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  • porous silicon  (61)
  • morphology  (55)
  • Springer  (113)
  • Berlin-Brandenburgische Akademie der Wissenschaften
  • Cell Press
  • Förderverein Akademie 2. Lebenshälfte im Land Brandenburg
  • 2000-2004  (113)
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Verlag/Herausgeber
  • Springer  (113)
  • Berlin-Brandenburgische Akademie der Wissenschaften
  • Cell Press
  • Förderverein Akademie 2. Lebenshälfte im Land Brandenburg
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  • 1
    Digitale Medien
    Digitale Medien
    Porosified Silicon Wafer Structures Impregnated With Platinum Anti-Tumor Compounds: Fabrication, Characterization, and Diffusion Studies (2000)
    Springer
    Biomedical microdevices 2 (2000), S. 265-272 
    Details
    ISSN: 1572-8781
    Schlagwort(e): porous silicon ; cis-platin ; drug delivery ; calcium phosphate ; carbo-platin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Abstract In this work, the incorporation and characterization of cis-platin (cis-diammine dichloroplatinum(II)), carbo-platin [cis-diammine(cyclobutane-1,1-dicarboxylato] platinum(II)), and Pt(en)Cl2 (ethylenediamminedichloro platinum(II)) within layers of calcium phosphate on porous Si/Si substrates are described. These materials have been characterized by scanning electron microscopy, secondary ion mass spectrometry, and X-ray energy dispersive spectroscopy. The diffusion of platinum species from the doped calcium phosphate layers has also been investigated by UV-visible absorption spectrometry and inductively-coupled plasma spectroscopy. The influence of initial platinum concentration, the impact of thermal annealing of the calcium phosphate/porous Si/Si matrix, as well as the effect of varying the ligand coordination sphere of the Pt complex on its ability to be delivered to the surroundings have also been analyzed. For the case of cis-platin, it is found that increasing the concentration of platinum complex in the electrolyte during cathodic growth of calcium phosphate results in a relatively greater concentration of Pt incorporated into the calcium phosphate layers and a larger amount of Pt which subsequently can be delivered to the surrounding medium upon exposure to solvent.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009951121205
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  • 2
    Digitale Medien
    Digitale Medien
    Submersible observations of Equatorial Atlantic mantle: The St. Paul Fracture Zone region (2000)
    Springer
    Marine geophysical researches 21 (2000), S. 529-560 
    Details
    ISSN: 1573-0581
    Schlagwort(e): Structure ; morphology ; petrology ; peridotite-basalt
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The St. Paul F.Z. is a large structural domain made up of multiple transform faults interrupted by several Intra-Transform Ridge (ITR) spreading segments. Two regions were studied in details by submersible: (1) The ITR short (〈20 km in length) segment near 0° 37′N–25° 27′W and 1° N–27° 42′W and (2) The St. Peter and St. Paul's Rocks (SPPR) massif located at 29° 25′W (¡3700 m depth). (1) The short ITR segments consist of a magma starved rift valley with recent volcanic activities at 4700 m depth. A geological profile made along the rift valley wall showed localized volcanics (basalts and dykes) which are believed to overlay and intrude the ultramafics. The geological setting and the high ultramafic/volcanic ratio suggest an extremely low magmatic supply and crustal-mantle uplift during lithospheric stretching and denudation. (2) The St. Peter and St. Paul's Rocks (SPPR) massif consists of a sigmoidal ridge within the active transform zone. The SPPR is divided into two different geological domains called the North and the South Ridges. The North Ridge consists of strongly tectonized fault scarps composed of banded and mylonitized peridotite, sporadic gabbros (3900–2500 m) and metabasalts (2700–1700 m). The South Ridge is less tectonized with undeformed, serpentinized spinel lherzolite (2000–1400 m) and basalts. Extensional motion and denudation accompanied by diapirism affected the South Ridge within a transform domain. Instead, the North Ridge was formed during an important strike-slip and faulting motion resulting in the uplifted portion of the St. Paul F.Z. transverse ridge. There is a regional compositional variation of the volcanics where E-MORBs and alkali basalts are produced on the SPPR massif and are comparable to the adjacent northern segments of the Mid-Atlantic Ridge. On the other hand, N and T- MORBs collected from the eastern part of the St. Paul F.Z. (25° 27′ W IRT) are similar to the volcanics from the southern segments of the MAR. The peridotites exposed in these provinces (SPPR and ITR) are similar in their REE and trace element distribution. Different degrees (3–15%) of partial melting of a mixed composite mantle consisting of spinel and amphibole bearing lherzolite veined with 5–40% clinopyroxenite gave rise to the observed MORBs and alkali basalts.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004819701870
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  • 3
    Digitale Medien
    Digitale Medien
    T.H. Huxley's Criticism of German Cell Theory: An Epigenetic and Physiological Interpretation of Cell Structure (2000)
    Springer
    Journal of the history of biology 33 (2000), S. 247-289 
    Details
    ISSN: 1573-0387
    Schlagwort(e): cell theory ; morphology ; Thomas Henry Huxley ; physiology ; Schleiden-Schwann cell theory ; Romantic biology ; scientific zoology ; cytology ; preformationism ; natural history ; epigenesis ; Kernmonopol ; histology ; Albert von Kölliker ; embryology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geschichte
    Notizen: Abstract In 1853, the young Thomas Henry Huxley published a long review of German cell theory in which he roundly criticized the basic tenets of the Schleiden-Schwann model of the cell. Although historians of cytology have dismissed Huxley’s criticism as based on an erroneous interpretation of cell physiology, the review is better understood as a contribution to embryology. “The Cell-theory” presents Huxley’s “epigenetic” interpretation of histological organization emerging from changes in the protoplasm to replace the “preformationist” cell theory of Schleiden and Schwann (as modified by Albert vonKölliker), which posited the nucleus as the seat of organic vitality. Huxley’s views influenced a number of British biologists, who continued to oppose German cell theory well into the twentieth century. Yet Huxley was pivotal in introducing the new German program of “scientific zoology” to Britain in the early 1850s,championing its empiricist methodology as a means to enact broad disciplinary and institutional reforms in British natural history.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004881730937
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  • 4
    Digitale Medien
    Digitale Medien
    TMDSC and Atomic Force Microscopy Studies of Morphology and Recrystallization in Polyesters Including Oriented Films (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 227-243 
    Details
    ISSN: 1572-8943
    Schlagwort(e): atomic force microscopy (AFM) ; morphology ; polyester ; recrystallization ; TMDSC
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The thermal and crystal morphological properties of poly[ethylene teraphthalate] (PET) and poly(ethylene-2,6-naphthalenedicarboxylate) (PEN) biaxially oriented films were compared to amorphous and other isotropic semi-crystalline samples. Crystal melting as a function of temperature was characterized by temperature modulated DSC (TMDSC) and found to begin just above the glass transition for both oriented films. About 75°C above the glass transitions, substantial exothermic recrystallization begins and continues through the final melting region in oriented films. The maximum in the non-reversing TMDSC signal for the oriented films signifies the maximum recrystallization exothermic activity with peaks at 248°C and 258°C for PET and PEN, respectively. The final melting endotherm detected was 260°C and 270°C for PET and PEN, and is shown by the TMDSC data and by independent rapid heating rate melting point determinations to be due to the melting of species recrystallized during the heating scan. The results are compared with TMDSC data for initially amorphous and melt crystallized samples. The volume fraction of rigid species (Frigid=total crystal fraction plus ‘rigid amorphous or non-crystalline species’) were measured by TMDSC glass transition data, and contrasted with the area fraction of rigid species at the oriented film surface characterized with very high resolution atomic force microscopy (AFM) phase data. The data suggest that the 11 nm wide hard domains in PET, and 21 nm wide domains in PEN film detected by AFM consist of both crystal and high stiffness interphase species.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010148331705
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  • 5
    Digitale Medien
    Digitale Medien
    Polypropylene Crystallization in an Ethylene-propylene-diene Rubber Matrix (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 437-450 
    Details
    ISSN: 1572-8943
    Schlagwort(e): crystallization ; EPDM ; kinetics ; morphology ; PP ; rubber
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The effect of the incorporation of an amorphous immiscible polymer (ethylene-propylene-diene- terpolymer) on the PP crystallization kinetics and thermodynamics is investigated by thermal analysis. The results of the investigation have shown that EPDM acts as a nucleant agent. A marked decrease of the half time of PP crystallization, τ1/2 , as well as a sensible increase of the overall crystallization rate, K n , has been observed in the presence of EPDM. Moreover, at any crystallization temperature, a minimum of τ1/2 , is obtained at 25% EPDM content in the blend. The Avrami model has been successfully applied to describe the crystallization kinetics of the blend. The kinetic curves obtained under non-isothermal conditions confirm the results obtained under isothermal conditions and demonstrate the nucleant action of the EPDM phase on the PP crystallization.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010165317028
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  • 6
    Digitale Medien
    Digitale Medien
    Mechanical Properties of Natural Fibre Mat Reinforced Thermoplastic (2000)
    Springer
    Applied composite materials 7 (2000), S. 403-414 
    Details
    ISSN: 1573-4897
    Schlagwort(e): flax fibres ; natural fibres ; thermoplastics ; tensile properties ; impact properties ; anisotropy ; electron microscopy ; morphology ; compression moulding ; processing
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The use of natural fibres instead of man made fibres, as reinforcements in thermoplastics, gives interesting alternatives for production of low cost and ecologically friendly composites. In this work different commercially available semi-finished natural fibre mat reinforced thermoplastics (NMT) composites have been studied. Mechanical properties and microstructure of different NMT composites were investigated and compared to conventional GMT (glass fibre mat reinforced thermoplastic) composites and pure polypropylene (PP). The study included also NMT composites manufacturing processing parameters as processing temperatures and pressure during compression moulding. The results showed that NMT composites have a high stiffness compared to pure polymer and the NMT with a high fibre content (50% by weight) showed even better stiffness than the GMT. The GMT composites had superior strength and impact properties compared to the NMT which might be due to the relatively low strength of the natural fibres but also to poor adhesion to the PP matrix. The NMT materials showed a large dependence on direction and are therefore believed to have more fibres oriented in one direction. The stronger direction (0°) of the NMT was in some cases as much as 45% better than the 90° direction.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026546426764
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  • 7
    Digitale Medien
    Digitale Medien
    MoSx Thin Films by Thermolysis of a Single-Source Precursor (2000)
    Springer
    Journal of sol gel science and technology 19 (2000), S. 821-824 
    Details
    ISSN: 1573-4846
    Schlagwort(e): MoS x ; thin film ; liquid film coating ; thermolysis ; morphology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Thin films of MoS x have been prepared on silicon substrates by spin coating and thermolysis of 0.5 M solutions of alkyldiammonium tetrathiomolybdates in 1,2-ethanediamine (EDA) and 1,2-propanediamine (12PDA). The films have been heat treated in air at temperatures between 80 and 250°C and under N2 atmosphere at temperatures between 300 and 800°C. X-ray diffraction shows a restricted crystallisation and amorphous residues in both kind of films. EDA-based films exhibit a high tendency to crystallise whereas 12PDA-based films form associated structures with the solvent preventing precursor crystallisation. An insight into the processes occurring in film formation is gained by infrared spectroscopy which indicates a beginning of the decomposition of the 12PDA-based film at temperatures as low as 80°C with incorporation of the diamine solvent. In contrast, the EDA-based films show first signs of a decomposition at 150°C. The decomposition of the intermediate MoS3 in both cases starts between 250 and 300°C. By means of SNMS depth profiles carbon contents up to 21 and 32 atom-% were found in EDA- and 12PDA-based films, respectively. The films show a significant deficit of sulphur which is compensated by the carbon. Near the surface of the coatings a loss of carbon is observed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008728604305
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  • 8
    Digitale Medien
    Digitale Medien
    Influence of the Layer Morphology on the Electrical Properties of Sol Gel Transparent Conducting Oxide Coatings (2000)
    Springer
    Journal of sol gel science and technology 19 (2000), S. 435-439 
    Details
    ISSN: 1573-4846
    Schlagwort(e): morphology ; electrical properties ; transparent conductive coatings
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Tranparent conducting coatings have been prepared by sol gel methods either by a conventional sol-gel process (Antimony doped Tin Oxide—ATO, Aluminium doped Zinc Oxide—AZO) or a new wet chemical process using fully dispersed crystalline nanoparticles (ATO, Indium Tin Oxide—ITO). The dip coating technique has been used as deposition technique with single coating thickness varying from a few nanometer to ca. 400 nm. The layers have been fired in a furnace. Structural properties have been determined by x-ray diffraction and TEM analysis and the electrical properties by the van der Pauw/Hall measurement. Three different coating procedures have been used to investigate the effect on the structure, morphology and the electrical properties of the coatings. It is shown that the individual layer thickness in multilayer coatings influences dramatically the mentioned properties. Very thin individual layers favour a heterogeneous nucleation with dense columnar growth of the crystallites leading to low electrical resistivity (ρ ≈ 10−3Ω cm), while thick individual layers result in a porous morphology made of small crystallites leading to resistivities in the 10−2Ω cm range.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008747429862
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  • 9
    Digitale Medien
    Digitale Medien
    The First Finding of the Actinia Synandwakia hozawai in the Sea of Okhotsk (2000)
    Springer
    Russian journal of marine biology 26 (2000), S. 445-449 
    Details
    ISSN: 1608-3377
    Schlagwort(e): actinia ; Synandwakia hozawai ; Sea of Okhotsk ; morphology ; nematocysts
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The finding of the actinia Synandwakia hozawai in the coastal waters of northern Sakhalin (Sea of Okhotsk) suggests a wider range of this species, which was previously only known to inhabit the coastal waters of eastern Japan. Data are presented on the morphology of the S. hozawai specimen from the Sea of Okhotsk and the types of its nematocysts.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009455007047
