A resolução temporal é uma questão-chave em Paleontologia, uma vez que a sua magnitude define a precisão dos estudos não somente paleoecológicos como também evolutivos. A resolução temporal é estimada pela magnitude de time-averaging (mistura de gerações em uma camada, uma amostra). Tais estimativas têm sido amplamente conduzidas em ambientes marinhos recentes. A plataforma continental do sul do Brasil (PSB; 22°S – 34°S) tem sido um laboratório natural para estudos desta natureza desde o início do século XXI. Consequentemente, possui um amplo acervo de dados disponíveis para comparação. Neste contexto, esta tese visou responder (i) qual a magnitude do time-averaging em acumulações de bivalves da PSB? (ii) como este processo varia ao longo de gradientes espaciais? e (iii) como o time-averaging reflete na informação biológica preservada no registro fóssil? Para isto, mais de 140 espécimes de bivalves foram datados integrando racemização de aminoácidos e 14C AMS. Além disto, análises tafonômicas foram realizadas em todas as amostras datadas, incluindo mais sete amostras em sedimentos lamosos. A resolução temporal (time-averaging) e a variabilidade total de idades (mistura temporal) basearam-se em uma nova abordagem numérica, a estatística bayesiana, que integra os erros e as incertezas derivadas da distribuição posterior dos resíduos associados com os modelos resultantes das calibrações das idades. As tendências onshore-offshore — aumento da mediana e da uniformidade das curvas de frequência de distribuição de idades, redução da variabilidade tafonômica, ainda que a escala do time-averaging seja invariante — provavelmente refletem a interação entre as mudanças do nível relativo do mar e da bioprodutividade mais elevada em águas menos profundas. / The temporal resolution of the fossil record plays a key role in paleontology because it determines the scale and the precision of paleoecological and evolutionary studies. The temporal resolution of the fossil record is estimated by the magnitude of time-averaging (non-contemporaneous generations preserved in a single layer, a bulk-sample). Quantitative estimates of time-averaging have been conducted primarily on mollusk shells from modern shallow-water marine settings. Most of them have been addressed in the Southern Brazilian continental shelf (SBS; 22°S up to 34°S), which is considered a natural laboratory for several similar studies since the earlier of current century (XXI). Consequently, the SBS has several available datasets that allow comparisons of the new results displayed here with those previous data. Thus, this thesis aimed answer (i) what is the magnitude of time-averaging on SBS mollusk death assemblages? (ii) how does time-averaging vary across spatial gradients? and (iii) how does time-averaging can reflect on the preservation of the fossil record? Here, >140 specimens were individually dated using amino acid racemization calibrated using radiocarbon ages (14C). In addition, taphonomic analyses were conducted in all samples, including more seven muddy sites. The time-averaging and the total age variability was based on a Bayesian approach that integrates the estimation errors and uncertainties derived from the posterior distribution associated with the 14C–AAR calibration average model. The onshore-offshore trends — increased median age, decreased skewness of age distributions, decreased taphonomic variation, yet the invariant scale of time-averaging — likely reflect the interplay between sea-level changes and elevated bioproductivity in shallower water settings.

This thesis explores the temporal analysis of text using the implicit temporal cues present in document. We consider the case when all explicit temporal expressions such as specific dates or years are removed from the text and a bag of words based approach is used for timestamp prediction for the text. A set of gold standard text documents with times- tamps are used as the training set. We also predict time spans for Wikipedia biographies based on their text. We have training texts from 3800 BC to present day. We partition this timeline into equal sized chronons and build a probability histogram for a test document over this chronon sequence. The document is assigned to the chronon with the highest probability. We use 2 approaches: 1) a generative language model with Bayesian priors, and 2) a KL divergence based model. To counter the sparsity in the documents and chronons we use 3 different smoothing techniques across models. We use 3 diverse datasets to test our mod- els: 1) Wikipedia Biographies, 2) Guttenberg Short Stories, and 3) Wikipedia Years dataset. Our models are trained on a subset of Wikipedia biographies. We concentrate on two prediction tasks: 1) time-stamp prediction for a generic text or mid-span prediction for a Wikipedia biography , and 2) life-span prediction for a Wikipedia biography. We achieve an f-score of 81.1% for life-span prediction task and a mean error of around 36 years for mid-span prediction for biographies from present day to 3800 BC. The best model gives a mean error of 18 years for publication date prediction for short stories that are uniformly distributed in the range 1700 AD to 2010 AD. Our models exploit the temporal distribu- tion of text for associating time. Our error analysis reveals interesting properties about the models and datasets used. We try to combine explicit temporal cues extracted from the document with its implicit cues and obtain combined prediction model. We show that a combination of the date-based predictions and language model divergence predictions is highly effective for this task: our best model obtains an f-score of 81.1% and the median error between actual and predicted life span midpoints is 6 years. This would be one of the emphasis for our future work. The above analyses demonstrates that there are strong temporal cues within texts that can be exploited statistically for temporal predictions. We also create good benchmark datasets along the way for the research community to further explore this problem. / text

A resolução temporal é uma questão-chave em Paleontologia, uma vez que a sua magnitude define a precisão dos estudos não somente paleoecológicos como também evolutivos. A resolução temporal é estimada pela magnitude de time-averaging (mistura de gerações em uma camada, uma amostra). Tais estimativas têm sido amplamente conduzidas em ambientes marinhos recentes. A plataforma continental do sul do Brasil (PSB; 22°S – 34°S) tem sido um laboratório natural para estudos desta natureza desde o início do século XXI. Consequentemente, possui um amplo acervo de dados disponíveis para comparação. Neste contexto, esta tese visou responder (i) qual a magnitude do time-averaging em acumulações de bivalves da PSB? (ii) como este processo varia ao longo de gradientes espaciais? e (iii) como o time-averaging reflete na informação biológica preservada no registro fóssil? Para isto, mais de 140 espécimes de bivalves foram datados integrando racemização de aminoácidos e 14C AMS. Além disto, análises tafonômicas foram realizadas em todas as amostras datadas, incluindo mais sete amostras em sedimentos lamosos. A resolução temporal (time-averaging) e a variabilidade total de idades (mistura temporal) basearam-se em uma nova abordagem numérica, a estatística bayesiana, que integra os erros e as incertezas derivadas da distribuição posterior dos resíduos associados com os modelos resultantes das calibrações das idades. As tendências onshore-offshore — aumento da mediana e da uniformidade das curvas de frequência de distribuição de idades, redução da variabilidade tafonômica, ainda que a escala do time-averaging seja invariante — provavelmente refletem a interação entre as mudanças do nível relativo do mar e da bioprodutividade mais elevada em águas menos profundas. / The temporal resolution of the fossil record plays a key role in paleontology because it determines the scale and the precision of paleoecological and evolutionary studies. The temporal resolution of the fossil record is estimated by the magnitude of time-averaging (non-contemporaneous generations preserved in a single layer, a bulk-sample). Quantitative estimates of time-averaging have been conducted primarily on mollusk shells from modern shallow-water marine settings. Most of them have been addressed in the Southern Brazilian continental shelf (SBS; 22°S up to 34°S), which is considered a natural laboratory for several similar studies since the earlier of current century (XXI). Consequently, the SBS has several available datasets that allow comparisons of the new results displayed here with those previous data. Thus, this thesis aimed answer (i) what is the magnitude of time-averaging on SBS mollusk death assemblages? (ii) how does time-averaging vary across spatial gradients? and (iii) how does time-averaging can reflect on the preservation of the fossil record? Here, >140 specimens were individually dated using amino acid racemization calibrated using radiocarbon ages (14C). In addition, taphonomic analyses were conducted in all samples, including more seven muddy sites. The time-averaging and the total age variability was based on a Bayesian approach that integrates the estimation errors and uncertainties derived from the posterior distribution associated with the 14C–AAR calibration average model. The onshore-offshore trends — increased median age, decreased skewness of age distributions, decreased taphonomic variation, yet the invariant scale of time-averaging — likely reflect the interplay between sea-level changes and elevated bioproductivity in shallower water settings.

