Trust-based algorithms for fusing crowdsourced estimates of continuous quantities

Crowdsourcing has provided a viable way of gathering information at unprecedented volumes and speed by engaging individuals to perform simple micro–tasks. In particular, the crowdsourcing paradigm has been successfully applied to participatory sensing, in which the users perform sensing tasks and provide data using their mobile devices. In this way, people can help solve complex environmental sensing tasks, such as weather monitoring, nuclear radiation monitoring and cell tower mapping, in a highly decentralised and parallelised fashion. Traditionally, crowdsourcing technologies were primarily used for gathering data for classifications and image labelling tasks. In contrast, such crowd–based participatory sensing poses new challenges that relate to (i) dealing with human–reported sensor data that are available in the form of continuous estimates of an observed quantity such as a location, a temperature or a sound reading, (ii) dealing with possible spatial and temporal correlations within the data and (ii) issues of data trustworthiness due to the unknown capabilities and incentives of the participants and their devices. Solutions to these challenges need to be able to combine the data provided by multiple users to ensure the accuracy and the validity of the aggregated results. With this in mind, our goal is to provide methods to better aid the aggregation process of crowd–reported sensor estimates of continuous quantities when data are provided by individuals of varying trustworthiness. To achieve this, we develop a trust–based in- formation fusion framework that incorporates latent trustworthiness traits of the users within the data fusion process. Through this framework, we develop a set of four novel algorithms (MaxTrust, BACE, TrustGP and TrustLGCP) to compute reliable aggregations of the users’ reports in both the settings of observing a stationary quantity (Max- Trust and BACE) and a spatially distributed phenomenon (TrustGP and TrustLGCP). The key feature of all these algorithm is the ability of (i) learning the trustworthiness of each individual who provide the data and (ii) exploit this latent user’s trustworthiness information to compute a more accurate fused estimate. In particular, this is achieved by using a probabilistic framework that allows our methods to simultaneously learn the fused estimate and the users’ trustworthiness from the crowd reports. We validate our algorithms in four key application areas (cell tower mapping, WiFi networks mapping, nuclear radiation monitoring and disaster response) that demonstrate the practical impact of our framework to achieve substantially more accurate and informative predictions compared to the existing fusion methods. We expect that results of this thesis will allow to build more reliable data fusion algorithms for the broad class of human–centred information systems (e.g., recommendation systems, peer reviewing systems, student grading tools) that are based on making decisions upon subjective opinions provided by their users

Nodal staging in head and neck squamous cell carcinoma by combining different imaging techniques

Head and neck cancer accounts for around 4% of all malignancies. The presence of cervical lymph node metastases will reduce expected survival with approximately 50%. Therapy should thus be as effective as possible with a minimum of therapeutic side effects and depends next to tumour size on the presence or absence of nodal metastases. Physical examination and imaging with magnetic resonance imaging (MRI), positron emission tomography – computed tomography (PET-CT), ultrasound (US), ultrasound guided fine needle aspiration (USgFNAC) are commonly used to examine cervical lymph node metastases, but in 30% of the cases, they are still overlooked. New imaging techniques such as real time image fusion of ultrasound and PET-CT and micro flow imaging (MFI) are thus developed. The aim of this thesis was to improve the detection rate of lymph node metastases by improving the selection criteria of nodes for ultrasound guided fine needle aspiration to prove cytological malignancy.<br/

Effects of intracranial stimulation and the involvement of the human parahippocampal cortex in perception

