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1.
Debanjan Bhattacharjee Parameswara Rao Alapati 《Molecular Crystals and Liquid Crystals》2017,648(1):66-76
This article represents the electrical studies of an interdigitated highly skewed N(4-n-pentyloxybenzylidene) 4-n-alkylaniline (5O.16) compound. Interestingly the compound is partially bent like and unsymmetrical in alkyl chain length. Dielectric and impedance spectroscopy studies indicate the coupling between the liquid crystal and the electrical field. Studies were carried out as a function of temperature as well as frequency. Semicircular nature of the Cole–Cole plots indicates the reorientation of the molecule with the applied field. Using the experimental data and the theoretically fitted results the effective equivalent model circuit was designed. Which used to explain the behavior of the compound under the external electric effect and the influence of the electrodes with different variable represent the resistor circuit. However, the effect of the conductivity of temperature and frequency are also reported. 相似文献
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Ramanuj Mishra Ayon Bhattacharjee Debanjan Bhattacharjee Keisham Nanao Singh Binod Gogoi 《Liquid crystals》2018,45(9):1333-1341
Raman spectra of pure and 2 wt.% gold nanoparticles (GNPs) dispersed liquid crystalline compound 4-n-Hexyloxy-4?- cyanobiphenyls (6OCB) has been recorded as a function of temperature from room temperature (solid crystal) to 80°C (isotropic liquid) in the spectral region of 500–2500 cm?1. The variation of Raman spectral parameters (peak positions and line width) with temperature is used to explain the changes in molecular alignment and its effect on inter-/intra-molecular interactions at crystal-Nematic (K-N) transition. To understand the change in molecular structure during phase transition and on account of dispersion of gold nanoparticles in pure liquid crystal more precisely, two spectral regions 1000–1500 cm?1 and 1500–2400 cm?1 have been selected separately. From the detailed study, it is concluded that increased orientational/vibrational freedom of the molecules as well as delocalisation of electron clouds results in the spectral anomalies at K-N transition. The geometrical structure of 6OCB was optimised using density functional theory (DFT) and theoretical Raman spectra have been obtained for comparison with experimental spectra. The tentative assignment of vibrational modes observed in our region of study was calculated based on potential energy distribution (PED) using vibrational energy distribution analysis (VEDA) calculation. 相似文献
3.
Debanjan Sarkar 《Polymer Degradation and Stability》2007,92(11):1994-2004
Oxidative and enzymatic degradations of l-tyrosine based polyurethanes were studied for biomaterial applications. Oxidative degradation was performed with 0.1 M cobalt chloride (CoCl2) in hydrogen peroxide solutions at 37 °C and the degradation was assessed by ATR-FTIR. Results indicate that polyurethane with polyethylene glycol (PEG) shows soft segment degradation while polyurethane based on polycaprolactone (PCL) shows hard segment degradation. Enzymatic degradation of the polyurethanes was studied using proteolytic enzyme α-chymotrypsin in phosphate buffer solution (pH 7.4) at 37 °C. The enhanced degradability of l-tyrosine based polyurethanes is due to both the presence of amino acid based chain extender and the action of enzyme. The changes in the morphology of polyurethanes were analyzed by SEM. The results of the degradation study were correlated to the structure of the polyurethanes. 相似文献
4.
In this paper, numerical simulation is conducted to investigate the generation, transmission and detection of a 110 Gbps optical Minimum Shift Keying (MSK) signal. The transmitter has been designed using a Quad Mach-Zehnder IQ Modulator. At the transmitter, a 110 Gbps optical MSK signal with constant envelope and a continuous phase is generated by combining signals of I-arm and \(90^\circ\) phase shifted of Q-arm. Error-free transmission of 110 Gbps optical MSK signal is achieved after traversing a distance of 240 km, also a comparison is made with respect to Differential Phase Shift Keying (DPSK) to show its effectiveness. At the receiver side, the original signal is recovered through a balanced detection method, with a power penalty of around 3.34 dB. Also, BER curves of different bit rates for MSK are studied ranging from 40 to 120 Gbps and found that maximum 110 Gbps can be achieved error-free. The optical spectrum of both MSK and DPSK signals are observed and found that MSK is having narrower main lobes with smaller side lobes compared with that of DPSK, which in turn results in an increase in spectral efficiency and reduction in intersymbol interference. 相似文献
5.
