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Pressure effects on magnetic properties of two La0.7Ca0.3MnO3 nanoparticle samples with different mean particle sizes were investigated. Both the samples were prepared by the glycine-nitrate method: sample S-as-prepared (10 nm), and sample S-900-subsequently annealed at 900 A degrees C for 2 h (50 nm). Magnetization measurements revealed remarkable differences in magnetic properties with the applied pressure up to 0.75 GPa: (i) for S sample, both transition temperatures, para-to-ferromagnetic T (C) = 120 K and spin-glass-like transition T (f) = 102 K, decrease with the pressure with the respective pressure coefficients dT (C)/dP = -2.9 K/GPa and dT (f)/dP = -4.4 K/GPa; (ii) for S-900 sample, para-to-ferromagnetic transition temperature T (C) = 261 K increases with pressure with the pressure coefficient dT (C)/dP = 14.8 K/GPa. At the same time, saturation magnetization M (S) recorded at 10 K decreases/increases with pressure for S/S-900 sample, respectively. Explanation of these unusual pressure effects on the magnetism of sample S is proposed within the scenario of the combined contributions of two types of disorders present in the system: surface disorder introduced by the particle shell, and structural disorder of the particle core caused by the prominent Jahn-Teller distortion. Both disorders tend to vanish with the annealing of the system (i.e., with the nanoparticle growth), and so the behavior of the sample S-900 is similar to that previously observed for the bulk counterpart.

Calcium hydroxyapatite (CHA) formation was produced by biomimetic deposition on the surfaces of silica layers of the steel bands, using slightly modified simulated body fluid (SBF). The used SBF had a pH value of 7.4 and a similar ionic composition like human plasma. Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) method was used to analyse obtained phases on the surfaces of silica films after various times of sample soaking in SBF. Atomic force microscopy (AFM) investigations pointed out the mechanism of CHA nucleation. Mass changes investigations of the CHA thin films showed that the depth of CHA films was dependent on the aging time of silica substrate in SBF.

Diffuse infiltration of glioma cells into normal brain tissue is considered to be a main reason for the unfavorable outcomes of patients with malignant gliomas. Invasion of glioma cells into the brain parenchyma is facilitated by metalloprotease-mediated degradation of the extracellular matrix. Metalloproteases are released as inactive pro-forms and get activated upon cleavage by membrane bound metalloproteases. Here, we show that membrane type 1 metalloprotease (MT1-MMP) is up-regulated in glioma-associated microglia, but not in the glioma cells. Overexpression of MT1-MMP is even lethal for glioma cells. Glioma-released factors trigger the expression and activity of MT1-MMP via microglial toll-like receptors and the p38 MAPK pathway, as deletion of the toll-like receptor adapter protein MyD88 or p38 inhibition prevented MT1-MMP expression and activity in cultured microglial cells. Microglial MT1-MMP in turn activates glioma-derived pro-MMP-2 and promotes glioma expansion, as shown in an ex vivo model using MT1-MMP-deficient brain tissue and a microglia depletion paradigm. Finally, MyD88 deficiency or microglia depletion largely attenuated glioma expansion in 2 independent in vivo models.

In this paper, the kinetics and sintering mechanism of hydro-thermally synthesized hydroxyapatite in the temperature range 900-1100 degrees C are presented. It was found that at 900 degrees C, the sintering process is very slow, whereas at 1000, 1050, and 1100 degrees C is much faster, caused by activated sintering with liquid phase/phase of solution on spots with concentrated material impurity and the formation of reaction/polyeutectic mixtures dominates. The activation energies of sintering were also determined. At all the investigated sintering temperatures, an approximate value of 90 kJ mol(-1) was found. (c) 2008 Elsevier B.V. All rights reserved.

Nanosized mixed valent perovskite manganites CaMnO3, La doped Ca0.7La0.3MnO3 (S1) and Cc co-doped Ca0.7La0.3Mn0.8Ce0.2O3 (S2) samples were synthesized by the modified glycine-nitrate procedure. Their magnetic properties were investigated by M(T) measurements in both ZFC and FC regimes in several applied DC magnetic fields, as well as by AC susceptibility measurements. Nanosized CaMnO3 exhibits similar behavior as its bulk counterpart with the antiferromagnetic transition temperature T-N = 120 K. Obtained magnetization curves for S1 and S2 display behavior typical for magnetic nanoparticle systems, such as irreversibility of ZFC and FC curves, and field dependence of the magnetization maximum in ZFC branches. Field dependence of the magnetization maxima (T-max versus H-2/3) as well as AC susceptibility behavior (frequency dependence of T-max) point to the presence of considerable interparticle interactions. Consequently, below T-max the formation of super spin-glass state can be assumed. (c) 2007 Elsevier B.V. All rights reserved.

