Boundedness and Stability for Discrete-Time Delayed Neural Network with Complex-Valued Linear Threshold Neurons

The discrete-time delayed neural network with complex-valued linear threshold neurons is considered. By constructing appropriate Lyapunov-Krasovskii functionals and employing linear matrix inequality technique and analysis method, several new delay-dependent criteria for checking the boundedness and global exponential stability are established. Illustrated examples are also given to show the effectiveness and less conservatism of the proposed criteria

Photoluminescence Properties of Novel Red-Emitting Mn2+-Activated MZnOS (M = Ca, Ba) Phosphors

Photoluminescence properties of novel red-emitting Mn2+-activated MZnOS (M = Ca, Ba) phosphors were investigated. Mn2+-activated MZnOS phosphors show a single symmetric narrow red emission band in the wavelength range of 550-700 nm due to the 4T1(4G) ¿ 6A1(6S) transition of Mn2+. Peak centers are at about 614 nm for M = Ca and 634 nm for M = Ba, regardless of the excitation wavelength and Mn2+ doping concentration. A comparison is made between the luminescence properties of Mn2+ in the Ca versus Ba compound. A similarity between them is that both Mn2+-activated CaZnOS and BaZnOS can be efficiently excited under host lattice excitation in the wavelength range of 250-350 nm due to efficient energy transfer between the host lattice (MZnOS) and activator (Mn2+). An unexpected difference is that Mn2+-activated CaZnOS can also be efficiently excited under the excitation of Mn2+ itself (d-d transitions) in the wavelength range of 350-500 nm. This difference is ascribed to different crystal structures, different coordination environments, and point symmetries for Mn in these two compounds. The potential applications of these phosphors are pointed out. Among them, Mn2+-activated CaZnOS shows great potential for application as an alternative red-emitting LED conversion phosphor due to its high absorption and strong excitation bands in the wavelength range of 350-500 n

Red emission from Mn2+ on a tetrhedral site in MgSiN2

Solubility and photoluminescence properties of Mn2+ in MgSiN2 host lattice are reported in this paper. X-ray diffraction (XRD) analysis shows that Mn2+ ions can be totally incorporated into MgSiN2 host lattice, forming a complete solid solution with MnSiN2. Mn2+ on a tetrahedral site exhibits a red emission band in the wavelength range of 550–750 nm in MgSiN2. The long-wavelength emission of Mn2+ despite tetrahedral coordination in MgSiN2 is attributed to the effect of strong crystal field experienced by Mn2+ in a nitrogen coordination environment. Also there exists energy transfer between MgSiN2 host lattice and Mn2+ activator. The potential applications of this phosphor have been pointed out

Rare-earth doped alkaline-earth silicon nitride phosphor, method for producing and radiation converting device comprising such a phosphor

The invention relates to a method of manufacturing a rare-earth doped alkaline-earth silicon nitride phosphor of a stoichiometric composition. Said method comprising the step of selecting one or more compounds each comprising at least one element of the group comprising the rare-earth elements (RE), the alkaline-earth elements (AE), silicon (Si) and nitrogen (N) and together comprising the necessary elements to form the rare-earth doped alkaline-earth silicon nitride phosphor (AE2Si5N8:RE). The method further comprises the step of bringing the compounds at an elevated temperature in reaction for forming the rare-earth doped alkaline-earth silicon nitride phosphor (AE2Si5N8:RE). In such a method normally a small amount of oxygen, whether intentionally or not-intentionally added, will be incorporated in the rare-earth doped alkaline-earth silicon nitride phosphor (AE2Si5N8:RE).; According to the invention the creation of defects by formation of a non-stoichiometric oxygen containing phosphor is at least partly prevented by partly substituting for the ions (AE, Si, N) of the alkaline-earth silicon nitride phosphor (AE2Si5N8:RE) suitable further elements of the periodic system by which vacancies are created, filled or annihilated resulting in the formation of a modified alkaline-earth silicon nitride phosphor (AE2Si5N8:RE) having a stoichiometric composition. In this way a modified phosphor is obtained having excellent and stable optical properties. The invention further relates to a modified phosphor obtainable by the above-mentioned method and a radiation converting device comprising such a phospho

