Uncovering the Fresh Snowfall Microbiome and Its Chemical Characteristics with Backward Trajectories in Daejeon, the Republic of Korea

Snow covers a large surface area of the Earth and provides a surface for the exchange of biological and chemical components. However, the microbial composition and chemical components of snow are poorly understood. We assessed the bacterial and fungal diversity and chemical characteristics in freshly deposited snowfall samples collected from a sub-urban site in Daejeon, the Republic of Korea. We analyzed the snow samples using DNA amplification followed by Illumina MiSeq Sequencing for the microbiome, ion chromatography for the cations (Na+, Ca2+, Mg2+, and NH4+) and anions (SO42−, NO3−, and Cl−), and a water-soluble organic carbon (WSOC) and water-soluble nitrogen (WSTN) analyzer for WSOC and WSTN. NO3−, Actinobacteria (bacteria), and Ascomycota (fungi) were the most abundant components in the fresh snowfall samples. The air mass backward trajectories arrived mostly at this site from the northwest direction during this study period, which included the regions belonging to Russia, China, Mongolia, the Gobi Desert, the Yellow Sea, and South Korea. Principal component analysis suggested that the snow components were associated with sources belonging to secondary chemical compounds, dust, and sea salt during the study period

Uncovering the Fresh Snowfall Microbiome and Its Chemical Characteristics with Backward Trajectories in Daejeon, the Republic of Korea

Snow covers a large surface area of the Earth and provides a surface for the exchange of biological and chemical components. However, the microbial composition and chemical components of snow are poorly understood. We assessed the bacterial and fungal diversity and chemical characteristics in freshly deposited snowfall samples collected from a sub-urban site in Daejeon, the Republic of Korea. We analyzed the snow samples using DNA amplification followed by Illumina MiSeq Sequencing for the microbiome, ion chromatography for the cations (Na+, Ca2+, Mg2+, and NH4+) and anions (SO42−, NO3−, and Cl−), and a water-soluble organic carbon (WSOC) and water-soluble nitrogen (WSTN) analyzer for WSOC and WSTN. NO3−, Actinobacteria (bacteria), and Ascomycota (fungi) were the most abundant components in the fresh snowfall samples. The air mass backward trajectories arrived mostly at this site from the northwest direction during this study period, which included the regions belonging to Russia, China, Mongolia, the Gobi Desert, the Yellow Sea, and South Korea. Principal component analysis suggested that the snow components were associated with sources belonging to secondary chemical compounds, dust, and sea salt during the study period

Idle Vibration Reduction of a Diesel Sport Utility Vehicle

This paper presents a study on the idle vibration reduction of a diesel sport utility vehicle (SUV). To reduce idle vibration, the transmission paths of vibration from the engine to the driver seat floor were investigated with the vehicle components related to idle vibration. Furthermore, operational deflection shape (ODS) tests were conducted to visualize the vibration shapes during engine idling. Experimental modal analyses were performed to obtain the natural frequencies and mode shapes. Through the ODS and modal tests, the vibration characteristics of the diesel SUV during idling were identified. Considering these vibration characteristics, a multi-body dynamic model for the diesel SUV described by differential equations of motion was established to evaluate the idle vibration. To implement the dynamic model effectively, the equivalent stiffnesses and damping coefficients included in the model were determined experimentally or analytically. The established dynamic model was verified by comparing the natural frequencies and idle vibration levels between simulations. Using this dynamic model, we analyzed the effects of various design variables on idle vibration and obtained an optimal design for reducing the idle vibration level. Finally, we present a design guide to reduce the idle vibration for diesel SUVs

Design of Tool Clamping Device Based on a Shape Memory Alloy

This paper describes a tool-clamping/unclamping mechanism for application of a micro-spindle. The mechanism is based on one-way shape memory effect and interference-fit. The corresponding mathematical models and a few considerable design parameters are mentioned in this paper. Especially, necessary conditions for the clamping and unclamping operation are investigated through finite element analysis. The analysis results show that the differences between the diametral deformations of the tool holder in high temperature and that in low temperature are increased according to amounts of the interference. Thus the less interference between the tool-holder and the ring, the less tolerance to allow the clamping and unclamping operation because the inner diameter of the tool holder in high temperature should be smaller than the diameter of the tool shank, and that in low temperature should be larger than the diameter of the tool shank. In addition, the design for maximization of clamping force are investigated based on finite element analysis. The results show that the more amounts of the interference, the more clamping force. As the result, the interference should be considered as a important factor to maximize the tool clamping force.clos

Derivation of a Universally Valid Array Factor of a Conformal Arrays Based on Phase Compensation and Genetic Learning Particle Swarm Optimization

