Numerical analysis of reproducing kernel collocation method for linear nonlocal models

Hydraulic fracturing has played a major role in north America's “shale revolution” over the past decades. Modeling of the hydraulic fracture propagation is challenging. Peridynamics, a nonlocal theory of continuum mechanics, has been used to model complex hydraulic fracturing processes in recent years. While the peridynamics-based hydraulic fracturing model has shown promising simulations results, its current numerical discretization lacks any mathematical analysis. This dissertation is motivated by the numerical solution of the peridynamics-based hydraulic fracturing model. The major objective is to develop a robust numerical method, under the change of the modeling parameters, for linear nonlocal diffusion models and peridynamic Navier equation, which are decoupled models of the peridynamics-based hydraulic fracturing model. Reproducing kernel (RK) collocation method is of our interest due to its mesh-free nature. By choosing special RK support sizes, we have developed a RK collocation method for nonlocal models and numerical solutions converge to the nonlocal solution and also to the corresponding local limit independent of the modeling parameters as the nonlocal interactions vanish. Accurate evaluation of the stiffness matrix for nonlocal models is computationally prohibitive even for collocation method. To save computational costs, the concept of RK approximation is generalized to approximate integrals and the quasi-discrete nonlocal operator, which uses a finite number of symmetric quadrature points to evaluate the integral, is proposed. We have shown RK collocation on the quasi-discrete nonlocal diffusion and peridynamic Navier equation converge to their classical counterparts. Finally, for the pure displacement form of the classical linear elasticity model, finite element solutions deteriorate when the material is nearly incompressible. A common remedy is to introduce an additional variable, pressure, and rewrite the equation in a mixed formulation, but the discrete functional spaces need to satisfy the famous inf-sup condition. For the the mixed form of the quasi-discrete peridynamic Navier equation, the discretization obtained using RK collocation with equal order interpolation for displacements and pressure passes the inf-sup test; the solution does not suffer from instability. Hence, with the use of penalty techniques or artificial compressibility, the proposed RK collocation method is promising in solving the peridynamics-based hydraulic fracturing model, which has an embedded saddle-point problemPetroleum and Geosystems Engineerin

What Does It Take to Synergistically Combine Sub-Potent Natural Products into Drug-Level Potent Combinations?

10.1371/journal.pone.0049969PLoS ONE711

Scoring method of a Situational Judgment Test:influence on internal consistency reliability, adverse impact and correlation with personality?

textabstractSituational Judgment Tests (SJTs) are increasingly used for medical school selection. Scoring an SJT is more complicated than scoring a knowledge test, because there are no objectively correct answers. The scoring method of an SJT may influence the construct and concurrent validity and the adverse impact with respect to non-traditional students. Previous research has compared only a small number of scoring methods and has not studied the effect of scoring method on internal consistency reliability. This study compared 28 different scoring methods for a rating SJT on internal consistency reliability, adverse impact and correlation with personality. The scoring methods varied on four aspects: the way of controlling for systematic error, and the type of reference group, distance and central tendency statistic. All scoring methods were applied to a previously validated integrity-based SJT, administered to 931 medical school applicants. Internal consistency reliability varied between .33 and .73, which is likely explained by the dependence of coefficient alpha on the total score variance. All scoring methods led to significantly higher scores for the ethnic majority than for the non-Western minorities, with effect sizes ranging from 0.48 to 0.66. Eighteen scoring methods showed a significant small positive correlation with agreeableness. Four scoring methods showed a significant small positive correlation with conscientiousness. The way of controlling for systematic error was the most influential scoring method aspect. These results suggest that the increased use of SJTs for selection into medical school must be accompanied by a thorough examination of the scoring method to be used

The BELFRAIL (BFC80+) study: a population-based prospective cohort study of the very elderly in Belgium

In coming decades the proportion of very elderly people living in the Western world will dramatically increase. This forthcoming "grey epidemic" will lead to an explosion of chronic diseases. In order to anticipate booming health care expenditures and to assure that social security is funded in the future, research focusing on the relationship between chronic diseases, frailty and disability is needed. The general aim of the BELFRAIL cohort study (BFC80+) is to study the dynamic interaction between health, frailty and disability in a multi-system approach focusing on cardiac dysfunction and chronic heart failure, lung function, sarcopenia, renal insufficiency and immunosenescence

