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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
151

Study of the effect of modulation of the refractive index nonlinear couplers in photonic crystals / Estudo do efeito da modulaÃÃo do Ãndice de refraÃÃo nÃo linear em acopladores de cristais fotÃnicos

Ana Gardennya Linard SÃrio Oliveira Mendes 23 January 2014 (has links)
CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / This paper presents a numerical investigation of the propagation and cover (100fs) short pulse switching in a nonlinear coupler dual-core photonic crystal fiber with periodically modulated constructed fiber nonlinearity ( PMN - PFC ). Our main objective was to study the effect of amplitude modulations (AM) and frequency modulation (Wm) in the refractive index of nonlinearity (gamma) at a spread of Photonic Crystal Fiber with initially fixed range with frequency and amplitude periodically varying modulation. The implementation of modulation was inserted into dual-fiber couplers, which has been studied for its use as a whole using ultra switching optical switch and as an optical processor. Our simulations are taking into account the amplitude and frequency modulations of different PMN - PFC. Coupler for coupling whose length is Lc = 1.8 cm, the transmission characteristics of the compression factor , the crosstalk ( Xtalk ) and extinction rate ( Xratio ) levels were studied in the first descending order solitons of high energy pump for considering 2LC. An analysis of the reference (channel 2) channel was observed that the low frequency modulation is an increase in the switching power by increasing the transmission efficiency. For high modulation frequencies transmitted energy efficiency loses. The switching pulses are stronger in the low frequency and high amplitude modulation. The Xtalk is a function of the measurement made on the secondary channel (channel 1) revealed that this increase in unwanted high-frequency energy, to reduce the extent of amplitude modulation. In summary, we have demonstrated that the introduction of a non- linear profile leads to a frequency modulated PMN - PFC high variations in transmission efficiency , Xtalk , Xratio function of frequency and modulation amplitude and the input power. / Este trabalho apresenta uma investigaÃÃo numÃrica da propagaÃÃo e a comutaÃÃo de pulsos curtos capa ( 100fs ) em um acoplador nÃo-linear de dois nÃcleos de fibras de cristal fotÃnico construÃdos com periodicamente modulada a fibra nÃo-linearidade (PMN - PFC). Nosso principal objetivo foi estudar o efeito das modulaÃÃes de amplitude (Am) e modulaÃÃo da frequÃncia (Wm) no Ãndice de refraÃÃo da nÃo-linearidade (gama) em uma propagaÃÃo de Fibra de Cristais FotÃnicos, com o gama inicialmente fixo com frequÃncia e amplitude de modulaÃÃo variando periodicamente. A execuÃÃo da modulaÃÃo foi inserida em uma fibra com acopladores duplo, que tem sido estudados quanto à sua utilizaÃÃo como um todo utilizando ultracomutaÃÃo Ãptica e processador como interruptor Ãptico. Nossas simulaÃÃes estÃo levando em conta da amplitude e frequÃncia diferentes modulaÃÃes do PMN - PFC. Foram estudados acoplador para acoplamento cujo comprimento à Lc = 1,8 centÃmetros, as caracterÃsticas de transmissÃo, o fator de compressÃo, o crosstalk (Xtalk) e taxa de extinÃÃo ( Xratio ) nos nÃveis dos primeiros sÃlitons de ordem decrescente para altas energias bomba considerando 2LC. Uma anÃlise do canal de referÃncia ( canal 2 ) , observou-se que a baixas frequÃncias de modulaÃÃo ocorre um aumento na potÃncia de comutaÃÃo aumentando a eficiÃncia da transmissÃo. Para alta modulaÃÃo freqÃÃncias a eficiÃncia energÃtica transmitida perde. Os pulsos de comutaÃÃo sÃo mais fortes para a baixa frequÃncia e alta amplitude de modulaÃÃo. O Xtalk à uma funÃÃo da mediÃÃo feita no canal secundÃrio ( canal 1 ) , observou-se que este aumento de energia indesejados de alta frequÃncia, para reduzir a medida da modulaÃÃo de amplitude. Em resumo, temos demonstrado que a introduÃÃo de um perfil nÃo-linearidade leva a uma periodicidade modulada PMN - PFC a fortes variaÃÃes na eficiÃncia de transmissÃo, Xtalk , Xratio funÃÃo da freqÃÃncia e modulaÃÃo de amplitude e a potÃncia de entrada.
152

