Formamidinium‐Based Dion‐Jacobson Layered Hybrid Perovskites: Structural Complexity and Optoelectronic Properties

Layered hybrid perovskites have emerged as a promising alternative to stabilizing hybrid organic–inorganic perovskite materials, which are predominantly based on Ruddlesden‐Popper structures. Formamidinium (FA)‐based Dion‐Jacobson perovskite analogs are developed that feature bifunctional organic spacers separating the hybrid perovskite slabs by introducing 1,4‐phenylenedimethanammonium (PDMA) organic moieties. While these materials demonstrate competitive performances as compared to other FA‐based low‐dimensional perovskite solar cells, the underlying mechanisms for this behavior remain elusive. Here, the structural complexity and optoelectronic properties of materials featuring (PDMA)FA_n–1Pb_nI_3n+1 (n = 1–3) formulations are unraveled using a combination of techniques, including X‐ray scattering measurements in conjunction with molecular dynamics simulations and density functional theory calculations. While theoretical calculations suggest that layered Dion‐Jacobson perovskite structures are more prominent with the increasing number of inorganic layers (n), this is accompanied with an increase in formation energies that render n > 2 compositions difficult to obtain, in accordance with the experimental evidence. Moreover, the underlying intermolecular interactions and their templating effects on the Dion‐Jacobson structure are elucidated, defining the optoelectronic properties. Consequently, despite the challenge to obtain phase‐pure n > 1 compositions, time‐resolved microwave conductivity measurements reveal high photoconductivities and long charge carrier lifetimes. This comprehensive analysis thereby reveals critical features for advancing layered hybrid perovskite optoelectronics.     

CHARACTERIZATION AND DEPOSIT FORMING-TENDENCY OF POLAR COMPOUNDS IN CRACKED COMPONENTS OF GASOLINE. PART 1 GENERAL SEPARATION SCHEME AND IDENTIFICATION OF BASIC FRACTION.

Polar compounds were isolated from one gollon of FCC by acid-base extraction followed by aluminum oxide adsorption chromatography. Fractions were tested with an Induction System Deposit (ISO( apparatus and the basic fraction was characterized by hydrogen-1, carbon-13 and nitrogen-15 NMR spectroscopy and GC/MS. The fraction resulting from the acid-base extraction and direct elution from the chromatographic column showed a low sulfur content (114 ppm( and no detectable nitrogen. Fractions obtained by elution from the chromatographic column with ethyl acetate and methanol showed a high tendency to form deposits as tested by the ISD apparatus. The main compounds in the basic fraction were identified as methyl and dimethylanilines that showed low tendencies to deposit formation in ISD.     

The AETL methodology as a potential solution to current challenges associated with the development and use of acute exposure levels in Seveso II applications

This paper analyses current trends in the development and use of acute exposure levels in Europe for the implementation of the Seveso II Directive [Council Directive 96/82/EC of December 9, 1996 on the control of major-accident hazards involving dangerous substances. Official Journal of the European Communities, vol. L 10, January 14, 1997, Luxembourg, pp. 13-33]. It also describes a new initiative to develop a European methodology for deriving acute exposure threshold levels that responds to emerging needs in this area. The need for acute exposure values to predict human health effects of potential accidents on exposed populations has burgeoned in recent years. As the driving legislation for managing industrial hazards in Europe, the Seveso II Directive has particularly influenced this trend. Yet at this time it is questionable whether the availability and range of acute exposure values for toxic substances has kept apace with the growing need. Results of a survey of Seveso II competent authorities in the EU-15 revealed that a variety of different types of acute exposure values (AEGLs, EPRGs, etc.) are used for Seveso II applications. Moreover, a comparison of these values indicates gaps in coverage of substances as well as inconsistencies in terms of how health effects and exposure periods are defined for each type. These findings highlight an opportunity for greater collaboration on scientific inputs to application of the Directive in Europe. The ACUTEX project is an EU-funded research project aimed at furthering scientific exchange and collaboration in support of the development of acute exposure levels for toxic substances in Europe. Its goal is to develop a European methodology for deriving acute exposure threshold levels (AETLs). In particular, it provides the possibility for a common European platform for developing additional acute exposure values to meet emerging needs and cover more chemical substances. To maximise success, the work plan is designed to meet two very important challenges, the need to complement and add value to the existing array of acute exposure methodologies and the necessity of meeting requirements of a diverse range of European stakeholders. As such the project will draw on collaboration among European scientists and process of deliberation among stakeholders to deliver the following key results: (1) to facilitate wide acceptance of the methodology in Europe by both the scientific community and communities of different end-users; (2) to provide greater equivalence and transparency in implementation of the Seveso II Directive across the Member States, specifically through the development of common scientific bases for assessing risks and making risk management decisions related to toxic releases; (3) to produce a methodology that remains open to future collaboration on derivation of acute exposure levels on a European and a global basis.     

