Calculation of all-time apparent resistivity of large loop transient electromagnetic method with very fast simulated annealing

In large loop transient electromagnetic method(TEM),the late time apparent resistivity formula cannot truly reflect the geoelectric model,thus it needs to define the all-time apparent resistivity with the position information of measuring point.Utilizing very fast simulated annealing(VFSA) to fit the theoretical electromagnetic force(EMF) and measured EMF could obtain the all-time apparent resistivity of the measuring points in rectangular transmitting loop.The selective cope of initial model of VFSA could be confirmed by taking the late time apparent resistivity of transient electromagnetic method as the prior information.For verifying the correctness,the all-time apparent resistivities of the geoelectric models were calculated by VFSA and dichotomy,respectively.The results indicate that the relative differences of apparent resistivities calculated by these two methods are within 3%.The change of measuring point position has little influence on the tracing pattern of all-time apparent resistivity.The first branch of the curve of all-time apparent resistivity is close to the resistivity of the first layer medium and the last branch is close to the resistivity of the last layer medium,which proves the correctness of the arithmetics proposed.

Electric potential and apparent resistivity in rocks containing non-uniformly distributed cracks

In this paper, the formula of electric field distribution and ground apparent resistivity of high resistance rock medium containing low resistance crack are deduced and simulated. The result shows that interstitial parameters, such as buried depth, scale, strike, and real resistivity, etc, have influence on observation and computing result of apparent resistivity. This study provided a useful foundation for earthquake prediction using apparent resistivity method.

Contrast between 2D inversion and 3D inversion based on 2D high-density resistivity data

The 2D data processing adopted by the high-density resistivity method regards the geological structures as two degrees, which makes the results of the 2D data inversion only an approximate interpretation;the accuracy and effect can not meet the precise requirement of the inversion. Two typical models of the geological bodies were designed, and forward calculation was carried out using finite element method. The forward-modeled profiles were obtained. 1% Gaussian random error was added in the forward models and then 2D and 3D inversions using a high-density resistivity method were undertaken to realistically simulate field data and analyze the sensitivity of the 2D and 3D inversion algorithms to noise. Contrast between the 2D and 3D inversion results of least squares inversion shows that two inversion results of high-density resistivity method all can basically reflect the spatial position of an anomalous body. However, the 3D inversion can more effectively eliminate the influence of interference from Gaussian random error and better reflect the distribution of resistivity in the anomalous bodies. Overall, the 3D inversion was better than 2D inversion in terms of embodying anomalous body positions, morphology and resistivity properties.

Glass transition kinetics of La_(55)Al_(25)Ni_(10)Cu_(10) bulk metallic glass by electrical resistivity measurement

The glass transition behavior of La55A125-Ni10CU10 bulk metallic glass was investigated using elec-trical resistivity and differential-scanning calorimetry measurements. There are good agreements of the onset temperature （Tg-onset） and the end temperature （Tg-end） of the glass transition between the DSC curve and tempera-ture dependent electrical resistivity （TER） curve in the same heating rate. Kinetics of the glass transition is studied with the electrical resistivity data. The apparent activation energy of the glass transition （△Eg） is found to be 306.4 kJ.mol^-1. Fragility parameter D^＊ and VFT temper-ature To are 9.8 and 324.9 K, respectively.

Pharmacoepidemiologic study of association between apparent treatment resistant hypertension, cardiovascular disease and interaction effect by sex and age

BACKGROUND A limited number of studies have been conducted to test the magnitudes of the association between apparent treatment resistant hypertension(aTRH)and risk of cardiovascular disease(CVD).AIM To investigate the association between aTRH and risk of CVD and examine whether sex and age modify this association.METHODS We applied an observational analysis study design using data from the United States Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial(ALLHAT).ALLHAT recruited participants(n=25516)from 625 primary care settings throughout the United States,Canada,Puerto Rico,and United States Virgin Islands,aged 55 and older with hypertension and at least one additional risk factor for heart disease.aTRH was assessed from the year 2 visit.CVD event was defined as one of the following from the year 2 follow-up visit:Fatal or non-fatal myocardial infarction,coronary revascularization,angina,stroke,heart failure,or peripheral artery disease.Cox proportional hazards regression was used to examine the effect of aTRH on CVD risk.Potential modifications of sex and age on this association were examined on the multiplicative scale by interaction term and additive scale by joint effects and relative excess risk for interaction.RESULTS Of the total study participants(n=25516),5030 experienced a CVD event during a mean of 4.7 years follow-up.aTRH was associated with a 30%increase in risk of CVD compared to non-aTRH[hazards ratio(HR)=1.3,95%CI:1.19-1.42].Sex and age modified this relationship on both multiplicative and additive scales independently.Stratified by sex,aTRH was associated with a 64%increase in risk of CVD(HR=1.64,95%CI:1.43–1.88)in women,and a 13%increase in risk of CVD(HR=1.13,95%CI:1.01–1.27)in men.Stratified by age,aTRH had a stronger impact on the risk of CVD in participants aged<65(HR=1.53,95%CI:1.32–1.77)than it did in those aged≥65(HR=1.18,95%CI:1.05–1.32).Significant two-way interactions of sex and aTRH,and age and aTRH on risk of CVD were observed(P<0.05).The observed joint effect of aTRH and ages≥65 years(HR=1.85,95%CI:1.22–2.48)in males was less than what was expected for both additive and multiplicative models(HR=4.10,95%CI:3.63–4.57 and 4.88,95%CI:3.66–6.31),although three-way interaction of sex,age,and aTRH on the risk of CVD and coronary heart disease did not reach a statistical significance(P>0.05).CONCLUSION aTRH was significantly associated with an increased risk of CVD and this association was modified by both sex and age.Further studies are warranted to test these mechanisms.

