How Theoretical Simulations Can Address the Structure and Activity of Nanoparticles

Theoretical simulations in the field of heterogeneous catalysis started about two decades ago when the main goal was to understand the activation of small molecules on infinite surfaces. The improvements in the accuracy and the large availability of computers with increasing power have raised the quality of the calculations, the reliability of the results and prompted the interest in their predictions. Such changes have also allowed the study of nanoparticles by the combined investigation of different facets or by taking into account the complete structures. As for the reactivity, theoretical simulations allow the comparison of different synthetic conditions within the same approximation. Consequently, large systematic studies with the same theoretical models can provide databases for properties, structures, prove and disprove hypothetical reaction paths, identify intermediates, and complete the understanding of reaction mechanisms. In some cases, simulations support and give explanations to experiments but new emerging aspects such as the prediction of new properties or the analysis of complex systems are possible. Several challenges are ahead the simulations of reactions on nanoparticles: (i) how to drive the synthesis to achieve the desired architectures and (ii) how to stabilize the active phase under reaction conditions.     

Individual metering of energy in existing buildings: potential and critical aspects

Individual metering of energy in flats is a real opportunity to save energy and money for the occupiers of collective-ownership buildings with centralised heating systems. The individual management of energy, through such devices, make users more responsible and also stimulates them to implement energy retrofit interventions in their flats. The use of individual metering systems in existing apartments, however, could have some critical aspects. The purpose of this paper is to analyse the application of individual energy systems in existing collective-ownership residential buildings, highlighting the critical aspects and providing practical solutions to overcome them. A study has been made of an individual metering application in an existing residential block of flats located in Milan (Italy) with poor thermal insulation between the various dwellings themselves and for the outside walls of the building. Although a net reduction of 50.4 % in the global costs for winter heating, obtained exclusively through plant-modification works, represents an optimum goal for energy savings, the study highlight some critical aspects. The savings for different apartments differ greatly and depend upon the criteria chosen for burden sharing. This study shows that the phenomenon of “heat theft” can prove to be important and provides the possibility of reducing to zero the quota of expenses from consumption whilst still benefiting from comfortable temperatures. Once the problems have been identified, the paper then proposes solutions to overcome them through a revision of the criteria for the allocation of energy costs.     

Calibration and validation of a solar thermal system model in Modelica

Recent advancements in the domain of modeling physical processes offer opportunities to use equation based modeling environments, such as Modelica, for the simulation of building heating, ventilation, and air-conditioning (HVAC) systems. The current work demonstrates Modelica capabilities in a case study of real building solar thermal system simulation. The simulated system is part of an innovative ENERGYbase building, designed according to the so called Passivhaus standard. Model calibration and validation procedure is developed to include optimization based parametric adjustments of component models using the monitoring data during a single week. The calibrated system adequately reproduces half a year of real system operation. Future work will concentrate on application of the developed calibration and validation methodology in the whole year overall building energy simulation.     

Temperature and energy performance of refrigerated retail display and commercial catering cabinets under test conditions

An analysis of the performance of well freezers, chest freezers, frozen and chilled door cabinets (solid or glass door) and open fronted chilled cabinets under EN441 test conditions demonstrated that maximum temperatures in cabinets were generally in the most exposed (to ambient) areas and that minimum temperatures were located in the least exposed areas. Detailed positions of maximum and minimum temperature varied between cabinet types. In chest freezers 95% of the maximum temperature positions were located in the top layer and 95% of the minimum temperature positions were located in the middle layer of the cabinets. In full door frozen cabinets the maximum temperature position was in the majority of cases on the top shelf (64%) with most maximum packs being at the front of the top shelf (53%). In the chilled full door cabinets 94% of the maximum temperature packs were situated at the front of the cabinet. In open fronted cabinets the majority of maximum temperature packs (97%) were located at the front of the cabinet, the largest number (60%) being at the front of the base of the cabinet. In well cabinets the majority of maximum temperature packs (81%) were located in the top layer of the cabinet and the majority (91%) of minimum temperature packs were located in the bottom of the cabinet.Large differences in energy consumed by cabinets of similar size and temperature performance were found indicating that large reductions in energy and CO₂ emissions could be achieved by selection of the most efficient cabinets.     

Shell Perturbations of an Acoustic Thermometer Determined from Speed of Sound in Gas Mixtures

With the goal of achieving a better understanding of gas–shell coupling perturbations in the acoustic resonators used at INRiM for the determination of the Boltzmann constant, we measured the variation of their acoustic and microwave resonances induced by changing the composition of a binary He–Ar mixture which filled the cavity at constant temperature and pressure. As a consequence of the progressive dilution of a sample of initially pure He with Ar, the radial acoustic modes of the resonator spanned decreasing frequency intervals, partially overlapping, for several modes. In addition to the expected breathing mode of the shell, the results evidenced the presence of several other shell resonances at lower and higher frequencies, confirming that the elastic response of the assembled resonator significantly differs from that of a simple spherical shell. Experimental results are reported for two resonators which differ in design, dimensions, and constructing material. In spite of their being preliminary and susceptible of significant improvement, these results favor the interpretation of acoustic thermometry measurements with pure gases.     

