• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 251
  • 81
  • 70
  • 33
  • 16
  • 14
  • 12
  • 6
  • 5
  • 5
  • 4
  • 4
  • 4
  • 4
  • 4
  • Tagged with
  • 605
  • 605
  • 411
  • 99
  • 77
  • 71
  • 67
  • 59
  • 57
  • 52
  • 51
  • 49
  • 48
  • 48
  • 44
  • 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.
291

Validation of tissue oxygen saturation determined by near-infrared spectroscopy in canine models of hypoxemia and hemorrhagic shock

Pavlisko, Noah Dawson 08 October 2014 (has links)
The objective of this study was to evaluate the relationship between tissue oxygen saturation (StO2) and oxygen delivery index (DO2I). Oxygen delivery index is product of two factors arterial oxygen content (CaO2) and cardiac index (CI). In this study the relationship between DO2I and StO2 was evaluated by manipulating both of these factors independently. In phase one of the study, CaO2 was altered by manipulating the fractional inspired oxygen (FiO2) concentration. Anesthetized dogs were evaluated at both high (0.40 and 0.95) and low (0.15 and 0.10) FiO2 sequences. In phase two of the study, CI was altered by manipulating the volemic state. Anesthetized dogs were evaluated at hypovolemic, normovolemic and hypervolemic states. In each phase dogs were instrumented for thermodilution cardiac index (CI) and sartorius muscle StO2. Data collected included hemoglobin concentration, heart rate (HR), MAP, CI, StO2. Arterial oxygen content and DO2I were calculated at each time point. Data analysis included Pearson's correlation and mixed model ANOVA (p < 0.05). In both phases one (r = 0.97; p = 0.0013) and two (r = 0.97; p = 0.005) there was a strong correlation between StO2 and DO2I. Under the conditions of this study, there was a strong correlation between StO2 and DO2I, suggesting that StO2 may be used to estimate the adequacy of oxygen delivery in dogs. / Master of Science
292

Examining the neurovisceral integration model through fNIRS

Condy, Emma Elizabeth 10 September 2018 (has links)
The neurovisceral integration model (NVM) proposes that an organisms ability to flexibly adapt to their environment is related to biological flexibility within the central autonomic network. One important aspect of this flexibility is behavioral inhibition (Thayer and Friedman, 2002). During a behavioral inhibition task, the central autonomic network (CAN), which is comprised of a series of feedback loops, must be able to integrate information and react to these inputs flexibly to facilitate optimal performance. The functioning of the CAN is shown to be associated with respiratory sinus arrhythmia (RSA), as the vagus nerve is part of this feedback system. While the NVM has been examined through neural imaging and RSA, only a few studies have examined these measures simultaneously during the neuroimaging procedure. Furthermore, these studies were done at rest or used tasks that were not targeted at processes associated with the NVM, such as behavior inhibition and cognitive flexibility. For this reason, the present study assessed RSA and neural activation in the prefrontal cortex simultaneously while subjects completed a behavior inhibition task. Using a series of go/no-go tasks, RSA and functional near-infrared spectroscopy (fNIRS) were collected to investigate the relationship between prefrontal activation and vagal activity at rest and during behavioral inhibition. There are three primary aims of this study. First, examine prefrontal activation during various inhibition tasks through fNIRS. Second, evaluate the NVM during a cognitive task using simultaneous fNIRS and RSA analysis. Third, relate task performance, imaging, and RSA measures during behavioral inhibition to deficits in flexible everyday responding, as indicated by self-report measures of behavior. Doing so will elucidate the connection with prefrontal activation and RSA as proposed by the NVM model and determine whether neural and RSA metrics can be related to broader symptoms of inflexibility. / PHD / The neurovisceral integration model (NVM) proposes that the ability to adapt to the environment is related to biological flexibility within the brain. One important aspect of the ability to adapt to the environment is behavior inhibition (e.g., the ability to stop from engaging in a habitual response, Thayer & Friedman, 2002). During a behavior inhibition task, the brain must be able to integrate information and react to these inputs flexibly to facilitate optimal performance. The brain’s ability to do this is related to a measure of heart activity known as respiratory sinus arrhythmia (RSA). The present study assessed RSA and brain activity while subjects completed a behavior inhibition task. Neural activation was measured through functional near-infrared spectroscopy (fNIRS). fNIRS measures the amount of oxygenated blood in different areas of the brain. Greater concentrations of oxygenated blood indicated greater brain activity in an area. Through simultaneous fNIRS and RSA measurement the present study examined their relationship during various inhibition tasks. Doing so clarified the connection between brain activation and RSA as proposed by the NVM model.
293

