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The discovery of high-temperature superconductivity in a layered iron arsenide has led to an intensive search to optimize the superconducting properties of iron-based superconductors by changing the chemical composition of the spacer layer between adjacent anionic iron arsenide layers. Superconductivity has been found in iron arsenides with cationic spacer layers consisting of metal ions (for example, Li+, Na+, K+, Ba2+) or PbO- or perovskite-type oxide layers, and also in Fe1.01Se (ref. ) with neutral layers similar in structure to those found in the iron arsenides and no spacer layer. Here we demonstrate the synthesis of Lix(NH2)y(NH3)1?yFe2Se2 (x~0.6; y~0.2), with lithium ions, lithium amide and ammonia acting as the spacer layer between FeSe layers, which exhibits superconductivity at 43(1)?K, higher than in any FeSe-derived compound reported so far. We have determined the crystal structure using neutron powder diffraction and used magnetometry and muon-spin rotation data to determine the superconducting properties. This new synthetic route opens up the possibility of further exploitation of related molecular intercalations in this and other systems to greatly optimize the superconducting properties in this family. [ABSTRACT FROM AUTHOR]

Purpose Student radiographers must possess certain abilities to progress in their training; these can be assessed in various ways. Bandura's social cognitive theory identifies self-efficacy as a key psychological construct with regard to how people adapt to environments where new skills are developed. Use of this construct is common in health care literature but little has been noted within radiographic literature. The authors sought to develop a self-efficacy scale for student radiographers. Method The scale was developed following a standard format. An initial pool of 80 items was generated and psychometric analysis was used to reduce this to 68 items. Radiography students drawn from 7 universities were participants (N=198) in validating the scale. Results The psychometric properties of the scale were examined using analysis of variance (ANOVA), factor analysis and item analysis. ANOVA demonstrated an acceptable level of known group validity: first-year, second-year, and third-year students all scored significantly differently (P=.035) from one another. Factor analysis identified the most significant factor as confidence in image appraisal. The scale was refined using item and factor analysis to produce the final 25-item scale. Conclusion This is the first published domain-specific self-efficacy scale validated specifically for student radiographers. In its current format it may have pedagogical utility. The authors currently are extending the work to add to the scale's validity and embedding it into student training to assess its predictive value. [ABSTRACT FROM AUTHOR]

Phenylsilsesquioxane fluid (PSF) is used widely in the personal care industry and is a common component of skin and oral care products. The potential developmental toxicity of PSF was evaluated in rats and rabbits. Groups of 25 sperm-positive Sprague-Dawley rats (Taconic Farms) and 15 sperm-positive New Zealand White rabbits (HRP) were administered dose levels of 50, 500, or 1000 mg/kg PSF in corn oil. Vehicle control groups of equal size were administered corn oil alone. Rats were dosed daily (5 ml/kg) on gestation d 6–15 and sacrificed on gestation d 20, while rabbits were dosed daily (1.5 ml/kg) on gestation d 6–18 and sacrificed on gestation d 29. The fetuses were removed by cesarean section and examined for gross external, visceral, cephalic, and skeletal anomalies. No treatment-related clinical signs of toxicity were observed. No marked effects upon maternal food consumption, body weight, body weight gain, or uterus or liver weight were detected. Fetal viability and body weight, as well as developmental endpoints, were unaffected by treatment. Accordingly, exposure of pregnant rats or rabbits to 50, 500, or 1000 mg/kg of PSF during the period of major organogenesis did not result in any biologically significant adverse or teratogenic effects in the dams or fetuses. [ABSTRACT FROM AUTHOR]

Studies reported here assessed the potential adverse effects of silicone gel, Dow Corning Q7-2159A, on general reproduction and fetal development in male and female Charles River CD rats and New Zealand white rabbits. Two control and three treatment groups of 30 male and 30 female rats and 25 female rabbits per group were used in the one-generation reproduction and developmental toxicity studies, respectively. The silicone gel was implanted subcutaneously in two flank sites at dosage levels of 3, 10, and 30 ml/kg. The highest dose was selected on the basis of likely human body burden. Control groups received either sterile saline or carboxymethylcellulose solution in two flank implantation sites. The control and test articles were implanted in male and female rats 61 and 47 days, respectively, prior to mating (in the rat reproduction study) and approximately 42 days prior to insemination of female rabbits (in the rabbit developmental toxicity study). There were no treatmentrelated effects on F parental general conditions and reproductive performance, F neonatal viability, or growth in the rat reproduction study. No maternal nor developmental effects, including teratogenicity, were observed in rabbits in the groups implanted with Q7-2159A gel in the developmental toxicitystudy. [ABSTRACT FROM PUBLISHER]

