920 resultados para multiple change-points
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In this work, we demonstrate how it is possible to sharply image multiple object points. The Simultaneous Multiple Surface (SMS) design method has usually been presented as a method to couple N wave-front pairs with N surfaces, but recent findings show that when using N surfaces, we can obtain M image points when N
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The current study examined whether variables that have been found to influence treatment outcome serve as mediators of a child and adolescent cognitive behavioral treatment (CBT) anxiety program at multiple time points throughout the intervention. The study also examined mediating variables measured at multiple time points during treatment to determine the time lags necessary for changes in the mediator variable to translate into changes on treatment gains. Participants were 168 youth (ages 6 to 16 years; 54% males) and their mothers who presented to the Child Anxiety and Phobia Program (CAPP) at Florida International University (FIU). Overall, results indicate that the mediators at multiple time points influenced youth anxiety in a fluctuating manner, such that a decrease in skills at one given session caused changes in youth anxiety at a later session. This dynamic between the mediator and outcome may be reflective of the process of therapeutic change and suggests that skills gained from session to session took time to exert their effect on youth anxiety. The methodology employed helps to elucidate how variables mediate treatment outcome in youth anxiety disorders.
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In recent papers, Wied and his coauthors have introduced change-point procedures to detect and estimate structural breaks in the correlation between time series. To prove the asymptotic distribution of the test statistic and stopping time as well as the change-point estimation rate, they use an extended functional Delta method and assume nearly constant expectations and variances of the time series. In this thesis, we allow asymptotically infinitely many structural breaks in the means and variances of the time series. For this setting, we present test statistics and stopping times which are used to determine whether or not the correlation between two time series is and stays constant, respectively. Additionally, we consider estimates for change-points in the correlations. The employed nonparametric statistics depend on the means and variances. These (nuisance) parameters are replaced by estimates in the course of this thesis. We avoid assuming a fixed form of these estimates but rather we use "blackbox" estimates, i.e. we derive results under assumptions that these estimates fulfill. These results are supplement with examples. This thesis is organized in seven sections. In Section 1, we motivate the issue and present the mathematical model. In Section 2, we consider a posteriori and sequential testing procedures, and investigate convergence rates for change-point estimation, always assuming that the means and the variances of the time series are known. In the following sections, the assumptions of known means and variances are relaxed. In Section 3, we present the assumptions for the mean and variance estimates that we will use for the mean in Section 4, for the variance in Section 5, and for both parameters in Section 6. Finally, in Section 7, a simulation study illustrates the finite sample behaviors of some testing procedures and estimates.
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In this study, the Schwarz Information Criterion (SIC) is applied in order to detect change-points in the time series of surface water quality variables. The application of change-point analysis allowed detecting change-points in both the mean and the variance in series under study. Time variations in environmental data are complex and they can hinder the identification of the so-called change-points when traditional models are applied to this type of problems. The assumptions of normality and uncorrelation are not present in some time series, and so, a simulation study is carried out in order to evaluate the methodology’s performance when applied to non-normal data and/or with time correlation.
