Among the different graphene synthesis methods, chemical vapor deposition of graphene on low cost copper foil shows great promise for large scale applications. Here, we present growth experiments to ...obtain high quality graphene and its clean transfer onto any substrates. Bilayer-free monolayer graphene was obtained by a careful pre-annealing step and by optimizing the H sub(2) flow during growth. The as-grown graphene was transferred using an improved wet chemical graphene transfer process. Some major flaws in the conventional wet chemical, polymethyl methacrylate (PMMA) assisted, graphene transfer process are addressed. The transferred graphene on arbitrary substrates was found to be free of metallic contaminants, defects (cracks, holes or folds caused by water trapped beneath graphene) and PMMA residues. The high quality of the transferred graphene was further evidenced by angle resolved photoelectron spectroscopy studies, for which the linear dependency of the electronic band structure characteristic of graphene was measured at the Dirac point. This is the first Dirac cone observation on the CVD grown graphene transferred on some 3D bulk substrate.
Nanometric biocompatible Metal-Organic Frameworks (nanoMOFs) are promising candidates for drug delivery. Up to now, most studies have targeted the intravenous route, related to pain and severe ...complications; whereas nanoMOFs for oral administration, a commonly used non-invasive and simpler route, remains however unexplored. We propose here the biofriendly preparation of a suitable oral nanocarrier based on the benchmarked biocompatible mesoporous iron(III) trimesate nanoparticles coated with the bioadhesive polysaccharide chitosan (CS). This method does not hamper the textural/structural properties and the sorption/release abilities of the nanoMOFs upon surface engineering. The interaction between the CS and the nanoparticles has been characterized through a combination of high resolution soft X-ray absorption and computing simulation, while the positive impact of the coating on the colloidal and chemical stability under oral simulated conditions is here demonstrated. Finally, the intestinal barrier bypass capability and biocompatibility of CS-coated nanoMOF have been assessed in vitro, leading to an increased intestinal permeability with respect to the non-coated material, maintaining an optimal biocompatibility. In conclusion, the preservation of the interesting physicochemical features of the CS-coated nanoMOF and their adapted colloidal stability and progressive biodegradation, together with their improved intestinal barrier bypass, make these nanoparticles a promising oral nanocarrier.
Marine debris accumulation was analyzed from three exposed beaches of the Canary Islands (Lambra, Famara and Las Canteras). Large microplastics (1–5mm), mesoplastics (5–25mm) and tar pollution were ...assessed twice a month for a year. There was great spatial and temporal variability in the Canary Island coastal pollution. Seasonal patterns differed at each location, marine debris concentration depended mainly of local-scale wind and wave conditions. The most polluted beach was Lambra, a remote beach infrequently visited. The types of debris found were mainly preproduction resin pellets, plastic fragments and tar, evidencing that pollution was not of local origin, but it cames from the open sea. The levels of pollution were similar to those of highly industrialized and contaminated regions. This study corroborates that the Canary Islands are an area of accumulation of microplastics and tar rafted from the North Atlantic Ocean by the southward flowing Canary Current.
•Marine debris in the Canary Islands was documented over an annual cycle.•High seasonal variability above an order of magnitude was found.•Coastal orientation, local wind and waves determined debris concentration.•Tar and resin-pellet pollution was high in two beaches.•The type of debris found indicated an open-sea source.
The structural and electronic properties of twisted bilayer graphene (TBG) on SiC(000) grown by Si flux-assisted molecular beam epitaxy were investigated using scanning tunneling microscopy (STM) and ...angle-resolved photoelectron spectroscopy with nanometric spatial resolution. STM images revealed a wide distribution of twist angles between the two graphene layers. The electronic structure recorded in single TBG grains showed two closely-spaced Dirac π bands associated to the two stacked layers with respective twist angles in the range 1-3°. The renormalization of velocity predicted in previous theoretical calculations for small twist angles was not observed.
The practical difficulties to use graphene in microelectronics and optoelectronics is that the available methods to grow graphene are not easily integrated in the mainstream technologies. A growth ...method that could overcome at least some of these problems is chemical vapour deposition (CVD) of graphene directly on semiconducting (Si or Ge) substrates. Here we report on the comparison of the CVD and molecular beam epitaxy (MBE) growth of graphene on the technologically relevant Ge(001)/Si(001) substrate from ethene (C2H4) precursor and describe the physical properties of the films as well as we discuss the surface reaction and diffusion processes that may be responsible for the observed behavior. Using nano angle resolved photoemission (nanoARPES) complemented by transport studies and Raman spectroscopy as well as density functional theory (DFT) calculations, we report the direct observation of massless Dirac particles in monolayer graphene, providing a comprehensive mapping of their low-hole doped Dirac electron bands. The micrometric graphene flakes are oriented along two predominant directions rotated by 30° with respect to each other. The growth mode is attributed to the mechanism when small graphene "molecules" nucleate on the Ge(001) surface and it is found that hydrogen plays a significant role in this process.
