Effects of the Mount Pinatubo eruption on the radiative and chemical processes in the troposphere and stratosphere

The Lawrence Livermore National Laboratory two-dimensional zonally-averaged chemical-radiative-transport model of the global atmosphere was used to study the effects of the 15 June 1991 eruption of the Mt. Pinatubo volcano on stratospheric processes. SAGE 2 time-dependent aerosol surface area density and optical extinction data were used as input into the model. By 22 December 1991, a maximum equatorial change of -1.8 percent in column ozone was derived from heterogeneous chemical processes that convert NO(x) into HNO3 on sulfuric acid aerosols. Radiative feedbacks from increased aerosol optical thickness independently changes column ozone by approximately -3.5 percent for the same period. This occurs from increasing the net heating of the lower stratosphere, which indirectly increases chemical reaction rates via their temperature dependence and from changes in actinic fluxes, which directly modify photodissociation rates. Including both heterogeneous and radiative effects changes column ozone by -5.5 percent. The model-derived change overestimates the decrease in column ozone relative to the TOMS instrument on the Nimbus 7 satellite. Maximum local ozone decreases of 12 percent were derived in the equatorial region, at 25 km. Model-derived column NO2 peaked (-14 percent) at 30 deg S in October 1991. The timing of the NO2 peak is consistent with observation, but the model underestimates the magnitude of the decrease. Local concentrations of NO(x) (NO + NO2), ClO(x) (Cl + ClO), and HO(x) (OH + HO2), in the lower stratosphere between 30 deg S and 30 deg N, were calculated to have changed by -40 percent, +100 to +160 percent, and +120 to +140 percent respectively

Numerical study of a multiple-segment metal foam-PCM latent heat storage unit: Effect of porosity, pore density and location of heat source

This study numerically investigates the performance of the melting process for a PCM based heat storage system under the effect of different variables in a vertical container with a copper metal foam. Different cases were studied and compared including the effects of variable porosities and pore densities, non-equilibrium porous medium model, a multiple-segment metal foam case and different heater locations in the system on the liquid fraction and temperature as presented by contour plots and diagrams. The results show high performance for the copper foam-PCM unit compared with on its own PCM, for reducing the melting time by almost 85%. By changing the location of constant temperature heater from the bottom to the side and top surface, the melting time decreases by 70.5% and 4.7%, respectively. By using a multiple-segment porous system, the melting time reduces by 3.5% compared with the case of uniform porosity. Furthermore, the more accurate non-equilibrium numerical model shows a 7.4% difference in the melting time compared with the equilibrium model. This study optimises the design to improve practical application performance and to reduce waste energy

Numerical modelling of phase change material melting process embedded in porous media: Effect of heat storage size

The aim of this paper is to study the influence of enclosure size in latent heat thermal energy storage systems embedded in a porous medium for domestic usage of latent heat thermal energy storage heat exchangers. A 2-D rectangular enclosure is considered as the computational domain to study the heat transfer improvement for a phase change material embedded in a copper foam considering a constant heat flux from the bottom surface. Different dimensions of the composite system are examined compared with a system without a porous medium. The thermal non-equilibrium model with enthalpy-porosity method is employed for the effects of porous medium and phase change in the governing equations, respectively. The phase change material liquid fraction, temperature, velocity, stream lines and the rate of heat transfer are studied. The presence of a porous medium increases the heat transfer significantly, but the improvement in melting performance is strongly related to the system's dimensions. For the dimensions of 200 × 100 mm (W × H), the melting time of porous-phase change material with the porosity of 95% is reduced by 17% compared with phase change material-only system. For the same storage volume and total amount of thermal energy added, the melting time is lower for the system with a lower height, especially for the phase change material-only system due to a higher area of the input heat. The non-dimensional analysis results in curve-fitting correlations between the liquid fraction and Fo.Ste.Ra−0.02 for rectangular latent heat thermal energy storage systems for both phase change material-only and composite-phase change material systems within the parameter range of 1.16 less than less than Lf less than 1 and 0 less than Fo.Ste.Ra−0.02 less than 0.57. Over a range of system's volume, heat flux and surface area of the input heat flux, the benefit of composite phase change material is variable and, in some cases, is negligible compared with the phase change material-only system

Discharge of a composite metal foam/phase change material to air heat exchanger for a domestic thermal storage unit

