739 research outputs found
Associative properties of the perirhinal network
No full textThe perirhinal cortex (PRC), comprised of Brodmann areas 35 and 36, is a rostrocaudally-oriented strip of cortex in the medial temporal lobe, whose lesion produces memory impairments. Previous in vivo recording studies have revealed that a reduction in the responsiveness of perirhinal neurons to familiar stimuli underlies object recognition memory; whereas the opposite behavior, an increase in responsiveness, is required for associative memory formation between two paired stimuli. Both phenomena rely on long-term plasticity in the PRC. However, it is currently unclear how, as a result of experience, the same network could support these two seemingly opposite forms of long-term plasticity. PRC receives topographically organized projections from many high-order neocortical areas, mostly from the adjacent temporal neocortex; and it possesses an intrinsic network that distributes these neocortical inputs throughout its rostrocaudal axis. Previous studies suggest that neocortical inputs strongly recruit perirhinal inhibitory interneurons located at the same transverse level. In contrast, distant neocortical inputs only lead to excitation because longitudinal perirhinal connections engage few inhibitory interneurons. Given these facts, it is possible that the PRC acts as a Hebbian network to associate coincident but spatially distributed inputs. Consequently, the main objective of this thesis is to shed light on the mechanisms allowing neocortical inputs to undergo long-term depression (LTD) or potentiation (LTP), depending on to what extent they recruit the intrinsic perirhinal connections. Thus, using electrophysiological and imaging techniques in the whole guinea pig brain in vitro, I show that theta-frequency stimulation (TFS) at a single neocortical site leads to an input-specific group I mGluR-dependent LTD at all perirhinal levels, whereas paired TFS of two distant neocortical sites recruits the intrinsic circuit of the PRC and results in a NMDAR-dependent LTP to the paired inputs. Consistent with these results, utilizing anterograde tracing in rats and electron microscopic observations, this thesis shows that there are more inhibitory synapses formed by direct neocortical inputs to PRC and short-range perirhinal connections compared to long-range neocortical and perirhinal axons coursing in the PRC. Together, these findings suggest a mechanism whereby PRC associates temporally relevant but spatially distributed neocortical inputs.Ph.D.Includes bibliographical referencesIncludes vitaby Gunes Una
Exploitation of homogeneous isotropic turbulence models for optimization of turbulence remote sensing
No full textHomogeneous isotropic turbulence (HIT) models are compared, with respect to optimization of turbulence remote sensing. HIT models have different applications such as load calculation for wind turbines (Mann, 1998) or droplet track modelling (Pinsky and Khain, 2006). Details of vortices seem of less relevance for modelling `realistic measurements', where the single purpose is to retrieve the eddy dissipation rate (EDR). Without the need for modelling the vortices, a faster and simpler approach might be favorable. The cascade turbulence model (CTM) is suggested. The CTM solution is scale invariant and a fast solution for one-dimensional HIT modelling. In this presentation modelled radar measruments for scanning mode (rotating antenna) are compared for different HIT models. The consequences for turbulence remote sensing optimization are discussed
Le complexe universitaire du bassin parisien : un colosse aux pieds d'argile
No full textThe author has been consulting when the renovation of the universities of the Paris Basin took place. This contribution is a call for action. Taking into account the history of the development of the universities in the main cities of the Paris Basin, and the analysis of the recent consultation held in the Basin about the question (1994-1997), the author gives a series of proposals in order to avoid that the universities of the Basin remain "beginners".Alimentée par l'expérience de l'auteur, engagée comme consultant dans le chantier du développement universitaire du Bassin parisien, cette contribution est un appel à l'action. A partir d'un rappel de la problématique du développement universitaire dans les villes de la grande couronne et d'un regard sur la consultation qui s'est déroulée sur la question (1994-97), sont proposées la création d'une structure permanente fédérant les acteurs concernés et des orientations pour éviter que l'enseignement supérieur dans le Bassin ne soit pas qu'un "enseignement de premier cycle".Unal Marion. Le complexe universitaire du bassin parisien : un colosse aux pieds d'argile. In: Travaux de l'Institut Géographique de Reims, vol. 25, n°97-98, 1998. Le bassin parisien : un espace en construction, sous la direction de Anna Geppert-Hebrard . pp. 109-116
Paraoxonase and Arylesterase Activities, Lipid Profile, and Oxidative Damage in Experimental Ischemic Colitis Model
