Peter J. Schmidt

Narrow-band red-emitting Sr[LiAl3N4]:Eu2+ as a next-generation LED-phosphor material

To facilitate the next generation of high-power white-light-emitting diodes (white LEDs), the discovery of more efficient red-emitting phosphor materials is essential. In this regard, the hardly explored compound class of nitridoaluminates affords a new material with superior luminescence properties. Doped with Eu(2+), Sr[LiAl3N4] emerged as a new high-performance narrow-band red-emitting phosphor material, which can efficiently be excited by GaN-based blue LEDs. Owing to the highly efficient red emission at λ(max) ~ 650 nm with a full-width at half-maximum of ~1,180 cm(-1) (~50 nm) that shows only very low thermal quenching (>95% relative to the quantum efficiency at 200 °C), a prototype phosphor-converted LED (pc-LED), employing Sr[LiAl3N4]:Eu(2+) as the red-emitting component, already shows an increase of 14% in luminous efficacy compared with a commercially available high colour rendering index (CRI) LED, together with an excellent colour rendition (R(a)8 = 91, R9 = 57). Therefore, we predict great potential for industrial applications in high-power white pc-LEDs.

Cathepsin L deficiency as molecular defect of furless: hyperproliferation of keratinocytes and pertubation of hair follicle cycling

Lysosomal cysteine proteinases of the papain family are involved in lysosomal bulk proteolysis, major histocompatibility complex class II mediated antigen presentation, prohormone processing, and extracellular matrix remodeling. Cathepsin L (CTSL) is a ubiquitously expressed major representative of the papain‐like family of cysteine proteinases. To investigate CTSL in vivo functions, the gene was inactivated by gene targeting in embryonic stem cells. CTSL‐deficient mice develop periodic hair loss and epidermal hyperplasia, acanthosis, and hyperkeratosis. The hair loss is due to alterations of hair follicle morphogenesis and cycling, dilatation of hair follicle canals, and disturbed club hair formation. Hyperproliferation of hair follicle epithelial cells and basal epidermal keratinocytes–both of ectodermal origin–are the primary characteristics underlying the mutant phenotype. Pathological inflammatory responses have been excluded as a putative cause of the skin and hair disorder. The phenotype of CTSL‐deficient mice is reminiscent of the spontaneous mouse mutant furless(fs). Analyses of the ctsl gene of fs mice revealed a G149R mutation inactivating the proteinase activity. CTSL is the first lysosomal proteinase shown to be essential for epidermal homeostasis and regular hair follicle morphogenesis and cycling.—Roth, W., Deussing, J., Botchkarev, V. A., Pauly‐Evers, M., Saftig, P., Hafner, A., Schmidt, P., Schmahl, W., Scherer, J., Anton‐Lamprecht, I., von Figura, K., Paus, R., Peters, C. Cathepsin L deficiency as molecular defect of furless: hyperproliferation of keratinocytes and pertubation of hair follicle cycling. FASEB J. 14, 2075–2086 (2000)

A revolution in lighting

Key materials discoveries have prompted the rise of inorganic light-emitting diodes in the lighting industry. Remaining challenges are being addressed to further extend the impact of this technology in lighting, displays and other applications.

Sr5Al5+xSi21−xN35−xO2+x:Eu2+ (x≈0)—A Novel Green Phosphor for White‐Light pcLEDs with Disordered Intergrowth Structure

Sr(5)Al(5+x)Si(21-x)N(35-x)O(2+x) (x approximately 0) was obtained by high-temperature synthesis (1600 to 1750 degrees C). Upon doping with Eu(2+), the thermally very stable material shows an efficient broadband emission in the green spectral range (lambda(max) approximately 510 nm, FWHM = 69 nm) under UV to blue light excitation. The compound exhibits a complex intergrowth structure (space group Pmn2(1) (no. 31); a = 23.614, b = 7.487, c = 9.059 A; V = 1601.5(6) A(3); Z = 2, R1 = 0.067), which consists of highly condensed dreier ring layers alternating with sechser ring layers that include both vertex- and edge-sharing (Si,Al)(O,N)(4) tetrahedra. Both layer types exhibit pseudotranslational symmetry, which leads to a more or less pronounced disorder of the sechser ring layers. The Sr atoms are located in channel-like voids of the silicate framework with coordination number nine. The compound has been characterized by single-crystal and powder X-ray diffraction, as well as high-resolution electron microscopy and electron diffraction. The structure and chemical composition has been confirmed by (29)Si solid-state NMR spectroscopy, lattice energy calculations, and diverse elemental analyses.

