125 research outputs found
First Row Transition Metal Aminopyridinates – the Missing Complexes
No full textLithiated 4-methyl-2-[(trimethylsilyl)amino]pyridine (Ap(TMS)H) undergoes a salt metathesis reaction with [SCCl(3)(thf)(3)] and FeCl(3), at low temperature in thf, to yield the homoleptic complexes [Sc(Ap(TMS))(3)] (1) and [Fe(Ap(TMS))(3)] (2). An analogous reaction with MnCl(2), CoCl(2) and FeCl(2) using two equivalents of 4-tert-butylpyridine (tBuPy) as additional donor ligand affords the structurally analogous cis complexes [Mn(Ap(TMS))(2)(tBuPy)(2)] (3), [Co(Ap(TMS))(2)(tBuPy)(2)] (4) and [Fe(Ap(TMS))(2)(tBuPy)(2)] (5). If FeCl(3), is used without tBuPy, the highly symmetric trinuclear complex [Fe(3)(Ap(TMS))((6)Li(2)O] (6) is obtained. Furthermore, the use of ZnCl(2) in a reaction with lithiated Ap(TMS)H yields the dimeric complex [Zn(Ap(TMS))(4)] (7) in which two Ap(TMS) ligands bridge the two metals. All complexes have been characterised by X-ray crystal structure analysis. To the best of our knowledge, complexes 1 and 2 and 5 are the first scandium and iron aminopyridinates, respectively, and complex 3 is the first manganese aminopyridinate complex which contains no additional anionic ligand. Complexes 4 and 7 are rare examples of cobalt and zinc aminopyridinates. This study proves that aminopyridinato ligands are highly universal ligands since they are able to stabilize early and late transition metals. Aminopyridinates of every first row transition metal are now available. The magnetic properties of all paramagnetic complexes were investigated. All complexes are high-spin complexes and the trinuclear iron complex 6 exhibits a weak antiferromagnetic coupling. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)Deutsche Forschungsgerneinschaft (DFG
Enhanced electromagnetic microwave absorption properties of SiCN(Fe) ceramics produced by additive manufacturing via in-situ reaction of ferrocene
No full textShort text authorship attribution via sequence kernels, Markov chains and author unmasking: An investigation
No full textWe present an investigation of recently proposed character and word sequence kernels for the task of authorship attribution based on relatively short texts. Performance is compared with two corresponding probabilistic approaches based on Markov chains. Several configurations of the sequence kernels are studied on a relatively large dataset (50 authors), where each author covered several topics. Utilising Moffat smoothing, the two probabilistic approaches obtain similar performance, which in turn is comparable to that of character sequence kernels and is better than that of word sequence kernels. The results further suggest that when using a realistic setup that takes into account the case of texts which are not written by any hypothesised authors, the amount of training material has more influence on discrimination performance than the amount of test material. Moreover, we show that the recently proposed author unmasking approach is less useful when dealing with short texts
Short Text Authorship Attribution via Sequence Kernels, Markov Chains and Author Unmasking: An Investigation
No full textWe present an investigation of recently proposed character and word sequence kernels for the task of authorship attribution based on relatively short texts. Performance is compared with two corresponding probabilistic approaches based on Markov chains. Several configurations of the sequence kernels are studied on a relatively large dataset (50 authors), where each author covered several topics. Utilising Moffat smoothing, the two probabilistic approaches obtain similar performance, which in turn is comparable to that of character sequence kernels and is better than that of word sequence kernels. The results further suggest that when using a realistic setup that takes into account the case of texts which are not written by any hypothesised authors, the amount of training material has more influence on discrimination performance than the amount of test material. Moreover, we show that the recently proposed author unmasking approach is less useful when dealing with short texts.
