32 research outputs found
Assessing the performance of ground source heat pumps in neighboring medium-size households
No full textThe Master's programme Industrial Ecology is jointly organised by Leiden University and Delft University of Technology. This research project was done during an internship of 8 months completed with Royal Dutch Shell within the department of Future Energy Technologies of The Netherlands. It is focused on a case study of a medium size house (2202) situated in The Hague, NL and the neighboring households with the same characteristics along the same street. Homes in the Netherlands are likely to have their heat requirements fulfilled by conventional natural gas systems due to the relatively cheap cost compared to other systems (installation and investment wise) that could have a lower carbon footprint. However, innovative installations could make other more environmentally friendly systems as accessible as conventional systems. The Netherlands as one of the European member states have the goal of reducing CO2 emissions to accomplish their Kyoto targets; however, The Netherlands was not able to meet this target by 3.24% (target of 200.4 megaton CO2-eq). Besides, there is a general lack of financial incentives, making it in many cases an obvious decision to keep and use standard fossil fuel energy systems (both large- and small-scale) regardless of the environmental impact they may have. The building energy consumption sector provides a great opportunity and focus area for trying to reduce even more those emissions, and efforts have been made to introduce into the market more environmentally friendly systems. Until now, exploitation of geothermal shallow energy using a Ground Source Heat Pump (GSHP) has generally been limited to large commercial / industrial units. One reason for this is that the technology used for obtaining the geothermal energy and raising it to an appropriate temperature for the heat requirements of a typical house requires a big space for its installation which in turn proves to be a disruptive and complex process that requires the use of heavy and bulky machinery which immediately translates in a restriction for small homes. Innovations for installations of Ground Source heat pumps are starting to appear in the market, giving the possibility and the opportunity to install those systems in smaller areas, with less disruption and lower investment costs, although some concerns may arise when considering the thermal interference between the boreholes. This project examined the geological characteristics of the case study as determined by a Thermal Response Test (TRT) where parameters such as the thermal conductivity, the thermal resistance and the thermal diffusivity of the ground were obtained. Furthermore, the heat requirements of the test house were calculated with real data obtained during a year between 2012 and 2013 in order to determine the size of the system that would be required for each one of the houses assuming they all have the same demand throughout the year, having a peak demand for a winter day of 16 KW and an average demand of 10 KW in the winter months. Calculations of the length required of every Borehole Heat Exchanger (BHE) and the distance between them were made for the area of each house assuming no thermal interference. The first set of results indicated that a BHE length of 268 m would be needed, and with borehole thermal interference introducing a temperature penalty calculated with an analytical model, the length required increased to 332 m, 68 m more. After this a proposed design of borehole arrangement is suggested for the test house considering the space constraints. Calculations on the Economic and Environmental advantage from Ground Source Heat Pump (GSHP) compared to a Gas Boiler is done, taking into consideration two scenarios for the GSHP, 1) with a Seasonal Performance Factor (SPF) of 3.5 and 2) with a SPF of 3.0. Domestic gas and electricity price fluctuations over the past years were included, extrapolating this behavior for the years 2015 and 2020. Gas prices are considered to have changed 9% per year given the data from 1996 – 2013. Having extrapolated the prices, calculations are done on running costs and investment cost, to give the payback times when considering current power and gas prices for 2015 and 2020. The current situation (2013) seems the more expensive moment for having the system with a payback time of 24 years however a GSHP system in 2020 with electricity and gas prices following a 9% increase for gas prices would take just 8 years to have the investment back. For the environmental