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  • 1
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: A complete Barrovian sequence ranging from unmetamorphosed shales to sillimanite–K-feldspar zone metapelitic gneisses crops out in a region extending from the Hudson River in south-eastern New York state, USA, to the high-grade core of the Taconic range in western Connecticut. NNE-trending subparallel biotite, garnet, staurolite, kyanite, sillimanite and sillimanite–K-feldspar isograds have been identified, although the assignment of Barrovian zones in the high-grade rocks is complicated by the appearance of fibrolitic sillimanite at the kyanite isograd.Thermobarometric results and reaction textures are used to characterize the metamorphic history of the sequence. Pressure–temperature estimates indicate maximum metamorphic conditions of 475 °C, c. 3–4 kbar in the garnet zone to 〉720 °C, c. 5–6 kbar in the highest grade rocks exposed. Some samples in the kyanite zone record anomalous (low) peak conditions because garnet composition has been modified by fluid-assisted reactions.There is abundant petrographic and mineral chemical information indicating that the sequence (with the possible exception of the granulite facies zone) was infiltrated by a water-rich fluid after garnet growth was nearly completed. The truncation of fluid inclusion trails in garnet by rim growth or recrystallization, however, indicates that metamorphic reactions involving garnet continued subsequent to initial infiltration.The presence of these textures in some zones of a well-constrained Barrovian sequence allows determination of the timing of fluid infiltration relative to the P–T  paths. Thermobarometric results obtained using garnet compositions at the boundary between fluid–inclusion-rich and inclusion-free regions of the garnet are interpreted to represent peak metamorphic conditions, whereas rim compositions record slightly lower pressures and temperatures. Assuming that garnet grew during a single metamorphic event, infiltration must have occurred at or slightly after the peak of metamorphism, i.e. 4–5 kbar and a temperature of c. 525–550 °C for staurolite and kyanite zone rocks.
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  • 2
    ISSN: 0168-583X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Planta 133 (1976), S. 15-19 
    ISSN: 1432-2048
    Keywords: Tropaeolum, Embryogenesis ; Differentiation ; Plastids ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Embryogeny in the nasturtium is characterized by the development of a large, tripartite suspensor and storing cotyledons. A light and electron microscopic study revealed an early diversification of the plastids in the various regions of the suspensor and the embryo proper. Amyloplasts are found in the developing cotyledons of the heart-like embryo, while chloroplasts occur within the meristematic part of the embryo and the adjacent portion of the suspensor. The cells between the meristem and the storing cotyledons display undifferentiated leukoplasts, whereas leukoplasts with an electron-dense matrix occur in the basal cell mass of the embryo-suspensor. Etioplasts develop in several cells of the placental haustorium of the suspensor. The carpel haustorium shows rather undifferentiated leukoplasts, which are transformed into electron-dense plastids during autolysis of the suspensor. This early plastidal differentiation in discussed with respect to its control and functional significance.
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  • 4
    ISSN: 0044-2313
    Keywords: Methylindium Compound ; Heterocubane ; Synthesis ; X-ray Structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The X-Ray Structure Determination of tert-Butylimido Methylindane, [CH3In—NC(CH3)3]4The reaction of MeInCl2 with LiN(H)tBu in a 1 : 2 molar ratio forms [MeIn—NtBu]4 in high yield, lithium chloride, and the free amine H2NtBu. The crystal structure of the imidomethylindane with a cubic In4N4 skeleton has been determined.
    Additional Material: 1 Ill.
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  • 5
    ISSN: 0044-2313
    Keywords: Methyl metal imido compounds ; cage structures (Ga, In) ; diazadistannetidine derivatives (Al, In) ; preparation ; spectra ; X-ray ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Methyl Metal(III)-Nitrogen Compounds with an Oligocyclic as well as Cage Structures (MIII = Al, Ga, In)Tetrameric trimethylsilylimidomethylgallane, (MeGa=NSiMe3)4 (Me=CH3), is formed in ca. 60% yield by the reaction of Br2Ga-N(H)SiMe3 with lithium methanide in a 1:2 ratio. The high melting (278°C), volatile (MS), and even in the gas phase assoziated compound crystallizes in the monoclinic space group C2/c with the cell parameters a = 2001.0(4), b = 1011.6(2), c = 1932.2(4) pm, β = 120.13(2)°, and Z = 4 tetramers. The Ga4N4-skeleton is nearly a perfect cube with Ga-N bonds of 199 pm (average) and Ga—N—Ga angles of 90°.Diazadistannetidine, (Me2Sn=NtBu)2 (tBu=C(CH3)3) and AlMe3 (1 : 1) forms in toluene at 45-50°C tetramethylstannane and heterocyclic Me2Sn(NtBu)2AlMe. In solution and in the solid state a centrosymmetric dimer (point symmetry Ci) is formed (monoclinic space group P21/n, a = 1154.7(3), b = 921.17(12), c = 1463.9(3) pm, β = 101.08(2)°, and Z = 2 dimers). The relatively short Al-N (183.1(3) pm) and Sn-N (202.0(3) pm) distances in this tricyclic system have been used for a comparitive discussion of MIII-N bond lengths (MIII = Al, Ga, In). Therefore, the X-ray structure of the known Ga(N(SiMe3)2)3 has been re-investigated at -100°C. At least (MeIn=NtBu)4 has been prepared from (Me2Sn=NtBu)2 and base-free InMe3 (1:2 ratio) in toluene at 75-85°C. The NMR, ir, and Raman spectra are compared with the data of the corresponding Al and Ga homologues, respectively.
