Characteristics of radiation safety for synchrotron radiation and X-ray free electron laser facilities

Radiation safety problems are discussed for typical electron accelerators, synchrotron radiation (SR) facilities and X-ray free electron laser (XFEL) facilities. The radiation sources at the beamline of the facilities are SR, including XFEL, gas bremsstrahlung and high-energy gamma ray and photo-neutrons due to electron beam loss. The radiation safety problems for each source are compared by using 8 GeV class SR and XFEL facilities as an example.     

Size exclusion chromatography for semipreparative scale separation of Au38(SR)24 and Au40(SR)24 and larger clusters

Size exclusion chromatography (SEC) on a semipreparative scale (10 mg and more) was used to size-select ultrasmall gold nanoclusters (<2 nm) from polydisperse mixtures. In particular, the ubiquitous byproducts of the etching process toward Au(38)(SR)(24) (SR, thiolate) clusters were separated and gained in high monodispersity (based on mass spectrometry). The isolated fractions were characterized by UV-vis spectroscopy, MALDI mass spectrometry, HPLC, and electron microscopy. Most notably, the separation of Au(38)(SR)(24) and Au(40)(SR)(24) clusters is demonstrated.     

tert-Butylhydroquinone as a spectroscopic probe for the superoxide radical scavenging activity assay of biological samples

As a more convenient and less costly alternative to electron spin resonance (ESR) and nonspecific nitroblue tetrazolium (NBT) and cytochrome c assays of superoxide radical (SR, O(2)(?-)) detection, a novel probe, tert-butylhydroquinone (TBHQ), is introduced for SR nonenzymatically generated in the phenazine methosulfate-β-nicotinamide adenine dinucleotide (PMS-NADH) system. SR attacks both TBHQ and SR scavengers incubated in solution for 30 min where scavengers compete with TBHQ for the O(2)(?-) produced. TBHQ, but not its O(2)(?-) oxidation product, tert-butyl-1,4-benzoquinone (TBBQ), is responsive to the CUPRAC (cupric reducing antioxidant capacity) spectrophotometric assay. The CUPRAC absorbance of the ethyl acetate extract of the incubation solution arising from the reduction of Cu(II)-neocuproine reagent by the remaining TBHQ was higher in the presence of O(2)(?-) scavengers (due to less conversion to TBBQ), the difference being correlated to the SR scavenging activity (SRSA) of the analytes. With the use of this reaction, a kinetic approach was adopted to assess the SRSA of amino acids, vitamins, and plasma and thiol antioxidants. This assay, applicable to small-molecule antioxidants and tissue homogenates, proved to be efficient for cysteine, uric acid, and bilirubin, for which the widely used NBT test is nonresponsive. Thus, conventional problems of NBT assay arising from formazan insolubility and direct reduction of NBT by tested scavengers were overcome.     

同步辐射及其在无机材料中的应用进展

同步辐射是环形加速器中做循环运动的高速电子在经过弯转磁铁时, 沿电子轨道切线方向发射的电磁辐射。作为一类平台型科技基础设施, 同步辐射光源对无机材料的研究和发展起到了重要支撑作用。同步辐射实验技术已经成为现代科学技术不可或缺的研究手段, 无机材料研究是同步辐射技术的主要应用领域之一。相对于用于材料研究的常规光源来说, 同步辐射技术研究无机材料有以下优势: 1)获取的数据质量更高; 2)空间分辨和时间分辨的能力更强; 3)原位和材料服役环境更易模拟; 4)多尺度、多方面、多种类的结构信息同步获取; 5)探测新的结构特性更有可能。同步辐射实验技术有助于解决无机材料领域中的一些关键科学问题, 从而极大地推动了无机材料的研究进展。本文首先简要介绍了同步辐射光源的现状, 以及国内现有三个同步辐射装置: 北京同步辐射装置(Beijing Synchrotron Radiation Facility, BSRF)、上海同步辐射装置(Shanghai Synchrotron Radiation Facility, SSRF)和国家同步辐射实验室(National Synchrotron Radiation Laboratory, NSRL)。然后, 从X射线衍射、散射、谱学、成像等四个方面, 列举了同步辐射技术在无机材料研究中的应用实例。最后, 对同步辐射光源和结构表征技术及其在无机材料中的应用进行了总结与展望。     

Frequency-angle characteristics of superradiance pulses generated by ultrarelativistic electron bunches propagating in an undulator field

Terahertz superradiance (SR) from ultrarelativistic electron bunches propagating in an undulator field has been theoretically described using the averaged ponderomotive force method. In addition to the energy characteristics of SR pulses, the formation of a directivity pattern and the dependence of the spectral density of radiation on the angle of observation have been studied.     

