Sonali Chakraborty

Bio: Sonali Chakraborty is an academic researcher from University of Calcutta. The author has contributed to research in topic(s): Interferometry & Polarization (waves). The author has an hindex of 3, co-authored 11 publication(s) receiving 27 citation(s).

Lipid Profiles of Pomfret Fish (Pampus argenteus) Organs

Abstract: The study of the lipid matter content from the different organs of Pomfret (Pampus argenteus) fish indicates that a major amount of lipid accumulates in the brain while the organs like digestive tract and muscle contain relatively much lower amount. The composition of the lipid matter of various organs points out that cholesterol is in much greater proportion than that of the phospholipid. Cholesterol is present in highest amount in the brain lipid compared with other organs while the content of phospholipid is lowest in the digestive tract. The fatty acid composition reveals that the lipids of each organ of pomfret fish are enriched in the saturated fatty acids. Also a distinct variation exists in the amount of the individual saturated fatty acids. The eye ball lipid has the highest amount of saturated fatty acid (84%) followed by digestive tract (69%), muscle (52%) and brain (34%). The polyunsaturated fatty acids are the next major fatty acids, with significant amount of C22:6 fatty acid.

Real-time edge detection by cyclic-path polarization interferometer

Abstract: In a triangular path cyclic interferometer employing a polarizing beam splitter (PBS), the two counterpropagating beams are orthogonally polarized. A sample placed almost equidistant from the PBS is imaged by a lens placed in the path of the emerging beams so that two defocused images of the sample are recorded on a CCD. Using a linear polarizer in the path of the orthogonally polarized imaging beams, it is possible to achieve amplitude subtraction between the two images, resulting in an edge-enhanced image of the sample. The proposed real-time edge-enhancement technique is experimentally demonstrated.

Quantitative birefringence microscopy with collinearly propagating orthogonally polarized beams.

Abstract: Full-field evaluation of spatially varying birefringence is realized by allowing two mutually orthogonally polarized collinearly propagating laser beams to be incident on a birefringent sample. This is achieved by use of a modified Sagnac interferometer. A half-wave plate is placed in the exit path of the interferometer to adjust the polarizations of the incident beams as required. Amplitude components of the light emerging from the birefringent object are then selected and/or combined by a polarizer, and intensities for required orientation of the half-wave plate and the analyzer are digitally recorded. It is shown that a maximum of four frames of intensity data is sufficient for complete evaluation of birefringence. The proposed technique is aimed towards birefringence measurements in microscopic biological specimens where the magnitude of retardation lies in the range of 0-π radians. Simulated and experimental results are presented.

Achromatic half-wave combination of birefringent plates

Abstract: Half-wave retarders are primarily used in rotating the plane of polarization of polarized light. These retarders usually exhibit strong wavelength dependence. In this paper, the design and characteristics of an achromatic half-wave plate, formed by a cascaded system of birefringent plates, have been studied. Pancharatnam proposed a combination of three retarders in series and discussed the possibility of fabricating reasonably good achromatic quarter-wave plate with a suitable combination of their retardance. The system studied here is similar in construction to Pancharatnam configuration and behaves as an achromatic half-wave plate over a wide spectral range. The proposed configuration exhibits a maximum variation of only about ±1.4 degree over the entire wavelength range of 500–750 nm. In our analysis we have used Jones matrix formalism for the derivation of the general expression for the equivalent retardation and the azimuth of the combination.

Lipid Profiles of Bhola Bhetki (Nibea soldado) Organs

Abstract: The fish, namely Bhola bhetki (Nibea soldado) was examined for lipid composition of its specific organs. The fish had a much higher lipid content in brain in comparison with its other organ while the muscle and digestive tract had nearly equal amount of total lipids. Cholesterol content in lipid part of various organs was significantly high in Bhola (Nibea sp.) while the phospholipid content was low. Fatty acid compositions of eye and digestive tract of Nibea soldado were richer in variety than those of muscle and brain. The total saturated and poly unsaturated acids were more or less equal in muscle and brain lipid. The total monounsaturated fatty acids are more or less same in the muscle, brain and eye. Eicosapentaenoic acid (C20:5) is very high in all the organs. Arachidonic acid (C20:4) is also present in considerable amount in brain, eye and digestive tract. The variation of cholesterol, phospholipid and fatty acid composition in fish organs would be beneficial for human consumption from health point of view.

Amino acid and fatty acid compositions and nutritional quality of muscle in the pomfret, Pampus punctatissimus

Abstract: The pomfret, Pampus punctatissimus , is an important fisheries resource in China, but little is known about its amino acid and fatty acid compositions. Pomfret muscle contained 18.6% crude protein and 4.95% crude fat. Pomfret protein has a well-balanced amino acid composition, with high amounts of glutamic acid (114 mg/g), lysine (82.8 mg/g), leucine (76.7 mg/g), and aspartic acid (76.0 mg/g). Twenty two fatty acids were found in pomfret oil and saturated fatty acids were the most abundant (48.3%). Palmitic acid (16:0) was the dominant fatty acid, followed by oleic acid (18:1), DHA (22:6n-3), myristic acid (14:0) and stearic acid (18:0), with percentages of 30.5, 26.3, 12.2, 7.37 and 6.86, respectively. The ratio of n-3/n-6 polyunsaturated fatty acids (PUFAs) was 8.04; thus, pomfret muscle is rich in n-3 PUFA.

