Decision Support System of Innovative High-Temperature Latent Heat Storage for Waste Heat Recovery in the Energy-Intensive Industry

Reductions in energy consumption, carbon footprint, equipment size, and cost are key objectives for the forthcoming energy-intensive industries roadmaps. In this sense, solutions such as waste heat recovery, which can be replicated into different sectors (e.g., ceramics, concrete, glass, steel, aluminium, pulp, and paper) are highly promoted. In this line, latent heat thermal energy storage (TES) contributes as an innovative technology solution to improve the overall system efficiency by recovering and storing industrial waste heat. To this end, phase-change material (PCM) selection is assisted through a decision-support system (DSS). A simplified tool based on the MATLAB(R) model, based on correlations among the most relevant system parameters, was developed to prove the feasibility of a cross-sectorial approach. The research work conducted a parametric analysis to assess the techno-economic performance of the PCM-TES solution under different working conditions and sectors. Additionally, a multicriteria assessment was performed comparing the tool outputs from metal alloys and inorganic hydrated PCM salts. Overall, the inorganic PCMs presented higher net economic and energy savings (up to 25, 000 euro/yr; 480 MWh/yr), while metal alloys involved promising results, shorter cycles, and competitive economic ratios; its commercial development is still limited

The Role of Hydrogen Bonds in the Stabilization of Silver-Mediated Cytosine Tetramers

Peer reviewe

A QM/MM approach for the study of monolayer-protected gold clusters

We report the development and implementation of hybrid methods that combine quantum mechanics (QM) with molecular mechanics (MM) to theoretically characterize thiolated gold clusters. We use, as training systems, structures such as Au25(SCH2-R)18 and Au38(SCH2-R)24, which can be readily compared with recent crystallographic data. We envision that such an approach will lead to an accurate description of key structural and electronic signatures at a fraction of the cost of a full quantum chemical treatment. As an example, we demonstrate that calculations of the 1H and 13C NMR shielding constants with our proposed QM/MM model maintain the qualitative features of a full DFT calculation, with an order-of-magnitude increase in computational efficiency.Comment: Journal of Materials Science, 201

First enantioseparation and circular dichroism spectra of Au38 clusters protected by achiral ligands

Bestowing chirality to metals is central in fields such as heterogeneous catalysis and modern optics. Although the bulk phase of metals is symmetric, their surfaces can become chiral through adsorption of molecules. Interestingly, even achiral molecules can lead to locally chiral, though globally racemic, surfaces. A similar situation can be obtained for metal particles or clusters. Here we report the first separation of the enantiomers of a gold cluster protected by achiral thiolates, Au38(SCH2CH2Ph)24, achieved by chiral high-performance liquid chromatography. The chirality of the nanocluster arises from the chiral arrangement of the thiolates on its surface, forming 'staple motifs'. The enantiomers show mirror-image circular dichroism responses and large anisotropy factors of up to 4×10−3. Comparison with reported circular dichroism spectra of other Au38 clusters reveals that the influence of the ligand on the chiroptical properties is minor

ANÁLISIS DE LA SATISFACCIÓN DEL USUARIO EN CENTROS DE SALUD DEL PRIMER NIVEL DE ATENCIÓN EN LA PROVINCIA DE CÓRDOBA, ARGENTINA.

Objective: To identify users´ satisfaction about services provide for health centers in the province of Cordoba. Method: Surveys was implemented to the health centers´ users in the the province of Cordoba, asking about sociodemographic aspects, type of health care, motive of consultation, accessibility and general opinion about care received. The information collected was processed and analyzed according to the nature of the variable and comparisons were made by ANOVA and for data categorized coefficient of contingency was utilized (significance level 0.05). Results: Geographic access was considered acceptable by respondents as the waiting time and the conditions buildings. The professional performance during care, the link between the practitioner and users and the service provided by the health center were factors valued by respondents. Conclusion: The analysis of users´satisfaction of health centers is important to provide valid information for generate opportune answers and to optimize the sanitary resources.Objetivo: Identificar el nivel de satisfacción de los destinatarios de los centros de salud de la provincia de Córdoba. Método: Se implementó encuestas a los destinatarios de los centros de salud de la provincia de Córdoba indagando acerca de aspectos sociodemográficos, tipo de asistencia sanitaria, motivo de consulta, accesibilidad y opinión general de la atención recibida. La información recabada fue procesada y analizada de acuerdo a la naturaleza de la variable y las comparaciones se efectuaron por ANOVA y para datos categorizados se utilizó coeficiente de contingencia (nivel de significación 0,05). Resultados: El acceso geográfico fue considerado aceptable por los encuestados al igual que el tiempo de espera y las condiciones edilicias. El desempeño profesional durante la atención, el vínculo establecido entre el profesional y el destinatario y el servicio brindado por el centro de salud fueron factores valorizados por los encuestados. Conclusión: El análisis de la satisfacción de los destinatarios de los centros de salud es importante para proporcionar información válida para generar respuestas oportunas y optimizar los recursos sanitarios

Current Applications of Computational Chemistry in JACS

Article discussing molecules, mechanisms, and materials and current applications of computational chemistry in the Journal of the American Chemical Society (JACS)

Electronic Structure and Bonding of Icosahedral Core-Shell Gold-Silver Nanoalloy Clusters Au_(144-x)Ag_x(SR)_60

Atomically precise thiolate-stabilized gold nanoclusters are currently of interest for many cross-disciplinary applications in chemistry, physics and molecular biology. Very recently, synthesis and electronic properties of "nanoalloy" clusters Au_(144-x)Ag_x(SR)_60 were reported. Here, density functional theory is used for electronic structure and bonding in Au_(144-x)Ag_x(SR)_60 based on a structural model of the icosahedral Au_144(SR)_60 that features a 114-atom metal core with 60 symmetry-equivalent surface sites, and a protecting layer of 30 RSAuSR units. In the optimal configuration the 60 surface sites of the core are occupied by silver in Au_84Ag_60(SR)_60. Silver enhances the electron shell structure around the Fermi level in the metal core, which predicts a structured absorption spectrum around the onset (about 0.8 eV) of electronic metal-to-metal transitions. The calculations also imply element-dependent absorption edges for Au(5d) \rightarrow Au(6sp) and Ag(4d) \rightarrow Ag(5sp) interband transitions in the "plasmonic" region, with their relative intensities controlled by the Ag/Au mixing ratio.Comment: 4 figure

Chemical analysis of the superatom model for sulfur-stabilized gold nanoparticles

The superatom model for nanoparticle structure is shown to be inadequate for the prediction of the thermodynamic stability of gold nanoparticles. The observed large HOMO-LUMO gaps for stable nanoparticles predicted by this model are, for sulfur-stabilized gold nanoparticles, attributed to covalent interactions of the metal with thiyl adsorbate radicals rather than ionic interactions with thiolate adsorbate ions, as is commonly presumed. In particular, gold adatoms in the stabilizing layer are shown to be of Au(0) nature, subtle but significantly different from the atoms of the gold core owing to the variations in the proportion of gold-gold and gold-sulfur links that form. These interactions explain the success of the superatom model in describing the electronic structure of both known and informatory nanoparticle compositions. Nanoparticle reaction energies are, however, found not to correlate with the completion of superatom shells