Removal of mercury (II) from aqueous solution by using rice residues

Sorption potential of rice residues for Hg(II) removal from aqueous solution was investigated. Rice husk (RH) and rice straw (RS) were selected and treated with sodium hydroxide (NaOH). The raw and modified adsorbents were characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and BET surface area measurements. The effects of pH, initial ion concentration, and agitation time on the removal process were studied in batch adsorption experiments. Two simple kinetic models, which are pseudo-first-order and pseudo-second-order, were tested to investigate the adsorption mechanisms. The kinetic data fits to pseudo second order model with correlation coefficients greater than 0.99 for all adsorbents. The equilibrium data fitted well with the Langmuir compared to Freundlich isotherm models. Alkali-treated adsorbent obtained larger surface area and RH-NaOH showed highest adsorption capacity followed by RS-Pure > RH-Pure > RS-NaOH. The maximum removal efficiency obtained by RH-NaOH and RS-Pure was 42 mg/l (80%) at pH 6.5 and with 2 days contact time (for 50 mg/l initial concentration and 25 mg adsorbents)

Review and New Case Reports on Scanning Electron Microscopy of Pili Annulati, Monilethrix and Trichothiodystrophy

Pili annulati, Monilethrix and Trichothiodystrophy are uncommon conditions in which the hair shaft has a distinct appearance as seen by optical microscopy and scanning electron microscopy (SEM). We report several new cases and review the characteristic ultrastructural abnormalities investigated by SEM. Pili annulati: abnormal areas which show a longitudinal, curtain-like folding of the cuticular cells, alternating with normal areas. The latter present regularly non-systematized, superficial depressions. Hair specimens of the patient\u27s mother show the same surface irregularities. Monilethrix: most hair shafts show variations in thickness giving a typical nodal appearance. In the isthmus area we noticed longitudinal ridging and cuticular scales that are extended lengthwise in a fish-scale-like pattern. In the nodus area a smooth surface due to a complete loss of cuticular cells, was observed. Trichothiodystrophy: the hair morphology observed by SEM is characterized by severe cuticular and secondary cortical degeneration along the entire length of the flattened hair shaft, with longitudinal ridging, cuticle loss, trichorrhexis nodosa formation and trichoschisis. SEM observations show morphological abnormalities which are characteristic for each pathological condition described. This method may provide data that add some clarity in the surface changes of the different hair shaft anomalies

Consistency test of general relativity from large scale structure of the Universe

We construct a consistency test of General Relativity (GR) on cosmological scales. This test enables us to distinguish between the two alternatives to explain the late-time accelerated expansion of the universe, that is, dark energy models based on GR and modified gravity models without dark energy. We derive the consistency relation in GR which is written only in terms of observables - the Hubble parameter, the density perturbations, the peculiar velocities and the lensing potential. The breakdown of this consistency relation implies that the Newton constant which governs large-scale structure is different from that in the background cosmology, which is a typical feature in modified gravity models. We propose a method to perform this test by reconstructing the weak lensing spectrum from measured density perturbations and peculiar velocities. This reconstruction relies on Poisson's equation in GR to convert the density perturbations to the lensing potential. Hence any inconsistency between the reconstructed lensing spectrum and the measured lensing spectrum indicates the failure of GR on cosmological scales. The difficulties in performing this test using actual observations are discussed.Comment: 7 pages, 1 figur

q-Deformation of W(2,2) Lie algebra associated with quantum groups

An explicit realization of the W(2,2) Lie algebra is presented using the famous bosonic and fermionic oscillators in physics, which is then used to construct the q-deformation of this Lie algebra. Furthermore, the quantum group structures on the q-deformation of this Lie algebra are completely determined.Comment: 12 page

Off-shell effects in dilepton production from hot interacting mesons

The production of dielectrons in reactions involving a_1 mesons and pions is studied. We compare results obtained with different phenomenological Lagrangians that have been used in connection with hadronic matter and finite nuclei. We insist on the necessity for those interactions to satisfy known empirical properties of the strong interaction. Large off-shell effects in dielectron production are found and some consequences for the interpretation of heavy ion data are outlined. We also compare with results obtained using experimentally-extracted spectral functions.Comment: 14 pages, LaTeX2e, 2 figure

Very Long Baseline Array observations of the Intraday Variable source J1128+592

Short time-scale flux density variations of flat spectrum radio sources are often explained by the scattering of radio waves in the turbulent, ionized Interstellar Matter of the Milky Way. One of the most convincing observational arguments in favor of this is the annual modulation of the variability time-scale caused by the Earth orbital motion around the Sun. J1128+592 is an IDV source with a possible annual modulation in its variability time-scale. We observed the source in 6 epochs with the VLBA at 5, 8 and 15 GHz in total intensity and polarization. The VLBA observations revealed an east-west oriented core-jet structure. Its position angle agrees with the angle of anisotropy derived from the annual modulation model. No significant long-term structural changes were observed with VLBI on mas-scales, however, compared to archival data, the VLBI core size is expanded. This expansion offers a possible explanation to the observed decrease of the strength of IDV. VLBI polarimetry revealed significant changes in the electric vector position angle and Rotation Measure of the core and jet. Part of the observed RM variability could be attributed to a scattering screen (37 pc distance), which covers the source (core and jet) and which may be responsible for the IDV. Superposition of polarized sub-components below the angular resolution limit may affect the observed RM as well.Comment: accepted for A&A (11 pages, 11 figures

Bunching Transitions on Vicinal Surfaces and Quantum N-mers

We study vicinal crystal surfaces with the terrace-step-kink model on a discrete lattice. Including both a short-ranged attractive interaction and a long-ranged repulsive interaction arising from elastic forces, we discover a series of phases in which steps coalesce into bunches of n steps each. The value of n varies with temperature and the ratio of short to long range interaction strengths. We propose that the bunch phases have been observed in very recent experiments on Si surfaces. Within the context of a mapping of the model to a system of bosons on a 1D lattice, the bunch phases appear as quantum n-mers.Comment: 5 pages, RevTex; to appear in Phys. Rev. Let

General Localization Lengths for Two Interacting Particles in a Disordered Chain

The propagation of an interacting particle pair in a disordered chain is characterized by a set of localization lengths which we define. The localization lengths are computed by a new decimation algorithm and provide a more comprehensive picture of the two-particle propagation. We find that the interaction delocalizes predominantly the center-of-mass motion of the pair and use our approach to propose a consistent interpretation of the discrepancies between previous numerical results.Comment: 4 pages, 2 epsi figure