Effect of copper foam thickness on pool boiling heat transfer of HFE-7100 Manetti, Leonardo Lachi; Moita, Ana Sofia Oliveira Henriques; de Souza, Reinaldo Rodrigues ...
International Journal of Heat and Mass Transfer/International journal of heat and mass transfer,
20/May , Volume:
152
Journal Article
Peer reviewed
Open access
•Pool boiling using HFE-7100 and copper foams at three thicknesses were tested;•An optimum thickness to enhance the boiling heat transfer was found;•Vapor bubbles get trapped in the foam cell with ...higher thickness;•The lowest foam reduces the entrapped vapor into it and improves the wickability;•The foam thickness effects on pool boiling are summarized.
Pool boiling is a low-cost technique for cooling electronic devices; HFE-7100 is a dielectric fluid with advantageous properties for such application but its high wettability can cause temperature overshoot in the system. Hence, the use of porous heating surfaces improves the heat transfer performance, eliminating the temperature overshoot due to their interconnected porous, which increase the wetted area and active nucleation site density. This work addressed pool boiling tests by using HFE-7100 and copper foams with three different thicknesses: 3 mm, 2 mm, and 1 mm in order to study the vapor bubble dynamics into the foam cell and find out an optimum thickness to enhance the boiling heat transfer. The results show that high thickness, 2 mm and 3 mm, has the best performance at low heat fluxes while the lowest thickness has the best performance at high heat fluxes. At heat fluxes lower than 50 kW/m², the higher surface wetted area increases the natural convection zone even though the latent heat also plays an important role. At higher heat fluxes, mainly after 200 kW/m², the vapor bubbles are trapped at the foam structure leading to an unstable boiling pattern and prevent the liquid from rewetting the surface. Therefore, the lowest foam thickness reduces the vapor trapping into the cell; additionally, the capillary-wicking ability increases and it also improves the HTC and the dryout heat flux due to the prevention of hotspots within the foam surface.
Effect of open-cell metal foam thickness on pool boiling of HFE-7100 Display omitted .
Neutrophil migration and its role during inflammation has been the focus of increased interest in the past decade. Advances in live imaging and the use of new model systems have helped to uncover the ...behaviour of neutrophils in injured and infected tissues. Although neutrophils were considered to be short-lived effector cells that undergo apoptosis in damaged tissues, recent evidence suggests that neutrophil behaviour is more complex and, in some settings, neutrophils might leave sites of tissue injury and migrate back into the vasculature. The role of reverse migration and its contribution to resolution of inflammation remains unclear. In this Review, we discuss the different cues within tissues that mediate neutrophil forward and reverse migration in response to injury or infection and the implications of these mechanisms to human disease.
Angiotensin-Converting Enzyme 2 (ACE2) has been proved to be the main host cell receptor for the binding of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus responsible for ...the COVID-19 pandemic. The SARS-CoV-2 spike (S) protein binds to ACE2 to initiate the process of replication. This enzyme is widely present in human organ tissues, such as the heart and lung. The pathophysiology of ACE2 in SARS-CoV-2 infection is complex and may be associated with several factors and conditions that are more severe in COVID-19 patients, such as age, male gender, and comorbidities, namely, cardiovascular diseases, chronic respiratory diseases, obesity, and diabetes. Here we present a comprehensive review that aims to correlate the levels of expression of the ACE2 in patients with comorbidities and with a poor outcome in COVID-19 disease. Significantly higher levels of expression of ACE2 were observed in myocardial and lung tissues in heart failure and COPD patients, respectively. An age-dependent increase in SARS2-CoV-2 receptors in the respiratory epithelium may be also responsible for the increased severity of COVID-19 lung disease in elderly people. Although the role of ACE2 is highlighted regarding the damage that can arise upon the SARS-CoV-2 invasion, there was no association observed between renin-angiotensin-aldosterone system (RAAS) inhibitors and the severity of COVID-19.
Introduction: Antiretroviral Therapy (ART) gives people living with HIV/AIDS (PLWHA) a new perspective of life, although some develop changes in impaired body composition. This study aimed to assess ...the factors associated with changes in body composition in PLWHA using ART, depending food consumption. Material and methods: It was a cross-sectional study and took place through interviews with patients treated at an University Hospital. Secondary data: CD4+ T cells, ART time and age. The level of physical activity and smoking were self-reported. For the assessment of body composition, electrical bioimpedance and measurements of weight, height and waist circumference were used. Results: The highest percentages of fat mass and fat-free mass, in treatment for more than 5 years, were in the female group (p <0.01), aged> 50 years (p = 0.02) and in the male group (p <0.01), young adult (p <0.01), respectively. The final linear regression model for both free fat mass and fat mass had sex, age, smoking and nutritional diagnosis as relevant factors. The frequency of food consumption was inadequate for calories, carbohydrates, proteins and lipids was high, however it did not significantly influence body composition. Conclusions: Gender, age, smoking and nutritional diagnosis by BMI significantly influence body composition.
One of the main highlights of additive manufacturing (AM) processes is the ability of building components of different sizes and geometries from the build-up of deposition of layers up on layers. ...However, the deposition heat cycle and amount of heat coming from successively deposited layers poses a challenge on the control of microstructure, particularly for alloys with a complex metallurgy, such as duplex stainless steels (DSSs). Due to successive cycles of rapid cooling and reheating of previously deposited layers, obtaining the ferrite and austenite phases in the adequate proportion needs to be addressed for each process and processing conditions. This manuscript addresses this metallurgical challenge aiming at reviewing the main features of DSSs processed by AM processes, particularly directed energy deposition (DED) processes. The discussion brings the main points that have been investigated on AM of DSSs, including the impact of thermal cycles (effect of heat input or energy density and reheated layers) and post processing heat treatment (PPHT) on the multilayer microstructure. Results obtained by plasma transferred arc directed energy deposition (PTA-DED) and laser directed energy deposition (L-DED) additive processes, electric arc and high energy beam techniques, respectively, are used to illustrate and highlight the response of a gas atomized superduplex stainless steel 2507 to multilayer processing and subsequent PPHT. The relevance of controlling the microstructure on the properties and performance of DSSs processed by AM is also addressed.
