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1.
ACS Appl Mater Interfaces ; 16(15): 19681-19690, 2024 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-38564236

RESUMO

Swirling spin textures, including topologically nontrivial states, such as skyrmions, chiral domain walls, and magnetic vortices, have garnered significant attention within the scientific community due to their appeal from both fundamental and applied points of view. However, their creation, controlled manipulation, and stability are typically constrained to certain systems with specific crystallographic symmetries, bulk or interface interactions, and/or a precise stacking sequence of materials. Recently, a new approach has shown potential for the imprint of magnetic radial vortices in soft ferromagnetic compounds making use of the stray field of YBa2Cu3O7-δ superconducting microstructures in ferromagnet/superconductor (FM/SC) hybrids at temperatures below the superconducting transition temperature (TC). Here, we explore the lower size limit for the imprint of magnetic radial vortices in square and disc shaped structures as well as the persistence of these spin textures above TC, with magnetic domains retaining partial memory. Structures with circular geometry and with FM patterned to smaller radius than the superconductor island facilitate the imprinting of magnetic radial vortices and improve their stability above TC, in contrast to square structures where the presence of magnetic domains increases the dipolar energy. Micromagnetic modeling coupled with a SC field model reveals that the stabilization mechanism above TC is mediated by microstructural defects. Superconducting control of swirling spin textures, and their stabilization above the superconducting transition temperature by means of defect engineering holds promising prospects for shaping superconducting spintronics based on magnetic textures.

2.
Phys Rev Lett ; 132(6): 066001, 2024 Feb 09.
Artigo em Inglês | MEDLINE | ID: mdl-38394577

RESUMO

The normal-state conductivity and superconducting critical temperature of oxygen-deficient YBa_{2}Cu_{3}O_{7-δ} can be persistently enhanced by illumination. Strongly debated for years, the origin of those effects-termed persistent photoconductivity and photosuperconductivity (PPS)-has remained an unsolved critical problem, whose comprehension may provide key insights to harness the origin of high-temperature superconductivity itself. Here, we make essential steps toward understanding PPS. While the models proposed so far assume that it is caused by a carrier-density increase (photodoping) observed concomitantly, our experiments contradict such conventional belief: we demonstrate that it is instead linked to a photo-induced decrease of the electronic scattering rate. Furthermore, we find that the latter effect and photodoping are completely disconnected and originate from different microscopic mechanisms, since they present different wavelength and oxygen-content dependences as well as strikingly different relaxation dynamics. Besides helping disentangle photodoping, persistent photoconductivity, and PPS, our results provide new evidence for the intimate relation between critical temperature and scattering rate, a key ingredient in modern theories on high-temperature superconductivity.

3.
Nat Commun ; 14(1): 3010, 2023 May 25.
Artigo em Inglês | MEDLINE | ID: mdl-37230971

RESUMO

Memristors, a cornerstone for neuromorphic electronics, respond to the history of electrical stimuli by varying their electrical resistance across a continuum of states. Much effort has been recently devoted to developing an analogous response to optical excitation. Here we realize a novel tunnelling photo-memristor whose behaviour is bimodal: its resistance is determined by the dual electrical-optical history. This is obtained in a device of ultimate simplicity: an interface between a high-temperature superconductor and a transparent semiconductor. The exploited mechanism is a reversible nanoscale redox reaction between both materials, whose oxygen content determines the electron tunnelling rate across their interface. The redox reaction is optically driven via an interplay between electrochemistry, photovoltaic effects and photo-assisted ion migration. Besides their fundamental interest, the unveiled electro-optic memory effects have considerable technological potential. Especially in combination with high-temperature superconductivity which, in addition to facilitating low-dissipation connectivity, brings photo-memristive effects to the realm of superconducting electronics.