How the human brain translates photons hitting the retina into conscious perception remains an open question. Throughout the medial temporal lobe (MTL), there are neurons (called concept cells) that change their firing rate when that neuron's preferred concept, e.g., a specific person or object, is seen. The firing rate of concept cells is correlated with perception. Nevertheless, it remains unclear whether or to what extent concept cells are involved in perceptogenesis, i.e., the creation of conscious percepts. Inferring from studies in monkeys, concept-specific neurons involved in perceptogenesis would be expected along the ventral and dorsal stream of visual processing (also called the what and where pathway, respectively). Various regions that are part of the dorsal stream are connected to the parahippocampal cortex (PHC), a region within the MTL. Compared to other MTL regions, lower selectivity, the absence of multimodal responses, and especially the shorter response latencies do not exclude an involvement of the PHC in perceptogenesis. In fact, damage to the parahippocampal place area (PPA, a part of the PHC) results in topographical disorientation. The goal of this thesis is to test the involvement of the PHC in perception by using electrical stimulation during a forced-choice categorization task involving landscapes versus animals. First, we determined effective parameters for intracranial stimulation of brain tissue in epilepsy patients implanted with depth-electrodes for seizure monitoring. We investigated the effects of amplitude, phase width, frequency, and pulse-train duration on neuronal firing, the local field potential (LFP), and behavioral responses to evoked percepts. Frequency and charge per phase were the most influential parameters on all three signals. Both parameters showed a positive effect on event-related potentials (ERPs) in the LFP. Higher frequencies (especially around 200 Hz) lead to a short-term inhibition of neuronal firing, while higher charge per phase can have an inhibitory or excitatory effect on neuronal firing. All parameters had a positive effect on the reports of evoked percepts; on reports of phosphenes in response to stimulating close to the optic radiation as well as on reports of auditory verbal hallucinations in response to stimulating Heschl's gyrus. Using functional magnetic resonance imaging (fMRI), we found that the PPA, i.e., the part of the PHC that is most selective towards images of landscapes, is rather small (up to 1‰ of total brain volume per hemisphere) with varying degrees of hemispheric laterality. Stimulating the PHC outside of the PPA - using a 100 ms high-frequency pulse train delivered at the natural response latency of the PHC - had no effect on categorizing landscapes. However, stimulating inside the PPA, close to the peak activation of the fMRI cluster, resulted in a 7% to 10% increase in landscape responses to ambiguous stimuli. Furthermore, stimulating the PPA also led to an increase in behavioral response time, especially to images with a predominant landscape component. None of our patients reported visual hallucinations of places or scenes in response to our stimulation protocols. Our data suggests that the PPA is involved in the perceptogenesis of landscapes at a stage that does not reach awareness, while the rest of the PHC is unlikely to be involved in perceptogenesis, at least not as it pertains to the perception of landscapes or animals. We also developed an online spike sorting algorithm and an adaptive screening procedure for concept cells to pave the way for new paradigms involving informed feedback

Estudio in vitro de factores que afectan la durabilidad y la eficacia adhesiva de la interfase circona-resina

