Asymmetric synthesis of bicyclic pyrazolidinones through alkaloid-catalyzed [3 + 2]-cycloadditions of ketenes and azomethine imines

A versatile asymmetric synthesis of bicyclic pyrazolidinones through alkaloid-catalyzed formal [3 + 2]- and [3 + 2 + 2]-cycloadditions of ketenes with azomethine imines is described. The methodology was found to be tolerant of ketene and a variety of monosubstituted ketenes (R = alkyl, OAc). The products were formed in good to excellent yields (71-99% for 24 examples, 39 examples in all), with good to excellent diastereoselectivity in many cases (dr 3:1 to 27:1 for 22 examples), and with excellent enantioselectivity for most examples (≥93% ee for 34 products). In the case of most disubstituted ketenes, the reaction proceeded through a [3 + 2 + 2]-cycloaddition to form structurally interesting bicyclic pyrazolo-oxadiazepinediones with moderate diastereoselectivity (dr up to 3.7:1) and as racemic mixtures (3 examples). The method represents the first unambiguous example of an enantioselective reaction between ketenes and a 1,3-dipole

Multiproxy study of anthropogenic and climatic changes in the last two millennia from a small mire in central Poland

The Żabieniec kettle-hole is the first peatland in central Poland analysed quantitatively with four biotic proxies (plant macrofossils, pollen, testate amoebae and chironomids) in order to reconstruct past environmental change. Palaeoecological data were supported by historical and archaeological records. We focused on autogenic vegetation change and human impact in relation to climatic effects. The aims of our study were: (a) to describe the development history of the mire during the last 2000 years, (b) to date and reconstruct the anthropogenic land-use changes, and (c) to discuss a possible climatic signal in the peat archive. The combination of proxies revealed dramatic shifts that took place in the peatland since the Roman Period. Żabieniec was a very wet telmatic habitat until ca AD 600. Then the water table declined and the site transformed into a Sphagnum-dominated mire. This dry shift took place mainly during the Early Medieval Period. Human impact was gradually increasing and it was particularly emphasized by deforestation since AD 1250 (beginning of the Late Medieval Period). Consequently, surface run-off and aeolian transport from the exposed soils caused the eutrophication of the mire. Furthermore, chironomids and testate amoebae reveal the beginning of a wet shift ca AD 1350. Openness considerably increased in the Late Medieval and the Modern Periods. The highest water table during the last 1000 years was recorded between AD 1500 and 1800. This wet event is connected with deforestation but it could be also associated with the Little Ice Age. Our study shows plant succession in the Żabieniec peatland, which can be explained with the recent landscape transformation. However, such changes are also possibly linked with the major climatic episodes during the last two millennia, such as the Medieval Warm Period and the Little Ice Age

Towards an approach for analysing external representations created during sensemaking using generative grammar

During sensemaking, users often create external representations to help them make sense of what they know, and what they need to know. In doing so, they necessarily adopt or construct some form of representational language using the tools at hand. By describing such languages implicit in representations we believe that we are better able to describe and differentiate what users do and better able to describe and differentiate interfaces that might support them. Drawing on approaches to the analysis of language, and in particular, Mann and Thompson’s Rhetorical Structure Theory, we analyse the representations that users create to expose their underlying ‘visual grammar’. We do this in the context of a user study involving evidential reasoning. Participants were asked to address an adapted version of IEEE VAST 2011 mini challenge 3 (interpret a potential terrorist plot implicit in a set of news reports). We show how our approach enables the unpacking of the heterogeneous and embedded nature of user-generated representations and allows us to show how visual grammars evolve and become more complex over time in response to evolving sensemaking needs

Should causal models always be Markovian? The case of multi-causal forks in medicine

