400 research outputs found

    Low-E paints enhanced building components: Performance, limits and research perspectives

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    In the latest years, different solutions have been developed in order to increase the energy performance of opaque building envelopes as far as the heat losses are concerned. Most of them are mainly focused on the bulk properties of materials and are aimed at reaching very low values of thermal conductivity, i.e., super insulating materials. Contemporarily research has been carried out aimed at exploiting the low emissivity in order to reduce the radiative heat transfer between surfaces separated by cavities and, if applied as an internal coating, in order to increase the indoor thermal comfort. In this paper, several solutions that have been experimentally investigated in the latest two years by the authors are presented

    Dynamic Insulation Systems: Experimental Analysis on a Parietodynamic Wall

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    This paper shows the results of an extensive experimental campaign on a ventilated opaque double skin façade based on hollow clay bricks. The winter thermal performances of the dynamic insulated systems were investigated on two different full scale façade configurations through an experimental campaign in double climatic chamber and guarded heat flow meter apparatus. The laboratory tests on dynamic insulated façade (DIF) in both exhaust and supply configurations show respectively an effective reduction of heat losses and the capability of pre-heat the supply air passing across the ventilated external channel. The results confirm the extra insulation offered by the ventilated gap, which allows for a reduction of the wall insulation thickness, providing heat loss reduction and high level of indoor air quality in thin wall constructio

    Laboratory Vs Field Performance of Innovative Thermal Insulating Plasters

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    Thermal insulating plasters and renders are becoming a popular solution for the energy retrofit of existing and historic buildings because of their suitability/compatibility with the existing masonry supports. However, as for most of the insulating products, the actual performance of these materials might significantly differ from the one determined with simplified methods (EN ISO 6946 standard) that are commonly adopted by the designers. In this study, an overview of the latest Authors researches that involve three different thermal insulating plasters, containing respectively perlite, vegetal and aerogel aggregates, are presented. The developed plasters were characterized in the laboratory and successively applied in three demonstration buildings. From the in-field thermal monitoring activities, all the analysed thermal insulating plasters showed a decrease in the thermal performance between 25 and 30% if compared to the laboratory measurements

    -In silico functional characterization of a double histone fold domain from the Heliothis zea virus 1

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    BACKGROUND: Histones are short proteins involved in chromatin packaging; in eukaryotes, two H2a-H2b and H3-H4 histone dimers form the nucleosomal core, which acts as the fundamental DNA-packaging element. The double histone fold is a rare globular protein fold in which two consecutive regions characterized by the typical structure of histones assemble together, thus originating a histone pseudodimer. This fold is included in a few prokaryotic histones and in the regulatory region of guanine nucleotide exchange factors of the Sos family. For the prokaryotic histones, there is no direct structural counterpart in the nucleosomal core particle, while the pseudodimer from Sos proteins is very similar to the dimer formed by histones H2a and H2b RESULTS: The absence of a H3-H4-like histone pseudodimer in the available structural databases prompted us to search for proteins that could assume such fold. The application of several secondary structure prediction and fold recognition methods allowed to show that the viral protein gi|22788712 is compatible with the structure of a H3-H4-like histone pseudodimer. Further in silico analyses revealed that this protein module could retain the ability of mediating protein-DNA interactions, and could consequently act as a DNA-binding domain. CONCLUSION: Our results suggest a possible functional role in viral pathogenicity for this novel double histone fold domain; thus, the computational analyses here reported will be helpful in directing future biochemical studies on gi|22788712 protein

    Thermal Performance Assessment of an Opaque Ventilated Façade in the Summer Period: Calibration of a Simulation Model through in-field Measurements

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    In recent years, several studies have been performed to evaluate the actual contribute of Opaque Ventilated Façades (OVF) as far as the energy efficiency of buildings in the summer period is concerned. In this framework an experimental real-scale module of an OVF was built and tested. Results demonstrated a reduction of ~58% of the thermal load obtained by using a OVF with respect to the unventilated façade configuration. In this paper the experimental measurements were used to calibrate dynamic simulations using ESP-r software, in order to identify the input factors and the key issues mainly impacting on the results discrepancy

    Vacuum Insulation Panels: Analysis of the Thermal Performance of Both Single Panel and Multilayer Boards

