• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 85
  • 43
  • 28
  • 24
  • 9
  • 6
  • 4
  • 4
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 227
  • 43
  • 26
  • 21
  • 18
  • 14
  • 13
  • 13
  • 11
  • 10
  • 10
  • 10
  • 9
  • 9
  • 9
  • 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.
21

System Level Exploration of RRAM for SRAM Replacement

Dogan, Rabia January 2013 (has links)
Recently an effective usage of the chip area plays an essential role for System-on-Chip (SOC) designs. Nowadays on-chip memories take up more than 50%of the total die-area and are responsible for more than 40% of the total energy consumption. Cache memory alone occupies 30% of the on-chip area in the latest microprocessors. This thesis project “System Level Exploration of RRAM for SRAM Replacement” describes a Resistive Random Access Memory (RRAM) based memory organizationfor the Coarse Grained Reconfigurable Array (CGRA) processors. Thebenefit of the RRAM based memory organization, compared to the conventional Static-Random Access Memory (SRAM) based memory organization, is higher interms of energy and area requirement. Due to the ever-growing problems faced by conventional memories with Dynamic Voltage Scaling (DVS), emerging memory technologies gained more importance. RRAM is typically seen as a possible candidate to replace Non-volatilememory (NVM) as Flash approaches its scaling limits. The replacement of SRAMin the lowest layers of the memory hierarchies in embedded systems with RRAMis very attractive research topic; RRAM technology offers reduced energy and arearequirements, but it has limitations with regards to endurance and write latency. By reason of the technological limitations and restrictions to solve RRAM write related issues, it becomes beneficial to explore memory access schemes that tolerate the longer write times. Therefore, since RRAM write time cannot be reduced realistically speaking we have to derive instruction memory and data memory access schemes that tolerate the longer write times. We present an instruction memory access scheme to compromise with these problems. In addition to modified instruction memory architecture, we investigate the effect of the longer write times to the data memory. Experimental results provided show that the proposed architectural modifications can reduce read energy consumption by a significant frame without any performance penalty.
22

Simulação e Análise da Fragmentação do Desmonte de Rochas na Pedreira Herval – BARREIROS – PE

SILVA, Andrêvhity Carlos Santos da 09 December 2015 (has links)
Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-07-20T13:16:55Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) dissertação final - andrevhity - cd - bdtd.pdf: 7048267 bytes, checksum: 0a2bd5941283791f51f6e1671f68b201 (MD5) / Made available in DSpace on 2016-07-20T13:16:55Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) dissertação final - andrevhity - cd - bdtd.pdf: 7048267 bytes, checksum: 0a2bd5941283791f51f6e1671f68b201 (MD5) Previous issue date: 2015-12-09 / CAPEs / As operações unitárias em pedreiras tais como: desmonte, perfuração e britagem são imprescindíveis, e são etapas que exige controle na produção e que demandam quantidade razoável de elementos essenciais para a produção e que desgastam rapidamente, por essa razão estes procedimentos necessitam de análise e acompanhamento contínuo. Uma maneira de otimizar a produção em pedreiras e garantir com isso melhor controle na produção é realizando uma análise estrutural mais detalhada do maciço rochoso e determinando previamente as suas descontinuidades, seu estágio de deformação e o seu comportamento mediante a aplicação de explosivos. Um modelo matemático pode ser aplicado para simular a fragmentação do desmonte de rochas e posteriormente adequar a granulometria proveniente da mina (ROM – Run of Mine) obtendo uma melhoria no desempenho do desmonte e otimizando a britagem com o aumento da eficiência/produtividade. O modelo consiste nas equações propostas de Kuznetsov (1973), Cunningham (1983), Lilly (1986) e Tidman e Rosin-Rammler (1933), e são utilizadas para maior interação entre explosivo e rocha. / The unit operations in quarries such as blasting, drilling and crushing are essential, and are steps that require control in production and demand reasonable amount of essential elements for the production and wear out quickly, therefore these procedures require analysis and monitoring continuous. One way to optimize the production in quarries and thereby ensure better control of production, making it a more detailed structural analysis of the rock mass and previously determining the discontinuities, its deformation stage and its behavior upon the application of explosives. A mathematical model can be applied to simulate the rock blasting fragmentation and then tailor the grain size from the mine (ROM - Run of Mine) obtaining an improvement in the performance of dismantling and optimizing crushing with increasing efficiency and productivity. The model consists of the equations proposed Kuznetsov (1973), Cunningham (1983), Lilly (1986) and Rosin - Rammler and Tidman (1933), and are used for higher interaction between explosive and rock.
23

Estudo de célula de memória dinâmica de apenas um transistor SOI de óxido enterrado ultrafino. / Study of dynamic memory cell of only one SOI transistor with ultrathin buried oxide.

