961 resultados para Radiometric correction
Resumo:
This work explores a concept for motion detection in brain MR examinations using high channel-count RF coil arrays. It applies ultrashort (<100 μsec) free induction decay signals, making use of the knowledge that motion induces variations in these signals when compared to a reference free induction decay signal. As a proof-of-concept, the method was implemented in a standard structural MRI sequence. The stability of the free induction decay-signal was verified in phantom experiments. Human experiments demonstrated that the observed variations in the navigator data provide a sensitive measure for detection of relevant and common subject motion patterns. The proposed methodology provides a means to monitor subject motion throughout a MRI scan while causing little or no impact on the sequence timing and image contrast. It could hence complement available motion detection and correction methods, thus further reducing motion sensitivity in MR applications.
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Human perception of bitterness displays pronounced interindividual variation. This phenotypic variation is mirrored by equally pronounced genetic variation in the family of bitter taste receptor genes. To better understand the effects of common genetic variations on human bitter taste perception, we conducted a genome-wide association study on a discovery panel of 504 subjects and a validation panel of 104 subjects from the general population of São Paulo in Brazil. Correction for general taste-sensitivity allowed us to identify a SNP in the cluster of bitter taste receptors on chr12 (10.88- 11.24 Mb, build 36.1) significantly associated (best SNP: rs2708377, P = 5.31 × 10(-13), r(2) = 8.9%, β = -0.12, s.e. = 0.016) with the perceived bitterness of caffeine. This association overlaps with-but is statistically distinct from-the previously identified SNP rs10772420 influencing the perception of quinine bitterness that falls in the same bitter taste cluster. We replicated this association to quinine perception (P = 4.97 × 10(-37), r(2) = 23.2%, β = 0.25, s.e. = 0.020) and additionally found the effect of this genetic locus to be concentration specific with a strong impact on the perception of low, but no impact on the perception of high concentrations of quinine. Our study, thus, furthers our understanding of the complex genetic architecture of bitter taste perception.
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Amb aquest projecte s'ha treballat en la direcció de: 1) Implementar un nou recurs en un projecte global de millora de la qualitat docent i d’aplicació de les TIC a l’ensenyament de les diferents assignatures de la matèria d’Història de la Música a la UdL en curs des de fa alguns anys. Concretament, diverses eines per a l’autoavaluació de l’alumnat a través d’un banc de preguntes segons el format de les proves psicomètriques (proves objectives en l’avaluació del rendiment acadèmic dels estudiants o d’elecció múltiple). 2) Arribar a disposar d’un extens banc de preguntes d’elecció múltiple i correcció objectiva en diferents formats, ordenades per blocs, temes, nivells de dificultat, etc., que reuneixin els criteris mínims de fiabilitat, objectivitat i validesa necessaris per a una correcta avaluació del rendiment acadèmic. Entenem que l’avaluació ha de tenir utilitats diferents que van més enllà de la simple puntuació de l’alumnat. Ha de servir també per millorar la docència, per facilitar l’aprenentatge de l’alumne, per assegurar un nivell de competència mínim, per discriminar entre estudiants o per informar la pròpia institució. 3) Aconseguir que l’alumne, a través de l’autoavaluació, entengui que aquest tipus de proves són instruments per continuar aprenent. En aquest sentit les proves d’elecció múltiple permeten tot un seguit d’opcions que ho afavoreixen. 4) Elaborar una eina amb capacitat de generar estadístiques, índex de discriminació i de fer l’anàlisi d’items, tot permetent anar redefinint i millorant els ítems.