The explosive activity of the 2021 Tajogaite eruption eludes pigeonholing into well‐defined eruption styles, with a variety of pyroclast ejection modes occurring both alternately and simultaneously ...at multiple vents. Visually, we defined four endmembers of explosive activity, referred to as fountaining, spattering, ash‐poor jets and ash‐rich jets. To capture the physical parameters of these activities, we deployed a camera array including one high‐speed camera and three high‐definition cameras in two field campaigns. Transitions between and fluctuations within activity occurred at the time scale of minutes to hours, likely driven by the same shallow conduit and vent processes controlling Strombolian activity at other volcanoes, but at higher gas and magma fluxes. From a physical standpoint, mean pyroclast rise velocity ranged 5–50 m/s, maximum ejection velocity 10–220 m/s, and sub‐second mass flux of lapilli to bomb‐sized pyroclasts at the vent 0.2–200 × 103 kg/s. The largest mass flux occurred during fountaining, which contributed by far more than other activities to cone building. All explosive activity exhibited well‐defined pyroclast ejection pulses, and we found a positive correlation between the occurrence rate of ejection pulses and maximum pyroclast ejection velocity. Despite orders of magnitude variations, physical parameters shift gradually with no boundary from one activity endmember to another. As such, attributing this explosive activity specifically to any currently defined style variations is arbitrary and potentially misleading. The highly variable explosive activity of the Tajogaite eruption recalls previous definitions of violent Strombolian eruptions, an eruption style whose pyroclast ejection dynamics, however, were so far largely undefined.
Plain Language Summary
The 2021 Tajogaite volcanic eruption offered a rare opportunity to study in detail the physical properties and the controlling factors of explosive activity driven by basaltic magmas. The activity lasted almost uninterrupted for almost 3 months and had visually different manifestations occurring simultaneously and alternating at different volcanic vents. To study the explosive activity, we used one high‐speed camera, taking short, slow motion videos, and three commercial grade high‐definition camcorders recording for many hours. We found that the activity changed in features and intensity at the time scale of minutes to hours, largely controlled by changes in the size and debris cover of the vent, magma viscosity, and magma flux and gas content. The ejection velocity of large volcanic particles ranged 5–220 m/s, with mean values around 10–50 m/s. The mass flux of particles erupted reached peaks of 200 metric tons per second. Particle ejection was never steady but always proceeded in pulses, which were more frequent if the ejection velocity was higher. Our measurements show that the current classification schemes for explosive eruptions of basaltic magmas do not adequately describe the activity of the Tajogaite eruption, which represents a type of eruption that was not yet measured in detail.
Key Points
High‐definition and high‐speed imaging record the velocity, size, and mass flux of pyroclasts
Activity shifted in location, nature and vigor at the time scale of hours and progressed in ejection pulses at the time scale of seconds
Physical parameters of explosive activity vary gradually between apparently different activity styles, without any clear boundary
Magnetic heating has recently been demonstrated as an efficient way to perform catalytic reactions after deposition of the heating agent and the catalyst on a support. Here we show that in solution, ...and under mild conditions of mean temperature and pressure, it is possible to use magnetic heating to carry out transformations that are otherwise performed heterogeneously at high pressure and/or high temperature. As a proof of concept, we chose the hydrodeoxygenation of acetophenone derivatives and of biomass‐derived molecules, namely furfural and hydroxymethylfurfural. These reactions are difficult, require heterogeneous catalysts and high pressures, and, to the best of our knowledge, have no precedent in standard solution. Here, hydrodeoxygenations are fully selective under mild conditions (3 bar H2, moderate mean temperature of the solvent). The reason for this reactivity is the fast heating of the particles well above the boiling temperature of the solvent and the local creation of hot spots surrounded by a vapor layer, in which high temperature and pressure may be present. This technology may be practicable for many organic transformations.
Hot iron: Magnetic heating of Fe2.2C@Ru nanoparticles in solution gives rise to high local temperatures which make it possible to perform the selective hydrodeoxygenation of acetophenone derivatives and platform molecules such as furfural (see figure) and hydroxymethylfurfural under mild conditions (3 bar H2). These reactions are otherwise carried out with standard heterogeneous catalysts at high H2 pressures and temperatures.
