The effect of MnCO3 on the gain coefficient for the 4I13/2 → 4I15/2 transition of Er3+ ions and near-infrared emission bandwidth flatness of Er3+/Tm3+/Yb3+ co-doped barium zinc silicate glasses.

The roles of Mn2+ ions in the MnCO3 compound, leading to the formation of an Mn2+-Yb3+ dimer and affecting the gain coefficient for the 4I13/2 → 4I15/2 transition of Er3+ ions and near-infrared (NIR) emission bandwidth flatness of Er3+/Tm3+/Yb3+ co-doped in SiO2-ZnO-BaO (SZB) barium zinc silicate glasses, were investigated in this work. The composition of all elements from the original raw materials that exist in the host glasses was determined using energy-dispersive X-ray spectroscopy (EDS). Under the excitation of a 980 nm laser diode (LD), the NIR emission of Er3+/Tm3+/Yb3+-co-doped SZB glasses produced a bandwidth of about 430 nm covering the O, E, and C bands. The effects of Mn2+ ions and the Mn2+-Yb3+ dimer on the gain coefficient for the 4I13/2 → 4I15/2 transition of Er3+ ions and bandwidth flatness of NIR emission of Er3+/Tm3+-co-doped and Er3+/Tm3+/Yb3+-co-doped SZB glasses were also assigned. The optimal molar concentration of Mn2+ ions was determined such that the NIR bandwidth flatness of Er3+/Tm3+/Yb3+-co-doped SZB glasses was the flattest. In addition, the role of Mn2+ ions in reducing the gain coefficient for the 4I13/2 → 4I15/2 transition of Er3+ ions was also calculated and discussed.

First-principles study of SiC and GeC monolayers with adsorbed non-metal atoms.

Chemical adsorption of non-metal atoms may lead to the emergence of novel features in two-dimensional (2D) materials. In this work, the electronic and magnetic properties of graphene-like XC (X = Si and Ge) monolayers with adsorbed H, O, and F atoms are investigated using spin-polarized first-principles calculations. Deeply negative adsorption energies suggest strong chemical adsorption on XC monolayers. Despite the non-magnetic nature of both host monolayer and adatom, SiC is significantly magnetized by H adsorption inducing the magnetic semiconductor nature. Similar features are observed in GeC monolayers upon adsorbing H and F atoms. In all cases, an integer total magnetic moment of 1 µB is obtained, originating mainly from adatoms and their neighbor X and C atoms. In contrast, O adsorption preserves the non-magnetic nature of SiC and GeC monolayers. However, the electronic band gaps exhibit significant reduction of the order of 26% and 18.84%, respectively. These reductions are consequences of the middle-gap energy branch generated by the unoccupied O-pz state. The results introduce an efficient approach to develop d0 2D magnetic materials to be applied in spintronic devices, as well as to widen the working region of XC monolayers in optoelectronic applications.

Optical band gaps and spectroscopy properties of Bi m+/Eu n+/Yb3+ co-doped (m = 0, 2, 3; and n = 2, 3) zinc calcium silicate glasses.

In this study, the indirect/direct optical band gaps and spectroscopy properties of Bi m+/Eu n+/Yb3+ co-doped (m = 0, 2, 3; and n = 2, 3) zinc calcium silicate glasses under different excitation wavelengths were investigated. Zinc calcium silicate glasses with the main compositions of SiO2-ZnO-CaF2-LaF3-TiO2 were prepared by the conventional melting method. EDS analysis was performed to determine the elemental composition existing in the zinc calcium silicate glasses. Visible (VIS)-, upconversion (UC)-, and near-infrared (NIR)-emission spectra of Bi m+/Eu n+/Yb3+ co-doped glasses were also investigated. Indirect optical band gaps and direct optical band gaps of Bi m+-, Eu n+- single-doped, and Bi m+-Eu n+ co-doped SiO2-ZnO-CaF2-LaF3-TiO2-Bi2O3-EuF3-YbF3 zinc calcium silicate glasses were calculated and analyzed. CIE 1931(x, y) color coordinates for VIS and UC emission spectra of Bi m+/Eu n+/Yb3+ co-doped glasses were determined. Besides, the mechanism of VIS-, UC-, NIR-emissions, and energy transfer (ET) processes between Bi m+ and Eu n+ ions were also proposed and discussed.

Phosphate Adsorption by Silver Nanoparticles-Loaded Activated Carbon derived from Tea Residue.

This study presents the removal of phosphate from aqueous solution using a new silver nanoparticles-loaded tea activated carbon (AgNPs-TAC) material. In order to reduce costs, the tea activated carbon was produced from tea residue. Batch adsorption experiments were conducted to evaluate the effects of impregnation ratio of AgNPs and TAC, pH solution, contact time, initial phosphate concentration and dose of AgNPs-AC on removing phosphate from aqueous solution. Results show that the best conditions for phosphate adsorption occurred at the impregnation ratio AgNPs/TAC of 3% w/w, pH 3, and contact time lasting 150 min. The maximum adsorption capacity of phosphate on AgNPs-TAC determined by the Langmuir model was 13.62 mg/g at an initial phosphate concentration of 30 mg/L. The adsorption isotherm of phosphate on AgNPs-TAC fits well with both the Langmuir and Sips models. The adsorption kinetics data were also described well by the pseudo-first-order and pseudo-second-order models with high correlation coefficients of 0.978 and 0.966, respectively. The adsorption process was controlled by chemisorption through complexes and ligand exchange mechanisms. This study suggests that AgNPs-TAC is a promising, low cost adsorbent for phosphate removal from aqueous solution.

The pursuit of equity: a health sector case study from Vietnam.

The health care system in Vietnam has long been cited as an example of primary health care that has worked well. The achievements of the system during the past decades have indeed been impressive, but the changing economic situation in Vietnam has consequences for all public sector activities, including health care. Liberalization of economic policies has encouraged private medical practice and free trade in medicines and drugs, while financial support for the state health system is decreasing. Equity has always been an important goal for the vietnamese health system, but it becomes harder and harder to realize under the new conditions of financing. The restrictions in centralized planning and funding brought about by recent changes also reveal weak points in the system, from planning to training to management at the different levels. This situation is discussed and issues concerning policy, legislation and human resources are highlighted in terms of their effect on equity.

Spectrin breakdown products increase with age in telencephalon of mouse brain.

Calcium activated proteolysis of brain spectrin produces characteristic breakdown products (BDPs), the concentrations of which increase markedly in many instances of brain pathology. Results reported here indicate that levels of the BDPs rise with age (3-30 months) in the telencephalon but not in the hindbrain of Balb/c mice. These observations suggest that spectrin breakdown is a pathologic biochemical marker which increases with age in some but not all brain regions.

Theophylline half-life in infants and young children.

Pharmacokinetics of theophylline elimination were studied in a 54-child population. Subjects' ages ranged from three months to six years. The mean half life was 4.92 hours, with S.D. +/- 1.88 hours. This is at variance with previous reports. Ages and half lives were compared and there were no correlations in this young age group.