A. Rahman Ashraf

University of Bonn | Uni Bonn

Late Miocene sediments from the Beli Breg Coal Basin, Western Bulgaria, were investigated using spore-pollen analysis. Based on palynological characteristics, we describe dynamics and development of vegetation in the studied basin. The main types of palaeocoenoses are distinguished. The fossil flora is characterised by a variable structure of plant...

The problem of paleoclimate reconstruction is an extremely interesting issue, which has been repeatedly discussed in many publications. This topic engages the attention of numerous specialists in many and various scientific disciplines. Fossil plants have vast potential as a source of information about past climatic conditions in the terrestrial re...

The application of quantitative techniques such as Coexistence Approach and interpretation of diversity of plant functional types (pfts) on the palaeobotanical record allows for detailed reconstructions of continental climate and its variability. For the NW European Cenozoic, recent studies based on macro- and microflora reveal a close correlation...

This study presents a detailed continental palaeoclimate record for the Neogene of Northwestern Europe. Palynomorph samples from continental to marginal marine deposits in 5 correlated sections from the Lower Rhine Basin (NW Germany) covering the time-span from Burdigalian to Zanclean are analysed. Independent time-control in the sections is provid...

A profile 63 m thick in the Late Miocene in the Gotse-Delchev Basin (SW Bulgaria) was sampled for pollen analysis in the Kanina opencast mine. The exposed sequence comprises a basal unit with brown coal-clay cycles and clayey/siliciclastic cover layers partly representing a lacustrine facies. A total of 60 pollen samples were analyzed, but quantita...

Recent studies carried out into the flora-bearing sediments of Beli Breg Lignite Basin have provided a total of 19 identified taxa at the species level, 13 of them new for that site. The new results confirm dominance of the Fagaceae family and high diversity of genus Quercus in the palaeoflora. Quercus gigas, Q. aff. acrodonta and genus Euonymus ar...

The Upper Triassic to Middle Jurassic strata are well exposed and basically continuous in the Junggar Basin of Xinjiang, Northwest China. The Upper Triassic strata include the Huangshanjie Formation (lacustrine facies mainly) and Haojiagou Formation (fluvial to fluvial-swamp facies). The Lower Jurassic consists of the coal-bearing Badaowan Formatio...

Background: Inhibition of angiogenesis is a major target in the fight against cancer and other diseases. The effects of electromagnetic fields on cell development and growth have been investigated. In this research we investigated the effects of electromagnetic fields with 100, 200 & 300 gauss on angiogenesis in chorioalantoic membrane of chick emb...

We present a palynological analysis of the blackshales from the late Oligocène maar lake of Enspel, derived from material recovered from the research core Enspel 1996/1. In the second part of this systematic analysis we demonstrate the angiosperms as well as an overview on the palaeoecological interpretation of the palynofloras. In a preceding part...

The sixth part of the atlas treating the recent spores of Pteridophytes from State of Rio Grande so Sul, Brazil represents a supplement to the five preceding publications, including additional records from the families Schizaeaceae, Pteridaceae, Dennstaedtiaceae, Lycopodiaceae, Selaginellaceae und Isoetaceae, totalling 23 species. The analysis of h...

A late Miocene paludal to lacustrine sequence from a carbonate basin in NW Bulgaria (Staniantsi Basin) is analysed displaying up to 27 rhythmically bedded sedimentary cycles. In the lower part of the sequence, the cycles consist of alternating autochthonous brown coal and marls containing diverse mollusc assemblages. The upper part of the sequence...

This 14th and final monograph on the Mesozoic plant micro- and macrofossils of Iran and Afghanistan deals with the leptosporangiate ferns. After the introduction, the stratigraphic distribution of more than 200 different plant species in the flora is treated with the aid of a number of tables. The climatic changes accompanying the floristic changes...

We present a palynological analysis of the blackshales from the late Oligocène maar lake of Enspel, derived from material recovered from the research core Enspel 1996/1. In the first part of this systematic analysis we present the (landplan t-)spores and gymnosperms. In a following second part of this analysis we will present the angiosperms as wel...

First results of palynological studies on Neogene freshwater deposits of Staniantsi Basin (West Bulgaria, SE Europe) are presented. The basin is rela- tively poorly known with respect to di�erent points of view in geosciences. The age of sediments in Staniantsi Basin covers the time span from the late Miocene to the Pliocene as available geological...

The results of palynological studies of the Oligo-Miocene in the western part of the Euxinian Basin (Eastern Paratethys) are based on the analysis of 57 samples from core C-136A drilled near the town of Balchik, Varna district. Some samples were barren or contained very little pollen and were not included in the analysis. Quantitative data are thus...

The results of palynological studies of Neogene freshwater deposits of the Beli Breg Graben (West Bulgaria) are presented. We analysed pollen and spores with the aim of obtaining data about the composition and structure of fossil vegetation and climate conditions. The main vegetation paleocommunities, which existed during the fossilization process,...

