Em diversos levantamentos científicos, nos deparamos com a dificuldade de coletar os dados devido ao objeto em estudo ser de difícil observação, como por exemplo em estudos com indivíduos portadores de doenças raras, ou dotados de um comportamento evasivo, ou ainda indivíduos que distribuem-se de maneira geograficamente esparsa. Neste trabalho estudamos esquemas de amostragem voltados para populações raras com especial atenção às populações raras e agrupadas. Nos aprofundamos nas técnicas de amostragem por conglomerados adaptativos e amostragem seqüencial em dois estágios, fornecendo ao leitor subsídio teórico para entender os fundamentos das técnicas, bem como compreender a eficácia de seus estimadores apresentada em estudos de simulações. Em nossos estudos de simulação, mostramos que a técnica de amostragem seqüencial em dois estágios não apresenta perdas de eficiência quando o agrupamento dos elementos é menor. Entretanto, os estudos comparativos revelam que quando a população é rara e agrupada, a eficiência para a amostragem por conglomerados adaptativos é maior na maioria das parametrizações utilizadas. Ao final deste trabalho, fornecemos recomendações para as situações a respeito do conhecimento da raridade e agrupamento da população em estudo. / In many surveys we find hard observing individuals, like in rare diseases, elusive individuals or sparsely distributed individuals. This work is about sampling schemes for rare populations, more specifically rare and clustered, driving our attention to adaptive cluster sampling and two stage sequential sampling giving readers their theoretical basis and simulated efficiencies evaluation. In our simulation studies, we found that the efficiency of two-stage sequential sampling does not decrease when sample clustering is low. However, the comparison studies show that when sample is rare and clustered, adaptive cluster sampling in the majority of tested cases has better efficiency. At the end of this study, there are recommendations for each situation of knowing rarity and clustering of the population in study.

Made available in DSpace on 2014-08-20T14:31:30Z (GMT). No. of bitstreams: 1 dissertacao_andrio_zafalon_silva.pdf: 3030038 bytes, checksum: a10638c2996d28623646b9fa7980b243 (MD5) Previous issue date: 2013-07-05 / The fragmentation of natural environments is a major concern among conservation ecologists nowadays, especially in areas with a great diversity of habitats as the coastal plains of Rio Grande do Sul. In order to provide the basis to the managers responsible for the maintenance of natural areas, as well as to develop the knowledge of the Muscidae family in the southern Brazil, this study aimed to determine the biodiversity of the Muscidae family, in addition to proposing a method to evaluate the pattern of the species-area relationship (SAR) without using a different sampling effort between the areas of different sizes. To do that, 140 Malaise traps were installed distributed in 35 areas of five regions in the Coastal Plains. Each region was composed of seven areas with four traps at proportional distances. A total of 6102 individuals were collected distributed among 120 species/morphspecies in the five regions. Based on the lists it can be stated the degree of conservation and the anthropic influence on the studied areas, mainly by the presence of the species of Muscinae and Coenosiinae. The similarity between the communities of Muscidae was determined by the proximity of the collection places or by the climatic conditions of the period, and it was also observed a positive relationship in the species-area relationship for the linear and logistic models. Although the model with the power function is not significant, it showed coefficients that allow the interpretation of the types of fragments that occur in the coastal plains of RS. / A fragmentação das áreas naturais é uma das maiores preocupações entre os ecólogos da conservação na atualidade, principalmente em áreas com uma grande diversidade de habitats como a Planície Costeira do Rio Grande do Sul. A fim de prover embasamento aos gestores responsáveis pela manutenção das áreas naturais e desenvolver o conhecimento sobre a família Muscidae no sul do Brasil, o presente estudo objetivou conhecer a biodiversidade da família Muscidae, além de propor um método para a avaliação do padrão de relacionamento espécie área (SAR) sem utilizar esforço amostral distinto entre as áreas de diferentes tamanhos. Para isso, foram instaladas 140 armadilhas Malaise distribuídas em 35 áreas de cinco regiões na Planície Costeira. Cada região foi composta por sete áreas com quatro armadilhas com distâncias proporcionais. Foram coletados 6102 indivíduos distribuídos entre 120 espécies/morfoespécies nas cinco regiões. A partir das listas podemos constatar o grau de conservação e a influência da ação antrópica nas áreas naturais amostradas, principalmente pela presença de espécies de Muscinae e Coenosiinae. A similaridade entre as comunidades de Muscidae foi determinada pela proximidade entre os locais de coletas ou pelas condições climáticas do período, e observamos ainda uma relação positiva no relacionamento espécie-área para os modelos linear e logístico. Apesar do modelo com a função de poder não ser significativo, apresentou coeficientes que possibilitam a interpretação dos tipos de fragmentos que existem na planície costeira do RS.

