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1.
J Prof Nurs ; 52: 80-85, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-38777530

RESUMEN

BACKGROUND: Psychiatric nurses are responsible for maintaining professional boundaries. However, professional boundaries are as described as unclear and psychiatric nursing students are at risk of crossing these boundaries. Educational instruction regarding professional boundaries within psychiatric nursing often lacks foundational structure placing students at risk of transgressions. PURPOSE: The purpose of the study was to describe boundaries in psychiatric nursing practice, identify strategies effective in teaching professional boundaries, and inform curriculum development in psychiatric nursing education. METHOD: Interpretive description was utilized to answer: How do psychiatric nurse educators interpret and explain professional boundaries in psychiatric nursing undergraduate education? Psychiatric nurse educators and psychiatric nurses were recruited from an academic institution in western Canada. Twenty participants engaged in semi-structured interviews. Eight of those participants also attended a focus group. RESULT: Participants reported that 'textbook' definitions of boundaries were insufficient in illustrating the complexities of the construct. Rather, relational forms of learning such as educators sharing clinical stories, role play activities, clinical supervision, and clinical debriefing were described as helpful strategies. CONCLUSION: Foundational knowledge regarding professional boundaries in psychiatric nursing practice appears to be incorporated in the formal curriculum. However, learning is enhanced through the informal and hidden curriculum.


Asunto(s)
Docentes de Enfermería , Enfermería Psiquiátrica , Enfermería Psiquiátrica/educación , Humanos , Docentes de Enfermería/psicología , Canadá , Curriculum , Femenino , Masculino , Adulto , Grupos Focales , Educación en Enfermería
2.
PNAS Nexus ; 3(5): pgae170, 2024 May.
Artículo en Inglés | MEDLINE | ID: mdl-38745567

RESUMEN

Lack of nitrogen limits food production in poor countries while excessive nitrogen use in industrial countries has led to transgression of the planetary boundary. However, the potential of spatial redistribution of nitrogen input for food security when returning to the safe boundary has not been quantified in a robust manner. Using an emulator of a global gridded crop model ensemble, we found that redistribution of current nitrogen input to major cereals among countries can double production in the most food-insecure countries, while increasing global production of these crops by 12% with no notable regional loss or reducing the nitrogen input to the current production by one-third. Redistribution of the input within the boundary increased production by 6-8% compared to the current relative distribution, increasing production in the food-insecure countries by two-thirds. Our findings provide georeferenced guidelines for redistributing nitrogen use to enhance food security while safeguarding the planet.

3.
Insects ; 15(5)2024 May 14.
Artículo en Inglés | MEDLINE | ID: mdl-38786910

RESUMEN

The hymenopteran subfamily Charipinae (Cynipoidea: Figitidae) consist of a group of parasitic wasps that are exclusive hyperparasitoids of Hemipteran. The species boundaries in Charipinae have historically been unclear. While diagnostic morphological features have been established for the stepwise separation of species, it is recommended to confirm those limits using molecular data. Here, we focus on the genera Alloxysta Förster, 1869 and Phaenoglyphis Förster, 1869, both of which contain species that are hyperparasitoids of aphids. We sequenced three genes (mitochondrial COI and 16S rDNA, and nuclear ITS2 rDNA) from specimens that were identified as belonging to five species: Alloxysta brevis (Thomson, 1862), A. castanea (Hartig, 1841), A. ramulifera (Thomson, 1862), A. victrix (Westwood, 1833), and Phaenoglyphis villosa (Hartig, 1841). The phylogeny resulting from concatenating these genes supported the species status of the five morphologically identified taxa, with P. villosa nested within Alloxysta. Our study thus indicates that these molecular markers can successfully distinguish charipine species, and also indicates that the genera Alloxysta and Phaenoglyphis may be more closely related than previously hypothesized. We also present the first estimates of genetic distances for these species. Future studies that include more species, loci, and/or genomic data will complement our research and help determine species relationships within the Charipinae subfamily.

