Die Struktur des PrCl3 bei verschiedenen Temperaturen

Structural investigations on PrCl3 were performed from room temperature down to 40 K (powder) and from room temperature down to 83 K (single crystal). Special interest was focussed on the changes of the coordination geometry of the Pr3+-ion

Comparing the Ligand Behavior of N-Heterocyclic Phosphenium and Nitrosyl Units in Iron and Chromium Complexes

N-Heterocyclic phosphenium (NHP) and nitro-sonium (NO+) ligands are often viewed as isolobal analogues that share the capability to switch between different charge states and thus display redox "noninnocent" behavior. We report here on mixed complexes [(NHP)M(CO)(n)(NO)] (M = Fe, Cr; n = 2, 3), which permit evaluating the donor/acceptor properties of both types of ligands and their interplay in a single complex. The crystalline target compounds were obtained from reactions of N-heterocyclic phosphenium triflates with PPN[Fe(CO)(3)(NO)] or PPN[Cr(CO)(4)-(NO)], respectively, and fully characterized (PPN = nitride-bistriphenylphosphonium cation). The structural and spectroscopic (IR, UV-vis) data support the presence of carbene-analogue NHP ligands with an overall positive charge state and pi-acceptor character. Even if the structural features of the M-NO unit were in all but one product blurred by crystallographic CO/NO disorder, spectroscopic studies and the structural data of the remaining compound suggest that the NO units exhibit nitroxide (NO-) character. This assignment was validated by computational studies, which reveal also that the electronic structure of iron NHP/ NO complexes is closely akin to that of the Hieber anion, [Fe(CO)(3)(NO)](-). The electrophilic character of the NHP units is further reflected in the chemical behavior of the mixed complexes. Cyclic voltammetry and IR-SEC studies revealed that complex [(NHP)Fe(CO)(2) (NO)] (4) undergoes chemically reversible one-electron reduction. Computational studies indicate that the NHP unit in the resulting product carries significant radical character, and the reduction may thus be classified as predominantly ligand-centered. Reaction of 4 with sodium azide proceeded likewise under nucleophilic attack at phosphorus and decomplexation, while super hydride and methyl lithium reacted with all chromium and iron complexes via transfer of a hydride or methyl anion to the NHP unit to afford anionic phosphine complexes. Some of these species were isolated after cation exchange or trapped with electrophiles (H+, SnPh3(+)) to afford neutral complexes representing the products of a formal hydrogenation or hydrostannylation of the original M=P double bond.Peer reviewe

Anforderungsmanagement in der Agilen Entwicklung Mechatronischer Systeme - ein Widerspruch in sich?

Anforderungen sind ein Kernbestandteil agiler Entwicklung und aufgrund der Charakteristika mechatronischer Systeme ist eine Bündelung von Anforderungen zur Realisierung von Entwicklungsgenerationen als Inkremente wirtschaftlich sinnvoll. Folglich ist ein Management der Anforderungen hinsichtlich ihrer Entwicklung, Verifizierung und Wiederverwendung notwendig. Anhand der Entwicklung von Werkzeugmaschinen werden die beobachteten Charakteristika der Entwicklung mechatronischer Systeme mit Einfluss auf Durchlaufzeit, Materialkosten und Aufwand beschrieben, diese sind: Fertigungsdokumentation, Bestellung, Lieferung, Hilfsmittel, Montage und Inbetriebnahme. Unter Berücksichtigung dieser Einflussfaktoren wird anschließend ein Vorgehen zur systematischen Wiederverwendung von Anforderungen bei der Entwicklung neuer Produkt- und Entwicklungsgenerationen von Werkzeugmaschinen vorgestellt. Dabei werden Qualitätsanforderungen, funktionale Anforderungen und Randbedingungen unterschieden. Für Qualitäts- und funktionale Anforderungen werden spezifische Vorgehensweisen im Rahmen der Realisierung einer Entwicklungsgeneration vorgeschlagen. Während die Erfüllung von Qualitätsanforderungen für eine Entwicklungsgeneration nach der Realisierung abzuprüfen ist, sind funktionale Anforderungen direkter Ausgangspunkt von Entwicklungsaktivitäten in einem Sprint. Randbedingungen werden als Begründung für Anforderungen nachvollziehbar und wiederverwendbar dokumentiert. Wesentliche Bestandteile des Vorgehens wurden in Jira implementiert und im Rahmen zweier Entwicklungsprojekte positiv evaluiert

