140AMeV 58,64Ni+9Be反应中同位旋标度规律的研究

利用反对称化的分子动力学（AMD）模型模拟140 AMeV 58,64Ni+9Be反应,并利用同位旋标度法研究两相似反应系统的△μ_n（p）/T随时间演化趋势。分析比较不同碰撞参数和不同反应系统间的△μ_n（p）/T随时间演化结果,结果表明碰撞参数对重核的对称能影响大,系统不对称度越大对对称能的影响越大,为间接研究激发核体系对称能系数的能量依赖提供了帮助。We have simulated the reactions 140 AMeV 58,64Ni+9Be by antisymmetric molecular dynamics model (AMD) and studied the evolution of △μ_n(p)/T with collision time from 20 fm/c to 1 000 fm/c. To study nuclear symmetry energy influencing factors, a comparative analysis has been proceed among theses results with different impact parameters and the difference reactions system. The results show that the impact parameters have a great influence on the symmetry energy of the heavy nucleus, and the greater the asymmerty degree of the system, the greater the influence on the symmetry energy. These results are helpful for the indirect study of the energy dependence of the symmetry energy coefficient of the excited nuclear system.     

PuO2颗粒对自发α射线的能量自吸收效应评估研究

构建PuO₂颗粒状α发射体的球体几何模型,采用蒙特卡罗和射程经验公式模拟计算α射线在PuO₂颗粒中的射程能量关系式及α射线从PuO₂颗粒表面出射的能谱分布,研究因PuO₂颗粒对自发α射线的能量自吸收效应导致的对人体内照射剂量评估的影响。研究结果表明,PuO₂粒径越大,其对自发α射线的能量自吸收效应越明显,内照射剂量的修正效果越好;当PuO₂粒径在2 μm以上时,内照射剂量的修正效果大于5%。本研究的结果对吸入放射性物质所致人体内照射剂量的准确估算有重要的参考价值,并可应用于放射性核素肿瘤治疗等领域的微剂量学研究。A sphere geometry model for plutonium oxide-based alpha emitter was setup.The range of alpha particle in plutonium oxide pellet versus its energy and the spectral distribution of alpha particle emerging from the emitter surface were calculated using Monte Carlo method combined with the empirical formula of range.The internal radiation dose resulted by self-absorption effect of α-rays emitted spontaneously in plutonium oxide was investigated accordingly.The result shows that the larger particle size the plutonium oxide-based alpha emitter has,the more obvious the self-absorption effect is and the better the correction effect of the intake absorbed dose that effects on human lung has.For plutonium oxide pellet with its particle size exceeding 2 μm,the correction quantity is expected to be larger than 5%.Our work is beneficial for a precise evaluation of internal radiation dose induced by inhaled radioactive material and microdosimetry study in radionuclide tumor therapy.     

球形平均场加四极-四极和对力模型在单j壳内的量子相交叉行为(英文)

介绍了单j壳的球形平均场加几何四极-四极和标准对力模型的量子相交叉行为。在单j=15/2的壳内,计算了随模型控制参数变化的多个物理量如低激发能级、激发态间重叠积分、低激发态间的B（E2）比值和电四极矩比值。结果显示,在类转动到对激发相的演化中,多个物理量在交叉区存在非常明显的变化,如B（E2;4₁ → 2₁）/B（E2;2₁ → 0_g）,B（E2;4₂ → 2₁）/B（E2;2₁ → 0_g）等,并且这些变化在核子数达到半满壳时尤为显著。此外,尽管当j较小时,由几何四极-四极相互作用得到的低激发能级不满足转动谱规律,但当j值足够大时,这些低激发能级满足转动谱规律。The analysis of the quantum phase crossover behavior in the spherical shell model mean-field plus the geometric quadrupole-quadrupole (Q·Q) and standard pairing model within a single-j shell is reported. Several quantities, such as low-lying excitation energies, the overlaps of excited states, ratios of some B(E2) and electric quadrupole moments of some low-lying states as functions of the control parameter of the model in a j=15/2 shell are calculated. The results show that there are noticeable changes in the crossover region of the rotational-like to the pair-excitation phase transition, such as B(E2;4₁ → 2₁)/B(E2;2₁ → 0_g) and B(E2;4₂ → 2₁)/B(E2;2₁ → 0_g), especially in the half-filling case. Though the low-lying excitation energies generated from the geometric quadrupole-quadrupole interaction not satisfy the pattern of a rotational spectrum when j is small, these energies follow the pattern of a rotational spectrum when j is sufficiently large.     

