Jan Vermeiren

Validation of a new antiserum directed towards the synthetic c-terminus of the FOS protein in avian species: immunological, physiological and behavioral evidence.

In the past 10 years, the study of the expression of immediate early genes, such as c-fos, in the brain has become a common method for the identification of brain areas involved in the regulation of specific physiological and behavioral functions. The use of this method in avian species has been limited by the paucity of suitable antibodies that cross-react with the FOS protein in birds. We describe in this paper the preparation of an antibody directed against a synthetic fragment of the protein product of the c-fos gene in chickens (Gallus domesticus). We demonstrate that this new antibody can be used in several avian species to study FOS expression induced by a variety of pharmacological, physiological and behavioral stimuli. Western blot studies indicated that this antibody recognizes a protein of the expected size (47 kDa) but also cross reacts to some extent with proteins of lower molecular weight that share sequence homology with FOS (Fos-related antigens). FOS immunocytochemistry was performed with this antibody in four species of birds in three different laboratories utilizing diverse variants of the immunocytochemical procedure. In all cases the antibody provided a reliable identification of the FOS antigen. The new antibody described here appears to be suitable for the study of FOS expression in several different avian species and situations. It is available in substantial amounts and will therefore make it possible to use FOS expression as a tool to map brain activity in birds as has now been done for several years in mammalian species.

Dynamic fiber optic strain measurements and aliasing suppression with a PDA-based spectrometer

Dynamic fiber optic strain measurements at 3.3 kHz were performed employing a photodiode array spectrometer. The occurrence of aliasing components in the spectral data is investigated, and their dependence on the spectrometer integration time is analyzed. A theoretical model describing the aliasing components is discussed and could be confirmed by the experimental data. It is shown that the aliasing components can be partly suppressed by maximizing the duty cycle of the spectrometer.

Simultaneous Interrogation of Multiple Fiber Bragg Grating Sensors Using an Arrayed Waveguide Grating Filter Fabricated in SOI Platform

A novel fiber Bragg grating (FBG) interrogator is demonstrated based on an optimized arrayed waveguide grating (AWG) filter. The AWG response is optimized to achieve large crosstalk between the output channels, which allows simultaneous detection of multiple FBG peaks, using centroid signal processing techniques, without constraints on the minimum FBG peak spectral width. The measured interrogator resolution is 2.5 pm, and the total measurement range is 50 nm. The device is fabricated in a silicon-on-insulator platform and has a footprint of only 2.2 × 1.5 mm. A novel approach to minimize the polarization dependence of the device is proposed and experimentally demonstrated.

Micromachined poly-SiGe bolometer arrays for infrared imaging and spectroscopy

The state-of-the-art characteristics of micromachined polycrystalline SiGe microbolometer arrays are reported. An average NETD of 85 mK at a time constant of 14 ms is already achievable on typical self-supported 50 μm pixels in a linear 64-element array. In order to reach these values, the design optimization was performed based on the performance characteristics of linear 32-, 64- and 128-element arrays of 50-, 60- and 75-μm-pixel bolometers on several detector lots. The infrared and thermal modeling accounting for the read-out properties and self-heating effect in bolometers resulted in improved designs and competitive NETD values of 80 mK on 50 μm pixels in a 160x128 format at standard frame rates and f-number of 1. In parallel, the TCR-to-1/f noise ratio and the mechanical design of the pixels were improved making poly-SiGe a good candidate for a low-cost uncooled thermal array. The technological CMOS-based process possesses an attractive balance between characteristics and price, and allows the micromachining of thin structures, less than 0.2 μm. The resistance and TCR non-uniformity with σ/μ better than 0.2% combined with 99.93% yield are demonstrated. The first lots of fully processed linear arrays have already come from the IMEC process line and the results of characterization are presented. Next year, the first linear and small 2D arrays will be introduced on the market.

Monolithic lead-chalcogenide IR-diode arrays on silicon: fabrication and use in thermal imaging applications

A narrow gap semiconductor layer grown directly on a Si-substrate is the preferable approach to realize large IR-focal plane arrays. We report on our new work on lead chalcogenide photovoltaic IR-detector arrays, grown monolithically on Si (111) substrates using a stacked CaF2/BaF2 buffer layer. The sensor fabrication process is described, and a simple thermal camera system is used to verify the functionality of our arrays. An epitaxial narrow gap lead chalcogenide layer of only 3 micrometers thickness is grown on an 0.3 micrometers thick CaF2/BaF2 buffer layer on Si (111), both using Molecular Beam Epitaxy. Photovoltaic IR-detectors are formed by deposition of a blocking Pb contact on the p-type semiconducting surface. We fabricated staggered linear sensor arrays with up to 2 X 128 pixels and with the cut off ranging from 3 to 12 micrometers . For demonstration, we built up a simple thermal camera using our detector arrays as the IR sensitive element. The read out is done using a new multiplexed direct injection device, capable to store large charge packages and offering individual biasing for each diode. The IR-diodes are fabricated monolithically on the completely finished readout chip.

