58622 research outputs found
Sort by
<i>Meta</i>-amino substituted naphthalimides exhibit large charge transfer and strong N-H vibrations enabling use as ratiometric fluorescent probe
Get PDFFluorescent probes based on intramolecular charge transfer (ICT) have obvious advantages for accurate quantitative analysis. To obtain high-performance ratiometric probes requires distinct photophysical properties during recognition reaction process, which is closely related to their ICT characteristics. 1,8-Naphthalimide is known as a typical fluorophore with desirable ICT property when functionalized with an electron-donating moiety at the para-position of the naphthalene chromophore. Although the photophysical properties of para-substituted 1,8-naphthalimide have been well studied, its meta-substituted counterpart has not been fully evaluated since the meta-position is conventionally thought to be weakly conjugated. Herein, combined experimental and theoretical studies are performed which consistently indicate that stronger charge transfer (CT) is exhibited by the meta-amino substituted 1,8-naphthalimide (m-NH2) compared to the para-amino substituted one (p-NH2). The ratiometric response of fluorescence with significant changes in wavelength and intensity upon acetylation (m-NAc and p-NAc) can be attributed to the larger ICT and stronger -NH2 vibrations. This observation is further demonstrated by deuterium oxide experiments, viscosity experiments and quantum chemical calculations. The practical application of meta-amino-1,8-naphthalimide ICT-based probes is also confirmed. This research is expected to bring an in-depth understanding of π-conjugated systems with ICT characteristics, and facilitates the design of sensitive ICT fluorescent probes with meta-amino substitution.</p
<i>Meta</i>-amino substituted naphthalimides exhibit large charge transfer and strong N-H vibrations enabling use as ratiometric fluorescent probe
Get PDFFluorescent probes based on intramolecular charge transfer (ICT) have obvious advantages for accurate quantitative analysis. To obtain high-performance ratiometric probes requires distinct photophysical properties during recognition reaction process, which is closely related to their ICT characteristics. 1,8-Naphthalimide is known as a typical fluorophore with desirable ICT property when functionalized with an electron-donating moiety at the para-position of the naphthalene chromophore. Although the photophysical properties of para-substituted 1,8-naphthalimide have been well studied, its meta-substituted counterpart has not been fully evaluated since the meta-position is conventionally thought to be weakly conjugated. Herein, combined experimental and theoretical studies are performed which consistently indicate that stronger charge transfer (CT) is exhibited by the meta-amino substituted 1,8-naphthalimide (m-NH2) compared to the para-amino substituted one (p-NH2). The ratiometric response of fluorescence with significant changes in wavelength and intensity upon acetylation (m-NAc and p-NAc) can be attributed to the larger ICT and stronger -NH2 vibrations. This observation is further demonstrated by deuterium oxide experiments, viscosity experiments and quantum chemical calculations. The practical application of meta-amino-1,8-naphthalimide ICT-based probes is also confirmed. This research is expected to bring an in-depth understanding of π-conjugated systems with ICT characteristics, and facilitates the design of sensitive ICT fluorescent probes with meta-amino substitution.</p
Experimental assessment of stiffening geometries for thin-walled structural steel plates made by wire arc additive manufacturing
Get PDFAn innovative strategy of imposing geometric sinusoidal waves has been proven effective in enhancing the local buckling resistance of steel plates made by selective laser melting (SLM). However, its efficiency on wire arc additively manufactured (WAAM) steel, which is a more economically and environmentally viable alternative, remains unexplored, particularly given the manufacturing defects such as material anisotropy and geometric inaccuracy associated with WAAM. This work presents an experimental investigation into the stiffening effect of sinusoidal wave patterns on WAAM-fabricated steel plated sections. Stub column tests and geometric measurements were conducted on square hollow sections (SHS) and I-sections fabricated in 316 L stainless steel. The specimens incorporated the sinusoidal wavy geometries previously validated in equal-leg angle sections under external plate boundary conditions. The present study extends their application to internal plate elements in SHS stub columns and examines the combined behaviour of internal and outstanding plate elements in I-sections with sinusoidal stiffening. The obtained results demonstrate a normalised strength enhancement of up to 9% with equal or even less material consumption (0.2% to -4.5%). Comparisons are made with conventionally manufactured and existing WAAM-fabricated stainless steel plated elements, as well as with current Eurocode 3 design equations and provisional design rules proposed for SLM-fabricated stiffened plates. Based on the findings, design recommendations for such structures have been made.</p
Dataset for "Assessing the susceptibility to mould growth of mycelium-based composite insulation"
No full textThis dataset contains the raw experimental results generated in the characterisation of mycelium-based composite (MBC) insulation materials. It includes primary measurement data for laboratory-produced specimens (MBC A) and two commercially sourced materials (MBC B and MBC C), covering thermal conductivity measurements, liquid water absorption by immersion, surface wettability (contact angle) measurements, and mould susceptibility assessments. The mould dataset includes individual specimen ratings after 28 days of incubation across five temperature and relative humidity conditions, as well as ratings after subsequent liquid-water exposure. All files report unprocessed specimen-level results used to generate the figures and statistical summaries in the associated publication
Afraid to Be Vulnerable?:Women, Leadership, and the Constructive Role of Vulnerability for Organizations
