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Geoarchaeological and chronometrical evidence of early human occupation on Lanzarote (Canary Islands) (2003)

Ludwig Zöller Hans von Suchodoletz Nils Küster

Two desert loess–paleosol sequences in sediment traps were investigated using (pedo-) stratigraphy, sedimentology, soil mineralogy and IRSL dating. So far we cannot recognise significant IRSL age-underestimates from the polymineral fine-grain fraction of our samples. We establish a first palaeoclimatic sequence spanning the past ca 200 ka which can be compared to data from other Canary Islands and surrounding areas, including terrestrial and deep sea records. More humid phases on Lanzarote are apparently triggered by Milankovich forcing, but the climate remained semi-arid to arid all over the past 200 ka. The onset of human occupation of the island during a slightly moister period is bracketed between 5 and 10 ka, based on the occurrence of archaeosediments containing bones of ovicaprid. This is the first proof of much earlier occupation than witnessed so far from archaeological records. The early subsidiary economy had a strong impact on soil stability and landscape shaping of the island.

Response to the „Comment on ’Geoarchaeological and chronometrical evidence …’ ” by J.C. Carracedo et al. (2004)

Ludwig Zöller Hans von Suchodoletz Henrik Blanchard Dominik Faust Ulrich Hambach

This paper is a reply to the comments made by Carracedo et al. (Quaternary Science Reviews 23, 2045-2049) to the original paper by Zöller, L., Suchodoletz, H.von & N. Küster (2003): Geoarchaeological and chronometrical evidence of early human occupation on Lanzarote (Canary Islands), Quaternary Science Reviews 22, 1299-1307. The reply copes with comments concerning chronometrical dating, the origin of investigated material and geomorphologic and geoarchaeologic problems.

Modeling Pattern Formation in Biopolymer Systems induced by Reaction Kinetics and Molecular Motors (2006)

Falko Ziebert

In my thesis I studied pattern formation in nonequilibrium (NE) polymer systems motivated from cell biology. Actin and microtubules (MTs) can be met in a state of continuous de-/polymerization (D/P), which is used by the cell e.g. during locomotion. This is a NE state since the polymerization is actively coupled to ATP or GTP hydrolysis. A second NE state of biological relevance is caused by motor proteins. These are mobile crosslinkers that walk on the filaments whereby creating forces and reorienting or transporting the latter. The cell displays filament-related ordered structures like aster patterns in the mitotic spindle, bundles in actin stress fibers and also oscillating structures e.g. in muscle bundles. The question is to what extent these structures inside the cell are governed by the physics of active polymers. In part I of my work, we proposed a pattern forming mechanism in a filament solution at high density that is subject to a D/P state. Since actin and MTs are rod-like objects, at high filament concentration a transition to lyotropic nematic order occurs. This transition is first order and thus accompanied by a phase separation. In the absence of D/P kinetics, the solution will thus tend to decompose into an isotropic domain with low density and a domain of high density and nematic order, i.e. the filaments preferentially aligned in one direction. To highlight that the D/P process interplays with this transition, we assumed that filaments are generated and decaying with some specific rates, implying a finite lifetime for the filaments. Accordingly the latter can only diffuse a finite length during their lifetime, which competes with the tendency of the system to phase separate and gives rise to a finite wavelength instability towards a pattern with alternating isotropic and nematic regions with a wavelength of the order of 10 microns. The model developed to describe these patterns is also interesting since it allows a feasible linear stability analysis of the homogeneous nematic state. Part II is devoted to the NE interaction of motor proteins with the filaments. As the starting point of our modeling efforts we chose a mesoscopic approach, namely a Smoluchowski equation which can be coarse-grained to obtain equations for the density and the orientation of the filaments. The main difference to a passive solution of rods are active motor-mediated currents caused by a motor density assumed sufficiently high and homogeneously distributed. These active contributions can be determined to leading order, introducing phenomenological motor transport rates containing details like active motor density, duty ratio, etc. After a thorough linear analysis of the model we obtained a rich instability diagram with an orientational finite wavelength instability which is either stationary or oscillatory and a demixing instability similar to spinodal decomposition but also motor-mediated. The finite wavelength instability has been analyzed by perturbative techniques and numerical simulations of the model equations. In the stationary case, we calculated the existence and stability regions of stripes and squares, which could be related to bundle-like structures and regular lattices of asters respectively. In the oscillatory case, there is competition between traveling and standing waves in one dimension and between traveling and alternating waves in two dimensions, the latter being a four mode solution built from two standing waves in perpendicular directions with a phase shift of 90 degrees. The long-wavelength demixing instability has also been investigated, showing coarsening aster-like structures. Experiments on MT-motor solutions display dissipative patterns in the NE state. Recent experiments on actin filaments and myosin oligomers show a rather different behavior, namely cluster patterns do not appear until ATP is nearly depleted. We proposed two mechanisms to explain these patterns: first, motors lacking ATP form rigor bonds with actin inducing small bundles, which through a combination of reduced diffusivity and enhanced interaction cross-section can be transported more efficiently, allowing the system to cross one of the instabilities discussed above. A second important feature is the presence of crosslinking proteins in the experiments. We propose that these can be interpreted as a parametric disorder. Assuming in the model a random contribution to the active current, a Ginzburg-Landau equation with multiplicative stationary noise could be derived leading to a threshold reduction. To conclude, it seems to be fruitful to apply and combine methods from statistical physics and pattern formation to NE problems in cell biology to foster the understanding of actively polymerizing filament and motor proteins in their different NE states.

