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We present a method for developing potential-energy surfaces for abstraction reactions with four or more atoms which combines spline fits to high quality ab initio results for the three degrees of freedom that are most active in the reaction (two stretches and a bend) with simple empirical functions (Morse stretches, cosine bends, and torsions) for the spectator variables. The geometry and force constants associated with the spectator modes are allowed to vary along the reaction path so as to match stationary point properties from the ab initio calculations. In an application of this approach to the H+H[sub 2]O reaction, we are able to generate a global surface for the H[sub 3]O system that accurately matches ab initio properties, and is globally smooth and free of artifacts. Quasiclassical trajectory (QCT) calculations are used with this surface to study the H+H[sub 2]O reaction dynamics for both the ground and local mode excited states. The resulting ground-state angular distributions, product state vibrational and rotational distributions, and rotational alignment factors are in excellent agreement with all known experiments. This represents an improvement over the results obtained using previous surfaces, but like the past surfaces, the calculated integral cross sections are below experiment by at least a factor of 2. For studies of the H+H[sub 2]O reaction involving local mode excited states of water, the new surface is consistent with ab initio threshold behavior, with the (04)[sup -] local mode state having zero activation energy. However the reactive rate coefficients are substantially smaller than the observed total reactive plus inelastic rate coefficient. This indicates that recent experiments due to Barnes, Sharkey, Sims, and Smith are dominated by energy transfer rather than reaction. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The hierarchical carbon-coated lithium iron phosphate (LiFePO 4 ) nano-grain microspheres are prepared by chemical co-precipitation method. The microstructure and cycling performance are compared for samples treated at 975 K and 1025 K. Transmission electron micrograph (TEM) analysis confirms the existence of ferric pyrophosphate phase of the general formula Fe 4 (P 2 O 7 ) 3 . Reasons for the formation of the crystalline Fe 4 (P 2 O 7 ) 3 phase are intensively discussed. It is considered that a little amount of Fe 4 (P 2 O 7 ) 3 phase has no distinct detrimental effect on the cycling capacity of samples. Although there is a big decrease from 132 to 74.5 mAh/g in discharge capacity at a current rate of 1C for the sample treated at 975 K from 400 to 500 cycles. The capacities for the sample were observed to be recovered to its theoretical value in discharge at a current rate of 0.1C after 500 cycles. It is demonstrated that the degradation behavior for the sample treated at 975 K is attributed to the increase of diffusion resistance of the lithium ions into the bulk of LiFePO 4 electrode materials, which is not reported before in the literatures. [ABSTRACT FROM AUTHOR]

Abstract: The hierarchical carbon-coated LiFePO4 nano-grain microspheres are prepared by a chemical co-precipitation method. The microstructure and electrochemical properties of LiFePO4/C composites treated at 950–1025 K are intensively investigated. The rate discharge capability has been obviously enhanced when sample is treated at 1025 K. This attributes to its improved electric conductivity of 0.09 S cm−1 due to the in-situ formation of Fe2P phase. The cycling stabilities are excellent until 300 cycles for all the samples at the rate 1C in discharge, which is very difficult to reach for nano-grains with large specific surface area and high reaction activity. Our samples with hierarchical microstructures exhibit high Li-ion diffusion rate (10−9–10−13 cm2 S−1) with enhanced tap density (1.30 g cm−3). It is considered in our paper that the rate capacities increased by Li-ion diffusion rate are not as obvious as electric conductivity. Therefore, the LiFePO4/FePO4 reaction is a non-diffusional controlled process. [Copyright &y& Elsevier]

