EPR在体测量专用调制磁场驱动装置

利用电子顺磁共振（electron paramagnetic resonance,EPR）在体测量人牙齿可以实现无损伤地快速评估人体辐射剂量,具有实际应用价值.本文针对EPR在体测量牙齿剂量的应用特点,研制了专用调制磁场驱动装置,包括功率放大器、调制磁场激励线圈、调制频率设定模块、感应型调制幅度显示模块等.功率放大器采用脉冲功率放大方式取代传统的线性放大方式,用多N-MOSFET管H桥电路,功率容量大、效率高、结构简单,且调制频率设定自如.实验结果表明：（1）此装置可在大于9 cm磁极间距的中心样品位置产生调制幅度为0~0.9 mT的调制磁场,调制频率为10~100 kHz;（2）用该装置与EPR在体测量谱仪配合使用,可以明显观测到1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl,DPPH）样品谱线调制增宽过程以及辐射诱发的整体牙齿中的自由基信号,验证了该装置的高调制效率和实用性.     

In Vivo EPR For Dosimetry

As a result of terrorism, accident, or war, populations potentially can be exposed to doses of ionizing radiation that could cause direct clinical effects within days or weeks. There is a critical need to determine the magnitude of the exposure to individuals so that those with significant risk have appropriate procedures initiated immediately, while those without a significant probability of acute effects can be reassured and removed from the need for further consideration in the medical/emergency system. In many of the plausible scenarios there is an urgent need to make the determination very soon after the event and while the subject is still present. In vivo EPR measurements of radiation-induced changes in the enamel of teeth is a method, perhaps the only such method, which can differentiate among doses sufficiently for classifying individuals into categories for treatment with sufficient accuracy to facilitate decisions on medical treatment. In its current state, the in vivo EPR dosimeter can provide estimates of absorbed dose with an error approximately +/- 50 cGy over the range of interest for acute biological effects of radiation, assuming repeated measurements of the tooth in the mouth of the subject. The time required for acquisition, the lower limit, and the precision are expected to improve, with improvements in the resonator and the algorithm for acquiring and calculating the dose. The magnet system that is currently used, while potentially deployable, is somewhat large and heavy, requiring that it be mounted on a small truck or trailer. Several smaller magnets, including an intraoral magnet are under development, which would extend the ease of use of this technique.     

Visualization and Characterization of Atherosclerotic Plaques by Micro-MRI at 4.7 T In Vivo and 11.7 T Ex Vivo

The aim of this study was to evaluate the capability of using micro-magnetic resonance imaging (MRI) to visualize and characterize atherosclerotic plaques of mouse models. Twenty five apolipoprotein E-knockout mice were fed atherogenic diet, which enabled creation of aortic atherosclerotic plaques. Aortic plaques were examined in vivo by 4.7 T MRI and then characterized ex vivo by 11.7 T three-dimensional MRI. MR images were correlated with subsequent histological confirmation. In vivo 4.7-T MRI demonstrated unevenly thickened aortic walls due to formation of atherosclerotic plaques. Ex vivo 11.7-T MRI enabled not only to acquire full volume-rendered images of the entire vessels but also to characterize plaque components (such as lipid cores and fibrous caps) at any level and any projection, which were confirmed by histological correlation. Micro-MRI provides an excellent imaging tool for basic science to investigate atherosclerosis in small animal models, which may become a supplement to histopathology of atherosclerotic cardiovascular disease.     

共振拉曼光谱在体测量类胡萝卜素含量

类胡萝卜素是人体内重要的抗氧化剂,能够消除体内的自由基和其它有害氧分。研究表明类胡萝卜素含量与癌症、心血管疾病、老化等疾病发病率呈反比关系。目前检测方法为采用血清液相色谱检测方法,不能做到在体无损伤、实时测量。文章介绍了一种用于测量类胡萝卜素的新技术——共振拉曼光谱技术,具有在体无损伤、灵敏度高和实时检测等特点。该技术利用强度远小于美国ANSI Z136.1-2000标准的473 nm激光激发拇指中类胡萝卜素,产生强荧光和叠加在其上的弱共振拉曼光,通过测量拉曼散射光强度在体评估类胡萝卜素的含量。同时,利用组织通透技术,改善了测量信噪比。测量了不同饮食习惯志愿者的类胡萝卜素含量,说明其含量与其摄入量成正比。该技术在临床应用和科学研究等领域具有重要意义。     

Electric Field in a Gravitational Field

The potential of a static electric charge located in a Schwarzschild gravitational field is given by Linet. The expressions for the field lines derived from this potential are calculated by numerical integration and drawn for different locations of the static charge in the gravitational field. The field lines calculated for a charge located very close to the central mass can be compared to those calculated by Hanni–Ruffini. Maxwell equations are used to analyze the dynamics of the falling electric field in a gravitational field.     

Assessment of Nitrones as In Vivo Redox Sensors

Spin traps such as 5,5-dimethyl-1-pyrroline N-oxide, α-phenyl-tert-butyl nitrone, α-(4-pyridyl-1-oxide)-N-tert-butyl nitrone and newer generation 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline N-oxide analogs have been known for years. What are the desired properties of good probes for measuring in vivo redox reactions in biological systems? These are specificity, sensitivity, rapid, high yield kinetics, low toxicity, high stability and easy to administer and target. Unfortunately, the nitrones perform poorly in almost all of these categories. Typical in vivo concentrations of spin trap approach 100 mM (assuming solubility and toxicity are not an issue), frequently yield 1% nitroxide or less stoichiometry, are typically unstable with time and frequently lack specificity. In vivo electron paramagnetic resonance (EPR) experiments need to have strong signals that correlate with redox chemistry. The resultant signal should be stable and not rapidly interconvert to other diamagnetic species. Fortunately, some newer probes of in vivo redox reactions in biological systems have come upon the horizon. In fact some have been around for a long time, but their virtues are becoming increasingly appreciated. This paper summarizes the disadvantages of nitrones versus the clear advantages of other probes of free radicals, redox state and the like by EPR. It also expands on the properties of nitroxides and nitrones as therapeutics.     

