Organic ligands, such as EDTA, accelerate the dissolution of silicate and oxide minerals. In natural systems, oxyanions can compete with organic ligands for mineral surface sites thereby affecting ligand-promoted dissolution rates, either enhancing or inhibiting dissolution, depending upon pH. The influence of selenite, molybdate and phosphate on the EDTA-promoted dissolution of goethite has been examined and a mechanism proposed for the observed differences in dissolution rates over a pH range of 4–8. We propose that the surface complex formed by EDTA is the controlling factor for the observed dissolution rate, with mononuclear complexes accelerating dissolution compared to bi- or multinuclear complexes. Dissolution results from our experiments suggest that EDTA forms multinuclear complexes at pH values ⩾6 and mononuclear complexes at pH values <6. Dissolution results show that when the oxyanion and the EDTA are present in the system at concentrations nearly equalling the surface sites available for adsorption, the oxyanion reduces the adsorption of EDTA and inhibits dissolution. However, if the oxyanion is present at lower concentrations at pH values ⩾6, EDTA is adsorbed but the number of carboxylic groups that can bind to the surface is reduced causing the formation of mononuclear complexes. This shift to a weaker surface complex enhances the EDTA-promoted dissolution of goethite in the presence of the oxyanions compared to EDTA-promoted dissolution in their absence.

Numerous studies have investigated the ligand-promoted dissolution of Fe (oxyhydr)oxides. In natural environments, inorganic ligands can compete with organic ligands for surface sites on (oxyhydr)oxides which may influence dissolution rates. Published research of this interaction and its effect on the dissolution of (oxyhydr)oxides is rare. The objective of the present study was to examine the extent to which silica, as a naturally occurring competitive ligand added in the form of silicic acid, impacts the oxalate-promoted dissolution of the common soil Fe (oxyhydr)oxide goethite. Sorbed silica reduced the oxalate-promoted dissolution rate of goethite at all surface coverages investigated. As initial silica solution concentrations increased from 0.50 mM to 5.0 mM, relatively little change in the dissolution rate was observed. Fourier-transform infrared (FTIR) spectra indicated that, as silica-surface coverages increased, the silica underwent polymerization on the goethite surface. Initially, silicate was associated with surface functional groups, but as polymerization occurred some of the silica appeared to desorb from the goethite surface without being released into the bulk solution, suggesting that silica polymers formed discrete islands or surface clusters that grew away from the goethite surface rather than expanding epitaxially across the surface. Minimal changes were observed in the quantity of reactive goethite surface, which is responsible for the observed dissolution rates, as silica-surface coverages increased.

Arnold & Porter has been honored to be able to host the annual “L” Reception for current and former members of the Legal Adviser's Office. It was a highlight for me to attend when I was the Legal Adviser. It has been a highlight to sponsor it. We, of course, invite friends of “L” like the two panelists that we have today.

We introduce the concept of infinite cochain sequences and initiate a theory of homological algebra for them. We show how these sequences simplify and improve the construction of infinite coclass families (as introduced by Eick and Leedham-Green) and also how they can be applied to prove that almost all groups in such a family have equivalent Quillen categories. We also include some examples of infinite families of $p$-groups from different coclass families that have equivalent Quillen categories.

Amylose-free (waxy) maize has been a vegetable (cooked ears) and staple food in Southeast Asia for centuries, resulting in hundreds of landraces (LRs) across the region. The recessive waxy allele induces soft grains with preferred cooking and flavour properties. We hypothesized that eating preferences resulted in the additional selection for different starch properties, reflected in altered starch granule morphology or amylopectin structure. A total of 41 LRs were available as starting material that had been used by different ethnic groups in Vietnam and Thailand. Unluckily, some LR were not pure waxy, but we successfully regained the original pure waxy status for most. Twenty LR were chosen for analysis of starch traits according to their purity. Four different waxy mutations were identified, including two unknown alleles. This is a strong proof for parallel independent selection of waxy maize in the region. Starch granule morphology and size were similar among all LRs. Gelatinization properties differed only between waxy and wild-type LR, and all waxy LR were comparable to a commercial waxy hybrid. The fine structure of waxy amylopectin had fewer short chains compared with that in wild-type. So far, the differences observed in starch properties are likely associated exclusively with the waxy trait. Despite the strong selection for amylose-free starch, there was no evidence for additional region wide selection for other special starch properties in our collection. In conclusion, all analyses did not encourage further targeted research on allelic variation of other starch metabolism genes for future use in the food and feed industry.

