403 resultados para NIRS-SPM
Resumo:
The content-based image retrieval is important for various purposes like disease diagnoses from computerized tomography, for example. The relevance, social and economic of image retrieval systems has created the necessity of its improvement. Within this context, the content-based image retrieval systems are composed of two stages, the feature extraction and similarity measurement. The stage of similarity is still a challenge due to the wide variety of similarity measurement functions, which can be combined with the different techniques present in the recovery process and return results that aren’t always the most satisfactory. The most common functions used to measure the similarity are the Euclidean and Cosine, but some researchers have noted some limitations in these functions conventional proximity, in the step of search by similarity. For that reason, the Bregman divergences (Kullback Leibler and I-Generalized) have attracted the attention of researchers, due to its flexibility in the similarity analysis. Thus, the aim of this research was to conduct a comparative study over the use of Bregman divergences in relation the Euclidean and Cosine functions, in the step similarity of content-based image retrieval, checking the advantages and disadvantages of each function. For this, it was created a content-based image retrieval system in two stages: offline and online, using approaches BSM, FISM, BoVW and BoVW-SPM. With this system was created three groups of experiments using databases: Caltech101, Oxford and UK-bench. The performance of content-based image retrieval system using the different functions of similarity was tested through of evaluation measures: Mean Average Precision, normalized Discounted Cumulative Gain, precision at k, precision x recall. Finally, this study shows that the use of Bregman divergences (Kullback Leibler and Generalized) obtains better results than the Euclidean and Cosine measures with significant gains for content-based image retrieval.
Resumo:
En plus de contribuer à améliorer la santé de façon générale, l’activité physique chronique pourrait modérer le déclin cognitif associé au vieillissement normal et pathologique (Colcombe et Kramer, 2003; Heyn et al., 2004). Plus précisément, la pratique à long terme d’activités cardiovasculaires aurait des effets positifs sur la cognition des ainés et plus particulièrement sur le contrôle attentionnel, un aspect précocement touché au cours du vieillissement (Raz, 2000; Bherer et al., 2008). Toutefois, les mécanismes par lesquels l’exercice physique aigu améliore la cognition demeurent limités. Malgré ses nombreuses implications théoriques et pratiques, la réponse aiguë de l’oxygénation cérébrale à l’exercice physique et sa relation avec la cognition sont trop peu étudiées. Cette thèse se consacre à cette question. Des études récentes en neuro-imagerie chez les jeunes adultes démontrent que la relation entre l’oxygénation cérébrale et l’intensité de l’exercice suit la forme d’un U inversé. Il existe un seuil au-delà duquel l’oxygénation cérébrale diminue avec l’augmentation de l’intensité de l’exercice. Supposant que les performances cognitives dépendent de la disponibilité de l’oxygène cérébral, cette relation en U inversé devrait affecter les performances cognitives. Avant de préciser le rôle exact de l’oxygénation cérébrale sur les fonctions cognitives, nous avons d’abord examiné le temps nécessaire pour que l’oxygénation cérébrale atteigne un état stable et la durée pendant laquelle cette période stable peut être maintenue lors de paliers de sept minutes à une puissance sous-maximale (40%, 60% et 85% de la puissance aérobie maximale). Nos résultats soulignent l’existence d’une relation inverse entre la durée de l’état stable et l’intensité de l’exercice. Suite à cette vérification méthodologique, la prochaine étape a été de tester la possible relation entre l’oxygénation cérébrale, l’intensité de l’exercice et les performances cognitives, au cours du processus de vieillissement. Les résultats de ces études démontrent que la chute de l’oxygénation cérébrale observée lors des exercices de haute intensité est associée avec une diminution des performances cognitives. Les résultats de cette thèse corrigent l’écart existant dans la documentation entre l’exercice, les fonctions cognitives et les mécanismes neurophysiologiques.
