3,945 research outputs found

    Google search intensity, mortgage default and house prices in regional residential markets

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    The internet provides a new way for households to access relevant information, while their online search behaviour may also contain information for their concerns and intentions, or even be used to predict real economic activity. This thesis explores the use of Google search data to predict mortgage default and regional house price dynamics in an empirical macroeconomic framework. The thesis is composed of three independent empirical studies. The first study examines the dynamic interdependence between mortgage default and house price across different housing market segments, i.e., top-tier vs. bottom-tier houses and recourse states vs. non-recourse states, based on a Panel VAR model. In particular, this study uses the Mortgage Default Risk Index (MDRI) proposed by Chauvet et al. (2016). It captures the intensity of Google search for keywords and phrases such as “mortgage foreclosure” or “foreclosure help” and measures the potential default risk of households. It is shown that shocks to house price returns have a significantly stronger effect on actual foreclosures in non-recourse states than in recourse states. The results suggest that borrowers are financially sophisticated and strategic as they are less likely to default in recourse states. Additionally, the MDRI has a stronger negative impact on top-tier home price returns, while the foreclosure rate of homes more pronouncedly decreases bottom-tier home price returns. These findings hold for the entire sample and recourse states. However, in non-recourse states, the impacts of the MDRI and the HF on bottom- and top-tier house price returns are about the same. The second study examines the impact of house prices on the foreclosure rates in the local housing market and explores whether the MDRI helps predict future house prices and foreclosures. In particular, this study uses an error correction framework to capture both the long-run equilibrium fundamental component of house prices as well as the short-run dynamics of house prices, including the component of bubbles. It is found that the MDRI shows a negative impact on both components of house prices but, more importantly, a negative impact on foreclosure rates. Furthermore, it is shown that foreclosure rates are negatively affected by the fundamental component of house prices but are not sensitive to their bubble component. This study sheds new light on the predictive power of household sentiment derived from Google searches on prices and foreclosure rates in local housing markets. The third study recognizes that, by searching online, households are transmitting information to and simultaneously receiving information from the Google Search engine. While they might divulge information about their financial concerns or vulnerability, they are also gathering information and learning through their search behaviour. This chapter aims to examine the comprehensive impact of the disclosure and information-learning effects of online searches on mortgage default. To that end, based on the assumption of different pre-existing knowledge of households, this study defines two kinds of Google search activities of households, i.e., naïve and sophisticated searches, and practically performed by aggregating the search activities for different query terms. It is found that sophisticated search activity has a positive impact on mortgage delinquency but a negative impact on foreclosure starts, while naïve search activity only positively affects foreclosure starts. The results suggest that the Google search activity of households is a combination of information disclosure and information-learning processes. Furthermore, borrowers are more likely to learn from sophisticated online searches, and they can use the information to avoid foreclosure starts

    LIPIcs, Volume 251, ITCS 2023, Complete Volume

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    LIPIcs, Volume 251, ITCS 2023, Complete Volum

    Bayesian Nonlinear Tensor Regression with Functional Fused Elastic Net Prior

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    Tensor regression methods have been widely used to predict a scalar response from covariates in the form of a multiway array. In many applications, the regions of tensor covariates used for prediction are often spatially connected with unknown shapes and discontinuous jumps on the boundaries. Moreover, the relationship between the response and the tensor covariates can be nonlinear. In this article, we develop a nonlinear Bayesian tensor additive regression model to accommodate such spatial structure. A functional fused elastic net prior is proposed over the additive component functions to comprehensively model the nonlinearity and spatial smoothness, detect the discontinuous jumps, and simultaneously identify the active regions. The great flexibility and interpretability of the proposed method against the alternatives are demonstrated by a simulation study and an analysis on facial feature data

    Diagnostics of ion generation and fluxes from cathodic arc spots for a better understanding of energetic deposition of thin films

