γ线照后PHA、ConA和PWM激活的人血淋巴细胞转化、DNA单链断裂及其修复比较

本文采用~3H-TdR参入法和羟基磷灰石层析法,比较了~(60)Coγ射线照射后PHA、ConA、PWM激活的人血淋巴细胞的转化、DNA单链断裂及其修复,结果表明:受照后淋巴细胞转化受抑,在0—8Gy剂量范围内,剂量效应呈双相线性关系,其中PWM激活的细胞对射线的敏感性最低。三种细胞受照后DNA发生单链断裂,在0—30Gy范围内,与剂量呈线性相关,三者之间无显著差异。受15Gy照射后,细胞在37℃条件下能重接DNA断链,但重接不完全,重接后如经较长时间保温仍会发生再断裂,PWM激活的细胞重接修复率最高。淋巴细胞转化对辐射的敏感性可能与DNA断链的重接修复能力有关。     

~(60)Coγ射线诱发的中国田鼠V_(79)细胞和小鼠胸腺细胞DNA单链断裂及其修复的研究

本文对~(60)Co γ射线诱发的中国田鼠肺成纤维细胞(V79)和小鼠离体胸腺细胞 DNA 单链断裂及其重接修复进行了实验研究。实验结束表明,两种细胞 DNA 单链断裂的程度分别在30Gy 和10Gy 剂量范围内与剂量呈线性相关;V79细胞 DNA 单链断裂的重接修复包含有快修复和慢修复过程;在不加血清的 TC199培养液中 V79细胞 DNA 断链仍能重接修复,而离体小鼠胸腺细胞在不加血清的 TC199或 RPM11640培养液中其 DNA 断链均不能重接修复,表明不同细胞 DNA 断链的重接修复所要求的细胞培养条件不同。     

哺乳动物细胞DNA单链断裂与重接修复的研究

本文运用羟基磷灰石柱层析法对~(60)Coγ线引起的中国田鼠肺细胞(CHL)和615小鼠离体脾细胞DNA单链断裂和重接进行了研究。在1～10Gy剂量范围内,两种细胞DNA单链断裂的程度均与剂量呈线性关系。两种细胞每单位剂量诱发的DNA单链断裂的数量是相似的。CHL细胞DNA单链断裂能迅速进行重接,其重接速率和程度与剂量呈负相关。同时,单链重接与培养条件也密切相关,CHL细胞在无血清培养液中比在含小牛血清培养液中其DNA断链重接速率慢、程度低,而离体的小鼠脾细胞DNA断链在无血清培养液中甚至未见重接修复。     

~(60)Co γ射线对肿瘤细胞DNA损伤与修复的效应研究

应用碱洗脱法研究了~(60)Coγ射线及其联合高温对L_(5178y)细胞DNA链断裂与修复的影响。结果表明:43℃加温30min能显著抑制γ射线引起DNA断链后的修复,照前比照后加温的增敏效果更好。又应用羟基磷灰石层析法分析得知:HL-60细胞和HL-60(VCR)细胞受照后两者DNA单链断裂程度无显著差异,而DNA断链的修复能力有非常显著的差别,这反映了HL-60(VCR)细胞的重接修复能力强。且细胞的DNA合成功能对γ射线的抗性也较HL-60细胞大,即照后~3H-TdR掺入的受抑制程度低,揭示耐药的白血病细胞对辐射的抗性较大。     

PHA、Con A和PWM激活的人血淋巴细胞的辐射敏感性比较

采用~3H-TdR掺入法和羟基磷灰石层析法,比较了~(60)Coγ射线照射后PHA、ConA、PWM激活的人血淋巴细胞的转化、DNA链断裂及其修复。结果表明,受照后这3种细胞转化受抑,在0～8Gy范围内,剂量效应呈双相线性关系,其中PWM细胞对射线敏感程度最低。3种细胞受照后DNA发生链断裂,在0～30Gy范围内,与剂量呈线性关系,三者之间无显著差异。受15Gy照射后,3种细胞在37℃条件下能修复DNA断链,10min内修复很快,30min修复到高峰,但修复不完全,修复后DNA分子发生再断裂。PWM细胞DNA修复率最高。淋巴细胞转化对辐射的敏感性可能与DNA断链的修复能力有关。     

