Results 1 - 10 of 11
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[en] Waste iron was used to treat high concentration chromate (534 mg/L as Cr) from electroplating wastewater by plug flow reactor (PFR) due to the following reasons: (1) two wastes are treated simultaneously, (2) low pH of the electroplating wastewater (∼2) benefits the reaction between these two wastes, (3) effluent pH is elevated in the PFR, reducing the base requirement to meet the pH discharge standard for wastewater (pH 6-9). Complete chromate reductions were achieved at pH 1.7 for hydraulic retention time (HRT) of 98 min, pH 1.5 for HRT of 40 min and pH 1.3 for HRT of 20 min. Consequently, optimum HRT for complete chromate reduction was obtained for different pHs. Although more acids were used to lower influent pH to reduce HRT, effluent pH was higher due to more hydrogen ion reacting with chromate. Eventually, fewer bases are required to fulfill the discharge pH requirement of wastewater. Effluent pH 3-5 was observed with high turbidity, indicating the precipitations of chromium oxide and hydroxide were enhanced by the dissolved iron coagulation. X-ray diffraction was conducted to examine the remaining species. Other than chromium oxide and hydroxide species, an iron-chromium complex (Cr2FeO4) was also observed
[en] The ferritin homolog, BfrB (Rv3841), from Mycobacterium tuberculosis has been purified, crystallized, and diffraction data were collected to 2.5 Å resolution. Here, preliminary crystallographic characterization and SAXS analyses are reported. Mycobacterium tuberculosis (Mtb) is the causative agent of the deadly disease tuberculosis. Iron acquisition, regulation and storage are critical for the survival of this pathogen within a host. Thus, understanding the mechanisms of iron metabolism in Mtb will shed light on its pathogenic nature, as iron is important for infection. Ferritins are a superfamily of protein nanocages that function in both iron detoxification and storage, and Mtb contains both a predicted ferritin and a bacterioferritin. Here, the cloning, expression, purification, crystallization and preliminary X-ray diffraction analysis of the ferritin homolog (Mtb BfrB, Rv3841) is reported. An Mtb BfrB crystal grown at pH 6.5 using the hanging-drop vapor-diffusion technique diffracted to 2.50 Å resolution and belonged to space group C2, with unit-cell parameters a = 226.2, b = 226.8, c = 113.7 Å, β = 94.7° and with 24 subunits per asymmetric unit. Furthermore, modeling the crystal structure of a homologous ferritin into a low-resolution small-angle X-ray scattering (SAXS) electron-density envelope is consistent with the presence of 24 subunits in the BfrB protein cage quaternary structure
[en] Microlensing can provide a useful tool to probe binary distributions down to low-mass limits of binary companions. In this paper, we analyze the light curves of eight binary-lensing events detected through the channel of high-magnification events during the seasons from 2007 to 2010. The perturbations, which are confined near the peak of the light curves, can be easily distinguished from the central perturbations caused by planets. However, the degeneracy between close and wide binary solutions cannot be resolved with a 3σ confidence level for three events, implying that the degeneracy would be an important obstacle in studying binary distributions. The dependence of the degeneracy on the lensing parameters is consistent with a theoretical prediction that the degeneracy becomes severe as the binary separation and the mass ratio deviate from the values of resonant caustics. The measured mass ratio of the event OGLE-2008-BLG-510/MOA-2008-BLG-369 is q ∼ 0.1, making the companion of the lens a strong brown dwarf candidate.
[en] The Galactic bulge source MOA-2010-BLG-523S exhibited short-term deviations from a standard microlensing light curve near the peak of an A max ∼ 265 high-magnification microlensing event. The deviations originally seemed consistent with expectations for a planetary companion to the principal lens. We combine long-term photometric monitoring with a previously published high-resolution spectrum taken near peak to demonstrate that this is an RS CVn variable, so that planetary microlensing is not required to explain the light-curve deviations. This is the first spectroscopically confirmed RS CVn star discovered in the Galactic bulge.