4.
Adv Mater ; : e2404815, 2024 May 08.
Artículo en Inglés | MEDLINE | ID: mdl-38719211

RESUMEN

The solid electrolyte interphase (SEI) with lithium fluoride (LiF) is critical to the performance of lithium metal batteries (LMBs) due to its high stability and mechanical properties. However, the low Li ion conductivity of LiF impedes the rapid diffusion of Li ions in the SEI, which leads to localized Li ion oversaturation dendritic deposition and hinders the practical applications of LMBs at high-current regions (>3 C). To address this issue, a fluorophosphated SEI rich with fast ion-diffusing inorganic grain boundaries (LiF/Li3P) is introduced. By utilizing a sol electrolyte that contains highly dispersed porous LiF nanoparticles modified with phosphorus-containing functional groups, a fluorophosphated SEI is constructed and the presence of electrochemically active Li within these fast ion-diffusing grain boundaries (GBs-Li) that are non-nucleated is demonstrated, ensuring the stability of the Li || NCM811 cell for over 1000 cycles at fast-charging rates of 5 C (11 mA cm-2). Additionally, a practical, long cycling, and intrinsically safe LMB pouch cell with high energy density (400 Wh kg-1) is fabricated. The work reveals how SEI components and structure design can enable fast-charging LMBs.

5.
J Phys Condens Matter ; 36(34)2024 May 24.
Artículo en Inglés | MEDLINE | ID: mdl-38740049

RESUMEN

Complex environments in advanced manufacturing usually involve ultrafast laser or ion irradiation which leads to rapid heating and cooling and drives grain boundaries (GBs) to non-equilibrium states, featuring distinct energetics and kinetic behaviors compared to conventional equilibrium or near-equilibrium GBs. In this topical review, we provide an overview of both recent experimental and computational studies on metastable GBs, i.e. their energetics, kinetic behaviors, and mechanical properties. In contrast to GBs at thermodynamic equilibrium, the inherent structure energy of metastable GBs exhibits a spectrum instead of single value for a particular misorientation, due to the existence of microstructural and chemical disorder. The potential energy landscape governs the energetic and kinetic behaviors of metastable GBs, including the ageing/rejuvenating mechanism and activation barrier distributions. The unique energetics and structural disorder of metastable GBs lead to unique mechanical properties and tunability of interface-rich nanocrystalline materials. We also discuss that, in addition to structural disorder, chemical complexity in multi-components alloys could also drive the GBs away from their ground states and, subsequently, significantly impact on the GBs-mediated deformation. And under some extreme conditions such as irradiation, structural disorders and chemical complexity may simultaneously present at interfaces, further enriching of metastability of GBs and their physical and mechanical behaviors. Finally, we discuss the machine learning techniques, which have been increasingly employed to predict and understand the complex behaviors of metastable GBs in recent years. We highlight the potential of data-driven approaches to revolutionize the study of disorder systems by efficiently extracting the relationship between structural features and material properties. We hope this topical review paper could shed light and stimulate the development of new GBs engineering strategies that allow more flexibility and tunability for the design of nano-structured materials.

7.
Ecol Evol ; 14(5): e11201, 2024 May.
Artículo en Inglés | MEDLINE | ID: mdl-38799386

RESUMEN

Identification of taxonomically cryptic species is essential for the effective conservation of biodiversity. Freshwater-limited organisms tend to be genetically isolated by drainage boundaries, and thus may be expected to show substantial cryptic phylogenetic and taxonomic diversity. By comparison, populations of diadromous taxa, that migrate between freshwater and marine environments, are expected to show less genetic differentiation. Here we test for cryptic diversity in Australasian populations (both diadromous and non-diadromous) of two widespread Southern Hemisphere fish species, Galaxias brevipinnis and Galaxias maculatus. Both mtDNA and nuclear markers reveal putative cryptic species within these taxa. The substantial diversity detected within G. brevipinnis may be explained by its strong climbing ability which allows it to form isolated inland populations. In island populations, G. brevipinnis similarly show deeper genetic divergence than those of G. maculatus, which may be explained by the greater abundance of G. maculatus larvae in the sea allowing more ongoing dispersal. Our study highlights that even widespread, 'high-dispersal' species can harbour substantial cryptic diversity and therefore warrant increased taxonomic and conservation attention.

