Representació no-lineal de les imatges per a codificació perceptiva

JPEG2000 és un estàndard de compressió d’imatges que utilitza la transformada wavelet i, posteriorment, una quantificació uniforme dels coeficients amb dead-zone. Els coeficients wavelet presenten certes dependències tant estadístiques com visuals. Les dependències estadístiques es tenen en compte a l'esquema JPEG2000, no obstant, no passa el mateix amb les dependències visuals. En aquest treball, es pretén trobar una representació més adaptada al sistema visual que la que proporciona JPEG2000 directament. Per trobar-la utilitzarem la normalització divisiva dels coeficients, tècnica que ja ha demostrat resultats tant en decorrelació estadística de coeficients com perceptiva. Idealment, el que es voldria fer és reconvertir els coeficients a un espai de valors en els quals un valor més elevat dels coeficients impliqui un valor més elevat d'aportació visual, i utilitzar aquest espai de valors per a codificar. A la pràctica, però, volem que el nostre sistema de codificació estigui integrat a un estàndard. És per això que utilitzarem JPEG2000, estàndard de la ITU que permet una elecció de les distorsions en la codificació, i utilitzarem la distorsió en el domini de coeficients normalitzats com a mesura de distorsió per a escollir quines dades s'envien abans.

Government information transparency

This paper studies a model of announcements by a privately informed government about the future state of the economic activity in an economy subject to recurrent shocks and with distortions due to income taxation. Although transparent communication would ex ante be desirable, we find that even a benevolent government may ex-post be non-informative, in an attempt to countervail the tax distortion with a "second best" compensating distortion in information. This result provides a rationale for independent national statistical offices, committed to truthful communication. We also find that whether inequality in income distribution favors or harms government transparency depends on labor supply elasticity.

Dynamic calibration of our sense of time.

An accurate sense of time contributes to functions ranging from the perception and anticipation of sensory events to the production of coordinated movements. However, accumulating evidence demonstrates that time perception is subject to strong illusory distortion. In two experiments, we investigated whether the subjective speed of temporal perception is dependent on our visual environment. By presenting human observers with speed-altered movies of a crowded street scene, we modulated performance on subsequent production of "20s" elapsed intervals. Our results indicate that one's visual environment significantly contributes to calibrating our sense of time, independently of any modulation of arousal. This plasticity generates an assay for the integrity of our sense of time and its rehabilitation in clinical pathologies.

Repair of schistosomal intestinal vascular lesions after curative treatment

The process of repairing intestinal vascular lesions induced by schistosomiasis in mice was studied before and after curative chemotherapy, by means of histopathology coupled with injections of the mesenteric veins with India ink or plastic, in this case followed by corrosion in strong acid. The granulomas were avascular, mainly formed while within blood vessels, and were associated with distortion of the intestinal vasculature in their proximity, represented by tortuosities, focal dilatation, narrowing, and anastomosis of the mucosal and submucosal veins. Two to four months after cure of schistosomiasis involuting granulomas were seen to be slowly vascularized, a process going from the periphery toward the center of the granulomas. No intravascular granulomas were seen four months after treatment. The previously distorted mucosal and submucosal veins gradually regained their normal appearance, only a slight tortuosity remaining.

Former eating disorder impairs 3rd person but not 1st person perspective taking. Does dance training help?

The mental ability to take the perspective of another person may depend on one's own bodily awareness and experience. In the present study, the former was defined as having a history of an eating disorder, and the latter variable was defined as formal experience with dance. The study used a 2 × 2 × 2 factorial design in which reaction times in two mental perspective taking tasks were compared between female dancers and non-dancers with and without a former eating disorder. Participants were asked to imagine two perspectives: i) the position of front-facing and back-facing figures (3rd person perspective taking task) and ii) that these same figures are a self reflection in a mirror (1st person perspective taking task). In both tasks, a particular hand was indicated in the presented figures, and the participants had to decide whether the hand represented their own left or right hand. Overall, responses were slower for front-facing than back-facing figures in the 3rd person perspective taking task, and for back-facing than front-facing figures in the 1st person perspective taking task. Importantly, having a former history of an eating disorder related to a decreased performance in the 3rd person perspective taking task, but only in participants without dance experience. Results from an additional control group (a history of exercise but no dance experience) indicated that dance is particularly beneficial for mental bodily perspective taking. Dance experience, more so than exercise in general, can benefit 3rd person or extrapersonal perspective taking, supporting the favourable impact this exercise has on own body processing

