46,109 research outputs found
Some electrochemical aspects of the Becher process
No full textThe Becher process is used to upgrade ilmenite (~60% TiO2) to synthetic rutile (92-95% TiO2). Reduced ilmenite (FeTiO2) is an intermediate mineral product and the industrial process whereby metallic iron is corroded from the TiO2 matrix (leaving synthetic rutile) using air and ammonium chloride solutions is termed aeration. This thesis is concerned with the electrochemistry of the corrosion reaction that is the heart of this aeration step.
Synthetic rutile is almost exclusively used as a feedstock for the chloride process which produces pigment grade TiO2. The Becher process is but one a number of processes that produce feedstocks for the chloride process. Together with the Becher process, these alternative processes are briefly reviewed in Chapter 1 followed by a detailed review of the Becher aeration step. Also included in Chapter 1 is a brief review of the thermodynamics for the iron-water system and, following a literature review on ferrous-ammine chemistry, a new Eh-pH diagram for the iron-water-ammonia system is presented using recently published data.
The investigation of the electrochemistry of anodic iron dissolution in Chapter 3 reveals some interesting results about the influence of aqueous NH4Cl. An air-formed film only a few monolayers thick (9-18 Å) passivates iron after surface preparation. Ammonium ion is responsible for the rapid removal of this film after immersion which then allows fast active dissolution to occur upon anodic polarisation. Without ammonium ion the air-formed film passivates the iron during polarisation. Ammonium ion also increases the active dissolution current density while chloride inhibits active dissolution. However, chloride is responsible for breaking down the air- and anodicallyformed films at relatively high anodic potentials. The activation energy for anodic iron dissolution in 0.2 M NH4Cl up to 150°C is reported.
In Chapter 4 it is shown that oxygen is reduced on iron via a 4-electron mechanism in air-saturated 0.2 M NH4Cl and that reduction is diffusion controlled. On gold, every oxygen molecule requires between 0 and 4 electrons depending on the potential. The oxygen reduction current density is proportional to the oxygen partial pressure up to 300 kPa. At 300 kPa oxygen partial pressure, the current density nearly doubled between 80 and 130_C due to the combination of three different effects.
In Chapter 5 it is shown that in air-saturated 0.2 M NH4Cl the air-formed film inhibits iron corrosion for the first 20 to 30 minutes but then is removed allowing iron to corrode quickly and uniformly. _-FeOOH forms continuously as a porous film adhering to the surface and begins to inhibit corrosion only after 3 hours immersion. Ammonium ion is necessary for the removal of the air-formed film while chloride alone results in the localised breakdown of the film leading to pitting corrosion. However, above pH 7.5, the air-formed film is stable even in the presence of ammonium ion and, in the presence of chloride, pitting corrosion also results. Even though iron corrosion is essentially oxygen diffusion controlled at ambient pressures, the corrosion rate is not proportional to the oxygen partial pressure due to the formation of a thick _-FeOOH film. Increasing the temperature to above 80°C increases the corrosion rate at high pressure largely due to solubilisation of the thick film.
A novel application of the carbon paste electrode technique to the investigation of the electrochemistry of anodic iron dissolution from whole reduced ilmenite grains is described in Chapter 6. Anodic dissolution is potential dependent but strongly limited by an air-formed passive film. Ammonium ions do not assist in the removal of this film; rather, chloride ions were found to increase the anodic current density by assisting in the breakdown of the air-formed passive film. Also presented in this Chapter is some preliminary evidence linking the variability of the aeration time with the stability of the air-formed film: the less stable the air-formed film, the shorter the aeration time
Letter from Arno B. Cammerer to J. R. Eakin
No full textLetter from Arno B. Cammerer to J. R. Eakin describing the procedure for purchasing Bright Angel Trail
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Picosecond kinetics of the fluorescence from the chromophore of the purple membrane protein of Halobacterium halobium
No full textDispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Measurement of the ratio of branching fractions B(B0→K∗0γ )/B(B0s→φγ ) and the directCP asymmetry inB 0→K∗0γ
No full textThe ratio of branching fractions of the radiative B decays B0→K⁎0γ and B0s→ϕγ has been measured using an integrated luminosity of 1.0 fb−1 of pp collision data collected by the LHCb experiment at a centre-of-mass energy of s√=7TeV. The value obtained is
B(B0→K⁎0γ)B(B0s→ϕγ)=1.23±0.06(stat.)±0.04(syst.)±0.10(fs/fd),
where the first uncertainty is statistical, the second is the experimental systematic uncertainty and the third is associated with the ratio of fragmentation fractions fs/fd. Using the world average value for B(B0→K⁎0γ), the branching fraction B(B0s→ϕγ) is measured to be (3.5±0.4)×10−5.