Complex TERRain and ECOlogical Heterogeneity (TERRECO);WP 1-02: Spatial assessment of atmosphere-ecosystem exchanges via micrometeorological measurements, footprint modeling and mesoscale simulations ; Documentation of the Observation Period May 12th to Nov. 8th, 2010, Haean, South Korea (2011)

Peng Zhao Johannes Lüers Johannes Olesch Thomas Foken

no abstract

Template-Controlled Synthesis of Magnetic/Semiconducting Nanoparticles within Amphiphilic Core-Shell Cylindrical Polymer Brushes (2004)

Mingfu Zhang

Core-shell cylindrical polymer brushes with poly(t-butyl acrylate)-b-poly(n-butyl acrylate) (PtBA-b-PnBA) diblock copolymer side chains were synthesized via the “grafting from” technique using a combination of anionic polymerization (for the synthesis of the backbone) and atom transfer radical polymerization (ATRP, for the synthesis of the side chains). The formation of well-defined brushes was confirmed by 1H-NMR and GPC. The selective hydrolysis of the PtBA block of the side chains resulted in novel amphiphilic core-shell cylindrical polymer brushes with poly(acrylic acid)-b-poly(n-butyl acrylate) (PAA-b-PnBA) side chains. The characteristic core-shell cylindrical structure of the brushes was directly visualized on mica by scanning force microscopy (SFM). Amphiphilic brushes with 1500 block copolymer side chains and a length distribution of lw/ln = 1.04 at a total length ln = 179 nm were obtained. These amphiphilic polymer brushes can be regarded as unimolecular cylindrical micelles, because of the core-shell structure and the amphiphilicity of side chains. The amphiphilic brushes can be used as single molecular templates for the synthesis of inorganic nanoparticles, because the carboxylic acid groups (or carboxylate groups, after neutralization) in the polymer core can coordinate with various metal ions. The hydrophilic core of polymer brushes, poly(acrylic acid), was neutralized by NaOH and afterward iron cations (Fe3+ and Fe2+) were loaded into the polymer core via ion exchange. The formation of the polychelates of polymer brushes and iron cations was confirmed and characterized by various techniques such as Fourier transform infrared spectroscopy (FTIR), UV/vis spectroscopy, transmission electron microscopy (TEM) and SFM. A peculiar “pearl necklace” morphology was observed for the polychelates, which is caused by the physical cross-linking of the side chains via multivalent iron cations. Formation of crystalline alpha-Fe2O3 (hematite) was observed during the He-Ne laser irradiation in the confocal Raman microscopy measurement of the polychelate containing Fe3+ ions. Magnetic nanoparticles were successfully produced from the coordinated iron cations within polymer brushes via single molecule templating technique, as confirmed by various techniques such as SFM, TEM, and UV/visible spectroscopy. Superconducting quantum interference device (SQUID) magnetization measurements show that the hybrid nanocylinders are superparamagnetic at room temperature. The polymer shell provides not only the stability of the nanoparticles but also the solubility of the hybrid nanocylinders. After the formation of the magnetic nanoparticles, the carboxylate coordination sites within the polymer brushes are liberated and ready for further coordination with more iron ions, thus it is possible to increase the amount and/or particle size of the nanoparticles by multi-cycles of iron ion loading and particle formation. The as-prepared hybrid nanocylinders combine the promising properties of polymers and superparamagnetic nanoparticles, and may find potential applications such as in ferrofluids. Similarly, using the amphiphilic core-shell cylindrical polymer brush with PAA core and PnBA shell as template, wire-like assemblies of CdS nanoparticles were successfully synthesized under mild solution conditions, as confirmed by various characterization techniques. Quantum confinement of the CdS nanoparticles was observed, indicated by the blue shift of the absorbance edge in UV/visible spectrum. The technique using a single cylindrical molecule as template for inorganic nanoparticle fabrication presented in this thesis is not restricted to magnetic/semiconductor nanoparticles, but can also be used for the preparation of a number of metal, metal oxide, and metal chalcogenide nanoparticles.