Characterisation of Coincidence Data of the Gerda Experiment to Search for Double Beta Decays to Excited States

Wester, Thomas 29 January 2020 (has links)
The GERDA experiment is searching for the neutrinoless double beta (0vbb) decay of Ge-76. By that, it tries to answer two long standing questions about the neutrino: 'How large is the neutrino mass?' and 'Is the neutrino either Dirac or Majorana particle?'. Additionally, an observation would imply that lepton number is not conserved, which is an important puzzle piece for theories explaining the asymmetry between matter and anti-matter in the universe. The effective Majorana electron neutrino mass can be extracted from the half-life of the 0vbb -decay. However, during that conversion large uncertainties are added through nuclear matrix elements, that are calculated by a variety of theoretical models. Experimental input is required to constrain such models and their parameters to improve the reliability of the calculations. Additional input can be obtained by comparing the model predictions for the two neutrino double beta (2vbb) decay to the ground state, but also for decay modes to excited states of the daughter nuclide with measurements. The latter decay modes have not yet been observed in the case of Ge-76. The event signature of transitions to excited states is enhanced by de-excitation gamma-rays. The GERDA experiment employs an array of bare germanium semi-conductor detectors in a liquid argon cryostat. This array is suited to search for excited state transition in the 2vbb and 0vbb -decay modes using data with coincident energy depositions in multiple detectors. This work presents the preparation and characterisation of this data set, which includes the evaluation and correction of crosstalk between detector channels, the determination of the energy resolution of the detectors and the modelling of background. In an analysis combining 22 kgyr of Phase I data with the first 35 kgyr of Phase II data of GERDA, no signal has been observed for 2/0vbb -decays of Ge-76 to the energetically lowest three excited states in Se-76. New limits have been set for the two neutrino decay modes at T1/2(2v)(0+g.s. to 0+1) > 3.1x10^23 yr, T1/2(2v)(0+g.s. to 2+1) > 3.4x10^23 yr T1/2(2v)(0+g.s. to 2+2) > 2.5x10^23 yr with 90% credibility using a Bayesian approach, improving upon the limits obtained in Phase I. The corresponding sensitivities are 3.6x10^23 yr, 6.7x10^23 yr and 3.7x10^23 yr, respectively. First limits are set for the neutrinoless decay modes in the order of (10^24-10^25) yr. Reaching the desired Phase II exposure of 100 kgyr, the sensitivities will increase by up to 50%.
153

