Chemical Fixation of CO2 and Other Heterogeneous Catalytic Studies by Employing a Layered Cu‐Porphyrin Prepared Through Single‐Crystal to Single‐Crystal Exchange of a Zn Analogue

A solvothermal reaction of Zn(NO₃)₂ ? 6 H₂O, tetra‐(4‐pyridyl)porphyrin (H₂TPyP), and 4,4′‐oxybis(benzoic acid) (H₂OBA) resulted in a new two‐dimensional Zn‐ porphyrin metal–organic framework compound, [Zn₂(C₄₀H₂₄N₈)_0.5(C₁₄H₈O₅)(DMA)](DMA)(H₂O)₆ ( 1 ; DMA=N,N‐dimethylacetamide). The Zn^II ions present in 1 could be exchanged by using a solution of Cu(NO₃)₂ ? 3 H₂O in DMA at room temperature to give [Cu₂(C₄₀H₂₄N₈)_0.5(C₁₄H₈O₅)(DMA)](DMA)(H₂O)₃ ( Cu∈1 ). The extra‐framework solvent molecules have been shown to be reversibly removed or exchanged without collapse of the framework. Solvent‐free Cu∈1 was explored as an active heterogeneous catalyst towards three different organic reactions: 1) the chemical fixation of CO₂ into cyclic carbonate at room temperature and 1 atm; 2) the nitroaldol reaction under solvent‐free conditions, and 3) the three‐component coupling of aminopyridine, benzaldehyde, and aryl alkynes followed by 5‐exo‐dig cyclization to produce the important pharmacophore imidazopyridine.     

Soft Phonon Modes Leading to Ultralow Thermal Conductivity and High Thermoelectric Performance in AgCuTe

Crystalline solids with intrinsically low lattice thermal conductivity (κ_L) are crucial to realizing high‐performance thermoelectric (TE) materials. Herein, we show an ultralow κ_L of 0.35 Wm^?1 K^?1 in AgCuTe, which has a remarkable TE figure‐of‐merit, zT of 1.6 at 670 K when alloyed with 10 mol % Se. First‐principles DFT calculation reveals several soft phonon modes in its room‐temperature hexagonal phase, which are also evident from low‐temperature heat‐capacity measurement. These phonon modes, dominated by Ag vibrations, soften further with temperature giving a dynamic cation disorder and driving the superionic transition. Intrinsic factors cause an ultralow κ_L in the room‐temperature hexagonal phase, while the dynamic disorder of Ag/Cu cations leads to reduced phonon frequencies and mean free paths in the high‐temperature rocksalt phase. Despite the cation disorder at elevated temperatures, the crystalline conduits of the rigid anion sublattice give a high power factor.     

Nido‐Carboranes: Donors for Thermally Activated Delayed Fluorescence

An approach to the design of nido‐carborane‐based luminescent compounds that can exhibit thermally activated delayed fluorescence (TADF) is proposed. 7,8‐Dicarba‐nido‐undecaboranes (nido‐carboranes) having various 8‐R groups (R=H, Me, i‐Pr, Ph) are appended to the meta or para position of the phenyl ring of the dimesitylphenylborane (PhBMes₂) acceptor, forming donor–acceptor compounds (nido‐ m1 – m4 and nido‐ p1 – p4 ). The bulky 8‐R group and meta substitution of the nido‐carborane are essential to attain a highly twisted arrangement between the donor and acceptor moieties, leading to a very small energy splitting between the singlet and triplet excited states (ΔE_ST <0.05 eV for nido‐ m2 , ‐ m3 , and ‐ p3 ). These compounds exhibit efficient TADF with microsecond‐range lifetimes. In particular, nido‐ m2 and ‐ m3 display aggregation‐induced emission (AIE) with TADF properties.     

Thermal analysis of heat-treated silver fir wood and larval frass

Glasses having composition 5Li₂O–5ZnO– xBi₂O₃ –(90 ? x) P₂O₅ (x = 5, 10, 15, 20 and 25 mol%) were prepared by the normal melt quenching technique. Nanocomposite glass containing bismuth phosphate BiPO₄ nanocrystals was obtained, which can be attributed to homogeneous nucleation process. The formation of BiPO₄ nanocrystals was confirmed and characterized by X-ray diffraction patterns (XRD), transmission electron microscopy (TEM), differential scanning calorimetry, optical absorption (UV–Vis) and micro-hardness studies. The morphological analysis by XRD and TEM microscopy showed the formation of hexagonal BiPO₄ nanocrystals, and its estimated nanocrystalline sizes were found to be varying from 5.35 to 11.53 nm depending on the Bi₂O₃ concentrations. The density (ρ) and molar volume (V _m) were also determined and found to be in compositional dependence. Glass transition temperature (T _g) and glass crystallization temperature (T _c) were obtained and found to be increased (from 240.0 to 337.2 °C) with increasing Bi₂O₃ up to 20 mol% and then decreased (from 337.2 to 331.8 °C) due to the structural changes in the glass network. Effect of BiPO₄ content on the optical properties had been investigated. From the UV–Vis spectra, it was observed that the fundamental absorption edge shifts toward lower wavelengths, i.e., blueshifts with increasing Bi₂O₃ mol% up to 20 mol%, and then shifts toward higher wavelengths, i.e., redshifts beyond 20 mol%. It was also observed that the obtained E _opt (for indirect and direct transitions) increases with gradual increase in Bi₂O₃ content up to 20 mol% and then decreases beyond 20 mol%. This may be due to the introduction of Bi cations into the glass network as a network former up to 20 mol% causing a decrease in ΔE values, beyond 20 mol%, the introduction of Bi ions into the glass network interstitially leads to increase the values of ΔE. The optical properties of the present nanocrystallized glasses showed a quantum size dependence, in which the optical band gap energy (E _opt) was changed as a function of BiPO₄ nanocrystalline sizes.     

