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  • 1
    Publication Date: 2017-11-08
    Description: Silicon is a keystone nutrient in the ocean for understanding climate change because of the importance of Southern Ocean diatoms in taking up CO 2 from the surface ocean–atmosphere system and sequestering carbon into the deep sea. Here we report on silicon isotopes and germanium-to-silicon ratios in giant glass spicules of deep-sea sponge Monorhaphis chuni over the past 17,000 years. In-situ measurements of Si isotopes and Ge concentrations show systematic variations from rim to center of the cross sections. When calibrated against seawater concentrations using data from modern spicule rims, sponge data indicate that dissolved silica concentrations in the deep Pacific were ~12 % higher during the early deglacial. These deep Pacific Ocean data help to fill an important global gap in paleo-nutrient records. Either continental sources supplied more silica to the deglacial ocean and/or biogenic silica burial was lower, both of which may have affected atmospheric CO 2 .
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
    Publication Date: 2014-10-11
    Description: ABSTRACT Late Quaternary fluvial deposits in the Tunica Hills region of Louisiana and Mississippi are rich in spruce macrofossils of the extinct species Picea critchfieldii , the one recognized plant extinction of the Late Quaternary. However, the morphology of P. critchfieldii pollen is unknown, presenting a barrier to the interpretation of pollen spectra from the last glacial of North America. To address this issue, we undertook a morphometric study of Picea pollen from Tunica Hills. Morphometric data, together with qualitative observations of pollen morphology using Apotome fluorescence microscopy, indicate that Picea pollen from Tunica Hills is morphologically distinct from the pollen of P. glauca , P. mariana and P. rubens . Measurements of grain length, corpus width and corpus height indicate that Picea pollen from Tunica Hills is larger than the pollen of P. mariana and P. rubens , and is slightly larger than P. glauca pollen. We argue that the morphologically distinctive Tunica Hills Picea pollen was probably produced by the extinct spruce species P. critchfieldii . These morphological differences could be used to identify P. critchfieldii in existing and newly collected pollen records, which would refine its paleoecologic and biogeographic history and clarify the nature and timing of its extinction in the Late Quaternary.
    Print ISSN: 0267-8179
    Electronic ISSN: 1099-1417
    Topics: Geography , Geosciences
    Published by Wiley
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  • 3
    Publication Date: 2014-03-15
    Description: 4,5-Dinitroimidazole ( 1 ) (4,5-DNI) was synthesized by nitration of commercially available 4-nitro-imidazole. Several alkaline and alkaline earth metal salts of 4,5-dinitro-1,3-imidazole were synthesized by reaction of DNI with stoichiometric amounts of the corresponding metal hydroxides and carbonates. The synthesized salts, LiDNI · 3H 2 O ( 2 ), NaDNI · H 2 O ( 3 ), KDNI · H 2 O ( 4 ), Ca(DNI) 2 · 5H 2 O ( 5 ), Sr(DNI) 2 · 3H 2 O ( 6 ), and Ba(DNI) 2 · 4H 2 O ( 7 ) were characterized comprehensively by means of single-crystal X-ray diffraction, NMR and vibrational (IR/Raman) spectroscopy, mass spectrometry, elemental analysis, and differential scanning calorimetry (DSC). A detailed description of their potential use as flame colorants in pyrotechnical compositions is also given. Their color properties regarding the dominant wavelength, spectral purity, luminous intensity and luminous efficiency were measured. Last but not least the investigated salts were found to be insensitive in terms of friction and impact tested with BAM methods.
    Print ISSN: 0044-2313
    Electronic ISSN: 1521-3749
    Topics: Chemistry and Pharmacology
    Published by Wiley
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  • 4
    Publication Date: 2015-01-09
    Description: We report on the single crystal structure of Na 2 PtF 6 , which was synthesized from (NH 4 ) 2 PtCl 6 and NaCl in a flow of 10 % F 2 in argon. The light yellow compound crystallizes in the Na 2 SiF 6 structure type with the trigonal space group P 321 and the lattice parameters a = 9.2981(2), c = 5.1147(1) Å, and V = 382.95(1) Å 3 at 123 K with Z = 3. Na 2 PtF 6 reacts with liquid ammonia yielding bis triamminesodium hexafluoridoplatinate(IV) [Na(NH 3 ) 3 ] 2 [PtF 6 ]. It crystallizes in the monoclinic space group C 2/ c with a = 14.0508(4), b = 8.4894(1), c = 12.8820(4) Å, β = 120.495(4)°, and V = 1324.05(6) Å 3 at 123 K with Z = 4. In contrast to the aqueous system, the solvolysis in NH 3 does not lead to the cleavage of the Pt–F bonds, at least not at the temperatures employed in this study.
