Ultrawideband temperature-dependent dielectric properties of animal liver tissue in the microwave frequency range

The development of ultrawideband (UWB) microwave diagnostic and therapeutic technologies, such as UWB microwave breast cancer detection and hyperthermia treatment, is facilitated by accurate knowledge of the temperature- and frequency-dependent dielectric properties of biological tissues. To this end, we characterize the temperature-dependent dielectric properties of a representative tissue type-animal liver-from 0.5 to 20 GHz. Since discrete-frequency linear temperature coefficients are impractical and inappropriate for applications spanning wide frequency and temperature ranges, we propose a novel and compact data representation technique. A single-pole Cole-Cole model is used to fit the dielectric properties data as a function of frequency, and a second-order polynomial is used to fit the Cole-Cole parameters as a function of temperature. This approach permits rapid estimation of tissue dielectric properties at any temperature and frequency.     

MRI拉莫尔频率范围内人体脑胶质瘤组织的介电特性

目的:研究人体脑胶质瘤组织在MRI拉莫尔频率范围内（50~500 MHz）的介电特性,建立人体脑胶质瘤组织介电参数频率谱图,为磁共振断层成像技术提供理论依据和数据参考。方法:以神经外科手术中切下的脑胶质瘤组织为标本,在温度为37 °C的恒温水箱中,利用开端同轴线法,在50~500 MHz频率范围内使用AV 3656A网络分析仪测量脑胶质瘤组织标本的介电特性。以四阶Cole-Cole模型为基础,利用最小二乘曲线拟合方法,提取人体脑胶质瘤组织的介电特征参数。同时,将实验测得的脑胶质瘤组织介电特性与健康人体组织介电特性数据库中的正常脑组织进行比较。结果:在测频率范围内,人体脑胶质瘤组织实测数据与Cole-Cole模型吻合良好,且有人体脑胶质瘤组织的相对介电常数比正常脑组织高29.5%~36.6%,电导率比正常脑组织高56.1%~64.8%。结论:本文报道了37 °C下人体脑胶质瘤组织在MRI拉莫尔频率范围内（50~500 MHz）的介电特性数据及相应的Cole-Cole模型介电特征参数,可为人体脑胶质瘤组织介电特性研究和磁共振断层成像技术提供基础数据。     

大鼠腓肠肌细胞介电谱测量和Cole-Cole数学模型分析

测量大鼠腓肠肌细胞介电谱,利用Cole-Cole方程的曲线拟合建立Cole-Cole数学模型参数.在100 Hz～100 MHz频率范围,使用Agilent 4294A阻抗分析仪对电场与肌纤维方向呈平行和垂直的大鼠腓肠肌进行了阻抗测量,并利用Cole-Cole方程的数值计算,对细胞介电谱、Cole-Cole图、介电损耗因子频谱、电导率虚部频谱和损耗角正切频谱进行曲线拟合分析和残差分析,比较电场与肌纤维方向呈平行或垂直两种情况的介电行为区别.结果表明:骨骼肌细胞的介电弛豫具有两个特征频率,其平行方向的特征频率低于垂直方向;平行方向的介电增量高于垂直方向的介电增量;平行方向的低频极限量高于垂直方向的低频极限量;平行方向和垂直方向的介电常数高频极限量相等;平行方向和垂直方向的电导率高频极限量存在一定差距.平行方向的电导率虚部频谱和损耗角正切分别高于垂直方向的值,但是,平行方向的电导率虚部最大值低于其垂直方向的值.腓肠肌细胞的介电常数和电导率存在频率依存性和各向异性,其介电行为存在α和β两个介电散射,并满足Cole-Cole数学模型.     

