Isotope Abundance Ratios of Sr In Wine Provenance Determinations,in A Tree-Root Activity Study,and Of Pb in A Pollution Study on Tree-Rings

Abstract

In this contribution, the various and fundamentally different uses and applications of isotope signatures (of both heavy and light elements) are discussed. Examples are given for the successful use of ⁸⁷Sr/⁸⁶Sr in uncovering fraud in wine trade. Also, in an experiment related to “Waldsterben”, ⁸⁷Sr/⁸⁶Sr analyses reveal rather unexpected responses of spruces and maple-trees to mechanical damage of their roots. In another study, from ²⁰⁶Pb/²⁰⁷Pb (and ²⁰⁸Pb/²⁰⁷Pb) analyses of tree growth-rings it is demonstrated that they do not accurately record lead burdens in the environment. This is contrary to current views on the subject of tree-rings as reliable banks of past heavy metal pollutions of the biosphere. Furthermore, new perspectives of applications of isotopes in biological tissues, including those of cosmogenic and nucleogenic origin will be shortly outlined.     

Investigation of the local structure of Cu2+ ions doped in alkali lead tetraborate glasses by their electron paramagnetic resonance and optical spectra

The local structure of the Cu²⁺ centers in alkali lead tetraborate glasses was theoretically studied based on the optical spectra data and high-order perturbation formulas of the spin Hamiltonian parameters (electron paramagnetic resonance g factors g_∥, g_⊥ and hyperfine structure constants A_∥, A_⊥) for a 3d⁹ ion in a tetragonally elongated octahedron. In these formulas, the relative axial elongation of the ligand O^2? octahedron around the Cu²⁺ due to the Jahn–Teller effect is taken into account by considering the contributions to the g factors from the tetragonal distortion which is characterized by the tetragonal crystal-field parameters Ds and Dt. From the calculations, the ligand O^2? octahedral around Cu²⁺ is determined to suffer about 19.2% relative elongation along the C₄ axis of the alkali lead tetraborate glass system, and a negative sign for A_∥ and a positive sign for A_⊥ for these Cu²⁺ centers are suggested in the discussion.     

A Liquid Membrane-Based Green Method for the Separation and Determination of Lead in Saline Waters

In this work, the authors proposed a new liquid membrane-based method for the determination of lead in saline waters. In this case, the new method is based on lead quantification by inductively coupled plasma-mass spectrometry (ICP-MS) after a preconcentration step by means of a bulk liquid membrane (BLM) system. With no sample manipulation, the system transports and preconcentrates the analyte ions in the sample into the acidic receiving solution, by means of an organic membrane containing di-(2-ethylhexyl)-phosphoric acid (DEHPA) acting as a chemical carrier. The chemical variables controlling Pb²⁺ permeation through the membrane were studied by use of a modified simplex approach. The most appropriate preconcentration rates were found at sample pH 4.7, maintained with a 0.08-M acetate buffer solution, a 0.07-M DEHPA concentration, and a 0.23-M HNO₃ receiving solution. Under these conditions, an extraction yield of 93.8 ± 0.1% and a preconcentration factor of 4.2 were obtained, thus allowing lead selective separation and accurate determination in real samples at environmental concentration levels. The system was tested with several real samples from the Gulf of Cádiz containing lead at the low ppb levels.     

The specific heat of potassium holmium double tungstate

The results of measurements of thermal properties (specific heat) of potassium holmium double tungstate KHo(WO₄)₂ as a function of temperature (from 0.5 to 300?K) and magnetic field (up to 2?T) are presented. The total specific heat without the phonon and Schottky contributions is found to have the anomaly with maximum at T _SPT?～?5?K. This anomaly is likely related with the structural phase transition (SPT) caused by the cooperative Jahn–Teller effect. The increase of specific heat at very low temperatures and its shift towards high temperatures with increasing magnetic field are observed. The origin of this behaviour can be connected with possible magnetic phase transition induced by magnetic field.     

