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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.
31

Modelos mecânicos e fisiológicos do exercício nos domínios pesado e severo: comparação da potência e da resposta lactacidêmica nas condições de nado atado e desimpedido e da cinética do VO2 durante o crawl desimpedido

Pessôa Filho, Dalton Müller [UNESP] 13 April 2010 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:30:53Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-04-13Bitstream added on 2014-06-13T19:00:57Z : No. of bitstreams: 1 pessoafilho_dm_dr_rcla.pdf: 1143306 bytes, checksum: b016fc73fb992fb299381a40997bc60e (MD5) / Não se tem observado a preocupação com a descrição dos domínios de intensidade na natação e poucas tentativas foram realizadas para ajustar o modelo de P-tLim às condições desta modalidade de exercício. Este estudo pretendeu ajustar o modelo P-tLim à natação com o recurso do controle de cargas possibilitado pelo nado em condição atada. Assim como, seu significado fisiológico para a descrição dos domínios pesado/severo obtido pelas relações a serem estabelecidas com a velocidade crítica (VC - limite superior do domínio pesado), com a máxima fase estável do lactato (MFEL, que disputa com VC a indexação do limite superior do domínio pesado) e com a caracterização dos domínios pesado e severo pelos parâmetros de cinética e amplitude do VO2. Em um primeiro estudo, 24 nadadores (16,5 ± 2,7 anos e 67,7 ± 13,5 kg) submeteram-se à estimativa da força de arrasto (Fr = A  v2). A Fr encontrada em máxima velocidade foi fracionada para compor quatro estágios de teste, com tempos de exaustão entre 3-20 min. em crawl-atado. A VC foi estimada empregando quatro distâncias entre 200-1500m. A potência crítica atada (PCAtada) linear (81,9W) e não linear (71,1W) não se diferenciaram (  0,05) dos valores de PC linear (108,2W) e não linear (96,3W) estimados por VC linear (1,2m.s-1) e não linear (1,14m.s-1), através da equação do desempenho. Neste primeiro estudo, pode-se concluir que PCAtada é correlata a VC, podendo representar a capacidade aeróbia. No segundo estudo, dez nadadores (16,6  1,4 anos e 69,8  9,5 kg) foram submetidos às estimativas de PCAtado (equações lineares e hiperbólica de 2-parâmetros), VC (ajuste linear do tempo pela velocidade nos desempenhos de 200, 400 e 800m), PAtadaMFEL (3 ou 4 esforços entre 95 a 105% da carga em PCAtada hiperbólica) e à vMFEL (3 ou 4 esforços entre 85 a 95% do velocidade máxima do crawl nos 400m)... / There is a lack of studies describing the domains of intensity in swimming, and few works approaches the P-tLim model in swimming. This study provided a way to assess the P-tLim model in swimming, applying the load controlled environment in full-tethered condition. The physiological meaning for the description of heavy and severe domains was established from the relationships of critical velocity (CV - upper boundary of heavy domain) to maximal lactate steady state (MLSS, conflicting with VC to demarcate the upper boundary of heavy domain), and from the descriptive characterization of kinetic and amplitude parameters of VO2. In he first study, 24 swimmers with 16.5 ± 2.7 years and 67.7 ± 13.5 kg were undertaken to drag force (Fr) estimation (Fr = A  v2). The Fr at maximal crawl velocity was the load that was fractioned to build the sets, lasting 3-20min until exhaustion. CV was calculated from distance between 200-1500m. The linear (81.9W) and non-linear (71.1W) PTethCrit were not different (  0.05) from the values of linear (108.2W) and non-linear (96.3W) PC estimative obtained from linear (1.2m.s-1) and non-linear (1.14m.s-1) CV through swim performance equation. It was conclude that PCTeth was related to CV, and reliable to indexes aerobic capacity. The second work, did analyze ten male swimmers (16.6  1.4 years and 69.8  9.5kg) that were submitted to the measurements of the CPTeth (linear and non-linear two parameters equation), CV (linear adjustment between time and velocity performance in the 200, 400 and 800m), PTethMLSS (3 or 4 trials ranging from 95 to 105% of the load at non-linear PCAtada), and vMLSS (3 or 4 trials ranging from 85 to 95% of the 400-m crawl performance). The results shown that neither CV (1.19  0.12m.s-1) nor the CPTeth (99.4  23.0W) matches the statements for MLSS, once differences were observed to the vMLSS (1.17  0.11m.s-1)... (Complete abstract click electronic access below)
32

