Effective base point free theorem for log canonical pairs--Koll\'ar type theorem

We prove Koll\'ar's effective base point free theorem for log canonical pairs.Comment: 9 pages, v2: Appendix was added, minor revisions, v3: minor modifications, title changed, v4: minor modifications, to appear in Tohoku Math.

Study on magnetic thermal seeds coated with thermal-responsive molecularly imprinted polymers

We conceived a novel hybrid carrier of a thermal-responsive molecularly imprinted polymer (MIP) and a magnetic thermal seed (MTS) that showed a heat-generating ability under an alternate current (AC) magnetic field. Compared to our previous publications, we modify both the MIP and MTS to improve the feasibility for the hybrid carrier, briefly we have to achieve the accurate size control and narrower size distribution of MTS, and higher molecular recognition/release ability of MIP. Firstly, uniformly sized particles which are expected to show a large heat-generating ability under an AC magnetic field were successfully prepared by controlling the core creation. Then, an MIP targeted for selective adsorption of pemetrexed (PMX), a well-known anti-cancer drug, was prepared using N-carbobenzoxy-L-glutamic acid as a pseudo template. Finally, the preliminary hybridization of the MTS and the MIP-equivalent polymer coating was examined by introducing vinyl groups as methacrylic acid using a ligand exchanging method

Structural control of magnetite nanoparticles for hyperthermia by modification with organic polymers: Effect of molecular weight

Hyperthermia treatment using appropriate magnetic materials in an alternating magnetic field to generate heat has been recently proposed as a low-invasive cancer treatment method. Magnetite (Fe3O4) nanoparticles are expected to be an appropriate type of magnetic thermal seed for this purpose, and the addition of organic substances during the synthesis process has been studied for controlling particle size and improving biological functions. However, the role of the properties of the organic polymer chosen as the modifier in the physical properties of the thermal seed has not yet been comprehensively revealed. Therefore, this study clarifies these points in terms of the molecular weight and the charge of the functional groups of the added polymers. Excepting polyethyleneimine, the Fe3O4 crystallite size decreased with increasing polymer molecular weight. Neutral polymers did not suppress the Fe3O4 formation regardless of the difference in molecular weight, while suppression of the Fe3O4 formation was observed for low molecular weight anionic polymers and high molecular weight cationic polymers. Samples with a small amount of Fe3O4 or with crystallite size less than 10 nm induced low heat generation under an alternating magnetic field

Synthesis of Ni Carbide Nanoparticles with Ni 3 C-Type Structure in Polyol Solution Containing Dispersant

Nanoparticles of Ni carbide of about 50 nm in diameter were synthesized by the reduction of Ni salt in a polyol solution in the presence of polyvinylpyrrolidone (PVP). It was found that the aggregation of nanoparticles was suppressed when PVP was added to the polyol solution during synthesis. Diffraction peaks of the fcc and hexagonal structures were observed for the specimen synthesized without PVP. On the other hand, no peaks assigned to the fcc structure and no spontaneous magnetization were observed for the specimen synthesized with 50 g/L PVP, although pure bulk Ni are fcc structure and ferromagnetic at room temperature. Additionally, small peaks were observed in the X-ray diffraction pattern at 2ª = 26.2, 35.7 and 47.8°, originated not from the impurity phase but from the hexagonal phase. The specimen synthesized with 50 g/L PVP was fundamentally identified as Ni carbide with a Ni 3 C-type structure, as small peaks mentioned above were assigned to superlattice peaks. The structure parameters of the Ni carbide were refined by Rietveld analysis. It is concluded that the formation of the Ni carbide nanoparticles with Ni 3 C-type structure in the polyol solution is enhanced by the addition of PVP

Magnetic properties of mechanically milled Sm-Co permanent magnetic materials with the structure

The magnetic properties of Sm(Co,Fe,Cu,Zr) 7 compound with the TbCu 7 structure are studied for the mechanically milled samples. The coercivity could be varied, without affecting the saturation magnetization, from 44 kA/m for the micron sized particles to 280 kA/m by reducing the particle size to sub-micron size (600-900 nm) using high-energy ball milling. The enhancement in the coercivity is attributed to the particles approaching single domain size. The presence of dipolar coupling suggests that the grain sizes are well above the exchange length for the milled samples. The thermal measurements indicate that the compound with the TbCu 7 structure is not stable at high temperatures beyond 743 K

Nonequilibrium Magnetic Response of Anisotropic Superparamagnetic Nanoparticles and Possible Artifacts in Magnetic Particle Imaging

Magnetic responses of superparamagnetic nanoparticles to high-frequency AC magnetic fields with sufficiently large amplitudes are numerically simulated to exactly clarify the phenomena occurring in magnetic particle imaging. When the magnetic anisotropy energy inevitable in actual nanoparticles is taken into account in considering the magnetic potential, larger nanoparticles exhibit a delayed response to alternations of the magnetic fields. This kind of delay is rather remarkable in the lower-amplitude range of the field, where the assistance by the Zeeman energy to thermally activated magnetization reversal is insufficient. In some cases, a sign inversion of the third-order harmonic response was found to occur at some specific amplitude, despite the lack in DC bias magnetic field strength. Considering the attenuation of the AC magnetic field generated in the human body, it is possible that the phases of the signals from nanoparticles deep inside the body and those near the body surface are completely different. This may lead to artifacts in the reconstructed image. Furthermore, when the magnetic/thermal torque-driven rotation of the anisotropic nanoparticles as well as the magnetic anisotropy energy are taken into account, the simulated results show that, once the easy axes are aligned toward the direction of the DC bias magnetic field, it takes time to randomize them at the field-free point. During this relaxation, the third-order harmonic response depends highly upon the history of the magnetic field. This is because non-linearity of the anhysteretic magnetization curve for the superparamagnetic nanoparticles varies with the orientations of the easy axes. This history dependence may also lead to another artifact in magnetic particle imaging, when the scanning of the field-free point is faster than the Brownian relaxations