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  • 10
    Digitale Medien
    Digitale Medien
    A newLeptographium species associated withTomicus piniperda in south-western China (2000)
    Springer
    Mycoscience 41 (2000), S. 573-578 
    Details
    ISSN: 1618-2545
    Schlagwort(e): China ; Leptographium ; morphology ; taxonomy ; Tomicus piniperda
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Tomicus species (Coleoptera: Scolytidae) are serious pests of pines with a wide distribution in Europe, Asia and America. In Yunnan, south-western China,T. piniperda has destroyed more than 0.5 million ha ofPinus yunnanensis in the past 15 years. A blue stain fungus belonging to the genusLeptographium is associated with both the shoot-feeding and trunk-attacking stages of the beetle's life cycle. The fungus is morphologically similar to the anamorph ofOphiostoma crassivaginatum and toL. pyrinum, which are both characterised by short robust conidiophores and hyphae covered by a granular layer. Both these species have been isolated from conifers and are associated with insects. After comparing the fungus fromT. piniperda with similarLeptographium species, using light and scanning electron microscopy, we concluded that it represents a new taxon, which is described here asL. yunnanense sp. nov.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02460923
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  • 11
    Digitale Medien
    Digitale Medien
    Phylogeny ofCyclamen L. (Primulaceae): Evidence from morphology and sequence data from the internal transcribed spacers of nuclear ribosomal DNA (2000)
    Springer
    Plant systematics and evolution 220 (2000), S. 147-160 
    Details
    ISSN: 1615-6110
    Schlagwort(e): Primulaceae ; Cyclamen ; phylogeny ; rDNA sequences ; ITS ; morphology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A molecular phylogenetic study of the genusCyclamen L. (Primulaceae) has been undertaken, based on sequence data from the 5.8S gene in the ribosomal nuclear DNA and its flanking internal transcribed spacers ITS1 and ITS2. Sequence data from 15 species ofCyclamen and seven outgroup taxa selected from Primulaceae and Myrsinaceae were analyzed phylogenetically. A second analysis based on a combined morphological and molecular dataset was performed to evaluate earlier hypotheses of character evolution in the genus. The results indicate that four monophyletic subgroups may be recognized in the genus, viz.Cyclamen, Psilanthum Schwarz,Eucosme Schwarz andGyrophoebe Schwarz. Each of the four subgenera is diagnosed by distinct basic chromosome number, as well as by morphological and molecular characteristics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00985043
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  • 12
    Digitale Medien
    Digitale Medien
    Quantitative morphological variation inTetramolopium (Asteraceae) in Hawaii and the Cook Islands (2000)
    Springer
    Plant systematics and evolution 221 (2000), S. 1-13 
    Details
    ISSN: 1615-6110
    Schlagwort(e): Asteraceae ; Tetramolopium ; morphology ; systematics ; Hawaii
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Multivariate analyses of quantitative characters were undertaken to examine the pattern of variation resulting from adaptive radiation ofTetramolopium in Hawaii and to investigate the systematics of an undescribed species in the Cook Islands and a group of populations of uncertain affinity on Kalaupapa Peninsula in Hawaii. Taxa differentiated on quantitative characters in the absence of qualitative characters. Differentiation was observed in multiple characters which could be organized into a few principal components. The analyses supported the species rank of the Cook Islands plants. The relationship of the Kalaupapa Peninsula populations to the rest of the taxa needs further study.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01086376
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  • 13
    Digitale Medien
    Digitale Medien
    A search for the phylogenetic position of the seven-son flower (Heptacodium, Dipsacales): Combining molecular and morphological evidence (2000)
    Springer
    Plant systematics and evolution 225 (2000), S. 185-199 
    Details
    ISSN: 1615-6110
    Schlagwort(e): Cladistic analyses ; Dipsacales ; Heptacodium ; morphology ; ndhF ; phylogeny ; rbcL
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A first report on the problematic phylogenetic position ofHeptacodium (2 spp.; China) using molecular data from chloroplast DNA is presented. Amplification of ORF2280 homolog region was executed in a number of representative taxa in order to determine ifHeptacodium shows similar structural rearrangements as other Dipsacales. DNA sequences ofndhF were generated to clarify the phylogenetic position ofHeptacodium among Caprifoliaceae (s.l.). Six outgroup taxa and fifteen representatives of Dipsacales were sampled and more than 2100 basepairs ofndhF sequence were used in a cladistic analysis. Parsimony analysis produced two shortest trees and showedHeptacodium as sister to all members of Caprifoliaceae (s.str.), although weakly supported. Additionally, trees were constructed withndhF data supplemented with availablerbcL sequences and a morphological data set. Results of all analyses support an unresolved basal position forHeptacodium among Caprifoliaceae (s.l.), which in part explains the difficulty experienced previously in classifying the genus.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00985467
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  • 14
    Digitale Medien
    Digitale Medien
    Electrical Characterisation of Photovoltaic Porous Si (2000)
    Springer
    Journal of porous materials 7 (2000), S. 295-298 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; photo-voltage ; d.c. conductivity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract In this study n-type and p-type PV devices have been fabricated by anodising Si wafers with various resistivities in aqueous ethanoic HF solution followed by deposition of semitransparent contacts. semitransparent deposition onto the porous layers. Various methods have been used for the optimisation of problematic contact to nanoporous layers. The measurements of importance are current-voltage (I-V) characteristics, the photovoltaic (PV) decay time spectrum, and the PV response as a function of excitation energy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009600619044
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  • 15
    Digitale Medien
    Digitale Medien
    Laser Induced Degradation of Photoluminescence Intensity of Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 307-310 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; photoluminescence ; degradation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract The evolution, under vacuum, of the photoluminescence (PL) intensity of porous silicon (PS) has been studied as function of anodisation conditions, laser line and post-anodisation treatments. It was shown that the degradation of the PL intensity depends on the internal structure of PS. In particular, the degradation is important for PS layers formed essentially by crystallites having small size or where amorphous phase exists. The experimental results have been interpreted using a theoretical model, which takes into account the variation with time of the local concentration of the luminescent centers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009613004932
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  • 16
    Digitale Medien
    Digitale Medien
    Stress Measurement Technique to Monitor Porous Silicon Processing (2000)
    Springer
    Journal of porous materials 7 (2000), S. 319-321 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; stress measurements ; thermal annealing
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Macroscopic stress measurements are used to monitor Porous Silicon processing. Silicon wafer of 1Ω cm resistivity, n-type and 〈1 0 0〉 orientation were used as starting material. Porous Silicon layers with a porosity of 57% and a thickness of 85 μm, fabricated by electrochemical anodisation, were differently dried, then the evolution of the wafer deflection has been followed with storage time in air. Thermal treatments both in inert and oxidant atmosphere have been performed up to 1000°C. The stress behaviour vs. temperature allows to estimate the hydrogen desorption activation energy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009621206749
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  • 17
    Digitale Medien
    Digitale Medien
    Superlattices as Characterisation Tool for the Beginning of PS Formation (2000)
    Springer
    Journal of porous materials 7 (2000), S. 373-376 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; superlattices ; oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Initial stage of porous silicon (PS) formation has been studied in an original way. Multilayer structures constituting of very thin layers of low porosity and thick layers of high porosity have been fabricated and characterised by optical tools and electron microscopy. The non linear behaviour resulting in a change in the dissolution velocity has been quantified by using a stack layer structure. Finally using thermal oxidation it has been shown that, due to the selective oxidation as a function of the porosity, porous silicon can be used to produce a Si/SiO2 like structure.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009618517652
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  • 18
    Digitale Medien
    Digitale Medien
    Laplacian Growth Models for Porous Silicon Formation—Stability Analysis (2000)
    Springer
    Journal of porous materials 7 (2000), S. 345-348 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; interface growth ; Laplacian growth ; linear stability analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract We develop a Laplacian model of interface growth which includes basic features of the anodisation of silicon in hydrofluoric acid. Our aim is to find mechanisms for the characteristic properties of porous silicon formation, such as the transition from electropolishing to pore formation and the typical pore distance. The local etching rate of the interface between the semiconductor and the electrolyte is determined by the local current density. We model the diffusive transport of charge carriers in the semiconductor and of reactants in the electrolyte including the basic features of the electrochemical reaction at the interface. A linear stability analysis of a flat and planar interface is performed in order to study the initial state of pore formation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009630920378
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  • 19
    Digitale Medien
    Digitale Medien
    Orientation Effect of the Wafer on the Structural Properties of P+ Type Porous Silicon Layers (2000)
    Springer
    Journal of porous materials 7 (2000), S. 357-361 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; X-ray diffraction ; differential scanning calorimetry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract The structural properties of (111) oriented p+ type Porous Silicon (PS) samples are investigated using various X-ray diffraction techniques and compared to (001) p+ type PS layer structure. High resolution X-ray diffractometry was used to record rocking curves and reciprocal space maps, giving indications about the crystalline quality of the PS samples as well as about the pore orientation. X-ray diffraction and reflectivity performed on thin PS layers allow to estimate the layer thickness, porosity and roughness of the PS/substrate interface.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009691122195
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  • 20
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    Digitale Medien
    AC Conductivity of Porous Silicon from Monte Carlo Simulations (2000)
    Springer
    Journal of porous materials 7 (2000), S. 107-110 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; conductivity ; percolation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract The AC conductivity of a percolation model with local energetical disorder for porous Silicon in three dimensions, σ(ω), is studied by Monte Carlo simulations. The model includes both diffusion and recombination processes and σ(ω) is obtained by a Fourier transform of the mean-square displacement of the carriers, where hopping diffusion of a single type of carrier (either an electron or an exciton) and two types of carriers (an electron and a hole) are considered. It is found that at low temperatures, the behavior of σ(ω) depends sensitively on the type of carrier considered.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009678502689
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  • 21
    Digitale Medien
    Digitale Medien
    Porous Semiconductor Micropatterns Formed on Focussed Ion Beam Implants (2000)
    Springer
    Journal of porous materials 7 (2000), S. 233-237 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; integrated optics ; wave guides
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract In this work we report a principle that allows one to write visible light emitting silicon patterns of arbitrary shape down to the sub-micrometer scale. We demonstrate that porous Si growth can electrochemically be initiated preferentially at surface defects created in an n-type Si substrate by Si++ ion bombardment. Using a focused ion beam (FIB) as a source of ions, arbitrary defect patterns can be written into a substrate. The growth of light emitting porous silicon is then selectively achieved by an electrochemical treatment which triggers Si dissolution only at these defect sites. The selectivity of the electrochemical dissolution reaction can be attributed to a facilitated Schottky barrier breakdown at the implanted surface defects which leads to the desired pore formation in confined surface areas.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009655324979
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  • 22
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    Digitale Medien
    Electroluminescence from Porous Silicon Studied Experimentally (2000)
    Springer
    Journal of porous materials 7 (2000), S. 267-270 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; photoluminescence ; electroluminescence ; band structure ; experimental
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Electroluminescence, photoluminescence, and current-voltage measurements have been carried out on a series of samples consisting of porous silicon on top of crystalline silicon. The electroluminescence spectral distributions are markedly shifted towards long wavelengths in comparison to those seen with photoluminescence. The results are discussed and explained in terms of the energy-band structure of porous silicon. The problem of injecting electrons as well as holes into the porous silicon layer is pointed out and discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009675829522
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  • 23
    Digitale Medien
    Digitale Medien
    Self-consistent Recombination Scheme in Porous Silicon Under Intense Laser Excitation (2000)
    Springer
    Journal of porous materials 7 (2000), S. 315-318 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; nonradiative ; radiative recombination
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract An experimental investigation of the general characteristics of nonradiative and radiative recombination of charge carriers in strongly excited porous silicon is presented. It is shown that photoconductivity, photomagnetoelectric effect, quantum yield, and intensity of visible radiation of porous silicon demonstrates strong nonlinearities against laser excitation intensity. It is suggested that the band-to-band Auger recombination is dominant similar to that in crystalline silicon, whereas the visible luminescence is determined by the bimolecular process. The nonequilibrium density of charge carriers Δn ≈ 1019 cm−3, and the bimolecular radiative recombination coefficient Brad ≤ 9 × 10−14 cm3/s have been found.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009669122679