Knockout studies of Panc1 cells / Knockout studier av Panc1 celler

Sundin, Martin January 2021 (has links)
Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal form of cancerwith very few available treatment options of which none has great effect.Cancer cells and stromal cells such as stellate cells which exist in abundancein PDAC interact by crosstalk, resulting in a tumorigenic collective response.With the help of a previously developed 3D co-culture spheroid model theeffect of a CRISPR/cas9 knockout of the cellular communication cetworkfactor 1 (CCN1) gene together with gemcitabine (GEM) treatment has beeninvestigated in terms of Panc1 cell viability and gene expression. Spheroidsconsisting of wild-type and knockout cell lines, each identified by westernblots were cultured, imaged and treated. Viability assays and RNA extractionfollowed by PCR showed that the viability of the cancer cells in the spheroidswere higher for the cells with CCN1 knockout. Cancer cells were also coculturedwith stellate cells with the goal of investigating the effect of thecellular crosstalk on chemoresistance. / Pankreatisk duktal adenokarcinom (PDAC)  är en ytterst dödlig form av cancermed få tillgängliga behandlingsalternativ, varav ingen är särskilt effektiv.Cancerceller och stromala celler så som de stellatceller som rikligt förekommeri PDAC interagerar med varandra genom överhörning, vilket leder till en effektsom hjälper tumören att proliferera. Effekten av en CRISPR/cas9 knockoutav genen CCN1 tillsammans med behandling med gemcitabin vad gällercellviabilitet och genuttryck studerades med hjälp av en tidigare utveckladfleratig sfäroidmodell. Sfäroider, bestående av vildtypceller och knockoutcellerlinjersom identifierades med western blots, odlades, fotades och behandlades.Viabilitetstester och extraktion av RNA följt av PCR visade att viabilitetenav cancerceller i sfäroiderna var högre för de celler som var knockout.Cancerceller samodlades även med stellatceller med målet att undersökaeffekten av cellernas överhörning på motståndet mot kemoterapi.
154

Magnetic field separation for current prediction in three-phase systems : Regression-based current prediction

Lenman, Sara, Blaad, Sofia January 2023 (has links)
Current controls the motion of a manipulator. The manipulators at ABB are powered by a three-phase alternating current system where shunt resistors are utilised to measure the current to the motors. Magnetic field sensors are instead investigated to eliminate issues with power losses, the number of components and the cost of the shunt resistors. Since current produces a magnetic field, it can be measured without contact using a magnetic field sensor. However, employing non-contact magnetic field sensors in three-phase implementations introduces problems with stray magnetic fields due to the three traces being in close proximity to each other. This magnetic crosstalk will influence the sensors, hence the current measurement for each trace. In this thesis separating this influence of the magnetic fields is done through a software approach. Initially, two magnetic field sensors, a tunnel magnetoresistance sensor and a Fluxgate sensor, were tested and evaluated to gain knowledge and understanding. From the different tests, it was decided to continue with the Fluxgate sensor. Further, a partial least-squares regression was constructed to separate the magnetic field and predict the current in each trace from the Fluxgate sensor output. From a simulation created, the current could be predicted with an error of approximately 1 nA, meaning less than 0.1% when considering a simulated linear model of the Fluxgate sensor.
155

Hepatic Hedgehog Signaling Participates in the Crosstalk between Liver and Adipose Tissue in Mice by Regulating FGF21

Ott, Fritzi, Körner, Christiane, Werner, Kim, Gericke, Martin, Liebscher, Ines, Lobsien, Donald, Radrezza, Silvia, Shevchenko, Andrej, Hofmann, Ute, Kratzsch, Jürgen, Gebhardt, Rolf, Berg, Thomas, Matz-Soja, Madlen 09 October 2023 (has links)
The Hedgehog signaling pathway regulates many processes during embryogenesis and the homeostasis of adult organs. Recent data suggest that central metabolic processes and signaling cascades in the liver are controlled by the Hedgehog pathway and that changes in hepatic Hedgehog activity also affect peripheral tissues, such as the reproductive organs in females. Here, we show that hepatocyte-specific deletion of the Hedgehog pathway is associated with the dramatic expansion of adipose tissue in mice, the overall phenotype of which does not correspond to the classical outcome of insulin resistance-associated diabetes type 2 obesity. Rather, we show that alterations in the Hedgehog signaling pathway in the liver lead to a metabolic phenotype that is resembling metabolically healthy obesity. Mechanistically, we identified an indirect influence on the hepatic secretion of the fibroblast growth factor 21, which is regulated by a series of signaling cascades that are directly transcriptionally linked to the activity of the Hedgehog transcription factor GLI1. The results of this study impressively show that the metabolic balance of the entire organism is maintained via the activity of morphogenic signaling pathways, such as the Hedgehog cascade. Obviously, several pathways are orchestrated to facilitate liver metabolic status to peripheral organs, such as adipose tissue.
156

