiency,but also in ensuring reproducibility of perovskite solar cell characterization.展开更多
A multi-stage stress relaxation test was performed on a granodiorite sample to understand the deformation process prior to the macroscopic failure of brittle rocks,as well as the transient response during stress relax...A multi-stage stress relaxation test was performed on a granodiorite sample to understand the deformation process prior to the macroscopic failure of brittle rocks,as well as the transient response during stress relaxation.Distributed optical fiber sensing was used to measure strains across the sample surface by helically wrapping the single-mode fiber around the cylindrical sample.Close agreement was observed between the circumferential strains obtained from the optical fibers and the extensometer.The reconstructed full-field strain contours show strain heterogeneity from the crack closure phase,and the strains in the later deformation phase are dominantly localized within the former high-strain zone.The Gini coefficient was used to quantify the degree of strain localization and shows an initial increase during the crack closure phase,a decrease during the linear elastic phase,and a subsequent increase during the post-yielding phase.This behavior corresponds to a process of initial localization from an imperfect boundary condition,homogenization,and eventual relocalization prior to the macroscopic failure of the sample.The transient strain rate decay during the stress relaxation phase was quantified using the p-value in the“Omori-like"power law function.A higher initial stress at the onset of relaxation results in a lower p-value,indicating a slower strain rate decay.As the sample approaches macroscopic failure,the lowest p-value shifts from the most damaged zone to adjacent areas,suggesting stress redistribution or crack propagation in deformed crystalline rocks under stress relaxation conditions.展开更多
Integrated sensing and communication(ISAC)is an appealing approach to address spectrum congestion and beamforming is an effective method to realize ISAC.In this paper,we investigate the beamforming design problem for ...Integrated sensing and communication(ISAC)is an appealing approach to address spectrum congestion and beamforming is an effective method to realize ISAC.In this paper,we investigate the beamforming design problem for multiple-input multipleoutput(MIMO)ISAC systems and propose to maximize the radar beampattern gain of the target direction while ensuring the signal-to-interference-plus-noise ratio(SINR)constraints of communication users.Particularly,we discuss two cases of ISAC transmit beamforming,i.e.,Case-Ⅰand Case-Ⅱ,which do not have and do have the dedicated probing signal,respectively.For these two cases of transmit beamforming design problems,we start from the single-user scenario and provide the closed-form solutions for MIMO ISAC beamforming vectors.Then,we consider the multiuser scenario and utilize the semidefinite relaxation technique to convert the beamforming design problems into convex semidefinite programming problems.Furthermore,we investigate the impact of the channel correlation between radar and communication on the performance gain of MIMO ISAC systems and characterize the performance tradeoff.Numerical results validate that the dedicated probing signal is unnecessary in the single-user scenario,whereas it has a slight improvement in target detection performance at low SINR thresholds in the multi-user scenario.It is also shown that the stronger the correlation between radar and communication channels,the greater the performance gain of the system.展开更多
In this paper,we study a class of Linear Fractional Programming on a nonempty bounded set,called the Problem(LFP),and design a branch and bound algorithm to find the global optimal solution of the problem(LFP).First,w...In this paper,we study a class of Linear Fractional Programming on a nonempty bounded set,called the Problem(LFP),and design a branch and bound algorithm to find the global optimal solution of the problem(LFP).First,we convert the problem(LFP)to the equivalent problem(EP2).Secondly,by applying the linear relaxation technique to the problem(EP2),the linear relaxation programming problem(LRP2Y)was obtained.Then,the overall framework of the algorithm is given,and the convergence and complexity of the algorithm are analyzed.Finally,experimental results are listed to illustrate the effectiveness of the algorithm.展开更多
