Structure and ionization energies of some analogues of iron-only hydrogenases studied by density functional theory methods

Density functional theory calculations using both the B3LYP and BP86 functional in conjunction with a medium and large size basis set have been used to predict the structures and ionization energies of 12 models of iron-only hydrogenases. Although the structural predictions do not allow a clear discrimination between the different computational models, these models do yield significantly different adiabatic and vertical ionization energies. The closest agreement with experiment is given by the BP86 functional and the large all-electron basis. At this level of theory the adiabatic ionization energies are very close to experiment, but the vertical values are uniformly too small, leading to an underestimation of the reorganization energies. The calculations also suggest that measured ionization energies may help in identifying both the bridge-head group and whether CO bridging takes place upon ionization.     

Plasma-Spray Ionization (PLASI): A Multimodal Atmospheric Pressure Ion Source for Liquid Stream Analysis

A new ion generation method, named plasma-spray ionization (PLASI) for direct analysis of liquid streams, such as in continuous infusion experiments or liquid chromatography (LC), is reported. PLASI addresses many of the analytical limitations of electrospray ionization (ESI) and has potential for real time process stream analysis and reaction monitoring under atmospheric conditions in non-ESI friendly scenarios. In PLASI-mass spectrometry (MS), the liquid stream is pneumatically nebulized and partially charged at low voltages; the resultant aerosol is thus entrained with a gaseous plasma plume from a distal glow discharge prior to MS detection. PLASI-MS not only overcomes ESI-MS limitations but also generates simpler mass spectra with minimal adduct and cluster formation. PLASI utilizes the atomization capabilities of an ESI sprayer operated below the ESI threshold to generate gas-phase aerosols that are then ionized by the plasma stream. When operated at or above the ESI threshold, ionization by traditional ESI mechanisms is achieved. The multimodal nature of the technique enables readily switching between plasma and ESI operation. It is expected that PLASI will enable analyzing a wide range of analytes in complex matrices and less-restricted solvent systems, providing more flexibility than that achievable by ESI alone. Figure

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An Effective Approach for Coupling Direct Analysis in Real Time with Atmospheric Pressure Drift Tube Ion Mobility Spectrometry

Drift tube ion mobility spectrometry (DTIMS) has evolved as a robust analytical platform routinely used for screening small molecules across a broad suite of chemistries ranging from food and pharmaceuticals to explosives and environmental toxins. Most modern atmospheric pressure IM detectors employ corona discharge, photoionization, radioactive, or electrospray ion sources for efficient ion production. Coupling standalone DTIMS with ambient plasma-based techniques, however, has proven to be an exceptional challenge. Device sensitivity with near-ground ambient plasma sources is hindered by poor ion transmission at the source–instrument interface, where ion repulsion is caused by the strong electric field barrier of the high potential ion mobility spectrometry (IMS) inlet. To overcome this shortfall, we introduce a new ion source design incorporating a repeller point electrode used to shape the electric field profile and enable ion transmission from a direct analysis in real time (DART) plasma ion source. Parameter space characterization studies of the DART DTIMS setup were performed to ascertain the optimal configuration for the source assembly favoring ion transport. Preliminary system capabilities for the direct screening of solid pharmaceuticals are briefly demonstrated. Figure

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Synthesis and Spectroscopic Distinction of Benzonaphthonaphthyridine and Its Isomer

Distinction of benzo[h]naphtho[1,2-b][1,6]naphthyridine and its isomeric benzo[b]naphtho[1,2-h][1,6]naphthyridine is well explained on the basis of various spectroscopic techniques. Initially these isomers were prepared from their respective chloroquinolines via anilinoquinolines as potential intermediates. Spectroscopic dissimilarities of their precursors and intermediates have also been considered and compared with the final benzonaphthonaphthyridine isomers.     

Assessing the mechanical,phase inversion,and rheological properties of poly-[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyvalerate] (PHBV) blended with poly-(l-lactic acid) (PLA)

Poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly-(l-lactic acid) (PLA) have attracted much interest in recent years since they are biodegradable, thus can replace synthetic non-degradable materials. In this study, improvements of PHBV, mechanical, phase inversions, and rheological properties were investigated after blending with PLA in varying ratio’s. Three different blends of commercially available PLAs with 92–98% l-lactide units and one grade of PHB with 5% valerate content were blended using a micro-compounder at 175 °C. The composition of PHBV in blends ranged from 50% to 80%. With the addition of PLA, increases in the flexural strength and elastic modulus were observed for several blends, while minor to no changes were detected in the elongation at break and tensile strength as compared to pure PHBV material. Like many conventional plastics, the complex viscosity decreased with increasing rotational frequency due to decreasing entanglements and molecular weight. The complex viscosity with respect to time was very stable for the blends, but no improvements in the PHBV viscosity were observed with the addition of PLA at 170 °C. Three phase inversion models were used to predict the continuity of the blends, and the results showed both dual- and PLA-continuity phase for the blends. In summary, the mechanical results showed improvements in the tensile and flexural properties, while the rheological observation showed minor improvements in the complex viscosity for numerous concentrations.     

New Effective Synthetic Method for Preparation of N,N-Dichlorocarbamates

A rapid, efficient, economical, and easy-to-scale method for the effective conversion of carbamates to corresponding N,N-dichlorocarbamates by using sodium hypochlorite in acidic medium has been described. N,N-Dichlorocarbamates were obtained in quantitative yield through a simple workup in reduced reaction time.

Pressure distribution on a roof in presence of the Moving Surface Boundary-layer Control

The paper studies effect of momentum injection, accomplished through circular cylindrical rotating elements, on the pressure distribution at the roof of a model house. Extensive wind tunnel tests, complemented by flow visualization, suggest that such Moving Surface Boundary-layer Control (MSBC) effectively delays separation and significantly increases the pressure, both on leeward and windward surfaces. This would assist in protection of the roof against wind storms and snow accumulation.     

On the effect of SHI irradiation on dielectric properties of Y3+xFe5−xO12 (x=0.0–0.6) system

The present work aims to investigate the pre- and post-effect of 50 MeV Li³⁺ ion irradiation at a fluence of 5×10¹³ ions/cm² on the dielectric properties of Y_3+xFe_5?xO₁₂, x=0.0, 0.2, 0.4 and 0.6, garnet system over broad temperature, 300–673 K, and frequency, 100 Hz–13 MHz, ranges. Thermal variation of ac resistivity measurements suggests that the mechanism responsible for conduction in the system is polaron hopping. The observed modifications in dielectric properties after swift heavy ion irradiation are mainly due to the modifications of the metal–insulator contacts due to radiation damage-induced disorder and irradiation-induced point/cluster of defects in the material and also compressive strain generated in the lattice structure. The electric modulus presentation and the complex impedance spectral analysis have been employed to study the relaxation process. The YFeO₃ phase is found to be irradiation hard phase as compared with the garnet phase.