New Applications of Fluorescence Correlation Spectroscopy in Materials Science (2006)

Heiko Zettl

In this work we have developed new concepts for the usage of fluorescence correlation spectroscopy. A classical FCS setup was modified in such a way that fluorescent species in aqueous as well as organic environments can be studied at varying temperature. We have synthesised a set of dye-labelled polymers that served as a well-defined system to study polymer diffusion and that was used to characterise the beam path and focal volume in environments with refractive indices different from that of water. Furthermore a new method for the labelling of ionic species was developed. The adaptation of the microscope optics to non-aqueous environments was done by replacing the present microscope objective by a multi-immersion objective. Secondly, a sample chamber was developed that was not only resistant to organic solvents in all parts but also allowed temperature control of the solution. Determining diffusion coefficients of polymers in solution and their concentrations requires the exact knowledge of shape and size of the observation volume. For this purpose we have synthesised a set of polystyrenes with molecular weights ranging from 4 to 1550 kg/mol each chain being labelled with a single dye molecule. All species were anionically polymerised in order to grant a very low polydispersity and with this a high reliability in the determination of the observation volume. This concept can be transferred to other solvents and, hence, shows an easy way to calibrate fluorescence correlation microscopes to different solvents and to investigate non-aqueous solutions. Furthermore, we have shown exemplarily for polystyrene that FCS is capable of determining the crossover between the dilute and the semi-dilute concentration regime. Dye-labelled polymer chains were mixed with unlabelled polymer chains of the same length and their mobility was measured by FCS for different mixing ratios. The change of the mobilities leads to the respective overlap concentrations, which are shown to follow a scaling law in a range of molecular weights from 4 to 1550 kg/mol. This is in excellent agreement with the predictions made by Flory and Huggins. The data shown demonstrate that FCS can measure diffusion properties in ranges that were not accessible before. Another part of this work focusses on concepts to monitor the aggregation of molecules by FCS. Taking low-molecular-weight surfactants as an example it is shown that with the help of Coulomb interaction cationic surfactants can be labelled with anionic dye molecules and vice versa. Moreover, micelle formation is observed already at concentrations slightly below the critical micelle concentration found with classical methods. This findings are in excellent agreement with the predictions made by Israeliachvili in the 1990ies. Additionally, it was demonstrated that by using insoluble dye molecules, which are incorporated by the forming aggregates, aggregate formation can be followed by FCS on a single-molecule level. This procedure was shown to work in both aqueous and organic polymer solutions. The high sensitivity of FCS permitted to determine the critical aggregation concentration of Janus micelles in THF to the very low value of around 8 mg/L. No other experimental method available today is capable of determining aggregation concentrations in such a low concentration regime. In the same way the critical aggregation concentration of block copolymer polystyrene-Amylose in THF was determined. Finally, temperature-dependent correlation curves allowed the determination of reaction constants and enthalpies. This is of particular interest in biochemical contexts, as the amount of available material can be minute. Exemplarily, the binding enthalpy of an RPA protein to a single-stranded DNA strain is determined by temperature-dependent correlation curves. The modifications made to a classical FCS setup were shown to enhance the spectrum of possible applications to new experimental fields. The methods and concepts developed in the framework of this thesis are expected to play an important role in meeting future challenges of polymer physics and microbiology.

