Intelligent reversible watermarking technique in medical images using GA and PSO

The advances in recording, editing, and broadcasting multimedia contents in digital form motivate to protect these digital contents from illegal use, such as duplication, manipulation, and redistribution. However, watermarking algorithms are designed to satisfy requirements of applications, as different applications have different concerns. We intend to design a watermarking algorithm for applications which require high embedding capacity and imperceptibility, to maintain the integrity of the host signal as well as embedded information. Reversible watermarking is a promising technique which satisfies our requirements. In this paper, we concentrate on improving the watermark capacity and reducing the perceptual degradation of an image. We investigated the Luo's [1] additive interpolation-error expansion algorithm and enhanced it by incorporating with two intelligent techniques: genetic algorithm (GA), and particle swarm optimization (PSO). Genetic algorithm is applied to exploit the correlation of image pixel values to obtain better estimation of neighboring pixel values, which results in optimal balance between information storage capacity and imperceptibility. Particle swarm optimization (intelligent technique) is also applied for the same purpose. Experimental results show that PSO and GA nearly give the same results, but GA outperforms the PSO. Experimental results also reveal that the proposed strategy outperforms the state of art works in terms of perceptual quality and watermarking payload.     

4‐[3‐(3,4‐Di­methoxy­phenyl)­prop‐2‐enoyl]­phenyl methacryl­ate and 4‐[3‐(2‐bromo­phenyl)­prop‐2‐enoyl]­phenyl methacryl­ate

Chalcones (α,β‐unsaturated ketones) are effective antitumour agents. It has been proved that having halogen or methoxy groups substituted in various positions of the phenyl ring enhances the activity of chalcones many times. The title compounds, C₂₁H₂₀O₅ and C₁₉H₁₅BrO₃, respectively, were chosen for crystallographic study in order to determine their structures and conformations. In both compounds, the keto group is in the s‐cis conformation and is almost planar. There are weak intramolecular interactions in both structures.     

Functional Groups Assisted Tunable Dielectric Permittivity of Guest-Free Zn-Based Coordination Polymers for Gate Dielectrics

The dielectric properties of coordination polymers has been a topic of recent interest, but the role of different functional groups on the dielectric properties of these polymers has not yet been fully addressed. Herein, the effects of electron-donating (R=NH₂) and electron-withdrawing (R=NO₂) groups on the dielectric behavior of such materials were investigated for two thermally stable and guest-free Zn-based coordination polymers, [Zn(L₁)(L₂)]_n ( 1 ) and [Zn(L₁)(L₃)]_n ( 2 ) [L₁=2-(2-pyridyl) benzimidazole (Pbim), L₂=5-aminoisophthalate (Aip), and L₃=5-nitroisophthalate (Nip)]. The results of dielectric studies of 1 revealed that it possesses a high dielectric constant (κ=65.5 at 1 kHz), while compound 2 displayed an even higher dielectric constant (κ=110.3 at 1 kHz). The electron donating and withdrawing effects of the NH₂ and NO₂ substituents induce changes in the polarity of the polymers, which is due to the inductive effect from the aryl ring for both NO₂ and NH₂. Theoretical results from density functional theory (DFT) calculations, which also support the experimental findings, show that both compounds have a distinct electronic behavior with diverse wide bandgaps. The significance of the current work is to provide information about the structure-dielectric property relationships. So, this study promises to pave the way for further research on the effects of different functional groups on coordination polymers on their dielectric properties.     

Designing spirobifullerene core based three-dimensional cross shape acceptor materials with promising photovoltaic properties for high-efficiency organic solar cells