4.
Adv Mater ; 35(33): e2211176, 2023 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-37046341

RESUMO

Generation, manipulation, and sensing of magnetic domain walls are cornerstones in the design of efficient spintronic devices. Half-metals are amenable for this purpose as large low field magnetoresistance signals can be expected from spin accumulation at spin textures. Among half metals, La1- x Srx MnO3 (LSMO) manganites are considered as promising candidates for their robust half-metallic ground state, Curie temperature above room temperature (Tc = 360 K, for x = 1/3), and chemical stability. Yet domain wall magnetoresistance is poorly understood, with large discrepancies in the reported values and conflicting interpretation of experimental data due to the entanglement of various source of magnetoresistance, namely, spin accumulation, anisotropic magnetoresistance, and colossal magnetoresistance. In this work, the domain wall magnetoresistance is measured in LSMO cross-shape nanowires with single-domain walls nucleated across the current path. Magnetoresistance values above 10% are found to be originating at the spin accumulation caused by the mistracking effect of the spin texture of the domain wall by the conduction electrons. Fundamentally, this result shows the importance on non-adiabatic processes at spin textures despite the strong Hund coupling to the localized t2g electrons of the manganite. These large magnetoresistance values are high enough for encoding and reading magnetic bits in future oxide spintronic sensors.

5.
Can J Microbiol ; 69(5): 185-198, 2023 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-36753728

RESUMO

Dimorphic species of Mucor, which are cosmopolitan fungi belonging to subphylum Mucoromycotina, are metabolically versatile. Some species of Mucor are sources of biotechnological products, such as biodiesel from Mucor circinelloides and expression of heterologous proteins from Mucor lusitanicus. Furthermore, Mucor lusitanicus has been described as a model for understanding mucormycosis infections. However, little is known regarding the relationship between Mucor lusitanicus and other soil inhabitants. In this study, we investigated the potential use of Mucor lusitanicus as a biocontrol agent against fungal phytopathogens, namely Fusarium oxysporum f. sp. lycopersici, Fusarium solani, and Alternaria solani, which destroy economically important crops. Results showed that aerobic cell-free supernatants of the culture broth (SS) from Mucor lusitanicus inhibited the growth of the fungal phytopathogens in culture, soil, and tomato fruits. The SS obtained from a strain of Mucor lusitanicus carrying the deletion of rfs gene, which encodes an enzyme involved in the synthesis of siderophore rhizoferrin, had a decreased inhibitory effect against the growth of the phytopathogens. Contrarily, this inhibitory effect was more evident with the SS from an rfs-overexpressing strain compared to the wild-type. This study provides a framework for the potential biotechnological use of the molecules secreted from Mucor lusitanicus in the biocontrol of fungal phytopathogens.


Assuntos
Mucor , Mucormicose , Mucor/genética , Sideróforos , Mucormicose/microbiologia , Doenças das Plantas
6.
Microb Ecol ; 86(1): 727-741, 2023 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-35948833

RESUMO

Pseudomonas aeruginosa is an opportunistic pathogenic bacterium for humans, animals, and plants, through producing different molecular factors such as biofilm, siderophores, and other virulence factors which favor bacterial establishment and infection in the host. In P. aeruginosa PAO1, the production of these factors is regulated by the bacterial quorum sensing (QS) mechanisms. From them, siderophores are involved in iron acquisition, transport, and homeostasis. They are also considered some of the main virulence factors in P. aeruginosa; however, detailed mechanisms to induce bacterial pathogenesis are poorly understood. In this work, through reverse genetics, we evaluated the function of bacterial pathogenesis in the pvd cluster genes, which are required for synthesizing the siderophore pyoverdine (PVD). Single pvdI, pvdJ, pvdL, and double mutant strains were analyzed, and contrary to expected, the pvdL and pvdI mutations increased the concentration of PVD and other phenazines, such as pyocyanin (PYO) and phenazine-1-carboxylic acid (PCA) and also an increased biofilm production and morphology depending on the autoinducer 2-alkyl-4-quinolone (PQS) and the QS molecules acyl-homoserine lactones. Consequently, in the in vivo pathogenicity model of Caenorhabditis elegans, the mutations in pvdI, pvdJ, and pvdL increased the survival of the worms exposed to supernatants or biofilms of the bacterial cultures. However, the double mutant pvdI/pvdJ increased its toxicity in agreeing with the biofilm production, PVD, PYO, and PCA. The findings indicate that the mutations in pvd genes encode non-ribosomal peptide synthetases impacted the biofilm's structure, but suppressively also of the phenazines, confirming that the siderophores contribute to the bacterial establishment and pathogenicity of P. aeruginosa PAO1.