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    This thesis is devoted to the investigation of ion generation and fluxes from cathodic arc spots for a better understanding of energetic deposition of thin film. The ion generation is related to the arc spot properties, and ion fluxes influence the film deposition. Significantly, the cathodic arc has the explosion characteristic for the ignition process, which is the generation process of ions. Thus, it is not easy to observe the spot characteristics, and some fundamental questions related to cathodic arc spot motion are still open. The multiply charged ions produced from the arc spot ignition process have a higher ion potential energy than ions of other deposition techniques; therefore, consideration of the effect of ion potential energy on film growth is required for the cathodic arc technique. The first part of this thesis deals with fundamental arc spot characteristics, especially the trend of spot motion in a magnetically steered arc source placed in vacuum or in a reactive gas atmosphere. This is investigated with a streak camera having high spatial and temporal resolutions. To answer the fundamental question of whether the spots have characteristic times, such as a 'periodic spot lifetime' or a 'the periodic characteristic time between spot ignitions”, the streak images were analyzed by fast Fourier transformation (FFT). It was found that the power spectrum of the arc spot fluctuations does not show any specific frequencies, which means the arc spot ignition process can be described by a fractal model, and the spectral slope in the log-log power-frequency diagram has a tendency to be reduced in the presence of a compound (for example oxide or nitride) layer on the cathode surface. Through the fractal analysis and measurements of optical emission spectroscopy, the fundamental limitation of the temporal resolution for the optical emission method is determined and considered. The second part of this thesis considers cathodic arc’s application aspects: the energetic deposition of thin films and coatings. Most studies related to energetic deposition have previously investigated the effects of ion kinetic energy on film deposition; however, this thesis focuses on the effects of ion potential energy on film growth. To investigate the effect of ion potential energy on film growth, plasma diagnostic by energy-resolved mass spectrometry and deposited film characterization by XRD, XRR, AFM, profilometry and SEM were carried out. The ion potential energy influences the preferential direction of film growth or a polycrystalline growth in the case of aluminum deposition. This result could be a starting point for further research into the effect of ion potential energy on film deposition

    Subgroup discovery for structured target concepts

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    The main object of study in this thesis is subgroup discovery, a theoretical framework for finding subgroups in data—i.e., named sub-populations— whose behaviour with respect to a specified target concept is exceptional when compared to the rest of the dataset. This is a powerful tool that conveys crucial information to a human audience, but despite past advances has been limited to simple target concepts. In this work we propose algorithms that bring this framework to novel application domains. We introduce the concept of representative subgroups, which we use not only to ensure the fairness of a sub-population with regard to a sensitive trait, such as race or gender, but also to go beyond known trends in the data. For entities with additional relational information that can be encoded as a graph, we introduce a novel measure of robust connectedness which improves on established alternative measures of density; we then provide a method that uses this measure to discover which named sub-populations are more well-connected. Our contributions within subgroup discovery crescent with the introduction of kernelised subgroup discovery: a novel framework that enables the discovery of subgroups on i.i.d. target concepts with virtually any kind of structure. Importantly, our framework additionally provides a concrete and efficient tool that works out-of-the-box without any modification, apart from specifying the Gramian of a positive definite kernel. To use within kernelised subgroup discovery, but also on any other kind of kernel method, we additionally introduce a novel random walk graph kernel. Our kernel allows the fine tuning of the alignment between the vertices of the two compared graphs, during the count of the random walks, while we also propose meaningful structure-aware vertex labels to utilise this new capability. With these contributions we thoroughly extend the applicability of subgroup discovery and ultimately re-define it as a kernel method.Der Hauptgegenstand dieser Arbeit ist die Subgruppenentdeckung (Subgroup Discovery), ein theoretischer Rahmen für das Auffinden von Subgruppen in Daten—d. h. benannte Teilpopulationen—deren Verhalten in Bezug auf ein bestimmtes Targetkonzept im Vergleich zum Rest des Datensatzes außergewöhnlich ist. Es handelt sich hierbei um ein leistungsfähiges Instrument, das einem menschlichen Publikum wichtige Informationen vermittelt. Allerdings ist es trotz bisherigen Fortschritte auf einfache Targetkonzepte beschränkt. In dieser Arbeit schlagen wir Algorithmen vor, die diesen Rahmen auf neuartige Anwendungsbereiche übertragen. Wir führen das Konzept der repräsentativen Untergruppen ein, mit dem wir nicht nur die Fairness einer Teilpopulation in Bezug auf ein sensibles Merkmal wie Rasse oder Geschlecht sicherstellen, sondern auch über bekannte Trends in den Daten hinausgehen können. Für Entitäten mit zusätzlicher relationalen Information, die als Graph kodiert werden kann, führen wir ein neuartiges Maß für robuste Verbundenheit ein, das die etablierten alternativen Dichtemaße verbessert; anschließend stellen wir eine Methode bereit, die dieses Maß verwendet, um herauszufinden, welche benannte Teilpopulationen besser verbunden sind. Unsere Beiträge in diesem Rahmen gipfeln in der Einführung der kernelisierten Subgruppenentdeckung: ein neuartiger Rahmen, der die Entdeckung von Subgruppen für u.i.v. Targetkonzepten mit praktisch jeder Art von Struktur ermöglicht. Wichtigerweise, unser Rahmen bereitstellt zusätzlich ein konkretes und effizientes Werkzeug, das ohne jegliche Modifikation funktioniert, abgesehen von der Angabe des Gramian eines positiv definitiven Kernels. Für den Einsatz innerhalb der kernelisierten Subgruppentdeckung, aber auch für jede andere Art von Kernel-Methode, führen wir zusätzlich einen neuartigen Random-Walk-Graph-Kernel ein. Unser Kernel ermöglicht die Feinabstimmung der Ausrichtung zwischen den Eckpunkten der beiden unter-Vergleich-gestelltenen Graphen während der Zählung der Random Walks, während wir auch sinnvolle strukturbewusste Vertex-Labels vorschlagen, um diese neue Fähigkeit zu nutzen. Mit diesen Beiträgen erweitern wir die Anwendbarkeit der Subgruppentdeckung gründlich und definieren wir sie im Endeffekt als Kernel-Methode neu