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Current procedures for flood risk estimation assume flood distributions are stationary over time, meaning annual maximum flood (AMF) series are not affected by climatic variation, land use/land cover (LULC) change, or management practices. Thus, changes in LULC and climate are generally not accounted for in policy and design related to flood risk/control, and historical flood events are deemed representative of future flood risk. These assumptions need to be re-evaluated, however, as climate change and anthropogenic activities have been observed to have large impacts on flood risk in many areas. In particular, understanding the effects of LULC change is essential to the study and understanding of global environmental change and the consequent hydrologic responses. The research presented herein provides possible causation for observed nonstationarity in AMF series with respect to changes in LULC, as well as a means to assess the degree to which future LULC change will impact flood risk. Four watersheds in the Midwest, Northeastern, and Central United States were studied to determine flood risk associated with historical and future projected LULC change. Historical single framed aerial images dating back to the mid-1950s were used along with Geographic Information Systems (GIS) and remote sensing models (SPRING and ERDAS) to create historical land use maps. The Forecasting Scenarios of Future Land Use Change (FORE-SCE) model was applied to generate future LULC maps annually from 2006 to 2100 for the conterminous U.S. based on the four IPCC-SRES future emission scenario conditions. These land use maps were input into previously calibrated Soil and Water Assessment Tool (SWAT) models for two case study watersheds. In order to isolate effects of LULC change, the only variable parameter was the Runoff Curve Number associated with the land use layer. All simulations were run with daily climate data from 1978-1999, consistent with the 'base' model which employed the 1992 NLCD to represent 'current' conditions. Output daily maximum flows were converted to instantaneous AMF series and were subsequently modeled using a Log-Pearson Type 3 (LP3) distribution to evaluate flood risk. Analysis of the progression of LULC change over the historic period and associated SWAT outputs revealed that AMF magnitudes tend to increase over time in response to increasing degrees of urbanization. This is consistent with positive trends in the AMF series identified in previous studies, although there are difficulties identifying correlations between LULC change and identified change points due to large time gaps in the generated historical LULC maps, mainly caused by unavailability of sufficient quality historic aerial imagery. Similarly, increases in the mean and median AMF magnitude were observed in response to future LULC change projections, with the tails of the distributions remaining reasonably constant. FORE-SCE scenario A2 was found to have the most dramatic impact on AMF series, consistent with more extreme projections of population growth, demands for growing energy sources, agricultural land, and urban expansion, while AMF outputs based on scenario B2 showed little changes for the future as the focus is on environmental conservation and regional solutions to environmental issues.
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No passado, as acções publicitárias eram rotuladas como above the line e below the line, referindo-se à dicotomia de pontos de contacto com os públicos-alvo via Meios de Comunicação Social ou via Ponto de Venda. A esta dicotomia de meios e instrumentos, os anos 90 vieram trazer um terceiro ponto de contacto, crescentemente omnipresente e hegemónico, a world wide web ou rede, a que se acedia via computador. As acções de marketing e comunicação passaram então a rotular-se como online e offline, passando, não já a referir-se aos pontos de contacto, mas aos canais pelos quais circulavam as mensagens e acções das marcas. Desde o início deste século, o poder do digital veio crescendo, em software e hardware, em terminais e tecnologias, assistindo-se a uma transferência de esforços de comunicação, da esfera real para a esfera do digital. O deslumbramento pelo digital conquistou mesmo algumas marcas de dimensão mundial que hoje apostam integralmente o seu orçamento nesta forma de marketing, nas suas múltiplas facetas. Contudo, e porque se tem tornado óbvio que os públicos distribuem os seus favores por múltiplos touch points, para maximizar o impacto, assiste-se agora a um fenómeno único, potenciado por novas tecnologias que surgem todos os dias: em estratégias que se podem denominar de all-line, verifica-se a fusão entre dois mundos, mundo real e mundo digital, em múltiplas actividades de marketing que fazem convergir estas duas realidades em plataformas que vão do computador ao tablet, do smartphone à vending machine interactiva, do facebook ao Google maps, da imprensa tradicional ao pinterest. É esta convergência mundo real - mundo digital que abre agora novas oportunidades à comunicação publicitária, potenciando os ingredientes das marcas de sucesso no futuro: sensações (estímulo dos sentidos), intimidade e mistério, num cocktail suportado por uma nova criatividade.
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Multifocal intraocular lenses (MF IOLs) have concentric optical zones with different dioptric power, enabling patients to have good visual acuity at multiple focal points. However, several optical limitations have been attributed to this particular design. The purpose of this study is to access the effect of MF IOLs design on the accuracy of retinal optical coherence tomography (OCT). Cross-sectional study conducted at the Refractive Surgery Department of Central Lisbon Hospital Center. Twenty-three eyes of 15 patients with a diffractive MF IOL and 27 eyes of 15 patients with an aspheric monofocal IOL were included in this study. All patients underwent OCT macular scans using Heidelberg Spectralis®. Macular thickness and volume values and image quality (Q factor) were compared between the two groups. There were no statistically significant differences between both groups regarding macular thickness or volume measurements. Retinal OCT image quality was significantly lower in the MF IOL group (p < 0.01). MF IOLs are associated with a significant decrease in OCT image quality. However, this fact does not seem to compromise the accuracy of spectral domain OCT retinal measurements.