可能的原子核形状及硬度演化性质:基于能量面计算的系统分析(英文)

基于（β₂,γ,β₄）形变空间下对-形变自洽的原子核能量面计算方法,系统研究分析了50 < Z < 82区偶偶核的形状及硬度演化特征。计算的平衡形变与其它理论预言及存在的实验值进行了对比。从相应的形变势能曲线提取了与β₂及γ相关的硬度参数C_β,C_γ,这与实验观测到的低位β及γ振动带信息相符。还简要讨论了转动情况下的硬度演化,例如基于蜈蚣型E-GOS曲线,表明存在不可忽略的振动效应。Nuclear shape and stiffness evolutions in even-even nuclei with 50 < Z < 82 are systematically analyzed in terms of the pairing-deformation self-consistent nuclear-energy-surface calculation in (β₂,γ,β₄) deformation space. Calculated equilibrium deformations are presented and compared with other theoretical predictions and available experimental data. The stiffness parameters C_β and C_γ respectively related to quadrupole deformations β₂ and γ are determined from the deformation energy curves, which are consistent with the observed low-lying β and/or γ bands. The stiffness evolution under rotation along the yrast line is briefly discussed, e.g., on the basis of the centipidelike E-GOS curves, showing an unnegligible vibration effect.     

随机相互作用系综内的镉同位素电磁矩线性演化

在随机相互作用系综内,镉同位素11/2-同质异能态的电四极矩与磁偶极矩总是倾向于随中子数的增加呈线性演化,这与近年来的实验观测是一致的。除了对力对磁矩线性演化的决定性影响之外,特定形式的质子-中子相互作用被认为是这种线性演化的主要驱动力:电矩的线性演化要求质子中子之间的四极相互作用;磁矩则要求质子中子之间的短程相互作用,并且这种相互作用应具有与真实核相互作用一致的相对强度与正负性。In random-interaction ensembles, the electric quadrupole moments (Q) and magnetic moments (μ) of the Iπ=11/2- isomers of the Cd isotopes predominantly present linear correlation with neutron numbers, corresponding to the recently emphasized linear Q and μ systematics in realistic nuclear system. Although the seniority scheme enhances such predominance (more essentially for μ), the configuration mixing due to quadrupolelike and δ-force-like proton-neutron interactions is responsible for the linear Q and μ systematics, respectively, at least in random-interaction ensembles. Especially, the linear μ systematics further requires the proton-neutron interaction have similar relative strength and attractive-repulsive property to realistic nuclear interaction.     

