113 resultados para Diffusion limitations
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Summary: Current UK Government policy is concerned with the possible connections between childhood adversity, social exclusion and negative outcomes in adulthood. Understanding the impact of adverse childhood experiences on outcomes in adulthood is therefore key to informing effective policy and practice. In this article, the research on the impact of childhood adversity on outcomes in adulthood is reviewed in the broad categories of: mental health and social functioning; physical health; offending; service use; and economic impact. The literature on resilience that focuses on those who experience adversity, but do not have associated negative outcomes is also briefly considered. The strengths and limitations of the range of research methods used are then examined. Findings: Previous studies have tended to focus on specific forms of adversity, predominantly abuse and neglect, and either: specific populations and specific outcomes; specific populations and general outcomes; or general populations and specific outcomes. This means there may be incomplete understanding of the inputs (the range of adverse experiences in childhood), the processes (how these may affect people) and the outcomes (across domains in adulthood). Applications: It is concluded that it is important for social work researchers to engage in the current debate about how to prevent harmful childhood adversity and there is an important gap in the research for more interdisciplinary large-scale general population studies that consider the full range of childhood adversity and associated impacts across time and the possible processes involved.
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Background: The response rate of aminolaevulinic acid (ALA)-based photodynamic therapy (PDT) in certain subtypes of actinic keratosis (AK), such as hypertrophic and hyperkeratotic lesions, is variable, an effect attributable to a supposed lack of ALA penetration. A detailed and depth-related profile of spatial ALA permeation in AK following drug administration would lead to a greater understanding of concentrations achievable before protoporphyrin IX biosynthesis and subsequent PDT.
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In this paper, a method for modeling diffusive boundaries in finite difference time domain (FDTD) room acoustics simulations with the use of impedance filters is presented. The proposed technique is based on the concept of phase grating diffusers, and realized by designing boundary impedance filters from normal-incidence reflection filters with added delay. These added delays, that correspond to the diffuser well depths, are varied across the boundary surface, and implemented using Thiran allpass filters. The proposed method for simulating sound scattering is suitable for modeling high frequency diffusion caused by small variations in surface roughness and, more generally, diffusers characterized by narrow wells with infinitely thin separators. This concept is also applicable to other wave-based modeling techniques. The approach is validated by comparing numerical results for Schroeder diffusers to measured data. In addition, it is proposed that irregular surfaces are modeled by shaping them with Brownian noise, giving good control over the sound scattering properties of the simulated boundary through two parameters, namely the spectral density exponent and the maximum well depth.
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The proteasome has been validated as a therapeutic target, with proteasome inhibitors showing particular efficacy in the treatment of Multiple Myeloma. A wide range of methods have been developed to profile proteasome activity. These include the current method of choice fluorogenic peptide substrates, as well as bioluminescent imaging, immunological methods, and more recently, site-specific fluorescent probes. The aim of this review is to evaluate the currently available methods for profiling proteasome activity and their suitability for use in translational studies. Ongoing development of techniques for profiling proteasome activity will facilitate future research into proteasome-related pathologies, thus accelerating the development of more specific drug regimes. (C) 2010 Elsevier Ltd. All rights reserved.
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In this paper, a method for modeling diffusion caused by non-smooth boundary surfaces in simulations of room acoustics using finite difference time domain (FDTD) technique is investigated. The proposed approach adopts the well-known theory of phase grating diffusers to efficiently model sound scattering from rough surfaces. The variation of diffuser well-depths is attained by nesting allpass filters within the reflection filters from which the digital impedance filters used in the boundary implementation are obtained. The presented technique is appropriate for modeling diffusion at high frequencies caused by small surface roughness and generally diffusers that have narrow wells and infinitely thin separators. The diffusion coefficient was measured with numerical experiments for a range of fractional Brownian diffusers.
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The validity of load estimates from intermittent, instantaneous grab sampling is dependent on adequate spatial coverage by monitoring networks and a sampling frequency that re?ects the variability in the system under study. Catchments with a ?ashy hydrology due to surface runoff pose a particular challenge as intense short duration rainfall events may account for a signi?cant portion of the total diffuse transfer of pollution from soil to water in any hydrological year. This can also be exacerbated by the presence of strong background pollution signals from point sources during low flows. In this paper, a range of sampling methodologies and load estimation techniques are applied to phosphorus data from such a surface water dominated river system, instrumented at three sub-catchments (ranging from 3 to 5 km2 in area) with near-continuous monitoring stations. Systematic and Monte Carlo approaches were applied to simulate grab sampling using multiple strategies and to calculate an estimated load, Le based on established load estimation methods. Comparison with the actual load, Lt, revealed signi?cant average underestimation, of up to 60%, and high variability for all feasible sampling approaches. Further analysis of the time series provides an insight into these observations; revealing peak frequencies and power-law scaling in the distributions of P concentration, discharge and load associated with surface runoff and background transfers. Results indicate that only near-continuous monitoring that re?ects the rapid temporal changes in these river systems is adequate for comparative monitoring and evaluation purposes. While the implications of this analysis may be more tenable to small scale ?ashy systems, this represents an appropriate scale in terms of evaluating catchment mitigation strategies such as agri-environmental policies for managing diffuse P transfers in complex landscapes.
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Supported ionic liquid membranes (SILMs) has the potential to be a new technological platform for gas/organic vapour separation because of the unique non-volatile nature and discriminating gas dissolution properties of room temperature ionic liquids (ILs). This work starts with an examination of gas dissolution and transport properties in bulk imidazulium cation based ionic liquids [Cnmim][NTf2] (n = 2.4, 6, 8.10) from simple gas H2, N2, to polar CO2, and C2H6, leading to a further analysis of how gas dissolution and diffusion are influenced by molecular specific gas-SILMs interactions, reflected by differences in gas dissolution enthalpy and entropy. These effects were elucidated again during gas permeation studies by examining how changes in these properties and molecular specific interactions work together to cause deviations from conventional solution–diffusion theory and their impact on some remarkably contrasting gas perm-selectivity performance. The experimental perm-selectivity for all tested gases showed varied and contrasting deviation from the solution–diffusion, depending on specific gas-IL combinations. It transpires permeation for simpler non-polar gases (H2, N2) is diffusion controlled, but strong molecular specific gas-ILs interactions led to a different permeation and selectivity performance for C2H6 and CO2. With exothermic dissolution enthalpy and large order disruptive entropy, C2H6 displayed the fastest permeation rate at increased gas phase pressure in spite of its smallest diffusivity among the tested gases. The C2H6 gas molecules “peg” on the side alkyl chain on the imidazulium cation at low concentration, and are well dispersed in the ionic liquids phase at high concentration. On the other hand strong CO2-ILs affinity resulted in a more prolonged “residence time” for the gas molecule, typified by reversed CO2/N2 selectivity and slowest CO2 transport despite CO2 possess the highest solubility and comparable diffusivity in the ionic liquids. The unique transport and dissolution behaviour of CO2 are further exploited by examining the residing state of CO2 molecules in the ionic liquid phase, which leads to a hypothesis of a condensing and holding capacity of ILs towards CO2, which provide an explanation to slower CO2 transport through the SILMs. The pressure related exponential increase in permeations rate is also analysed which suggests a typical concentration dependent diffusion rate at high gas concentration under increased gas feed pressure. Finally the strong influence of discriminating and molecular specific gas-ILs interactions on gas perm-selectivity performance points to future specific design of ionic liquids for targeted gas separations.