Luciano Mendes Almeida 25 September 2012 (has links)
Neste trabalho foi analisado o comportamento de um transistor UTBOX (Ultra Thin Buried Oxide) FD SOI MOSFET (Fully Depleted Silicon-on-Insulator Metal- Oxide-Semiconductor Field-Effect-Transistor) planar do tipo n, operando como uma célula de memória 1T-FBRAM (single transistor floating body random access memory). A memória em questão trata-se de uma evolução das memórias 1T1C-DRAM convencionais formada, porém, de apenas um transistor, sendo o próprio transistor o responsável pelo armazenamento da informação por meio do efeito de corpo flutuante. Assim, foram realizadas simulações numéricas bidimensionais, obtendo-se curvas dinâmicas e, a partir destas, foi possível extrair e analisar alguns dos principais parâmetros da memória tais como tensão de disparo no dreno, margem de sensibilidade, janela de leitura e tempo de retenção, além dos mecanismos atuantes em cada estado da memória (escrita, leitura e repouso). Foram estudadas as polarizações da célula de memória. Dentre as possíveis maneiras de programação do dado 1 desta tecnologia foram abordadas neste trabalho a programação pelos métodos GIDL (Gate Induced Drain Leakage) e BJT (Bipolar Junction Transistor). Pelo método de escrita por GIDL foi possível operar a célula de memória em alta velocidade sem dissipar potência expressiva. Mostrou-se que esse método é bastante promissor para a tecnologia low-power high-speed. E ainda, obteve-se maior estabilidade na operação de leitura quando esta é polarizada no ponto ZTC (Zero Temperature-Coefficient) devido ao nível de corrente do dado 0 ficar estável mesmo com a variação da temperatura. Pelo método de escrita por BJT, estudou-se a influência das espessuras do filme de silício e também do óxido enterrado, notou-se uma forte dependência da tensão mínima de dreno para a programação do dado 1 em função destas espessuras e também em função da temperatura. Conforme a espessura do filme de silício torna-se mais fina, a tensão de disparo aplicada ao dreno aumenta devido ao maior acoplamento. Porém, observou-se que o nível da tensão de disparo do dreno pode ser modulada através da tensão aplicada ao substrato, tornando possível operar a célula em uma tensão de disparo menor aumentando a vida útil do dispositivo. Quanto à temperatura, com o seu aumento observou-se que a tensão mínima de dreno necessária para disparar a escrita do dado 1 diminuiu favorecendo a programação da célula. Porém o tempo de retenção é prejudicado (torna-se menor) por causa do aumento da corrente de fuga na junção PN. Na análise sobre o impacto que a primeira e a segunda porta causam na margem de sensibilidade de corrente e no tempo de retenção, verificou-se que dependendo da tensão aplicada à porta durante a condição de armazenamento do dado, o tempo de retenção pode ser limitado ou pela geração ou pela recombinação dos portadores (lacunas). Notou-se que há um compromisso entre a obtenção da melhor margem de sensibilidade de corrente e o melhor tempo de retenção. Como o tempo retenção é um parâmetro mais crítico, mais atenção foi dada para a otimização deste. Concluiu-se nesta análise que a melhor polarização para reter o dado por mais tempo é a primeira interface estar em modo acumulação e a segunda em modo depleção. No estudo da polarização de dreno durante a operação de leitura, observou-se que quando aplicado alta tensão de dreno é obtido alta margem de sensibilidade, porém ao mesmo tempo esta polarização prejudica o dado 0 devido ao alto nível de geração de lacunas induzidas pela ionização por impacto, o qual diminui o tempo de retenção e destrói o dado 0 quando operações de múltiplas leituras são realizadas. Já para baixo nível de tensão de dreno durante a leitura notou-se que é possível realizar múltiplas operações de leitura sem perder o dado armazenado e também maior tempo de retenção foi obtido. / In this study was analyzed the behavior of one transistor called UTBOX (Ultra Thin Buried Oxide) FD SOI MOSFET (Fully Depleted Silicon-on-Insulator Metal- Oxide-Semiconductor Field-Effect-Transistor) working as a 1T-FBRAM (Single Transistor Floating Body Random Access Memory). This memory device is an evolution from conventional memories 1T1C-DRAM, however formed by only one transistor, the device itself is responsible for the storage of the information through the floating body effect. Thus two dimensional simulations were performed, where were obtained dynamic curves, and from these curves it was possible to extract and analyze some of the main parameters, such as, trigger drain voltage, sense margin current, read window, and the retention time, beyond the mechanisms in each state of memory (write, read and hold). Among the possible ways to program the data 1 in this technology were used the methods GIDL (Gate Induced Drain Leakage) and BJT (Bipolar Junction Transistor). By the GIDL method it was possible to operate the memory cell at high speed without spending significant power, showing that this method is very promising for low-power high-speed. Furthermore, greater stability was obtained in read operation when it is biased at point ZTC (zero-Temperature Coefficient) due to the current level of datum \'0\' remain stable even with temperature variation. By the BJT method, it was studied the influence of the silicon film thickness and the buried oxide thickness, and it was noted a strong dependence on minimum drain voltage for programming the data \'1\' as a function of both thicknesses. As the thickness of the silicon film becomes thinner, the trigger drain voltage increases due to stronger coupling. However, it was observed that the level of the trigger drain voltage can be modulated by the substrate bias in this way it is possible to operate the cell with lower voltage avoiding the damage and increasing the lifetime of the device. About the temperature, with its increase it was observed that the minimum drain voltage required to trigger the writing datum \'1\' decreased favoring the programming the cell. However the retention time is harmed (becomes smaller) due to the increment of leakage current in the PN junction. Analyzing the impact of the first and second gate on sense margin current and retention time, it was verified that depending on the voltage applied to the gate during the hold condition, the retention time may be limited by the generation or recombination of the carriers (holes). It was noted that there is a compromise between obtaining the best sense margin current and the best retention time. Since the retention is the most critical parameter, more attention should be given in order to obtain the optimization of this latter. It is concluded in this analysis that the best bias to retain the datum for longer time is the first interface being in accumulation mode and the second in depletion mode. In the study of biasing the drain during the read operation, it has been observed that the use of high drain voltage provides high sense margin, but at the same time, this polarization affect the data \'0\' due to high level of holes generation induced by impact ionization, which shortens the retention time and destroys the data \'0\' in multiple read operations. However, for low drain voltage during read operations it was possible to perform multiple read operations without losing the stored data and also higher retention time was obtained.
24

