Superkonvexe analysis

Ohne Zusammenfassung     

The separation of platinum and iridium by ion flotation

The anionic chlorocomplexes of platinum(IV) and iridium(III) are separated by ion flotation from acidic, aqueous solutions with cationic surfactants of the type C₁₆H₃₃NR'₃Br, where R' is methyl, ethyl, n-propyl, or n-butyl. The PtCl₆^2-, which forms readily floatable salts with each of the surfactants, is selectively floated from the IrCl₆^3- and recovered after flotation in n-butyl acetate. The efficiency of the separation increases as the R' chain length increases and a quantitative separation is obtained with hexadecyltributyl-ammonium bromide (HTBAB) in 0.1 M HCl solutions. Since the flotation properties of Ir(IV) are similar to those of Pt(IV), hydroxylamine hydrochloride is used to reduce Ir(IV) to Ir(in) selectively in the presence of Pt(IV).     

“I Actually Learned A Lot from This”: A Field Assignment to Prepare Future Preservice Math Teachers for Culturally Diverse Classrooms

Teacher education programs are cognizant of the need to prepare preservice teachers (PTs) to work effectively with children from diverse cultural backgrounds. Well-constructedfield experiences can help PTs develop awareness and gain understanding of important cultural considerations related to effective teaching and learning ( Sleeter, 2001 ). This paper describes a unique field assignment created for an Elementary Math Methods course in which 61 PTs were trained to conduct a semi-structured interview with a student whose cultural background was different than their own. PTs transcribed their own interviews and completed a guided reflection on their experiences. Reflections were submitted and analyzed for emerging themes. Analyses suggest that the structured interview component of this field assignment provided PTs with increased insight into mathematics instruction and the learning needs of diverse students. We also discuss the value and limitations of this instructional innovation and propose avenues by which to continue to help PTs grow toward becoming culturally relevant pedagogists ( Irvine, 2003 ).     

Estimating the measurement uncertainty in forensic breath-alcohol analysis

The evidentiary weight attributed to forensic breath alcohol results in drunk-driving prosecutions requires that measurement uncertainty be established and shown to be fit-for-purpose. The principal components contributing to breath alcohol measurement uncertainty include: (1) biological/sampling, (2) instrumental, (3) traceability and (4) the water/air partition coefficient for control standards. Employing duplicate breath results from over 92,000 subjects to estimate the biological/sampling component and assuming reasonable forensic values for the other components, the combined and expanded uncertainty is determined for a practical example. The combined uncertainty for an unbiased single determination breath alcohol measurement was: . Employing the expanded uncertainty (k = 2.58), the 99% confidence interval for a mean breath alcohol concentration of 0.0935 g/210 L was 0.0866 to 0.1004 g/210 L. The proportion of combined uncertainty associated with each component was determined to be: biological/sampling 73%, analytical 10%, traceability 13% and water/air partition coefficient 4%. These are forensically acceptable estimates and demonstrate fitness-for-purpose of breath alcohol measurement when employing appropriate elements of quality control.     

Electrospray mass spectrometry of neuac oligomers associated with the c fragment of the tetanus toxin

The Clostridial neurotoxins, botulinum and tetanus, gain entry into motor neurons by binding to the sialic or N-acetylneuraminic acid (NeuAc) residues of gangliosides and specific protein receptors attached to the cell's surface. While the C-fragment of tetanus toxin (TetC) has been identified to be the ganglioside binding domain, remarkably little is known about how this domain discriminates between the structural features of different gangliosides. We have used electrospray ionization mass spectrometry (ESI-MS) to examine the formation of complexes between TetC and carbohydrates containing NeuAc groups to determine how NeuAc residues contribute to ganglioside binding. ESI-MS was used to obtain an estimate of the dissociation constants (KD values) for TetC binding to a number of related NeuAc-containing carbohydrates (sialyllactose and disialyllactose), as well as six (NeuAc)n oligomers (n = 1-6). KD values were found to range between approximately 10-35 microM. The strength of the interactions between the C fragment and (NeuAc)n are consistent with the topography of the targeting domain of tetanus toxin and the nature of its carbohydrate binding sites. These results suggest that the targeting domain of tetanus toxin contains two binding sites that can accommodate NeuAc (or a dimer) and that NeuAc may play an important role in ganglioside binding and molecular recognition, a process critical for normal cell function and one frequently exploited by toxins, bacteria, and viruses to facilitate their entrance into cells.     

A holonomy characterisation of Fefferman spaces

We prove that Fefferman spaces, associated to non-degenerate CR structures of hypersurface type, are characterised, up to local conformal isometry, by the existence of a parallel orthogonal complex structure on the standard tractor bundle. This condition can be equivalently expressed in terms of conformal holonomy. Extracting from this picture the essential consequences at the level of tensor bundles yields an improved, conformally invariant analogue of Sparling’s characterisation of Fefferman spaces.     

Construction of p-1 Irreducible Modules with Fundamental Highest Weight for the Symplectic Group in Characteristic p

Let K be a field and let V be a vector space of dimension 2mover K. Let V denote the exterior algebra of V and ^kV its kthexterior power for 0k2m. Let f be a non-degenerate alternatingbilinear form defined on VxV. The symplectic group Sp_2m(K) isthe group of all isometries of f and it acts as a group of vectorspace automorphisms on ^kV. In the case that K is algebraicallyclosed and 1km, it is known that ^kV contains a composition factorcorresponding to the fundamental weight _k of a root system oftype C_m. We shall refer to the irreducible module for Sp_2m(K)given by this composition factor as a fundamental module.     

The separation of iridium and ruthenium by ion flotation

Mixtures of iridium(IV) and ruthenium(III) as IrCl^2?₆ and RuCl^t—₆ are separated by ion flotation. Iridium (IV) is selectively floated from mixtures of the metal complexes in aqueous 1.0 M hydrochloric acid with hexadecylpyridinium bromide (HPB) and nitrogen. Ruthenium(III) does not float under the same conditions. In order to assess the usefulness of this procedure, the separation was also investigated with hexadecyltrimethylammonium bromide and hexadecyltripropylammonium bromide, from solutions of varying concentrations of sodium chloride, sodium nitrite and hydrochloric acid. Under optimal conditions at the 5 × 10^?5 M level, 78% of the iridium is recovered free of ruthenium, provided that excess of HPB and > 1 M chloride are present.