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Understanding strain dynamics and their relationship with crystallographic facets have been largely unexplored. Here the authors demonstrate how the 3D lattice displacement and strain evolution depend on the crystallographic facets of Pt nanoparticles during CO oxidation reaction, providing new insights in the relationship between facet-related surface strain and chemistry.

At the nanoscale, elastic strain and crystal defects largely influence the properties and functionalities of materials. Here, the authors report an unusual twin boundary migration process in a single platinum nanoparticle during carbon monoxide oxidation using Bragg coherent diffraction imaging.

The aim of this contribution is to present numerical comparisons of model-order reduction methods for geometrically nonlinear structures in the general framework of finite element (FE) procedures. Three different methods are compared: the implicit condensation and expansion (ICE), the quadratic manifold computed from modal derivatives (MD), and the direct normal form (DNF) procedure, the latter expressing the reduced dynamics in an invariant-based span of the phase space. The methods are first presented in order to underline their common points and differences, highlighting in particular that ICE and MD use reduction subspaces that are not invariant. A simple analytical example is then used in order to analyze how the different treatments of quadratic nonlinearities by the three methods can affect the predictions. Finally, three beam examples are used to emphasize the ability of the methods to handle curvature (on a curved beam), 1:1 internal resonance (on a clamped-clamped beam with two polarizations), and inertia nonlinearity (on a cantilever beam).

Abstract For the characterization of the mechanical properties of materials the precise measurements of stress‐strain curves is indispensable. In situ nano‐mechanical testing setups, however, may lack the precision either in terms of strain or stress determination. Recently, the custom‐built scanning force microscope SFINX was developed which is compatible with third‐generation synchrotron end‐stations allowing for in situ nano‐mechanical tests in combination with nanofocused synchrotron x‐ray diffraction that is highly sensitive to strain and defects. The usage of a self‐actuating and self‐sensing cantilever tremendously increases the compactness of the system but lacks deflection sensitivity and, thus the force measurement. This deficiency is resolved by in situ monitoring the diffraction peaks of the Si cantilever by Laue microdiffraction during the nano‐indentation of a gold crystal. The orientation and, hence, the deflection of the Si cantilever is deduced from the displacement of the Si Laue spots on the detector giving force accuracies of better than 90 nN. At the same time, the dislocation density in the indented Au crystal is tracked by monitoring the Au Laue spots eventually resulting in complete stress‐dislocation density curves.

Abstract We explore the use of continuous scanning during data acquisition for Bragg coherent diffraction imaging, i.e., where the sample is in continuous motion. The fidelity of continuous scanning Bragg coherent diffraction imaging is demonstrated on a single Pt nanoparticle in a flow reactor at $$400\,^\circ \hbox {C}$$ 400 ∘ C in an Ar-based gas flowed at 50 ml/min. We show a reduction of 30% in total scan time compared to conventional step-by-step scanning. The reconstructed Bragg electron density, phase, displacement and strain fields are in excellent agreement with the results obtained from conventional step-by-step scanning. Continuous scanning will allow to minimise sample instability under the beam and will become increasingly important at diffraction-limited storage ring light sources.

The microstructure of a sub-micrometric gold crystal during nanoindentation is visualized by in situ multi-wavelength Bragg coherent X-ray diffraction imaging. The gold crystal is indented using a custom-built atomic force microscope. A band of deformation attributed to a shear band oriented along the (221) lattice plane is nucleated at the lower left corner of the crystal and propagates towards the crystal center with increasing applied mechanical load. After complete unloading, an almost strain-free and defect-free crystal is left behind, demonstrating a pseudo-elastic behavior that can only be studied by in situ imaging while it is invisible to ex situ examinations. The recovery is probably associated with reversible dislocations nucleation/annihilation at the side surface of the particle and at the particle-substrate interface, a behavior that has been predicted by atomistic simulations. The full recovery of the particle upon unloading sheds new light on extraordinary mechanical properties of metal nanoparticles obtained by solid-state dewetting.

