Large Sheets Research Articles

Graben type calderas: The Bolaños case, Sierra Madre Occidental, Mexico

Graben calderas are volcano-tectonic structures that use the faults of a graben as main vents from which magma is massively erupted from a shallow magma chamber during collapse of intra-graben blocks. These eruptions are generally silicic and explosive and form large volume ignimbrite sheets without a previous Plinian major depressurization event. Graben calderas can be associated to tectonic settings ranging from pure extension to strike-slip transtension, including complete grabens, half-grabens or pull-apart grabens. The Sierra Madre Occidental (SMO) in western Mexico includes several of these graben type calderas with the corresponding large volume ignimbrite sheets that result from fissure type eruptions along the graben's border and interior faults. The Bolaños graben constitutes one of the best examples of these tectonically controlled collapse calderas and is the second largest caldera of the world after Toba caldera. It is a 90 × 25 km rectangular caldera and the vent of the 25.37 ± 0.36 Ma silicic Alacrán ignimbrite, with a minimum Dense Rock Equivalent volume of 2650 km3 (3800 km3 rock volume). Post-collapse silicic domes were emplaced just after the Alacrán ignimbrite from 25.02 ± 0.33 Ma to 23.94 ± 0.33 Ma, with a total minimum lava volume of 171 km3. Both ignimbrite and domes account for at least 2800 km3 rhyolitic magma output from Bolaños graben caldera, without considering the distal deposits, and in particular the co-ignimbrite ash-cloud deposit. We describe the characteristics of the Bolaños graben caldera focusing on its major products, the Alacrán ignimbrite and the post-collapse dome volcanism, providing the geological frame of the Bolaños graben area documented with 40Ar-39Ar ages. We finally propose a conceptual model to explain the dynamics of the Bolaños graben that can be applied to other similar volcano-tectonic depressions of the Sierra Madre Occidental and elsewhere in the world with similar geological settings.

The role of land cover in the climate of glacial Europe

Abstract. Earth system models show wide disagreement when simulating the climate of the continents at the Last Glacial Maximum (LGM). This disagreement may be related to a variety of factors, including model resolution and an incomplete representation of Earth system processes. To assess the importance of resolution and land–atmosphere feedbacks on the climate of Europe, we performed an iterative asynchronously coupled land–atmosphere modelling experiment that combined a global climate model, a regional climate model, and a dynamic vegetation model. The regional climate and land cover models were run at high (18 km) resolution over a domain covering the ice-free regions of Europe. Asynchronous coupling between the regional climate model and the vegetation model showed that the land–atmosphere coupling achieves quasi-equilibrium after four iterations. Modelled climate and land cover agree reasonably well with independent reconstructions based on pollen and other paleoenvironmental proxies. To assess the importance of land cover on the LGM climate of Europe, we performed a sensitivity simulation where we used LGM climate but present-day (PD) land cover. Using LGM climate and land cover leads to colder and drier summer conditions around the Alps and warmer and drier climate in southeastern Europe compared to LGM climate determined by PD land cover. This finding demonstrates that LGM land cover plays an important role in regulating the regional climate. Therefore, realistic glacial land cover estimates are needed to accurately simulate regional glacial climate states in areas with interplays between complex topography, large ice sheets, and diverse land cover, as observed in Europe.

Liquid Crystal-Mediated 3D Printing Process to Fabricate Nano-Ordered Layered Structures.

The emergence of three-dimensional (3D) printing promises a disruption in the design and on-demand fabrication of smart structures in applications ranging from functional devices to human organs. However, the scale at which 3D printing excels is within macro- and microlevels and principally lacks the spatial ordering of building blocks at nanolevels, which is vital for most multifunctional devices. Herein, we employ liquid crystal (LC) inks to bridge the gap between the nano- and microscales in a single-step 3D printing. The LC ink is prepared from mixtures of LCs of nanocellulose whiskers and large sheets of graphene oxide, which offers a highly ordered laminar organization not inherently present in the source materials. LC-mediated 3D printing imparts the fine-tuning required for the design freedom of architecturally layered systems at the nanoscale with intricate patterns within the 3D-printed constructs. This approach empowered the development of a high-performance humidity sensor composed of self-assembled lamellar organization of NC whiskers. We observed that the NC whiskers that are flat and parallel to each other in the laminar organization allow facile mass transport through the structure, demonstrating a significant improvement in the sensor performance. This work exemplifies how LC ink, implemented in a 3D printing process, can unlock the potential of individual constituents to allow macroscopic printing architectures with nanoscopic arrangements.

