A h-Adaptive Algorithm Using Residual Error Estimates for Fluid Flows

Algorithms for adaptive mesh refinement using a residual error estimator are proposed for fluid flow problems in a finite volume framework. The residual error estimator, referred to as the ℜ-parameter is used to derive refinement and coarsening criteria for the adaptive algorithms. An adaptive strategy based on the ℜ-parameter is proposed for continuous flows, while a hybrid adaptive algorithm employing a combination of error indicators and the ℜ-parameter is developed for discontinuous flows. Numerical experiments for inviscid and viscous flows on different grid topologies demonstrate the effectiveness of the proposed algorithms on arbitrary polygonal grids.     

Characterizing the learning curve of the VBLaST-PT© (Virtual Basic Laparoscopic Skill Trainer)

Background

Mastering laparoscopic surgical skills requires considerable time and effort. The Virtual Basic Laparoscopic Skill Trainer (VBLaST-PT^©) is being developed as a computerized version of the peg transfer task of the Fundamentals of Laparoscopic Surgery (FLS) system using virtual reality technology. We assessed the learning curve of trainees on the VBLaST-PT^© using the cumulative summation (CUSUM) method and compared them with those on the FLS to establish convergent validity for the VBLaST-PT^©.

Methods

Eighteen medical students from were assigned randomly to one of three groups: control, VBLaST-training, and FLS-training. The VBLaST and the FLS groups performed a total of 150 trials of the peg-transfer task over a 3-week period, 5 days a week. Their CUSUM scores were computed based on predefined performance criteria (junior, intermediate, and senior levels).

Results

Of the six subjects in the VBLaST-training group, five achieved at least the “junior” level, three achieved the “intermediate” level, and one achieved the “senior” level of performance criterion by the end of the 150 trials. In comparison, for the FLS group, three students achieved the “senior” criterion and all six students achieved the “intermediate” and “junior” criteria by the 150th trials. Both the VBLaST-PT^© and the FLS systems showed significant skill improvement and retention, albeit with system specificity as measured by transfer of learning in the retention test: The VBLaST-trained group performed better on the VBLaST-PT^© than on FLS (p = 0.003), whereas the FLS-trained group performed better on the FLS than on VBLaST-PT^© (p = 0.002).

Conclusions

We characterized the learning curve for a virtual peg transfer task on the VBLaST-PT^© and compared it with the FLS using CUSUM analysis. Subjects in both training groups showed significant improvement in skill performance, but the transfer of training between systems was not significant.     

Breast cancer in patients with schizophrenia

Background

Schizophrenia has a powerful impact on the outcomes of treatment for physical disorders. This study sought to estimate how the presence of schizophrenia disrupts the course of diagnosis and initial treatment of breast cancer.

Methods

We searched the Patient Treatment File, a comprehensive computer-based system for inpatient data in the Department of Veterans Affairs (DVA) medical system, to identify patients with codes for schizophrenia or schizoaffective disorder who later developed breast cancer. These data were augmented with chart-based clinical data.

Results

There were 56 evaluable patients from 34 DVA facilities; 37 (66%) were female. Delay in diagnosis was common. The mean size of the primary tumor was 4 cm in those for whom these data were recorded. Delay in diagnosis was common and many never received the indicated surgery. Distant metastases were present on diagnosis in 12 (21%) and developed after diagnosis in 14 (25%) others, including 7 who inappropriately delayed or refused indicated surgery and 4 who inappropriately delayed or refused indicated neoadjuvant chemotherapy. Twelve verbally abused or physically attacked caregivers.

Conclusions

Patients with schizophrenia who later develop breast cancer often deny they have cancer. They often have high-stage disease at diagnosis and often delay or refuse therapy. Breast-conserving multimodality therapy is often not feasible.     

Experimental and finite element analysis of dynamic loading of the mouse forearm

Bone formation is reported to initiate in osteocytes by mechanotransduction due to dynamic loading of bone. The first step towards this is to characterize the dynamic strain fields in the overall bone. Here, the previously developed mouse forearm ulna‐radius model, subjected to static loading, has been further enhanced by incorporating a loading cap and applying a cyclic dynamic load to more closely approximate experimental biological conditions. This study also incorporates data obtained from strain gauging both the ulna and radius simultaneously. Based on separate experiments, the elastic modulus of the ulna and radius were determined to be 13.8 and 9.9 GPa, respectively. Another novel aspect of the numerical model is the inclusion of the interosseous membrane in the FE model with membrane stiffness ranging from 5–15 N/mm that have been found to give strain values closer to that from the experiments. Interestingly, the inclusion of the interosseous membrane helped to equalize the peak strain magnitudes in the ulna and radius (～1800 at 2 N load and ～3200 at 3.5 N), which was also observed experimentally. This model represents a significant advance towards being able to simulate through FE analysis the strain fields generated in vivo upon mechanical loading of the mouse forearm. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:1580–1588, 2014.     

Chronic Proton Pump Inhibitor Therapy Associated with Increased Development of Fundic Gland Polyps

Background  

Fundic gland polyps (FGP) have been implicated with long-term proton pump inhibitor (PPI) use.     

Recurrent Kawasaki disease

We describe an infant who had recurrence of Kawasaki disease and responded to therapy with Intravenous Immune globulin (IVIG) and highlight the need for recognition of this vasculitis, which is being increasingly recognised in the Indian subcontinent.     

Effect of diltiazem isomers and thiamine on piglet liver microsomal peroxidation using dichlorofluorescein.

PURPOSE: We investigated a potential hepatoprotective role of d-cis diltiazem, l-cis diltiazem, thiamine and the combination d-cis diltiazem and thiamine against lipid peroxidation in a piglet liver microsomal model. A modified in vitro dichlorofluorescein assay was developed to assess the extent of peroxidative damage induced by reactive oxygen species in the piglet liver microsomal fraction. METHODS: Microsomal membrane fraction, obtained from 3 week old female piglets, was treated with either the biologically vasoactive d-cis diltiazem or the non-vasoactive stereoisomer l-cis diltiazem (5-1000 microM) for 1 hour at 37 degrees C followed by one hour incubation with the free radical generator AAPH (2,2'-azobis-(2-amidinopropane) dihydrochloride; 1 mM) to initiate lipid peroxidation. In a separate study, piglet liver microsomes were pre-treated with d-cis diltiazem (50 or 500 microM) and thiamine (10-100 microM) to assess the antioxidant activity of the combination. RESULTS: A dose dependant inhibition of membrane lipid peroxidation was observed with d-cis diltiazem (p<0.05) but not with l-cis diltiazem, suggesting that diltiazem is stereospecific in protecting against microsomal lipid peroxidation. Combining diltiazem with thiamine further protected microsomes against lipid peroxidation compared to use of individual drugs. CONCLUSION: We conclude that diltiazem and the combination of diltiazem and thiamine offers a hepatoprotective effect against free radicals.