Microfluidic-SANS: flow processing of complex fluids

Understanding and engineering the flow-response of complex and non-Newtonian fluids at a molecular level is a key challenge for their practical utilisation. Here we demonstrate the coupling of microfluidics with small angle neutron scattering (SANS). Microdevices with high neutron transmission (up to 98%), low scattering background ([Image: see text]), broad solvent compatibility and high pressure tolerance (≈3–15 bar) are rapidly prototyped via frontal photo polymerisation. Scattering from single microchannels of widths down to 60 μm, with beam footprint of 500 μm diameter, was successfully obtained in the scattering vector range 0.01–0.3 Å(−1), corresponding to real space dimensions of [Image: see text]. We demonstrate our approach by investigating the molecular re-orientation and alignment underpinning the flow response of two model complex fluids, namely cetyl trimethylammonium chloride/pentanol/D(2)O and sodium lauryl sulfate/octanol/brine lamellar systems. Finally, we assess the applicability and outlook of microfluidic-SANS for high-throughput and flow processing studies, with emphasis of soft matter

Memory of the Earth and Human Memory of Natural Disasters: the 1953 Earthquake in Western Aragón (Spain)

Occurred in 1953 in Used (Zaragoza province), an earthquake of magnitude 4.7 and intensity VII was the last destructive earthquake in the Aragón region, Spain. The remaining social memory of that event (a type of intangible geological heritage) and its influence on the perception of seismic hazard in the area are explored by means of interviews and a population survey. The results indicate that the memory is lively amongst the population within the epicentral area, both in the generation that experienced it and, to a lesser extent, in the following generations. However, this does not translate into a significant perception of seismic hazard, the latter being more influenced by cultural factors: in the epicentral area it is greater amongst people who did not live through the earthquake, but who have heard familiar stories or have had external information highlighteing its importance. The study of social perception is part of a citizen science project, in which the social memory enters into dialogue with the Memory of the Earth, i.e. the record left by that and other previous earthquakes in geology and landscape. The research on the effects of the shake on people, buildings, and environment has benefited from numerous testimonies from the elderly. Reciprocally, such knowledge is scientifically processed and returned to the citizens in the form of scientific outreach products (book, documentary film, talks), with the aim of promoting scientific culture about natural disasters

In vivo analysis of the Escherichia coli ultrastructure by small-angle scattering

The flagellated Gram-negative bacterium Escherichia coli is one of the most studied microorganisms. Despite extensive studies as a model prokaryotic cell, the ultrastructure of the cell envelope at the nanometre scale has not been fully elucidated. Here, a detailed structural analysis of the bacterium using a combination of small-angle X-ray and neutron scattering (SAXS and SANS, respectively) and ultra-SAXS (USAXS) methods is presented. A multiscale structural model has been derived by incorporating well established concepts in soft-matter science such as a core-shell colloid for the cell body, a multilayer membrane for the cell wall and self-avoiding polymer chains for the flagella. The structure of the cell envelope was resolved by constraining the model by five different contrasts from SAXS, and SANS at three contrast match points and full contrast. This allowed the determination of the membrane electron-density profile and the inter-membrane distances on a quantitative scale. The combination of USAXS and SAXS covers size scales from micrometres down to nanometres, enabling the structural elucidation of cells from the overall geometry down to organelles, thereby providing a powerful method for a noninvasive investigation of the ultrastructure. This approach may be applied for probing in vivo the effect of detergents, antibiotics and antimicrobial peptides on the bacterial cell wall

Lipid Bilayers and Membrane Dynamics: Insight into Thickness Fluctuations

Thickness fluctuations have long been predicted in biological membranes but never directly observed experimentally. Here, we utilize neutron spin echo spectroscopy to experimentally reveal such fluctuations in a pure, fully saturated, phosphocholine lipid bilayer system. These fluctuations appear as an excess in the dynamics of undulation fluctuations. Like the bending rigidity, the thickness fluctuations change dramatically as the lipid transition temperature is crossed, appearing to be completely suppressed below the transition. Above the transition, the relaxation rate is on the order of 100 ns and is independent of temperature. The amplitude of the thickness fluctuations is $3.7 \AA ±0.7 \AA$, which agrees well with theoretical calculations and molecular dynamics simulations. The dependence of the fluctuations on lipid tail lengths is also investigated and determined to be minimal in the range of 14 to 18 carbon tails

Measurement of glucose exclusion from the fully hydrated DOPE inverse hexagonal phase

The degree of exclusion of glucose from the inverse hexagonal HII phase of fully hydrated DOPE is determined using contrast variation small angle neutron scattering and small angle X-ray scattering. The presence of glucose is found to favour the formation of the non-lamellar HII phase over the fluid lamellar phase, over a wide range of temperatures, while having no significant effect on the structure of the HII phase. Glucose is preferentially excluded from the lipid¿water interface resulting in a glucose concentration in the HII phase of less than half that in the coexisting aqueous phase. The degree of exclusion is quantified and the results are consistent with a hydration layer of pure water adjacent to the lipid head groups from which glucose is excluded. The osmotic gradient created by the difference in glucose concentration is determined and the influence of glucose on the phase behaviour of non-lamellar phase forming lipid systems is discussed