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  • 24
    Digitale Medien
    Digitale Medien
    Structural Changes of Porous Silicon Surface with Thermal Annealing Studied by 29Si Nuclear Magnetic Resonance Spectroscopy and Fourier Transform Infrared Spectroscopy (2000)
    Springer
    Journal of porous materials 7 (2000), S. 327-330 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; thermal annealing ; nuclear magnetic resonance spectroscopy ; infrared spectroscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract 29Si nuclear magnetic resonance (NMR) spectra and infrared spectra were measured for as-prepared and annealed porous silicon (PS) samples to characterize the change of PS structure. Annealing changed the infrared spectra remarkably: after 4-h annealing, the signals due to SiH2 disappeared and the intensity of the signals due to SiH decreased. On the other hand, the 29Si NMR spectra with magic-angle spinning (MAS) were not much affected by the annealing. The linewidth of spectra without MAS, however, increased with annealing time with the peak location unchanged. Annealing caused hydrogen on the PS surface to be desorbed, especially in the case of SiH2 species, and (SiH)2 dimer structure was produced during the annealing.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009677332673
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  • 25
    Digitale Medien
    Digitale Medien
    Investigations of Activation Energy of Porous Silicon Oxidation Using Calorimetric Methods (2000)
    Springer
    Journal of porous materials 7 (2000), S. 335-338 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; oxidation ; calorimeter ; desorption ; activation energy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract The oxidation of porous silicon has been studied using differential scanning calorimeter. The oxidation was found to consist of two parts with different activation energies. This indicates the existence of two different reaction mechanism. The results from the hydrogen desorption measurements have been used to study the different oxidation behaviour of the n- and p+-type porous silicon. The results show that the dihydride structure dominates on the surface of the n-type porous silicon, contrary to p+-type porous silicon, where the monohydride is the major structure. Explanations of these features are discussed. Using the activation energy, the surface termination effects are investigated. The best improvement in the activation energy was observed in the sample, whose surface was partially stabilized by ammonium groups.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009674702631
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  • 26
    Digitale Medien
    Digitale Medien
    Effect of Light Exposure and Ultrasound on the Formation of Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 381-383 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; microstructure ; infrared spectroscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract We have investigated the effect of light exposure and ultrasonic (US) treatment on the formation of porous Si layers grown by electroless stain-etching technique. It was shown that; the He-Ne laser exposure resultedin a considerable increase in both the hydrogenation and the oxidation amounts in n-type Si, but a decrease in p-type wafers. The effect is attributable to effective change in the concentration of free hole carriers. The UV light exposure has led to the shift at the peak positions, indicating probably a change in bonding configuration, and increase in oxidation. Also, a correlation was established between the ultrasonic treatment and the microstructure. The US treated samples exhibit a decrease in hydrogenation and oxidation. UV exposure together with the US has led to a further decrease in both hydrogen and oxygen amounts, which was rather indicative of an excessive surface etching.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009687021287
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  • 27
    Digitale Medien
    Digitale Medien
    Photoluminescence Decay and Hydrogen Desorption of n-Type Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 385-388 
    Details
    ISSN: 1573-4854
    Schlagwort(e): hydrogen desorption ; photoluminescence decay ; porous silicon
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract The decay under illumination of the photoluminescence (PL) intensity ofn-type porous silicon (PS) samples prepared by electrochemical etching has been investigated. We have found that the PL evolution with illumination time presents two different stages: an initial very fast decay which lasts ∼300 s, followedby a second one, much slower, which extends for times longer than 104 s. Thisevolution suggests that two different mechanisms could be responsible for the PLintensity decay. Samples subjected to different illumination times were studied byThermal Desorption Spectroscopy (TDS). The desorption rate of H2 and SiHx species was monitored during linear heating of the samples. A qualitative correlationbetween the decay of the PL intensity under illumination and the amount of H2 and SiHx species evolved from the illuminated samples has been observed. Experimentaldata suggest that H2 could be desorbed from the sample during the illuminationtime through a photoinduced H2 desorption process, inducing the decrease of the PLintensity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009647307174
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  • 28
    Digitale Medien
    Digitale Medien
    An Investigation of Porous Silicon by Means of Positron Annihilation (2000)
    Springer
    Journal of porous materials 7 (2000), S. 323-326 
    Details
    ISSN: 1573-4854
    Schlagwort(e): positron annihilation ; porous silicon
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Positron lifetime spectroscopy has been used to investigate a porous silicon film subjected to heat treatments up to 1170°C. Annealings between 300 and 500°C resulted in a 17% mass increase of the film due to oxygen uptake following the effusion of hydrogen. The positron data also indicate that vacancy clusters are formed in the silicon oxide layer or the silicon oxide—silicon interface surrounding the nanocrystallites as oxygen replaces the effusing hydrogen. The vacancy cluster concentration, which may have a bearing on the photoluminescent properties, increased by a factor of three with heating to 500°C and then decreased to one-third the original value at higher temperatures. Above 900°C vacancy migration and clustering occurred, accompanied by visible deterioration of the film.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009625307658
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  • 29
    Digitale Medien
    Digitale Medien
    Study on the Si–Si Vibrational States of the Near Surface Region of Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 339-343 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; infrared spectroscopy ; oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract The Si–Si vibrational states near the surface region of porous silicon has been characterized using Fourier Transform Infrared Spectroscopy (FTIR) due to its enlarged surface area. By means of anodic etch and oxidization experiments, two Si–Si vibration modes of porous silicon have been identified as near the surface regions and in the bulk, respectively. The intensity of absorption peak at 620 cm−1, which originates from the Si–Si bonds vibrations on the surface and near surface regions of porous silicon, is found to vary depending on the length of etch and degree of oxidation of porous silicon, which exists before etching and is recovered again after fully oxidation. The peak of 610 cm−1 doesn't change throughout the oxidation experiment, and to be assigned for Si–Si bond vibrations in the bulk. With an extra irradiation of Nd:Yag laser on the PS sample the Raman and FTIR spectra reveal a red shift. These results can give an interpretation to explain the different phenomenon of Si–Si vibrations of Raman and FTIR spectroscopy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009622601723
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  • 30
    Digitale Medien
    Digitale Medien
    Laser Structuring of Luminescent Porous Silicon During Etching (2000)
    Springer
    Journal of porous materials 7 (2000), S. 367-371 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; luminescence ; light assisted chemical etching
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract A new approach to the problem of preparation of laterally structured luminescent porous silicon is proposed. The effect is based on the photosensitivity of chemical etching of silicon. Contrary to the other technique recently reported where the porous layer was modified with light assisted chemical dissolution, a one stage anodisation-free process is used. Any desired lateral structure can be produced, depending on the illumination pattern, which is defined by optical imaging. A 2D micro-array was prepared as an example of this fast mask-free technology with an accuracy of 5 μm. Samples have a broadband visible photoluminescence centred at 680 nm when illuminated with UV or blue light. The results are analysed to determine the possible achievable accuracy of the technique and to improve our understanding of the mechanism of light assisted etching.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009695223104
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  • 31
    Digitale Medien
    Digitale Medien
    Raman Scattering from Metal-Deposited Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 397-400 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; Raman spectroscopy ; immersion plating ; silver
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Raman scattering from porous silicon layer into which silver is immersion-plated was studied. Ag-deposited samples show extra Raman bands. Heat treatment of the Ag-deposited samples results in a great decrease in such Raman bands. Also dipping in hydrofluoric acid solution causes a spectral change. Some comments on the assignment of the Raman peaks of the Ag-deposited porous silicon are given, and the structure of porous silicon on which metal is immersion-plated is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009603524921
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  • 32
    Digitale Medien
    Digitale Medien
    A Systematic Study of Synchrotron Light Induced Luminescence from Porous Silicon: Implications to Morphology and Chemical Effect Dependent Electronic Behaviour (2000)
    Springer
    Journal of porous materials 7 (2000), S. 165-168 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; photoluminescence ; synchrotron radiation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Using synchrotron as a tunable excitation source, we have carried out a study on the photoluminescence systematics from a series of porous silicon samples prepared under different conditions, Luminescence spectra were recorded with excitation photon energies tuned to the Si L3,2 absorption edge (∼100 eV). The luminescence yield was in turn used to monitor the Si L3,2-edge absorption characteristics of porous silicon. A trend of luminescence wavelength and intensity as a function of preparation conditions emerges. Other related observations are also noted.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009618216802
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  • 33
    Digitale Medien
    Digitale Medien
    Nature of the Silicon-Animal Cell Interface (2000)
    Springer
    Journal of porous materials 7 (2000), S. 191-195 
    Details
    ISSN: 1573-4854
    Schlagwort(e): cell growth ; porous silicon ; cytotoxicity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract The paper reports the results of the study of cell culture growth at the surface of porous silicon. They show that porous and poly(nano)crystalline Si offer significant advantages over bulk Si surfaces for cell adherence and viability: these materials do not require coating with substances such as polylysine to support cell growth; porous Si is light-addressable because of photoluminescence and photovoltaic effects noted [Unal and Bayliss, J. Appl. Phys. 80, 3532 (1996)], allowing the potential for optical data transfer and less susceptibility to interference from external electronic equipment; finally nanostructured coatings can be applied to most object shapes, giving flexibility in their application.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009686704506
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  • 34
    Digitale Medien
    Digitale Medien
    Light Emission from Highly Reflective Porous Silicon Multilayer Structures (2000)
    Springer
    Journal of porous materials 7 (2000), S. 209-213 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; superlattices ; photoluminescence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Porous silicon photoluminescence and electroluminescence can be controlled by periodically modulating the material porosity to form high quality multilayer stacks and microcavities. Important issues not yet fully addressed are (a) the precise role played by this microstructuring, given that the luminescence is distributed throughout the entire structure and that the low porosity layers are highly absorbing at short wavelengths, and (b) whether the quality of such microcavities could be sufficient to support lasing. Using both experimental and theoretical techniques, the emission and reflection properties of different porous silicon single and multilayer structures have been investigated in order to understand further and exploit the nature of light propagation within them.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009694906324
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  • 35
    Digitale Medien
    Digitale Medien
    Formation of Porous Silicon Filter Structures with Different Properties on Small Areas (2000)
    Springer
    Journal of porous materials 7 (2000), S. 223-225 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; patterning ; photolythography dielectric filters ; reactive ion etching (RIE) ; microoptics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Porous silicon (PS) layer systems have a broad range of possible applications. An advantage is the good control of the refractive index and the etch rate of the layers by the applied current density and the time respectively. For micro-optical devices you need patterned PS. For some optical devices it is not sufficient to have only one filter but it is necessary to form filters with different properties on a small area. We applied a method (M. Frank, U.B. Schallenberg, N. Kaiser, and W. Buß, in Conference on Miniaturized Systems with Microoptics and Micromechanics, edited by M.E. Moamedi, L.J. Hornbeck, and K.S.J. Pister (SPIE, San Jose, 1997), SPIE Proceedings Series 3008, p. 265) to PS which fits this goal by the following steps: fabrication of the desired reflectors below each other and partial removal of upper reflectors with reactive ion etching (RIE). The technological aspects of patterning PS after the fabrication are an important topic of this work. Problems are discussed in detail and solutions are given.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009651224071
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  • 36
    Digitale Medien
    Digitale Medien
    Probing Carrier Transport in Porous Silicon with Synchrotron Radiation (2000)
    Springer
    Journal of porous materials 7 (2000), S. 115-118 
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    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; synchrotron radiation ; coulomb blocade
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract In this paper we demonstrate that photo-electron emission excited by X-UV synchrotron radiation can be used as a “contactless” probe of the gross conduction processes in porous silicon. Moreover we demonstrate that this approach reveals the underlying conduction geometry. We show that conduction in porous silicon is to some degree controlled by percolation phenomena and finally present data which support the notion that the fundamental blocking process may be Coulomb Blockade [P.A. Lee, Physica B 189, 1–5 (1993); D. Ali and H. Ahmed, Appl. Phys. Lett. 64, 2119–2120 (1994)].