Deterioration estimation of paintings by means of combined 3D and hyperspectral data analysis

Deterioration of artwork, in particular paintings, can be produced by environmental factors such as temperature fluctuations, relative humidity variations, ultraviolet radiation and biological factors among others. The effects of these parameters produce changes in both the painting structure and chemical composition. While well established analytical methodologies, such as those based in Raman Spectroscopy and FTIR Spectroscopy require the extraction of a sample for its inspection, other approaches such as hyperspectral imaging and 3D scanning present advantages for in-situ, noninvasive analysis of artwork. In this paper we introduce a novel system and the related methodology to acquire process, generate and analyze 4D data of paintings. Our system is based on non-contact techniques and is used to develop analytical tools which extract rich 3D and hyperspectral maps of the objects, which are processed to obtain accurate quantitative estimations of the deterioration and degradation present in the piece of art. In particular, the construction of 4D data allows the identification of risk maps on the painting representation, which can allow the curators and restorers in the task of painting state evaluation and prioritize intervention actions.

Back-gate induced random telegraph signal noise in fully-depleted silicon-on-insulator nMOSFETs

Abstract Back-gate induced Random Telegraph Signal (RTS) noise in the front-channel drain current is demonstrated for the first time experimentally, in fully-depleted Silicon-on-Insulator (SOI) nMOSFETs. The RTS is observed when the back-interface is in accumulation and is absent for zero, or positive back-gate bias. As will be demonstrated, hole-trapping at the back-interface occurs, generating a low-frequency, large-amplitude drain current step. This trapping is related to mobile charges in the back-oxide, which therefore causes a metastable switching of the threshold voltage.

Design, integration, and testing of a compact FBG interrogator, based on an AWG spectrometer

Fiber Bragg Grating or FBG sensors are gaining more and more interest in structural health monitoring of composite materials. Often, the weakest point in such a system is the ingress point of the fiber sensing chain into the composite material. For this reason we have developed a strongly miniaturized FBG interrogator unit with wireless power and data transmission, which can be incorporated in the composite structure. The interrogator is based on an arrayed waveguide grating (AWG) filter fabricated in a SOI technology, which is tailored in such a way to give large cross-talk between neighboring channels. The AWG signals are read by a linear 128 pixel InGaAs array flip-chipped on top of the Photonic Circuit (PIC). The spectrometer unit is completed with a ROIC mounted on the same substrate. The SLED and remaining electronics are integrated on a small and thin substrate and surrounded by the wireless antenna. The interrogator has an overall dimension of 100 mm diameter by max 7 mm height. The power dissipation of the electronics unit is limited to 1.5 W. The unit is capable of measuring strain values as low as 5 micro-strain.

SYDDARTA: new methodology for digitization of deterioration estimation in paintings

The SYDDARTA project is an on-going European Commission funded initiative under the 7th Framework Programme. Its main objective is the development of a pre-industrial prototype for diagnosing the deterioration of movable art assets. The device combines two different optical techniques for the acquisition of data. On one hand, hyperspectral imaging is implemented by means of electronically tunable filters. On the other, 3D scanning, using structured light projection and capturing is developed. These techniques are integrated in a single piece of equipment, allowing the recording of two optical information streams. Together with multi-sensor data merging and information processing, estimates of artwork deterioration and degradation can be made. In particular, the resulting system will implement two optical channels (3D scanning and short wave infrared (SWIR) hyperspectral imaging) featuring a structured light projector and electronically tunable spectral separators. The system will work in the VIS-NIR range (400-1000nm), and SWIR range (900-2500nm). It will be also portable and user-friendly. Among all possible art work under consideration, Baroque paintings on canvas and wooden panels were selected as the project case studies.

3000 pixel linear InGaAs sensor for the Proba-V satellite

We report on the design and development of the large linear SWIR focal plane arrays to be deployed in the multispectral instrument of the Proba-V satellite. These sensors are based on mechanical butting of three InGaAs photodiode arrays with 1024 pixels on 25 μm pitch, forming a nearly continuous line of 3072 pixels. A new read-out integrated circuit (ROIC) for photocurrent integration and signal multiplexing with 1024 inputs was designed and manufactured by stitching due to the length of the chip. The ROIC (XRO3508) includes both correlated double sampling (CDS) and autozero features, enabling a very low Dark Signal Non Uniformity (DSNU) and Photoresponse Non-Uniformity (PRNU) less than 0.5% of the available signal range.