A Study of the Catalytic Properties of Synthetic Aluminosilicates of Different Morphologies in Cracking Reactions of the Byproducts of Isoprene Synthesis

Glass Physics and Chemistry - The catalytic activity of synthetic samples of aluminosilicates of various morphologies and chemical compositions in a cascade of reactions that are byproducts (BPs)...     

多毛细管柱色谱

应用直径范围为5～50μm的毛细管色谱柱可以使分离速度最大化.然而它们所需要的样品量很小,以至于难以进样和检测.本文设计的多毛细管柱克服了单毛细管柱在流速、体积、样品容量等方面的限制,并且可以与所有的常规色谱设备兼容.     

Localized Excitation of Neural Activity via Rapid Magnetothermal Drug Release

Hysteretic heat dissipation by magnetic nanoparticles (MNPs) in alternating magnetic fields (AMFs) allows these materials to act as local transducers of external stimuli. Commonly employed in cancer research, MNPs have recently found applications in remote control of heat‐dependent cellular pathways. Here, a thermally labile linker chemistry is adapted for the release of neuromodulatory compounds from the surfaces of MNPs via local nanoscale heating. By examining a range of MNP sizes, and considering individual particle loss powers, AMF conditions and nanomaterials suitable for rapid and complete release of a payload from MNP surfaces are selected. Local release of allyl isothiocyanate, an agonist of the Ca²⁺ channel TRPV1 (transient receptor potential vanilloid cation channel subfamily member 1), from iron oxide MNPs results in pharmacological excitation of neurons with latencies of ≈12 s. When targeted to neuronal membranes, these MNPs trigger Ca²⁺ influx and action potential firing at particle concentrations three orders of magnitude less than those previously used for magnetothermal neuromodulation accomplished with bulk heating.     

Visualization of the native shape of bodipy‐labeled DNA in Escherichia coli by correlative microscopy

The native shape and intracellular distribution of newly synthesized DNA was visualized by correlative (light and electron) microscopy in ice embedded whole cells of Escherichia coli. For that purpose, the commercially available modified nucleoside triphosphate named BODIPY® FL‐14‐dUTP was enzymatically incorporated in vivo into the genome of E. coli mutant K12 strain, which cannot synthesize thymine. The successful incorporation of this thymidine analogue was confirmed first by fluorescence microscope, where the cells were stained in the typical for bodipy green color. Later the preselected labeled E. coli were observed by Hilbert Differential Transmission Electron Microscope (HDC TEM) and the distribution of elemental boron (contained in bodipy) was visualized at high‐resolution by an electron spectroscopic imaging (ESI) technique. The practical detection limit of boron was found to be around 5 ～ 10 mmol/kg in area of 0.1 μm², which demonstrated that ESI is a suitable approach to study the cytochemistry and location of labeled nucleic fragments within the cytoplasmic chromosomal area. In addition, the fine cellular fibrous and chromosomal ultrastructures were revealed in situ by combing of phase‐plate HDC TEM and ESI. The obtained results conclude that the correlation between fluorescent microscopy with phase‐plate HDC TEM and ESI is a powerful approach to explore the structural and conformation dynamics of DNA replication machinery in frozen cells close to the living state.     

Investigation of nanostructured oxides: synthesis, structure and properties

The process of forming three-component nanocrystalline fibers and powders of zirconia, yttria and alumina is studied depending on the component ratio and heat treatment temperature. It has been found that in the investigated system at 500-600 degrees C a nanocrystalline triple solid solution is formed, which exists up to 1200 degrees C. Beyond the above temperature, the triple solid solution decomposes into individual components. Specific regularities of changes in the crystalline structure and size of nanograins of oxides of triple solid solutions in the ZrO2(Y2O3)-Al2O3 system are established depending on the composition and thermal action. The structure--crystallite size--physical-chemical property relationship is also considered. The proposed synthesis method enables preparing nanocrystalline fibers and powders with a high degree of dispersion and reactive activity, whose use in composite materials and ceramics improves their service properties.     

