Free convection effects and radiative heat transfer in MHD Stokes problem for the flow of dusty conducting fluid through porous medium

The present note deals with the effects of radiative heat transfer and free convection in MHD for a flow of an electrically conducting, incompressible, dusty viscous fluid past an impulsively started vertical non-conducting plate, under the influence of transversely applied magnetic field. The heat due to viscous dissipation and induced magnetic field is assumed to be negligible. The governing linear partial differential equations are solved by finite difference technique. The effects of various parameters (like radiation parameter N, Prandtl number Pr, porosity parameter K) entering into the MHD Stokes problem for flow of dusty conducting fluid have been examined on the temperature field and velocity profile for both the dusty fluid and dust particles.     

CRDS of water vapor at 0.1 Torr between 6886 and 7406 cm−1

The absorption spectrum of water vapor in “natural” isotopic abundance has been recorded by high sensitivity CW-Cavity Ring Down Spectroscopy (CW-CRDS) between 6885.79 and 7405.91 cm^?1. This strong absorbing region includes the first hexad of interacting vibrational bands which was previously studied by Fourier Transform Spectroscopy. The achieved sensitivity of the recordings varies from α_min～2×10^–11 to 2×10^?10 cm^?1 allowing us to use a sample pressure of 0.1 Torr, making pressure broadening of the line profile mostly negligible. Weak lines in the vicinity of much stronger lines could then be accurately measured. The weakest lines have intensity on the order of 5×10^–28 cm/molecule at 296 K. A set of 4471 lines were assigned to 4916 transitions of five water isotopologues (H₂ ¹⁶O, H₂ ¹⁸O, H₂ ¹⁷O, HD¹⁶O and HD¹⁸O). A small number of new energy levels was determined mostly for the H₂ ¹⁷O isotopologue. The previous investigations and existing databases are critically evaluated. In particular, a number of corrections and new assignments are proposed for the water list provided by the HITRAN database in the considered region. As a result, a complete list of 12,700 transitions for water in “natural” isotopic abundance is provided as Supplementary Material for the 6885–7408 cm^?1 region.     

A RECONSIDERATION OF THE PROPERTIES OF A PULSED RUBY LASER IN RELATION TO MICROSURGERY

Abstract— The properties of a pulsed ruby laser beam focused through a triocular microscope were studied in relation to microsurgery. Quantitative studies on 'model tissues' with different absorbencies at 6943 Å revealed that the spot diameter of the focused microbeam was dependent upon several factors. It decreased with (1) a decrease in the absorption by the object at 6943 Å; (2) a decrease in the energy of the microbeam; and (3) an increase in the magnification of the microscope. The existence of the 'tube of effect' in the optical path of the focused micro-beam was realized by irradiating the object at different planes. The depth of the tube of effect increased with (1) increase in laser energy or (2) decrease in magnification. By employing certain plant species ( Spirogyra praetensis Transeau, Ulva lactuca Linnaeus, Porphyra miniata (Lyngbye) C. Agardh and Elodea sp.) the reaction of the protoplasm to the laser microbeam in terms of 'primary damage' and 'secondary damage' was defined. Based on these experimental data the concept of minimal visible spot size in laser microsurgery and its limitations are discussed.     

High sensitivity ICLAS of H2O in the 12,580-13,550 cm transparency window

High-sensitivity Intracavity Laser Absorption Spectroscopy (ICLAS) is used to measure the high resolution absorption spectrum of H₂¹⁸O between 12,580 and 13,550 cm⁻¹. This spectral region covers the 3v+δ polyad of very weak absorption. Four isotopologues of water (H₂¹⁸O, H₂¹⁶O, H₂¹⁷O, HD¹⁸O) are found to contribute to the observed spectrum. Spectrum analysis is performed with the aid of variational calculations and allowed for assigning 1126 lines belonging to H₂¹⁸O, while only 160 H₂¹⁸O lines are included in the HITRAN-2008 database. Altogether, 823 accurate energy levels of H₂¹⁸O are determined from transitions attributed to 26 upper vibrational states, 438 of them being reported for the first time. New information includes energy levels of four newly observed vibrational states of H₂¹⁸O: (2 4 0), (1 4 1), (0 4 2) and (2 3 1) at 13,167.718, 13,212.678, 13,403.71 and 15,073.975 cm⁻¹, respectively. H₂¹⁸O transitions involving highly excited bending states like (1 6 0), (0 6 1), (0 7 1), (1 7 0), (0 9 0) and even (0 10 0) have been identified as a result of an intensity borrowing from stronger bands via high-order resonance interactions. Thirty-six new energy levels of H₂¹⁷O, present with a 2% relative concentration in our sample, could be determined. The rotational structure of the (0 2 3) state of HD¹⁸O at 13,245.497 cm⁻¹ is also reported for the first time.     

D2O: ICLAS between 13 600 and 14 020 cm and normal mode labeling of the vibrational states

The high resolution absorption spectrum of dideuterated water, D₂¹⁶O, has been recorded by Intracavity Laser Absorption Spectroscopy (ICLAS) in the 13 600-14 020 cm⁻¹ spectral region which is the highest energy region reported so far for this water isotopologue. Because the HD¹⁶O absorption is stronger by three orders of magnitude in the region under study, it was necessary to use high deuterium enrichment in order to minimize the HD¹⁶O absorption lines overlapping the D₂¹⁶O spectrum. With the high sensitivity achieved (noise equivalent absorption α_min ∼10⁻⁹ cm⁻¹), transitions with line strengths on the order of 5 × 10⁻²⁸ cm molecule⁻¹ could be detected. The spectrum analysis, based on recent variational calculations has provided a set of 177 new rovibrational energy levels belonging to six vibrational states.The most complete set of 53 vibrational energy levels of D₂¹⁶O, including the three newly determined band origins, was constructed from an exhaustive review of the literature data. The fitting of the parameters of the vibrational effective Hamiltonian has allowed to reproduce the whole set of vibrational energies with an rms deviation of 0.055 cm⁻¹. This simple model gave consistent vibrational labels of the D₂¹⁶O states up to 18 000 cm⁻¹. Above 15 000 cm⁻¹, Fermi and Darling-Dennison resonance interaction were found to induce strong vibrational mixings of the wave functions in the normal mode basis, leading to ambiguous vibrational labeling.     

