在体剂量检测专用EPR数据采集与控制系统

研制了X波段在体剂量检测专用EPR谱仪的数据采集与控制系统,利用阿尔泰USB2812数据采集卡作为控制卡,在LabVIEW图形化编程开发环境中进行程序开发,实现了扫场电源的控制、微波模的显示、微波功率的控制和EPR信号的采集等功能. 数据处理程序可实现存储数据的查询、谱线基线校正和积分等基本功能,为下一步开展牙齿剂量试验研究提供了平台.     

在体EPR专用磁场装置性能的改进

为测试在体EPR牙齿辐射剂量测量专用磁场装置,开展了初步性能试验. 针对扫描磁场非线性造成谱线的畸变情况,对在体EPR专用磁场装置性能进行了改进,给出了一种校正扫描磁场非线性的实现方法,通过对扫描磁场驱动电流进行反向刻度校正,可有效改善EPR谱线的畸变情况. 初步试验进一步证明了水平磁场在体测量方案的可行性,磁场装置性能的改进为实现X波段EPR辐射剂量在体测量向实际应用奠定基础.     

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.     

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.     

The Individual Form of the Background Signal in EPR Dosimetry of Tooth Enamel

The dependence of the calculated individual absorbed dose on the form factor, degree of anisotropy, and the model line width of the background component of the EPR spectrum of tooth enamel established. It is shown that an incorrect choice of the model line form for the background component can lead to inadequate evaluation of reconstructed load dose.     

Development of X-Band TE111 Mode ESR Cavity for In Vivo Tooth Dosimetry

Electron spin resonance (ESR) tooth spectroscopy offers the possibility of in vivo dosimetry for radiation accident emergency. We developed an X-band ESR cavity for in vivo measurement of tooth enamel, which is a cylindrical cavity working at TE₁₁₁ mode. A narrow rectangular aperture to fix incisors was opened on the cavity wall, where there were strong microwave magnetic field component H₁ and weak microwave electronic field component E₁ inside the cavity. The external modulated magnetic field was applied to the incisors from both sides of the aperture. Theoretical calculations and simulations were discussed to optimize the characteristics and predict the cavity working conditions and performances. The characteristics were evaluated by measuring DPPH and whole incisor samples. Remarkable radiation induced signal of 2Gy irradiated tooth could be obtained by one 5-min ESR spectroscopy. This result indicated that the cavity was sensitive enough to detect the radiation-induced signal in human teeth. This paper describes the operation principle, configuration, and characteristics, and reports the DPPH and tooth experiments to verify the cavity.     

A Deployable In Vivo EPR Tooth Dosimeter for Triage After a Radiation Event Involving Large Populations

In order to meet the potential need for emergency large-scale retrospective radiation biodosimetry following an accident or attack, we have developed instrumentation and methodology for in vivo electron paramagnetic resonance spectroscopy to quantify concentrations of radiation-induced radicals within intact teeth. This technique has several very desirable characteristics for triage, including independence from confounding biologic factors, a non-invasive measurement procedure, the capability to make measurements at any time after the event, suitability for use by non-expert operators at the site of an event, and the ability to provide immediate estimates of individual doses. Throughout development there has been a particular focus on the need for a deployable system, including instrumental requirements for transport and field use, the need for high throughput, and use by minimally trained operators.Numerous measurements have been performed using this system in clinical and other non-laboratory settings, including in vivo measurements with unexposed populations as well as patients undergoing radiation therapies. The collection and analyses of sets of three serially-acquired spectra with independent placements of the resonator, in a data collection process lasting approximately five minutes, provides dose estimates with standard errors of prediction of approximately 1 Gy. As an example, measurements were performed on incisor teeth of subjects who had either received no irradiation or 2 Gy total body irradiation for prior bone marrow transplantation; this exercise provided a direct and challenging test of our capability to identify subjects who would be in need of acute medical care.     

Implementing EPR Dosimetry for Life-Threatening Incidents: Factors Beyond Technical Performance

Starting with the assumption that a device to detect unplanned radiation exposures is technically superior to current technology, we examine the additional stakeholders and processes that must be considered to move the device from the lab into use. The use is to provide reliable information to triage people for early treatment of exposure to ionizing radiation that could lead to the Acute Radiation Syndrome. The scenario is a major accident or terrorist event that leaves a large number of people potentially exposed, with the resulting need to identify those to treat promptly or not. In vivo EPR dosimetry is the exemplar of such a technique.Three major areas are reviewed: policy considerations, regulatory clearance, and production of the device. Our analysis of policy-making indicates that the current system is very complex, with multiple significant decision-makers who may have conflicting agendas. Adoption of new technologies by policy-makers is further complicated because many sources of expert input already have made public stances or have reasons to prefer current solutions, e.g., some may have conflicts of interest in approving new devices because they are involved with the development or adoption of competing techniques. Regulatory clearance is complicated by not being able to collect evidence via clinical trials of its intended use, but pathways for approval for emergency use are under development by the FDA. The production of the new device could be problematical if the perceived market is too limited, particularly for private manufacturers; for in vivo EPR dosimetry the potential for other uses may be a mitigating factor.Overall we conclude that technical superiority of a technique does not in itself assure its rapid and effective adoption, even where the need is great and the alternatives are not satisfactory for large populations. Many important steps remain to achieve the goals of approval and adoption for use.     