Manganese-activated metal nitrido-silicate luminescent substance

The invention relates to a luminescent substance made of metal nitrido-silicate that is actived using divalent manganese. Said luminescent substance can be described by general formula MxSiyN2/3x+4/3y:Mn2+ (wherein 0 <x and 0 <y), wherein M represents one or more metal ions, Si represents silicon which can be partially substituted by germanium, aluminum, boron, gallium, scandium, and/or phosphorus, and N represents nitrogen which can be partially substituted by oxygen. The invention further relates to a white-emitting LED comprising an element that emits exciting radiation and at least the disclosed luminescent substance which absorbs some of the exciting radiation and emits in a different spectral region

Ce3+, Eu2+ and Mn2+-activated alkaline earth silicon nitride phosphors and white-light emitting LED

The invention refers to an alkaline earth silicon nitride phosphor of the MSiN2 type that is activated by Ce3+ and/or Eu2+ and/or Mn2+ ions. A preferred embodiment of the phosphor is defined by the general formula MSiN2:A, wherein M is a divalent metal ion, especially Mg, Ca, Sr, Ba, Be and/or Zn, and A is an activator chosen from the group Ce3+, Eu2+ and/or Mn2+. A preferred application for this phosphors is a white-light emitting LED using the phosphor for conversion of radiation

Effect of volume ratio on thermocapillary convection in annular liquid pools in space

In systems with liquid/liquid or liquid/gas interface under microgravity, and even in shallow liquid layers in the terrestrial conditions, thermocapillary force takes the principal role to drive natural convections. A series of numerical simulations are conducted to investigate the stability limit of axisymmetric steady thermocapillary flow in annular liquid pools with curved and adiabatic liquid surface for eight volume ratios 0.809 <= Vr <= 1.173, where Vr is defined as (liquid vol/vol of the annular gap). Simulations provide the critical temperature difference Delta T-c, frequency f(c), and azimuthal wave number mc for each liquid pool. At the critical condition, oscillations start in form of standing wave. At the slightly supercritical condition (Delta T*), the standing waves turn to traveling oscillations. The calculated Delta T-c values decrease with the increase of Vr. A simulation code with a convective thermal boundary condition in the liquid surface suggests that heat transfer through the liquid surface significantly increases the Delta T-c value

Preparation, characterization, and photoluminescence properties of Tb 3+-, Ce3+-, and Ce3+/Tb3+-activated RE2Si4N6C (RE = Lu, Y, and Gd) phosphors

Photoluminescence properties of Tb3+ and Ce3+ singly doped and Ce3+/Tb3+-codoped RE2Si 4N6C (RE = Lu, Y, and Gd) phosphors were investigated. Tb3+ shows similar luminescence properties in RE2Si 4N6C (RE = Lu, Y, and Gd) host lattices and emits bright green light under UV excitation around 300 nm. The luminescence properties of Ce3+ in RE2Si4N6C host lattices are influenced by the size of the RE3+ ions (Lu2Si 4N6C and Y2Si4N6C vs Gd2Si4N6C). Both Ce3+-activated Lu2Si4N6C and Y2Si4N 6C phosphors exhibit a broad band emission in the wavelength range of 450-750 nm with peak center at about 540 nm, while Ce3+-activated Gd2Si4N6C shows a broad emission band in the wavelength range of 500-800 nm with peak center at about 610 nm. This difference is ascribed to the different site occupations of Ce3+ on the two crystallographic sites in Gd2Si4N6C as compared to the Y and Lu compounds. In Ce3+/Tb3+-codoped RE 2Si4N6C (RE = Lu, Y, and Gd) phosphors, it is observed that energy transfer takes place from Ce3+ to Tb 3+ in Ce3+/Tb3+-codoped Lu2Si 4N6C and Y2Si4N6C but in the reversed direction from Tb3+ to Ce3+ in Ce 3+/Tb3+-codoped Gd2Si4N 6C, depending on the position of the 5d level of Ce3+ versus the 5D4 level of Tb3+. The potential applications of these phosphors are pointed out

