K. Sivaji

Fluorescence spectra of blood components for breast cancer diagnosis.

OBJECTIVE To explore whether fluorescence emission spectroscopy of blood components can differentiate normal from early and advanced stages of breast cancer using stepwise discriminant analysis. MATERIALS AND METHODS Fluorescence emission spectra were measured for blood components of three different groups: 35 normal controls, 28 with early-stage, and 18 with advanced-stage breast cancer. The data from the spectra were subjected to Fishers linear discriminant analysis. Classification accuracy, specificity, and sensitivity of the technique were calculated for breast cancer diagnosis. RESULTS Fluorescence emission spectra of blood components accurately distinguished normal from early-stage and advanced-stage breast cancer in 91.4% of original cases and 90.1% for cross-validated cases. The sensitivity and specificity were 80.4% and 100%, respectively, in distinguishing subjects with breast cancer from normal controls. CONCLUSION Our statistical evaluation indicates that porphyrin in blood can be used as a reliable tumor marker. Fluorescence emission spectroscopy of blood components and statistical evaluations should be further investigated for a variety of tumors.

Identification of sublattice damages in swift heavy ion irradiated N-doped 6H-SiC polytype studied by solid state NMR.

We have studied N-doped 6H-SiC in its pristine and Swift Heavy Ion (SHI) irradiated (150 MeV Ag(12+) ions) forms by solid state Nuclear Magnetic Resonance (NMR) at 7.01 T using (13)C and (29)Si as probe nuclei under magic angle spinning. We show that increased levels of nitrogen doping, than used before, lead to the observation of Knight shifts emanating from an increase in electron density in the conduction band, which in (13)C far exceed those in (29)Si MAS spectra. We have rationalized the differential effects in the MAS spectra and site-dependent paramagnetic shifts in terms of the nitrogen doping at the A, B, and C lattice sites. N-doping has a profound effect on (29)Si spin-lattice relaxation, and the site-dependent relaxation behavior is attributed to a difference in conduction electron properties at the different lattice sites. (29)Si T(1) measurements serve to identify the sublattice damages in SHI irradiated 6H-SiC. By determining the spin-lattice relaxation rates as a function of the SHI irradiation ion fluences, the change in relaxation behavior is correlated to the damage production mechanism. The sublattice damage leads to discernable changes in the interaction between the mobile unpaired electrons in the conduction band and the nuclear site, which profoundly influence the NMR relaxation properties. Our relaxation studies also provide evidence for site-dependent localized effects and a decrease in carrier spin density in the conduction band for the SHI irradiated 6H-SiC.

Study of Electrical Properties in SHI Irradiated 6H‐SiC Crystals using Low Temperature Impedance Spectroscopy

In the present work, low temperature impedance measurements were made on the pristine and Ag12+ ions irradiated 6H‐SiC samples. The conductivity properties were studied at low temperature. The activation energies were calculated from the Arrhenius plot of d.c conductivity and impedance relaxation time. The activation energy was comparatively higher for the irradiated samples and found to be electronic conduction. From the study we observe the lower conductivity values exhibited for 300 K irradiated sample due to severe damage than the 80 K irradiated sample. The damage production mechanism and the change in electrical properties are discussed.

Low temperature relaxation properties of SHI irradiated N-doped 6H-SiC

The low-temperature behavior of conductivity relaxation of disordered N-doped 6H-SiC is investigated. This work presents the effect of swift heavy ion (SHI) irradiation on 6H-SiC studied using impedance spectroscopy (IS). SHI irradiation was done with the fluences 8 × 1012 and 2 × 1013 ions/cm2 at 300 K. The observed changes in the Modulus spectra depict the disorder induced due to high energy loss of Ag12+ ions in 6H-SiC. The results indicate that the relaxation times were affected by the free charge carriers trapped at the electrically active defect states.