Thermal Bimorph Micro-Cantilever Based Nano-Calorimeter for Sensing of Energetic Materials

The objective of this study is to develop a robust portable nano-calorimeter sensor for detection of energetic materials, primarily explosives, combustible materials and propellants. A micro-cantilever sensor array is actuated thermally using bi-morph structure consisting of gold (Au: 400 nm) and silicon nitride (Si3N4: 600 nm) thin film layers of sub-micron thickness. An array of micro-heaters is integrated with the microcantilevers at their base. On electrically activating the micro-heaters at different actuation currents the microcantilevers undergo thermo-mechanical deformation, due to differential coefficient of thermal expansion. This deformation is tracked by monitoring the reflected ray from a laser illuminating the individual microcantilevers (i.e., using the optical lever principle). In the presence of explosive vapors, the change in bending response of microcantilever is affected by the induced thermal stresses arising from temperature changes due to adsorption and combustion reactions (catalyzed by the gold surface). A parametric study was performed for investigating the optimum values by varying the thickness and length in parallel with the heater power since the sensor sensitivity is enhanced by the optimum geometry as well as operating conditions for the sensor (e.g., temperature distribution within the microcantilever, power supply, concentration of the analyte, etc.). Also, for the geometry present in this study the nano-coatings of high thermal conductivity materials (e.g., Carbon Nanotubes: CNTs) over the microcantilever surface enables maximizing the thermally induced stress, which results in the enhancement of sensor sensitivity. For this purpose, CNTs are synthesized by post-growth method over the metal (e.g., Palladium Chloride: PdCl2) catalyst arrays pre-deposited by Dip-Pen Nanolithography (DPN) technique. The threshold current for differential actuation of the microcantilevers is correlated with the catalytic activity of a particular explosive (combustible vapor) over the metal (Au) catalysts and the corresponding vapor pressure. Numerical modeling is also explored to study the variation of temperature, species concentration and deflection of individual microcantilevers as a function of actuation current. Joule-heating in the resistive heating elements was coupled with the gaseous combustion at the heated surface to obtain the temperature profile and therefore the deflection of a microcantilever by calculating the thermally induced stress and strain relationship. The sensitivity of the threshold current of the sensor that is used for the specific detection and identification of individual explosives samples - is predicted to depend on the chemical kinetics and the vapor pressure. The simulation results showed similar trends with the experimental results for monitoring the bending response of the microcantilever sensors to explosive vapors (e.g., Acetone and 2-Propanol) as a function of the actuation current

The AIM2 inflammasome is critical for innate immunity to Francisella tularensis.

Francisella tularensis, the causative agent of tularemia, infects host macrophages, which triggers production of the proinflammatory cytokines interleukin 1beta (IL-1beta) and IL-18. We elucidate here how host macrophages recognize F. tularensis and elicit this proinflammatory response. Using mice deficient in the DNA-sensing inflammasome component AIM2, we demonstrate here that AIM2 is required for sensing F. tularensis. AIM2-deficient mice were extremely susceptible to F. tularensis infection, with greater mortality and bacterial burden than that of wild-type mice. Caspase-1 activation, IL-1beta secretion and cell death were absent in Aim2(-/-) macrophages in response to F. tularensis infection or the presence of cytoplasmic DNA. Our study identifies AIM2 as a crucial sensor of F. tularensis infection and provides genetic proof of its critical role in host innate immunity to intracellular pathogens

Caspase-8 scaffolding function and MLKL regulate NLRP3 inflammasome activation downstream of TLR3

TLR2 promotes NLRP3 inflammasome activation via an early MyD88-IRAK1-dependent pathway that provides a priming signal (signal 1) necessary for activation of the inflammasome by a second potassium-depleting signal (signal 2). Here we show that TLR3 binding to dsRNA promotes post-translational inflammasome activation through intermediate and late TRIF/RIPK1/FADD-dependent pathways. Both pathways require the scaffolding but not the catalytic function of caspase-8 or RIPK1. Only the late pathway requires kinase competent RIPK3 and MLKL function. Mechanistically, FADD/caspase-8 scaffolding function provides a post-translational signal 1 in the intermediate pathway, whereas in the late pathway it helps the oligomerization of RIPK3, which together with MLKL provides both signal 1 and 2 for inflammasome assembly. Cytoplasmic dsRNA activates NLRP3 independent of TRIF, RIPK1, RIPK3 or mitochondrial DRP1, but requires FADD/caspase-8 in wildtype macrophages to remove RIPK3 inhibition. Our study provides a comprehensive analysis of pathways that lead to NLRP3 inflammasome activation in response to dsRNA

Longitudinal Microbiome Analysis in a Dextran Sulfate Sodium-Induced Colitis Mouse Model

