UCL University College London Eprints
UCL Eprints collects the work of UCL researchers and makes it freely available over the web, helping the worldwide scholarly community to discover UCL research. Institutional repositories like UCL Eprints complement the traditional academic publishing and scholarly communications processes. They raise the visibility of research and help to maximise its impact. UCL researchers are encouraged to deposit a copy of each journal article, conference paper, working paper, and any other research output, in the UCL Eprints at the earliest opportunity, ensuring that their research reaches as wide an audience as possible.
The EChO payload instrument – an overview - Eccleston, P; Swinyard, B; Ferlet, M; Irshad, R; Lim, T; Middleton, K; Adriani, A; Reess, J-M; Ollivier, M; Ottensamer, R; Rataj, M; Zapata, GR; Schrader, J-R; Selig, A; Isaak, K; Linder, M; Puig, L; Tessenyi, M; Tinetti, G; Waldmann, I; Bradshaw, T; Crook, M; Hunt, T; Winter, B; Bryson, I; Bezawada, N; Taylor, W; Bowles, N; Pascale, E; Morgante, G; Pace, E
The Exoplanet Characterisation Observatory (EChO) mission was one of the proposed candidates for the European Space Agency’s third medium mission within the Cosmic Vision Framework. EChO was designed to observe the spectra from transiting exo-planets in the 0.55–11 micron band with a goal of covering from 0.4 to 16 micron. The mission and its associated scientific instrument has undergone a rigorous technical evaluation phase. This paper provides an overview of the payload instrument design for the mission, showing how the system acts together to fulfill the mission objectives. We report on the results of an extensive simulation of the instrument...
Transit spectroscopy of exoplanets from space: how to optimize the wavelength coverage and spectral resolving power - Encrenaz, T; Drossart, P; Coustenis, A; Tinetti, G; Tessenyi, M; Hartogh, P
The study of exoplanets is an exploding field in astronomy. Recent discoveries have made possible the development of a new research field, the spectroscopic characterization of the exoplanetary atmospheres, using both primary and eclipse transits. A dedicated space mission will make possible the characterization of many classes of exoplanets, from the hot Jupiters to the temperate super-Earths. In this paper, we discuss how the spectral range and the spectral resolving power can be optimized for identifying a maximum number of candidate atmospheric species. Spectral modeling shows that the simultaneous observation of the whole spectral range, from 0.55 to 16 μm...
The phase 0/A study of the ESA M3 mission candidate EChO - Puig, L; Isaak, K; Linder, M; Escudero, I; Crouzet, P-E; Ribas, I; Snellen, I; Swinyard, B; Tinetti, G; Eccleston, P; Walker, R; Ehle, M; Hübner, J; Timm, R; De Vogeleer, B; Drossart, P; Ollivier, M; Hartogh, P; Lovis, C; Micela, G
EChO, the Exoplanet Characterisation Observatory, has been one of the five M-class mission candidates competing for the M3 launch slot within the science programme Cosmic Vision 2015–2025 of the European Space Agency (ESA). As such, EChO has been the subject of a Phase 0/A study that involved European Industry, research institutes and universities from ESA member states and that concluded in September 2013. EChO is a concept for a dedicated mission to measure the chemical composition and structure of hundreds of exoplanet atmospheres using the technique of transit spectroscopy. With simultaneous and uninterrupted spectral coverage from the visible to infrared...
Aortic Valve Function Under Support of a Left Ventricular Assist Device: Continuous vs. Dynamic Speed Support. - Bozkurt, S; van de Vosse, FN; Rutten, MC
Continuous flow left ventricular devices (CF-LVADs) support the failing heart at a constant speed and alters the loads on the aortic valve. This may cause insufficiency in the aortic valve under long-term CF-LVAD support. The aim of this study is to assess the aortic valve function under varying speed CF-LVAD support. A Medtronic freestyle valve and a Micromed DeBakey CF-LVAD were tested in a mock circulatory system. First, the CF-LVAD was operated at constant speeds between 7500 and 11,500 rpm with 1000 rpm intervals. The mean pump outputs obtained from these tests were applied in varying speed CF-LVAD support mode using a...
