Friction and Wear Behaviors of the Polydimethylsiloxane Bishydroxyalkyl-Terminated Modified Polyurethane Composites Filled with the Barium Sulfate in Dry Friction and Water Lubrication

The addition of less than 20 wt% of approximate 1 micron barium sulfate (BaSO₄) into polyurethane (PU) composites modified by bishydroxyalkyl-terminated polydimethylsiloxane (PDMSBH) resulted in increases in mechanical strength and thermal conductivity and, at the same time, resulted in improvements in the friction and wear properties of the polyurethane composites. These polyurethane composites were suitable for marine use for bearings at high load under dry friction and at fast sliding speed under water lubrication. Characterization with Fourier transform infrared (FTIR) spectroscopy, thermogravimetry analysis (TGA), scanning electron microscope (SEM), and an MRH-3 ring-on-block wear tester indicated that the addition of BaSO₄ disrupts the organic phase separation in the polyurethane, resulting in better tribological properties, but there is no special chemical reaction between the particles and polyurethane. Adding too much BaSO₄ resulted in higher wear rate because of inorganic–organic phase separation.     

Mechanistic study of the reaction of methyl peroxy radical (CH3O2) with formaldehyde (CH2O)

ABSTRACT

A direct dynamic study on the reactions of CH₃O₂?+?CH₂O was carried out over the temperature range of 300–1500?K. All stationary points were calculated with the M06-2X/6-311++G(d,p) level of theory and identified for local minimum. The energetic parameters were refined at QCISD (T)/cc-pVTZ and CCSD (T)/cc-pVTZ levels of theory. Three channels were explored and a reaction of hydrogen abstraction from CH₂O by CH₃O₂ was identified as dominant channel which involves the formation of a prereactive complex in the entrance channel. The rate coefficient of the dominant channel was calculated with TST and TST/Eck and the Eckart tunnelling effect is only important over the lower temperature region. The calculated rate coefficient of the dominant channel has positive temperature dependence and agrees reasonably with the available literature data.     

Syntheses,Characterization, and Fluorescence Properties of Four Divalent Lead Coordination Polymers based on Zwitterionic Ligands

Four novel divalent lead coordination polymers based on a series of zwitterionic ligands, Pb₂Cl₄L₁ ( 1 ), [Pb₂Cl₄L₂]·2H₂O ( 2 ), Pb₂Cl₂(CH₃COO)₂L₂ ( 3 ), and Pb₃Cl₄(NO₃)₂L₃ ( 4 ) were solvothermally synthesized and successfully characterized. Single crystal structure studies reveal that compound 1 is a chain structure based on the inorganic “PbCl₂” chain motif, whereas compounds 2 – 4 are sheet structures each constructed by inorganic “PbCl₂”, “PbCl(CH₃COO)”, and “Pb₃Cl₄” chain motifs. Hydrogen bonding interactions in term of C–H ··· Cl and C–H ··· O play a key role to form supramolecular 3D structures of 1 – 4 . Additionally, studies of solid state fluorescence indicate 1 – 4 emit in the ultraviolet and visible region that can be assigned to the inter‐ligand π*–π and/or π*–n transitions.     

“善行河北”主题道德实践活动与大学教育

"善行河北"主题道德实践活动是将社会主义核心价值体系融入百姓生活,提升公民道德素质的有效途径。教育是继往开来的伟业,大学是培养高层次人才之所在。"善行河北"主题道德实践活动进入大学校园、融入大学教育、走入课堂教学,有助于克服教育功利化的倾向,树牢"把立德树人作为教育的根本任务"的新教育理念;有助于理解和践行学校教育"培养德智体美全面发展的社会主义建设者和接班人的根本目标";有助于充实大学思想政治理论教育的教学内容,克服教学过程中的虚、空、大。     

Preparation of bovine hemoglobin-imprinted polymer beads via the photografting surface-modified method

Molecularly imprinted polymers (MIPs), based on photografting surface-modified polystyrene beads as matrices, were prepared with acrylamide as the functional monomer, bovine hemoglobin as the template molecule and N, N′-methylene bisacrylamide as the crosslinker in a phosphate buffer. The results of IR, scanning electron microscope (SEM) and elemental analyses demonstrated the formation of a grafting polymer layer on the polystyrene-bead surface. Subsequent removal of the template left behind cavities on the surface of the polymer matrix with a shape and an arrangement of functional groups having complementary binding sites with the original template molecule. The adsorption studies showed that the imprinted polymers have a good adsorption capacity and specific recognition for bovine hemoglobin as the template molecule. Our results demonstrated that the polymer prepared via the photografting surface-modified method exhibited better selectivity for the template. Attempts to employ the new method in molecular imprinting techniques may introduce new applications for MIPs and facilitate probable protein separation and purification. __________ Translated from Chemical Journal of Chinese Universities, 2008, 29(1): 64–70     

