The duration compression effect is mediated by adaptation of both retinotopic and spatiotopic mechanisms

The duration compression effect is a phenomenon in which prior adaptation to a spatially circumscribed dynamic stimulus results in the duration of subsequent subsecond stimuli presented in the adapted region being underestimated. There is disagreement over the frame of reference within which the duration compression phenomenon occurs. One view holds that the effect is driven by retinotopic-tuned mechanisms located at early stages of visual processing, and an alternate position is that the mechanisms are spatiotopic and occur at later stages of visual processing (MT+). We addressed the retinotopic-spatiotopic question by using adapting stimuli – drifting plaids - that are known to activate global-motion mechanisms in area MT. If spatiotopic mechanisms contribute to the duration compression effect, drifting plaid adaptors should be well suited to revealing them. Following adaptation participants were tasked with estimating the duration of a 600ms random dot stimulus, whose direction was identical to the pattern direction of the adapting plaid, presented at either the same retinotopic or the same spatiotopic location as the adaptor. Our results reveal significant duration compression in both conditions, pointing to the involvement of both retinotopic-tuned and spatiotopic-tuned mechanisms in the duration compression effect.

Maternal breastfeeding in Portugal: factors associated with the duration and premature cessation

Tese de mestrado em Bioestatística, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2013

Effects of Local Anesthetic on the Time Between Analgesic Boluses and the Duration of Labor in Patient-Controlled Epidural Analgesia: Prospective Study of Two Ultra-Low Dose Regimens of Ropivacaine and Sufentanil

BACKGROUND: Patient-controlled epidural analgesia with low concentrations of anesthetics is effective in reducing labor pain. The aim of this study was to assess and compare two ultra-low dose regimens of ropivacaine and sufentanil (0.1% ropivacaine plus 0.5 μg.ml-1 sufentanil vs. 0.06% ropivacaine plus 0.5 μg.ml-1 sufentanil) on the intervals between boluses and the duration of labor. MATERIAL AND METHODS: In this non-randomized prospective study, conducted between January and July 2010, two groups of parturients received patient-controlled epidural analgesia: Group I (n = 58; 1 mg.ml-1 ropivacaine + 0.5 μg.ml-1 sufentanil) and Group II (n = 57; 0.6 mg.ml-1 ropivacaine + 0.5 μg.ml-1 sufentanil). Rescue doses of ropivacaine at the concentration of the assigned group without sufentanil were administered as necessary. Pain, local anesthetic requirements, neuraxial blockade characteristics, labor and neonatal outcomes, and maternal satisfaction were recorded. RESULTS: The ropivacaine dose was greater in Group I (9.5 [7.7-12.7] mg.h-1 vs. 6.1 [5.1-9.8 mg.h-1], p < 0.001). A time increase between each bolus was observed in Group I (beta = 32.61 min, 95% CI [25.39; 39.82], p < 0.001), whereas a time decrease was observed in Group II (beta = -1.40 min, 95% CI [-2.44; -0.36], p = 0.009). The duration of the second stage of labor in Group I was significantly longer than that in Group II (78 min vs. 65 min, p < 0.001). CONCLUSIONS: Parturients receiving 0.06% ropivacaine exhibited less evidence of cumulative effects and exhibited faster second stage progression than those who received 0.1% ropivacaine.

Impact of duration of chest tube drainage on pain after cardiac surgery.

OBJECTIVE: This study was designed to analyze the duration of chest tube drainage on pain intensity and distribution after cardiac surgery. METHODS: Two groups of 80 cardiac surgery adult patients, operated on in two different hospitals, by the same group of cardiac surgeons, and with similar postoperative strategies, were compared. However, in one hospital (long drainage group), a conservative policy was adopted with the removal the chest tubes by postoperative day (POD) 2 or 3, while in the second hospital (short drainage group), all the drains were usually removed on POD 1. RESULTS: There was a trend toward less pain in the short drainage group, with a statistically significant difference on POD 2 (P=0.047). There were less patients without pain on POD 3 in the long drainage group (P=0. 01). The areas corresponding to the tract of the pleural tube, namely the epigastric area, the left basis of the thorax, and the left shoulder were more often involved in the long drainage group. There were three pneumonias in each group and no patient required repeated drainage. CONCLUSIONS: A policy of early chest drain ablation limits pain sensation and simplifies nursing care, without increasing the need for repeated pleural puncture. Therefore, a policy of short drainage after cardiac surgery should be recommended.

