On the Complexity of List Ranking in the Parallel External Memory Model

We study the problem of list ranking in the parallel external memory (PEM) model. We observe an interesting dual nature for the hardness of the problem due to limited information exchange among the processors about the structure of the list, on the one hand, and its close relationship to the problem of permuting data, which is known to be hard for the external memory models, on the other hand. By carefully defining the power of the computational model, we prove a permuting lower bound in the PEM model. Furthermore, we present a stronger \Omega(log^2 N) lower bound for a special variant of the problem and for a specific range of the model parameters, which takes us a step closer toward proving a non-trivial lower bound for the list ranking problem in the bulk-synchronous parallel (BSP) and MapReduce models. Finally, we also present an algorithm that is tight for a larger range of parameters of the model than in prior work

De Chirico and Walker in light of Nietzsche and Guattari: the enigma of partial bodies in illogical spaces

If one concedes that the Freudian unconscious is inseparable from a society attached to its past, for example, its phallocentric traditions, Guattari’s alternative model dealing with "the production of subjectivity" offers a new perspective (1995: 11). From this vantage point, it is possible to map the way "every individual and social group" models the creation of subjectivity, a subjectivity "composed of cognitive references as well as mythical, ritual and symptomatological references" (1995: 11)

Resuming the dialogue: rhizomic actualisations

Since 1996, we have organised conferences on the discourse of the arts. The conferences have, in turn, led to a journal entitled Double Dialogues, the first of which was in hard copy under the sole editorship of Ann McCulloch and has been distributed internationally. After innumerable obstacles, we decided to situate articles, essays, exhibitions, and the like, from both these conferences and contributions related to our themes from interested parties, on-line. This refereed electronic journal deals with the discourse and practice of the arts, ranging across the visual arts, film, multi-media, dance, music, creative writing and theatre. Our decision to do this is manifold, but one of the reasons has been determined by our wish to become part of a global debate. We recognise that our interests are ones that are being experienced within academic institutions and art-centres world-wide. Before exploring the central theme of this Issue, perhaps we ought to contextualise it in terms of a journey over the last six years and into the future.<br /

Mice Infected with Low-virulence Strains of Toxoplasma gondii Lose their Innate Aversion to Cat Urine, Even after Extensive Parasite Clearance

Toxoplasma gondii chronic infection in rodent secondary hosts has been reported to lead to a loss of innate, hard-wired fear toward cats, its primary host. However the generality of this response across T. gondii strains and the underlying mechanism for this pathogen mediated behavioral change remain unknown. To begin exploring these questions, we evaluated the effects of infection with two previously uninvestigated isolates from the three major North American clonal lineages of T. gondii, Type III and an attenuated strain of Type I. Using an hour-long open field activity assay optimized for this purpose, we measured mouse aversion toward predator and non-predator urines. We show that loss of innate aversion of cat urine is a general trait caused by infection with any of the three major clonal lineages of parasite. Surprisingly, we found that infection with the attenuated Type I parasite results in sustained loss of aversion at times post infection when neither parasite nor ongoing brain inflammation were detectable. This suggests that T. gondii-mediated interruption of mouse innate aversion toward cat urine may occur during early acute infection in a permanent manner, not requiring persistence of parasitecysts or continuing brain inflammation.Comment: 14 pages, 3 figure

Isotope discrimination by the stearoyl desaturase of Neurospora crassa

In wild type Neurospora crassa, we previously observed an unexpectedly low proportion of label in unsaturated fatty acids that should have been derived from deuterated palmitate (16:0). Interpretation of whether the position of deuteration could account for these results was inconclusive, because wild type had a low proportion of total fatty acids derived from the deuterated supplement. The N. crassa cel-1 strain is ideally suited for studies of fatty acid enrichment, because cel-1 must obtain its fatty acids exogenously. We supplemented cel-1 with 16:0\u27s deuterated at different positions. With each of the labelled 16:0\u27s, cel-1 desaturated the stearate (18:0) derived from the 16:0 more efficiently than wild type. However, when the 16:0 was deuterated at the site of future desaturation, we indeed observed effects on fatty acid composition and label distribution consistent with inhibition of the 18:0 desaturase

A systematic survey of the fatty acid composition of Neurospora strains

Numerous studies have examined aspects of lipid metabolism in Neurospora crassa, N. tetrasperma and N. sitophila, but little systematic comparison has been done on lipids of the different species. Most obviously missing, however, is comparison of the fatty acid composition of lipids among Neurospora species. Fatty acid composition (especially the production of particular polyunsaturated fatty acids) is often a key factor in genus or species identification, particularly in bacteria, but also in other fungi such as Aspergillus, Penicillium and Mortierella (Kock and Botha 1998 In Frisvad et al. (eds), Chemical Fungal Taxonomy, Marcel Dekker, NY, p. 219-246). Until this study, reports of the fatty acid composition of Neurospora lipids have been limited to a few laboratory strains of N. crassa

An Entomopathogenic Nematode by Any Other Name

Among the diversity of insect-parasitic nematodes, entomopathogenic nematodes (EPNs) are distinct, cooperating with insect-pathogenic bacteria to kill insect hosts. EPNs have adapted specific mechanisms to associate with and transmit bacteria to insect hosts. New discoveries have expanded this guild of nematodes and refine our understanding of the nature and evolution of insect–nematode associations. Here, we clarify the meaning of “entomopathogenic” in nematology and argue that EPNs must rapidly kill their hosts with the aid of bacterial partners and must pass on the associated bacteria to future generations