Solvothermal synthesis of magnetic Fe_3O_4 microparticles via self-assembly of Fe_3O_4 nanoparticles

Ferromagnetic Fe 3 O 4 nanoparticles were synthesized and then self-assembled into microparticles via a solvothermal method,using FeCl 3 ·6H 2 O as the iron source,sodium oleate as the surfactant,and ethylene glycol as the reducing agent and solvent.The obtained Fe 3 O 4 microparticles were characterized by X-ray powder diffraction (XRD),X-ray photoelectron spectroscopy (XPS),Raman spectroscopy and vibrating sample magnetometer (VSM).The size and morphology of the particles were examined using transmission ...     

Surface structure of cationic surfactant solutions investigated by angular resolved X‐ray photoelectron spectroscopy with calibrated transmission function

The main goal of the present work is to investigate the surface structure of cationic surfactant solutions by angular resolved X‐ray photoelectron spectroscopy (ARXPS) after calibrating transmission function of the spectrometer. We have estimated the transmission function of the ARXPS spectrometer, and with it, we investigated solution of tetrabutylammonium iodide in a nonaqueous polar solvent. By genetic algorithm, the fractional concentration‐depth profiles of constituents were reconstructed. These depth profiles evidence the enrichment of surfactant and the depletion of solvent in the surface regime and verify the separate distributions of oppositely charged surfactant ions. From those profiles we draw a conclusion that there is a preferred orientation for cation present at the surface, and the possibility for cation to take this orientation is related to its surface amount. Copyright © 2010 John Wiley & Sons, Ltd.     

X-ray photoelectron spectroscopic studies on oxidation behavior of nickel and iron aluminides under oxygen atmosphere at low pressures

Oxidation behaviors of NiAl, Ni₃Al, and FeAl under oxygen atmosphere at low pressures were studied by X-ray photoelectron spectroscopy (XPS). Clean surfaces of these aluminides were prepared by fracturing in an ultra high vacuum, and then the fractured surfaces were oxidized by exposing to high-purity oxygen at pressures up to 1.3 Pa without exposing to air. The oxides formed on NiAl and FeAl surfaces were Al₂O₃, whereas the oxide on Ni₃Al was NiAl₂O₄. Aluminum, nickel, and iron on clean surfaces were oxidized even at a pressure of 1.3 × 10⁻⁶ Pa. The oxidation evolves with an increase in the pressure of oxygen, and further oxidation of aluminum occurs prior to that of nickel or iron. The oxidation behaviors under such oxygen atmosphere were similar to those of the aluminides oxidized in air, and these behaviors could be predicted from thermodynamic consideration.     

Synthesis and photophysical properties of soluble low‐bandgap thienothiophene polymers with various alkyl side‐chain lengths

We report the facile synthesis and characterization of a class of thienothiophene polymers with various lengths of alkyl side chains. A series of 2‐alkylthieno[3,4‐b]thiophene monomers (Ttx) have been synthesized in a two‐step protocol in an overall yield of 28–37%. Poly(2‐alkylthieno[3,4‐b]thiophenes) (PTtx, alkyl: pentyl, hexyl, heptyl, octyl, and tridecyl) were synthesized by oxidative polymerization with FeCl₃ or via Grignard metathesis (GRIM) polymerization methods. The polymers are readily soluble in common organic solvents. The polymers synthesized by GRIM polymerization method (PTtx‐G) have narrower molecular weight distribution (?) with lower molecular weight (M_n) than those synthesized by oxidative polymerization (PTtx‐O). The band structures of the polymers with various lengths of alkyl side chains were investigated by UV–vis spectroscopy, cyclic voltammetry, and ultraviolet photoelectron spectroscopy. These low‐bandgap polymers are good candidates for organic transistors, organic light‐emitting diodes, and organic photovoltaic cells. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Diameter of P.A. random graphs with edge‐step functions

In this work we prove general bounds for the diameter of random graphs generated by a preferential attachment model whose parameter is a function f:N→[0,1] that drives the asymptotic proportion between the numbers of vertices and edges. These results are sharp when f is a regularly varying function at infinity with strictly negative index of regular variation ?γ. For this particular class, we prove a characterization for the diameter that depends only on ?γ. More specifically, we prove that the diameter of such graphs is of order 1/γ with high probability, although its vertex set order goes to infinity polynomially. Sharp results for the diameter for a wide class of slowly varying functions are also obtained.     