Efeitos fisiológicos do treinamento unipodal em cicloergômetro com e sem irradiação LED / Physiological effects of one-legged cycling with and without LED therapy

Figueira, Thiago Gomes 01 December 2017 (has links)
A melhora na capacidade física e/ou reserva funcional de um indivíduo deve-se, entre outros, a um treinamento sistemático e bem padronizado. O exercício aeróbio é uma modalidade frequentemente empregada em um programa de treinamento, especialmente naqueles com objetivo de melhora do condicionamento físico. Contudo atualmente, o uso da fototerapia tem ganhado espaço no que tange ao aumento de desempenho de atletas. Baseado nisso o objetivo deste estudo foi verificar o efeito do treinamento unipodal, terapia LED e treinamento associado à terapia LED sobre parâmetros ergoespirométricos de performance (VO2max, AT e RCT) e na concentração sanguínea de creatina quinase. Para esse estudo participaram 24 voluntários do sexo masculino, os quais foram submetidos a uma avaliação pré-intervenção, foram submetidos a um período de oito semanas de treinamento em cicloergômetro com irradiação LED ou placebo. Após esse período foram submetidos a uma nova avaliação, pós-treino. Para a aplicação da terapia LED, foi utilizado um arranjo contendo 50 LEDs com comprimento de onda de 850 nm e aplicado por 60 segundos após cada sessão de treino. Os voluntários foram separados nos seguintes grupos experimentais: Não Treinados e LED desligado (Grupo NTLD), Não Treinados e LED ligado (Grupo NTLL), Treinados e LED desligado (Grupo TLD), Treinados e LED ligado (Grupo TLL). A perna que recebeu a intervenção foi eleita por sorteio e foi chamada de perna ativa (A) e a perna contralateral, chamada de controle (C). Durante o teste em exercício crescente, até a fadiga, foram quantificadas as variáveis ergoespirométricas, ventilação (Ve), consumo de oxigênio (VO2), equivalente ventilatório de oxigênio (EqVO2), também foi coletada amostra de sangue para dosagem da lactacidemia e foi mensurada a concentração da enzima creatina quinase (CK). Como resultados das respostas agudas frente ao ato de pedalar com uma perna notou-se que a pedalada unipodal apresentou menor valor de intensidade, VO2, Ve, lactacidemia e maior incremento de CK, quando comparada com a pedalada bipodal (convencional). Ao se concluir as oito semanas de treinamento notou-se que a perna ativa na pedalada unipodal apresentou melhoras nas variáveis mensuradas nos grupos TLL, NTLL e algumas no TLD. Também foi encontrada melhora para a perna controle, em algumas variáveis, dos grupos que receberam a terapia LED. Com esse estudo conclui-se que o treinamento unipodal é capaz de melhorar parâmetros como intensidade, ventilação, consumo de oxigênio, eficiência aeróbia, e ainda minimiza os danos musculares induzido pelo exercício no membro que efetuou o treinamento. A terapia LED é capaz de promover as mesmas melhoras em intensidades, consumo de oxigênio e eficiência aeróbia que o treinamento proporcionou, contudo em magnitudes diferentes, ainda é capaz de proporcionar efeito protetor contra lesão muscular induzida pelo exercício. A terapia LED associada ao treinamento potencializa os efeitos conseguidos com cada um isoladamente. / The improvement in physical capacity and/or functional reserve is due to, among other factors, a systematic and organized training program. Aerobic exercise is a frequently used modality in a training program, especially among those who aim to improve physical fitness. However phototherapy has currently gained space in regard to improving the performance of athletes. Based on this information, the purpose of the study was to verify the effect of one-legged cycling, LED therapy and their association on ergospirometric parameters of performance (VO2max, AT and RCT) and on blood concentration of CK. 24 male subjects volunteered for the study and were submitted to a pre-intervention evaluation and an 8-week period of one-legged cycling with LED therapy or placebo. After the intervention period subjects were submitted to a second evaluation. An arrangement containing 50 LEDs and a wavelength of 850 nm was applied during 60 seconds after each training session. Volunteers were divided into the following experimental groups: untrained and LED off (ULOf), untrained and LED on (ULOn), trained and LED off (TLOf) and trained and LED on (TLOn). The leg that received the intervention (training and/or LED therapy) was selected randomly and named active leg (A) and the contralateral limb was named control (C). During the incremental exercise test to volitional failure the ergospirometric variables ventilation (Ve), oxygen uptake (VO2) and oxygen ventilatory equivalent (EqVO2) were measured and blood samples were collected after each stage for lactate and before and 24 hours after the test for the analysis of blood CK. Acute responses from the pre-intervention evaluation showed that the intensity of one-legged cycling led to lower intensity, VO2, Ve, blood lactate and higher increase in blood CK compared to traditional cycling (two-legged). After the 8 weeks of intervention, the active leg showed improvements in the measured variables for the TLOn, ULOn and TLOf groups and, in some of the variables for the groups that received LED therapy. With these data we conclude that one-legged cycling is capable of increasing parameters such as intensity, ventilation, oxygen uptake, aerobic efficiency and minimizes the blood CK responses to exercise in the exercised limb. The association between exercise and Led therapy potentiates the effects achieved with either of the interventions.
33

