Two new passive safety systems for LWR applications

In a research activity that SIET has been conducting for years about safety systems for light water reactors (LWRs), attention has been paid to developing two passive injection systems representing an innovative solution in mitigating the consequences of loss of coolant accidents. Both systems allow the completely passive injection of cold water into a pressurised vessel. They are triggered by a low-level signal and work on the base of phenomena like natural circulation and condensation. The simplest system, Sistema Iniezione Passiva 1 (SIP-1), injects water contained in a tank into a circuit at the same pressure as the circuit. The most complex system, injection cyclic system (ICS), injects cold water, by filling cyclically a proper tank with the water stored in an atmospheric pressure pool. Thanks to the ENEA sponsorship, this activity has been conducted in three steps: the definition of the conceptual design of the systems; the application of the Relap5 code to simulate their behaviour; and the proposal of their specific applications to pressurised and boiling LWR. In this paper, both systems are presented in their structural and operating characteristics together with the main results of the code application for their simulation. Some proposals of application of SIP-1 and ICS to pressurised water reactors and boiling water reactors are also shown. The developments and reached goals of the prosecution of the research are also summarised here, together with future needs.     

Perceptually weighted optical flow for motion-based segmentation inMPEG-4 paradigm

In the MPEG-4 paradigm, the sequence must be described in terms of meaningful objects. This meaningful, high-level representation should emerge from low-level primitives such as optical flow and prediction error which are the basic elements of previous-generation video coders. The accuracy of the high-level models strongly depends on the robustness of the primitives used. It is shown how perceptual weighting in optical flow computation gives rise to better motion estimates which consistently improve motion-based segmentation compared to equivalent unweighted motion estimates     

The VCG-CCII: a novel building block and its application to capacitance multiplication

A new current mode building block named voltage and current gain second generation current conveyor (VCG-CCII) is introduced. The voltage and current buffers of the standard CCII are replaced by voltage and current amplifiers with tunable gains so to obtain an extremely flexible and versatile building block. The VCG-CCII can be used in place of the standard CCII in impedance conversion applications so to utilize only one active component. A circuit implementation in a standard 0.35 μm CMOS process is presented and used to multiply, as an example, a 10 pF capacitor by a factor tunable from 1 up to about 3100, achieving a capacitance multiplication for more than 6 decades frequency range (from 0.15 to 865 KHz for the highest multiplication factor).     

The composition,structure and optical properties of weakly magnetic Co-containing amorphous Si and Ge films

This study investigated the composition, structure and optical properties of amorphous SiCo and GeCo films. The samples were prepared by radio frequency sputtering. Films were deposited with Co atomic concentrations in the range of 1.7–10.3 at.%. After deposition, the films were submitted to thermal treatments up to 900 °C and investigated by energy dispersive X-ray spectrometry, X-ray diffraction, Raman scattering and optical transmission spectroscopy. Additionally, magnetic force microscopy measurements were performed at room temperature. For comparison purposes, Co-free samples were also prepared, annealed and characterized following a similar procedure. The experimental results indicated the following: (1) the Co atoms were effectively and homogeneously incorporated into the amorphous hosts; (2) the as-deposited films (either pure or containing Co) were essentially amorphous; (3) annealing the films at high temperatures induced crystallization; (4) after crystallization, non-magnetic CoSi₂ (silicide) and CoGe₂ (germanide) phases were identified in the Co-containing Si and Ge films, respectively; (5) the optical properties of the films were significantly affected by the insertion of Co and by the annealing temperature; and (6) the samples exhibited a reduced magnetic signal at room temperature. These experimental observations were systematically studied, which are presented and discussed in this report.     

Considerations about sample-size sensitivity of a family of editednearest-neighbor rules

The edited nearest neighbor classification rules constitute a valid alternative to k-NN rules and other nonparametric classifiers. Experimental results with synthetic and real data from various domains and from different researchers and practitioners suggest that some editing algorithms (especially, the optimal ones) are very sensitive to the total number of prototypes considered. This paper investigates the possibility of modifying optimal editing to cope with a broader range of practical situations. Most previously introduced editing algorithms are presented in a unified form and their different properties (acid not just their asymptotic behavior) are intuitively analyzed. The results show the relative limits in the applicability of different editing algorithms.     