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009667627705
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  • 37
    Digitale Medien
    Digitale Medien
    Porous Silicon Studied with Time-Resolved Photoluminescence (2000)
    Springer
    Journal of porous materials 7 (2000), S. 263-266 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; time-resolved photoluminescence ; decays
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Porous silicon has been studied with time-resolved photoluminescence, and growth as well as decay curves have been measured at several detection energies, with sample temperatures between 10 and 300 K. In the decay curves, three components are mainly observed, a small one which is very fast, with time scales of the order of nanoseconds or faster, the main component having time scales of the order of milliseconds, and a very small, very slow component, with time scales of the order of seconds. The main components can in most—but not all—cases be fitted well with stretched exponentials containing two fitting parameters. Of these, it comes out that the parameter accounting for disorder or the like depends only little upon detection energy and temperature, whereas the parameter accouting for the development in time decreases substantially for increasing temperature. The results are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009623812684
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  • 38
    Digitale Medien
    Digitale Medien
    Optical Absorption in Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 279-282 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; optical absorption ; theoretical modelling
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract The optical properties of porous silicon (p-Si) are calculated from the electronic band structure obtained by means of an sp3s* tight-binding Hamiltonian and a supercell model, in which the pores are columns detched in crystalline silicon (c-Si). The disorder in the pore sizes and the undulation of the silicon wires are considered by the existence of arandom perturbative potential, which produces non-vertical interband transitions, otherwise forbidden. A typical interval around each k-vector (optical window), where non-vertical transitions make an important contribution, depends on the value of the disorder and its order of magnitude is given by l−1, where l is the localization length. The calculated absorption spectra are compared with experiments, showing good agreement.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009684131340
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  • 39
    Digitale Medien
    Digitale Medien
    Cathodoluminescence from Implanted and Anodized Polycrystalline Silicon Films (2000)
    Springer
    Journal of porous materials 7 (2000), S. 291-294 
    Details
    ISSN: 1573-4854
    Schlagwort(e): nanocrystalline silicon ; porous silicon ; cathodoluminescence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Luminescence emission of LPCVD polycrystalline silicon films has been studied by cathodoluminescence (CL) in the scanning electron microscope. As-deposited films show visible luminescence with dominant blue band. The relative intensity of blue emission is enhanced by implantation and by slight anodization treatments. Our investigations are consistent with previous PL results and indicate that the origin of blue emission is related to quantum confinement effects. On the other hand, the effect of annealing in these samples is a reduction of the CL signal that could be related to the increase of the nanocrystals size.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009644401297
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  • 40
    Digitale Medien
    Digitale Medien
    The Energy-Band Structure of Porous Silicon Studied with Photoluminescence Excitation and Photoacoustic Spectroscopy (2000)
    Springer
    Journal of porous materials 7 (2000), S. 173-176 
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    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; photoacoustic spectroscopy ; energy band
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Porous silicon has been studied with photoluminescence, photoluminescence excitation, and photoacoustic spectroscopy. From the luminescence data, an energy-level diagram related to the luminescence is constructed. The diagram is confirmed in detail by the photoacoustic spectra. The results are discussed with the conclusion that they are in good agreement with the surface-band oxyhydride-like emitter, which recently has been established as the source for the photoluminescence from porous silicon.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009674401781
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  • 41
    Digitale Medien
    Digitale Medien
    Raman Light Scattering in System of Oriented Wires in Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 275-278 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; Raman spectroscopy ; morphology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Raman-light scattering in porous silicon samples with oriented quantum wires was studied. It was shown, that the experimental data depends on the type of organization of wire system. The explanation of observed effect is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009632114501
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  • 42
    Digitale Medien
    Digitale Medien
    Sensitivity of Porous Silicon Photoluminescence to Low Concentrations of CH4 and CO (2000)
    Springer
    Journal of porous materials 7 (2000), S. 287-290 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; sensors ; gas absorption
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract In this paper we report the sensitivity of porous silicon photoluminescence (PL) to diluted mixtures of methane and carbon monoxide in synthetic air. We also investigate the separate effect of synthetic air, purified nitrogen and relative humidity on both photoluminescence and conductance (G). Porous silicon samples have been prepared from n-type silicon substrates. We find that PL intensity and G decrease in synthetic air with respect to their values in N2. Presence of carbon monoxide reduces the PL intensity while methane provokes the opposite behaviour. The dependence of the PL spectra on methane and carbon monoxide concentrations has been investigated. The observed effects can be related to gas induced modifications in porous surface and suggest that porous silicon can be employed in gas sensor technology.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009640316318
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  • 43
    Digitale Medien
    Digitale Medien
    Studies on Gold/Porous Silicon/Crystalline Silicon Junctions (2000)
    Springer
    Journal of porous materials 7 (2000), S. 299-301 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; Schottky emission ; photoluminescence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Electrical transport in Gold/porous silicon/crystalline silicon junctions has been studied. The junctions are found to improve when the porous silicon is exposed to a hydrogen plasma before depositing the top metal. The hydrogen passivated junctions exhibited higher current levels and emitted light at lower voltages as compared to the unhydrogenated ones. Internal photoemission measurements were carried out to investigate the gold/porous silicon barrier. The barrier height determined from the Fowler plot is independent of the top material. The temperature dependence of the barrier height is similar to that of the crystalline silicon energy gap.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009604703115
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  • 44
    Digitale Medien
    Digitale Medien
    Electrochemical Aspects of Porous Silicon Formation (2000)
    Springer
    Journal of porous materials 7 (2000), S. 11-16 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; kinetics electrochemistry ; etching ; surface analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract The electrochemistry of porous silicon formation has been investigated by different electrochemical as well as surface analytical methods. The kinetics of pore nucleation was observed as small steps in fast current and potential pulse transients. Oxidic intermediates were identified by ex-situ XPS. Cyclic voltammetry in solutions of different HF concentration was correlated with the etching rate of silicon dioxide. On the basis of these experimental data, an electrochemical model for the porous silicon formation is presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009667411891
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  • 45
    Digitale Medien
    Digitale Medien
    Contactless Characterization of Porous Silicon Structures by Four-Wave Mixing and Microwave Techniques (2000)
    Springer
    Journal of porous materials 7 (2000), S. 303-306 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; four-wave mixing ; microwave harmonics generation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract We apply optical contactless techniques, namely the four-wave-mixing and microwave harmonics generation for the characterization of nanocrystalline free-standing films and platelets of microcrystalline porous silicon. We observe (i) full carrier localization and significant lifetime shortening in free-standing films, which is thought to be a manifestation of their low-dimensional confinement, (ii) increased carrier lifetime in microcrystalline porous silicon, presumably originating from passivated surface states at the surface of pores.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009660820862
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  • 46
    Digitale Medien
    Digitale Medien
    Towards the Morphology Control of Stain Etched Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 407-410 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; stain etching ; morphology ; HREM ; reflectance spectrometry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Porous silicon films, nearly 100 nm thick, were produced by stain etching of n+-type silicon substrates. The films were studied by a non-destructive technique: dielectric function profiles were deduced by spectral reflectance via a finite difference model, and porosity was computed by the Effective Medium Approximation. The obtained information, combined with High Resolution Electron Microscopy observations,provided a deeper insight on the relations among technological process, morphology and reflective properties. Our preliminary results outline the possibility to control the porosity profile as well the reflectance of the porous films via the oxidising species concentration in the stain etching solution.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009607725830
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  • 47
    Digitale Medien
    Digitale Medien
    Location of genes involved in ear compactness in wheat (Triticum aestivum) by means of molecular markers (2000)
    Springer
    Molecular breeding 6 (2000), S. 247-255 
    Details
    ISSN: 1572-9788
    Schlagwort(e): mapping ; morphology ; QTL ; RFLP ; spike density ; Triticeae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Quantitative trait loci (QTLs) for three traits related to ear morphology (spike length, number of spikelets, and compactness as the ratio between number of spikelets and spike length) in wheat (Triticum aestivum L.) were mapped in a doubled-haploid (DH) population derived from the cross between the cultivars Courtot and Chinese Spring. A molecular marker linkage map of this cross that had previously been constructed based on 187 DH lines and 380 markers was used for QTL mapping. The genome was well covered (85%) except chromosomes 1D and 4D and a set of anchor loci regularly spaced (one marker each 15.5 cM) were chosen for marker regression analysis. The presence of a QTL was declared at a significance threshold α = 0.001. The population was grown in one location under field conditions during three years (1994, 1995 and 1998). For each trait, 4 to 6 QTLs were identified with individual effects ranging between 6.9% and 21.8% of total phenotypic variation. Several QTLs were detected that affected more than one trait. Of the QTLs 50% were detected in more than one year and two of them (number of spikelets on chromosome 2B, and compactness on chromosome 2D) emerged from the data from the three years. Only one QTL co-segregated with the gene Q known to be involved in ear morphology, namely the speltoid phenotype. However, this chromosome region explained only a minor part of the variation (7.5–11%). Other regions had a stronger effect, especially two previously unidentified regions located on chromosomes 1A and 2B. The region on the long arm of chromosome 1A was close to the locus XksuG34-1A and explained 12% of variation in spike length and 10% for compactness. On chromosome 2B, the QTL was detected for the three traits near the locus Xfbb121-2B. This QTL explained 9% to 22% of variation for the traits and was located in the same region as the gene involved in photoperiod response (Ppd2). Other regions were located at homoeologous positions on chromosomes 2A and 2D.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009688011563
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  • 48
    Digitale Medien
    Digitale Medien
    In-Situ Surface-Roughness Measurements during the Preparation of Chemically Etched Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 47-49 
    Details
    ISSN: 1573-4854
    Schlagwort(e): stain etching ; porous silicon ; neutron reflection
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract We have monitored the stain-etching of silicon in real time using neutron reflection. The etching process does not occur uniformly with time and possible dynamics of the process is under consideration. Distinct irregularities are produced on the PS surface and some gas bubbling from the cell is observed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009638504564
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  • 49
    Digitale Medien
    Digitale Medien
    Localized Photo-Assisted Electro-Deposition of Zinc Selenide into p-Type Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 77-80 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; ZnSe ; electrochemical deposition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Electroplating of II-VI semiconductors like ZnSe into porous silicon can be an efficient and low cost method to fill the porous volume with a transparent and conductive material. With n-type porous layers, ZnSe impregnation is more effective near the sample surface because of reaction rate limitations due to diffusion in the electrolyte. In this paper, it is shown that the deposition of ZnSe into p-type porous silicon can be localized in the lower part of the porous layer if the reduction reaction rate is monitored by limiting the charge carrier supply. This can be done by controlling the power of the laser beam which photo-generates the carriers at the bottom of the pores. Studying the porous layer chemical composition by Auger electron spectroscopy confirms that the deposit is localized at the pore bottom, whereas the changes in the chemical composition of the porous silicon surface are analyzed by infra-red spectroscopy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009611225946
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  • 50
    Digitale Medien
    Digitale Medien
    AC Impedance Study of Porous Silicon Aging in HF Solution (2000)
    Springer
    Journal of porous materials 7 (2000), S. 97-101 
    Details
    ISSN: 1573-4854
    Schlagwort(e): AC impedance ; porous silicon ; residual moisture ; aging effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract The present work aims to study the AC impedance of porous silicon films left in the contact with the anodizing bath after their growth is over. It is shown that the layers grown at p-type silicon experience noticeable changes of their impedance behavior resulting in the gradual growth of electrical resistance of the p-PS layer. This change is assumed to be related with the deposition of a passive layer at the pore bottoms associated with reabsorption of dissolved Si-containing material from the electrolyte. The layers formed at n-Si also show changes of the electrical impedance, although they are much more complicated than in the previous case (dependence of the kinetics of changes on the polarization current and polarization time, presence of the inductive loops at the impedance spectra, etc.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009619415893
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  • 51
    Digitale Medien
    Digitale Medien
    New EXAFS Measurements by XEOL and TEY on Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 169-172 
    Details
    ISSN: 1573-4854
    Schlagwort(e): EXAFS ; XEOL ; porous silicon
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Results of an EXAFS investigation on porous Silicon carried out by X-ray Excited Optical Luminescence (XEOL) and Total Electron Yield (TEY) techniques, at the Si K absorption edge, are reported. For the first time XEOL spectra of porous silicon have been recorded in a wide energy range (1800–2500 eV) and EXAFS signals have been singled out from them. Simultaneous TEY and XEOL measurements yield to different results: in particular TEY-EXAFS is sensitive up to the third coordination shell of Si, while XEOL-EXAFS reveals only the contributions of the first two coordination shells; moreover they show a different dependence on changes of the etching parameters. This evidences the sensitivity of XEOL technique to the local structure of the quantum confined luminescent sites. The dependence of the light emission properties on the main preparation parameters and their influence on the short-range structure of red and yellow porous silicon samples are also investigated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009622417710
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  • 52
    Digitale Medien
