Designing biostable polyurethane elastomers for biomedical implants

The chemical structure, synthesis, morphology, and properties of polyurethane elastomers are briefly discussed. The current understanding of the effect of chemical structure and the associated morphology on the stability of polyurethanes in the biological environments is reviewed. The degradation of conventional polyurethanes appears as surface or deep cracking, stiffening, and deterioration of mechanical properties, such as flex-fatigue resistance. Polyester and poly( tetramethylene oxide) based polyurethanes degrade by hydrolytic and oxidative degradation of ester and ether functional groups, respectively. The recent approaches to develop polyurethanes with improved long-term biostability are based on developing novel polyether, hydrocarbon, polycarbonate, and siloxane macrodiols to replace degradation-prone polyester and polyether macrodiols in polyurethane formulations. The new approaches are discussed with respect to synthesis, properties and biostability based on reported in vivo studies. Among the newly developed materials, siloxane-based polyurethanes have exhibited excellent biostability and are expected to find many applications in biomedical implants.

Management of isolated orbital floor blow-out fractures: a survey of Australian and New Zealand oral and maxillofacial surgeons

Background: This is the first report of involvement of Australian and New Zealand oral and maxillofacial surgeons in the management of isolated orbital floor blow-out fractures and was conducted to obtain comparisons with the results from a recent similar survey of British oral and maxillofacial surgeons. Methods: A questionnaire survey was sent to all 113 practising members of the Australian and New Zealand Association of Oral and Maxillofacial Surgeons in April 2002 with a second mailout 1 month later. Results: Sixty-nine per cent of the respondents were referred isolated orbital floor blow-out fractures for manage-ment, and just over half of these respondents estimated that 50% or more of the cases went to surgery. The materials most commonly used in orbital floor reconstruction were resorbable membrane for small defects and autologous bone for large defects. Conclusion: As in Britain, management of isolated orbital floor blow-out fractures comprises part of the surgical spectrum for many oral and maxillofacial surgeons in Australia and New Zealand. The management protocol was observed to be very similar between the two groups.

Theory-of-mind development in oral deaf children with cochlear implants or conventional hearing aids

Background: In the context of the established finding that theory-of-mind (ToM) growth is seriously delayed in late-signing deaf children, and some evidence of equivalent delays in those learning speech with conventional hearing aids, this study's novel contribution was to explore ToM development in deaf children with cochlear implants. Implants can substantially boost auditory acuity and rates of language growth. Despite the implant, there are often problems socialising with hearing peers and some language difficulties, lending special theoretical interest to the present comparative design. Methods: A total of 52 children aged 4 to 12 years took a battery of false belief tests of ToM. There were 26 oral deaf children, half with implants and half with hearing aids, evenly divided between oral-only versus sign-plus-oral schools. Comparison groups of age-matched high-functioning children with autism and younger hearing children were also included. Results: No significant ToM differences emerged between deaf children with implants and those with hearing aids, nor between those in oral-only versus sign-plus-oral schools. Nor did the deaf children perform any better on the ToM tasks than their age peers with autism. Hearing preschoolers scored significantly higher than all other groups. For the deaf and the autistic children, as well as the preschoolers, rate of language development and verbal maturity significantly predicted variability in ToM, over and above chronological age. Conclusions: The finding that deaf children with cochlear implants are as delayed in ToM development as children with autism and their deaf peers with hearing aids or late sign language highlights the likely significance of peer interaction and early fluent communication with peers and family, whether in sign or in speech, in order to optimally facilitate the growth of social cognition and language.

