Brain antigens in functionally distinct antigen-presenting cell populations in cervical lymph nodes in MS and EAE

Drainage of central nervous system (CNS) antigens to the brain-draining cervical lymph nodes (CLN) is likely crucial in the initiation and control of autoimmune responses during multiple sclerosis (MS). We demonstrate neuronal antigens within CLN of MS patients. In monkeys and mice with experimental autoimmune encephalomyelitis (EAE) and in mouse models with non-inflammatory CNS damage, the type and extent of CNS damage was associated with the frequencies of CNS antigens within the cervical lymph nodes. In addition, CNS antigens drained to the spinal-cord-draining lumbar lymph nodes. In human MS CLN, neuronal antigens were present in pro-inflammatory antigen-presenting cells (APC), whereas the majority of myelin-containing cells were anti-inflammatory. This may reflect a different origin of the cells or different drainage mechanisms. Indeed, neuronal antigen-containing cells in human CLN did not express the lymph node homing receptor CCR7, whereas myelin antigen-containing cells in situ and in vitro did. Nevertheless, CLN from EAE-affected CCR7-deficient mice contained equal amounts of myelin and neuronal antigens as wild-type mice. We conclude that the type and frequencies of CNS antigens within the CLN are determined by the type and extent of CNS damage. Furthermore, the presence of myelin and neuronal antigens in functionally distinct APC populations within MS CLN suggests that differential immune responses can be evoked

Optical properties of (oxy)nitride materials : a review

(Oxy)nitride materials, consisting mainly of transition metal and ionic-covalent (oxy)nitrides, show a vast number of interesting physical and chemical properties due to their substantial structural diversity. The optical properties of these (oxy)nitrides, in combination with their excellent mechanical strength, thermal properties, and chemical stability, enable (oxy)nitrides to be used in a variety of industrial fields, such as photovoltaic, photothermal, photocatalytic, pigment, lighting and display, optoelectronic, and defense industries. The optical properties are extremely related to the electronic band structure of (oxy)nitrides, and can be varied significantly by changing the chemical composition (e.g., the oxygen to nitrogen ratio) and preparation/processing conditions. This article overviews the optical properties (including refractive index, reflectance, absorbance, band gap, photoluminescence, and transmittance) of (oxy)nitride materials that are in the form of thin films, powders, or bulk ceramics, and highlights their applications as antireflection coatings, solar spectral selectivity coatings, visible-light-driven photocatalysts, ecological pigments, phosphors for light-emitting diodes, and transparent window materials.\u3cbr/\u3

First-principles electronic structure calculations of BaSi7N10 with both corner- and edge-sharing SiN4 tetrahedra

First-principles band structure calcns. were performed for the ternary alk.-earth silicon nitride BaSi7N10 using the d. functional theory (DFT) within the pseudo-potential (PP) method. The calcns. show that both the coordination no. of nitrogen by silicon (N[x]) as well as the way of sharing SiN4 tetrahedra (corner vs. edge) influence the local electronic structure of these atoms. The top of the valence band is dominated by the 2p states of the N[2] atoms, while the N[3] 2p states are positioned lower in energy. It is also noted that edge-sharing N[3] atoms show N[2] character. The conduction band is detd. by Ba 6s states. The compd. is calcd. to be a wide band gap semiconductor with an indirect energy gap of about 3.8 eV. The direct energy gap is predicted to be about 4.0 eV, in agreement with the exptl. value of 4-4.5 eV

High efficiency nitride based phosphores for white LEDs

In this overview paper, novel rare-earth doped silicon nitride based phosphors for white LEDs applications have been demonstrated. The luminescence properties of orange-red-emitting phosphors (M2Si5N8:Eu2+) and green-to-yellow emitting phosphors (MSi2N2O2:Eu2+, M = Ca, Sr, Ba) are discussed in detail with a focus on the relationship between the properties and structures. With high conversion efficiency in the near UV/blue region, along with high chemical/physical stability, Eu2+ - and Ce3+ - activated alkaline-earth silicon nitride and oxynitride materials are excellent wavelength-conversion phosphors for white LED