Viatge als país dels somnis...perduts? : Aspectes de la sociabilitat nord-americana

Els objectius finals són diversos: comprovar els diferents punts de vista i les diferents perspectives socials dels autors esmentats, comparar-los amb les situacions reals que es donen cada dia, mirar d'esbrinar el perquè d'aquestes situacions, fer un estudi comparatiu des del punt de vista d'un europeu que visita els Estats Units i, sobretot, mirar d'entendre què porta els nord-americans a comportar-se d'aquesta manera i què porta autors com Leavitt i Ellis a reproduir o desdibuixar els trets més significatius de la societat nord-americana.

Advantages of digital holographic microscopy for real-time full field absolute phase imaging

Different interferometric techniques were developed last decade to obtain full field, quantitative, and absolute phase imaging, such as phase-shifting, Fourier phase microscopy, Hilbert phase microscopy or digital holographic microscopy (DHM). Although, these techniques are very similar, DHM combines several advantages. In contrast, to phase shifting, DHM is indeed capable of single-shot hologram recording allowing a real-time absolute phase imaging. On the other hand, unlike to Fourier phase or Hilbert phase microscopy, DHM does not require to record in focus images of the specimen on the digital detector (CCD or CMOS camera), because a numerical focalization adjustment can be performed by a numerical wavefront propagation. Consequently, the depth of view of high NA microscope objectives is numerically extended. For example, two different biological cells, floating at different depths in a liquid, can be focalized numerically from the same digital hologram. Moreover, the numerical propagation associated to digital optics and automatic fitting procedures, permits vibrations insensitive full- field phase imaging and the complete compensation for a priori any image distortion or/and phase aberrations introduced for example by imperfections of holders or perfusion chamber. Examples of real-time full-field phase images of biological cells have been demonstrated. ©2008 COPYRIGHT SPIE

Redox dysregulation in schizophrenia : implication for oligodendrocyte maturation and structural connectivity