Psykodynamisk grupphandledning på tre utbildningsnivåer : - erfarenheter av att handleda inom psykoterapi- och handledarutbildningar

Bernhard, Lisa January 2006 (has links)
<p>Studien är utförd i anslutning till ett pågående forskningsprojekt om grupphandledning i psykoterapi, GUT-projektet. Studiens syfte var att nå ökad kunskap om handledares upplevelse och erfarenhet av att handleda grupper på olika utbildningsnivåer med psykodynamisk inriktning. En kvalitativ ansats valdes för att besvara studiens syfte. Frågeställningarna omfattade handledares tankar om mål och bedömningskriterier för grupphandledning, erfarenheter av tillvägagångssätt i grupphandledning, gruppens inverkan på handledningen samt den organisatoriska ramens betydelse för grupphandledning på olika utbildningsnivåer. Nio handledare ingick i studien. Data har samlats in via öppna semistrukturerade intervjuer och har bearbetats genom tematisk analys. Målen uppgavs skilja sig mellan olika utbildningsnivåer, främst genom olika grad av fördjupning inom till stora delar gemensamma områden. Nivåspecifika skillnader i tillvägagångssätt i handledning redovisades medan respondenternas erfarenheter av gruppens inverkan på handledningen var likartad oavsett utbildningsnivå. Svårigheter förenade med utbildningshandledning i grupp redovisades och den organisatoriska ramens avgörande betydelse för grupphandledningen betonades. Studiens resultat diskuterades i förhållande till befintlig teori.</p>
25

Automotive embedded systems software reprogramming

Schmidgall, Ralf January 2012 (has links)
The exponential growth of computer power is no longer limited to stand alone computing systems but applies to all areas of commercial embedded computing systems. The ongoing rapid growth in intelligent embedded systems is visible in the commercial automotive area, where a modern car today implements up to 80 different electronic control units (ECUs) and their total memory size has been increased to several hundreds of megabyte. This growth in the commercial mass production world has led to new challenges, even within the automotive industry but also in other business areas where cost pressure is high. The need to drive cost down means that every cent spent on recurring engineering costs needs to be justified. A conflict between functional requirements (functionality, system reliability, production and manufacturing aspects etc.), testing and maintainability aspects is given. Software reprogramming, as a key issue within the automotive industry, solve that given conflict partly in the past. Software Reprogramming for in-field service and maintenance in the after sales markets provides a strong method to fix previously not identified software errors. But the increasing software sizes and therefore the increasing software reprogramming times will reduce the benefits. Especially if ECU’s software size growth faster than vehicle’s onboard infrastructure can be adjusted. The thesis result enables cost prediction of embedded systems’ software reprogramming by generating an effective and reliable model for reprogramming time for different existing and new technologies. This model and additional research results contribute to a timeline for short term, mid term and long term solutions which will solve the currently given problems as well as future challenges, especially for the automotive industry but also for all other business areas where cost pressure is high and software reprogramming is a key issue during products life cycle.
26

Criopreservação do sêmen ovino com incorporação de colesterol por ciclodextrina / Criopreservation of ram semen with colesterol loaded cyclodextrin