Skillnader i fysisk prestation inomhus och utomhus : En randomiserad kontrollerad experimentell cross-over studie

Martinsson, Emilia January 2019 (has links)
Bakgrund: Träning i naturliga miljöer har hälsofrämjande effekter och ökar välbefinnandet i jämförelse med träning som sker i inomhusmiljöer. Individer som utför träning i utomhusmiljöer visar sig ha högre hastighet, hjärtfrekvens och blodlaktatkoncentration, i jämförelse med individer som tränar inomhus vilket påverkar den fysiska prestationen.Syfte: Syftet med denna studie var att undersöka mätbara skillnader i fysisk prestation inomhus och utomhus genom ett maxpulstest.Metod: Studien genomfördes med en randomiserad kontrollerad cross- over design där åtta män och fem kvinnor (medelålder 26 ± 3.67), fysiskt aktiva, genomförde ett beeptest vid två tillfällen. Testet utfördes av samma person vid ett tillfälle inomhus och ett tillfälle utomhus. Analysen utgick från uppskattat VO2 max genom protokoll av beeptest, objektiv mätning och kontroll av puls direkt före tester och direkt efter genomförda tester.Resultat: Resultaten visade en signifikant skillnad i VO2 max (O2ml/kg/min) (p= 0.047), genom en högre fysisk prestation inomhus i jämförelse med utomhus (46.08 ± 8.76 och 44.73 ± 8.84). Puls (slag/min) efter genomförda tester visade ett högre medelvärde inomhus i jämförelse med utomhus (192.36 ± 10.13 och 190.45 ± 9.11), men ingen signifikant skillnad (p=0.11). Puls före tester visade ingen signifikant skillnad (p=0.898) mellan inomhusmiljön och utomhusmiljön (107.16 ± 18.78 och 107. 75 ± 18.49).Slutsats: Resultaten indikerar på att det är skillnader i fysisk prestation i olika miljöer. VO2 max var signifikant högre i inomhusmiljön i jämförelse med utomhusmiljön. Medel-maxpulsen tenderade ha ett högre medelvärde inomhus i jämförelse med utomhus. / Background: Exercise performed in natural environments produces health-promoting effects and increases well-being, in comparison with exercises performed in indoors-environments. Individuals who exercise outdoors has higher velocity, heartrate and blood lactate concentration compared to individuals who exercise indoors, which affects the physical performance.Purpose: The purpose of this study was to investigate measurable differences in physical performance indoors and outdoors through a maximum heartrate test.Method: The study was conducted with a randomized controlled cross over design where five women and eight men, physical active, in the middle age of 26 ± 3.67 years, performed a shuttle run test at two times. The test was repeated by the same individual one time indoors and one time outdoors. The analysis was made by estimated VO2 max using a protocol from the performed shuttle run test, and controlled objective measurements of pulse levels, directly before the test started and directly after finished test.Results: Significant differences were found between indoors and outdoors, where VO2 max (O2ml/lbs/min) (p= 0.047) was higher indoors than outdoors (46.08 ± 8.76 and 44.73 ± 8.84). Pulse levels (beats/min) was higher indoors than outdoors (192.36 ± 10.13 and 190.45 ± 9.11) after finished test, but significant differences were not found (p=0.11). Significant differences were not found in pulse levels before the test (p=0.898), between the different environments (107.16 ± 18.78 and 107. 75 ± 18.49).Conclusion: The results in this study show that there are differences in physical performance between different environments. VO2 max was significantly higher in the indoor environment compared to the outdoor environment. The average maximum pulse tended to have a higher average indoors compared to outdoors.
34

