Transition Barrier Research Articles

Synthesis of Honeycomb-Structured Beryllium Oxide via Graphene Liquid Cells.

Using high-resolution transmission electron microscopy and electron energy-loss spectroscopy, we show that beryllium oxide crystallizes in the planar hexagonal structure in a graphene liquid cell by a wet-chemistry approach. These liquid cells can feature van-der-Waals pressures up to 1 GPa, producing a miniaturized high-pressure container for the crystallization in solution. The thickness of as-received crystals is beyond the thermodynamic ultra-thin limit above which the wurtzite phase is energetically more favorable according to the theoretical prediction. The crystallization of the planar phase is ascribed to the near-free-standing condition afforded by the graphene surface. Our calculations show that the energy barrier of the phase transition is responsible for the observed thickness beyond the previously predicted limit. These findings open a new door for exploring aqueous-solution approaches of more metal-oxide semiconductors with exotic phase structures and properties in graphene-encapsulated confined cells.

Synthesis of Honeycomb‐Structured Beryllium Oxide via Graphene Liquid Cells

AbstractUsing high‐resolution transmission electron microscopy and electron energy‐loss spectroscopy, we show that beryllium oxide crystallizes in the planar hexagonal structure in a graphene liquid cell by a wet‐chemistry approach. These liquid cells can feature van‐der‐Waals pressures up to 1 GPa, producing a miniaturized high‐pressure container for the crystallization in solution. The thickness of as‐received crystals is beyond the thermodynamic ultra‐thin limit above which the wurtzite phase is energetically more favorable according to the theoretical prediction. The crystallization of the planar phase is ascribed to the near‐free‐standing condition afforded by the graphene surface. Our calculations show that the energy barrier of the phase transition is responsible for the observed thickness beyond the previously predicted limit. These findings open a new door for exploring aqueous‐solution approaches of more metal‐oxide semiconductors with exotic phase structures and properties in graphene‐encapsulated confined cells.

Systemic Design for Policy-Making: Towards the Next Circular Regions

The vast transformation the circular economy that will occur in the upcoming years inevitably will change the EU panorama, designing new scenarios from an economical-social-environmental perspective. To best build a circular economy, it is necessary innovative policy-planning with a holistic and systemic perspective that fosters a cohesive and smooth transition to circular business models. This paper explores the impacts of circular economy policy design processes driven by a systemic design and how this expertise could ease innovative and effective paths for policy-planning on a circular transition in EU regions. This examination of systemic design features recent approaches to design as a discipline addressing complex problems, and the literature review on systems and design thinking for sustainable development, and policy design, focusing on existing barriers to circular economy. The discussion is narrowed to the specific case study in which the systemic design methodology is applied to provide a path for five European regions towards the CE: the Interreg Europe RETRACE (A Systemic Approach for Regions Transitioning towards a Circular Economy) project. Including an in-depth examination of how systemic design can address current barriers for a circular transition within an effect in the short, medium, and long-term policy horizon in the transition of the European regions towards the circular economy.

Longitudinal analysis reveals transition barriers between dominant ecological states in the gut microbiome

The Pioneer 100 Wellness Project involved quantitatively profiling 108 participants' molecular physiology over time, including genomes, gut microbiomes, blood metabolomes, blood proteomes, clinical chemistries, and data from wearable devices. Here, we present a longitudinal analysis focused specifically around the Pioneer 100 gut microbiomes. We distinguished a subpopulation of individuals with reduced gut diversity, elevated relative abundance of the genus Prevotella, and reduced levels of the genus Bacteroides We found that the relative abundances of Bacteroides and Prevotella were significantly correlated with certain serum metabolites, including omega-6 fatty acids. Primary dimensions in distance-based redundancy analysis of clinical chemistries explained 18.5% of the variance in bacterial community composition, and revealed a Bacteroides/Prevotella dichotomy aligned with inflammation and dietary markers. Finally, longitudinal analysis of gut microbiome dynamics within individuals showed that direct transitions between Bacteroides-dominated and Prevotella-dominated communities were rare, suggesting the presence of a barrier between these states. One implication is that interventions seeking to transition between Bacteroides- and Prevotella-dominated communities will need to identify permissible paths through ecological state-space that circumvent this apparent barrier.

The Cascadia Subduction Zone earthquake: Will emergency managers be willing and able to report to work?