A practical comparison of several algorithms for reliability calculations

This is a report on the time complexity of several algorithms for symbolic fault-tree analysis. The investigations are limited to the Boolean domain. Mostly, Boolean functions are transformed to short sums of disjoint terms, such that in the case of stochastically independent binary state indicator variables X_i ( = 1 for component i being in a faulty state) simply X has to be replaced by U (for unavailability) or R(t) (for unreliability) in order to obtain system unavailability or unreliability, respectively. The main overall result is that the Shannon decomposition is almost always the best approach.     

Dynamic aspects of the interaction between microtubules and actin filaments

This paper summarizes observations on the motility and behavior of microtubule asters in polymorphonuclear leukocytes under a variety of experimental conditions. These observations suggest that the location and organization of microtubules is influenced, at least in part, by the activity of the cortical actin network. Aster motility may therefore serve as an indicator of the interaction between the centrosomal microtubules and the cell cortex, and it is speculated that this interaction is of importance for leukocyte translocation.     

Flavonoid concentrations in the inner leaves of head lettuce genotypes

Typical HPLC profiles of phenolics from head lettuce (butter lettuce) genotypes showed quercetin (Qu) compounds Qu 3-O-glucuronide, Qu 3-O-(6-malonylglucoside), an acidic luteolin (Lu) glycoside, chlorogenic acid and chicoric acid as the main compounds in outer and - except the Lu conjugate - inner leaves.The outer leaves of some genotypes additionally contained cyanidin 3-O-(6-malonylglucoside). The generally marginal flavonoid concentrations of the cores of lettuce heads increased between 10-fold and 20-fold during the illumination of opened inner leaves. This indicated the competence of inner leaves of lettuce heads to perform the light-dependent flavonoid biosynthesis. After hydrolysis of flavonoid extracts from 15 head lettuce varieties, Qu concentrations were detected between 19.4 and 152.1 µg/g dry plant material (DW) in inner leaves and from 417.3 to 2482.7 µg/g DW in outer leaves. While the Qu concentrations of the inner leaves of most genotypes, including the commercial varieties, amounted to about 3% of those found in outer leaves, these proportions were 15% and 19% in two genotypes. Two other varieties showed relatively high Qu values of cores in connection with maximum flavonoid levels of outer leaves. It is indicated that such genotypes may be useful in increasing the flavonoid concentrations in the inner leaves of commercial head lettuce varieties by conventional breeding methods.     

Occurrence of Fusarium species and trichothecenes in Nigerian maize

A total of 180 maize samples meant for human consumption from four maize-producing states of southwestern Nigeria were screened for twelve major Fusarium mycotoxins (trichothecenes). Mycological examination of the samples showed that Fusarium verticillioides was the most commonly isolated fungi (71%), followed by F. sporotrichioides (64%), F. graminearum (32%), F. pallidoroseum (15%), F. compactum (12%), F. equiseti (9%), F. acuminatum (8%), F. subglutinans (4%) and F. oxysporum (1%). The trichothecenes include deoxynivalenol (DON), 3, mono-acetyldeoxynivalenol (3-AcDON), 15, mono-acetyldeoxynivalenol (15-AcDON), nivalenol (NIV), HT-2 toxin (HT-2), neosolaniol (NEO), T-2 toxin (T-2), T-2 tetraol and T-2 triol, diacetoxyscirpenol (DAS), MAS-monoacetoxyscirpenol (MAS) and fusarenone-X. Quantification was by high performance liquid chromatography coupled with mass spectroscopy (HPLC/MS); the detection limits for each of the mycotoxins varied between 20 and 200 microg kg(-1). Sixty six samples (36.3%) were contaminated with trichothecenes, DON (mean: 226.2 microg kg(-1); range: 9.6-745.1 microg kg(-1)), 3-AcDON (mean: 17.3 microg kg(-1); range: 0.7-72.4 microg kg(-1)) and DAS (mean: 16.0 microg kg(-1); range: 1.0-51.0 microg kg(-1)) were detected in 22%, 17% and 9% of total samples respectively. There were no 15-AcDON, NIV, HT-2, NEO, T-2, T-2 tetraol, T-2 triol, MAS and fusarenone-X detected. This is the first comprehensive report about the natural occurrence of DON, AcDON and DAS in maize for direct human consumption in Nigeria.     

