Mesa-isolated GaAs Schottky-barrier photodiodes

The design, fabrication and characterisation of GaAs Schottky-barrier photodiodes with evaporated, free-standing-metal airbridges is reported. The photodiodes were fabricated using all dry-etching techniques. Anisotropic chemically assisted ion beam etching was used to etch vertical sidewall mesas, and isotropic reactive ion etching was used to etch a lateral tunnel. A free-standing-metal airbridge created by the lateral tunnel etch results in isolation of the active area at the same time providing free-standing-metal interconnection to the contact pad.<>     

High pass filter with above IC integrated SrTiO3 high K MIM capacitors

This paper describes realization and characterization of SrTiO₃ (STO) high K MIM capacitors above BiCMOS integrated circuit (IC). These capacitances are connected to IC and are used as coupling capacitors in order to realize a high pass filter. Surface capacitance achieved is 10 nF/mm² with capacitance value of 1.2 nF. The process for STO MIM fabrication does not exceed 400 °C, which is compatible with interconnections. Typical K and dielectric losses values obtained are, respectively 110% and 2%. Yield obtained reaches 83% for capacitors. A functional high pass filter using these STO capacitors was realized in this study. It exhibits a cut-off frequency at 6.5 kHz and a constant gain at higher frequencies of −1.3 dB.     

PSOBLAP: Particle Swarm Optimization-Based Bandwidth and Link Availability Prediction Algorithm for Multipath Routing in Mobile Ad Hoc Networks

Wireless Personal Communications - In mobile ad hoc network (MANET), optimal path identification is the main problem for implementing the Multipath routing technique. MANET desires an efficient...     

Scaling limitations of silicon multichannel recording probes

This paper describes the scaling limitations of multichannel recording probes fabricated for use in neurophysiology using silicon integrated circuit technologies. Scaled silicon probe substrates 8 microns thick and 16 microns wide can be fabricated using boron etch-stop techniques. Theoretical expressions for calculating the thickness and width of silicon substrates have been derived and agree closely with experimental results. The effects of scaling probe dimensions on its strength and stiffness are described. The probe shank dimensions can be designed to vary the strength and stiffness for different applications. The scaled silicon substrates have a fracture stress of about 2 x 10(10) dyn/cm2, which is about six times that of bulk silicon, and are strong and very flexible. Scaling the feature sizes of recording electrode arrays down to 1 micron is possible with less than 1 percent electrical crosstalk between channels.     

FBDR-Fuzzy Based DDoS Attack Detection and Recovery Mechanism for Wireless Sensor Networks

Wireless sensor networks (WSN) is considered as one of the exploring technology for its deployment of the massive number of dedicated sensor nodes which sense the environment and collect the data. The collected data are sent to the sink node through the intermediate nodes. Since the sensors node data are exposed to the internet, there is a possibility of vulnerability in the WSN. The common attack that affects most of the sensor nodes is the Distributed Denial of Services (DDoS) attack. This paper aims to identify the DDoS (Flooding) attack quickly and to recover the data of sensor nodes using the fuzzy logic mechanism. Fuzzy based DDoS attack Detection and Recovery mechanism (FBDR) uses type 1 fuzzy logic to detect the occurrence of DDoS attack in a node. Similarly fuzzy- type 2 is used for the recovery of data from the DDoS attack. Both the type 1 fuzzy-based rule and type 2 fuzzy-based rule perform well in terms of identifying the DDoS attack and recover the data under attack. It also helps to reduce the energy consumption of each node and improves the lifetime of the network. The proposed FBDR scheme is also compared with other related existing schemes. The proposed method saves energy usage by up to 20% compared with the related schemes. The experimental results represent that the FBDR method works better than other similar schemes.

     

A correlation-based approach to calculate rotation and translation of moving cells.

We present a noniterative image cross-correlation approach to track translation and rotation of crawling cells in time-lapse video microscopy sequences. The method does not rely on extracting features or moments, and therefore does not impose specific requirements on the type of microscopy used for imaging. Here we use phase-contrast images. We calculate cell rotation and translation from one image to the next in two stages. First, rotation is calculated by cross correlating the images' polar-transformed magnitude spectra (Fourier magnitudes). Rotation of the cell about any center in the original images results in translation in this representation. Then, we rotate the first image such that the cell has the same orientation in both images, and cross correlate this image with the second image to calculate translation. By calculating the rotation and translation over each interval in the movie, and thereby tracking the cell's position and orientation in each image, we can then map from the stationary reference frame in which the cell was observed to the cell's moving coordinate system. We describe our modifications enabling application to nonidentical images from video sequences of moving cells, and compare this method's performance with that of a feature extraction method and an iterative optimization method.     

Solid-State Electrodes for Multichannel Multiplexed Intracortical Neuronal Recording

Thin-film arrays of extracellular recording electrodes have been developed for use in studies of information processing in neural structures and eventual use in closed-loop control of neural prostheses. These probes consist of a silicon substrate which supports an array of thin-film conductors. The conductors are insulated above and below with deposited dielectrics. The electrode sites are defined by openings in the upper dielectric layer and are inlaid with gold to form low-impedance recording surfaces. The probes are typically 15 pim in thickness with shank widths as narrow as 20 ?m. The probe fabrication process is compatible with the inclusion of signal processing circuitry directly on the probe substrate. A 12 channel on-chip signal processor design with per-channel gain of 100, bandwidth of 100 Hz-6 kHz, multiplexed output, and recording-site impedance check capability is described. The probes have adequate strength to penetrate the gerbil pia-arachnoid layer and have recorded single neuron activity of over 500 ?V peak-to-peak from tip, side, and mid-carrier sites. Signal-to-noise ratios as high as 10:1 have been achieved. An equivalent circuit model for the conducting leads, the recording site, and the electrode-electrolyte interface is described. Development of biocompatible insulation and encapsulation materials for long-term implantation of active probes is underway.     

Active sites for outer-sphere, inner-sphere, and complex multistage electrochemical reactions at polycrystalline boron-doped diamond electrodes (pBDD) revealed with scanning electrochemical cell microscopy (SECCM)

The local rate of heterogeneous electron transfer (HET) at polycrystalline boron-doped diamond (pBDD) electrodes has been visualized at high spatial resolution for various aqueous electrochemical reactions, using scanning electrochemical cell microscopy (SECCM), which is a technique that uses a mobile pipet-based electrochemical cell as an imaging probe. As exemplar systems, three important classes of electrode reactions have been investigated: outer-sphere (one-electron oxidation of ferrocenylmethyltrimethylammonium (FcTMA(+))), inner-sphere (one-electron oxidation of Fe(2+)), and complex processes with coupled electron transfer and chemical reactions (oxidation of serotonin). In all cases, the pattern of reactivity is similar: the entire pBDD surface is electroactive, but there are variations in activity between different crystal facets which correlate directly with differences in the local dopant level, as visualized qualitatively by field-emission scanning electron microscopy (FE-SEM). No evidence was found for enhanced activity at grain boundaries for any of the reactions. The case of serotonin oxidation is particularly interesting, as this process is known to lead to deterioration of the electrodes, because of blocking by reaction products, and therefore cannot be studied with conventional scanning electrochemical probe microscopy (SEPM) techniques. Yet, we have found this system nonproblematic to study, because the meniscus of the scanning pipet is only in contact with the surface investigated for a brief time and any blocking product is left behind as the pipet moves to a new location. Thus, SECCM opens up the possibility of investigating and visualizing much more complex heterogeneous electrode reactions than possible presently with other SEPM techniques.