PHA、Con A和PWM激活的人血淋巴细胞的辐射敏感性比较

采用~3H-TdR掺入法和羟基磷灰石层析法,比较了~(60)Coγ射线照射后PHA、ConA、PWM激活的人血淋巴细胞的转化、DNA链断裂及其修复。结果表明,受照后这3种细胞转化受抑,在0～8Gy范围内,剂量效应呈双相线性关系,其中PWM细胞对射线敏感程度最低。3种细胞受照后DNA发生链断裂,在0～30Gy范围内,与剂量呈线性关系,三者之间无显著差异。受15Gy照射后,3种细胞在37℃条件下能修复DNA断链,10min内修复很快,30min修复到高峰,但修复不完全,修复后DNA分子发生再断裂。PWM细胞DNA修复率最高。淋巴细胞转化对辐射的敏感性可能与DNA断链的修复能力有关。     

~(60)Coγ射线对肿瘤细胞DNA损伤与修复的效应研究

应用碱洗脱法研究了~(60)Co γ射线及其联合高温对L_(5178y)细胞DNA链断裂与修复的影响。结果表明:43℃加温30min能显著抑制γ射线引起DNA断链后的修复,照前比照后加温的增敏效果更好。又应用羟基磷灰石层析法分析得知:HL-60细胞和HL-60(VCR)细胞受照后两者DNA单链断裂程度无显著差异,而DNA断链的修复能力有非常显著的差别,     

小鼠乳癌细胞辐射敏感突变株SX-9DNA双链断裂及其重接修复研究

本研究采用一种新的细胞DNA双链断裂检测方法——脉冲电场电泳法,检测了两株来源相同而辐射敏感性不同的细胞SR-1和SX-9的X线照射所致DNA双链断裂的产生和修复。结果表明两株细胞的DNA双链断裂产生没有差别,而辐射敏感细胞SX-9的DNA双链断裂重接修复能力明显低于SR-1细胞,本文对此结果与细胞辐射敏感性的关系进行了讨论。     

碱性单细胞凝胶电泳预测肿瘤细胞内在放射敏感性研究

应用克隆形成法和碱性单细胞凝胶电泳技术检测辐射诱导的人红白血病细胞株K562、人结肠腺癌细胞株LS-T-117和鼠胶质瘤细胞株C6的初始DNA单链断裂数及单链断裂后的修复与细胞内在放射敏感性之间的关系。结果表明,3种细胞系的放射敏感性依次为K562>LS-T-117>C6;3种细胞系的DNA迁移距离都随着照射剂量的增加而增大,呈良好的剂量-效应关系。在相同剂量下,辐射诱导的DNA单链的初始断裂数目也依次为K562>LS-T-117>C6;3种细胞系经10Gy X射线照射并在PBS中培养不同时间后DNA迁移距离都有较大幅度的下降,但下降幅度依次为C6>LS-T-117>K562,在相同剂量下辐射诱导的DNA单链断裂后的修复能力也依次为C6>LS-T-117> K562。结果显示,辐射诱导的DNA单链断裂及修复与细胞内在放射敏感性有很好的相关性,可用于人体肿瘤细胞内在放射敏感性的预测。     

小鼠扁桃体免疫细胞受照射后DNA双链断裂损伤修复的忠实性

观察了受照射小鼠瓦尔代尔扁桃体环（WRE）在体细胞出现DNA双链断裂修复的忠实性，用^60Coγ射线照后观察WRE细胞凋亡的最高峰，在此时间点处死小鼠，取WRE细胞分别有脂质体和电穿孔方法介导的基因转染技术，将双标记基因质粒pPMH16导入细胞。研究WRE细胞DNA双链修复的忠实性。结果表明，未照射WRE细胞的抗G418转化克隆有69．75％的gpt基因表达，说明大部分断裂的gpt基因被忠实性地修复；2Gy、4Gy射线照射的WRE细胞的转化克隆只有36．05％和21．50％的克隆能正确表达gpt基因功能，说明WRE细胞照射后DNA双链断裂的修复显著低于正常细胞，且剂量越大，修复的忠实性质越低。脂质体和电穿孔方法介导的基因转染技术可用于原代细胞基因转染的研究，照射后的WRE细胞易发生DNA双链断裂错误重接。     

