NMR relaxation and diffusion studies to probe the motional dynamics of risperidone within PLGA microsphere

The present study aims to investigate the motional dynamics of risperidone within polylactic co-glycolic acid(PLGA)microsphere by employing solution state'H and 19F nuclear magnetic resonance(NMR)measurements.Risperidone,a second-generation fluorinated antipsychotic drug used for the treatment of schizophrenia is commercially marketed as PLGA microsphere formulation resulting in prolonged release of the drug in solution.Although the current trend in the pharmaceutical market is to develop drug formulation with long-acting release(LAR)products,complete physicochemical characterization of such formulations are scarce.Especially the effects of microsphere encapsulation on the motional properties and diffusion behavior of the drugs are not discussed adequately in any of the earlier reports.We therefore,have employed NMR relaxation and diffusion measurements to decipher the interaction of PLGA cavity water with risperidone.A detailed analysis of NMR relaxation rates confirmed the event of encapsulation and the presence of local motion in the non-fluorinated end of risperidone.Further,the relaxation data indicated a significant alteration in 19F chemical shift anisotropy(CSA)and CSA/dipole-dipole(DD)cross-correlated relaxation mechanism and decreased effect of solvent relaxation pointing out reduced water concentration within the microsphere cavity.'H and 19F diffusion coefficients of risperidone led to the information about hydrodynamic radius of risperidone in free and encapsulated states.Measurement of hydrodynamic radius supported the presence of limited water in PLGA cavity allowing higher translational mobility of risperidone after the encapsulation.

Universal properties of relaxation and diffusion in condensed matter

By and large the research communities today are not fully aware of the remarkable universality in the dynamic properties of many-body relaxation/diffusion processes manifested in experiments and simulations on condensed matter with diverse chemical compositions and physical structures. I shall demonstrate the universality first from the dynamic processes in glass-forming systems. This is reinforced by strikingly similar properties of different processes in contrasting interacting systems all having nothing to do with glass transition. The examples given here include glass-forming systems of diverse chemical compositions and physical structures, conductivity relaxation of ionic conductors（liquid, glassy, and crystalline）,translation and orientation ordered phase of rigid molecule, and polymer chain dynamics. Universality is also found in the change of dynamics when dimension is reduced to nanometer size in widely different systems. The remarkable universality indicates that many-body relaxation/diffusion is governed by fundamental physics to be unveiled. One candidate is classical chaos on which the coupling model is based, Universal properties predicted by this model are in accord with diverse experiments and simulations.

Phase Transition and Oxygen Ion Diffusion in （La1-xLnx）2Mo2O9 （Ln=Nd, Gd, x=0.05-0.25） Using Dielectric Relaxation Method

Dielectric relaxation method was employed to study the properties of oxygen ion diffusion and phase transition in the oxide-ion conductors （Lal-xLnx）2Mo209 （Ln=Nd, Gd, x=0.05-0.25）. Two dielectric loss peaks were observed： peak Pd at about 600 K and peak P5 around 720 K. Peak Pd is a relaxational peak and associated with the short-range diffusion of oxygen ions, while peak P5 hardly changes its position and dramatically decreases in height with increasing frequency, exhibiting non-relaxational nature. With increasing Ln^3＋ concentration, the heights of peak Ph and Pd increase at first and then decrease after passing a maximum at 15% doping. It is suggested that peak P5 is related to the phase transition of a static disordered state to a dynamic disordered state in oxygen ions/vacancies distribution. It is found that the 15%Gd or 15%Nd doped La2Mo209 samples exhibit the highest conductivity in accordance with the highest height of peak Pd at this doping content.

Stretched Exponential Relaxation in Disordered Complex Systems： Fractal Time Random Walk Model

We have analytically derived the relaxation function for one-dimensional disordered complex systems in terms of autocorrelation function of fractal time random walk by using operator formalism. We have shown that the relaxation function has stretched exponential, i.e. the Kohlrausch-Williams-Watts character for a fractal time random walk process.

