Coupled dynamics in the physics of molten salt reactors

The present paper is devoted to the analysis of the coupled thermo-fluid and neutronic dynamics of fast fluid-fuel multiplying nuclear systems. A completely coupled model is needed since in some fast reactors designs, the velocity pattern could be very complicated and strongly affected by the neutron dynamics via the heat source from fission reactions. Furthermore, the neutron dynamics is strongly affected by the thermohydrodynamics via the motion of precursors and by feedback effects. The methods typical of solid fuel reactors of previous generations are not sufficient to handle these more highly coupled concepts. In the preset paper, we consider the coupling between neutronics and thermohydrodynamics with simple but realistic hypotheses assumed to model the evolution of all the variables involved in the calculation. The numerical scheme used represents the current state of the art in the solution of non-linear systems: the Newton–Krylov algorithm. Several calculations are presented to demonstrate the ability of the methods described here to study the behavior of molten salt reactors in both steady state and transient situations.     

AMnO3 (A=La, Nd, Sm) and Sm1−xSrxMnO3 perovskites as combustion catalysts: structural, redox and catalytic properties

Catalytic combustion of methane has been investigated over AMnO₃ (A = La, Nd, Sm) and Sm_1−xSr_xMnO₃ (x = 0.1, 0.3, 0.5) perovskites prepared by citrate method. The catalysts were characterized by chemical analysis, XRD and TPR techniques. Catalytic activity measurements were carried out with a fixed bed reactor at T = 623–1023 K, space velocity = 40 000 N cm³ g⁻¹ h⁻¹, CH₄ concentration = 0.4% v/v, O₂ concentration = 10% v/v.

Specific surface areas of perovskites were in the range 13–20 m² g⁻¹. XRD analysis showed that LaMnO₃, NdMnO₃, SmMnO₃ and Sm_1−xSr_xMnO₃ (x = 0.1) are single phase perovskite type oxides. Traces of Sm₂O₃ besides the perovskite phase were detected in the Sm_1−xSr_xMnO₃ catalysts for x = 0.3, 0.5. Chemical analysis gave evidence of the presence of a significant fraction of Mn(IV) in AMnO₃. The fraction of Mn(IV) in the Sm_1−xSr_xMnO₃ samples increased with x. TPR measurements on AMnO₃ showed that the perovskites were reduced in two steps at low and high temperature, related to Mn(IV) → Mn(III) and Mn(III) → Mn(II) reductions, respectively. The onset temperatures were in the order LaMnO₃ > NdMnO₃ > SmMnO₃. In Sm_1−xSr_xMnO₃ the Sr substitution for Sm caused the formation of Mn(IV) easily reducible to Mn(II) even at low temperature. Catalytic activity tests showed that all samples gave methane complete conversion with 100% selectivity to CO₂ below 1023 K. The activation energies of the AMnO₃ perovskites varied in the same order as the onset temperatures in TPR experiments suggesting that the catalytic activity is affected by the reducibility of manganese. Sr substitution for Sm in SmMnO₃ perovskites resulted in a reduction of activity with respect to the unsubstituted perovskite. This behaviour was related to the reduction of Mn(IV) to Mn(II), occurring under reaction conditions, hindering the redox mechanism.     

Biomarkers in Prostate Cancer Diagnosis: From Current Knowledge to the Role of Metabolomics and Exosomes

Early detection of prostate cancer (PC) is largely carried out using assessment of prostate-specific antigen (PSA) level; yet it cannot reliably discriminate between benign pathologies and clinically significant forms of PC. To overcome the current limitations of PSA, new urinary and serum biomarkers have been developed in recent years. Although several biomarkers have been explored in various scenarios and patient settings, to date, specific guidelines with a high level of evidence on the use of these markers are lacking. Recent advances in metabolomic, genomics, and proteomics have made new potential biomarkers available. A number of studies focused on the characterization of the specific PC metabolic phenotype using different experimental approaches has been recently reported; yet, to date, research on metabolomic application for PC has focused on a small group of metabolites that have been known to be related to the prostate gland. Exosomes are extracellular vesicles that are secreted from all mammalian cells and virtually detected in all bio-fluids, thus allowing their use as tumor biomarkers. Thanks to a general improvement of the technical equipment to analyze exosomes, we are able to obtain reliable quantitative and qualitative information useful for clinical application. Although some pilot clinical investigations have proposed potential PC biomarkers, data are still preliminary and non-conclusive.     