Les nouveaux besoins en communications sans fil pussent le développement de systèmes de transmission RF en termes the reconfigurabilité, multistandard et à basse consommation. Ces travaux de thèse font l’objet de la proposition d’une nouvelle architecture de réception capable d’adresser ces aspects dans le contexte des réseaux WPAN. La technique de sous échantillonnage (BPS-Bandpass Sampling) est appliquée et permet d’exploiter et certain nombre d’avantages liées au traitement du signal à Temps Discret (DT-Discrete Time signal processing), notamment le filtrage et la décimation. Si comparées à la Radio Logicielle, ces techniques permettent de relâcher les contraintes liées aux ADCs en maintenant des caractéristiques multistandard et de reconfigurabilité. Un simulateur dans le domaine fréquentiel large bande a été développé sous MATLAB pour répondre à des limitations au niveau système comme par exemple le repliement spectral et le produit gain bande. En addition avec une nouvelle méthode de conception système, cet outil permet de séparer les différentes contraintes des blocs pour la définition d’un plan de fréquence et the filtrage optimaux. La séparation des différentes contributions dans la dégradation du SNDR (notamment le bruit thermique, bruit de phase, non linéarité et le repliement), permet de relâcher de spécifications critiques liées à la consommation de puissance. L’architecture à sous échantillonnage proposée dans la thèse est résultat d’une comparaison quantitative des différentes architectures à sous échantillonnage, tout en appliquant la méthode et l’outil de conception système développés. Des aspects comme l’optimisation du filtrage entre les techniques à temps continu et temps discret et le plan de fréquence associé, permettent de trouve l’architecture qui représente le meilleur compromis entre la consommation électrique et l’agilité, dans le contexte voulu. Le bloc de filtrage à temps discret est identifié comme étant critique, et une étude sur les limitations d’implémentation circuit est menée. Des effets come les capacités parasites, l’imparité entre les capacités, le bruit du commutateur, la non linéarité, le gain finit de Ampli OP, sont évalués à travers d’une simulation comportementale en VHDL-AMS. On observe la robustesse des circuits orientés temps discret par rapport les contraintes des nouvelles technologies intégrés. Finalement, le système est spécifié en termes de bruit de phase, qui peuvent représenter jusqu’à 30% de la consommation en puissance. Dans ce but, une nouvelle méthode numérique est proposée pour être capable d’évaluer le rapport signal sur distorsion due au jitter SDjR dans le processus de sous échantillonnage. En plus, une conclusion non intuitive est survenue de cette étude, où on que réduire la fréquence d’échantillonnage n’augmente pas les contraintes en termes de jitter pour le système. L’architecture proposée issue de cette étude est sujet d’un développement circuit pour la validation du concept. / New needs on wireless communications pushes the development in terms reconfigurable, multistandards and low power radio systems. The objective of this work is to propose and design new receiver architecture capable of addressing these aspects in the context of the WPAN networks. The technique of Bandpass Sampling (BPS) is applied and permits to exploit a certain number of advantages linked to the discrete time (DT) signal processing, notably filtering and decimation. Compared to the Software-defined Radio (SDR), these techniques permit to relax the ADC constraints while keeping the multi standard and reconfigurable features. A wide band system level simulation tool is developed using MATLAB platform to overcome system level limitations such spectral aliasing and gain bandwidth product. In addition to a new system design method, the tool helps separating the blocks constraints and defining the optimum frequency plan and filtering. Separating the different contributions on the SNDR degradation (noise, phase noise, non linearity, and aliasing), critical specifications for power consumption can be relaxed. The proposed BPS architecture on the thesis is a result of a quantitative comparison of different BPS architectures, applying the system design method and tool. Aspects such filtering optimization between continuous and discrete time filtering and the associated frequency plan permitted to find the architecture which represents the best trade-off between power consumption and agility on the aimed context. The DT filtering block is therefore identified as critical block, which a study on the circuit implementation limitations is carried out. Effects such parasitic capacitances and capacitance mismatch, switch noise, non linear distortion, finite gain OTA, are evaluated through VHDL-AMS modelling. It is observed the robustness of discrete time oriented circuits. Finally, phase noise specifications are given considering that frequency synthesis circuits may represent up to 30% of the power consumption. For that goal, a new numerical method is proposed, capable of evaluating the signal to jitter distortion ratio SDjR on the BPS process. Moreover, a non intuitive conclusion is given, where reducing the sampling frequency does not increase the constraints in terms of jitter. The proposed architecture issue from this study is in stage of circuit level design in the project team of LETI for final proof of concept.

