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Articles by Sandeep Kumar
Total Records ( 7 ) for Sandeep Kumar
  Ghulam Abbas , Sonny Irawan , Sandeep Kumar , Khalil Rehman Memon and Shuaib Ahmed Khalwar
  Polymers have been used in oil well cementing for improving the properties of cement slurry. Polysaccharides and their derivatives are mostly used as multifunctional additive in cement slurry. But these polymers present number of limitations at high temperature. Polysaccharides do not reveal an appropriate thickening of viscosity in cement slurry at high temperature which turn gives the fluid loss, gas migration and loss of economics. It is necessary to use such type of polymer in cement slurry that increases viscosity at high temperature. Therefore, this study present Hydroxypropylmethylcellulose (HPMC) polymer that is able to increase viscosity at high temperature and improve the properties of cement slurry. Laboratory experiments were performed to determine the characteristics of HPMC based cement slurry. The viscosity of 2 wt.% solution of HPMC polymer was determined at various temperatures. Further 0.20-0.50 gallon sack-1 concentration of HPMC polymer was used in cement slurry to evaluate the API properties of HPMC based cement slurry in term of rheology, free water, fluid loss, thickening time and compressive strength. It was observed that HPMC polymer was stable at high temperature and increases viscosity at elevated temperature. In cement slurries HPMC polymer resulted less than 50 mL of fluid loss; zero free water and predictable thickening time as well as enhanced final compressive strength with some other additives. The experimental result showed that HPMC has significantly improved the properties of cement slurry at high temperature.
  Santanu Kumar Pal , Sandeep Kumar and Jhumur Seth
  Microwave-promoted synthesis of novel rufigallol-based liquid crystalline oligomers, containing six rod-like cyanobiphenyl moieties connected to the rufigallol core via flexible alkyl spacers, is reported. The synthesis of the target compounds was challenging since classical reactions failed to produce these oligomers. Differential scanning calorimetry and polarising optical microscopy analysis revealed the existence of a nematic phase with a shorter spacer and a smectic A (SmA) phase with a longer spacer. The compound with medium alkyl spacer exhibits both nematic and SmA phases at higher temperature and a re-entrant nematic phase at lower temperature.
  Md Lutfor Rahman , Jahimin Asik , Sandeep Kumar and Carsten Tschierske
  Three banana-shaped monomers, i.e. 2,7-naphthalene bis[4-(4-allyloxyphenylazo)-benzoate], 2,7-naphthalene bis[4-(4-allyloxy-3-fluorophenylazo)benzoate] and 2,7-naphthalene bis{4-[4-(10-undecenyloxy)phenylazo]benzoate}, containing azobenzene as side arms, 2,7-dihydroxynaphthalene as central units and terminal double bonds as polymerisable functional groups, were synthesised and their mesophase behaviour investigated. Polarizing optical microscopy and DSC measurements reveal that all compounds exhibit nematic mesophases. The absorption spectrum of the trans-azobenzene groups displays a high-intensity π-π* transition at about 365 nm and a low-intensity n-π* transition at around 450 nm for all compounds. Hence, photochromism can be achieved by the introduction of the azo linkage to banana-shaped liquid crystals molecules.
  Sandeep Kumar
  The hierarchical self-assembly of disc-shaped molecules leads to the formation of discotic liquid crystals. These intriguing materials are of fundamental importance not only as models for the study of energy and charge migration in self-organised systems, but also as functional materials for various device applications. This has fostered numerous developments in this field. In this article, we have summarised the author's and the collaborators' research work on discotic liquid crystals.
  Hari Krishna Bisoyi and Sandeep Kumar
  Synthetic carbon allotropes such as fullerene, carbon nanotubes and graphene exhibit a liquid crystalline phase behaviour upon appropriate chemical functionalisation and/or physical dispersion in suitable media. This article deals with both thermotropic and lyotropic liquid crystalline phases obtained from these isotropic and anisotropic carbon building blocks along with the carbonaceous mesophase. Different strategies adopted to obtain such ordered fluid phases of carbon are summarised and their subsequent exploitation in the fabrication of carbon-based materials and devices are highlighted. Fluid phase assembly of carbon materials seems to be very promising in the context of high-performance films, fibres and carbon electronics.
  Satish Tiwari , Arvind Arya and Sandeep Kumar
  The present investigation is an attempt towards finding an effective sterilization protocol for two, field grown sugarcane varieties, CoS 88230 and CoS 767 from Meerut region and to establish the callus culture protocol. Four sterilizing agents EtOH, NaOCl, HgCl2 and H2O2 were used alone and in combination. Our finding suggests that the use of only one sterilizing agent is not successful for the sterilization of leaf sheath explant of sugarcane. HgCl2 (0.1%) for 5 min and EtOH (90%) for 10 min was found best when used along with prior washing and surface sterilization with 20 and bavistin. An increased response of callus initiation was achieved on MS medium supplemented with 2,4-D (1 mg L-1) and antibiotic amoxicillin (2 mL L -1). present research attempt will allow mass multiplication of economically important sugarcane varieties through tissue culture technology can be used further to complete the demand of farmer for the planting material of the genetically superiors sugarcane varieties.
  Subodh Kumar and Sandeep Kumar
  1,3- and 1,4-bis-[1-(4-nitrophenyl)-benzimidazolium-3-methylene]benzene-based molecular probes interact selectively with cyanide ion to switch the absorbance from 270 nm to 376 nm and elaborate ratiometric chromogenic probes for the estimation of 1–270 μM cyanide ion—the desirable concentration range for practical applications.
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