Ehrenzweig and the Statute of Frauds: An Inquiry Into the Rule of Validation

Graphics processing units (GPUs) are used today in a wide range of applications, mainly because they can dramatically accelerate parallel computing, are affordable and energy efficient. In the field of medical imaging, GPUs are in some cases crucial for enabling practical use of computationally demanding algorithms. This review presents the past and present work on GPU accelerated medical image processing, and is meant to serve as an overview and introduction to existing GPU implementations. The review covers GPU acceleration of basic image processing operations (filtering, interpolation, histogram estimation and distance transforms), the most commonly used algorithms in medical imaging (image registration, image segmentation and image denoising) and algorithms that are specific to individual modalities (CT, PET, SPECT, MRI, fMRI, DTI, ultrasound, optical imaging and microscopy). The review ends by highlighting some future possibilities and challenges

Droit international, relations sociales de propriété et processus de paix en Colombie : Une réarticulation politico-juridique

Cet article propose une analyse du processus de transition vers la paix en Colombie sous l’angle de la place cruciale qu’y occupe le droit. La démobilisation des paramilitaires met en lumière le rôle instrumental du droit qui, dans la tension entre ordre et justice, s’avère un moyen pragmatique de faire reconnaître de jure, et donc de légaliser, un rapport de force construit de facto au sein du conflit. La norme de justice est appréciée (et donc nuancée) de manière à ne pas compromettre l’effectivité du processus de transition, et permet à une paix « négative » de se mettre en place, qui n’est finalement que le reflet d’un statu quo social. Implications et conséquences de la recherche de la paix à tout prix se doivent d’être examinées. Pour cela, il est impératif de revoir les divisions disciplinaires qui occultent souvent ces questions essentielles.This essay analyses the Colombian peace process while considering the vital role of law. It stresses the instrumental character of law in fostering the demobilization process of Colombian paramilitaries. The tension between order and justice is understood as a pragmatic way to acknowledge the de jure character, institutionalized by law, of the power relations built de facto throughout the conflict. It further argues that the standard of justice has been purposely used in order to avoid compromising the peace process. The result is the implementation of a « negative » peace, which can be considered as nothing more than a social statu quo. This process, aimed at achieving peace at any cost, has many implications and consequences, which issues can only be addressed by challenging the disciplinary divisions between Law and Politics

Paramaterized beams as effective human lip models

There are numerous mathematical equations used by animators and modelers to describe the curves of the human face and, specifically, the human lip. Physically-based polynomial models, b-splines, and other arbitrarily parameterized equations are used to describe facial and lip contours, though with varied degrees of complexity and resolution. This study examined the constraints and conditions necessary to utilize a standard Euler-Bernoulli beam as an effective model for the human lip. Through this analysis it was determined that general beam theories are flexible enough to create models that can generate curves comparable to actual lip shapes, though no single model studied was appreciably better suited for aU possible Up shapes. Such models could still, however, be utilized in the development of computer-based animation as well as motion tracking systems, computer user interfaces, and teleoperational devices. Beam characteristics such as cross sectional shape, length, and elasticity were investigated in order to define deflection models for four different beam configurations: a clamped prismatic beam, a simply supported prismatic beam, a clamped tapered beam, and a simply supported tapered beam. Multiple beam loading scenarios were simulated to determine the optimal number and arrangement of loads to reproduce the desired deflection curves. Deflection curves defined by each of the four beam models were compared to actual deflection curves digitized from photographs of the human lip and have been presented here

