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search.filters.applied.f.access: openAccess × End date: 2019 × Start date: 2018 × End date: 2009 × Start date: 2000 × WGL Institute: ISAS ×

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    Emission fluxes and atmospheric degradation of monoterpenes above a boreal forest: Field measurements and modelling
    (Milton Park : Taylor & Francis, 2001) Spanke, Jörg; Rannik, Üllar; Forkel, Renate; Nigge, Walter; Hoffman, Thorsten
    The contribution of monoterpenes to aerosol formation processes within and above forests is not well understood. This is also true for the particle formation events observed during the BIOFOR campaigns in Hyytiälä, Finland. Therefore, the diurnal variation of the concentrations of several biogenic volatile organic compounds (BVOCs) and selected oxidation products in the gas and particle phase were measured on selected days during the campaigns in Hyytiälä, Finland. α-pinene and Δ3-carene were found to represent the most important monoterpenes above the boreal forest. A clear vertical gradient of their concentrations was observed together with a change of the relative monoterpene composition with height. Based on concentration profile measurements of monoterpenes, their fluxes above the forest canopy were calculated using the gradient approach. Most of the time, the BVOC fluxes show a clear diurnal variation with a maximum around noon. The highest fluxes were observed for α-pinene with values up to 20 ng m−2 s−1 in summer time and almost 100 ng m−2 s−1 during the spring campaign. Furthermore, the main oxidation products from α-pinene, pinonaldehyde, and from β-pinene, nopinone, were detected in the atmosphere above the forest. In addition to these more volatile oxidation products, pinic and pinonic acid were identified in the particle phase in a concentration range between 1 and 4 ng m−3. Beside these direct measurement of known oxidation products, the chemical sink term in the flux calculations was used to estimate the amount of product formation of the major terpenes (α-pinene, β-pinene, Δ3-carene). A production rate of very low volatile oxidation products (e.g., multifunctional carboxylic) from ·OH- and O3-reaction of monoterpenes of about 1.3·104 molecules cm−3 s−1 was estimated for daylight conditions during summer time. Additionally, model calculations with the one-dimensional multilayer model CACHE were carried out to investigate the diurnal course of BVOC fluxes and chemical degradation of terpenes.
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    Recent developments in peptide-based nucleic acid delivery
    (Basel : MDPI, 2008) Veldhoen, Sandra; Laufer, Sandra D.; Restle, Tobias
    Despite the fact that non-viral nucleic acid delivery systems are generally considered to be less efficient than viral vectors, they have gained much interest in recent years due to their superior safety profile compared to their viral counterpart. Among these synthetic vectors are cationic polymers, branched dendrimers, cationic liposomes and cellpenetrating peptides (CPPs). The latter represent an assortment of fairly unrelated sequences essentially characterised by a high content of basic amino acids and a length of 10-30 residues. CPPs are capable of mediating the cellular uptake of hydrophilic macromolecules like peptides and nucleic acids (e.g. siRNAs, aptamers and antisenseoligonucleotides), which are internalised by cells at a very low rate when applied alone. Up to now, numerous sequences have been reported to show cell-penetrating properties and many of them have been used to successfully transport a variety of different cargos into mammalian cells. In recent years, it has become apparent that endocytosis is a major route of internalisation even though the mechanisms underlying the cellular translocation of CPPs are poorly understood and still subject to controversial discussions. In this review, we will summarise the latest developments in peptide-based cellular delivery of nucleic acid cargos. We will discuss different mechanisms of entry, the intracellular fate of the cargo, correlation studies of uptake versus biological activity of the cargo as well as technical problems and pitfalls.
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    Untersuchungen zur chemischen Zusammensetzung der organischen Komponente des troposphärischen Aerosols : AFS-Abschlußbericht
    (Hannover : Technische Informationsbibliothek (TIB), 2002) Hoffmann, Th.; Warscheid, Bettina; Nigge, Walter; Kückelmann, Ulrich
    [no abstract available]
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    Overview of the international project on biogenic aerosol formation in the boreal forest (BIOFOR)
    (Milton Park : Taylor & Francis, 2001) Kulmala, M.; Hämeri, K.; Aalto, P.P.; Mäkelä, J.M.; Pirjola, L.; Nilsson, E. Douglas; Buzorius, G.; Rannik, Ü.; Dal Maso, M.; Seidl, W.; Hoffman, T.; Janson, R.; Hansson, H.-C.; Viisanen, Y.; Laaksonen, A.; O’dowd, C.D.
