Sharad Gupta

Recovery of turbidity free fluorescence from measured fluorescence: an experimental approach.

Fluorescence from fluorophores embedded in a turbid medium like biological tissue gets strongly modulated by the wavelength dependent absorption and scattering properties of tissue. This makes it extremely difficult to extract valuable biochemical information from tissue which is present in the intrinsic line shape and intensity of fluorescence from tissue fluorophores. We present an experimental approach to remove the distorting effect of scattering and absorption on intrinsic fluorescence of fluorophores embedded in a turbid medium like tissue. The method is based on simultaneous measurement of polarized fluorescence and polarized elastic scattering spectra from a turbid medium. The polarized fluorescence normalized by the polarized elastic scattering spectra (in the wavelength range of fluorescence emission) was found to be free from the distorting effect of absorption and scattering properties of the medium. The applicability range of this technique to recover intensity and line shape information of intrinsic fluorescence has been investigated by carrying out studies on a variety of tissue phantoms having different absorption and scattering properties. The results obtained show that this technique can be used to recover intrinsic line shape and intensity information of fluorescence from fluorophores embedded in a scattering medium for the range of optical transport parameters typically found in biological tissue.

Wavelet transform of breast tissue fluorescence spectra: a technique for diagnosis of tumors

Polarized fluorescence spectra of malignant, benign, and normal human breast tissues in the emission range of 500-700 nm, with an excitation wavelength of 488 nm, are analyzed through discrete wavelet transform. The multiresolution and localization properties of the wavelets are shown to be ideally suited for identifying characteristic features distinguishing these tissue types. Analysis of a number of data sets, belonging to both parallel and perpendicular polarized spectra, have led to several key distinctions between different tumors and corresponding normal breast tissues, revealing the usefulness of polarized fluorescence in the diagnosis of tumors. Wavelet transform also naturally leads to the dimensional reduction of the data set, in the form of low-pass coefficients, making it amenable for physical modeling.

Thin Film Composite Polyamide Membrane Parameters Estimation for Phenol-Water System by Reverse Osmosis

ABSTRACT A commercial thin film composite polyamide reverse osmosis membrane is used to separate an aqueous phenol-water binary system. The separation data are analyzed using a combined film theory-solution-diffusion (CFSD) model and a combined film theory-Spiegler-Kedem (CFSK) model. In the present investigation a new phenomenon is observed: there exists a maximum in the rejection when it is plotted against the product flux through the membrane. This behavior is explained for both models. An equation for Jv,min, which is the value of the product flux Jv at which the rejection reaches a maximum, is derived from both models. Although the parameters for both models are consistent over the range of operating conditions, the CFSK model is more accurate for the phenol-water system.

Wavelet-based characterization of spectral fluctuations in normal, benign, and cancerous human breast tissues

Fluorescence intensity fluctuations in the visible wavelength regime in normal, benign, and cancerous human breast tissue samples are studied through wavelet transform. The analyses have been carried out in unpolarized, parallel and perpendicularly polarized channels, for optimal tissue characterization. It has been observed that polarized fluorescence data, particularly the perpendicular components, differentiate various tissue types quite well. Wavelet transform, because of its ability for multiresolution analysis, provides the ideal tool to separate and characterize fluctuations in the fluorescence spectra at different scales. We quantify these differences and find that the fluctuations in the perpendicular channel of the cancerous tissues are more randomized as compared to their normal counterparts. Furthermore, for cancerous tissues, the same is very well described by the normal distribution, which is not the case for normal and benign samples. It has also been observed that, up to a certain point, fluctuations at larger scales are more sensitive to tissue types. The differences in the average, low-pass wavelet coefficients of normal, cancerous, pericanalicular, and intracanalicular benign tissues are also pointed out.

Influence of size parameter and refractive index of the scatterer on polarization-gated optical imaging through turbid media

The influence of incident polarized light, refractive index, and size parameter of the scatterer on achievable resolution and contrast (image quality) of polarization-gated transillumination imaging in turbid media is reported here. Differential polarization detection led to significant improvement of image quality of an object embedded in a medium of small-sized scatterers (diameter D<<lambda, isotropic scattering medium, anisotropy parameter g<or=0.2), especially using circular polarization. In contrast, for anisotropic scattering media composed of larger-sized scatterers (D>or=lambda,g>or=0.7), the improvement in image quality was less pronounced using either linear or circular polarization gating when the refractive index of the scatterer was high (ns=1.59), but for a lower value of refractive index (ns=1.37), image quality improved with the differential circular polarization gating. We offer a plausible explanation for these observations.

Experimental and theoretical investigation of fluorescence photobleaching and recovery in human breast tissue and tissue phantoms

Photobleaching and recovery of 488-nm excited fluorescence from resected human breast tissue samples have been studied. Profiles of photobleaching decay were seen to be faster in cancerous tissue than in those of the normal tissue. The reverse behavior was observed in profiles of recovery after photobleaching. A theoretical model based on one-dimensional diffusion theory has been developed to provide insight into the phenomena of fluorescence during photobleaching and recovery in a multiply scattering medium such as tissue. To understand photobleaching and recovery with the help of this theoretical model, we carried out experiments with model media that were prepared with authentic fluorophores, scatterers, and absorbers. The results of these studies suggest that the fluorescence photobleaching profiles are affected more by the absorption than by the scattering properties of a turbid medium such as tissue. In contrast, the scattering properties of the medium are found to affect the fluorescence recovery profiles to a greater extent. These observations could be related to the observed difference in fluorescence photobleaching and recovery profiles of normal and cancerous breast tissues.

Bioconversion of sugars to ethanol in a chemostat employing S. cerevisiae — dynamic response to perturbations in process parameters

Dynamic responses during start-up performance and following perturbations in single process parameters (dilution rate and feed sugar concentration) were studied in a continuous stirred tank bioreactor employing S. cerevisiae for the bioconversion of sugars to ethanol. The attainment of the steady state at the start-up of the bioreactor was found to be a function of feed sugar concentration and dilution rate. A third-degree polynomial fit resulted in the theoretical computation of the number of reactor volumes necessary to attain a steady state. Step changes in the feed sugar concentration or the dilution rate showed overshoots and undershoots in the specific growth and ethanol formation rates. The system performance was dependent on the input noise and the operating conditions. Increased productivity could be obtained during the transition phase. The dynamic behaviour was simulated by making a non-steady-state mass balance. The simultaneous differential equations were solved by the fourth-order Runge-Kutta method. Theoretical analysis adequately described the dynamic response.

Geo-spatial Technology for Landslide Hazard Zonation and Prediction

Similar to other geo hazards, landslides cannot be avoided in mountainous terrain. It is the most common natural hazard in the mountain regions and can result in enormous damage to both property and life every year. Better understanding of the hazard will help people to live in harmony with the pristine nature. Since India has 15% of its land area prone to landslides, preparation of landslide susceptibility zo‐ nation (LSZ) maps for these areas is of utmost importance. These susceptibility zo‐ nation maps will give the areas that are prone to landslides and the safe areas, which in-turn help the administrators for safer planning and future development activities. There are various methods for the preparation of LSZ maps such as based on Fuzzy logic, Artificial Neural Network, Discriminant Analysis, Direct Mapping, Regression Analysis, Neuro-Fuzzy approach and other techniques. These different approaches apply different rating system and the weights, which are area and fac‐ tors dependent. Therefore, these weights and ratings play a vital role in the prepa‐ ration of susceptibility maps using any of the approach. However, one technique that gives very high accuracy in certain might not be applicable to other parts of the world due to change in various factors, weights and ratings. Hence, only one meth‐ od cannot be suggested to be applied in any other terrain. Therefore, an under‐ standing of these approaches, factors and weights needs to be enhanced so that their execution in Geographic Information System (GIS) environment could give better results and yield actual ground like scenarios for landslide susceptibility mapping. Hence, the available and applicable approaches are discussed in this chapter along with detailed account of the literature survey in the areas of LSZ mapping. Also a case study of Garhwal area where Support Vector Machine (SVM) technique is used for preparing LSZ is also given. These LSZ maps will also be an important input for preparing the risk assessment of LSZ.

Fluorescence photobleaching and recovery of human breast tissues and tissue phantoms

Changes in the fluorescence intensity at 530 nm and 630 nm are measured as a function of incident intensity and exposure time with 488 nm excitation of Argon ion laser. Photobleaching curves of normal and diseased tissues display double exponential behaviour with different decay rates. Photobleaching rates of fluorophores in solutions mostly display single exponential behaviour while addition of absorber and scatterers results in double exponential profiles. The decay profile of FAD + Protoporphyrin indicates the contribution of both fluorophores in tissue photobleaching at 530 nm. Photobleaching profiles of normal tissues with blood show a fast decay in comparison to the normal and diseased tissues without blood. The fast decay rates of tumors indicate absorption of flavin by porphyrin. Fluorescence photobleaching recovery (FPR) profiles of tissue displays single exponential behaviour but the rates of growth of normal and diseased tissues are different.

Molecular information from fluorescence spectroscopic investigations of breast tissues and tissue phantoms

Polarized fluorescence spectroscopy in the visible range can be used to discriminate different types of human breast tissue, namely, malignant, benign and normal. The bandwidth of the 580nm band of the polarized spectra shows excellent discrimination among the different tissue types. This difference in the bandwidth of the 580nm band provides bio-molecular information of the breast tissues. The spatially dependent fluorescence spectra are recorded from different radial distances of the tissue sample. These spectral profiles show differences in broadening as one goes away from the excitation point. This broadening also provides information on the presence of porphyrin in the breast tissues. Various concentrations of two fluorophores with varying concentrations of scatterers have been studied based on the assumption that porphyrin plays a major role in progress of tumor. Correlations have been made with polarized fluorescence spectra as well as spatial profiles of fluorescence spectra of the different tissues with the measurements of tissue phantoms. Such correlations hint at porphyrin accumulation and scattering effects playing major roles in spectral differences among normal, benign and malignant tumor breast tissues.