45,840 research outputs found
New optical fibre based technologies and their application in highly nonlinear systems
No full textThis thesis investigates new fibre technologies and their application in nonlinear optical systems, designed mainly for telecommunications. The thesis includes a study of two different directions in achieving a high nonlinearity in a fibre system, namely holey fibres filled with nonlinear liquids and soft glass, small core microstructured fibres. The challenges arising from the development of liquid-filled structures have made soft glass microstructured fibres the technology of choice for the realisation of highly nonlinear systems.Amongst the various soft glasses, commercially available lead-silicate glasses are identified as the material for the development of highly nonlinear fibres. Small-core, leadsilicate fibres with different designs are considered within this thesis. A solid core holey fibre design as well as two all-solid designs, a multi-ring cladding and a simpler W-index profile, are characterised. The measurements confirm the advantages of the all-solid designs over the holey structures and reveal the possibility to achieve simultaneously a high nonlinear coefficient and a novel dispersion profile in such fibres. Some of the presented fibres are employed in all-optical wavelength conversion schemes based on four-wave-mixing. Numerical simulations and experimental results are combined to study the performance of the fibres and demonstrate their use in wavelength conversion devices. In particular, a lead-silicate W-index profile fibre, showing a high nonlinear coefficient of 820W-1km-1 with a near zero dispersion profile at telecoms wavelengths, is employed to demonstrate a flat conversion gain in the whole C-band. The same fibre is then employed in FWM-based systems to demonstrate multi-channel wavelength conversion, generation of high repetition rate pulses and all-optical demultiplexing. The experiments presented in this thesis clearly reveal the potential of small-core soft-glass fibres for nonlinear applications.The use of soft glass microstructured fibres in the mid-IR is also investigated. Tellurite holey fibres with different core sizes and hole arrangements are employed in a supercontinuum generation scheme
Wavelength conversion in a short length of a solid lead-silicate fibre
No full textWe experimentally demonstrate a four-wave-mixing-based wavelength conversion scheme at 1.55 µm using a 1.1-m length of highly nonlinear, dispersion tailored W-type lead–silicate optical fibe
Settling of finite-size particles in isotropically forced, homogeneous turbulence: interface-resolved simulations
No full textWe have simulated the gravity-induced settling of finite-size particles in a turbulent background flow which is forced in a statistically-stationary fashion. The simulations are accurately resolving the solid-fluid interface with the aid of an immersed boundary technique [1]. The parameters of the simulation are (apart from background turbulence) identical to those of reference [2], where particle clustering was observed at a Galileo number of 178 and a solid volume fraction of 0.005. In the present case, it is found that a relative turbulence intensity of 0.24 leads to the disappearance of the clusters; as a consequence, the increase in average particle settling velocity found in [2] also vanishes. [1] M. Uhlmann. An immersed boundary method with direct forcing for the simulation of particulate flows. J. Comput. Phys., 209(2):448–476, 2005. [2] M. Uhlmann and T. Doychev. Sedimentation of a dilute suspension of rigid spheres at intermediate Galileo numbers: the effect of clustering upon the particle motion. J. Fluid Mech., 752:310–348, 2014
Mesophilic-hydrothermal-thermophilic (M-H-T) digestion of green corn straw
No full textMesophilic-hydrothermal (80-160 degrees C, 30 min)-thermophilic (M-H-T) digestion and control tests of mesophilic (M), thermophilic (T), hydrothermal-mesophilic (H-M), and mesophilic-thermophilic digestion (M-T) of green corn straw were conducted for a 20-day fermentation period. The results indicate that M-H-T is an efficient method to improve methane production. A maximum methane yield of 371.74 mL/g volatile solid was obtained by the M (3 days)-H (140 degrees C)-T (17 days) process, which was 20.44%, 16.55%, 31.44%, and 14.31% higher than the yields of the M, T, 140-M, and M-T processes. The enhanced methane production was attributed to (1) the improved hemicellulose degradation and lignin disorganization; (2) prevention of the degradation of soluble sugar, easily hydrolyzed hemicellulose and cellulose into furfural and methylfurfural; and (3) lack of formation of Maillard reaction products during initial hydrothermal treatment. (C) 2015 Elsevier Ltd. All rights reserved
Dr. Glendon Swarthout
No full textHosted by Roger M. Busfield, MSU Assistant Professor of Speech and Theater, Meet the Author is designed to introduce a general audience to a contemporary author and their work through in-depth interviews. This episode features a conversation between Dr. Glendon Swarthout, prolific author and English professor at MSU, and assistant professors Sam S. Baskett and Theodore B. Strandness
Intravenous Heparin Started Within the First 3 Hours After Onset of Symptoms as a Treatment for Acute Nonlacunar Hemispheric Cerebral Infarctions.