We compare different models describing the buckling, post-buckling and vibrations of elastic beams in the plane. Focus is put on the first buckled equilibrium solution and the first two vibration modes around it. In the incipient post-buckling regime, the classic Woinowsky-Krieger model is known to grasp the behavior of the system. It is based on the von Kármán approximation, a 2nd order expansion in the strains of the buckled beam. But as the curvature of the beam becomes larger, the Woinowsky-Krieger model starts to show limitations and we introduce a 3rd order model, derived from the geometrically-exact Kirchhoff model. We discuss and quantify the shortcomings of the Woinowsky-Krieger model and the contributions of the 3rd order terms in the new model, and we compare them both to the Kirchhoff model. Different ways to nondi-mensionalize the models are compared and we believe that, although this study is performed for specific boundary conditions, the present results have a general scope and can be used as abacuses to estimate the validity range of the simplified models.

The quantification and localization of elastic strains and defects in crystals are necessary to control and predict the functioning of materials. The X-ray imaging of strains has made very impressive progress in recent years. On the one hand, progress in optical elements for focusing X-rays now makes it possible to carry out X-ray diffraction mapping with a resolution in the 50–100 nm range, while lensless imaging techniques reach a typical resolution of 5–10 nm. This continuous evolution is also a consequence of the development of new two-dimensional detectors with hybrid pixels whose dynamics, reading speed and low noise level have revolutionized measurement strategies. In addition, a new accelerator ring concept (HMBA network: hybrid multi-bend achromat lattice) is allowing a very significant increase (a factor of 100) in the brilliance and coherent flux of synchrotron radiation facilities, thanks to the reduction in the horizontal size of the source. This review is intended as a progress report in a rapidly evolving field. The next ten years should allow the emergence of three-dimensional imaging methods of strains that are fast enough to follow, in situ, the evolution of a material under stress or during a transition. Handling massive amounts of data will not be the least of the challenges.

Nanolaminates are extensively studied due to their unique properties, such as impact resistance, high fracture toughness, high strength, and resistance to radiation damage. Varieties of nanolaminates are being fabricated to achieve high strength and fracture toughness. In this study, one such nanolaminate fabricated through accumulative roll bonding (Cu(16)/Nb(16) ARB nanolaminate, where 16 nm is the layer thickness) was used as a test material. Cu(16)/Nb(16) ARB nanolaminate exhibits crystallographic anisotropy due to the existence of distinct interfaces along the rolling direction (RD) and the transverse direction (TD). Nanoindentation was executed using a Berkovich tip, with the main axis oriented either along TD or RD of the Cu(16)/Nb(16) ARB nanolaminate. Subsequently, height profiles were obtained along the main axis of the Berkovich indent for both TD and RD using scanning probe microscopy (SPM), which was later used to estimate the pile-up along the RD and TD. The RD exhibited more pile-up than the TD due to the anisotropy of the Cu(16)/Nb(16) ARB interface and the material plasticity along the TD and RD. An axisymmetric 2D finite element analysis (FEA) was also performed to compare/validate nanoindentation data, such as load vs. displacement curves and pile-up. The FEA simulated load vs. displacement curves matched relatively well with the experimentally generated load–displacement curves, while qualitative agreement was found between the simulated pile-up data and the experimentally obtained pile-up data. The authors believe that pile-up characterization during indentation is of great importance to documenting anisotropy in nanolaminates.

