RESUMEN
Colorless transparent single crystals of a new europium-doped calcium aluminum silicon nitride, Ca0.99Eu0.01AlSi4N7, were synthesized by heating a mixture of binary nitrides (Ca3N2, EuN, AlN, Si3N4, and Mg3N2) at 2150 °C under a nitrogen gas pressure of 0.85 MPa. The X-ray diffraction reflections from a single crystal were indexed with orthorhombic cell parameters a = 11.6819(3) Å, b = 21.0193(6) Å, and c = 4.91770(10) Å. The crystal structure was isomorphic to that of SrAlSi4N7:Eu (space group Pna21). One of the Ca/Eu sites was split into two sites of 4-fold and 8-fold nitrogen coordination. A white-light emission spectrum with two peaks at wavelengths of 498 and 614 nm was observed from the single crystals under 400 nm near-ultraviolet-light irradiation. The CIE1931 chromaticity of the white light was plotted at x = 0.378 and y = 0.429; the mean color-rendering index Ra was 81.
RESUMEN
Single crystals of new boron-aluminum-silicon nitrides, Sr3BAl5Si9N20 and Sr2.91Eu0.09BAl5Si9N20, were synthesized by heating binary nitride mixtures at 2030 °C under a N2 pressure of 0.85 MPa. The X-ray diffraction spots from single crystals of these two compounds were indexed with the trigonal cell parameters a = 22.7406(8) Å, c = 5.7066(2) Å and a = 22.7439(8) Å, c = 5.7050(2) Å, respectively, and the crystal structures were determined to have the space group P3 c1, with B atoms situated at planar 3-fold-coordinated N sites. A three-dimensional framework structure is constructed for these materials based on the sharing of N atoms of Al/Si-N4 tetrahedra and B-N3 triangles. In this framework, Sr/Eu atoms are located at three sites, surrounded by 10 N atoms. Single crystals of Sr2.91Eu0.09BAl5Si9N20 emitted yellow light with a peak wavelength of 565 nm and a full width at half-maximum of 106 nm under 450 nm light irradiation. The emission intensity of these crystals at 200 °C was found to be 12% of the intensity at 25 °C.
RESUMEN
Red Ca0.99Al(1-4δ/3-x)Si(1+δ+x)N(3-x)C(x):Eu(2+)0.01 (δ = 0.345; x = 0-0.2) nitride phosphors exhibit a blue-shifted emission with increased eye sensitivity function and excellent thermal stability. The variations in the photoluminescence in the Ca0.99Al(1-4δ/3-x)Si(1+δ+x)N(3-x)C(x):Eu(2+)0.01 (δ = 0.345; x = 0-0.2) system are thoroughly investigated. The enhanced emission energy and the improved thermal stability with increasing x are dominated by the second-sphere shrinkage effect via the substitution of small Si(4+) for large Al(3+) with simultaneous charge compensation. Related proofs of the second-sphere shrinkage effect control for photoluminescence are confirmed via high-resolution neutron powder diffraction, EXAFS, and (29)Si solid-state NMR techniques.
RESUMEN
A 24-year-old female patient who had a type A influenza virus infection prior to admission visited our hospital complaining of a fever and right sternoclavicular pain. Blood culture was positive for penicillin-sensitive Streptococcus pneumoniae (pneumococcus). Magnetic resonance imaging of the right sternoclavicular joint (SCJ) showed a high signal intensity area on the diffusion-weighted images. Consequently, the patient was diagnosed with septic arthritis due to invasive pneumococcus. When a patient complains of gradually increasing chest pain after an influenza virus infection, SCJ septic arthritis should be considered in the differential diagnosis.
RESUMEN
Lower gastrointestinal perforation is rare and challenging to diagnose in patients presenting with an acute abdomen. However, no study has examined the frequency and associated factors of diagnostic errors related to lower gastrointestinal perforation. This large-scale multicenter retrospective study investigated the frequency of diagnostic errors and identified the associated factors. Factors at the level of the patient, symptoms, situation, and physician were included in the analysis. Data were collected from nine institutions, between January 1, 2015 and December 31, 2019. Timely diagnosis was defined as diagnosis at the first visit in computed tomography (CT)-capable facilities or referral to an appropriate medical institution immediately following the first visit to a non-CT-capable facility. Cases not meeting this definition were defined as diagnostic errors that resulted in delayed diagnosis. Of the 439 cases of lower gastrointestinal perforation identified, delayed diagnosis occurred in 138 cases (31.4%). Multivariate logistic regression analysis revealed a significant association between examination by a non-generalist and delayed diagnosis. Other factors showing a tendency with delayed diagnosis included presence of fever, absence of abdominal tenderness, and unavailability of urgent radiology reports. Initial misdiagnoses were mainly gastroenteritis, constipation, and small bowel obstruction. In conclusion, diagnostic errors occurred in about one-third of patients with a lower gastrointestinal perforation.