Steepest descent as Linear Quadratic Regulation

Concorder un modèle à certaines observations, voilà qui résume assez bien ce que l’apprentissage machine cherche à accomplir. Ce concept est maintenant omniprésent dans nos vies, entre autre grâce aux percées récentes en apprentissage profond. La stratégie d’optimisation prédominante pour ces deux domaines est la minimisation d’un objectif donné. Et pour cela, la méthode du gradient, méthode de premier-ordre qui modifie les paramètres du modèle à chaque itération, est l’approche dominante. À l’opposé, les méthodes dites de second ordre n’ont jamais réussi à s’imposer en apprentissage profond. Pourtant, elles offrent des avantages reconnus qui soulèvent encore un grand intérêt. D’où l’importance de la méthode du col, qui unifie les méthodes de premier et second ordre sous un même paradigme. Dans ce mémoire, nous établissons un parralèle direct entre la méthode du col et le domaine du contrôle optimal ; domaine qui cherche à optimiser mathématiquement une séquence de décisions. Et certains des problèmes les mieux compris et étudiés en contrôle optimal sont les commandes linéaires quadratiques. Problèmes pour lesquels on connaît très bien la solution optimale. Plus spécifiquement, nous démontrerons l’équivalence entre une itération de la méthode du col et la résolution d’une Commande Linéaire Quadratique (CLQ). Cet éclairage nouveau implique une approche unifiée quand vient le temps de déployer nombre d’algorithmes issus de la méthode du col, tel que la méthode du gradient et celle des gradients naturels, sans être limitée à ceux-ci. Approche que nous étendons ensuite aux problèmes à horizon infini, tel que les modèles à équilibre profond. Ce faisant, nous démontrons pour ces problèmes que calculer les gradients via la différentiation implicite revient à employer l’équation de Riccati pour solutionner la CLQ associée à la méthode du gradient. Finalement, notons que l’incorporation d’information sur la courbure du problème revient généralement à rencontrer une inversion matricielle dans la méthode du col. Nous montrons que l’équivalence avec les CLQ permet de contourner cette inversion en utilisant une approximation issue des séries de Neumann. Surprenamment, certaines observations empiriques suggèrent que cette approximation aide aussi à stabiliser le processus d’optimisation quand des méthodes de second-ordre sont impliquées ; en agissant comme un régularisateur adaptif implicite.Machine learning entails training a model to fit some given observations, and recent advances in the field, particularly in deep learning, have made it omnipresent in our lives. Fitting a model usually requires the minimization of a given objective. When it comes to deep learning, first-order methods like gradient descent have become a default tool for optimization in deep learning. On the other hand, second-order methods did not see widespread use in deep learning. Yet, they hold many promises and are still a very active field of research. An important perspective into both methods is steepest descent, which allows you to encompass first and second-order approaches into the same framework. In this thesis, we establish an explicit connection between steepest descent and optimal control, a field that tries to optimize sequential decision-making processes. Core to it is the family of problems known as Linear Quadratic Regulation; problems that have been well studied and for which we know optimal solutions. More specifically, we show that performing one iteration of steepest descent is equivalent to solving a Linear Quadratic Regulator (LQR). This perspective gives us a convenient and unified framework for deploying a wide range of steepest descent algorithms, such as gradient descent and natural gradient descent, but certainly not limited to. This framework can also be extended to problems with an infinite horizon, such as deep equilibrium models. Doing so reveals that retrieving the gradient via implicit differentiation is equivalent to recovering it via Riccati’s solution to the LQR associated with gradient descent. Finally, incorporating curvature information into steepest descent usually takes the form of a matrix inversion. However, casting a steepest descent step as a LQR also hints toward a trick that allows to sidestep this inversion, by leveraging Neumann’s series approximation. Empirical observations provide evidence that this approximation actually helps to stabilize the training process, by acting as an adaptive damping parameter

Paramilitarisme et scandale de la parapolitique en Colombie

La divulgation récente de nombreux documents et témoignages démontrent qu’une portion de la classe politique colombienne est sous influence d’un groupe armé irrégulier : les paramilitaires. Cette situation, pour le moins délicate, représente une menace à la légitimité de plusieurs institutions gouvernementales et fait évidemment scandale autant à l’interne qu’à l’international. Nous tenterons donc de comprendre les origines et la dynamique du scandale médiatique désormais connu comme la crise de la parapolitique. Ces événements sont centraux afin de saisir le contexte politique actuel en Colombie. Contexte d’autant plus important que le président colombien, Álvaro Uribe Vélez et le Premier ministre Stephen Harper, s’entendirent en juillet 2007 pour négocier un traité de libre échange entre les deux pays