Through the example of a project for the removal of two hydroelectric dams of 16 and 36 metres in height spanning the Sélune River, this article examines the importance of the landscape in such a project and in the discussions concerning its implementation. The removal of obstacles spanning a river leads to a major reconfiguration of river environments and landscapes. The restoration of the river ecosystems involves defining new landscapes and at the same time this process is hampered by the great variety of representations of the stakeholders and by their different profiles. The aim is to see how the variety of views regarding the landscape can be crucial in addressing resistance to the ecological restoration of watercourses. This article is based on a confrontation of the representations of landscapes by residents and users in a survey, administered as part of a participant observation process, which involved qualitative interviews, implicit proposals made by the people promoting the levelling of the dams, and the concrete landscape project proposals made by design offices. The comparison of the landscape projects presented by the experts and the expectations expressed by the inhabitants pleads in favour of finding ways of more effectively taking the landscape into account. Since dismantling such structures results in the generation of new landscapes and raises the question of choices for the development of the dewatered areas, it seems necessary to take into consideration the expectations of local populations.

The simultaneous measurement of two Bragg reflections by Bragg coherent X-ray diffraction is demonstrated on a twinned Au crystal, which was prepared by the solid-state dewetting of a 30 nm thin gold film on a sapphire substrate. The crystal was oriented on a goniometer so that two lattice planes fulfill the Bragg condition at the same time. The Au 111 and Au 200 Bragg peaks were measured simultaneously by scanning the energy of the incident X-ray beam and recording the diffraction patterns with two two-dimensional detectors. While the former Bragg reflection is not sensitive to the twin boundary, which is oriented parallel to the crystal–substrate interface, the latter reflection is only sensitive to one part of the crystal. The volume ratio between the two parts of the twinned crystal is about 1:9, which is also confirmed by Laue microdiffraction of the same crystal. The parallel measurement of multiple Bragg reflections is essential for future in situ and operando studies, which are so far limited to either a single Bragg reflection or several in series, to facilitate the precise monitoring of both the strain field and defects during the application of external stimuli.

The piezoelectric properties of lanthanum-modified lead zirconate titanate Pb1−xLax(Zr0.52Ti0.48)1−x/4O3 thin films, with x = 0, 3 and 12 mol% La, were studied by in situ synchrotron X-ray diffraction under direct (DC) and alternating (AC) electric fields, with AC frequencies covering more than four orders of magnitude. The Bragg reflections for thin films with low lanthanum concentration exhibit a double-peak structure, indicating two contributions, whereas thin films with 12% La possess a well-defined Bragg peak with a single component. In addition, built-in electric fields are revealed for low La concentrations, while they are absent for thin films with 12% of La. For static and low frequency AC electric fields, all lanthanum-modified lead zirconate titanate thin films exhibit butterfly loops, whereas linear piezoelectric behavior is found for AC frequencies larger than 1 Hz.

We describe the impact of tensile strains on the structural properties of thin films composed of PffBT4T-2OD π-conjugated polymer and PC71BM fullerenes coated on a stretchable substrate, based on a novel approach using in situ studies of flexible organic thin films. In situ grazing incidence X-ray diffraction (GIXD) measurements were carried out to probe the ordering of polymers and to measure the strain of the polymer chains under uniaxial tensile tests. A maximum 10% tensile stretching was applied (i.e., beyond the relaxation threshold). Interestingly we found different behaviors upon stretching the polymer: fullerene blends with the modified polymer; fullerene blends with the 1,8-Diiodooctane (DIO) additive. Overall, the strain in the system was almost twice as low in the presence of additive. The inclusion of additive was found to help in stabilizing the system and, in particular, the π–π packing of the donor polymer chains.

Phase change materials are attractive materials for non-volatile memories because of their ability to switch reversibly between an amorphous and a crystal phase. The volume change upon crystallization induces mechanical stress that needs to be understood and controlled. In this work, we monitor stress evolution during crystallization in thin GeTe films capped with SiOx, using optical curvature measurements. A 150 MPa tensile stress buildup is measured when the 100 nm thick film crystallizes. Stress evolution is a result of viscosity increase with time and a tentative model is proposed that renders qualitatively the observed features.

