Feedback-related Brain Potential Activity Complies with Basic Assumptions of Associative Learning Theory

Feedback-related negativity (FRN) is an ERP component that distinguishes positive from negative feedback. FRN has been hypothesized to be the product of an error signal that may be used to adjust future behavior. In addition, associative learning models assume that the trial-to-trial learning of cueoutcome mappings involves the minimization of an error term. This study evaluated whether FRN is a possible electrophysiological correlate of this error term in a predictive learning task where human subjects were asked to learn different cueoutcome relationships. Specifically, we evaluated the sensitivity of the FRN to the course of learning when different stimuli interact or compete to become a predictor of certain outcomes. Importantly, some of these cues were blocked by more informative or predictive cues (i.e., the blocking effect). Interestingly, the present results show that both learning and blocking affect the amplitude of the FRN component. Furthermore, independent analyses of positive and negative feedback event-related signals showed that the learning effect was restricted to the ERP component elicited by positive feedback. The blocking test showed differences in the FRN magnitude between a predictive and a blocked cue. Overall, the present results show that ERPs that are related to feedback processing correspond to the main predictions of associative learning models. ■

Post-processing and analysis of tracked hand trajectories

In this thesis, the suitability of different trackers for finger tracking in high-speed videos was studied. Tracked finger trajectories from the videos were post-processed and analysed using various filtering and smoothing methods. Position derivatives of the trajectories, speed and acceleration were extracted for the purposes of hand motion analysis. Overall, two methods, Kernelized Correlation Filters and Spatio-Temporal Context Learning tracking, performed better than the others in the tests. Both achieved high accuracy for the selected high-speed videos and also allowed real-time processing, being able to process over 500 frames per second. In addition, the results showed that different filtering methods can be applied to produce more appropriate velocity and acceleration curves calculated from the tracking data. Local Regression filtering and Unscented Kalman Smoother gave the best results in the tests. Furthermore, the results show that tracking and filtering methods are suitable for high-speed hand-tracking and trajectory-data post-processing.

Anti-Leishmania titers and positive skin tests in patients cured of kala-azar

Visceral leishmaniasis (VL), also known as kala-azar, is an important public health problem. If not treated, virtually all clinically symptomatic patients die within months. The diagnosis is based on the Montenegro skin test (MST) and anti-Leishmania titers. Nevertheless, the time required for cured individuals living in a leishmaniasis-endemic area to present a positive skin test and negative anti-Leishmania serology is known. To determine the cellular and humoral immune response profile in relation to different times post-VL cure, a cross-sectional study was conducted on subjects from a kala-azar endemic area in Paço do Lumiar, MA, Brazil, on the basis of 1995-2005 notifications reported by the National Health Foundation/Regional Coordination of Maranhão. We visited cured individuals with a history of VL within the last 10 years. Seventy-four subjects (30 females) ranging in age from 1 to 44 years were included, all of them symptom free at the time of the study. A cellular immune response was observed in 73 (98.6%) subjects, whereas no significant antibody titers were detected by indirect immunofluorescence (IIF) in the sera of 69 (93.2%) cases. Ten years post-cure, 39 (52%) subjects had a positive MST and negative IIF reaction, while in one subject the skin and anti-Leishmania serology tests were negative. Two other subjects were positive in both tests 1 year after cure. These data suggest that a cellular immune response may still be present in subjects cured of VL regardless of post-cure time, and that the parasite persists in the host after clinical cure of the disease. This would explain the persistence of significant Leishmania sp antibody titers in some subjects after treatment.

The expression of melanopsin and clock genes in Xenopus laevis melanophores and their modulation by melatonin

