O objetivo deste trabalho é o desenvolvimento de um laser de centro de cor para aplicações em espectroscopia. O laser opera em regime CW e a cavidade óptica utilizada é do tipo X, com dois espelhos esféricos intracavidade astigmáticamente compensados. O meio ativo utilizado foi um cristal de KCl:Li+ com centros FA (II), e como fonte de bombeamento foi empregado um laser de Ar+ em 514nm. O limiar de potência de bombeamento foi de 120 mW, a eficiência energética foi de 2,8% e o intervalo de sintonia obtido vai de 2,56 a 2,82 &#956m numa potência de bombeamento de 700mW. O laser opera também com a cavidade na configuração anel. Para testar o LCC foram feitas aplicações empregando a técnica de espectroscopia intercavidade em cristais de KCl: Li+: NO-2: NO-3 e KBr:OH-. / The present work shows the development of a color Center laser for spectroscopy application. It is a CW laser which uses an X-type cavity with two astigmatically compensated intracavity spherical mirrors. The laser can be converted to a ring laser. The used active medium was a KCl:Li+ single crystal with a FA (II) centers and the pumping source was an Ar+ laser (&#955= 514nm, 700mW). Pump power at threshold was measured to be 120mW. The tuning range was 2.56&#60 &#955 &#60 2.82 &#956m and the slope efficiency was 2,8%. To test the color center laser we measured intracavity spectra of KCl: Li+: NO-2: NO-3 and KBr:OH- single crystals.

New optical technologies were developed to continuously measure cerebral blood flow (CBF) and oxygen metabolism (CMRO2) non-invasively through the skull. Methods and devices were created to improve the performance of near-infrared spectroscopy (NIRS) and diffuse correlation spectroscopy (DCS) for use in experimental animals and humans. These were employed to investigate cerebral metabolism and cerebrovascular reactivity under different states of anesthesia and during models of pathological states. Burst suppression is a brain state arising naturally in pathological conditions or under deep general anesthesia, but its mechanism and consequences are not well understood. Electroencephalography (EEG) and cortical hemodynamics were simultaneously measured in rats to evaluate the coupling between cerebral oxygen metabolism and neuronal activity in the burst suppressed state. EEG bursts were used to deconvolve NIRS and DCS signals into the hemodynamic and metabolic response function for an individual burst. This response was found to be similar to the stereotypical functional hyperemia evoked by normal brain activation. Thus, spontaneous burst activity does not cause metabolic or hemodynamic dysfunction in the cortex. Furthermore, cortical metabolic activity was not associated with the initiation or termination of a burst. A novel technique, time-domain DCS (TD-DCS), was introduced to significantly increase the sensitivity of transcranial CBF measurements to the brain. A new time-correlated single photon counting (TCSPC) instrument with a custom high coherence pulsed laser source was engineered for the first-ever simultaneous measurement of photon time of flight and DCS autocorrelation decays. In this new approach, photon time tags are exploited to determine path-length-dependent autocorrelation functions. By correlating photons according to time of flight, CBF is distinguished from superficial blood flow. Experiments in phantoms and animals demonstrate TD-DCS has significantly greater sensitivity to the brain than existing transcranial techniques. Intracranial pressure (ICP) modulates both steady-state and pulsatile CBF, making CBF a potential marker for ICP. In particular, the critical closing pressure (CrCP) has been proposed as a surrogate measure of ICP. A new DCS device was developed to measure pulsatile CBF non-invasively. A novel method for estimating CrCP and ICP from DCS measurement of pulsatile microvascular blood flow in the cerebral cortex was demonstrated in rats. / 2018-03-08T00:00:00Z