A Method to Apply Structure Relevant Impact Damage to Small Structure Relevant Specimens for Damage Tolerance Studies

An approach is presented to represent stiffened composite panels by small but ‘structure relevant’ (SR) specimens in compression tests to study failure mechanisms. The necessary support conditions to be applied during low velocity impact tests were determined for the SR specimens in order to obtain damage that is similar to the damage found in stiffened panels. Fractography revealed that the locations of the major delaminations in the SR specimens due to impact were the same as in stiffened panels. These delaminations occurred where they were expected, suggesting that they can be ‘placed’ deep inside a laminate for optimum damage tolerance. Initial compression tests on stiffened panels confirmed the high damage tolerance of the configuration considered.     

Development of a tamsulosin hydrochloride controlled-release capsule consisting of two different coated pellets

Tamsulosin hydrochloride (TSH) controlled-release capsule (pellets) was successfully prepared using a novel, simple, and flexible multiunit drug delivery system, which consisted of two different coated pellets. The TSH-loaded core pellets consisting of microcrystalline cellulose (MCC), lactose, Carbopol(R) 974P, and the active agent, were prepared by extrusion/spheronization method. Eudragit NE30D and Eudragit L30D-55 were used as the coating materials to prepare sustained-release (SR) pellets and enteric-release (ER) pellets. The coated pellets were prepared using two different equipments: centrifugal coater and fluidized-bed coater. By adjusting the ratio of SR and ER pellets, more than one blend ratios, which meet the in vitro release criterion were obtained. A similarity factor (f(2)) was employed to choose the optimum proportion compared with the commercial product (Harnal capsule). The morphology of the pellet surfaces was examined by scanning electron microscopy (SEM) before and after dissolution. The release profiles were significantly affected by changing the proportions of SR and ER. The optimum ratio is SR:ER = 2:1 using a centrifugal coater (f(2) = 61.93) and SR:ER = 3:1 using a fluidized coater (f(2) = 66.42). This result suggests that blending these two-part pellets (SR and ER) can provide an alternative to preparing a controlled-release dosage form, instead of blending of the coating polymer.     

Study on leakage via the radial clearance in a novel synchronal rotary refrigeration compressor

The leakage flow characteristics at the radial clearance between the rotor and the cylinder in a novel synchronal rotary (SR) refrigeration compressor were analyzed, and the oil-refrigerant two-phase leakage flow model was established. The leakage at different temperatures caused by wall velocity and pressure difference was calculated, and their influences on the total leakage were analyzed, respectively. The calculation results indicate that the leakage of the oil-refrigerant mixture decreases firstly and then increases with the increase in the temperature. However, the refrigerant leakage always decreases when the temperature increases. Moreover, the leakage caused by wall velocity has great influence on the total leakage, especially when the radial clearance is small.     

一个生产爆破管理系统的开发

在露天矿生产爆破数据库基础上 ,结合宜阳矿的实际 ,分析了数据库管理系统的功能和结构。通过上述工作 ,为宜阳矿开发了一个生产爆破管理系统 ,实现了某些功能如生产爆破数据的处理、综合利用、查询以及报表打印等的计算机管理 ,为该矿的生产和管理部门提供了现代化的管理手段和决策依据     

基于反应谱分析的建(构)筑物爆破振动响应安全评估方法研究

利用大量爆破振动实际监测数据,对爆破振动速度反应谱谱面积SR与爆破地震波信号各特征量进行了关联分析,研究了SR对建筑结构振动损伤的影响和关联。研究发现SR值能较全面地反映爆破振动的综合作用效果,以及结构动力特性对结构振动破坏的影响。根据研究结果,提出了用SR作为爆破振动安全评估特征值的爆破地震效应评估新方法。132组爆破振动数据的计算与分析表明,SR>5.5时爆破地震波将对一般民房结构产生破坏的概率显著增加,可将[SR2]≤5.5作为二类建(构)筑物爆破振动破坏安全判据标准的补充。在此研究的基础上,通过引入建(构)筑物爆破振动反应谱安全系数Prs的概念,初步建立了以SR为特征值,考虑爆破振动综合作用效应和结构振动特性的爆破振动安全统一判据。     

Mechanical properties, fire performance and thermal stability of magnesium hydroxide sulfate hydrate whiskers flame retardant silicone rubber

