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This study explored the complex relationships between immigration, volunteering, and life-long learning among older adults. It investigated adult teaching and learning and active ageing from the pe...

Co-doping of Yb3+ with Mn2+ is a promising way to realize broadband up-conversion (UC) luminescence. The tunable broadband emission has been widely demonstrated in crystal materials, but the research on Yb3+/Mn2+ co-doped transparent optical glass has been scare, especially in fluoride-based transparent glass ceramics (GC) that can realize the uniform ions incorporation and efficient UC emission. Herein, a series of Yb3+/Mn2+ activated transparent fluorosilicate GCs containing perovskite KMgF3 nanocrystals were successfully prepared, and the effect of heat-treatment process and/or Mn2+ ion content on the UC luminescence modulation has been investigated. Our results show that the spontaneous crystallized precursor sample exhibits only a green emission at ~538 nm, while additional orange-emitting band centered at ~613 nm is noticeable in the GCs with the gradual precipitation of KMgF3 nanocrystals after heat-treatment. The controllable luminescence can be assigned to the formation of Yb3+-Mn2+ dimers that are located in multiple coordination environments provided by the glass matrix and crystalized nanocrystals. In addition, the prepared GC samples exhibit excellent reversible emission characteristics during heating and cooling cycles. This research not only provides a new option to design desirable coordination environment for Yb3+-Mn2+ dimers, also helps to recognize the UC process in the transparent matrix in detail.

Ca2YZr2Al3O12:Bi3+,Eu3+ phosphors were elaborated by a traditional solid-state reaction method. The luminescence of Ca2YZr2Al3O12:Bi3+ samples, energy transfer from Bi3+ to Eu3+, and the temperature sensing properties of Ca2YZr2Al3O12:Bi3+,Eu3+ samples have been systematically researched. Under the excitation of ultraviolet light, Bi3+ single doped phosphors give 313 and 392 nm emission bands, which origin from the substitutions of Bi3+ instead of Ca2+ and Y3+ sites, respectively. And the color-adjustable emission from blue to red were observed by increasing Eu3+ content in Ca2YZr2Al3O12:Bi3+,Eu3+ samples. Relying on different temperature dependent variation tendency, the fluorescence intensity ratio (FIR) values present outstanding temperature sensing properties. The absolute and relative sensitivity can be up to 0.826 %K-1 and 0.664 %K-1, respectively. All above results suggest that Ca2YZr2Al3O12:Bi3+,Eu3+ phosphor is a potential alternative for optical thermometer.

In comparison to narrow-band upconversion (UC) luminescence from lanthanide-doped systems, broadband UC emission enables a broad and tailorable emissive color, which is desirable for tunable lasers and multicolor display applications. Herein, dual continuous broadband UC emission covering the visible spectral region at 480–720 nm has been achieved for the first time in Yb3+/Mn2+ co-doped glass ceramics (GCs) functionalized with the precipitation of dual-phase γ-Ga2O3/β-YF3 nanocrystals. A tunable UC emissive color from yellowish to orange could be obtained under 980 nm excitation by varying the Mn2+ doping content and heat treatment temperature of GCs. We ascribe this phenomenon to the typical transition of exchange-coupled Yb3+-Mn2+ dimers in tetrahedral and octahedral ligand environments. The Stokes and power-dependent UC luminescence properties, fluorescence lifetimes, site occupation and the involved UC mechanism are discussed in detail. This research contributes to a better understanding of the UC process between Yb3+ and Mn2+ in transparent hosts and provides a novel perspective for designing broadband-emitting UC materials.

