A twelve-node hybrid stress brick element for beam/column analysis

In this paper, a hybrid stress 12-node brick element is presented. Its assumed stress field is derived by first examining the deformation modes of a geometrically regular element and then generalizing to other element configurations using tensorial transformation. The total number of stress modes is 30 which is minimal for securing the element rank. To reduce the computational cost associated with the fully populated flexibility matrix, the admissible matrix formation is employed to induce high sparsity in the matrix. Popular beam bending benchmark problems are examined. The proposed elements deliver encouraging accuracy.postprin

Poisson-Boltzmann calculations of ions in charged capillaries

The Poisson-Boltzmann (PB) equation of ions inside an infinitely long charged pore is solved using two different boundary conditions of the electric field due to the pore wall. The results show that the boundary condition generally adopted in the literature leads to a violation of electroneutrality in the ion-pore system. © 1994 American Institute of Physics.published_or_final_versio

Infectious complications of liver transplantation

Sixteen (50%) of the 32 patients who received liver transplantations from October 1991 to March 1993 at Queen Mary Hospital, Hong Kong, developed viral, bacterial, or fungal infections. The viral infections were largely a result of immunosuppression while accidental bowel perforation, bile leak at the anastomosis, and delayed onset of stricture of the bile duct anastomosis were responsible for the intra-abdominal bacterial or fungal infections. Although the incidence of infectious complications was high, all patients were managed effectively and only one patient with lymphoproliferative disorder died. Infectious complications can lead to a prolonged hospital stay and a substantially increased hospital cost. The adoption of new immunosuppressive regimes that can better prevent acute graft rejection and adherence to meticulous surgical technique will help to reduce the infectious complications of liver transplantation in the future.published_or_final_versio

Popular benchmark problems for geometric nonlinear analysis of shells

In most, if not all, of the previous work on finite element formulation and nonlinear solution procedures, results of geometric nonlinear benchmark problems of shells are presented in the form of load-deflection curves. In this paper, eight sets of popularly employed benchmark problems are identified and their detailed reference solutions are obtained and tabulated. It is hoped that these solutions will form a convenient basis for subsequent comparison and that the tedious yet inaccurate task of reconstructing data points by graphical measurement of previously reported load-deflection curves can be avoided. Moreover, the relative convergent difficulty of the problems are revealed by the number of load increments and the total number of iterations required by an automatic load incrementation scheme for attaining the converged solutions under the maximum loads. © 2003 Elsevier B.V. All rights reserved.postprin

A stabilized eighteen-node solid element for hyperelastic analysis of shells

The objective of the present study is to develop a solid element for large deformation analysis of hyperelastic shell structures. To attain high computational efficiency and annihilate shear and membrane lockings, a hybrid-strain stabilization approach is adopted. To overcome the thickness locking of the element, the enhanced assumed thickness strain modes are incorporated. Starting from the virtual work principle and a weak form that enforces the equality of the hybrid-strain and the strain arising from the displacement and the enhanced assumed strain, an eighteen-node element for large deformation analysis of hyperelastic shells is developed. The salient feature of the present element for higher computational efficiency is that the element uses only the second-order quadrature for integration along the two in-plane natural coordinates and the stabilization vectors can be formed without using any integration loops. Efficacy of the element is illustrated by popular benchmark problems. © 2003 Elsevier B.V. All rights reserved.postprin

Long-Term Outcomes for Older Patients with Papillary Thyroid Carcinoma: Should Another Age Cutoff Beyond 45 Years Be Added?

© 2014, Society of Surgical Oncology. Background: Although an age cutoff of 45 years has often been adopted to stratify cancer risk in papillary thyroid carcinoma (PTC), both cancer-specific survival (CSS) and disease-specific survival (DFS) continue to worsen beyond this cutoff. This study aimed to determine whether advanced age (i.e., >60 years) at diagnosis was an independent predictor of CSS and DFS in older (≥45 years) patients. Methods: This study analyzed 407 PTC patients with a minimal follow-up period of 7 years. Standard protocol was followed. Both CSS and DFS were estimated using the Kaplan–Meier method and compared with the log-rank test. Variables shown to be significant by the log-rank test were entered into the Cox regression analysis. Results: During a median follow-up period of 15.1 years, 51 patients (12.5 %) died of PTC, whereas 80 (20.5 %) experienced at least one recurrence. For CSS, age beyond 60 years (hazard ratio [HR], 3.027; 95 % confidence interval [CI] 1.369–6.690; p = 0.006), tumor size greater than 4 cm (HR 2.043; 95 % CI 1.141–4.255; p = 0.049), central nodal metastases (HR 2.726; 95 % CI 1.198–6.200; p = 0.017), lateral nodal metastases (HR 5.247; 95 % CI 2.987–9.216; p < 0.001), and distant metastases (HR 4.297; 95 % CI 1.726–2.506; p = 0.002) were independent predictors. For DFS, only tumor size greater than 4 cm (HR 1.733; 95 % CI 1.030–3.058; p = 0.049), central nodal metastases (HR 2.362; 95 % CI 1.010–5.523; p = 0.047), and lateral nodal metastases (HR 4.383; 95 % CI 2.388–8.042; p < 0.001) were independent predictors. Conclusions: Advanced age was an independent predictor of CSS, and cancer-related death risk showed a continuing increase beyond the age of 60 years. However, advanced age was not an independent predictor of DFS. Therefore, having another age cutoff appears justifiable for stratifying risk of cancer-related death but less justifiable for disease recurrence. Tumor size as well as central and lateral nodal metastases independently predicted CSS and DFS.postprin

Periodontal conditions in adults resident in Lhasa, Tibet

published_or_final_versio

The effectiveness of the biannual application of silver nitrate solution followed by sodium fluoride varnish in arresting early childhood caries in preschool children: study protocol for a randomised controlled trial

published_or_final_versio