performance the Dutch footprint of power generation is calculated for the average predicted trends of different scenarios in the future for European power generation where GSHP with a SPF of 3.5 in 2020 seems to have the best Carbon Footprint advantage of all with 59% advantage of the compared systems. Recommendations are made in order to come up with connected scenarios of Dutch power and natural gas to have a coherent and timely understanding of GSHP and other renewable systems in the Dutch heating market for the coming years. Further recommendations are made in order to have a clear understanding on all the interrelated factors that have an impact on the efficiency, feasibility and performance of GSHP systems and how this research project could be broadened.Industrial EcologyChemical EngineeringTechnical University of Technolog
Towards numerical modelling of cooling water discharges and related phenomena
No full textThis thesis describes the numerical modelling of discharges where density differences play an important role, in particular positive buoyant cooling water discharges. Two regions, in which the hydrodynamics are influenced by the discharge, can be distinguished; the near-field and the far-field. In the former region the initial jet characteristics of momentum flux, buoyancy flux and outfall geometry influence the jet trajectory and mixing. In the far-field the discharge characteristics become less important and ambient conditions will control trajectory and dilution through buoyant spreading and diffusion due to ambient turbulence. Density differences between the discharged and the ambient water are even smaller than in case of salt and fresh-water problems when cooling water problems are considered. Gravitational forces are therefore less dominant and turbulence plays an important role in heat transport. Laboratory experiments are used to verify the results from the 3-D shallow water model TRISULA, which computes the far-field hydrodynamics and mass transport. The turbulence model used, a common isotropic k-e model which takes stratification into account, seems not appropriate to simulate the (low Reynolds number) laboratory experiments. Vertical mixing is overestimated and the front lags behind and is very steep. The consequences of assuming hydrostatic pressure for the front shape are investigated, by developing a 2-DV model in which a non-hydrostatic pressure correction term, is incorporated. A significant improvement is gained as far as the shape of the front and the flow pattern is concerned. This is especially true for thermals. The celerity of the (horizontal travelling) fronts, however, remains the same.Hydraulic EngineeringCivil Engineering and Geoscience
Prevalence of Systemic Hypertension and Control of Systolic Blood Pressure in a Cohort of 14 Dogs with Adrenal-Dependent Hypercortisolism during the First Year of Trilostane Treatment or after Adrenalectomy
No full textAuthor Contributions: Conceptualization, P.G.S.J., M.D.P.-A. and C.A.B.; data curation, P.G.S.J.; formal analysis, P.G.S.J.; investigation, P.G.S.J., M.D.P.-A., D.A.-M., S.G.S. and C.A.B.; methodology, P.G.S.J., M.D.P.-A. and C.A.B.; resources, P.G.S.J., M.D.P.-A., D.A.-M., S.G.S. and C.A.B.; supervision, M.D.P.-A. and C.A.B.; visualization, P.G.S.J., M.D.P.-A., D.A.-M. and C.A.B.; writing—original draft, P.G.S.J.; writing—review and editing, P.G.S.J., M.D.P.-A., D.A.-M. and C.A.B. All authors have read and agreed to the published version of the manuscript.Hypercortisolism in dogs is frequently associated with systemic hypertension (SH). However, there are no studies evaluating the changes in systolic blood pressure (SBP) in dogs with adrenal-dependent hypercortisolism (ADH) during trilostane treatment or after adrenalectomy and their response to antihypertensive treatments. For this reason, the objectives of this study were to evaluate the changes in SBP in dogs with ADH during the first year of trilostane treatment or after adrenalectomy, the relation with clinical control of hypercortisolism and certain laboratory parameters, and the response to antihypertensive drugs. Fourteen dogs newly diagnosed with ADH were prospectively included and evaluated at diagnosis (T0) and 1, 3, 6, and 12 months after (T1, T3, T6, and T12, respectively). Dogs were classified as hypertensive (HT; SBP ≥ 160 mmHg) and non-hypertensive. In HT dogs, benazepril was considered as the first-line drug, and, if necessary, amlodipine was prescribed. The prevalence of SH at T0 was 79%, and it was reduced to 25% at T12. Blood pressure (BP) was not associated with disease control or selected laboratory parameters