Pressurized heavy water reactor fuel behaviour in power ramp conditions

In order to check and improve the quality of the Romanian CANDU fuel, an assembly of six CANDU fuel rods has been subjected to a power ramping test in the 14 MW TRIGA reactor at INR. After testing, the fuel rods have been examined in the hot cells using post-irradiation examination (PIE) techniques such as: visual inspection and photography, eddy current testing, profilometry, gamma scanning, fission gas release and analysis, metallography, ceramography, burn-up determination by mass spectrometry, mechanical testing. This paper describes the PIE results from one out of the six fuel rods. The PIE results concerning the integrity, dimensional changes, oxidation, hydriding and mechanical properties of the sheath, the fission-products activity distribution in the fuel column, the pressure, volume and composition of the fission gas, the burn-up, the isotopic composition and structural changes of the fuel enabled the characterization of the behaviour of the Romanian CANDU fuel in power ramping conditions performed in the TRIGA materials testing reactor.     

高放废液中铁的分光光度测定

建立了高放废液中铁的萃取分光光度测定法。在强酸介质中,以醋酸异戊酯萃取将铁与大量杂质分离,再以水反萃。加入磺基水杨酸使反萃液中的铁显色,以浓氨水使有色络合物转变为更稳定、摩尔吸光系数较高的络合物,进行光度测定。     

Impurity behaviour,radiation losses and wall effects in the T.F.R. machine

Spectroscopic, bolometric, soft X-rays and electrical measurements have been performed on T.F.R. up to 400 kA-60 kG. Light impurities appear very early. They are recycling in a stationary state during the current plateau. The heavy impurities density grows during the current rise, then levels off or increases slightly during the current plateau. The production of fast electrons is evaluated. Densities and fluxes of impurities are given. Photodesorption, photoelectron induced desorption, ion desorption, thermal desorption, evaporation and sputtering are discussed as possible candidates for the pollution.     

N—235萃取色层法分离和测定镎

提出了用N-235/聚四氟乙烯柱萃取色层法自铀、钚、镅和铕中分离镎的方法。镎自2.0mol·lHNO_3溶液中被吸附,用1.0 mol·l~1 HNO_3溶液洗涤后,再用HNO_3-H_2C_2O_4溶液洗脱。镎的回收率为98.1+2.6%。     

Development of a silver ion source using nanosecond pulses of a Nd:YAG laser at different wavelengths

A silver ion source was designed by focusing the fundamental and harmonics of Q-switched Nd:YAG laser pulses onto a silver target and simultaneously applying an electric potential in an argon environment. The silver ions were detected at a distance of 2 cm from the target surface using a Faraday cup ion probe after letting them pass through a retarding mesh grid (copper electrode). We aim to produce and characterize the silver ions generated by the laser radiation of different wavelengths and pulse energy, ambient gas pressure and the electrode spacing under applied electric field. In addition to this, the effect of laser radiation on plasma under vacuum and at different argon gas pressures was investigated. The velocity distribution function of the plasma emitted from the silver target was investigated under argon discharge. These measurements demonstrated clearly that the velocity distribution function and current signals depend on laser power, laser wavelength and argon pressure. We observed a ten fold increase in the plume current with increase in the applied voltage and ion velocity in the presence of a laser field. The surface morphology of the laser irradiated samples was investigated using reflection optical microscopy.     

