Articles de revues : « Coupled fiber rings »

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Smirnov, Sergey V., Maxim O. Makarenko, Sergey V. Suchkov, Dmitry Churkin et Andrey A. Sukhorukov. « Bistable lasing in parity-time symmetric coupled fiber rings ». Photonics Research 6, n^o 4 (20 mars 2018) : A18. http://dx.doi.org/10.1364/prj.6.000a18.

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Sun, Wenbo. « Modeling a Fully Polarized Optical Fiber Suitable for Photonic Integrated Circuits or Sensors ». Photonics 11, n^o 10 (14 octobre 2024) : 961. http://dx.doi.org/10.3390/photonics11100961.

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A method is developed to make an optical fiber that only transmits fully linearly polarized light and maintains the polarization state. The method for efficient ingesting laser into this fiber is also reported. Using an optical fiber with a prism head, we can compress a plane wave into the thin rectangular cross-section fiber, and the light intensity within the fiber is much larger than that of the incidence wave. Our finite-difference time-domain (FDTD) simulation results show that the compressed light in the fiber becomes fully polarized and maintains the polarization state, and can be well coupled out by the resonance rings. This method is suitable for developing highly efficient polarization-maintaining optical fibers in a much simpler way, for applications in photonic integrated circuits or optical sensors.

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Maitland, Calum, Daniele Faccio et Fabio Biancalana. « Modulation instability of discrete angular momentum in coupled fiber rings ». Journal of Optics 21, n^o 6 (28 mai 2019) : 065504. http://dx.doi.org/10.1088/2040-8986/ab18eb.

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Quang. « SUPERCONTINUUM GENERATION IN SOLID-CORE PHOTONIC CRYSTAL FIBER INFILTRATED WITH WATER-ETHANOL MIXTURE ». Journal of Military Science and Technology, n^o 66A (6 mai 2020) : 92–102. http://dx.doi.org/10.54939/1859-1043.j.mst.66a.2020.92-102.

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In this paper, we report a numerical study of the supercontinuum (SC) generation in solid-core photonic crystal fibers infiltrated with water-ethanol mixtures. A photonic crystal fiber is constructed as borosilicate glass NC21, which consists of 7 rings of air holes infiltrated with water-ethanol mixtures. We also considered numerically the influence of concentration of the ethanol solution on the dispersion of the fundamental mode. SC generation was demonstrated for the fiber long 20 cm with a pump pulse of 200 fs, the coupled energy of 0.5 nJ at the center wavelength of 1064 nm in the normal dispersion regime. The concentration of ethanol infiltrated to the fiber, the pulse of duration and the pump energy are investigated.

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Sauzeau, Vincent, Hélène le Jeune, Chrystelle Cario-Toumaniantz, Nathalie Vaillant, Alain-Pierre Gadeau, Claude Desgranges, Elizabeth Scalbert, Pierre Chardin, Pierre Pacaud et Gervaise Loirand. « P2Y1, P2Y2, P2Y4, and P2Y6 receptors are coupled to Rho and Rho kinase activation in vascular myocytes ». American Journal of Physiology-Heart and Circulatory Physiology 278, n^o 6 (1 juin 2000) : H1751—H1761. http://dx.doi.org/10.1152/ajpheart.2000.278.6.h1751.

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In the cardiovascular system, activation of ionotropic (P2X receptors) and metabotropic (P2Y receptors) P2 nucleotide receptors exerts potent and various responses including vasodilation, vasoconstriction, and vascular smooth muscle cell proliferation. Here we examined the involvement of the small GTPase RhoA in P2Y receptor-mediated effects in vascular myocytes. Stimulation of cultured aortic myocytes with P2Y receptor agonists induced an increase in the amount of membrane-bound RhoA and stimulated actin cytoskeleton organization. P2Y receptor agonist-induced actin stress fiber formation was inhibited by C3 exoenzyme and the Rho kinase inhibitor Y-27632. Stimulation of actin cytoskeleton organization by extracellular nucleotides was also abolished in aortic myocytes expressing a dominant negative form of RhoA. Extracellular nucleotides induced contraction and Y-27632-sensitive Ca2+ sensitization in aortic rings. Transfection of Swiss 3T3 cells with P2Y receptors showed that Rho kinase-dependent actin stress fiber organization was induced in cells expressing P2Y1, P2Y2, P2Y4, or P2Y6 receptor subtypes. Our data demonstrate that P2Y1, P2Y2, P2Y4, and P2Y6 receptor subtypes are coupled to activation of RhoA and subsequently to Rho-dependent signaling pathways.