Plasmalogens, fatty acids and alkyl glyceryl ethers of marine and freshwater clams and mussels

Abstract: Shelled molluscs constitute an excellent source of protein, sugars and lipids, and the demand for various mollusks species is increasing. We analysed lipid composition of different bivalves, quite important in the diet of East Mediterranean inhabitants. Plasmamlogens, glyceryl ethers, and diacyl phospholipid forms as well as their fatty aldehydes, fatty alcohols, and fatty acid derivatives were examined. PE of clams and mussels, containing aldehydes C16 (variations from 4% to 31%), C18 (29–46%), C9–18:1(6–32%), C11–20:1 (3–19%), and several minor aldehydes, were detected. The major saturated 1-O-alkyl glycerol ethers C16 and C18. Eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids in both PE and PS plasmalogens were dominated acids. The sum of these acids in PE varied from 33% to 43%, and in PS, from 45% to 66%. EPA levels in PE (30–37%) and PS (39–57%) of marine species were higher than those in freshwater species (PE, 13–16%; PS, 23–29%), and levels of DHA were higher in freshwater than in marine mollusks. A series of saturated fatty aldehydes C12–C24, with major C18:0 in all studied species (over 40%) and C16:0 (10–25%), as well as of unsaturated C16:1 (1–7%) and 18:1 (18–36%) species were isolated from neutral plasmalogens. Predominant fatty acids in neutral plasmalogens were found to be 16:0 (12–17%), 20:5n−3 (9–27%), and 22:6n−6 (9–18%). Distribution of plasmalogens, alkyl glyceryl ethers, and their fatty aldehydes and fatty alcohols in mollusks and other invertebrates is discussed.

Polarization-based spatial filtering for directional and nondirectional edge enhancement using an S-waveplate

Abstract: Using polarization as an additional parameter apart from amplitude and phase in spatial filtering experiments offers additional advantages and possibilities. An S-waveplate that can convert a linearly polarized light into radially or azimuthally polarized light can also be used for isotropic edge enhancement. For anisotropic edge enhancement, introduction of a polarizer at the output was recommended and edge selection was done by orientation of the polarizer. But the full potential of the S-waveplate as a spatial filter has not been exploited so far. Unlike the standard amplitude and phase-based Fourier filters, which are independent to the state of polarization of the illuminating beam, the S-waveplate acts in a different way depending on the state of polarization. The edge selection does not need to be carried out by changing the orientation of the polarizer. With a fixed polarizer at the output, we show that either isotropic or anisotropic edge enhancement in any desired orientation can be performed by operating the same spatial filter setup in different illuminating polarization states.

Biochemical composition of juvenile cultured vs. wild silver pomfret, Pampus argenteus: determining the diet for cultured fish.

Abstract: We evaluated the biochemical composition of juvenile cultured and wild silver pomfret Pampus argenteus. Cultured silver pomfret (SF) had significantly (P < 0.05) lower crude protein content and higher crude lipid content than wild SF. Concentrations of almost all amino acids, except glycine and arginine, were significantly higher (P < 0.05) in wild SF compared to cultured SF. Further, wild SF had a significantly (P < 0.05) higher concentration of total amino acids (TAA), essential amino acids (EAA), and a higher essential amino acid index (EAAI) than cultured SF. Saturated fatty acids (SFA) in cultured SF were significantly higher than in wild SF. However, the content of poly-unsaturated fatty acids (PUFA) and n-3 fatty acids in wild SF was significantly higher than in cultured SF. Mono-unsaturated fatty acids (MUFA) in cultured and wild SF were not significantly different. Fatty acids C16:0 and C18:1 were the principal fatty acids of the SFAs and MUFAs, respectively, in both cultured and wild SF. The results will be useful for determining the dietary requirements for culture of SF.

Trace elements and POPs in two commercial shark species from Djibouti: Implications for human exposure.

Abstract: Within Djibouti (Gulf of Aden), the scalloped hammerhead shark (Sphyrna lewini) and milk shark (Rhizoprionodon acutus) are important components of the artisanal fishery and they are caught to be exported or sold for local consumption. However, little scientific information exists on the contamination load of these species in this area of the world. With global populations of elasmobranchs in decline, understanding the extent of contaminant exposure is critical to future conservation as well as to assess the health risks for consumers of these species. The contaminants analyzed in this study comprised PCB, DDT and trace elements in livers, muscles and fins of both hammerhead sharks and milk sharks. The overall organochlorine compounds (OCs) and trace elements concentrations were similar among the two sharks' species and the pattern of PCB and DDT tissue distribution showed the highest burdens in livers compared with muscles and fins. However, the different accumulation profiles of OCs among shark species suggest species-specific accumulation of these contaminants. The p,p'DDE/∑DDT ratios were equal or slightly higher than the critic value of 0.6, suggesting possible recent inputs of technical DDT in the area. Concentration of trace elements from this study were generally comparable to those found in sharks from other areas of the world and, highlight the wide variation in metal concentrations between species, individuals and tissues. As far as Hg is concerned, scalloped hammerhead sharks showed higher accumulation in muscles compared with milk sharks. Both species showed elevated concentration of Se, which might be related to high Hg levels since Se inhibits Hg toxicity. The potential cancer risk for PCB, Cd, Ni, Cr and As fell within the range of 10-6-10-4, suggesting some concerns for the overall contamination levels in both species. Indeed, consuming of fish involves a mixture of all analyzed elements, and therefore, some potential risk might arise from regularly consuming these species.