This study examines the factors that are likely to influence emergency managers’ willingness and ability to report to work after a catastrophic event using the Cascadia Subduction Zone earthquake threat as an example. The population approached for participation in this study was state-level emergency managers in Oregon and Washington, the areas anticipated to be the most impacted by the Cascadia Subduction Zone earthquake. Concept mapping was utilized to elucidate factors influencing emergency managers’ ability and willingness to report to work following a catastrophic earthquake, as well as to identify specific strategies for addressing these factors to facilitate reporting to work. The six-step concept mapping process (i.e., preparation, generation, structuring, representation, interpretation, and utilization) is a structured and integrated mixed-method process that employs both qualitative and quantitative components to gather ideas and concepts of participants, and subsequently produces visual representation of these ideas and concepts through multivariate statistical methods (Caracelli and Green in Eval ProgramPlan 12(1):45–52, 1993; Kane and Trochim in Concept mapping for planning and evaluation, Sage Publications, Thousand Oaks, 2007). Results influence across a wide range of the levels of the ecological framework for both ability (transit barriers and infrastructure impacts, family/pet health and safety, social support and preparedness, work-related influences, personal health and resources, professional obligations, and location) and willingness (family/community preparedness and safety, emergency management responsibility and professionalism, motivation to come to work, transit barriers and infrastructure impacts, professional contribution, physical and mental health, worksite operations: structure and process, family first, personal contribution and history).

Model Calculation for Enthalpy Relaxation of Polystyrene to Estimate the Size of Cooperative Rearranging Region for Glass Transition

The structural relaxation process has been studied for polystyrene samples by conducting physical ageing experiments. The energy barrier of the conformational transition in the isolated chain was d...

IL-6 deficiency exacerbates allergic asthma and promotes Streptococcus pneumoniae pathogenesis

Abstract Allergic asthma consists of diverse immune phenotypes exhibiting differential lung pathology, remodeling of the respiratory tract and mucociliary bronchial clearance. These diverse inflammatory immune mechanisms may promote or resist microbial infections in allergic human and mouse models. IL-6 governs optimal T-cell and inflammatory response leading to the resolution of bacterial and viral infections in respiratory airways. Additionally, IL-6 plays an important role in maintaining the integrity of airway barrier response during microbial infections. We hypothesized that lung IL-6 responses alleviate Streptococcus pneumoniae (Spn) pathogenesis during fungal allergic asthma caused by Aspergillus fumigatus. Using a murine Aspergillus fumigatus asthma model, we show that IL-6 deficiency exacerbates lung inflammation and promotes Spn disease pathogenesis in allergic host. IL-6 deficiency was associated with increased lung damage, which correlated with higher levels of lung eosinophilia, inflammatory cytokines and chemokines. Additionally, IL-6 deficiency correlated with increased TGF-β1 cytokine levels, increased epithelial-mesenchymal transition and dysregulated epithelial barrier proteins in asthmatic mice. We conclude that IL-6 offers a significant protective role in the control of Spn pathogenesis during allergic asthma by regulation of immune cell recruitment and maintenance of lung epithelial barrier integrity.

Chemomechanical Design Factors for High Performance in Manganese-Based Spinel Cathode Materials for Advanced Sodium-Ion Batteries.

Manganese-based spinel cathode materials for sodium-ion batteries (SIBs) are promising candidates for next-generation batteries; especially, Na[Ni0.5Mn1.5]O4 (NNMO) should get attention because of its relatively high operating voltage and firm octahedral host structure. Here, first-principles calculations and the phase field method are used to elucidate the reasons for the low performance of NNMO compared with Li[Ni0.5Mn1.5]O4, and we determine the requirements for realizing high-performance cathode materials for SIBs. Owing to the Ni2+/Ni4+ double redox, NNMO could operate at a high voltage; however, the large Na+ increases the local site energy of the redox center, promoting electron extraction from the redox center, leading to unexpected voltage loss. Additionally, the homogeneous free energy confirms that NNMO would undergo phase separation into fully intercalated and deintercalated phases, inducing lattice misfits along the interfaces of the two phases. Particularly, a higher phase transition barrier and large Na+ cause fast phase separation, inducing increased polarization and severe stress field upon cycling. The present analysis with comprehensive first-principles calculations and the phase field method provides three critical factors toward high electrochemical performance: (i) strengthening Ni-O bonding to avoid undesirable voltage loss, (ii) increasing the vacancy/Na solubility during (de)sodiation to enhance cyclability, and (iii) suppressing the structural distortion during (de)sodiation to prevent mechanical failure. Based on these crucial points, additionally, we suggest the M-pillared Na1-xMx[Ni0.5Mn1.5]O4 (monovalent or divalent species, M), where the M works to strengthen the redox center for improved energy density and to alleviate the drastic structural change and voltage hysteresis for better cyclability, would have superior electrochemical performance as a cathode material for SIBs.