Detection of Salinity by the Lobster, Homarus americanus

Changes in the heart rates of lobsters (Homarus americanus) were used as an indicator that the animals were capable of sensing a reduction in the salinity of the ambient seawater. The typical response to a gradual (1 to 2 ppt/min) reduction in salinity consisted of a rapid increase in heart rate at a mean threshold of 26.6 ± 0.7 ppt, followed by a reduction in heart rate when the salinity reached 22.1 ± 0.5 ppt. Animals with lesioned cardioregulatory nerves did not exhibit a cardiac response to changes in salinity. A cardiac response was elicited from lobsters exposed to isotonic chloride-free salines but not to isotonic sodium-, magnesium- or calcium-free salines. There was little change in the blood osmolarity of lobsters when bradycardia occurred, suggesting that the receptors involved are external. Furthermore, lobsters without antennae, antennules, or legs showed typical cardiac responses to low salinity, indicating the receptors are not located in these areas. Lobsters exposed to reductions in the salinity of the ambient seawater while both branchial chambers were perfused with full-strength seawater did not display a cardiac response until the external salinity reached 21.6 ± 1.8 ppt. In contrast, when their branchial chambers were exposed to reductions in salinity while the external salinity was maintained at normal levels, changes in heart rate were rapidly elicited in response to very small reductions in salinity (down to 29.5 ± 0.9 ppt in the branchial chamber and 31.5 ± 0.3 ppt externally). We conclude that the primary receptors responsible for detecting reductions in salinity in H. americanus are located within or near the branchial chambers and are primarily sensitive to chloride ions

Electrocorticographic recording of cerebral cortex areas manipulated using an adeno-associated virus targeting cofilin in mice

The use of electrocorticographic (ECoG) recordings in rodents is relevant to sleep research and to the study of a wide range of neurological conditions. Adeno-associated viruses (AAVs) are increasingly used to improve understanding of brain circuits and their functions. The AAV-mediated manipulation of specific cell populations and/or of precise molecular components has been tremendously useful to identify new sleep regulatory circuits/molecules and key proteins contributing to the adverse effects of sleep loss. For instance, inhibiting activity of the filamentous actin-severing protein cofilin using AAV prevents sleep deprivation-induced memory impairment. Here, a protocol is described that combines the manipulation of cofilin function in a cerebral cortex area with the recording of ECoG activity to examine whether cortical cofilin modulates the wakefulness and sleep ECoG signals. AAV injection is performed during the same surgical procedure as the implantation of ECoG and electromyographic (EMG) electrodes in adult male and female mice. Mice are anesthetized, and their heads are shaved. After skin cleaning and incision, stereotaxic coordinates of the motor cortex are determined, and the skull is pierced at this location. A cannula prefilled with an AAV expressing cofilinS3D, an inactive form of cofilin, is slowly positioned in the cortical tissue. After AAV infusion, gold-covered screws (ECoG electrodes) are screwed through the skull and cemented to the skull with gold wires inserted in the neck muscles (EMG electrodes). The animals are allowed three weeks to recover and to ensure sufficient expression of cofilinS3D. The infected area and cell type are verified using immunohistochemistry, and the ECoG is analyzed using visual identification of vigilance states and spectral analysis. In summary, this combined methodological approach allows the investigation of the precise contribution of molecular components regulating neuronal morphology and connectivity to the regulation of synchronized cerebral cortex activity during wakefulness and sleep

Prospectives

Tiré de: Prospectives, vol. 1, no 2, avril 1965Titre de l'écran-titre (visionné le 24 janv. 2013)Bibliogr