Resumo:
Rivers represent a transition zone between terrestric and aquatic environments, and between methane rich and methane poor environments. The Elbe River is one of the important rivers draining into the North Sea and with the Elbe potentially high amounts of methane could be imported into the water column of the North Sea. Twelve cruises from October 2010 until June 2013 were conducted from Hamburg towards the Elbe mouth at Cuxhaven. The dynamic of methane concentration in the water column and its consumption via methane oxidation was measured. In addition, physico-chemical parameters were used to estimate their influence on the methanotrophic activity. We observed high methane concentrations at the stations in the area of Hamburg harbor ("inner estuary") and about 10 times lower concentrations in the outer estuary (median of 416 versus 40 nmol/L). The methane oxidation (MOX) rate mirrowed the methane distribution with high values in the inner estuary and low values in the outer estuary (median of 161 versus 10 nmol/L/d respectively) Methane concentrations were significantly influenced by the river hydrology (falling water level) and the trophic state of the water (biological oxygen demand). In contrast to other studies no clear relation to the amount of suspendended particulate matter (SPM) was found. Methane oxidation rates were significantly influenced by methane concentration and to a weaker extent by temperature. Methane oxidation accounted for 41 ± 12% of the total loss of methane in summer/fall, but only for 5 ± 3% of the total loss in winter/spring. We applied a modified box model taking into account the residence times of a water parcel depending on discharge and tidal impact. We observed almost stable methane concentrations in the outer estuary, despite a strong loss of methane through diffusion and oxidation. Thus we postulate that in the outer Elbe estuary a strong additional input of methane is required, which could be provided by the extensive salt marshes near the river mouth.
Resumo:
Membrane lipids of marine planktonic archaea have provided unique insights into archaeal ecology and paleoceanography. However, past studies of archaeal lipids in suspended particulate matter (SPM) and sediments mainly focused on a small class of fully saturated glycerol dibiphytanyl glycerol tetraether (GDGT) homologues identified decades ago. The apparent low structural diversity of GDGTs is in strong contrast to the high diversity of metabolism and taxonomy among planktonic archaea. Furthermore, adaptation of archaeal lipids in the deep ocean remains poorly constrained. We report the archaeal lipidome in SPM from diverse oceanic regimes. We extend the known inventory of planktonic archaeal lipids to include numerous unsaturated archaeal ether lipids (uns-AELs). We further reveal i) different thermal regulations and polar headgroup compositions of membrane lipids between the epipelagic (<= 100 m) and deep (> 100 m) populations of archaea; ii) stratification of unsaturated GDGTs with varying redox conditions; and iii) enrichment of tetra-unsaturated archaeol and fully saturated GDGTs in epipelagic and deep oxygenated waters, respectively. Such stratified lipid patterns are consistent with the typical distribution of archaeal phylotypes in marine environments. We thus provide an ecological context for GDGT-based paleoclimatology and bring about the potential use of uns-AELs as biomarkers for planktonic Euryarchaeota. This article is protected by copyright. All rights reserved.
Resumo:
Nitrogen fixation, the biological reduction of dinitrogen gas (N2) to ammonium (NH4+), is quantitatively the most important external source of new nitrogen (N) to the open ocean. Classically, the ecological niche of oceanic N2 fixers (diazotrophs) is ascribed to tropical oligotrophic surface waters, often depleted in fixed N, with a diazotrophic community dominated by cyanobacteria. Although this applies for large areas of the ocean, biogeochemical models and phylogenetic studies suggest that the oceanic diazotrophic niche may be much broader than previously considered, resulting in major implications for the global N-budget. Here, we report on the composition, distribution and abundance of nifH, the functional gene marker for N2 fixation. Our results show the presence of eight clades of diazotrophs in the oxygen minimum zone (OMZ) off Peru. Although proteobacterial clades dominated overall, two clusters affiliated to spirochaeta and archaea were identified. N2 fixation was detected within OMZ waters and was stimulated by the addition of organic carbon sources supporting the view that non-phototrophic diazotrophs were actively fixing dinitrogen. The observed co-occurrence of key functional genes for N2 fixation, nitrification, anammox and denitrification suggests that a close spatial coupling of N-input and N-loss processes exists in the OMZ off Peru. The wide distribution of diazotrophs throughout the water column adds to the emerging view that the habitat of marine diazotrophs can be extended to low oxygen/high nitrate areas. Furthermore, our statistical analysis suggests that NO2- and PO43- are the major factors affecting diazotrophic distribution throughout the OMZ. In view of the predicted increase in ocean deoxygenation resulting from global warming, our findings indicate that the importance of OMZs as niches for N2 fixation may increase in the futur
