168 research outputs found
van der Waals epitaxy of monolayer hexagonal boron nitride on copper foil : growth, crystallography and electronic band structure
We investigate the growth of hexagonal boron nitride (h-BN) on copper foil by low pressure chemical vapour deposition (LP-CVD). At low pressure, h-BN growth proceeds through the nucleation and growth of triangular islands. Comparison between the orientation of the islands and the local crystallographic orientation of the polycrystalline copper foil reveals an epitaxial relation between the copper and h-BN, even on Cu(100) and Cu(110) regions whose symmetry is not matched to the h-BN. However, the growth rate is faster and the islands more uniformly oriented on Cu(111) grains. Angle resolved photoemission spectroscopy measurements reveal a well-defined band structure for the h-BN, consistent with a band gap of 6 eV, that is decoupled from the copper surface beneath. These results indicate that, despite a weak interaction between h-BN and copper, van der Waals epitaxy defines the long range ordering of h-BN even on polycrystalline copper foils and suggest that large area, single crystal, monolayer h-BN could be readily and cheaply produced
Is graphene on copper doped?
Angle-resolved photoemission spectroscopy (ARPES) and X-ray photoemission spectroscopy have been used to characterise epitaxially ordered graphene grown on copper foil by low-pressure chemical vapour deposition. A short vacuum anneal to 200 °C allows observation of ordered low energy electron diffraction patterns. High quality Dirac cones are measured in ARPES with the Dirac point at the Fermi level (undoped graphene). Annealing above 300 °C produces n-type doping in the graphene with up to 350 meV shift in Fermi level, and opens a band gap of around 100 meV.
Dirac cone dispersion for graphene on Cu foil after vacuum anneals (left: 200 °C, undoped; right: 500 °C, n-doped). Centre: low energy electron diffraction from graphene on Cu foil after 200 °C anneal. Data from Antares (SOLEIL)
Role of Growth Factor Receptors in Neural Stem Cells Differentiation and Dopaminergic Neurons Generation
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Large-area epitaxial growth of curvature-stabilized ABC trilayer graphene.
The properties of van der Waals (vdW) materials often vary dramatically with the atomic stacking order between layers, but this order can be difficult to control. Trilayer graphene (TLG) stacks in either a semimetallic ABA or a semiconducting ABC configuration with a gate-tunable band gap, but the latter has only been produced by exfoliation. Here we present a chemical vapor deposition approach to TLG growth that yields greatly enhanced fraction and size of ABC domains. The key insight is that substrate curvature can stabilize ABC domains. Controllable ABC yields ~59% were achieved by tailoring substrate curvature levels. ABC fractions remained high after transfer to device substrates, as confirmed by transport measurements revealing the expected tunable ABC band gap. Substrate topography engineering provides a path to large-scale synthesis of epitaxial ABC-TLG and other vdW materials
Ultra-Performance Liquid Chromatography-Ion Mobility Separation-Quadruple Time-of-Flight MS (UHPLC-IMS-QTOF MS) Metabolomics for Short-Term Biomarker Discovery of Orange Intake: A Randomized, Controlled Crossover Study
A major problem with dietary assessments is their subjective nature. Untargeted
metabolomics and new technologies can shed light on this issue and provide a more complete
picture of dietary intake by measuring the profile of metabolites in biological samples. Oranges
are one of the most consumed fruits in the world, and therefore one of the most studied for their
properties. The aim of this work was the application of untargeted metabolomics approach with
the novel combination of ion mobility separation coupled to high resolution mass spectrometry
(IMS-HRMS) and study the advantages that this technique can bring to the area of dietary biomarker
discovery, with the specific case of biomarkers associated with orange consumption (Citrus reticulata)
in plasma samples taken during an acute intervention study (consisting of a randomized, controlled
crossover trial in healthy individuals). A total of six markers of acute orange consumption, including
betonicines and conjugated flavonoids, were identified with the experimental data and previous
literature, demonstrating the advantages of ion mobility in the identification of dietary biomarkers
and the benefits that an additional structural descriptor, as the collision cross section value (CCS), can
provide in this area
Chiral photocurrent in a Quasi-1D TiS3 (001) phototransistor
The presence of in-plane chiral effects, hence spinâorbit coupling, is evident in the changes in the photocurrent produced in a TiS3(001) field-effect phototransistor with left versus right circularly polarized light. The direction of the photocurrent is protected by the presence of strong spinâorbit coupling and the anisotropy of the band structure as indicated in NanoARPES measurements. Dark electronic transport measurements indicate that TiS3 is n-type and has an electron mobility in the range of 1â6 cm2Vâ1sâ1. IâV measurements under laser illumination indicate the photocurrent exhibits a bias directionality dependence, reminiscent of bipolar spin diode behavior. Because the TiS3 contains no heavy elements, the presence of spinâorbit coupling must be attributed to the observed loss of inversion symmetry at the TiS3(001) surface
Characterization of Argentinian Endemic Aspergillus flavus Isolates and Their Potential Use as Biocontrol Agents for Mycotoxins in Maize