Although the role of muscle LIM protein (MLP, also known as CRP3), a LIM-only protein of LIM domain-containing protein family, is well-characterized, the mechanism by which the MLP gene expresses remains unclear. Herein, we demonstrate that myogenin and myocyte enhancer factor 2C (MEF2C) cooperate in activating the MLP gene in myogenesis. RT-PCR, real-time PCR and Western blotting showed that overexpression of myogenin or myogenin plus MEF2C led to induction of the MLP gene in differentiating C2C12 and NIH3T3 fibroblasts. By contrary, knocking-down of myogenin by RNA interference (RNAi) suppressed MLP expression in differentiating C2C12. Deletion and reporter enzyme assay revealed that the promoter activity was determined largely by the region extending from −260 to −173, which containing three E-box (CANNTG motif) candidates. Site-directed mutagenesis demonstrated that the E-box at position −186 to −180 was crucial for activating the promoter by myogenin. Furthermore, MEF2C could enhance myogenin-mediated activation of the promoter. In addition, chromatin immunoprecipitation (ChIP) and re-ChIP showed that myogenin and MEF2C were associated with the activated MLP promoter. Together, these results suggest that myogenin and MEF2C cooperate in the MLP gene activation. The linking of the MLP gene activation with myogenin and MEF2C may facilitate myogenin-mediated differentiation of striated muscle. [ABSTRACT FROM AUTHOR]

Pearlitic transformation mechanisms have been investigated in ultra-fine grained GCr15 steel. The ultrafine-grained steel, whose grain size was less than 1µm, was prepared by thermo-mechanical treatment at 873K and then annealing at 923K for 2h. Pearlitic transformation was conducted by reheating the ultra-fine grained samples at 1073K and 1123K for different periods of time and then cooling in air. Scanning electron microscope observation shows that normal lamellar pearlite, instead of granular cementite and ferrite, cannot be formed when the grain size is approximately less than 4(±0.6)µm, which yields a critical grain size for normal lamellar pearlitic transformations in this chromium alloyed steel. The result confirms that grain size has a great influence on pearlitic transformation by increasing the diffusion rate of carbon atoms in the ultra-fine grained steel, and the addition of chromium element doesn't change this pearlitic phase transformation rule. Meanwhile, the grain growth rate is reduced by chromium alloying, which is beneficial to form fine grains during austenitizing, thus it facilitating pearlitic transformation by divorced eutectoid transformation. Moreover, chromium element can form a relatively high gradient in the frontier of the undissolved carbide, which promotes carbide formation in the frontier of the undissolved carbide, i.e., chromium promotes divorced eutectoid transformation. [ABSTRACT FROM AUTHOR]

Curcuminoids are well known for their capabilities to combat risk factors that are associated with ageing and cellular senescence. Recent reports have demonstrated that curcuminoids can extend the lifespan of model organisms. However, the underlying mechanisms by which these polyphenic compounds exert these beneficial effects remain unknown. In this study, t-BHP-induced premature senescence model in human fibroblasts was chosen to explore the protective effects of a curcuminoid, bisdemethoxycurcumin (BDMC), on cellular senescence. The results demonstrated that BDMC attenuated oxidative stress-induced senescence-like features which include the induction of an enlarged cellular appearance, higher frequency of senescence-associated β-galactosidase staining activity, appearance of senescence-associated heterochromatic foci in nuclei, decrease in proliferation capability, and alteration in related molecules such as pl6 and retinoblastoma protein. Notably, we found that BDMC treatment activated Sirt1/AMPK signaling pathway. Moreover, downregulating Sirtl by the pharmacological inhibitor nicotianamine or small interfering RNA blocked BDMC-mediated protection against f-BHP-mediated decrease in proliferation. These results suggested that BDMC prevented t-BHP-induced cellular senescence, and BDMC-induced Sirtl may be a mechanism mediating its beneficial effects. [ABSTRACT FROM AUTHOR]

Furanodiene (FUR) is a natural terpenoid isolated from Curcumae Rhizoma, a well-known Chinese medicinal herb that presents antiproliferation activities in several cancer cell lines. In this study, we demonstrated that FUR concentration dependently inhibits the cell proliferation of A549, NIH-H1299, and 95-D lung cancer cells. β-elemene, another terpenoid isolated from Curcumae Rhizoma, exhibited weaker antiproliferative effects in A549 and NIH-H1299 cells and activities similar to FUR in 95-D cells. FUR significantly inhibited colony formation in A549 and 95-D cells and upregulated both the mRNA and protein expression levels of binding immunoglobulin protein (BIP) and C/EBP homologous protein (CHOP), indicating that endoplasmic reticulum (ER) stress is induced. FUR treatment led to the accumulation of CHOP in the nucleus, which further confirms induction of ER stress. Furthermore, combined treatment of FUR with paclitaxel showed significant synergetic activities in NIH-H1299 and 95-D cells, suggesting its potential roles in combination therapy. These findings provide a basis for the further study of the anticancer effects in vivo and the internal mechanisms of FUR. [ABSTRACT FROM AUTHOR]

