Three-dimensional porous solid structures, which accrue from the coordination of imidazole-based ion with metal ions and topologically mimic well-known zeolitic materials, afford the potential platform to achieve photocatalytic reactions and organic transformations in environmentally friendly conditions, using transition metals with partially or fully filled 3d orbitals. Cobalt and copper-based zeotypes and metal-organic frameworks (MOFs) have been evaluated for a CrossDehydrogenative Coupling (CDC) reaction under the irradiation of visible light and the presence of molecular oxygen. The highest conversion was obtained for the cobalt-based zeolitic imidazole framework ZIF-9, while the cobalt isomorphously substituted aluminophosphate (CoAlPO-5) did not appear promising. Interesting photocatalytic activities were demonstrated for the copper-based AlPO-5 and MOF.Aiming to correlate the structural properties to the catalytic performance of the materials, detailed physicochemical and spectroscopic characterization was performed with pXRD, SEM/EDX, BET and ICP. Further investigation of the nature of the active sites was conducted with Electron Paramagnetic Resonance and Diffuse Reflectance UV-VIS. Oxidation states of the transition metals in the scaffolds were identified utilizing XPS, while the occurrence, reversibility and stability between oxidation states were measured in the application of potential with Cyclic Voltammetry to reflect electrochemical behaviour.ZIF-9 and the rest of the synthesized materials were additionally assessed for catalytic reduction applications with borohydrides. Employed for the conversion of 4-nitrophenol to 4-aminophenol, ZIF-9 outperformed the AlPOs and MOFs and structural & surface characterization was applied to the spent material to probe the changes it undergoes during the reaction. Kinetic studies showed that ZIF-9 performs efficiently as a heterogeneous catalyst, but with the material having been reported for a series of non-catalytic applications in the literature, it was further challenged under dye decolouration reactions. Due to the nature of its structural units, ZIF-9 was applied in aqueous and non-aqueous dye-solutions and achieved decolourisation of Oil-Red-O dye and dyed wastewater.Overall, ZIF-9, comprising properties from different classes of crystalline porous materials, has superior photocatalytic and catalytic properties for a range of chemical reactions. For this reason, the material has been characterised further for its photocatalytic properties with time-resolved absorption spectroscopy to gain insight into the lifetime of its excited states. Successful modification of its basic structure with graphene suggests an additional role of ZIF-9 in materials’ science and engineering.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Country: United Kingdom
It is shown that for practical pump powers ( 33 dB) and low noise figure (3 dB) cannot simultaneously be achieved with a conventional codirectionally pumped EDFA. However, using a codirectionally pumped composite EDFA incorporating an isolator overcomes the problem, and an amplifier with 51 dB (54 dB) gain and 3.1 dB noise figure (NF) for only 45 mW (93 mW) of pump power is demonstrated. >
With a new climate change agreement signed by 200 countries at the Paris Summit in December 2015, it has become more important for both governments and companies to understand the impact of companies’ environmental performance. For the past decades, scholars have shown great interest in how the corporate environmental performance influences the corporates’ financial performance. However, the results are contradictory and there is a lack of agreement on the theoretical framework. This study investigates the impact of multi-dimensional corporate environmental performance on the corporate financial performance by taking consideration of both environmental management and operation performance. We use a sample of carbon-intensive firms in the UK with their carbon emissions disclosed from 2005 to 2012, and find a positive influence of the companies’ environmental operational performance – carbon emission performance - on their financialperformance. Our results indicate that while the effect on financial performance is linear for environmental operational performance on the same year and with one year lag, it becomes U-shape for 2-year lag. The results also suggest that corporate environmental management performance has significantly negative impact on the financial performance. When considering the interaction between environmental management and the carbon performance, we then find that corporate environmental management performance has a weak moderation effect on the relationship between environmental operational performance and financial performance. The overall picture of the results suggests that environmental management generates costs for the firms and jeopardises the financial performance, while better environmental operational performance would help the firms to achieve better performance financially, hence engaging in environmental initiatives benefits firms’ financial performance in the long term.
