Study of width and height of EIT resonance in a Doppler broadened five-level system with varying probe power

We report the experimental observation of electromagnetically induced transparency (EIT) in a Doppler broadened rubidium vapour at room temperature for different probe intensities at a fixed pump intensity in a five-level Λ-type system formed by the D₂ transition of ⁸⁵Rb. For a constant pump intensity, we find that the EIT width and height change with the variation of probe intensity. We observe a nonlinear variation of the height of the EIT peak and a linear variation of the width (FWHM) of the EIT signal with probe intensity. In the Doppler broadened multilevel system, we also observe the velocity selective dips along with the EIT signal. A numerical simulation of the probe response signal based on density matrix representation in a five-level system is carried out to reproduce the experimentally observed spectra.     

Hysteresis and Horizontal Redistribution in Porous Media

It is well known that multiphase flow in porous media exhibits hysteretic behaviour. This is caused by different fluid–fluid behaviour if the flux reverses. For example, for flow of water in unsaturated soils the process of imbibition and drainage behaves differently. In this paper we study a new model for hysteresis that extends the current playtype hysteresis model in which the scanning curves between drainage and imbibition are vertical. In our approach the scanning curves are non-vertical and can be constructed to approximate experimentally observed scanning curves. Furthermore our approach does not require any book-keeping when the flux reverses at some point in space. Specifically, we consider the problem of horizontal redistribution to illustrate the strength of the new model. We show that all cases of redistribution can be handled, including the unconventional flow cases. For an infinite column, our analysis involves a self-similar transformation of the equations. We also present a numerical approach (L-scheme) for the partial differential equations in a finite domain to recover all redistribution cases of the infinite column provided time is not too large.     

Anisotropic charge transport properties of chrysene derivatives as organic semiconductor: A computational study

We used density functional theory to calculate the angular resolution anisotropic charge mobility of the substituted chrysene molecules, viz, 4,10‐diphenoxychrysene (DPC), 4,10‐bis(phenylsulfanyl)chrysene (BPSC), and ethyl 8,9,12‐trimethoxychrysene‐6‐carboxylate (ETCC). The highest occupied molecular orbital–lowest unoccupied molecular orbital gap for DPC, BPSC, and ETCC was calculated to be 3.92, 3.83, and 3.81 eV, respectively, which inferred the compounds to be wide‐band‐gap semiconductors indicating that the compounds should have high stability in atmospheric conditions. The fact is also supported by electronic band‐structure calculation. In addition, higher electron affinity of studied compounds as compared with the bare chrysene molecule imparts enhancement of n‐type character in the compounds. The maximum hole ( ) and electron mobilities ( ) for DPC compound were found to be 0.739 cm²V^?1s^?1 and 0.319 cm²V^?1s^?1, respectively, at Φ = 0°. On the other hand, in the case of BPSC crystal, comparatively larger anisotropic electron mobility (0.709 cm²V^?1s^?1 at Φ = 0° and Φ = 179.90°) than the hole mobility (0.208 cm²V^?1s^?1 at Φ = 127.19° and Φ = 307.10°) was noted. Similarly, in ETCC, the parallel dimers were found to contribute maximum and of 0.052 and 0.102 cm²V^?1s^?1, respectively, at Φ = 0°. The substitution of ‐SPh in BPSC and ‐OCH₃ and ‐CO₂CH₂CH₃ in ETCC have relatively more impact on band reduction than ‐OPh in DPC, thus facilitating electron transport in BPSC and ETCC.     

Assessment of recovery and recrystallisation behaviours of cold rolled IF steel through non-destructive electromagnetic characterisation

The recovery and recrystallisation behaviours of cold rolled IF steel have been investigated by destructive (optical microscopy and hardness) and non-destructive electromagnetic sensor, (which allows direct measurement of strip samples with no surface preparation) techniques. The onset and completion of recrystallisation are clearly monitored through destructive techniques of optical microscopy and hardness measurements. The nucleation of new recrystallised grains is observed in the sample annealed at 600 °C/15 min, while completion of recrystallisation takes place at 700 °C/15 min. The destructive techniques are not very accurate in monitoring recovery, for example, changes in hardness of <20% are seen. In contrast, the magnetic properties of annealed steel show the onsets of both recovery and recrystallisation, with recovery accounting for ≈60% change in the coercivity value. Therefore, the measurement of magnetic softening through an electromagnetic sensor acts a crucial role for understanding recovery and recrystallisation behaviours of steels during industrial processing. The present investigation is aimed not only for controlling product quality but also saving characterisation time through off line monitoring during steel processing at industry.     