Schizophrenia, which results from an interaction between gene and environmental factors, is a psychiatric disorder characterized by reality distortion. The clinical symptoms, which are generally diagnosed in late adolescence or early adulthood, partly derive from altered brain connectivity especially in prefrontal cortex. Disruption of neuronal networks implies oligodendrocyte and myelin abnormalities in schizophrenia pathophysiology. The mechanisms of these impairments are still unclear. Converging evidences indicate a role of redox dysregulation, generated by an imbalance between pro-oxidants and antioxidant defense mechanisms, in the development of schizophrenia pathophysiology. In particular, genetic and biochemical data indicate impaired synthesis of glutathione, the main cellular antioxidant and redox regulator. As oligodendrocyte maturation is dependent on redox state, we evaluated whether abnormal redox control could contribute to oligodendrocyte and myelin impairments in schizophrenia. We found that glutathione in prefrontal cortex of early psychosis patients and control subjects positively correlated with white matter integrity. We then further explored the interplay between glutathione and myelin using a translational approach. Our data showed that in mice with genetically impaired glutathione synthesis, oligodendrocyte late maturation as well as myelination was delayed in the anterior cingulate cortex. Specifically, oligodendrocyte number and myelin levels were lowered at peripubertal age, coincident in time with the peak of myelin- related gene expression during normal brain development. These data suggest that early adolescence is a vulnerable developmental period during which an adequate redox control is required for oligodendrocyte maturation and active myelination process. Consistently, oxidative stress mediated by psychosocial stress also delayed myelination in peripubertal mice. At cellular levels, impaired glutathione synthesis altered oligodendrocyte development at several levels. Using oligodendrocyte progenitor cells cultures, our data showed that glutathione deficiency was associated with (i) cell cycle arrest and a reduction in oligodendrocyte proliferation, and (ii) an impairment in oligodendrocyte maturation. Abnormal oligodendrocyte proliferation was mediated by upregulation of Fyn kinase activity. Consistently, under oxidative stress conditions, we observed abnormal regulation of Fyn kinase in fibroblasts of patients deficient in glutathione synthesis. Together, our data support that a redox dysregulation due to glutathione deficit could underlie myelination impairment in schizophrenia, possibly mediated by dysregulated Fyn pathway. Better characterization of Fyn mechanisms would pave the way towards new drug targets. -- La schizophrénie est une maladie psychiatrique qui se définit par une distorsion de la perception de la réalité. Les symptômes cliniques sont généralement diagnostiqués durant l'adolescence ou au début de l'âge adulte et proviennent de troubles de la connectivité, principalement au niveau du cortex préfrontal. Les dysfonctionnements des réseaux neuronaux impliquent des anomalies au niveau des oligodendrocytes et de la myéline dans la pathophysiologie de la schizophrénie. Les mécanismes responsables des ces altérations restent encore mal compris. Dans le développement de la schizophrénie, des évidences mettent en avant un rôle de la dérégulation rédox, traduit par un déséquilibre entre facteurs pro-oxydants et défenses antioxydantes. Des données génétiques et biochimiques indiquent notamment un défaut de la synthèse du glutathion, le principal antioxydant et rédox régulateur des cellules. Etant donné que la maturation des oligodendrocytes est dépendante de l'état rédox, nous avons regardé si une dérégulation rédox contribue aux anomalies de la myéline dans le cadre de la schizophrénie. Dans le cortex préfrontal des sujets contrôles et des patients en phase précoce de psychose, nous avons montré que le glutathion était positivement associé à l'intégrité de matière blanche. Afin d'explorer plus en détail la relation entre le glutathion et la myéline, nous avons mené une étude translationnelle. Nos résultats ont montré que des souris ayant un déficit de la synthèse du glutathion présentaient un retard dans les processus de maturation des oligodendrocytes et de la myélinisation dans le cortex cingulaire antérieure. Plus précisément, le nombre d'oligodendrocytes et le taux de myéline étaient uniquement diminués durant la période péripubertaire. Cette même période correspond au pic de l'expression des gènes en lien avec la myéline. Ces données soulignent le fait que l'adolescence est une période du développement particulièrement sensible durant laquelle un contrôle adéquat de l'état rédox est nécessaire aux processus de maturation des oligodendrocytes et de myélinisation. Ceci est en accord avec la diminution de myéline observée suite à un stress oxydatif généré par un stress psychosocial. Au niveau cellulaire, un déficit du glutathion affecte le développement des oligodendrocytes à différents stades. En effet, dans des cultures de progéniteurs d'oligodendrocytes, nos résultats montrent qu'une réduction du taux de glutathion était associée à (i) un arrêt du cycle cellulaire ainsi qu'une diminution de la prolifération des oligodendrocytes, et à (ii) des dysfonctionnements de la maturation des oligodendrocytes. Par ailleurs, au niveau moléculaire, les perturbations de la prolifération étaient générées par une augmentation de l'activité de la kinase Fyn. Ceci est en accord avec la dérégulation de Fyn observée dans les fibroblastes de patients ayant une déficience en synthèse du glutathion en condition de stress oxydatif. Les résultats de cette thèse soulignent qu'une dérégulation rédox induite par un déficit en glutathion peut contribuer aux anomalies des oligodendrocytes et de la myéline via le dysfonctionnement des voies de signalisation Fyn. Une recherche plus avancée de l'implication de Fyn dans la maladie pourrait ouvrir la voie à de nouvelles cibles thérapeutiques.

Perspectives of auto-correcting lens distortions in mosaic-based underwater navigation

When unmanned underwater vehicles (UUVs) perform missions near the ocean floor, optical sensors can be used to improve local navigation. Video mosaics allow to efficiently process the images acquired by the vehicle, and also to obtain position estimates. We discuss in this paper the role of lens distortions in this context, proving that degenerate mosaics have their origin not only in the selected motion model or in registration errors, but also in the cumulative effect of radial distortion residuals. Additionally, we present results on the accuracy of different feature-based approaches for self-correction of lens distortions that may guide the choice of appropriate techniques for correcting distortions

Pattern recognition of sleep in rodents using piezoelectric signals generated by gross body movements.