Diffusion activation enthalpy of nanocrystalline metals

The atomic diffusion of nanocrystalline metals showed significant difference in comparison to poycrystalline metals, this property is analyzed by considering the effect of temperature - time history on the interfacial structure. The interfacial structure is approximated by a dilated perfect crystal. Based on LeClair’s diffusi on theory, diffusbo activation enthalpy in nanocrysta1line meta1s was calculated. The results show that the change of diffusion activation enthalpy is closely related to the structure relaxation of the interfaces and the interfacial migration, the structure relaxation of the interfaces will increase the diffusion activation enthalpy when the crystallite growth can be negligible, whereas the migration of the interfaces will lead to the further increase of the diffusion activation enthalpy when crystallite growth proceeds rapid1y. The theoretical prediction is found to be in accoedance with experimental observations.

Response of thermal source in a transversely isotropic thermoelastic half-space with mass diffusion by using a finite element method

The two-dimensional problem of generalized thermoelastic diffusion material with thermal and diffusion relaxation times is investigated in the context of the Lord-Shulman theory. As an application of the problem, a particular type of thermal source is considered and the problem is solved numerically by using a finite element method. The components of displacement, stress, temperature distribution chemical potential and mass concentration are obtained. The resulting quantities are depicted graphically for a special model. An appreciable effect of relaxation times is observed on various resulting quantities.

Oxygen diffusion in c-textured epitaxial YBa_2Cu_3O_(7-δ) thin films

Isothermal oxygen in diffusion in c textured epitaxial YBa 2Cu 3O 7- δ thin films was studied by in situ X ray diffraction. Thermal expansion coefficients of c axis length with different oxygen contents are α c (6.91, O 2)=19.1×10 -6 K -1 and α c (6.0, N 2)=19.3×10 -6 K -1 respectively. Chemical diffusion process of oxygen was described by relaxation time. From the Arrhenius plot of relaxation time, an activation energy of lattice diffusion was obtained as 1.1?eV, which is close to the results of SIMS (0.95?eV) and internal friction (1.02?eV).

CONVERGENCE RESULTS FOR NON-OVERLAP SCHWARZ WAVEFORM RELAXATION ALGORITHM WITH CHANGING TRANSMISSION CONDITIONS

In this paper,we establish a new algorithm to the non-overlapping Schwarz domain decomposition methods with changing transmission conditions for solving one dimensional advection reaction diffusion problem.More precisely,we first describe the new algorithm and prove the convergence results under several natural assumptions on the sequences of parameters which determine the transmission conditions.Then we give a simple method to estimate the new value of parameters in each iteration.The interesting advantage of our method is that one may update the better parameters in each iteration to save the computational cost for optimizing the parameters after many steps.Finally some numerical experiments are performed to show the behavior of the convergence rate for the new method.

Difference Analysis of MRI Apparent Diffusion Coefficient and R_(2)^(*)Value Between Small Hepatocellular Carcinoma and Cirrhosis Nodules

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.

Simulation Analysis of the Effect of Relaxation Time on Flight Delays Propagation

Relaxation time of flights is one of the main factors that affect the diffusion of flight delays, but the specific relationship between them is ambiguous.？Gaining a clear idea of their relationship conduces to the control of flight delays.？Through the establishment of the aviation network model and simulation analysis of the effect of relaxation time on delay spread, it can be found that the relaxation time is inversely proportional to the total delay time and the number of airports that have been delayed due to the delay spread, and there is no evident linear relationship between the relaxation time and the average delay time.？This demonstrates that increasing the relaxation time properly can reduce the propagation of flight delays and improve the punctuality rate of flights.