Chemical Similarity and Threshold of Toxicological Concern (TTC) Approaches: Report of an ECB Workshop held in Ispra, November 2005

There are many national, regional and international programmes – either regulatory or voluntary – to assess the hazards or risks of chemical substances to humans and the environment. The first step in making a hazard assessment of a chemical is to ensure that there is adequate information on each of the endpoints. If adequate information is not available then additional data is needed to complete the dataset for this substance. For reasons of resources and animal welfare, it is important to limit the number of tests that have to be conducted, where this is scientifically justifiable. One approach is to consider closely related chemicals as a group, or chemical category, rather than as individual chemicals. In a category approach, data for chemicals and endpoints that have been already tested are used to estimate the hazard for untested chemicals and endpoints. Categories of chemicals are selected on the basis of similarities in biological activity which is associated with a common underlying mechanism of action. A homologous series of chemicals exhibiting a coherent trend in biological activity can be rationalised on the basis of a constant change in structure. This type of grouping is relatively straightforward. The challenge lies in identifying the relevant chemical structural and physicochemical characteristics that enable more sophisticated groupings to be made on the basis of similarity in biological activity and hence purported mechanism of action. Linking two chemicals together and rationalising their similarity with reference to one or more endpoints has been very much carried out on an ad hoc basis. Even with larger groups, the process and approach is ad hoc and based on expert judgement. There still appears to be very little guidance about the tools and approaches for grouping chemicals systematically. In November 2005, the ECB Workshop on Chemical Similarity and Thresholds of Toxicological Concern (TTC) Approaches was convened to identify the available approaches that currently exist to encode similarity and how these can be used to facilitate the grouping of chemicals. This report aims to capture the main themes that were discussed. In particular, it outlines a number of different approaches that can facilitate the formation of chemical groupings in terms of the context under consideration and the likely information that would be required. Grouping methods were divided into one of four classes – knowledge-based, analogue-based, unsupervised, and supervised. A flowchart was constructed to attempt to capture a possible work flow to highlight where and how these approaches might be best applied.JRC.I.3-Toxicology and chemical substance

A proposal for calculating the no-observed-adverse-effect level (NOAEL) for organic compounds responsible for liver toxicity based on their physicochemical properties

Objectives: Both environmental and occupational exposure limits are based on the no-observed-adverse-effect level (NOAEL), lowest-observed-adverse-effect level (LOAEL) or benchmark dose (BMD) deriving from epidemiological and experimental studies. The aim of this study is to investigate to what extent the NOAEL values for organic compounds responsible for liver toxicity calculated based on their physicochemical properties could be used for calculating occupational exposure limits. Material and Methods: The distribution coefficients from air to the liver (log Kliver) were calculated according to the Abraham solvation equation. NOAEL and LOAEL values for early effects in the liver were obtained from the literature data. The descriptors for Abraham's equation were found for 59 compounds, which were divided into 2 groups: "non-reactive" (alcohols, ketones, esters, ethers, aromatic and aliphatic hydrocarbons, amides) and "possibly reactive" (aldehydes, allyl compounds, amines, benzyl halides, halogenated hydrocarbons, acrylates). Results: The correlation coefficients between log-log K and log NOAEL for non-reactive and reactive compounds amounted to r = -0.8123 and r = -0.8045, respectively, and were statistically significant. It appears that the Abraham equation could be used to predict the NOAEL values for compounds lacking information concerning their liver toxicity. Conclusions: In view of the tendency to limit animal testing procedures, the method proposed in this paper can improve the practice of setting exposure guidelines for the unstudied compounds

The neonicotinoid thiacloprid causes transcriptional alteration of genes associated with mitochondria at environmental concentrations in honey bees