O presente trabalho apresenta proposições para seleção de variáveis em avaliações sensoriais descritivas e de espectro infravermelho que contribuam com a indústria de alimentos e química através da utilização de métodos de análise multivariada. Desta forma, os objetivos desta tese são: (i) Estudar as principais técnicas de análise multivariada de dados, como são comumente organizadas e como podem contribuir no processo de seleção de variáveis; (ii) Identificar e estruturar técnicas de análise multivariada de dados de forma a construir um método que reduza o número de variáveis necessárias para fins de caracterização, classificação e predição dos produtos; (iii) Reduzir a lista de variáveis/atributos, selecionando aqueles relevantes e não redundantes, reduzindo o tempo de execução e a fadiga imposta aos membros de um painel em avaliações sensoriais; (iv) Validar o método proposto utilizando dados reais; e (v) Comparar diferentes abordagens de análise sensorial voltadas ao desenvolvimento de novos produtos. Os métodos desenvolvidos foram avaliados através da aplicação de estudos de caso, em exemplos com dados reais. Os métodos sugeridos variam com as características dos dados analisados, dados altamente multicolineares ou não e, com e sem variável dependente (variável de resposta). Os métodos apresentam bom desempenho, conduzindo a uma redução significativa no número de variáveis e apresentando índices de adequação de ajuste dos modelos ou acurácia satisfatórios quando comparados aos obtidos mediante retenção da totalidade das variáveis ou comparados a outros métodos dispostos na literatura. Conclui-se que os métodos propostos são adequados para a seleção de variáveis sensoriais e de espectro infravermelho. / This dissertation presents propositions for variable selection in data from descriptive sensory evaluations and near-infrared (NIR) spectrum analyses, based on multivariate analysis methods. There are five objectives here: (i) review the main multivariate analysis techniques, their relationships and potential use in variable selection procedures; (ii) propose a variable selection method based on the techniques in (i) that allows product prediction, classification, and description; (iii) reduce the list of variables/attributes to be analyzed in sensory panels identifying those relevant and non-redundant, such that the time to collect panel data and the fatigue imposed on panelists is minimized; (iv) validate methodological propositions using real life data; and (v) compare different sensory analysis approaches used in new product development. Proposed methods were evaluated through case studies, and vary according to characteristics in the datasets analyzed (data with different degrees of multicollinearity, presenting or not dependent variables). All methods presented good performance leading to significant reduction in the number of variables in the datasets, and leading to models with better adequacy of fit. We conclude that the methods are suitable for datasets from descriptive sensory evaluations and NIR analyses.

Children who struggle to learn math are often identified by their poor performance on common math learning activities, such as number line estimations. While such behavioral assessments are useful in the classroom, naturalistic neuroimaging of children engaged in real-world math learning activities has the potential to identify concurrent behavioral and neurological correlates to poor math performance. Such correlates may help pinpoint effective teaching strategies for atypical learners, and may highlight instructional methods that elicit typical neurological response patterns to such activities. For example, multisensory stimulation that contains information about number enhances infants' and preschool children's behavioral performance on many numerical tasks and has been shown to elicit neural activation in areas related to number processing and decision-making. Thus, when applied to math teaching tools, multisensory stimulation may provide a platform through which both behavioral and neural math-related processes may be enhanced. Common approaches to neuroimaging of math processing lack ecological validity and are often not analogous to real-world learning activities. However, because of its liberal tolerance of movement, near-infrared spectroscopy (NIRS) provides an ideal platform for such studies. Here, NIRS is used to provide the first concurrent examination of neurological and behavioral data from number line estimation performance within children and adults. Moreover, in an effort to observe the behavioral and neurological benefits to number line estimations that may arise from multisensory stimulation, differential feedback (i.e., visual, auditory, or audiovisual) about estimation performance is provided throughout a portion of the task. Results suggest behavioral and neural performance is enhanced by feedback. Moreover, significant effects of age suggest young children show greater neurological response to feedback, and increase in task difficulty resulted in decreased behavioral performance and increased neurological activation associated with mathematical processing. Thus, typical math learners effectively recruit areas of the brain known to process number when math activities become increasingly difficult. Data inform understanding typical behavioral and neural responses to real-world math learning tasks, and may prove useful in triangulating signatures of atypical math learning. Moreover, results demonstrate the utility of NIRS as a platform to provide simultaneous neurological and behavioral data during naturalistic math learning activities.