Current research on sleep using experimental animals is limited by the expense and time-consuming nature of traditional EEG/EMG recordings. We present here an alternative, noninvasive approach utilizing piezoelectric films configured as highly sensitive motion detectors. These film strips attached to the floor of the rodent cage produce an electrical output in direct proportion to the distortion of the material. During sleep, movement associated with breathing is the predominant gross body movement and, thus, output from the piezoelectric transducer provided an accurate respiratory trace during sleep. During wake, respiratory movements are masked by other motor activities. An automatic pattern recognition system was developed to identify periods of sleep and wake using the piezoelectric generated signal. Due to the complex and highly variable waveforms that result from subtle postural adjustments in the animals, traditional signal analysis techniques were not sufficient for accurate classification of sleep versus wake. Therefore, a novel pattern recognition algorithm was developed that successfully distinguished sleep from wake in approximately 95% of all epochs. This algorithm may have general utility for a variety of signals in biomedical and engineering applications. This automated system for monitoring sleep is noninvasive, inexpensive, and may be useful for large-scale sleep studies including genetic approaches towards understanding sleep and sleep disorders, and the rapid screening of the efficacy of sleep or wake promoting drugs.

3-d residual eddy current field characterisation: applied to diffusion weighted magnetic resonance imaging.

Clinical use of the Stejskal-Tanner diffusion weighted images is hampered by the geometric distortions that result from the large residual 3-D eddy current field induced. In this work, we aimed to predict, using linear response theory, the residual 3-D eddy current field required for geometric distortion correction based on phantom eddy current field measurements. The predicted 3-D eddy current field induced by the diffusion-weighting gradients was able to reduce the root mean square error of the residual eddy current field to ~1 Hz. The model's performance was tested on diffusion weighted images of four normal volunteers, following distortion correction, the quality of the Stejskal-Tanner diffusion-weighted images was found to have comparable quality to image registration based corrections (FSL) at low b-values. Unlike registration techniques the correction was not hindered by low SNR at high b-values, and results in improved image quality relative to FSL. Characterization of the 3-D eddy current field with linear response theory enables the prediction of the 3-D eddy current field required to correct eddy current induced geometric distortions for a wide range of clinical and high b-value protocols.

Genetic and environmental effects on early life-history traits in salmonids

Les changements environnementaux, tels la température ou les maladies infectieuses, peuvent influencer l'évolution en induisant de la sélection, mais ceci à la seule condition qu'il y ait assez de diversité génétique pour les traits en question ou pour l'expression plastique de ces traits. Au cours cette thèse, nous avons étudié l'effet de potentielles pressions environnementales sur différents phénotypes de trois représentants des sous familles des salmonidés: l'ombre commun (Thymallus thymallus; Thymallinae), la truite de rivière {Salmo trutta; Salmoninae) et le corégone Coregonus palaea (Coregoninae). Les salmonidés se prêtent particulièrement bien à ce type d'expériences car étant hautement sensibles aux conditions environnementales, ils montrent une large variabilité dans leurs traits morphologiques, comportementaux ainsi que d'histoire de vie, tout en bénéficiant d'un large intérêt général. Nous avons testé si le sexe de l'ombre commun pouvait être modifié par la température, ce qui pourrait ainsi expliquer un changement abrupte de sex ratio observé dans l'une des plus grandes populations de Suisse. Nous n'avons trouvé aucun indice permettant de conclure que la température puisse induire ce changement chez l'ombre commun ou chez la truite de rivière. De plus nous avons étudié la plasticité de développement ainsi que d'éclosion, et avons observé des différences entre familles ainsi qu'entre populations. Alors que ces différences comportementales entre populations suggéraient une adaptation aux conditions environnementales locales, cette prédiction n'a pas été confirmée par une expérience de transplantation réciproque d'embryons entre cinq rivières de la même région. Cette étude a montré que les embryons ne survivaient pas mieux dans leur rivière d'origine, indiquant donc une absence d'adaptation locale. Nous avons aussi montré que la mortalité embryonnaire était influencée autant par des "bons gènes" que par des "gènes compatibles", que la qualité des mâles pouvait être signalée par leur coloration, et que le fait d'élever des poissons dans une pisciculture pouvait aboutir a des relations contre-intuitives entre la coloration des mâles et la qualité de leur jeunes. Nos résultats contribuent ainsi à une meilleure compréhension de l'effet de diverses pressions environnementales sur la morphologie, le comportement ou les traits d'histoire de vie chez les salmonidés. - Environmental changes, such as changes in temperatures or infection levels, can induce selection and drive evolution if there is sufficient genetic variation for the traits or the plasticity in trait expression. In this thesis, we investigated the influence of potential environmental stressors on various phenotypes in representatives of the three salmonid subfamilies: the European grayling (Thymallus thymallus; Thymallinae), the brown trout (,Salmo trutta; Salmoninae), and the whitefish Coregonus palaea (Coregoninae). Salmonids are ideal study species, as they seem sensitive to changing environmental conditions, show considerable variability in morphological, behavioral, and life history traits, and are of broad public interest. We investigated whether temperature-induced sex reversal could explain the sex-ratio distortion found in one of Switzerland's largest grayling populations. We found no evidence of temperature-induced sex reversal in either graylings or brown trout. We also examined plasticity in embryo development and the timing of hatching. We found variation at the level of family and population. Although behavioral differences between populations suggested adaptation to local environmental conditions, no indications of local adaptation could be found in reciprocal transplant experiments carried out over five rivers in the same region. We also demonstrate that embryo development and viability is influenced by 'good genes' and 'compatible genes', that the genetic quality of sires can be signaled by their grey coloration, and that raising larvae in a hatchery environment can produce counter-intuitive relationships between male phenotypes and offspring viability. Our results contribute to the understanding of how changing environmental conditions affect the phenotypes and the heritability of early life-history traits in salmonids.