Solid–Liquid Equilibria for the CO<Subscript>2</Subscript> + R23 and N<Subscript>2</Subscript>O + R23 Systems

A recently built experimental setup was employed for the estimation of the solid–liquid equilibria of alternative refrigerant systems. In this paper two binaries, i.e., carbon dioxide + trifluoromethane (CO₂ + R23) and nitrous oxide + trifluoromethane (N₂O + R23), were studied down to temperatures of 117 K. In order to check the reliability of the apparatus, the triple points of the pure fluids contained in the mixture were measured, revealing good consistency with the literature. The results obtained for the mixtures were interpreted by means of the Schröder equation.     

Luminescence dating of quaternary deposits in geology in Brazil

In the present work, systematic dating by luminescence methods has been done on 50 Quaternary geological samples within the study area of S?o Paulo State, Brazil. Bleaching experiments showed that residual TL intensity of 375 degrees C peak, of the quartz, was obtained after 10 h of sunlight exposition. Intensities decays of the 325 and 375 degrees C TL peaks can be fitted using second order exponential equation. Paleodose values were evaluated using regeneration methods with multiple aliquots. Samples dated indicate preliminary ages varying from 9 +/- 1 to 935 +/- 130 ka for colluvio-elluvial deposits, and from 17 +/- 2 to 215 +/- 30 ka for alluvial deposits of the study area. They cover four peneplained surfaces shaped during the Quaternary: I (1000-400 ka), II (400-120 ka), III (120-10 ka) and IV (10 ka until today), in decreasing order.     

Enzymatic cross-linking of human recombinant elastin (HELP) as biomimetic approach in vascular tissue engineering

The use of polymers naturally occurring in the extracellular matrix (ECM) is a promising strategy in regenerative medicine. If compared to natural ECM proteins, proteins obtained by recombinant DNA technology have intrinsic advantages including reproducible macromolecular composition, sequence and molecular mass, and overcoming the potential pathogens transmission related to polymers of animal origin. Among ECM-mimicking materials, the family of recombinant elastin-like polymers is proposed for drug delivery applications and for the repair of damaged elastic tissues. This work aims to evaluate the potentiality of a recombinant human elastin-like polypeptide (HELP) as a base material of cross-linked matrices for regenerative medicine. The cross-linking of HELP was accomplished by the insertion of cross-linking sites, glutamine and lysine, in the recombinant polymer and generating ε-(γ-glutamyl) lysine links through the enzyme transglutaminase. The cross-linking efficacy was estimated by infrared spectroscopy. Freeze-dried cross-linked matrices showed swelling ratios in deionized water (≈2500%) with good structural stability up to 24 h. Mechanical compression tests, performed at 37°C in wet conditions, in a frequency sweep mode, indicated a storage modulus of 2/3 kPa, with no significant changes when increasing number of cycles or frequency. These results demonstrate the possibility to obtain mechanically resistant hydrogels via enzymatic crosslinking of HELP. Cytotoxicity tests of cross-linked HELP were performed with human umbilical vein endothelial cells, by use of transwell filter chambers for 1-7 days, or with its extracts in the opportune culture medium for 24 h. In both cases no cytotoxic effects were observed in comparison with the control cultures. On the whole, the results suggest the potentiality of this genetically engineered HELP for regenerative medicine applications, particularly for vascular tissue regeneration.     

Hysteretic Critical State in Coplanar Josephson Junction with Monolayer Graphene Barrier

Coplanar Al/graphene/Al junctions fabricated on the same graphene sheet deposited on silicon carbide (SiC), show robust Josephson coupling at subKelvin temperature, when the separations between the electrodes is below 400 nm. Remarkably, a hysteretic Critical State sets in when ramping an orthogonal magnetic field, with a sudden collapse of the Josephson critical current I _c when turning the field on, and a revival of I _c when inverting the sweep. Similar hysteresis can be found in granular superconducting films which may undergo the Berezinskii-Kosterlitz-Thouless transition. Here, we give quantitative arguments to prove that this odd behavior of the magnetoconductance gives evidence for an incipient Berezinskii-Kosterlitz-Thouless transition with drift and pinning of fluctuating free vortices induced by the current bias.     

Rheumatoid nodules: MR/pathological correlation

A 62-year-old female who had a complaint of palpitation was diagnosed as bicuspid aortic stenosis and left single coronary artery by the echocardiographic examination, cardiac catheterization study and coronary artery angiography. Aortic valve replacement was performed and the patient was discharged 22 days after surgery with good post-operative course. Preoperative coronary artery angiography was important in the case of aortic valvular disease.