226Ra translocation from soil to selected vegetation in the Crucea (Romania) uranium mining area

A two year field survey of ²²⁶Ra translocation from soil to selected spontaneous plants growing in the Crucea (Romania) uranium mining area is presented. Since Crucea is a large and relatively highly contaminated area, an easy and cheap way for a desired lowering of radiopollution represents phytoremediation using plentifully occurring plant species. The ²²⁶Ra translocation from soil was affected by analyzed species, collecting sites and vegetation periods. The specific ²²⁶Ra activities of the roots were considerably higher than the aboveground parts confirming the root tropism of radioisotopes. Mentha piperita was found to be highly effective in phytoremediation, especially in autumn.     

Measurement of the radioactivity of 238U, 226Ra, 210Pb, 228Th, 232Th, 228Ra, 137Cs and 40K in tea using gamma-spectrometry

The aim of the present work was to determine the concentration of radionuclides in all kinds of tea available at the local Egyptian market. Radioactivity of the nuclides ²³⁸U, ²²⁶Ra, ²¹⁰Pb, ²²⁸Th, ²³²Th, ²²⁶Ra, ¹³⁷Cs and ⁴⁰K were measured in tea by direct γ-ray spectrometry using HPGe detector and their mean values were 16.0±5.3, 3.1±0.7, 34.3±3.4, 3.4±1.2, 3.0±0.6, 3.1±0.8, 0.9±0.2 and 623±25 Bq·kg⁻¹, respectively.     

Die Thorium-Folgeprodukte MsTh1 (228Ra), MsTh2 (228Ac), ThB (212Pb) und ThC (212Bi)

Ohne Zusammenfassung     

A biomonitoring study: 210Po and heavy metals in marine organisms from the Adriatic Sea (Italy)

In various samples of marine organisms from the central Adriatic Sea ²¹⁰Po was determined by alpha spectrometry and thirteen heavy metals (Mn, Fe, Co, Cr, V, Ni, Cu, Zn, Cd, As, Sn, Hg and Pb) by energy dispersive, polarised X ray fluorescence spectrometry (EDPXRF). ²¹⁰Po activity concentration ranged between 0.3 and 44.6 Bq kg⁻¹ fresh weight. The data obtained depend upon the type of the marine organism; among the pelagic species, anchovy displayed the highest polonium concentration. Typical concentration ( \upmu \textg·\textg_(\textfresh) ^{- 1} ) \left( {\upmu {\text{g}}\cdot{\text{g}}_{{({\text{fresh}})}}^{ - 1} } \right) ranges were as follows: Mn: <1.32–1.73; Fe: 4.11–94.27; Co < 0.13–0.23; Ni: <0.13–0.52; Cu: 0.37–145.31; Zn: 0.46–16.46; Cd: <0.10–0.25; As: 0.36–60.52; Hg: <0.13–0.70; Pb: <0.13–0.35, Sn: <0.20–12.67; V and Cr were always <1.32. The data obtained are also compared with those obtained by other authors for the same organism coming from other Italian seas.     

Rapid determination of 226Ra in drinking water samples using dispersive liquid-liquid microextraction coupled with liquid scintillation counting

A new radioanalytical method was developed for rapid determination of ²²⁶Ra in drinking water samples. The method is based on extraction and preconcentration of ²²⁶Ra from a water sample to an organic solvent using a dispersive liquid-liquid microextraction (DLLME) technique followed by radiometric measurement using liquid scintillation counting. In DLLME for ²²⁶Ra, a mixture of an organic extractant (toluene doped with dibenzo-21-crown-7 and 2-theonyltrifluoroacetone) and a disperser solvent (acetonitrile) is rapidly injected into the water sample resulting in the formation of an emulsion. Within the emulsion, ²²⁶Ra reacts with dibenzo-21-crown-7 and 2-theonyltrifluoroacetone and partitions into the fine droplets of toluene. The water/toluene phases were separated by addition of acetonitrile as a de-emulsifier solvent. The toluene phase containing ²²⁶Ra was then measured by liquid scintillation counting. Several parameters were studied to optimize the extraction efficiency of ²²⁶Ra, including water immiscible organic solvent, disperser and de-emulsifier solvent type and their volume, chelating ligands for ²²⁶Ra and their concentrations, inorganic salt additive and its concentration, and equilibrium pH. With the optimized DLLME conditions, the accuracy (expressed as relative bias, B _r ) and method repeatability (expressed as relative precision, S _B ) were determined by spiking ²²⁶Ra at the maximum acceptable concentration level (0.5 Bq L⁻¹) according to the Guidelines for Canadian Drinking Water Quality. Accuracy and repeatability were found to be less than −5% (B _r ) and less than 6% (S _B ), respectively, for both tap water and bottled natural spring water samples. The minimum detectable activity and sample turnaround time for determination of ²²⁶Ra was 33 mBq L⁻¹ and less than 3 h, respectively. The DLLME technique is selective for extraction of ²²⁶Ra from its decay progenies.     