The Dynamics of Diachronous Extinction Associated With Climatic Deterioration Near the Neogene/Quaternary Boundary

AbstractTo predict extinction, we must understand the processes leading to terminal population decline. Once a critical threshold of population size is reached, small environmental perturbations can push a species over the cliff‐edge to extinction, so the main drivers of extinction are the factors that cause the initial reduction in population size. Most studies of population decline leading up to extinction focus on modern species in a human‐dominated world. The drivers of population decline leading to non‐human mediated extinctions are less well known but changes in climate are arguably the most widely invoked mechanism. Here, we report data on >16,000 individuals of the planktonic foraminifer Globoconella puncticulata from six sites in the Atlantic Ocean along an 83 degree‐long latitudinal transect, over a 600,000‐years interval leading up to the species’ global extinction during the late Pliocene‐earliest Pleistocene intensification of Northern Hemisphere glaciation. We show changes in geographic range, abundance, and body size. We find that populations do not follow a North‐to‐South sequence in extinction as Earth cooled and developed large ice sheets in the high latitudes of the Northern Hemisphere. Instead, our results suggest that (a) populations are differentially adapted to local environmental conditions such as nutrient availability, (b) population dynamics in core populations differ from those at the edge of their range, and (c) individual population responses to external pressures are essential to understanding the drivers of global extinction. Our study demonstrates the potential to transform our understanding of extinction dynamics through spatially replicated sampling of the highly resolved marine microfossil record.

TaN-Based Combined Barrier+Liner Materials to Beat the Interconnect Bottleneck

In order to prolong the lifetime of Cu as an interconnect metal in CMOS devices, as transistors continue to decrease in size, materials that combine properties of diffusion barriers and seed liners are needed. Such a material will have to allow for successful electroplating of Cu and must be as thin as possible in order to facilitate the coating of high-aspect ratio interconnect vias. One possible way to achieve such a material is presented in this study. Through density functional theory we investigate the behaviour Cu on Ru-doped and Ru passivated ε-TaN (1 1 0). Adsorption and diffusion of one and two Cu atoms on these surfaces were studied initially, in order to understand the early stages of film growth. This showed that while adsorption and surface diffusion were more favourable on the Ru passivated surface, Ru dopants act as a nucleation site for Cu atoms and enhance the metal-surface interaction.To understand the growth mechanism of Cu films on these surfaces in more detail, and to discover the optimum Ru content for the surface, large Cu sheets are adsorbed to the Ru passivated surface as well as to Ru-doped surfaces with a variety of surface doping concentrations.On the Ru-doped films, Cu spontaneously transitions into a two-layer structure, while atoms remain in a single layer on the Ru-passivated surface. However, ab initio molecular dynamics and activation energies of pathways for migration of atoms to form further layers show that the Ru dopants inhibit further 3D growth of the Cu structures.

Determination of the elastic moduli of CVD graphene by probing graphene/polymer Bragg stacks

Graphene has been widely used in the form of micro-flakes to fabricate composite materials with enhanced mechanical properties. Due to the small size of the inclusions and their random orientation within the matrix, the superior mechanical properties of graphene cannot be fully exploited. Recently, attempts have been made to fabricate nanolaminate composites by interleaving large sheets of chemical vapor deposition (CVD) monolayer graphene between thin layers of polymer matrices. However, CVD graphene is inevitably accompanied by wrinkles that are formed in the synthesis process, and it remains unknown how the wrinkles affect the mechanical properties of graphene. Here, we employ Brillouin light spectroscopy to study the elastic moduli of CVD graphene by probing graphene/poly(methylmethacrylate) hybrid Bragg stacks at zero strain. We find the Young’s and shear moduli of the CVD graphene, which has wrinkles in the form of sharp elevations with a height of about 6 nm and a fullwidth at half maximum (FWHM) of ca. 30 nm, to be 680 ± 16 and 290 ± 10 GPa, respectively, with the former being about 30% lower than that of exfoliated, flat graphene. This work sheds light on the elastic properties of CVD graphene and provides a method that can be extended to studying the wrinkle-induced softening effect in other two-dimensional materials.

