三角帆蚌对水体Cr,Pb和Cd的净化与吸收

三角帆蚌（Hyriopsis cumingii Lea）对水体Cr,Pb,Cd污染有明显的净化能力，持续处理12d，能使水体Cr,Pb,Cd含量分别下降83％，77．6％和72％。蚌体的斧足、鳃、外磁膜、体表粘液、肝脏、肠道和生殖腺等组织对3种污染物的吸收和富集作用不尽相同，其中分别以体表粘液、鳃和肝脏最为显著。3种污染物进入蚌体的速度很快，其组织吸收量一般在第3天即可达到较高水平。进入蚌体的污染物，可在组织转移和重新分布。研究结果为生物治理Cr,Pb,Cd等重金属污染积累了资料。     

氯代5-氟脲嘧啶卟啉的红外光谱特性的研究

本文对新合成的对位及间位两类氯代苯基 5 氟脲嘧啶卟啉的红外光谱吸收峰进行了归属和总结 ,讨论了其红外吸收频率随取代基位置变化的规律。指出了苯环上的取代基为电负性强的基团时 ,由于场效应的存在 ,使被测化合物的羰基伸缩振动吸收峰的相对强度发生改变。同时 ,表明了嘧啶环上N原子发生了取代 ,形成单、双取代 5 氟脲嘧啶卟啉化合物的红外光谱特性。     

Spectral Properties of Thioflavin T and Its Complexes with Amyloid Fibrils

Comparative analysis of the absorption and fluorescence spectra and fluorescence excitation spectra of thioflavin T (ThT) in various solvents and in the composition of amyloid fibrils has shown that ThT, when excited in the region of the long-wavelength absorption band, fluoresces in the spectral region with a maximum at 478–484 nm. The appearance in aqueous and alcohol solutions of a fluorescence band with a maximum near 440 nm has been attributed to the presence in the composition of the ThT preparations of an impurity with an absorption band in the 340–350-nm range. The literature data showing that in glycerol ThT has a wide fluorescence spectrum with two maxima are due to the artifact connected with the use of a high concentration of the dye. It has been suggested that the cause of the low quantum yield of ThT aqueous and alcohol solutions is the breakage of the system of conjugated bonds due to the reorientation of the benzothiozole and benzaminic rings of ThT in the excited state with respect to one another. The main factor determining the high quantum yield of fluorescence of ThT incorporated in fibrils is the steric restriction of the rotation of the rings about one another under these conditions. The suggestions made have been verified by the quantum-chemical calculation of the ThT molecule geometry in the ground and excited states.     

Identification of a dissipation coefficient by a variational method

A generalized inverse problem for the identification of the absorption coefficient for a hyperbolic system is considered. The well-posedness of the problem is examined. It is proved that the regular part of the solution is an L ₂ function, which reduces the inverse problem to minimizing the error functional. The gradient of the functional is determined in explicit form from the adjoint problem, and approximate formulas for its calculation are derived. A regularization algorithm for the solution of the inverse problem is considered. Numerical results obtained for various excitation sources are displayed.     

57Fe Mössbauer spectroscopic study of (25−x)MnO–xZnO–15Fe2O3–60B2O3 glasses

The ⁵⁷Fe Mössbauer technique has been used to investigate the effect of zinc oxide substitution in (25???x)MnO–xZnO–15Fe₂O₃–60B₂O₃ glass system (x?=?0, 5, 10, 15 and 20 mol% of ZnO ). Mössbauer absorption spectra for all the samples recorded at room temperature suggest the existence of the two paramagnetic quadrupole doublets. The observed variations in hyperfine parameters have been explained on the basis of cations distribution and exchange interaction at the lattice sites and it is concluded that B–B interaction increases while the metal–metal interaction decreases due to replacement of manganese oxide by zinc oxide. These results suggest that the present glass system exhibits a paramagnetic behaviour that changes towards the weak paramagnetic when manganese oxide was replaced with zinc oxide.     

Determination of gold in ore by flame atomic absorption spectrometry with flow-injection on-line sorbent extraction preconcentration

Gold in ores was determined by flame atomic absorption spectrometry following on-line preconcentration by sorbent extraction in a flow-injection system. The medium polarity adsorption resin Amberlite XAD-8 packed in a 220-μl micro-column was used to collect gold(III) from hydrochloric acid sample solutions for 40 s at 7.6 ml/min. Ethanol was used to elute the adsorbed analytes into the nebulizer. Optimization studies were made on sample loading rate, elution rate and sample acidity. Some possible interferences on the determination are discussed. A 35-fold enrichment was achieved at a sampling frequency of 60 h^?1 and with an RSD of 1.4%. The detection limit (3σ) and 2 μg l^?1. Results for gold in ore samples showed good agreement with those obtained using activated carbon adsorption preconcentration. The recoveries were 97–108%.     

Sequential nonlinear estimation with nonaugmented priors

How can the basic compatibility of theory and observations be investigated for nonlinear processes without requiring stochastic characterizations for residual error terms? The present paper proposes a flexible least-cost approach. For each possible estimatex for the sequence of process states, letc _D (x) andx _M(x) denote the costs incurred for deviations away from the prior dynamic specifications and prior measurement specifications, respectively. Define the cost-efficiency frontier to be the greatest lower bound for the set of all possible cost pairs [c _D (x),c _M(x)], conditional on the given observations. State sequence estimatesx that attain the cost-efficiency frontier indicate the possible ways that the actual process could have developed over time in a manner minimally incompatible with the prior dynamic and measurement specifications. An algorithm is developed for the exact sequential updating of the cost-efficient state sequence estimates as the duration of the process increases and additional observations are obtained.     

Hawking Absorption and Planck Absolute Entropy of Kerr-Newman Black Hole

We find the existence of a quantum thermal effect, “Hawking absorption.” near the inner horizon of the Kerr–Newman black hole. Redefining the entropy, temperature, angular velocity, and electric potential of the black hole, we give a new formulation of the Bekenstein–Smarr formula. The redefined entropy vanishes for absolute zero temperature of the black hole and hence it is interpreted as the Planck absolute entropy of the KN black hole.     

Nd∶NaR(WO_4)_2晶体生长(R=Bi,Y)

采用提拉法生长出了掺钕钨酸铋钠[Nd∶NaBi(WO4)2,简称Nd∶NBW]和掺钕钨酸钇钠[Nd∶NaY(WO4)2,简称Nd∶NYW]晶体,并给出了制备无开裂优质Nd∶NBW和Nd∶NYW晶体的最佳生长工艺参数。从XRD分析得到Nd∶NBW和Nd∶NYW晶体的晶胞参数,并分析了晶体的拉曼光谱,认为二者结构基本相同,为四方晶系、白钨矿结构、I41/a空间群。由吸收光谱可以看出,Nd∶NBW在802nm有较强的吸收峰,Nd∶NYW在804nm、752nm、586nm附近有较强、较宽的吸收峰,二者均适合于LD泵浦;计算了晶体中Nd3+的吸收截面积。