This study presents and verifies a hybrid methodology for reliable determination of parameters in structural rheological models(Zener,Burgers,and Maxwell)describing the viscoelastic behavior of polyurethane specimens ...This study presents and verifies a hybrid methodology for reliable determination of parameters in structural rheological models(Zener,Burgers,and Maxwell)describing the viscoelastic behavior of polyurethane specimens manufactured using extrusion-based 3D printing.Through comprehensive testing,including cyclic compression at strain rates ranging from 0.12 to 120 mm/min(0%-15%strain)and creep/relaxation experiments(10%-30%strain),the lumped parameters were independently determined using both analytical and numerical solutions of the models’differential equations,followed by cross-verification in additional experiments.Numerical solutions for creep and relaxation problems were obtained using finite element analysis,with the three-parameter Mooney-Rivlin model and Prony series employed to simulate elastic and viscous stress components,respectively.Energy dissipation per cycle was quantified during cyclic compression tests.The results demonstrate that all three models adequately describe material behavior within the 0%-15%strain range across various strain rates.Comparative analysis revealed the Burgers model’s superior performance in characterizing creep and stress relaxation at low strain levels.While Zener and Burgers model parameters from uniaxial compression showed limited applicability for energy dissipation calculations,the generalized Maxwell model effectively captured viscoelastic properties across different strain rates.Notably,parameters derived from creep tests provided a more universal assessment of dissipative properties due to optimization based on characteristic curve regions.Both parameter sets described polyurethane’s elastic-hysteretic behavior with approximately 20%error,proving significantly more accurate than the linear strain-time dependence hypothesis.Finite element analysis(FEA)complemented numerical modeling by demonstrating that while the generalized Maxwell model effectively describes initial rapid stress-strain changes,FEA provides superior characterization of steady-state processes.This computational approach yields more physically representative results compared to simplified analytical solutions,despite certain limitations in transient analysis.展开更多
Distributions of nuclear magnetic resonance(NMR)relaxation times provide detailed information about the water in wood.This study documents the water dynamics analysis of T_(2)and T_(1)distributions for saturated delig...Distributions of nuclear magnetic resonance(NMR)relaxation times provide detailed information about the water in wood.This study documents the water dynamics analysis of T_(2)and T_(1)distributions for saturated delignified sapwood(DSW),delignified heartwood(DHW)and lignocellulose(LC)samples at different temperatures.Results indicate that below the freezing point of bulk water,free water freezes,causing its signal to disappear from the distribution.Then,the low temperature distributions of the unfrozen bound water contain more information about its components,with DSW,DHW and LC containing two distinct states of bound water(OH bound water(B-water)and more freely bound water(C-water)).Furthermore,it was observed that within the temperature range of−3°C to−60°C,B-water in DSW,DHW and LC maintained a higher unfrozen water content(UWC)value than C-water,and the T_(1)/T_(2)ratios for B-water were consistently higher than that for C-water,indicating that B-water has a greater antifreeze capacity.T_(2)and T_(1)distributions offer different kinds of information about water components,and all peaks within the distribution have been assigned.展开更多
文摘Oxopentanedioic acid isonicotinoyl hydrazone (H_2L) and its five rare earth complexes were synthesized with a view to further investigating MRI activities of the polycarboxylic Schiff base complexes. The complexes were characterized on the basis of elemental analyses, IR, UV, (()~1H) NMR spectra and thermal analyses. The general formula of the complexes is [Ln(HL)(H_2O)_2]Cl_2·H_2O (where Ln(Ⅲ)=La, Pr, Nd, Eu and Gd). In addition, the relaxivity ( R _1) of the Gd-complex was determined by INVREC Au program.
基金Project supported by the Chinese Academy of Sciences and the State Sciences and Technology Commission of China.
文摘Five neutral macromolecular polyester gadolinium (Ⅲ) complexes with pendant hydrophobic alkyland aromatic functional groups were prepared. The longitudinal relaxation rates of these complexes weremeasured. One of these Gd (Ⅲ) complexes was chosen for the acute toxicity test and T_1-weighted imagingmeasurement. Preliminary results showed that. compared with Gd-DTPA. the neutral macromoleculargadolinium (Ⅲ) complexes provide higher T_1 relaxivity enhancement and longer function duration.
文摘Fifteen new polyester ligands were prepared by copolymerndion Of EDTA(ethylenediaminetetraacetic acid ) dianhydride or DTPA (dikthylenetriaminepenlaacetic acid) dianhydrtde and dihydric alcohol or dihydric phenol. Theirparanzagnetic metal complexes were also synthesized. All polyester ligands andmetal complexes were characterized by IHNMR, IR spectra and elemental analyses. Preliminary study showed that the polyester .metal complexes had higher relaxation effectiveness as compared to corresponding small molecular metal complexes.
基金National Natural Science Foundation of China(22201279 and 22171100)for financial support.