Deposição de nano-camadas de VO2 por Magnetron Sputtering / Deposition of VO2 Nanolayers by Magnetron Sputtering

Santos, Claudiosir Roque dos 13 April 2007 (has links)
The vanadium dioxide (VO2) shows a metal-insulator transition (MIT) near the room temperature with huge changes in its electrical and optical behavior. Both the electrical and optic properties, and even the transition temperature, depend on the morphologic characteristics of the metal. In this work, vanadium oxide nanolayers were deposited onto glass substrate by reactive magnetron sputtering. The aim was to obtain the best deposition parameters, like substrate temperature (Ts) and oxygen partial pressure (PO2), for the VO2M1 phase synthesis. Samples deposited with oxygen partial pressures ranging from 10 to 20% of the total pressure, and Ts=400°C, have shown metal insulator transition when submitted to a 550°C ex-situ thermal treatment. The analysis of the x-ray diffraction spectra has shown that all the samples were formed simultaneously by more than one phase of vanadium oxides. Moreover, we identify a reciprocal correspondence between the 2q = 27,8° peak, corresponding to (011) plan in VO2M1, and the MIT transition. The measured resistance in samples with VO2M1, in the temperature range of 25 to 100°C, showed variations of almost three orders of magnitude. The transition critical temperature took place between 59 and 82°C and the hysteresis loops width ranged between 9 and 13°C / O dióxido de Vanádio (VO2) apresenta uma transição metal isolante (MIT) próxima da temperatura ambiente com uma grande variação em suas propriedades elétricas e ópticas. Tanto as propriedades elétricas e ópticas quanto a própria temperatura de transição dependem das características morfológicas do material. Neste trabalho, nano-camadas de óxido de Vanádio foram produzidas sobre substratos de vidro pela técnica de magnetron sputtering reativo, visando determinar os parâmetros de deposição, em especial a temperatura do substrato (Ts) e pressão parcial de Oxigênio (PO2), adequadas para a obtenção da fase VO2M1. Amostras depositadas com pressões parciais de Oxigênio entre 10 e 20% da pressão total e Ts=400°C apresentaram MIT quando submetidas a tratamentos térmicos ex-situ a 550°C. A análise dos espectros de difração de raios-x mostrou que houve formação de mais de uma fase simultaneamente em todas as amostras, no entanto há uma correspondência recíproca entre o pico de difração de raios-x em 2q = 27,8° , correspondente ao plano (011) do VO2M1, e a transição MIT na resistividade. As medidas de resistência em função da temperatura, realizadas entre 25 e 100°C, mostraram, nas amostras com VO2M1, transição com variação na resistência em até três ordens de grandeza com temperaturas críticas entre 59 e 82°C e curvas de histerese com larguras entre 9 e 13°C
35

Efeitos fisiológicos do treinamento unipodal em cicloergômetro com e sem irradiação LED / Physiological effects of one-legged cycling with and without LED therapy