To better understand the evolutionary history, intergeneric relationships and circumscription of Chrysanthemum and Ajania and the taxonomic position of some small Asian genera (Anthemideae, Asteraceae), the sequences of the nuclear ribosomal internal transcribed spacer (nrDNA ITS) and the chloroplast trnL-F intergenic spacer (cpDNA IGS) were newly obtained for 48 taxa and combined with those already deposited in GenBank. Phylogenies with an emphasis on Chrysanthemum, Ajania and its allies, by both maximum parsimony and Bayesian analysis, were constructed using either the ITS sequence alone, the IGS sequence alone or combined sequences. The IGS sequence was low phylogenetically informative, but some deletions and insertions were informative for interspecific and intergeneric delimitations. The ITS and the ITS/IGS phylogenies both suggested the presence of two major clades. The monophyly of subtribe Artemisiinae (clade A) could be retrieved when the phylogenetic positions of some ambiguous taxa were renewedly considered. Subtribe Artemisiinae was chiefly divided into two groups, (1) one corresponding to Chrysanthemum, Arctanthemum, Ajania, Opisthopappus and Elachanthemum (the Chrysanthemum group), (2) another to Artemisia, Crossostephium, Neopallasia and Sphaeromeria (the Artemisia group). Within the Chrysanthemum group, Chrysanthemum Arctanthemum and Ajania were closely related to each other, and the generic circumscription was ambiguous; Phaeostigma was excluded from this group that was also confirmed by the 6-bp insertion in the IGS sequence; radiate or rare discoid Brachanthemum was excluded, and discoid Elachanthemum without ray florets was added to this group; at the same time, Opisthopappus in subtribe Tanacetinae should be transferred to subtribe Artemisiinae and became one of the components of the Chrysanthemum group. Based on the molecular phylogenetic framework, the evolution of pollen and capitulum characters was inferred. [ABSTRACT FROM AUTHOR]

We demonstrate that activation of nuclear factor κB (NF-κB) in neurons is neuroprotective in response to kainic acid (KA)-induced excitotoxicity. Combination of Western blotting, immunocytochemistry, and electrophoresis mobility shift assay showed that KA exposure induced a fast but transient nuclear translocation of the NF-κB p65 subunit and increased DNA-binding activity of NF-κB in primary cultured cortical neurons. The transient NF-κB activity was associated with upregulation of antiapoptotic Bcl-xL and XIAP gene products revealed by real-time PCR. Knockdown of p65 decreased neuronal viability and antiapoptotic gene expression. In addition, we showed that KA-stimulated DNA-binding activity of NF-κB was associated with reactive oxygen species and calcium signals, using AMPA/KA receptor antagonist, calcium chelator, and antioxidant. These results suggest that the fast and transient activation of NF-κB initiated by calcium signals is one of the important proximal events in response to KA-induced excitotoxicity, which has neuroprotective effect against KA-induced apoptosis. [ABSTRACT FROM AUTHOR]

The nanocomposites consist of nanometer silica fillers embedded in thermoset polymers, which were prepared by means of irradiation of ultraviolet light. The nanomechanic properties had been investigated by load--displacement analysis from nanoindentation experiments. The results obtained showed that the nanoindentation hardness is decreasing and tends to a certain value with increasing indentation depth, the value is among 1.91-4.11 GPa while the nanosilica contents varied from 0 to 5% within nanocomposites. Young's modulus measured by nanoindentation is higher than the value by tensile test, namely EI/ET = 2.63 and the enhancement of Young's modulus due to the presence of nanosilica with the above contents, EI/EI,0 = 1.7-2.0 from nanoindentation test and ET/ET,0 = 1.8-2.2 from tensile test, was compared to be consistent with each other in two different methods. So nanoindentation technique has been successfully applied for the valuation of the nanomechanic properties of nanocomposites with nanosilica. [ABSTRACT FROM AUTHOR]