文摘Multifunctional lanthanide complexes have been extensively studied in recent years owing to their widespread applications in physics,chemistry and biology,including quantum information processing,molecular spintronics and theranostics.The multifunctionality includes chirality,luminescence,magnetism,ferroelectricity,fluorescence/magnetic resonance imaging etc.Although various N-and O-donor ligands have shown the ability to synthesize these complexes,Schiff bases are still the most widely used in constructing air-stable species.Herein,we report the facile gram-level synthesis of three pairs of lanthanide macrocycle enantiomers via an in situ[2+2]imine condensation with a trivalent lanthanide ion as a template.Eu_((III))-based compounds,R/S-Eu and R/S-Eu-Ph_(3)PO,both show efficient circularly polarized luminescence(CPL)with maximum dissymmetry factors(glum)of 0.098 and 0.110,respectively.The latter exhibited stronger emission intensity and a longer luminescence lifetime than the former due to the lower vibrational coordination structures around the Eu_((III))ion.Gd_((III))-based species,R/S-Gd,possess a relatively high relaxivity of up to 35.04 and 34.09 mM^(-1)s^(-1)for R-and S-enantiomers,benefitting from the presence of one coordinated water molecule and abundant intermolecular H-bonds.In addition,the results of the MTT assay and in vitro experiments demonstrated the low toxicity and efficient MRI of Gd_((III))-chelates in A549 cells.
基金the financial support from Universitàdel Piemonte Orientale(Ricerca locale 2019)This work was carried out within the framework of the COST CA15209 Action‘European Network on NMR Relaxometry’.
文摘A homogeneous series of polynuclear structures containing from 2 to 6 GdAAZTA complexes(AAZTA=6-amino-6-methylperhydro-1,4-diazepine tetraacetic acid)were synthesized covering a broad range of molecular weights,ca.1200-6000 Da.A frequency and temperature dependent 1H and 17O NMR relaxometric study on the Gd(III)polynuclear complexes clearly highlights a considerable gain of relaxivity(per Gd)passing from the monomer to the hexanuclear complex,with an enhancement of+370%at 1.5 T and 298 K(+470%at 310 K).In particular,the relaxivity of the hexamer reaches a remarkable value of 28.2 mM^(−1)s^(−1)at 1.5 T and 298 K(23.8 mM^(−1)s^(−1)at 310 K).The NMR study,supported by DFT calculations,allows analysis in detail of the dependence of the rotational dynamics on the size and molecular geometry of the multimers,considering both the global tumbling of the system and the local motions of the monomer units.In addition,T1-weighted phantom MR-images at 1,3 and 7 T on selected polynuclear complexes highlighted the effective signal enhancement of the new MRI probes at clinically relevant magnetic field strengths in comparison with the clinically approved contrast agent ProHance®.Finally,the results obtained enable us to highlight effective strategies for relaxation enhancement,each suitable for a well-defined range of applied magnetic field strength.
基金the Hungarian National Research,Development and Innovation Office-NKFIH under the Grant NKFI NN 128368.D.H.:University of Debrecen,Faculty of Science and Technology,Department of Physical Chemistry,Doctoral School of Chemistry.
文摘Gadolinium(III)complexes have been employed for more than 30 years as contrast agents in magnetic resonance imaging(MRI).In order to further improve the diagnostic accuracy of enhanced magnetic resonance images or to provide comparable enhancement at a reduced administered dose,current research is focusing on the development of Gd^(Ⅲ)-complexes characterized by higher relaxivity.In this study we describe the synthesis and the equilibrium,kinetic,relaxation and structural properties of two new Gd^(Ⅲ)-complexes based on modified 10-(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid(HP-DO3A)structure which,due to an intramolecular prototropic exchange,display more than two-fold higher relaxivity compared to currently available Gd^(Ⅲ)-based MRI contrast agents.
基金supported in part by SNF Strategic Japanese-Swiss Science and Technology Program(IZLJZ2_183660,YY)JSPS,under the Joint Research Program implemented in association with SNF(20191508,H.M.and N.Y.-S),SNF Project Funding(205321_173018,Y.Y.)+4 种基金ETH Research Grants(ETH-21_15-2ETH-36_20-2,Y.Y.)JSPS KAKENHI(Grant-in-Aid for Scientific Research[A],6251004,H.M.Grants-in-Aid for Scientific Research on Innovative Areas,21H00264,22H04707,H.M.Grant-in-Aid for Scientific Research[C],15K07164,N.Y.-S).