    Aerosol formation and subsequent particle growth in ambient air have been frequently observed at a boreal forest site (SMEAR II station) in Southern Finland. The EU funded project BIOFOR (Biogenic aerosol formation in the boreal forest) has focused on: (a) determination of formation mechanisms of aerosol particles in the boreal forest site; (b) verification of emissions of secondary organic aerosols from the boreal forest site; and (c) quantification of the amount of condensable vapours produced in photochemical reactions of biogenic volatile organic compounds (BVOC) leading to aerosol formation. The approach of the project was to combine the continuous measurements with a number of intensive field studies. These field studies were organised in three periods, two of which were during the most intense particle production season and one during a non-event season. Although the exact formation route for 3 nm particles remains unclear, the results can be summarised as follows: Nucleation was always connected to Arctic or Polar air advecting over the site, giving conditions for a stable nocturnal boundary layer followed by a rapid formation and growth of a turbulent convective mixed layer closely followed by formation of new particles. The nucleation seems to occur in the mixed layer or entrainment zone. However two more prerequisites seem to be necessary. A certain threshold of high enough sulphuric acid and ammonia concentrations is probably needed as the number of newly formed particles was correlated with the product of the sulphuric acid production and the ammonia concentrations. No such correlation was found with the oxidation products of terpenes. The condensation sink, i.e., effective particle area, is probably of importance as no nucleation was observed at high values of the condensation sink. From measurement of the hygroscopic properties of the nucleation particles it was found that inorganic compounds and hygroscopic organic compounds contributed both to the particle growth during daytime while at night time organic compounds dominated. Emissions rates for several gaseous compounds was determined. Using four independent ways to estimate the amount of the condensable vapour needed for observed growth of aerosol particles we get an estimate of 2–10×107 vapour molecules cm−3. The estimations for source rate give 7.5–11×104 cm−3 s−1. These results lead to the following conclusions: The most probable formation mechanism is ternary nucleation (water-sulphuric acid-ammonia). After nucleation, growth into observable sizes (~3 nm) is required before new particles appear. The major part of this growth is probably due to condensation of organic vapours. However, there is lack of direct proof of this phenomenon because the composition of 1–5 nm size particles is extremely difficult to determine using the present state-of-art instrumentation.
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    Grundlagen der lasergestützten vor-Ort Bodenanalytik : Thema: Grundlegende Untersuchungen zur Diodenlaser-Raman-Sensorik für die organische Spurenanalytik von Böden ; Abschlußbericht
    (Hannover : Technische Informationsbibliothek (TIB), 2000) Hill, Wieland; Kostrewa, S.; Viets, C.; Kahl, M.; Voges, E.
    [no abstract available]
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    Oxaliplatin-DNA adduct formation in white blood cells of cancer patients
    (London : Nature Publishing Group, 2008) Pieck, A.C.; Drescher, A.; Wiesmann, K.G.; Messerschmidt, J.; Weber, G.; Strumberg, D.; Hilger, R.A.; Scheulen, M.E.; Jaehde, U.
    In this study, we investigated the kinetics of oxaliplatin-DNA adduct formation in white blood cells of cancer patients in relation to efficacy as well as oxaliplatin-associated neurotoxicity. Thirty-seven patients with various solid tumours received 130 mg m−2 oxaliplatin as a 2-h infusion. Oxaliplatin-DNA adduct levels were measured in the first cycle using adsorptive stripping voltammetry. Platinum concentrations were measured in ultrafiltrate and plasma using a validated flameless atomic absorption spectrometry method. DNA adduct levels showed a characteristic time course, but were not correlated to platinum pharmacokinetics and varied considerably among individuals. In patients showing tumour response, adduct levels after 24 and 48 h were significantly higher than in nonresponders. Oxaliplatin-induced neurotoxicity was more pronounced but was not significantly different in patients with high adduct levels. The potential of oxaliplatin-DNA adduct measurements as pharmacodynamic end point should be further investigated in future trials.
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    Expression stability of commonly used reference genes in canine articular connective tissues
    (London : BioMed Central, 2007) Ayers, Duncan; Clements, Dylan N.; Salway, Fiona; Day, Philip J.R.
    Background: The quantification of gene expression in tissue samples requires the use of reference genes to normalise transcript numbers between different samples. Reference gene stability may vary between different tissues, and between the same tissue in different disease states. We evaluated the stability of 9 reference genes commonly used in human gene expression studies. Realtime reverse transcription PCR and a mathematical algorithm were used to establish which reference genes were most stably expressed in normal and diseased canine articular tissues and two canine cell lines stimulated with lipolysaccaride (LPS). Results: The optimal reference genes for comparing gene expression data between normal and diseased infrapatella fat pad were RPL13A and YWHAZ (M = 0.56). The ideal reference genes for comparing normal and osteoarthritic (OA) cartilage were RPL13A and SDHA (M = 0.57). The best reference genes for comparing normal and ruptured canine cranial cruciate ligament were B2M and TBP (M = 0.59). The best reference genes for normalising gene expression data from normal and LPS stimulated cell lines were SDHA and YWHAZ (K6) or SDHA and HMBS (DH82), which had expression stability (M) values of 0.05 (K6) and 0.07 (DH82) respectively. The number of reference genes required to reduce pairwise variation (V) to <0.20 was 4 for cell lines, 5 for cartilage, 7 for cranial cruciate ligament and 8 for fat tissue. Reference gene stability was not related to the level of gene expression. Conclusion: The reference genes demonstrating the most stable expression within each different canine articular tissue were identified, but no single reference gene was identified as having stable expression in all different tissue types. This study underlines the necessity to select reference genes on the basis of tissue and disease specific expression profile evaluation and highlights the requirement for the identification of new reference genes with greater expression stability for use in canine articular tissue gene expression studies.