Ablative response of a silica phenolic to simulated liquid propellant rocket engine operating conditions

Ablative response of silica phenolic to simulated liquid propellant rocket engine operating condition

A study of the boundary flow in a rocket combustion chamber. Part 2 - Data analysis, correlation, and theoretical prediction Final report

Processing data on heat flux and chemical composition in rocket combustion chamber boundary flow - table

Bone Health Improvement Protocol

Introduction. Metabolic bone disease is a malady that causessignificant morbidity and mortality to a patient who has sustaineda fragility fracture. There is currently no protocol toprevent secondary fragility fracture at our institution. The objectiveof this study was to create an appropriate protocol forimplementing clinical pathways for physicians to diagnose andtreat osteoporosis and fragility fractures by educating patients. Methods. A multidisciplinary team created an appropriateprotocol that could be implemented in an inpatient setting.A thorough literature review was conducted to evaluatepotential barriers and efficacious methods of protocol design. Results. A bone health improvement protocol was developed.Any patient over the age of 50 who sustains a fracture from lowenergy trauma, such as a fall from standing or less, should beconsidered to place into this protocol. These patients receivededucation on metabolic bone disease, a prescription for highdose vitamin D therapy, and laboratory testing to determinethe etiology of their metabolic bone disease. Continuity of careof these patients with their primary care provider was providedfor further management of their metabolic bone disease andevaluation of their disease after discharged from the hospital. Conclusion. Comprehensive secondary prevention should consistof osteoporosis assessment and treatment together with afall risk assessment. With this protocol, secondary fragility fracturespotentially could be prevented. KS J Med 2017;10(3):62-66

Interdigitation between surface-anchored polymer chains and an elastomer : consequences for adhesion promotion

We study the adhesion between a cross-linked elastomer and a flat solid surface where polymer chains have been end-grafted. To understand the adhesive feature of such a system, one has to study both the origin of the grafted layer interdigitation with the network, and the end-grafted chains extraction out of the elastomer when it comes unstuck from the solid surface. We shall tackle here the first aspect for which we develop a partial interdigitation model that lets us analytically predict a critical surface grafting density $\sigma^{*} \simeq P^{{1/10}}N^{-{3/5}}$ beyond which the layer no longer interdigitates with the elastomer. We then relate this result with recent adhesion measurements

Tensile Fracture of Welded Polymer Interfaces: Miscibility, Entanglements and Crazing

Large-scale molecular simulations are performed to investigate tensile failure of polymer interfaces as a function of welding time $t$. Changes in the tensile stress, mode of failure and interfacial fracture energy $G_I$ are correlated to changes in the interfacial entanglements as determined from Primitive Path Analysis. Bulk polymers fail through craze formation, followed by craze breakdown through chain scission. At small $t$ welded interfaces are not strong enough to support craze formation and fail at small strains through chain pullout at the interface. Once chains have formed an average of about one entanglement across the interface, a stable craze is formed throughout the sample. The failure stress of the craze rises with welding time and the mode of craze breakdown changes from chain pullout to chain scission as the interface approaches bulk strength. The interfacial fracture energy $G_I$ is calculated by coupling the simulation results to a continuum fracture mechanics model. As in experiment, $G_I$ increases as $t^{1/2}$ before saturating at the average bulk fracture energy $G_b$. As in previous simulations of shear strength, saturation coincides with the recovery of the bulk entanglement density. Before saturation, $G_I$ is proportional to the areal density of interfacial entanglements. Immiscibiltiy limits interdiffusion and thus suppresses entanglements at the interface. Even small degrees of immisciblity reduce interfacial entanglements enough that failure occurs by chain pullout and $G_I \ll G_b$

Has the phasing out of stavudine in accordance with changes in WHO guidelines led to a decrease in single-drug substitutions in first-line antiretroviral therapy for HIV in sub-Saharan Africa?

