Geometry optimization of unidirectional integrated ring laser

Ring lasers, evanescently coupled to an adjacent optical waveguide, are essential components for the upcoming generation of integrated sources. In an ideally symmetric resonator, emission occurs from the both clockwise and counter-clockwise directions, resulting in a potential waste of emitted optical power, while unidirectional emission has been reported in different configurations, for example when asymmetric external reflectivities are used for the coupling waveguide. In the integrated form, a common approach consists in the inserting an S-bend waveguide in the ring, in such a way that the field propagating in the direction that we want to suppress is reinjected in the other direction. The S-bend waveguide must be carefully designed to reduce optical losses and to ensure a sufficient suppression of the undesired field. Using 2D finite- difference time-domain simulations performed with Synopsys RSof

S-shaped waveguide-induced asymmetry between counter-propagating modes in a racetrack resonator

Ongoing progress in photonic integrated circuits necessitates the integration of semiconductor ring lasers (SRLs) with high performance and predictable behavior, which can be achieved when the symmetry of the SRL, which supports both clockwise and counterclockwise beam propagation, is unbalanced through loss mechanisms inside the resonator. In this work, numerical simulations were carried out on the symmetric layout of the racetrack resonator equipped with an asymmetric S-shaped internal waveguide. The simulations results were compared with the ones of analogue structures without internal waveguide showing the benefit induced by this additional element in term of the unidirectionality of the SRL

Involvement of pro-inflammatory cytokines and growth factors in the pathogenesis of Dupuytren's contracture: a novel target for a possible future therapeutic strategy?

Dupuytren's contracture (DC) is a benign fibro-proliferative disease of the hand causing fibrotic nodules and fascial cords which determine debilitating contracture and deformities of fingers and hands. The present study was designed to characterize pro-inflammatory cytokines and growth factors involved in the pathogenesis, progression and recurrence of this disease, in order to find novel targets for alternative therapies and strategies in controlling DC. The expression of pro-inflammatory cytokines and of growth factors was detected by immunohistochemistry in fibrotic nodules and normal palmar fascia resected respectively from patients affected by DC and carpal tunnel syndrome (CTS; as negative controls). Reverse transcription (RT)-PCR analysis and immunofluorescence were performed to quantify the expression of transforming growth factor (TGF)-β1, interleukin (IL)-1β and vascular endothelial growth factor (VEGF) by primary cultures of myofibroblasts and fibroblasts isolated from Dupuytren's nodules. Histological analysis showed high cellularity and high proliferation rate in Dupuytren's tissue, together with the presence of myofibroblastic isotypes; immunohistochemical staining for macrophages was completely negative. In addition, a strong expression of TGF-β1, IL-1β and VEGF was evident in the extracellular matrix and in the cytoplasm of fibroblasts and myofibroblasts in Dupuytren's nodular tissues, as compared with control tissues. These results were confirmed by RT-PCR and by immunofluorescence in pathological and normal primary cell cultures. These preliminary observations suggest that TGF-β1, IL-1β and VEGF may be considered potential therapeutic targets in the treatment of Dupuytren's disease (DD)

Integrated multi-band WSS: from design to performance evaluation

Modern day optical communications require ever-increasing bandwidths and capacity, in order to keep up with the growth of traffic and resource-intensive applications. This increase in network capacity can be achieved through the use of the residual capacity of current-day infrastructure, although this requires switching and routing devices capable of wide-band operation in multiple transmission windows. In this work, we describe the design principle, architecture, and performance simulation of a photonic integrated circuit (PIC) based multi-band WSS, which is envisioned to operate on the S+C+L windows. While the architecture is scalable to an arbitrary channel and port count, we showcase a 24-channel implementation deployed on the 400ZR standard, providing both the penalty evaluation through DSP simulations, as well as a footprint evaluation based on the components design

Neuronal dynamics of signal selective motor plan cancellation in the macaque dorsal premotor cortex

