The nature of static and dynamic correlation in nearly degenerate singlet and triplet states of N-heterocyclic chromophores

In this paper we investigate the role of electron correlation in predicting the S$_1$-S$_0$ and T$_1$-S$_0$ excitation energies and hence, the singlet-triplet gap ($\Delta$E$_{ST}$) in a set of cyclazines which act as templates for potential candidates for 5th generation Organic Light Emitting Diode (OLED) materials. This issue has recently garnered much interest with the focus being on the inversion of the $\Delta$E$_{ST}$, although experiments have indicated near degenerate levels with both positive and negative being within the experimental error bar (J. Am. Chem. Soc., 102: 6068 , J. Am. Chem. Soc., 108: 17 ). We have carried out a systematic and exhaustive study of various excited state electronic structure methodologies and identified the strengths and shortcomings of the various approaches and approximations in view of this challenging case. We have found that near degeneracy can be achieved either with a proper balance of static and dynamic correlation in multireference theories or with state-specific orbital corrections including its coupling with correlation. The role of spin contamination is also discussed. Eventually, this paper seeks to produce benchmark numbers for establishing cheaper theories which can then be used for screening derivatives of these templates with desirable optical and structural properties. Additionally we would like to point out that the use of DLPNO-STEOM-CCSD as the benchmark for $\Delta$E$_{ST}$ (as used in J. Phys. Chem. A, 126: 8: 1378, Chem. Phys. Lett., 779: 138827) is not a suitable benchmark for this class of molecules.Comment: 13 pages, 10 figures, submitted for revie

Non-perturbative calculation of orbital- and spin effects in molecules subject to non-uniform magnetic fields

External non-uniform magnetic fields acting on molecules induce non-collinear spin-densities and spin-symmetry breaking. This necessitates a general two-component Pauli spinor representation. In this paper, we report the implementation of a General Hartree-Fock method, without any spin constraints, for non-perturbative calculations with finite non-uniform fields. London atomic orbitals are used to ensure faster basis convergence as well as invariance under constant gauge shifts of the magnetic vector potential. The implementation has been applied to an investigate the joint orbital and spin response to a field gradient---quantified through the anapole moments---of a set of small molecules placed in a linearly varying magnetic field. The relative contributions of orbital and spin-Zeeman interaction terms have been studied both theoretically and computationally. Spin effects are stronger and show a general paramagnetic behaviour for closed shell molecules while orbital effects can have either direction. Basis set convergence and size effects of anapole susceptibility tensors have been reported. The relation of the mixed anapole susceptibility tensor to chirality is also demonstrated

A local tensor that unifies kinetic energy density and vorticity dependent exchange-correlation functionals

We present a kinetic energy tensor that unifies a scalar kinetic energy density commonly used in meta-Generalized Gradient Approximation functionals and the vorticity density that appears in paramagnetic current-density-functional theory. Both types of functionals can thus be subsumed as special cases of a novel functional form that is naturally placed on the third rung of Jacob's ladder. Moreover, the kinetic energy tensor is related to the exchange hole curvature, is gauge invariant, and has very clearcut $N$-representability conditions. The latter conditions enable the definition of effective number of non-negligible orbitals. Whereas quantities such as the Electron Localization Function can discriminate effective one-orbital regions from other regions, the present kinetic energy tensor can discriminate between one-, two-, three-, and four-or-more orbital regions

Record of the largest big eye hound shark Iago omanensis (Norman, 1939) from Gujarat, North West Coast of India

A female specimen of big eye hound sharkIago omanensis measuring 66 cm was landed at Mangrol fishing harbor on 17th September 2013. The specimen was collected along with 13 others of the same species. I. omanensis was not recorded earlier from Gujarat

Occurrence of a serranid fish, Sacura boulengeri (Heemstra, 1973) at Veraval, Gujarat

On 28th October, 2013, a single specimen of Sacura boulengeri (locally known as ‘Vekhli’) belonging to the family Serranidae was collected from Veraval landing centre. The family serranidae, comprises of three subfamily Serraninae, Epinephelinae and Anthiinae. Fishes belonging to Anthiine are beautifully colored that inhabit coral and deep-reef habitats in tropical and warm temperate seas, and some of these species are taxonomically confusing. Many Anthiine fishes are very few in collection because of their rarit

Occurrence of pelagic thresher shark, Alopias pelagicus Nakamura, 1935 from Porbandar, Gujarat

The red frog crab otherwise called spanner crab is a coastal water species and single representative of genus Ranina under family Raninidea. They prefer to inhabit in bare sandy areas of intertidal and coastal waters of more than 100m depth. Distribution of this crab is confined to tropical and sub topical coastal waters of Indian and Pacific oceans, from the coast of South Africa to Hawaii and the Great Barrier Reef. Occurrence of this species is very sparse in Indian waters and has been recorded once in Gulf of Mannar (Kasinathan et al., 2007)

Feeding habits of milk shark, Rhizoprionodon acutus (Ruppell, 1837) in the Gujarat coastal waters of north-eastern Arabian Sea

The feeding habit of milk shark Rhizoprionodon acutus was investigated in 684 specimens collected along Gujarat coast (India) of north-eastern Arabian Sea from January 2013 to December 2014. The length range of females was 32–89.6 cm and males 33.5–89 cm. The shark foraged on diversified prey items which were pooled into four distinct groups i.e., teleosts, crustaceans, mollusks and annelids. Teleosts (Dietary coefficient, %QI = 83.05 and index of relative importance, %IRI = 78.40) were found to be the preferred food items followed by crustaceans (%QI = 16.21; %IRI = 19.78), which formed the secondary food item group. Mollusks (%QI = 0.74; %IRI = 1.69) and annelids (%QI = 0.01; %IRI = 0.14) constituted the accidental or accessory food items. The species, though is a pelagic predator, probably performs vertical movements in search of prey items. The shark also showed some sorts of preference and selectivity for clupeids, engraulids and carangids. Females though showed significantly lower index of relative fullness (IRF) (P ≤ 0.5) and comparatively lower vacuity index and lower mean number of preys per stomach compared to the males, the preference for prey items was not found to be significantly different between the females and males. Juveniles were found to have significantly higher IRF (P ≤ 0.5) and comparatively higher vacuity index than that of the adults, whereas the mean preys per stomach was found to be lower than that of the adults. Moreover, the prey preference was also significantly different between the juveniles and adults. The study provides necessary baseline information about the feeding habits of the shark in the region which will be helpful in understanding the trophodynamics of the species under the influence of overfishing and climate change

Population dynamics and stock assessment of spadenose shark Scoliodon laticaudus Muller and Henle 1839 along Gujarat coast of India

423-433Stock assessment of Scoliodon laticaudus Muller and Henle, 1839 was made along with analysis of its few biological characteristics from its commercial landings during 2012-2016 from Gujarat waters of India to understand the population dynamics and stock status of the species. The average annual landing of the species was 5442 t, which constituted about 67% of the total shark landings at Gujarat coast. L∞, K and t0 were estimated as 75.53 cm and 0.54/yr, and -0.4 yr, respectively. Total mortality rate, fishing mortality rate and natural mortality rate were estimated as 1.95 yr-1, 1.04 yr-1 and 0.91 yr-1, respectively. The length at capture (Lc50) and length at maturity (Lm50) were 39.74 cm and 35.79 cm, respectively, which indicate that most of the sharks are exploited after attaining the sexual maturity. Length-weight relationship showed that the growth was isometric. The species was a continuous breeder and showed peak recruitment during September. The current exploitation ratio (Ecur) was found to be 0.53, which is lower than E0.1 estimated for the species using Beverton and Holt yield per recruit analysis. Thompson and Bell prediction model showed that maximum sustainable yield for S. laticaudus could be obtained by increasing fishing effort by almost 2.4 times higher than the present level which would deplete the spawning stock biomass (SSB) to 20%. Maximum economic yield could be obtained by increasing the fishing effort by 1.8 times which would also decrease the SSB, but to a comparatively safer 26.5% level. Considering 30% SSB as a precautionary management reference point, the effort could be increased by 50% exclusively for the sharks to increase the yield and revenue from fishery while maintain SSB at a safer 30% level

Egg case of Arabian carpet shark, Chiloscyllium arabicum from Gujarat

It is common in the waters off Gujarat. The shark which is a bottom dwelling species predominantly inhabits coral reefs, lagoons, rocky shores and mangrove estuaries, between depths of 3-100 m on the bottom. It has been reported that the species grows up to 70 cm and matures between 45- 54 c