Indirect inference for locally stationary ARMA processes with stable innovations

The class of locally stationary processes assumes that there is a time-varying spectral representation, that is, the existence of finite second moment. We propose the $\alpha$-stable locally stationary process by modifying the innovations into stable distributions and the indirect inference to estimate this type of model. Due to the infinite variance, some of interesting properties such as time-varying auto-correlation cannot be defined. However, since the $\alpha$-stable family of distributions is closed under linear combination which includes the possibility of handling asymmetry and thicker tails, the proposed model has the same tail behavior throughout the time. In this paper, we propose this new model, present theoretical properties of the process and carry out simulations related to the indirect inference in order to estimate the parametric form of the model. Finally, an empirical application is illustrated.Comment: 31 pages, 14 figures. Submitted to the Journal of Statistical Computation and Simulatio

Intrinsically stretchable and transparent thin-film transistors based on printable silver nanowires, carbon nanotubes and an elastomeric dielectric.

Thin-film field-effect transistor is a fundamental component behind various mordern electronics. The development of stretchable electronics poses fundamental challenges in developing new electronic materials for stretchable thin-film transistors that are mechanically compliant and solution processable. Here we report the fabrication of transparent thin-film transistors that behave like an elastomer film. The entire fabrication is carried out by solution-based techniques, and the resulting devices exhibit a mobility of ∼30 cm(2) V(-1) s(-1), on/off ratio of 10(3)-10(4), switching current >100 μA, transconductance >50 μS and relative low operating voltages. The devices can be stretched by up to 50% strain and subjected to 500 cycles of repeated stretching to 20% strain without significant loss in electrical property. The thin-film transistors are also used to drive organic light-emitting diodes. The approach and results represent an important progress toward the development of stretchable active-matrix displays

A bayesian hierarchical spatio-temporal model with count data: application to the HIV/AIDS in Costa Rica

Los modelos espaciales que suavizan las tasas de mortalidad estandarizada o los riesgos relativos son utilizados ampliamente en el mapeo de enfermedades, con el objetivo de explorar y describir patrones espaciales de un evento de interés. Generalmente, la estimación de estos riesgos relativos es imprecisa cuando los eventos son raros. Cuando se quiere incluir la tendencia temporal, el problema es aún más grave pues el conteo de las defunciones en el perı́odo dado se divide en varios años, lo que resulta en que los conteos sean aún más bajos. En este trabajo, se analizan los modelos Bayesianos espacio-temporales que toman en cuenta la información geográfica y temporal, además de algunas covariables como el porcentaje de viviendas urbanas, porcentaje de personas entre 24 y 49 años y la tasa de mortalidad infantil de cada cantón en el año 2011. Se concluyó que estos modelos producen mejores estimaciones de riesgos relativos por cantón y año, además de que el modelo que asume una interacción espacio-temporal más simple ajusta mejor. Finalmente, se comparan los riesgos relativos estimados con el modelo seleccionado, contra la estimación obtenida vı́a máxima verosimlitud, y resulta que el método propuesto es más eficiente y preciso.Spatial models that smooth standardized mortality ratios are widely used in disease mapping. Usually, estimation is imprecise when events are rare. In situations where each areal count splits into different time periods, this problem is more evident because of the presence of even lower counts for the areal units for each time period. In this work, we analyze models that include geographic and temporal information and some covariates such as percentage of urban household, percentage of people between 24 and 49 years old, and infant mortality ratio of each county in 2011. As a result, these models produce better estimations, especially for the model with the simplest space-time interaction. Finally, HIV/AIDS mortality data in Costa Rica (1998-2012) are used as an illustration to compare classic standardized mortality ratios and posterior means of relative risk. The proposed method is more efficient and more precise than the maximum likelihood.UCR::Vicerrectoría de Docencia::Ciencias Sociales::Facultad de Ciencias Económicas::Escuela de EstadísticaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Sociales::Centro Centroamericano de Población (CCP

Accelerated colorimetric immunosensingusing surface-modified porous monolithsand gold nanoparticles

A rapid and sensitive immunoassay platform integrating polymerized monoliths and gold nanoparticles (AuNPs) has been developed. The porous monoliths are photopolymerized in situ within a silica capillary and serve as solid support for high-mass transport and high-density capture antibody immobilization to create a shorter diffusion length for antibody–antigen interactions, resulting in a rapid assay and low reagent consumption. AuNPs are modified with detection antibodies and are utilized as signals for colorimetric immunoassays without the need for enzyme, substrate and sophisticated equipment for quantitative measurements. This platform has been verified by performing a human IgG sandwich immunoassay with a detection limit of 0.1 ng ml−1. In addition, a single assay can be completed in 1 h, which is more efficient than traditional immunoassays that require several hours to complete

Septic Pulmonary Embolism Requiring Critical Care: Clinicoradiological Spectrum, Causative Pathogens and Outcomes