    Digitale Medien
    An Investigation into Silane Evolution from Porous Silicon by Temperature Programmed Desorption Method (2000)
    Springer
    Journal of porous materials 7 (2000), S. 187-190 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; temperature programmed desorption ; FTIR ; silane
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract The gaseous species desorbed from porous silicon (PS) were investigated using the method of temperature programmed desorption (TPD) and fourier transform infrared spectroscopy (FTIR). Silicon wafers (25–50 Ω cm, p−, FZ) were anodised in 40% HF and HF/C2H5OH electrolytes. The PS samples were linearly heated at 1.5 K s−1 using a custom built heating unit in a oil-free pump backed vacuum chamber at a base pressure of 〈10−8 torr. A quadrupole mass spectrometer, which was used as the detector, was fitted in line of sight of the sample at a distance of about 6 mm. It was observed that silane was liberated during the heating of porous silicon samples produced from both electrolytes. The peak temperature at which this occurred was at 570 ± 10 K. This temperature coincides with the temperature of silicon-silicon bond breakage in ≡Si–SiH3 groups on the pore walls, as shown by the FTIR results. It is proposed that silane formation involves the reaction of the Si-silyl group with moisture: ≡Si–SiH3 + H2O → ≡Si–OH + SiH4.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009682603598
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  • 53
    Digitale Medien
    Digitale Medien
    Electrical Control of the Reflectance of Porous Silicon Layers (2000)
    Springer
    Journal of porous materials 7 (2000), S. 205-208 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; oxidation ; liquid crystal
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract In this paper we demonstrate the filling of porous silicon (PS) layers with liquid crystals (LC's) in order to control the reflectance electrically. The preparation of PS and the choice of the right group of LC's will be presented. Especially an oxidation of PS is necessary so that the methods and parameters of oxidation will also be discussed. As a first result the increasing and decreasing of the thickness oscillations in the reflectance as a function of the applied voltage can be observed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009642922253
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  • 54
    Digitale Medien
    Digitale Medien
    Porous Silicon Micromachining to Position Optical Fibres in Silicon Integrated Optical Circuits (2000)
    Springer
    Journal of porous materials 7 (2000), S. 227-231 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; micromachining ; localised anodisation ; fibre positioning
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Low-loss optical fibre connections require deep grooves etched in silicon substrate for accurate fibre positioning. As shown in this paper these grooves can be obtained by using localised formation of porous silicon on patterned substrates. Cr-Au masking layer with a duration in HF solution longer than 30 min is used to fabricate grooves with a depth higher than 75 μm. N+-type silicon provides grooves with a pseudo-V shape which is compatible with accurate fibre alignment. By using this technology, arrays of optical fibres are positioned with an accuracy higher than 1 μm.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009603308141
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  • 55
    Digitale Medien
    Digitale Medien
    Optical Waveguides Fabricated from Oxidised Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 243-246 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; oxidation ; refractive index ; optical waveguide ; optical losses
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Further results on the optical properties of oxidised porous silicon as a function of porosity and oxidation conditions are presented in this paper. The refractive index varies logarithmically with the oxidation time irrespective of the porosity of the sample and the oxidation temperature. Burried waveguides have been realised from as-prepared and oxidised porous silicon. Optical losses of 18 dB cm−1 at λ = 1.3 μm have been obtained after oxidation at 800°C for 35 min.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009659409958
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  • 56
    Digitale Medien
    Digitale Medien
    Novel Structures for Porous Silicon Light-Emitting Diodes (2000)
    Springer
    Journal of porous materials 7 (2000), S. 119-123 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; light-emitting diode ; series resistance ; external quantum efficiency
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract In this paper, two novel structures of porous silicon (PS) light-emitting diodes (LEDs) are proposed aiming at the reduction of series resistance, Rs. The basic idea of the novel structures is to suppress the excessive growth of nanoporous silicon (nano-PS) layer that is electroluminescence- (EL-) active but highly resistive. The initial wafer of the first structure consists of a lightly-doped layer stacked on a highly-doped substrate. As a consequence of anodization, nano-PS layer is formed only in the lightly-doped layer, while meso-PS layer with moderate resistivity is formed in the highly-doped substrate. The second structure consists of alternately stacked nano- and meso-PS layers, since it is expected that multiple thin nano-PS layers connected in series are less resistive than a single thick nano-PS layer. Preliminary experimental results proved the effectiveness of these novel structures on the reduction of Rs.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009671728614
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  • 57
    Digitale Medien
    Digitale Medien
    The Electrical Band-Gap Energy of Porous Silicon Measured Versus Sample Temperature (2000)
    Springer
    Journal of porous materials 7 (2000), S. 271-273 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; photoconductivity ; energy band gap
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Photocurrent measurements have been carried out on a series of samples consisting of porous silicon on top of crystalline silicon, in the temperature range 10–300 K. From the experimental data set, the electrical band-gap energy of porous silicon is deduced to be (1.80 ± 0.01) eV, independent of sample temperature. The results are discussed with the conclusion that for the samples studied here, the electrical bandgap in porous silicon is of molecular nature and cannot be related to quantum-confinement properties of nanocrystals of elemental silicon.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009679930431
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  • 58
    Digitale Medien
    Digitale Medien
    Morphological and Biomechanical Studies of Pedicle Screw Fixation for the Lower Cervical Spine (2000)
    Springer
    Journal of systems integration 10 (2000), S. 55-66 
    Details
    ISSN: 1573-8787
    Schlagwort(e): biomechanics ; morphology ; cervical spine ; pedicle screw fixation ; finite element analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract Based on eight specimens removedfrom fresh cadavers, the morphology of the pedicles of the C3–7cervical vertebrae was determined. Three preliminary designsof pedicle screw and finite element models of the screw withcervical vertebra were developed. The feasibility of pediclescrew fixation for the lower cervical spine is presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026559301696
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  • 59
    Digitale Medien
    Digitale Medien
    Nonaqueous Phase Liquid Dissolution in Porous Media: Current State of Knowledge and Research Needs (2000)
    Springer
    Transport in porous media 38 (2000), S. 3-28 
    Details
    ISSN: 1573-1634
    Schlagwort(e): NAPL ; dissolution ; mass transfer ; morphology ; multicomponent ; up‐scaling ; inverse modeling
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Technik allgemein
    Notizen: Abstract Our understanding of nonaqueous phase liquid (NAPL) dissolution in the subsurface environment has been increasing rapidly over the past decade. This knowledge has provided the basis for recent developments in the area of NAPL recovery, including cosolvent and surfactant flushing. Despite these advances toward feasible remediation technologies, there remain a number of unresolved issues to motivate environmental researchers in this area. For example, the lack of an effective NAPL‐location methodology precludes effective deployment of NAPL recovery technologies. The objectives of this paper are to critically review the state of knowledge in the area of stationary NAPL dissolution in porous media and to identify specific research needs. The review first compares NAPL dissolution‐based mass transfer correlations reported for environmental systems with more fundamental results from the literature involving model systems. This comparison suggests that our current understanding of NAPL dissolution in small‐scale (on the order of cm) systems is reasonably consistent with fundamental mass transfer theory. The discussion then expands to encompass several issues currently under investigation in NAPL dissolution research, including: characterizing NAPL morphology (i.e. effective size and surface area); multicomponent mixtures; scale-related issues (dispersion, flow by-passing); locating NAPL in the subsurface and enhanced NAPL recovery. Research needs and potential approaches are discussed throughout the paper. This review supports the following conclusions: (1) Our knowledge related to local dissolution and remediation issues is maturing, but should be brought to closure with respect to the link between NAPL emplacement theory (as it impacts NAPL morphology) and NAPL dissolution; (2) The role of nonideal NAPL mixtures, and intra-NAPL mass transfer processes must be clarified; (3) Valid models for quantifying and designing NAPL recovery schemes with chemical additives need to be refined with respect to chemical equilibria, mass transfer and chemical delivery issues; (4) Computational and large-scale experimental studies should begin to address parameter up-scaling issues in support of model application at the field scale; and (5) Inverse modeling efforts aimed at exploiting the previous developments should be expanded to support field-scale characterization of NAPL location and strength as a dissolving source.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006667318234
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  • 60
    Digitale Medien
    Digitale Medien
    Intraspecific Variation in the Vocalizations and Hand Pad Morphology of Southern Lesser Bush Babies (Galago moholi): A Comparison with G. senegalensis (2000)
    Springer
    International journal of primatology 21 (2000), S. 537-555 
    Details
    ISSN: 1573-8604
    Schlagwort(e): galago ; taxonomy ; vocalization ; morphology ; zoogeography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Previous studies have shown the taxonomic value of vocal repertoires and hand (volar) pad characteristics in the classification of cryptic nocturnal primates such as bush babies. However, no study included quantitative comparisons within the geographical range of any one species. We investigated levels of intraspecific variation in calls and hand pad characteristics of the southern lesser bush baby (Galago moholi), using the northern lesser bush baby (Galago senegalensis) for interspecific comparisons. Examination of calls recorded from different regions along a transect of 1500 km across southern Africa revealed low levels of intraspecific variation in Galago moholi, whereas comparisons with homologous call-types in G. senegalensis revealed them to be significantly different. Volar pad measurements across the ranges of both species also showed low levels of intraspecific variation and relatively high interspecific variation. These findings demonstrate that vocal and volar pad characteristics can be used as consistent measures of difference between species that look almost identical. These methods provide a practical means of distinguishing between cryptic species, whether in the field, in captivity, or, in the case of volar pads, of preserved specimens.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005400205038
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  • 61
    Digitale Medien
    Digitale Medien
    Penile Morphology and Classification of Bush Babies (Subfamily Galagoninae) (2000)
    Springer
    International journal of primatology 21 (2000), S. 815-836 
    Details
    ISSN: 1573-8604
    Schlagwort(e): Galago ; bush baby ; classification ; penis ; morphology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The penile morphologies of nocturnal prosimians are complex and vary considerably between genera and species. Accordingly, comparative morphology can be useful in taxonomic studies, particularly when assessing the status of newly discovered species. I measured features of penile morphology—surface area of the glans penis; shape and size of the keratinized spines on the glans—for populations representing 14 species within the subfamily Galagoninae. Intraspecific variations in penile morphology were relatively minor. By contrast, there are significant differences in several morphological features among closely related, sympatric species, e.g., in the greater bush babies (Otolemur crassicaudatus and O. garnettii) and lesser bush babies (Galago senegalensis and Galago moholi). Assessment of glans area resulted in the recognition of a second needle-clawed form: Euoticus pallidus. Similar divisions exist in the dwarf and greater bush babies with respect to proportional spiny area and characteristics of spine size. I constructed a key based on the presence/absence of certain features—penile spines, dermal markings on the glans, penile lappets—as well as the shape of the baculum and possession of different spinal morphotypes. This key may be used to identify all 14 species of bush babies. Penile morphologies provide a useful guide to specific identity in the Galagoninae, which may be true also for other groups of nocturnal mammals.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005542609002
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  • 62
    Digitale Medien
    Digitale Medien
    Blue Photoluminescence of Oxidized Films of Porous Silicon (2000)
    Springer
    Journal of applied spectroscopy 67 (2000), S. 852-856 
    Details
    ISSN: 1573-8647
    Schlagwort(e): porous silicon ; photoluminescence spectrum ; photoexcitation spectrum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract It is found that the films of n +-type porous silicon of low (10–50%) porosity exhibit photoluminescence in the region 400–500 nm after a 5-month storage in an air atmosphere. The spectrum of blue photoluminescence of the least porous but strongly oxidized films has maxima at 417, 435, and 465 nm. The same spectrum structure manifests itself upon the introduction of an Er3+- and Yb3+-containing complex. The mechanisms of blue photoluminesence are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004163700281
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  • 63
    Digitale Medien
    Digitale Medien
    Increasing the efficiency of reed plantations on stressed lake and river shores by using special clones of Phragmites australis (2000)
    Springer
    Wetlands ecology and management 8 (2000), S. 415-424 
    Details
    ISSN: 1572-9834
    Schlagwort(e): expansion ; morphology ; nitrogen content ; Phragmites australis ; planting design ; shore restoration ; stand structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In an investigation aimed at comparing the variationin growth and expansion of different reed clones, 10reed clones were planted in spring of 1995 on sixexperimental fields on the River Dahme and the RiverHavel in Berlin. Their sites of origin differed innutrient supply, substrate quality and shoreexposition. The main aim of this large-scaleexperiment was to search for reed clones that would beable to colonize lake shores rapidly and to expandinto deeper water. Two years after planting thedeveloping reed stands differed significantly inmorphology and stand structure, both among clones andamong sites. This indicates that the development ofreed stands depended on the environment as well as onthe genotype. The differences in development impliedthat some of the clones would be more suited thanothers for restoration purposes, so that successfulrestoration of a degraded river or lake shores mightdepend on the selection of the best suited clones.The nitrogen contents in the aboveground biomass oftwo clones differing in nitrogen dynamics at theiroriginal sites (described as `assimilation' and`translocation' types in the literature) did notdiffer in this experiment, even though the two clonesdid differ in some morphological traits. These resultsmight be influenced by the fact that stands were stilldeveloping and that possibly clones had reached adifferent degree of maturity. Nevertheless, theysuggest that nitrogen content depends more on siteconditions, with only little genetically determineddifference, and that morphological variation isdetermined by factors other than variation in nitrogenuptake.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026510018318
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  • 64
    Digitale Medien
    Digitale Medien
    Crystallization of Lactose from Carbopol Gels (2000)
    Springer
    Pharmaceutical research 17 (2000), S. 879-886 
    Details
    ISSN: 1573-904X
    Schlagwort(e): lactose ; crystallization ; Carbopol gels ; morphology ; crystal form ; crystal habit