Batissaco, Leonardo 31 October 2014 (has links)
A preocupação com a qualidade do sêmen ovino congelado tem sido motivo de muitas pesquisas, principalmente pela dificuldade da transposição cervical durante a inseminação artificial. Contudo, a inseminação intra-cervical é frequentemente usada em ovinos e resulta em redução da fertilidade com o uso do sêmen congelado. Neste sentido, esse estudo foi dividido em dois experimentos. No 1o experimento foi verificado o potencial da ciclodextrina pré-carregada com colesterol como aditivo ao diluidor na proteção da cinética espermática, integridade das membranas plasmática e acrossomal, função mitocondrial, capacitação espermática e produção de espécies reativas ao oxigênio (ROS) em espermatozoides criopreservados ovinos. Cinco ejaculados de seis carneiros (n = 30) foram divididos em três tratamentos: apenas diluidor (CON); diluidor + colesterol incorporado a ciclodextrina (CLC + CHO); e diluidor + ciclodextrina pura (CLCP). Após a diluição (50x106 espermatozóides/mL), o sêmen foi envasado em palhetas, identificado e criopreservado utilizando um sistema automatizado. Duas palhetas da mesma partida de cada tratamento foram descongeladas (a 37°C durante 30 segundos) e analisadas quanto motilidade (CASA), morfologia dos espermatozoides (DIC), integridade do plasma (PI-H342) e acrossomal (FITC-PSA) membranas, potencial mitocondrial (JC-1), produção de radicais livres (CellRox), peroxidação lipídica (BODIPY) e fluidez da membrana celular (merocianina 540). As comparações entre os grupos foram analisadas pelo PROC MIXED do SAS e o efeito de grupo foi detectado pelo teste de Tukey (p&lt;0,05) ou pela estatística não paramétrica de ordem (Kruskal-Wallis), quando era necessário. No 2º experimento os mesmos ejaculados foram divididos por congelabilidade baseados na motilidade total pós-descongelação (MTPD) e na porcentagem de redução na motilidade total (%RMT) quando comparados o sêmen in natura e o sêmen pós-descongelação (somente diluidor), sendo divididos nos grupos alta (MTPD&gt;60% e %RMT&lt;40%), intermediária (60%&gt;MTPD&gt;40% e 60%&gt;RMT&gt;40%) e baixa (MTPD&lt;40% e %RMT&gt;60%) congelabilidade. Foram analisados os tratamentos CON e CLC+CHO dentro de cada animal e de cada grupo quanto a motilidade (CASA), a integridade das membranas plasmática (PI-H342) e acrossomal (FITC-PSA), potencial mitocondrial (JC-1), peroxidação lipídica (BODIPY) e fluidez da membrana celular (merocianina 540). As comparações foram realizadas por análise de variância (ANOVA) em arranjo fatorial 3X3 (Tratamento CLC+CHO, CON e in natura X grupos alta, intermediária e baixa congelabilidade), as comparações entre os grupos foram analisadas pelo PROC MIXED do SAS e o efeito de grupo foi detectado pelo teste de Tukey (p &lt;0,05) ou pela estatística não paramétrica de ordem (Kruskal-Wallis), quando era necessário. No 1o experimento o tratamento CLC+CHO se mostrou mais eficaz em preservar os parâmetros de motilidade, integridade de membranas e potencial mitocondrial quando comparado aos demais tratamentos. O grupo CLCP mostrou queda nos parâmetros de motilidade, integridade de membrana, potencial mitocondrial, mostrando, com isso, uma queda na preservação espermática. No 2o experimento observou-se que o tratamento CLC+CHO mostrou maior grau de preservação para motilidade total e progressiva, células rápidas, preservação de membranas plasmática e acrossomal e potencial mitocondrial quando comparado ao CON. Esse efeito teve maior significância nos grupos de baixa e intermediária congelabilidade, não sendo tão expressivo no grupo de alta. Pode-se concluir com esse estudo que o tratamento com ciclodextrina acrescida de colesterol contribui para uma melhor preservação dos parâmetros espermáticos do sêmen ovino, principalmente em animais apresentando baixa congelabilidade, contudo não apresenta diferença em ejaculados de alta congelabilidade. / Frozen ram semen has been the subject of many researches, mainly due to the difficulty of cervical transposition during artificial insemination. However, intra-cervical insemination in sheep is often used, resulting in reduced fertility with the use of frozen semen. To this end, this study was divided into two experiments. In the first experiment was verified the potential of cyclodextrin loaded with cholesterol as an additive to the extender in the protection of sperm kinetics, integrity of plasmatic and acrosomal membranes, mitochondrial function, sperm capacitation and production of reactive oxygen species (ROS) in cryopreserved sheep sperm. Five ejaculates from six rams (n = 30) were divided into three treatments: only extender (CON); extender + cyclodextrin loaded with cholesterol (CLC + CHO); and extender + pure cyclodextrin (CLCP). After dilution (50x106 spermatozoa/mL), semen was stored in straws, identified and cryopreserved using an automated system. Two straws from each ejaculate and treatment were thawed (at 37° C for 30 seconds) and analyzed for motility (CASA), morphology of spermatozoa (DIC), plasmatic (PI-H342) and acrosomal (FITC-PSA) membrane integrity, mitochondrial potential (JC-1), production of free radicals (CellRox), lipid peroxidation (BODIPY) and cell membrane permeability (Merocyanine 540). Comparisons between groups were analyzed using PROC MIXED of SAS and the effect of group was detected by Tukey (p &lt;0.05) or by the order of nonparametric statistics (Kruskal-Wallis) test, when necessary. In the 2nd experiment the same ejaculates were divided by freezability based on the total post-thaw motility (TPTM) and the percentage of reduction in total motility (%RTM) when compared fresh and post-thaw semen (only extender), and divided into the groups: high (TPTM &ge; 60% and %RTM &le; 40%), intermediate (60%&gt; TPTM &gt; 40% and 60%&gt; %RTM &gt; 40%) and low (TPTM &le; 40% and %RTM &ge; 60%) freezability. CON and CLC + CHO treatments were analyzed within each animal and each group for motility (CASA), plasmatic (PI-H342) and acrosomal (FITC-PSA) membrane integrity, mitochondrial potential (JC-1), lipid peroxidation (BODIPY) and cell membrane permeability (Merocyanine 540). Comparisons were performed by analysis of variance (ANOVA) with a factorial arrangement 3x3 (groups CLC+CHO, CON and fresh X groups high, medium and low freezability), comparisons between groups were analyzed using PROC MIXED of SAS and the group effect was detected by the Tukey test (p &lt; 0.05) or no statistical order parametric (Kruskal-Wallis), when necessary. In the first experimente, CLC + CHO treatment was more effective in preserving the parameters of motility, membrane integrity, and mitochondrial potential compared to other treatments. The CLCP group showed a fall in the parameters of motility, membrane integrity, mitochondrial potential, showing thereby a decrease in sperm preservation. In the 2nd experiment, it was observed that the treatment CLC + CHO showed greater preservation for total and progressive motility, rapid cell preservation, plasmatic and acrosomal membranes and mitochondrial potential when compared to CON. This effect was most significant in the groups of low and intermediate freezability, not being as significant in the group of high freezability. We can conclud from this study that treatment with cyclodextrin loaded with cholesterol contributes to better preservation of sperm parameters in ram semen, especially in animals displaying low freezability, however there where no diference in the high freezability group.
27

