relaxation time

松弛时间
  • 文章类型: Journal Article
    我们旨在评估T1、T2*的准确性和可重复性,和使用ISMRM/NISTMRI系统体模通过定量参数映射(QPM)获得的质子密度(PD)值,并将其与计算机模拟进行比较。我们将通过QPM获得的弛豫时间和PD与ISMRM/NISTMRI系统体模和常规方法的参考值进行了比较。此外,我们通过将获得的变异系数(CV)与模拟结果进行比较,评估了QPM获得的T1和T2*值中是否存在噪声以外的影响。T1、T2*、通过QPM的PD值与测量值和参考值具有很强的相关性。为每个球体计算的QPM的模拟CV显示出与实际扫描相似的趋势。
    We aimed to evaluate the accuracy and repeatability of the T1, T2*, and proton density (PD) values obtained by quantitative parameter mapping (QPM) using the ISMRM/NIST MRI system phantom and compared them with computer simulations. We compared the relaxation times and PD obtained through QPM with the reference values of the ISMRM/NIST MRI system phantom and conventional methods. Furthermore, we evaluated the presence or absence of influences other than noise in T1 and T2* values obtained by QPM by comparing the obtained coefficient of variation (CV) with simulation results. The T1, T2*, and PD values by QPM showed a strong correlation with the measured values and the referenced values. The simulated CVs of QPM calculated for each sphere showed similar trends to those of the actual scans.
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  • 文章类型: Journal Article
    该手稿描述了一种使用生物阻抗谱测量的特征频率研究组织和细胞中弛豫动力学的新方法。生物阻抗形式主义允许在频域和时域中同时研究生物电参数,提供对在感兴趣的组织或细胞中发生的可能的松弛过程的洞察。Cole-Cole分析的结果表明,没有与异质性相关的多个松弛过程,与女性相比,男性明显的年龄组分离。对时域弛豫动力学的研究表明,β参数可用于分析组织中的电荷载流子。细胞,或者癌细胞,可能导致癌症和其他疾病的新诊断和治疗方法。总的来说,这种方法提出了一个有前途的研究领域,以获得洞察的电性质的组织和细胞使用生物阻抗方法。
    This manuscript describes a novel methodology for studying relaxation dynamics in tissues and cells using characteristic frequency of bioimpedance spectroscopy measurements. The Bioimpedance Formalism allows for the simultaneous study of bioelectrical parameters in the frequency and time domains, providing insight into possible relaxation processes occurring in the tissue or cell of interest. Results from the Cole-Cole analysis showed no multiple relaxation processes associated with heterogeneity, with a visible age group separation in males compared with females. The study of the relaxation dynamic in the time domain revealed that the β parameter can be used to analyse the charge carriers in tissues, cells, or cancer cells, potentially leading to new diagnostic and therapeutic approaches for cancer and other diseases. Overall, this approach presents a promising area of research for gaining insights into the electrical properties of tissues and cells using bioimpedance methods.
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  • 文章类型: Journal Article
    使用被称为绿色工艺的智能或低盐度水由于其独特的功能和对环境的积极影响而受到越来越多的关注。鉴于这一事实,并且由于关于设计浓度或二元混合物和原油馏分下的盐对树脂(RSO)和沥青合成油(ASO)的界面张力(IFT)降低和润湿性改变的影响的知识有限,目前的调查是第一次设计和执行。此外,仔细研究了IFT变化的动态行为,并获得了弛豫时间并进行了建模,以查看单个和二价盐的影响以及在二元条件下的影响。弛豫时间表明,与所检查的ASO和RSO的油类型无关,NaCl/CaCl2盐水的吸附时间最低,这是由于极性官能团对界面的高移动亲和力,因此减少了覆盖和包装所需的时间。界面上的活性剂。最后,测得的接触角值揭示了二元盐对强水湿条件下润湿性变化的显着影响,特别是与原油相比,RSO和ASO。
    Using smart or low salinity waters known as green processes gained increasing attention due to their unique features and their positive impacts on the environment. In light of this fact and since there is limited knowledge about the effects of salts under engineered concentrations or binary mixtures and crude oil fractions on the interfacial tension (IFT) reduction and wettability alteration of the resinous (RSO) and asphaltenic synthetic oil (ASO), the current investigation is designed and performed for the first time. Moreover, the dynamic behavior of the IFT variation was carefully investigated and the relaxation time was obtained and modeled to see the impact of mono and divalent salts individually and in binary conditions. The relaxation times revealed that the lowest adsorption times were obtained for NaCl/CaCl2 brine regardless of the examined oil types of ASO and RSO due to the high movement affinity of the polar functional groups toward the interface consequently reducing the required time for coverage and packing of active agents at the interface. Finally, the measured contact angle values revealed a significant effect of binary salts on the wettability alteration toward strongly water-wet conditions, especially for the RSO and ASO compared with crude oil.
