电子束辐照对透明质酸功能及结构特性的影响

为了探讨电子束辐照对透明质酸功能及结构特性的影响,选择5、10、20、40、80 、100和150 kGy的电子束辐照固体透明质酸,测定透明质酸辐照前后分子量、特性粘度 、pH值、抗氧化性、紫外光谱、红外光谱、电镜图片的变化.结果表明,辐照降低透明 质酸的分子量、特性粘度、pH值;透明质酸在辐照前后的吸收特征峰没有显著的改变, 吸收强度增强;透明质酸形状随着辐照剂量的升高,由块状逐渐变成颗粒状;透明质酸 对DPPH·自由基的清除作用和还原力随着辐照剂量的增大逐渐增强.电子束辐照对透明 质酸分子结构和功能有一定的影响,但对其一级结构没有影响.     

Statistical process control for electron beam monitoring

PurposeTo assess the electron beam monitoring statistical process control (SPC) in linear accelerator (linac) daily quality control. We present a long-term record of our measurements and evaluate which SPC-led conditions are feasible for maintaining control.MethodsWe retrieved our linac beam calibration, symmetry, and flatness daily records for all electron beam energies from January 2008 to December 2013, and retrospectively studied how SPC could have been applied and which of its features could be used in the future. A set of adjustment interventions designed to maintain these parameters under control was also simulated.ResultsAll phase I data was under control. The dose plots were characterized by rising trends followed by steep drops caused by our attempts to re-center the linac beam calibration. Where flatness and symmetry trends were detected they were less-well defined. The process capability ratios ranged from 1.6 to 9.3 at a 2% specification level. Simulated interventions ranged from 2% to 34% of the total number of measurement sessions. We also noted that if prospective SPC had been applied it would have met quality control specifications.ConclusionsSPC can be used to assess the inherent variability of our electron beam monitoring system. It can also indicate whether a process is capable of maintaining electron parameters under control with respect to established specifications by using a daily checking device, but this is not practical unless a method to establish direct feedback from the device to the linac can be devised.     

Infrared picosecond laser for perforation of single plant cells

The functional analysis of plant cells at the cellular and subcellular levels requires novel technologies for the directed manipulation of individual cells. In this report, we demonstrate the use of an infrared (1,064 nm) picosecond laser for the perforation of tobacco cell protoplasts. A single pulse was sufficient to perforate the plasma membrane enabling the uptake of dye from the surrounding medium into the cytosol. Moreover, the procedure was shown to be suitable for the efficient delivery of DNA expression constructs to the nucleus, as demonstrated by the subsequent expression and correct targeting of a recombinant fluorescent protein. Single cell perforation using this novel optoporation method shows that isolated plant cells can be permeabilized without direct manipulation. This is a valuable procedure for cell-specific applications, particularly where the import of specific molecules into plant cells is required for functional analysis.     

白纹伊蚊对光线与二氧化碳的行为反应

白纹伊蚊Aedesalbopictus是重要的媒介昆虫 ,骚扰叮咬、传播病菌 ,严重危害人体健康。该文利用市场上流行的不同型号的 2种驱蚊灯和 4种诱蚊灯分别处理白纹伊蚊种群 ,观测其行为反应 ,结果表明白纹伊蚊在活动、取食和存活等方面均产生保护性行为反应。未照射 (CK)蚊子生长正常、活动性强、取食活跃、存活率高。除虫灯光线照射后 ,初期 ( 1d内 )蚊子活泼、活动量较大、存活率较高 ;前期 ( 1～ 3d间 )活动加剧、取食减少而存活率降低 ;一定时期 ( 3d)后活动性逐渐降低、取食越来越少、存活率明显下降。除虫效果检测表明 ,诱蚊灯的诱杀效果比驱蚊灯的驱逐作用对减少蚊虫的数量更明显 ;同时显示 ,诱蚊灯的灭蚊效果均较好 ,但诱蚊作用不十分理想。继而探索出一个对白纹伊蚊具有较好引诱效应的二氧化碳 (CO2 )浓度 4 464× 1 0 -4mol L ,并与紫外线诱蚊灯结合试验表明 ,一定浓度的CO2 能够显著提高诱蚊灯的诱杀效果 ,这可为开辟蚊虫物理防治新途径提供理论依据。     

离子束介导任意引物PCR差异片段转化在育种中的可行性及前景

离子束作为一种介导DNA转化技术逐渐得到了越来越广泛的应用,并且在促进DNA转化上存在很大优势。育种过程中任意引物PCR技术通过对诱变前后整个基因组的分析,在分子水平上提供了与宏观优势性状密切联系的特异性DNA片段,这些差异DNA片段在育种过程中是很重要的。借助离子束将这些片段转化于生物体细胞继续进行选育,可能对稳定品系及保持优良性状起到很大的作用。本文探讨了利用离子束转化RAPD差异片段的可行性,优势及其在育种中的前景。     