Manifestations of drag reduction by polymer additives in decaying, homogeneous, isotropic turbulence

The existence of drag reduction by polymer additives, well established for wall-bounded turbulent flows, is controversial in homogeneous, isotropic turbulence. To settle this controversy, we carry out a high-resolution direct numerical simulation of decaying, homogeneous, isotropic turbulence with polymer additives. Our study reveals clear manifestations of drag-reduction-type phenomena: On the addition of polymers to the turbulent fluid, we obtain a reduction in the energy-dissipation rate, a significant modification of the fluid energy spectrum especially in the deep-dissipation range, a suppression of small-scale intermittency, and a decrease in small-scale vorticity filaments.     

Polyacrylamide Grafted Carboxymethyl Tamarind (CMT-g-PAM): Development and Application of a Novel Polymeric Flocculant

Water is scarce commodity now. Recycling of municipal wastewater, industrial and mineral processing effluents require treatment with the inorganic or organic flocculants. Both synthetic and natural polymers are used as flocculants. Natural polymers are biodegradable and are effective at very large dosages but are very shear stable. The synthetic polymers are highly effective flocculants at very small dosages and have high tailorability, but have poor shear stability. In the authors' laboratory, a novel polymeric flocculant has been developed by grafting polyacrylamide onto the backbone of carboxymethyl tamarind (CMT-g-PAM). Various grades were developed to optimize the best flocculant. The grafted polymers were characterized by various characterization techniques such as intrinsic viscosity measurement, FTIR spectroscopy, ¹³C-NMR spectroscopy, elemental analysis etc. The flocculation studies were carried out using turbidity test as well as settling test. The optimized CMT-g-PAM was then compared with some of the commercial flocculants available in national and international markets in colloidal suspensions and it has been found that our synthesized flocculant surpasses most of the commercial flocculants in performance.     

Evidence for the charged θ-meson

A K-meson is found to decay at rest into a nearly relativistic secondary particle. The secondary particle produces a nuclear disintegration in flight and is identified as a π-meson of kinetic energy ～ 110 MeV. The event is interpreted as the decay of a θ^±-meson according to the scheme:

$$\theta ^ \pm \to \pi ^ \pm + \pi ^0 + (222 \pm 12 MeV.)$$     

Introduction to Linear Programming

Journal of the Operational Research Society -     

Spectroscopic studies on nanodispersions of CdS,HgS, their core-shells and composites prepared in micellar medium

CdS is a large band gap material compared to HgS. Both are interesting from academic and technological points of view. The nanodispersions (colloids) of CdS and HgS as well their core-shell products and composites (co-colloids) were prepared by varied modes of precursor addition in micellar solution of cationic surfactant cetyltrimethylammonium bromide (CTAB). The prepared dispersions were studied by spectroscopic and electron microscopic techniques.This revised version was published online in August 2005 with a corrected issue number.     

Continuous, on-line monitoring of haloacetic acids via membrane extraction

Haloacetic acids are an important class of disinfection byproducts that are being regulated. In this paper we report novel instrumentation for continuous monitoring of the nine haloacetic acids. Hollow fiber liquid-liquid membrane extraction (LLME) and supported liquid membrane extraction (SLME) followed by on-line HPLC-UV detection were studied. With continuous LLME, seven halo-acetic acids could be analyzed and enrichment factor (EF) was around 50. All the nine acids could be extracted and quantified by continuous SLME. Experiments with laboratory standards demonstrated that EF and extraction efficiency could be as high as 500 and 54%, respectively. Relative standard deviations based on seven replicates were between 3.3 and 10.3%, and the MDLs were at sub-ppb levels.