The purpose of these studies was to assess the potential adverse effects of silicone breast implant envelope elastomer on general reproduction and fetal development in rats and rabbits. One control and one treatment group of 30 male and 30 female Charles River CD rats and 25 inseminated New Zealand white rabbits per group were used in the one-generation reproductive and developmental toxicity studies, respectively. Two 1.2-cm discs of silicone elastomer were subcutaneoulsy implanted in one site in the left flank and one site in the right-flank of the treated group of rats, while four 2.5-cm discs were implanted in two sites in the left flank and two sites in the right flank of the treated group of rabbits. The size of the elastomer implants was chosen to approximate the expected body burden of women with breast implants. The control animlas in both studies received subcutaneous implantion of either 1.2- or 2.5-cm discs of polyethylene of the same number in the same locations. The control and tests articles were implanted in the male and female rats at 61 and 47 days, respectively, prior to mating (in the rat reproduction study) and approximately 42 days prior to insemination of femalel rabbits (in the rabbit developmental toxicity study). Subcutaneously implanted discs of silicone breast implant envelope elastomer did not induce maternal or devlopmental toxicity before or during pregnancy or during lactation, did not cause any adverse effects on the parents or neonates, and did not impair reproductive performance in the rat reproduction study. No maternal toxicity or adverse developmental effects including teratogenicity, were observed in the treated groups in the rabbit developmental toxicity study. [ABSTRACT FROM PUBLISHER]

Mixed-valent transition metal compounds display complex structural, electronic and magnetic properties which can often be exquisitely tuned. Here the charge-ordered state of stoichiometric CaFe3O5 is probed using neutron powder diffraction, Monte Carlo simulation and symmetry analysis. Magnetic ordering is dominated by the formation of ferromagnetic Fe3+–Fe2+–Fe3+ trimers which are evident above the magnetic ordering transition. Between TN = 289 K and 281 K an incommensurate magnetically ordered phase develops due to magnetic frustration, but a spin Jahn-Teller distortion lifts the frustration and enables the magnetic ordering to lock in to a charge-ordered commensurate state at lower temperatures. Stoichiometric CaFe3O5 exhibits single phase behaviour throughout and avoids the phase separation into two distinct crystallographic phases with different magnetic structures and Fe valence distributions reported recently, which likely occurs due to partial Fe2+ for Ca2+ substitution. This underlines the sensitivity of the magnetism and chemistry of these mixed-valent systems to composition. A significant challenge in understanding the behaviour of strongly correlated materials is their sensitivity to composition. Here the authors show that stoichiometric CaFe3O5 avoids the electronic phase separation reported in a non-stoichiometric sample, and also exhibits an incommensurate magnetic phase. [ABSTRACT FROM AUTHOR]

Abstract: The effect of the isovalent substitution of Sr2+ by Ca2+ on the structure and superconducting properties of Sr2−x Ca x VO3FeAs is described in the compositional range 0≤x≤0.5. SQUID magnetometry measurements reveal that after an initial increase in T c , which is maximised at 29.5K in Sr1.95Ca0.05VO3FeAs, a rapid suppression of superconductivity is observed with increasing x. XANES spectra of Sr2−x Ca x VO3FeAs collected on the Fe and V absorption K-edges show that the position of both edges are invariant with composition within the experimental uncertainty. A combination of synchrotron X-ray powder diffraction and neutron powder diffraction techniques is used to rationalise the observed changes in T c with x, in terms of changes to the structure of the FeAs layer upon partial Ca substitution. These findings demonstrate that superconductivity in the Fe-based superconductors is extremely sensitive to the crystal structure with T c maximised in samples with regular FeAs4-tetrahedra. [Copyright &y& Elsevier]

We use in situ synchrotron X-ray diffraction measurements to monitor the solvothermal crystallization mechanism of the aperiodic metal-organic framework TRUMOF-1. Following an initial incubation period, TRUMOF-1 forms as a metastable intermediate that subsequently transforms into an ordered product with triclinic crystal symmetry. We determine the structure of this ordered phase, which we call msw-TRUMOF-1, and show that it is related to TRUMOF-1 through topotactic reorganization of linker occupancies. Our results imply that the connectivity of TRUMOF-1 can be reorganized, as required for data storage and manipulation applications.

We report the magnetic behavior of the hybrid perovskites [Gua]Mn 1- x Fe 2 x /3 □ x /3 (HCOO) 3 (0 ≤ x ≤ 0.88), showing that vacancy ordering drives bulk ferrimagnetism for x > 0.6. The behavior is rationalized in terms of a simple microscopic model of percolation-induced ferrimagnetism. Monte Carlo simulations driven by this model reproduce the experimental dependence of magnetic susceptibility on x and show that, at intermediate compositions, domains of short-range vacancy order lead to the emergence of local magnetization. Our results open up a new avenue for the design of multiferroic hybrid perovskites.