The automation of most of our activities has led to the continuous production of data that arrive in the form of fast-arriving streams. In a supervised learning setting, instances in these streams are labeled as belonging to a particular class. When the number of classes in the data stream is more than two, such a data stream is referred to as a multi-class data stream. Multi-class imbalanced data stream describes the situation where the instance distribution of the classes is skewed, such that instances of some classes occur more frequently than others. Classes with the frequently occurring instances are referred to as the majority classes, while the classes with instances that occur less frequently are denoted as the minority classes. Classification algorithms, or supervised learning techniques, use historic instances to build models, which are then used to predict the classes of unseen instances. Multi-class imbalanced data stream classification poses a great challenge to classical classification algorithms. This is due to the fact that traditional algorithms are usually biased towards the majority classes, since they have more examples of the majority classes when building the model. These traditional algorithms yield low predictive accuracy rates for the minority instances and need to be augmented, often with some form of sampling, in order to improve their overall performances. In the literature, in both static and streaming environments, most studies focus on the binary class imbalance problem. Furthermore, research in multi-class imbalance in the data stream environment is limited. A number of researchers have proceeded by transforming a multi-class imbalanced setting into multiple binary class problems. However, such a transformation does not allow the stream to be studied in the original form and may introduce bias. The research conducted in this thesis aims to address this research gap by proposing a novel online learning methodology that combines oversampling of the minority classes with cluster-based majority class under-sampling, without decomposing the data stream into multiple binary sets. Rather, sampling involves continuously selecting a balanced number of instances across all classes for model building. Our focus is on improving the rate of correctly predicting instances of the minority classes in multi-class imbalanced data streams, through the introduction of the Synthetic Minority Over-sampling Technique (SMOTE) and Cluster-based Under-sampling - Data Streams (SCUT-DS) methodologies. In this work, we dynamically balance the classes by utilizing a windowing mechanism during the incremental sampling process. Our SCUT-DS algorithms are evaluated using six different types of classification techniques, followed by comparing their results against a state-of-the-art algorithm. Our contributions are tested using both synthetic and real data sets. The experimental results show that the approaches developed in this thesis yield high prediction rates of minority instances as contained in the multiple minority classes within a non-evolving stream.

Le déclin du thon rouge de l'Atlantique nord-est et de Méditerranée (ABFT, Thunnus thynnus) qui faisait suite à une forte surexploitation a été largement médiatisé au cours de la dernière décennie. Pour contrer cette tendance et reconstituer ce stock, d’importantes mesures de gestion ont été mises en place à partir de 2007. En dehors des difficultés liées à leur mise en œuvre et à leur contrôle, la gestion des pêcheries thonières est aussi limitée dans les capacités à suivre précisément les variations d’abondance de ces espèces dont les observations reposent principalement sur les données de pêche. Le manque d’indice d’abondance fiable fait que l’évaluation du thon rouge, comme celle des autres espèces de poissons grands pélagiques, est entachée d’importantes incertitudes. Cependant, les suivis aériens pourraient permettre de fournir un indice d’abondance du thon rouge. Ils sont en effet fréquemment utilisés pour l'évaluation de l'abondance des mammifères marins et aussi par les pêcheurs pour détecter les poissons épipélagiques, comme les thons. Dans ce contexte général, cette thèse a pour objectifs : (i) d'évaluer des facteurs qui affectent potentiellement la détectabilité des thons pendant les suivis aériens, (ii) d’analyser leur comportement horizontal et vertical et les facteurs environnementaux qui l’influencent, et (iii) d’intégrer les connaissances acquises pour développer un indice abondance robuste du thon rouge en Méditerranée Nord Occidentale. Les analyses reposent sur des suivis aériens conduits depuis 2000 dans le golfe du Lion, une zone de nourricerie importante pour le thon rouge. Une modélisation des données basée sur le « distance sampling » montre des effets significatifs des observateurs, de la taille des bancs de thons et de l'état de la mer sur l’estimation d’abondance. Cette étude confirme par ailleurs une augmentation importance des abondances entre 2003 et 2009, probablement en réponse aux mesures de gestion mises en œuvre depuis 2007 (notamment la taille minimale de débarquement de 30 kg). Pour évaluer les effets du comportement sur les estimations d'abondance, une étude a porté sur les trajectoires de thons issues du marquage électronique. Ces analyses montrent une disponibilité des thons rouge ainsi qu’une présence en surface dans la zone et la période (Août-Octobre) des suivis aériens ; résultat confortant la