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Zhou, Ruling, Chenggang Guan, Hui Lv, Shasha Li, Puchu Lv, Haixin Qin, Wenxiu Chu, Yikai Zhou, Yihao Zhang et Xiaoqiang Li. « The Performance Characterization and Optimization of Fiber-Optic Acoustic Pressure Sensors Based on the MOEMS Sensitized Structure ». Sensors 23, n^o 19 (7 octobre 2023) : 8300. http://dx.doi.org/10.3390/s23198300.

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In order to investigate the factors affecting the acoustic performance of the extrinsic Fabry–Perot interferometer (EFPI) fiber-optic acoustic pressure sensor and to effectively improve its detection capability, this paper enhances the sensor’s detection sensitivity by adding more sensitized rings to its acoustic pressure-sensitive film. Furthermore, a novel real-time coupled acoustic test method is proposed to simultaneously monitor the changes in the spectral and acoustic metrics of the sensor to characterize its overall performance. Finally, an EFPI-type fiber-optic acoustic pressure sensor was developed based on the Micro-Optical Electro-Mechanical System (MOEMS). The acoustic tests indicate that the optimized fiber-optic acoustic pressure sensor has a sensitivity as high as 2253.2 mV/Pa, and the acoustic overload point (AOP) and signal-to-noise ratios (SNRs) can reach 108.85 dB SPL and 79.22 dB, respectively. These results show that the sensor produced through performance characterization experiments and subsequent optimization has a very high acoustic performance index, which provides a scientific theoretical basis for improving the overall performance of the sensor and will have broad application prospects in the field of acoustic detection.

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Mizuta, Kentaro, Yi Zhang, Fumiko Mizuta, Hiroshi Hoshijima, Toshiya Shiga, Eiji Masaki et Charles W. Emala. « Novel identification of the free fatty acid receptor FFAR1 that promotes contraction in airway smooth muscle ». American Journal of Physiology-Lung Cellular and Molecular Physiology 309, n^o 9 (1 novembre 2015) : L970—L982. http://dx.doi.org/10.1152/ajplung.00041.2015.

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Obesity is one of the major risk factors for asthma. Previous studies have demonstrated that free fatty acid levels are elevated in the plasma of obese individuals. Medium- and long-chain free fatty acids act as endogenous ligands for the free fatty acid receptors FFAR1/GPR40 and FFAR4/GPR120, which couple to Gq proteins. We investigated whether FFAR1 and FFAR4 are expressed on airway smooth muscle and whether they activate Gq-coupled signaling and modulate airway smooth muscle tone. We detected the protein expression of FFAR1 and FFAR4 in freshly dissected native human and guinea pig airway smooth muscle and cultured human airway smooth muscle (HASM) cells by immunoblotting and immunohistochemistry. The long-chain free fatty acids (oleic acid and linoleic acid) and GW9508 (FFAR1/FFAR4 dual agonist) dose-dependently stimulated transient intracellular Ca2+ concentration ([Ca2+]i) increases and inositol phosphate synthesis in HASM cells. Downregulation of FFAR1 or FFAR4 in HASM cells by small interfering RNA led to a significant inhibition of the long-chain free fatty acids-induced transient [Ca2+]i increases. Oleic acid, linoleic acid, or GW9508 stimulated stress fiber formation in HASM cells, potentiated acetylcholine-contracted guinea pig tracheal rings, and attenuated the relaxant effect of isoproterenol after an acetylcholine-induced contraction. In contrast, TUG-891 (FFAR4 agonist) did not induce the stress fiber formation or potentiate acetylcholine-induced contraction. These results suggest that FFAR1 is the functionally dominant free fatty acid receptor in both human and guinea pig airway smooth muscle. The free fatty acid sensors expressed on airway smooth muscle could be an important modulator of airway smooth muscle tone.