Timescales of impact melt sheet crystallization and the precise age of the Morokweng impact structure, South Africa

Impact cratering was a fundamental geological process in the early Solar System and, thus, constraining the timescales over which large impact structures cool is critical to understanding the thermal evolution and habitability of early planetary crusts. Additionally, impacts can induce mass extinctions and establishing the precise timing of the largest impacts on Earth can shed light on their role in such events. Here we report a high-precision zircon U–Pb geochronology study of the Morokweng impact structure, South Africa, which appears to have a maximum present-day diameter of ∼80 km. Our work provides (i) constraints on the cooling of large impact melt sheets, and (ii) a high-precision age for one of Earth's largest impact events, previously proposed to have overlapped the ca. 145 Ma Jurassic–Cretaceous (J–K) boundary. High-precision U–Pb geochronology was performed on unshocked, melt-grown zircon from five samples from a borehole through approximately 800 m of preserved impact melt rock. Weighted mean 206Pb/238U dates for the upper four samples are indistinguishable, with relative uncertainties (internal errors) of better than 20 ka, whereas the lowermost sample is distinguishably younger than the others. Thermal modeling suggests that the four indistinguishable dates are consistent with in situ conductive cooling of melt at this location within 30 kyr of the impact. The younger date from the lowest sample cannot be explained by in situ conductive cooling in line with the overlying samples, but the date is within the ∼65 kyr timeframe for melt-present conditions in footwall rocks below the impact melt sheet that is indicated by our thermal model. The Morokweng impact event is here constrained to 146.06 ± 0.16 Ma (2σ; full external uncertainty), which precedes current estimates of the age of the J–K boundary by several million years.

Record summer rains in 2019 led to massive loss of surface and cave ice in SE Europe

Abstract. Glaciers worldwide are shrinking at an accelerated rate as the climate changes in response to anthropogenic influence. While increasing air temperature is the main factor behind glacier mass and volume loss, variable patterns of precipitation distribution also play a role, though these are not as well understood. Furthermore, while the response of surface glaciers (from large polar ice sheets to small alpine glaciers) to climatic changes is well documented and continuously monitored, little to nothing is known about how cave glaciers (perennial ice accumulations in rock-hosted caves) react to atmospheric warming. In this context, we present here the response of cave and surface glaciers in SE Europe to the extreme precipitation events occurring between May and July 2019 in SE Europe. Surface glaciers in the northern Balkan Peninsula lost between 17 % and 19 % of their total area, while cave glaciers in Croatia, Greece, Romania and Slovenia lost ice at levels higher than any recorded by instrumental observations during the past decades. The melting was likely the result of large amounts of warm water delivered directly to the surface of the glaciers, leading to rapid reduction in the area of surface glaciers and the thickness of cave glaciers. As climate models predict that such extreme precipitation events are set to increase in frequency and intensity, the presence of cave glaciers in SE Europe and the paleoclimatic information they host may be lost in the near future. Moreover, the same projected continuous warming and increase in precipitation extremes could pose an additional threat to the alpine glaciers in southern Europe, resulting in faster-than-predicted melting.

Cholesterol-phospholipid interactions resist the detergent effect of bovine bile

Sphingomyelin (SM) and cholesterol complexation gives rise to detergent-resistant liquid-ordered domains. The persistence of these domains and subsequent mixed micelle formation was examined in the presence of bile under physiological digestive in vitro conditions for vesicles comprising either SM/cholesterol, porcine brain phosphatidylcholine (BPC)/cholesterol, or soy phosphatidylcholine (SPC)/cholesterol bilayers, the latter two systems having no liquid-ordered domains. Micellization of these digested phospholipid multilamellar vesicle systems was confirmed by transmission electron microscopy. Bovine bile was found to consist of large multilamellar sheets which subsumed phospholipid vesicles to form aggregated superstructures. Budding off from these superstructures were vesicle-to-micelle transition intermediates: unilamellar vesicles and cylindrical micelles. The presence of cholesterol (60/40 phospholipid/cholesterol mol/mol) delayed the initial rapid onset of digestion, but not for BPC and SPC vesicle systems. Acyl chain order/disorder before and after vesicle-to-micelle transition of all three phospholipid/cholesterol systems was examined using Raman spectroscopy. The addition of bovine bile to both PC/cholesterol vesicle systems reduced the overall ratio of acyl chain disorder to order. In SM/cholesterol vesicles with ≤ 20% mol cholesterol, only the lateral inter-acyl chain packing was reduced, whereas for SM/cholesterol vesicles with ≥ 30% mol cholesterol, a higher proportion of gauche-to-trans isomerization was apparent, demonstrating that SM/cholesterol complexes modify the acyl chain structure of micelles.

