Madhusudan Roy

Computational Investigation on the Photoacoustics of Malaria Infected Red Blood Cells

A computer simulation study on the possibility of using photoacoustic (PA) technique to differentiate intraerythrocytic stages of malarial parasite is reported. This parasite during its development substantially converts hemoglobin into hemozoin. This conversion is expected to alter the cellular absorption leading to changes in the PA emission of a red blood cell (RBC) at certain incident optical wavelengths. The PA signals from blood samples corresponding to ring, trophozoite and schizont stages were computed and compared with that of normal blood. A Monte Carlo algorithm was implemented generating random locations of RBCs in 3D to simulate blood samples. The average PA amplitude for wide bandwidth signals decreases for 434 nm incident radiation, but increases for 700 nm as the parasite matures. The spectral power at 7.5 MHz for the blood sample at the schizont stage compared to the normal blood is nearly reduced by 6 dB and enhanced by 22 dB at those incident wavelengths, respectively. Bandlimited signals for transducers of 15 and 50 MHz center frequencies were studied and found to exhibit similar characteristics. The presence of hemozoin inside the cells was examined and an excellent estimation was made. The simulation results suggest that intraerythrocytic stages of malarial parasite may be assessed using the PA technique.

Validity of a theoretical model to examine blood oxygenation dependent optoacoustics

A theoretical model investigating the dependence of optoacoustic (OA) signal on blood oxygen saturation (SO(2)) is discussed. The derivations for the nonbandlimited and bandlimited OA signals from many red blood cells (RBCs) are presented. The OA field generated by many RBCs was obtained by summing the OA field emitted by each RBC approximated as a fluid sphere. A Monte Carlo technique was employed generating the spatial organizations of RBCs in two-dimensional. The RBCs were assumed to have the same SO(2) level in a simulated configuration. The fractional number of oxyhemoglobin molecules, confined in a cell, determined the cellular SO(2) and also defined the blood SO(2). For the nonbandlimited case, the OA signal amplitude decreased and increased linearly with blood SO(2) when illuminated by 700 and 1000 nm radiations, respectively. The power spectra exhibited similar trends over the entire frequency range (MHz to GHz). For the bandlimited case, three acoustic receivers with 2, 10, and 50 MHz as the center frequencies were considered. The linear variations of the OA amplitude with blood SO(2) were also observed for each receiver at those laser sources. The good agreement between simulated and published experimental results validates the model qualitatively.

A preliminary study on the nature of particulate matters in vehicle fuel wastes

Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and tunneling electron microscopy (TEM) studies of two solid vehicle wastes (pollutants) from petrol- and diesel-fueled engines of Kolkata (India) have detected a significant amount of ultrafine particles in the nanometer scale in these wastes. Both powder XRD and selected area electron diffraction from TEM have confirmed the existence of inhomogeneous distribution of nanocrystallites in these pollutants. Energy dispersive X-ray spectrometry shows that these wastes contain mainly carbon and oxygen as the constituent components. These pollutants are magnetic in nature as seen with SQUID magnetometry, and the presence of a high amount of carbon presumably is likely the origin of the magnetic property.

Thermal Decomposition Study of Ferrocene [(C5H5)2Fe]

A single-step thermal decomposition of ferrocene [(C5H5)2Fe] using nonisothermal thermogravimetry (TG) has been studied using single- as well as multiple-heating rate programs. Both mechanistic and nonmechanistic methods have been used to analyze the TG data to estimate the kinetic parameters for the solid state reaction. Two different isoconversional methods (improved iterative method and model-free method) have been employed to analyze the TG results to find out whether the activation energy of the reaction depends on the extent of decomposition and to predict the most probable reaction mechanism of thermal decomposition as well. A comparison of the activation energy values for the single-step thermal reaction of ferrocene estimated by different methods has been made in this work. An appraisal on the applicability of single-heating rate data for the analysis of single-step thermal decompositions over the recommendations by the International Confederation for Thermal Analysis and Calorimetry (ICTAC) is made to look beyond the choice.

Effect of Sol-Gel-Derived Nano-silica on the Properties of Natural Rubber-Poly Butadiene Rubber-Reclaim Rubber Ternary Blends/Silica Nanocomposites

Silica incorporation into natural rubber (NR)-polybutadiene rubber (PBR)-reclaim rubber (RR) ternary blend system was carried out by sol-gel technique at different temperatures. The effect of RR on silica reinforcement was studied for NR-PBR-RR blend systems. The physicochemical properties of sol-gel vulcanizates indicates that the reinforcing efficiency of the nanocomposites increases with increasing RR content. Sol-gel vulcanizates prepared at 50°C shows superior mechanical properties than others. The amount of silica incorporated by sol-gel technique was determined through thermogravimetry analysis, which indicates the increasing trend of thermal stability with silica content. SEM studies indicate the coherency and homogeneity in the NR-PBR-RR/SiO 2 nanocomposites.