XPS and IGC characterization of steam treated triticale straw

The surface chemical composition and surface energy of native and steam treated triticale straws have been investigated by X-ray photoelectron spectroscopy (XPS) and inverse gas chromatography (IGC) to reveal the effect of steam treatment temperature and time. The XPS results show that the contents of C elements and C-C group on the exterior surface of native triticale straw are much higher than those on the interior surface, indicating that there was a high quantity of wax on the exterior surface of the native triticale straw. Upon steam treatment, both carbon levels and C-C groups reduce with increasing steam temperature and treatment time of the exterior surfaces. However, the effect of steam treatment on the interior surface is very limited. In terms of the surface acid and base properties, the steam treated samples exhibited higher acid and base properties than the native sample, indicating a more polar surface of the steam treated sample.     

Compatibility as underlying mechanism behind the evolution of networks

In this work we propose a dynamic network model based on an evolutive rule called compatibility. The presence of common topological properties observed in two real complex networks are well reproduced by the proposed model. These results suggest that the compatibility between nodes is sufficient to generate the complexity observed in real systems even considering that the new added nodes do not have the ability to know global information of the system.     

Mouse bone marrow‐derived mesenchymal stem cell response to nanostructured titanium substrates produced by high‐pressure torsion

Mesenchymal stem cells (MSCs) with the ability to differentiate into various mesoderm‐like cells are known to migrate to various organs to repair injured tissues. They can attach to the implant surface, differentiate into bone‐forming cells, and ultimately osseointegrate with the prosthesis. This study investigates bone marrow‐derived mesenchymal stem cellular response to the grain structure of titanium substrates produced by high‐pressure torsion and annealing processes. Cell attachment, proliferation, viability, and morphology are evaluated on the surface of differently processed nanostructured and coarse‐grained samples. The bacterial adhesion and calcium phosphate crystal formation and growth are also assessed on the surface of the substrates. The nanostructured titanium shows significantly higher cell adhesion, proliferation, spreading, and viability compared with the untreated and coarse‐grained titanium substrates. The adhesion of bacteria is lower and surface bioactivity is higher on the surface of the nanostructured titanium substrate. The results demonstrate the superior MSC compatibility, antibacterial efficacy, and surface bioactivity of the nanostructured titanium substrates, which could lead to early implant fixation and improved osseointegration. Copyright © 2012 John Wiley & Sons, Ltd.     

Ultraviolet Photoelectron Spectra of Mono Metal Atom Encapsulated Fullerenes

Abstract

Ultraviolet photoelectron spectra of mono metal atom encapsulated fullerenes, M@C₈₂ (M = La, Gd and Sc), are measured with a synchrotron radiation light source. When the excitation energy is tuned, spectral intensity oscillation is observed in these mono metal atom encapsulated fullerenes as was in empty fullerene, C₈₂. Their incident photon energy dependence is essentially the same. Their spectra deeper than 5 eV are almost identical and are similar to those of empty fullerene. The noticeable difference among the spectra is in the energy region between the Fermi level and 4 eV, which reveals the degree of electron transfer from the metal atom to the fullerene cage.     

Surface chemical composition of human maxillary first premolar as assessed by X-ray photoelectron spectroscopy (XPS)

The surface chemical composition of dental enamel has been postulated as a contributing factor in the variation of bond strength of brackets bonded to teeth, and hence, the probability of bracket failure during orthodontic treatment. This study systematically investigated the chemical composition of 98 bonding surfaces of human maxillary premolars using X-ray photoelectron spectroscopy (XPS) to ascertain compositional differences between right and left first premolars. The major elements detected in all samples were calcium, phosphorus, oxygen, nitrogen and carbon. Surface compositions were highly variable between samples and several elements were found to be highly correlated. No statistical significant difference in the chemical composition of the maxillary right and left first premolars was found (p > 0.05). Knowledge of the chemical composition of enamel surfaces will facilitate future studies that relate this information to the variations in dental enamel bond strength.