Thiago Gomes Figueira 01 December 2017 (has links)
A melhora na capacidade física e/ou reserva funcional de um indivíduo deve-se, entre outros, a um treinamento sistemático e bem padronizado. O exercício aeróbio é uma modalidade frequentemente empregada em um programa de treinamento, especialmente naqueles com objetivo de melhora do condicionamento físico. Contudo atualmente, o uso da fototerapia tem ganhado espaço no que tange ao aumento de desempenho de atletas. Baseado nisso o objetivo deste estudo foi verificar o efeito do treinamento unipodal, terapia LED e treinamento associado à terapia LED sobre parâmetros ergoespirométricos de performance (VO2max, AT e RCT) e na concentração sanguínea de creatina quinase. Para esse estudo participaram 24 voluntários do sexo masculino, os quais foram submetidos a uma avaliação pré-intervenção, foram submetidos a um período de oito semanas de treinamento em cicloergômetro com irradiação LED ou placebo. Após esse período foram submetidos a uma nova avaliação, pós-treino. Para a aplicação da terapia LED, foi utilizado um arranjo contendo 50 LEDs com comprimento de onda de 850 nm e aplicado por 60 segundos após cada sessão de treino. Os voluntários foram separados nos seguintes grupos experimentais: Não Treinados e LED desligado (Grupo NTLD), Não Treinados e LED ligado (Grupo NTLL), Treinados e LED desligado (Grupo TLD), Treinados e LED ligado (Grupo TLL). A perna que recebeu a intervenção foi eleita por sorteio e foi chamada de perna ativa (A) e a perna contralateral, chamada de controle (C). Durante o teste em exercício crescente, até a fadiga, foram quantificadas as variáveis ergoespirométricas, ventilação (Ve), consumo de oxigênio (VO2), equivalente ventilatório de oxigênio (EqVO2), também foi coletada amostra de sangue para dosagem da lactacidemia e foi mensurada a concentração da enzima creatina quinase (CK). Como resultados das respostas agudas frente ao ato de pedalar com uma perna notou-se que a pedalada unipodal apresentou menor valor de intensidade, VO2, Ve, lactacidemia e maior incremento de CK, quando comparada com a pedalada bipodal (convencional). Ao se concluir as oito semanas de treinamento notou-se que a perna ativa na pedalada unipodal apresentou melhoras nas variáveis mensuradas nos grupos TLL, NTLL e algumas no TLD. Também foi encontrada melhora para a perna controle, em algumas variáveis, dos grupos que receberam a terapia LED. Com esse estudo conclui-se que o treinamento unipodal é capaz de melhorar parâmetros como intensidade, ventilação, consumo de oxigênio, eficiência aeróbia, e ainda minimiza os danos musculares induzido pelo exercício no membro que efetuou o treinamento. A terapia LED é capaz de promover as mesmas melhoras em intensidades, consumo de oxigênio e eficiência aeróbia que o treinamento proporcionou, contudo em magnitudes diferentes, ainda é capaz de proporcionar efeito protetor contra lesão muscular induzida pelo exercício. A terapia LED associada ao treinamento potencializa os efeitos conseguidos com cada um isoladamente. / The improvement in physical capacity and/or functional reserve is due to, among other factors, a systematic and organized training program. Aerobic exercise is a frequently used modality in a training program, especially among those who aim to improve physical fitness. However phototherapy has currently gained space in regard to improving the performance of athletes. Based on this information, the purpose of the study was to verify the effect of one-legged cycling, LED therapy and their association on ergospirometric parameters of performance (VO2max, AT and RCT) and on blood concentration of CK. 24 male subjects volunteered for the study and were submitted to a pre-intervention evaluation and an 8-week period of one-legged cycling with LED therapy or placebo. After the intervention period subjects were submitted to a second evaluation. An arrangement containing 50 LEDs and a wavelength of 850 nm was applied during 60 seconds after each training session. Volunteers were divided into the following experimental groups: untrained and LED off (ULOf), untrained and LED on (ULOn), trained and LED off (TLOf) and trained and LED on (TLOn). The leg that received the intervention (training and/or LED therapy) was selected randomly and named active leg (A) and the contralateral limb was named control (C). During the incremental exercise test to volitional failure the ergospirometric variables ventilation (Ve), oxygen uptake (VO2) and oxygen ventilatory equivalent (EqVO2) were measured and blood samples were collected after each stage for lactate and before and 24 hours after the test for the analysis of blood CK. Acute responses from the pre-intervention evaluation showed that the intensity of one-legged cycling led to lower intensity, VO2, Ve, blood lactate and higher increase in blood CK compared to traditional cycling (two-legged). After the 8 weeks of intervention, the active leg showed improvements in the measured variables for the TLOn, ULOn and TLOf groups and, in some of the variables for the groups that received LED therapy. With these data we conclude that one-legged cycling is capable of increasing parameters such as intensity, ventilation, oxygen uptake, aerobic efficiency and minimizes the blood CK responses to exercise in the exercised limb. The association between exercise and Led therapy potentiates the effects achieved with either of the interventions.
36

Hur påverkar effekten av styrkan och dragfrekvensen vid ett 1000 m roddmaskinstest?