The Effects of Negative Values of Apparent Resistivity in TEM Surveys

The calculation of apparent resistivity in electrical methods is relatively simple and consolidated in the literature. Furthermore, in the case of DC methods, the apparent resistivity values are for the most part, intuitive and enable an initial interpretation of the results. On the other hand, in TEM method the apparent resistivity values are not very intuitive and interpretation based only on the apparent resistivity values cannot be done reasonably. In this way, this paper presents a discussion about the reasons and effects of the negatives values of apparent resistivity in TEM soundings. The main objective of this paper is to clarify the meanings of these negatives values and the possible effects in TEM inversion.

Apparent resistivity of azimuthal anisotropy layered media

The electric field, equations of boundary conditions and calculation formula of apparent resistivity are derived for the azimuthal anisotropy layered media with the DC method based on the anisotropic Ohm's law. Taking the Schlumberger symmetric system as an example and using the recurrence formula of nuclear function, the paper theoretically simulates a model of four layers with the same anisotropy coefficient for each layer. The deep sounding curves of resistivity and the pattern of contours are obtained for the model. The results show that the theoretical formula is correct, and the deep sounding curves not only exhibit the difference of resistivity among layers but also indicate the anisotropy characteristics of layers.

A new approach for calculating the apparent resistivity tensor

The apparent resistivity tensor pB is an electromagnetic transfer function,which can be used to analyze and explain the underground electrical structure.Conventional method for obtaining the parameter requires controlled sources and can be easy to be disturbed by cultural noises.We present a new method for calculating the apparent resistivity tensor,the current density is first obtained by measuring the curl operator of the magnetic field on the Earth's surface.This approach is independent of the assumption of a plane wave,and may be used irrespective of source types and field areas.We derived the analytical expressions of the apparent resistivity tensor based on synthetic horizontally layered models with a vertical magnetic dipole source.We then calculate the responses of Pb through numerical modeling examples using both natural sources and controlled sources.Compared to traditional apparent resistivity definitions,our apparent resistivity tensor has the same amplitude value but with more sensitive phases in the far zone,and shows few distortions in the transition zone.And in the near-field zone,it is closer to the resistivity distribution under the ground.The simulation results have demonstrated the effectiveness of the proposed method for calculating the apparent resistivity tensor.

Inverse Spline Interpolation for All-time Resistivity of Central-Loop TEM

A convenient numerical calculation method (inverse spline interpolation) for all-time apparent resistivity intransient electromagnetic method (TEM) is proposed in this paper. Characteristic of early and late normalized inductiveelectromotive force was investigated. According to the turning point, the transient process is divided into the earlyphase, the turning point, and the late phase. Afterwards, apparent resistivity is obtained through inverse spline interpo-lation in the early and the late phases, respectively. Finally, the resistivities of the early-time and the late-time wereconnected together by the turning point. The result shows that the inverse spline method is feasible and the method alsolays a foundation for initial model construction in the TEM automatic inversion.

