One crucial challenge for subwavelength optics has been the development of a tunable source of coherent laser radiation for use in the physical, information and biological sciences that is stable at room temperature and physiological conditions. Current advanced nearfield imaging techniques using fibre-optic scattering probes 1,2 have already achieved spatial resolution down to the 20-nm range. Recently reported far-field approaches for optical microscopy, including stimulated emission depletion 3 , structured illumination 4 , and photoactivated localization microscopy 5 , have enabled impressive, theoretically unlimited spatial resolution of fluorescent biomolecular complexes. Previous work with laser tweezers 6-8 has suggested that optical traps could be used to create novel spatial probes and sensors. Inorganic nanowires have diameters substantially below the wavelength of visible light and have electronic and optical properties 9,10 that make them ideal for subwavelength laser and imaging technology. Here we report the development of an electrode-free, continuously tunable coherent visible light source compatible with physiological environments, from individual potassium niobate (KNbO 3 ) nanowires. These wires exhibit efficient second harmonic generation, and act as frequency converters, allowing the local synthesis of a wide range of colours via sum and difference frequency generation. We use this tunable nanometric light source to implement a novel form of subwavelength microscopy, in which an infrared laser is used to optically trap and scan a nanowire over a sample, suggesting a wide range of potential applications in physics, chemistry, materials science and biology.Nanometre-scale photonics is emerging as a key ingredient in novel sensing and imaging applications, as well as for advanced information technology, cryptography, and signal processing circuits. A versatile and useful nonlinear circuit element for integrated optical networks must be able to double the frequency of light using second harmonic generation (SHG), a second-order nonlinear optical phenomenon. In this process, two photons with the fundamental angular frequency v 1 are converted through a nonlinear crystal polarization into a single photon v 2 at twice the fundamental frequency (v 2 5 2v 1 , the field still lacks sufficiently small devices that efficiently generate tunable coherent photons. Here we show that the large second-order susceptibility x (2) of KNbO 3 nanowires facilitates the generation of tunable, coherent visible radiation that is sufficient for in situ scanning and fluorescence microscopy.We chose the perovskite oxide KNbO 3 as the nanowire material because of its low toxicity, chemical stability, large effective nonlinear optical coefficients (d eff 5 10.8-27 pm V 21 at l 5 1,064 nm) at room temperature (298 K) 19 , large refractive indices (n 5 2.1-2.5) 20 , as well as its transparency in a wide range of wavelengths including the visible spectral region 21 . Single-crystalline KNbO 3 nanowires were synthesized usi...

In primary monolayer cultures of rat mature hepatocytes, many metabolic functions as well as cell growth are regulated by cell density. There are two types of regulatory response of these functions to change of cell density. Growth-related functions, such as DNA synthesis, induction of glucose-6-phosphate dehydrogenase, 2-aminoisebutyric acid transport, synthesis of cellular protein, and cholesterogenesis, are stimulated by low cell density. In contrast, functions related to hepatocyte-specific characters, such as the inductions of tyrosine aminotransferase, serine dehydratase, and malic enzyme and synthesis of triglycerides, are stimulated by high cell density. The reciprocal responses of these cellular activities to cell density were mimicked by addition of plasma membranes purified from adult rat liver to hepatocytes cultured at low cell density. The modulator activity was heat labile and trypsin sensitive. The activity was also found in plasma membranes from kidney, brain, and erythrocytes, although the specific activities of these preparations seemed to be different. These results suggest that the reciprocal regulations of cell growth and hepatocyte-specific functions are mediated by some surface components via cell-cell contact.Adult rat hepatocytes in primary culture retain in vivo levels of various liver functions and respond to various hormones (1)(2)(3)(4) Cell Isolation and Monolayer Culture. Parenchymal hepatocytes were isolated from male Wistar rats weighing 150-200 g by in-situ perfusion on the liver with collagenase, essentially as described by Seglen (11). The isolated cells were suspended at 5 X 10' cells per ml in Williams medium E containing 2% calf serum and 2 nM insulin. The cell density at inoculation was varied from 5 X 105 to 2.5 x 106 cells per 5-cm (diameter)Corning plastic culture dish. Over 80% of the cells became attached in 1 hr at 37C under 5% C02/30% 02 in air. After culture for 2 hr. the medium -was changed to hormone-free Williams medium E containing 5% calf serum. In experiments on the effect of addition of plasma membranes, rat hepatocytes were inoculated at a low density (7 x 105 cells per 5-cm dish). After 2 hr. the medium was changed to hormone-free medium containing 5% calf serum and then various amounts of plasma membranes were added to the cultures. Hormones were added to the medium after 22 hr of culture. Incubation was continued for 24 or 45 hr further and then various activities were assayed.Assay of DNA Synthesis. DNA synthesis was assayed by measuring incorporation of [3H]thymidine into DNA with or without hydroxyurea in 2 hr. Radioactivity in the hot trichloroacetic acid-soluble fraction was measured as described (6). Assays of Enzyme Activities. The cells were harvested with a rubber policeman in 0.2-1.0 ml of 20 mM potassium phosphate buffer (pH 7.5) containing 0.1 mM dithiothreitol and 5 mM EDTA for the glucose-6-phosphate dehydrogenase (Glc-6-P-DHase) assay, in 0.1-0.5 ml of 5 mM Tris-HCl buffer (pH

