Crystal chemical characterization of mullite-type aluminum borate compounds

Al-rich aluminum borates were prepared by different synthesis routes using various Al/B ratios, characterized by diffraction methods, spectroscopy and prompt gamma activation analysis. The 11B NMR data show a small amount of BO4 species in all samples. The chemical analysis indicates a trend in the Al/B ratio instead of a fixed composition. Both methods indicate a solid solution Al5−xB1+xO9 where Al is substituted by B in the range of 1–3%. The structure of B-rich Al4B2O9 (C2/m, a=1488 pm, b=553 pm, c=1502 pm, ß=90.6°), was re-investigated by electron diffraction methods, showing that structural details vary within a crystallite. In most of the domains the atoms are orderly distributed, showing no signal for the postulated channel oxygen atom O5. The absence of O5 is supported by density functional theory calculations. Other domains show a probable disordered configuration of O5 and O10, indicated by diffuse scattering along the b direction.17318

Highly stable and porous porphyrin-based zirconium and hafnium phosphonates - electron crystallography as an important tool for structure elucidation

The Ni-metallated porphyrin-based tetraphosphonic acid (Ni-tetra(4-phosphonophenyl)porphyrin, Ni-H8TPPP) was used for the synthesis of highly porous metal phosphonates containing the tetravalent cations Zr4+ and Hf4+. The compounds were thoroughly characterized regarding their sorption properties towards N-2 and H2O as well as thermal and chemical stability. During the synthesis optimization the reaction time could be substantially decreased under stirring from 24 to 3 h in glass vials. M-CAU-30, [M-2(Ni-H2TPPP)(OH/F)(2)]H2O (M = Zr, Hf) shows exceptionally high specific surface areas for metal phosphonates of a(BET) = 1070 and 1030 m(2) g(-1) for Zr- and Hf-CAU-30, respectively, which are very close/correspond to the theoretical values of 1180 and 1030 m(2) g(-1). CAU-30 is always obtained as mixtures with one mol ZrO2/HfO2 per formula unit as proven by TEM, electron diffraction, TG and elemental analysis. Hence experimentally derived specific surface areas are 970 and 910 m(2) g(-1), respectively. M-CAU-30 is chemically stable in the pH range 0 to 12 in HCl/NaOH and thermally up to 420 degrees C in air as determined by variable-temperature powder X-ray diffraction (VT-PXRD). The crystal structure of M-CAU-30 was determined by combining electron diffraction tomography for structure solution and powder X-ray diffraction data for the structure refinement. The crystal structure consists of chains of corner sharing MO6 octahedra interconnected by the partly deprotonated linker molecules Ni-H2TPPP6-. Thus 1D channels with pore diameters of 1.3 x 2.0 nm are formed. The redox activity of Zr-CAU-30 was investigated by cyclic voltammetry resulting in a reversible redox process at a half-wave potential of E-1/2 = -0.649 V

Trends in admission rates of primary angle closure diseases for the urban population in China, 2011–2021

BackgroundCataract surgery and laser peripheral iridotomy (LPI) are effective approaches for preventing primary angle closure diseases (PACDs), as well as acute primary angle closure (APAC). Due to the development of population screening and increases in cataract surgery rates, this study aimed to examine trends in the admission rates of PACD among the urban population in China.MethodsThis cross-sectional study examined patients who were admitted to a hospital for PACD, and who underwent cataract surgery or LPI operations. The data were obtained from the Yinzhou Regional Health Information Platform (YRHIP) from 2011 to 2021. The annual rates of PACD and APAC admissions, cataract surgery and LPI were analyzed, with the number of cases used as numerators and the annual resident population in Yinzhou district used as denominators.ResultsA total of 2,979 patients with PACD admissions, 1,023 patients with APAC admissions, 53,635 patients who underwent cataract surgery and 16,450 patients who underwent LPI were included. The number of annual admissions for PACD gradually increased from 22 cases (1.6/100000) in 2011 to 387 cases (30.8/100000) in 2016, after which it decreased to 232 cases (16.2/100000) in 2019 and then increased to 505 cases (30.6/100000) in 2021. The number of cataract surgeries gradually increased from 1728 (127.7/100000) in 2011 to 7002 (424.9/100000) in 2021. Similarly, the number of LPI gradually increased from 109 (8.0/100000) in 2011 to 3704 (224.8/100000) in 2021.ConclusionThe admission rates of PACD for the urban population in China have declined in recent years after a long increasing trend in the rates of cataract surgery and LPI. However, it increased rapidly during the COVID-19 epidemic. The national health database should be further utilized to investigate temporal trends in the prevalence of PACD

Structural Characterization of Crystalline Microporous Materials Using Transmission Electron Microscopy