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  • 文章类型: Journal Article
    尽管弱小,范德华层间耦合,光诱导电荷转移垂直跨越原子薄的界面可以发生在令人惊讶的快速,低于50fs的时间尺度。对电荷转移的早期理论理解是基于非相互作用的图像,忽略控制此类材料光学特性的激子效应。我们采用了从头算的多体扰动理论方法,明确解释了异质结构中的激子和声子。我们的大规模第一性原理计算直接探测了激子-声子耦合在WS2/MoS2异质双层电荷动力学中的作用。我们发现,在MoS2和WS2的K谷处,光激发的激子-声子相互作用引起的弛豫时间在300K时为67和15fs,分别,这设置了层内到层间激子转移时间的下限,并且与实验报告一致。我们进一步表明,电子-空穴相关性促进了新的转移途径,否则非相互作用的电子和空穴无法进入。
    Despite the weak, van der Waals interlayer coupling, photoinduced charge transfer vertically across atomically thin interfaces can occur within surprisingly fast, sub-50 fs time scales. An early theoretical understanding of charge transfer is based on a noninteracting picture, neglecting excitonic effects that dominate optical properties of such materials. We employ an ab initio many-body perturbation theory approach, which explicitly accounts for the excitons and phonons in the heterostructure. Our large-scale first-principles calculations directly probe the role of exciton-phonon coupling in the charge dynamics of the WS2/MoS2 heterobilayer. We find that the exciton-phonon interaction induced relaxation time of photoexcited excitons at the K valley of MoS2 and WS2 is 67 and 15 fs at 300 K, respectively, which sets a lower bound to the intralayer-to-interlayer exciton transfer time and is consistent with experiment reports. We further show that electron-hole correlations facilitate novel transfer pathways that are otherwise inaccessible to noninteracting electrons and holes.
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  • 文章类型: Journal Article
    本文的目的是证明有关材料与非常低的无线电频率之间相互作用的新发现。具体来说,当使用特定频率(约2-4kHz)照射目标药物样品如阿司匹林或对乙酰氨基酚药物时,我们观察到惯性有源传感器上的反馈响应.这种现象的特点,如激励和弛豫时间,减速度与物料数量之间的关系,和信号幅度,进行了介绍和分析。尽管这种现象的基本物理学尚不清楚,我们已经证明了它在化合物的远程识别中具有潜在的应用,检测,和位置感应,以及在不需要任何处理的情况下识别植物中存在的物质。这种方法是快速的,准确,低成本,非破坏性的,非侵入性,使其成为进一步研究的宝贵领域,将来可能会产生惊人的结果。
    The purpose of this paper is to demonstrate a new discovery regarding the interaction between materials and very low radio frequencies. Specifically, we observed a feedback response on an inertia active sensor when specific frequencies (around 2-4 kHz) are used to irradiate targeted pharmaceutical samples like aspirin or paracetamol drugs. The characteristics of this phenomenon, such as excitation and relaxation time, the relation between deceleration and a material\'s quantity, and signal amplitude, are presented and analyzed. Although the underlying physics of this phenomenon is not yet known, we have shown that it has potential applications in remote identification of compounds, detection, and location sensing, as well as identifying substances that exist in plants without the need for any processing. This method is fast, accurate, low-cost, non-destructive, and non-invasive, making it a valuable area for further research that could yield spectacular results in the future.
