פרסומים

In this study we systematically explored the mixed cation perovskite Cs-x(CH3NH3)(1-x)PbI3. We exchanged the A-site cation by dipping MAPbI(3) films into a CsI solution, thereby incrementally replacing the MA(+) in a time-resolved dipping process and analysed the resulting thin-films with UV-Vis, XRD, EDAX, SEM and optical depth-analysis in a high-throughput fashion. Additional in situ UV-Vis and time-resolved XRD measurements allowed us to look at the kinetics of the formation process. The results showed a discontinuity during the conversion. Firstly, small amounts of Cs+ are incorporated into the structure. After a few minutes, the Cs content approaches a limit and grains of delta-CsPbI3 occur, indicating a substitution limit. We compared this cation exchange to a one-step crystallisation approach and found the same effect of phase segregation, which shows that the substitution limit is an intrinsic feature rather than a kinetic effect. Optical and structural properties changed continuously for small Cs incorporations. Larger amounts of Cs result in phase segregation. We estimate the substitution limit of Cs(x)MA(1-x)PbI(3) to start at a Cs ratio x = 0.13, based on combined measurements of EDAX, UV-Vis and XRD. The photovoltaic performance of the mixed cation perovskite shows a large increase in device stability from days to weeks. The initial efficiency of mixed Cs(x)MA(1-x)PbI(3) devices decreases slightly, which is compensated by stability after a few days.

Vegh and Vuletin (2015) have shown that statutory tax rates are acyclical in developed economies and procyclical in developing ones. This paper extends their analysis by checking the interaction of statutory tax rates with countries' external public debt. In general we found that the V.A.T rates are changed procyclically in both developed and developing countries (i.e., taxes are raised in bad times and reduced in good times). However, when the external debt is high, in the developing countries the procyclicality increases, while the opposite result holds for developed economies. This pattern occurs mainly in times of recession, when the need for loans is the highest. Although we found that there was a reduction in procyclicality after the 2000s, these findings pose a challenge to policy-makers, who should think of ways of dealing with lack of foreign funds in difficult times.

Previous studies on cytokinin (CK) and drought have suggested that the hormone has positive and negative effects on plant adaptation to restrictive conditions. This study examined the effect of CK on transpiration, stomatal activity, and response to drought in tomato (Solanum lycopersicum) plants. Transgenic tomato plants overexpressing the Arabidopsis thaliana CK-degrading enzyme CK oxidase/dehydrogenase 3 (CKX3) maintained higher leaf water status under drought conditions due to reduced whole-plant transpiration. The reduced transpiration could be attributed to smaller leaf area and reduced stomatal density. CKX3-overexpressing plants contained fewer and larger pavement cells and fewer stomata per leaf area than wild-type plants. In addition, wild-type leaves treated with CK exhibited enhanced transpiration and had more pavement cells and increased numbers of stomata per leaf area than untreated leaves. Manipulation of CK levels did not affect stomatal movement or abscisic acid-induced stomatal closure. Moreover, we found no correlation between stomatal aperture and the activity of the CK-induced promoter Two-Component Signaling Sensor (TCS) in guard cells. Previous studies have shown that drought reduces CK levels, and we propose this to be a mechanism of adaptation to water deficiency: the reduced CK levels suppress growth and reduce stomatal density, both of which reduce transpiration, thereby increasing tolerance to prolonged drought conditions.

Abscission of flower pedicels and leaf petioles of tomato (Solanum lycopersicum) can be induced by flower removal or leaf deblading, respectively, which leads to auxin depletion, resulting in increased sensitivity of the abscission zone (AZ) to ethylene. However, the molecular mechanisms that drive the acquisition of abscission competence and its modulation by auxin gradients are not yet known. We used RNA-Sequencing (RNA-Seq) to obtain a comprehensive transcriptome of tomato flower AZ (FAZ) and leaf AZ (LAZ) during abscission. RNA-Seq was performed on a pool of total RNA extracted from tomato FAZ and LAZ, at different abscission stages, followed by de novo assembly. The assembled clusters contained transcripts that are already known in the Solanaceae (SOL) genomics and NCBI databases, and over 8823 identified novel tomato transcripts of varying sizes. An AZ-specific microarray, encompassing the novel transcripts identified in this study and all known transcripts from the SOL genomics and NCBI databases, was constructed to study the abscission process. Multiple probes for longer genes and key AZ-specific genes, including antisense probes for all transcripts, make this array a unique tool for studying abscission with a comprehensive set of transcripts, and for mining for naturally occurring antisense transcripts. We focused on comparing the global transcriptomes generated from the FAZ and the LAZ to establish the divergences and similarities in their transcriptional networks, and particularly to characterize the processes and transcriptional regulators enriched in gene clusters that are differentially regulated in these two AZs. This study is the first attempt to analyze the global gene expression in different AZs in tomato by combining the RNA-Seq technique with oligonucleotide microarrays. Our AZ-specific microarray chip provides a cost-effective approach for expression profiling and robust analysis of multiple samples in a rapid succession. © 2016 Sundaresan, Philosoph-Hadas, Riov, Mugasimangalam, Kuravadi, Kochanek, Salim, Tucker and Meir.