Holocene coastal environmental changes are interpreted from a 590 cm long core taken from Itapeva Lake in the northern coastal plain, Rio Grande do Sul, Brazil. The sediment core is radiocarbon dated at 211 cm depth (6460±40 yr B.P.) and studied by geochemistry and palynomorph analyses. The Pleistocene-Holocene boundary is predicted at the top of a...

The fifth part of the atlas about the recent spores of peridophytes of the State of Rio Grande do Sul, Brazil, presents the study of the family Polypodiaceae (including Grammitidaceae), represented by the tribe Polypodieae- Genera Campyloneurum, Microgramma, Niphidium,Pecluma, Pleopeltis, Polypodium - and tribe Grammitideae - genera Ceradenia, Coch...

RESUMO – Mudanças ambientais durante o Holoceno foram interpretadas na Planície Costeira Norte do Rio Grande do Sul com base no testemunho de sondagem QU-RS-B09 da lagoa dos Quadros. A análise de palinofácies foi realizada em quarenta e uma amostras sedimentares selecionadas ao longo dos 405 cm do testemunho de sondagem datado em 6.700 ± 40 anos AP...

Abstract Ivanova, D., Ivanov, D., Ashraf, A. R. & Mosbrugger, Y.: Pteridophyte spores of Bulgaria - preliminary results. – Bocconea 16(2): 975-984. 2003. – ISSN 1120-4060. An atlas with morphological descriptions of the recent pteridophyte spores of Bulgaria is being prepared. The main object of the project is to illustrate the spores of pteridop...

This paper represents the second part of the atlas devoted to the recent pteridophytes of Rio Grande do Sul State, Brazil, with special emphasis on the morphology of spores. Spores of 39 pteridophyte species from 9 genera and 6 families (Gleicheniaceae, Hymenophyllaceae, Plagiogyriaceae, Dicksoniaceae, Lophosoriaceae and Cyatheaceae) are described...

Based on recent studies, the impact of global sea-level and climate change on the paleogeographic and sedimentary evolution of the Tertiary of the Lower Rhine Basin is analysed. It is shown that major changes in global climate and sea-level, such as the high-stand during the Middle Miocene climate optimum, the extreme low-stands near the base of th...

We reconstruct quantitatively the Middle to Upper Miocene climate evolution in the southern Forecarpathian Basin (Central Paratethys area, Northwest Bulgaria) by applying the coexistence approach to 101 well-dated palynofloras isolated from three cores. The climatic evolution is compared with changes in vegetation and palaeogeography. The Middle Mi...

Absrract A new geological section recognized in Baishantou of JiaYln. Heilongjiang l'rovll1ce, China, was stud­ ied preliminarily in searching for the KIT boundary. An early Paleocene f10mle characterized by abundant Tiliaephyllum rsagajanicllm leaves and irs associated plants. was collected from the Balshanwu Member (new member repre.~enting the l...

In this study we reconstruct quantitatively the Middle to Upper Miocene climate evolution in the southern Forecarpathian Basin (Central Paratethys area, Northwest Bulgaria) by applying the coexistence approach to 101 well-dated palynofloras isolated from three cores. The climatic evolution is compared with changes in vegetation and palaeogeography....

This third part of the atlas about the recent spores of pteridophytes of Rio Grande do Sul State, Brazil is devoted to the family Pteridaceae, with a total of 39 species from 10 genera (Acrostichum, Adiantopsis, Adiantum, Anogramma, Cheilanthes, Doryopteris, Eriosorus, Hemionitis, Pityrogramma and Pteris). The spores are described in detail with SE...

The first detailed reconstruction of the continental paleoclimate evolution of the Northwest German Tertiary (Late Oligocene to Pliocene) is presented. The paleoclimate data are derived from the paleobotanical record using the coexistence approach, a method recently introduced that employs climatic requirements of the Nearest Living Relatives of a...

The first detailed reconstruction of the continental palaeoclimate evolution of the Northwest German Tertiary (Late Oligocene to Pliocene) is presented. The paleoclimate data are derived from the paleobotanical record using the coexistence approach, a method recently introduced that employs climatic requirements of the Nearest Living Relatives of a...

New methods of sampling, preparing and identifying fossil wood fragments preserved in browncoal are presented and used to aid in reconstructions of the vegetation from the Miocene Lower Rhine Basin (Germany). The technique involves laboratory charring wood specimens followed by routine identification with reflected light microscopy. Problems concer...

A complete Triassic-Jurassic transition is well documented in the Haojiagou valley section 40 km to the west of Urumqi Xinjiang, China. The results of the preliminary palynological study from the first field work with 13 samples reveal a well preserved microflora which confirm that the Hojiagou Formation belongs to the Concavisporites-Duplexisporit...

This paper represents the second part of the atlas devoted to the recent pteridophytes of Rio Grande do Sul State, Brazil, with special emphasis on the morphology of spores. Spores of 39 pteridophyte species from 9 genera and 6 families (Gleicheniaceae, Hymenophyllaceae, Plagiogyriaceae, Dicksoniaceae, Lophosoriaceae and Cyatheaceae) are described...