Vertebrates have a central clock and also several peripheral clocks. Light responses might result from the integration of light signals by these clocks. The dermal melanophores of Xenopus laevis have a photoreceptor molecule denominated melanopsin (OPN4x). The mechanisms of the circadian clock involve positive and negative feedback. We hypothesize that these dermal melanophores also present peripheral clock characteristics. Using quantitative PCR, we analyzed the pattern of temporal expression of Opn4x and the clock genes Per1, Per2, Bmal1, and Clock in these cells, subjected to a 14-h light:10-h dark (14L:10D) regime or constant darkness (DD). Also, in view of the physiological role of melatonin in the dermal melanophores of X. laevis, we determined whether melatonin modulates the expression of these clock genes. These genes show a time-dependent expression pattern when these cells are exposed to 14L:10D, which differs from the pattern observed under DD. Cells kept in DD for 5 days exhibited overall increased mRNA expression for Opn4x and Clock, and a lower expression for Per1, Per2, and Bmal1. When the cells were kept in DD for 5 days and treated with melatonin for 1 h, 24 h before extraction, the mRNA levels tended to decrease for Opn4x and Clock, did not change for Bmal1, and increased for Per1 and Per2 at different Zeitgeber times (ZT). Although these data are limited to one-day data collection, and therefore preliminary, we suggest that the dermal melanophores of X. laevis might have some characteristics of a peripheral clock, and that melatonin modulates, to a certain extent, melanopsin and clock gene expression.

Characterization and effect of clarified araçá (Psidium guineenses Sw.) juice on postprandial glycemia in healthy subjects

Brazilian native fruits are excellent sources of bioactive compounds of phenolic nature. Some of these compounds are able to inhibit carbohydrate- metabolizing enzymes (in vitro), α-amylase and α-glucosidase, delaying carbohydrate digestion. This study aimed to evaluate the effect of clarified araçá (Psidium guineenses Sw.) juice on postprandial glycemia in humans after consumption of 25 g of available carbohydrates (approximately 50 g of white bread) and characterize the phenolic compounds and in vitro antioxidant capacity of araçá juice and pulp. The results showed that the clarified juice had a positive effect on postprandial glycemia reducing the total amount of glucose absorbed, lengthening the time to reach maximum blood glucose concentration, reducing glucose incremental velocity, and decreasing glucose incremental percentage. Both frozen pulp and clarified juice had high amounts of phenolic compounds, antioxidant capacity, and proanthocyanidins, among which oligomers (monomers to tetramers), pentamers, hexamers, heptamers, octamers, nonamers, decamers, and polymers were detected, and they are probably associated with in vivo effects.

Organizational creativity – Hegemonic and alternative discourses

SUMMARY Organizational creativity – hegemonic and alternative discourses Over the course of recent developments in the societal and business environment, the concept of creativity has been brought into new arenas. The rise of ‘creative industries’ and the idea of creativity as a form of capital have attracted the interests of business and management professionals – as well as academics. As the notion of creativity has been adopted in the organization studies literature, the concept of organizational creativity has been introduced to refer to creativity that takes place in an organizational context. This doctoral thesis focuses on organizational creativity, and its purpose is to explore and problematize the hegemonic organizational creativity discourse and to provide alternative viewpoints for theorizing about creativity in organizations. Taking a discourse theory approach, this thesis, first, provides an outline of the currently predominant, i.e. hegemonic, discourse on organizational creativity, which is explored regarding themes, perspectives, methods and paradigms. Second, this thesis consists of five studies that act as illustrations of certain alternative viewpoints. Through these exemplary studies, this thesis sheds light on the limitations and taken-for-granted aspects of the hegemonic discourse and discusses what these alternative viewpoints could offer for the understanding of and theorizing for organizational creativity. This study leans on an assumption that the development of organizational creativity knowledge and the related discourse is not inevitable or progressive but rather contingent. The organizational creativity discourse has developed in a certain direction, meaning that some themes, perspectives, and methods, as well as assumptions, values, and objectives, have gained a hegemonic position over others, and are therefore often taken for granted and considered valid and relevant. The hegemonization of certain aspects, however, contributes to the marginalization of others. The thesis concludes that the hegemonic discourse on organizational creativity is based on an extensive coverage of certain themes and perspectives, such as those focusing on individual cognitive processes, motivation, or organizational climate and their relation to creativity, to name a few. The limited focus on some themes and the confinement to certain prevalent perspectives, however, results in the marginalization of other themes and perspectives. The negative, often unintended, consequences, implications, and side effects of creativity, the factors that might hinder or prevent creativity, and a deeper inquiry into the ontology and epistemology of creativity have attracted relatively marginal interest. The material embeddedness of organizational creativity, in other words, the physical organizational environment as well as the human body and its non-cognitive resources, has largely been overlooked in the hegemonic discourse, although thereare studies in this area that give reason to believe that they might prove relevant for the understanding of creativity. The hegemonic discourse is based on an individual-centered understanding of creativity which overattributes creativity to an individual and his/her cognitive capabilities, while simultaneously neglecting how, for instance, the physical environment, artifacts, social dynamics and interactions condition organizational creativity. Due to historical reasons, quantitative as well as qualitative yet functionally- oriented studies have predominated the organizational creativity discourse, although studies falling into the interpretationist paradigm have gradually become more popular. The two radical paradigms, as well as methodological and analytical approaches typical of radical research, can be considered to hold a marginal position in the field of organizational creativity. The hegemonic organizational creativity discourse has provided extensive findings related to many aspects of organizational creativity, although the con- ceptualizations and understandings of organizational creativity in the hegemonic discourse are also in many respects limited and one-sided. The hegemonic discourse is based on an assumption that creativity is desirable, good, necessary, or even obligatory, and should be encouraged and nourished. The conceptualiza- tions of creativity favor the kind of creativity which is useful, valuable and can be harnessed for productivity. The current conceptualization is limited to the type of creativity that is acceptable and fits the managerial ideology, and washes out any risky, seemingly useless, or negative aspects of creativity. It also limits the possible meanings and representations that ‘creativity’ has in the respective discourse, excluding many meanings of creativity encountered in other discourses. The excessive focus on creativity that is good, positive, productive and fits the managerial agenda while ignoring other forms and aspects of creativity, however, contributes to the dilution of the notion. Practices aimed at encouraging the kind of creativity may actually entail a risk of fostering moderate alterations rather than more radical novelty, as well as management and organizational practices which limit creative endeavors, rather than increase their likelihood. The thesis concludes that although not often given the space and attention they deserve, there are alternative conceptualizations and understandings of organizational creativity which embrace a broader notion of creativity. The inability to accommodate the ‘other’ understandings and viewpoints within the organizational creativity discourse runs a risk of misrepresenting the complex and many-sided phenomenon of creativity in organizational context. Keywords: Organizational creativity, creativity, organization studies, discourse theory, hegemony

