Magnetic properties of one-dimensional embedded nickel nanostructures in gold nanowires

Magnetic nanostructures of nickel embedded in gold were successfully fabricated by electrochemical deposition in porous alumina templates. Structural characterization of the samples confirmed the formation of pure phase, crystalline multi-segmented Au-Ni-Au nanowires. Magnetic characterization of the wires reveals that ferromagnetism arises as a result of Ni embedded in Au segments. An interesting behavior of coercivity was observed that showed a rapid decrease of coercivity for smaller Ni segments while a monotonic decrease was found for the larger segments. Finally, the saturation magnetization of the wires exhibited a slower increase for smaller Ni segments while a sharp increase was observed for larger Ni segments.     

Phase transition characteristics of Ge–Sb–Te pseudobinary alloys in laser irradiation measurement

Optical switching and structural transformation of GeTe–Sb₂Te₃ pseudobinary alloys, Ge₂Sb₂Te₅, Ge₁Sb₂Te₄, and Ge₁Sb₄Te₇, were studied for data storage application. As-deposited Ge₂Sb₂Te₅, Ge₁Sb₂Te₄, and Ge₁Sb₄Te₇ thin films were amorphous and they crystallized to FCC and HCP upon heat treatment. Crystallization was accelerated by increasing the proportion of Sb₂Te₃ rather than GeTe in Ge–Sb–Te compounds; this was observed by reflectivity changes under nanosecond laser irradiation in static tester. The different crystallization kinetics according to composition might be affected by the structural incompatibility of GeTe under the ‘Umbrella Flip’ theory.     

Upregulation of extracellular matrix metalloproteinase inducer (EMMPRIN) and gelatinases in human atherosclerosis infected with Chlamydia pneumoniae: the potential role of Chlamydia pneumoniae infection in the progression of atherosclerosis

Chlamydia pneumoniae infection implicated as an important etiologic factor of atherosclerosis, especially in coronary artery disease (CAD), was found in vitro to be associated with the induction of matrix metalloproteinases (MMPs). An extracellular matrix metalloproteinase inducer (EMMPRIN)/ membrane-type 1 matrix metalloproteinase (MT1-MMP) system which induces and activates MMPs, is suggested to be functional and were upregulated in the failing myocardium. However, the upstream regulation of MMPs by C. pneumoniae within atheroma itself remains unclear. We evaluated the seroepidemiologic study of C. pneumoniae infection in CAD patients (n= 391) and controls (n=97) and performed histopathological and in vitro analysis in atherosclerotic vascular tissues obtained from patients with seropositive to C. pneumoniae (n=20), by using immunochemistry for C. pneumoniae, EMMPRIN/MT1-MMP, MMP-2, and MMP-9. The seropositive rates of both anti-C. pneumoniae IgG and IgA were 56.7% in CAD group and 43.3% in control group (P=0.033). Seropositive rate was increased in subgroups of CAD patients without conventional coronary risk factors compared to those with conventional risk factors. Immunoreactivities of EMMPRIN, MT1-MMP, MMP-2, and MMP-9 were increased in the atheromatous plaque itself, predominantly in immunoreactive macrophages/mononuclear cells to C. pneumoniae. Furthermore, Western blot analysis showed that EMMPRIN and MMP-2 were detected more prominently in atherosclerotic tissues infected with C. pneumoniae compared to control tissues. Zymographic analysis revealed that activities of MMP-2 and MMP-9 were more increased in atherosclerotic tissues infected with C. pneumoniae compared to control tissues. The present study demonstrated upstream regulation of MMPs can be induced by C. pneumoniae within atheromatous plaque itself. These findings help to understand the potential role of C. pneumoniae in the progression of atherosclerosis.     

Layered perovskites with giant spontaneous polarizations for nonvolatile memories

A series of titanate-based layered perovskites having large values of the spontaneous polarization P(s) were developed for their applcations to nonvolatile ferroelectric random access memories. Among these, the Nd-modified bismuth titanate [Bi(4-x)Nd(x)Ti(3)O(12) (BNdT)] system exhibited the most remarkable ferroelectric properties. The c-axis oriented BNdT capacitor was characterized by a switchable remanent polarization 2P(r) of over 100 microC/cm(2) and imprinting and fatigue-free behavior. The active Ti site responsible for the giant P(s) was identified with the help of Rietveld analysis, x-ray absorption near-edge structure study, and ab initio quantum computations.     

