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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 398 (1973), S. 1-14 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Preparation and Crystal Structure of Ka[Yb(NH2)4].Na[Yb(NH2)4] was obtained by ammonothermal synthesis at 190°C and 5000 atm. The properties of the compound are communicated, Na[Yb(2NH2)4] crystallises orthorhombically with a = 14.70, b = 10.02, c = 7.44 Å; Z = 8, space group D2h6, P 2/n 21/n 2/a, No. 52. The atomic positions are given. The amide ions are distorted cubic close-packed. Na+ and Yb3+ occupy strongly distorted octahedral interstices. The arrangement of the cations has a layerlike character along [100].
    Notes: Durch Ammonothermalsynthese bei 190°C und 5000 atm wurde Na[Yb(NH2)4] erhalten; seine Eigenschaften werden angegeben.Na[Yb(NH2)4] kristallisiert orthorhombisch mit a = 14,70 Å, b = 10,02 Å, c = 7,44 Å, N = 8, in Raumgruppe D2h6, P 2/n 21/n 2/a, Nr. 52. Die Punktlagen werden angegeben. NH2- ist verzerrt kubisch dicht angeordnet, Na+ und Yb3+ befinden sich in stark verzerrten Anionen-Oktaedern. Die Anordnung der Kationen bedingt die Ausbildung eines Schichtencharakters in Richtung [100].
    Additional Material: 2 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 395 (1973), S. 291-300 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Amides of YttriumNa3[Y(NH2)6] and Na[Y(NH2)4] were prepared by the reaction of the metals in the atomic ratios 3:1 and 1:1 respectively with ammonia under high pressure (∼5000 atm) and temperatures of 250°C. Y(NH2)3 was obtained when Na[Y(NH2)4] reacted with NH4J or YJ3 with KNH2 in liquid NH3 at room temperature. YN was prepared from Y-metal at 350°C and ammonia at 600 atm.Thermal degradation of the ternary sodium compounds directly yields YN, whereas NaNH2 remains unattacked.By single crystal x-ray investigations the structure of Na3[Y(NH2)6] was determined, it crystallizes orthorhombically:\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} {\rm a = 7,24 }{\AA}{\rm, b = 10,93 }{\AA}{\rm \,und\, c = 21,68 }{\AA}; Z = \,8,\,F2/d \,2/d \,2/d, \,Nr. \,70 \\ \end{array} $$\end{document}X-ray powder patterns show that Na3[Y(NH2)4] is isotypic with Na3[Yb(NH2)4] and that Y(NH2)3 is isotypic with Yb(NH2)3. Na3[Y(NH2)4] crystallizes Orthorhombically: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l}{\rm a = 14,80 }{\AA}{\rm, b = 10,07 }{\AA}{\rm und c = 7,47 }{\AA}; Z = \,8, \,P2/n \,2_1 /n \,2/a \,Nr. \,52 \\ \end{array} $$\end{document}
    Notes: Na3[Y(NH2)6] und Na[Y(NH2)4] wurden durch Reaktion der Metalle in den Atomverhältnissen 3:1 bzw. 1:1 mit Ammoniak unter hohen Drücken (etwa 5000 atm) bei 250°C erhalten. Y(NH2)3 ließ sich nur durch Umsetzung von Na[Y(NH2)4] mit NH4J bzw. von YJ3 mit KNH2 in fl. NH3 bei Zimmertemperatur darstellen. YN wurde aus Y-Metall bei 350°C und 600 atm NH3-Druck erhalten.Die thermische Zersetzung der Natriumamidometallate führte direkt zu YN; daneben trat unzersetztes NaNH2 auf.Röntgenuntersuchungen an Einkristallen führten zur Aufklärung der Kristallstruktur des Na3[Y(NH2)6] es kristallisiert rhombisch mit \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} {\rm a = 7,24 }{\AA}{\rm, b = 10,93 }{\AA}{\rm \,und\, c = 1,68 }{\AA}; Z = \,8,\,F2/d \,2/d \,2/d, \,Nr. \,70 \\ \end{array} $$\end{document}Na[Y(NH2)4] ist auf Grund von Röntgenpulverdaten dem Na[Yb(NH2)4] isotyp; es kristallisiert orthorhombisch mit: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l}{\rm a = 14,80 }{\AA}{\rm, b = 0,07 }{\AA}{\rm und c = 7,47 }{\AA}; Z = \,8, \,P2/n \,2_1 /n \,2/a \,Nr. \,52 \\ \end{array} $$\end{document}Röntgenpulveraufnahmen und IR-spektroskopische Messungen weisen auf Isotypie von Y(NH2)3 mit Yb(NH2)3 hin.