A resolução temporal é uma questão-chave em Paleontologia, uma vez que a sua magnitude define a precisão dos estudos não somente paleoecológicos como também evolutivos. A resolução temporal é estimada pela magnitude de time-averaging (mistura de gerações em uma camada, uma amostra). Tais estimativas têm sido amplamente conduzidas em ambientes marinhos recentes. A plataforma continental do sul do Brasil (PSB; 22°S – 34°S) tem sido um laboratório natural para estudos desta natureza desde o início do século XXI. Consequentemente, possui um amplo acervo de dados disponíveis para comparação. Neste contexto, esta tese visou responder (i) qual a magnitude do time-averaging em acumulações de bivalves da PSB? (ii) como este processo varia ao longo de gradientes espaciais? e (iii) como o time-averaging reflete na informação biológica preservada no registro fóssil? Para isto, mais de 140 espécimes de bivalves foram datados integrando racemização de aminoácidos e 14C AMS. Além disto, análises tafonômicas foram realizadas em todas as amostras datadas, incluindo mais sete amostras em sedimentos lamosos. A resolução temporal (time-averaging) e a variabilidade total de idades (mistura temporal) basearam-se em uma nova abordagem numérica, a estatística bayesiana, que integra os erros e as incertezas derivadas da distribuição posterior dos resíduos associados com os modelos resultantes das calibrações das idades. As tendências onshore-offshore — aumento da mediana e da uniformidade das curvas de frequência de distribuição de idades, redução da variabilidade tafonômica, ainda que a escala do time-averaging seja invariante — provavelmente refletem a interação entre as mudanças do nível relativo do mar e da bioprodutividade mais elevada em águas menos profundas. / The temporal resolution of the fossil record plays a key role in paleontology because it determines the scale and the precision of paleoecological and evolutionary studies. The temporal resolution of the fossil record is estimated by the magnitude of time-averaging (non-contemporaneous generations preserved in a single layer, a bulk-sample). Quantitative estimates of time-averaging have been conducted primarily on mollusk shells from modern shallow-water marine settings. Most of them have been addressed in the Southern Brazilian continental shelf (SBS; 22°S up to 34°S), which is considered a natural laboratory for several similar studies since the earlier of current century (XXI). Consequently, the SBS has several available datasets that allow comparisons of the new results displayed here with those previous data. Thus, this thesis aimed answer (i) what is the magnitude of time-averaging on SBS mollusk death assemblages? (ii) how does time-averaging vary across spatial gradients? and (iii) how does time-averaging can reflect on the preservation of the fossil record? Here, >140 specimens were individually dated using amino acid racemization calibrated using radiocarbon ages (14C). In addition, taphonomic analyses were conducted in all samples, including more seven muddy sites. The time-averaging and the total age variability was based on a Bayesian approach that integrates the estimation errors and uncertainties derived from the posterior distribution associated with the 14C–AAR calibration average model. The onshore-offshore trends — increased median age, decreased skewness of age distributions, decreased taphonomic variation, yet the invariant scale of time-averaging — likely reflect the interplay between sea-level changes and elevated bioproductivity in shallower water settings.