Modelagem, otimização, construção e avaliação de um protótipo de carneiro hidráulico. / Modeling, optimization and evaluation of a hydraulic ram.

Zarate Rojas, Ricardo Nicolas 05 December 2002 (has links)
Este trabalho foi realizado no Laboratório de Hidráulica do Departamento de Engenharia Rural da ESALQ/USP, com o objetivo de modelar, otimizar e avaliar um carneiro hidráulico. Para isso foi desenvolvido um modelo teórico, validado no laboratório através da construção de uma eletroválvula comandada eletronicamente por computador. Através da filmagem do jato de água e utilizando método das coordenadas determinou-se a velocidade do jato de água da tubulação de alimentação do carneiro, para três alturas de alimentação e três comprimentos diferentes. Posteriormente foi construído o carneiro hidráulico em PVC, sendo utilizada a eletroválvula como válvula de escape e, por meio de um microprocessador, obtive-se diferentes tempos para o fechamento da válvula, variando entre 0,2 s e 1,6 s. Foram testados dois materiais como tubulação de alimentação, PVC 25mm de diâmetro nominal e aço galvanizado 19,05 mm de diâmetro nominal para três comprimentos e alturas de alimentação. A máxima vazão de recalque obtida foi de 224 L/h, sendo a pressão de recalque de 54 kPa, sendo a tubulação de alimentação PVC, e a altura de alimentação de 2,23 m, para um tempo de pulso da eletroválvula de 0,2 s. O maior rendimento obtido foi 62 % sendo a tubulação de alimentação de PVC, para um tempo de pulso de 0,2 s com uma pressão de 74 kPa e vazão de recalque de 112 L/h. / This work was developed in the Hydraulics Laboratory of the Department of Rural Engineering at ESALQ/USP., with the goal of modeling, optimize and to evaluate a hydraulic ram. For that was developed a theoretical model, validated in the laboratory through the construction of an electronic valve commanded by a computer. Through the filming of water jet and using method of the coordinates tot determined the speed of water jet of the alimentation piping of the ram for three different heights and lengths. It afterwards was built the hydraulic ram in PVC, being used an electronic valve as pulse valve, and by means of the microprocessor Basic Step, was obtained different times to the shutdown of the valve, varying between 0,2 s and 1,6 s. Were tried two material as alimentation piping, PVC 25mm nominal diameter and galvanized steel 19,05 mm nominal diameter for three alimentation lengths. The flow maxim obtained was 224 L/h, being the pressure of emphasizes of 54 kPa, having as alimentation piping PVC, and the height of alimentation of 2,23 m for, for a time of .shutdown of electronic valve of 0,2 s. The biggest obtained revenue was 62%, being the alimentation piping of PVC, for a time of shutdown of 0,2 s with a pressure 74 kPa and a flow of 112 L/h.
28

Criopreservação do sêmen ovino com incorporação de colesterol por ciclodextrina / Criopreservation of ram semen with colesterol loaded cyclodextrin