“It's a very different world”: work transition and employability of higher education graduates

PurposeThis study addresses the specific topic of transition between higher education and the world of work, taking differences naturally inherent to the individual and to the surrounding micro and macro contexts. With a holistic approach, this paper aimed to provide a deeper understanding about the university-to-work transition process in a period of turbulence and continuous changes in the labour market.Design/methodology/approachThe three research questions that guide this qualitative study are as follows: (1) What are the factors that facilitate the transition to the labour market? (2) What are the factors that constrain the transition to the labour market? (3) What are graduates' perceptions of their employability? To answer these questions, eleven graduates were interviewed about facilitators and barriers of the transition process and perceptions of employability. Data collected from the interviews were then related to categories previously defined from the literature review. Version 12.0 of the NVivo software was used to support the process of data analysis.FindingsOverall, participants' discourse refer to a multidimensional and dynamic perspective of factors related with work transition and employability. The obtained results indicate that the lack of career agency during graduation and professional experiences, together with late career exploration processes, represent possible barriers of transition, especially in study fields with targeted job offers. Likewise, experiences promoting the development of competencies through supportive practice from teachers, mentors and colleagues are referred as facilitators of transition.Practical implicationsOne of the most consistent outcomes of the interviews conducted concerns the importance of a stronger focus on developing practical experiences during higher education studies. This empirical study demonstrated how this type of experience can mitigate the impact of the transition from university to the labour market.Originality/valueThis empirical study demonstrated how work being integrated into learning in curricula can mitigate the impact of the transition from university to the labour market. It offers important insights about possible strategies that could be adopted to promote graduates' employability from a perspective of shared responsibility.

Theoretical study on martensitic-type transformation path from rutile phase to α-PbO2 phase of Ti2O**Project supported by the National Natural Science Foundation of China (Grant Nos. 51872227, 51572219, and 11447030).

The martensitic-type phase transformation paths from the rutile to the α-PbO2 phase of TiO2 are studied with linear interpolation and NEB/G-SSNEB methods based on first-principles calculations. Its potential energy surface and the lowest energy path are revealed. Our results indicate that the titanium atoms of the rutile phase shuffle along the [0–11]rut crystal direction to form the α-PbO2 phase. During the phase transition, the oxygen atoms are dragged by the heavier titanium atoms and then reach their new equilibrium positions. The barrier of phase transition from nudged elastic band theory is about 231 meV, which is qualitatively consistent with previous theoretical calculations from the monoclinic phase to the tetragonal phase for ZrO2 and HfO2. Debye model can also be successfully used to predict the pressure and temperature of the phase transformation.

Effect of Oriented External Electric Fields on the Photo and Thermal Isomerization of Azobenzene.

Azobenzene is a prototype molecule with potential applications in molecular switches, solar thermal batteries, sensors, photoresponsive membranes, molecular electronics, data storage, and nonlinear optics. Photo and thermal isomerization pathways exhibit different charge-transfer character and dipole moments, implying that the use of electric fields can be used to modulate the reactivity of azobenzene. This article examines the differential effect of orientated electric fields on the rotation and inversion thermal and photoisomerization pathways of azobenzene to explore the feasibility of using electric fields in the design of azobenzene-based molecular devices. Our findings demonstrate that the application of orientated electric fields modifies the accessibility of the S0/S1 seam of electronic degeneracy, as well as changes the energetically favored relaxation pathway in the branching space to yield different photoproducts. In addition, we observed strong-field dipole-inversion effects that cause a topographical change in the response of the potential energy surface to the applied field and can result in geometric minima that do not exist under field-free conditions. On the S0 surface, transition barriers can be modified on the order of ±10 kcal mol-1, enabling control of thermal isomerization rates.

Growth and structural characteristics of metastable β-In2Se3 thin films on H-terminated Si(111) substrates by molecular beam epitaxy**Project supported by the National Key Research and Development Program of China (Grant Nos. 2018YFA0306102 and 2018YFA0306703), the National Natural Science Foundation of China (Grant Nos. 61474014 and U1601208), and the Sichuan Science and Technology Program, China (Grant Nos. 2019YJ0202 and 20GJHZ0229).

Epitaxial growth and structural characteristics of metastable β-In2Se3 thin films on H-terminated Si(111) substrates are studied. The In2Se3 thin films grown below the β-to-α phase transition temperature (453 K) are characterized to be strained β-In2Se3 mixed with significant γ-In2Se3 phases. The pure-phased single-crystalline β-In2Se3 can be reproducibly achieved by in situ annealing the as-deposited poly-crystalline In2Se3 within the phase equilibrium temperature window of β-In2Se3. It is suggeted that the observed γ-to-β phase transition triggered by quite a low annealing temperature should be a rather lowered phase transition barrier of the epitaxy-stabilized In2Se3 thin-film system at a state far from thermodynamic equilibrium.

