Effective hard x-ray spectrum of a tabletop Mather-type plasma focus optimized for flash radiography of metallic objects

The effective spectrum of the hard x-ray output of a Mather-type tabletop plasma focus device was determined from attenuation data on metallic samples using commercial radiographic film coupled to a Gd2 O2 S:Tb phosphor intensifier screen. It was found that the radiation has relevant spectral components in the 40-150 keV range, with a single maximum around 60-80 keV. The radiation output allows for 50 ns resolution, good contrast, and introspective imaging of metallic objects even through metallic walls. A numerical estimation of the induced voltage on the focus during the compressional stage is briefly discussed. © 2007 American Institute of Physics.Fil:Raspa, V. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Moreno, C. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Sigaut, L. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Rab27a controls HIV-1 assembly by regulating plasma membrane levels of phosphatidylinositol 4,5-bisphosphate

During the late stages of the HIV-1 replication cycle, the viral polyprotein Pr55(Gag) is recruited to the plasma membrane (PM), where it binds phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) and directs HIV-1 assembly. We show that Rab27a controls the trafficking of late endosomes carrying phosphatidylinositol 4-kinase type 2 α (PI4KIIα) toward the PM of CD4(+) T cells. Hence, Rab27a promotes high levels of PM phosphatidylinositol 4-phosphate and the localized production of PI(4,5)P2, therefore controlling Pr55(Gag) membrane association. Rab27a also controls PI(4,5)P2 levels at the virus-containing compartments of macrophages. By screening Rab27a effectors, we identified that Slp2a, Slp3, and Slac2b are required for the association of Pr55(Gag) with the PM and that Slp2a cooperates with Rab27a in the recruitment of PI4KIIα to the PM. We conclude that by directing the trafficking of PI4KIIα-positive endosomes toward the PM, Rab27a controls PI(4,5)P2 production and, consequently, HIV-1 replication.Universidad de Buenos Aires and CONICET doctoral fellowships, Agencia Nacional de Pro- moción Científica y Tecnológica (Argentina) grants: (2010-1681, 2012-00353), Creative and Novel Ideas in HIV Research Program, University of Alabama at Birmingham Center for AIDS Research funding grant P30 AI027767-24

Loss of the Wnt/β-catenin pathway in microglia of the developing brain drives pro-inflammatory activation leading to white matter injury

Microglia-mediated neuroinflammation is key in numerous brain diseases including encephalopathy of the preterm born infant. Microglia of the still-developing brain have unique properties but little is known of how they regulate their inflammatory activation. This is important information as every year 9 million preterm born infants acquire persisting neurological injuries associated with encephalopathy and we lack strategies to prevent and treat these injuries. Our study of activation state regulators in immature brain microglia found a robust down-regulation of Wnt/β-catenin pathway receptors, ligands and intracellular signalling members in pro-inflammatory microglia. We undertook our studies initially in a mouse model of microglia-mediated encephalopathy including the clinical hallmarks of oligodendrocyte injury and hypomyelination. We purified microglia from this model and applied a genome-wide transcriptomics analysis validated with quantitative profiling. We then verified that down-regulation of the Wnt/β-catenin signalling cascade is sufficient and necessary to drive microglia into an oligodendrocyte-damaging phenotype using multiple pharmacological and genetic approaches in vitro and in vivo in mice and in humans and zebrafish. We also demonstrated that genomic variance in the WNT/β-catenin pathway is associated with the anatomical connectivity phenotype of the human preterm born infant. This integrated analysis of genomics and connectivity, as a surrogate for oligodendrocyte function/myelination, is agnostic to cell type. However, this data indicates that the WNT pathway is relevant to human brain injury and specifically that WNT variants may be useful clinically for injury stratification and prognosis. Finally, we performed a translational experiment using a BBB penetrant microglia-specific targeting 3DNA nanocarrier to deliver a Wnt agonist specifically and directly to microglia in vivo. Increasing the activity of the Wnt/β-catenin pathway specifically in microglia in our model of microglia-mediated encephalopathy was able to reduce microglial pro-inflammatory activation, prevent the typical hypomyelination and also prevent the long-term memory deficit associated with this hypomyelination. In summary, the canonical Wnt/β-catenin pathway regulates microglial activation and up-regulation of this pathway could be a viable neurotherapeutic strategy

Middle Neolithic farming of open-air sites in SE France: new insights from archaeobotanical investigations of three wells found at Les Bagnoles (L'Isle-sur-la-Sorgue, Dépt. Vaucluse, France)