Assuntos
Percepção de Quorum , Sideróforos , Humanos , Animais , Pseudomonas aeruginosa/genética , Piocianina , Biofilmes , Fatores de Virulência/genética , Fenazinas , Proteínas de Bactérias/genética
7.
Metas enferm ; 25(10): 14-22, dic. 2022. tab
Artigo em Espanhol | IBECS | ID: ibc-213281

RESUMO

Objetivo: describir la percepción actual que tiene la sociedad sobre la Enfermería y conocer cómo ha variado la representación de la profesión enfermera en el imaginario social con la situación de emergencia sanitaria de COVID-19. Método: estudio descriptivo transversal en población general y en profesionales sanitarios, captados a través de muestreo no probabilístico (el tamaño muestral alcanzado, n= 1.109, arrojó una precisión absoluta de 2,94%), a través de un cuestionario diseñado ad hoc. Resultados: la Enfermería fue considerada una profesión dedicada al cuidado e imprescindible dentro de la sanidad (83,7%), pero poco reconocida socialmente (53,8%), mal remunerada (48,4%) y percibida como profesión de riesgo (93,3%). A sus profesionales se les atribuía formación de grado universitario (84,8%) y su cualidad más destacable era el conocimiento (85,2%). El estereotipo mayoritario era el de una mujer (92,8%), de mediana edad (53,9%), que vestía “pijama” sanitario (85,3%). El 52,4% creía que la pandemia de COVID-19 había cambiado su percepción de la Enfermería; a sus profesionales les reconocían su relevancia, valorando su desempeño positivamente, inspirándoles sentimientos de admiración y respeto. Conclusiones: la Enfermería ha sido considerada una profesión dedicada al cuidado e imprescindible dentro de la sanidad, pero poco reconocida socialmente, mal remunerada y percibida como profesión de riesgo. La experiencia de emergencia sanitaria ha dado visibilidad a los cuidados enfermeros. La pandemia COVID-19 ha influido positivamente en la imagen social de la Enfermería, revalorizándola como profesión.(AU)


Objective: to describe the current perception of Nursing by society, and to understand how the representation of the Nursing profession in the social consciousness has changed with the healthcare emergency scenario of COVID-19. Method: a descriptive cross-sectional study in the overall population and healthcare professionals, recruited through non-probabilistic sampling (the sample size achieved, n= 1.109, delivered absolute accuracy of 2,94%), through a questionnaire designed ad hoc. Results: Nursing was considered a profession devoted to care and essential within the healthcare system (83.7%), but with low social recognition (53.8%), underpaid (48.4%) and perceived as a high-risk profession (93.3%). These professionals were considered to have university degree education (84.8%), and their most outstanding quality was knowledge (85.2%). The stereotype profile was a woman (92.8%), middle-aged (53.9%), wearing sanitary “pyjamas” (85.3%). 52.4% of the sample believed that the COVID-19 pandemic had changed their perception of Nursing; the importance of these professionals was acknowledged, and their performance was valued positively, inspiring feelings of admiration and respect towards them. Conclusions: Nursing has been considered a profession devoted to care and essential within the healthcare system, but with low social recognition, underpaid, and perceived as a high-risk profession. The healthcare emergency experience has given visibility to nursing care. There has been a positive impact by the COVID-19 pandemic upon the social image of Nursing, revaluing it as a profession.(AU)


Assuntos
Humanos , Masculino , Feminino , Percepção Social , Enfermagem , Pandemias , Infecções por Coronavirus , Opinião Pública , Epidemiologia Descritiva , Estudos Transversais
8.
Adv Sci (Weinh) ; 9(27): e2201753, 2022 09.
Artigo em Inglês | MEDLINE | ID: mdl-35901494

