Consistency aspects of out-of-plane bending, torsion and shear in a quadratic curved beam element

Curved beams in civil engineering applications call for out-of-plane bending and torsion under the action of13; out-of-plane transverse shear loads. The design of a quadratic displacement curved beam element capable of13; representing shear deformation as in the Timoshenko beam theory requires special attention to the manner in which the shear strain is represented. Field-inconsistent representations of the out-of-plane transverse shear strain will result in a loss of efficiency and introduce spurious oscillations in the bending moment, torsional moment and shear force. The optimal field-consistent assumed strain interpolation for shear is derived and it is demonstrated to posses very high accuracy which is free from spurious force and moment oscillations

Perpendicular electron collisions in drift and acoustic wave instabilities

Perpendicular electron dynamics and the associated collisions are discussed in relation to the collisional drift wave instability. In addition, the limit of small parallel wave numbers of this instability is studied and it is shown to yield a reduced wave frequency. It is also shown that in this case the growth rate in fact {\em decreases} for smaller parallel wave numbers, instead of growing proportional to $1/k_z^2$. As a result, the growth rate appears to be angle dependent and to reach a maximum for some specific direction of propagation. The explanation for this strange behavior is given. A similar analysis is performed for acoustic perturbations in plasmas with unmagnetized ions and magnetized electrons, in the presence of a density gradient.Comment: 7 figure

Robust hybrid global asymptotic stabilization of rigid body dynamics using dual quaternions

A hybrid feedback control scheme is proposed for stabilization of rigid body dynamics (pose and velocities) using unit dual quaternions, in which the dual quaternions and veloc- ities are used for feedback. It is well-known that rigid body attitude control is subject to topological constraints which often result in discontinuous control to avoid the unwinding phenomenon. In contrast, the hybrid scheme allows the controlled system to be robust in the presence of uncertainties, which would otherwise cause chattering about the point of discontinuous control while also ensuring acceptable closed-loop response characteristics. The stability of the closed-loop system is guaranteed through a Lyapunov analysis and the use of invariance principles for hybrid systems. Simulation results for a rigid body model are presented to illustrate the performance of the proposed hybrid dual quaternion feedback control scheme

A projective Dirac operator on CP^2 within fuzzy geometry

We propose an ansatz for the commutative canonical spin_c Dirac operator on CP^2 in a global geometric approach using the right invariant (left action-) induced vector fields from SU(3). This ansatz is suitable for noncommutative generalisation within the framework of fuzzy geometry. Along the way we identify the physical spinors and construct the canonical spin_c bundle in this formulation. The chirality operator is also given in two equivalent forms. Finally, using representation theory we obtain the eigenspinors and calculate the full spectrum. We use an argument from the fuzzy complex projective space CP^2_F based on the fuzzy analogue of the unprojected spin_c bundle to show that our commutative projected spin_c bundle has the correct SU(3)-representation content.Comment: reduced to 27 pages, minor corrections, minor improvements, typos correcte

Expert systems and finite element structural analysis - a review

Finite element analysis of many engineering systems is practised more as an art than as a science . It involves high level expertise (analytical as well as heuristic) regarding problem modelling (e .g. problem specification,13; choosing the appropriate type of elements etc .), optical mesh design for achieving the specified accuracy (e .g . initial mesh selection, adaptive mesh refinement), selection of the appropriate type of analysis and solution13; routines and, finally, diagnosis of the finite element solutions . Very often such expertise is highly dispersed and is not available at a single place with a single expert. The design of an expert system, such that the necessary expertise is available to a novice to perform the same job even in the absence of trained experts, becomes an attractive proposition. 13; In this paper, the areas of finite element structural analysis which require experience and decision-making capabilities are explored . A simple expert system, with a feasible knowledge base for problem modelling, optimal mesh design, type of analysis and solution routines, and diagnosis, is outlined. Several efforts in these directions, reported in the open literature, are also reviewed in this paper

Subcutaneous Phycomycosis in a Child

Subcutaneous phycomycosis is a rare entity. We hereby report a case of subcutaneous phycomycosis in 18 months old female child who presented with a painless, non-tender swelling on the thigh. Skin biopsy showed eosinophilic granuloma lying deep in the subcutaneous tissue, with sparse hyphae. Culture on Sabouraud's dextrose agar showed characteristic colonies. Patient was started on oral potassium iodide. The swelling was completely resolved after one month of treatment

Structural basis of complement membrane attack complex formation

In response to complement activation, the membrane attack complex (MAC) assembles from fluid-phase proteins to form pores in lipid bilayers. MAC directly lyses pathogens by a ‘multi-hit’ mechanism; however, sublytic MAC pores on host cells activate signalling pathways. Previous studies have described the structures of individual MAC components and subcomplexes; however, the molecular details of its assembly and mechanism of action remain unresolved. Here we report the electron cryo-microscopy structure of human MAC at subnanometre resolution. Structural analyses define the stoichiometry of the complete pore and identify a network of interaction interfaces that determine its assembly mechanism. MAC adopts a ‘split-washer’ configuration, in contrast to the predicted closed ring observed for perforin and cholesterol-dependent cytolysins. Assembly precursors partially penetrate the lipid bilayer, resulting in an irregular β-barrel pore. Our results demonstrate how differences in symmetric and asymmetric components of the MAC underpin a molecular basis for pore formation and suggest a mechanism of action that extends beyond membrane penetration

Cardiac transplantation with cyclosporin A and prednisone

Influenced by continuing improvement in results from Stanford, cardiac transplantation was resumed at the University Health Center of Pittsburgh in June 1980. Cyclosporin A (CyA) became available to the authors early in 1981. This report describes the preliminary experience with 21 patients who were treated between March 1981 and April 10, 1982 with cyclosporin A and low-dose steroids. Ages ranged from eight to 53 years, median 46 years. Median age of ten patients disabled because of idiopathic myocardiopathy was 33 years; it was 45 years in the 11 suffering from ischemic heart disease. Sixteen of the 21 patients survived. Eleven have survived for three months, of which six have survived for six months, giving a cumulative survival of 74 and 66%, respectively. Four died perioperatively; one died at six weeks and one at four months. Hyperacute rejection resulted in one death at 12 hours even though the warm and cold lymphocytotoxic crossmatch for T and B cells was negative as evaluated by trypan blue. The two late deaths were related to infection. No late death has occurred because of rejection, and a unique feature is that three recipients with a lymphocytotoxic mismatch did not develop hyperacute rejection. The number of infectious episodes and nonviral infections appears to be less than that associated with the use of azathiaprine and larger doses of steroids. Cyclosporin A (5-10 mg/kg/d) and low-dose prednisone (rapidly tapered in seven days from 200 mg to 15-20 mg/d) is effective in preventing early morbid rejection of the transplanted heart