小型宇宙射线探测仪的模拟和测量

介绍了一款小型宇宙射线探测仪。该仪器具有宇宙射线科普演示功能,主要用于实时测量μ子射线并显示计数,以及长时间尺度下（年）稳定地对不同角度的次级宇宙线通量进行监控记录。简要地展示了探测器的硬件构造和探测效率的模拟计算。探测仪单个探测器的探测效率为93.1%,两个探测器符合测量的探测效率为86.6%。根据探测器的计数率以及模拟计算的探测效率,估计了次级宇宙射线垂直地面方向的通量,为J=29±3 m-2 sr-1 s-1。另外,利用该宇宙射线探测仪,测量了兰州市区的次级宇宙射线的天顶角分布。其结果很好地满足I（θ）=IH+I₀ cosα θ经验公式,其中的角度依赖参数α=2.42±0.52。A small cosmic ray device is introduced in this paper.It has the demonstration function for popularization of science,and can be used mainly to display the μ counts in a real-time measurement,and to monitor the secondary cosmic ray flux at different angles in a very long time scale (years).We briefly show the hardware of the device and the detecting efficiency calculation by simulation.The detecting efficiency for one detector of the device is 93.1%,and the detecting efficiency is 86.6% for the coincidence measurement of two detectors.Based on the count rate by the detector and the simulated efficiency,the secondary cosmic ray flux perpendicular to the ground surface is measured,which is J=29±3 m-2sr-1 s-1.Moreover,with an application of the device,we measured the angular distribution of the secondary cosmic ray rate in Lanzhou City.The resulting angular distribution agrees well with the empirical formula as I(θ)=IH+I₀ cosα θ,in which the parameter for the angle-dependence is α=2.42±0.53.     

稀土区奇A核晕带存在从转动到振动形状演化的直接证据(英文)

原子核的形状演化效应是核结构研究的重要基础问题之一。通常认为,A=160质量区的奇A核位于大形变核区域,它们的激发态能谱将呈现出典型的转动激发特征。然而,基于E-GOS曲线方法,发现随着角动量的增加,该质量区奇A核的晕带具有显著地从转动激发演化成为振动激发的形状演化现象。此外,为深入理解原子核形状演化的微观机制,采用Total-Routhian-Surface（TRS）方法针对稀土区的奇A核进行了理论计算,结果表明,165Yb和157Dy同位素在低激发态时具有稳定的长椭形变,当角动量大于0.50 MeV后,核芯的四极形变显著减小并开始产生三轴形变。The phase transition of nuclei with increasing angular momentum (or spin) and excitation energy is one of the most fundamental topics of nuclear structure research. The odd-N nuclei with A ≈160 are widely considered belonging to the well-deformed region, and their excitation spectra are energetically favored to exhibit the rotational characteristics. In this work, however, the evidence suggesting that the nuclei changes from rotation to vibration along the yrast lines as a function of spin was found. The simple method, named as E-Gamma Over Spin (E-GOS) curves, would be used to discern the evolution from rotational to vibrational structure in nuclei for various spin ranges. Meanwhile, in order to understand the band structure properties of nuclei, theoretical calculations have been performed for the yrast bands of the odd-A rare-earth nuclei within the framework of the total routhian surface (TRS) model. The TRS plots predict that the 165Yb and 157Dy isotopes have large quadrupole shapes at low spin states. At higher rotational frequency (hω~ >0.50 MeV), a clear reduction of the quadrupole deformation is indicated by the present results, and the isotopes become rigid in the γ deformation.     

SO（8）对关联和代数壳模型中的SU（3）四极基底（英文）

建立了SO（8） 同位旋标量、同位旋矢量及总的配对基与微观壳模型坐标空间部分的Elliott SU（3） 基之间的对应关系。从该代数间的互补关系导出了在壳模型的粒子数守恒代数U（4Ω） 中所包含的具有同位旋T 及自旋S 的Wigner 超多重态（不可约） 表示。其重要性在于,该结果能用于研究对相互作用和四极-四极相互作用在核谱中的竞争效应并揭示其配对基中的SU（3） 组份。虽然仅展示了该理论对ds 壳的计算,其方法也适用于研究多壳的情形。We establish a correspondence between the SO(8) isoscalar, isovector and total pairing bases and the Elliott's SU(3) basis in the algebraic structure of the spatial part of the microscopic shell model. It is derived from the complementarity of these algebras to the same T, S, (S,T) irreducible representations (irreps) of the Wigners supermultiplets, contained in the shell-model number-conserving algebra U(4Ω). This important result allows for the evaluation of the content of SU(3) irreps into the different types of pairing bases which leads to an investigation of the complementarity and competitive effects of pairing and the quadrupole-quadrupole interactions on the energy spectra of the nuclear systems. The theory is valid for any shell and for a number of shells as well, but we illustrate it with the results for a single ds-shell.     

