Predicting the steady state thickness of passive films in order to prevent degradations of implant

Some implants have approximately a lifetime of 15 years. The femoral stem, for example, should be made of 316L/316LN stainless steel. Fretting corrosion, friction under small displacements, should occur during human gait, due to repeated loadings and un-loadings, between stainless steel and bone for instance. Some experimental investigations of fretting corrosion have been practiced. As well known, metallic alloys and especially stainless steels are covered with a passive film that prevents from the corrosion and degradation. This passive layer of few nanometers, at ambient temperature, is the key of our civilization according to some authors. This work is dedicated to predict the passive layer thicknesses of stainless steel under fretting corrosion with a specific emphasis on the role of proteins. The model is based on the Point Defect Model (micro scale) and an update of the model on the friction process (micro-macro scale). Genetic algorithm was used for finding solution of the problem. The major results are, as expected from experimental results, albumin prevents from degradation at the lowest concentration of chlorides; an incubation time is necessary for degrading the passive film; under fretting corrosion and high concentration of chlorides the passive behavior is annihilated

Thermodynamics of nickel-cadmium and nickel-hydrogen batteries

Thermodynamic parameters for Nickel-Cadmium (NiCad) and Nickel-Hydrogen (NiH2) batteries are calculated for temperatures ranging from 273.15K (0 C) to 373.15K (100 C). For both systems, we list equilibrium and thermoneutral voltages for the cells, and in the case of the NiH2 battery, these data are provide for hydrogen fugacities ranging from 0.01 to 100 (atm) to simulate the full discharged and charged states. The quality of the input thermodynamic data are assessed and the effect of assuming different cell reactions is analyzed

Optimising Community-Based Forest Management Policy in Indonesia: a Critical Review

Community-based forest management (CBFM) is a popular concept in many countries, covering over 400 million hectares worldwide. In Indonesia, CBFM is viewed as an important component of the forestry sector with the government's goal to establish 5.6 million hectares of CBFM by 2011 (twice the area of industrial plantation forests). The Indonesian government is pursuing CBFM as a strategy to reduce deforestation of tropical forests, to alleviate poverty in rural communities, and to contribute timber supplies to the processing industry.There has been a belief that CBFM can lead to a physical and socio-economic transformation at the local level. However, in practice, especially in Indonesia, this claim appears problematic because in over 35 years since it has been officially introduced it does not appear to have contributed significantly to address the problems of deforestation and rural poverty.Despite the government's ambitious goal for CBFM, there are several challenges, for instance the entrenched poverty of many rural communities and inconsistent and unsupportive policies of CBFM at the national, provincial, and local government. This paper is intended to explore, discusses, and criticize the implementation of CBFM policies in various countries and in particular in Indonesia. This paper also aims to explore its challenges in the future development in Indonesia

Communicating REDD+ Issues at Local Level: Creating Latent and Manifest Conflict

”Carbon offsetting”in forestry-related projects is widely regarded as the ideal solution to the three challenges of the 21st Century: climate change, biodiversity conservation andsocio-economic development. At the same time, there is scepticism about the Reducing Emissions from Deforestation and Forest Degradation (REDD) proposal particularly because of the weak governance and institutional capacities in many developing countries, which could jeopardize the delivery of benefits at the local level. One major problem is that most people have little knowledge on the causes and consequences of the climate change. This is partly because the information is largely scattered among scientific journals, and obscured by jargon and sophisticated mathematical models. Consequently, REDD+ is beyond thereach of manyof the people affected by REDD+. This paper examines the efforts and the capacity of the local governments and other development agents in explaining the REDD + issues and its impacts on the local people, especially customary communities. The research shows that lack of policy communication and promotion, as well as consultations with the affected groups arethe main contributing factors to latent and manifest conflicts. In turn, this conflicth as proven that NGOs, district governments and scientists have not been successful intermediaries. Thus, in the future policy communication on REDD+ should beaimed at improved network formation (i.e. between farmer groups with business partners and NGOs and other related actors), learning, negotiation and relationship building (i.e. between members of farmer groups, not only withtheir leaders within the farmer groups but also with governmental and business sectors). Policy communication should also create a new configuration of support and services in form of advocacy, empowerment and management skills and technical skills for conserving their natural resources, for adaptation to climate change and building more equitable governance and transparency at local level

Bio-physical closure criteria without reference sites: Realistic targets in modified rivers

The use of reference sites for establishing closure criteria in areas disturbed by mining activities is common practice. ‘Reference’ sites are those considered to be largely unimpacted by anthropogenic activity (retaining desirable natural characteristics), and occurring near disturbed sites. Sites are considered rehabilitated when their biophysical condition approximates that of the reference site. However, this approach often creates impossible or unrealistic targets for miners seeking to close rehabilitated lands. For example, reference sites are often limited in availability (or non-existent) due to impacts by other land uses. Further, any available reference sites might not be realistic matches for the rehabilitated sites – in many rivers (for example) it is questionable whether sites which superficially appear similar are actually ecologically similar. We propose a more achievable approach to mine closure by comparing the bio-physical characteristics of rehabilitated sites to overall ecosystem variability, rather than specific target reference sites. Using multivariate ordination - a classic data clustering technique in ecology - as an applied management tool allows managers to measure how different their rehabilitated sites are from co-occurring sites, and how the rehabilitated sites are tracking over time. Our approach also identifies the key biological, physical, and chemical parameters that potentially differentiate a rehabilitated site and, therefore, the necessary actions to bring a rehabilitation site within range of normal river variability. Further, this conceptual paper introduces two unique case studies used to develop the model, involving microbes as indicators of rehabilitation progress and mine water impact in Australian rivers. The challenges and benefits associated with implementation of this approach from the practitioners’ perspectives are discussed. The outcome of this new approach to closure will allow miners to create realistic and definable targets for relinquishing rehabilitation land in already modified landscapes, potentially simplifying closure and project approvals

Diagnosis of vertebral fractures in children: is a simplified algorithm-based qualitative technique reliable?