Temporal variation of dielectric properties of preserved blood

Rabbit blood was preserved at 277 K in Alsever's solution for 37 days, and its dielectric permittivity was monitored in a frequency range from 0.05 to 110 MHz throughout the period. The relaxation time and Cole-Cole parameter of the interfacial polarization process for erythrocytes remained nearly constant during the first 20 days and then started to increase and decrease, respectively. On the other hand, the relaxation strength and the cell volume fraction continued to decrease for 37 days, but the decrease rates of both changed discontinuously on about the 20th day. Microscope observation showed that approximately 90% of the erythrocytes were spinous echinocytes at the beginning of preservation and started to be transformed into microspherocytes around the 20th day. Therefore, dielectric spectroscopy is a sensitive tool to monitor the deterioration of preserved blood accompanied by morphological transition of erythrocytes through the temporal variation of their dielectric properties.     

Electrical properties of the epidermal stratum corneum

The electrical properties of the epidermal stratum corneum were investigated by cellulose adhesive tape stripping. The distribution function of the relaxation times on the impedance locus of stratum corneum was deduced. It was found that this function of the thin layer does not satisfy the Cole-Cole circular arc, but the skin impedance remaining after some strippings compares favourably with the Cole-Cole circular arc. The various dispersions appearing in the skin impedance can be separated and evaluated. The average resistivity and dielectric constant of the stratum corneum and deeper tissues were determined. The direct current resitivity σ of the stratum corneum can be mathematically expressed by the exponential law ρ=ρ_o ^-αx where x is the distance from the skin surface. The maximum resistivity ρ_o on the outermost surface of the stratum corneum and the attenuation coefficient α are evaluated.     

Does prenylation predict progression in NAFLD?

Non-alcoholic fatty liver disease (NAFLD) often develops in concert with related metabolic diseases, such as obesity, dyslipidemia and insulin resistance. Prolonged lipid accumulation and inflammation can progress to non-alcoholic steatohepatitis (NASH). Although factors associated with the development of NAFLD are known, triggers for the progression of NAFLD to NASH are poorly understood. Recent findings published in The Journal of Pathology reveal the possible regulation of NASH progression by metabolites of the mevalonate pathway. Mevalonate can be converted into the isoprenoids farnesyldiphosphate (FPP) and geranylgeranyl diphosphate (GGPP). GGPP synthase (GGPPS), the enzyme that converts FPP to GGPP, is dysregulated in humans and mice during NASH. Both FPP and GGPP can be conjugated to proteins through prenylation, modifying protein function and localization. Deletion or knockdown of GGPPS favors FPP prenylation (farnesylation) and augments the function of liver kinase B1, an upstream kinase of AMP-activated protein kinase (AMPK). Despite increased AMPK activation, livers in Ggpps-deficient mice on a high-fat diet poorly oxidize lipids due to mitochondrial dysfunction. Although work from Liu et al provides evidence as to the potential importance of the prenylation portion of the mevalonate pathway during NAFLD, future studies are necessary to fully grasp any therapeutic or diagnostic potential. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Application de la spectrométrie mécanique et diélectrique à i'analyse du comportement du poly(téréphtalate d'éthylène). Influence de la cristallinité

In order to correlate crystallinity and dynamic mechanical properties, poly(ethylene terephthalate) (PETP) samples were prepared and subjected to viscoelastic measurements. The evolution of the glass-rubber transition is analyzed for samples annealed at different temperatures. Multiplexing analysis allows to draw the Cole-Cole plot and to develop a rheological model for the polymer behaviour. In the case of the amorphous PETP, the asymmetric Cole-Cole plot may be represented by a “biparabolic” rheological model. On the other hand, for the semi-crystalline polymer, the Cole-Cole plot is symmetrical and the corresponding rheological model is the “liquid Cole” one. Dielectric spectroscopy experiments are in good agreement with the previous method. Particularly, the Cole-Cole plot for semi-crystalline samples is perfectly symmetric. The previous rheological models with, in addition, a static modulus are applicable to glass-fibre reinforced PETP. These new models are called “limited biparabolic” and “Zener parabolic” model, respectively.     

