Heteroepitaxial technologies on Si for high-efficiency solar cells

The improvements of the AlGaAs crystal quality grown on Si substrate and the AlGaAs/Si tandem solar cell have been studied with varying the growth conditions. The crystal quality of the AlGaAs layer was evaluated by photoluminescence, deep level transient spectroscopy, time-resolved photoluminescence and double crystal X-ray diffraction while varying the thermal cycle annealing temperature. The optimum thermal cycle annealing temperature and the buffer layer thickness for the growth of high efficiency AlGaAs/Si tandem solar cells have been presented. The active-area conversion efficiency of 21.2% and 21.4% (AMO and 1 sun at 27°C) has been demonstrated with two-terminal and four-terminal configuration, respectively, by the perfect photocurrent matching between the top cell and the bottom cell.     

Diffusion coefficient of the protein in various crystallization solutions: The key to growing high-quality crystals in space

The diffusion coefficients of lysozyme and alpha-amylase were measured in the various polyethylene glycol (PEG) solutions. Obtained diffusion coefficients were studied with the viscosity coefficient of the solution. It was found that the diffusion process of the protein was suppressed with a factor of v^γ, where ν is a relative viscosity coefficient of the PEG solution. The value of γ is ?0.64 at PEG1500 for both proteins. The value increased to ?0.48 at PEG8000 for lysozyme, while decreased to ?0.72 for alpha-amylase. The equation of an approximate diffusion coefficient at certain PEG molecular weight and concentration was roughly obtained.     

Direct fabrication of metavanadate phosphor films on organic substrates for white-light-emitting devices

White-light-emitting materials have attracted considerable attention because of their applications, such as large-surface emitting devices. Inorganic phosphor films are expected to be applied to these devices because of good chemical stability; however, a substantial reduction of fabrication temperature is required for future industrial uses such as lighting materials fabricated onto flexible organic substrates. Here we show the optical properties of white-light-emitting metavanadate phosphors, AVO3 (A: K, Rb and Cs), and we report a new direct fabrication process for RbVO3 films onto flexible polyethylene terephthalate (PET) substrates by means of a vacuum ultraviolet irradiation using an excimer lamp. In addition, the (Ca,Sr,Pr)TiO3/a-Al2O3/RbVO3/PET heterostructure prepared by an excimer-laser-assisted metal-organic deposition process has demonstrated the possibility of colour modification for RbVO3 films on PET. Our findings suggest new possibilities for further development of large-surface emitting lighting devices.     

Phase-modulation fluorometer using a dynode-voltage burst-modulated photomultiplier tube

We propose a new scheme for a phase-modulation fluorometer (PMF) in which a photomultiplier tube (PMT) is used as a photo detector whose gain is modulated sinusoidally with a burst signal of period T and duty ratio 0.5. The carrier wave of the burst modulation signal is synchronized with an incident fluorescence signal. In order to modulate the gain of the PMT, one of the dynodes in the PMT was deeply biased and the burst signal was superimposed. Because the fluorescence signal is converted to a direct current (dc) signal by the PMT internal modulation, we can make the value of the load resistance of the PMT relatively large under the condition tau < or = T/2, where tau is a time constant of a low-pass filter attached to the output of the PMT. The proposed scheme brings about advantages in sensitivity and noise immunity in detecting weak fluorescence in comparison with those of the conventional PMF. The combined technique of the burst modulation of the gain of the PMT and the alternating current (ac) signal detection alleviates the influence of the background light.     

Intrinsic ferromagnetism in nanocrystalline Mn-doped ZnO depending on Mn concentration

The physical properties of Zn(1-x)Mn(x)O nanoparticles synthesized by thermal decomposition are extensively investigated by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman light scattering and Hysteresis measurements. XRD and XPS spectra reveal the absence of secondary phase in nanocrystalline ZnO doped with 5% or less Mn; and, later confirms that the valance state of Mn to be 2+ for all the samples. Raman spectra exhibit a peak at 660 cm(-1) which we attribute to the intrinsic lattice defects of ZnO with increasing Mn concentration. Overall, our results demonstrate that ferromagnetic properties can be realized while Mn-doped ZnO obtained in the nanocrystalline form.     