Increasing nonlinearity in today’s grid challenges the conventional small-signal (modal) analysis (SSA) tools. For instance, the interactions among modes, which are not captured by SSA, may play significant roles in a stressed power system. Consequently, alternative nonlinear modal analysis tools, notably Normal Form (NF) and Modal Series (MS) methods are being explored. However, they are computation-intensive due to numerous polynomial coefficients required. This paper proposes a fast NF technique for power system modal interaction investigation, which uses characteristics of system modes to carefully select relevant terms to be considered in the analysis. The Coefficients related to these terms are selectively computed and the resulting approximate model is computationally reduced compared to the one in which all the coefficients are computed. This leads to a very rapid nonlinear modal analysis of the power systems. The reduced model is used to study interactions of modes in a two-area power system where the tested scenarios give same results as the full model, with about 70% reduction in computation time.

The three-point bending behavior of a single Au nanowire deformed by an atomic force microscope was monitored by coherent X-ray diffraction using a sub-micrometer sized hard X-ray beam. Three-dimensional reciprocal-space maps were recorded before and after deformation by standard rocking curves and were measured by scanning the energy of the incident X-ray beam during deformation at different loading stages. The mechanical behavior of the nanowire was visualized in reciprocal space and a complex deformation mechanism is described. In addition to the expected bending of the nanowire, torsion was detected. Bending and torsion angles were quantified from the high-resolution diffraction data.

Cyanobacteria are ubiquitous microorganisms considered as important contributors to the formation of Earth's atmosphere and nitrogen fixation. However, they are also frequently associated with toxic blooms. Indeed, the wide range of hepatotoxins, neurotoxins and dermatotoxins synthesized by these bacteria is a growing environmental and public health concern. This paper provides a state of the art on the occurrence and management of harmful cyanobacterial blooms in surface and drinking water, including economic impacts and research needs. Cyanobacterial blooms usually occur according to a combination of environmental factors e.g., nutrient concentration, water temperature, light intensity, salinity, water movement, stagnation and residence time, as well as several other variables. These environmental variables, in turn, have promoted the evolution and biosynthesis of strain-specific, gene-controlled metabolites (cyanotoxins) that are often harmful to aquatic and terrestrial life, including humans. Cyanotoxins are primarily produced intracellularly during the exponential growth phase. Release of toxins into water can occur during cell death or senescence but can also be due to evolutionary-derived or environmentally-mediated circumstances such as allelopathy or relatively sudden nutrient limitation. Consequently, when cyanobacterial blooms occur in drinking water resources, treatment has to remove both cyanobacteria (avoiding cell lysis and subsequent toxin release) and aqueous cyanotoxins previously released. Cells are usually removed with limited lysis by physical processes such as clarification or membrane filtration. However, aqueous toxins are usually removed by both physical retention, through adsorption on activated carbon or reverse osmosis, and chemical oxidation, through ozonation or chlorination. While the efficient oxidation of the more common cyanotoxins (microcystin, cylindrospermopsin, anatoxin and saxitoxin) has been extensively reported, the chemical and toxicological characterization of their by-products requires further investigation. In addition, future research should also investigate the removal of poorly considered cyanotoxins (β-methylamino-alanine, lyngbyatoxin or aplysiatoxin) as well as the economic impact of blooms. Keywords: Drinking water treatment, Microcystin, Anatoxin, Cylindrospermopsin, Saxitoxin, BMAA