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GREC CLÀSSIC. Curs d’autoaprenentatge introductori. Dos anys. El curs consta de tretze lliçons i d’una gramàtica estructurada en quatre blocs: 1. Alfabet i diacrítics, fenòmens fonètics. 2. Morfologia nominal. 3. Morfologia verbal. 4. Infinitius i participis. Sintaxi de les oracions. L’estructura de les lliçons, excepte la primera que inclou l’alfabet, combina qüestions de morfologia nominal i verbal o de morfologia i sintaxi, tal com acostumen a fer els mètodes d’aprenentatge de les llengües modernes. Cada lliçó formula els seus objectius específics, desenvolupa la seva part de continguts i conclou amb uns exercicis pràctics d’autocorrecció. La Gramàtica, per la seva banda, està organitzada com un manual elemental de llengua grega on la persona que segueixi el curs pot ampliar la seva formació i consultar els dubtes. Parts complementàries: presentació on es formulen els objectius, la metodologia i les instruccions concretes per a seguir el curs; terminologia on s’ordenen alfabèticament els conceptes gramaticals emprats en el curs; avaluació final per tal que, més enllà dels exercicis de cada lliçó, hom pugui comprovar si ha assolit els coneixements previstos o si, en cas de no arribar-hi, ha de reforçar algunes lliçons o parts de les mateixes abans de tornar a fer l’avaluació; lèxic, ordenat alfabèticament per tal que hom pugui conèixer el significat dels mots emprats en el curs sense necessitat de consultar un diccionari. A la part d’avaluació hi ha també una enquesta per tal que les persones que segueixin el curs en facin una valoració i ens permetin corregir els seus dèficits o mancances. El projecte 2007MQD00178 ha continuat ampliant els dossiers electrònics, els exercicis autoavaluatius del seu web www.ub.edu/filologiagrega/electra i ha dedicat una part important de la seva tasca a elaborar els continguts i els programes de les assignatures dels dos primers cursos del nou grau de Filologia Clàssica.
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En aquest projecte s’ha analitzat i optimitzat l’enllaç satèl·lit amb avió per a un sistema aeronàutic global. Aquest nou sistema anomenat ANTARES està dissenyat per a comunicar avions amb estacions base mitjançant un satèl·lit. Aquesta és una iniciativa on hi participen institucions oficials en l’aviació com ara l’ECAC i que és desenvolupat en una col·laboració europea d’universitats i empreses. El treball dut a terme en el projecte compren bàsicament tres aspectes. El disseny i anàlisi de la gestió de recursos. La idoneïtat d’utilitzar correcció d’errors en la capa d’enllaç i en cas que sigui necessària dissenyar una opció de codificació preliminar. Finalment, estudiar i analitzar l’efecte de la interferència co-canal en sistemes multifeix. Tots aquests temes són considerats només per al “forward link”. L’estructura que segueix el projecte és primer presentar les característiques globals del sistema, després centrar-se i analitzar els temes mencionats per a poder donar resultats i extreure conclusions.
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Els sistemes automatitzats que requereixen d’un control d’estabilitat o moviment es poden trobar cada cop en més àmbits. Aplicacions UAV o de posicionament global són les més comunes per aquest tipus de sistemes, degut a que necessiten d’un control de moviment molt precís. Per a dur a terme aquest procés s’utilitzen unitats de mesura inercial, que mitjançant acceleròmetres i giroscopis degudament posicionats, a més a més d’una correcció del possible error que puguin introduir aquests últims, proporcionen una acceleració i una velocitat angular de les quals es pot extreure el camí efectuat per aquestes unitats. La IMU, combinada amb un GPS i mitjançant un filtre de Kalman, proporcionen una major exactitud , a més d’un punt de partida (proporcionat per el GPS), un recorregut representable en un mapa y, en el cas de perdre la senyal GPS, poder seguir adquirint dades de la IMU. Aquestes dades poden ser recollides i processades per una FPGA, que a la vegada podem sincronitzar amb una PDA per a que l’usuari pugui veure representat el moviment del sistema. Aquest treball es centra en el funcionament de la IMU i l’adquisició de dades amb la FPGA. També introdueix el filtre de Kalman per a la correcció de l’error dels sensors.
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The aim of this project is to evaluate the importance of submarine groundwater discharge sector in order to improve the water balance in Málaga-Granada region. The approach of this study arose from the the geology and the aquifers that indicate that there could be some discharge to the sea between Maro (Málaga) and Almuñécar (Granada) and the Andalusian’s Government and its Water Agence were really interested in evaluating it because there is a lot of population and few water available and the magnitude of groundwater discharge has generated controversy. Is well known that water is a scarce resource in this area and it’s very important for the society and for the environment. The legislation, the water policies, the knowledge of the aquifer and the geology, the water dynamics, the land use and the water perception in the society might help the management of this resource not just in Andalusia but in all the Mediterranean basin. The main objective is to evaluate the submarine groundwater discharge from the Alberquillas Aqufier to the sea by measuring 222Rn and Ra isotopes. Specific objectives have been established to achieve the main objective: A) Reveal the importance of water resources in the Mediterranean basin; B) Learn radiometric techniques for the study of groundwater discharge to the sea; C) Learn of sampling techniques of water samples for the measurement of Ra and Rn; D) Learn the techniques for measuring Ra (RaDeCC) and Rn (RAD7); E) Interpretation and discussion of results. During this semester, and in addition of the present study in Málaga- Granada region, the author has participated in the initial phase (sampling, analysis and interpretation of preliminary results) of other research projects focused on the study of submarine groundwater discharges through the use of Ra isotopes and 222Rn. These studies have been developed in different areas, including Alt Empordà (Roses and Sant Pere Pescador), Maresme with CMIMA’s group (Mediterranean Center for Marine and Environmental Research), Delta de l’Ebre, Peñíscola and Mallorca with the IMEDEA’s group (Mediterranean Institute for Advanced Studies).
