Effectiveness of Mechanisms and Models of Coordination between Organizations, Agencies and Bodies Providing or Financing Health Services in Humanitarian Crises: A Systematic Review.

BACKGROUND: Effective coordination between organizations, agencies and bodies providing or financing health services in humanitarian crises is required to ensure efficiency of services, avoid duplication, and improve equity. The objective of this review was to assess how, during and after humanitarian crises, different mechanisms and models of coordination between organizations, agencies and bodies providing or financing health services compare in terms of access to health services and health outcomes. METHODS: We registered a protocol for this review in PROSPERO International prospective register of systematic reviews under number PROSPERO2014:CRD42014009267. Eligible studies included randomized and nonrandomized designs, process evaluations and qualitative methods. We electronically searched Medline, PubMed, EMBASE, Cochrane Central Register of Controlled Trials, CINAHL, PsycINFO, and the WHO Global Health Library and websites of relevant organizations. We followed standard systematic review methodology for the selection, data abstraction, and risk of bias assessment. We assessed the quality of evidence using the GRADE approach. RESULTS: Of 14,309 identified citations from databases and organizations' websites, we identified four eligible studies. Two studies used mixed-methods, one used quantitative methods, and one used qualitative methods. The available evidence suggests that information coordination between bodies providing health services in humanitarian crises settings may be effective in improving health systems inputs. There is additional evidence suggesting that management/directive coordination such as the cluster model may improve health system inputs in addition to access to health services. None of the included studies assessed coordination through common representation and framework coordination. The evidence was judged to be of very low quality. CONCLUSION: This systematic review provides evidence of possible effectiveness of information coordination and management/directive coordination between organizations, agencies and bodies providing or financing health services in humanitarian crises. Our findings can inform the research agenda and highlight the need for improving conduct and reporting of research in this field

Diffusion to electrodes

This thesis develops diffusion models for modern electrochemical experiments involving the transport of particles to electrodes and adsorbing surfaces. In particular, the models are related to the 'impact' method where particles stochastically arrive at an electrode and detected electrochemically. The studies are carried out using numerical simulations and also analytical methods. Chapter 1 is introductory and outlines some fundamental concepts in mass transport and kinetics, and their relation to electrochemical measurements which are of importance for the reader. Chapter 2 describes the numerical methods which are used for electrochemical simulations. Chapter 3 focuses on a specific two dimensional simulation system and the development of a high performance voltammetry simulation. Chapters 4 and 5 study the stochastic impacts of particles at an electrode surface. In Chapter 4, a 'diffusion only' model is developed using a probabilistic study and random walk simulations in order to provide expressions that can be used in so-called `impact' experiments. In Chapter 5, the practical cases of microdisc and microwire electrodes are investigated. Expressions for the number of impacts are developed and the concept of the lower limit of detection in ultra-dilute solutions is introduced. Then, a comparison study between the microwire electrode and the microdisc electrode explores a geometrical effect and its implications for experimental setups. In Chapter 6, a numerical and analytical study is developed to examine the effect of hindered diffusion as a particle moves close to an adsorbing surface. The study identifies the conditions under which this hindered diffusion is signiffcant even in a non-confined space. The study shows that the domination of hindered diffusion is strongly dependant on the sizes of both the particle and the target. The study focuses on a variety of target shapes and allows the number of hits/impacts to be estimated in practical 'impact' experiments. Moreover, a drastic effect on the calculation of the mean first passage time is observed for a sub-micron sized target, showing the importance of this effect not only for electrochemistry but also in biological systems. Chapters 7 and 8 investigate the properties of an adsorbing insulating surface adjacent to an electrode. In Chapter 7, a numerical study of the effect of 'shielding' by the insulating sheath is carried out. The study examines the in uence of this effect on the magnitude of the current in chronoamperometry experiments. Chapter 8 explores the case of reversible adsorption on the insulating surface for voltammetric enhancement by pre-concentration on the sheath surface. The results identify the conditions under which enhancement of the voltammetric signal can be observed. Finally, Chapter 9 looks at geometrical effects on the current response of insulating particles modified with an electroactive surface layer. Numerical models are developed to model the diffusion of charge transfer between electro-active sites on a modified surface of insulating particles. The current-time responses are simulated for particles with the shape of a sphere, a cube/cuboid, and a cylinder on an electrode. The characteristic currenttime responses are calculated for the various shapes. The observations show that the model can be utilised in experiments to determine the coverage or the diffusion coeficient of charge dissipation on modified insulating particles and, in some situations to identify the particle shape.</p