The development of organic electron acceptor materials is one of the key factors for realizing high-performance organic solar cells (OSCs). Nonfullerene electron acceptors, compared to traditional fullerene acceptor materials, have gained much impetus owing to their better optoelectronic tunabilities and lower cost, as well as higher stability. Therefore, 5 three-dimensional (3D) cross-shaped acceptor materials having a spirobifullerene core flanked with 2,1,3-benzothiadiazole are designed from a recently synthesized highly efficient acceptor molecule SF(BR) ₄ and are investigated in detail with regard to their use as acceptor molecules in OSCs. The density functional theory (DFT) and time-dependent DFT (TDDFT) calculations have been performed for the estimation of frontier molecular orbital (FMO) analysis, density of states analysis, reorganization energies of electron and hole, dipole moment, open-circuit voltage, photo-physical characteristics, and transition density matrix analysis. In addition, the structure-property relationship is studied, and the influence of end-capped acceptor modifications on photovoltaic, photo-physical, and electronic properties of newly selected molecules ( H1-H5 ) is calculated and compared with reference ( R ) acceptor molecule SF(BR) ₄ . The structural tailoring at terminals was found to effectively tune the FMO band gap, energy levels, absorption spectra, open-circuit voltage, reorganization energy, and binding energy value in selected molecules H1 to H5 . The 3D cross-shaped molecules H1 to H5 suppress the intermolecular aggregation in PTB7-Th blend, which leads to high efficiency of acceptor material H1 to H5 in OSCs. Consequently, better optoelectronic properties are achieved from designed molecules H1 to H5 . It is proposed that the conceptualized molecules are superior than highly efficient spirobifullerene core-based SF(BR) ₄ acceptor molecules and, thus, are recommended to experiments for future developments of highly efficient solar cells.     

Kinetic modeling of ZnO-rGO catalyzed degradation of methylene blue

Photodegradation of organic pollutants strongly depends on design of metal oxide semiconductor photocatalysts. Graphene, if composited with ZnO, can effectively enhance its photocatalytic performance for the eradication of pollutants from aqueous medium. Here in, ZnO-rGO is reported as highly active catalyst for degradation of methylene blue. A 200-mg/L solution of methylene blue dye was completely degraded within 1 h in comparison to 74% and 56% degradation over ZnO and rGO, respectively. The commonly used mechanisms of heterogeneous catalytic reactions, the Langmuir-Hinshelwood mechanism, and the Eley-Rideal mechanisms, were used to describe the reaction kinetics. The Langmuir-Hinshelwood mechanism was found as more favorable in this study. Apparent activation energy, E_ap, true activation energy, E_T, entropy, ΔS, and enthalpy, ΔH were calculated as 36.2 kJ/mol, 13.1 kJ/mol, 197.5 J/mol, and 23.1 kJ/mol, respectively.     

Through-Space Spin Coupling in a Silver(II) Porphyrin Dimer upon Stepwise Oxidations: AgII⋅⋅⋅AgII,AgII⋅⋅⋅AgIII,and AgIII⋅⋅⋅AgIII Metallophilic Interactions

Metallophilic interactions between closed-shell metal ions are becoming a popular tool for a variety of applications related to high-end materials. Heavier d⁸ transition-metal ions are also considered to have a closed shell and can be involved in such interactions. There is no systematic investigation so far to estimate the structure and energy characteristics of metallophilic interactions in Ag^II/Ag^II (d⁹/d⁹), Ag^III/Ag^III (d⁸/d⁸), and mixed-valent Ag^II/Ag^III (d⁹/d⁸) complexes, which have been demonstrated in the present study. Both interporphyrinic and intermetallic interactions were investigated on stepwise oxidation by using a rigid ethene-bridged cis silver(II) porphyrin dimer and the results compared with those for highly flexible ethane-bridged analogues. By controlling the nature of chemical oxidants and their stoichiometry, both 1e and 2e oxidations were done stepwise to generate Ag^II/Ag^III mixed-valent and Ag^III/Ag^III porphyrin dimers, respectively. Unlike all other ethene-bridged metalloporphyrin dimers reported earlier, in which 2e oxidation stabilizes only the trans form, such an oxidation of silver(II) porphyrin dimer stabilizes only the cis form because of the metallophilic interaction. Besides silver(II) ⋅⋅⋅ silver(II) interactions in cis silver(II) porphyrin dimer, stepwise oxidations also enabled us to achieve various hitherto-unknown silver(II) ⋅⋅⋅ silver(III) and silver(III) ⋅⋅⋅ silver(III) interactions, which thereby allow significant modulation of their structure and properties. The strength of Ag ⋅⋅⋅ Ag interaction follows the order Ag^II/Ag^II (d⁹/d⁹)<Ag^II/Ag^III (d⁹/d⁸)<Ag^III/Ag^III (d⁸/d⁸). Single-crystal XRD, X-ray photoelectron spectroscopy (XPS), ¹H NMR and EPR spectroscopy, and variable-temperature magnetic investigations revealed various oxidation states of silver and metallophilic interactions, which are also well supported by computational analysis.     