Interaction Strength and a Generalized Bak—Sneppen Evolution Model

The Bak-Sneppen evolution model is generalized in terms of a new concept and quantity:interaction strength.Based on a quantitative definition,the interaction strength describes the strength of the interaction between the nearest-neighbour individuals in the model.Self-organized criticality is observed for the generalized model with ten different values of interactionstrength.The gap equation governing the self-organization is derived.It is also found that the self-organized threwshold depends on the value of the interaction strength.     

Skyrme张量相互作用对可能的等待点原子核β衰变半衰期的影响(英文)

使用基于Skyrme相互作用的HFB+QRPA模型研究N~82和126的同中子异位素链的β-衰变的半衰期。在计算中所使用的张量相互作用和同位旋标量（IS）对相互作用都是很好地被约束了的。比较了张量相互作用和IS对相互作用对半衰期的影响。IS对相互作用的强度与相应的同位旋矢量（IV）对相互作用的强度相当时,对N~82和126的同中子异位素链中有大的中子过剩的原子核的半衰期影响很微弱。而张量相互作用采用最近约束的强度时对半衰期的影响非常显著。The β-decay half-lives of N ~ 80 and 126 isotonic chains are calculated with HFB+QRPA models based on Skyrme force. In the calculations, the well constrained Skyrme tensor interaction and isoscalar spin-triplet (IS) pairing interaction are included so that to study their effects on the half-lives. The effects of tensor interaction and IS pairing interaction on the half-lives are compared. The IS pairing interaction with strength similar to that of isovector (IV) one produces only a trivial effect in N ~82 nuclei, and N ~126 nuclei with big neutron excess. While the tensor interaction with presently constrained strengths produces an obvious effect.     

相干反斯托克斯拉曼及相干反斯托克斯超拉曼光谱微观极化率张量元的简化方案-C∞v对称性

相干反斯托克斯拉曼光谱(CARS)和四阶相干反斯托克斯超拉曼光谱(CAHRS)广泛应用于分子界面和生物膜表面的研究。然而,高阶非线性光学过程中分子微观极化率张量元数量众多,关系复杂,使研究者对CARS和CAHRS很难进行定量分析。采取以下方案对属于C_∞v对称性的分子基团的CARS和CAHRS的微观极化率张量元进行简化。首先将CARS微观极化率张量元β_{i′j′k′l′}表示成拉曼微观极化率张量元微分α′_i′j′的乘积,CAHRS微观极化率张量元β_{i′j′k′l′m′}表示成超拉曼微观极化率张量元微分β′_i′j′k′和拉曼微观极化率张量元微分α′_i′j′的乘积,再利用α′_i′j′之间的比值及β′_i′j′k′之间的比值得到β_{i′j′k′l′}和β_{i′j′k′l′m′}之间的比值。使用这些CARS和CAHRS微观极化率张量元之间的关系,能够得到CARS和CAHRS光谱的广义取向泛函及其广义取向参数,进而对界面分子取向信息进行定量分析。     

