Development of oxidative sample preparation for the analysis of forensic soil samples with near‐IR Raman spectroscopy

Forensic soil samples have been traditionally analysed via examinations of colour, texture and mineral content by physical or chemical methods. These methods leave any organic or water‐soluble fractions unexamined. A range of analytical techniques have been applied in this area and these procedures have been reviewed recently. This study uses Raman Spectroscopy to assess both the mineralogical and the water‐soluble organic fractions in soil samples. Soil samples were collected from both urban and rural environments comprising the city of Bradford, England, and an arable farming district in Lincolnshire. This study demonstrates how, with the use of oxidative preparation methods, Raman spectroscopy can be used to successfully discriminate between soil types using mineralogy as well as the organic and water‐soluble fractions of soils. Copyright © 2011 John Wiley & Sons, Ltd.     

On effective determination of modular forms by twists of critical L-values

We address the problem of identifying a newform f from the central values of the twisted L-functions ${L(1/2,f\otimes \chi)}We address the problem of identifying a newform f from the central values of the twisted L-functions L(1/2,f?c){L(1/2,f\otimes \chi)} where χ runs through the set of real characters. We prove a quantitative result in this direction.     

IRMPD Action Spectroscopy,ER-CID Experiments,and Theoretical Studies of Sodium Cationized Thymidine and 5-Methyluridine: Kinetic Trapping During the ESI Desolvation Process Preserves the Solution Structure of [Thd+Na]<Superscript>+</Superscript>

Thymidine (dThd) is a fundamental building block of DNA nucleic acids, whereas 5-methyluridine (Thd) is a common modified nucleoside found in tRNA. In order to determine the conformations of the sodium cationized thymine nucleosides [dThd+Na]⁺ and [Thd+Na]⁺ produced by electrospray ionization, their infrared multiple photon dissociation (IRMPD) action spectra are measured. Complementary electronic structure calculations are performed to determine the stable low-energy conformations of these complexes. Geometry optimizations and frequency analyses are performed at the B3LYP/6-311+G(d,p) level of theory, whereas energies are calculated at the B3LYP/6-311+G(2d,2p) level of theory. As protonation preferentially stabilizes minor tautomers of dThd and Thd, tautomerization facilitated by Na⁺ binding is also considered. Comparisons of the measured IRMPD and computed IR spectra find that [dThd+Na]⁺ prefers tridentate (O2,O4',O5') coordination to the canonical 2,4-diketo form of dThd with thymine in a syn orientation. In contrast, [Thd+Na]⁺ prefers bidentate (O2,O2') coordination to the canonical 2,4-diketo tautomer of Thd with thymine in an anti orientation. Although 2,4-dihydroxy tautomers and O2 protonated thymine nucleosides coexist in the gas phase, no evidence for minor tautomers is observed for the sodium cationized species. Consistent with experimental observations, the computational results confirm that the sodium cationized thymine nucleosides exhibit a strong preference for the canonical form of the thymine nucleobase. Survival yield analyses based on energy-resolved collision-induced dissociation (ER-CID) experiments suggest that the relative stabilities of protonated and sodium cationized dThd and Thd follow the order [dThd+H]⁺ < [Thd+H]⁺ < [dThd+Na]⁺ < [Thd+Na]⁺.

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Synthesis of 2-amino-3-carbethoxy-1-hydroxyindoles

A general method is described for the synthesis of 2-amino-3-carbethoxy-l-hydroxyindoles by the reductive cyclization of 2-nitrophenylcyanoacetates using zinc and acetic acid at temperatures of 15–28°.     

Density of positive rank fibers in elliptic fibrations

A question of Mazur asks whether for any non-constant elliptic fibration {Er}_r∈Q, the set {r∈Q:rank(Er(Q))>0}, if infinite, is dense in R (with respect to the Euclidean topology). This has been proved to be true for the family of quadratic twists of a fixed elliptic curve by a quadratic or a cubic polynomial. Here we settle Mazur's question affirmatively for the general quadratic and cubic fibrations. Moreover we show that our method works when Q is replaced by any real number field.     

Effect of polydispersity on the bulk‐heterojunction morphology of P3HT:PCBM solar cells

Bulk heterojunctions (BHJs) based on semiconducting electron–donor polymer and electron–acceptor fullerene have been extensively investigated as potential photoactive layers for organic solar cells (OSCs). In the experimental studies, poly‐(3‐hexyl‐thiophene) (P3HT) polymers are hardly monodisperse as the synthesis of highly monodisperse polymer mixture is a near impossible task to achieve. However, the majority of the computational efforts on P3HT: phenyl‐C61‐butyric acid methyl ester (P3HT:PCBM)‐based OSCs, a monodisperse P3HT is usually considered. Here, results from coarse‐grained molecular dynamics simulations of solvent evaporation and thermal annealing process of the BHJ are shared describing the effect of variability in molecular weight (also known as polydispersity) on the morphology of the active layer. Results affirm that polydispersity is beneficial for charge separation as the interfacial area is observed to increase with higher dispersity. Calculations of percolation and orientation tensors, on the other hand, reveal that a certain polydispersity index ranging between 1.05 and 1.10 should be maintained for optimal charge transport. Most importantly, these results point out that the consideration of polydispersity should be considered in computational studies of polymer‐based OSCs. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 895–903     

Predicting Accurate Lead Structures for Screening Molecular Libraries: A Quantum Crystallographic Approach

Optimization of lead structures is crucial for drug discovery. However, the accuracy of such a prediction using the traditional molecular docking approach remains a major concern. Our study demonstrates that the employment of quantum crystallographic approach-counterpoise corrected kernel energy method (KEM-CP) can improve the accuracy by and large. We select human aldose reductase at 0.66 Å, cyclin dependent kinase 2 at 2.0 Å and estrogen receptor β at 2.7 Å resolutions with active site environment ranging from highly hydrophilic to moderate to highly hydrophobic and several of their known ligands. Overall, the use of KEM-CP alongside the GoldScore resulted superior prediction than the GoldScore alone. Unlike GoldScore, the KEM-CP approach is neither environment-specific nor structural resolution dependent, which highlights its versatility. Further, the ranking of the ligands based on the KEM-CP results correlated well with that of the experimental IC₅₀ values. This computationally inexpensive yet simple approach is expected to ease the process of virtual screening of potent ligands, and it would advance the drug discovery research.     

Spectrophotometric studies of complexing equilibria of hafnium with some azo-dyes in aqueous solution

Hafnium forms three chelates 1:2 (M:L) (pH 1.0, 520 nm), 1:1 (pH 1.4, 520 nm), and 2:1 (pH 2.0, 520 nm) with PAR; and 1:2 chelate with EBB (pH 0.8, 590 nm), SVRS (pH 1.2, 560 nm), and CLM (0.25 M, 590 nm), respectively. In all the systems, only for 1:2 chelates, the exact nature of the equilibrium involved in chelation has been evaluated. The kinetic study and the number of protons liberated during chelation reaction have been studied. From the values of the equilibrium constant, the values of absolute stability constants for these complexes have also been evaluated.