Designing new materials for the effective detoxification of chemical warfare agents (CWAs) is of current interest given the recent use of CWAs. Although halogenated boron-dipyrromethene derivatives ...(4,4-difluoro-4-bora-3a,4a-diaza-s-indacene or BDP or BODIPY) at the 2 and 6 positions have been extensively explored as efficient photosensitizers for generating singlet oxygen (1O2) in homogeneous media, their utilization in the design of porous organic polymers (POPs) has remained elusive due to the difficulty of controlling polymerization processes through cross-coupling synthesis pathways. Our approach to overcome these difficulties and prepare halogenated BODIPY-based porous organic polymers (X-BDP-POP where X = Br or I) represents an attractive alternative through post-synthesis modification (PSM) of the parent hydrogenated polymer. Upon synthesis of both the parent polymer, H-BDP-POP, and its post-synthetically modified derivatives, Br-BDP-POP and I-BDP-POP, the BET surface areas of all POPs have been measured and found to be 640, 430, and 400 m2 ·g–1, respectively. In addition, the insertion of heavy halogen atoms at the 2 and 6 positions of the BODIPY unit leads to the quenching of fluorescence (both polymer and solution-phase monomer forms) and the enhancement of phosphorescence (particularly for the iodo versions of the polymers and monomers), as a result of efficient intersystem crossing. The heterogeneous photocatalytic activities of both the parent POP and its derivatives for the detoxification of the sulfur mustard simulant, 2-chloroethyl ethyl sulfide (CEES), have been examined; the results show a significant enhancement in the generation of singlet oxygen (1O2). Both the bromination and iodination of H-BDP-POP served to shorten by 5-fold of the time needed for the selective and catalytic photo-oxidation of CEES to 2-chloroethyl ethyl sulfoxide (CEESO).
Experimental studies on the performances of both new developed environmental friendly vegetable based cutting fluids (refined sunflower and canola oils) including different percentage of extreme ...pressure (EP) additive and two commercial cutting fluids (semi-synthetic and mineral cutting fluids) in turning processes were reported in this work. Performances of cutting fluids were compared with respect to surface roughness, cutting and feed forces and tool wear during longitudinal turning of AISI 304L. Experimental results were also compared with dry cutting conditions. The results indicated that 8% of EP included canola based cutting fluid performed better than the rest.
► We investigate the performance of new vegetable based cutting fluids in turning. ► Different percentages of extreme pressure additive are used. ► Surface roughness, cutting force and tool wear are measured. ► Vegetable based cutting fluids can be used efficiently in turning.
Protection of enzymes with synthetic materials is a viable strategy to stabilize, and hence to retain, the reactivity of these highly active biomolecules in non-native environments. Active synthetic ...supports, coupled to encapsulated enzymes, can enable efficient cascade reactions which are necessary for processes like light-driven CO2 reduction, providing a promising pathway for alternative energy generation. Herein, a semi-artificial systemcontaining an immobilized enzyme, formate dehydrogenase, in a light harvesting scaffoldis reported for the conversion of CO2 to formic acid using white light. The electron-mediator Cp*Rh(2,2′-bipyridyl-5,5′-dicarboxylic acid)Cl was anchored to the nodes of the metal–organic framework NU-1006 to facilitate ultrafast photo-induced electron transfer when irradiated, leading to the reduction of the coenzyme nicotinamide adenine dinucleotide at a rate of about 28 mM·h–1. Most importantly, the immobilized enzyme utilizes the reduced coenzyme to generate formic acid selectively from CO2 at a high turnover frequency of about 865 h–1 in 24 h. The outcome of this research is the demonstration of a feasible pathway for solar-driven carbon fixation.
In this study, the metallographic structure and wear behaviour of boron-coated rail steels were investigated. For this purpose, the wear behaviour of boronized rail steels was examined under two ...different load and sliding speed conditions. According to the results, the thickness and hardness values of the boride layer increased with increasing boronizing temperature. The hardness of the rail steel, initially ∼300 HV, reached the value of 1886, 2145 and 2590 HV at 700-800-900 °C, respectively. When the wear behaviour of the boronized rail steel was analyzed, a considerable increase in wear resistance was achieved compared to the untreated sample. Topographic images showed that boronized samples have a smoother surface form, while untreated samples have deep valleys and intense fluctuations.
•Rail steels were boronized with powder pack boriding.•The maximum hardness (2590 HV) was obtained in a 4 h boronized sample at 900 °C.•The interaction of load, sliding speed and boronization was investigated.•The B2O3 layer formed on the surface has minimized the friction coefficient.•No significant wear mechanism was observed in the boronized samples.
In this study, the tribological performance of nano-silver particles prepared at different concentrations was investigated by the parameters of temperature, friction coefficient, weight loss and ...surface roughness. Moreover, the effects of the aggregation behaviour of nanoparticles were analysed. According to the results, when the nano-silver concentration increased from 4% to 12%, weight loss decreased by 33.99%, surface quality increased by 21.13%, friction coefficient decreased by 18.16% and wear zone temperature decreased by 74.31%. Increased aggregation behaviour adversely affected the wear resistance. Additionally, it was determined that the ethylene glycol has a significant effect on the penetration ability of the nanoparticles.