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  • 文章类型: Journal Article
    关于凝析气储层中多相流的常规假设通常与现场生产无关。这种差异源于影响多相过程的各种机制,在数值模型中没有充分表示。最不了解的机制之一是非平衡热力学对井筒区域流动的影响,其中储层压力低于露点压力。为了解决这个问题,实验和数学分析是使用微流体装置进行的,该装置旨在复制凝析气系统中的流动动力学。实验结果表明,与数值模型中局部平衡的常规假设相比,凝析油饱和的初始压力有11%的偏差。同样,冷凝液的实验体积和模拟体积之间有14%的偏差。这些发现强调了现有模型不足以准确预测冷凝相的饱和曲线。应用基于弛豫参数的数学模型来解释微流体实验中观察到的气溶胶的非平衡相分离和雾状。结合松弛参数(τ)可提高对冷凝物饱和度初始压力的预测精度,并将冷凝物体积的预测从76%提高到97.2%。因此,它为恒定流态下凝析油系统的非平衡相行为提供了有价值的框架和见解。
    Conventional assumptions about multiphase flow in gas condensate reservoirs often do not correlate with field production. This discrepancy stems from the various mechanisms influencing the multiphase process, which are inadequately represented in numerical models. One of the least understood mechanisms is the influence of the non-equilibrium thermodynamics on the flow in the wellbore region, where the reservoir pressure is below the dew point pressure. To address this problem, experimental and mathematical analyses were conducted using a microfluidic device designed to replicate the flow dynamics in a gas condensate system. The experimental results showed an 11% deviation from the initial pressure of condensate saturation when compared with the conventional assumption of local equilibrium in numerical models. Similarly, there is a 14% deviation between the experimental and simulated volumes of the condensate. These findings underscore the inadequacy of existing models to accurately predict the saturation profile of the condensate phase. A mathematical model based on a relaxation parameter was applied to account for non-equilibrium phase separation and the fog state of the aerosol as observed in the microfluidic experiment. Incorporating a relaxation parameter ( τ ) enhanced the accuracy of the prediction of the initial pressure of the condensate saturation and an improvement in the prediction of the condensate volumes from 76% to 97.2%. Consequently, it provides a valuable framework and insight on the non-equilibrium phase behavior of gas condensate systems under constant flow regimes.
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  • 文章类型: Journal Article
    这项研究使用悬滴法研究了各种盐度中沥青质和二价离子的浓度如何影响模型油/盐水之间的界面张力(IFT)。油酸相由甲苯和正庚烷(庚烷)的混合物组成,加入沥青质以研究沥青质分子如何影响表面性质。制备的基础流体的盐度为40,000ppm,并产生浓度为4000ppm(低盐度)和80,000ppm(高盐度)的另外两种溶液。结果表明,在某些盐度范围内增加沥青质的浓度会导致IFT降低。在40,000ppm盐度水平下观察到最低的IFT,表明在这个最佳盐度下,最大沥青质浓度迁移到庚烷/盐水界面,将IFT从23mN/m降低到16mN/m。此外,0.5重量%的沥青质证明了天然表面活性剂的显著胶束化浓度,表明界面几乎被沥青质饱和。因此,高于该值的浓度不会显着改变IFT。在研究的最后部分,研究了二价离子的影响,揭示了随着Ca2+离子浓度增加到四倍,IFT降至15mN/m,比基本情况少10%左右。与Mg2+和SO42-相比,该值代表最低的IFT。此外,建模结果表明,弛豫时间随着盐度的增加而减少,表明较高的盐度加速了界面处沥青质的吸收过程。
    This study examined how the concentration of asphaltene and divalent ions in various salinities affects the interfacial tension (IFT) between a model oil/brine using the pendant drop method. The oleic phase consisted of a mixture of toluene and n-heptane (heptol), to which asphaltene was added to investigate how asphaltene molecules affect the surface properties. The base fluid was prepared with a salinity of 40,000 ppm, and two additional solutions with concentrations of 4000 ppm (low salinity) and 80,000 ppm (high salinity) were created. The results revealed that increasing the concentration of asphaltene within certain salinity ranges led to a decrease in IFT. The lowest IFT was observed at the 40,000 ppm salinity level, indicating that at this optimal salinity, the maximum asphaltene concentration migrated to the heptol/brine interface, reducing the IFT from 23 mN/m to 16 mN/m. Additionally, a 0.5 % wt of asphaltene demonstrated a significant concentration of micellization of natural surfactants, suggesting that the interface was nearly saturated with asphaltene. Consequently, concentrations higher than this value did not significantly alter the IFT. In the final part of the study, the impact of divalent ions was investigated, revealing that as the concentration of Ca2+ ions increased up to fourfold, the IFT decreased to 15 mN/m, about 10 % less than the base case. This value represented the lowest IFT compared to Mg2+ and SO42-. Moreover, modeling the results indicated that the relaxation time decreased with increasing salinity, suggesting that higher salinity accelerated the process of asphaltene absorption at the interface.