Synthesis, structure, and luminescence properties of Eu2+ and Ce3+ activated BaYSi4N7

BaYSi4N7 and its phosphors activated with Eu2+ and Ce3+ were synthesized by solid-state reaction at 1400–1650 °C under nitrogen mixed with hydrogen atmosphere. The crystal structure of BaYSi4N7 was solved by direct methods and refined by the Rietveld method from powder X-ray diffraction data. BaYSi4N7 crystallizes in the hexagonal space group P63mc (No.186), with a = 6.0550 (2) Å, c = 9.8567 (1) Å, V = 312.96 (2) Å3, and Z = 2, which is isotypic with BaYbSi4N7. The photoluminescence properties have been studied for the solid solutions of Ba1-xEuxYSi4N7 (x = 0 – 0.4) and BaY1-xCexSi4N7 (x = 0 – 0.1) at room temperature. Eu2+-doped BaYSi4N7 gives a broad green emission band centered between 503 and 527 nm depending on the Eu2+ concentration. The Eu2+ emission band shows a red-shift formulation with increasing Eu2+ concentration mainly caused by the change of the crystal field strength and Stokes shift. Concentration quenching of Eu2+ emission is observed for x = 0.05 due to energy transfer between Eu2+ ions by electric dipole–dipole interactions with a critical interaction distance of about 20 Å. Ce3+-doped BaYSi4N7 exhibits a bright blue emission band with a maximum at about 417 nm, which is independent of Ce3+ concentration. This is ascribed to a lower solubility of Ce3+ ions in BaYSi4N7 lattice as shown by X-ray powder diffraction analysis

Luminescence properties of Eu2+-doped MAl2-xSixO4-xNx (M = Ca, Sr, Ba) conversion phosphor for white LED applications

Undoped and Eu-doped MAl2-xSixO4-2Nx (M = Ca, Sr, Ba) were synthesized by a solid-state reaction method at 1300 - 1400 ¿C under nitrogen-hydrogen atmosphere. The solubility of (SiN)+, in MAl2O4 was determined. Nitrogen can be incorporated into MAl2O4 by replacement of (AlO)+ by (SiN)+, whose amount of solubility depends on the M cation. The solubility of (SiN)+ is very low in CaAl2O4 and SrAl2O4 lattices (x = 0.025 and 0.045 respectivily), whereas a large amount of (SiN)+ can be incorporated into BaAl2O4 (x = 0.6). Incorporation of (SiN)+ hardly modifies the luminescence properties of Eu2+ -doped MAl2O4 (M = Ca, Sr) because of limited solubility of (SiN)+, showing the blue and green emission at almost constant wavelentght of 440 and 515 nm, respectively. Eu2+ -doped BaAl2-xSixO4-xNx exhibits a broad green emission band with a maximum in the range of 500 - 526 nm, depending on the concentration of (SiN)+ and Eu2+. In addition, both excitation and emission bands of Eu2+ show a significant red shift as nitrogen is incorporated. BaAl2-xSixO4-xNx:Eu2+ can be efficiently excited in the range of 390-440 nm radiotion, which makes this material attractive as conversion phosphor for white light-emitting diode (LED) lighting application

Device for converting electromagnetic radiation energy into electrical energy and method of manufacturing such a device

Application: WO 2007-EP52089 20070306. Priority: NL 2006-2000033 20060320. AN 2007:1090242 Patent Family Information Patent No. Kind Date Application No. Date WO 2007107452 A1 20070927 WO 2007-EP52089 20070306 Priority Application NL 2006-2000033 A 20060320 Abstract Device (10) for converting electromagnetic radiation energy into elec. energy, comprising at least a photovoltaic element (11) with a radiation-sensitive surface, wherein a covering layer (12) of a material comprising a silicon compd., to which a rare earth element has been added, is present on said radiation-sensitive surface, characterized in that the material of the covering layer comprises a compd. of silicon and nitrogen. Good results were obtained with a compd. such as Sr2Si5N8:Eu

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