L'objectif général de cette thèse était d'exalter l'émission dans le proche infrarouge en utilisant des antennes plasmoniques. Les antennes plasmoniques permettent de modifier la dynamique de désexcitation ainsi que le diagramme d'émission d'un émetteur; ces deux aspects permettent donc d'améliorer/exalter la photoluminescence par rapport à un émetteur non couplé à une antenne. Au cours de cette thèse, deux émetteurs ont été étudiés : les nanotubes de carbone et les centres G dans le silicium.Les antennes plasmoniques sont, par exemple, des nanoparticules métalliques. Ainsi, dans un premier temps, nous avons étudié les propriétés de diffusion de nanoparticules métalliques. Ceci a permis de développer une technique permettant de déposer des nanoparticules uniques sur un substrat. La caractérisation optique de diverses nanoparticules déposées sur divers substrats fut réalisée par des mesures de spectres de diffusion. Des études en polarisation sur le signal excitateur ainsi que sur le signal diffusé ont permis de sonder l'origine des résonances plasmoniques apparaissant dans les spectres de diffusion. Les influences de la température et du substrat sur les spectres de diffusion ont aussi été étudiées.Dans une deuxième partie, nous nous sommes intéressés à un premier émetteur dans le proche infrarouge : les nanotubes de carbone semi-conducteurs. Nous avons caractérisé la photoluminescence d'un ensemble de nanotubes puis d'uniques nanotubes. La photoluminescence d'un nanotube de carbone unique est caractérisée par un faiblement rendement radiatif (de l'ordre du %) ce qui implique que, dans notre montage expérimental, l'émission par un unique nanotube est à la limite de détectabilité. Afin d’obtenir des applications optiques viables à base de nanotubes de carbone, nous avons essayé d'exalter leur photoluminescence grâce à des antennes plasmoniques. Nous avons donc déposé des nanoparticules métalliques au-dessus d’une couche de nanotubes de carbone. Nous avons observé ponctuellement l'exaltation de la photoluminescence, mais cette exaltation cessait sur des durées de l'ordre de la minute.Enfin, nous avons étudié un deuxième émetteur dans le proche infrarouge : les centres G dans le silicium. La caractérisation optique d'un ensemble de centre G a été réalisé. Le spectre d'émission a été mesuré et analysé quantitativement. Le temps de vie du centre G a aussi été mesuré pour la première fois. Ces deux types d'études (spectrales et temporelles) ont aussi été réalisées à diverses températures afin de sonder la dynamique de désexcitation des centres G. La saturation d'un ensemble de centres G a aussi été étudiée quantitativement. Enfin, nous avons réalisé des mesures laissant penser que le régime du centre G unique est presque atteint. L'exaltation de l'émission des centres G par des antennes plasmoniques n'a pas pu être étudiée par manque de temps. / The goal of this work was to enhance the photoluminescence in the near infrared using plasmonic antennas. Plasmonic antennas can modify both the recombination dynamics and the emission diagram; these two aspects can thus be used to enhance the photoluminescence of an emitter in comparison to an emitter not coupled with an antenna. During this thesis, two emitters were studied: carbon nanotubes and G-centers in silicon.Plasmonic antennas can be metallic nanoparticles for instance. Thus, we first studied the scattering properties of metallic nanoparticles. During this study, we developed a technique to deposit single nanoparticles on a substrate. The optical characterization of several nanoparticles on different substrates was realized through scattering spectrum measurements. Polarization studies on both the excitation light and the emitted light were realized in order to analyze the origin of plasmonic resonances in the scattering spectrum. The influence of the temperature and the substrate on the scattering spectrums was also investigated.Secondly, we looked into a first near infrared emitter: semi-conducting carbon nanotubes. We characterized the photoluminescence from an assembly of carbon nanotubes and then from single carbon nanotubes. The photoluminescence of a single carbon nanotube is characterized by a low quantum yield (typically, a few %) which implied, in our experimental setup, that the emission from a single nanotube is at the limit of detectability. In order to propose viable optical applications based on carbon nanotubes, we tried to enhance their photoluminescence with plasmonic antennas. We thus deposited metallic nanoparticles on top of a layer of carbon nanotubes. We occasionally observed some enhancements, but this typically ceased in less than a minute.Finally, we studied a second emitter in the near infrared: the G-centers in silicon. The optical characterization was realized. The emission spectrum was measured and quantitatively analyzed. The lifetime of the G-center was measured for the first time. These two studies (spectrally resolved and temporally resolved) were also realized for different temperatures in order to characterize the recombination dynamics of the G-centers. The saturation of an assembly of G-centers was also quantitatively studied. We also realized measurements suggesting that the single G-center regime has nearly been achieved. The enhancement of the photoluminescence of G centers with plasmonic antennas was not realized due to lack of time.

The closed shell structures of certain all-carbon fragments originally observed in mass spectroscopy experiments leads to the enhanced stability of these species, known as fullerenes, which have excited sufficient interest amongst chemists and physicists over the last decade to warrant the award of the 1996 Nobel Prize for Chemistry to their discoverers. ¶ Studies of the stability, symmetry, and consequent remarkable properties of fullerenes began in earnest in 1991 with the development of a technique enabling the production and purification of macroscopic quantities of material. The best known and most widely studied fullerene is the truncated icosahedral C[subscript 60] molecule, which forms the basis of the present work. ¶ One important property of C[subscript 60] is that it forms salts with sufficiently electropositive species, such as the alkali metals. The resulting salts contain C[subscript 60] anions and are known as fullerides. Certain of these salts display metallic behaviour, and some superconduct at temperatures as high as 33 K. ¶ Three aspects of fulleride research are addressed in this work. These are: i) the preparation, crystal structure determination and superconductivity characterization of several new fullerides, particularly those including ammonia as an additional intercalant; ii) the electronic structure of the C[superscript n-, subscript 60] (n = 1 - 6) anions, as probed by solution-phase near infrared absorption spectroscopy; and iii) the molecular dynamics of a number of fullerides, superconducting and non-superconducting, by inelastic neutron scattering. ¶ This work has grown out of an Honours project also concerning C[subscript 60], the combined duration of the two studies covering essentially the entire history of this widely and competitively studied field.