Resumo:
At present, when the influence of human economic activity is progressively increasing, significant attention is devoted to the state of water ecosystems. All researchers engaged in these problems agree that the state of the water system (pollution and eutrophication) can only be estimated on the basis of long-term researches. Systemic monitoring (at least once per month) of ionic components (Ca2+, Mg2+, Na+, K+, bicarbonates, sulfates, and chlorides) in unfiltered water of Lake Baikal and its tributaries had been carried out under the supervision of Votintsev since 1947. Based on the analysis of systematic data on trophic components obtained during 1965-2005, we tried to estimate the present-day trophic status of the pelagic zone in the lake, define the trend of long-term changes of trophic components and understand the reasons of the distortion of cyclicity in the development of spring diatom algae, which create a favorable environment in any water basin. It should be noted that the station near Cape Polovinnyi is located 20 km away from the town of Baikal'sk. Wastewaters of the Baikal'sk pulp and paper mill is the main source of dioxins and furans in Baikal. Based on the significant difference between sulfate contents in wastewaters of the plant (>300 mg/l), tributaries of Baikal (7.5 mg/l), and waters in the southern part of the lake (3.9 mg/l), we defined the following periods: (i) period of natural seasonal patterns until 1967-1968 (prior to putting the Baikal'sk Mill into operation; (ii) period of weak anthropogenic pollution (1969-1985); and (iii) period of strong anthropogenic pollution since 1986.
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Study of biogeochemical processes in waters and sediments of the Chukchi Sea in August 2004 revealed atypical maxima of biogenic element (N, P, and Si) concentrations and rate of microbial sulfate reduction in the surface layer (0-3 cm) of marine sediments. The C/N/P ratio in organic matter (OM) of this layer does not fit the Redfield-Richards stoichiometric model. Specific features of biogeochemical processes in the sea are likely related to the complex dynamics of water, high primary produc¬tivity (110-1400 mg C/m**2/day), low depth of the basin (<50 m for 60% of the water area), reduced food chain due to low population of zooplankton, high density of zoobenthos (up to 4230 g/m**2), and high activity of microbial processes. Drastic decrease in concentrations of biogenic elements, iodine, total alkalinity, and population of microorganisms beneath the 0-3 cm layer testify to large-scale OM decay at the water-seafloor barrier. Our original experimental data support high annual rate of OM mineralization at the bottom of the Chukchi Sea.
Resumo:
Long chain diols are lipids that have gained interest over the last years due to their high potential to serve as biomarkers and diol indices have been proposed to reconstruct upwelling conditions and sea surface temperature (SST). However, little is known about the sources of the diols and the mechanisms impacting their distribution. Here we studied the factors controlling diol distributions in the Iberian Atlantic margin, which is characterized by a dynamic continental shelf under the influence of upwelling of nutrient-rich cold deep waters, and fluvial input. We analyzed suspended particulate matter (SPM) of the Tagus river, marine SPM and marine surface sediments along five transects off the Iberian margin, as well as riverbank sediments and soil from the catchment area of the Tagus river. Relatively high fractional abundances of the C32 1,15-diol (normalized with respect to the 1,13- and 1,15-diols) were observed in surface sediments in front of major river mouths and this abundance correlates strongly with the BIT index, a tracer for continental input of organic carbon. Together with an even higher fractional abundance of the C32 1,15-diol in the Tagus river SPM, and the absence of long chain diols in the watershed riverbank sediments and soils, we suggest that this long chain diol is produced in-situ in the river. Further support for this hypothesis comes from the small but distinct stable carbon isotopic difference of 1.3? with the marine C28 1,13-diol. The 1,14-diols are relatively abundant in surface sediments directly along the northern part of the coast, close to the upwelling zone, suggesting that Diol Indices based on 1,14-diols would work well as upwelling tracers in this region. Strikingly, we observed a significant difference in stable carbon isotopic composition between the monounsaturated C30:1 1,14- and the saturated C28 1,14-diol (3.8±0.7 per mil), suggesting different sources, in accordance with their different distributions. In addition, the Long chain Diol Index (LDI), a proxy for sea surface temperature, was applied for the surface sediments. The results correlate well with satellite SSTs offshore but reveal a significant discrepancy with satellite-derived SSTs in front of the Tagus and Sado rivers. This suggests that river outflow might compromise the applicability of this proxy.