RESUMO

Resistive switching effects offer new opportunities in the field of conventional memories as well as in the booming area of neuromorphic computing. Here the authors demonstrate memristive switching effects produced by a redox-driven oxygen exchange in tunnel junctions based on NdNiO3 , a strongly correlated electron system characterized by the presence of a metal-to-insulator transition (MIT). Strikingly, a strong interplay exists between the MIT and the redox mechanism, which on the one hand modifies the MIT itself, and on the other hand radically affects the tunnel resistance switching and the resistance states' lifetime. That results in a very unique temperature behavior and endows the junctions with multiple degrees of freedom. The obtained results bring up fundamental questions on the interplay between electronic correlations and the creation and mobility of oxygen vacancies in nickelates, opening a new avenue toward mimicking neuromorphic functions by exploiting the electric-field control of correlated states.


Assuntos
Elétrons , Oxigênio , Eletrônica , Metais
9.
J Plant Physiol ; 275: 153738, 2022 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-35690030

RESUMO

Plants being sessile organisms are exposed to various biotic and abiotic factors, thus causing stress. The Pseudomonas aeruginosa bacterium is an opportunistic pathogen for animals, insects, and plants. Direct exposure of Arabidopsis thaliana to the P. aeruginosa PAO1 strain induces plant death by producing a wide variety of virulence factors, which are regulated mainly by quorum sensing systems. Besides virulence factors, P. aeruginosa PAO1 also produces cyclodipeptides (CDPs), which possess auxin-like activity and promote plant growth through activation of the target of the rapamycin (AtTOR) pathway. On the other hand, plant defense mechanisms are regulated through the production of phytohormones, such as salicylic acid (SA) and jasmonic acid (JA), which are induced in response to pathogen-associated molecular patterns (PAMPs), activating defense genes associated with SA and JA such as PATHOGENESIS-RELATED-1 (PR-1) and LIPOXYGENASE2 (LOX2), respectively. PR proteins are suggested to play critical roles in coordinating the Systemic Acquired Resistance (SAR). In contrast, LOX proteins (LOX2, LOX3, and LOX4) have been associated with the production of JA by producing its precursors, oxylipins. The activation of defense mechanisms involves signaling cascades such as Mitogen-Activated Protein Kinases (MAPKs) or the TOR pathway as a switch for re-directing energy towards defense or growth. In this work, we challenged A. thaliana (wild type, mpk6 or mpk3 mutants, and overexpressing TOR) seedlings with P. aeruginosa PAO1 strains to identify the role of bacterial CDPs in the plant immune response. Results showed that the pre-exposure of these Arabidopsis seedlings to CDPs significantly reduced plant infection of the pathogenic P. aeruginosa PAO1 strains, indicating that plants that over-express AtTOR or lack MPK3/MPK6 protein-kinases are more susceptible to the pathogenic effects. In addition, CDPs induced the GUS activity only in the LOX2::GUS plants, indicative of JA-signaling activation. Our findings indicate that the CDPs are molecules that trigger SA-independent and JA-dependent defense responses in A. thaliana; hence, bacterial CDPs may be considered elicitors of the Arabidopsis immune response to pathogens.


Assuntos
Proteínas de Arabidopsis , Arabidopsis , Animais , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Ciclopentanos/metabolismo , Imunidade , Oxilipinas/metabolismo , Desenvolvimento Vegetal , Doenças das Plantas/microbiologia , Pseudomonas aeruginosa , Ácido Salicílico/metabolismo , Fatores de Virulência/metabolismo , Fatores de Virulência/farmacologia
10.
Nat Mater ; 21(2): 188-194, 2022 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-34857910

RESUMO

The Josephson effect results from the coupling of two superconductors across a spacer such as an insulator, a normal metal or a ferromagnet to yield a phase coherent quantum state. However, in junctions with ferromagnetic spacers, very long-range Josephson effects have remained elusive. Here we demonstrate extremely long-range (micrometric) high-temperature (tens of kelvins) Josephson coupling across the half-metallic manganite La0.7Sr0.3MnO3 combined with the superconducting cuprate YBa2Cu3O7. These planar junctions, in addition to large critical currents, display the hallmarks of Josephson physics, such as critical current oscillations driven by magnetic flux quantization and quantum phase locking effects under microwave excitation (Shapiro steps). The latter display an anomalous doubling of the Josephson frequency predicted by several theories. In addition to its fundamental interest, the marriage between high-temperature, dissipationless quantum coherent transport and full spin polarization brings opportunities for the practical realization of superconducting spintronics, and opens new perspectives for quantum computing.