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Hanh, Duong Thi, Ha Thu Trinh, Phan Quang Thang, Nguyen Trung Dung et Nguyen Tran Dien. « OPTIMIZATION OF ULTRASONICATION EXTRACTION FOR DETERMINATION OF 16 POLYCYCLIC AROMATIC HYDROCARBONS IN AIR PARTICLE ». Vietnam Journal of Science and Technology 56, n^o 3 (11 juin 2018) : 324. http://dx.doi.org/10.15625/2525-2518/56/3/11096.

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The aim of this study is to develop the quick ultrasonication extraction procedure for determination of 16 typical polycyclic aromatic hydrocarbons (PAHs) in air particles. The determination and quantification of PAHs in air particles samples were performed using gas chromatography coupled to mass spectrometry (GC-MS) with the aid of deuterated PAH internal standards. 1ug mixture of PAHs was spiked to a quarter of quartz fiber filter and extracted with four different solvents/solvent mixtures (methanol:dichloromethane, acetone:dichloromethane; acetone:hexane; dichloromethane). Ultrasonication extraction was carried out in dark at uncontrolled and controlled ultrasonication temperature (25-28oC). The unique extraction time (20 minutes) was applied for all experiments. The results showed that high recovery rate of PAHs (82-108%) were obtained with dichloromethane (as extraction solvent) in dark at ultrasonication temperature of 25 to 28oC, while generally low recovery rate of PAHs, especially naphthalene (57%) were obtained with methanol:dichloromethane (1:1). The ultrasonication extraction method with dichloromethane showed good reproductively and repeatability with relative standard deviation of 16 PAHs below 6,14%, confirming that samples analyses were precise. Analytical results of PAHs in air particles collected in Hanoi using the developed ultrasonication extraction procedure showed that 15 out of 16 PAHs were detected, in which high molecular weight (MW) PAHs (>5 rings) were abundance compared to low molecular weight PAHs (< 3 rings). This developed ultrasonication extraction method is quick, easy and sufficient for determination of PAHs in air particle

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Azlan Sulaiman, Azlan Sulaiman, Sulaiman Wadi Harun Sulaiman Wadi Harun et Harith Ahmad Harith Ahmad. « Ring microfiber coupler erbium-doped fiber laser analysis ». Chinese Optics Letters 12, n^o 2 (2014) : 021403–21406. http://dx.doi.org/10.3788/col201412.021403.

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Sun Guangwei, 孙广伟, 辛国锋 Xin Guofeng, 朱韧 Zhu Ren, 陈迪俊 Chen Dijun, 冯盼 Feng Pan, 侯霞 Hou Xia, 蔡海文 Cai Haiwen et 陈卫标 Chen Weibiao. « 小型全光纤耦合非平面环形腔固体激光器 ». Chinese Journal of Lasers 49, n^o 13 (2022) : 1301002. http://dx.doi.org/10.3788/cjl202249.1301002.

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Li, Ying, Brian Via, Qingzheng Cheng et Yaoxiang Li. « Lifting Wavelet Transform De-noising for Model Optimization of Vis-NIR Spectroscopy to Predict Wood Tracheid Length in Trees ». Sensors 18, n^o 12 (6 décembre 2018) : 4306. http://dx.doi.org/10.3390/s18124306.

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The data analysis of visible-near infrared (Vis-NIR) spectroscopy is critical for precise information extraction and prediction of fiber morphology. The objectives of this study were to discuss the de-noising of Vis-NIR spectra, taken from wood, to improve the prediction accuracy of tracheid length in Dahurian larch wood. Methods based on lifting wavelet transform (LWT) and local correlation maximization (LCM) algorithms were developed for optimal de-noising parameters and partial least squares (PLS) was employed as the prediction method. The results showed that: (1) The values of tracheid length in the study were generally high and had a great positive linear correlation with annual rings (R = 0.881), (2) the optimal de-noising parameters for larch wood based Vis-NIR spectra were Daubechies-2 (db2) mother wavelet with 4 decomposition levels while using a global fixed hard threshold based on LWT, and (3) the Vis-NIR model based on the optimal LWT de-noising parameters ( R c 2 = 0.834, RMSEC = 0.262, RPD c = 2.454) outperformed those based on the LWT coupled with LCM algorithm (LWT-LCM) ( R c 2 = 0.816, RMSEC = 0.276, RPD c = 2.331) and raw spectra ( R c 2 = 0.822, RMSEC = 0.271, RPD c = 2.370). Thus, the selection of appropriate LWT de-noising parameters could aid in extracting a useful signal for better prediction accuracy of tracheid length.

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Liu Jingliang, 刘京亮, 李晓琼 Li Xiaoqiong, 戴键 Dai Jian, 银军 Yin Jun, 徐守利 Xu Shouli, 余若祺 Yu Ruoqi, 斛彦生 Hu Yansheng, 许春良 Xu Chunliang et 倪涛 Ni Tao. « 基于非保偏光纤环腔的启钥式耦合光电振荡器 ». Chinese Journal of Lasers 49, n^o 18 (2022) : 1815001. http://dx.doi.org/10.3788/cjl202249.1815001.

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Zhang Dong, 张东, 路桥 Lu Qiao et 李文彩 Li Wencai. « 基于耦合环的主动调Q平滑脉冲光纤激光器 ». Chinese Journal of Lasers 51, n^o 21 (2024) : 2101002. http://dx.doi.org/10.3788/cjl240870.

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MOK, SENG-PENG, CHAO-HSING WANG, JYH-CHENG CHEN et REN-SHYAN LIU. « PERFORMANCE EVALUATION OF THE HIGH RESOLUTION SMALL ANIMAL PET SCANNER ». Biomedical Engineering : Applications, Basis and Communications 15, n^o 04 (25 août 2003) : 143–49. http://dx.doi.org/10.4015/s1016237203000213.

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Molecular imaging is an important technology to clarify biological and medical uncertainties in the 21th century. This is best realized via in vivo imaging of biological processes in small animals. Thus, a special high resolution imager dedicated for small animals is required. We recently installed a high resolution animal positron emission tomography (PET) scanner (microPET R4) for doing in vivo molecular imaging of gene expression. This paper describes the performance evaluation of our microPET R4 scanner. The microPET R4 scanner is a dedicated PET for studies of rodents. The system is composed of 96 detector modules, each with an 8 × 8 array of 2.1 × 2.1 × 10 mm3 lutetium oxyorthosilicate (LSO) crystals, arranged as 32 crystal rings and 14.8 cm in diameter. The detector crystals are coupled to a Hamamatsu R5900-C8 position sensitive photomultiplier tube (PS-PMT) via a 10 cm long optical fiber bundle. The system operates in 3D mode without inter-plane septa, acquiring data in list mode. A number of scanner parameters such as sensitivity, spatial resolution and energy resolution were determined in this work. In the center of field of view (FOV) a maximal sensitivity of 21.04 cps/kBq was calculated from a measurement with a germanium-68 point source with an energy window of 250-750 keV. Spatial resolution of 2.03 mm (FORB+2D-FBPJ/1.61 mm (FORB + 2D-OSEM) full width at half maximum (FWHM) in the tangential direction and 2.07 mm (2D-FBP)/1.65 mm (2D-OSEM) FWHM in the radial direction were measured in the center with a 0.28 mm diameter 18F-FDG line source. The energy resolution of the scanner was measured across all crystals ranging from 13.9% to around 34.6% with a mean of 18.45%. The results show that the microPET R4 is a suitable PET scanner for imaging small animals like mice and rats.

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Chalise, Pratikshya, et Achyut Tiwari. « Wood anatomical features of Juniperus squamata Buch.-Ham. ex. D. Don from high mountains of Trans-Himalayan Zone of central Nepal ». Banko Janakari 34, n^o 2 (22 novembre 2024) : 4–15. http://dx.doi.org/10.3126/banko.v34i2.67754.

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Wood anatomical characters were investigated for Juniperus squamata Buch.-Ham. ex. D. Don from high mountains of Trans-Himalayan Zone of Manang District of Central Nepal. We studied the anatomical features and the inter-relationship between the anatomical parameters of Himalayan Juniper from 30 different wood samples collected at 4600 m above the mean sea level (msl). Wood samples were boiled at 100ºC in oven, and sectioning was done using the KD-3390 Semi-automatic Microtome. The sections were then dehydrated in alcohol stained with 1% Safranin and fast green solutions, and permanent slides were prepared and observed under microscope. J. squamata is a softwood species and is characterized by the presence of distinct narrow annual growth rings with gradual to abrupt transition from earlywood to latewood. Both earlywood and latewood tracheids comprising square to polygonal cells, circular bordered pits and few resin cells arranged in loose tangential bands. The rays were found to be exclusively uniseriate and homogenous; most of the ray cells contained prismatic crystals while cupressoid pits were present in the ray cells.The annual-ring-width showed a positive correlation with both the earlywood and latewood width but a negative correlation with tracheids length. In softwood species like Junipers, tracheid length is an important characteristic, not only for wood and fiber quality, but also for the tree's hydraulic architecture. Furthermore, this is also coupled with the acclimatization of the species in harsh climatic condition of the arid trans-Himalayan region. Dwarf individuals with reduced growth ring dimensions and increased tracheid length ensure effective water transportation towards the shoot system. Therefore, this intra-specific variation in wood anatomical features of J.squamata is due to variation in micro-habitat types.

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Yanosky, Thomas M., et Charles J. Robinove. « Digital image measurement of the area and anatomical structure of tree rings ». Canadian Journal of Botany 64, n^o 12 (1 décembre 1986) : 2896–902. http://dx.doi.org/10.1139/b86-382.

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A microcomputer coupled to a video digitizer was used to develop methods for measuring areas of tree rings and for delineating and measuring microscopic anatomical features. Digitally imaged areas of individual rings of a loblolly pine cross section were within 2.6% of areas measured with a planimeter and were more accurate than areas calculated from radius widths. Various anatomical features were "mapped" within digitized images of consecutive rings, individual rings, and highly magnified parts of the rings of green ash. Fibers within various ring zones, including those known to have formed when trees were flooded, were readily differentiated on the basis of image brightness. The image-determined ratio of lumen to wall material within different groups of fibers was considered a measure of structural comparability. These techniques thus provide a rapid, accurate method to study relationships between tree rings and factors affecting their development. Methods could be improved by increasing both spatial and brightness resolution.

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Fang, Xinyue, Wenjun He, Wen Wang, Yi Liu, Yajun You, Qing Yan, Yafei Hou et al. « All-Optical Single-Longitudinal-Mode Forward Brillouin Microwave Oscillator with an Unbalanced Fiber Mach–Zehnder Interferometer ». Micromachines 16, n^o 2 (12 février 2025) : 209. https://doi.org/10.3390/mi16020209.

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An all-optical single-longitudinal-mode (SLM) forward Brillouin microwave oscillator (FB-MO) with an unbalanced Fiber Mach–Zehnder interferometer (UF-MZI) for microwave photonics (MWP) generation is proposed and experimentally investigated. UF-MZI consists of an optical coupler (OC), a polarization controller (PC), and two asymmetric length arms with 5 km and 500 m single-mode fibers (SMFs), which implements two unbalanced length feedback rings that are connected to one another. One long-length ring with a forward Brillouin gain cooperates with the other short-length ring to maintain a spectral Vernier effect and improve the effective free spectral range (FSR). By contrast with traditional optoelectronic oscillators (OEOs), this design does not require any photoelectric conversion devices and additional modulation, avoids external electromagnetic interference, and side-mode suppression and linewidth are favorable. Experimental results reveal that the 3-dB linewidth of the all-optical SLM FB-MO with UF-MZI is about 140 Hz. The acoustic-mode and side-mode suppression ratios are 26 dB and 31 dB. Within 60 min of the stability experiment, the power and frequency stability fluctuation were ±1 dB and ±100 Hz. Thanks to its long main ring cavity length, our all-optical SLM FB-MO with UF-MZI maintains good phase-noise performance. The measurement shows that a phase noise as low as −120 dBc/Hz at an offset frequency of 100 kHz is achieved. This SLM MWP generation technology holds great potential for applications in radar monitoring and wireless communication systems.

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Haws, Cori, Edgar Perez, Marcelo Davanco, Jin Dong Song, Kartik Srinivasan et Luca Sapienza. « Broadband, efficient extraction of quantum light by a photonic device comprised of a metallic nano-ring and a gold back reflector ». Applied Physics Letters 120, n^o 8 (21 février 2022) : 081103. http://dx.doi.org/10.1063/5.0082347.

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To implement quantum light sources based on quantum emitters in applications, it is desirable to improve the extraction efficiency of single photons. In particular, controlling the directionality and solid angle of the emission are key parameters, for instance, to couple single photons into optical fibers and send the information encoded in quantum light over long distances, for quantum communication applications. In addition, fundamental studies of the radiative behavior of quantum emitters, including studies of coherence and blinking, benefit from such improved photon collection. Quantum dots grown via Stranski–Krastanov technique have shown to be good candidates for bright, coherent, indistinguishable quantum light emission. However, one of the challenges associated with these quantum light sources arises from the fact that the emission wavelengths can vary from one emitter to the other. To this end, broadband light extractors that do not rely on high-quality factor optical cavities would be desirable, so that no tuning between the quantum dot emission wavelength and the resonator used to increase the light extraction is needed. Here, we show that metallic nano-rings combined with gold back reflectors increase the collection efficiency of single photons, and we study the statistics of this effect when quantum dots are spatially randomly distributed within the nano-rings. We show an average increase in the brightness of about a factor 7.5, when comparing emitters within and outside the nano-rings, in devices with a gold back reflector, and we measure count rates exceeding 7 × 106 photons per second and single photon purities as high as 85% ± 1%. These results are important steps toward the realization of scalable, broadband, easy to fabricate sources of quantum light for quantum communication applications.

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McGarry, J. P., J. Fu, M. T. Yang, C. S. Chen, R. M. McMeeking, A. G. Evans et V. S. Deshpande. « Simulation of the contractile response of cells on an array of micro-posts ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 367, n^o 1902 (13 septembre 2009) : 3477–97. http://dx.doi.org/10.1098/rsta.2009.0097.

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A bio-chemo-mechanical model has been used to predict the contractile responses of smooth cells on a bed of micro-posts. Predictions obtained for smooth muscle cells reveal that, by converging onto a single set of parameters, the model captures all of the following responses in a self-consistent manner: (i) the scaling of the force exerted by the cells with the number of posts; (ii) actin distributions within the cells, including the rings of actin around the micro-posts; (iii) the curvature of the cell boundaries between the posts; and (iv) the higher post forces towards the cell periphery. Similar correspondences between predictions and measurements have been demonstrated for fibroblasts and mesenchymal stem cells once the maximum stress exerted by the stress fibre bundles has been recalibrated. Consistent with measurements, the model predicts that the forces exerted by the cells will increase with both increasing post stiffness and cell area (or equivalently, post spacing). In conjunction with previous assessments, these findings suggest that this framework represents an important step towards a complete model for the coupled bio-chemo-mechanical responses of cells.

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Lechevalier, Corentin, Clément Evain, Pierre Suret, François Copie, Alberto Amo et Stéphane Randoux. « Single-shot measurement of the photonic band structure in a fiber-based Floquet-Bloch lattice ». Communications Physics 4, n^o 1 (17 novembre 2021). http://dx.doi.org/10.1038/s42005-021-00750-w.

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AbstractFloquet-Bloch lattices are systems in which wave packets are subjet to periodic modulations both in time and space, showing rich dynamics. While this type of lattice is difficult to implement in solid-state physics, optical systems have provided excellent platforms to probe their physics: among other effects, they have revealed genuine phenomena such as the anomalous Floquet topological insulator and the funnelling of light into localised interface modes. Despite the crucial importance of the band dispersion in the photon dynamics and the topological properties of the lattice, the direct experimental measurement of the Floquet-Bloch bands has remained elusive. Here we report the direct measurement of the Floquet-Bloch bands of a photonic lattice with a single shot method. We use a system of two coupled fibre rings that implements a time-multiplexed Floquet-Bloch lattice. By Fourier transforming the impulse response of the lattice we obtain the band structure together with an accurate characterization of the lattice eigenmodes, i. e. the amplitudes and the phases of the Floquet-Bloch eigenvectors over the entire Brillouin zone. Our results open promising perspectives for the observation of topological effects in the linear and nonlinear regime in Floquet systems.

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Hanoon, Reem A., Ali H. Abdulhadi et Abdulla K. Abass. « Design of high nonlinear photonic crystal fiber for ultrashort pulse laser generation ». Journal of Optical Communications, 24 janvier 2025. https://doi.org/10.1515/joc-2024-0209.