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. To crystallize lactose under static conditions with a view topreparing crystals of well-defined morphology. Methods. α-Lactose monohydrate was crystallized from neutralizedCarbopol 934 gels. When the majority of crystals had grown to maturity,the gels were acidified using diluted hydrochloric acid and the crystalswere harvested by filtration or centrifugation and washed with ethanol-watermixtures. Results. Crystals prepared from the gel had a consistently narrowersize distribution than control crystals, prepared from solution underconstant stirring. If crystallization was effected in the gel withoutsedimentation of the crystals, then the resultant crystals had smoothsurfaces without visually detectable surface roughness or asperitiesviewed by optical microscopy. The crystals from Carbopol gels alsoexhibited the uniform shape of an elongated tomahawk regardless of thecrystallization conditions, in contrast to crystallization under constantstirring, where the crystal shape of lactose changed with crystallizationconditions especially as a function of the initial concentration of lactose.All batches of lactose crystals prepared from Carbopol gels existedas α-lactose monohydrate, which showed better flowability than thecontrols of a similar particle size. Conclusions. Crystallization from Carbopol gel produces lactose crystalsof uniform size, regular shape, smooth surface, and improvedflowability.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007572612308
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  • 65
    Digitale Medien
    Digitale Medien
    Phylogeny of the tribe Antirrhineae (Scrophulariaceae) based on morphological andndhF sequence data (2000)
    Springer
    Plant systematics and evolution 220 (2000), S. 223-239 
    Details
    ISSN: 1615-6110
    Schlagwort(e): Scrophulariaceae ; Antirrhineae ; morphology ; ndhF ; phylogeny ; pollination
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Phylogenetic relationships within the tribe Antirrhineae (Scrophulariaceae) are analysed and discussed on the basis of parsimony analyses of morphological andndhF gene sequence data. The results indicate that the tribe Antirrhineae consists of four major groups of genera, theAnarrhinum clade, theGambelia clade, theMaurandya clade, and theAntirrhinum clade. TheAnarrhinum clade, consisting of the Old World bee-pollinated generaAnarrhinum andKickxia, is sister to the rest of the tribe. TheGambelia clade consists of the New World generaGambelia andGalvezia, which are very closely related and pollinated by hummingbirds. TheMaurandya clade consists of one subclade includingMaurandya and a number of related bee- or hummingbird-pollinated New World genera and another subclade with the Old World bee-pollinated generaAsarina andCymbalaria. TheAntirrhinum clade consists mainly of bee-pollinated Old World genera, such asAntirrhinum, Linaria, Chaenorhinum, and their segregates, but also includes the New World generaMohavea andHowelliella, of which the latter is known to be partly pollinated by hummingbirds. It is concluded that hummingbirdpollination has evolved independently within Antirrhineae at least three times from bee-pollinated ancestors.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00985047
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  • 66
    Digitale Medien
    Digitale Medien
    Implications of morphological phylogenetics for the placement of the generaAdenocaulon andEriachaenium (Asteraceae) (2000)
    Springer
    Plant systematics and evolution 223 (2000), S. 229-250 
    Details
    ISSN: 1615-6110
    Schlagwort(e): Asteraceae ; Cichorioideae ; Adenocaulon ; Eriachaenium ; problematic genera ; morphology ; phylogenetic analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Adenocaulon andEriachaenium are two problematic genera because their tribal and subfamilial placement in Asteraceae is uncertain. Previous cladistic analyses based on molecular data undertaken to analyze the relationships within Asteraceae, placeAdenocaulon in the tribe Mutisieae (Cichorioideae). This paper investigates cladistic relationships amongAdenocaulon andEriachaenium and tribes of subfamilies Cichorioideae and Asteroideae using morphological data. Thirty-eight characters were scored across 52 genera selected as exemplar taxa to represent the current classification system. In the analysis (one tree, length = 86, c.i. = 0.55, r.i. = 0.64)Adenocaulon andEriachaenium are sister taxa and appear as an isolated clade nested in Cichorioideae. A new, tentative position among the tribes of the paraphyletic Cichorioideae is proposed for these two isolated genera.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00985282
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  • 67
    Digitale Medien
    Digitale Medien
    Software dependent phenetic relationships of non-nodulating African species ofAcacia (2000)
    Springer
    Plant systematics and evolution 220 (2000), S. 139-146 
    Details
    ISSN: 1615-6110
    Schlagwort(e): Acacia ; classification ; Leguminosae ; morphology ; phenetics ; RAPD ; software ; taxonomy ; UPGMA
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The phenetic analysis of non-nodulatingAcacia species by Harrier et al. (1997) was repeated to illustrate how different computer programs may generate alternative UPGMA trees for the very same data, even in the absence of data input order effects (ties). For example, all Harrier et al.'s UPGMA dendrograms produced by software from the Scottish Agricultural Statistics Service differed from those obtained by the packages NTSYS and MVSP87. Particularly, the positions ofA. albida, A. rovumae, andA. pentagona, as well as the relationships betweenDiacanthae andTriacanthae were affected by this phenomenon. Hence, whenever clustering techniques are used, care should be taken to consider possible software-dependent caveats and artefacts. Nevertheless, all programs provided clusterings that largely coincided with the subgeneric and sectional groupings proposed by Vassal (1972) although the positions of some species varied depending on whether morphological or molecular data were considered (e.g.A. albida andA. rovumae).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00985042
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  • 68
    Digitale Medien
    Digitale Medien
    Phylogenetic signal common to three data sets: Combining data which initially appear heterogeneous (2000)
    Springer
    Plant systematics and evolution 221 (2000), S. 179-198 
    Details
    ISSN: 1615-6110
    Schlagwort(e): Gesneriaceae ; congruence ; morphology ; ndhF ; rbcL ; phylogeny
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract This study makes use of three sources of data, morphology and two chloroplast DNA sequences,ndhF andrbcL, to resolve relationships in Gesneriaceae. Cladograms from each of the three data sets separately are not topologically congruent. Statistical indices suggest that each data set is congruent with thendhF data althoughrbcL and morphology are themselves incongruent. Consensus methods provide no resolution of taxonomic relationships when trees from the different data sets are combined. Combining data sets generally results in cladograms that are more fully resolved than each of the data sets analyzed separately and support for the clades increases based on higher decay index and bootstrap values. These results indicate that there is a phylogenetic signal common to each of the data sets, however, the noise (errors due to homoplasy, mis-scoring, etc.) unique to each data source masks this signal. In combining the data, the evidence for the common evolutionary history in each data set overcomes the noise and is apparent in the resulting trees.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01089293
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  • 69
    Digitale Medien
    Digitale Medien
    Mycelium of Arbuscular Mycorrhizal fungi (AMF) from different genera: form, function and detection (2000)
    Springer
    Plant and soil 226 (2000), S. 131-151 
    Details
    ISSN: 1573-5036
    Schlagwort(e): arbuscular mycorrhizas ; ecological function ; isozymes ; morphology ; mycelium architecture ; molecular probes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract It is often assumed that all species of arbuscular mycorrhizal fungi (AMF) have the same function because of the ubiquity of the arbuscular mycorrhizal symbiosis and the fact that all AMF occupy the same plant/soil niche. Despite apparent differences in the timing of evolutionary divergence and the morphological characteristics of AMF from the different genera, the majority of studies on these fungi use only species of Glomus. There is increasing evidence, however, that the mechanisms involved in the establishment of a mycorrhiza may differ for species and genera of AMF and influence their subsequent function. The aim of this paper is to highlight the diversity in the form and function of AMF from different genera, knowledge of which is vital in understanding their ecological roles. Potential use of biochemical and molecular approaches to detect AMF in planta and ex planta is also discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026574828169
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  • 70
    Digitale Medien
    Digitale Medien
    Morphological relationships among 15 species of Trifolium occurring in Poland (2000)
    Springer
    Genetic resources and crop evolution 47 (2000), S. 267-272 
    Details
    ISSN: 1573-5109
    Schlagwort(e): morphology ; numerical taxonomy ; phenetics ; Trifolium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Populations of 15 Trifolium species were morphologically assayed to elucidate species relationships and taxonomic arrangements in the genus. Twenty-one characters were scored and analyzed by numerical methods. All species proved to be heterogenous. The levels of dissimilarity among populations of the same species ranged from around 0.05 to around 0.6. Cluster analysis divided all taxa into two major groups of species which were joined at D (Euclidean Distance) around 0.9. Within the first group three major sub-groups were revealed, comprising T. hybridum L., T. repens L., T. strepens Cr., T. dubium Sibth., T. campestre Schreb., T. patens Schreb. and T. fragiferum L. The second major group consisted of T. pannonicum L., T. arvense L., T. montanum L., T. incarnatum L., T. alpestre L., T. rubens L., T. pratense L. and T. medium L. The present results proved that the genus is very heterogenous, and support the hypothesis that the section Lotoidea was probably the stock from which other sections derived. Morphological relationships among 15 Trifolium species support their taxonomic arrangements proposed by Zohary & Heller (1984), with some exceptions. Sectional positions of T. montanum and T. strepens should be reexamined. Conspecific ranks for three species of section Chronosemum – T. dubium, T. campestre and T. patens – should be considered.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008707024828
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  • 71
    Digitale Medien
    Digitale Medien
    Diversity of the Sheanut tree (Vitellaria paradoxa C.F. Gaertn.) in Ghana (2000)
    Springer
    Genetic resources and crop evolution 47 (2000), S. 293-304 
    Details
    ISSN: 1573-5109
    Schlagwort(e): clinal trends ; isozymes ; morphology ; population variance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The Sheanut tree (Vitellaria paradoxa C.F. Gaertn.) is highly valued for oil obtained from its seeds and frequently maintained in the semi-arid parklands of sub-Saharan Africa from Senegal to Uganda. Although variation has been noted for V. paradoxa subsp. paradoxa, few studies have been undertaken on patterns of phenotypic or genotypic diversity. Results are presented from 294 accessions collected in Ghana, using easily quantifiable morphological parameters. Productive mature trees varied from shrubby multi-stemmed individuals (height 〈5 m) to 30-m straight-boled trees with high compact canopies. The leaf lamina (tree mean ±% coefficient of variation of total mean) varied from 9.2 to 22.5 cm (±15.0%); seed length from 1.74 to 3.74 cm (±11.7%); and fat content from 29.1 to 61.9% of dry kernel weight (±9.4%). Clinal trends significantly correlated with location parameters that in turn related to environmental variation. Population variation of seed characteristics increased to the Northeast, perpendicular to the annual movement of the inter-tropical convergence zone. It is proposed that this is a consequence of past climatic changes, coupled with a lack of methodical selection for seed type when trees are maintained on agricultural land. Isozyme analysis revealed moderate to high levels of heterozygosity (He 0.2142) and high geneflow (Fst = 0.0124, Nm = 19.9), supporting results obtained from morphological studies. Isozyme and multivariate morphology analyses showed similar but weak geographical separation patterns.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008710331325
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  • 72
    Digitale Medien
    Digitale Medien
    A phenetic analysis of morphological variation in Citrullus lanatus in Namibia (2000)
    Springer
    Genetic resources and crop evolution 47 (2000), S. 385-393 
    Details
    ISSN: 1573-5109
    Schlagwort(e): Citrullus lanatus ; cluster analysis ; evolution ; morphology ; watermelon
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Morphological data recorded from field trials using Citrullus lanatus germplasm collected in Namibia were used to analyse and compare the various morphotypes of this species. The experiment comprised wild types and local landraces as well as commercial cultivars. Cluster analysis supported the indigenous classification system used in Namibia, in which Citrullus types are distinguished based on gross morphology, ecology and usage and grouped into seed, cooking and fresh-eating (watermelon) types. Commercial watermelon cultivars formed a distinct cluster. Wide variation was found within the local types whereas the genetic basis of the commercial type appears to be narrow. The commercial cultivars were most closely related to local watermelon types and more distantly related to the wild types, whereas the cooking melons form an intermediate group.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008751319879
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  • 73
    Digitale Medien
    Digitale Medien
    The ontogeny of the cypridid ostracod Eucypris virens (Jurine, 1820) (Crustacea, Ostracoda) (2000)
    Springer
    Hydrobiologia 419 (2000), S. 31-63 
    Details
    ISSN: 1573-5117
    Schlagwort(e): morphology ; ontogeny ; Ostracoda ; evolution ; fifth limb ; crustacean phylogeny
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The chaetotaxy (shape, structure and distribution of setae) of appendages and valve allometry during the post embryonic ontogeny of the cyprididine ostracod Eucypris virens are described. It is shown that the basic ontogenetic development of E. virens is very similar to that of other species of the family Cyprididae. During ontogeny, the chaetotaxy shows continual development on all podomeres of the limbs with the exception of the last podomere on the antennulae. The long setae on the exopodite and protopodite of the antennae have a natatory function until the actual natatory setae develop in later instars. Aesthetascs (presumed chemoreceptors) ya and y3 are the first to develop and may have an important function in the first instars. Cyprididae require a pediform limb in the posterior of the body presumably to help them to attach to substrates and this is reflected by the pediform nature of one limb at all times throughout all instars. This study has also shown that the fifth limb is most probably of thoracic origin and hence ostracods have only one pair of maxillae.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1003985908460
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  • 74
    Digitale Medien
    Digitale Medien
    Differences in the apportionment of molecular and morphological variation in North American strawberry and the consequences for genetic resource management (2000)
    Springer
    Genetic resources and crop evolution 47 (2000), S. 647-657 
    Details
    ISSN: 1573-5109
    Schlagwort(e): Fragaria chiloensis ; Fragaria virginiana ; genetic resources ; morphology ; RAPD
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Variation for 24 morphological traits measured in a greenhouse environment and 36 randomly amplified polymorphic DNA (RAPD) markers was assessed among 318 wild octoploid strawberry (Fragariaspp.) genotypes from diverse habitats across the northern USA. RAPD marker frequencies and certain leaf and flower morphology traits (petiole color, leaf mass/area ratio, leaflet length and width, flower and receptacle diameter, petal width, flowers/inflorescence) were significantly different between the F. chiloensis-platypetala and F. virginiana-glauca species complexes. The proportion of variation accounted for by provenance effects was lower for the RAPD markers than for most morphological traits, especially in the F. virginiana-glauca species complex. Morphological traits of potential adaptive importance group the collection into provenances within each species-complex, and reflect the significant habitat and geographic differences across the region from which the germplasm was collected. Variation among populations within provenances was low for the molecular and most morphological traits, with a much larger amount of variability among plants within populations. Most of the variation for the presumably more selectively-neutral RAPD data was among plants within populations and populations within provenances rather than among the provenances that were recognized based on morphological traits, especially in the F. virginiana-glauca complex. Patterns of diversity for morphological traits must be considered, along with more selectively-neutral molecular characters such as RAPDs, to formulate effective sampling strategies and to properly estimate the quantity and apportionment of diversity within this germplasm.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026530125493
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  • 75
    Digitale Medien
    Digitale Medien
    Preface: Ostracoda and the four pillars of evolutionary wisdom (2000)
    Springer
    Hydrobiologia 419 (2000), S. 7-11 
    Details
    ISSN: 1573-5117
