344 research outputs found

    Terrorist transgressions: exploring the gendered representations of the terrorist

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    Abstract: The primary aim of the Terrorist Transgressions network which is presented here was to analyse the myths inscribed in images of the terrorist and identify how agency is attributed to representation through invocations and inversions of gender stereotypes. Although terrorism, its contexts, histories and forms, has been the focus of intense academic activity in recent years, especially in the fields of politics and international relations, cultural representations of the terrorist have received less attention. While the terrorist is predominantly aligned with masculinity, women have been active in terrorist organizations since the late nineteenth century. Particularly since the 1980s, women have perpetrated suicidal terrorist attacks, including suicide bombing, where the body becomes a weapon. Such attacks have confounded constructions of femininity and masculinity, with profound implications for the gendering of violence and horror. The network established that there is a shift away from analyses of cultural representations of the Red Army Faction, which have dominated the literature since the 1980s. New work has emerged examining representations of the terrorist and gender, including investigations of material from the 1970s, recently made available in archives. There also has been a shift in terms of military discourses around the figure of the enemy or terrorist insurgent in relation to visualizing the invisible enemy. Emerging work on colonial insurgencies contributed to a historical understanding of such debates

    The Peru-Chile undercurrent

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    The presence of a southward-moving undercurrent along the west coast of South America, underlying the Peru Current at depths of several hundred meters, has been established by direct measurements with parachute drogues, by calculations of geostrophic motion, and by analysis of the distributions of salinity and dissolved oxygen...

    Spontaneous thermal runaway as an ultimate failure mechanism of materials

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    The first theoretical estimate of the shear strength of a perfect crystal was given by Frenkel [Z. Phys. 37, 572 (1926)]. He assumed that as slip occurred, two rigid atomic rows in the crystal would move over each other along a slip plane. Based on this simple model, Frenkel derived the ultimate shear strength to be about one tenth of the shear modulus. Here we present a theoretical study showing that catastrophic material failure may occur below Frenkel's ultimate limit as a result of thermal runaway. We demonstrate that the condition for thermal runaway to occur is controlled by only two dimensionless variables and, based on the thermal runaway failure mechanism, we calculate the maximum shear strength σc\sigma_c of viscoelastic materials. Moreover, during the thermal runaway process, the magnitude of strain and temperature progressively localize in space producing a narrow region of highly deformed material, i.e. a shear band. We then demonstrate the relevance of this new concept for material failure known to occur at scales ranging from nanometers to kilometers.Comment: 4 pages, 3 figures. Eq. (6) and Fig. 2a corrected; added references; improved quality of figure

    Spontaneous dissipation of elastic energy by self-localizing thermal runaway

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    Thermal runaway instability induced by material softening due to shear heating represents a potential mechanism for mechanical failure of viscoelastic solids. In this work we present a model based on a continuum formulation of a viscoelastic material with Arrhenius dependence of viscosity on temperature, and investigate the behavior of the thermal runaway phenomenon by analytical and numerical methods. Approximate analytical descriptions of the problem reveal that onset of thermal runaway instability is controlled by only two dimensionless combinations of physical parameters. Numerical simulations of the model independently verify these analytical results and allow a quantitative examination of the complete time evolutions of the shear stress and the spatial distributions of temperature and displacement during runaway instability. Thus we find that thermal runaway processes may well develop under nonadiabatic conditions. Moreover, nonadiabaticity of the unstable runaway mode leads to continuous and extreme localization of the strain and temperature profiles in space, demonstrating that the thermal runaway process can cause shear banding. Examples of time evolutions of the spatial distribution of the shear displacement between the interior of the shear band and the essentially nondeforming material outside are presented. Finally, a simple relation between evolution of shear stress, displacement, shear-band width and temperature rise during runaway instability is given.Comment: 16 pages, 7 figures. Extended conclusion; added reference

    Dynamics of Large-Scale Plastic Deformation and the Necking Instability in Amorphous Solids

