Polymers are among the most commonly used materials in our everyday life. They are generally transparent to terahertz (THz) radiation, but are quite difficult to differentiate using optical techniques as few or no characteristic features exist in the spectral range of <2.0 THz for small and portable radiation systems. In this work, we report experimental measurement of refractive indices and absorption coefficients of styrene acrylonitrile (SAN) and Bakelite in the spectral range of 0.2-2.0 THz for the first time. Additionally, we demonstrate that by combining principle component analysis (PCA) with THz time-domain spectroscopy one can differentiate such polymers. In this analysis, the first three principle components PC1, PC2, and PC3 depict >94% variance with a distribution of 72.45%, 11.52%, and 9.38%, respectively.

We present a simple technique for simultaneous determination of thickness and refractive index of plane-parallel samples in the terahertz radiation domain. The technique uses time-of-flight measurements of the terahertz pulse. It has been employed on nine different polymers and semiconductor materials, which are transparent for terahertz frequencies. Our results of thickness measurement are in good agreement with micrometer reading. The accuracy in the determination of refractive index is on the order of two decimal points.

This study is intended to develop a screening method for female breast cancer (BRC) from whole blood using Raman spectroscopy. A multivariate partial least squares (PLS) regression model is developed which is based upon Raman spectra of BRC-positive and healthy participants. It yields coefficients of regression at the corresponding Raman shifts. These coefficients represent the changes in molecular structures which are associated with the progress of disease. The present study pointed out some specific molecules which differentiated BRC-positive and healthy groups. In the BRC-positive group, a rising trend of calcium oxalate, calcium hydroxyapatite, phosphatidylserine and qunoid ring, and a lowering trend of tryptophan, tyrosine, and proline were observed in PLS-based coefficients of regression. The R-square value of the model was found to be 0.987, which is accepted clinically. The model was tested for the prediction of 50 randomly collected samples at a cutoff value of 0.5 with the gray region defined in the range of 0.4-0.6. Goodness of fit was estimated using accuracy, sensitivity, specificity, receiver operating characteristic (ROC) curve, and area under ROC curve. All of these parameters were found to be very promising.

The refractive index, absorption coefficient, dielectric constant and conductivity of titanium dioxide at different doping concentrations of antimony (Sb) have been investigated using the non-contact and damage-free technique of terahertz time-domain spectroscopy. Simple effective medium theory has been applied to composite samples to extract the dielectric and conductive response in the range of 0.2–1.2 THz. The frequency-dependent values of these parameters are observed to increase with doping concentration and also with calcination temperature. Drude–Smith model fitting with the measured conductivity curves reveals that back-scattering is the major conductivity mechanism.

This study reports the molecular characterization of foot-and-mouth disease virus (FMDV) in the provinces of Punjab and Sindh, Pakistan during 2014-17. FMDV genome was detected in 42 and 41 out of 46 samples (epithelial tissue and saliva) by reverse transcriptase loop-mediated isothermal amplification (RT-LAMP) and reverse transcriptase polymerase chain reaction (RT-PCR), respectively. Sequences of the complete VP1 coding region of the samples (n = 33) was achieved showing that 10, 4 and 19 samples belonged to serotype O, A and Asia1 respectively. Phylogenetic analysis of serotype O revealed that at least one novel sublineage within the ME-SA topotype is circulating in the region, named here as PAK-14. This sublineage showed similarity with the viruses circulating in Turkey and Pakistan during 2010 indicating that viruses circulating in these countries have common origin. Analysis of serotype A viruses revealed a new lineage is circulating in the region, reported here as A-PAK14 showing close identity with the strain prevalent in Pakistan during 2007. Circulation of these new linages in the region shows continuous evolution of the viruses. Two of the undisclosed serotype A sublineages within the Iran-05 lineage were also found circulating in the region. In addition, molecular investigation of the VP1 coding region sequences of serotype Asia1 strains revealed that they belong to Group-VII (Sindh-08). Interestingly some of the serotype Asia1 isolates (n = 6) showed 99.9% similarity (among themselves) although they were collected from different districts more than 100 Km apart from one another. This unusual conservation among serotype Asia1 over long distances can be explored by studying the role of wild animals, slaughter houses and milk collection centres in the spread the disease.