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  • 2005-2009  (69)
  • 2000-2004  (117)
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  • 1
    Electronic Resource
    Electronic Resource
    Gain spectra of (GaIn)(NAs) laser diodes for the 1.3-μm-wavelength regime (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 3009-3011 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optical gain spectra of (GaIn)(NAs)/GaAs quantum-well lasers operating in the 1.3-μm-emission-wavelength regime are measured and compared to those of a commercial (GaIn)(AsP)/InP structure. Good agreement of the experimental results with computed spectra of a microscopic many-body theory is obtained. Due to the contributions of a second confined subband, a spectrally broad gain region is expected for (GaIn)(NAs)/GaAs at elevated carrier densities. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1371963
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  • 2
    Electronic Resource
    Electronic Resource
    (GaIn)(NAs)/GaAs vertical-cavity surface-emitting laser with ultrabroad temperature operation range (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 271-272 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature dependence of the emission of a (GaIn)(NAs)/GaAs vertical-cavity surface-emitting laser is investigated. We find laser emission over an extremely broad temperature range from 30 K up to 388 K. The laser threshold varies from 5 kW/cm2 at 373 K down to a minimum of 1 kW/cm2 at 180 K and increases again to 4 kW/cm2 at 30 K. Picosecond emission dynamics after femtosecond optical excitation is obtained with peak delays below 33 ps and pulse widths below 20 ps over the entire operation range. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125744
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  • 3
    Electronic Resource
    Electronic Resource
    Spatial patterning of pigmentation in evergreen leaves in response to freezing stress (2003)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 26 (2003), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Evergreen leaves of temperate climate plants are often subject to frosts. Changes in carbon gain patterns arise from freezing-related tissue damage, and from interactions between light and temperature stress. We examined relationships between spatial patterns in freezing and concentrations of chlorophyll. Spatial patterns in pigmentation in leaves that had or had not been exposed to naturally occurring frosts were determined by conventional extraction techniques combined with high-resolution hyperspectral imaging of reflectance from intact leaves. Predictive indices were developed to relate reflectance to chlorophyll content and chlorophyll a/b ratios within intact leaves. Leaves exposed to frosts had lower chlorophyll contents and more variable a/b ratios than protected leaves. In frost-affected leaves, chlorophyll content was highest near leaf centres and decreased toward leaf tips and margins. Decline in chlorophyll content was associated with shifts in chlorophyll a/b ratios and increases in red pigmentation due to anthocyanin, with effects being greater on leaf sides exposed directly to the sun. These altered pigmentation patterns were consistent with patterns in freezing. The present results illustrate the fine scale of spatial variation in leaf response to freezing, and raise important questions about impacts of freezing on photosynthetic function in over-wintering evergreens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2003.01106.x
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  • 4
    Electronic Resource
    Electronic Resource
    Species enrichment in an agriculturally improved grassland and its effects on botanical composition, yield and forage quality (2005)
    Oxford, UK : Blackwell Science Ltd
    Grass and forage science 60 (2005), S. 0 
    Details
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: In a field experiment, the effects of different management treatments on the botanical development and productivity of a previously species-poor, intensively managed, lowland permanent grass sward were investigated over a 4-year period. Fertilizer inputs were stopped and nine main treatments, based on three pre-sowing and three post-sowing cutting regimes, were applied. Half of each treatment plot was oversown with a mixture of forb (wildflower) species and half left unsown. The aims were: (1) to investigate the effect of cutting regimes on the establishment of introduced forb species, (2) to assess the development and dry-matter (DM) yield potential of these introduced species, and (3) to compare the DM yield and forage quality of swards with and without introduced species. Seedling establishment was recorded until the end of the second year. From the third year onwards, a common twice-yearly cutting regime was imposed on all treatments, and the development of the introduced species was recorded. The DM yield of the nine oversown sub-treatments was compared with the sub-treatments not oversown. Frequent cutting after oversowing resulted in the greatest number of established plants and three times greater harvested DM yield of introduced species, compared with infrequent cutting. Plantago lanceolata and Trifolium pratense were the best performing introduced species. By years 3 and 4, there was proportionately 0·15 and 0·23, respectively, additional herbage DM yield harvested from the oversown treatments compared with unsown treatments, and up to 0·60 more in some treatments. The introduction of forbs increased the crude protein concentration, but decreased the digestibility of the forage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2494.2005.00460.x
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  • 5
    Electronic Resource
    Electronic Resource
    Thermal Performance of Mechanically Activated Tetracalcium Phosphate (2005)
    Oxford, UK : Blackwell Science Inc
    Journal of the American Ceramic Society 88 (2005), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Prolonged high-energy ball milling of tetracalcium phosphate (TTCP) resulted in a mechanical activation with the formation of nanocrystalline or amorphous domains within the compound. This mechanically activated material demonstrated a completely different thermal behavior compared with highly crystalline TTCP. Differential scanning calorimetry (DSC) measurements indicated the presence of exothermic reactions between 370° and 480°C and between 630° and 930°C for 24 h-milled TTCP, which could be related to conversion to an apatitic phase and calcium oxide (CaO) and crystallization of these products during heating. X-ray diffraction analyses showed that mechanically activated TTCP began converting to an apatitic phase at ∼200°C and fully converted to an apatitic phase and amorphous CaO at 600°C, and a crystalline phase of CaO subsequently appeared around 800°–1200°C. Reconversion to TTCP was observed between 1200° and 1400°C. In contrast, crystalline TTCP remained stable up to 500°C and decomposed to an apatitic phase and CaO around 600°–1000°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00232.x
