涡流发生器污垢特性实验台的设计

为了研究涡流发生器的污垢特性设计了一个能够在线监测温度、流量以及压差进而可以直接得到污垢热阻的实验台。通过验证实验、准确性分析与误差分析,验证了实验台设计精度在允许的误差范围内。示例实验结果表明实验台具有研究涡流发生器的污垢特性、压力特性以及换热特性的功能。     

Coconut coir dust extract: a novel eco-friendly corrosion inhibitor for Al in HCl solutions

Abstract

Corrosion inhibition of aluminium in 1 M HCl by coconut coir dust extract (CCDE) was studied using weight loss and hydrogen evolution techniques at 30 and 60°C. It was found that the studied extract exhibits a very good performance as inhibitor for aluminium corrosion in 1 M HCl. Results show that the inhibition efficiency increases with increasing temperature and concentration of the extract. Inhibitive effect was afforded by adsorption of the extracts' components which was found to accord with Langmuir adsorption isotherm. Inhibition mechanism is deduced from the temperature dependence of the inhibition efficiency and was further corroborated by the values of activation parameters obtained from the experimental data.     

Development and validation of a LC‐MS/MS method for quantitation of fosfomycin – Application to in vitro antimicrobial resistance study using hollow‐fiber infection model

Extensive use and misuse of antibiotics over the past 50 years has contributed to the emergence and spread of antibiotic‐resistant bacterial strains, rendering them as a global health concern. To address this issue, a dynamic in vitro hollow‐fiber system, which mimics the in vivo environment more closely than the static model, was used to study the emergence of bacterial resistance of Escherichia coli against fosfomycin (FOS). To aid in this endeavor we developed and validated a liquid chromatography–tandem mass spectrometry (LC‐MS/MS) assay for quantitative analysis of FOS in lysogeny broth. FOS was resolved on a Kinetex HILIC (2.1 × 50 mm, 2.6 μm) column with 2 mm ammonium acetate (pH 4.76) and acetonitrile as mobile phase within 3 min. Multiple reaction monitoring was used to acquire data on a triple quadrupole mass spectrometer. The assay was linear from 1 to 1000 μg/mL. Inter‐ and intra‐assay precision and accuracy were <15% and between ±85 and 115% respectively. No significant matrix effect was observed when corrected with the internal standard. FOS was stable for up to 24 h at room temperature, up to three freeze–thaw cycles and up to 24 h when stored at 4°C in the autosampler. In vitro experimental data were similar to the simulated plasma pharmacokinetic data, further confirming the appropriateness of the experimental design to quantitate antibiotics and study occurrence of antimicrobial resistance in real time. The validated LC‐MS/MS assays for quantitative determination of FOS in lysogeny broth will help antimicrobial drug resistance studies.     

Multiple Keys for a Single Lock: The Unusual Structural Plasticity of the Nucleotidyltransferase (4′)/Kanamycin Complex

The most common mode of bacterial resistance to aminoglycoside antibiotics is the enzyme‐catalysed chemical modification of the drug. Over the last two decades, significant efforts in medicinal chemistry have been focused on the design of non‐ inactivable antibiotics. Unfortunately, this strategy has met with limited success on account of the remarkably wide substrate specificity of aminoglycoside‐modifying enzymes. To understand the mechanisms behind substrate promiscuity, we have performed a comprehensive experimental and theoretical analysis of the molecular‐recognition processes that lead to antibiotic inactivation by Staphylococcus aureus nucleotidyltransferase 4′(ANT(4′)), a clinically relevant protein. According to our results, the ability of this enzyme to inactivate structurally diverse polycationic molecules relies on three specific features of the catalytic region. First, the dominant role of electrostatics in aminoglycoside recognition, in combination with the significant extension of the enzyme anionic regions, confers to the protein/antibiotic complex a highly dynamic character. The motion deduced for the bound antibiotic seem to be essential for the enzyme action and probably provide a mechanism to explore alternative drug inactivation modes. Second, the nucleotide recognition is exclusively mediated by the inorganic fragment. In fact, even inorganic triphosphate can be employed as a substrate. Third, ANT(4′) seems to be equipped with a duplicated basic catalyst that is able to promote drug inactivation through different reactive geometries. This particular combination of features explains the enzyme versatility and renders the design of non‐inactivable derivatives a challenging task.     

Origin of dc and ac electric transport phenomena in carbon/manganese oxide nanocomposite

Hybrid organic/inorganic nanocomposites based on manganese oxide nanoparticles enriched pyrogallol-formaldehyde matrix (PF/MnO) were synthesized by sol-gel technique. After a drying step, the samples were heated during 2 h at different pyrolysis temperatures between 600 and 1000 °C in tubular furnace under open nitrogen atmosphere. The obtained nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and electrical technics in the measurement temperature range between 80 and 300 K. The XRD spectra show that PF/MnO nanocomposites are crystallized with the appearance of different phases: the graphite (C), the manganese oxide (MnO), the metallic manganese (Mn) and the manganese dioxide (MnO₂) with proportions depending on pyrolysis temperature. The measurement temperature dependence conductivity can be explained by Godet-Variable Range Hopping (3D-GVRH) conduction model in all samples with the presence of an exponential distribution of localized states. The voltage-current V(I) characteristics show the presence of negative differential resistance (NDR) in some samples. The ac conductance exhibits the dominance of hopping conduction mechanism and the Small Polaron Hopping (SPH) model. The Nyquist plots for the PF/MnO-650 °C nanocomposite obey at Cole-Cole model. The impedance spectra were fitted by an equivalent circuit involving two contributions attributed to grains and grain boundaries.     

