Recent Research Highlights


https://sites.google.com/a/gauhati.ac.in/research/#kb Probing the neutrinos at DUNE 

https://sites.google.com/a/gauhati.ac.in/research/#sk Gravitational theories at galactic centre 

https://sites.google.com/a/gauhati.ac.in/research/#bks Fabrication of Ag/ZnO heterostructure

https://sites.google.com/a/gauhati.ac.in/research/#rt1 Synthesis of Olanzapine salts

https://sites.google.com/a/gauhati.ac.in/research/#rg Solitary waves in dusty plasmas

 Drug-drug, drug-nutraceutical cocrystal

 C-H functionalization in water
Probing the neutrinos

Dr Kalpana Bora and her collaborators explore the physics of Majorana neutrinos with reference to the Deep Underground Neutrino Experiment near Fermilab (DUNE, formerly LBNE). This work is published in Physical Review D.



Authors
Kalpana Bora, Debasish Borah, and Debajyoti Dutta

Abstract
This study probes different texture zero neutrino mass matrices at long baseline neutrino experiment DUNE particularly focusing on its sensitivity to the octant of atmospheric mixing angle θ23 and leptonic Dirac CP phase δcp. Assuming a diagonal charged lepton basis and Majorana nature of light neutrinos, the authors first classify the possible light neutrino mass matrices with one and two texture zeros and then numerically evaluate the parameter space which satisfies the texture zero conditions. Apart from using the latest global fit values of neutrino oscillation parameters, they also use the latest bound on the sum of absolute neutrino masses (Σi|mi|) from the Planck mission data and the updated bound on effective neutrino mass Mee from neutrinoless double beta decay (0νββ) experiment to find the allowed Majorana texture zero mass matrices. For the allowed texture zero mass matrices from all these constraints, they then feed the corresponding light neutrino parameter values satisfying the texture zero conditions into the numerical analysis in order to study the capability of DUNE to allow/exclude them once it starts taking data. The authors also find that the DUNE will be able to exclude some of these texture zero mass matrices which restrict the (θ23 − δcp) to a very specific range of values, depending on the values of the parameters that Nature has chosen.

Journal Reference
https://sites.google.com/a/gauhati.ac.in/research/physics/#top 




Gravitational theories near the galactic centre

Dr Sanjeev Kalita explores the properties of gravity near the galactic centre, the telltale sign of which may be detected by the Extremely Large Telescope (ELT). This work is published in Astrophysical Journal.

https://en.wikipedia.org/wiki/Extremely_Large_Telescope


Author
Sanjeev Kalita

Abstract
The author has used the Parameterised Post Newtonian (PPN) framework of General Relativity to examine the modification of the law of gravity near the Galactic Centre Black Hole, Sgr A*. Quantum gravity near black hole singularities largely expect such modifications. This is the first astrophysical test of new gravitational physics near the Galactic Centre. Periastron anomaly of the S-stars having compact orbits (within the central milli parsec, r = 50-100 au) near the black hole has been used to see the difference between General Relativity and Brans-Dicke scalar-tensor gravity and f(R) theories which are serious rivals to General Relativity and are capable of addressing several cosmological issues. Mild to strong values of spin and quadrupole of the black hole have been used. Possibility of detection of such deviation through upcoming astrometric observations of the Extremely Large Telescopes (ELTs) are discussed. New observational strategies for measuring the black hole spin and extracting modified gravity signals are also suggested. The work also reports possibility of black hole hair and super Kerr spin (naked singularity) which are otherwise unanticipated in existing black hole physics.

Journal Reference
https://sites.google.com/a/gauhati.ac.in/research/#top 




Fabrication of Ag/ZnO heterostructure

Dr Bimal Kumar Sarma and his collaborator describe fabrication of Ag/ZnO heterostructure and the role of surface coverage of ZnO microrods by Ag nanoparticles on its photophysical and photocatalytic properties. This work is published in Applied Surface Sceince.



Authors
Bikash Sarma and Bimal K Sarma

Abstract
This report presents findings on microstructural, photophysical, and photocatalytic properties of Ag/ZnO heterostructure grown on flexible and silicon substrates. ZnO microrods are prepared by thermal decomposition method for different solute concentrations and Ag/ZnO heterostructure are fabricated by photo-deposition of Ag nanoparticles on ZnO microrods. X-ray diffraction and electron microscopy studies confirm that ZnO microrods belong to the hexagonal wurtzite structure and grown along [001] direction with random alignment showing that majority microrods are aligned with (100) face parallel to the sample surface. Plasmonic Ag nanoparticles are attached to different faces of ZnO. In the optical reflection spectra of Ag/ZnO heterostructure, the surface plasmon resonance peak due to Ag nanoparticles appears at 445 nm. Due to the oxygen vacancies the band gaps of ZnO microrods turn out to be narrower compared to that of bulk ZnO. The presence of Ag nanoparticles decreases the photoluminescence intensity which might be attributed to the non-radiative energy and direct electron transfer in the plasmon–exciton system. The quenching of photoluminescence in Ag/ZnO heterostructure at different growth conditions depend on the extent of surface coverage of ZnO by plasmonic Ag nanoparticles. Photocatalytic degradation efficiency of Ag/ZnO heterostructure is higher than that of ZnO microrods. The extent of surface coverage of ZnO microrods by Ag nanoparticles is crucial for the observed changes in photophysical and photochemical properties.