Get PDFObjective. In the present study, since PON1 is known as an HDL-associated antioxidant enzyme that inhibits the oxidative modification of LDL and oxidative stress plays a role in the pathogenesis of mesenteric ischemia, we investigated the changes in PON1 activity and lipid profile in an experimental ischemic colitis model. Methods. Forty male Wistar albino rats were divided into two groups: the control group (N=15) and the experimental group (N=25). All animals were anesthetized with ether and ketamine anesthesia to undergo a midline laparotomy. Ischemic colitis was induced by marginal vessel ligation in the splenic flexura (devascularization process). A sham laparotomy was performed in the control group. All animals were sacrificed on the seventh postoperative day. Oxidative stress marker (malonyldialdehyde, MDA), lipid profile, and paraoxonase (PON-1) and arylesterase activities were determined. Histopathological evaluation was done under light microscopy, after sectioning and staining with hematoxyline and eosin. Statistical analysis was conducted using Student’s t-test and Mann-Whitney U test, and P0.05). Conclusions. PON1 and arylesterase play an important role in the pathophysiology of ischemic colitis
Open-source software for automated rodent behavioral analysis
Get PDFRodent behavioral analysis is a major specialization in experimental psychology and behavioral neuroscience. Rodents display a wide range of species-specific behaviors, not only in their natural habitats but also under behavioral testing in controlled laboratory conditions. Detecting and categorizing these different kinds of behavior in a consistent way is a challenging task. Observing and analyzing rodent behaviors manually limits the reproducibility and replicability of the analyses due to potentially low inter-rater reliability. The advancement and accessibility of object tracking and pose estimation technologies led to several open-source artificial intelligence (AI) tools that utilize various algorithms for rodent behavioral analysis. These software provide high consistency compared to manual methods, and offer more flexibility than commercial systems by allowing custom-purpose modifications for specific research needs. Open-source software reviewed in this paper offer automated or semi-automated methods for detecting and categorizing rodent behaviors by using hand-coded heuristics, machine learning, or neural networks. The underlying algorithms show key differences in their internal dynamics, interfaces, user-friendliness, and the variety of their outputs. This work reviews the algorithms, capability, functionality, features and software properties of open-source behavioral analysis tools, and discusses how this emergent technology facilitates behavioral quantification in rodent research
Simplified prediction equation for ultimate stress in beams prestressed with hybrid tendons
No full textThe use of unbonded tendons is getting more widespread in post-tensioning industry; especially in rehabilitation and strengthening of existing damaged concrete members. The prediction of the stress at ultimate in unbonded tendon is important in calculating the capacity of structural members. This thesis presents a simplified prediction equation for concrete beams prestressed with hybrid (a combination of bonded and unbonded) tendons. The proposed equation is based on the Generalized Incremental Analysis (GIA) which uses the trussed-beam model developed by Ozkul et al. (2008) and Nassif et al. (2003). The main objective of this research is to develop a simple, but accurate design equation for the prediction of the stress at ultimate in unbonded tendon. Most important parameters such as loading type, effective prestress of unbonded tendon, concrete strength, area of steel reinforcement and span-to-depth ratio are taken into consideration. The equation is applicable to beams prestressed with unbonded or hybrid, FRP or steel, external or internal tendons. For the validation of the proposed simplified equation, test results available in the literature (199 beams) are collected. The results show that the proposed simplified equation exhibited very good accuracy for the calculation of stress at ultimate in unbonded tendon. The simplified equation is easy to use, accurate and applicable to any material type and combination of tendons.M.S.Includes bibliographical referencesby Gonca Una
The effect of Philosophy for Children (P4C) activities on the development of moral perception and social rules of preschool children