Halogen-free flame retardant silicone rubber (SR) composites, using magnesium hydroxide sulfate hydrate (MHSH) whiskers as flame retardant have been prepared by a two-roll mill. Moreover, microencapsulated red phosphorus (MRP) was used as a synergist. Mechanical tests were performed to determine the tensile strength, elongation at break, and shore hardness of the composites. The morphology of fracture surface was observed by environmental scanning electron microscopy (ESEM). The results showed MHSH slightly reduced the tensile strength of the composites, but had obvious influence on the elongation at break. Meanwhile, Shore A hardness presented uptrend with increasing MHSH content. The addition of vinyl silicone fluid (VSF) could improve the compatibility of the MHSH whiskers in SR matrix, and therefore improved the mechanical properties of composites. The flammability properties of composites were investigated by limited oxygen index (LOI), UL-94 tests, and cone calorimetry experiments. It is found that MHSH whiskers can effectively improve the flame retardancy of SR composites due to the endothermic degradation of MHSH whiskers accompanied with the release of water vapor, and the formation of fibrous magnesia acting as a barrier layer. The incorporation of MRP in SR/MHSH whiskers system had a synergic fire retardant effect in the condensed and gas phase. In addition, thermogravimetric analysis (TGA) indicated the presence of MRP enhanced thermal stability of the SR/MHSH composites at higher temperature range, and remarkably promoted char residue yield.     

A novel assembled carbon black/carbon nanotubes (CB/MWCNT) nano-structured composite for pressure-sensitive conductive silicon rubber (SR)

In this paper, a novel “grape string” carbon black/multi-wall carbon nanotubes (CB/MWCNT) structure was obtained by electro-static assembly method to enhance the resistance stability of the carbon material filled silicone rubber (SR). Carbon black (CB) and multi-wall carbon nanotubes (MWCNT) were surface modified by sulfonic dodecyl benzene sodium and cetyltrimethylammonium bromide to provide negatively charge and positively charge, respectively. Electric conductive sheet of CB/MWCNT/SR composite was obtained by mixing and vulcanizing. The assembly effect and dispersion state of the composites were analyzed by transmission electron microscopy and scanning electron microscopy. The electrical conductivity and dynamic pressure-resistance characteristic of CB/MWCNT/SR with different doping ratio and dosage were tested. The results show that the proper weight ratio 3:2 of CB:MWCNT for electrostatic assembly can cause the stable “grape string” nano-structure. The conductivity and pressure-resistance characteristic are superior when the volume fraction of “grape string” nano-composites reaches 22%, which will provided with less filler fraction and better stress sensitivity, compared with single component carbon black filler.     

Development of SPring-8 vacuum system

SPring-8 storage ring has been available for user operation with low emittance and extreme stability for over 10 years. However there occurred some problems in the components of the storage ring due to high-brightness synchrotron radiation (SR) and low-emittance operation. On the vacuum system of the storage ring, an accurate pressure could not be measured near the photon absorber due to scattered high-energy SR to the gauge head. High-energy SR activated dissolved oxygen in cooling water, and the activated dissolved oxygen corroded the inside of the photon absorbers in SR irradiation part. Air leakage occurred at an injection chamber due to impact by a small-size electron beam produced by low-emittance operation.We investigated the cause of the aforementioned difficulties with the vacuum system and prescribed the treatments described in this paper. In addition, we are making continual efforts at further system upgrades such as developing an RF shield that suppresses temperature increase in the shield in possible high-current operation.     

Experimental study of the electron beam compressed state breakup

The dynamics of breakup of the compressed state of an electron beam with a virtual cathode (VC) transported in a two-section drift tube of a high-current electron accelerator has been studied. Based on the results of numerical simulations, the method of partial capture of the injected beam current during the applied voltage pulse is proposed and implemented, which can ensure the conditions necessary for the breakup of the electron beam compressed state. The VC velocity during the breakup of the electron beam compressed state amounts to 6–8% of the velocity of light in vacuum. The experimental data qualitatively agree with the results of analytical estimations and numerical simulations.     

