Films (ca. 150 microm thick) of twelve acrylate mixtures, which contained various proportions of hydrocarbon acrylates [mainly oligo(ethylene glycol) diacrylate, (OEGDA)] and small amounts of a silicone hexaacrylate (in proportion of 5% or less), were cured on a nickel substrate, and X-ray photoelectron spectroscopy analysis of the nickel-side surface compositions showed that for formulations with and without the silicone hexaacrylate, this surface was enriched with OEGDA and saturated (up to 50%) with the silicone hexaacrylate, respectively. The silicone hexaacrylate phase-separated and formed micelles which migrated to the resin-nickel interface. Silicone hexaacrylate, inherently less reactive, also significantly slowed the photopolymerization of the mixtures. The sequential homopolymerization of OEGDA and silicone hexaacrylate in a formulation was elicited using real-time Fourier transform infrared spectroscopy. The design-of-experiment approach was used to quantify the influence of the components on gelation time and the nickel-side surface composition as well as provide the statistical models to predict these two properties for new compositions. 相似文献
A simple and sensitive high performance liquid chromatography (HPLC) method was developed to determine residual Pluronic F-68 (PF-68) in in-process samples of monoclonal antibody (MAb) preparations. The method permits the direct injection of proteinaceous samples after simple sample dilution and is able to quantitate as low as 50 mg/L of PF-68 in the presence of up to approximately 30 g/L of protein. The PF-68 molecule was separated on a restricted access reversed phase column using a step gradient and then measured by an evaporative light scattering detector (ELSD). The method was successfully applied to demonstrate PF-68 clearance in MAb purification processes. A modified colorimetric method using liquid-liquid extraction and cobalt thiocyanate to derivatize PF-68 is also described. The results obtained by both the HPLC and colorimetric methods were compared. In addition to its ease of use and simplicity, the HPLC method had better accuracy and higher throughput than the colorimetric method. 相似文献
Neutron inelastic scattering measurements on ErFe2 reveal an unusual doubling of the two lowest energy spin wave branches over a wide temperature range. Crystal field calculations suggest that one member of each doublet is associated with transitions from the ground state of Er3+ to the first excited state, while the other is associated with transitions between excited states. The gapless acoustic mode appearing at high temperatures is identified as a propagating excited state spin wave. 相似文献
Bacterial cellulose (BC) is often regarded as a prime candidate nano‐reinforcement for the production of renewable nanocomposites. However, the mechanical performance of most BC nanocomposites is often inferior compared with commercially available polylactide (PLLA). Here, the manufacturing concept of paper‐based laminates is used, i.e., “PaPreg,” to produce BC nanopaper reinforced PLLA, which has been called “nanoPaPreg” by the authors. It is demonstrated that high‐performance nanoPaPreg (vf = 65 vol%) with a tensile modulus and strength of 6.9 ± 0.5 GPa and 125 ± 10 MPa, respectively, can be fabricated. It is also shown that the tensile properties of nanoPaPreg are predominantly governed by the mechanical performance of BC nanopaper instead of the individual BC nanofibers, due to difficulties impregnating the dense nanofibrous BC network.
One of the significant technical developments in magnetism of the early 1970's was the discovery of a new class of rare earth intermetallic compounds, the RFe2 Laves phases, which were found to exhibit room temperature magnetostrictive strains approaching 2 × 10−3, an order of magnitude larger than any previously known. Since that time both the fundamental and technical properties of these materials have been of intense interest, and they remain the subject of active research even today. The large strains available are useful in such applications as production of high amplitude, low frequency sound waves in water, certain types of strain gages, vibration compensation and compensation for temperature induced strains in large laser mirrors. Because the performance of these materials depends critically on such fundamental properties as the magnetic anisotropy, magnetization and grain orientation of the material, there has been a very strong interplay between fundamental studies and applications. In this article we briefly review the fundamental magnetic and magnetostrictive properties of the RFe2 Laves phases, focusing especially on the complex behavior of the anisotropy and the success of crystal field theory in explaining it. We also present neutron measurements of magnetic excitation spectra and explain how they provide an understanding of the remarkable success of mean field theory for these systems. 相似文献
A neutral tetradentate ligand L1 [L1?=?3,6-bis(pyrazol-1-yl)-pyridazine] reacts with Ni(ClO4)2·6H2O and undergoes counterion exchange with PF?6 to give di- and tetranuclear complexes [Ni2(L1)2(CH3CN)4](PF6)4·4H2O (1) and [Ni4(L1)4(µ-OH)4](ClO4)4·2H2O (2), respectively. The presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as base controls the nuclearity of the complex formation. Both complexes were structurally characterized by physicochemical and spectroscopic techniques. Their crystal structures revealed that both complexes are centrosymmetric and adopt slightly distorted octahedral geometry. Complex 1 crystallizes in monoclinic space group C2/c as the Ni(II) center is octahedrally bound to L1 in a trans-isomer arrangement. Complex 2 crystallizes in tetragonal space group I41/amd with four L1 and four hydroxy bridging ligands linked to Ni(II) center in cis-isomer arrangement. Cyclic voltammograms of complexes 1 and 2 were measured under Ar and CO2. Under CO2, the quasireversible peaks of both complexes become irreversible and a current enhancement occurs under reduction.
Mass spectrometry has become an indispensable tool for the global study of metabolites (metabolomics), primarily using electrospray ionization mass spectrometry (ESI‐MS). However, many important classes of molecules such as neutral lipids do not ionize well by ESI and go undetected. Chemical derivatization of metabolites can enhance ionization for increased sensitivity and metabolomic coverage. Here we describe the use of tris(2,4,6,‐trimethoxyphenyl)phosphonium acetic acid (TMPP‐AA) to improve liquid chromatography (LC)/ESI‐MS detection of hydroxylated metabolites (i.e. lipids) from serum extracts. Cholesterol which is not normally detected from serum using ESI is observed with attomole sensitivity. This approach was applied to identify four endogenous lipids (hexadecanoyl‐sn‐glycerol, dihydrotachysterol, octadecanol, and alpha‐tocopherol) from human serum. Overall, this approach extends the types of metabolites which can be detected using standard ESI‐MS instrumentation and demonstrates the potential for targeted metabolomics analysis. Published in 2009 by John Wiley & Sons, Ltd. 相似文献