Photocarrier generation in organic thin-film solar cells with an organic heterojunction

Photocurrent–voltage characteristics for organic solar cells with a heterojunction formed between copper phthalocyanine and a perylene derivative (or C₆₀) were studied. The photocurrent was observed under both reverse and forward biases. From the analysis of the photocurrent action spectra, the origin of the reverse photocurrent was attributed to the excitons formed in both the organic layers, whereas that of the forward photocurrent was attributed to the excitons formed in the perylene derivative (or C₆₀) layer. The photocurrent density under reverse bias increased at higher temperatures, suggesting that the charge recombination possibility was lowered at higher temperatures. On the basis of the time responses of the photocurrents observed after pulsed photoirradiation, the charge separation and transport processes are discussed.     

Isotropic photo-decomposition of spherical organic polymers on rutile TiO₂(110) surfaces

We observed the photo-decomposition process of polystyrene latex (PSL) spheres on a rutile TiO?(110) single crystal surface by using atomic force microscopy. During the decomposition process, both the height and width of the PSL spheres linearly decreased with the irradiation time in a similar way from the beginning, suggesting that the PSL spheres are isotropically decomposed. This indicates that the interface between the PSL spheres and the TiO? surface is not a dominant reaction site, as expected from normal photocatalytic reactions.     

Significance of the detection of staphylococcal enterotoxin A gene in low fat milk which caused a serious outbreak of food poisoning

In June 2000, there was a large-scale outbreak of food poisoning after consumption of Snow Brand low fat milk. In the evening of a day the incident made public, some cartons of low fat milk were brought to our laboratory for examination. Next day, we detected only staphylococcal enterotoxin (SE) A gene among SE (A-E) genes by PCR in left-over milk samples or samples from the same lots that patients had consumed. We presumed that the outbreak was caused by the intake of SEA. We subsequently confirmed the presence of SEA in these samples. To investigate the existence of SE (A-E) genes in milk, we examined 100 samples of commercial low fat milk and milk by PCR, but none of the genes was detected. We estimated the detection limit of SEA gene in low fat milk by PCR. Four strains of SEA-producing Staphylococcus aureus cultures were serially diluted in low fat milk. The SEA gene was detected at levels of 5.5 x 10(2) to 1.6 x 10(4) cfu/mL of S. aureus. These amounts of S. aureus are higher than the values in raw milk reported previously. Therefore we consider that SE genes in low fat milk should usually be undetectable by our PCR. This study shows that quick detection of SE genes by PCR is very helpful to analyze outbreaks, especially if no significant bacterium can be cultured.     

Generalized KYP lemma: unified frequency domain inequalities with design applications

The celebrated Kalman-Yakubovic/spl caron/-Popov (KYP) lemma establishes the equivalence between a frequency domain inequality (FDI) and a linear matrix inequality, and has played one of the most fundamental roles in systems and control theory. This paper first develops a necessary and sufficient condition for an S-procedure to be lossless, and uses the result to generalize the KYP lemma in two aspects-the frequency range and the class of systems-and to unify various existing versions by a single theorem. In particular, our result covers FDIs in finite frequency intervals for both continuous/discrete-time settings as opposed to the standard infinite frequency range. The class of systems for which FDIs are considered is no longer constrained to be proper, and nonproper transfer functions including polynomials can also be treated. We study implications of this generalization, and develop a proper interface between the basic result and various engineering applications. Specifically, it is shown that our result allows us to solve a certain class of system design problems with multiple specifications on the gain/phase properties in several frequency ranges. The method is illustrated by numerical design examples of digital filters and proportional-integral-derivative controllers.     

Chlorine auto-doping by chloride vapor phase epitaxial growth of InP

Chlorine auto-doping phenomenon was found for the first time in InP epitaxial growth by using a PCl₃/InP/H₂ system. Chlorine atoms act as a donor in the epitaxial layer and the carrier concentration is dependent on the facet of InP substrate. The carrier concentration of the InP layer on ( 111)B facet was over 10³ times higher than that on (111)A substrate.     

Simvastatin suppresses glomerular cell proliferation and macrophage infiltration in rats with mesangial proliferative nephritis

Inhibition of 3-hydro-3-methylglutaryl coenzyme A reductase inhibits the production of mevalonate and has been shown to suppress proliferation in many cell types. Therefore, 3-hydro-3-methylglutaryl coenzyme A reductase inhibitors may have a beneficial effect in glomerular disease, because glomerular cell proliferation is a central feature in the active glomerular injury. This study examines the effect of simvastatin on glomerular pathology in a rat mesangial proliferative glomerulonephritis (GN) induced by anti-thymocyte antibody (anti-Thy 1.1 GN). There was no difference in the degree of the antibody and complement-mediated initial injuries between simvastatin-treated and control GN rats. The most pronounced feature of simvastatin-treated GN was the suppression of the early glomerular cell proliferation. The proliferative activity was maximal at day 4 after disease induction (26.5+/-7.0 of proliferating cell nuclear antigen-positive cells/glomerulus); however, approximately 70% of proliferation was suppressed by simvastatin treatment. At day 4 after disease induction, simvastatin administration also decreased alpha-smooth muscle actin expression in the glomerulus, which is a marker for mesangial cell activation. Inhibition of monocyte/macrophage recruitment into glomeruli by simvastatin was also a prominent feature. There was a 30% decrease in the number of glomerular ED-1+ cells by simvastatin treatment at day 2 after disease induction. Furthermore, simvastatin remarkably suppressed subsequent mesangial matrix expansion and type IV collagen accumulation in glomeruli. We also found that the platelet-derived growth factor expression was reduced in simvastatin-treated nephritic rats, which might simply reflect the reduction in mesangial cell proliferation and mesangial cellularity. There was no significant difference in plasma cholesterol or triglyceride levels between simvastatin- and vehicle-treated nephritic rats at day 2 and day 4, which corresponded to the times when simvastatin treatment resulted in a reduction in mesangial cell proliferation. In conclusion, this is the first report to find that mesangial cell proliferation and matrix expansion have been blocked by simvastatin in vivo. The protective effect of simvastatin in the matrix expansion in anti-Thy1.1 GN was partly by inhibition of mesangial cell proliferation and monocyte/ macrophage recruitment into glomeruli, which were independent of a change in circulating lipids.     

A recursive construction algorithm for covariance control

This paper proposes an algorithm to compute solutions X to the linear matrix equation and inequality of the type (I-BB⁺)(AX+XA'+W)(I-BB⁺)=0, X>0. This problem arises in the synthesis of covariance controllers; the set of symmetric matrices X assignable as a closed-loop state covariance by a stabilizing controller is characterized by these conditions. Our algorithm generates analytical solutions to the above problem in a recursive manner. In this sense, our algorithm is essentially different from other computational methods pertinent to this problem, such as convex programming. As a result, the algorithm does not involve the issue of convergence and terminates in an a priori known finite number of steps. Thus, the computational complexity is expected to be much less than that of other methods     

Interpretation of Hydrated States of Sodium Silicate Glasses by Infrared and Raman Analysis

Infrared spectra of thin films (a few micrometers) of hydrated sodium silicate glasses after heating at temperatures from 100° to 400°C were measured in the spectral region from 400 to 4300 cm⁻¹. Also, Raman spectra of hydrated glasses were measured in the region from 100 to 1400 cm⁻¹. Water molecules in hydrated glasses were classified into three types by the bonding configuration: water molecules interacting with Si–OH groups, nonbridging oxygens, and bridging oxygens. On the basis of the fundamental bands observed here, we calculated the wave numbers of the combination-overtone bands of water molecules and SiOH groups in hydrated glasses. The calculated wave numbers satisfactorily agreed with observed wave numbers in the nearinfrared region.     

Scanning-laser-beam semiconductor pH-imaging sensor

We have constructed a two-dimensional (2-D) pH-imaging sensor that enables us to observe th H⁺ distribution produced by living cells. The pH-sensing principle is similar to that of thelight-addressable potentiometric sensor. The electrolyte-insulator-semiconductor (EIS) structure (electrolyte---Si₃N₄---SiO₂---Si) is illuminated by a focused (1 μm) and modulated (1–10 kHz) He—Ne laser bean from the backside of the semiconductor, and the a.c. photocurrent flowing through the EIS structure is measured. By scanning the laser beam, 2-D pH images can be obtained. By using this sensor, pH distributions of colonies of yeast (Saccharomyces cerevisiae) have been observed. The spatial resolution of this sensor could be improved by thinning the Si wafer.