An inexpensive, portable and microcontrolled near infrared LED-photometer for screening analysis of gasoline

A microcontrolled, portable and inexpensive photometer is proposed. It uses a near infrared light emitting diode (NIR LED) as radiation source, a PbSe photoresistor as infrared detector and a programmable interrupt controller (PIC) microcontroller as control unit. The detector system presents a thermoresistor and a thermoelectric cooling to control the detector temperature and keep the noise at low levels. The microcontroller incorporated total autonomy on the proposed photometer. As its components are inexpensive and of easy acquisition, the proposed NIR LED-photometer is an economical alternative for chemical analyses in small routine, research and/or teaching laboratories. By being portable and microcontrolled, it also allows carrying out field chemical analyses. The instrument was successfully applied on the screening analysis to verify adulteration in gasoline samples.     

Novel Strong Cation‐exchange Monolithic Column Using Poly(vinyl ester resin) as Stationary Phase Materials for Lysozyme Separation by HPLC

本实验合成了一种以聚乙烯基酯树脂为原料的聚合物整体柱。在聚合反应中,聚乙烯基酯树脂在聚合中既作为单体同时也作为交联剂,偶氮二异丁腈作为引发剂,十六醇为致孔剂。聚合物制得后以扫描电镜考察了该聚合物的内部形态。同时联合高效液相色谱分别考察了该整体柱的分离能力和载样量。在分离实验中,考察了流动相的浓度及pH值对分离效果的影响。结果表明,溶菌酶可成功的从鸡卵清中分离出,并在较短的时间内取得了较好的分离效果。     

Folding kinetics of a naturally occurring helical peptide: implication of the folding speed limit of helical proteins

The folding mechanism and dynamics of a helical protein may strongly depend on how quickly its constituent alpha-helices can fold independently. Thus, our understanding of the protein folding problem may be greatly enhanced by a systematic survey of the folding rates of individual alpha-helical segments derived from their parent proteins. As a first step, we have studied the relaxation kinetics of the central helix (L9:41-74) of the ribosomal protein L9 from the bacterium Bacillus stearothermophilus , in response to a temperature-jump ( T-jump) using infrared spectroscopy. L9:41-74 has been shown to exhibit unusually high helicity in aqueous solution due to a series of side chain-side chain interactions, most of which are electrostatic in nature, while still remaining monomeric over a wide concentration range. Thus, this peptide represents an excellent model system not only for examining how the folding rate of naturally occurring helices differs from that of the widely studied alanine-based peptides, but also for estimating the folding speed limit of (small) helical proteins. Our results show that the T-jump induced relaxation rate of L9:41-74 is significantly slower than that of alanine-based peptides. For example, at 11 degrees C its relaxation time constant is about 2 micros, roughly seven times slower than that of SPE(5), an alanine-rich peptide of similar chain length. In addition, our results show that the folding rate of a truncated version of L9:41-74 is even slower. Taken together, these results suggest that individual alpha-helical segments in proteins may fold on a time scale that is significantly slower than the folding time of alanine-based peptides. Furthermore, we argue that the relaxation rate of L9:41-74 measured between 8 and 45 degrees C provides a realistic estimate of the ultimate folding rate of (small) helical proteins over this temperature range.     

Thiol-functionalized Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/SiO<Subscript>2</Subscript> microspheres with superparamagnetism and their adsorption properties for Au(III) ion separation

Thiol-functionalized Fe₃O₄/SiO₂ microspheres (Fe₃O₄/SiO₂-SH) with high saturation magnetization (69.3 emu g^–1), superparamagnetism, and good dispersibility have been prepared by an ethylene glycol reduction method in combination with a modified Stöber method. The as-prepared composite magnetic spheres are characterized with fourier transform infrared spectroscopy (FT-IR), zeta potential, X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and superconducting quantum interference magnetometer, and tested in separation of Au(III) ions from aqueous solutions. The data for Au(III) adsorption on Fe₃O₄/SiO₂-SH are analyzed with the Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm models, and the pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetics models. The adsorption behaviors of Au(III) on Fe₃O₄/SiO₂-SH follow the Langmuir isotherm model, and the adsorption process conforms to the pseudo-second-order kinetic model. The maximum adsorption capacity of Au(III) on Fe₃O₄/SiO₂-SH is 43.7 mg g^–1. Acetate anions play an important role yet Cu(II) ions have little interference in the adsorption of Au(III) on the adsorbent. A satisfactory recovery percentage of 89.5% is acquired by using an eluent with 1 M thiourea and 5% HCl, although thiols have a high affinity to Au(III) ions based on the hard-soft acid-base (HSAB) theory by Pearson.