<p>The European Union Water Framework Directive (WFD), with initiatives to manage surface water resources, has increased the need for fast and inexpensive methods for monitoring conditions in streams. The objective of this thesis is to assess the potential of near-infrared spectroscopy (NIRS) of epilithic material to become such method. NIRS, which is a technique that is commonly used in industry for process monitoring and quality control of products, registers the chemical properties of organic material on a molecular level. Epilithic material, i.e. the layer of dead and alive material that covers stone surfaces in streams, is continuously influenced by the stream water that flows over it, and it has the potential to integrate chemical and biological conditions over time. The temporal integration is a significant factor, since conditions in streams can change within hours or days. The thesis consists of two published papers. In the first paper a new sampler for epilithic material, the Stone Brusher, was described and the performance evaluated. The Stone Brusher is designed to take qualitative or semi-quantitative samples of epilithic material from stones at 7–50 cm water depth. The epilithic material is dislodged from the stone surface with a rotating brush enclosed in a chamber, and the material is drawn up directly into the sample bottle with an air-cylinder. The operator takes a sample quickly and without putting hands into the water. The sampler is made of plastic, stainless steel and aluminium and weighs 3.1 kg. It is designed to meet the demand for standardized sampling for research and environmental monitoring and to improve working conditions for sampling personnel. The equipment allows sampling from surfaces of bedrock and large stones that cannot be lifted from the bottom. Using data of near-infrared spectroscopy and diatom analyses, this new sampler was evaluated in comparison to the toothbrush method, a primitive method which is the current standard in EU. The results indicate that the Stone Brusher reduces sampling variability compared with the toothbrush method.</p><p>In the second paper, the Stone Brusher was used to collect epilithic material from 65 sites (42 uncontaminated and 23 contaminated) from streams in the widespread mining area called the Skellefte-district in Västerbotten, northern Sweden, in order to test the hypothesis that impact on the epilithic material caused by emissions from mining and mining-related industries can be detected using NIRS. The epilithic material was filtered onto glass fibre filters, measured by NIRS, and the results were modelled using Principal Component Analysis (PCA). The NIRS approach was evaluated by comparing it with the results of chemical and diatom analyses of the same samples. Based on PCA, the NIRS data distinguished contaminated from uncontaminated sites and performed slightly better than chemical analyses and clearly better than diatom analyses. Of the streams designated a priori as contaminated, 74 % were identified as contaminated by NIRS, 65 % by chemical analysis and 26 % by diatom analysis. Unlike chemical analyses of water or of epilithic material samples, NIRS data reflect biological impacts in the streams. Given that, and the simplicity of NIRS-analyses, further studies to assess the use of NIRS of epilithic material are justified. NIRS has the potential to become a fast method for screening in regions where large numbers of streams occur to find impacted streams or as a routine method for temporal monitoring in selected streams for early detection of environmental impact, similar to process monitoring in industry.</p>

Near infrared reflectance spectroscopy (NIRS) and geostatistical techniques were used to predict diet quality of sub-Saharan African (SSA) livestock, and to create cokriged estimated diet quality maps for cattle across a landscape. Rations of native vegetation were stall-fed to cattle (Bos indicus), sheep (Ovis aries), and goats (Capra hircus) to generate diet-fecal pair data. Trials were conducted in Ethiopia, Kenya, Uganda, Tanzania, and Ghana. Historical data from Ethiopia, Nigeria, and Niger were included. Diet samples were analyzed for crude protein (CP%), and digestible organic matter (DOM%), while feces were scanned for NIR spectra. NIRS equations were developed from data using modified partial least square (MPLS) regression. Coefficients of determination (R2) of CP for cattle, sheep, and goats were 0.92, 0.95, and 0.97, with corresponding standard errors of calibration (SEC) being 0.90, 0.79, and 0.80, respectively. Standard errors of cross validation (SECV) for CP were 1.12%, 1.08%, and 1.03% for cattle, sheep, and goats, respectively. R2 and SEC values for DOM were 0.88, 0.94, 0.94 and 2.82%, 1.68%, and 2.65%, for cattle, sheep, and goats, respectively. Corresponding SECV values for DOM were 3.26%, 2.07%, and 3.30%, respectively. The statistics reported were within the acceptable limits for NIRS calibrations. The results indicate that dietary CP and DOM of free-ranging SSA livestock can be predicted with the same precision as that of conventional wet chemistry methods. The cattle equation was used to predict cattle fecal samples collected, from February to August 2000, from selected households located within the northern Ghana savanna. The predicted CP% and DOM% were used with Normalized Differential Vegetation Index (NDVI) data, and cokriging technique to create diet quality maps for March and July 2000 for the northern Ghana savanna. Cross validation results indicated a moderate capability of cokriging to estimate predicted CP% for March (r2 = 0.687, SEp = 1.736) and July (r2 = 0.513, SEp = 1.558). Cokriged-estimated DOM value for July was above average (r2 = 0.584, SEp = 3.611), while March DOM% estimation was rather poor (r2 = 0.132, SEp = 3.891). The techniques of cokriging and creation of diet quality maps were moderately successful in this study.

