Glass-Like Phonon Dynamics and Thermal Transport in a GeTe Nano-Composite at Low Temperature.

In this work, the experimental evidence of glass-like phonon dynamics and thermal conductivity in a nanocomposite made of GeTe and amorphous carbon is reported, which is of interest for microelectronics, and specifically phase change memories. It is shown that, the total thermal conductivity is reduced by a factor of three at room temperature with respect to pure GeTe, due to the reduction of both electronic and phononic contributions. This latter, similarly to glasses, is small and weakly increasing with temperature between 100 and 300 K, indicating a mostly diffusive thermal transport and reaching a value of 0.86(7) Wm-1K-1 at room temperature. A thorough investigation of the nanocomposite's phonon dynamics reveals the appearance of an excess intensity in the low energy vibrational density of states, reminiscent of the Boson peak in glasses. These features can be understood in terms of an enhanced phonon scattering at the interfaces, due to the presence of elastic heterogeneities, at wavelengths in the 2-20 nm range. The findings confirm recent simulation results on crystalline/amorphous nanocomposites and open new perspectives in phonon and thermal engineering through the direct manipulation of elastic heterogeneities.

Enhancement and anticipation of the Ioffe-Regel crossover in amorphous/nanocrystalline composites.

Nanocomposites made of crystalline nanoinclusions embedded in an amorphous matrix are at the forefront of current research for energy harvesting applications. However, the microscopic mechanisms leading alternatively to an effectively reduced or enhanced thermal transport still escape understanding. In this work, we present a molecular dynamics simulation study of model systems, where for the first time we combine a microscopic investigation of phonon dynamics with the macroscopic thermal conductivity calculation, to shed light on thermal transport in these materials. We clearly show that crystalline nanoinclusions represent a novel scattering source for vibrational waves, modifying the nature of low energy vibrations and significantly anticipating the propagative-to-diffusive crossover (Ioffe-Regel), usually located at energies of few THz in amorphous materials. Moreover, this crossover position can be tuned by changing the elastic contrast between nanoinclusions and the matrix, and anticipated by a factor as large as 10 for a harder inclusion. While the propagative contribution to thermal transport is drastically reduced, the calculated thermal conductivity is not significantly affected in the chosen system, as the diffusive contribution dominates heat transport when all phonons are thermally populated. These findings allow finally to understand the panoply of contradictory results reported on thermal transport in nanocomposites and give clear indications to the characteristics that the parent phases should have for efficiently reducing heat transport in a nanocomposite.

Localization of a novel autosomal recessive non-syndromic hearing impairment locus DFNB63 to chromosome 11q13.3-q13.4.

Hereditary hearing impairment is the most genetically heterogeneous trait known in humans. So far, 50 published autosomal recessive non-syndromic hearing impairment (ARNSHI) loci have been mapped, and 23 ARNSHI genes have been identified. Here, we report the mapping of a novel ARNSHI locus, DFNB63, to chromosome 11q13.3-q13.4 in a large consanguineous Tunisian family. A maximum LOD score of 5.33 was obtained with microsatellite markers D11S916 and D11S4207. Haplotype analysis defined a 5.55 Mb critical region between microsatellite markers D11S4136 and D11S4081. DFNB63 represents the sixth ARNSHI locus mapped to chromosome 11. We positionally excluded MYO7A from being the DFNB63-causative gene. In addition, the screening of two candidate genes, SHANK2 and KCNE3, failed to reveal any disease-causing mutations.

Porous silicon as functionalized material for immunosensor application.

Recently, for sensor application, porous silicon has received a great deal of attention due to the high specific surface area and the easy fabrication using some established processes of the usual silicon technology. We herein, report the development of a novel immunosensors based on porous silicon for antigen detection. The multilayer immunosensor structure was fabricated following the successive steps: APTS self-assembled monolayer (SAM) layer, glutaaldehyde linker, anti-rabbit IgG binding. The insulating properties of the aminopropyl-triethoxysilane (APTS) monolayer were studied with cyclic voltammetry and the molecular structure was characterized with Fourier-transform infrared (FTIR) technique. The binding between antibody and different antigen concentration (rabbit IgG) was monitored by measuring the capacitance-voltage curve of the antibody functionalized EIS structure. A detection limit of 10ng/ml of antigen can be detected.

Refined mapping of the autosomal recessive non-syndromic deafness locus DFNB13 using eight novel microsatellite markers.

The locus for a type of an autosomal recessive non-syndromic deafness (ARND), DFNB13, was previously mapped to a 17-cm interval of chromosome 7q34-36. We identified two consanguineous Tunisian families with severe to profound ARND. Linkage analyses with microsatellites surrounding the previously identified loci detected linkage with markers corresponding to the DFNB13 locus in both families. Haplotype analyses assigned this locus to a 3.2-Mb region between markers D7S2468 and D7S2473. In order to refine this interval, we identified nine dinucleotide repeats in the 7q34 region. To investigate the polymorphism of these repeats, a population study of 74 unrelated individuals from different regions of Tunisia was carried out. Our results demonstrated that eight of the nine repeats are polymorphic. The average number of alleles at these informative loci was 9.12 with a polymorphism information content of 0.71. Little evidence for linkage disequilibrium between some marker pairs was found. Haplotype analysis using these microsatellites refined the DFNB13 interval to an area of 2.2 Mb between the D7S5377 and D7S2473. In order to identify the DFNB13 gene, we sequenced and eliminated three candidate genes. Other known and predicted genes are being screened for deafness-causing mutations.