Investigation of high nighttime CO2-fluxes at the Wetzstein spruce forest site in Thuringia, Germany (2008)

Marcelo Zeri

Nighttime fluxes of CO2 are uncommonly high at the Wetzstein spruce site, in Thuringia, Germany (Anthoni et al., 2004). As a result, the annual sums of CO2- flux obtained for this site are not comparable with the ones obtained at similar spruce ecosystems (Rebmann, 2004; Grünwald and Bernhofer, 2007). The site is located on a hill and subject to strong winds and high levels of turbulence for continuous periods. The unusual high fluxes of CO2 are predominantly associated with these situations. As reported by Anthoni et al. (2004), measurements of soil respiration performed with automatic chambers in 2003 did not explain such high ecosystem respiration. Also, recent results of soil respiration have revealed that the ecosystem respiration Reco should be comparable to the value obtained for the similar spruce site of Waldstein/Weidenbrunnen (Rebmann, 2004). According to the modeling work of Finnigan and Belcher (2004), the flow over low hills as the Wetzstein site disturbs the wind field at the sub-canopy space across the ridge. As a consequence, advective fluxes of scalars as CO2 are generated at the upwind and lee sides of the hill. Two results from the model were confirmed for the first time in an experiment, namely (1) higher wind speeds below the canopy at the slope, when compared with the same level at the crest, and (2) the flows above and below the canopy in opposite direction at the lee side of the hill. Besides the agreement of the measured wind field with the model results, the existence of horizontal advection was confirmed by Feigenwinter et al. (2007), using data from the advection experiment ADVEX. However, the sign of the advective flux was positive on average, meaning that CO2 was flushed out of the control volume enclosed by the additional towers. This result was not directly related to the high nighttime fluxes of CO2, as these situations were rarely observed during the experiment. However, it has shown that sub-canopy flows exist at the site and should be further investigated. The analysis of several cospectra of the vertical flux of CO2 have shown that the frequencies, or time scales, associated with the high nocturnal fluxes are mainly the turbulent ones, typically observed for nighttime turbulent regimes. The high turbulent activity observed during neutral situations leads then to enhanced turbulent fluxes of CO2. High nocturnal fluxes of CO2 were related to specific micrometeorological conditions, namely high values of friction velocity, southwesterly and northeasterly winds, and neutral stratification. These conclusions were used in a gap-filling approach as annual sums of CO2 were calculated (Rebmann et al., in preparation). As a result of this new approach the site presented a higher uptake of CO2 by the vegetation. Additionally, the newly found results have shown that the uptake of CO2 has been increasing since 2003, caused by factors as the improved growth rate induced by a thinning operation (after snow damage) in 2002, and the recovery from the drought of 2003. The tendency observed in the annual sums of CO2-flux indicates that the site may be in a transition period after the disturbances described above. The proposed removal of unusually high values of CO2-fluxes (with objective criteria) for the determination of annual sums should be also applied in future analysis, in order to capture changes in uptake rates. In this case the CO2 balance for the Wetzstein site would be more comparable to similar ecosystems as Waldstein/Weidenbrunnen (Rebmann, 2004) and Tharandt (Bernhofer et al., 2003; Grünwald and Bernhofer, 2007).

Trends, Discourses and Representations in Religions in Africa (2012)

Meron Zeleke Halkano Abdi Wario

Religion in Africa has for long been a woven cultural fabric of life, a great moving force that guided people’s behavior, interaction and action since time immemorial. A decade after the United States experience of the 9/11, the unfortunate event has set the landmark for a geopolitics in contemporary Africa that securitizes religious movements and that identify them with the so-called global war on terror, a phenomenon within which most African nations play a significant regional role. The current wave of developments related to religion in the contingent became fossilized through religious manipulation and politicization in the post-colonial era. Three thematic concepts have been identified, i.e., religious trends, cultural discourses and representation, in order to capture some of the most contemporary issues of concern to Muslim, Christian and indigenous religious communities in Africa. Nine papers in this second issue of BIGSAS Works! hence targeted current doctoral researches from a wide range of disciplines and successfully integrated a cross-disciplinary approach to appreciate the complexity of faith matters in the continent.

