Perfringolysin O pore formation dynamics: from soluble monomer to membrane insertion and beyond

Perfringolysin O (PFO) is a cholesterol dependent cytolysin (CDC) secreted by Clostridium perfringens, which forms pores in cholesterol containing membranes. CDCs are part of the larger Membrane attack complex-Perforin/CDC (MACPF/CDC) superfamily, containing pore formers responsible for controlling infectious disease and cancer in humans. CDCs are secreted as soluble hydrophilic monomers which oligomerise on lipid bilayers, ultimately forming bilayer spanning closed ring or open arc-shaped β-barrel pores. Perfringolysin O (PFO) was the first CDC to have its crystallographic structure resolved in its soluble monomeric form and has since become the prototypical CDC for investigating pore-forming mechanism. Previous studies on PFO have revealed a general outline of the steps involved in CDC pore formation; recognition of cholesterol and membrane binding, oligomerisation and ultimately membrane insertion to form large amphipathic pores. These steps have been elucidated using bulk assays and static imaging techniques such as electron microscopy or atomic force microscopy, however key mechanistic details remain uncharacterised due to the lack of time resolved data at a single pore level. Here we present a novel assay using microfluidics and total internal reflection microscopy to track PFO pore formation dynamics. Fluorescently labelled PFO and dye encapsulating liposomes were employed in conjunction to measure the kinetics of PFO binding from solution, nucleation, and oligomerisation on the surface of cholesterol containing liposomes. By visualising fluorescent dye release from our liposomes, we were able to determine the number of molecules necessary for an oligomer to insert and form a bilayer spanning pore. This information was collected from a large number of liposomes and used to build a mathematical model to quantify parameters controlling PFO accumulation and insertion kinetics on liposomes. We have also demonstrated how a different membrane composition affects these parameters by performing the assay on virus-like particles derived from HIV. This also displayed the adaptability of the assay which can be applied to different membranes and other pore forming proteins

Diseño y desarrollo de un encoder óptico con interrogación remota para la medida de la velocidad de giro y ángulo de paso en aerogeneradores

El presente documento técnico presenta el proyecto de final de Grado en Ingeniería Industrial y Automática titulado “Diseño y Desarrollo de un Encoder Óptico con interrogación remota para la medida de la velocidad de giro y ángulo de paso en aerogeneradores" realizado en el departamento de Tecnología Electrónica de la Universidad Carlos III de Madrid bajo la supervisión del Prof. David Sánchez Montero. El sistema propuesto consta de un sensor de fibra óptica (FOS, “Fiber Optic Sensor”), que opera por reflexión de la luz sobre una superficie reflectora, que permite emular el comportamiento de un giróscopo óptico y a su vez medir la velocidad angular del objeto al que se une. El proyecto además cuenta con un sistema de comunicación inalámbrica que usa el protocolo de comunicación ZigBee. En el presente documento, hemos enfocado el proyecto a los aerogeneradores, que pertenecen a un campo que está en auge por el incremento del uso de energías renovables. El sistema diseñado es capaz de medir los parámetros de velocidad de rotación de las aspas (velocidad de giro) de un aerogenerador y el ángulo de paso de las mismas mediante un sensor óptico. El presente proyecto pretende proporcionar una solución de sensado de bajo coste con el objetivo de monitorizar y controlar la velocidad de giro para evitar que ésta llegue a velocidades muy altas, poniendo así en peligro la integridad de la turbina. Adicionalmente, a una determinada velocidad de rotación, este tipo de instalaciones genera su potencia nominal, por lo que nos interesa mantener la turbina girando a esa velocidad. Esto se puede controlar mediante el ángulo de paso de las aspas, siendo capaz el sistema desarrollado de monitorizar de manera simultánea dicho parámetro. Cabría destacar que el alcance del proyecto se centra en un diseño correcto del sistema de sensado (de instrumentación) propuesto y no en la mecánica de fluidos que define el comportamiento de una turbina eólica...Ingeniería Electrónica Industrial y Automátic