文摘Three water-soluble Mn(III)-porphyrin complexes with cationic pyridyl side groups bearing COOH-or OH-terminated carbon chains in the meta or para positions have been synthesized as probes for both magnetic resonance imaging(MRI)and photodynamic therapy(PDT).The complexes Mn-1,Mn-2,and Mn-3 are highly water-soluble,and their relaxivities range between 10 and 15 mM^(-1) s^(-1),at 20-80 MHz and 298 K,2-3 times higher than that of commercial Gd(III)-based agents.The complexes containing carboxylate(Mn-2)or alcoholic(Mn-3)side chains in the para position are endowed with higher relaxivities and have also shown efficient photoinduced DNA cleavage and singlet oxygen(^(1)O_(2))generation.Mn-3 with stronger photoinduced DNA cleavage has also revealed stabilizing and binding activities for G4 DNA,at a similar level as the known G4 binder Mn-TMPyP4.Nevertheless,the G4-binding activity of Mn-3 was nonspecific.Preliminary tests evidenced photocytotoxicity of Mn-3 on HeLa cells without a significant effect in the absence of light.Altogether,these results underline the potential of such water-soluble Mn(III)-porphyrins for the development of multimodal approaches combining MRI and PDT.
文摘Nuclear magnetic resonance (NMR) relaxation of fluids in porous media is affected by the solid-liquid interface. Quantitative determination of the surface relaxivity is significantly important for both investigation and application of relaxation mechanisms in porous media. A method to estimate the surface relaxivity with the combination of relaxation and diffusion measurements is proposed. According to this method, a criterion for testing the current diffusion and relaxation theory for porous media is available.
文摘Synthesis of ligand, α-oxo-pentanedioic acid benzoyl hydrazone (H2LPB), and its six rare earth (La, Pr, Nd, Sm, Gd and Er) complexes are reported. The composition and the properties of the complexes were characterized by element analysis, thermal analysis, UV, IR and H NMR spectra. Besides, relaxivity (R1) of Gd-complex has been determined by INVREC.Au program, using inversion recovery pulse sequences, R1=8.05 mmol ·L-1 · s-1. The acute toxicity of Gd-complex in animal has also been tested, and the median lethal dose (LD50) is equal to (468.2±30) mg/kg.
基金The National Natural Science Foundations of China (12202219)the Natural Science Foundations of Ningxia (2024AAC02009, 2023AAC05001)the Ningxia Youth Top Talents Training Project。
文摘The fast solution of linear equations has always been one of the hot spots in scientific computing.A kind of the diagonal matrix splitting iteration methods are provided,which is different from the classical matrix splitting methods.Taking the decomposition of the diagonal elements for coefficient matrix as the key point,some new preconditioners are constructed.Taking the tri-diagonal coefficient matrix as an example,the convergence domains and optimal relaxation factor of the new method are analyzed theoretically.The presented new iteration methods are applied to solve linear algebraic equations,even 2D and 3D diffusion problems with the fully implicit discretization.The results of numerical experiments are matched with the theoretical analysis,and show that the iteration numbers are reduced greatly.The superiorities of presented iteration methods exceed some classical iteration methods dramatically.
文摘A novel ligand of DTPA-dihydropyridine derivative was synthesized by reaction of DTPA-dianhydride with 4-aniline-1,4-dihydropyridine. Its complexes of gadolinium, manganese and iron were prepared. Their spin-lattice relaxivities (T1) were investigated. The results show that the NMR T1 relaxivitives (R1) for complexes of Fe(Ⅲ), Mn(Ⅱ) are less than that of Gd(Ⅲ) complex,which has a high relaxivity (R1) on the surrounding water protons, indicating that the Gd(Ⅲ) complex possesses the precondition to be contrast agents for magnetic resonance imaging.
基金Project supported by the Municipal Natural Science Foundation of Beijing （No. 2022011）.
文摘X-ray single crystal analysis of a new paramagnetic manganese（Ⅱ） complex with DTPA-BpABA （a DTPAbisamide derivative）, Mn（DTPA-BpABA）·4H2O, shows that four oxygen atoms and three nitrogen atoms from the ligand coordinate to Mn（Ⅱ） cation, forming a seven-coordinate distorted pentagonal bipyramid polyhedron. In the crystal, the carboxyl groups and the nitrogen atoms extensively form hydrogen bonds with the lattice water molecules, building a 3D-network. The relaxometric study indicates that the R1 value of the paramagnetic manganese（Ⅱ）complex is 5.12 mmol·L·s^-1. The higher R1 value means that this complex may find an application in magnetic resonance imaging （MRI） technique.
文摘It’s never too early in the year to start planning a break from the stress of city life,and southwest China’s charming Guizhou Province is a destination that should be right at the top of your list.