11.
Front Microbiol ; 12: 785112, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34867927

RESUMO

The pathogenic bacterium Pseudomonas aeruginosa possesses high metabolic versatility, with its effectiveness to cause infections likely due to its well-regulated genetic content. P. aeruginosa PAO1 has at least six fadD paralogous genes, which have been implicated in fatty acid (FA) degradation and pathogenicity. In this study, we used mutagenesis and a functional approach in P. aeruginosa PAO1 to determine the roles of the fadD4 gene in acyclic terpene (AT) and FA assimilation and on pathogenicity. The results indicate that fadD4 encodes a terpenoyl-CoA synthetase utilized for AT and FA assimilation. Additionally, mutations in fadD paralogs led to the modification of the quorum-sensing las/rhl systems, as well as the content of virulence factors pyocyanin, biofilm, rhamnolipids, lipopolysaccharides (LPS), and polyhydroxyalkanoates. In a Caenorhabditis elegans in vivo pathogenicity model, culture supernatants from the 24-h-grown fadD4 single mutant increased lethality compared to the PAO1 wild-type (WT) strain; however, the double mutants fadD1/fadD2, fadD1/fadD4, and fadD2/fadD4 and single mutant fadD2 increased worm survival. A correlation analysis indicated an interaction between worm death by the PAO1 strain, the fadD4 mutation, and the virulence factor LPS. Fatty acid methyl ester (FAME) analysis of LPS revealed that a proportion of the LPS and FA on lipid A were modified by the fadD4 mutation, suggesting that FadD4 is also involved in the synthesis/degradation and modification of the lipid A component of LPS. LPS isolated from the fadD4 mutant and double mutants fadD1/fadD4 and fadD2/fadD4 showed a differential behavior to induce an increase in body temperature in rats injected with LPS compared to the WT strain or from the fadD1 and fadD2 mutants. In agreement, LPS isolated from the fadD4 mutant and double mutants fadD1/fadD2 and fadD2/fadD4 increased the induction of IL-8 in rat sera, but IL1-ß cytokine levels decreased in the double mutants fadD1/fadD2 and fadD1/fadD4. The results indicate that the fadD genes are implicated in the degree of pathogenicity of P. aeruginosa PAO1 induced by LPS-lipid A, suggesting that FadD4 contributes to the removal of acyl-linked FA from LPS, rendering modification in its immunogenic response associated to Toll-like receptor TLR4. The genetic redundancy of fadD is important for bacterial adaptability and pathogenicity over the host.

12.
3 Biotech ; 11(7): 311, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-34109096

RESUMO

Mucor circinelloides is a fungus that produces diverse spores throughout its life cycle. The sporangiospores, which are the most well-studied spores in this fungus, are asexual spores produced during aerial mycelial development. M. circinelloides has the potential to be used in diverse biotechnological applications. In this study, we propose rice (Oryza sativa) grains as an alternative substrate for inexpensive and large-scale sporangiospore production. The sporangiospores produced from rice and a yeast extract-peptone-glucose (YPG) medium exhibited similar protein and nucleic acid contents and phenotypes in terms of germination under different conditions and culture media, including similar virulence rates against the nematode Caenorhabditis elegans. Transgenic strains carrying self-replicative plasmids were sporulated on rice and showed plasmid stability similar to that of spores produced on the YPG medium. Approximately 20% of the spore population lost plasmids after the first passage on rice. These results reveal that rice is a suitable substrate for the mass production of sporangiospores in M. circinelloides. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13205-021-02853-1.