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Motivation. The study of human brain development in itsearly stage is today possible thanks to in vivo fetalmagnetic resonance imaging (MRI) techniques. Aquantitative analysis of fetal cortical surfacerepresents a new approach which can be used as a markerof the cerebral maturation (as gyration) and also forstudying central nervous system pathologies [1]. However,this quantitative approach is a major challenge forseveral reasons. First, movement of the fetus inside theamniotic cavity requires very fast MRI sequences tominimize motion artifacts, resulting in a poor spatialresolution and/or lower SNR. Second, due to the ongoingmyelination and cortical maturation, the appearance ofthe developing brain differs very much from thehomogenous tissue types found in adults. Third, due tolow resolution, fetal MR images considerably suffer ofpartial volume (PV) effect, sometimes in large areas.Today extensive efforts are made to deal with thereconstruction of high resolution 3D fetal volumes[2,3,4] to cope with intra-volume motion and low SNR.However, few studies exist related to the automatedsegmentation of MR fetal imaging. [5] and [6] work on thesegmentation of specific areas of the fetal brain such asposterior fossa, brainstem or germinal matrix. Firstattempt for automated brain tissue segmentation has beenpresented in [7] and in our previous work [8]. Bothmethods apply the Expectation-Maximization Markov RandomField (EM-MRF) framework but contrary to [7] we do notneed from any anatomical atlas prior. Data set &Methods. Prenatal MR imaging was performed with a 1-Tsystem (GE Medical Systems, Milwaukee) using single shotfast spin echo (ssFSE) sequences (TR 7000 ms, TE 180 ms,FOV 40 x 40 cm, slice thickness 5.4mm, in plane spatialresolution 1.09mm). Each fetus has 6 axial volumes(around 15 slices per volume), each of them acquired inabout 1 min. Each volume is shifted by 1 mm with respectto the previous one. Gestational age (GA) ranges from 29to 32 weeks. Mother is under sedation. Each volume ismanually segmented to extract fetal brain fromsurrounding maternal tissues. Then, in-homogeneityintensity correction is performed using [9] and linearintensity normalization is performed to have intensityvalues that range from 0 to 255. Note that due tointra-tissue variability of developing brain someintensity variability still remains. For each fetus, ahigh spatial resolution image of isotropic voxel size of1.09 mm is created applying [2] and using B-splines forthe scattered data interpolation [10] (see Fig. 1). Then,basal ganglia (BS) segmentation is performed on thissuper reconstructed volume. Active contour framework witha Level Set (LS) implementation is used. Our LS follows aslightly different formulation from well-known Chan-Vese[11] formulation. In our case, the LS evolves forcing themean of the inside of the curve to be the mean intensityof basal ganglia. Moreover, we add local spatial priorthrough a probabilistic map created by fitting anellipsoid onto the basal ganglia region. Some userinteraction is needed to set the mean intensity of BG(green dots in Fig. 2) and the initial fitting points forthe probabilistic prior map (blue points in Fig. 2). Oncebasal ganglia are removed from the image, brain tissuesegmentation is performed as described in [8]. Results.The case study presented here has 29 weeks of GA. Thehigh resolution reconstructed volume is presented in Fig.1. The steps of BG segmentation are shown in Fig. 2.Overlap in comparison with manual segmentation isquantified by the Dice similarity index (DSI) equal to0.829 (values above 0.7 are considered a very goodagreement). Such BG segmentation has been applied on 3other subjects ranging for 29 to 32 GA and the DSI hasbeen of 0.856, 0.794 and 0.785. Our segmentation of theinner (red and blue contours) and outer cortical surface(green contour) is presented in Fig. 3. Finally, torefine the results we include our WM segmentation in theFreesurfer software [12] and some manual corrections toobtain Fig.4. Discussion. Precise cortical surfaceextraction of fetal brain is needed for quantitativestudies of early human brain development. Our workcombines the well known statistical classificationframework with the active contour segmentation forcentral gray mater extraction. A main advantage of thepresented procedure for fetal brain surface extraction isthat we do not include any spatial prior coming fromanatomical atlases. The results presented here arepreliminary but promising. Our efforts are now in testingsuch approach on a wider range of gestational ages thatwe will include in the final version of this work andstudying as well its generalization to different scannersand different type of MRI sequences. References. [1]Guibaud, Prenatal Diagnosis 29(4) (2009). [2] Rousseau,Acad. Rad. 13(9), 2006, [3] Jiang, IEEE TMI 2007. [4]Warfield IADB, MICCAI 2009. [5] Claude, IEEE Trans. Bio.Eng. 51(4) (2004). [6] Habas, MICCAI (Pt. 1) 2008. [7]Bertelsen, ISMRM 2009 [8] Bach Cuadra, IADB, MICCAI 2009.[9] Styner, IEEE TMI 19(39 (2000). [10] Lee, IEEE Trans.Visual. And Comp. Graph. 3(3), 1997, [11] Chan, IEEETrans. Img. Proc, 10(2), 2001 [12] Freesurfer,http://surfer.nmr.mgh.harvard.edu.