Journal Reference
https://sites.google.com/a/gauhati.ac.in/research/#top 




Mechanochemical synthesis of Olanzapine salts and their hydration stability

Dr Ranjit Thakuria and his collaborators study mechanochemical properties of Olanzapine salts using X-ray diffraction. This work is published in Crystal Growth & Design.



Authors
Kashyap Kumar Sarmah, Pranamika Sarma, Dharmaraj R Rao, Poonam Gupta, Naba K Nath, Mihails Arhangelskis, and Ranjit Thakuria

Abstract
A series of olanzapine (OLN) dicarboxylic acid salts including earlier reports on olanzapinium malonate (1:1) and maleate (1:1 and 1:2) were prepared mechanochemically using liquid assisted grinding (LAG) in order to study their hydration stability. Powder X-ray diffraction was used as a characterization tool during the investigation. On the basis of the single crystal structures of respective OLN salts, a negative correlation between the dicarboxylic acid chain length and the hydration stability of the corresponding OLN salt was found. Our observations suggest that the overall crystal packing, beyond the stronger hydrogen bond synthon (N+–H···O– in OLN salts compared to O–H···N in OLN hydrates) plays an important role in designing OLN salts with better hydration stability. In addition, melting point analysis showed that OLN dicarboxylic acid salts follow melting point alteration behavior similar to the pure diacids.

Journal Reference
https://sites.google.com/a/gauhati.ac.in/research/#top 




Solitary waves in dense dusty plasmas

Rajita Goswami analyses a phenomena which is expected to be seen in dense dusty plasmas. This communication is published in Physics of Plasmas.



Authors
Rajita Goswami and Madhurjya P Bora

Abstract
In this report the authors present an analysis of the effect of polarization force on dust acoustic solitons with self-consistent inclusion of the polarization effect into the dust-charging model. This has been carried out considering the dependence of dust-charge number on dust potential which is affected by the polarization force. Their analysis shows that inclusion of polarization effect into the dust-charging model results solitons of much higher amplitudes.

Journal Reference
https://sites.google.com/a/gauhati.ac.in/research/#top 




A
 review on drug-drug and drug-nutraceutical cocrystal/salt

Dr Ranjit Thakuria and his collaborator write about drug-drug and drug-nutraceutical cocrystal/salt in a review article published in the journal Crystals.



Authors
Ranjit Thakuria and Bipul Sarma

Abstract
The pre-formulation of pharmaceutical cocrystals and salts is a concept of crystal engineering that has emerged as a promising technique for drug development in pharmaceutical industry. Recent introduction of pharmaceutical cocrystals in regulatory guidelines of US Food and Drug Administration (FDA) made them one of the potential alternatives when salt preparation is not feasible. Apart from generally regarded as safe (GRAS) coformers, drug‑drug and drug‑nutraceutical cocrystals are recent additions to pharmaceutical cocrystal family that have additional health benefits. Indeed, preparation of salt forms is a routine practice to deal with inadequacies associated with the active pharmaceutical ingredient (API) and happens to be a potentially reliable method. Amongst them, drug-drug and drug-nutraceutical cocrystals have drawn significant importance in the recent past as they reduce drug load and cost effects during multiple disease diagnosis. However, one has to be prudent in the selection of drug molecules, the presence of complementary hydrogen bond synthon, disease management during multiple disease therapy, etc. that play important roles in their preparation. That is the reason why drug–drug cocrystals are scarce in the literature compared to pharmaceutical cocrystals containing GRAS coformers and salt forms. Herein, we discuss case studies preferably the reported drug‑drug, drug‑nutraceutical cocrystals, and a few salts with an emphasis on their role in physicochemical property modulation.

Journal Reference
https://sites.google.com/a/gauhati.ac.in/research/#top 




C
-H functionalization in water in presence of only molecular oxygen

Dr Pranjal K Baruah and his collaborators demonstrate what is believed to be the first example of C-H functionalization in water in presence of only molecular oxygen without any catalyst. The related article is published in journal Green Chemistry.




Authors
Mohit L Deb, Choitanya D Pegu, Paran J Borpatra, Prakash J Saikia, and Pranjal K Baruah
Department of Applied Sciences (Chemical Science Division), GUIST, GU


Abstract
Recently, C-H functionalization has been in the centre of attraction for being atom and step economical, directive, and environment-friendly than cross-coupling reactions which require prefunctionalization of substrates. Multi-component C-H functionalization gained much interest in synthetic chemistry due to their atom economy, easy mode of operation, and energy savings. We have reported catalyst-free 3-component reaction of naphthols, aldehydes and tetrahydroisoquinolines to synthesize 1,3-oxazines. It is one-pot multi-component C-H functionalization reaction carried out in water using only molecular oxygen as the sole oxidant. No catalyst or chemically synthesized oxidant is required for the reaction. We believe, this is the first example of C-H functionalization taking place in water in presence of only molecular oxygen. 


Journal Reference
https://sites.google.com/a/gauhati.ac.in/research/#top