Economic and chemometric studies to supplement food-grade soybean variety development in the Mid-Atlantic region

Lord, Nilanka 07 January 2021 (has links)
Sustainability of the soybean industry relies on the growth of new industries and the continued improvement of seeds for utilization. Grower adoption and growth of the edamame industry has been slow in part due to insufficient information on its potential profitability and marketability. As such, the first and second objectives of this thesis aimed at 1) determining production costs of hand-harvested fresh edamame enterprise and 2) exploring consumer willingness-to-pay (WTP) for fresh, local, organic, and "on-the-stalk" marketed edamame. Sucrose, raffinose, and stachyose sugars hold tremendous implications for utilization of soybean seeds in livestock, soyfood, and probiotics industries. Current sugar phenotyping methods using high-performance liquid chromatography (HPLC) are costly and inefficient. Therefore, the third objective of this study was to develop calibrations to predict sugar content using near-infrared reflectance spectroscopy (NIRS). Results showed that labor accounted for 72% of production costs for edamame pods, which largely limits its profit potential. Mean WTP for fresh and local edamame exceeded their frozen and non-local counterparts by 94 and 88 cents, respectively. In addition, mean WTP for organic edamame exceeded non-GMO edamame by 33 cents. Pro-environmental attitudes appeared to be a consistent driver of WTP these three attributes. Meanwhile, a 40-cent discount for "on-the-stalk" edamame compared to pods indicates convenience may also be a factor in edamame marketability. Calibration development for sucrose and stachyose was successful, with R2cal, R2cv, RMSEC, and RMSECV of 0.901, 0.869, 0.516, and 0.596, and 0.911, 0.891, 0.361, and 0.405, respectively. Alternative methods should be investigated for quantification of raffinose. / Master of Science / Sustainability of the soybean industry relies on the growth of new industries and the continued improvement of seeds for utilization. Grower adoption and growth of the edamame industry has been slow in part due to insufficient information on its potential profitability and marketability. As such, the first and second objectives of this thesis aimed at 1) determining production costs of hand-harvested fresh edamame and 2) exploring relative marketing potential of fresh, local, organic, and "on-the-stalk" edamame. Sucrose, raffinose, and stachyose sugars hold tremendous implications for utilization of soybean seeds in livestock, soyfood, and probiotics industries. Current methods of quantifying sugar are costly and time inefficient. Therefore, the third objective of this study was to develop prediction models to estimate sugar content using near-infrared reflectance spectroscopy (NIRS). Results showed that labor accounted for 72% of production costs for edamame pods, which largely limits its profit potential. Fresh and local edamame showed considerable marketing potential over frozen and non-local edamame. In addition, organic edamame showed marginal marketing benefit over non-GMO. Pro-environmental attitudes were an important driver of these results. Meanwhile, on-the-stalk edamame shows poor marketing potential, likely due to preference for convenience of food preparation in the U.S. NIRS prediction models for sucrose and stachyose showed strong predictive accuracy and low error, suggesting potential for implementation. The prediction model for raffinose, however, remained poor.
294

A novel transflectance near infrared spectroscopy technique for monitoring hot melt extrusion