Resonators for In Vivo Imaging: Practical Experience

Resonators for preclinical electron paramagnetic resonance imaging have been designed primarily for rodents and rabbits and have internal diameters between 16 and 51 mm. Lumped-circuit resonators include loop-gap, Alderman–Grant, and saddle coil topologies and surface coils. Bimodal resonators are useful for isolating the detected signal from incident power and reducing dead time in pulse experiments. Resonators for continuous wave, rapid scan, and pulse experiments are described. Experience at the University of Chicago and University of Denver in design of resonators for in vivo imaging is summarized.     

MRI评价药物投递性能方法研究

采用MRI评价自制肝组织特异性非离子型高分子磁共振造影剂在小鼠体内药物投递效果. 分别在注射造影剂后0.1 h、6 h、12 h、24 h及7天采集磁共振T₁加权图像. 所有扫描均在1.5T临床磁共振成像仪上完成, 以固定体线圈为射频发射线圈, 三英寸圆形表面线圈为信号接收线圈. 数据分析前采用线圈非均匀性校正和信号非稳定性校正进行预处理. 实验结果显示,线圈空间敏感性校正使得小鼠组织图像信号强度空间更加均匀,稳定性校正后使得图像数据更加准确可靠,MRI是一种在体评价顺磁性标记高分子化合物药物投递效果的有效方法.     

Field theory

The possibility of determining the preferred stable trajectories of macroparticles when the initial conditions of their motion in a central field remain indeterminate is investigated. The concept of field-dynamical equilibrium is introduced, an equation is derived for it, and one of the possible physical interpretations of this state is submitted. General considerations are advanced with regard to the solution of the equation, and a similarity is noted between the resulting equation and the quantum-mechanical Schrödinger equation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 10, pp. 46–52, October, 1971.I wish to gratefully acknowledge State Prize Laureate and member of the international Commission on Gravitation, Prof. D. D. Ivanenko, and the Director of the Astronomical Observatory of Kiev University, Prof. A. F. Bogorodskii, for affording me the opportunity on several occasions to present papers at seminars under their direction, as well as for their valuable consultations on individual aspects of the present study.     

二维核磁共振定域谱及其在活体中的应用

核磁共振定域谱(MRS)是获得活体生化定量信息和诊断信息的无损检测技术,是核磁共振成像强有力的补充技术,可为临床诊断和疾病预测提供重要的信息. 然而,活体1D ¹H MRS通常存在代谢物谱峰拥挤、分辨率较低和归属难等问题. 引入2D MRS可在较大程度上解决¹H MRS谱峰重叠和谱峰归属难的问题. 该文简述和分析了几种典型的2D MRS新方法及其优缺点,并讨论了它们在脑部、肌肉、乳腺、前列腺等活体组织中的应用. 虽然2D MRS存在着实验时间较长的局限,但最新研究表明其具有一些独特的优势及较好的发展前景.     

Two-Photon Excitation Fluorescence Microscopy of Rat Elastin Fiber In Vivo

Russian Physics Journal - The paper presents the results of two-photon excitation fluorescence microscopy of rat elastin fiber in vivo. It is shown that in approximating the fluorescence...     

电场穿透对高温超导体场致发射电流的影响

高温超导体在场致发射时伴随正常态部分的空穴的产生 ,会出现非平衡现象。这会引起超导体电子平衡态的化学势偏移 ,增加外电场在高温超导体发射体内的穿透深度 ,使导带底弯曲影响超导体场致发射的电流。     

Current Problems and Potential Techniques in In Vivo Glucose Monitoring

Accurate in vivo monitoring of glucose concentration would be a valuable asset, particularly for management of diabetes and preterm infants during critical care. In vivo glucose monitoring devices can be divided into two categories: implanted and non-invasive. Extensive research into in vivo glucose monitoring over recent decades has not resulted in the widespread use of clinically reliable monitoring systems. For implanted devices, poor biocompatibility of the materials used for fabrication remains a major challenge, whilst progress in the commercial development of non-invasive devices is hampered by the problem of multiple interference between the detected signals and the biological components. In this review, the methods available for in in-vivo glucose monitoring are described and the associated problems are discussed.     

Relativistic Quantum Field Inertia and Vacuum Field Noise Spectra

The equivalence statements for quantum scalar field vacuum states that havebeen used for the thermal-like Hawking effect and Unruh effect are surveyed.An important ingredient in this framework is the concept of a vacuum field noisespectrum, by which one can obtain information about the curvature invariants ofclassical worldlines (relativistic classical trajectories). It is argued, in the spiritof the free-fall-type universality, that the preferred quantum field vacua withrespect to accelerated worldlines should be chosen from the class of all thosepossessing stationary spectra for their quantum fluctuations. For scalar quantumfield vacua there are six stationary cases, as shown by Letaw some time ago,and reviewed here. However, nonstationary vacuum noises can be treated by afew mathematical methods that are mentioned as well. Since the informationabout the kinematical curvature invariants of the worldlines is of radiometricorigin, suggestions are given on the more useful application of such an academicformalism to radiation and beam radiometric standards for high-energyaccelerators and in astrophysics. We conclude with a look at related axiomaticquantum field topics and some other recent work.