Microfluidic chip with temporal and spatial concentration generation capabilities for biological applications

This paper details the control and operation of a new microfluidic chip whose architecture of three sets of five fluidic channels is capable of generating both spatially and temporally varying concentration gradients. It is housed in a Petri dish where the cells are first seeded and preconditioned and then exposed to the biochemical gradients produced by the chip. The flow in the fluidic channels is regulated by crisscrossing control channels with the contact interfaces acting as valves. The pneumatic control and operation of the chip have been automated with LABVIEW and thoroughly tested. The results for the single channel case have also been validated by a comprehensive computational model whose formulation is described.     

Biological Effects of 25 to 150 GHz Radiation After In Vitro Exposure of Human Fibroblasts: a Comparison of Experimental Results

In this paper, we present a comprehensive discussion of the results obtained after in vitro exposure of human fetal fibroblasts and human adult fibroblasts to pulsed radiation in a wide band between 100 and 150 GHz and to continuous wave radiation at 25 GHz. In order to assess potential effects of exposure, the genome integrity, cell cycle, cytological ultrastructure, and proteins expression were evaluated.     

Turning an organic semiconductor into a low-resistance material by ion implantation

We report on the effects of low energy ion implantation on thin films of pentacene, carried out to investigate the efficacy of this process in the fabrication of organic electronic devices. Two different ions, Ne and N, have been implanted and compared, to assess the effects of different reactivity within the hydrocarbon matrix. Strong modification of the electrical conductivity, stable in time, is observed following ion implantation. This effect is significantly larger for N implants (up to six orders of magnitude), which are shown to introduce stable charged species within the hydrocarbon matrix, not only damage as is the case for Ne implants. Fully operational pentacene thin film transistors have also been implanted and we show how a controlled N ion implantation process can induce stable modifications in the threshold voltage, without affecting the device performance.     

Disperse and cationic dyes from 2-(o,m, p-Aminophenyl)oxazolo [4,5-b]pyridine

2-(o,m,p-Aminophenyl)oxazolo[4,5-b]pyridines were diazotized and coupled with N,N-disubstituted anilines, giving monoazo dyes suitable for polyamide fabrics. Some of the dyes were quaternized to give cationic dyes for acrylic fibres. The colour of dyed materials was assessed in terms of tristimulus colorimetry. Electronic spectra of the amines and NMR spectra of the cationic dyes are briefly discussed.     

Electron sources utilizing thin CsBr coatings

We present experimental results obtained in solid Cu targets coated with ～18 nm thick CsBr films operating in a reflection mode. The results indicate a factor of 50X increase in quantum efficiency relative to uncoated Cu samples. The CsBr/Cu samples are very robust allowing brief exposures to air without a substantial decrease in quantum efficiency and lifetime. The results are very encouraging from the point of view of reliable high efficiency electron sources for lithography or other applications including free electron lasers.     

Tectonic and magmatic evolution of the active volcanic front in El Salvador: insight into the Berlín and Ahuachapán geothermal areas

In El Salvador, Central America, active deformation takes the form of a major dextral strike-slip fault system, the El Salvador Fault Zone, resulting from the oblique subduction of the Cocos Plate. The fault system is laterally discontinuous, being subdivided into different major en-echelon segments that partially overlap to form pull-apart structures. Volcanic activity is spatially confined to the fault segments and absent in the intervening pull-apart basins; no significant temporal gap exists in the erupted products, at least during the Plio-Quaternary. Detailed analyses within the geothermal fields of Berlín and Ahuachapán have revealed important volcano-structural and petrologic differences between the two areas. In the Berlín area active deformation is controlled by the regional transcurrent stress field, resulting in the development of systems of right-lateral E–W-trending strike-slip faults. Conversely, the structural setting of the Ahuachapán area is more complex, reflecting an interaction among different stress fields. Berlín products exhibit a marked geochemical and isotopic homogeneity indicating the presence of a single magmatic system. At Ahuachapán, on the other hand, the rocks display significant variations in both Sr isotopes and the LILE/HFSE ratios: this area is characterized by multiple volcanic centres, fed by different magma batches that reach the surface without reciprocal interactions in shallow reservoirs. Thus, the characteristics of the volcanic products at Berlín and Ahuachapán reflect their different tectonic settings, with important implications for geothermal investigations.