A quantum chemical study on the formation of ethanimine (CH<Subscript>3</Subscript>CHNH) in the interstellar ice

Ethanimine (CH₃CHNH) is an important prebiotic molecule since it is a precursor of amino acid \(\alpha \)-alanine in Strecker synthesis. Two isomers (E and Z) of ethanimine were detected in the molecular cloud Sagittarius B2 north during GBT-PRIMOS survey. A possible radical-molecule reaction pathway has been proposed for the formation of ethanimine in the interstellar medium (ISM) from some previously detected interstellar molecules like methylene (both triplet CH₂ (³B₁) and singlet CH₂ (¹A₁)) and methyenimine (CH₂NH). The mechanism has been studied in the gas phase and in water ice with the help of density functional theory at B2PLYPD/6-311++G (2d, p) level of theory. It is observed that E-ethanimine forms efficiently in gas phase but ice reactions are favorable only in the hot core of molecular clouds. Same is true for the formation of Z-ethanimine which forms only at the surface of water cluster as the height of entrance barrier for formation of Z-ethanimine is similar to that of E-ethanimine. Isomerization from E to Z form is also studied and found to be forbidden due to large entrance barrier. Out of the two reaction system CH₂ (³B₁) + CH₂NH and CH₂ (¹A₁) + CH₂NH, later is more favorable then the former one due to the small entrance barrier. Still, much of the detected abundance of ethanimine comes from the reaction of CH₂ (³B₁) with CH₂NH as since CH₂ (¹A₁) has very low abundance compared to the CH₂ (³B₁) in ISM. The proposed pathway seems to be a promising candidate for the ethanimine formation in ISM.     

Suggestion for searh of ethylene oxide ($$-C2H4O) in a osmi objet

Ethylene oxide (\(c\)-C₂H₄O) and its isomer acetaldehyde (CH₃CHO) are important organic molecules because of their potential role in the formation of amino acids. The \(c\)-C₂H₄O molecule is a \(b\)-type asymmetric top molecule and owing to half-spin of each of the four hydrogen atoms, it has two distinct ortho (nuclear spin one) and para (nuclear spin zero and two) species. It has been detected in the Sgr B2N. Using the rotational and centrifugal distortion constants along with the electric dipole moment, we have calculated energies of 100 rotational levels of each of the ortho and para species of \(c\)-C₂H₄O molecule and the Einstein \(A\)-coefficients for radiative transitions between the levels. The values of Einstein \(A\)-coefficients along with the scaled values for the collisional rate coefficients are used for solving a set of statistical equilibrium equations coupled with the equations of radiative transfer.Brightness-temperatures of five rotational transitions of each of the ortho and para species of \(c\)-C₂H₄O molecule are investigated. Out of these ten transitions, three transitions are found to show the anomalous absorption and rest seven are found to show the emission feature. We have also investigated seven transitions observed unblended in the Sgr B2(N). We have found that the transitions \(3_{3 0} - 3_{2 1}\) (23.134 GHz), \(2_{2 0} - 2_{1 1}\) (15.603 GHz), \(3_{3 1} - 3_{2 2}\) (39.680 GHz) and \(1_{1 1} - 0_{0 0}\) (39.582 GHz) may play important role for the identification of ethylene oxide in a cosmic object.     

Slippage of Jets Explained by the Magnetic Topology of NOAA Active Region 12035

We present the investigation of 11 recurring solar jets that originated from two different sites (site 1 and site 2) close to each other (\({\approx}\,11~\text{Mm}\)) in NOAA active region (AR) 12035 during 15?–?16 April 2014. The jets were observed by the Atmospheric Imaging Assembly (AIA) telescope on board the Solar Dynamics Observatory (SDO) satellite. Two jets were observed by the telescope of the Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital, India, in H\(\upalpha\). On 15 April, flux emergence is strong in site 1, while on 16 April, flux emergence and cancellation mechanisms are involved in both sites. The jets of both sites have parallel trajectories and move to the south with a speed between 100 and 360 km?s^?1. The jets of site 2 occurred during the second day have a tendency to move toward the jets of site 1 and merge with them. We conjecture that the slippage of the jets could be explained by the complex topology of the region, which included a few low-altitude null points and many quasi-separatrix layers (QSLs), which could intersect with one another.     

Scanning sky monitor (SSM) onboard AstroSat

Scanning Sky Monitor (SSM) onboard AstroSat is an Xray sky monitor in the soft X-ray band designed with a large field of view to detect and locate transient X-ray sources and alert the astronomical community about interesting phenomena in the X-ray sky. SSM comprises position sensitive proportional counters with 1D coded mask for imaging. There are three detector units mounted on a platform capable of rotation which helps covering about 50% of the sky in one full rotation. This paper discusses the elaborate details of the instrument and few immediate results from the instrument after launch.     

