MAPbBr3 perovskite solar cells via a two-step deposition process

Organometal halide perovskite solar cells are becoming one of the most competitive emerging technologies. They have reached a power conversion efficiency (PCE) of 22.7% in 10 years. Their high efficiency and simple fabrication process render perovskite solar cells a promising player in the field of third-generation photovoltaics. The deposition methods play an important role in the fabrication of a high quality films. In this paper, we report the preparation of methylammonium lead bromide (MAPbBr₃) thin film using a two-step method based on the transformation of PbBr₂ into MAPbBr₃ perovskite after dipping in a MABr solution. The effects of the dipping time and the annealing time on the photovoltaic, optical and structural properties of the devices were studied. The dipping time treatments of the inorganic film in organic solution were conducted from 30 s to 15 min. The obtained result showed that the PCE of the devices was improved with the increase of dipping time. In addition, an increase of annealing time induces an enhancement of the perovskite properties. Furthermore, the as-fabricated perovskite solar cell dipped and annealed for 10 min exhibited the highest power conversion efficiency of 4.8% with a short circuit current density of 16.16 mA cm⁻², an open circuit voltage of 0.84 V, and a fill factor of 35.50.

Organometal halide perovskite solar cells are becoming one of the most competitive emerging technologies.     

Prospective,multicenter study on value of computerized tomography (CT) in gallstone disease in predicting response to bile acid therapy

The aim of the study was to assess the value of quantitative attenuation values (Hounsfield units) and of gallstone pattern by computerized tomography in predicting response to bile acid therapy. We carried out a prospective study in a multicenter setting on 90 consecutive outpatients with radiolucent gallstones. All received bile acid therapy (UDCA 10 mg/kg/day or UDCA+CDCA 5 mg/kg/day of each) up to two years. Hounsfield units for gallstones were recorded using standardized criteria and six categories of patterns were defined: hypodense, isodense, homogenously dense, laminated, rimmed and speckled. We assessed gallstone dissolution rate (percent reduction in volume), response to therapy (>25% reduction in volume), and final outcome of therapy. Eighty-one percent of patients with hypodense/isodense and all four patients with speckled stone pattern responded to therapy, whereas none of the 10 patients with laminated/rimmed and only 45% of patients with homogenously dense stone pattern did. Complete dissolution was achieved by 68%, 50%, 35%, 0% of the hypodense/isodense, speckled, homeogenously dense, rimmed/laminated gallstones, respectively. The use of Hounsfield units did not show an advantage over gallstone pattern for predicting either response or final outcome to bile acid therapy. We conclude that computerized tomography analysis of gallstones is of value in predicting response to bile acid therapy and that gallstone pattern alone predicts response in most cases without the need for quantitative assessment.This study was carried out under the auspices of the British-Italian Gallstone Study Group, which was supported by a grant from Schwarz Pharma Italia.Preliminary results from this work have been presented at the 93rd Annual Meeting of the American Gastroenterological Association in 1992 and published in abstract form (Gastroenterology 102:A329, 1992).     

Tumor necrosis factor-α (TNF-α) −863C/A promoter polymorphism is associated with type 2 diabetes in Tunisian population

Aims

Tumor necrosis factor α (TNFα) plays a key role in orchestrating the complex events involved in inflammation and immunity. Accordingly, TNF α has been implicated in a wide range of autoimmune and infectious diseases, but also in conditions such as obesity and insulin resistance. The aim of the present study was to investigate the association between the −863C/A polymorphism in the promoter of the TNFα gene and type 2 diabetes in the Tunisian population.

Methods

The polymorphism −863C/A in the TNFα gene was determined in 211 type 2 diabetes patients and 345 healthy controls using the Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) analysis.

Results

A significant difference in genotype distribution and allele frequency was observed between patients and controls. Patients with type 2 diabetes had significantly higher frequency of the CA + AA genotypes compared to controls [35.5% vs. 22.3%; OR (95%CI), 1.91 (1.31–2.8); p = 0.001]. The type 2 diabetes patient group showed a significant higher frequency of the A allele compared to the controls (0.19 vs. 0.11; p = 0.001). After adjustment by a stepwise logistic regression method, hypertension, dyslipidemia, and CA + AA genotype were found to be significantly associated with T2D.

Conclusion

The present study showed a significant and independent association between the −863C/A polymorphism of the TNFα gene and type 2 diabetes in the Tunisian population.     

Arthrophytum scoparium inhibits melanogenesis through the down‐regulation of tyrosinase and melanogenic gene expressions in B16 melanoma cells

Melanin performs a crucial role in protecting the skin against harmful ultraviolet light. However, hyperpigmentation may lead to aesthetic problems and disorders such as solar lentigines (SL), melasma, postinflammatory hyperpigmentation and even melanoma. Arthrophytum scoparium grows in the desert in the North African region, and given this type of environment, A. scoparium exhibits adaptations for storing water and produces useful bioactive factors. In this study, the effect of A. scoparium ethanol extract (ASEE) on melanogenesis regulation in B16 murine melanoma cells was investigated. Cells treated with 0.017% (w/v) ASEE showed a significant inhibition of melanin biosynthesis in a time‐dependent manner without cytotoxicity. To clarify the mechanism behind the ASEE‐treated melanogenesis regulation, the expressions of tyrosinase enzyme and melanogenesis‐related genes were determined. Results showed that the expression of tyrosinase enzyme was significantly decreased and Tyr, Trp‐1, Mitf and Mc1R mRNA expressions were significantly down‐regulated. LC‐ESI‐TOF‐MS analysis of the extract identified the presence of six phenolic compounds: coumaric acid, cinnamic acid, chrysoeriol, cyanidin, catechol and caffeoylquinic acid. The melanogenesis inhibitory effect of ASEE may therefore be attributed to its catechol and tetrahydroisoquinoline derivative content. We report here that ASEE can inhibit melanogenesis in a time‐dependent manner by decreasing the tyrosinase protein and Tyr, Trp‐1, Mitf and Mc1R mRNA expressions. This is the first report on the antimelanogenesis effect of A. scoparium and on its potential as a whitening agent.