High Performance, Low-Dose Radiography Systems for Space and Remote Site Applications

Medical imaging applications using X- and gamma-rays have reached outstanding levels of complexity and performance, thanks to technology achievements in the fields of radiography, tomography and high resolution synchrotron devices. The operability of the related instrumentation resides in the availability of highly qualified specialists, as well as of medical doctors for diagnoses and treatment. This is a problem for personnel working in difficult ambient conditions as can be found in remote sites like Arctica, Antarctica and under-populated, desolated or mountainous regions on Earth. Astronauts, during long permanence at the Space Station or on future mission to Mars are potentially subject to risks such as traumas, fractures or diseases which would require semi-automated, easy-to-handle application of X-ray radiographic devices. For this purpose, the possible use of imaging instrumentation based on solid state detectors is discussed with special regard to CdZnTe pixel devices, now available with sub-mm resolution. The use of these semiconductor detectors will also allow to perform image diagnostics at much lower doses compared to the current plate-based radiographic techniques.     

Extracting local mechanical properties of steel bars by means of instrumented flat indentation

The evaluation of local mechanical properties of metal parts can be used for the prediction of forming and cutting forces during the following working stages. In order to show the feasibility of using indentation tests for work-piece characterization, C40 steel disks were cut from an extruded bar and machined by facing operation under different conditions. Indentation tests were carried out with 1 mm and 2 mm diameter indenters made of tungsten carbide; yield strength and indentation pressure values were extracted along the diameter of each disk. For the first time, indentation results were used to extract local mechanical properties of steel bars as a function of their process conditions: it was observed that small pins gave information on the effect of the machining process whereas large pins were more suitable to evaluate work-piece bulk properties.     

Reliable indirect competitive ELISA used for a survey of ochratoxin A in green coffee from the North of Paraná State, Brazil.

The performance of an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) based on a monoclonal antibody (mAb) for ochratoxin A (OTA) detection was evaluated in a comparative study with high-performance liquid chromatography (HPLC) analysis using 68 freshly harvested coffee samples from the North of Paraná State, Brazil. The anti-OTA mAb showed high specificity and low cross-reactivity with OTA analogues (OTB and OTalpha), but cross-reacted with OTC. This ic-ELISA showed a detection limit of 3.75 ngg-1 sample, when compared to 0.80 ngg-1 by HPLC, with an ic-ELISA/HPLC correlation coefficient of 0.90. As regards OTA analysis of these coffee samples, natural contamination was detected in 10 samples (14.7%) by both methods, where the ic-ELISA values (range 3.9-7.3 ngg-1) were 1.1 to 1.6-fold higher than HPLC data (2.7-4.7 ngg-1). Five samples (7.4%) were OTA positive (range 0.84-1.30 ngg-1) only by HPLC assay, probably due to the higher detection limit reached by ic-ELISA. OTA was undetectable in 53 samples (77.9%) by both methods, while all positive samples (range 0.84-7.30 ngg-1) showed OTA levels lower than 8 ngg-1 (maximum limit recommended by the European Union). The matrix interference of green coffee was minimized by dilution of sample extracts before carrying out the ELISA assay. This mAb-based ic-ELISA can be effectively applied for OTA screening in coffee, because it is simple, sensitive and sample preparation is easy.     

Assessment of the susceptibility to hydrogen embrittlement. II: Effect of specimen geometry on delayed failure time of 38 NiCrMo 4 steel

Delayed failure tests, in which suitable samples were cathodically charged with hydrogen (current density 8 mA·cm^?2) in 0.1N sulphuric acid, while under sustained tensile loads, were carried out on a low alloyed Ni-Cr steel (UNI 38 NiCrMo 4). The effect of the geometry on the delayed failure time was assessed using specimens with different diameters (2,3,4 mm) and different lengths (13, 23, 33 mm). The experimental results showed that the specimen geometry does not influence the material behaviour: only a minor effect on the threshold stress value was noted due to diameter variations.     

