Density control of electrodeposited Ni nanoparticles/nanowires inside porous anodic alumina templates by an exponential anodization voltage decrease

International audiencePorous alumina templates have been fabricated by applying an exponential voltage decrease at the end of the anodization process. The time constant η of the exponential voltage function has been used to control the average thickness and the thickness distribution of the barrier layer at the bottom of the pores of the alumina structure. Depending on the η value, the thickness distribution of the barrier layer can be made very uniform or highly scattered, which allows us to subsequently fine tune the electrodeposition yield of nickel nanoparticles/nanowires at low voltage. As an illustration, the pore filling percentage with Ni has been varied, in a totallyreproducible manner, between ∼3 and 100%. Combined with the ability to vary the porediameter and repetition step over ∼2 orders of magnitude (by varying the anodization voltageand electrolyte type), the control of the pore filling percentage with metal particles/nanowires could bring novel approaches for the organization of nano-objects

What is poststructuralism?

In this essay, I discuss the vitality and the limits of the poststructural archive. I argue against the temptation to essentialise poststructuralism or define its ‘ontology’, instead I present some of the avenues that can be taken to further its theoretical practice. With Trump and the rise of ‘post-truth’ politics, poststructural political thought has recently come back to the centre of political debate. By using Pierre Macherey and François Châtelet’s perspective on Marxism, I turn to contemporary problems and studies to imagine how to renew the poststructuralist experience of thought. Following Boris Groys, I suggest that by producing theory as form, artists had a more immediate recourse to theoretical practice, by using all sorts of media to perform knowledge. Finally, by mainly referring to the work of Gilles Deleuze and Michel Foucault, I present some elements of a poststructural critique of political economy. I do this not by forcing the application of poststructural theories or concepts onto a supposedly external reality, but by immanently integrating more and more social and political problems into the schemes of thought. A poststructural theoretical practice means integrating into thought problems and events, in order to compose with them, and not simply study discursive strategies.<br/

Meningitis Dipstick Rapid Test: Evaluating Diagnostic Performance during an Urban Neisseria meningitidis Serogroup A Outbreak, Burkina Faso, 2007

Meningococcal meningitis outbreaks occur every year during the dry season in the “meningitis belt” of sub-Saharan Africa. Identification of the causative strain is crucial before launching mass vaccination campaigns, to assure use of the correct vaccine. Rapid agglutination (latex) tests are most commonly available in district-level laboratories at the beginning of the epidemic season; limitations include a short shelf-life and the need for refrigeration and good technical skills. Recently, a new dipstick rapid diagnostic test (RDT) was developed to identify and differentiate disease caused by meningococcal serogroups A, W135, C and Y. We evaluated the diagnostic performance of this dipstick RDT during an urban outbreak of meningitis caused by N. meningitidis serogroup A in Ouagadougou, Burkina Faso; first against an in-country reference standard of culture and/or multiplex PCR; and second against culture and/or a highly sensitive nested PCR technique performed in Oslo, Norway. We included 267 patients with suspected acute bacterial meningitis. Using the in-country reference standard, 50 samples (19%) were positive. Dipstick RDT sensitivity (N = 265) was 70% (95%CI 55–82) and specificity 97% (95%CI 93–99). Using culture and/or nested PCR, 126/259 (49%) samples were positive; dipstick RDT sensitivity (N = 257) was 32% (95%CI 24–41), and specificity was 99% (95%CI 95–100). We found dipstick RDT sensitivity lower than values reported from (i) assessments under ideal laboratory conditions (>90%), and (ii) a prior field evaluation in Niger [89% (95%CI 80–95)]. Specificity, however, was similar to (i), and higher than (ii) [62% (95%CI 48–75)]. At this stage in development, therefore, other tests (e.g., latex) might be preferred for use in peripheral health centres. We highlight the value of field evaluations for new diagnostic tests, and note relatively low sensitivity of a reference standard using multiplex vs. nested PCR. Although the former is the current standard for bacterial meningitis surveillance in the meningitis belt, nested PCR performed in a certified laboratory should be used as an absolute reference when evaluating new diagnostic tests

Characteristics and conditions of production of transient luminous events observed over a maritime storm

International audienceOn the night of 15/16 November 2007, cameras in southern France detected 30 transient luminous events (TLEs) over a storm located in the Corsican region (France). Among these TLEs, 19 were sprites, 6 were halos, and 5 were elves. For 26 of them, a positive “parent” cloud‐to‐ground lightning (P+CG) flash was identified. The peak current of the P+CG flashes for the sprites had an average value of 63 kA and had a maximum value of 125 kA. The flashes for the halos and the elves had average values of 272 and 351 kA, respectively, and they had maximum values of 312 and 384 kA, respectively. No TLEs were detected after negative CG flashes with very large peak currents. Among the 26 P+CG flashes, 23 were located in a stratiform region with reflectivity values lower than 45 dBZ. The CG flashes in this region were classified into two groups according to the time interval separating them from the following flash: one group with values less than 2 s and one with values greater than 2 s. About 79% of all CGs were produced in a sequence of at least two flashes less than 2 s apart. For 65.5% of the sequences, the first flash was positive with an average peak current of 73 kA, while the later +CG flashes in a sequence had much lower peak currents. Several triangulated sprites were found to be shifted from their P+CG flashes by about 10 to 50 km and preferentially downstream. The observations suggest that the P+CG flashes can initiate both sprites and other CG flashes in a storm