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  • 文章类型: Journal Article
    最近,我们应用溶液2H-核磁共振波谱(2HNMR)分析水(氧化氘,D2O)在环境温度下几种生物聚合物中的结构。我们确定具有良好血液相容性的聚合物(即,聚(丙烯酸2-甲氧基乙酯)(PMEA))与本体水相比在高磁场(上场)下观察到水。含有聚(丙二醇)(PPG)或聚(环氧丙烷)(PPO)的聚合物表现出良好的相容性;然而,原因尚不清楚。此外,关于PPO/PPG血液相容性的报道有限。因此,制备了PPG二酯(PPGest)作为模型聚合物,并对其血液相容性和水结构进行了研究。PPGest表现出优异的血液相容性。通过2HNMR在上场观察到PPGest中的水,通过差示扫描量热法将其定义为非冷冻水。基于这些观察,通过与PMEA的比较,讨论了PPGest的血液相容性与水结构之间的关系,并讨论了PPG/PPO基聚合物性能良好的原因。
    Recently, we applied solution 2H-nuclear magnetic resonance spectroscopy (2H NMR) to analyze the water (deuterium oxide, D2O) structure in several biopolymers at ambient temperature. We established that polymers with good blood compatibility (i.e. poly(2-methoxyethyl acrylate) (PMEA)) have water observed at high magnetic fields (upfield) compared with bulk water. Polymers containing poly(propylene glycol) (PPG) or poly(propylene oxide) (PPO) exhibit good compatibility; however, the reason for this remains unclear. In addition, reports on the blood compatibility of PPO/PPG are limited. Therefore, PPG diester (PPGest) was prepared as a model polymer, and its blood compatibility and water structure were investigated. PPGest exhibited excellent blood compatibility. The water in PPGest was observed upfield by 2H NMR, and it was defined as non-freezing water via differential scanning calorimetry. Based on these observations, the relationship between the blood compatibility and water structure of PPGest is discussed by comparing with those of PMEA, and the reason for the good performance of PPG/PPO-based polymers is discussed.
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  • 文章类型: Journal Article
    为了研究定量纵向弛豫时间(T1)的值,横向弛豫时间(T2),和来自合成磁共振成像(MRI)的质子密度(PD)图,用于评估无淋巴结转移(LNM)的宫颈鳞状细胞癌(CSCC)中淋巴管间隙侵犯(LVSI)的状态。
    收集2020年5月至2023年3月在我院就诊的疑似宫颈癌患者。所有患者术前均行MRI检查,包括常规序列和合成MRI。本研究包括经病理证实无淋巴结转移的CSCC患者。根据LVSI的状态将受试者分为阴性和阳性LVSI组。使用独立样本t检验比较两组之间来自合成MRI的T1,T2和PD值的定量参数。接收器工作特性曲线用于确定参数的诊断功效。
    59例患者纳入本研究,分为阳性(n=32)和阴性LVSI组(n=27)。T1和T2值显示出负LVSI与正LVSICSCC之间的显着差异(1307.39±122.02与1193.03±107.86,P<0.0001;88.42±7.24vs.分别为80.99±5.50,P<0.0001)。T1,T2值以及T1和T2值的组合的曲线下面积(AUC)分别为0.756,0.799,0.834,各参数单独诊断和联合诊断的诊断效能差异无统计学意义。
    从合成MRI得出的定量参数可用于评估没有LNM的CSCC患者的LVSI状态。
    UNASSIGNED: To investigate the value of quantitative longitudinal relaxation time (T1), transverse relaxation time (T2), and proton density (PD) maps derived from synthetic magnetic resonance imaging (MRI) for evaluating the status of lymphovascular space invasion (LVSI) in cervical squamous cell carcinoma (CSCC) without lymph node metastasis (LNM).