Background Identification of osteoporotic vertebral fractures allows treatment opportunity reducing future risk. There is no agreed standardised method for diagnosing paediatric vertebral fractures. Objective To evaluate the precision of a modified adult algorithm-based qualitative (ABQ) technique, applicable to children with primary or secondary osteoporosis. Materials and methods Three radiologists independently assessed lateral spine radiographs of 50 children with suspected reduction in bone mineral density using a modified ABQ scoring system and following simplification to include only clinically relevant parameters, a simplified ABQ score. A final consensus of all observers using simplified ABQ was performed as a reference standard for fracture characterisation. Kappa was calculated for interobserver agreement of the components of both scoring systems and intraobserver agreement of simplified ABQ based on a second read of 29 randomly selected images. Results Interobserver Kappa for modified ABQ scoring for fracture detection, severity and shape ranged from 0.34 to 0.49 Kappa for abnormal endplate and position assessment was 0.27 to 0.38. Inter- and intraobserver Kappa for simplified ABQ scoring for fracture detection and grade ranged from 0.37 to 0.46 and 0.45 to 0.56, respectively. Inter- and intraobserver Kappa for affected endplate ranged from 0.31 to 0.41 and 0.45 to 0.51, respectively. Subjectively, observers’ felt simplified ABQ was easier and less time-consuming. Conclusion Observer reliability of modified and simplified ABQ was similar, with slight to moderate agreement for fracture detection and grade/severity. Due to subjective preference for simplified ABQ, we suggest its use as a semi-objective measure of diagnosing paediatric vertebral fracture

Pressure dependence of the sound velocity in a 2D lattice of Hertz-Mindlin balls: a mean field description

We study the dependence on the external pressure $P$ of the velocities $v_{L,T}$ of long wavelength sound waves in a confined 2D h.c.p. lattice of 3D elastic frictional balls interacting via one-sided Hertz-Mindlin contact forces, whose diameters exhibit mild dispersion. The presence of an underlying long range order enables us to build an effective medium description which incorporates the radial fluctuations of the contact forces acting on a single site. Due to the non linearity of Hertz elasticity, self-consistency results in a highly non-linear differential equation for the "equation of state" linking the effective stiffness of the array with the applied pressure, from which sound velocities are then obtained. The results are in excellent agreement with existing experimental results and simulations in the high and intermediate pressure regimes. It emerges from the analysis that the departure of $v_{L}(P)$ from the ideal $P^{1/6}$ Hertz behavior must be attributed primarily to the fluctuations of the stress field, rather than to the pressure dependence of the number of contacts

Building Success in Online Educational Programs for Adult Learners

The purpose of this symposium is to explore multiple perspectives on building and maintaining high quality online educational programs in university settings for adult learners

Granular Packings: Nonlinear elasticity, sound propagation and collective relaxation dynamics

Experiments on isotropic compression of a granular assembly of spheres show that the shear and bulk moduli vary with the confining pressure faster than the 1/3 power law predicted by Hertz-Mindlin effective medium theories (EMT) of contact elasticity. Moreover, the ratio between the moduli is found to be larger than the prediction of the elastic theory by a constant value. The understanding of these discrepancies has been a longstanding question in the field of granular matter. Here we perform a test of the applicability of elasticity theory to granular materials. We perform sound propagation experiments, numerical simulations and theoretical studies to understand the elastic response of a deforming granular assembly of soft spheres under isotropic loading. Our results for the behavior of the elastic moduli of the system agree very well with experiments. We show that the elasticity partially describes the experimental and numerical results for a system under compressional loads. However, it drastically fails for systems under shear perturbations, particularly for packings without tangential forces and friction. Our work indicates that a correct treatment should include not only the purely elastic response but also collective relaxation mechanisms related to structural disorder and nonaffine motion of grains.Comment: 21 pages, 13 figure

Neurological update: COVID-19

Abstract: Coronavirus Disease 2019 is predominantly a disorder of the respiratory system, but neurological complications have been recognised since early in the pandemic. The major pathophysiological processes leading to neurological damage in COVID-19 are cerebrovascular disease, immunologically mediated neurological disorders and the detrimental effects of critical illness on the nervous system. It is still unclear whether direct invasion of the nervous system by the Severe Acute Respiratory Syndrome Coronavirus 2 occurs; given the vast numbers of people infected at this point, this uncertainty suggests that nervous system infection is unlikely to represent a significant issue if it occurs at all. In this review, we explore what has been learnt about the neurological complications of COVID-19 over the course of the pandemic, and by which mechanisms these complications most commonly occur