    Jake pozicione igre

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    In this thesis, we study 2-player combinatorial games on graphs. We devote a lot of attention to strong positional games, where both players have the same goal. First, we consider the so-called fixed graph strong Avoider-Avoider game in which two players called Red and Blue alternately claim edges of the complete graph Kn, and the player who first completes a copy of a fixed graph F loses the game. If neither of the players claimed a copy of F in his graph and all the elements of the board are claimed, the game is declared a draw. Even though these games have been studied for decades, there are very few known results. We make a step forward by proving that Blue has a winning strategy it two different games of this kind. Furthermore, we introduce strong CAvoiderCAvoider F games where the claimed edges of each player must form a connected graph throughout the game. This is a natural extension of the strong Avoider-Avoider games, with a connectedness constraint. We prove that Blue can win in three standard CAvoider-CAvoider F games. Next, we study strong Maker-Maker F games, where now, the player who first occupies a copy of F is the winner. It is well-known that the outcome of these games when both players play optimally can be either the first player's win or a draw. We are interested in finding the achievement number a(F) of a strong Maker-Maker F game, that is, the smallest n for which Red has a winning strategy. We can find the exact value a(F) for several graphs F, including paths, cycles, perfect matchings, and a subclass of trees on n vertices. We also give the upper and lower bounds for the achievement number of stars and trees. Finally, we introduce generalized saturation games as a natural extension of two different types of combinatorial games, saturation games and Constructor-Blocker games. In the generalized saturation game, two graphs H and F are given in advance. Two players called Max and Mini alternately claim unclaimed edges of the complete graph Kn and together gradually building the game graph G, the graph that consists of all edges claimed by both players. The graph G must never contain a copy of F, and the game ends when there are no more moves, i.e. when G is a saturated F-free graph. We are interested in the score of this game, that is, the number of copies of the graph H in G at the end of the game. Max wants to maximize this score, whereas Mini tries to minimize it. The game is played under the assumption that both players play optimally. We study several generalized saturation games for natural choices of F and H, in an effort to locate the score of the game as precisely as possible.У овој тези проучавамо комбинаторне игре на графовима које играју 2 играча. Посебну пажњу посвећујемо јаким позиционим играма, у којима оба играча имају исти циљ. Прво, посматрамо такозвану јаку Авојдер-Авојдер игру са задатим фиксним графом у којој два играча, Црвени и Плави наизменично селектују гране комплетног графа Kn, а играч који први селектује копију фиксног графа F губи игру. Ако ниједан од играча не садржи копију од F у свом графу и сви елементи табле су селектовани, игра се проглашава нерешеном. Иако су ове игре проучаване деценијама, врло је мало познатих резултата. Ми смо направили корак напред доказавши да Плави има победничку стратегију у две различите игре ове врсте. Такође, уводимо јаке ЦАвојдер-ЦАвојдер F игре у којима граф сваког играча мора остати повезан током игре. Ово је природно проширење јаких Авојдер-Авојдер игара, са ограничењем повезаности. Доказујемо да Плави може да победи у три стандардне ЦАвојдер-ЦАвојдер F игре. Затим проучавамо јаке Мејкер-Мејкер F игре, у којима је