The Use of Biomarker and Stable Isotope Analyses in Palaeopedology / Reconstruction of Middle and Late Quaternary Environmental and Climate History, with examples from Mt. Kilimanjaro, NE Siberia and NE Argentina (2006)

Michael Zech

Palaeosols are important terrestrial archives for the reconstruction of the Quaternary landscape and climate history. In order to derive reliable information from these archives about sedimentation, vegetation and climate history, various methods and proxies are traditionally applied, e.g. texture analysis, numeric dating methods and mineral analysis. The aim of this dissertation is to evaluate the potential of biomarker and stable isotope analyzes. Specifically, I focused on plant leaf wax-derived n-alkanes, amino acid enantiomers, stable carbon and nitrogen isotopes (d13C and d15N) in bulk soil organic matter (SOM) and on compound-specific isotope analysis (CSIA) of n-alkanes. The respective methods were partly optimized and then applied in multi-proxy analytical approaches to three selected palaeosol records, representing different ecological environments. In all three study areas, long-chain n-alkane ratios, nC31/nC27 and (nC31+nC29)/nC27, respectively, proved to be straightforward biomarker proxies for the reconstruction of the terrestrial palaeovegetation at plant community level (especially grasses and herbs versus trees). Short- and mid-chain n-alkanes (nC17–nC19 and nC20–nC25, respectively) were successfully used for detecting algal- and aquatic macrophyte-derived organic matter (OM) in the sediment core Arg. D4. Amino acid enantiomers as nitrogen (N) biomarkers allowed a further characterization of the SOM in the Tumara Palaeosol Sequence: On the one hand, the depth functions of D/L-aspartic acid (Asp) and D/L-lysine (Lys) could be roughly described by exponential fits, reflecting SOM aging. On the other hand, brown interglacial/-stadial palaeosols generally revealed higher D/L-ratios than dark gray glacial palaeosols. This finding suggests that D/L-aspartic acid and D/L-lysine may serve as palaeotemperature proxies. In the Arg. D4 record, d13C varied in a wide range (from -30.1‰ to -17.4‰), indicating C3-C4 vegetation changes and hence allowing a reconstruction of the palaeovegetation. However, the natural abundance of 13C was no straightforward proxy for the interpretation of the palaeosol sequences on Mt. Kilimanjaro and in the Tumara Valley. There, the interpretation of smaller d13C variations – assumed to be independent of C3-C4 vegetation changes – needed multi-proxy analytical approaches for disentangling the various possibly influencing environmental factors: On Mt. Kilimanjaro, d13C is higher in palaeosols, which developed under ericaceous vegetation (~ -25‰) compared to those developed under tropical montane forests (~ -27‰), suggesting that such vegetation changes are responsible for the observed d13C pattern. In the Tumara Palaeosol Sequence, d13C correlates negatively with total organic carbon (TOC) and TOC/N. As both parameters may serve as proxies for SOM decomposition, it is assumed that degradation processes have contributed significantly to this d13C record. Furthermore, also changing water stress conditions for the plants could have played a crucial role for d13C in the Tumara Palaeosol Sequence. In contrast to d13C, d15N in the Tumara Palaeosol Sequence does not correlate with any of the other SOM characterizing parameters (TOC, TOC/N and d13C). Although other processes than SOM decomposition like (i) denitrification, (ii) N fixation, (iii) N losses by frequent fire events, and (iv) changes in the atmospheric 15N deposition are discussed as factors contributing to an open N cycle, d15N in the Tumara Palaeosol Sequence seems not to be a straightforward proxy. The compound-specific d13C analysis (CSIA) of n-alkanes was optimized and applied to selected samples from the Arg. D4 record. The highly significant correlations of the compound-specific isotope results with bulk d13C corroborate the reliability of the d13C vegetation proxy. Furthermore, the increasing d13C amplitudes from nC27 to nC33 validate the origin of these biomarker molecules, with nC27 and nC29 mainly deriving from C3 trees and shrubs and nC31 and nC33 mainly deriving from C3 or C4 grasses and herbs. Eventually, the multi-proxy analytical approaches (including the innovative biomarker and stable isotope analyzes) enabled detailed reconstructions of the Middle and Late Quaternary palaeoenvironmental changes in the three study areas: Accordingly, the deep black palaeosols on the southern slopes of Mt. Kilimanjaro reflect periods of climatic deterioration during the Last Glacial Maximum (LGM) and the Late Glacial, which coincided with a descent of the ericaceous vegetation belt. The palaeopedologic findings from the Tumara Palaeosol Sequence suggest that the dark gray and brown stratigraphic units of this record describe alternating glacial and interglacial/-stadial periods during the last ~240 ka. The stratigraphic units of the Arg. D4 record were correlated with climatic events on the Bolivian Altiplano and discussed in terms of an intensified palaeo-South American Summer Monsoon (SASM).