Kelly, Adrian L., Halsey, S.A., Bottom, R.A., Korde, Sachin A., Gough, Timothy D., Paradkar, Anant R 2015 July 1915 (has links)
Yes / A transflectance near infra red (NIR) spectroscopy approach has been used to simultaneously measure drug and plasticiser content of polymer melts with varying opacity during hot melt extrusion. A high temperature reflectance NIR probe was mounted in the extruder die directly opposed to a highly reflective surface. Carbamazepine (CBZ) was used as a model drug, with polyvinyl pyrollidone-vinyl acetate co-polymer (PVP-VA) as a matrix and polyethylene glycol (PEG) as a plasticiser. The opacity of the molten extrudate varied from transparent at low CBZ loading to opaque at high CBZ loading. Particulate amorphous API and voids formed around these particles were found to cause the opacity. The extrusion process was monitored in real time using transflectance NIR; calibration and validation runs were performed using a wide range of drug and plasticiser loadings. Once calibrated, the technique was used to simultaneously track drug and plasticiser content during applied step changes in feedstock material. Rheological and thermal characterisations were used to help understand the morphology of extruded material. The study has shown that it is possible to use a single NIR spectroscopy technique to monitor opaque and transparent melts during HME, and to simultaneously monitor two distinct components within a formulation.
295

Vibrational spectroscopic characterisation of salmeterol xinafoate polymorphs and a preliminary investigation of their transformation using simultaneous in situ portable Raman spectroscopy and differential scanning calorimetry

Ali, H.R.H., Edwards, Howell G.M., Hargreaves, Michael D., Munshi, Tasnim, Scowen, Ian J., Telford, Richard 15 October 2019 (has links)
No / Knowledge and control of the polymorphic phases of chemical compounds are important aspects of drug development in the pharmaceutical industry. Salmeterol xinafoate, a long acting β-adrenergic receptor agonist, exists in two polymorphic Forms, I and II. Raman and near infrared spectra were obtained of these polymorphs at selected wavelengths in the range of 488–1064 nm; significant differences in the Raman and near-infrared spectra were apparent and key spectral marker bands have been identified for the vibrational spectro-scopic characterisation of the individual polymorphs which were also characterised with X ray diffractometry. The solid-state transition of salmeterol xinafoate polymorphs was studied using simultaneous in situ portable Raman spectroscopy and differential scanning calorimetry isothermally between transitions. This method assisted in the unambiguous characterisation of the two polymorphic forms by providing a simultaneous probe of both the thermal and vibrational data. The study demonstrates the value of a rapid in situ analysis of a drug polymorph which can be of potential value for at-line in-process control.
296

Creation of Luminescent Materials with Narrow Energy Gaps Based on Boron-Fused Azobenzene Complexes / 縮環型アゾベンゼンホウ素錯体を基盤とした狭エネルギーギャップ発光材料の創出

Nakamura, Masashi 25 March 2024 (has links)
京都大学 / 新制・課程博士 / 博士(工学) / 甲第25246号 / 工博第5205号 / 京都大学大学院工学研究科高分子化学専攻 / (主査)教授 田中 一生, 教授 大北 英生, 教授 大内 誠 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM
297

Die Beeinflussung der cerebralen Oxygenierung bei partieller Flüssigkeitsbeatmung gesunder Ferkel

