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The present overview is intended to point the readers' attention to the important subject of calcium orthophosphates. This type of materials is of the special significance for the human beings because they represent the inorganic part of major normal (bones, teeth and antlers) and pathological (i.e. those appearing due to various diseases) calcified tissues of mammals. For example, atherosclerosis results in blood vessel blockage caused by a solid composite of cholesterol with calcium orthophosphates. Dental caries and osteoporosis mean a partial decalcification of teeth and bones respectively that results in replacement of a less soluble and harder biological apatite by more soluble and softer calcium hydrogenphosphates. Therefore, the processes of both normal and pathological calcifications are just an in vivo crystallization of calcium orthophosphates. Similarly, dental caries and osteoporosis might be considered as in vivo dissolution of calcium orthophosphates. Conversely, due to a great chemical similarity with the biological calcified tissues, many calcium orthophosphates possess remarkable biocompatibility and bioactivity. Materials scientists extensively use this property to construct artificial bone grafts that are either entirely made of or only surface-coated by the biologically relevant calcium orthophosphates. For example, self-setting hydraulic cements made of calcium orthophosphates are helpful in bone repair, while titanium substitutes covered by a surface layer of calcium orthophosphates are used for hip joint endoprostheses and tooth substitutes. Porous scaffolds made of calcium orthophosphates are very promising tools for tissue engineering applications. In addition, calcium orthophosphates of a technical grade are very popular mineral fertilizers. There is a great significance of calcium orthophosphates for the humankind and, in this paper, an overview on the current knowledge on this subject is provided. To assist and guide the readers, a great number of references to the related publications detalizing various specific aspects of the matter has been collected.

We describe a solid-state material formed from binary assembly of atomically precise molecular clusters. [Co₆Se₈(PEt₃)₆][C₆₀]₂ and [Cr₆Te₈(PEt₃)₆][C₆₀]₂ assembled into a superatomic relative of the cadmium iodide (Cdl₂) structure type. These solid-state materials showed activated electronic transport with activation energies of 100 to 150 millielectron volts. The more reducing cluster Ni₉Te₆(PEt₃)₈ transferred more charge to the fullerene and formed a rock-salt—related structure. In this material, the constituent clusters are able to interact electronically to produce a magnetically ordered phase at low temperature, akin to atoms in a solid-state compound.

Purpose It has been known that noise correlation plays an important role in the determination of the performance of spectral imaging based on two‐material decomposition (2‐MD). To further understand the basics of spectral imaging in photon‐counting CT toward optimal design and implementation, we study the noise correlation in multi‐MD (m‐MD) and its impact on the performance of spectral imaging. Method We derive the equations that characterize the noise and noise correlation in the material‐specific (basis) images in m‐MD, followed by a simulation study to verify the derived equations and study the noise correlation's impact on the performance of spectral imaging. Using a specially designed digital phantom, the study of noise correlation runs over the cases of two‐, three‐, and four‐MD (2‐MD, 3‐MD, and 4‐MD). Then, the noise correlation's impact on the performance of spectral imaging in photon‐counting CT is investigated, using a modified Shepp–Logan phantom. Results The results in 2‐MD show that, in‐line with what has been reported in the literature, the noise correlation coefficient between the material‐specific images corresponding to the basis materials approaches −1. The results in m‐MD (m ≥ 3) are more complicated and interesting, as the noise correlation coefficients between a pair of the material‐specific images alternate between ±1, and so do in the case of 4‐MD. The m‐MD data show that the noise in virtual monochromatic imaging (a form of spectral imaging) is moderate even though the noises in material‐specific (basis) images vary drastically. Conclusions The observation of noise correlation in 3‐MD, 4‐MD, and beyond (i.e., m‐MD) is informative to the community. The relationship between noise correlation and the performance of spectral imaging revealed in this work may help clinical medical physicists understand the fundamentals of spectral imaging based on MD and optimize the performance of spectral imaging in photon‐counting CT and other X‐ray imaging modalities.

Reduced graphene oxide (RGO)–BiOCl hybrid materials were prepared by a novel benzyl alcohol route. The formation of uniform RGO–BiOCl hybrids was attributed to the interaction of introduced graphene oxide and BiOCl, which resulted in a selective growth of BiOCl along (110) orientation. The RGO–BiOCl hybrids showed both enhanced visible-light and ultraviolet light photocatalytic activities compared to nano-BiOCl with similar particle size. In particular, the first-order kinetic constant ( k ) of Rhodamine B on the optimal RGO (0.73 %)–BiOCl hybrid was 2.5 times that on bare nano-BiOCl under visible-light irradiation. For RGO–BiOCl hybrids, RGO probably acted as a photosensitizer in photocatalytic reaction and resulted in the improved visible-light photocatalytic performance. However, RGO was an excellent electron transfer and inhibited the recombination of electron–hole pairs on BiOCl under ultraviolet light.

Silicon nitride (Si 3 N 4 ) is used in a variety of important technological applications. The high fracture toughness, hardness and wear resistance of Si 3 N 4 -based ceramics are exploited in cutting tools and anti-friction bearings 1 ; in electronic applications, Si 3 N 4 is used as an insulating, masking and passivating material 2 . Two polymorphs of silicon nitride are known, both of hexagonal structure: α- and β-Si 3 N 4 . Here we report the synthesis of a third polymorph of silicon nitride, which has a cubic spinel structure. This new phase, c-Si 3 N 4 , is formed at pressures above 15 GPa and temperatures exceeding 2,000 K, yet persists metastably in air at ambient pressure to at least 700 K. First-principles calculations of the properties of this phase suggest that the hardness of c-Si 3 N 4 should be comparable to that of the hardest known oxide (stishovite 3 , a high-pressure phase of SiO 2 ), and significantly greater than the hardness of the two hexagonal polymorphs.

