A Spectral Finite Element Approach to Modeling Soft Solids Excited with High-Frequency Harmonic Loads

An approach for efficient and accurate finite element analysis of harmonically excited soft solids using high-order spectral finite elements is presented and evaluated. The Helmholtz-type equations used to model such systems suffer from additional numerical error known as pollution when excitation frequency becomes high relative to stiffness (i.e. high wave number), which is the case, for example, for soft tissues subject to ultrasound excitations. The use of high-order polynomial elements allows for a reduction in this pollution error, but requires additional consideration to counteract Runge's phenomenon and/or poor linear system conditioning, which has led to the use of spectral element approaches. This work examines in detail the computational benefits and practical applicability of high-order spectral elements for such problems. The spectral elements examined are tensor product elements (i.e. quad or brick elements) of high-order Lagrangian polynomials with non-uniformly distributed Gauss-Lobatto-Legendre nodal points. A shear plane wave example is presented to show the dependence of the accuracy and computational expense of high-order elements on wave number. Then, a convergence study for a viscoelastic acoustic-structure interaction finite element model of an actual ultrasound driven vibroacoustic experiment is shown. The number of degrees of freedom required for a given accuracy level was found to consistently decrease with increasing element order. However, the computationally optimal element order was found to strongly depend on the wave number.     

Porous composites of hydroxyapatite‐filled poly[ethylene‐co‐(vinyl acetate)] for tissue engineering

A novel porous composite of hydroxyapatite/poly[ethylene‐co‐vinyl acetate)] (HAP/EVA) having better osteointegration was fabricated by gas foaming technique using a non toxic gas blowing agent intended for bone replacement applications. Combined techniques of scanning electronic microscopy (SEM) and X‐ray microcomputed tomography (µCT) analysis showed that the pore size and pore volume of the porous composite decrease with the increase of HAP content. The gravimetric analysis evidenced for good pore interconnectivity within the porous composites. Energy dispersive X‐ray analysis (EDX) studies inveterated the even scattering of Ca ions which in turn indicate the uniform dispersion of HAP particles in the composites. The significant gradation in Ca ion concentration seen in EDX studies is well accordance with the amount of HAP loading in the sample. Mechanical properties of the porous composite having different HAP content were measured to have the compressive strength varying from 1.06 to 2.2 MPa. Non‐cytotoxic character of the material was observed by the cytocompatibility studies. The metabolic activity of L929 cells seeded on the material assessed by [3‐(4,5‐dimethylthiazol)‐2‐yl]‐2,5‐diphenyltertrazolium bromide (MTT) assay was found to be 91.8%. The adhesion and migration of the cells inside the pore walls were visualized by confocal microscopy. Copyright © 2010 Society of Chemical Industry     

Stay on Your Feet Safety Walks Group

The Safety Walks Group is an initiative that evolved from the Stay on Your Feet Program. The strategies used in this program target both behavioural and environmental change and are based on the five areas for action under the Ottawa Charter (WHO, 1986) and Jakarta Declaration (WHO, 1997). The Safety Walks Group addresses the issue of public hazards via the use of a standard checklist covering pedestrian areas, business houses and accommodation. The project provided a forum for seniors to be proactive, working with the authorities to address the issue of public hazards and make the environment safer.     

Pharmacokinetics of 2-oxothiazolidine-4-carboxylate, a cysteine prodrug, and cysteine

The pharmacokinetics of both 2-oxothiazolidine-4-carboxylate (OTZ), a prodrug of cysteine, and total blood cysteine (cysteine plus cystine) were investigated in 18 healthy volunteers. OTZ was given either as a single, 2-hour intravenous infusion (56-66 mg/kg) or similarly infused (70-100 mg/kg) every 8 hours for four doses. Blood was assayed for OTZ, total blood cysteine, and glutathione. The pharmacokinetics of OTZ were analyzed alone and simultaneously with total cysteine using the NONMEM software package (University of California at San Francisco. The pharmacokinetics of OTZ were best described by Michaelis-Menten kinetics with parallel first-order elimination. OTZ was efficiently removed from the plasma. The Michaelis-Menten route of elimination was attributed to conversion of OTZ to total cysteine. At plasma OTZ concentrations equal to the Michaelis constant Km, 84% of OTZ was converted to total cysteine. These findings suggest that OTZ administered intravenously is an efficient means of increasing total blood cysteine.     

Double free-flap reconstruction of massive defects involving the lip, chin, and mandible

Men develop perioperative ulnar neuropathies more frequently than women. To determine the role of anatomical gender differences in the development of these neuropathies, we performed several studies of the anatomy of the ulnar nerve, cubital tunnel, and elbow region. These studies included detailed dissection of male and female embalmed and unembalmed cadavers, ultrasound measurements of the tissue layers at the elbow, and measurement of various dimensions of the coronoid process of the ulna in multiple skeletal sets. No gross anatomical differences were found between genders regarding the course of the ulnar nerve through the upper limb. However, there was a strikingly larger (2-19 times greater) fat content on the medial aspect of the elbow in women compared to men, and the tubercle of the coronoid process was approximately 1.5 times larger in men (P < or = .002, rank sum test). Our finding suggest that the tubercle of the coronoid process is a likely area for external compression-induced ischemia of the ulnar nerve because the nerve and its arterial supply (the posterior ulnar recurrent artery) are covered at the tubercle only by skin, subcutaneous fat, and a very thin aponeurosis of the flexor carpi ulnaris. Importantly, this tubercle is larger and the nerve and blood vessels passing by it are less protected by subcutaneous fat in men than in women. These two anatomical differences between men and women may contribute to the increased frequency of perioperative ulnar neuropathy induced by external pressure at the medial aspect of the elbow in men.