Branched-chain Amino Acid Biosensing Using Fluorescent Modified Engineered Leucine/Isoleucine/Valine Binding Protein

A novel fluorescence sensing system for branched-chain amino acids (BCAAs) was developed based on engineered leucine/isoleucine/valine-binding proteins (LIVBPs) conjugated with environmentally sensitive fluorescence probes. LIVBP was cloned from Escherichia coli and Gln149Cys, Gly227Cys, and Gln254Cys mutants were generated by genetic engineering. The mutant LIVBPs were then modified with environmentally sensitive fluorophores. Based on the fluorescence intensity change observed upon the binding of the ligands, the MIANS-conjugated Gln149Cys mutant (Gln149Cys-M) showed the highest and most sensitive response. The BCAAs Leu, Ile, and Val can each be monitored at the sub-micromolar level using Gln149Cys-M. Measurements were also carried out on a mixture of BCAFAs and revealed that Gln149Cys-M-based measurement is not significantly affected by the change in the molar ratio of Leu, Ile and Val in the sample. Its high sensitivity and group-specific molecular recognition ability make the new sensing system ideally suited for the measurement of BCAAs and the determination of the Fischer ratio, an indicator of hepatic disease involving metabolic dysfunction.     

Screening of Peptide Ligands for Pyrroloquinoline Quinone Glucose Dehydrogenase Using Antagonistic Template-Based Biopanning

We have developed a novel method, antagonistic template-based biopanning, for screening peptide ligands specifically recognizing local tertiary protein structures. We chose water-soluble pyrroloquinoline quinone (PQQ) glucose dehydrogenase (GDH-B) as a model enzyme for this screening. Two GDH-B mutants were constructed as antagonistic templates; these have some point mutations to induce disruption of local tertiary structures within the loop regions that are located at near glucose-binding pocket. Using phage display, we selected 12-mer peptides that specifically bound to wild-type GDH-B but not to the antagonistic templates. Consequently, a peptide ligand showing inhibitory activity against GDH-B was obtained. These results demonstrate that the antagonistic template-based biopanning is useful for screening peptide ligands recognizing the specific local tertiary structure of proteins.     

Protein Aggregation Landscape in Neurodegenerative Diseases: Clinical Relevance and Future Applications

Intrinsic disorder is a natural feature of polypeptide chains, resulting in the lack of a defined three-dimensional structure. Conformational changes in intrinsically disordered regions of a protein lead to unstable β-sheet enriched intermediates, which are stabilized by intermolecular interactions with other β-sheet enriched molecules, producing stable proteinaceous aggregates. Upon misfolding, several pathways may be undertaken depending on the composition of the amino acidic string and the surrounding environment, leading to different structures. Accumulating evidence is suggesting that the conformational state of a protein may initiate signalling pathways involved both in pathology and physiology. In this review, we will summarize the heterogeneity of structures that are produced from intrinsically disordered protein domains and highlight the routes that lead to the formation of physiological liquid droplets as well as pathogenic aggregates. The most common proteins found in aggregates in neurodegenerative diseases and their structural variability will be addressed. We will further evaluate the clinical relevance and future applications of the study of the structural heterogeneity of protein aggregates, which may aid the understanding of the phenotypic diversity observed in neurodegenerative disorders.     

Chiral PAF agonists: synthesis, theoretical analysis of their stereoelectronic properties and structure activity relationships

A series of chiral PAF agonists were synthesized. Modifications at the PAF structure were undertaken as far as the C2 substituents and the onium head groups are concerned. In parallel, molecular modelling studies including a MOPAC geometry optimization and the analysis of the electrostatic potential were performed on the newly synthesized and on already known PAF agonists, in order to gain a better insight into the stereoelectronic features required for interaction with the PAF receptor.