This version is the Accepted Manuscript and is published in final edited form as: AIDS. 2017 January 02; 31(1): 147–157. doi:10.1097/QAD.0000000000001307OBJECTIVE: We assessed the relationship between phasing out stavudine in first-line antiretroviral therapy (ART) in accordance with WHO 2010 policy and single-drug substitutions (SDS) (substituting the nucleoside reverse transcriptase inhibitor in first-line ART) in sub-Saharan Africa. DESIGN: Prospective cohort analysis (International epidemiological Databases to Evaluate AIDS-Multiregional) including ART-naive, HIV-infected patients aged at least 16 years, initiating ART between January 2005 and December 2012. Before April 2010 (July 2007 in Zambia) national guidelines called for patients to initiate stavudine-based or zidovudine-based regimen, whereas thereafter tenofovir or zidovudine replaced stavudine in first-line ART. METHODS: We evaluated the frequency of stavudine use and SDS by calendar year 2004-2014. Competing risk regression was used to assess the association between nucleoside reverse transcriptase inhibitor use and SDS in the first 24 months on ART. RESULTS: In all, 33 441 (8.9%; 95% confience interval 8.7-8.9%) SDS occurred among 377 656 patients in the first 24 months on ART, close to 40% of which were amongst patients on stavudine. The decrease in SDS corresponded with the phasing out of stavudine. Competing risks regression models showed that patients on tenofovir were 20-95% less likely to require a SDS than patients on stavudine, whereas patients on zidovudine had a 75-85% decrease in the hazards of SDS when compared to stavudine. CONCLUSION: The decline in SDS in the first 24 months on treatment appears to be associated with phasing out stavudine for zidovudine or tenofovir in first-line ART in our study. Further efforts to decrease the cost of tenofovir and zidovudine for use in this setting is warranted to substitute all patients still receiving stavudine

Delineating the spatial drivers of agri-environment scheme adoption at field and farm levels

Agri-environment schemes (AES), introduced by the EU Common Agricultural Policy (CAP), aim to compensate land owners for implementing environmentally-friendly practices. Whilst literature has examined their effectiveness and how farmer characteristics govern AES adoption, there is a lack of knowledge about the spatial drivers of AES, particularly structural, biophysical and landscape factors in the UK. Using the Humber region as a case study, this paper explores how the uptake of Countryside Stewardship options has varied from 2016 to 2021. It also examines 2500 farms from the field- and farm-level data of 2019 to better understand what type of land British farmers are adopting AES on. Logistic regression analysis is used to identify the factors (including farm and landscape characteristics, designated sites and land quality) that best explain overall AES adoption, as well as specific scheme adoption, at the field- and farm-level. Our analysis reveals that ‘buffer strips’, ‘hedgerow management’, ‘permanent grassland’, and ‘winter bird food’ are the most commonly adopted schemes of 2019. AES are generally adopted on larger fields and farms that feature marginalised, unproductive and vulnerable land, except for ‘buffer strips’ which showed a larger tendency to appear on fields with more profitable, higher quality land. This study, therefore, supports the notion that AES are generally placed on lower quality land and that large proportions of agricultural land owners are not effectively targeted. With the expected loss of direct payments to farmers in the UK as a result of the Department for Environment, Food & Rural Affairs (DEFRA) post-Brexit re-evaluation of rural policy, these results call for the Sustainable Farming Incentive (SFI) to be made more accessible and inclusive to a broader diversity of farmers

Development of Fecal Coliform TMDL Protocols for Bass and Cinder Creeks on Kiawah Island

2008 S.C. Water Resources Conference - Addressing Water Challenges Facing the State and Regio

Non-Equilibrium in Adsorbed Polymer Layers

High molecular weight polymer solutions have a powerful tendency to deposit adsorbed layers when exposed to even mildly attractive surfaces. The equilibrium properties of these dense interfacial layers have been extensively studied theoretically. A large body of experimental evidence, however, indicates that non-equilibrium effects are dominant whenever monomer-surface sticking energies are somewhat larger than kT, a common case. Polymer relaxation kinetics within the layer are then severely retarded, leading to non-equilibrium layers whose structure and dynamics depend on adsorption kinetics and layer ageing. Here we review experimental and theoretical work exploring these non-equilibrium effects, with emphasis on recent developments. The discussion addresses the structure and dynamics in non-equilibrium polymer layers adsorbed from dilute polymer solutions and from polymer melts and more concentrated solutions. Two distinct classes of behaviour arise, depending on whether physisorption or chemisorption is involved. A given adsorbed chain belonging to the layer has a certain fraction of its monomers bound to the surface, f, and the remainder belonging to loops making bulk excursions. A natural classification scheme for layers adsorbed from solution is the distribution of single chain f values, P(f), which may hold the key to quantifying the degree of irreversibility in adsorbed polymer layers. Here we calculate P(f) for equilibrium layers; we find its form is very different to the theoretical P(f) for non-equilibrium layers which are predicted to have infinitely many statistical classes of chain. Experimental measurements of P(f) are compared to these theoretical predictions.Comment: 29 pages, Submitted to J. Phys.: Condens. Matte