8.
Br J Nurs ; 33(10): S10-S14, 2024 May 23.
Artículo en Inglés | MEDLINE | ID: mdl-38780982

RESUMEN

Receiving a diagnosis of cancer and receiving treatment can be physically and psychologically onerous for cancer patients. Alongside their nursing skills, cancer clinical nurse specialists (CCNSs) are trained to provide psychological support, assessment and intervention following a cancer diagnosis. Mental health specialists, usually clinical psychologists, provide clinical supervision to CCNSs to support them with this. One of the regular themes that comes up in clinical supervision with CCNSs is how to maintain a supportive and therapeutic relationship with 'challenging' patients. These patients may be considered challenging because they are inconsistent, demanding or ambivalent about their care, which puts a strain on the relationship with their CCNS. By using the emotional seesaw model to reflect on and attend to the emotional boundaries of the relationship, within clinical supervision, these challenging relationships can be understood and managed, and better outcomes for the patient can be achieved.


Asunto(s)
Neoplasias , Enfermeras Clínicas , Relaciones Enfermero-Paciente , Humanos , Neoplasias/enfermería , Neoplasias/psicología , Enfermeras Clínicas/psicología , Emociones , Enfermería Oncológica , Modelos de Enfermería
10.
Small Methods ; : e2400368, 2024 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-38745535

RESUMEN

The development of highly efficient electrocatalysts for the ethanol oxidation reaction (EOR) is essential for the commercialization of direct ethanol fuel cells, yet challenges remain. In this study, a one-pot solution-phase method to synthesize Pd nanowire networks (NNWs) with very high surface-to-volume ratio having numerous twin and grain boundaries is developed. Using the same method, the Pd lattice is further engineered by introducing Ag and Cu atoms to produce AgPd, and CuPd alloy structure which significantly shifts the Pd d-band center upward and downward, respectively due to strain and ligand effects. Theoretical analysis employing density functional theory (DFT) demonstrates that such modification of the d-band center significantly influences the adsorption energies of reactants on the catalytic surface. Owing to their notably high surface-to-volume ratio and the presence of multiple twin and grain boundaries, Pd NNWs demonstrate significantly enhanced electrocatalytic activity toward EOR, ≈7.2 times greater than that of commercial Pd/C. Remarkably, compared to Pd NNWs, AgPd, and CuPd NNWs display enlarged and reduced electrocatalytic activity toward EOR, respectively. Specifically, Ag4Pd7 NNWs achieve a remarkable mass activity of 9.00 A mgpd -1 for EOR, which is 13.6 times higher than commercial Pd/C.

11.
Angew Chem Int Ed Engl ; 63(23): e202404983, 2024 Jun 03.
Artículo en Inglés | MEDLINE | ID: mdl-38563622

RESUMEN

Syngas conversion serves as a gas-to-liquid technology to produce liquid fuels and valuable chemicals from coal, natural gas, or biomass. During syngas conversion, sintering is known to deactivate the catalyst owing to the loss of active surface area. However, the growth of nanoparticles might induce the formation of new active sites such as grain boundaries (GBs) which perform differently from the original nanoparticles. Herein, we reported a unique Cu-based catalyst, Cu nanoparticles with in situ generated GBs confined in zeolite Y (denoted as activated Cu/Y), which exhibited a high selectivity for C5+ hydrocarbons (65.3 C%) during syngas conversion. Such high selectivity for long-chain products distinguished activated Cu/Y from typical copper-based catalysts which mainly catalyze methanol synthesis. This unique performance was attributed to the GBs, while the zeolite assisted the stabilization through spatial confinement. Specifically, the GBs enabled H-assisted dissociation of CO and subsequent hydrogenation into CHx*. CHx* species not only serve as the initiator but also directly polymerize on Cu GBs, known as the carbide mechanism. Meanwhile, the synergy of GBs and their vicinal low-index facets led to the CO insertion where non-dissociative adsorbed CO on low-index facets migrated to GBs and inserted into the metal-alkyl bond for the chain growth.