The large MIS 4 and long MIS 2 glacier maxima on the southern tip of South America

Robust glacial chronologies are needed to address the fundamental questions of when and why Ice Age climates begin and end. Well-preserved glacial deposits left by large ice sheet lobes adjacent to Estrecho de Magallanes (53°S; Chile) in southernmost South America provide a unique opportunity to reconstruct the timing and fine structure of the last two major glaciations, as well as the last termination. We present a new precise 10Be surface exposure dataset of 34 moraine boulders directly tied to a recently published, high resolution glacial geomorphic map of the deposits left by the Magallanes lobe.We find that the southern section of the Patagonian Ice Sheet was more extensive during Marine Isotope Stage 4 (MIS 4) than during MIS 2, representing the first direct dating of the MIS 4 glacier culmination in South America. Similar to the MIS 2 glacial maxima, within MIS 4 there were multiple advances that we date (n = 6 samples) to between 67.5 ± 2.1 and 62.1 ± 2.0 ka. A similarly timed MIS 4 advance was identified in New Zealand, indicating that this is a hemisphere-wide glacier-climate signal, which is further corroborated by South Atlantic and Pacific temperature proxy records. Inboard of the MIS 4 moraine complex, we date a sequence of geomorphically distinct MIS 2 moraines that represent separate major periods of glacial stability. The MIS 2 maximum extent occurred by 27.4 ± 0.8 ka (n = 4; arithmetic mean, with the standard error of the mean and 3% propagated production rate error) and was followed by at least four more full glacial culminations at 25.7 ± 0.8 (n = 3), 23.9 ± 0.8 (n = 5), 19.1 ± 0.7 (n = 3), and 18.1 ± 0.6 ka (n = 3), which represent periods when the glacier was in equilibrium with the climate for long enough to form major moraines. About 18 km inboard, this sequence is followed by smaller-scale recessional moraine crests, deposited on drumlinized terrain rather than a moraine drift, that we date to 18.0 ± 0.8 ka, indicating the glacier was in net retreat at this time. Tentative results from a 2D ice sheet model suggest that the Magallanes lobe may have reached mapped inner and outer MIS 2 moraines from a climate with approximately 4.5 °C and 5.5 °C cooler summers, respectively, assuming ∼25% less annual precipitation, relative to modern climate. We hypothesize that during the last glacial cycle, shifts in the subtropical and subantarctic fronts, and related ocean-atmosphere patterns, explain MIS 4 to 2 glacial behavior in the southern mid-latitudes.

Tuning of ionic transport through graphene oxide fibers by sheets size ‎

In this study, graphene oxide fibers are introduced as new graphene oxide (GO) membranes with the ‎capability of ion selectivity‏.‏‎ Graphene oxide fibers, like other macro structured membranes, are always ‎associated with cavities and defects. To solve this problem, a 50% combination of graphene oxide ‎suspension including small sheets with an average size of ~ 0.5 µm2 and large sheets with an area of more ‎than 10 µm2 was used. According to the morphological results of scanning electron microscopy, as well as ‎the amount of ionic transport through the fiber, reduction of cavities and its defects were confirmed. ‎Moreover, it was found that ionic current through fibers consist of large and small GO sheets is more ‎controllable. This leads to more ionic selectivity via tunable swelling. Finally, the scalability of graphene ‎oxide fibers investigated and found that increasing number and length of the fibers increases the ionic ‎current as linear trend‎.

P‐36: Effective Cleaning of Glass Substrates

Surface contamination is one of the major causes of yield loss, with a unique set of challenges for large display glass sheets that support the industry. Here, we review the use of different cleaning approaches applied to display glasses during manufacturing, discussing the advantages of some choices over others.

Resistance is not futile: The use of projections for resistance joining of metal additively and conventionally manufactured parts

Metal additive manufacturing processes can produce geometrically complex and lightweight components. While conventionally manufactured components are frequently assembled to form larger parts, additive manufacturing can be used to print an entire part without needing any assembly. However, additive manufacturing processes are frequently limited in the size of the part they can produce, and it is often more economically favourable to conventionally manufacture larger or simpler geometries, such as large sheets. In this study, we demonstrate the use of a resistance joining process to facilitate the assembly of additive manufactured components. Projections are designed into additive manufactured parts to allow for joining with a conventional metal sheet. Joint performance is evaluated as a function of design choices, including the type of infill, part thickness, and proximity to adjacent joints, as well as the resistance joining process parameters. High strength joints capable of withstanding an applied torque of up to 80 Nm were obtained and functional parts were assembled to a conventionally manufactured sheet as a demonstration of the process. Incorporating projections for resistance joining into the design stage of additive manufactured parts has the potential to facilitate the use of additive manufactured components in larger assemblies and broaden the adoption of additive manufacturing in industry.

Lightweight thermal interface materials based on hierarchically structured graphene paper with superior through-plane thermal conductivity

Graphene-based papers have recently triggered considerable interests in developing the application as thermal interface materials (TIMs) for addressing the interfacial heat transfer issue, but their low through-plane thermal conductivity (κ⊥), resulting from the layer-by-layer stacked architecture, limits the direct use as TIMs. Although various hybrid graphene papers prepared by combining the graphene sheets and the thermally conductive insertions have been proposed to solve this problem, achieving a satisfactory κ⊥ higher than that of commercial TIMs (>5 W m−1 K−1) remains challenging. Here, a strategy aimed at the construction of heat pathways along the through-plane direction inside the graphene paper for achieving a high κ⊥ was demonstrated through the simultaneous filtration of graphene sheets with two different lateral sizes. The as-prepared graphene paper presented a hierarchical structure composed of loosely stacked horizontal layers formed by large graphene sheets, intercalated by a random arrangement of small graphene sheets. Due to the heat pathways formed by small graphene sheets along the through-plane direction, the hierarchically structured graphene paper exhibited an improved κ⊥ as high as 12.6 W m−1 K−1 after a common graphitization post-treatment. In the practical test, our proposed paper as an all-graphene TIM achieved an enhancement in cooling efficiency of ≈ 2.2 times compared to that of the state-of-the-art TIM, demonstrating its superior performance to meet the ever-increasing heat dissipation requirement.

Soft X-ray absorption and emission spectra of nanographene prepared from pentacene with hot mesh deposition and soft X-ray irradiation

The molecular orientation and partial density of states were evaluated using NewSUBARU by soft X-ray absorption spectroscopy (XAS) and soft X-ray emission spectroscopy measurements. The degree of molecular alignment was degraded by increasing mesh temperature in hot mesh deposition (HMD), in other words, was changed from pentacene (Pn) to 6,13-dihydropentacene (DHP). At a mesh temperature of 1450 °C, the different XAS was obtained due to the mixing effect of Pn and DHP, and presence of Pn oligomer. The HMD carbon film transformed into the graphite-like film and the graphene on the quartz substrate and the Ni/quartz substrate after soft X-ray irradiation, respectively. The HMD carbon film after soft X-ray irradiation showed the peaks due to terminal carbon such as CH n and COOH in comparison with the reported large graphene sheet. It indicates that the flake size of the graphene on the Ni/quartz substrate was small and had many edges.

The Long Timeline of the Ice

Ice ages constitute a significant part of Earth’s climate history with the first signs of widespread ice sheets occurring at about 2.4 billion years ago. In 2004, a nearly 450 metres thick accumulation of seafloor sediments on the submarine Lomonosov Ridge in central Arctic Ocean was drilled by the international Arctic Coring Expedition (ACEX). This geological archive has provided insights into the long-term history of the Arctic Ocean back to 56 million years. The first signs of extensive sea ice along the Arctic coasts appear 47.5 million years ago (Ma), while evidence for the type of pack ice we have today that survives more than one season occurs first 15–13 Ma. The Earth’s climate changed mode at about 2.6 Ma. Cold periods, characterized by large ice sheets covering the Northern Hemisphere, were intervened by warmer periods with climates more similar of today. These glacial-interglacial cycles were largely controlled by changes in solar insolation resulting from cyclical variations in Earth’s orbit around the Sun. In this article, I tell the personal story of how we mapped the Lomonosov Ridge and found evidence supporting a controversial hypothesis of the existence of kilometre-thick floating ice shelves in the Arctic Ocean during past glaciations.