    Schlagwort(e): morphology ; palaeontology ; ecology ; genetics ; Ostracoda ; evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Morphology, palaeontology, genetics and ecology are the main scientific domains contributing theories, concepts and new data to evolutionary biology. Ostracods are potentially very good model organisms for evolutionary studies because they combine an excellent fossil record with a wide extant distribution and, therefore, allow studies on both patterns and processes leading to extant diversity. This preface provides an overview of the 15 contributions to the present volume and concludes that this set of papers supports the claim that ostracod studies are situated in all main evolutionary domains.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1003994820756
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  • 76
    Digitale Medien
    Digitale Medien
    Redescription and assignment of the chydorid Indialona ganapati Petkovski, 1966 (Branchiopoda: Anomopoda: Aloninae) to Indialonini, new tribus (2000)
    Springer
    Hydrobiologia 439 (2000), S. 161-178 
    Details
    ISSN: 1573-5117
    Schlagwort(e): Cladocera ; Anomopoda ; Chydoridae ; Indialona ; morphology ; systematics ; Indialonini n. trib. ; evolutionary relationships
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The chydorid Indialona ganapati Petkovski, 1966 is redescribed based on material from the sublittoral plankton of Ajwa Reservoir, Ahmedabad, India, and a neotype is selected. Lateral head pores are recorded, and all thoracic limbs are studied in detail. Gamogenetic specimens are described for the first time. Evolutionarily relationships of Indialona and other Aloninae are discussed. A new tribe Indialonini n. trib. is proposed for the sole genus Indialona, while all other genera of Aloninae, as far as is known, compose the tribe Alonini s. str. A diagnosis of both tribes and a key for their discrimination is proposed. Sharp differences between these tribes are found in some characters of the thoracic limbs. The limbs of the Indialonini are more oligomerized than those of the Alonini, and a strong oligomerization is characteristic of limbs I–II.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004187007890
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  • 77
    Digitale Medien
    Digitale Medien
    Phylogenetic implications of the Crustacean nauplius (2000)
    Springer
    Hydrobiologia 417 (2000), S. 91-99 
    Details
    ISSN: 1573-5117
    Schlagwort(e): evolution ; phylogeny ; larval characters ; morphology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The plesiomorphic mode of crustacean development is widely accepted to be via a larva called the nauplius. Extant taxa like the Cephalocarida, Branchiopoda, Ostracoda, Mystacocarida, Copepoda, Cirripedia, Ascothoracida, Facetotecta, Euphausiacea and Penaeidea hatch from an egg as a free-living nauplius. Other crustaceans show an embryonic phase of development suggestive of a naupliar organization. Several features of the nauplius larva have been proposed as diagnostic characters for the Crustacea: a median (nauplius) eye; at least three pairs of head appendages (antennules, antennae, mandibles); a posteriorly directed fold (the labrum) extending over the mouth and a cephalic (nauplius) shield. The relationship between trilobite protaspis with at least four appendages and the crustacean nauplius remains unclear, but reports of a copepod orthonauplius with four appendages are rejected. Swimming is suggested to represent the underived mode of locomotion for the crustacean nauplius, and that naupliar swimming directly results in naupliar feeding which also is underived.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1003886818724
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  • 78
    Digitale Medien
    Digitale Medien
    The dinoflagellate genus Prorocentrum along the coasts of the Mexican Pacific (2000)
    Springer
    Hydrobiologia 418 (2000), S. 111-121 
    Details
    ISSN: 1573-5117
    Schlagwort(e): dinoflagellates ; Prorocentrum ; morphology ; taxonomy ; Mexican Pacific ; red tides
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We surveyed the dinoflagellate genus Prorocentrum Ehrenberg in Mexican Pacific waters, where it is rather common and sometimes causes red tides in coastal areas or shrimp farms. Material collected from Baja California and the Gulf of California was analyzed. Thirteen species were identified, all of them planktonic (although P. mexicanum is also epiphytic). All species are described by light microscopy, and most are also described by scanning electron microscopy; comments on morphology, taxonomy and distribution are made. Red tides were caused by P. dentatum, P. minimum and P. triestinum. Prorocentrum mexicanum and P. minimum were suspected of being toxic. Four species, previously reported in the Gulf of California, were not found. A total of 18 species, including the new records P. dactylum and P. lebourae have been to date reported from the Mexican Pacific.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1003806719515
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  • 79
    Digitale Medien
    Digitale Medien
    Redescription of Diaphanosoma dubium Manuilova, 1964 (Branchiopoda: Ctenopoda: Sididae), and description of a new, related species (2000)
    Springer
    Hydrobiologia 441 (2000), S. 73-92 
    Details
    ISSN: 1573-5117
    Schlagwort(e): Diaphanosoma dubium ; D. pseudodubium sp.nov. ; morphology ; taxonomy ; geographical distribution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The poorly known D. dubium Manuilova is redescribed on extensive material from more than 80 populations from the Russian Far East, Central Asia, Mongolia, China, Japan, Vietnam, the Philippines, Thailand, Malaysia, Bangladesh, India and Sri Lanka. Its morphological variability and geographical distribution are analysed and supplemented by notes on biology. The conspecificity of morphologically different distant populations is discussed. In the northern part of its range, D. dubium was long confused with D. brachyurum or D. leuchtenbergianum, and in the south with D. modigliani. It seems that the recent appearance of D. dubium in fish ponds of Uzbekistan and Kazakhstan was an introduction, together with Far Eastern fish. D. pseudodubium sp.nov., close to but markedly different, is described from two lakes in the lower Amur river system. D. dubium, D. pseudodubium, D. tropicum and D. modigliani s. str. form a group of related species, widely distributed in Eastern and Southern Asia.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1017574921558
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  • 80
    Digitale Medien
    Digitale Medien
    A new Ceratium species (Dinophyceae) from Lake Doïrani, Macedonia, Greece (2000)
    Springer
    Hydrobiologia 424 (2000), S. 101-108 
    Details
    ISSN: 1573-5117
    Schlagwort(e): Ceratium ; freshwater ; ecology ; morphology ; taxonomy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A new taxon of Ceratium is described from Lake Doïrani, Greece. It is proposed as a new species and named Ceratium monoceras. It differs morphologically from known species of Ceratium by having only one horn, the apical horn. Accordingly, the vegetative cells form cysts that have only one spine. Details of its ecology and occurence are given.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1003957129071
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  • 81
    Digitale Medien
    Digitale Medien
    Redescription of Ilyocryptus tuberculatus Brehm, 1913 (Anomopoda, Branchiopoda) (2000)
    Springer
    Hydrobiologia 428 (2000), S. 115-128 
    Details
    ISSN: 1573-5117
    Schlagwort(e): `Cladocera' ; Anomopoda ; Ilyocryptus tuberculatus ; morphology ; redescription ; Africa
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The morphology of Ilyocryptus tuberculatus Brehm, 1913 is redescribed, based on material from the Niger basin, Africa. The species name was given by Brehm erroneously, because under an optical microscope he mistook internal structures (the columns between the outer and inner walls of the valves) for the tubercules on the valve surface. But this species is undoubtedly valid, and `incorrect' species names must be conserved. Differences between I. tuberculatus and the most similar I. agilis (probably absent from the majority of African waters), I. spinifer (common in Africa), and some other species are discussed. Currently, I. tuberculatus is known for the Central African Republic, Mali and Niger.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1003933430624
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  • 82
    Digitale Medien
    Digitale Medien
    Lithoglyptes cornutus, new species (Cirripedia: Acrothoracica), a boring barnacle from the Seychelles, with some data on its ultrastructure (2000)
    Springer
    Hydrobiologia 438 (2000), S. 185-191 
    Details
    ISSN: 1573-5117
    Schlagwort(e): systematics ; morphology ; organ ; relationship ; SEM
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A new species of the Lithoglyptes from the Seychelles is described. The external morphology of the mantle sac and the body were examined under SEM. The position of a new species within Lithoglyptes and the ultrastructural characters of different species of this genus are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004102926964
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  • 83
    Digitale Medien
    Digitale Medien
    External morphology of the burrowing barnacle shape Lithoglyptes bicornis (Crustacea: Cirripedia: Acrothoracica) (2000)
    Springer
    Hydrobiologia 438 (2000), S. 193-203 
    Details
    ISSN: 1573-5117
    Schlagwort(e): Cirripedia ; Acrothoracica ; morphology ; organs ; trophi ; SEM
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The external morphology of female and male Lithoglyptes bicornis was examined under SEM. The structure of the mantle, the thorax and, especially, the trophi were thoroughly examined. The data on the mantle and the thorax structures were compared with the previous data on the acrothoracican ultrastructure. The data on the structure and the character of trophi setation allow to speculate about a relationship with other cirripede taxa.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004150806491
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  • 84
    Digitale Medien
    Digitale Medien
    Morphological characterization of new populations of the copepod Eurytemora velox (Lilljeborg, 1853) (Calanoida, Temoridae) found in Austria and Hungary (2000)
    Springer
    Hydrobiologia 438 (2000), S. 205-216 
    Details
    ISSN: 1573-5117
    Schlagwort(e): Eurytemora velox ; morphology ; distribution ; Austria ; Hungary ; Danube River
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The calanoid copepod Eurytemora velox (Lilljeborg, 1853) was found in the backwater system of the Danube River upstream of Vienna (km 1948) in 1994. Since that time, the species has invaded the side arms of the river between kms 1897 and 1988, as confirmed by findings from 10 different localities. In Hungary, the species has been known since 1992. In the present article, we report 15 new sites in the westernmost part of this country. A brief diagnosis of the morphology of male and female of the Austrian specimens is presented, including detailed illustrations of the structures used in this paper for taxonomic analysis. Females show morphological variability mainly on the structure of the fifth leg pair. Right and left legs frequently have a different spinulation pattern. Males show less morphological variability, particularly in the structure of the basis and the distal section of exopod 2 of the fifth left leg. Morphological variation within E. veloxwas determined by comparing specimens from Austria, Hungary and Rumania. The geographic distribution of the species in the Palearctic region, Austria and Hungary is presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004173704289
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  • 85
    Digitale Medien
    Digitale Medien
    Absorption of glucose, amino acids, and dipeptides by the intestines of Atlantic salmon (Salmo salar L.) (2000)
    Springer
    Fish physiology and biochemistry 22 (2000), S. 33-44 
    Details
    ISSN: 1573-5168
    Schlagwort(e): diffusion ; everted sleeve method ; morphology ; nutrients ; pyloric ceca ; transport
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Rates of glucose, amino acid and dipeptide absorption by the intestine of Atlantic salmon (Salmo salar L.) were measured in vitro at 10 °C as functions of concentration and region using intact tissues (everted sleeve method). Salmon (weight range 300–1300 g) fed a commercial, extruded salmon feed, were kept at 12–13 °C in freshwater. Maximum rates (V max) of glucose and dipeptide transport were low compared to most amino acid V max values. There was a declining proximal-to-distal gradient of absorption along the post-gastric intestinal tract. A saturable component of absorption was not evident for proline and glycyl-proline in the distal intestine, and glycyl-sarcosine in any region. `Apparent diffusion', which may include low affinity, high capacity carrier systems and carrier-independent influx, appears to account for the majority of total uptake at higher concentrations of amino acids and dipeptides. There was competition between the dipeptides for transporter sites in the pyloric ceca and mid intestine, suggesting a common carrier. There was also indication of hydrolysis of these dipeptides by brush border membrane enzymes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007872929847
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  • 86
    Digitale Medien
    Digitale Medien
    Tight Junctions of the Blood–Brain Barrier (2000)
    Springer
    Cellular and molecular neurobiology 20 (2000), S. 57-76 
    Details
    ISSN: 1573-6830
    Schlagwort(e): tight junction ; blood–brain barrier ; morphology ; freeze–fracture ; cadherins ; catenins ; occludin ; cytoskeleton
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract 1. The blood–brain barrier is essential for the maintainance and regulation of the neural microenvironment. The blood–brain barrier endothelial cells comprise an extremely low rate of transcytotic vesicles and a restrictive paracellular diffusion barrier. The latter is realized by the tight junctions between the endothelial cells of the brain microvasculature, which are subject of this review. Morphologically, blood–brain barrier-tight junctions are more similar to epithelial tight junctions than to endothelial tight junctions in peripheral blood vessels. 2. Although blood–brain barrier-tight junctions share many characteristics with epithelial tight junctions, there are also essential differences. However, in contrast to tight junctions in epithelial systems, structural and functional characteristics of tight junctions in endothelial cells are highly sensitive to ambient factors. 3. Many ubiquitous molecular constituents of tight junctions have been identified and characterized including claudins, occludin, ZO-1, ZO-2, ZO-3, cingulin, and 7H6. Signaling pathways involved in tight junction regulation comprise, among others, G-proteins, serine, threonine, and tyrosine kinases, extra- and intracellular calcium levels, cAMP levels, proteases, and TNFα. Common to most of these pathways is the modulation of cytoskeletal elements which may define blood–brain barrier characteristics. Additionally, cross-talk between components of the tight junction– and the cadherin–catenin system suggests a close functional interdependence of the two cell–cell contact systems. 4. Recent studies were able to elucidate crucial aspects of the molecular basis of tight junction regulation. An integration of new results into previous morphological work is the central intention of this review.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006995910836
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  • 87
    Digitale Medien
    Digitale Medien
    Morphological and biochemical characterization of the exocellular investments of polysaccharide-producing Nostoc strains from the Pasteur Culture Collection (2000)
    Springer
    World journal of microbiology and biotechnology 16 (2000), S. 655-661 
    Details
    ISSN: 1573-0972
    Schlagwort(e): Exocellular investments ; exopolysaccharide ; morphology ; Nostoc ; Pasteur Culture Collection
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract A total of 40 Nostoc strains, belonging to the Pasteur Culture Collection and originally isolated from different habitats, were photoautotrophically grown in liquid cultures and tested for the presence of exocellular polysaccharidic investments surrounding the trichomes. However, 25 of them showed a significant presence of these structures, coupled with the release of polysaccharidic material (RPS) into the medium. A rather large number of different morphological forms was observed in the cultures during growth, but at the time of harvesting the predominant morphological form was, in most cases, the vegetative trichome. With regard to the exocellular mucilaginous investments, three main types of morphologies were observed: (i) capsules surrounded by an external pellicle, (ii) capsules with sharp outlines but without an external pellicle, (iii) slimy investments that either loosely surrounded the trichomes without following their shape or were organized in large globular lumps. Among the twenty-five strains that released polysaccharides into the culture medium, three showed mean daily productivities ranging from 30 to 50 mg (RPS) l−1 d−1, values comparable with those of the most productive cyanobacterial strains so far described. The morphological characteristics of the polysaccharidic investments produced by the Nostoc strains seem not to be related to their original habitats. Furthermore, the differences in RPS productivities observed among the strains seem not to be related to the shape of the mucilaginous exocellular investments. Chemical analysis of purified samples of the polysaccharides demonstrated that all the polymers possess an acidic nature, due to the presence of uronic acids, and that they are characterized by the presence of a peptidic moiety and of amino sugars.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008985722388
