A Two-Dimensional NMR Study of Birch Milled Wood Lignin

Chemical structures of underivatized and acetylated birch Milled Wood Lignins were investigated in solution by various two-dimensional NMR experiments such as COSY, HOHAHA, HMQC, and HMBC.     

Novel synthesis and solution properties of hyperbranched poly(ethyl methacrylate)s by quasi‐living radical copolymerization using photofunctional inimer

Hyperbranched poly(ethyl methacrylate)s (PEMA) were prepared by quasi‐living radical copolymerization of 2‐(N,N‐diethylaminodithiocarbamoyl)‐ethyl methacrylate (inimer: DTEM) with ethyl methacrylate (EMA) under UV irradiation. DTEM monomers play an important role in this copolymerization system as inimers capable of initiating living radical polymerization of the vinyl group. Two monomers (DTEM and EMA) showed almost equal reactivity toward both propagating species, and the copolymer composition was the same as the comonomer feed. This result means that both the branching and chain length of the hyperbranched molecules can be controlled statistically by the feed monomer ratios. The compact nature of the hyperbranched macromolecules is demonstrated by comparison of their solution properties with the linear analogues. Copyright © 2004 Society of Chemical Industry     

Interleukin (IL)-6 as a pancreas carcinoma-derived vascular permeability regulator in vitro

The interaction between pancreas adenocarcinoma and vascular endothelial cells in vitro was investigated. Culture media of pancreas carcinoma cells PCI-10, but not PCI-24, induced an augmented albumin permeability across the endothelial monolayer, an event which was blocked by the calmodulin antagonist, W-7. Only marginal inhibitory effects were obtained using protein kinase inhibitors, H-7 and HA-1004. When cytokine production by pancreas carcinoma cells was examined, production of IL-6 in large amounts by PCI-10, but not by PCI-24 cells was evident. As recombinant IL-6 generated a dose-dependent permeability increase, and as this effect was inhibited by W-7, we considered that the enhancement of vascular permeability was mediated by this cytokine. The activity of culture supernatants for enhanced permeability was almost completely absorbed by the addition of an antibody specific for IL-6. Tumor-derived IL-6 as a soluble mediator regulates vascular permeability in vitro, and the production of this factor by pancreas adenocarcinoma cells presumably modulates biologic behavior.     

Preparation of tri-O-benzylcellulose by the use of nonaqueous cellulose solvents

A procedure has been developed for preparing tri-O-benzylcellulose with higher yields than 90%. In this procedure, cellulose was dissolved in a nonaqueous cellulose solvent, SO₂–diethylamine (DEA)–dimethyl sulfoxide (DMSO), and then powdered sodium hydroxide was added. To the suspension thus prepared, benzyl chloride was added in four portions under heating. Chemical and physical properties of tri-O-benzylcellulose were studied, and tri-O-benzylcellulose prepared from microcrystalline cellulose powder shows the characteristic of thermotropic liquid crystal.     

Magnetic particles stabilized by chemically adsorbed monolayers for use in functional fluids

Chemically adsorbed monolayers were applied to magnetic particle surfaces for preparing functional fluids. Fluorocarbon silanes were used to form the monolayers, as the methoxysilyl groups of fluorocarbon silanes can form a strong chemical bond with the surface of a magnetic particle without degrading its properties. Fluorocarbon oils were used as the carrier liquid because of their high affinity with the fluorocarbon group of the monolayers, enabling the particles to disperse easily in it. Also, fluorocarbon oils can sustain high temperature and low pressure. The functional fluids prepared using these materials showed magnetorheological characteristics and can be used under high-vacuum and/or high-temperature conditions like those encountered in space.     