Thermal degradation of a molecular magnetic material: {N(n-C4H9)4[FeIIFeIII(C2O4)3]}∞

Thermal degradation of a mixed-valence oxalate based molecular material {N(n-C4H9)4[FeIIFeIII(C2O4)3]}∞ was investigated by thermogravimetric (TG) analysis. Considering the mass loss at each step of TG profile, possible step-wise thermal degradation reaction pathways of the precursor material are proposed which indicate the formation of hematite and magnetite as the solid end product of the degradation reaction. The IR spectroscopy and powder X-ray diffraction (XRD) studies of the thermally degraded samples supplement the proposed reaction pathways.

Photoacoustic imaging of nanoparticle- containing cells using single-element focused transducer: a simulation study

A new theoretical approach for photoacoustic (PA) image simulation of an ensemble of cells with endocytosed gold nanoparticles is presented. Each cell was approximated as a fluid sphere and suspended in a nonabsorbing fluid medium. It was assumed that the cellular optical absorption coefficient changed greatly because of endocytosis of nanoparticles; however, thermophysical parameters remained unchanged because nanoparticles occupied negligible intracellular volume. A frequency-domain method was used to obtain a PA signal from a single cell and resultant signal detected by a focused single-element transducer was evaluated by convolving signals from many cells with the spatial impulse response function of the receiver. The proposed model was explored to simulate PA images of numerical phantoms. It was observed that features of the phantoms are retained precisely in those simulated images. Also, speckles in PA images are significantly suppressed because of strong boundary buildup when cells are bounded to a region. Nevertheless, speckle visibility increases when cells are not bounded to a region. This approach may be developed as a realistic simulation tool for PA imaging of tissue medium utilizing its cellular feature.

Anisotropy of the texture in the ultra-sonogram of human livers

In the present study, discrimination between Ultra-sonograms USGs of human livers of fatty and normal kind, based on the difference of their image textures, is attempted. Different texture features have been suggested in the literature for this purpose. Most popular of them are GLCM based features. Other features have also been proposed for classification. However, a visual scrutiny of the ultra-sonograms indicates that a dominant characteristic of the textures in liver is the presence of small narrow line segments perpendicular to the motion of the beam line. For the most of the images these lines appear to run in nearly horizontal direction with increasingly higher radius of curvature in subsequent lower portions of the images. The texture of the image is therefore visually anisotropic. In this paper, we have first attempted to establish the anisotropy of the texture by statistical computations and proposed some features which explicitly take this directional asymmetry into account. We have extracted these new features from a data set comprising of human liver USG of normal and fatty class. Effectiveness of these new features is estimated by the p value of Welchs test.

Preparation, characterization and electrical study of gum arabic/ZnO nanocomposites

Gum arabic (GA)-mediated chemical synthesis was carried out for obtaining ZnO nanoparticles (ZnO-NPs) (particle size of ZnO ≈ 40 nm) which, in turn, was used for preparing ZnO–biopolymer nanocomposites. The dielectric study of this synthesized products is reported in this paper. The synthesized products were characterized by X-ray diffraction, Fourier transform infrared, and transmission electron microscopy for their structure and morphology study. The frequency dependence of dielectric constant and dielectric loss of these GA–ZnO nanocomposites were analysed in the frequency range of 100 Hz–5 kHz. In addition, the dielectric property of these nanocomposites (0–15 wt% filler concentration) was analysed with respect to frequency in the temperature range 30–80°C. A high dielectric constant of 275 is achieved for the sample with 10 wt% of ZnO filler. The dielectric property of GA–ZnO nanocomposites is attributed to the interfacial and orientation polarization.

Thermally induced single crystal to single crystal transformation leading to polymorphism

The robust complex [La(1,10-phen)2(NO3)3] (1,10-phen=1,10-phenanthroline) exhibits thermally induced single crystal to single crystal transformation from one polymorphic phase to another. The complex crystallizes in monoclinic C2/c space group with C2 molecular symmetry at 293K while at 100K it shows P21/c space group with C1 molecular symmetry. Supramolecular investigation shows that at 100K the complex forms 2D achiral sheets whereas at 293K forms two different homochiral 2D sheets. Low temperature DSC analysis indicates that this structural transformation occurs at 246K and also this transformation is reversible in nature. We have shown that thermally induced coherent movement of ligands changes the molecular symmetry of the complex and leads to polymorphism. Photoluminescence property of complex has been studied in both solid state and in methanolic solution at room temperature. The effect of the presence low-lying LUMO orbital of π-character in the complex is elucidated by theoretical calculation using DFT method.