Orbital currents and charge density waves in a generalized Hubbard ladder

We study a generalized Hubbard model on the two-leg ladder at zero temperature, focusing on a parameter region with staggered flux (SF)/d-density wave (DDW) order. To guide our numerical calculations, we first investigate the location of a SF/DDW phase in the phase diagram of the half-filled weakly interacting ladder using a perturbative renormalization group (RG) and bosonization approach. For hole doping 6 away from half-filling, finite-system density-matrix renormalizationgroup (DMRG) calculations are used to study ladders with up to 200 rungs for intermediate-strength interactions. In the doped SF/DDW phase, the staggered rung current and the rung electron density both show periodic spatial oscillations, with characteristic wavelengths 2/delta and 1/delta, respectively, corresponding to ordering wavevectors 2k(F) and 4k(F) for the currents and densities, where 2k(F) = pi(1 - delta). The density minima are located at the anti-phase domain walls of the staggered current. For sufficiently large dopings, SF/DDW order is suppressed. The rung density modulation also exists in neighboring phases where currents decay exponentially. We show that most of the DMRG results can be qualitatively understood from weak-coupling RG/bosonization arguments. However, while these arguments seem to suggest a crossover from non-decaying correlations to power-law decay at a length scale of order 1/delta, the DMRG results are consistent with a true long-range order scenario for the currents and densities. (c) 2005 Elsevier Inc. All rights reserved.

Periocular and Orbital Amyloidosis. Clinical Characteristics, Management, and Outcome

Objective: To present the clinical features and management outcome in a large series of patients with periocular and orbital amyloidosis. Design: Retrospective, noncomparative, interventional case series. Patients: All patients diagnosed with periocular and orbital amyloidosis in 6 oculoplastic and orbital units. Methods: Clinical records of all patients were reviewed. Main Outcome Measures: Clinical presentation, radiological and histological findings, treatment modalities, and outcome. Results. The study included 24 patients (15 female, 9 male) with a mean age of 57 17 years. Nineteen cases were unilateral, and 5 were bilateral. Clinical signs and symptoms included a visible or palpable periocular mass or tissue infiltration (95.8%), ptosis (54.2%), periocular discomfort or pain (25%), proptosis or globe displacement (21%), limitations in ocular motility (16.7%), recurrent periocular subcutaneous hemorrhages (12.5%), and diplopia (8.3%). Seven cases had orbital involvement, and 17 were periocular. Immunohistochemistry in 7 patients showed B cells or plasma cells producing monoclonal immunoglobulin chains that were deposited as amyloid light chains. Only 1 patient was diagnosed with systemic amyloid light chain amyloidosis. Treatment modalities were mainly observation and surgical debulking. During a mean follow-up period of 39 months, 21% showed significant progression after treatment, whereas 79% were stable or showed no recurrence after treatment. Conclusion: Periocular and orbital amyloidosis may present with a wide spectrum of clinical findings and result in significant ocular morbidity. Complete surgical excision is not feasible in many cases, and the goal of treatment is to preserve function and to prevent sight-threatening complications.

Idiopathic sclerosing orbital inflammation

Objective: To perform a multicenter review of the clinical features and treatment of 31 patients with idiopathic sclerosing orbital inflammation. Methods: We included all patients with histologically confirmed idiopathic sclerosing orbital inflammation from 5 regional orbital centers. We reviewed the case notes to determine the clinical presentation, diagnostic features, and response to treatment. The main outcome measures were duration and nature of symptoms, anatomical location of disease, histopathological findings, treatment modalities, treatment efficacy and adverse effects, and final clinical status. Results: We included 13 male and 18 female patients ranging in age from 7 to 83 years. The average duration of symptoms at presentation was 13.4 months. There was a predilection for the lateral and superior quadrants. Thirteen patients had apical disease, and 4 had extraorbital involvement. Histopathological findings invariably showed sclerosis associated with a sparse mixed cellular infiltrate. Twenty- seven patients were treated with oral prednisolone, response to which was good in 9 patients, partial in 11, and poor in 7. Six patients were treated with a second- line immunosuppressive agent, and 6 received radiotherapy. The response to radiotherapy was generally poor. Conclusions: Idiopathic sclerosing orbital inflammation is a rare condition that can be difficult to diagnose and manage. Early intervention with immunosuppression in the form of corticosteroids combinedwith secondline agents can result in control and even regression of the disease.