A ternary complex of aqua(18‐crown‐6)bis(o‐nitrophenolato)barium(II), the triaqua(18‐crown‐6)(o‐nitrophenolato)barium(II) cation and the o‐nitrophenolate anion

In the title compound [systematic name: tri­aqua(1,4,7,10,13,16‐hexaoxa­cyclo­octa­decane‐κ⁶O)(2‐nitro­phenolato‐κO)­barium(II)–aqua(1,4,7,10,13,16‐hexaoxa­cyclo­octa­decane‐κ⁶O)‐ bis(2‐nitro­phenolato‐κ²O,O′)­barium(II)–2‐nitro­phenolate (1/1/1)], [Ba(C₁₂H₂₄O₆)(C₆H₄NO₃)(H₂O)₃][Ba(C₁₂H₂₄O₆)(C₆H₄NO₃)₂(H₂O)](C₆H₄NO₃), the two Ba^II atoms encapsulated by the 18‐crown‐6 rings have different coordinations. Although both Ba^II atoms are coordinated to the six O atoms of the crowns, in the neutral moiety, the Ba^II atom is coordinated to one terminal O atom from a water mol­ecule, two phenolate O atoms and two nitro‐group O atoms, while in the cationic moiety, the Ba^II atom is coordinated to three terminal O atoms from water mol­ecules and one phenolate O atom. Both the crowns are eclipsed and translated along the b direction. In the asymmetric unit, the three components are interconnected by four O—H?O interactions. The packing is stabilized by two intermolecular C—H?O interactions and by one O—H?O interaction.     

Recent Advances and Perspectives in the Synthesis and Applications of Tetrahydrocarbazol‐4‐ones†

Tetrahydrocarbazol‐4‐one represents a prevalent framework of numerous natural products and pharmaceuticals. This review summaries the recent synthetic progresses of this core structure, including Fischer indolization, oxidative and reductive coupling, α‐arylative cyclization by means of transition‐ metal catalysis or under metal‐free conditions, and other methods. The recently emerged enantioselective catalytic methods of tetrahydrocarbazol‐4‐ ones are also described. The mechanistic insights and applications of these strategies as a key step in the total (formal) synthesis of complex alkaloids are highlighted as well.     

Syn‐ and anticlinal isomers of 2a′‐acetoxy‐1,7′‐diacetyl‐7′,7a′‐dihydro‐2‐oxospiro[1H‐indole‐3(2H),2′(2a′H)‐oxeto[3,2‐b]indole]

In the syn‐ and anticlinal isomers of the title compound, C₂₂H₁₈N₂O₆, the indole moiety is not completely planar, with the pyrrolidine ring being distorted very slightly towards a conformation intermediate between half‐chair and envelope. The molecular and packing structures in the crystals of these isomers are stabilized by C—H?O interactions.     

Adsorption Behavior and Dynamic Interactions of Anionic Acid Blue 25 on Agricultural Waste

In this study, adsorption characteristics of a negatively charged dye, Acid Blue 25 (AB25), on pomelo pith (PP) was studied by varying the adsorption parameters, with the aim of evaluating the adsorption mechanism and establishing the role of hydrogen bonding interactions of AB25 on agricultural wastes. The kinetics, intraparticle diffusion, mechanism, and thermodynamics of the AB25 adsorption were systematically evaluated and analyzed by pseudo-first-order and pseudo-second-order kinetic models, the Weber–Morris intraparticle and Boyd mass transfer models, the Langmuir, Freundlich, Dubinin–Radushkevich, and Temkin isotherm models, and the Van’t Hoff equation. It was found that AB25 adsorption followed pseudo-second-order kinetics, governed by a two-step pore-volume intraparticle diffusion of external mass transfer of AB25 onto the PP surface. The adsorption process occurred spontaneously. The adsorption mechanism could be explained by the Langmuir isotherm model, and the maximum adsorption capacity was estimated to be 26.9 mg g⁻¹, which is comparable to many reported adsorbents derived from agricultural wastes. Changes in the vibrational spectra of the adsorbent before and after dye adsorption suggested that AB25 molecules are bound to the PP surface via electrostatic and hydrogen bonding interactions. The results demonstrated that the use of pomelo pith, similar to other agricultural wastes, would provide a basis to design a simple energy-saving, sustainable, and cost-effective approach to remove negatively charged synthetic dyes from wastewater.