    UNASSIGNED: Patients with suspected cervical cancer who visited our hospital from May 2020 to March 2023 were collected. All patients underwent preoperative MRI, including routine sequences and synthetic MRI. Patients with pathologically confirmed CSCC without lymphatic metastasis were included in this study. The subjects were divided into negative- and positive-LVSI groups based on the status of LVSI. Quantitative parameters of T1, T2, and PD values derived from synthetic MRI were compared between the two groups using independent samples t-test. Receiver operating characteristic curves were used to determine the diagnostic efficacy of the parameters.
    UNASSIGNED: 59 patients were enrolled in this study and were classified as positive (n = 32) and negative LVSI groups (n = 27). T1 and T2 values showed significant differences in differentiating negative-LVSI from positive-LVSI CSCC (1307.39 ± 122.02 vs. 1193.03 ± 107.86, P<0.0001; 88.42 ± 7.24 vs. 80.99 ± 5.50, P<0.0001, respectively). The area under the curve (AUC) for T1, T2 values and a combination of T1 and T2 values were 0.756, 0.799, 0.834 respectively, and there is no statistically significant difference in the diagnostic efficacy between individual and combined diagnosis of each parameter.
    UNASSIGNED: Quantitative parameters derived from synthetic MRI can be used to evaluate the LVSI status in patients with CSCC without LNM.
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  • 文章类型: Journal Article
    高性能静电储能电介质的发展对于脉冲功率技术等各种应用至关重要,电动汽车(EV)电子设备,和高温航空业。然而,铅作为常规高性能介电材料中的关键成分的使用引起了严重的环境问题。因此,迫切需要探索无铅替代品。铁电陶瓷提供高能量密度,但在高温下缺乏稳定性。在这里,我们提出了一种具有低介电损耗的无铅(1-x)BiFeO3-xCaTiO3(x=0.6、0.7和0.8;BFO-CTO)陶瓷电容器,热稳定性高,和高达200°C的高能量密度在BFO矩阵中引入CTO(x=0.7)触发了从正常铁电体到弛豫铁电体状态的转变,在190°C时产生1.18Jcm-3的高可恢复能量密度,超快介电弛豫时间为44μs。这些结果提供了一个有希望的,环保,用于高频和高温应用的高容量陶瓷电容器材料。
    The development of high-performance electrostatic energy storage dielectrics is essential for various applications such as pulsed-power technologies, electric vehicles (EVs), electronic devices, and the high-temperature aviation sector. However, the usage of lead as a crucial component in conventional high-performance dielectric materials has raised severe environmental concerns. As a result of this, there is an urgent need to explore lead-free alternatives. Ferroelectric ceramics offer high energy density but lack stability at high temperatures. Here we present a lead-free (1 - x)BiFeO3-xCaTiO3 (x = 0.6, 0.7, and 0.8; BFO-CTO) ceramic capacitor with low dielectric loss, high thermal stability, and high energy density up to ∼200 °C. The introduction of CTO (x = 0.7) to the BFO matrix triggers a transition from the normal ferroelectrics to the relaxor ferroelectrics state, resulting in a high recoverable energy density of 1.18 J cm-3 at 190 °C with an ultrafast dielectric relaxation time of 44 μs. These results offer a promising, environmentally friendly, high-capacity ceramic capacitor material for high-frequency and high-temperature applications.
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