Isoenzymatic forms of human cytidine deaminase

Cytidine deaminase (CDA) purified from human placenta revealed the presence of five isoenzymatic forms that differ only in their isoelectric point. Since human cytidine deaminase exists in two variants (CDA 1 and CDA 2) with a non-conservative amino acid substitution at codon 27, in this work we demonstrate that these two variants may combine together in vitro, giving five CDA isoforms as observed in vivo from human placenta. For this purpose, each of the two forms of CDA was purified close to homogeneity and dissociated into monomers in the presence of a small amount of sodium dodecyl sulfate as a dissociating agent. The monomers were mixed together and subjected to anion-exchange chromatography and to chromatofocusing analysis in order to visualize the formation of the five isoforms. Furthermore, for both CDA 1 and CDA 2 some substrates and inhibitors of CDA were assayed, with the aim of demonstrating different kinetic behavior between the two natural variants.     

A 5-GHz highly integrated receiver front-end

In this paper a radio front-end for a IEEE 802.11a and HIPERLAN2 sliding-IF receiver is presented. The circuit, implemented in a low-cost 46-GHz-f _T silicon bipolar process, includes a variable-gain low noise amplifier and a double-balanced mixer. Thanks to monolithic LC filters and on-chip single-ended-to-differential conversion of the RF signal, the proposed solution does not require the expensive image rejection filter and an external input balun. The receiver front-end exhibits a 4.3-dB noise figure and a power gain of 21 dB, providing an image rejection ratio higher than 50 dB. By using a 1-bit gain control, it achieves an input 1-dB compression point of −11 dBm, while drawing only 22 mA from a 3-V supply voltage.     

Robot vision with cellular neural networks: a practical implementation of new algorithms

Cellular neural networks (CNNs) are well suited for image processing due to the possibility of a parallel computation. In this paper, we present two algorithms for tracking and obstacle avoidance using CNNs. Furthermore, we show the implementation of an autonomous robot guided using only real‐time visual feedback; the image processing is performed entirely by a CNN system embedded in a digital signal processor (DSP). We successfully tested the two algorithms on this robot. Copyright © 2006 John Wiley & Sons, Ltd.     

Application of near (NIR) infrared and mid (MIR) infrared spectroscopy as a rapid tool to classify extra virgin olive oil on the basis of fruity attribute intensity

A sensory analysis of 112 virgin olive oils was performed by a fully trained taste panel. The samples were divided in “defective” and “not defective” on the basis of their olfactory attributes. Then, the “not defective” samples were classified into “low”, “medium” and “high” according to the fruity aroma intensity perceived by assessors. All samples were also analysed by FT-NIR and FT-IR spectroscopy and processed by classification methods (LDA and SIMCA). The results showed that NIR and MIR spectroscopy coupled with statistical methods are an interesting technique compared with traditional sensory assessment in classifying olive oil samples on the basis of the fruity attribute. The prediction rate varied between 71.6% and 100%, as average value. The spectroscopic methods, combined with chemometric strategies, could represent a reliable, cheap and fast classification tool, able to draw a complete fingerprint of a food product, describing its intrinsic quality attributes, that include its sensory attributes.     

Single thermoplastic pellet molding by means of diode laser for micromolding application

An innovative system for thermoplastic micromolding is presented. A completely transparent mold is used, and a diode laser is used as heating source. Laser heating is performed on a single thermoplastic pellet positioned inside the mold between two glass plates. A very low force is necessary for shaping. Molding tests were performed on commercial ABS and several process parameters were investigated such as laser power, interaction time, focalization condition, and support material properties. High pellet formability was observed in all the cases. Using nontransparent pellet supports it is possible to increase molding efficiency even if the risk of polymer degradation increases. A master curve can be fabricated for molding test results providing a correct comparison among the different process conditions. POLYM. ENG. SCI., 47:168–173, 2007. © 2007 Society of Plastics Engineers