Tetrathiatriarylmethyl radicals (TAM or trityl) are receiving increasing attention in various fields of magnetic resonance, such as imaging, dynamic nuclear polarization, spin labeling, and, more recently, molecular magnetism and quantum information technology. Here, a trityl radical attached via a phenyl bridge to a copper(II)tetraphenylporphyrin was synthesized, and its magnetic properties studied by multi-frequency continuous-wave electron paramagnetic resonance (EPR) spectroscopy and magnetic measurements. EPR revealed that the electron spin-spin coupling constant J between the trityl and Cu2+ spin centers is ferromagnetic with a magnitude of 2.3 GHz (0.077 cm-1 (JS1S2 convention) and a distribution width of 1.2 GHz (0.040 cm-1). With the help of density functional theory (DFT) calculations, the obtained ferromagnetic exchange coupling, which is unusual for para-substituted phenyl-bridged biradicals, could be related to the almost perpendicular orientation of the phenyl linker with respect to the porphyrin and trityl ring planes in the energy minimum, while the J distribution was rationalized by the temperature weighted rotation of the phenyl bridge about the molecular axis connecting both spin centers. This study exemplifies the importance of molecular dynamics for the homogeneity (or heterogeneity) of the magnetic properties of trityl-based systems., (© 2022 Wiley-VCH GmbH.)

Sr 2 NiO 2 Cu 2 Se 2 , comprising alternating [Sr 2 NiO 2 ] 2+ and [Cu 2 Se 2 ] 2- layers, is reported. Powder neutron diffraction shows that the Ni 2+ ions, which are in a highly elongated NiO 4 Se 2 environment with D 4 h symmetry, adopt a high-spin configuration and carry localized magnetic moments which order antiferromagnetically below ∼160 K in a √2 a × √2 a × 2 c expansion of the nuclear cell with an ordered moment of 1.31(2) μ B per Ni 2+ ion. The adoption of the high-spin configuration for this d 8 cation in a pseudo-square-planar ligand field is supported by consideration of the experimental bond lengths and the results of density functional theory (DFT) calculations. This is in contrast to the sulfide analogue Sr 2 NiO 2 Cu 2 S 2 , which, according to both experiment and DFT calculations, has a much more elongated ligand field, more consistent with the low-spin configuration commonly found for square-planar Ni 2+ , and accordingly, there is no evidence for magnetic moment on the Ni 2+ ions. Examination of the solid solution Sr 2 NiO 2 Cu 2 (Se 1- x S x ) 2 shows direct evidence from the evolution of the crystal structure and the magnetic ordering for the transition from high-spin selenide-rich compounds to low-spin sulfide-rich compounds as a function of composition. Compression of Sr 2 NiO 2 Cu 2 Se 2 up to 7.2 GPa does not show any structural signature of a change in the spin state. Consideration of the experimental and computed Ni 2+ coordination environments and their subtle changes as a function of temperature, in addition to transitions evident in the transport properties and magnetic susceptibilities in the end members, Sr 2 NiO 2 Cu 2 Se 2 and Sr 2 NiO 2 Cu 2 S 2 , suggest that simple high-spin and low-spin models for Ni 2+ may not be entirely appropriate and point to further complexities in these compounds., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

The development of sustainable and efficient cryogenic cooling materials is currently the subject of extensive research, with the aim of relieving the dependence of current low-temperature cooling methods on expensive and nonrenewable liquid helium. One potential method to achieve this is the use of materials demonstrating the magnetocaloric effect, where the cycling of an applied magnetic field leads to a net cooling effect due to changes in magnetic entropy upon application and removal of an external magnetic field. This study details the synthesis and characterization of a Ln 3 (adipate) 4.5 (DMF) 2 series (where Ln = Gd-Er) of metal-organic framework (MOF) materials incorporating a flexible adipate ligand and their associated magnetocaloric and thermal expansion properties. The magnetocaloric performance of the Gd 3 (adipate) 4.5 (DMF) 2 material was found to exhibit the highest magnetic entropy changes of the series, with a peak entropy change of 36.4 J kg -1 K -1 for a 5-0 T field change at a temperature of 2 K, which is suited for ultra-low-temperature cooling applications. Thermal expansion properties were also investigated within these materials, demonstrating modest negative and large positive thermal expansion identified along the different crystallographic axes within the MOF structures over a 100-300 K temperature range that demonstrated the novel mechanical properties of these adipate framework structures.

Intercalation of lithium and ammonia into the layered semiconductor Bi 2 Se 3 proceeds via a hyperextended (by >60%) ammonia-rich intercalate, to eventually produce a layered compound with lithium amide intercalated between the bismuth selenide layers which offers scope for further chemical manipulation.

