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  • 1
    Publication Date: 2017-06-05
    Description: In the Kongsfjorden–Krossfjorden system (Spitsbergen), increasing temperatures enhance glacier melting and concomitant intrusion of freshwater. These altered conditions affect the timing, intensity, and composition of the phytoplankton spring bloom in Kongsfjorden; yet, the effects on prokaryotes (bacteria and archaea) are not well understood. The aim of this study was to examine springtime prokaryote communities in both fjords as a function of hydrographic and phytoplankton variability. Prokaryote community composition was studied in two consecutive years by molecular fingerprinting of the 16S rRNA gene. In addition, we measured bacterial abundance, productivity (3H-Leucine uptake), and single-cell activity using catalyzed reporter deposition fluorescence in situ hybridization combined with microautoradiography. Differences in bacterial and archaeal communities were found etween Kongsfjorden and Krossfjorden. Furthermore, an increase in productivity, abundance, and proportion of active bacterial cells was observed during the course of spring. Bacteroidetes were the most abundant bacterial group among the assessed taxa in both Kongsfjorden and Krossfjorden. Multivariate analysis of the microbial community fingerprints revealed a strong temporal shaping of both the bacterial and archaeal communities in addition to a spatial separation between the two fjords. A significant part of the observed bacterial variation could be explained by cyanobacterial biomass, as deduced from pigment analysis, and by phosphate concentration. Archaea were mainly controlled by abiotic factors. We speculate that the bacterial response to hydrographic changes and glacier meltwater is mediated through shifts in phytoplankton abundance and composition, whereas archaea are directly influenced by abiotic environmental variables.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 2
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Fluorine Chemistry 54 (1991), S. 173 
    ISSN: 0022-1139
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0022-328X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 36 (1980), S. 1191-1194 
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Depth distribution of kelp species in Helgoland (North Sea) is characterized by occurrence of Laminaria digitata in the upper sublittoral, whereas L. saccharina and L. hyperborea dominate the mid and lower sublittoral region. Laminaria digitata is fertile in summer whereas both other species are fertile in autumn/winter. To determine the light sensitivity of the propagules, zoospores of L. digitata, L. saccharina and L. hyperborea were exposed in the laboratory to different exposure times of photosynthetically active radiation (PAR; 400–700 nm), PAR + UVA radiation (UVAR; 320–400 nm) and PAR + UVAR + UVB radiation (UVBR; 280–320 nm). Optimum quantum yield of PSII and DNA damage were measured after exposure. Subsequently, recovery of photosynthetic efficiency and DNA damage repair, as well as germination rate were measured after 2 and 3 d cultivation in dim white light. Photosynthetic efficiency of all species was photoinhibited already at 20 µmol photons m−2 s−1 PAR, whereas UV radiation (UVR) had a significant additional effect on photoinhibition. Recovery of the PSII function was observed in all species but not in spores exposed to irradiation longer than 4 h of PAR + UVA + UVB and 8 h of PAR + UVA. The amount of UVB-induced DNA damage measured as cyclobutane–pyrimidine dimers (CPDs) increased with exposure time and highest damage was detected in the spores of lower subtidal L. hyperborea relative to the other two species. Significant removal of CPDs indicating repair of DNA damage was observed in all species after 2 d in low white light especially in the spores of upper subtidal L. digitata. Therefore, efficient DNA damage repair and recovery of PSII damage contributed to the germination success but not in spores exposed to 16 h of UVBR. UV absorption of zoospore suspension in L. digitata is based both on the absorption by the zoospores itself as well as by exudates in the medium. In contrast, the absorption of the zoospore suspension in L. saccharina and L. hyperborea is based predominantly on the absorption by the exudates in the medium. This study indicates that UVR sensitivity of zoospores is related to the seasonal zoospore production as well as the vertical distribution pattern of the large sporophytes.
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  • 6
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The response of the bipolar moss Sanionia uncinata (Hedw.) Loeske to ambient and enhanced UV-B radiation was investigated at an Antarctic (Léonie Island, 67°35′ S, 68°20′ W) and an Arctic (Ny-Alesund, 78°55′ N, 11°56′ E) site, which differed in ambient UV-B radiation (UV-BR: 280–320 nm) levels. The UV-BR effects on DNA damage and photosynthesis were investigated in two types of outdoor experiments. First of all, sections of turf of S. uncinata were collected in an Arctic and Antarctic field site and exposed outdoors to ambient and enhanced UV-BR for 2 d using UV-B Mini-lamps. During these experiments, chlorophyll a fluorescence, chlorophyll concentration and cyclobutyl pyrimidine dimer (CPD) formation were measured. Secondly, at the Antarctic site, a long-term filter experiment was conducted to study the effect of ambient UV-BR on growth and biomass production. Additionally, sections of moss turf collected at both the Antarctic and the Arctic site were exposed to UV-BR in a growth chamber to study induction and repair of CPDs under controlled conditions. At the Antarctic site, a summer midday maximum of 2·1 W m−2 of UV-BR did not significantly affect effective quantum yield (ΔF/Fm′) and the ratio of variable to maximal fluorescence (Fv/Fm). The same was found for samples of S. uncinata exposed at the Arctic site, where summer midday maxima of UV-BR were about 50% lower than at the Antarctic site. Exposure to natural UV-BR in summer did not increase CPD values significantly at both sites. Although the photosynthetic activity remained largely unaffected by UV-B enhancement, DNA damage clearly increased as a result of UV-B enhancement at both sites. However, DNA damage induced during the day by UV-B enhancement was repaired overnight at both sites. Results from the long-term filter experiment at the Antarctic site indicated that branching of S. uncinata was reduced by reduction of ambient summer levels of UV-BR, whereas biomass production was not affected. Exposure of specimens collected from both sites to UV-BR in a growth chamber indicated that Antarctic and Arctic S. uncinata did not differ in UV-BR-induced DNA damage. It was concluded that S. uncinata from both the Antarctic and the Arctic site is well adapted to ambient levels of UV-BR.