    Print ISSN: 0044-2313
    Electronic ISSN: 1521-3749
    Topics: Chemistry and Pharmacology
    Published by Wiley
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  • 5
    Publication Date: 2011-04-12
    Description: Chemical examination of the fungus Aspergillus ustus isolated from the Mediterranean sponge Suberites domuncula yielded the five new ophiobolin-type sesterterpenoids 1 – 5 and the two new pyrrolidine alkaloids 6 and 7 , together with the known compound aurantiamine and cerebroside D. The structures of the new compounds were unambiguously elucidated on the basis of extensive spectroscopic-data analysis (1D- and 2D-NMR, MS, and UV) and comparison with literature data. All compounds were evaluated for their cytotoxicity against murine lymphoma cell line L5178Y.
    Print ISSN: 0018-019X
    Electronic ISSN: 1522-2675
    Topics: Chemistry and Pharmacology
    Published by Wiley
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  • 6
    Publication Date: 2016-06-22
    Description: The synthesis of ammine metal azides is achieved through a simple route in liquid ammonia solution. Azides of silver, sodium, manganese, and zinc were obtained as ammine complexes from liquid ammonia and the solid compounds were characterized. The NH 3 solutions were investigated by means of NMR spectroscopy as well. The triamminesilver(I) azide as well as the unusual tetraamminesilver(I) and pentaamminesodium(I) azides are presented. The structures of the hexaamminemanganese(II) and hexaamminezinc(II) azides, which crystallize with four ammonia molecules of solvation, are elucidated. From these compounds the binary azides Mn(N 3 ) 2 and Zn(N 3 ) 2 were obtained by (careful) heating.
    Print ISSN: 0044-2313
    Electronic ISSN: 1521-3749
    Topics: Chemistry and Pharmacology
    Published by Wiley
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  • 7
    Publication Date: 2014-12-18
    Description: We analyze the variability of mean age of air (AoA) and of the local effects of the stratospheric residual circulation and eddy mixing on AoA within the framework of the isentropic zonal mean continuity equation. AoA for the period 1988–2013 has been simulated with the Lagrangian chemistry transport model CLaMS driven by ERA-Interim winds and diabatic heating rates. Model simulated AoA in the lower stratosphere shows good agreement with both in-situ observations and satellite observations from MIPAS (Michelson Interferometer for Passive Atmospheric Sounding), even regarding interannual variability and changes during the last decade. The interannual variability throughout the lower stratosphere is largely affected by the QBO-induced circulation and mixing anomalies, with year-to-year AoA changes of about 0.5 years. The decadal 2002–2012 change shows decreasing AoA in the lowest stratosphere, below about 450 K. Above, AoA increases in the NH and decreases in the SH. Mixing appears to be crucial for understanding AoA variability, with local AoA changes resulting from a close balance between residual circulation and mixing effects. Locally, mixing increases AoA at low latitudes (40S-40N) and decreases AoA at higher latitudes. Strongest mixing occurs below about 500 K, consistent with the separation between shallow and deep circulation branches. The effect of mixing integrated along the air parcel path, however, significantly increases AoA globally, except in the polar lower stratosphere. Changes of local effects of residual circulation and mixing during the last decade are supportive of a strengthening shallow circulation branch in the lowest stratosphere and a southward shifting circulation pattern above.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
    Publication Date: 2013-10-16
    Description: [1]  Soot particles are a major absorber of shortwave radiation in the atmosphere. The mass absorption cross section is an essential quantity to describe this light absorption process. This work presents new experimental data on the mass absorption cross section of soot particles in the troposphere over Central Europe. Mass absorption cross sections were derived as the ratio between the light absorption coefficient determined by multi angle absorption photometry (MAAP), and the soot mass concentration determined by Raman spectroscopy. The Raman method is sensitive to graphitic structures present in the particle samples, and was calibrated in the laboratory using Printex ® 90 model particles. M ass absorption cross sections were determined for a number of seven observation sites, ranging between 3.9 and 7.4 m 2 g − 1 depending on measurement site and observational period. The highest values were found in a continentally aged air mass in winter, where soot particles were assumed to be mainly internally mixed . Our values are in the lower range of previously reported values, possibly due to instrumental differences to the former photometer and mass measurements. Overall, a value of 5.3 m 2 g − 1 from orthogonal regression over all samples is considered to be representative for the soot mass absorption cross section in the troposphere over Central Europe.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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