Debanjan Chakraborty Shyamapada Nandi Rahul Maity Dr. Radha Kishan Motkuri Dr. Kee Sung Han Sean Collins Dr. Paul Humble Dr. James C. Hayes Prof. Tom K. Woo Dr. Ramanathan Vaidhyanathan Dr. Praveen K. Thallapally 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(55):12544-12548
Molecular confinement plays a significant effect on trapped gas and solvent molecules. A fundamental understanding of gas adsorption within the porous confinement provides information necessary to design a material with improved selectivity. In this regard, metal–organic framework (MOF) adsorbents are ideal candidate materials to study confinement effects for weakly interacting gas molecules, such as noble gases. Among the noble gases, xenon (Xe) has practical applications in the medical, automotive and aerospace industries. In this Communication, we report an ultra-microporous nickel-isonicotinate MOF with exceptional Xe uptake and selectivity compared to all benchmark MOF and porous organic cage materials. The selectivity arises because of the near perfect fit of the atomic Xe inside the porous confinement. Notably, at low partial pressure, the Ni–MOF interacts very strongly with Xe compared to the closely related Krypton gas (Kr) and more polarizable CO2. Further 129Xe NMR suggests a broad isotropic chemical shift due to the reduced motion as a result of confinement. 相似文献
6.
Ramanuj Mishra Jayanta Hazarika Anil Hazarika Binod Gogoi Ragini Dubey Debanjan Bhattacharjee 《Liquid crystals》2018,45(11):1661-1671
This study focuses on the electrical characteristics of a strongly polar nematic liquid crystal, Hexyloxy-cyanobiphenyl (6OCB), doped with a low concentration (2% by weight) of citrate buffer stabilised gold nanoparticles (GNPs) at low frequencies between 20 Hz and 35 MHz. The doped samples have lower values of nematic–isotropic transition temperature, permittivity (both parallel and perpendicular to the field direction) and dielectric anisotropy; however, relaxation time and activation energy were increased. The observed results could be explained on the basis of weakly anisotropic nature of GNPs and a local rearrangement of liquid crystal molecules surrounding the nanoparticles. Moreover, a complimentary suggestion on a possible change in the dipole–dipole correlation is made to explain the difference in changes (qualitative and quantitative) observed for permittivity of the host nematic liquid crystal doped with GNP. Temperature dependent dielectric relaxation studies indicate an increase in viscosity and potential barrier; and hence a change in strength of inter-molecular and intra-molecular interactions is suggested. 相似文献
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[reaction; see text] A general and practical procedure for the highly diastereoselective preparation of either the cis- or trans-beta,gamma-disubstituted-gamma-butyrolactones by appropriate choice of Lewis or Bronsted acid catalysts during crotylboration or lactonization is reported. The cis-stereochemistry of the Z-crotylboration product can be inverted with strong acids during lactonization. A carbocation mechanism and catalytic cycle has been proposed. 相似文献
9.
Billal Zayat Debanjan Mitra Ahamed Irshad Aravamuthan Sundar Rajan Sri R Narayanan 《Current Opinion in Electrochemistry》2021
The instability of iron under anodic conditions makes iron-based electrode substrates unsuitable for alkaline electrolyzers and rechargeable alkaline batteries. Therefore, significantly more expensive substrates such as nickel foam or sintered nickel are used. Nickel adds a significant cost to electrolysis and energy storage systems. We show that iron substrates can be stabilized using a unique protective thermal coating. These coatings can also yield some of the most electrocatalytically active electrodes in addition to showing no notable change in performance even after 1500 h of anodic polarization. Besides sintered iron, low-carbon steel mesh can be stabilized similarly. Low-carbon steel protected by a thin layer of lithium-doped cobalt spinel was found to be an excellent current collector for positive nickel hydroxide electrodes in alkaline batteries. Thus, surface-modified iron substrates, 40 times less expensive than nickel, are promising for lowering the material costs of alkaline water electrolyzers and rechargeable alkaline batteries. 相似文献
10.
Ramanuj Mishra Ayon Bhattacharjee Debanjan Bhattacharjee Keisham Nanao Singh 《Liquid crystals》2019,46(3):327-339
Temperature-dependent micro-Raman study of C-H in-plane bending mode of aromatic rings, C-N and C=N stretching of linking group (-C(H)=N) and C=C stretching of rings of pure and silver nanoparticles dispersed (0.5% and 1% by weight) Schiff’s base liquid crystal (LC) compound, N-(4-n-heptyloxybenzylidene)-4’-n-butylaniline (7O.4) in 500–2250 cm?1 region has been done. The change in Raman spectral parameters (peak position and linewidth) at crystal–smecticG (K–smG) and smecticG–smecticC (smG–smC) gives the evidence of charge shift at phase transition which is associated with changes in orientation and vibrational freedom of the molecules. The peak position of the Raman bands shows blue shift for 0.5 wt% dispersed sample, whereas it shows red shift for 1 wt% dispersed sample. The blue and red shifts of the Raman bands indicate an increase and decrease in the charge density, respectively. The optimised structure and theoretical room temperature Raman spectra of 7O.4 were obtained using density functional theory. The vibrational assignment using potential energy distribution is reported using vibrational energy distribution analysis (VEDA). 相似文献