Light propagation in statistically homogeneous and isotropic universes with general matter content

We derive the relationship of the redshift and the angular diameter distance to the average expansion rate for universes which are statistically homogeneous and isotropic and where the distribution evolves slowly, but which have otherwise arbitrary geometry and matter content. The relevant average expansion rate is selected by the observable redshift and the assumed symmetry properties of the spacetime. We show why light deflection and shear remain small. We write down the evolution equations for the average expansion rate and discuss the validity of the dust approximation.Comment: 42 pages, no figures. v2: Corrected one detail about the angular diameter distance and two typos. No change in result

On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)

Post-capitalist property

When writing about property and property rights in his imagined post-capitalist society of the future, Marx seemed to envisage ‘individual property’ co-existing with ‘socialized property’ in the means of production. As the social and political consequences of faltering growth and increasing inequality, debt and insecurity gradually manifest themselves, and with automation and artificial intelligence lurking in the wings, the future of capitalism, at least in its current form, looks increasingly uncertain. With this, the question of what property and property rights might look like in the future, in a potentially post-capitalist society, is becoming ever more pertinent. Is the choice simply between private property and markets, and public (state-owned) property and planning? Or can individual and social property in the (same) means of production co-exist, as Marx suggested? This paper explores ways in which they might, through an examination of the Chinese household responsibility system (HRS) and the ‘fuzzy’ and seemingly confusing regime of land ownership that it instituted. It examines the HRS against the backdrop of Marx’s ideas about property and subsequent (post-Marx) theorizing about the legal nature of property in which property has come widely to be conceptualized not as a single, unitary ‘ownership’ right to a thing (or, indeed, as the thing itself) but as a ‘bundle of rights’. The bundle-of-rights idea of property, it suggests, enables us to see not only that ‘individual’ and ‘socialized’ property’ in the (same) means of production might indeed co-exist, but that the range of institutional possibility is far greater than that between capitalism and socialism/communism as traditionally conceived

The Prospective Dutch Colorectal Cancer (PLCRC) cohort: real-world data facilitating research and clinical care

Real-world data (RWD) sources are important to advance clinical oncology research and evaluate treatments in daily practice. Since 2013, the Prospective Dutch Colorectal Cancer (PLCRC) cohort, linked to the Netherlands Cancer Registry, serves as an infrastructure for scientific research collecting additional patient-reported outcomes (PRO) and biospecimens. Here we report on cohort developments and investigate to what extent PLCRC reflects the “real-world”. Clinical and demographic characteristics of PLCRC participants were compared with the general Dutch CRC population (n = 74,692, Dutch-ref). To study representativeness, standardized differences between PLCRC and Dutch-ref were calculated, and logistic regression models were evaluated on their ability to distinguish cohort participants from the Dutch-ref (AU-ROC 0.5 = preferred, implying participation independent of patient characteristics). Stratified analyses by stage and time-period (2013–2016 and 2017–Aug 2019) were performed to study the evolution towards RWD. In August 2019, 5744 patients were enrolled. Enrollment increased steeply, from 129 participants (1 hospital) in 2013 to 2136 (50 of 75 Dutch hospitals) in 2018. Low AU-ROC (0.65, 95% CI: 0.64–0.65) indicates limited ability to distinguish cohort participants from the Dutch-ref. Characteristics that remained imbalanced in the period 2017–Aug’19 compared with the Dutch-ref were age (65.0 years in PLCRC, 69.3 in the Dutch-ref) and tumor stage (40% stage-III in PLCRC, 30% in the Dutch-ref). PLCRC approaches to represent the Dutch CRC population and will ultimately meet the current demand for high-quality RWD. Efforts are ongoing to improve multidisciplinary recruitment which will further enhance PLCRC’s representativeness and its contribution to a learning healthcare system

Holocene vegetation history of Flinders Island

Two swamp sites on Flinders Island in Bass Strait provide evidence of vegetation cover for the period 10000 BP to present. Steppe vegetation in which Compositae Liguliflorae taxa and chenopods were important was present on the Flinders Island part of the Bassian Isthmus during the earliest part of the record. However, it was replaced by eucalypt forest or woodland with a grassy understorey and some shrubs as sea level rose to form the present island by 6000 BP. The eucalypt dominated vegetation became less important about 940 BP when Callitris became prominent until very recently. This change may be related to a drier climate. Flinders Island is one of the few sites in Australia where humans were absent for an extended time (c. 4700 to 200 BP) during the Holocene. There is no particular indication of pollen or charcoal changes which can be related to the disappearance of humans from the island. However, at Killiecrankie Swamp the arrival of Europeans 200 yr ago probably caused the increased charcoal input to the swamp sediments and the vegetation change observed. Likewise Middle Patriarch Swamp records changes due to clearing and swamp drainage in the most recent times. The fact that the swamp deposits contain charcoal and pollen, together with the density of swamps on the eastern side of the island means the area is very favourably placed to provide detailed information on firing regimes unaffected by humans, in a sclerophyll vegetation very similar to that in large areas of southeastern Australia. In the light of the pollen evidence from this study and that from other southeastern mainland and Tasmanian sites it is suggested that the apparent prominence of Casuarina in the southwest of Victoria and southeast of South Australia during the early Holocene was due to local soil factors and drier climate. Later changes in soil and climate led to a decrease in Casuarina and increase in Eucalyptus

A phenomenological-connectionist theory of computational agency

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN042796 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

On the foundations of perceptial symbol systems: Specifying embodied representations via connectionism

Embodied theories of cognition propose that symbol systems are analogue (e.g. Barsalou, 1999; Glenberg, 1997), as opposed to the classicist view that they are amodal e.g. Newell and Simon (1976), Fodor (1998). The fundamental problem of symbol grounding (Harnad, 1990) is resolved in embodied theories by admitting only theories of symbolic representation that are grounded in the perceptual system’s representation (rather than by reference or mapping of amodal symbols through the sensory systems of the agent). These are often called analogical representations (Mandler, 1998). Barsalou’s (1999) proposal for perceptual symbol systems (PSS) provides just such a framework for how analogue symbols might come into being, but remains agnostic on the implementation of these PSSs. In this paper, we advance an implementation of PSSs which might fill this explanatory gap. We provide descriptions, an implementation and results from a model and its consequences for Barsalou’s theory and embodied representations generally. We constrain our model to the visual modality, but without loss of generality

Object representation-by-fragments in the visual system: A neurocomputational model

The paper presents a model of visual object representation by fragment views, rather than canonically-oriented whole-object views used in Chorus systems. Following recent results (Sheinberg and Logothetis, 2001) on object representation in inferotemporal cells during free viewing, we implemented a simplified attentional system which yields fragment views of objects, which are then used to train object-tuned modules. Each object is represented by a complete RBF module, instantiating a representation space. We show that such a system can produce distributed representations, like Chorus of views systems, and that dissociating objects from retinotopy enables a fuller model of scene geometry analysis to be advanced