Polyoxometalates (POMs) have conducive properties such as controlled Brønsted and Lewis acidity, high thermal stability, nontoxic nature, tunable solubility, and less corrosiveness. POMs have been ...extensively applied in catalytic organic reactions and have an exciting prospect for industrial applications. This review summarized recent progress in the application of POMs as acid catalysts for various organic reactions including CC bond formation, CN bond formation, CO bond formation, heterocyclic synthesis reactions, cyanosilylation and hydrolysis reactions. Various POMs catalysts including heteropoly acids (HPAs) and cationic functionalized HPAs with Brønsted acidity, HPAs supported on non-precious metal support with Brønsted acidity (or both Brønsted and Lewis acidity), transition metal substituted POMs with Lewis acidity were applied in above reactions. This review attempts to provide up-to-date information about POMs acid-catalyzed organic reactions and propose future prospects.
This review summarized recent progress in the POMs acid-catalyzed organic reactions including the CC bond formation, CN bond formation, CO bond formation, heterocyclic synthesis, cyanosilylation and hydrolysis reactions. Display omitted
In practical application, it is necessary to preserve the superconducting properties, including the critical temperature (Tc) of MgB2 in the form of tapes and wires that bond to a metallic substrate ...with a buffer layer. In this work, we investigate the relationship between the Tc and local structure of MgB2 films on ZnO buffered-Hastelloy substrate with various thicknesses using X-ray absorption fine structure. X-ray absorption near edge structure spectra reveal fluctuation of the boron σ-band near the Fermi level indicating an existence of lattice distortion inside the MgB2 films. Variations in the bond lengths of Mg–B and Mg–Mg from the extended X-ray absorption fine structure prove that the distortion in the MgB2 lattice is owing to the ZnO buffer layer. Besides the bond length, the Mg–B bond ordering was found to significantly affect the Tc behavior, which was attributed to the inter-plane strain caused by the ZnO buffer layer. Understanding the effect of the ZnO buffer layer on the local structure of MgB2 may help in determining the optimal conditions for enhancing the superconducting properties of MgB2 for power applications.
People have kept companion animals for millennia, a tradition that implies mutual benefits due to its persistence; however, scientific investigations present mixed results. Some research suggests pet ...owners are less lonely than non-owners, but other findings suggest pet owners have higher psychological distress. Research comparing owners with non-owners is limited, and methodological inconsistencies need to be addressed. This study investigated social support and wellbeing (positive functioning) in cat and dog owners, informed by social support theory, attachment, and social exchange theories. It was hypothesized that (1) pet support would predict wellbeing in addition to human support and (2) at least one aspect of pet-owner relationship quality would influence the relationship between social support and wellbeing. An adult sample of 89 cat owners and 149 dog owners (n = 238; 205 females and 33 males) completed an online survey comprising a demographics questionnaire, the Multidimensional Scale of Perceived Social Support, the Cat/Dog-Owner Relationship Quality Scale, the Psychological Wellbeing Scale, and Satisfaction with Life Scale. Social support measures included some demographics on theoretical grounds to measure the construct multidimensionally. Hierarchical and multiple regressions were conducted, and results indicated that both hypotheses were supported: having more pets significantly predicted greater psychological wellbeing in addition to human social support. Unexpectedly, perceived pet support significantly, positively predicted life satisfaction when perceived emotional closeness with pet was low. These findings indicate that pets may improve psychological functioning and that emotional closeness is an important moderating factor. Practical implications include the social benefits of pets for those who could benefit from greater psychological functioning and improved life satisfaction.
Even though numerous studies have looked at the spillover effects in Shari'ah compliant equity returns, little attention has been paid to exploring global shocks' transmission to the sukuk (Islamic ...Bond) returns. Our paper attempts to fill this void by quantifying spillovers from developed countries on the sukuk returns of Islamic countries. In this paper, we create sukuk indices for financial and non-financial companies on country basis and, examine the global linkages with those sukuk indices. We have found that global sukuk markets affect the sukuk indices at different levels. A clear distinction would be that global sukuk markets have a substantial impact on the spillovers of the sukuk issued by financial corporations, while sukuk issued by non-financial corporations are more affected by the overall spillover effect the sukuk markets than spillovers from the global Islamic bond markets. Sub-sample analysis during the COVID-19 pandemic yield interesting findings, show that spillover of returns on the sukuk issued by financial corporations during the COVID-19 pandemic was higher than the sukuk issued by non-financial corporations. These findings are mostly consistent for all markets included in our sample and evidently, urge portfolio holders to make clear distinctions between sukuk issued by financial and non-financial corporations.