Leonardo Batissaco 31 October 2014 (has links)
A preocupação com a qualidade do sêmen ovino congelado tem sido motivo de muitas pesquisas, principalmente pela dificuldade da transposição cervical durante a inseminação artificial. Contudo, a inseminação intra-cervical é frequentemente usada em ovinos e resulta em redução da fertilidade com o uso do sêmen congelado. Neste sentido, esse estudo foi dividido em dois experimentos. No 1o experimento foi verificado o potencial da ciclodextrina pré-carregada com colesterol como aditivo ao diluidor na proteção da cinética espermática, integridade das membranas plasmática e acrossomal, função mitocondrial, capacitação espermática e produção de espécies reativas ao oxigênio (ROS) em espermatozoides criopreservados ovinos. Cinco ejaculados de seis carneiros (n = 30) foram divididos em três tratamentos: apenas diluidor (CON); diluidor + colesterol incorporado a ciclodextrina (CLC + CHO); e diluidor + ciclodextrina pura (CLCP). Após a diluição (50x106 espermatozóides/mL), o sêmen foi envasado em palhetas, identificado e criopreservado utilizando um sistema automatizado. Duas palhetas da mesma partida de cada tratamento foram descongeladas (a 37°C durante 30 segundos) e analisadas quanto motilidade (CASA), morfologia dos espermatozoides (DIC), integridade do plasma (PI-H342) e acrossomal (FITC-PSA) membranas, potencial mitocondrial (JC-1), produção de radicais livres (CellRox), peroxidação lipídica (BODIPY) e fluidez da membrana celular (merocianina 540). As comparações entre os grupos foram analisadas pelo PROC MIXED do SAS e o efeito de grupo foi detectado pelo teste de Tukey (p&lt;0,05) ou pela estatística não paramétrica de ordem (Kruskal-Wallis), quando era necessário. No 2º experimento os mesmos ejaculados foram divididos por congelabilidade baseados na motilidade total pós-descongelação (MTPD) e na porcentagem de redução na motilidade total (%RMT) quando comparados o sêmen in natura e o sêmen pós-descongelação (somente diluidor), sendo divididos nos grupos alta (MTPD&gt;60% e %RMT&lt;40%), intermediária (60%&gt;MTPD&gt;40% e 60%&gt;RMT&gt;40%) e baixa (MTPD&lt;40% e %RMT&gt;60%) congelabilidade. Foram analisados os tratamentos CON e CLC+CHO dentro de cada animal e de cada grupo quanto a motilidade (CASA), a integridade das membranas plasmática (PI-H342) e acrossomal (FITC-PSA), potencial mitocondrial (JC-1), peroxidação lipídica (BODIPY) e fluidez da membrana celular (merocianina 540). As comparações foram realizadas por análise de variância (ANOVA) em arranjo fatorial 3X3 (Tratamento CLC+CHO, CON e in natura X grupos alta, intermediária e baixa congelabilidade), as comparações entre os grupos foram analisadas pelo PROC MIXED do SAS e o efeito de grupo foi detectado pelo teste de Tukey (p &lt;0,05) ou pela estatística não paramétrica de ordem (Kruskal-Wallis), quando era necessário. No 1o experimento o tratamento CLC+CHO se mostrou mais eficaz em preservar os parâmetros de motilidade, integridade de membranas e potencial mitocondrial quando comparado aos demais tratamentos. O grupo CLCP mostrou queda nos parâmetros de motilidade, integridade de membrana, potencial mitocondrial, mostrando, com isso, uma queda na preservação espermática. No 2o experimento observou-se que o tratamento CLC+CHO mostrou maior grau de preservação para motilidade total e progressiva, células rápidas, preservação de membranas plasmática e acrossomal e potencial mitocondrial quando comparado ao CON. Esse efeito teve maior significância nos grupos de baixa e intermediária congelabilidade, não sendo tão expressivo no grupo de alta. Pode-se concluir com esse estudo que o tratamento com ciclodextrina acrescida de colesterol contribui para uma melhor preservação dos parâmetros espermáticos do sêmen ovino, principalmente em animais apresentando baixa congelabilidade, contudo não apresenta diferença em ejaculados de alta congelabilidade. / Frozen ram semen has been the subject of many researches, mainly due to the difficulty of cervical transposition during artificial insemination. However, intra-cervical insemination in sheep is often used, resulting in reduced fertility with the use of frozen semen. To this end, this study was divided into two experiments. In the first experiment was verified the potential of cyclodextrin loaded with cholesterol as an additive to the extender in the protection of sperm kinetics, integrity of plasmatic and acrosomal membranes, mitochondrial function, sperm capacitation and production of reactive oxygen species (ROS) in cryopreserved sheep sperm. Five ejaculates from six rams (n = 30) were divided into three treatments: only extender (CON); extender + cyclodextrin loaded with cholesterol (CLC + CHO); and extender + pure cyclodextrin (CLCP). After dilution (50x106 spermatozoa/mL), semen was stored in straws, identified and cryopreserved using an automated system. Two straws from each ejaculate and treatment were thawed (at 37° C for 30 seconds) and analyzed for motility (CASA), morphology of spermatozoa (DIC), plasmatic (PI-H342) and acrosomal (FITC-PSA) membrane integrity, mitochondrial potential (JC-1), production of free radicals (CellRox), lipid peroxidation (BODIPY) and cell membrane permeability (Merocyanine 540). Comparisons between groups were analyzed using PROC MIXED of SAS and the effect of group was detected by Tukey (p &lt;0.05) or by the order of nonparametric statistics (Kruskal-Wallis) test, when necessary. In the 2nd experiment the same ejaculates were divided by freezability based on the total post-thaw motility (TPTM) and the percentage of reduction in total motility (%RTM) when compared fresh and post-thaw semen (only extender), and divided into the groups: high (TPTM &ge; 60% and %RTM &le; 40%), intermediate (60%&gt; TPTM &gt; 40% and 60%&gt; %RTM &gt; 40%) and low (TPTM &le; 40% and %RTM &ge; 60%) freezability. CON and CLC + CHO treatments were analyzed within each animal and each group for motility (CASA), plasmatic (PI-H342) and acrosomal (FITC-PSA) membrane integrity, mitochondrial potential (JC-1), lipid peroxidation (BODIPY) and cell membrane permeability (Merocyanine 540). Comparisons were performed by analysis of variance (ANOVA) with a factorial arrangement 3x3 (groups CLC+CHO, CON and fresh X groups high, medium and low freezability), comparisons between groups were analyzed using PROC MIXED of SAS and the group effect was detected by the Tukey test (p &lt; 0.05) or no statistical order parametric (Kruskal-Wallis), when necessary. In the first experimente, CLC + CHO treatment was more effective in preserving the parameters of motility, membrane integrity, and mitochondrial potential compared to other treatments. The CLCP group showed a fall in the parameters of motility, membrane integrity, mitochondrial potential, showing thereby a decrease in sperm preservation. In the 2nd experiment, it was observed that the treatment CLC + CHO showed greater preservation for total and progressive motility, rapid cell preservation, plasmatic and acrosomal membranes and mitochondrial potential when compared to CON. This effect was most significant in the groups of low and intermediate freezability, not being as significant in the group of high freezability. We can conclud from this study that treatment with cyclodextrin loaded with cholesterol contributes to better preservation of sperm parameters in ram semen, especially in animals displaying low freezability, however there where no diference in the high freezability group.
29