Analysis on Apparent Resistivity Variations of Garzê Station before the 2013 Lushan M_S 7. 0 Earthquake

A trend increase in apparent resistivity has been observed in the N30°E monitoring direction at Garze Seismic Station since July 2011. This increase trend in geo-electric resistivity has been observed in the N60°W direction since 2012. During the period of the increase, the national highway No.317 was expanded in the monitoring area, so the potential electrodes in the N30°E direction had to be moved 10m towards the current electrodes. We interpreted the electric sounding data of Garz6 Seismic Station with a horizontally layered model. Analysis based on this model showed that the shift of potential electrodes can cause a 4 l-l.m rise to the measurements in the N30°E direction. Therefore, apparent resistivity of the two directions increased in the same time in 2012 after offsetting the effects from electrodes shift. Sensitivity coefficients of the two observation directions were also obtained using the model. Sensitivity coefficients of both directions were negative for the shallow layers, which can well explain the unexpected annual variations of Garze Seismic Station. In order to quantitatively analyze the effects from the expansion of the national highway on the observation, we constructed a finite element model based on the electrical structure. Analysis results also suggested that the expansion of the national highway could only cause a 0. 15 Ω·m decrease in the N60°W monitoring direction and 0. 1 Ω· m increase in the N30°E direction. Additionally, the valley values of annual variation of 2013 were distinctively higher than that of other years since 2008, meaning that there was an abnormal rise in apparent resistivity in the two observation directions at Garz~ Seismic Station before the Lushan earthquake. However, the rise was contrary to the decline variation before the Wenchuan earthquake. Therefore, it is still unsure whether or not the rise variation is related to the Lushan earthquake.

Hydrodynamic resistance of pore–throat structures and its effect on shale oil apparent permeability

Oil transport is greatly affected by heterogeneous pore–throat structures present in shale.It is therefore very important to accurately characterize pore–throat structures.Additionally,it remains unclear how pore–throat structures affect oil transport capacity.In this paper,using finite element(FE)simulation and mathematical modeling,we calculated the hydrodynamic resistance for four pore–throat structure.In addition,the influence of pore throat structure on shale oil permeability is analyzed.According to the results,the hydrodynamic resistance of different pore throat structures can vary by 300%.The contribution of additional resistance caused by streamline bending is also in excess of 40%,even without slip length.Fur-thermore,Pore–throat structures can affect apparent permeability by more than 60%on the REV scale,and this influence increases with heterogeneity of pore size distribution,organic matter content,and organic matter number.Clearly,modeling shale oil flow requires consideration of porous–throat structure and additional resistance,otherwise oil recovery and flow capacity may be overestimated.

已上市K-Ras^(G12C)靶向药物的研发及其耐药性的最新研究进展

在多种类型癌症中KRAS发生突变,KRAS是人类癌症中最常见的突变癌基因。KRAS突变阳性癌症的发病人数一直呈上升趋势。由于KRAS缺乏经典的药物结合位点,导致靶向KRAS的抑制剂药物研发一直以来面临着巨大挑战性。随着K-Ras^(G12C)抑制剂的出现,KRAS不可成药的神话已被攻破。目前全球范围内上市的两种K-Ras^(G12C)抑制剂是AMG-510和MRTX849,仍然面临着巨大的用药需求。了解成功上市药物有利于更好地研发新药。本文针对两款上市K-Ras^(G12C)抑制剂的研究以及该靶点面临的耐药机制研究进行总结和讨论,并总结了K-Ras^(G12C)抑制剂与其他治疗方法联合治疗克服耐药性的方法。

Cone-shaped source characteristics and inductance effect of transient electromagnetic method

Small multi-turn coil devices are used with the transient electromagnetic method （TEM） in areas with limited space, particularly in underground environments such as coal mines roadways and engineering tunnels, and for detecting shallow geological targets in environmental and engineering fields. However, the equipment involved has strong mutual inductance coupling, which causes a lengthy turn-off time and a deep “blind zone”. This study proposes a new transmitter device with a conical-shape source and derives the radius formula of each coil and the mutual inductance coefficient of the cone. According to primary field characteristics, results of the two fields created, calculation of the conical-shaped source in a uniform medium using theoretical analysis, and a comparison of the inductance of the new device with that of the multi-turn coil, show that inductance of the multi-turn coil is nine times greater than that of the conical source with the same equivalent magnetic moment of 926.1 A·m2. This indicates that the new source leads to a much shallower “blind zone.” Furthermore, increasing the bottom radius and turn of the cone creates a larger mutual inductance but increasing the cone height results in a lower mutual inductance. Using the superposition principle, the primary and secondary magnetic fields for a conical source in a homogeneous medium are calculated; results indicate that the magnetic behavior of the cone is the same as that of the multi-turn coils, but the transient responses of the secondary field and the total field are more stronger than those of the multi-turn coils. To study the transient response characteristics using a cone-shaped source in a layered earth, a numerical filtering algorithm is then developed using the fast Hankel transform and the improved cosine transform, again using the superposition principle. During development, an average apparent resistivity inverted from the induced electromotive force using each coil is defined to represent the comprehensive resistivity of the conical source. To verify the forward calculation method, the transient responses of H type models and KH type models are calculated, and data are inverted using a “smoke ring” inversion. The results of inversion have good agreement with original models and show that the forward calculation method is effective. The results of this study provide an option for solving the problem of a deep “blind zone” and also provide a theoretical indicator for further research.