Resumo:
In the reconstruction of sea surface temperature (SST) from sedimentary archives, secondary sources, lateral transport and selective preservation are considered to be mainly negligible in terms of influencing the primary signal. This is also true for the archaeal glycerol dialkyl glycerol tetraethers (GDGTs) that form the basis for the TEX86 SST proxy. Our samples represent four years variability on a transect off Cape Blanc (NW Africa). We studied the subsurface production, vertical and lateral transport of intact polar lipids and core GDGTs in the water column at high vertical resolution on the basis of suspended particulate matter (SPM) samples from the photic zone, the subsurface oxygen minimum zone (OMZ), nepheloid layers (NL) and the water column between these. Furthermore we compared the water column SPM GDGT composition with that in underlying surface sediments. This is the first study that reports TEX86 values from the precursor intact polar lipids (IPLs) associated with specific head groups (IPL -specific TEX86). We show a clear deviation from the sea surface GDGT composition in the OMZ between 300 and 600 m. Since neither lateral transport nor selective degradation provides a satisfactory explanation for the observed TEX-derived temperature profiles with a bias towards higher temperatures for both core- and IPL -specific TEX86 values, we suggest that subsurface in situ production of archaea with a distinct relationship between lipid biosynthesis and temperature is the responsible mechanism. However, in the NW-African upwelling system the GDGT contribution of the OMZ to the surface sediments does not seem to affect the sedimentary TEX86 as it shows no bias and still reflects the signal of the surface waters between 0 and 60 m.
Resumo:
In oceans, estuaries, and rivers, nitrification is an important nitrate source, and stable isotopes of nitrate are often used to investigate recycling processes (e.g. remineralisation, nitrification) in the water column. Nitrification is a two-step process, where ammonia is oxidised via nitrite to nitrate. Nitrite usually does not accumulate in natural environments, which makes it difficult to study the single isotope effect of ammonia oxidation or nitrite oxidation in natural systems. However, during an exceptional flood in the Elbe River in June 2013, we found a unique co-occurrence of ammonium, nitrite, and nitrate in the water column, returning towards normal summer conditions within 1 week. Over the course of the flood, we analysed the evolution of d15N-[NH4]+ and d15N-[NO2]- in the Elbe River. In concert with changes in suspended particulate matter (SPM) and d15N SPM, as well as nitrate concentration, d15N-NO3 - and d18O-[NO3] -, we calculated apparent isotope effects during net nitrite and nitrate consumption. During the flood event, > 97 % of total reactive nitrogen was nitrate, which was leached from the catchment area and appeared to be subject to assimilation. Ammonium and nitrite concentrations increased to 3.4 and 4.4 µmol/l, respectively, likely due to remineralisation, nitrification, and denitrification in the water column. d15N-[NH4]+ values increased up to 12 per mil, and d15N-[NO2]- ranged from -8.0 to -14.2 per mil. Based on this, we calculated an apparent isotope effect 15-epsilon of -10.0 ± 0.1 per mil during net nitrite consumption, as well as an isotope effect 15-epsilon of -4.0 ± 0.1 per mil and 18-epsilon of -5.3 ± 0.1 per mil during net nitrate consumption. On the basis of the observed nitrite isotope changes, we evaluated different nitrite uptake processes in a simple box model. We found that a regime of combined riparian denitrification and 22 to 36 % nitrification fits best with measured data for the nitrite concentration decrease and isotope increase.