In this study, we investigated the recent deterioration of the radiation pattern performance of conformal arrays, which are applied to fields such as aircraft and vehicles. We analyzed the radiation pattern of conformal arrays in the array factor stage by combining previous studies on various beam-forming techniques for conformal arrays. To efficiently calculate and utilize the radiation pattern of conformal arrays, we derived an array factor based on phase composition for nonplanar arrays of three-dimensional (3D) coordinate systems. As an amplitude tapering method for controlling the sidelobe level of the derived 3D array factor, we propose a Bernstein polynomial generalization method based on Genetic Learning Particle Swarm Optimization. The proposed 3D array factor was verified using a cavity-backed patch antenna operating at the X-band through EM simulation of conformal arrays as a single element

Enhanced Durability of Polymer Electrolyte Membrane Fuel Cells by Functionalized 2D Boron Nitride Nanoflakes

We report boron nitride nanoflakes (BNNFs), for the first time, as a nanofiller for polymer electrolyte membranes in fuel cells. Utilizing the intrinsic mechanical strength of two-dimensional (2D) BN, addition of BNNFs even at a marginal content (0.3 wt %) significantly improves mechanical stability of the most representative hydrocarbon-type (HC-type) polymer electrolyte membrane, namely sulfonated poly(ether ether ketone) (sPEEK), during substantial water uptake through repeated wet/dry cycles. For facile processing with BNNFs that frequently suffer from poor dispersion in most organic solvents, we non-covalently functionalized BNNFs with 1-pyrenesulfonic acid (PSA). Besides good dispersion, PSA supports efficient proton transport through its sulfonic functional groups. Compared to bare sPEEK, the composite membrane containing BNNF nanofiller exhibited far improved long-term durability originating from enhanced dimensional stability and diminished chronic edge failure. This study suggests that introduction of properly functionalized 2D BNNFs is an effective strategy in making various HC-type membranes sustainable without sacrificing their original adventurous properties in polymer electrolyte membrane fuel cells.

Incorporation of functionalized gold nanoparticles into nanofibers for enhanced attachment and differentiation of mammalian cells

<p>Abstract</p> <p>Background</p> <p>Electrospun nanofibers have been widely used as substrata for mammalian cell culture owing to their structural similarity to natural extracellular matrices. Structurally consistent electrospun nanofibers can be produced with synthetic polymers but require chemical modification to graft cell-adhesive molecules to make the nanofibers functional. Development of a facile method of grafting functional molecules on the nanofibers will contribute to the production of diverse cell type-specific nanofiber substrata.</p> <p>Results</p> <p>Small molecules, peptides, and functionalized gold nanoparticles were successfully incorporated with polymethylglutarimide (PMGI) nanofibers through electrospinning. The PMGI nanofibers functionalized by the grafted AuNPs, which were labeled with cell-adhesive peptides, enhanced HeLa cell attachment and potentiated cardiomyocyte differentiation of human pluripotent stem cells.</p> <p>Conclusions</p> <p>PMGI nanofibers can be functionalized simply by co-electrospinning with the grafting materials. In addition, grafting functionalized AuNPs enable high-density localization of the cell-adhesive peptides on the nanofiber. The results of the present study suggest that more cell type-specific synthetic substrata can be fabricated with molecule-doped nanofibers, in which diverse functional molecules are grafted alone or in combination with other molecules at different concentrations.</p

Metallic Phase Transition Metal Dichalcogenide Quantum Dots as Promising Bio-Imaging Materials

Transition metal dichalcogenide-based quantum dots are promising materials for applications in diverse fields, such as sensors, electronics, catalysis, and biomedicine, because of their outstanding physicochemical properties. In this study, we propose bio-imaging characteristics through utilizing water-soluble MoS2 quantum dots (MoS2-QDs) with two different sizes (i.e., ~5 and ~10 nm). The structural and optical properties of the fabricated metallic phase MoS2-QDs (m-MoS2-QDs) were characterized by transmission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, UV&ndash;vis absorption spectroscopy, and photoluminescence. The synthesized m-MoS2-QDs showed clear photophysical characteristic peaks derived from the quantum confinement effect and defect sites, such as oxygen functional groups. When the diameter of the synthesized m-MoS2-QD was decreased, the emission peak was blue-shifted from 436 to 486 nm under excitation by a He-Cd laser (325 nm). Density functional theory calculations confirmed that the size decrease of m-MoS2-QDs led to an increase in the bandgap because of quantum confinement effects. In addition, when incorporated into the bio-imaging of HeLa cells, m-MoS2-QDs were quite biocompatible with bright luminescence and exhibited low toxicity. Our results are commercially applicable for achieving high-performance bio-imaging probes