6,218 research outputs found
Statistical Estimation of Mechanical Parameters of Clarinet Reeds Using Experimental and Numerical Approaches
A set of 55 clarinet reeds is observed by holography, collecting 2 series of
measurements made under 2 different moisture contents, from which the resonance
frequencies of the 15 first modes are deduced. A statistical analysis of the
results reveals good correlations, but also significant differences between
both series. Within a given series, flexural modes are not strongly correlated.
A Principal Component Analysis (PCA) shows that the measurements of each series
can be described with 3 factors capturing more than of the variance: the
first is linked with transverse modes, the second with flexural modes of high
order and the third with the first flexural mode. A forth factor is necessary
to take into account the individual sensitivity to moisture content. Numerical
3D simulations are conducted by Finite Element Method, based on a given reed
shape and an orthotropic model. A sensitivity analysis revels that, besides the
density, the theoretical frequencies depend mainly on 2 parameters: and
. An approximate analytical formula is proposed to calculate the
resonance frequencies as a function of these 2 parameters. The discrepancy
between the observed frequencies and those calculated with the analytical
formula suggests that the elastic moduli of the measured reeds are frequency
dependent. A viscoelastic model is then developed, whose parameters are
computed as a linear combination from 4 orthogonal components, using a standard
least squares fitting procedure and leading to an objective characterization of
the material properties of the cane \textit{Arundo donax}
Dynamics of Vaccinium myrtillus patches in mountain spruce forest
International audienceThe dynamics of Vaccinium myrtillus (bilberry) patches were studied in spruce (Picea abies) forest at the higher montane and lower subalpine level in the Tarentaise valley (Savoy, France). Although aerial parts of the shrub may give some indication of age and density of the patches, the annual growth and death of rhizomes are better indicators of patch dynamics. In some cases, dead and young rhizomes may occur simultaneously in the same patch, indicating that growth and death proceed continuously on the inside of dense patches. At mountain sites, slope position of plants significantly influences rhizome growth. A theoretical model of growth of bilberry patches is proposed which takes into account the anisotropic influence of slope and the postulated independence of different rhizome units belonging to the same individual
Effect of Nd substitution on the magnetic order in Ce_xNd_{1-x}B_6 solid solutions
Neutron powder diffraction measurements have been performed on
Ce_xNd_{1-x}B_6 (x = 0.5, 0.6, 0.7, and 0.8) solid solutions to determine the
type of magnetic order occurring in these compounds as a result of the
interplay between magnetic dipole exchange and antiferroquadrupolar
interactions. In the Ce-rich range, the sequence of two magnetic phases, with
an incommensurate order [k = (1/4 -\delta, 1/4 -\delta, 1/2)] forming below T N
followed by a lock-in--type transition at lower temperature, is quite similar
to that reported earlier for Ce_xPr_{1-x} B_6. For x = 0.5, on the other hand,
the same antiferromagnetic order as in pure NdB6 first occurs at TN, then
coexists with an incommensurate component below the lower transition
temperature. These results are in good agreement with previous resistivity
measurements and support the idea that Ce and Nd magnetic moments in this
system can be relatively decoupled.Comment: 7 page
A Strategy for Multiple Immunophenotyping by Image Cytometry: Model Studies Using Latex Microbeads Labeled with Seven Streptavidin-Bound Fluorochromes
Multiple immunophenotyping is aimed at identifying several cell populations in a single labeling procedure by their ability to bind combinations of specific labeled antibodies. The present work demonstrates the simultaneous discrimination by using image cytometry of aminomethylcoumarin acetate (AMCA), Lucifer yellow (LY), fluorescein isothiocyanate (FITC), R-phycoerythrin (PE), PE-Texas red tandem (Red613), peridinin-chlorophyll protein (PerCP), and allophycocyanin (APC), which were all bound to latex beads as streptavidin-conjugated fluorochromes. This has been the result of a step-by-step optimization of the several factors affecting the sensitivity and specificity of multiple immunofluorescence analysis. First, 14 streptavidin-conjugated fluorochromes were evaluated by using spectrofluorometry. A primary selection was then made of ten spectrally separable dyes that could be evaluated by using image cytometry. These dyes were bound to latex particles, and specific filter combinations were assembled to minimize crosstalk between fluorophores while preserving sufficient fluorescence intensity and counting statistics. Potential probe associations were then assessed by measuring the emissions of all fluorochromes that were detected by each filter combination. The resulting crosstalk matrix served as the basic tool both for final selection of the optimal filter combination and for dye set (composed, in this case, of the seven fluorochromes described above) and for mathematical correction of residual spectral overlap. Next, an image cytometry system was adapted to collect seven images of matched brightness with the selected combination of excitation/emission filters and dichroic mirrors. Finally, seven-parameter synthetic images were generated by digital image processing
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