Regulation of Microglial Functions by Purinergic Mechanisms in the Healthy and Diseased CNS

Illes, Peter, Rubini, Patrizia, Ulrich, Henning, Zhao, Yafei, Tang, Yong 17 April 2023 (has links)
Microglial cells, the resident macrophages of the central nervous system (CNS), exist in a process-bearing, ramified/surveying phenotype under resting conditions. Upon activation by cell-damaging factors, they get transformed into an amoeboid phenotype releasing various cell products including pro-inflammatory cytokines, chemokines, proteases, reactive oxygen/nitrogen species, and the excytotoxic ATP and glutamate. In addition, they engulf pathogenic bacteria or cell debris and phagocytose them. However, already resting/surveying microglia have a number of important physiological functions in the CNS; for example, they shield small disruptions of the blood–brain barrier by their processes, dynamically interact with synaptic structures, and clear surplus synapses during development. In neurodegenerative illnesses, they aggravate the original disease by a microglia-based compulsory neuroinflammatory reaction. Therefore, the blockade of this reaction improves the outcome of Alzheimer’s Disease, Parkinson’s Disease, multiple sclerosis, amyotrophic lateral sclerosis, etc. The function of microglia is regulated by a whole array of purinergic receptors classified as P2Y12, P2Y6, P2Y4, P2X4, P2X7, A2A, and A3, as targets of endogenous ATP, ADP, or adenosine. ATP is sequentially degraded by the ecto-nucleotidases and 5′-nucleotidase enzymes to the almost inactive inosine as an end product. The appropriate selective agonists/antagonists for purinergic receptors as well as the respective enzyme inhibitors may profoundly interfere with microglial functions and reconstitute the homeostasis of the CNS disturbed by neuroinflammation.
157

METABOLIC ACIDOSIS AND THE DIVERSE ROLES OF THE Cl/HCO<sub>3</sub> EXCHANGER (AE3) IN INTRACELLULAR pH HOMEOSTASIS

Salameh, Ahlam Ibrahim January 2016 (has links)
No description available.
158

Acopladores direcionais de fibras Ãpticas com perfis de dispersÃo / Directional optic staple dispersion profile fiber(DPF)

Almir Wirth Lima Junior 05 March 2007 (has links)
nÃo hà / Nosso trabalho apresenta uma anÃlise numÃrica da propagaÃÃo e comutaÃÃo de solitons fundamentais em acopladores de dois nÃcleos de fibras nÃo lineares construÃdos com fibras de perfis de dispersÃo (DPF). NÃs mostramos, que o formato apropriado do perfil DPF à muito eficaz na recuperaÃÃo, quase total, do comportamento da comutaÃÃo do sinal original associado à situaÃÃo sem perdas. O estudo da comutaÃÃo de solitons em acopladores nÃo lineares de fibras DPF proporciona possibilidades de se alcanÃar alta eficiencia no processamento de sinais ultra-rÃpidos em sistemas totalmente Ãticos, especialmente para comutadores e transistors Ãticos. Iniciamos, estudando as equaÃÃes de Maxwell, os Solitons Ãpticos, as EquaÃÃes dos Modos Acoplados, e a EquaÃÃo NÃo Linear de SchrÃdinger - NLSE (mÃtodos analÃtico, e numÃrico). A seguir, detalhamos a PropagaÃÃo e Chaveamento de Sinais Ãpticos âCWâ e âQuasi-CWâ em Acopladores Ãpticos, bem como analisamos de forma teÃrica os acopladores duplos nÃo lineares de Fibras Ãpticas com Perfis de DispersÃo Decrescente (DPF). Os Ãltimos capÃtulos tratam do objetivo real de nossa DissertaÃÃo, ou seja, a AnÃlise Detalhada de Acopladores Ãpticos de Fibras com Perfis de DispersÃo (DPF), Com, e Sem Perdas Ãpticas, incluindo dois tipos de configuraÃÃo(PA1 e PB1). Encerramos a DissertaÃÃo com as ConclusÃes sobre os estudos acima referidos / We present a numerical investigation of the propagation and the switching of fundamental solitons in a two-core nonlinear fiber coupler constructed with Dispersion Profile Fiber (DPF). We have shown that appropriate shaping of the DPF profile is quite effective to recover, almost completely, the original switching behavior associated to the lossless situation. The study of soliton switching in DPF nonlinear fiber couplers provides possibilities for achieving, high efficiency in ultrafast all-optical signal processing, especially for optical switches and optical transistors. We initiate, studying the Maxwell Equations, the Coupled-Mode Equations, and the the Nonlinear SchrÃdinger Equation - NLSE, (analytic, and numerical approaches). After this, we detail the Propagation and Switching of "CW" and "Quasi-CW" Optical Signals in Optical Couplers, as well like we analyze, through theoretical form, the nonlinear double couplers of Dispersion Profiles Fibers (DPF). The last chapters explain the real objective of our Dissertation, or be, Detailed Analysis of the Optical Couplers of Profiles Dispersion Fiber (DPF), With, and Without Optical Losses, including two kinds of configuration (PA1 and PB1). We enclose the Dissertation with the Conclusions about the above referred studies
159