OBJECTIVES: Septic pulmonary embolism is an uncommon but life-threatening disorder. However, data on patients with septic pulmonary embolism who require critical care have not been well reported. This study elucidated the clinicoradiological spectrum, causative pathogens and outcomes of septic pulmonary embolism in patients requiring critical care. METHODS: The electronic medical records of 20 patients with septic pulmonary embolism who required intensive care unit admission between January 2005 and December 2013 were reviewed. RESULTS: Multiple organ dysfunction syndrome developed in 85% of the patients, and acute respiratory failure was the most common organ failure (75%). The most common computed tomographic findings included a feeding vessel sign (90%), peripheral nodules without cavities (80%) or with cavities (65%), and peripheral wedge-shaped opacities (75%). The most common primary source of infection was liver abscess (40%), followed by pneumonia (25%). The two most frequent causative pathogens were Klebsiella pneumoniae (50%) and Staphylococcus aureus (35%). Compared with survivors, nonsurvivors had significantly higher serum creatinine, arterial partial pressure of carbon dioxide, and Acute Physiology and Chronic Health Evaluation II and Sequential Organ Failure Assessment scores, and they were significantly more likely to have acute kidney injury, disseminated intravascular coagulation and lung abscesses. The in-hospital mortality rate was 30%. Pneumonia was the most common cause of death, followed by liver abscess. CONCLUSIONS: Patients with septic pulmonary embolism who require critical care, especially those with pneumonia and liver abscess, are associated with high mortality. Early diagnosis, appropriate antibiotic therapy, surgical intervention and respiratory support are essential

Spatio-temporal Downscaling Emulator for Regional Climate Models: a Comparative Study

Regional Climate Models (RCM) describe the meso scale global atmospheric and oceanic dynamics and serve as dynamical downscaling models. In other words, RCMs use atmospheric and oceanic climate output from General Circulation Models (GCM) to develop a higher resolution climate output. They are computationally demanding and, depending on the application, require several orders of magnitude of computer time more than statistical climate downscaling. In this paper we describe how to use a spatio-temporal statistical model with varying coefficients (VC), as a downscaling emulator for a RCM using varying coefficients. In order to estimate the proposed model, two options are compared: INLA, and varycoef. We set up a simulation to compare the performance of both methods for building a statistical downscaling emulator for RCM, and then show that the emulator works properly for NARCCAP data. The results show that the model is able to estimate non-stationary marginal effects, which means that the downscaling output can vary over space. Furthermore, the model has flexibility to estimate the mean of any variable in space and time, and has good prediction results. INLA was the fastest method for all the cases, and the approximation with best accuracy to estimate the different parameters from the model and the posterior distribution of the response variable

Bayesian spatio-temporal model with INLA for dengue fever risk prediction in Costa Rica

Due to the rapid geographic spread of the Aedes mosquito and the increase in dengue incidence, dengue fever has been an increasing concern for public health authorities in tropical and subtropical countries worldwide. Significant challenges such as climate change, the burden on health systems, and the rise of insecticide resistance highlight the need to introduce new and cost-effective tools for developing public health interventions. Various and locally adapted statistical methods for developing climate-based early warning systems have increasingly been an area of interest and research worldwide. Costa Rica, a country with micro-climates and endemic circulation of the dengue virus (DENV) since 1993, provides ideal conditions for developing projection models with the potential to help guide public health efforts and interventions to control and monitor future dengue outbreaks

東澳嶺崩塌地之地形演育分析

梅姬颱風 (2010) 與東北季風之共伴效應於台灣宜蘭縣蘇澳地區帶來了豐沛降雨，高累積雨量造成了台9 線蘇花公路群集性土砂災害，尤其在115.9K 上邊坡更誘發了約210 萬m3 之大規模崩塌土砂災害。本文從現地地質調查、致災機制、水文分析及遙測影像判釋等面向進行討論。由降雨-延時-頻率分析得知近年來誘發重大崩塌事件的雨量皆高於200 年回歸週期，並獲致良好判別致災雨場之I-R 圖降雨臨界線關係(Re+53.5Iave=1,146)。多時期遙測影像判釋指出東澳嶺坡頂之弧型張力裂隙仍有持續溯源發展之趨勢。裸露崩塌地不連續面方位密度分布圖之裂隙位態大致與區域地質構造位態 (N70°W) 相近，顯示本區域崩塌主要仍受地質條件主控。此外，蝕溝溯源侵蝕、剪裂帶分布及凹漥坡型亦為影響研究區崩塌地地貌變遷之重要因子，而前期地震或長延時高強度降雨則為外在促崩因子。Typhoon Megi coupled with the northeastern monsoon induced an extreme rainfall of 939 mm on the Suao area, Yilan County, in eastern Taiwan on October 21st, 2010, causing the Dong-Ao Peak landslide of 2.1 million m3 along the coastal Su-Hua Section of Highway Route 9. This study adopts a geological survey, rainfall data, satellite images, orthophotos, and high-resolution DEM based on airborne laser scanner surveys to quantify the morphological changes before and after landslide events following major rainfall events since 2010. Rainfall frequency analysis indicates the cumulative precipitation triggering landslide events is greater than the 200-year return period. In addition, both the entrainment effect of debris flow and toe erosion on the down-slope is shown to induce regressive sliding failure at the adjacent roadbed. The results suggest that geological factors such as head-cutting erosion and the concave landform shape the landform evolution of the catchment. The occurrence of landslides also depends on antecedent earthquake events and extreme intense rainfalls