12.
New Phytol ; 242(6): 2746-2762, 2024 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-38666352

RESUMEN

Legume plants develop two types of root postembryonic organs, lateral roots and symbiotic nodules, using shared regulatory components. The module composed by the microRNA390, the Trans-Acting SIRNA3 (TAS3) RNA and the Auxin Response Factors (ARF)2, ARF3, and ARF4 (miR390/TAS3/ARFs) mediates the control of both lateral roots and symbiotic nodules in legumes. Here, a transcriptomic approach identified a member of the Lateral Organ Boundaries Domain (LBD) family of transcription factors in Medicago truncatula, designated MtLBD17/29a, which is regulated by the miR390/TAS3/ARFs module. ChIP-PCR experiments evidenced that MtARF2 binds to an Auxin Response Element present in the MtLBD17/29a promoter. MtLBD17/29a is expressed in root meristems, lateral root primordia, and noninfected cells of symbiotic nodules. Knockdown of MtLBD17/29a reduced the length of primary and lateral roots and enhanced lateral root formation, whereas overexpression of MtLBD17/29a produced the opposite phenotype. Interestingly, both knockdown and overexpression of MtLBD17/29a reduced nodule number and infection events and impaired the induction of the symbiotic genes Nodulation Signaling Pathway (NSP) 1 and 2. Our results demonstrate that MtLBD17/29a is regulated by the miR390/TAS3/ARFs module and a direct target of MtARF2, revealing a new lateral root regulatory hub recruited by legumes to act in the root nodule symbiotic program.


Asunto(s)
Regulación de la Expresión Génica de las Plantas , Ácidos Indolacéticos , Medicago truncatula , Proteínas de Plantas , Nodulación de la Raíz de la Planta , Raíces de Plantas , Factores de Transcripción , Medicago truncatula/genética , Medicago truncatula/microbiología , Medicago truncatula/metabolismo , Medicago truncatula/crecimiento & desarrollo , Proteínas de Plantas/metabolismo , Proteínas de Plantas/genética , Factores de Transcripción/metabolismo , Factores de Transcripción/genética , Nodulación de la Raíz de la Planta/genética , Raíces de Plantas/crecimiento & desarrollo , Raíces de Plantas/genética , Raíces de Plantas/metabolismo , Ácidos Indolacéticos/metabolismo , Regiones Promotoras Genéticas/genética , MicroARNs/genética , MicroARNs/metabolismo , Técnicas de Silenciamiento del Gen , Simbiosis/genética , Nódulos de las Raíces de las Plantas/metabolismo , Nódulos de las Raíces de las Plantas/genética , Nódulos de las Raíces de las Plantas/crecimiento & desarrollo
13.
Sociol Health Illn ; 2024 Apr 15.
Artículo en Inglés | MEDLINE | ID: mdl-38619094

RESUMEN

This article explores the meanings and uses of a hospital corridor through 98 diary entries produced by the staff of an English specialist hospital during the early stages of the COVID-19 pandemic. Drawing on Lefebvre's (1991, The production of space. Blackwell) threefold theorisation of space, corridors are seen as conceived, perceived and lived spaces, produced through and enabling the reconfiguration and reinterpretation of social interactions. The diaries depict two distinct versions of the central hospital corridor: its 'normal' operation prior to the pandemic when it was perceived as a social and symbolic space for collective sensemaking and the 'COVID-19 empty corridor' described as a haunting place that divided hospital staff along ostensibly new social and moral boundaries that impacted negatively on lived work experiences and staff relationships. The mobilisation of the central hospital corridor in the daily social construction of meaning and experience during a period of organisational and societal crisis suggests that corridors should not be only seen as a material backdrop for work relationships but as social entities that come into being and are maintained and reproduced through the (lack of) performance of social relations.