Lumiramic: a new phosphor technology for high performance solid state light sources

A new phosphor technology for phosphor converted light-emitting diodes (pcLEDs) is presented. A polycrystalline ceramic plate (LumiramicTM) of Ce (III) doped yttrium gadolinium aluminum garnet (Y,GdAG:Ce) is combined with a blue LED to produce white light in the range of 5000 K correlated color temperature. Scattering and light extraction means of the Lumiramic ceramic color converter plates enable production of reliable and efficient white pcLEDs. Measurement of the optical properties of the Lumiramic plates before the final LED assembly allows pick and place packaging with exact targeting of the desired white color point of the LED. Combination with a red phosphor powder layer, coated onto the Lumiramic plate, results in high quality white pcLEDs with any color temperature required for the general lighting market.

Actions and interactions of growth hormone and insulin-like growth factor-II: body and organ growth of transgenic mice

To characterize long-term actions and interactions of growth hormone (GH) and insulin-like growth factor-II (IGF-II) on postnatal body and organ growth, hemizygous phosphoenolpyruvate carboxykinase (PEPCK)-human IGF-II transgenic mice were crossed with hemizygous PEPCK-bovine GH transgenic mice. The latter are characterized by two-fold increased serum levels of IGF-I and exhibit markedly increased body, skeletal and organ growth. Four different genetic groups were obtained: mice harbouring the IGF-II transgene (I), the bGH transgene (B), or both transgenes (IB), and non- transgenic controls (C). These groups of mice have previously been studied for circulating IGF-I levels (Wolf et al., 1995a), whereas the present study deals with body and organ growth. Growth curves (week 3 to 12) were estimated by regression with linear and quadratic components of age on body weight and exhibited significantly (p < 0.001) greater linear coefficients in B and IB than in I and C mice. The linear coefficients of male I and C mice were significantly (p < 0.001) greater than those of their female counterparts, whereas this sex-related difference was absent in the bGH transgenic groups. The weights of internal organs as well as the weights of abdominal fat, skin and carcass were recorded from 3.5- to 8- month-old mice. In addition, organ weight-to-body weight-ratios (relative organ weights) were calculated. Except for the weight of abdominal fat, absolute organ weights were as a rule significantly greater in B and IB than in I and C mice. IGF-II overproduction as a tendency increased the weights of kidneys, adrenal glands, pancreas and uterus both in the absence and presence of the bGH transgene. Analysis of relative organ weights demonstrated significant (p < 0.05) effects of elevated IGF- II on the relative growth of kidneys (males and females) and adrenal glands (females), confirming our previous report on organ growth of PEPCK-IGF-II transgenic mice. In females, IGF-II and GH overproduction were additive in stimulating the growth of spleen and uterus, providing evidence for tissue-specific postnatal growth promoting effects by IGF-II in the presence of elevated IGF-I

Altered growth of mice divergently selected for body weight is associated with complex changes in the growth hormone/insulin-like growth factor system.

Mice investigated in this study were generated by selecting a sub-population of the NMRI out-bred stock (C), for high (H) or low (L) 8-week body weight. After 58 generations of selection, 8-week body weights of the sub-populations were markedly different if compared to controls. To investigate endocrine changes causing the altered growth performance in the different lines of mice, we analysed several components of the growth hormone (GH)/insulin-like growth factor (IGF) system. Pituitary weights of male and female L mice were significantly smaller than those of C and H mice. Relative to body weight, pituitary weights of male mice from the three lines did not differ, however pituitary weight-to-body weight-ratios of female L mice were significantly greater than those of H females. Mean volume densities of somatotropic cells were significantly smaller in L mice than in C and H mice. Serum IGF-I concentrations were significantly lower in the L line than in the C and H lines. H mice displayed significantly increased serum insulin levels both after ad libitum feeding and after a 14 hour fasting period. Ligand blot analysis of serum IGF-binding proteins (IGFBPs) revealed a significant reduction of circulating IGFBP-3 in L mice as compared to C and H mice. In contrast, serum IGFBP-2 mRNA levels were significantly increased in male L mice and showed non significant increases in female L mice. Hepatic IGFBP-2 mRNA levels were significantly increased in L mice and decreased in H mice as compared to C mice. Expression of IGFBP-4 mRNA in the liver was significantly decreased in both selection lines (L, H) as compared to the random-bred controls. Our findings demonstrate that altered growth of mice resulting from selection for body weight is associated with complex changes in the endocrine network of the GH/IGF system.