Notch signaling orchestrates the regulation of cell proliferation, differentiation, migration and apoptosis of epidermal cells by strictly interacting with other cellular pathways. Any disruption of ...Notch signaling, either due to direct mutations or to an aberrant regulation of genes involved in the signaling route, might lead to both hyper- or hypo-activation of Notch signaling molecules and of target genes, ultimately inducing the onset of skin diseases. The mechanisms through which Notch contributes to the pathogenesis of skin diseases are multiple and still not fully understood. So far, Notch signaling alterations have been reported for five human skin diseases, suggesting the involvement of Notch in their pathogenesis: Hidradenitis Suppurativa, Dowling Degos Disease, Adams-Oliver Syndrome, Psoriasis and Atopic Dermatitis. In this review, we aim at describing the role of Notch signaling in the skin, particularly focusing on the principal consequences associated with its alterations in these five human skin diseases, in order to reorganize the current knowledge and to identify potential cellular mechanisms in common between these pathologies.
In open-plan offices (OPO), workspaces without ground-to-ceiling dividers, noise is one of the most complained about aspects, causing physical and psychological impacts. With the increasing interest ...for a human-centric design, notably after the publication of ISO 22955, this review aims to identify the main noise sources in this office layout and the employees’ perception of related health effects, evaluating the interventions proposed to overcome their impacts. Following the PRISMA guidelines, a review was conducted using the Scopus and PubMed databases, considering subjective questionnaires distributed in offices, which could include physical workspace assessment. It excluded studies limited to: (a) laboratory experiments; (b) isolated cognitive tests; (c) office layouts other than OPO; (d) systematic reviews; and (e) mathematical models. Sixty studies were identified and the screening process resulted in 11 selected for inclusion, which indicated irrelevant speech, chatting, and telephone ringing as the main noise sources causing productivity loss, stress, and low comfort rates due to distraction and lack of privacy. To overcome these impacts, researchers suggested the use of sound-absorbing surfaces, separated zones for different tasks and headphones, although their effectiveness relies on human behaviour and economic feasibility. Thus, the evidence indicates that noise is a recurrent issue in OPOs, it demonstrates the importance of appropriate acoustic performance of the workspace and the necessity of new studies regarding OPO workers’ perception of noise and their health, particularly after the COVID-19 new safety guidelines.
Abstract
To explore the connection between chloroplast and coffee resistance factors, designated as S
H
1 to S
H
9, whole genomic DNA of 42 coffee genotypes was sequenced, and entire chloroplast ...genomes were de novo assembled. The chloroplast phylogenetic haplotype network clustered individuals per species instead of S
H
factors. However, for the first time, it allowed the molecular validation of
Coffea arabica
as the maternal parent of the spontaneous hybrid “Híbrido de Timor”. Individual reads were also aligned on the
C. arabica
reference genome to relate S
H
factors with chloroplast metabolism, and an in-silico analysis of selected nuclear-encoded chloroplast proteins (132 proteins) was performed. The nuclear-encoded thioredoxin-like membrane protein HCF164 enabled the discrimination of individuals with and without the S
H
9 factor, due to specific DNA variants linked to chromosome 7c (from
C. canephora
-derived sub-genome). The absence of both the thioredoxin domain and redox-active disulphide center in the HCF164 protein, observed in S
H
9 individuals, raises the possibility of potential implications on redox regulation. For the first time, the identification of specific DNA variants of chloroplast proteins allows discriminating individuals according to the S
H
profile. This study introduces an unexplored strategy for identifying protein/genes associated with S
H
factors and candidate targets of
H. vastatrix
effectors, thereby creating new perspectives for coffee breeding programs.
Neutrophils play a pivotal role in the innate immune response. The small cytokine CXCL8 (also known as IL-8) is known to be one of the most potent chemoattractant molecules that, among several other ...functions, is responsible for guiding neutrophils through the tissue matrix until they reach sites of injury. Unlike mice and rats that lack a CXCL8 homolog, zebrafish has two distinct CXCL8 homologs: Cxcl8-l1 and Cxcl8-l2. Cxcl8-l1 is known to be upregulated under inflammatory conditions caused by bacterial or chemical insult but until now the role of Cxcl8s in neutrophil recruitment has not been studied. In this study we show that both Cxcl8 genes are upregulated in response to an acute inflammatory stimulus, and that both are crucial for normal neutrophil recruitment to the wound and normal resolution of inflammation. Additionally, we have analyzed neutrophil migratory behavior through tissues to the site of injury in vivo, using open-access phagocyte tracking software PhagoSight. Surprisingly, we observed that in the absence of these chemokines, the speed of the neutrophils migrating to the wound was significantly increased in comparison with control neutrophils, although the directionality was not affected. Our analysis suggests that zebrafish may possess a subpopulation of neutrophils whose recruitment to inflamed areas occurs independently of Cxcl8 chemokines. Moreover, we report that Cxcl8-l2 signaled through Cxcr2 for inducing neutrophil recruitment. Our study, therefore, confirms the zebrafish as an excellent in vivo model to shed light on the roles of CXCL8 in neutrophil biology.
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