Arastoo-Pour, Danial January 2017 (has links)
Rodd är en sport som kräver hög kondition då de flesta av kroppens stora muskler används och kroppens alla tre energisystem är inblandade. Därmed har kroppen ett stort behov av energi vid rodd.    Roddmaskin är en utrustning som används av roddare under vintersäsongen för att utveckla prestationen och göra fysiologiska tester.    Syftet med projektet var att undersöka hur takt (drag per minut) och styrka (1RM marklyft) påverkade, sluttiden (s) vid 1000 m rodd på roddergometrar. Studien utfördes på 9 manliga deltagare över 18 år och sambanden studerades med linjär regressionsanalys. Hypotesen var att lägre takt leder till högre kraft i draget och högre takt leder till lägre kraft. Resultaten visade inget samband mellan takt, högre vikt i marklyft och sluttid där en lägre takt och högre medeleffekt gav en lägre sluttid, p och r2 värdet för sambandet mellan tid och takt var 0.109 för r2och p=0.385, p= 0.210 och r2 värdet 0.214 för sambandet mellan tid och marklyft, för sambandet mellan tid och medeleffekt var r2 värdet 0.75 och p = 0.0025, vilket tyder på ett starkt samband.    Det är troligen större fördel om man drar med större kraft på roddmaskin än om man skulle ro på vatten och resultaten är därför inte direkt överförbara till rodd på vatten. Vidare antyder resultaten att det kan vara en fördel om roddarna tränar mer styrka då mer styrka leder till kraftigare drag, vilket i sin tur leder till en lägre tid. / Rowing is a sport dependent on high endurance capacity, where most of the large muscles in the body are used, the three energy systems are involved and the body is in need of a large amount of energy. Concept 2 rowing ergometers is a sport of itself but is performed mostly during the winter season for outdoor rowers to see the performance and do physiological tests. The purpose of this project was to see if there is any correlation between stroke rate, average power, 1RM deadlift and finishing time on 1000 m rowing machine performance, for 9 adult male rowers. The correlation was studied with linear regression analysis.    The hypothesis was that lower rate leads to higher mean power in each stroke and higher stroke rate leads to lower power in each stroke.    The results showed no correlation between stroke rate, heavier weight lifted in deadlift and finishing time. Where a lower stroke rate and higher mean effect lead to a lower finishing time, p and r2 value for the correlation between time and stroke rate was 0.109 for r2 and p=0.385, p=0.210 and r2 value 0.214 for the correlation between time and deadlift, for the correlation between time and mean effect, the r2 value was 0.75 and p=0.0025, which indicate a strong correlation.        It is more benefit if one row with higher force on the rowing machine than rowing on the water. Further, the results show that it is an advantage if the rowers train more strength, because more power leads to a more powerful stroke and lower time.
37

