High-overtone Bulk-Acoustic Resonator gravimetric sensitivity: towards wideband acoustic spectroscopy

In the context of direct detection sensors with compact dimensions, we investigate the gravimetric sensitivity of High-overtone Bulk Acoustic Resonators, through modeling of their acoustic characteristics and experiment. The high frequency characterizing such devices is expected to induce a significant effect when the acoustic field boundary conditions are modified by a thin adlayer. Furthermore, the multimode spectral characteristics is considered for wideband acoustic spectroscopy of the adlayer, once the gravimetric sensitivity dependence of the various overtones is established. Finally, means of improving the gravimetric sensitivity by confining the acoustic field in a low acoustic-impedance layer is theoretically established.Comment: 9 pages, 10 figures in J. Appl. Phys. 201

Shear effects in lateral piezoresponse force microscopy at 180∘^\circ ferroelectric domain walls

In studies using piezoresponse force microscopy, we observe a non-zero lateral piezoresponse at 180$^\circ$ domain walls in out-of-plane polarized, c-axis-oriented tetragonal ferroelectric Pb(Zr$_{0.2}$Ti$_{0.8}$)O$_3$ epitaxial thin films. We attribute these observations to a shear strain effect linked to the sign change of the $d_{33}$ piezoelectric coefficient through the domain wall, in agreement with theoretical predictions. We show that in monoclinically distorted tetragonal BiFeO$_3$ films, this effect is superimposed on the lateral piezoresponse due to actual in-plane polarization, and has to be taken into account in order to correctly interpret the ferroelectric domain configuration.Comment: 4 pages, 3 figure

LiTaO3/Silicon Composite Wafers for the Fabrication of Low Loss Low TCF High Coupling Resonators for Filter Applications

AbstractSAW devices are widely used for radio-frequency (RF) telecommunication filtering and the number of SAW filters, resonators or duplexers is still increasing in RF stage of cellular phones. Therefore, a strong effort is still dedicated to reduce as much as possible their sensitivity to environmental parameter and more specifically to temperature. Bounding processes have been developed at FEMTO-ST and CEA-LETI using either Au/Au or direct bonding techniques for the fabrication of composite wafers combining materials with very different thermoelastic properties, yielding innovative solutions for about-zero temperature coefficient of frequency (TCF) bulk acoustic wave devices. In the present work, this approach has been applied to (YXl)/42∘ lithium tantalate plates, bounded onto (100) silicon wafers and thinned down to 25μm. The leading idea already explored by other groups as mentioned in introduction consists in impeding the thermal expansion of the piezoelectric material using silicon limited expansion. 2GHz resonators have been built on such plates and tested electrically and thermally, first by tip probing. A dramatic reduction of the TCF is observed for all the tested devices, allowing to reduce the thermal drift of the resonators down to a few ppm.K-1 within the standard temperature range. We then propose an analysis of the frequency-temperature behavior of the device to improve the resonator design to use these wafers for industrial applications

The first survey using high-throughput sequencing of cereal and barley yellow dwarf viruses in Irish spring and winter barley crops

Yellow dwarf viruses (YDVs) are the most economically important plant viruses impacting cereal production worldwide and include viruses from the genus Luteovirus (e.g., barely yellow dwarf virus (BYDV)-PAV, BYDV-PAS, BYDV-MAV, BYDV-kerII, BYDV-kerIII) and Polerovirus (e.g., cereal yellow dwarf virus (CYDV)-RPV, CYDV-RPS). Until now, much of our knowledge on YDVs infecting Irish barley crops (Hordeum vulgare L.) has come from serological assays; however, due to cross-reactivity it can be difficult to discriminate between viruses of different species. In this study, we have carried out a high-throughput sequencing survey of symptomatic crops, positive with serological assays, to identify YDVs infecting Irish spring and winter barley crops and establish reference genomes to support further development of molecular surveillance tools. In total, RNA was extracted from 45 symptomatic crop samples that were collected across Ireland over 2 yr and sequenced following rRNA depletion. Three samples of barley plants from BYDV-infected aphid colonies were also included. BYDV-MAV was identified in all field samples sequenced. This confirms previous evidence based on serological assays that BYDV-MAV is the dominant YDV in Irish barley crops. We have also identified BYDV-PAS in 29% of symptomatic field samples, the first report of this species in Ireland. In addition, BYDV-PAV was also found, and crop samples with mixed infections were common; although in mixed infections the greatest proportion of YDV reads originated from BYDV-MAV. Finally, CYDV-RPS, the more severe variant of CYDV-RPV belonging to the genus Polerovirus, was identified in a single sample. The complete genomes, assembled from this first sequence-based survey, will enable the development of molecular surveillance tools with greater virus specificity, to further support the Irish aphid and YDV monitoring network

Physical Principles of Retroviral Integration in the Human Genome

Some retroviruses, including HIV, insert their DNA in a non-random manner in the host genome through a poorly understood selection mechanism. Here the authors develop a biophysical model of retroviral integration, identifying previously unnoticed universal principles that regulate this phenomenon