磁共振增强T1 mapping和IVIM-DWI技术评估乙型肝炎肝硬化患者肝脏储备功能价值研究

目的分析应用磁共振(MR)体素内不相干运动扩散加权成像(IVIM-DWI)和钆塞酸二钠增强T1 mapping参数评估乙型肝炎肝硬化患者肝脏储备功能的价值。方法2020年3月~2022年3月我院诊治的乙型肝炎肝硬化患者60例,接受吲哚菁绿15 min滞留率检测和MR增强扫描,测量增强前20 min和增强后20 min T1弛豫时间,计算肝细胞增强分数,并应用Mltalytics 1.0.1软件自动测算表观扩散系数(ADC)和真性水分子扩散系数(D)。应用受试者工作特征(ROC)曲线分析参数评估肝储备的效能。结果在60例肝硬化患者中,吲哚菁绿15 min滞留率<10%者30例(A组),≥10%但<30%者16例(B组),≥30%者14例(C组);C组增强前T1弛豫时间和增强后T1弛豫时间分别为(700.5±71.2)ms和(324.1±99.6)ms,显著长于A组【分别为(612.2±28.3)ms和(148.3±51.9)ms,P<0.05】或B组【分别为(682.5±73.1)ms和(256.2±88.1)ms,P<0.05】,而ADC、D和肝细胞增强分数分别为(0.5±0.1)×10^(3)、(0.5±0.1)×10^(3)和(50.2±11.6)%,均显著低于A组【分别为(1.2±0.1)×10^(3)、(1.0±0.4)×10^(3)和(80.8±10.9)%,P<0.05】或B组【分别为(0.8±0.2)×10^(3)、(0.7±0.2)×10^(3)和(59.4±19.7)%,P<0.05】;ROC曲线分析显示,增强前和增强后20 min T1弛豫时间、ADC、D和肝细胞增强分数评估乙型肝炎肝硬化患者肝脏储备功能均具有较高的价值(灵敏度均在70.0%以上,特异度均在76.7%以上)。结论应用MR IVIM-DWI和T1 mapping参数评估乙型肝炎肝硬化患者肝脏储备功能具有很大的临床价值,可为临床决策提供影像学依据。

Diffusion and Relaxation Dynamics of Supercooled Polymer Melts

The dynamic properties of polymer melts are investigated in the range of normal liquid regime to the supercooled liquid regime. The polymer is modeled as a coarse-grained bead-spring model with chain length ranging from 5 to 160. The mean squared displacement and non-Gaussian parameter are used to describe the self diffusion of polymer beads. We find slow dynamics with decreasing temperature and increasing chain length. The time evolution of non-Gaussian parameters shows two peaks （or one peak one shoulder） in the a-relaxation time, τa, regime and sub-diffusion time regime, respectively, where the first primary peak indicates the dynamic heterogeneity stemmed from the motion of beads, and the secondary peak is the result of correlated motion along a polymer chain. Moreover, the relaxation of polymer beads shows clear two-step decay in supercooled melts and the dynamics shows growing heterogeneity with decreasing temperature. As chain length is increased, a peak of the dynamic susceptibility occurs, and the peak height, x＊4, increases and then reaches a plateau. The curves of the height of the first peak of a2, a2＊, versus τa and the curves of x＊4 versus τa follow two master curves for different chain lengths. Our results indicate the similarity of dynamic heterogeneity dominated by the motion of single bead even the chain length is different. It is interesting to find that the Stokes-Einstein （SE） relation between ra and diffusion coefficient D, D-rq 1, is highly length-scale dependent. The SE relation breaks down in both normal melts regime and supercooled regime at large magnitude of wave vectors, attributed to the non-Brownian motion arising from the chain connectivity and growing heterogeneity due to supercooling. However, the SE relation is reconstructed when the probing length scale is large （at small magnitude of wave vectors）. Our results show a hierarchical physical picture of the supercooled polymeric dynamics.

Domain structure and dielectric diffusion-relaxation characteristics of ternary Pb(In_(1/2)Nb_(1/2))O_(3)-Pb(Mg_(1/3)Nb_(2/3))O_(3)-PbTiO_(3)ceramics

Relaxor-based ternary Pb(In1/2Nb1/2)O_(3)-Pb(Mg_(1/3)Nb_(2/3))O_(3)-PbTiO_(3)(PIN-PMN-PT)single crystals and ceramics are promis­ing candidates for high-performance electromechanical conversion devices.It is known that the domain structure and dielectric diffusion-relaxation characteristics are crucial to the excellent performances of relaxor ferroelectrics.In this work,we prepared the PIN-PMN-PT ceramics with various PIN/PMN proportions and systematically investigated their domain structure and dielec­tric diffusion-relaxation properties.The effect of PIN/PMN proportion on the domain size and dielectric diffusion-relaxation characteristics was also studied.The investigations showed that PIN-PMN-PT ceramics presented multi-type domain patterns comprising irregular island domains and regular lamellar domains.Moreover,the dependent relations of PIN/PMN proportions on the dielectric diffusion and domain size indicated that the PIN composition has a stronger lattice distortion than PMN composi­tion;increasing the PIN proportion can enhance the dielectric diffusion and decrease the domain size.Our results could deepen the understanding of structure-property relationships of multicomponent relaxor ferroelectrics and guide the design and exploration of new high-performance ferroelectric materials.