Burkhardt, Wolfram 13 September 2005 (has links)
Die intratracheale Applikation von Perfluorcarbonen (PFC) in ungeschädigte Lungen, z.B. als Röntgenkontrastmittel und zur PFC-induzierten cerebralen Kühlung, wird derzeit diskutiert. Ob es aufgrund der Dichte und Sauerstofflöslichkeit der PFC zu einer Beeinflussung der cerebralen Oxygenierung und Hämodynamik durch die pulmonale PFC Applikation kommt, ist bisher unbekannt. Änderungen der Konzentration von cerebralem oxygeniertem und totalem Hb koennen mittels Near-infrared Spectroscopy gemessen werden. I.) Effekt durch die PFC-Applikation in gesunde Lungen neugeborener Ferkel: Es wurden zwei verschiedene Applikationsgeschwindigkeiten (30 ml PFC pro kg Körpergewicht als Bolusgabe versus 1,5 ml/min pro kg) und zwei Füllvolumen (30 versus 10 ml/kg) verglichen. Die Bolusgabe bewirkt einen sofortigen Abfall des PaO2 und der cerebralen Oxygenierung, bei langsamer Gabe des gleichen Volumens ist dies weniger ausgeprägt. Mit 10 ml/kg PFC fand sich nahezu keine Beeinflussung der Parameter. II.) Effekte der Änderung der FiO2 in PFC-gefüllten Lungen: Hierfür wurden Änderungen der FiO2 unter konventioneller Druckbeatmung vor PFC-Applikation und unter PFC-Füllung (30 oder 10 ml/kg PFC) verglichen. Beide PFC-Volumen (mit FiO2 1,0) bedingten PaO2-Werte wie unter CMV mit FiO2 von 0,5. Mit 30 ml/kg PFC kam es unter FiO2 von 0,5 zur Abnahme des cerebralen oxygenierten Hb. Zusammenfassend ergibt sich, dass die Applikation von 10 ml PFC/kg bevorzugt werden sollte. Bei kompletter Füllung der Lungen werden durch langsame Applikation cerebrale Nebenwirkungen minimiert. In PFC-gefüllten gesunden Lungen ist zum Erhalt der systemischen und cerebralen Oxygenierung die FiO2 zu erhöhen. / Intratracheal administration of perfluorochemicals (PFC) has been suggested for reasons other than respiratory insufficiency, such as pulmonary imaging and PFC-associated brain cooling. Due to their high density and oxygen solubility, PFC application has been described to affect systemic hemodynamics and oxygenation during liquid ventilation. Whether the PFC application into healthy lungs or changes in inspired oxygen fraction (FiO2) in PFC-filled healthy lungs affects cerebral hemodynamics is not known. Changes in the concentration of cerebral oxygenated and total Hb can be measured by near-infrared spectroscopy (NIRS). I.) Initial effects of PFC application into healthy lungs of newborn piglets: Two different filling modes (rapid versus slow) and two different filling volumes (slow filling of 30 versus 10 ml PFC/kg body weight) were compared. Rapid filling caused an immediate drop of systemic and cerebrale oxygenation, which was less prominent by filling 30 ml/kg PFC slowly. Almost no changes for all parameters were found with 10 ml kg/PFC. II.) Effects of variations in FiO2 in the PFC filled lungs of healthy piglets: Changes in FiO2 during conventional mechanical ventilation (CMV) prior to PFC-application and in the PFC-filled lungs (30 ml/kg or 10 ml/kg PFC) were compared. Both PFC-volumes (at a FiO2 of 1.0) caused PaO2-values that were similar to CMV with FiO2 of 0.5. In the 30 ml/kg PFC group a reduction of cerebral oxygenated Hb was found at FiO2 of 0.5. According to the data application of 10 ml/kg PFC should be preferred. If complete filling of the lung is needed, the slow administration of PFC minimizes cerebral side effects. In PFC- filled healthy lungs an increase in FiO2 is necessary to maintain systemic and cerebral oxygenation.
298

Combinaison des techniques de biologie moléculaire et de la spectrométrie dans le proche infrarouge pour l'authentification des denrées destinées à l'alimentation humaine et animale

