A Projective C*-Algebra Related to K-Theory

The C*-algebra qC is the smallest of the C*-algebras qA introduced by Cuntz in the context of KK-theory. An important property of qC is the natural isomorphism of K0 of D with classes of homomorphism from qC to matrix algebras over D. Our main result concerns the exponential (boundary) map from K0 of a quotient B to K1 of an ideal I. We show if a K0 element is realized as a homomorphism from qC to B then its boundary is realized as a unitary in the unitization of I. The picture we obtain of the exponential map is based on a projective C*-algebra P that is universal for a set of relations slightly weaker than the relations that define qC. A new, shorter proof of the semiprojectivity of qC is described. Smoothing questions related the relations for qC are addressed.Comment: 11 pages. Added a result about the boundary map in K-theor

Assessment by finite element analysis of the impact of osteoporosis and osteoarthritis on hip resurfacing

Hip resurfacing is proposed as an alternative to total hip replacement (THR) for treatment of osteoarthritis (OA), especially for younger, heavier and more active sufferers. There is however, concern with regards to the incidence of post operative femoral neck fractures. We have investigated, with finite element models, the changes in stress and strain in the femoral neck following hip resurfacing. We have included several different bone material property values representing normal, elderly, osteoarthritic and osteoporotic bone. We have also modelled two different hip implant orientations. We have shown that hip resurfacing may increase the magnitude of stress and strain in the femoral neck, especially in osteoporotic bone. We have also shown that the superolateral offset associated with the valgus orientation, not the valgus orientation itself, may be what reduces the stress and strain in the neck and leads to lower incidence of fracture

Lowest 2\u3csup\u3e+\u3c/sup\u3e, \u3cem\u3eT\u3c/em\u3e = 2 States in \u3csup\u3e20\u3c/sup\u3eMg and \u3csup\u3e20\u3c/sup\u3eF

A recent experiment located the lowest 2+ state in 20Mg and discovered that the corresponding 2+, T = 2 state in 20F does not fit expectations of the isobaric multiplet mass equation without a d term.We have calculated the energies of the ground and 2+ states in 20Mg and the 2+ in 20F in a potential model, using shell-model spectroscopic factors. We conclude that this important 20F state has likely never been observed, and suggest a reaction to find it

Duration judgements in patients with schizophrenia

Background. The ability to encode time cues underlies many cognitive processes. In the light of schizophrenic patients' compromised cognitive abilities in a variety of domains, it is noteworthy that there are numerous reports of these patients displaying impaired timing abilities. However, the timing intervals that patients have been evaluated on in prior studies vary considerably in magnitude (e.g. 1 s, 1 min, 1 h etc.). Method. In order to obviate differences in abilities in chronometric counting and place minimal demands on cognitive processing, we chose tasks that involve making judgements about brief durations of time (<1 s). Results. On a temporal generalization task, patients were less accurate than controls at recognizing a standard duration. The performance of patients was also significantly different from controls on a temporal bisection task, in which participants categorized durations as short or long. Although time estimation may be closely intertwined with working memory, patients' working memory as measured by the digit span task did not correlate significantly with their performance on the duration judgement tasks. Moreover, lowered intelligence scores could not completely account for the findings. Conclusions. We take these results to suggest that patients with schizophrenia are less accurate at estimating brief time periods. These deficits may reflect dysfunction of biopsychological timing processes

Draft Genome Sequence for Desulfovibrio africanus Strain PCS.

Desulfovibrio africanus strain PCS is an anaerobic sulfate-reducing bacterium (SRB) isolated from sediment from Paleta Creek, San Diego, CA. Strain PCS is capable of reducing metals such as Fe(III) and Cr(VI), has a cell cycle, and is predicted to produce methylmercury. We present the D.&nbsp;africanus PCS genome sequence

Stock Return Seasonalities and the Tax-Loss Selling Hypothesis: Analysis of the Arguments and Australian Evidence

A ‘tax-loss selling’ hypothesis has frequently been advanced to explain the ‘January effect’ reported in this issue by Keim. This paper concludes that U.S. tax laws do not unambiguously predict such an effect. Since Australia has similar tax laws but a July–June tax year, the hypothesis predicts a small-firm July premium. Australian returns show pronounced December–January and July–August seasonals, and a premium for the smallest-firm decile of about four percent per month across all months. This contrasts with the U.S. data in which the small-firm premium is concentrated in January. We conclude that the relation between the U.S. tax year and the January seasonal may be more correlation than causation

Almost Commuting Matrices, Localized Wannier Functions, and the Quantum Hall Effect

For models of non-interacting fermions moving within sites arranged on a surface in three dimensional space, there can be obstructions to finding localized Wannier functions. We show that such obstructions are $K$-theoretic obstructions to approximating almost commuting, complex-valued matrices by commuting matrices, and we demonstrate numerically the presence of this obstruction for a lattice model of the quantum Hall effect in a spherical geometry. The numerical calculation of the obstruction is straightforward, and does not require translational invariance or introducing a flux torus. We further show that there is a $Z_2$ index obstruction to approximating almost commuting self-dual matrices by exactly commuting self-dual matrices, and present additional conjectures regarding the approximation of almost commuting real and self-dual matrices by exactly commuting real and self-dual matrices. The motivation for considering this problem is the case of physical systems with additional antiunitary symmetries such as time reversal or particle-hole conjugation. Finally, in the case of the sphere--mathematically speaking three almost commuting Hermitians whose sum of square is near the identity--we give the first quantitative result showing this index is the only obstruction to finding commuting approximations. We review the known non-quantitative results for the torus.Comment: 35 pages, 2 figure