Abstract Floating structures are often secured in position with a taut mooring system and suction caissons. Large seabed trenches have been observed adjacent to some suction caisson anchors with taut-line mooring systems. The trenches may jeopardise the geotechnical capacity of the caissons and in turn the stationkeeping of the floating structures. Finite-element method is employed to examine the geotechnical capacity of suction caissons in a trenching seabed. The results show that the reduction in the geotechnical capacity becomes more significant with increasing trench width due to the loss of soil support and a change in failure mechanism as the caisson rotates into the trench. For a given trench width, the reduction in capacity becomes more significant as the load inclination angle to the horizontal decreases. However, the shape of the normalised failure envelopes for combined vertical and horizontal load is insensitive to trench width. A strategy to design for inevitable trenching by moving the padeye shallower to reduce the depth of trench formation is not straightforward. The gain from a shallower trench may often be outweighed by the reduction in capacity from rotation of the caisson at failure for loading angles typical of taut moorings.
fMRI studies have implicated the medial prefrontal cortex and medial temporal lobe, components of the default mode network (DMN), in episodic prospection. This study compared quantitative EEG localized to these DMN regions during prospection and during resting and while waiting for rewards. EEG was recorded in twenty-two adults while they were asked to (i) envision future monetary episodes; (ii) wait for rewards and (iii) rest. Activation sources were localized to core DMN regions. EEG power and phase coherence were compared across conditions. Prospection, compared to resting and waiting, was associated with reduced power in the medial prefrontal gyrus and increased power in the bilateral medial temporal gyrus across frequency bands as well as greater phase synchrony between these regions in the delta band. The current quantitative EEG analysis confirms prior fMRI research suggesting that medial prefrontal and medial temporal gyrus interactions are central to the capacity for episodic prospection.
Transfer matrices are used widely for the dynamic analysis of engineering structures, increasingly so for static analysis, and are particularly useful in the treatment of repetitive structures for which, in general, the behaviour of a complete structure can be determined through the analysis of a single repeating cell, together with boundary conditions if the structure is not of infinite extent. For elastostatic analyses, non-unity eigenvalues of the transfer matrix of a repeating cell are the rates of decay of self-equilibrated loading, as anticipated by Saint-Venant's principle. Multiple unity eigenvalues pertain to the transmission of load, e.g. tension, or bending moment, and equivalent (homogenized) continuum properties, such as cross-sectional area, second moment of area and Poisson's ratio, can be determined from the associated eigen- and principal vectors. Various disparate results, the majority new, others drawn from diverse sources, are presented. These include calculation of principal vectors using the Moore–Penrose inverse, bi- and symplectic orthogonality and relationship with the reciprocal theorem, restrictions on complex unity eigenvalues, effect of cell left-to-right symmetry on both the stiffness and transfer matrices, eigenvalue veering in the absence of translational symmetry and limitations on possible Jordan canonical forms. It is shown that only a repeating unity eigenvalue can lead to a non-trivial Jordan block form, so degenerate decay modes cannot exist. The present elastostatic analysis complements Langley's (Langley 1996 Proc. R. Soc. A 452 , 1631–1648) transfer matrix analysis of wave motion energetics.
This study investigated the correlation between vocabulary knowledge and reading comprehension. To address the correlation picture under Chinese logographical scripts, the researchers investigated the potential explanation for the correlation via Reading Stage, Information Gap, Content-based Approach, and Cognition and Creativity Theory approaches. This study undertook a meta-analysis to synthesize 89 independent samples from primary school stage to Master's degree stage. Results showed the correlation picture as an inverted U-shape, supporting the idea that vocabulary knowledge contributed a large proportion of variance on text comprehension and might also support the independent hypothesis of the impact of vocabulary knowledge on reading comprehension. In each education stage, the correlation between vocabulary knowledge and reading comprehension was independent in that it did not interact with any significant moderators. This study informed that the vocabulary knowledge not only determined text comprehension progress through facial semantic meaning identification but also suggested that the coordinate development of vocabulary knowledge, grammatical knowledge, and inference would be better in complexity comprehension task performance.
The objective of our research has been to analyse the advantages that result from the language contextualisation when students actively create the necessary context. This contextualisation is created by the trainees with a methodology consisting on a comparative analysis of structurally analogous texts in terms of behaviour patterns. We have applied the method to B2 / C1 level Spanish language students In addition, we have used Don Quixote and El Mundo de Custodio books, which seem to share similar lines of behaviour. Furthermore, through this "Modern Quixote" we wanted to familiarise our students with the work of Cervantes
Herein, we describe the first enantioselective cyclopropanation of enals using benzyl chlorides as bifunctional (nucleophilic and electrophilic) reagents. The reaction is simply catalyzed by chiral secondary amines to afford the formyl cyclopropane derivatives in good yields with moderate to excellent stereoselectivities.