Previous reviews of Middle Neolithic agricultural practice (4400–3500 cal bc) in southern France have highlighted a change in crop assemblages after 4000 cal bc, with a reduction of naked wheat and an increase of emmer and partly of einkorn. The recent investigation of three wells from the site of Les Bagnoles (4250–3800 cal bc) in the periphery of the southern Rhône valley yielded an unprecedented amount of waterlogged uncharred and charred plant macro remains that offer new insights into crop diversity and its changes over time. The results from the wells at Les Bagnoles were compared with other dated sunken features from open-air sites (in contrast to caves and rock shelters), with the aim of identifying patterns sug-gesting changes in the crop spectra between the early (MN1) and late (MN2) Middle Neolithic phases from taphonomically comparable contexts. The results from Les Bagnoles demonstrate that oil crops and pulses are underrepresented in dry sites and that they were a significant part of Middle Neolithic agriculture. They also indicate an increase in the representation of einkorn (instead of emmer) during MN2 that is also visible in other open-air sites. The comparison of the archaeobotani-cal results with silo storage capacity values as a proxy for average production capacity per household leads us to propose a possible drop in naked wheat productivity and opens new questions in factors affecting crop choice at the beginning of the 4th millennium cal bc

Enactive individuation: technics, temporality and affect in digital design and fabrication

The nature of creative engagement with computers and software presents a number of challenges to 4E cognition and requires the development of analytical frameworks that can encompass cognitive processes as they extend across material and informational realms. Here I argue that an enactive view of mind allows for better understanding of digital practice by advancing a dynamic, transactional, and affective framework for the analysis of computational design. This enactive framework is in part developed through the Material Engagement Theory (MET) put forward by Lambros Malafouris, in part from the phenomenologically inspired philosophy of Bernard Stiegler. Both advance temporality, technics and technique as key to understanding human creative imagination and their work can support each other in different ways; Stiegler allows for a theorisation of digital tools largely missing from the cognitive archaeology of Malafouris, whilst Malafouris provides a cognitive theory to further develop key ideas in Stiegler’s philosophy. Bringing their work together through Gilbert Simondon’s theory of individuation, I develop the concept of enactive individuation and apply this to the analysis of a case of robotic design and fabrication from my fieldwork with digital architects and engineers. This case allows for further exploration of how enactivism might productively be extended into the digital realm by underscoring the explorative engagement at heart of even highly systematic work with computers and software

International evidence-based recommendations on ultrasound-guided vascular access

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Effective hard x-ray spectrum of a tabletop Mather-type plasma focus optimized for flash radiography of metallic objects

The effective spectrum of the hard x-ray output of a Mather-type tabletop plasma focus device was determined from attenuation data on metallic samples using commercial radiographic film coupled to a Gd2 O2 S:Tb phosphor intensifier screen. It was found that the radiation has relevant spectral components in the 40-150 keV range, with a single maximum around 60-80 keV. The radiation output allows for 50 ns resolution, good contrast, and introspective imaging of metallic objects even through metallic walls. A numerical estimation of the induced voltage on the focus during the compressional stage is briefly discussed. © 2007 American Institute of Physics.Fil:Raspa, V. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Moreno, C. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Sigaut, L. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Membrane lipid organization and nicotinic acetylcholine receptor function : a two-way physiological relationship

Nicotinic acetylcholine receptors (nAChRs) are involved in a great range of physiological and pathological conditions. Since they are transmembrane proteins, they interact strongly with the lipids surrounding them. Thus, the plasma membrane composition and heterogeneity play an essential role for the correct nAChR function, on the one hand, and the nAChR influences its immediate lipid environment, on the other hand. The aim of this work was to investigate in more detail the role of the biophysical properties of the membrane in nAChR function and vice versa, focusing on the relationship between Chol and nAChRs. To this end, we worked with different model systems which were treated either with (i) more Chol, (ii) cholesteryl hemisuccinate, or (iii) the enzyme cholesterol oxidase to generate different membrane sterol conditions and in the absence and presence of γTM4 peptide as a representative model of the nAChR. Fluorescence measurements with crystal violet and patch-clamp recordings were used to study nAChR conformation and function, respectively. Using confocal microscopy of giant unilamellar vesicles we probed the membrane phase state/order and organization (coexistence of lipid domains) and lipid-nAChR interaction. Our results show a feedback relationship between membrane organization and nAChR function, i.e. whereas the presence of a model of nAChRs conditions membrane organization, changing its lipid microenvironment, membrane organization and composition perturb nAChRs function. We postulate that nAChRs have a gain of function in disordered membrane environments but a loss of function in ordered ones, and that Chol molecules at the outer leaflet in annular sites and at the inner leaflet in non-annular sites are related to nAChR gating and desensitization, respectively. Thus, depending on the membrane composition, organization, and/or order, the nAChR adopts different conformations and locates in distinct lipid domains and this has a direct effect on its function

Plasma focus as a powerful hard X-ray source for ultrafast imaging of moving metallic objects

Using high energy, pulsed X-rays, generated by a 4.7 kJ Plasma Focus operated with deuterium - argon admixtures, images of fast rotating metallic pieces were obtained. This illustrates the potential application of Plasma Focus devices for non invasive scanning of moving metallic objects. The samples for radiographic imaging were located outside the plasma focus chamber. High-sensitivity, fast-response commercial radiographic film was used as X-ray detector. The use of small doses of argon helps to enhance both the neutron production and the hard X-ray emission. By analyzing the mean attenuation of the studied radiation in different metals, an X-ray effective energy of about 100 keV was obtained.Fil:Raspa, V. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Sigaut, L. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Llovera, R. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Knoblauch, P. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Vieytes, R. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Moreno, C. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina