Gas chromatography-electron ionization-mass spectrometry analysis of O,O'- dialkyl methylphosphonites for verification analysis of the Chemical Weapons Convention

Gas chromatography-mass spectrometry (GC-MS) analysis of O,O'-dialkyl methylphosphonites (DAMPs) was carried out with a view to developing a database and understanding the mechanism of fragmentation. DAMPs are included in the list of schedule 2B4 chemicals of the Chemical Weapons Convention. GC-MS analysis of DAMPs and their deuterated analogs revealed that their fragmentations were dominated by α-cleavages, alkenyl radical loss and hydrogen rearrangements. Based on fragment ions of deuterated analogs and density functional theory calculations, the fragmentation routes were rationalized.     

Crystallization of Semiconductor Nanorods into Perfectly Faceted Hexagonal Superstructures

Super crystallization of ligand‐capped nanocrystals into defined periodic solids from solution is the definitive demonstration of their self‐organizing properties. To date, this has been mainly limited to spherical nanocrystals where organization emulates atom or molecule packing in regular crystals with the most thermodynamically stable arrangement being eventually preferred. Here, the crystallization of wurtzite CdS nanorods into micrometer‐sized CdS superstructures with regular hexagonal symmetry is demonstrated by fine‐tuning the nanorod dispersibility over time. It is shown that the supercrystals have a long nucleation stage to form monolayer hexagons followed by a relatively faster growth stage both occurring rod by rod (in‐plane) and layer by layer (out of plane). The perfectly symmetrical hexagon shape of the final structure is mapped from the wurtzite crystal structure of each individual nanorod where they pack in side by side and end to end arrangements. These well‐defined superstructures are highly attractive for applications that collectively exploit electronic or optical properties that are synthetically tunable through the size and shape of each nanorod building block.     

H2 storage and equilibrium isotope effect for Be,Li, and Ti-doped closoborate complexes

Structural Chemistry - This work reports hydrogen uptake capacity and equilibrium isotope effect (EIE) for the Be, Li, and Ti-doped closoborate (B6H6) complexes using first-principles calculations...     

Torsionally broken symmetry assists infrared excitation of biomimetic charge-coupled nuclear motions in the electronic ground state

The concerted interplay between reactive nuclear and electronic motions in molecules actuates chemistry. Here, we demonstrate that out-of-plane torsional deformation and vibrational excitation of stretching motions in the electronic ground state modulate the charge-density distribution in a donor-bridge-acceptor molecule in solution. The vibrationally-induced change, visualised by transient absorption spectroscopy with a mid-infrared pump and a visible probe, is mechanistically resolved by ab initio molecular dynamics simulations. Mapping the potential energy landscape attributes the observed charge-coupled coherent nuclear motions to the population of the initial segment of a double-bond isomerization channel, also seen in biological molecules. Our results illustrate the pivotal role of pre-twisted molecular geometries in enhancing the transfer of vibrational energy to specific molecular modes, prior to thermal redistribution. This motivates the search for synthetic strategies towards achieving potentially new infrared-mediated chemistry.

Channelling vibrational excitation energy to achieve ground-state charge-transfer (CT)-assisted isomerization in a donor-bridge-acceptor molecule in solution.     

Die Bestimmung von Sulfat und Chlorid

Ohne Zusammenfassung     

Multilevel Monte Carlo in approximate Bayesian computation

In the following article, we consider approximate Bayesian computation (ABC) inference. We introduce a method for numerically approximating ABC posteriors using the multilevel Monte Carlo (MLMC). A sequential Monte Carlo version of the approach is developed and it is shown under some assumptions that for a given level of mean square error, this method for ABC has a lower cost than i.i.d. sampling from the most accurate ABC approximation. Several numerical examples are given.     

Drevogenin A und Drevogenin B,zusätzlicher Strukturbeweis. Glykoside und Aglykone, 306. Mitteilung

Drevogenin B is shown to be 11-O-acetyl-drevogenin P. The earlier derived structure for drevogenin A (11-O-acetyl-drevogenin P) is further confirmed by conversion of 3-O-acetyl-drevogenin A.     

Evaluation of the aquifer characteristics of the basaltic terrain of Maharashtra in India

The paper attempts to evaluate the permeability data obtained from 75 aquifer performance tests conducted on open wells tapping the water table aquifer of the basaltic lava flows spread over the three different basins of Maharashtra. The permeability has been computed by Thiem’s formula and the modified Theis non-equilibrium formula. The statistical analysis of the permeability data of the study basins,viz., Bhima, Godavari and Wardha, reveal a decrease in permeability range as one proceeds from the Bhima basin (low rainfall area) through the Godavari basin (assured rainfall area) to the high rainfall area of Wardha basin. The permeability frequency graphs of the three study basins reveal different hydrogeological characteristics for each.