14.
BMC Public Health ; 24(1): 1099, 2024 Apr 22.
Artículo en Inglés | MEDLINE | ID: mdl-38649890

RESUMEN

BACKGROUND: Self-initiated and proactive changes in working conditions through crafting are essential for shaping work and improving work-related well-being. Recently, the research stream of job crafting has been extended to other life domains. The present paper aims to study a novel crafting concept-work-nonwork balance crafting-investigating the role of its antecedents and identifying relevant outcomes. Work-nonwork balance crafting is defined as individuals' unofficial techniques and activities to shape their work-nonwork balance, here considering their life domain boundary preferences. METHODS: In the study, 1,060 employees in three European countries (Austria, Germany and Switzerland) were surveyed in a longitudinal three-wave study with three-month intervals. We explored the influences of job/home demands and resources as antecedents of work-nonwork balance crafting. Important constructs for employee health and well-being (i.e., work engagement, work-related burnout, mental well-being and detachment from work) were investigated as outcomes. RESULTS: The findings suggest that resources and demands in the context of work or home are key antecedents of work-nonwork balance crafting. Work-nonwork balance crafting was also predictive for important employee health and well-being outcomes over three months, mainly in a positive and health-promoting way. CONCLUSION: This study provides insights into the antecedents of proactive efforts to balance the complex interplay of life domains. By studying work-nonwork balance crafting, we provide a new perspective on crafting beyond job crafting, which may help maintain or improve employees' mental health and well-being.


Asunto(s)
Equilibrio entre Vida Personal y Laboral , Humanos , Masculino , Femenino , Adulto , Persona de Mediana Edad , Alemania , Estudios Longitudinales , Suiza , Encuestas y Cuestionarios , Austria , Agotamiento Profesional/psicología , Compromiso Laboral , Satisfacción en el Trabajo , Salud Laboral
15.
BMC Health Serv Res ; 24(1): 510, 2024 Apr 24.
Artículo en Inglés | MEDLINE | ID: mdl-38658968

RESUMEN

BACKGROUND: This qualitative study explores the experiences of peer support workers (PSWs) and service users (or peers) during transition from in-person to virtual mental health services. During and following the COVID-19 pandemic, the need for accessible and community-based mental health support has become increasingly important. This research aims to understand how technological factors act as bridges and boundaries to mental health peer support services. In addition, the study explores whether and how a sense of community can be built or maintained among PSWs and peers in a virtual space when connections are mediated by technology. This research fills a gap in the literature by incorporating the perspectives of service users and underscores the potential of virtual peer support beyond pandemic conditions. METHODS: Data collection was conducted from a community organization that offers mental health peer support services. Semi-structured interviews were conducted with 13 employees and 27 service users. Thematic analysis was employed to identify key themes and synthesize a comprehensive understanding. RESULTS: The findings highlight the mental health peer support needs that were met through virtual services, the manifestation of technology-based boundaries and the steps taken to remove some of these boundaries, and the strategies employed by the organization and its members to establish and maintain a sense of community in a virtual environment marked by physical distancing and technology-mediated interrelations. The findings also reveal the importance of providing hybrid services consisting of a mixture of in person and virtual mental health support to reach a broad spectrum of service users. CONCLUSIONS: The study contributes to the ongoing efforts to enhance community mental health services and support in the virtual realm. It shows the importance of virtual peer support in situations where in-person support is not accessible. A hybrid model combining virtual and in-person mental health support services is recommended for better accessibility to mental health support services. Moreover, the importance of organizational support and of equitable resource allocation to overcome service boundaries are discussed.