Tuning the spin dependent behavior of monatomic carbon wires between nickel electrodes

Spin polarized Density Functional Theory combined with Non-Equilibrium Green?s Function Formalism is applied to investigate the spin dependent transport in carbon based monatomic systems. Both one-dimensional linear and ring structures sandwiched between spin polarized nickel electrodes are examined. Incorporating of nickel electrodes and rings leads to interesting spin dependent properties. The influence of electrode structure is also addressed, using the Ni(100) pyramidal and plane electrodes. It is revealed that spin dependent behavior is largely determined by the atomic arrangement of the monatomic system, and that both the transport and magnetic properties can be tuned by odd–even disparity and/or appropriate ring(s). The mechanisms governing the spin dependent properties in these structures are discussed.     

A Raman study of high-pressure phases of lead chalcogenides PbX (X=S,Se, Te)

Pressure-induced phase transitions of lead chalcogenides were studied by Raman spectroscopy. The number of Raman modes observed for the first high-pressure phases was found to be significantly less than expected from selection rules for the proposed GeS-type orthorhombic structure. The observations are consistent with the alternative assignment as CrB-type. In the case of PbS, the disappearance of the intermediate-phase Raman lines in the pressure range of 19–25 GPa, i.e., in the vicinity of the orthorhombic to CsCl-type phase transition, is accompanied by a strong increase in a structureless background. The Raman background is attributed to light scattering by charge carriers in the metallic CsCl-type phase.     

Structurally different cadmium(II) and lead(II) supramolecular polymers with the same benzene-1,2,3,4-tetracarboxylate dianion as bridging ligands from hydrothermal reactions

Two crystalline metal-organic frameworks, [Cd₂(o-BTC)(H₂O)₂] _n (1) and [Pb₂(o-BTC)] _n (2) (o-BTC?=?benzene-1,2,3,4-tetracarboxylic), were synthesized under hydrothermal conditions and characterized by analytical, spectroscopic and single crystal X-ray diffraction studies, which reveal three-dimensional reticular structures via M²⁺ and carboxylate ligands. All carboxyl groups of o-BTC are deprotonated, in agreement with the IR data. The Cd²⁺ centers of 1 have one coordination environment, while Pb²⁺ centers of 2 have two coordination environments. Both 1 and 2 form 3D interpenetrated grid structures along the b and c axes, respectively.     

Stable and Low‐Cost Mesoscopic CH3NH3PbI2Br Perovskite Solar Cells by using a Thin Poly(3‐hexylthiophene) Layer as a Hole Transporter

Mesoscopic perovskite solar cells using stable CH₃NH₃PbI₂Br as a light absorber and low‐cost poly(3‐hexylthiophene) (P3HT) as hole‐transporting layer were fabricated, and a power conversion efficiency of 6.64 % was achieved. The partial substitution of iodine with bromine in the perovskite led to remarkably prolonged charge carrier lifetime. Meanwhile, the replacement of conventional thick spiro‐MeOTAD layer with a thin P3HT layer has significantly reduced the fabrication cost. The solar cells retained their photovoltaic performance well when they were exposed to air without any encapsulation, presenting a favorable stability. The combination of CH₃NH₃PbI₂Br and P3HT may render a practical and cost‐effective solid‐state photovoltaic system. The superior stability of CH₃NH₃PbI₂Br is also promising for other photoconversion applications.     

四种不同约束形式隔板式铅耗能器的试验研究

铅耗能器主要利用金属铅塑性耗能,是一种构造简单、耗能性能优良而又经济的耗能减震元件。本文提出了一种隔板式铅耗能器。根据其构造和耗能原理,设计了四种不同约束形式的耗能元件,并通过EHF-EM电液伺服疲劳试验机进行了低周循环试验,分析了这四种约束形式对隔板式铅耗能器的力学性能与耗能性能的影响,揭示了其耗能机制。研究结果表明:隔板式铅耗能器主要具有屈服位移小、造价低廉、构造简单、工作性能稳定、耗能性能优良的特点,在建筑结构和大型机械减振控制方面具有广泛的应用前景;对比分析表明,其中B型耗能器力学性能尤为优越,耗能能力大且随位移增大刚度增强,同时对结构振动还具有限位功能。