Short text authorship attribution via sequence kernels, Markov chains and author unmasking: An investigation
No full textWe present an investigation of recently proposed character and word sequence kernels for the task of authorship attribution based on relatively short texts. Performance is compared with two corresponding probabilistic approaches based on Markov chains. Several configurations of the sequence kernels are studied on a relatively large dataset (50 authors), where each author covered several topics. Utilising Moffat smoothing, the two probabilistic approaches obtain similar performance, which in turn is comparable to that of character sequence kernels and is better than that of word sequence kernels. The results further suggest that when using a realistic setup that takes into account the case of texts which are not written by any hypothesised authors, the amount of training material has more influence on discrimination performance than the amount of test material. Moreover, we show that the recently proposed author unmasking approach is less useful when dealing with short texts
Epigrafía maya: Tabasco
No full textLa información de esta miniguía está basada en los trabajos de M. Coe, N. Grove, S. Guenter, S. Martín, P. Mathews, Linda Schele, D. Stuart y M. U. Zender.Cuatro de las grandes culturas desarrolladas en Mesoamérica poseían un sistema propio de escritura: zapoteca, maya, mixteca y náhuatl. La escritura maya fue el sistema más complejo y el que más correspondencia tuvo con la lengua hablada. Parece haber surgido alrededor del 100 o 200 d.C., y según la mitología fue el dios ltzamná quien la inventó. Sus últimas expresiones se sitúan alrededor de 1696. Los mayas utilizaron diferentes soportes para plasmar la escritura y su historia escrita, como códices de papel vasijas de barro, textiles, pieles, estelas y altares de piedra, dinteles y cajas de madera, pendientes de hueso y hasta finas puntas de cola de mantarraya, entre otros.</p
Furthering the Professional development of teachers - some observations, ideas and visions from the view point of a research mathematician at a German University
No full textThe talk starts with a short description of the system of teacher education in Germany as well as with an overview on the German school system. Presently the author is running a project entitled Mathematik Anders Machen which translates to Mathematics Done Differently to spread and to broaden existing local or regional professional development programs. This massive project is sponsored by the Deutsche Telekom Foundation (T-Mobile) in collaboration with the German Mathematicians\u27 Association (DMV). In describing the theoretical framework of the program the author will refer to recent international research results in the area of professional development
Myra Warhaftigs Berliner Zimmer
No full textIn the article, the floor plans of Myra Warhaftig's Dessauer Strasse 38-40 are examined as part of the floor plan development of the Berlin apartment building. The references to the "Berlin Room" (Berliner Zimmer), a special historical feature in the development of the Berlin apartment building, play an important role. For the author, the special achievement of this project lies in the synthesis of this type with modern sociological and emancipatory demands on the floor plan
Performance and welfare of laying hens in conventional and enriched cages
No full textConcerns regarding the welfare of laying hens raised in battery cages have led to the development of enriched cages that allow hens to perform natural behaviors including nesting, roosting, and scratching. This study was conducted to compare indices of production and welfare in birds housed in 2 different caging systems. Shaver White hens were housed from 21 to 61 wk in either conventional battery cages (n = 500; 10 cages; 5 hens/cage; floor space = 561.9 cm(2)/hen) or enriched cages (n = 480; 2 cages; 24 hens/cage; floor space = 642.6 cm(2)/hen) and were replicated 10 times. Enriched cages provided hens with a curtained nesting area, scratch pad, and perches. Production parameters and egg quality measures were recorded throughout the experiment. Plumage condition was evaluated at 37 and 61 wk. Bone quality traits and immunological response parameters were measured at 61 wk, and 59 and 61 wk, respectively. Hen-day egg production, feed consumption, egg weight, and percentage of cumulative mortality of laying hens were not affected by the cage designs. Specific gravity and the percentage of cracked and soft-shelled eggs were also similar between the 2 housing systems. The incidence of dirty eggs was, however, significantly higher (P < 0.0001) in enriched cages than in conventional cages. Feather scores were similar between birds except for the wing region, which was higher (P < 0.05) for hens housed in conventional cages. Bone quality measures tended to be higher for hens housed in enriched cages compared with hens in conventional cages. However, the increase was significant only for bone mineral density. Immunological response parameters did not reveal statistically significant differences. Overall, laying performance, exterior egg quality measures, plumage condition, and immunological response parameters appear to be similar for hens housed in the 2 cage systems tested. Enrichment of laying hen cages resulted in better bone quality, which could have resulted from increased activity
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