A social-cognitive model of monitoring and its relationship to behaviour in a naturalistic observation : development and individual differences

years 8 months) and 24 older (M == 7 years 4 months) children. A Monitoring Process Model (MPM) was developed and tested in order to ascertain at which component process ofthe MPM age differences would emerge. The MPM had four components: (1) assessment; (2) evaluation; (3) planning; and (4) behavioural control. The MPM was assessed directly using a referential communication task in which the children were asked to make a series of five Lego buildings (a baseline condition and one building for each MPM component). Children listened to instructions from one experimenter while a second experimenter in the room (a confederate) intetjected varying levels ofverbal feedback in order to assist the children and control the component ofthe MPM. This design allowed us to determine at which "stage" ofprocessing children would most likely have difficulty monitoring themselves in this social-cognitive task. Developmental differences were obselVed for the evaluation, planning and behavioural control components suggesting that older children were able to be more successful with the more explicit metacomponents. Interestingly, however, there was no age difference in terms ofLego task success in the baseline condition suggesting that without the intelVention ofthe confederate younger children monitored the task about as well as older children. This pattern ofresults indicates that the younger children were disrupted by the feedback rather than helped. On the other hand, the older children were able to incorporate the feedback offered by the confederate into a plan ofaction. Another aim ofthis study was to assess similar processing components to those investigated by the MPM Lego task in a more naturalistic observation. Together the use ofthe Lego Task ( a social cognitive task) and the naturalistic social interaction allowed for the appraisal of cross-domain continuities and discontinuities in monitoring behaviours. In this vein, analyses were undertaken in order to ascertain whether or not successful performance in the MPM Lego Task would predict cross-domain competence in the more naturalistic social interchange. Indeed, success in the two latter components ofthe MPM (planning and behavioural control) was related to overall competence in the naturalistic task. However, this cross-domain prediction was not evident for all levels ofthe naturalistic interchange suggesting that the nature ofthe feedback a child receives is an important determinant ofresponse competency. Individual difference measures reflecting the children's general cognitive capacity (Working Memory and Digit Span) and verbal ability (vocabulary) were also taken in an effort to account for more variance in the prediction oftask success. However, these individual difference measures did not serve to enhance the prediction oftask performance in either the Lego Task or the naturalistic task. Similarly, parental responses to questionnaires pertaining to their child's temperament and social experience also failed to increase prediction oftask performance. On-line measures ofthe children's engagement, positive affect and anxiety also failed to predict competence ratings.

