Molecular dynamics study of the fragmentation of silicon doped fullerenes

Tight binding molecular dynamics simulations, with a non orthogonal basis set, are performed to study the fragmentation of carbon fullerenes doped with up to six silicon atoms. Both substitutional and adsorbed cases are considered. The fragmentation process is simulated starting from the equilibrium configuration in each case and imposing a high initial temperature to the atoms. Kinetic energy quickly converts into potential energy, so that the system oscillates for some picoseconds and eventually breaks up. The most probable first event for substituted fullerenes is the ejection of a C2 molecule, another very frequent event being that one Si atom goes to an adsorbed position. Adsorbed Si clusters tend to desorb as a whole when they have four or more atoms, while the smaller ones tend to dissociate and sometimes interchange positions with the C atoms. These results are compared with experimental information from mass abundance spectroscopy and the products of photofragmentation.Comment: Seven two-column pages, six postscript figures. To be published in Physical Review

Total Elbow Arthroplasty

Total elbow arthroplasty has continued to evolve over time. Elbow implants may be linked or unlinked. Unlinked implants are attractive for patients with relatively well preserved bone stock and ligaments, but many favor linked implants, since they prevent instability and allow replacement for a wider spectrum of indications. Inflammatory arthropathies such as rheumatoid arthritis represent the classic indication for elbow arthroplasty. Indications have been expanded to include posttraumatic osteoarthritis, acute distal humerus fractures, distal humerus nonunions and reconstruction after tumor resection. Elbow arthroplasty is very successful in terms of pain relief, motion and function. However, its complication rate remains higher than arthroplasty of other joints. The overall success rate is best for patients with inflammatory arthritis and elderly patients with acute distal humerus fractures, worse for patients with posttraumatic osteoarthritis. The most common complications of elbow arthroplasty include infection, loosening, wear, triceps weakness and ulnar neuropathy. When revision surgery becomes necessary, bone augmentation techniques provide a reasonable outcome

Total elbow replacement for complex fractures of the distal humerus

The treatment of multifragmentary, intra-articular fractures of the distal humerus is difficult, even in young patients with bone of good quality, but is worse in elderly patients who have varying degrees of osteopenia. We have evaluated the functional outcome of primary total elbow replacement (TER) in the treatment of these fractures in ten elderly patients followed for a minimum of one year. There were no complications in regard to the soft tissues, bone or prosthesis. The mean range of flexion obtained was 125° (110 to 140) and loss of extension was 23.5° (0 to 50). The mean Mayo score was 94 points (80 to 100) and patient satisfaction was high. We feel that TER provides an alternative to open reduction and internal fixation in the management of these complicated fractures in the elderly. </jats:p

Um procedimento versátil para o cálculo de malhas de terra pelo método dos elementos finitos

Neste trabalho utiliza-se o método dos elementos finitos para estudar a distribuição de potencial elétrico na área de influencia da malha de terra de uma subestação. A formulação é tridimensional, mas são também admitidos elementos bidimensionais e unidimensionais, mas são também admitidos elementos bidimensionais e unidimensionais, que são úteis para representar tubulações ou caminhos metálicos da instalação. O método de solução descrito tem a vantagem de utilizar uma técnica de manipulação de matrizes esparsas, que não obriga á tradicional no Método dos elementos Finitos. É apresentado um exemplo, de caso real, onde são mostradas as curvas equipotenciais calculadas

Nationalist Lionel Thomas Courtenay addressing a meeting at the St James Hall, 7 March 1931, 1 [picture].

Title devised from accompanying information where available.; Part of the: Fairfax archive of glass plate negatives.; Fairfax number: 3636 and 2603.; Also available online at: http://nla.gov.au/nla.pic-vn6217758; Acquired from Fairfax Media, 2012

Pressure and temperature as tools for investigating the role of individual non-covalent interactions in enzymatic reactions: Sulfolobus solfataricus carboxypeptidase as a model enzyme

Sulfolobus solfataricus carboxypeptidase, (CPSso), is a heat- and pressure-resistant zinc-metalloprotease. Thanks to its properties, it is an ideal tool for investigating the role of non-covalent interactions in substrate binding. It has a broad substrate specificity as it can cleave any N-blocked amino acid (except for N-blocked proline). Its catalytic and kinetic mechanisms are well understood, and the hydrolytic reaction is easily detectable spectrophotometrically. Here, we report investigations on the pressure- and temperature-dependence of the kinetic parameters (turnover number and Michaelis constant) of CPSso using several benzoyl- and 3-(2-furyl)acryloyl-amino acids as substrates. This approach enabled us to study these parameters in terms of individual rate constants and establish that the release of the free amino acid is the rate-limiting step, making it possible to dissect the individual non-covalent interactions participating in substrate binding. In keeping with molecular docking experiments performed on the 3D model of CPSso available to date, our results show that both hydrophobic and energetic interactions (i.e., stacking and van der Waals) are mainly involved, but their contribution varies strongly, probably due to changes in the conformational state of the enzyme