играч који први селектује копију од F победник. Познато је да исход ових игара уколико оба играча играју оптимално може бити или победа првог играча или нерешено. Циљ нам је да пронађемо ачивмент број а(F) јаке Мејкер-Мејкер F игре, односно најмање n за које Црвени има победничку стратегију. Дајемо тачну вредност a(F) за неколико графова F, укључујући путеве, циклусе, савршене мечинге и поткласу стабала са n чворова. Такође, дајемо горње и доње ограничење ачивмент броја за звезде и стабла. Коначно, уводимо уопштене игре сатурације као природно проширење две различите врсте комбинаторних игара, игара сатурације и Конструктор-Блокер игара. У уопштеној игри сатурације унапред су дата два графа H и F. Два играча по имену Макс и Мини наизменично селектују слободне гране комплетног графа Kn и заједно постепено граде граф игре G, који се састоји од свих грана које су селектовала оба играча. Граф G не сме да садржи копију од F, а игра се завршава када више нема потеза, односно када је G сатуриран граф који не садржи F. Занима нас резултат ове игре, односно, број копија графа H у G на крају игре. Макс жели да максимизира овај резултат, док Мини покушава да га минимизира. Игра се под претпоставком да оба играча играју оптимално. Проучавамо неколико уопштених игара сатурације за природне изборе F и H, у настојању да што прецизније одредимо резултат игре.U ovoj tezi proučavamo kombinatorne igre na grafovima koje igraju 2 igrača. Posebnu pažnju posvećujemo jakim pozicionim igrama, u kojima oba igrača imaju isti cilj. Prvo, posmatramo takozvanu jaku Avojder-Avojder igru sa zadatim fiksnim grafom u kojoj dva igrača, Crveni i Plavi naizmenično selektuju grane kompletnog grafa Kn, a igrač koji prvi selektuje kopiju fiksnog grafa F gubi igru. Ako nijedan od igrača ne sadrži kopiju od F u svom grafu i svi elementi table su selektovani, igra se proglašava nerešenom. Iako su ove igre proučavane decenijama, vrlo je malo poznatih rezultata. Mi smo napravili korak napred dokazavši da Plavi ima pobedničku strategiju u dve različite igre ove vrste. Takođe, uvodimo jake CAvojder-CAvojder F igre u kojima graf svakog igrača mora ostati povezan tokom igre. Ovo je prirodno proširenje jakih Avojder-Avojder igara, sa ograničenjem povezanosti. Dokazujemo da Plavi može da pobedi u tri standardne CAvojder-CAvojder F igre. Zatim proučavamo jake Mejker-Mejker F igre, u kojima je igrač koji prvi selektuje kopiju od F pobednik. Poznato je da ishod ovih igara ukoliko oba igrača igraju optimalno može biti ili pobeda prvog igrača ili nerešeno. Cilj nam je da pronađemo ačivment broj a(F) jake Mejker-Mejker F igre, odnosno najmanje n za koje Crveni ima pobedničku strategiju. Dajemo tačnu vrednost a(F) za nekoliko grafova F, uključujući puteve, cikluse, savršene mečinge i potklasu stabala sa n čvorova. Takođe, dajemo gornje i donje ograničenje ačivment broja za zvezde i stabla. Konačno, uvodimo uopštene igre saturacije kao prirodno proširenje dve različite vrste kombinatornih igara, igara saturacije i Konstruktor-Bloker igara. U uopštenoj igri saturacije unapred su data dva grafa H i F. Dva igrača po imenu Maks i Mini naizmenično selektuju slobodne grane kompletnog grafa Kn i zajedno postepeno grade graf igre G, koji se sastoji od svih grana koje su selektovala oba igrača. Graf G ne sme da sadrži kopiju od F, a igra se završava kada više nema poteza, odnosno kada je G saturiran graf koji ne sadrži F. Zanima nas rezultat ove igre, odnosno, broj kopija grafa H u G na kraju igre. Maks želi da maksimizira ovaj rezultat, dok Mini pokušava da ga minimizira. Igra se pod pretpostavkom da oba igrača igraju optimalno. Proučavamo nekoliko uopštenih igara saturacije za prirodne izbore F i H, u nastojanju da što preciznije odredimo rezultat igre