[EN] The introduction of ceramic zirconium oxide as a restorative material dealt a major clinical and research interest in the dental community. The zirconia bioceramic presents as a wide range of applications due to its high biocompatibility and good physical and optical properties. This is a relatively new and promising material, but remains controversial from a scientific point of view, the best method to optimize and promote their effective substrates used in dental adhesion. Conventional bonding techniques are ineffective on the surface of zirconia, given their relative chemical resistance (molecular composition unpolarized) and its pure crystalline structure (no glassy phase). For these reasons, adherence (defined as integration ultrastructural substrates through a contact interface) is difficult to achieve and, to date, no clear guidelines for clinicians to ensure sustainable and effective adhesion. The objectives of this thesis were: 1) review the literature on zirconia, with special focus on state of the art of its recent use as implant abutment; 2) evaluate the effect of particle size on the blasting force of adhesion at the interface of zirconia / resin; 3) investigate the effect of surface treatment of zirconia with tribochemical silica coating and / or irradiation of Er: YAG laser on bond strength of zirconia / resin interface; 4) determine whether the composition of resin cement influences its bond strength to zirconia and what is the best combination of cement type and surface conditioning to provide reliable adhesion zirconia / resin; 5) assess the impact of thermocycling on the bond strength of various self-adhesive cements resin pretreated zirconia. Experimental tests of this thesis were designed to determine some guidelines for action to improve the interface of zirconia / resin. The in vitro study was conducted to evaluate the factors that affect the durability and strength of adhesion on zirconia / resin interface. For this study, two hundred and eighty zirconia blocks were used and divided into two experiments: A) Forty-shaped cylinder block (Ø 19.5 mm x 10.25 mm height) which were selected to evaluate the influence of grain size sandblasting and composition of the resin cement bond strength to zirconia microtensile; and B) 240 square specimens (measuring 3 x 3 x 1 mm) were used to evaluate the effect of thermal cycling on the adhesion strength to micro-shear test of zirconia treated with Er: YAG and tribochemical silica coating and surface conditioning. In the first trial, zirconia blocks were polished and separated randomly as follows: Group 1 (NT): no treatment; Group 2 (PAC-I): sanding (APA) using particles of aluminum oxide (Al2O3) of 25 microns; in Group 3 (APA-II): APA with Al2O3 particles with 50 microns, and Group 4 (EPA-III): APA using Al2O3 particles 110 microns. The ceramic blocks were duplicated in composite. Samples of each pretreatment group were randomly divided into two subgroups according to the resin cement used for joining composite blocks treated surfaces of zirconia: Subgroup 1 (PAN), which employs a system containing cemented 10-MDP (Panavia F 2.0, Kuraray Medical Ltd., Osaka, Japan) and Subgroup 2 (BIF) in which a self-adhesive cement (Bifix SE, VOCO, Cuxhafen, Germany) was used. After 24 h, the samples were cut into bars 1 micro ± 0.1mm2. In the second trial the zirconia samples were polished and randomized into four groups according applied surface treatment as follows: 1) no treatment (NT); 2) silica coating Rocatec (Rocatec Soft, 3M ESPE, Seefeld, Germany) (ROC), 3) irradiation with Er: YAG (LAS: 2.940 nm, 200 mJ, 10 Hz), and 4) laser followed by Rocatec (LAROC). A small cylinder of a resin cement with 1 mm diameter and 2 mm in height each joined ceramic samples. Each group was divided into two subgroups according to the resin used: A) BIF (Bifix SE, VOCO, Cuxhafen, Germany) and B) CLE (Clearfil SA, Kuraray Medical Ltd., Osaka, Japan). After 24 hours, half of the samples of each group were tested. The other half was stored and subjected to thermocycling (5th-55/5000 cycles). The values ​​of the resistance tests of adherence to the microtensile (MTBS) and microcizalla strength (MSBS) were obtained using a universal testing machine (crosshead speed = 0.5 mm / min). The failure modes were recorded and the morphology of the interfacial zone was observed severed by scanning electron microscopy (SEM). Data were analyzed with ANOVA, Student tests, chi-square tests and linear regression (p <0.05). The main results to note are: A) in the first study, despite the fineness of sanded, sandblasted surfaces joined PAN reaches the highest values ​​of MTBS and often showed mixed fractures, BIF showed significant differences in MTBS depending on the method of conditioning, and recorded the highest rates of premature failure and adhesives, and B) in the second experiment, before thermal cycling, both cements showed superior results with ROC and LAROC MSBS; after artificial aging, all BIF specimens show a severe decrease in adhesion, mainly adhesive failures. Furthermore CLE maintains baseline in ROC and LAROC groups (still better than LAROC ROC). Findings indicate that although laser treatment creates a rougher surface, it did not improve the bond strength to zirconia. In conclusion: 1) the use of zirconia abutments on implants is well documented in the literature with several in vitro studies and some clinical studies support the indication, these pillars of zirconia are similar to titanium abutments marginal fit, used universally and display a low bacterial adhesion and high biocompatibility, but zirconia pillars have resistance values ​​lower than the fracture titanium are shown in the prosthetic rehabilitation of the anterior sector, providing a superior aesthetic and functional result; 2) application of sandblasting before cementation is crucial to ensure good adhesion at the interface of zirconia / resin regardless of the size of the particles of alumina, however, there is a clear trend between the increase of the particle size distribution sandblasting and bond strength at the interface zirconia / resin if a cement containing 10-MDP used; 3) the effectiveness of the adhesive is greater if the surface is driven only with silica coating (without applying the laser), zirconia engraving laser Er: YAG is not effective in increasing the strength of adhesion to the resin ; 4) presence of 10-MDP monomer in the cement composition positively influences the adhesion once is able to improve chemical adhesion to a substrate of zirconia, a system applying cement containing 10-MDP, either in the first and in the resin matrix on a silica coated or sandblasting may be the key to the success of zirconia / adhesion resin substrate; 5) thermocycling the impact strength of the joint depends on the materials used, specifically a self adhesive cement, resin with 10-MDP in composition on a pretreated surface of zirconia coated silica (with or without Er : YAG associated) is unaffected by thermal cycling. [ES] La introducción de la cerámica de óxido de circonio como un material de restauración propinó un gran interés clínico e investigador en la comunidad odontológica. La circona como biocerámica presenta una amplia gama de aplicaciones dada su alta biocompatibilidad y buenas propiedades físicas y ópticas. Se trata de un material relativamente nuevo y prometedor, aunque sigue generando controversia, desde el punto de vista científico, sobre el mejor método