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Magnetic resonance studies of j.ts in a gas-solid fluidised bed

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Particuology 2012年第2期10卷 161-169页

作者： Meenal Pore Thusara C. Chandrasekera Daniel j. Holland Aining Wang Fei Wang Qussai Marashdeh Michael D. Mantle andrew j. sederman Liang-Shih Fan Lynn F. Gladden j.hn S. Dennis Department of Chemical Engineering and Biotechnology University of Cambridge Pembroke Street Cambridge CB2 3RA United Kingdom The William G. Lowrie Department of Chemical and Biomolecular Engineering Ohio State University Columbus OH 43210 USA

Magnetic resonance imaging （MRI） has been used to study the behaviour Of j.ts at the distributor of a 50 mm diameter fluidised bed of 0.5 mm diameter poppy seeds. Two perforated-plate distributors were examined, containing either 10 or 14 holes, each 1 mm diameter. Ultra-fast MR imaging was able to show the transient nature of the upper parts of the j.ts, where discrete bubbles are formed. Imaging in 3D showed that the central j.ts were the longest for flow rates below minimum fluidisation. Above minimum fluidisation, the outer j.ts, nearest the wall of the fluidised bed, arched inward towards the central axis. In this latter case, interpretation of the time-averaged 3D image required the use of ultra-fast MR imaging to identify the approximate height above the distributor at which discrete bubbles were formed. The apparently continuous void extending along the central axis above this height in the time-averaged 3D image was thus identified, using ultra-fast MR imaging, as representing the averaged paths of released bubbles. Time-averaged MR velocity mapping was also used to identify dead zones of stationary particles resting on the distributor between the j.ts. The dead zones could be observed when the superficial velocity of the gas approached minimum fluidisation, but they were smaller than those observed at lower gas superficial velocity. Comparable images of a single j.t through 1.2 mm diameter poppy seeds from MRI and electrical capacitance volume tomography （ECVT） are also demonstrated.

关键词： Fluidised bedMRIECVTj.tsDistributor design

Testing decreasing variabililty of cockroach forewings through time using four Recent species： Blattella germanica, Polyphaga aegyptiaca, Shelfordella lateralis and Blaberus craniifer, with implications for the study of fossil cockroach forewings

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Insect Science 2012年第2期19卷 129-142页

作者： andrew j. Ross Department of Natural Sciences National Museums Scotland Edinburgh UK

Vrsansky, （2000） considered there is decreasing variability in the forewings of cockroaches through time, based on a study of fossil and Recent species. This study tests his theory, based on a study of four Recent species of cockroaches： Blattella germanica （Blattellidae）, Polyphaga aegyptiaca （Polyphagidae）, Shelfordella lateralis （Blattidae） and Blaberus craniifer （Blaberidae）. The new results, based on the coefficient of variation （CV） of the number of veins, indicate that Recent species can be more variable than fossil species and therefore do not support the theory. The results also show that at least 30 complete wings of the same species are required for a reliable CV value that is compa- rable between species.

关键词： Blaberidae Blattellidae Blattidae cockroach Polyphagidae variation

Validation of a discrete element model using magnetic resonance measurements

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Particuology 2009年第4期7卷 297-306页

作者： Christoph R.Müller Stuart A.Scott Daniel j.Holland Belinda C.Clarke andrew j.sederman j.hn S.Dennis Lynn F.Gladden Department of Chemical Engineering and Biotechnology University of CambridgePembroke StreetCambridge CB2 3RAUnited Kingdom