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The increase of the body's capacity to transport oxygen is a prime target for doping athletes in all endurance sports. For this pupose, blood transfusions or erythropoiesis stimulating agents (ESA), such as erythropoietin, NESP, and CERA are used. As direct detection of such manipulations is difficult, biomarkers that are connected to the haematopoietic system (haemoglobin concentration, reticulocytes) are monitored over time (Athlete Biological Passport (ABP)) and analyzed using mathematical models to identify patterns suspicious of doping. With this information, athletes can either be sanctioned directly based on their profile or targeted with conventional doping tests. Key issues for the appropriate use of the ABP are correct targeting and use of all available information (e.g. whereabouts, cross sectional population data) in a forensic manner. Future developments of the passport include the correction of all concentration-based variables for shifts in plasma volume, which might considerably increase sensitivity. New passport markers from the genomic, proteomic, and metabolomic level might add further information, but need to be validated before integration into the passport procedure. A first assessment of blood data of federations that have implemented the passport show encouraging signs of a decreased blood-doping prevalence in their athletes, which adds scientific credibility to this innovative concept in the fight against ESA- and blood doping. Copyright © 2012 John Wiley & Sons, Ltd.
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We evaluate the performance of different optimization techniques developed in the context of optical flowcomputation with different variational models. In particular, based on truncated Newton methods (TN) that have been an effective approach for large-scale unconstrained optimization, we develop the use of efficient multilevel schemes for computing the optical flow. More precisely, we evaluate the performance of a standard unidirectional multilevel algorithm - called multiresolution optimization (MR/OPT), to a bidrectional multilevel algorithm - called full multigrid optimization (FMG/OPT). The FMG/OPT algorithm treats the coarse grid correction as an optimization search direction and eventually scales it using a line search. Experimental results on different image sequences using four models of optical flow computation show that the FMG/OPT algorithm outperforms both the TN and MR/OPT algorithms in terms of the computational work and the quality of the optical flow estimation.
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Fluid that fills boreholes in crosswell electrical resistivity investigations provides the necessary electrical contact between the electrodes and the rock formation but it is also the source of image artifacts in standard inversions that do not account for the effects of the boreholes. The image distortions can be severe for large resistivity contrasts between the rock formation and borehole fluid and for large borehole diameters. We have carried out 3D finite-element modeling using an unstructured-grid approach to quantify the magnitude of borehole effects for different resistivity contrasts, borehole diameters, and electrode configurations. Relatively common resistivity contrasts of 100:1 and borehole diameters of 10 and 20 cm yielded, for a bipole length of 5 m, apparent resistivity underestimates of approximately 12% and 32% when using AB-MN configurations and apparent resistivity overestimates of approximately 24% and 95% when using AM-BN configurations. Effects are generally more severe at shorter bipole spacings. We report the results obtained by either including or ignoring the boreholes in inversions of 3D field data from a test site in Switzerland, where approximately 10,000 crosswell resistivity-tomography measurements were made across six acquisition planes among four boreholes. Inversions of raw data that ignored the boreholes filled with low-resistivity fluid paradoxically produced high-resistivity artifacts around the boreholes. Including correction factors based on the modeling results fora ID model with and without the boreholes did not markedly improve the images. The only satisfactory approach was to use a 3D inversion code that explicitly incorporated the boreholes in the actual inversion. This new approach yielded an electrical resistivity image that was devoid of artifacts around the boreholes and that correlated well with coincident crosswell radar images.
