The similitude of indoor airflow in natural ventilation for a reduced-scale model: Investigation of nonisothermal flow fields by RANS simulation

Jiang Z., Kobayashi T., Yamanaka T., et al. The similitude of indoor airflow in natural ventilation for a reduced-scale model: Investigation of nonisothermal flow fields by RANS simulation. Building and Environment 262, 111842 (2024); https://doi.org/10.1016/j.buildenv.2024.111842.Reduced-scale experiments and simulations are important approaches in natural ventilation research, and the similarity requirement is fundamental for generalising the flow characteristics obtained from reduced-to full-scale conditions. However, the similarity requirement of a nonisothermal natural ventilation flow in a reduced-scale model poses additional challenges because of the reduced approaching flow, which can potentially result in Reynolds dependence issues. This study investigated the Reynolds number (Re) independence of indoor airflow in natural ventilation under isothermal and nonisothermal conditions using computational fluid dynamics (CFD) with Reynolds-averaged Navier–Stokes. A wind tunnel experiment was first conducted to validate the accuracy of the CFD using a reduced-scale model. Indoor airflow fields characterised by the same Archimedes number (Ar) but with varying approaching wind velocities and temperatures were compared between the full-scale and 1/10 reduced-scale simulations. The dimensionless ventilation rate showed the least dependence on the Re number, while the temperature field was very sensitive to the Re number, especially in the near-wall region. However, the temperature field on the ventilation pathway is much less dependent on the Re number, the deviation of which is less than 10 % compared to the full-scale simulation. The temperature distribution in the reduced-scale simulation exhibits a thermal stratification pattern similar to that in the full-scale simulation

Unsteady analysis of non-isothermal natural ventilation airflow using domain decomposition technique with LES

Matsubara T., Kobayashi T., Yamanaka T., et al. Unsteady analysis of non-isothermal natural ventilation airflow using domain decomposition technique with LES. Building and Environment 262, 111763 (2024); https://doi.org/10.1016/j.buildenv.2024.111763.A Large Eddy Simulation (LES) can predict an unsteady airflow with high accuracy. However, the application of LES to indoor airflows is difficult because of the large computational burden of the coupled simulation of both the indoor/outdoor domains. To address this issue, a domain decomposition technique (DDT) was proposed so that the outdoor simulation results could be applied as boundary conditions for the indoor air simulation by decoupling the indoor/outdoor domains. However, most previous studies have only investigated the applicability of DDT under steady-state and isothermal conditions. In an actual natural ventilation design, if buoyancy force is expected as the primary natural ventilation driving force, the temperature difference between indoor/outdoor cannot be neglected. This study aimed to validate the DDT under non-isothermal conditions. First, wind tunnel experiments were conducted on an isolated building under non-isothermal conditions to obtain data for the computational fluid dynamics boundary conditions and accuracy verification. The wind pressure coefficient, velocity distribution, and temperature distribution were measured during the experiment. Then, unsteady analysis (i.e., whole domain simulation) was performed using LES to reproduce the wind tunnel experiment. Finally, DDT was applied to the Large Eddy Simulation, and its accuracy was verified by comparing the velocity distribution, temperature, and airflow rate between the whole domain and DDT. As a result, in the present study where the total number of grids in the entire domain was approximately 10 times that in the indoor domain, DDT exhibited good accuracy, and decreased the computational load by over 70 %

Experimental infection of dogs with a feline endogenous retrovirus RD-114

<p>Abstract</p> <p>Background</p> <p>The feline endogenous retrovirus RD114 is contained in the genome of cats. The virus may contaminate live canine vaccines based on cultured feline cells. The <it>in vivo </it>infectivity, acute and subacute pathogenicity, and viral proliferation of the RD114 virus were evaluated by experimental infection of dogs.</p> <p>Methods</p> <p>Nine specific pathogen free dogs were divided into three groups, with each group consisting of one female and two male dogs. Dogs were subcutaneously inoculated in the neck with either 1 ml RD114 stock virus (group A), inactivated RD114 virus suspension (group B), or cell culture medium (group C) as a negative control. To assess blood cell counts and biochemical properties, blood samples from each group were collected 5 days before inoculation, just prior to inoculation, and 1, 3, 7 and 10 days post-inoculation.</p> <p>Result</p> <p>During the experimental period of 51 days, none of the dogs inoculated with RD114 virus showed any clinical signs, significant increases in rectal temperature or abnormal blood biochemical characteristics including C-reactive protein when compared with the negative controls. We were not able to re-isolate the RD114 virus from buffy coat cells of group A dogs. Additionally, we could not detect RD114 provirus in the genomic DNA isolated from peripheral blood leukocytes, lymph node, spleen and sternal bone marrow cells.</p> <p>Conclusions</p> <p>Signs of RD114 virus proliferation were not found after subcutaneous infection of dogs. Although the potential risk caused by infection with RD114 virus in dogs could not be assessed in this study, we suspect that RD114 virus has little or no virulence in dogs.</p

Regulating Higher-Order Organization through the Synergy of Two Self-Sorted Assemblies

The extracellular matrix (ECM) is the natural fibrous scaffold that regulates cell behavior in a hierarchical manner. By mimicking the dynamic and reciprocal interactions between ECM and cells, higher-order molecular self-assembly (SA), mediated through the dynamic growth of scaffold-like nanostructures assembled by different molecular components, was developed. Designed and synthesized were two self-sorted coumarin-based gelators, a peptide molecule and a benzoate molecule, which self-assemble into nanofibers and nanobelts, respectively, with different dynamic profiles. Upon the dynamic growth of the fibrous scaffold assembled from peptide gelators, nanobelts assembled from benzoate gelators transform into a layer-by-layer nanosheet, reaching ninefold increase in height. By using light and an enzyme, the spatial-temporal growth of the scaffold can be modified, leading to in situ height regulation of the higher-order architecture