Experimental Search for Non-Newtonian Forces in the Nanometer Scale with Slow Neutrons

Improved limits for new gravity-like short-range interactions, in which a scattering potential is modeled by the Yukawa-type parametrization, have been obtained by measuring the angular distribution of 6 \AA\ neutrons scattering from atomic xenon gas. We have collected approximately $1.4 \times 10^8$ small-angle neutron scattering events. The data are interpreted as no evidence of new forces and show improved upper limits on the coupling strength in the interaction range of $0.3$ nm to $9$ nm. These improved constraints are also interpreted as new limits for a model, in which a charge of the new forces is expressed as a linear combination of the baryon number and the lepton number.Comment: 8 pages, 2 figures, 14TH ASIA-PACIFIC PHYSICS CONFERENCE (APPC2019

La cuenca neógena extensional de El Pobo (Teruel, Cordillera Ibérica): sedimentología, estructura y relación con la evolución del relieve

This work integrates the stratigrahical and sedimentological analysis of the Neogene sedimentary record, the extensional structure and the development of coeval planation surfaces of the El Pobo Depression (eastern Iberian Chain, Spain), which has allowed defining the new El Pobo sedimentary basin and its evolution. The Neogene El Pobo Basin is located on the footwall block of the Sierra de El Pobo fault zone, and is separated into two subbasins. Such subbasins have a double control: (i) differential erosion of soft rocks (Late Jurassic-Early Cretaceous in age) on both sides of the Ababuj anticline core, which created the initial accommodation space; (ii) tectonic structure: two N-S trending half-grabens whose eastern boundaries are extensional faults synthetic with the Sierra de El Pobo fault zone, with their respective western boundaries representing passive margins in which gently tilting Neogene beds onlap Mesozoic units. The stratigraphical and sedimentological study of the Neogene in-fill shows that the western subbasin was characterized by alluvial systems with a concentric drainage, while in the eastern subbasin a fluvial-alluvial system with northwards axial drainage prevailed. Pale-ostress systems inferred from mesostructures (faults, solution lineations in conglomerate pebbles) indicate that basin development occurred within an extensional tectonic regime. Two main planation surfaces developed at the El Pobo area: intra-Miocene Erosion Surface (SEI, topping the Sierra de El Pobo relief), and Fundamental Erosion Sun, ace (SEF, modeling the eastern El Pobo pediment and splitting into three levels). The SEF upper level correlates with the upper limit of sedimentation over most of the basin, while the SEF middle, main level developed after Neogene sediments were deposited and then tilted by a major deformation episode. Such evolutionary millstones, together with correlations of megasequential patterns with the Teruel Basin, constrain the age of the El Pobo Basin between ca. 9.0 Ma and 3.8 Ma.eo del anticlinal de Ababuj, que creó el espacio de aco- modación inicial; (ii) estructura tectónica extensional: dos semigrabens con sendas fallas N-S en los bordes orientales, y con márgenes occidentales pasivos donde el Neógeno se dispone en onlap sobre el Mesozoico. La subcuenca occidental está rellena por sistemas aluviales concéntricos, y la oriental por cajada en la Superficie de Erosión Intramiocena que corona la Sierra de El Pobo, modela el piede- monte de enlace con la depresión y se desdobla en tres niveles. El nivel superior se correlaciona con el techo de la sedimentación; el nivel intermedio se desarrolla tras concluir la sedimentación y ser bas- culados los depósitos por un episodio tectónico. Estos hitos evolutivos, junto con la evolución de pale- oesfuerzos y la correlación de patrones megasecuenciales con la Cuenca de Teruel, acotan la edad de la Cuenca de El Pobo entre 9, 0 y 3, 8 Ma

Lamellar-to-MLV transformation in SDS/octanol/brine examined by microfluidic-SANS and polarised microscopy

The lamellar-to-multilamellar vesicle (MLV) transformation in a model surfactant system, sodium dodecyl sulfate (SDS), octanol and brine, is investigated under continuous and oscillatory microfluidic contraction–expansion flows, employing polarised optical microscopy and small angle neutron scattering (SANS), with sample volume probed down to ≃20 nL. We determine the lamellar-to-MLV transition requirements at varying flow velocity, oscillation amplitude, frequency, and number of oscillatory cycles. The spatio-temporal evolution of the hierarchical fluid structure is elucidated: lamellar sheets initially align with flow direction upon entering a constriction and then perpendicularly upon exiting; the formation of MLVs at the nanoscale is first observed by SANS within a few (<5) oscillatory cycles, followed by the gradual appearance of a regular (albeit not crystalline) MLV arrangement, at the micronscale, by optical microscopy after tens of cycles, under the conditions investigated. Once MLVs form under flow, these remain metastable for several days