Source identification of nitrate by means of stable nitrogen isotopes in the river Daugava and loads of nitrogen to the Gulf of Riga

Nitrogen isotope ratio of nitrate provides a powerful tool to investigate nitrate sources and cycling mechanisms. Although the use of an isotope ratio method for ¹⁵N/¹⁴N allows identifying the nitrate sources in rivers by estimating a seasonal variation of N-NO₃ concentration, however, there are some restrictions. Nitrification, the conversion of NH₄⁺ to NO₃-, can proceed with significant nitrogen isotope fractionation, preferentially accumulating ¹⁴N in the produced NO₃-, and can make it difficult to identify the nitrate source with a high proportion of the isotope δ¹⁵N. However, the uptake and assimilation of NH₄⁺ and NO₃- have the capability of affecting isotopic compositions of riverine nitrogen compounds, and this may hinder the determination of whether the impact of the nitrate source with a high proportion of the isotope δ¹⁵N reduces. In addition, this study demonstrates that nitrate nitrogen concentration may correlate with δ¹⁵N_NO3 values both positively and negatively. Such correlations are the result of isotope effects during nitrogen transformation processes (e.g. nitrification and assimilation) and isotopic variability in the various nitrate sources. A comparison of NO₃- concentration and δ¹⁵N_NO3 can be used to further distinguish mixing from biological processing. However, in order to get a more precise answer regarding the nitrate sources, it would be useful to take both the data of nitrogen isotopes and data of oxygen isotopes present in nitrates.     

Asymmetric Induction by a Nitrogen 14N/15N Isotopomer in Conjunction with Asymmetric Autocatalysis

Chirality arising from isotope substitution, especially with atoms heavier than the hydrogen isotopes, is usually not considered a source of chirality in a chemical reaction. An N²,N²,N³,N³‐tetramethyl‐2,3‐butanediamine containing nitrogen (¹⁴N/¹⁵N) isotope chirality was synthesized and it was revealed that this isotopically chiral diamine compound acts as a chiral initiator for asymmetric autocatalysis.     

On a multidimensional model for the codiffusion of isotopes: localization and asymptotic behavior

The paper deals with a system of parabolic–hyperbolic partial differential equations, which models the diffusion of N species of isotopes of the same element, possibly radioactive, in a multidimensional medium. Some qualitative properties of the solutions, such as localization property, are studied together with the asymptotic behavior for large times. Copyright © 2015 John Wiley & Sons, Ltd.     

Utilisation of Non-Edible Source (Pongamia pinnata Seeds Shells) for Producing Methyl Esters as Cleaner Fuel in the Presence of a Novel Heterogeneous Catalyst Synthesized from Waste Eggshells

Waste eggshells were considered for synthesising a precursor (CaO) for a heterogeneous catalyst, further impregnated by alkali caesium oxide (Cs₂O). The following techniques were used to characterise the synthesised catalysts: X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and Temperature Programmed Desorption (CO₂-TPD). The synthesised catalyst revealed its suitability for transesterification to produce biodiesel. The biodiesel production process was optimised, and it showed that the optimal biodiesel yield is 93.59%. The optimal set of process parameters is process temperature 80 °C, process time 90 min, methanol-to-oil molar ratio 8 and catalyst loading 3 wt.%. It has been found that the high basicity of the catalyst tends to give a high biodiesel yield at low methanol-to-oil ratio 8 when the reaction time is also less (90 min). The fuel properties of biodiesel also satisfied the standard limits defined by ASTM and the EN standards. Thus, the synthesised catalyst from waste eggshells is highly active, improved the biodiesel production conditions and PPSS oil is a potential nonedible source.     

Description of the Superdeformed Bands of the Lutetium Isotopes

In the cases with and without a perturbation possessing the S0_sdg(5) (or SU_sdg(5)) symmetry in the supersymmetry scheme with many-body interactions, superdeformed bands in the odd-A Lu isotopes ^163,165,167Lu are investigated. Quantitatively good results of γ-ray energies and dynamical moments of inertia are obtained in both of the two cases. It shows that the supersymmetry scheme with many-body interactions has almost the same power to describe the triaxial superdeformed bands as to the other superdeformed bands.     