Shielding of a Microdisc Electrode Surrounded by an Adsorbing Surface

Microdisc electrodes are usually made by surrounding a metal wire with a diameter of a few microns in a flat insulating sheath made of glass or another insulating material. The sheath is generally assumed to play no role in the voltammetry at the microdisc electrode. However, in some cases, and especially for experiments with nanoparticles, significant adsorption can occur onto the sheath, perturbing the current response measured at the disc. We report theoretical calculations of the effect of shielding by the insulating sheath of microelectrodes and show that it can significantly influence the magnitude of the current, even for relatively small levels of adsorption, not least because of the typically very large area of the insulation relative to the electrode size. Working curves are provided to permit the analysis of experimental data

Shielding of a Microdisc Electrode Surrounded by an Adsorbing Surface

Microdisc electrodes are usually made by surrounding a metal wire with a diameter of a few microns in a flat insulating sheath made of glass or another insulating material. The sheath is generally assumed to play no role in the voltammetry at the microdisc electrode. However, in some cases, and especially for experiments with nanoparticles, significant adsorption can occur onto the sheath, perturbing the current response measured at the disc. We report theoretical calculations of the effect of shielding by the insulating sheath of microelectrodes and show that it can significantly influence the magnitude of the current, even for relatively small levels of adsorption, not least because of the typically very large area of the insulation relative to the electrode size. Working curves are provided to permit the analysis of experimental data

Voltammetric Sensitivity Enhancement by Using Preconcentration Adjacent to the Electrode: Simulation, Critical Evaluation, and Insights

© 2014 American Chemical Society. A popular approach to enhancing the sensitivity of voltammetry is the surface modification of electrodes to provide adsorption sites which allow preconcentration of target species to promote sensitivity and reduced limits of detection. The surface modifier is typically inert other than providing enhanced adsorption and hence preconcentration and nonconductive so that after preconcentration the adsorbent must desorb and diffuse to the electrode before detection. We report the simulation of an idealized model for this type of voltammetry, focusing in particular on the effects of adsorption coverage and binding strength on the surface on the voltammetry response

Voltammetric Sensitivity Enhancement by Using Preconcentration Adjacent to the Electrode: Simulation, Critical Evaluation, and Insights

© 2014 American Chemical Society. A popular approach to enhancing the sensitivity of voltammetry is the surface modification of electrodes to provide adsorption sites which allow preconcentration of target species to promote sensitivity and reduced limits of detection. The surface modifier is typically inert other than providing enhanced adsorption and hence preconcentration and nonconductive so that after preconcentration the adsorbent must desorb and diffuse to the electrode before detection. We report the simulation of an idealized model for this type of voltammetry, focusing in particular on the effects of adsorption coverage and binding strength on the surface on the voltammetry response

General Model of Hindered Diffusion

The diffusion of a particle from bulk solution is slowed as it moves close to an adsorbing surface. A general model is reported that is easily applied by theoreticians and experimentalists. Specifically, it is shown here that in general and regardless of the space size, the magnitude of the effect of hindered diffusion on the flux is a property of the diffusion layer thickness. We explain and approximate the effect. Predictions of concentration profiles show that a "hindered diffusion layer" is formed near the adsorbing surface within the diffusion layer, observed even when the particle radius is just a 0.1% of the diffusion layer thickness. In particular, we focus on modern electrochemistry processes involving with impact of particles with either ultrasmall electrodes or particles in convective systems. The concept of the "hindered diffusion layer" is generally important for example in recent biophysical models of particles diffusion to small targets

Charge diffusion on the surface of particles with simple geometries

© 2015 American Chemical Society. The diffusion of charge transfer between electroactive sites on a modified surface of insulating particles is modeled assuming charge injection from an electrode supporting the particle. The current-time responses are studied for particles with shapes of a cylinder, sphere, and cube and can be used directly to determine the coverage of sites on the particle surface in a chronoamperometry measurement whereby the particles impacting an electrode hold at a suitable potential. It is shown that the current response has a characteristic behavior reflecting the particle shape and aspect ratio which allows the transient to distinguish between the various shapes and their orientations on the electrode. It is clearly shown that spherical particles have a non-Cottrellian behavior while cylinders and cubes have a characteristic Cottrellian current at sufficiently short times. Additionally, various aspect ratios of cylinders, such as flakelike, tube, or bamboolike particles, change the current response, and the shape can be assumed by comparing the current values at short and long times

Implementing high performance voltammetry simulation using the implicit parallel algorithm

The numerical simulation of voltammetry and amperometry at a microdisc electrode is implemented with a parallel algorithm using GPU (CUDA in C ++) and adapting the implicit finite difference approximation with the ADI method. This leads to high performance simulation of the current response whilst maintaining the high standard of accuracy required for such electrochemical systems. We gained a maximum speed-up of 20 times with a standard graphic card specifications (Quadro K4000) in comparison to a single core of 3.2 GHz CPU. The simplified allocation and data flow allows an accessible code which produces a starting point for researchers to manipulate the code to study new problems in electrochemical and surface reaction systems that require high performance simulation