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  • 3
    Publication Date: 2016-02-02
    Description: Author(s): G. S. Tucker, J. S. White, J. Romhányi, D. Szaller, I. Kézsmárki, B. Roessli, U. Stuhr, A. Magrez, F. Groitl, P. Babkevich, P. Huang, I. Živković, and H. M. Rønnow We have used inelastic neutron scattering to measure the magnetic excitation spectrum along the high-symmetry directions of the first Brillouin zone of the magnetic skyrmion hosting compound Cu 2 OSeO 3 . The majority of our scattering data are consistent with the expectations of a recently proposed mod… [Phys. Rev. B 93, 054401] Published Mon Feb 01, 2016
    Keywords: Magnetism
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
    Topics: Physics
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  • 4
    Publication Date: 2018-09-07
    Description: Author(s): M. Pregelj, O. Zaharko, U. Stuhr, A. Zorko, H. Berger, A. Prokofiev, and D. Arčon We investigate magnetic excitations in the frustrated zigzag spin-1/2 chain compound β − TeVO 4 by inelastic neutron scattering. In the magnetically ordered ground state, the excitation spectrum exhibits coexisting magnon dispersion, characteristic of long-range magnetic order, and a spinon-like contin... [Phys. Rev. B 98, 094405] Published Thu Sep 06, 2018
    Keywords: Magnetism
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
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  • 5
    Publication Date: 2016-04-08
    Description: Author(s): M. Ruminy, L. Bovo, E. Pomjakushina, M. K. Haas, U. Stuhr, A. Cervellino, R. J. Cava, M. Kenzelmann, and T. Fennell Recent experimental results have emphasized two aspects of Tb 2 Ti 2 O 7 , which have not been taken into account in previous attempts to construct theories of Tb 2 Ti 2 O 7 : the role of small levels of structural disorder, which appears to control the formation of a long-range ordered state of as yet unknown … [Phys. Rev. B 93, 144407] Published Wed Apr 06, 2016
    Keywords: Magnetism
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
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  • 6
    Publication Date: 2017-10-14
    Description: We present inelastic neutron scattering data across the Verwey transition in magnetite, obtained for a single crystal via a detwinning method. We provide direct evidence of the influence of the charge order on the transverse-acoustic phonons, associated with discontinuous hardening and narrowing at the transition temperature, and energy splitting for different polarizations. This contrasts with the behavior of the transverse-optical X 3 mode, which does not present any critical anomaly, contrary to theoretical expectations. Our data indicate that the incommensurate fluctuations occurring above the critical temperature become locked to the lattice at the transition point, through a mechanism similar to the crystallization of a two-dimensional liquid on a solid surface. Our results also contribute to clarify the different dynamics and mutual interactions of the electronic and structural modes in the Verwey transition.
