A5029174891- Liquid Crystal Research Advancements
- Molecular spectroscopy and chirality
- Microwave Engineering and Waveguides
- Surfactants and Colloidal Systems
- Photoacoustic and Ultrasonic Imaging
- Semiconductor Lasers and Optical Devices
- Superconducting and THz Device Technology
- Photochemistry and Electron Transfer Studies
- Crystallization and Solubility Studies
- Optical Polarization and Ellipsometry
- Gyrotron and Vacuum Electronics Research
- Optical Imaging and Spectroscopy Techniques
- X-ray Diffraction in Crystallography
- Photochromic and Fluorescence Chemistry
- Radio Frequency Integrated Circuit Design
- Thermography and Photoacoustic Techniques
- Antenna Design and Analysis
- Photonic and Optical Devices
- Silicon and Solar Cell Technologies
- Radio Astronomy Observations and Technology
- Melanoma and MAPK Pathways
- Material Properties and Failure Mechanisms
- bioluminescence and chemiluminescence research
- Ultrasound Imaging and Elastography
- Advanced Photonic Communication Systems
Pennsylvania State University
2023-2024
Presidency University
2022
Indian Institute of Engineering Science and Technology, Shibpur
2021
University of Groningen
2019
Indian Association for the Cultivation of Science
1997
North Bengal University
1987-1989
ABSTRACT Observations of the redshifted 21-cm hyperfine line neutral hydrogen from early phases Universe such as Cosmic Dawn and Epoch Reionization promise to open a new window onto formation stars galaxies. We present first upper limits on power spectrum brightness temperature fluctuations in redshift range z = 19.8–25.2 (54–68 MHz frequency range) using 14 h data obtained with LOFAR-Low Band Antenna (LBA) array. also demonstrate application multiple pointing calibration technique calibrate...
Photoacoustic (PA) imaging provides deep tissue molecular of chromophores with optical absorption contrast and ultrasonic resolution. Present PA techniques are predominantly limited to one 2-D plane per acquisition. The ultrasound (US) transducers, required for real-time 3-D imaging, high cost, complex fabricate, have scalability in design. We present novel printed circuit board (PCB)-based matrix US transducer arrays that capable being bulk manufactured at low cost without using laborious...
Abstract Vascular diseases are a leading cause of death and disability worldwide. Despite having precursor conditions like peripheral arterial disease (PAD), they often only diagnosed after the onset stroke or heart attack. Low‐cost, portable, noninvasive, point‐of‐care (POC), label‐free assessment deep vascular function benefits PAD diagnosis, especially in resource poor settings world. Doppler ultrasound‐based blood flow measurements can diagnose PAD, albeit with limited sensitivity...
Abstract We have measured the refractive indices (no , ne ) and densities of four members (nonyl, decyl, undecyl dodecyl) a homologous series cyanobiphenyl alkyl ether over their entire mesomorphic range in isotropic phases. The molecular polarizabilities been calculated from using both Vuks' Neugebauer's relations. additive rule bond has also employed to calculate compounds assuming two different configurations chains. orientational order parameter values at temperatures for each compound...
Abstract The diamagnetic susceptibility of three alkoxyphenyl trans-4-alkyl cyclohexane carboxylates and p-cyanophenyl trans-4-pentyl carboxylate are reported as a function temperature in the solid, nematic isotropic phases. Assuming that molecules effectively axially symmetric, dependence orientational order parameter (P 2) has been investigated from anisotropy at different temperatures. values agree reasonably well with predictions Maier Saupe theory except near clearing point where lower...
A theoretical study of the relationship between electrical series resistance (R/sub s/) an IMPATT diode and threshold current for oscillation corresponding frequency has been carried out, considering inequality ionization rates drift velocities two types charge carriers in silicon. The obtained experimentally by measuring with X-band silicon SDR device embedded a resonant-cap cavity. results indicate that method is suitable one determining R/sub s/, they agree manufacturer's data. would be...
Abstract In this paper we have reported results of X-ray diffraction studies and refractive index measurements the compound p-n-butoxybenzylidene-p'-n-butylaniline (BBBA). The BBBA possesses three smectic phases, cybotactic nematic phase ordinary phase. Orientational order parameters aligned sample been determined using data indices values. (P 2) values from optical agree with Maier-Saupe theoretical but 2), 4) intensity differ
Abstract The refractive indices no, nc and the order parameters are measured as a function of temperature for Schiffs base compound PBBA. From experimental data molecular polarisabilities its anisotropies at different wavelengths calculated using internal field models. merits each model discussed. Order (P 2), 4) other PBBA EBBA also X-ray diffraction techniques temperatures. Comparison with theoretical values shows relative techniques. 2) members Schiff's compounds, already reported from...