Determination of Immunosuppressive Pharmaceuticals in Whole Blood Following Kidney Transplantation by High-performance Liquid Chromatography–Tandem Mass Spectrometry

Cyclosporine, tacrolimus, sirolimus, and everolimus are commonly used immunosuppressants following organ transplantation. Their monitoring is used to determine the optimal dose for therapeutic effectiveness and minimize toxicity. High-performance liquid chromatographic–tandem mass spectrometry with positive electrospray ionization and multiple reaction monitoring mode was validated for the determination of cyclosporine A, tacrolimus, sirolimus, and everolimus in whole blood. A C18 analytical column was employed with a gradient elution of pH 4.0 aqueous 10?mmol/L ammonium acetate and acetonitrile. For the pretreatment of whole blood, simple protein precipitation was used with methanol:zinc sulfate. The calibration curves were linear from 20.0 to 1000?ng/mL for cyclosporine A, 1.0 to 50?ng/mL for tacrolimus and sirolimus, and 1.0 to 30?ng/mL for everolimus. The intra-assay precision and inter-assay precision were less than 15%. The method provides reliable and reproducible results according to the linearity, precision, accuracy, recovery, and matrix effects. The method has been introduced to routine clinical practice in Slovakia for the determination of immunosuppressants in patients after kidney transplantation.     

The inclusion-exclusion principle for <Emphasis Type=Italic>IF</Emphasis>-events

The inclusion-exclusion principle is one of the basic theorems in combinatorics. In this paper the inclusion-exclusion principle for IF-sets on generalized probability measures is studied. The basic theorems are proved.     

Quality assessment process for dynamic geometry resources in Intergeo project

One of the objectives of the Intergeo project was to provide European mathematics teachers with ??good quality?? pedagogical material supporting the use of dynamic geometry software in classrooms. With this aim in view, an online repository/platform was developed to gather various dynamic geometry resources, based on the idea of a teachers?? community feeding the repository, (re)using available resources and sharing practices related to the use of dynamic geometry in classrooms. The repository is thus open to contributions of any user who can deposit, browse, download and use resources, which naturally raises the question how to handle the resource quality issue in such an open environment. This paper reports on the way we tackled this issue in the Intergeo project. We first explain what we mean by a ??good quality?? dynamic geometry resource. We then provide a rationale behind the design of a questionnaire, the main tool for resource quality reviews, which are at the core of the quality assessment process implemented in the repository. Several experiments carried out with groups of teachers in order to confront our research-based view of the resource quality with the teachers?? one and to observe teachers?? usages of the quality assessment process are also reported in the paper. The outcomes of these experiments highlight strengths and limitations of the resource quality assessment process. They also tend to show that the idea of involving teachers into the resource quality assessment is a promising way of stimulating the use of dynamic geometry in classrooms, provided that teachers benefit from a support to make the quality process their own.     

Finite-sample density and its small sample asymptotic approximation

To derive the exact density of a statistic, which can be intractable, is sometimes a difficult problem. The exact densities of estimates of the shift or regression parameters can be derived with the aid of score functions. Moreover, extremely accurate approximations can be obtained by the small sample asymptotics, based on the saddlepoint method. It is of interest to compare these two approaches, at least for small samples. We numerically compare the exact densities of estimates of the shift parameter with their small sample approximations for various parent distributions of the data. For some distributions both methods are in surprising concordance even under very small samples.     

Orlicz capacities and Hausdorff measures on metric spaces

In the setting of doubling metric measure spaces with a 1-Poincaré inequality, we show that sets of Orlicz Φ-capacity zero have generalized Hausdorff h-measure zero provided thatwhere Θ⁻¹ is the inverse of the function Θ(t)=Φ(t)/t, and s is the “upper dimension” of the metric measure space. This condition is a generalization of a well known condition in Rⁿ. For spaces satisfying the weaker q-Poincaré inequality, we obtain a similar but slightly more restrictive condition. Several examples are also provided.