Iterative method for optical modelling of perovskite-based tandem solar cells.

We present an iterative method to model the optical properties of a complete semitransparent perovskite solar cell. It is based on spectroscopic characterizations and accounts for porosity and incoherence effects. We provide the complex refractive indices of each layer, and we identify the main sources of optical losses. The optical model is also coupled to an electrical model of 4T perovskite/silicon tandem solar cells. It allows to evaluate the interplay between the optical and electrical losses, and the balance between the efficiency of the top and bottom cells. These models provide an effective way to design future tandem devices.

Cerebellar cortical-layer-specific control of neuronal migration by pituitary adenylate cyclase-activating polypeptide.

Migration of immature neurons is essential for forming the cortical layers and nuclei. Impairment of migration results in aberrant neuronal cytoarchitecture, which leads to various neurological disorders. Neurons alter the mode, tempo and rate of migration when they translocate through different cortical layers, but little is known about the mechanisms underlying this process. Here we show that endogenous pituitary adenylate cyclase-activating polypeptide (PACAP) has short-term and cortical-layer-specific effects on granule cell migration in the early postnatal mouse cerebellum. Application of exogenous PACAP significantly slowed the migration of isolated granule cells and shortened the leading process in the microexplant cultures of the postnatal day (P)0-3 cerebella. Interestingly, in the cerebellar slices of P10 mice, application of exogenous PACAP significantly inhibited granule cell migration in the external granular layer (EGL) and molecular layer (ML), but failed to alter the movement in the Purkinje cell layer (PCL) and internal granular layer (IGL). In contrast, application of PACAP antagonist accelerated granule cell migration in the PCL, but did not change the movement in the EGL, ML and IGL. Inhibition of the cAMP signaling and the activity of phospholipase C significantly reduced the effects of exogenous PACAP on granule cell migration. The PACAP action on granule cell migration was transient, and lasted for approximately 2 h. The duration of PACAP action on granule cell migration was determined by the desensitization of its receptors and prolonged by inhibiting the protein kinase C. Endogenous PACAP was present sporadically in the bottom of the ML, intensively in the PCL, and throughout the IGL. Collectively, these results indicated that PACAP acts on granule cell migration as "a brake (stop signal) for cell movement." Furthermore, these results suggest that endogenous PACAP slows granule cell migration when the cells enter the PACAP-rich PCL, and 2 h later the desensitization of PACAP receptors allows the cells to accelerate the rate of migration and to actively move within the PACAP-rich IGL. Therefore, endogenous PACAP may provide a cue that regulates granule cell migration in a cerebellar cortical-layer-specific manner.

Mutagenicity of nitro- and amino-substituted carbazoles in Salmonella typhimurium. III. Methylated derivatives of 9H-carbazole.

The mutagenic potency of nine methylnitrocarbazoles, four methylaminocarbazoles and the methylcarbazole parent compounds was evaluated in Salmonella typhimurium TA98 and TA100, in the absence and presence of S9 isolated from Aroclor-induced rat liver. Nitro derivatives were additionally tested in TA98NR and TA98/1,8DNP6, and mutagenicity of nitrocarbazoles bearing methyl groups in positions 1 and 4 was also determined in TA1537 and TA1977, with and without S9. The addition of methyl groups on non-mutagenic carbazole can induce a mutagenic response where the intensity and nature of the effect depends on the position of the substitution: base-pair substitutions were only observed for N-methylated carbazoles, whereas 1,4-dimethylated compounds exhibited frameshift mutagenicity. All these activities depended on the presence of S9. From its dependence on classical nitroreductases, direct mutagenicity of methylnitro derivatives should be attributed to bacterial reduction of nitro groups. The influence of the methyl groups (and other additional substituents) on mutagenicity of these derivatives is discussed through their effects on life-time and reactivity of the intermediates (i.e., hydroxylamines and nitrenium ions), taking into account the nature, the position and the number of substituted sites Mutagenic activity of methylnitrocarbazoles was also tentatively correlated with various molecular descriptors. Among them hydrophobicity was found to be strongly correlated with the mutagenicity of the 1,4diMe3NC isomers. On the other hand, mutagenic potency of the nitrated and aminated methylcarbazoles varied independently of parameters linked to their oxidoreduction properties (i.e., reduction and oxidation potentials, LUMO and HOMO energies).