The direct CP asymmetry in B0→K⁎0γ decays has also been measured with the same data and found to be
ACP(B0→K⁎0γ)=(0.8±1.7(stat.)±0.9(syst.))%.
Both measurements are the most precise to date and are in agreement with the previous experimental results and theoretical expectations
Branching fraction and CP asymmetry of the decays B+→K0Sπ+ and B+→K0SK+
No full textAn analysis of B+ → K0
Sπ+ and B+ → K0
S K+ decays is performed with the LHCb experiment. The pp
collision data used correspond to integrated luminosities of 1 fb−1 and 2 fb−1 collected at centre-ofmass
energies of
√
s = 7 TeV and
√
s = 8 TeV, respectively. The ratio of branching fractions and the
direct CP asymmetries are measured to be B(B+ → K0
S K+
)/B(B+ → K0
Sπ+
) = 0.064 ± 0.009 (stat.) ±
0.004 (syst.), ACP(B+ → K0
Sπ+
) = −0.022 ± 0.025 (stat.) ± 0.010 (syst.) and ACP(B+ → K0
S K+
) =
−0.21 ± 0.14 (stat.) ± 0.01 (syst.). The data sample taken at
√
s = 7 TeV is used to search for
B+
c
→ K0
S K+ decays and results in the upper limit ( fc · B(B+
c
→ K0
S K+
))/( fu · B(B+ → K0
Sπ+
)) <
5.8 × 10−2 at 90% confidence level, where fc and fu denote the hadronisation fractions of a ¯b
quark
into a B+
c or a B+ meson, respectively
General Protocol to Obtain D‐Glucosamine from Biomass Residues: Shrimp Shells, Cicada Sloughs and Cockroaches
No full textBertuzzi, Diego L., Becher, Tiago B., Capreti, Naylil M. R., Amorim, Julio, Jurberg, Igor D., Megiatto, Jackson D., Ornelas, Catia (2018): General Protocol to Obtain D-Glucosamine from Biomass Residues: Shrimp Shells, Cicada Sloughs and Cockroaches. Global Challenges (Hoboken, NJ) 2 (11), No. 1800046: 1-6, DOI: 10.1002/gch2.201800046, URL: http://dx.doi.org/10.1002/gch2.20180004
Detailed proteome analysis of growing cells of the planctomycete Rhodopirellula baltica SH1T
No full textRhodopirellula baltica SH1(T), which was isolated from the water column of the Kieler Bight, a bay in the southwestern Baltic Sea, is a marine aerobic, heterotrophic representative of the ubiquitous bacterial phylum Planctomycetes. We analyzed the R. baltica proteome by applying different preanalytical protein as well as peptide separation techniques (1-D and 2-DE, HPLC separation) prior to MS. That way, we could identify a total of 1115 nonredundant proteins from the intracellular proteome and from different cell wall protein fractions. With the contribution of 709 novel proteins resulting from this study, the current comprehensive R. baltica proteomic dataset consists of 1267 unique proteins (accounting for 17.3% of the total putative protein-coding ORFs), including 261 proteins with a predicted signal peptide. The identified proteins were functionally categorized using Clusters of Orthologous Groups (COGs), and their potential cellular locations were predicted by bioinformatic tools. A unique protein family that contains several YTV domains and is rich in cysteine and proline was found to be a component of the R. baltica proteinaceous cell wall. Based on this comprehensive proteome analysis a global schema of the major metabolic pathways of growing R. baltica cells was deduced
Convex B-Spline Surfaces
No full textThis paper gives a definition for the convexity of B-spline surfaces and points out the conditions on which the convexity depends. A back shift smoothing method is introduced. This method is built on the basis of the convexity conditions. Application of this smoothing method gives a strictly convex curv
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