Investigation of particles size effects in Dissipative Particle Dynamics (DPD) modelling of colloidal suspensions

In the Dissipative Particle Dynamics (DPD) simulation of suspension, the fluid (solvent) and colloidal particles are replaced by a set of DPD particles and therefore their relative sizes (as measured by their exclusion zones) can affect the maximal packing fraction of the colloidal particles. In this study, we investigate roles of the conservative, dissipative and random forces in this relative size ratio (colloidal/solvent). We propose a mechanism of adjusting the DPD parameters to properly model the solvent phase (the solvent here is supposed to have the same isothermal compressibility to that of water)

Emergency room surgical workload in an inner city UK teaching hospital

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.TA Mai-Phan was funded by Vietnam Overseas Scholarship Program (VOSP) of Vietnam's Ministry of Education and Training for his MSc studentship. HM Kocher is funded by the Department of Health (UK) Clinician Scientist Fellowship

A dissipative particle dynamics model for thixotropic materials exhibiting pseudo-yield stress behaviour

Many materials (e.g., gels, colloids, concentrated cohesive sediments, etc.) exhibit a stable solid form at rest, and liquify once subjected to an applied stress exceeding a critical value – a yield-stress behaviour. This can be qualitatively explained by the forming and destruction of the fluid microstructure [1], and it may be modelled as a thixotropic and yield stress material. In this paper, we propose a mesoscopic model which is able to mimic a thixotropic and yield stress behaviour using a particle-based technique known as dissipative particle dynamics (DPD). The DPD technique satisfies conservation of mass and momentum and it has been applied successfully for a number of problems involving complex-structure fluids, such as polymer solutions, suspensions of rigid particles, droplets, biological fluids, etc. In this work, an indirect linkage dissipative particle model (ILDP) is proposed based on qualitative microstructural physics, which results in a non-Newtonian fluid with observed yield stress and thixotropic properties. The model comprises of two types, or species, of DPD particles – with only repulsive conservative force between the same species, and with repulsive force at short range and attractive force at long range between different species. Numerical results show that the proposed DPD fluid can represent some observed complex behaviours, such as yield stress and thixotropic effects

Strongly overdamped dissipative particle dynamics for fluid-solid systems

In this paper, a numerical scheme is used to study strongly-overdamped Dissipative Particles Dynamics (DPD) systems for the modelling of fluid-solid systems. In the scheme, the resultant set of algebraic equations for the velocities are directly solved in an iterative manner. Different test problems, e.g., viscometric flows, particulate suspensions and flows past a periodic square array of cylinders, are used to verify the proposed method. In the simulation of particulate suspensions, a new simple model for massless suspended particles is presented. A DPD fluid in the overdamped limit is shown to possess several attractive properties including much faster dynamic response and near-incompressibility

A microstructure model for viscoelastic–thixotropic fluids

A microstructure model to describe the viscoelasticity and thixotropy properties of complex fluids is proposed. The model is based on the Lodge–Yamamoto network theory and is an extension of the Phan-Thien–Tanner model, with a kinetic process in which specific forms of creation and destruction rates are assumed. The final equation is simple with a small number of empirical parameters required and can be conveniently employed in engineering simulations. The predictions based on the model in a variety of shear and oscillatory shear flows are given. The stress response obtained from the model prediction agrees well with experiments on both shear and oscillatory flow histories

Rapid assessment of Hib disease burden in Vietnam

<p>Abstract</p> <p>Background</p> <p>Several countries have applied the <it>Haemophilus influenzae </it>type b (Hib) rapid assessment tool (RAT) to estimate the burden of Hib disease where resources for hospital- or population-based surveillance are limited. In Vietnam, we used the Hib RAT to estimate the burden of Hib pneumonia and meningitis prior to Hib vaccine introduction.</p> <p>Methods</p> <p>Laboratory, hospitalization and mortality data were collected for the period January 2004 through December 2005 from five representative hospitals. Based on the WHO Hib RAT protocol, standardized MS Excel spreadsheets were completed to generate meningitis and pneumonia case and death figures.</p> <p>Results</p> <p>We found 35 to 77 Hib meningitis deaths and 441 to 957 Hib pneumonia deaths among children < 5 years of age annually in Vietnam. Overall, the incidence of Hib meningitis was estimated at 18/100,000 (95% confidence interval, CI, 15.1-21.6). The estimated Hib meningitis incidence in children < 5 years age was higher in Ho Chi Minh City (22.5/100,000 [95% CI, 18.4-27.5]) compared to Hanoi (9.8/100,000 [95% CI, 6.5-14.8]). The Hib RAT suggests that there are a total of 883 to 1,915 cases of Hib meningitis and 4,414 to 9,574 cases of Hib pneumonia per year in Vietnam.</p> <p>Conclusions</p> <p>In Hanoi, the estimated incidence of Hib meningitis for children < 5 years of age was similar to that described in previous population-based studies of Hib meningitis conducted from 1999 through 2002. Results from the Hib RAT suggest that there is a substantial, yet unmeasured, disease burden associated with Hib pneumonia in Vietnamese children.</p

TESOL Teachers’ Engagement with the Native Speaker Model: How Does Teacher Education Impact on Their Beliefs?

© 2017, © The Author(s) 2017. This research investigates non-native English teachers’ engagement with the native speaker model, i.e. whether they agree/disagree with measuring English teaching and learning performance against native speaker standards. More importantly, it aims to unearth the impact of teacher education on teachers’ attitudes and beliefs about “native-speakerness”. Data were gathered from an online survey delivered to 85 Vietnamese TESOL teachers who had completed one of 19 Master’s level TESOL programmes offered overseas and in Vietnam, followed by in-depth interviews with 20 participants. The results revealed that teacher education strengthened the teachers’ beliefs about the linguistic diversity of English and led them to question the native and non-native divide by providing relevant input and opportunities to engage in critical discussion on nativeness, as well as fruitful learning experience. However, language proficiency is an area where “native-speakerness” still dominates, and where teacher education did not exert much influence. These findings shed light on the role of TESOL teacher training in influencing teacher beliefs about the native speaker model, and suggest that teacher education programmes dedicate more space for teachers to critically explore the construct of language teacher proficiency

Emerging concepts in biomarker discovery; The US-Japan workshop on immunological molecular markers in oncology

Supported by the Office of International Affairs, National Cancer Institute (NCI), the "US-Japan Workshop on Immunological Biomarkers in Oncology" was held in March 2009. The workshop was related to a task force launched by the International Society for the Biological Therapy of Cancer (iSBTc) and the United States Food and Drug Administration (FDA) to identify strategies for biomarker discovery and validation in the field of biotherapy. The effort will culminate on October 28th 2009 in the "iSBTc-FDA-NCI Workshop on Prognostic and Predictive Immunologic Biomarkers in Cancer", which will be held in Washington DC in association with the Annual Meeting. The purposes of the US-Japan workshop were a) to discuss novel approaches to enhance the discovery of predictive and/or prognostic markers in cancer immunotherapy; b) to define the state of the science in biomarker discovery and validation. The participation of Japanese and US scientists provided the opportunity to identify shared or discordant themes across the distinct immune genetic background and the diverse prevalence of disease between the two Nations