Asunto(s)
COVID-19 , Grupo Paritario , Investigación Cualitativa , Humanos , Femenino , Masculino , COVID-19/psicología , Adulto , Persona de Mediana Edad , Telemedicina , Apoyo Social , SARS-CoV-2 , Servicios Comunitarios de Salud Mental/organización & administración , Servicios de Salud Mental/organización & administración , Pandemias
16.
Artículo en Inglés | MEDLINE | ID: mdl-38619983

RESUMEN

The alphaproteobacterial order Hyphomicrobiales consists of 38 families comprising at least 152 validly published genera as of January 2024. The order Hyphomicrobiales was first described in 1957 and underwent important revisions in 2020. However, we show that several inconsistencies in the taxonomy of this order remain and we argue that there is a need for a consistent framework for defining families within the order. We propose a common genome-based framework for defining families within the order Hyphomicrobiales, suggesting that families represent monophyletic groups in core-genome phylogenies that share pairwise average amino acid identity values above ~75 % when calculated from a core set of 59 proteins. Applying this framework, we propose the formation of four new families and to reassign the genera Salaquimonas, Rhodoblastus, and Rhodoligotrophos into Salaquimonadaceae fam. nov., Rhodoblastaceae fam. nov., and Rhodoligotrophaceae fam. nov., respectively, and the genera Albibacter, Chenggangzhangella, Hansschlegelia, and Methylopila into Methylopilaceae fam. nov. We further propose to unify the families Bartonellaceae, Brucellaceae, Phyllobacteriaceae, and Notoacmeibacteraceae as Bartonellaceae; the families Segnochrobactraceae and Pseudoxanthobacteraceae as Segnochrobactraceae; the families Lichenihabitantaceae and Lichenibacteriaceae as Lichenihabitantaceae; and the families Breoghaniaceae and Stappiaceae as Stappiaceae. Lastly, we propose to reassign several genera to existing families. Specifically, we propose to reassign the genus Pseudohoeflea to the family Rhizobiaceae; the genera Oricola, Roseitalea, and Oceaniradius to the family Ahrensiaceae; the genus Limoniibacter to the emended family Bartonellaceae; the genus Faunimonas to the family Afifellaceae; and the genus Pseudochelatococcus to the family Chelatococcaceae. Our data also support the recent proposal to reassign the genus Prosthecomicrobium to the family Kaistiaceae.


Asunto(s)
Alphaproteobacteria , Beijerinckiaceae , Humanos , Filogenia , Análisis de Secuencia de ADN , Ácidos Grasos/química , ARN Ribosómico 16S/genética , ADN Bacteriano/genética , Composición de Base , Técnicas de Tipificación Bacteriana , Beijerinckiaceae/genética
17.
Sci Rep ; 14(1): 9316, 2024 04 23.
Artículo en Inglés | MEDLINE | ID: mdl-38654027

RESUMEN

Floatation-REST (Reduced Environmental Stimulation Therapy) minimizes stimulation of the nervous system by immersing subjects in an environment without sound or light while they effortlessly float in thermoneutral water supersaturated with Epsom salt. Here we investigated the relationship between altered states of consciousness (ASC) and its association with the affective changes induced by Floatation-REST. Using a within-subject crossover design, 50 healthy subjects were randomized to 60 min of Floatation-REST or 60 min of Bed-REST (an active control condition that entailed lying supine on a warm waterbed in a dark and quiet room). Following Floatation-REST, subjects felt significantly more relaxed, less anxious, and less tired than after Bed-REST. Floatation-REST also induced significantly more pronounced ASC characterized by the dissolution of body boundaries and the distortion of subjective time. The loss of body boundaries mediated the loss of anxiety, revealing a novel mechanism by which Floatation-REST exerts its anxiolytic effect.