A Case Report of Chondrosarcoma of Temporomandibular Joint

In this case report we describe a rare case of chondrosarcoma of the Temporomandibular joint in a 70 years old female who presented with a right preauricular swelling, trismus and neuralgic pain. On examination, firm and tender swelling was noted in the right preauricular region. CT Scan revealed 3.48 × 3.0 cm size mass lesion in the region of mandibular condyle and extending into the right temporomandibular joint space. The cytopathological report was suggestive of chondroid malignancy. The tumor was excised and histopathological examination showed large sheets of atypical tumor cells with cartilaginous matrix and diagnosis of a well differentiated Chondrosarcoma was confirmed. Post-surgical resection, patient remains disease free at 15 months follow up.

Deep Heat: Proxies, Miocene Ice, and an End in Sight for Paleoclimate Paradoxes?

AbstractThe mid Miocene represents an important target for paleoclimatic study because the atmospheric CO2 concentration ranged from near modern values to ∼800 ppm, while a large, dynamic Antarctic ice sheet was likely to have been present throughout much of this interval. In this special issue, Modestou et al. (2020) (doi.org/10.1029/2020PA003927) reconstruct deep ocean warmth based on the clumped isotopic composition of benthic foraminifera, a technique that allows the ice volume and thermal components of the benthic oxygen isotope stack to be separated. These data reveal a very warm deep ocean while simultaneously suggesting that continental ice volume may, at times, have been greater than today. Here, I review these results in the context of recent developments in geochemical proxies and ice sheet modeling, and explore how the presence of a large Miocene ice sheet could be reconciled with CO2 at least as high as present. More broadly, I argue that many of the 'paradoxes' that pepper the paleoclimate literature result as much from our imperfect understanding of the proxies, as from our understanding of the climate system. Robust proxies with a well‐understood mechanistic basis, as employed by Modestou et al. (2020), as well as advances in model‐data comparability usher in a new era of palaeoclimate research; an exciting future of untangling Earth's myriad past climate states awaits.

Composition optimization of InAsxSb1−x/AlyIn1−ySb quantum wells for Hall sensors with high sensitivity and high thermal stability

The band diagrams of InAsxSb1−x/AlyIn1−ySb quantum wells (QWs) were calculated covering a wide range of compositions of x and y. Various combinations of active (InAsxSb1−x) and barrier (AlyIn1−ySb) layers were investigated to optimize the Hall elements with high sensitivity and high thermal stability. For high sensitivity, x of 0.1–0.6 is desirable due to the band bowing effect to realize lower bandgaps compared with that of InSb in the active layer. Under the lattice matched conditions (y ∼ 1.22x), the QWs are type II QWs and the bottom of the conduction band is always lower than the Fermi level. Therefore, the QWs with x of 0.6 show large sheet carriers of 4.1 × 1011 cm−2 for 4.2 K without intentional doping, which contributes to the reduction in the temperature dependence of the transport properties. The barrier height monotonously increases with increasing y, and accordingly, the penetration depth of the wave function probability inside the barrier decreases. Under the lattice matched condition, the penetration depth drops significantly toward x = 0.4 (corresponding y ∼ 0.5) and then decreases slowly. Thus, x ≥ 0.4 (y ≥ 0.5) is preferable for a strong confinement effect, which could reduce interface scattering and, as a result, improve the electron mobility. Judging from these results, the optimized composition of the InAsxSb1−x/AlyIn1−ySb QW is x = 0.4–0.6 (under the lattice matched condition, corresponding y = 0.5–0.7).

Palladium Nanosheet-Carbon Black Powder Composites for Selective Hydrogenation of Alkynes to Alkenes

Ultrathin palladium nanosheets on carbon black grains have been straightforwardly prepared under reductant-free conditions using ultrasonication. The as-prepared composites (showing a quite unusual morphology of Pd-deposits) have been scrutinized as catalysts in the selective alkyne-to-alkene hydrogenation under mild operational conditions. Their activity, selectivity, and robustness in the process are outstanding, opening new horizons for simpler synthetic procedures for this class of composites. Moreover, the tight anchorage of the large and thin metal sheets to the carbon grains of the support dramatically reduces the active phase surface mobility during catalysis. Besides preserving the catalyst performance, this peculiar palladium morphology strongly limits the environmental risks stemming from metal nanoparticles leaching in heterogeneous catalysts.