Primates adopt various strategies to interact with the environment. Yet, no study has examined the effects of behavioural strategies with regard to how movement inhibition is implemented at the neuronal level. We used a modified version of the stop-task by adding an extra signal – termed the Ignore signal – capable of influencing the inhibition of movements only within a specific strategy. We simultaneously recorded multisite neuronal activity from the dorsal premotor (PMd) cortex of macaque monkeys during the task and applied a state-space approach. As a result, we found that movement generation is characterized by neuronal dynamics that evolve between subspaces. When the movement is halted, this evolution is arrested and inverted. Conversely, when the Ignore signal is presented, inversion of the evolution is observed briefly and only when a specific behavioural strategy is adopted. Moreover, neuronal signatures during the inhibitory process were predictive of how PMd processes inhibitory signals, allowing the classification of the resulting behavioural strategy. Our data further corroborate the PMd as a critical node in movement inhibition

A finite element framework for distortion gradient plasticity with applications to bending of thin foils

© 2016 Elsevier Ltd A novel general purpose Finite Element framework is presented to study small-scale metal plasticity. A distinct feature of the adopted distortion gradient plasticity formulation, with respect to strain gradient plasticity theories, is the constitutive inclusion of the plastic spin, as proposed by Gurtin (2004) through the prescription of a free energy dependent on Nye's dislocation density tensor. The proposed numerical scheme is developed by following and extending the mathematical principles established by Fleck and Willis (2009). The modeling of thin metallic foils under bending reveals a significant influence of the plastic shear strain and spin due to a mechanism associated with the higher-order boundary conditions allowing dislocations to exit the body. This mechanism leads to an unexpected mechanical response in terms of bending moment versus curvature, dependent on the foil length, if either viscoplasticity or isotropic hardening are included in the model. In order to study the effect of dissipative higher-order stresses, the mechanical response under non-proportional loading is also investigated.Dr. Andrea Panteghini and Prof. Samuel Forest are acknowledged for helpful discussions. The authors gratefully acknowledge financial support from the Danish Council for Independent Research under the research career programme Sapere Aude in the project “Higher Order Theories in Solid Mechanics”. E. Martínez-Pañeda also acknowledges financial support from the Ministry of Science and Innovation of Spain through grant MAT2011-28796-CO3-03, and the University of Oviedo through grant UNOV-13-PF and an excellence mobility grant within the International Campus of Excellence programme. L. Bardella additionally acknowledges financial support from the Italian Ministry of Education, University, and Research (MIUR)

Simulation and Analysis of Dynamic Regimes Involving Ground and Excited State Transitions in Quantum Dot Passively Mode-Locked Lasers

n/

Possible involvement of pro-inflammatory cytokines and growth factors in the pathogenesis of the Dupuytren’s contracture: a novel target for a future therapeutic strategy?

Dupuytren’s contracture (DC) is a benign fibroproliferative disease causing fibrotic nodules and fascial cords with resultant debilitating flexion contracture deformities. The present study was designed to characterize pro-inflammatory cytokines and growth factors involved in the genesis, progression and recurrence of the disease to optimize therapeutic agents and strategies for controlling Dupuytren’s disease. The expression of pro-inflammatory cytokines and other growth factors was detected by immunohistochemistry and immunofluorescence in the fibrotic nodules and normal palmar fascia resected respectively from patients affected by Dupuytren’s contracture and Carpal Tunnel Syndrome (as negative controls). RT-PCR analysis was performed to quantify the expression of TGF-β1, IL-1β and VEGFa in the myofibroblasts and fibroblasts isolated from Dupuytren’s nodules. Histological analysis showed the high cellularity and rate of proliferation of Dupuytren’s tissue with the presence of myofibroblastic isotypes. Our data showed the strong expression of TGF-β1, IL-1β and VEGFa in Dupuytren’s fibromatosis nodules suggesting a direct role of these markers in the onset, progression and recurrence of the disease. Our observations suggest that TGF-β1, IL-1β and VEGFa may be considered potential therapeutic targets in the treatment of Dupuytren’s disease. Moreover, a new innovative therapy may be represented by the combined use of specific inhibitors of these growth factors