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In legal medicine, the post mortem interval (PMI) of interest covers the last 50 years. When only human skeletal remains are found, determining the PMI currently relies mostly on the experience of the forensic anthropologist, with few techniques available to help. Recently, several radiometric methods have been proposed to reveal PMI. For instance, (14)C and (90)Sr bomb pulse dating covers the last 60 years and give reliable PMI when teeth or bones are available. (232)Th series dating has also been proposed but requires a large amount of bones. In addition, (210)Pb dating is promising but is submitted to diagenesis and individual habits like smoking that must be handled carefully. Here we determine PMI on 29 cases of forensic interest using (90)Sr bomb pulse. In 12 cases, (210)Pb dating was added to narrow the PMI interval. In addition, anthropological investigations were carried out on 15 cases to confront anthropological expertise to the radiometric method. Results show that 10 of the 29 cases can be discarded as having no forensic interest (PMI>50 years) based only on the (90)Sr bomb pulse dating. For 10 other cases, the additional (210)Pb dating restricts the PMI uncertainty to a few years. In 15 cases, anthropological investigations corroborate the radiometric PMI. This study also shows that diagenesis and inter-individual difference in radionuclide uptake represent the main sources of uncertainty in the PMI determination using radiometric methods.
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Access audio, video and slides from the launch of the report The Institute of Public health in Ireland (IPH) produces population prevalence estimates and forecasts for a number of chronic conditions among adults. IPH has now applied the methodology to longstanding health conditions among young children across the island of Ireland. This report, based on a systematic analysis of data from the Growing Up in Ireland National Longitudinal Study of Children in the Republic of Ireland, is the first comprehensive look at longstanding health conditions among young children in Ireland. Estimated prevalence (per cent and number of cases) of longstanding health conditions among three-year-olds in the Republic of Ireland in 2011 by administrative counties/cities. The conditions are carer-reported: - "Longstanding illness, condition or disability” (where longstanding was defined as “anything that has troubled him/her over a period of time or that is likely to affect him/her over a period of time”) - Diagnosed asthma or asthma symptoms - Diagnosed eczema/any kind of skin allergy - Sight problem that required correction - Hearing problem that required correction - The estimates are based on data from the Growing Up in Ireland National Longitudinal Study of Children (www.growingup.ie) and population data. See the Chronic Conditions Hub for more details.
Resumo:
Access audio, video and slides from the launch of the report The Institute of Public health in Ireland (IPH) produces population prevalence estimates and forecasts for a number of chronic conditions among adults. IPH has now applied the methodology to longstanding health conditions among young children across the island of Ireland. This report, based on a systematic analysis of data from the Growing Up in Ireland National Longitudinal Study of Children in the Republic of Ireland, is the first comprehensive look at longstanding health conditions among young children in Ireland. Estimated prevalence (per cent and number of cases) of longstanding health conditions among three-year-olds in the Republic of Ireland in 2011 by administrative counties/cities. The conditions are carer-reported: - "Longstanding illness, condition or disability” (where longstanding was defined as “anything that has troubled him/her over a period of time or that is likely to affect him/her over a period of time”) - Diagnosed asthma or asthma symptoms - Diagnosed eczema/any kind of skin allergy - Sight problem that required correction - Hearing problem that required correction - The estimates are based on data from the Growing Up in Ireland National Longitudinal Study of Children (www.growingup.ie) and population data. See the Chronic Conditions Hub for more details.
Resumo:
Access audio, video and slides from the launch of the report The Institute of Public health in Ireland (IPH) produces population prevalence estimates and forecasts for a number of chronic conditions among adults. IPH has now applied the methodology to longstanding health conditions among young children across the island of Ireland. This report, based on a systematic analysis of data from the Growing Up in Ireland National Longitudinal Study of Children in the Republic of Ireland, is the first comprehensive look at longstanding health conditions among young children in Ireland. Estimated prevalence (per cent and number of cases) of longstanding health conditions among three-year-olds in the Republic of Ireland in 2011 by administrative counties/cities. The conditions are carer-reported: - "Longstanding illness, condition or disability” (where longstanding was defined as “anything that has troubled him/her over a period of time or that is likely to affect him/her over a period of time”) - Diagnosed asthma or asthma symptoms - Diagnosed eczema/any kind of skin allergy - Sight problem that required correction - Hearing problem that required correction - The estimates are based on data from the Growing Up in Ireland National Longitudinal Study of Children (www.growingup.ie) and population data. See the Chronic Conditions Hub for more details.