In this thesis, the structural characterization of functional, especially crystalline microporous materials, was performed by electron diffraction tomography (EDT) technique using transmission electron microscope (TEM) and supported in combination with complementary methods. The structural elucidation of materials at the atomic level is a key step to understand their chemical and physical properties and is therefore of great importance for the development of specific applications and for the targeted design of novel materials with desired properties. Microporous materials show unique structural features - a periodic arrangement of cavities and channels with high internal surface areas. This type of material is suitable for numerous applications in industry as well as in daily life. Since microporous materials often emerge with the factors of nano crystal size, disorder, multiple phase and low crystallinity, the structural characterization of these materials is challenging with traditional and conventional diffraction methods like single-crystal X-ray diffraction (XRD) or X-ray powder diffraction (XRPD). The used method in this dissertation, namely automated diffraction tomography (ADT), enables structure analysis directly from single nanosized crystals and can overcome the mentioned challenges. In this work, the structural characterization started with an electron beam stable ceramic (Al4B2O9) with a disordered structure and then focused on several beam sensitive microporous materials. The first phase of structural analysis of microporous materials comprises of crystal structure determinations of two metal-organic frameworks (Zr-MOFs) with large lattice parameters and a novel zeolite (THK-2) in a multiphase mixture. Subsequently, zeolites with industrial interests were structurally investigated after targeted modifications. On basis of the known crystal structure, the crystal disorder could be described for the metal interlayer expanded zeolites (M-IEZ-RUB-36) by structural modelling and simulation of electron diffraction patterns in the program package DISCUS. In addition, the positions of organic structure directing agents (OSDAs) in the pore of the porous materials: SSZ-51 and SOD; the Cu atom position in a dehydrogenated selective catalytic reduction (SCR) catalyst (Cu-chabazite) were determined from three-dimensional ADT data. This work provides an important contribution to the overall structure characterization of microporous nanomaterials including ab initio structure determination, disorder analysis, determining the position of OSDAs in zeolites and detecting the metal atom position in dehydrated zeolite, which would not be accessible to elucidate the structural features with a reliable accuracy as shown in this work using the conventional methods

Evaluation of choroidal thickness and retinal nerve fiber layer thickness in Chinese pregnant women and healthy non-pregnant women

Purpose: To evaluate choroidal thickness and retinal nerve fiber layer (RNFL) thickness in different trimesters using enhanced depth imaging optical coherence tomography (EDI-OCT). Methods: A prospective comparative study included 45 healthy pregnant women in the first trimester, 45 women in the second, 45 women in the third and 45 healthy non-pregnant women as the control group. Macular choroidal thickness was measured at three locations: The subfoveal, 1 ​mm temporal, and 1 ​mm nasal from the fovea with EDI-OCT. Peripapillary choroidal thickness (PPCT) and RNFL thickness parameters were automatically calculated by the Spectralis OCT. Results: The subfoveal, temporal and nasal macular choroidal thickness were all significantly thicker in the second trimester, compared with those parameters in the first, the third trimesters and the control group (all P ​< ​0.05). The PPCT was significantly increased in the second trimeter compared with the control group at global, temporal, temporal inferior, nasal and nasal inferior positions (all P ​< ​0.05). The RNFL thickness was also significantly increased in pregnant women at nasal superior and nasal inferior quadrants (all P ​< ​0.05). Conclusions: The choroidal thickness in pregnant women was found to be thicker than the control group, regardless of macular or optic disc location. Findings of RNFL thickening might indicate subclinical involvement of the central nervous system

Highly stable and porous porphyrin-based zirconium and hafnium phosphonates - electron crystallography as an important tool for structure elucidation

The Ni-metallated porphyrin-based tetraphosphonic acid (Ni-tetra(4-phosphonophenyl)porphyrin, Ni-H8TPPP) was used for the synthesis of highly porous metal phosphonates containing the tetravalent cations Zr4+ and Hf4+. The compounds were thoroughly characterized regarding their sorption properties towards N2 and H2O as well as thermal and chemical stability. During the synthesis optimization the reaction time could be substantially decreased under stirring from 24 to 3 h in glass vials. M-CAU-30, [M2(Ni-H2TPPP)(OH/F)2]·H2O (M = Zr, Hf) shows exceptionally high specific surface areas for metal phosphonates of aBET = 1070 and 1030 m2 g-1 for Zr- and Hf-CAU-30, respectively, which are very close/correspond to the theoretical values of 1180 and 1030 m2 g-1. CAU-30 is always obtained as mixtures with one mol ZrO2/HfO2 per formula unit as proven by TEM, electron diffraction, TG and elemental analysis. Hence experimentally derived specific surface areas are 970 and 910 m2 g-1, respectively. M-CAU-30 is chemically stable in the pH range 0 to 12 in HCl/NaOH and thermally up to 420 °C in air as determined by variable-temperature powder X-ray diffraction (VT-PXRD). The crystal structure of M-CAU-30 was determined by combining electron diffraction tomography for structure solution and powder X-ray diffraction data for the structure refinement. The crystal structure consists of chains of corner sharing MO6 octahedra interconnected by the partly deprotonated linker molecules Ni-H2TPPP6-. Thus 1D channels with pore diameters of 1.3 × 2.0 nm are formed. The redox activity of Zr-CAU-30 was investigated by cyclic voltammetry resulting in a reversible redox process at a half-wave potential of E1/2 = -0.649 V.status: publishe