13.
Nat Commun ; 12(1): 3283, 2021 Jun 02.
Artigo em Inglês | MEDLINE | ID: mdl-34078889

RESUMO

The anomalous Hall effect (AHE) is an intriguing transport phenomenon occurring typically in ferromagnets as a consequence of broken time reversal symmetry and spin-orbit interaction. It can be caused by two microscopically distinct mechanisms, namely, by skew or side-jump scattering due to chiral features of the disorder scattering, or by an intrinsic contribution directly linked to the topological properties of the Bloch states. Here we show that the AHE can be artificially engineered in materials in which it is originally absent by combining the effects of symmetry breaking, spin orbit interaction and proximity-induced magnetism. In particular, we find a strikingly large AHE that emerges at the interface between a ferromagnetic manganite (La0.7Sr0.3MnO3) and a semimetallic iridate (SrIrO3). It is intrinsic and originates in the proximity-induced magnetism present in the narrow bands of strong spin-orbit coupling material SrIrO3, which yields values of anomalous Hall conductivity and Hall angle as high as those observed in bulk transition-metal ferromagnets. These results demonstrate the interplay between correlated electron physics and topological phenomena at interfaces between 3d ferromagnets and strong spin-orbit coupling 5d oxides and trace an exciting path towards future topological spintronics at oxide interfaces.

14.
PeerJ ; 9: e11127, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33850658

RESUMO

Multi-walled carbon nanotubes (MWCNTs) are of multidisciplinary scientific interest due to their exceptional physicochemical properties and a broad range of applications. However, they are considered potentially toxic nanoparticles when they accumulate in the environment. Given their ability to oxidize resistant polymers, mycorremediation with lignocellulolytic fungi are suggested as biological alternatives to the mineralization of MWCNTs. Hence, this study involves the ability of two fungi specie to MWCNTs biotransformation by laccase and peroxidases induction and evaluation in vivo of its toxicity using Caenorhabditis elegans worms as a model. Results showed that the fungi Penicillium chrysogenum and Pleurotus ostreatus were capable to grow on media with MWCNTs supplemented with glucose or lignin. Activities of lignin-peroxidase, manganese-peroxidase, and laccase in cultures of both fungi were induced by MWCNTs. Raman, FTIR spectroscopy, HR-TEM, and TGA analyses of the residue from the cultures of both fungi revealed structural modifications on the surface of MWCNTs and its amount diminished, correlating the MWCNTs structural modifications with the laccase-peroxidase activities in the fungal cultures. Results indicate that the degree of toxicity of MWCNTs on the C. elegans model was enhanced by the structure modification associated with the fungal ligninolytic activity. The toxic effect of MWCNTs on the in vivo model of worms reveals the increment of reactive oxygen species as a mechanism of toxicity. Findings indicate that the MWCNTs can be subject in nature to biotransformation processes such as the fungal metabolism, which contribute to modify their toxicity properties on susceptible organisms and contributing to environmental elimination.

15.
Sensors (Basel) ; 21(4)2021 Feb 22.
Artigo em Inglês | MEDLINE | ID: mdl-33671504

RESUMO

Recent years have seen the proliferation of different techniques for outdoor and, especially, indoor positioning. Still being a field in development, localization is expected to be fully pervasive in the next few years. Although the development of such techniques is driven by the commercialization of location-based services (e.g., navigation), its application to support cellular management is considered to be a key approach for improving its resilience and performance. When different approaches have been defined for integrating location information into the failure management activities, they commonly ignore the increase in the dimensionality of the data as well as their integration into the complete flow of networks failure management. Taking this into account, the present work proposes a complete integrated approach for location-aware failure management, covering the gathering of network and positioning data, the generation of metrics, the reduction in the dimensionality of such data, and the application of inference mechanisms. The proposed scheme is then evaluated by system-level simulation in ultra-dense scenarios, showing the capabilities of the approach to increase the reliability of the supported diagnosis process as well as reducing its computational cost.