Design and Optimization of Resistive RAM-based Storage and Computing Systems

January 2019 (has links)
abstract: The Resistive Random Access Memory (ReRAM) is an emerging non-volatile memory technology because of its attractive attributes, including excellent scalability (< 10 nm), low programming voltage (< 3 V), fast switching speed (< 10 ns), high OFF/ON ratio (> 10), good endurance (up to 1012 cycles) and great compatibility with silicon CMOS technology [1]. However, ReRAM suffers from larger write latency, energy and reliability issue compared to Dynamic Random Access Memory (DRAM). To improve the energy-efficiency, latency efficiency and reliability of ReRAM storage systems, a low cost cross-layer approach that spans device, circuit, architecture and system levels is proposed. For 1T1R 2D ReRAM system, the effect of both retention and endurance errors on ReRAM reliability is considered. Proposed approach is to design circuit-level and architecture-level techniques to reduce raw Bit Error Rate significantly and then employ low cost Error Control Coding to achieve the desired lifetime. For 1S1R 2D ReRAM system, a cross-point array with “multi-bit per access” per subarray is designed for high energy-efficiency and good reliability. The errors due to cell-level as well as array-level variations are analyzed and a low cost scheme to maintain reliability and latency with low energy consumption is proposed. For 1S1R 3D ReRAM system, access schemes which activate multiple subarrays with multiple layers in a subarray are used to achieve high energy efficiency through activating fewer subarray, and good reliability is achieved through innovative data organization. Finally, a novel ReRAM-based accelerator design is proposed to support multiple Convolutional Neural Networks (CNN) topologies including VGGNet, AlexNet and ResNet. The multi-tiled architecture consists of 9 processing elements per tile, where each tile implements the dot product operation using ReRAM as computation unit. The processing elements operate in a systolic fashion, thereby maximizing input feature map reuse and minimizing interconnection cost. The system-level evaluation on several network benchmarks show that the proposed architecture can improve computation efficiency and energy efficiency compared to a state-of-the-art ReRAM-based accelerator. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2019
30

FLOW-CYTOMETRIC SORTING OF RAM SPERMATOZOA: PRODUCTION OF LAMBS OF A PRE-DETERMINED SEX USING IN VIVO AND IN VITRO FERTILISATION