The role of the gut microbiota in the pathogenesis of inflammatory bowel disease (IBD) has been in focus for decades. Although metagenomic observations in patients/animal colitis models have been attempted, the microbiome results were still indefinite and broad taxonomic presumptions were made due to the cross-sectional studies. Herein, we conducted a longitudinal microbiome analysis in a dextran sulfate sodium (DSS)-induced colitis mouse model with a two-factor design based on serial DSS dose (0, 1, 2, and 3%) and duration for 12 days, and four mice from each group were sacrificed at two-day intervals. During the colitis development, a transition of the cecal microbial diversity from the normal state to dysbiosis and dynamic changes of the populations were observed. We identified genera that significantly induced or depleted depending on DSS exposure, and confirmed the correlations of the individual taxa to the colitis severity indicated by inflammatory biomarkers (intestinal bleeding and neutrophil-derived indicators). Of note, each taxonomic population showed its own susceptibility to the changing colitis status. Our findings suggest that an understanding of the individual susceptibility to colitis conditions may contribute to identifying the role of the gut microbes in the pathogenesis of IBD

Inactivation of p38 kinase delays the onset of senescence in rabbit articular chondrocytes

Replicative senescence limits cellular proliferation in vivo and in vitro. Recently, other groups and we reported that p38 kinase plays a key role on the onset of senescence. In this study, we demonstrated that replicative senescence can be delayed in rabbit chondrocytes in vitro by that p38 kinase inactivation. We found that the activity of p38 kinase is elevated in senescent chondrocytes as compared to pre-senescent counterparts. To examine the role of p38 kinase on the onset of senescence, we inactivated the kinase pharmacologically or genetically using either a chemical inhibitor, SB203580, or dominant negative mutant forms of MKK6 and p38 (MKK6A and p38dn, respectively). We show that the inactivation of p38 kinase leads to the stimulation of proliferation, the extension of life span, and a delay in the onset of senescence, thus implying that p38 kinase limits the life span of rabbit articular chondrocytes in vitro.The National Research Laboratory Program of the Korean Ministry of Science and Technology (to S.D.Y.) and Molecular Aging Research Center (to S.D.Y.) support this research

Identification of Fine Dust in Schools through Comprehensive Chemical Characterization

Abstract The chemical characteristics of particulate matters collected from 53 schools in 2019 through 2022 were closely investigated to determine the main sources of classroom PM2.5. On average, indoor PM2.5 measured during class hours distributed from 3.3 μg/m3 to 45.97 μg/m3, and it consisted of 45% of ions, 33% of carbons, 17% of metals and others. The average indoor-to-outdoor ratio (I/O) of PM2.5 was 0.73. Values for I/O ranged from 0.6 to 0.91 for inorganic elements; 0.3 to 0.8 for ions; 0.50 to 2.69 for elemental carbons (EC), and 0.52 to 8.50 for organic carbons (OC). The linear correlation of indoor EC with concentrations of K+ and NO3− indicates that the contribution of combustion-related sources to classroom PM2.5 is significant in roadside schools. The findings from this study should help establish construction guidelines for urban schools near high-traffic areas

Investigation of Material and Structural Performance of Mireuksaji Stone Pagoda

The Mireuksaji stone pagoda (the only remaining building in Mireuksaji temple) has existed for 1400 years. More than half of the Mireuksaji stone pagoda has collapsed. Due to the historical, cultural, and architectural value of the Mireuksaji stone pagoda, which reflects the style of wooden buildings of that era, it is necessary to evaluate and investigate the cause of collapse for reconstruction and restoration plans and the structural stability of this cultural heritage. For this reason, in the first step, material properties of stones in the pagoda were investigated by taking samples from some of the separated stones that originally constituted the pagoda. Uniaxial and triaxial compressive strength tests, tensile strength tests, and nondestructive tests for the porosity and absorption rate of the stone were carried out. In the next step, three-dimensional numerical analysis software for discontinuous modeling based on the distinct-element method was used to model and analyze the pagoda as accurately as possible. Because the interface between stone blocks is a critical part of the main load-bearing system in the discontinuous structure, some sensitivity analysis was done to consider the effects of structural performance. The analysis also considered different imperfections due to weathering deterioration (material degradation) and irregular shape of remaining stones (surfaces are partially in contact) and their interfaces.N

Large-Eddy Simulation of Turbulent Buoyant Flow in a Corium Pool

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Preparation of Carbon Nanowall and Carbon Nanotube for Anode Material of Lithium-Ion Battery

Carbon nanowall (CNW) and carbon nanotube (CNT) were prepared as anode materials of lithium-ion batteries. To fabricate a lithium-ion battery, copper (Cu) foil was cleaned using an ultrasonic cleaner in a solvent such as trichloroethylene (TCE) and used as a substrate. CNW and CNT were synthesized on Cu foil using plasma-enhanced chemical vapor deposition (PECVD) and water dispersion, respectively. CNW and CNT were used as anode materials for the lithium-ion battery, while lithium hexafluorophosphate (LiPF6) was used as an electrolyte to fabricate another lithium-ion battery. For the structural analysis of CNW and CNT, field emission scanning electron microscope (FE-SEM) and Raman spectroscopy analysis were performed. The Raman analysis showed that the carbon nanotube in composite material can compensate for the defects of the carbon nanowall. Cyclic voltammetry (CV) was employed for the electrochemical properties of lithium-ion batteries, fabricated by CNW and CNT, respectively. The specific capacity of CNW and CNT were calculated as 62.4 mAh/g and 49.54 mAh/g. The composite material with CNW and CNT having a specific capacity measured at 64.94 mAh/g, delivered the optimal performance