Hot cognition and activation of the medial prefrontal cortex: Self-regulating in contexts involving motivational pressures

The medial prefrontal cortex (mPFC) is involved in performance-monitoring and has been implicated in the generation of several electrocortical responses associated with self-regulation. The error-related negativity (ERN), the inhibitory Nogo N2 (N2), and the feedback-related negativity (FRN) are event-related potential (ERP) components which reflect mPFC activity associated with feedback to behavioural (ERN, N2) and environmental (FRN) consequences. Our main goal was to determine whether or not rnPFC activation varies as a function of motivational context (e.g., those involving performance-related incentives) or the use of internally versus externally generated feedback signals (i.e., errors). Additionally, we assessed medial prefrontal activity in relation to individual differences in personality and temperament. Participants completed a combination of tasks in which performance-related incentives were associated with task performance and feedback generated from internal versus external responses. MPFC activity was indexed using both ERP scalp voltage peaks and intracerebral current source density (CSD) of dorsal and ventral regions. Additionally, participants completed several questionnaires assessing personality and temperament styles. Given previous studies have shown that enhanced mPFC activity to loss (or negative) feedback, we expected that activity in the mPFC would generally be greater during the Loss condition relative to the Win condition for both the ERN and N2. Also, due to the evidence that the (vmPFC) is engaged in arousing contexts, we hypothesized that activity in the ventromedial prefrontal cortex (vmPFC) would be greater than activity in the dorsomedial prefrontal cortex (dmPFC), especially in the Loss condition of the GoNogo task (ERN). Similarly, loss feedback in the BART (FRN) was expected to engage the vmPFC more than the dmPFC. Finally, we predicted that persons rating themselves as more willing to engage in approach-related behaviours or to exhibit rigid cognitive styles would show reduced activity of the mPFC. Overall, our results emphasize the role of affective evaluations of behavioural and environmental consequences when self-regulating. Although there were no effects of context on brain activity, our data indicate that, during the time of the ERN and N2 on the MW Go-Nogo task and the FRN on the BART, the vrnPFC was more active compared to the dmPFC. Moreover, regional recruitment in the mPFC was similar across internally (ERN) and externally (FRN) generated errors signals associated with loss feedback, as reflected by relatively greater activity in the vmPFC than the dmPFC. Our data also suggest that greater activity in the mPFC is associated with better inhibitory control, as reflected by both scalp and CSD measures. Additionally, deactivation of the subgenual anterior cingulate cortex (sgACC) and lower levels of self-reported positive affect were both related to increased voluntary risk-taking on the BART. Finally, persons reporting higher levels of approach-related behaviour or cognitive rigidity showed reduced activity of the mPFC. These results are in line with previous research emphasizing that affect/motivation is central to the processes reflected by mediofrontal negativities (MFNs), that the vmPFC is involved in regulating demands on motivational/affective systems, and that the underlying mechanisms driving these functions vary across both individuals and contexts.

Calmodulin/KCa3.1 channel interactions as determinant to the KCa3.1 Ca2+ dependent gating : theoretical and experimental analyses