Hearing in noise is facilitated by the auditory system’s ability to separate sound into small auditory segments. Separation of sound is achieved using an auditory mechanism called temporal resolution that codes for small silent gaps in an acoustic stimulus. This thesis proposes a new method for measuring temporal resolution and applied it to a small pilot group of individuals with tinnitus. Previous studies have postulated that tinnitus can “fill” in silent gaps thereby making gap detection more difficult. This was shown in studies using the gap prepulse inhibition acoustic startle where the amplitude of a startle response indicates the subject’s ability to detect a small silent gap. However studies using behavioural gap detection do not show significant differences in people with reported tinnitus. Thus the behavioural evidence does not appear to support the hypothesis that tinnitus can “fill” in silent gaps. In this thesis a new method was proposed for measuring neural gap detection: the mismatch negativity response (MMN). The mismatch negativity responses were compared to behavioural measures of gap detection in thirty-five normal hearing adults: five with reported tinnitus and thirty without tinnitus. They underwent recordings to gapped stimuli ranging from 2- to 40-ms gap durations. The stimuli were either a broadband or narrowband noise presented in the absence or presence of a filler noise. Results of these experiments found the broadband and narrowband noises elicited MMNs to silent gaps. The amplitude of the MMN increased with larger gap durations. When filled, the amplitude of the entire waveform was proportionally reduced for all gap durations. However, for the tinnitus group the filler reduced the largest gap durations elicited MMNs amplitudes disproportionately more than for the smaller gap durations. The high and low filler noise reduced the amplitude of the 40-ms gap MMNs. This was not reflective in the behavioural performance of gap detection as there were no significant group differences. These studies show that neural gap detection can be measured using mismatch negativities. Reduced behavioural gap detection performance is reflected by a smaller amplitude of the MMN for suprathrehold gaps. This was shown in both normal hearing participants with elevated behavioural gap detection thresholds and participants with tinnitus. Therefore, electrophysiological recordings to gaps may provide further information on the underlying mechanisms involved in impaired gap detection that may not be captured by behavioural measures alone.

Dyslexia is a clinical diagnosis often associated with phonological processing deficits. There are, however, other areas of concern, such as the presence of auditory temporal processing (ATP) disorders. One method of investigating ATP is the gap detection (GD) paradigm. This study investigated GD performance using the Gaps-in-Noise © (GIN) test in three groups of 30 children, aged 8 to 9 years. GD thresholds and gap identification scores (%) were determined for each participant. The three groups of participants included (Group I) children with dyslexia and phonological deficits, (Group II) children with dyslexia and no significant phonological deficits, and (Group III) normal reading peers. Repeated-measures ANOVA showed that GD thresholds for the three groups were significantly different. Group I showed longer GD thresholds (RE, 8.5 msec; LE, 8 msec), than did Group II (4.9 msec for both ears) or Group III (RE, 4.2 msec; LE, 4.3 msec). Close inspection of the threshold values for the three groups revealed that the thresholds for Group II overlapped substantially with those of Group III, but not with those of Group I. Similar trends were also noted for the gap identification analysis. From a clinical perspective, the majority of participants in Group II and all participants in Group III performed within normal limits on both measures (i.e., thresholds and identifications), while performance of participants in Group I fell below established norms on these measures. Finally, additional analyses revealed that ATP was highly correlated with phonological processing measures indicating a relationship between the presence of phonological deficits and ATP deficits. This study confirmed that ATP deficit is a factor to be considered in dyslexia and suggested that the GIN © test is a promising clinical tool that should be incorporated in the evaluation procedures for children with reading difficulties.