Nanomaterials for energy storage

Armstrong, Graham M. January 2007 (has links)
Nanotubes (inner diameter of 8nm and outer diameter of 10nm with a length of up to several hundred nm) and nanowires (diameter 20 – 50nm and up to several μm in length) of TiO₂-B have been synthesised and characterised for the first time. These exhibit excellent properties as a host for lithium intercalation and are able to accommodate lithium up to a composition of Li₀.₉₈TiO₂-B for the nanotubes and Li₀.₈₉TiO₂-B for the nanowires. Following some irreversible capacity on the first cycle, which could be reduced to 4% for the nanowires, capacity retention for the nanowires is 99.9% and for the nanotubes is 99.5% per cycle. In both cases, the cycling occurs at ~1.6V versus lithium. The cycling performance was compared with other forms of bulk and nano-TiO₂, all of which were able to intercalate less lithium. Nanowires of VO₂-B (50 – 100nm in diameter and up to several μm in length) were synthesised by a hydrothermal reaction and characterised. By reducing the pressure inside the hydrothermal bomb, narrower VO₂-B nanowires with a diameter of 2 – 5nm and length of up to several hundred nm were created - some of the narrowest nanowires ever made by a hydrothermal reaction. These materials are isostructural with TiO₂-B and were also found to perform well in rechargeable lithium ion batteries, being able to intercalate 0.84Li for the ultra-thin nanowires and 0.57Li for the standard nanowires. The standard VO₂-B nanowires have a capacity retention of 99.8% and the ultra-thin nanowires have 98.4% per cycle after some irreversible capacity on the first cycle. This was found to improve markedly when different electrolytes were used. Macroporous Co₃O₄ (pore size 400nm with a surface area of 208m²/g) was prepared and cycled in rechargeable lithium cells with capacities of 1500mAh/g being achieved. The structure was found to break down on the first cycle and after this the material behaved in the manner of Co₃O₄ nanoparticles. Finally a new candidate for next generation rechargeable lithium batteries was examined; Li/O₂ cells. The cathode is composed of porous carbon in which Li⁺, e⁻ and O₂ meet to form Li₂O₂ on discharge. The reaction is reversible on charge. Capacities of 2800mAh/g can be achieved when 5%mole of αMnO₂ nanowires catalyst is used. Fade is high at 3.4% per cycle meaning that there is much work to do to develop these into a commercial prospect.
38

VO2-based Thermochromic and Nanothermochromic Materials for Energy-Efficient Windows : Computational and Experimental Studies

Li, Shuyi January 2013 (has links)
VO2-based films are thermochromic and exhibit high or low infrared transmittance when the temperature is below or above a critical temperature. The thermochromic switching is passive and reversible, and therefore VO2 based films are promising for energy-efficient window appli­cations. However the practicaluse of VO2 for energy-efficient windows has long been hampered by low luminous transmittance and low solar energy transmittance modulation. The main goal of this dissertation work is to address these issues. The first half of the work proposes the concept of nanothermochromics for simultaneous improvement of luminous transmittance and modulation of solar energy throughput. nanoth­ermochromics considers VO2 nanoparticle composite layers, whose optical properties were modeled by effective medium theories. Calculations on VO2 spheroids have shown that VO2 nanoparticles, especially nanospheres, can offer dramatically improved luminous transmittance and solar transmittance modulation that are not possible for films. Calculations done on coreshell nanoparticles showed comparable improvements and offer an opportunity to reduce the material costs. It was also found that the composite of In2O3:Sn (ITO) and VO2 can yield moderately high luminous transmittance, solar transmittance modulation and low-emittance properties. In the second half of the dissertation work, Mg-doped VO2 films were sputter deposited. Their band gaps and Mg-content were investigated by means of optical absorption measurement and Rutherford backscattering spectrometry, respectively. The band gaps of VO2 were found to increase by ∼3.9±0.5 eV per unit of atom ratio Mg/(Mg+V) for 0<Mg/(Mg+V)<0.21. Computations based on effective medium theory were done to estimate the performance of Mg­-doped VO2 films and nanoparticle composite layers. The results suggest that moderately doped VO2 films with 0<Mg/(Mg+V)<0.06 perform better than un-doped films and that the perfor­mance can be further enhanced with one layer of antireflection coating. The best results were achieved by un-doped VO2 nanospheres, closely followed by the VO2 nanospheres with low Mg-content. Furthermore, the an experimental study on sputter deposited VO2 nanorods has identified the geometry of the oxygen gas inlet, the type of substrate, the substrate temperature and the layer thickness as important factors that influence the growth morphology. Taken as a whole, nanothermochromics offered by VO2 nanoparticles was shown to be the best solution for VO2 based thermochromic energy-efficient window coatings.
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The therapeutic effect of dietary nitrate supplementation in healthy adults, individuals with type 2 diabetes mellitus and chronic obstructive pulmonary disease