Thermal, dynamic mechanical, and dielectric analyses of some polyurethane biocomposites

Polymer biocomposites based on segmented poly(ester urethane) and extracellular matrix components have been prepared for the development of tissue engineering applications with improved biological characteristics of the materials in contact with blood and tissues for long periods. Thermal, dynamical, and dielectrical analyses were employed to study the molecular dynamics of these materials and the influence of changing the physical network morphology and hydrogen bond interactions accompanied by phase transitions, interfacial effects, and polarization or conductivity. All phenomena that concur in the tested materials are evaluated by cross-examination of the dynamic mechanical characteristic properties (storage modulus, loss modulus, and loss factor) and dielectric properties (relative permittivity, relative loss factor, and loss tangent) as a function of temperature. Comparative aspects were elucidated by calculating the apparent activation energies of multiplex experiments.     

Dielectric properties of mammalian breast milk at radiofrequencies

The relative permittivity and AC conductivity of breast milk have been investigated in four different mammalian species, human, cow, goat and sheep, in the frequency range 0.1-100 MHz and at a room temperature of 26.5 +/- 0.5 degrees C. The results showed that the sheep milk exhibited the largest dielectric dispersion, followed in decreasing order by milks from the goat, cow and human. The dielectric data were fitted to the Debye and Cole-Cole structural equations and the fitted parameters have been presented for the different species. The curve-fitting analysis has shown that for all the milk samples the Cole-Cole model gave a better fit to the dielectric data than the Debye model, thus suggesting heterogeneity of structure in milk. On the basis of the Cole-Cole model, the relaxation times in the mammalian milks were found to be distributed about the mean values of 162 +/- 10, 171 +/- 9, 177 +/- 14 and 192 +/- 12 ns for human, cow, goat and sheep milks, respectively.     

A large-scale study of the ultrawideband microwave dielectric properties of normal breast tissue obtained from reduction surgeries

The efficacy of emerging microwave breast cancer detection and treatment techniques will depend, in part, on the dielectric properties of normal breast tissue. However, knowledge of these properties at microwave frequencies has been limited due to gaps and discrepancies in previously reported small-scale studies. To address these issues, we experimentally characterized the wideband microwave-frequency dielectric properties of a large number of normal breast tissue samples obtained from breast reduction surgeries at the University of Wisconsin and University of Calgary hospitals. The dielectric spectroscopy measurements were conducted from 0.5 to 20 GHz using a precision open-ended coaxial probe. The tissue composition within the probe's sensing region was quantified in terms of percentages of adipose, fibroconnective and glandular tissues. We fit a one-pole Cole-Cole model to the complex permittivity data set obtained for each sample and determined median Cole-Cole parameters for three groups of normal breast tissues, categorized by adipose tissue content (0-30%, 31-84% and 85-100%). Our analysis of the dielectric properties data for 354 tissue samples reveals that there is a large variation in the dielectric properties of normal breast tissue due to substantial tissue heterogeneity. We observed no statistically significant difference between the within-patient and between-patient variability in the dielectric properties.     

生物组织粘弹性动力学分析的有限元新方法

应用线性粘弹性模型和电网模型间的两个重要结论,以及滤波方法,推导得出一种适用于生物组织粘弹性动力学分析的有限元新方法。粘弹性材料的复杂性可简单地视为各向同性,亦可将其逐步趋地复杂而直臻极端各向异性,描述生物组织力学特性的线性粘弹性模型可以是两种不同的元件和三种不同的基本模型的任意组合,多方法,多角度地证实本文推导得出了一般的系统的和高精度的快速有限元分析法,该分析法可用于分析以线性粘弹性为模型的生物组织和工程材料的动力学响应。     

人血液细胞介电谱的实验研究

在0．01～100MHz范围内，测量人血液细胞的介电谱，确立人血液细胞对交流电场的介电响应的数据特征。利用频域阻抗技术测量了正常人血液细胞交流阻抗，绘制细胞的介电常数和电导率与电场频率的关系曲线。建立了人血液细胞的介电谱和Cole—Cole图，明确了人血细胞的介电频响的数据特征。在射频电场中，人血液细胞的介电常数和电导率具有频率依赖性，表现为具有两个特征频率的介电弛豫：第一介电弛豫发生在fc。为1．42MHz，第二介电弛豫产生在fcz为3．32MHz。     