•Aggregation tendency of nanoparticles has been analysed for wear performance.•The effect of nano-silver concentration rate was investigated.•The penetration behavior of colloidal suspensions was compared.•Wear resistance increased at concentrations above 4%.•The ethylene glycol showed higher performance in terms of penetration ability.
Host-microbe symbioses play a critical role in the evolution of biological diversity and complexity. In a notably intricate system, southern pine beetles use symbiotic fungi to help overcome ...host-tree defenses and to provide nutrition for their larvae. We show that this beetle-fungal mutualism is chemically mediated by a bacterially produced polyunsaturated peroxide. The molecule's selective toxicity toward the beetle's fungal antagonist, combined with the prevalence and localization of its bacterial source, indicates an insect-microbe association that is both mutualistic and coevolved. This unexpected finding in a well-studied system indicates that mutualistic associations between insects and antibiotic-producing bacteria are more common than currently recognized and that identifying their small-molecule mediators can provide a powerful search strategy for therapeutically useful antimicrobial compounds.
Image formation algorithms in a variety of applications have explicit or implicit dependence on a mathematical model of the observation process. Inaccuracies in the observation model may cause ...various degradations and artifacts in the reconstructed images. The application of interest in this paper is synthetic aperture radar (SAR) imaging, which particularly suffers from motion-induced model errors. These types of errors result in phase errors in SAR data, which cause defocusing of the reconstructed images. Particularly focusing on imaging of fields that admit a sparse representation, we propose a sparsity-driven method for joint SAR imaging and phase error correction. Phase error correction is performed during the image formation process. The problem is set up as an optimization problem in a nonquadratic regularization-based framework. The method involves an iterative algorithm, where each iteration of which consists of consecutive steps of image formation and model error correction. Experimental results show the effectiveness of the approach for various types of phase errors, as well as the improvements that it provides over existing techniques for model error compensation in SAR.
Prompted by a knowledge of the photoprotective mechanism operating in photosystem supercomplexes and bacterial antenna complexes by pigment binding proteins, we have appealed to a boxlike synthetic ...receptor (ExBox·4Cl) that binds a photosensitizer, 5,15-diphenylporphyrin (DPP), to provide photoprotection by regulating light energy. The hydrophilic ExBox 4+ renders DPP soluble in water and modulates the phototoxicity of DPP by trapping it in its cavity and releasing it when required. While trapping removes access to the DPP triplet state, a pH-dependent release of diprotonated DPP (DPPH2 2+) restores the triplet deactivation pathway, thereby activating its ability to generate reactive oxygen species. We have employed the ExBox 4+-bound DPP complex (ExBox 4+⊃DPP) for the safe delivery of DPP into the lysosomes of cancer cells, imaging the cells by utilizing the fluorescence of the released DPPH2 2+ and regulating photodynamic therapy to kill cancer cells with high efficiency.
Collisional intermolecular interactions between excited states form short-lived dimers and complexes that lead to the emergence of excimer/exciplex emission of lower energy, a phenomenon which must ...be differentiated from the photoluminescence (PL) arising from the monomeric molecules. Although the utilization of noncovalent bonding interactions, leading to the generation of excimer/exciplex PL, has been investigated extensively, precise control of the aggregates and their persistence at very low concentrations remains a rare phenomenon. In the search for a fresh approach, we sought to obtain exciplex PL from permanent structures by incorporating anthracene moieties into pyridinium-containing mechanically interlocked molecules. Beyond the optical properties of the anthracene moieties, their π-extended nature enforces π···π stacking that can overcome the Coulombic repulsion between the pyridinium units, affording an efficient synthesis of an octacationic homo2catenane. Notably, upon increasing the ionic strength by adding tetrabutylammonium hexafluorophosphate, the catenane yield increases significantly as a result of the decrease in Coulombic repulsions between the pyridinium units. Although the ground-state photophysical properties of the free cyclophane and the catenane are similar and show a charge-transfer band at ∼455 nm, their PL characters are distinct, denoting different excited states. The cyclophane emits at ∼562 nm (quantum yield ϕF = 3.6%, emission lifetime τs = 3 ns in MeCN), which is characteristic of a disubstituted anthracene–pyridinium linker. By contrast, the catenane displays an exciplex PL at low concentration (10–8 M) with an emission band centered on 650 nm (ϕF = 0.5%, τs = 14 ns) in MeCN and at 675 nm in aqueous solution. Live-cell imaging performed in MIAPaCa-2 prostate cancer cells confirmed that the catenane exciplex emission can be detected at micromolar concentrations.
A prism-shaped cage was obtained via the Friedel–Crafts reaction in a 2:3 mixture of trisfuryl and bis-isopropenyl precursors, in a remarkable yield of 40% considering six C–C bonds formed in a ...one-pot manner. The cage contains two π-electron rich trisfuryl platforms bridged in a face-to-face manner with three p-xylylene linkers. Therefore, it enables accommodation of π-electron poor guests with complementary size, including biscationic viologen.
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