Hollinshead, Fiona Kate January 2003 (has links)
Abstract Birth of offspring of a pre-determined sex using flow cytometrically sorted fresh spermatozoa was first achieved in rabbits by Johnson et al. (1989). Since then offspring have been produced using sex-sorted spermatozoa from several different species (reviewed by Johnson, 2000). Initially, efficiency of the sex-sorting technology was poor with only low numbers of spermatozoa sorted per hour. Thus, the offspring derived from flow cytometrically sorted spermatozoa were produced with the use of artificial reproductive technologies (ART) such as in vitro fertilisation (IVF) and culture (IVC), intracytoplasmic sperm injection (ICSI) and deep artificial insemination (AI) which facilitated low dose insemination of potentially compromised spermatozoa. More recently, the development of high-speed sorters (Johnson and Welch, 1999) has facilitated the production of offspring using conventional AI techniques with low dose inseminates (Seidel et al., 1999) and successful cryopreservation of sorted spermatozoa (Schenk et al., 1999; Johnson et al., 2000; Lindsey et al., 2002; Schenk and DeGrofft, 2003). Increased efficiency of sorting bull spermatozoa has evolved through significant instrumentation and biological developments which have enabled the commercialization of the sperm sexing technology in the dairy industry, although conception rates in cows after low dose AI with sexed frozen-thawed spermatozoa are still lower than after standard frozen semen AI (Seidel et al., 1999). Subsequently, over 20 000 calves of pre-determined sex have been produced from commercially available sex-sorted frozen-thawed bull spermatozoa (Seidel, 2003). However, similar developments have not been made in the sheep industry and were examined in this thesis. In this study, successful cryopreservation of sex-sorted ram spermatozoa and production of offspring of the pre-determined sex (X: 94.4 %; Y: 100 %) was achieved after low dose (2-4 x 106 total) insemination using conventional laparoscopic intrauterine (IU) AI. However, the overall pregnancy rate for ewes inseminated with sex-sorted frozen-thawed spermatozoa was low (25 %) compared to ewes inseminated with a commercial dose (140 x 106 total) of non-sorted frozen-thawed spermatozoa (54 %). Cryopreservation has been found to not only reduce the proportion of motile spermatozoa, but cause the remaining spermatozoa to undergo changes that advance membrane maturation thereby shortening their lifespan, especially after in vivo fertilisation (Gillan and Maxwell, 1999). It was found that sorting prior to cryopreservation accelerated the maturation of sperm membranes and after co-incubation with oviducal cells in vitro, sorted frozen-thawed spermatozoa were released more rapidly than non-sorted (control) frozen-thawed spermatozoa. The potentially reduced lifespan of sorted frozen-thawed spermatozoa, and practical constraints on the number of spermatozoa that can be sorted for an insemination dose, makes insemination close to the site of fertilisation and time of ovulation critical for successful fertilisation. After treatment of ewes with GnRH to increase the precision of insemination in respect to the time of ovulation, there was no difference in pregnancy rate between ewes inseminated before, during or after the assumed time of ovulation. Furthermore, there was no difference in pregnancy rate after IU AI with similar doses of sorted frozen-thawed and non-sorted frozen-thawed spermatozoa in GnRH-treated ewes. The minimum dose of sorted frozen-thawed spermatozoa required for commercially acceptable pregnancy rates determined after IU AI was high (20 x 106 motile). Consequently, alternative methods for efficiently producing large numbers of offspring of a pre-determined sex using flow cytometrically sorted ram spermatozoa were investigated. Ram spermatozoa can be stored for short periods of time in a chilled state (liquid storage) or for an indefinite period of time in a frozen state (frozen storage; Salamon and Maxwell, 2000). The fixed location of the sperm sorter requires the need for transport of semen from the point of collection to the site of sorting and processing, but also from the sperm sorter site to the recipient females under artificial conditions. In this study, ram spermatozoa liquid stored for 24 h prior to sorting were efficiently sorted, frozen, thawed and after in vitro fertilisation and culture produced a high proportion of grade 1 blastocysts. Similarly, spermatozoa stored at reduced temperatures after sorting maintained high sperm quality for up to 6 days. Furthermore, frozen-thawed spermatozoa from rams and some non-human primates were successfully prepared for sorting and efficiently sorted producing spermatozoa with high quality in vitro parameters. The quality of frozen-thawed ram spermatozoa after sorting was such that successful re-cryopreservation after sorting was possible. Low numbers of frozen-thawed sorted and re-frozen and thawed spermatozoa were optimal for IVF and a high proportion of grade 1 in vitro embryos of a pre-determined sex were produced. These embryos were either transferred immediately or vitrified prior to transfer, extending the application of the sperm sexing technology further. The birth of lambs of pre-determined sex after transfer of both fresh and vitrified embryos derived from frozen-thawed sorted spermatozoa was achieved. The findings in this thesis suggest that sorted frozen-thawed ram spermatozoa may have more advanced membrane maturation state than non-sorted frozen-thawed spermatozoa, resulting in a decreased fertilizing lifespan in the female reproductive tract. Despite this, the use of sexed ram spermatozoa in a number of physiological states (fresh, liquid, frozen) with several different ARTs is possible in producing significant numbers of offspring of a pre-determined sex. Improved efficiency in both sperm sexing and associated reproductive technologies is required for commercialization to be achieved in the sheep industry.

Page generated in 0.427 seconds