Franck-Condon factors and r -centroids for the E 1Πu- X 1Σ g+ system of Ag2

An array of Franck-Condon factors and r-centroids is reported for the bands of the E ¹Π_u-X ¹Σ _g ⁺ system of the Ag₂ molecule. Both parameters were calculated using the Morse and Rydberg-Klein-Rees potentials. The results showed a reasonable agreement between the two sets of data for transitions, including lower vibrational levels (v ≤ 6). Differences appear with increasing v, but two sets of calculated Franck-Condon factors follow the same pattern. The predicted intensity distribution was compared with the estimated band intensity in the experimental spectrum. The text was submitted by the authors in English.     

BH分子X 1Σ+、A 1Π和B 1Σ+ 态的势能函数

利用SAC/SAC-CI方法，使用D95++、6-311++g及cc-PVTZ等基组，对BH分子的基态(X ¹Σ⁺)、第一简并激发态(A ¹Π)及第二激发态(B ¹Σ⁺)的平衡结构和谐振频率进行了优化计算． 通过对三个基组计算结果的比较，得出了cc-PVTZ基组为三个基组中的最优基组的结论；使用cc-PVTZ基组，利用SAC的GSUM(group sum of operators)方法对基态(X ¹Σ⁺)， SAC-CI的GSUM方法对激发态(A ¹Π 和B ¹Σ⁺)进行单点能扫描计算, 用正规方程组拟合Murrell-Sorbie函数，得到了相应电子态的完整势能函数；从得到的势能函数计算了与基态(X ¹Σ⁺)、第一简并的激发态(A ¹Π)和第二激发态(X ¹Σ⁺)相对应的光谱常数(Be、αe、ωe 和ωeχe)，结果与实验数据较为一致． 其中基态、第一激发态与实验数据吻合得较好．     

Pu(7Fg)＋CO(X 1Σ＋，0，0)的分子反应动力学

基于PuCO分子基态()的分析势能函数， 用准经典的Monte Carlo轨线法对Pu(7Fg)＋CO(0，0)的分 子反应动力学过程进行了计算.结果表明, Pu(7Fg)与CO(0，0)碰撞易生成PuCO络合物分子，该反应是无阈能反应，反应截面σ随能量Et的升高而下降，当Et=502.1 kJ•mol－1时，σ几乎为零.     

Threshold energies for production of CH2(3B1) and CH2(1A1) from ketene photolysis. The CH2(3B1) ↔ CH2(1A1) energy splitting

By measuring the relative CO quantum yields from ketene photolysis as a function of photolysis wavelength we have determined the threshold energy at 25° for CH₂CO(¹A₁) → CH₂(³B₁) + CO(¹Σ⁺) to be 75.7 ± 1.0 kcal/mole. This corresponds to a value of 90.7 ± 1.0 kcal/mole for ΔH_f298⁰[CH₂(³B₁)]. By measuring the relative ratio of CH₂(¹A₁)/CH₂(³B₁) from ketene photolysis as a function of photolysis wavelength we have determined the threshold energy at 25°C for CH₂CO(¹A₁) → CH₂(¹A₁) + CO(¹Σ⁺) to be 84.0 ± 0.6 kcal/mole. This corresponds to a value of 99.0 ± 0.6 kcal/mole for ΔH_f298⁰[CH₂(¹A₁)]. Thus a value for the CH₂(³B₁) ? CH₂(¹A₁) energy splitting of 8.3 ± 1 kcal/mole is determined, which agrees with three other recent independent experimental estimates and the most recent quantum theoretical calculations.     

NMR study (1H, 13C and 29Si) of the methylallylsilanes

¹H, ¹³C and ²⁹Si NMR data for the compounds (CH₃)_xSi(CH₂CHCH₂)_4-x are reported. The ¹H resonances from the π system are indicative of the electron-supplying inductive effect (+I) of the (CH₃SiCH₂, moiety but the corresponding ¹³C_π chemical shifts seem to be influenced by a sterically induced polarization of the C-H bonds. The ¹³C_All, ¹³C_Me and ²⁹Si chemical shift data reveal an important neighbour anisotropy contribution originating from the π system. Ultraviolet study of the compounds mentioned above gives indication of a σ—π conjugation in accordance with PES and ab initio results [1—5]. The trend observed in the various coupling constants is too small to be Interpreted.     

Repulsive potentials for Ne*(3P)—He and Ar*(3P)—He from differential scattering

Crossed beam measurements of differential scattering of metastable Ne and Ar by He are used to derive the repulsive parts of the respective interatomic potentials. The potentials are similar to one obtained for Li—He. They show non-exponential behavior at small r suggestive of a core-interaction effect.     

Electron-gas interaction potentials for collisions of CaCl(X 2Σ+) and KCl(X 1Σ+) with Ar

Interaction potentials for CaCl(X ²Σ⁺)-Ar and KCl(X ¹Σ⁺)-Ar have been determined. They include a Gordon-Kim electron-gas repulsive part smoothly joined to the long-range van der Waals potential. The van der waals potential for KClAr was taken from Meyer and Toennies. For CaClAr, the necessary molecular parameter were estimated from the Rittner model, which predicts both the dipole and quadrupole moments fairly accurately. The CaClAr interaction potential is quite different from that of KClAr. Due to the outer 4s electron on the Ca⁺ ion. the CaClAr potential exhibits a deep minimum in the odd-order Legendre terms which is expected to have a large effect on the cross sections for collisional rotational excitation. The KClAr potential determined here also shows significant differences in the repulsive and well regions from that predicted by Meyer and Toennies using a site-site model for the repulsive contribution.     