fiabilité de l’indice d’abondance. On note également des changements saisonniers du comportement, avec un approfondissement des thons à partir de mi-Novembre correspondant à la dé-stratification de la colonne d’eau. Le comportement de plongée profonde était particulièrement fréquent pendant les mois de forte productivité biologique (février-Mai), mais des plongées profondes ont également été observées à la fin de l'été en relation avec des fronts thermiques. La variabilité des schémas migratoires sur l’horizontale et du comportement sur la verticale indique une forte composante opportuniste, probablement liée à la disponibilité des ressources alimentaires. Les résultats obtenus durant cette thèse démontrent la faisabilité d’obtenir un indice d’abondance de thon rouge robuste à partir des suivis aériens (donc indépendants des données de pêche) et fournissent un cadre théorique et méthodologique pour une extension de ce type de suivi afin de diminuer les incertitudes autour de l’évaluation de ce stock. Outre le thon rouge, les suivis aériens ont également permis un suivi du rorqual commun (Balaenoptera physalus) et des dauphins rayés (Stenella coeruleoalba). La présence des mammifères marins semble également être liée à la productivité élevée et l'activité méso-échelle de la zone d'étude. Si les dauphins présentent une distribution spatiale en partie corrélée à celle du thon rouge, les rorquals ne présentent pas de forte co-occurrence avec le thon rouge, résultat qui confirmerait une certaine proximité des régimes alimentaires des thons et des dauphins. / Declines in Atlantic bluefin tuna stocks (ABFT, Thunnus thynnus), due to extensive over-fishing, have been widely publicized in recent decades. To counteract this trend, regulatory measures have been introduced by the fisheries managers, aiming at the rebuilding of ABFT stocks. However, apart from difficulties in controlling the implementation of these measures, fisheries management is limited in its capabilities to track their efficiency due to major uncertainties in the stock assessment. Indeed, there is a general need of reliable indicators of ABFT abundance. Aerial surveys may provide a helpful tool for the abundance monitoring of this highly exploited fish species. They are frequently used for the abundance assessment of marine mammals and also by fishermen to detect epipelagic fish, such as tunas. The aim of this thesis was to address these issues and to create a robust fishery-independent abundance index for ABFT through aerial surveys. To achieve this goal, the focus was set on (i) the assessment of factors that potentially affect the detectability of ABFT during the aerial surveys, (ii) the habitat use of ABFT, i.e. their horizontal and vertical behaviour as well as the factors driving it, and (iii) the integration of the knowledge gained through these analyses in the development of a robust index of ABFT abundance. Surveys were conducted from 2000 onwards in the Gulf of Lions, an important nursery ground for ABFT in the Northwestern Mediterranean Sea. Line transect modelling of the sighting data revealed significant effects of detectability changes on abundance estimates, related to the observer teams employed, the size of detected ABFT schools and the sea state during the aerial surveys. Derived estimates of ABFT abundance confirmed a significant increase from 2003 to 2009, likely reflecting the success of recently implemented management measures (e.g. minimum landing size of 30 kg since 2007). To assess behavioural effects on abundance estimates, auxiliary archival tagging experiments, conducted since 2007, focused on the presence and surface availability of ABFT during the aerial surveys, and aimed to identify factors influencing these variables. The data gained from these experiments demonstrated seasonal changes in the migratory behaviour of ABFT, but also a high area and surface presence of ABFT in the study zone during the survey period (August–October), supporting the reliability of the abundance index. Surface presence of ABFT decreased with the breakdown of the thermal stratification of the water column (mid-November), when the fish left the survey zone and moved South. By contrast, deep diving behaviour was particularly frequent during months of high biological productivity (February--May), although deep and unusual long spike dives were also observed during late summer in relation to thermal fronts. However, the variability in the migration patterns indicates a strong opportunistic component in both, the horizontal and vertical behaviour of ABFT, probably related to the availability of food resources. Apart from ABFT, the aerial surveys also allowed an abundance monitoring of fin whales (Balaenoptera physalus) and striped dolphins (Stenella coeruleoalba) as well as an analysis of their co-occurrence with ABFT. In fact, similar to ABFT, the presence of these species appeared to be related to the high productivity and mesoscale activity of the study zone, improving our understanding of their habitat use, essential for the conservation of these much less abundant and endangered species. Regarding the stock assessment of ABFT, the results gained through this thesis prove the feasibility to derive robust fishery independent abundance indicators for ABFT through aerial surveys, providing the theoretical and methodological background for an extension of these efforts for a more sustainable management of the stocks of this species.