    Notes: Tetrameres Trimethylsilylimido-methylgallan, (MeGa=NsiMe3)4 (Me=CH3), entsteht in ca. 60%iger Ausbeute bei der Umsetzung von Br2Ga-N(H)SiMe3 mit Lithiummethanid im Molverhältnis 1:2. Die hochschmelzende (278°.C), im Vakuum flüchtige und auch in der Gasphase assoziierte (MS) Verbindung kristallisiert in der monoklinen Raumgruppe C2/c mit den Gitterkonstanten a = 2001,0(4), b = 1011,6(2), c = 1932,2(4) pm, β = 120,13(2)° und Z = 4 Tetramere. Das nahezu perfekt-kubische Ga4N4-Käfiggerüst weist Ga—N-Abstände von durchschnittlich 199 pm und Ga—N—Ga-Bindungswinkel von 90° auf.Diazadistannetidin, (Me2Sn=NtBu)2 (tBu—C(CH3)3), und AlMe3 (1:1) bilden in Toluol bei 45-50°C unter Eliminierung von Tetramethylstannan heterocyclisches Me2Sn(NtBu)2AlMe, welches im Kristall und in Lösung ein zentrosymmetrisches Dimer (Punktgruppe Ci) ausbildet (monokline Raumgruppe P21/n, a = 1154,7(3), b = 921,17(12), c = 1463,9(3) pm, β = 101,08(2)° und Z = 2 Dimere).Die z.T. relativ kurzen Abstände Al-N (183,1(3) pm) und Sn—N (202,0(3) pm) in diesem tricyclischen System führten zu einer vergleichenden Diskussion von MIII-N-Bindungslängen (MIII = Al, Ga, In). Hierfür ist die Röntgenstrukturanalyse des schon bekannten Ga(N(SiMe3)2)3 bei -100°C neu durchgeführt worden. Schließlich konnte (MeIn=NtBu)4 aus (Me2Sn=NtBu)2 und basefreiem InMe3 (1:2) in Toluol bei 75-85°C dargestellt werden. Die NMR-, IR- und Ramanspektren werden mit den entsprechenden Daten der homologen Al- und Ga-Käfigverbindung verglichen.
    Additional Material: 4 Ill.
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  • 6
    Publication Date: 2012-11-01
    Description: The cytokinesis-block micronucleus assay (CBMN assay) with cultured human lymphocytes is a well-established assay in genotoxicity testing and human biomonitoring. For both approaches, human lymphocytes are stimulated by phytohaemagglutinin (PHA) and cultured for about 72h; 44h after PHA stimulation, cytochalasin B (CytB) is added and micronuclei (MN) are scored in binucleated cells. The main difference between these two applications is the way lymphocytes are exposed to mutagens. In order to maximise the probability of detecting a mutagen, the OECD guideline 487 recommends starting the exposure to the test substance at 44–48h after PHA stimulation. In human biomonitoring, blood samples are taken from subjects exposed to environmental mutagens in vivo and lymphocytes with induced DNA damage at the start of the cell culture are investigated with regard to potentially increased MN frequencies in binuclear lymphocytes. We compared the sensitivity of these two protocols by either treating lymphocyte cultures for 2h with known DNA-damaging mutagens at the start of the culture or 42h after PHA stimulation. The mutagens used were methyl methanesulfonate (MMS), ethyl methanesulfonate (EMS), N-nitroso-N-ethylurea (ethyl nitrosourea; ENU), styrene oxide (SO), (±)-anti-B[a]P-7,8-dihydrodiol-9,10-epoxide (BPDE) and mitomycin C (MMC). All substances induced MN under the conditions of the standard in vitro CBMN assay but only MMC clearly induced MN in lymphocytes exposed at the start of the culture. All mutagens (except MMC, a known crosslinker) were tested by the comet assay with blood cultures exposed at the start of the culture and clearly induced DNA migration. The nuclear division index (NDI) indicated that damaged lymphocytes proliferated well in these experiments. The lack of increased MN frequencies despite increased damage levels and good proliferation suggests that the CBMN assay is rather insensitive for the detection of mutagens/clastogens when damage is induced at the start of the blood cultures. Potential consequences for the interpretation of human biomonitoring studies are discussed in this article.
