Mechanisms of disruption of meristematic competence by microgravity in Arabidopsis seedlings

16 p.-2 fig.Experiments performed in actively proliferating plant cells both in space and simulated microgravity have evidenced a common effect: cell proliferation appears enhanced whereas cell growth is depleted. Coordination of cell growth and proliferation, called meristematic competence, is a major feature of meristematic cells and its disruption may lead to important alterations in the developmental pattern of the plant. Auxin is known to be a mediator of the transduction of the gravitropic signal and a regulator of the rates of growth and proliferation in meristematic cells, as well as of their further differentiation. Therefore, gravity sensing, gravitropism, auxin levels and meristematic competence are mutually interrelated. However, our experiments in simulated microgravity, using both mechanical and magnetic levitation technologies, have revealed that this interdependence is neither strict nor univocal and may include additional factors and mechanisms. Available data indicate that altered gravity may affect cell growth and proliferation by mechanisms alternative to the transduction of the gravitropic signal perceived by columella cells in the root tip. These mechanisms would include gravity sensing independent from statolith displacement and transduction mediators other than polar auxin transport.Work performed in the authors’ laboratory was supported by grants of the Spanish National Plan for Research and Development, Ref. Nos. AYA2010-11834-E, and AYA2012-33982 and by ESA Access to GBFs contract numbers 4200022650 & 4000105761. MAV was supported by the Spanish FPI Program (Ref. BES-2010-035741) and KY by the Spanish CSIC JAE-PreDoc Program (Ref. JAEPre_2010_01894).Peer reviewe

Electronic structure of titanylphthalocyanine layers on Ag(111)

We have investigated the electronic structures of axially oxo functionalized titanylphthalocyanine (TiOPc) on Ag(111) by X-ray and ultraviolet photoelectron spectroscopies, two-photon photoemission, X-ray absorption spectroscopy, and X-ray magnetic circular dichroism. Furthermore, we use complementary data of TiOPc on graphite and planar copper phthalocyanine (CuPc) on Ag(111) for a comparative analysis. Both molecules adsorb on Ag(111) in a parallel orientation to the surface, for TiOPc with an oxygen-up configuration. The interaction of nitrogen and carbon atoms with the substrate is similar for both molecules, while the bonding of the titanium atom to Ag(111) in the monolayer is found to be slightly more pronounced than in the CuPc case. Ultraviolet photoemission spectroscopy reveals an occupation of the lowest unoccupied molecular orbital (LUMO) level in monolayer thick TiOPc on Ag(111) related to the interaction of the molecules and the silver substrate. This molecule-metal interaction also causes an upward shift of the Ag(111) Shockley state that is transformed into an unoccupied interface state with energies of 0.23 and 0.33 eV for the TiOPc monolayer and bilayer, respectively, at the Brillouin zone center.The authors acknowledge financial support from the Deutsche Forschungsgemeinschaft through SFB 1083 “Structure and Dynamics of Internal Interfaces”, the Spanish CSIC I-Link programm, the Spanish Ministry of Economy and Competitiveness, MINECO (under Contract No. MAT2016-78293-C6-2-R, and Severo Ochoa No. SEV-2013-0295.), and by the Secretariat for Universities and Research, Knowledge Department of the Generalitat de Catalunya (2014 SGR 715). M. Paradinas thanks the Spanish Government for financial support through PTA2014-09788-I fellowships. ICN2 is funded by the CERCA Programme/Generalitat de Catalunya.Peer Reviewe

Electronic Structure of Titanylphthalocyanine Layers on Ag(111)

We have investigated the electronic structures of axially oxo functionalized titanylphthalocyanine (TiOPc) on Ag(111) by X-ray and ultraviolet photoelectron spectroscopies, two-photon photoemission, X-ray absorption spectroscopy, and X-ray magnetic circular dichroism. Furthermore, we use complementary data of TiOPc on graphite and planar copper phthalocyanine (CuPc) on Ag(111) for a comparative analysis. Both molecules adsorb on Ag(111) in a parallel orientation to the surface, for TiOPc with an oxygen-up configuration. The interaction of nitrogen and carbon atoms with the substrate is similar for both molecules, while the bonding of the titanium atom to Ag(111) in the monolayer is found to be slightly more pronounced than in the CuPc case. Ultraviolet photoemission spectroscopy reveals an occupation of the lowest unoccupied molecular orbital (LUMO) level in monolayer thick TiOPc on Ag(111) related to the interaction of the molecules and the silver substrate. This molecule-metal interaction also causes an upward shift of the Ag(111) Shockley state that is transformed into an unoccupied interface state with energies of 0.23 and 0.33 eV for the TiOPc monolayer and bilayer, respectively, at the Brillouin zone center

Tuning the Magnetic Anisotropy of Lanthanides on a Metal Substrate by Metal–Organic Coordination