Pulsed Electron Spin Resonance Ex Situ Probe for Tooth Biodosimetry

An electron spin resonance (ESR) probe that includes a static field source and a microwave resonator for the measurement of paramagnetic defects in tooth enamel is presented. Such defects are known to be a good marker for quantifying the amount of ionizing radiation dose absorbed in the tooth. The probe can measure the tooth when it is positioned just above its outer surface, i.e., in ex situ geometry. It is operated in pulsed mode at a frequency of ~6.2 GHz that corresponds to the magnitude of the static magnetic field of its permanent magnet. A detailed design of the probe is provided, together with its specifications in terms of measurement volume and signal-to-noise-ratio for a typical sample. Experimental results that verify its sensitivity and capability to measure gamma-irradiated teeth are provided. The current minimal detected signal by the probe corresponds to a radiation dose of ~4 Gy.     

Experimental and Theoretical In Situ Spectral Magneto-Ellipsometry Study of Layered Ferromagnetic Structures

JETP Letters - The influence of antiadiabatic phonons on the superconducting transition temperature is considered within Eliashberg-McMillan approach in the model of discrete set of (optical)...     

Feasibility of Q-Band EPR Dosimetry in Biopsy Samples of Dental Enamel, Dentine and Bone

Electron paramagnetic resonance (EPR) dosimetry of tooth enamel in X-band has been established as a suitable method for individual reconstruction of doses 0.1 Gy and higher. The objective was to demonstrate the feasibility of using Q-band EPR in small biopsy tooth enamel samples to provide accurate measurements of radiation doses. Q-band spectra of small (<10 mg) irradiated samples of dentine and bone were studied to investigate the possibility of using Q-band EPR for dose measurements in those materials if there are limited amounts of enamel available, and there is no time for the chemical sample preparation required for accurate X-band measurements in dental enamel. Our results have shown that Q-band provides accurate measurements of radiation doses higher than 0.5 Gy in tooth enamel biopsy samples as small as 2 mg. Q-band EPR spectra in powdered dentine and bone demonstrated significantly higher resolution and sensitivity than in conventional X-band measurements.     

Core–Shell Composite Synthesized through In Situ Polymerization in Emulsion with High Electrical Conductivity Sensitive to Humidity

A core–shell composite has been synthesized through in situ polymerization in emulsion with an average of 205 nm of diameter. Each composite consists of a graphene oxide (GO) core and a poly(methyl methacrylate/butyl acrylate) shell. The latex is homogeneous without any aggregation after stability testing in normal temperature for 100 d and can be applied as an ideal conductive adhesive whose glass transition temperature (T _g) is under ?30 °C and lucid conductive film whose T _g is above 17 °C. There exists half core–shell structure in the composite with part of GO exposed which contributes to the electrical conductivity of film formed by composite. The electrical conductivity of the composite is sensitive to humidity, increasing from 0.233 to 0.357 S m^?1, while the related humidity ranges from 0% to 60%. The flexible aliphatic shell established by polyacrylate chains with nanolevel of interspaces makes it easy for hydrone to move in and interact with the oxygen groups on the chains, and then the interaction enhances the difficulty for hydrone to move out, on account of which film formed by core–shell composite can hold hydrone and exhibit advanced electrical conductivity in high humidity atmosphere.     

In Situ Measurement of Excitation Intensity for Fluorescence Excitation Spectroscopy

It is argued that the double-beam method for the automatic correction of fluorescence excitation spectra, which proved to be a great boon in the days of analog instrumentation, has become, after the advent of digital techniques for acquiring and manipulating spectral data, more of a hindrance than a help; the benefits of reverting to a single beam device and making in situ measurement of the excitation intensity are pointed out.     

一款小角X射线散射原位测量专用简易样品加热装置

原位加热实验是同步辐射小角X射线散射领域的新热点。本文针对同步辐射小角X射线散射中需要加热并原位实时检测的实验而设计的一款样品简易原位加热专用装置,该装置主要由温控器、样品池、固定架组成,它具有结构简单、操作容易的特点。本文介绍该装置的基本结构、特点并采用该装置进行原位加热干燥褐煤实验,通过分析实验结果验证装置的可行性。     

A Novel Fluorescent Nanoparticle for Sensitive Detection of Cry1Ab Protein In Vitro and In Vivo

Here, we report the synthesis and characterization of CoFe₂O₄ doping Ag₂S dendrimer-modified nanoparticles (CoFe₂O₄-Ag₂S DMNs) in Cry1Ab protein detection and imaging. The near-infrared Ag₂S quantum dots were first prepared by using the thermal decomposition method, followed by modification of the water-soluble quantum dots using the method of solvent evaporation and ligand exchange, and finally the fluorescent magnetic bifunctional nanoparticles were obtained by binding with CoFe₂O₄. As-prepared CoFe₂O₄-Ag₂S DMNs were characterized by fluorescence (FL) spectroscopy and transmission electron microscopy (TEM). Results showed that Ag₂S DMNs could sensitively detect Cry1Ab both in vitro and in vivo. In vitro, the enhanced FL intensity as a function of the concentration is notably consistent with the Langmuir binding isotherm equation in the range of 0–200 ng/mL of Cry1Ab proteins. The detection limit of this method was found to be 0.2 ng/mL. Meanwhile, the fluorescence wavelength was extended to the second near-infrared range (NIR-II, 1.0~1.4 μm), which enables in vivo imaging. This study highlights the importance of NIR QDs doping magnetic materials as a new method to trace Bacillus thuringiensis (Bt) in insects and their potential applications in in vivo NIR tissue imaging.     

In Situ Epitaxy of Pure Phase Ultra-Thin InAs-Al Nanowires for Quantum Devices

We demonstrate the in situ growth of ultra-thin InA s nanowires with an epitaxial Al film by molecular-beam epitaxy.Our InAs nanowire diameter(～30 nm) is much thinner than before(～100 nm).The ultra-thin InAs nanowires are pure phase crystals for various different growth directions.Transmission electron microscopy confirms an atomically abrupt and uniform interface between the Al shell and the InAs wire.Quantum transport study on these devices resolves a hard induced superconducting gap and 2 e-p...