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    The requirements for improvement in the energy efficiency of buildings, mandatory in many EU countries, entail a high level of thermal insulation of the building envelope. In recent years, super-insulation materials with very low thermal conductivity have been developed. These materials provide satisfactory thermal insulation, but allow the total thickness of the envelope components to be kept below a certain thickness. Nevertheless, in order to penetrate the building construction market, some barriers have to be overcome. One of the main issues is that testing procedures and useful data that are able to give a reliable picture of their performance when applied to real buildings have to be provided. Vacuum Insulation Panels (VIPs) are one of the most promising high performing technologies. The overall, effective, performance of a panel under actual working conditions is influenced by thermal bridging, due to the edge of the panel envelope and to the type of joint. In this paper, a study on the critical issues related to the laboratory measurement of the equivalent thermal conductivity of VIPs and their performance degradation due to vacuum loss has been carried out utilizing guarded heat flux meter apparatus. A numerical analysis has also been developed to study thermal bridging effect when VIP panels are adopted to create multilayer boards for building applications

    Coupling VIPs and ABPs: Assessment of Overall Thermal Performance in Building Wall Insulation

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    Super Insulating Materials (SIMs) such as Vacuum Insulation Panels (VIPs) and Aerogel Based Products (ABPs), are characterised by lower thermal conductivities if compared with traditional insulating materials. The objective of the present work is to suggest a new technical solution to reduce the thermal bridging effects in buildings SIMs assemblies. A typological façade where VIPs and ABPs are coupled was numerically analysed to assess the global average thermal transmittance. Moreover results were compared with common solutions based on VIPs coupled with traditional insulating materials (EPS, MDF), considering both thermal and economic aspects

    The effect of different materials joint in Vacuum Insulation Panels

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    During recent years the use of Vacuum Insulation Panels in buildings applications has been improved, because of their both higher performances and lower thickness compared to traditional insulation materials. These performances are due to the interior vacuum degree, which represent also the main problem connected with the applications of this technological solution in buildings constructions: to maintain the vacuum condition the panels are enclosed in an envelope layer, characterized by an higher thermal conductivity. Moreover they have to be assembled to each other or to additional different joint materials in practical building application, generating a thermal bridging effect. The aim of present work is to analyse the critical aspects related to this insulation technology for building application. An experimental campaign through heat flow meter apparatus was carried out with the purpose of assessing the decrease of performance due to the thermal bridges effects considering different joint materials in VIPs assemblies

    The Effect of Temperature on Thermal Performance of Fumed Silica Based Vacuum Insulation Panels for Buildings

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    Vacuum Insulation Panels are characterized by very low thermal conductivity, which makes them alluring for building and civil sectors. However, considering the structure and composition of these materials, their application in buildings may be defined by a number of issues which need to be properly taken into account. The real performance of VIPs can be influenced by the boundary conditions (e.g. temperature) at which they work during their operation. In this paper experimental analyses aimed at characterising the relationship between the centre of panel thermal conductivity and average temperature were carried out. The experiments were performed on two VIP samples with different thickness. Moreover a comparison with non-evacuated panels and a traditional insulating material was performed

    Fast Generation of Broken-Symmetry States in a Large System Including Multiple Iron-Sulfur Assemblies: Investigation of QM/MM Energies, Clusters Charges, and Spin Populations

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    A density functional theory study is presented regarding the energetics and the Mulliken population analyses of a quantum mechanical/molecular mechanical (QM/MM) system including multiple iron-sulfur clusters in the QM region. The [FeFe]-hydrogenase from Desulfovibrio desulfuricans was studied, and both the active site (an Fe6S6 assembly generally referred to as the H-cluster) and an ancillary Fe4S4 site were treated at the BP86-RI/TZVP level. The antiferromagnetic coupling that characterizes both sites was modeled using the broken-symmetry (BS) approach. For such a QM system, 36 different BS couplings can be defined, depending on the localization of spin excess on the various spin centers. All the BS states were obtained by means of an effective and simple method for spin localization, that is here described and compared with more sophisticated approaches already available in literature. The variation of the QM/MM energy among the various geometry-optimized protein models was found to be less than 25 kJ mol(-1). This energy variation almost doubles if no geometry optimization is performed. A detailed analysis of the additive nature of these variations in QM/MM energy is reported. The Mulliken charges show very small variations among the 36 BS states, whereas the Mulliken spin populations were found to be somewhat more variable. The relevance of such variations is discussed in light of the available Mossbauer and Electron Paramagnetic Resonance (EPR) spectroscopic data for the enzyme. Finally, the influence of the basis set on the spin populations, charges, and structural parameters of the models was investigated, by means of QM/MM computations on the same system at the BP86-RI/SVP level. (C) 2010 Wiley Periodicals, Inc. Int J Quantum Chem 111: 3949-3960, 201
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