Abstract The molecular polarizabilities (α0, αe,) of the four members homologous series cyano-alkyloxy-biphenyl (CnH2n+1.O.φ.φ.CN for n = 5 to 8) in nematic range have been calculated using two different internal field models. additive rule bond has adopted get mean polarizability (α) and principal anisotropy (α1 - α1) values these compounds. orientational order parameters from results. ordering exhibits an odd-even alternation along series. results compared with theories. Possible causes...
Abstract Anisylidene-p-aminophenyl acetate, a nematogenic Schiff's base, is studied by X-ray diffraction and optical methods. Orientational order parameters (P 2) 4) of magnetically aligned samples have been calculated from photographs. Order also determined refractive index measurements. values obtained both the methods agree well with MS while differ much. Average intermolecular distances apparent molecular lengths calculated.
Abstract In this paper we have reported the results of X-ray diffraction studies on magnetically aligned samples four closely related compounds. These compounds are (1) p-methoxy phenyl trans-4-pentyl cyclohexane carboxylate (2) p-propoxy (3) p-ethoxy trans-4-bulyl and (4) p-cyano carboxylate. Structural parameters orientational order been determined at different temperatures. The way in which molecules stacked has discussed.
Abstract The molecular polarizabilities of the homologous series cyano-alkyl-biphenyl (C n H2n+1.φφ.CN for = 5 to 9) have been calculated using two different internal field models. From these values orientational order parameters obtained. ordering exhibits an odd-even alteration along series. variations with increase alkyl chain length are discussed. relative stabilities alkyl-cyano-biphenyls also discussed in terms parameters.
Transparent ultrasound transducers (TUTs) have gained significant traction in the fields of photoacoustic (PA) and (US) applications. TUTs possess unique capability to transmit receive waves while maintaining optical transparency. As a result, simplify PA imaging process facilitate seamless integration with other modalities. However, limited sensitivity has been primary challenge hampering their widespread adoption setups. One often overlooked factor contributing this limitation is...
2-D Ultrasound (US) Transducer (2D-UST) arrays facilitate scan-less volumetric photoacoustic imaging (3D-PAI), but are typically high-cost, involve laborious fabrication process, and permit limited scalability in design with respect to array parameters like element count, aperture size, center frequency ( 𝑓<i><sub>c</sub></i>) pitch. In this work, we report a novel, matrix UST fabricated on printed circuit board (PCB) substrate (2D-PCB-UST array) at low-cost without the need of advanced...
Vascular diseases are a leading cause of death and disability worldwide. Despite having precursor conditions like peripheral arterial disease (PAD), they often only diagnosed after the onset strokes or heart attacks. Low-cost, portable, non-invasive, point-of-care (POC) assessment deep vascular function benefits PAD diagnosis, especially in low-and-middle-income countries. Doppler ultrasound-based blood flow measurements can diagnose PAD, albeit, with limited sensitivity specificity. To...
Abstract The refractive indices (n o , n e ) and densities of two mesogens have been measured in their liquid crystalline phases. molecular polarizabilities (x x were evaluated by Vuks' Neugebauer's relations. thus obtained are compared with those estimated from the bond polarizabilities, orientational order parameters, <P 2 >, mean field theory Maier Saupe, modified Humphries, James Luckhurst. continuum suggested T. E. Faber. We also calculated three parameters (<P ), τ, σ)...
A detailed experimental investigation has been made on the electronic tuning of resonant-cap IMPATT oscillators at X-band. The is extended to include mechanical properties, i.e. studies dependence properties diameter and cap height. study gives an interesting insight regarding behaviour for various ranges d.c. bias current. From these optimum size cavity realizing maximum power output tunability a given diode can be obtained, which would useful in design oscillators.
Abstract This paper reports the results of measurement refractive indices and densities p-ethoxyphenyl trans-4-butyl cyclohexane carboxylate at different temperatures. The molecular polarizabilities have been calculated from using Vuks' formula orientational order parameters are determined polarizability values. parameter values compared with those obtained Maier-Saupe theory. compound shows anomalous behaviour regarding variation density, ordinary index temperature. is consistent our...
The purpose of the present paper is to report experimental studies on process steps for fabrication IMPATT diodes using diffusion route. Also corresponding dc breakdown voltage fabricated devices have been studied by varying parameters.
Abstract The binary mixtures of 6OCB and 8OCB exhibit reentrant nematic behavior ova a narrow range compositions. We have studied mixture having 27. 12% by weight neutron scattering technique. experimental intensity values I(Q) are fitted with Lorentzian function. From the parameters we calculated short-range correlation length (ζ) perpendicular to director (ñ) intermolecular distance (D) throughout mesomorphic range. results discussed.