弛豫时间分布阻抗分析PEMFC气体扩散层传质现象

电化学阻抗谱是电化学中常用的技术,而传统方法在分析EIS数据时不够准确直观,为此,弛豫时间分布法可以更有效地解决该问题。基于弛豫时间分布法在处理电化学阻抗数据的直观有效性上,对燃料电池的气体扩散层在不同压缩率与不同操作条件下的传质情况进行分析。测试结果表明低压缩率的电池接触电阻较大,高压缩率的电池存在被压塌的可能,10%与20%表现较好。低电流密度下,不同压缩率的性能与阻抗无明显差别,电流密度逐渐升高时,传质阻力影响最大,电荷传输次之。改变操作条件,背压的改变会影响水传质的效果;在性能相近的不同压缩率下,过量系数会改善气体传输阻力;而加湿度变低,会增大传质,峰值的位置也会产生偏移现象。

岩心孔隙介质中流体的核磁共振弛豫

弛豫时间是核磁共振研究中的一个重要参数,岩心孔隙介质流体的弛豫过程是自由流体弛豫机制、表面弛豫机制和流体的扩散弛豫机制共同作用的结果,它包含了丰富的孔隙和流体本身的信息.弛豫时间和自扩散系数的测量及对弛豫时间的分析是核磁共振技术应用于岩心分析和石油勘测的重要内容.

2D NMR技术在石油测井中的应用

近几年,2D NMR技术得到迅速发展,特别是在核磁共振测井领域.该文将主要介绍2D NMR技术的脉冲序列、弛豫原理以及2D NMR技术在石油测井中应用.2D NMR技术是在梯度场的作用下,利用一系列回波时间间隔不同的CPMG脉冲进行测量,利用二维的数学反演得到2D NMR.2D NMR技术可以直接测量自扩散系数、弛豫时间、原油粘度、含油饱和度、可动水饱和度、孔隙度、渗透率等地层流体性质和岩石物性参数.从2D NMR谱上,可以直观的区分油、气、水,判断储层润湿性,确定内部磁场梯度等.2D NMR技术为识别流体类型提供了新方法.

水驱油过程的核磁共振二维谱研究

岩心水驱油过程中油水分布状况是岩心多孔介质的重要性质.水驱油过程的研究是进一步进行提高采收率研究的基础.核磁共振扩散-弛豫二维谱提供了岩心中流体性质的多方面信息,与核磁共振一维弛豫谱相比极大地提高了区分油水的能力.该文通过2组岩心水驱油实验,从不同含油饱和度的扩散-弛豫二维谱中提取出水的一维弛豫谱,在原油粘度比较高的情况下获得了驱替过程中油水在不同孔隙中的分布状况以及润湿性等信息,解决了单独用一维弛豫谱方法难以区分油水的问题.该文的研究方法对油田提高采收率的研究有比较大的参考价值.

锂离子动力电池高倍率充放电过程中弛豫行为的仿真

基于电化学热耦合模型研究了动力锂离子电池高倍率充放电过程中的弛豫行为,分析对比了不同充放电机制对电池弛豫行为的影响.研究发现:充放电过程中,欧姆极化是造成电压骤变的主要原因;而恒流-恒压的充电模式能够缓慢消除欧姆极化,避免电池电压的骤变;利用恒流恒压对电池进行充电能够充进更多的电量,有利于电池性能的完全发挥;固相锂离子浓度的弛豫时间比液相锂离子浓度的弛豫时间长,并且在放电后期,固相扩散的特征时间与液相扩散特征时间的比值不断增大,固相扩散造成的极化在整个放电过程不可忽略.