This paper evaluates the discharging mechanism in a PCM (phase change material) to air heat exchanger for the purpose of space heating using a composite of copper foam and PCM. The composite system is modelled with both 2-D and 3-D computational fluid dynamics approach for different inlet air temperatures to consider the effect of room temperature using the thermal non-equilibrium model for the porous medium compared with the thermal equilibrium one. The results show the significant advantages of composite heat exchanger compared with a PCM only case. For the inlet air temperature of 22 °C, the composite unit is solidified in 43% shorter time with 73% higher heat retrieval rate compared with that for the PCM only. After 10 h, the temperature variation between the inlet and outlet of the air channels for latent heat storage heat exchanger system with the composite system is 41 °C and 34 °C for the inlet air temperatures of 0 °C and 22 °C, respectively, while it is 33 °C and 29 °C for the system with PCM only. This study show the possible usage of PCMs in the energy storage heaters by introducing metal foams which is not possible using PCM only alternatives

Status of the solar and infrared radiation submodels in the LLNL 1-D and 2-D chemical-transport models

The authors have implemented a series of state of the art radiation transport submodels in previously developed one dimensional and two dimensional chemical transport models of the troposphere and stratosphere. These submodels provide the capability of calculating accurate solar and infrared heating rates. They are a firm basis for further radiation submodel development as well as for studying interactions between radiation and model dynamics under varying conditions of clear sky, clouds, and aerosols. 37 refs., 3 figs

The Digital Support Platform: a qualitative research study investigating the feasibility of an internet-based, post-diagnostic support platform for families living with dementia.

Objectives  To establish the feasibility of the Digital Support Platform (DSP), an internet-based, post-diagnostic tool designed for families living with a diagnosis of dementia. Design  Qualitative methods, using Normalisation Process Theory (NPT) as an analysis framework for semi-structured interview transcriptions. Setting  A community care setting in the South-East Scotland. ParticipantsWe interviewed ten dyads of people with Alzheimer’s, vascular or mixed dementia (PWD), and their family carers, who had been given and had used the DSP for at least 2 months. Results  Our analysis revealed that the DSP was predominantly understood and used by the carers rather than PWD, and was used alongside tools and methods they already used to care for their relative. The DSP was interpreted as a tool that may be of benefit to those experiencing later stages of dementia or with physical care needs. Carers stated that the DSP may be of benefit in the future, reflecting a disinclination to prepare for or anticipate for future needs, rather than focus on those needs present at the time of distribution. PWD spoke positively about an interest in learning to use technology more effectively and enjoyed having their own tablet devices. Conclusions  The DSP was not wholly appropriate for families living with dementia in its early stages. The views of carers confirmed that post-diagnostic support was valued, but emphasised the importance of tailoring this support to the exact needs and current arrangements of families. There may be a benefit to introducing, encouraging, providing and teaching internet-enabled technology to those PWD who do not currently have access. Training should be provided when introducing new technology to PWD

A Unified Framework for the Infection Dynamics of Zoonotic Spillover and Spread.

A considerable amount of disease is transmitted from animals to humans and many of these zoonoses are neglected tropical diseases. As outbreaks of SARS, avian influenza and Ebola have demonstrated, however, zoonotic diseases are serious threats to global public health and are not just problems confined to remote regions. There are two fundamental, and poorly studied, stages of zoonotic disease emergence: 'spillover', i.e. transmission of pathogens from animals to humans, and 'stuttering transmission', i.e. when limited human-to-human infections occur, leading to self-limiting chains of transmission. We developed a transparent, theoretical framework, based on a generalization of Poisson processes with memory of past human infections, that unifies these stages. Once we have quantified pathogen dynamics in the reservoir, with some knowledge of the mechanism of contact, the approach provides a tool to estimate the likelihood of spillover events. Comparisons with independent agent-based models demonstrates the ability of the framework to correctly estimate the relative contributions of human-to-human vs animal transmission. As an illustrative example, we applied our model to Lassa fever, a rodent-borne, viral haemorrhagic disease common in West Africa, for which data on human outbreaks were available. The approach developed here is general and applicable to a range of zoonoses. This kind of methodology is of crucial importance for the scientific, medical and public health communities working at the interface between animal and human diseases to assess the risk associated with the disease and to plan intervention and appropriate control measures. The Lassa case study revealed important knowledge gaps, and opportunities, arising from limited knowledge of the temporal patterns in reporting, abundance of and infection prevalence in, the host reservoir.Natural Environment Research Council (project no.: NEJ001570-1), Department for International Development, Economic and Social Research Council, National Institute for Health Research, Science and Technology Directorate, Department of Homeland Security, Fogarty International Center USA, European Union FP7 (project ANTIGONE (contract number 278976)), Royal Society (Wolfson Research Merit Award), Alborada Trust, US National Institute of Health (P20GM103501, BAANIAID-DAIT-NIHQI2008031, HHSN272201000022C, HHSN272200900049C, 1U19AI109762, 1R01AI104621, 2R44AI088843), USAID/NIH PEER Health grant.This is the final version of the article. It first appeared from the Public Library of Science via http://dx.doi.org/10.1371/journal.pntd.000495

Using modelling to disentangle the relative contributions of zoonotic and anthroponotic transmission: the case of lassa fever.