LaNi_5和LaNi_(4 .7)Al_(0 .3)氢化物柱内氢氘间的排代

进行了室温附近LaNi5和LaNi4 .7Al0 .3 两种材料上气 固间氢氘的排代实验。两种材料的排代效果都较好 ,相比之下 ,LaNi5的更优。可以推测 ,在不要求得到高纯氚的情况下 ,都可以用作氚的冷卸载贮存床。初步的理论探讨揭示 ,气 固界面的化学交换反应是产生排代效应的原因 ,宏观交换规律决定排代效果。理想化的塔板理论模型对排代流出曲线的描述是有效和适用的 ,塔板高度是材料排代性能优劣的指标 ,在确定的排代条件下 ,如果塔板高度小于 1.0cm ,应该认为具有较好的排代效果。     

Three new acid M+ arsenates and phosphates with multiply protonated As/PO4 groups

The crystal structures of caesium dihydrogen arsenate(V) bis[trihydrogen arsenate(V)], Cs(H₂AsO₄)(H₃AsO₄)₂, ammonium dihydrogen arsenate(V) trihydrogen arsenate(V), NH₄(H₂AsO₄)(H₃AsO₄), and dilithium bis(dihydrogen phosphate), Li₂(H₂PO₄)₂, were solved from single‐crystal X‐ray diffraction data. NH₄(H₂AsO₄)(H₃AsO₄), which was hydrothermally synthesized (T = 493 K), is homeotypic with Rb(H₂AsO₄)(H₃AsO₄), while Cs(H₂AsO₄)(H₃AsO₄)₂ crystallizes in a novel structure type and Li₂(H₂PO₄)₂ represents a new polymorph of this composition. The Cs and Li compounds grew at room temperature from highly acidic aqueous solutions. Li₂(H₂PO₄)₂ forms a three‐dimensional (3D) framework of PO₄ tetrahedra sharing corners with Li₂O₆ dimers built of edge‐sharing LiO₄ groups, which is reinforced by hydrogen bonds. The two arsenate compounds are characterized by a 3D network of AsO₄ groups that are connected solely via multiple strong hydrogen bonds. A statistical evaluation of the As—O bond lengths in singly, doubly and triply protonated AsO₄ groups gave average values of 1.70 (2) Å for 199 As—OH bonds, 1.728 (19) Å for As—OH bonds in HAsO₄ groups, 1.714 (12) Å for As—OH bonds in H₂AsO₄ groups and 1.694 (16) Å for As—OH bonds in H₃AsO₄ groups, and a grand mean value of 1.667 (18) Å for As—O bonds to nonprotonated O atoms.     

Level statistics for the even-even Yb isotopes

The level statistics of the even-even Yb isotopes are studied by using the energy levels calculated by the projected shell model. The spectrum of intrinsic states and band energies are also studied to discuss the generation of chaoticity. The energy dependence of the chaoticity is investigated, and a chaos to order transition is found.     

Matrix effects on the multi-collector inductively coupled plasma mass spectrometric analysis of high-precision cadmium and zinc isotope ratios

Resin-derived contaminants added to samples during column chemistry are shown to cause matrix effects that lead to inaccuracy in multi-collector inductively coupled plasma mass spectrometry measurement of small natural variations in Cd and Zn isotopic compositions. These matrix effects were evaluated by comparing pure Cd and Zn standards and standards doped with bulk column blank from the anion exchange chromatography procedure. Doped standards exhibit signal enhancements (Cd, Ag, Zn and Cu), instrumental mass bias changes and inaccurate isotopic compositions relative to undoped standards, all of which are attributed to the combined presence of resin-derived organics and inorganics. The matrix effect associated with the inorganic component of the column blanks was evaluated separately by doping standards with metals at the trace levels detected in the column blanks. Mass bias effects introduced by the inorganic column blank matrix are smaller than for the bulk column blank matrix but can still lead to significant changes in ion signal intensity, instrumental mass bias and isotopic ratios. Chemical treatment with refluxed HNO₃ or HClO₄/HNO₃ removes resin-derived organic components resulting in matrix effects similar in magnitude to those associated with the inorganic component of the column blank.Mass bias correction using combined external normalization-SSB does not correct for these matrix effects because the instrumental mass biases experienced by Cd and Zn are decoupled from those of Ag and Cu, respectively. Our results demonstrate that ion exchange chromatography and associated resin-derived contaminants can be a source of error in MC-ICP-MS measurement of heavy stable element isotopic compositions.