Get PDFThis article draws attention to the value, for leaders and organizations, of recognizing and working with vulnerability. In the opening, we mobilize the “writing differently” approach. Specifically, we present a poem co-written by the authors to sensitize ourselves and readers to the importance of acknowledging and embracing vulnerability, which we view as an existential condition and an inherent aspect of the leadership experience. We then discuss insights from our qualitative study, based on photo-elicitation interviews with thirty-five senior women leaders in Poland, highlighting the role of vulnerability in their experiences and practices. Our research suggests that, in response to organizational norms that often discourage the expression of emotions and the display of vulnerability, especially by leaders, women leaders consciously manage and even suppress their sense of vulnerability. We argue that embracing vulnerability can bring much more positive outcomes for individuals and organizations. The article concludes with practice-oriented implications for leaders, organizations, and researchers, promoting a more sustainable and integrated approach to vulnerability in professional life
Rational points in a family of conics over <sub>2</sub>(<i>t</i>)
Get PDFSerre famously showed that almost all plane conics over (Formula presented.) have no rational point. We investigate versions of this over global function fields, focusing on a specific family of conics over (Formula presented.) which illustrates new behavior. We obtain an asymptotic formula using harmonic analysis, which requires a Tauberian theorem over function fields for Dirichlet series with branch point singularities.</p
Novel adaptive sliding-mode control of digital hydraulic systems with nonlinear flow prediction and friction identification
Get PDFDigital hydraulics has emerged as a novel technology widely utilized in engineering equipment, heavy-duty manipulators, and new energy vehicles. However, the high-frequency discrete fluid generated by high-speed on/off valves (HSVs) exacerbates the nonlinear characteristics of digital hydraulic systems (DHSs), thereby limiting control accuracy during fluid transmission. To address this issue, a model-based adaptive sliding-mode control method (ASMC) is proposed, which incorporates two soft measurement methods that integrate friction identification for the DHS with nonlinear flow prediction for the HSV to accurately describe the kinetic model. Subsequently, the coupling parameters in the Stribeck friction model are precisely identified using the particle swarm optimization-least squares algorithm, replacing previous empirical values. Additionally, a high-precision output flow prediction model for the HSV is constructed utilizing a back propagation neural network to address the drawbacks associated with mechanical inertia in the flowmeter. A second-order integral sliding-mode surface is designed to eliminate steady-state error. By incorporating a boundary layer saturation function, the error jitter can be effectively suppressed, allowing the DHS to converge rapidly to a quasi-sliding mode. Furthermore, the stability of the controlled system is validated by the Lyapunov theory. Results indicate that ASMC significantly enhances the dynamic-static performance of the DHS compared to the traditional integral sliding-mode control method, which overlooks the nonlinear behaviors of output flow and friction force. The response characteristic’s setting time is dramatically reduced from 0.86 s to 0.36 s, while the maximum average steady-state error under various loads greatly decreases from 112.4 μm to 23.4 μm. Therefore, the proposed ASMC with the two soft measurement methods presents an innovative solution for the high-precision motion control of the DHS and holds significant engineering application value
Will hope light the way? The interplay of hope, loneliness and extraversion in shaping entrepreneurs’ business exit intentions
Get PDFPurposeThe neglect of hope, a powerful yet under-researched psychological capital in entrepreneurship research, has left an obtrusive gap in understanding entrepreneurial behaviour. This study develops and tests a model showing that trait hope reduces entrepreneurs’ business exit intentions by alleviating their loneliness. It also shows how extraversion influences this relationship, highlighting when trait hope affects business exit.Design/methodology/approachWe conducted two three-wave, time-lagged surveys with entrepreneurs in Indonesia (n = 227) and the United States (US) (n = 215).FindingsOur findings reveal that entrepreneurs’ loneliness mediates the relationship between trait hope and business exit intentions in both countries. Extraversion further shapes this relationship, with stronger effects of trait hope on entrepreneurs’ loneliness and exit intentions generally observed among more extraverted entrepreneurs.Originality/valueThis research highlights trait hope as a psychologically potent yet dependent on entrepreneurs’ extraversion as an individual difference. We thereby contribute to hope research in the entrepreneurship context and the business exit literature. In addition, our study extends current research on entrepreneurs’ loneliness by identifying hope as a factor that can act as the source of “light” to combat loneliness in entrepreneurs
Insight into the alkali metal poisoning sensitivity of V<sub>2</sub>O<sub>5</sub>-WO<sub>3</sub>/TiO<sub>2</sub> catalysts for NO<sub>x</sub> abatement via machine learning and in situ Raman spectroscopy
Get PDFV2O5–WO3/TiO2 (VWTi) catalysts for NH3–SCR suffer severe poisoning by alkali metals, especially K, yet the site-specific poisoning mechanism remains unclear. Herein, we elucidate the poison mechanism based on a comprehensive investigation consisting of experimental work, theory calculation, and machine learning, conducted by controlling the VOx density and K/V ratio. Using a variety of characterization techniques, we found that the SCR activity of a VWTi catalyst was governed by its redox ability and the Lewis acidity dominated by V4+. The terminal V=O group is a Lewis acid and can adsorb NH3, while the bridging V–O–V group serves as a redox center, capable of activating NO/O2. K poisons a VWTi catalyst by attacking the strong Brønsted acids first and then the strong Lewis sites, resulting in a nonlinear progression of activity decline, which is slow initially but accelerates with increasing K accumulation. This phenomenon is especially evident for high–V loading catalysts dominated by the polymeric VOx species. Density functional theory calculations reveal that K poisons VWTi catalysts by binds K to the terminal V=O sites, forming the chemically inactive KVO3 compound and weakening the NH3 adsorption on the neighboring VOx. This work offers a comprehensive understanding of the site-specific sensitivity of VOx species to alkali metal poisoning and provides important insights to the deactivation process, which could be used to design practical VWTi catalysts for commercial applications.</p
Access Repository Dashboard
Do you manage Open Research Online? Become a CORE Member to access insider analytics, issue reports and manage access to outputs from your repository in the CORE Repository Dashboard! 👇