The discrete element model （DEM） is a very promising modelling strategy for two-phase granular systems. However, owing to a lack of experimental measurements, validation of numerical simulations of two-phase granular systems is still an important issue. In this study, a small two-dimensional gas- fluidized bed was simulated using a discrete element model. The dimensions of the simulated bed were 44mm × 10mm × 120 mm and the fluidized particles had a diameter dp = 1.2 mm and density ρp = 1000 kg/m^3. The comparison between DEM simulations and experiments are performed on the basis of time-averaged voidage maps. The drag-law of Beetstra et al. [Beetstra, R., van der Hoef, M.A., ＆ Kuipers,j. A. M. （2007b）. Drag force of intermediate Reynolds number flow past mono- and bidispersed arrays of spheres. AIChE j.urnal, 53,489-501 ] seems to give the best results. The simulations are fairly insensitive to the coefficient of restitution and the coefficient of friction as long as some route of energy dissipation during particle-particle and particle-wall contact is provided. Changing the boundary condition of the gas phase at the side-walls from zero-slip to full-slip does not affect the simulation results. Care is to be taken that the cell sizes are chosen so that a reasonable number of particles can be found in a fluid cell.

关键词： Discrete element modelling Magnetic resonance imaging Voidage Gas-fluidized beds

Magnetic resonance studies of a gas-solids fluidised bed:j.t-j.t and j.t-wall interactions

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Particuology 2010年第6期8卷 617-622页

作者： Meenal Pore Daniel j.Holland Thusara C.Chandrasekera Christoph R.Müller andrew j.sederman j.hn S.Dennis Lynn F.Gladden j.hn F.Davidson Department of Chemical Engineering and Biotechnology University of CambridgePembroke StreetCambridgeCB2 3RAUK Department of Mechanical and Process Engineering ETH ZurichSonneggstrasse 38092 ZurichSwitzerland

Magnetic resonance imaging （MRI） gave images of air j.ts from orifices in the distributor plate of a bed of poppy seeds. Attention focused on two features：（1） The interaction between nearby vertical j.ts from two, three or four orifices; （2） Wall effects, where one or more orifices created vertical j.ts near the vertical wall of the cylinder containing the particle bed. The results show that nearby j.ts are mutually attracted. Likewise a j.t near a wall bends out of the vertical, towards the wall, For multiple adj.cent j.ts, the j.t lengths show dependence on orifice layout： the lengths are in reasonable agreement with published measurements, by other methods, for single j.ts. The MRI gives three-dimensional images of the single j.ts and of multiple j.ts, separate or merging.

关键词： Fluidised bed MRI j.ts Distributor design

Invariant Measures and Asymptotic Gaussian Bounds for Normal Forms of Stochastic Climate Model

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Chinese Annals of Mathematics,Series B 2011年第3期32卷 343-368页

作者： Yuan YUAN andrew j. MAj.A Department of Mathematics Courant Institute New York University 251 Mercer Street New York NY 10012 USA Department of Mathematics and Center for Atmospheric Ocean Sciences Courant Institute New York University 251 Mercer Street New York NY 10012 USA

The systematic development of reduced low-dimensional stochastic climate models from observations or comprehensive high dimensional climate models is an important topic for atmospheric low-frequency variability,climate sensitivity,and improved extended range ***,techniques from applied mathematics have been utilized to systematically derive normal forms for reduced stochastic climate models for low-frequency *** was shown that dyad and multiplicative triad interactions combine with the climatological linear operator interactions to produce a normal form with both strong nonlinear cubic dissipation and Correlated Additive and Multiplicative(CAM) stochastic *** probability distribution functions(PDFs) of low frequency climate variables exhibit small but significant departure from Gaussianity but have asymptotic tails which decay at most like a ***,rigorous upper bounds with Gaussian decay are proved for the invariant measure of general normal form stochastic *** Gaussian lower bounds are also established under suitable hypotheses.