para optimizar y promover su adhesión efectiva a los sustratos utilizados en odontología. Las técnicas de adhesión convencionales resultan ineficaces en la superficie de óxido de circonio, dada su relativa inalterabilidad química (composición molecular no polarizada) y su estructura cristalina pura (sin fase vítrea). Por estas razones, la adhesión (entendida como integración ultraestructural de sustratos a través de una interfase de contacto) es difícil de lograr y, hasta la fecha, no hay directrices claras para que los clínicos puedan garantizar una adhesión duradera y eficaz. Los objetivos de esta tesis fueron: 1) revisar la literatura sobre la circona, con especial enfoque al estado del arte de su reciente uso como pilar del implante; 2) evaluar el efecto del tamaño de partícula de arenado en la fuerza de adhesión en la interfase de circona/resina; 3) investigar el efecto del tratamiento de superficie de la circona con recubrimiento triboquímico de sílice y/o con irradiación de Er: YAG en la fuerza de adhesión de la interfase circona/resina; 4) determinar si la composición de cemento de resina influye en su fuerza de adhesión al óxido de circonio y cuál es la mejor combinación de tipo de cemento y de acondicionamiento de superficie para proporcionar una adhesión fiable circona/resina; 5) valorar el impacto del termociclado en la fuerza de adhesión de varios cementos de resina auto-adhesivos a circona pretratada. Los ensayos experimentales de esta tesis se diseñaron para determinar algunas pautas de actuación para mejorar la interfase de circona/resina. El estudio in vitro se llevó a cabo para evaluar los factores que afectan la durabilidad y la resistencia de la adhesión en el interfase circona/resina. Para este estudio se usaron doscientos ochenta bloques de circona y se dividieron en dos experimentos: A) cuarenta bloques en forma de cilindro (Ø 19,5 mm x 10,25 mm de alto) que se seleccionaron para evaluar la influencia de la granulometría de arenado y de la composición de cemento de resina la resistencia de la adhesión de microtensión a circona; y B) 240 especímenes cuadrados (midiendo 3 x 3 x 1 mm) que se utilizaron para evaluar el efecto del termociclado en la fuerza de adhesión al test de micro-cizalla de la circona tratada con laser de Er:YAG y revestimiento triboquímico de sílice como acondicionamiento de la superficie. En el primer ensayo, los bloques de circona fueron pulidos y separados al azar de la siguiente manera: Grupo 1 (NT): ningún tratamiento; Grupo 2 (APA-I): arenado (APA) usando partículas de óxido de aluminio (Al2O3) de 25 micras; en Grupo 3 (APA-II): APA con partículas de Al2O3 con 50 micras, y Grupo 4 (APA-III): APA utilizando partículas de Al2O3 de 110 micras. Los bloques cerámicos se duplicaron en composite. Las muestras de cada grupo de tratamiento previo fueron divididas aleatoriamente en dos subgrupos en función del cemento de resina utilizado para la unión de los bloques de composite a las superficies de circona tratadas: Subgrupo 1 (PAN), que emplea un sistema de cementado que contiene 10-MDP (Panavia F 2.0, Kuraray Medical Ltd, Osaka, Japón), y el Subgrupo 2 (BIF) en el que se utilizó un cemento autoadhesivo (Bifix SE, VOCO, Cuxhafen, Alemania). Después de 24 h, las muestras fueron cortadas en micro barras 1 ± 0.1mm2. En el segundo ensayo las muestras de óxido de circonio fueron pulidas y asignados al azar en cuatro grupos de acuerdo tratamiento de superficie aplicada de la siguiente manera: 1) sin tratamiento (NT); 2) revestimiento de sílice con Rocatec (Rocatec Soft, 3M Espe, Seefeld, Alemania) (ROC), 3) irradiación con láser de Er:YAG (LAS: 2.940 nm, 200 mJ, 10 Hz) y, 4) láser seguido por Rocatec (LAROC). Un pequeño cilindro de un cemento de resina con 1 mm de diámetro y 2 mm de altura se unió a cada una de las muestras de cerámica. Cada grupo se dividió en dos subgrupos según la resina utilizada: A) BIF (Bifix SE, VOCO, Cuxhafen, Alemania) y B) CLE (Clearfil SA, Kuraray Medical Ltd, Osaka, Japón). Después de 24 horas, la mitad de las muestras de cada subgrupo se pusieron a prueba. La otra mitad se almacenó y sometió a termociclado (5º-55ºC/5000 ciclos). Los valores de los tests de resistencia de la adhesión a la microtensión (MTBS) y a la fuerza microcizalla (MSBS) se obtuvieron utilizando una máquina universal de ensayo (velocidad de la cruceta = 0.5mm/min). Los modos de fallo se registraron y la morfología de la zona interfacial desunida se observó por microscopía electrónica de barrido (SEM). Los datos se analizaron estadísticamente con ANOVA, tests de Student, pruebas de chi cuadrado y regresión lineal (p < 0,05). Los principales resultados a señalar son los siguientes: A) en el primer estudio, a pesar de la granulometría de arenado, PAN adherido a superficies arenadas alcanza los valores más altos de MTBS y con frecuencia mostró fracturas mixtas, BIF registró diferencias significativas de la MTBS en función del método de acondicionado, y registró las mayores tasas de fallos prematuros y adhesivos, y B) en el segundo experimento, antes del termociclado, ambos cementos mostraron resultados superiores de MSBS con ROC y LAROC; después del envejecimiento artificial, todos los especímenes BIF evidencian una disminución severa de la adhesión, con fallos principalmente adhesivos. Por otro lado CLE mantiene los valores iniciales en los grupos ROC y LAROC (siendo LAROC mejor que ROC). Evidenciamos que aunque el tratamiento con láser crea una superficie más rugosa, ésta no mejoró la resistencia de la adhesión a la circona. En conclusión: 1) el uso de pilares circona sobre implantes está bien documentado en la literatura con varios estudios in vitro y algunos trabajos clínicos que avalan su indicación, estos pilares de circona tienen un ajuste marginal similar a los pilares de titanio, utilizados universalmente, y ostentan una baja adherencia bacteriana y una alta biocompatibilidad, aunque los pilares de circona tienen valores de resistencia a la fractura inferiores a los de titanio, se indican en la rehabilitación protésica del sector de anterior, proporcionando un resultado estético y funcional superior; 2) la aplicación de arenado antes de la cementación es determinante para asegurar una buena adhesión en la interfase de circona/resina, independientemente del tamaño de las partículas de alumina, sin embargo, hay una tendencia evidente entre el aumento de la granulometría de la partícula del arenado y la resistencia de la unión en la interfase circona/resina si se utiliza un cemento que contiene 10-MDP; 3) la eficacia de adhesivo es mayor si la superficie sólo está condicionado con revestimiento de sílice (sin aplicar el láser), el grabado de circona con laser de Er: YAG no es eficaz en el aumento de su resistencia de la adhesión a la resina; 4) la presencia de monómero de 10-MDP en la composición de cemento influye positivamente en la adhesión una vez que es capaz de mejorar la adhesión química a un sustrato de circona, la aplicación de un sistema de cemento que contiene 10-MDP, tanto en el primer como en la matriz de resina sobre un sustrato recubierto de sílice o arenado puede ser la clave para el éxito de la adhesión circona/resina; 5) el impacto del termociclado en la resistencia de la unión depende de los materiales utilizados, un cemento auto-adhesivo específico, de resina con 10-MDP en su composición, sobre una superficie de circona pretratada con revestimiento de sílice (con o sin Er: YAG asociada) no se afecta por el termociclado