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    We use the shear transformation zone (STZ) theory of dynamic plasticity to study the necking instability in a two-dimensional strip of amorphous solid. Our Eulerian description of large-scale deformation allows us to follow the instability far into the nonlinear regime. We find a strong rate dependence; the higher the applied strain rate, the further the strip extends before the onset of instability. The material hardens outside the necking region, but the description of plastic flow within the neck is distinctly different from that of conventional time-independent theories of plasticity.Comment: 4 pages, 3 figures (eps), revtex4, added references, changed and added content, resubmitted to PR

    Fluid flow due to collective non-reciprocal motion of symmetrically-beating artificial cilia

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    Using a magneto-mechanical solid-fluid numerical model for permanently magnetic artificial cilia, we show that the metachronal motion of symmetrically beating cilia establishes a net pressure gradient in the direction of the metachronal wave, which creates a unidirectional flow. The flow generated is characterised as a function of the cilia spacing, the length of the metachronal wave, and a dimensionless parameter that characterises the relative importance of the viscous forces over the elastic forces in the cilia

    Illicit and Counterfeit Drug Analysis by Morphologically Directed Raman Spectroscopy

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    Morphologically directed Raman spectroscopy (MDRS) is a novel tool for the forensic analysis of illicit and counterfeit drug samples. MDRS combines Raman microspectroscopy with automated particle imaging so that physical and chemical information about the components of a mixture sample can be obtained. Results of automated particle imaging are used to determine samples for Raman analysis. The use of MDRS for these types of samples can be employed for both forensic investigations and adjudications of cases. The method provides insight about the physical and chemical composition of the sample, as well as about manufacturing and sample history. Here, MDRS was used in four different illicit and counterfeit drug analyses: (1) examination of a multicomponent drug mixture where the results could be used for comparative source attribution, (2) the detection of low (or trace) concentration particles in a drug sample, (3) the analysis of synthetic cathinone samples (i.e., bath salts), and (4) a study of counterfeit pharmaceutical products

    Using zeta-potential measurements to quantify peptide partition to lipid membranes

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    © The Author(s) 2011. This article is published with open access at Springerlink.com.Open Access: This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.Many cellular phenomena occur on the biomembranes. There are plenty of molecules (natural or xenobiotics) that interact directly or partially with the cell membrane. Biomolecules, such as several peptides (e.g., antimicrobial peptides) and proteins, exert their effects at the cell membrane level. This feature makes necessary investigating their interactions with lipids to clarify their mechanisms of action and side effects necessary. The determination of molecular lipid/water partition constants (Kp) is frequently used to quantify the extension of the interaction. The determination of this parameter has been achieved by using different methodologies, such as UV-Vis absorption spectrophotometry, fluorescence spectroscopy and ζ-potential measurements. In this work, we derived and tested a mathematical model to determine the Kp from ζ-potential data. The values obtained with this method were compared with those obtained by fluorescence spectroscopy, which is a regular technique used to quantify the interaction of intrinsically fluorescent peptides with selected biomembrane model systems. Two antimicrobial peptides (BP100 and pepR) were evaluated by this new method. The results obtained by this new methodology show that ζ-potential is a powerful technique to quantify peptide/lipid interactions of a wide variety of charged molecules, overcoming some of the limitations inherent to other techniques, such as the need for fluorescent labeling.This work was partially supported by project PTDC/QUI/ 69937/2006 from Fundação para a Ciência e Tecnologia-Ministério da Ciência, Tecnologia e Ensino Superior (FCT-MCTES, Portugal), and by Fundação Calouste Gulbenkian (Portugal). JMF and MMD also thank FCT-MCTES for grants IMM/BT/37-2010 and SFRH/BD/41750/2007, respectively

    A large-strain radial consolidation theory for soft clays improved by vertical drains

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    A system of vertical drains with combined vacuum and surcharge preloading is an effective solution for promoting radial flow, accelerating consolidation. However, when a mixture of soil and water is deposited at a low initial density, a significant amount of deformation or surface settlement occurs. Therefore, it is necessary to introduce large-strain theory, which has been widely used to manage dredged disposal sites in one-dimensional theory, into radial consolidation theory. A governing equation based on Gibson's large-strain theory and Barron's free-strain theory incorporating the radial and vertical flows, the weight of the soil, variable hydraulic conductivity and compressibility during the consolidation process is therefore presented
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