A nanocomposite consisting of lead sulfide (PbS) nanoparticles (NPs) with average diameter of 26 angstrom, according to absorption threshold shift, and polyvinyl alcohol (PVA) was characterized using far-infrared absorption spectroscopy. The experimental results are consistent with theoretical calculations that include proper mechanical boundary conditions at the nanocrystal-host interface.

Evaluation of biomaterials as safe and effective therapies needs preclinical models to estimate their biologic potential. This paper investigates biocompatibility by the in vivo assessment of the muscle tissue reaction after implantation of the hidrothermally produced calciumhydroxyapatite. Specific attention has to be given to the synthesis technique which influences the stereology of the material and the behaviour of the material in living tissues. The synthesized powders of hydroxyapatite are preferentially carbonated hydroxyapatite of the 8 type in the form of agglomerates that accommodate two-modal size pores of 1.5-10 nm and 50-200 nm. The particles are built from crystallites of 8-22 nm in size, bind inside of the prime particles sized is between 10 and 63 nm. They form agglomerates of 200 nm in size and these were further clustered building up the biggest agglomerates of 520 mu m. Biocompatibility assessment revealed that only mild to moderate inflammatory reaction was seen around the calciumhydroxyapatite implants. Calciumhydroxyapatite failed to show any substantional toxicity.

The influence of precursor concentration, pressure, temperature and time of hydrothermal synthesis on the development of calcium hydroxyapatite structure has been analyzed. The obtained results show that it is possible to adjust the conditions of hydrothermal synthesis from solutions of relatively high concentrations to obtain calcium hydroxyapatite nanopowders of well-defined structure. The relationship between the synthesis and the lattice parameters, as well as the crystallite size and the microstructure of synthesized hydroxyapatite has been established. The synthesized powders are preferentially carbonated hydroxyapatite of the B type in the form of agglomerates that accommodate two-modal size pores of 1.5-10 and 50-200 nm. The structure of calcium hydroxyapatite particles consists of crystallites 8-22 nm in size, bound within prime particles, which size is between 10 and 63 nm, that in turn form bigger agglomerates 200 nm in size, which further cluster building up agglomerates 5-20 mu m in size.

The influence of the magnetic ions dilution on the crystal and magnetic structures of CoxZn1-xO (x = 1, 0.90, 0.83, 0.75) solid solutions has been studied by the neutron diffraction and magnetic susceptibility measurements. It has been concluded that magnetic ordering of CoO is preserved in CoxZn1-xO regardless of the magnetic dilution for x greater than or equal to 0.75. This is confirmed independently by three different methods: Rietveld refinement of the magnetic structure, dependence of magnetic moments vs. temperature, and variation of the reduced Neel temperatures t = T-N(x)/T-N(1) with concentration. (C) 2004 Elsevier B.V. All rights reserved.

In order to study the influence of the magnetic ions dilution on the crystal and magnetic structure of polycrystalline CoxZn1-xO (x = 1, 0.90, 0.83, 0.75) samples we have performed neutron-diffraction experiments at several temperatures in the 10-295 K range. Magnetic transition temperatures were determined by magnetic susceptibility measurements over the 50-350 K temperature interval. The Rietveld refinements of the neutron data for all samples show that lowering of the crystal symmetry from cubic in the paramagnetic region to monoclinic in the magnetically ordered state occurs. It is found that the magnetic unit cell is double the monoclinic crystal cell along the c-axis, which points to the onset of antiferromagnetic ordering along that axis. Magnetic ordering of CoO is preserved in all the samples despite the magnetic dilution. This finding is confirmed by comparing the variation of magnetic moments with temperature for all samples, as well as by the concentration dependence of the reduced Neel temperatures t = T-N(x)/T-N(1). The exchange interaction between Co2+ ions was found to be of the Heisenberg type. (C) 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim.