Selection of endurance capabilities and the trade-off between pressure and volume in the evolution of the human heart

Chimpanzees and gorillas, when not inactive, engage primarily in short bursts of resistance physical activity (RPA), such as climbing and fighting, that creates pressure stress on the cardiovascular system. In contrast, to initially hunt and gather and later to farm, it is thought that preindustrial human survival was dependent on lifelong moderate-intensity endurance physical activity (EPA), which creates a cardiovascular volume stress. Although derived musculoskeletal and thermoregulatory adaptations for EPA in humans have been documented, it is unknown if selection acted similarly on the heart. To test this hypothesis, we compared left ventricular (LV) structure and function across semiwild sanctuary chimpanzees, gorillas, and a sample of humans exposed to markedly different physical activity patterns. We show the human LV possesses derived features that help augment cardiac output (CO) thereby enabling EPA. However, the human LV also demonstrates phenotypic plasticity and, hence, variability, across a wide range of habitual physical activity. We show that the human LV’s propensity to remodel differentially in response to chronic pressure or volume stimuli associated with intense RPA and EPA as well as physical inactivity represents an evolutionary trade-off with potential implications for contemporary cardiovascular health. Specifically, the human LV trades off pressure adaptations for volume capabilities and converges on a chimpanzee-like phenotype in response to physical inactivity or sustained pressure loading. Consequently, the derived LV and lifelong low blood pressure (BP) appear to be partly sustained by regular moderate-intensity EPA whose decline in postindustrial societies likely contributes to the modern epidemic of hypertensive heart disease

3D Visualization of the Iron Oxidation State in FeO/Fe3O4 Core-Shell Nanocubes from Electron Energy Loss Tomography

The physicochemical properties used in numerous advanced nanostructured devices are directly controlled by the oxidation states of their constituents. In this work we combine electron energy-loss spectroscopy, blind source separation, and computed tomography to reconstruct in three dimensions the distribution of Fe and Fe ions in a FeO/FeO core/shell cube-shaped nanoparticle with nanometric resolution. The results highlight the sharpness of the interface between both oxides and provide an average shell thickness, core volume, and average cube edge length measurements in agreement with the magnetic characterization of the sample

Spatial variation in scent emission within flowers

Floral scent is considered an important long-distance signal that attracts pollinators, but also has been suggested to function at shorter distances such as within-flower nectar guides or as a defense against antagonists. Indeed, in some species floral scent production and emission show spatial patterns of variation within flowers, as certain compounds are exclusively emitted from specific floral tissues. In other species, the different volatile organic compounds that constitute the floral bouquet are emitted evenly from the entire flower. Here, we summarize the current evidence on floral scent variation within flowers by combining a literature review of published data on tissue-level floral scent variation (41 species) with floral scent dissections (17 species). For each species, we recorded the total number of volatile compounds separately and grouped in major chemical classes. To facilitate comparisons across diverse species, we compared volatiles emitted by 1) the whole flower, 2) the visual floral tissues (i.e. petals and colored structures), 3) non-visual floral tissues (i.e. green parts and reproductive structures), as well as 4) the compounds emitted by both visual and non-visual tissues. Results show that floral scent variation is frequent, but by no means ubiquitous, occurring in species from distantly related groups. We discuss the two main functional hypotheses promoting floral scent variation within flowers, i.e. as a pollinator attractant at short-distances or a defensive function against antagonists, together with non-functional hypotheses (e.g. pleiotropic effects, ecological costs). We point out further directions on this topic and suggest experimental approaches testing the attractiveness of compounds emitted by different floral parts alone and in combination with other floral signals. Our synthesis provides a foundation for future studies on the functional ecology of floral scent and reinforces the idea of high complexity in floral chemical signals

Selective oxidation of Fe-Mn (1wt%) binary alloy during continuous annealing

International audienceThe study presented here focuses on the selective oxidation of Fe-Mn (1 wt.%) binary alloy.The samples were annealed by means of a laboratory furnace with a temperature profile relevant to the galvanizing line practice. The sample was first heated to 800°C at a rate of approximately 6°Cs-1. It was kept at that temperature for 60 s before being cooled to room temperature. The gas atmosphere consists in a mixture of N2 – 5 vol.% H2 with a dew point of -40°C. To obtain information on the nucleation and growth of oxide particles, we interrupted annealing at 700°C during the heating phase. Some specimens were held at 800°C during 0, 60, 120 and 300 seconds. The rapid cooling of the samples, that occurs when the annealing furnace is stopped, is considered to act like a quench for selective oxidation reactions.During annealing, the native iron oxides are reduced and the manganese diffuses to the surface where it is preferentially oxidized and forms MnO oxide particles. These selective oxide particles were characterized using several complementary analysis techniques. The surface of the samples was observed in a Field Emission Gun Scanning Electron Microscope (FEG-SEM) to obtain high resolution images and analyzed by Electron Back-Scattered Diffraction (EBSD). Image analysis was used to measure the geometric parameters that characterize oxide particles in two dimensions. Thin cross-sections were extracted from the oxidized samples using a Focused Ion Beam Microscope (FIB) and characterized in a Transmission Electron Microscope (TEM).We studied the oxide particles present on three ferrite grain orientations: Fe(100), Fe(110) and Fe(111) as a function of annealing time. It has been demonstrated that, on our model material, MnO particles are monocrystalline. Their shape, size, nucleation and growth depend on the ferrite grain orientation where they are formed. Elementary mechanisms of the oxidation reaction are proposed and discussed to explain this behavior

In situ TEM Characterization of Phase Transformations and Kirkendall Void Formation During Annealing of a Cu–Au–Sn–Cu Diffusion Bonding Joint

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Development of new multifunctional coatings: transparent, with superhydrophobicity properties and wear resistance

In the last decade, superhydrophobicity (SH) phenomenon has aroused a great interest. This fact has been motivated by large and important functionalities that can be achieved by these SH surfaces: self-cleaning solutions, water repellancy, anticorrosive, anti-stain, anti-icing, antifouling, among others. SH is defined by the low surface energy of the material as well as the morphology of the own surface. However, due to the fact that hydrophobicity is a superficial property, its main disadvantage is its limited wear resistance, which causes a low durability and a limited comercial use. This fact, together with the complexity and low effectiveness, from the economic point of view compared with the existing coatings fabrication techniques, makes necessary the research of new alternatives for the demanding market, being a technological challenge to find them. Moreover, organic coatings are widely used in industry in a number of surfaces due to the ease and low cost of application methods. Concretely, nanocomposites fabrication from organic polymers using nanoparticles as additives, has been creating  high expectatives in the coatings industry sector. In this work, new organic coatings based on the integration of surface modified nanoparticles with hydrophobic moieties have been developed, in order to achieve hidrophobicity in organic polymeric matrices (paints). Likewise, different nanoparticles have been used in order to achieve synergistic effects that could provide a determined superficial rugosity and then, reaching simultaneously transparent, hydrophobic and abrasion wear resistant coatings

A synchrotron transmission X-ray microscopy study on precipitate evolution during solid-state thermal cycling of a stainless steel

International audienceDuring additive manufacturing of stainless steels, sub-micron sized oxide (i.e., MnSiO3 , SiO2 , and CrMn2O4) and non-oxide (i.e., sulfide, in particular MnS, and possibly carbides, phosphides and nitrides) precipitates form during solidification. But do they evolve during the subsequent solid-state thermal cycling (SSTC) until the end of the printing process? A recent study on subjecting thin-film lamellae extracted from an additively manufactured stainless steel to heating-cooling treatments inside a transmission electron microscope (TEM) confirmed that precipitate composition can indeed evolve during SSTC. However, that study could not provide any conclusive evidence on precipitate volume fraction, density, and size evolution. In this work, we have quantified these changes using a novel experimental procedure combining (i) micropillar extraction from an additively manufactured stainless steel, (ii) subjecting them to different SSTC (including annealing) inside a TEM, (iii) performing synchrotron transmission X-ray microscopy to identify precipitates, and (iv) using a machine learning model to segment precipitates and quantify precipitate volume fraction, density, and size. Comparing these quantities before and after each SSTC/annealing sequence reveals that new oxides nucleated during rapid SSTC with high maximum temperature. However, during slow SSTC with high maximum temperature and annealing, precipitates dissolve because of oxygen evaporation during SSTC inside the TEM. A new empirical relationship correlating precipitate sizes and cooling rates is proposed. It is in good agreement with data collected from conventional casting, directed energy deposition, and powder bed fusion processes