CO分子振转光谱的理论研究

采用从头算的多参考组态相互作用(MRCI)方法并结合基组aug-cc-pCVQZ计算了CO分子基态(X1Σ+)的势能曲线和偶极矩曲线,得到的势能曲线、偶极矩曲线分别与RKR势、文献的偶极矩曲线吻合较好。利用所得的势能,求解双原子分子核运动的Schrdinger方程找到了CO分子X1Σ+态转动量子数J=0时的70个振动态,对于每一振动态,分别计算了其振动能级G(v)、转动惯性常数B_v和离心畸变常数D_v,并把计算结果与已知的42个实验值做了详细比较,结果表明,计算的振动能级G(v)、转动惯性常数B_v、离心畸变常数D_v与实验值符合较好。利用G(v),B_v导出的光谱常数[谐振频率ω_e(2 160.1 cm-1)、非谐振频率ω_eχ_e(13.1 cm-1)、转动常数B_e(1.918 cm-1)、振转耦合常数α_e(0.017 3 cm-1)]也与实验值的光谱常数[ω_e(2 169.8 cm-1),ω_eχ_e(13.3 cm-1),B_e(1.931 cm-1),α_e(0.017 5 cm-1)]较为符合,这在一定程度上证明了方法MRCI/Aug-cc-pCVQZ对CO分子基态性质的计算是合适而可靠的。利用乘积近似方法计算了CO分子在常温、中温、高温时的配分函数,在此基础上,计算了CO分子在T=296 K时的1-0跃迁带的谱线强度,通过比较发现,计算所得的线强度与HITRAN数据库符合较好。进一步计算的CO分子X1Σ+态1-0,2-0,3-0,4-0,2-1,3-1和4-1跃迁带的带强度也与实验值较为吻合,同时首次计算了CO分子X1Σ+态3-2跃迁带、4-2跃迁带的线强度及带强度。     

1H(17F,α)14O反应截面测量

14O （α,p）17F是天体X射线暴中重要的突破反应。本工作通过厚靶方法测量其逆反应1H （17F,α）14O的反应截面来研究这一关键反应。本实验工作是在日本东京大学原子核科学研究中心（CNS）的低能次级束流线（CRIB）上完成的,后续的扣除本底实验是在兰州放射性束流线（RIBLL1）上完成的。CRIB实验是通过2H （16O,n）17F转移反应产生17F次级束,经过CRIB分离提纯之后,利用该次级束轰击氢气靶。在氢气靶后布置了三套望远镜探测器系统,用以探测不同实验角度的反冲α粒子,在数据处理的过程中经过动力学重构后得到了1H （17F,α）14O反应在质心系能区E_c.m.=2.7~3.4 MeV的反应截面。实验结果在3 MeV以上的高能区与前人的薄靶实验数据是一致的,在低能区本工作获得了新的实验数据,倾向于支持干涉相消的理论预言结果。The 14O(α, p)17F reaction is one of the important breakout reactions in type I X-ray burst. This work reported a new cross section measurement of its reverse reaction of 1H(17F,α)14O. The experiment was performed using the CNS radioactive ion beam separator (CRIB), located at the Center for Nuclear Study (CNS), the University of Tokyo. The sequent background measurement was carried out at Radioactive Beam Line in Lanzhou (RIBLL1). 17F beam was produced via the transfer reaction of 2H(16O, n)17F, subsequently separated and purified by CRIB and bombarded a thick hydrogen H₂ gas target. The recoiling α particles were measured by three △E-E silicon telescopes at three different angles. The total cross sections of 1H(17F,α)14O have been derived at E_c.m.=2.7~3.4 MeV based on an isotropic angular distribution assumption. Our results are consistent with the previous ones in the energy region of E_c.m.>3 MeV, and we also obtained some new data in the low energy region, which partly support the destructive interference between the direct and resonant reaction mechanism predicted by the theory.     

HL-2A 装置中高能量捕获电子鱼骨模不稳定性研究

结合HL-2A 装置的参数,在电子回旋共振加热(ECRH)离(在)轴加热的情况下,研究高能量捕获电子驱动的鱼骨模不稳定性。数值结果表明,高能量电子极向比压β_h 大于某一个比压阈值β_h,crit 时,鱼骨模会被高能量电子激发,其频率随高能量电子极向比压的增大而缓慢增加且与高能量电子的环向进动频率一致;比压阈值β_h,crit 随着高能量电子密度剖面峰化程度的增加而减小,但当密度剖面增大到一定值时比压阈值β_h,crit 趋近于一个常数。此外,还分析了箍缩角和扰动能对鱼骨模实频和增长率的影响。发现在箍缩角α₀ =1附近增长率有一极小值,表明高能量勉强通行电子对鱼骨模具有稳定作用;而扰动能 δWˆ_c增大时,鱼骨模表现出实频变大而增长率变小的特征,这表明了本底等离子体对鱼骨模有一定的稳定效果。     