BACKGROUND: Zoonotic infections, which transmit from animals to humans, form the majority of new human pathogens. Following zoonotic transmission, the pathogen may already have, or may acquire, the ability to transmit from human to human. With infections such as Lassa fever (LF), an often fatal, rodent-borne, hemorrhagic fever common in areas of West Africa, rodent-to-rodent, rodent-to-human, human-to-human and even human-to-rodent transmission patterns are possible. Indeed, large hospital-related outbreaks have been reported. Estimating the proportion of transmission due to human-to-human routes and related patterns (e.g. existence of super-spreaders), in these scenarios is challenging, but essential for planned interventions. METHODOLOGY/PRINCIPAL FINDINGS: Here, we make use of an innovative modeling approach to analyze data from published outbreaks and the number of LF hospitalized patients to Kenema Government Hospital in Sierra Leone to estimate the likely contribution of human-to-human transmission. The analyses show that almost [Formula: see text] of the cases at KGH are secondary cases arising from human-to-human transmission. However, we found much of this transmission is associated with a disproportionally large impact of a few individuals ('super-spreaders'), as we found only [Formula: see text] of human cases result in an effective reproduction number (i.e. the average number of secondary cases per infectious case) [Formula: see text], with a maximum value up to [Formula: see text]. CONCLUSIONS/SIGNIFICANCE: This work explains the discrepancy between the sizes of reported LF outbreaks and a clinical perception that human-to-human transmission is low. Future assessment of risks of LF and infection control guidelines should take into account the potentially large impact of super-spreaders in human-to-human transmission. Our work highlights several neglected topics in LF research, the occurrence and nature of super-spreading events and aspects of social behavior in transmission and detection.This work for the Dynamic Drivers of Disease in Africa Consortium, NERC project no. NE-J001570-1, was funded with support from the Ecosystem Services for Poverty Alleviation (ESPA) programme. The ESPA programme is funded by the Department for International Development (DFID), the Economic and Social Research Council (ESRC) and the Natural Environment Research Council (NERC). See more at: http://www.espa.ac.uk/about/identity/acknowledging-espafunding# sthash.UivKPObf.dpuf. GL, JLNW, AAC, CTW and EFC also benefit from the support of the small mammal disease working group, funded by the Research and Policy for Infectious Disease Dynamics (RAPIDD) programme of the Science and Technology Directorate, Department of Homeland Security, and Fogarty International Center, USA. JLNW and AC were also supported by the European Union FP7 project ANTIGONE (contract number 278976). AAC is supported by a Royal Society Wolfson Reearch Merit Award. JLNW is also supported by the Alborada Trust. JSS, LM, RG, and JGS were supported by the US National Institute of Health (JSS: NIH grant P20GM103501; LM, RG, JGS: NIH grant BAA-NIAID-DAIT-NIHQI2008031).This is the final published version. It first appeared at http://www.plosntds.org/article/info%3Adoi%2F10.1371%2Fjournal.pntd.0003398

Exogenous double-stranded RNA inhibits the infection physiology of rust fungi to reduce symptoms in planta

Rust fungi (Pucciniales) are a diverse group of plant pathogens in natural and agricultural systems. They pose ongoing threats to the diversity of native flora and cause annual crop yield losses. Agricultural rusts are predominantly managed with fungicides and breeding for resistance, but new control strategies are needed on non-agricultural plants and in fragile ecosystems. RNA interference (RNAi) induced by exogenous double-stranded RNA (dsRNA) has promise as a sustainable approach for managing plant-pathogenic fungi, including rust fungi. We investigated the mechanisms and impact of exogenous dsRNA on rust fungi through in vitro and whole-plant assays using two species as models, Austropuccinia psidii (the cause of myrtle rust) and Coleosporium plumeriae (the cause of frangipani rust). In vitro, dsRNA either associates externally or is internalized by urediniospores during the early stages of germination. The impact of dsRNA on rust infection architecture was examined on artificial leaf surfaces. dsRNA targeting predicted essential genes significantly reduced germination and inhibited development of infection structures, namely appressoria and penetration pegs. Exogenous dsRNA sprayed onto 1-year-old trees significantly reduced myrtle rust symptoms. Furthermore, we used comparative genomics to assess the wide-scale amenability of dsRNA to control rust fungi. We sequenced genomes of six species of rust fungi, including three new families (Araucariomyceaceae, Phragmidiaceae, and Skierkaceae) and identified key genes of the RNAi pathway across 15 species in eight families of Pucciniales. Together, these findings indicate that dsRNA targeting essential genes has potential for broad-use management of rust fungi across natural and agricultural systems