Adaptation to experimental alterations of the operational sex ratio in populations of Drosophila melanogaster.

Theory predicts that males adapt to sperm competition by increasing their investment in testis mass to transfer larger ejaculates. Experimental and comparative data support this prediction. Nevertheless, the relative importance of sperm competition in testis size evolution remains elusive, because experiments vary only sperm competition whereas comparative approaches confound it with other variables, in particular male mating rate. We addressed the relative importance of sperm competition and male mating rate by taking an experimental evolution approach. We subjected populations of Drosophila melanogaster to sex ratios of 1:1, 4:1, and 10:1 (female:male). Female bias decreased sperm competition but increased male mating rate and sperm depletion. After 28 generations of evolution, males from the 10:1 treatment had larger testes than males from other treatments. Thus, testis size evolved in response to mating rate and sperm depletion, not sperm competition. Furthermore, our experiment demonstrated that drift associated with sex ratio distortion limits adaptation; testis size only evolved in populations in which the effect of sex ratio bias on the effective population size had been compensated by increasing the numerical size. We discuss these results with respect to reproductive evolution, genetic drift in natural and experimental populations, and consequences of natural sex ratio distortion.

Spatial Hyperschematia without Spatial Neglect after Insulo-Thalamic Disconnection.

Different spatial representations are not stored as a single multipurpose map in the brain. Right brain-damaged patients can show a distortion, a compression of peripersonal and extrapersonal space. Here we report the case of a patient with a right insulo-thalamic disconnection without spatial neglect. The patient, compared with 10 healthy control subjects, showed a constant and reliable increase of her peripersonal and extrapersonal egocentric space representations - that we named spatial hyperschematia - yet left her allocentric space representations intact. This striking dissociation shows that our interactions with the surrounding world are represented and processed modularly in the human brain, depending on their frame of reference.

Le multiple evanescent white dot syndrome: une prédisposition génétique [Multiple evanescent white dot syndrome: a genetic predisposition?]

BACKGROUND: Multiple evanescent white dot syndrome (MEWDS) is a benign acquired isolated chorioretinal disorder. Symptoms include photopsia, visual blur and scotomas. Ocular examination reveals multiple white dots at the level of the deep retina. A parainfectious disorder was suggested but the exact mechanism of MEWDS is still unknown. Postulating that MEWDS might be an antigen driven inflammatory reaction, we analyzed HLA subtypes in patients with MEWDS. PATIENTS AND METHODS: Sixteen patients were diagnosed with MEWDS in Lausanne from 1985 to 1994. Blood was withdrawn in 9/16 patients. HLA-A, -B and -DR were sought. RESULTS: HLA-B51 was detected in 4/9 patients (44.4%). Other HLA subtypes were detected sporadically. CONCLUSIONS: The frequency of HLA-B51 haplotype was found to be 3.7 times more elevated than in a normal control caucasian group. This suggests the possibility that MEWDS might be a genetically determined disorder as it is the case for other ocular diseases like Birdshot chorioretinopathy (HLA-A29), Harada's disease (HLA-DRMT3), acute anterior uveitis (HLA-B27) or Behçet's disease (HLA-B51). We have no explanation for the presence of HLA-B51 in both Behçet's disease and MEWDS. The association of HLA-B51 and MEWDS needs confirmation by further testing.