    30th European Congress on Obesity (ECO 2023)

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    This is the abstract book of 30th European Congress on Obesity (ECO 2023

    An examination of the temperamental and ability characteristics of large animals under open-field and stress conditions

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    In this study an attempt was made to adapt two tests, developed for use with rats and mice, for work with the larger animals in order to assess their worth for measuring the temperamental and ability characteristics of domestic farm species. To assess the temperamental characteristics an open-field, scaled to 72 feet by 72 feet, was used to score 30 pigs, 30 sheep and 44 cows on three criteria; ambulation, elimination and vocalisation. These scores were correlated with dairymen’s ratings of the cows and plasma cortisol levels in the sheep. It became clear that the open-field test requires further modification before it can provide meaningful results for domestic stock. The closed-field test was used with 63 pigs, 103 sheep, and 73 cows to measure the “intelligence” of normal farm animals. Time and error scores and general behaviour were recorded and analysed, and showed characteristic species differences. In the evaluation of scores from both tests the importance of group effects found in herd animals was considered. A relationship between the closed-field test performance, and the social status of the animals in each test group was considered. Practical problems such as; animal-experimenter interactions; adequate motivation of ruminants; the impossibility of man-handling large animals like cows, and the kind of modifications which must be made to apparatus for this type of work ,are fully discussed. Isolating herd or flock animals appears to cause stress. The results of the closed-field test were compared with similar results from other studies where mice, rats, cats, dogs, ferrets, hens and other species have been tested in smaller versions of the closed-field. The general conclusion is that the potential for training, or utilising in other ways the ability inherent in the farm animal in New Zealand has hardly been touched. Though a number of experimenters have commented on these abilities during trials in research institutions such information has not been fully exploited in normal farm practice

    Prognostic research:Methodological aspects and applications in acute care

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    The effectiveness and determinants of effectiveness of antiretroviral therapy for adults in the Western Cape Province of South Africa

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    Antiretroviral therapy (ART) first became available in the public sector in the Western Cape Province in Khayelitsha in 2001. This thesis describes the effectiveness of ART in Khayelitsha and the Province, following adult patients for up to five years on ART, and examining temporal trends over seven years during which time the availability of ART in the Province increased dramatically. Associations are explored with a range of clinical outcomes, and regimen durability and tolerability are described, together with regimen effectiveness when ART is administered to patients co-infected with tuberculosis. The results chapters of the thesis are presented in the form of published or submitted papers. The first paper corrects for under-ascertainment of mortality through linkages with the death registry. After five years on ART, four out of five patients were still alive. Survival did not deteriorate in more recent years despite the large increase in patient numbers. Patients who remained virologically suppressed experienced on average continued CD4 count recovery throughout follow-up to five years. The second paper describes the tolerability of each commonly used first-line antiretroviral drug in two townships in the Western Cape. Treatment-limiting toxicities were frequent and continued throughout follow-up in patients on stavudine (21% by 3 years on ART). Symptomatic hyperlactataemia or lactic acidosis as well as lipodystrophy were strongly associated with women initiating ART with a high initial body mass. The third paper explores the effectiveness of ART when co-administered with tuberculosis treatment, identifying that co-infected patients initiating nevirapinebased ART may be at a higher risk of virological failure, but that concurrent tuberculosis treatment did not otherwise compromise ART outcomes. The fourth paper, based on a household survey, provides an in-depth description of the Khayelitsha population demonstrating comparability with many of the urban settings in which ART is provided in the region. The final paper demonstrates that outcomes have not been compromised by the wider availability of ART in the Western Cape Province. The thesis concludes that the Khayelitsha and Provincial analyses provide considerable reassurance that the anticipated benefits of ART have not to date been eroded by health system weaknesses or contextual challenges
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