at any endpoint. Only 22% of dogs with SH needed more than one drug to normalize their SBP. In all dogs surgically treated that were HT at T0, BP normalized at T3.Simple Summary: Cushing’s syndrome is a common disease in middle-aged and old dogs, characterized by steroid overproduction by the adrenal glands. This steroid excess can be caused by an adrenal tumor (adrenal dependent hypercortisolism) and is associated with systemic hypertension. In people with this disease, it is known that hypertension can be difficult to manage and, sometimes, several drugs are necessary to treat it. However, there are no studies focused on the changes in the blood pressure during treatment in dogs with adrenal-dependent hypercortisolism. In this study, 14 dogs with this disease were followed during the first year of medical treatment or during 1 year after surgery to remove the adrenal tumor (adrenalectomy), and the changes in their blood pressure were evaluated. We observed that blood pressure in medically treated dogs decreased during the study period using, in most cases, a single antihypertensive drug. Also, in those dogs surgically treated, blood pressure normalized three months after surgery, and in one case, antihypertensive medications could be reduced. Thus, when adrenalectomy is performed, it is important to carefully address blood pressure after the procedure as these dogs might require reductions in their antihypertensive treatment.Depto. de Medicina y Cirugía AnimalFac. de VeterinariaTRUEpu
Effects of habitat fragmentation on the abortion and predation of seeds in Chaco Serrano = Efectos de la fragmentación sobre la aborción y depredación de semillas en el Chaco Serrano
No full textHabitat fragmentation can have consequences on plant reproduction through several interactions with insects. We studied the effects of habitat fragmentation in die proportion of aborted, predated and undamaged seeds of Acacia aroma and Cercidium praecox. We performed this study in the Chaco Serrano of Argentina. We found that fragmentation effects differed between species. In small patches, the number of aborted seeds of A. aroma increased and the number of pre–dispersal predated seeds and undamaged seeds of C. praecox decreased and increased, respectively. However, higher numbers of aborted seeds in small patches did not lead to fewer available seeds for dispersion. For these species, seed predation by bruchids was about 35 percent and aborted seeds were around 7 percent. Because of the elevated levels of damage and the high specificity of bruchids, the changes caused by habitat fragmentation may be very important for the populations of these two species. Habitat fragmentation effects on pollination and pre–dispersal seed predation of these legumes may determine higher availability of seeds for dispersion in fragmented habitats
Design strategies for shape-controlled magnetic iron oxide nanoparticles
No full textFerrimagnetic iron oxide nanoparticles (magnetite or maghemite) have been the subject of an intense research, not only for fundamental research but also for their potentiality in a widespread number of practical applications. Most of these studies were focused on nanoparticles with spherical morphology but recently there is an emerging interest on anisometric nanoparticles. This review is focused on the synthesis routes for the production of uniform anisometric magnetite/maghemite nanoparticles with different morphologies like cubes, rods, disks, flowers and many others, such as hollow spheres, worms, stars or tetrapods. We critically analyzed those procedures, detected the key parameters governing the production of these nanoparticles with particular emphasis in the role of the ligands in the final nanoparticle morphology. The main structural and magnetic features as well as the nanotoxicity as a function of the nanoparticle morphology are also described. Finally, the impact of each morphology on the different biomedical applications (hyperthermia, magnetic resonance imaging and drug delivery) are analysed in detail. We would like to dedicate this work to Professor Carlos J. Serna, Instituto de Ciencia de Materiales de Madrid, ICMM/CSIC, for his outstanding contribution in the field of monodispersed colloids and iron oxide nanoparticles. We would like to express our gratitude for all these years of support and inspiration on the occasion of his retirement
Relationship between physico-chemical properties of magnetic fluids and their heating capacity