Resumo:
Cryolithological, ground ice and fossil bioindicator (pollen, diatoms, plant macrofossils, rhizopods, insects, mammal bones) records from Bol'shoy Lyakhovsky Island permafrost sequences (73°20'N, 141°30'E) document the environmental history in the region for the past c. 115 kyr. Vegetation similar to modern subarctic tundra communities prevailed during the Eemian/Early Weichselian transition with a climate warmer than the present. Sparse tundra-like vegetation and harsher climate conditions were predominant during the Early Weichselian. The Middle Weichselian deposits contain peat and peaty soil horizons with bioindicators documenting climate amelioration. Although dwarf willows grew in more protected places, tundra and steppe vegetation prevailed. Climate conditions became colder and drier c. 30 kyr BP. No sediments dated between c. 28.5 and 12.05 14C kyr BP were found, which may reflect active erosion during that time. Herb and shrubby vegetation were predominant 11.6-11.3 14C kyr BP. Summer temperatures were c. 4 °C higher than today. Typical arctic environments prevailed around 10.5 14C kyr BP. Shrub alder and dwarf birch tundra were predominant between c. 9 and 7.6 kyr BP. Reconstructed summer temperatures were at least 4 °C higher than present. However, insect remains reflect that steppe-like habitats existed until c. 8 kyr BP. After 7.6 kyr BP, shrubs gradually disappeared and the vegetation cover became similar to that of modern tundra. Pollen and beetles indicate a severe arctic environment c. 3.7 kyr BP. However, Betula nana, absent on the island today, was still present. Together with our previous study on Bol'shoy Lyakhovsky Island covering the period between about 200 and 115 kyr, a comprehensive terrestrial palaeoenvironmental data set from this area in western Beringia is now available for the past two glacial-interglacial cycles.
Resumo:
In the past decade, several major food safety crises originated from problems with feed. Consequently, there is an urgent need for early detection of fraudulent adulteration and contamination in the feed chain. Strategies are presented for two specific cases, viz. adulterations of (i) soybean meal with melamine and other types of adulterants/contaminants and (ii) vegetable oils with mineral oil, transformer oil or other oils. These strategies comprise screening at the feed mill or port of entry with non-destructive spectroscopic methods (NIRS and Raman), followed by post-screening and confirmation in the laboratory with MS-based methods. The spectroscopic techniques are suitable for on-site and on-line applications. Currently they are suited to detect fraudulent adulteration at relatively high levels but not to detect low level contamination. The potential use of the strategies for non-targeted analysis is demonstrated.
Resumo:
Energy policies around the world are mandating for a progressive increase in renewable energy production. Extensive grassland areas with low productivity and land use limitations have become target areas for sustainable energy production to avoid competition with food production on the limited available arable land resources and minimize further conversion of grassland into intensively managed energy cropping systems or abandonment. However, the high spatio-temporal variability in botanical composition and biochemical parameters is detrimental to reliable assessment of biomass yield and quality regarding anaerobic digestion. In an approach to assess the performance for predicting biomass using a multi-sensor combination including NIRS, ultra-sonic distance measurements and LAI-2000, biweekly sensor measurements were taken on a pure stand of reed canary grass (Phalaris aruninacea), a legume grass mixture and a diversity mixture with thirty-six species in an experimental extensive two cut management system. Different combinations of the sensor response values were used in multiple regression analysis to improve biomass predictions compared to exclusive sensors. Wavelength bands for sensor specific NDVI-type vegetation indices were selected from the hyperspectral data and evaluated for the biomass prediction as exclusive indices and in combination with LAI and ultra-sonic distance measurements. Ultrasonic sward height was the best to predict biomass in single sensor approaches (R² 0.73 – 0.76). The addition of LAI-2000 improved the prediction performance by up to 30% while NIRS barely improved the prediction performance. In an approach to evaluate broad based prediction of biochemical parameters relevant for anaerobic digestion using hyperspectral NIRS, spectroscopic measurements were taken on biomass from the Jena-Experiment plots in 2008 and 2009. Measurements were conducted on different conditions of the biomass including standing sward, hay and silage and different spectroscopic devices to simulate different preparation and measurement conditions along the process chain for biogas production. Best prediction results were acquired for all constituents at laboratory measurement conditions with dried and ground samples on a bench-top NIRS system (RPD > 3) with a coefficient of determination R2 < 0.9. The same biomass was further used in batch fermentation to analyse the impact of species richness and functional group composition on methane yields using whole crop digestion and pressfluid derived by the Integrated generation of solid Fuel and Biogas from Biomass (IFBB) procedure. Although species richness and functional group composition were largely insignificant, the presence of grasses and legumes in the mixtures were most determining factors influencing methane yields in whole crop digestion. High lignocellulose content and a high C/N ratio in grasses may have reduced the digestibility in the first cut material, excess nitrogen may have inhibited methane production in second cut legumes, while batch experiments proved superior specific methane yields of IFBB press fluids and showed that detrimental effects of the parent material were reduced by the technical treatment
Resumo:
La compréhension du discours, et son évolution au cours du vieillissement, constitue un sujet d’une grande importance par sa complexité et sa place dans la préservation de la qualité de vie des aînés. Les objectifs de cette thèse étaient d’évaluer l’influence du vieillissement et du niveau de scolarité sur les capacités de compréhension du discours et sur l’activité cérébrale s’y rattachant. Pour ce faire, trois groupes (jeunes adultes ayant un niveau universitaire de scolarité, personnes âgées ayant un niveau universitaire de scolarité et personnes âgées ayant un niveau secondaire de scolarité) ont réalisé une tâche où ils devaient lire de courtes histoires, puis estimer la véracité d’une affirmation concernant cette histoire. Les capacités de compréhension correspondant aux traitements de trois niveaux du modèle de construction-intégration de Kintsch (la microstructure, la macrostructure et le modèle de situation) ont été évaluées. L’imagerie optique (NIRS) a permis d’estimer les variations d’oxyhémoglobine (HbO) et de déoxyhémoglobine (HbR) tout au long de la tâche. Les résultats ont démontré que les personnes âgées étaient aussi aptes que les plus jeunes pour rappeler la macrostructure (essentiel du texte), mais qu’ils avaient plus de difficulté à rappeler la microstructure (détails) et le modèle de situation (inférence et intégration) suite à la lecture de courts textes. Lors de la lecture, les participants plus âgés ont également montré une plus grande activité cérébrale dans le cortex préfrontal dorsolatéral gauche, ce qui pourrait être un mécanisme de compensation tel que décrit dans le modèle CRUNCH. Aucune différence significative n’a été observée lors de la comparaison des participants âgés ayant un niveau universitaire de scolarité et ceux ayant un niveau secondaire, tant au niveau des capacités de compréhension que de l’activité cérébrale s’y rattachant. Les deux groupes ont cependant des habitudes de vie stimulant la cognition, entre autres, de bonnes habitudes de lecture. Ainsi, ces habitudes semblent avoir une plus grande influence que l’éducation sur les performances en compréhension et sur l’activité cérébrale sous-jacente. Il se pourrait donc que l’éducation influence la cognition en promouvant des habitudes favorisant les activités cognitives, et que ce soit ces habitudes qui aient en bout ligne un réel impact sur le vieillissement cognitif.
Resumo:
This research is based on a numerical model for forecasting the three-dimensional behavior of (sea) water motion due to the effect of a variable wind velocity. The results obtained are then analyzed and compared with observation. This model is based on the equations that overcome the current and distribution of temperature by applying the method of finite difference with assuming Δx, Δy as constant and Δz, variable. The model is based on the momentum equation, continuity equation and thermodynamic energy equation and tension at the surface and middle layers and bottom stress. The horizontal and vertical eddy viscosity and thermal diffusivity coefficients we used in accordance with that of the Bennet on Outario Lake (1977). Considering the Caspian Sea dimension in numerical model the Coriolis parameter used with β effects and the approximation Boussines have been used. For the program controlling some simple experiment with boundary condition similar to that of the Caspian Sea have been done. For modeling the Caspian Sea the grid of the field was done as follows: At horizontal surface grid size is 10×10km extension and at vertical in 10 layers with varying thickness from surface to bed respectively as: 5, 10, 20, 3, 50, 100, 150, 200, 25, 500 and higher. The data of wind as velocity، direction and temperature of water related to 15th September 1995 at 6،12 and 18 o’clock were obtained from synoptic station at the Caspian Sea shore and the research marine of Haji Alief. The information concerning shore wind was measured and by the method of SPM (shore protection manual) was transferred to far shore winds through interpolation and by use of inverse square distance of position distribution of the wind velocity at the Caspian surface field was obtained. The model has been evaluated according to the reports and observations. Through studying the position of the current in different layers، the velocity in the cross section in the northern، southern and the middle layers، will be discussed. The results reveal the presence of the circulation cells in the three above mentioned areas. The circulation with depth is reduced too. The results obtained through the numerical solution of the temperature equation have been compared with the observation. The temperature change in different layers in cross section illustrates the relative accordance of the model mentioned.