The 5-th element. A new high pressure high temperature allotrope (2010)

Evgeniya Zarechnaya

Boron is the fifth element in the Periodic Table known for its structural complexity, unusual types of bonding, and for a rich variety of compounds that it forms. Even the number of its existing or hitherto proven elemental modifications is still under discussion. The present study of boron behavior at high pressures and high temperatures (HPHT) comprises various experimental techniques for HP synthesis and material characterization, as well as theoretical modeling. A series of high pressure (up to 20 GPa) and high temperature (up to 1900 °C) synthesis experiments were conducted in multianvil apparatus at Bayerisches Geoinstitut. For testing of the reproducibility of HPHT experiments different types of boron precursors and assemblages for large-volume presses were used. The synthesis products were studied by X-ray diffraction and spectroscopic methods. The diffraction patterns collected from samples synthesized from highly purified boron powders (> 99.99 % purity) resemble those published by R.H. Wentorf in 1965 and described as a new boron form, but later effectively forgotten. To eliminate any possible contaminations that could take place during the synthesis process, the purity of the HP boron samples was confirmed by scanning electron and transmission electron microscopy and electron microprobe analysis. The structure of this HPHT boron polymorph was first unknown, but subsequently determined from our X-ray powder diffraction data and further refined using single-crystal synchrotron diffraction data. The structure was found to be orthorhombic with a Pnnm space group and composed of B12 icosahedra and B2 dumbbells. The unit cell contains 28 atoms (two icosahedra and two dumbbells) and will be called here B28. Atoms in B28 are bonded covalently as revealed experimentally by single-crystal X-ray diffraction studies and calculated Electron Localization Function. The X-ray density of 2.52 g cm-3 of this boron allotrope is the highest among its other known modifications. In order to determine the phase transition boundary between beta-and B28 boron phases, in situ HP laser heating experiments were performed at European Synchrotron Radiation Facilities (ESRF). It was demonstrated that B28 is a stable phase above 9 GPa. Systematic investigations aimed at the development of the technique of the HP single crystal growth of B28 were undertaken. It was found that single crystals of the orthorhombic boron can be grown from metal solutions (Au, Cu, or Pt), i.e. after dissolution in metals at high temperature boron precipitates in form of single crystals with temperature decrease. Experimental products were free from any borides only when Au was used. The maximal length of synthesized B28 crystals was ~100 µm and after their isolation high quality X-ray diffraction data was obtained. Synthesized single crystals of the orthorhombic high-pressure boron phase were studied by means of polarized Raman spectroscopy at ambient conditions. Among all possible 42 Raman-active modes, 32 modes were registered and assigned. Investigation of the high pressure behavior of B28 orthorhombic boron was carried out through combining single crystal X-ray diffraction up to 65 GPa and Raman spectroscopy measurements performed up to 105 GPa. Above 40 GPa discontineous behavior in the mode Grueneisen parameter was detected. At the same pressure an inflection in the dependence of the relative volume of a unit cell versus pressure occurs. However, the structure of the material does not change. It is suggested that B28 undergoes an isostructural phase transformation, probably due to reducing of the polarity of covalent bonds. The orthorhombic B28 boron reveals extraordinary physical properties. Due to very strong covalent bonding it has a very high Vickers hardness HV=58 GPa, making B28 to be the second hardest elemental material after diamond. The electrical resistance and IR-spectroscopic measurements demonstrated the semiconducter nature of B28. Combination of these properties makes the high-pressure boron polymorph a prospective material for industrial applications.

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