In vivo PIXE-PIGE study of enhanced retention of fluorine in tooth enamel after laser irradiation

The presence of fluoride in tooth enamel reduces the solubility of hydroxylapatite by acid attack. Fluoride presence (even at low concentration) in the oral cavity is efficient against caries process. We propose a new approach of the explanation of the increase of fluoride retention in the tooth enamel when low power laser irradiation is applied after the treatment with fluoride gel (fluoridation). External beam PIGE measurements of fluorine on extracted teeth have been made in order to determine the best sequence of the operations. The laser irradiation after fluoride application is more efficient than the reverse procedure. This observation is in agreement with previous observations that the fluorine penetration in the enamel takes place first in the soft organic material present between the polycrystalline (prismatic) structure before being integrated in the crystalline composition of hydroxylapatite in order to produce fluoro-apatite. As those in vitro measurements do not reflect the whole process in the saliva, in vivo PIGE measurements have been also performed. We have demonstrated, by repeating the PIGE measurements (at least five times at various time intervals) that a significant increase of the fluoride retention took place even 18 months after the unique laser treatment. The complete experimental procedure is described: fluoride application, laser irradiation, PIGE measurements with 2.7 MeV protons (repeated measurements at the same place on the same tooth in order to follow the evolution) and safety tests before in vivo analyses.     

Algorithms for three-dimensional chemical analysis via multi-energy synchrotron X-ray tomography

The conversion of X-ray tomography images into three-dimensional chemical composition requires accurate mass absorption values, high-quality images, and a robust fitting algorithm. The least-squares fits of the images to a three-dimensional chemical composition can proceed with several different options such as minimal vs. over-determined and/or constrained parameters. This project has investigated the impact of XAFS features and a limited CCD dynamic range. These simulated results are compared to a recent experimental project in which synchrotron X-ray tomography was used to image a polymer blend, and from those images, calculated three-dimensional chemical composition maps of the two-component flame retardant, a brominated phthalimide dimer, Saytex^™ BT-93 and a synergist, antimony(III) oxide (Sb₂O₃).     

Cold atoms photoassociation with intense laser pulses

We study the vibrational dynamics produced when two cold atoms are photoassociated in a diatomic molecule by an intense laser pulse (with the duration of hundreds ps), inducing a resonance condition at small interatomic distances. The example analysed is the population transfer from the continuum to the 1_g(6s + 6p_3/2) excited electronic potential of the Cs₂ molecule, at a temperature T ≈ 0.11 mK. We use a non-perturbative treatment by following the wavepackets dynamics on the ground and excited surfaces. We show that cold molecules can be efficiently produced in both ground and excited electronic potentials.     

Investigations on the effect of 100 MeV Ni ions irradiated chloride vapour phase epitaxy (Cl-VPE) grown GaN epilayers

Gallium nitride (GaN) epilayers have been grown by chloride vapour phase epitaxy (Cl-VPE) technique and the grown GaN layers were irradiated with 100 MeV Ni ions at the fluences of 5 × 10¹² and 2 × 10¹³ ions/cm². The pristine and 100 MeV Ni ions irradiated GaN samples were characterized using X-ray diffraction (XRD), UV-visible transmittance spectrum, photoluminescence (PL) and atomic force microscopy (AFM) analysis. XRD results indicate the presence of gallium oxide phases after Ni ion irradiation, increase in the FWHM and decrease in the intensity of the GaN (0 0 0 2) peak with increasing ion fluences. The UV-visible transmittance spectrum and PL measurements show decrease in the band gap value after irradiation. AFM images show the nanocluster formation upon irradiation and the roughness value of GaN increases with increasing ion fluences.     

Deformation and microstructure of neutron irradiated stainless steels with different stacking fault energy

The influence of the stacking fault energy (SFE) on the microstructure, mechanical property and deformation behaviour of stainless steels before and after irradiation was investigated. The mechanical properties, such as strength, ductility, strain hardening and irradiation induced hardening behaviours of 3 alloys with various SFEs are quite different. Such significant variations of mechanical properties must result from the different microstructures, deformation mechanisms and defects accumulation behaviours. Thus, the microstructures, deformation mechanisms and irradiation induced small defect clusters (including their types, natures, densities and size distributions) of 3 alloys are determined in detail by transmission electron microscopy. It indicated that before irradiation, alloy with low SFE has more localised deformation behaviour than alloy with high SFE. After irradiation, in the samples with low SFE, the irradiation induced stacking fault tetrahedral was observed, while in the ones with high SFE, the dominant defects are Frank loops. All the results shown that, SFE has a strong effect on both the deformation mechanism and irradiation induced defect accumulation behaviour of stainless steels.