Among the different sensory modalities that play a role in sexual selection, acoustic communication plays an important one. Acoustic communication has been known to be used for male-male competition (territory maintenance, male aggression during mating),for advertisement to the opposite sex (mating status, body condition, genetic quality, nutritional status) and used by females to sample and choose conspecific preferred males. The use of acoustic communication for sexual display and information exchange has been extensively studied in multiple taxa, including insects, anurans, birds and mammals. Among insects, crickets have proven to be good model systems to study sexual selection based on acoustic communication as most species have an elaborate acoustic communication system, male advertisements, diverse types of mating incentives for females (such as glandular feeding) and a female dominated mating system. Generally, in crickets males produce species-specific calls which are used by females to localize conspecific males. Besides, calls show high levels of intraspecific variation and are energetically costly to produce. Moreover, as in crickets predominantly the females show phonotaxis towards male calls, calls also can play a role in mate sampling and choice by acting as indicators of preferred male quality. Despite being studied for many decades there are certain gaps in the studies examining mate choice in crickets. Some of them are, lack of understanding of the variation of male calling traits in nature and its role in signal evolution, lack of understanding regarding the ecological context of mate sampling and the evolution of alternative mating strategies. Hence, the tree cricket Oecanthus henryi was chosen as a study system to address these gaps in the understanding of female choice based on acoustic signals. In the tree cricket Oecanthus henryi, males call and females use calls to localize conspecific males and hence potentially females can choose males based on acoustic cues. To understand the evolution of female preference for male acoustic cues it is important to understand the variation in the calling songs in the field and identify repeatable call features that are reliable indicators of preferred male traits (morphological, developmental or genetic). I measured repeatability of male call traits in the field to understand their variation, reliability and consistency. Carrier frequency was the only call trait that was highly repeatable and hence was reliable and consistent. Following this I examined whether any of these call traits were indicators of male morphological traits (such as male size and fluctuating asymmetry) which are known to be preferred by females. It was found that carrier frequency was negatively correlated with body size; hence carrier frequency was both reliable and indicated male size. I also found that females preferred larger males during mating, as revealed by the longer mating durations and longer spermatophore retention time. Interestingly, though this study indicated that females could in principle use lower call carrier frequency to localize preferred larger males, simultaneous choice experiments done in the laboratory revealed that the females do not use this cue. These contrasting results may be because females are incapable of discriminating small differences in frequency or because they use non-acoustic cues for mate choice. However, whichever cues the females use to discriminate between males in the laboratory conditions, often these preferences are not realized in the field. The main reason behind this is that searching for preferred mates in the field can be costly and this might force females to choose sub-optimal males. Theoretical models predict that male movement and spacing in the field should influence female sampling tactics and in turn, females should drive the evolution of male movement and spacing to sample them optimally. Moreover, simultaneous sampling of males using the best-of-n or comparative Bayes strategy should yield maximum mating benefits to females. Many of the theoretical mate sampling strategies involves recall of the quality and location of individual males, which in turn requires male positions to be stable within a night. Calling males of O. henryi showed high site fidelity within a night, potentially enabling female sampling strategies that require recall. To examine the possibility of simultaneous acoustic sampling of males, I estimated male acoustic active spaces using information on male spacing, call transmission and female phonotactic threshold. Males were found to be spaced far apart and active space overlap was rare. I then examined female sampling scenarios by studying female spacing relative to male acoustic active spaces. Only 15% of sampled females could hear multiple males, suggesting that simultaneous mate sampling is rare in the field. Moreover, the relatively large distances between calling males suggest high search costs, which may favor threshold strategies that do not require memory. Using the insights gathered from these two studies I examined a unique calling behaviour from leaf holes, baffling, observed in this species. Baffling behaviour has been found in multiple species of the genus Oecanthus where the males call from selfmade holes in leaves rather than calling from