Differentes études ont montré que la sensibilité au Ca2+ du canal KCa3.1, un canal potassique indépendant du voltage, était conférée par la protéine calmoduline (CaM) liée de façon constitutive au canal. Cette liaison impliquerait la région C-lobe de la CaM et un domaine de $\ikca$ directement relié au segment transmembranaire S6 du canal. La CaM pourrait égalment se lier au canal de façon Ca2+ dépendante via une interaction entre un domaine de KCa3.1 du C-terminal (CaMBD2) et la région N-lobe de la CaM. Une étude fut entreprise afin de déterminer la nature des résidus responsables de la liaison entre le domaine CaMBD2 de KCa3.1 et la région N-lobe de la CaM et leur rôle dans le processus d'ouverture du canal par le Ca2+. Une structure 3D du complexe KCa3.1/CaM a d'abord été générée par modélisation par homologie avec le logiciel MODELLER en utilisant comme référence la structure cristalline du complexe SK2.2/CaM (PDB: 1G4Y). Le modèle ainsi obtenu de KCa3.1 plus CaM prévoit que le segment L361-S372 dans KCa3.1 devrait être responsable de la liaison dépendante du Ca2+ du canal avec la région N-lobe de la CaM via les résidus L361 et Q364 de KCa3.1 et E45, E47 et D50 de la CaM. Pour tester ce modèle, les résidus dans le segment L361-S372 ont été mutés en Cys et l'action du MTSET+ (chargé positivement) et MTSACE (neutre) a été mesurée sur l'activité du canal. Des enregistrements en patch clamp en configuration ``inside-out`` ont montré que la liaison du réactif chargé MTSET+ au le mutant Q364C entraîne une forte augmentation du courant, un effet non observé avec le MTSACE. De plus les mutations E45A et E47A dans la CaM, ont empêché l'augmentation du courant initié par MTSET+ sur le mutant Q364C. Une analyse en canal unitaire a confirmé que la liaison MTSET+ à Q364C cause une augmentation de la probabilité d'ouverture de KCa3.1 par une déstabilisation de l'état fermé du canal. Nous concluons que nos résultats sont compatibles avec la formation de liaisons ioniques entre les complexes chargés positivement Cys-MTSET+ à la position 364 de KCa3.1 et les résidus chargés négativement E45 et E47 dans la CaM. Ces données confirment qu'une stabilisation électrostatique des interactions CaM/KCa3.1 peut conduire à une augmentation de la probabilité d'ouverture du canal en conditions de concentrations saturantes de Ca2+.

Étude du contrôle postural quasi-statique et dynamique en position debout des personnes ayant une lésion médullaire incomplète.

L’atteinte sensorimotrice découlant d’une lésion médullaire traumatique affecte la capacité à se tenir debout de façon sécuritaire. Chez les individus ayant une lésion médullaire incomplète, les chutes lors des tâches locomotrices sont fréquentes après la réadaptation, entraînant des blessures qui affectent la participation sociale et la qualité de vie. Une meilleure compréhension du contrôle postural en clinique aiderait à cibler des interventions efficaces à ce niveau. L’objectif général de cette thèse était donc d’étudier le contrôle postural debout lors de tâches variées chez les personnes avec lésion médullaire traumatique en utilisant une approche biomécanique. Les objectifs spécifiques étaient d’étudier divers aspects du contrôle postural en lien avec chacune des tâches et d’identifier les variables prédictives de la stabilité. Vingt-cinq (25) personnes ayant une lésion médullaire traumatique incomplète ont été recrutées. Elles ont été évaluées au laboratoire d’analyse de mouvement lors du maintien de la station debout quasi-statique yeux ouverts et fermés, de l’exécution d’un test des limites de stabilité multidirectionnelles, de la marche naturelle et de l’initiation et l’arrêt de la marche. Des mesures biomécaniques caractérisant le déplacement du centre de pression (COP) ainsi que le modèle du contrôle postural dynamique des forces stabilisantes et déstabilisantes ont été utilisés pour comparer le contrôle postural des patients à celui d’un groupe formé de 33 personnes en santé. Les résultats ont montré une diminution du contrôle postural quasi-statique et dynamique chez les personnes ayant une lésion médullaire comparativement aux personnes en santé. Cette diminution s’accompagnait d’une contribution élevée des informations visuelles à la station debout quasi-statique qui était associée au score du mini BESTest. Le déplacement du COP lors du test des limites de stabilité multidirectionnelle se caractérisait par une difficulté à suivre la direction indiquée. Ce manque de précision causait une augmentation du trajet nécessaire pour atteindre la distance maximale dans chacune des directions. Les résultats au maintien de la station debout quasi-statique et au test des limites de stabilité multidirectionnelle n’étaient pas corrélés. La phase unipodale de la marche des personnes ayant une lésion médullaire différait de celle des personnes en santé par une force stabilisante maximale moindre et une force déstabilisante plus grande alors que l’arrêt de la marche se révélait plus instable que l’initiation de la marche chez les personnes ayant une lésion médullaire. Pour l’ensemble des tâches de marche, la vitesse du COM et la distance entre le COP et la base de support étaient les facteurs explicatifs principaux des forces stabilisantes et déstabilisantes. En somme, les résultats confirment l’impression clinique d’une atteinte générale du contrôle postural debout des personnes ayant une lésion médullaire; ils en précisent les caractéristiques et ciblent les paramètres à considérer dans la rééducation.