The development of causal modelling since the 1950s has been accompanied by a number of controversies, the most striking of which concerns the Markov condition. Reichenbach's conjunctive forks did satisfy the Markov condition, while Salmon's interactive forks did not. Subsequently some experts in the field have argued that adequate causal models should always satisfy the Markov condition, while others have claimed that non-Markovian causal models are needed in some cases. This paper argues for the second position by considering the multi-causal forks, which are widespread in contemporary medicine (Section 2). A non-Markovian causal model for such forks is introduced and shown to be mathematically tractable (Sections 6, 7, and 8). The paper also gives a general discussion of the controversy about the Markov condition (Section 1), and of the related controversy about probabilistic causality (Sections 3, 4, and 5

Pre-emption cases may support, not undermine, the counterfactual theory of causation

Pre-emption cases have been taken by almost everyone to imply the unviability of the simple counterfactual theory of causation. Yet there is ample motivation from scientific practice to endorse a simple version of the theory if we can. There is a way in which a simple counterfactual theory, at least if understood contrastively, can be supported even while acknowledging that intuition goes firmly against it in pre-emption cases – or rather, only in some of those cases. For I present several new pre-emption cases in which causal intuition does not go against the counterfactual theory, a fact that has been verified experimentally. I suggest an account of framing effects that can square the circle. Crucially, this account offers hope of theoretical salvation – but only to the counterfactual theory of causation, not to others. Again, there is (admittedly only preliminary) experimental support for this account

Sedimentologic properties of neoholocene slope deposits in the Łódź Region and their value for interpretation

Studies focused on the Holocene series of deposits that fill dry valleys, especially common in the Łódz Plateau. The series are underlain by Vistulian complex filling dry valleys (Klatkowa 1965, 1989 a, b, 1990), Wartian fluvioglacial sands and sporadically Holocene sandy or mudy alluvia. As a rule, the Holocene sediments were directly laid down on Neoholocene fossil soils which contain charcoal in land occupation hohizons. Thickness of the studied series, approximately 1.5 m, in suitable conditions might have reached 2.8 m. Within the series, it is possible to distinguish three sedimentary members: 1. anthropogenic soil deluvia, which from the bottom, 2. deposits of gully erosion (proluvia), which cut or cover deluvia, 3. agricultural diamictons due to long-lasting ploughing, which create the top. Anthropogenic deluvia consist of two lithofacies: deluvial sands and deluvial sandy silts (Fig. 1, Fot. 1, 2). Deluvial sands (Mz = 1-3 φ, Sk₁ = 0.2-0.5, σ₁ = 0.5-2) lack of an organic admixture and from subhorizontal layers, up to a few cm thick. Organic deluvial sandy silts (Mz = 3-5 φ, Sk₁ to+ 0.6, σ₁ = 1.75-2.75) create layers of a similar thickness and reveal subtle internal lamination. Deluvial sands and sandy silts alternate, which gives a character of rhythmicallity. The rhythmicallity is additionally underlined by the variation of colours of the lithofacies, which occurs by the different content of an organic admixture. Rhythmical lamination is a general feature of deluvial sediments (Stochlak 1976, 1978, 1996, Teisseyre 1994) and is explained by variable activity of wash process in time and its modes (sheetwash, rillwash) . Deposits of gullying occasionally interlayer the deluvial member (Photo 1, 2). They are coarse-grained (Mz = - 6 to 1 φ), very poorly sorted ( σ₁ to 5.5) and contain an admixture of coarser (Sk₁ = -0.3 to -0.5) gravel and boulder particles. This sediment type must have been deposited under turbulent flow condition of episodic waters. The development of gullies took place after deluvial deposition between V/VI and XVI century AD (Twardy 1995), and often provided conditions for partial destruction of the older deluvial member. Development of agricultural diamictons (Niewiarowski et al. 1992, Sinkiewicz 1994, 1995) followed the introduction of a plough, and afterwards inccreased in XIX and XX century with the use of agricultural machinery. Vari-grained, structurless, compact and organic deposits originated, whose structure is due to soil mixing during ploughing (Photo 1, 2). In the Łódź region, the start of the deluvial deposition occurred at the turn of the Bronze and Iron Age and coincided with the settlement of farming tribes