Dynamic analysis of non-linear wake-up behavior in Hf0.7Zr0.3O2 thin film

We report on the nonlinear wake-up behavior against the external electric field cycling in the ferroelectric Hf0.7Zr0.3O2 thin film. Two distinct scaling regimes during the increase of the remnant polarization with different activation energies were observed in TiN/Hf0.7Zr0.3O2/TiN cells. The transmission electron microscopy revealed the structural phase transition from the monoclinic structure to the orthorhombic structure of the Hf0.7Zr0.3O2 film after the wake-up behavior. During the phase change, as the remnant polarization enhanced, the dielectric constant of the Hf0.7Zr0.3O2 film increased with the external field cycling. The temperature dependence of the wake-up behavior revealed that each estimated activation energies for the early and later enhancement of the remnant polarization are 1.12 eV and 0.73 eV, respectively. First principle calculations show that the oxygen vacancies can reduce the activation energy barrier for the structural phase transition.

Study on the enhanced electron-hole separation capability of IrxZn1-xO/Ti electrodes with high photoelectrocatalysis efficiency

Making full use of low-energy photons and reducing photogenerated carriers' recombination rate have been considered important ways to raise photoelectrocatalysis (PEC) efficiency. In this study, Ir-doped ZnO PEC electrodes were prepared by thermal decomposition method, first principles calculations were used to study the effects of Ir content on the electronic structure and optical properties of IrxZn1-xO coatings, the PEC degradation mechanism of the IrxZn1-xO/Ti electrodes was also tentatively presented. The results indicated that with numbers of Zn atoms replaced by Ir atoms, impurity energy level appeared in ZnO band gap, which reduced the electron transition barriers and increased the number of photogenerated carriers. Besides, IrO2 nanoparticles covered on ZnO nanorods surface, acting as highly efficient electron transfer channels and electrocatalytic active sites, could separate photogenerated electron-hole pairs and enhance PEC performance effectively. PEC performance of IrxZn1-xO/Ti electrodes with different Ir contents under UV irradiation was evaluated by rhodamine B (RhB) removal rate. Compared with pure ZnO electrodes, IrxZn1-xO/Ti ones exhibited much stronger degradation capacity. Specifically, Ir0.09375Zn0.90625O/Ti electrodes showed the highest degradation rate of 99.4 %, and a relatively high rate of 95.2 % after working 100 h continuously, indicating its excellent long-term stability.

Crowdsourced Mapping for Healthy Food Accessibility in Dallas, Texas: A Feasibility Study.

Since its first use for describing a neighborhood lacking access to food in the 1990's, “food deserts” has been widely addressed by researchers and adopted as an indicator of neighborhood-level food insecurity by governmental agencies, such as USDA. However, mostly due to cost and difficulty in collecting georeferenced data and characteristics of grocery stores, the USDA Food Access Research Atlas is infrequently released, and considers only income, vehicle ownership, and distance to the nearest grocery store. In this paper, we explored the feasibility of a crowdsourced geospatial data source, coupled with additional measures, in supplementing the USDA's current designation of food deserts. We used Yelp data to map food deserts in the city of Dallas and compared them with those based on the 2015 USDA food retailer database. Although direct comparison was not possible due to time mismatch between the two data sources, the discrepancies highlighted the need of a more frequent identification of food deserts for timely policy intervention. Furthermore, we extended mapping to reveal other potential areas of concerns, by adding the Transit Score metric and Yelp's price descriptor of businesses. The resulting maps illustrated the areas with grocery stores nearby but with limited accessibility due to lack of public transit or potential financial barriers in purchasing foods due to high prices. Our findings demonstrate the current status and future potential of up-to-date crowdsourced, georeferenced data as a complement of official government data, which could serve to extend food access research and guide health policies.

Ultrasonic vibration accelerated aging in La-based bulk metallic glasses

The effect of ultrasonic vibrations on the thermodynamic properties of La68.5Al14Ni16Co1.5 bulk metallic glasses is systematically studied at various temperatures. We find a significant enthalpy lowering for the glasses after the ultrasonic treatment, due to the structural relaxation towards lower energetic states, coinciding with the finding that the pretreated samples have a noticeable higher energetic barrier for glass transition. With increasing the ultrasound-treating time, the reduced enthalpy saturates in the long-time regime, which is reachable by the isothermal annealing. Based on these results, we conclude that the ultrasonic vibration has, qualitatively, the same effect as that of the annealing process. This is interpreted by the fact that the ultrasonic perturbation is weak for the technique we utilized, and most of the atoms could linearly respond to it. The ultrasound-accelerated aging has also been shown on the aspect of the hardness that was monotonically enhanced with the treating time.