Taming the magnetic anisotropy of lanthanides through coordination environments is crucial to take advantage of the lanthanides properties in thermally robust nanomaterials. In this work, the electronic and magnetic properties of Dy-carboxylate metal–organic networks on Cu(111) based on an eightfold coordination between Dy and ditopic linkers are inspected. This surface science study based on scanning probe microscopy and X-ray magnetic circular dichroism, complemented with density functional theory and multiplet calculations, reveals that the magnetic anisotropy landscape of the system is complex. Surface-supported metal–organic coordination is able to induce a change in the orientation of the easy magnetization axis of the Dy coordinative centers as compared to isolated Dy atoms and Dy clusters, and significantly increases the magnetic anisotropy. Surprisingly, Dy atoms coordinated in the metallosupramolecular networks display a nearly in-plane easy magnetization axis despite the out-of-plane symmetry axis of the coordinative molecular lattice. Multiplet calculations highlight the decisive role of the metal–organic coordination, revealing that the tilted orientation is the result of a very delicate balance between the interaction of Dy with O atoms and the precise geometry of the crystal field. This study opens new avenues to tailor the magnetic anisotropy and magnetic moments of lanthanide elements on surfaces.The ALBA synchrotron is acknowledged for providing beam time at BOREAS beamline (proposal number 2015091454). This project has received funding from the European Research Council (ERC, grant 766555) and Marie Sklodowska-Curie Actions (MSCA, project 894924) under the European Union's Horizon 2020 research and innovation programme. This work has been financed by the Spanish Ministerio de Economía, Industria y Competitividad (projects FIS2016-78591-C3-1-R, RTI2018-097895-B-C42, MAT2016-78293-C6-2-R, MAT2017-85089-C2-1-R, and PID2019-107338RB-C65); the Comunidad de Madrid (Projects S2013/MIT-2850, P2018/NMT4321, and S2018/NMT-4367); the European Regional Development Fund (ERDF) under the program Interreg V-A España-Francia-Andorra (Contract No. EFA 194/16 TNSI); and “Severo Ochoa” Programme for Centres of Excellence in R&D (grants SEV-2016-0686, and SEV-2017-0706)

Experimental demonstration of a magnetically induced warping transition in a topological insulator mediated by rare-earth surface dopants

Magnetic topological insulators (MTI) constitute a novel class of materials where the topologically protected band structure coexists with long-range ferromagnetic order, which can lead to the breaking of time-reversal symmetry (TRS), introducing a bandgap in the Dirac cone-shaped topological surface state (TSS). The gap opening in MITs has been predicted to be accompanied by a distortion in the TSS, evolving its warped shape from hexagonal to trigonal. In this work, we demonstrate such a transition by means of angle-resolved photoemission spectroscopy after the deposition of low concentrations of magnetic rare earths, namely Er and Dy, on the ternary three-dimensional prototypical topological insulator Bi$_2$Se$_2$Te. Signatures of the gap opening occurring as a consequence of the TRS breaking have also been observed, whose existence is supported by the observation of the aforementioned transition. Moreover, increasing the Er coverage results in a tunable p-type doping of the TSS. As a consequence, the Fermi level (E$_{\textrm{F}}$) of our Bi$_2$Se$_2$Te crystals can be gradually tuned towards the TSS Dirac point, and therefore to the magnetically induced bandgap; thus fulfilling two of the necessary prerequisites for the realization of the quantum anomalous Hall effect (QAHE) in this system. The experimental results are rationalized by a theoretical model where a magnetic Zeeman out-of-plane term is introduced in the hamiltonian governing the TSS band dispersion. Our results offer new strategies to control magnetic interactions with TSSs based on a simple approach and open up viable routes for the realization of the QAHE

Engineering periodic dinuclear lanthanide-directed networks featuring tunable energy level alignment and magnetic anisotropy by metal exchange

The design of lanthanide multinuclear networks is an emerging field of research due to the potential of such materials for nanomagnetism, spintronics, and quantum information. Therefore, controlling their electronic and magnetic properties is of paramount importance to tailor the envisioned functionalities. In this work, a multidisciplinary study is presented combining scanning tunneling microscopy, scanning tunneling spectroscopy, X-ray absorption spectroscopy, X-ray linear dichroism, X-ray magnetic circular dichroism, density functional theory, and multiplet calculations, about the supramolecular assembly, electronic and magnetic properties of periodic dinuclear 2D networks based on lanthanide-pyridyl interactions on Au(111). Er- and Dy-directed assemblies feature identical structural architectures stabilized by metal–organic coordination. Notably, despite exhibiting the same +3 oxidation state, there is a shift of the energy level alignment of the unoccupied molecular orbitals between Er- and Dy-directed networks. In addition, there is a reorientation of the easy axis of magnetization and an increment of the magnetic anisotropy when the metallic center is changed from Er to Dy. Thus, the results show that it is feasible to tune the energy level alignment and magnetic anisotropy of a lanthanide-based metal-organic architecture by metal exchange, while preserving the network desig