leaf edges (their natural calling surface) thus increasing their loudness many fold. I started by examining the natural history of baffling and found that baffling is an extremely rare behaviour in the field. However field observations and laboratory experiments revealed that many males can baffle and hence it is not an obligatory behaviour shown only by a few males. It was hypothesized that one reason for the rarity of baffling could be resource limitation. It was found that baffling males prefer larger leaves possibly due to higher SPL gains achieved by baffling on the larger leaves, which is a limited resource in the field. However this alone was insufficient to explain extreme rarity of bafflers in the field. Hence I examined which males were using this behaviour in the field. Using field observations and laboratory experiments it was found that less preferred males (smaller and quieter) baffled more which provided them with higher calling SPL and greater sound-field volume and thus a higher number of potential mates. Moreover, baffling also increased the mating duration for the less preferred males thus providing more time to these males for sperm transfer. The females could not differentiate between an inherently loud caller and a caller whose SPL was increased artificially (as if it was baffling). Hence I concluded that baffling is probably a cheater strategy used by the less preferred males to fool the females into approaching them and mating for longer durations. To my knowledge, this is the first study that has estimated male call variation in the field to understand its role in female choice in tree crickets. Moreover this is also the first study to examine the ecological context of mate choice in tree crickets. This is also the first study to examine the advantages of baffling behaviour and its potential evolutionary implications. the different sensory modalities that play a role in sexual selection, acoustic communication plays an important one. Acoustic communication has been known to be used for male-male competition (territory maintenance, male aggression during mating),for advertisement to the opposite sex (mating status, body condition, genetic quality, nutritional status) and used by females to sample and choose conspecific preferred males. The use of acoustic communication for sexual display and information exchange has been extensively studied in multiple taxa, including insects, anurans, birds and mammals. Among insects, crickets have proven to be good model systems to study sexual selection based on acoustic communication as most species have an elaborate acoustic communication system, male advertisements, diverse types of mating incentives for females (such as glandular feeding) and a female dominated mating system. Generally, in crickets males produce species-specific calls which are used by females to localize conspecific males. Besides, calls show high levels of intraspecific variation and are energetically costly to produce. Moreover, as in crickets predominantly the females show phonotaxis towards male calls, calls also can play a role in mate sampling and choice by acting as indicators of preferred male quality. Despite being studied for many decades there are certain gaps in the studies examining mate choice in crickets. Some of them are, lack of understanding of the variation of male calling traits in nature and its role in signal evolution, lack of understanding regarding the ecological context of mate sampling and the evolution of alternative mating strategies. Hence, the tree cricket Oecanthus henryi was chosen as a study system to address these gaps in the understanding of female choice based on acoustic signals. In the tree cricket Oecanthus henryi, males call and females use calls to localize conspecific males and hence potentially females can choose males based on acoustic cues. To understand the evolution of female preference for male acoustic cues it is important to understand the variation in the calling songs in the field and identify repeatable call features that are reliable indicators of preferred male traits (morphological, developmental or genetic). I measured repeatability of male call traits in the field to understand their variation, reliability and consistency. Carrier frequency was the only call trait that was highly repeatable and hence was reliable and consistent. Following this I examined whether any of these call traits were indicators of male morphological traits (such as male size and fluctuating asymmetry) which are known to be preferred by females. It was found that carrier frequency was negatively correlated with body size; hence carrier frequency was both reliable and indicated male size. I also found that females preferred larger males during mating, as revealed by the longer mating durations and longer spermatophore retention time. Interestingly, though this study indicated that females could in principle use lower call carrier frequency to localize preferred larger males, simultaneous choice experiments done in the laboratory revealed that the females do not use this cue. These contrasting results may be because females are incapable of discriminating small differences in frequency or because they use non-acoustic cues for mate choice. However, whichever cues the females use to discriminate between