16.
Phys Rev Lett ; 125(8): 087002, 2020 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-32909764

RESUMO

Recent experiments have shown that proximity with high-temperature superconductors induces unconventional superconducting correlations in graphene. Here, we demonstrate that those correlations propagate hundreds of nanometers, allowing for the unique observation of d-wave Andreev-pair interferences in YBa_{2}Cu_{3}O_{7}-graphene devices that behave as a Fabry-Perot cavity. The interferences show as a series of pronounced conductance oscillations analogous to those originally predicted by de Gennes-Saint-James for conventional metal-superconductor junctions. The present demonstration is pivotal to the study of exotic directional effects expected for nodal superconductivity in Dirac materials.

17.
PeerJ ; 8: e8634, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32351779

RESUMO

BACKGROUND: Multi-walled carbon nanotubes (MWCNTs) are nanoparticles with countless applications. MWCNTs are typically of synthetic origin. However, recently, the formation of MWCNTs in nature after forest fires has been documented. Previous reports have demonstrated the positive effects of synthetic MWCNTs on the germination and development of species of agronomic interest; nevertheless, there is practically no information on how synthetic or natural MWCNTs affect forest plant development. In this report, based on insights from dose-response assays, we elucidate the comparative effects of synthetic MWCNTs, amorphous carbon, and natural MWCNTs obtained after a forest fire on Eysenhardtia polystachya plant. METHODS: E. polystachya seeds were sown in peat moss-agrolite substrate and conserved in a shade house. Germination was recorded daily up to 17 days after sowing, and plant development (manifested in shoot and root length, stem diameter, foliar area, and root architecture parameters) was recorded 60 days after sowing. RESULTS: The treatments with natural MWCNTs accelerated the emergence and improved the germination of this plant, thus while untreated seeds achieve 100% of germination within 16th day, seeds supplemented with natural MWCNTs at doses of 20 µg/mL achieve the above percentage within the 4th day. Natural MWCNTs also promoted fresh and dry biomass in all applied treatments, specially at doses of 40 µg/mL where natural MWCNTs significantly promoted leaf number, root growth, and the dry and fresh weights of shoots and roots of seedlings. Seeds supplemented with doses between 20 and 40 µg/mL of amorphous carbon achieving 100% of germination within the 6th day; however, seeds supplemented either with doses of 60 µg/mL of the above carbon or with synthetic MWCNTs at all the tested concentrations could achieve at most 80 % and 70% of germination respectively within the 17 days. Finally, neither treatments added with amorphous carbon nor those added with synthetic MWCNTs, showed significant increases in the fresh and dry biomass of the tested plant. Likewise, the survival of seedlings was reduced between 10 and 20 % with 40 and 60 µg/mL of amorphous carbon, and with synthetic MWCNTs in all the doses applied was reduced at 30% of survival plants. CONCLUSIONS: These findings indicate that MWCNTs produced by wildfire act as plant growth promoters, contributing to the germination and development of adapted to fire-prone conditions species such as E. polystachya.

18.
Nat Commun ; 11(1): 658, 2020 Jan 31.
Artigo em Inglês | MEDLINE | ID: mdl-32005810

RESUMO

The term tunnel electroresistance (TER) denotes a fast, non-volatile, reversible resistance switching triggered by voltage pulses in ferroelectric tunnel junctions. It is explained by subtle mechanisms connected to the voltage-induced reversal of the ferroelectric polarization. Here we demonstrate that effects functionally indistinguishable from the TER can be produced in a simpler junction scheme-a direct contact between a metal and an oxide-through a different mechanism: a reversible redox reaction that modifies the oxide's ground-state. This is shown in junctions based on a cuprate superconductor, whose ground-state is sensitive to the oxygen stoichiometry and can be tracked in operando via changes in the conductance spectra. Furthermore, we find that electrochemistry is the governing mechanism even if a ferroelectric is placed between the metal and the oxide. Finally, we extend the concept of electroresistance to the tunnelling of superconducting quasiparticles, for which the switching effects are much stronger than for normal electrons. Besides providing crucial understanding, our results provide a basis for non-volatile Josephson memory devices.