Influence of thermal and UV treatment on the polypropylene/graphite composite

Electrically conductive polypropylene/graphite (PP/graphite) composites were prepared via blending granulated PP with maleic anhydride grafted PP and natural graphite. Electrical conductivity of prepared samples containing either 65, 70, or 75 wt% of graphite was measured and the most conductive sample containing 75 wt% of graphite was exposed to UV irradiation for 1 and 24 h or thermally treated at 170 °C for 1 h. The influence of thermal and UV exposure on the structural and electrical changes in such treated samples was studied. Local current measurements on the surface were made using scanning spreading resistance microscopy and morphology of the surface was studied by atomic force microscopy. X-ray diffraction analysis, infrared and Raman spectroscopy were also used for the structural characterization. Properties of treated and untreated samples are compared and differences are discussed.     

Polymer complexes. LXXVI. Synthesis,characterization, CT‐DNA binding,molecular docking and thermal studies of sulfoxine polymer complexes

Novel polymer complexes of 8‐hydroxyquinoline‐5‐sulfonic acid hydrate ( H ₂ L ) with Cu²⁺, Co²⁺ and Ni²⁺ chloride were prepared and characterized. Microanalysis, magnetic susceptibility, IR spectra, electron spin resonance, mass spectra, X‐ray, molar conductance, thermal, and UV–Vis spectra studies have been used to confirm the structure of the prepared polymer complexes. The molecular and electronic structures of the hydrogen bond conformers for ligand ( H ₂ L ) were optimized theoretically and the quantum chemical parameters were calculated. On the basis of elemental and IR data, the chemical structure of metal chelates commensurate that the tri‐dentate (H₂L) coordinate to metal chlorides through oxygen atom of phenolic OH and oxygen atom of SO₃‐H group by replacing H atoms and nitrogen of the quinoline ring. The magnetic studies suggested the octahedral geometrical structure for all produced polymer complexes with general formula {[ML (OH₂)₃] .xH₂O}_n (M = Cu²⁺, x = 1.; Co²⁺, x = 2 and Ni²⁺, x = 2) in molar ratio (1:1). Coats–Redfern and Horowitz–Metzger methods have been used for calculating the activation thermodynamic parameters of the thermal decomposition for H ₂ L and its polymer complexes. The interaction between H ₂ L and its transition metal complexes with the calf thymus DNA (CT‐DNA) was determined by UV–Vis spectra. Binding efficiency between H ₂ L with the receptors of the prostate cancer (PDB code 2Q7L Hormone) and the breast cancer (PDB code 1JNX Gene regulation) was studied by molecular docking. The inhibition behaviour of H ₂ L against the corrosion of carbon steel / HCl (2 M) solution was studied by weight loss, Tafel polarisation, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques. The adsorption isotherm was found to be Friendlish isotherm. The morphology of inhibited carbon steel? s surface was studied using scanning electron microscope (SEM) and energy dispersive X‐ray spectroscopy (EDS).     

Environmentally Stable Polymer Gels with Super Deformability and High Recoverability Enhanced by Sub‐5 nm Particles in the Nonvolatile Solvent

It remains challenging to satisfy the combined performances for hydrogels with excellent mechanical behavior, high deformability, and super recoverability under harsh environmental conditions. In this study, we first established a strong polymer network via the crosslinking of polymer chains on the surfaces of sub‐5‐nm calcium hydroxide nanospherulites in ethylene glycol solvent. The organic gel expressed excellent mechanical properties such as a recoverable compressive engineering stress of 249 MPa and an elongation stress of 402 KPa, which was attributed to the uniform nanosized crosslinking structure as characterized by SEM. Moreover, the nonvolatile solvent remained in the gel, meaning that the sample can resist a wide temperature range of ?56 to 100 °C without losing the elastic properties. This novel organic gel could provide promising routes to develop the ideal elastic carriers for wearable devices, smart skin sensors, and damping materials. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 713–721     

Assessment of Nematic Guest-Host Systems for Application to Integrated Liquid Crystal Displays

An optimized configuration of the nematic guest-host effect is described in which a 90° twist cell is used. In order to assess the suitability of nematic guest-host systems for use in integrated displays in which a significant dc voltage may appear across the liquid crystal, several dye/host systems were tested with up to 1.5V dc superimposed on the normal 5V r.m.s. drive signal. Degradation was monitored by measurement of tilt, clearing point and absorbance. One system tested showed no significant degradation after 9 × 10³ hr. Excellent correlation was observed between stability of a dye/host system in a driven display and the reversibility of the reduction of the dye in acetonitrile solution at a platinum electrode.