One pot occurrence of two polymorphs of Rb2Sc[Si4O10]F and their structural, spectroscopic and computational characterization

Single crystal growth experiments in the system RbF Sc2O3 SiO2 resulted in the simultaneous crystallization of two polymorphs of Rb2ScSi4O10F within the same run. Basic crystallographic data of the two forms at ambient conditions are as follows phase I space group I 4 m, a 11.2619 3 , c 8.3053 4 , V 1053.36 6 3, Z 4; phase II space group P 21 m, a 11.5085 6 , b 8.3805 3 , c 11.6750 6 , amp; 946; 111.147 6 , V 1050.19 9 3, Z 4. The structures were determined by direct methods and refined to residuals of R F 0.0231 phase I for 516 and 0.0249 phase II for 2050 independent observed reflections with I gt; 2 amp; 963; I . Phase I showed twinning by merohedry which was accounted for during the refinement process. Both compounds are based on multiple chains of [SiO4] tetrahedra forming closed columns or tubes. The multiplicity of the unbranched fundamental chains is two for phase I and four for phase II , respectively. The periodicity of the multiple chains has a value of four in both modifications which is also reflected in similar translation periods along the chain directions phase I t[001] 8.30 ; phase II t[010] 8.38 . Alternatively, both polymorphs can be described as mixed octahedral tetrahedral frameworks, which can be classified according to their polyhedral microensembles. A topological analysis of both networks is presented. Structural investigations have been supplemented by micro Raman spectroscopy. The interpretation of the spectroscopic data, including the allocation of the bands to certain vibrational species as well as considerations concerning the stabilities of both modifications, have been aided by DFT calculation

Investigations on the Crystal Structure and the Stability Field of FCAM-I (Ca3MgAl6Fe10O28), an Iso-structure to SFCA-I

In a study on parts of the system Fe2O3-CaO-Al2O3-MgO, the previously unknown compound Ca3MgAl6Fe10O28 or FCAM-I (iso-structural with SFCA-I) has been synthesized. The two principal aims of our investigations have been (i) analysis of the stability field of the new phase as a function of T and fO2 and (ii) determination of its crystal structure. Two experimental series in air and under controlled oxygen fugacity via the hematite-magnetite buffer were conducted. Pure polycrystalline FCAM-I has been obtained at 1463.15 K (1190 C) in air. While increasing the temperature from 1573.15 K to 1673.15 K (1300 C to 1400 C), the FCAM-I phase breaks down forming a variety of new compounds depending on T and fO2. Ca3MgAl6Fe10O28 has a triclinic crystal structure (space group P 1~). Basic crystallographic data are as follows: a = 10.2980(4) Å, b = 10.4677(4) Å, c = 11.6399(4) Å, alpha = 94.363(3), beta = 111.498(3), gamma = 109.744(3), V = 1069.81(7) Å3, Z = 2.(VLID)456933

Superparamagnetic iron oxide nanoparticles: diagnostic magnetic resonance imaging and potential therapeutic applications in neurooncology and central nervous system inflammatory pathologies, a review

Superparamagnetic iron oxide nanoparticles have diverse diagnostic and potential therapeutic applications in the central nervous system (CNS). They are useful as magnetic resonance imaging (MRI) contrast agents to evaluate: areas of blood–brain barrier (BBB) dysfunction related to tumors and other neuroinflammatory pathologies, the cerebrovasculature using perfusion-weighted MRI sequences, and in vivo cellular tracking in CNS disease or injury. Novel, targeted, nanoparticle synthesis strategies will allow for a rapidly expanding range of applications in patients with brain tumors, cerebral ischemia or stroke, carotid atherosclerosis, multiple sclerosis, traumatic brain injury, and epilepsy. These strategies may ultimately improve disease detection, therapeutic monitoring, and treatment efficacy especially in the context of antiangiogenic chemotherapy and antiinflammatory medications. The purpose of this review is to outline the current status of superparamagnetic iron oxide nanoparticles in the context of biomedical nanotechnology as they apply to diagnostic MRI and potential therapeutic applications in neurooncology and other CNS inflammatory conditions