INTRODUCTION Crambescins and crambescidins are guanidine alkaloids first reported in the early 90s. They are produced by the red encrusting marine sponge Crambe crambe widely distributed in the Western Mediterranean Sea but also in the Macaronesian archipelagos (Berlinck et al., 1990;Berlinck et al., 1993). There are few studies about the biological activity of these compounds and their pharmaceutical potential, mainly due to difficulties to obtain large quantities of pure compounds (Jares-Erijman et al., 1993). An antagonistic activity of crambescidin 816 (Cramb816) on voltage-sensitive calcium channels, higher than the one elicited by the selective blocker of L-type Ca+2 channels, nifedipine (NIF) has been reported (Berlinck et al., 1993). Moreover, several representative compounds of the crambescin family (norcrambescinA2, crambescinC1 and crambescinA2) partially blocked voltage gated potassium channels and Crambescin C1 (CrambC1) and Cramb816 partially blocked voltage gated Na+ channels (Martin et al., 2013). Furthermore, we pharmacologically isolated the two main fractions of neuronal high voltage activated (HVA) Ca+2 channels in cortical neurons and described that Cav1 or L-type calcium channels are the main target for Cramb816 in cortical neurons (Martin et al., 2013). In the present study, the effect of Cramb816 and CrambC on neuronal viability as well as the effect of Cramb816 in cytosolic calcium concentration was evaluated in order to get an approach of the possible mechanism by which Cramb816 is cytotoxic in cortical neurons. MATERIAL AND METHODS Primary cultures of cortical neurons. Primary cortical neurons were prepared from Swiss mice embryos (E15-18) as previously described (Martin et al., 2013). The cell suspension was seeded in 18 mm glass coverslips precoated with poly-D-lysine and incubated in 12 multiwell plates for 4-7 days in vitro in a humidified 5 % CO2/95 % air atmosphere at 37 ºC. Determination of cellular viability. Cell viability was assessed by the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5- diphenyltetrazolium bromide) test, in cultures grown in 96 well plates and exposed to different concentrations of C816 or CrambC1 for 24 h. Saponin was used as cellular death control. After the exposure time, cells were rinsed and incubated for 60 min with a solution of MTT dissolved in Locke’s buffer. After washing off excess MTT, cells were disaggregated with 5% SDS and the absorbance of the colored formazan salt was measured at 595 nM in a spectrophotometer plate reader. Measurement of cytosolic free Ca+2. Cell cultures of 7 days seeded onto 18-mm glass coverslips were washed twice with cold Locke’s buffer. Cells were loaded with the calcium sensitive dye Fura-2 AM (0.5 μM) for 8 min at 37ºC in Locke’s buffer containing 0.1% bovine serum albumin (BSA). After incubation, the loaded cells were washed three times with cold Locke’s buffer. The glass coverslips were inserted into a thermostated chamber at 37ºC and cells were viewed with a Nikon Diaphot 200 microscope, equipped with epifluorescence optics. The excitation wavelengths for Fura-2 AM were 340 and 380 nm, and emission was collected at 505 nm. The experiments were performed in triplicate. Toxins and drugs used. Cramb816 and CrambC were extracted and isolated from the Mediterranean sponge Crambe crambe (Bondu et al., 2012). Nifedipine (NIF) and D(-)-2-amino-5-phosphonopentanoic acid (APV) were purchased from Sigma- Aldrich and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) was from Tocris. The final concentration of NIF, Cramb816 and CrambC solvent (DMSO), was less than 0.01%. APV and CNQX were solved in H2O. Statistical Analysis. All data are expressed as means ± SEM of n determinations. Statistical comparison was by paired Student’s t test. P-values

In the last decades, nature has played a significant role as source of new drugs and recent trends in medicines research emphasize that marine environment has a high potential for discovery of new pharmaceutical compounds. Harsh chemical and physical conditions in the marine environment provide a production of quite specific and potent active molecules. The aim of this study was to evaluate the antitumor activity of isolated fractions obtained from seaweed Fucus spiralis on three human tumor cell lines (HepG-2; MCF-7; SH-SY5Y). In this study, five fractions obtained by Vacuum Liquid Chromatography (VLC) from Fucus spiralis methanolic extracts were tested on HepG-2, MCF-7 and SH-SY5Y cells through cytotoxicity and anti-proliferative assays. The results were obtained the according MTT method. The highest cytotoxicity was exhibited by F3 fraction on HepG-2 cells and by F1 and F5 fractions on SH-SY5Y cells, reduced the cells viability (1 mg/ml; 24 hours) in 83%, 97% and 91%, respectively. The smallest IC50 was exhibited by F1 fraction on SH-SY5Y with 308.0µg/ml. In cell proliferation assays, F1, F3, F4 and F5 fractions showed anti-proliferative activity on all cell lines tested. (1 mg/ml; 24 hours). However, the effects were more marked on HepG-2 and SH-SY5Y cells. The smallest IC50 was exhibited on SH-SY5Y cells by F1 and F3 fraction with an IC50 of 153.2 and 136.4µg/ml, respectively. In conclusion, Fucus spiralis is a promising source of new molecules with therapeutically applications in cancer.