Sleep in vitro : Erk pathway regulates sleep duration and sleep related genes

To date, for most biological and physiological phenomena, the scientific community has reach a consensus on their related function, except for sleep, which has an undetermined, albeit mystery, function. To further our understanding of sleep function(s), we first focused on the level of complexity at which sleep-like phenomenon can be observed. This lead to the development of an in vitro model. The second approach was to understand the molecular and cellular pathways regulating sleep and wakefulness, using both our in vitro and in vivo models. The third approach (ongoing) is to look across evolution when sleep or wakefulness appears. (1) To address the question as to whether sleep is a cellular property and how this is linked to the entire brain functioning, we developed a model of sleep in vitro by using dissociated primary cortical cultures. We aimed at simulating the major characteristics of sleep and wakefulness in vitro. We have shown that mature cortical cultures display a spontaneous electrical activity similar to sleep. When these cultures are stimulated by waking neurotransmitters, they show a tonic firing activity, similar to wakefulness, but return spontaneously to the "sleep-like" state 24h after stimulation. We have also shown that transcriptional, electrophysiological, and metabolic correlates of sleep and wakefulness can be reliably detected in dissociated cortical cultures. (2) To further understand at which molecular and cellular levels changes between sleep and wakefulness occur, we have used a pharmacological and systematic gene transcription approach in vitro and discovered a major role played by the Erk pathway. Indeed, pharmacological inhibition of this pathway in living animals decreased sleep by 2 hours per day and consolidated both sleep and wakefulness by reducing their fragmentation. (3) Finally, we tried to evaluate the presence of sleep in one of the most primitive species with a neural network. We set up Hydra as a model organism. We hypothesized that sleep as a cellular (neuronal) property may occur with the appearance of the most primitive nervous system. We were able to show that Hydra have periodic rest phases amounting to up to 5 hours per day. In conclusion, our work established an in vitro model to study sleep, discovered one of the major signaling pathways regulating vigilance states, and strongly suggests that sleep is a cellular property highly conserved at the molecular level during evolution. -- Jusqu'à ce jour, la communauté scientifique s'est mise d'accord sur la fonction d'une majorité des processus physiologiques, excepté pour le sommeil. En effet, la fonction du sommeil reste un mystère, et aucun consensus n'est atteint le concernant. Pour mieux comprendre la ou les fonctions du sommeil, (1) nous nous sommes d'abord concentré sur le niveau de complexité auquel un état ressemblant au sommeil peut être observé. Nous avons ainsi développé un modèle du sommeil in vitro, (2) nous avons disséqué les mécanismes moléculaires et cellulaires qui pourraient réguler le sommeil, (3) nous avons cherché à savoir si un état de sommeil peut être trouvé dans l'hydre, l'animal le plus primitif avec un système nerveux. (1) Pour répondre à la question de savoir à quel niveau de complexité apparaît un état de sommeil ou d'éveil, nous avons développé un modèle du sommeil, en utilisant des cellules dissociées de cortex. Nous avons essayé de reproduire les corrélats du sommeil et de l'éveil in vitro. Pour ce faire, nous avons développé des cultures qui montrent les signes électrophysiologiques du sommeil, puis quand stimulées chimiquement passent à un état proche de l'éveil et retournent dans un état de sommeil 24 heures après la stimulation. Notre modèle n'est pas parfait, mais nous avons montré que nous pouvions obtenir les corrélats électrophysiologiques, transcriptionnels et métaboliques du sommeil dans des cellules corticales dissociées. (2) Pour mieux comprendre ce qui se passe au niveau moléculaire et cellulaire durant les différents états de vigilance, nous avons utilisé ce modèle in vitro pour disséquer les différentes voies de signalisation moléculaire. Nous avons donc bloqué pharmacologiquement les voies majeures. Nous avons mis en évidence la voie Erkl/2 qui joue un rôle majeur dans la régulation du sommeil et dans la transcription des gènes qui corrèlent avec le cycle veille-sommeil. En effet, l'inhibition pharmacologique de cette voie chez la souris diminue de 2 heures la quantité du sommeil journalier et consolide l'éveil et le sommeil en diminuant leur fragmentation. (3) Finalement, nous avons cherché la présence du sommeil chez l'Hydre. Pour cela, nous avons étudié le comportement de l'Hydre pendant 24-48h et montrons que des périodes d'inactivité, semblable au sommeil, sont présentes dans cette espèce primitive. L'ensemble de ces travaux indique que le sommeil est une propriété cellulaire, présent chez tout animal avec un système nerveux et régulé par une voie de signalisation phylogénétiquement conservée.