Heat transfer in MHD flow of dusty viscoelastic (Walters’ liquid model-B) stratified fluid in porous medium under variable viscosity

The paper investigates the effects of heat transfer in MHD flow of viscoelastic stratified fluid in porous medium on a parallel plate channel inclined at an angle θ. A laminar convection flow for incompressible conducting fluid is considered. It is assumed that the plates are kept at different temperatures which decay with time. The partial differential equations governing the flow are solved by perturbation technique. Expressions for the velocity of fluid and particle phases, temperature field, Nusselt number, skin friction and flow flux are obtained within the channel. The effects of various parameters like stratification factor, magnetic field parameter, Prandtl number on temperature field, heat transfer, skin friction, flow flux, velocity for both the fluid and particle phases are displayed through graphs and discussed numerically.     

ICLAS of HDO between 13,020 and 14,115 cm

The high resolution absorption spectrum of monodeuterated water, HDO, has been recorded by Intracavity Laser Absorption Spectroscopy (ICLAS) in the 13,020–14,115 cm⁻¹ region dominated by the 4ν₃ band. The achieved noise equivalent absorption (α_min10⁻⁹ cm⁻¹) allowed detecting transitions with line strengths as small as 2×10⁻²⁷ cm/molecule which is about 10 times lower than the smallest line intensities previously detected in the region.The rovibrational assignment of the spectrum was based on the results of the variational calculations of Schwenke and Partridge (SP) as well as recent calculations using a new potential energy surface performed by Voronin, Tolchenov and Tennyson (VTT). 2157 transitions involving 21 upper vibrational states were assigned to HD¹⁶O while only four bands were previously reported in the region. A set of 157 new energy levels could be derived. It includes rotational levels of several highly excited bending states, in particular the (0 11 0) pure bending state. For some states like the (1 0 3) and (0 2 3) Fermi dyad, effective Hamiltonian modelling was needed to establish the vibrational assignments of some rotational levels. VTT calculations were found to significantly improve the SP results, the rms deviation of the calculated and observed energies being decreased from 0.23 to 0.06 cm⁻¹.Finally, 79 transitions of the 4ν₃ band of the HD¹⁸O isotopologue were assigned, leading to the derivation of 48 levels, which are the most excited energy levels reported so far for this isotopologue.     

Effect of Zr,Ti substitutions onT c in superconducting YBa2Cu3O7−δ system

Zr and Ti have been substituted in the system Y_1−x M _x Ba₂Cu₃O_7−δ(M=Zr, Ti,x=0.05,0.1). We find that theT _c value is unchanged, ∼90K for Zr substitutions up to 10% and in the case of Ti substitutions theT _c drops significantly. These changes may arise from their site preference.     

High sensitivity CRDS of the aΔg−XΣg band of oxygen near 1.27 μm: Extended observations, quadrupole transitions, hot bands and minor isotopologues

The CW-Cavity Ring Down Spectroscopy (CW-CRDS) technique has been used to record the high sensitivity absorption spectrum of the a¹Δ_g-X³Σ_g⁻ band of oxygen near 1.27 μm. The spectra were obtained between 7640 and 7917 cm⁻¹ with “natural” oxygen and with a sample highly enriched in ¹⁸O. The absolute intensities of 376 and 643 oxygen transitions were measured in the two spectra. They include the a¹Δ_g−X³Σ_g⁻ (0-0) bands of ¹⁶O₂, ¹⁶O¹⁸O, ¹⁶O¹⁷O, ¹⁷O¹⁸O and ¹⁸O₂. The (0-0) bands of ¹⁶O₂ and ¹⁸O₂ show weak quadrupole transitions with line intensities ranging from 1×10⁻³⁰ to 1.9×10⁻²⁸ cm/molecule. They are accompanied by the a¹Δ_g−X³Σ_g⁻ (1-1) hot bands, which are reported for the first time. The line profiles of the transitions of the ¹⁶O¹⁷O and ¹⁷O¹⁸O isotopologues were observed to be broadened due to an unresolved magnetic hyperfine structure. Accurate spectroscopic parameters of the different energy levels involved in the observed bands were derived from a global fit of the observed line positions, combined with microwave and Raman measurements available in the literature.     

Intracavity laser absorption spectroscopy of D2O between 11 400 and 11 900 cm

The weak absorption spectrum of dideuterated water, D₂O, has been recorded by Intracavity Laser Absorption Spectroscopy (ICLAS) between 11 400 and 11 900 cm⁻¹. This spectrum is dominated by the 3ν₁ + ν₂ + ν₃ and the ν₁ + ν₂ + 3ν₃ centered at 11 500.25 and 11 816.64 cm⁻¹, respectively. A total of 530 energy levels belonging to eight vibrational states were determined. The rovibrational assignment process of the 840 lines attributed to D₂O was mostly based on the results of new variational calculations consisting in a refinement of the potential energy surface of Shirin et al. [J. Chem. Phys., 120 (2004) 206] on the basis of recent experimental observations, and a dipole moment surface from Schwenke and Partridge [J. Chem. Phys. 113 (2000) 6592]. The overall agreement between these calculations and the observed spectrum is very good both for the line positions and the line intensities.