Sr 2 CrO 2 Cr 2 As 2 and Ba 2 CrO 2 Cr 2 As 2 with Cr 2+ ions in CrO 2 sheets and in CrAs layers crystallize with the Sr 2 Mn 3 Sb 2 O 2 structure (space group I 4/ mmm , Z = 2) and lattice parameters a = 4.00800(2) Å, c = 18.8214(1) Å (Sr 2 CrO 2 Cr 2 As 2 ) and a = 4.05506(2) Å, c = 20.5637(1) Å (Ba 2 CrO 2 Cr 2 As 2 ) at room temperature. Powder neutron diffraction reveals checkerboard-type antiferromagnetic ordering of the Cr 2+ ions in the arsenide layers below T N1_Sr , of 600(10) K (Sr 2 CrO 2 Cr 2 As 2 ) and T N1_Ba 465(5) K (Ba 2 CrO 2 Cr 2 As 2 ) with the moments initially directed perpendicular to the layers in both compounds. Checkerboard-type antiferromagnetic ordering of the Cr 2+ ions in the oxide layer below 230(5) K for Ba 2 CrO 2 Cr 2 As 2 occurs with these moments also perpendicular to the layers, consistent with the orientation preferences of d 4 moments in the two layers. In contrast, below 330(5) K in Sr 2 CrO 2 Cr 2 As 2 , the oxide layer Cr 2+ moments are initially oriented in the CrO 2 plane; but on further cooling, these moments rotate to become perpendicular to the CrO 2 planes, while the moments in the arsenide layers rotate by 90° with the moments on the two sublattices remaining orthogonal throughout [behavior recently reported independently by Liu et al. [Liu et al. Phys. Rev. B 2018, 98, 134416]]. In Sr 2 CrO 2 Cr 2 As 2 , electron diffraction and high resolution powder X-ray diffraction data show no evidence for a structural distortion that would allow the two Cr 2+ sublattices to couple, but high resolution neutron powder diffraction data suggest a small incommensurability between the magnetic structure and the crystal structure, which may account for the coupling of the two sublattices and the observed spin reorientation. The saturation values of the Cr 2+ moments in the CrO 2 layers (3.34(1) μ B (for Sr 2 CrO 2 Cr 2 As 2 ) and 3.30(1) μ B (for Ba 2 CrO 2 Cr 2 As 2 )) are larger than those in the CrAs layers (2.68(1) μ B for Sr 2 CrO 2 Cr 2 As 2 and 2.298(8) μ B for Ba 2 CrO 2 Cr 2 As 2 ) reflecting greater covalency in the arsenide layers.

The synthesis and structure of two new transition metal oxide tellurides, Sr 2 MnO 2 Cu 1.82(2) Te 2 and Sr 2 CoO 2 Cu 2 Te 2 , are reported. Sr 2 CoO 2 Cu 2 Te 2 with the purely divalent Co 2+ ion in the oxide layers has magnetic ordering based on antiferromagnetic interactions between nearest neighbors and appears to be inert to attempted topotactic oxidation by partial removal of the Cu ions. In contrast, the Mn analogue with the more oxidizable transition metal ion has a 9(1)% Cu deficiency in the telluride layer when synthesized at high temperatures, corresponding to a Mn oxidation state of +2.18(2), and neutron powder diffraction revealed the presence of a sole highly asymmetric Warren-type magnetic peak, characteristic of magnetic ordering that is highly two-dimensional and not fully developed over a long range. Topotactic oxidation by the chemical deintercalation of further copper using a solution of I 2 in acetonitrile offers control over the Mn oxidation state and, hence, the magnetic ordering: oxidation yielded Sr 2 MnO 2 Cu 1.58(2) Te 2 (Mn oxidation state of +2.42(2)) in which ferromagnetic interactions between Mn ions result from Mn 2+/3+ mixed valence, resulting in a long-range-ordered A-type antiferromagnet with ferromagnetic MnO 2 layers coupled antiferromagnetically.

The structures of two new oxide chalcogenide phases, Sr 2 CuO 2 Cu 2 S 2 and Sr 2 CuO 2 Cu 2 Se 2 , are reported, both of which contain infinite CuO 2 planes containing Cu 2+ and which have Cu + ions in the sulfide or selenide layers. Powder neutron diffraction measurements show that Sr 2 CuO 2 Cu 2 Se 2 exhibits long-range magnetic ordering with a magnetic structure based on antiferromagnetic interactions between nearest-neighbor Cu 2+ ions, leading to a √2 a × √2 a × 2 c expansion of the nuclear cell. The ordered moment of 0.39(6) μ B on the Cu 2+ ions at 1.7 K is consistent with the value predicted by density functional theory calculations. The compounds are structurally related to the cuprate superconductors and may also be considered as analogues of the parent phases of this class of superconductor such as Sr 2 CuO 2 Cl 2 or La 2 CuO 4 . In the present case, however, the top of the chalcogenide-based valence band is very close to the vacant Cu 2+ 3d states of the conduction band, leading to relatively high measured conductivity.