Ras反义寡核苷酸对胰腺癌Pc-2细胞多药耐药的影响

目的探讨Ras反义寡核苷酸(ASODN)对胰腺癌Pc-2细胞多药耐药的影响。方法应用RasASODN抑制Pc-2细胞中Ras和P-糖蛋白(P-glyoprotein,P-gp)表达,采用MTT法测定Pc-2细胞化疗敏感性,荧光定量RT-PCR法检测细胞内MDR-1基因水平,流式细胞仪检测细胞内阿霉素(ADR)浓度的改变。结果RasASODN能明显抑制胰腺癌Pc-2细胞中Ras和P-gp蛋白的表达(P<0.05),提高Pc-2细胞的化疗敏感性(P<0.05),降低Pc-2细胞中MDR-1基因水平(P<0.05),增加Pc-2细胞中的ADR摄入量(P<0.05)。结论RasASODN可能通过调控MDR-1基因水平,增加多药耐药胰腺癌Pc-2细胞对化疗药物的敏感性。

RNAi沉默卵巢癌耐药细胞株SKOV3/ADM内源H-ras基因表达对细胞增殖能力的影响

目的:构建靶向于卵巢癌耐药细胞株中高表达的H-ras癌基因的短发夹状RNA重组质粒,研究它对卵巢癌耐药细胞株SKOV3/ADM内源H-ras基因表达的抑制作用以及H-ras基因与卵巢癌发生和耐药的关系。方法:运用基因克隆技术构建靶向于H-ras基因的重组质粒pshRNA/H-ras并转染至卵巢癌耐药细胞株SKOV3/ADM,通过W est-ern blot、RT-PCR检测H-ras蛋白的表达及mRNA转录水平的变化;MTT法检测它对SK-OV3/ADM细胞增殖的抑制作用,AO/EB实验检测pshRNA/H-ras对SKOV3/ADM细胞凋亡的影响。结果:构建的两重组质粒pshRNA/H-ras1、2均能明显抑制H-ras基因的表达。蛋白质印迹结果表明,转染重组质粒pshRNA/H-ras1、2的SKOV3/ADM细胞靶蛋白的抑制率分别为86.87%和92.21%,RT-PCR检测到H-ras基因mRNA转录水平下降;pshR-NA/H-ras1、2明显抑制SKOV3/ADM细胞的增殖,MTT检测转染48h后的抑制率分别为62.4%和47.9%,AO/EB实验观测到转染24h和48h的细胞凋亡率分别为20.3%和35.6%。结论:H-ras基因在耐药的卵巢癌细胞增殖与凋亡过程中发挥作用,重组质粒pshRNA/H-ras可有效地抑制SKOV3/ADM细胞内源H-ras基因的表达和mRNA的转录,并抑制细胞的增殖和促进凋亡的发生,为化疗耐受的肿瘤细胞提供了新的基因治疗手段。

结肠癌K-ras突变与对西妥昔单抗耐药的实验研究

目的:研究结肠癌K-ras基因突变导致对西妥昔单抗耐药的可能机制。方法:通过基因测序及免疫细胞化学染色,筛选表皮生长因子受体(EGFR)表达阳性,同时K-ras基因呈突变型及野生型的结肠癌细胞各1株,应用细胞增殖实验(CCK8方法)、流式细胞技术(Annexin V标记),检测西妥昔单抗(C225)在体外对结肠癌细胞增殖和凋亡的影响。同时用K-ras呈野生型和突变型的结肠癌细胞株,分别建立裸鼠皮下移植瘤模型,分成HT29-C225、HT29-NS、SW620-C225及SW620-NS组,给予西妥昔单抗(每3天注射1次,每次0.5mL,共4周)。治疗后,绘制肿瘤生长曲线,用TDT介导的缺口末端标记技术(TUNEL)检测细胞凋亡,用定量PCR、免疫组织化学染色(IHC)及蛋白印迹(Western-blot)等技术检测移植瘤标本中EGFR信号转导通路中AKT及其磷酸化蛋白的表达。结果:体外增殖及凋亡实验显示,西妥昔单抗对不同K-ras基因型的结肠癌细胞均未能显示细胞毒作用。而体内研究发现,西妥昔单抗能明显抑制K-ras野生型结肠癌裸鼠皮下移植瘤的生长,但对K-ras突变型者抑制作用较差。对K-ras突变型结肠癌裸鼠皮下移植瘤的定量PCR检测结果显示,西妥昔单抗治疗组裸鼠的AKT基因表达率高于对照组。IHC及Western-blot显示,西妥昔单抗治疗组与对照组间AKT蛋白的表达率无明显差异,但西妥昔单抗治疗组裸鼠的p-AKT表达率高于对照组。结论:K-ras突变状态与西妥昔单抗的疗效相关,K-ras突变型者EGFR信号通路中的衔接蛋白AKT呈自主激活状态,该基因突变可能是导致对西妥昔单抗耐药的机制之一。