Modelování rušení pro xDSL / Interference modelling for xDSL

Čermák, Josef January 2008 (has links)
This work is focused on the subject of the interference modelling for xDSL technologies. First, the xDSL technologies are explained. Following is the presentation and description of the different kinds of the xDSL technologies. The next part deals with the basic parameters of metallic cable lines – especially the primary and secondary parameters. Nowadays wider bandwidths are used for the achievement of higher data transmission rates. During a higher frequency signal transmission a more intensive line attenuation appears. To identify the transfer characteristics of the lines while using an xDSL system, mathematic models of transmission lines are applied. That is why these mathematic models are dealt with in the next chapter. At the end of this section the mathematic models are compared using the modular and phase characteristics. The main aim of the work is to describe the different impacts which influence the efficiency of the xDSL systems. First, the causes interfering from the inside of the cable are deeply explained: Near End Crosstalk (NEXT), Far End Crosstalk (FEXT), Additive White Gaussian Noise (AWGN). Following is the explanation of the external interfering impacts: Radio Frequency Interference (RFI) and Impulse Noise. The next goal of this thesis is a design of a workstation for the tests of spectral features and the efficiency of the xDSL systems. The work also presents a designed GUI application and its description. The GUI application is an instrument for the choice or data entry of the final interference. The last chapter describes a realization of a measurement and shows the measured characteristics which were recorded on the ADSL tester and oscilloscope.
160

Analýza a modelování přeslechů / Crosstalk analysis and modelling

Novotný, František January 2013 (has links)
The thesis concerns the problem of interference modelling for xDSL technologies and Ethernet. The introduction describes the origin of crosstalk, that arise during the operation of the systems and the physical properties of the lines, therefore, the next section describes the properties of the primary and secondary parameters of the homogenous line and their modelling. In order to achieve higher data rates on the metallic line, systems with larger frequency spectrum are applied, resulting in a greater attenuation of the line. This issue and the characteristics determination of the transmission systems are subjects of the mathematical models, which are divided according to the modelling of primary or secondary parameters. The main goal of this work is to describe the effects which influence the performance of data transfer via xDSL and Ethernet technology focusing on internal and external disturbances acting on the cable lines. This is the crosstalk at the near and far end, adaptive white noise, radio frequency interference RFI and impulse noise. Following part of the thesis deals with the properties of xDSL technologies, specifically ADSL2+ and VDSL2 and Ethernet. Another aim is to design applications which enable to test the performance of xDSL and Ethernet transmission systems with its own award simulations interference. The conclusion describes the design and implementation of laboratory experiments for measuring of the efficiency and spectral properties of xDSL. The proposed laboratory protocols are annexed to this thesis, including the measured waveforms.

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