Effect of underpotential deposition of lead on polarization behavior of nickel in acidic perchlorate solutions at room temperature

The effect of Pb²⁺ on polarization behavior of nickel has been investigated in 0.1 M NaClO₄ + 10⁻² M HClO₄ + x M PbO solutions (x = 0, 10⁻⁵, 10⁻⁴, 10⁻³) at room temperature. The cyclic voltammogram has suggested that Pb²⁺ degrades the stability of the passive film on Ni. The corrosion potential of Ni shifted to the more noble direction and the anodic current peak of Ni dissolution decreased with increasing Pb²⁺ concentration in solution, indicating that Pb²⁺ suppresses significantly the anodic dissolution. The underpotential deposition (UPD) of lead on Ni in the potential range more noble than −0.215 V (SHE) corresponding to the equilibrium potential of the Pb²⁺ (10⁻³ M)/Pb electrode was confirmed by XPS and GDOES analyses. The anodic Tafel slope, b⁺, of Ni dissolution changed from b⁺ = 40 mV decade⁻¹ in the absence of Pb²⁺ to b⁺ = 17 mV decade⁻¹ in the presence of 10⁻⁴ or 10⁻³ M Pb²⁺, which was ascribed to the increase in active sites of Ni surface emerged as a result of electrodesorption of Pb adatoms. The roles of Pb adatoms in active dissolution and active/passive transition of Ni were discussed from the above results.     

不同pH条件下几种铜缓蚀剂的比较研究

采用交流阻抗法研究了在不同ｐＨ条件下的３％ＮａＣｌ溶液中３种缓蚀剂４ＣＢＴＡ,５ＣＢＴＡ,ＣＢＴ－１在浓度为４０ｍｇ／ｋｇ时对铜电极的缓蚀行为并与ＢＴＡ进行了比较,实验结果表明在ｐＨ＝６及ｐＨ＝９时这３种缓蚀剂均无缓蚀作用,而在ｐＨ＝３时它们的缓蚀作用比较明显,缓蚀效果均比ＢＴＡ好,尤以４ＣＢＴ缓蚀效果最佳。     

Matrix Vesicle-Mediated Mineralization and Osteocytic Regulation of Bone Mineralization

Bone mineralization entails two mineralization phases: primary and secondary mineralization. Primary mineralization is achieved when matrix vesicles are secreted by osteoblasts, and thereafter, bone mineral density gradually increases during secondary mineralization. Nearby extracellular phosphate ions (PO₄³⁻) flow into the vesicles via membrane transporters and enzymes located on the vesicles’ membranes, while calcium ions (Ca²⁺), abundant in the tissue fluid, are also transported into the vesicles. The accumulation of Ca²⁺ and PO₄³⁻ in the matrix vesicles induces crystal nucleation and growth. The calcium phosphate crystals grow radially within the vesicle, penetrate the vesicle’s membrane, and continue to grow outside the vesicle, ultimately forming mineralized nodules. The mineralized nodules then attach to collagen fibrils, mineralizing them from the contact sites (i.e., collagen mineralization). Afterward, the bone mineral density gradually increases during the secondary mineralization process. The mechanisms of this phenomenon remain unclear, but osteocytes may play a key role; it is assumed that osteocytes enable the transport of Ca²⁺ and PO₄³⁻ through the canaliculi of the osteocyte network, as well as regulate the mineralization of the surrounding bone matrix via the Phex/SIBLINGs axis. Thus, bone mineralization is biologically regulated by osteoblasts and osteocytes.     

Joint User Association and Power Allocation for Millimeter-Wave Ultra-Dense Networks

Mobile Networks and Applications - To meet the demand of various high-speed data rate services as well as serving an exponential increment of mobile devices, millimeter-Wave (mmWave) communication...     

Numerical modeling on a reciprocating active magnetic regenerator refrigeration in room temperature

Considering the unignorable factors in practice, a new time independent, 2-dimensional porous media model of room-temperature Active Magnetic Regenerative Refrigeration (AMRR) has been proposed. The 2-D model improved the existing 1-dimensional model by introducing the influence of heat transfer effect though the regenerator wall and conduction for y-axis inside the regenerator. This study compared the previous 1-D model with the 2-D model and concluded that the system can lose 22% of cooling capacity caused by air convection and the conduction loss in y can reach to 10% of cooling capacity. It is concluded that the new model will be useful to predict the performance of room AMRR for more practical conditions.