Characterization of microspherical semi-transparent solar cells and modules

Microspherical solar cells and modules have been fabricated. The spherical nature of these semi-transparent devices allows the microspherical cells to harvest both directly incident and diffuse components of sunlight thereby improving the solar energy conversion efficiency. Indoor and outdoor characterizations of these three dimensional semi-transparent cells and modules are carried out using a Lambertian reflector in order to assess the maximum efficiency of the devices. In the absence of the reflector the cell efficiency is 13.5% under standard illumination (100 mW cm⁻², A.M. 1.5, 25 °C). However, this is significantly enhanced in the presence of the reflector. Microspherical modules with the reflector are directly compared to similar semi-transparent modules comprised of traditional planar devices, in outdoor tests at low light intensity (2.5–25 mW cm⁻²) to further demonstrate the benefits of the design particularly at low angle of incident radiation.     

Development of an image evaluation method for skin color distribution in facial images and its application: Aging effects and seasonal changes of facial color distribution

In this article, we present an evaluation method for the skin color distribution in the face area. Unlike previous methods that extract a specific area, our method subdivides the entire face into small regions and analyzes detailed, per-frame textures. Our evaluation method for skin color distribution is based on facial feature points and includes segmentation that takes into account the facial skeleton and muscle orientation. The use of facial feature points enables a comparison at relatively equal positions on the face without depending on the shape or size of the individual's face. Our evaluation method is versatile, and as an application, we clarified age-specific features and seasonal variations of facial color distribution. As a result of applying this evaluation method to the facial images of women aged 20 to 78 years, we confirmed that the lightness of the face decreased as age increased. In particular, the decrease in lightness was remarkable in the region along the cheekbone, from the temple to the center of the cheek. Furthermore, we analyzed the seasonal changes of melanin distribution in the face area. This showed that the melanin index increased particularly in the cheekbone area in the summer when the influence of ultraviolet rays became large. Our novel methodology and the data presented in this article will be useful in various fields, such as dermatology, cosmetics, and computer vision.     

Proteolytic activity and recombinant protein production in virus-infected Sf-9 insect cell cultures supplemented with carboxyl and cysteine protease inhibitors

In insect cell-baculovirus expression systems for recombinant protein production, it is sometimes necessary to supplement cultures with protease inhibitors to protect recombinant proteins against proteolysis. To date, however, there is no information available concerning protease activities in inhibitor-supplemented cultures. The aim of the present study was to investigate intracellular and extracellular protease activities in cultures of virus-infected Sf-9 insect cells which were supplemented with inhibitors against carboxyl and cysteine proteases produced during culture. Prior to the supplementation culture, the cell toxicity of several protease inhibitors was determined. As a result, pepstatin A (carboxyl protease inhibitor) and E64, cystatin, leupeptin, and antipain (cysteine protease inhibitors) tested in this study showed no apparent negative effects on the growth and viability of noninfected Sf-9 insect cells at low concentrations. In addition, E64 and pepstatin A could rapidly permeate virus-infected Sf-9 cells and inhibit the respective intracellular protease activities. A virus-infected culture with a multiplicity of infection of 1 was carried out with E64 and pepstatin A which were added to the culture medium at 2 d post-infection. As a result of inhibitor supplementation, the cellular activity for recombinant protein biosynthesis was reduced by 5-30%. However, a significant reduction in carboxyl and cysteine protease activities was observed not only in the medium but also intracellularly. This is the first study that directly demonstrates a reduction in extracellular and intracellular protease activities in protease inhibitor-supplemented cultures of virus-infected insect cells.     

Raman fiber oscillator as optical amplifier

A Raman fiber oscillator used for optical amplification is demonstrated to have lower double Rayleigh scattering, transient spikes, cross-phase modulation, and higher saturation input threshold compared with a conventional discrete Raman amplifier at similar operating conditions. This could be a promising technology for deployment in practical systems.     

Chaos control and noise suppression in external-cavitysemiconductor lasers

Feedback-induced chaos and intensity noise enhancement in a laser diode with external optical feedback are studied by computer simulations. The enhancement of relative intensity noise (RIN) that is often observed in experiments is considered as a result of the feedback-induced deterministic chaos and the intensity noise suppression is treated from the viewpoint of chaos control. Especially, the conventional noise suppressing technique known as a high-frequency injection modulation is turned into a problem of stabilizing chaos through parameter modulations. We developed an analytical method which allows to optimize the modulation frequency from the linear stability analysis of the dynamical model that describes the laser diode with external feedback. The robustness of the modulation with respect to the modulation frequency and depth is verified and the results suggest the feasibility of applying our method to actual noise suppression. The RIN in the low-frequency region (up to 100 MHz) is shown to be reduced to the solitary laser level when the feedback-induced chaos is effectively controlled with the optimized modulation frequency     