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Abstract This work demonstrates an optimal design for photonic crystal fiber (PCF) as a saturable absorber with high nonlinearity and low confinement losses. Using COMSOL Multiphysics 6.1 as simulation software, the propagation characteristics of the proposed PCF in terms of effective refractive index, effective mode area, chromatic dispersion, confinement loss, and nonlinearity were successfully simulated and examined in detail. A Finite Element Method (FEM) combined with a Perfectly Matched Layer (PML) absorbing boundary condition was applied to evaluate the PCF structure across a broad wavelength range from 1,000 nm to 2,000 nm. The proposed PCF features five concentric rings of air-filled holes symmetrically arranged in a hexagonal structure, with the silica core doped with a uniform level of concentration of 10 % mol of germanium (Ge). Simulation results indicate a remarkably low confinement loss at a wavelength of 1,550 nm, specifically on the order of 5 × 10−7 (dB/m). Additionally, it reveals a high nonlinearity of 11.2 (1/W.Km) coupled with a simultaneously low negative chromatic dispersion of −14.2 (ps/nm.m). This makes it an excellent candidate for various applications involving advanced nonlinear optical systems. Such findings highlight the possibility of the proposed Ge-PCF as a promising saturable absorber for ultrashort pulse laser generation, offering a viable and practical alternative to traditional saturable absorbers in the mid-infrared region.

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McKee, Michael, et Faramarz Gordaninejad. « Reciprocating Shaft Seals for High-Temperature and High-Pressure Applications : A Review ». Journal of Tribology 140, n^o 3 (6 décembre 2017). http://dx.doi.org/10.1115/1.4038354.

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This study reviews the work performed in the field of reciprocating shaft seals from the advent of the scientific topic in the 1940s. Concepts of leakage, film layers, friction, wear, and other concerns with shaft seals are discussed. The importance of shaft seals as it pertains to liquid springs is brought to light along with issues requiring a need for these seals to withstand high temperatures and high pressures. Issues resulting from a seal exposure to high temperatures, such as thermosetting and embrittlement, are discussed in conjunction with materials and properties that allow seals to operate in high-temperature environments. High-pressure sealing challenges are identified along with the techniques currently employed to overcome these issues, such as fiber reinforcement and backup rings. Sealing solutions have been implemented independently for both high-pressure and high-temperature applications; however, the combination of high pressures coupled with high temperatures is still a challenge today.

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Ayalew, Hailu Dessalegn, Srinivas Talabattula, Pushparaghavan Annamalai et Pragya Mishra. « High speed 8PSK optical modulator using silicon/electro-optic polymer hybrid coupled ring resonator ». Journal of Optical Communications, 11 mars 2025. https://doi.org/10.1515/joc-2024-0320.

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Abstract In this paper, we proposed high speed 8PSK optical modulator using silicon/electro-optic polymer hybrid coupled ring resonators (Si/EO-PHCRR). The design comprises of two coupled ring resonator (CRRs) that has a primary and secondary rings and a single ring resonator (SRR), which acts as a delay line. The two CRRs are arranged in parallel within the two branches of the Mach–Zehnder interferometer (MZI), collectively producing a quadrature phase shift keying (QPSK) at the output terminal of MZI. The SRR is also configured in series with MZI and functions as an angle modulator, essentially serving as a π/4 phase shift modulator that operates based on the bit pattern applied to it. The CRR ensures a high energy storing capability that enhances the modulation efficiency and enables relatively high extinction ratio with better design flexibility and negligible losses. Thus, in this system, a 3 dB modulation bandwidth f 3dB = 51.14 GHz is realized with the moderate quality factor of Q = 3,839 and tunability of the modulator is found to be 723.65 pm/V with an extinction ratio of 29 dB. Also, the performance analysis of the modulator have be done at the bit rate of 150 Gbps and resulted in a high optical signal to noise ratio (OSNR) of 17.98 dB with a BER of 10−9 at the span of 100 Km dispersion shifted fiber.

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De Martini, Francesco. « Gravitational wave detection by hollow-core fiber-optics Mach-Zehnder interferometry ». Physics & ; Astronomy International Journal 8, n^o 2 (26 avril 2024). http://dx.doi.org/10.15406/paij.2024.08.00337.