The current cardiac computed tomography (CT) technology is mainly limited by motion blurring and radiation dose. The conceptual multi-source interior CT scheme has provided a potential solution to reduce motion artifacts and radiation exposure. This dissertation work conducted multi-facet investigations on a novel multi-source interior CT architecture (G. Cao, et. al, IEEE Access, 2014;2:1263-71) which employs distributed stationary multi-beam Carbon-nanotube (CNT) X-ray sources and simultaneously operates multiple source-detector chains to improve temporal resolution. The collimation based interior CT is integrated in each imaging chain, to suppress radiation dose. The central thesis statement is: Compared to conventional CT design, this distributed source array based multi-source interior CT architecture shall provide ultra-fast CT scan of region-of-interest (ROI) inside body with comparable image quality at lower radiation dose. Comprehensive studies were conducted to separately investigate three critical aspects of multi-source interior CT: interior CT mode, X-ray scattering, and scatter correction methods. First, a single CNT X-ray source based interior micro-CT was constructed to serve as a down-scaled experimental verification platform for interior CT mode. Interior CT mode demonstrated comparable contrast-noise-ratio (CNR) and image structural similarity to the standard global CT mode, while inducing a significant radiation dose reduction (< 83.9%). Second, the data acquisition of multi-source interior CT was demonstrated at clinical geometry, via numerical simulation and physical experiments. The simultaneously operated source-detector chains induced significant X-ray forward / cross scattering and thus caused severe CNR reduction (< 68.5%) and CT number error (< 1122 HU). To address the scatter artifacts, a stationary beam-stopper-array (BSA) based and a source-trigger-sequence (STS) based scatter correction methods were proposed to enable the online scatter measurement / correction with further radiation dose reduction (< 50%). Moreover, a deterministic physics model was also developed to iteratively remove the scatter-artifacts in the multi-source interior CT, without the need for modifications in imaging hardware or protocols. The three proposed scatter correction methods improved CNR (< 94.0%) and suppressed CT number error (< 48 HU). With the dedicated scatter correction methods, the multi-source interior CT could provide ROI-oriented imaging with acceptable image quality at significantly reduced radiation dose. / Ph. D.

Les gamètes femelles appelés ovocytes sont produits par un type spécifique de division cellulaire appelée méiose. Afin de produire des gamètes haploïdes, et contrairement aux divisions mitotiques des cellules somatiques, la méiose implique une seule étape de réplication du génome suivie de deux étapes de ségrégation des chromosomes. La fidélité de la ségrégation des chromosomes pendant la méiose est cruciale pour éviter l’aneuploïdie embryonnaire qui entraînerait des défauts de développement ou un avortement spontané. Dans la plupart des types cellulaires, la ségrégation des chromosomes repose sur un fuseau composé de microtubules. En parallèle à l'assemblage du fuseau, des complexes multi-protéiques appelés kinétochores s’assemblent sur le côté des chromosomes et leur permettent d’interagir avec les microtubules dynamiques du fuseau. Étonnamment, la ségrégation des chromosomes dans l'ovocyte de C. elegans se déroule d'une manière atypique indépendante des kinétochores. Le mécanisme alternatif utilisé dans ces oocytes pour la ségrégation des chromosomes est cependant inconnu. Au cours de mon doctorat, j'ai utilisé une combinaison d'imagerie photonique à haute résolution temporelle, corrélée à de la microscopie électronique à haute résolution spatiale. J’ai également utilisé de la photoablation par laser des microtubules et réalisé l'inhibition ciblée de protéines clés pour disséquer le mécanisme atypique de ségrégation des chromosomes dans l'ovocyte de C. elegans. Mes résultats montrent que la ségrégation des chromosomes est produite par une force dépendante des microtubules qui pousse les chromosomes. Par une analyse détaillée de l’organisation des microtubules dans des fuseaux en anaphase partiellement reconstruits par microscopie électronique en tomographie, je propose un modèle impliquant la génération de force par l'allongement d’un réseau de courts microtubules formant le fuseau central. De plus, je démontre que l'activité de l'orthologue de CLASP chez C. elegans (CLS-2) est essentielle pour l'assemblage du fuseau en anaphase. Ce travail est actuellement sous presse dans le journal Nature Communications. Parallèlement, j'ai disséqué le rôle de CLS-2 dans l'assemblage du fuseau d'ovocytes et la ségrégation chromosomique. J'ai perturbé de manière systématique les domaines individuels et les résidus conservés de manière évolutive dans CLS-2 pour déterminer leur contribution à la fonction et à la localisation de cette protéine pendant la première méiose femelle. Dans l'ensemble, mes résultats montrent que la ségrégation chromosomique dans l'ovocyte de C. elegans consiste en un mécanisme de poussée chromosomique atypique et dépendant de CLS-2. / Female gametes called oocytes are produced through a specific type of celldivision termed meiosis. In order to produce haploid gametes, and unlike mitoticdivisions of somatic cells, meiosis involves a single round of genome replication followed by two rounds of chromosome segregation. Accuracy of chromosome segregation during meiosis is crucial to avoiding embryonic aneuploidy that wouldlead to developmental defects or spontaneous abortion. In most cell types,chromosome segregation relies on a microtubule-based spindle. Concomitant tospindle assembly, multi-protein complexes termed kinetochores assemble on the side of chromosomes and couple microtubule dynamics to chromosomal movements. Strikingly, in the C. elegans oocyte chromosome segregation occurs in an atypical kinetochore-independent manner. The alternative mechanism used in these oocytes for chromosome segregation is however unknown. During my PhD, I used a combination of high spatial and temporal resolution live imaging, correlated light and electron tomography, laser-mediated photoablation of microtubules, and targeted inhibition of key proteins to dissect this a typical mechanism of chromosome segregation in the C. elegans oocyte. Myresults show that chromosome segregation is driven by a microtubule-dependent force that pushes the segregating chromosomes apart during anaphase. Aftercareful analysis of partially reconstructed anaphase spindles by electrontomography for microtubule quantity, length, orientation, and overlaps, I proposea model involving the elongation and/or sliding of tiled microtubules in the central spindle as the candidate structure responsible for this force generation. Additionally, I demonstrate that the activity of the C. elegans CLASP ortholog CLS-2 is essential for proper anaphase spindle assembly. This work is currently in press at Nature Communications.In parallel, I have more closely examined the role of the C. elegans CLS-2 in oocyte spindle assembly and chromosome segregation. I have thoroughly and systematically perturbed the individual domains and evolutionarily conserved residues in CLS-2 to determine their contribution to the function and localization ofthis protein during the first female meiosis. Overall my results show that chromosome segregation in the C. elegans

Objective: Deficits in temporal resolution may be one element underlying the speech understanding difficulties experienced by older listeners in degraded acoustic environments. In real listening environments, important temporal cues are surrounded by stimuli of varying frequencies. This study was designed to assess temporal resolution as a function of frequency region, frequency-disparity, and age in listeners with normal hearing. Design: Gap duration difference limens (GDDLs) were measured using leading and trailing markers that were fixed at the same frequency (fixed-frequency) or at frequencies one-half octave apart (frequency-disparate) for two groups of listeners with normal hearing: (1) 18-22 years and (2) 55-66 years. Two distinct frequency regions were represented, 500 Hz and 4000 Hz. Results: The results indicated significant effects of age, frequency region, and frequency disparity on GDDLs. Poorer overall performance was observed for the older listeners, the lower frequency region, and the frequency-disparate condition. Conclusions: Gap discrimination is negatively affected by advanced age, lower marker frequencies, and larger marker frequency disparities.

Based on the acquisition trajectory, PROPELLER MRI repeatedly sampled the center k-space in every blade, which was used to provide most of the energy of an image. The purpose of view sharing PROPELLER is to improve the spatio-temporal resolution of dynamic imaging by reducing the acquisition time of single frame to that of single blade. With the center k-space provided by only one blade, which is called the target blade, the high spatial-frequency components were appropriately contributed by a set of neighboring blades with different rotation angles, leading to the high spatial resolution after reconstruction. In this study, a flow phantom experiment with the injection of T1-shortening Gd-DTPA solution was performed to exam the feasibility and accuracy of view-sharing PROPELLER. Furthermore, cardiac imaging of healthy volunteer obtained by the proposed technique was also done with ECG gating to test the image quality without any injection of contrast agent. The in-vivo experiment was done with and without breath holding. In addition to slight aliasing artifact due to insufficient FOV, no other artifact was observed.