Ras基因与鼻咽癌西妥昔单抗耐药的相关性研究

目的探讨ras基因与鼻咽癌西妥昔单抗耐药的相关性。方法以人鼻咽癌细胞株5-8F细胞为研究对象,采用逐步增加剂量法诱导建立西妥昔单抗耐药细胞5-8F/Erbitux;MTT法检测西妥昔单抗对细胞的半数抑制浓度IC50,计算耐药指数(RI);Western Blot法检测细胞H-ras、K-ras的蛋白表达;实时荧光定量PCR检测细胞ras-p21、H-ras以及K-ras基因的表达量;测序方法检测H-ras和K-ras基因第12、13、59、61密码子是否突变。结果建立了西妥昔单抗耐药的人鼻咽癌细胞系5-8F/Erbitux,西妥昔单抗作用3天和5天的RI分别为1.2和1.1;5-8F/Erbitux细胞H-ras和K-ras蛋白表达水平显著升高(P<0.001),H-ras基因表达量显著升高(P=0.016),K-ras基因表达量显著下降(P=0.000);ras-p21基因表达量有所升高,但差异不显著(P=0.113);通过比对,5-8F/Erbitux细胞H-ras基因、K-ras基因第12、13、59、61密码子均无突变。结论 H-ras基因扩增与过表达是导致5-8F/Erbitux细胞对西妥昔单抗耐药的主要机制之一。

养殖环境中耐氟喹诺酮类药物大肠杆菌gyrA基因的检测与序列分析

该文探讨从养殖场动物、环境、饲养员等分离的大肠杆菌耐氟喹诺酮类药物的靶位基因gyrA突变特征.对养殖环境中分离的8株大肠杆菌进行临床常用氟喹诺酮类药物的耐药性分析、PCR扩增gyrA基因并测序,并采用DNASTAR软件对gyrA基因的氟喹诺酮耐药决定区进行生物信息学分析.结果表明:养殖场环境中分离的菌株编号为1,6和8的3株大肠杆菌对环丙沙星、左氧氟沙星、诺氟沙星敏感,菌株2,3,4,5和7的5株大肠杆菌对环丙沙星、左氧氟沙星、诺氟沙星耐药;氨基酸序列分析发现,敏感菌株氨基酸位点未发生突变或83位发生单突变;耐药菌株的突变发生在83位Ser→Leu替代和87位Asp→Asn替代,且发生氨基酸双替代的菌株均为高度耐药菌株.表明不同来源的耐氟喹诺酮类药物的大肠杆菌gyrA基因的氨基酸变异具有多种类型,该研究将更好地诠释养殖场大肠杆菌的氟喹诺酮类耐药机制.

RAS野生型转移性结直肠癌EGFR抑制剂耐药机制的研究进展

抗表皮生长因子受体(epidermal growth factor receptor,EGFR)抗体的应用是转移性结直肠癌治疗进展中的里程碑。抗EGFR单抗和其他靶向药物的出现使转移性结直肠癌患者的中位总生存期从6个月提高至将近30个月,显著改善转移性结直肠癌患者的生存质量及预后。目前KRAS和NRAS被公认为是抗EGFR治疗原发耐药的结直肠癌患者疗效预测标志物,用于抗EGFR治疗的转移性结直结癌患者筛选。除了RAS,其他分子改变也可能影响抗EGFR的疗效。即使是抗EGFR治疗有效的患者也会在13~18个月间产生获得性耐药。本文将对目前已知的抗EGFR治疗耐药机制进行综述,并展望可能的逆转耐药策略,以期为转移性结直肠癌患者精准分子靶向治疗提供依据和指导。

掺RA抗车辙剂沥青混合料路用性能研究

文章分析了车辙的成因与发生机理,阐述了RA抗车辙剂对沥青混合料的作用机理,并对不同RA掺量下的沥青混合料进行了路用性能研究,证明了RA抗车辙剂能有效改善沥青混合料的稳定度、水稳定性、高温稳定性和低温抗裂性,同时确定了RA抗车辙剂的最佳掺量。