Determinants of bankruptcy protection duration for Canadian firms

The present thesis examines the determinants of the bankruptcy protection duration for Canadian firms. Using a sample of Canadian firms that filed for bankruptcy protection between the calendar years 1992 and 2009, we fmd that the firm age, the industry adjusted operating margin, the default spread, the industrial production growth rate or the interest rate are influential factors on determining the length of the protection period. Older firms tend to stay longer under protection from creditors. As older firms have more complicated structures and issues to settle, the risk of exiting soon the protection (the hazard rate) is small. We also find that firms that perform better than their benchmark as measured by the industry they belong to, tend to leave quickly the bankruptcy protection state. We conclude that the fate of relatively successful companies is determined faster. Moreover, we report that it takes less time to achieve a final solution to firms under bankrupt~y when the default spread is low or when the appetite for risk is high. Conversely, during periods of high default spreads and flight for quality, it takes longer time to resolve the bankruptcy issue. This last finding may suggest that troubled firms should place themselves under protection when spreads are low. However, this ignores the endogeneity issue: high default spread may cause and incidentally reflect higher bankruptcy rates in the economy. Indeed, we find that bankruptcy protection is longer during economic downturns. We explain this relation by the natural increase in default rate among firms (and individuals) during economically troubled times. Default spreads are usually larger during these harsh periods as investors become more risk averse since their wealth shrinks. Using a Log-logistic hazard model, we also fmd that firms that file under the Companies' Creditors Arrangement Act (CCAA) protection spend longer time restructuring than firms that filed under the Bankruptcy and Insolvency Act (BIA). As BIA is more statutory and less flexible, solutions can be reached faster by court orders.

Educational inequalities in quantity, duration and type of tobacco consumption among lung cancer patients in Asturias : Epidemiological analices

Resumen tomado de la publicaci??n

The persistent colombian conflict bubnational analysis of the duration of violence

The growing empirical literature on the analysis of civil war has recently included the study of conflict duration at the cross-country level. This paper presents, for the first time, a within-country analysis of the determinants of violence duration. I focus on the experience of the Colombian armed conflict. While the conflict has been active for about five decades, local violence ebbs and flows and areas experiencing continuous conflict coexist with places that have been able to resile and where violence is mostly absent. I examine a wide range of factors potentially associated with violence duration at the municipal level, including scale variables, geographical conditions, economic and social variables, institutions and state presence, inequality, government intervention, and victimization variables. I characterize a few variables robustly correlated with the persistence of localized conflict, both across specifications and using different econometric models of duration analysis.

Information externalities and export trade duration at the firm level

Recent empirical work emphasizes the importance of the extensive margin of trade (new exporters, new export activities) for long run export growth. In this context, understanding the determinants of duration of new exporters is key for underpinning the dynamics of exports growth. As new exporters tend to show low survival rates, identifying the determinants of export duration is highly relevant for academic and policy purposes. In this paper, we explore whether information externalities arising from different levels of spatial interaction allow new exporters to increase the duration of their trade activities. For this, we use transaction level data on Colombian exports between 2004 and 2011. Results show that export networks, understood as the agglomeration of exporting firms at different spatial levels, reduce the risk of dropping out from exporting and that this effect is stronger the more similar are export activities carried out by firms

Oaxaca-Blinder type counterfactual decomposition methods for duration outcomes

Los métodos disponibles para realizar análisis de descomposición que se pueden aplicar cuando los datos son completamente observados, no son válidos cuando la variable de interés es censurada. Esto puede explicar la escasez de este tipo de ejercicios considerando variables de duración, las cuales se observan usualmente bajo censura. Este documento propone un método del tipo Oaxaca-Blinder para descomponer diferencias en la media en el contexto de datos censurados. La validez de dicho método radica en la identificación y estimación de la distribución conjunta de la variable de duración y un conjunto de covariables. Adicionalmente, se propone un método más general que permite descomponer otros funcionales de interés como la mediana o el coeficiente de Gini, el cual se basa en la especificación de la función de distribución condicional de la variable de duración dado un conjunto de covariables. Con el fin de evaluar el desempeño de dichos métodos, se realizan experimentos tipo Monte Carlo. Finalmente, los métodos propuestos son aplicados para analizar las brechas de género en diferentes características de la duración del desempleo en España, tales como la duración media, la probabilidad de ser desempleado de largo plazo y el coeficiente de Gini. Los resultados obtenidos permiten concluir que los factores diferentes a las características observables, tales como capital humano o estructura del hogar, juegan un papel primordial para explicar dichas brechas.

Integration of duration and frequency in discrimination between pure tones

This dissertation investigates discrimination between pure tones. Three questions were investigated: can listeners integrate frequency and duration information in the discrimination of pure tones; how does the discriminability of duration-frequency compounds relate to the discriminability of the changes in the individual dimensions; and how is the integration of these two dimensions affected by the parameters of the stimuli in which the changes in duration and frequency are introduced.

Auditory difference limen for duration in deaf and hearing listeners

This paper reviews a study to determine if deaf children can discriminate fine durational changes in acoustic signals or whether the impairment of the peripheral auditory system interferes with the temporal precision necessary for such tasks.