Enantioselective Organo‐Photocatalysis Mediated by Atropisomeric Thiourea Derivatives

Can photocatalysis be performed without electron or energy transfer? To address this, organo‐photocatalysts that are based on atropisomeric thioureas and display lower excited‐state energies than the reactive substrates have been developed. These photocatalysts were found to be efficient in promoting the [2+2] photocycloaddition of 4‐alkenyl‐substituted coumarins, which led to the corresponding products with high enantioselectivity (77–96 % ee) at low catalyst loading (1–10 mol %). The photocatalytic cycle proceeds by energy sharing via the formation of both static and dynamic complexes (exciplex formation), which is aided by hydrogen bonding.     

Distribution of uranium in groundwaters of Bathinda and Mansa districts of Punjab,India: inferences from an isotope hydrochemical study

This paper presents the isotope hydrochemical results of groundwaters from southwest Punjab for assessing the uranium contamination and evaluating the factors leading to elevated uranium concentration. A total of 35 samples covering shallow and deep zones were collected for hydrochemistry and isotopes. Uranium concentration ranges between 2.3 and 357 µg L^?1 and 66% of the samples are contaminated. Both shallow and deep zones show U contamination but high incidences are noticed in shallow zone. Hydrochemical correlations infer geological sources rather than anthropogenic sources responsible for U contamination. Isotopically there is no clear distinction between high and low U groundwater.     

The renaissance in redox flow batteries

Although redox flow batteries were invented as early as 1954, no system development took place until NASA demonstrated an Fe/Cr redox flow battery system in 1970s. In hibernation for several years, redox flow battery systems have begun to catch the attention of policy makers globally. The resurrection of redox flow batteries rests heavily on their techno-economic feasibility as large-scale energy storage systems for emerging grid network that are being developed by climate change mitigation industries, namely, wind and solar. This article reviews various redox flow battery technologies with a cost and market prognosis.     

Molecular fine structure and transition dipole moment of NO2 using an external cavity quantum cascade laser

Rotational vibrational fine structure and transition dipole moment of NO₂ is measured using Doppler free saturation spectroscopy with an external grating cavity quantum cascade laser (QCL). The QCL wavelength is calibrated using a 310 cm long internally coupled Fabry–Perot interferometer. We obtain a frequency splitting of 139.68 ± 0.06 MHz (0.0047 cm⁻¹) between the spin doublets (17) of 000 → 001 transition of NO₂. The resolution of the QCL based saturation spectrometer is limited by the QCL linewidth of 3.99 MHz ( 0.00013 cm⁻¹) deduced from the half width of the Lamb dips. The Lamb dip spectroscopy is utilized to obtain a vibrational dipole moment of 0.37 Debye for the (17) transitions.     

Synthesis of NaP zeolite at room temperature and short crystallization time by sonochemical method

NaP zeolite nano crystals were synthesized by sonochemical method at room temperature with crystallization time of 3 h. For comparison, to insure the effect of sonochemical method, the hydrothermal method at conventional synthesis condition, with same initial sol composition was studied. NaP zeolites are directly formed by ultrasonic treatment without the application of autogenous pressure and also hydrothermal treatment. The effect of ultrasonic energy and irradiation time showed that with increasing sonication energy, the crystallinity of the powders decreased but phase purity remain unchanged. The synthesized powders were characterized by XRD, IR, DTA TGA, FESEM, and TEM analysis. FESEM images revealed that 50 nm zeolite crystals were formed at room temperature by using sonochemical method. However, agglomerated particles having cactus/cabbage like structure was obtained by sonochemical method followed by hydrothermal treatment. In sonochemical process, formation of cavitation and the collapsing of bubbles produced huge energy which is sufficient for crystallization of zeolite compared to that supplied by hydrothermal process for conventional synthesis. With increasing irradiation energy and time, the crystallinity of the synthesized zeolite samples increased slightly.     

Effects of periodic masker interruption on the intelligibility of interrupted speech

When listeners hear a target signal in the presence of competing sounds, they are quite good at extracting information at instances when the local signal-to-noise ratio of the target is most favorable. Previous research suggests that listeners can easily understand a periodically interrupted target when it is interleaved with noise. It is not clear if this ability extends to the case where an interrupted target is alternated with a speech masker rather than noise. This study examined speech intelligibility in the presence of noise or speech maskers, which were either continuous or interrupted at one of six rates between 4 and 128 Hz. Results indicated that with noise maskers, listeners performed significantly better with interrupted, rather than continuous maskers. With speech maskers, however, performance was better in continuous, rather than interrupted masker conditions. Presumably the listeners used continuity as a cue to distinguish the continuous masker from the interrupted target. Intelligibility in the interrupted masker condition was improved by introducing a pitch difference between the target and speech masker. These results highlight the role that target-masker differences in continuity and pitch play in the segregation of competing speech signals.     

Enhanced ionic conductivity in La3+ and Sr2+ co-doped ceria: carbonate nanocomposite

Ionics - A series of ceria-based nanocomposites consisting of Ce0.85La0.125Sr0.025O1.9125 (LSCO) and binary carbonate mixture Li2CO3–Na2CO3 (LNCO) have been prepared as functional...     

Constructing Potential Energy Surface with Correlated Theory for Dipeptides Using Molecular Tailoring Approach

We demonstrate a cost-effective alternative employing the fragment-based molecular tailoring approach (MTA) for building the potential energy surface (PES) for two dipeptides viz. alanine-alanine and alanine-proline employing correlated theory, with augmented Dunning basis sets. About 1369 geometries are generated for each test dipeptide by systematically varying the dihedral angles and . These conformational geometries are partially optimized by relaxing all the other Z-matrix parameters, fixing the values of and . The MP2 level PES is constructed from the MTA-energies of chemically intact geometries using minimal hardware. The fidelity of MP2/aug-cc-pVDZ level PES is brought out by comparing it with its full calculation counterpart. Further, we bring out the power of the method by reporting the MTA-based CCSD/aug-cc-pVDZ level PES for these two dipeptides containing 498 and 562 basis functions respectively.     

ChemInform Abstract: High Pressure Phase Transitions in Scheelite Structured Fluoride: ErLiF4.

ErLiF₄ is prepared by solid state reaction of stoichiometric amounts of LiF and ErF₃ (1.