Inter-niche competition on ice? Socio-technical drivers, benefits and barriers of the electric vehicle transition in Iceland

This paper investigates the drivers, benefits and barriers of battery electric vehicle (BEV) development and an ongoing BEV transition in Iceland from a sociotechnical perspective. We focus on the following research questions: 1) What are the most promising driving forces behind BEV growth? 2) Why are BEVs restricted mostly to the niche level? 3) What are the possible opportunities for BEV future development? and 4) How viable are BEVs as a solution to harnessing low-carbon renewable sources in Iceland? The study uses original qualitative data comprising 29 research interviews involving experts from a wide range of sectors. The conceptual framework of multi-mode interaction, or “inter-niche competition”, is incorporated into the MLP to illustrate the interaction between BEVs and other technologies, in particular, plugin hybrid electric vehicles. We find that BEVs may take de-alignment and re-alignment pathway or reconfiguration pathway depending on the multi-technology interaction modes.

Unraveling the Molecular Mechanism of Prion H2 C-Terminus Misfolding by Metadynamics Simulations

Conformational transition from the normal cellular form of prion protein (PrPC) to the pathogenic "scrapie" form (PrPSc) is considered to be a key event in the occurrence of prion disease. Additionally, the H2 C-terminus is widely considered to be a vital site for PrP conformational transition, which can be used as an important region to explore the potential mechanism of PrP misfolding. Therefore, to study the misfolding mechanism of PrP, 500 ns well-tempered metadynamics simulations were performed by focusing on the H2 C-terminus of PrP. For comparison, three systems were designed in total, including PrP in neutral and acidic conditions, as well as H187R mutant. The resulting free energy surfaces (FESs) obtained from metadynamics simulations reveal that acidic conditions and H187R mutation can facilitate PrP misfolding by decreasing free energy barriers for conformational transition and forming energy stable conformational states. Further analyses aimed at H2 C-terminus show that due to the increase of positive charge on residue 187 in both acidic and H187R systems, the electrostatic repulsion of residue 187 and R136/R156 increases greatly, which disrupts the electrostatic interaction network around H2 C-terminus and exposes the hydrophobic core to the solvent. Taken together, acidic conditions and H187R mutation can accelerate PrP misfolding mainly by forming more energetically stable metastable conformations with lower free energy barriers, and electrostatic network disruption involving residue 187 drives the initial misfolding of H2 C-terminus. This study provides quantitative insight into the related function of the H2 C-terminus in the PrP misfolding process, which may guide H2 C-terminus mediated drug design in the future.

Lost in Transition: A Risk Factor for Mortality in Youth Living With HIV.

Lost in Transition: A Risk Factor for Mortality in Youth Living With HIV.

A transition program to adult health services for teenagers receiving long-term home mechanical ventilation: A longitudinal qualitative study.

Adolescents receiving long-term home mechanical ventilation (HMV) who survive into adulthood must transition to adult health care services. Lack of transition readiness is reported to result in poor health outcomes. The objective of this study is to explore longitudinally the pediatric-to-adult health care transition experience involving a transition program for adolescents receiving HMV including transition readiness, barriers, facilitators, and modifiable features. A prospective qualitative longitudinal interview study of adolescent and family caregiver dyads recruited through a pediatric-to-adult HMV transition program jointly established by two collaborating health centers: The Hospital for Sick Children and West Park Healthcare Centre in Toronto, Canada. Eligible dyads were interviewed at three time points: pretransition, transition, and 12-months posttransition. Interviews were transcribed verbatim and analyzed using directed content analysis methods. Ventilator-assisted adolescents (VAAs) and caregiver participants perceived a lack of transition readiness in their ability to manage health communication and coordination across multiple adult providers. Transition facilitators included early transition discussion, opportunities for VAAs to speak directly with HMV providers during appointments, receipt of print informational materials regarding adult services, and a joint pediatric-adult team handover meeting. Modifiable transition barriers included lack of other specialist referrals, insufficient information about adult homecare service funding, and limited involvement of family doctors. Unresolved transition barriers resulted in perceptions of service fragmentation. Although the pediatric-to-adult HMV transition program conferred benefits service fragmentation was perceived. Transition barriers may be overcome through early planning and staged transition with all specialists, community providers, and the family and adolescent working in collaboration.