Method for Synthesizing Bulk Ceramics and Structures from Polymeric Ceramic Precursors

A method and product made by using a liquid polymeric ceramic precursor to synthesize dense, crack-free bulk ceramics in a technique using a sacrificial mold provides a ceramic structure for many technical, medical and industrial applications. The novel process uses an open cell material as a sacrificial mold to shape a liquid ceramic precursor during curing. The cured ceramic green body can be machined and shaped to form the desired ceramic structure prior to final pyrolysis. The open cell material forms gas release paths to release large amount of gases generated during the pyrolysis of the cured ceramic precursor. After pyrolysis, an intact, dense, crack-free ceramic structure with high purity, strength and durability is obtained. Uses of the present invention include, but are not limited to, bulk ceramic parts, ceramic crucibles, a replacement material in some applications involving glass, silicon carbides, silicon nitrides, hafnium carbide and the like

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Oxidation/Corrosion Of Polymer-Derived Sialcn Ceramics In Water Vapor

Fully dense polymer-derived SiAlCN ceramics were exposed to pure water vapor flowing at the rate of 4.4 cm/s at 1100°C. Weight changes as a function of annealing time were recorded to illustrate the oxidation/corrosion behavior of the materials. The paralinear kinetic model was used to determine the parabolic and linear rate constants from the experimental data. The results show that the polymer-derived SiAlCN ceramics have a much better water-vapor corrosion resistance than pure silicon-based ceramics. © 2005 The American Ceramic Society

Effect of Dry-Wet Cycles and Freeze-Thaw Cycles on the Antierosion Ability of Fiber-Reinforced Loess

Compared with plain soil, polypropylene (PP) fiber-reinforced soil has markedly improved mechanical properties and can be used in slope protection projects. To investigate the reduction law of the antierosion ability parameters of PP fiber-reinforced loess under dry-wet (D-W) cycles and freeze-thaw (F-T) cycles, we took loess from Yan’an, China, mixed them with PP fiber, and did shear strength tests, disintegration tests, and permeability tests under D-W cycles and F-T cycles. The experimental results show that D-W cycles or F-T  cycles had a less deteriorating effect on the cohesion, disintegration rate, and permeability coefficient of the fiber-reinforced samples than on plain loess; however, the reduction in their internal friction angle was more obvious. Under D-W cycles or F-T cycles, the cohesion and internal friction angle of the reinforced soil decreased as the number of cycles increased, while the disintegration rate and permeability coefficient increased as the number of cycles increased. The relation between the reduction in the antierosion ability parameters of reinforced soil and the number of D-W cycles or F-T cycles accorded with the hyperbolic function fitting results. The most obvious reduction effect the D-W cycles had on the reinforced soil was on the disintegration rate, followed by cohesion, internal friction angle, and permeability coefficient. The most obvious effect of F-T cycles was also on the disintegration rate, followed by cohesion, permeability coefficient, and internal friction angle. Compared with D-W cycles, F-T cycles had a stronger effect on the reduction in the cohesion, disintegration rate, and permeability coefficient of reinforced soil, but the reduction in the friction angle was greater in D-W cycles

A convenient strategy to clone small RNA and mRNA for high-throughput sequencing

High-throughput sequencing has become a standard tool for analyzing RNA and DNA. This method usually needs a cDNA/DNA library ligated with specific 5' and 3' linkers. Unlike mRNA, small RNA often contains modifications including 5' cap or triphosphate and 2'-O-methyl, requiring additional processing steps before linker additions during cloning processes; due to low expression levels, it is difficult to clone small RNA with a small amount of total RNA. Here we present a new strategy to clone 5' modified or unmodified small RNA in an all-liquid-based reaction carried out in a single PCR tube with as little as 20 ng total RNA. The 7-h cloning process only needs ∼1 h of labor. Moreover, this method can also clone mRNA, simplifying the need to prepare two cloning systems for small RNA and mRNA; the barcoded PCR primers are also compatible with non-cDNA cloning applications, including the preparation of genomic libraries. Not only is our method more convenient for cloning modified RNA than available methods, but it is also more sensitive, versatile, and cost-effective. Moreover, the all-liquid-based reaction can be performed in an automated manner

Superhydrophobic Mats Of Polymer-Derived Ceramic Fibers

Solid preceramic polyaluminasilazane was synthesized through the reaction between liquid cyclosilazane and aluminum tri-sec-butoxide at 160°C. Electrospinning of polyaluminasilazane/polyethyleneoxide (1/0.0001 mass ratio) in chloroform solutions generated smooth fibers while the electrospun fibers from the chloroform/N,N-dimethylformamide solutions had submicrometer structures on the fiber surfaces. Smooth and rough SiCNO ceramic fibers were obtained by the pyrolysis of the green fibers with an 80% yield. Superhydrophobic mats of ceramic fibers were fabricated via a chemical vapor deposition of perfluorosilane onto the rough fibers. These superhydrophobic mats possess good chemical and thermal stability. © 2008 The American Ceramic Society

On the Microstructure, Residual Stress and Fatigue Performance of Laser Metal Deposited TC17 Alloy Subjected to Laser Shock Peening

Laser shock peening (LSP) has been employed to improve the mechanical properties of repaired aerospace engine components via laser metal deposition (LMD). This study looked at cross-sectional residual stress, microstructure and high cyclic fatigue performance. The outcomes demonstrated that a compressive residual stress layer with a value of 240 MPa was formed at a depth of 200 μm in the laser melting deposited zone and the microhardness was improved by 13.1%. The findings of electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) analysis revealed that misorientation increased and dislocation features were observed after LSP which is beneficial to the enhancement of fatigue performance. The high cycle fatigue data illustrated that the LMD+LSPned samples exhibited 61% improvement in comparison to the as-LMD samples. In the aerospace sector, LSP and LMD are therefore very effective and promising techniques for restoring high-value components

Influenza A virus utilizes noncanonical cap-snatching to diversify its mRNA/ncRNA

Influenza A virus (IAV) utilizes cap-snatching to obtain host capped small RNAs for priming viral mRNA synthesis, generating capped hybrid mRNAs for translation. Previous studies have been focusing on canonical cap-snatching, which occurs at the very 5' end of viral mRNAs. Here we discovered noncanonical cap-snatching, which generates capped hybrid mRNAs/noncoding RNAs mapped to the region ∼300 nucleotides (nt) upstream of each mRNA 3' end, and to the 5' region, primarily starting at the second nt, of each virion RNAs (vRNA). Like canonical cap-snatching, noncanonical cap-snatching utilizes a base-pairing between the last nt G of host capped RNAs and a nt C of template RNAs to prime RNA synthesis. However, the nt upstream of this template C is usually A/U rather than just U; prime-realignment occurs less frequently. We also demonstrate that IAV can snatch capped IAV RNAs in addition to host RNAs. Noncanonical cap-snatching likely generates novel mRNAs with start AUG encoded in viral or host RNAs. These findings expand our understanding of cap-snatching mechanisms and suggest that IAV may utilize noncanonical cap-snatching to diversify its mRNAs/ncRNAs