Unexpected Luminescence Properties of Sr0.25Ba0.75Si2O2N2:Eu2+—A Narrow Blue Emitting Oxonitridosilicate with Cation Ordering

Owing to a parity allowed 4f(6)((7)F)5d(1)→4f(7)((8)S(7/2)) transition, powders of the nominal composition Sr(0.25)Ba(0.75)Si(2)O(2)N(2):Eu(2+) (2 mol% Eu(2+)) show surprising intense blue emission (λ(em)=472 nm) when excited by UV to blue radiation. Similarly to other phases in the system Sr(1-x)Ba(x)Si(2)O(2)N(2):Eu(2+), the described compound is a promising phosphor material for pc-LED applications as well. The FWHM of the emission band is 37 nm, representing the smallest value found for blue emitting (oxo)nitridosilicates so far. A combination of electron and X-ray diffraction methods was used to determine the crystal structure of Sr(0.25)Ba(0.75)Si(2)O(2)N(2):Eu(2+). HRTEM images reveal the intergrowth of nanodomains with SrSi(2)O(2)N(2) and BaSi(2)O(2)N(2)-type structures, which leads to pronounced diffuse scattering. Taking into account the intergrowth, the structure of the BaSi(2)O(2)N(2)-type domains was refined on single-crystal diffraction data. In contrast to coplanar metal atom layers which are located between layers of condensed SiON(3)-tetrahedra in pure BaSi(2)O(2)N(2), in Sr(0.25)Ba(0.75)Si(2)O(2)N(2):Eu(2+) corrugated metal atom layers occur. HRTEM image simulations indicate cation ordering in the final structure model, which, in combination with the corrugated metal atom layers, explains the unexpected and excellent luminescence properties.

I-cell disease-like phenotype in mice deficient in mannose 6-phosphate receptors.

Mannose 6-phosphate receptor deficient mice were generated by crossing mice carrying null alleles for Igf2 and the 300 kDa and 46 kDa mannose 6-phosphate receptors, Mpr300 and Mpr46. Pre- and perinatal lethality of mice nullizygous for Igf2, Mpr300 and Mpr46 was increased. Triple deficient mice surviving the first postnatal day had normal viability and developed a phenotype resembling human I-cell disease. The triple deficient mice were characterized by dwarfism, facial dysplasia, waddling gait, dysostosis multiplex, elevated lysosomal enzymes in serum and histological signs of lysosomal storage predominantly in fibroblasts, but also in parenchymal cells of brain and liver. A paternally inherited Mpr300 wild type allele that is normally inactive in mice due to imprinting was reactivated in some tissues of mice lacking IGF II and MPR 46 and carrying a maternal Mpr300 null allele. Inspite of the partial reactivation the phenotype of these mice was similar to that of triple deficient mice.

HP-Ca2Si5N8—A New High-Pressure Nitridosilicate: Synthesis, Structure, Luminescence, and DFT Calculations

HP-Ca2Si5N8 was obtained by means of high-pressure high-temperature synthesis utilizing the multianvil technique (6 to 12 GPa, 900 to 1200 degrees C) starting from the ambient-pressure phase Ca2Si5N8. HP-Ca2Si5N8 crystallizes in the orthorhombic crystal system (Pbca (no. 61), a=1058.4(2), b=965.2(2), c=1366.3(3) pm, V=1395.7(7)x10(6) pm3, Z=8, R1=0.1191). The HP-Ca2Si5N8 structure is built up by a three-dimensional, highly condensed nitridosilicate framework with N[2] as well as N[3] bridging. Corrugated layers of corner-sharing SiN4 tetrahedra are interconnected by further SiN4 units. The Ca2+ ions are situated between these layers with coordination numbers 6+1 and 7+1, respectively. HP-Ca2Si5N8 as well as hypothetical orthorhombic o-Ca2Si5N8 (isostructural to the ambient-pressure modifications of Sr2Si5N8 and Ba2Si5N8) were studied as high-pressure phases of Ca2Si5N8 up to 100 GPa by using density functional calculations. The transition pressure into HP-Ca2Si5N8 was calculated to 1.7 GPa, whereas o-Ca2Si5N8 will not be adopted as a high-pressure phase. Two different decomposition pathways of Ca2Si5N8 (into Ca3N2 and Si3N4 or into CaSiN2 and Si3N4) and their pressure dependence were examined. It was found that a pressure-induced decomposition of Ca2Si5N8 into CaSiN2 and Si3N4 is preferred and that Ca2Si5N8 is no longer thermodynamically stable under pressures exceeding 15 GPa. Luminescence investigations (excitation at 365 nm) of HP-Ca2Si5N8:Eu2+ reveal a broadband emission peaking at 627 nm (FWHM=97 nm), similar to the ambient-pressure phase Ca2Si5N8:Eu2+.