Evolutionary journey and characterisation of a novel pan-gene associated with beer strains of Saccharomyces cerevisiae

The sequencing of over a thousand Saccharomyces cerevisiae genomes revealed a complex pangenome. Over one third of the discovered genes are not present in the S. cerevisiae core genome but instead are often restricted to a subset of yeast isolates and thus may be important for adaptation to specific environmental niches. We refer to these genes as “pan-genes,” being part of the pangenome but not the core genome. Here, we describe the evolutionary journey and characterisation of a novel pan-gene, originally named hypothetical (HYPO) open-reading frame. Phylogenetic analysis reveals that HYPO has been predominantly retained in S. cerevisiae strains associated with brewing but has been repeatedly lost in most other fungal species during evolution. There is also evidence that HYPO was horizontally transferred at least once, from S. cerevisiae to Saccharomyces paradoxus. The phylogenetic analysis of HYPO exemplifies the complexity and intricacy of evolutionary trajectories of genes within the S. cerevisiae pangenome. To examine possible functions for Hypo, we overexpressed a HYPO-GFP fusion protein in both S. cerevisiae and Saccharomyces pastorianus. The protein localised to the plasma membrane where it accumulated initially in distinct foci. Time-lapse fluorescent imaging revealed that when cells are grown in wort, Hypo-gfp fluorescence spreads throughout the membrane during cell growth. The overexpression of Hypo-gfp in S. cerevisiae or S. pastorianus strains did not significantly alter cell growth in medium-containing glucose, maltose, maltotriose, or wort at different concentrations.     

Pyrane-derivatives as fragrances and flavors-a study on structure/odour relationships

Summary In this study several 2/H-3,4-dihydropyrane-derivatives, substituted with different unsaturated alkyl groups, have been synthesized. These compounds exhibit pleasant green, fruity and flowery fragrances. The syntheses start from 2H-3,4-dihydropyrane-2-carbaldehydes which are available by dimerisation of acroleine, meth-ylacroleine and ethylacroleine. It was shown that it is possible to induce dimerisation by ultrasonic irradiation. Subsequent Wittig and Horner-Emmons olefinations lead to the desired pyrane derivatives. The odorous character of these compounds is fully described and remarkable structure/odour relationships are discussed.

---

Pyran-Derivate als Aroma- und Duftstoffe. Eine Studie über Struktur/Geruchs-Beziehungen

Zusammenfassung In der vorliegenden Untersuchung werden die Synthese und der Geruch verschiedener 2H-3,4-Dihydropyrane, die unterschiedliche olefinische Seitenketten tragen, beschrieben. Alle diese Verbindungen besitzen ein ausgeprägtes grünes, fruchtiges und blumiges Aroma. Die Synthesen nehmen ihren Ausgang von den durch Dimerisation von Acrolein, Methyl- und Ethyl-acrolein zugänglichen 2H-3,4-Dihydropyran-2-carbalde-hyden, wobei gezeigt werden konnte, daß durch Ultraschall-Bestrahlung ebenfalls Dimerisation induziert werden kann. Anschließende Wittig- bzw. Horner-Emmons Reaktionen führen zu den gewünschten Zielverbindungen. Die Geruchseigenschaften dieser Substanzen werden ausführlich beschrieben und etwaige Struktur/Wirkungsbeziehungen diskutiert.