Even if the isopentenyl diphosphate (IPP) isomerases have been discovered in the 50s, it is only in the last decade that the genetical, enzymatical, structural richness and cellular importance of ...this large family of crucial enzymes has been uncovered. Present in all living kingdoms, they can be classified in two subfamilies: type 1 and type 2 IPP isomerases, which show clearly distinct characteristics. They all perform the regulatory isomerization of isopentenyl diphosphate into dimethylallyl diphosphate, a key rate-limiting step of the terpenoid biosynthesis, via a protonation/deprotonation mechanism. Due to their importance in the isoprenoid metabolism and the increasing interest of industry devoted to terpenoid production, it is foreseen that the biotechnological development of such enzymes should be under intense scrutiny in the near future.
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► Two types of IDIs exist: IDI1 and IDI2. ► IDI1 and IDI2 originate from different enzyme families. ► IDI1 and IDI2 differ in their structure and activity. ► IDI2 is a flavoenzyme. ► Their enzymatic mechanisms are based on the formation of a carbocation intermediate.
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•Two biocompatible fluorescent polymers based polyethyleneimine were synthesized.•The polymers could detect as well as discriminate between Cu2+ and Zn2+ ions.•The sensitivity as well ...as selectivity changed with the nature of the aromatic residue.•The fluorescent polymers could achieve trace-level detection via signal amplification.•The in-situ synthesized metallopolymers showed different interaction with PPI.
Fluorescent conjugates, based on polyethyleneimine were prepared by incorporating salicylaldehyde and 2-hydroxynaphthaldehdye respectively in the aqueous medium. The polymer derived from salicylaldehyde showed a dual-mode response with Cu2+ and Zn2+ ions. The addition of Zn2+ could change the cyan fluorescence into a blue-colored one, while the Cu2+ ion could result in a turn-off response. On the contrary, the polymer functionalized with 2-hydroxynaphthaldehdye showed fluorescence response only with Cu2+ ions. The fluorescent polymers prepared at different polyethyleneimine and salicylaldehyde ratios not only showed the formation of nanoparticles of different sizes but also, interacted with Cu2+ ions to different extents. The mechanistic investigation suggested that the enhanced sensitivity of such fluorescent nanoparticles was due to the signal amplification attributed to the polymeric backbone. Further, the in-situ synthesized Cu and Zn complex of polymers showed interaction with pyrophosphate in the aqueous medium. However, the mode of interaction as well as fluorescence response depended on the nature of the metal ions involved.
Motivated by the European sovereign debt crisis, we propose a hybrid sovereign default model that combines an accessible part taking into account the evolution of the sovereign solvency and the ...impact of critical political events, and a totally inaccessible part for the idiosyncratic credit risk. We obtain closed‐form formulas for the probability that the default occurs at critical political dates in a Markovian setting. Moreover, we introduce a generalized density framework for the hybrid default time and deduce the compensator process of default. Finally, we apply the hybrid model and the generalized density to the valuation of sovereign bonds and explain the significant jumps in long‐term government bond yields during the sovereign crisis.
This article provides a discussion on the nature of bonding between noble gases (Ng) and noble metals (M) from a quantum chemical perspective by investigating compounds such as NgMY (Y=CN, O, NO
, SO
..., CO
), NgM-(bipy)+, NgMCCH, and MCCNgH complexes, where M=Cu, Ag, Au and Ng=Kr-Rn, with some complexes containing the lighter noble gas atoms as well. Despite having very low chemical reactivity, noble gases have been observed to form weak bonds with noble metals such as copper, gold, and silver. In this study, we explore the factors that contribute to this unusual bonding behavior, including the electronic structure of the atoms involved and the geometric configuration of the concerned fragments. We also investigate the metastable nature of the resulting complexes by studying the energetics of their possible dissociation and internal isomerization channels. The noble gas-binding ability of the bare metal cyanides are higher than most of their bromide counterparts, with CuCN and AgCN showing higher affinity than their chloride analogues as well. In contrast, the oxides seem to have lower binding power than their corresponding halides. In the oxide and the bipyridyl complexes, the Ng-binding ability follows the order Au > Cu > Ag. The dissociation energies calculated, considering the zero-point energy correction for possible dissociation channels, increase as we move down the noble gas group. The bond between the noble gases and the noble metals in the complexes are found to have comparable weightage of orbital and electrostatic interactions, suggestive of a partial covalent nature. The same is validated from the topological analysis of electron density.
We study price discovery in municipal bonds, an important OTC market. As in markets for consumer goods, prices "rise faster than they fall." Round-trip profits to dealers on retail trades increase in ...rising markets but do not decrease in falling markets. Further, effective half-spreads increase or decrease more when movements in fundamentals favor dealers. Yield spreads relative to Treasuries also adjust with asymmetric speed in rising and falling markets. Finally, intraday price dispersion is asymmetric in rising and falling markets, as consumer search theory would predict.
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