Dielectric properties of human normal, malignant and cirrhotic liver tissue: in vivo and ex vivo measurements from 0.5 to 20 GHz using a precision open-ended coaxial probe

Hepatic malignancies have historically been treated with surgical resection. Due to the shortcomings of this technique, there is interest in other, less invasive, treatment modalities, such as microwave hepatic ablation. Crucial to the development of this technique is the accurate knowledge of the dielectric properties of human liver tissue at microwave frequencies. To this end, we characterized the dielectric properties of in vivo and ex vivo normal, malignant and cirrhotic human liver tissues from 0.5 to 20 GHz. Analysis of our data at 915 MHz and 2.45 GHz indicates that the dielectric properties of ex vivo malignant liver tissue are 19 to 30% higher than normal tissue. The differences in the dielectric properties of in vivo malignant and normal liver tissue are not statistically significant (with the exception of effective conductivity at 915 MHz, where malignant tissue properties are 16% higher than normal). Also, the dielectric properties of in vivo normal liver tissue at 915 MHz and 2.45 GHz are 16 to 43% higher than ex vivo. No statistically significant differences were found between the dielectric properties of in vivo and ex vivo malignant tissue (with the exception of effective conductivity at 915 MHz, where malignant tissue properties are 28% higher than normal). We report the one-pole Cole-Cole parameters for ex vivo normal, malignant and cirrhotic liver tissue in this frequency range. We observe that wideband dielectric properties of in vivo liver tissue are different from the wideband dielectric properties of ex vivo liver tissue, and that the in vivo data cannot be represented in terms of a Cole-Cole model. Further work is needed to uncover the mechanisms responsible for the observed wideband trends in the in vivo liver data.     

正常人血小板射频段介电响应测量

目的在射频段测量正常人血小板介电谱,建立血小板对交流电场介电响应的数据特征。方法利用频域阻抗技术测量人血小板交流阻抗,经过介电谱、Cole-Cole图、介电损耗因子Δε”、导电率虚部Δκ”、介电损耗角正切Δtgδ等频谱,明确人血小板介电频响的数据特征。结果在射频电场中,人血小板的介电常数和电导率具有频率依赖性;血小板介电响应具有两个中心特征频率:第一中心特征频率fC1=6.66MHz,第二中心特征频率fC2=9.81MHz。结论交流阻抗技术能够测量血小板射频段介电响应。     

Fractal dynamics of polarized bioelectrodes

This study is concerned with mathematical modelling of the fundamental relationship which exists between the current density and the overpotential across the metalsolution interface in the linear range using methods of system theory enhanced by ‘fractal’ concepts. A primer for both 1/f-type scaling and ‘anomalous’ relaxation/dispersion concepts is provided, followed by a brief review of the research history pertinent to the metal electrode polarization dynamics. Next, the ‘fractal relaxation systems’ approach is introduced to characterize, systems which attenuate with a fractional power-low dependence on frequency through a ‘scaling exponent’. The ‘singularity structure’ which is a scaling, rational system function is proposed to expand fractal systems in terms of basic subsystems individually representing elementary exponential relaxations and collectively exhibiting scaling properties. We stress that the ‘singularity structure’ carries scaling information identical to the conventional ‘distribution of relaxation times’ function. ‘Structure scale’ and ‘view scale’ concepts are presented in the due course to streamline the analysis of scaling phenomena in general and the polarization impedance in particular. System theory-wise, the notable result is that the fractional power function attenuation, or equivalently, the logarithmic nature of the distribution function translates into the ‘self-similar’ pattern replication of the system singularities in the s-plane. The singularity arrangement is governed by a recursive rule solely based on the knowledge of the fractional power factor or the scaling exponent.     