文摘In order to enable wing morphing(e.g.change in camber or folds)without incurring additional weight to the aircraft,lightweight flexible materials such as membrane are needed.However,the research on fluid-structure coupling of membranes has mainly focused on parachutes in low-speed conditions,while that in supersonic flow conditions is lacking.Here,the degraded shell method is proposed to study membrane deformation by using shell element,which is more effective than using membrane elements directly.A fluid-structure interaction computational framework is proposed,whereby the aerodynamic module is composed of either the piston theory or computational fluid dynamics.A rectangular membrane of length 0.4 m and width 0.6 m is investigated in supersonic conditions.The characteristics of the limit cycle and steady deformation are analyzed,considering the effects of angle of attack and dynamic pressure.It is found that the structural response exhibits significant differences under various angles of attack.Furthermore,initial relaxation of membrane has significant influence on the structural deformation.Finally,the aeroelastic scaling method for membrane structures is derived,providing guidance for the design of wind tunnel models.This study provides a theoretical foundation for the analysis and application of membrane structures under supersonic conditions in future research.
基金supported by a National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(RS-2023-NR076521,RS-2025-00519481)the Research Grant of Kwangwoon University in 2023.
文摘The photovoltaic performance of metal halide perovskite solar cells often respond divergently to environmental conditions during storage.In particular,light exposure can either enhance or degrade device efficiency,yet the mechanisms underlying these antithetical behaviors are still under investigation.In this study,we explore the modulation of the open-circuit voltage(Voc)in triple-cation mixed-halide perovskite solar cells by systematically controlling storage environments.While light intensity exhibits minimal impact during storage,the spectral composition of illumination selectively enhances Voc comprising reversible and irreversible contributions.Structural characterization reveals that prolonged storage degrades the quality of perovskite crystals in the upper region of the perovskite layer,whereas light storage promotes the relaxation of microstrain at the buried interface with a p-type organic layer.This structural reorganization at the interface,accompanied by lattice expansion,accounts for suppressed nonradiative recombination and a corresponding increase in quasi-Fermi level splitting.Consequently,devices fabricated without chemical defect passivation achieve a power conversion efficiency of higher than 40%under indoor lighting conditions after preconditioned by continuous exposure to ambient light during storage.These findings highlight the critical role of controlled light exposure during storage not only in enhancing efficiency,but also in ensuring reproducibility of perovskite solar cell characterization.
基金support of her postdoctoral research at the GFZ Helmholtz Centre for Geosciences.P.Pan acknowledges the financial support of the National Natural Science Foundation of China(Grant No.52339001)H.Hofmann and Y.Ji acknowledge the financial support of the Helmholtz Association's Initiative and Networking Fund for the Helmholtz Young Investigator Group ARES(contract number VH-NG-1516).
文摘A multi-stage stress relaxation test was performed on a granodiorite sample to understand the deformation process prior to the macroscopic failure of brittle rocks,as well as the transient response during stress relaxation.Distributed optical fiber sensing was used to measure strains across the sample surface by helically wrapping the single-mode fiber around the cylindrical sample.Close agreement was observed between the circumferential strains obtained from the optical fibers and the extensometer.The reconstructed full-field strain contours show strain heterogeneity from the crack closure phase,and the strains in the later deformation phase are dominantly localized within the former high-strain zone.The Gini coefficient was used to quantify the degree of strain localization and shows an initial increase during the crack closure phase,a decrease during the linear elastic phase,and a subsequent increase during the post-yielding phase.This behavior corresponds to a process of initial localization from an imperfect boundary condition,homogenization,and eventual relocalization prior to the macroscopic failure of the sample.The transient strain rate decay during the stress relaxation phase was quantified using the p-value in the“Omori-like"power law function.A higher initial stress at the onset of relaxation results in a lower p-value,indicating a slower strain rate decay.As the sample approaches macroscopic failure,the lowest p-value shifts from the most damaged zone to adjacent areas,suggesting stress redistribution or crack propagation in deformed crystalline rocks under stress relaxation conditions.