Get PDFThe purpose of the study was to examine the effects of P4C implementations on children\u27s perceptions of moral and social rules. The study was carried out with a total of 48 children aged five years old, 23 of them in the experimental group and 25 of them in the control group, attending a public school in the 2023–2024 academic years. A quasi-experimental design was used in the research, and the fully mixed sequential equal status design, one of the mixed research typologies, was applied. The Preschool Children\u27s Conceptions of Moral and Social Rules Scale was applied in the quantitative dimension of the research, and observation, interviews, and anecdotal records constituted the qualitative data collection dimension. Briefly, after the implementation process, the experimental group\u27s perception of moral and social norms improved. In the current study, a substantial difference between the children\u27s moral rule and social rule perceptions after the P4C sessions was discovered when the experimental group\u27s moral rule and social rule perception scale scores were analyzed before and after the implementation. A noticeable improvement in cognitive and social-emotional development was seen. It was determined that positive behaviors improved, particularly in moral situations requiring tolerance, in the experimental group. The study came to the conclusion that teaching children philosophy helps them enhance their critical thinking skills
High-Resolution Raindrop Size Distribution Retrieval Based on the Doppler Spectrum in the Case of Slant Profiling Radar
No full textDoppler spectra from vertically profiling radars are usually considered to retrieve the raindrop size distribution (DSD). However, to exploit both fall velocity spectrum and polarimetric measurements, Doppler spectra acquired in slant profiling mode should be explored. Rain DSD samples are obtained from simultaneously measured vertical and slant profile Doppler spectra and evaluated. In particular, the effect of the horizontal wind and the averaging time are investigated. The Doppler spectrum provides a way to retrieve the DSD, the radial wind, and a spectral broadening factor by means of a nonlinear optimization technique. For slant profiling of light rain when the horizontal wind is strong, the DSD results can be affected. Such an effect is demonstrated on a study case of stratiform light rain. Adding a wind profiler mode to the radar simultaneously supplies the horizontal wind and Doppler spectra. Before the retrieval procedure, the Doppler spectra are shifted in velocity to remove the mean horizontal wind contribution. The DSD results are considerably improved. Generally, averaged Doppler spectra are input into this type of algorithm. Instead, high-resolution, low-averaged Doppler spectra are chosen in order to take into account the small-scale variability of the rainfall. Investigating the linear relations at fixed median volume diameter, measured reflectivity-retrieved rainfall rate, for a slant beam, the consistency of the integrated parameters is established for two averaging periods. Nevertheless, the corresponding DSD parameter distributions reveal differences attributed to the averaging of the Doppler spectra. The new aspects are to obtain the same retrieval quality as vertically profiling and highly averaged spectra in an automated way.Geoscience and Remote SensingCivil Engineering and Geoscience
Multi-beam raindrop size distributions retrievals on the Doppler spectra: Influence of averaging and mean horizontal wind correction
No full textAcquiring the raindrop size distribution (DSD) from radar data is still a challenge. For profiling radar, this distribution can be estimated from the Doppler spectra. However the Doppler spectrum is not a direct measure of the DSD. The radial component of the wind shifts the Doppler spectrum related to the raindrop size distribution along the Doppler velocity interval. Furthermore, the Doppler spectrum may be broadened by turbulence effect. The Doppler spectra of rain are modelled using Rayleigh scattering, the gamma distribution for the raindrop size, a size-shape relationship and a Gaussian kernel for the turbulence. Comparing the measured Doppler spectrum with the modelled one, a non-linear least-square fit technique is employed to obtain the parameters of the raindrop size distribution (D0, ?) and the turbulence broadening factor of the raindrop size spectrum (?0). The intercept parameter (Nw) and the radial wind component (v0) are estimated by scaling the broadened DSD along the spectral reflectivity axis and the Doppler velocity axis respectively. This approach has been proposed in [1]. So far, this technique has not been further developed, exploited and validated. It is our intention to investigate this methodology using the S-band Doppler-polarimetric TARA radar to retrieve raindrop size distribution from drizzle to heavy precipitation with high spatial and time resolution. Since TARA can profile in three directions, three raindrop size distribution profiles are estimated, which can give insight in the microphysical homogeneity of the precipitation. Because TARA can be used as wind profiler, the mean horizontal wind is estimated and a correction to remove the effect of the radial mean horizontal wind is implemented in the retrieval procedure. Comparison with and without correction is done. Another issue is averaging. Should the Doppler spectra be averaged before the non-linear least-square fit? How should they be averaged and how many averages should be carried out? These questions are discussed. High resolution multi-beams raindrop size distribution retrievals are illustrated and discussed.Geoscience & Remote SensingCivil Engineering and Geoscience
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