Study of suitability of cheap AvaSpec array spectrometer for solar UV field measurements

International audienceA system to record the ultraviolet (UV) spectra of atmospheric global irradiance with the miniature fiber optic spectrometer AvaSpec-256 was developed for continuous computer-aided spectrometry at Tartu Observatory in 2005. As a result, the database of spectra recorded with 15-min-interval round 24 h over 300?400 nm, has been developed. The quantities retrieved from the spectra have been compared with those measured by the Scintec erythemal UV-SET sensor and the Kipp&Zonen narrowband 306 nm sensor. Almost clear and overcast days were selected for comparison. Reliable results on the spectral distribution of the UV global irradiance as well as the integrated daily spectral doses could be obtained at least during the bright half-year. The results were compared with the calculations performed by means of the LibRadtran package. The biases in irradiance were significant at SZA above 70?75°. At dominating larger SZA the recorded values need sophisticated corrections and remain less reliable. At lower latitudes than that of the study site (58.3 degrees), the reliability of the spectrometer is expected to increase due to a smaller contribution of data measured at large SZA. The variations of the ratio of UV-A/UV-B irradiance, retrieved from the spectra, were investigated. Also the covariation of the narrowband 306 nm irradiance and the irradiance integrated over the whole UV-B range was studied. The biases between calculated by means of the LibRadtran package and the measured ratio of UV-A/UV-B irradiance were small at SZA below 70°. At larger SZA the values of the ratio as well as the biases increased, significantly depending on total ozone

Study of suitability of AvaSpec array spectrometer for solar UV field measurements

A system to record the ultraviolet (UV) spectra of atmospheric global irradiance with the miniature fiber optic spectrometer AvaSpec-256 was developed for continuous computer-aided spectrometry at Tartu Observatory in 2005. As a result, the database of spectra recorded with 15-min-interval round 24 h over 300–400 nm, has been developed. The quantities retrieved from the spectra have been compared with those measured by the Scintec erythemal UV-SET sensor and the Kipp & Zonen narrowband 306 nm sensor. Almost clear and overcast days were selected for comparison. Reliable results on the spectral distribution of the UV global irradiance as well as the integrated daily spectral doses could be obtained at least during the bright half-year. The results were compared with the calculations performed by means of the LibRadtran package. The biases in irradiance were significant at SZA above 70–75°. At dominating larger SZA the recorded values need sophisticated corrections and remain less reliable. At lower latitudes than that of the study site (58.3°), the reliability of the spectrometer is expected to increase due to a smaller contribution of data measured at large SZA. <br></br> The variations of the ratio of UV-A/UV-B irradiance, retrieved from the spectra, were investigated. Also the covariation of the narrowband 306 nm irradiance and the irradiance integrated over the whole UV-B range was studied. The biases between the UV-A/UV-B irradiances calculated by means of the LibRadtran package and measured with the AvaSpec were small at SZA below 70°. At larger SZA the values of the ratio as well as the biases increased, significantly depending on total ozone

Plasma neurofilament light protein correlates with diffusion tensor imaging metrics in frontotemporal dementia

Neurofilaments are structural components of neurons and are particularly abundant in highly myelinated axons. The levels of neurofilament light chain (NfL) in both cerebrospinal fluid (CSF) and plasma have been related to degeneration in several neurodegenerative conditions including frontotemporal dementia (FTD) and NfL is currently considered as the most promising diagnostic and prognostic fluid biomarker in FTD. Although the location and function of filaments in the healthy nervous system suggests a link between increased NfL and white matter degeneration, such a claim has not been fully elucidated in vivo, especially in the context of FTD. The present study provides evidence of an association between the plasma levels of NfL and white matter involvement in behavioral variant FTD (bvFTD) by relating plasma concentration of NfL to diffusion tensor imaging (DTI) metrics in a group of 20 bvFTD patients. The results of both voxel-wise and tract specific analysis showed that increased plasma NfL concentration is associated with a reduction in fractional anisotropy (FA) in a widespread set of white matter tracts including the superior longitudinal fasciculus, the fronto-occipital fasciculus the anterior thalamic radiation and the dorsal cingulum bundle. Plasma NfL concentration also correlated with cortical thinning in a portion of the right medial prefrontal cortex and of the right lateral orbitofrontal cortex. These results support the hypothesis that blood NfL levels reflect the global level of neurodegeneration in bvFTD and help to advance our understanding of the association between this blood biomarker for FTD and the disease process

The e+e- -> Z gamma gamma -> q q gamma gamma Reaction at LEP and Constraints on Anomalous Quartic Gauge Boson Couplings

The cross section of the process e^+ e^- -> Z \gamma\gamma -> qq \gamma \gamma is measured with 215 pb^-1 of data collected with the L3 detector during the final LEP run at centre-of-mass energies around 205 GeV and 207 GeV. No deviation from the Standard Model expectation is observed. The full data sample of 713 pb^-1, collected above the Z resonance, is used to constrain the coefficients of anomalous quartic gauge boson couplings to: -0.02 GeV^-2 < a_0/\Lambda^2 < 0.03 GeV^-2 and -0.07 GeV^-2 < a_c/\Lambda^2 < 0.05 GeV^-2, at 95% confidence level