    Print ISSN: 0267-8357
    Electronic ISSN: 1464-3804
    Topics: Biology , Medicine
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  • 7
    Publication Date: 2013-02-14
    Description: The comet assay is increasingly used to measure the repair of various types of DNA damage. Modifications of the standard protocol have been introduced to determine the repair capacity of specific DNA repair pathways by the removal of pathway-specific DNA lesions. Recently, a cellular phenotype assay for nucleotide excision repair (NER) by quantifying the DNA strand breaks after in vitro challenge of peripheral blood mononucleated cells with benzo[ a ]pyrene diol epoxide (BPDE) in the presence or absence of the DNA polymerase inhibitor aphidicolin (APC) was developed (Vande Loock, K., Decordier, I., Ciardelli, R., Haumont, D. and Kirsch-Volders, M. (2010) An aphidicolin-block nucleotide excision repair assay measuring DNA incision and repair capacity. Mutagenesis , 25, 25–32). Individual repair capacity (RC) was defined as the amount of DNA damage induced by BPDE in the presence of APC minus the damage induced by BPDE and APC alone. This value should mainly reflect the incision capacity of the NER enzymes. Following this approach, we investigated the RC of cultured isolated peripheral blood mononuclear cells of nine donors in repeated experiments. We also performed the same experiments with peripheral whole blood cultures from these donors. Our results indicated considerable intra- and inter-individual variability and substantial differences between the RC of isolated mononuclear cells and whole blood from the same donor. Furthermore, the RC of unstimulated blood did not differ significantly from the repair capacity of stimulated blood but also showed considerable inter-individual variability. Altogether, our results suggest that there is still need for standardisation and validation of this assay before it can be reliably used in human biomonitoring studies.
    Print ISSN: 0267-8357
    Electronic ISSN: 1464-3804
    Topics: Biology , Medicine
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  • 8
    Publication Date: 2019-07-13
    Description: The howardite, eucrite, and diogenite (HED) meteorites are a group of achondrites thought to be derived from the asteroid 4 Vesta, though there is active debate as to whether all diogenites are part of the HED suite. Petrologic investigation of the HED meteorite group provides a means of understanding early planetary differentiation processes and early evolution of planets in our solar system. Diogenites are predominantly coarse grained ortho-pyroxenites with some samples containing appreciable amounts of clinopyroxene, olivine, chromite, and plagioclase. Accessory metal, troilite, and apatite are common. Many diogenites are brecciated, however, there are few poorly to unbrecciated samples. Diogenites are important because they may represent the lower crust of 4 Vesta. Although Mg isotope data indicates that the sources of diogenites are ancient, their crystallization ages are difficult to constrain due to their protracted thermal histories. The limited chronologic data for diogenites also limits the ability to test petrogenetic connections with eucrites and even parent body. A reliable and high closure-temperature isotope system, such as U-Pb in zircon, is needed to address the timing of diogenite igneous crystallization. Description of the textures and mineralogy of diogenites are essential to their classification and understanding their formation, in particular, whether all phases are petrogenetically related. Here, we present detailed petrographic data from a rare zircon-bearing feldspathic diogenite, Northwest Africa (NWA) 10666 and provide textural evidence for igneous crystallization of the zircon.
    Keywords: Geosciences (General); Lunar and Planetary Science and Exploration
    Type: JSC-CN-38704 , Lunar and Planetary Science Conference; 20-24 Mar. 2017; The Woodlands, TX; United States
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  • 9
    Publication Date: 2019-07-12
    Description: The applicability of ion microprobe (IMP) for quantitative analysis of minor elements (Sr, Y, Zr, La, Sm, and Yb) in the major phases present in natural Ca-, Al-rich inclusions (CAIs) was investigated by comparing IMP results with those of an electron microprobe (EMP). Results on three trace-element-doped glasses indicated that it is not possible to obtain precise quantitative analysis by using IMP if there are large differences in SiO2 content between the standards used to derive the ion yields and the unknowns.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 53; 3115-313
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