Fabrication of nano-structured polythiophene nanoparticles in aqueous dispersion

The synthetic route of unsubstituted polythiophene (PT) nanoparticles was investigated in aqueous dispersion via Fe³⁺-catalyzed oxidative polymerization. With this new synthetic method, high conversion of thiophene monomers was obtained with only a trace of FeCl₃. The dispersion state showed that the PT nanoparticles were well dispersed in many polar solvents, compared to non-polar solvents, such as acetone, chloroform, hexane, and ethyl acetate. To compare the photoluminescence properties between PT nanoparticle dispersion and PT bulk polymers, the PL intensities were measured in the same measuring conditions. Further, core–shell poly(styrene/thiophene) (poly(St/Th)) latex particles were successfully prepared by Fe³⁺-catalyzed oxidative polymerization during emulsifier-free emulsion polymerization. The different polymerization rates of each monomer resulted in core–shell structure of the poly(St/Th) latex particles. The PL data of the only crumpled shells gave evidence that the shell component of core–shell poly(St/Th) latex particles is indeed PT, which was corroborated by SEM data. PL intensity of the core–shell poly(St/Th) nanoparticle dispersion was much higher than that of the PT nanoparticle dispersion, due to its thin shell layer morphology, which was explained by the self-absorption effect.     

Release of N(2) from the carbon nanotubes via high-temperature annealing

Nitrogen (N)-doped carbon nanotubes (CNTs) were heated to 1000 degrees C under an ultrahigh vacuum. X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge structure (XANES) reveal three different N structures; graphitelike, pyridine-like, and molecular N(2). The vibrationally resolved XANES peaks of N(2) were first observed, suggesting the existence of molecular N(2) as intercalated and trapped forms. The annealing process can decrease the average N content from 6.3 at. % to 3.3 at. %, mainly by releasing molecular N(2). Electron energy-loss spectroscopy (EELS) confirms that the annealing releases molecular N(2) from the CNTs.     

Nonparallelism between reaction rate and dienophile-catalyst affinity in catalytic enantioselective Diels-Alder reactions

[reaction: see text] The above reaction is much faster with Y = CF(3)CH(2)O than with Y = CH(3)O. However, the methyl ester is a strong inhibitor of the Diels-Alder reaction of the trifluoroethyl ester, since it has a higher affinity for the catalyst 1.     

Torsional wave experiments with a new magnetostrictive transducer configuration

For the efficient long-range nondestructive structural health inspection of pipes, guided waves have become widely used. Among the various guided wave modes, the torsional wave is most preferred since its first branch is nondispersive. Our objective in this work is to develop a new magnetostrictive transducer configuration to transmit and receive torsional waves in cylindrical waveguides. The conventional magnetostrictive transducer for the generation and measurement of torsional waves consists of solenoid coils and a nickel strip bonded circumferentially to test pipes. The strip must be premagnetized by a permanent magnet before actual measurements. Because of the premagnetization, the transducer is not suitable for the long-term on-line monitoring of pipes buried underground. To avoid the cumbersome premagnetization and to improve the transduction efficiency, we propose a new transducer configuration using several pieces of nickel strips installed at 45 degrees with respect to the pipe axis. If a static bias magnetic field is also applied, the transducer output can be substantially increased. Several experiments were conducted to study the performance of the proposed transducer configuration. The proposed transducer configuration was also applied for damage detection in an aluminum pipe.     

Waveform preservation of the backscattered stimulated Brillouin scattering wave by using a prepulse injection

We have found that it is possible to preserve the temporal waveform of the reflected wave generated from stimulated Brillouin scattering (SBS) by using a prepulse technique. The waveform of the SBS wave usually shows a steep rising edge in the ordinary SBS process. It has been found that the waveform of the reflected wave depends on both the prepulse energy and the time delay between the main pulse and the prepulses. A prepulse energy of 5 mJ and a time delay of 5 ns have been measured to be the optimum values under the experimental conditions. This prepulse method is useful in developing a multistage system employing several SBS cells in series for high-power laser applications.