Inhomogeneous Bulk Viscous Fluid Universe with Electromagnetic Field and Variable ∧-Term

Cylindrically symmetric inhomogeneous cosmological model for bulk viscous fluid distribution with electro- magnetic field is obtained. The source of the magnetic field is due to an electric current produced along the z-axis. F12 is the non-vanishing component of electromagnetic field tensor. To get the deterministic solution, it has been assumed that the expansion 0 in the model is proportional to the shear σ. The values of cosmological constant for these models are found to be small and positive at late time, which are consistent with the results from recent supernovae Ia observations. Physical and geometric aspects of the models are also discussed in presence and absence of magnetic field.     

Trace detection of C<Subscript>2</Subscript>H<Subscript>2</Subscript> in ambient air using continuous wave cavity ring-down spectroscopy combined with sample pre-concentration

Continuous wave cavity ring-down spectroscopy (cw-CRDS) coupled with sample pre-concentration has been used to measure acetylene (C₂H₂) mixing ratios in ambient air. Measurements were made in the near-infrared region (λ∼1535.393 nm), using the P(17) rotational line of the (ν₁+ν₃) vibrational combination band, a region free from interference by overlapping spectral absorption features of other air constituents. The spectrometer is shown to be capable of fast, quantitative and precise C₂H₂ mixing ratio determinations without the need for gas chromatographic (GC) separation. The current detection limit of the spectrometer following sample pre-concentration is estimated to be 35 parts per trillion by volume (pptv), which is sufficient for direct atmospheric detection of C₂H₂ at concentrations typical of both urban and rural environments. The CRDS apparatus performance was compared with an instrument using GC separation and flame ionization detection (GC-FID); both techniques were used to analyze air samples collected within and outside the laboratory. These measurements were shown to be in quantitative agreement. The indoor air sample was found to contain C₂H₂ at a mixing ratio of 3.87±0.22 ppbv (3.90±0.23 ppbv by GC-FID), and the C₂H₂ fractions in the outside air samples collected on two separate days from urban locations were 1.83±0.20 and 0.69±0.14 ppbv (1.18±0.09 and 0.60±0.04 ppbv by GC-FID). The discrepancy in the first outdoor air sample is attributed to degradation over a 2-month interval between the cw-CRDS and GC-FID analyses. PACS 82.80.Gk; 39.30.+w; 42.62.Fi; 42.68.Ca     

Polarized spectral features of human breast tissues through wavelet transform and principal component analysis

Fluorescence characteristics of human breast tissues are investigated through wavelet transform and principal component analysis (PCA). Wavelet transform of polarized fluorescence spectra of human breast tissues is found to localize spectral features that can reliably differentiate different tissue types. The emission range in the visible wavelength regime of 500–700 nm is analysed, with the excitation wavelength at 488 nm using laser as an excitation source, where flavin and porphyrin are some of the active fluorophores. A number of global and local parameters from principal component analysis of both high- and low-pass coefficients extracted in the wavelet domain, capturing spectral variations and subtle changes in the diseased tissues are clearly identifiable.     

Effect of non-Newtonian characteristics of blood on magnetic targeting in the impermeable micro-vessel

In this investigation we consider to extended the work of Furlani and Furlani [15] by taking non-Newtonian fluid model for the blood in the impermeable micro-vessel. The behavior of blood is considered as the Herschel-Bulkley fluid which is more suitable for the micro-vessel of radius 50 μm. The expression for the fluidic force for the carrier particle traversing in the Herschel-Bulkley fluid is obtained first. Several factors that influence the magnetic targeting of the carrier particles in the microvasculature, such as the size of the carrier particle, the volume fraction of embedded magnetic nanoparticles, and the diameter of the micro-vessel are considered in the present problem. An algorithm is given to solve the system of coupled equations for trajectories of the carrier particle in the invasive case. The trajectories of the carrier particles are found in both invasive and noninvasive targeting systems. A comparison is make regarding the trajectories in these cases. Also, a prediction of the capture of therapeutic magnetic nanoparticle in the human microvasculature is made for different radii and volume fractions in both the invasive and noninvasive cases.     

Defect driven multiferroicity in Gd doped BiFeO3 at room temperature

This paper reports that defect driven magnetism can be obtained at room temperature by optimizing metal ion concentration in bismuth ferrite (BFO) following our novel slow step solid state sintering route. We observed a clean signature of enhanced multiferroic behavior in Gd doped bismuth ferrite (Gd-BFO) bulk ceramics at room temperature (RT). Bismuth rich iron deficient Gd-BFO ceramics were prepared by solid state route through slow step sintering schedule at 850 °C. At particular composition, (Bi_1.2Gd_0.1Fe_0.8O₃), this materials completely transform from rhombohedral R3c to orthorhombic Pn2₁a space group. We emphasized that excess bismuth is expected to act as point defects and occupy interstitials positions, which in turn interact by oxygen vacancies. These defects are likely to promote defect driven ferromagnetism in BFO system. Incorporation of Gd in presence of excess bismuth in BFO enhanced both spin and electric polarization at room temperature. We also infer that Gd substitution in BFO is likely to suppress spiral spin modulation, which also favors ferromagnetism in Gd-BFO.     

Raman Spectroscopy of Formamidinium-Based Lead Mixed-Halide Perovskite Bulk Crystals

In recent years, there has been an impressively fast technological progress in the development of highly efficient lead halide perovskite solar cells. Nonetheless, the stability of perovskite films and associated solar cells remains a source of uncertainty and necessitates sophisticated characterization techniques. Here, we report low- to mid-frequency resonant Raman spectra of formamidinium-based lead mixed-halide perovskites. The assignment of the different Raman lines in the measured spectra is assisted by DFT simulations of the Raman spectra of suitable periodic model systems. An important result of this work is that both experiment and theory point to an increase of the stability of the perovskite structure with increasing chloride doping concentration. In the Raman spectra, this is reflected by the appearance of new lines due to the formation of hydrogen bonds. Thus, higher chloride doping results in less torsional motion and lower asymmetric bending contributing to higher stability. This study yields a solid basis for the interpretation of the Raman spectra of formamidinium-based mixed-halide perovskites, furthering the understanding of the properties of these materials, which is essential for their full exploitation in solar cells.