Role of Gremlins in the Aortic Arch of Spontaneously Hypertensive and Hyperlipidemic Rats

Atherosclerosis is a lifestyle-related disease that plays a major role in cardiovascular disease. Recently, we found that gene expression of Gremlin 2, an antagonist of bone morphogenetic protein (BMP), was significantly increased in the aorta of spontaneously hypertensive and hyperlipidemic rats (SHHRs) fed a high-fat, 30% sucrose solution diet (HFDS). However, the role of Gremlin 1 (Grem1) and Gremlin 2 (Grem2) in the aortic arch of rats under hypertensive, hyperlipidemic, and hyperglycemic conditions remains unclear. Therefore, in the present study we investigated the molecular role of Gremlins in the aorta of SHHRs. Four-month-old male Sprague-Dawley rats and SHHRs were fed a normal diet or the HFDS ad libitum for 4 months. Then, gene and protein expression was analyzed using quantitative polymerase chain reaction and western blotting, respectively. Grem1 and Grem2 protein expression was increased, whereas phosphorylated Smad1/5 protein expression was low, in the aorta of SHHRs fed the HFDS. In addition, the expression of the downstream gene targets of BMP, namely inhibitor of DNA binding 1 (Id1) and atonal homolog 8 (Atoh8), was decreased in aortas of SHHRs fed the HFDS. Furthermore, mRNA expression of Snail, α-smooth muscle actin (αSMA), and Fibronectin was increased in SHHRs fed the HFDS. These findings suggest that upregulation of Gremlins attenuates the activation of BMP signaling, which contributes to fibrogenesis of the aorta

Ras signaling directs endothelial specification of VEGFR2+ vascular progenitor cells

Vascular endothelial growth factor receptor 2 (VEGFR2) transmits signals of crucial importance to vasculogenesis, including proliferation, migration, and differentiation of vascular progenitor cells. Embryonic stem cell–derived VEGFR2+ mesodermal cells differentiate into mural lineage in the presence of platelet derived growth factor (PDGF)–BB or serum but into endothelial lineage in response to VEGF-A. We found that inhibition of H-Ras function by a farnesyltransferase inhibitor or a knockdown technique results in selective suppression of VEGF-A–induced endothelial specification. Experiments with ex vivo whole-embryo culture as well as analysis of H-ras−/− mice also supported this conclusion. Furthermore, expression of a constitutively active H-Ras[G12V] in VEGFR2+ progenitor cells resulted in endothelial differentiation through the extracellular signal-related kinase (Erk) pathway. Both VEGF-A and PDGF-BB activated Ras in VEGFR2+ progenitor cells 5 min after treatment. However, VEGF-A, but not PDGF-BB, activated Ras 6–9 h after treatment, preceding the induction of endothelial markers. VEGF-A thus activates temporally distinct Ras–Erk signaling to direct endothelial specification of VEGFR2+ vascular progenitor cells

The characteristic response of domestic cats to plant iridoids allows them to gain chemical defense against mosquitoes

ネコのマタタビ反応の謎を解明 --マタタビ反応はネコが蚊を忌避するための行動だった--. 京都大学プレスリリース. 2021-01-21.Domestic cats and other felids rub their faces and heads against catnip (Nepeta cataria) and silver vine (Actinidia polygama) and roll on the ground as a characteristic response. While this response is well known, its biological function and underlying mechanism remain undetermined. Here, we uncover the neurophysiological mechanism and functional outcome of this feline response. We found that the iridoid nepetalactol is the major component of silver vine that elicits this potent response in cats and other felids. Nepetalactol increased plasma β-endorphin levels in cats, while pharmacological inhibition of μ-opioid receptors suppressed the classic rubbing response. Rubbing behavior transfers nepetalactol onto the faces and heads of respondents where it repels the mosquito, Aedes albopictus. Thus, self-anointing behavior helps to protect cats against mosquito bites. The characteristic response of cats to nepetalactol via the μ-opioid system provides an important example of chemical pest defense using plant metabolites in nonhuman mammals

The Quiescent Intracluster Medium in the Core of the Perseus Cluster

Clusters of galaxies are the most massive gravitationally-bound objects in the Universe and are still forming. They are thus important probes of cosmological parameters and a host of astrophysical processes. Knowledge of the dynamics of the pervasive hot gas, which dominates in mass over stars in a cluster, is a crucial missing ingredient. It can enable new insights into mechanical energy injection by the central supermassive black hole and the use of hydrostatic equilibrium for the determination of cluster masses. X-rays from the core of the Perseus cluster are emitted by the 50 million K diffuse hot plasma filling its gravitational potential well. The Active Galactic Nucleus of the central galaxy NGC1275 is pumping jetted energy into the surrounding intracluster medium, creating buoyant bubbles filled with relativistic plasma. These likely induce motions in the intracluster medium and heat the inner gas preventing runaway radiative cooling; a process known as Active Galactic Nucleus Feedback. Here we report on Hitomi X-ray observations of the Perseus cluster core, which reveal a remarkably quiescent atmosphere where the gas has a line-of-sight velocity dispersion of 164+/-10 km/s in a region 30-60 kpc from the central nucleus. A gradient in the line-of-sight velocity of 150+/-70 km/s is found across the 60 kpc image of the cluster core. Turbulent pressure support in the gas is 4% or less of the thermodynamic pressure, with large scale shear at most doubling that estimate. We infer that total cluster masses determined from hydrostatic equilibrium in the central regions need little correction for turbulent pressure.Comment: 31 pages, 11 Figs, published in Nature July