Maize (Zea mays L.) is a highly valuable crop in Argentina, frequently contaminated with the mycotoxins produced by Aspergillus flavus. Biocontrol products formulated with atoxigenic (nontoxic) strains of this fungal species are well known as an effective method to reduce this contamination. In the present study, 83 A. flavus isolates from two maize regions of Argentina were characterized and evaluated for their ability to produce or lack of producing mycotoxins in order to select atoxigenic strains to be used as potential biocontrol agents (BCA). All of the isolates were tested for aflatoxin and cyclopiazonic acid (CPA) production in maize kernels and a liquid culture medium. Genetic diversity of the nonaflatoxigenic isolates was evaluated by analysis of vegetative compatibility groups (VCG) and confirmation of deletions in the aflatoxin biosynthesis cluster. Eight atoxigenic isolates were compared for their ability to reduce aflatoxin and CPA contamination in maize kernels in coinoculation tests. The A. flavus population was composed of 32% aflatoxin and CPA producers and 52% CPA producers, and 16% was determined as atoxigenic. All of the aflatoxin producer isolates also produced CPA. Aflatoxin and CPA production was significantly higher in maize kernels than in liquid medium. The 57 nonaflatoxigenic strains formed six VCG, with AM1 and AM5 being the dominant groups, with a frequency of 58 and 35%, respectively. In coinoculation experiments, all of the atoxigenic strains reduced aflatoxin from 54 to 83% and CPA from 60 to 97%. Members of group AM1 showed a greater aflatoxin reduction than members of AM5 (72 versus 66%) but no differences were detected in CPA production. Here, we described for the first time atoxigenic isolates of A. flavus that show promise to be used as BCA in maize crops in Argentina. This innovating biological control approach should be considered, developed further, and used by the maize industry to preserve the quality properties and food safety of maize kernels in Argentina.Instituto de PatologĂa VegetalFil: Camiletti, B.X. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Instituto Multidisciplinario de BiologĂa Vegetal; Argentina.Fil: Camiletti, B.X. Universidad Nacional de CĂłrdoba. Facultad de Ciencias Agropecuarias; ArgentinaFil: Moral, Juan. University of CĂłrdoba. Campus de Rabanales. Departamento de AgronomĂa; EspañaFil: Moral, Juan. University of California. Kearney Agricultural Research and Extension Center; Estados UnidosFil: Asensio, Claudia M. Universidad Nacional de CĂłrdoba. Facultad de Ciencias Agropecuarias. QuĂmica BiolĂłgica; ArgentinaFil: Asensio, Claudia M. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Torrico Ramallo, Ada Karina. Instituto Nacional de TecnologĂa Agropecuaria (INTA). Instituto de PatologĂa Vegetal; ArgentinaFil: Lucini, Enrique I. Universidad Nacional de CĂłrdoba. Facultad de Ciencias Agropecuarias. MicrobiologĂa AgrĂcola; ArgentinaFil: Gimenez, Maria De La Paz. Instituto Nacional de TecnologĂa Agropecuaria (INTA). Instituto de PatologĂa Vegetal; ArgentinaFil: Michailides, Themis J. University of California. Kearney Agricultural Research and Extension Center; Estados Unido
Associations between taste perception profiles and empirically derived dietary patterns: an exploratory analysis among older adults with metabolic syndrome
Taste perception is a primary driver of food choices; however, little is known about how perception of all five tastes (sweet, salt, sour, bitter, umami) collectively inform dietary patterns. Our aim was to examine the associations between a multivariable measure of taste perceptionâtaste perception profilesâand empirically derived dietary patterns. The cohort included 367 community-dwelling adults (55â75 years; 55% female; BMI = 32.2 ± 3.6 kg/m2) with metabolic syndrome from PREDIMED-Plus, Valencia. Six taste perception profiles were previously derived via data-driven clustering (Low All, High Bitter, High Umami, Low Bitter and Umami, High All But Bitter, High All But Umami); three dietary patterns were derived via principal component analysis (% variance explained = 20.2). Cross-sectional associations between profiles and tertials of dietary pattern adherence were examined by multinomial logistic regression. Overall, there were several significant differences in dietary pattern adherence between profiles: the vegetables, fruits, and whole grains pattern was significantly more common for the High All But Umami profile (OR range for high vs. low adherence relative to other profiles (1.45â1.99; 95% CI minimum lower, maximum upper bounds: 1.05, 2.74), the non-extra virgin olive oils, sweets, and refined grains pattern tended to be less common for Low All or High Bitter profiles (OR range: 0.54â0.82), while the alcohol, salty foods, and animal fats pattern tended to be less common for Low Bitter and Umami and more common for High All But Bitter profiles (OR range: 0.55â0.75 and 1.11â1.81, respectively). In conclusion, among older adults with metabolic syndrome, taste perception profiles were differentially associated with dietary patterns, suggesting the benefit of integrating taste perception into personalized nutrition guidance
Magnetobiochronology of lower Pliocene marine sediments from the lower Guadalquivir Basin: insights into the tectonic evolution of the Strait of Gibraltar area
The Gibraltar Arc is a complex tectonic region, and several competing models have been proposed to explain its evolution. We studied the sedimentary fill of the Guadalquivir Basin to identify tectonic processes that were occurring when the reopening of the Strait of Gibraltar led to the reestablishment of Mediterranean outflow. We present a chronostratigraphic framework for the Lower Pliocene sediments from the lower Guadalquivir Basin (SW Spain). The updated chronology is based on magnetobiostratigraphic data from several boreholes. Our results show that the studied interval in the La Matilla core is in the early Pliocene section, providing better constraints on the sedimentary evolution of the basin during that period. Migrating depositional facies led to a younger onset of sandy deposition basinward. At the northwestern passive margin, a 0.7 m.y. period of sedimentary bypass related to a sharp decrease in sedimentation rates and lower sea levels resulted from the tectonic uplift of the forebulge. In contrast, high sedimentation rates with continuous deep-marine sedimentation are recorded at the basin center due to continuous tectonic subsidence and west-southwestward progradation of axial depositional systems. The marginal forebulge uplift, continuous tectonic basinal subsidence, and southward progradation of clinoforms in the early Pliocene can be explained by the pull of a lithospheric slab beneath the Gibraltar Arc as the Strait of Gibraltar opened. These findings are, to our knowledge, the first reported sedimentary expression of slab pull beneath the Betics related to the opening of the Strait of Gibraltar after the Messinian salinity crisis
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