Tungsten and Molybdenum 2,4,6‐Trimethylbenzylidyne Complexes as Robust Pre‐Catalysts for Alkyne Metathesis

A series of 2,4,6‐trimethylbenzylidyne tungsten and molybdenum complexes was prepared from the tribromides mer‐[MesCMBr₃(dme)] ( 9a , M=W; 9b , M=Mo, dme=1,2‐dimethoxyethane). Successive reaction of complexes 9 with lithium or potassium hexafluoro‐tert‐butoxide and lithium 1,3‐di‐tert‐butylimidazolin‐2‐imide, (Im^t‐BuN)Li, afforded the imidazolin‐2‐iminato complexes [MesCM{OC(CF₃)₂Me}₂(Im^t‐BuN)] ( 10a , M=W; 10b , M=Mo), whereas the reactions of 9 with three equivalents of LiOSi(O‐t‐Bu)₃ or KOC(CF₃)₃ gave [MesCM{OSi(O‐t‐Bu)₃}₃] ( 11a , M=W; 11b , M=Mo) and [MesCM{OC(CF₃)₃}₃] ( 12a , M=W; 12b , M=Mo), respectively. For comparison, the benzylidyne complex [PhCMo{OSi(O‐t‐Bu)₃}₃] ( 7b ) was also prepared, and its molecular structure together with those of 10a , 10b , 11b , 12a and 12b were established by X‐ray diffraction analysis. Complexes 10 and 11 were employed as pre‐catalysts for the alkyne metathesis of the test substrate 3‐pentynyl benzyl ether ( 13 ) at low catalyst loadings (1 mol%) in the presence of molecular sieve (5 Å). Comparative studies of these 2,4,6‐trimethylbenzylidyne species (MesCM) with their benzylidyne analogues (PhCM) revealed that the increased steric bulk renders the former more stable and manageable in air in solid form for shorter periods of time, but at the expense of a slower initiation, which requires higher temperatures or longer reaction times.

     

Increased Presence of Complement Factors and Mast Cells in Alveolar Bone and Tooth Resorption

Periodontitis is the inflammatory destruction of the tooth-surrounding and -supporting tissue, resulting at worst in tooth loss. Another locally aggressive disease of the oral cavity is tooth resorption (TR). This is associated with the destruction of the dental mineralized tissue. However, the underlying pathomechanisms remain unknown. The complement system, as well as mast cells (MCs), are known to be involved in osteoclastogenesis and bone loss. The complement factors C3 and C5 were previously identified as key players in periodontal disease. Therefore, we hypothesize that complement factors and MCs might play a role in alveolar bone and tooth resorption. To investigate this, we used the cat as a model because of the naturally occurring high prevalence of both these disorders in this species. Teeth, gingiva samples and serum were collected from domestic cats, which had an appointment for dental treatment under anesthesia, as well as from healthy cats. Histological analyses, immunohistochemical staining and the CH-50 and AH-50 assays revealed increased numbers of osteoclasts and MCs, as well as complement activity in cats with TR. Calcifications score in the gingiva was highest in animals that suffer from TR. This indicates that MCs and the complement system are involved in the destruction of the mineralized tissue in this condition.     

Towards a deeper understanding of managerial green investment patterns – a USA–Germany comparison

Green investments are crucial mechanisms for translating green operation strategies into managerial action. We examine the impact of external pressures on green investment patterns in terms of their scope, type and time horizon across 251 German and US managers. A scenario-based experiment was conducted using a 2 × 2 × 2 factorial design in which managers were assigned to high and low consumer, community, and resource treatment groups before being asked to make green investment decisions. Our hypotheses are developed based on resource advantage theory and tested in a number of regression models. The results demonstrate that German and US managers respond differently to external pressures in their green investment decisions. Regarding the scope of green investments, German and US managers invest differently if end consumer pressure increases and partially differently if resource scarcity increases, but they act in a similar way if community pressure increases. Moreover, we detected specific variations in the type and time horizon of green investments across US and German managers. The theoretical and practical implications of these findings for green operations management research and for firms operating in multinational settings are explained.     

Tweezing-adsorptive bubble separation. Analytical method for the selective and high enrichment of metalloenzymes

A novelly developed tweezing-adsorptive bubble separation (ABS) method for the enrichment of metalloenzymes (laccase C and horseradish peroxidase) is introduced. The method is based on the chelation of the enzymes' active center and can also be applied for analysis. N-(2-acetamido)iminodiacetic acid served as a chelator and was synthesized with an octyl unit to become ADA-C8. Laccase was enriched 13.3-fold (66.31% recovery) and HPOX 17.8-fold (85.34%) without a significant loss of enzymatic activity. To prove that the entire enzyme is tweezed at the active center, ABS trials were done using ADA-C8 already complexed with Cu2+ and Fe3+. As only marginal enrichment occurred (ER laccase, 0.17; ER HPOX, 0.44), no chelating effect was concluded. It was determined how the chelation toward the active center was directed by applying other chelators such as EDTA, NTA, N,N-dimethylaminoglycine, oxalic acid, malonic acid, adipinic acid, and tripropylamine, which are similar in structure to ADA-C8. The results concluded that the chelation is 3-fold coordinated on the type 1 copper center of laccase, whereas that of HPOX only 1-fold at Fe3+ and additionally at the cationic amino acid arginine, which is also located at the active center. Tweezing-ABS has been proven to selectively and effectively enrich metalloenzymes.     

Foam fractionation of exo-lipases from a growing fungus (<Emphasis Type="Italic">Pleurotus sapidus</Emphasis>)

Active lipases were isolated from the culture supernatant of the basidiomycetous fungus Pleurotus sapidus by foam fractionation. The pH value, the gas flow, and the foaming period were systematically varied to optimize the transport of the enzymes into the foam phase. On a 70-mL scale, a maximum recovery of hydrolytic activity of 95% was obtained at pH 7.0 and 60 mL N₂ min⁻¹ after 50 min. The procedure, with minor modifications, was also applicable to native pellet cultures of P. sapidus. The same recovery of 95% was achieved, with purification and enrichment factors of 11.6 and 28.0, respectively.     

Mikrowellen‐PECVD für kontinuierliche Großflächenbeschichtung bei Atmosphärendruck

Microwave PECVD for continuous wide area coating at atmospheric pressure Plasma processes are applied for a variety of surface modifications. Examples are coatings to achieve an improved corrosion and scratch protection, or surface cleaning. Normally, these processes are vacuum based and therefore suitable to only a limited extend for large area industrial applications. By use of atmospheric pressure plasma technology integration in continuously working manufacturing lines is advantageously combined with lower costs and higher throughput. Microwave plasma sources present powerful modules for plasma enhanced chemical vapour deposition at atmospheric pressure. At Fraunhofer IWS processes and equipment as well as application specific materials are developed. The coatings are suitable for scratch resistant surfaces, barrier and corrosion protective layers or anti‐reflex layers on solar cells. The film properties achieved are comparable with those produced by low pressure processes.