Characteristic Study of the Boundary Layer Parameters over the Arabian Sea and the Bay of Bengal Using the QuikSCAT Dataset

The marine atmospheric boundary layer (MABL) plays a vital role in the transport of momentum and heat from the surface of the ocean into the atmosphere. A detailed study on the MABL characteristics was carried out using high-resolution surface-wind data as measured by the QuikSCAT (Quick scatterometer) satellite. Spatial variations in the surface wind, frictional velocity, roughness parameter and drag coe±cient for the di®erent seasons were studied. The surface wind was strong during the southwest monsoon season due to the modulation induced by the Low Level Jetstream. The drag coe±cient was larger during this season, due to the strong winds and was lower during the winter months. The spatial variations in the frictional velocity over the seas was small during the post-monsoon season (»0.2 m s¡1). The maximum spatial variation in the frictional velocity was found over the south Arabian Sea (0.3 to 0.5 m s¡1) during the southwest monsoon period, followed by the pre-monsoon over the Bay of Bengal (0.1 to 0.25 m s¡1). The mean wind-stress curl during the winter was positive over the equatorial region, with a maximum value of 1.5£10¡7 N m¡3, but on either side of the equatorial belt, a negative wind-stress curl dominated. The area average of the frictional velocity and drag coe±cient over the Arabian Sea and Bay of Bengal were also studied. The values of frictional velocity shows a variability that is similar to the intraseasonal oscillation (ISO) and this was con¯rmed via wavelet analysis. In the case of the drag coe±cient, the prominent oscillations were ISO and quasi-biweekly mode (QBM). The interrelationship between the drag coe±cient and the frictional velocity with wind speed in both the Arabian Sea and the Bay of Bengal was also studied.

Geostatistics for constrained variables: positive data, compositions and probabilities. Applications to environmental hazard monitoring

Aquesta tesi estudia com estimar la distribució de les variables regionalitzades l'espai mostral i l'escala de les quals admeten una estructura d'espai Euclidià. Apliquem el principi del treball en coordenades: triem una base ortonormal, fem estadística sobre les coordenades de les dades, i apliquem els output a la base per tal de recuperar un resultat en el mateix espai original. Aplicant-ho a les variables regionalitzades, obtenim una aproximació única consistent, que generalitza les conegudes propietats de les tècniques de kriging a diversos espais mostrals: dades reals, positives o composicionals (vectors de components positives amb suma constant) són tractades com casos particulars. D'aquesta manera, es generalitza la geostadística lineal, i s'ofereix solucions a coneguts problemes de la no-lineal, tot adaptant la mesura i els criteris de representativitat (i.e., mitjanes) a les dades tractades. L'estimador per a dades positives coincideix amb una mitjana geomètrica ponderada, equivalent a l'estimació de la mediana, sense cap dels problemes del clàssic kriging lognormal. El cas composicional ofereix solucions equivalents, però a més permet estimar vectors de probabilitat multinomial. Amb una aproximació bayesiana preliminar, el kriging de composicions esdevé també una alternativa consistent al kriging indicador. Aquesta tècnica s'empra per estimar funcions de probabilitat de variables qualsevol, malgrat que sovint ofereix estimacions negatives, cosa que s'evita amb l'alternativa proposada. La utilitat d'aquest conjunt de tècniques es comprova estudiant la contaminació per amoníac a una estació de control automàtic de la qualitat de l'aigua de la conca de la Tordera, i es conclou que només fent servir les tècniques proposades hom pot detectar en quins instants l'amoni es transforma en amoníac en una concentració superior a la legalment permesa.