Asunto(s)
Estado de Conciencia , Humanos , Masculino , Femenino , Adulto , Estado de Conciencia/fisiología , Ansiedad , Adulto Joven , Estudios Cruzados , Reposo en Cama , Descanso/fisiología
18.
Adv Mater ; : e2401118, 2024 Apr 19.
Artículo en Inglés | MEDLINE | ID: mdl-38641859

RESUMEN

As an empirical tool in materials science and engineering, the iconic phase diagram owes its robustness and practicality to the topological characteristics rooted in the celebrated Gibbs phase law free variables (F) = components (C) - phases (P) + 2. When crossing the phase diagram boundary, the structure transition occurs abruptly, bringing about an instantaneous change in physical properties and limited controllability on the boundaries (F = 1). Here, the sharp phase boundary is expanded to an amorphous transition region (F = 2) by partially disrupting the long-range translational symmetry, leading to a sequential crystalline-amorphous-crystalline (CAC) transition in a pressurized In2Te5 single crystal. Through detailed in situ synchrotron diffraction, it is elucidated that the phase transition stems from the rotation of immobile blocks [In2Te2]2+, linked by hinge-like [Te3]2- trimers. Remarkably, within the amorphous region, the amorphous phase demonstrates a notable 25% increase of the superconducting transition temperature (Tc), while the carrier concentration remains relatively constant. Furthermore, a theoretical framework is proposed revealing that the unconventional boost in amorphous superconductivity might be attributed to an intensified electron correlation, triggered by a disorder-augmented multifractal behavior. These findings underscore the potential of disorder and prompt further exploration of unforeseen phenomena on the phase boundaries.

19.
ACS Appl Mater Interfaces ; 16(17): 22676-22688, 2024 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-38632875

RESUMEN

Two-dimensional polymorphic transition-metal dichalcogenides have drawn attention for their diverse applications. This work explores the complex interplay between strain-induced phase transformation and crack growth behavior in annealed nanocrystalline MoS2. Employing molecular dynamics (MD) simulations, this research focuses on the effect of grain size, misorientation, and annealing on phase evolution and their effects on the mechanical behavior of MoS2. First, examining phase transformation in monocrystalline MoS2 under various stress states reveals distinct behaviors depending on the initial phase (1T or 2H) and crystallographic orientation with respect to loading directions. Notably, transformation from a layered hexagonal to a body-centered tetragonal structure is more noticeable when strain in a zigzag direction is applied to the 1T sample. As such, single crystalline MoS2 with a 1T phase exhibits a 16% lower fracture stress in the armchair direction compared to that with a 2H phase. On the other hand, the 1T phase shows a 5% higher phonon lifetime compared to the 2H phase with similar phonon group velocities. Next, the influence of thermal energy and mechanical stress on the phase transformation of nanocrystalline MoS2 is investigated through annealing and quenching cycles, uncovering 60 and 44% irreversibility of phase transformation for an average grain size of 3 and 11 nm, respectively. Besides, the evolution of nanocrystalline samples with different initial phases and grain sizes is studied under uniaxial and biaxial stress. This study shows an inverse pseudo-Hall-Petch effect with exponents of 0.11 and 0.09 for 2H and 1T, respectively. The study reveals that phase transformation can occur concurrently with crack initiation and propagation with the 1T phase exhibiting a 19% lower grain size sensitivity of fracture stress compared to the 2H phase.

20.
Nano Lett ; 24(18): 5474-5480, 2024 May 08.
Artículo en Inglés | MEDLINE | ID: mdl-38652833

RESUMEN

Grain boundaries (GBs) and twin boundaries (TBs) in copper (Cu) are two major planar defects that influence electrical conductivity due to their complex electron transport characteristics, involving electron scattering and electron concentration. Understanding their local electronic states is crucial for the design of future conductor materials. In this study, we characterized electron behaviors at TBs and GBs within one Cu grain using atomic force microscopy. Our findings revealed that, compared with GBs, TBs exhibit better current transport capability (direct-current mode) and larger electromagnetic loss (high-frequency microwave mode). Both kelvin probe force microscopy and theoretical analysis suggested that TBs with smaller lattice disorder possess lower density of states at the Fermi level. The reduced density of states may result in decreased electron scattering and a lower electron concentration at TBs. The latter can be highlighted by the high-frequency skinning effect, manifested as larger electromagnetic loss and weaker high-frequency conductivity.

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