Rate constants for O(3P) recombination and association with N(4S)

It is shown that N(⁴S) and O(³P) atom quenching effects upon chemiluminescence from NO(B²π) (θ = 0) are of importance when this emissio Values of k₂ = (1.74 ± 0.13) × 10⁹ and (4.05 ± 0.17) × 10⁹ &² mole^-2 sec^-1 are found at 298 and 196°K respectiv     

A conjecture for some partial differential operators on L 2( R n)

OnX =L ²(R ⁿ), letQ = (Q ₁,Q ₂,…,Q _n) andP = (P ₁,P ₂, …,P _n) be the operators given by (Q _jf) (x) =x _jf(x),P _j = - i∂/∂x _j. For anyC ^∞ functionh:R ⁿ →R putH ₀ =h(P) andH =H ₀ + (1 +Q ²)^-δ, where δ > 1/2. By the method of scattering theory we prove thatH _ac, the absolutely continuous part ofH is unitarily equivalent toH ₀ when (a)n = 1 and (b) forn ≥ 2, whenh is in a large class of polynomials. It is conjectured that the results are true for any polynomialh. We use the techniques of Enss’ method and the idea of bound states for momentum.     

Sensitization of the OH(A 2Σ+ → X 2Πi) emission by Hg(6 3P0) metastables

The electronic energy transfer process Hg(6 ³P₀) + OH(X²Π_i, υ = 0,K) → Hg(6 ¹S₀) + OH(A ²Σ⁺, υ,K) has been studied by the sensitized fluorescence method. A rather broad spectrum of rotational population, N_υ′K′, was obtained under conditions of minimum relaxation, which illustrates the non-resonant and non-optical nature of this energy transfer process. The fractions of the exoergicity, above electronic excitation of OH(A ²Σ⁺, υ = 0, K = 0), going into vibrational, rotational and translational excitation are 0.11, 0.31, and 0.58, respectively. A statistical mode of energy partitioning, such as would result from long-lived complex formation, seems to account well for these observations.     

Energy transfer from Ca(3P) to Sr and quenching of Sr(3P) by the inert gases

A laser-induced fluorescence technique has been used to measure the rate of the energy-transfer reaction Ca(³P) + Sr(¹S) α Ca(¹S) + Sr(³P). Rates for quenching Sr(³P) by inert gases were also measured and correlated with an orbiting model.     

Potential energy curves for the X1∑ g, B1△g and B''''1∑ g states of C2 using MRCI and approximate CI methods

The potential energy curves for the X1∑ g, B1△g and B′1∑ g states of C2 have been studied by using MRCI and approximate CI methods, and are benchmarked against the calculations of full configuration interaction (FCI). The results obtained by MRCI method agree with the FCI very well, and even are accurate enough to compare other approximate methods as benchmark, when the calculations of FCI are not feasible. The approximate CI methods mentioned in this paper are reliable for treating chemical problems.     

Mechanism of the thermal decomposition of (η5-C5H5)Fe(CO)2(η1-acenaphthenyl)

The complexes (η⁵-C₅H₅)Fe(CO)₂(η¹-acenaphthenyl) (I), (η⁵-C₅H₅)Fe(CO)₂ (η¹-trans-β-deuterioacenaphthenyl) (II), and (η-C₅D₅)Fe(CO)₂, (η¹-acenaphthenyl) (XIII) have been prepared and their thermal decomposition studied in vacuo and in refluxing toluene. All three complexes decompose to produce mixtures of acenaphthene (VII), acenaphthylene (VIII), and [C₅H₅Fe(CO)₂]₂ (VI). Biacenaphthenyl (IX) is also obtained from the thermolysis of I in toluene. The formation of alkene VIII, and, to a lesser extent, alkane VII is suppressed by external CO. Thermolysis of I in toluene-d₈ and of II in vacuo and in toluene produces deuterium-enriched VII. The acenaphthene generated from the decomposition of XIII also contains deuterium. The above observations are accomodated by a mechanistic scheme involving competing β-elimination, ironcarbon bond homolysis to produce the acenaphthenyl radical, and CpH abstraction by an undetermined pathway.     

Distortions in trihapto-allyls induced by electronic asymmetry: A comparison of the structures of (η5-C5H5)Mo(CO)2(η3-C3H5) and (η5-C5H5)Mo(NO(I)(η3-C3H5)

The electronic asymmetry induced by replacing two carbonyls by a nitrosyl and iodide ligand causes severe distortion in the allyl moiety. The allyl group in the nitrosyl complex is bound in a sigma-pi mode rather than the symmetrical mode found in the dicarbonyl. This change in ground state structure alters the exo—endo conformer interconversion mechanism from a rotation of the allyl in the dicarbonyl to a sigma-pi interconversion in the nitrosyl iodide.