On the Mechanism of Formation of Bimodal Grain Structure in Al–4.5Mg–0.7Sc–0.3Zr Alloy Processed by Laser Powder Bed Fusion

Scalmalloy is an Al–Mg alloy with additions of Sc and Zr originally developed as a high-strength aluminum alloy with σ_0.2 ≥ 450 MPa for aerospace industry. It is now well understood that the alloy is amendable for processing by laser powder bed fusion (LPBF). However, the mechanism of formation of the equiaxed-columnar bimodal grain structure during LPBF is not ascertained yet, fully. Herein, this gap is addressed with special focus on the distributions of critical elements such as Sc and various particles that form during LBPF. It is found that strong and weak segregation of Mg and Sc, respectively, occurs in the final solidification areas of the fine- and equiaxed-grain regions. The coarser and columnar grain regions show weak segregation of Mg and no Sc segregation. A priori knowledge on the Al–Sc eutectic reaction, its dependence on cooling rates, and the well-known thermal and solidification conditions related to the track location during LPBF is used to ascertain the mechanism of formation of the bimodal grain structure. The mechanism suggested is substantiated by the location-dependent elemental distributions and the various particles that are observed.     

Energetic and magnetic properties of chitosan with embedded Co clusters

Ab initio DFT simulations of cobalt clusters adsorbed on polymer chitosan molecules with increasing size of both Co clusters and polymer molecules are reported. Small cobalt clusters (Co_N, N = 2–19 atoms) in the ground state are bound to polymer chitosan molecules containing up to four monomers. The different kinds of binding for Co clusters to chitosan were taken in special attention, such as inside and outside connection. It is shown that O- and N-binding types are competitive for outside linking. Co nanoparticles embedded into the internal part of chitosan helix lose greater energy as compared with outside binding. The size of not only Co clusters, but also the chitosan polymer molecules is significant during the simulation. Magnetic moments of the Co–chitosan system depend strongly on the size of neither Co clusters nor chitosan molecules and tend to be slightly decreased in the case of inside connected clusters with increasing the system’s size.     

Vectors for rapid selection of integrants with different plasmid copy numbers in the yeast Hansenula polymorpha DL1

Plasmids with different selectable markers were constructed and used to transform the Hansenula polymorpha strain DL1. It was shown that, depending on the host mutant strain, the use of these plasmids enables rapid selection of transformants with plasmids integrated in low (1–2), moderate (6–9) or high (up to 100) copy numbers. The vectors and mutants described are potentially useful for the construction of efficient producers of heterologous proteins in H. polymorpha. Copyright © 1999 John Wiley & Sons, Ltd.     

Versatile and Easily Designable Polyester-Laser Toner Interfaces for Site-Oriented Adsorption of Antibodies

Laser toners appear as attractive materials for barriers and easily laminated interphases for Lab-on-a-Foil microfluidics, due to the excellent adhesion to paper and various membranes or foils. This work shows for the first time a comprehensive study on the adsorption of antibodies on toner-covered poly(ethylene terephthalate) (PET@toner) substrates, together with assessment of such platforms in rapid prototyping of disposable microdevices and microarrays for immunodiagnostics. In the framework of presented research, the surface properties and antibody binding capacity of PET substrates with varying levels of toner coverage (0–100%) were characterized in detail. It was proven that polystyrene-acrylate copolymer-based toner offers higher antibody adsorption efficiency compared with unmodified polystyrene and PET as well as faster adsorption kinetics. Comparative studies of the influence of pH on the effectiveness of antibodies immobilization as well as measurements of surface ζ-potential of PET, toner, and polystyrene confirmed the dominant role of hydrophobic interactions in adsorption mechanism. The applicability of PET@toner substrates as removable masks for protection of foil against permanent hydrophilization was also shown. It opens up the possibility of precise tuning of wettability and antibody binding capacity. Therefore, PET@toner foils are presented as useful platforms in the construction of immunoarrays or components of microfluidic systems.     

Octacalcium Phosphate for Bone Tissue Engineering: Synthesis,Modification, and In Vitro Biocompatibility Assessment

Octacalcium phosphate (OCP, Ca₈H₂(PO₄)₆·5H₂O) is known to be a possible precursor of biological hydroxyapatite formation of organic bone tissue. OCP has higher biocompatibility and osseointegration rate compared to other calcium phosphates. In this work, the synthesis of low-temperature calcium phosphate compounds and substituted forms of those at physiological temperatures is shown. Strontium is used to improve bioactive properties of the material. Strontium was inserted into the OCP structure by ionic substitution in solutions. The processes of phase formation of low-temperature OCP with theoretical substitution of strontium for calcium up to 50 at.% in conditions close to physiological, i.e., temperature 35–37 °C and normal pressure, were described. The effect of strontium substitution range on changes in the crystal lattice of materials, the microstructural features, surface morphology and biological properties in vitro has been established. The results of the study indicate the effectiveness of using strontium in OCP for improving biocompatibility of OCP based composite materials intended for bone repair.