Customizing MRI-Compatible Multifunctional Neural Interfaces through Fiber Drawing

Fiber drawing enables scalable fabrication of multifunctional flexible fibers that integrate electrical, optical, and microfluidic modalities to record and modulate neural activity. Constraints on thermomechanical properties of materials, however, have prevented integrated drawing of metal electrodes with low-loss polymer waveguides for concurrent electrical recording and optical neuromodulation. Here, two fabrication approaches are introduced: 1) an iterative thermal drawing with a soft, low melting temperature (T_m) metal indium, and 2) a metal convergence drawing with traditionally non-drawable high T_m metal tungsten. Both approaches deliver multifunctional flexible neural interfaces with low-impedance metallic electrodes and low-loss waveguides, capable of recording optically-evoked and spontaneous neural activity in mice over several weeks. These fibers are coupled with a light-weight mechanical microdrive (1 g) that enables depth-specific interrogation of neural circuits in mice following chronic implantation. Finally, the compatibility of these fibers with magnetic resonance imaging is demonstrated and they are applied to visualize the delivery of chemical payloads through the integrated channels in real time. Together, these advances expand the domains of application of the fiber-based neural probes in neuroscience and neuroengineering.     

Multilayer SiC for thermal protection system of space vehicles with decreased thermal conductivity through the thickness

Tape casting combined with layer stacking, debinding and sintering proved to be a suitable technique for processing SiC-based multilayers to be used as thermal protection system for space vehicles. In this paper two methods have been evaluated in order to decrease the thermal conductivity through the thickness of the material: the insertion of layers containing a pore forming agent able to leave residual porosity; the deposition of an external insulating coating made of yttria-partially stabilized zirconia (YPSZ). Both techniques contribute to the reduction of thermal conductivity. The insertion into the multilayered structure of porous layers with a high level of residual porosity halves the thermal conductivity but 25% decrease in bending strength is observed. The fracture surface however shows that highly porous layers activates crack deflection mechanism, increasing fracture energy. The use of an YPSZ coating allows for a less evident reduction of thermal conductivity (from 102 to 75 W/(m K) at room temperature) but good mechanical properties are maintained (340 MPa bending strength).     

Wavelet packet-based EMI signal processing and sourceidentification

Existing techniques for recognizing and identifying disturbed signals waveforms are primarily based on visual inspection. This paper proposes a wavelet packet based technique to perform a feature extraction from the disturbance signal and a classification of the extracted features in order to identify the possible causes of the disturbance. The same wavelet based procedure is applied to signal compression and denoising in order to make the EMC analysis of the data easier     

A Low-Frequency Accurate Cavity Model for Transient Analysis of Power-Ground Structures

With increased operating frequencies and circuit component density, signal and power integrity problems caused by voltage bounces have become more important for high-speed digital systems. This paper presents a systematic macromodeling of power-bus structures based on the cavity model: first, more accurate models are used to describe conductor and dielectric losses, thus improving accuracy at low frequencies; second, a rational model of the overall power/ground structure in the Laplace domain is presented, and third, the rational macromodel is used to identify the dominant poles, and a simplified SPICE-compatible equivalent circuit is synthesized by using only the selected poles. The numerical results confirm the correctness and effectiveness of the method.     

Selective CO-oxidation over Ru-based catalysts in H2-rich gas for fuel cell applications

Topics in Catalysis - Ru-based catalysts supported on A zeolites and alumina were synthesised, characterised (XRD, SEM-EDS, TPR) and tested under realistic conditions for the preferential oxidation...     

Nonorthogonal PEEC formulation for time- and frequency-domain EM and circuit modeling

Electromagnetic solvers based on the partial element equivalent circuit (PEEC) approach have proven to be well suited for the solution of combined circuit and EM problems. The inclusion of all types of Spice circuit elements is possible. Due to this, the approach has been used in many different tools. Most of these solvers have been based on a rectangular or Manhattan representation of the geometries. In this paper, we systematically extend the PEEC formulation to nonorthogonal geometries since many practical EM problems require a more general formulation. Importantly, the model given in this paper is consistent with the classical PEEC model for rectangular geometries. Some examples illustrating the application of the approach are given for both the time and frequency domain.     

PEEC capacitance extraction of 3-D interconnects

As feature size of electronic devices decreases, fast and accurate capacitance extraction has become increasingly critical for verification and analysis as regard as electromagnetic compatibility and signal integrity issues. The partial element equivalent circuit method is implemented for three-dimensional capacitance extraction of interconnects and very large-scale integration circuits with multiple dielectrics. The electric field coupling due to free and bound charges are analysed and modelled separately thus allowing to distinguish their contribution. The proposed approach provides physical insight, totally compatible fast methods for accelerating matrix-vector products, allows an easy treatment of lossy and dispersive dielectrics and is well suited for applying model order reduction techniques     

SPICE equivalent circuits of frequency-domain responses

The paper proposes a method for the synthesis of SPICE-compatible broad-band electrical models of frequency-domain responses approximated by rational functions. First- and second-order equivalent circuits with controlled sources are used as building blocks to generate equivalent circuit representations-totally compatible with commercial circuit solvers - of the frequency-dependent responses. Fundamental properties of the method are discussed and details of its implementation are described. The proposed approach has demonstrated to be suitable for providing equivalent circuits of interconnects, power/ground plane structures and PCB discontinuities.     

Neuropeptide S receptor: recent updates on nonpeptide antagonist discovery

Neuropeptide?S (NPS) is a 20-amino acid peptide of great interest due to its possible involvement in several biological processes, including food intake, locomotion, wakefulness, arousal, and anxiety. Structure-activity relationship studies of NPS have identified key points for structural modifications with the goal of modulating NPS receptor (NPSR) agonist activity or achieving antagonism at the same receptor. Only limited information is available for nonpeptide NPSR antagonists. In the last year, several studies have been reported in literature which present various series of small molecules as antagonists of this receptor. The results allow a comparison of the structures and activities of these molecules, leading to the design of new ligands with increased potency and improved pharmacological and pharmacokinetic profiles. This work presents a brief overview of the available information regarding structural features and pharmacological characterization of published nonpeptide NPSR antagonists.