A one-step approach to synthesize Na 2 SiF 6 :Mn 4+ and K 2 SiF 6 :Mn 4+ red phosphors by co-precipitation is reported in this paper. The phosphors were precipitated from a silicon fluoride solution with NaF and Na 2 MnO 4 (Na 2 SiF 6 :Mn 4+ preparation) or KF and K 2 MnO 4 (K 2 SiF 6 :Mn 4+ preparation) using H 2 O 2 to reduce Mn 7+ to Mn 4+ at room temperature. Na 2 SiF 6 :Mn 4+ was also prepared through a convenient two-step route with K 2 MnF 6 as a raw material. The obtained Na 2 SiF 6 :Mn 4+ phosphors have hexagonal structures with space group D 3 2 -P321 and no impurity phase when they were examined via X-ray diffraction. Photoluminescence, photoluminescence excitation, thermal luminescence, and luminescence decay time were considered to determine the optical properties of the fluoride complexes. The prepared phosphors exhibited bright red emission under 460 nm light excitation and low-thermal quenching ($92% of the luminescent intensity at 423 K). Increasing the concentration of Mn 4+ enhanced the luminescence intensity. A warm white light LED with high color rendering index (R a ¼ 86 and R9 ¼ 61) was fabricated by employing Na 2 SiF 6 :Mn 4+ as red phosphors and commercial Y 3 Al 5 O 12 :Ce 3+ as yellow phosphors on a blue-InGaN chip.

A facile approach for coating red fluoride phosphors with a moisture-resistant alkyl phosphate layer with a thickness of 50-100 nm is reported. K2 SiF6 :Mn(4+) particles were prepared by co-precipitation and then coated by esterification of P2 O5 with alcohols (methanol, ethanol, and isopropanol). This route was adopted to encapsulate the prepared phosphors using transition-metal ions as cross-linkers between the alkyl phosphate moieties. The coated phosphor particles exhibited a high water tolerance and retained approximately 87 % of their initial external quantum efficiency after aging under high-humidity (85 %) and high-temperature (85 °C) conditions for one month. Warm white-light-emitting diodes that consisted of blue InGaN chips, the prepared K2 SiF6 :Mn(4+) phosphors, and either yellow Y3 Al5 O12 :Ce(3+) phosphors or green β-SiAlON: Eu(2+) phosphors showed excellent color rendition.

With the technology available through 1991, neither CT nor MRI proved superior in the detection of the earliest signs of stroke.

A new Rb2SiF6:Mn4+phosphor has been successfully synthesized through a one-step co-precipitation method.

A structural analysis is reported of roughly 150 transition-metal (TM)-chalcogenido complexes in a variety of chemical environments. With few exceptions, agreement between calculated and experimental geometries is excellent. The research provides convincing evidence that computational methods employed are adequately describing the bonding in these diverse T M complexes. Interesting trends in relative TMCh (RMc~J-RMc~) bond lengths are found. Experimental and computational data show that other than the zirconocene-and hafnocene-oxos there is similar behavior in relative bond lengths for widely varying TM-chalcogenido complexes. Relative bond lengths versus oxo (S-0, Se-0, and Te-0) in group IVB metallocenes tend to be larger than for other families of complexes and show less variation among the heavier chalcogens (Se-S, Te-S, and T e S e ) . Analysis of localized wave functions for CpZZrCh point to a greater contribution from a singly-bonded Zr-Ch structure (relative to Z1-Ch) when Ch is 0 compared to heavier chalcogens.Taken together, the data suggest that there is a fundamental difference in the Zr-oxo (and Hf-oxo) bond in relation to heavier chalcogens, consistent with recent experimental data. In previous studies of multiply bonded T M complexes we have focused on the ability of ECPs to make computations feasible for complexes incorporating even the heaviest transition metals. The present work also evaluates ECP methods for heavier main group (MG) elements. Thechalcogens (Ch) 0, S, Se, and Te are included in this study.

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This study measured the level of knowledge, attitudes and practices towards COVID-19 prevention and examined associated factors among patients at a national tertiary general hospital in Vietnam. Methods: Adult patients admitted to University Medical Center during research period were recruited in a cross-sectional study, which employed a convenience sampling method with a 4-component questionnaire in order to examine the patients' consciousness towards COVID-19 spreading prevention based on four aspects: demographic characteristics (10 items), knowledge (14 items), attitudes (6 items), and practices (7 items). Results: The study involved 2769 respondents (18-90 years) with the mean age of 38.05 ±13.91 years. About two thirds of the respondents obtained diploma degree or higher (63.4%) and shared their living space with others (64.4%). The majority of patients settled in urban area (74.9%). All participants stayed informed about COVID-19, with the most commonly used channels like television (75.2%), the Internet (72.2%) and phone (69.8%). The vast majority showed sufficient knowledge (93.7%) and positive attitudes (76.3%). Just over half of participants remained good practiced of COVID-19 prevention (57.7%). On average, the factors of younger age, higher educational level, frequency and department of admission, and the number of COVID-19 informative channels were significantly associated with sufficient knowledge, positive attitudes, and good practices regarding preventive action against COVID-19 spreading. The optimistic attitude and having more undergoing chronic diseases were associated with the likelihood of well-practiced COVID-19 preventive measures (OR 3.63, 95% CI 1.54-8.55, p=0.003 and OR 0.86, 95% CI 0.78-0.98, p=0.02, respectively). Conclusion:The results of this study demonstrated that the likelihood of good preventive practices in the fight against COVID-19 pandemic was influenced by attitudes and several sociodemographic factors. More drastic interventions for the prevention of COVID-19 should be widely furnished and equipped in hospitals, through various routes to maximize the efficiency and adherence to prevention practices.