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NIPE - WP 01/ 2016
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PURPOSE: Several studies observed a female advantage in the prognosis of cutaneous melanoma, for which behavioral factors or an underlying biologic mechanism might be responsible. Using complete and reliable follow-up data from four phase III trials of the European Organisation for Research and Treatment of Cancer (EORTC) Melanoma Group, we explored the female advantage across multiple end points and in relation to other important prognostic indicators. PATIENTS AND METHODS: Patients diagnosed with localized melanoma were included in EORTC adjuvant treatment trials 18832, 18871, 18952, and 18961 and randomly assigned during the period of 1984 to 2005. Cox proportional hazard models were used to calculate hazard ratios (HRs) and 95% CIs for women compared with men, adjusted for age, Breslow thickness, body site, ulceration, performed lymph node dissection, and treatment. RESULTS: A total of 2,672 patients with stage I/II melanoma were included. Women had a highly consistent and independent advantage in overall survival (adjusted HR, 0.70; 95% CI, 0.59 to 0.83), disease-specific survival (adjusted HR, 0.74; 95% CI, 0.62 to 0.88), time to lymph node metastasis (adjusted HR, 0.70; 95% CI, 0.51 to 0.96), and time to distant metastasis (adjusted HR, 0.69; 95% CI, 0.59 to 0.81). Subgroup analysis showed that the female advantage was consistent across all prognostic subgroups (with the possible exception of head and neck melanomas) and in pre- and postmenopausal age groups. CONCLUSION: Women have a consistent and independent relative advantage in all aspects of the progression of localized melanoma of approximately 30%, most likely caused by an underlying biologic sex difference.
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This paper compares the forecasting performance of different models which have been proposed for forecasting in the presence of structural breaks. These models differ in their treatment of the break process, the parameters defining the model which applies in each regime and the out-of-sample probability of a break occurring. In an extensive empirical evaluation involving many important macroeconomic time series, we demonstrate the presence of structural breaks and their importance for forecasting in the vast majority of cases. However, we find no single forecasting model consistently works best in the presence of structural breaks. In many cases, the formal modeling of the break process is important in achieving good forecast performance. However, there are also many cases where simple, rolling OLS forecasts perform well.
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This paper compares the forecasting performance of different models which have been proposed for forecasting in the presence of structural breaks. These models differ in their treatment of the break process, the parameters defining the model which applies in each regime and the out-of-sample probability of a break occurring. In an extensive empirical evaluation involving many important macroeconomic time series, we demonstrate the presence of structural breaks and their importance for forecasting in the vast majority of cases. However, we find no single forecasting model consistently works best in the presence of structural breaks. In many cases, the formal modeling of the break process is important in achieving good forecast performance. However, there are also many cases where simple, rolling OLS forecasts perform well.
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Background: Cardiovascular diseases are ranked among the leading causes of death in the industrialized countries. This study is aimed at ascertaining the mortality trends by ischemic heart disease (IHD) and cerebrovascular diseases (CVD) in Andalusia within the 1975-2004 period. Method: Based on the official IHD and CVD death statistics and the related populations, the gross rates (GR) and age-adjusted rates (TS) and the Potential Years of Life Lost (PYLL) were calculated. To quantify the trends and their change points, a joinpoint regression analysis was made. Results: The number of IHD deaths for females rose from 2,086 deaths in 1975 to 3,336 in 2004, the TS having dropped from 74.29 to 50.94 deaths/100,000 females, the PYLL having dropped from 173.65 years to 90.56 years/100,000 females. The number of deaths for males rose from 2,854 deaths in 1975 to 4,085 in 2004, the TS having dropped from 147, 67 to 104.96 deaths /100,000 males. The PYLL showed a like behaviour from the first to the last year of the series, showing values of 716.46 and 460.04 years / 100,000 males. For the IHD in females, the number of deaths in absolute numbers dropped from 4,712 to 4,221, the TS having dropped from 166.00 to 62.08 deaths in females, and the PYLL from 338.08 to 87.63 years / 100,000 females. For males, the number of deaths dropped from 3,714 to 2,951, the TS from 206.88 deaths /100,000 males in 1975 to 76.12 /100,000 males in 2004, and the PYLL dropping from 533.12 to 182.38 years / 100,000 males. Conclusions: The trend in mortality due to IHD was not constant either among females or males, although it has always been a downward trend, the drop being statistically significant. The drop in the CVD has been such a major one that both the absolute numbers and the gross rates are lower for the most recent years that the first years in the series studied despite the aging of Andalusia’s population.