There is growing interest in relating taste perception to diet and healthy aging. However, there is still limited information on the influence of age, sex and genetics on taste acuity as well as on ...the relationship between taste perception and taste preferences. We have analysed the influence of age on the intensity rating of the five basic tastes: sweet, salty, bitter, sour and umami (separately and jointly in a "total taste score") and their modulation by sex and genetics in a relatively healthy population (men and women) aged 18⁻80 years (
= 1020 Caucasian European participants). Taste perception was determined by challenging subjects with solutions of the five basic tastes using standard prototypical tastants (6-n-propylthiouracil (PROP), NaCl, sucrose, monopotassium glutamate and citric acid) at 5 increasing concentrations (I to V). We also measured taste preferences and determined the polymorphisms of the genes taste 2 receptor member 38 (TAS2R38), taste 1 receptor member 2 (TAS2R38) and sodium channel epithelial 1 beta subunit (SCNN1B), as TAS2R38-rs713598, TAS1R2-rs35874116 and SCNN1B-rs239345 respectively. We found a statistically significant decrease in taste perception ("total taste score") with increasing age for all the concentrations analysed. This association was stronger for the higher concentrations (
= 0.028;
= 0.012;
= 0.005;
= 4.20 × 10
and
= 1.48 × 10
, for I to V in the multivariable-adjusted models). When we analysed taste qualities (using concentration V), the intensity rating of all the 5 tastes was diminished with age (
0.05 for all). This inverse association differed depending on the test quality, being higher for bitter (PROP) and sour. Women perceived taste significantly more intense than men (
= 1.4 × 10
for total taste score). However, there were differences depending on the taste, umami being the lowest (
= 0.069). There was a complex association between the ability to perceive a taste and the preference for the same. Significant associations were, nevertheless, found between a higher perception of sour taste and a higher preference for it in women. In contrast, the higher perception of sweet was significantly associated with a higher preference for bitter in both, men and women. The TAS2R38-rs713598 was strongly associated with bitter (PROP) taste (
= 1.38 × 10
), having a significant interaction with sex (
= 0.030). The TAS1R2-rs35874116 was not significantly associated with sweet, whereas the SCNN1B-rs239345 was associated (
= 0.040) with salty taste. In conclusion, the inverse association between age and perceived taste intensity as well as the additional influence of sex and some genetic polymorphisms give rise to large inter-individual differences in taste perception and taste preferences that should be taken into account in future studies and for applications in precision nutrition for healthy aging.
In recent years there has been growing interest in the electronic properties of 'few layer' graphene films. Twisted layers, different stacking and register with the substrate result in remarkable ...unconventional couplings. These distinctive electronic behaviours have been attributed to structural differences, even if only a few structural determinations are available. Here we report the results of a structural study of bilayer graphene on the Si-terminated SiC(0001) surface, investigated using synchrotron radiation-based photoelectron diffraction and complemented by angle-resolved photoemission mapping of the electronic valence bands. Photoelectron diffraction angular distributions of the graphene C 1s component have been measured at different kinetic energies and compared with the results of multiple scattering simulations for model structures. The results confirm that bilayer graphene on SiC(0001) has a layer spacing of 3.48 Å and an AB (Bernal) stacking, with a distance between the C buffer layer and the first graphene layer of 3.24 Å. Our work generalises the use of a versatile and precise diffraction method capable to shed light on the structure of low-dimensional materials.
Background. Despite the widespread use of organophosphate (OP) pesticides, information on predictors of children's exposure to such pesticides is scarce.
Objective. To assess exposure to OP ...pesticides in children 3-11 year-old living in agricultural communities and urban areas from Andalusia (Southern Spain), and to identify the main determinants of exposure.
Methods. A longitudinal study was conducted in children 3-11-year-old children living in agricultural communities and urban areas from the provinces of Almeria, Granada and Huelva (Andalusia, Spain) between 2010 and 2011. Urinary levels of six dialkylphosphate (DAP) metabolites were measured by UHPLC-QqQ-MS/MS at the periods of low and high pesticide use in the agriculture (LPU and HPU, respectively). Information on sociodemographic characteristics, parental occupation, residential history, lifestyle and diet, among other relevant factors, was obtained from questionnaires administered to the mothers.
Results. A total of 559 and 597 children participated in LPU and HPU periods, respectively. The proportion of urine samples below LOD was 67.4% for ΣDMs (sum of dimethyl metabolites), 77% for ΣDEs (sum of diethyl metabolites) and 58.5% for ΣDAPs (sum of total dialkylphosphate metabolites) in LPU period, and 50.4% for ΣDMs, 65.3% for ΣDEs and 43.9% for ΣDAPs in HPU period. Significantly greater urinary ΣDAP, ΣDM and ΣDE levels were observed in HPU relative to LPU period. Maternal schooling years, proximity of the house to crops or greenhouses, use of insecticides at home, spraying the garden with pesticides, storage of pesticides at home, house cleaning frequency, as well as child's frequency of bath/shower, were found to be the major predictors of urinary levels of ΣDAP. Likewise, not washing fruit and vegetables before consumption and banana consumption were also identified as determinants of the exposure levels.
Conclusions. Urinary levels of metabolites of OP pesticides found in this study were relatively lower compared to similar studies. DAP levels were significantly increased in HPU period. Maternal schooling years and variables related to residential environment and home exposures were identified as the most relevant determinants of DAP metabolites. Regarding diet, banana consumption and not washing fruit before consumption were also identified as determinants of the exposure levels. This study contributes to improve our knowledge on the main sources and determinants of children exposure to OPS, and given that children are more vulnerable than adults this information is essential to reduce children exposure and protect their health.
Display omitted
•A longitudinal study was conducted in children 3-11-year-old from Southern-Spain.•Urinary levels of dialkylphosphates and predictors were assessed at two time points.•Maternal education was identified as a sociodemographic predictor of DAP levels.•Residential use and storage of pesticides at home also predicted DAP levels.•Banana intake was the only dietary item associated with DAP levels.
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