High temperature catalytic combustion of methane and propane over hexaaluminate catalysts: NOx emission characteristics

Several hexaaluminate-related materials were prepared via hydrolysis of alkoxide and powder mixing method for high temperature combustion of CH₄ and C₃H₈, in order to investigate the effect of the concentration of the fuels, O₂ and H₂O on NO_x emission and combustion characteristics. Among the hexaaluminate catalysts, Sr_0.8La_0.2MnAl₁₁O₁₉₋ prepared by the alkoxide method exhibited the highest activity for methane combustion and low NO_x emission capability. NO_x emission at 1500 °C was increased linearly with O₂ concentration, whereas water vapor addition decreased NO_x emission in CH₄ combustion over the Sr_0.8La_0.2MnAl₁₁O₁₉₋ catalyst. In the catalytic combustion of C₃H₈ over the Sr_0.8La_0.2MnAl₁₁O₁₉₋ catalyst, the amount of NO_x emitted was raised in the temperature range between 1000 and 1500 °C when the C₃H₈ concentration increased from 1 to 2 vol.%. It was found that NO_x emission in this temperature range was reduced effectively by adding water vapor.     

Melting and glass transition of radiation-induced graft polyethylene

Melting and glass transition data are reported employing DSC for styrene-grafted high-density polyethylene obtained by γ radiation. Judging from the data of the melting point and the heat of fusion, the grafted polystyrene had no effect on the polyethylene crystallites, but the half-width of the thermogram was observed to increase slightly, showing an effect on the crystallite size distribution. As no effect was observed on the glass transition temperature by grafting, the amorphous region of the polyethylene apparently was not affected. It is suggested, therefore, that the free volume or segmental mobility will not be decreased by radiation-induced grafting. Very few but long grafted chains had negligible effect on the average polyethylene chain length available for segmental motion, and grafted polystyrene should be expected to differ little from the styrene homopolymer in thermal motions.     

Effects of 6-anilino-1,3,5-triazine-2,4-dithiol,zinc stearate,and barium stearate on the thermal stabilization of PVC

Individual action and synergistic effect in the combination of 6-anilino-1,3,5-triazine-2,4-dithiol (AF), zinc stearate, and barium stearate on the color stabilization of PVC were investigated. In this system, AF selectively reacts with allylic chlorine atoms in PVC. Consequently, unstable allylic chlorine units were converted to thermally stable allylic structures, thus retarding the development of polyene sequences. Zinc stearate accelerated the reaction of AF with allylic chlorine atoms in PVC, forming the zinc salts of AF (AFZ_nSt, St?C₁–H₃₅COO? ) by reacting with AF. Barium stearate reacted with ZnCl₂ which is formed in the above reaction to give St₂Zn and BaCl₂. Consequently, barium stearate led to the selective reaction of AF with allylic chlorine atoms in PVC and the remarkable retarding effect of discoloration of PVC.     

Catching a molecule at the air-water interface: Dynamic pore array for molecular recognition

As a soft and flexible porous structure, a pore array of a steroid cyclophane SC(OH), which consists of the rigid 1,6,20,25-tetraaza[6.1.6.1]paracyclophane ring connected to four steroid moieties (cholic acid) through flexible L-lysine spacers, was prepared at the air-water interface. As confirmed by surface pressure (π)-molecular area (A) isotherms, transition between open conformation and cavity conformation of the SC(OH) molecule was reversibly induced upon repeated compression and expansion of its monolayer at pH 11 where amino groups of the lysine residues are not fully deprotonated. Capture and release of an aqueous fluorescent guest (TNS) by SC(OH) was observed upon dynamic cavity formation through surface fluorescence spectroscopy. At pH 12, dynamic cavity formation of SC(OH) was sufficiently suppressed, and the capture and release of an aqueous TNS by the monolayer was not virtually observed. Lessened electrostatic repulsion between the SC(OH) molecules due to conversion of ammonium to free amine may prevent the cavity from reopening. The importance of dynamic nature of cavity formation on the guest binding was also proved by control experiments using SC(H), which cannot form cavity conformation at any surface pressures at both pH 11 and 12.     

A method to modify coordinates of detectors in positron emission tomography systems

A new method to modify coordinates of detectors in any positron emission tomography (PET) system using a radioactive point source is developed. This method is based on selecting a centered detector in each detector block of PET and measuring coincidence counts between the two centered detectors in opposite detector blocks to find the coordinates of their LOR (Line of Response). Due to slight misalignment of detector positions, measured LORs may not intersect at a single point. Based on the proposed method, the coordinates of detectors can be measured with very high accuracy and the coordinate of the center of the gantry (which is normally the same as the center of field of view) can be defined correctly. The results of the application of our method to a small animal PET system (FinePET), which was recently developed at Tohoku University, Japan, are shown here. The method is expected to contribute to the design and development of PET systems which can realize a very high spatial resolution of less than 1 mm FWHM.