The climate sensitivity and its components diagnosed from Earth Radiation Budget data

One of the major uncertainties in the ability to predict future climate change, and hence its impacts, is the lack of knowledge of the earth's climate sensitivity. Here, data are combined from the 1985-96 Earth Radiation Budget Experiment (ERBE) with surface temperature change information and estimates of radiative forcing to diagnose the climate sensitivity. Importantly, the estimate is completely independent of climate model results. A climate feedback parameter of 2.3 +/- 1.4 W m(-2) K-1 is found. This corresponds to a 1.0-4.1-K range for the equilibrium warming due to a doubling of carbon dioxide (assuming Gaussian errors in observable parameters, which is approximately equivalent to a uniform "prior" in feedback parameter). The uncertainty range is due to a combination of the short time period for the analysis as well as uncertainties in the surface temperature time series and radiative forcing time series, mostly the former. Radiative forcings may not all be fully accounted for; however, all argument is presented that the estimate of climate sensitivity is still likely to be representative of longer-term climate change. The methodology can be used to 1) retrieve shortwave and longwave components of climate feedback and 2) suggest clear-sky and cloud feedback terms. There is preliminary evidence of a neutral or even negative longwave feedback in the observations, suggesting that current climate models may not be representing some processes correctly if they give a net positive longwave feedback.

A link between low-frequency mesoscale eddy variability around Madagascar and the large-scale Indian Ocean variability

A connection is shown to exist between the mesoscale eddy activity around Madagascar and the large-scale interannual variability in the Indian Ocean. We use the combined TOPEX/Poseidon-ERS sea surface height (SSH) data for the period 1993–2003. The SSH-fields in the Mozambique Channel and east of Madagascar exhibit a significant interannual oscillation. This is related to the arrival of large-scale anomalies that propagate westward along 10°–15°S in response to the Indian Ocean dipole (IOD) events. Positive (negative) SSH anomalies associated to a positive (negative) IOD phase induce a shift in the intensity and position of the tropical and subtropical gyres. A weakening (strengthening) results in the intensity of the South Equatorial Current and its branches along east Madagascar. In addition, the flow through the narrows of the Mozambique Channel around 17°S increases (decreases) during periods of a stronger and northward (southward) extension of the subtropical (tropical) gyre. Interaction between the currents in the narrows and southward propagating eddies from the northern Channel leads to interannual variability in the eddy kinetic energy of the central Channel in phase with the one in the SSH-field.

Identification of stimulatory and inhibitory inputs to the hypothalamic-pituitary-adrenal axis during hypoglycaemia or transport in ewes

This study used the novel approach of statistical modelling to investigate the control of hypothalamic-pituitary-adrenal (HPA) axis and quantify temporal relationships between hormones. Two experimental paradigms were chosen, insulin-induced hypoglycaemia and 2 h transport, to assess differences in control between noncognitive and cognitive stimuli. Vasopressin and corticotropin-releasing hormone (CRH) were measured in hypophysial portal plasma, and adrenocorticotropin hormone (ACTH) and cortisol in jugular plasma of conscious sheep, and deconvolution analysis was used to calculate secretory rates, before modelling. During hypoglycaemia, the relationship between plasma glucose and vasopressin or CRH was best described by log(10) transforming variables (i.e. a positive power-curve relationship). A negative-feedback relationship with log(10) cortisol concentration 2 h previously was detected. Analysis of the 'transport' stimulus suggested that the strength of the perceived stimulus decreased over time after accounting for cortisol facilitation and negative-feedback. The time course of vasopressin and CRH responses to each stimulus were different However, at the pituitary level, the data suggested that log(10) ACTH secretion rate was related to log(10) vasopressin and CRH concentrations with very similar regression coefficients and an identical ratio of actions (2.3 : 1) for both stimuli. Similar magnitude negative-feedback effects of log(10) cortisol at -110 min (hypoglycaemia) or -40 min (transport) were detected, and both models contained a stimulatory relationship with cortisol at 0 min (facilitation). At adrenal gland level, cortisol secretory rates were related to simultaneously measured untransformed ACTH concentration but the regression coefficient for the hypoglycaemia model was 2.5-fold greater than for transport. No individual sustained maximum cortisol secretion for longer than 20 min during hypoglycaemia and 40 min during transport. These unique models demonstrate that corticosteroid negative-feedback is a significant control mechanism at both the pituitary and hypothalamus. The amplitude of HPA response may be related to stimulus intensity and corticosteroid negative-feedback, while duration depended on feedback alone.