Spectral relationships for atmospheric correction. I. Validation of red and near infra-red marine reflectance relationships.

The present study provides an extensive overview of red and near infra-red (NIR) spectral relationships found in the literature and used to constrain red or NIR-modeling schemes in current atmospheric correction (AC) algorithms with the aim to improve water-leaving reflectance retrievals, ρw(λ), in turbid waters. However, most of these spectral relationships have been developed with restricted datasets and, subsequently, may not be globally valid, explaining the need of an accurate validation exercise. Spectral relationships are validated here with turbid in situ data for ρw(λ). Functions estimating ρw(λ) in the red were only valid for moderately turbid waters (ρw(λNIR) < 3.10(-3)). In contrast, bounding equations used to limit ρw(667) retrievals according to the water signal at 555 nm, appeared to be valid for all turbidity ranges presented in the in situ dataset. In the NIR region of the spectrum, the constant NIR reflectance ratio suggested by Ruddick et al. (2006) (Limnol. Oceanogr. 51, 1167-1179), was valid for moderately to very turbid waters (ρw(λNIR) < 10(-2)) while the polynomial function, initially developed by Wang et al. (2012) (Opt. Express 20, 741-753) with remote sensing reflectances over the Western Pacific, was also valid for extremely turbid waters (ρw(λNIR) > 10(-2)). The results of this study suggest to use the red bounding equations and the polynomial NIR function to constrain red or NIR-modeling schemes in AC processes with the aim to improve ρw(λ) retrievals where current AC algorithms fail.

Spectral relationships for atmospheric correction. II. Improving NASA's standard and MUMM near infra-red modeling schemes.

Spectral relationships, reflecting the spectral dependence of water-leaving reflectance, ρw(λ), can be easily implemented in current AC algorithms with the aim to improve ρw(λ) retrievals where the algorithms fail. The present study evaluates the potential of spectral relationships to improve the MUMM [Ruddick et al., 2006, Limnol. Oceanogr. 51, 1167-1179] and standard NASA [Bailey et al., 2010, Opt. Express 18, 7521-7527] near infra-red (NIR) modeling schemes included in the AC algorithm to account for non-zero ρw(λNIR), based on in situ coastal ρw(λ) and simulated Rayleigh corrected reflectance data. Two modified NIR-modeling schemes are investigated: (1) the standard NASA NIR-modeling scheme is forced with bounding relationships in the red spectral domain and with a NIR polynomial relationship and, (2) the constant NIR ρw(λ) ratio used in the MUMM NIR-modeling scheme is replaced by a NIR polynomial spectral relationship. Results suggest that the standard NASA NIR-modeling scheme performs better for all turbidity ranges and in particular in the blue spectral domain (percentage bias decreased by approximately 50%) when it is forced with the red and NIR spectral relationships. However, with these new constraints, more reflectance spectra are flagged due to non-physical Chlorophyll-a concentration estimations. The new polynomial-based MUMM NIR-modeling scheme yielded lower ρw(λ) retrieval errors and particularly in extremely turbid waters. However, including the polynomial NIR relationship significantly increased the sensitivity of the algorithm to errors on the selected aerosol model from nearby clear water pixels.

[Pathologic characteristics of the most frequent peripheral nerve tumors]. / Aspects histopathologiques des principales tumeurs des nerfs périphériques.

Benign tumors of the peripheral nerves come from ectodermic tissues. This chapter describes the most common forms: the schwannomas and the neurofibromas. Schwannomas have two possible patterns of cells: Antoni A and B types. Neurofibromas are most often associated with neurofibromatosis NF1 and may be localized, diffuse, or plexiform. The benign tumor structures account for the fact that they can be removed with or without preserving the concerned nerve. Malignant tumors (malignant peripheral sheath tumors) come from degeneration of neurofibromas in two out of three cases and have a poor prognosis.

Single Day 2 embryo versus blastocyst-stage transfer: a prospective study integrating fresh and frozen embryo transfers.

BACKGROUND: Whether extended culture allowing selection of embryos with high development potential has any advantage over cleavage-stage embryo transfer remains a matter of debate. Among the currently unsolved questions, the cumulative delivery rate resulting from fresh and frozen embryo transfers needs to be taken into account in both strategies. The aim of our study was, therefore, to compare the efficacy of single embryo transfer either on Day 2 or on Day 5/6 combining fresh and frozen embryo transfers. METHODS: A prospective study including 478 couples assigned on a voluntary basis to undergo elective single embryo transfer (eSET, n = 243) on Day 2 or single blastocyst transfer (SBT, n = 235) on Day 5/6 was performed. The primary outcome measurement was the cumulative delivery rate including fresh and frozen-thawed cycles in both groups. RESULTS: The delivery rate per cycle following fresh embryo transfer was significantly higher in the SBT group compared with the eSET group (P < 0.01). Conversely, frozen embryo and/or blastocyst transfers tended to result in a higher number of deliveries in the eSET compared with the SBT group. Altogether, the cumulative delivery rate per couple, including fresh and frozen embryo transfers, was similar between the two groups (37.9% versus 34.2% in the SBT and eSET groups, respectively). CONCLUSIONS: The observed cumulative delivery rates in this study do not allow us to take a position in favor of SBT or eSET. An improvement in blastocyst cryopreservation may change this attitude.

Senescence in Podospora anserina: a possible role for nucleic acid interacting proteins suggested by the sequence analysis of a mitochondrial DNA region specifically amplified in senescent cultures.

In Podospora anserina, the phenomenon of senescence was previously shown to be correlated with the presence of a senescence-specific DNA (sen-DNA) resulting from the amplification of some regions (alpha, beta, gamma, epsilon) of the mitochondrial chromosome. The beta region gives rise to sen-DNAs with variable sizes and junctions which share a 1,100-bp common sequence. Here we report the complete nucleotide sequence of one 4-kb beta sen-DNA. Included in the sequence are a large part of the first intron open reading frame (ORF) of the gene ND4L and three short unidentified ORFs more precisely located in the common beta region. The primary structure of the polypeptide possibly encoded by one of them is very similar to the glycine-rich domains present in various single-stranded DNA-binding proteins. The comparison of the information content of this beta sen-DNA with that of other previously sequenced sen-DNAs suggests that the role in the senescence process attributed to the sen-DNAs could be related to the overproduction of a variety of proteins which interact with nucleic acids.

Hypotrophic and dying-back nerve fibers in Friedreich's ataxia.

Eight patients with Friedreich's ataxia showed profound reduction in the density of large myelinated fibers in sural nerve biopsies. The density of small myelinated fibers was normal, but the axonal size and myelin thickness were reduced. Demyelination, presumably secondary to axonal dysfunction, was observed in 3% of the isolated fibers. There was axonal degeneration, including dying-back axons isolated in three specimens, in 2.6% of the isolated fibers. The low incidence of degenerating fibers did not account for loss of myelinated fibers in children. There is probably a defect in maturation of fibers, followed by a dying-back process.