The European Union Water Framework Directive (WFD), with initiatives to manage surface water resources, has increased the need for fast and inexpensive methods for monitoring conditions in streams. The objective of this thesis is to assess the potential of near-infrared spectroscopy (NIRS) of epilithic material to become such method. NIRS, which is a technique that is commonly used in industry for process monitoring and quality control of products, registers the chemical properties of organic material on a molecular level. Epilithic material, i.e. the layer of dead and alive material that covers stone surfaces in streams, is continuously influenced by the stream water that flows over it, and it has the potential to integrate chemical and biological conditions over time. The temporal integration is a significant factor, since conditions in streams can change within hours or days. The thesis consists of two published papers. In the first paper a new sampler for epilithic material, the Stone Brusher, was described and the performance evaluated. The Stone Brusher is designed to take qualitative or semi-quantitative samples of epilithic material from stones at 7–50 cm water depth. The epilithic material is dislodged from the stone surface with a rotating brush enclosed in a chamber, and the material is drawn up directly into the sample bottle with an air-cylinder. The operator takes a sample quickly and without putting hands into the water. The sampler is made of plastic, stainless steel and aluminium and weighs 3.1 kg. It is designed to meet the demand for standardized sampling for research and environmental monitoring and to improve working conditions for sampling personnel. The equipment allows sampling from surfaces of bedrock and large stones that cannot be lifted from the bottom. Using data of near-infrared spectroscopy and diatom analyses, this new sampler was evaluated in comparison to the toothbrush method, a primitive method which is the current standard in EU. The results indicate that the Stone Brusher reduces sampling variability compared with the toothbrush method. In the second paper, the Stone Brusher was used to collect epilithic material from 65 sites (42 uncontaminated and 23 contaminated) from streams in the widespread mining area called the Skellefte-district in Västerbotten, northern Sweden, in order to test the hypothesis that impact on the epilithic material caused by emissions from mining and mining-related industries can be detected using NIRS. The epilithic material was filtered onto glass fibre filters, measured by NIRS, and the results were modelled using Principal Component Analysis (PCA). The NIRS approach was evaluated by comparing it with the results of chemical and diatom analyses of the same samples. Based on PCA, the NIRS data distinguished contaminated from uncontaminated sites and performed slightly better than chemical analyses and clearly better than diatom analyses. Of the streams designated a priori as contaminated, 74 % were identified as contaminated by NIRS, 65 % by chemical analysis and 26 % by diatom analysis. Unlike chemical analyses of water or of epilithic material samples, NIRS data reflect biological impacts in the streams. Given that, and the simplicity of NIRS-analyses, further studies to assess the use of NIRS of epilithic material are justified. NIRS has the potential to become a fast method for screening in regions where large numbers of streams occur to find impacted streams or as a routine method for temporal monitoring in selected streams for early detection of environmental impact, similar to process monitoring in industry.

Functional neuroimaging techniques such as near-infrared spectroscopy (NIRS) have been studied in brain-computer interface (BCI) development. Previous research has suggested that the addition of a second brain-monitoring modality may improve the accuracy of a NIRS-BCI. The objective of this study was to determine whether the classification accuracies achievable by a multimodal BCI, which combines NIRS and transcranial Doppler ultrasonography (TCD) signals, can exceed those attainable using a unimodal NIRS-BCI or TCD-BCI. Nine able-bodied subjects participated in the study. Simultaneous measurements were made with NIRS and TCD instruments while participants were prompted to perform a verbal fluency task or to remain at rest, within the context of a block-stimulus paradigm. In five of nine (55.6%) participants, classification accuracies with the NIRS-TCD system were significantly higher (p<0.05) than with NIRS or TCD systems alone. Our results suggest that multimodal neuroimaging may be a promising approach towards improving the accuracy of future BCIs.