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  • 7
    ISSN: 0044-2313
    Keywords: Lithium [tris(trimethylsilyl)silyl]tellanide · DME ; covalent radius of DME complexed Li ; [tris(trimethylsilyl)silyl]tellane ; methyl-[tris(trimethylsilyl)silyl]tellane ; bis[tris(trimethylsilyl)silyl]ditellane ; Te—H bond ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Metal Derivatives of Molecular Compounds. IV Synthesis, Structure, and Reactivity of Lithium [Tris(trimethylsilyl)silyl]tellanide · DMELithium tris(trimethylsilyl)silanide · 1,5 DME [3] and tellurium react in 1,2-dimethoxyethane to give colourless lithium [tris(trimethylsilyl)silyl]tellanide · DME (1). An X-ray structure determination {-150 · 3·C; P21/c; a = 1346.6(4); b = 1497.0(4); c = 1274.5(3) pm; β = 99.22(2)·; Z = 2 dimers; R = 0.030} shows the compound to be dimeric forming a planar Li—Te—Li—Te ring with two tris(trimethylsilyl)silyl substituents in a trans position. Three-coordinate tellurium is bound to the central silicon of the tris(trimethylsilyl)silyl group and to two lithium atoms; the two remaining sites of each four-coordinate lithium are occupied by the chelate ligand DME {Li—Te 278 and 284; Si—Te 250; Li—O 200 pm (2X); Te—Li—Te 105°; Li—Te—Li 75°; O—Li—O 84°}. The covalent radius of 154 pm as determined for the DME-complexed lithium in tellanide 1 is within the range of 155 ± 3 pm, also characteristic for similar compounds. In typical reactions of the tellanide 1 [tris(trimethylsilyl)silyl]tellane (2), methyl-[tris(trimethylsilyl)silyl]tellane (4) and bis[tris(trimethylsilyl)silyl]ditellane (5) are formed.
    Notes: Lithium-tris(trimethylsilyl)silanid · 1,5 DME [3] reagiert mit Tellur in 1,2-Dimethoxyethan zu farblosem Lithium-[tris(trimethylsilyl)silyi]tellanid · DME (1). Nach der Röntgenstrukturanalyse {-150 ± 3°C; P21/c; a = 1346,6(4); b = 1497,0(4); c = 1274,5(3) pm; β = 99,22(2)°; Z = 2 Dimere; R = 0,030} ist Verbindung 1 im Festkörper dimer; die beiden Tris(trimethylsilyl)silyl-Gruppen sind am planaren Li—Te—Li—Te-Ring trans-ständig zueinander angeordnet. Tellur erreicht durch Bindung an zwei Lithium und ein Silicium die Koordinationszahl 3, Lithium durch Bindung an zwei Tellur und den Chelatliganden DME die Koordinationszahl 4 {Li—Te 278 und 284; Si—Te 250; Li—O 200 pm (2X); Te—Li—Te 105°, Li—Te—Li 75°; O—Li—O 84°}. Der hier zu 154 pm ermittelte kovalente Radius des DME-komplexierten Lithiumatoms fällt in den auch für andere Verbindungen typischen Bereich von 155 ± 3 pm. Charakteristische Umsetzungen des Tellanids 1 führen zu [Tris(trimethylsilyl)silyl]tellan (2), Methyl-[tris(trimethylsilyl)silyl]tellan (4) und Bis[tris(trimethylsilyl)silyl]ditellan (5).
    Additional Material: 3 Ill.
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  • 8
    ISSN: 0044-2313
    Keywords: Ag1 complexes ; N-acyl thiourea complexes ; potentiometry ; stability constants ; X-ray structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Coordination of Silver(I) by N,N-Diethyl-N′-benzoyl Thiourea in Solution and in the Solid StateSilver(I) reacts in dioxane/water solution with N,N-diethyl-N′-benzoyl thiourea HL to give cationic, neutral, and anionic complexes depending on the pH value, the molar ratio of the reactants and their concentrations. The ligand in these complexes coordinates in various ways. Complex stability constants have been determined by pAg and pH potentiometry. Representative complexes have been isolated in the solid state. One of them is a cyclic tetramer [AgL]4 the structure of which has been determined by X-ray diffraction.
