Alien Registration- Larochelle, Antoine (Winslow, Kennebec County)

https://digitalmaine.com/alien_docs/16357/thumbnail.jp

Signalisation par les récepteurs toll-like dans un contexte d'excitotoxicité

L’excitotoxicité est un processus pathologique responsable de la mort neuronale dans plusieurs désordres neurologiques. La mort des neurones par excitotoxicité libère dans le milieu extracellulaire des molécules capables d’activer les microglies adjacentes aux sites lésés. L’activation du système immunitaire suite à une blessure cérébrale est généralement vue comme nocive pour les neurones. Les récepteurs toll-like (TLR) font partie des principaux récepteurs responsables de la reconnaissance des dommages cérébraux après une lésion excitotoxique. Les résultats de ce mémoire démontrent qu’un préconditionnement induit par l’injection systémique d’un ligand TLR2 ou TLR4 permet d’augmenter la survie neuronale face à une lésion excitotoxique. La neuroprotection est dépendante de la signalisation MyD88 et est associée avec une activation microgliale bénéfique. Des souris chimériques pour les cellules de la moelle osseuse ont révélé que la signalisation MyD88 au niveau des cellules résidentes du système nerveux central joue un rôle favorable dans la survie neuronale contre l’excitotoxicité.Excitotoxicity is a pathological process responsible for the death of neurons as observed in multiple neurological disorders. This process releases danger signals in the extracellular space that alert and activate surrounding microglial cells. Immune system activation following acute brain injury is often considered detrimental, contributing to further neuronal damage. Toll-like receptors (TLR) are among the main receptors that recognize cell damage and initiate an inflammatory response following cell damage. The study presented in this report shows that a systemic injection of a TLR2 or TLR4 agonist induces a state of preconditioning that increases neuron survival against acute excitotoxicity. The neuroprotective effects are associated with a beneficial activation of microglial cells and depend upon MyD88 signaling. Furthermore, bone marrow chimeric mice revealed that MyD88 signaling in cells of the central nervous system has a protective effect against excitotoxicity

Slow light in subwavelength grating waveguides

Structural slow light is the dispersion engineering process by which the group velocity of light can be drastically reduced in a periodic waveguide structure. Enabling large group delay and enhancing the light-matter interaction on a subwave- length scale, on-chip slow light is of great interest in a vast array of fields such as non-linear optic, sensing, laser physics, telecommunication and computing. In this work, we experimen- tally demonstrate, for the first time, slow light in subwavelength grating waveguides on the silicon-on-insulator platform. We present a comprehensive numerical study in analytical modelling and 3D FDTD. Multiple waveguides variations were fabricated using an electron-beam lithography process. Figures of merit such as group index, bandwidth and loss-per-delay are examined in both theory and experiment. A maximum measured group index of 47.74 with a loss-per-delay of 103.37 dB/ns has been achieved near the wavelength of 1550 nm. A broad bandwidth of 8.82 nm was measured, in which the group index remains larger than 10. We also show that the region of slow light operation can be shifted over a large wavelength span by controlling a single design parameter

Design of slow-light subwavelength grating waveguides for enhanced on-chip methane sensing by absorption spectroscopy

The performance of on-chip gas sensors using absorption spectroscopy are currently limited by the small overlap and reduced interaction length between the light and the analyte. Here, the use of slow-light in subwavelength grating (SWG) waveguide integrated on a silicon photonic chip is proposed to improve methane sensing by tunable diode laser absorption spectroscopy in the near infrared. Such SWG waveguide increases the interaction by two means. First, close to the photonic bandgap edge, a SWG waveguide no longer acts as a metamaterial with a homogeneous index, but rather as a 1D photonic crystal in which slow-light effect enhances the light-analyte interaction. Second, the subwavelength segmentation of the waveguide increases the modal overlap with the air. These two enhancement mechanisms results in a six-fold improvement of the interaction with respect to strip waveguides. In this paper, we discuss how to engineer the group index of SWG waveguides to exploit slow-light effect for the first time. Design guidelines for minimizing propagation loss and disorder effect are discussed considering limitations of typical fabrication processes. SWG waveguides could improve the sensitivity and the limit of detection of on-chip trace-gas sensors that provide a compact, fabrication tolerant, inexpensive, and selective sensing technology