BACKGROUND: We aimed to assess, for the first time, the nature of the indoor air contamination of hospitals. METHODS AND FINDINGS: More than 40 volatile organic compounds (VOCs) including aliphatic, aromatic and halogenated hydrocarbons, aldehydes, alcohols, ketones, ethers and terpenes were measured in a teaching hospital in France, from sampling in six sampling sites--reception hall, patient room, nursing care, post-anesthesia care unit, parasitology-mycology laboratory and flexible endoscope disinfection unit--in the morning and in the afternoon, during three consecutive days. Our results showed that the main compounds found in indoor air were alcohols (arithmetic means ± SD: 928±958 µg/m³ and 47.9±52.2 µg/m³ for ethanol and isopropanol, respectively), ethers (75.6±157 µg/m³ for ether) and ketones (22.6±20.6 µg/m³ for acetone). Concentrations levels of aromatic and halogenated hydrocarbons, ketones, aldehydes and limonene were widely variable between sampling sites, due to building age and type of products used according to health activities conducted in each site. A high temporal variability was observed in concentrations of alcohols, probably due to the intensive use of alcohol-based hand rubs in all sites. Qualitative analysis of air samples led to the identification of other compounds, including siloxanes (hexamethyldisiloxane, octamethyltrisiloxane, decamethylcyclopentasiloxane), anesthetic gases (sevoflurane, desflurane), aliphatic hydrocarbons (butane), esters (ethylacetate), terpenes (camphor, α-bisabolol), aldehydes (benzaldehyde) and organic acids (benzoic acid) depending on sites. CONCLUSION: For all compounds, concentrations measured were lower than concentrations known to be harmful in humans. However, results showed that indoor air of sampling locations contains a complex mixture of VOCs. Further multicenter studies are required to compare these results. A full understanding of the exposure of healthcare workers and patients to complex mixtures of chemical compounds can then be related to potential health outcomes.

R-lineage mitochondrial DNA represents over 90% of the European population and is significantly present all around the planet (North Africa, Asia, Oceania, and America). This lineage played a major role in migration "out of Africa" and colonization in Europe. In order to determine an accurate dating of the R lineage and its sublineages, we analyzed 1173 individuals and complete mtDNA sequences from Mitomap. This analysis revealed a new coalescence age for R at 54.500 years, as well as several limitations of standard dating methods, likely to lead to false interpretations. These findings highlight the association of a striking under-accumulation of synonymous mutations, an over-accumulation of non-synonymous mutations, and the phenotypic effect on haplogroup J. Consequently, haplogroup J is apparently not a Neolithic group but an older haplogroup (Paleolithic) that was subjected to an underestimated selective force. These findings also indicated an under-accumulation of synonymous and non-synonymous mutations localized on coding and non-coding (HVS1) sequences for haplogroup R0, which contains the major haplogroups H and V. These new dates are likely to impact the present colonization model for Europe and confirm the late glacial resettlement scenario.

Quelque part, dans le centre d’une ville française. Dans cette rue piétonne, le badaud (entendu ici, sans connotation péjorative et selon le Petit Robert, comme une « personne qui s’attarde à regarder le spectacle de la rue ») peut remarquer, sur le rebord d’une vitrine de pharmacie, un curieux dispositif… Il s’agit de plaques métalliques soudées entre elles qui forment une sorte de triangle à sommet aigu. L’ensemble est vissé dans la pierre, ce qui inscrit le ...

