Connected Pt–Fe nanoparticle catalysts with beaded network structure show both high activity and durability for oxygen reduction.

Recent advances in nanotechnology, materials science, and biotechnology have led to innovations in the field of nanomedicine. Improvements in the diagnosis and treatment of cancer are urgently needed, and it may now be possible to achieve marked improvements in both of these areas using nanomedicine. Lipid-coated nanoparticles containing diagnostic or therapeutic agents have been developed and studied for biomedical applications and provide a nanomedicine strategy with great potential. Lipid nanoparticles have cationic headgroups on their surfaces that bind anionic nucleic acids and contain hydrophobic drugs at the lipid membrane and hydrophilic drugs inside the hollow space in the interior. Moreover, researchers can design nanoparticles to work in combination with external stimuli such as magnetic field, light, and ionizing radiation, which adds further utility in biomedical applications. In this Account, we review several examples of lipid-based nanoparticles and describe their potential for cancer treatment and diagnosis. (1) The development of a lipid-based nanoparticle that included a promoter-enhancer and transcriptional activator greatly improved gene therapy. (2) The addition of a radiosensitive promoter to lipid nanoparticles was sufficient to confer radioisotope-activated expression of the genes delivered by the nanoparticles. (3) We successfully tailored lipid nanoparticle composition to increase gene transduction in scirrhous gastric cancer cells. (4) When lipophilic photosensitizing molecules were incorporated into lipid nanoparticles, those particles showed an increased photodynamic cytotoxic effect on the target cancer. (5) Coating an Fe(3)O(4) nanocrystal with lipids proved to be an efficient strategy for magnetically guided gene-silencing in tumor tissues. (6) An Fe(16)N(2)/lipid nanocomposite displayed effective magnetism and gene delivery in cancer cells. (7) Lipid-coated magnetic hollow capsules carried aqueous anticancer drugs and delivered them in response to a magnetic field. (8) Fluorescent lipid-coated and antibody-conjugated magnetic nanoparticles detected cancer-associated antigen in a microfluidic channel. We believe that the continuing development of lipid-based nanomedicine will lead to the sensitive minimally invasive treatment of cancer. Moreover, the fusion of different scientific fields is accelerating these developments, and we expect these interdisciplinary efforts to have considerable ripple effects on various fields of research.

The anisotropic magnetotransport properties of a (Ga,Mn)As epilayer and the magnetization switching are studied as a function of temperature. The magnetization switching field shows asymmetry for crystallographically equivalent [110] and [1̄10] directions at 4 K, and the asymmetry is more significant at 40 K. The magnetization switching features clearly show that cubic magnetocrystalline anisotropy along 〈100〉, which is biased by a small uniaxial anisotropy along the [110] easy axis, is dominant at 4 K. On the other hand, the [110] uniaxial anisotropy competes with the cubic anisotropy and dominates the magnetization switching at 40 K. Accordingly, the magnetization reversal in the (Ga,Mn)As epilayer occurs via 90° and 180° domain-wall displacement at 4 and 40 K, respectively. A mechanism of the change in the magnetic anisotropy is discussed within a theoretical description of the hole band structure.

Two different ferromagnetic-paramagnetic transitions are detected in (Ga,Mn)As/GaAs(001) epilayers from ac susceptibility measurements: transition at a higher temperature results from (Ga,Mn)As cluster phases with [110] uniaxial anisotropy and that at a lower temperature is associated with a ferromagnetic (Ga,Mn)As matrix with 100 cubic anisotropy. A change in the magnetic easy axis from [100] to [110] with increasing temperature can be explained by the reduced contribution of 100 cubic anisotropy to the magnetic properties above the transition temperature of the (Ga,Mn)As matrix.Ferromagnetism in Mn-doped p−type semiconductors can theoretically be understood by the p − d exchange interaction between hole carriers and doped Mn spins [1,2,3,4], which can be manipulated by electric-field [5] or optical-hole generation [6]. Recent studies of magnetic anisotropy in (Ga,Mn)As/GaAs(001) epilayers, on the other hand, have shown a significant change in the magnetic anisotropy with increasing temperature [7,8,9,10]; uniaxial anisotropy along [110] ([110] uniaxial anisotropy) [7,8,9,10,11,12] becomes predominant with increasing temperature [7,8,9, 10] as well as increasing hole concentration [13]. In spite of these intensive studies, the origin of [110] uniaxial anisotropy is still unclear within the current theoretical framework and an understanding of the change in the magnetic anisotropy with temperature is therefore of fundamental importance in revealing the physics of magnetic semiconductors.The aim of this study is to give a comprehensive description of the magnetic anisotropy in (Ga,Mn)As epilayers.In this Letter, two different peaks in temperature-dependent ac susceptibility that are associated with ferromagnetic-paramagnetic transitions are clearly shown. The peak profile at a higher transition temperature has a considerable dependence on frequency, indicating a blocking process in magnetic clusters, while that at a lower transition temperature shows no frequency dependence. The results provide evidence that the magnetic transitions at the lower and higher temperatures are associated with magnetic phases with cubic anisotropy and [110] uniaxial anisotropies, respectively, and the crossover of the magnetic easy axis from 100 to [110] can be interpreted by the ferromagneticparamagnetic transition of the magnetic phase with 100 cubic magnetocrystalline anisotropy accordingly. 100 nm-thick (Ga,Mn)As epilayers were grown on top of a 400-nm-thick GaAs buffer layer grown at 590• C on a semi-insulating GaAs (001) substrate using lowtemperature molecular beam epitaxy (MBE) at 190 − 235• C under an As-rich growth condition. To increase the hole carrier concentration, some epilayers were subject to post-growth annealing in an N 2 atmosphere for 60 − 240 min at 250• C [14]; hole concentration was controlled by changing the Mn content and/or lowtemperature annealing [13]. Hole carrier concentrations p (= ionized Mn acceptor concentration) were measured with electrochemical capacitance-voltage (ECV) method at room temper...