Impact of compact TiO2 interface modification on the crystallinity of perovskite solar cells.

The effect of TiO2 interfacial morphology on perovskite crystallinity was investigated by modifying the micro and nanoscale surface roughness of compact TiO2. While surface treatments of the compact TiO2 layer are recognized as effective strategies to enhance the photovoltaic performance of perovskite solar cells, the discussion regarding the crystallinity of perovskite atop TiO2 has been limited. In this study, we explored the impact of micro and nano scale interface morphology on perovskite crystal formation and its subsequent effects on device performance. Surprisingly, despite the absence of noticeable voids at the interface between the compact TiO2 and perovskite layers, the perovskite crystal morphology exhibited significant improvement following either micro or nanoscale interfacial modification. This enhancement ultimately led to improved photoconversion efficiency and reduced I-V hysteresis. These results emphasize the importance of underlayer surface morphology in the perovskite crystallization and suggest that the presence of grain boundaries within the perovskite layer may also contribute to I-V hysteresis in perovskite solar cells.

Determination of unique power conversion efficiency of solar cell showing hysteresis in the I-V curve under various light intensities.

Energy harvesting at low light intensities has recently attracted a great deal of attention of perovskite solar cells (PSCs) which are regarded as promising candidate for indoor application. Anomalous hysteresis of the PSCs a complex issue for reliable evaluation of the cell performance. In order to address these challenges, we constructed two new evaluation methods to determinate the power conversion efficiencies (PCEs) of PSCs. The first setup is a solar simulator based on light emitting diodes (LEDs) allowing evaluation of the solar cells at wider range of light intensities, ranging from 102 to 10-3 mW·cm-2. As the overestimate error, we found that the PCEs of dye sensitized solar cell (DSC) and PSCs increase dramatically at low light intensities conditions. Due to the internal capacitance at the interfaces on hybrid solar cells, the measurement of current below 10-2 mW·cm-2 shows constant value given high PCE, which is related to the capacitive current and origin of the hysteresis. The second setup is a photovoltaic power analyzing system, designed for tracking the maximum power (P max) with time. The paper suggests the combination of the LED solar simulator and P max tracking technique as a standard to evaluate the PCE of capacitive solar cells.

Results of extracorporeal shock wave lithotripsy for the treatment of upper urinary tract stones.

The treatment results of 697 renal units in 687 patients treated for upper urinary tract stones using a Piezolith 2500 at the Ageo Central General Hospital during the 5-year period between August 1999 and July 2004 were analyzed. The stone-free rate and the success rate were calculated according to the stone size and location. Univariate and multivariate logistic regression analyses were performed to estimate the effect of the patient age, sex, affected side, stone location and stone size on the stone-free rate and the success rate. Overall, the stone-free rate and the success rate at 3 months after treatment were 82.6% and 91.9%, respectively. The stone-free rates in renal and ureteral stones were 60.5% and 88.7%, respectively. The success rates for renal and ureteral stones were 93.6% and 91.6%, respectively. In a univariate logistic regression analysis, patient age and stone size were significant negative factors for both the stone-free rate and the success rate and the stone location in ureter was a significant positive factor only for the stone-free rate. In a multivariate analysis, stone location in the ureter had a positive effect on the stone-free rate, although a negative effect on the success rate. Extracorporeal shock wave lithotripsy for upper urinary tract stones was an effective and safe treatment modality. However, if pre-treatment factors indicate unfavorable outcome, the other treatment options should be considered for the first line therapy.

Reduction of carry-over in column-switching HPLC/MS system with automated system washing procedure for highly sensitive direct analysis of donepezil in dog plasma.

To solve the problem of carry-over--a persistent chromatographic challenge for bioanalytical assays with highly sensitive detector such as a mass spectrometry (MS)--a new on-line sample pretreatment HPLC/MS system using a column-switching technique was established. This system was designed to reduce carry-over based on a hydrophobic interaction mechanism using a washing function (multi-mobile phase flow system), as well as to remove impurities on-line in a mobile phase for the pretreatment. As a result, a washing function in this system was enabled to reduce carry-over and to remove impurities in a mobile phase by automatic operation. Therefore, concentration levels of donepezil (DH) in dog plasma as low as 10 pg/mL could be determined using this on-line sample pretreatment HPLC/MS system. In addition, method validation results of specificity, linearity, accuracy, precision, lower limit of quantitation (LLOQ), and carry-over demonstrated that this on-line sample pretreatment HPLC/MS system was robust and valid as a practical assay of drugs and metabolites in the biological samples.

Cloning and expression of afpA, a gene encoding an antifreeze protein from the arctic plant growth-promoting rhizobacterium Pseudomonas putida GR12-2.

The Arctic plant growth-promoting rhizobacterium Pseudomonas putida GR12-2 secretes an antifreeze protein (AFP) that promotes survival at subzero temperatures. The AFP is unusual in that it also exhibits a low level of ice nucleation activity. A DNA fragment with an open reading frame encoding 473 amino acids was cloned by PCR and inverse PCR using primers designed from partial amino acid sequences of the isolated AFP. The predicted gene product, AfpA, had a molecular mass of 47.3 kDa, a pI of 3.51, and no previously known function. Although AfpA is a secreted protein, it lacked an N-terminal signal peptide and was shown by sequence analysis to have two possible secretion systems: a hemolysin-like, calcium-binding secretion domain and a type V autotransporter domain found in gram-negative bacteria. Expression of afpA in Escherichia coli yielded an intracellular 72-kDa protein modified with both sugars and lipids that exhibited lower levels of antifreeze and ice nucleation activities than the native protein. The 164-kDa AFP previously purified from P. putida GR12-2 was a lipoglycoprotein, and the carbohydrate was required for ice nucleation activity. Therefore, the recombinant protein may not have been properly posttranslationally modified. The AfpA sequence was most similar to cell wall-associated proteins and less similar to ice nucleation proteins (INPs). Hydropathy plots revealed that the amino acid sequence of AfpA was more hydrophobic than those of the INPs in the domain that forms the ice template, thus suggesting that AFPs and INPs interact differently with ice. To our knowledge, this is the first gene encoding a protein with both antifreeze and ice nucleation activities to be isolated and characterized.