Germanium-tin (GeSn) alloy is considered a promising candidate for a Si-based short-wavelength infrared range (SWIR) detector and laser source due to its excellent carrier mobility and bandgap tunability. Pulsed laser annealing (PLA) is one of the preeminent methods for preparing GeSn crystal films with high Sn content. However, current reports have not systematically investigated the effect of different pulse-width lasers on the crystalline quality of GeSn films. In addition, the intensity of the spot follows the gaussian distribution. As a result, various regions would have different crystalline properties. Therefore, in this study, we first provide the Raman spectra of several feature regions in the ablation state for single spot processing with various pulse-width lasers (continuous-wave, nanosecond, femtosecond). Furthermore, the impact of laser pulse width on the crystallization characteristics of GeSn film is explored for different single-spot processing states, particularly the Sn content incorporated into GeSn crystals. The transient heating time of the film surface and the faster non-equilibrium transition of the surface temperature inhibit the segregation of the Sn component. By comparing the Raman spectra of the pulsed laser, the continuous-wave laser shows the most acute Sn segregation phenomenon, with the lowest Sn content of approximately 2%. However, the femtosecond laser both ensures crystallization of the film and effective suppression of Sn expulsion from the lattices, and the content of Sn is 8.07%, which is similar to the origin of GeSn film.

GaSbS–AgI–Ag2S glass system was successfully prepared through the traditional method of vacuum melt quenching. The network structure and physical properties of the system response to the substitution of AgI with Ag2S were investigated by differential scanning calorimeter (DSC), Raman, and electrochemical impedance spectroscopic techniques. The glass transition temperature (Tg), density and hardness of the glass system improved as Ag2S content was increased. The ionic conductivity (room temperature) of the glass system was maintained at the order of ~10−4 S/cm when a high concentration of Ag+ was introduced in the glass matrix. The variation in conductivity originated from structural changes in ionic channels. The optimal glass composition for improving the mechanical and thermal stability and conductivity of solid-state electrolyte materials was inferred from analytical results.

A new glass system of (100-x) (0.2Ga2S3-0.8Sb2S3)-xNaI (x = 5–30 mol%) was investigated through a melt-quenching method for solid-state electrolyte application. Na+ was added into the glass matrix as a conductive ion to study its effect on the properties of glass samples. XRD result indicated that the glasses retained their amorphous state until the NaI content exceeded 30 mol%. With increased NaI component, the density and hardness of glasses slightly decreased. DSC measurement showed that the glass-transition temperature of samples decreased, whereas the glass thermal stability improved. We speculated that the incorporation of NaI may have caused the destruction of [S3Ga–GaS3] ethane-like units and formation of [GaS4−xIx] structure, thereby decreasing the connectivity of the glass network. The conductivity of glass samples was further determined using the AC impedance method.

Interactions of glycans with proteins, cells, and microorganisms play important roles in cell-cell adhesion and host-pathogen interaction. Glycan microarray technology, in which multiple glycan structures are immobilized on a single glass slide and interrogated with glycan-binding proteins (GBPs), has become an indispensable tool in the study of protein-glycan interactions. Despite its great success, the current format of the glycan microarray requires expensive, specialized instrumentation and labor-intensive assay and image processing procedures, which limit automation and possibilities for high-throughput analyses. Furthermore, the current microarray is not suitable for assaying interaction with intact cells due to their large size compared to the two-dimensional microarray surface. To address these limitations, we developed the next-generation glycan microarray (NGGM) based on artificial DNA coding of glycan structures. In this novel approach, a glycan library is presented as a mixture of glycans and glycoconjugates, each of which is coded with a unique oligonucleotide sequence (code). The glycan mixture is interrogated by GBPs followed by the separation of unbound coded glycans. The DNA sequences that identify individual bound glycans are quantitatively sequenced (decoded) by powerful next-generation sequencing (NGS) technology, and copied numbers of the DNA codes represent relative binding specificities of corresponding glycan structures to GBPs. We demonstrate that NGGM generates glycan-GBP binding data that are consistent with that generated in a slide-based glycan microarray. More importantly, the solution phase binding assay is directly applicable to identifying glycan binding to intact cells, which is often challenging using glass slide-based glycan microarrays.

The advancement of glycoscience is critically dependent on the access to a large number of glycans for their functional study. Naturally occurring glycans are considered a viable source for diverse and biologically relevant glycan libraries. A mixture of free reducing glycans released from natural sources can be fluorescently tagged and separated by chromatography to produce a natural glycan library. Anthranilic acid (AA) has been widely used to fluorescently tag reducing glycans for HPLC or LC/MS analysis. However, AA conjugated glycans are not efficiently immobilized on microarray slides due to the lack of a primary alkylamine functional group. In this study, we have developed simple and efficient chemistry for bioconjugation and further functionalization of glycan-AA conjugates. This new approach enables quick preparation of glycan microarrays and neoglycoproteins from glycan-AA conjugates, which can be separated by weak anion exchange (WAX) and C18 reversed-phase HPLC.

Crystalline phase evolution through merely adjusting composition was achieved in silicate glass ceramics containing Lu n O n-1 F n+2 (n = 5–10) nanocrystals. Orthorhombic or cubic phase nanocrystals were precipitated in the aluminosilicate glass matrix after thermal treatment together with varying the Na 2 O/NaF ratio. Oxyfluoride nanocrystals with quasi-spherical shape show homogenous and dense distribution in glass matrix by transmission electron microscopy measurement. Intense upconversion and mid-infrared emissions were realized in these glass ceramics compared to the precursor glass, and the emission spectral shapes, relative emission intensity and fluorescence decay curves of Er 3+ in cubic LuOF embedded samples exhibit remarkable differences due to the crystal phase dependent effect in glass ceramics. These results indicate that the crystallization and luminescence properties of oxyfluoride glass ceramics could be modified through the alteration of glass composition, which could be used for the development of novel glass ceramics and design of luminescent properties.

Intense 2.7 μm emission was achieved in transparent glass ceramics containing NaYF 4 :Er 3+ nanocrystals. The effect of adjusting Na 2 O/NaF ratio in glass composition on the crystallizing and luminescence behavior in the glass ceramics was investigated. The controllable crystallization property of NaYF 4 nanocrystals was remained after modifying the glass composition and the crystallization temperature was largely reduced for the samples with high Na 2 O content. The X-ray diffraction and transmission electron microscopy analysis evidenced the shrink of lattice parameter with increasing Na 2 O content. High transparency was kept for these glass ceramic samples, and intense upconversion, near- and mid-infrared emissions were obtained in Er 3+ -doped glass ceramics with an increase of red/green ratio and prominent Stark splits in the sample with high Na 2 O content, indicating the change of crystal field around Er 3+ in the host matrix. Our results indicate that the crystallization and luminescence properties of glass ceramics could be modified through adjusting the glass composition, and it is an effective route to develop glass ceramics with favorable properties.

GeS 2.5 chalcogenide glass was selected for studying effects of Ga addition on physical and structural properties. Glassy and partially crystallized samples of (100− x )GeS 2.5 − x Ga (5 mol% ≤ x ≤ 40 mol%) were prepared, and their thermal and optical properties were characterized. With increasing Ga content ( x ), values of T g and optical band gap of glasses initially increased and then decreased, showing a maximal value at x = 25 mol%, that is, with stoichiometric composition of 85.7GeS 2 ·14.3Ga 2 S 3 . These changes were discussed and correlated to evolution of network structure, which was investigated by Raman spectra recorded in glassy matrices of (100− x )GeS 2.5 − x Ga (5 mol% ≤ x ≤ 40 mol%). This work contributes to understanding of composition–structure–property relationship of chalcogenide glasses.

Transparent oxyfluoride glass ceramics containing NaYF 4 :Er 3+ nanocrystals have been prepared by melt quenching and subsequent thermal treatment. X-ray diffraction and high-resolution transmission electron microscopy analysis confirmed the precipitation of NaYF 4 nanocrystals in glass. Energy dispersive spectrometer results evidenced the preferential concentration of Er 3+ ions in nanocrystals. Mid-infrared, upconversion, and near-infrared emissions were measured upon excitation with 980 nm laser diode and the luminescence mechanisms were discussed. Intense 2.7 μm emission originating from the Er 3+ : 4 I 11/2 → 4 I 13/2 transition was achieved due to the incorporation of Er 3+ ions into the precipitated low phonon energy fluoride nanocrystals. The results indicate that oxyfluoride glass ceramic containing NaYF 4 :Er 3+ nanocrystals is a promising candidate material for 2.7 μm laser.