Productivity of Spartina alterniflora in Proximity to Mangroves

Mangroves are salt-tolerant trees that coexist with marsh grasses and forbs at subtropical latitudes. Occasional freeze events keep mangroves from completely overgrowing marsh plants. There have not been severe freeze events within recent years which are changing the abundance of mangroves. Black mangroves (Avicennia germinans) could be outcompeting marsh plants for light or nutrients and that may decrease smooth cordgrass (Spartina alterniflora) productivity. The purpose of this study is to determine if mangroves are out-competing Spartina alterniflora by limiting nutrient availability. Field measurements of above and belowground data were quantified by measuring the growth, chlorophyll-a content, and nutrient content (carbon, nitrogen, and phosphorus) of S. alterniflora roots in plants growing within the A. germinans rhizosphere and in plants outside the area influenced by mangrove roots. The number of new leaves results suggest that A. germinans affects the productivity of S. alterniflora by limiting the above ground production

PowerAqua: fishing the semantic web

The Semantic Web (SW) offers an opportunity to develop novel, sophisticated forms of question answering (QA). Specifically, the availability of distributed semantic markup on a large scale opens the way to QA systems which can make use of such semantic information to provide precise, formally derived answers to questions. At the same time the distributed, heterogeneous, large-scale nature of the semantic information introduces significant challenges. In this paper we describe the design of a QA system, PowerAqua, designed to exploit semantic markup on the web to provide answers to questions posed in natural language. PowerAqua does not assume that the user has any prior information about the semantic resources. The system takes as input a natural language query, translates it into a set of logical queries, which are then answered by consulting and aggregating information derived from multiple heterogeneous semantic sources

Modelling the impact and cost-effectiveness of the HIV intervention programme amongst commercial sex workers in Ahmedabad, Gujarat, India.

BACKGROUND: Ahmedabad is an industrial city in Gujarat, India. In 2003, the HIV prevalence among commercial sex workers (CSWs) in Ahmedabad reached 13.0%. In response, the Jyoti Sangh HIV prevention programme for CSWs was initiated, which involves outreach, peer education, condom distribution, and free STD clinics. Two surveys were performed among CSWs in 1999 and 2003. This study estimates the cost-effectiveness of the Jyoti Sangh HIV prevention programme. METHODS: A dynamic mathematical model was used with survey and intervention-specific data from Ahmedabad to estimate the HIV impact of the Jyoti Sangh project for the 51 months between the two CSW surveys. Uncertainty analysis was used to obtain different model fits to the HIV/STI epidemiological data, producing a range for the HIV impact of the project. Financial and economic costs of the intervention were estimated from the providers perspective for the same time period. The cost per HIV-infection averted was estimated. RESULTS: Over 51 months, projections suggest that the intervention averted 624 and 5,131 HIV cases among the CSWs and their clients, respectively. This equates to a 54% and 51% decrease in the HIV infections that would have occurred among the CSWs and clients without the intervention. In the absence of intervention, the model predicts that the HIV prevalence amongst the CSWs in 2003 would have been 26%, almost twice that with the intervention. Cost per HIV infection averted, excluding and including peer educator economic costs, was USD 59 and USD 98 respectively. CONCLUSION: This study demonstrated that targeted CSW interventions in India can be cost-effective, and highlights the importance of replicating this effort in other similar settings.Published versio

Measurement and valuation of health providers' time for the management of childhood pneumonia in rural Malawi - An empirical study

Background: Human resources are a major cost driver in childhood pneumonia case management. Introduction of 13-valent pneumococcal conjugate vaccine (PCV-13) in Malawi can lead to savings on staff time and salaries due to reductions in pneumonia cases requiring admission. Reliable estimates of human resource costs are vital for use in economic evaluations of PCV-13 introduction. Methods: Twenty-eight severe and twenty-four very severe pneumonia inpatients under the age of five were tracked from admission to discharge by paediatric ward staff using self-administered timesheets at Mchinji District Hospital between June and August 2012. All activities performed and the time spent on each activity were recorded. A monetary value was assigned to the time by allocating a corresponding percentage of the health workers' salary. All costs are reported in 2012 US$. Results: A total of 1,017 entries, grouped according to 22 different activity labels, were recorded during the observation period. On average, 99 min (standard deviation, SD = 46) were spent on each admission: 93 (SD = 38) for severe and 106 (SD = 55) for very severe cases. Approximately 40$ 2 per bed-day and, on average, US$29.5 per severe pneumonia admission and US$ 37.7 per very severe admission. Conclusions: Self-reporting was successfully used in this context to generate reliable estimates of human resource time and costs of childhood pneumonia treatment. Assuming vaccine efficacy of 41 % and 90 % coverage, PCV-13 introduction in Malawi can save over US$ 2 million per year in staff costs alone

Performance studies of the CMS strip tracker before installation

Peer reviewe