males in the laboratory conditions, often these preferences are not realized in the field. The main reason behind this is that searching for preferred mates in the field can be costly and this might force females to choose sub-optimal males. Theoretical models predict that male movement and spacing in the field should influence female sampling tactics and in turn, females should drive the evolution of male movement and spacing to sample them optimally. Moreover, simultaneous sampling of males using the best-of-n or comparative Bayes strategy should yield maximum mating benefits to females. Many of the theoretical mate sampling strategies involves recall of the quality and location of individual males, which in turn requires male positions to be stable within a night. Calling males of O. henryi showed high site fidelity within a night, potentially enabling female sampling strategies that require recall. To examine the possibility of simultaneous acoustic sampling of males, I estimated male acoustic active spaces using information on male spacing, call transmission and female phonotactic threshold. Males were found to be spaced far apart and active space overlap was rare. I then examined female sampling scenarios by studying female spacing relative to male acoustic active spaces. Only 15% of sampled females could hear multiple males, suggesting that simultaneous mate sampling is rare in the field. Moreover, the relatively large distances between calling males suggest high search costs, which may favor threshold strategies that do not require memory. Using the insights gathered from these two studies I examined a unique calling behaviour from leaf holes, baffling, observed in this species. Baffling behaviour has been found in multiple species of the genus Oecanthus where the males call from self- made holes in leaves rather than calling from leaf edges (their natural calling surface) thus increasing their loudness many fold. I started by examining the natural history of baffling and found that baffling is an extremely rare behaviour in the field. However field observations and laboratory experiments revealed that many males can baffle and hence it is not an obligatory behaviour shown only by a few males. It was hypothesized that one reason for the rarity of baffling could be resource limitation. It was found that baffling males prefer larger leaves possibly due to higher SPL gains achieved by baffling on the larger leaves, which is a limited resource in the field. However this alone was insufficient to explain extreme rarity of bafflers in the field. Hence I examined which males were using this behaviour in the field. Using field observations and laboratory experiments it was found that less preferred males (smaller and quieter) baffled more which provided them with higher calling SPL and greater sound-field volume and thus a higher number of potential mates. Moreover, baffling also increased the mating duration for the less preferred males thus providing more time to these males for sperm transfer. The females could not differentiate between an inherently loud caller and a caller whose SPL was increased artificially (as if it was baffling). Hence I concluded that baffling is probably a cheater strategy used by the less preferred males to fool the females into approaching them and mating for longer durations. To my knowledge, this is the first study that has estimated male call variation in the field to understand its role in female choice in tree crickets. Moreover this is also the first study to examine the ecological context of mate choice in tree crickets. This is also the first study to examine the advantages of baffling behaviour and its potential evolutionary implications.

Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Synchronous sampling is currently the most widely used analog to digital conversion method, mainly due to its implementation ease, since it employs a constant sampling rate. However, a fixed sampling rate can cause unnecessary activations of the sample and hold circuit, increasing power consumption. Asynchronous analog to digital converters can be used to solve this problem, sampling only when particulars events occur, such as amplitude level crossings. This approach has been intensely studied over the last decades, and arose as an alternative to synchronous sampling. Another asynchronous sampling approach is the one proposed by Voelcker (1966), where sampling instants are the zero crossings of the signal. According to him complex zeros must be sampled for perfect signal reconstruction, in addition to real zeros. Although being physically undetectable, Voelcker proposes that complex zeros can be “transformed” using the real zeros of all nth signal derivatives. Nevertheless this can be unfeasible and this work proposes the use of the Zero Crossing method with a limited number of derivatives. Such approach is justifiable because in consecutive derivatives, real zeros tends to be close or even repeat themselves, thus not aggregating any more information about the original signal. Therefore, this work verifies the applicability of the proposed method for systems that need low power consumption and a good reconstruction of the sampled signal, being suggest from the results of this work as a good solution of compromise between synchronous