    Notes: Silber(I) bildet mit N,N-Diethyl-N′-benzoyl-thioharnstoff HL in Dioxan/Wasser-Mischung, abhängig vom pH-Wert, dem molaren Verhältnis der Reaktanden und ihren Konzentrationen, kationische, neutrale und anionische Komplexe, in denen der Ligand in unterschiedlicher Weise koordiniert. Für diese Komplexe wurden pAg- und pH-potentiometrisch Stabilitätskonstanten bestimmt. Repräsentative Komplexe konnten in festem Zustand isoliert werden, darunter ein cyclischer Komplex [AgL]4, dessen Struktur durch Röntgenbeugung bestimmt wurde.
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  • 9
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Fluorides and Fluoro Acids. V. Crystal Structure of the 1:4 Phase in the System Water-Hydrogen Fluoride and a New Investigation of One of the 1:2 PhasesIn the quasi binary system H2O—HF the 1:2 phase of known crystal structure was recognized as the stable high-temperature phase. A more accurate redetermination of its structure (monoclinic, space group P21/c, Z = 4, a = 3.477, b = 6.024, c = 11.358 Å, β = 96.70° at -100°C, R = 0.032 for 1356 observed MoKα data) confirmed the previous results of a layer structure formed by strong hydrogen bonds. H3OF · HF appears besides H3OHF2 as a possible structural formula.  -  The crystal structure of the 1:4 phase of the system was also determined (triclinic, P1, Z = 2, a = 5.574, b = 6.429, c = 6.874 Å, α = 115.79, β = 96.63, γ = 108.79° at -113°C, R = 0.049 for 1942 observed MoKα data). By strong hydrogen bonds the atoms form rings, which are condensed to parallel ribbons. Possible structural formulae, based on the distribution of interatomic distances, are H3OH3F4, H3OH2F3 · HF and H3OF · 3 HF.  -  Interatomic distances in the hydrogen bonds F—H…F and O—H…F of both structures and the known one of the 1:1 phase are discussed in comparison.
    Notes: Im quasibinären System H2O—HF wurde die 1:2-Phase mit bekannter Kristallstruktur als die stabile Hochtemperaturphase erkannt. Eine genauere Neubestimmung ihrer Struktur (monoklin, Raumgruppe P21/c, Z = 4, a = 3,477, b = 6,024, c = 11,358 Å, β = 96,70° bei -100°C, R = 0,032 für 1356 beobachtete MoKα-Daten) bestätigte die früheren Ergebnisse einer durch starke Wasserstoffbrücken gebildeten Schichtstruktur. Neben H3OHF2 erscheint H3OF · HF als mögliche Strukturformel.  -  Die Kristallstruktur der 1:4-Phase des Systems wurde ebenfalls bestimmt (triklin, P1, Z = 2, a = 5,574, b = 6,429, c = 6,874 Å, α = 115,79, β = 96,63, γ = 108,79° bei -113°C, R = 0,049 für 1942 beobachtete MoKα-Daten). Die Atome bilden durch starke Wasserstoffbrücken Ringe, die zu parallelen Bändern kondensiert sind. Auf Grund der Verteilung der interatomaren Abstände mögliche Strukturformeln sind H3OH3F4, H3OH2F3 · HF und H3OF · 3 HF.  -  Interatomare Abstände in den Wasserstoffbrücken F—H…F und O—H…F beider Strukturen und der bekannten der 1:1-Phase werden vergleichend diskutiert.
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  • 10
    Publication Date: 2017-06-05
    Description: The hydrographic properties of the Kongsfjorden–Krossfjorden system (79° N, Spitsbergen) are affected by Atlantic water incursions as well as glacier meltwater runoff. This results in strong physical gradients (temperature, salinity and irradiance) within the fjords. Here, we tested the hypothesis that glaciers affect phytoplankton dynamics as early as the productive spring bloom period. During two campaigns in 2007 (late spring) and 2008 (early spring) we studied hydrographic characteristics and phytoplankton variability along two transects in both fjords, using high-performance liquid chromatography (HPLC)-CHEMTAX pigment fingerprinting, molecular fingerprinting (denaturing gradient gel electrophoresis, or DGGE) and sequencing of 18S rRNA genes. The sheltered inner fjord locations remained colder during spring as opposed to the outer locations. Vertical light attenuation coefficients increased from early spring onwards, at all locations, but in particular at the inner locations. In late spring meltwater input caused stratification of surface waters in both fjords. The inner fjord locations were characterized by overall lower phytoplankton biomass. Furthermore HPLC-CHEMTAX data revealed that diatoms and Phaeocystis sp. were replaced by small nano- and picophytoplankton during late spring, coinciding with low nutrient availability. The innermost stations showed higher relative abundances of nano- and picophytoplankton throughout, notably of cyanophytes and cryptophytes. Molecular fingerprinting revealed a high similarity between inner fjord samples from early spring and late spring samples from all locations, while outer samples from early spring clustered separately. We conclude that glacier influence, mediated by early meltwater input, modifies phytoplankton biomass and composition already during the spring bloom period, in favor of low biomass and small cell size communities. This may affect higher trophic levels especially when regional warming further increases the period and volume of meltwater.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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