基于紫外-可见光光谱法研究长期不同施肥对砖红壤溶解性有机质化学性质的影响

溶解性有机质（DOM）是土壤中最为活跃的一部分,具有重要的生态环境意义。明确不同施肥方式对DOM化学性质的影响,可为土壤肥力管理提供依据。因此,该试验以连续四年的不同施肥管理为基础,结合紫外-可见吸收光谱,探求不同施肥方式下,土壤中溶解性有机质的含量和化学性质的变化情况。试验共设置4个处理：CK（不施肥）;CF（化肥）;OG（有机肥）;ST（秸秆）。结果表明,与CK组相比,OG和ST的DOC(溶解性有机碳)含量为95.97和104.89 mg·kg-1,分别是CK组的129%和141%。相反,CF的DOC含量为15.32 mg·kg-1,仅为CK组的21%。OG显著提高了有色溶解性有机质[CDOM,以α（355）表征]含量,是CK组的2.76倍,ST无明显变化;CF则显著降低CDOM含量,仅为CK组的0.55倍。施用OG导致土壤紫外吸收曲线红移,表明有机肥的施用能够提高土壤DOM的共轭双键物质含量和腐殖化程度;与CK相比,OG中DOM的芳香性、疏水性、腐殖化程度的特征常数SUVA₂₅₄,SUVA₂₆₀和SUVA₂₈₀增大,揭示了有机肥的施用能够提高DOM的芳香性、疏水性组分以及腐殖化程度,秸秆处理增加不明显。施用化肥则出现明显降低。吸光度比值A₂₅₀/A₃₅₄,相比CK,CF显著增加,表明施用化肥使DOM分子变小,OG和ST处理无明显变化;秸秆施用导致A₄₆₅/A₆₆₅显著增加,表明秸秆能够有效提高DOM中蛋白质和碳水化合物含量;施用有机肥和秸秆A₃₀₀/A₄₀₀均大于3.5,表明土壤中DOM主要以富里酸为主,而施用化肥A₃₀₀/A₄₀₀明显低于3.5,表明土壤中DOM主要以胡敏酸为主。施用化肥出现S_R＞1,不施肥、有机肥、秸秆三者的S_R＜1,也表明了有机肥、秸秆能够增加分子量。有机肥和秸秆能有效增加土壤DOM含量,提升土壤肥力。尤其是施用有机肥,更能显著增加土壤DOM的共轭物质、腐殖化程度、疏水比例、芳香性以及分子量。而长期施用化肥则导致耕层土壤肥力降低。     

铜铅离子胁迫下玉米污染程度的光谱识别

重金属铜离子(Cu2+)与铅离子(Pb2+)污染对玉米叶片光谱的影响微弱、隐蔽而难于探测。研究中设置不同浓度Cu2+, Pb2+胁迫的玉米盆栽实验,测定了玉米叶片光谱、叶片中Cu2+, Pb2+含量与叶绿素相对含量,分析了Cu2+, Pb2+污染胁迫下玉米叶片光谱响应特征,并选取480～670与670～750 nm范围来进行分析,在光谱维中定义了光谱微分差信息熵指数与在频率域中通过谐波分析提取了前三次谐波振幅(c₁, c₂与c₃)指数,并用所定义的指数探测分别受Cu2+, Pb2+胁迫玉米叶片光谱微弱差异。实验结果表明,在480～670与670～750 nm范围内,玉米叶片中重金属离子浓度越大,其光谱微分差信息熵就越大;在480～670 nm波段,谐波分解后第一谐波振幅c₁与第二谐波振幅c₂可用于识别Cu2+, Pb2+污染程度;在670～750 nm波段,第一谐波振幅c₁、第二谐波振幅c₂与第三谐波振幅c₃可用于识别Cu2+污染程度,而c₂则可以识别Pb2+污染程度,污染胁迫越大振幅越大。在480～670与670～750 nm波段内,光谱微分差信息熵与前三次谐波振幅可作为识别玉米受Cu2+, Pb2+污染胁迫程度的指数,从光谱维与频率域两种维度来识别玉米受Cu2+, Pb2+胁迫程度的方法可行,文中定义的两类指数可稳健、可靠地探测与识别玉米受Cu2+, Pb2+影响所产生的光谱微弱差异,研究结果对利用高光谱来探测植被受重金属污染胁迫程度具有一定的参考价值。     