We exhibit a practical algorithm for solving the constructive membership problem for discrete free subgroups of rank $2$ in $\mathrm{PSL}_2(\mathbb{R})$ or $\mathrm{SL}_2(\mathbb{R})$. This algorithm, together with methods for checking whether a two-generator subgroup of $\mathrm{PSL}_2(\mathbb{R})$ or $\mathrm{SL}_2(\mathbb{R})$ is discrete and free, have been implemented in Magma for groups defined over real algebraic number fields.

Supplementary materials are available with this article.

We describe an effective algorithm to compute a set of representatives for the conjugacy classes of Hall subgroups of a finite permutation or matrix group. Our algorithm uses the general approach of the so-called ‘trivial Fitting model’.

The present work shows results on elemental distribution analyses in Cu(In,Ga)Se2 thin films for solar cells performed by use of wavelength-dispersive and energy-dispersive X-ray spectrometry (EDX) in a scanning electron microscope, EDX in a transmission electron microscope, X-ray photoelectron, angle-dependent soft X-ray emission, secondary ion-mass (SIMS), time-of-flight SIMS, sputtered neutral mass, glow-discharge optical emission and glow-discharge mass, Auger electron, and Rutherford backscattering spectrometry, by use of scanning Auger electron microscopy, Raman depth profiling, and Raman mapping, as well as by use of elastic recoil detection analysis, grazing-incidence X-ray and electron backscatter diffraction, and grazing-incidence X-ray fluorescence analysis. The Cu(In,Ga)Se2 thin films used for the present comparison were produced during the same identical deposition run and exhibit thicknesses of about 2 μm. The analysis techniques were compared with respect to their spatial and depth resolutions, measuring speeds, availabilities, and detection limits.

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

Almost forty years since the publication of Cutler's landmark “Oral history—its nature and uses for educational history,” growing numbers of historians of education have adopted oral interviews as the basis for historical analysis. Furthermore, questions about the objectivity of oral sources in view of memory's fallibility have been more productively redirected toward exploring, in light of credibility standards borrowed from the social sciences and literary theory, the many hues of subjectivity of oral historical testimonies, and their implications for understanding same past events from multiple perspectives. As Portelli aptly states, “the first thing that makes oral history different, is that it tells us less about events than about their meaning” He boldly asserts that “what informants believe is indeed a historical fact “that is, the fact that they believe it”, as much as what really happened.” Oral historians not only reproblematized memory for historians by focusing attention on understanding the subjectivity of memory as a manifestation of historical consciousness, but they also brought to our attention how memories are gendered, racialized, and class based. They brought to our attention the importance of examining why different individuals and groups experience the same event in very different ways. Today, oral sources, particularly since the 1990s when historians began investigating the construction of identities, are compared less pejoratively with documentary sources by academic disciplinarians. And oral historians continue to break down “boundaries between the educational institution and the world, between the [history] profession and ordinary people.” However, they also continue to be faced with the challenge of articulating “the connection between individual and social historical consciousness.”

This article contributes to our historical understanding of student experience in general, and more particularly, to our understanding of developing cross-group relationships within desegregated schools over the second half of the twentieth century. The article draws from a broader study that examines students' evolving relationships within a matrix of intersecting identities in a Baltimore County comprehensive high school in Maryland between 1950 and 2000. The focus in this article is on Miller High students of the 1950s and 1960s during the early years of desegregation. Relationships remembered by graduates bring to light the hierarchical structure that distinguished white students along class and gender lines within an academically tracked system and the limitations and possibilities afforded African-American youth across class and gender as they encountered Miller High established norms for the first time in 1956 when the school desegregated.

The authors present an algorithm to construct conjugacy class representatives of the solvable primitive subgroups of Sd for a given degree d. Using this method, they determine the solvable primitive permutation groups of degree at most 6560 (that is, 38 – 1), up to conjugacy.

Historically, most SEM operators used accelerating voltages that were fairly high, quite often in the range of 15–20 kV. Now progress in electron optics has made low-voltage observations a routine mode of SEM operation. The greatly improved range of utilized accelerating voltages provides the SEM operator with additional flexibility and with additional responsibilities for choosing the right SEM settings for image acquisition.