Parasitic Effects Reduction for Wafer-Level Packaging of RF-Mems

In RF-MEMS packaging, next to the protection of movable structures, optimization of package electrical performance plays a very important role. In this work, a wafer-level packaging process has been investigated and optimized in order to minimize electrical parasitic effects. The RF-MEMS package concept used is based on a wafer-level bonding of a capping silicon substrate to an RF-MEMS wafer. The capping silicon substrate resistivity, substrate thickness and the geometry of through-substrate electrical interconnect vias have been optimized using finite-element electromagnetic simulations (Ansoft HFSS). Test structures for electrical characterization have been designed and after their fabrication, measurement results will be compared with simulations.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

Anomalous conductivity tensor in the Dirac semimetal Na_3Bi

Na3Bi is a Dirac semimetal with protected nodes that may be sensitive to the breaking of time-reversal invariance in a magnetic field B. We report experiments which reveal that both the conductivity and resistivity tensors exhibit robust anomalies in B. The resistivity $\rho_{xx}$ is B-linear up to 35 T, while the Hall angle exhibits an unusual profile approaching a step-function. The conductivities $\sigma_{xx}$ and $\sigma_{xy}$ share identical power-law dependences at large B. We propose that these significant deviations from conventional transport result from an unusual sensitivity of the transport lifetime to B. Comparison with Cd3As2 is made.Comment: 8 pages, 5 figure

A method for aligning RNA secondary structures and its application to RNA motif detection

BACKGROUND: Alignment of RNA secondary structures is important in studying functional RNA motifs. In recent years, much progress has been made in RNA motif finding and structure alignment. However, existing tools either require a large number of prealigned structures or suffer from high time complexities. This makes it difficult for the tools to process RNAs whose prealigned structures are unavailable or process very large RNA structure databases. RESULTS: We present here an efficient tool called RSmatch for aligning RNA secondary structures and for motif detection. Motivated by widely used algorithms for RNA folding, we decompose an RNA secondary structure into a set of atomic structure components that are further organized by a tree model to capture the structural particularities. RSmatch can find the optimal global or local alignment between two RNA secondary structures using two scoring matrices, one for single-stranded regions and the other for double-stranded regions. The time complexity of RSmatch is O(mn) where m is the size of the query structure and n that of the subject structure. When applied to searching a structure database, RSmatch can find similar RNA substructures, and is capable of conducting multiple structure alignment and iterative database search. Therefore it can be used to identify functional RNA motifs. The accuracy of RSmatch is tested by experiments using a number of known RNA structures, including simple stem-loops and complex structures containing junctions. CONCLUSION: With respect to computing efficiency and accuracy, RSmatch compares favorably with other tools for RNA structure alignment and motif detection. This tool shall be useful to researchers interested in comparing RNA structures obtained from wet lab experiments or RNA folding programs, particularly when the size of the structure dataset is large