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It is well known that multiple-input multiple-output (MIMO) techniques can bring numerous benefits, such as higher spectral efficiency, to point-to-point wireless links. More recently, there has been interest in extending MIMO concepts tomultiuser wireless systems. Our focus in this paper is on network MIMO, a family of techniques whereby each end user in a wireless access network is served through several access points within its range of influence. By tightly coordinating the transmission and reception of signals at multiple access points, network MIMO can transcend the limits on spectral efficiency imposed by cochannel interference. Taking prior information-theoretic analyses of networkMIMO to the next level, we quantify the spectral efficiency gains obtainable under realistic propagation and operational conditions in a typical indoor deployment. Our study relies on detailed simulations and, for specificity, is conducted largely within the physical-layer framework of the IEEE 802.16e Mobile WiMAX system. Furthermore,to facilitate the coordination between access points, we assume that a high-capacity local area network, such as Gigabit Ethernet,connects all the access points. Our results confirm that network MIMO stands to provide a multiple-fold increase in spectralefficiency under these conditions.
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Aquest projecte es basa en l'aplicació de models de simulació de processos a un exemple d'empresa de producció i la seva adaptació en dimensió i recursos al mercat en un entorn de poca capacitat d'inversió i finançament, de forma que l'entorn de simulació digital aporti valor a la presa de decisions emmarcada en l'estratègia de l'empresa en cada escenari de mercat en que aquesta es trobi. Es realitza el treball sobre el cas d'una empresa, INNOVANAUTIC, dedicada a la innovació, desenvolupament i producció de sistemes de propulsió d'embarcacions. La simulació es una tècnica que permet optimitzar els processos, representant-ne i comprovant el funcionament dels processos, tant entorns físics, de producció com dels serveis associats o subcontractacions de diferents processos i els seus impactes en la disponibilitat de recursos, espais i terminis d'entrega, sense haver de recórrer a procediments de prova i error sobre sistemes reals que impliquen costos a tots nivells en l'empresa. Aquestes metodologies son habitualment emprades en d'altres països o també en el nostre país però en empreses de gran tamany. El present treball, emmarcat dins un entorn socioeconòmic convuls, amb grans limitacions financeres i de recursos per les empreses, demostra com la utilització d'eines de simulació és útil per a PIMES en aquest entorn i permet el dimensionament i la modelització dels processos de forma que es permeti trobar els punts òptims en els que l'empresa ha de donar un pas de creixement en alguns dels paràmetres. La metodologia amb que s'elabora el present treball es la de plantejar una simulació complerta del procés, i definir diversos escenaris de mercat per als productes fabricats, cercant els punt òptims de canvi de dimensió de l'empresa atenent a espai físic, sotscontractació de processos, personal i recursos.
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Hypoferremia observed during systemic inflammatory disorders is regulated by hepcidin. Hepcidin up-regulation is particularly important during acute inflammation, as it restricts the availability of iron, which is necessary for pathogenic microorganism growth before adaptive immunity occurs. The aim of this study was to evaluate the clinical findings and hepatic hepcidin mRNA expression in horses using a Freund's complete adjuvant (FCA) model of inflammation. The expression of hepcidin mRNA in the liver was determined in healthy horses following two intramuscular injections of FCA at 0 h and 12 h. Plasma iron and fibrinogen concentrations were measured at multiple time points between 0 h and 240 h post-FCA injection (PI). Hepcidin mRNA expression was determined by RT-qPCR using liver biopsy samples performed at 0 h (control), 6 h and 18 h PI. The mean plasma fibrinogen level was significantly different from the control values only between 120 and 216 h PI. The mean plasma iron level was significantly lower than the control between 16 and 72 h PI, reaching the lowest levels at 30 h PI (33 % of the initial value), and returned to the reference value from 96 h PI to the end of the experiment. Hepcidin mRNA expression increased at 6 h PI and remained high at 18 h PI. The iron plasma concentration was an earlier indicator of inflammatory processes in horses when compared with fibrinogen and might be useful for the early detection of inflammation in the horse. FCA administration caused the rapid onset of hypoferremia, and this effect was likely the result of up-regulated hepatic hepcidin gene expression. This study emphasizes the importance of hepcidin and iron metabolism during inflammation in horses.