Yb3 +/Tm3 + co-doped fluorogermanate glasses have been prepared by the melt-quenching method. Their luminescent properties were investigated by absorption spectra, excitation and emission spectra, and dynamic luminescence decay curves. The energy transfer parameters were analyzed by the phonon sideband theory and the energy transfer mechanism between Yb3 + and Tm3 + was proposed. An efficient 1.8 μm luminescence with reduced up-conversion emission is achieved under excitation of 980 nm laser diode. It is found that the emission at 800 nm is the main path of energy loss in the up-conversion process and it can be lowered at a higher Tm3 + doping level. In addition, the forward energy transfer parameter from Yb3 + to Tm3 + is approximately two orders of magnitude greater than the backward one, supporting efficient 1.8 μm emission.

The structure, magnetocrystalline anisotropy compensation, magnetic properties, and magnetostriction of TbxHo0.8-xPr0.2(Fe0.8Co0.2)(1.93) (0 axis (x axis (x >= 0.15), accompanied by a rhombohedral distortion with large spontaneous magnetostriction coefficients lambda(m). The analysis of XRD, [MD and magnetostriction shows that TbxHo0.8-xPr0.2(Fe0.8Co0.2)(1.93) is an anisotropy compensation system, and the critical compensation point is realized around x=0.15, which shifts to the Tb-poor side compared with the Pr-free counterpart. An optimized effect on magnetostriction especially at a relatively low field (lambda(S)similar to 445 ppm, lambda(a)similar to 510 ppm/3 kOe) was obtained in Tb0.15Ho0.65Pr0.2(Fe0.8Co0.2)(1.93) compound, which is much larger than that of the Pr-free counterpart Tb0.15Ho0.85(Fe0.8Co0.2)(1.93) (lambda(S)similar to 300 ppm) and the Tb0.15Ho0.85Fe2 (lambda(S)similar to 325 ppm), due to the 20 at% Pr introduction. Low content of heavy rare earth Tb, low anisotropy, high saturation magnetostriction and large low-field magnetostriction are obtained in Tb0.15Ho0.65Pr0.2(Fe0.8Co0.2)(1.93) compound, which may make it a promising magnetostrictive material. (C) 2015 Elsevier B.V. All rights reserved.

Structure, magnetization and magnetostriction of Tb 0.3 Dy 0.6 Nd 0.1 (Fe 1-x Co x ) 1.93 (0 ≤ x ≤ 0.40) compounds have been investigated. X-ray diffraction (XRD) analysis shows the presence of single Laves phase with a cubic MgCu 2 -type structure. The easy magnetization direction (EMD) is observed to be direction when x ≤ 0.10, and deviates away with further increasing Co contents. The Co contributes an opposite role in the resultant magnetocrystalline-anisotropy compared to Tb. A small amount of Co substitution for Fe can enhance the Curie temperature for x ≤ 0.25. The magnetocrystalline-anisotropy compensation can be achieved in this system. A minimum in anisotropy is obtained for the Tb 0.3 Dy 0.6 Nd 0.1 (Fe 0.8 Co 0.2 ) 1.93 compound, which has good magneto-elastic properties, e.g., the large saturation magnetostriction λ S (∼930 ppm) and the high low-field magnetostriction λ a (∼670 ppm/3 kOe), and may make it technological interest in the field of magnetostrictive materials.