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  • 88
    Digitale Medien
    Digitale Medien
    Photosynthetic acclimation of shade-grown red pine (Pinus resinosa Ait.) seedlings to a high light environment (2000)
    Springer
    New forests 19 (2000), S. 1-11 
    Details
    ISSN: 1573-5095
    Schlagwort(e): chlorophyll fluorescence ; competition ; morphology ; photosynthesis ; red pine ; stomatal conductance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Photosynthetic light acclimation in red pine (Pinus resinosa Ait.) seedlings was examined in a greenhouse study to better understand the physiological response of this species to increased light intensity following release from competition. Seedlings grown in a high (HL), medium (ML) or low (LL) light environment for 12 weeks were transferred to high light. Gas exchange and chlorophyll fluorescence of ML and LL seedlings were measured prior to and following transfer and compared with the HL control treatment. Photosynthetic characteristics were related to initial light treatment and time after transfer. Acclimation of gas exchange features to high light in shade formed ML and LL foliage was relatively rapid, with similar values among light treatments within 57 days of transfer. Acclimation of net photosynthetic rate was similar in ML and LL seedlings, and was associated primarily with increased mesophyll conductance to CO2. The ratio of variable to maximal chlorophyll fluorescence (Fv/Fm) decreased initially after transfer, especially in LL seedlings, but recovered to normal values after 57 days. Red pine seedlings appear to be well adapted for photosynthetic acclimation to high light intensity, consistent with that reported for other early successional tree species.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006668928091
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  • 89
    Digitale Medien
    Digitale Medien
    Ilyocryptus spinifer Herrick 1882 (Anomopoda, Branchiopoda): a redescription based on North American material and designation of a neotype from Minnesota (2000)
    Springer
    Hydrobiologia 428 (2000), S. 67-84 
    Details
    ISSN: 1573-5117
    Schlagwort(e): Anomopoda ; Ilyocryptidae ; Ilyocryptus spinifer ; morphology ; North America ; neotype ; redescription
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The morphology of Ilyocryptus spinifer Herrick, 1882 is redescribed based on material from USA and Canada with special attention to features, regarded now as important for Ilyocryptidae taxonomy. Morphological variability is analysed, and a neotype of this species is designated from Lake Alice Bog, MN, USA. Scanning electron microscopy is used to illustrate fine morphological details. Males, ephippial females and ephippia are described for the first time for North American populations. Historical descriptions of well-known previous North American authors are critically discussed. Only a single species from I. spinifer s. lat. species group is present in USA and Canada, Ilyocryptus longiremis Sars 1888 is a junior synonym of I. spinifer.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1003983723896
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  • 90
    Digitale Medien
    Digitale Medien
    Analysis of the Ilyocryptus spinifer-species group (Anomopoda, Branchiopoda), with description of a new species (2000)
    Springer
    Hydrobiologia 428 (2000), S. 85-113 
    Details
    ISSN: 1573-5117
    Schlagwort(e): Anomopoda ; `Cladocera' ; Ilyocryptus ; morphology ; variability ; systematics ; world fauna
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We studied the morphology and variability of Ilyocryptus spinifer Herrick, 1882 from different parts of the world using optical microscopy and SEM, re-examining type material wherever possible. Morphometric analysis failed to reveal significant regional differences between populations. The following species names for members of Ilyocryptus spinifer group, I. halyi Brady, 1886; I. longiremis Sars, 1888; I. immundus F. Mueller in Ihering, 1895; I. verrucosus Daday, 1905; and I. tetraspinatus Berganim, 1939, are junior synonyms of I. spinifer. A new species from this group is described from Queensland, Australia. Ilyocryptus timmsi n. sp. shows unique morphological characters in the armature of the lateral swimming setae of the antennal endopod, its apical segment and the postabdominal claws.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1003977208875
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  • 91
    Digitale Medien
    Digitale Medien
    Taxonomic re-evaluation of Aphanizomenon flos-aquae NH-5 based on morphology and 16S rRNA gene sequences (2000)
    Springer
    Hydrobiologia 438 (2000), S. 99-105 
    Details
    ISSN: 1573-5117
    Schlagwort(e): Aphanizomenon ; Cyanobacteria ; 16S rRNA ; morphology ; sequences ; taxonomy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The taxonomy of Aphanizomenon flos-aquae strain NH-5, a producer of cyanotoxins, was re-evaluated by comparison with six other Aphanizomenon strains using morphological characteristics and 16S rRNA gene sequences. Strain NH-5 was concluded to be improperly identified as Aph. flos-aquae based upon (1) lack of bundle formation in the trichomes, (2) location of akinetes next to heterocytes, (3) lower similarities (less than 97.5%) in the 16S rRNA gene sequences relative to Aph. flos-aquae strains, and (4) comparison within a phylogenetic tree constructed from 16S rRNA gene sequences. The Aphanizomenon strains investigated in this study are classified to four morphological groups as described by the classical taxonomy of Komárek & Kovácik (1989). This classification was supported from the phylogenetic results of 16S rRNA gene sequences. This study also discusses the generic boundaries between Aphanizomenon and Anabaena.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004166029866
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  • 92
    Digitale Medien
    Digitale Medien
    Taxonomic studies of planktic species of Anabaena based on morphological characteristics in cultured strains (2000)
    Springer
    Hydrobiologia 438 (2000), S. 117-138 
    Details
    ISSN: 1573-5117
    Schlagwort(e): Anabaena ; cyanobacteria ; identification ; morphology ; planktic ; taxonomy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Fifty (50) strains of planktic species of Anabaena (cyanobacteria), including collections from Japan and China and from different culture collections, were induced to form akinetes at low temperature (15 °C). Their morphologies were then observed and described. Fourty seven strains successfully formed akinetes and these were classified into 20 species comprising seven with straight trichomes and 13 with coiled trichomes. Three strains, which did not form akinetes, were separated into two taxonomic groups, but could not be identified to any described species. In addition, a key to the planktic species of Anabaena described in the study is presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004170230774
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  • 93
    Digitale Medien
    Digitale Medien
    A eukaryotic alga from picoplankton of Lake Baikal: morphology, ultrastructure and rDNA sequence data (2000)
    Springer
    Hydrobiologia 435 (2000), S. 83-90 
    Details
    ISSN: 1573-5117
    Schlagwort(e): Lake Baikal ; picoplankton ; Choricystis minor ; morphology ; ultrastructure ; rDNA sequence data
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract An eukaryotic alga (strain BAC 9708) from the picoplankton of Lake Baikal (Eastern Siberia) has been cultivated in order to investigate its morphology, ultrastructure, growth requirements, pigment composition and nuclear-encoded 18S and chloroplast-encoded 16S rDNA sequences. Cells of strain BAC 9708 contain a nucleus, a single chloroplast without a pyrenoid, one mitochondrion, a poorly visible dictyosome, a large vacuole and a cell wall with an outer sporopollenin-containing layer. Ellipsoidal cells, 1.5–2.0 × 1.0–1.5 μm in size, propagate usually by two, or infrequently by four autospores. Sequence analysis of nuclear-encoded rDNA showed that all 581 nucleotides of the 5′-end of the 18S rDNA were identical to that of Choricystis minor (Skuja) Fott (Chlorococcales, Chlorophyta) obtained earlier (Krienitz et al., 1996). The chloroplast-encoded rDNA sequence of this strain showed identity with one of three chloroplast sequences, selected by PCR-amplification with 16S rDNA specific primers from total picoplanktonic DNA, obtained previously.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004056604534
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  • 94
    Digitale Medien
    Digitale Medien
    Apoptosis evaluation in epithelial cells exposed to different chemicals: relevance of floating cells (2000)
    Springer
    Cell biology and toxicology 16 (2000), S. 53-62 
    Details
    ISSN: 1573-6822
    Schlagwort(e): apoptosis ; cell adhesion ; cytotoxicity tests ; epithelial cells ; morphology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The recent increase in understanding of cell death has promoted new approaches in toxicological studies, mainly those dealing within vitro systems where the evaluation of cell death has been the most widely adopted end-point in measuring the effects of chemical toxicants. The aim of this study was to investigate the possibility of improving the traditional cytotoxicity test protocols in order to produce more specific information on the type of cell death induced by exposure to toxicants. In particular, we characterized the mode of cell death in an established epithelial cell line, HEp-2 cells, which is frequently used in cytotoxicity testing owing to its easy handling and standardization of culture conditions. Reference chemicals for apoptosis and necrosis were selected as controls, together with other molecules that have been shown, in preliminary studies, to induce various morphological and structural modifications in relation to cell death. The results obtained show that: (a) the floating fraction of treated cells gives the clearest picture of the necrotic/apoptotic distribution; (b) morphological analysis is crucial for characterization of apoptosis; (c) more than one cytotoxic end-point is necessary to clearly identify the type of cell death.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007696604725
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  • 95
    Digitale Medien
    Digitale Medien
    Improvement of Porous Si Luminescence Intensity Durability by Nitrogen Ion Irradiation Using an ECR Ion Source (2000)
    Springer
    Journal of porous materials 7 (2000), S. 73-76 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; passivation ; photoluminescence intensity stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract We have investigated the effects of the porous Si surface passivation by oxygen or nitrogen ion processing on the photoluminescence (PL) intensity and its stability using an electron cyclotron resonance ion source. The results indicate that an anneal before exposure to ion beam causes a PL intensity enhancement upon exposure to oxygen or nitrogen ion beam. A combination of an anneal and a passivation by exposure to nitrogen ion beam enhances the PL intensity by a factor of ∼2.5 compared to the intensity of the initial as-anodized PS and the enhanced intensity is stabilized for more than 180 min under Ar+-laser illumination while oxygen-ion-exposed PS exhibits an enhancement in PL intensity only by ∼1.4 and a decay in PL intensity by ∼20% after 180 min Ar+-laser illumination. The results suggest that the reaction of nitrogen with a PS surface plays a key role for the PL intensity enhancement and stability.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009659109107
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  • 96
    Digitale Medien
    Digitale Medien
    Near-Field Electron Energy Loss Spectroscopy in Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 159-163 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; EELS ; NFEELS ; SiO2 layer
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract First results of an Electron Energy Loss Spectroscopy in the Near Field (NFEELS) mode of n+ porous silicon are described here. Sequences of EELS spectra in the low loss energy range (0–30 eV) were recorded, using a scanning transmission electron microscope, as the e-beam was scanned across a nano-hole surrounded by Si platelets. This technique is shown to be very sensitive to spectral and spatial changes in the electromagnetic field distribution outside the surface of nanoparticles, governed by their local nature and shape.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009666132731
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  • 97
    Digitale Medien
    Digitale Medien
    Processing of Infrared Spectroscopy Data on Thin Porous Films Using Software “Prospect” (2000)
    Springer
    Journal of porous materials 7 (2000), S. 239-242 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; interference fringes ; infrared-spectroscoy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Here we present the software utility “ProSpect” which allows to process and interpret the data of infrared spectrophotometry studies of thin porous films. These spectra are often complicated by the presence of interference fringes. The program allows to remove fringes and thus enhance the intensity of useful IR bands as well as calculate optical parameters of the films (medium thickness value, refractive index, deviation of the thickness from medium value). Application of ProSpect in analysis of the FT-IR spectra of non-uniform porous silicon films is illustrated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009607409050
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  • 98
    Digitale Medien
    Digitale Medien
    Electro-, Photo- and Scanning Tunneling—Luminescence Studies of Efficient Light-Emitting Porous Silicon (2000)
    Springer
    Journal of porous materials 7 (2000), S. 125-130 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; photoluminescence ; electroluminescence ; scanning tunneling microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Porous silicon films as used in efficient blue-green electroluminescent devices (internal efficiency about 0.1%) were studied by scanning tunneling microscopy light emission spectroscopy (STMLES) as well as photoluminescence (PL) and electroluminescence (EL) spectroscopy. Areas of the n-type porous Si surfaces with small particles of about 5 nm dimensions gave STMLE, but areas with larger structures gave no emission. Clear STMLE spectra gave a peak at 630 nm, quite different from the EL peak at 500 nm. Whereas the PL peak at 700 nm was consistent with the STM indication of quantised entities, the EL seemed more readily explicable in terms of defects at the metal contact barrier.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009627913593
    Standort Signatur Erwartet Verfügbarkeit
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  • 99
    Digitale Medien
    Digitale Medien
    Deposition of Erbium Containing Film in Porous Silicon from Ethanol Solution of Erbium Salt (2000)
    Springer
    Journal of porous materials 7 (2000), S. 37-40 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; erbium containing films ; electrochemical cathode treatment
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Electrochemical treatment of porous silicon (PS) in ethanol solution of Er(NO3)3 was investigated to obtain material suitable for optoelectronic application. The voltammograms of n+-type and p-type PS vs. an Ag/AgCl reference electrode were examined and compared with these of a Pt electrode. The basic cathode reactions were marked out the voltammograms: (i) the formation and the adsorption of atomic hydrogen; (ii) the formation of molecular hydrogen; (iii) the electrolysis of water and ethanol. No zones relating to on electrochemical transitions of Er ions were revealed on the voltammograms. Nevertheless, with the cathode polarization, the formation of an Er-containing deposit was observed at the surface of the cathode. The IR and SIMS analysis were used to study the composition of the deposits. The scheme of the electrochemical and chemical reactions at the cathode is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009647903656
    Standort Signatur Erwartet Verfügbarkeit
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  • 100
    Digitale Medien
    Digitale Medien
    Oxidation of Porous Silicon in Dry and Wet Environments under Mild Temperature Conditions (2000)
    Springer
    Journal of porous materials 7 (2000), S. 63-66 
    Details
    ISSN: 1573-4854
    Schlagwort(e): porous silicon ; oxidation ; IR spectroscopy ; vibrational analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Oxidation behavior of porous silicon under various environments of dry and wet air, and solution with and without appropriate oxidant at mild temperatures has been investigated. The progress of oxidation was followed by infrared spectroscopy. The presence of water vapor greatly accelerates the oxidation rate in comparison with the rate in dry air. The oxidized states are clarified with the help of oxidation experiments of partially hydrogen-desorbed porous silicon, which does not contain SiH2 and SiH3 as the hydride species. An oxidation mechanism is proposed to explain that oxidation is accelerated in the presence of water vapor and at the partially hydrogen-desorbed porous silicon. Further, oxidation behavior of porous silicon in solution containing appropriate oxidant is also investigated. The rate is very rapid and the oxidation does not produce the back-bond oxidized state of OySiHx in contrast to the oxidation in air.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009694608199
    Standort Signatur Erwartet Verfügbarkeit
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