529 research outputs found
Role of osmotic and hydrostatic pressures in bacteriophage genome ejection
A critical step in the bacteriophage life cycle is genome ejection into host
bacteria. The ejection process for double-stranded DNA phages has been studied
thoroughly \textit{in vitro}, where after triggering with the cellular receptor
the genome ejects into a buffer. The experimental data have been interpreted in
terms of the decrease in free energy of the densely packed DNA associated with
genome ejection. Here we detail a simple model of genome ejection in terms of
the hydrostatic and osmotic pressures inside the phage, a bacterium, and a
buffer solution/culture medium. We argue that the hydrodynamic flow associated
with the water movement from the buffer solution into the phage capsid and
further drainage into the bacterial cytoplasm, driven by the osmotic gradient
between the bacterial cytoplasm and culture medium, provides an alternative
mechanism for phage genome ejection \textit{in vivo}; the mechanism is
perfectly consistent with phage genome ejection \textit{in vitro}.Comment: 5 pages, 2 figures, references update
Research on the Geography of Agricultural Change: Redundant or Revitalized?
Future research directions for agricultural geography were the subject of debate in Area in the late 1980s. The subsequent application of political economy ideas undoubtedly revived interest in agricultural research. This paper argues that agricultural geography contains greater diversity than the dominant political economy discourse would suggest. It reviews βotherβ areas of agricultural research on policy, post-productivism, people, culture and animals, presenting future suggestions for research. They should ensure that agricultural research continues revitalized rather than redundant into the next millennium
Exploiting the archive: and the animals came in two by two, 16mm, CD-ROM and BetaSp
This a post-print, author-produced version of an article accepted for publication in Area. Copyright Β© 1999 Wiley Blackwell. The definitive version is available at www3.interscience.wiley.comUsing an account of the construction and subsequent exploitation of the film archive at the BBC's Natural History Unit, this paper explores the ways in which animals are embedded in the different cultures of care, control and commodification in the zoo and the wildlife film-making unit. Network analysis is used to account for the similarities and tensions between these forms of animal exhibition, as revealed in the electronic zoo at Wildscreen World
Arguably big biology: Sociology, spatiality and the knockout mouse project
Β© 2013 copyright Palgrave MacmillanThis is a post-peer-review, pre-copyedit version of an article published in BioSocieties. The definitive publisher-authenticated version BioSocieties, 2013, Vol. 8, pp. 417-431 is available online at: http://www.palgrave-journals.com/biosoc/journal/v8/n4/full/biosoc201325a.htmlFollowing the completion of the Human Genome Project (HGP), a critical challenge has been how to make biological sense of the amassed sequence data and translate this into clinical applications. A range of large biological research projects, as well as more distributed experimental collaborations, are seeking to realise this through translational research initiatives and postgenomic approaches. Drawing on interviews with key participants, this article explores the biological assumptions, sociological challenges and spatial imaginaries at play in arguments around one of these developments, which is using genetically altered mice to understand gene function. The knockout mouse project (KOMP) is a large-scale initiative in functional genomics, seeking to produce a βknockout mouseβ for each gene in the mouseβs genome, which can then be used to answer questions about gene function in mammals. KOMP is frequently framed as one successor to the HGP, emblematic of the ambitions of internationally coordinated biological research. However, the development of new technologies for generating and managing genetically altered mice, alongside the challenge of asking biologically meaningful questions of vast numbers of animals, is creating new frictions in this extension and intensification of biological research practices. This article introduces two separate approaches to the future of international research using mutant mice as stakeholders to negotiate the biological, sociological and spatial challenges of collaboration. The first centres on the directed research practices and sociological assumptions of KOMP, as individual researchers are reorganised around shared animals, databases and infrastructures. The second highlights an alternative vision of the future of biomedical research, using distributed management to enhance the sensitivities and efficiencies of existing experimental practices over space. These exemplify two different tactics in the organisation of an βarguablyβ big biology. They also critically embody different sociological and spatial imaginaries for the collaborative practices of international translational research
Electrostatic model of atomic ordering in complex perovskite alloys
We present a simple ionic model which successfully reproduces the various
types of compositional long-range order observed in a large class of complex
insulating perovskite alloys. The model assumes that the driving mechanism
responsible for the ordering is simply the electrostatic interaction between
the different ionic species. A possible new explanation for the anomalous
long-range order observed in some Pb relaxor alloys, involving the proposed
existence of a small amount of Pb^4+ on the B sublattice, is suggested by an
analysis of the model.Comment: 4 pages, two-column style with 1 postscript figure embedded. Uses
REVTEX and epsf macros. Also available at
http://www.physics.rutgers.edu/~dhv/preprints/index.html#lb_orde
Rapid evolution of virulence and drug resistance in the emerging zoonotic pathogen Streptococcus suis
Background: Streptococcus suis is a zoonotic pathogen that infects pigs and can occasionally cause serious infections in
humans. S. suis infections occur sporadically in human Europe and North America, but a recent major outbreak has been
described in China with high levels of mortality. The mechanisms of S. suis pathogenesis in humans and pigs are poorly
understood.