Preparation, electronic structure, and photoluminescence properties of Eu2+- and Ce3+/Li+-activated alkaline earth silicon nitride MSiN2 (M = Sr, Ba)

The electronic structure of alkaline-earth silicon nitride MSiN2 (M = Sr, Ba) was calculated using the CASTEP code. BaSiN2 is calculated to be an intermediate band gap semiconductor with a direct energy gap of about 2.9 eV, while SrSiN2 is an intermediate band gap semiconductor with an indirect energy gap of about 3.0 eV. As expected, the calculated optical band gaps of MSiN2 (M = Ba, Sr) are lower compared to the experimentally determined values (about 4.1 eV for BaSiN2 and 4.2 eV for SrSiN2). In addition, the luminescence properties of Eu2+ and Ce3+ in MSiN2 (M = Sr, Ba) have been studied. Ba1-xEuxSiN2 (0 &lt;x = 0.1) shows a broad emission band in the wavelength range of 500–750 nm with maxima from about 600 to 630 nm with increaseing Eu2+ concentration, while Sr1-xEuxSiN2 (0 &lt;x = 0.1) shows a broad emission band in the wavelength range of 550–850 nm with maxima from 670 to 685 nm with increasing Eu2+ concentration. The high absorption and strong excitation bands of M1-xEuxSiN2 (0 &lt;x = 0.1; M = Sr, Ba) in the wavelength range of 300–530 m are very favorable properties for application as light-emitting-diode conversion phosphors. Ce3+- and Li+- codoped MSiN2 (M = Sr, Ba) exhibits a broad emission band in the wavelength range of 400–700 nm with a peak center at about 485 nm for BaSiN2 and about 535 nm for SrSiN2. A comparison is made between the luminescence properties of Eu2+ and Ce3+ in the Sr versus Ba compounds. The long-wavelength excitation and emission of Eu2+ and Ce3+ ions in the host of MSiN2 (M = Sr, Ba) are attributed to the effect of a high covalency and a large crystal field splitting on the 5d bands of Eu2+ and Ce3+ in the nitrogen coordination environment

Mechanical overloading-induced miR-325-3p reduction promoted chondrocyte senescence and exacerbated facet joint degeneration

Abstract Objective Lumbar facet joint (LFJ) degeneration is one of the main causes of low back pain (LBP). Mechanical stress leads to the exacerbation of LFJ degeneration, but the underlying mechanism remains unknown. This study was intended to investigate the mechanism of LFJ degeneration induced by mechanical stress. Methods Here, mice primary chondrocytes were used to screen for key microRNAs induced by mechanical overloading. SA-β-gal staining, qRT-PCR, western blot, and histochemical staining were applied to detect chondrocyte senescence in vitro and in vivo. We also used a dual-luciferase report assay to examine the targeting relationship of miRNA-325-3p (miR-325-3p) and Trp53. By using NSC-207895, a p53 activator, we investigated whether miR-325-3p down-regulated trp53 expression to reduce chondrocyte senescence. A mice bipedal standing model was performed to induce LFJ osteoarthritis. Adeno-associated virus (AAV) was intraarticularly injected to evaluate the effect of miR-325-3p on facet joint degeneration. Results We observed chondrocyte senescence both in human LFJ osteoarthritis tissues and mice LFJ after bipedally standing for 10 weeks. Mechanical overloading could promote chondrocyte senescence and senescence-associated secretory phenotype (SASP) expression. MicroRNA-array analysis identified that miR-325-3p was obviously decreased after mechanical overloading, which was further validated by fluorescence in situ hybridization (FISH) in vivo. Dual-luciferase report assay showed that miR-325-3p directly targeted Trp53 to down-regulated its expression. MiR-325-3p rescued chondrocyte senescence in vitro, however, NSC-207895 reduced this effect by activating the p53/p21 pathway. Intraarticular injection of AAV expressing miR-325-3p decreased chondrocyte senescence and alleviated LFJ degeneration in vivo. Conclusion Our findings suggested that mechanical overloading could reduce the expression of miR-325-3p, which in turn activated the p53/p21 pathway to promote chondrocyte senescence and deteriorated LFJ degeneration, which may provide a promising therapeutic strategy for LFJ degeneration