Involvement of the Glycogen Synthase Kinase-3 Signaling Pathway in TBI Pathology and Neurocognitive Outcome

BACKGROUND: Traumatic brain injury (TBI) sets in motion cascades of biochemical changes that result in delayed cell death and altered neuronal architecture. Studies have demonstrated that inhibition of glycogen synthase kinase-3 (GSK-3) effectively reduces apoptosis following a number of stimuli. The Wnt family of proteins, and growth factors are two major factors that regulate GSK-3 activity. In the absence of stimuli, GSK-3 is constitutively active and is complexed with Axin, adenomatous polyposis coli (APC), and casein kinase Iα (CK1α) and phosphorylates ß-Catenin leading to its degradation. Binding of Wnt to Frizzled receptors causes the translocation of GSK-3 to the plasma membrane, where it phosphorylates and inactivates the Frizzled co-receptor lipoprotein-related protein 6 (LRP6). Furthermore, the translocation of GSK-3 reduces ß-Catenin phosphorylation and degradation, leading to ß-Catenin accumulation and gene expression. Growth factors activate Akt, which in turn inhibits GSK-3 activity by direct phosphorylation, leading to a reduction in apoptosis. METHODOLOGY/PRINCIPAL FINDINGS: Using a rodent model, we found that TBI caused a rapid, but transient, increase in LRP6 phosphorylation that is followed by a modest decrease in ß-Catenin phosphorylation. Phospho-GSK-3β immunoreactivity was found to increase three days post injury, a time point at which increased Akt activity following TBI has been observed. Lithium influences several neurochemical cascades, including inhibiting GSK-3. When the efficacy of daily lithium was assessed, reduced hippocampal neuronal cell loss and learning and memory improvements were observed. These influences were partially mimicked by administration of the GSK-3-selective inhibitor SB-216763, as this drug resulted in improved motor function, but only a modest improvement in memory retention and no overt neuroprotection. CONCLUSION/SIGNIFICANCE: Taken together, our findings suggest that selective inhibition of GSK-3 may offer partial cognitive improvement. As a broad spectrum inhibitor of GSK-3, lithium offers neuroprotection and robust cognitive improvement, supporting its clinical testing as a treatment for TBI

What is known about the patient's experience of medical tourism? A scoping review

<p>Abstract</p> <p>Background</p> <p>Medical tourism is understood as travel abroad with the intention of obtaining non-emergency medical services. This practice is the subject of increasing interest, but little is known about its scope.</p> <p>Methods</p> <p>A comprehensive scoping review of published academic articles, media sources, and grey literature reports was performed to answer the question: what is known about the patient's experience of medical tourism? The review was accomplished in three steps: (1) identifying the question and relevant literature; (2) selecting the literature; (3) charting, collating, and summarizing the information. Overall themes were identified from this process.</p> <p>Results</p> <p>291 sources were identified for review from the databases searched, the majority of which were media pieces (<it>n </it>= 176). A further 57 sources were included for review after hand searching reference lists. Of the 348 sources that were gathered, 216 were ultimately included in this scoping review. Only a small minority of sources reported on empirical studies that involved the collection of primary data (<it>n </it>= 5). The four themes identified via the review were: (1) decision-making (e.g., push and pull factors that operate to shape patients' decisions); (2) motivations (e.g., procedure-, cost-, and travel-based factors motivating patients to seek care abroad); (3) risks (e.g., health and travel risks); and (4) first-hand accounts (e.g., patients' experiential accounts of having gone abroad for medical care). These themes represent the most discussed issues about the patient's experience of medical tourism in the English-language academic, media, and grey literatures.</p> <p>Conclusions</p> <p>This review demonstrates the need for additional research on numerous issues, including: (1) understanding how multiple information sources are consulted and evaluated by patients before deciding upon medical tourism; (2) examining how patients understand the risks of care abroad; (3) gathering patients' prospective and retrospective accounts; and (4) the push and pull factors, as well as the motives of patients to participate in medical tourism. The findings from this scoping review and the knowledge gaps it uncovered also demonstrate that there is great potential for new contributions to our understanding of the patient's experience of medical tourism.</p

The use of mesenchymal stem cells for cartilage repair and regeneration: a systematic review.