Fumière, Olivier 11 May 2010 (has links)
Résumé: Lauthentification est un concept large dans lequel il sagit de pouvoir contrôler ladéquation entre le produit et les informations indiquées sur létiquette. Les techniques utilisant la spectrométrie dans le proche infrarouge dune part, et celles basées sur la PCR dautre part, permettent daborder lauthentification des produits alimentaires sous des angles totalement différents. Loriginalité de ce travail était de les associer pour résoudre deux problèmes précis : 1. lauthentification des poulets de chair à croissance lente utilisés dans des productions de qualité différenciée soumises à des cahiers des charges contraignants ; 2. la détection des farines animales dans lalimentation pour le bétail. Nos travaux sur les poulets de chair nous ont permis de développer des modèles de discrimination reposant sur les spectres dans le proche infrarouge de la viande de poulet. Ils distinguent, pour plus de 80 % des individus, les poulets issus de souches à croissance lente de ceux issus de souches à croissance rapide. Les résultats dune expérimentation animale ont également démontré que la spectrométrie dans le proche infrarouge était capable de mettre évidence des fraudes au niveau de lalimentation des animaux. Deux marqueurs moléculaires spécifiques du type de souche de poulets ont été mis en évidence et caractérisés. Pour le marqueur moléculaire caractéristique des poulets à croissance rapide, un test rapide utilisable en routine a été développé. Dans le cas de la détection des farines animales dans lalimentation du bétail, une méthode de PCR en temps réel sensible et spécifique a été mise au point participant avec succès à des études inter-laboratoires internationales. Associée dans une stratégie originale à la MPIR (microscopie dans le proche infrarouge), elle permet la détection spécifique de particules de farines de viande et dos. Summary: Authentication is a large concept focussing on the control of the correspondance between the product and the information provided on the label. Techniques based on near infrared spectroscopy on the one hand, and those based on PCR on the other hand, allow to tackle the authentication of food and feed products by different sides. The originality of this work was to associate both techniques to solve two specific problems : 1. authentication of slow growing chickens bred in high quality productions according to restricting specifications ; 2. the detection of meat and bone meals in feedingstuffs. The work on the chicken allowed us to develop discriminant models using the near infrared spectra of chicken meat. These models discriminate the chicken from slow- vs. fast-growing chicken for more than 80 % of the animals. The results of an animal experimentation also showed that near infrared spectroscopy was able to detect feeding frauds. Two molecular markers specific of the type of chicken strains were found and characterised. For the one related to the fast-growing chicken strains, a rapid assay applicable in routine testing was conceived. In the case of the meat and bone meal detection in feedingstuffs, a specific and sensitive real time PCR method was developed. It participated succesfully to international inter-laboratory studies. Its combination with NIRM (near infrared microscopy) through an original strategy allows the specific detection of meat and bone meal particles.
299

Towards a Reliable and Valid Analysis of VO2m Off-Kinetics / Mot en tillförlitlig och giltig analys av VO2m off-kinetics