Infant Formula Supplemented With Milk Fat Globule Membrane, Long-Chain Polyunsaturated Fatty Acids, and Synbiotics Is Associated With Neurocognitive Function and Brain Structure of Healthy Children Aged 6 Years: The COGNIS Study

Background: Adequate nutrient intake during the first few months of life plays a critical role on brain structure and function development. Objectives: To analyze the long-term effects of an experimental infant formula (EF) on neurocognitive function and brain structure in healthy children aged 6 years compared to those fed with a standard infant formula or breastfed. Methods: The current study involved 108 healthy children aged 6 years and participating in the COGNIS Study. At 0-2 months, infants were randomized to receive up to 18 months of life a standard infant formula (SF) or EF enriched with milk fat globule membrane (MFGM), long-chain polyunsaturated fatty acids (LC-PUFAs) and synbiotics. Furthermore, a reference group of breastfed (BF) infants were also recruited. Children were assessed using neurocognitive tests and structural Magnetic Resonance Imaging (MRI) at 6 years old. Results: Experimental infant formula (EF) children showed greater volumes in the left orbital cortex, higher vocabulary scores and IQ, and better performance in an attention task than BF children. EF children also presented greater volumes in parietal regions than SF kids. Additionally, greater cortical thickness in the insular, parietal, and temporal areas were found in children from the EF group than those fed with SF or BF groups. Further correlation analyses suggest that higher volumes and cortical thickness of different parietal and frontal regions are associated with better cognitive development in terms of language (verbal comprehension) and executive function (working memory). Finally, arachidonic acid (ARA), adrenic acid (AdA), docosahexaenoic acid (DHA) levels in cheek cell glycerophospholipids, ARA/DHA ratio, and protein, fatty acid, and mineral intake during the first 18 months of life seem to be associated with changes in the brain structures at 6 years old. Conclusions: Supplemented infant formula with MFGM components, LC-PUFAs, and synbiotics seems to be associated to long-term effects on neurocognitive development and brain structure in children at 6 years old.This project has been funded by Laboratorios Ordesa, S.L. Contract University of Granada General Foundation, No. 3349 and SMARTFOODS (CIEN) Contract University of Granada General Foundation, No. 4003, Spanish Ministry of Economy, Industry and Competitiveness. Furthermore, the project has been partially funded by HORIZON 2020 EU DynaHEALTH Project (GA No. 633595).S

Slow Magnetic Relaxation of Dy Adatoms with In-Plane Magnetic Anisotropy on a Two-Dimensional Electron Gas

We report on the magnetic properties of Dy atoms adsorbed on the (001) surface of SrTiO3. X-ray magnetic circular dichroism reveals slow relaxation of the Dy magnetization on a time scale of about 800 s at 2.5 K, unusually associated with an easy-plane magnetic anisotropy. We attribute these properties to Dy atoms occupying hollow adsorption sites on the TiO2-terminated surface. Conversely, Ho atoms adsorbed on the same surface show paramagnetic behavior down to 2.5 K. With the help of atomic multiplet simulations and first-principles calculations, we establish that Dy populates also the top-O and bridge sites on the coexisting SrO-terminated surface. A simple magnetization relaxation model predicts these two sites to have an even longer magnetization lifetime than the hollow site. Moreover, the adsorption of Dy on the insulating SrTiO3 crystal leads, regardless of the surface termination, to the formation of a spin-polarized two-dimensional electron gas of Ti 3dxy character, together with an antiferromagnetic Dy-Ti coupling. Our findings support the feasibility of tuning the magnetic properties of the rare-earth atoms by acting on the substrate electronic gas with electric fields.We acknowldege funding from the National Research Council (CNR) within the CNR/CAS Cooperative Programme project "Advanced characterization methods for the study of rare-earth single-ion magnets on oxide substrates", from the Czech Academy of Sciences (Mobility Plus Project No. CNR-19-03), and from the Swiss National Science Foundation (200020_176932 and 200021_175941). ICN2 was funded by the CERCA Programme/Generalitat de Catalunya and supported by the Spanish Ministry of Economy and Competitiveness, MINECO (grant nos. SEV-2017-0706 and PID2019-107338RB-C65/AEI/10.13039/501100011033). IMDEA Nanociencia acknowledges support from the Severo Ochoa Programme for Centres of Excellence in R&D (MINECO, grant SEV-2016-0686).Peer reviewe

The RNA Binding Protein Csx1 Promotes Sexual Differentiation in Schizosaccharomyces pombe

Sexual differentiation is a highly regulated process in the fission yeast Schizosaccharomyces pombe and is triggered by nutrient depletion, mainly nitrogen source