No full textThe final goal in magnetic hyperthermia research is to use nanoparticles in the form of a colloidal suspension injected into human beings for a therapeutic application. Therefore the challenge is not only to develop magnetic nanoparticles with good heating capacities, but also with good colloidal properties, long blood circulation time and with grafted ligands able to facilitate their specific internalisation in tumour cells. Significant advances have been achieved optimising the properties of the magnetic nanoparticles, showing extremely large specific absorption rate values that will contribute to a reduction in the concentration of the magnetic fluid that needs to be administered. In this review we show the effect of different characteristics of the magnetic particles, such as size, size distribution and shape, and the colloidal properties of their aqueous suspensions, such as hydrodynamic size and surface modification, on the heating capacity of the magnetic colloids. © 2013 Informa UK Ltd.Peer Reviewe
Dopamine release modifies intracellular calcium levels in tyrosine hydroxylase-transfected C6 cells
No full textGlioma cell line C6, transfected with tyrosine hydroxylase (TH) cDNA under the control of the glial fibrillary acid protein promoter (C6-THA cells), elicited a reduction in the apomorphine-induced turning behavior when they are implanted in Parkinson's disease models. Nevertheless, dopamine (Da) release has not been explicitly demonstrated nor has a possible mechanism of release been implicated. In this study, the in vitro Da release by C6 and C6-THA cells after chemical stimulation with KCl or glutamate was quantified using HPLC. Modifications in intracellular calcium levels in response to KCl stimulation and participation of Da receptor-mediated feedback in calcium regulation were also studied using FLUO 3 as a calcium concentration indicator. C6-THA cells release dopamine in basal conditions, and increase its release after KCl or glutamic acid stimulation. In a fraction of C6 and C6-THA cells, a transient intracellular calcium increase was observed after KCl stimulation, but C6-THA cells demonstrated a faster rate of calcium removal. C6 cells express mRNA from all five subtypes of Da receptors as demonstrated by real time PCR. D1 receptors were most abundant in C6 cells and its expression was further increased in C6-THA cells. Blocking D1-like receptors in C6-THA cells with the specific antagonist drug SCH-23390 induced a decrease in intracellular calcium removal rate, resembling non-manipulated C6 cells' calcium clearance. Da release by C6-THA cells could be related to calcium dependent mechanisms. Furthermore, production of Da by C6-THA cells seems to upregulate the expression of D1 receptors' mRNA. Zapotitlán 2007 Elsevier Inc. All rights reserved
Cytochrome c Reduction by H2S Potentiates Sulfide Signaling.
No full textThis is the author accepted manuscript. The final version is available from American Chemical Society via the DOI in this record.Hydrogen sulfide (H2S) is an endogenously produced gas that is toxic at high concentrations. It is eliminated by a dedicated mitochondrial sulfide oxidation pathway, which connects to the electron transfer chain at the level of complex III. Direct reduction of cytochrome c (Cyt C) by H2S has been reported previously but not characterized. In this study, we demonstrate that reduction of ferric Cyt C by H2S exhibits hysteretic behavior, which suggests the involvement of reactive sulfur species in the reduction process and is consistent with a reaction stoichiometry of 1.5 mol of Cyt C reduced/mol of H2S oxidized. H2S increases O2 consumption by human cells (HT29 and HepG2) treated with the complex III inhibitor antimycin A, which is consistent with the entry of sulfide-derived electrons at the level of complex IV. Cyt C-dependent H2S oxidation stimulated protein persulfidation in vitro, while silencing of Cyt C expression decreased mitochondrial protein persulfidation in a cell culture. Cyt C released during apoptosis was correlated with persulfidation of procaspase 9 and with loss of its activity. These results reveal a potential role for the electron transfer chain in general, and Cyt C in particular, for potentiating sulfide-based signaling.This work was supported by the French State in the frame of the “Investments for the future” Programme IdEx Bordeaux, reference ANR-10-IDEX-03-02, and by an ATIP-AVENIR grant (to M.R.F.), the National Institutes of Health (GM112455 to R.B. and R01GM113030 to M.D.P.), the Medical Research Council, UK (MR/M022706/1 to M.W.), the National Science Foundation (DGE-1309047 to A.K.S.), and the Brian Ridge Scholarship (R.T.). The authors are grateful to M.-F. Giraud for the help with purification of mitochondria