基金National Natural Science Foundation of China under Grant 62571248 and Grant 62201266Key Laboratory of Intelligent Space TTC&O(Space Engineering University),Ministry of Education under Grant CYK2025-01-12。
文摘Integrated sensing and communication(ISAC)is an appealing approach to address spectrum congestion and beamforming is an effective method to realize ISAC.In this paper,we investigate the beamforming design problem for multiple-input multipleoutput(MIMO)ISAC systems and propose to maximize the radar beampattern gain of the target direction while ensuring the signal-to-interference-plus-noise ratio(SINR)constraints of communication users.Particularly,we discuss two cases of ISAC transmit beamforming,i.e.,Case-Ⅰand Case-Ⅱ,which do not have and do have the dedicated probing signal,respectively.For these two cases of transmit beamforming design problems,we start from the single-user scenario and provide the closed-form solutions for MIMO ISAC beamforming vectors.Then,we consider the multiuser scenario and utilize the semidefinite relaxation technique to convert the beamforming design problems into convex semidefinite programming problems.Furthermore,we investigate the impact of the channel correlation between radar and communication on the performance gain of MIMO ISAC systems and characterize the performance tradeoff.Numerical results validate that the dedicated probing signal is unnecessary in the single-user scenario,whereas it has a slight improvement in target detection performance at low SINR thresholds in the multi-user scenario.It is also shown that the stronger the correlation between radar and communication channels,the greater the performance gain of the system.
基金Supported by the National Natural Science Foundation of China(Grant Nos.12571317 and 12071133).
文摘In this paper,we study a class of Linear Fractional Programming on a nonempty bounded set,called the Problem(LFP),and design a branch and bound algorithm to find the global optimal solution of the problem(LFP).First,we convert the problem(LFP)to the equivalent problem(EP2).Secondly,by applying the linear relaxation technique to the problem(EP2),the linear relaxation programming problem(LRP2Y)was obtained.Then,the overall framework of the algorithm is given,and the convergence and complexity of the algorithm are analyzed.Finally,experimental results are listed to illustrate the effectiveness of the algorithm.
文摘This study presents and verifies a hybrid methodology for reliable determination of parameters in structural rheological models(Zener,Burgers,and Maxwell)describing the viscoelastic behavior of polyurethane specimens manufactured using extrusion-based 3D printing.Through comprehensive testing,including cyclic compression at strain rates ranging from 0.12 to 120 mm/min(0%-15%strain)and creep/relaxation experiments(10%-30%strain),the lumped parameters were independently determined using both analytical and numerical solutions of the models’differential equations,followed by cross-verification in additional experiments.Numerical solutions for creep and relaxation problems were obtained using finite element analysis,with the three-parameter Mooney-Rivlin model and Prony series employed to simulate elastic and viscous stress components,respectively.Energy dissipation per cycle was quantified during cyclic compression tests.The results demonstrate that all three models adequately describe material behavior within the 0%-15%strain range across various strain rates.Comparative analysis revealed the Burgers model’s superior performance in characterizing creep and stress relaxation at low strain levels.While Zener and Burgers model parameters from uniaxial compression showed limited applicability for energy dissipation calculations,the generalized Maxwell model effectively captured viscoelastic properties across different strain rates.Notably,parameters derived from creep tests provided a more universal assessment of dissipative properties due to optimization based on characteristic curve regions.Both parameter sets described polyurethane’s elastic-hysteretic behavior with approximately 20%error,proving significantly more accurate than the linear strain-time dependence hypothesis.Finite element analysis(FEA)complemented numerical modeling by demonstrating that while the generalized Maxwell model effectively describes initial rapid stress-strain changes,FEA provides superior characterization of steady-state processes.This computational approach yields more physically representative results compared to simplified analytical solutions,despite certain limitations in transient analysis.
基金supported by Natural Science Foundation of Inner Mongolia Autonomous Region of China (2023MS03027)the National Natural Science Foundation of China (31860185 and 31160141)
文摘Distributions of nuclear magnetic resonance(NMR)relaxation times provide detailed information about the water in wood.This study documents the water dynamics analysis of T_(2)and T_(1)distributions for saturated delignified sapwood(DSW),delignified heartwood(DHW)and lignocellulose(LC)samples at different temperatures.Results indicate that below the freezing point of bulk water,free water freezes,causing its signal to disappear from the distribution.Then,the low temperature distributions of the unfrozen bound water contain more information about its components,with DSW,DHW and LC containing two distinct states of bound water(OH bound water(B-water)and more freely bound water(C-water)).Furthermore,it was observed that within the temperature range of−3°C to−60°C,B-water in DSW,DHW and LC maintained a higher unfrozen water content(UWC)value than C-water,and the T_(1)/T_(2)ratios for B-water were consistently higher than that for C-water,indicating that B-water has a greater antifreeze capacity.T_(2)and T_(1)distributions offer different kinds of information about water components,and all peaks within the distribution have been assigned.