Abstract Background Dendritic cells (DCs) are antigen presenting cells capable of inducing innate and adaptive immune responses. According to the stimulus and their maturation state, DCs induce immunogenic or tolerogenic responses. Platelets (PLTs), which are involved in haemostasis and inflammation, can also interact with DCs. In this study, we examined the effect of PLTs on DC maturation in vitro. Human monocyte-derived DCs were co-cultured for 2 days with homologous PLTs either in the same well or in 0.4 μm-pore size filter-separated compartments. Results Confocal microscopy showed the attachment of PLTs to DC membranes. The DC receptor involved in this interactions was found to be CD162. In addition, we observed that DCs co-cultured with PLTs in filter-separated compartments acquired a mature phenotype (high CD80, CD86, and intermediate CD83 expression; IL-12(p70) production; efficient stimulation of autologous CD4+ T cell proliferation), while DCs co-cultured with PLTs in the same compartment did not undergo phenotypic maturation, did not secrete IL-12(p70) or IL-1β, but instead induced moderate Th2-polarized T cell proliferation. Conclusion These data indicate that (i) PLTs secrete a soluble DC-activating factor that was demonstrated not to be soluble CD40-Ligand (CD154; as could have been expected from in vivo and previous in vitro work) but to be nucleotide, and (ii) that cell-to-cell contact did not induce DC maturation, possibly because nucleotide release by PLTs was prevented by direct contact with DCs. This work demonstrates that PLTs are active elements of the immune system that might play a role in balancing the ability of DCs to polarize T cell responses, therefore making them critical factors in transfusion processes.

En el ámbito de una cada vez más acelerada integración entre México y los Estados Unidos propiciada por el Tratado de LibreComercio, el papel de la frontera entre ambos países como catalizador de un desarrollo económico más amplio ha emergido como una preocupación central para ambos gobiernos. Sin embargo, como sugiere este ensayo, los contextos socioculturales e intelectuales para el desarrollo transfronterizo se caracterizan por enfoques distintos de las posibilidades políticas inherentes a una auténtica integración transfronteriza. El autor intenta explicar las razones de esta discrepancia, buscando en discursos que encuentran sus raíces en tradiciones divergentes de modernidad, modernismo y modernización, haciendo hincapié en la negociación intelectual latinoamericana de la condición posmoderna. En lugar de concebir la frontera entre Estados Unidos y México como espacio posmoderno de apertura radical o defender su rol como baluarte inviolable contra la disolución de proyectos heroicos dirigidos hacia la construcción del Estado-nacion, el ensayo abarca ambos discursos desde el punto de vista de un espacio intermedio y todavía frágil, además de indicar posibles vínculos (y solidaridades) con otras modernidades incompletas que perviven de manera marginal en Occidente.

The implementation of actions in favour of the conservation or of the restoration of the biodiversity often leans on the highlit of symbolic species attached to a biotope regularly presented as a heritage. Concerning the water environment, and quite particularly as regards the assertion of the principles of ecological management mobilizing the restoration of the ecological continuity of streams, the Atlantic salmon is one of the main migratory amphihalins fishes used to make sensitive the decision-makers, the financiers and the general public. In this article, the objective is to wonder about the place of this « not human » actor in the construction of programs with ecological aim such as the removal of dams. The analysis joins two scales : that of the national and European strategies intended to restore the stocks of salmons, and that of a local project of dismantling of dams in the valley of Selune (Manche). By this way, the objective is to put in mirror the ecological challenge of preservation of the species with the local reality of a project of new arrangement of a stream in a territory. In fine, this article demonstrates that the instrumentalization of the salmon can turn out to be a wrong path for the species but also for the deployment of the water-related environmental policies.