No full textBackground and Purpose—Heparin is widely used for acute stroke to prevent thrombus propagation and/or multiple emboli generation, although there is, as yet, no demonstrated efficacy. However, all of the available clinical studies allowed long intervals from stroke to treatment. The purpose of this study was to try an intravenous regimen of unfractionated heparin the acute cerebral infarction starting treatment within the first 3 hours of the onset of symptoms.
Methods—The study was an outcome evaluator-blind design trial. Patients had to display signs of a nonlacunar hemispheric infarction. Selected patients were randomly allocated to receive intravenous heparin sodium or saline.
Heparin was infused at a rate to maintain activated partial thromboplastin time ratio 2.0 to 2.5 _ control for 5 days. The primary end point was recovery of a modified Rankin score zero to 2 at 90 days of stroke at phone interview by a single physician blind to treatment. Safety end points were death, symptomatic intracranial hemorrhages, and major extracranial bleedings by 90 days of stroke.
Results—A total of 418 stroke patients were included. In the heparin group, there were more self-independent patients (38.9% versus 28.6%; P=0.025). In addition, in the same group, there were fewer deaths (16.8% versus 21.9%; P=0.189), more symptomatic brain hemorrhages (6.2% versus 1.4%; P_0.008), and more major extracerebral bleedings (2.9% versus 1.4%; P_0.491).
Conclusions—Intravenous heparin sodium could be of help in the earliest treatment of acute nonlacunar hemispheric cerebral infarction, even keeping into account an increased frequency of intracranial symptomatic brain hemorrhages
Malignancy and sensory neuropathy of unexplained cause : a prospective study of 51 patients
No full textTo investigate the frequency of cancer developing in patients with peripheral sensory neuropathy of unexplained cause
The maternal immune system during pregnancy and its influence on fetal development
No full textThe maternal immune system plays a critical role in the establishment, maintenance, and completion of a healthy pregnancy. However, the specific mechanisms utilized to achieve these goals are not well understood. Various cells and molecules of the immune system are key players in the development and function of the placenta and the fetus. Effector cells of the immune system act to promote and yet limit placental development. The T helper 1 (Th1)/T helper 2 (Th2) immune shift during pregnancy is well established. A fine balance between proinflammatory and anti-inflammatory influences is required. We herein review the evidence regarding maternal tolerance of fetal tissues and the underlying cell-mediated immune and humoral (hormones and cytokines) mechanisms. We also note the many unanswered questions in our understanding of these mechanisms. In addition, we summarize the clinical manifestations of an altered maternal immune system during pregnancy related to susceptibility to common viral, bacterial, and parasitic infections, as well as to autoimmune diseases.Peer reviewe
Erosie door open taludbekledingen. Samenvattend verslag + Bijlage A t/m D
No full textOpen taludbekledingen die bestaan uit in verband geplaatste betonblokken met gaten, bieden de mogelijkheid vegetatie te doen groeien, waardoor mogelijk een milieuvriendelijke oever kan worden verkregen. In het pioniersstadium van de vegetatie is het evenwel ongewenst dat de gatvulling uitspoelt. Teneinde de relatie tussen waterbeweging en erosie van de gatvulling vast te stellen, is door de Dienst Weg- en Waterbouwkunde van Rijkswaterstaat per brief d.d. 16 maart 1987 (kenmerk WB 570), opdracht verleend aan het Waterloopkundig Laboratorium tot het uitvoeren van onderzoek naar de erosie door open taludbekledingen. Het doel van het onderzoek is het ontwikkelen van ontwerprichtlijnen voor taludbekledingen met gaten die groter zijn dan de zand- of filterkorrels eronder. Hiertoe dient de kritieke waterbeweging bij een oever- of dijkbekleding te worden vastgesteld, waarbij nog toelaatbare erosie is te verwachten. De toelaatbare erosie mag daarbij maximaal gelijk zijn aan de hoeveelheid sediment in de gaten. Filter- of basismateriaal gelegen onder de elementen mag dus niet uitspoelen. Bij oeverbekledingen waar vegetatie een rol moet gaan spelen, is de toelaatbare erosie kleiner, dat wil zeggen in de gaten dient sediment achter te blijven.Steenzettingen - TAW/EN
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