BACKGROUND: The management of articular cartilage defects presents many clinical challenges due to its avascular, aneural and alymphatic nature. Bone marrow stimulation techniques, such as microfracture, are the most frequently used method in clinical practice however the resulting mixed fibrocartilage tissue which is inferior to native hyaline cartilage. Other methods have shown promise but are far from perfect. There is an unmet need and growing interest in regenerative medicine and tissue engineering to improve the outcome for patients requiring cartilage repair. Many published reviews on cartilage repair only list human clinical trials, underestimating the wealth of basic sciences and animal studies that are precursors to future research. We therefore set out to perform a systematic review of the literature to assess the translation of stem cell therapy to explore what research had been carried out at each of the stages of translation from bench-top (in vitro), animal (pre-clinical) and human studies (clinical) and assemble an evidence-based cascade for the responsible introduction of stem cell therapy for cartilage defects. This review was conducted in accordance to PRISMA guidelines using CINHAL, MEDLINE, EMBASE, Scopus and Web of Knowledge databases from 1st January 1900 to 30th June 2015. In total, there were 2880 studies identified of which 252 studies were included for analysis (100 articles for in vitro studies, 111 studies for animal studies; and 31 studies for human studies). There was a huge variance in cell source in pre-clinical studies both of terms of animal used, location of harvest (fat, marrow, blood or synovium) and allogeneicity. The use of scaffolds, growth factors, number of cell passages and number of cells used was hugely heterogeneous. SHORT CONCLUSIONS: This review offers a comprehensive assessment of the evidence behind the translation of basic science to the clinical practice of cartilage repair. It has revealed a lack of connectivity between the in vitro, pre-clinical and human data and a patchwork quilt of synergistic evidence. Drivers for progress in this space are largely driven by patient demand, surgeon inquisition and a regulatory framework that is learning at the same pace as new developments take place

ICAR: endoscopic skull‐base surgery

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Improving care for people with heart failure in Uganda: serial in-depth interviews with patients' and their health care professionals

Abstract Background The short prognosis of patients with advanced heart failure (HF) and the associated multidimensional distress as illustrated in literature from high income countries necessitates the integration of palliative care into the care of advanced HF patients to address these needs and improve their quality of life. These needs, which are subjective, have not been described from the patients’ and health care professionals’(HPs) view point in the Ugandan setting, a low income country with a different socio-cultural context. This study aimed at bridging this gap in knowledge by eliciting patients’ and HPs’ views of HF patients’ needs over the course of their illness to enable generalists, cardiologists and palliative care clinicians to develop guidelines to provide patient-centred realistic care in Uganda. Methods Serial qualitative in-depth interviews were conducted with HF patients who were purposively sampled and recruited in Mulago National Referral Hospital (MNRH) until thematic saturation. In-depth interviews were conducted at three time points with intervals of 3 month between interviews over the course of their illness in the hospital and their home context. One-off interviews were conducted with HPs that manage HF in MNRH. We used a grounded theory approach in data analysis. The Uganda National Council of science and technology approved the research. Results Forty-eight interviews were conducted with 21 patients and their carers and eight interviews with their HPs. Multidimensional needs including physical, psychological, social, spiritual and information needs were identified. These highlighted the underpinning need to have normal functioning, control, to cope and adapt to a changed life and to find meaning. Spiritual needs were less recognised by HPs than the other multidimensional needs. Information needs were commonly unmet. Patients and HPs suggested improvements in care that were congruent with the recommendations in chronic disease care and the six pillars of the WHO health systems strengthening approach. Conclusion Management of HF in Uganda requires an approach that targets multidimensional needs, embraces multidisciplinary care and strengthens health systems which are all important tenets of palliative care