Arterial pulsatility improvement in a feedback-controlled continuous flow left ventricular assist device: an ex-vivo experimental study. - Bozkurt, S; van Tuijl, S; Schampaert, S; van de Vosse, FN; Rutten, MC
Continuous flow left ventricular assist devices (CF-LVADs) reduce arterial pulsatility, which may cause long-term complications in the cardiovascular system. The aim of this study is to improve the pulsatility by driving a CF-LVAD at a varying speed, synchronous with the cardiac cycle in an ex-vivo experiment. A Micromed DeBakey pump was used as CF-LVAD. The heart was paced at 140 bpm to obtain a constant cardiac cycle for each heartbeat. First, the CF-LVAD was operated at a constant speed. At varying-speed CF-LVAD assistance, the pump was driven such that the same mean pump output was generated. For synchronization purposes, an...
Improving arterial pulsatility by feedback control of a continuous flow left ventricular assist device via in silico modeling. - Bozkurt, S; van de Vosse, FN; Rutten, MC
Continuous flow left ventricular assist devices (CF-LVADs) generally operate at a constant speed, which causes a decrease in pulse pressure and pulsatility in the arteries and allegedly may lead to late complications such as aortic insufficiency and gastrointestinal bleeding. The purpose of this study is to increase the arterial pulse pressure and pulsatility while obtaining more physiological hemodynamic signals, by controlling the CF-LVAD flow rate.
Evaluating the hemodynamical response of a cardiovascular system under support of a continuous flow left ventricular assist device via numerical modeling and simulations. - Bozkurt, S; Safak, KK
Dilated cardiomyopathy is the most common type of the heart failure which can be characterized by impaired ventricular contractility. Mechanical circulatory support devices were introduced into practice for the heart failure patients to bridge the time between the decision to transplant and the actual transplantation which is not sufficient due to the state of donor organ supply. In this study, the hemodynamic response of a cardiovascular system that includes a dilated cardiomyopathic heart under support of a newly developed continuous flow left ventricular assist device--Heart Turcica Axial--was evaluated employing computer simulations. For the evaluation, a numerical model which describes the...
Application of data mining techniques for detecting asymptomatic carotid artery stenosis - Bilge, U; Bozkurt, S; Durmaz, S
Asymptomatic carotid stenosis, one of the etiological factors for stroke, has several risk factors such as hypertension, cardiac morbidity, smoking, diabetes, and physical inactivity. Understanding and determining factors that predispose to asymptomatic carotid stenosis will help in the design of acute stroke trials and in prevention programs. The goal of this study is to explore rules and relationships that might be used to detect possible asymptomatic carotid stenosis by using data mining techniques. For this purpose, Genetic Algorithms (GAs), Logistic Regression (LR), and Chi-square tests have been applied to the patient dataset. Results of these tests have also been compared....
Sol karincik destek cihazlari i̇çin kontrol stratejileri - Bozkurt, S; Şafak, KK; Sorgüven, E; Çiblak, N; Okyar, AF; Akgün, MA; Ahn, H; Eǧrican, AN; Küçükaksu, S; Lazoǧlu, I
In this study numerical models for the cardiovascular system and an axial left ventricular assist device were developed and control studies have been done in the scope of a TUBITAK funded project entitled 'Design, analysis, and prototype production of a miniature implantable rotary blood pump.' Diseased cardiovascular system model was obtained by adjusting the parameters of the cardiovascular system model and the rotary blood pump model was integrated to this model. At first the effects of the rotation speed of the pump was considered and then control studies have been done for the pressure difference between outlet and inlet of...
An integrated approach to packaging and interconnection for neuroprostheses - Vanhoestenberghe, A; donaldson,
INTRODUCTION: Implantable electronic devices are now an integral part of modern medical practice, with products such as the pacemaker and cochlear implants changing thousands of lives every year. Yet this field could offer much more, as demonstrated by the early trials of retinal prosthesis and other neurostimulation devices. Unfortunately the impact of these promising developments is weakened by the absence of a suitable packaging technology, seriously delaying otherwise successful projects or pushing medical teams to “make do” with non optimal solutions because medical progress can not wait for engineering advances. METHODS: We are working on complete packaging and interconnection methods...
The Ideal Refugees - Fiddian-Qasmiyeh, E
Refugee camps are typically perceived as militarized and patriarchal spaces, and yet the Sahrawi refugee camps and their inhabitants have consistently been represented as ideal in nature: uniquely secular and democratic spaces, and characterized by gender equality. Drawing on extensive research with and about Sahrawi refugees in Algeria, Cuba, Spain, South Africa, and Syria, Fiddian-Qasmiyeh explores how, why, and to what effect such idealized depictions have been projected onto the international arena. In The Ideal Refugees, the author argues that secularism and the empowerment of Sahrawi refugee women have been strategically invoked to secure the humanitarian and political support of...