关键词： Reduced stochastic climate model Invariant measure Fokker-Planck equation Comparison principle Global estimates of probability density function

Challenges in studying geographic atrophy(GA) age-related macular degeneration: the potential of a new mouse model with GA-like features

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Neural Regeneration Research 2020年第5期15卷 863-864页

作者： j. Arj.na Ratnayaka andrew j. Lotery Clinical and Experimental Sciences Faculty of MedicineUniversity of SouthamptonSouthamptonUK Eye Unit University Hospital Southampton NHS Foundation TrustSouthamptonUK

Loss of central vision critical to everyday activities such as reading,face-recognition and driving due to damage in the central retina (the macula) is the leading cause of irreversible blindness amongst adults in the developed *** condition,termed age-related macular degeneration (AMD),is a complex,chronic degenerative disease driven by a combination of genetic and lifestyle risk *** signs of retinal changes in people as young as 30–40 years have been reported,although these individuals appear to be ***,by the age of 65,the disease is present in ~3% of individuals,which increases dramatically to affect 1/3 of individuals by the eighth decade of *** to intermediate AMD is estimated to affect ~150 million individuals globally,with another 10 million individuals suffering from end-stage,sight-threatening *** terminal stages are broadly grouped into dry (geographic atrophy,GA) or wet (choroidal neovascular,CNV) AMD (Sarks et al.,1988;Bird et al.,2014),with similar frequencies reported in *** advances in identifying genetic risk factors,including our discoveries in this field,indicate an initial shared pathology before progressing to aforementioned late-stage ***,GA patients have no effective treatment,which may in part be due to the lack of good in vivo models for GA ***,we summarize our new findings that describe an altogether new mouse model with GA-like features which shows progressive outer retinal pathology (Ibbett et al.,2019) that can be used to gain novel insights into GA and potentially as a tool for drug development.

关键词： macula central vision degenerative disease

Inflammasome links traumatic brain inj.ry, chronic traumatic encephalopathy, and Alzheimer's disease

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Neural Regeneration Research 2025年第6期20卷 1644-1664页

作者： Gabriela Seplovich Yazan Bouchi j.an Pablo de Rivero Vaccari j.nnifer C.Munoz Parej. andrew Reisner Laura Blackwell Yehia Mechref Kevin K.Wang j.Adrian Tyndall Binu Tharakan Firas Kobeissy Department of Surgery Morehouse School of MedicineAtlantaGAUSA Department of Neurobiology Center for NeurotraumaMultiomics&Biomarkers(CNMB)Neuroscience InstituteMorehouse School of MedicineAtlantaGAUSA Department of Neurological Surgery and the Miami Proj.ct to Cure Paralysis University of Miami Miller School of MedicineMiamiFLUSA Division of Pediatric Critical Care Department of PediatricsUniversity of Miami Miller School of MedicineMiamiFLUSA Department of Pediatrics Emory UniversityAtlantaGAUSA Department of Neurosurgery Children’s Healthcare of AtlantaAtlantaGAUSA Department of Chemistry and Biochemistry Texas Tech UniversityLubbockTXUSA Morehouse School of Medicine AtlantaGAUSA

Traumatic brain inj.ry, chronic traumatic encephalopathy, and Alzheimer's disease are three distinct neurological disorders that share common pathophysiological mechanisms involving neuroinflammation. One sequela of neuroinflammation includes the pathologic hyperphosphorylation of tau protein, an endogenous microtubule-associated protein that protects the integrity of neuronal cytoskeletons. Tau hyperphosphorylation results in protein misfolding and subsequent accumulation of tau tangles forming neurotoxic aggregates. These misfolded proteins are characteristic of traumatic brain inj.ry, chronic traumatic encephalopathy, and Alzheimer's disease and can lead to downstream neuroinflammatory processes, including assembly and activation of the inflammasome complex. Inflammasomes refer to a family of multimeric protein units that, upon activation, release a cascade of signaling molecules resulting in caspase-induced cell death and inflammation mediated by the release of interleukin-1β cytokine. One specific inflammasome, the NOD-like receptor protein 3, has been proposed to be a key regulator of tau phosphorylation where it has been shown that prolonged NOD-like receptor protein 3 activation acts as a causal factor in pathological tau accumulation and spreading. This review begins by describing the epidemiology and pathophysiology of traumatic brain inj.ry, chronic traumatic encephalopathy, and Alzheimer's disease. Next, we highlight neuroinflammation as an overriding theme and discuss the role of the NOD-like receptor protein 3 inflammasome in the formation of tau deposits and how such tauopathic entities spread throughout the brain. We then propose a novel framework linking traumatic brain inj.ry, chronic traumatic encephalopathy, and Alzheimer's disease as inflammasomedependent pathologies that exist along a temporal continuum. Finally, we discuss potential therapeutic targets that may intercept this pathway and ultimately minimize long-term neurological decline.