Tunable slow-light in silicon photonics subwavelength grating waveguides

Slow-light is experimentally demonstrated in subwavelength grating waveguides integrated on a silicon photonic chip. At the band-edge, a group index up to 30 is measured. We show that the band-edge wavelength varies linearly with the subwavelength grating period and can be shifted by thermal tuning

Brain Tumor Segmentation with Deep Neural Networks

In this paper, we present a fully automatic brain tumor segmentation method based on Deep Neural Networks (DNNs). The proposed networks are tailored to glioblastomas (both low and high grade) pictured in MR images. By their very nature, these tumors can appear anywhere in the brain and have almost any kind of shape, size, and contrast. These reasons motivate our exploration of a machine learning solution that exploits a flexible, high capacity DNN while being extremely efficient. Here, we give a description of different model choices that we've found to be necessary for obtaining competitive performance. We explore in particular different architectures based on Convolutional Neural Networks (CNN), i.e. DNNs specifically adapted to image data. We present a novel CNN architecture which differs from those traditionally used in computer vision. Our CNN exploits both local features as well as more global contextual features simultaneously. Also, different from most traditional uses of CNNs, our networks use a final layer that is a convolutional implementation of a fully connected layer which allows a 40 fold speed up. We also describe a 2-phase training procedure that allows us to tackle difficulties related to the imbalance of tumor labels. Finally, we explore a cascade architecture in which the output of a basic CNN is treated as an additional source of information for a subsequent CNN. Results reported on the 2013 BRATS test dataset reveal that our architecture improves over the currently published state-of-the-art while being over 30 times faster

Analytical modeling of silicon microring and microdisk modulators with electrical and optical dynamics

We propose an analytical time-domain model for microring and microdisk modulators, which considers both their electrical and optical properties. Theory of the dynamics of microring/microdisk is discussed, and general solutions to the transfer matrix representation are presented. Both static and dynamic predictions from the model are compared to measurement results to demonstrate the accuracy of our model. Static predictions and measurements are presented for power and phase responses, whereas dynamic predictions and measurements are presented for small-signal and large-signal operations. The model verifies that the chirping and modulation bandwidth of the modulators depend on the detuning state. Finally, the accuracy and scalability of several techniques employed in the model are discussed

Multiple Promoters and Alternative Splicing: Hoxa5 Transcriptional Complexity in the Mouse Embryo

The genomic organization of Hox clusters is fundamental for the precise spatio-temporal regulation and the function of each Hox gene, and hence for correct embryo patterning. Multiple overlapping transcriptional units exist at the Hoxa5 locus reflecting the complexity of Hox clustering: a major form of 1.8 kb corresponding to the two characterized exons of the gene and polyadenylated RNA species of 5.0, 9.5 and 11.0 kb. This transcriptional intricacy raises the question of the involvement of the larger transcripts in Hox function and regulation.We have undertaken the molecular characterization of the Hoxa5 larger transcripts. They initiate from two highly conserved distal promoters, one corresponding to the putative Hoxa6 promoter, and a second located nearby Hoxa7. Alternative splicing is also involved in the generation of the different transcripts. No functional polyadenylation sequence was found at the Hoxa6 locus and all larger transcripts use the polyadenylation site of the Hoxa5 gene. Some larger transcripts are potential Hoxa6/Hoxa5 bicistronic units. However, even though all transcripts could produce the genuine 270 a.a. HOXA5 protein, only the 1.8 kb form is translated into the protein, indicative of its essential role in Hoxa5 gene function. The Hoxa6 mutation disrupts the larger transcripts without major phenotypic impact on axial specification in their expression domain. However, Hoxa5-like skeletal anomalies are observed in Hoxa6 mutants and these defects can be explained by the loss of expression of the 1.8 kb transcript. Our data raise the possibility that the larger transcripts may be involved in Hoxa5 gene regulation.Our observation that the Hoxa5 larger transcripts possess a developmentally-regulated expression combined to the increasing sum of data on the role of long noncoding RNAs in transcriptional regulation suggest that the Hoxa5 larger transcripts may participate in the control of Hox gene expression

Forty years of carabid beetle research in Europe - from taxonomy, biology, ecology and population studies to bioindication, habitat assessment and conservation

Volume: 100Start Page: 55End Page: 14