    Electronic ISSN: 1367-2630
    Topics: Physics
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  • 7
    Publication Date: 2013-01-29
    Description: Author(s): B. Náfrádi, T. Keller, H. Manaka, U. Stuhr, A. Zheludev, and B. Keimer We have used a combination of neutron resonant spin-echo and triple-axis spectroscopies to determine the energy and linewidth of the magnon resonance in IPA-Cu(Cl 0.95 Br 0.05 ) 3 , a model spin-1/2 ladder antiferromagnet where Br substitution induces bond randomness. We find that the bond defects induce ... [Phys. Rev. B 87, 020408] Published Mon Jan 28, 2013
    Keywords: Magnetism
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
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  • 8
    Publication Date: 2015-10-30
    Description: Nitrogen fixation by filamentous cyanobacteria supplies significant amounts of new nitrogen (N) to the Baltic Sea. This balances N loss processes such as denitrification and anammox and forms an important N source supporting primary and secondary production in N-limited post-spring bloom plankton communities. Laboratory studies suggest that filamentous diazotrophic cyanobacteria growth and N2-fixation rates are sensitive to ocean acidification with potential implications for new N supply to the Baltic Sea. In this study, our aim was to assess the effect of ocean acidification on diazotroph growth and activity as well as the contribution of diazotrophically-fixed N to N supply in a natural plankton assemblage. We enclosed a natural plankton community in a summer season in the Baltic Sea near the entrance to the Gulf of Finland in six large-scale mesocosms (volume ~ 55 m3) and manipulated fCO2 over a range relevant for projected ocean acidification by the end of this century (average treatment fCO2: 365–1231 μatm). The direct response of diazotroph growth and activity was followed in the mesocosms over a 47 day study period during N-limited growth in the summer plankton community. Diazotrophic filamentous cyanobacteria abundance throughout the study period and N2-fixation rates (determined only until day 21 due to subsequent use of contaminated commercial 15N-N2 gas stocks) remained low. Thus estimated new N inputs from diazotrophy were too low to relieve N limitation and stimulate a summer phytoplankton bloom. Instead regeneration of organic N sources likely sustained growth in the plankton community. We could not detect significant CO2-related differences in inorganic or organic N pools sizes, or particulate matter N : P stoichiometry. Additionally, no significant effect of elevated CO2 on diazotroph activity was observed. Therefore, ocean acidification had no observable impact on N cycling or biogeochemistry in this N-limited, post-spring bloom plankton assemblage in the Baltic Sea.
    Print ISSN: 1810-6277
    Electronic ISSN: 1810-6285
    Topics: Biology , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 9
    Publication Date: 2012-09-20
    Description: Impacts of ocean acidification (OA) on marine biota have been observed in a wide range of marine systems. We used a mesocosm approach to study the response of a high Arctic coastal protozooplankton (PZP in the following) community during the post-bloom period in the Kongsfjorden (Svalbard) to direct and indirect effects of high pCO2/low pH. We found almost no direct effects of OA on PZP composition and diversity. Both, the relative shares of ciliates and heterotrophic dinoflagellates as well as the taxonomic composition of protozoans remained unaffected by changes in pCO2/pH. The different pCO2 treatments did not have any effect on food availability and phytoplankton composition and thus no indirect effects e.g. on the total carrying capacity and phenology of PZP could be observed. Our data points at a high tolerance of this Arctic PZP community to changes in pCO2/pH. Future studies on the impact of OA on plankton communities should include PZP in order to test whether the observed low sensitivity of protozoans to OA is typical for coastal communities where changes in seawater pH occur frequently.
    Print ISSN: 1810-6277
    Electronic ISSN: 1810-6285
    Topics: Biology , Geosciences
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  • 10
    Publication Date: 2012-09-14
    Description: Ocean acidification and carbonation, driven by anthropogenic emissions of carbon dioxide (CO2), have been shown to affect a variety of marine organisms and are likely to change ecosystem functioning. High latitudes, especially the Arctic, will be the first to encounter profound changes in carbonate chemistry speciation at a large scale, namely the under-saturation of surface waters with respect to aragonite, a calcium carbonate polymorph produced by several organisms in this region. During a CO2 perturbation study in 2010, in the framework of the EU-funded project EPOCA, the temporal dynamics of a plankton bloom was followed in nine mesocosms, manipulated for CO2 levels ranging initially from about 185 to 1420 μatm. Dissolved inorganic nutrients were added halfway through the experiment. Autotrophic biomass, as identified by chlorophyll a standing stocks (Chl a), peaked three times in all mesocosms. However, while absolute Chl a concentrations were similar in all mesocosms during the first phase of the experiment, higher autotrophic biomass was measured at high in comparison to low CO2 during the second phase, right after dissolved inorganic nutrient addition. This trend then reversed in the third phase. There were several statistically significant CO2 effects on a variety of parameters measured in certain phases, such as nutrient utilization, standing stocks of particulate organic matter, and phytoplankton species composition. Interestingly, CO2 effects developed slowly but steadily, becoming more and more statistically significant with time. The observed CO2 related shifts in nutrient flow into different phytoplankton groups (mainly diatoms, dinoflagellates, prasinophytes and haptophytes) could have consequences for future organic matter flow to higher trophic levels and export production, with consequences for ecosystem productivity and atmospheric CO2.
    Print ISSN: 1810-6277
    Electronic ISSN: 1810-6285
    Topics: Biology , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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