关键词： Alzheimer's disease caspase-1 chronic traumatic encephalopathy inflammasomes neurodegeneration neuroinflammation NLRP1 NLRP3 pyroptosis tauopathy traumatic brain inj.ry

Saturation in wavelength-division multiplexing free-space optical communication systems

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Frontiers of Optoelectronics 2019年第2期12卷 197-207页

作者： j.remiah O. BANDELE Malcolm WOOLFSON andrew j. PHILLIPS Department of Electrical Electronics and Computer Engineering College of EngineeringAfe Babalola UniversityAdo-EkitiEkiti StateP.M.B 5454Nigeria Department of Electrical and Electronic Engineering Faculty of EngineeringUniversity of Nottingham University ParkNottinghamNG7 2RDUK

The performance of a wavelength-division multiplexing (WDM) free-space optical (FSO) commu-nication system in a turbulent atmosphere employing optical amplifiers to improve capacity is investigated, in the presence of amplified spontaneous emission noise, scintillation, beam spreading, atmospheric attenuation and interchannel crosstalk. Using on-off keying modulation, Monte Carlo simulation techniques are used to obtain the average bit error rate and system capability due to scintillation and the effect of introducing a power control algorithm (PCA) to the system is investigated. The PCA ensures that at any receiving instant, the same turbulence- free powers are received by all the receiving lenses. The performance of various WDM FSO communication system configurations such as non-amplified systems with an adaptive decision threshold (NOAADT), non- amplified systems with a non-adaptive decision threshold, fixed gain amplified systems with an adaptive decision threshold, fixed gain amplified systems with a non- adaptive decision threshold and saturated gain amplified systems with a non-adaptive decision threshold (SOA- NADT) are investigated. Results obtained show that the SOANADT is superior to the NOAADT and the PCA is only beneficial in amplified systems.

关键词： wavelength-division multiplexing (WDM) free-space optical (FSO) communication crosstalk optical amplifier (OA) gain saturation decision threshold

Vibration induced flow in hoppers:DEM 2D polygon model

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Particuology 2008年第6期6卷 455-466页

作者： Feras Y. Fraige Paul A. Langston andrew j. Matchett j.hn Dodds Faculty of Mining and Environmental Engineering Al-Hussein Bin Talal University Jordan Chemical and Environmental Engineering Nottingham University University Park Chemical Engineering University of Teesside Centre RAPSODEE Ecole Des Mines

A two-dimensional discrete element model （DEM） simulation of cohesive polygonal particles has been developed to assess the benefit of point source vibration to induce flow in wedge-shaped hoppers. The particle-particle interaction model used is based on a multi-contact principle. The first part of the study investigated particle discharge under gravity without vibration to determine the critical orifice size （Bc） to j.st sustain flow as a function of particle shape. It is shown that polygonal-shaped particles need a larger orifice than circular particles. It is also shown that Bc decreases as the number of particle vertices increases. Addition of circular particles promotes flow of polygons in a linear manner. The second part of the study showed that vibration could enhance flow, effectively reducing Bc. The model demonstrated the importance of vibrator location （height）, consistent with previous continuum model results, and vibration amplitude in enhancing flow.

关键词： Bulk solids Vibration DEM Hoppers Materials handling Polygon