Thermal Performance of Facades Based on Experimental Monitoring of Outdoor Test Cells in Tropical Climate

The high cost of energy consumption in buildings highlights the importance of research focused on improving the energy efficiency of building’s envelope systems. It is important to characterize the real behavior of these systems to know the effectiveness in terms of energy reduction. Therefore, the aim of this paper is to characterize the thermal performance of facades based on experimental monitoring of outdoor test cells in tropical climate. To carry out this research, a case study was presented to compare two construction systems. One of them is a light façade (M1) and the other a reference façade (M2). A thermal simulation was performed for the opaque and glazed facades. In addition, several parameters were measured with different types of sensors, as well as environmental variables to evaluate the thermal and lighting behavior of multiple facades systems under real conditions. The findings show that light façade behavior was the opposite of what was expected, since by incorporating a window in the façade it has allowed solar radiation to increase the interior temperature in both modules. In the case of the light facade the penalization was higher than the reference facade, which has a lower thermal transmittance than M1. Doi: 10.28991/cej-2021-03091773 Full Text: PDF

DNMT3A with Leukemia-Associated R882 Mutations Promotes Fitness Advantage through Functional Heterogeneity within HSCs

Mutations in DNA damage regulators and epigenetic modifier genes including those in DNA methyltransferase 3A (DNMT3A) are common in pre-malignant clonal hematopoiesis (CH) and are recurrent in myeloid malignancies such as myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). While loss-of-function (LOF) mutations in DNMT3A are predominant in CH, single amino-acid substitutions at residue 882, usually from an arginine to a histidine or cysteine (DNMT3A R882H / DNMT3A R882C), are strongly enriched in AML, suggesting a role in promoting pre-malignant clonal evolution. In this study, we compared and contrasted the effects of DNMT3A R882 and LOF on hematopoietic stem cell (HSC) function by investigating self-renewal capacity in vitro and bone marrow repopulation potential in vivo in a genetic mouse model. Bone marrow (BM) from mice conditionally expressing Dnmt3a R878H (equivalent to human DNMT3A R882H) from the endogenous locus, denoted as +/mut, was subjected to colony forming unit (CFU) assays in semisolid media (MethoCult GF M3434, Stem Cell Technologies) to detect hematopoietic progenitors with serial replating every 14 days as a surrogate measure of stem cell self-renewal. Dnmt3a +/mut cells were compared to bone marrow derived from mice with heterozygous or homozygous Dnmt3a knockout (+/- and -/-, respectively), or wild-type control (+/+). Dnmt3a +/- BM cells showed a trend towards a slight increase in the number of replatings compared to wild-type controls (2.83±0.41 in +/+ vs 3.75±0.89 in +/-, n=6,8, Mann-Whitney test p=0.053). In contrast, Dnmt3a +/mut BM occasionally resulted in a significant gain of self-renewal with replating for 6+ passages observed in 4/10 independent trials (6.00±2.06 in +/mut, n=10, p=0.001 vs +/+), yet failed to reach continuous replating of complete Dnmt3a loss that served as a positive control (terminated at passage 10, n=5). Substantial heterogeneity in the Dnmt3a +/mut self-renewal capacity ex vivo was further reflected by increased statistical variance (Welch's F-test p=0.037 compared to +/-). To extend these studies to the in vivo setting, we performed gold-standard serial competitive bone marrow repopulation assays. Here, 250 FACS-sorted Lineage -Sca1 +cKit +CD48 -CD150 + (LSK-SLAM) test cells marked with CD45.2 were mixed with 0.25x10 6 unfractionated wild-type competitor bone marrow cells marked with CD45.1 and engrafted into pre-conditioned congenic recipients (CD45.1). Peripheral blood CD45.2/CD45.1 chimerism is used as a readout for the ability of test cells to reconstitute hematopoiesis; self-renewal potential is assessed via serial retransplantation. In this setting, Dnmt3a +/+ cells showed a decline in their ability to reconstitute hematopoiesis in secondary transplant recipients, while Dnmt3a haploinsufficiency resulted in a competitive advantage over wild-type (CD45.2 chimerism 2.4±2.7% in +/+ vs 75.6±13.0% in +/-, n=4, Welch's t-test p=0.001). In contrast, Dnmt3a +/mut cells displayed a high degree of variability in their long-term stem cell function in some cases yielding high levels of chimerism (CD45.2 >40% in 3/9 recipients) and in other cases not (26.0±21.0%, n=9, p=0.01 vs +/+), in agreement with CFU assays. Collectively, these data suggest that the DNMT3A R882 mutations endow normal HSCs with phenotypic heterogeneity yielding a population of cells with variable stem cell function, some of which may have higher fitness thus accelerating clonal evolution towards malignancy. These findings will be built upon in future experiments aiming to identify underlying molecular mechanisms and to improve our understanding of the pathophysiology and prognostication of clonal hematopoiesis. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Stay cool without fossil fuel. A passive eco-cooler for low-income population in informal settlements