等离子束玉米自交系选育初探

2 .0Me氦离子束不同的剂量注入玉米自交系 478干种子胚 ,其结果表明 ,玉米自交系 478以 1× 10 1 6 cm2的剂量处理后 ,其后代主要性状变异明显。出现了比亲本早熟 2 3天的自交系和籽粒产量特高的自交系。并初步组配、筛选出配合力强、抗逆性强的杂交新组合。     

Molecular templates for bio-specific recognition by low-energy electron beam lithography

Protein patterning has become an important topic as advances are made in biologically integrated devices and protein chip technology. Versatile and effective patterning requires substrates that can be quantified, with active presentation of proteins and control over protein density and orientation. Herein we describe a model system and the use of low-energy electron beam lithography to pattern molecular templates for immobilization of antibodies through ligand recognition. The templates were patterned over a background of poly(ethylene glycol) (PEG) modified silicon oxide (SiO _x ). These substrates were exposed to a low-voltage (2 keV) electron beam to remove PEG selectively from exposed regions. These regions were then functionalized with a dinitrophenyl (DNP) ligand and tested for specific binding of fluorescently labeled anti-DNP antibodies. The PEG modified regions in conjunction with ligand-presenting regions in the patterned arrays substantially reduces non-specific adsorption of proteins, yielding a specific/nonspecific ratio of approx 10. The surface coverage of the biologically active DNP groups on SiO _x and the amount of immobilized antibody on DNP were measured with a fluorescence-based, enzyme-linked immunosorbent assay. The specificity of the interaction between DNP ligand and fluorescently labeled anti-DNP antibodies was evaluated with fluorescence microscopy. This approach to patterning of molecular templates and assays for quantification are generally applicable to immobilization of any ligand-receptor pair on a wide range of substrates.     

Experimental assessment of proton dose calculation accuracy in inhomogeneous media

PurposeProton therapy with Pencil Beam Scanning (PBS) has the potential to improve radiotherapy treatments. Unfortunately, its promises are jeopardized by the sensitivity of the dose distributions to uncertainties, including dose calculation accuracy in inhomogeneous media. Monte Carlo dose engines (MC) are expected to handle heterogeneities better than analytical algorithms like the pencil-beam convolution algorithm (PBA). In this study, an experimental phantom has been devised to maximize the effect of heterogeneities and to quantify the capability of several dose engines (MC and PBA) to handle these.MethodsAn inhomogeneous phantom made of water surrounding a long insert of bone tissue substitute (1 × 10 × 10 cm³) was irradiated with a mono-energetic PBS field (10 × 10 cm²). A 2D ion chamber array (MatriXX, IBA Dosimetry GmbH) lied right behind the bone. The beam energy was such that the expected range of the protons exceeded the detector position in water and did not attain it in bone. The measurement was compared to the following engines: Geant4.9.5, PENH, MCsquare, as well as the MC and PBA algorithms of RayStation (RaySearch Laboratories AB).ResultsFor a γ-index criteria of 2%/2 mm, the passing rates are 93.8% for Geant4.9.5, 97.4% for PENH, 93.4% for MCsquare, 95.9% for RayStation MC, and 44.7% for PBA. The differences in γ-index passing rates between MC and RayStation PBA calculations can exceed 50%.ConclusionThe performance of dose calculation algorithms in highly inhomogeneous media was evaluated in a dedicated experiment. MC dose engines performed overall satisfactorily while large deviations were observed with PBA as expected.     

Tumor therapy and track structure

The elevated relative biological effectiveness (RBE) of heavy ions like carbon is the main reason for their use in radiotherapy and is due to the microscopic distribution of dose inside each particle track. High local doses produce lesions that are expected to have a diminished possibility of repair. Thus, RBE depends on track structure and on the biological repair capacity of the tissue that is affected by the irradiation. For tumor treatment planning with heavy ions, the beam quality and the tissue sensitivity have to be taken into account. Using the dependence of radial dose distribution on particle energy and atomic number on the physical side and x-ray dose response for the repair capacity on the biological side, the response to particle irradiation can be calculated in the local effect model (LEM) and used for treatment planning. This article traces the route from electron emission as the basis of track structure to the RBE calculation and the application in treatment planning. Received: 21 April 1999 / Accepted in revised form: 1 September 1999     

Aberration corrections of doughnut beam by adaptive optics in the turbid medium

The doughnut beam is a spatially structured beam which has been widely used in super‐resolution microscopy, laser trapping and so on. However, when it passes through thick scattering medium, aberrations will seriously affect its performance. Currently, adaptive optics (AO) has become one of the most powerful tools to compensate aberrations. However, conventional AO always suffers from limited corrected field of view (FOV). Here, we propose a method with conjugate AO system based on coherent optical adaptive technique. The results show that the corrected FOV can be improved effectively. For a wide range of the optical applications with doughnut beam, our method has potentials in correcting aberrations with high speed in turbid media.(A) Mouse brain slice, (B) the distribution of r _PAO, (C) the distribution of r _CAO. The vortex beam focus of the blue point in (B) and (C) among a 137.5 × 137.5 μm FOV (D1) ideally, (D2) with scattering, (D3) in pupil AO system and (D4) in conjugate AO system.