Methodology/Principal Findings: The sequencing of whole genomes of S. suis isolates provides opportunities to
investigate the genetic basis of infection. Here we describe whole genome sequences of three S. suis strains from the same
lineage: one from European pigs, and two from human cases from China and Vietnam. Comparative genomic analysis was
used to investigate the variability of these strains. S. suis is phylogenetically distinct from other Streptococcus species for
which genome sequences are currently available. Accordingly, ,40% of the ,2 Mb genome is unique in comparison to
other Streptococcus species. Finer genomic comparisons within the species showed a high level of sequence conservation;
virtually all of the genome is common to the S. suis strains. The only exceptions are three ,90 kb regions, present in the two
isolates from humans, composed of integrative conjugative elements and transposons. Carried in these regions are coding
sequences associated with drug resistance. In addition, small-scale sequence variation has generated pseudogenes in
putative virulence and colonization factors.
Conclusions/Significance: The genomic inventories of genetically related S. suis strains, isolated from distinct hosts and
diseases, exhibit high levels of conservation. However, the genomes provide evidence that horizontal gene transfer has
contributed to the evolution of drug resistance
Qualitative methods: are you enchanted or are you alienated?
Copyright Β© 2007 SAGE Publications. Author's draft version; post-print. Final version published by Sage available on Sage Journals Online http://online.sagepub.com/Since the last report on qualitative methods
(Crang, 2005), many of the practical procedures
of doing qualitative research remain the
same. Human geographers continue to study
texts, to conduct interviews, to convene focus
groups and to engage in ethnography. Indeed,
it is hard, though perhaps not impossible,
to imagine what a radically new form of
qualitative research practice might look like.
So, for the time being, this suite of methods
remains the backbone of qualitative research in
human geography. Yet we would like to contend
that, while these activities continue as
before, there are changes in the way they are
being conceived and carried out, and related to
this there are transformations in the way these
methods are being used to make claims to
understanding and intervening in the world. In
the first of our three reports, it is this link
between qualitative methodologies and interpretative
strategies we would like to reflect on
(Dis)entangling Barad: Materialisms and ethics
In the wake of the widespread uptake of and debate surrounding the work of Karen Barad, this article revisits her core conceptual contributions. We offer descriptions, elaborations, problematizations and provocations for those intrigued by or invested in this body of work. We examine Baradβs use of quantum physics, which underpins her conception of the material world. We discuss the political strengths of this position but also note tensions associated with applying quantum physics to phenomena at macro-scales. We identify both frictions and unacknowledged affinities with science and technology studies in Baradβs critique of reflexivity and her concept of diffraction. We flesh out Baradβs overarching position of βagential realismβ, which contains a revised understanding of scientific apparatuses. Building upon these discussions, we argue that inherent in agential realism is both an ethics of inclusion and an ethics of exclusion. Existing research has, however, frequently emphasized entanglement and inclusion to the detriment of foreclosure and exclusion. Nonetheless, we contend that it is in the potential for an ethics of exclusion that Baradβs work could be of greatest utility within science and technology studies and beyond
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