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  • 6
    Electronic Resource
    Electronic Resource
    Evidence for spin–charge separation in quasi-one-dimensional organic conductors (2002)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 418 (2002), S. 614-617 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Interacting conduction electrons are usually described within Fermi-liquid theory, which states that, in spite of strong interactions, the low-energy excitations are electron-like quasiparticles with charge and spin. In recent years there has been tremendous interest ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature00913
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  • 7
    Electronic Resource
    Electronic Resource
    Magnetic order in RCr $\mathsf{_{2}}$ Si $\mathsf{_{2}}$ intermetallics (2003)
    Springer
    The European physical journal 36 (2003), S. 511-518 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The magnetic structure and ordering temperatures of three intermetallic compounds which crystallize in the tetragonal ThCr2Si2 structure, TbCr2Si2, HoCr2Si2 and ErCr2Si2, have been determined by neutron diffraction, differential scanning calorimetry and magnetization measurements. The Cr-sublattice orders anti-ferromagnetically with Néel temperatures of 758 K for TbCr2Si2, 718 K for HoCr2Si2 and 692 K for ErCr2Si2. Chromium atoms located at 4d crystallographic sites are aligned anti-parallel along the c-axis, with G Z Cr magnetic modes. In contrast with metallic bcc Cr, the refined room temperature value of the ordered Cr moment is anomalously large for all three compounds. No long range magnetic order of the R sublattice in TbCr2Si2 and HoCr2Si2 is observed, whilst the Er sublattice in ErCr2Si2 orders independently of the Cr sublattice below 2.4 K with moments ferromagnetically aligned in the basal plane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2004-00006-4
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  • 8
    Electronic Resource
    Electronic Resource
    Magnetic phases in Mn Fe WO studied by neutron powder diffraction (2003)
    Springer
    The European physical journal 32 (2003), S. 35-42 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 75.30.Kz Magnetic phase boundaries (including magnetic transitions, metamagnetism, etc.) – 61.12.Ld Neutron diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The magnetic structures of Mn1-xFexWO4 with x = 0.0, 0.16, 0.21, 0.225, 0.232, 0.24, 0.27, 0.29, and 1.0 were refined from neutron powder diffraction data. The magnetic phase diagram could be completed in the coexistence range of different magnetic structures up to x = 0.29. For the magnetic state at 1.5 K a commensurate antiferromagnetic structure with a propagation vector = (±1/4, 1/2, 1/2) was found for x ⩽ 0.22 while the magnetic spins order with = (1/2, 0, 0) for x ≥ 0.22. In the latter phase, additionally, weak magnetic reflections indexed to an incommensurate ordering with = (- 0.214, 1/2, 0.457) occur in the diffraction pattern up to x = 0.29 indicating the occurence of a reentrant phase. For 0.12 ⩽ x ⩽ 0.29 the low temperature phases are separated from a magnetic high temperature phase showing only magnetic reflections indexed to a spin arrangement with = (1/2, 0, 0). The magnetic phase diagram is discussed qualitatively considering random superexchange between the statistically distributed Mn2+- and Fe2+-ions in the coexistence range 0.12 ⩽ x ⩽ 0.29 of different magnetic structures related to those of pure MnWO4 and FeWO4.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2003-00071-1
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  • 9
    Electronic Resource
    Electronic Resource
    Crystal structure and magnetic ordering of RNi Si compounds (2002)
    Springer
    The European physical journal 30 (2002), S. 25-32 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 61.12.-q Neutron diffraction and scattering – 61.50.Ks Crystallographic aspects of phase transformations; pressure effects – 75.25.+z Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source X-ray scattering, etc.)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The element distributions and the magnetic ordering behaviour of compounds RNi10Si2 (R = Tb, Dy, Ho, Er, Tm) have been studied by neutron powder diffraction down to temperatures of 1.6 K. The compounds crystallize in an ordered variant of the ThMn12 structure type in the tetragonal space group P4/nmm. An ordered 1:1 distribution of Ni and Si on sites 4d and 4e, respectively, corresponds to a modulation vector [0, 0, 1] with respect to the space group I4/mmm of the ThMn12 structure. TbNi10Si2 orders antiferromagnetically below T N = 4.5 K with a magnetic propagation vector of [0, 0, 1/2]. The magnetic Tb moments, 8.97(2) /Tb atom at 1.6 K, are aligned along the c-axis. The Ni sites in TbNi10Si2 do not carry any ordered magnetic moments. The compounds with R = Dy, Ho, Er, and Tm are paramagnetic down to 1.6 K and 3.0 K, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2002-00334-3
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  • 10
    Electronic Resource
    Electronic Resource
    Spectral filtering of femtosecond laser pulses by interference filters (2000)
    Springer
    Applied physics 70 (2000), S. S63 
    Details
    ISSN: 1432-0649
    Keywords: PACS: 45.15.Eq; 42.25.Bs; 42.40.Pa; 42.60.Da; 42.65k; 42.79.Bh; 42.90.V
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Phase properties of optical thin film interference filters are discussed from the aspect of their usage for phase-error free wavelength separation of broadband femtosecond laser pulses. It is shown that both transmissive or reflective interference filters with high contrast ratios exhibit high cubic phase shifts on transmission or reflection, respectively, causing intolerable distortion in the temporal pulse shape. We show, however, that high efficiency wavelength separation of broadband femtosecond laser pulses can be achieved by using low contrast, properly designed reflective optical interference filters directly built into the cavity of the broad spectrum, femtosecond pulse lasers or parametric oscillators. For demonstrative purposes, we implemented the idea for a Kerr-lens mode-locked Ti:sapphire laser, and obtained two-color, inherently synchronized, unchirped, femtosecond pulse outputs from a single laser oscillator.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003400000366
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