Thiacloprid is widely used in agriculture and may affect pollinators. However, its molecular effects are poorly known. Here, we report the global gene expression profile in the brain of honey bee foragers assessed by RNA-sequencing. Bees were exposed for 72 h to nominal concentrations of 25 and 250 ng/bee via sucrose solution. Determined residue concentrations by LC-MS/MS were 0.59 and 5.49 ng/bee, respectively. Thiacloprid exposure led to 5 and 71 differentially expressed genes (DEGs), respectively. Nuclear genes encoding mitochondrial ribosomal proteins and enzymes involved in oxidative phosphorylation, as well as metabolism enzymes and transporters were altered at 5.49 ng/bee. Kyoto Encylopedia of Genes and Genomes (KEGG) analysis revealed that mitochondrial ribosome proteins, mitochondrial oxidative phosphorylation, pyrimidine, nicotinate and nicotinamide metabolism and additional metabolic pathways were altered. Among 21 genes assessed by RT-qPCR, the transcript of farnesol dehydrogenase involved in juvenile hormone III synthesis was significantly down-regulated. Transcripts of cyp6a14-like and apolipophorin-II like protein, cytochrome oxidase (cox17) and the non-coding RNA (LOC102654625) were significantly up-regulated at 5.49 ng/bee. Our findings indicate that thiacloprid causes transcriptional changes of genes prominently associated with mitochondria, particularly oxidative phosphorylation. This highlight potential effects of this neonicotinoid on energy metabolism, which may compromise bee foraging and thriving populations at environmentally relevant concentrations.ISSN:0269-7491ISSN:1878-2450ISSN:1873-642

Anti-Inflammatory Activity of Cyanobacterial Serine Protease Inhibitors Aeruginosin 828A and Cyanopeptolin 1020 in Human Hepatoma Cell Line Huh7 and Effects in Zebrafish (Danio rerio)

Intensive growth of cyanobacteria in freshwater promoted by eutrophication can lead to release of toxic secondary metabolites that may harm aquatic organisms and humans. The serine protease inhibitor aeruginosin 828A was isolated from a microcystin-deficient Planktothrix strain. We assessed potential molecular effects of aeruginosin 828A in comparison to another cyanobacterial serine protease inhibitor, cyanopeptolin 1020, in human hepatoma cell line Huh7, in zebrafish embryos and liver organ cultures. Aeruginosin 828A and cyanopeptolin 1020 promoted anti-inflammatory activity, as indicated by transcriptional down-regulation of interleukin 8 and tumor necrosis factor α in stimulated cells at concentrations of 50 and 100 µmol·L−1 aeruginosin 828A, and 100 µmol·L−1 cyanopeptolin 1020. Aeruginosin 828A induced the expression of CYP1A in Huh7 cells but did not affect enzyme activity. Furthermore, hatched zebrafish embryos and zebrafish liver organ cultures were exposed to aeruginosin 828A. The transcriptional responses were compared to those of cyanopeptolin 1020 and microcystin-LR. Aeruginosin 828A had only minimal effects on endoplasmic reticulum stress. In comparison to cyanopeptolin 1020 our data indicate that transcriptional effects of aeruginosin 828A in zebrafish are very minor. The data further demonstrate that pathways that are influenced by microcystin-LR are not affected by aeruginosin 828A

Anforderungsmanagement in der Agilen Entwicklung Mechatronischer Systeme - ein Widerspruch in sich?

Anforderungen sind ein Kernbestandteil agiler Entwicklung und aufgrund der Charakteristika mechatronischer Systeme ist eine Bündelung von Anforderungen zur Realisierung von Entwicklungsgenerationen als Inkremente wirtschaftlich sinnvoll. Folglich ist ein Management der Anforderungen hinsichtlich ihrer Entwicklung, Verifizierung und Wiederverwendung notwendig. Anhand der Entwicklung von Werkzeugmaschinen werden die beobachteten Charakteristika der Entwicklung mechatronischer Systeme mit Einfluss auf Durchlaufzeit, Materialkosten und Aufwand beschrieben, diese sind: Fertigungsdokumentation, Bestellung, Lieferung, Hilfsmittel, Montage und Inbetriebnahme. Unter Berücksichtigung dieser Einflussfaktoren wird anschließend ein Vorgehen zur systematischen Wiederverwendung von Anforderungen bei der Entwicklung neuer Produkt- und Entwicklungsgenerationen von Werkzeugmaschinen vorgestellt. Dabei werden Qualitätsanforderungen, funktionale Anforderungen und Randbedingungen unterschieden. Für Qualitäts- und funktionale Anforderungen werden spezifische Vorgehensweisen im Rahmen der Realisierung einer Entwicklungsgeneration vorgeschlagen. Während die Erfüllung von Qualitätsanforderungen für eine Entwicklungsgeneration nach der Realisierung abzuprüfen ist, sind funktionale Anforderungen direkter Ausgangspunkt von Entwicklungsaktivitäten in einem Sprint. Randbedingungen werden als Begründung für Anforderungen nachvollziehbar und wiederverwendbar dokumentiert. Wesentliche Bestandteile des Vorgehens wurden in Jira implementiert und im Rahmen zweier Entwicklungsprojekte positiv evaluiert