Fertilization promoting peptide, a tripeptide similar to thyrotrophin-releasing hormone, stimulates the capacitation and fertilizing ability of human spermatozoa in vitro

Recent studies have demonstrated that a prostatic tri-peptidesimilar in structure to thyrotrophin-releasing hormone (TRH)can stimulated the in-vitro capacitation and fertilizing abilityof epididymal mouse spermatozoa. Therefore we have proposedthat this tripeptide be referred to as fertilization promotingpeptide (FPP). Using chlortetracycline fluorescence analysisand the hamster oocyte penetration test (HOPT), we have obtainedevidence that FPP can also promote the capacitation and fertilizingability of ejaculated human spermatozoa in vitro. FPP (25–200nM) caused a significant increase in the proportion of B-patterncapacitated cells and a decrease in the proportion of F-patternuncapacitated cells, with no significant stimulation of acrosomalexocytosis. Comparison of FPP with two structurally similartripeptides, TRH and pyro-glutamyl phenylalanylprolineamide,at 50 nM revealed that only FPP could significantly promotecapacitation. Finally, after a brief exposure to progesteroneto induce acrosomal exocytosis in capacitated cells, FPP-treatedsuspensions penetrated a significantly higher proportion ofoocytes than the untreated controls when assessed in the HOPT.The presence of FPP in human seminal plasma at concentrationssimilar to those used here suggests that, in vivo, FPP may playa positive role in promoting human sperm function.     

细胞外灌流对骨骼肌细胞介电谱的影响

通过灌流的方法,探讨细胞外液对骨骼肌细胞介电谱的影响,应用非线性Co le-Co le公式的曲线拟合与数值计算,比较灌流后骨骼肌细胞介电谱参数,结果表明:(1)低频段介电常数Lε和高频段电导率hκ随着细胞外灌流液电导率的降低而减少;(2)细胞外灌流对骨骼肌细胞介电谱的特征频率(fC 1,fC 2)影响不大;(3)细胞外灌流主要影响骨骼肌细胞Δε″和tgδ的峰值。     

Dielectric properties of human placenta, umbilical cord and amniotic fluid

The dielectric properties of freshly delivered human placenta, umbilical cord and amniotic fluid have been acquired at 37 °C and in the frequency range of 200 MHz-10 GHz. The experimental data were fitted to a Cole-Cole expression. The results show that dielectric properties of the umbilical cord are significantly higher than placenta due to the presence of high water content Wharton's jelly. The results also demonstrate large differences in the dielectric properties of amniotic and cerebrospinal fluids. The data presented can be used in numerical simulations of the exposure of pregnant women to electromagnetic fields.     

Isolation and properties of yeast mutants affected in farnesyl diphosphate synthetase

Summary Two yeast mutant strains auxotrophic for ergosterol and blocked in farnesyl diphosphate synthetase (EC 2.5.1.1) were isolated. Genetic analysis has shown that these mutant strains carry additional mutations in the ergosterol pathway besides erg20-1 and erg20-2 which affect FPP synthetase. The novel feature of these mutants is their ability to excrete prenyl alcohols (farnesol and geraniol). As geraniol is toxic for yeast cells, the above leaky mutations in FPP synthetase have to be associated with others in the sterol pathway, in order to slow down geraniol synthesis.Abbreviations FPP farnesyl diphosphate - GPP geranyl diphosphate - IPP isopentenyl diphosphate - DMAPP dimethylallyl diphosphate - MVAP mevalonate phosphate - MVAPP mevalonate diphosphate - HMG CoA 3-hydroxy-3-methylglutaryl-CoA - MIC minimal inhibitory concentration     

正常人血小板介电谱的实验研究

在100KHz～110MHz范围内,测量人血小板的介电谱,分析了人血小板对交流电场的介电响应的数据特征。利用频域阻抗技术首次测量了正常人血小板交流阻抗,绘制血小板的介电常数和电导率与电场频率的关系曲线。建立了人血小板的介电谱和Cole-Cole图,明确了人血小板的介电频响的数据特征。在射频电场中,人血小板的介电常数和电导率具有频率依赖性,血小板介电谱具有两个特征频率:第一特征频率fC1为6.66MHz,第二特征频率fC2为9.81MHz。