Stacking sequences for extensionally isotropic, fully isotropic and quasi-homogeneous orthotropic laminates

Stacking sequence listings are presented for fully uncoupled Extensionally Isotropic (EILs), Fully Isotropic (FILs) and Quasi-Homogeneous Orthotropic (QHOLs) angle-ply Laminates, with up to 21 plies. All are sub-sets of a definitive list of Fully Orthotropic Laminates (FOLs), containing generally non-symmetric stacking sequences that are characterized in terms of angle- and cross-ply sub-sequence symmetries. Dimensionless parameters are given for each stacking sequence, from which the ABD matrix is readily derived. Expressions relating these dimensionless parameters to the well-known lamination parameters are also given, together with graphical representations of the feasible domains for Pi/3 and Pi/4 EILs and angle-ply QHOLs containing two and three ply orientations. The feasible domain for Pi/3 FILs is represented graphically by a single point, whereas the domain for angle-ply QHOLs containing four ply orientations is represented by a single stacking sequence

On the Decomposition of Clifford Algebras of Arbitrary Bilinear Form

Clifford algebras are naturally associated with quadratic forms. These algebras are Z_2-graded by construction. However, only a Z_n-gradation induced by a choice of a basis, or even better, by a Chevalley vector space isomorphism Cl(V) \bigwedge V and an ordering, guarantees a multi-vector decomposition into scalars, vectors, tensors, and so on, mandatory in physics. We show that the Chevalley isomorphism theorem cannot be generalized to algebras if the Z_n-grading or other structures are added, e.g., a linear form. We work with pairs consisting of a Clifford algebra and a linear form or a Z_n-grading which we now call 'Clifford algebras of multi-vectors' or 'quantum Clifford algebras'. It turns out, that in this sense, all multi-vector Clifford algebras of the same quadratic but different bilinear forms are non-isomorphic. The usefulness of such algebras in quantum field theory and superconductivity was shown elsewhere. Allowing for arbitrary bilinear forms however spoils their diagonalizability which has a considerable effect on the tensor decomposition of the Clifford algebras governed by the periodicity theorems, including the Atiyah-Bott-Shapiro mod 8 periodicity. We consider real algebras Cl_{p,q} which can be decomposed in the symmetric case into a tensor product Cl_{p-1,q-1} \otimes Cl_{1,1}. The general case used in quantum field theory lacks this feature. Theories with non-symmetric bilinear forms are however needed in the analysis of multi-particle states in interacting theories. A connection to q-deformed structures through nontrivial vacuum states in quantum theories is outlined.Comment: 25 pages, 1 figure, LaTeX, {Paper presented at the 5th International Conference on Clifford Algebras and their Applications in Mathematical Physics, Ixtapa, Mexico, June 27 - July 4, 199

Perforated acute appendicitis resulting from appendiceal villous adenoma presenting with small bowel obstruction: a case report

<p>Abstract</p> <p>Background</p> <p>A villous adenoma is an extremely rare benign tumour in the appendix, in contrast to other benign appendiceal lesions. The clinical features are usually asymptomatic. Acute appendicitis is the most common complication with the lesion obstructing the orifice of the appendiceal lumen. Thus, a villous adenoma is usually found during surgical intervention for acute appendicitis. Mechanical obstruction induced by acute perforated appendicitis has been previously reported. Acute appendicitis caused by a villous adenoma presenting with acute intestinal obstruction has not been previously reported.</p> <p>Case presentation</p> <p>A 78-year-old woman presented to our Emergency Department with diffuse abdominal pain and tenderness. The abdominal plain film and computed tomography revealed an intestinal obstruction. After surgical intervention, the ruptured appendix was shown to be associated with intestinal obstruction. The post-operative pathologic diagnosis was an appendiceal villous adenoma.</p> <p>Conclusions</p> <p>This is the first report describing an appendiceal villous adenoma, which is an occasional cause of perforated acute appendicitis, presenting as a complete intestinal obstruction. We emphasize that in elderly patients without a surgical history, the occult cause of complete intestinal obstruction must be determined. If an appendiceal tumour is diagnosed, an intra-operative frozen section is suggested prior to selecting a suitable method of surgical intervention.</p

Double Counting Ambiguities in the Linear Sigma Model

We study the dynamical consequences imposed on effective chiral field theories such as the quark-level SU(2) linear $\sigma$ model (L$\sigma$M) due to the fundamental constraints of massless Goldstone pions, the normalization of the pion decay constant and form factor, and the pion charge radius. We discuss quark-level double counting L$\sigma$M ambiguities in the context of the Salam-Weinberg $Z = 0$ compositeness condition. Then SU(3) extensions to the kaon are briefly considered.Comment: 23 pages To be published in Journal of Physics