CuInS₂ nanocrystals with the wurtzite structure show promise for applications requiring efficient energy transport due to their anisotropic crystal structure. We investigate the source of photoluminescence in the near-infrared spectral region recently observed from these nanocrystals. Spectroscopic studies of both wurtzite CuInS₂ itself and samples alloyed with Cd or Zn allow the assignment of this emission to a radiative point defect within the nanocrystal structure. Further, by varying the organic passivation layer on the material, we are able to determine that the atomic species responsible for nonradiative decay paths on the nanocrystal surface are Cu- or S-based. Density functional theory calculations of defect states within the material allow identification of the likely radiative species. Understanding both the electronic structure and optical properties of wurtzite CuInS₂ nanocrystals is necessary for their efficient integration into potential biological, photovoltaic, and photocatalytic applications.

The sensitivity of classical and quantum sensing is impaired in a noisy environment. Thus, one of the main challenges facing sensing protocols is to reduce the noise while preserving the signal. State-of-the-art quantum sensing protocols that rely on dynamical decoupling achieve this goal under the restriction of long noise correlation times. We implement a proof-of-principle experiment of a protocol to recover sensitivity by using an error correction for photonic systems that does not have this restriction. The protocol uses a protected entangled qubit to correct a single error. Our results show a recovery of about 87% of the sensitivity, independent of the noise probability.

NMR chromatog. is a promising and superior alternative to NMR spectroscopy for analyzing mixts. since it simultaneously separates the spectra of the compds. and supplies information about their structure. This implies that there is no need for extn., purifn. or synthesis of stds., that are expensive, time consuming and usually impractical. The main aim of NMR chromatog. is to increase the differences in the diffusivities of different analytes in a mixt., allowing them to be more easily and reliably identified. The selection of surfactants and other components of microemulsions for the best performance as NMR chromatog. media was studied. Attention was focused on the selection of the proper cosolvent in three types of water-dilutable microemulsions: two anionic (deuterated ionic and the previously published fluorinated ionic) and one nonionic (undeuterated Tween-based). The diffusivities of several analytes are compared. The study also examines the effect of diln. and dets. the best compns. for the NMR chromatog. performance. For the anionic microemulsions, 1-butanol was found to be the most promising cosurfactant in the deuterated system 1-butanol-d10:toluene-d8:SDS-d25 in a 6:3:1 wt.-ratio dild. by D2O. This compn., dild. with a 85 wt% D2O, formed a microemulsion that was even stable at relatively elevated temps. (70 °C) and can serve as good medium for chromatog. NMR. Another possibility that was studied consists of nonionic-based microemulsions of iso-Pr alc. (IPA) in IPA:toluene:Tween 20 that could also be easily dild. indefinitely with water. IPA was found to be a very efficient cosurfactant at resolving diffusivities of all the components. However, the lack of availability of deuterated Tween makes it impractical for use as an NMR chromatog. formulation. [on SciFinder(R)]

Protein kinase RNA-activated (PKR) plays an important role in a broad range of intracellular regulatory mechanisms and in the pathophysiology of many human diseases, including microbial and viral infections, cancer, diabetes and neurodegenerative disorders. Recently, several potent PKR inhibitors have been synthesized. However, the enzyme’s multifunctional character and a multitude of PKR downstream targets have prevented the successful transformation of such inhibitors into effective drugs. Thus, the need for additional PKR inhibitors remains. With the help of computer-aided drug-discovery tools, we designed and synthesized potential PKR inhibitors. Indeed, two compounds were found to inhibit recombinant PKR in pharmacologically relevant concentrations. One compound, 6-amino-3-methyl-2-oxo-N-phenyl-2,3-dihydro-1H-benzo[d]imidazole-1-carboxamide, also showed anti-apoptotic properties. The novel molecules diversify the existing pool of PKR inhibitors and provide a basis for the future development of compounds based on PKR signal transduction mechanism.