19.
PeerJ ; 7: e7494, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31523498

RESUMO

BACKGROUND: Pseudomonas aeruginosa is an opportunistic and pathogenic bacterium with the ability to produce cyclodipeptides (CDPs), which belong to a large family of molecules with important biological activities. Excessive amounts of CDPs produced by Pseudomonas strains can activate an auxin response in Arabidopsis thaliana and promote plant growth. Target of rapamycin (TOR) is an evolutionarily conserved eukaryotic protein kinase that coordinates cell growth and metabolic processes in response to environmental and nutritional signals. Target of rapamycin kinase phosphorylates various substrates, of which S6 ribosomal protein kinase (S6K) is particularly well known. The PI3K/Akt/mTOR/S6K signaling pathway has been studied extensively in mammals because of its association with fundamental biological processes including cell differentiation. However, evidences suggest that this pathway also has specific and conserved functions in plants and may thus be conserved, as are several of its components like TOR complex 1 and S6K proteins. In plants, TOR-S6K signaling has been shown to be modulated in response to plant growth promoters or stressors. METHODS: In this study, we evaluated the effects of P. aeruginosa CDPs on the growth and root development of maize plants (Zea mays L.) by adding different CDPs concentrations on culture plant media, as well as the effect on the phosphorylation of the maize S6K protein (ZmS6K) by protein electrophoresis and western blot. RESULTS: Our results showed that P. aeruginosa CDPs promoted maize growth and development, including modifications in the root system architecture, correlating with the increased ZmS6K phosphorylation and changes induced in electrophoretic mobility, suggesting post-translational modifications on ZmS6K. These findings suggest that the plant growth-promoting effect of the Pseudomonas genus, associated with the CDPs production, involves the TOR/S6K signaling pathway as a mechanism of plant growth and root development in plant-microorganism interaction.

20.
Educ. med. (Ed. impr.) ; 20(3): 184-192, mayo-jun. 2019. graf, tab
Artigo em Espanhol | IBECS | ID: ibc-191572

RESUMO

Una buena gestión y calidad de la Formación Sanitaria Especializada (FSE) exige el compromiso explícito de los responsables de las CCAA y de los centros sanitarios. Esto implica la acreditación y reconocimiento de tutores, desarrollar el marco normativo que establece el RD 183/2008 (a los nueve años de su publicación sólo Cataluña, Canarias, Castilla y León, Extremadura, La Rioja y el País Vasco, lo han hecho), una mención explícita de la FSE en los planes estratégicos de las organizaciones sanitarias y en los contratos-programa con las unidades docentes y una participación activa de los jefes de estudio en los consejos de dirección de los centros. Por parte del Ministerio de Sanidad, es preciso agilizar la acreditación de las nuevas unidades docentes y abordar, junto con las CCAA, los problemas de financiación del proyecto de troncalidad y la organización de las unidades docentes troncales. Respecto al sentido de la formación, esta se ha de centrar en la seguridad del paciente, aquí la simulación es una metodología formativa idónea, y en la humanización, con una práctica de la medicina bajo un modelo deliberativo, siendo los formadores ejemplo para los que aprenden


The commitment of the heads of the Autonomous Communities and the health centers is key to a good management and the quality of the Specialized Healthcare Training (SHT). This implies the accreditation and recognition of tutors, developing the regulatory framework established by Royal Decree 183/2008 (nine years after its publication, only Catalonia, the Canary Islands, Castilla y León, Extremadura, La Rioja and the Basque Country have done so), an explicit mention of the SHT in the strategic plans of the health organizations and an active participation of the heads of SHT in the boards of directors. On the part of the Ministry of Health, it is necessary to speed up the accreditation process of new teaching units and, together with the Autonomous Communities, and address the financing problems of the core curriculum project and the organization of the core teaching units. Regarding the sense of training, this has to focus on safety patient, here the simulation is a suitable training methodology, and in the humanization, with a practice of medicine under a deliberative model, being the trainers an example for those who learn


Assuntos
Humanos , Fóruns de Discussão , Mentores/legislação & jurisprudência , Educação Médica/legislação & jurisprudência , Acreditação/normas , Educação Médica/normas , Grupos Focais/normas
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