Unique Er 3+ doped transparent BaLuF 5 based glass–ceramics were triumphantly elaborated for the first time by melt-quenching technique and subsequent thermal treatment. The structural and luminescent properties were systemically investigated by XRD, TEM, absorption, excitation, down-shift and up-conversion spectra. All samples exhibit intense characteristic emissions of Er 3+ ( 2 H 11/2 , 4 S 3/2 , 4 F 9/2 → 4 I 15/2 ) excited by 980 nm laser. The dramatically enhanced up-conversion (6500 times) and longer lifetime in glass–ceramics confirm that most Er 3+ ions have preferentially entered into BaLuF 5 nanocrystals with lower phonon energy after crystallization. Our results indicate BaLuF 5 based transparent glass–ceramics may be excellent hosts for rare earth ions doping.

Novel Tb3+–Yb3+ co-doped transparent glass–ceramics containing NaLuF4 nanocrystals were successfully fabricated by melt-quenching technique for the first time. The structural and luminescent properties were investigated by XRD, TEM, absorption and upconversion spectra systemically. All samples exhibit intense characteristic emissions of Tb3+ (5D4 → 7FJ (J = 3–5) and 5D3 → 7FJ (J = 4–6)) and cooperative luminescence of Yb3+ ion pairs (476 nm) excited by 980 nm laser. The dramatically enhanced upconversion in glass–ceramics suggests that most rare earth ions have preferentially entered into NaLuF4 nanocrystals with lower phonon energy after crystallization. Our results indicate NaLuF4 based transparent glass–ceramics may be excellent hosts for rare earth ions doping.

Novel Ho3+ doped highly transparent NaYbF4 glass-ceramics were successfully fabricated by melt-quenching technique. Their structural and luminescent properties were systemically investigated by XRD, TEM, absorption spectra, upconversion spectra, and lifetime measurements. Excited by 980-nm laser, samples exhibit characteristic emissions of Ho3+. Impressively, the luminescent color can be tuned easily from red for precursor glass to green for glass-ceramics. Such novel phenomenon was elaborately investigated and is owing to the reduced multiphonon nonradiative relaxation and enhanced cross-relaxation of Ho3+ in NaYbF4 nanocrystals after crystallization. Our results indicate that NaYbF4 transparent glass-ceramics is an excellent host for upconversion.

A new three-layered streaming media network architecture based on the fusion of P2P and CDN which can be used for mobile device users is proposed in this paper. It uses P2P network as the backbone, selects nodes of high-performance, high-bandwidth, and stable online time as CDN edge servers, and provides mobile device users with streaming media services under the schedule of the load-balancing servers. Since P2P has the inherent drawback of flow disorder, an optimized idea of P4P has been introduced into P2P network in this architecture to make the flow ordered. Theoretical analysis and experimental results show that this architecture has optimized P2P network with higher transmission efficiency, lower bandwidth utilization of the backbone network and lower cost and fewer resources to provide streaming media services as higher network scalability and quality as possible. A streaming media system for videoon-demand which uses the method proposed in the paper has good performance when a large numbe...

Pseudobinary high Pr-content Tb1−xPrx(Fe0.4Co0.6)1.93 (0.70≤x≤1.00) magnetostrictive alloys have been fabricated by a melt-spinning method. The effects of the composition, spinning, and annealing processes on the structure, thermal stability, and magnetic properties are investigated. At a wheel speed of v≤30 m/s, the as-spun ribbons consist of a mixture of (Tb,Pr)(Fe,Co)2 cubic Laves phase and some non-cubic phases. A single (Tb,Pr)(Fe,Co)2 phase with MgCu2-type structure is formed with the process for the speed of v≥35 m/s and subsequent annealing at 500 °C for 30 min. The lattice parameter of the Tb1−xPrx(Fe0.4Co0.6)1.93 Laves phase increases from 0.7354 nm for x=0.70 to 0.7384 nm for x=1.00 and approximately follows the linear Vegard's law. The Curie temperature decreases, while the saturation magnetization increases as increasing Pr content. The Pr-rich alloys possess the relatively lower coercivity and the faster saturation of magnetostriction as compared with the Tb-rich alloys, which can be understood by their lower magnetic anisotropy.