sampling and Level Crossing. / A amostragem síncrona é o método mais amplamente utilizado na conversão analógica/ digital para sinais do cotidiano, principalmente devido à facilidade de implementálos, pois a taxa de amostragem é constante. Entretanto, a taxa de amostragem fixa pode causar ativações desnecessárias do circuito de Sample and Hold, gerando um alto consumo energético. Os conversores analógicos digitais assíncronos podem ser utilizados para resolver este problema, amostrando somente quando ocorrem eventos particulares, tais como os cruzamentos de níveis de amplitude (em inglês - Level Crossing). Esta abordagem está sendo intensamente estudada nas últimas décadas, e surgiu como alternativa à amostragem síncrona. Outra alternativa de amostragem assíncrona e a abordagem proposta por Voelcker, onde os instantes de amostragem são os cruzamentos por zero do sinal. Segundo ele, para que seja possível obter a perfeita reconstrução do sinal, além dos zeros reais, os zeros complexos devem ser amostrados. Embora eles sejam fisicamente indetectáveis, Voelcker propôs que estes podem ser “transformados” em zeros reais a partir das informações de todos os zeros reais das n-ésimas derivadas do sinal. Contudo isto pode ser impraticável, e neste trabalho é proposto um novo método de Zero Crossing que utiliza somente até a 3a derivada. Tal abordagem é justificada pela possibilidade, aqui apresentada de que ao realizar muitas derivadas do sinal, os zeros reais tendem a ficar muito próximos, ou até se repetir, não agregando mais informação sobre o sinal original. Diante disso, foi verificado neste trabalho a aplicabilidade do método proposto para sistemas que necessitem de um baixo consumo energético e uma boa reconstrução do sinal amostrado, sendo apontado a partir dos resultados deste trabalho como uma boa solução de compromisso entre a amostragem síncrona e o Level Crossing.

The rapid increase of data volumes makes sampling a crucial component of modern data management systems. Although there is a large body of work on database sampling, the problem of automatically determine the optimal sample for a given query remained (almost) unaddressed. To tackle this problem the authors propose a sample advisor based on a novel cost model. Primarily designed for advising samples of a few queries specified by an expert, the authors additionally propose two extensions of the sample advisor. The first extension enhances the applicability by utilizing recorded workload information and taking memory bounds into account. The second extension increases the effectiveness by merging samples in case of overlapping pieces of sample advice. For both extensions, the authors present exact and heuristic solutions. Within their evaluation, the authors analyze the properties of the cost model and demonstrate the effectiveness and the efficiency of the heuristic solutions with a variety of experiments.

Indiana University-Purdue University Indianapolis (IUPUI) / Paper spray - mass spectrometry (PS-MS) has been developed as a rapid and direct ionization method for qualitative and quantitative analysis of complex samples at trace levels. In this work, different sampling devices for PS-MS were investigated to improve the assay’s simplicity and sensitivity over traditional approaches. In particular, chapter two characterizes an alternate paper substrate to enhance drug detection on surfaces like asphalt, cloth, concrete, aluminum, and glass. Analysis occurs on a single spray ticket coated with pressure-sensitive adhesive (PSA), also known as Post-it notes to detect and quantify drug residues. A PS-MS method utilizing PSA paper was developed to detect a mixture of ten drugs off of various surfaces to evaluate the qualitative and quantitative capabilities of the aforementioned substrate. After the method development on a conventional linear ion trap mass spectrometer, the assay was translated for use on a portable mass spectrometer to evaluate the suitability of the pressure-sensitive adhesive paper substrate in the field in chapter three. Chapter four introduces a sampling device combined with a snap-in solid-phase extraction (SPE) column. The new cartridge design not only inherits the functions from the first iteration SPE cartridge, including extraction and preconcentration from complex samples, but also exhibits greater flexibility in volume control and ease of use for on-site sample collection.

Diploma thesis deals with the assessment of volatile organic compounds contamination of selected working environment in Gumotex, joint stock company using passive sampling. The theoretical part contains description of these compounds and their reactions in the atmosphere, practical use of these substances and their effect on human health. The possibilities of passive sampling and determination of these substances are described as well. The experimental part contains analysis of volatile organic compounds at two selected workplaces in Gumotex, joint stock company using passive samplers Radiello. Final determination by gas chromatography with flame ionization detector was preceded by adsorption surface extraction of sampler with carbon disulfide. In conclusion, obtained data are compared with the permissible exposure limits and maximum allowable concentrations, which are defined by the National Health Institute.