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Many superconductors do not entirely expel magnetic flux-rather, magnetic flux can penetrate the superconducting state in the form of vortices. Moving vortices create resistance, so they must be 'pinned' to permit dissipationless current flow. This is a particularly important issue for the high-transition-temperature superconductors, in which the vortices move very easily. Irradiation of superconducting samples by heavy ions produces columnar defects, which are considered to be the optimal pinning traps when the orientation of the column coincides with that of the vortex line. Although columnar defect pinning has been investigated using macroscopic techniques, it has hitherto been impossible to resolve individual vortices intersecting with individual defects. Here we achieve the resolution required to image vortex lines and columnar defects in Bi2Sr2CaCu2O8+delta (Bi-2212) thin films, using a 1-MV field-emission electron microscope. For our thin films, we find that the vortex lines at higher temperatures are trapped and oriented along tilted columnar defects, irrespective of the orientation of the applied magnetic field. At lower temperatures, however, vortex penetration always takes place perpendicular to the film plane, suggesting that intrinsic 'background' pinning in the material now dominates.

Electrolyte is a key material for success in the research and development of next-generation rechargeable batteries. Aluminium rechargeable batteries that use aluminium (Al) metals as anode materials are attractive candidates for next-generation batteries, though they have not been developed yet due to the lack of practically useful electrolytes. Here we present, for the first time, non-corrosive reversible Al electrolytes working at room temperature. The electrolytes are composed of aluminium chlorides, dialkylsulfones, and dilutants, which are realized by the identification of electrochemically active Al species, the study of sulfone dependences, the effects of aluminium chloride concentrations, dilutions and their optimizations. The characteristic feature of these materials is the lower chloride concentrations in the solutions than those in the conventional Al electrolytes, which allows us to use the Al metal anodes without corrosions. We anticipate that the sulfone-based electrolytes will open the doors for the research and development of Al rechargeable batteries.

Critical-current density (Jc) is a parameter of primary importance for potential applications of high-temperature copper oxide superconductors. It is limited principally by the breakdown of zero-resistive current due to thermally activated flux flow at high temperatures and high magnetic fields. One promising method to overcome this limitation is to introduce efficient pinning centers into crystals that can suppress the flux flow. A marked increase in Jc was observed in Bi2Sr2CaCu2O8+delta (Bi-2212) single crystals doped with a large amount of Pb. By electron microscopy, characteristic microstructures were revealed that probably underlie the observed enhancement in Jc: thin (10 to 50 nanometers), platelike domains having a modulation-free structure appeared with spacings of 50 to 100 nanometers along the b axis.

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