不同核函数支持向量机和可见-近红外光谱的多种植被叶片生化组分估算

氮、磷、钾元素是植物有机质的重要生化组分,准确估算其含量对监测管理植被的新陈代谢和健康状况具有重要意义。可见-近红外光谱结合多种建模方法已被用于植被生化参数的监测,其中支持向量机回归方法被证明能够较好拟合反射光谱和植被生化参数之间的非线性关系,而选取适当的核函数是其成功的关键。以宜兴地区水稻、玉米、芝麻、大豆、茶叶、草地、乔木和灌木等八种植被叶片样本为研究对象,分析比较基于径向基核函数、多项式核函数和S形核函数的支持向量回归模型估算叶片氮、磷、钾元素含量的能力。利用一阶微分变换、标准正态变量变换和反对数变换对叶片可见-近红外光谱进行预处理,运用bootstrapping法生成1 000组校正集和验证集,分别建立基于三种核函数的支持向量回归估算模型,以决定系数（R2）和相对分析误差（RPD）的均值作为评价指标。结果显示,结合一阶微分和反对数变换光谱,采用径向基核函数模型对氮、钾元素估算精度最高（氮：平均R2=0.64,平均RPD=1.67;钾：平均R2=0.56,平均RPD=1.48）,结合一阶微分变换光谱,采用径向基核函数模型对磷元素估算精度最高（磷：平均R2=0.68,平均RPD=1.73）。研究表明,结合不同预处理的可见-近红外光谱,基于径向基核函数的支持向量回归模型具有较好的估算多种植被叶片生化组分含量的潜力。     

基于氧化石墨烯模拟酶比色法检测汞离子

基于富T碱基序列能特异性识别Hg2+、氧化石墨烯(GO)对单链DNA(ssDNA)和T-Hg2+-T复合物的亲和力不同以及GO自身具有的模拟酶催化性能,构建了一种可视化检测水样中痕量Hg2+的新方法。在pH 4.0的NaAc-HAc缓冲溶液中,通过π—π堆积作用力,ssDNA可以吸附在GO表面,致使GO的类过氧化物酶活性减弱,从而催化H₂O₂氧化3,3’,5,5’-四甲基联苯胺(TMB)产生的蓝色产物减少,体系位于波长652 nm处的吸光度值降低;当待测体系中存在Hg2+时,ssDNA上的胸腺嘧啶碱基(T)与Hg2+发生特异性结合作用,形成T-Hg2+-T类似双链结构的稳定复合物,该复合物与GO的作用力较弱,不易吸附于其表面,因此不影响GO的模拟酶活性,体系吸光度值增强。在一定条件下Hg2+浓度越大,覆盖在GO表面的ssDNA越少,体系吸光度越强,据此建立检测Hg2+的新方法。当汞离子浓度在3.26×10-8~9.0×10-7 mol·L-1范围内时,体系的ΔA值与汞离子浓度呈现良好的线性关系。其线性方程为ΔA=41.75c(nmol·L-1)+0.048 7,相关系数r=0.997 3,检出限为9.79×10-9mol·L-1。该方法简单、直观,抗干扰能力强、无需昂贵仪器设备,可用于检测环境水样中Hg2+的含量。     

Sr2-x-yAl2SiO7:x％Sm3+,y％Li+荧光粉的合成与发光特性研究

硅铝酸盐由于其化学性质稳定、原材料易得，是发光材料的一种有效基质，所以受到广泛关注。其中，硅铝酸锶(Sr₂Al₂SiO₇)属于四方晶系，具有稳定的晶体学结构。Sm3+作为一种常用的激活剂，其特征峰在波段300~750 nm内都有分布，有些特征激发峰位于近紫外光区，在近紫外区有强的吸收。因此，以Sr₂Al₂SiO₇为基质、Sm3+为激活剂可以制备出符合LED要求的红色荧光粉。本工作采用高温固相法合成一系列Sr_2-x-yAl₂SiO₇∶x%Sm3+, y%Li+荧光粉。通过X射线衍射(XRD)、光致荧光光谱(PL)、绝对量子效率测量系统对样品的晶体结构、发光特性以及内量子效率进行表征和测量，并且对样品的XRD进行精修，色纯度计算。结果表明：合成样品均为单相Sr₂Al₂SiO₇，掺杂Sm3+和电荷补偿剂Li+后，没有引起相变。相对于其他阳离子Sm3+(r=1.079 Å)、Li+(r=0.920 Å)的半径与Sr2+(r=1.260 Å)半径最为相近，因此更容易替代Sr2+的格位，并且两种离子半径比Sr2+小而使得样品晶体结构参数a，b，c和v逐渐减小。样品的最佳激发峰在403 nm处，相比于Ca₃Y₂(Si₃O₉)₂∶Sm3+的激发峰出现了3 nm蓝移，表明样品在近紫外光下有较强的吸收，这种长紫外波长的光有利于在照明领域的应用。在403 nm近紫外光激发下，可以看出，在500～750 nm范围内，Sm3+的发射峰位于564 nm(4G_5/2→6H_5/2)，601 nm(4G_5/2→6H_7/2)，648 nm(4G_5/2→6H_9/2)和713 nm(4G_5/2→6H_11/2)，其中601 nm发射峰强度最大，使样品呈现强烈的橙红色光。发射峰在607与618 nm处出现劈裂现象，是因为晶体场的相互作用引起了能级劈裂。单掺Sm3+的发射光谱强度随着浓度的增加先增大后减小，当掺杂浓度为2%时发光强度最大。利用Blasse提出的能量传递临界距离公式，计算得出临界距离R_C≈19.734 Å，从而说明了浓度猝灭原因是Sm3+之间的多级相互作用。根据Dexter理论，计算出多极相互作用函数θ≈6，表明Sr_2-xAl₂SiO₇∶x%Sm3+的浓度猝灭机理是电偶极-电偶极(d-d)相互作用。为进一步提高发光强度，掺杂了电荷补偿剂Li+，使晶体内部电荷达到平衡。实验结果表明，Li+最佳掺杂浓度为2%，与未加入电荷补偿剂相比，发光强度提高了2倍并测试其内量子效率为43.6%。荧光粉色坐标均在(0.60，0.39)附近，位于橙红色区域，具有较高色纯度(约92.2%)。该荧光粉在三基色白光LED中的红色成分有应用潜力。     

Measurements of interaction cross sections and radii of He isotopes

Secondary beams of ³He, ⁴He, ⁶He, and ⁸He were produced through the projectile fragmentation of an 800 MeV/nucleon ¹¹B primary beam. Interaction cross sections (σ_I) of all He isotopes of 790 MeV/nucleon on Be, C, and Al targets were measured by a transmission-type experiment. The interaction nuclear radii of He isotopes R_I(He) = (σ_I/π)^1/2 − R _I(T) where R_I(T) is the radius of the target nucleus, have been deduced to be R_I(³He) = 1.59 ± 0.06 fm, R_I(⁴He) = 1.40 ± 0.05 fm, R_I(⁶He) = 2.21 ± 0.06 fm, and R_I(⁸He) = 2.52 ± 0.06 fm.