Quantum dot bioconjugates for imaging, labelling and sensing

One of the fastest moving and most exciting interfaces of nanotechnology is the use of quantum dots (QDs) in biology. The unique optical properties of QDs make them appealing as in vivo and in vitro fluorophores in a variety of biological investigations, in which traditional fluorescent labels based on organic molecules fall short of providing long-term stability and simultaneous detection of multiple signals. The ability to make QDs water soluble and target them to specific biomolecules has led to promising applications in cellular labelling, deep-tissue imaging, assay labelling and as efficient fluorescence resonance energy transfer donors. Despite recent progress, much work still needs to be done to achieve reproducible and robust surface functionalization and develop flexible bioconjugation techniques. In this review, we look at current methods for preparing QD bioconjugates as well as presenting an overview of applications. The potential of QDs in biology has just begun to be realized and new avenues will arise as our ability to manipulate these materials improves.     

纳米颗粒对葡萄糖生物传感器性能影响的研究

制备了纳米金颗粒和纳米铜颗粒，分别用以修饰葡萄糖生物传感器，并选用丝网印刷金电极测试研究了纳米颗粒对葡萄糖生物传感器性能的影响。结果表明：纳米铜颗粒不能增强葡萄糖生物传感器的响应电流，并且延长了其响应时间；纳米金颗粒增强了葡萄糖生物传感器的响应电流，缩短了其响应时间，提高了其抗干扰性，但不能拓宽其检测的线性范围，并且响应电流受工作电压的影响较大；随着工作电压的下降，响应电流迅速下降，与未修饰葡萄糖生物传感器响应电流下降趋势一致。     

Spin relaxation in U2D23He

The spin relaxation in the U2D2 phase of solid ³ He is investigated theoretically. Following the procedure similar to the spin-wave theory of the electronic anti-ferromagnetic resonance, the multimagnon Hamiltonian is derived with the use of the Holstein-Primakoff method. We calculate the spin-relaxation rate due to three- and four-magnon processes that dominate at low temperatures and compare it with the linewidth of cw-NMR measured by Sasaki et al.     

Operable conditions of the beam-fanning novelty filter for the c axis and the incident angle

We analyze the operable angle range of the c axis and the incident angle of the input beam in the beam-fanning novelty filter (BFNF). With Fourier transforms we show the analysis method for the beam-fanning phenomenon. We investigate the beam-fanning phenomenon for not only the c axis but also the incident angle of the input beam in order to operate the BFNF sufficiently. Consequently, we clarify the angle range of the c axis and the incident angle, from which sufficient strong beam-fanning effect can be obtained to operate the BFNF. In addition, we verify the numerical results experimentally.     

Characterization and resolution of evaporation-mediated osmolality shifts that constrain microfluidic cell culture in poly(dimethylsiloxane) devices

Evaporation is a critical problem when handling submicroliter volumes of fluids. This paper characterizes this problem as it applies to microfluidic cell culture in poly(dimethylsiloxane) (PDMS) devices and provides a practical solution. Evaporation-mediated osmolality shifts through PDMS membranes with varying thicknesses (10, 1, 0.2, or 0.1 mm) were measured over 96 h. Even in humidified cell culture incubators, evaporation through PDMS and associated shifts in the osmolality of culture media was significant and prevented mouse embryo and human endothelial cell growth and development. A simple diffusion model, where the measured diffusion coefficient for PDMS matches reported values of approximately 10-9 m2/s, accounts for these evaporation and osmolality shifts. To overcome this problem, a PDMS-parylene-PDMS hybrid membrane was developed that greatly suppresses evaporation and osmolality shifts, yet possesses thinness and the flexibility necessary to interface with deformation-based microfluidic actuation systems, maintains the clarity for optical microscopy, and enables the successful development of single-cell mouse embryos into blastocysts under static conditions and culture of human endothelial cells under dynamic recirculation of submicroliter volumes of media. These insights and methods demonstrated specifically for embryo and endothelial cell studies will be generally useful for understanding and overcoming evaporation-associated effects in microfluidic cell cultures.