Econometrics meets sentiment : an overview of methodology and applications

The advent of massive amounts of textual, audio, and visual data has spurred the development of econometric methodology to transform qualitative sentiment data into quantitative sentiment variables, and to use those variables in an econometric analysis of the relationships between sentiment and other variables. We survey this emerging research field and refer to it as sentometrics, which is a portmanteau of sentiment and econometrics. We provide a synthesis of the relevant methodological approaches, illustrate with empirical results, and discuss useful software

What do we know about knowledge integration : fusing micro- and macro-organizational perspectives

Knowledge integration is the raison d’etre for the existence of the firm (Grant, 1996a; Kogut & Zander, 1992) and has been widely studied across many subfields in management and organizational studies. However, few constructs have received as much scholarly attention as knowledge integration while remaining so equivocally defined and measured, leading to a confusing array of conceptualizations, undermining its theoretical, empirical, and practical usefulness. As a theoretical construct, knowledge integration also cuts across the macro- and microlevels, gaining attention from scholars interested in explaining the microfoundations of strategy and capabilities (e.g., Felin & Hesterly, 2007; Lewin, Massini, & Peeters, 2011). However, the interplay among these micro and macro factors is often overlooked, and its implications for theory building are ignored. To address these issues, we examine and integrate micro- and macro-organizational perspectives on knowledge integration. We provide a review of its definitions and offer our definition based on key dimensions identified. We discuss and analyze the micro and macro perspectives, presenting key assertions, propositions, limitations, and conclusions from representative studies. Finally, we integrate the diverse perspectives we discuss, showing how their interplay can enrich future scholarship and our understanding of knowledge integration as a key organizational construct