Grey wolf optimizer: a new strategy to invert geophysical data sets

There is no meta‐heuristic approach best suited for solving all optimization problems making this field of study highly active. This results in enhancing current approaches and proposing new meta‐heuristic algorithms. Out of all meta‐heuristic algorithms, swarm intelligence is preferred as it can preserve information about the search space over the course of iterations and usually has fewer tuning parameters. Grey Wolves, considered as apex predators, motivated us to simulate Grey Wolves in the optimization of geophysical data sets. The grey wolf optimizer is a swarm‐based meta‐heuristic algorithm, inspired by mimicking the social leadership hierarchy and hunting behaviour of Grey Wolves. The leadership hierarchy is simulated by alpha, beta, delta and omega types of wolves. The three main phases of hunting, that is searching, encircling and attacking prey, is implemented to perform the optimization. To evaluate the efficacy of the grey wolf optimizer, we performed inversion on the total gradient of magnetic, gravity and self‐potential anomalies. The results have been compared with the particle swarm optimization technique. Global minimum for all the examples from grey wolf optimizer was obtained with seven wolves in a pack and 2000 iterations. Inversion was initially performed on thin dykes for noise‐free and noise‐corrupted (up to 20% random noise) synthetic data sets. The inversion on a single thin dyke was performed with a different search space. The results demonstrate that, compared with particle swarm optimization, the grey wolf optimizer is less sensitive to search space variations. Inversion of noise‐corrupted data shows that grey wolf optimizer has a better capability in handling noisy data as compared to particle swarm optimization. Practical applicability of the grey wolf optimizer has been demonstrated by adopting four profiles (i.e. surface magnetic, airborne magnetic, gravity and self‐potential) from the published literature. The grey wolf optimizer results show better data fit than the particle swarm optimizer results and match well with borehole data.     

Importance Profiles for Water Vapor

Motivated by the scientific desire to align observations with quantities of physical interest, we survey how scalar importance functions depend on vertically resolved water vapor. Definitions of importance begin from familiar examples of water mass I ^m and TOA clear-sky outgoing longwave flux I ^OLR, in order to establish notation and illustrate graphically how the sensitivity profile or “kernel” depends on whether specific humidity S, relative humidity R, or ln(R) are used as measures of vapor. Then, new results on the sensitivity of convective activity I ^con to vapor (with implied knock-on effects such as weather prediction skill) are presented. In radiative-convective equilibrium, organized (line-like) convection is much more sensitive to moisture than scattered isotropic convection, but it exists in a drier mean state. The lesson for natural convection may be that organized convection is less susceptible to dryness and can survive and propagate into regions unfavorable for disorganized convection. This counterintuitive interpretive conclusion, with respect to the narrow numerical result behind it, highlights the importance of clarity about what is held constant at what values in sensitivity or susceptibility kernels. Finally, the sensitivities of observable radiance signals I ^sig for passive remote sensing are considered. While the accuracy of R in the lower free troposphere is crucial for the physical importance scalars, this layer is unfortunately the most difficult to isolate with passive remote sensing: In high emissivity channels, water vapor signals come from too high in the atmosphere (for satellites) or too low (for surface radiometers), while low emissivity channels have poor altitude discrimination and (in the case of satellites) are contaminated by surface emissions. For these reasons, active ranging (LiDAR) is the preferred observing strategy.     

Investigation of Hemispherical Variations of Soft X-Ray Solar Flares during Solar Cycles 21 to 24

Solar System Research - In the current investigation we have studied the distribution as well as the asymmetry of solar X-ray flares during the period 1976–2017 which corresponds to solar...     

Fundamental yet simplified model for liquefaction instability

A fundamental procedure is proposed for the identification of liquefaction in saturated soils based on the instability in the material's microstructure. The disturbed state concept (DSC) provides a unified constitutive model for the characterization of entire stress–strain behaviour under cyclic loading, and the values of disturbance at threshold states in the deforming microstructure provides the basis for the identification of liquefaction. The procedure is verified with respect to laboratory behaviour of two sands, saturated Ottawa and Reid Bedford. A mathematical analysis of the DSC constitutive matrix is also performed. Procedures for the application of the DSC for simplified analysis and design, and in finite element procedures are presented. It is believed that the proposed model can provide a fundamental yet simplified procedure for liquefaction analysis, and as a result, it is considered to be an improvement over the available empirical and energy-based procedures. © 1998 John Wiley & Sons, Ltd.