Modulation of drug (metoprolol succinate) release by inclusion of hydrophobic polymer in hydrophilic matrix

The objective of this study was to develop sustained release (SR) matrix tablets of metoprolol succinate (MS), by using different polymer combinations and fillers, to optimize by response surface methodology and to evaluate biopharmaceutical parameters of the optimized product. Matrix tablets of various combinations were prepared with cellulose-based polymers: hydroxy propyl methyl cellulose (HPMC) and ethyl cellulose (EC); and lactose and dibasic calcium phosphate dihydrate (DCP) as fillers. Study of pre-compression and post-compression parameters facilitated the screening of a formulation with best characteristics that underwent here optimization study by response surface methodology (Central Composite Design). The optimized tablet was subjected to further study like scanning electron microscopy, swelling study and in vivo study in rabbit model. Both in vitro and in vivo study revealed that combining of HPMC K100M (21.95%) with EC (8.85%), and use of DCP as filler sustained the action up to 12 h. The in vivo study of new SR tablets showed significant improvement in the oral bioavailability of MS in rabbits after a single oral dose of 25 mg. The delayed T(max) and lower C(max) indicated a slow and SR of MS from the optimized matrix tablets in comparison with the immediate release dosage form. The developed SR (MS) tablet of improved efficacy can perform therapeutically better than conventional tablet.     

Development of a Tamsulosin Hydrochloride Controlled-Release Capsule Consisting of Two Different Coated Pellets

Tamsulosin hydrochloride (TSH) controlled-release capsule (pellets) was successfully prepared using a novel, simple, and flexible multiunit drug delivery system, which consisted of two different coated pellets. The TSH-loaded core pellets consisting of microcrystalline cellulose (MCC), lactose, Carbopol^® 974P, and the active agent, were prepared by extrusion/spheronization method. Eudragit^® NE30D and Eudragit^® L30D-55 were used as the coating materials to prepare sustained-release (SR) pellets and enteric-release (ER) pellets. The coated pellets were prepared using two different equipments: centrifugal coater and fluidized-bed coater. By adjusting the ratio of SR and ER pellets, more than one blend ratios, which meet the in vitro release criterion were obtained. A similarity factor (f₂) was employed to choose the optimum proportion compared with the commercial product (Harnal^® capsule). The morphology of the pellet surfaces was examined by scanning electron microscopy (SEM) before and after dissolution. The release profiles were significantly affected by changing the proportions of SR and ER. The optimum ratio is SR:ER?=?2:1 using a centrifugal coater (f₂?=?61.93) and SR:ER?=?3:1 using a fluidized coater (f₂?=?66.42). This result suggests that blending these two-part pellets (SR and ER) can provide an alternative to preparing a controlled-release dosage form, instead of blending of the coating polymer.     

An instrument for the detection of optimal working conditions in stochastic systems

Stochastic resonance (SR) is an active research topic in the area of nonlinear system theory. It has been used to explain the behavior of both natural systems and man-made produced devices. SR conditions are generally investigated by mathematical analysis of complex systems or by realizing nonlinear systems (a typical example being the Schmitt trigger) that are known to be characterized by the presence of SR and performing experimental studies on them. This paper introduces a novel instrument for the detection of SR conditions that does not require any human intervention and, hence, allows independent validation of results concerning SR.     

Measuring the virtual cathode velocity

An electron beam with a virtual cathode (VC) transported in a two-section drift tube of a SINUS-7 high-current electron accelerator has been studied. The dependence of the VC velocity on the injected current has been experimentally determined for the first time. It is established that the VC motion in the drift tube is accompanied by microwave oscillations, which are caused by transient processes involved in the formation of a compressed electron beam.     

Terahertz superradiance of an extended electron bunch propagating over a corrugated surface

We propose to generate high-power electromagnetic pulses by using the phenomenon of Cherenkov superradiance (SR) of extended electron bunches that propagate in free space over a corrugated surface. Both an analysis performed in the framework of a quasi-optical approximation and a direct particle-in-cell simulation demonstrate the possibility of generating multimegawatt picosecond pulses of radiation in the terahertz range using the proposed mechanism.     

Preparation of the crosslinked poly(vinyl alcohol)/blocked isocyanate prepolymers nanofibers with hydrolyzed products of Scutellariae Radix

We report on the preparation and characterizations of Scutellariae Radix (SR) blended poly(vinyl alcohol) (PVA)/blocked isocyanate prepolymer (BIP) composite nanofibers via electrospinning process. In order to improve the biocompatibility properties, SR biological macromolecules were blended in PVA/BIP composite nanofibers. SEM images revealed that the composite nanofibers were well-oriented and had good incorporation of SR. Ultraviolet (UV) absorbance spectra revealed that the maximum measured absorbance intensities were linearly increased with increasing SR in the composite nanofibers. TEM images revealed a peculiar morphology by the additive SR. This additive SR possesses a lower molecular component which was exhibited at the outside of the nanofibers structure due to strong applied electric field during electrospinning process. These results indicated that the PVA/BIP blended SR composite nanofibers might be utilized for many biomedical applications including control release and wound dressing.