With climate change severe events, more and more vulnerable populations suffer from extreme heat waves. This paper presents a hands-on experimental idea for testing vernacular passive cooling strategies using traditional Shisha clay funnels for the Egyptian hot dry climate. Several clay funnels were investigated in terms of shape, size and form. The clay funnels were measured and simulated for their efficiency in accelerating air flow inside residential units and ability to enhance the air velocity if used combined with cross ventilation strategies. Computational Fluid Dynamics (CFD) simulations were conducted in ANSYS Fluent to understand the airflow behaviour inside the simulated test shoe boxes resembling living rooms - using the standard k-∈ turbulence model - for single and multi-units’ configurations. Followed by experimental test cells application for the cooling system and monitoring for testing thermal performance. The simulation results showed significant enhancement in air flow and air speed inside the test room compared to conventional windows, while the test cells monitoring showed an average reduction in indoor temperature and humidity with 2 degrees and 15 % respectively. Further monitoring is needed for other alternations of the eco-cooler funnel design for better performance.

Indoor Thermal Environment Challenges of Light Steel Framing in the Southern European Context

Over the past decades, Southern European residential architecture has been typically associated with heavyweight hollow brick masonry and reinforced concrete construction systems; however, more industrialised alternative systems have been gaining a significant market share, such as the light steel framing (LSF). Regardless of the proliferation of LSF buildings, a lack of experimental research studies have been performed on this construction system in terms of the indoor thermal environment and thermal comfort in the Southern European climate context. Moreover, a research gap also exists regarding experimental comparisons with typical brick masonry buildings. The present study focused on this research gap by characterising and comparing the performance of these two construction systems. A long-term experimental campaign was carried out, involving the construction and monitoring of two identical test cells, differing only by construction system. The test cells were located in Portugal and were monitored over an entire year. The results revealed that the LSF experimental test cell presented higher daily indoor air temperature fluctuations, leading to more extreme maximum and minimum values, closely following the outdoor dry bulb temperature variations. The more responsive behaviour was also reflected in the indoor thermal comfort analysis, with the LSF cell presenting slightly worse performance; however, some advantages were also observed regarding the LSF construction system, which could provide benefits during intermittent residential occupation, especially in mild climates, in which overheating is not a major concern.

An explorative study on the potential of green roofs providing thermal comfort conditions for indoor spaces in Kumasi, Ghana

PurposeAs the global population keeps increasing with its associated urbanisation and climate change issues being experienced in various degrees worldwide, there is the need to find mitigating measures to improve thermal conditions within spaces. The study aimed to evaluate green roofs to determine whether they could provide thermal comfort within residential buildings.Design/methodology/approachForty-two-year weather data were retrieved from the Kumasi weather station to establish the pattern of the climatic variables. Furthermore, an experiment was conducted by constructing test cells to determine the potential of vegetation/green roofs on temperature development within spaces. This approach led to a simulation-based exploration of the thermal performance of the test cells to probe variables that could lead to the reduction in temperature after the models in the software (design-builder) had been validated.FindingsThe results on the 42 years (1976–2018) weather data showed a significant (p = 0.05) mean temperature increment of 2.0 °C. The constructed test cell with Setcreasea purpurea (Purple Heart) vegetation showed an annual mean temperature reduction of 0.4 °C (p = 0.05). In addition, the exploration using the simulation application showed combinations of various soil depth (70–500 mm) and leaf area indices (leaf area index of 2–5) having a potential to lower indoor temperature by 1.5 °C and its associated reduction in energy use. The option of green roofs as a valuable alternative to conventional roofs, given their potential in mitigating climate change, must be encouraged. A survey of occupants in six selected neighbourhoods in Kumasi showed varying subjective perceptions of several green issues (24–98%) and increases in temperature values because of the loss of greenery in the city.Originality/valueEmpirical data that point to the significant reduction of indoor temperature values and a subsequent reduction in energy use have been unearthed. Therefore, built environment professionals together with city authorities could invest in these sustainable measures to help humanity.

Influence of Temperature and Moisture Content on Thermal Performance of Green Roof Media

The influence of moisture content on substrate thermal conductivity at different temperatures was investigated for four different commercially available substrates for green roofs. In the unfrozen state, as moisture content increased, thermal conductivity increased linearly. In the phase transition zone between +5 and −10 °C, as temperature decreased, thermal conductivity increased sharply during the transition from water to ice. When the substrate was frozen, thermal conductivity varied exponentially with substrate moisture content prior to freezing. Power functions were found between thermal conductivity and temperature. Two equally sized, green roof test cells were constructed and tested to compare various roof configurations including a bare roof, varying media thickness for a green roof, and vegetation. The results show that compared with the bare roof, there is a 75% reduction in the interior temperature’s amplitude for the green roof with 150 mm thick substrate. When a sedum mat was added, there was a 20% reduction in the amplitude of the inner temperature as compared with the cell without a sedum mat.