Shepherd, Anthony Ian January 2015 (has links)
Introduction and aim: Increases in the bioavailability of nitric oxide have been shown to reduce the oxygen (O2) cost of exercise, improve exercise performance, alter gastric blood flow and mediate glucose uptake in healthy individuals. Aim: Does dietary nitrate reduce the O2 cost of exercise, improve walking performance in individuals with type 2 diabetes mellitus (T2DM) and chronic obstructive pulmonary disease (COPD) or alter hepatic diffusion and positively affect glucose homeostasis in healthy adults? Methods: Experimental chapters utilised a double-blind, placebo-controlled, randomised, experimental design. Breath by breath pulmonary gas analysis was utilised to assess the O2 cost of exercise in 48 individuals with T2DM and 13 with COPD. Walking performance was assessed via the six minute walk test (6MWT) in cohorts 1 and 2. Magnetic resonance imaging was used to assess portal vein flux, velocity and the apparent diffusion coefficient, in order to assess hepatic microvascular diffusion (apparent diffusion coefficient (ADC)). Blood pressure (BP) was measured in all trials. Results: Relative to placebo, beetroot juice resulted in a significant increase in plasma nitrate and nitrite. There were no differences between placebo vs. beetroot juice for the O2 cost of walking (T2DM: placebo; 946 ± 221 vs. beetroot juice; 939 ± 223 ml.min-1; P=0.59) or cycling (COPD: placebo; 933 ± 323 vs. beetroot juice; 939 ± 302 ml: min-1; P=0.88), distance covered in the 6MWT (T2DM: placebo; 550 ± 83 vs. beetroot juice; 554 ± 90m; P=0.17 or COPD: placebo; 456 ± 86 vs. beetroot juice; 449 ± 79 m; P=0.37) or BP (T2DM: systolic: placebo; 134 ± 10 vs. beetroot juice; 132 ± 12 mmHg, P=0.17; diastolic: placebo; 77 ± 7: vs. beetroot juice; 76 ± 11 mmHg, P=0.27. COPD: systolic: placebo; 123 ± 14 vs. beetroot juice; 123 ± 14 mmHg; P=0.91; diastolic: placebo; 77 ± 9 vs. beetroot juice; 79 ± 9 mmHg; P=0.27). No differences were seen between placebo and beetroot juice for ADC (young adults: F(3, 45) = 0.25, P = 0.74; older adults; F(3, 42) = 1.3, P = 0.28), portal vein flux (young adults: F(3, 45) = 0.339, P = 0.79; older adults; F(3, 42) = 1.65, P = 0.19) however, there was an interaction effect in the young adults: (F(3, 45) = 2.9, P = 0.04) but not in the older adults; F(3, 42) = 1.8, P = 0.16) between visits for portal vein velocity. Nitrate supplementation did not reduce plasma glucose concentrations (young adults: F(3, 45) = 0.96, P = 0.42; older adults; F(3, 42) = 0.04, P = 0.99). Nitrate supplementation did not reduce systolic blood pressure (young adults: F(3, 45) = 0.20, P = 0.89; older adults; F(3, 42) = 1.7, P = 0.18) or diastolic blood pressure (young adults: F(3, 45) = 0.25, P = 0.86; older adults; F(3, 42) = 0.45, P = 0.72). Conclusion Dietary nitrate supplementation does not alter the O2 cost of exercise, improve walking performance or reduce BP in individuals with T2DM or COPD. Nitrate supplementation does not alter hepatic diffusion, glucose homeostasis or BP.
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The Effect of Mode and Intensity on Vo2 Kinetics in the Severe Intensity Domain

Updyke, Rhonda S. 05 1900 (has links)
The purpose of this study was to evaluate the effect of mode and intensity on VO2 kinetics in the severe intensity domain. Seventeen participants completed 3-7 tests each on a cycle ergometer and treadmill. For each test, Tfatigue, VO2max, Tmean response, VO2GAIN, TVO2max and T@VO2max were determined. Linear regression techniques were used to describe the relationship between TVO2max and Tfatigue . VO2max values were higher in running. The VO2 response profile was faster for running than cycling and faster at higher intensities. The faster VO2 response in running may be associated with larger active muscle mass or differences in muscle activation patterns. The faster response at higher intensities may suggest that VO2 response is driven by O2 demand.

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