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Recent advances in the field of very long distance optical communication suggest the adoption of the advanced technology based on Hollow Core Nested Anti- resonant Nodeless Fiber (HC-NANF) within the endeavour of Gravitational Wave detection using a Mach-Zehnder optical interferometer (MZ-IF). The proposal, consisting of a summary project of the device emphasizes the favorable properties of (MZ- IF) in comparison with Michelson Interferometer (M-IF) currently in operation. The key feature of the proposed method consists of the use of a couple of “fibrated” metallic antennas enfolded by a very large number (h x 7,7 x 104 with h= 1,2,3 etc.) of coiled rings or of straight sections of the (HC-NANF) fiber. This amounts to a corresponding fiber length: L (K) = h x 1500 Km. The relevant properties of the device are noise reduction, absence of critical optical mirror alignment in a noisy environment, reduced spatial extension of the apparatus, exploration of the entire sky scenario by freely orientable antennas, a substantial cost reduction of the apparatus. The remarkable properties of (HC-NANF), invented by F. Poletti in 2013 are currently investigated by his group at the University of Southampton, UK.

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Feng, Liuyang, Hao Gao, Nan Qi, Mark Danton, Nicholas A. Hill et Xiaoyu Luo. « Fluid–structure interaction in a fully coupled three-dimensional mitral–atrium–pulmonary model ». Biomechanics and Modeling in Mechanobiology, 26 mars 2021. http://dx.doi.org/10.1007/s10237-021-01444-6.

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AbstractThis paper aims to investigate detailed mechanical interactions between the pulmonary haemodynamics and left heart function in pathophysiological situations (e.g. atrial fibrillation and acute mitral regurgitation). This is achieved by developing a complex computational framework for a coupled pulmonary circulation, left atrium and mitral valve model. The left atrium and mitral valve are modelled with physiologically realistic three-dimensional geometries, fibre-reinforced hyperelastic materials and fluid–structure interaction, and the pulmonary vessels are modelled as one-dimensional network ended with structured trees, with specified vessel geometries and wall material properties. This new coupled model reveals some interesting results which could be of diagnostic values. For example, the wave propagation through the pulmonary vasculature can lead to different arrival times for the second systolic flow wave (S2 wave) among the pulmonary veins, forming vortex rings inside the left atrium. In the case of acute mitral regurgitation, the left atrium experiences an increased energy dissipation and pressure elevation. The pulmonary veins can experience increased wave intensities, reversal flow during systole and increased early-diastolic flow wave (D wave), which in turn causes an additional flow wave across the mitral valve (L wave), as well as a reversal flow at the left atrial appendage orifice. In the case of atrial fibrillation, we show that the loss of active contraction is associated with a slower flow inside the left atrial appendage and disappearances of the late-diastole atrial reversal wave (AR wave) and the first systolic wave (S1 wave) in pulmonary veins. The haemodynamic changes along the pulmonary vessel trees on different scales from microscopic vessels to the main pulmonary artery can all be captured in this model. The work promises a potential in quantifying disease progression and medical treatments of various pulmonary diseases such as the pulmonary hypertension due to a left heart dysfunction.

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El Sokhen, Rabih, Álvaro Gómez-León, Albert F. Adiyatullin, Stéphane Randoux, Pierre Delplace et Alberto Amo. « Edge-dependent anomalous topology in synthetic photonic lattices subject to discrete step walks ». Physical Review Research 6, n^o 2 (17 juin 2024). http://dx.doi.org/10.1103/physrevresearch.6.023282.

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Anomalous topological phases, where edge states coexist with topologically trivial Chern bands, can only appear in periodically driven lattices. When the driving is smooth and continuous, the bulk-edge correspondence is guaranteed by the existence of a bulk invariant known as the winding number. However, in lattices subject to periodic discrete step walks the existence of edge states does not only depend on bulk invariants but also on the boundary. This is a consequence of the absence of an intrinsic time dependence or micromotion in discrete step walks. We report the observation of edge states and a simultaneous measurement of the bulk invariants in anomalous topological phases in a two-dimensional synthetic photonic lattice subject to discrete step walks. The lattice is implemented using time multiplexing of light pulses in two coupled fibre rings, in which one of the dimensions displays real-space dynamics and the other one is parametric. The presence of edge states is inherent to the periodic driving and depends on the properties of the boundary in the implemented two-band model with zero Chern number. We provide a suitable expression for the topological invariants whose calculation does not rely on micromotion dynamics. Published by the American Physical Society 2024

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