The dynamics of block copolymers provide the basis for developing these nanostructured materials for applications in nanotechnologies. Defect dynamics determine the minimum defect density within a desired structure. Here we examine defect dynamics of model ABC triblocks that consist of styrene (S), isoprene (I), and a random copolymer of styrene an...

The polydomain nanostructures of block copolymers can be extended to the macroscale by external fields, such as flow. Here we examine the alignment behaviors of two-nanophase-separated ABC triblock copolymers and blends. These triblocks are consist of styrene (S), isoprene (I), and a random copolymer of styrene and isoprene (R). Polymers with equal...

A detailed stable carbon isotopic profile of a late Miocene browncoal seam from the Lower Rhine Embayment, Germany, reveals two clear separate cycles of different frequency: this is the first instance of this type of isotopic signature being recognized within coals. The ratio of the two frequencies suggests this isotopic signal possibly resulted fr...

Nanostructures and processing behavior of block copolymers are of interest for potential applications in nanotechnology. Here we focus on the effect of molecular size on morphologies, dynamics, and flow-alignment behavior of a model ABC triblock system composed of styrene (S), isoprene (I), and a random copolymer segment of styrene and isoprene (R)...

The reliability and reproducibility of Tertiary palynostratigraphic studies were tested based on four closely spaced well logs near Julich in the Lower Rhine Embayment (NW Germany) covering the Upper Pliocene. It turned out that the basic palynostratigraphic patterns were the same in all profiles and that data noise was less important than expected...

Based on palynological studies we present a detailed palaeovegetation analysis of the Middle Miocene Garzweiler seam of the Lower Rhine Embayment (NW Germany). The palynological data were analysed with multivariate statistical methods (e.g. correlation analysis, cluster analysis) to recognize vegetation units which can be interpreted in terms of ec...

A methodologically new approach to regional palaeoclimate reconstructions in the terrestrial Neogene has been proposed by Mosbrugger and Schilling (1992) in which regional scale atmospheric climate modeling and interpretation of geological-palaeontological palaeoclimate proxies are combined and coupled in an iterative process to obtain detailed and...

The Tertiary of the Lower Rhine Embayment (NW Germany) comprises a lignite deposit of eminent economic importance. We studied the Middle Miocene to Pliocene Rhenish Main Seam to Reuver series palynoflora (horizons 6A to 11 after SCHNEIDER & THIELE 1965) in the open-pit mines Inden and Bergheim. Based on 959 samples, we identified 227 species from t...

The description of two sieving devices to remove organic debris and other fine, insoluble particles from palynological preparations is given. The main constituents are a lower plastic container, an upper glass cylinder, a nylon screen fitted between these two, and a vacuum source. Clogging of the sieve is prevented by periodically reversing the vac...

Ordered diblock copolymer blends have recently become the subject of tremendous research interest since they can be used to elucidate the intramicrodomain segregation of blocks differing in length, as well as to identify the molecular and blend parameters yielding phase immiscibility. In this work, we explore the influence of molecular architecture...

Linear multiblock copolymers, like their diblock analogues, are capable of ordering into periodic microstructures when the blocks are sufficiently incompatible. In this work, a series of four linear poly(styrene-b-isoprene)n (SI)n (1 ≤ n ≤ 4) multiblock copolymers with nearly equal block lengths has been synthesized via living sequential anionic po...

Palaeovegetation reconstructions, particularly of fossil forests, are generally restricted to scant information on the taxonomic composition, relative abundance of individual taxa, or on tree density. We have developed new techniques for the analysis of stump horizons that result in a relatively detailed three-dimensional reconstruction of ancient...

Bulletin of the American Physical Society bf 39 699

The microphase-separated morphologies of a series of four poly[styrene-b-(d-styrene-grad-isoprene)-b-isoprene] tapered block copolymers have been explored in this work with small-angle neutron scattering (SANS) and transmission electron microscopy (TEM). Each of the copolymers consists of two pure end blocks and a selectively deuterated statistical...

Linear multiblock copolymers, like their diblock analogs, undergo microphase separation and order into periodic morphologies when the blocks are sufficiently incompatible. To explore the conformations of such materials, four symmetric poly(styrene-[ital b]-isoprene)[sub [ital n]] copolymers with 2[ital n] (1[le][ital n][lt]=4) perfectly alternating...

While numerous efforts have been put forth to correlate the morphology of microphase-separated diblock and triblock copolymers with molecular characteristics such as composition and chain length, far fewer studies have been devoted to elucidating the role of molecular architecture on microstructure in more complex linear copolymers. This is particu...

Polyvinyl methyl ether) PVME with polydispersity of less than 1.1 has been synthesized. This material has been used to study the effects of molecular weight on the phase diagram of blends of PVME with polystyrene (PS). The role of specific interactions in the phase behavior of the PS/PVME system also was studied using specifically deuterated PVME....