This work provides a new approach for the solution laser synthesis of magnetic Fe/Fe 2 O 3 nanoparticles (15–25 nm average size), as well as core–shell nanoparticles consisting of crystalline Fe/Fe 2 O 3 cores (5–15 nm average size), and amorphous carbon-shells. Laser irradiation of iron pentacarbonyl, Fe(CO) 5 , in different organic solvents (toluene, tetrahydrofuran, dimethyl sulphoxide, and acetonitrile) using the 532- and 355-nm wavelengths was investigated. The mechanism operating in the laser synthesis involves photodecomposition of Fe(CO) 5 and the formation of iron and/or an iron oxide core surrounded by a carbon-shell depending on the nature of the solvent. In the case of toluene as a solvent, a magnetic Fe/Fe 2 O 3 core surrounded by a carbon-shell was formed, while in the other solvents investigated (tetrahydrofuran, dimethyl sulphoxide, and acetonitrile), both Fe and Fe 2 O 3 nanoparticles were formed without carbon-shells. Characterization techniques including X-ray photoelectron spectroscopy, transmission electron microscopy, X-ray diffraction, and Raman spectroscopy were used to determine the composition and morphology of the laser-synthesized magnetic Fe/Fe 2 O 3 nanoparticles and the core–shell nanoparticles. In addition, the data revealed that the Fe/Fe 2 O 3 -nanoparticles produced in all the solvents used except tetrahydrofuran had good magnetic properties.

We investigated the effect of energy loss of ions on the ion irradiation-induced tuning of surface plasmon resonance (SPR) wavelength of Au nanoparticles (NPs) in fullerene C 70 matrix. The transformation of fullerene C 70 into amorphous carbon (a-C) under ion irradiation was used to tune the SPR wavelength of Au–C 70 nanocomposite thin films. It is found that the range of tuning of SPR wavelength increases with increase in electronic energy loss of the incoming beam. The growth of Au NPs with increasing fluence was observed in all the cases and total growth is proportional to the electronic energy loss. The average diameter of Au NPs in pristine film is ~4.8 nm and a maximum growth of ~3 nm was observed at a fluence of 3 × 10 13  ions/cm 2 , when the film was irradiated with 120 MeV Ag ions. It was also observed that nuclear energy loss via collision cascades has lower efficiency for SPR tuning in comparison with the electronic excitations.

The magnetic Fe 3 O 4 nanoparticles supported imidazolium-based ionic liquids (MNPs–IILs), namely 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium hydrogen sulfate (MNPs–IIL–HSO 4 ), 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium acetate (MNPs–IIL–OAc) and 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium chloride (MNPs–IIL–Cl) were used as efficient new catalysts for the one-pot synthesis of 3,4-dihydropyrimidin-2(1 H )-ones under microwave irradiation and solvent-free conditions in excellent yields. Utilization of easy reaction conditions, catalyst with high catalytic activity and good reusability, and simple magnetically work-up, makes this green protocol as an interesting option for the economic synthesis of Biginelli compounds. Microwave technology as an eco-friendly green synthetic approach has gradually been used in this organic procedure. Combining the advantages of microwave irradiation and magnetically nanocatalyst, this method provides an efficient and much improved modification of the original Biginelli reaction. We believe that this procedure appears to have a broad scope with respect to variation in the 3,4-dihydropyrimidin-2(1 H )-ones (thiones). Graphical Abstract we have developed a rapid, effective, validated and environmental-friendly method for the synthesis of dihydropyrimidinones (thiones) using Fe 3 O 4 nanoparticles immobilized imidazolium salt catalyst in microwave irradiation and solvent-free conditions. Reduced reaction times, high turnover frequency, high yields of products, absence of solvent and recyclability of catalyst make our catalyst a valuable system addition to previously reported methods. This green methodology should be amenable to construct new substituted dihydropyrimidinones scaffolds with potential biological applications.

Magnetic resonance imaging and spectroscopy systems use coils, either singly or as arrays, to intercept radio-frequency (RF) magnetic flux from regions of interest, often deep within the body. Here, we show that a new magnetic material offers novel possibilities for guiding RF flux to the receiver coil, permitting a clear image to be obtained where none might otherwise be detectable. The new material contains microstructure designed according to concepts taken from the field of photonic band gap materials. In the RF range, it has a magnetic permeability that can be produced to specification while exhibiting negligible direct-current magnetism. The latter property is vital to avoid perturbing the static and audio-frequency magnetic fields needed to obtain image and spectral data. The concept offers a new paradigm for the manipulation of RF flux in all nuclear magnetic resonance systems.

The intercalation of ions into layered compounds has long been exploited in energy storage devices such as batteries and electrochemical capacitors. However, few host materials are known for ions much larger than lithium. We demonstrate the spontaneous intercalation of cations from aqueous salt solutions between two-dimensional (2D) Ti₃C₂ MXene layers. MXenes combine 2D conductive carbide layers with a hydrophilic, primarily hydroxyl-terminated surface. A variety of cations, including Na⁺, K⁺, NH₄⁺, Mg²⁺, and Al³⁺, can also be intercalated electrochemically, offering capacitance in excess of 300 farads per cubic centimeter (much higher than that of porous carbons). This study provides a basis for exploring a large family of 2D carbides and carbonitrides in electrochemical energy storage applications using single- and multivalentaions.