Toward an Anthropology of Mathematizing

This essay investigates the practical ways that artists and craftspeople cultivate mathematical sensibilities through their practical immersion in making and problem-solving. Mathematical sensibilities refer to skilled kinds of perception and heightened levels of attention and discernment regarding the qualitative properties of an object or composition, such as its shape, proportion, balance, symmetry, centredness, alignment or levelness. It also includes an ‘intuitive’ quantitative sense of volume, mass, weight, thickness and dimension. The objective of the investigation is not to describe the ways that a maker’s existing knowledge and training in formal mathematics is put into practice, but rather to elucidate the ways that their practices of making produce kinds of ‘non-formalised’, context-dependent mathematical understanding and knowledge. The starting point for exploring embodied mathematizing is therefore not from the cognitive or neurosciences, psychology or formal mathematics, it is argued, but rather from a phenomenological approach – ‘an opening on the world’ – that attends to person, materials, tools and other physical and qualitative features that make up the total environment in which activity unfolds

Kant’s epigenesis: specificity and developmental constraints

In this paper, I argue that Kant adopted, throughout his career, a position that is much more akin to classical accounts of epigenesis, although he does reject the more radical forms of epigenesis proposed in his own time, and does make use of preformationist sounding terms. I argue that this is because Kant (1) thinks of what is pre-formed as a species, not an individual or a part of an individual; (2) has no qualm with the idea of a specific, teleological principle or force underlying generation, and conceives of germs and predispositions as specific constraints on such a principle or force. Neither of these conceptions of what is “preformed”, I argue, is in strict opposition to classical epigenesis. I further suggest that Kant’s lingering use of preformationist terminology is due to (1) his belief that this is required to account for the specificity of the specific generative force; (2) his resistance towards the unrestricted plasticity of the generative force in radical epigenesis, which violates species-fixism; and (3) his insistence on the internal, organic basis of developmental plasticity and variation within species. I conclude by suggesting that this terminological and interpretative peculiarity is partly due to a larger shift in the natural philosophical concerns surrounding the debate on epigenesis and preformation. Specifically, it is a sign that the original reasons for resisting epigenesis, namely its use of specific, teleological principles and its commitment to the natural production of biological structure, became less of a concern, whereas unrestricted plasticity and its undermining of fixism became a real issue, thereby also becoming the focal point of the debate

Is the meiofauna a good indicator for climate change and anthropogenic impacts?

Our planet is changing, and one of the most pressing challenges facing the scientific community revolves around understanding how ecological communities respond to global changes. From coastal to deep-sea ecosystems, ecologists are exploring new areas of research to find model organisms that help predict the future of life on our planet. Among the different categories of organisms, meiofauna offer several advantages for the study of marine benthic ecosystems. This paper reviews the advances in the study of meiofauna with regard to climate change and anthropogenic impacts. Four taxonomic groups are valuable for predicting global changes: foraminifers (especially calcareous forms), nematodes, copepods and ostracods. Environmental variables are fundamental in the interpretation of meiofaunal patterns and multistressor experiments are more informative than single stressor ones, revealing complex ecological and biological interactions. Global change has a general negative effect on meiofauna, with important consequences on benthic food webs. However, some meiofaunal species can be favoured by the extreme conditions induced by global change, as they can exhibit remarkable physiological adaptations. This review highlights the need to incorporate studies on taxonomy, genetics and function of meiofaunal taxa into global change impact research

Odorous childhoods and scent(ed) worlds of learning: A sensory history of health and outdoor education initiatives in Western Europe (1900s-1960s)

This paper develops a sensory history of health and outdoor education initiatives which featured (non-)formal schooling, analyzing these as belonging to (a) scent(ed) and more generally sense(d) world(s) of learning. Working with photographs as sensory objects of affect, and using as examples Belgian and Luxembourg open-air schools and associated sanitary and social welfare provisions, the paper explores issues so far under-researched in sensuous scholarship internationally: those of precise educational purposes, methods, processes and effects of sensory engagement, particularly pertaining to “smell”. Sensory practices and experiences and uses of senses generally are thereby traced in/as “situated, embodied” movements inextricably “enmeshed” with symbolism. The paper argues that while the educational goals underpinning the initiatives investigated and the approaches and practices characterizing these have changed, some (un)intended effects still have an impact today, for instance through Forest School as given shape in the United Kingdom. The concept of “odorous”, or rather “sensuous childhoods”, is proposed to denote ways that particular target groups have come to be imagined as in need of explicitly sensorial health and outdoor education