Fonctionnement et gestion des écosystèmes forestiers contractés sahéliens

La structure contrastée de la brousse tigrée a un fonctionnement hydrique et biologique particulier. Une bande nue sert d'impluvium à la bande de végétation située en aval, qui bénéficie ainsi d'un apport en eau supérieur à la pluie. L'apport du ruissellement de la zone nue sur le fonctionnement hydrique et biologique de l'écosystème a été étudié. Les observations effectuées sur deux bandes de végétation pendant quatre années ont permis de quantifier la redistribution de l'eau dans l'écosystème et ses conséquences sur le cycle biologique des espèces ligneuses et herbacées dominantes. On montre que la suppression de l'apport d'eau de la zone nue (par construction d'une digue) modifie le cycle de vie et réduit notamment la fructification des espèces végétales. A terme, elle pourrait perturber la survie des espèces ligneuses, et particulièrement celles situées en amont du fourré, dans la zone pionnière. Ces résultats permettent d'apporter plusieurs propositions pour une gestion raisonnée de ce type de forêt contractée. (Résumé d'auteur

Advanced endoscopic imaging for diagnosis of inflammatory bowel diseases : present and future perspectives

Crohn's disease and ulcerative colitis are chronic inflammatory bowel diseases (IBD) causing severe damage of the luminal gastrointestinal tract. Differential diagnosis between both disease entities is sometimes awkward requiring a multifactorial pathway, including clinical and laboratory data, radiological findings, histopathology and endoscopy. Apart from disease diagnosis, endoscopy in IBD plays a major role in prediction of disease severity and extent (i.e. mucosal healing) for tailored patient management and for screening of colitis-associated cancer and its precursor lesions. In this state-of-the-art review, we focus on current applications of endoscopy for diagnosis and surveillance of IBD. Moreover, we will discuss the latest guidelines on surveillance and provide an overview of the most recent developments in the field of endoscopic imaging and IBD

Differential Optical Absorption Spectroscopy (DOAS) Measurements of Ozone in the 280--290 nm Wavelength Region

The differential absorption structure of the ozone spectrum between 250 and 330 nm has been investigated in order to determine the optimal wavelength region to be utilized for active differential optical absorption spectroscopy (DOAS) measurements. Considering aspects of atmospheric attenuation and interference from other species as well as the magnitude of the differential absorption cross section, an interval around 283 nm was found to be a good candidate for this application. This result was also verified during 12 months of continuous ozone monitoring in an urban environment

Measurement of Aromatic-hydrocarbons With the DOAS Technique

Long-path DOAS (differential optical absorption spectroscopy) in the ultraviolet spectral region has been shown to be applicable for low-concentration measurements of light aromatic hydrocarbons. However, because of spectral interferences among different aromatics as well as with oxygen, ozone, and sulfur dioxide, the application of the DOAS technique for this group of components is not without problems. This project includes a study of the differential absorption characteristics, between 250 and 280 nm, of twelve light aromatic hydrocarbons representing major constituents in technical solvents used in the automobile industry. Spectral overlapping between the different species, including oxygen, ozone, and sulfur dioxide, has been investigated and related to the chemical structure of the different aromatics. Interference effects in the DOAS application due to spectral overlapping have been investigated both in quantitative and in qualitative terms, with data from a field campaign at a major automobile manufacturing plant

Leaving colorectal polyps in place can be achieved with high accuracy using blue light imaging (BLI)

Objectives: A negative predictive value of more than 90% is proposed by the American Society of Gastrointestinal Endoscopy Preservation and Incorporation of Valuable Endoscopic Innovations (PIVI) statement for a new technology in order to leave distal diminutive colorectal polyps in place without resection. To our knowledge, no prior prospective study has yet evaluated the feasibility of the most recently introduced blue light imaging (BLI) system for real-time endoscopic prediction of polyp histology for the specific endpoint of leaving hyperplastic polyps in place. Aims: Prospective assessment of real-time prediction of colorectal polyps by using BLI. Material and methods: In total, 177 consecutive patients undergoing screening or surveillance colonoscopy were included. Colorectal polyps were evaluated in real-time by using high-definition endoscopy and the BLI technology without optical magnification. Before resection, the endoscopist described each polyp according to size, shape and surface characteristics (pit and vascular pattern, colour and depression), and histology was predicted with a level of confidence (high or low). Results: Histology was predicted with high confidence in 92.5% of polyps. Sensitivity of BLI for prediction of adenomatous histology was 92.68%, with a specificity and accuracy of 94.87 and 93.75%, respectively. Following the recommendation of the PIVI statement, positive and negative predictive values were calculated with values of 95 and 92.5%, respectively. Prediction of surveillance based on both US and European guidelines was correctly predicted in 91% of patients. Conclusion: The most recently introduced BLI technology is accurate enough to leave distal colorectal polyps in place without resection. BLI also allowed for assignment of postpolypectomy surveillance intervals. This approach therefore has the potential to reduce costs and risks associated with the redundant removal of diminutive colorectal polyps

Feasibility trial of the newly introduced optical enhancement technology in patients with gastroesophageal reflux disease

BACKGROUND: Optical Enhancement technology (OE) combines bandwidth-limited light and image enhancement processing technology to enhance subtle mucosal and vascular details. This is the first study assessing the new technology for the diagnosis of gastroesophageal reflux disease (GERD). PATIENTS AND METHODS: Consecutive patients with GERD and controls were prospectively included. The distal esophagus was examined in all quadrants with high definition white-light endoscopy (HD-WLE) followed by OE and biopsies for histopathological analysis. Features observed only by OE were compared between controls and patients with GERD. RESULTS: A total of 100 areas were evaluated. About 56% of patients had a diagnosis of GERD. The mean age of patients was 53 years (range 27-89 years), 60% were female. Compared to controls, patients with diagnosis of GERD showed significantly more often tortuosity (p = 0.042), dilation (p = 0.0003), and increased number (p = 0.001) of intrapapillary capillary loops (IPCLs). In addition, increased vascularity and mucosal breaks were significantly more often found in patients with GERD as compared to controls (p < 0.05). On multivariate analysis, increased number and dilation of IPCL were the best predictors of GERD. CONCLUSIONS: The newly introduced OE technology significantly improves the diagnosis of GERD compared to HD-WLE. The results should be confirmed in a multicenter trial

High emission rate of sulfuric acid from Bezymianny volcano, Kamchatka

High concentrations of primary sulfuric acid (H2SO4) in fumarolic gases and high emission rate of sulfuric acid aerosol in the plume were measured at Bezymianny volcano, an active dome-growing andesitic volcano in central Kamchatka. Using direct sampling, filter pack sampling, and differential optical absorption spectroscopy measurements, we estimated an average emission of H2SO4 at 243 ± 75 t/d in addition to an average SO2 emission of 212 ± 65 t/d. The fumarolic gases of Bezymianny correspond to arc gases released by several magma bodies at different stages of degassing and contain 25-92% of entrained air. H2SO4 accounts for 6-87 mol% of the total sulfur content, 42.8 mol% on average, and SO2 is the rest. The high H2SO4 in Bezymianny fumaroles can be explained by catalytic oxidation of SO2 inside the volcanic dome. Because sulfate aerosol is impossible to measure remotely, the total sulfur content in a plume containing significant H2SO4 may be seriously underestimated

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