Þráinsson, Hrafnkell January 2022 (has links)
Non-invasive methods to evaluate skeletal muscle oxidative capacity have beenemerging as a viable substitute for invasive methods in recent years. One ofthose methods utilises near-infrared spectroscopy (NIRS) to calculate V O2mrecovery off-kinetics following an exercise. The data analysis of the measuredsignals from the NIRS is still done manually in a time-consuming and dauntingprocess. The present thesis aimed to develop software, associated with theNIRS method, capable of analysing the recovery from a repeated arterialocclusion protocol following an exercise to assess muscle oxidative capacity.Additionally, to analyse the recovery from ischemic preconditioning as a singletest to assess muscle oxidative capacity. A method that has never been utilisedbefore.11 active, healthy subjects were analysed to calculate their recovery rate.Subjects underwent ischemic preconditioning before exercising for 6 minutesat 80% of gas exchange threshold. A repeated arterial occlusion protocol wascarried out after the exercise. A software was developed in R that utilised linearregression as well as exponential fitting to calculate the recovery rate of eachsubject during both the ischemic preconditioning and the occlusion protocol.The calculated results were compared to predetermined recovery rate results ofeach subject. The calculated results of the repeated arterial occlusion protocolgave similar results to the predetermined ones and even more data on eachsubject’s recovery from an exercise. The calculated results of the ischemicpreconditioning were promising and implied that ischemic preconditioning asa single test can be utilised as a method to assess muscle oxidative capacity.However, further research is required to confirm it. / Icke-invasiva metoder för att utvärdera skelettmuskulaturens oxidativa förmågahar på senare år blivit en användbar ersättning för invasiva metoder. Nearinfrared spectroscopy (NIRS) är en utav dessa metoder och har använts föratt beräkna V O2m återhämtning off-kinetics efter träning. Dataanalysen av deuppmätta signalerna från NIRS görs fortfarande manuellt i en tidskrävandeoch felbenägen process. Syftet med den här uppsatsen var att utveckla enprogramvara som kopplad till NIRS metoden, kan analysera återhämtningenfrån ett protokoll med upprepade arteriella ocklusioner efter träning för attutvärdera skelettmuskulaturens oxidativa förmåga. Dessutom att analyseraåterhämtningen från ischemic preconditioning som ett enda test för att utvärderaskelettmuskulaturens oxidativa förmåga. En metod som aldrig tidigare använts.11 aktiva, friska försökspersoner analyserades för att beräkna deras återhämtningshastighet.Försökspersonerna genomgick ischemic preconditioning innan de tränadei 6 minuter med 80% av gasutbyteströskeln. Ett protokoll med upprepadearteriella ocklusioner genomfördes efter träningen. En programvara utveckladesi R som använde sig av linjär regression och monoexponentiell funktionsanpassningför att beräkna återhämtningshastigheten för varje försöksperson under bådeichemic preconditioning och ocklusionprotokollet. De beräknade resultatenjämfördes med förutbestämda resultat av återhämtningshastigheten för varjeförsöksperson. De beräknade resultaten av ocklusionprotokollet gav liknanderesultat som de förutbestämda och gav ännu fler uppgifter om varje försökspersonåterhämtning efter träning. De beräknade resultaten av ischemic preconditioningvar lovande och indikerade att ischemic preconditioning som ett enda testkan användas som en metod för att utvärdera skelettmuskulaturens oxidativaförmåga. Det krävs dock ytterligare forskning för att bekräfta detta.
300

Using saturated absorption spectroscopy on acetylene-filled hollow-core fibers for absolute frequency measurements

Knabe, Kevin January 1900 (has links)
Doctor of Philosophy / Department of Physics / Kristan L. Corwin / Current portable near-infrared optical frequency references offer modest accuracy and instability compared to laboratory references. Low pressure reference cells are necessary to realize features narrower than the Doppler broadened overtone transitions, and most setups to date have occurred in free-space. Hollow-core photonic crystal fibers offer a potential alternative to free-space setups through their small cores (~10’s of µm) and low-loss guidance. Furthermore, HC-PCF can be made into fiber cells that could be directly integrated into existing telecommunications networks. Efforts were made to fabricate these fiber cells with a low pressure of molecules trapped inside, but this has proven to be quite challenging. Therefore, investigation of these fibers is conducted by placing the ends of the fiber inside vacuum chambers loaded with acetylene (12C2H2). The linewidths of several P branch transitions (near 1.5 µm) are investigated as a function of acetylene pressure and optical pump power in three different HC-PCFs. Frequency modulation spectroscopy is then implemented on the acetylene-filled HC-PCF to generate sub-Doppler dispersion features that are useful for frequency stabilization using standard servo electronics. Instability and accuracy of this near-IR optical reference were then determined by analysis of heterodyne experiments conducted with frequency combs referenced to a GPS-disciplined rubidium oscillator. The instability and accuracy of this HC-PCF reference are within an order of magnitude of free-space experiments, as expected based on the ratio of linewidths observed in the two experiments. Therefore, HC-PCF has been shown to be suitable for potential frequency references. Further work is necessary to fabricate gas fiber cells with high optical transmission and low molecular contamination.

Page generated in 0.0775 seconds